Seminar: Prof. Regina Ragan

Seminar series
Physical Chemistry Seminar
Mon, Dec 3 4:00pm
Young Hall 2033
Speaker Regina Ragan
University of California Irvine

Driving chemical reactions at interfaces to control physical properties of nanomaterials 


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 at scale but offer new functionality for probing and interacting with molecular systems. I will present how understanding external driving forces in chemical assembly allows for achieving metamaterial architectures exhibiting large near field enhancements and magnetic fields at optical frequency. Specifically, our recently demonstrated 2-dimensional physically activated chemical (2PAC) assembly method uses electrokinetic driving forces to drive chemical reactions at interfaces leading to nanogaps with spacing controlled by molecular crosslinkers.  This enables uniform billion fold enhancements to surface enhanced Raman scattering (SERS) signal, overcoming longstanding challenges in using SERS as a robust sensing technology.  The reproducible response allows for acquisition of large data sets needed for deep learning analysis; 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 inoculation.  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. In another example, 3-dimensional, high-surface-area templates are formed via phase separation of immiscible systems.  Graphene constructs are then formed on templates with controlled and continuous pore morphology that offers high mass transport.  We investigate how chemical composition of the scaffold can be used to tune the number of graphene layers in the 3D system in order to achieve high conductivity and how the molecular environment can be modified to tune surface electronic structure for chemical reactions on surfaces.