Surface Engineering of Au36(SR)24 Nanoclusters for Photoluminescence Enhancement

Abstract

The luminescence of metal nanoparticles constitutes an area of significant interest in recent years, in particular the luminescence of ultrasmall gold and silver nanoparticles. Gold has particular surface characteristics and low toxicity compared to other luminescent nanoparticles. However, gold often has weaker luminescence; thus, a major goal of research is to enhance gold nanoparticle luminescence. In this work, surface ligand engineering is performed on atomically precise Au36(SR)24 nanocrystals (also called nanoclusters, whereSR represents thiolates) to determine different optical and luminescent properties affected by different ligands (i.e., the R groups). The gold nanocluster formula, structure, luminescence, and lifetime are characterized by techniques including electrospray ionization mass spectrometry, UV–vis and fluorescence spectroscopies. It is found that the surface ligands (i.e., different R groups) can affect the charge density transfer between the ligands and the metal core, which in turn influences the luminescence intensity. The luminescence intensity is found to correlate with the electronegativity of the surface ligands that are exchanged onto Au36. The effects of surface engineering on the luminescence properties of gold nanoclusters may open up exploration for applications such as biolabeling, luminescent probes, and other applications.