Na-doped ZnO UV filters with reduced photocatalytic activity for sunscreen applications

Due to its physical and chemical stability in addition to its transparency in the visible region with ultraviolet protective activity, ZnO can be used in sunscreen applications. In our article, Na-doped zinc oxide nanoparticles were prepared in different concentrations by sol–gel and solvothermal techniques to reduce their photocatalytic activity. The photocatalytic activity of the doped samples was suppressed effectively at a concentration of 0.03 at% Na doping up to 90% by conducting the sol–gel process rather than the solvothermal process which resulted in about 70% photocatalytic reduction in a period of time from (0–30 min) when exposed to ultraviolet and visible light. In addition, the nanoparticles resulted by sol–gel route show a reduction in photoactivity under solar simulation about 98% rather than those resulted via solvothermal process which shows a reduction around 92% for 30 min which is the same period of time used for the photocatalytic degradation test. The particle size was around 64.6–84.6 nm for samples prepared by both methods.