Thiolated β-cyclodextrin-based host–guest interactions: investigating and tuning chemical interface damping in single gold nanorods

Abstract

Chemical interface damping (CID) in gold nanorods (AuNRs) results from the direct hot electron transfer from Au to adsorbed molecules. Although CID has been studied extensively, its tunability at the single-particle level remains limited. In this study, we employed a β-cyclodextrin (βCD)-based host–guest system, using methyl orange (MO) and cholesterol (Cho) as competing guests, to investigate and control CID in single AuNRs. CID was tuned by leveraging competitive binding and exchange reactions between guest molecules. Various spectroscopic and electrochemical analyses confirmed the release of encapsulated MO and the competitive inclusion of Cho within the βCD cavity. Additionally, the desorption of thiolated βCD from the AuNR surface using sodium borohydride (NaBH₄) was demonstrated, offering an alternative route for CID control. This study introduces a strategy for directly tuning CID in single AuNRs through βCD-based host–guest supramolecular chemistry and the reversible adsorption–desorption of SH-βCD.