Key engineering materials  volume ii  interdisciplinary concepts and research

K Haghi and G E Zaikov 2 Smart Delivery of Drugs

University of Guilan, Rasht, Iran.

Tver State University, Zheliabova str 33, Tver–170100, Russia.

V Bychkova and M Rosenfeld 3 Modern Basalt Fibers and Epoxy Basaltoplastics: Properties

Federal State Budgetary Institution of Science Emanuel Institute of Biochemical Physics of Russian Academy of Sciences, Kosygina str 4, Moscow-119334, Russia

A A Dalinkevich Сеntral Scientific Research Institute of Special Mashine-Building, Zavodskaya str 1, Khotkovo-141371, Moscow region, Russia.

Dagestan State Pedagogical University, Yaragskii str 57, Makhachkala-367003, Russian Fed- eration.

Moscow State University, Chemistry Faculty, Department of Chemical Enzymology, Leninskye gory MSU 1/11, Moscow-119991, Russia, Phone: +7(495) 939-5083, Fax: +7(495) 939-5417. E-mail: vp_murygina@mail.ru, vpm@enzyme.chem.msu.ru

N N Semenov Institute of Chemical Physics, RAS, Kosygin str 4, Moscow-119991, Russia. E-mail: guklara@yandex.ru

Volzhsky Polytechnical Institute, Branch of Federal State Budgetary Educational Institu- tion of Higher Professional Education, Volgograd State Technical University, Engels str 42a, Volzhsky-404121, Volgograd Region, Russia.

E-mail: d.provotorova@gmail.com; www.volpi.ru

N M Emanuel Institute of Biochemical Physics of Russian Academy of Sciences, Kosygin str

N M Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Kosygin str 4, Moscow-119334, Russia.

E-mail: Chembio@sky.chph.ras.ru

Dagestan State Pedagogical University, Makhachkala-367003, Yaragskii str 57, Russian Fed- eration.

S S Marakhovsky ôArmoprojectằ Companyằ LLC, dominion 27 Malakhitovaya str., Moscow-129128,

E-mail: cmc@aproject.ton.ru

Semenov Institute of Chemical Physics of Russian Academy of Sciences, Kosygin str 4, Moscow-119991.

Lomonosov Moscow State University for Fine Chemical Technology.

K U of Leuven, Department Chemical Engineering, Willem de Croylaan 46, Leuven- B-3001, Belgium.

Moscow State University, Chemistry Faculty, Department of Chemical Enzymology, Leninskye gory MSU, 1/11, Moscow-119991, Russia, Phone: +7(495) 939-5083, Fax: +7(495) 939-5417. E-mail: vp_murygina@mail.ru, vpm@enzyme.chem.msu.ru

JSC “Sea oil company”, “KazMunayTeniz”, Kazakhstan

Tver State University, Zheliabova str., 33, Tver-170100, Russia.

G.V Plekhanov Russian Economic University, 36 Stremyannyi way, Moscow-117997 Russia.E-mail: pekhtashevael@mail.ru

Lomonosov Moscow State University for Fine Chemical Technology

Volzhsky Polytechnical Institute, branch of Federal State Budgetary Educational Institu- tion of Higher Professional Education, Volgograd State Technical University, Engels str 42a, Volzhsky-404121, Volgograd Region, Russia.

Federal state budgetary institution of science Emanuel Institute of Biochemical Physics of Russian Academy of Sciences, Kosygina str 4, Moscow-119334, Russia.

The Institute of General and Inorganic Chemistry, National Academy of Sciences, Uzbekistan.

Ufa State Petroleum Technological University, Russia.

V Soukhanov, Dalinkevich, K Z Gumargalieva, and S S Marakhovsky 4 Calculations of Bond Energy in Cluster Water Nanostructures

ôArmoprojectằ Companyằ LLC, dominion 27 Malakhitovaya str., Moscow-129128,

Moscow State University, Chemistry Faculty, Department of Chemical Enzymology,Leninskye gory MSU, 1/11, Moscow-19991, Russia, Phone: +7(495) 939-5083, Fax: +7(495) 939-5417. E-mail: vp_murygina@mail.ru, vpm@enzyme.chem.msu.ru

Ufa State Petroleum Technological University, Russia.

EPDM Ethylene propylene diene monomer

ESEM Environment scanning electron microscope

FPLC Fast protein liquid chromatography

HPLC High-performance liquid chromatography

IR MDCIR Infrared microscopy of multiply disturbed complete inner reflection LDPE Low density polyethylene

NMR MAS Nuclear magnetic resonance, magic-angle spinning

PEG Poly(ethy1ene glycol)

PMPA Polyelectrolyte-mediated protein adsorption

PMPAS Polyelectrolyte mediated protein association

RHR Rate of heat release

SALS Small angle light scattering

"Key Engineering Materials: Volume II: Interdisciplinary Concepts and Research" offers a thorough yet accessible exploration of essential engineering materials, catering to graduate students and scientists across related disciplines This volume is organized into distinct sections that focus on key materials and their applications, incorporating recent discoveries and emphasizing fundamental concepts Readers will gain a comprehensive understanding of the field, satisfying both direct and lateral interests in engineering materials.

This book offers groundbreaking insights into the expansion of research activities among chemists, biologists, and chemical engineers, fostering communication between global academia and industry It features pivotal research and reviews on innovative methodologies and key applications in industrial chemistry, polymers, and biotechnology Additionally, it highlights recent advancements in chemical databases and the development of new computational methods and algorithms for chemical software and polymer engineering.

This book offers an in-depth exploration of recent advancements in polymers and advanced materials, highlighting their diverse applications across various scientific disciplines, including physics, chemistry, and biology.

• provides physical principles in explaining and rationalizing polymeric phenomena

• features classical topics that are conventionally considered part of chemical technology

• covers the chemical principles from a modern point of view

• analyzes theories to formulate and prove the polymer principles

• presents future outlook on application of bioscience in chemical concepts

• focuses on topics with more advanced methods

— Franỗois Kajzar, PhD, Eli M Pearce, PhD, Nikolai A Turovskij, PhD, and Omari Vasilii Mukbaniani, DSc

CASE STUDIES ON KEY ENGINEERING MATERIALS IN NANOSCALE:

1.6 Key Concepts and Basic Criteria 28

The advancement of technology necessitates the development of innovative materials that are stronger, more reliable, and durable, featuring enhanced properties Current projects focused on material creation increasingly leverage nanotechnology to achieve these goals.

Nanotechnology represents a significant advancement in human development, encompassing a broad range of fields such as information technology, medicine, military applications, and robotics This article focuses specifically on the application of nanotechnology in polymeric materials and their composite derivatives.

The prefix "nano-" refers to technologies involving materials and objects sized at 10^-9 meters Remarkably, science has long explored the nanolevel; however, the application of these advancements in mass production remains challenging due to low productivity and high costs.

Nanotechnology and nanomaterials are currently limited to research laboratories, but their eventual implementation in manufacturing promises significant advantages for producers The unique properties of nanoparticles, which differ markedly from their micro- and macroparticle counterparts, arise from their reduced size For instance, transitioning palladium to nanocrystals can enhance its thermal capacity by over 1.5 times, increase bismuth solubility in copper by 4000 times, and elevate copper's self-diffusion coefficient at room temperature by 21 orders These remarkable changes in material properties are attributed to the increased ratio of surface to volume atoms in nanoparticles, resulting in a high surface area By incorporating nanoparticles into traditional polymer matrices, manufacturers can unlock new qualitative and quantitative possibilities for material applications.

Laminated nanocomposites are advanced materials composed of a thermoplastic matrix combined with natural, laminated inorganic structures like montmorillonite or vermiculite, commonly found in clays These composites are created by saturating a thin layer of filler, approximately 1 nm thick, with a monomer solution that is subsequently polymerized Compared to traditional polymeric matrices, laminated nanocomposites exhibit significantly lower permeability to liquids and gases, making them ideal for applications in the medical and food processing industries They are particularly suitable for manufacturing pipes and containers for carbonated beverages.

These composite materials are eco-friendly, absolutely harmless to the person and possess fire-resistant properties The derived thermoplastic laboratory samples have been tested and really confirmed those statements.

It should be noted that manufacturing technique of thermoplastic materials causes difficulties for today, notably dispersion of silicate nanoparticles in monomer solution

To solve this problem it is necessary to develop the dispersion technique, which could be transferred from laboratory conditions into the industrial ones.

Manufacturers can benefit significantly by reorganizing their production to incorporate advanced materials, which offer superior mechanical and gas barrier properties compared to traditional thermoplastics This transition not only enhances the performance of plastic containers and pipes but also promotes material efficiency by allowing for a reduction in product thickness, ultimately leading to cost savings and sustainability in manufacturing processes.

The enhancement of physical and mechanical properties in nanocomposite products enables their use in high-pressure and high-temperature environments This advancement addresses challenges such as the thermal treatment of plastic containers Additionally, the beneficial characteristics of laminated nanocomposites find significant applications in the automotive industry.

Metal-containing nanocomposites are materials that leverage the unique properties of metal particles, which can form ordered structures or clusters These clusters, typically ranging from 1 to 10 nm in size, provide a significant specific surface area As a result, these nanocomposites exhibit remarkable characteristics such as superparamagnetism and catalytic activity, making them suitable for applications in the manufacturing of semiconductors, catalysts, and optical and luminescent devices.

Such valuable materials can be produced in several ways, for example, by means of chemical or electrochemical reactions of isolation of metal particles from solutions

The primary challenge lies not in the restoration of metal but in preserving its particles, specifically preventing agglutination and the formation of large metal pieces.

Under controlled laboratory conditions, metals are deposited onto thin polymeric films designed to capture nano-sized particles This process involves evaporating the metal using high energy sources, which generates these nano-sized particles that must be carefully preserved Methods for metal evaporation include the use of explosive energy, high-voltage electric discharge, or elevated temperatures in specialized furnaces.

Metal-containing nanocomposites can be utilized to develop polymers that exhibit valuable metallic properties For instance, a polyethylene plate infused with minute amounts of palladium demonstrates catalytic properties akin to those of a pure palladium plate.

Metallic composites, such as packing materials infused with silver, are increasingly utilized for their bactericidal properties Various countries have already adopted paints and polymer coatings containing silver nanoparticles, leveraging their antibacterial effects in public spaces These applications include wall painting and handrail coatings, contributing to enhanced hygiene in communal facilities.

K Haghi and G E Zaikov 5 Experimental Research on Desalting of Instable Gas

R Abdurakhmonov, Z S Salimov, Sh M Saydakhmedov, and G E Zaikov 7 A Study on the Effect of Anthropogenic Pollution on the

The Institute of General and Inorganic Chemistry, National Academy of Sciences, Uzbekistan.

N M Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Kosigin str 4 Moscow-119334, Russia.

V Ilyashenko, A I Ivanova, and Yu G Oleneva 8 Phase Transitions in Water-in-Water BSA/Dextran Emulsion in

A Antonov and P Moldenaers 9 Development of Stable Polymer-Bitumen Binders for Asphalts

N M Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Kosigin str 4 Moscow-119334, Russia.

