Abstract
The relationship between the structure and properties of nanoscale conductometric sensors based on binary mixtures of metal oxides in the detection of reducing gases in the environment is considered. The sensory effect in such systems is determined by the chemisorption of oxygen molecules and the detected gas on the surface of metal oxide catalytically active particles, the transfer of the reaction products to electron-rich nanoparticles, and subsequent reactions. Particular attention is paid to the doping of nanoparticles of the sensitive layer. In particular, the effect of doping on the concentration of oxygen vacancies, the activity of oxygen centers, and the adsorption properties of nanoparticles is discussed. In addition, the role of heterogeneous contacts is analyzed.
Highlights
The main qualities that sensors used in various fields should have are sensitivity to analytes even at their concentration at the ppb level, speed, and stability
Despite the change in the sensory effect observed upon isovalent doping, the primary attention of researchers is focused on the heterovalent doping of metal oxide nanocrystals, which is much more effective for increasing the sensitivity and selectivity of sensors
Investigation of sensory systems based on oxides such as SnO2 [35, 66, 67], In2O3 [35,36,37, 68,69,70,71,72], ZnO [73], and Co3O4 [70,71,72, 74] doped with various ions showed that the dependence of the sensory effect on the concentration of different types of doping ions has the same form as the dependence of the amount of chemisorbed oxygen
Summary
The main qualities that sensors used in various fields should have are sensitivity to analytes even at their concentration at the ppb level, speed, and stability. The most widely used conductometric chemical sensors that meet these requirements are those using semiconductor metal oxides with nanosized crystals as a sensitive layer Such sensors are reliable and easy to manufacture and are used both in everyday life and in production for monitoring the environment, in medicine, and in other applications, in particular for the detection of ammonia at refrigeration plants, methane in mines, and carbon monoxide in exhaust gases [1,2,3]. The selectivity and the sensitivity of conductometric sensors are improved when using multicomponent composite systems that combine metal oxides with different electronic characteristics and chemical properties (see, for example, [10,11,12,13,14,15]) The primary attention is paid to the influence of this interaction on the chemical processes that determine the operational properties of composite sensors to detect reducing gases in the atmosphere
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