Browsing by Author "Pattar, J."

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An insight into noticeable dielectric response and effect of fe doping on photocatalytic efficiency (visible light) of ZnO nanoparticles synthesized through solution precipitation for harmful textile dye degradation
(Springer Science and Business Media B.V., 2024) Mahendra, K.; Fernandes, J.M.; James, A.; B.s, N.; Pattar, J.; Sunitha, D.V.; Gopal, K.; Udayashankar, N.K.
Iron (Fe)-incorporated zinc oxide (ZnO) nanoparticles (NPs) were synthesized via chemical precipitation technique and studied using powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), and UV–vis diffuse reflectance spectroscopy. PXRD analysis reveals a hexagonal wurtzite structure for all the synthesized samples. UV–visible measurements demonstrate a reduction in the bandgap of ZnO with an increase in Fe concentration. The ZnO and Fe-incorporated ZnO NPs are studied for the degradation of organic textile dye under visible light irradiation. All the nanoparticles are thoroughly investigated using impedance and dielectric measurements in the frequency range of 20 Hz to 1 MHz. The results obtained are compared, interpreted, and presented in this paper. © The Author(s), under exclusive licence to Springer Nature B.V. 2024.
Efficient removal of toxic dyes and nitrophenol using Graphene Oxide-ZrO2 hybrid catalysts
(Elsevier Ltd, 2025) Amudha, A.; Mahendra, K.; Yashodhara, I.; Pattar, J.; Anil Rao, H.N.; Shashikala, H.D.; Hosakoppa, S.N.
In the current study, efficient removal of industrial dyes and nitrophenol by ZrO2–GO catalyst has been reported. ZrO2–GO nanoparticles were prepared using the hydrothermal technique and are characterized using X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Transmission Electron Microscopy (TEM), Photoluminescence (PL), Raman, and UV–visible spectroscopy techniques. The ability of the nanoparticles to degrade Methylene Blue (MB), Crystal Violet (CV), and Nitrophenol (NP) was examined for their photocatalytic activities. Results revealed that there is an increase in the crystallite size and pore size increased almost 2 times after adding 2 % GO in ZrO2. The addition of GO into ZrO2 also caused a decrease in the PL intensity and energy gap indicating an increase in the charge carriers. ZrO2–GO nanoparticles showed photocatalytic degradation of 90 % (70 min), 98 % (90 min), and 70 % (120 min) for MB, CV, and NP respectively. © 2025 Elsevier B.V.
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.
Synthesis of ZnO and CuO–ZnO nanocomposites for photo-conducting and dielectric applications
(Elsevier Ltd, 2024) Advaitha, M.; Mahendra, K.; Pattar, J.; Das, P.P.
Zinc oxide (ZnO) and its composites has garnered a tremendous attention lately due to its effective role in electronic and optoelectronic applications. The present manuscript reports the synthesis and characterization of ZnO and CuO–ZnO nanocomposites. These samples were synthesized using precipitation technique and studied for voltage-dependent dielectrics and photoconductivity properties. Structural properties were thoroughly investigated using powder X-ray diffraction (PXRD) measurements. The composite material revealed decreased crystallinity and increased strain in the material. Optical absorption measurements were recorded using UV–vis diffusion reflectance measurements and the changes in the absorbance spectrum corresponding bandgap is explored. The obtained band gap is comparatively less for the composite material when compared with prestine ZnO. Structural morphology of the synthesized materials was observed and compared and changes in the composites when compared with the ZnO. Drastic changes in the morphology is witnessed. Electrical response of these synthesized semiconductors was studied using I–V and dielectric measurements. CuO–ZnO samples show a very clear sensitivity to the voltage dependent dielectric properties compared to ZnO. The composite and ZnO are studied using I–V measurements and the light dependent I–V measurements and composite revealed photo sensitivity. Drastic change in the conductivity is witnessed inferring the material to be used in optoelectronic application. Dielectric, Impedance, dielectric loss, AC conductivity and modulus index of the materials were explored by subjecting the materials to impedance measurements. The materials were also explored with different voltages and compared. The composite material revealed drastic variations for change in the voltage and measured parameters were compared with the ZnO. © 2024
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.
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.