ZnO nanoparticles-laden cellulose nanofibers-armored Pickering emulsions with improved UV protection and water resistance

Abstract

This study introduces a new type of Pickering emulsion system with enhanced UV-blocking and water-resisting performance, in which hydrophobically modified ZnO composite cellulose nanofibers (HCNFZnO) were employed to form an oil-in-water (O/W) interface. For this, we first deposited ZnO nanoparticles (NPs) on CNFs by reducing the zinc precursor and subsequently grafted hexadecyltrimethoxysilane on the ZnO NPs. We observed that the HCNFZnO favoured the formation of a fibrillary solid layer at the O/W interface, thus producing a structurally stable Pickering emulsion. The Pickering emulsion showed synergistic UV-blocking performance when prepared with a chemical UV filter in the oil phase. Interestingly, owing to the inter-fibrillary attraction of cellulose bodies, the HCNFZnO-armored Pickering emulsion drops adhere to each other, thus exhibiting significant resistance to repeated rinsing with water. These results highlight that our HCNFZnO enables the development of a UV-blocking emulsion system with excellent water resistance without the aid of conventional emulsifiers.