A Antonov and Paula Moldenaers 12 Comparison of Two Bioremediation Technologies for Oil

P Murygina, S N Gaidamaka, and S Ya Trofimov 13 Unsaturated Rubber Modification by Ozonation

Z Gumargalieva and G E Zaikov 15 Semicrystalline Polymers as Natural Hybrid Nanocomposites

M Magomedov, K S Dibirova, V Kozlov, and E Zaikov 16 Degradation Mechanism of Leather and Fur

Lomonosov Moscow State University for Fine Chemical Technology

M Lomakin, P A Sakharov, and G E Zaikov

Introduction

The advancement of technology necessitates the development of innovative materials that are stronger, more reliable, and durable, featuring enhanced properties Current projects focused on material creation are increasingly leveraging nanotechnology.

Nanotechnology represents a significant advancement in human progress, impacting various fields such as information technology, medicine, military equipment, and robotics This article focuses specifically on nanotechnology in relation to polymeric materials and the composites derived from them.

The prefix "nano-" refers to technologies involving materials and objects at a scale of 10^-9 meters Remarkably, science has already advanced to the nanolevel; however, the application of these developments in mass production remains challenging due to low productivity and high costs.

Nanotechnology and nanomaterials are currently confined to research laboratories, but their future implementation in manufacturing promises significant advantages for manufacturers Nanoparticles exhibit unique properties that differ drastically from micro- or macroparticles due to the changes in physical characteristics when materials are reduced to nanometric sizes For instance, palladium in nanocrystal form shows over a 1.5-fold increase in thermal capacity, while bismuth's solubility in copper rises by 4000 times, and copper's self-diffusion coefficient increases by 21 orders at room temperature These remarkable changes stem from the higher surface area-to-volume ratio of nanoparticles By incorporating these nanoparticles into a polymeric matrix, manufacturers can unlock qualitatively and quantitatively new applications for traditional materials.

Laminated nanocomposites are advanced materials that combine a thermoplastic matrix with natural, laminated inorganic structures, such as montmorillonite or vermiculite found in clays These composites are created by saturating a thin layer of filler, approximately 1 nm thick, with a monomer solution, which is then polymerized Compared to the original polymeric matrix, laminated nanocomposites exhibit significantly reduced permeability to liquids and gases This enhanced property makes them ideal for applications in the medical and food processing industries, including the production of pipes and containers for carbonated beverages.

These composite materials are eco-friendly, absolutely harmless to the person and possess fire-resistant properties The derived thermoplastic laboratory samples have been tested and really confirmed those statements.

It should be noted that manufacturing technique of thermoplastic materials causes difficulties for today, notably dispersion of silicate nanoparticles in monomer solution

To solve this problem it is necessary to develop the dispersion technique, which could be transferred from laboratory conditions into the industrial ones.

Manufacturers can gain significant advantages by reorganizing their production processes to incorporate advanced materials These materials offer superior mechanical properties and gas barrier capabilities compared to traditional thermoplastics, enabling the creation of thinner plastic containers and pipes This shift not only enhances product performance but also leads to material savings, making manufacturing more efficient and sustainable.

The enhancement of physical and mechanical properties in nanocomposite products enables their use in high-pressure and high-temperature applications This advancement addresses issues such as the thermal treatment of plastic containers Additionally, the beneficial characteristics of laminated nanocomposites find significant applications in the automotive industry.

Metal-containing nanocomposites are materials that leverage the unique properties of metal particles, which can form ordered clusters ranging from 1 to 10 nm in size These clusters have a significant specific surface area, enabling the nanocomposites to exhibit valuable characteristics such as superparamagnetism and catalytic activity As a result, they are ideal for applications in manufacturing semiconductors, catalysts, and optical and luminescent devices.

Such valuable materials can be produced in several ways, for example, by means of chemical or electrochemical reactions of isolation of metal particles from solutions

The primary challenge lies not in the restoration of metal but in preserving its particles, specifically by preventing agglutination and the formation of large metal pieces.

In laboratory settings, metal is deposited onto thin polymeric films designed to capture nano-sized particles This process involves evaporating metal through high-energy methods, which produce these nano-sized particles that need to be preserved Techniques for metal evaporation include using explosive energy, high-voltage electric discharge, or elevated temperatures in specialized furnaces.

Metal-containing nanocomposites can enhance the properties of polymers, allowing them to exhibit valuable characteristics similar to metals For instance, a polyethylene plate infused with minute fractions of palladium demonstrates catalytic properties comparable to those of a pure palladium plate.

Metallic composites, such as packing materials infused with silver, are increasingly utilized for their bactericidal properties Several countries have begun using paints and polymer coatings that contain silver nanoparticles, which are particularly effective in public facilities These applications include wall painting and handrail coatings, enhancing hygiene in shared spaces.

The advancement of polymeric nanocomposite technology focuses on simplifying and reducing the costs of producing composite materials that incorporate nanoparticles As nanotechnology evolves rapidly, innovations that once seemed unattainable are now becoming feasible for commercial application in the near future.

Nanotechnologies are driving advancements in polymeric composite materials, as the growing demand from manufacturers for innovative and high-quality materials encourages scientists to explore solutions at the nanoscale.

The successful mass production of nanomaterials relies heavily on effective collaboration between scientists and manufacturers Today, many applied technological challenges are effectively addressed through strong partnerships between the scientific community and the business sector.

Case Study I

This case study explores the formation of chemical bonds between polymer coating components and carbon metal-containing nanostructures, enhanced with silver or zinc, to improve electrical conductivity in coatings.

The analysis has been conducted by the X-ray photoelectron spectroscopy (XPS) method The XPS allows to investigate an electronic structure, chemical bond, and nearest surrounding of an atom.

The study focused on a specialized automated X-ray electron magnetic spectrometer featuring double focusing capabilities, enabling the analysis of samples in both solid and liquid states This advanced instrument boasts impressive performance specifications, particularly in resolution.

The electron magnetic spectrometer offers several advantages over electrostatic spectrometers, including consistent luminosity and resolution that remain unaffected by electron energy, as well as high spectral contrast Additionally, the X-ray photoelectron spectroscopy (XPS) method is a non-destructive technique, making it particularly valuable for the examination of metastable systems.

Two samples of polymer coatings were studied:

• Silver-containing coating modified with carbon metal-containing nanostructures (70% Ag and 1% nanostructures) and

• Zinc-containing coating modified with carbon metal-containing nanostructures (60% Zn, and 1% nanostructures).

Low-temperature synthesis was used to prepare carbon metal-containing nanostructure samples, which were combined with polyethylene-polyamine (H2N[CH2-CH2-NH]m H, where m = 1–8) through mechanical activation To enhance the interaction between the polymer coating and the nanostructures, silver (Ag) and zinc (Zn) were incorporated The study focused on the C1s, Ag3d, Ag3p, and Zn2p core level spectra, as well as the valence band spectra of the resulting composites, which included carbon metal-containing nanostructures with silver and a polymer coating Reference samples of Ag, Zn, and carbon copper-containing nanostructures were also analyzed Surface cleanliness was monitored using the O1s spectrum, revealing no oxygen presence at 300°C.

The decomposition of spectra into individual components was achieved using a least squares method-based program This process involved inputting the energy positions, widths, and intensities of spectrum components derived from reference samples The peak position accuracy was 0.1 eV, and the error in determining the contrast of the electronic spectra was under 5%.

The C1s-spectrum (Figure 1 (a)) of carbon copper-containing nanostructures consists of three components: С-Cu(283 eV), С-Н (285 eV), and С-О (287 eV).

FIGURE 1 С1s spectrum ((а) С1s spectrum of the copper/carbon nanocomposite, (b) С1s spectrum of the copper/carbon nanocomposite with silver, and (с) С1s spectrum coating) filled by silver and modified by copper/carbon nanocomposite.

The C1s-spectrum analysis of the composite featuring carbon and copper-containing nanostructures functionalized with silver reveals a significant increase in the intensity of the first component, C-Me This change, observed at a binding energy of 283.8 eV, aligns with experimental findings and indicates a greater localization of d electrons in silver compared to copper.

Models illustrate the relationship between multiplet splitting parameters in XPS 3s spectra and spin states Specifically, the relative intensity of multiplet maxima correlates with the magnetic moment of d-metal system atoms, while the distance between these maxima (D) reveals insights into the exchange interaction between the 3s and 3d shells Variations in atomic distance and average atomic volume affect the overlap of these shells Additionally, changes in the shape of the 3s spectra indicate alterations in the chemical bonds of surrounding atoms in the composite.

The analysis of the parameters of the multiplet splitting in the Cu3s and Ag4s spectra shows the presence of the atomic magnetic moments on the copper atoms (1.6 мB,

Copper-containing nanostructures exhibit a notable decrease in the distance between multiplets, highlighting an enhanced chemical bond between copper d electrons and carbon p electrons, leading to the formation of strong covalent bonds In contrast, the presence of a magnetic moment on silver atoms is linked to the formation of non-compensated d electrons, which participate in covalent bonding with carbon atoms.

FIGURE 2 Ag3d spectrum ((а) Ag3d spectrum of the carbon copper-containing nanostructures at interaction with silvera and (b) Ag3d spectrum of coating).

The Ag3d 5/2 and 3/2 spectra of pure silver are composed of two components due to spin-orbital splitting A comparable phenomenon is seen in carbon nanostructures that contain copper and are functionalized with silver.

The complex composite Ag3d spectrum features distinct maxima, with the primary peak representing Ag or Ag-C-Cu Notably, at a distance of 7 eV from this peak, a less intense maximum is observed, which corresponds to the ionic component of the chemical bond between silver and carbon.

The valence band spectra of various nanostructures reveal significant interactions with silver Specifically, the spectrum of the valence band in nanostructures interacting with silver is depicted alongside the spectrum of the valence band coating Additionally, the spectra include that of Ag2O, carbon (C), and pure silver (Ag), providing a comprehensive overview of the electronic properties in these materials.

The analysis of the valence band spectrum of the Ag or Ag-C composite reveals a distinct additional maximum at the Fermi level (E f), indicating the hybridization of Ag4d5s electrons with the 2p electrons from carbon, unlike pure silver This hybridization is further supported by the shape and intensity of the valence band around 7 eV, which aligns with the presence of the Ag-C-O component, corroborated by similarities with the valence band maxima of pure graphite and oxygen density of states calculations.

The rise in the density of states at the Fermi level (E f) enhances the electron density within the polymer composite, resulting in improved electrical conduction This phenomenon is comparable to the behavior observed in Ag2O, which is essential for enhancing conductivity and is a crucial component in the production of conductive glass.

The data on the measurement of electrical resistance show that when 1% carbon metal-containing nanostructures is added in polymer, the electrical resistance decreases from 10 –4 down to 10 –5 Ω cm.

It is shown that nanomodification of the argentum-containing polymer coating im- proves the electrical conduction in it by one order of magnitude.

