Optical sensors coated with carbon nanotube (CNT) clusters can distinguish between carbon monoxide (CO) and carbon dioxide (CO2). This is due to a subtle difference in how well the two molecules stick to the CNTs. As reported in Nanotechnology, a sensor platform – which directly interfaces the CNT clusters with the optical sensor – is able to detect this very small difference under normal atmospheric conditions. This approach combines chemically selective nanomaterials with ultrasensitive devices and could enable a wide range of experiments and diagnostic methods.
The detection and analysis of vapours and gases in air is particularly challenging because there are very few ways to selectively identify a gas. Many gases exhibit preferential absorption to many nanomaterials. Therefore, a vapour or gas sensor can be created by depositing a chemically selective nanomaterial directly on a sensor surface.
Coating with CNT clusters
To demonstrate this type of hybrid sensor system, researchers from the University of Southern California coat an optical sensor with CNT clusters. After regenerating the CNT clusters with argon, the CNTs are saturated with either CO or CO2. The researchers then measure the optical sensor signal as gas desorbed from the CNT cluster at different temperatures.
Temperature impacts
Because of the strong attraction between CO2 and the CNT clusters, it was necessary to heat the sensor to high temperatures for very long periods of time to fully remove all of the CO2. In contrast, the CO desorbed at moderate temperatures.
This work improves our ability to measure the temperature-dependent interaction of gases with surfaces in real-world conditions. This could result in advancements in a range of fields; for example, the design of more robust coatings for aircraft or cars or new materials for filters.
