Green and ultrafast preparation of layered CuO nanoparticles and its ultrahigh-performance ethanol sensing application

•Ultrasonic spray method was firstly applied to prepare layered CuO nanoparticles.•CuO nanoparticles were directly prepared without organic solvent or assembly template.•The ethanol sensing performance was greatly improved, and the optimal detecting temperature was reduced immensely.•The whole process only took several minutes.