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Herein, we reported a gas sensor based on MXene/Graphene composite sensitive film for low-concentration ammonia detection. Specifically, we use the electrophoretic deposition method to uniformly deposit MXene on the graphene film surface of the graphene sensor, thereby constructing the MXene/Graphene composite sensitive film. The ammonia sensitivity test results show that the MXene/Graphene composite film sensor exhibits fast response, high sensitivity and excellent selectivity to ammonia at room temperature and high humidity. At the same test concentration (100 ppm), the sensitivity of the MXene/Graphene sensor is 3 times higher than that of the graphene sensor, 2 times higher than that of the MXene film sensor, reaching 25%, and its theoretical limit of detection is 56 ppb. The response time is only 26 s and the recovery time is 148 s, while the response time of the graphene sensor is 228 s. The MXene/Graphene sensitive film takes full advantage of the hydrophilicity and abundant surface functional groups of MXene, and the excellent electrical conductivity of graphene, which solves the problems of low sensitivity, slow response speed, and inability to completely desorb ammonia gas of pure MXene or graphene. Potential applications in designing next-generation portable gas sensors for human breath detection analysis. [Display omitted] [ABSTRACT FROM AUTHOR]

The ammonia (NH 3)-sensing performance of phosphorus-doped graphene sensors is systematically investigated in this paper. Using a chemical vapor deposition (CVD) system, phosphorus pentoxide was used as the phosphorus source to achieve stable phosphorus doping of graphene at 480 oC. The NH 3 -sensing test results showed that the NH 3 response of phosphorus-doped graphene increased by 2.4 times on average, the response (recovery) time shortened by 70.6% (73.4%) on average, and the theoretical limit of detection (LOD) was 68.76 ppb. In addition, the phosphorus-doped graphene sensor also exhibits excellent repeatability, stability, and ultra-high selectivity to NH 3. XPS, EDS, and FTIR analysis show that the P-O groups introduced on graphene are the key to improving the NH 3 sensitivity of graphene. The P-O groups provide sufficient O atoms to assist graphene to adsorb NH 3 molecules, thereby improving the NH 3 sensitivity of graphene. A simple, large-scale implementable, and effective phosphorus doping by the CVD method was proposed to improve the NH 3 sensitivity of graphene in this work, which is of great significance for promoting the practical application of graphene gas sensors. • After phosphorus doping, the NH 3 response of graphene sensor increased by 2.4 times. • The detection limit of the phosphorus-doped graphene sensor towards NH 3 is 69 ppb. • The response time of phosphorus-doped graphene sensor shortened by 70.6%. • Low-cost and stable phosphorus doping of graphene is achieved at 480 °C by CVD. [ABSTRACT FROM AUTHOR]