This review article is an effort to combine the recent developments, concerns and prospective applications of environmentally friendly nano- with micro-structured polymeric materials such as chitin, starch, polycaprolactone and nanocellulose.
Journal of Science: Advanced Materials and Devices (2018) 263e288 Contents lists available at ScienceDirect Journal of Science: Advanced Materials and Devices journal homepage: www.elsevier.com/locate/jsamd Review Article Recent progress in selected bio-nanomaterials and their engineering applications: An overview Raghvendra Kumar Mishra a, Sung Kyu Ha b, **, Kartikey Verma c, Santosh K Tiwari b, d, * a International and Inter University Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala, India Department of Mechanical Engineering, Hanyang University, South Korea c Department of Chemical Engineering, Indian Institute of Technology, Kanpur, Uttar Pradesh, India d Department of Applied Chemistry, Indian Institute of Technology (ISM), Dhanbad, Jharkhand, India b a r t i c l e i n f o a b s t r a c t Article history: Received March 2018 Received in revised form 21 May 2018 Accepted 28 May 2018 Available online June 2018 Nowadays, the rapid climate change, water pollution and harmful gas emissions are largely caused by the extensive use of petrochemicals and the burning of plastic materials The government authorities across the globe and experts mentioned that the dumping of plastic waste and non-biodegradable materials is a principal problem of the environmental pollution In their numerous chemical forms, cellulose and various other biodegradable materials can be possible alternatives to resolve these challenging issues This review article is an effort to combine the recent developments, concerns and prospective applications of environmentally friendly nano- with micro-structured polymeric materials such as chitin, starch, polycaprolactone and nanocellulose Nanocellulose has been considered as one of the most important biopolymers having significant advancements in research and their application in the various fields Herein, cellulose-based materials for engineering and interdisciplinary applications, comprising approaches for the transformation of cellulose to nanocellulose, and the fabrication method for their blends and composites have been reviewed Moreover, the structural-functional relationship, the thermomechanical properties of starch, poly (Lactic) acid, polycaprolactone, lignin and some of their composite and potential applications of these materials in various fields of engineering have been elaborated © 2018 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) Keywords: Green materials Biopolymers Cellulose Nanocellulose Biodegradable materials Introduction The prevailing development in polymeric composites applications is gaining momentum around the world [1e3] The extraordinary features of innovative polymeric composites and their establishment with existing environmentally friendly analytical techniques adduce considerable triumph to improve the era of environmental research [2,3] The food packaging materials obtained from petroleum-derived polymers are widely employed in several different functions due to their lesser density, more affordable cost, and extraordinary mechanical as well as barrier properties [1e3] Even though, various forms of petroleum-based product packaging polymer materials are generally recoverable * Corresponding author Department of Applied Chemistry, Indian Institute of Technology (ISM), Dhanbad, Jharkhand, India ** Corresponding author E-mail addresses: sungha@hanyang.ac.kr (S.K Ha), ismgraphene@gmail.com (S.K Tiwari) Peer review under responsibility of Vietnam National University, Hanoi and reused, huge ranges of these types of materials completely turn out in the form of landfill [2,3] Consequently, progressive biosphere issues parallelled the growth and development of versatile barrier bio-based product packaging materials as a reasonable alternative when dealing with these materials [2] Together, the lack of fossil fuel energy sources and the raised costs of crude oil have heightened the worldwide interest in bio-based materials [1e3] It turned out by analysers that the petroleum sources would appear to be inadequate in successive 60 years [2e4] Controlling the forthcoming concerns because of the plastic wastes as well as petroleum resources triggers the production of leading-edge and more environmentally friendly materials in the modern era Severe efforts are undertaken for growth and development of bio-based composites composed of renewable sources to replace petroleum-based polymers by obtaining ecofriendly materials [1e4] Edible coatings and films involved with an appreciable unique class of packaging materials that offer an additional strategy over the traditional packaging materials likely due to their outstanding biodegradable, biocompatible as well as https://doi.org/10.1016/j.jsamd.2018.05.003 2468-2179/© 2018 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) 264 R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 edibility characteristics [2e5] Although a sizeable number of bio extracted materials are analysed for their precise practical applications, scientists and experts have anticipated a fair number of persistent issues that confine their wider industrial applications [3] For example, some bio-degradable polymer materials in general exhibit poor mechanical properties in comparison with a lot of petroleum-based polymers This is exactly due to the intrinsic low stiffness as well as strength characteristics of biodegradable polymer materials Enhancing the properties of these kinds of biopolymers can often lead to innovative materials Low production levels, competition with food crops and high costs are the important aspects that can further reduce the broader technical applications of biopolymer packaging materials Thus, scientists are attempting to enhance the mechanical and barrier characteristics of bio-based films There are several options available to enhance the barrier and mechanical properties of packaging [4] Nowadays, studies regarding bio-polymer nanocomposites have witnessed a considerable improvement in the targeted properties in both industrial and academic laboratories According to the recent studies, the worldwide foods and beverage trade are going to display progression rates of near to 8% CAGR over the expected duration [4,5] The total food and beverage business enterprise in 2005 were approximately around USD trillion and achieved around USD 15 trillion in 2015; a development related to, among other activities, an increasing middle class of the community with an amplified customer investing potential in the Asia Pacific and Latin America The huge research and development on this material around the globe (Scopus data 2017, Fig a and b), have produced extensive items for the various industries, that would eventually raise the total biopolymer sell capacity by 20,246, as shown in Fig Therefore, this review article is a boon for the research outputs regarding the bio-polymer inspired micro and nanomaterials Green materials and their derivatives 2.1 Bio-polymer Biopolymers are usually polymeric biomolecules consisting monomeric units, which are generally covalently joined to fabricate larger sized molecules [1,2] The term ‘bio’ implies that these are in fact naturally degradable materials derived from formal living microorganisms [1] A group of materials generally manufactured from organic natural resources just to illustrate microbes, crops, or even plants are defined by means of the expression “biopolymer” Materials based synthetic routes derived from the biological resources for instance vegetable oils; sucrose, fats, resins, proteins, amino acids, etc are also referred to as biopolymer (because of the natural compositions) [2e4] In comparison with artificial polymers that contain a less complicated and additional random configuration, biopolymers are complicated molecular assemblies that employ accurate, described 3D patterns and architectural structures [5] This is certainly one vital character rendering biopolymers active molecules in-vivo Their specified shapes together with structure are key elements of their performance As an illustration, haemoglobin is unable to have oxygen in the blood when it was not folded inside a quaternary architecture Biopolymers are categorized in various ways according to distinct scales [5,6] According to their degradability, biopolymers are split into two wide categories, specifically biodegradable in addition to non-biodegradable, and alternatively, into bio-based as well as non-bio-based biopolymers [6] On the structure of their polymer main chain, biopolymers are undoubtedly grouped generally into the following categories: polyesters, polysaccharides, polycarbonates, polyamides, as well as vinyl polymers These types of classes are further defined directly into a bunch of subgroups in agreement with their source [3,4] Biopolymers are grouped, dependent upon the type of the repeating unit which is composed of three classes: (i) polysaccharides which are produced of sugars, (ii) proteins that come from different amino acids and (iii) nucleic acids that are composed of nucleotides Relevant to the application, biopolymers are known for their role of bioplastics, biosurfactant, bio detergent, bio-adhesive, bioflocculant, etc [6,7] 2.2 Biopolymer source and preparation Biopolymers are usually a variety of plastics produced from environmentally friendly biomass sources, for example, corn starch, pea starch, vegetable oil, and so on [6,7] Combined with bio-inspired polymeric materials (also many biopolymers) which are artificially extracted from particular polymers for preferred applications [6] The existence of unique natural polymers in crops, vegetation and plants grant a bio-renewable opportunity for their preparation It is noticeable that, almost all regular manmade polymers, are created in bulk after which they are moulded for the purpose of scientific research works Various types of microbes performed a key part in creating a variety of biopolymers, for example, polyesters, polysaccharides, as well as polyamides within the range of viscous solutions to plastics (Table 1) [7,8] Their physical characteristics are influenced by the constitution, design of repeated units as well as the molecular weight of the polymer [8] The physical, as well as chemical characteristics of a variety of biopolymers synthesized by the help of microbes, may be tailored to the consistent treatment of microorganisms which makes it suitable for healthcare applications, for example, drug delivery and tissue mechanism [9] Biopolymers which are generated by making use of microorganisms require specific nutrition as well as maintained surrounding environment These are commercially developed by means of direct fermentation or even by chemical polymerization by using repeating units that are consequently prepared by means of fermentation procedure Generally, most of the biopolymers are biocompatible as well as biodegradable without negative impact on biological systems [9] The functional mechanism of manufacturing of biopolymers from the microorganism origin is widely seen either as a result of their particular defence mechanism or as the storage material [9] It is well recognized that these types of materials tend to get degraded by natural processes as that of microorganisms and enzymes to ensure that it may lastly be reabsorbed in the environment [9,10] By focussing our concentration, a bit more into the biopolymers, the modification of fossil materials as well reducing of CO2 pollutants are achieved, therefore promoting environmental friendly development [10] Among the variety of microorganisms, algae work as an outstanding feedstock for the plastic generation because of their high output along with its potential to cultivate in a variety of conditions [9,10] The application of algae reveals the chance for making use of carbon as well as neutralizing greenhouse gas emissions from all sorts of industrial facilities Algae-based plastics have been a newly released inclination in the period of bioplastics in comparison with conventional strategies of employing feedstocks of corn and potatoes as plastics [1,10] Although algaebased plastics are in their infancy, once they are into commercialization they likely find applications in a wide range of industries At present, microbial plastics are viewed in the form of a crucial root of polymeric material which has an incredible opportunity for commercialization in the next generation They can tailor the movement abilities of fluids, be encapsulating materials, flocculate particles, create emulsions as well as stabilize suspensions [10] R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 265 Fig (a) Scopus database (09/12/2017) for the research output in form of research articles from the top ten countries and (b) applications of bio-polymer inspired micro and nanomaterials (Scopus database 09/12/2017) Table Different sources and methods of preparation for bio-polymer and related materials [1] Polymer Source or Method Basic materials used for synthesis Hybrid plastics Introducing denatured algae biomass to petroleum-based plastics exactly like polyurethane and polyethene in the role of fillers Biopolymer of glucose Filamentous green algae, Cladophores Cellulose-based plastics Poly-lactic acid (PLA) Bio-polyethylene Bio-Polyesters Polyhydroxybutyrate (PHA) Polycaprolactone (PCL) Chitosan Gelatin Alginic acid Polymerization of lactic acid lactic acid Ethylene manufactured from ethanol, by a chemical reaction called cracking Ethanol derived from natural gas/petroleum sources Biomass Obtained as a carbon and energy storage polymer under nutrient limiting growth environments Ring-opening polymerization using dibutyl zinc-triisobutylaluminum as a catalyst Alkali NaOH treatment Partial hydrolysis of collagen Treatment Brown algae in aqueous alkali solutions 25e30% of the biomass created after extraction of algal oil is known to comprise cellulose Microorganism fermentation of algal biomass Microorganism fermentation of algal biomass Microorganism like Akaligeneseurrophus, Escherichia coli, etc Microorganism such as Alcaligenes eutrophus ε-caprolactone Treating shrimp and other crustacean shells such as crabs and krills Collagen from white connective tissue, animal bones and skin Brown algae, including Laminaria hyperborea, Laminaria digitata, Laminaria japonica, Ascophyllum nodosum, and Macrocystis pyrifera 266 R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 Structure- property relationship of green polymeric materials Bio-polymers are adaptable in structure as well as properties and hence regarded as the most preferred biomaterials The demand for polymeric biomaterials in healthcare enterprise is about 60% of the global market, which has been expanding exponentially in recent years [9] This is due to the structure and surface properties of polymers, which can be tuned according to the specific desires of the biomaterials for various applications [9,10] The polymer-based materials derived from renewable resources support the development of sustainable composites via economically feasible and environmentally friendly technology [1,9] If a polymer or a polymeric blend or a polymer composite material with biodegradation property is obtained solely from a sustainable source, then it is called as a green polymeric product Nature presents a wide range of polymers with biodegradability property and exhibits the potential aspects to replace conventional fossil fuel-based polymers [1e3] The common examples for naturally derived polymers include proteins, starch, chitin and cellulose [1e3] In addition to this, natural rubber latex (NR), polylactic acid (PLA) derived from corn and polyhydroxyalkanoates (PHA) produced from bacteria serve as examples for other green polymers Polymers such as poly(a-hydroxy acid)s, poly(ε-caprolactone), poly(glycolic acid), poly(methyl methacrylate), poly(dimethylsiloxane), PU, cellulose, silk etc are utilized as biomaterials for various applications like contact lenses, bone cement, wound dressings, artificial organs, tissue scaffolds, cardio-vascular apparatus, breast implants, catheters, drug delivery, sutures and so forth [1e3] Green composites include a group of materials, which are gathered from renewable resources and undergo complete degradation through microorganisms [1e3] These materials act as a potential substitute for conventional petroleum-based polymeric materials for which recycling seems to be unpractical or uneconomical The biodegradability aspect of green polymers associated with their biocompatibility makes them an efficient advanced biomaterial [10,11] However, lack of adequate mechanical strength, as well as bioactivity characteristics, insufficient control with respect to degradation rate and poor biomimetic structural or compositional features, limit their practical applications, Table shows a list of frequently used polymers and their applications [10,11] Cellulose Cellulose is an abundantly available natural biopolymer and can be readily obtained from sustainable sources [2,10] The examples of fibrous form of cellulose include cotton, wool and hemp As sugar constitutes the monomeric units of cellulose, it falls under the category of the polysaccharide [11] The molecular formula for an organic cellulose is (C6H10O5)n This denotes polysaccharide, which consists of hundreds or thousands of 1e4 linked D-glucose units that are linked together in a linear fashion [10e13] It is found that certain bacterial species also secrete cellulose to promote the formation of biofilms In general, plants consist of 33% of cellulose content on an average [12,13] The plant sources rich in cellulose include cotton and wood The cotton consists of ~90% cellulose, whereas the cellulose content present in wood corresponds to ~50% Table Most frequently used polymers for different applications with remarks on their pros and cons [10] Polymer Applications Remarks Poly(methyl methacrylate) Polyurethane(PU) Contact lenses, bone cements, dentures etc Comparable elastic modulus to bone, bio-stable or bio-inert, brittle, low tolerance to the organic solvents, inability to modify with biomolecules etc Tuneable properties, blood-compatibility, biodegradable with no significant pH change, Toxic degradation products, lack of bio-stability for permanent implants etc Skin protectant, bio-durable, immunogenic activation of anti-silicon antigens etc Good toughness, resistance to fats and oil, cannot withstand sterilization temperature etc Hydrophilicity, biocompatibility, low immunogenic, insufficient strength, high degradation rate etc Good ductility, biocompatible, low tensile strength, slow degradation rate etc Excellent biodegradability, good processability, acidic degradation product etc Haemostatic, non-immunogenic, pro-angiogenic, biodegradable as well as biocompatible, cross-linked to form hydrogels etc Wound dressings, artificial organs, tissue scaffolds, cardio-vascular devices, etc Poly(dimethylsiloxane) Contact lenses, breast implants etc Polyethylene Orthopaedic joint implants, components of catheters etc Poly(ethylene glycol) Wound dressings, fillers etc Polycaprolactone Drug delivery, sutures and scaffolds etc Poly(lactideco-glycolide) Gelatin Resorbable suture scaffolds, bone grafts, stents, drug delivery etc Tissue engineering, wound dressing, gene transfection, drug delivery, weight loss as well as for treating osteoarthritis, rheumatoid arthritis, for foods, cosmetics, and medicines etc Paper, textiles as well as adhesives, pharmaceutical tablets, pesticides, cosmetics, detergents, oil-drilling fluids etc