First Combined Electron Paramagnetic Resonance and FT-IR Spectroscopic Evidence for Reversible O₂Adsorption on In₂O_3–<i>x</i>Nanoparticles

Abstract

Adsorption-induced electronic property changes determine the performance of nanostructured transparent conductive oxides and sensor materials. For the study of O 2 adsorption on electron rich In 2 O 3– x nanoparticles we used transmission FT-IR spectroscopy in combination with electron paramagnetic resonance (EPR). The reversible emergence and annihilation of conduction band electrons is subject to O 2 adsorption and was tracked at different oxygen pressures via IR active Drude absorptions. Corresponding results were related to EPR measurements that were performed under identical experimental conditions. For the first time we identified a weak adsorption complex between O 2 and the surface of In 2 O 3– x nanoparticles in the temperature range between T = 90 K and T = 298 K. Complementing and supporting our FT-IR observations, this evidence opens the way to study sensing relevant adsorption processes at room temperature with spectroscopy.