Ultrafast Spectroscopy of Commercial Sunscreen Formulations in Thin Films and on a Skin Mimic.

The photodynamics of a given chromophore are usually affected by the surrounding environment (e.g., solvent or matrix). As a result, it is often assumed that the 'fundamental' spectroscopic behavior of a given chromophore, usually studied in dilute solution, is not relevant to the understanding of more complex mixtures. In this work, we demonstrate that the 'fundamental' photodynamics of common sunscreen UV filters are comparable to those observed in formulation, including the complex interactions between them, and even for formulation applied to a skin mimic. In particular, we have carried out ultrafast laser spectroscopy studies directly on sunscreen formulations containing methyl anthranilate (MA), ethylhexyl methoxycinnamate (EHMC), and octocrylene (OCR) as commonly used UV filters. Our results not only have significant implications for the sunscreen industry, providing direct evidence of UV filter interactions in formulation, but importantly they are demonstrative of the relevance of 'fundamental' spectroscopic techniques to understanding real-life systems.