Which Nanoparticle Shape is the Most Effective in Generating Hot Charge Carriers from Plasmon Excitation?

Abstract

Hot charge carrier generation is one of the most importantpropertiesof plasmonic nanoparticles with a wide range of applications, includingsolar water splitting, photovoltaics, and photocatalysis. Thus, understandingthe relationship between the physical parameters of plasmonic nanoparticlesand hot carrier generation efficiency is essential for technologicaladvancements. In this study, we investigate how the shape of goldnanoparticles influences the efficiency of generating hot charge carriersfrom plasmon decay. We synthesize Au nanospheres (AuNSs), Au nanocubes(AuNCs), Au nanorods (AuNRs), and Au nanotriangular prisms (AuNTs)with the same capping ligand and similar size. These nanoparticlesare then adsorbed onto self-assembled monolayers of 4-mercaptobenzoicacid (MBA) on gold films to form nanoparticle-on-mirror (NPoM) systems.By irradiating the NPoM at 785 or 633 nm, plasmons are created, andtheir subsequent decay leads to the production of hot carriers thatare used to transform MBA into benzenethiol (BT). We find that AuNRsin NPoM exhibit the highest production of BT, followed by AuNSs & AP;AuNCs > AuNTs when excited at 785 nm. Dividing the reaction yieldsby the absorption cross section at the specific wavelength determinesthe hot carrier generation efficiency. For an accurate evaluationof the absorption cross sections, we obtain the calculated scatteringspectra that closely match the experimentally measured dark-fieldsingle-particle scattering spectra. Using the same calculation parameters,we then determine the absorption cross sections of each NPoM. Basedon this approach, we quantify the hot carrier generation efficiencyfor each NPoM and find that AuNRs are the most effective in generatinghot carriers from plasmon excitation compared to any other shapes.These findings provide valuable insights into the design of highlyefficient plasmonic photocatalysts.