La-doped ZnO nanoflower as photocatalyst for methylene blue dye degradation under UV irradiation

Lanthanum doped ZnO flower-like structured nanoparticles were synthesized through microwave assisted sol-gel technique. X-ray diffraction, scanning electron microscopy, transmission electron microscopy analysis confirmed the size, structural morphology and successful compound formation of the samples. The band gap was calculated from Tauc's plot using UV-Vis spectroscopy data. Lanthanum doped ZnO nanoparticles were used for the photocatalytic degradation of methylene blue dye under UV light irradiation. Compared to pure ZnO sample, La-doped samples exhibited higher photocatalytic dye degradation under UV light irradiation with short time duration. Among the different amounts of dopant, 3 mol% La-doped ZnO nano rods showed the highest degradation with short time UV light irradiation (60 min). Other factors such as particle size, morphology and defects also affect the photocatalytic activity. In our study, the main factor that influence photocatalytic activity is the separation of photo induced electron-hole pair due to defects formation in the sample. The 3 mol% sample has the appropriate electron-hole separation due to defects compared to pure ZnO. The influence of defects on the photocatalytic activity of all samples has been revealed using photoluminescence spectroscopy analysis. Furthermore, the effect of various operational parameters such as photocatalyst quantity, dye concentration and dopant concentrations were also optimized.