Reduction of hazardous reactive oxygen species (ROS) production of ZnO through Mn inclusion for possible UV-radiation shielding application.

Mnx - ZnO(1-x) nanopowders were successfully synthesised through a simple sol-gel method. The samples were annealed at 300 °C to enhance their crystallinity. The lattice structure, morphology and optical properties of the prepared powdered samples were extensively studied using different characterization techniques, confirming the formation of Mnx - ZnO(1-x). The inclusion of Mn did not cause any change to the wurtzite structure of ZnO; however slight peak shifting and increase in lattice parameters were indicated. The normal absorption spectra pointed to a cut-off edge extending beyond the UV region and a Burstein- Moss type band gap broadening induced by the Mn doping. ZnO showed excellent photodegradation activity against methylene blue (MB) upon UV irradiation. Intensifying the dopant concentration resulted in further diminution of photoactivity against MB. This reduction of photocatalytic activity of ZnO upon doping can be drawn to be due to the presence of Mn in the ZnO lattice, which acted as recombination sites for the photogenerated charge carriers. The results demonstrated that doping ZnO with Mn can be used to suppress the oxidative stress induced by reduced oxygen species (ROS) through generation of recombination centres. The suppression of toxic ROS generation implies possible application in fabrics and ointments for UV shielding applications.

Extraction of nanocellulose and in-situ casting of ZnO/cellulose nanocomposite with enhanced photocatalytic and antibacterial activity.

Polymer hosted metallic nanostructures with diverse applications have become a prominent area of materials science, engineering and technology. In this study nanocellulose (NC) was synthesized from oil palm empty fruit bunches biomass via alkaline treatment and acid hydrolysis and characterized. The obtained NC was used as a host polymer for the synthesis of zinc oxide (ZnO) nanostructures through in-situ solution casting method. Alkaline treatment and acid hydrolysis increased the percentage crystalline index from 35.7% to 43.3% and 53.3% respectively. X-ray diffraction studies pointed to cellulose I, with a monoclinic structure. Zinc oxide/cellulose nanocomposite displayed more photocatalytic activity than pure ZnO nanostructures upon degradation of methylene blue, and also improved antibacterial activity against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli.