Synthesis and characterization of Sr-doped ZnO nanoparticles for photocatalytic applications

Highlights: • Sr doped ZnO nanoparticles were successfully synthesized by mechanical milling method. • The ZnO containing 3 molar% Sr was the optimum sample. • Sr doping led to enhanced photocatalytic activity by reduction the band gap and increasing the specific surface area. • Sr doping increased the chemical stability of ZnO, and increased its efficiency and recycling in removing color contaminants. • Sr doping caused the photocurrent and antibacterial activity to increase 3 and 2 times, respectively. -- Abstract: The use of semiconductors that respond to the visible light as a photocatalyst is an effective way to remove pollution resulting from the chemical industries. In this project, with the aim of increasing its photocatalytic activity, zinc oxide (ZnO) was doped with 1, 3, 5 and 7 M% strontium (Sr) by mechanical milling method. Characterization of the synthesized powders was done by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). The optical behavior was evaluated using UV–Vis diffuse reflectance spectra (UV–Visible DRS) and photoluminescence. The XRD results showed successful doping of Sr in ZnO. The results of microscopic characterization revealed that the size of Sr-doped particles was in the range of 20–60 nm. Just about all results showed that the 3% Sr-doped ZnO sample (ZnO–Sr3) revealed the best performance. Its band gap decreased from 3.34 to 3.17 eV. Investigated by radiation of the HMI lamp for degradation of methylene blue (MB) dye, the photocatalytic efficiency of ZnO–Sr3 sample increased from 56 to 97%. Also, the results of chronoamperometry test showed a 3-fold increase in the photocurrent of ZnO–Sr3. Antibacterial studies of the samples on Escherichia coli (E. coli) bacterium also revealed that the ZnO–Sr3 sample had the highest antibacterial property.