Surfactant Headgroup-Dependent Growth of Large-Aspect-Ratio Single-Crystalline Gold Nanorods and Their Linear Assembly
Xiaoshan Kou, Man Hau Yeung, Jianfang Wang
surfactant, gold nanorods, assembly
Gold nanorods have great potentials in optical, optoelectronic, and biotechnological applications because gold is chemically inert, biologically compatible, and gold nanorods exhibit rich localized surface plasmon properties. To fully realize their potential applications, gold nanorods of narrow size distributions and plasmon wavelengths tunable from the visible to infrared spectral range are strongly desired. We have recently developed methods for the preparation of nearly monodisperse gold nanorods in high yields. Specifically, we have used cetyltrialkylammonium bromide surfactants with increasingly larger headgroups to grow single-crystalline gold nanorods of average aspect ratios from 2 to 70 (corresponding plasmon wavelengths from ~ 600 nm to ~ 3 m). Moreover, we have developed an approach for the continuous shortening of single-crystalline gold nanorods through mild oxidation. The shortening rate can be controlled by temperature and acid concentration. With this shortening approach, gold nanorods of any aspect ratio below that of the starting nanorods can be produced. Furthermore, we have used glutathione and cysteine to assemble gold nanorods and nanospheres in a linear fashion into necklace structures. Taken together, our developed growth, shortening, and assembly approaches will facilitate the use of gold nanorods in the areas of optics, optoelectronics, and biotechnology.
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Nanotech 2007 Conference Program Abstract