SnO₂ Quantum Dots-Functionalized MoO₃ Nanobelts for High-Selectivity Ethylene Sensing

Highly selective and sensitive detection of the phytohormone ethylene, especially at low concentrations, is essential for control of plant growth, development, senescence, and fruit ripening. Metal oxide semiconductors exhibit excellent sensing properties due to their excellent physicochemical properties and unique structures. This study developed SnO2 quantum dots (QDs)-functionalized MoO3 nanobelts (NBs) for highly selective and sensitive ethylene detection. The prepared nanocomposite is composed of MoO3 NBs surface loaded with fine SnO2 QDs, and the n-n heterojunction is formed at the interface. Sensing properties of the SnO2 QDs/MoO3 NBs to ethylene are measured, and results reveal that 2.5%-SnO2 QDs/MoO3 NBs exhibited excellent response (100 ppm 40%), low detection limit (500 ppb), and selectivity to ethylene at a low operating temperature (150 °C) compared with pure MoO3 NBs and SnO2 QDs. The enhanced gas-sensing performance is explained based on the modulation of the interface barrier caused by the formation of n-n heterojunctions at the SnO2/MoO3 interface and the synergetic effect of these two materials. This heterojunction indicates that SnO2 QDs/MoO3 NBs are promising sensing materials for the ethylene gas sensor.