SnO 2 QDs sensitized ZnFe 2 O 4 spheres with enhanced acetone sensing performance.

Herein, SnO 2 QDs (<10 nm) with small size instead of conventional nanoparticles was employed to modify ZnFe 2 O 4 to synthesize porous and heterogeneous SnO 2 /ZnFe 2 O 4 (ZFSQ) composites for gas sensing. By an immersion process combined with calcination treatment, the resultant porous ZFSQ composites with different contents of SnO 2 QDs were obtained, and their sensing properties were investigated. Compared with bare ZnFe 2 O 4 and SnO 2 QDs, porous ZFSQ composites based-sensors showed much improved sensor response to acetone. For contrast, the sensor performance of ZFSQ composites was also compared with that of ZnFe 2 O 4 sphere modified by SnO 2 nanoparticles with different size. The porous ZFSQ composite with 5 wt% SnO 2 QDs (ZFSQ-5) showed a better acetone sensing response than that of other ZFSQ composites, and it exhibited a high response value of 110-100 ppm of acetone and a low detection limit of 0.3 ppm at 240 °C. In addition to the rich heterojunctions and porous structure, the size effect of SnO 2 QDs was other indispensable reasons for the improved sensor performance. Finally, the ZFSQ-5 composite sensor was attempted to be applied for acetone sensing in exhaled breath, suggesting its great potential in monitoring acetone.