Construction Of TiO₂ Nano-smart Surfaces And Their Relationship Between Antibacterial And Anti-adhesion Properties And Surface Wettability

Bacteria are the oldest and largest number of biological groups on the earth.Bacteria are easy to adhere to the surface of various materials to form biofilms that are difficult to remove,which seriously endanger human health and economic development.In recent years,titanium-based materials have been widely used in aircraft,ships,biomedicine and other high-tech industries due to their excellent mechanical and chemical properties.Once bacteria adhere to the surface of titanium-based materials,it will lead to metal corrosion,deterioration of drinking water,food origin disease,bacterial infection and other issues,serious harm to human health and cause great economic loss.Therefore,preventing bacteria from adhering to the surface of titanium-based materials has attracted much attention.Constructing superhydrophobic TiO₂/Ti composite surface with release-killing and photocatalytic bactericidal performances has been proved to be an effective strategy for preventing bacterial adhesion,however,there also exists some limitations,such as efficient bactericidal performance of TiO₂only for UV photocatalysis but low efficiency for solar photocatalytic,and the obstacles of slow-release effect of the air layer to the release of antibacterial agents.Herein,a strategy to enhance the photocatalytic antibacterial performance of TiO₂was proposed to realize the synergistic antibacterial effect of released reactive oxygen species(ROS)and metal ions,and successfully construct a superhydrophobic/superhydrophilic convertible bacterial anti-adhesive surface.The presence of TiO₂nanotube arrays on Ti endows it with hydrophobicity-hydrophilicity switch under ultraviolet radiation.The antibacterial and bacterial anti-adhesive properties of the composite surface under two different wetting conditions were tested and analyzed.The difference and correlation of antibacterial and bacterial anti-adhesion of composite surfaces under two wetting conditions were explored,and the internal mechanism of antibacterial and bacterial anti-adhesion of composite surfaces was revealed.The main research contents are as follows:(1)Construction of antibacterial and anti-adhesive smart composite surface:The TiO₂nanotube array structure(TNTs)surface was constructed on the titanium plate by anodic oxidation and AgCl nanoparticles(NPs)were decorated on the surface of TNTs by successive ionic layer adsorption and reaction(SILAR).Then,part of AgCl NPs was reduced to Ag NPs by photoreduction to obtain Ag/AgCl NPs.A series of superhydrophobic antibacterial and bacterial anti-adhesive surfaces with different Ag/AgCl NPs loading were obtained by modifying the composite surface with perfluorodecyltrimethoxysilane(PFDTMS).Based on the photo-induced hydrophilicity of TiO₂,the reversible conversion of superhydrophobicity/superhydrophobicity of the composite surface was realized by UV irradiation and dark storage.(2)Study of the antibacterial performance test and antibacterial mechanism of composite surface:The antibacterial test results showed that the antibacterial activity of the composite surface increased with the increase of the loading amount of Ag/AgCl NPs,and only loading 3.66?g cm^-2Ag/AgCl NPs could make the antibacterial rate of the composite surface against S.aureus and E.coli reach 98.65%and 99.15%,respectively.The antibacterial mechanism study shows that the synergistic bactericidal effect of ROS and silver ions released by the composite surface under solar irradiation is the internal mechanism for achieving efficient antibacterial activity of the composite surface.(3)The influence of surface wettability on the antibacterial properties of composite surfaces and the exploration of the internal mechanism:The antibacterial test results confirmed that the antibacterial performance under superhydrophilic condition was better than that under superhydrophobic condition for the same series of samples.By measuring the release rate of silver ions by the composite surface under two wetting states,and combining with molecular dynamics(MD)simulation,it was revealed that the rejection effect of superhydrophobic surface was the internal reason for the difference in antibacterial properties of the composite surface under two wetting states.(4)Study of the bacterial anti-adhesive performance test and antibacterial mechanism of composite surface:the test results showed that the composite surface had excellent superhydrophobicity,oleophobicity and low surface adhesion under superhydrophobicity,which made it difficult for bacteria to adhere to the surface,and the formation of air layer on the surface could also repel bacteria.Under the synergistic effect of active-attack antibacterial mechanism,the bacterial anti-adhesive rates of E.coli and S.aureus reached 99.47%and98.50%,respectively.(5)Study on the durability of the composite surface:The abrasion resistance and chemical corrosion resistance of the composite surfaces were studied by friction tests,acid tests(p H=1),alkali tests(p H=14)and salt tests(Na Cl:1 mol L^-1).In addition,the cyclic antibacterial test results showed that after 14 cycles,the antibacterial rate of the composite surface could still reach more than 74%.The results of cyclic bacterial anti-adhesive test showed that after 12 cycles,the bacterial anti-adhesive rate of the composite surface could still reach more than 78%.