Self-assembled 3D hierarchical S-doped SnO2 nanoflowers based room temperature ammonia sensor

This paper reports an ammonia sensor at room temperature (20 +/- 2 degrees C) without heating device. Pristine SnS2 precursor was synthesized by hydrothermal method and three-dimensional (3D) hierarchical SnS2 nanoflowers were successfully obtained after being calcined at 450 degrees C. According to synthesis mechanism, 3D hierarchical nanoflowers were self-assembled from two-dimensional (2D) nanosheets; meanwhile 2D nanosheets were assembled from nanoparticles. The materials were characterized by XPS, SEM, TEM and XRD to investigate morphological and element content. The gas sensing performance of sensors at 20 +/- 2 degrees C and 40 +/- 5% relative humidity have been systematically investigated for ammonia. The results demonstrated that the response of S-doped SnO2 (460%) is about 2.5 times of pristine SnS2 (181%). The S-doped SnO2 exhibited great selectivity and excellent stability at 20 +/- 2 degrees C. Compared to the pristine SnS2, the conductivity of the S-doped SnO2 material is noticeably improved, and the sensitization mechanism might be ascribed to SnO2/SnS2 heterostructure and the special 3D hierarchical nanoflower structure. The sensing properties of 3D hierarchical S-doped SnO2 nanoflowers make it a prospective material for the detection of ammonia.