The X-ray photoelectron spectroscopy analysis of the nanomodified composite reveals the formation of covalent bonds between Ag, C, and Cu atoms, alongside an increase in electron density at the Fermi level, attributed to the hybridization of C2p and Ag4d5sp electrons.

Case Study II

Modifying functional groups in protein macromolecules is a key strategy in biotechnology for pharmaceuticals Ensuring virus protection in plasma-based pharmaceutical preparations is a critical global challenge It is essential to identify albumin modifiers that are safe and do not adversely affect the human body.

This study aims to uncover the patterns in the energy spectra formation of electrons and to analyze the chemical bonds between protein atoms and a modifier using X-ray photoelectron spectroscopy This approach will guide the research towards enhancing protein stability and selecting the most effective modifier for albumin.

The X-ray photoelectron spectroscopy (XPS) method has been selected for its non-destructive nature, distinguishing it from ion and electron beam techniques An X-ray electron magnetic spectrometer offers several advantages over electrostatic spectrometers, including constant luminosity, resolution that is independent of electron energy, and high spectral contrast Furthermore, the design of the magnetic energy analyzer, which is separated from the spectrometer's vacuum chamber, allows for varied sample treatment in vacuum during spectrum acquisition.

The method for decomposing X-ray photoelectron spectra into individual components has been developed to identify spectral parameters that indicate the stabilization transition of protein atoms.

• The development of the method for the determination of the temperature of the protein change and the establishment of a criterion for structural transitions

• The investigation of the spectra of ordinary and compound amino acids with the purpose of the interpretation of the protein C1s, O1s, and N1s spectra.

• The study of the formation of the chemical bond between the atoms of protein and modifiers, namely, copolymers, super-dispersed particles of d metals and carbon metal-containing nanoforms.

• The study of the influence of the degree of the modification of protein with polymer (vinyl pyrrolidone–acrolein diacetal copolymer) on the protein thermal stability.

• The study of the influence of the protein modification on the protein thermal stability

• The selection of an optimal modifier for protein, which would provide the best protein thermal stability.

This study focuses on the investigation of native and modified proteins, specifically examining the modification of proteins with carbon metal-containing nanostructures and functional sp groups to enhance their interaction with the environment The research utilizes NiO super-dispersed powder and vinyl pyrrolidone–acrolein diacetal copolymer, with temperature variations ranging from room temperature to 623K The carbon metal-containing nanostructures consist of multilayer nanotubes that form on metal particles through carbon atom penetration and adsorption Samples were synthesized using a low energy method involving polymers and metal systems, employing 3D metals like Cu and Ni in oxide and super-dispersed particle forms To boost synthesis activity, ammonium polyphosphate's functional sp elements were incorporated The study aims to elucidate the formation of specific bionanostructures and their properties through an analysis of interatomic interactions and the hybridization of d electrons from metal atoms with p electrons from sp element atoms.

The C1s, O1s, and N1s core level spectra of both native and modified albumin were analyzed across temperatures ranging from room temperature to 573°C To explore the atomic states of carbon, oxygen, and nitrogen, reference samples including amino acids (glycine and histidine), copolymers, carbon metal-containing nanostructures, and super-dispersed metal particles were examined, utilizing data on the electronic structures of graphite and hydrocarbons.

Figure 4 shows the X-ray photoelectron 1s spectra of carbon and nitrogen taken from glycine and albumin samples at room temperature.

FIGURE 4 The X-ray photoelectron C1s and N1s spectra of glycine (a), histidine (b), and albumin (c) at 300K.

At room temperature, the C1s spectrum of glycine reveals three components associated with different carbon atom environments: C-H at 285 eV, CH-NH at 286.5 eV, and COOH at 290.1 eV Similarly, the N1s spectrum of glycine shows two components linked to distinct nitrogen atom surroundings: CH-NH at 398.5 eV and N-O at 401 eV In contrast, the C1s spectrum of histidine comprises four components reflecting various carbon atom environments: C-C at 283.5 eV and C-H at 285 eV.

The study analyzes the X-ray photoelectron spectroscopy (XPS) of histidine and albumin, revealing distinct spectral components for nitrogen and carbon bonds The histidine N1s spectrum shows two components: CH-NH at 398.5 eV and N-O at 401 eV, indicating different nitrogen environments Similarly, the albumin C1s spectrum consists of four components: C-C (283.5 eV), C-H (285 eV), CH-NH (286.5 eV), and COOH (289.1 eV), with a satellite peak at 306 eV confirming the presence of C-C bonds The N1s spectrum of albumin displays nitrogen bonds with hydrogen (N-H) and oxygen (N-O), suggesting potential oxidation of the protein on the surface Notably, as the temperature exceeds 350 K, significant changes occur in the spectra, with the C1s spectrum revealing new contributions from C=O (287.1 eV) while the CH-NH and COOH components disappear, indicating sample decomposition The N1s spectrum also reflects this change, ultimately consisting of a single N-O component at 401 eV.

The oxidation of proteins leads to their degradation, as evidenced by the presence of carbonyl groups (C=O), which indicate the extent of protein destruction The concentration of these carbonyl groups correlates with the degree of damage, while the formation of C-C bonds suggests the partial breakdown of C-H bonds Analysis of the X-ray photoelectron spectra reveals the presence of NH components in the N1s spectrum and COOH in the C1s spectrum, confirming the existence of proteins Conversely, the absence of these components, along with an increase in N-O and C=O bonds, signifies oxidative protein degradation Additionally, the amino groups of glycine, histidine, and albumin exhibit similar behavior with temperature variations.

FIGURE 5 The X-ray photoelectron C1s and N1s spectra of albumin––(a) T = 300 K and (b)

The study focuses on the vinyl pyrrolidone–acrolein diacetal copolymer, which comprises 84% vinyl pyrrolidone and 16 mol% acrolein diacetal X-ray photoelectron spectroscopy was utilized to analyze the C1s and N1s spectra of the copolymer at room temperature and upon heating to 473K At room temperature, the C1s spectrum reveals three distinct components associated with various carbon atom environments: C-H at 285 eV, N-CH at 287.3 eV, and COOH at 290.1 eV As the temperature rises to 373K, further analysis is warranted to observe the changes in the copolymer's structure.

K, the contribution of the COOH component decreases in the carbon spectra and the components C-H (285 eV) and N-С (N-CH) (287.3 eV) remain At the temperature above 473, the component С=O (287.1 eV) appears in the C1s spectrum At room temperature and at the temperatures up to 373K the N1s spectrum consists of two components N-C (397 eV) and N-O (401 eV) and at the temperature above 373K there is one component N-O (401 eV) in the N1s spectrum.

FIGURE 6 The X-ray photoelectron C1s and N1s spectra of (a) albumin, (b) vinyl pyrrolidone– acrolein diacetal copolymer, and (c) conjugate.

The C1s spectra comparison at room temperature reveals distinct differences among albumin, vinyl pyrrolidone–acrolein diacetal copolymer, and the albumin modified with the copolymer (conjugate) Notably, the conjugate formed from albumin and vinyl pyrrolidone–acrolein diacetal copolymer exhibits unique spectral characteristics, indicating a specific interaction at the prepared ratio.

1:5, there are three components characteristic of albumin, that is С-С (283.5 eV), С-Н

The study investigates the binding energies of various components in a vinyl pyrrolidone–acrolein diacetal copolymer and its conjugate with albumin, highlighting key values such as 285 eV for COOH and 290.1 eV for another component, along with 286.8 eV for the CH-N bond The N1s spectra reveal characteristic components of both albumin and the copolymer in the conjugate, indicating stronger C-N bonds that enhance thermal stability compared to albumin alone The thermal stability of the conjugate was analyzed based on different modification degrees of albumin with the copolymer in ratios of 1:1, 1:3, and 1:5, with XPS method employed to study the C1s and N1s spectra of all samples.

FIGURE 7 The X-ray photoelectron C1s spectra of protein modified with vinyl pyrrolidone– acrolein diacetal copolymer in the ratios––(a) 1:1, (b) 1:3, and (c) 1:5.

The C1s spectrum of the 1:1 sample of vinyl pyrrolidone–acrolein diacetal copolymer and albumin reveals three components: C-C, C-H, and C=O Meanwhile, the N1s spectrum shows a single component, N-O, with the absence of N-H and COOH contributions typically associated with proteins at room temperature.

In the analysis of a sample comprising protein and vinyl pyrrolidone–acrolein diacetal copolymer in a 1:3 ratio, the C1s spectrum reveals peaks associated with C-C, C-H, C-NH, and COOH bonds Additionally, the N1s spectrum displays maxima indicative of C-NH, NH, and N-O bonds These findings confirm the presence of N-H and COOH components, which are characteristic of protein.

Case Study III

For years, enhancing the mechanical properties of structural materials primarily relied on developing new alloys with innovative chemical and phase compositions Recently, alternative methods have emerged, focusing on the targeted formation of micro- and nanocrystalline structures However, the range of experimental techniques available for studying the chemical structure of carbon cluster nanostructures is limited Consequently, a key objective is to advance diagnostic methods that enable the monitoring of both intermediate and final outcomes in the creation of new materials.

Current analysis of carbon nanostructures primarily utilizes classical techniques such as transmission electron microscopy, electron diffraction, and Raman spectroscopy to determine their shapes, sizes, and compositions However, there is a growing trend in the literature towards employing X-ray photoelectron spectroscopy (XPS) for the investigation of these nanostructures The continued advancement of the XPS method and related surface analysis techniques, which focus on depths ranging from 1 to 10 nm, is expected to expand the array of methods available for studying the compositions, electronic properties, and structures of nanostructures.

X-ray Photoelectron Spectroscopy (XPS) is an effective technique for analyzing carbon structures, providing insights into the electron configuration, chemical bonding, and atomic environment A key advantage of XPS is its non-destructive nature, as the X-ray radiation used for photoelectron excitation typically does not damage most materials This contrasts with surface analysis methods that rely on ion or electron bombardment, which can alter the sample Consequently, samples analyzed with XPS can often be utilized for additional investigations afterward.

The X-ray photoelectron spectroscopy (XPS) method is crucial for analyzing thin layers and films, particularly in the formation of fullerenes, nanotubes, and nanoparticles, while providing insights into the chemical composition and purity of materials through spectral data Utilizing an X-ray photoelectron magnetic spectrometer, XPS enables the investigation of electron structures, chemical bonds, and atomic environments Automated control systems in these spectrometers match the performance of leading foreign models XPS is preferred over electrostatic spectrometers due to its superior spectrum contrast, consistent optical efficiency, and resolution that remains unaffected by electron energy, making it a valuable non-destructive analysis technique.

This study investigates iron powder samples modified with fullerenes or graphite, utilizing the XPS method for analysis The samples were prepared through two techniques: fusion and pressing, aimed at creating nano-carbon structures within metal matrices to enhance material strength X-ray diffraction confirmed that the predominant structure of the samples was face-centered cubic (fcc) iron, with detailed descriptions provided in Table 1.

