Mesoporous In₂O₃/ZnO heterogeneous microtubes replicated from waste willow catkins for high response and rapid detection of NO₂ gas at low temperature

Development of low-temperature NO2 sensors has recently gained extensive interests. However, how to realize their over-all sensing abilities of high response and rapid detection is still challenging. Herein, adhering to the concept of sustainable development, waste willow catkins have been selected as template and soaked in Zn/In nitrates solution with two types of molar ratios. Then, the obtained precursors were placed in a furnace to un-dergo calcination at 500 celcius, generating two biomorphic In2O3/ZnO heterogeneous microtubes. All the tubes were assembled by well-crystallized small-size nanoparticles. Thereinto, 16.4 wt% In2O3/ZnO sensor exhibits well comprehensive gas-sensing performances towards trace NO2 at low 92 degrees C. That is, its response value (S = 883) and recovery time (10 s) to 10 ppm NO2 are higher and faster than those of most one-dimensional ZnO-based NO2 sensors reported so far. Meanwhile, it also has good selectivity and low detection limit (10 ppb), as well as satisfactory long-term stability and humidity resistance. Therefore, the mesoporous 16.4 wt% In2O3/ZnO het-erogeneous microtubes rich in oxygen vacancy defects are available as a candidate for detecting trace NO2 at low temperature.