Direct synthesis of branched gold nanocrystals and their transformation into spherical nanoparticles

被引:113
作者
Wu, Hsiang-Yang [1 ]
Liu, Michael [1 ]
Huang, Michael H. [1 ]
机构
[1] Natl Tsing Hua Univ, Dept Chem, Hsinchu 30013, Taiwan
关键词
D O I
10.1021/jp063711d
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
We report a facile synthesis of branched gold nanocrystals by the addition of a suitable amount of NaOH to an aqueous solution of cetyltrimethylammonium bromide (CTAB), HAuCl4, and ascorbic acid. The branched nanocrystals were formed within minutes of reaction and showed monopod, bipod, tripod, and tetrapod structures. They are crystalline and have smooth surfaces. These gold multipods are kinetically controlled products and are thermodynamically unstable. The branched nanocrystals quickly transformed into spherical nanoparticles within 1 h of reaction, and the process was essentially complete after 2 days. The morphological transformation has been monitored by both UV-vis absorption spectroscopy and electron microscopy. The appearance of two major absorption bands for the branched gold nanocrystals eventually became only a single band at 529 nm for the spherical nanoparticles. The resulting nanoparticles are single crystals with diameters of 20-50 nm and do not show a faceted structure. When the freshly prepared branched nanocrystals are kept in a refrigerator at 4 degrees C, their multipod structure can be preserved for over a month without significant spectral shifts.
引用
收藏
页码:19291 / 19294
页数:4
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