Flame-Synthesized Zinc Oxide Tetrapods for Photoprotection in Sunscreen Formulations

ZnO nanoparticles are widely used in sunscreen formulations due to their strong light absorption in the ultraviolet (UV) and ease of synthesis. Here, we explore flame-synthesized tetrapod-shaped zinc oxide (ZnO) nanostructured particles (NPs) as UV-absorbing materials for sunscreen formulations. We compare their optical properties to conventional sol–gel-synthesized ZnO NPs. We then tested sunscreen formulations of each and measured and compared their optical, colloidal, and cosmetic properties. Notably, the test sunscreen containing mass-equalized tetrapodal ZnO absorbs in the UVB region and has a sun protection factor (SPF) value comparable to that of sol–gel-synthesized ZnO. Furthermore, colloidal and white cast evaluations of flame-synthesized tetrapodal ZnO demonstrated favorable properties for the storage and usage of sunscreen formulations.