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SO 2 sensor is highly demanded in the application fields such as environmental protection and food manufactory. Herein, an integrated microsensor is developed for SO 2 gas detection. For the fabrication of microsensor, ZnO nanosheets sensing material is firstly loaded onto the sensing area of the microsensor by using inkjet printing technology. Then, Al 2 O 3 loaded with Ru nanoparticles (Ru/Al 2 O 3 ) as catalyst are locally deposited onto the surface of ZnO nanosheets layer. Gas sensing performance measurements indicate that the fabricated microsensor exhibits a selective response to SO 2 , and a good linear relationship in the range of 5–115 ppm SO 2 gases. Besides, this integrated microsensor has short response and recovery time. On-line mass spectrometry (on-line MS) experiment further reveals the formation of sulfur monoxide (SO ) radical as an intermediate product for SO 2 sensing. During the sensing process, Ru/Al 2 O 3 as catalyst layer brings SO 2 molecules to be broken down into easily detectable species (i.e. SO ), and then ZnO nanosheets with abundant gas transport channels capture the produced SO generating output signals. Therefore, this kind of sensing material configuration exploits the advantage of each element, and makes it possible for trace and selective detection of SO 2 gas. [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]