Materials World Network: The Designer Nanoparticle

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.

[1] Potential non-academic beneficiaries of the proposed research include: functional chemicals manufacturers seeking controlled or improved processes for producing nanoparticulate products; also users of nanoparticulate end-products - e.g. manufacturers of coatings, catalyst, healthcare, household products, pigments, paints, self cleaning glass, pharmaceuticals, electronics (thin film circuits). Producers of nanoparticle-based systems for, e.g., environmental protection or low temperature, more efficient, 'green' industrial processes. Industries seeking novel processes for products based on renewable feedstocks. [2] Dissemination to commercial and professional users: Besides the abovementioned conferences, ensuring that the new research impacts non-academic target audiences, ongoing interaction with and opportunities for feedback from potentially relevant industrial partners and, should they arise, opportunities for commercial exploitation of generated IP, will be pursued through the technology transfer support systems of the Universities, e.g., UMIP (University of Manchester Intellectual Property). This will be supported by existing international interest from relevant multinational industries and SMEs, with which SLMS and RAWD have existing links through funded projects. [3] New links and capacity building in UK science: through this project new links will be formed across the interfaces between Physics, Chemistry, Chemical Engineering and Materials Science, especially through the interdisciplinary integration through the synchrotron radiation community. Local dissemination will benefit the Schools of Chemistry, of Chemical Engineering and Analytical Science, of Materials and of Physics. Contributions within the University Community will include seminars and presentations in the associated Schools. Association with the Northwest Development Agency-funded Knowledge Centre for Materials Chemistry (KCMC) provides a vibrant knowledge-transfer network (KTN) spanning the whole Northwest of England, including the Chemistry Innovation KTN, the STFC site in Daresbury and, very importantly, the University of Liverpool (a recognised world-centre in metal NP Materials Chemistry). This industry/academia network, together with the transatlantic dissemination activities, will assist in broadening the scope of the research as well as build capacity and interest in a high-profile area of research. The UK side of the project will be based in two Schools who participate in the EPSRC-funded NowNano Doctoral Training Centre at Manchester. Thereby opportunities for students in the DTC will be provided to pursue relevant world-leading PhD research. The investigators will also disseminate novel findings to the NowNano community through seminars and other presentations. DIAMOND Light Source will benefit from technical expertise in X-ray reflectivity and surface scattering measurements by the US partner, which will be welcome for the upgrade of beamline I07 with an down-reflecting mirror in 2011. The US institutions will benefit from the expertise in liquid/liquid interface electrochemistry and in situ XAS measurements developed by the UK partners. [4] Career development of a Research Associate: This project provides a unique opportunity for a scientist with a proven track record of broad research skills and interests to develop an independent academic reputation by taking the lead in an area of science that attracts interest from a very large community. Outstanding training opportunities will be provided through a combination of hands-on research supported by the expertise, the established dissemination forums and the previous research in the field by the project team. A most important transferable skills to be developed by the Research Associate is the acquisition of knowledge and technical language from each participant discipline, facilitating the ability to devise, deliver and contextualise and communicate research outcomes.