A 10-millisecond flash heated a powder to 1,811°C, then cooled it quickly enough to leave behind tiny flakes with individual platinum atoms spread across their surfaces. The material, made by researchers in South Korea, detected nitrogen dioxide at room temperature—a useful step toward sensors that can spot harmful gases without needing to be heated.
Nitrogen dioxide, or NO2, can harm health, so detecting small amounts matters for air-quality monitoring and industrial safety. One challenge is building a sensor material with enough active spots to react to the gas. Molybdenum disulfide, a thin material often shortened to MoS2, has promising reactive edges, but ordinary heating can make those edges harder to preserve. Added metals can also clump together instead of staying as single atoms.
The research team used intense pulsed light in a process called flash thermal synthesis. In one step, the flash turned a molybdenum-containing starting material into thin MoS2 flakes and incorporated atoms of platinum, iridium or gold. The 10-millisecond pulse drove the temperature as high as 1,811°C before the material rapidly cooled in ambient air. The brief treatment helped keep the flakes small and the metal atoms dispersed rather than gathered into larger particles.
The study was jointly led by Professor Il-Doo Kim of the Korea Advanced Institute of Science and Technology, known as KAIST, and Assistant Professor Dong-Ha Kim of Hanyang University ERICA. Dr. Euichul Shin of KAIST was the first author. Their paper appeared in Advanced Materials.
In tests, the flash-made MoS2 responded 23.6 times more strongly to 5 parts per million of NO2 than material prepared with a conventional solvothermal method. Adding 1.2% platinum by weight raised the response further: it reached 100.8% at 400 parts per billion of NO2, at room temperature. The platinum-enhanced material detected concentrations down to 17.2 parts per billion and showed a stronger response to NO2 than to several other gases tested.
The sensor also kept a stable response across 25 cycles of gas exposure and recovery. After three weeks in ambient air, its response had fallen by just 2.6%. The researchers’ calculations suggested that platinum strengthens the interaction between NO2 and the sensing material, helping explain the measured improvement.
The results point to a potentially useful way to make sensitive gas sensors without long furnace treatments. The process used 8.6 kilojoules of electrical energy per gram, and its light source can illuminate a relatively broad area, which may help with larger-scale production. The approach could also be explored for catalysts and materials used in clean-energy technologies.
For now, the sensor has been tested in a laboratory, not under changing outdoor conditions or in commercial devices. Those tests will be needed to show how well it works in everyday use. Still, a brief flash that makes both the sensing flakes and their isolated platinum atoms in one step offers researchers a promising route to explore.