Journal of Science: Advanced Materials and Devices xxx (xxxx) xxx Contents lists available at ScienceDirect Journal of Science: Advanced Materials and Devices journal homepage: www.elsevier.com/locate/jsamd Original Article Green synthesis of AgeZnO nanoparticles: Structural analysis, hydrogen generation, formylation and biodiesel applications L.S Reddy Yadav a, b, S Pratibha c, K Manjunath d, M Shivanna e, T Ramakrishnappa b, N Dhananjaya c, G Nagaraju a, * a Department of Chemistry, Siddaganga Institute of Technology, Tumakuru 572103, India Department of Chemistry, BMS Institute of Technology, Bengaluru 560064, India Department of Physics, BMS Institute of Technology, Bengaluru 560064, India d Centre for Nano and Material Sciences, Jain University, Bengaluru 562112, India e Chemistry and Physics of Materials Unit, JNCASR, Bengaluru 560064, India b c a r t i c l e i n f o a b s t r a c t Article history: Received 26 January 2019 Received in revised form 27 February 2019 Accepted March 2019 Available online xxx The present work reveals the green combustion preparation of the Ag-doped ZnO nanoparticles (NPs) using turmeric root extract as a fuel The structure and morphology of Ag-doped ZnO NPs were investigated by several analytical techniques such as XRD (X-Ray Diffraction), SEM (Scanning Electron Microscopy), TEM (Transmission Electron Microscopy), FTIR (Fourier Transform Infrared), Raman, XPS (XRay Photoelectron Spectroscopy), and UV-Visible Spectroscopy (UVeVis) From XRD, the crystallite size was found to be about 45 nm which agrees with the TEM results SEM micrographs reveal the spherical shaped agglomerated particles XPS measurement anticipates that Ag is mainly in the metallic state and ZnO is in the Wurtzite structure UVeVisible spectroscopy shows the absorbance peak at 368 nm Biodiesel synthesis from Terminalia belerica oil with AgeZnO as a nanocatalyst has been studied AgeZnO nanoparticles show hydrogen evolution up to 214 mmolgÀ1hÀ1 A convenient synthesis of Na-protected formamides from protected amino acids was described using AgeZnO as a catalyst This method provides good yield of formamides with excellent purity after removal of the catalyst © 2019 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) Keywords: AgeZnO TEM XPS Biodiesel H2 generation Formylation Introduction Due to the extensive range of applications in interdisciplinary fields from biology/medicine to electronics, metal oxide nanoparticles have gained much attention in scientific community [1] The catalytic and biological applications were addressed by the low-cost metal oxides such as ZnO, CuO, MgO, TiO2 etc., instead of noble metals like gold, silver, and platinum [2,3] Among these, low cost and easily accessible ZnO nanostructures are considered as promising materials for numerous applications such as photocatalysis, emerging optical devices, sensor technology etc., because of its excellent properties: large band gap, fast charge carrier recombination, high quantum efficiency, optical transparency, high surface area and electrochemical activity * Corresponding author E-mail address: nagarajugn@rediffmail.com (G Nagaraju) Peer review under responsibility of Vietnam National University, Hanoi ZnO nanostructures can be synthesized by various methods namely, hydrothermal, solvothermal, ionothermal, co-precipitation methods, etc [4e6] But these methods generally require hightemperature treatments, long preparation time, usage of expensive apparatus and harmful chemicals, etc According to the literature survey, the green synthesis of AgeZnO nanoparticles has not been widely reported It includes the synthesis of nanoparticles using plant parts It is a cost-effective, safe, biocompatible method that needs less processing time with low-cost equipment, and is capable of high quality and purity of product [1,2] Archana et al synthesized ZnO nanoparticles by green synthesis using Moringa Oleifera natural extract and studied the enhanced photocatalytic hydrogen generation and photostability [7] Ali et al