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In recent years, with the rapid development of the Internet of Things (IoT) and connected automation technologies, sensor technologies have gained attention for their important role in ensuring accurate monitoring and adaptive signaling. Gas sensors are a class of devices that are widely used to detect and measure the concentration of gases and play a vital role in environmental monitoring, industrial safety, medical diagnostics, and other fields (Figure 1). These sensors generate electrical or other output signals by sensing changes in specific components of a gas, thereby providing information about the gas concentration, type, and related details. The following section describes in detail the basic operating principles of gas sensors and the generation of analytical signals from gases. The preparation of gas sensing materials with good selectivity, high sensitivity, stability and fast response/recovery times is essential for practical applications. While the development of gas sensors has focused on improving sensitivity, which has a direct impact on detection limits, balancing sensitivity and selectivity is also critical, especially in mixed gas environments. Sensor selectivity plays an important role in practical applications and should not be ignored. Among the various sensor technologies, SMO gas sensors stand out as indispensable sensors for the detection of toxic and exotic gases due to their superior sensitivity, fast response, low cost and excellent long-term stability.
The main point of this paper
Gas sensitivity enhancement strategies:
Design of sensitive materials to enhance gas sensitivity, including porous structures, metal doping, and heterojunctions
Gas sensitization mechanism of SMOs:
The gas sensitization mechanism of SMOs is closely related to oxygen, involving surface adsorption and catalytic oxidation processes.
Oxygen adsorption model:
The gas sensitization mechanism of SMOs is based on the oxygen adsorption model, and the resistance change is related to the chemical adsorption of oxygen
Gas sensor working principle:
The operating principle of n-type and p-type SMO gas sensors depends on the type of majority carriers
Composites are compared and analyzed:
The review also extends to composites with a comprehensive comparison and analysis of the above strategies
Multi-string standing wave electrospinning device optimization:
Process parameters such as string spacing, number and phase difference were optimized by electric field simulation to improve spinning yield
Effectiveness of multi-string standing wave electrospinning device:
The optimal string array parameters of 40 mm string spacing, two strings, and half cycle phase difference increased the yield by 88.7% to 2.17 g/h
Precious metal modified gas sensor for SMOs:
Precious metal modification can significantly enhance the sensing performance of SMOs gas sensors, and the intrinsic mechanisms include electronic sensitization effect and chemical sensitization effect (spillover effect)
Synergistic effect between dual noble metals:
The synergistic effect between the two noble metals can further improve the physical and chemical properties of the materials and effectively enhance the gas sensing performance.
Impact of electrospinning technology:
Electrospinning technology has revolutionized the field of SMO gas sensors, and SMO has an important role in gas detection.
Advantages of SMO gas sensors:
Known for their high sensitivity, fast response and exceptional selectivity.
Features of SMO synthesized by electrospinning:
High porosity, large specific surface area, tunable morphology and composition, and diverse structural designs to enhance gas sensing performance.
Strategies to enhance gas sensing performance:
Including noble metal modification and doping of transition metals, rare earth elements and metal cations to improve sensitivity and selectivity.
Applications of composite materials:
Fabrication of composite SMOs from polymers or carbon nanofibers to meet the challenges of high temperature operation.
Structural Advantages Explored:
The advantages of layered and core-shell structures are discussed, as well as the unique chemical composition and crystal structure of spinel and perovskite crystal structures to achieve high sensitivity and selectivity for specific gases.
Innovative Material Integration and Structural Design:
The critical role of innovative material integration and structural design in realizing high performance gas sensors is emphasized.
SMO-based gas sensors fabricated by electrospinning are leading the way in current environmental monitoring and industrial safety applications due to their superior sensitivity, selectivity and operational stability. The application of electrospinning technology has ushered in a new era in gas sensor design. This technology has enabled SMOs to have high porosity, large surface area, and tunable morphology, qualities that are essential for achieving superior gas sensing performance. This review systematically explores the evolution and current status of SMO-based gas sensors, focusing on significant advances in material synthesis and functionalization. We detail the use of electrospinning methods to design various nanostructures favorable for gas diffusion and SMOs with ultra-high specific surface area, which are essential for the preparation of high-performance gas sensors. In addition, the introduction of additives into SMOs is the most common method for tuning the sensitivity, selectivity, and stability of gas sensors. Therefore, several strategies such as precious metal decoration as well as transition metal, alkali metal and rare earth element doping are discussed in depth. We also rationalize the associated chemical and electronic sensitization mechanisms and the role of different structures. Finally, we provide insights into the influence of the composition and structure of the composites on the performance of the gas sensors.
