Nowadays, metal oxide semiconductors (MOS)-reduced graphene oxide (rGO) nanocomposites have attracted significant research attention for gas sensing applications. Herein, a novel composite material is synthesized by combining two p-type semiconductors, i.e., Cu2O and rGO, and a p-p-type gas sensor is assembled for NO2 detection. Briefly, polypyrrole-coated cuprous oxide nanowires (PPy/Cu2O) are prepared via hydrothermal method and combined with graphene oxide (GO). Then, the nanocomposite (rGO/PPy/Cu2O) is obtained by using high-temperature thermal reduction under Ar atmosphere. The results reveal that the as-prepared rGO/PPy/Cu2O nanocomposite exhibits a maximum NO2 response of 42.5% and is capable of detecting NO2 at a low concentration of 200 ppb. Overall, the as-prepared rGO/PPy/Cu2O nanocomposite demonstrates excellent sensitivity, reversibility, repeatability, and selectivity for NO2 sensing applications.

This study presents three-dimensional (3D) MoS2/reduced graphene oxide (rGO)/graphene quantum dots (GQDs) hybrids with improved gas sensing performance for NO2 sensors. GQDs were introduced to prevent the agglomeration of nanosheets during mixing of rGO and MoS2. The resultant MoS2/rGO/GQDs hybrids exhibit a well-defined 3D nanostructure, with a firm connection among components. The prepared MoS2/rGO/GQDs-based sensor exhibits a response of 23.2% toward 50 ppm NO2 at room temperature. Furthermore, when exposed to NO2 gas with a concentration as low as 5 ppm, the prepared sensor retains a response of 15.2%. Compared with the MoS2/rGO nanocomposites, the addition of GQDs improves the sensitivity to 21.1% and 23.2% when the sensor is exposed to 30 and 50 ppm NO2 gas, respectively. Additionally, the MoS2/rGO/GQDs-based sensor exhibits outstanding repeatability and gas selectivity. When exposed to certain typical interference gases, the MoS2/rGO/GQDs-based sensor has over 10 times higher sensitivity toward NO2 than the other gases. This study indicates that MoS2/rGO/GQDs hybrids are potential candidates for the development of NO2 sensors with excellent gas sensitivity.

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We report a simple fabrication of a gas sensor using a nanohybrid composite of reduced graphene oxide/cuprous oxide (rGO/Cu2O). The deoxidation of GO occurs meanwhile with the synthesis of Cu2O. The Cu2O component of the nanohybrid material has a linear morphology and a micron size, which is homogeneously mixed with rGO. The rGO/Cu2O gas sensor can effectively detect ppm level of NO2 gas, showing an outstanding reusability. Because rGO/Cu2O has a large specific surface area, it is more conducive to gas adsorption on its surface. Its good effect on detecting NO2 proves that the sensor has good commercial prospects.

In this work, we prepared a novel nanoscale tubular graphene (TG) by depositing it on the surface of nickel nanowires (Ni-NWs). This method allowed us to synthetize Ni-NWs by a chemical reduction process carried out under water-bath heat and magnetic field. The TG was subsequently deposited on the as-prepared Ni-NWs through a chemical vapor deposition (CVD) process under atmospheric pressure. Scanning electron microscopy (SEM) and Raman spectroscopy revealed the presence of Ni-NWs and TG/Ni-NW composites containing a few layers of graphene. The diameters of the Ni-NWs and TG/Ni-NW composites were ca. 300–500 and 500–1000 nm, respectively. The novel tubular structure of graphene provided this material with large specific surface area and excellent electrical conductivity, making it an ideal for sensor applications.