In situ assembled ZnO flower sensors based on porous nanofibers for rapid ethanol sensing

Hierarchical three-dimensional ZnO precursor flowers were synthesized by a wet chemistry route. Following subsequent calcinations, unprecedented 3D hierarchical ZnO flowers assembled by spiderweb-like architectures are obtained. Close examination reveals that the 2D spiderweb-like ‘petals’ are composed of 1D porous nanoparticle chains with the diameter about 20–30 nm, in which the nanoparticle chains are assembled by 0D nanoparticles. The surface area to volume ratio of the ZnO flowers was measured to be 27.7 m2/g using the BET method. Such ZnO flowers grew onto a ceramic tube in situ to form a deposited film sensor. The ZnO flowers were also coated onto a ceramic tube to form a coated film sensor for comparison. This deposited film sensor exhibited an improved ethanol sensing performance with an ultrafast response time of 0.3 s and a low detection limit of 0.1 ppm, which was resulted from the 3D hierarchical architecture remaining on the surface of the deposited film sensor.