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NITROGEN DOPED GRAPHENE OXIDE / NICKEL OXIDE HYBRIDS FOR DYE SENSITIZED SOLAR CELL APPLICATIONS
(Centre for NanoScience and Technology, Institute of Science and Technology, Jawaharlal Nehru Technological University Hyderabad, Hyderabad, 2018-10-04) Shanmugapriya T; Balavijayalakshmi J
Solar energy plays a vital type of renewable energy because of its environmental friendliness and the potential for high power conversion efficiency in solar energy harvesting devices. Dye-sensitized solar cells (DSSCs) are gaining considerable interest as alternatives to the semiconductor-based thin film solar cells. Natural dye sensitized solar cells are becoming promising candidates for replacing synthetic dyes. Graphene oxide exhibits impressive photoelectric properties, large surface area, high charge-carrier mobility, high conductance and fast electron transfer.These great features offer graphene oxide as most promising materials for various potential applications. Nickel Oxide are of particular interest because of its good electro-catalytic properties, low toxicity and low cost, which makes them suitable for photo-anode in dye sensitized solar cells. In the present work,a hybrid material consisting of nickel oxide nanoparticles anchored onto the nitrogen doped graphene oxide sheets are prepared by chemical precipitation method. The structural and morphological of the prepared nanocomposites areinvestigated by X-Ray diffraction analysis and electron microscopy (FE-SEM). The presence of functional groups in the synthesized nanocomposites are studied by Fourier transform infrared spectroscopy(FT-IR). The electrochemical activity of the prepared nanocomposites is investigated by cyclic voltammetry (CV).The prepared nanocomposites are suitable for dye sensitized solar cell applications.
SYNTHESIS AND CHARACTERIZATION OF GRAPHENE OXIDE BASED METAL NANOCOMPOSITES
(Royal Book publishers / PSGR Krishnammal College for Women, Coimbatore, 2018-01-03) Yuvashree S; Balavijayalakshmi J; Sharvasri S
Graphene, a monolayer of carbon atoms packed into a dense honeycomb crystal structure has attracted considerable attention and numerous investigations because of its unique nanostructure and its extraordinary properties. Graphene and its derivatives, such as graphene oxide (GO) and reduced graphene oxide (rGO), are ideal platforms for constructing graphene-based nanostructures for various applications. In this present work, metal nanoparticles are decorated onto the graphene surface which helps to increase the conductivity of nanocomposites and enhances the properties of the material. Thus graphene based metal nanocomposites are prepared by chemical reduction method. The structural and morphological properties of the prepared nanocomposites are investigated by X-Ray diffraction analysis and Field emission scanning electron microscopy (FE-SEM). The presence of functional groups in the synthesized nanocomposites are studied by Fourier transform infrared spectroscopy(FT-IR). XRD reveals that the product is well crystallized. Thus the prepared nanocomposites can be applied for biomedical applications.
INFLUENCE OF IRON ON THE STRUCTURAL AND OPTICAL PROPERTIES OF NICKEL SULPHIDE NANOPARTICLES
(Royal Book publishers / PSGR Krishnammal College for Women, Coimbatore., 2018-01-03) Sonia D; Balavijayalakshmi J
Transition metal sulphides exhibit excellent optical, photo electrical and thermoelectric properties. These materials have attracted much attention because of its applications in the field of electroluminescence devices, light emitting displays, cathode material for rechargeable lithium battery, magnetic devices, dye degradation and optical sensors. In the present work, iron doped Nickel sulphide nanopartciles are synthesized using chemical precipitation method. Nickel chloride and Ferric chloride are used as precursors and sodium sulphide as a stabilizing agent. The synthesized nanoparticles are characterized using FT-IR, XRD, SEM, UV-Vis, and PL studies. The presence of function groups are confirmed from FT-IR spectral analysis. The XRD analysis shows the crystalline nature of nanoparticles and the average nano-crystalline size is calculated using Debye – Scherrer formula. The morphology of the samples is analyzed using scanning electron microscope. The optical properties are characterized using UV-Vis spectral analysis and PL study. The synthesized nanoparticles may be used as a catalyst for degradation of organic dyes.
