A group of researchers from the Cambridge Graphene Centre in the United Kingdom has created a new detector for formaldehyde using aerogel technology. Formaldehyde, a volatile organic compound (VOC), can be toxic to the immune system, nervous system, developmental system, and respiratory system. Formaldehyde can also cause cancer. This chemical is difficult to identify using existing gas-detecting devices. Gas-detecting devices currently in use can sense VOCs, but these devices only yield a single concentration number regardless of the type of VOC contaminant present in the air, and most cannot function unless heated. The new detector from the Cambridge Graphene Centre addresses these issues because it is engineered to work at room temperature, meaning the device uses between 10–100 times less power than existing sensors, and can identify which specific VOC contaminants are present. See also: Formaldehyde

Polyurethane foam can contain formaldehyde, a cancer-causing substance. Sensors made from a new type of graphene aerogel can detect toxic formaldehyde in homes and offices. (Credit: anatoliy_gleb/Getty Images)

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Existing gas detectors, generally metal oxide semiconductors (MOS), are widely used for detecting harmful gases that contribute to indoor air pollution. MOS detectors are diverse, stable, simple in structure, and cost-effective to produce. Unfortunately, these sensors have a slow response time and are further hindered by poor sensitivity at room temperature and high-power consumption when heated to working temperature. Notably, the sensors also face the barrier of poor contaminant specificity due to interference from background “noise” in the air. See also: Gas; Indoor air pollution

Researchers are pursuing graphene-based aerogels to solve these problems. Graphene is a two-dimensional, one-atom-thick layer of carbon atoms arranged in a hexagonal pattern. 3D printing of graphene layers into a structure infused with quantum dots (a type of photodetector) allows for specific shapes to fine-tune the detectors’ sensitivity. Precise engineering of the shape of the printed graphene lattice allows the sensors to be specific to formaldehyde, and the porous nature of the resulting aerogel permits gases to freely diffuse through the sensor. The sensor also relies on artificial intelligence, trained via machine learning on background noise interference, which helps to further improve accuracy by filtering out unrelated data. See also: 3D printing; Artificial intelligence; Graphene; Machine learning

Graphene sheet consisting of a hexagonal array of covalently bonded carbon atoms.

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The new aerogel sensors have an ultralow limit of detection at 8.02 parts per billion (ppb) while consuming only about 130 microwatts of power. This sensitivity is more than sufficient to measure formaldehyde levels at or below the workplace exposure limit set at 2 parts per million (ppm) in the United Kingdom, 0.75 ppm in the United States, and other regulatory limits set worldwide. Because of the new sensor material’s specificity, low minimum detection levels, and low power consumption, this technology shows great promise for future use. The researchers also suggest the same technique could be used to develop sensors for other VOCs, altering the material’s structure as necessary to be specific to other gases. In theory, a device the size of a standard carbon monoxide detector could be constructed with several different sensor types inside it, providing real-time levels of multiple hazardous gases in a home or business. See also: Gel