Scientists from Shanghai University of Electric Power and University of Adelaide have developed a fluorescent sensor capable of detecting small quantities of explosives, reports the journal, Sensors and Actuators B: Chemical.
The sensor works in a way that it detects explosives in concentrations as low as 6.3 parts per million by employing a process called quenching â€“ the ability of certain materials to reduce the fluorescence intensity of light. Moreover, since nitroaromatics found in most commonly used explosive materials—trinitrotoluene (TNT), dinitrotoluene (DNT) and picric acid (PA)—happen to have high electron deficiency, they are suitable for quenching florescence.
To test the technique, scientists used samples of explosives sucked through capillary action in the holes of the fiber. Also, the fibers were previously coated with special plastic designed to emit red light when illuminated by a green laser.
So how exactly did it work? Scientists pointed the green laser at fibers containing different quantities of explosives â€“ the more explosive materials were present in a sample, the more fluorescence was quenched. This caused the fiber to emit a reduced amount of red light and gave researchers not only the ability to detect explosives, but also to measure their amount.
This is a major breakthrough for bomb detecting, because so far contemporary techniques have been designed to look for the metals that coat explosive materials in devices such as landmines instead of the materials themselves. Meanwhile, many homemade explosive devices made nowadays don't even feature any metal parts. This new method gives law enforcers the ability to detect explosives themselves without the risk of setting them off in the process.