Design of novel p-n heterojunction ZnBi2O4-ZnS photocatalysts with impressive photocatalytic and antibacterial activities under visible light.

Heterojunction structures have attracted considerable attention for enhancing electron migration across interfaces. In this report, ZnBi2O4-ZnS(12%) heterojunction photocatalysts was found to be capable of degrading over 94% of indigo carmine in a 15 mg/L solution within 90 min of visible light irradiation at a catalytic dose of 1.0 g/L and pH 4. Furthermore, more than 82% of the total organic carbon (TOC) was removed, confirming the almost complete mineralization of the indigo carmine by ZnBi2O4-ZnS(12%). Moreover, the photocatalyst exhibited high stability and retained its photocatalytic activity up to the 5th cycle of operation without photocorrosion. The dramatic enhancement in the visible-light photocatalytic performance of the ZnBi2O4-ZnS heterojunctions over pristine ZnBi2O4 and ZnS was due to the formation of a superior heterojunction between the n-type semiconductor, ZnS, and the p-type semiconductor, ZnBi2O4. This heterojunction facilitated the separation and transfer of the photoinduced electron at the interfaces of the two semiconductors. Furthermore, the ZnBi2O4-ZnS(12%) exhibited an inhibition zone of 15 mm against fecal Escherichia coli (ATCC 8739), with a minimum inhibitory concentration (MIC) of 150 µg/mL. These results demonstrated that the novel ZnBi2O4-ZnS p-n-type heterojunction is a promising visible-light active photo-catalyst for the degradation of organic pollutants and inhibition of fecal E. coli.

Novel reduced graphene oxide/ZnBi2O4 hybrid photocatalyst for visible light degradation of 2,4-dichlorophenoxyacetic acid.

A new highly efficient rGO/ZnBi2O4 hybrid catalyst has been successfully synthesized through oxidation-reduction and co-precipitation methods, followed by heating at 450 °C. The obtained rGO/ZnBi2O4 catalyst was characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The catalytic activity of rGO/ZnBi2O4 under visible light irradiation was tested using 2,4-dichlorophenoxyacetic acid (2,4-D) in aqueous solution. The rGO/ZnBi2O4 hybrid catalyst containing 2% rGO (2.0rGO/ZnBi2O4) showed the best catalytic performance. More than 90% of 2,4-D in a 30 mg/L solution was degraded after 120 min of visible light irradiation using 2.0rGO/ZnBi2O4 at 1.0 g/L concentration. Moreover, the 2.0rGO/ZnBi2O4 catalyst showed excellent stability over four consecutive cycles, with no significant changes in the photocatalytic degradation rate. This study demonstrated that rGO/ZnBi2O4 may be a promising, low-cost, and green photocatalyst for environmental remediation applications.

Green synthesis of silver nanoparticles using Nelumbo nucifera seed extract and its antibacterial activity.

Silver nanoparticles (AgNPs) were synthesized using a Nelumbo nucifera dry seed extract, which is a simple, non-toxic, eco-friendly "green material". The synthesized nanoparticles were confirmed by the color changes and characterized by UV-visible spectroscopy. The AgNPs were stable at room temperature for 2 months. Scanning electron microscopy (SEM) revealed the formation of well-dispersed and spherical shapes. Transmission electron microscopy (TEM) of the synthesized AgNPs showed the formation of spherical nanoparticles, 5.03-16.62 nm in size. Fourier transform infrared spectroscopy (FTIR) indicated the involvement of amine, aromatic and alkynes groups in the synthetic process. X-ray diffraction (XRD) confirmed the crystalline nature of AgNPs. These AgNPs were highly toxic to found to Gram negative bacteria.