Abstract:
The generation of reactive oxygen species (ROS) during the photolysis of sunscreens and sun blockers poses
consumer safety concerns while necessitating proper identification and quantitation of ROS species. Here, a
colorimetric sensing approach has been developed based on a molecular probe (2,3-bis-(2-methoxy-4-nitro-5-
sulfophenyl)-2-H-tetrazolium-5-carboxanilide (XTT) tetrazolium salt) to quantitatively measure the photo-induced
superoxide anion radicals (%O2
.) generated from the photocatalysis of zinc oxide nanoparticles (ZnO-NPs)
in aqueous solutions. Note that superoxide anion radicals are assumed to be the main reactive oxygen species
(ROS) generated from such photocatalysis. The characterisation of ZnO-NPs before and after irradiation showed
average particle sizes of 616.5 and 295.3 nm and ζ-potential values of 0 and -24.4 mV, respectively. It is hoped
that this proposed protocol can be further developed to efficiently detect other ROS present in inorganic sun
blockers and to optimize the utility of various sunscreen formulations.