Synthesis of gold nanocrystals of different diameters using a soft template of polyethyleneglycols (PEG)-sodium dodecyl sulfate (SDS) is described. The aqueous solution containing HAuCl₄ and PEG was sonicated to synthesize the seeds of gold nanoparticles. The seeds were then added to a series of PEG-SDS aqueous solution and mixed well, and the solution was irradiated with UV for 15 hours at 25±3^oC thereafter. Samples were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The concentrations of PEG (CPEG) and SDS (CSDS) were found to have a dramatic influence on the formation of gold nanoparticles. At a certain concentration of PEG, when the concentration of SDS is between 0 and 31.6 mM, the more the SDS the smaller the diameter of gold nanocrystals was. SDS can capsule the gold crystals so that it stabilized the gold sols and affect the growth of gold nanoparticles. PEG was mainly used as stabilizer, and it can reduce Au³⁺. At a certain concentration of SDS (3.16 mM), the more PEG (0.5-2 wt.%) in the solution the smaller the gold nanoparticles were. UV-vis absorption spectra indicated that the intensity of the absorption maximum (540nm) increased during the growth of gold nanoparticles. The possible mechanism of soft template was discussed as well.

^† corresponding author: Yun FANG

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