Study On Preparation And Properties Of Graphene-based Antibacterial Materials

In recent years,microbial and pathogenic contaminations have become major concerns on a global level with serious impact on human health and safety.Microbial infections or cross-infections caused by pathogenic microbes can occur in various environments.Graphene-based materials have shown great potential in many domains due to their unique physical and chemical structure and their unique way of interaction with microorganisms which makes them stand out in the antibacterial area.However,with the increasing variety and quantity of antibacterial products,the increasing microbial resistance leads to higher requirements for antibacterial agents.N-halamine compounds have gained much attention owing to their attributes such as antibacterial activity against a broad spectrum of bacteria,stability,durability,high efficiency and rechargeable antibacterial property.Based on this,it is highly imperative to develop efficient,safe and durable novel composite antibacterial agent to meet the increasing market demand.Firstly,N-halamine precursor 5,5-dimethyl-3-?3'-triethoxysilylpropyl?hydantoin was synthesized from 3-chloropropyltriethoxysilane and 5,5-dimethylhydantoin.After polymerization,the polymeric N-halamine precursor PSPH was bonded to the surface of graphene oxide?GO?via a surface grafting method.The sample was characterized by Fourier transform infrared?FT-IR?spectra and X-ray photoelectron spectroscopy?XPS?,and the results confirmed that PSPH was chemically grafted onto the surface of GO.According to the scanning electron microscope?SEM?analysis,there was no obvious effect on the original structure of GO.After chlorination,the chlorinated sample GO-PSPH-Cl exhibited great antibacterial activity,and 6.76 log of Staphylococcus aureus?S.aureus?and 8.08 log of Escherichia coli?E.coli O157:H7?were inactivated within 30 min and 10 min,respectively.However,the dispersity of surface grafted GO decreased,which was not beneficial to the subsequent processing and utilization of the materials.In order to obtain better dispersity of the antibacterial materials,N-halamine precursor monomer APDMH was in-situ polymerized between the layers of GO sheets.Moreover,the end group could react with the oxygen-containing groups on GO to obtain GO-PAPDMH.After modification,the dispersity of GO-based materials was improved,and the GO-PAPDMH could be well dispersed in polar solvents like water or N,N-dimethylformamide.Meanwhile,in the absence of a reducing substance or bacteria,GO as a good carrier endowed GO-PAPDMH-Cl with sustained release property and significantly long storage stability.After 5 months,the chlorine content was still 96%of the initial oxidative chlorine of GO-PAPDMH-Cl.GO-PAPDMH-Cl showed great antibacterial activity,and could completely inactivate S.aureus and E.coli O157:H7 with log reductions of 7.20and 7.06 within 30 min of contact time,respectively.In-situ polymerization method could improve the dispersity of GO-based materials.But compared with the original graphene-based materials,the obtained sample was still easy to aggregate or even restack into graphitic structure,thus affecting the intrinsic properties of graphene-based materials,such as high specific surface area,excellent mechanical property,and etc.In addition,covalent functionalization compromised the sp² structure of graphitic lattices,thus resulting in defects and loss of the electronic properties.A green,facile,and economic method“Spray-Penetration-Flocculation”was utilized to fabricate GO/quaternary ammonium salts?QAS?hybrid macroscopic aerogels to avoid the sudden precipitation of GO when it was combined with polycations and the irregular shape of three dimensional?3D?monolith during the subsequent freeze-drying procedure.QAS was synthesized and bonded to GO via electrostatic interaction,into which a benzene ring was introduced to enhance the combination through?