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.