Formation mechanism of nonspherical gold nanoparticles during seeding growth: roles of anion adsorption and reduction rate |
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Authors: | Cao Linyou Zhu Tao Liu Zhongfan |
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Institution: | Center for Nanoscale Science and Technology, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, People's Republic of China. lc87@drexel.edu |
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Abstract: | A small section of nonspherical particles can be observed in the further growth of spherical gold colloids exposed to a mixture of NH2OH and HAuCl4. The concentration ratio of NH2OH]:HAuCl4] is critical for the formation of nonspherical particles as higher ratios produce lower yields and smaller of such particles. These concentrations also affect the reaction kinetics; the reaction rate increases with NH2OH], while independent of HAuCl4], which we believe is due to the specific adsorption of AuCl4- onto gold surface. These nonspherical particles come from the preferential growth of {111} facets as indicated by their TEM images and electron diffraction patterns. We propose this preferential growth is ascribed to the preferential adsorption of AuCl4- on {111} facets, and some competition which determines the yield of nonspherical particles exists between the AuCl4- adsorption and the AuCl4- reduction, faster reduction counteracting the effect of this preferential adsorption and thus suppressing nonspherical particle. This result probably provides some guidance to develop a shape-controlled synthesis of gold particles without any additives. |
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