-?conjugation.To minimize the effect of electrostatic interaction between GO and QAS on antibacterial efficacy,another kind of antibacterial agent,N-halamine,was introduced into the main structure of QAS.The obtained GQA after freeze-drying not only possessed low density??18.1 mg/cm³?and ultrahigh porosity?92?97%?,but also exhibited hierarchically porous structure both on the surface and the cross-section.GQA had higher adsorption capacities toward soluble dyes,organic solvents and oils.The as-constructed 3D monolithic GQA possessed great antibacterial activity,causing 6.00 log reductions of S.aureus and 6.26 log reductions of E.coli O157:H7 within 5min of contact time.The composite aerogels prepared by electrostatic interaction had potential application in the adsorption of dyes.Most organic dyes released from textile industries are highly toxic and nonbiodegradable.A new method was adapted to replace the previous covalent and non-covalent modifications by introducing heteroatoms into the main structure of graphene to improve its catalytic activity while keeping the inherent properties of graphene-based materials.With GO as the reactive graphitic template and phenyl hydrazine as the dopant,an innovative low-temperature?100^oC?ring-forming reaction was proposed.After the reaction,the indole structure grew at the edge of the graphene,and finally the N-doped graphene?NG?was obtained.X-ray diffraction?XRD?,Raman spectroscopy?Raman?and XPS results indicated that N atoms were successfully introduced into graphene,and pyrrolic N was dominant in the doped N.Under UV light irradiation,NG showed ultrafast and powerful photocatalytic activity and completely decomposed methylene blue molecules within 10 min.Radical·O₂^-played a vital role in the photocatalytic efficiency of NG72 towards MB.In addition,NG72 exhibited good photocatalytic biocidal activity and could inactivate 100%of S.aureus and 99.86%of E.coli O157:H7 within 120 min of irradiation time.Carbon dots are also a new type of carbon nanomaterials,which have attracted much attention due to their unique optical properties.Carbon dots passivated by nitrogenous compounds exhibited unique photo-induced antibacterial properties.Several carbon/TiO₂hybrid dots with the configuration of nanoscale carbon domains incorporated with different sizes of TiO₂ nanoparticles?8 nm and 25 nm in diameter?were obtained through a microwave-assisted method.The hybrid carbon dots could be well dispersed in deionized water.According to the absorption spectrum,fluorescence spectrum,and particle size analysis of the samples,they showed very similar absorption spectrum and fluorescence spectrum despite the fact that the configurations of several carbon dots were different since their optical properties were mainly related to the nano-carbon region in the carbon dots.However,in these carbon dots,the relative sizes and configurations of carbon core and TiO₂ led to significant differences in antimicrobial performance.Compared with the carbon dots containing TiO2 with smaller size?8 nm diameter?,the carbon dots containing larger TiO2?25nm?showed higher antibacterial properties.The carbon region activated by visible light could not only directly act on bacteria,but also act as photo-initiator of TiO2,thus improving the antibacterial performance of the material.The introduction of nano-carbon made the excitation region of TiO2 shift from the ultraviolet region to the visible region,thus broadening the application range of TiO₂.The characterization analysis of intracellular ROS production,lipid peroxidation test,and cell fluorescence image showed that lipid peroxidation mainly caused by ROS led to the rupture of bacterial cell membrane,which then reacted with each component in the cell,and finally led to bacterial death.GO-PSPH as the raw material was loaded on the surface of cotton fabrics through the ultrasonic-assisted dipping-drying method,and the modified cotton fabric with multiple functions was prepared after reduction treatment.The obtained cotton/r GO-PSPH possessed the highest UV blocking ability,with the UPF value of 187;and its contact angle was about130^o,indicating great hydrophobic property.After chlorination,the UPF of cotton/rGO-PSPH-Cl can still reach 132.And the hydrophobic property was further improved?contact angle was 140^o?,which endowed cotton/rGO-PSPH-Cl with great self-cleaning performance.The cotton/rGO-PSPH-Cl possessed great antibacterial activity,and was able to completely inactivate all inoculated 5.07 logs S.aureus and 5.18 log E.coli O157:H7 within 1min and 5 min,respectively.In addition,the chlorine content in the chlorinated cotton/rGO-PSPH fabric was negatively related to the electrical conductivity;therefore,the electrical signals of the chlorinated cotton/rGO-PSPH fabrics could be used to monitor the chlorine content for determining the time of recharging chlorine in order to keep its high antimicrobial efficacy.