IIT Madras develops a very sensitive TNT sensor

Identifying TNT explosives present at a very low concentration — nine molecules — has become possible with a nanostructure-sized sensor developed by T. Pradeep of the Department of Chemistry, IIT Madras.

There is a complete change in luminescence from red to green when TNT is added to the sensor. All that is required to detect the change in luminescence is a fluorescence microscope. The results can be double checked by Raman spectroscopy. Raman spectrum specific to TNT gets enhanced and hence identifying the signature becomes easy.

“Multiple confirmations improve accuracy and are essential in sensor-like applications.” Explaining the principle behind the sensor, he said: “The amine groups of the protein form a complex with TNT. This complex quenches the red luminescence of the silver cluster; the red light therefore goes missing. But absence of luminescence alone is not sufficient as the object would appear dark.” Prof. Pradeep said it is possible to make one billion sensors with one gram of gold. “So it is not worth reusing the sensors after cleaning them,” he said.

A device based on this principle is under development. Work on the mesoflower started in 2008 with P.R. Sajanlal, who is currently doing his post doctorate course. In 2010, Ammu Mathew, a doctoral student, began the work of developing the sensor. “We could get the sensor in place in just one-and-half years,” he said. The results were published on Monday in the journal Angewandte Chemi .

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