IMPACT OF ALUMINIUM ON STRUCTURAL, OPTICAL AND MORPHOLOGICAL PROPERTIES OF COPPER OXIDE NANOPARTICLES
(Royal Book publishers / PSGR Krishnammal College for Women, Coimbatore., 2018-01-03) Vidhya Priya P; Balavijayalakshmi J
Metal-oxide-semiconductors have been widely used for the optoelectronic applications like smart windows, solar cells, light emitting diodes and flat panel displays. Among all the metal oxides, copper oxide nanomaterials have a great attention due to its unique properties. It is mostly used in recent research works because of its low cost, rich availability and used in latent applications like antibacterial activities. Aluminium nanoparticles are a good conductor and it enhances the conductivity. Hence an attempt is made to synthesize CuO and Al doped CuO nanoparticles by hydrothermal method. The prepared samples are characterized by XRD, FT-IR, SEM, UV-Vis and PL analysis.The crystallite structures of CuO and Al doped CuO nanoparticles are identified by XRD analysis. The Fourier transform Infrared spectroscopy is used to determine the functional groups present in the prepared nanoparticles. UV-Vis Spectral analysis is performed to determine the band gap energy of the synthesized nanoparticles. PL spectral studies are used to study the optical properties of the nanoparticles. The morphology of the samples is determined by using scanning electron microscopy analysis. The impact of aluminium on structural, optical and morphological properties is investigated. The antibacterial activities of prepared CuO and Al doped CuO nanoparticles are probed.
GRAPHENE BASED NANOCOMPOSITES FOR ELECTROCHEMICAL DETECTION OF H2O2
(Royal Book publishers / PSGR Krishnammal College for Women, Coimbatore., 2018-01-01) Yuvashree S; Balavijayalakshmi J
In this study, a novel reduced graphene oxide-based nanocomposite electrochemical biosensor for the reliable detection of H2O2 is developed. Reduced graphene oxide-chitosan nanocomposites are successfully prepared by chemical reduction method. XRD, FT-IR, SEM and EDAX analysis are performed to characterize the structural, spectral, morphology and composition of the prepared nanocomposites. The response of the modified electrode to H2O2 is examined by cyclic voltammetry. Under optimal experimental conditions, the RGO-CS biosensor showed outstanding catalytic activity toward H2O2 reduction. The H2O2 reduction peaks are observed about 0.1V. These results confirm that RGO-CS nanocomposites with the high surface area and electrocatalytic activity offer a promising candidate for the detection of H2O2 in biological environment.
A FACILE APPROACH TO SYNTHESIZE GRAPHENE OXIDE AND REDUCED GRAPHENE OXIDE NANOMATERIALS
(BIT, Sathyamangalam, 2017-08-17) Ramalakshmi V; Yuvashree S; Balavijayalakshmi J
Technology research in nanotechnology promises breakthroughs in areas such as materials and manufacturing nanoelectronics, medicine, healthcare, energy, biotechnology, information technology, and national security. One of the crucial bottlenecks for the application of graphene-based systems in materials science is their mass production. Meeting the requirements, graphene oxide (GO) has been considered widely as a prominent precursor and a starting material for the synthesis of this processable material [1]. This work describes the synthesis and characteristic analysis of Graphene oxide (GO) and reduced graphene oxide. Graphene Oxide (GO) is synthesized in large quantity from Natural Flake Graphite (NFG) by modified Hummer’s method. The synthesized GO is chemically reduced to Reduced Graphene Oxide (RGO) using hydrazine monohydrate as reducing agent via wet chemical method. The synthesized samples are characterized using Fourier Transform Infrared (FTIR) spectroscopy, X-ray Diffraction analysis (XRD), Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray (EDS). The characterized samples have been tested for the removal of dye from water in water purification process.
