Fabrication and Functionalization of CuO for Tuning Superhydrophobic Thin Film and Cotton Wool

Copper oxide thin film has been fabricated on a smooth glass substrate from a mild and low temperature (similar to 80 degrees C) wet-chemical method exploiting Cu(II)-acetate as a precursor and pyridine as a hydrolyzing agent. The surface of CuO is known for its hydrophilic nature. A transition of the film character from hydrophilic to hydrophobic happens when the as-synthesized CuO film is exposed to the surrounding at room temperature, but it takes several weeks. Surprisingly, the as-synthesized hydrophilic CuO film is readily transformed to a hydrophobic surface when it is modified with various long chain amine or thiols. The surface readily acquires superhydrophobicity showing a water contact angle of 150 degrees. The procedure easily turns natural fiber hydrophobic, and the modified fiber finds useful application. The wettability and the surface structure of CuO films have been examined by using a field emission scanning electron microscope and water contact angle measurement. The CuO thin films are characterized by X-ray photoelectron spectroscopy. The consequence of surface modification with amine and thiols relating to the evolution of the hydrophobic CuO thin film surface has been discussed. The focus of this paper is to develop a simple and reproducible method for fabrication of superhydrophobic CuO thin films and the chemistry of surface modification.