The photo is sourced from news.itmo.ru
Hydrogen halides are compounds of halogens – chlorine, bromine, iodine and other elements of group 17 in the periodic table – with hydrogen that result in the formation of colourless gases, which are toxic to humans, including hydrogen chloride, hydrogen bromide and hydrogen iodide. These chemical compounds are used in the manufacturing industry, i.e., to produce sodium bicarbonate or detergents. Hydrogen halides are dangerous for human health: they can lead to poisoning in case of inhalation, which is why businesses seek to use touch sensors that can detect these substances in both high (more than 1,000 molecules per 1 million molecules of air) and low concentrations (less than 10 molecules per 1,000 molecules of air).
The most widely used sensors are gas electrode ones, which produce results with a low level of accuracy and often fail to detect gas if its concentration is too low or, alternately, too high. An alternative to these sensors is the use of optical analysers based on photon crystals (materials that can manipulate light thanks to their physical structure) and circular microresonators, i.e., silicon optical elements that can trap light. A key advantage of such sensors – higher sensitivity – is offset by the complexity of the production process.
Researchers from the Faculty of Physics of ITMO University and North Ossetian State University named after K.L. Khetagurov have developed an alternative solution – a simple and sensitive photon sensor based on perovskite nanolasers. The scientists used an inorganic lead halide perovskite (CsPbBr3) as a nanolaser, which has a nanoscale whisker structure and looks like a small match.
“Perovskite is an optically active material, which is why regular-shaped perovskite nanostructures serve as both resonators and an active medium that can generate laser radiation. A particular feature of laser radiation is that its emission line is very narrow spectrally, in contrast to the wide peak of spontaneous luminescence. This is why it occurred to us that if the narrow line begins to change in some way, for instance, by shifting spectrally, even within the deciles of a nanometre, this will make it easier to notice changes in any external parameters. That got us thinking about the possible applications of this feature, until we realised that it enabled us to create a highly sensitive gas detector,” Darya Markina, participant in the study, is quoted as saying by ITMO University.
Experiments conducted as part of the study have shown that the new method helps detect leakages of hydrogen chloride (HCI) in concentrations from 5 to 500 HCI molecules per 1 million molecules of air. The sensor can also be adapted to detect other types of hydrogen halides.