Scientists from Russia have transformed carbon nanotubes into the detector ammonia

© Photo : Ivan Bobrinetskiy of ammonia, created by Russian scientists of nanotubesScientists from Russia have transformed carbon nanotubes into the detector ammonia© Photo : Ivan Bobrinetsky

Physics from Zelenograd and their foreign colleagues have developed ultra-sensitive sensors of ammonia from carbon nanotubes capable of detecting the presence of molecules of this gas in human breath, according to a paper published in the journal Nanotechnology.

«Our detectors are suitable for use in medical purposes. For example, we can analyze the human condition in his breath,» says Ivan Bobrinetsky of the National research University «MIET», Zelenograd, whose word brings the press service of the Russian science Foundation.

Since the discovery of carbon nanotubes in 1991, they predicted a future in modern industry. They have many useful properties — good electrical and thermal conductivity, high strength and mechanical resistance. First experiments have shown that nanotubes are extremely difficult to apply in practice due to their small size and difficulties in their connection and interweaving into a single fiber.

On the other hand, the addition of nanotubes in other materials, or their «insert» in the cells of living creatures were more promising thing. For example, recently scientists have found that embedding the nanotubes into the leaves of plants makes them ultra-sensitive detectors of explosives, glowing with the appearance in the air of traces of their molecules and triples the efficiency of photosynthesis.

Bobrynets’kyi and his colleagues found another application for the nanotubes, making them ultra-sensitive sensor of ammonia gas, is widely applied in industry, and involved in many life processes in humans and other animals. For example, the presence of ammonia in exhaled air can indicate problems with the kidneys, liver, or infection with the bacteria Helicobacter pylori.

This sensor, as they say, the researchers are working around the same principle as the plant is the»detector» of explosives – nanotubes conductivity change much, if they are temporarily joined by a molecule of ammonia.

Following this idea, bobrynets’kyi and his colleagues produced several prototypes of such detectors, «glue» two types of nanotubes not containing impurities and covered by molecules of formic acid. These tubes, as explained physics, react to the presence of ammonia molecules with different power that allows you to accurately measure its concentration even in that case, if the air contains only a few dozen molecules of ammonia per million of other molecules.

As shown by experiments with these sensors, such sensors ammonia have several advantages compared to conventional metal detectors the gas, they work at room temperature, require significantly less electricity and do not require cleaning. Accordingly, they can be used not only for medical purposes, but observations of the environmental conditions on city streets and indoors.