An example of a flexible gas sensor made with the new nanocomposite. Photo: Cheng Lab, Penn State.
An example of a flexible gas sensor made with the new nanocomposite. Photo: Cheng Lab, Penn State.

A stretchable, wearable gas sensor for environmental sensing has been developed and tested by researchers from Penn State, Northeastern University and five universities in China. As the researchers report in a paper in Materials Today Physics, the sensor combines a newly developed laser-induced graphene foam material with a nanocomposite made from a unique form of molybdenum disulfide and reduced graphene oxide.

The researchers were interested in seeing how different morphologies, or shapes, of the gas-sensitive nanocomposite affects the material's sensitivity for detecting nitrogen dioxide molecules at very low concentrations. Nitrogen dioxide is a noxious gas emitted by vehicles that can irritate the lungs at low concentrations, and lead to disease and death at high concentrations.

To change the morphology of the nanocomposite, the researchers packed a canister with very finely ground salt crystals. When they then added molybdenum disulfide and reduced graphene oxide precursors to the canister, the nanocomposite formed in the small spaces between the salt crystals.

The researchers tried this with a variety of different salt crystal sizes and tested the sensitivity of the resulting nanocomposites on conventional interdigitated electrodes, as well as on the newly developed laser-induced graphene foam. When the salt was removed by dissolving it with water, the researchers found that the smallest salt crystals produced the most sensitive sensor.

"We have done the testing to 1 part per million and lower concentrations, which could be 10 times better than conventional design," says Huanyu 'Larry' Cheng, assistant professor of engineering science and mechanics and materials science and engineering at Penn State. "This is a rather modest complexity compared to the best conventional technology, which requires high-resolution lithography in a cleanroom."

"The paper investigated the sensing performance of the reduced graphene oxide/moly disulfide composite," said Ning Yi and Han Li, doctoral students at Penn State and co-authors of the paper. "More importantly, we find a way to enhance the sensitivity and signal-to-noise ratio of the gas sensor by controlling the morphology of the composite material and the configuration of the sensor-testing platform. We think the stretchable nitrogen dioxide gas sensor may find applications in real-time environmental monitoring or the healthcare industry."

This story is adapted from material from Penn State, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.