Agenda

prof. Raymond Phaneuf, University of Maryland - DAIS

The seminar will take place on Zoom https://unive.zoom.us/j/89730737431
meeting ID: 897 3073 7431

Abstract:
Strong resonant coupling between light and collective oscillations of the conduction electrons, or “plasmons” in noble metallic nanostructures leads to a number of striking and technologically important optical effects, among them surface enhanced Raman scattering (SERS) and the enhancement of fluorescence from nearby molecules. While each of these show great promise for the development of highly sensitive biomolecule detectors, fluorescence remains the technique of choice for many biological assays. Significant fluorescence enhancement would greatly enhance the sensitivity of these assays to a host of target biomolecules. As yet the maximum enhancement available in fluorescence has not been definitively established. This is largely due both to difficulties in controlling the size and shape of the particles, and to the multiplicity of contributing factors including increased radiative decay rate and enhanced electric fields at resonance, as well as the possible role of “hot spots”, or regions of high field between closely spaced particles. In this talk I will present results demonstrating that a multiplicity of effects are important in determining the enhancement of fluorescence available from proximity of molecules or nanocrystals to metal nanostructures. The possibility of enhancing light absorption via the intense field generated by plasmon excitation at a fluorescent species leads to a dependence on the size, shape and dielectric surroundings of a metallic nanostructure, while the possibility of scattering of a plasmon into far field radiation leads to a dependence on additional factors, including the periodicity of the array. Substrate effects are strong and lead to an additional level of tunability which promises to be useful in a number of applications.

Bio Sketch:
Ray Phaneuf is a Professor and Past Interim Chair in the Materials Science and Engineering Department at the University of Maryland. He joined the University of Maryland in 1985, where he used electron diffraction to study phase transformations on stepped Si(111) surfaces, resulting in the identification of a thermodynamically driven faceting associated with the formation of the (7x7) reconstruction. In 1989 he visited with Ernst Bauer’s group in Clausthal, Germany, using low energy electron microscopy (LEEM) to image this faceting in real time. In 2000 he joined the Materials Science and Engineering Department, and began studies of directed self-organization during growth and sublimation on semiconductor surfaces, using lithographic patterning. In 2006 he was a visiting professor at the National Nanotechnology Laboratory, in Lecce, Italy. He is the author of more than 100 papers and has given over 40 invited talks on his work in the US, Europe and Japan. He was named the Laboratory for Physical Sciences Faculty Researcher of the year in 2002. In addition to MSE, he has affiliate positions in Physics and ECE, and was a founding member of the UM-MRSEC at the University of Maryland.
He was the founding Coordinator of the Interdisciplinary Minor Program in Nanoscience and Technology. His current research is in the fields of directing self-assembly of nanostructures at the mesoscale, plasmonics, and application of nanotechnology to the conservation of cultural heritage objects.
Present Position: Professor, Department of Materials Science and Engineering, Affiliate Professor, Department of Physics, and Department of Electrical and Computer Engineering University of Maryland, College Park, MD 20742