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High-performance catalysts are crucial for many applications, including high-performance gas sensors. However, the catalysts used in gas sensors need to be screened through many experimental measurements, which is time-consuming and labor-intensive. Herein, the catalytic activity of ZSM-5 zeolites with different Si/Al ratios is quantitatively evaluated using a resonant microcantilever that enables in-situ temperature-programmed desorption (cantilever-TPD) measurements. Since the frequency shift obtained by the cantilever-TPD measurement is proportional to the number of probe molecules, the cantilever-TPD experiment can successfully measure the number of active sites and desorption activation energy of the catalyst. Therefore, the cantilever-TPD experiment quantitatively characterizes the catalytic activity through the comprehensive analysis of the number of active sites and the desorption activation energy, eliminating the need for the traditional trial-and-error method to study the gas-sensing performance. According to the test results of cantilever-TPD, the ZSM-5 zeolite with satisfactory performance is preferred as the catalytic material, and the ZnO/ZSM-5 double-layer sensor is made to detect trace amounts of the greenhouse gas Freon R134a. The gas sensing results show that the optimized ZSM-5 sensor has good sensitivity, limit of detection (LOD), repeatability, and selectivity, fully confirming the evaluation results of the cantilever-TPD. • Resonant microcantilever is used for TPD measurements of catalytic-induced sensing materials. • The catalytic activity of ZSM-5 zeolites with different Si/Al ratios has been quantitatively evaluated. • ZSM-5 zeolite, with satisfactory performance, was selected as the catalytic-induced sensing material. [ABSTRACT FROM AUTHOR]

For the first time, ultrasensitive detection of 10 ppb CO has been realized using metal organic framework (MOF) crystals of Ni-MOF-74 as gravimetric-type sensing material with resonant microcantilever sensors. Due to the specific interaction between CO molecules and the active transitional metal centers of Ni 2+ in the Ni-MOF-74 crystal, the Ni-MOF-74 material with ultra-high surface area and nanoporous structure possesses large absorption capacity to CO gas. By loading the Ni-MOF-74 material onto the resonant microcantilever, the formed gravimetric sensor exhibits high-performance sensing to CO at trace level. The experimentally obtained limit of detection (LOD) of the sensor to CO reaches finer than 10 ppb (parts per billion in volume), which indicates an extremely high CO-detection sensitivity of the sensor. Besides the excellent sensitivity, the sensor also shows remarkable repeatability and long-term stability. Eight kinds of interfering gases are tested and a fine selectivity of the sensor is verified. This work indicates that MOF materials such as Ni-MOF-74 are promising in gravimetric-type gas sensing applications. [ABSTRACT FROM AUTHOR]

Aromatic amine such as aniline is one kind of carcinogenic substances that needs to be detected at low concentration. To sense trace level aniline, high performance sensing material is of great importance. Herein, metal organic framework of Zn 4 O(1,4-benzenedicarboxylate) 3 (commonly abbreviated as MOF-5) with abundant hierarchical nanopores is firstly employed as mass-type sensing material for low concentration aniline detection. By using one typical micro-gravimetric transducer of resonant microcantilever, the aniline-adsorbing induced mass-addition of MOF-5 is transformed to the detectible sensing signal of frequency shift. Based on resonant microcantilever with mass resolution of 1.5 pg/Hz, the fabricated sensor exhibits good sensitivity for aniline detection. The limit of detection is better than 1.4 ppm, and the selectivity is satisfactory to nine kinds of common interfering gases. The three-cycle repeatability of the sensor is also investigated with a relative standard deviation (RSD) of 4%. After 20 days, the sensor only shows a negligible response degradation which represents a good reproducibility. Materials Studio simulation results manifest that 1,4-benzenedicarboxylic ligand in MOF-5 crystals is the preferential site for aniline molecules adsorbing. [ABSTRACT FROM AUTHOR]