Fabrication of Zn-Ti layered double hydroxide by varying cationic ratio of Ti4+ and its application as UV absorbent

ZnTi-layered double hydroxides (LDHs) with varying Zn/Ti ratio have been synthesized by coprecipitation of zinc and titanium salts from homogeneous solution. The obtained ZnTi-LDHs possess high crystallinity and hierarchical structure with improved UV-absorbance property. The UV-vis spectra show that the UV absorbing properties of ZnTi-LDHs is stronger and broader than both MgAl-LDH and ZnAl-LDH due to the existence of Ti. Moreover, the UV absorption property increased with the content of Ti, which can be ascribed to the decrease in the band gap energy, as clearly confirmed by density functional theory calculations. When irradiated by UV rays, the property of the samples with generated free radicals (OH center dot and O-2(center dot-)) was evaluated by means of electron spin resonance (EPR). ZnTi-LDHs generated a relatively lower active radicals in contrast with TiO2 and ZnO, which implied an increased safety used as sunscreens. Therefore, this work provides a detailed understanding of UV shielding properties of ZnTi-LDHs which was unrevealed previously, and demonstrates the expansive application prospects of ZnTi-LDHs in the field of sunscreens. (C) 2016 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.