New Ultra-Thin Sensor Can Detect Tiny Amounts of Harmful Air Pollution in Your Home

April 18, 2016 | Joanne Kennell

A common air filter, being cleaned with a vacuum cleaner.
Photo credit: Janwikifoto/Wikipedia (CC BY-SA 3.0)

Is the air in your home making you sick?

We spend a lot of time indoors, probably more than we should. And sometimes we have the misconception that the air inside our homes is cleaner than the air outside. But unless you swap your high-quality furnace filter every six months, and keep your home immaculately spotless, your indoor air is likely polluted.

Unfortunately, harmful chemical gases, such as carbon dioxide (CO2) and volatile organic compounds (VOCs), are found in numerous materials, including furniture and household goods. Over the years, these gases have resulted in an increasing health problem known as sick building syndrome (SBS) or sick car syndrome. The pollutants are also thought to contribute to diabetes and obesity.

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To help combat SBS, scientists from the University of Southampton, in partnership with the Japan Advanced Institute of Science and Technology (JAIST), have developed a graphene-based (single atomic sheet of carbon atoms arranged in a honeycomb-like hexagonal crystal lattice structure) sensor and switch that can detect harmful air pollution in the home with very low power consumption.

Harmful chemical gases have low concentrations of parts per billion (ppb) levels and are extremely difficult to detect with current environmental sensor technology, which are only sensitive to concentrations of parts per million (ppm).

The research group, led by Hiroshi Mizuta, Jian Sun, and Manoharan Muruganathan, developed the sensor to detect individual CO2 molecules “adsorbed” (bonded) to the suspended graphene one-by-one by applying an electric field across the structure (see diagram below).

graphene sensor

Photo credit: University of Southampton

By monitoring the electrical resistance of the graphene, the adsorption and desorption of the individual CO2 molecules onto the graphene was detected as “quantized” changes in resistance.

In the study, published in the journal of the American Association for the Advancement of Science (AAAS), a small volume of CO2 gas (equivalent to a concentration of approximately 30 ppb) was released and the detection time was just a few minutes, which is pretty fantastic.

"In contrast to the commercially available environmental monitoring tools, this extreme sensing technology enables us to realise significant miniaturisation, resulting in weight and cost reduction in addition to the remarkable improvement in the detection limit from the ppm levels to the ppb levels," said Mizuta in a press release.

Research group members, Harold Chong, Marek Schmidt, and Jian Sun, have also recently developed graphene-based switches using a uniquely thin film produced at the University of Southampton. The switches require very low voltages (below 3 volts), and can be used to power electronic components on demand — improving the battery lifetime of personal electronic devices.

Mizuta and the team are now hoping to bring the two technologies together to create ultra-low-power environmental sensor systems that can detect several different types of single molecules.

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