Synthesis and stability evaluation of size-controlled gold nanoparticlesvia nonionic fluorosurfactant-assisted hydrogen peroxide reduction

Abstract

We report an aqueous synthesis of gold nanoparticles (AuNPs) by chemical reduction of HAuCl₄ with hydrogen peroxide (H₂O₂) in the presence of nonionic fluorosurfactant (FSN). Here, FSN acts as a co-reducing and stabilizing agent. The diameters of the FSN-stabilized spherical AuNPs were 18 ± 3.8, 23 ± 2.5, 29 ± 3.4, 36 ± 4.0 nm by varying the H₂O₂–gold molar ratio. The formation mechanism of the FSN-stabilized AuNPs was proposed by UV-visible spectroscopy, powder X-ray diffraction (XRD) measurements, transmission electron microscopy (TEM) images, Fourier transform infrared (FT-IR) spectroscopy, and electronic spinning resonance (ESR) measurements. High temperature decomposition of H₂O₂ can generate hydroxyl radicals (˙OH), which can rapidly oxidize R–CH₂CH₂–OH in FSN molecules to R–CH₂CH˙–OH radicals. The rapid formation of Au(0) is ascribed to the reduction of Au(III) by R–CH₂CH˙–OH radicals. The Au(0) aggregation on the gold crystal nucleus is restrained due to the steric hindrance effect of FSN ligands, leading to the formation of small AuNPs. More interestingly, the FSN-stabilized AuNPs show excellent colloidal stability in the presence of high salt concentrations and over a wide range of pH values (2–11) without particle aggregation at room temperature for at least one month.