This study has been conducted with the objective of investigating the effects of zinc oxide nanoparticles on the structural and electrical properties of polyvinyl alcohol films. The fabricated nanocomposites were characterised by Fourier transform infrared spectroscopy, UV-visible (vis) spectra, X-ray diffraction and SEM techniques. UV-vis spectra showed that the addition of ZnO nanoparticles did not affect the absorbance in the visible region of nanocomposites. The SEM image showed that ZnO nanoparticles were homogeneously dispersed throughout the entire film's polymeric matrix. The dielectric properties were found to be strongly dependent on frequency and nanofiller content. AC conductivity s ac of polyvinyl alcohol/ZnO nanocomposites increased with increasing frequency. The dissipation factor tan d also increased with nanoparticle addition and decreased with frequency. At low nanofiller concentrations, nanocomposites exhibited low dielectric values at higher frequency, thus behaving like a lossless material, making them suitable for utilisation in microwave applications.

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The objective of this study was to investigate the effects of CuO nanoparticles on the structural, thermal and electrical properties of polyvinyl alcohol (PVA) thin films. The thin films were prepared by a solution casting technique with different weight percentages viz., 0.5, 1.0, 1.5 and 2.0 wt% of CuO nanoparticles in PVA matrix. The fabricated nanocomposite thin films were structurally characterised by Fourier transform infrared spectroscopy and X-ray diffraction, while differential scanning calorimetry indicated the effect of CuO nanoparticles on thermal properties of PVA. The surface morphology of the films was determined by scanning electron microscopy technique. Dielectric properties were analysed using high frequency LCR metre and were found to be dependent on frequency and CuO concentration. Dielectric constant decreased with increase in both frequency and CuO concentration. Dielectric loss increased with frequency increase and decreased with increase in CuO concentration. AC conductivity increased with increase in frequency. PVA-2.0 wt% CuO nanocomposite was found to possess desirable properties such as low dielectric constant and low dielectric loss which makes it a desirable material for use in microelectronics industry.

In the present communication, we report a comparative study of Cr (VI) removal using biologically synthesized nano zero valent iron (BS-nZVI) and chemically synthesized nZVI (CS-nZVI), both immobilized in calcium alginate beads. The parameters like initial Cr (VI) concentration, nZVI concentration, and the contact time for Cr (VI) removal were optimized based on Box-Behnken design (BBD) by response surface modeling at a constant pH 7. Under the optimized conditions (concentration of nZVI = 1000 mg L(-1), contact time = ∼ 80 min, and initial concentration of Cr (VI) = 10 mg L(-1)), the Cr (VI) removal by the immobilized BS-nZVI and CS-nZVI alginate beads was 80.04 and 81.08 %, respectively. The adsorption of Cr (VI) onto the surface of alginate beads was confirmed by scanning electron microscopy with energy-dispersive x-ray spectroscopy (SEM-EDX), Fourier transform infrared spectroscopy (FT-IR), and Brunauer-Emmett-Teller (BET) analysis. The applicability of the process using both the sorbents was successfully test medium Cr (VI) spiked environmental water samples. In order to assess the ecotoxic effects of nZVI, the decline in cell viability, generation of intracellular reactive oxygen species (ROS), cell membrane damage, and biouptake was studied at 1000 mg L(-1) concentration, with five indigenous bacterial isolates from chromium-contaminated lake sediments and their consortium.

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