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Encapsulating TiO₂ in Lignin-Based Colloidal Spheres for High Sunscreen Performance and Weak Photocatalytic Activity

Li, Yuanyuan, Yang, Dongjie, Lu, Shuo, Qiu, Xueqing, Qian, Yong, Li, PengWei
ACS sustainable chemistry & engineering 2019 v.7 no.6 pp. 6234-6242
color, contact angle, dispersibility, encapsulation, hydrogen bonding, hydrophobicity, lignin, photocatalysis, sunscreens, titanium dioxide
TiO₂ is widely used in cosmetic products but its poor dispersibility and photocatalytic degradation hazard still affect its performance. In this work, quaternized alkali lignin (QAL) is applied to encapsulate TiO₂ by self-assembly and endows TiO₂ with excellent sunscreen performance and safety. Results show that the nano TiO₂ particles were well trapped in lignin colloidal spheres (LCS) via hydrogen bonding. The LCS encapsulated TiO₂ (LCS@TiO₂) had a water contact angle as high as 89° in comparison to only 22° in the TiO₂ disk control sample. Thus, compatibility with the hydrophobic cream was improved. The photocatalytic activity of TiO₂ could be effectively eliminated after modification. The dark color of QAL was significantly whitened by trapped TiO₂. When the ratio (w/w) of LCS to TiO₂ was 0.5, the LCS@TiO₂ presented the best synergistic effect; the sun protection factor (SPF) value of the cream containing 25 wt % LCS@TiO₂ reached 84.82.