Biomedical field, Textile applications etc Starch Cellulose Chitin Chitosan Polylactic acid Poly-vinyl-Alcohol Polyvinyl acetate Collagen Water treatment, biomedical applications such as Fibroblast migration and proliferation wound dressing, raw materials for chitosan etc Drug carrier, coating agent, gel former etc Medical implants, wound management, drugs delivery etc Thickener in glues, paper-making, a sizing agent in textiles, water-soluble films useful for packing, coatings, optical, pharmaceutical, medical applications Biomedical, synthesis of metal nanoparticles, sensing activity etc Medical such as healing and repairing of the body's tissues and skin-deep application Cheap as well as degradable, sensitivity to moisture and poor mechanical properties etc Natural biological polymer, environment-friendly, biodegradable, remarkable strength etc It is insoluble in most of the solvents, as applicability, oxygen permeability, water sorptivity, blood coagulating property etc The excellent film forming property etc Biodegradable thermoplastic, aliphatic polyester, soluble in many organic solvents, higher transparency compare with other biodegradable polymers, superior in weather resistance etc Colourless, white, and odourless, water-soluble synthetic polymer etc Polyvinyl ester family, Thermoplastic resin etc Damage the production of collagen includes sunlight, smoking, and high sugar consumption R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 or more [12,13] Apart from cellulose, several natural components namely lignin, hemicellulose and pectin are also present in plant fibres As cellulose is an abundantly available raw material in nature and has attractive features, it is considered to meet the growing demand for eco-friendly products with ensured biocompatibility [12,13] It is well known that cellulose is insoluble in many solvents, which brings a limitation to its reactivity and processability for utilization [11e13] In thermoplastic-based polymer matrices, cellulose fibres are recognized as an efficient reinforcement in the recent years This is mainly due to the significant features of cellulose, which include low density, reduced wear problems while processing and readily active surface for functionalization, costeffective nature and easy availability [13] The cellulose reinforced polymer composites can be easily combusted during a recycling process as compared to polymer matrices filled with inorganic fillers [13,14] Despite all these advantages, the utilization of cellulose fibres in the industrial scale is limited The reason behind this problem is the inability in attaining satisfactory dispersion levels in polymer matrices [14] 4.1 The basic structure of cellulose It is well known that cellulose is a polysaccharide with glucose as its monomeric units Structural isomers of glucose include fructose and galactose [14,15] Throughout the cellulose chain, glucose molecules are linked via glycosidic bridges which are formed by loss of hydrogen atom from one monomer and hydroxyl groups to another monomeric unit [15] This leads to the formation of microfibrils [14] These microfibrils are arranged together by the intermolecular hydrogen bonding to form bigger fibrils It can be observed that a cellulose homopolymer consists of D-anhydroglucopyranose units which are then linked via (1e4) glycosidic bonds As glucose exists as a six-membered ring in the cellulose structure, it is named as pyranose [15] The oxygen linkages provide a connection between the pyranose monomeric units Native cellulose refers to the cellulose produced by plants, which exists in two types of crystalline structure namely cellulose I and cellulose II Type II cellulose is found to exist in marine algae [15,16] Cellulose II is usually crystalline in nature and can be produced when cellulose I is subjected to undergo treatment with aqueous phase sodium hydroxide Apart from type I and type II cellulose, other forms such as cellulose III and cellulose IV exist Cellulose I is recognized to be less stable as compared to other polymorphs, whereas cellulose II is known to present a highly durable structure among all the types [16] 267 chains are stacked parallel to each other by Van Der Waal's interaction [17,18] Cellulose Ib has a monoclinic unit with two hydrogen bonding chains per unit cell These two forms of cellulose I mutually co-exist and their percentage varies with varying sources of cellulose [18] Cellulose obtained from primitive organisms (bacteria, algae) is rich in cellulose Ia while cellulose obtained from developed higher woody plants are rich in cellulose Ib Cellulose Ia can be transformed into more stable Ib by annealing at around 2600 C to 2800 C in some special solvents [18] 4.2.2 Cellulose II Cellulose II is much more thermodynamically stable than Cellulose I It was in 1844 that John Mercer first invented the technique of mercerization for converting cellulose I to Cellulose II [17e19] In the process of mercerization cellulose is treated with alkali with a concentration of about 17%e20% w/v [17e19] This leads to the swelling of cellulose bres when Naỵ ions penetrate the spaces between the cellulose molecules without causing any dissolution During the process, the parallel chain arrangement of the cellulose molecules gets reversed into antiparallel chains In 2015, B J C Duchemin was able to convert cellulose I into cellulose II by using only 1% w/v NaOH solution at the temperature below C without changing the crystallinity of the cellulose microstructure This was indeed a great advancement in the mercerization technique Another process of dissolution and regeneration can also convert cellulose I into cellulose II [18,19] As the name suggests, this process involves the complete dissolution of cellulose followed by regeneration of cellulose fibres Regeneration of cellulose can be done by various processes like copper ammonium and N-methyl morpholine N-oxide (NMMO) processes [19] The cellulose I to II conversion was reported by regeneration using phosphoric acid The alteration of cellulose I to cellulose II is an irreversible process indicating cellulose II is much more thermodynamically stable [19] 4.2.3 Cellulose III Interestingly, Cellulose III exists in two forms: Cellulose IIII and Cellulose IIIII Cellulose IIII is obtained by the ammonia mercerization of Cellulose I and Cellulose IIIII is obtained by the ammonia mercerization of Cellulose II In 1986, Yatsu did the stable transformation of cellulose I to cellulose III by immersing cellulose in ammonia solution followed by degassing [20] The conversion to Cellulose III is reversible in nature where chain orientation is not changed However, fragmentation of crystal takes place during the transformation of Cellulose I to cellulose III During the reverse transformation, distortion of the morphological structure is not restored [20] 4.2 Polymorphisms of cellulose Polymorphism is the property by virtue, a compound can appear in more than one form Cellulose consists of many hydroxyl groups contributing to more intramolecular and intermolecular hydrogen bonds which lead to separate ordered arrangements [17] In one cellulose bonding unit, there prevails six hydroxyl groups and three oxygen atoms Hence, there are many possibilities of crystal packaging, different cellulose units, and change in chain polarity The polymorphs of cellulose are classified generally into four heads [17]: 4.2.1 Cellulose I Cellulose I is a native cellulose, and it is abundantly found in the environment [2,3] In 1984, Atalla and Vander Hart discovered that the native cellulose is present in two forms, namely Ia and Ib They used 13C CP/MAS NMR spectra to characterize native cellulose into two distinct allomorphs [17,18] Cellulose Ia has a triclinic unit with one hydrogen bonding chain per unit cell, where the cellulose 4.2.4 Cellulose IV Cellulose IV is obtained from Cellulose III by treating it with glycerol at a higher temperature In 1946, Hermans and Weidinger were able to convert mercenaries' ramie cellulose fibres into cellulose IV by treating it at high temperature in the presence of glycerol [21] 4.3 Nanocellulose Nanocellulose is one of the dominant biodegradable and sustainable nanomaterials found in nature In simpler terms nanocellulose corresponds to cellulose in the nanometer scale [20e22] Till 1970, humans have been making cellulose from plant materials like wood, plants, waste materials and algae [22,23] In 1970, Turbak, Snyder and Sandberg could successfully synthesize microfibrillated cellulose by homogenization at high temperature and high pressure accompanied by an impact ejection at a hard surface [22,23] Generally, cellulose is slightly crystalline and amorphous in 268 R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 nature [23] It is extremely difficult to break the crystalline part of cellulose because of its remarkably strong hydrogen bonds [23] Hence, cellulose has to go through a sequence of chemical and mechanical treatments in order to extract crystalline nanocellulose and nanocellulose fibres [22] Cellulose nanofibrils (CNF) include extremely thin (nearly 5e20 nm) and in length (up to several mm) fibrils with significantly high surface area (aspect ratio) Every microfibril is usually defined as a chain of cellulose crystals connected along the microfibril axis disordered amorphous domains [22,23] In small quantities, it makes a translucent gel-like material that can be used for developing biodegradable combined with ecofriendly safe, uniform, as well as dense films for several purposes, specifically in the biomedical area [23] Extraction of CNF is being discussed from a variety of resources such as coir, banana, sugar beet, hemp, softwood, in addition to wood pulps [23] After employing a range of plasticizers, range of thermal, mechanical, barrier, and also physical features of the cellulose are enhanced in order that it has been employed in a variety of market applications [23] Plasticizing enhances the features such as oil and grease protection, and significant barrier against oxygen transfer particularly at a dry environment [23,24] Almost all cellulose-synthesizing microorganisms consisting microbes, algae, tunicates, as well as considerably higher plants possess cellulose syntheses proteins, which catalyse the polymerization reaction of glucan chains [24] At present, cellulose is generally obtained from a vast variety of crops, vegetation, plants, animals, as well as bacteria [17,23] The origin is crucial as it influences the dimensions as well as characteristics of the obtained cellulose An array of the crop, vegetable and plant materials are being analysed in relation to the extraction of cellulose as well as nanocellulose, which includes timber, rice husk, sisal, hemp, flax, kenaf, and in the coconut husk Cotton fibres have likewise been applied in form of an efficient source material, benefiting from their low non-cellulosic constituent content than wood Wood is an elegant initiating material for cellulose as well as nanocellulose isolation, due to its terrific quantity [23] It is a natural composite material with a hierarchical structure comprised of cellulose, hemicelluloses, as well as lignin [23,24] Wood includes a porous anisotropic configuration, which displays an extraordinary combination of excellent strength, rigidity, resilience, as well as lesser density [25] The preparation of nanocellulose from wood involves a multistage operation concerning vigorous chemical and/ or mechanical treatments Tunicates are aquatic invertebrate animals, particularly, members of the subphylum Tunicata Most of the study in this field includes a highlighted category of tunicates which are typically referred to as sea squirts (Ascidiacea), that is a breed of aquatic invertebrate filter feeders Experts are working over 2300 varieties of Ascidiacea and cellulose microfibrils to understand above mentioned phenomenon For the same reason, scientists are also working on many dissimilar species like Halocynthia roretzi, Halocynthia papillosa and Metandroxarpa uedai [23,26,27] The tunicates create cellulose in the external tissue, referred to as tunic, from which a refined cellulose portion referred to as tunicin is obtained Tunicate cellulose consists of nearly fresh cellulose of CIb allomorph form with significant crystallinity [26] The nano/microfibrils of tunicate cellulose contain a huge aspect ratio as well as the excellent specific surface area Algae of a variety of breeds, green, red as well as brown, are also defined as cellulose as well as nanocellulose sources For example, Valonia, Micrasterias denticulate, Micrasterias rotate, Cladophora, Boergesenia, as well as other kinds of algae are being employed [26,27] Cellulose microfibrils with a huge aspect ratio (>40) are generally obtained from an algae cell wall by way of acid hydrolysis or mechanical refining [27] The architectural structures of CMFs separated from various kinds of algae change To illustrate, Valonia microfibrils hold square cross-sectional area (nm2) as they are mainly of Ia crystalline form [26] However, M denticulate microfibrils possess rectangular cross-sectional area (nm2) because they are mainly of the CIb crystalline form Bacterial cellulose (BC) is a result of the major metabolic operations of a particular kind of bacteria [26,27] The most well-known BC-producing bacterial breeds are Gluconacetobacter xylinus [23,26,27] Under specific culturing environment, these types of bacteria create a dense gel which is made up of cellulose microfibrils together with 97e99% water [23,26,27] Bacteria cellulose crystallites are predominantly of the CIa crystalline form along with the degree of polymerization (DP) of bacterial cellulose, which is commonly between two thousand and six thousand The benefit of bacterial cellulose is the fact that it is easy to adapt the culturing environment to modify the microfibril configuration as well as crystallization [23] The supplementary vital ability of bacterial cellulose is its superior chemical purity, which distinguishes it from the kinds of plant cellulose that are generally related to hemicelluloses as well as lignin In spite of this, both celluloses synthesized by bacteria or cellulose obtained from a number of plants contain identical molecular arrangements [15,23,26] The different kinds of nanocellulose are generally categorized into various subcategories according to their shape, dimension, functionality, as well as generation strategy, which predominantly rely on the cellulosic resource together with processing environment [23,26] Various terminologies can be employed for the different types of nanocellulose [26] A serious problem that needs to be eliminated for effective commercialization of cellulose nano-fibrils is the excessive energy consumption needed for the mechanical disintegration of the preliminary cellulose microfibers into nano-fibres, may possibly consist of many passes through the disintegration machine To deal with, it looks like the mode of cellulose feedstock performs a noteworthy role in the energy consumption; despite this, it seems to have merely any effect on the resultant cellulose nano-fibrils features It should be mentioned that cellulose nano-fibrils experience some specific unfavourable characteristics, which reduce their application in several sectors, for illustration, in papermaking due to sluggish dewatering or even as polymer composites because of inadequate compatibility of hydrophilic reinforces with hydrophobic polymers A possible method for fixing this issue is the chemical modification of cellulose nanofibrils to decrease the quantity of hydrophilic hydroxy active groups [28] Cellulose nanocrystals (CNCs) show an elongated rod-like appearance and provide very limited flexibility in comparison to cellulose nanofibrils, due to its considerably higher crystallinity [28,29] Cellulose nanocrystals are usually called as nanocrystalline cellulose, nanowhiskers, nanorods, or rod-like cellulose crystals [29] The nanocrystalline particles structure are produced through the splitting of amorphous domains, along with the splitting of localized crystalline contacts between nanofibrils, by means of hydrolysis with concentrated acids (6e8 M) This chemical type method is accompanied by high-power mechanical or sometimes ultrasonic treatment methods [29] A significant feature of cellulose nanocrystals made from sulfuric acid is the negative particle charge, because of the generation of sulphate ester active groups, which improves the phase durability of the nanocrystalline particles in an aqueous environment [28,29] The geometrical shapes and sizes of cellulose nanocrystals may vary extensively, with a diameter ranging from to 50 nm as well as a length within the range of 100e500 nm The dimensions, as well as the crystallinity of a cellulose nanocrystal, are controlled by the cellulose resource and consequently extraction circumstances Researchers have described that nanocrystalline particles obtained from tunicates and bacteria cellulose are likely to be bigger in comparison to cellulose nanocrystals received from wood or cotton This is R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 because tunicates or bacteria cellulose are extremely crystalline and possess extended nanocrystallites Cellulose nanocrystals derived from pure cellulose materials display greater crystallinity Nanocrystalline cellulose particles manifest outstanding mechanical characteristics [29,30] The theoretical Young's modulus of a cellulose nanocrystal along the cellulose chain axis is expected to be 167.5 GPa, which is certainly just like the modulus of Kevlar or maybe greater than the modulus of steel [30] The experimental Young's modulus of cotton cellulose nanocrystals is 105 GPa, in addition the modulus of tunicate cellulose nanocrystals is 143 GPa Amorphous Nanocellulose is generally extracted by using acid hydrolysis of regenerated cellulose with succeeding ultrasound disintegration Amorphous nanocellulose particles commonly contain an elliptical shape with typical diameters of 50e200 nm [30,31] Due to its amorphous configuration and arrangement, amorphous nanocellulose has extraordinary capabilities, including a much higher functional group content, a significant availability, an improved sorption, as well as an enriched thickening potential [3,17,22] Even though, amorphous nanocellulose particles possess inadequate mechanical characteristics because they are inappropriate to be used in the form of reinforcing nanofillers [3,17] Thereby, the main applications of amorphous nanocellulose are in the role of carriers for 269 bioactive ingredients, thickening agents in a variety of aqueous systems, etc [30e34] Cellulose Nanoyarn is another form of nanocellulose, it is produced by electrospinning a solution composed of cellulose or cellulose derivatives However, it has not been widely studied till date [34e37] A transmission electron microscope (TEM) image of nanocellulose forms, produced from different sources is shown as an example in Fig 4.4 Preparation of nanocellulose When plant cell wall is exposed to powerful mechanical disintegration, the initial structure of cellulose fibre is transformed, therefore the fibres transform into nanofibrils (CNF) or even their microfibrils bundles (CMF) with diameters which range from 10 to 100 nm based on the disintegration power [33e37] Many mechanical methods are often used to obtain cellulose nanofibrils or cellulose microfibrils from a variety of feedstocks, which include homogenization, microfluidization, grinding, cryocrushing, as well as ultrasonication, as shown in Fig [36] The preparation of nanocellulose consists of many steps which includes mechanical and chemical treatments Such treatments are assigned