Photoelectrochemical Probing of Hot Carrier Generation and Transfer in Gold Nanospheres

Understanding the generation and transfer of hot carriers in gold nanoparticles (AuNPs) is critical for advancing plasmonic photocatalysis and photovoltaics. Hot carriers are produced via nonradiative plasmon decay, yet the size dependence of their generation and the spatial range of their transfer remain underexplored. Here, we employ photoelectrochemical (PEC) methods to directly quantify the generation and transfer efficiencies of hot carriers in AuNPs. Size-controlled gold nanospheres (AuNSs) with diameters of 20, 32, 56, 74, and 98 nm are immobilized on ITO electrodes. Upon 532 nm laser excitation in a citrate-containing solution, hot holes oxidize citrate, and the resulting electron accumulation is measured via a photocurrent or open-circuit potential. We find that the hot carrier generation efficiency per absorbed photon decreases with an increasing AuNS size, exhibiting an inverse-square dependence on the AuNS diameter. To evaluate distance-dependent transfer efficiency, we introduce alkanethiol self-assembled monolayers (SAMs) of varying lengths onto the AuNS surfaces. The photocurrent decays exponentially with SAM thickness, revealing the spatial attenuation of the hot hole transfer. Our findings demonstrate the utility of PEC methods for probing plasmonic hot carriers and provide direct evidence for both size- and distance-dependent efficiencies.