TiO2@Ag-GO Composite Materials with Enhanced Photocatalytic and Antimicrobial Activities
Environmental pollution has become an increasingly serious issue.Numerous studies have revealed that the increased incidence of cancer and other diseases can be associated with environmental pollution.Pollutants include not only inorganic matter,but also bacteria and organic matter.Photocatalytic breakdown of contaminants in the environment is considered an ideal cleaning technology,and one of the most promising photocatalytic compounds is titanium dioxide(TiO2).However,their utilization efficiency and range are limited because of their narrow energy bandwidth and the quick recombination of photogenerated electrons and holes.Therefore,developing efficient TiO2-based photocatalytic composites is crucial.A simple sol-gel and one-step Marangoni methods were used to efficiently combine TiO2,Ag nanoparticles(AgNPs),and graphene oxide(GO)to make composites of TiO2@Ag-GO with significantly enhanced photocatalytic activity and antibacterial capabilities.GO has multiple catalytically active centers that can efficiently degrade pollutants via photocatalytic reactions.Simultaneously,it can improve charge separation,restrict the recombination of photogenerated electrons and holes,and boost the photocatalytic activity of TiO2.AgNPs can hold electrons,facilitate charge separation,and release Ag+,making them a material with diverse antibacterial properties.Ag-doped TiO2 sol-gel was prepared by the sol-gel method,and the prepared sol-gel was then coated on the surface of an Si substrate via spin-coating.An anatase-type Ag-doped TiO2 film(TiO2@Ag)was prepared via heat treatment.Finally,the TiO2@Ag-GO nanocomposite photocatalytic material was effectively prepared by transferring a large-area ultrathin GO film,produced via the single-step Marangoni process,onto its surface.The compositions of the films made of TiO2 and TiO2@Ag were examined using X-ray Diffraction(XRD),Transmission Electron Microscope(TEM),High Resolution Transmission Electron Microscopy(HRTEM),and X-ray Photoelectron Spectroscopy(XPS).the Ag in the TiO2@Ag sample was primarily in the form of Ag2O nanoparticles,and the TiO2 sample was primarily composed of anatase crystals.Ion-release experiments demonstrated that TiO2@Ag-GO could stably release Ag+from Phosphate Buffered Saline(PBS)for at least 12 d.The rates of TiO2 and TiO2@Ag degradation in a 2 h photocatalytic methylene blue degradation test were 42.4 and 52.5％,respectively.Simultaneously,the degradation rate increased considerably after the addition of GO,reaching 74.5％for TiO2@Ag-GO.These findings suggest that Ag doping and GO loading enhance the photocatalytic activity of TiO2.This is because when TiO2 is modified by AgNPs and GO,TiO2 absorbs UV radiation;the electrons generated by TiO2 are transferred to the AgNPs,which demonstrate electron storage capability,serving as electron traps that promote charge separation.In contrast,GO on the semiconductor surface contains numerous catalytically active centers that can efficiently break down pollutants in a photocatalytic reaction.Furthermore,GO significantly enhances photocatalysis by increasing the degree of charge separation and preventing the recombination of photogenerated electrons and holes in the semiconductor.Seeding assays with Gram-negative(Pseudomonas aeruginosa)and Gram-positive bacteria(Staphylococcus aureus)were used to assess the broad-spectrum antibacterial capabilities of the composites.Scanning Electron Microscope(SEM)images and statistical analyses of bacterial adhesion and proliferation revealed that many bacteria attached to and proliferated on the TiO2 surface,and the bacteria tended to aggregate to form colonies.The wrinkled shape of the GO surface prevented bacterial aggregation,resulting in a more even distribution of the bacteria on the TiO2-GO surface,with significantly fewer bacteria present.The TiO2@Ag and TiO2@Ag-GO surfaces drastically reduced the number of bacteria and severely damaged their morphology,demonstrating significant bactericidal activity.AgNPs and Ag+can bind to negatively charged bacterial biofilms,disrupting the bacterial membrane potential,and leading to bacterial death.This simple TiO2-based composite,with significant photocatalytic and antibacterial activities,has considerable potential for use in photocatalytic cleaning.
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