Sonochemical synthesis of bioinspired graphene oxide-zinc oxide hydrogel for antibacterial painting on biodegradable polylactide film.

Graphene oxide nanosheet (GO) is a multifunctional platform for binding with nanoparticles and stacking with two dimensional substrates. In this study, GO nanosheets were sonochemically decorated with zinc oxide nanoparticles (ZnO) and self-assembled into a hydrogel of GO-ZnO nanocomposite. The GO-ZnO hydrogel structure is a bioinspired approach for preserving graphene-based nanosheets from van der Waals stacking. X-ray diffraction analysis (XRD) showed that the sonochemical synthesis led to the formation of ZnO crystals on GO platforms. High water content (97.2%) of GO-ZnO hydrogel provided good property of ultrasonic dispersibility in water. Ultraviolet-visible spectroscopic analysis (UV-vis) revealed that optical band gap energy of ZnO nanoparticles (∼3.2 eV) GO-ZnO nanosheets (∼2.83 eV). Agar well diffusion tests presented effective antibacterial activities of GO-ZnO hydrogel against gram-negative bacteria (E. coli) and gram-positive bacteria (S. aureus). Especially, GO-ZnO hydrogel was directly used for brush painting on biodegradable polylactide (PLA) thin films. Graphene-based nanosheets with large surface area are key to van der Waals stacking and adhesion of GO-ZnO coating to the PLA substrate. The GO-ZnO/PLA films were characterized using photography, light transmittance spectroscopy, coating stability, scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopic mapping (EDS), antibacterial test and mechanical tensile measurement. Specifically, GO-ZnO coating on PLA substrate exhibited stability in aqueous food simulants for packaging application. GO-ZnO coating inhibited the infectious growth ofE. colibiofilm. GO-ZnO/PLA films had strong tensile strength and elastic modulus. As a result, the investigation of antibacterial GO-ZnO hydrogel and GO-ZnO coating on PLA film is fundamental for sustainable development of packaging and biomedical applications.

Effectiveness of photocatalysis of MMT-supported TiO2 and TiO2 nanotubes for rhodamine B degradation.

The aim of this paper is to synthesize montmorillonite/TiO2-nanoparticles (MMT/TiO2 and montmorillonite/TiO2-nanotubes (MMT/TiO2-NTs) photocatalysts through a simple wet agitation method based on TiO2 nanoparticles and MMT. They are likely to accumulate the effect of adsorption and photodegradation. Then, the photocatalysts are applied to degrade the rhodamine B in dye effluents. The structural characterizations of photocatalysts are investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDX). The photocatalytic activities and effectiveness of photocatalysts are evaluated through rhodamine B degradation at different concentrations under dark and UV-C irradiation conditions. The results show that the synthesized TiO2-NTs have an average tube diameter of 5 nm and a tube length at least about 110 nm, which are intercalated into MMT sheets in MMT/TiO2-NTs photocatalyst. Meanwhile, TiO2 nanoparticles are immobilized on the surface of MMT sheets in the MMT/TiO2 photocatalyst. The photocatalytic effectiveness of rhodamine B degradation of TiO2-NTs shows a significantly enhance compared to that of TiO2 nanoparticles. However, photocatalytic performance of MMT/TiO2-NTs is lower than that of MMT/TiO2. The degradation effectiveness of MMT/TiO2 photocatalyst reaches to 100% for 3 ppm and 90% at 10 ppm of rhodamine B, while these values are 97.5% and 85.5%, respectively, recorded for MMT/TiO2-NTs.