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The development of high-sensitivity NO2 sensors is a research hotspot in the field of semiconductor nanomaterials. How to select sensing materials with excellent response to gases is the prerequisite for achieving high sensitivity detection of NO2. There is a close relationship between the response of the sensing material to the measured gas and its adsorption thermodynamics on the surface of the material. The standard molar adsorption enthalpy of the gas on the semiconductor surface represents the strength of gas binding on the semiconductor surface, and the performance of the gas sensor. It is decisive.
Therefore, in the field of gas sensor research, how to establish the corresponding relationship between the standard molar adsorption enthalpy and the response of the sensor, and how to obtain the standard molar adsorption enthalpy from the sensor test, is of great significance for the development of the sensor theory and the actual measurement and development of the sensor.
The ppb-level NO2 sensor based on rGO/TiO2 (reduced graphene oxide/titanium dioxide) nanoheterojunction materials was designed and prepared for the first time by researchers of the Research Institute of Environmental Science and Technology, Xinjiang Institute of Physics and Chemistry, Chinese Academy of Sciences. The sensor has excellent response to NO2. The detection limit is 1.5 ppb at 200°C. Based on this sensing material modeling, the researchers proposed the concept of gas field effect nanosensors with gas as the gate voltage from the perspective of gas adsorption changing the surface potential of the material, and based on this as a premise, a pioneering interpretation of gas adsorption and sensor signals. Intrinsic relationship with adsorption thermodynamics.
Researchers have organically linked the gas concentration, surface potential and field-effect transistor theory to establish a quantitative relationship between the size of the sensor response and the standard molar adsorption enthalpy, gas concentration, and temperature. By measuring the response of the sensor at different concentrations and temperatures, the standard molar adsorption capacity of NO2 on TiO2 surface is -25.51 kJ/mol, which is in good agreement with the theoretical value of -23.56 kJ/mol reported in the literature. Based on this, the researchers established the model and the obtained standard molar adsorption enthalpy for the calibration of the sensor, and achieved a quantitative correspondence between the response size, temperature and concentration with only a small amount of testing. In addition, it has been verified that the error between the calculated value and the measured value in the range of 0-1 ppm is less than 9% at 200°C.
This study not only lays a theoretical and experimental basis for the electrical measurement of the standard molar adsorption enthalpies of gases on the surface of semiconductors, but also has an important guiding role in the design of high-performance gas-sensing materials, and more non-specific gas sensors from the The perspective of establishing gas identification mode provides a new idea.
Related research results were published in The Journal of Physical Chemistry C. The work was funded by projects such as the "Light of the Western Region" of the Chinese Academy of Sciences, the National Natural Science Foundation of China, the "Hundred Talents Program" of the Chinese Academy of Sciences, the Xinjiang Uygur Autonomous Region International Cooperation, and Xinjiang Uyghur Autonomous Region Youth Science and Technology Innovation Talent Training Project.
Pressure sensor usually consists of a pressure sensor and a signal processing unit for measuring the pressure of liquids and gases. According to different test pressure types, pressure sensors can be divided into gauge pressure sensors, differential pressure sensors and absolute pressure sensors. According to the working principle, it can be divided into Ceramic Pressure Sensor, diffusion silicon pressure sensor, piezoresistive pressure sensor, sapphire pressure sensor and so on.
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