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Item CARICA PAPAYA PEEL MEDIATED SYNTHESIS OF SILVER NANOPARTICLES AND ITS ANTIBACTERIAL ACTIVITY AGAINST HUMAN PATHOGENS(Elsevier, 2017-10-01) Balavijayalakshmi J; Ramalakshmi VMetallic nanoparticles are traditionally synthesized by wet chemical techniques, in which the chemicals used are quite often toxic and flammable. Ripe carica papaya peel is found to be a suitable source for green synthesis of silver nanoparticles. In the present work, a cost effective and environmental friendly technique for the green synthesis of silver nanoparticles from 1 mM silver nitrate (AgNO3) solution through the extract of ripe Carica papaya peel of various concentrations (5 ml, 10 ml, 15 ml, 20 ml, 25 ml) is described. The synthesized silver nanoparticles are characterized by using the UV–vis absorption spectroscopy, FT-IR, XRD, SEM and TEM. The formation of silver nanoparticles is confirmed by surface plasmon resonance, determined by UV–vis spectra at 400–435 nm. The shift in the absorption bands and variation in the calculated optical band gaps for the various concentrations of papaya peels extracts are also observed. The FT-IR spectra reveal that an increase in the concentration of the papaya peel extract shifts the bands to higher wavelengths. The average crystallite size for various concentrations of papaya peel extract is observed from XRD spectral analysis and is found to be around 16–20 nm, which is in good agreement with the TEM analysis. The SEM analysis shows the spherical structure of the silver nanoparticles with some agglomeration for higher concentrations of papaya peel extract. The synthesized silver nanoparticles show good antibacterial activity against human pathogens such as Escherichia coli and Staphylococcus aureus and it has many medical applicationsItem SYNTHESIS OF SILVER NANOPARTICLES USING NATURAL REDUCING AGENTS(Sastra University, Thanjavur, 2015-01-29) Balavijayalakshmi J; Ramalakshmi VGreen synthesis of nanoparticle is a novel way to synthesize nanoparticles by using biological sources. It is gaining attention due to its cost effective, eco friendly and large scale production possibilities. Silver nanoparticles are usually synthesized by chemicals which are quite toxic and flammable in nature. This study deals with an environmental friendly and biosynthesis process of antibacterial silver nanoparticles from 2mM aqueous AgNO3 using extract of carica papaya peel, well adorned for its wide availability and medical property. It is observed that the use of ripe carica papaya peel extract makes a fast and convenient method for the synthesis of silver nanoparticles and can reduce silver ions into silver nanoparticles without using any severe conditions. The formation and characterisation of silver nanoparticles (AgNPs) are confirmed by UV-Vis spectroscopy, Scanning electron microscopy (SEM), X-Ray diffraction (XRD), Fourier Transmission infrared spectroscopy (FTIR). Fourier transform infrared spectroscopy analysis revealed that bio molecules are involved in the synthesis and capping of silver nanoparticles. The XRD analysis confirmed that the silver nanoparticles (AgNPs) are crystalline in nature. The morphology of the AgNPs is studied using SEM analysis. The silver nanoparticles synthesized via green route are highly toxic to multidrug resistant human pathogens hence it has a great potential in biomedical application.Item A FACILE APPROACH TO SYNTHESIZE GRAPHENE OXIDE AND REDUCED GRAPHENE OXIDE NANOMATERIALS(BIT, Sathyamangalam, 2017-08-17) Ramalakshmi V; Yuvashree S; Balavijayalakshmi JTechnology 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.Item STRUCTURAL AND MORPHOLOGICAL INVESTIGATION ON THE GRAPHENE OXIDE NANOSHEETS FUNCTIONALIZED TRIMETALLIC NANOPARTICLES(Vizhi Chudar Pathippagam / Anna University, Chennai, 2017-01-06) Ramalakshmi V; Balavijayalakshmi JIn 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.Item INVESTIGATION ON STRUCTURAL AND MORPHOLOGICAL ANALYSIS OF ZINC OXIDE ENSEMBLED GRAPHENE OXIDE ELECTRODE MATERIAL(Institute of Applied Science & Computations / Journal of Applied Science and Computations, 2018) Ramalakshmi V; Balavijayalakshmi JGraphene has received considerable attention of all researchers employing globally in the area of materials science and technology. In this present work, Zinc oxide nanoparticles (GO-ZnO) anchored graphene oxide nancomposite is synthesized using chemical reduction method. The synthesized GO-ZnO nanocmopsites are subjected to FT-IR, XRD, SEM and EDAX techniques, in order to examine the functional, structural, morphological and elemental analysis. The X-ray diffraction analysis confirms the anchoring of well crystalline zinc oxide nanoparticles with the crystallite size of about 19 nm on the surface of graphene oxide. SEM analysis reveals the formation of spherical shape zinc oxide nanoparticles on the layered structured surface of graphene oxide. The enhanced electrochemical sensing property of the GO-ZnO nanocomposites is studied using cyclic voltammetry analysis. A glassy carbon electrode (GCE) modified with GO-ZnO nanocomposites (GO-ZnO/GCE) is fabricated for the rapid detection of onitrophenol. Under the optimal conditions, the GO-ZnO/GCE modified electrode shows the reduction potential at -0.6 V for the concentration of 220 μM of o-Nitrophenol in PBS buffer solution.Item CARICA PAPAYA PEEL MEDIATED SYNTHESIS OF SILVER NANOPARTICLES AND ITS ANTIBACTERIAL ACTIVITY AGAINST HUMAN PATHOGENS(Elsevier /Journal of Applied Research and Technology, 2017-10-01) Balavijayalakshmi J; Ramalakshmi VMetallic nanoparticles are traditionally synthesized by wet chemical techniques, in which the chemicals used are quite often toxic and flammable. Ripe carica papaya peel is found to be a suitable source for green synthesis of silver nanoparticles. In the present work, a cost effective and environmental friendly technique for the green synthesis of silver nanoparticles from 1 mM silver nitrate (AgNO3) solution through the extract of ripe Carica papaya peel of various concentrations (5 ml, 10 ml, 15 ml, 20 ml, 25 ml) is described. The synthesized silver nanoparticles are characterized by using the UV–vis absorption spectroscopy, FT-IR, XRD, SEM and TEM. The formation of silver nanoparticles is confirmed by surface plasmon resonance, determined by UV–vis spectra at 400–435 nm. The shift in the absorption bands and variation in the calculated optical band gaps for the various concentrations of papaya peels extracts are also observed. The FT-IR spectra reveal that an increase in the concentration of the papaya peel extract shifts the bands to higher wavelengths. The average crystallite size for various concentrations of papaya peel extract is observed from XRD spectral analysis and is found to be around 16–20 nm, which is in good agreement with the TEM analysis. The SEM analysis shows the spherical structure of the silver nanoparticles with some agglomeration for higher concentrations of papaya peel extract. The synthesized silver nanoparticles show good antibacterial activity against human pathogens such as Escherichia coli and Staphylococcus aureus and it has many medical applications.