| Compared with traditional organic fluorescent dyes,quantum dots have excellent optical properties such as high quantum yields,large specific surface area,anti-photobleaching,fluorescence adjustment and water solubility,making it a superior fluorescent material and show great application potential in the field of analytical detection.Therefore,fluorescent nanomaterials such as semiconductor quantum dots,carbon quantum dots and black phosphorus quantum dots with high fluorescence performance by hydrothermal methods were prepared in this thesis.Their structural characteristics and fluorescence properties were studied.The corresponding fluorescence sensing methods for the detection of copper ions,?-glucosidase and glutathione were constructed.The mechanism of interaction between fluorescent quantum dots and target analytes was revealed,enabling real-time,highly sensitive and highly selective detection of target analytes in real samples.The main research content of this dissertation is divided into three parts as following:(1)A fast,simple,and visual ratiometric fluorescence sensing system based on carbon quantum dots(CDs)and CdTe/CdS quantum dots(CdTe/CdS QDs)was constructedfor the detection of Cu2+.In the detection system,Cu2+ reacts with 3-mercaptopropionic acid(3-MPA)-stabilized quantum dots to form S-Cu,which can compete with S-Cd on the surface of quantum dots,resulting in the aggregation of quantum dots.The fluorescence intensity of QDs was reduced or quenched.However,as the internal reference signal,the fluorescence of carbon quantum dots was not affected by Cu2+.Finally,the fluorescent color change of the traffic light type can be observed.Under the optimal conditions,there was a good linear relationship in the range from 0 to 2.5 ?M and the detection limit was about 38 nM.The fluorescent sensing system was also successfully used for the analysis of Cu2+ in real water samples with satisfactory results.(2)A highly sensitive,highly selective andinsitufluorescence biosensor was established to determine ?-glucosidase and its inhibitors based on the inner filter effect of 4-nitrophenol(4-NP)on near-infrared quantum dots(NIR QDs).Among them,?-glucosidase can catalytically hydrolyze its substrate?-D-4-nitrophenyl-pyranoside(4-NGP)to yield 4-NP.The UV-Vis absorption spectrua of 4-NP have a good overlap with the excitation spectrua of NIR QDs,which can induce IFE,resulting in fluorescence quenching of NIR QDs.The addition of the enzyme inhibitor(acarbose)can inhibit ?-glucosidase activity,which decreasedthe amount of 4-NP and the fluorescence of NIR QDscan be gradually recovered.Based on this principle,the linear range of ?-glucosidase concentration was 0-0.001 U/mL and the detection limit was 0.00065 U/mL.The half inhibition concentration(IC50)of acarbose was 256 ?M.In addition,near-infrared fluorescent biosensor was also used for the study of a-glucosidase activity in CaCo-2 cells and for screening potential anti-diabetic drugs from natural products.(3)A fluorescence sensing platform based on black phosphorus quantum dots(BPQDs)-MnO2 nanosheet was designed for the determination of GSH in living cells and cell imaging.Due to the fluorescence resonance energy transfer between MnO2 nanosheets and BPQDs,the blue fluorescence of BPQDs was quenched by MnO2 nanosheets.When GSH was added,MnO2 nanosheet will be reduced to Mn2+by GSH,so that the FRET effect disappeard and the fluorescence of quenched BPQDs was recovered.On the one hand,the sensitive detection range of GSH in water solutions using fluorescence sensing platform based on the BPQDs-MnO2 nanocomposite was 0.1-200 ?M,and the detection limit was 35 nM.On the other hand,the sensing platform was successfully used for bioimaging of GSH and monitoring the content changes of GSH in different cell types. |
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