Browsing by Subject "Explosives detection"
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Item Open Access Comparison of terahertz technologies for detection and identification of explosives(SPIE, 2014-05) Beigang, R.; Biedron, S. G.; Dyjak, S.; Ellrich, F.; Haakestad, M.W.; Hübsch, D.; Kartaloglu, Tolga; Özbay, Ekmel; Ospald, F.; Palka, N.; Puc, U.; Czerwiñska, E.; Sahin, A. B.; Sešek, A.; Trontelj, J.; Švigelj, A.; Altan, H.; Van Rheenen, A.D.; Walczakowski, M.We present results on the comparison of different THz technologies for the detection and identification of a variety of explosives from our laboratory tests that were carried out in the framework of NATO SET-193 THz technology for stand-off detection of explosives: from laboratory spectroscopy to detection in the field under the same controlled conditions. Several laser-pumped pulsed broadband THz time-domain spectroscopy (TDS) systems as well as one electronic frequency-modulated continuous wave (FMCW) device recorded THz spectra in transmission and/or reflection. © 2014 SPIE.Item Open Access Fluorescent Si QD decoration onto a flexible polymeric electrospun nanofibrous mat for the colorimetric sensing of TNT(Royal Society of Chemistry, 2017) Arslan, O.; Aytac Z.; Uyar, TamerUV range light was used for the facile, effective and large-scale synthesis of visible light emitting, surface-protected silicon quantum dots (Si QDs) starting from an amine-functionalized alkoxy silane precursor. Within mild and easy hydrolysis/condensation environments, the use of an amine-functionalized precursor together with a reducing agent resulted in a bright visible green light that could be used for fluorescent analytical detection systems. Visible light emitting Si QDs were investigated and it was found that their emission character depends on the illumination time, hydrolysis/condensation conditions and pretreatments for the silane coupling agents. A Nylon 6,6 electrospun nanofibrous mat was selected as a substrate for decoration by the Si QDs in order to fabricate a flexible and free-standing polymeric nanofibrous mat posessing a visible light emitting character so that it could act as a visible colorimetric sensor. The visible light emitting Si QDs were decorated onto the Nylon 6,6 nanofibrous mats via covering the surfaces as a ‘nanodress’ by a simple impregnation/dip-coating and heat-curing methods. The analytical results revealed that the Si QDs decorated flexible polymeric nanofibrous mats could be utilized for colorimetric trinitrotoluene (TNT) detection in low concentrations.Item Open Access Highly fluorescent pyrene-functional polystyrene copolymer nanofibers for enhanced sensing performance of TNT(American Chemical Society, 2015) Senthamizhan, A.; Celebioglu A.; Bayir, S.; Gorur, M.; Doganci, E.; Yilmaz, F.; Uyar, TamerA pyrene-functional polystyrene copolymer was prepared via 1,3-dipolar cycloaddition reaction (Sharpless-type click recation) between azide-functional styrene copolymer and 1-ethynylpyrene. Subsequently, nanofibers of pyrene-functional polystyrene copolymer were obtained by using electrospinning technique. The nanofibers thus obtained, found to preserve their parent fluorescence nature, confirmed the avoidance of aggregation during fiber formation. The trace detection of trinitrotoluene (TNT) in water with a detection limit of 5 nM was demonstrated, which is much lower than the maximum allowable limit set by the U.S. Environmental Protection Agency. Interestingly, the sensing performance was found to be selective toward TNT in water, even in the presence of higher concentrations of toxic metal pollutants such as Cd2+, Co2+, Cu2+, and Hg2+. The enhanced sensing performance was found to be due to the enlarged contact area and intrinsic nanoporous fiber morphology. Effortlessly, the visual colorimetric sensing performance can be seen by naked eye with a color change in a response time of few seconds. Furthermore, vapor-phase detection of TNT was studied, and the results are discussed herein. In terms of practical application, electrospun nanofibrous web of pyrene-functional polystyrene copolymer has various salient features including flexibility, reproducibility, and ease of use, and visual outputs increase their value and add to their advantage.Item Open Access Template-free synthesis of organically modified silica mesoporous thin films for TNT sensing(American Chemical Society, 2010) Yildirim, A.; Budunoglu, H.; Deniz, H.; Güler, Mustafa O.; Bayındır, MehmetIn this paper, we present a facile, template-free sol−gel method to produce fluorescent and highly mesoporous organically modified silica (ORMOSIL) thin films for vapor phase sensing of TNT. An alkyltrifunctional, methyltrimethoxysilane MTMS precursor was used to impart hydrophobic behavior to gel network in order to form the spring back effect. In this way, porous films (up to 74% porosity) are obtained at ambient conditions. Fluorescent molecules are physically encapsulated in the ORMOSIL network during gelation. Fluorescence of the films was found to be stable even after 3 months, proving the successful fixing of the dye into the ORMOSIL network. The functional ORMOSIL thin films exhibited high fluorescence quenching upon exposition to TNT and DNT vapor. Fluorescence quenching responses of the films are thickness-dependent and higher fluorescence quenching efficiency was observed for the thinnest film (8.6% in 10 s). The prepared mesoporous ORMOSIL thin films have great potential in new sensor and catalysis applications.