AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Investigation of Enhanced Raman Spectroscopy of Aerosol Particles
VASANTHI SIVAPRAKASAM, Matthew B. Hart, Jay D. Eversole, Naval Research Laboratory
Abstract Number: 203 Working Group: Single Aerosol Particle Studies - Techniques and Instrumentation
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. We are currently exploring a technique to obtain an enhanced Raman signal by combining metallic nano-particles (MNPs) with larger aerosol particles (Sivaprakasam et. al. 2014). In this aspect, our approach could be regarded as an extension of surface enhanced Raman scattering (SERS). We plan to compare measurements of spontaneous Raman spectra with MNP-enhanced Raman spectra using identical aerosol particles under controlled conditions. The repeatability of spectral response and enhancement factors, and their dependence on factors such as, MNP composition, MNP concentration and aerosol composition will be investigated.
In order to study Raman spectral signatures from aerosol particles with controlled composition and size, we have constructed an experiment where aerosol particles are suspended for extended periods of time (up to hours) using a linear electrodynamic quadrupole (LEQ) trap. Aerosol particles are created 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. For validation and calibration, droplets of materials such as glycerol and dibutly sebacate are being studied, using a 532 nm laser for excitation. We plan to expand the study to include other materials (laser dyes and proteins). Raman spectra from both aerosol particles and bulk samples each with and without the addition of MNPs will be compared. The latest results in terms of spectral signatures resulting the addition of the MNP’s to these materials will be presented.