When 10:30 AM - 11:30 AM Feb 02, 2018
Where 1670 Beyster
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Hierarchical Self-Assembly to Form Nanodevice Architectures

Chemical Engineering and Materials Science, University of California, Irvine

While availability of nanoscale fabrication tools has uncovered a rich area of physical phenomena with applications including sensing, energy, and imaging - scalable nanomanufacturing techniques allowing for technological impact still remain elusive. Self-assembly of nanoarchitectured systems, with control on atomic and molecular length scales, not only hold promise for device fabrication but offer new functionality for probing and interacting with molecular systems. For example, understanding hierarchical driving forces in assembly of nanospheres from colloid enables arranging 2D ‘metamolecule’ building blocks where the geometry of resultant oligomers, gap spacing, and dielectric environment provide additional degrees of freedom for tuning electromagnetic response. I will present metasurface geometries exhibiting magnetic fields at optical frequency and surface enhanced Raman scattering (SERS) surfaces with uniform, billion-fold enhancements at low integration times and laser power over mm2 areas. The reproducibility offered by controlling nanogap spacing with chemical crosslinkers allows for acquisition of large data sets needed for machine learning analysis. Multivariate statistical analysis of SERS data from nanogaps incorporated in microfluidic devices shows bacterial metabolite concentration can be quantified across five orders of magnitude and detected in supernatant from Pseudomonas aeruginosa cultures as early as three hours after innoculation. Bacteria exposed to a bactericidal antibiotic were differentially less susceptible after 10 h of growth, indicating that these devices may be useful for early intervention of bacterial infections. Analysis with artificial neural networks pushes quantification down to the femtomolar regime offering the promise of quantification down to the single molecule limit. In terms of energy systems, fabrication of 3-dimensional, high-surface-area, carbon scaffolds with controlled and continuous pore morphology offers high mass transport, high conductivity and tunable surface electronic structure. Investigations to identify single molecule catalysts via experimental and first principle investigations will also be presented. 

Biosketch: Prof. Ragan is Associate Professor in the Department of Chemical Engineering and Material Science and Engineering at UC Irvine and the Stacey Nicholas Endowed Chair for Diversity in Engineering Education. She is a recipient of the National Science Foundation Faculty Early CAREER Award and a Fulbright Fellow. She received her B.S. summa cum laude in Material Science and Engineering from the University of California, Los Angeles and Ph.D. in Applied Physics from the California Institute of Technology. As a PhD student she was awarded as a NSF, Bell Laboratories, and Intel Fellow. After, she was a postdoctoral scholar in the Information & Quantum Systems Laboratory at Hewlett Packard. At Hewlett Packard, Ragan worked on emerging technologies including molecular electronics that provided fundamental understanding leading to memristors, a resistive RAM technology before joining the Faculty at UC Irvine in 2004. Ragan is particularly interested in self-assembly as a disruptive technology solution in regards to manufacturing nanosystems that will affect technology from energy systems to optical communications and sensing. 


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