Controllable Preparation And Application Investigation Of Carbon Nanomaterial-Based Bio-functional Composites

Graphene and its derivatives have good biocompatibility,large specific surface area,excellent mechanical and electrical properties,which have shown widely applications in biosensors,tissue engineering,antibacterial devices,biomedicine,etc.Three-dimensional graphene-based gel is the most representative type of macroscopic metamaterial owing to its ultra-light density,large surface area,controllable pore size,good mechanical compressibility and structural stability,which is considered to be an ideal carrier for the other functional materials.This paper mainly studied the preparation of three-dimensional graphene-based composite materials and explored its potential application in bone tissue engineering scaffolds and sewage filtration antibacterial devices.In addition,to meet the antibacterial requirements of clinical materials,we made full use of the unique upconversion properties of carbon quantum dots under natural light,and synthesized carbon quantum dots/zinc oxide composites on the surface of brackets,focused on improving the antibacterial properties of the bracket.The main research includes the following four aspects1).The prepation of three-dimensional reduced graphene oxide/hydroxyapatite composite aerogel and its properties study.Reduced graphene aerogel(rGOA)was synthesized by using graphene oxide(GO)as a precursor via hydrothermal method and lyophilization way.To further promote the deposition of hydroxyapatite in the rGOA,the alkaline solution containing calcium and phosphorus ions were pumped into rGOA by a vacuum filtration method,aiming at improving the mechanical properties and the biological properties of the composite materials by finite element simulation for micro-nano scale structure design.The experimental results showed that the mineralized microspheres composed of rod-shaped hydroxyapatite evenly distributed on the surface of rGOA.The mechanical measurement showed that the composite materials exhibited 90% recoverable non-linear elastic compression deformation in a liquid phase environment,which can be attributed to the stability of the microstructure of rGOA.Compared with the unmineralized groups,the mechanical strength wasincreased by more than 350% at 90% strain.What's more,the materials showed low cytotoxicity owing to the introduction of hydroxyapatite.2).The preparation of three-dimensional reduced graphene oxide/copper composite aerogel and its antibacterial properties research:rGOA/copper composites were prepared by injecting the precursor solution of copper ions under a "bottom-up" vacuum condition,and then the samples were placed in a 40 ? water bath.The synthesized rGOA/copper composites could maintain the stability of microstructure and macroscopic three-dimensional structure of the rGOA.Experimental results showed that copper micron-particles were successfully grown onto the surface of rGOA,and the composite exhibited excellent antibacterial activity against Escherichia coli and Staphylococcus aureus(antibacterial rate reaches 100%).In addition,the composite material was installed in a PVC pipe to test the antibacterial properties by using E.coli solution as an example sample of sewage water.The test results showed that the designed device had a good bactericidal ability against pathogenic microorganisms in the sewage water.The detailed mechanism can be attributed to as follows: 1.The sharp edge of the GO can produce a cutting effect on pathogenic microorganisms,which can destroy the integrity of the cell membrane;2.The rGO can reduce the aggregation of copper particles and the synergistic effect derived from the rGOA and copper particles,which enhances the oxidation capacity of the composite materials,finally causing the lysis and death of pathogenic microorganisms.3).Enhanced antibacterial properties of the bracket under natural light via decoration with ZnO/carbon quantum dots composite coating:Carbon quantum dots(CQDs)were prepared by a hydrothermal method and coated on the surface of common orthodontic stainless steel brackets,and then ZnO thin films were deposited onto the surface of CQDs by magnetron sputtering.The results showed that CQDs bound with zinc oxide through the carbon-oxygen bonds and located between zinc oxide and stainless steel brackets.The modified bracket had a strong antibacterial effect on common pathogenic microorganisms under natural light(Antibacterial rate against Streptococcus mutans is 96.13%,antibacterial rate against Staphylococcus aureus is 90.28% and antibacterial rate against Escherichia coli is 92.35%).In addition,the antibacterial mechanism of the brackets modified with carbon quantum dot/zinc oxide film under the condition of the natural light was discussed,which could be ascribed to the unique upconversion fluorescencecharacteristics of CQDs and interaction between CQDs and ZnO,enabling to promote the separation of electron-hole pairs and increase the photoelectric conversion response.