News & Events

Single-Molecule Spectroscopy Using Metallic Nanomaterials

Date: 
Monday, September 30, 2019 - 16:00 to 17:00
Speaker: 
Dr. Alexandre Brolo
Affiliation: 
Department of Chemistry, University of Victoria
Event Category: 
External Examiner Seminar
Host: 
Edward Grant
Location: 
Chemistry D213

Abstract:

A variety of new properties emerges in nanostructured metallic materials. These new properties are consequence of the collective excitation of conducting electrons, known as surface-plasmon resonances (SPR). For instance, the color of noble metals, such as gold and silver, can be controlled at the nanoscale by tuning the geometric characteristics of the nanostructures. A very interesting consequence of SPR is the phenomenon of electric field localization. Once the SPR condition is established, metallic nanostructures can act as tiny antennas that capture visible radiation and concentrate it in sub-wavelength regions. Molecules exposed to the localized fields can experience a large increase in their spectroscopic response. This leads to unique spectroscopic phenomena, such as the surface-enhanced Raman scattering (SERS) effect. The optical fields achieved in certain metallic nanostructures can be very strong and only accessible to a very small number of molecules (since they are also confined to very small regions). Ultimately, in certain conditions, SERS allows the detection of single adsorbed species. In this work, we will show that the spectroscopic response from single molecules is dynamic and carries information about the local field strength, resonance energy and local nanometric geometry. Moreover, the detection of single molecules leads to a new analytical quantification technology with very low limits of detection.  Finally, we will also demonstrate that organized metallic nanostructures can also be used as a platform for single molecule spectroscopy. In that case, we will explore the plasmonics characteristics of single nanoapertures in gold films to follow fluctuations in spectroscopic response using methods for super-resolution imaging.​​