Titanium dioxide modified by polydopamine used as stabilizer of Pickering emulsion and characterized for its sunscreen properties

Abstract

The high hydrophilicity of titanium dioxide (TiO2) caused by surface hydroxyl groups limited their application in Pickering emulsions. Inspired by the structure and function of mussel adhesion protein, polydopamine-modified TiO2 (PDA-TiO2) was successfully prepared in this study. The effect of modified conditions on emulsifying capacity of Pickering emulsions stabilized by PDA-TiO2 were investigated, including pH, material ratio, reaction time, and temperature. The morphology and structure properties of modified TiO2 were characterized by SEM, TEM, FTIR, UV, TG, XPS, and XRD. The results suggested that PDA were successfully bonded to the TiO2 surface, which might improve the hydrophilicity of TiO2. PDA-TiO2 could stabilized Pickering emulsion with more uniform emulsified drops when m(TiO2)/m(DA) was 1/0.1, the reaction pH was 8.5, the reaction time was 3 h, and the reaction temperature was 50 °C. In addition, the introduction of polydopamine effectively improved the sun protection ability of TiO2. Compared to traditional sunscreen emulsion, Pickering emulsion stabilized by polydopamine-modified TiO2 could increase the sunscreen value by 55%, which broadened its application in cosmetic and other fields.