Heterolayered SnO2/SnSe Nanosheets for Detection of NO2 at Room Temperature
The construction of heterogeneous structures could boost the performance of materials in gas sensing applications since the interface may enhance charge transfer. However, appropriate design and containable synthesis methods of heterogeneous structures with high-quality interfaces remain challenging. In this paper, heterolayered SnO2/SnSe nanosheet composites were prepared by regulating the alkali concentration to control the self-assembly rates of SnSe nanosheets while forming defect point oxidation. Heterolayered SnO2/SnSe nanosheets were synthesized by a one-step hydrothermal method and then used as a highly sensitive sensor for the detection of NO2 at room temperature. The as-obtained SnO2/SnSe materials were characterized using scanning electron microscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and I–V polarization to analyze the relationships between the heterogeneous structural morphology, crystallography, chemical components, electrical properties, and sensitivity mechanism. The results showed that the SnO2/SnSe-0.4 sample was prepared by the one-step hydrothermal method at the NaOH concentration of 0.04 mol/L. The SnO2/SnSe-0.4 sensor showed great sensitivity and higher selectivity to 1 ppm NO2 (resistance ratio = 7.8) at room temperature, roughly 7.1 and 2.7 times higher than that of pure SnSe and SnO2, respectively. In addition, the sensor exhibited a lower detection limit of 0.1 ppm. The improved sensing performance could be attributed to the large number of P–N heterojunctions of the SnO2/SnSe-0.4 material, enhanced interface charge transfer, and increased defect point oxidation in the material surface. The experimental results showed that SnO2/SnSe-0.4 is a very promising room-temperature NO2 gas sensing material, providing guidance for the rational design of heterogeneous structural sensors.
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