Scientists headed by Professor Gang Meng from the Hefei Institutes of Physical Science (HFIPS) of the Chinese Academy of Sciences have found five volatile organic compounds (VOCs) with various functional groups, and they designed a smart system to precisely determine five BTX (toluene, benzene and three xylene isomers) molecules.
VOCs are known to be the most general pollutant discharged. Its supervision is of huge significance for regulating air pollution. As for VOCs monitoring, metal oxide semiconductor VOC sensors stand out for being more compact and affordable than other monitoring tools. But it displays poor selectivity since it has a broad scope for redox reaction. Several gases have the ability to react with its surface. This is particularly true for VOCs molecules, which restricts its applications.
P-type oxides sensor - a metal oxide semiconductor VOCs sensor - has outstanding catalytic oxidation properties toward VOCs. Initially, the scientists examined the p-type NiO sensor by a thermal modulation to verify its great potential to identify VOCs. In their experiment, the sensor could determine five VOCs with various functional groups.
The researchers carried their work further to enhance the recognition capability of NiO-based sensor arrays and extended the number of NiO-based sensors by a range of extrinsic doping with the assistance of a unique programmed cooling temperature modulation waveform, through which the recognition capability was highly enhanced.
This latest assembling helped to obtain the quantitative recognition of three alcohol VOCs with similar structure, properties and concentrations through extracting the delicate features of tested VOCs.
Furthermore, depending on their previous work, the scientists developed another smart recognition system with thermal modulation, such as electronic circuits, sensor arrays and Wi-Fi modules, which can rapidly, stably and precisely determine five BTX molecules, as well as, a group of VOCs, in an ambient air background.
The findings emphasize that proper thermal modulation provides a strong route in extracting the feature variations of VOCs molecules with similar structures. Also, it offers a new way to explore the latest VOCs recognition electronics.