Research paper by Terefe Habteyes team is published... and Spotlighted!

March 31, 2017

Terefe Habteyes

Terefe Habteyes

Spotlights is a new initiative of The Journal of Physical Chemistry Letters designed to expand awareness of, and enthusiasm for, physical chemistry by presenting accessible plain-language summaries of select articles in each issue. Spotlighted articles are chosen in a three-tier process that emphasizes how well the abstract of each article communicates an intriguing story to the nonspecialist. The Spotlights summaries are then written as an accessible preview of physical chemistry research and used to actively promote researchers’ work across a broad network, similar to a news release.

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Surface Ligand-Mediated Plasmon-Driven Photochemical Reactions

Research has shown that localized surface electromagnetic fields can drive photochemical reactions at low photon flux at room temperature. This finding is significant in two increasingly important areas: harvesting solar energy and decontaminating chemical waste. Although plasmon-driven surface photo- chemical reactions have been the subject of recent study, less work has been done to determine the effect of surface ligands, which has been thought to be limited to poisoning catalytic activity of nanocrystals by blocking the active sites. In their Letter, Kafle et al. (10.1021/acs.jpclett.7b00106) provide experimental evidence that surface ligands can enhance the reactivity of surfaces and induce important reaction pathways in plasmon-driven photochemical reactions. They used the plasmon-driven photochemistry of p-aminothiophenol on resonant plasmonic gold nanorods as a model reaction to study the effect of surface ligands on reaction selectivity by comparing the results obtained in the presence of citrate, hexadecyltrimethylammonium bromide, and no surface ligands. The authors found that the same plasmonic nanocrystals can lead to different photochemical reaction pathways depending on the surface ligands.

Abstract:

From the Journal of Physical Chemistry Letters

Contrary to the general expectation that surface ligands reduce the reactivity of surfaces by blocking the active sites, we present experimental evidence that surface ligands can in fact increase reactivity and induce important reaction pathways in plasmon-driven surface photochemistry. The remarkable effect of surface ligands is demonstrated by comparing the photochemistry of p -aminothiophenol (PATP) on resonant plasmonic gold nanorods (AuNRs) in the presence of citrate, hexadecyltrimethylammonium bromide (CTAB), and no surface ligands under visible light irradiation. The use of AuNRs with citrate and no surface ligand results in the usual azo-coupling reaction. In contrast, CTAB-coated AuNRs oxidize PATP primarily to p -nitrothiophenol (PNTP). Strong correlation has been observed between the N–O and Au–Br vibration band intensities, suggesting that CTAB influences the reaction pathway through the Br – counterions that can minimize the electron–hole recombination rate by reacting with the hole and hence increasing the concentration of hot electrons that drive the oxidation reaction.