Paul Whiteside | University of Missouri Columbia (original) (raw)
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We demonstrate the rapid detection of explosive vapors based on a fiber-based optical Fabry-Péro... more We demonstrate the rapid detection of explosive vapors based on a fiber-based optical Fabry-Pérot (FP) gas sensor. The sensing probe of the FP sensor is composed of a thin metal layer and a vapor-sensitive polymer layer that are deposited sequentially on a cleaved fiber endface to form an FP cavity. The interference spectrum generated from the reflected light at the metal-polymer and polymer-air interfaces changes upon the absorption of gas analyte. By monitoring the interference shift, we are able to obtain quantitative and knetic information of the interaction between the analyte and the polymer layer. We further assemble the FP sensor with a short fused silica capillary into a sensor module, and employ it in a gas chromotgraphy (GC) system for selevtive rapid on-column detection. In this report, we specifically target 2, 4- dinitrotoluene (DNT) and 2, 4, 6-trinitrotoluene (TNT) for their obvious defense applications. This work could lead to a portable sensor capable of detecting low concentrations of DNT, TNT, and other explosive chemicals.
Total Internal Reflection Photoacoustic Spectroscopy (TIRPAS) is a method that exploits the evane... more Total Internal Reflection Photoacoustic Spectroscopy (TIRPAS) is a method that exploits the evanescent field of a nanosecond duration laser pulse reflecting off a glass/water interface to generate photoacoustic responses. These photoacoustic events are generated in light absorbing analytes suspended in the fluid medium in contact with the glass that are within the penetration depth of the evanescent wave. This method has been employed in previous studies by Hinoue et al. Hinoue et al. used an optically chopped HeNe laser at 632.8 nm to detect Brilliant Blue FCF dye at different angles of incidence. In recent years, the advent of high power nanosecond pulsed tunable lasers has allowed for the re-visitation of the TIRPAS idea under stress confinement and orders of magnitude larger peak energy conditions. Compared to conventional detection methods, this approach has the potential to detect much smaller quantities of disease indicators, such as circulating tumor cells and hemazoin crystals in malaria, than other optical methods. The detection limit of the TIRPAS system was quantified using chlorazol black solution with an absorption coefficient of 55 cm-1 at 532 nm. Interaction with the evanescent field was verified by varying the angle of incidence of the probe laser beam that generated the photoacoustic waves, thereby changing the penetration depth of the evanescent field as well as the photoacoustic spectroscopy effect from angled excitation.
We demonstrate the rapid detection of explosive vapors based on a fiber-based optical Fabry-Péro... more We demonstrate the rapid detection of explosive vapors based on a fiber-based optical Fabry-Pérot (FP) gas sensor. The sensing probe of the FP sensor is composed of a thin metal layer and a vapor-sensitive polymer layer that are deposited sequentially on a cleaved fiber endface to form an FP cavity. The interference spectrum generated from the reflected light at the metal-polymer and polymer-air interfaces changes upon the absorption of gas analyte. By monitoring the interference shift, we are able to obtain quantitative and knetic information of the interaction between the analyte and the polymer layer. We further assemble the FP sensor with a short fused silica capillary into a sensor module, and employ it in a gas chromotgraphy (GC) system for selevtive rapid on-column detection. In this report, we specifically target 2, 4- dinitrotoluene (DNT) and 2, 4, 6-trinitrotoluene (TNT) for their obvious defense applications. This work could lead to a portable sensor capable of detecting low concentrations of DNT, TNT, and other explosive chemicals.
Total Internal Reflection Photoacoustic Spectroscopy (TIRPAS) is a method that exploits the evane... more Total Internal Reflection Photoacoustic Spectroscopy (TIRPAS) is a method that exploits the evanescent field of a nanosecond duration laser pulse reflecting off a glass/water interface to generate photoacoustic responses. These photoacoustic events are generated in light absorbing analytes suspended in the fluid medium in contact with the glass that are within the penetration depth of the evanescent wave. This method has been employed in previous studies by Hinoue et al. Hinoue et al. used an optically chopped HeNe laser at 632.8 nm to detect Brilliant Blue FCF dye at different angles of incidence. In recent years, the advent of high power nanosecond pulsed tunable lasers has allowed for the re-visitation of the TIRPAS idea under stress confinement and orders of magnitude larger peak energy conditions. Compared to conventional detection methods, this approach has the potential to detect much smaller quantities of disease indicators, such as circulating tumor cells and hemazoin crystals in malaria, than other optical methods. The detection limit of the TIRPAS system was quantified using chlorazol black solution with an absorption coefficient of 55 cm-1 at 532 nm. Interaction with the evanescent field was verified by varying the angle of incidence of the probe laser beam that generated the photoacoustic waves, thereby changing the penetration depth of the evanescent field as well as the photoacoustic spectroscopy effect from angled excitation.