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Korean scientists have developed a sensor built from polymer nanostructures that can detect extremely minute concentrations of nerve gas, is less expensive than current models, lightweight, wearable, and can be used continuously.
Jyongsik Jang, a polymer scientist at Seoul National Laboratory, says the sensor can detect nerve gas at concentrations as low as 10 parts per trillion, reports Katherine Bourzac of Chemical & Engineering News. With further development, the flexible sensor could mean that it could be worn by those needing to detect chemical weapons, the scientists hope.
The key to the sensor’s effectiveness is its increased surface area caused by the nanostructures. Bourzac explains the manufacturing process:
Jang’s sensors use the inexpensive conductive polymer poly(3,4-ethylenedioxythiophene). When chemists add hydroxyl groups to PEDOT’s sidechains, the polymer can interact with organophosphates via hydrogen bonds. This interaction changes the polymer’s electrical resistance, which simple electronics can easily measure. The more surface area a PEDOT sensor has to interact with gases in the environment, the stronger the response, Jang’s team reasoned. Based on that idea, they wanted to make hydroxylated PEDOT nanostructures to maximize surface area, and in turn produce ultrasensitive sensors.
The manufacturing process starts by electrospinning mass of the polymer to make the nanotubes. Scientists then use vapor to coat the tubes’ surfaces with nanosized nodules. The coating doubles the surface area. Scientists make resistors out of mats of these tubes and place them between two wires on a plastic sheet to give the sensing device flexibility.
To test the sensors, the researchers used dimethyl methyl phosphonate, a standard gas used as a stand-in for the nerve gas, sarin. The tubes coated with nanorods performed the best, measuring changes in resistance at concentrations as low as 10 parts per trillion. This ability at detection is two to three orders of magnitude more sensitive than previously reported sensors, Jang says.
Currently, soldiers and police use mass spectroscopy-based devices to detect organophosphates, a group of chemicals that include sarin. Jang’s sensor would be less expensive, more sensitive, and lighter, he says. His team is now developing ways to make the device, with its power source and all other necessary parts, wearable.
One advantage of these sensors is that they can be used continuously because the gas molecules don’t stay bound to the polymer for long, freeing up its detection capacity, says Paul Rhodes, a team manager at the chemical sensor company, nanoscience.
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