Amino Acid-Based Redox Active Amphiphiles to In Situ Synthesize Gold Nanostructures: From Sphere to Multipod
Amino Acid-Based Redox Active Amphiphiles to In Situ Synthesize Gold Nanostructures: From Sphere to Multipod
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DOI：
10.1021/cg100281z
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发表时间：
2010-05-01
影响因子：
3.8
通讯作者：
Mandal, Tarun K.
中科院分区：
文献类型：
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作者：
Dinda, Enakshi;Rashid, Md. Harunar;Mandal, Tarun K.
在碱性条件下，利用新设计的氨基酸基氧化还原活性两亲体，采用原位还原技术合成了形状可控的金（Au）纳米结构（球形和多pod）。这些两亲体是脂肪酸（如己酸、辛酸和癸酸）和氧化还原活性氨基酸（色氨酸）的偶联物。两亲体的性质（特别是脂肪酸相关的烷基链长度）和两亲体与HAuCl4的摩尔比(R)对形成的金纳米结构的形貌有显著影响。例如，以己酸和辛酸为基础的两亲体，在R值为4-8的范围内，主要产生多荚形的金纳米结构。然而，在R为1.3-2.0的范围内，这些两亲体仅产生球形金纳米颗粒（NPs）。然而，无论R值是多少，癸酸基两亲化合物只生成平均直径在3.5-6.2 nm范围内的球形Au NPs。红外光谱（FTIR）和热重分析证实了金纳米结构具有两亲性盖层。XRD结果表明，形成了以{11 11}面为界的高结晶球形和多荚形金纳米结构。基于高分辨率透射电子显微镜（HRTEM）和随时间变化的紫外可见光谱研究，讨论了球形/多荚形金纳米结构的形成机制。HRTEM分析表明，初始形成的较小的球形Au NPs定向附着形成了多豆粒状的Au分支，并沿< 1 1 1 >方向生长。HRTEM结果进一步表明，球形Au NPs也沿< 1 1 1 >方向生长。
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.