Trinitrotoluene sensor

An important demonstrated application of this artificial nose system is the high-speed detection of low levels of explosives and explosive-like vapors. Several sensors, based on Nile Red attached to silica microspheres, show high sensitivity to nitroaromatic compounds (NAC) within a mixture12. Different fluorescence response profiles were observed for several NAC s, such as 1,3,5-trinitrotoluene (TNT) and 1,3-dinitrobenzene (DNB), despite their similar structures. These responses were monitored at low concentrations of the NAC vapors (ca. 5 ppb) and at short vapor exposure... 

Building onto the concept of molecularly wired sensors for signal amplification, Swager reported in 1998 the synthesis of a series of porous PPE derivatives in which pentiptycene modules are incorporated into the PPE main chain. The incorporation of the pentypticene moieties makes 29 and 30a (Chart 5) efficient solid-state emitters unaffected by aggregation i.e., their emission spectra in solution and in the solid state are almost identical. The authors found that thin films of these highly fluorescent PPEs are excellent sensors for the detection of trinitrotoluene and dinitrotoluene. Both aromatics suppress the fluorescence of 29 or 30a effectively but reversibly. The headspace, i.e., the atmospheric volume above land mines, contains measurable quantities of dinitrotoluene. As a consequence, polymers 29 and 30 coated on top of a fiber optic sensor will allow their simple detection by these very sensitive molecular wire-type materials. This elegant concept should be extendable and applicable to any other analyte, (a) which has the ability to quench fluorescence and (b) for which a receptor can be attached to PPEs. 

Fe ) has also been shown to remove As(III) from contaminated soils (15,16), and assist in the remediation of aquifers contaminated with polycyclic aromatic hydrocarbons (26). Other nanomaterials have been developed to act as pollutant sensors, such as the trinitrotoluene (TNT) sensor, which can detect TNT at concentrations as low as 20ng/mL(27). 

Composites of PANI-NFs, synthesized using a rapid mixing method, with amines have recently been presented as novel materials for phosgene detection [472]. Chemiresistor sensors with nanofibrous PANI films as a sensitive layer, prepared by chemical oxidative polymerization of aniline on Si substrates, which were surface-modified by amino-silane self-assembled monolayers, showed sensitivity to very low concentration (0.5 ppm) of ammonia gas [297]. Ultrafast sensor responses to ammonia gas of the dispersed PANI-CSA nanorods [303] and patterned PANI nanobowl monolayers containing Au nanoparticles [473] have recently been demonstrated. The gas response of the PANI-NTs to a series of chemical vapors such as ammonia, hydrazine, and triethylamine was studied [319,323]. The results indicated that the PANI-NTs show superior performance as chemical sensors. Electrospun isolated PANI-CSA nanofiber sensors of various aliphatic alcohol vapors have been proven to be comparable to or faster than those prepared from PANI-NF mats [474]. An electrochemical method for the detection of ultratrace amount of 2,4,6-trinitrotoluene with synthetic copolypeptide-doped PANI-NFs has recently been reported [475]. PANI-NFs, prepared through the in situ oxidative polymerization method, were used for the detection of aromatic organic compounds [476]. 

L-Cysteine-fimctionalized CdTe QD-based sensor was developed for simple and selective detection of trinitrotoluene (TNT) based on the formation of a Meisenheimer complex between TNT and cysteine... 

Chen Y, Chen Z, He Y, Lin H, Sheng P, Liu C, Luo S, Cai Q (2010) L-cysteine-capped CdTe QD-based sensor for simple and selective detection of trinitrotoluene. Nanotechnology 21 125502-125507... 

Conjugated polymers are good sensing platforms for the detection of vapours of nitroaromatic explosives such as trinitrotoluene (TNT) [31]. Fluorescence quenching occurs due to electron transfer from the conjugated polymer to the nitroaromatic species. Common classes of CPs used in nitroaromatics sensing are poly(acetylenes), poly(p-phenylenevinylenes), poly(p-phenyleneethynylenes) and polysilanes. CP sensor platforms have been successfully deployed outside the laboratory for the detection of hidden landmines, where impressive femtogram detection limits for TNT were obtained [32]. 

Bozic RG, West AC, Levicky R (2008) Square wave voltammetric detection of 2,4,6-trinitrotoluene and 2,4-dinitrotoluene on a gold electrode modified with self-assembled monolayers. Sensor Actuat B 133 509-515... 

Alizadeh T, Zare M, Ganjali MR, Norouzi P, Tavana B (2010) A new molecularly imprinted polymer (MlP)-based electrochemical sensor for monitoring 2,4,6-trinitrotoluene (TNT) in natural waters and soil samples. Biosens Bioelectron 25 1166-1172... 

Rose et al. demonstrated ultratrace detection of 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (DNT) vapors (which are of interest for the detection of buried landmines) by semiconduaing polymer-based optical sensors. The detection mechanism process involves electron transfer from the electron-rich polymer (and a subsequent quenching of its fluorescence) to the analyte, due to the electron-deficient, acidic nature of these analytes. The emission quenching is enhanced as exdtons rapidly difluse within a ptolymer chain, probing multiple sites... 

Disposable screen-printed electrodes are useful single-use sensors for routine analysis. Method of screen printing allows one to construct the whole-electrode systems. Screen-printed carbon thick-film electrodes were used to measure 2,4,6 trinitrotoluene by square wave voltammetry in as little as 50 pL sample volume. This assay was coupled with a solid-phase extraction and the preconcentration factor of 1 500 yielded a 100-fold higher sensitivity resulting in a calibration range of 2 ppb to 2 ppm for 2,4,6-trinitrotoluene. A polyphenol-coated... 

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