Background:

• "Aguirre-Basualdo" award for Sciences, Sorbonne (France), 1996
• SPIE scholarship in Optical Science and Engineering, 2000.

Current research interests include principles of virus self-assembly, biophotonic applications of nanoparticles, and dynamics in supramolecular aggregates such as molecular microcrystals, viruses, and curvature-strained self-assembled molecular layers. Building upon the lessons we learn from the study of these systems, we are developing new instruments of near-field intracellular imaging and microspectroscopy at spatial scales and sensitivities down to one molecule.

Examples of ongoing projects:

Encapsulated gold particles as probes of virus capsid transformations. Functionalized gold particles with diameters between 2.5 and 4.5 nm have been introduced in the inner cavity of an icosahedral virus. The optical properties of single gold-marked virions are being tested in-vitro with respect to the characteristic plasmon polariton resonance of the gold particle dimer (figure). The dependence of the two-particle surface plasmon spectrum on the inter-particle distance and the strong particle/capsid wall interaction suggest that, in the future, it will be possible to use encapsulated Au particles to track changes in the viral capsid volume in real-time and in a physiological environment.

Near-field optical trapping of sub-100 nm nanoparticles. We use evanescent light in confined geometries to trap and study the properties of very small particles in a fluid. Nanolithography and finite-element calculations are used to design and create sub-wavelength structures with the desired trapping characteristics. This method is potentially useful for in-vitro kinetic studies of aggregation of single complex molecular systems.

Selected Publications:

"Field-induced interfacial changes of gold nanoparticles in AC electrophoretic experiments", Kloepper, K, Onuta, T., Amarie, D., Dragnea, B., J. Phys. Chem B (submitted).

"Chemical Imaging NSOM", Dragnea, B. in the Dekker Encyclopedia of Nanoscience and Nanotechnology, 1st edition, Marcel Dekker, NY, 2004.

"Gold Nanoparticles as Spectroscopic Enhancers for In-vitro Studies of Single Viruses", Dragnea, B., Chen, C., Kwak, E-S, Stein, B., Kao, C. C., J. Am. Chem. Soc. 2003, 125(21), 6374-6375 (communication)

"Water Vapor Uptake in Photolithographic Polymers Observed by Infrared Near-Field Scanning Optical Microscopy in a Controlled Environment", McDonough, L. A.; Dragnea, B.; Preusser, J.; Leone, S. R.; Hinsberg, W. D.;

J. Phys. Chem. B. 2003; 107(21); 4951-4954.

"Near-Field Surface Plasmon Excitation on Structured Gold Films" Dragnea, B.; Szarko, J. M.; Kowarik, S.; Weimann, T.; Feldmann, J.; Leone, S. R.; Nano Lett.; (Cover); 2003; 3(1); 3-7 (communication).