| As a new promising topic,superhydrophobic surfaces have arisen increasing interests in both fundamental researches and practical applications due to the excellent water-repellent and self-cleaning properties.In the wake of the advancements of superhydrophobic surfaces,more and more multi-functionalities have been found,such as the low-/high-adhesion,anisotropy,antibacterial,antiplatelets,chirality,icephobicity,anti-corrosion,drug reduction,water-collecting,electro-wetting,antireflection,structural color and high transparency.The fabrications also diversified greatly,ranging from template,sol-gel,hydrothermal method,self-assembly to electrochemical deposition.Obviously,the multi-functional properties of superhydrophobic surfaces endow such surfaces with great potential in numerous applications in certain areas,for instance,microfluidic transport,anti-pollution,biomedical devices,drug release,photoelectric material,Waterproof and self-cleaning,drag and noise reduction,oil/water separation.In particular,it is of the greatest concern in recent years to offer a brand-new idea for developing efficient,automated and recyclable oil/water separation materials,since they can thoroughly separate a water-and-oil mixture without exhausting any external energy.Furthermore,compared with the traditional separation methods,the special wettability-controlled methods show big advantages in both of the separating speed and the efficiency of separation.Additionally,most of the traditional methods cannot be employed for the separation of immiscible oil/water mixtures,especially for the surfactant-stabilized microemulsions with a droplet size below 20 ?m,while extremely wettable materials can separate emulsions with droplet size from micro to nano-sacle.What is more,due to the surfactant adsorption and pore plugging by oil droplets,most of filtration membranes for emulsion separation are with low flux and quick decline of permeation,which can be overcame by the novel superwetting materials.Firstly,we briefly explained the basic theories of superhydrophobic surfaces,then we introduced the research status of superwetting copper-based materials with multifunctional properties as well as their applications in oil/water separations.Based on these,some methods for fabricating superhydrophobic copper-based materials are presented,the properties and applications of them are also explored.1)By using a simple chemical vapor corrosion method,we obtained copper meshes with surface morphology of nanorod Cu(OH)2,which can be verified by scanning electron microscope(SEM)images.Subsequently,we chose stearic acid and decylmercaptan as modifying agents to discuss the modification effects on Cu(OH)2 surfaces.All of the samples are of great wettabilities after modification with contact angles(CAs)greater than 150°.However,it indicated that surface modified by decylmercaptan directly was more stable and time-saving than that of stearic acid.To further characterize the crystal structure and chemical composition,we applied X-Ray Diffraction(XRD)and X-ray photoelectron spectroscopy(XPS),the results showed that thiol can react with Cu(OH)2 to form a strong interaction,resulting in the stability of superhydrophobicity,while stearic acid is simply adsorbed to cover the surface.For the reason of both superhydrophobicity and superoleophilicity possessed by the as-prepared thioled Cu(OH)2 film,that is,the oil can permeate the mesh easily while water cannot,we used it to separate oil/water mixtures.What is more,choosing copper sheet as another substrate,we prepared superhydrophobic and superoleophilic surface via the same method,and the as-prepared surfaces can resist water effectively and show excellent self-cleaning property.2)Based on the previous experiments,we further explored the process of water/oil separation in detail and firstly proposed the idea of orderly water/oil separation.Combining the chemical vapor corrosion method with thiol modification,we fabricated superhydrophobic/superoleophilic phosphor copper meshes with different mesh numbers to separate water/oil mixtures.It is found that the as-prepared films can separate water/oil mixtures orderly with removing oil from water first and spontaneously collecting water later,which might be attributed to the cooperation of the surface properties and oil influence on wettability.3)We fabricated nanowired Cu(OH)2 films on copper mesh using a common,facile and cost-effective oxidation method by a mixed solution of NaOH and(NH4)2S2O8 at room temperature for a certain time.After thiol-modification,the superhydrophobic superoleophilic copper mesh films were accomplished.We characterized the surface morphology,crystal structure and chemical composition using SEM,XRD and XPS respectively.Surprisingly,the as-prepared films can control the oil permeation and water collection step by step.We found that the density of nanowires can be adjusted by the reaction times.So we discussed the effect of pore for oil/water separation.It was found that all of resultant films with different pore sizes are applicative for separating layered oil/water mixtures.In addition to immiscible oil/water mixture,water-in-oil emulsion also be separated successfully using the resultant films with greatly reduced pore sizes.In our experiment,As reaction time going up to 15 min,the meshes was totally covered with thick nanowires with the pore size less than 2?m.Therefore,it can be confirmed that such films are good candidates to separate water-in-oil emulsions.4)To explore the effect of surface chemical composition on order oil/water mixtures separation by a simple and fast,low cost solution-immersion method,we fabricated Ag-coated copper meshes.After assembling different modifiers including decanethiol,1,1,2,2-tetrahydroperfluorodecanethiol and perfluorohexylethyltrichlorosilane,the as-prepared films are superhydrophobic with different chemical compositions.It was found that all of the resultant films are available to separate oil/water orderly.It indicated that chemical composition was not the main factor to determine the orderly separation process. |
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