Study On Ag-Doped TiO₂ Cyclodextrin Antibacterial Materials

Cyclodextrin is a chemically stable and selectively modified substance obtained by enzymatic degradation of starch.Cyclodextrins and their many derivatives are widely used in many fields of science and technology.The hydrophobic cavity of cyclodextrins can provide inclusion with guests,including inorganic,organic,and chiral guest molecules.The formed host-guest inclusion complex or supramolecular complex is nontoxic,easy to prepare,inexpensive and biodegradable.Therefore,cyclodextrin can synthesize many important functional materials in many fields such as agriculture,medicine,hygiene,food processing and fragrance,among which the preparation of nano-antibacterial materials is an important aspect.TiO₂ is a photocatalytic semiconductor material,which can achieve antibacterial function through photocatalysis.TiO₂ is readily available in nature,has good biocompatibility,low purchase cost,non-toxicity and material stability.In addition,silver has the characteristics of broad-spectrum antibacterial,high temperature resistance,low toxicity and can broaden the light response range of TiO₂,which can cooperate with TiO₂ to adapt to antibacterial under no light and low light conditions.However,the two have common shortcomings,such as easy aggregation and poor dispersion,which affect the overall antibacterial performance of the material.Based on the problem of poor dispersibility,in this paper,a non-toxic,easy to prepare,low-cost,biodegradable modified?-cyclodextrin was used as the host,and the organically modified Ag-TiO₂ composite antibacterial agent was used as the guest.Synthesize cyclodextrin functional materials to solve the problem of poor Ag-TiO₂ dispersibility and enhance the antibacterial function of cyclodextrin materials.The main research contents and results are as follows:(1)Synthesis and modification of Ag-doped TiO₂ antibacterial composite agent:Three methods were used to synthesize Ag-TiO₂ nano antibacterial agent.Through the analysis of synthesis influencing factors,the sol-gel method was the best to synthesize Ag-TiO₂,and the optimal conditions were as follows:The reaction kettle time is 2h,the temperature is 200?,the p H value is 3,that is,the optimal combination is A₂B₂C₃,the best yield is 2.21g,and the highest yield is 83.91%.The FTIR characterization showed the hydroxyl stretching and bending vibration absorption peaks of water adsorbed on the surface of Ag-TiO₂ and the stretching vibration absorption peak of Ti-O-Ti,indicating the existence of TiO₂;the SEM morphology showed that Ag-TiO₂synthesized by sol-gel method The particles on the surface of the material have good dispersibility and are spherical particles,and EDS shows that it contains three elements of Ti,O and Ag;XRD analysis shows new diffraction peaks and weakened diffraction peaks,indicating that the crystal form changes greatly after Ag doping,but The existence of the original 2?diffraction peak indicates that the anatase crystal form is still maintained;there are obvious Raman peaks in the Raman Shiftanalysis,which are the O-Ti-O variable angle vibration peaks,and the E_g Raman activity of anatase TiO₂.Vibrational mode,B_1g Raman active vibrational mode and Raman active vibrational mode of A_1g and B_1g coincident;the characteristic peaks of Ti,Ag and O are clearly seen in the full spectrum of XPS scanning,and the analytical binding energy of Ti is457.6 for Ti 2p_3/2,respectively.At 457.6 e V and 463.4 e V of Ti2p_1/2,the spin energy gap is 5.8e V,which is Ti⁴⁺,which is basically corresponding to pure anatase TiO₂.The binding energies of Ag analysis are 366.4 e V for 3d_5/2and 372.5 e V for 3d_3/2,respectively.The spin energy gap is 6.1 e V,indicating that the Ag contained is Ag⁰.(2)Silane coupling agents KH550,KH560 and KH570 were selected as organic modifiers.Through the analysis of influencing factors,the sol-gel method modified by KH570 was used to synthesize Ag-TiO₂ with the best yield of 1.47 g and the highest yield of 73.53%,the optimal conditions are that the coupling agent type is KH570,the coupling agent volume is 4 m L,and the water bath temperature is 80°C,that is,the optimal combination is A₃B₃C₃;through FTIR analysis,antisymmetric stretching vibrations of-CH₃ and-CH₂ appear,Asymmetric bending vibration,antisymmetric stretching of C-O-C,Si-O-Si and Ti-O-Si bands,Ti-O stretching peak,which indicate that KH570 is also successfully modified and grafted onto the surface of TiO₂;SEM analysis showed that after modification by KH570,the large and small particles were evenly arranged with each other,and the dispersion,uniformity and integrity were greatly improved;The change of TiO₂ crystal form is relatively small,and KH570 has little damage to the antibacterial agent.The above substances are modified by introducing adamantane formyl chloride,and adamantane hydrophobic group is introduced,so that the guest molecule has the ability to recognize the host and the guest,which lays the foundation for the guest selection of?