Oxygen Atom Transfer Reactions of Colloidal Metal Oxide Nanoparticles.

Lee, Justin L; Gentry, Noreen Elizabeth; Peper, Jennifer L; Hetzel, Staci; Quist, Christine; Menges, Fabian S; Mayer, James M · ACS Nano · 2025

basic_science · Level V

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Abstract

Redox transformations at metal oxide (MO<sub><i>x</i></sub>)/solution interfaces are broadly important, and oxygen atom transfer (OAT) is one of the simplest and most fundamental examples of such reactivity. OAT is a two-electron transfer process, well-known in gas/solid reactions and catalysis. However, OAT is rarely directly observed at oxide/water interfaces, whose redox reactions are typically proposed to occur in one-electron steps. Reported here are stoichiometric OAT reactions of organic molecules with aqueous colloidal titanium dioxide and iridium oxide nanoparticles (TiO<sub>2</sub> and IrO<sub><i>x</i></sub> NPs). Me<sub>2</sub>SO (DMSO) oxidizes reduced TiO<sub>2</sub> NPs with the formation of Me<sub>2</sub>S, and IrO<sub><i>x</i></sub> NPs transfer O atoms to a water-soluble phosphine and a thioether. The reaction stoichiometries were established and the chemical mechanisms were probed using typical solution spectroscopic techniques, exploiting the high surface areas and transparency of the colloids. These OAT reactions, including a catalytic example, utilize the ability of the individual NPs to accumulate many electrons and/or holes. Observing OAT reactions of two different materials, in opposite directions, is a step toward harnessing oxide nanoparticles for valuable multi-electron and multi-hole transformations.