towards restructuring the specific coherent organization of microfibrils present in a natural cellulose [23,36] The nature and properties of Fig TEM micrographs of (a) Microcrystalline Cellulose from fodder grass [32], (b) Cellulose microfibril from sugar beet [33], (c) Cellulose nanofibril from banana peel [34], (d) Cellulose nanocrystal from ramie fiber [35], (e) Amorphous Nanocellulose from MCC [36] 270 R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 the ultimate nanocellulose product that we receive depend upon the individual steps involved as well as the individual length of step The aspect ratio of the final nanocellulose depends upon the length of de-structuring that the raw material undergoes [38] 4.4.1 Methods of nanocellulose preparation There are several different extraction techniques to collect nanofibrils (Fig 3) They are often carried out by mechanical strategies, for example, grinding, cryocrushing in the presence of liquid nitrogen, high-pressure homogenization, and so forth Similarly, various chemical alkali, as well as enzymatic hydrolyses, are applied before mechanical techniques to be able to increase the gain access of hydroxyl active groups, which improve the inner surface, modify the crystallinity, split cellulose hydrogen bonds, thereby enhancing the reactivity of the fibres [37,38] 4.4.2 Pre-treatment Two main issues frequently take place during the fibrillation stage, and most importantly throughout the mechanical fibrillation of cellulose are: (i) fibril aggregation, whenever slurry is pumped by means of the disintegration equipment in addition to (ii) excessive energy intake involved with fiber delamination, may possibly engage multiple feeds into the disintegration equipment until effective delamination of cell walls is attained [36e39] The excessive energy contribution is essential with the intention to produce the nanofibers In order to reduce the interfibrillar hydrogen bonding, based on earlier scientific studies, an effective pre-treatment can reduce the energy intake The selection of pretreatment methodology is based on the cellulose source [39] It is worthwhile stating that a suitable pre-treatment of cellulose fibres supports reliability, improves the inner surface, adjusts crystallinity, decreases the energy demand and promotes the process of nanocellulose generation [40] As an example, the pre-treatment of vegetable, crop, fruit, plant materials enhances the total or even limited elimination of noncellulose constituents hemicellulose, lignin as well as the isolation of specific fibres Pre-treatment of tunicate entails the elimination of the proteins matrix, isolation of the mantel, along with the isolation of specific cellulose fibrils Fig Schematic diagram for the recent process to achieve nanocellulose [39] R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 [36e40] Pre-treatment of algae usually helps in the elimination of the matrix material of algae cell walls, while pre-treatment of bacterial NC is targeted on the elimination of microbes as well as other contaminants from the slurry [39] Pre-treatment is an extremely crucial stage since it can adjust the structural foundation, crystallinity, as well as polymorphism of the cellulose, in addition to numerous characteristics of the pre-treated feedstock The pretreatment method is employed to assist the cell wall delamination together which produces nano-sized fibrils The well-known pretreatment approach includes pulping techniques, bleaching, alkaline-acid-alkaline treatment, enzymatic treatment, ionic liquids, oxidation, and steam explosion [1,38e40] 4.4.3 High-pressure homogenization High-pressure homogenization refers to a technique for the large-scale fabrication of CNF, along with laboratory-scale preparation of nanofibrils [41,42] This approach includes pushing the solution by using an extremely trim channel or alternatively an orifice taking advantage of a piston, under an elevated pressure of 50e2000 MPa [41,42] The width of the homogenization gap is dependent upon the viscosity of the solution along with the exerted pressure [42] The consequential high solution streaming velocity leads to an intensification of the dynamic pressure as well as a lowering the static pressure underneath the vapour pressure of the aqueous phase This contributes to the production of gas bubbles, which breakdown instantly if the liquid departs from the homogenization gap, getting once again under a standard air pressure [41,42] The gas bubble production, as well as implosion incident, can cause the creation of shockwaves and cavitations, which trigger disturbances of the fibrillar configuration of the cellulose Cellulose fibre size drop is accomplished by means of a significant pressure drop, excessive shear forces, turbulent flow, as well as interparticle collisions The level of the cellulose fibrillation is determined by the range of homogenization cycles as well as on the exerted pressure [42] 4.4.4 Microfluidization A microfluidizer is an additional technique which can be employed for cellulose nanofibrils or even cellulose microfibrils production In contrast to the homogenizer, which works at the steady pressure, the microfluidizer performs at a consistent shear rate The fluid slurry is pumped via a z-shaped chamber, which attains an elevated shear force [42,43] The pressure can achieve ranges up to 40,000 psi, which is about 276 MPa [42] Purposely designed predetermined-geometry microchannels are placed inside the chamber, by which the slurry speeds up to higher velocities The preferred shear, as well as impact forces, are built whenever the slurry stream strikes on wear-resistant surfaces Several check valves enable recirculation of the slurry Upon leaving the interaction section, the product is sent in a heat exchanger, recirculated in the system for additional operation, or perhaps sent from the outside to the subsequent step in the operation It is required to perform repeatedly the process many times to adapt to different sized chambers to be able to enhance the level of fibrillation Authors inspected the influence of the number of passes of microcrystalline cellulose MCC slurry in a microfluidizer on the morphology of the extracted cellulose nanofibrils [44] They identified that the aspect ratio of the nanofibrillar bundles enhanced after 10e15 transferring cycles, while extra flows resulted in agglomeration of the CNFs because of the expanded surface area as well as a greater level of the surface hydroxyl group [45] 4.4.5 Grinding An additional method for isolating cellulose fibres into nanosized fibrils is grinding process [46] Throughout grinding process, a 271 fibre fibrillation operation is performed by transferring the cellulose slurry between static as well as rotating grindstones rotating at about 1500 rpm, which exert a shearing stress to the fibres [46] The fibrillation procedure in the grinder makes use of shear forces to decompose the cell wall configuration and arrangement as well as separate the nanoscale fibrils [45,46] The level of fibrillation relies upon the distance between the disks, the actual morphology of the disk tunnels, along with the number of feeds into the grinder Regarding a homogenizer, numerous passes have been instructed to produce the fibrillated cellulose The requirement for disk stone routine maintenance as well as a replacement may be a downside of this method since wood pulp fibres are able to deteriorate the grooves as well as grit [46,47] But, an important benefit of grinder operation is the fact that extra mechanical pre-treatments are usually not required [47] 4.4.6 Cryocrushing Cryocrushing is a mechanical fibrillation way to cellulose in a refrigerated condition This process generates fibrils with reasonably big diameters, varying within 0.1 to mm Within this method, water-swollen cellulose fibres are usually refrigerated in liquid nitrogen and after that progressively crushed [46,48] The use of substantial collision forces to the frozen cellulosic fibres contributes to breaking of the cell walls because of the pressure implemented by the help of the ice crystals This draws out the nanofibers The cryo-crushed fibres can subsequently be distributed as well as dispersed uniformly in water with the help of a routine disintegrator [49] This technique is relevant to numerous cellulose materials which enable it to be considered as a fibre pre-treatment procedure before homogenization Authors developed nanofibers from soybean stock by means of cryocrushing together with succeeding high-pressure fibrillation TEM confirmed that the nanofiber diameters have been found in the 50e100 nm range [48] The nanofibers produced manifested outstanding dispersion capability in the acrylic emulsion in comparison to water In spite of this, the cryocrushing technique offers a low efficiency and is not cost worthy, due to its high energy expenses [49] 4.4.7 High-intensity ultrasonication High-intensity ultrasonication is a very common laboratory mechanical treatment method employed for cell disturbances in aqueous conditions [50,51] This technique produces effective cavitation which includes the growth, extension, as well as collapsing of microscopic gas bubbles once the water molecules intercept ultrasonic energy The effect of the hydrodynamic forces of the ultrasound on the pulp contributes to the defibrillation of the cellulose fibres [50] Number of researchers have investigated the use of high-intensity ultrasonication (HIUS) to the separation of nanofibers from a variety of cellulosic resources, for example, plain cellulose, microcrystalline cellulose, pulp, culinary banana peel, rice waste, as well as microfibrillated cellulose [3,17,50,51] The test results confirm that a mixture of microscale as well as nanoscale fibrils can be accomplished directly after ultrasonication of the cellulose samples; the diameters of the extracted fibrils are extensively found in the range from 20 nm to several microns, suggesting that a few nanofibrils are extracted from the fibres, although a few stay on the fibre surface [50] As a result, this process provides aggregated fibrils with a vast width distribution It is additionally noticed that the crystalline structure of certain cellulose fibres is modified by means of ultrasonic treatment method [50] These types of alterations change for individual cellulose resources, for instance, the crystallinity after remedy enhanced for 100% pure cellulose, diminished for microcrystalline cellulose, although it continued to be consistent for pulp fibre Authors examined the consequences of temperature, concentration, power, 272 R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 dimensions, duration, as well as distance from the probe tip on the level of fibrillation of plenty of cellulose fibres with the help of HIUS treatment [51] They claimed that outstanding fibrillation was due to a higher power as well as temperature, even though lengthier fibres were much less defibrillated Greater pulp fraction and larger sized distance from the probe to beaker were not beneficial for the fibrillation [51] These researchers noticed that a conjunction of HIUS together with HPH enhances the fibrillation together with uniformity of the nanofibers, in comparison to high-intensity ultrasonication (HIUS) alone The nanofibrils cellulose output is additionally improved if TEMPO-oxidized pulp is employed for HIUS treatment method [50,51] 4.4.8 Acid hydrolysis To extract cellulose nanocrystals, acid hydrolysis of purified cellulosic material can be carried out by intense mineral acids (6e8 M) under-governed environment, time, agitation, and acid/ cellulose ratio conditions [52] Various mineral acids are employed for this specific purpose, for example, sulfuric acid, hydrochloric, phosphoric, maleic, hydrobromic, nitric, as well as formic acids [3,17,52] A combination made up of hydrochloric together with organic acids (acetic or butyric) has been discussed in the previous sections Sulfuric is regarded as the most widely applied acid for cellulose nanocrystals production Throughout hydrolysis, disordered amorphous regions, as well as interfibrillar contacts of cellulose, are selectively hydrolysed; on the other hand, consistent crystallites stay unchanged which enable it to be separated as rodlike nanocrystalline materials [52] The cellulose nanocrystals dispersion in an intense acid is antiquated by using water and cleaned via consecutive centrifugations Neutralization or even dialysis by using distilled water is conducted to take away remaining acid from the dispersion Supplementary steps for example filtration, centrifugation, or perhaps ultracentrifugation, in addition to mechanical or possibly ultrasound disintegration, have likewise been discussed [53,54] In case cellulose nanocrystals are produced taking advantage of cellulose hydrolysis together with hydrochloric acid, the uncharged nanocrystalline particles are likely to flocculate in the aqueous medium [53,54] The other hydrolysis techniques are hydrolysis with solid acids, hydrolysis with gaseous acids, hydrolysis with metal Salt catalyst (Novo et al., 2015) The main benefits of hydrolysis in the presence of the solid acid are easy restore of the solid acid, relative safe, lesser corrosion rate of the equipment [52e54] Hydrolysis with gaseous acids method could provide numerous environmentally harmful as well as timeconsuming steps which are used for traditional acid hydrolysis is ruled out Without any doubt, less quantity of water is required, the acid reusing is much easier, and in fact the dialysis stage is left out The cellulose nanocrystals output is considerably more, due to lesser cellulose feedstock damage throughout the gaseous hydrolysis operation [53] Hydrolysis with metal salt catalyst is performed using a transition metal-dependent catalyst A transition metal-dependent catalyst offers a satisfactory, preferential, as well as feasible hydrolysis operation with minor acidity The valence condition of the metal ion is the paramount aspect to induce the hydrolysis performance, in which an acidic solution (Hỵ) produces during the period of polarization between metal ions as well as water molecules [55,56] A greater valence state produces much more Hỵ ions, which behave efciently in the co-catalysed acid hydrolysis reaction in the existence of metal ions [1e3] 4.5 Chitin Chitin is a polysaccharide which is highly basic in nature Chitin falls under the category of natural polymer usually found in shells of crabs After cellulose, chitin is recognised as the most abundantly available polymer in nature Both chitin and cellulose belong to polysaccharide category Chitin differs from cellulose by the presence of acetamide group rather than hydroxyl group It is estimated that the crab and shrimp shell waste generated from fishing industry contains 8e33% of chitin polymer Chitin consists of b-1, 4N-acetyl-D-glucosamine monomer units arranged in a linear fashion, as shown in Fig [57,58] The isolation of chitin starts with the choice of shells Preferably, shells of the identical size, as well as kinds, are selected For shrimp shells, the relatively slim walls render restoration of chitin more convenient [57,58] The washing, as well as drying of the shells pursued by extensive crushing, is the subsequent step in the method The small shell fragments are dealt with dilute hydrochloric acid to take away calcium carbonate Proteins along with other organic contaminants are eliminated by an alkali treatment Fig Chemical structure of chitin and deacetylated chitin (chitosan) [58] 274 R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 Table Constituents of different lignins [64] Table Thermal stability of different kinds of lignin Lignin type Mn (g molÀ1) COOH (%) OH phenolic (%) Methoxy (%) Soda (bagasse) Soda (wheat straw) Kraft (softwood) Organosolv (hardwood) Organosolv (bagasse) 2160 1700 3000 800 2000 13.6 7.2 4.2 3.6 7.7 5.1 2.6 2.6 3.7 3.4 10.0 16.0 14.0 19.0 15.1 superiority of kraft lignin is due to the high-density network like hydrogen bonding between the constituents of kraft lignin and therefore Glass transition temperature (Tg) is another imperative property that affects the properties of the final product [63] The hydrogen bonding between stilbene and amylose of lignin is shown in Fig Tg of different Lignin Processed by Using Different techniques, as displayed in Table Leskinen et al have reported in their widespread research that Tg depends upon the amount of polysaccharides and water in the lignin, along with the molecular weight and functionalities present in the lignins [64,65] Different chemical procedures are being used to process Lignin from different resources and each process has some advantage and disadvantage and most of the procedures follow either an acid or base-catalysed mechanism [65] Thus Lignin is broken down into low molecular weight fractions while handling through these processes, and its properties got affected greatly [65] In the same line, many researchers have developed a new technique for the processing of lignin, in which sulfite, kraft, and soda, are three major processes along with many others [64e66] The sulfite process is an acid-catalysed process, conventionally used in pulping technology, involves the cleavage of the aether linkages and b-ether linkages of lignin [65,66] In this method, a chemical reaction between free sulphurous acid and lignin leads to the formation of lignosulfonic acid, soluble lignosulfonates formation with cations and lignosulfonates fragmentation along with the production of carbohydrates take place [65,66] Kraft lignin is a product of kraft pulping process, which exhibit a dark colour and is insoluble in solvents including water [66] The kraft lignin comprises the highest quantity of the phenolic eOH in contrast to other of lignins [65,66] With a decrease in the molecular mass of lignin, an increment in the number of eOH is reported Types of lignin Tg ( C) Milled wood lignin steam explosion lignin Hardwood Softwood Organosolv lignin Kraft lignin 113e139 110e130 138e160 91e97 124e174 Because of cleavage of the bonds, ionic strength, temperature, and pH of the solution also influence the solvency of kraft lignin in an aqueous medium [66] Commonly, diluted NaOH is used as the cooking chemical to produce wood pulp in soda pulping process Soda lignin usually exhibits similar properties such as high phenolic hydroxyl content, relatively low glass transition temperature (Tg) and low molecular weight Gupta et al used spray-dried lignincoated cellulose a bio-based filler in PLA host matrix, to modify the rheological and thermo-mechanical properties of poly(lactic acid) (PLA) composites The lignin coating on CNCs improves the dispersion of CNCs as well as improved their interfacial interaction with the PLA matrix, resulting in a substantial enhancement in thermo-mechanical and rheological properties, which make them a suitable candidate for the end user applications [67] The composites show significantly higher storage modulus (G0 ) than the neat PLA at all loading of L-CNCs in both glassy and rubbery region in the Dynamic Mechanical Analysis [67] In the presence of L-CNCs, crystallization behaviour of the PLA matrix was also found to improve significantly [67] Kai et al synthesized a series of the composite with different loading of lignin in PLA via the ring-open polymerization of lactide onto selectively alkylated lignin [68] First, this copolymer was blended with poly(L-Lactide) (PLLA) and then the electrospun process is taken place to fabricate uniform nanofibres with controlled fibre diameters To examine the biocompatibility of PLAlignin composites, three different cell types ePC12, human mesenchymal stem cells (MSCs) and human dermal fibroblasts (HDFs) were