synthesized AgeZnO nanocomposite using Valeriana officinalis L root extract and investigated the application as a recyclable substance for the decrease of organic dyes in an actual small period [8] Since the first demonstration of photoelectrochemical H2 generation by Fujishima and Honda [9], rigorous research efforts have been devoted towards the semiconductor photocatalytic https://doi.org/10.1016/j.jsamd.2019.03.001 2468-2179/© 2019 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) Please cite this article as: L.S.R Yadav et al., Green synthesis of AgeZnO nanoparticles: Structural analysis, hydrogen generation, formylation and biodiesel applications, Journal of Science: Advanced Materials and Devices, https://doi.org/10.1016/j.jsamd.2019.03.001 L.S.R Yadav et al / Journal of Science: Advanced Materials and Devices xxx (xxxx) xxx generation of H2 in recent years [10] ZnO is a promising semiconductor having large exciton binding energy (60 meV) at room temperature [11,12] Also, oxygen vacancies in ZnO increase its visible light photocatalytic activity [13,14] The metal-metal oxide, oxide-sulphide, oxide-nitride heterostructures [15] and noblemetal/oxide nanocrystals show excellent photocatalytic performance [16] Cheng et al observed the better photocatalytic properties due to enhanced charge transfer and separation process from ZnOeTiO2 hybrid structures [17] The major disadvantage of ZnO photocatalyst is that the suffering from photo-corrosion and it has been suppressed by doping, decorating with the optimum amount of carbonaceous material or by modifying the synthetic protocol [18] Biodiesel, which is known as fatty acid methyl ester, is an alternative fuel of diesel which is renewable, non-toxic, ecofriendly and recyclable Presently, the homogeneous catalysts of NaOH and KOH remain widely recycled for biodiesel production [19] These catalysts have many disadvantages, i.e needs a large amount of H2O, increased functioning and high cost [20] Solid mixed catalysts (SrO, CaO, MgO), mixed metal oxides (Ca/Zn, Ca/ Mg), and alkali-doped metal oxides are ecologically promising materials for biodiesel production as it is easy to separate and purify the ultimate yields [21] Compared to these mixed catalysts, the use of nanocatalyst gives higher catalytic activity, easy separation of products, recyclability and regenerates less pollution [22,23,26] Presently, non-edible oils such as Jatropha curcas, Pongamia pinnata, and Cotton seeds are widely used for the production of biodiesel [24] According to the literature survey, no reports available on biodiesel synthesis from Terminalia belerica oil with AgeZnO as a nanocatalyst In the present study, Terminalia belerica oil was used for the biodiesel production employing AgeZnO nanocatalysts Formamide products such as imidazoles, fluoroquinones, and nitrogen connected heterocycles etc., are valuable compounds for general applications in medicine and organic chemistry [25e28] They also serve as useful reagents in the asymmetric allylation, Vilsmeier formylation reactions and hydrosilylation of carbonyl compounds Many useful formylation catalysts such as zinc metal, CeO2, VB1, and HEU Zeolite with aq HCOOH has been reported [19,29,30] However, many of these have drawbacks such as high toxicity, harsh reaction conditions, and prolonged reaction time demanding special care Thus, we presented an alternative, convenient method for the N-formylation of protected amino acids in the presence of AgeZnO nanoparticles Curcuma longa (Turmeric) belonging to Zingiberaceae family was used in Asia for thousands of years It is a key part of Ayurveda, Siddha medicine, Unani, and traditional Chinese medicine Because of its high antibiotic nature, it can be used in skin treatments It is widely used in Indian cuisine since the daily intake of turmeric will enhance the immunity of the human body The present work reports the eco-friendly synthesis of Wurtzite AgeZnO nanoparticles by Curcuma longa root extract using solution combustion method The obtained nanoparticles