A novel porous nanosized humidity-sensing material of amine-functionalized titanium metal organic framework (MOF), NH 2 -MIL-125(Ti), was investigated. NH 2 -MIL-125(Ti) nanoparticles with high phase purity and good physicochemical property were synthesized by a simple hydrothermal method. The nanosized MOF was characterized by X-ray diffraction and scanning electron microscope. The average size of the MOF nanoparticles is around 300 nm. Then NH 2 -MIL-125(Ti) humidity sensor was fabricated by coating the nanosized materials on interdigitated electrodes. The humidity sensor based on NH 2 -MIL-125(Ti) shows good linearity of RH (11–95 % RH), as well as fast response and recovery time. The RH detecting range is from 11 to 95 % RH at 100 Hz. The response and recovery time are about 45 and 50 s, respectively. Moreover, the sensing mechanism was discussed by complex impedance analysis in detail. These results indicate the potential application of NH 2 -MIL-125(Ti) in humidity sensors.
Considering the harmfulness of nitrogen dioxide (NO2), it is important to develop NO2 sensors with high responses and low limits of detection. In this study, we synthesize a novel SnO–Sn3O4 heterostructure through a one-step solvothermal method, which is used for the first time as an NO2 sensor. The material exhibits three-dimensional flower-like microparticles assembled by two-dimensional nanosheets, in situ-formed SnO–Sn3O4 heterostructures, and large specific surface area. Gas sensing measurements show that the responses of the SnO–Sn3O4 heterostructure to 500 ppb NO2 are as high as 657.4 and 63.4 while its limits of detection are as low as 2.5 and 10 parts per billion at 75 °C and ambient temperature, respectively. In addition, the SnO–Sn3O4 heterostructure has an excellent selectivity to NO2, even if exposed to mixture gases containing interferential part with high concentration. The superior sensing properties can be attributed to the in situ formation of SnO–Sn3O4 p–n heterojunctions and large specific surface area. Therefore, the SnO–Sn3O4 heterostructure having excellent NO2 sensing performances is very promising for applications as an NO2 sensor or alarm operated at a low operating temperature.
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