New sensor detects low air humidity

New sensor detects low air humidity
Structural and chemical characterization of Mo2CTx MXene. a) XRD patterns of Mo2Ga2C nanolaminated carbide precursor (black) and Mo2CTx MXene multilayer (red). b) SEM image of a Mo2CTx MXene multilayer. c) TEM image of Mo2CTx MXene single flakes on lacey carbon grid, inset is a high-resolution image. d) The SAED pattern taken from the single Mo2CTx flake in c). e) AFM image and height profile over an exemplary Mo2CTx flake. f–h) High-resolution XPS spectra recorded from a Mo2CTx MXene layer at Mo-3d f), C-1s g), and O-1s h) energies. Credit: DOI: 10.1002/adma.202104878

Measuring air humidity is important in many areas. However, conventional sensors in hygrometers have so far not been able to determine a very low water vapor content. Physicists at the University of Duisburg-Essen (UDE) and the Yuri Gagarin Technical University in Russia have now developed a new sensor. It detects even the smallest amounts of water molecules that sink to its surface. The detector is based on highly conductive materials known as MXenes.

Good indoor air is not only important for health. Certain are also needed in production or laboratories, for example in biomedicine or microelectronics. It must be possible to control these precisely. Although powerful are built into commercial measuring devices, they are not able to detect water vapor concentrations below 50 ppm, i.e. below 0.3 percent relative humidity. Consequently, such sensors are not suitable for all purposes.

This problem was tackled by the physics team from the UDE and the Russian University Yuri Gagarin in Saratov with a completely new strategy. They used two-dimensional nanometric materials. These can detect minute amounts of water molecules that sink to their surface. "In this way, the sensor performance improves enormously—the detection limit is pushed far below the previous state of the art. More is really not possible," says UDE experimental physicist Dr. Hanna Pazniak, who played a key role in the development.

These highly conductive materials are called MXenes, or more precisely: Mo2CTx MXenes. They consist of compounds of transition metal carbides or transition metal nitrides. The compounds are stacked into layers and are only a few atoms thick. The advantage: The new sensors are ultra-thin and highly sensitive. "They detect vapors down to 10 ppm, or 0.06 percent relative humidity. That's the lowest value known so far," Pazniak says. The sensors are also promising in another respect: they can be used in mass production.

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More information: Hanna Pazniak et al, Two‐Dimensional Molybdenum Carbide MXenes for Enhanced Selective Detection of Humidity in Air, Advanced Materials (2021). DOI: 10.1002/adma.202104878
Journal information: Advanced Materials

Provided by Universität Duisburg-Essen
Citation: New sensor detects low air humidity (2021, October 20) retrieved 7 December 2021 from
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