Fabrication Of ZnO-based Antibacterial Cotton Fabrics And Mechanism Study

Safety of life and health is the basic guarantee for human survival,social progress and economic development.Microbial contamination of exposed surfaces is particularly common in daily life and represents a potential safety hazard for human health.Cotton textiles with superior antibacterial properties not only effectively prevent microbial contamination of surfaces,but also improve the service life of natural cotton fabrics.Therefore,the development of antibacterial functional cotton textiles is of great importance.Zinc oxide nanoparticles（Zn O NPs）are inexpensive,non-toxic,less prone to drug resistance and stable,making them ideal antibacterial materials.However,the low antimicrobial activity of Zn O NPs and the fact that they are not easily immobilised on cotton substrates by physical methods make it difficult for a single Zn O antimicrobial agent to meet the practical application requirements of cotton textiles.To address the above problems,this paper successfully synthesized Zn O nano-based antibacterial cotton fabrics with highly efficient antibacterial properties by improving the antibacterial properties of Zn O NPs through organic antibacterial agent hybridization and copper phosphide nanoparticles（Cu_xP NPs）compounding.The specific studies are as follows:（1）The organic-inorganic hybrid antimicrobial material（Zn O/QAS/cotton）was prepared by using a simple and green dip-rolling-hot-drying method to co-load organic antimicrobial material quaternary ammonium salt compounds（QAS）and Zn O NPs on the surface of cotton fabric using neutral silica sol as a binder.The physical properties such as structure,composition and morphology of the hybrid materials have been systematically investigated using many characterization tools.X-ray diffraction（XRD）,scanning electron microscope（SEM）and inductively coupled plasma atomic emission spectrometer（ICP-OES）show that Zn O and QAS antimicrobial agents can be successfully and uniformly loaded onto natural cotton fabrics by dipping and rolling process without changing the structure of natural cotton fabrics.Fourier transform infrared spectroscopy（FTIR）and X-ray photoelectron spectroscopy（XPS）results verified that the antimicrobial agent firmly adheres to the cotton fiber by forming chemical covalent bonds and gelling structures.Through the joint modification of QAS and Zn O NPs,the hybrid cotton fabric has superior hydrophobic properties,good thermal stability and mechanical properties,UV resistance and self-cleaning properties.The results of antibacterial experiments showed that the organic-inorganic hybrid cotton fabric had excellent antibacterial properties,and Zn O/QAS/cotton achieved 99.99%bactericidal activity against Gram-negative bacteria Escherichia coli（E.coli）and Gram-positive bacteria Staphylococcus aureus（S.aureus）within 8 h.At the cell level,changes in bacterial morphology before and after antimicrobial activity were analyzed by confocal laser scanning microscopy（CLSM）and SEM,which confirmed that most bacteria were killed on the Zn O/QAS/cotton surface.The antibacterial mechanism of the hybrid material was systematically investigated based on four common antibacterial mechanisms:electrostatic interaction,ion spillover,reactive oxygen species（ROS）generation,and mechanical damage effect.The results of Zeta potential analysis confirm that the introduction of QAS can substantially increase the surface potential of the substrate material,inferring that the contact mechanism of QAS may be the main antibacterial mechanisms of Zn O/QAS/cotton hybrid material.Experimental results using inductively coupled plasma mass spectrometry（ICP-MS）and ion spillover validation experiments,and zone of inhibition（ZOI）confirmed the presence of Zn²⁺ion leaching from the hybrid materials and that it has an effect on the antibacterial activity of the hybrids.The small effect of ROS on antibacterial activity was confirmed by ROS capture experiments.The mechanical damage effect of the hybridized material was evaluated using the colony counting method（difference）.Combined with the results of the experimental analysis of the above four antimicrobial mechanisms,the antimicrobial mechanism of the organic-inorganic hybrid antimicrobial material（Zn O/QAS/cotton）was deduced.The antibacterial mechanism is mainly the contact mechanism of the"N⁺"in the quaternary ammonium salt molecule（electrostatic interaction）.Beyond this,ROS and the release of Zn²⁺play a minor role and the mechanical damage to the material itself is minimal.（2）In response to the problem that current commercial Cu-based antimicrobial agents mainly rely on Cu ions for sterilisation,this paper designs and develops a highly effective Cu-based antimicrobial cotton fabric based on ROS antimicrobial.Synthesis of copper oxide-zinc oxide nanoparticles（Cu O-Zn O NPs）by alkali precipitation using Zn O NPs as a carrier and copper acetate as a copper source.Subsequently,Cu O-Zn O NPs were phosphated to obtain copper phosphide-zinc oxide nanoparticles（Cu_xP-Zn O NPs）.The composite antimicrobial material（Cu_xP-Zn O/cotton）was then prepared using neutral silica sol as a binder and Cu_xP-Zn O NPs as an antimicrobial agent,which was loaded onto the cotton substrate by the dip-rolling-hot-drying method.The physical properties such as structure and morphology of the composite were investigated by a series of characterization instruments.Characterization results such as XRD,SEM and ICP-OES show that the dip-rolling-hot-drying process can load small particles of Cu_xP-Zn O NPs onto natural cotton fabrics in a uniformly dispersed manner without changing their own structure.FTIR and XPS results showed that Cu_xP-Zn O NPs were firmly attached to the cotton fiber surface,possibly through the formation of partial chemical covalent bonds and gelling structures.The composite antibacterial cotton fabric has good thermal stability,self-cleaning and mechanical properties.Cu_xP-Zn O/cotton could achieve 99.99%bactericidal activity against E.coli and S.aureus within 8 h.After 50 washes,94.7%antibacterial efficiency was retained,indicating that the composite has excellent antibacterial properties and resistance to water washing.At the cellular level,the changes in cell morphology before and after antimicrobial activity were analyzed by CLSM and SEM,which confirmed that most bacteria were killed on the Cu_xP-Zn O/cotton surface.Based on the four major antimicrobial mechanisms（electrostatic interaction,ion spillover,ROS generation,and mechanical damage effect）of the current antimicrobial material,the antimicrobial mechanism of the material was systematically studied and analyzed.The results of Zeta potential analysis show that the negative Zeta potential of the composite antimicrobial material facilitates the mutual contact between the antimicrobial agent and the bacteria,thus improving the antibacterial properties of Cu_xP-Zn O/cotton.The presence of Cu²⁺and Zn²⁺ions leaching from the composites was confirmed by ICP-MS,ion spillover verification and ZOI experimental results,and had some effect on the antibacterial activity of the composites.The ROS capture experiments of the composites and electron paramagnetic resonance spectroscopy（EPR）further explored and verified that a large amount of singlet oxygen（¹O₂）is produced in the Cu_xP-Zn O/cotton antibacterial system,indicating that ¹O₂ in ROS is the main contributor to the antibacterial activity.The mechanical damage of the composites was evaluated by the colony counting method（difference）.Combining the experimental results of the above four antibacterial mechanisms,it is inferred that the antibacterial mechanism of the composite（Cu_xP-Zn O/cotton）is mainly due to ¹O₂ in the ROS.Apart from this,the contact mechanism between the carrier material and the bacteria,the release of metal ions(Cu²⁺,Zn²⁺)play a minor role and the mechanical damage to the material itself is minimal.Both antimicrobial cotton fabrics maintain good overall performance and are textile materials universally applicable to a wider range of fields such as health care,hygiene,air purifiers,and food packaging.This paper is expected to provide a more comprehensive and useful clue and idea for the practical application and antimicrobial mechanism research of organic-inorganic composite antimicrobial cotton fabrics and metal phosphide-zinc oxide antimicrobial cotton fabrics in the future.