DNA‐Templated Silver Nanorings
DNA‐Templated Silver Nanorings
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DOI：
10.1002/adma.200501549
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发表时间：
2005-12
影响因子：
29.4
通讯作者：
A. Zinchenko;K. Yoshikawa;D. Baigl
中科院分区：
文献类型：
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作者：
A. Zinchenko;K. Yoshikawa;D. Baigl
具有良好形状和尺寸的贵金属纳米结构正日益引起催化、电子学、光子学、信息存储、光电子学、生物标记等领域科学家的关注，纳米结构的进一步发展和实际应用有望因其有趣的光学、电学和磁学性质而迅速增加。在这方面，在过去几年中，关于直接制备尺寸和形状可控的金属纳米结构的重要知识已经发展起来，现在可以以可控的方式制备各种形貌，如球形纳米颗粒、纳米立方体、纳米棱柱、纳米平板或纳米带。然而，由于这些技术是基于反应介质中粒子的定向生长，它们只能产生简单拓扑的形状，如椭球体、椭球体或多面体。相反，环状(纳米环)的纳米颗粒不能通过直接生长技术来生产。因此，产生这种形态的唯一方法是使用纳米尺度的环形模板。基于使用纳米颗粒阵列或介孔薄膜作为主要模板来制备银环或金环的精细而成功的方法，最近分别由夏和同事以及严和戈德尔描述。然而，这些技术提供的环的最小尺寸为0.5lm，不能直接分散在水介质中。另一方面，由于DNA与银离子之间的特殊相互作用，DNA是构建银纳米结构的理想模板。这一原理已成功地用于在DNA支架或DNA模板银纳米线上制造纳米颗粒阵列。然而，到目前为止，材料科学家还没有注意到DNA链由于DNA折叠转变(DNA缩合)而形成环状凝聚体的能力。DNA凝聚成定义明确的环状结构的能力提供了一个独特的机会，可以将它们用作模板来创建形状和尺寸可控的银环状纳米结构(纳米环)。在这篇通讯中，我们描述了一种一锅三步简单的制备分散在水中的定义良好的银纳米环(直径100 nm)的方法，基于使用DNA凝聚物的稀溶液作为纳米结构模板。DNA是一种半柔性、高带电的聚电解质，由于带负电荷的单体之间的静电斥力，它在水中呈拉长线圈构象。在亲水性中性聚合物的存在下，或在稀释的DNA溶液中添加少量的缩合剂，如阳离子多胺、多价金属阳离子和阳离子表面活性剂时，DNA分子通常折叠成紧密堆积的环状凝聚体，外径通常为70-90 nm。缩合剂的作用是诱导DNA单体之间的吸引(链中和或拥挤效应)，由于DNA双链链的固有刚性，采用环状形态。高级材料0000、00、0-0 1
Nanostructures of noble metals with well-defined shapes and sizes are increasingly attracting the attention of scientists in the fields of catalysis, electronics, photonics, information storage, optoelectronics, biological labeling, etc. The further development and practical applications of nanostructures are expected to increase rapidly because of their interesting optical, electronic, and magnetic properties. In this context, important knowledge of the direct preparation of metallic nanostructures of controlled size and shape has been developed over the past few years, and various morphologies, such as spherical nanoparticles, nanocubes, nanoprisms, nanoplates, or nanobelts, can now be prepared in a controlled way. However, since these techniques are based on the directed growth of particles in the reaction medium, they can only lead to shapes of a simple topology, such as spheroids, ellipsoids, or polyhedrons. In contrast, nanoparticles with a toroidal shape (nanoring) can not be produced by a direct growth technique. Hence, the only way to produce such a morphology is to use a toroidal template of nanometer-scale dimensions. Elaborate and successful methods to prepare silver or gold rings based on the use of a nanoparticle array or a mesoporous membrane as a primary template, were recently described by Xia and co-workers and Yan and Goedel, respectively. However, these techniques provide rings with a minimal size of 0.5 lm that can not be directly dispersed in an aqueous medium. On the other hand, due to the specific interaction between DNA and silver ions, DNA is an ideal template to build silver nanostructures. This principle has been used successfully to produce nanoparticle arrays on a DNA scaffold, or DNA-templated silver nanowires. However, the ability of DNA chains to form toroidal condensates as a result of the DNA-folding transition (DNA condensation) has not been hitherto noticed by materials scientists. The ability of DNA to condense into well-defined toroids provides a unique opportunity to use them as templates to create silver toroidal nanostructures (nanorings) of controlled shape and dimensions. In this communication, we describe a one-pot, three-step, simple preparation of well-defined silver nanorings (100 nm in diameter) dispersed in water, based on the use of dilute solutions of DNA condensates as nanostructured templates. DNA is a semiflexible, highly charged polyelectrolyte that assumes an elongated-coil conformation in water due to the electrostatic repulsion between the negatively charged monomers. DNA molecules usually fold into tightly packed toroidal condensates with an outer diameter of typically 70–90 nm in the presence of hydrophilic neutral polymers, or upon the addition of a small amount of condensing agent, such as cationic polyamines, multivalent metal cations, and cationic surfactants, to a dilute DNA solution. The role of the condensing agents is to induce an attraction between the DNA monomers (chain neutralization or crowding effect), and the toroidal morphology is adopted because of the native rigidity of the DNA double-stranded chain. Advanced Materials 0000, 00, 0–0 1