A research team recently came up with a new kind of nanosensor that can determine presence as well as quantity of explosives like TNT. The new technique offers a strong replacement for sniffer dogs and will open up doors for better sensing applications for several target analytes. The nanosensors are composed of two components mainly: field effect transistors based on silicon nanowires and metal-organic polyhedral molecular cages. The blend of these two parts permits the sensor to detect 2, 4, 6 -trinitrotoluene (TNT).
Imagine a very small chemical cage that only has space to accommodate a single molecule like TNT. Apart from getting the right size you will have to ensure that target molecule also matches up with the cage just like a piece of puzzle. One of the team members, Louis de Smet, further explains, “In the case of relatively small molecules, as with explosives, the challenge is to ensure that the cage structure is not only the right size but that it also has the right anchor points so that the molecule can click into place—thus rendering it detectable.”
MOPs have proved their worth in terms of sensing applications as these can be tuned for various molecules. De Smet further adds, “Through variation with a large number of geometric and electronic properties of these complex cage molecules, we are able to capture the ‘explosive’ molecules we are looking for.” However, the creating a cage for trapping TNT molecule is just the beginning. You also need some other way to see if you have catched the right one and that’s the point where FETs based on SINW enter the scene.
Whenever a local change takes place in the charge density of these devices, the current passing through SINW channel changes. This change in the charge density gets induced with the binding of a molecule or an ion. SO, when multiple MOP cages are placed over a SINW chip, a system is created that responds well to target analyte. De SMet also adds, “The presence of [TNT molecules] causes the electrical conductance of the underlying silicon nanowires to change in a very characteristic way. We can measure this and thus confirm that we have actually found TNT molecules from an explosive.”
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