Synthesis and gas sensing characteristics of highly crystalline ZnO–SnO2 core–shell nanowires

The ZnO–SnO2 core–shell nanowires (NWs) were synthesized by a continuous two-step vapor growth method at different synthesis temperatures. A crystalline 15–20 nm-thick, SnO2 shell layer was pseudo-epitaxially coated on ZnO NWs with a diameter of 50–80 nm. The gas response of the ZnO–SnO2 core–shell NW sensor to 10 ppm NO2 reached ∼33 times enhancement compared to that of the ZnO NWs at 200 °C. In addition, the ZnO–SnO2 core–shell NW sensors showed selective detection to NO2 at 200–300 °C and to C2H5OH at 400 °C. The enhanced gas responses to NO2 and C2H5OH are discussed in relation to the thin SnO2 shell layer and core–shell configuration of the NWs.