were further characterized using various techniques 2.2 Synthesis of AgeZnO nanoparticles Zinc nitrate [99% purity] and silver nitrate [98% purity] were purchased from Sigma Aldrich and used without further purification 60 ml of crude turmeric root powder solution is used as fuel Stoichiometric quantities of zinc nitrate, silver nitrate (1, 3, 5, mol %) were taken in a beaker and agitated well by a magnetic stirrer for about 5e10 The mixture was placed in a pre-heated muffle furnace maintained at 400 ± 10 C The mixed combination boils and thermally becomes dry to form a foamy product The whole procedure was ended in less than The obtained product was further calcined at 600 C for h and then used for structural analysis and further studies A similar procedure is followed for the synthesis of AgeZnO nanoparticles with different dopant concentrations of silver nitrate (1, 3, 5, mol %) 2.3 Photochemical H2 generation AgeZnO was utilized in photochemical water splitting and generated hydrogen is measured by gas chromatography at room temperature (25 C) The experimental procedure for photochemical H2 generation was similar to our previously reported work [33] 2.4 Biodiesel synthesis and formylation reaction The Biodiesel Synthesis and Formylation reaction have been carried out using Ag/ZnO NpS as nanocatalysts and the procedure followed is similar to our previously published work and represented as in Scheme [19] The spectral data of the selected Naformamide derivatives protected amino acids has been given as supplementary 2.5 Characterization The phase purity and crystallinity of the nanoparticles were examined by Shimadzu X-Ray Diffractometer using Cu Ka radiation (1.5406 Å) with nickel filter The surface morphology of the nanoparticles was examined using a Hitachi 3000 scanning electron microscope (SEM) Transmission electron microscopy measurements were carried out in a Jeol 200CX Transmission electron microscope Absorbance was recorded by a Shimadzu UV-Visible spectrophotometer The Fourier transform infrared spectroscopy studies have been performed on a Perkin Elmer Spectrometer (Spectrum 1000) with KBr pellets The Raman spectrum is recorded with a Peak Seeker Pro TM Raman system The sample has been excited with an inbuilt 785 nm wavelength laser Photoluminescence (PL) spectra were examined by Agilent Cary Eclipse Fluorescence spectrometer using Xe lamp with an excitation wavelength of 397 nm X-ray photoelectron spectroscopy (XPS) analysis was carried out on an ESCALAB 250 (Thermo-VG Scientific), using Al Ka as the excitation source The instrument was standardized against the C1s spectral line at 284.600 eV The H2 generation was performed by Perkin Elmer Clarus 580 GC R1 Materials and methods 2.1 Collection of turmeric root ZnO: Ag nanoparticles were prepared via a self-propagating green combustion process using different concentrations of turmeric root powder as a fuel The turmeric root was collected from the local market in Bangalore The turmeric root was made into well-grinded powder and used as a fuel OH PgHN O i NMM, EtOCOl THF, aq NaN3 ii Toluene, R1 PgHN O N H H iii HCOOH, nano MgO CH2Cl2 R1 = Amino acid side chains Scheme Synthesis of Na-formamide derivatives protected amino acids Please cite this article as: L.S.R Yadav et al., Green synthesis of AgeZnO nanoparticles: Structural analysis, hydrogen generation, formylation and biodiesel applications, Journal of Science: Advanced Materials and Devices, https://doi.org/10.1016/j.jsamd.2019.03.001 L.S.R Yadav et al / Journal of Science: Advanced Materials and Devices xxx (xxxx) xxx mol% $ $ * $ mol% * $ $ $ *$ * * $ $ $ * * * *$ $ $ * $$ Intensity (a.u.) $Zn *Ag $ $ mol% $ $ $ $ mol% * $ * $ $ 20 30 Results and discussion Fig shows the XRD pattern of the AgeZnO nanoparticles with crystal structure as the wurtzite phase of ZnO (JCPDS No 75-576, with unit cell parameters a ¼ 3.242 c ¼ 5.195, P63mc space group) The extra peaks signify the cubic phase of the Ag (JCPDS No 4-783, with unit cell parameters a ¼ 4.0862, Fm-3m