Synthesis of Al-doped and Fe–doped ZnO nanoparticles as UV filters in sunscreens

Abstract

In this work, Al-doped ZnO and Fe-doped ZnO nanoparticles have been synthesized through the coprecipitation-annealing method to create new and safer UV filters for sunscreen. The effects of metal doping on phase composition, crystal structure, surface morphology, specific surface area, and elemental composition were characterized by X-ray diffraction, Raman spectroscopy, field emission electron scanning microscopy, nitrogen adsorption-desorption experiments and energy-dispersive X-ray spectroscopy, respectively. The optical properties and photocatalytic activity of prepared powders were studied through UV-visible diffuse reflectance spectroscopy and photocatalytic degradation of methylene blue under UV radiation. According to the experimental results, Al or Fe-doped ZnO nanoparticles showed better UV absorption but significantly lower photocatalytic activity than the undoped ZnO sample, which enables the metal doped ZnO samples to become more effective and safer UV filter in sunscreen. The decline of photocatalytic activity can be attributed to the bulk defects caused by the insertion of Al3+ or Fe3+ ions in ZnO lattice. In particular, the sunscreen formulations using the metal doped ZnO nanoparticles display high SPF values and diverse colors changing from ivory to yellow-brown, preventing leaving white cast on the skin, which is very suitable as sunscreen for people of color.