Synthesis of aqueous Au core-Ag shell nanoparticles using tyrosine as a pH-dependent reducing agent and assembling phase-transferred silver nanoparticles at the air-water interface.
Synthesis of aqueous Au core-Ag shell nanoparticles using tyrosine as a pH-dependent reducing agent and assembling phase-transferred silver nanoparticles at the air-water interface.
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DOI：
10.1021/la049258j
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发表时间：
2004-07
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影响因子：
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通讯作者：
P. Selvakannan;A. Swami;D. Srisathiyanarayanan;Pravin S. Shirude;R. Pasricha;A. B. Mandale;M. Sastry-M.-Sast
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文献类型：
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作者：
P. Selvakannan;A. Swami;D. Srisathiyanarayanan;Pravin S. Shirude;R. Pasricha;A. B. Mandale;M. Sastry-M.-Sast
我们证明氨基酸酪氨酸在碱性条件下是一种优异的还原剂，可用于还原Ag+离子以合成水中稳定的银纳米粒子。酪氨酸还原的银纳米颗粒可以作为易于再分散在水中的粉末形式分离出来。高pH值下银离子的还原是由于酪氨酸中酚基的电离而发生的，酪氨酸中的酚基能够还原Ag+离子，进而转化为半醌结构。这些银纳米粒子可以通过静电络合过程轻松转移到含有阳离子表面活性剂十八胺的氯仿中。现在的疏水性银纳米颗粒可以铺展在水表面并组装成高度有序的线性超结构，可以通过多功能的 Langmuir-Blodgett 技术将其作为多层转移到合适的支撑物上。此外，通过氨基酸中的胺基与Au纳米颗粒表面结合的酪氨酸分子可用于在高pH值下选择性还原Au纳米颗粒表面上的银离子，从而形成一种实现相纯Au核-Ag壳纳米结构的简单策略。
We demonstrate that the amino acid tyrosine is an excellent reducing agent under alkaline conditions and may be used to reduce Ag+ ions to synthesize stable silver nanoparticles in water. The tyrosine-reduced silver nanoparticles may be separated out as a powder that is readily redispersible in water. The silver ion reduction at high pH occurs due to ionization of the phenolic group in tyrosine that is then capable of reducing Ag+ ions and is in turn converted to a semi-quinone structure. These silver nanoparticles can easily be transferred to chloroform containing the cationic surfactant octadecylamine by an electrostatic complexation process. The now hydrophobic silver nanoparticles may be spread on the surface of water and assembled into highly ordered, linear superstructures that could be transferred as multilayers onto suitable supports by the versatile Langmuir-Blodgett technique. Further, tyrosine molecules bound to the surface of Au nanoparticles through amine groups in the amino acid may be used to selectively reduce silver ions at high pH on the surface of the Au nanoparticles, thus leading to a simple strategy for realizing phase-pure Au core-Ag shell nanostructures.