cultured In mechanical properties study, it was found that elongation at break and toughness of PLA/lignin composites are five times higher than neat pure PLA Antioxidant activities were evaluated by DPPH assay for PLA-lignin copolymers and ligninbased nanofibres It is observed that Neat PLLA nanofibers show low antioxidant activities [68] Even after 72 h, it attains only 15.5 ± 6.2% free radical inhibitions, which is much lower than lignincontaining nanofibers Such type of lignin-based nanofibers used as biomaterials may reduce oxidative stress-related tissue damages or functional disorders The biocompatibility of PLLA/PLA-lignin was studied Due to the oxidative stress induced by the polyester itself, all three cell types show low metabolic activities on neat PLLA nanofibers [67,68] Higher cell proliferation values were found for all lignin-containing nanofibers which indicate that the antioxidant activities may enhance the viability of the cells In locally attenuating cellular oxidative stress, such materials could be used as tissue engineering scaffolds In the same line, Kai D et al [68], again evaluated the antioxidant activities of lignin-PCLLA copolymers and their electrospun nanofibres by DPPH assay They proved that higher lignin loaded copolymer shows the higher antioxidant property Even all PLLA/lignin-PCLLA nanofibers exhibit antioxidant activity more than 70% which enables their application for biomaterials and food packaging to address issues of oxidative stress [67,68] 4.7 Unvulcanised natural rubber particles Fig Hydrogen bonding between stilbene and amylose of lignin Natural rubber (NR) is the main biopolymer and it is commonly utilized in many fields such as medical, tyre and glove due to its R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 good physical properties [69] Natural rubber (NR) is a bio-based polymer which can be derived from renewable resources namely Hevea brasiliensis The overall production of natural rubber in 2003 was million tonnes with the major producers being Thailand (2.8 million tonnes), Indonesia (1.8 million tonnes), Malaysia (0.9 million tonnes) and India (0.6 million tonnes) [69] In India, 90% of the rubber production is accounted from Kerala NR has excellent extrudability and launderability and has a high rate of cure Apart from its application in the tyre industry, NR is employed in the production of thin-walled soft products with high strength This is because; NR can crystallize easily upon stretching [69] The physical properties of NR are enhanced by the addition of filler, chemical alteration and blending with other polymers such as polyethene (PE), propylene (PP) and nitrile rubber (NBR) The green fibre and ‘natural fibre’ covers a broad range of vegetable fibres such as wood fibre and plant-based bast, leaf, seed, stem fibre and animal fibres such as collagen, keratin and fibroin [69,70] Recently, they are used as reinforcements in polymer composites to improve the mechanical properties The natural fibres were also blended with NR to enhance its modulus and biodegradability properties [70] In the past work, the raw materials were picked up from many natural sources such as sugar beet pulp as well as eucalyptus kraft pulp because H2SO4, HCl, HClO4, NaOH are capable to react with cellulose fibre [69,70] The problem with NR composite is poor adhesion between NR and cellulose fibre The factors affecting the properties of the NR-based polymer composite are fibre type, fibre amount, and chemical treatment, the shape of the fibre, adhesion and arrangement of fibres in the polymer matrix [69,70] 4.8 Properties of starch, separation and applications: an overview Starch is a sustainable and cheap biodegradable polymer [71] After cellulose, starch is recognised as the widely available polymer [3,71] The main sources from which starch is obtained include rice, wheat, potato as well as corn However, the certain features of the plants namely shape as well as size; morphology along with the composition of different plant sources used for starch production varies from each other [71] The United States is reported to be as the World's top producers of starch The European countries contribute next to the United States in starch production in the World Both of these nations play significant contribution towards half of the World's starch production [71e73] Native starch is naturally composed of nano-sized blocklets which have semicrystalline arrangements of starch chains It is now well established that the crystalline regime is made up of thin lamellar domains by the intertwining of amylopectin side chains to result in the formation of double helices [71e73] Such double helices are tightly packed such that they tend to lead to the basis of crystalline domains In the amorphous regime, the molecules of starch are arranged in a single-chain conformation whereas the crystalline regime is so ordered such that the molecules of starch exist in the double-helix state Both the amorphous as well as crystalline regions get arranged resulting in the formation of the ring structure which in turn encompasses the initiation point for the granule [71e73] The presence of ring structure which initiates the formation of the granule is visible via optical and electron microscopy The morphological view of starch represents granules of spherical shape The diameter of the spherical starch granules ranges from to 100 mm, which depends on the botanical source from where the starch is produced Irrespective of the source used for the production of starch, the density is found to be consistent and reported to be 1.5 kg/m3 [72,73] Those components include amylose, an essentially linear or slightly branched (1e4)-a-D-glucan, which exhibits molecular mass as high as 106 g molÀ1, and amylopectin, with the molecular 275 weight between 106 and 107 g molÀ1 [72,73] The amylopectin is a branched polymer with a short length of (1e4)-a-D-glucan units linked through a-(1e6) bonds In most of the starch varieties, the amylose content varies in the range of 72e82%, whereas the amylopectin content varies from 18 to 28% [73,74] Morphologically, the branched amylopectin component consists of crystalline areas and the linear amylose is mostly composed of amorphous or semi-crystalline Amylose is therefore soluble in hot water whereas amylopectin is insoluble In Industries, the steps used for extraction of starch from plant sources include wet grinding, washing, serving and finally drying The white powder which resembles like flour after its extraction from plant sources is termed as “native starch” If the white powder obtained is subjected to undergo chemical treatment to meet significant characteristics, then it is termed as “modified starch” [71,73] Native starch is classified into three different classes namely class A, class B and Class C The XRD analysis suggests a long-range order for the starch granules irrespective of three different classes The chain length of amylopectin was known to influence the crystallinity of starch biopolymer [73] To figure out the difference between class A and class B type of starch, authors proposed a model which represents double-helix packing It is found that the transition occurs from class A to class B and vice-versa via rearrangement phenomenon of double-helix structure It is found that the A-type adopts a closely packed arrangement in which the water molecules exist in between every double-helix structure [73,74] However, in the case of class B, the packing is more open such that the water molecules exist in the central cavity created by six double helices Class c is reported to exhibit the combination of both the class A and class B types, which is confirmed from the diffractogram obtained from XRD analysis [74] The class C starch is found to be present in bean starch It has been reported by authors that the class B and C type starch granules are larger in diameter than that of class A [74] The diameter of class B and C types are found to be in the range of 400e500 nm whereas class A type demonstrated only 25e100 nm Several reports are available on the investigation of structural characteristics of class C starch derived from pea seeds [74] The reports suggest that the class C starch exhibit polymorphism of both the class A and class B It has been found that the class B is present at the central part of the starch granule whereas class A exists in the surrounding or peripheral region It is found that the starch crystals belonging to class A and C show much resistance towards acid hydrolysis as compared to class B [73e75] It has also been reported that amylose and branched amylopectin contribute to the amorphous regime and amylopectin with the short form of branched chains correspond to the crystalline regime for the starch [74,75] However, it is not established whether the presence of side chains of amylopectin with clustered form leads to the partial crystallinity of the starch [75] The ratio of amylose to amylopectin is dependent on the type of plant source used for extraction In fact, the ratio also depends on the steps involved in the extraction process In recent decades, even though considerable efforts are made on the investigation of the molecular structure of starch, significant information at the molecular level remains unclear Starch demonstrates highly complex structure that could be better understood when classified into several levels of the organization as shown in Fig [74e76] Starch granules can be gelatinized in water at lower temperatures and in alkaline solutions The starch in its paste form can be used for glueing or stiffening agent The application of starch in industrial level is limited due to its functional difficulties These natural limitations can be substantially solved using a variety of modifications, including physical, chemical and enzymatic techniques [74e76] The physical methods include heat treatment to remove moisture, an annealing process, pregelatinization, treatment under high pressure, radiation process 276 R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 Fig The starch structure at different levels of organization [76] and sonication The chemical methods include modification using substitution or cross-linking reactions, oxidation process and hydrolysis under acidic conditions [71,73] A good number of published reports have described the development of starch-based polymers for decreasing the environmental effects and to increase the range of applications for biopolymers The two main properties which make starch as unique and one of the promising biopolymers are its (i) natural biodegradability in water and soil into sugar and organic acids and (ii) undeniable merits to the environment In addition to this, unique chemical features of starch which are responsive to a large variety of chemical and enzymatic alterations allow the incorporation of new functionalities in starch [76,77] Since starch is hydrophilic in nature, it is vulnerable to moisture attack which in turn leads to variations in terms of dimensional stability and poor mechanical characteristics [75,76] Moreover, the crystallization, as well as retrogradation of movable starch chains, causes adverse changes in thermo-mechanical properties [75] Such type of limitation makes the starch to be unsatisfactory for packaging application Even though certain problems can be reduced by the addition of plasticizers, it is not possible to meet all the necessities required for packaging application [77] In a recent study, corn-derived starch films incorporated with two different types of essential oils from Zataria multiflora Boiss and Mentha pulegium plasticizers are fabricated Improvement in terms of film characteristics was achieved via emulsification process [77,78] The water vapour barrier property for the films is also found to be improved Even though some modifications in physical and mechanical properties are achieved, starch-based films remain to be unsuitable for general packaging application [77] A comparable barrier and mechanical characteristics in comparison with fossil fuel derived plastics is important if starch-based films should find application in packaging industries [77] Therefore, additional enhancement in mechanical as well as barrier properties is required [77,78] The most widely used way to enhance the mechanical, as well as barrier properties, is to fabricate starch-based nanocomposites The enhancement in the properties can rely on the shape of the particles being incorporated The reinforced filler can exist in different shapes namely (i) particulates, (ii) elongated materials and (iii) layered structures The particulates can be nanoparticles with the well-defined morphology [78] A series of terms are used to define several forms of starch in the literature, which includes starch crystallites, starch nanocrystals, microcrystalline starch and hydrolysed starch [77,78] All of them are crystalline in nature and obtained via hydrolysis However, the crystallinity of different forms of starch differs from each other [78] The onion structure of starch granules is due to the co-existence of the amorphous and crystalline regime [79,80] Through clustering organization procedure, the amylopectin chains become spiral The nanometric subunits stack together to form crystalline regions [80] As the starch granule is inherently made up of nanoscale crystalline blocklets, it results in the formation of starch nanocrystals [80] By the addition of natural starch into acid hydrolysis, low lateral order areas and amorphous region present in starch start to dissolve [79] However, the highly crystalline region with thick lamellar remains undissolved in water Various studies conducted an experiment to check whether starch from different sources could be used to synthesize starch nanocrystals and they also checked whether amylose content and/or botanical origin of the starch influenced their final characteristics It was revealed that diverse sources like maize, wheat and potato with similar amylose content displayed no difference in crystal sizes However, various crystal sizes are more noticeable when sourced from same botanical origin but with different amylose content, signifying the great influence of composition and molecular structure on resulting crystallite dimensions [79] Commonly starch nanocrystals are stated to be derived from starch granule crystallites It is obtained via disrupting the semi-crystalline arrangement of native starch at temperatures below the gelatinization temperature [80,81] Under such conditions, the amorphous regime in starch gets hydrolysed and leads to the separation of nanoscale crystalline residues [80] This is due to the higher resistance to hydrolysis of crystalline lamellae than amorphous lamellae by either chemicals or enzymes [80] It is because of the difference in acid susceptibility and crystalline dextran in starch granules can be formed by the hydrolysis of mild acids in the amorphous region [81] There seems to be same or no variation in hydrolysis temperature used, which are usually between 35 and 45 C The important cause for maintaining this lowtemperature range might be to avoid gelatinization of starch and any type of destruction crystalline structure of starch Starch nanocrystals of various size and shape can be gained depending on R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 the origin of starch and isolation procedure Different sources of starch namely barley, tapioca, potato, mung bean and chicken pea are used to synthesize starch nanocrystals via acid hydrolysis [80] Even though starch granules from diverse sources differed in size and shape, no understandable variation in terms of shape between several types of starch nanocrystals produced Researchers have also found that the structure and morphology of starch nanocrystals mainly relied on several factors like botanical origin, crystallinity, the ratio of amylose to amylopectin and morphology of starch granules It was found that the acid hydrolysis process of starch granules showed influence on the morphological features of starch nanocrystals [82,83] It was reported that platelet-like morphology of starch nanocrystals was obtained which is confirmed by TEM examinations as reported by various researchers [81e85] The plate-like starch nanocrystals exhibited a thickness of 5e7 nm and diameters varying from 15 to 40 nm However, in the case of other sources of starch, nanocrystals of different sizes and shapes were gained [81] To cite an example, Chen et al., reported that round and grape-like nanocrystals were obtained from potato starch granules with size varying from 40 to 100 nm [84,85] Researchers carried out an experiment to decrease the size of starch granules from the micro level to nanoscale by using high-pressure homogenization technique [85] As a result, it was experienced that the particle size of starch can be reduced significantly from to mm to as low as 10e20 nm [85,86] This was possible only after subjecting the starch granules to 20 passes of high-pressure homogenization [82] Starch nanocrystals can be compounded as reinforcements in diverse types polymer matrices for preparing nanocomposite because of its unique properties like nanoscale platelet-like morphology, greater crystallinity, reduced permeability level and rigidity [84,85] Researchers reported a method to obtain natural rubber-based nanocomposites reinforced with starch nanocrystals derived from maize Some reports were available on natural rubber reinforced with starch nanocrystals [84] Enhancing effects in terms of properties for the composites have been noticed if the content of starch nanocrystals was maintained to be below 20% and vice-versa [84,85] Sorbitol-plasticized pullulan films containing waxy maize starch nanocrystals exhibit improved mechanical and water barrier properties [78,80] The enhancement is due to the strong interaction that developed among starch nanocrystals and the polymer matrix Exciting results were also reported for starch nanocrystal-reinforced/plasticized starch films using glycerol and sorbitol plasticizers Other researchers found that if the content of starch nanocrystals was maintained to be below wt% in soy protein matrix, Young's modulus for the composite films increased However, the presence of starch nanocrystals in soy protein matrix decreased the elongation-at-break (%) values [78e80] Various groups of researchers described the extraction and characterization of starch nanocrystals from potato source The same group fabricated natural rubber nanocomposites reinforced with starch nanocrystals using sulfuric acid at a temperature condition of 40 C The structure and performance of the nanocomposites were examined by SEM and Atomic Force Microscopy (AFM) The analysis confirmed the uniformly dispersed starch nanocrystals in the rubber latex a moderately uniform dispersion of starch nanocrystals when it incorporated in the rubber latex Acid hydrolysis is the most commonly used approach to yield starch nanocrystals The treatment with acid dissolves the area of low lateral order for revealing the concentric lamellar portion present in starch By using acid hydrolysis method, crystalline residues insoluble in water gets transformed into stable suspensions via the strong action of shearing For modification of starch and its characteristics, acid hydrolysis process has been practised for several years [79,80] There are different approaches that can be used to convert starch 277 particles into nanocrystals which include the following: extraction by acid hydrolysis, enzymatic hydrolysis or co-crystallization during the regeneration process [82,83] The irreplaceable properties of starch nanocrystals like biodegradability, outstanding mechanical characteristics, lower