Small Change, Big Difference: Photoelectrochemical Behavior of Au Nanocluster-Sensitized TiO₂ Altered by Core Restructuring

Abstract

Ultrasmall gold nanoclusters (Au NCs) have recently gained enormous popularity as a newly emerging light harvester, but many fundamental aspects of their photoelectrochemical behavior are still largely unknown. Unlike traditional photoactive nanoparticles, the NC’s core structure, rather than its size, is a key factor that dictates the physical properties of NCs because of a strong quantum confinement effect. Despite this importance, no effort has been made to elucidate the effect of the core structure on the photoelectrochemistry of Au NC-sensitized TiO2 (Au NC–TiO2). Using Au25 NC as a model system, we delicately tailored the icosahedral Au13 core of Au25 NC into a cuboctahedral Au15 core of Au23 NC. This subtle core manipulation has a drastic impact on the entire interfacial behavior of Au NC–TiO2, which in turn significantly affects the photoelectrochemical performance. This new insight highlights the overlooked effect of the core structure on the photoelectrochemistry of Au NC–TiO2.