Researchers at MIT have created a new detector that can continuously monitor toxic gases, offering a low-cost and effective solution for industrial and domestic settings.
Traditional gas detection systems often can only be used a few times, but this innovative detector provides continuous, long-term monitoring.
The new system combines two existing technologies in a way that maintains their benefits while eliminating their drawbacks.
The team used a material called a metal-organic framework (MOF), which is highly sensitive to tiny gas traces but quickly degrades. They combined it with a polymer material that is durable and easy to process but much less sensitive.
The results of this research were published in the journal Advanced Materials by MIT professors Aristide Gumyusenge, Mircea Dinca, Heather Kulik, and Jesus del Alamo, along with graduate student Heejung Roh and postdocs Dong-Ha Kim, Yeongsu Cho, and Young-Moo Jo.
MOFs are highly porous materials with large surface areas, making them excellent for capturing gas molecules. The MOFs used in this work are highly electrically conductive and can be tailored to be selective for specific gases.
“If you are using them as a sensor, you can recognize if the gas is there if it affects the resistivity of the MOF,” says Gumyusenge, the senior author of the paper.
However, MOFs can become saturated and stop detecting new gases, which is not ideal for continuous monitoring. To address this, the team used a polymer composite that can respond to gases without permanently binding to them.
“The polymer, even though it doesn’t have the high surface area that the MOFs do, will at least provide this recognize-and-release type of phenomenon,” Gumyusenge explains.
The team mixed the polymers in a liquid solution with the MOF material in powdered form and applied this mixture to a substrate, creating a uniform, thin coating. By combining the polymer with the MOFs in a one-to-one ratio, they achieved a sensor that has both the high sensitivity of the MOF and the reversibility provided by the polymer.
When gas molecules are temporarily trapped in the material, the electrical resistance changes. These changes can be continuously monitored by attaching an ohmmeter to track the resistance over time.
The team demonstrated the material’s ability to detect nitrogen dioxide, a toxic gas produced by many combustion processes, in a small lab-scale device. The material maintained its performance for 100 detection cycles, with only a slight variation of about 5 to 10 percent.
This new composite material is much more sensitive than most existing detectors for nitrogen dioxide. Reliable detection of this gas is important, as it has been linked to many asthma cases in the U.S. The team demonstrated that their composite could detect nitrogen dioxide at concentrations as low as 2 parts per million.
While the demonstration focused on nitrogen dioxide, Gumyusenge says the chemistry can be adjusted to target other toxic gases. The polymer allows the material to be deposited as a very thin, uniform film, unlike traditional MOFs, which are usually in powder form. This thin film requires little material, making production costs low and compatible with industrial coating processes.
The next steps for the team will be to test the material in real-life settings. For example, it could be applied as a coating on chimneys or exhaust pipes to continuously monitor gases through readings from an attached resistance monitoring device.
“We need tests to check if we truly differentiate it from other potential contaminants that we might have overlooked in the lab setting,” Gumyusenge says. “Let’s put the sensors out in real-world scenarios and see how they do.”
This breakthrough in continuous gas detection technology offers a promising solution for better safety in both industrial and domestic environments.
Source: MIT.
