Metal Modified CNT Sensors for Monitoring Landfill Gas

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(The pictures above are of the vertically aligned carbon nanotubes with 5nm platinum, ruthenium, and silver nanoparticles sputtered to the surface of the nanotubes.)


Unmodified and metal-modified Carbon Nanotube (CNT) sensors are arranged in an array to create an electrochemical resistor used to monitor landfill gas content.  This single array is capable of continuously monitoring carbon dioxide, carbon monoxide, nitrous oxide, hydrogen, and methane gas emissions from landfills.  Some of these emissions are greenhouse gases while others are contributors to malodors. 

The array is composed of four chips arranged on an aluminum substrate.  Each chip is composed of vertically aligned CNTs grown on substrates covered in an iron nanofilm catalyst.  Three of the chips contain 5nm thick platinum, ruthenium and silver nanoclusters, while the fourth chip has no added catalysts. 

On top of the CNT array are two strips, one a 20nm thick layer of chromium and the other a 300nm thick layer of gold, creating contacts for the electrical current.  The presence of gas changes the resistance of the electrical current, allowing for real-time, precise measurement of the individual gases that make up landfill gas.  This technology can be used in environmental monitoring and remote sensing of odorous and climate altering gases.

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This technology is used for the monitoring and identification of landfill gases and their respective concentrations.




Benefit Summary: 

This technology allows for accurate, real-time monitoring of landfill gases and their concentrations in waste and waste to energy facilities.


Risk Summary: 

While fixed small aspect nanoparticles and nanocoatings pose no immediate biological health risks, the free small aspect nanoparticles may pose biological health risks. During the manufacturing of the platinum nanoparticles, disposal of nanoparticle containers, and fabrication of the nanocoatings on the membrane anodes there is a potential for human, ecological, and environmental health risks. Platinum is a heavy metal from the platinum group, and platinum nanoparticles have been shown to be potentially toxic. Studies have shown that Platinum nanoparticles transfer to animal tissues and are recycling in organic synthesis—they can be passed through animal faeces and to offspring. Nanoparticles however have not been shown to be bio-accumulating. Additionally, free large aspect nanoparticles such as carbon nanotubes have been shown to be very disruptive because they can pierce cell membranes. CNTs are also one of the strongest nanomaterials and do not readily biodegrade. Research has shown that they may be comparable to asbestos in their cytotoxicity, making them a possible carcinogen. There is likely little risk of release of the CNTs in this application since they are grown directly on the end-use substrate, but the risk may still be present.

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