Decoration of Co nanoparticles on ZnO-branched SnO2 nanowires to enhance gas sensing

We sputtered zinc-oxide (ZnO)-branched tin oxide (SnO2) nanowires with a Co shell layer with subsequent annealing to produce cobalt (Co) nanoparticles on the ZnO branches. X-ray diffraction, selected area electron diffraction, and lattice-resolve TEM images showed that the nanoparticles corresponded to a hexagonal Co phase. We further studied the NO2 sensing performance of Co-decorated ZnO branched structures in the range of 2–10 ppm at 250 °C. Sensor characteristics were examined in terms of sensitivity (i.e., sensor response), response time, and recovery time; we further proposed the possible mechanisms of enhancement of sensing behavior by the attachment of Co nanoparticles. Co-functionalization enhanced the sensor response and significantly decreased the recovery times. The Co-decorated ZnO branched structures showed promising sensing performance toward NO2 gas at concentrations as low as 2 ppm.