Materials World Network: The Designer Nanoparticle

如果将反应物（即金属离子和还原剂）置于两种（不混相）液相中，使它们相互物理分离，则金属纳米颗粒生长过程的研究将大大简化。纳米颗粒的成核和生长发生在这两种液相之间的界面上。伊利诺伊大学芝加哥分校和英国曼彻斯特大学之间的这项合作使用了最先进的x射线光谱学、表面散射和电化学技术来研究液体/液体界面上分子水平上的颗粒生长。这种在界面上的定位允许使用x射线吸收，它不容易检测在整个溶液体积中均匀分散的颗粒，但可以应用于界面情况，因为颗粒高度集中在界面上。x射线吸收光谱探测非晶体体系的局部几何和电子结构，包括测定化学种类和原子的化学状态。除了这种光谱探针，研究人员还使用了一种结构探针，x射线表面散射，来研究面内和面外结构，包括颗粒的形状、大小和组织，以及界面附近反应物的消耗。这些x射线技术与液/液界面反应的电化学控制相结合，既可以监测颗粒生长的进展，也可以研究应用电位对控制颗粒产生的影响。该项目为学生提供了一个由英国和美国的科学专业知识塑造的研究环境。学生们参加联合小组会议（通过视频电话会议），并前往两国的实验室学习x射线光谱学、表面散射和广泛的电分析化学技术，以研究界面上的纳米颗粒。预计对金属纳米颗粒成核和生长的分子水平的理解将允许生产具有设计性能的纳米颗粒。这将影响纳米颗粒在许多领域的应用发展，包括设计用于催化、光电和涂层应用的新材料。

The study of the growth process of metal nanoparticles is greatly simplified if reactants (i.e., metal ion and reducing agent) are physically separated from one another, by their location in two (immiscible) liquid phases. Nucleation and growth of the nanoparticles then takes place at the interface between these two liquid phases. This collaboration between the University of Illinois at Chicago and the University of Manchester in the United Kingdom uses state-of-the-art X-ray spectroscopy, surface scattering and electrochemistry techniques to investigate particle growth on the molecular level as it occurs at the liquid/liquid interface. Such localization at the interface allows for the use of X-ray absorption, which would not readily detect particles dispersed homogeneously throughout a solution volume, but can be applied in the interfacial case because the particles are highly concentrated at the interface. X-ray absorption spectroscopy probes the local geometric and electronic structure in non-crystalline systems, including determination of the chemical species and the chemical state of the atoms. In addition to this spectroscopic probe, the investigators use a structural probe, X-ray surface scattering, to study the in-plane and out-of-plane structure, including the shape, size, and organization of the particles, as well as the depletion of reactant species near the interface. These X-ray techniques are combined with electrochemical control of the interfacial reaction at the liquid/liquid interface, both to monitor the progress in particle growth as well as to investigate the influence of the applied potential in controlling particle production.This project provides students with a research environment shaped by scientific expertise from the UK and USA. Students participate in joint group meetings (by video teleconferencing) and travel to laboratories in both countries to learn X-ray spectroscopy, surface scattering, and a broad range of electro-analytical chemistry techniques for the study of nanoparticles at interfaces. It is anticipated that a molecular-level understanding of metal nanoparticle nucleation and growth will allow for the production of nanoparticles with designed properties. This should influence the development of applications of nanoparticles in a number of areas, including the design of new materials for catalytic, opto-electronic, and coating applications.