Probing the adsorption behavior of triphenylphosphine oxide on the surface of Ga–SiO2 with different binding sites
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Abstract
This study theoretically investigates the adsorption dynamics and fluorescence characteristics of triphenylphosphine oxide (TPPO) as a fluorescent probe on Lewis acid (Ga–La) and Brønsted acid (Ga–Ba) sites of gallium silicate (Ga–SiO2) surfaces. It was determined that TPPO binds to the Ga–La site via a coordination bond and to the Ga–Ba site through a hydrogen bond. When excited to the first singlet (S1) state, the coordination interactions at the Ga–La sites experienced slight weakening, which caused a blue shift in the fluorescence emission of TPPO from 478 nm to 453 nm. The excited state intermolecular proton transfer occurring at the Ga–Ba site leads to a red shift of the TPPO fluorescence peak to 528 nm. The contrasting fluorescence behaviors provide a sensitive probe for distinguishing Ga–La and Ga–Ba sites, advancing the detection and mechanistic understanding of Ga–SiO2's catalytic acid centers. This work highlights the potential of fluorescence spectroscopy in elucidating surface-active sites for catalysis.
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