Materials World Network: The Designer Nanoparticle

纳米技术的进步依赖于纳米颗粒的生产。在过去的十年中，已经引入了许多从溶液相合成纳米粒子的方法，包括不同组成、形状和结构（如核和壳结构）的粒子。尽管我们做了大量的工作，但我们缺乏对纳米粒子成核和生长的分子水平的理解，这可能导致它们的理性设计，而不是经验设计。我们提出了一种基于x射线探针和不断变化的纳米颗粒结构的界面定位相结合的新方法。大多数通往金属纳米颗粒的液相途径都是利用还原剂还原金属离子。这种物质（或其他物质）可以作为封盖配体，决定颗粒大小。如果反应物（即金属离子和还原剂）在两种（不混相）液相中被物理分离，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。这种定位允许使用x射线吸收，它不容易检测均匀分散在溶液体积上的颗粒，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，我们建议使用结构探针，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。我们建议将这些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。英国和美国科学家的合作计划将使用最先进的x射线光谱学、表面散射和电化学技术。来自美国的PI具有将x射线表面散射与液-液界面的原位电化学控制相结合的专业知识。来自英国的pi结合了同步加速器x射线光谱和液-液界面金属纳米颗粒的生长和表征方面的专业知识。这组不同寻常的互补技术和方法将用于研究金属纳米颗粒的成核和生长，目的是在分子水平上理解这些过程，以便为合理的合成方法提供基础。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特性的纳米颗粒。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。该合作计划利用最先进的x射线光谱和表面散射，以及电化学分析，将提供一种罕见的，可能是独特的技术和方法集合。尽管这些技术在表征材料方面具有互补性，但具有x射线光谱学和表面散射专业知识的研究人员并不多。同样，同步加速器x射线技术的专家很少熟悉广泛的分析化学技术。在这些领域进行交叉培训的机会将为早期职业研究人员在其职业生涯开始时提供独特的视角。

Progress in nanotechnology relies upon the production of nanoparticles. During the past decade many recipes have been introduced for the synthesis of nanoparticles from the solution phase, including particles of different composition, shape, and architecture such as core and shell structures. In spite of this extensive work we lack a molecular level understanding of the nucleation and growth of nanoparticles that could lead to their rational, rather than empirical, design. We propose a new approach based upon a combination of X-ray probes and interfacial localization of the evolving nanoparticle structure.Most of the solution phase routes to metal nanoparticles exploit the reduction of the metal ion by a reducing agent. This agent (or another species) can act as a capping ligand, defining the particle size. 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 locaton in two (immiscible) liquid phases. Nucleation and growth of the nanoparticles then takes place at the interface between these two liquid phases. Such localization allows for the use of X-ray absorption, which would not readily detect particles dispersed homogeneously across 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, we propose to 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. We propose to combine these X-ray techniques 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.The proposed collaboration of scientists from the UK and the USA will use state-of-the-art X-ray spectroscopy, surface scattering and electrochemistry techniques. The PI from the USA has expertise combining X-ray surface scattering with in situ electrochemical control of the liquid-liquid interface. ThePIs from the UK have combined expertise in synchrotron X-ray spectroscopy and in the growth and characterization of metal nanoparticles at the liquid-liquid interface. This unusual and complementary set of techniques and approaches will be used to investigate the nucleation and growth of metalnanoparticles with the aim of understanding these processes at the molecular level in order to provide the basis for a rational approach to their synthesis.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.The proposed collaboration utilizing state-of-the-art X-ray spectroscopy and surface scattering, as well as electrochemical analysis will provide a rare, possibly unique, collection of techniques and approaches. There are not many researchers with expertise in both X-ray spectroscopy and surfacescattering, in spite of the complementarity of these techniques in characterizing materials. Similarly, experts in synchrotron X-ray techniques are rarely familiar with a broad range of analytical chemistry techniques. The opportunity for cross training in these areas will provide early career researchers with a unique perspective at the beginning of their careers.