Transforming Noble Metal Nanostructure Synthesis Using Unconventional Synthetic Levers

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Non-Technical Abstract:Underpinning the electronics industry is a wafer-based processing science that is able to form intricate patterns of dissimilar materials with well-defined properties and interfaces that collectively perform a useful function. One of the biggest challenges is the establishment of a corresponding processing science that integrates these wafer-based technologies with the extraordinary optical, electronic, and chemical properties derived from metallic nanoparticles. Device prototyping has, however, been stifled by an inability to define complex metal nanostructures in organized patterns where interactions are possible between adjacent structures and with the underlying wafer material. The project being carried out aims to overcome this impediment by redefining the methodologies, instrumentation, and processing science needed to define wafer-based metal nanostructures, and in doing so, provide the capabilities inaccessible through conventional methods. The research activities are being integrated with undergraduate education that involves the supervision of research internships geared toward the advancement of laboratory instrumentation by students from the College of Engineering. Outreach activities place emphasis on the matriculation of women into the engineering profession.Technical Abstract:The research being carried out aims to provide an understanding of the altered chemistry that arises when well-understood seed-mediated noble metal nanostructure growth modes are subjected to four unconventional synthetic levers that become accessible when seeds are immobilized on a rigid crystalline substrate. It is founded on a synthetic strategy that is able to realize periodic arrays of complex noble metal nanostructures through a three stage synthetic scheme that uses (i) a lithography-defined shadow mask to fabricate nanostructured precursors at site-specific locations, (ii) directed assembly to transform them into single crystal templates, and (iii) solution-based chemistry to further transform them into complex nanostructures. Within the scope of this strategy lies the opportunity to incorporate a new set of synthetic levers into nanostructure synthesis that fundamentally alter well-established growth modes. The project is advancing the use and understanding of four such synthetic levers: (i) a flow of reactants past an anchored substrate, (ii) synthetically-active substrate materials, (iii) substrate-imposed epitaxy, and (iv) lithographically-imposed barriers to growth. Graduate students are being trained in nanostructure synthesis and characterization, lithographic techniques, and the preparation nanostructured surfaces. This work is, hence, contributing to the grander vision that sees the extraordinary physicochemical properties of nanomaterials united with the wafer-based materials, processing techniques, and electronic devices.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.