Role of Hydration in Photoexcited Electron Transfer between a Gold Nanocluster and a Water Molecule

The photoexcitation of noble metal nanoparticles causes various electrochemical phenomena in the neighboring molecules. To understand these phenomena, it is required to obtain atomic and electronic scale insights into the role of the interface between a noble metal nanoparticle and molecules in photochemical processes. In addition, protic solvents are widely employed in photoelectronic systems and have local intermolecular interactions such as hydrogen bonding that could play an important role in determining the electronic and optical properties. In this study, we investigate the electronic structure and the photoexcited electron transfer of a Au₁₄₇/H₂O complex in aqueous solution using an original theoretical approach that is a hybrid formula of the quantum mechanical method for photoexcitation of nanomaterials and a statistical mechanical theory for molecular liquids. The analysis of the solvation structure reveals that the gold surface excludes the water molecules within the proximity of the adsorbed H₂O oxygen. Therefore, the hydration increases the orbital energy of the adsorbed H₂O and enhances the photoexcited electron transfer from H₂O to Au₁₄₇.