Oxygen Radicals Entrapped between MgO Nanocrystals: Formation, Spectroscopic Fingerprints, and Reactivity toward Water.

Compaction of dehydroxylated MgO nanocrystal powders produces adsorbed oxygen radicals with characteristic UV-vis spectroscopic fingerprints. Identical absorption bands arise upon UV excitation in an oxygen atmosphere but in the absence of uniaxial pressure. Photophysical calculations on MgO gas-phase clusters reveal that the observed optical transitions at 4.4 and 3.0 eV are consistent with adsorbed superoxide (O2·-) and ozonide (O3·-) species, respectively. The presence of these oxygen radicals is corroborated by electron paramagnetic resonance spectroscopy. Upon reaction with interfacial water, oxygen radicals convert into diamagnetic products with no absorptions in the UV-vis range. Since superoxide O2·- and ozonide anions O3·- play a key role in a variety of processes in heterogeneous catalysis, sensing, or as transient species in cold sintering, their UV-vis spectroscopic detection will enable in situ monitoring of transient oxygen radicals inside metal oxide powders. © 2023 The Authors. Published by American Chemical Society.

Citation

Thomas Schwab, Eva Muchová, Korbinian Aicher, Thomas Berger, Milan Ončák, Oliver Diwald. Oxygen Radicals Entrapped between MgO Nanocrystals: Formation, Spectroscopic Fingerprints, and Reactivity toward Water. The journal of physical chemistry. C, Nanomaterials and interfaces. 2023 Dec 07;127(48):23332-23339

PMID: 38090143

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