Sample No Sample composition Sample form

The X-ray photoelectron investigations were carried out for studying the changes in the nearest environment of the carbon atoms in the samples prepared in different ways.

The investigations were carried out using the X-ray photoelectron magnetic spectrometer with double focusing and instrumental resolution of 0.1 eV at the excitation of AlKa-lines (1486.6 eV).

In the XPS investigations of carbon-metal cluster nanomaterials, the identification of C1s spectra was achieved through the analysis of satellite structures Reference samples were examined, including carbon components that produced the C1s spectrum such as C-H hydrocarbons, C-C (sp²) graphite, and C-C (sp³) diamond The parameters of the spectra, including binding energy (E_b), satellite position energy (E_sat), satellite intensity (I_sat), and the intensity of the main maximum (I₀), are detailed in Table 2.

TABLE 2 The C1s spectra parameters for reference samples

The C1s spectra of carbon nanostructures were analyzed to identify the structures studied in reference [6] These nanostructures were produced through the electric arc method during the sputtering of graphite electrodes, resulting in the formation of fullerenes (C60), single-walled and multi-walled carbon nanotubes, as well as amorphous carbon.

The C1s spectra exhibit a satellite structure linked to various phenomena, including shake-up processes and characteristic losses such as plasmons, facilitating a calibration technique that enables the determination of both energy positions and intensities of components Notably, in the C1s spectrum of fullerenes like C60, a satellite appears at a binding energy of 313 eV, with a relative intensity of 15% compared to the main peak, which is indicative of the sp² hybridization of carbon atom valence electrons.

The C1s spectrum of single-walled carbon nanotubes reveals a gradual increase in the high-energy region, alongside two distinct satellite peaks indicative of C-C bonds with sp² and sp³ hybridization of carbon's valence electrons In one-layer nanotubes, these components appear at binding energies of 284.3 eV and 286.1 eV, with intensity ratios of 1:0.1 and 1:0.15, and a width of 1.8 eV The ratio of sp² to sp³ hybridized C-C bonds is 2, a trend also observed in the C1s spectrum of multi-walled carbon nanotubes.

In the amorphous carbon spectrum, a satellite feature at 313 eV indicates sp³ hybridization of valence electrons, with a relative intensity of 15% The C1s spectrum reveals a component related to C-C bonds with sp³ hybridization, positioned 27 eV from the satellite This suggests that amorphous carbon contains carbon inclusions resembling globe-shaped graphite Developing a calibration method for X-ray photoelectron spectra of reference samples enables the decomposition of the C1s spectrum to identify chemical bonds, hybridization types of carbon's s-p valence electrons, and the surrounding environment of carbon atoms Analyzing nanoparticles with known structures facilitates the identification of carbon structures through the examination of C1s spectrum shapes.

The C1s spectra identification method developed by us was successfully used for the investigation of nanostructures in the iron matrix.

The XPS method was employed to analyze the C1s, O1s, and Fe2p spectra, revealing significant amounts of adsorbed oxygen and iron oxides on the sample surfaces The Fe2p spectra indicate the presence of an oxidized iron layer, while no spectral shifts were observed during the experiment The experimental C1s line spectra for samples №1 and №2 are illustrated in Figure 9 (a) and (b).

FIGURE 9 The experimental C1s spectra of samples №1 (a) and №2 (b).

The mathematical treatment of the C1s spectra was performed that is the back- ground subtraction and the procedure of the spectra smoothing and decomposition The results are given in Figure 10.

FIGURE 10 The X-ray photoelectron C1s spectra obtained from samples №1 (a) and №2 (b) after the spectra were decomposed into their components.

The X-ray photoelectron spectrum of the C1s line from sample №1, collected without heating in the spectrometer chamber, reveals two satellites indicative of sp² and sp³ hybridization of carbon's valence electrons, corresponding to binding energies of 306.0 eV and 313.0 eV Analysis of the C1s spectrum, as shown in Table 2, identifies components associated with C-C (sp²) and C-C (sp³) bonds at approximately 22 eV and 27 eV, respectively The intensity ratio of C-C (sp²) to C-C (sp³) bonds is about 2, which is typical for carbon nanostructures Additionally, the spectrum includes components representing C-H and C-O bonds, indicating the presence of surface contaminants.

Upon heating the sample, the C-C bonds break due to the sp³ hybridization of the carbon atoms' valence electrons Continued heating reveals a component in the C1s spectrum that indicates the presence of Fe-C bonds.

In addition, at heating, the Fe2p spectra are observed on the sample surface, which is indicative of the fact that the sample surface is being cleaned during heating.

In Figure 10 (b), the C1s spectrum is displayed, which is obtained from sample

In the spectrometer chamber without heating, a satellite at approximately 306.0 eV indicates sp² hybridization of carbon's valence electrons The C1s spectrum reveals a component at around 22 eV associated with C-C bonds exhibiting sp² hybridization, alongside components representative of C-H and C-O bonds.

The X-ray photoelectron investigations of samples 3, 4, 5, and 6 show that the C1s spectra do not have a satellite and they have low intensity Thus, only hydrocarbon contaminations are present on the surfaces of these samples.

Case Study IV

Understanding the mechanisms behind modified cast irons and steels, as well as the factors contributing to the formation of ordered phases, is crucial for developing new materials with improved performance characteristics.

Despite extensive theoretical and experimental research on nanostructures, a unified model to explain the structure and properties of steel and cast iron samples remains elusive Additionally, the range of experimental techniques available for analyzing the atomic-level chemical structure of nanostructures is quite limited.

This study investigates industrial samples of nano-modified cast irons and steels using X-ray Photoelectron Spectroscopy (XPS) on an EMS-100 photoelectron magnetic spectrometer with double focusing XPS enables the analysis of electronic structures, chemical bonds, and local atomic environments The selection of a photoelectron magnetic spectrometer is based on its significant advantages compared to traditional electrostatic spectrometers.

X-ray Photoelectron Spectroscopy (XPS) offers consistent light power and precise measurements regardless of electron energies, along with exceptional spectral sharpness This non-destructive technique is especially valuable for studying metastable systems.

The study focused on the analysis of cast iron samples produced through rotary casting, enhanced with modified aluminum doping agents, alongside samples of 08X18N10T steel Additionally, the research included the examination of nonmagnetic stainless modified nanostructures of 08X21G11AN6 steel, which incorporated carbon and nitrogen as significant elements.

The chemical composition of the samples is shown in Table 3.

TABLE 3 Results of chemical analysis

C Mn Si Cr Ni Cu Al N

Modified cast iron 3.06 0.55 2.07 0.27 0.12 0.30 1.40 0.01 Stainless steel 0.08 1.20 0.50 18.10 9.85 0.25 0.10 0.01 Modified stainless steel 0.05 10.84 0.36 20.98 5.39 0.09 0.01 0.61

Experiments were conducted using an EMS 100 automatic X-ray photoelectron magnetic spectrometer, achieving a resolution of 10⁻⁴ and a luminosity of 0.185% The study focused on the inner energy levels of Fe2p, Al2p, C1s, and O1s, with signal accumulation times ranging from 3 to 30 seconds per spectrum point Surface purity was assessed through C1s and O1s spectra, and spectral decomposition utilized software based on the least squares method Key parameters such as energy status, spectral width, and intensity were analyzed and compared with reference spectra Decomposition employed a Gaussian function to ensure optimal fitting of the experimental curve, achieving peak position accuracy of 0.1 eV and a maximum error of 5% in determining spectral sharpness.

The analysis of the C1s spectrum focused on understanding the chemical bonds, sp hybridization of valence electrons, and the local atomic environment of carbon atoms This was achieved by examining reference spectra, including C–C (sp²) graphite, C–C (sp³) fullerene, and C–H hydrocarbons.

Figure 11 shows the С1s spectra of carbon in the ordinary and modified cast irons

FIGURE 11 C1s spectra of carbon in (a) ordinary and (b) modified cast iron.

The spectra of the samples exhibit a shift of 1.7 eV towards each other, indicating that the C1s energy level in ordinary cast iron is similar to that in the Fe3C spectrum and the C–C bond in graphite, suggesting comparable bonding between carbon and iron All investigated samples contained hydrocarbon and adsorbed oxygen impurities due to exposure to air In modified cast iron, the C1s energy values align with those of diamond, indicating the formation of diamond-like structures with an sp3 electron configuration in the carbon atoms The C1s spectra of C60 carbon nanostructures, produced via electric arc diffusion of the carbon electrode, revealed a satellite peak at 313 eV with 15% intensity relative to the main peak, characteristic of sp3 hybridization Additionally, satellite peaks in graphite and diamond spectra were observed at 22 eV and 27 eV, respectively, with relative intensities of 10% and 15%.

The values of the bond energies of the electrons of the Fe2p line of the cast iron samples are shown in Table 4.

TABLE 4 Values of electron bond energies of inner bonds

Substance Energy level, eV C1s energy level

In contrast to the spectra of pure iron and like Fe 3 C in highly carbon phase, the Fe2p spectra have no clear features.

Figure 12 presents the XPS spectrum of a C1s line obtained from the surface of the modified steel sample

Two satellites in the high-energy region indicate the presence of sp2 (306.0 eV) and sp3 (313.0 eV) hybridizations of carbon's valence electrons The C1s spectrum reveals components associated with C–C (sp2) and C–C (sp3) bonds, observed at approximately 22 eV.

The intensity ratio of the main maximum of C–C (sp²) to C–C (sp³) bonds is approximately 2, highlighting a characteristic of carbon structures Additionally, the spectral components of C–H and C–O bonds suggest surface contamination The findings indicate that the produced steel exhibits 1.5 to 3 times greater durability while maintaining or enhancing plasticity.

TABLE 5 Mechanical properties of samples

Sample Yield limit, σ 0.2 , kgf/mm 2 Breakdown limit, σ t , kgf/mm 2 Relative elongation, δ, %

Iron and aluminum atoms exhibit distinct properties in cast irons and steels Aluminum, known for its high chemical activity, acts as a powerful reductant in these materials, effectively interacting with oxygen and attracting it towards itself.

The high carbon phase is crucial for the structural formation of cast iron and steel, particularly in triple Fe–Al–C alloys, where a significant qualitative change occurs In addition to the two known high carbon phases, graphite and cement carbide, unique carbon types such as spherical graphite and the Fe–Al phase emerge in these alloys Aluminum atoms preferentially interact with carbon at crystal faces with available free bonds, which inhibits the spread of graphite along the base planes and slows down graphitization This interaction fosters transverse crystal growth and leads to the development of compact spherical graphite inclusions These findings are supported by optical microscopy, as illustrated in the accompanying microstructure photographs.

During the production of modified iron through rotary casting and aluminum alloying, direct Fe–Al and C–C bonds with sp³ hybridization of valence electrons begin to form This process introduces new structural elements in the electron spectra, distinguishing it from traditional cast irons that primarily exhibit Fe–Si and C–C bonds with sp² hybridization The incorporation of aluminum significantly enhances the durability of cast irons due to the stronger interatomic interactions of Fe–Al bonds compared to Fe–Si bonds, resulting in the formation of hybrid 3d(Fe) and 3p(Al) bonds.

