Title

Nanomaterials Fabrication and Surface Enhanced Raman Spectroscopy

Speaker

Prof. Baohua Gu

Environmental Sciences Division, Oak Ridge National laboratory & Dept. of Biosystems Engineering & Soil Science, University of Tennessee, USA

Time

10:00am, July 2, 2010

Place

Room 9004 at the HFNL building

Baohua Gu is a distinguished senior research scientist at Oak Ridge National Laboratory (ORNL). He received his Ph.D. from University of California, Berkeley, in 1991 in environmental chemistry and became a research staff member in Environmental Sciences Division at ORNL since 1993. Dr. Gu is also an adjunct professor at the University of Tennessee, Knoxville, and has published more than 130 research articles with citation of more than 3000 times. Dr. Gu’s main research interests include nanomaterials synthesis and its environmental and energy applications, surface enhanced Raman spectroscopy, and the chemical and biological transformation and fate of pollutants in the environment.

Abstract

Large electromagnetic field (E) enhancement enabling ultra-sensitive surface enhanced Raman spectroscopy (SERS) has been realized within a gap region of noble metallic nanostructures serving as a plasmonic nanoantenna. However, despite 30+ years of extensive research, SERS is yet to be realized as a routine analytical tool partly due to our inability to controllably fabricate clean and reproducible nano-gap sizes and our limited understanding of underlying enhancement mechanisms. This talk will cover three general topics on SERS. First, I will discuss our current understanding of SERS and its underlying mechanisms. Second, I will present recent progresses in nanofabrication leading to improved understanding of the gap-dependent electromagnetic field enhancement and SERS. In particular, I report the use of Ag@SiO2 core-shell nanoparticles for probing spatial distribution of the E field enhancement via SERS and the use of novel suspended gold bowtie nanoantenna arrays capable of generating plasmonic nanocavities that enable reproducible, single-molecule Raman spectroscopy. With these idealized bowtie arrays, we reveal an anomalously weak power law dependence of E on the gap size and provide a definitive proof of the existence of the collective photonic effect. Finally, I will provide future research perspectives on SERS and its potential in biological, environmental, and security applications.