Enhanced field emission of CuO nanowires by aluminum coating for volatile organic compound detection

This work reports-a novel ionization gas sensor assembled by the building blocks of CuO nanowires coated with a thin layer of aluminum. The superficial aluminum is then partially oxidized to alumina forming an Al₂O₃/Al/CuO hybrid nanocomposite. It is revealed that this nanocomposite enables the discharge of volatile organic compound at ppm level at an ultralow ionization voltage (several tens of volts) with high stability. Typical organic gases, including toluene, acetone, isopropanol, and methanol can be identified by this sensor with the specific threshold voltages in the cleanroom. In addition, the concentration of isopropanol gas has also been detected at a low limit down to 5 ppm. The gas sensing mechanism is due to the variation of voltages that are required to ionize a specific gas as the fingerprint. Based on the comparative discharge experiments along with the energy band analysis, the high enhancement of gas ionization is attributed to the optimized low work function and intermediate energy interlayer in combination with the tip effect of Al₂O₃, Al, and CuO. This work may pave a new way for the design of the similar material system to advance ionization gas sensing.