FIGURE 13 Graphite in modified and non modified cast iron.

The process of modifying cast iron with aluminum facilitates the transfer of aluminum valence electrons to graphite atoms, resulting in the creation of a proportion of atoms that exhibit more energetically stable, diamond-like sp3 hybridization of electrons.

Investigations into iron modified by fullerene have shown that carbon nanostructures on the surface enhance durability Carbide nanostructures are not present in steels alloyed with metals such as vanadium, chromium, and manganese, which are instead alloyed with nitrogen Nitrogen is the most effective hardener among the incorporated elements in solid alloys, as nitrides separate more easily than carbides Additionally, nitrogen exhibits high solubility in solid alloys of the Fe–Cr system due to its strong austenite-forming properties.

Key Concepts and Basic Criteria

Nanostructures play a crucial role in self-organization processes, primarily influenced by their surface energy, which determines their interaction with the environment As particle size diminishes, both surface energy and activity increase significantly To assess this activity, the ratio a = ε S /ε V is proposed, highlighting the relationship between surface and volumetric energy.

Where, ε S ––nanoparticle surface energy and ε V ––nanoparticle volume energy.

In this scenario, the surface energy (ε S) significantly exceeds the volume energy (ε V) due to the higher defectiveness of the surface compared to the volume of the nanoparticle To analyze the relationship between activity, size, and shape, we define ε S as ε S °––S and ε V as ε V °––V, where ε S ° represents the average energy of a surface unit (S) and ε V ° denotes the average energy of a volume unit (V).

Then the Equation (1) is converted to: a = dãε S °/ε V ° · S/V, (2)

The ratio of surface area (S) to volume (V) for various nanostructure shapes highlights the relationship between the number defined by the nanostructure's geometry and its linear dimensions, specifically the radius or thickness.

The Equation (3) can be given as: a = dãε S °/ε V ° · N/r(h) = ε S °/ε V ° 1/B (3)

Where, B equals r(h)/N, r––radius of bodies of revolution including hollow ones, h–– film thickness depending upon its “distortion from plane”, and N––number varying depending upon the nanostructure shape

The parameter d characterizes the thickness of the nanostructure's surface layer, while the energies of surface and volume units are influenced by the nanostructure's composition For bodies of revolution, parameter B indicates the effective range of linear sizes that affect activity within a specified interval of 1 to 1000 nm Table 6 illustrates this for spherical and cylindrical bodies In the case of nanofilms, both surface and volume properties are determined by the degree of defectiveness and the conformational changes based on crystallinity Notably, the ability to alter nanofilm shapes in response to medium activity surpasses that of pre-formed nanostructures Additionally, the size and defectiveness of formed nanofilms, including surface disruptions and cracks, play a crucial role.

TABLE 6 Changes in interval B depending upon the nanoparticle shape

Nanostructure shape Internal radius as related to the external radius

The nanosized interval (B) serves as a key parameter for demonstrating the activity of nanostructures, which varies based on the internal wall structure and composition of nanoreactors, as well as their shape and size A proposed correlation between surface energy—factoring in the thickness of the surface layer—and volume energy can effectively measure the activity of nanostructures, nanoreactors, and nanosystems.

The relative dimensionless activity value (A) of nanostructures and nanoreactors can be assessed by analyzing the differences between the modules of surface and volume energies in relation to their total sum.

If ε S °d/ε V ° ≈ 1, the equation for relative activity value is simplified as follows:

If we accept the same condition for a, the relative activity can expressed via the absolute activity:

At the same time, if a >>1, the relative activity tends to 1

Nanoreactors are nanosized cavities, often nanopores within various matrices, utilized for producing specific nanoproducts Their primary function is to facilitate the formation of the "transition state" of activated complexes, allowing for the transformation into nanoproducts with minimal activation energy loss The progress and direction of this process are significantly influenced by the entropic factor in the Arrhenius equation, which relates to the statistical sums and the activity of the nanoreactor's walls and participating components.

The surface energy of nanostructures is defined as the total contribution from various motion types occurring in the surface layer, including forward motion (ε fm), rotation (ε rot), vibration (ε vib), and electron motion (ε em) This can be expressed mathematically as ε S = Σ(ε fm + ε rot + ε vib + ε em).

The assignment of values to nanostructure components is influenced by their nature and the surrounding medium As nanostructures decrease in size and quantity, the surface energy vibration component tends to increase, particularly in high-viscosity media Smaller nanostructures facilitate stabilization of electron motion, resulting in reduced energy levels and a diminished likelihood of coordination reactions with medium molecules Consequently, the vibration component of surface energy aligns closely with the total surface energy.

Nanostructures created within polymeric matrix nanoreactors can act as oscillators with high oscillation frequencies Notably, fullerenes and nanotubes exhibit absorption characteristics in the wave number range of 1300–1450 cm⁻¹ These wave numbers translate to frequencies between 3.9 and 4.35 × 10¹³ Hz, aligning with ultrasound frequency ranges.

When a nanostructure is placed in a medium that restricts its translational or rotational motion, allowing only oscillatory movement, its surface energy can be approximated as its vibrational energy This relationship can be expressed mathematically as ε S ≈ ε v = mυ v² /2, where m represents the mass of the nanostructure and υ v denotes the velocity of its vibrations.

Knowing the nanostructure mass, its specific surface and having identified the surface energy, it is easy to find the velocity of nanostructure vibrations: υ v = √2ε v /m (9)

To ensure the preservation of nanostructure vibrations, it is crucial that the amplitude of these oscillations remains within the limits of their linear nanosize, specifically where the wavelength (λ) is less than the radius (r) Consequently, the frequency of nanostructure oscillations can be calculated using the formula: ν v = υ v / λ.

Therefore, the wave number can be calculated and compared with the experimental results obtained from IR spectra

However, with the increasing of nanostructures numbers in medium the action of nanostructures field on the medium is increased by the inductive effect.

The reactivity of nanostructure or the energy of coordination interaction may be represent as: Σε coord = Σ[(μ ns ãμ m )/r 3 ] (11) and thus, the activity of nanostructure: a = {[ε vib + Σ[(μ ns ãμ m )/r 3 ]}/ε V (12)

When ε vib → 0, the activity of nanostructures is proportional product μ ns ãμ m , where, μ ns ––dipole moment of nanostructure and μ m ––dipole moment of medium molecule.

Materials Modified by Nanostructures

The definition of nanomaterials and nanocomposites is currently challenging due to the inherent complexities of the terms The prefix "nano" indicates that these materials possess small-dimensional characteristics, while "material" refers to a macroscopic context Unlike a pure substance, a material has a heterogeneous or heterophase composition, complicating the classification and understanding of nanomaterials.

Nanomaterials are defined as nanoparticles or aggregates of nanoparticles with unique properties essential for applications in fields like nanoelectronics and nanomachine building By utilizing UV-laser radiation, active nanoparticles can be interconnected to form spatial structures, which are then compacted using pulse electrostatic or electromagnetic fields This process leads to the creation of materials known as nanomaterials, which may not entirely replicate the characteristics of the individual nanoparticles When nanoparticles vary in nature, the resulting material is referred to as a nanocomposite, a term that encompasses a broader range of macroheterophase materials made from two or more distinct components with differing physical or mechanical properties Composites typically consist of multicomponent and multiphase materials that combine mineral and organic substances, often polymers, to achieve unique characteristics The definition of nanocomposites is similarly complex, with examples including fullerenes and nanotubes filled with various materials, which also provide insights into the capillary properties of these structures.

Nanotubular composites consist of intercalated nanotubes or thread-like bundles of nanotubes arranged in ordered layers, combined with various matrix materials The term "nanocomposite" traditionally encompasses heterogeneous nanostructures, including those with encapsulated nanoparticles or nanocrystals Nanoparticles refer to nanoformations that lack a strict internal order Additionally, larger structures such as gigantic tubules and fullerenes, which may contain multiple spheres or tubes filled with different microphases, can be described using terms like "onions" or "beads."

The formation of extensive structures like tubules or nanofibers can lead to their interlacing into nets or braids, with particles from other components and phases situated between them These mixtures, despite having the same composition, can be classified as nanocomposites due to their varying shapes and structures Changes in shape and ordering can alter the properties of nanoparticles, affecting their surface energy and interaction potentials compared to homogeneous nanoparticles This concept aligns with established principles in polymeric, ceramic, and metallic composites Unique multiphase materials can be developed through mechanical-chemical processes, such as monoaxial pulling of polymer melts, resulting in alternating crystalline and amorphous regions Additionally, the presence of other components that can form diverse nanophases enhances the capabilities of the resulting nanocomposite.

Nanophase refers to a homogeneous segment of a nanosystem, distinguished by physical boundaries at the nanometer scale from other similar segments While the properties of different nanophases may exhibit minimal differences, this phenomenon is driven by the system's tendency to minimize total energy.

Recent research has increasingly focused on nanocrystals and nanoclusters, expanding the definition of "cluster" to include particles with nuclei and nonmetallic components with varying energy and composition The stability of nanoclusters is primarily determined by their shape and surface characteristics While nanoclusters can sometimes be synonymous with nanocrystals lacking protective shells, they can be classified based on crystalline structure, composition, size, and form Notably, the term "cluster" refers to a group of chemical particles, and advancements now allow for the production of clusters with a specific number of atoms These small particles exhibit unique structures and properties that differ significantly from larger crystal volumes, with even minor atom removal leading to substantial property changes Clusters can range from aggregates of 2 to 10,000 atoms, including weakly bound condensed molecules The distinction between nanoclusters and nanocrystals lies in the strength of the bonds; nanoclusters have weaker interactions, while nanocrystals possess a crystalline lattice that enhances bond strength Additionally, nanoclusters can consist of uniform elements, such as carbon or metals, with noble metal nanoclusters typically containing fewer atoms than those formed from more reactive elements.

FIGURE 14 Nanoclusters of elements given according to the decrease of electronegativity of metals––(а) gold, (b) silicon, and (c) aluminum.

The arrangement of elements based on their activity in redox processes is as follows: Au < Si < Al Notably, gold nanoclusters contain the fewest atoms, with a composition of just 6 atoms (c Au = 2.54, according to Polling), while silicon nanoclusters consist of 7 atoms (c Si = 1).

Nanoclusters exhibit diverse geometric structures based on their atomic composition, such as gold forming six-term rings, silicon creating pentagonal pyramids, and aluminum forming icosahedral shapes with 13 atoms The minimum number of atoms in a nanocluster is influenced by the size of the components and their aggregation capabilities Elements from the second period, like carbon, demonstrate higher activity, resulting in smaller stable clusters, such as a six-term ring with 32 atoms Silicon, similar to carbon, can form stable three-term rings, while phosphorus can create four-term rings Clusters are categorized by the number of atoms or valence electrons involved in their formation, with group 1 elements consistently forming clusters with even numbers of valence electrons Cluster stability is determined by the electron composition and the external potential of the surrounding medium Neutral clusters can be converted into ionic forms to enhance stability, leading to classifications including neutral clusters, cluster anions, and cluster cations, which are studied using photoelectron spectroscopy For metallic clusters, stable electron shells are observed at odd numbers of atoms, such as in Cu7, where the p orbital is fully filled, and similar complete filling occurs in d orbitals for certain clusters.

