Tianjin Key Laboratory of Advanced Functional Porous Materials, Institute for New Energy Materials & Low-Carbon Technologies, School of Materials Science and Engineering, Tianjin University of Technology , Tianjin 300384, China.
Department of Chemical and Biomolecular Engineering, National University of Singapore , Singapore 117576, Singapore.
Langmuir. 2017 Oct 31;33(43):12254-12259. doi: 10.1021/acs.langmuir.7b02497. Epub 2017 Oct 20.
Segmented metallic nanorods with well-defined shapes and controllable components play an important role on the systematic investigation of their shape-dependent catalytic, electric, and plasmonic properties of metal nanostructures. Unfortunately, the shape and composition of segmented nanorods are difficult to be precisely controlled via colloidal methods. Here, we reported the growth of Pd-Au-Pd bimetallic heterostructures by using Au 5-fold twinned bipyramids (BPs) as seeds, with KI as a structure-directing reagent. Through a series of control experiments we revealed that two parameters were identified as critical factors for the growth of segmented Pd-Au-Pd nanorods. First, 5-fold twinned Au BPs with low-index end facets and high-index side facets function as a unique template for directed growth. Second, iodide can switch the deposition of Pd on the Au BPs. A high concentration of iodide is believed to block the high-index facets of the Au BPs and lower the reaction kinetics to promote the selective growth of two Pd segments on the Au BPs. As a result, uniformed segmented Pd-Au-Pd nanorods were obtained. The segmented nanorods exhibit intense extinction in the near-IR range and could be a potential candidate for plasmon-based biological applications such as thermal therapy.
分段金属纳米棒具有明确的形状和可控的组成，在系统研究金属纳米结构的形状依赖性催化、电学和等离子体性质方面发挥着重要作用。不幸的是，通过胶体方法很难精确控制分段纳米棒的形状和组成。在这里，我们报告了通过使用 Au 5 倍孪晶双锥 (BP) 作为种子，以 KI 作为结构导向剂，生长 Pd-Au-Pd 双金属异质结构。通过一系列对照实验，我们揭示了两个参数被确定为生长分段 Pd-Au-Pd 纳米棒的关键因素。首先，具有低指数端面和高指数侧面的 5 倍孪晶 Au BP 作为定向生长的独特模板。其次，碘化物可以在 Au BP 上切换 Pd 的沉积。高浓度的碘化物被认为可以阻挡 Au BP 的高指数面，并降低反应动力学，从而促进两段 Pd 在 Au BP 上的选择性生长。结果，得到了均匀的分段 Pd-Au-Pd 纳米棒。分段纳米棒在近红外范围内表现出强烈的消光，可能是基于等离子体的生物应用（如热疗）的潜在候选材料。
