Facile Synthesis of Rodlike TiO2/Lignin Nanostructures as Multifunctional Emulsifiers for High Internal Phase Emulsions

The application of high internal phase emulsions (HIPEs) in food, medicine, and cosmetics has been greatly limited due to lack of anti-ultraviolet and anti-oxidant structures. Herein, a series of rodlike TiO2/lignin nanoparticles were prepared by using TiO2 as a hardcore and modified lignin as a coating and dispersion stabilizer. SEM images show that samples have well dispersity and present a rodlike morphology. However, the aspect ratio (AR) values of samples have significant differences due to the presence of different contents of carboxyl and hydroxyl groups in lignin derivatives. Subsequently, their emulsification was predicted by the spreading coefficient and adsorption energy. The results show that the higher AR value of samples, the lower dispersion coefficient and the higher adsorption energy, indicating better emulsification activity. The emulsification test suggests that 0.16 wt % TiO2/arginine-modified lignin with highest AR value could stabilize HIPEs with 90 vol % oil phase volume due to a strong bridging effect. Existing literature shows that the dosage of nanoparticles in HIPEs is the lowest value of other biomass emulsifiers, which shows good biocompatibility. Meanwhile, the oil phase volume of HIPEs in this work is the highest value of other HIPEs prepared with biomass-based particles, which means that these HIPEs would have a higher load capacity for active substances and longer shelf life due to the low water content. The antioxidant experiment shows that TAML could completely clear the •OH, and the scavenging efficiency is 17 times that of pure TiO2. The UV-protection test indicates that the sun protection factor value of TAML reached 149.5, which is the highest value of other lignin-based sunscreen particles. This work provides a method for the preparation of high-performance and multifunctional emulsifiers, which expands the application of lignin and enhances the application potential of HIPEs in medicine, food, cosmetics, and other fields.