Department of Physics

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    TIGHT FOCUSING PROPERTIES OF PHASE MODULATED AZIMUTHALLY POLARIZED DOUGHNUT GAUSSIAN VORTEX BEAM BY HIGH NA PARABOLIC MIRROR
    (Elsevier B.V, 2020) Umamageswari, N; Lavanya, M; Udhayakumar, M; Rajesh, K. B.; Zaroszewicz, Z
    The intensity distribution in the focal region of a high NA parabolic mirror for the incident azimuthally polarized doughnut Gaussian vortex beam (DGVB) transmitted through a multi belt complex phase filter (MBCF) is studied using vector diffraction theory. By properly designing the phase of the incident beam using MBCF and by tuning the beam parameters of a DGVB, it is possible to switch the focal spot with sub wavelength dimension and long focal depth in to multiple focal spots suitable for particle acceleration, atom optical experiments, and near-field scanning optical microscopy.
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    GRAPHENE BASED NANOCOMPOSITES FOR ELECTROCHEMICAL DETECTION OF H2O2
    (Elsevier B.V, 2019) 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.
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    DECORATION AND FUNCTIONALIZATION OF GRAPHENE OXIDE NANOCOMPOSITES FOR SENSING APPLICATIONS
    (Elsevier B.V, 2019) Ramalakshmi, V; Balavijayalakshmi, J
    In the present work, β-cyclodextrin functionalized reduced graphene oxide-silver nanocomposites (GO-β-CD-Ag) are effectively synthesized using wet chemical method. The GO-β-CD nanocomposites are initially produced via hydrazine reduction. The various concentrations (0.002 M, 0.004 M, 0.006 M, 0.008 M and 0.01 M) of silver nanoparticles are decorated on the GO-β-CD surface by the reduction of silver nitrate with sodium borohydrate as a reducing agent. The produced GO-β-CD-Ag nanocomposites are well characterized using XRD, SEM and EDAX analysis. The XRD results firmly established that the β-CD molecules are satisfactorily coated on the rGO surface and also the Ag nanoparticles with an average size of 23 nm are evenly decorated on the GO-β-CD surface. The GO-β-CD-Ag nanocomposites modified glassy carbon electrode is captivated for the selective detection of o-Nitrophenol. Cyclic voltammetry test is employed to determine the presence of o-Nitrophenol compound. The result shows the oxidation and reduction potential for o-Nitrophenol at -0.25 V and -0.5 V respectively, indicating the successful determination of o-Nitrophenol by using the GO-CD-Ag nanocomposite modified electrode.
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    IMPACT OF ALUMINIUM ON “STRUCTURAL, OPTICAL AND MORPHOLOGICAL PROPERTIES OF COPPER OXIDE NANOPARTICLES”
    (Elsevier B.V, 2019) 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.
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    IMPACT OF ANNEALING ON STRUCTURAL AND MAGNETIC PROPERTIES OF MANGANESE CO-DOPED MAGNESIUM-COBALT FERRITE NANOPARTICLES
    (Springer Link, 2017-05-04) Balavijayalakshmi, J; Annie Josphine, C
    Manganese co-doped magnesium-cobalt ferrite nanoparticles (Mg0.4Co0.4Mn0.2Fe2O4) are synthesized by co-precipitation method and are annealed at 130, 600 and 900 °C. The synthesized nanoparticles are characterized using X-ray diffraction (XRD) analysis, FT-IR spectral analysis, Scanning Electron Microscopy (SEM) analysis, Transmission Electron Microscopy (TEM ) analysis and Vibrating Sample Magnetometer (VSM ) analysis. The crystallite size is found to be 17 and 19.6 nm for the samples annealed at 600 and 900 °C respectively. The crystallite size and lattice constant increases as the samples are annealed at higher temperatures. FT-IR analysis confirms the characteristic absorption bands at 590 and 546 cm−1 for tetrahedral sites and 416 cm−1 for octahedral sites. SEM analysis shows uniformly distributed spherical shaped nanoparticles. The microstructure and particle size are analyzed by TEM analysis. The saturation magnetization, remanent magnetization and coercivity increases due to the inclusion of manganese and as the annealing temperature increases. These samples can be used for gas sensing applications.
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    EFFECT OF COBALT SUBSTITUTION ON STRUCTURAL AND MAGNETIC PROPERTIES OF MAGNESIUM FERRITE NANOPARTICLES
    (Springer Link, 2017-05-04) Balavijayalakshmi, J; Sudha, T
    Cobalt substituted magnesium ferrite (Mg(1−x)CoxFe2O4, where x = 0.2, 0.4, 0.6 and 0.8) nanoparticles are prepared by co-precipitation method and samples are annealed at 600 °C. The synthesized nanoparticles are characterized using FT-IR spectral analysis, X-ray diffraction (XRD) analysis, Scanning Electron Microscopy (SEM) analysis, Transmission Electron Microscopy (TEM ) analysis and Vibrating Sample Magnetometer (VSM) analysis. The FT-IR spectra show main absorption bands are shifted to higher values as the concentration of cobalt increases. The average nano-crystallite sizes are found to be in the range 7–9 nm. The SEM micrographs show uniformly distributed granular like structure. TEM indicate the presence of rectangular shaped nanoparticles. The magnetic properties of these samples are studied using Vibrating Sample Magnetometer (VSM). As the magnetic properties are enhanced due to the cobalt substitution the synthesized samples can be used as a gas sensor.