-cyclodextrin.Through the analysis of influencing factors,the yield of KH570-Ag-TiO₂ modified with adamantanecarbonyl chloride is the highest,which is 56.69%.The optimal combination is A₂B₂C₃;further FTIR analysis showed C-H bending vibration peaks,C-N stretching vibration peaks,C-C benzene ring skeleton stretching vibration peaks,and C=O stretching vibration peaks,indicating that adamantanecarbonyl chloride was successfully grafted with adamantyl group.TiO₂;SEM analysis maintains the dispersity and uniformity of the guest molecules;XRD analysis material diffraction peaks weaken,and new diffraction peaks appear,indicating that the crystal form of KH570-Ad-Ag-TiO₂ has changed greatly.(3)Synthesis of cyclodextrin functional materials:?-cyclodextrin(?-CD)itself and the guest need to be activated to recognize the host-guest group with the guest material,and N-methylol acrylamide is recrystallized.The latter?-CD undergoes a chemical reaction,and N-methylol acrylamide is used to connect?-CD with a double bond,that is,alkenyl cyclogelatinization,to prepare alkenyl?-CD derivatives.The NMA-?-CD material was prepared,and then the Ad-Ag-TiO₂ modified with adamantanecarbonyl chloride was identified by the host and the guest to be included in it,and the optimal influence conditions for the synthesis were found.The factors influencing the preparation of?-CD-NMA were analyzed.The optimal conditions were that the amount of DMF was 15 m L,the temperature was 5°C,and the reaction time was 5 h.The best yield of?-CD-NMA was 1.70 g and the highest yield was 85.04%;After comparing the preparation of?-CD-NMA-Ag-Ad-TiO₂ by ultrasonic and freeze-drying,the freeze-drying method was selected.That is,when the optimal combination is A₂B₁C₂,the maximum yield of inclusion compound is 1.60 g,and the maximum yield is 79.93%.FTIR analysis of the?-CD-NMA-Ag-Ad-TiO₂ inclusion by sol-gel method shows that the characteristic peak of adamantane is weakened or nearly disappeared,indicating that the inclusion is successful;SEM analysis shows that the particles are smaller and more uniform,and the voids become smaller.,and evenly arranged inlaid with each other,with good integrity;XRD analysis showed new diffraction peaks or weakened diffraction peaks,indicating that the crystal form of?-CD-NMA-Ag-Ad-TiO₂ inclusion complex changed greatly.There are obvious Raman peaks in the Raman Shiftanalysis,which are the O-Ti-O variable angle vibration peak,the E_g Raman active vibration mode of anatase TiO₂,the B_1g Raman active vibration mode,and the coincident Raman mode of A1g and B_1g.Active vibration mode;the characteristic peaks of Ti,Ag,O,C are clearly seen in the full spectrum of XPS scanning,showing that the characteristics of Ti⁴⁺and Ag⁰ are maintained.Finally,the inclusion compound?-CD-NMA-Ag-Ad-TiO₂ was polymerized with acrylic acid to synthesize acrylic antibacterial composite material.(4)Antibacterial research:the raw material TiO₂,Ag element,?-CD-Ad-KH570-TiO₂,low temperature synthesis?-CD-Ad-Ag-KH570-TiO₂,sol-gel synthesis?-CD-Ad-Ag-KH570-TiO₂ and physically doped?-CD-Ad-Ag-KH570-TiO₂ show that sol-gel synthesized?-CD-Ad-Ag-KH570-TiO₂ has stronger antibacterial properties,and its antibacterial effect on Escherichia coli The maximum circle is 16.35mm,and the maximum inhibition circle for Staphylococcus aureus is 10.75mm.The antibacterial performance of the antibacterial emulsion shows that the antibacterial activity under light conditions is better than that under no light conditions,and the antibacterial effect on Gram-negative bacteria is better than that on Gram-positive bacteria.The maximum inhibition zone of Ad-KH570-Ag-TiO₂ antibacterial emulsion against Escherichia coli is 13.98mm,and the maximum inhibition zone against Staphylococcus aureus is2.45mm.Overall,the antibacterial properties of Cyclodextrin antibacterial functional materials are better for Escherichia coli.