Hydroxyapatite coating on ZnO nanoparticles for ultraviolet filter agents

This experimental work aimed to investigate the effects of hydroxyapatite (HAp) coating on zinc oxide (ZnO) nanoparticles and the extent to which the HAp coating improves the protective efficacy of ZnO-based sunscreen against UV radiation. First, the HAp-coated ZnO nanoparticles were synthesized and characterized. Afterwards, they were mixed into a basic sunscreen lotion. Precipitation and spray coating methods were applied in the synthesis process of HAp and HAp-coated ZnO nanoparticles, which were then continued with a series of characterizations using XRF, XRD, UV-vis DRS, and SEM-EDS. The results show that an HAp coating on ZnO surfaces can make this nanomaterial's optical band gap wider. Also, it makes ZnO nanoparticles less capable of both absorbing UV light and performing photocatalytic reactions. Furthermore, the HAp layer on ZnO nanoparticles effectively increases UV radiation reflectance in sunscreens. Therefore, it is reasonable to assume that the HAp coating will improve inorganic sunscreen protection against UV radiation.