space group) and attribute to the formation of the second phase clusters It was observed that there is a constant intensification in the intensity of the Ag peaks with the increase in the fuel concentrations (1, 3, 5, and mol %) There is a change in the peak position at lower 2q values with increasing fuel concentrations which implies the partial substitution of Agỵ ions in ZnO lattice and the increase of lattice parameters a and c, as estimated The average crystallite size was found to be about 45 nm which was estimated from the DebyeScherer equation given by, [31] D¼ $$ 40 50 $ 60 $ 70 80 2θ(deg.) Fig XRD patterns of the AgeZnO nanoparticles with different fuel concentrations chromatograph equipped with a thermal conductivity detector (TCD) with N2 as the carrier gas Mass spectra of AgeZnO NPs were recorded on a Micromass Q-ToF Micro Mass Spectrometer 1H NMR and 13C NMR spectra of AgeZnO NPs using Me4Si as an internal standard and CDCl3 as a solvent by Bruker AMX 400 MHz spectrometer kl b cos q where, b ¼ FWHM, q is Bragg angle, k ¼ 0.9 and l ¼ 1.54 Å (X-ray wavelength) The microstructure and morphology of the AgeZnO nanoparticles are obtained in detail from SEM observations Fig shows the SEM images of AgeZnO nanoparticles of different sized spherical structures with agglomeration Fig shows the TEM and SAED images of the AgeZnO nanoparticles TEM image presents the size of the AgeZnO nanoparticles in the range 20e30 nm and the results are comparable with the XRD Selected Area Electron Diffraction (SAED) pattern indicates the polycrystalline nature of nanoparticles Fig shows the FT-IR spectrum for different fuel concentrations of AgeZnO nanoparticles between the range of 400e4000 cmÀ1 The obtained sharp peak at 440 cmÀ1 is attributed to the ZneO stretching vibration mode The presence of hydroxyl ions (OH) in Fig SEM images of AgeZnO nanoparticles; (a) (b) (c) and (d) mol % of fuel concentrations Please cite this article as: L.S.R Yadav et al., Green synthesis of AgeZnO nanoparticles: Structural analysis, hydrogen generation, formylation and biodiesel applications, Journal of Science: Advanced Materials and Devices, https://doi.org/10.1016/j.jsamd.2019.03.001 L.S.R Yadav et al / Journal of Science: Advanced Materials and Devices xxx (xxxx) xxx Fig (a, b) TEM images and (c) SAED pattern of AgeZnO nanoparticles AgeZnO nanoparticles is revealed by the peaks in the range of 3020e3650 cmÀ1 The peaks at 1580 cmÀ1 and 1410 cmÀ1 represent the symmetric and asymmetric bending modes of C]O bonds whereas the peak located at 2860 cmÀ1 and 2950 cmÀ1 were related to symmetric and asymmetric CeH stretching bonds, respectively The absorption band at 1020 cmÀ1 could be attributed to bending vibrational modes [34] mol % 368 nm mol % Absorbance (a.u.) -1 421 Cm 1383 Cm mol % 1652 Cm -1 -1 -1 mol % 3431 Cm Transmittance (a.u.) mol % The optical absorption spectra of the AgeZnO nanoparticles were analyzed by UV-visible spectrophotometer in the range of 200e800 nm as shown in Fig The strong UV absorption edge at 368 nm of AgeZnO nanoparticles indicates the existence of the wurtzite crystal structure Absorption edge is independent from the concentration of fuel used while preparing AgeZnO nanoparticles, which indicates that only doping causes variations in band structure due to the intercalation of the metal ion in the band gap [28] XPS spectra of Ag 3d, Zn 2p, and O 1s are shown in Fig Fig 6(a) shows two peaks at 1024 eV for Zn 2p3/2 corresponds to the hydroxyl groups attached to the Zn ions on the surface of nanoparticles Another peak at 1044.2 eV corresponds to Zn atoms mol % mol % mol % O-H 3500 3000 C=O 2500 2000 Zn-O 1500 1000 500 -1 Wavenumber (cm ) Fig FT-IR spectra of the as-synthesized AgeZnO nanoparticles with different fuel concentrations 225 300 375 450 525 600 Wavelength (nm) Fig UV-Visible spectra of AgeZnO nanoparticles with different fuel concentrations Please cite this article as: L.S.R Yadav et al., Green synthesis of AgeZnO nanoparticles: Structural analysis, hydrogen generation, formylation