Bifunctional investigation of ultra-small SnO2 nanoparticle decorated rGO for ozone sensing and supercapacitor applications.

Ultrasmall SnO2 nanoparticles with an average size of 7 nm were synthesized by a hydrothermal method and composited with reduced graphene oxide (rGO) through an ultrasonic assisted solution process. The structural, functional, morphological and compositional properties of synthesised SnO2 and rGO/SnO2 were studied by XRD, FTIR, HRSEM, HRTEM, XPS and Raman analyses. The prepared materials were developed as a film over a PVA/KOH conductive layer coated substrate with varying thickness of 3, 5 and 7 µm to study their ozone sensing characteristics at room temperature. The physico-chemical properties reveal that the fabricated SnO2 and rGO/SnO2 nanocomposite films have a strong interaction with the ozone gas. Among the fabricated composite films rGO/SnO2-S1 film exhibits high ozone sensing response (38%) at room temperature. Additionally, the electrochemical performance of SnO2 and rGO/SnO2 nanocomposites was analysed and the rGO/SnO2 nanocomposite exhibited higher specific capacitance (545 F g-1) than that of pure SnO2 (236 F g-1) at a current density of 1 A g-1 with higher cyclic stability (96%) than that of pure SnO2 (86%) at the current density of 20 A g-1 for a continuous 5000 charge-discharge cycles. Thus, the rGO/SnO2 nanocomposite showed an excellent ozone sensing and energy storage performance.

Eco-friendly preparation of zinc oxide nanoparticles using Tabernaemontana divaricata and its photocatalytic and antimicrobial activity.

The present work reports the green synthesis of Zinc Oxide Nanoparticles (ZnO NPs) using aqueous Tabernaemontana divaricata green leaf extract. ZnO NPs have been characterized by X-ray diffraction (XRD), Ultra Violet-Visible (UV-Vis) studies, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Fourier Transform-Infra Red (FT-IR) analysis. XRD pattern analysis confirms the presence of pure hexagonal wurtzite crystalline structure of ZnO. The TEM images reveal the formation of spherical shape ZnO NPs with the sizes ranging from 20 to 50 nm. The FT-IR analysis suggests that the obtained ZnO NPs have been stabilized through the interactions of steroids, terpenoids, flavonoids, phenyl propanoids, phenolic acids and enzymes present in the leaf extract. Mechanism for the formation of ZnO NPs using Tabernaemontana divaricata as bioactive compound is proposed. As prepared ZnO NPs reveals antibacterial activity against three bacterial strains, Salmonella paratyphi, Escherichia coli and Staphylococcus aureus. The ZnO NPs shows higher antibacterial activity against S. aureus and E. coli and lesser antibacterial activity against S. paratyphi compared to the standard pharmaceutical formulation. Photocatalytic activity of synthesized ZnO NPs was analyzed for methylene blue (MB) dye degradation with sunlight. Almost complete degradation of dye occurred in 90 min. This nano-ZnO, prepared by eco-friendly method will be much useful for dye removal and bacterial decontamination.