density level and reduced permeability allow it to be a perfect candidate to synthesize starch nanocrystal incorporated natural polymer composites Since starch nanocrystals are polar in nature and exhibit hydrophilicity, their dispersion level in non-polar solvents is limited This results in the lack of compatibility among starch nanocrystals and polymers of hydrophobic nature Auspiciously, starch nanocrystals exhibit reactive surfaces appropriate for chemical derivatization and grafting reactions such that their surface hydrophobicity can be manipulated and enable dispersion in non-polar solvents [81] Some researchers have found that the reduction of surface energy associated with starch nanocrystals to enable its dispersion in polymers is challenging The surface energy of starch nanocrystals increase their dispersion level in a polymer matrix [81,82] It is now accepted that the nature of the hydroxyl groups in starch nanocrystals offer the chance of alteration through chemical reaction approach [81] The shape of nanoparticles namely rod shape in the case of cellulose, as well as chitin and plate-like morphology for starch nanocrystals, mainly depends on the source of polysaccharides [83,84] Integrating the nanofillers obtained from these polysaccharides in crystalline forms with uniform structures can thus be a perfect choice for making bio-nanocomposites with high rigidity The shelf life of unpreserved packaged products can be pointedly extended by increasing the barrier properties of packaging materials It is known that polymeric materials with an outstanding barrier to water vapour usually lacks oxygen permeability and vice versa [83,84] Therefore, protection of packaged products from deterioration due to oxidation, high temperature, moisture and microorganisms can effectively be attained through the use of multilayer structures consisting of various polymers, each contributing to certain specific functions [83] The permeation rate of most of the vapour and gas through the polymeric materials depend on its chemical nature and physicochemical properties of permeating molecules [85] Improving the resistance to water vapour permeation and oxygen diffusion is an essential requirement in composites/nanocomposites for the packaging of several foods and drug products [84,85] The usage of starch nanocrystals with high crystallinity and their morphology along with intrinsic tortuosity that they impart can considerably limit the migration of water vapour and oxygen [86] Undeniably, platelet-shaped starch nanocrystals can potentially change the diffusion path of penetrative molecules more than rod-like cellulose nanocrystals and thus increase the barrier properties of polymer composites [85,86] Swelling is one of the useful techniques to regulate the presence of specific interaction between the fillers and the polymeric matrix by forming additional crosslinking action [84,85] From a technological perspective, the interaction of polymeric materials with several solvents is very important due to the changes in the material dimensions and physical characteristics imparted by the penetrating solvent molecules into the polymer [84,85] It has been well established that crosslinking alteration prevents starch from swelling The rate of inhibition towards swelling depends on the degree of cross-linking Several researchers have examined the effects of variables like nature of polymeric matrix (polar or nonpolar), the content of starch nanocrystal, chemical alteration of the nanocrystals, diverse swelling liquids (water, toluene) and reaction time on the swelling behaviour of the various nanocomposite [82e85] The results indicated that the rate of water uptake for most of the compositions containing starch nanocrystals improved rapidly at the earlier period of immersion After reaching a maximum point, the water uptake was found to be reduced until 278 R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 attaining the equilibrium Consequently, the absorption kinetics in the initial stages is faster, which is then followed by an absorption plateau [82,83] The detected reduction in the water uptake through this process can be ascribed to leaching or partial release of starch nanocrystals in water, although starch exhibits insolubility in water starch is insoluble at low-temperature conditions [82] The discharge of starch nanocrystals into aqueous phase while swelling is one of the reasons for the increase in the water uptake rate in the early phases It has been recommended that the interface between starch nanocrystals and a polymeric matrix namely natural rubber tends to decline by the swelling of the starch domains with respect to exposure time and hence the swelling rate seems to be improved due to “overshooting effect” The growth of biodegradable packaging materials with better thermal properties is the main reason to improve the processability of polymeric composites The thermal behaviour including determination of glass transition temperature (Tg), is normally determined by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) The DMA method is more broadly used for studying polymer chain movement via a-relaxation at the molecular level and Tg is usually determined at the point of modulation of the curve of loss tangent (tan d) as a function of temperature The thermal stability these polymeric particles can also be checked using thermogravimetric analysis (TGA) [84] It has been confirmed that the nanocomposites reinforced with nanocrystals generally demonstrate improved thermal characteristics when nanofillers are well dispersed into the matrix [86,87] Excitingly, the thermal properties of polysaccharide nanocrystals rely on the origin, synthesis process and type of surface modification [86] For example, sulfuric acid hydrolysis leads to the decoration of nanocrystal's surface with sulphate ester groups of acidic nature This, in turn, results in the reduction of degradation temperature significantly In the recent years, nanocrystals obtained from starch have shown better thermal properties and exceptional temperature resistance [86,87] Established data pertaining to the crystallinity of starch granules are obviously vital for the improved large-scale manufacture of starch nanocrystals [86,87] The main property of crystalline regime in starch granules is the polymorphism of a-glucans Since native starch granules have crystalline areas, their presence can be noticed using XRD The appearance of X-ray diffractograms is dependent on the extent of water content present in starch granules during analysis If more is the degree of starch hydration, thinner will be the diffraction pattern [85e87] Therefore, hydration remains the major and essential variables for the organization of crystalline areas in starch The change from crystalline to amorphous occurs primarily between 60 and 70 C in water by a method known as gelatinization Commonly, starch comprises of 15e45% crystalline content and XRD patterns have confirmed different types of starch based on crystalline arrangement, named as A, B and C [86] It can be considered as an appropriate polymer for making biodegradable nanoparticles due to its richness in nature and low cost Some methods for preparing starch nanocrystals have been advanced and improved over recent years [86] About improvement in methods, yield and resulting properties were found to be fruitful Novel and improved solutions have been discussed that aim to improve the preparation of starch nanocrystals [86] However, despite the recent growth in manufacturing nanocrystal, there is still a good number of serious issues that need to be considered In addition to the synthesis of starch nanocrystals, many procedures have also been established to realize and characterize the nature of several polymer matrices in which the particles have been filled [86,87] Several research activities in starch-based nanocrystals have been conducted and are going on, although the expected commercial success is yet to be documented [72,86] Researchers studied the morphology and grain size of native starch before and after hydrolysis The respective SEM images are presented in Fig The nanocrystals obtained from corn-starch are polyhedral granules whereas those from other starches are elliptical, spherical and/or irregular in shape [85e87] The largest nanocrystal with an average granular size of 41.3 mm was gathered from potato starch, accompanied by legume starch Interestingly, all the starch nanocrystals produced via acid hydrolysis exhibited a spherical shape irrespective of their origin [85e87] Some other nanomaterials compatible to biosystem 5.1 Titanium dioxide The arrival of green, facile and environmentally friendly modes has made the development of nanomaterials simple [88] Significant features required for such green methods include lowtemperature, fast reaction rate and reduced toxic agents [88,89] The applications of photoactive materials are diverse which include photocatalysts, water splitting reaction, chemical and biosensors, electrochromic displays, photoelectric conversion, and solar cells [88,89] Titanium dioxide (TiO2) is one of the most extensively employed photo-active nanomaterials [88] There are three distinct forms of TiO2 exist each of which can either be crystalline or amorphous They comprise anatase, rutile, brookite, or a combination of the three It is remarkable to indicate that pure crystalline anatase is the most photo-active phase of TiO2 The high stability of photoelectric chemistry and high photoelectric conversion efficiency provides TiO2 with peculiar properties [88] The photocatalytic properties of TiO2 nanoparticles grant the potential to immediately deteriorate pollutants in wastewater and split water into hydrogen and oxygen Organic pollutants can be degraded in the presence of TiO2 along with an energetic light source and an oxidizing agent [87,88] Many synthetic approaches are available to synthesize TiO2 photo-active nanoparticles including solegel processing, reverse microemulsion, dialysis hydrolysis, microwave-assisted emulsion polymerization, alcohol-thermal method, hydrothermal, combustion, and gas-phase methods [89,90] Amongst all the methods, the hydrothermal approach is regarded as an extremely effective procedure to prepare TiO2 In the hydrothermal method, the reaction can be performed at lower temperature condition (100 C) as compared to other methods The particle size, morphology and composition are tuneable by manipulating the reaction parameters such as temperature and heating time Remarkably small TiO2 nanoparticles ranging from nm to 10 nm can be prepared which enhances the photo-activity owing to the enormous surface area [88] Some of the other green and simplified methods are also often used to prepare the photo-active TiO2 nanomaterials In microwave-assisted hydrothermal process (MW-HT), TiO2 is prepared from TiCl4 whereas the hydrothermal process utilizes an oxidant and a reductant in aqueous solution Previous author's studies made a comparative investigation on the synthesis of TiO2 using conventional hydrothermal process and microwave-assisted hydrothermal technique [90] In the microwave-assisted hydrothermal technique, TiO2 nanoparticles were synthesized from metal alkoxides and hydrogen peroxide with a molar ratio of 0.05:0.12 (Ti:H2O2) The polymer-gel procedure is a straightforward and cost-effective approach for developing pure metal oxides [91,92] The preparation of nanosize anatase through the polymergel technique is far less complex than the hydrothermal technique [89,90] In general, the polymer-gel technique occurs by mixing a polymer in a metal added solution to achieve metal-polymer mixtures [94,95] The resulting nanoparticle size and purity are comparable to the products achieved by applying the hydrothermal R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 279 Fig SEM images of starches in different magnifications before (left) and after (right) hydrolysis from botanical sources [86] technique [91] There are various disadvantages with the hydrothermal approach when compared to polymer-gel technique For instance, the hydrothermal approach presents trouble adjusting the reaction time and involves autoclave treatment [93,94] The finished outputs must then be purified, unlike the polymer-gel technique which yields refined products [94] High-resolution transmission electron microscopy (HR-TEM) is used as a characterization technique and is adapted to produce leading information on the atomic scale [90,94,95] Fig shows HR-TEM image forTiO2 nanomaterial calcined at 400 C, which shows that the particle size is of 12 nm [95,96] The TiO2 nano-materials are a great deal of interest owing to their remarkable properties likeable, non-toxic and low cost However, the broadband gap of TiO2 (~3.2 eV) limits to absorbing only UV photons [95e97] In extension, TiO2 exhibits fast recombination of photo-induced electrons and holes leading to the reduction in photocatalytic activity [95e97] In order to overcome these limitations, there have been numerous synthetic methods established such as non-metal element doping, coupling with semiconductors, noble metal loading, and specifically the recombination of TiO2 with newly emerging carbon-based nanomaterials [91,95] 5.2 Zinc oxide (ZnO) and other nanomaterials compatible to biosystems Owing to the unique benign environmental impacts and extensive applications in diverse fields, zinc oxide (ZnO) is another commonly used semiconductor component ZnO presents a broadband gap which corresponds to 3.37 eV [98,99] In addition to this, ZnO shows high binding energy around 60 meV and therefore it can function as an efficient nanomaterial for many applications [37] It is due to the attractive physical as well as chemical characteristics associated with ZnO nanoparticles, they are being used in several applications like biomedicine, UV absorption, photocatalysis, solar cells and photonic materials [98] By taking the advantage of the photocatalytic activity of ZnO, the nanoparticles are applied for degradation of phenol and chlorinated phenols like 2,4,6-trichlorophenol [99] It is further adapted to carry out the degradation of methylene blue, direct dyes, acid red, and ethyl violet, which are common organic pollutants in wastewater [93,99] There has been a considerable deal of synthetic methods studied for the synthesis of ZnO nanoparticles including solvothermal method, solegel, vapour-liquid-solid technique, pulsed-laser process, thermal evaporation technique, template-assisted process, molecular beam epitaxy technique, chemical vapour and deposition, electrochemical process, and reverse micellar [98,99] However, these synthetic processes have certain limitations such as high temperature (850e925 C), high pressure (100 MPa), long reaction time (30 days), and utilization of toxic reagents (O3) Therefore, improvement of sustainable and efficient synthesis process is of great interest for the synthesis of nanoparticles Currently, certain green preparation techniques for synthesis of inorganic TiO2, and ZnO photo-active nanomaterials are also generated [94,98] Coupling of nanomaterials Each of these approaches delineates and elucidates the shortcomings of the TiO2 nanomaterials by coupling TiO2 with metal oxides or sulphides namely ZnO/TiO2, CuO/TiO2, SnO2/TiO2, CdS/ 280 R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 Fig High-resolution transmission electron microscopy (HR-TEM) characterization for TiO2 nanoparticles calcined at 400 C [92] TiO2, and ZnS/TiO2, which in turn will fulfil the electronehole pair separation under both UV and visible light illumination [95,96] A larger contact interface between titanium nanotubes (TNT) and graphene is supposed to build up the photo-induced charge separation which will enhance the photocatalytic activity [96] Analysts have been practising hydrogenation, metal and non-metal doping, and sensitizing with a small band gap semiconductor substance to diminish bandgaps and promote the performance via usage of sunlight [96] All these approaches have demonstrated advancement in the photocatalytic activities [96] Three types of hybrid synthetic photo-active nanomaterials have been newly established using green chemistry They can be produced appropriately by using metal oxides or metal sulphides (ZnO, CdS) to gain photoactive ZnO-TNT and CdS-TiO2 composites as reported by the par et al [97,100] Graphene oxide (GO) and graphene (GR) are carbonaceous substances which are completely suited to respond as catalyst supports [98] Graphene oxide can extend the dispersion of TiO2 catalyst and cut down the tendency of electronehole pair recombination [98] Both graphene oxide and graphene can be hybridized with TiO2 to form a graphene-TiO2 (TiO2/GR) or graphene oxide-TiO2 (TiO2/GO) nanocomposite, which can be employed to split water and degrade wastewater pollutants [98] TiO2 nanotubes with enhanced catalytic activity can be produced conveniently under definite conditions and in this area several researches are going on for the more efficacy [98,100,101] Titanium nanotube (TNT) incorporates the traditional TiO2 nanoparticles with its retained exceptional properties like high conductivity, large surface area, good mechanical as well as electrical properties, greater aspect ratio and a large contact interface [98,101] To improve TNT activity, it is suggested to increase the adsorption of reactant molecules and light owing to the enormous quantity of active sites [102,103] In extension, the huge aspect ratio of TNT nanostructure and a broader contact interface between TNT and GR are supposed to improve the photo-induced charge separation [103] All the preceding properties lead to the enhancement of the photocatalytic activity for TiO2 nanomaterials [98] Nanoencapsulation and their green properties A collection of nanoparticle-based systems produced from particular ingredients, sufficient for encapsulation of micronutrients, are highlighted in Fig [100] The exploration of technologies for nanoencapsulation is being carried out to provide safety for bioactive constituents namely vitamins, antioxidants, lipids and proteins [100] The nanoencapsulation is mainly used for the production of food with functional properties [100,101] Hence, this technology is expected to demonstrate promising advancements in terms of nutrition as well as public health [100,101] Several types of nanocarriers for incorporation of nutraceuticals for its subsequent application in food systems have been developed [99,101] Recently, bio-based phase change material (bio-PCM) has been effectively encapsulated in ultrafine fibres by means of coaxial electrospinning approach [100] Natural soy wax has been employed in form of the bio-PCM for thermal storage as well as Polyurethane (PU) is applied in the role of the covering or shell component for encapsulation [100e101] The bio-PCM fibres have been examined by various microscopy and spectroscopy techniques [101] The information reveals that coaxial electrospinning led to a consistent fibre morphology with a coreeshell configuration along with a homogeneous wax distribution across the core of the fibres [101] Thermal study data confirm that the enthalpy improves with wax quantity [101] The fibrous structures displayed well balanced thermal storage capacity as well as discharging characteristics for thermo-regulating functionality [101] The thermal characteristics are uncharged after hundreds of heating-cooling evaluation cycles, showing that the composite fibres possess excellent thermal durability as well as stability [100,101] In a further study, microencapsulation of vegetable-derived palmitic acid (PA) in bio-based polylactic acid (PLA) covering or shell by means of solvent evaporation and