Gold nanoparticles prepared by glycinate ionic liquid assisted multi-photon photoreduction.

We have successfully prepared gold nanoparticles (AuNPs) with flower-like and spherical morphology through multi-photon photoreduction (MPR) of an aqueous solution of HAuCl(4) and (2-hydroxyethyl) trimethylammonium glycinate ([HETMA][Gly]) ionic liquid (IL) through the use of a femtosecond laser. The results of (1)H NMR and UV-Vis absorption indicated that AuNPs were produced from the photoreduction of the [Gly]-Au(iii) complex. Spherical AuNPs of about 2.5 nm were obtained on the solution when irradiated for 2 h, then aggregated into flower-like AuNPs of several tens of nanometers assisted by the IL with an increase in the irradiation time. Furthermore, precipitates of spherical AuNPs with the size of around 15 nm were formed after being irradiated for 6 h. The mechanisms of the MPR reaction and controlled growth of AuNPs have also been discussed.