Role of UHPLC in evaluating as-synthesised ligand-protected gold nanoparticles products

Abstract

Analytical separation of metal nanoparticles (NPs) remains a significant challenge as it is very useful in assessing the purity, particle size, protecting ligands and dispersity of the as-synthesised NPs products. In this paper, two liquid chromatographic methods have been developed and their efficiencies in separating samples of polydisperse gold nanoparticles protected with N-acetyl-L-cysteine ligand (NAC-AuNPs) and other ultrasmall water-soluble ligand-protected gold NPs are compared. The total elution time for analysing a NAC-AuNPs sample by ultra high-performance liquid chromatography (UHPLC) is ten times shorter than that of high-performance liquid chromatography. The major attributes of UHPLC are smaller sample volume (1–2 μL) and better separation efficiency. More importantly, our proposed UHPLC method has been successfully applied to evaluate and compare polydisperse NAC-AuNPs products synthesised with the one-phase and two-phase Brust–Schiffrin methods. The results indicate that the two-phase method would harvest AuNPs product with smaller core size and less dispersity.