Gap mode induced photocatalytic reactions of p-methyl thiophenol and relating molecules

Masayuki Futamata; Kanae Tabei; Keitaro Akai

doi:10.1117/12.2538452

18 November 2019 Gap mode induced photocatalytic reactions of p-methyl thiophenol and relating molecules

Masayuki Futamata, Kanae Tabei, Keitaro Akai

Proceedings Volume 11194, Plasmonics IV; 111940A (2019) https://doi.org/10.1117/12.2538452
Event: SPIE/COS Photonics Asia, 2019, Hangzhou, China

Abstract

A gap mode plasmon induced photocatalytic oxidation of p-alkyl thiophenol (p-AlTP), encompassing methyl, iso-propyl and tert-butyl groups, to p-mercaptobenzoic acid (p-MBA), for which excitation 532 nm laser (<1 μW/μm²) impinged on a sample of silver (Ag) nanoparticles/p-AlTP/Ag films/BK-7 prism. Apparently, the oxidation of p-AlTP yielded p-MBA without leaving any signs of the intermediated species like p-mercaptobenzyl-aldehyde or -alcohol (p-MBAl) in the air. In contrast to p-AlTP, o-methyl TP and m-methyl TP were not oxidized, indicating preferential reactivity of the para position in TP molecules. Nonetheless, the site selectivity is not always valid in this type of photocatalytic reactions, as o-, m-, and p-MBAl molecules were oxidized to corresponding o-, m- and p-MBA. Similarly, all of o-, m-, and p-MBA molecules were decarboxylated to TP in the air. With respect to the reaction mechanism, we confirmed that the oxidation of p-MeTP is not induced by thermal heating of the samples up to 373 K. Subtle temperature increase (<10 K) during the gap mode-induced oxidation was also corroborated by the observed Stokes and anti-Stokes scattering intensity of p-MeTP. Oxygen molecules accelerated the oxidation of p-MeTP at room temperature, whereas nitrogen atmosphere generated an intermediate species attributable to p-mercaptobenzyl radical.

Citation Download Citation

Masayuki Futamata, Kanae Tabei, and Keitaro Akai "Gap mode induced photocatalytic reactions of p-methyl thiophenol and relating molecules", Proc. SPIE 11194, Plasmonics IV, 111940A (18 November 2019); https://doi.org/10.1117/12.2538452

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