Graphene foam detects explosives.

The latest piece of research conducted by  Rensselaer Polytechnic Institute demonstrates the potentially life saving advances that investing in graphene may bring to the security and law enforcement sector. Reports that graphene foam outperforms the best, commercially available, gas sensors in the detection of dangerous and explosive chemicals add further support to the notion that its use in sensors will be one of the market areas in which it comes to dominate. The discovery paves the way for a whole range of improvements in the equipment used by bomb squads, law enforcement officials, defense organizations, and in various industrial settings.

The new sensor successfully and repeatedly measured ammonia (NH3) and nitrogen dioxide (NO2) at concentrations as small as 20 parts-per-million. Made from continuous graphene nanosheets that grow into a foam-like structure about the size of a postage stamp and thickness of felt, the sensor is flexible, rugged, and finally overcomes the shortcomings that have prevented nanostructure-based gas detectors from reaching the marketplace.

The biggest breakthrough for the Rensselaer research team is the ability to produce a postage-stamp sized piece of foam-like graphene. The production process involves “growing” the graphene on a structure of nickel foam and then dissolving the substrate to leave a graphene network that can be used to detect gases. Yet again the production improvements make the whole concept of industrialisation of the process more feasible.

Graphene works well as a gas detector because the surface is particularly good at attracting and trapping alien molecules to it, which in turn affect the electrical conductivity of the material. Since the surface chemistry and therefore electrical resistance is changed differently by different chemicals the detector is capable of not only identifying the presence of a gas but also the constituent chemicals that may be present. In addition the sensor can be easily cleaned by simply applying a 100 milliampere current through it which detaches any trapped chemicals. The result is therefore a re-useable, highly sensitive, sensor that is one step closer to being a ready for market.

“We see this as the first practical nanostructure-based gas detector that’s viable for commercialization,” said Koratkar, a professor in the Department of Mechanical, Aerospace, and Nuclear Engineering at Rensselaer.

“Our results show the graphene foam is able to detect ammonia and nitrogen dioxide at a concentration that is an order of magnitude lower than commercial gas detectors on the market today… In a sense we have overcome the Achilles’ heel of nanotechnology for chemical sensing. A single nanostructure works great, but doesn’t mean much when applied in a real device in the real world. When you try to scale it up to macroscale proportions, the interfaces defeats what you’re trying to accomplish, as the nanostructure’s properties are dominated by interfaces. Now we’re able to scale up graphene in a way that the interfaces are not present. This allows us to take advantage of the intrinsic properties of the nanostructure, yet work with a macroscopic structure that gives us repeatability, reliability, and robustness, but shows similar sensitivity to gas adsorbtion as a single nanostructure.”

The advances in gas sensor technology is just one of the improvements resulting from institutional investment in graphene research. The list of potential devices grows on a daily basis, and with each advance comes a new investment opportunity.


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