Gold nanoparticles (AuNPs) were synthesized by two step electrolysis in three component system of cetyltrimethylammonium bromide (CTAB)-acetone-water assisted by ultrasonic irradiation. The constant current or potential step technique was applied to the first electrolysis, and small AuNPs were produced as seeds. The double potential step technique was applied to the second electrolysis for the growth of AuNP seeds. The results revealed that the size of the AuNP was dependent on the electrolysis coulomb. A clean Si(111) wafer was immerged into the colloid solution for the assembly of AuNP through the electrostatic interaction, and thus the AuNP covered Si(111) surfaces were obtained with different morphology. By using pyridine as probe molecule, the AuNP covered Si(111) surfaces were served as surface enhanced Raman scattering (SERS) substrate for studying the relationship between the SERS effect and the surface morphology of AuNP.

Key words: electrolysis, constant current, potential step, electrostatic assembly, surface enhanced Raman scattering