| TECHNOLOGY |
Other sensor systems rely on detecting the molecular shape or a specific spectroscopic signature of a chemical warfare agent. But an enemy could change the shape of the molecule slightly so the detectors don’t respond to it. As he’s fond of pointing out, “It isn’t the shape of the molecules that kills you—it’s their reactivity.” new chemosensor, detects nerve agents by how they react with an indicator molecule. One of their indicator molecules is a naphthalene derivative bearing a pyridyl and a hydroxy (or siloxy) substituent. (Y = H,SiR3). In the detection system, organophosphates, which are used as model compounds for the nerve agents, react with the hydroxy or siloxy group of the indicator to form a phosphate ester. Because this ester is a good leaving group, the indicator molecule spontaneously undergoes an intramolecular cyclization reaction, yielding a tetracyclic product that fluoresces at a different wavelength and intensity than the starting compound. Authors have shown that the sensor, in the form of a thin film, responds in seconds to 10 ppm of diisopropylfluorophosphate vapor, which is a less reactive relative of sarin gas. Visually, the sensor signals the presence of a toxic compound by shifting its fluorescence emission from blue to green. “It would be better visually if it was green to red,” author says, noting the dye could be modified to optimize the response. He believes that the sensor has the potential to detect nerve agents in the sub-parts-per-billion range. The system is not designed to identify the agents it detects. When used with the firm’s vapor-phase fluorescence sensor platform, he says, indicator compounds provide rapid detection of nerve agents. indicator also responds to similarly reactive toxic industrial chemicals, such as thionyl chloride (SOCl2), that could also pose a threat to homeland security
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