This paper describes the design and implementation of a wireless electronic nose (WEN) system which can online detect the combustible gases methane and hydrogen (CH₄/H₂) and estimate their concentrations, either singly or in mixtures. The system is composed of two wireless sensor nodes—a slave node and a master node. The former comprises a Fe₂O₃ gas sensing array for the combustible gas detection, a digital signal processor (DSP) system for real-time sampling and processing the sensor array data and a wireless transceiver unit (WTU) by which the detection results can be transmitted to the master node connected with a computer. A type of Fe₂O₃ gas sensor insensitive to humidity is developed for resistance to environmental influences. A threshold-based least square support vector regression (LS-SVR) estimator is implemented on a DSP for classification and concentration measurements. Experimental results confirm that LS-SVR produces higher accuracy compared with artificial neural networks (ANNs) and a faster convergence rate than the standard support vector regression (SVR). The designed WEN system effectively achieves gas mixture analysis in a real-time process.

Tungsten trioxide nanostructures have received considerable attention due to their enhanced gas sensing properties and promising applications in the sensing field. Herein, tungsten oxide (WO₃) with a lamellar structure was prepared by a facile but feasible hydrothermal process and applied for gas detection. The structures, morphologies and surface characteristics of the as-obtained products were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and Brunauer–Emmett–Teller analysis. The uniform nanolamellae were constructed from many substructures, primarily nanoparticles, resulting in desirable porous structures. To highlight the potential applications, gas sensors based on the as-synthesized products were fabricated to test their sensing performance. The test data indicated that the porous WO₃ nanolamellae had superb kinetic response and remarkable selectivity towards some volatile organic compounds (VOCs), particularly ethanol, at an operating temperature of 200 °C. As such, we believe that these porous WO₃ nanolamellae are promising as a potential high-performance sensing material for ethanol detection.

In order to overcome the many shortcomings of traditional hot-wire thermal conductivity sensor design, a new design method was proposed in which a graphene–composite carbon nanotube mixed carbon material was used as a thermal conductivity sensor carrier instead of nano-alumina particles. Taking advantage of the large specific surface area and high thermal conductivity of graphene, as well as the characteristics of a large number of gas transport channels modified by carbon nanotubes, a high-efficiency gas heat exchange medium is made. In order to improve the consistency of the product, electrochemical preparation of an aluminum oxide film material is used to make the chip substrate of the thermal conductivity sensor by MEMS process technology, and the heating sensitive electrode of the sensor is made by a thick film process. Experiments show that the sensor prepared by this method has high sensitivity and zero point stability and has greatly improved the detection accuracy and response time. The sensitivity of the sensor to hydrogen detection increases to 3.287 mV/1%H₂, and the response time is shorter than 5.4 s. The research results have good application prospects.

Aiming at solving the slow-response problem of traditional bead-type thermal conductivity gas sensors, a fast-response thermal conductivity gas sensor can be made by using multiwalled carbon nanotubes (MWNTs), combined with the technology of carrier modification, to modify the performance of the sensor carrier. The carrier material, granular nanoscale γ-Al₂O₃/ZrO₂, was synthesized by chemical precipitation, and its particle size was found to be 50–70 nm through SEM. After the carrier material was wet-incorporated into carbon nanotubes, the composite carrier γ-Al₂O₃/ZrO₂/MWNTs was obtained. The results show that the designed thermal conductivity sensor has a fast response to methane gas, with a 90% response time of 7 s and a recovery time of 16 s. There is a good linear relationship between the sensor output and CH₄ gas concentration, with an average sensitivity of 1.15 mV/1% CH₄. Thus, the response speed of a thermal conductivity sensor can be enhanced by doping carbon nanotubes into γ-Al₂O₃/ZrO₂.

Write-once-read-many-times (WORM) memory belonging to an important non-volatile memory type achieves the read-only state after the write operation and is used in the fields of data security storage widely. WORM memory has been developed based on a variety of materials. In recent years, halide perovskites have become the research hotspot material for this memory due to its excellent properties. Here, the all-inorganic CsPbBr₃ perovskite thin film was prepared on a FTO substrate by using a two-step method. The prepared CsPbBr₃ thin films have the characteristics of densely packed crystal grains and smooth surface. The device, having the FTO/CsPbBr₃/Al sandwich structure by evaporating the Al electrode onto the CsPbBr₃ thin film, represents the typical WORM behavior, with long data retention time (10⁴ s), a low operation voltage (2.1 V) and a low reading voltage (0.1 V). Additionally, the resistance transition mechanism of the resulting WORM devices was analyzed.