Targeted Deposition of Platinum onto Gold Nanorods by Plasmonic Hot Electrons

Photocatalytic assembly of heterometallic nanoarchitectures via plasmonic hot electrons is demonstrated by liquid-phase, reductive photodeposition of platinum (Pt) onto gold nanorods (AuNR) under longitudinal surface plasmon (LSP) excitation. Nucleation of Pt0 from PtCl62– was initiated by plasmonic hot electrons at the Au surface. Sub-5 nm epitaxial overgrowth of Pt followed a core–shell morphology. Measured 6.5 longitudinal:transversal growth aspect ratio revealed longitudinal growth preferentiality that was consistent with the LSP dipole polarity. In situ spectroscopic monitoring of the photocatalytic growth process permitted real-time feedback into Au surface functionalization with PtCl62– according to 16 nm red-shift in its Cl–Pt ligand-to-metal charge-transfer (LπMCT) band involving ligand π orbitals. Subsequent Pt0 growth kinetics were tracked using the LπMCT band. Discrete dipole models elucidated evolving light-matter interactions of Pt-decorated AuNR that were consistent with experimental characterization. These studies provide a foundational mechanistic understanding toward guided assembly of heterometallic nanoarchitectures at ambient conditions via plasmonic hot electrons.