Scientists find that a 10-millisecond flash could help build more sensitive gas sensors

Nitrogen dioxide is a harmful gas that requires sensitive detection. Researchers used intense light pulses lasting 10 milliseconds to make molybdenum disulfide flakes and anchor isolated metal atoms in one step. Adding platinum improved the material's room-temperature response to nitrogen dioxide, reaching 100.8% at 400 parts per billion and a detection limit of 17.2 parts per billion. This approach could support advanced gas sensors and applications in catalysis and energy technologies.

A light pulse preserves reactive sites

Many gas sensors detect gases through changes in a material's electrical properties. Molybdenum disulfide (MoS₂) is promising, but much of its surface is inactive. Its more reactive edges can be difficult to preserve during conventional heating, while added catalyst metals may clump together instead of remaining as individual atoms.

The research was jointly led by Professor Il-Doo Kim from Korea Advanced Institute of Science and Technology (KAIST) and Assistant Professor Dong-Ha Kim from Hanyang University-ERICA as co-corresponding authors, with Dr. Euichul Shin from KAIST serving as the first author.

They used flash thermal synthesis, driven by intense pulsed light, to turn a molybdenum-containing precursor into thin MoS₂ flakes. A single 10-millisecond pulse heated the material to as high as 1,811°C, then cooled it rapidly in ambient air. Platinum, iridium or gold atoms could be incorporated during the same step.

The paper is published in the journal Advanced Materials.

The brief, intense heating helped limit the growth of large flakes and kept the added metal atoms dispersed across the material rather than forming agglomerated metal nanoparticles.

Platinum boosts nitrogen dioxide detection

In tests, the flash-made MoS₂ produced a 23.6-fold stronger response to 5 parts per million of nitrogen dioxide (NO₂) than material made by a conventional solvothermal method. Adding 1.2 weight% platinum boosted response 22.8-fold: the sensor response reached 100.8% when exposed to 400 parts per billion of NO₂ at room temperature.

"The important advance is that we can form the sensing material and add isolated catalyst atoms in one rapid step, without needing a prolonged furnace treatment," said Kim.

The platinum-enhanced sensor detected NO₂ at concentrations as low as 17.2 parts per billion. It also showed selectivity for NO₂ compared with several other tested gases and retained a stable response through 25 exposure-and-recovery cycles. After three weeks in ambient air, its response had declined by only 2.6%.

Calculations suggested platinum atoms strengthen the interaction between the material and NO₂, supporting the measured improvement in sensing. "By adjusting the active sites on the material, this approach could help make sensitive and selective gas detection more practical, while offering a flexible way to prepare other functional nanomaterials," said Kim.

Scaling up still needs real-world testing

The process used 8.6 kilojoules of electrical energy per gram. Because the light can illuminate a relatively broad area, the approach may offer a route toward more scalable production than methods requiring hours of heating. However, the sensors were tested in a laboratory setup; real-world performance in varied outdoor conditions and commercial devices still needs evaluation.

The researchers suggest the synthesis strategy could also be explored for catalysts used in clean-energy technologies and other advanced materials and energy conversion.

This study presents flash thermal synthesis as a rapid way to make edge-rich molybdenum disulfide and anchor individual catalyst atoms. The results point to potential advances in room-temperature gas sensors for air-quality monitoring and industrial gas detection, pending further testing and development.

The strategy could also help researchers develop next-generation materials for cleaner energy and environmental technologies.