Subcategory: Physics (not Nanoscience)
Brianna Kenney - Alabama A&M University
Co-Author(s): Eshirdanya McGhee, Carlton Farley, Kenneth Garcia, and Anup Sharma, Alabama A&M University, Huntsville, AL
Detection of explosives is an ongoing concern for many agencies, including the U.S. Department of Homeland Security and the U.S. Army. There are many methods currently used to detect various types of explosives under various conditions. In this work, portable Raman spectroscopic system with 785 nm laser is used to detect sodium and ammonium nitrates concealed behind layers of fabrics and through plastic containers at integration times ranging between one and ten seconds. Typically, two layers of dry and wet colored fabrics were used to cover the plastic container filled with sodium and ammonium nitrate. Five different colors of wet and dry fabrics are used to study the efficacy of Raman spectroscopic technique for detection and identification of nitrates concealed under white, yellow, red, green and navy blue fabrics. It is found that, the Raman spectra of the nitrates kept in clear plastic container and placed beneath one layer of the fabrics can easily be detected using both the conventional Raman technique and at a standoff distances up to 1 meter. It was also observed that, for the same color of the fabrics, the signal-to-noise ratio of the Raman scattering signal measured from the nitrates covered with wet fabrics is nearly twice of the intensity of the Raman scatterings signals collected from the samples covered with dry fabrics. That is, due to the index-of-refraction matching property of water, the Raman measurements taken through wet fabrics resulted in a better signal-to-noise ratio as compared with the data collected through the dry fabrics. Similarly, the Raman measurements of nitrates collected through layers of white fabrics gave better signal-to-noise ratio as compared with the Raman measurements collected through colored fabrics.
References: Robinson, P. D., Kassu, A., Sharma, A., Kukhtareva, T., Farley III, C., Smith, C., Ruffin, P., Brantley, C. and Edwards, E. 2013. Surface-Enhanced Raman Spectroscopy Scattering from Gold-Coated Ceramic Nanopore Substrates: Effect of Nanopore Size. Journal of Nanophotonics. 7: 073592.
Sadate, S., Kassu, A., Farley, C. W., Sharma, A., Hardisty, J., Lifson, M. 2011. Standoff Raman Measurement of Nitrates in Water. Proc. of SPIE, 8156: 81560D.
Funder Acknowledgement(s): This work is supported by the U.S. Department of Homeland Security under the award numbers 2014-ST-062-000060 and 2010-ST-061-FD0001.
Faculty Advisor: Aschalew Kassu,