SnO₂/graphitic carbon nitride (g-C₃N₄) composites were synthesized via a facile solid-state method by using SnCl₄·5H₂O and urea as the precursor. The structure and morphology of the as-synthesized composites were characterized by the techniques of X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), thermogravimetry-differential thermal analysis (TG-DTA), X-ray photoelectron spectroscopy (XPS), and N₂ sorption. The results indicated that the composites possessed a two-dimensional (2-D) structure, and the SnO₂ nanoparticles were highly dispersed on the surface of the g-C₃N₄ nanosheets. The gas-sensing performance of the samples to ethanol was tested, and the SnO₂/g-C₃N₄ nanocomposite-based sensor exhibited admirable properties. The response value (Ra/Rg) of the SnO₂/g-C₃N₄ nanocomposite with 10 wt % 2-D g-C₃N₄ content-based sensor to 500 ppm of ethanol was 550 at 300 °C. However, the response value of pure SnO₂ was only 320. The high surface area of SnO₂/g-C₃N₄-10 (140 m²·g⁻¹) and the interaction between 2-D g-C₃N₄ and SnO₂ could strongly affect the gas-sensing property.

Development of high performances gas sensors to monitor and detect the volatile organic compound triethylamine is of paramount importance for health and environmental protection. The Co₃O₄-ZnO nanoparticles composite was successfully synthesized by the one-step hydrothermal route and annealing process in this work. The gas sensitivity test results show that the composite exhibits excellent triethylamine-sensing performance at a cobalt content of 1 at%, indicating potential application for triethylamine detection. The sensor based on the Co₃O₄-ZnO composite had higher sensitivity to triethylamine, better selectivity, and faster response recovery rate compared with pure ZnO sensor. Combined with the structural characteristics of the characterized Co₃O₄-ZnO nanocomposite, the optimized triethylamine sensing performances can be ascribed to the p-n heterojunction effect between Co₃O₄ and ZnO, as well as the catalytic and high oxygen adsorption properties of Co₃O₄.

Considering the facile effective synthesis approach and high gas sensing performance for ethanol vapor, the g-C ₃ N ₄ nanosheet modified SnO ₂ composite will be an ideal candidate for ethanol gas sensor applications.

Developing the triethylamine sensor with excellent sensitivity and selectivity is important for detecting the triethylamine concentration change in the environment. In this work, flower-like CeO₂-SnO₂ composites with different contents of CeO₂ were successfully synthesized by the one-step hydrothermal reaction. Some characterization methods were used to research the morphology and structure of the samples. Gas-sensing performance of the CeO₂-SnO₂ gas sensor was also studied and the results show that the flower-like CeO₂-SnO₂ composite showed an enhanced gas-sensing property to triethylamine compared to that of pure SnO₂. The response value of the 5 wt.% CeO₂ content composite based sensor to 200 ppm triethylamine under the optimum working temperature (310 °C) is approximately 3.8 times higher than pure SnO₂. In addition, CeO₂-SnO₂ composite is also significantly more selective for triethylamine than pure SnO₂ and has better linearity over a wide range of triethylamine concentrations. The improved gas-sensing mechanism of the composites toward triethylamine was also carefully discussed.

In this paper, a hierarchical structure of graphite carbon nitride (g-C₃N₄) modified ZnO (g-C₃N₄/ZnO) was synthesized using a simple precipitation-calcination method. Through this method, g-C₃N₄ nanosheets with a controlled content were successfully decorated on the petals of flower-like ZnO. Various techniques were used to confirm the successful formation of the g-C₃N₄/ZnO hierarchical structure. The methane (CH₄) sensing properties of g-C₃N₄/ZnO sensor were investigated. The result exhibited that after decorating ZnO with g-C₃N₄, the CH₄ sensing performances of the fabricated sensor were remarkably improved. At the optimum operating temperature of 320 °C, the response of the sensor fabricated with CNZ-3 (the sample with an optimum content of g-C₃N₄) towards 1000 ppm CH₄ was as high as 11.9 (R_a/R_g), which was about 2.2 times higher than that of the pure ZnO sensor (5.3). In addition, the CNZ-3 sensor also exhibited a fast response/recovery speed (15/28 s) and outstanding long-term stability. The enhancing CH₄ sensing mechanism may be contributed to enlarged surface area, pore structure, and g-C₃N₄-ZnO n-n junction.

The g-C₃N₄ decorated magnesium ferrite (MgFe₂O₄) porous microspheres composites were successfully obtained via a one-step solvothermal method. The structure and morphology of the as-prepared MgFe₂O₄/g-C₃N₄ composites were characterized by the techniques of X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), thermal gravity and differential scanning calorimeter (TG–DSC) and N₂-sorption. The gas sensing properties of the samples were measured and compared with a pure MgFe₂O₄-based sensor. The maximum response of the sensor based on MgFe₂O₄/g-C₃N₄ composites with 10 wt % g-C₃N₄ content to acetone is improved by about 145 times, while the optimum temperature was lowered by 60 °C. Moreover, the sensing mechanism and the reason for improving gas sensing performance were also discussed.