Controlling chemical interface damping by removing aromatic monothiol and dithiol groups from gold nanorods using sodium borohydride solution†

Chemical interface damping (CID) in gold nanorods (AuNRs) significantly influences their optical properties due to the direct transfer of hot electrons from the AuNRs to adsorbed molecules. Despite ongoing research on CID, reversible tuning of CID at the single particle level remains a challenging task. In this study, we investigated the adsorption and removal of thiol-functionalized aromatic molecules, specifically thiophenol (TP) and benzene-1,2-dithiol (BDT), using sodium borohydride (NaBH₄) solution as a reagent, with confirmation through surface-enhanced Raman scattering (SERS) measurements. We further examined the effect of NaBH₄ solution pH, immersion time in solution, and the number of thiol groups in the adsorbate (TP and BDT) on removal efficiency from the AuNR surfaces. Additionally, we extended this approach to directly control CID in single AuNRs via the adsorption and desorption of TP and BDT molecules under dark-field microscopy and spectroscopy. Therefore, this study provides insights into the removal of aromatic thiol molecules using NaBH₄, as well as the direct control of CID in individual AuNRs.