Investigation of size and shape effects of zinc oxide particles on optical properties

Materials such as ZnO (macro to nanoparticles) are valuable in a broad range of scientific domains. ZnO has gained appeal in cosmetics due to its low toxicity, higher biodegradability, superior antibacterial property, and excellent UV blocking capability in sunscreens. The use of ZnO particles, leveraging its optical property in sunscreens for skin protection against harmful UV radiation, has advanced technologically. The amount of radiation blocked by ZnO is dependent on scattering and absorption, and it has been shown in the literature that size and shape have a significant impact on the optical properties of micro and nanoparticles. The scientific objective of this thesis was to investigate the scattering and absorption of ZnO micro, and nanoparticles based on their shapes and sizes. A UV-VIS-NIR spectrophotometer was used to examine the optical characteristics of five ZnO solid powders with different particle sizes and shapes. The technological objective of this thesis was to contribute to the optimization of sunscreen products in terms of ZnO particle size ranges and shapes. As a result, sunscreens were formulated using the five ZnO samples. The solid ZnO powders results demonstrated that size and shape have a strong impact on optical characteristics of the powders. Compared to the other powders used, the MicNo-ZnO solid powder sample with a thickness of 0.0769 mm had the highest UV absorbance and transparency in the visible region, with absorption and extinction coefficients of 1015 cm-1 and 0.00207, respectively. Some of the outstanding optical characteristics seen in the solid ZnO powders were hidden in the formulation system used. Higher SPF values of 68.22 and 73.22 were nevertheless observed for reduced size MicNo-ZnO and 30-50nm spherical ZnO, respectively.