Preparation Of Carbon Quantum Dots And Their Applications In Biological Detection

Although organic fluorescent dyes,rare earth nanomaterials and semiconductor quantum dots have their own advantages,they are often used as classic luminescent probes,but they inevitably have disadvantages that limit their practical applications.Compared with these materials,carbon quantum dots have high photostability,good biocompatibility,easy preparation and other excellent properties are considered as an emerging fluorescent nanomaterial,and are widely used in biological imaging and biosensing.Fluorescence method has the advantages of high sensitivity,good selectivity,convenient operation,in-situ,real-time,non-destructive analysis of the target,and is widely used in environmental detection,food analysis,drug detection,etc.In this paper,on the basis of the excellent physical and chemical properties of carbon quantum dots and taking the advantages of fluorescent sensors,several fluorescent nanosensors have been constructed and applied to the efficient,sensitive and convenient detection of biomolecules.In the first chapter,we first introduced carbon quantum dots,and then summarized its fluorescence properties,synthesis methods,design and construction of fluorescent probes,and applications of carbon quantum dots in various fields.Finally,the main content and significance of this research are descrided.In the second chapter,we designed a fast and sensitive ratiometric fluorescence sensing platform for the detection of D-penicillamine（D-PA）.Yellow fluorescent carbon quantum dots（Y-CDs）were synthesized by hydrothermal method,and the emission peak was 566 nm.Thiamine（VB₁）can be oxidized by alkaline hydrolyzed artemisinin（a-ART）to form thiochrome（ox VB₁）,and its fluorescence emission peak is 466 nm.Therefore,Y-CDs can be combined with ox VB₁ to form a ratiometric fluorescence system.The addition of D-PA can inhibit the oxidation of VB₁,accompanied by a decrease in the fluorescence intensity at 466 nm,while the fluorescence of Y-CDs at 566 nm remains unchanged.Therefore,the ratiometric of fluorescence intensity at 566 nm and 466 nm can be monitored(I₅₆₆/I₄₆₆)to quantitatively analyze D-PA.The linear range of the sensing platform for D-PA detection is 0.5-50μM,and the detection limit is 0.33μM.In addition,the constructed fluorescence sensing platform is used for the detection of D-PA in drugs and human serum.Experimental results proved that this method has high accuracy and applicability.In the third chapter,by combining the peroxidase activity of Fe/NC nanozymes（Fe/NC NZs）and the fluorescence characteristics of orange fluorescent carbon quantum dots（O-CDs）,we designed a new colorimetric and fluorescent dual-mode sensing system for Captopril（CP）.In the presence of H₂O₂,Fe/NC NZs can catalyze the oxidation of the colorless substrate 3,3’,5,5’-tetramethylbenzidine（TMB）to produce a blue product（ox TMB）.Because the ultraviolet absorption of ox TMB overlaps with the fluorescence emission of O-CDs,the fluorescence of O-CDs can be quenched by ox TMB.After adding CP,the blue ox TMB was reduced to colorless TMB,and the fluorescence of O-CDs was restored.The increase in fluorescence signal and the decrease in absorbance depend on the concentration of CP.Fluorescence and colorimetric sensors have good linearity for CP,with detection limits as low as 0.47μM and 0.56μM,respectively.In addition,this method has been successfully used in the detection of CP in pharmaceutical formulations with satisfactory results.