3. Regulatory Compliance It is crucial for suppliers to adhere to industry regulations, especially in sectors like food, pharmaceuticals, and cosmetics. Reliable suppliers will ensure their products meet relevant regulatory standards, providing proper documentation and certifications.

4.Used as a white pigment, the hiding power is second only to titanium dioxide, but stronger than zinc oxide. The hiding power increases as the ZnS content increases, and the light resistance also improves, but the acid resistance decreases.

The vitaminC@P25TiO₂NPs, on the other side, did not have any effect on cell protection against ROS. This might be due to the fact that vitamin C, a well-known scavenger of ROS, could behave as prooxidant and even promote ROS and lipid peroxidation [39]. It was recently described that at small concentrations of vitamin C, the prooxidant effects dominate; while in large concentrations the antioxidant ones predominate [40]. The effect also depends on the cell state and the interaction of vitamin C with light. In this case, ascorbic acid may act as an antenna to harvest visible light when conjugated to P25TiO₂NPs. Indeed, it was previously found that this combination (in some ratios) could have an improved photocatalytic activity, possibly due to a red shift in its light absorbance [41]. Further studies on vitaminC@P25TiO₂NPs were not conducted, because of the poor antioxidant capacity [42].