Dr. Douglas A. Stuart
Office: 2125 TLC, Lab: 2121
I am a bioanlytical chemist with a research focus on the development and design of novel nanoparticle based methods of ultra-sensitive biomedical and environmental detection and analysis. Specifically, I exploit the unique optical properties of gold and silver structures such as intense absorption, wavelength selective photon scattering, localized surface plasmon resonance (LSPR), and the ability to support surface-enhanced Raman scattering (SERS). An important part of this research is the systematic investigation of the fundamental relationships between a particle’s physical properties (size, shape, composition) and its observed optical properties.
The sensitivity of the LSPR to the dielectric environment enables us to create sensors capable of measuring binding events by monitoring shifts in the UV-Vis spectrum of the nanomaterial. The nanoparticles are functionalized –e.g. with capture antibodies – to make them sensitive only to specific target molecules. Single particle experiments have demonstrated zeptomole sensitivities.
The intense electric fields generated localized surface plasmon are the single most important factor in observing the surface-enhanced Raman phenomenon. SERS is an attractive –but under utilized- analytical technique because it generates unique vibrational spectra that can be used for unambiguous determination of analytes. In that regard, Raman spectroscopy is similar to infra-red absorbance spectroscopy, but enjoys the advantages of being able to operate in aqueous environments, and on opaque surfaces and materials (e.g. pharmaceutical tablets and coatings). In SERS, the analyte is placed at or near a nanoscale roughened noble metal surface, yielding an increase in intensity of ten to a million fold over standard Raman scattering. SERS position as the only vibrational spectroscopy capable of single-molecule is due to these enormous gains in signal.
Wavelength selective scattering from silver nanoparticles observed by dark-field microscopy. Properly conjugated to a capture molecule, these particles can be made into very sensitive sensors.
An array of nanopyramids. These particles can support SERS.