Hot carriers in action: multimodal photocatalysis on Au@SnO₂ core-shell nanoparticles

Metal-semiconductor hybrid heteronanostructures exhibit intriguing multimodal photocatalytic behaviors dictated by multiple types of photoexcited charge carriers with distinct energy distribution profiles, excited-state lifetimes, and interfacial transfer dynamics. Here we take full advantage of the optical tunability offered by Au@SnO2 core-shell nanoparticles to systematically tune the frequencies of plasmonic electron oscillations in the visible and near-infrared over a broad spectral range well-below the energy thresholds for the interband transitions of Au and the excitonic excitations of SnO2. Employing Au@SnO2 core-shell nanoparticles as an optically tunable photocatalyst, we have been able to create energetic hot carriers exploitable for photocatalysis by selectively exciting the plasmonic intraband transitions and the d → sp interband transitions in the Au cores at energies below the band gap of the SnO2 shells. Using photocatalytic mineralization of organic dye molecules as model reactions, we show that the interband and plasmonic intraband hot carriers exhibit drastically distinct photocatalytic behaviors in terms of charge transfer pathways, excitation power dependence, and apparent photonic efficiencies. The insights gained from this work form an important knowledge foundation guiding the rational optimization of hot carrier-driven chemical transformations on nanostructured metal-semiconductor hybrid photocatalysts.