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%.