Construction Of Green Fluorescent Carbon Dots And Their Application In Cell Imaging And Fluorescence Sensing

Fluorescent carbon dots(CDs),as a new style of zero-dimensional nanomaterials,have attracted wide interest of researchers owing to its unique photoluminescence properties,catalytic activity,electronic properties.It is widely used in many fields,such as biochemical analysis,bioimaging,disease diagnosis and treatment,photocatalysis,photoelectric devices and so on.The advantages of simple synthesis methods,easy doping and surface modification of CDs endow them good water solubility,biocompatibility and excellent fluorescence properties.Although after more than ten years of development,CDs have made breakthroughs and innovations in many fields,the solvent residue in the preparation method,low quantum yield and lack of modification have restricted the application of carbon dots in cell imaging.In this paper,after prepared by one step solvothermal method and then purified by two-step purification,green fluorescent CDs with single luminescence and high quantum yield were obtained.And they were used in cell imaging and fluorescence sensing.Secondly,based on the lack of modification of amphiphilic graphene quantum dots,we introduced columnarenes to combine with them,and observed the difference between composite materials and single amphiphilic graphene quantum dots in cell imaging.The concrete contents of the thesis can be described in detail as follows:(1)Construction of green fluorescent carbon dots with high quantum yield for cancer cell recognition and Fe3+detectionGreen-emitting carbon dots(CDs)were synthesized using citric acid and urea as raw materials by one-pot solvothermal process.After purified by precipitation and silica column chromatography procedures,the pure CDs had uniform particle size and excellent fluorescence performance with absolute quantum yield(QY)of 16.5%in water.Upon excitation at 430 nm wavelength,the CDs exhibited the maximum emission at 530 nm.The CDs showed remarkable biocompatibility,low cytotoxicity,and good PL stability at different PH values.Different labeling distributions of CDs in cancer cells(MCF-7)and normal cells(QSG-7701)were achieved so that they could be used to identify cancer cell.Moreover,CDs could sensitively and selectively detect Fe3+ ions in aqueous solutions.(2)Detection of GSH by Carbon Dots-MnO2 Nanosheet Fluorescent ProbeThe as-prepared nitrogen-doped carbon dots(CDs)could be combined with MnO2 via electrostatic interaction.Based on fluorescence resonance energy transfer(FRET),MnO2 quenched the fluorescence of CDs,and the introduction of glutathione(GSH)could reduce and degrade MnO2,so that the fluorescence of the system could be restored.Therefore,rapid and sensitive detection of GSH could be achieved.The CDs/MnO2 sensor had a good linear relationship with the concentrations of GSH in the range of 0.1?1 mmol/L(R2=0.99),and the detection limit was 0.1 umol/L.(3)Water-soluble pillar[5]arene modified amphiphilic graphene quantum dots for cell imagingAmphiphilic graphene quantum dots(A-GQDs)with single-layer graphene structure were synthesized using 1,3,6-trinitropyrene and lauric acid as raw materials by one-pot hydrothermal method.It showed uniform size and excitation-independent emission.A-GQDs emitted bright fluorescence on the surface of the cell membrane when they were co-cultured with cancer cell(MCF-7)or normal cell(QSG-7701).The water-soluble pillar[5]arene(WP5)was then incorporated on to the A-CQDs via ?-?interaction and electrostatic interaction.The synthesized composites had a certain enhancement in fluorescence.Compared to individual A-GQDs,more WP5/A-CQDs passed through the cell membrane and entered the cells,making the whole cell have a bright fluorescent imaging effect.