Tuning of chemical interface damping in single gold nanorods through pH-dependent host–guest interactions using cucurbit[6]uril

Abstract

Chemical interface damping (CID) in gold nanorods (AuNRs) arises from direct hot electron transfer from Au to adsorbed molecules. Despite recent studies on CID, its tunability in single AuNRs remains challenging. Herein, we present a method for in situ control of CID in single AuNRs using pH-dependent host–guest supramolecular interactions. We employ cucurbit[6]uril (CB[6]), a well-known host molecule capable of encapsulating and releasing guest molecules, along with bis(3-aminopropyl)amine (BAPA) as guest molecules forming a complex with CB[6] (CB[6]–BAPA). CID is induced by attaching the CB[6]–BAPA complex on AuNR surfaces through a strong Au–amine interaction. In addition, in situ tuning of CID is achieved by releasing CB[6] from the complex using a NaOH solution. Successful CB[6]–BAPA complex formation, their attachment onto AuNRs, and CB[6] release from the complex are confirmed through changes in the localized surface plasmon resonance (LSPR) peak and LSPR linewidth, alongside mass analysis. Therefore, this study offers a new method for in situ CID tuning using CB[6]-based pH-sensitive host–guest interactions in individual AuNRs. This study can be further used in CB[6]-based photochemical processes and biosensing studies.