Nonlinear Plasmonics: SERS Hot Spot Isolation and Enhanced Laser Cell Transfection

Eric Diebold
Harvard University

Thursday, January 4, 2010 at 12:00pm
Engr IV Maxwell Room 57-124

Abstract
Surface-enhanced Raman scattering (SERS) is one of the most sensitive molecular spectroscopy techniques currently available. Using SERS, it is possible to obtain vibrational spectra from chemical quantities as small as a single molecule. However, it is challenging to have molecules of interest adsorb specifically to a substrate's "hot spots," or regions of largest electromagnetic enhancement. I will describe a nonlinear optical technique that enables masking of SERS substrates such that only hot spots are available as molecular adsorption sites. Using this approach, we have demonstrated a 27-fold improvement in the SERS signal from 4 femtomoles of a test molecule.

I will also describe the use of plasmonic substrates to enhance the interaction of ultrafast laser pulses with biological materials. In order to achieve high efficiency cell transfection, tightly focused femtosecond laser pulses have recently been employed to create sub-micron sized transient pores in cell membranes. Diffusion of external DNA through these pores can result in transfection of single cells. This process efficiently transfects cells, but suffers from extremely low throughput. I will describe our preliminary results in this area, achieved using large-area plasmonic substrates to eliminate the requirement of high numerical aperture focusing - an advance potentially enabling high efficiency cell transfection on clinically relevant scales.

Biography
Eric Diebold is a Ph.D. student at Harvard University in the department of applied physics, working in professor Eric Mazur's research group. His research experience lies in the areas of surface-enhanced optical phenomena, nonlinear optical microscopy, and biophotonics. Eric was a recipient of a National Defense Science and Engineering Graduate fellowship in 2005, and received undergraduate degrees summa cum laude in electrical engineering and physics from Duke University in 2004.