期刊
CRYSTAL GROWTH & DESIGN
卷 10, 期 5, 页码 2421-2433出版社
AMER CHEMICAL SOC
DOI: 10.1021/cg100281z
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资金
- Council of Scientific and Industrial Research India
- CSIR, India
- DST, New Delhi
Gold (Au) nanostructures of controllable shapes (spherical and multipod) were synthesized by an in situ reduction technique using newly designed amino acid-based redox active amphiphiles without any additional template in alkaline condition. These amphiphiles are the conjugates of fatty acids (e.g., caproic acid, caprylic acid, and capric acid) and a redox active amino acid (tryptophan). The nature of amphiphiles (especially the length of the alkyl chain associated with fatty acids) and the molar ratio (R) of amphiphile to HAuCl4 have a significant effect on the morphology of the formed Au nanostructures. For example, the caproic acid- and caprylic acid-based amphiphiles produce mostly multipod-shaped Au nanostructures at a value of R in the range 4-8. However, these amphiphiles produced only spherical Au nanoparticles (NPs) at R in the range 1.3-2.0. However, the capric acid-based amphiphile generates only spherical Au NPs with an average diameter in the range 3.5-6.2 nm, no matter what the value of R is. FTIR and thermogravimetric analysis confirmed the capping of Au nanostructures with amphiphile. XRD results indicated the formation of highly crystalline spherical and multipod-shaped Au nanostructures that were bounded by {1 1 1} facets. The mechanisms of formation of spherical/multipod-shaped Au nanostructures are discussed based on the high-resolution transmission electron microscopic (HRTEM) and time-dependent UV-vis spectroscopic studies. HRTEM analysis revealed that the multipod-shaped Au branches were formed by oriented attachment of the initially formed spherical Au NPs of smaller size and were grown along the < 1 1 1 > direction. HRTEM results further indicated that spherical Au NPs were also grown along the < 1 1 1 > direction.
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