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    EFFECT OF DIELECTRIC INTERFACE ON THE TIGHT FOCUSING PROPERTIES OF RADIALLY POLARIZED ANNULAR MULTI GAUSSIAN BEAMS
    (Springer Link, 2015) Lavanya, M; Prabakaran, K; Rajesh, K. B; Udhayakumar, M
    A super-length optical needle (44�) of strong transversally polarized field with homogeneous intensity along the optical axis and sub-diffraction beam size (0.48�) can be generated by focusing a radially polarized beam through a dielectric interface with an annular high numerical aperture (NA) lens. Moreover, the focal shifts induced by the mismatch of the refractive indices across the interface has been found. The dependence of focal shifts and spot size of the focused field on the probe depth and NA of the objective is also analyzed in detail by numerical calculations using vector diffraction theory. Such kind of non-diffracting optical needle may have applications in atom-optical experiments, such as with atom trap and atom switches.
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    EFFECT OF CONCENTRATION ON DIELECTRIC PROPERTIES OF CO-CU FERRITE NANO PARTICLES
    (Elsevier B.V, 2013) Balavijayalakshmi, J; Suriyanarayanan, N; Jayaprakash, R; Gopalakrishnan, V
    Nano-sized Cobalt ferrites doped with copper as an additive element CoxCu(1-x)Fe2O4 (where x =0,0.2,0.4,0.6,0.8,1) are synthesized using co-precipitation method. Cobalt-Copper ferrite samples sintered at 600○C are subjected to X-ray diffraction to calculate the average particle size and lattice parameters using Debye – Scherrer formula. The FT-IR spectra of these samples are recorded to ensure the presence of the metallic compounds. The variations of dielectric constant and dielectric loss for all the samples are studied as a function of frequency. The crystalline structure of composite nano particles are characterized by Transmission Electron Microscope (TEM).
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    AN AMALGAM OF MG-DOPED TIO2 NANOPARTICLES PREPARED BY SOL–GEL METHOD FOR EFFECTIVE ANTIMICROBIAL AND PHOTOCATALYTIC ACTIVITY
    (Springer Link, 2021-09-15) Nithya, N; Gopi, S; Bhoopathi, G
    In this study, undoped and Magnesium doped TiO2 nanoparticles (Mg-TiO2 NPs) are successfully synthesized via a simple sol–gel method cost-effectively. The prepared Mg- TiO2 NPs is characterized by UV–Vis, FTIR, PL, XRD, FESEM, TEM, and EDAX. UV–Visible Spectroscopy showed that an increase in the optical bandgap concerning the concentration of dopant Mg increases. The bandgap values were found to be 3.57–3.54 eV. FTIR spectra shows that the presence of the characteristic stretching and bending vibrational band of Ti–O bonding at 468 cm−1 and shifts in vibrational bands were observed for Mg-TiO2 NPs. PL spectra of Mg- TiO2 NPs at different concentrations exhibit a strong UV emission band. X-ray diffraction confirmed the formation of the tetragonal anatase phase. The average crystallite size of synthesized samples was found to be 22–19 nm. The average crystallite size of Mg- TiO2 NPs decreases with increasing the concentration of dopant Mg. The FESEM and TEM analysis confirmed that the spherical morphology for both TiO2 and Mg-TiO2 NPs. SAED pattern confirms the crystalline nature of prepared samples. EDAX spectra confirm the presence of Ti, O, and Mg and confirm that Mg2+ ions are present in the TiO2 lattices. The prepared samples were investigated against gram-positive and gram-negative bacteria. The prepared samples exhibit potent antibacterial activity against gram-negative bacteria than the gram-positive bacteria. The prepared samples exhibit significant photocatalytic degradation for Methylene blue (MB).
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    THEORETICAL INVESTIGATION OF INTERMOLECULAR DIHYDROGEN BONDS IN C2H2•••HM AND C2H4•••HM (M = LI, NA AND K) COMPLEXES: A DFT AND AB INITIO STUDY
    (Asian Journal of Chemistry, 2021-07-26) Parimala devi, D; Tom, Giju; Praveena, G; Abiram, A
    This study aims to investigate the dihydrogen bond formation in ethyne (C2H2) and ethene (C2H4) with alkali metal hydrides (HM; M = Li, Na and K) complexes using density functional theory (DFT) and ab initio methods. It mainly focuses on the comparison of the performances of different functionals of DFT and ab initio method on the intermolecular dihydrogen bonded complexes. The geometrical parameter and energy values agree with the formation of dihydrogen bonds in the complexes. Among the ethyne and ethene complexes, the smallest dihydrogen bond distance was formed by C2H2···HK and C2H4···HK, respectively. The C2H2 is found to form better dihydrogen bond (DHB) with alkali metal hydrides than C2H4. Among all the functionals, M06L was observed to predict shortest H···H bond distance, while M062X the longest. Natural bond orbital (NBO), quantum theory of atom in molecules (QTAIM) along with molecular electrostatic potential (MEP) analysis further confirms the dihydrogen bond formation.