Energy States of Ligand Capped Ag Nanoparticles: Relating Surface Plasmon Resonance to Work Function

The work function (WF) and surface plasmon resonance (SPR) of organic ligand capped Ag nanoparticles (NPs) have been studied experimentally and computationally. Experimental observations reveal a significant increase in WF as the size of ligand-capped Ag NPs increases, a trend contrary to that previously observed for bare Ag NPs. Computational results confirm the effect on the WF from simplified ligand molecules and relate it to charge transfer between the Ag core and surrounding ligands. We also observe a possible coupling between increases in WF and decreases in SPR transition energy, supported by computational results and attributed to the interplay between the 4d and 5s electron states of the system. These results, along with our observations of WF dependence on ligand choice, indicate the ability to strongly engineer the electronic structure of metal NPs through size and ligand control