Probing Matrix Effects in the Course of Electron Transfer across a Self-Assembled Monolayer

• Published in: Journal of physical chemistry. C Vol. 126; no. 40; pp. 17415 - 17423
• Main Authors: Das, Saunak, Zhao, Zhiyong, Terfort, Andreas, Zharnikov, Michael
• Format: Journal Article
• Language: English
• Published: American Chemical Society 13.10.2022
• Subjects: C: Physical Properties of Materials and Interfaces
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.2c05528

Charge transport across a self-assembled monolayer (SAM) can involve either individual molecules only (through-bond model) or also intermolecular pathways (through-film model or matrix effects). In this context, we test a possible involvement of the latter pathways in the electron transfer (ET) across a model, nitrile-terminated naphthalene-2-thiolate (NC-Nap) SAM on Au(111). For this purpose, we apply the so-called core-hole-clock approach in the framework of resonant Auger electron spectroscopy, allowing the measurement of the characteristic ET time from the nitrile tail group of NC-Nap to the substrate. The efficiency of possible intermolecular pathways depends on the electronic coupling between individual NC-Nap molecules, which was progressively reduced by mixing NC-Nap with short-chain alkanethiolates in binary SAMs. It turns out that the value of the characteristic ET time, estimated as 24 ± 4 fs for the reference, single-component NC-Nap SAM, does not vary noticeably in the binary monolayers, independent of the NC-Nap content. This means that the matrix effects play a negligible role for ET dynamics in the given model SAM, strongly favoring the through-bond CT model.