Construction Of Metal/g-C₃N₄ Nanocomposite Antibacterial Agent And Its Light-dark Dual-mode Antibacterial Performance

With the improvement of people's living standards,people are more and more aware of the importance of health,and pathogenic microbial contamination has become a common concern and an urgent problem to be solved.Traditional metal inorganic antibacterial agents and organic antibacterial agents have problems such as high cost,poor stability,easy to produce drug resistance and environmental pollution,etc.Therefore,the research and development of environmentally friendly,low-cost,efficient,stable,and non-drug resistant new antibacterial agents is of great significance.Photocatalytic semiconductor antibacterial materials use solar energy to generate active oxygen free radicals,which can kill pathogenic microorganisms in a green,efficient,and broad-spectrum manner.It is an emerging research field with great application potential.Graphite carbon nitride(g-C₃N₄)as a new type of non-metallic semiconductor material has become a research hotspot in the field of photocatalytic antibacterial due to its advantages of non-toxicity,low cost,and visible light absorption.But g-C₃N₄ has the problem of low photoelectron-hole separation efficiency,and all semiconductor materials must rely on light to produce reactive oxygen species,and there are problems such as no light conditions and no antimicrobial activity,which greatly limits its practical application scope.In response to the above two key scientific issues,In this paper,based on the standard reduction potential of the bacterial respiratory chain and the principle of energy level matching,Au and Ni metal nanoparticles that match the standard reduction potential of the respiratory chain are selected to construct a metal/g-C₃N₄ nanocomposite antibacterial material.Make full use of the energy levels matched by bacteria and composite materials,the excellent electron transport ability of metals,the large specific surface area of g-C₃N₄and the advantages of visible light response to realize the efficient antibacterial effect of composite materials in the light-dark dual mode.The specific research content is divided into the following two aspects:1)We prepared a series of Au-supported g-C₃N₄ nanocomposites through a simple calcination method,all Au/g-C₃N₄ nanocomposites exhibited good antibacterial properties against Escherichia coli with and without visible light illumination,breaking the limit of light illumination and realized 24 h long-lasting antibacteria.Under light conditions,the antibacterial efficiency of 0.9%Au/g-C₃N₄ reached 94.1%relative to 10⁷ CFU/m L E.coli.Under dark conditions,the antibacterial efficiency of 1.2%Au/g-C₃N₄ reached 99.1%relative to 10⁵ CFU(Colony-Forming Units)/m L E.coli.The effects of contact time,bacterial concentration and Au loading on its antibacterial performance are discussed in detail.And through photoelectrochemistry,SEM,TEM and reactive oxygen species(ROS)detection revealed the microscopic charge behavior in the system,and proposed a light-dark dual-mode antibacterial mechanism.2)In view of the high cost of precious metal gold,we further choose nickel metal with good conductivity and low cost as an alternative metal material.And by pre-treating the melamine and then calcining,the g-C₃N₄ with hierarchical pore structure and large specific surface area was obtained,and then a series of Ni-loaded g-C₃N₄ nanomaterials were prepared by the photoreduction method.The relationship between antibacterial performance and nickel loading and bacterial concentration was studied in detail,and the results showed that the Ni/g-C₃N₄ nanocomposite showed good antibacterial performance against E.coli and Staphylococcus aureus in the presence and absence of light.Under light and dark conditions,Ni/g-C₃N₄ nanocomposites have shown good antibacterial performance against E.coli and S.aureus.Under light conditions,the antibacterial efficiency of 2.5%Ni/g-C₃N₄ against E.coli and S.aureus reached 92.48%and 84.34%,respectively.Under dark conditions,the antibacterial efficiency of 3.0%Ni/g-C₃N₄ reached90.11%relative to 10⁶ CFU/m L E.coli.Photoelectrochemical and reactive oxygen species testing revealed the microscopic charge behavior of the system,which provided experimental and theoretical basis for the further design of high-efficiency metal/g-C₃N₄nanocomposite antibacterial agents.