Fabrication Of Fluorescent Carbon Dots,luminescence Mechanism And Application In Biomolecule Detection

Fluorescent carbon dots,as a new type of carbon-based nanomaterials,have attracted extensive attention due to its excellent and stable photoluminescence properties,excellent biocompatibility and good optical stability.After heteroatomic hybridization,the carbon dots have better luminescence properties,and the cytotoxicity does not change significantly.The application of carbon dots is based on its luminescent properties.However,the photoluminescence mechanism of carbon dots has not been determined yet,which has attracted more and more researchers'attention.Therefore,carbon dots of heteroatomic hybridization have also become a research hotspot in the field of analysis and detection(such as anion and cation,drug molecules,amino acids,etc.),and the detailed fluorescence mechanism of carbon dots also needs to be further studied.In this paper,different heteroatomic doped carbon dots were synthesized by one-step hydrothermal method and acid-base neutralization exothermic carbonization method.On the basis of these CDs,the controllable preparation and luminescence mechanism of carbon dots were studied,and the analysis and detection of drug vitamin B12(VB₁₂)and biomolecular protoporphyrin IX(Pp IX)were realized.Chapter 1:The properties,synthesis methods,luminescence mechanism and applications of fluorescent carbon dots are summarized.Chapter 2:Green,yellow and orange fluorescent carbon dots were prepared by using p-aminobenzoic acid+m-phenylenediamine,p-aminobenzoic acid+p-phenylenediamine,p-aminobenzoic acid+p-phenylenediamine as precursors,respectively.By adjusting the reaction conditions,including the precursor,the reaction solvent,the reaction atmosphere and the dissolved solvent,the controllable preparation of carbon dots can be realized.According to the results,it is speculated that the fluorescence of carbon dots is mainly affected by the degree of oxidation and amidation,which leads to the difference of nitrogen state and quantum size on the surface of carbon dots,and then affect the fluorescence behavior of three kinds of carbon dots.All three kinds of carbon dots have good luminescence properties,and they all show excellent imaging ability when used in imaging of four kinds of cancer cells(A549,SMMC7721,BEAS-2B,PC 12),indicating that the three kinds of carbon dots can be used as the excellent cell imaging reagents for multicolor fluorescence imaging.More importantly,the abundant active amino and carboxyl functional groups on the surface of carbon dots can be coupled to target small molecules,DNA,RNA and anti-cancer drugs to construct nanocomposites,which can be used to identify target materials and implement the slow release of drugs.These exploratory studies have laid a foundation for the controlled preparation of fluorescent carbon dots and further expanded its application in the biomedical field.Chapter 3:Nitrogen,phosphorus and sulfur co-doped carbon quantum dots(NPS-CQDs)were prepared by acid-base neutralization and exothermic carbonization with glucose as carbon source and ethylenediamine,concentrated phosphoric acid and concentrated sulfuric acid as nitrogen,phosphorus and sulfur dopants,respectively.The prepared NPS-CQDs can emit blue fluorescence(?_em=456 nm),and has excellent fluorescence properties and good biocompatibility.Based on the synergism of internal filtration effect(IFE)and static quenching,vitamin B12(VB₁₂)and protoporphyrin IX(Pp IX)could significantly quench the fluorescence of NPS-CQDs.Therefore,a bifunctional fluorescent probe for the detection of VB₁₂and Pp IX was constructed.The linear range of VB₁₂ detection was 0.49?24.90?M,and the detection limit was 39.21 n M.The linear range of Pp IX was 0.58?1.89?M and 2.04?19.53?M,and the detection limits were 10.07 n M and14.30 n M,respectively.NPS-CQDs nanoprobe has been successfully applied to the determination of VB₁₂ in drug samples and Pp IX in urine samples with satisfactory results.