Nitrogen dioxide (NO2) is an air pollutant emitted by fossil fuel-powered cars and gas-burning stoves that is not only bad for the climate, say the researchers, but has been linked to increased heart disease, respiratory diseases such as asthma, and infections in humans. Odorless and invisible, NO2 requires a special sensor that can accurately detect hazardous concentrations.
However, say the researchers, most currently available sensors are energy intensive as they usually must operate at high temperatures to achieve suitable performance. Their new 2D sensor on the other hand works at room temperature and thus consumes less power than conventional sensors.
The researchers say that the sensor - which is constructed from a monolayer alloy of rhenium niobium disulfide - also boasts superior chemical specificity and recovery time. Unlike other 2D devices made from materials such as graphene, the new 2D sensor electrically responds selectively to nitrogen dioxide molecules, with minimal response to other toxic gases such as ammonia and formaldehyde.
The new 2D sensor is able to detect ultra-low concentrations of nitrogen dioxide of at least 50 parts per billion, say the researchers. In addition, once a sensor based on molybdenum disulfide or carbon nanotubes has detected nitrogen dioxide, it can take hours to recover to its original state at room temperature, while the new sensor reportedly takes just a few minutes.
In addition to being ultrathin, the new sensor is also flexible and transparent, say the researchers, which makes it a great candidate for wearable environmental- and health-monitoring sensors.
"If nitrogen dioxide levels in the local environment exceed 50 parts per billion, that can be very dangerous for someone with asthma," says Amin Azizi, a postdoctoral scholar from UC Berkeley and lead author of the current study, "but right now, personal nitrogen dioxide gas sensors are impractical."
Their sensor, if integrated into smartphones or other wearable electronics, say the researchers, could fill that gap. For more, see "High-Performance Atomically-Thin Room-Temperature NO2 Sensor."