Ortiz Rivera, William

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    Standoff raman spectroscopy system for detection of explosives, chemical warfare agents simulants and toxic industrial compounds
    (2008) Ortiz Rivera, William; Hernández Rivera, Samuel P.; College of Arts and Sciences - Sciences; Cádiz García, Mayra E.; Mina Camilde, Nairmen; Department of Chemistry; Baigés Valentin, Ivan
    In this work a remote Raman system has been designed, assembled and tested for detecting explosives, Toxic Industrial Compounds (TIC) and Chemical Warfare Agents Simulants (CWAS) at laboratory scale up to 7 m target-telescope distance. The prototype system consists of a Renishaw Raman Microspectrometer, model RM2000, equipped with a charge-coupled device (CCD) detector, a telescope, a fiber optic assembly and a single wavelength/frequency laser source (514/488 nm and 532 nm). The telescope was coupled to the Raman microscope using an optical fiber and filters for rejection of laser radiation and Rayleigh scattering. Two convex lenses collimate the light from the telescope output, which is directed into the fiber optic from which the focusing objective was removed. The output of the fiber was directly coupled to the Raman system by a 5x objective. To test the standoff sensing system, the VIS Raman Telescope was used in detection of secondary explosives: 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4- DNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), triacetone triperoxide (TATP) and plastic explosive C4, with detection limits below 10 mg. The TICs used were benzene, toluene, xylenes, chloroform, CCl4 and CS2. Other compounds studied were Chemical Warfare Agents Simulants dimethylmethyl phosphonate (DMMP), 2-chloroethyl ethyl sulfide (2-CEES). Solid samples (explosives) were deposited on stainless steel plates and liquid samples were transferred into 5 mL glass vials. Both types of samples were placed at a distance of 7 m from the telescope. Raman spectra of compounds were acquired in the Raman shift range of 100-3200 cm-1 using laser powers varying from 50 mW to 1 W and integration times of 1 to 30 s.
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    Design and development of remote Raman spectroscopy system for detection of hazardous compounds
    (2012-11) Ortiz Rivera, William; Hernández Rivera, Samuel P.; College of Arts and Sciences - Sciences; Vega, Carmen A.; Rivera, Nilka; Briano Peralta, Julio G.; Department of Chemistry; Bellido, Carmen
    Remote Raman detection has become a powerful analytical technique for detection of hazardous compounds in situ and without sample preparation at distances away from the observation site. This study describes the design, assembly, testing and validation of Remote Raman Spectroscopy (RRS) systems intended for stand-off detection of hazardous chemicals such as explosives: TNT, PETN, RDX and TATP; chemical warfare agents simulants: dimethylmethylphosphonate, 2-chloroethyl ethyl sulfide and 2-(butylamino)-ethanethiol; and Toxic Industrial Compounds: benzene, chlorobenzene, toluene, carbon tetrachloride, cyclohexane and carbon disulfide. The prototype systems consisted of a spectrometer equipped with a CCD detector (for CW measurements) and an I-CCD camera with time-gated electronics (for pulsed laser measurements), a reflecting telescope, fiber optic assemblies, single-line continuous wave (CW) laser sources (514.5, 488.0, 351.1 and 363.8 nm) and a frequency-doubled single frequency Nd:YAG 532 nm pulse laser (5 ns pulses at 10 Hz repetition rate). The telescope was coupled to the spectrograph using an optical fiber and notch filters were used to reject laser radiation and Rayleigh scattering. Two quartz convex lenses were used to collimate the light from the telescope from which the telescope-focusing eyepiece was removed, and direct it to the fiber optic assembly. The stand-off detection systems were tested employing the compounds mentioned at different remote distances (2 to 141 m) using several sampling approaches. Quantification and classification of explosives (TNT and PETN) hidden in non-explosives matrices (4-NBA and APAP) with similar chemical structures were achieved in powder mixtures by using chemometrics techniques.