oil-in-water emulsification has been examined [102] Fourier transform infrared spectroscopy as well as scanning electron microscopy has been performed to verify the effective R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 encapsulation of palmitic acid in PLA shells [102] Differential scanning calorimetry has been accomplished to examine the thermal characteristics, thermal stability, and core content material of the manufactured phase change materials microcapsules (microphase change materials) [102] By means of many parametric tests, the impact of phase change materials as well as solvent quantity, oil phase-to-aqueous phase proportion, in addition to surfactant description together with the content on the morphology, particle dimensions, and consequently thermal characteristics of the phase change materials microcapsules have been studied [102,103] Precise Experimental results revealed that PVA is an excellent emulsifier [103] Furthermore, there additionally persisted an appropriate PVA content to minimize the typical dimensions of microphase change materials [103] If the PVA content crossed beyond this quantity, the emulsifier molecules are likely to produce micelles among by themselves [104,105] This resulted in the adhesion of very small microspheres on the top surface of microphase change materials along with larger sized micro-phase change materials [102,104] SEM microstructures demonstrate the micro phase change materials comprise of 0.4, 0.6, as well as 0.8 g of palmitic acid although maintaining a specified PLA amount (i.e 1.2 g) It is found that the micro-phase change materials shapes, and surface morphologies are practically unaffected if the PA content greater than before [102] Moreover, as the micro-phase change materials exhibited their sphericity, certain irregular surface morphologies with the existence of small microspheres are noticed [100e105] The utilization of electrohydrodynamic preparation method (EHDP) to encapsulate natural aloe Vera (AV, Aloe barbadensis Miller) making use of together the artificial polymers, i.e., poly vinylpyrrolidone (PVP) as well as poly(vinyl alcohol) (PVOH), and also naturally produced polymers, i.e., barley starch (BS), whey proteins concentrate (WPC), and also maltodextrin [106,107] The AV leaf juice was employed in form of water-based solvent for EHDP, therefore the prepared biopolymer solution characteristics were examined to figure out their influence on the procedure [106] The morphological evaluation demonstrated in the previous sections are depends on effective preparation situation, nature artificial polymers (primarily created fibre-like arrangements) [106] Typical dimensions ranged from one hundred nm to above three 281 mm Due to their distinct as well as optimum morphology and, therefore, greater AV quantity, PVP, in the shape of nanofibers, as well as WPC, of nanocapsules, were additionally preferred to examine the AV durability against ultraviolet (UV) light condition Fourier transform infrared (FTIR) spectroscopy revealed the effective encapsulation of AV in the biopolymer matrices, showing both together encapsulates an excellent chemical interaction with the bioactive ingredient [108,109] Ultraviolet-visible (UVevis) spectroscopy demonstrated that, although PVP nanofibers provided an unsatisfactory impact on the AV degradation throughout UV light exposure (~10% of stability after h), WPC nanobeads provided outstanding safeguard (stability of >95% after h) [102,108] This has been attributed to favourable interactions between WPC along with the hydrophilic components of AV in addition to the intrinsic UV-blocking as well as oxygen barrier features offered by the protein [102,108] Nature inspired hydrogels Hydrogels belong to a class of polymeric materials with hydrophilic features, which are of great importance in many different areas [103,104] Since five decades, hydrogels are being used because of their attractive physic-chemical as well as biological characteristics [103] Such properties are mainly due to the arrangement of the three-dimensional network, which in turn forms the hydrogel structure [103] The most relevant characteristics of hydrogels are undoubtedly the ability to absorb and retain a considerable amount of aqueous liquid [104] This results from the hydrophilic cross-linked network, which can retain threedimensional structure even in the swollen state without disintegration [104] This feature is due to the cross-linked points that hold the polymeric chains together, that form the network In most of the cases, chemical or physical pathways drive the cross-linking process during gel formation [103] The product that results due to chemical cross-linking process is called as chemical hydrogels These chemical hydrogels conduct the formation of irreversible covalent bonds among the polymeric chains of the hydrogel [103,104] On the other hand, in physically cross-linked hydrogels called as physical hydrogels, the polymeric chains are held by physical interaction which may be electrostatic, hydrogen bonding, Fig Colloid based delivery systems for encapsulation, protection and delivery of functional food constituents and deliver functional food ingredients at a targeted location with respect to dependency on hydrophilicity or hydrophobicity [100] 282 R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 van der Waals force of attraction and physical entanglement [103,104] Owing to the reversible character, physical hydrogels can be disintegrated due to impairment of physical interactions responsible for their crosslinking [103,104] Changes in the external medium such as pH, ionic strength and electric field can disintegrate the physical hydrogels [104] Despite the differences between the pathways that form chemical and physical hydrogels, it is possible to obtain hydrogels in several formats such as spheres, cylinders, films and membranes [103,104] In addition to this, hydrogels can also be produced in macro, micro and nano-scale dimensions In the last two decades, the applications of hydrogels are focussed not only on liquid absorption/retention The potential of this promising class of materials is now applied in very varied industrial, technological and biotechnological sectors This scenario is due to the formation of a new class of hydrogels called as smart hydrogels, which can provide different responses (e.g volume, porosity and mechanical changes) according to external and internal stimuli [103,104] In addition to such an evolution, the use of different classes of polymers considerably enhanced their properties and applicability [104] Biopolymers (such as polysaccharides and proteins) possess unique and desirable physicochemical and biological properties (i.e Biocompatibility, biodegradability, nontoxicity and some biological activities) that stimulate their use in preparation of different materials [103,104] For example, hydrogels prepared from biopolymers (mainly polysaccharides) have found great applicability as biomaterials Furthermore, the interesting properties of polysaccharides comes from their structure, which, in general, has a wide variety of functional moieties (eCOOH, eOH, eNH2, eNHOCCH3 and eOSO3H) that can be crosslinked by reaction with a coupling agent or that allow the insertion of crosslinkable groups or polymeric chains in the polysaccharide backbone [105,106] The preparation of polysaccharide-based hydrogels could also be carried out by polyelectrolyte complexation among macromolecules with functional groups having opposite electric charges [106] As discussed earlier, starch shows all the desirable features required for preparing chemical and physical hydrogels [103,105] Number of reports and review articles have described the preparation of starch-based hydrogels using several methodologies [105,106] In general, the main strategy adopted to prepare starchbased chemical hydrogels is based on the reaction of the hydroxyl moieties in the starch backbone with bi- or multifunctional compounds that work as coupling agents To date, the compounds most commonly used are glutaraldehyde and epichlorohydrin [104] Despite the production of interesting hydrogels by this strategy, the use of coupling agents is not encouraged when the aim is to prepare hydrogels for biomedical uses [106,107] This is because; the coupling agents might show some level of toxicity, which decreases the range of applicability of the chemical hydrogels obtained [107] An efficient strategy usually adopted to avoid the undesirable issue of the toxicity of the crosslinker is to perform radical reactions of unsaturated monomers with starch or starch-based macromonomers containing carbonecarbon double bonds In most cases, superabsorbent hydrogels result from this method [103,104] The copolymerization and simultaneous crosslinking of starch with vinyl-functionalized monomers have been reported [104e106] Generally, starch is chemically modified to add reactive vinyl groups to its backbone, and such groups allow crosslinking among the starch chains or/and crosslinking by grafting with other polymers or monomers Most of the hydrogels prepared using this methodology show semi-interpenetrating network characteristics [104,105] IUPAC defines a semi-IPN as a polymeric material comprising at least one network and at least one linear or branched polymer, which in turn is characterized by the penetration of both on a molecular scale Semi-interpenetrating network is distinct as compared to an interpenetrating network This is since the linear or branched polymers, which form semi-interpenetrating network could be subjected to separation from its constituent polymer network The separation process could be achieved in the absence of breakage of chemical bonds [105] In general terms, the basic reaction system for the radical polymerization of starch is composed of starch (raw or modified), a catalyst (responsible for the radical formation), the monomers with reactive functional groups and a crosslinker molecule [such as N,N-methylenebisacrylamide (MBA)] Using raw or chemically modified starch, it is possible to apply different techniques to form hydrogel networks from the reaction system The technique utilized can be chosen according to the hydrogel destination [71,103,104] It is very important to take the technique into account as it affects considerably the final properties of the hydrogel [71,103,104] A very positive aspect of this methodology is the possibility of preparing starch-based hydrogels in the presence of organic polymers and inorganic compounds [105] Numerous papers have described the incorporation of inorganic clays, magnetic and metallic nanoparticles, hydroxyapatite cellulose whiskers and waste residues in the starch-based hydrogel formulation, resulting in composite materials In most of the cases, these hydrogel composites show superior features compared with the conventional starch-based hydrogels, including the applicability and the capacity to respond to external stimuli [105] Fig 10 shows an illustrative scheme to produce a starch-based hydrogel nanocomposite developed In this case, cellulose nano-whiskers are inserted during the hydrogel formulation The main advantages of hydrogels include (i) liquid uptake capacity (swelling), (ii) network like morphology, (iii) molecular structure and (iv) mechanical properties There are a huge number of qualitative and quantitative techniques, which can be applied for characterization of these properties [107] As already mentioned, most of the starch-based hydrogel properties are directly connected with two main factors: (i) the polymers combined with starch and (ii) the method applied to form the hydrogels [103,104] These factors are known to affect the number of crosslinking points, porosity, and distribution of hydrophilic groups inside or at the surface of the hydrogel matrix Generally, these three aspects determine all the properties of hydrogel and it is difficult to establish how they are interconnected [103,104] The liquid uptake capacity, for example, depends on the hydrophilicity of the starchbased hydrogel matrix From this characteristic, another important aspect arises the capacity of liquid retention by the hydrogel matrix Several parameters control the change in either swelling or deswelling like temperature, pH, salinity as well as the ionic strength of the medium The starch-based hydrogels prepared from hydrophilic polymers/monomers, in a general way, possess the capacity for absorption and fluid retention, which classify these hydrogels as superabsorbent [104] Raw starch is not so hydrophilic owing to its granular structure and for this reason, the association of starch with more hydrophilic polymers is required in order to prepare materials with a high liquid uptake capacity [106] In the field of polymer science, hydrogels have evolved into materials with outstanding features and many potential applications, from soil conditioners and hygienic products to tissue engineering, drug delivery systems, and imprinted polymers [103e107] Therefore, it is not surprising that reports on hydrogels and hydrogel composites are still hot topics in the field of material science [104e106] In terms of hydrogel composites, regarded as those containing micro- and nano-sized particles in their formulation, the addition of the reinforcement phase is generally performed to improve thermal, mechanical and optical properties, water uptake capacity, release rate of solutes, response to external stimuli and degradation rate among other properties, tailoring for specific applications [104,105] Many different reinforcing phases have been studied, including mineral R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 283 Fig 10 Illustrative scheme for the preparation of a starch-g-poly(sodium acrylate)/cellulose nanowhiskers (CNWs) hydrogel composite matrix [106] clays, hydroxyapatite, metal and magnetic nanoparticles, carbon nanotubes, polysaccharide nanocrystals and quantum dots [107] Encouraged by the exceptional properties presented by the first micro-powder clay-reinforced starch hydrogel and the first clayreinforced nanocomposite hydrogel, the majority of starch hydrogel composites reported recently are those in which the reinforcing phase is based on mineral clays [103e105] This is supported by their natural abundance, low cost, and nanometric dimensions, with a high aspect ratio of exfoliated sheets providing good interfacial interactions between layered clays and polymers Modification of clays can be performed by replacing the metal cations existing in the pristine clay by organic cations, generating modified surfaces that can play a role in the interactions between the polymer and the clay This in turn, ultimately shows the effect on the composite properties [103e105] In spite, several varieties of nanogels have been reported; this field is still in the early stages of development The hydrogel-based nanomaterials prepared from polysaccharides/starch etc are especially used in medical applications [108] In this respect, nanogels based on biopolymercontaining nano-scale moieties remain hot topic for the soft materials research [105] The versatility of the green nanocomposites Unlike other nanomaterials, it is possible to easily synthesize green nanomaterials or bionanomaterials from plant and animal resources [109,110] The properties of nano-sized materials show similarity with perfect crystals The simple methods used for the preparation of nano crystallites include mechanical stirring and acid hydrolysis process [109] The acid hydrolysis will help in the removal/dissolution of lower order regions such that high crystalline regime insoluble in water could be converted into stable suspension via mechanical shearing [109] In the recent decades, several research activities are being undertaken to prepare biocomposites by blending/reinforcing bio-nanomaterials in a wide variety of polymer matrices [109,110] In the current section, new progression the fabrication and characterization of various types of polymer nanocomposites are discussed The applications of nanocomposites based on entirely renewable polymers/green polymers are versatile [109] The biopolymer nanocomposites emerged as a modern area of research in nanotechnology, which has drawn attention in the last decade There are significant challenges which need to be addressed in this research area which includes (i) effective separation route for extraction of nano-reinforcements from renewable resources, (ii) achieving compatibility between nano-reinforcement and the polymer matrix and (iii) finding suitable techniques for processing of bio-nanocomposites In addition to this, the energy consumption and cost are the two challenging factors involved in commercialization of bio-nanocomposite based products It is well known that the widely used method to improve the properties of biopolymers is the addition of nano-reinforcement in the polymer matrix [110] Though this approach has been practised for decades, it is still in the development phase Nanoparticles present the advantage of the relatively high surface to volume ratio compared to their macroscopic counterparts [84] There are a wide variety of commercially available nanofillers which include nanoclay, inorganic fillers, activated carbon, graphene and carbon nanotubes The drawback associated with these nanofillers is that they are not renewable whereas bio-nanofillers are renewable and biodegradable [110] It is expected that huge benefits and value addition to various industries could be brought up by the application of nanotechnology [110] Nanotechnology finds application in food sectors mainly in the areas of production, packaging and storage of food products Table summarizes the applications of nanotechnology in several fields Chitin whiskers, which exhibit high aspect ratio is used as reinforcing filler for preparation of polycaprolactone (PCL) based nanocomposite [111] The chitin whiskers prepared from Riftia tubes are reported to consist parallel rods [111] These parallel rods exhibited pipe-like structure with an aspect ratio of 1:20 [111] The fabrication techniques like solution casting, hot pressing and freeze drying are used to prepare the films, where matrix used is amorphous poly-(styrene-co-butyl acrylate) [111,112] The thermal properties of poly(vinyl alcohol) (PVA) films reinforced with chitin whiskers are evaluated The solution casting method was used to prepare the PVA composite films [112] The incorporation of chitin in the chitosan matrix has not shown any influence on the thermal stability and crystallization properties of chitosan composites [112] The tensile strength of chitosan composite films showed increasing trend with respect to the number of chitin whiskers incorporated The maximum tensile strength is obtained for the chitin whisker concentration of 2.96 wt % With a further rise in the concentration of chitin whisker, the elongationat-break (%) decreased [111,112] The X-ray diffractograms obtained for PVA/chitin whiskers composites showed amorphous peaks indicating the presence of chitin in the PVA matrix To know whether chitin affected the crystallinity of PVA matrix, FTIR spectroscopy measurements are made [113] The presence of peak position at 1144 cmÀ1 confirmed the presence of chitin in the PVA matrix However, the intensity of the corresponding peak did not increase with the rise in chitin content, which indicates that the crystallinity of PVA composites is not influenced by chitin 284 R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 Table Applications of the nanotechnology in different fields [110] Nanotechnology Agricultural production Nanosensors Hand-held systems Organic or inorganic additives based on nanoparticles Nano-pesticides Nanoencapsulates