Morphology controllable Fe2O3 nanostructures derived from Fe-based metal-organic frameworks for enhanced humidity sensing performances

Abstract

Porous metal oxides nanostructures with controlled shape have received great attention due to their promising applications in many fields. In the present investigation, three nano-sized (100～200 nm) Fe-based metal-organic frameworks (Prussian Blue) with different morphologies were synthesized. The morphologies of the Prussian Blue (PB) can evolve from cube, quasi-cube to sphere only by tuning the amount of PVP and the reaction temperature. And then, porous Fe2O3 nanostructures with the same shapes were obtained by calcining the PB templates at the optimal temperature 350 °C in air. The humidity sensing devices were fabricated by the three nanostructures. Humidity sensing tests reveal that the three sensors all displayed excellent humidity sensing performances, such as ultra-fast response, high response, good linear relationship, small humidity hysteresis. Among them, the quasi-cubic Fe2O3 nanostructures exhibited the best performance: the response time was less than 2 s, the response was 1568 in the humidity range of 11% ˜ 95%RH, the maximum humidity hysteresis was 0.59% and the value of the linearity fit correlation (R2) was 0.9922. Meanwhile, the sensor fabricated by the quasi-cubic nanostructures reveals that the capacitance change can reach 120% from 0% RH to 8%RH, demonstrating good potential to detect low humidity. Such outstanding humidity sensing performance of the sensor should be attributed to the synergic effect of the large specific surface area (169.7 m2/g) and highly porous structure of the quasi-cubic Fe2O3 nanostructures.