Carbon Nanotube-based Material for Chemical Weapons Protection

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Sarin gas can have lethal effect, Photo by Decoded Science.

Sarin gas can have lethal effect, Photo by Decoded Science.

Scientist from National Institute of Standards and Technology (NIST) have developed a material which can degrade chemical weapons, such as sarin nerve gas. The material is made with modified carbon nanotubes and potentially could be embedded in fabric, to make protective clothing.

Chemical Weapons: Nerve Gas

The use of chemical weapons during ongoing conflicts and/or by terrorist groups is one of the most scary and dangerous threats of our times.

The most common and toxic chemical weapons are molecules which contain an organo-phosphate group; they include Sarin (GB), Tabun (GA) and Soman (GD).

We call them nerve gases, as they interact with the nervous system and cause irreversible damage. More specifically, these chemicals degrade an enzyme – acetylcholine esterase – which takes part in nervous stimulus transmittance.

In the presence of this enzyme, muscles can relax after receiving the nervous stimulus; without it, on the other hand, the muscle is unable to relax and continues to get stimulated. This continuous process eventually leads to death.

Protection Against Nerve Gas

Nerve gases can be very dangerous, as they cause death few minutes after exposure; the contact of the gas with human skin, for instance, can be lethal. Moreover, when they not cause death, these chemicals can bring long term psychological and physical damages, which can include post-traumatic stress disorder (PTSD), diminished intellectual and motor capabilities, and heart damage.

To avoid this, it is necessary to use protection with clothing (i.e. cloths, gloves, etc.) which is chemically resistant; these protective items, however, have to be successively chemically treated and disposed, to avoid the contamination of the environment and/or accidental contact with other people.

Degrading Nerve Gas

A more effective approach to nerve gas protection is the development of materials which could degrade the gases themselves, with chemical reactions which turn them into non-toxic molecules.

Ideally it should be possible to embed these materials into fabric/protective items, to protect people who could come in contact with the gases, for instance during site decontamination.

Single wall carbon nanotube. Photo by Arnero.

Single wall carbon nanotube. Photo by Arnero.

Novel Developments: Carbon Nanotube Derivate

Scientists from the National Institute of Standards and Technology (NIST) developed a new material which, potentially, could be used for nerve gas protection. They published the results of their study in Nano Research in May 2014.

Their material is made of modified single wall carbon nanotubes (SWCNTs).

Carbon nanotubes are materials made of carbon (C) atoms; each atom is bonded to three more carbon, like in graphite sheets or graphene. In the nanotubes, however, the sheets are not planar but arranged in a tube-like form. As the name suggests, SWCNTs are made of a single tube; in multiwall carbon nanotubes (MWCNTs), on the contrary, there are several concentric tubes with different diameters.

SWCNTs Modification

In their study, NIST scientists used carboxylated SWCNTs, i.e. nanotubes in which a carboxylic group COOH could react with an amine group. They performed a reaction with a polymer containing an amine group and a copper salt – copper chloride (CuCl2). In this way, the product was a material made of SWCNTs with a side chain attached to it bearing a copper atom.

This is the “active” site which could degrade the nerve gas.

Testing the Material

To test the material’s performance, the researchers did not use real nerve gas, but 4-nitrophenol phosphate disodium, a less dangerous molecule which simulates the nerve gas behavior, as it reacts in the same way.

They placed some of their material on a cellulose-ester membrane; this membrane was successively placed in a solution containing the simulating molecule. The reaction was followed by monitoring the color absorption of the solution at a wavelength of 420 nm.

Control tests were also performed, using solutions containing the simulating molecule with either no material or unmodified SWCNTs.

Interesting Results

The results of this study were really interesting; in fact no color change was observed in the control experiments, while the solution containing the modified material became more and more yellow with time. This indicated that the phosphate molecule had been degraded by the material; this is a very positive and important result.

For a practical application, there is still a lot of work to do; in fact scientists have to optimize the system and find the best way to embed this material into a fabric or in any other matrix. This first test, however, showed that there is a material which can effectively degrade the dangerous chemicals nerve gases are made of.

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