Preparation Of Nitrogen,Chlorine,and Sulfur Doped Carbon Dots Based On Phenylenediamine And Its Fluorescence Sensing Application

Carbon dots（CDs）is an emerging photoluminescent carbon-based nanomaterial with outstanding characteristics such as easy preparation,adjustable fluorescence emission,good water solubility,high stability,good biocompatibility,and low toxicity.It has broad application prospects in sensors,biomedicine,photoelectric devices and other fields.In addition,due to its rich precursor and diverse synthesis methods,the properties of CDs are easy to be designed and regulated,which has attracted widespread attention from researchers and greatly promoted the application of CDs in the field of fluorescence sensing.Chapter 1:An overview of CDs.The preparation,luminescence mechanism and properties of CDs,as well as the application of CDs in chemical sensing,drug analysis,biological imaging and other fields are briefly described.Morever,the background of topic selection,research content and innovation points of this topic are briefly introduced.Chapter 2:Using m-phenylenediamine and m-chlorobenzoic acid as the precursor of solvothermal method,the synthetic nitrogen-chlorine co-doped carbon dots（N,Cl-CDs¹）have good selectivity and sensitivity to TCs.The N,Cl-CDs¹ have strong blue-green fluorescence emission,good stability and water solubility with a high quantum yield（QY）of 45.4%.Oxytetracycline（OTC）was selected as a detection model for TCs.Based on the internal filtration effect（IFE）,the fluorescence of N,Cl-CDs¹ at 493 nm is selectively quenched by OTC with a limit of detection（LOD）of 36.58 n M.The established fluorescence sensing method has been successfully used for the detection of OTC in water samples,and has potential application prospects in the fields of environmental monitoring and food safety.In addition,the N,Cl-CDs¹ can be used for fluorescence imaging of HT-29 cells due to thier high QY and good biocompatibility.Chapter 3:Using o-phenylenediamine and m-chlorobenzoic acid as raw materials,nitrogen-chlorine co-doped carbon dots（N,Cl-CDs²）that selectively respond to quercetin（QCT）were synthesized by one-step solvothermal method.The prepared N,Cl-CDs² have bright yellow-green fluorescence with a QY of 10.4%,and their surface is rich in functional groups such as-OH,-COOH,and-NH₂.Based on IFE and static quenching（SQE）,QCT can significantly quench the fluorescence of N,Cl-CDs².According to the fluorescence quenching signal of N,Cl-CDs²,a simple,fast and effective QCT detection method is established.The linear range of this method is 0.62-121.74μM and the LOD is52.63 nM.The N,Cl-CDs² was used to determine QCT in red wine with satisfactory recovery（96.48-102.41%）.And the N,Cl-CDs² was applied to the bioimaging of HT-29cells and CHO cells,which proved that it has certain application potential in bioimaging applications.Chapter 4:Using o-phenylenediamine and alizarin red as the precursor,yellow luminescent nitrogen-sulfur co-doped carbon dots（N,S-CDs）were prepared by hydrothermal method.The N,S-CDs have good water solubility,while their surface has a variety of functional groups,such as C=O,-OH and-COOH.The selectivity of N,S-CDs was studied,and it was found that Ag⁺could quench the fluorescence quickly（1 min）and specifically.The Ag⁺fluorescent probe based on N,S-CDs was successfully constructed with wide linear range（0.50-213.70μM）and low LOD（39.54 n M）,and were used for the detection of Ag⁺in ambient water samples.The N,S-CDs was used in HT-29 cells and CHO cells for fluorescence imaging,and the effect was good.