Ultrasensitive and Exclusive Chemiresistors with a ZIF-67-Derived Oxide Cage/Nanofiber Co3O4/In2O3 Heterostructure for Acetone Detection

Enhanced Oxygen Vacancy Formation in Pt-WO3 via W-OH Bond Cleavage Using Water-Based One-Step Electrospinning for High-Performance Gas Sensors

Oxygen vacancies play a crucial role in charge transport and surface states in semiconductor metal oxides, significantly influencing various research fields, such as photocatalysis and gas sensor. Developing effective strategies to generate oxygen vacancies and thereby enhance device performance is highly desirable. In this study, we proposed a water-based one-step electrospinning method to introduce hydroxyl groups, leading to the synthesis of Pt-decorated WO3 nanofibers (Pt-WO3(H2O)) with increased oxygen vacancies. Density functional theory calculations revealed that the dissociation energy of W-OH is lower than that of the W-O bonds, promoting the formation of oxygen vacancies via W-OH bond cleavage. These vacancies reduced the adsorption energy of acetone on the WO3 surface, enhancing surface interactions. Consequently, the Pt-WO3(H2O) sensor exhibited an ultrahigh response of 82 to 1.8 ppm acetone at 300 °C, which was about 1 order of magnitude higher than the one fabricated by conventional electrospinning. These findings indicate that water-based electrospinning is an effective technique for generating oxygen vacancies in metal oxide nanofibers. Our high-performance acetone sensor, capable of detecting low concentrations, holds great potential for applications in noninvasive health screening.

CsPbBr3 Quantum Dot Modified In2O3 Nanofibers for Effective Detection of ppb-Level HCHO at Room Temperature under UV Illumination

The design of high-performance and low-power formaldehyde (HCHO) gas sensors is of great interest to researchers for environmental monitoring and human health. Herein, In2O3/CsPbBr3 composites were successfully synthesized through an electrospinning and self-assembly approach, and their ultraviolet-activated (UV-activated) HCHO gas-sensing properties were investigated. The measurement data indicated that the In2O3/CsPbBr3 sensor possesses an excellent selectivity toward HCHO. The response of the In2O3/CsPbBr3 sensor to 2 ppm of HCHO was 31.4, which was almost 11 times larger than that of In2O3 alone. Besides, the In2O3/CsPbBr3 sensor also displayed extraordinary linearity (R2 = 0.9696), stable reversibility, and ideal humidity resistance. Interestingly, the gas-sensing properties of the In2O3/CsPbBr3 sensor were further improved (Ra/Rg = 54.8) under UV light irradiation. Meanwhile, the response/recovery time was shortened to 7/9 s. The improvement of HCHO-sensing properties might be ascribed to the distinctive structure of In2O3 nanofibers, the adsorption capacity of cesium lead bromide quantum dots (CsPbBr3 QDs) for UV light, and the synergistic effect of heterostructures between the components. Density functional theory (DFT) was implemented to discuss the adsorption ability and electronic characteristics of HCHO at the surface of In2O3/CsPbBr3 composites. Especially, this research points out new constructive thoughts for the exploitation of UV light improved gas-sensing materials.

Effectively Improved CH4 Sensing Performance of In2O3 Porous Hollow Nanospheres by Doping with Cd

Recently, due to the promising application of metal oxide semiconductors in high-performance methane (CH4) sensors, more attention has been paid to the development of feasible strategies for improving CH4 sensing performance. Herein, we present a strategy of cadmium (Cd) doping to improve the CH4 sensing property of In2O3 porous hollow nanospheres (PHNSs). The Cd-doped In2O3 PHNSs were prepared via an impregnation-calcination approach with self-made carbon nanospheres as a hard template. The samples were characterized by various techniques to evaluate their structure, morphology, surface state, composition, and band gap. When applied as a sensitive material in the CH4 sensor, the Cd-doped In2O3 PHNSs, compared with bare In2O3 PHNSs, showed some significant improvements in performance, especially a reduced operating temperature (200 °C vs 300 °C), an enhanced response (9.5 vs 2.5 for 500 ppm of CH4), a faster response speed (16 s vs 276 s), and better selectivity. In addition, the Cd-doped In2O3 sensor can also maintain a commendable long-term stability, and the range of its response amplitude within 30 days is only 6.3%. The sensitization effects of the Cd dopant on the In2O3 PHNSs are discussed.

Interface Defects and Carrier Regulation in MOF-Derived Co3O4/In2O3 Composite Materials for Enhanced Selective Detection of HCHO

Gas sensors for real-time monitoring of low HCHO concentrations have promising applications in the field of health protection and air treatment, and this work reports a novel resistive gas sensor with high sensitivity and selectivity to HCHO. The MOF-derived hollow In2O3 was mixed with ZIF-67(Co) and calcined twice to obtain a hollow Co3O4/In2O3 (hereafter collectively termed MZO-6) composite enriched with oxygen vacancies, and tests such as XPS and EPR proved that the strong interfacial electronic coupling increased the oxygen vacancies. The gas-sensitive test results show that the hollow composite MZO-6 with abundant oxygen vacancies has a higher response value (11,003) to 10 ppm of HCHO and achieves a fast response/recovery time (11/181 s) for HCHO at a lower operating temperature (140 °C). The MZO-6 material significantly enhances the selectivity to HCHO and reduces the interference of common pollutant gases such as ethanol, acetone, and xylene. There is no significant fluctuation of resistance and response values in the 30-day long-term stability test, and the material has good stability. The synergistic effect of the heterostructure and oxygen vacancies altered the formaldehyde adsorption intermediate pathway and reduced the reaction activation energy, enhancing the HCHO responsiveness and selectivity of the MZO-6 material.