H 2 S gas sensors with facile preparation, low detection limits, and high selectivity are crucial for environmental and human health monitoring. However, it is difficult to maintain a high response of H 2 S gas sensors under high humidity in practical applications. To face this dilemma, a layer-by-layer growth method is applied to in situ prepare a nanostructured Co(CO 3 ) 0.5 (OH)·0.11H 2 O/WO 3 coated by a hydrophobic hierarchical ZIF-67 as the H 2 S sensor. This novel composite exhibits excellent humidity immunity without sacrificing the excellent sensitivity and selectivity of H 2 S. At a low operating temperature of 90 °C, a remarkable response value of 1052.3 to 100 ppm H 2 S has been achieved, which is 779 and 9.36 times higher than that of pure WO 3 and Co(CO 3 ) 0.5 (OH)·0.11H 2 O/WO 3 , respectively. More importantly, an 82.2% relative response value remains at a high humidity of 75%RH. The sensing mechanisms are investigated using gas chromatography-mass spectrometry (GC-MS), which revealed that the reaction products are H 2 O and SO 2 . The high humidity immunity and fast response of the Co(CO 3 ) 0.5 (OH)·0.11H 2 O@ZIF-67/WO 3 demonstrate the layer-by-layer in situ synthesis method holds the potential application for the development of high-performance WO 3 -based H 2 S sensors.
Linlin Qian,Canxiang Fang,Yanghai Gui,Kuan Tian,Huishi Guo,Dongjie Guo,Xiang Guo,Peng Liu
NO2 is a very dangerous and toxic gas and is prone to cause acid rain in high humidity environments, so it is essential to prepare a real-time monitoring and humidity immunity NO2 sensor. WO3 nanomaterials are commonly applied to detect NO2, but their poor immunity to humidity is still a critical limitation for the application. ZnO-nanorod-decorated WO3 nanosheets coated with ZIF-71 (ZnO@ZIF-71/WO3) composites prepared by an in situ growth method displayed excellent gas sensing performance and good humidity immunity to detect NO2. Compared to WO3 nanosheets and ZnO-nanorod-decorated WO3 nanosheets (ZnO/WO3) heterojunction composites grown on ceramic substrates in situ, ZnO@ZIF-71/WO3 presented excellent selectivity, good long-term stability, and a remarkably high response of about 947.96 to 100 ppm NO2 at 180 °C, which is 3.07 times higher than that of the ZnO/WO3 sensor and 4.59 times higher than that of the pure WO3 sensor. Even at a relative humidity of 85%, the response of ZnO@ZIF-71/WO3 to NO2 remained essentially constant. The functional ZIF-71 layer not only improved the humidity immunity of ZnO@ZIF-71/WO3 but also enhanced the sensitivity and selectivity performance to NO2 at low operating temperatures. The ZnO@ZIF-71/WO3 sensor still provided a response of 88.41 to 100 ppm NO2 at room temperature.
Inspired by the ordered tubular structure inside the dog nose and its olfactory receptors, this paper reports a biochar/SnO 2 composite based on waste disposable bamboo chopsticks (DBC) combined with tin dioxide (SnO 2 ) nanoparticles . The response of optimized biochar/SnO 2 composite reaches 4513 to 500 ppm NH 3 , and the response/recovery times are 50.4 s and 3.7 s, respectively. The biochar/SnO 2 composite displays the dog-nose-like ultra-fast response (1 s response up to 1100) to 500 ppm NH 3 at room temperature (25 °C), which makes the biochar/SnO 2 composite with the application promising for rapid detection of NH 3 . The optimized biochar/SnO 2 sensor also exhibits good selectivity and linear response with a theoretical detection limit as low as 34 ppb NH 3 . In addition, the biochar/SnO 2 sensor has reliable humidity immunity and long-term stability. Within a period of up to six months, the response fluctuation of biochar/SnO 2 sensor to 500 ppm NH 3 at 25 °C is less than 3.7%. However, the susceptibility of biochar/SnO 2 composite to the operating temperature need to be overcome. The biochar/SnO 2 composite was prepared by low-temperature pyrolytic carbonization (300 °C) with the advantages of abundant raw materials, low cost and green environmental protection, providing a new outlet for solid waste.
危险品化学品经营许可证（带存储）