Resonant Enhancement of Photolysis through Plasmon-Vibrational Coupling

Abstract

The coupling of photonic modes and molecular vibrations is an emerging method for modifying the chemical reactivity of target molecules. However, since the photonic mode typically arises from a Fabry–Pérot cavity, it presents challenges for the systematic investigation of chemical reaction rates that require external stimuli due to the inherent closed nature of the cavity. Here, we use infrared-plasmonic colloidal nanocrystals (NCs) as building blocks in monolayer assemblies, which act as metasurfaces. We harness their strong local electric fields for coupling with molecular vibrations, allowing for control over the molecular reactivity through plasmon-vibrational coupling. After the assembly of the metasurface, we attached azidobenzoic acid to tin-doped indium oxide NCs, enabling the study of UV-driven photolysis. The photolysis rate varies when changing the frequency detuning between the azide asymmetric stretch and the collective plasmon resonance of the NC monolayer, which is controlled by the Sn doping concentration. We observe the greatest rate enhancement when the detuning approaches zero. We developed a theoretical model showing that the rate enhancement arises from vibrational excitation in the excited state of the molecules, assisted by the plasmon resonance of the NC assembly. We anticipate that our platform can serve as a scalable metasurface for controlling diverse chemical reactions and transport phenomena.