Microstructure Regulation And Anti-fouling Mechanism Of Copper Oxides

Marine biofouling hinders the development and utilization of marine resources and causes great harm to economy,environment,ecology and security.There is a long way to go to prevent marine biofouling.Among plenty of anti-fouling technologies,the most economic and convenient way to inhibit the growth and attachment of fouling organisms is dependent on the release of anti-fouling compounds.Copper oxides are widely used because of their excellent antibacterial capacity.Based on the unstable anti-fouling performance of copper oxides,the aim of this work is to prepare copper oxides with different morphologies/microstructures by adjusting process parameters.Copper oxides with long-term anti-fouling activity were obtained by regulating the morphologies/microstructures of copper oxides to tailor their ion release rate.Firstly,the concentration of reactants was varied to regulate the nucleation and growing mode and Cu₂O particles with similar size and different morphology were fabricated via liquid phase reducing method.Cu₂O particles were incorporated into self-polishing acrylic resin coating and the influence of morphology for Cu₂O particles on the anti-fouling performances of the as-prepared composite coatings was investigated.The structure-activity relationship between the morphology of Cu₂O and its anti-fouling property was established by measuring Zeta potential and ion leaching rate.The morphology of Cu₂O particle was able to cause the difference of anti-fouling performance by affecting its activity in aqueous solution.The more active in aqueous solution Cu₂O particle was,the easier copper ion released,and the better anti-fouling activity of the composite coating possessed.Meanwhile,the anti-fouling mechanism of Cu₂O particles was studied by observing the morphology variation of Gram-negative bacterium Escherichia coli（E.coli）and Gram-positive bacterium Bacillus subtilis（B.subtilis）before and after exposure to the composite coating.For E.coli,Cu₂O particles inhibited its growth mainly through the release of copper ion;For B.subtilis,Cu₂O particles accelerated its death mainly through the production of reactive oxygen species.The difference of antibacterial mechanism between the two bacteria was due to the thickness of cell wall.Secondly,nanowire structure,nanowire/microflower structure and nanosheet/microflower hierarchical structure were obtained on copper surface by changing solution concentration and etching time via solution etching method.The effects of surface microstructures and components on surface roughness and wettability were investigated.Etching treatment was capable to increase the surface roughness and hydrophilicity/hydrophobicity of copper surface.With different concentration of etching solution,the difference of wettability in early etching process was owing to the production of hydrophobic Cu₂O formed by incomplete oxidation of copper,and the difference of wettability in later etching process was attributed to the different area fraction of air pocket caused by different microstructure.The suppression effect of micro/nano structures on bacterial growth and attachment was investigated by cyclic antibacterial trial.Nanowire structure showed good ability to resist bacterial attachment because of the less contact area with bacteria.While nanowire structure was prone to being corroded in solution with high salinity and losed the ability to inhibit bacterial attachment on account of forming a relatively flat corrosion product layer.Nanosheet/microflower hierarchical structure was stable and difficult to corrode.Its capacity for restraining bacterial attachment was positively correlated to the density of microflower.When there were more microflower structures,the contact area between bottom nanosheet and bacteria was small,which was not conducive to bacterial attachment and made the copper surfaces own a good anti-fouling ability.