Single Atoms Couple Molecular Coordination to Near‐Resonant Charge Transfer in Surface‐Enhanced Raman Scattering

ABSTRACT

Chemical enhancement in surface‐enhanced Raman scattering (SERS) is generally attributed to interfacial charge transfer, yet how atomically defined coordination converts molecular binding into enhanced vibrational polarizability remains unresolved. Here we show that Au‐coordinated Pt single atoms function as charge‐transfer bridges within a TiO _x nanocavity/Au nanoparticle architecture, coupling molecular coordination to near‐resonant Raman enhancement. The Pt single atoms serve three interdependent roles: binding target molecules, modulating interfacial electronic states, and mediating charge transfer. Together with photonic confinement and plasmonic hotspots, this atomically defined pathway produces an apparent SERS enhancement factor of 3.6 × 10 ¹¹ and enables measurements within a statistically defined single‐molecule occupancy regime. We term this cooperative process Spatial–Plasmonic Atomic Coupling Enhancement (SPACE), which connects atomic‐scale coordination and energy‐level alignment with macroscopic Raman amplification. As a proof of analytical utility, cysteamine functionalization couples benzaldehyde capture through Schiff‐base formation to the single‐atom‐mediated enhancement pathway, enabling gas‐phase detection down to 0.3 ppbv. These findings establish single‐atom coordination as a general design principle for transforming interfacial molecular binding into near‐resonant vibrational amplification.