Ragan LabSelf-Organization of Nanosystems rragan@uci.eduhttp://ragan-group.eng.uci.edu

Research Summary: In the Ragan laboratory, nanosystem fabrication and characterization is conducted to contribute to 1) improving understanding of light-matter interactions for photovoltaics, plasmonics and metamaterial applications, 2) design of robust molecular sensors, and 3) improve design of selective and active nanocatalysts for energy and industrial chemical conversion. Self-organization techniques are used to fabricate systems on molecular length scales using methods that are easily translated into large-area production. Correlating physical properties with structure is conducted using scanning probe microscopy since device performance is typically affected by surface defects and local composition. We have three main projects in the group:

1. Metal nanostructures assembled in a periodic or cluster architecture are fabricated to achieve near field enhancements for surface enhance Raman scattering (SERS) sensors and narrow band resonances for signal transmission and filtering. Correlations between optical properties and nanoarchitecture are investigated to design and optimize structures.

2. Tethered lipid bilayer membranes (tLBM) that represent a simplified and versatile platform for cell membrane mimics are assembled on gold surfaces. This system is designed to measure protein-membrane interactions for biosensing and drug discovery applications.

3. Fabrication and scanning probe microscopy atomic scale characterization of clusters of metal atoms on crystalline surfaces are combined with measurements of chemical activity in order to elucidate physical mechanisms that lead to higher activity and selectivity in nanoscale catalysts.

Prof. Regina Ragan Associate Professor• B.S. Materials Science and

Engineering, University of California, Los Angeles (1996)• M.S. Applied Physics,

California Institute of Technology (1998)• Ph.D. Applied Physics,

California Institute of Technology (2002)

Key Publications:1. “Design of a versatile chemical assembly method for

patterning colloidal nanoparticles,” J. H. Choi, S. Adams, and R. Ragan Nanotechnology 20 (2009) 065301.

2. “A facile approach for assembling lipid bilayer membranes on gold electrodes” X. Wang. M. Shindel, S.-W. Wang, and R. Ragan Langmuir 26 (2010) 18239–18245

3. “Structural and Chemical Properties of Gold Rare Earth Disilicide Core-Shell Nanowires ” W. Ouyang, A. Shinde, Y. Zhang, J. Cao, R. Ragan, and R. Wu ACS Nano 5 (2011) 477.

SERS Signal Enhancement

Optimized structure