Fabrication Of Copper Surfaces With Controlled Underwater Oil Wettability

Underwater superoleophobic and superoleophilic interfacial materials areimportance and demanded for many applications, such as anti-pollution, waterseparation and microfluidic control. In this article, some copper surfaces withcontrolled oil wettability and adhesion were prepared.（1）The CuO microfowers/Cu（OH）₂nanorod arrays hierarchical structure wasprepared on the copper substrate through a simple one-step immersion approach andthen were modified with HS（CH₂）₁₁OH and HS（CH₂）₉CH₃. With the increase of XOH,surfaces wettabilitiy can be controlled from underwater superolophilic tosuperolophobic. The controllability can be ascribed to the cooperation between thesurface chemicals and hierarchical structure, espeacilally the existence ofmicrofowers/nanorod arrays hierarchical structure provide us a more convinent wayto control the surface wettability from superoleophobicity and superoleophilicity.（2） After alkali assistant surface oxidation, the copper was heated to changeCu（OH）₂to CuO, and then it was reduced to form Cu. Finally, HS（CH₂）₉CH₃andHS（CH₂）10COOH were modified on the surface, and then the surface withswitchable oil-wettability between the underwater superoleophobic andsuperoleophilic can be prepared. At low pH, the oil can spread quickly, and thesurface shows underwater superoleophilicity. As for high pH, the oil droplets cannotspread on solid surface, and result in underwater superoleophobic. The method canalso be applied on a nanostructured copper mesh surface to achieve a pH-controlledoil-water separation membrane.（3） Rough nano Cu2O structure was fabricated on the glas substrate using ionsputtering, and then modified with different carboxylic acid, and thesuperoleophobic surfaces with controllable oil adhesion can be prepared. Theoil-wettability of these surfaces was underwater superoleophobic, while theoil-adhesions were different. The sliding angle of a oil droplet on the surfacemodified with CH₃CH₂COOH was less than5°. While on the surface modified withCH₃CH₂COOH it increases to about12°. When the carbon chain length increased to8, the oil cannot slide on the surface. It was found that oil-adhesion increased inaccordance to the increase of carbon chain length.