Design of Metal Nanoarchitectures: Nanocatalysts to Nanophotonics
Prof. Regina Ragan
Department of Chemical Engineering and Materials Science
University of California, Irvine
WEDNESDAY, NOVEMBER 16, 2011
11:00 am – 12:00 pm
Fung Auditorium
ABSTRACT:
Advances in lithography, electron optics, scanning probe microscopies, and time-resolved spectroscopies allow us to assemble and probe matter at the atomic level on femtosecond time scales. Nevertheless many important technology platforms still require the ability to fabricate systems on molecular length scales using methods that are easily translated into large-area production. In my laboratory, self-organization techniques using both atomic structure on crystal templates and localized chemical reactions on substrates are used in order to fabricate functional molecular scale systems with controllable atomic structure. I will present unique processes for making size-controlled core-shell bimetallic nanostructures with atomic interfaces using non-solution based self-organization methods. The benefit of avoiding solution processing is that the resulting pristine surface provides an excellent model system for studying the relationship between surface electronic structure and chemical activity using scanning probe methods. For optical applications requiring greater order and less stringent requirements for pristine surfaces, we developed methods for assembling size and shape controlled metal nanoparticles from colloids on surfaces and scaled state of the art methods by an order of magnitude using covalent nanoparticle-substrate interactions. Optical properties resulting from local dipole moments in nanoparticles (NPs) assembled in a periodic or cluster architecture enable exploration of metamaterials, near field enhancement, and narrow band resonances. I will present surface enhanced Raman scattering measurements on chemically assembled NP systems that are found to achieve reproducible, high signal enhancements from point to point across the sample surface.
BIOSKETCH:
Prof. Regina Ragan received her B.S. summa cum laude in Material Science and Engineering in 1996 from the University of California, Los Angeles and Ph.D. in Applied Physics in 2002 from the California Institute of Technology. As a PhD student she was awarded as a NSF, Bell Laboratories and Intel Fellow. From 2002-2004 she was a postdoctoral scholar in the Information & Quantum Systems Laboratory at Hewlett Packard. She joined the University of California, Irvine in 2004 and is currently Associate Professor of Chemical Engineering and Materials Science. Her research interests include both fundamental understanding of physical properties as feature size reaches molecular length scales and understanding thermodynamic and chemical processes governing rational assembly of nanostructures on molecular length scales. She is a recipient of the National Science Foundation Faculty Early CAREER Award.