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

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.