and biodiesel applications, Journal of Science: Advanced Materials and Devices, https://doi.org/10.1016/j.jsamd.2019.03.001 L.S.R Yadav et al / Journal of Science: Advanced Materials and Devices xxx (xxxx) xxx (a) (b) Zn 2p3/2 1010 1020 1030 1040 1050 1060 526 Binding energy (eV) (c) O 1s Intensity (a.u.) Intensity (a.u.) Zn 2p1/2 528 530 532 534 536 538 Binding energy (eV) Ag 3d5/2 Intensity (a.u.) Ag 3d3/2 364 366 368 370 372 374 376 378 380 Binding energy (eV) Fig X-ray photoelectron spectroscopy of the AgeZnO nanoparticles bonded to oxygen atoms to form ZnO instead of ZneCeO alloys XPS spectrum of O 1s Fig 6(b) shows a strong peak at 530.2 eV which is the characteristic of lattice oxygen in ZnO: Ag Fig (c), i.e., Ag 3d5/2 and Ag 3d3/2 binding energies appeared at 369 eV and 375 eV respectively This is in good agreement with metallic silver values [32] Fig shows the room temperature PL spectra of Ag-doped ZnO nanoparticles excited by a wavelength of 325 nm All the samples have related emission peaks centered at 358, 405, 430, 440 and 534 nm As the dopant concentration increased, the emission peaks disappeared The peak at 358 nm dominates Generally, there are two emission bands in the PL spectra of ZnO nanoparticles One is due to near band edge emission through the collision between a 358nm Ag-ZnO 1mol % 3mol % 5mol % 7mol % 430nm 440nm 534nm -1 H2 ( μmolgh ) PL Intensity (a.u.) 405nm pair of an exciton in the UV region The other is due to the recombination of the electron-hole pair caused by the intrinsic and surface point defects in the visible region The near band edge emission peak is at 358 nm in as-synthesized pure ZnO and the peak originated due to the defect states is after 405 nm The emission at 430 nm was associated with an electron transition from a shallow donor level of neutral zinc interstitial to the top level of the valence band The emission at 440 nm is ascribed to surface defects of ZnO The green emission at 534 nm may be allocated to oxygen vacancies The asymmetric spectra are due to the native defect states of ZnO The size, structural morphology, surface porosity and addition of dopants for ZnO donate in the defect 350 400 450 500 550 600 Wavelength (nm) Fig PL spectrum of the AgeZnO nanoparticles with different fuel concentrations 20 40 60 80 100 120 Time (min) Fig Photocatalytic hydrogen evolution of the AgeZnO nanoparticles Please cite this article as: L.S.R Yadav et al., Green synthesis of AgeZnO nanoparticles: Structural analysis, hydrogen generation, formylation and biodiesel applications, Journal of Science: Advanced Materials and Devices, https://doi.org/10.1016/j.jsamd.2019.03.001 L.S.R Yadav et al / Journal of Science: Advanced Materials and Devices xxx (xxxx) xxx Table Fuel properties of Terminalia belerica biodiesel Properties Units Density Acid value Flash point Viscosity at 40 C Copper strip corrosion, 50 C, h Kg/m3 Mg KOH/g C mm2/sec e Testing procedure ASTM Terminalia belerica biodiesel Biodiesel standard ASTM 6751 D93 D664 D4052 D445 D130 880 0.32 64 4.5 1a 870e900 0.8 max >130 1.9-6.0 no max Table List of formamides derivatives of aromatic amines and amino acid esters using AgeZnO nanoparticles Entry 1a 1b Formamide 1c 1d NHCHO NHCHO NHCHO 1e NHCHO HO NHCHO HOOC O2N Cl Yield (%) 90 76 95 90 88 Entry 2a 2b 2c 2d 2e Formamide O H N H COOMe O 90 H N O O HN H COOMe H Yield (%) O S 80 N H COOMe H N H COOMe 86 states, which affects the luminescence Thus, the defects due to native oxygen vacancies were accountable for the visible emissions in ZnO samples But still, there is some dispute in allocating the defect emissions in ZnO [34] Fig shows the photocatalytic H2 evolution (Water splitting reaction) activity measured for AgeZnO nanoparticles calcined at 400 C for h The rate of hydrogen evolution for the water-ethanol system in the presence of AgeZnO nanoparticles was determined by gas chromatography The quantity of gas liberated is plotted as the function of UV exposure time We have experimentally observed that 214 mmolgÀ1hÀ1 of H2 produced