Cu 17 For clusters cations the increase in stability at odd number of atoms in a cluster is seen For instance, spherically asymmetrical particles of single-charged silver cations have the following numbers of atoms 9, 11, 15, and 21 The stability of nanoclusters and nanocrystals increases when the changes decreasing the cluster surface energy are introduced into the electron structure, this can be done when other atoms interacting with atoms “hosts” are introduced into the cluster, or the protective shell is formed on the cluster, or the cluster is precipitated on a certain substrate that stabilizes the cluster Thus, clusters and nanocrystals can be classified by the stabilization method Formation of clusters and nanocrystals on different surfaces is of great interest for researches There is the phenomenon of epitaxy was mentioned, when the formation of or change in the structure of clusters proceed under the influence of active centers of surface layer located in certain order, thus contributing to the minimization of surface energy The introduction of a certain structure of nanocrystals into the substrate surface layer results in the changes of nanoparticle electron structure and energy of corresponding active centers of surface layer providing the decrease of surface energy of the system being formed Since nanocrytsals have a rather active surface, their application to the substrate should proceed under definite conditions that could not considerably change their energy and shape However, depending upon the energy accumulated by a nanocrystal (nanocluster), even at identical element composition different results in morphology are achieved The influence of substrate increases due to the dissipation energy brought by the cluster onto the substrate surface (Figure 15)

FIGURE 15 Morphology of cluster-assembled films created on Mo (100) surface as a function of the cluster energy––(a) 0.1 eV/atom, (b) 1 eV/atom, and (c) 10 eV/atom.

Increasing nanoparticle energy from 0.1 eV to 10 eV significantly alters the formation of thin films, resulting in finer mixing of Mo clusters on a molybdenum (100) surface This morphology is also observed in various systems, including manganese clusters on silicon (111) surfaces covered with fullerenes C60, gold clusters on gold (111) surfaces, and cobalt and nickel clusters on glass In certain instances, the nanocrystals formed on surfaces merge to create stable dendritic or star-like structures consisting of hundreds of atoms Figure 16 illustrates these nanostructures of antimony on a graphite surface.

FIGURE 16 The tunnel electron microscopy (TEM) images of islands formed by similar doses of Sb clusters on HOPG at 298K (a) and 373K (b).

The "Island" structure consists of clusters of antimony containing 2,300 atoms These nanostructures are less pronounced on amorphous carbon and are influenced by both the substrate material and the number of atoms within the cluster.

When the number of atoms in antimony cluster goes down, the nanostructures formed join to a lesser extent and represent “drop-like” formations

FIGURE 17 The scanning transmission electron microscopy (STEM) images of islands formed by the deposition of different-sized Sb clusters on amorphous carbon––(a) Sb 4 , (b) Sb 60 , (c) Sb 150 , and (d) Sb 2200

The morphology of "islands" shifts from spherical to various shapes as the size increases from 4 to 2200 atoms In transition metals, the critical size required for the formation of branched nanostructures is significantly smaller compared to alkaline metals Additionally, thin films made from silver clusters containing fewer than 200 atoms exhibit specific junctions.

The morphology of formed structures can evolve over time, diverging from their original state This phenomenon is akin to Ostwald's maturation in polymer chemistry, where nanoparticles coalesce into larger formations.

Research on metallic and shifted nanocrystals is closely linked to the study of carbon-based nanoclusters, including metal carbides Nanocrystals can be categorized into one-, two-, and multi-element structures, with stability increasing in multi-element configurations The combination of active and passive elements based on redox potentials enhances the stability of these multi-element clusters Notable examples include clusters like Co/Cu, (Fe-Co)/Ag, Fe/Au, and Co/Pt, many of which are stabilized by protective shells made of oxides, carbides, or hydrides, such as Al2O3.

Sm 2 O 3 , SiO 2 , CO, Met x C y , and B 2n H 2n

Thus, clusters and nanocrystals can be classified based on the composition of the shell and nucleus, alongside with their evaluation based on size and shape

Nanocrystals are categorized based on the type of "superlattice," with an overview highlighting the classification of nanoclusters and nanosystems according to their production methods Notably, carbon clusters, such as fullerenes and tubules, hold a significant position, especially when metals or their compounds are intercalated within them Comprehensive insights have been gained through both theoretical and experimental studies of fullerene C60 filled with alkaline metals.

Definitions

In the fields of physics and chemistry concerning material surfaces, key concepts such as "surface," "interface layers," and "boundary layers" continue to spark debate Numerous round-table discussions, workshops, and conferences are held to evaluate these terms and analyze the appropriateness of their application.

When studying surfaces, we refer to a mathematical concept that represents geometrical spaces dividing different phases, although a surface cannot simply be illustrated as a line due to inherent irregularities at the boundaries of gas, liquid, and solid phases caused by energy fluctuations The physics of surfaces indicates that chemical particles at the surface interact with both solid or liquid particles and gas or liquid molecules in contact with the material To accurately assess the properties, structure, and composition of surface layers, which vary in thickness from 1 nm to 10 nm depending on the material type (conductor or dielectric) and the depth of influence on the inner layers, one must consider the morphology shaped by the material's formation and characteristics Surface energy is typically evaluated through the contact angles of wetting, where molecules within a 1 nm thick layer contribute to the overall surface energy, diminishing the influence of deeper layers Changes in surface energy are dictated by the chemical composition and structure of the surface layer, as well as the surrounding chemical particles The term "interface layer" encompasses both "surface layer" and "boundary layer," with the former addressing boundaries between gas, liquid, and solid phases, while the latter pertains to phase boundaries in solids, suspensions, and emulsions Interface layers are particularly relevant in complex compositions, whereas boundary layers are associated with multilayer materials and coatings Transitioning between phases is not abrupt, as surface energy seeks equilibrium with surrounding chemical particles, and the concept of "surface energy" applies to surface, interface, and boundary layers alike.

Investigating polymer films on metal substrates reveals that intermolecular interactions at the phase separation boundary lead to structural heterogeneity at both molecular and per-molecular levels This results in a defective and heterogeneous film structure, particularly in terms of thickness The nature and structure of the substrate can influence the polymer film's properties over distances exceeding 400 m cm Enhanced intermolecular interactions, either within the polymer or at the substrate boundary, correlate with more significant changes in the film's structure.

The surface characteristics of materials significantly influence their macroscopic properties, as these features are linked to the surface's chemical and physical structure, morphology, crystalline degree, shape, and roughness The chemical composition of a material's surface plays a crucial role in determining its reactivity and interaction rates with adjacent materials or media This composition includes the presence of molecular fragments or individual atoms that can either enhance or inhibit surface activity Additionally, solid surfaces typically contain layers of gases that are physically and chemically adsorbed, with the thickness of these layers varying based on the chemical activity of surface centers The interaction of gases and impurities with the surface is also affected by the surface geometry and roughness, which can be modeled to illustrate how active centers or heteroatoms interact with surrounding surface atoms.

FIGURE 19 Model of various surface roughness (a–c) (heteroatom × is surrounded by different numbers of other atoms).

The presence of heteroatoms on rough surfaces enhances their activity compared to surrounding atoms, leading to increased interactions with nearby chemical particles These surface characteristics create localized increases in surface energy and potential, significantly affecting the formation and thickness of adsorbed layers.

Monocrystals feature active centers on their surfaces, typically found at crystallographic steps or where dislocations intersect This positioning allows adsorbed particles to engage with multiple lattice atoms, significantly enhancing the total interaction For example, the adhesion of an oxygen molecule to a silicon stepped surface is 500 times more likely than to a smooth surface.

Surface layers within materials can exhibit variations in chemical composition, particularly in the presence of defects such as micro- and macro-cracks or pores In cellular plastics, the chemical composition of the surface layers is largely uniform, as the pores are interconnected with the material's surface Conversely, in foam plastics, where the pores are typically closed and not linked to the surface, the chemical composition of the material and its pores diverges significantly due to the differing gaseous environments within the foam bubbles compared to the surrounding atmosphere.

Polymers and nanocomposites are fundamentally linked through their nanoscale structures, highlighting the intersection of polymer science and the chemical physics of nanostructures The formation of polymer and nanoparticle structures is crucially influenced by their surface characteristics, which dictate the interaction area of polymeric molecules and nanoparticles Under non-equilibrium conditions, particle surfaces strive to reach thermodynamic equilibrium, with relaxation rates affected by environmental factors, temperature, and the nature of the materials involved Two key factors that shape the properties and structure of polymer and nanoparticle surfaces are the mobility of atomic and molecular groups, considering conformation energy, and surface energy In equilibrium, minimal surface energy is achieved through the mobility of chemical particles between the volume and surface, along with adsorption processes For instance, polystyrene coated with poly(ethylene oxide) demonstrates that the surface energy of polystyrene is lower, leading to an enrichment of polystyrene in the outer layer when heated above the vitrification temperature of both polymers Additionally, the surface energy and polarity of boundary layers in materials like vinylchloride–vinylacetate copolymers can vary based on substrate composition, affecting the distribution of polar groups in the copolymer's boundary region.

Substrate material Au Ni Al PTFE *

Surface energy, γ, mN/m of substrate material 43 37 33 19 copolymer 51 48 46 38

*PTFE––polytetrafluorine ethylene film (sheet)

XPS analysis reveals that the highest concentration of polar acetate groups is found at the layer boundary of gold substrates, which exhibit the greatest surface energy Additionally, the surface energy of polymers varies based on their formation conditions and the types of substrates used Table 7 illustrates the differences in surface energy (γ, mN/m) of various copolymers compared to polyethylene, highlighting the influence of these factors.

TABLE 7 Values of surface energy for sheets and films obtained on the boundary of different media

Sheets of polyester film obtained by hot pressing

Sheets of PTFE obtained by die casting

Film of PTFE obtained by bulge formation

Copolymer of vinylacetate ethylene (86:14) 33 32(33) 33

Statistic copolymer of ethylene and methacryl- ic acid (85:15) 44 37 38

Graft copolymer of maleic anhydride (2.1%) to high-density polyethylene

Graft copolymer of vinyltrime toxisilane

(1.1%) to copolymer of ethylene and vinylacetate (72:28)

Note: Values of surface energy during the mold water-cooling are given in brackets

The study utilized X-ray photoelectron spectroscopy (XPS) and infrared microscopy of multiply disturbed complete inner reflection (IR MDCIR) to gather results It highlights the importance of these investigation methods alongside widely recognized nanoscale techniques for analyzing nanostructures, nanosystems, and nanocomposites Various electron microscopy types, including scanning, transmission, tunneling, and atomic force microscopy, are employed to assess the morphology and shape of nanoparticles and nanosystems Additionally, diffractometric and spectroscopic methods are utilized to analyze the structure and composition of materials A comprehensive overview of methods for investigating the surface of materials, boundary layers, and nanostructures is presented in Table 8.

