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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 A FACILE SYNTHESIS AND INVESTIGATION ON METAL OXIDE NANOPARTICLES EMBELLISHED GRAPHENE OXIDE NANOCOMPOSITES(Royal Book publishers / PSGR Krishnammal College for Women, Coimbatore, 2018-01-03) Ramalakshmi V; Balavijayalakshmi J; Roshini PGraphene is a flat monolayer of carbon atoms with sp2-hybridized two-dimensional carbon structure. Graphene’s fascinating high conductivity, superior electron mobility, extremely high specific surface area and easy functionalization make graphene a good substrate to yield graphene-based nanocomposites. Metal oxides nanomaterials have considerable attention due to their unique properties that can be used for designing advanced nanodevices. Thus, in the present study metal oxide nanoparticles embellished graphene oxide nanosheets (GNs) is synthesized and characterized. The graphene oxide nanosheets are produced by modified Hummer’s method. The metal oxide nanoparticles are loaded on the synthesized graphene oxide nanosheets via chemical reduction method. The metal oxide nanoparticles embellished graphene oxide nanosheets are characterized using Fourier transform infrared spectroscopy (FT-IR), X-Ray diffraction analysis and Field emission scanning electron microscopy (FE-SEM). The structural properties of the synthesized nanocomposites are characterized using X-Ray diffraction analysis and the result confirms that the synthesized nanocomposites are well crystalline. The morphology of synthesized nanocomposites is analyzed using field emission scanning electron microscopy analysis.Item INVESTIGATION ON EMBELLISHMENT OF METAL NANOPARTICLES ON GRAPHENE NANOSHEETS AND ITS SENSING APPLICATIONS(Centre for Crystal Growth, VIT University, Vellore, 2017-10-09) Ramalakshmi V; Balavijayalakshmi JNanotechnology promises breakthroughs in areas such as manufacturing nanoelectronics, medicine and healthcare, energy, biotechnology, information technology, and national security. The present work describes a general approach for the preparation of cyclodextrin functionalized (CD) graphene oxide nanosheets (GNs) for the embellishment of different concentrations of silver nanoparticles (Ag) on the surface of GNs. The graphene oxide nanosheets are synthesized by modified Hummer’s method. Firstly, CD/RGO nanosheets are synthesized through hydrazine reduction. The different concentrations of Ag nanoparticles are loaded on the CD/RGO nanosheets by the reduction of AgNO3 with NaBH4 as reducing agent. The synthesized CD/RGO/Ag nanocomposites are well characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Raman spectroscopy and EDAX analysis. The results confirmed that the CD is effectively covered on the RGO surface and the Ag nanoparticles are uniformly decorated on the CD/RGO nanosheets [1]. The modified glassy carbon electrode was employed for the selective determination of phenolic compounds. Cyclic voltammetry measurements suggested that the CD/RGO/Ag nanocomposites exhibits an excellent electrochemical activity towards oxidation of phenolic compounds due to the host-guest recognition and enrichment capability of β-CD as well as the outstanding electronic properties of RGO and Ag nanoparticles [2].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 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.