Raspberry-like hollow SnO2-based nanostructures for sensing VOCs and ammonia

The raspberry-like hollow SnO2-based (bare SnO(2 )and Pd-doped SnO2) nanostructures with different dominant crystal facets were prepared facilely using carbon nanospheres as templates via solvothermal method. Volatile organic compounds (VOCs) and ammonia (NH3) gas sensing performances of the hollow SnO2-based structures were studied systematically. The gas sensing performances were investigated in a temperature range of 150-315 degrees C. It was found that 285 degrees C was the optimum operating temperature for both the sensors. The SnO(2)sensor showed excellent VOCs (1-100 ppm) sensing performances, with a fast response/recovery behavior (around 4 s/30 s) at 285 degrees C. While the Pd-SnO2 sensor displayed selective NH(3)sensing characteristics at low concentrations of 1.5-12 ppm, interestingly, with a response/recovery time of about 4 s/80 s at 285 degrees C. Both the SnO2 and Pd-SnO2 sensors showed great repeatability for 8 response/recovery cycles, and very slight response recession for a long period. It was found that not only the morphology, the synergistic effect from the heterojunctions of doped Pd and SnO2, and the Pd catalysis, but also the crystal facets could modulate the sensing performance of metal oxides.