AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Surface Enhanced Raman Spectroscopy of Aerosol Particles
Vasanthi Sivaprakasam, Matthew B. Hart, Paul Lane, Gary Kushto, JAY D. EVERSOLE, Naval Research Laboratory
Abstract Number: 625 Working Group: Instrumentation and Methods
Abstract Raman spectroscopy is a widely used technique to measure vibrational and rotational molecular modes which can provide very specific spectral signatures for chemical identification. However, typically low Raman scattering cross-sections have been a barrier to using this technique for in-situ characterization of environmental aerosols or monitoring hazardous materials present in the air. By combining metallic nano-particles (MNPs) with aerosol particles, we have been able to observe Surface Enhanced Raman Spectra from single suspended aerosol particles. We have explored the comparison measurements of spontaneous Raman spectra with MNP-enhanced Raman spectra using identical materials under controlled conditions both as aerosols and as bulk liquid samples. The experimental repeatability of this approach has enabled investigation of spectral responses and enhancement factors, and their dependence on factors such as, MNP composition, MNP concentration and material composition.
This presentation describes the design and construction of a Raman spectroscopy test-bed capable of interrogating single aerosol particles or bulk samples in a cuvette for comparison/validation studies. Aerosol particles are suspended in a linear Electrodynamic quadrupole (LEQ) trap, that provides ample time to study the weak spontaneous Raman. Aerosol particles are generated and charged using a customized nozzle-reservoir droplet generator, and particles ranging from 1 micron to 60 microns in diameter have been successfully generated and maintained. Droplets of materials such as glycerol, dibutly sebacate and ethyl cinnamate have been used for validation and calibration. SERS data has been obtained for Rhodamine 6G dye as bulk sample and aerosols, comparison of these measurements and enhancement factors will be discussed. Plans to extend the study to other chemicals are under way. The latest spectral signatures and enhancement factors resulting from the addition of the MNP’s to these materials will be presented.