Cupric oxide nanostructures were synthesized via a simple reaction between copper nitrate and sodium hydroxide using a sonochemical-assisted method. The synthesized CuO was then characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, ultraviolet-visible and photoluminescence spectroscopy. Our studies show that the CuO nanostructure can be used as a humidity sensor with a short response time (about 6 sec) and a long recovery time (up to 650 sec). Variation of relative sensor impedance (defined as sensing) at relative humidity of 90% was measured to be about 80, which indicates a high sensing of our designed sensor
