Faculty Publications
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Item A systematic investigation on structural, electrical, linear and nonlinear optical properties of Zn:CdO thin films for optoelectronic applications(Elsevier B.V., 2021) Nagaraja, B.S.; Gurumurthy, S.C.; Bairy, R.; Koduri, K.; K, B.; Rao, A.In the present work, a systematic study on structural, electrical, linear, and nonlinear optical properties of Zn doped CdO thin films prepared by Spray Pyrolysis (SP) technique is reported. X-ray diffraction (XRD) studies revealed the cubic, wurtzite structure, and polycrystalline nature of all the films. The observed results showed a decrease in lattice constant and unit cell volume with an increase in Zn doping concentration. Morphology study confirms uniform distribution of spherical grain-like structure with small voids. An increase in direct and indirect bandgap is observed with doping concentration up to 5 wt%, and the trend reverses at higher concentration. The significant effect of Zn doping on optical parameters such as absorption coefficient, extension coefficient, refractive index, optical dielectric constant, and optical conductivities are calculated for all thin films. Further, the optical studies were used to analyze the linear susceptibility, third-order nonlinear optical susceptibility, and nonlinear refractive index of the films. The observed values for ?(1),?(3) and n2 are in the range from 0.03 to 0.09 esu, 3.51×10?16 to 1.02×10?14 esu, and 1.09×10?14 to 2.67×10?13 esu for pure and Zn doped thin films respectively. Hall coefficient and electrical studies indicate that the Zn doping influences the electrical properties. An n-type and ohmic behavior is also observed for these films. Optical and electrical results suggest that these Zn:CdO films can be a potential candidate for optoelectronic applications. © 2021 Elsevier B.V.Item Systematic investigation and comparison of oxalic acid dihydrate, ammonium oxalate hydrate and ammonium hydrogen oxalate oxalic acid dihydrate single crystals(Elsevier Ltd, 2023) Mahendra, K.; Fernandes, B.J.; Pattar, J.; Pujar, S.; Nagaraja, B.S.; Ramesh, K.P.; Udayashankar, N.K.Semiorganic crystals are hybrid materials that have captured the interest of researchers due to their improved material characteristics and applications. In the current work, single crystals of oxalic acid dihydrate (OAD), Ammonium oxalate hydrate (AHO), and Ammonium hydrogen oxalate oxalic acid dihydrate (AHOOD) were grown using a slow evaporation method. Single crystal and powder XRD measurements were carried out to elucidate their unit cell parameters, crystal system, and structural information. To comprehend the interplay of light and matter, optical investigations like UV–Vis Spectroscopy and photoluminescence studies were performed. Interaction of ammonium with oxalic acid, and thus formed crystals, was investigated using impedance spectroscopy. Detailed dielectric parameters such as dielectric constant, dielectric loss, impedance, conductivity, and electric modulus were explored as a function of frequency. Vickers hardness test was used to calculate the hardness, Meyer's number, brittleness, and fracture toughness. The crystals were determined to be of the hard materials group. © 2022 Elsevier B.V.Item Visible-light-driven photocatalytic degradation of organic dyes over cubic-phase and hexagonal-phase CdS: a comparative study(Springer, 2023) Mahendra, K.; Anupriya, J.; Gajendra, N.; Madhusudhan, C.K.; Nagaraja, B.S.; Pattar, J.; Udayashankar, N.K.Organic effluents—the gift of industrial development is a critical menace to environs as well as raising a question mark toward the sustainability of humans. In such a scenario, achieving consistent sunlight-driven photocatalytic degradation gains widespread attention due to its eco-friendly low-cost approach with high efficiency. Herein, the CdS-cubic nanoparticles have been synthesized using a simple chemical precipitation technique and structural transition to CdS hexagonal is obtained through annealing. Morphology study has validated the reduction in particle size of CdS cubic and corresponding enhancement in the surface are put forth by BET analysis. The better degradation capability of CdS cubic is demonstrated through the visible-light-driven photocatalysis of MB dye with a degradation rate constant of k = 0.02/min. Meanwhile, CdS hexagonal possesses a rate constant k = 0.005/min. The scavenger study reveals the vital role of conduction band electron and superoxide radical in decolorization. Moreover, lesser carrier recombination with more charge transfer is observed from PL and EIS, respectively, emphasizing the CdS-cubic nanoparticle's catalytic activity. © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.Item Investigation of ZnO Nanoparticles Synthesized with Different Concentrations of NaOH for Dielectric and Photocatalytic Applications(Springer Science and Business Media Deutschland GmbH, 2025) Mahendra, K.; Fernandes, J.M.; James, A.; Nagaraja, B.S.; Pattar, J.; Udayashankar, N.K.In this study, ZnO nanoparticles are synthesized for photocatalytic and dielectric applications using precipitation technique. The properties of ZnO nanoparticles are investigated for various sodium hydroxide (NaOH) concentrations. The powder X-ray diffraction (PXRD) method is employed to analyse structural properties. PXRD reveals the decrease in cell volume from 47.92 to 47.73 Å and crystallite size varied from 31.96 to 22.53 nm. The scanning electron microscope (SEM) study explained the morphology and EDS measurements revealed the presence of zinc and oxygen distribution on the surface. Further, the particle size is also calculated to be 62.23 nm, 50.16 nm, 46.86 nm and 47.43 nm respectively. The diffuse reflectance spectroscopy (UV-DRS) study indicates that, as NaOH concentration increases, the optical bandgap of the ZnO nanoparticles decreases from 3.25 eV to 3.12 eV. The PL studies revealed blue emission for all ZnO nanoparticles. I–V measurements indicate improved conductivity for higher concentrations of NaOH. A photocatalyst (as synthesized) is examined in the presence of UV radiation for its ability to photodegrade organic pollutants (Methylene Blue dye) with adsorption capacity of 19.7%, 20.3%, 21.48% and 22.97% respectively. The increased adsorption could be due to the increased surface area of the samples. Further, the dielectric properties of the synthesized nanoparticles, including impedance, dielectric constant, conductivity, dielectric loss, and electric modulus is established and examined. © The Tunisian Chemical Society and Springer Nature Switzerland AG 2025.