Droplet-based Microfluidics as a Versatile Platform for the Determination of Reaction Mechanisms in Nanoscale Systems

TECHNICAL SUMMARY

The potential impact of nanoscale materials on emerging applications is immense, with the possibility of producing disruptive new technological advances in areas as diverse as alternative energy, computing, and medicine. 'Bottom-up' chemical methods that begin with molecular building blocks are ideal routes to nanoscale materials because they, in principal, are extremely versatile and permit the design and synthesis of arbitrary nanostructures. Despite several decades of research, we have very little mechanistic understanding of how certain molecular entities react to form nanostructures. All of the variables contributing to the formation of a particular nanostructure complicate this problem and make it impossible to design synthetic strategies apriori. This empiricism is due to the lack of in-situ information of how nanostructure nucleation and growth (isotropic or anisotropic) is influenced by the chemical and physical environment. The proposed research supported by the Solid State and Materials Chemistry Program will address the problem outlined above by developing the most thorough molecular-level understanding of nanostructure synthesis to date utilizing a versatile droplet-based microfluidic platform that can mimic bulk synthetic procedures and produce indistinguishable droplets within which nanostructure-forming reactions occur. The integrated device will be interfaced with synchrotron x-ray radiation for in-situ, real-time absorption and scattering measurements. We will utilize the microfluidic device to answer fundamental mechanistic unknowns regarding the influence of intrinsic/extrinsic anions on the rate of reduction and nucleation-growth during the formation of spherical transition metal nanoparticles (NPs), shape-controlled growth of Pt NPs and Au nanorods with a particular emphasis on capturing the initial chemical reactions that induce isotropic-to-anisotropic transformation.

NON-TECHNICAL SUMMARY

The results of this proposal will provide valuable information to develop continuous reactors for high-throughput production of nanostructures of any arbitrary size, shape and composition. The educational outreach of this proposal is to provide opportunity to graduate students, and undergraduates - especially those from underrepresented groups - to participate in fundamental research in nanoscience, microfabrication and synchrotron-based characterization. It is estimated that 1 in 100 children in the United States have an autism spectrum disorder (ASD) diagnosis. In Centre County, Pennsylvania, a non-profit, human services organization, NHS runs an after-school program - Stepping Stones - for ASD individuals between the ages of 8-14. The PI and his group will take the lead on developing simple and visually stimulating science lessons as part of 'Science Tuesdays'. Individuals diagnosed with ASD are sensory learners and our science lessons will be primarily accomplished through visual demonstrations enabling student participation which encourages social interaction with their peers, the PI and his graduate students. Visual experiments that cover concepts relevant to the proposed work (including solubility, supersaturation, nucleation and crystallography) include growing rock candy and cloud formation. These lessons will be recorded and disseminated via YouTube and through live demonstrations at the National Autism Conference held annually on the campus of the Pennsylvania State University.