Preparation And Characterization Of Functional Carbon Materials And Their Applications In Biomedicine

In recent years, the application of carbon nano materials in biomedicine attracts more and more attention, the carbon nano materials including graphene and its derivatives and carbon dots. They have with photothermal effect, unique fluorescence properties and characteristics of specific surface area, easy functionalization and, in drug sustained release controlled release, fluorescent tracer, photothermal therapy and other aspects have a unique application value. The carbon quantum dots(Carbon dots) as a new type of carbon nano materials, has received wide attention in recent years. The particle size of the carbon quantum dots is less than 10 nm, and the core of the carbon quantum dots is generally composed of sp2 hybrid nano crystalline carbon or amorphous carbon, while the outer part is made up of carbon atoms of sp3 structure. The surface containing carboxyl and hydroxyl of hydrophilic functional groups, it can exist stably in water. Since its surface contains a large number of functional groups, which also further provides a convenient condition for surface modification, and the quantum efficiency and fluorescence intensity of the modified carbon quantum dots will be greatly enhanced. Compared with the traditional semiconductor quantum dots and organic dyes, carbon quantum dots have small particle size, good water solubility, high quantum efficiency, strong fluorescence intensity, low toxicity and anti photobleaching and easy modification and other excellent properties. In this paper, the research group on the basis of previous work prepared a synergistic photothermal effect of materials, that is,rGO-CuS,and the application of hyperthermia cancer were examined. The focus on carbon quantum dots preparation and modification, we use several different methods to prepare the particle size distribution of uniform, high fluorescence quantum efficiency, with strong fluorescence intensity, non-toxic and water-soluble good nitrogen doped carbon quantum dots(N-CD), and studies its application in biological imaging as fluorescent probes. The specific contents are as follows:(1) One step hydrothermal method was used to prepare the reduced graphene oxide copper sulfide nanocomposites. The reduction of graphene oxide copper sulfide nano composite material(rGO-CuS) was synthesized by one-step hydrothermal method, this method is simple and efficient. In the power density of 1W/cm2 980 nm infrared light irradiation, rGO-CuS and other warming effects and the effect of killing cancer cells was significantly better than that of the composite CuS nano sheets and graphene oxide(GO). Cytotoxicity tests showed that rGO-CuS, GO and CuS were non-toxic. Animal experimental surface, mice of intra tumor injection of tumors of rGO-CuS group were all killed, the tumor volume was 0 mm3, however, GO injection and CuS group tumor still exist, and volume were 370 mm3 and 670 mm3. In conclusion, photothermal therapy, rGO-CuS is a more efficient nano composite material.(2) Using citric acid and ethylenediamine as raw materials by hydrothermal synthesis of nitrogen doped carbon quantum dots. Based on the treatment of ammonia water to improve the quantum efficiency, with citric acid and ethylenediamine respectively as carbon source and nitrogen source, CN-CD-1 were prepared by a one-step hydrothermal, again using ammonia the of hydrothermal treatment of 180 ℃ 12 hours to prepare high quantum efficiency CN-CD-2. After ammonia treatment, the particle size of the carbon quantum dots is small, and the distribution is even and has good water solubility and dispersion. The Raman results show that the ammonia hydrothermal treatment ID/IG prepared carbon dots more high, indicating that more defects may be due to the three carbon quantum dots is sp2 hybridized carbon and sp3 hybridized carbon on its surface with nitrogen or oxygen formed more surface defects. The structure of the amino group was analyzed and found that the amino group was obviously increased after ammonia treatment. Compared with the carbon quantum dots without ammonia water heat treatment, the fluorescence quantum efficiency is higher, which can reach 29%. After ammonia treatment, the prepared carbon quantum dots have excellent optical properties, such as fluorescence dependence, pH dependence, anti light bleaching, fluorescent stability and so on. Based on the above analysis, ammonia water plays a key role in improving the quantum efficiency. This method is economical, simple, and has high quantum efficiency and repeatability.(3) One step pyrolysis method to prepare carbon quantum dots. the pyrolysis method is simple and convenient. At the same time, the preparation of carbon quantum dots of the solvent and raw materials, non-toxic, low price. With ethylenediamine and hydrogen peroxide as raw materials, ultra pure water as solvent to prepare carbon quantum dots by one-step pyrolysis method. Study on the effect of pyrolysis temperature and fluorescence quantum efficiency of carbon quantum dots increases with the increase of temperature, the quantum efficiency of carbon quantum dots, but the maximum quantum efficiency reached in 250 ℃. Based on the preparation of carbon quantum dot composition, characterization of structure and fluorescence properties, carbon dots pure surface in hydrophilic groups, such as hydroxyl, carbonyl, so quantum of carbon in water solution was good and the presence of amino, is conducive to the surface for the formation of electron donating groups, effective provided high carbon quantum dot fluorescence quantum efficiency. The fluorescence properties of carbon quantum dots are excellent, with light stability and pH dependence, and the quantum efficiency changes slightly with the change of the concentration.(4) Alkali one step hydrothermal treatment enhanced the fluorescence quantum efficiency of carbon quantum dots. in the of preparation of carbon quantum dot based, respectively, using NaOH, KOH and ammonia of the hydrothermal treatment, the system by a stronger fluorescence intensity, quantum efficiency and higher nitrogen doped carbon quantum dots(N-CD). This method is simple and easy to operate and the raw material is easy to get. The optical properties of three kinds of carbon quantum dots N-CD-A1, N-CD-A2 and N-CD-A3 were studied, and the quantum efficiencies were 40%, 31% and 32%, respectively. This may be due to the separation of the nucleation and growth process, the surface defects of quantum dots are obviously improved, which can greatly improve the fluorescence quantum efficiency of the quantum dots. A large number of hydrophilic groups, such as carboxyl and hydroxyl groups, are attacked by OH- ions, such as carboxyl and hydroxyl groups, and the carbon quantum dots are finally released into the solution under the action of the hydrophilic force to form a smaller particle size. Again, by the hydrothermal treatment of ammonia water, the amount of nitrogen atoms can be improved, because the strong electron donating group has the capability of supplying electrons, it can effectively improve the quantum efficiency of the carbon quantum dots. In addition, the three kinds of carbon quantum dots with light stability, pH dependence and other excellent optical characteristics. Characterization of the discovery of the structure composition, after treated with NaOH and KOH hydrophilic group increased obviously, after amino increased with the treatment of ammonia, Raman show ID/IG ratio were 0.66, 0.62 and 0.62, indicating that the NaOH treatment, the defects in the formation of more. All of these provide a basis for the improvement of quantum efficiency.