(222b) Mid-Infrared Surface Plasmon-Enhanced Molecular Desorption

The strong light-matter interactions of localized surface plasmon resonances (LSPRs) offer opportunities to influence chemical reactions. Ultraviolet and visible LSPRs are known to impact reactions ranging from water splitting and hydrogen dissociation to ethylene epoxidation and methane formation. Doped semiconductor nanocrystals have emerged as a new class of materials that support LSPRs in the near and mid-infrared. Here, we use time-resolved in situ infrared spectroscopy to study the influence of mid-infrared LSPRs on molecular desorption. We find that the desorption rate for model molecules (e.g., indole, benzoic acid) on indium tin oxide (ITO) nanocrystals can be enhanced by as much as 2x upon illumination with mid-infrared light (~0.6-0.1 eV) at room temperature. The desorption rate is linearly dependent on light intensity, indicating a single photon process. Experiments as a function of LSPR energy, nanocrystal film thickness, and adsorbate concentration provide clues as to the mechanism of the enhancement. Our findings open new avenues to leverage low energy light for manipulating chemical reactions.