with triggered release properties Nano-sized agrochemicals Food processing Nano-structured or nano-textured food products Organic or inorganic based nano additives Nano-sized encapsulates Applications Functions Nano-based sprays They are useful in detecting contaminants, microbes and mycotoxins They are mainly useful in removing toxins from feed materials Binding and colouring microorganisms Nanoemulsions and nanoencapsulates Sustained release from nanoencapsulate Only meagre amount of additive is required to perform a function in specific Improved efficiency and water soluble Fertilizers, biopesticides and veterinary medicine Efficient in performance, possible to control the dose and avoid usage of solvents in the agricultural field Nanoemulsions Useful in forming stable emulsions, helps in avoiding utilization of excessive fat and other emulsifiers, ensure tasty food product Food and medicated food applications Improves stable dispersion and the meagre amount would be sufficient for improving the taste Provides protective barriers, flavour and improved taste Helps in achieving release in a controlled the manner and stable dispersion mainly for food ingredients which are not water soluble Enhanced absorption as well as bioavailability Used as nanocarrier systems like liposomes or biopolymer-based nanoencapsulated substances Nutraceuticals Nano ingredients Nano-carrier based systems for delivering nutrients Nano filters Nanofiltration using porous silica, regenerated cellulose membranes Food contact materials for handling and storage of the food product Nanomaterial based composites Incorporation of nanomaterials in a polymer to form a composite Nanocoatings Surface coating of food packaging materials “Active” packaging Materials The nanoparticles present in food packaging materials release active constituents in a controlled manner to prevent food from spoilage “Intelligent” food packaging Nanosensors are incorporated in the packaging material for materials monitoring food spoilage Surface active biocides Silver (Ag), Zinc oxide (ZnO) and Magnesium oxide (MgO) based nanoparticles are incorporated in packaging materials such that they provide surface biocide activity [112,113] The characteristics of natural rubber composites filled with chitin are evaluated [112] The presence of the rigid network of chitin whiskers in the natural rubber matrix is confirmed It is discussed that the rigid network of chitin results from the percolation mechanism through which hydrogen bonding interaction is formed among the chitin particles [113] The existence of the rigid 3D network of chitin in the natural rubber matrix is confirmed via several factors like the content of bound rubber, diffusion coefficient and weight loss Further, this is also evidenced by the mechanical behaviour of natural rubber/chitin composites [114] The structural and morphological characteristics of starch nanocrystal reinforced natural rubber composites are examined [113,114] The freeze-dried starch nanocrystals showed typical diffraction pattern The increase in crystallinity of the natural rubber composites is evidenced with respect to rising in the content of starch nanocrystals [113] The oxygen as well as water vapour permeation rate for natural rubber/starch nanocrystals is also investigated The composite films showed barrier effect to both oxygen and water vapour The toluene absorption of the natural rubber/starch nanocrystal composites decreased and rather water absorption phenomenon is found to increase The percolation threshold for the formation of hydrogen bonding network among starch nanocrystals present in natural rubber matrix is found to be 10 wt % [114,115] Several reports are documented on investigating the properties of PLA nanocomposites However, evaluation of antimicrobial properties of PLA nanocomposite films is limited in the literature [113e115] The influence of nanoclay on the antimicrobial properties of PLA films fabricated by solution casting method is investigated [114] Helps in water filtration and removing undesirable properties like bitterness in food Improvement in strength and durability of materials Improves barrier and biodegradability characteristics Oxygen scavenging and prevention of growth of pathogens Controlled monitor in deterioration of stored food can be possible For kenaf fibre reinforced PLA composite, tensile as well as flexural strength are found to increase about rise in the content of kenaf fibres till 50 wt % Specially designed garbage-processing equipment is used to assess the biodegradability aspects of kenaf fibre reinforced PLA composites [113e115] The PLA composite films are subjected to biodegradability test for 28 days It is evidenced that the PLA composites showed reduction in weight by ~38% at the end of biodegradation study [115] The investigation on the degree at which the ramie fibre content affects the properties of PLA composites is examined [114] The PLA composites are fabricated via compression moulding technique [114,115] When the ramie content is maintained in the range of 45e65 wt %, mechanical characteristics namely tensile as well as bending strength are found to be improved for the PLA composites [66e68] Significant improvement in terms of impact strength for ramie fibre reinforced PLA composites is also evidenced The effect of kenaf fibre content on the mechanical properties of PLA composites is studied [66e68,115] The tensile, as well as bending strength properties along with Young's modulus, is found to be improved up to 50 wt % of kenaf fibres Investigation on the mechanical properties of melt-mixed as well as injection moulded PLA/kenaf fibre composites showed improvement in tensile strength when 30 wt % of kenaf fibre is present in the PLA matrix [66e68,116] At 25 wt % of cordenka fibre in the polylactic acid (PLA) matrix, mechanical properties are found to be improved Improved impact strength is revealed by cordenka reinforced PLA composites in comparison with neat PLA [66,67] In the case of flax reinforced PLA composites, the impact strength is found to be inferior as compared to neat PLA [66e68] The injection moulded PLA composites reinforced with 25 wt % of cordenka fibres R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 exhibited improved mechanical properties The strength, as well as stiffness of the PLA/cordenka fibres, is found to be doubled than neat PLA [66,67] The impact strength is also found to be tripled for the composites as compared to neat PLA [68] Investigation of the mechanical properties of compression moulded PLA/lyocell composites is carried out Improvement in terms of tensile strength as well as modulus and impact strength properties is achieved for the PLA/lyocell composites as compared to neat PLA [66e68] The optimization of mechanical properties via different modification techniques for the reinforcement is also reported The modification of bamboo fibre is carried out by alkali treatment and steam explosion process The PLA/modified bamboo fibre composites are fabricated by injection moulding technique It is found that the reinforcement of bamboo fibres modified by steam explosion provided better bending strength as compared to neat PLA The greatest bending strength was achieved with steam-exploded fibres Rather, the hot-pressing technique is used to attain improvement in impact strength for the PLA/modified bamboo fibre composites Surface treatment for kenaf, jute and henequen fibres is done using tap water [66e68] The fibres are surface treated by soaking them in water under both static and dynamic conditions In dynamic mode, ultrasound treatment is provided for the fibres immersed in tap water [116] The surface treated fibres improved the mechanical properties of the resinbased composite The influence of alkali treatment for hemp fibre and its weight loading on the mechanical characteristics of polymer composite is examined When 40 wt % loading of hemp fibre treated with alkali is incorporated in the polymer matrix, better output in terms of morphological and mechanical properties is obtained The effect of silane functionalization and alkali treatment for kenaf fibres on the mechanical properties of PLA composites fabricated by compression moulding is studied [66e68] The impact strength is found to increase for both alkali and silane treated PLA composites, which is due to better adhesion between surface modified filler and the matrix [117] 10 Conclusion In this review article, the authors tried to incorporate all the fundamental aspects and recent progress about the different kinds of bio-inspired micro and nanomaterials, including cellulose, hemicellulose, lignin and their composites along with the brief historical development, the methods of processing, structural properties, and noteworthy scientific applications We have focused our special attention on cellulose, hemicellulose, lignin and on their recently developed composites for the mechanical, thermal, electrical and biodegradation applications These materials, not only abundant on our earth planet but also bio-compatible and suitable for biomedical applications (owing to the natural intrinsic structures, which make them first choice for the transformative device fabrications) In addition to this, the antioxidant action of the lignin as a nanofiller in different polymer matrices and their impact on different cell types cultured on electrospun nanofibers were also evaluated, revealing that these materials have potential to be used for healthcare applications Moreover, the structural aspects of all the mentioned bio-materials and recent advancement are well deliberated in this article In the last section of this review we have focused on lignin/cellulose based, low cost, environmentally friendly hydrogels for numerous applications like in tissue engineering, drug delivery and healthcare systems 11 Future prospect Our biosphere provides us plentiful substances that cater our different needs at every point in life These include several plant 285 extracts, vitamins, biopolymers, peptides, and proteins, sugars in form of glucose, fructose and many more Therefore, human being has been studying these materials for over 500 years and now these materials fall in the category of the most studied class of materials Nowadays, bio-derived nanomaterials are playing a vital role in the filed tissue engineering and biomedical science such as drug and gene delivery using different kinds of nanoparticles derived from the green sources Bio-inspired nano/micromaterials are mostly nontoxic and many of them are well appreciated as green reduction agents Soon, these nanomaterials can be used for a wide range of applications In this line, Elia and co-workers produced gold nanoparticles by using four different types of plant extracts which has been found to be a very efficient stabilization and reducing agent for the series of biochemical reactions [116] Similarly, biopolymers and their composites are another important class of materials and nowadays polymer scientists have a great affinity with the same Adhikari and co-workers reported the excellent application of graphene-based cellulose fibres for the supercapacitor applications and they stated that such functional materials can be produced at an industrial scale after a further comprehensive research on the extraction of cellulose fibres from the waste papers Similarly, carbohydrate and their derivatives have already been used in numerous businesses and are readily available for real time applications For instance, countless novel composites and new materials were developed or in the process of development using chitosan, cellulose, and dextran, which were isolated from the natural sources However, even after the rapid progress in biomedical engineering over the past few decades, we are still facing a lot of challenges to design a new podium that can assimilate new technologies for the more innovative, significant commercial output of these biomaterials From the above discussion, it is very clear that plant-based materials have a tremendous potential to be a leader of macro and nanomaterials in different applications However, the challenge for these materials is its mass production, easy availability, purification and their utilizations without any additional matrices still is a big issue Thus, we can say the foremost problem for these materials; we must overcome is upscaling ultrapure biomaterials production along with challenge which lies in conserving the commercial availability Chemist and biotechnologist around the globe are working hard for possible solutions of the mentioned challenges to push biomaterials from the patents to the market According to the authors, there is a need of an intense collaborative research to make biomaterials innovations affordable for all So, in one sentence we can say there is a need of affordable technologies and much innovation in the field of biomaterials and we are hoping that within 10 years all the biomaterial-based products will be in the market for the common people All of us have a great hope from nanotechnology and their application for biotechnology because it is one of the most noteworthy scientific and industrial revolutions of the 21st century Therefore, using technologies derived from nanoscience we might be able to produce more and desired biopolymer inspired micro and nanomaterials for a wide range of applications from medicines to electronics, and to cosmetics Acknowledgements All the authors are very thankful to the researchers whose works cited directly or indirectly in this review article The co-author Dr K.Verma is very appreciative to DST/SERB for providing a fund having file no.SB/FTP/ETA-165/2014 to partially accomplish this work Dr Tiwari and Prof S.K Ha are also very grateful to the Editorin-Chief of JSAMD, Prof Nguyen Huu Duc for the constructive suggestions during the revision 286 R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 References [1] R.K Mishra, A Sabu, S.K Tiwari, Materials chemistry and the futurist ecofriendly applications of nanocellulose: status and prospect, J Saudi Chem Soc (2018), https://doi.org/10.1016/j.jscs.2018.02.005 [2] K.G Zinoviadou, M Gougouli, C.G Biliaderis, Innovative biobased materials for packaging sustainability, in: Innov Strateg Food Ind Tools Implement., 2016, pp 167e189, https://doi.org/10.1016/B978-0-12-803751-5.00009-X [3] M.M Reddy, S Vivekanandhan, M Misra, S.K Bhatia, A.K Mohanty, Biobased plastics and bionanocomposites: current status and future opportunities, Prog Polym Sci 38 (2013) 1653e1689, https://doi.org/10.1016/ j.progpolymsci.2013.05.006 [4] S.A Attaran, A Hassan, M.U Wahit, Materials for food packaging applications based on bio-based polymer nanocomposites, J Thermoplast Compos Mater 30 (2017) 143e173, https://doi.org/10.1177/0892705715588801 [5] M Mohiuddin, B Kumar, S Haque, Biopolymer composites in photovoltaics and photodetectors, in: Biopolym Compos Electron., 2016, pp 459e486, https://doi.org/10.1016/B978-0-12-809261-3.00017-6 [6] X.Z Tang, P Kumar, S Alavi, K.P Sandeep, Recent advances in biopolymers and biopolymer-based nanocomposites for food packaging materials, Crit Rev Food Sci Nutr 52 (2012) 426e442, https://doi.org/10.1080/ 10408398.2010.500508 [7] T Mekonnen, P Mussone, H Khalil, D Bressler, Progress in bio-based plastics and plasticizing modifications, J Mater Chem A (2013) 13379, https:// doi.org/10.1039/c3ta12555f [8] S Kabasci, Bio-based plastics - introduction, Bio Based Plast Mater Appl (2014) 1e7, https://doi.org/10.1002/9781118676646.ch1 [9] A Mokhtarzadeh, A Alibakhshi, M Hejazi, Y Omidi, J Ezzati Nazhad Dolatabadi, Bacterial-derived biopolymers: advanced natural nanomaterials for drug delivery and tissue engineering, TrAC - Trends Anal Chem 82 (2016) 367e384, https://doi.org/10.1016/j.trac.2016.06.013 [10] B.D Ulery, L.S Nair, C.T Laurencin, Biomedical applications of biodegradable polymers, J Polym Sci Part B Polym Phys 49 (2011) 832e864, https:// doi.org/10.1002/polb.22259 € m, Grafting of cellulose by ring-opening [11] A Carlmark, E Larsson, E Malmstro polymerisation - a review, Eur Polym J 48 (2012) 1646e1659, https:// doi.org/10.1016/j.eurpolymj.2012.06.013 ^lu Hesenov, O Erbatur, Gasification effi[12] S Irmak, M Kurtulus¸, A Hasanog ciencies of cellulose, hemicellulose and lignin fractions of biomass in aqueous media by using Pt on activated carbon catalyst, Biomass Bioenergy 49 (2013) 102e108, https://doi.org/10.1016/j.biombioe.2012.12.016 [13] S Kalia, S Boufi, A Celli, S Kango, Nanofibrillated cellulose: surface modification and potential applications, Colloid Polym Sci 292 (2014) 5e31, https://doi.org/10.1007/s00396-013-3112-9 [14] T.H Mokhothu, M.J John, Review on hygroscopic aging of cellulose fibres and their biocomposites, Carbohydr Polym 131 (2015) 337e354, https:// doi.org/10.1016/j.carbpol.2015.06.027 [15] S.Y Ding, S Zhao, Y Zeng, Size, shape, and arrangement of native cellulose fibrils in maize cell walls, Cellulose 21 (2014) 863e871, https://doi.org/ 10.1007/s10570-013-0147-5 [16] A.D French, Idealized powder diffraction patterns for cellulose polymorphs, Cellulose 21 (2014) 885e896, https://doi.org/10.1007/s10570-013-0030-4 [17] C.M Lee, A Mittal, A.L Barnette, K Kafle, Y.B Park, H Shin, D.K Johnson, S Park, S.H Kim, Cellulose polymorphism study with sum-frequencygeneration (SFG) vibration spectroscopy: identification of exocyclic CH2OH conformation and chain orientation, Cellulose 20 (2013) 991e1000, https:// doi.org/10.1007/s10570-013-9917-3 [18] A.L Barnette, C Lee, L.C Bradley, E.P Schreiner, Y.B Park, H Shin, D.J Cosgrove, S Park, S.H Kim, Quantification of crystalline cellulose in lignocellulosic biomass using sum frequency generation (SFG) vibration spectroscopy and comparison with other analytical methods, Carbohydr Polym 89 (2012) 802e809, https://doi.org/10.1016/j.carbpol.2012.04.014 [19] A.L Barnette, L.C Bradley, B.D Veres, E.P Schreiner, Y.B Park, J Park, S Park, S.H Kim, Selective detection of crystalline cellulose in plant cell walls with sum-frequency-generation (SFG) vibration spectroscopy, Biomacromolecules 12 (2011) 2434e2439, https://doi.org/10.1021/bm200518n [20] J.M Moran-Mirabal, The study of cell wall structure and cellulose-cellulase interactions through fluorescence microscopy, Cellulose 20 (2013) 2291e2309, https://doi.org/10.1007/s10570-013-0010-8 [21] J.M Moran-Mirabal, Advanced-microscopy techniques for the characterization of cellulose structure and cellulose-cellulase interactions, in: Cellul Fundam Asp., InTech, 2013, https://doi.org/10.5772/56584 €ki, L.A Berglund, K Oksman, A Bismarck, On the use of [22] K.Y Lee, Y Aitoma nanocellulose as reinforcement in polymer matrix composites, Compos Sci Technol 105 (2014) 15e27, https://doi.org/10.1016/j.compscitech.2014 08.032 [23] O Nechyporchuk, M.N Belgacem, J Bras, Production of cellulose nanofibrils: a review of recent advances, Ind Crops Prod 93 (2016) 2e25, https://doi.org/ 10.1016/j.indcrop.2016.02.016 [24] S Li, L Bashline, Y Zheng, X Xin, S Huang, Z Kong, S.H Kim, D.J Cosgrove, Y Gu, Cellulose synthase complexes act in a concerted fashion to synthesize highly aggregated cellulose in secondary cell walls of plants, Proc Natl Acad Sci 113 (2016) 11348e11353, https://doi.org/10.1073/pnas.1613273113 €ki, A.P Mathew, G Siqueira, Q Zhou, S Butylina, [25] K Oksman, Y Aitoma S Tanpichai, X Zhou, S Hooshmand, Review of the recent developments in cellulose nanocomposite processing, Compos Part A Appl Sci Manuf 83 (2016) 2e18, https://doi.org/10.1016/j.compositesa.2015.10.041 [26] N Lin, A Dufresne, Nanocellulose in biomedicine: current status and future prospect, Eur Polym J 59 (2014) 302e325, https://doi.org/10.1016/ j.eurpolymj.2014.07.025 [27] N.H Kim, T Imai, M Wada, J Sugiyama, Molecular directionality in cellulose polymorphs, Biomacromolecules (2006) 274e280, https://doi.org/10.1021/ bm0506391 [28] N Saba, F Mohammad, M Pervaiz, M Jawaid, O.Y Alothman, M Sain, Mechanical, morphological and structural properties of cellulose nanofibers reinforced epoxy composites, Int J Biol Macromol 97 (2017) 190e200, https://doi.org/10.1016/j.ijbiomac.2017.01.029 [29] E Mascheroni, R Rampazzo, M.A Ortenzi, G Piva, S Bonetti, L Piergiovanni, Comparison of cellulose nanocrystals obtained by sulfuric acid hydrolysis and ammonium persulfate, to be used as coating on flexible food-packaging materials, Cellulose 23 (2016) 779e793, https://doi.org/10.1007/s10570015-0853-2 [30] J Lamaming, R Hashim, C.P Leh, O Sulaiman, T Sugimoto, M Nasir, Isolation and characterization of cellulose nanocrystals from parenchyma and vascular bundle of oil palm trunk (Elaeis guineensis), Carbohydr Polym 134 (2015) 534e540, https://doi.org/10.1016/j.carbpol.2015.08.017 [31] K.J De France, T Hoare, E.D Cranston, Review of hydrogels and aerogels containing nanocellulose, Chem Mater 29 (2017) 4609e4631, https:// doi.org/10.1021/acs.chemmater.7b00531 [32] E Kalita, B.K Nath, P Deb, F Agan, M.R Islam, K Saikia, High quality fluorescent cellulose nanofibers from endemic rice husk: isolation and characterization, Carbohydr Polym 122 (2015) 308e313, https://doi.org/10.1016/ j.carbpol.2014.12.075 , M.R Vignon, Mechanical behavior of sheets pre[33] A Dufresne, J.