ELECTROCHEMICAL BEHAVIOUR OF PREPARED REDUCED GRAPHENE OXIDE/ CHITOSAN NANOCOMPOSITES
(Sastra University, Thanjavur., 2017-02-27) Yuvashree S; Balavijayalakshmi J
Recently, efforts have been made to develop technologically feasible graphene-based devices. The development of composite materials based on graphene and natural polymers provides an ideal material in the biomedical field. However, the lack of good mechanical and thermal properties limits its applications. This drawback could be overcome by the reduction of graphene oxide into reduced graphene oxide (RGO). The RGO combined with the polymer helps to increase the conductivity of nanocomposites which thereby enhances the properties of the material to suit commercial applications. This present work is based on the investigation of the electrochemical behaviour of reduced graphene oxide/Chitosan nanocomposite synthesized by chemical reduction method. The synthesized rGO/CS nanocomposites are characterized using ultraviolet–visible (UV-Vis) spectral analysis, Fourier transform infrared (FT-IR) spectral analysis, X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) analysis. The surface charge as well as stability of the nanocomposites is examined by electrochemical characterization using cyclic voltammetry technique. The analytical responses and the redox mechanisms are evaluated which shows high current response for RGO/Chitosan nanocomposites compared to pure RGO nanosheets. This suggests that RGO/Chitosan nanocomposites have excellent electrochemical behaviour and is further applied for bio sensing applications.
GREEN SYNTHESIS OF FE2O3 NANOPARTICLES DERIVED USING BETA VULGARIUS LEAF EXTRACT AS ONE STEP PROCESS
(Vizhi Chudar Pathippagam/ Anna University, Chennai., 2017-01-06) Ponpoorani A; Balavijayalakshmi J
Iron oxide nanoparticles have been widely investigated due to their magnetic properties and its potential applications in the area of bioscience and medicine. The Iron oxide has several advantages such as it has better oxidation stability, compatibility in the non aqueous solution, chemical inertness and non toxicity [1]. The adsorption nature of iron oxide has the significant attention in the removal of inorganic chemical pollutants in waste water and underground water [2]. The synthesis of magnetic nanoparticles are done using several physical and chemical methods having drawbacks such as defective surface, low production rate, usage of toxic chemicals and hazardous products during synthesis. Green synthesis technique is the cost effective, eco friendly method and active organic compounds of plant materials used as the reducing agent instead of toxic compounds. The distinct advantages of the green synthesis technique are to overcome the drawbacks of other conventional and timescale biological synthesis techniques. Plant extract acts as the low capping and stabilizing agent. Iron oxide nanoparticles synthesis was done using different plant extracts [3]. In this study, green synthesis route is the one of the most advantageous routes to synthesize Fe2O3 nanoparticles using beet green extract (BETA VULGARIUS) with precursor as ferric chloride solution in a fixed ratio [4]. The iron oxide nanoparticles were synthesized by taking 0.1M of ferric chloride in 25ml of de-ionized water and 25ml of the aqueous solution of leaf extract of BETA VULGARIUS was added in it and colour change was observed. The synthesized iron oxide nanoparticles are characterized using UV-Vis spectroscopy, X-Ray diffraction (XRD), Fourier Transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), High Resolution Transmission Spectroscopy (HR-TEM) and Vibrating Sample Magnetometer (VSM). The UV-Vis spectral analysis of iron oxide nanoparticles from beta vulgarius leaf extract after removing the settled sample from the plant matrix solution. The UV-Vis spectral analysis confirms the formation and stability of iron oxide nanoparticles. The spectrum was recorded between the ranges of 