Seed-mediated co-reduction: a versatile route to architecturally-controlled bimetallic nanostructures

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Sara Skrabalak from Indiana University is supported by the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry to conduct research into rational syntheses and characterization of bimetallic nanoparticles with high structural monodispersity. Like their monometallic counterparts, bimetallic materials often display dramatic changes in their physicochemical properties at the nanoscale. To realize the full potential of bimetallic nanostructures, samples with structural monodispersity on-par with the best monometallic examples are needed; however, it remains a grand challenge to achieve structural and compositional control during the synthesis of bimetallic nanostructures. This challenge arises from reliance on co-reduction techniques to nucleate and grow a defined bimetallic phase, but the Skrabalak laboratory has demonstrated seed-mediated co-reduction as a strategy to overcome the limitations of co-reduction techniques by coupling them with the advantages of seeded methods which provide structurally defined crystals for bimetallic deposition. The aims of this project are i) to identify the synthetic parameters which govern morphology development during seed-mediated co-reduction and quantify their effects on the kinetics of co-reduction and crystal growth, ii) to identify the symmetry relationships between seed structure and the final morphologies of branched bimetallic nanocrystals prepared by seed-mediated co-reduction and quantify the effect of lattice mismatch between seed and overgrowth metals to morphology development, and iii) to identify the synthetic conditions which enable seed-catalyzed co-reduction of metal precursors and quantify the kinetics of this surface-mediated process via in situ synchrotron X-ray diffraction techniques. Collectively, the experiments being carried out are to identify and quantify the synthetic parameters which contribute to morphology development during seed-mediated co-reduction and enable new architecturally-controlled bimetallic nanostructures to be achieved. Additionally, the optical and catalytic properties of the unique nanostructures synthesized are being studied to understand how composition and architecture compound to impart new functionality. General design criteria for the synthesis of new bimetallic nanoarchitectures by seed-mediated co-reduction are being pursued, as well as the advancement of co-reduction techniques in general.Bimetallic nanostructures represent exciting multifunctional platforms with the potential to address critical needs in catalysis (e.g., in fuel cells), energy sustainability, chemical sensing, medicine, and beyond. However, predictably achieving architecturally-controlled bimetallic nanostructures has met with only modest success on account of the limitations of current synthetic strategies. This project is to obtain general design criteria for new bimetallic nanostructures and to move the nanosynthesis community closer to the predictive, on-demand synthesis of nanostructures with defined composition and architectures. This research also has the broader impacts of i) forging links between scientific disciplines that include nano/inorganic/solid-state chemistry and colloidal/surface/material sciences, ii) enhancing graduate/undergraduate education through multidisciplinary research and outreach activities that reinforce learning via teaching, iii) introducing nanoscale concepts to non-scientists and connecting undergraduates to their home communities through their research activities; iv) enabling the PI to serve the scientific community as an educator, journal and grant reviewer, and promoter of diversity in higher education; and v) generating and distributing new knowledge based on the proposed research through peer-reviewed publications and presentations.