The vitaminC@P25TiO2NPs, on the other hand, were obtained through an optimized method based on Mallakpour et al. [27]. Initially, 0.02 g of P25TiO2NPs were dispersed in 1 mL of ultrapure water and stirred in a Vortex. Next, 100 μL of HCl (0.01 M) were added (pH 2) to 100 uL of P25TiO2NPs to avoid gel formation. Then, 100 μL of vitamin C dissolved in ultra-pure water (5.0 × 10−3 M) solution were added to the mixture and was ultrasonicated for 30 min. Finally, vitamin C was added in excess to gain a beige-orange color suspension, and the ultrasonication continued for another 30 min. The pellet obtained after centrifuging the suspension for 10 min at 4500 rpm was resuspended in ultrapure water, centrifuged again, and then lyophilized.
For the production of titanium dioxide, the raw material of coatings, China coating Industry Association visited the production enterprises of titanium dioxide. During the visit, we found that Hebei Caixin Material Technology Co., LTD. (hereinafter referred to as Caiqing Technology) has done a lot of work in creating a green ecological industry in titanium dioxide production, and has achieved outstanding results.