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Novel Device Detects Air Pollution at the Nano Level

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Posted May 14, 2015

A group of researchers from the Nanoparticles by Design Unit at the Okinawa Institute of Science and Technology Graduate University (OIST), the Materials Centre Leoben Austria and the Austrian Centre for Electron Microscopy and Nanoanalysis has developed a novel way of detecting ambient air pollution at the nanoscale.

New gas sensing device promises efficient policing of greenhouse gases at the nanoscale. Image credit: Gilles Tarabiscuité via Pixabay, CC0 Public Domain.

New gas sensing device promises efficient policing of greenhouse gases at the nanoscale. Image credit: Gilles Tarabiscuité via Pixabay, CC0 Public Domain.

The new paper, recently published in the science journal Nanotechnology, details the way these researchers used a palladium (Pd) nanoparticle-covered copper oxide (CuO) nanowire to detect carbon monoxide (CO), which is one of the chief contributors to climate change.

Since copper oxide – a known semiconductor – can be made to undergo dramatic changes in its electrical properties by attaching foreign atoms to its surface at high temperatures, the research team incorporated the CuO nanowire into an electrical circuit, thereby enabling it to detect CO indirectly by measuring the change in the resulting circuit’s electrical resistance to it.

To make the new sensor more efficient, the researchers deployed a sophisticated technique which helped them to first sort the palladium nanoparticles according to size (around 5 nm) and then evenly deposit them onto the nanowire in a four point configuration. Test results demonstrated that the Pd-decorated version of the sensor shows a significantly greater increase in electrical resistance when operating in environments infused with carbon monoxide.

This technique can also be used to layer different nanoparticles at the same time on segregated areas of the sensor, making it capable of detecting a wider range of industrial pollutants.

Palladium nanoparticles were deposited on the entire wafer in an evenly distributed fashion, as seen in the background. They also attached on the surface of the copper oxide wire in the same evenly distributed manner, as seen in the foreground. On the upper right is a top view of a single palladium nanoparticle photographed with a transmission electron microscope(TEM) which can only produce black and white images. The nanoparticle is made up of columns consisting of palladium atoms stacked on top of each other. (This image has been modified from the original to provide a better visualization.) Image credit: OIST

Palladium nanoparticles were deposited on the entire wafer in an evenly distributed fashion, as seen in the background. They also attached on the surface of the copper oxide wire in the same evenly distributed manner, as seen in the foreground. On the upper right is a top view of a single palladium nanoparticle photographed with a transmission electron microscope(TEM) which can only produce black and white images. The nanoparticle is made up of columns consisting of palladium atoms stacked on top of each other. (This image has been modified from the original to provide a better visualization.) Image credit: OIST

While most other gas sensing devices are clunky and largely non-scalable, their tiny new counterparts could prove to be less expensive and easier to produce on a mass scale.

The only foreseeable hurdle to making this nano-contraption the default industrial gas sensor is the high temperatures needed to ensure the requisite electrical response – the study utilized a temperature as high as 350 degrees centigrade.

Further research will aim to examine different nanowire-nanoparticle combinations that might result in tweaks making such extreme heat unnecessary.

“I think nanoparticle-decorated nanowires have a huge potential for practical applications as it is possible to incorporate this type of technology into industrial devices,” said Stephan Steinhauer, a Japan Society for the Promotion of Science (JSPS) postdoctoral research fellow working under the supervision of Prof. Mukhles Sowwan at the OIST Nanoparticles by Design Unit.

The new conductometric (meaning based on fluctuations in electrical conductivity) gas sensor was tested in humid synthetic air that mimics the conditions of its deployment in the future.

Sources: study abstract, oist.jp.

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