Design Of Carbon Quantum Dots-based Fluorescence Sensor Systems And Its Application In The Detection Of Biothiols

Biothiols such as glutathione（GSH）,cysteine（Cys）and homocysteine（Hcy）play essential roles in human physiological activities.The abnormal levels of the biothiols are closely related to various human diseases,such as cancer,cardiovascular disease,dementia,etc.Thus it is extremely important to quantitatively detect biothiols in the body.Among the detection methods,fluorescence detection technology is receive increasing attentions due to the innate advantages of high sensitivity,high selectivity,simple operation and rapid response for biothiols detection.In this study,three kinds of fluorescence sensors were successfully constructed for the sensitive detection of three model biothiols（glutathione（GSH）,cysteine（Cys）and homocysteine（Hcy））on the basis of carbon quantum dots.Firstly,carbon quantum dots（CQDs）with various optical properties were synthezied according to a simple hydrothermal method.Three optical sensing platforms were constructed by combining CQDs with the MnO₂ nanosheets,Fe³⁺and Ellman’s reagent（DTNB）,respectively.Secondly,the surface morphology and crystal structure of the synthesized materials above-mentioned were systematically characterized using TEM,XPS,FTIR,XRD,Raman and UV-Vis.Then,the optical performance of the developed biosensor for biothiols detection was thoroughly investigated by fluorescence analysis and fluorescence-colorimetric dual signal analysis.Finally,the fluorescent probe was applied to the detection of GSH,Cys and Hcy.In this dissertation,we focused on following researchs:（1）Nitrogen and phosphorus co-doped CQDs（N,P-CQDs）and MnO₂ nanosheets were prepared according to the reference preliminarily.And the rapid and sensitive detection of glutathione was achieved through the N,P-CQDs/MnO₂ complex system（fluoresecent sensor）based on fluorescence resonance energy transfer（FRET）.The fabricated sensor presented a highly linear relationship in the GSH range of 0.05μM to50.00μM,with a detection limit of 2.27 nM（S/N=3）.In addition,the sensor also displayed strong anti-interference ability and excellent reproducibility（RSD<5%）in the actual detection application.A satisfactory recovery in the actual human serum samples（100.21%-101.78%）was obtained,indicating that the constructed sensor exhibits a great potential real applicaiton for sensitive and selective detection of glutathione in the human serum sample.（2）The blue fluorescent nitrogen-doped CQDs（N-CQDs）were prepared under the condition of 200℃through one step hydrothermal method with citric acid and ethylenediamine as precursor.A novel selective N-CQDs-Fe³⁺sensor was constructed based on photoinduced electron transfer（PET）for the detection of GSH,Cys and Hcy.The detection ranges of the three substances were 20⁵20μM（GSH）,1⁴0μM and60⁵60μM（Cys）,1²0μM and 80³60μM（Hcy）,and detection limits were 20.39 nM（GSH）,1.93 nM（Cys）and 9.31 nM（Hcy）（S/N=3）,respectively.Compared with the biothiols fluorescence sensor reported in the literature,this N-CQDs-Fe³⁺fluorescence sensor shows higher or at least comparable sensing performance in view of linear range and sensitivity.（3）The N-CQDs with green fluoresence were prepared by using catechol and ethylenediamine as carbon source and nitrogen source.The N-CQDs/DTNB dual signal nano optical sensor was constructed based on fluorescence inner filter effect（IFE）and used to detect GSH,Cys and Hcy.Fluorescence analysis and colorimetric analysis were performed to investigate the optical behavior of N-CQDs/DTNB.Fluorescence analysis results:the linear ranges of 0.01⁴0μM,0.05⁴0μM,0.05⁴0μM for GSH,Cys and Hcy,with the detection limits of 3.23 nM,1.01 nM,3.29 nM（S/N=3）,respectively.Colorimetric analysis results:the linear range from 1 to 140μM for Cys with a detection limit of 0.52μM.The developed N-CQDs/DTNB sensor displays an ideal recovery in the actual serum samples,which provides a new method for the rapid and accurate detection of glutathione,cysteine and homocysteine in real samples.