Synthesis of novel lanthanum-doped zinc oxide nanoparticles and their application for wastewater treatment

Wastewater treatment via photocatalytic activity is one of the most economical and environment-friendly method. However, obtaining an efficient photocatalyst remains a challenge for researchers in this most emerging field. In this study, pure and lanthnum (La)-(1%,2% and 3%) doped zinc oxide nanoparticles (ZnO-NPs) were synthesized via sol gel chemical technique to investigate their optical, chemical and structural properties. The synthesized NPs were characterized by using UV/VIS, SEM, EDS, XRD, FTIR, PL and Raman spectroscopy. Such nanoparticles (NPs) have been used as a photocatalyst for the degradation of rhodamine B (RhB) dye. Quite interestingly, the La-doped ZnO-NPs show unique results associated with the fact that by varying the concentration of dopant, the particle size is reduced (28.09 +/- 0.04 nm to 15.85 +/- 0.02 nm), which leads to a decrease in band gap, i.e., shifting toward visible (3.26 eV to 3.06 eV). This attributes to the fact that doping also helps to reduce electron-hole pair recombination rate during photocatalysis, which makes La-doped ZnO-NPs the most potential photocatalyst against RhB dye. We report a maximum degradation efficiency of 84.97% in 150 min observed from La0.02Zn0.98O, which reveals that 2% doping of La is the optimal value whereas further increase in concentration, i.e., at 3% (La) band gap increases whereas degradation efficiency reduces from 84.97 to 73.37%.