Synthesis Of Fluorescent Nanoprobe Based On Gold Clusters/carbon Dots And Research On Their Analytical Applications

Fluorescent probes have the advantages of high sensitivity,good reproducibility and short response time,more and more researchers begin to design fluorescent probes for environmental detection,biochemical analysis and biosensing.Gold nanoclusters(AuNCs)and carbon dots(CDs)have attracted much attention because of their excellent properties such as low toxicity,good light stability and so on.In this dissertation,three fluorescence probes were constructed based on AuNCs/CDs,then these probes were successfully used to detect glucose and Cu2+.Chapter 1.IntroductionIn this paper,we first introduce the fluorescent probe and fluorescent nanomaterials,and then introduce the characteristics,preparation methods and applications of AuNCs and CDs respectively.At the end of this chapter,the purpose and significance of our research are described.Chapter 2.Detection of glucose based on methylene blue quenching the fluorescence of gold nanoclusterIn this work,the quenching of fluorescence of gold nanoclusters by methylene blue(MB)and the catalytic reaction of glucose oxidase to glucose were used to detect glucose.First of all,bovine serum albumin(BSA)was used as a template for the synthesis of gold nanoclusters(BSA-AuNCs),which was then stored in PB buffer(pH=7.4)and negatively charged.MB is a kind of biological cationic dyes with a positive charge and can be adsorbed on the surface of BSA-AuNCs by electrostatic interaction.In addition,due to the emission spectrum of BSA-AuNCs and theabsorption spectrum of MB were both about 650nm,fluorescence of BSA-AuNCs can be quenched MB through electron transfer reaction.However,methylene white(MBH)had no effect on the fluorescence of BSA-AuNCs because the absorption value of MBH at 650nm was obviously less than MB.MB not only played the role of quencher,but also participated in the reaction of glucose oxidase and glucose in the form of electron mediator in this study.In the reaction of glucose and glucose oxidase,MB was reduced to MBH,thus the fluorescence of BSA-AuNCs can recover.Therefore,the probe can be used for the quantitative detection of glucose according to the quenching or recovery of the fluorescence of BSA-AuNCs.In addition,the color change of the MB and MBH can be observed by naked eyes.Chapter 3.Preparation of amino acid carbon dots and theirapplication in the detection Cu2+In this work,we chose six different kinds of amino acids as carbon sources and synthesized six kinds of carbon dots with blue fluorescence by hydrothermal method.The fluorescence spectra of these six kinds of carbon dots and their response to different metal ions were studied and compared.The results showed that the fluorescence intensity of lysine carbon dots was larger and its fluorescence can be quenched by Cu2+ selectively.When Cu2+ was added,the fluorescence intensity of lysine carbon dots decreased and the fluorescence intensity was linear with the concentration of Cu2+ in the range of 1 × 10-6-1 × 10-5 M,and the detection limit was 0.23 μM.Then it was applied to the detection of Cu2+ in copper alloy samples,and the accuracy of the method was reliable.Chapter 4.Hydrophobic-carbon-dot-based dual-emission micelle for ratiometric fluorescence biosensing and imaging of Cu2+ in liver cellsIn this paper,we developed a micelle-based dual-emission probe to detect Cu2+ratiometrically by single-wavelength excitation.TCPP is a porphyrin derivative with red fluorescence whose fluorescence can be selectively quenched by Cu2+ because the nitrogen in the porphyrin ring can coordinate with Cu2+.We synthesized hydrophobic carbon dots(HCDs)by using glucose as carbon source.HCDs could be encapsulated in polymer micelles which was formed by self-assembly of amphiphilic polymer DSPE-PEG and DSPE-PEG-TCPP,thus its biocompatibility and water solubility was improved.The fluorescence of HCDs encapsulated in micelles was inert to Cu2+.We used the fluorescence of HCDs as the reference signal while the fluorescence of TCPP as response signal.With the addition of Cu2+,the fluorescence intensity ratio of HCDs and TCPP(FTCPP/FHCD)changed linear with the concentration of Cu2+ in the range of 2 × 10-7-1 × 10-6 M and the detection limit of Cu2+ is 36 nM,indicating that the probe can be used for sensitive detection of Cu2+.In the end,we also studied the Cu2+response and confocal imaging of HL-7702 cells.