C60 mediated aggregation of gold nanoparticles
C60 mediated aggregation of gold nanoparticles
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DOI：
10.1021/ja982776u
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发表时间：
1998-12-02
影响因子：
15
通讯作者：
Schiffrin, DJ
中科院分区：
文献类型：
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作者：
Brust, M;Kiely, CJ;Schiffrin, DJ
自1985年富勒烯被发现以来，富勒烯在基础和应用领域引起了广泛的研究兴趣。1从纳米结构设计的角度来看，它们代表理想的结构单元，因为它们是单分散的（C60、C70、C76等）。和自钝化，即不需要保护配体或稳定剂来防止颗粒融合或不可逆聚集。金属和半导体纳米颗粒通常不满足这些标准。越来越多的制备库可用于获得具有相邻官能团的富勒烯，使其更适合随后的超分子反应。2富勒烯作为结构单元的突出作用最近受到硫醇钝化的金纳米粒子3的挑战，这些纳米粒子可作为单分散的、几乎纯的化合物获得，它们自发地形成高度有序的超晶格。这些颗粒表现出令人着迷的表面化学多样性，从制备的角度来看，它们的官能化比富勒烯要简单得多，这主要是由Murray及其同事在许多出版物中证明的。这些新材料在新型气体传感器器件中的首次实际应用正在进行中。在不存在硫醇的情况下，也可以获得金纳米颗粒在芳族溶剂中的稳定溶液，从而产生易于进行表面反应而不需要官能化的颗粒。4在这篇文章中，我们报告了一个令人惊讶的发现，即（C60）富勒烯吸附到这种直径为1.5 nm的颗粒上，这种颗粒通过在甲苯溶液中吸附溴离子和季铵离子4f而稳定。这导致富勒烯连接的金颗粒的沉淀。实验过程非常简单，类似于先前报道的二硫醇连接的金纳米结构。4按照公认的程序制备用溴化四辛基铵稳定的105 nm金颗粒的甲苯溶液。4a、e、h取200 mL该新鲜制备溶液的样品（约0.3μM，基于每个颗粒3500个Au原子）与25 mL 0.5 mM（C60）富勒烯的甲苯溶液混合。不排除空气，将反应混合物在黑暗中储存在带塞烧瓶中。强烈的红宝石色溶液在几小时内缓慢变色为蓝紫色，表明金颗粒4a，5的聚集，2天后观察到黑色沉淀物的形成。3周后，大部分物质沉淀，留下淡紫色上清液。为了通过电子显微镜检查，通过超声处理将沉淀物重悬，而不进行过滤或洗涤，6并且使该悬浮液的液滴在涂覆有无定形碳膜（约4 nm）的400目Cu网格（Ted Pella，USA）上缓慢蒸发。在200 kV下运行的JEOL 2000 EX透射电子显微镜上检查样本。观察到的直径为50-100 nm的三维聚集体串（图1a）由3-6 nm的离散金颗粒组成，较薄边界结构的高分辨率图像（图1b）清楚地显示，颗粒之间没有直接接触，但显然是通过富勒烯分子的外壳粘合在一起。这些图像与富勒烯单层覆盖每个金颗粒的假设一致，因此导致颗粒间间距为1.2 nm。由于TEM图像代表三维结构的二维投影，因此还观察到较小的间距。边缘
Since their discovery in 1985 the fullerenes have been attracting tremendous research interest covering a wide range of fundamental and applied aspects. 1 From the point of view of nanostructure design they represent ideal construction units since they are monodisperse (C60, C70, C76, etc.) and self-passivating, ie, no protecting ligands or stabilizing agents are required to prevent particle fusion or irreversible aggregation. Metal and semiconductor nanoparticles do not generally fulfill these criteria. An increasing preparative repertoire is available to obtain fullerenes with adjacent functional groups, making them more amenable to subsequent supramolecular reactions. 2 The prominent role of fullerenes as building blocks has recently been challenged by thiol passivated gold nanocrystals3 obtainable as monodisperse, practically pure compounds, which spontaneously form highly ordered superlattices. 3f These particles exhibit a fascinating diversity of surface chemistry and their functionalization3b is from the preparative point of view considerably more straightforward than that of fullerenes, as demonstrated mainly by Murray and coworkers in a number of publications. 3g, i, n First practical applications of these new materials in novel gas sensor devices are on the way. 3p Stable solutions of gold nanoparticles in aromatic solvents can also be obtained in the absence of thiols yielding particles readily amenable to surface reactions without the need of functionalization. 4 In this communication we report the surprising finding that (C60) fullerene adsorbs to such particles of∼ 5 nm diameter stabilized by the adsorption of bromide and quarternary ammonium ions4f in toluene solution. This leads to the precipitation of fullerene-linked gold particles. The experimental procedures are very simple and resemble those reported previously for dithiol-linked gold nanostructures. 4 A toluene solution of∼ 5 nm gold particles stabilized with tetraoctylammonium bromide was prepared following a well-established procedure. 4a, e, h A 200 mL sample of this freshly prepared solution (ca. 0.3 µM, based on 3500 Au atoms per particle) was mixed with 25 mL of a 0.5 mM solution of (C60) fullerene in toluene. Air was not excluded and the reaction mixture was stored in a stoppered flask in the dark. The intensely ruby colored solution changed color slowly to bluish violet within several hours, indicating the aggregation of gold particles, 4a, 5 and after 2 days the formation of a black precipitate was observed. After 3 weeks most of the material had precipitated leaving a weakly violet supernatant solution. For examination by electron microscopy the precipitate was resuspended by sonication without filtering or washing, 6 and a droplet of this suspension was allowed to evaporate slowly on a 400 mesh Cu grid coated with an ultrathin (∼ 4 nm) amorphous carbon film (Ted Pella, USA). Specimens were examined on a JEOL 2000 EX transmission electron microscope operating at 200 kV. The strings of three-dimensional aggregates of 50-100 nm diameter observed (Figure 1a) are composed of discrete gold particles of 3-6 nm, and highresolution images (Figure 1b) of the thinner border structures reveal clearly that the particles are not in direct contact with each other but are apparently glued together by a shell of fullerene molecules. The images are consistent with the assumption of a monolayer of fullerene covering each gold particle and hence leading to an interparticle spacing of∼ 2 nm. Smaller spacings are also observed since the TEM images represent a twodimensional projection of a three-dimensional structure. The fringe