Preparation and characterization of gradient wettability surface depending on controlling Cu(OH)_2 nanoribbon arrays growth on copper substrate

摘要

Gradient wettability surface was prepared on copper substrate via a facile alkali assistant surface oxidation technique. It was based on the control of cupric hydroxide (Cu(OH)_2) nanoribbon arrays growth from the upper part to lower part along the vertically placed copper substrate in an aqueous solution of NaOH and (NH_4)_2S_2O_8. Thus the gradient wettability functionalized Cu(OH)_2 nanoribbon arrays were directly fabricated on copper substrate by varying the immersing time of different positions along the substrate surface. By using a relative dilute NaOH solution (0.75 mol/L) and (NH_4)_2S_2O_8 solution (0.03 mol/L), and regulating dropping speed, the surface gradient wettability changing from the original contact angle of copper substrate (90.5°) to surperhydrophilicity (3.0°) was prepared. The surface fabricated on copper substrate may keep its gradient wetting property after immersed in water bath at 100℃ for 10h. The water contact angle measurement (CA), Scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were employed to analyze the wettability, morphologies, crystal structure, and surface chemical compositions of the Cu(OH)_2 nanoribbon arrays on copper substrate. This research is expected to be significant in providing a new strategy for the preparation of novel gradient wettability material with potential industrial applications on copper substrate.