Chemical terrorism has been a concern since the 1995 sarin attack in Tokyo's subway system. With that threat the need for quick identification of what chemical is being used in another attack is something scientists have been trying to devise.
That device may have finally been achieved by a team of chemical engineers from Massachusetts Institute of Technology(MIT), led by
Michael Strano. Their device can detect chemical agents in concentrations as low as 25 parts in a trillion.
Dr. Strano's invention was written up in Angewandte Chemie. The device contains an array of treated carbon nanotubes, each with a layer of carbon atoms that have been coated with nitrogen-containing molecules called amines and rolled into a cylinder with the amines on the outside. Each of the tiny tubes run between pairs of tiny electrodes. The entire device when activated carries an electric current with the power of about 300 microwatts.
A silicon chip passes the gases to be analysed to the nanotubes, which are 1/50,000th the size of a human hair, by way of a miniature column. Gases tend to stick to the sides of the column as they make their way to the nanotubes. Some gases stick more than others slowing the speed they travel down the column. As the components of the gases is puffed into the nanotubes it sticks to the carbon atoms. Those components then cause the conductivity of the nanotubes to change. Each gases changes the tubes in a different way.
The amines now go to work. Each nitrogen atom of amines have what chemists call a lone pair of electrons. This is what attaches each amine molecule to the nanotube. The lone pair interactions are what changes the chemical characteristics of the carbon.
If these gases stuck indefinitely to the nanotubes the device would have a short life as a detector. What makes Strano's device perfect in the fight against chemical warfare is that the amine-plastered carbon is not so sticky so that the gas molecules soon detach from it. The device is quickly able to start detecting the next errant gases that comes its way.
The small size of the device and the minute amount of power it requires to operate makes it a perfect match for the type of places a gas attack would be the most successful like in subways. It's even been suggested that policemen can carry one in their pocket.
While the device doesn't take away the threat it does speed up the time it takes to detect one and IDs the gas involved. That quick process could save countless lives if an attack were to occur in a busy subway station.
