Scientists develop gas sensor mechanism that works at room temperature
Researchers have developed a mechanism for detecting molecular hydrogen at room temperature, using green light to illuminate a nanocrystalline composite sensor based on zinc and indium oxides.
A study detailing the research from scientists at the Moscow Institute of Physics and Technology has been published in the journal Science Reports.
Tracking atmospheric pollution remains a vital concern in industrialised countries, meaning multisensor arrays for determining gas mixture composition are currently being developed. These monitoring systems target individual gases, and can be used to analyse air quality both outdoors and in closed spaces. Commercial gas mixtures such as gas fuels also need precise composition monitoring to ensure their purity and to maintain safety.
Until this latest research, gas sensors based on nanocrystalline metal oxides had operating temperatures between 300 and 500°C. This rendered them unsafe for the detection of explosive or combustible substances. On top of that, maintaining such temperatures requires a lot of power, meaning the gas sensors could never be embedded into the circuit boards of portable devices.
To solve this problem, professor Leonid Trakhtenberg of MIPT; Pavel Kashkarov, director of the Institute of Nano-, Bio-, Information, Cognitive and Socio-Humanistic Science and Technology; Alexander Ilin and Pavel Forsh from Lomonosov Moscow State University; and their colleagues from Semenov Institute of Chemical Physics, have developed a mechanism capable of operating at room temperature.
"The mechanism consists in the light-induced transition of the nanocrystalline sensor components into a nonequilibrium state and the resulting change in the photoconductivity of the sensor interacting with molecular hydrogen. This effect is linked with the dependence of photoconductivity on the nonequilibrium charge carrier recombination rate," explained Maria Ikim, a doctoral student at the Laboratory of Functional Nanocomposites of Semenov Institute of Chemical Physics of the Russian Academy of Sciences.
"The detectors that we have developed differ from the conventional semiconductor sensors in that they operate at room temperature. This eliminates the danger of combustion or explosion, when flammable or explosive substances are involved," said Leonid Trakhtenberg of the Department of Chemical Physics, MIPT.
"Most papers on sensor photoactivation discuss the effects of ultraviolet light on sensors and focus on the detection of oxidizing gases. But the efficiency of ultraviolet light diodes is low, while their cost is far greater than that of their counterparts emitting in the visible part of the spectrum. By working with hydrogen, we explore the possibilities of the detection of reducing gases."
The study proposes an innovative mechanism for sensor response photoactivation, illustrated in the image. It accounts for the transition of charge carriers into a nonequilibrium state. The process described in the study can be used to interpret sensing results in both oxidising and reducing gases.
According to a statement from MIPT, the sensors proposed by Trakhtenberg and colleagues could be used to monitor atmospheric air composition and analyse the chemical makeup of gases used in industrial processes. Although the study focuses on gases, the same sensors could be modified to target liquids.
