Polymer-Functionalized Platinum-On-Gold Bimetallic Nanorods
Polymer-Functionalized Platinum-On-Gold Bimetallic Nanorods
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DOI：
10.1002/anie.200903524
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发表时间：
2009-01-01
影响因子：
16.6
通讯作者：
Zubarev, Eugene R.
中科院分区：
文献类型：
--
作者：
Khanal, Bishnu P.;Zubarev, Eugene R.
纳米晶体的物理和化学性质是由它们的大小、形态和化学成分决定的。[1-6]因此，在过去的十年中，许多研究小组专注于控制无机纳米结构的形状，[7-12]并生产了许多低对称性纳米晶体。[13-20]在这方面，一维结构是特别有趣的对象，其光学和催化性能强烈依赖于它们的形状不对称。[14-17]金属纳米棒的这一独特特性已经在纳米技术和生物医学研究中得到了若干应用。[22,23]此外，在过去的几年中，已经描述了四个双金属纳米棒的例子[24-27]。认为金上铂和金上钯双金属纳米结构在催化领域开辟了新的方向。[28-30]然而，迄今为止报道的所有双金属纳米棒都只能溶于水，因此不能催化有机溶剂中的任何反应。事实上，没有任何铂或钯纳米结构与聚合物链共价功能化的例子，这可以使它们在有机介质中溶解。在这里，我们描述了聚合物功能化铂-金纳米结构的第一个例子。我们使用金纳米棒作为模板，并演示了如何在其表面沉积多晶连续铂壳，并随后与有机分子功能化。此外，我们还通过电子显微镜的直接可视化和1H NMR光谱的检测，为铂壳的功能化提供了确凿的证据。由Murphy及其同事[1]开发，后来由El-Sayed和Nikoobakht改进的种子介导方法产生了单晶金纳米棒（Au NRs）。然而，该方法中AuI离子向Au0的转化率仅为10-15%，且大部分离子在Au NRs生长完成后仍留在溶液中。我们的系统研究表明，用于还原AuI离子的抗坏血酸的量是至关重要的，并且在完成纳米棒生长后添加10mol%的抗坏血酸使其尺寸分布更窄。图1a为该改进方法制备的Au nmr的代表性TEM图像。图1a所示的250个纳米棒的分析揭示了它们的平均长度和宽度
Physical and chemical properties of nanosized crystals are known to be a function of their size, morphology, and chemical composition.[1–6] Hence, over the past decade many research groups have focused on controlling the shape of inorganic nanostructures,[7–12] and many low-symmetry nanocrystals have been produced.[13–20] In this respect, one-dimensional structures are particularly interesting objects whose optical and catalytic properties strongly depend on their shape anisometry.[14–17] This unique feature of metallic nanorods has already found several applications in nanotechnology [21] and biomedical research.[22, 23] Moreover, four examples of bimetallic nanorods [24–27] have been described in the last few years. It is believed that bimetallic platinum-on-gold and palladium-on-gold nanostructures may open a new direction in the area of catalysis.[28–30] However, all bimetallic nanorods reported to date are only soluble in water and therefore cannot catalyze any reactions in organic solvents. In fact, there are no examples of any platinum or palladium nanostructures covalently functionalized with polymer chains, which could render them soluble in organic media. Herein we describe the first example of polymer-functionalized platinum-on-gold nanostructures. We use gold nanorods as templates and demonstrate how a polycrystalline continuous shell of platinum can be deposited on their surface and subsequently functionalized with organic molecules. In addition, we provide conclusive evidence of the functionalization of the platinum shell by direct visualization of the polymer surface layer by electron microscopy and its detection by 1H NMR spectroscopy.The seed-mediated method developed by Murphy and coworkers [1] and later modified by El-Sayed and Nikoobakht [2] produces single-crystalline gold nanorods (Au NRs). However, the conversion of AuI ions to Au0 in this method is only 10–15%,[31] and the majority of ions remains in solution after the growth of Au NRs is complete. Our systematic studies revealed that the amount of ascorbic acid used for the reduction of AuI ions is critically important, and addition of 10mol% ascorbic acid after completed nanorod growth makes their size distribution much narrower. Figure1a shows a representative TEM image of Au NRs prepared by this modified method. The analysis of 250 nanorods shown in Figure1a revealed that their average length and width