Scientists in India have for the first time developed a thermally stable and economical polymer-based electronic sensor to rapidly detect nitro-aromatic chemicals used in high-energy explosives, the Department of Science and Technology (DST) said on Friday.
Detecting explosives without destroying them is essential for protection, and criminal investigations, minefield clearance, military applications, munitions decontamination sites, security applications and chemical sensors play a vital role in de such cases, he said.
Explosive poly-nitroaromatic compounds can generally be analyzed by sophisticated instrumental techniques. But the requirements for rapid decision-making in criminology labs or salvaged military sites or for detecting explosives in possession of extremists often require simple, inexpensive and selective field techniques, which will be non-destructive in nature, a declared the DST.
Non-destructive detection of nitroaromatic chemicals (NACs) is difficult, he said.
While previous studies are mainly based on the photoluminescent property, detection based on the conductive property has not been explored so far, he said.
The detection on the basis of the conductive property helps to make a practical detection device where the results can be seen using LEDs, the department said.
To overcome these drawbacks, a team of scientists, led by Neelotpal Sen Sarma of the Institute of Advanced Study in Science and Technology, Guwahati, an autonomous institute of the DST, developed a Layer-by-Layer Polymer Detector (LBL) composed of two organic polymers – poly-2-vinylpyridine with acrylonitrile (P2VP-Co-AN) and cholesteryl methacrylate copolysulfone with hexane (PCHMASH), he said.
This undergoes a drastic change in impedance (resistance in an AC circuit) in the presence of a very low concentration of NAC vapor within seconds, the DST said.
Here, picric acid (PA) was chosen as the NAC model, and a simple and cost-effective electronic prototype was developed for visual detection of PA. The team has filed for a patent for the new technology funded by the Department of Electronics and Information Technology, he said.
“An electronic detection device built around a polymer gas sensor can quickly detect the explosive on-site,” Sarma said.
The sensor device consists of three layers – copolysulfone polymers of cholesteryl methacrylate with 1-hexene (PCHMASH) and a copolymer of poly-2-vinylpyridine with acrylonitrile by sandwiching PCHMASH between two outer layers P2VP-Co- AN stainless steel (SS), declared daylight saving time.
The sensitivity of the system is determined by monitoring the change in the impedance response over time (seconds) in the presence of the analyte vapor (picric acid), he said.
The three-layer polymer matrix has been shown to be a very effective molecular scavenger for nitroaromatic chemicals. The sensor is fairly simple and reversible in nature, and its response does not change with the change in operating temperature in the presence of other common chemicals and humidity.
The device can be used at room temperature, has a low response time and negligible interference with other chemicals. The manufacture is very simple, is negligibly affected by humidity, and the cholesterol-based polymers used are biodegradable, the DST said.
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