Strategy to controllably release gold nanoparticles from hexadecyltrimethylammonium bromide-capped gold microparticles

As shown in the literature, cationic surfactants of hexadecyltrimethylammonium bromide (CTAB) were generally employed for syntheses of Au nanorods (NRs). For obtaining different aspect rations of NRs, the molar ratio of CTAB to Au(III) is ranging from 200 to 400. In this work, we report a new strategy to release Au nanoparticles (NPs) from CTAB-capped Au microparticles (MPs) by using sonoelectrochemical methods. In this optimal approach, the molar ratio of CTAB to Au(III) is ca. 0.6, which is far lower than the ratio used for synthesizing Au NRs. Au NPs with predominant (1 1 1) face and size of 10 nm in diameter can be readily obtained in solution, which is accompanied by the simultaneous reduction in pH, after complete removal of CTAB.