200-800nm. The characteristics peak at 234 nm indicates the presences of Fe2O3 nanoparticles [5]. The optical band gap was found to be 5.299 eV. The FT-IR characterization study is performed to identify the ferric ions and organic stabilizing plant compounds which acts as the reducing agent in ferric chloride ions to form the iron oxide nanoparticles. The FT-IR spectrum of iron oxide nanoparticles from beta vulgaris leaf extract recorded in the range 4000-400cm-1. The absorption bands around 3367cm-1 and 1638cm-1 represents O-H stretching vibrations. The characteristic absorption bands observed around 654 cm-1, 606cm-1 and 562 cm-1 indicates the Fe-O stretching, confirms the presence of iron oxide nanoparticles. These bands correspond to the tetrahedral sites of metal-oxygen bonds and the band around 420 cm-1 corresponds to the octahedral sites of metal-oxygen bonds [6]. FT-IR analysis confirms the bio reduction of ferric chloride into iron oxide nanoparticles.XRD analysis confirms the crystalline nature of iron oxide nanoparticles. The characteristic peaks correspond to (121), (122), (201), (210), (123), (132), (221), (042), (124) and (142) planes. All the diffraction patterns are in good agreement with the JCPDS Card no. 89-7047 corresponding to Fe2O3 in orthorhombic geometry. And the average crystallite size is found to be around 21 nm [7]. The morphological studies of synthesized nanoparticles were studied using the SEM and HR-TEM analysis. The SEM and HR-TEM analysis of different magnifications reveals the shape of iron oxide nanoparticles from beta vulgaris leaf extract. SEM analysis shows the distorted orthorhombic shape of iron oxide nanoparticles. The nanoparticles were agglomerated and coagulated in some places may be due to the beet green extract [8]. The particle size was found in the HR-TEM analysis to be around 21 nm which is good agreement with XRD analysis. The elemental composition of synthesized iron oxide nanoparticles were studied using EDAX spectra. It confirms the presence of Fe-O bond composition. The Selected Area Electron Diffraction pattern of synthesized iron oxide nanoparticles derived from beta vulgaris leaf extract. Each ring corresponds to the characteristic planes of XRD pattern. The magnetic behaviour of Iron oxide nanoparticles is studied using the vibrating sample magnetometer [9]. The saturation magnetization, remanent magnetization and coercivity are found to 788.9E-6 emu, 2.24 E-6 emu and 39.524G respectively.
STRUCTURAL AND MORPHOLOGICAL INVESTIGATION ON THE GRAPHENE OXIDE NANOSHEETS FUNCTIONALIZED TRIMETALLIC NANOPARTICLES
(Vizhi Chudar Pathippagam / Anna University, Chennai, 2017-01-06) Ramalakshmi V; Balavijayalakshmi J
In recent years, the trimetallic nanoparticles (NPs) are of having great interest because of their novel properties and applications. Trimetallic nanoparticles have improved physicochemical properties compared to their monometallic nanoparticles. Among the other metallic NPs, trimetallic NPs possess scientific and industrial importance because of their unique properties namely, magnetic, optical, electronic, and catalytic for practical applications [1]. In the present paper, the attempt has been made to synthesize trimetallic Au-Ag/Ni nanocomposites on β-cyclodextrin functionalized reduced nano graphene sheets (β-CD-NGS) as the platform. Graphene, a two-dimensional structure consists of sp2 hybridized carbon closely packed honeycomb lattices. It is considered as a basic building block for graphitic materials with all other dimensionalities [2]. It has considerable heed on both the experimental and theoretical fields because of its unique nanostructure and a variety of attracting thermal, mechanical, electrical properties. Based on these remarkable properties of graphene, these graphene nanosheets can be used as an ideal building block for nanocomposites and are broadly applied in many technological fields such as nanophotonics, sensors, catalysis, and supercapacitors [3]. But during the reduction process of graphene oxide (GO) to nano graphene sheets (NGS), NGS tends to agglomerates via Vander Waals interactions, due to the loss of oxygen containing functional groups in GO, and it is difficult for many potential applications. To overcome this problem, the β-Cyclodextrin (β-CD) is introduced into the graphene oxide before the reduction process is fully completed. The introduced β -CD onto the surface of NGS prevents the agglomeration of the NGS and improves the solubility of the β-CD-NGs in water [3]. This new composite have individual properties of two materials, such as large surface area and high conductivity of GO and supramolecular recognition and enrichment capability of β-CD. It is a macrocyclic allied oligosaccharides composed of seven glucose units. It is toroidal in shape with a hydrophobic inner cavity and a hydrophilic exterior which provides water solubility. The characteristic of β-CD facilitates them to selectively bind various organic, inorganic, and biological guest molecules into their cavities to form stable host guest inclusion complexes and also exhibits high molecular selectivity and enantioselectivity. Therefore, β-CD functionalized NGS are used as a platform for the preparation of nanocomposites [4]. In recent years metal nanoparticles (Au, Ag) have been used for many potential applications, because of their high surface to volume ratio and good catalytic activity compared to their respective bulk metals. The noble metals (Au, Pd, Pt etc.) doped with non-noble metals (Fe, Co, Ni etc.) is an admirable approach to intensify the catalytic activity and the sensitivity of nanomaterials [5]. The synthesized nanocomposites are characterized using UV-Vis, FT-IR, XRD, EDX and SEM analysis. Synthesized Pure NGS, β-CD, β-CD-NGS and β-CD-NGS-(Au-Ag/Ni) nanocomposites are characterized using UV-Vis spectroscopy. According to the UV-Vis spectral analysis, the absorption band for pure NGS are obtained around 240 nm and 300 nm for π-π* transition of the atomic C-C bonds and n-π* transitions of aromatic C-C bonds respectively and for β –CD the major peak observed around 260 nm. In the β-CD-NGS spectra, an absorption peak at 260 nm is observed, indicating the successful synthesis of β-CD-NGS. The UV-Vis spectra of β-CD-NGS-(Au-Ag/Ni) nanocomposite confirm the presence of all formed composites [3]. FT-IR spectra of pure NGS, β-CD, β-CD-NGS and β-CD-NGS-(Au-Ag/Ni) nanocomposites are recorded. From the results, the transmission bands of pure NGS obtained around 1100 cm-1, 1600 cm-1 and 3400 cm-1 may correspond to the bending vibrations of coupled C–C/C–O, O–H and O–H stretching vibration respectively. The FT-IR spectra of β-CD-NGS exhibits spectra for β-CD around 940 cm-1, 700 cm-1 and 570 cm-1 may due to the skeletal vibration and pyranose ring vibrations respectively, which is in good agreement with the pure β-CD spectrum. The main absorption peaks of pure NGS are also observed and it confirms the presence of β-CD molecules on the surface of GNS. The FT-IR spectra of β-CD-NGS-(Au-Ag/Ni) nanocomposites also confirm the presence of all the functional groups of synthesized nanocomposites [6]. The crystalline nature of the synthesized nanocomposites is studied using XRD analysis. By observing the sharp crystalline XRD peaks, the formation of pure nanoparticles without any impurities are confirmed .The microstructure of the Pure NGS, β-CD, β-CD-NGS and β-CD-NGS-(Au-Ag/Ni) nanocomposites are investigated by SEM analysis. In the SEM image of β-CD-NGS-(Au-Ag/Ni) nanocomposites, the bright spots are observed, which confirms the formation of trimetallic nanoparticles on CD-NGS [4]. The EDX spectrum of the prepared β-CD-NGS-(Au-Ag/Ni) nanocomposites confirms the presence of the β-CD, NGS, Au, Ag, Ni element in the prepared nanocomposites [7]. The as-synthesized nanocomposites may have many potential applications in removal of dye pollutants and waste water treatment technologies etc.
