In-situ deposition of POMA/ZnO nanorods array film by vapor phase polymerization for detection of trace ammonia in human exhaled breath at room temperature

The o-methoxyaniline (OMA) monomer was polymerized in-situ by vapor phase polymerization to form uniform and dense poly-o-methoxyaniline (POMA) film on the surface of ZnO nanorods array film which was pre-prepared by hydrothermal method. The as-prepared POMA/ZnO composite shows the best response at 40 min of vapor phase polymerization time. The response to 100 ppm ammonia at 25 °C is 8.88. The recovery time of 136 s has a certain advantage in the reported room temperature ammonia sensors. The lowest detectable concentration is as low as 0.01 ppm. The fast recovery time and low detection limit make the sensor have broad application prospects. In order to explore the response mechanism of POMA/ZnO composite to ammonia gas, the work function of POMA and ZnO and corresponding band gap energies were tested respectively. And the effect of the formation of p-n heterostructure on gas response was further explored. The actual application test results reflect that the sensor can effectively identify NH3 in the mixed gas during the production, storage and transportation of NH3. This can provide real-time early warning of NH3 leakage. Especially, the sensor can detect trace amount of NH3 in the human body's exhaled breath which is expected to realize the preliminary screening of patients with kidney disease through the detection of exhaled breath in the medical field. Thin film poly-o-methoxyaniline (POMA)/ZnO nanorods array composite sensor was prepared via in-situ vapor phase polymerization of o-methoxyaniline (OMA) monomer on the surface of ZnO nanorods arrays. The sensor shows the best response to NH3 at 40 min of vapor phase polymerization time. The response to 100 ppm NH3 reaches 8.88 at 25 °C. The composite exhibits the lowest detection limit, as low as 0.01 ppm and the shortest response/recovery time (150 s/136 s). The response to different concentrations of NH3 also has a good linear correlation in the range of 0.01–100 ppm. The interaction mechanism of POMA/ZnO composite with NH3 was discussed via the Kelvin probe technology and UV–vis reflection spectroscopy in detail. And the effect of composite the work function of POMA and ZnO and their corresponding band gap energies on gas response after formation of p-n heterostructure was further explored. The actual application test results reflect that the sensor can effectively identify NH3 in the mixed gas during the production, storage and transportation of NH3. This can provide real-time early warning of NH3 le