Research Projects

The development of robust and efficient photocatalysts is crucial for a sunlight-driven renewable energy infrastructure. Conventional molecular and semiconductor-based photocatalysts are limited by low photostability and narrow absorption bands, which constrain their effectiveness in solar energy conversion. In contrast, noble metal nanoparticles—particularly those made of gold—offer distinct advantages due to their exceptional photostability and unique plasmonic properties. The “antenna effect” associated with these particles enables absorption cross-sections that far exceed their physical dimensions at the surface plasmon resonance (SPR). Importantly, the SPR wavelength can be tuned by modifying the size and shape of the nanoparticles, allowing for efficient absorption across a broad range of the solar spectrum. Upon illumination, they convert incident photons into highly energetic ("hot") electrons and holes. These charge carriers can migrate to the adsorbed or chemically tethered molecules (reactant or catalysts) through a charge or energy transfer process and may initiate and/or boost a chemical reaction. This plasmon-driven process has been shown to facilitate energy-intensive reactions such as water splitting and carbon dioxide reduction, although with low photon-to-product yield. A significant challenge is the ultrafast relaxation of charge carriers within the metal, where the energy is rapidly dissipated—typically within a few picoseconds—via electron-electron and electron-phonon scattering processes. This rapid energy loss competes with the desired charge or energy transfer to reactants, reducing overall catalytic yields. This research aims to fundamentally elucidate and optimize the mechanisms of charge and energy transfer at the interface between plasmonic nanoparticles and molecular catalysts. The central hypothesis is that the rational design of nanoparticle–molecular catalyst hybrids, incorporating tailored ligand and/or linker chemistry and optimized interfacial orbital alignments, can significantly enhance the efficiency of charge or energy transfer from the metal to the molecular catalyst. This is expected to improve the overall performance of photocatalytic solar-to-chemical energy conversion. The project will systematically investigate and relate the chemical interface damping (CID) and hot carrier lifetimes to catalytic efficiency, to advance the understanding and application of plasmonic photocatalysis. To achieve these objectives, we will synthesize gold nanorods and nanoprisms functionalized with transition metal-based molecular catalysts. The formation of the nanohybrids will be confirmed through various microscopy and spectroscopic techniques. Charge and energy transfer efficiencies will be quantified at the single-nanoparticle level through by analysing plasmon resonance linewidth broadening. Femtosecond pump-probe spectroscopy will be employed to directly measure ultrafast hot carrier dynamics and lifetimes, with sub-50 femtosecond time resolution, enabling the tracking of carrier relaxation and migration to the molecular interface. Photocatalytic activity will be assessed through model redox reactions such as water splitting or with fluorogenic dyes, both at the single-particle and ensemble levels. These experimental studies will be complemented by first-principles quantum mechanical calculations, which will provide mechanistic frameworks for understanding charge and energy flow and guide the iterative optimization of catalyst design. Successful completion of the proposed work will establish a rational design principle for engineering next generation plasmonic photocatalysts with enhanced efficiency. Furthermore, the methodologies and mechanistic frameworks developed in this project will not be limited to catalysis but will be broadly applicable to other field where interfacial charge transfer processes play a major role (such as in light emitting devices).