Controlled Growth of Gold Nanoparticles in AOT/C12E4/Isooctane Mixed Reverse Micelles

✍ Scribed by Chen-Li Chiang

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 483 KB
• Volume: 239
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.2001.7590

✦ Synopsis

Stable anisotropic gold nanoparticles were prepared by the reduction of a relatively high concentration of tetrachloroauric acid with hydrazine in mixed reverse micelles formed with anionic surfactant AOT and nonionic surfactant tetraethylene glycol dodecyl ether (C 12 E 4 ) in isooctane. It was found that the C 12 E 4 serves not only as a structure modifier but also as a stabilizer for Au particles, to prevent their further growth and precipitation. By the analyses of a high-resolution electron microscope, electron diffraction patterns, and energy-dispersive X-ray analysis (EDX), the resultant particles have been found to be pure gold of face-centered cubic structure. In the presence of C 12 E 4 , the Au particle size is larger than that in the absence of C 12 E 4 , while the particle size decreases with increases in the concentration of C 12 E 4 . The molar ratio of hydrazine to HAuCl 4 was found to be an important parameter in the control of size and shape for the production of gold nanoparticles. A decrease in the molar ratio of hydrazine to HAuCl 4 resulted in larger Au particles with significantly more polydispersity. When the HAuCl 4 was injected directly into the mixed reversed micelles containing hydrazine, anisotropic gold nanoparticles, such as cylinders and trigons, were obtained at the molar ratio of hydrazine to HAuCl 4 of less than 0.5.