Optical properties of metallic nanoparticles have been subject of much interest recently. In particular, the effects of shape and environment are studied through their response to an electromagnetic excitation. For the past few years, several new types of bio-molecular sensors are developed based on Surface Enhanced Raman Scattering (SERS) and enhanced molecular fluorescence in the presence of metallic nanoparticles, making rapid detection possible of DNA sequences, and other target agents. The major advantage of SERS is that it allows one to establish the molecular identity on a single-molecule level. SERS active molecules adsorbed on nanoparticles were used recently as probes for detecting agents such as the HIV gene, the breast cancer susceptibility gene, and the Ebola virus. We find important size-dependent quantum corrections to the SERS spectra of small metallic nanoparticles, and show that molecular fluorescence can be enhanced in the presence of nanoparticles. We perform DFT-TDLDA simulations of the radiative and nonradiative decays of the “single molecule + nanoparticle” system and then, by the Green’s function method, investigate the case of the high coverage of a nanoparticle with molecules at regular and random distributions. We find a degeneracy in decay states. Only 3 eigenmodes survive at large distances from the nanoparticle. The total decay rate of the system is proportional to the number of molecules, while the fluorescence efficiency and emitted power rise only by a factor of 3 compared to the original ones.
Friday, February 26, 2010
Room 1229, Mary Townes Science Building
For addition information contact: Dr. Igor Bondarev (firstname.lastname@example.org, or 919-530-6623)