TABLE 8 Methods for investigating surface and boundary layers and nanostructures

Method Information Depth Sensitivity, profil- ing, nm %

X-Ray photoelectron spectroscopy (XPS) Element composition

Auger-electron spectroscopy (AES) Element composition < 5 10 –1

Ultraviolet electron spectroscopy (UVES) Chemical surroundings

Spectroscopy of ionic dissipation (SID) Element analysis < 1 10 -2

Secondary ionic mass spectrometry (SIMS) Element analysis < 1 10 –3

Laser microprobe mass analysis (LMMA) Element analysis 10 3 × 10 –7

Infrared microscopy of multiply disturbed complete inner reflection (IR MDCIR)

Spectroscopy of combination dissipation

(AFM) Surface morphology and polarity < 100 monolayer portions

Transmission electron microscopy with electron microdiffraction

Tunnel electron microscopy (TEM) Surface morphology 0.1 10 -2

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2.1 Introduction 54 2.2 Materials and Methods 56 2.2.1 Magnetic Sorbent Synthesis 56 2.2.2 Protein Coatings Formation 56 2.2.3 Study of Proteins Adsorption on MNPs 57 2.2.4 Coating Stability Analysis and Analysis of Selectivity of Free

Radical Process 582.2.5 Enzyme Activity Estimation 592.3 Results and Discussion 592.4 Conclusion 65Keywords 66References 67

A novel method for creating magnetically targeted nanosystems has been developed to enable smart drug delivery to target cells, utilizing stable protein coatings This method leverages the ability of proteins to form interchain covalent bonds through free radicals generated locally on the surface of nanoparticles Research employing various physical and biochemical techniques has demonstrated that free radical cross-linking of proteins results in stable single-layer coatings just a few nanometers thick on individual magnetic nanoparticles (MNPs) approximately 17 nm in diameter The spin labels technique was utilized to study macromolecule adsorption on these nanoparticles, revealing that the cross-linked protein coatings maintain the native properties of the proteins, as evidenced by thrombin coating This innovative approach opens new avenues for achieving biomedical objectives related to the smart delivery of drugs and biologically active substances, allowing for the design of multifunctional single-layer coatings on surfaces containing metals with variable valence.

Magnetic nanoparticles (MNPs) have diverse applications in biology and medicine, including hyperthermia, magnetic resonance imaging, immunoassays, purification of biological fluids, cell and molecular separation, and tissue engineering A promising area in nanobiotechnology is the design of magnetically targeted nanosystems (MNSs) for the smart delivery of drugs to specific cells These systems typically consist of one or more magnetic cores combined with biological or synthetic molecules that form multifunctional coatings on the MNPs' surface The coatings must be biocompatible, protect the magnetic cores from biological fluids, prevent agglomeration in dispersion, ensure localization in biological targets, and maintain uniform sizes of the MNPs Additionally, they should securely attach to the MNPs and incorporate therapeutic products, such as drugs or genes, along with biovectors for recognition by biological systems.

FIGURE 1 The classical scheme of magnetically targeted nanosystem for a smart delivery of therapeutic products.

Proteins are highly promising materials for developing coatings on magnetic nanoparticles (MNPs) in the fields of biology and medicine It is crucial for these proteins to retain their functional activity when incorporated into coatings However, achieving effective protein binding on the surface of MNPs presents significant scientific challenges Traditionally, bifunctional linkers such as glutaraldehyde and carbodiimide have been employed for cross-linking proteins to MNP surfaces, as well as for modifying coatings with therapeutic agents and biovectors.

Modified magnetic nanoparticles (MNPs) were treated with aminosilanes to facilitate protein attachment using glutaraldehyde, specifically adsorbing bovine serum albumin (BSA) in the presence of carbodiimide However, this method has several drawbacks, including the formation of protein clusters due to the linking of adsorbed molecules on different MNPs, desorption of proteins from the MNP surface due to incomplete linking, and uncontrollable protein linking in solution Addressing the challenge of creating stable protein coatings while preserving the native properties of the molecules remains a significant biomedical concern.

FIGURE 2 Nonselective linking of proteins on MNPs surface by bifunctional linkers leading to clusters formation and desorption of proteins from nanoparticles surface.

Proteins can undergo chemical modifications when exposed to free radicals, leading to the formation of cross-links This study aimed to develop a stable protein coating on the surface of individual magnetic nanoparticles (MNPs) through a novel method that leverages the ability of proteins to create interchain covalent bonds in the presence of free radicals Additionally, the research evaluated the activity of the proteins within the coating.

Nanoparticles of magnetite Fe 3 O 4 were synthesised by co-precipitation of ferrous and ferric salts in water solution at 4ºC andin the alkaline medium:

Introduction

Rheo-small angle light scattering (SALS), optical microscopy (OM), rheology, phase composition analysis, and environment scanning electron microscopy (ESEM) were utilized to investigate the influence of strong polyelectrolytes on the structure and phase-separation behavior of aqueous sodium caseinate-sodium alginate (W-SC-SA) emulsions The addition of 0.04–1.5 wt% dextran sulfate sodium (DSS) significantly reduced the compatibility between sodium caseinate (SC) and sodium alginate (SA) at pH 7.0 and ionic strength (I) = 0.002, leading to the loss of droplet morphology and altered solvent distribution, while enhancing the viscosity and moduli due to the formation of water-soluble SC-DSS associates The most significant changes in rheological properties occurred at a 10/1 SC/DSS molar ratio and 6–10 wt% SC content Beta casein showed less interaction with DSS compared to other casein fractions Near the critical point of phase separation, complexes formed through electrostatic interactions at lower SC concentrations (6 wt%), while at higher concentrations, secondary hydrogen bonds and hydrophobic interactions became prominent When DSS was added to emulsions far from the critical point, it reinforced the SC-DSS network and partially included SA, enhancing the cosolubility of SC with SA The strong interaction between SC and DSS at high concentrations, away from the caseins' isoelectric point, is discussed These findings suggest that small amounts of sulfate polysaccharide in aqueous biopolymer emulsions can effectively regulate their structure, phase behavior, and rheological properties.

Polysaccharides and proteins frequently coexist in biological and food systems, playing crucial roles in various industries, including food, pharmaceuticals, and cosmetics Their mixtures are particularly prevalent in dairy products, where casein is the primary protein component These natural polymers can undergo phase separation under specific conditions, allowing for the creation of unique morphologies and properties While extensive research has been conducted on the phase separation and morphologies of water-in-water biopolymer emulsions, there is limited understanding of how to modify the thermodynamic compatibility of biopolymers, especially in protein-acid polysaccharide systems, which remain largely insensitive to changes in pH, ionic strength, and temperature Recent studies have shown that a single-phase water-gelatin-pectin system can experience phase separation in the presence of dextran, attributed to the competitive interactions that block gelatin's functional groups The interactions among biopolymers can vary significantly due to differences in their structures and the solvent conditions.

15] The recent study shows [16] that intermacromolecular interactions caused by the presence of complexing agent in two-phase biopolymer mixture can affect the phase equilibrium in semidilute biopolymer mixtures.

This study investigates the impact of strong polyelectrolyte dextran sulfate on the structural formation and phase-separation behavior in water-in-water casein-alginate emulsions Utilizing techniques such as rheo Small Angle Light Scattering (SALS), optical microscopy (OM), rheology, phase analysis, and Environmental Scanning Electron Microscopy (ESEM), the research aims to identify the physicochemical parameters that govern thermodynamic compatibility and morphology development in this system The focus is on an aqueous two-phase system of sodium caseinate and sodium alginate, examining its behavior both close to and far from phase separation.

The phase diagram's critical points were selected to facilitate phase equilibrium changes with DSS salt at pH 7.0, which is above the isoelectric point of caseins The chosen materials exhibit a significant difference in refractive indices between the coexisting phases, enhancing contrast for the SALS experiment Notably, the complex formation of SC with DSS in dilute and semidilute solutions has been previously investigated, with detailed studies conducted recently.

W-SC-SA mixtures exhibit a two-phase system at high concentrations of biopolymers, which remains consistent across varying pH, ionic strength, and temperature under both quiescent conditions and shear flow This demixing effect can be replicated in other water-in-water emulsions that are more sensitive to physicochemical parameters The casein-alginate system is particularly noteworthy for its thermodynamic behavior and relevance in the food industry due to its textural and structuring properties Alginate, an anionic polysaccharide, consists of linear chains of (1–4)-linked β-D-mannuronic and α-L-guluronic acid residues, organized in alternating blocks Casein, a heterogeneous group of phosphoproteins, forms micelles, while salt casein (SC) is derived from disrupting this micellar structure, resulting in a random coil polymer and loss of the micelles' internal organization.

The isoelectric point of caseinate falls between pH 4.7 and 5.2, resulting in a negative charge at neutral pH, similar to alginate and DSS The thermodynamic and rheological properties of ternary systems comprising water, caseinate, and alginate have been well-documented in existing literature.

Most experiments were performed in the very dilute phosphate buffer (ionic strength, I = 0.002), in the absence of other low molecular salts at 23 o C.

Materials and Methods

At neutral pH, caseinate carries a negative charge, similar to alginate and DSS The SC sample, consisting of 90% protein, 5.5% water, 3.8% ash, and 0.02% calcium, was sourced from Sigma Chemical Co., with an isoelectric point around pH 4.7–5.2 The weight average molecular mass (Mw) of the SC in 0.15 M NaCl at pH 7.0 is 320 kDa Additionally, the α and β-casein fractions from bovine milk were chromatographically purified and produced by Sigma The medium viscosity sodium alginate, derived from brown seaweed (Macrocystis pirifera), also came from Sigma, exhibiting an Mw of 390 kDa in 0.15 M NaCl Lastly, the DSS salt, with a molecular weight (MW) of 500 kDa, a number average molecular weight (Mn) of 166 kDa, and intrinsic viscosity of 50 mL/g in 0.01 M NaCl, was produced by Fluka, Sweden, featuring 17% sulfate content and free SO4 levels below 0.5%.

10.2.1 PREPARATION OF THE PROTEIN/POLYSACCHARIDE MIXTURES

To create molecularly dispersed solutions of SC, SA, or DSS at the desired concentrations, a phosphate buffer (Na2HPO4/NaH2PO4, pH 7.0, I = 0.002) was gradually added to a measured amount of biopolymer at 25ºC, followed by stirring for one hour at this temperature and an additional hour at 45ºC The solutions were then cooled to 23ºC and stirred for another hour The pH was adjusted to 7.0 using 0.1–0.5M NaOH or HCl Insoluble particles were removed by centrifugation at 60,000 g for one hour at 23ºC, and the concentrations were determined by drying the solutions at 100ºC until a constant weight was achieved Ternary water–SC–SA systems with the required compositions were prepared by mixing the biopolymer solutions at 23ºC, followed by one hour of stirring and centrifugation at 60,000 g for one hour to separate the phases using a temperature-controlled rotor.

