Research On The Mechanism And Application Of Preparing Nano Silver Copper By Reduction Of Polyvinyl Alcohol (PVA

The research and development of new material antibacterial agents can help alleviate the problem of increasing bacterial resistance caused by the overuse of antibiotics.According to the current scientific research,it can be seen that Ag NPs and Ag-Cu NPs have excellent antibacterial properties,but they have defects such as high production cost,low yield and serious environmental pollution in their synthesis and preparation,and their stability and dispersion need to be paid attention to in actual use.It is the main trend of current research to screen raw materials,adjust experimental parameters,overcome defects in the production process,and obtain nano-antibacterial materials with few toxic side effects on the human body.Among them,polyvinyl alcohol(PVA)is a widely used non-ionic surfactant,which shows certain reducing ability at higher temperatures,and is a polyol with good biocompatibility.In this study,PVA was used as reducing agent and surfactant,nanometal particles were prepared by in situ chemical reduction,and the effects of preparation parameters on antibacterial properties and cytocompatibility were mainly studied,and the results were as follows:Firstly,the above method was used to prepare Ag NPs,and the effect of PVA on the particle size and dispersion degree of Ag NP was explored by setting different temperatures(80℃,100℃,120℃),the plasma absorption peak of Ag NPs at a concentration of 100 ppm was tested by ultraviolet-visible spectroscopy(UV-Vis),and the degree of reduction of silver ions in solution was tested by inductively coupled plasma emission spectroscopy(ICP-OES).Combined with high-resolution transmission electron microscopy(HR-TEM)analysis,the optimal conditions for the synthesis of Ag NPs were determined to be 80℃,at this moment,the characteristic absorption peak of silver appeared at 433 nm in the ultraviolet spectrum,the concentration of unreduced silver ions in the solution was the lowest,and the synthesized Ag NPs were spherical and the best dispersion.The antibacterial test showed that Ag NPs synthesized at 80℃ had the best bactericidal effect on Escherichia coli and Staphylococcus aureus,the minimum inhibitory concentration(MIC)was 6.25 mg/L,and the minimum bactericidal concentration(MBC)was 6.25mg/L and 12.5 mg/L,respectively.The cytocompatibility test with L929 as the prototype showed that the relative survival rate of the 80℃ sample was 111.9% and the cytotoxicity was grade 0 after co-culture with the cell in vitro for 24 h,showing good cytocompatibility,which further indicated that the reaction system using polyvinyl alcohol as raw material had no effect on cell activity.The same method was used to further prepare Ag-Cu NPs,and in the process of increasing the reaction temperature from 80℃ to 160℃,it was found that the presence of Cu ions inhibited the reduction of Ag ions by PVA aqueous solution,only when the molar ratio of silver-copper ions was controlled at 2:1 and above,the characteristic absorption peak of silver would appear on the ultraviolet spectrum of the nanoparticles but the peak strength was not obvious.Further characterization by transmission electron microscopy showed that the size of the synthetic particles increased to the micron level due to the agglomeration of the reduced Ag-Cu NPs,and there were many internal defects,the Ag-Cu NPs composed of them were independent of each other and had a bimetallic structure.In the range of silver-copper molar ratio1:1 to 4:1,MIC and MBC showed a trend of first decreasing and then increasing,among which Ag-Cu bimetallic particles with a molar ratio of 2:1 had the best antibacterial effect,and the MIC of Escherichia coli and Staphylococcus aureus was 4.6862 mg/L,the MBC of Escherichia coli was 9.3725 mg/L,and the MBC of Staphylococcus aureus was 4.6862 mg/L.Compared with the Ag NPs synthesized by the same method described above,its antibacterial properties are slightly enhanced,but due to its low degree of silver-copper reduction and large particle size,it is difficult to provide effective antibacterial applications.By further adjusting the silver-copper molar ratio to 6:1,obvious silver characteristic absorption peaks appeared on the ultraviolet spectrum of the nanoparticles,and the particle size was reduced to 75-100 nm under high-resolution transmission electron microscopy,and the Ag-Cu bimetallic structure did not change.Fourier transform infrared spectroscopy test confirmed that PVA aqueous solution was reduced by-OH group,and the presence of Cu made the hydroxyl group act preferentially on Cu itself without being able to reduce silver in large quantities.When the concentration of Cu ions is greatly reduced to a molar ratio of Ag to Cu of more than 14:1,the inhibitory effect of Cu on Ag is weakened,and the PVA aqueous solution works together to reduce it to Ag-Cu NP,forming a coexisting suspension of Ag NPs and Ag-Cu NPs.Compared with the Ag NPs suspension,the MIC and MBC of the coexisting suspension were significantly reduced,and its antibacterial performance was up to 25% higher than that of the same concentration of Ag NPs,indicating that there was a synergistic antibacterial enhancement between silver-copper metals.The activity of L929 cells tested by MIC concentration was 95.9% and 99.1%,and the toxicity performance was grade 0,and the coexistence suspension of Ag NPs and Ag-Cu NPs could achieve sterilization and no negative stimulation of cells,which is expected to be applied in biomedicine.