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 PtCl₆^2– 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 PtCl₆^2– according to 16 nm red-shift in its Cl–Pt ligand-to-metal charge-transfer (L_πMCT) band involving ligand π orbitals. Subsequent Pt⁰ growth kinetics were tracked using the L_πMCT 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.