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Nitrogen dioxide (NO 2) sensors experience the drawback of requiring high operating temperatures because of the low charge transfer ability of gas-sensing materials. Herein, an advanced NO 2 sensor resistant to interference is designed using the interfacial energy barriers of a hierarchical CuO/ZnO composite. With the benefits of abundant desirable defect features, and the amplification effect of heterojunctions, the sensor based on CuO/ZnO composite with 10% Cu(CH 3 COO) 2 ·H 2 O (S2) shows outstanding performance in terms of faster response and recovery time (1.8-fold/1.1-fold), higher response (3.1-fold), and lower power consumption (140℃ decrease) compared to the pristine ZnO sensor. Furthermore, the composite sensor exhibits long-term stability and reproducibility, indicating the potential promise of CuO/ZnO heterojunctions in interference-resistant detection of low-concentration NO 2 in real applications. This study not only provides a rational solution to designing advanced gas sensors by tuning the interfacial energy barriers of heterojunctions, but also provides a fundamental understanding of CuO structures in the gas-sensing field. • CuO/ZnO nano-materials are synthesized by a hydrothermal method. • The doping of CuO increases the absorbed site of ZnO nano-material. • Heterostructure and microspheres structure jointly promote the sensing performance. • Sensing mechanism and structural merits of hierarchical nanostructure are advanced. [ABSTRACT FROM AUTHOR]

Achieving rapid response and recovery rates at low operating temperatures for NO 2 is desirable for the application of sensors in industrial safety. In this study, we integrate a thickness tunable 2D graphdiyne (GDY) film into ZnO nanowalls (GDY/ZnO) via thermal evaporation of GDY, where ZnO nanowalls are used as the template to confine the growth space of the GDY film. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) is used to reveal the transformation process of NO 2. Ultraviolet photoemission spectroscopy (UPS) is utilized to analyze changes about the energy band of the materials. Density functional theory (DFT) calculations explain the reason for the selectivity of the samples to NO 2. The scanning electron microscopy (SEM) results demonstrate that the thickness of the GDY film with a specific mesoporous structure (25‐53 nm) increases as the thermal evaporation temperature rises from 400 to 800°C.The representative ZG-600, synthesized with a thickness of 46 nm via thermal evaporation at 600°C, exhibits superior NO 2 sensing performance. This is evidenced by its ultrahigh response (13.86, at 100 ppm and 150°C) and rapid response/recovery speeds (150 s/198 s), outperforming the ZnO sensor (198 s and 326 s). Moreover, it offers remarkable stability. • GDY nanoparticles were decorated on the surface of ZnO nanowall. • GDY/ZnO heterojunction with adsorbed oxygen and oxygen vacancies has been synthesized. • GDY/ZnO composite nanowall exhibited highly better NO 2 sensing performance. • The electrons transfer and redox reaction between GDY and ZnO has been discussed. [ABSTRACT FROM AUTHOR]

• The flower-like TiO 2 microspheres were synthesized by a tunable tetrabutyl titanate-assisted hydrothermal method. • The as-made gas sensors showed high sensitivity and selectivity to NH 3 at the room temperature. • The underlying mechanism for the high selectivity to NH 3 was discussed using DFT calculations. TiO 2 is proved to be a promising material in the detection of various hazardous gases at the high temperature. However, gas adsorption-diffusion capacity at the room temperature is limited by their insufficient specific surface area and surface active sites. Herein, we report a strategy to synthesis of flower-like TiO 2 microspheres assembled by nanosheets and characterize the selective adsorption of NH 3 by using density functional theory (DFT). The as fabricated flower-like TiO 2 microspheres show an outstanding gas sensitivities (∼122 to 50 ppm NH 3) and high selectivity for NH 3 detection at room temperature. The higher adsorption energy and smaller adsorption distance of NH 3 on TiO 2 (001) indicate the much stronger interaction NH 3 -TiO 2 system. The present studies provide useful gas sensing materials with fine morphologies for the development of high-performance room temperature NH 3 sensors. [ABSTRACT FROM AUTHOR]

In recent years, the potential use and development of acetone gas sensors in health monitoring and self-diagnostic applications has attracted increasing attention. Thus, accurate sensing of acetone is of crucial importance in the non-invasive diagnosis of diabetes. However, challenges remain in the detection of acetone, such as high concentrations detection limit, high operating temperature and slow response dynamics. Herein, vertically aligned Ce-doped mesoporous NiO nanowalls are prepared on Ag-Pd interdigitated electrode substrate using an in-situ growth method. The gas sensing performances show that the as-made 4 mol% Ce-doped NiO nanowalls has excellent gas response value (3.2) to 10 ppm acetone at a lower operating temperature (175 ℃) with fast adsorption and desorption equilibrium (13 s/7 s). Vertically aligned mesoporous NiO nanowalls doped by Ce element could pave the way for ultra-sensitive and low power consumption acetone gas sensors for breath gas detection. • Simple method: in situ growth method. • Excellent detection conditions: Low lower detection limits at lower temperatures. • The fast equilibrium of adsorption and desorption. [ABSTRACT FROM AUTHOR]

Fast detection of triethylamine, one of the effective indicators to assess the freshness of fish and seafood, becomes more and more important for the food safety. Yet, the gas transport and diffuse activity are limited by the solid internal structure or the unsuitable pores size of the gas sensing materials, which results in the sluggish surface reaction kinetics. Herein, a strategy was reported to synthesis of hollow Co 3 O 4 microtubes assembled by vertically aligned nanosheets via sacrificial template of MgO combined with the following thermal annealing. The gas sensing results reveal that the hollow Co 3 O 4 -200 microtubes exhibit fast response-recovery time (13 s and 81 s) and outstanding gas selectivity, stability towards 200 ppm TEA at 180 ℃, which is ascribed to the large specific surface area, rich oxygen vacancies, and suitable pore size. This unique approach sheds light on the designing potential gas sensing candidates for the fast detection of TEA gas used as safety food monitoring and healthcare. • The hollow nanosheet-assembled Co3O4microtubes were synthesized via a simple sacrificial template strategy. • The fabricated Co3O4-200sensor displayed excellent TEA-sensing performance with fast response and recovery properties. • The large specific surface area and suitable pore size are the main reasons for the improved sensing properties. [ABSTRACT FROM AUTHOR]