One-step synthesis and highly gas-sensing properties of hierarchical Cu-doped SnO2 nanoflowers

• We combine morphology, dopant and surfactant to enhance the gas-sensing properties.
• The Cu-doped SnO2 shows high selectivity and sensibility to acetone at 260 °C.
• The hierarchical SnO2 nanoflowers are synthesized by a low-cost and simple hydrothermal approach.

The hierarchical pure and Cu-doped SnO2 nanoflowers were synthesized by a low-cost and simple hydrothermal method at 160 °C for 20 h. These uniform SnO2 nanoflowers were composed of nanosheets. The morphology, structure and gas-sensing performance of the as-synthesized products were characterized by X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and gas-sensing measurement device. The results revealed that the average thickness of the nanosheets is around 18 nm. The XRD of the doped products were similar with the undoped, but had a shift slightly toward right, which indicated that Cu ions had entered into the crystal lattice of SnO2 without deteriorating the original crystal structure. The obtained samples were found that the gas sensors based on this structure had a low optimum operating temperature of 260 °C. Moreover, 2.5 wt% Cu-doped SnO2 displayed the maximum response and excellent selectivity to acetone at operating temperature of 260 °C among all these sensors, and the response value of 2.5 wt% Cu-doped SnO2 to 500 ppm acetone was 221.6 at 260 °C, which was about 11.5 times higher than that of ammonia (about 19.3). In addition, the response and recovery time of 2.5 wt% Cu-doped SnO2 were 9 and 6 s, respectively. It indicated that our sample showed high sensitivity, short response-recovery time and good selectivity to acetone. Finally, the possible formation mechanism of SnO2 nanoflowers and the gas-sensing mechanism of sensors were proposed, too.