High-performance liquid chromatographic analysis of as-synthesised N,N′-dimethylformamide-stabilised gold nanoclusters product

Abstract

Reverse-phase high-performance liquid chromatographic (RP-HPLC) separation and analysis of polydisperse water-soluble gold nanoclusters (AuNCs) stabilised with N,N′-dimethylformamide (DMF) were investigated. Under optimal elution gradient conditions, the separation of DMF–AuNCs was monitored by absorption and fluorescence spectroscopy. The UV-vis spectral characteristics of the separated DMF–AuNCs have been captured and they do not possess distinct surface plasmon resonance bands, indicating that all DMF–AuNCs are small AuNCs. The photoluminescence emission spectra of the separated DMF–AuNCs are in the blue-light region. Moreover, cationic DMF–AuNCs are for the first time identified by ion chromatography. Our proposed RP-HPLC methodology has been successfully applied to separate AuNCs of various Au atoms as well as DMF-stabilised ligands. Finally, the composition of the separated DMF–AuNCs was confirmed by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry and electrospray ionisation mass spectrometry, proving that the as-synthesised DMF–AuNCs product consists of Au₁₀⁺, Au₁₀, Au₁₁, Au₁₂, Au₁₃, and Au₁₄ NCs stabilised with various numbers of DMF ligands.