-Y Cavaille pared from sugar beet cellulose microfibrils, J Appl Polym Sci 64 (1997) 1185e1194, https://doi.org/10.1002/(SICI)1097-4628(19970509)64: 63.0.CO;2-V [34] F.M Pelissari, P.J.D.A Sobral, F.C Menegalli, Isolation and characterization of cellulose nanofibers from banana peels, Cellulose 21 (2014) 417e432, https://doi.org/10.1007/s10570-013-0138-6 [35] Y Habibi, A.-L Goffin, N Schiltz, E Duquesne, P Dubois, A Dufresne, Bionanocomposites based on poly(ε-caprolactone)-grafted cellulose nanocrystals by ring-opening polymerization, J Mater Chem 18 (2008) 5002, https://doi.org/10.1039/b809212e [36] M Ioelovich, Optimal conditions for isolation of nanocrystalline cellulose particles, Nanosci Nanotechnol (2012) 9e13, https://doi.org/10.5923/ j.nn.20120202.03 [37] A.R Jahanbaani, T Behzad, S Borhani, M.H.K Darvanjooghi, Electrospinning of cellulose nanofibers mat for laminated epoxy composite production, Fibers Polym 17 (2016) 1438e1448, https://doi.org/10.1007/s12221-016-6424-9 [38] C.S Julie Chandra, N George, S.K Narayanankutty, Isolation and characterization of cellulose nanofibrils from arecanut husk fibre, Carbohydr Polym 142 (2016) 158e166, https://doi.org/10.1016/j.carbpol.2016.01.015 [39] J Rojas, M Bedoya, Y Ciro, Current trends in the production of cellulose nanoparticles and nanocomposites for biomedical applications, in: Cellul Fundam Asp Curr Trends, InTech, 2015, https://doi.org/10.5772/61334 [40] C.A Carrillo, J Laine, O.J Rojas, Microemulsion systems for fiber deconstruction into cellulose nanofibrils, ACS Appl Mater Interfaces (2014) 22622e22627, https://doi.org/10.1021/am5067332 €, C Salas, J Arboleda, I.C Hoeger, O.J Rojas, Cellulose [41] Y Zhang, T Nypelo nanofibrils, J Renew Mater (2013) 195e211, https://doi.org/10.7569/ JRM.2013.634115 [42] J Kluge, G Muhrer, M Mazzotti, High pressure homogenization of pharmaceutical solids, J Supercrit Fluids 66 (2012) 380e388, https://doi.org/ 10.1016/j.supflu.2012.01.009 [43] M Van De Voorde, Industrialization - large-scale production of nanomaterials/components, in: Nano-micro Interface Bridg Micro Nano Worlds, second ed., 2015, pp 677e684, https://doi.org/10.1002/978352767 9195.ch33 [44] Y Peng, D.J Gardner, Y Han, Drying cellulose nanofibrils: in search of a suitable method, Cellulose 19 (2012) 91e102, https://doi.org/10.1007/ s10570-011-9630-z [45] N.A Jarrah, F Li, J.G van Ommen, L Lefferts, Immobilization of a layer of carbon nanofibres (CNFs) on Ni foam: a new structured catalyst support, J Mater Chem 15 (2005) 1946, https://doi.org/10.1039/b416977h [46] C Hu, Y Zhao, K Li, J.Y Zhu, R Gleisner, Optimizing cellulose fibrillation for the production of cellulose nanofibrils by a disk grinder, Holzforschung 69 (2015) 993e1000, https://doi.org/10.1515/hf-2014-0219 [47] S Josset, P Orsolini, G Siqueira, A Tejado, P Tingaut, T Zimmermann, Energy consumption of the nanofibrillation of bleached pulp, wheat straw and recycled newspaper through a grinding process, Nord Pulp Pap Res J 29 (2014) 167e175, https://doi.org/10.3183/NPPRJ-2014-29-01-p167-175 ska, Studies on isolation of cellulose fibres [48] E Kopania, J Wietecha, D Ciechan from waste plant biomass, Fibres Text East Eur 96 (2012) 167e172 [49] A Alemdar, M Sain, Isolation and characterization of nanofibers from agricultural residues - wheat straw and soy hulls, Bioresour Technol 99 (2008) 1664e1671, https://doi.org/10.1016/j.biortech.2007.04.029 R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 [50] A Villares, C Moreau, C Bennati-Granier, S Garajova, L Foucat, X Falourd, B Saake, J.G Berrin, B Cathala, Lytic polysaccharide monooxygenases disrupt the cellulose fibers structure, Sci Rep (2017), https://doi.org/10.1038/ srep40262 [51] J.D Redlinger-Pohn, M Grabner, P Zauner, S Radl, Separation of cellulose fibres from pulp suspension by froth flotation fractionation, Sep Purif Technol 169 (2016) 304e313, https://doi.org/10.1016/j.seppur.2016.06.004 [52] N.F Vasconcelos, J.P.A Feitosa, F.M.P da Gama, J.P.S Morais, F.K Andrade, M.D.S.M de Souza, M de Freitas Rosa, Bacterial cellulose nanocrystals produced under different hydrolysis conditions: properties and morphological features, Carbohydr Polym 155 (2017) 425e431, https://doi.org/10.1016/ j.carbpol.2016.08.090 [53] M Martínez-Sanz, A Lopez-Rubio, J.M Lagaron, Optimization of the nanofabrication by acid hydrolysis of bacterial cellulose nanowhiskers, Carbohydr Polym 85 (2011) 228e236, https://doi.org/10.1016/j.carbpol.2011.02.021 [54] L Hu, L Lin, Z Wu, S Zhou, S Liu, Chemocatalytic hydrolysis of cellulose into glucose over solid acid catalysts, Appl Catal B Environ 174e175 (2015) 225e243, https://doi.org/10.1016/j.apcatb.2015.03.003 €m, A Carlmark, Preparation [55] A Boujemaoui, S Mongkhontreerat, E Malmstro and characterization of functionalized cellulose nanocrystals, Carbohydr Polym 115 (2015) 457e464, https://doi.org/10.1016/j.carbpol.2014.08.110 [56] L.P Novo, J Bras, A García, N Belgacem, A.A.S Curvelo, Subcritical water: a method for green production of cellulose nanocrystals, ACS Sustain Chem Eng (2015) 2839e2846, https://doi.org/10.1021/acssuschemeng.5b00762 [57] V.S Yeul, S.S Rayalu, Unprecedented chitin and chitosan: a chemical overview, J Polym Environ 21 (2013) 606e614, https://doi.org/10.1007/s10924012-0458-x [58] M Zuber, K.M Zia, M Barikani, Chitin and chitosan based blends, composites and nanocomposites, (2013): pp 55e119 https://doi.org/10.1007/978-3642-20940-6_3 [59] W Arbia, L Arbia, L Adour, A Amrane, Chitin extraction from crustacean shells using biological methods - a review, Food Technol Biotechnol 51 (2013) 12e25, https://doi.org/10.1002/biot.200800027 [60] M Rinaudo, Chitin and chitosan: properties and applications, Prog Polym Sci 31 (2006) 603e632, https://doi.org/10.1016/j.progpolymsci.2006.06.001 [61] J.-I Kadokawa, Ionic liquid as useful media for dissolution, derivatization, and nanomaterial processing of chitin, Green Sustain Chem (2013) 19e25, https://doi.org/10.4236/gsc.2013.32A003 [62] T Paul, S.K Halder, A Das, K Ghosh, A Mandal, P Payra, P Barman, P.K Das Mohapatra, B.R Pati, K.C Mondal, Production of chitin and bioactive materials from Black tiger shrimp (Penaeus monodon) shell waste by the treatment of bacterial protease cocktail, Biotech (2015) 483e493, https:// doi.org/10.1007/s13205-014-0245-6 [63] S.H Ghaffar, M Fan, Lignin in straw and its applications as an adhesive, Int J Adhes Adhes 48 (2014) 92e101, https://doi.org/10.1016/j.ijadhadh.2013 09.001 [64] D Watkins, M Nuruddin, M Hosur, A Tcherbi-Narteh, S Jeelani, Extraction and characterization of lignin from different biomass resources, J Mater Res Technol (2015) 26e32, https://doi.org/10.1016/j.jmrt.2014.10.009 [65] T Leskinen, S.S Kelley, D.S Argyropoulos, Refining of ethanol biorefinery residues to isolate value added lignins, ACS Sustain Chem Eng (2015) 1632e1641, https://doi.org/10.1021/acssuschemeng.5b00337 [66] A Rahimi, A Ulbrich, J.J Coon, S.S Stahl, Formic-acid-induced depolymerization of oxidized lignin to aromatics, Nature 515 (2014) 249e252, https:// doi.org/10.1038/nature13867 [67] M.A.S Anwer, H.E Naguib, A Celzard, V Fierro, Comparison of the thermal, dynamic mechanical and morphological properties of PLA-Lignin & PLATannin particulate green composites, Compos Part B Eng 82 (2015) 92e99, https://doi.org/10.1016/j.compositesb.2015.08.028 [68] D Kai, W Ren, L Tian, P.L Chee, Y Liu, S Ramakrishna, X.J Loh, Engineering poly(lactide)-lignin nanofibers with antioxidant activity for biomedical application, ACS Sustain Chem Eng (2016) 5268e5276, https://doi.org/ 10.1021/acssuschemeng.6b00478 [69] K Cornish, Chemistry, manufacture and applications of natural rubber, Chem Manuf Appl Nat Rubber (2014) 3e29, https://doi.org/10.1533/ 9780857096913.1.3 [70] M Alberto, Introduction of fibre-reinforced polymers À polymers and composites: concepts, properties and processes, in: Fiber Reinf Polym Technol Appl Concr Repair, 2013, https://doi.org/10.5772/54629 [71] S Wang, C Li, L Copeland, Q Niu, S Wang, Starch retrogradation: a comprehensive review, Compr Rev Food Sci Food Saf 14 (2015) 568e585, https://doi.org/10.1111/1541-4337.12143 [72] U Sonnewald, J Kossmann, Starches-from current models to genetic engineering, Plant Biotechnol J 11 (2013) 223e232, https://doi.org/10.1111/ pbi.12029 [73] H.E Grommers, D.A van der Krogt, Potato starch: production, modifications and uses, in: Starch, 2009, pp 511e539, https://doi.org/10.1016/B978-0-12746275-2.00011-2 [74] Y Zhang, Q Guo, N Feng, J Rong Wang, S Jun Wang, Z Hu He, Characterization of A- and B-type starch granules in Chinese wheat cultivars, J Integr Agric 15 (2016) 2203e2214, https://doi.org/10.1016/S2095-3119(15)61305-3 [75] L Lin, D Guo, L Zhao, X Zhang, J Wang, F Zhang, C Wei, Comparative structure of starches from high-amylose maize inbred lines and their hybrids, Food Hydrocoll 52 (2016) 19e28, https://doi.org/10.1016/ j.foodhyd.2015.06.008 287 rous, E Pollet, Green nano-biocomposites, (2012): pp 1e11 https:// [76] L Ave doi.org/10.1007/978-1-4471-4108-2_1 [77] K Mahmood, H Kamilah, P.L Shang, S Sulaiman, F Ariffin, A.K Alias, A review: interaction of starch/non-starch hydrocolloid blending and the recent food applications, Food Biosci 19 (2017) 110e120, https://doi.org/ 10.1016/j.fbio.2017.05.006 ~es, W.J Santos, J.C Oliveira, [78] C.S Miranda, M.S Ferreira, M.T Magalha , Mechanical, thermal and barrier properties of starchJ.B.A Silva, N.M Jose based films plasticized with glycerol and lignin and reinforced with cellulose nanocrystals, in: Mater Today Proc., 2015, pp 63e69, https://doi.org/ 10.1016/j.matpr.2015.04.009 [79] S Wang, L Copeland, Effect of acid hydrolysis on starch structure and functionality: a review, Crit Rev Food Sci Nutr 55 (2015) 1081e1097, https://doi.org/10.1080/10408398.2012.684551 [80] D Lecorre, E Vahanian, A Dufresne, J Bras, Enzymatic pretreatment for preparing starch nanocrystals, Biomacromolecules 13 (2012) 132e137, https://doi.org/10.1021/bm201333k [81] J Zhou, J Tong, X Su, L Ren, Hydrophobic starch nanocrystals preparations through crosslinking modification using citric acid, Int J Biol Macromol 91 (2016) 186e1193, https://doi.org/10.1016/j.ijbiomac.2016.06.082 [82] Z Li, W Liu, Z Gu, C Li, Y Hong, L Cheng, The effect of starch concentration on the gelatinization and liquefaction of corn starch, Food Hydrocoll 48 (2015) 189e196, https://doi.org/10.1016/j.foodhyd.2015.02.030 [83] S Bel Haaj, A Magnin, C P??trier, S Boufi, Starch nanoparticles formation via high power ultrasonication, Carbohydr Polym 92 (2013) 1625e1632, https://doi.org/10.1016/j.carbpol.2012.11.022 [84] J.-W Rhim, H.-M Park, C.-S Ha, Bio-nanocomposites for food packaging applications, Prog Polym Sci 38 (2013) 1629e1652, https://doi.org/ 10.1016/j.progpolymsci.2013.05.008 [85] P Chen, F Xie, L Zhao, Q Qiao, X Liu, Effect of acid hydrolysis on the multiscale structure change of starch with different amylose content, Food Hydrocoll 69 (2017) 359e368, https://doi.org/10.1016/j.foodhyd.2017.03.003 [86] D Lecorre, J Bras, A Dufresne, Influence of native starch's properties on starch nanocrystals thermal properties, Carbohydr Polym 87 (2012) 658e666, https://doi.org/10.1016/j.carbpol.2011.08.042 [87] C Kapridaki, L Pinho, M.J Mosquera, P Maravelaki-Kalaitzaki, Producing photoactive, transparent and hydrophobic SiO2-crystalline TiO2 nanocomposites at ambient conditions with application as self-cleaning coatings, Appl Catal B Environ 156e157 (2014) 416e427, https://doi.org/10.1016/ j.apcatb.2014.03.042 [88] P.T.N Nguyen, C Salim, W Kurniawan, H Hinode, A non-hydrolytic solegel synthesis of reduced graphene oxide/TiO2 microsphere photocatalysts, Catal Today 230 (2014) 166e173, https://doi.org/10.1016/j.cattod.2013.10.017 ndez-Flores, T Ohno, High visible-light active Ir-doped-TiO2 [89] V.M Mene brookite photocatalyst synthesized by hydrothermal microwave-assisted process, Catal Today 230 (2014) 214e220, https://doi.org/10.1016/ j.cattod.2014.01.032 [90] W Fan, Q Lai, Q Zhang, Y Wang, Nanocomposites of TiO2 and reduced graphene oxide as efficient photocatalysts for hydrogen evolution, J Phys Chem C 115 (2011) 10694e10701, https://doi.org/10.1021/jp2008804 [91] S.M Gupta, M Tripathi, A review of TiO2 nanoparticles, Chin Sci Bull 56 (2011) 1639e1657, https://doi.org/10.1007/s11434-011-4476-1 [92] S.N Karthick, K Prabakar, A Subramania, J.T Hong, J.J Jang, H.J Kim, Formation of anatase TiO2 nanoparticles by simple polymer gel technique and their properties, Powder Technol 205 (2011) 36e41, https://doi.org/ 10.1016/j.powtec.2010.08.061 [93] T Bhuyan, K Mishra, M Khanuja, R Prasad, A Varma, Biosynthesis of zinc oxide nanoparticles from Azadirachta indica for antibacterial and photocatalytic applications, Mater Sci Semicond Process 32 (2015) 55e61, https://doi.org/10.1016/j.mssp.2014.12.053 [94] A Kolodziejczak-Radzimska, T Jesionowski, Zinc oxide-from synthesis to application: a review, Materials (Basel) (2014) 2833e2881, https://doi.org/ 10.3390/ma7042833 [95] S Rehman, R Ullah, A.M Butt, N.D Gohar, Strategies of making TiO2 and ZnO visible light active, J Hazard Mater 170 (2009) 560e569, https://doi.org/ 10.1016/j.jhazmat.2009.05.064 [96] M Antoniadou, V.M Daskalaki, N Balis, D.I Kondarides, C Kordulis, P Lianos, Photocatalysis and photoelectrocatalysis using (CdS-ZnS)/TiO2 combined photocatalysts, Appl Catal B Environ 107 (2011) 188e196, https://doi.org/10.1016/j.apcatb.2011.07.013 [97] H Park, Y Park, W Kim, W Choi, Surface modification of TiO2 photocatalyst for environmental applications, J Photochem Photobiol C Photochem Rev 15 (2013) 1e20, https://doi.org/10.1016/j.jphotochemrev.2012.10.001 [98] R Salehi, M Arami, N.M Mahmoodi, H Bahrami, S Khorramfar, Novel biocompatible composite (chitosanezinc oxide nanoparticle): preparation, characterization and dye adsorption properties, Colloids Surf B: Biointerfaces 80 (1) (2010) 86e93, https://doi.org/10.1016/j.colsurfb.2010.05.039 [99] X Lu, H Zhang, Y Ni, Q Zhang, J Chen, Porous nanosheet-based ZnO microspheres for the construction of direct electrochemical biosensors, Biosens Bioelectron 24 (1) (2008) 93e98, https://doi.org/10.1016/j.bios.2008.03.025 [100] I.J Joye, G Davidov-Pardo, D.J McClements, Nanotechnology for increased micronutrient bioavailability, Trends Food Sci Technol 40 (2014) 168e182, https://doi.org/10.1016/j.tifs.2014.08.006 [101] W Hu, X Yu, Encapsulation of bio-based PCM with coaxial electrospun ultrafine fibers, RSC Adv (2012) 5580, https://doi.org/10.1039/c2ra20532g 288 R.K Mishra et al / Journal of Science: Advanced Materials and Devices (2018) 263e288 [102] M Fashandi, S.N Leung, Preparation and characterization of 100% bio-based polylactic acid/palmitic acid microcapsules for thermal energy storage, Mater Renew Sustain Energy (2017) 14, https://doi.org/10.1007/s40243017-0098-0 , V.V Khutoryanskiy, Biomedical applications of hydrogels: a review of [103] E Calo patents and commercial products, Eur Polym J 65 (2015) 252e267, https:// doi.org/10.1016/j.eurpolymj.2014.11.024 [104] D Buenger, F Topuz, J Groll, Hydrogels in sensing applications, Prog Polym Sci 37 (2012) 1678e1719, https://doi.org/10.1016/j.progpolymsci.2012 09.001 [105] E.S Dragan, D.F Apopei, Multiresponsive macroporous semi-IPN composite hydrogels based on native or anionically modified potato starch, Carbohydr Polym 92 (2013) 23e32, https://doi.org/10.1016/j.carbpol.2012.08.082 [106] C Spagnol, F.H.A Rodrigues, A.G.B Pereira, A.R Fajardo, A.F Rubira, E.C Muniz, Superabsorbent hydrogel nanocomposites based on starch-gpoly(sodium acrylate) matrix filled with cellulose nanowhiskers, Cellulose 19 (2012) 1225e1237, https://doi.org/10.1007/s10570-012-9711-7 [107] S.R Caliari, J.A Burdick, A practical guide to hydrogels for cell culture, Nat Methods 13 (2016) 405e414, https://doi.org/10.1038/nmeth.3839 [108] X Tang, S Alavi, T.J Herald, Barrier and mechanical properties of starch-clay nanocomposite films, Cereal Chem 85 (2008) 433e439, https://doi.org/ 10.1094/CCHEM-85-3-0433 [109] M Rossi, F Cubadda, L Dini, M.L Terranova, F Aureli, A Sorbo, D Passeri, Scientific basis of nanotechnology, implications for the food sector and future trends, Trends Food Sci Technol 40 (2014) 127e148, https://doi.org/ 10.1016/j.tifs.2014.09.004 [110] A.J Uddin, J Araki, M Fujie, S Sembo, Y Gotoh, Interfacial interaction and mechanical properties of chitin whisker-poly(vinyl alcohol) gel-spun nanocomposite fibers, Polym Int 61 (2012) 1010e1015, https://doi.org/10.1002/ pi.4174 ski, A Bychowska, K Brzozowski, [111] J Kumirska, M Czerwicka, Z Kaczyn €ming, P Stepnowski, Application of spectroscopic methods for strucJ Tho tural analysis of chitin and chitosan, Mar Drugs (2010) 1567e1636, https://doi.org/10.3390/md8051567 [112] A.P Mathew, M.P.G Laborie, K Oksman, Cross-linked chitosan/chitin crystal nanocomposites with improved permeation selectivity and pH stability, Biomacromolecules 10 (2009) 1627e1632, https://doi.org/10.1021/ bm9002199 [113] C Santulli, D Puglia, M Rallini, P.M Visakh, J.M Kenny, S Thomas, Natural rubber composites filled with a low volume of crab chitin whiskers: mechanical and thermal characterization, Malaysian Polym J (2014) 18e23 [114] E Trovatti, A.J.F Carvalho, A Gandini, A new approach to blending starch with natural rubber, Polym Int 64 (2015) 605e610, https://doi.org/10.1002/ pi.4808 [115] P Elia, R Zach, S Hazan, S Kolusheva, Z.E Porat, Y Zeiri, Green synthesis of gold nanoparticles using plant extracts as reducing agents, Int J Nanomed 86 (2014) 4007, https://doi.org/10.2147/IJN.S57343 [116] A De Adhikari, R Oraon, S.K Tiwari, J.H Lee, G.C Nayak, Effect of waste cellulose fibres on the charge storage capacity of polypyrrole and graphene/ polypyrrole electrodes for supercapacitor application, RSC Adv 35 (2015) 27347e27355, https://doi.org/10.1039/C4RA16174B ... microbes and mycotoxins They are mainly useful in removing toxins from feed materials Binding and colouring microorganisms Nanoemulsions and nanoencapsulates Sustained release from nanoencapsulate... activity [96] Analysts have been practising hydrogenation, metal and non-metal doping, and sensitizing with a small band gap semiconductor substance to diminish bandgaps and promote the performance via... have evolved into materials with outstanding features and many potential applications, from soil conditioners and hygienic products to tissue engineering, drug delivery systems, and imprinted polymers