Triethylamine (TEA) is an organic compound that is commonly used in industries, but its volatile, inflammable, corrosive, and toxic nature leads to explosions and tissue damage. A sensitive, accurate, and in situ monitoring of TEA is of great significance to production safety and human health. Metal oxide semiconductors (MOSs) are widely used as gas sensors for volatile organic compounds due to their high bandgap and unique microstructure. This review aims to provide insights into the further development of MOSs by generalizing existing MOSs for TEA detection and measures to improve their sensing performance. This review starts by proposing the basic gas-sensing characteristics of the sensor and two typical TEA sensing mechanisms. Then, recent developments to improve the sensing performance of TEA sensors are summarized from different aspects, such as the optimization of material morphology, the incorporation of other materials (metal elements, conducting polymers, etc.), the development of new materials (graphene, TMDs, etc.), the application of advanced fabrication devices, and the introduction of external stimulation. Finally, this review concludes with prospects for using the aforementioned methods in the fabrication of high-performance TEA gas sensors, as well as highlighting the significance and research challenges in this emerging field.

In order to improve the sensitivity of the pure MoO ₃ sensor to ammonia and reduce its operating temperature, MoO ₃ /MoS ₂ /rGO was prepared in this work, and the gas-sensitive performance of MoO ₃ /MoS ₂ /rGO was studied. The results of the static gas sensitivity test show that, compared with pure MoO ₃ , MoO ₃ /MoS ₂ /rGO greatly improves the response of the sensor to ammonia at low temperature. Moreover, this article discusses the multigas detection methods by waveform-matched dynamic temperature modulation based on low-temperature gas sensor composites of rose-like MoO ₃ /MoS ₂ /rGO, which is used to solve the shortcoming of poor selectivity of metal-oxide-semiconductor gas sensor. Multigas (including acetone, methanol, ethanol, benzene, toluene, and ammonia) detection methods by waveform-matched dynamic temperature modulation are investigated, in which the experimental results show that the dynamic response curves of the sensor have obvious differences to each gas under different temperature waveform modulations. Temperature modulation waveforms with different periods and variations are investigated, including rectangular wave, triangular wave, and sine wave. This provides a feasible way to improve the selectivity of the sensor. In order to establish and verify the accuracy of the multigas detection model, 100 sets of response curves are selected for each waveform. Finally, the gas-sensing mechanism of gas-sensitive materials to ammonia is analyzed. Preparation of highly sensitive materials, dynamic testing, and gas identification methods can provide the technical basis for the application of gas sensors.

Semiconductor gas sensors have been widely applied to Volatile Organic Compounds (VOCs) detection. However, the poor selectivity in the actual complex gas environment has become a bottleneck to restrict the development of semiconductor gas sensors. In order to solve this problem, SnO ₂ gas sensor is prepared and temperature modulation measurement is carried out. In this paper, the method of zigzag-rectangular wave temperature modulation is first proposed, which improved the selectivity of the sensor and significantly increased the characteristic peak. Support vector machine (SVM) is used for pattern recognition, which proved the superior of the SVM in small sample size. The results demonstrate that the combination of zigzag-rectangular wave temperature modulation and SVM pattern recognition method can effectively improve the selectivity of the gas sensor.

Current semiconductor gas sensors still have significant limitations in achieving rapid measurement of hydrogen at lower operating temperatures. Therefore, in this paper, ZnO-In ₂ O ₃ sensors modified with noble metal Ag are designed by constructing a heterojunction and combining it with noble metal modification for the rapid detection of hydrogen at low (working) temperatures. In this paper, hydrogen gas sensors based on ZnO multilayer nanosheets and In ₂ O ₃ nanoparticle composites were firstly synthesized through a one-step hydrothermal route. Then, on top of this, the loading of Ag nanoparticles was successfully achieved by chemical reduction method, and finally the hydrogen gas sensors based on ZnO-In ₂ O ₃ ternary nanocomposite modified with Ag nanoparticles (NPs) was prepared. The physicochemical features of the gas-sensitive substances were described by various characterization techniques. The sensing performance of ZnO, ZnO-In ₂ O ₃ and Ag-modified ZnO-In ₂ O ₃ sensors was systematically tested. The test results manifest that the Ag NPs-loaded ZnO-In ₂ O ₃ sensor responds up to 103.75 to 100 ppm H ₂ at an inferior temperature of 160°C with response/recovery times of 1.6 s and 47.8 s, separately, and the lowest detectable gas concentration of 2 ppm. In addition, the gas-sensitive element exhibits favorable repeatability, stability, and excellent selectivity. Based on the experimental test results and characterization data resolution, the improved inductive capability of the sensors is chiefly attributed to the expansion of the specific surface area of the gas-sensitive material (39.8412 m ² /g), the constitution of the heterojunction interface, and the cooperation of chemical and electronic sensitization of noble metal Ag.

In this paper, the highly sensitive n-butanol sensors with high selectivity have been successfully fabricated based on spindle shaped α-Fe $_{2}$ O $_{3}$ nanorods modified by Au nanoparticles (Au NPs). Spindle shaped α-Fe $_{2}$ O $_{3}$ nanorods were synthesized by an improved facile hydrothermal method. Uniform Au NPs were deposited on the surface of the as-synthesized α-Fe $_{2}$ O $_{3}$ nanorods by a simple impregnation method. The achieved α-Fe $_{2}$ O $_{3}$ and Au/α-Fe $_{2}$ O $_{3}$ nanorods were analyzed by means of XPS, TEM, EDS, XRD and SEM. The sensing properties of both original and Au-modified spindle shaped α-Fe $_{2}$ O $_{3}$ samples were investigated and discussed. The experimental results indicate that the sensors based on Au/α-Fe $_{2}$ O $_{3}$ nanorods exhibit better responses and selectivity to n-butanol gas than the original α-Fe $_{2}$ O $_{3}$ , and the highest response towards 100 ppm n-butanol gas was enhanced from 51 to 177 at the optimal operating temperature of 250°C.

In this article, WS2 nanomaterials with different phases are Synthesized, and their gas-sensitive properties of ammonia are analyzed systematically. First, hydrothermal method and liquid phase method were used to prepared the different phase material. Moreover, the nanostructure and morphology are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). On the basis of result of the XRD, the difference between the peaks indicates different crystal structure. And SEM show the calcination temperature affects the morphology, and the same materials with different morphologies have similar optimum working temperature. Finally, the gas sensing performance of different WS2 sensor is investigated in different concentration of ammonia gas at optimal temperature. The results indicate that the mixed-phase exhibited a low detection limit, excellent selectivity and superb repeatability compared with 3R phase.