A FACILE SYNTHESIS OF REDUCED GRAPHENE OXIDE/CHITOSAN/AG NANOCOMPOSITES
(Vizhi Chudar Pathippagam / Anna University, Chennai., 2017-01-06) Yuvashree S; Balavijayalakshmi J
Graphene is a monolayer of carbon atoms, which is densely packed in a honeycomb lattice. Owing to its two-dimensional (2D) nanostructure, it has attracted enormous attention in the field of nanotechnology. Due to its unique catalytic, magnetic, optoelectronic and biological properties, Graphene and its derivatives has exhibited extensive and potential applications in electrode modifying materials, sensors, biomedical, bioengineering, drug delivery, gene delivery and semiconductors [1]. Chitosan (CS) is a natural bio polysaccharide and the most abundant polymer which is biocompatible and can be degraded by enzymes in human body. It has attracted considerable interest due to its biodegradability, biocompatibility, non-toxicity, good water permeability, high mechanical strength, adhesion and antibacterial properties, which leads to tremendous applications in agriculture, biopesticide, wine making, polyurethane coating, medicine etc., [2]. In addition to these, metal nanoparticles have been widely used for the fabrication of nanocomposites. Silver (Ag) nanoparticles, a well known and most popular, have also been used for long time in research areas because of its excellent chemical and physical properties. It has been applied in antimicrobial coatings, textiles, keyboards, wound dressings, and biomedical applications such as drug delivery, antibacterial etc. These biomedical devices now contain silver nanoparticles that continuously release a low level of silver ions to provide protection against bacteria. In this present work, reduced graphene oxide/Chitosan/Ag nanocomposites have been synthesized by chemical reduction method. Graphene Oxide (GO) is obtained from natural graphite powder according to a modified Hummers method, in which graphite is treated with a mixture of very strong oxidizers such as sulphuric acid, sodium nitrate and potassium permanganate. The carbon atoms in GO loses the electrical conductivity nature of graphene and it can be restored by reduction of GO into reduced graphene oxide (rGO). This is then followed by synthesizing rGO/CS, rGO/CS/Ag nanocomposties [3]. Thus the prepared GO, rGO, rGO/CS, rGO/CS/Ag nanocomposites is further characterized using ultraviolet–visible (UV-Vis) spectral analysis, Fourier transform infrared (FT-IR) spectral analysis, X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) analysis. It is observed from UV-Vis spectral analysis that the absorption spectra for GO has two characteristic peaks around 230 nm and 301nm due to π-π* transition of aromatic C=C bonds and n-π* transition of C=O bonds respectively. On further reducing GO, the peak gets shifted around 265 nm and the peak around 301nm gets disappeared, which confirms the reduction of GO into rGO [4]. A new peak formed around 430 nm indicates the formation of rGO/CS/Ag nanocomposites. FT-IR spectral analysis confirms the functional groups of the as-obtained GO, rGO, rGO/CS/Ag nanocomposites. The FT-IR spectra is observed in the region of 4000 to 400 cm-1.The absorption band around 3500 cm-1 attributes to O-H stretching vibrations due to hydroxyl groups in GO. The band around 1720 cm-1 indicates the –COOH vibrations, which shows the reduction of GO into rGO and the C-H stretching vibrations are assumed to be around 2854 cm-1. The band around 1680 cm-1 indicates the presence of acetyl amino groups and C=C stretching vibration is observed around 1387 cm-1[5]. The crystalline structure of the prepared GO, rGO, rGO/CS/Ag nanocomposites is confirmed by X-ray diffraction (XRD) analysis. The diffracted peak formed corresponds to the (002) plane of GO which exhibits inter-planner spacing of 0.80±3nm. On further adding CS and Ag nanoparticles, the diffraction peak of GO reduces and simultaneously the diffraction peak of Ag increases. RGO/CS/Ag nanocomposites shows diffraction peak for rGO, CS and Ag. The morphological studies have been carried out using Scanning Electron Microscope [6]. It indicates that CS/Ag nanocomposites are uniformly dispersed on to the rGO nanosheets. Thus the prepared rGO/Chitosan/Ag nanocomposites can be tested for biomedical applications [7].

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