Dependence of Core Electronics of Gold Nanoparticles on Ligand, Solvent, and Sample Preparation

Electron spin resonance (ESR) spectroscopy is used to probe the electronic properties of the metallic cores of small (∼2 nm) gold nanoparticles protected by 1-hexanethiol and 1-dodecanethiol, suspended in either n-hexane or THF. Analysis of the ESR spectra allows extraction of the principal components of the g-tensor for the metallic electrons in the core. We find that the values associated with the g-tensor are sensitive to the identity of both the ligand and the solvent. We also find that the handling of the samples can affect the measured g-values, with common manipulations such as freezing and thawing the sample or precipitating and resuspending the nanoparticles increasing the measurement-to-measurement distributions of the measured g-values. The degree of these perturbations also depends on the identity of the ligand and solvent. These results stress the importance of the design and handling of colloidal systems when seeking to use their electronic behaviors.