Implementation of serial amplifying fluorescent polymer arrays for enhanced chemical vapor sensing of landmines

Abstract

A sensor (known as Fido) that utilizes amplification of fluorescence quenching as the transduction mechanism for ultra-trace detection of nitroaromatic compounds associated with landmines has been described previously 1-3 . Previous sensor prototypes utilized a single band of amplifying polymer deployed inside a capillary waveguide to form the sensing element of the detector. A new prototype has been developed that incorporates multiple, discrete bands of different amplifying polymers deployed in a linear array inside the capillary. Vapor-phase samples are introduced into the sensor as a sharp pulse via a gated inlet. As the vapor pulse is swept through the capillary by flow of a carrier gas, the pulse of analyte encounters the bands of polymer sequentially. If the sample contains nitroaromatic explosives, the bands of polymer will respond with a reduction in emission intensity proportional to the mass of analyte in the sample. Because the polymer bands are deployed serially, the analyte pulse does not reach the bands of polymer simultaneously. Hence, a temporal response pattern will be observed as the analyte pulse traverses the length of the capillary. In addition, the intensity of response for each band will vary, producing a ratiometric response. The temporal and ratiometric responses are characteristic of a given analyte, enhancing discrimination of target analytes from potential interferents. This should translate into a reduction in sensor false alarm rates.

Diffusion of nitroaromatic vapours into fluorescent dendrimer films for explosives detection

“…Such sensors have been successfully incorporated in a lightweight, portable system, which is now commercially available under the brand name Fido (FLIR Systems, Inc.) [5,6].…”

Detection of Explosive Vapors: The Roles of Exciton and Molecular Diffusion in Real‐Time Sensing

“…Exciton diffusion plays a key role in a number of organic optoelectronic applications including organic light‐emitting diodes, photovoltaic cells, and fluorescence‐based sensors. The most widely studied and advanced fluorescence‐based sensors are those used to detect trace‐level concentrations of explosive vapors . The sensing mechanism is relatively simple: in the presence of explosive analyte molecules with sufficiently high electron affinity, electron transfer from the photoexcited sensing material to the analyte occurs, which results in non‐radiative relaxation via the analyte molecule and a loss of fluorescence intensity from the sensing material .…”

“…These recent results are at odds to the early work on explosive sensing using conjugated polymers, in which it was proposed that long exciton diffusion lengths resulted in high sensitivity. Those reports used poly(phenyleneethynylene)‐based (PPE) explosive vapor sensory materials, that contained pentiptycene moieties along the polymer backbone to increase the film porosity and reduce inter‐polymer interactions . Given the unique structure of these PPEs, it is possible that they could interact differently to the materials used in the more recently reported studies on amorphous fluorescent films.…”

“…The most widely studied and advanced fluorescence-based sensors are those used to detect trace-level concentrationso fe xplosive vapors. [1][2][3][4] The sensing mechanism is relativelys imple:i nt he presenceo fe xplosive analyte molecules with sufficiently high electron affinity,e lectron transfer from the photoexcited sensing material to the analyte occurs, which results in non-radiative relaxation via the analyte molecule and al oss of fluorescence intensity from the sensingm aterial. [1,2,5] Clearly this requires the analyte to be sufficiently close to an excited molecule to enablee lectron transfer.I nr eal-time sensing the required interaction can be achievedb ye ither excitond iffusion within the sensing film and/ora nalyte diffusion into the sensing film.…”

Sensing nitroaromatic analytes with a bifluorene-cored dendrimer

“…Chemosensors based on oxidative photoluminescence (PL) quenching of conjugated polymers have proven to be promising candidates, providing a portable technology capable of detecting the trace levels of vapors given off by explosive compounds. 4 For oxidative PL quenching to be effective in detecting explosive analytes, the sensing material needs to be highly luminescent in the solid state, have an affinity for the analyte, and have suitable energy levels for the oxidation process to occur spontaneously. In principle, the sensing mechanism is simple; in the absence of an analyte photoexcitation of the sensing material leads to the generation of an exciton, which in turn can decay radiatively.…”