Sunlight-driven enhanced photocatalytic activity of bandgap narrowing Sn-doped ZnO nanoparticles.

In this paper, we grab to utilize one of the trending techniques with efficient implications in wastewater treatment of organic pollutants, the photocatalytic degradation method shining out in the research field. Herein, tin (Sn)-doped zinc oxide (ZnO) nanoparticles (NPs) (Sn/ZnO) with different doping concentrations (1, 2, 3, 4, and 5 wt%) were synthesized via a simple co-precipitation assisted method and later subjected for their physico-chemical, morphological, and optical characterization. In addition, photocatalytic activity as the concerned study was investigated as to record the different doping levels of Sn/ZnO to examine the effect of doping concentration in relation with the degradation efficiency. We know that the optical bandgap of pure ZnO was 3.26 eV while it tends to increase slightly upon increasing the doping concentration. In the present investigation, methylene blue (MB) dye was used as a model pollutant to evaluate the photocatalytic activity of Sn/ZnO photocatalysts under natural sunlight. Varied doping concentrations of Sn/ZnO were compared with different characterization techniques while XRD analysis shows up 4-Sn/ZnO with sharp peak at (1 0 1) plane with smaller grain size in comparison to other Sn/ZnO samples. The morphological recognition depicts the hexagonal structure with smaller size for 4-Sn/ZnO which offers more active sites with improved photocatalytic activity, higher surface area for the transportation of pollutants. Fluorescence spectra results revealed that Sn dopant suppresses the charge carrier recombination. The lower intensity of PL indicated reduced recombination rate, which resulted in enhancing the photocatalytic activity. To investigate the possible mechanism, kinetics and reusability studies were performed. The 4% Sn-doped ZnO nanoparticle concentration showed highest photocatalytic activity when compared with other doping levels.