Suppressing the photocatalytic activity of ZnO nanoparticles by Al-doping for the application in sunscreen products

In this work, Al-doped ZnO nanoparticles were prepared with different Al contents by a simple co-precipitation method in order to suppress the photocatalytic activity without modifying their UV light absorption. The effects of Al-doping on the crystal structure, phase composition, surface morphology, surface structure, optical properties and photocatalytic activity of ZnO powder were investigated by XRD, TEM, Raman spectroscopy, UV-Visible diffuse reflectance and photocatalytic experiments for the degradation of methylene blue, respectively. According to the results, the photocatalytic activity of all Al-doped ZnO was notably lower than undoped ZnO sample. Among them, the 3 at% Al-doped ZnO sample nearly showed no photocatalytic performance under UV light irradiation, which can be attributed to the low crystallinity and the intrinsic defects created by Al-doping. Moreover, when Al3+ ions were inserted into ZnO lattice, the particle size tent to decrease but the UV light absorption remained unchanged in comparison with undoped ZnO sample. These results prove that the Al-doped ZnO nanoparticles can be a good candidate for the application in sunscreen products.