Analytical Characterization of Size-Dependent Properties of Larger Aqueous Gold Nanoclusters

Gold nanoclusters (AuNCs) with well-defined structure and arrangement possess particular physical and functional properties. AuNCs that differ only by less than 1 nm in diameter corresponding to one atomic layer show different structural, optical, and physicochemical properties in a size dependent mode, making their analytical characterization a challenge. Herein we describe an integrative approach to characterization of larger aqueous AuNC (Au-102-pMBA(44), Au(144)pMBA(60) and higher) selected by gel electrophoresis (PAGE). We employ UV-vis, dynamic light scattering, and zeta-potential in combination with high-performance analytical techniques such as multiwavelength analytical ultracentrifugation and electrospray ionization mass spectrometry were used to separate aqueous AuNCs hydrodynamic diameter, partial abundance, molecular weight, and mass/charge ratios when present in a complex mixture of AuNCs containing Au-102 (1.6 nm), A(144) (2 nm), and AU(288-328) (2.5 nm). Advanced analytical electron microscopy imaging (spherical aberration corrected BF/HAADF-STEM at low voltages dose) also revealed the structures of discrete arrangements of gold nanocluster populations.