Microwave irradiation synthesis and self-assembly of alkylamine-stabilized gold nanoparticles

The hydrophobic gold nanoparticles protected with octadecylamine, tetradecylamine and decylamine, respectively, were prepared by using ethanol reduction in reverse micelle through microwave dielectric heating. In this experiment, the commonly used toxic and highly volatile organic solvents such as chloroform, toluene and so on, which were an obstacle for preparing hydrophobic nanoparticles under microwave irradiation, were replaced by a safe organic mixed solvent n-heptane/ethanol used as an oil phase. The various alkylamine-stabilized gold nanoparticles obtained through this method were characterized and analyzed by ultraviolet visible spectroscopy (UV–vis), X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and elemental analysis. When the molar ratio of alkylamine to HAuCl4 was 40 : 1, the average diameters and standard deviations for octadecylamine-, tetradecylamine- and decylamine-capped gold nanoparticles were 4.53 ± 0.79, 5.22 ± 1.66, and 4.09 ± 1.22 nm, respectively. Furthermore, the composition of octadecylamine-stabilized gold nanoparticles was determined to be (C18H37NH2)265·Au2822, and the experimental result showed that both the monodispersity and stability of these gold nanoparticles were beneficial to forming large areas of ordered two-dimensional arrangement at the air/water interface.