Preparation And Antibacterial Activities Of Cellulose-based Schiff Base Copper(?) Complexes

Nowadays,with the rapid development of science,technology and economy,the people's awareness of environmental protection is gradually increasing,which promotes the development of the living environment towards a healthier,greener and safer direction.Therefore,research for developmentofbiodegradablematerialsisincreasing.Cellulose,a representative of biopolymers,presents many advantages.However,similar to the great majority of biopolymers,the characteristics of cellulosic materials determine that they can undergo bacterial attachment,thus affecting its performance.Therefore,in order to effectively solve the problem of bacterial infection,it is necessary to develop antimicrobial materials.At present,the methods of preparing cellulose-based antibacterial materials have some defects.This paper will propose an effective method to prepare cellulose-based antibacterial materials with excellent antibacterial activity.The softwood fiber as raw materials,first the selective oxidation was carried to obtain dialdehyde cellulose fiber.Then the dialdehyde cellulose fiber was used as intermediates.Second,the cellulose-based Schiff base ligand was prepared by the reaction of the aldehyde group and amino of glycine.Finally,the cellulose-based Schiff base ligand was complexed with copper ions,resulting in the cellulose-based Schiff base-Cu(II)complex.The obtained cellulose-based Schiff base ligands and complexes have broad spectrum antimicrobial effects.Dialdehyde cellulose fibers were prepared by the selective oxidization of softwood fibers.The results indicated that the weight loss rate of softwood fiber and aldehyde group content increased with the increase of sodium periodate oxidation concentration.The aldehyde content of the raw coniferous wood fiber was 1570?mol/g,and when the oxidant concentration was increased to 0.3 mol/L,the aldehyde group content increased by 205%to 4793?mol/g.There was a positive correlation between aldehyde group content and weight loss rate.In addition,with the increase of the oxidation concentration,the molecular structure of cellulose became loose and the crystallinity decreased significantly.The surface of oxidized fiber was smoother.Cellulose-based Schiff base ligand was prepared by Schiff base reaction between the aldehyde of dialdehyde cellulose fibers and amino of glycine,and then cellulose-based Schiff base copper complex was prepared by coordination reaction with copper ion.It was found that in the process of preparing cellulose-based Schiff base ligands,the aldehyde group content was significantly reduced,and the characteristic absorption peak of aldehyde carbonyl group at 1732 cm~-11 was weakened in the FT-IR,In addition,a new absorption peak appears at 1631 cm-1,which is a characteristic absorption peak of the imine group.These results showed the Schiff base reaction was successful.When cellulose-based Schiff base ligands were complexed with copper ion to prepare cellulose-based Schiff base copper complex,the red shift phenomenon was observed in the FT-IR of cellulose-based Schiff base copper complexes,and absorption peak of Cu-N and Cu-O also were observed.In addition,three new diffraction peaks appeared in the XRD spectra of cellulose-based Schiff base copper complexes.The UV-vis of cellulose-based Schiff base copper complex also showed a red shift phenomenon compared with the UV-vis of cellulose-based Schiff base ligand.All results indicated the cellulose-based Schiff base ligand and its copper complex were synthesized successfully.The prepared cellulose-based Schiff base ligands and its copper complexes have antibacterial ability against Gram-negative bacterium and Gram-positive bacterium.By the confocal laser microscopy to observe the quantities of live bacterial cells.And it was found that the number of bacterial cells surviving in the two bacterial suspensions was greatly reduced after adding cellulose-based Schiff base copper complex fiber.The surface morphology of bacterial cells was observed by SEM.It was found that both bacterial cells showed obvious shrinkage and damage after adding cellulose-based Schiff base copper complex fiber.AGAR plate diffusion method and OD600 method were used to evaluate the antibacterial properties of cellulose-based Schiff base ligand and its copper complex fiber against E.coli and S.aureus,respectively.The results show that the addition of copper ions significantly increased the inhibition zone width of the cellulose-based Schiff base copper complexes,which are 5.48 mm and 7.21mm,respectively,and the OD600 value decreased.Moreover,with the extension of reaction time,the width of antibacterial zone of cellulose-based Schiff base copper complex also increased,and the OD600 value decreased accordingly,that is,the antibacterial performance of cellulose-based Schiff base copper complex fiber increased with the extension of reaction time.Cellulose-based Schiff base ligand and its copper complex fiber have excellent antibacterial activity against Gram-negative bacterium and Gram-positive bacterium.