Improved photocatalytic degradation of malachite green, crystal violet and antibacterial activity of mesoporous Zn1-xCoxO nanoflakes

The photocatalytic ability of the Zinc Oxide nanoparticles can be significantly enhanced through transition metal doping. In this work, Zn1-xCoxO nanoparticles were synthesised by a chemical coprecipitation method at room temperature. XRD studies indicated non-monotonic decrease in the Scherrer's crystalline size from 19.79 nm for the pristine ZnO NPs to 14.81 nm for 2.5% Co2+ doped ZnO nanocrystals. The morphology of the nanoparticles was revealed by FESEM to resemble nanoflakes, and the existence of Co, Zn and O elements was verified by EDS findings. Tauc plots demonstrated a shrinkage of the optical band gap from 3.15 eV to 2.98 eV. The mesoporous nature and noteworthy increase in specific surface area (from 22.198 m(2)/gm to 54.159 m(2)/gm) were revealed by BET analysis of the N-2 adsorption of the nanoflakes. Further, the degradation experiments of cationic dyes Malachite Green (MG) and Crystal Violet (CV) were carried out in the presence of synthesised catalysts under a high-pressure mercury vapour (450W-UV) lamp. Among the doped ZnO nanocatalysts, 2.5% Co2+ doped ZnO nanoflakes showed the most efficient photocatalytic degradation against MG (97.87%) and CV (93.27%) in 20 minutes. Furthermore, antibacterial activity was investigated against pathogenic bacteria Staphylococcus aureus, Bacillus subtilis and Escherichia coli which revealed improved bactericidal effects of 2.5% Co2+ doped ZnO nanoflakes. Hence, the current finding explored 2.5% Co2+ doped ZnO nanoflakes can serve as dual role efficient and potential candidate for eradication of organic as well as microbial contaminants from wastewater.