Heterostructured SnO₂/CuO Hydrangea Nanocomposites for Highly Sensitive NO₂ Detection

The distinct electronic and chemical characteristics resulting from metal oxide semiconductor heterostructures are of crucial significance to develop advanced sensors. In this research, heterostructured CuO/SnO2 hydrangea nanocomposites are fabricated by atomic layer deposition (ALD) to achieve outstanding NO2 sensing properties. The CuO/SnO2-based sensor demonstrates an extremely high response of 159 to 5 ppm of NO2 at a relatively low operating temperature of 100 °C, which to our best knowledge outperforms the previous CuO-based sensors. The CuO/SnO2 sensor also possesses good selectivity, repeatability, short response-recovery time (45/55 s), and low detection limit (81 ppb). The remarkable sensor performances can be ascribed to the regulation of energy band structure and surface electronic state of the materials. Additionally, the ALD loading of SnO2 increases the crystalline size and strain calculated by X-ray diffraction (XRD) results, but the composite still maintains its nanoscale size (86.2 nm) and high specific surface area (60.11 m2/g). This work proposes an efficient strategy to construct heterojunctions with a regulated band structure at the surface, which endows a great potential in NO2 detection.