MIT Researchers Create Carbon Nanotube Pencils That Sniff Out Hazardous Gases

October 15, 2012, By Sanjeev Ramachandran

Pencils…I don’t remember the last time I used one. I do remember the times when a pencil was one of the most important possessions I had. Now with smartphones and tablets overflowing into our lives, I wonder whether a pencil could ever take up that innocent importance again.

While the common pencil might not be used as frequently by us again, a certain type of pencil might be used, not by everyday folks like us, but some other brains. This pencil, created by a MIT chemistry postdoctoral student, doesn’t have the same old graphite point.

Katherine Mirica and her colleagues have replaced the old lead with a highly compressed powder which is made of commercially available nanotubes. This new replacement can do something other than writing; it can carve out sensors on any paper surface.

With this new found ability in hands, the MIT team is planning to create sensors that can detect sulphur compounds. This could provide a useful tech to finding out natural-gas leaks.

The leader of the research team and a MIT chemistry professor, Timothy Swager, said that this could be used in sensing out almost anything volatile. “The beauty of this is we can start doing all sorts of chemically specific functionalized materials,” he said.

The German Journal Angewandte Chemie published a paper titled “Mechanical Drawing of Gas Sensors on Paper”, and in it describes sensors that can detect minute amounts of ammonia gas. Ammonia gas is a hazardous substance and colorless, and these sensors can sniff out almost any type of gas.

Carbon nanotubes have been found to be effective in smelling out gases. The gaseous substance binds to the nanotube and they obstruct the electron flow.

However, to create sensors with carbon nanotubes, they have to be dissolved in a solvent like dichlorobenzene, and the process involved is hazardous and unreliable. But the MIT brains have done it another way, bypassing the risky procedure.

The new fabrication method is entirely solvent-free. What the researchers did was draw a line of the carbon nanotubes on a sheet of paper which was imprinted with small electrodes; the electrodes were made of gold and this helps to measure the electric current that passes through the tiny cylinders.

The project had the backing of the military. The research received funds from the Army Research Office through MIT’s Institute for Soldier Nanotechnologies.

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