10.2.2 DETERMINATION OF THE PHASE DIAGRAM

The impact of DSS presence on the isothermal phase diagrams of the SC-SA system was examined using a methodology adapted from previous studies The weight ratio of DSS to SC in the system was maintained at 0.14 The threshold point was identified as the location where a line with a slope of -1 is tangent to the binodal curve Additionally, the critical point (CP) of the system was defined as the intersection of the binodal with the rectilinear diameter, which connects the centers of the tie lines.

A rheo-optical methodology utilizing small-angle light scattering (SALS) during flow is employed to investigate the in situ and time-resolved structural evolution of materials Light scattering experiments were performed using a Linkam CSS450 flow cell, which features a parallel-plate geometry This advanced system incorporates two highly polished quartz plates, maintained parallel to within 2 micrometers, and each plate is thermally connected to an independently controlled pure silver heater equipped with platinum resistors that are sensitive to temperature variations of 0.1°C.

A 5 mW He-Ne laser emitting at a wavelength of 633 nm served as the light source for the experiment The 2D scattering patterns were captured on a screen using semi-transparent paper and a beam stop, and recorded via a 10-bit progressive scan digital camera (Pulnix TM-1300) The images were subsequently stored on a computer using a digital frame grabber (Coreco).

The optical acquisition setup by Tci-Digital SE has been validated for scattering angles up to 18º, with a plate gap of 1 mm maintained at a controlled temperature of 23ºC using a water bath Intensity profiles and contour plots were generated using in-house developed software (New SALS SOFTWARE-K.U.L.), while turbidity measurements were conducted using a photodiode.

Microscopy observations during flow have been performed on a Linkham shearing cell mounted on a Leitz Laborlux 12 PolS optical microscope using different magnifica- tions.

Rheological measurements were conducted using a Physica Rheometer (CSL2 500 A/G H/R) with a cone-plate geometry (CP50-1/Ti, diameter 5 cm, angle 0.993º) from Anton Paar, maintaining a temperature of 23°C via a Peltier element Flow curves were obtained by increasing the shear rate from 0.1 to 150 s⁻¹, and frequency sweeps were performed in the range of 0.1–200 rad/s at a strain of 3.0%, ensuring the measurements remained within the linear response regime To prevent sample drying during the tests, the edges were coated with paraffin oil.

The microstructural investigation utilized the ESEM Philips XL30 ESEM FEG, where samples were freeze-fractured in freon and immediately placed in the ESEM chamber To maintain a relative humidity of 100%, a Peltier stage was employed, minimizing solvent loss and condensation while controlling sample etching Images were captured within five minutes of the samples entering the chamber, and multiple images were recorded across various samples to ensure reproducibility.

Discussion and Results

10.3.1 WATER-IN-WATER EMULSIONS WITH COMPOSITION CLOSE

TO THE CP––DSS-INDUCED DECOMPATIBILIZATION

The experimental results were derived from two-phase systems composed of water (91.35 wt%)-SC (8.54 wt%)-SA (0.11 wt%) and water (91.9 wt%)-SC (7.9 wt%)-SA (0.19 wt%), incorporating 3% vol and 15% vol alginate-enriched dispersed phases, respectively, represented as points A´ and A´´ in Figure 1.

FIGURE 1 Isothermal phase diagram of water- SC-SA system at 23ºC, pH 7.0, I = 0.002

● composition of coexisting phases; ■- other points on the phase diagram; ○ critical point; A, B,

The study focuses on emulsions characterized by specific compositions represented as points along the tie lines Notably, A´ and A´´ indicate emulsions with 3 wt% and 15 wt% sodium alginate enriched phases, respectively Meanwhile, B´, B´´, B´´´, and B´´´´ represent emulsions containing 10% vol., 15% vol., 25% vol., and 35% vol of the sodium alginate enriched phase Lastly, C´ signifies an emulsion with a 35% vol alginate enriched phase.

To investigate the impact of DSS on phase equilibrium, a flow history with three shear zones is implemented Initially, a preshear rate of 0.5 s⁻¹ is applied for 900 seconds, achieving 450 strain units to establish a consistent initial morphology Following this, the preshear is halted, allowing the sample to relax for 30 seconds to enable complete relaxation of the deformed droplets Subsequently, SALS patterns are observed.

The evolution of SALS patterns and scattering intensity with varying amounts of DSS is illustrated in Figure 2, highlighting emulsions with 3 wt% and 15 wt% SA enriched phases Each experiment utilized a freshly loaded sample, revealing that the addition of DSS significantly enhanced the SALS pattern, resulting in a broader area around the bean stop and increased light scattering intensity This effect was particularly notable in the dilute 3% emulsion, as shown in Figure 2 (a).

W-SC-DSS and W-SA-DSS systems exhibit homogeneity within the studied DSS concentration range of 0.25 to 2.0 wt% As the DSS concentration increases, both the SALS pattern and scattering intensity rise, indicating a shift in the binodal line of the phase diagram towards lower biopolymer concentrations For phase separation to occur, the driving force for decomposition must surpass the increase in interfacial free energy, which is determined by the product of interfacial tension and the total interfacial area during phase separation The interfacial tension can be approximated using the scaling relation g = Ο (kT/ξ²), where g represents interfacial tension and ξ denotes the width of the region where component concentrations differ from their bulk values in coexisting phases.

The critical point (CP) determined by a rheo-optical method is approximately ~10 –8 N/m, increasing to values between 5.2 × 10 −6 N/m and 8.8 × 10 −6 N/m as the distance from the CP increases The incorporation of DSS into the emulsion significantly shifts the system deeper into the two-phase range on the phase diagram Although directly measuring the interfacial tension of the W-SC-SA-DSS system is challenging due to the viscosity differences of the coexisting phases, it is reasonable to infer that the decompatibilization of the W-SC-SA system results in a similar increase in interfacial tension, as this tension is influenced by the system's deviation from the CP Additionally, the presence of DSS in water-in-water emulsions causes substantial morphological changes, evidenced by microscopy images that reveal a loss of droplet morphology due to decreased compatibility when DSS is present.

The presence of DSS significantly influences the SALS patterns and scattering intensity of water-SC-SA emulsions containing varying concentrations of sodium alginate Specifically, at 3% vol sodium alginate (point A' on Figure 1) and 15 wt% sodium alginate (point A’’ on Figure 1), the effects are observed at a temperature of 23°C, pH 7.0, and ionic strength of 0.002 The study examines different DSS concentrations (0.0, 0.25, 0.5, 1.0, and 2.0 wt%) after a preshear period at 0.5 s^-1 for 900 seconds.

Microscopy images of emulsions with 3% and 15% SA enriched phases were analyzed before and after the addition of DSS The concentrations of DSS in the emulsion were 0.0% (a, d), 0.5% (b, e), and 2.0% (c, f) These images were captured after halting preshear at 0.5 s^-1 for 900 seconds, at a temperature of 23°C, pH 7.0, and ionic strength of 0.002.

10.3.2 WATER-IN-WATER EMULSIONS WITH COMPOSITIONS FAR FROM THE CP––DSS-INDUCED COMPATIBILIZATION

Figure 4 shows the effect of the presence of dextran sulfate on the phase diagram of SC-SA system at q = 0.14 One can see that DSS greatly effect phase separation

At low concentrations of biopolymers, compatibility significantly decreases Within the two-phase range, compatibility shows a slight decrease near the critical point (CP), while at higher biopolymer concentrations, the co-solubility of alginate in the supercritical (SC) enriched phase increases considerably Point B on the phase diagram (Figure 4) represents the two-phase region with 92.53% W.

In a study of the SC (6.84%)-SA (0.63%) system, the absence of DSS resulted in the formation of two coexisting phases, with casein concentrated in the bottom phase (13.1 wt% SC and 0.05 wt% SA) and alginate in the upper phase (0.45 wt% SC and 1.24 wt% SA), maintaining equal volumes The introduction of 1.0% DSS significantly reduced the volume of the SA-enriched phase from 50% to 15%, while also decreasing the concentration of casein in the SC-enriched phase to 10.5 wt% SC and 0.29 wt% SA These changes suggest an increased compatibility between SC and SA.

The phase diagram of the W-SC-SA system is significantly influenced by dextran sulfate (DSS), as illustrated in Figure 4 The diagram features distinct compositions of coexisting phases, marked by symbols such as ● and ▲, while ■ represents additional points within the diagram The critical point (CP) is indicated by ○, and the midpoints of the tie lines are denoted by + The binodal line without DSS is labeled as 1, whereas the binodal line with DSS is marked as 2 Additionally, the tie lines for both the absence and presence of DSS are clearly delineated, highlighting the impact of DSS on the system's phase behavior.

The two-phase W (92.53%)-SC (6.84%)-SA (0.63%) system, identified at point B on the phase diagram (Figure 1), was subjected to centrifugation Emulsions with 15% vol and 35% vol of the SA enriched phase were then prepared The morphological changes of these emulsions following the addition of 1.0 wt% DSS were analyzed, corresponding to points B´-B´´´´ on Figure 1.

The scattering intensities of the B'' system (15% vol SA enriched phase) are illustrated in Figures 5, revealing that the addition of DSS significantly affects the scattering intensity, which is predominantly localized near the bean stop Additionally, microscopy images of this system indicate a lack of the dispersed phase.

FIGURE 5 The scattering intensities of W-SC(11.2 wt%)-SA(0.23 wt%) emulsion containing

The study examines the 15 wt% SA enriched phase (point B' in Figure 1) in relation to the distance from the bean stop, comparing data before (curve 1) and after the addition of DSS at q = 0.14 (curves 2) Additionally, microscopy images (images a and b) illustrate the same systems, captured after a preshear stop at 0.5 s^-1 for 900 seconds, under conditions of 23°C, pH 7.0, and ionic strength of 0.002.

The morphology of the system closely resembles that of the SC enriched phase without DSS, indicating that approximately 15% volume of the SA enriched phase is solubilized in the SC enriched phase when DSS is present Additionally, DSS significantly influences the slope of the tie line on the phase diagram, which reflects changes in biopolymer concentrations and affects water distribution between coexisting phases As the interplay of segregative and associative processes shapes the phase diagram, it can be inferred that at higher concentrations, the impact of weak complexation becomes more pronounced, or the differences in interaction intensities between SC and solvent, as well as SA and solvent, diminish.

Tiêu đề	Key Engineering Materials Volume II Interdisciplinary Concepts and Research
Tác giả	Nikolai A. Turovskij, PhD, Omari Vasilii Mukbaniani, DSc, Devrim Balkửse, PhD, Daniel Horak, PhD, Ladislav Šoltộs, DSc, Franỗois Kajzar, PhD
Trường học	Donetsk National University
Chuyên ngành	Physical Chemistry
Thể loại	book
Thành phố	Donetsk

Định dạng
Số trang	419
Dung lượng	21,34 MB