Transition metal oxide (TMO) nanoparticles (NP) have previously shown to both partially dissolve to release high valence transition metal ions, and spontaneously generate abiotic reactive oxygen species (ROS) in aqueous suspensions. The transformations of this class of nanomaterial have led to an increase in oxidative stress responses in model organisms. In particular, LiCoO2 NP has been found to generate H2O2, alongside the release of Co ion overtime. In this study, we aimed to monitor the dynamic transformation of a series of Co-containing TMO nanoparticles by monitoring the formation of H2O2 overtime using both a commercial fluorescence probe and amperometry techniques in biologically relevant media. We detected a burst of micro-molar levels of H2O2 from LiCoO2 when freshly suspended in biological media, followed by a decay to the base line after 24 hours. Yet preliminary examination of additional Co-containing nanoscale TMOs, such as CoOOH and a complex metal oxide, Nickle Manganese Cobalt oxide (Ni1/3Mn1/3Co1/3O2, NMC) did not follow this pattern. This study revealed a new aspect of TMO nanomaterial transformation which may induce additional biological and environmental impact.

Dynamic formation of H2O2 from nanoscale transition metal oxides (TMOs) in aqueous suspensions

ACS Spring 2022

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