for 2.5 h of UV exposure time The generation of H2 gas was also stopped indicating that the gas evolution was brought by the UV irradiation when the UV light was turned off From the graph, it is clear that AgeZnO nanoparticles act as a very good photocatalyst for hydrogen generation from water splitting reaction [33] Biodiesel applications using AgeZnO was carried out After the trans-esterification procedure, the yield of biodiesels originates by employing the AgeZnO nanocatalyst was found to be about 83% The AgeZnO catalyst shows better catalytic activity which could be a possible catalyst for the synthesis of biodiesel [19] In this direction, to assess the quality of biodiesel, fuel properties kinematic viscosity, flash point, density, acid value, and copper strip corrosion were evaluated and compared with ASTM standards as shown in Table Formylation reactions were performed using AgeZnO nanocatalysts at room temperature Improved effects were found associated with the reported protocols, once the reaction was catalyzed by 0.5 mmol of nanocatalyst AgeZnO at room temperature for protected amino acids Also, we tried the reaction in the presence of a huge amount of catalyst (>0.5 mmol) which was considerably decreased the percentage yield of products The list of formamides derivatives of aromatic amines and amino acid esters using AgeZnO nanoparticles is tabulated in Table Spectral data of the selected compounds are given as supplementary SH 80 O OH 88 Conclusions In this work, we have synthesized the AgeZnO NPs with different mol% concentration of Ag dopant using novel fuel by green combustion method based on Curcuma longa root extract It is an environmentally friendly, facile as well as a cost-effective method for the synthesis of nanoparticles XRD shows the hexagonal wurtzite structure AgeZnO NPs demonstrates as a promising material for photocatalytic hydrogen evolution Furthermore, it is a good catalyst for the synthesis of biodiesel from the Terminalia belerica oil About 83% yield has been achieved by the implementation of AgeZnO as a nanocatalyst for the synthesis of biodiesel Hence, AgZnO NPs shows prominence towards the biodiesel applications It also catalyzes the N-formylation reactions, which involves the clean procedure under milder reaction conditions with an excellent yield of the desired products These Formamides are of most significance in synthetic organic chemistry as they are preliminary materials for a variety of products such as isocyanides, monomethylated amines, and formamidines Acknowledgment The author G Nagaraju thanks to DST-Nano Mission, (SR/NM/ NS-1226/2013) Govt of India, for funding LSR Yadav acknowledges BMSIT, Bangalore for constant support and encouragement Appendix A Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.jsamd.2019.03.001 References [1] L Wu, Y Wu, X Pan, F Kong, Synthesis of ZnO nanorod and the annealing effect on its photoluminescence property, Opt Mater 28 (2006) 418 [2] J Xie, Q Wu, One-pot synthesis of ZnO/Ag nanospheres with enhanced photocatalytic activity, Mater Lett 64 (2010) 389 Please cite this article as: L.S.R Yadav et al., Green synthesis of AgeZnO nanoparticles: Structural analysis, hydrogen generation, formylation and biodiesel applications, Journal of Science: Advanced 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Yadav et al., Green synthesis of AgeZnO nanoparticles: Structural analysis, hydrogen generation, formylation and biodiesel applications, Journal of Science: Advanced Materials and Devices, https://doi.org/10.1016/j.jsamd.2019.03.001... Yadav et al., Green synthesis of AgeZnO nanoparticles: Structural analysis, hydrogen generation, formylation and biodiesel applications, Journal of Science: Advanced Materials and Devices, https://doi.org/10.1016/j.jsamd.2019.03.001... Yadav et al., Green synthesis of AgeZnO nanoparticles: Structural analysis, hydrogen generation, formylation and biodiesel applications, Journal of Science: Advanced Materials and Devices, https://doi.org/10.1016/j.jsamd.2019.03.001