Applications And Researches Of New Carbon Nitride Fluorescent Materials In Chemical Sensors And Bioimaging

In recent years,two-dimensional graphitic carbon nitride(g-C3N4)nanomaterials have attracted many researchers' attention due to their simple synthesis,low cost,anti-photobleaching,good biocompatibility,high quantum yield and tunable fluorescent emission.They are widely applied into the fields of photocatalysis,electrocatalysis,mimic enzyme catalysis,drug carrier,photosensitizer,chemical sensing and biosensing.Recently most of g-C3N4 nanosheets were derived from pristine bulk g-C3N4 with large band gap(2.7 eV)and emitted near ultraviolet-blue fluorescence.Compared to b-C3N4 nanomaterials with near ultraviolet-blue fluorescence,g-C3N4 nanomaterials with green or longer wavelength fluorescent emission showed greater potential in the application of chemical sensors and bio-imaging.In this thesis,two different g-C3N4 nanosheets with green fluorescence were prepared and applied into the chemical sensor and E.coli fluorescent imaging.In the chapter 1,the structure and properties of g-C3N4 were briefly introduced,and the preparing methods and application in chemical sensors and bioimaging of g-C3N4 nanosheets were emphasized.The main purpose and content of this paper were proposed at the end of this chapter.In the chapter 2,barbituric acid-modified graphitic carbon nitride(BCN)nanosheets with blue-green fluorescence were prepared by copolymerization of dicyandiamide with barbituric acid and then by a chemical oxidation and ultrasonic exfoliated process.A ratiometric fluorescent sensor for the detection of copper ions was designed by using BCN nanosheets as the fluorescent probe and Ru(bpy)3Cl2 as the reference.In the presence of copper ions,the fluorescence of the nanosheets was quenched through photoinduced electron transfer(PET),while the red fluorescent intensity of Ru(bpy)3Cl2 kept constant.In addition,the fluorescent color of the sensor changed from blue-green to red with the increasing concentration of copper ions,which realized the visual fluoresce,nt detection of copper ions.The linear range for the detection of copper ions was covered from 0.1?M to 1?M with a detection limit of 0.07?M.This proposed sensor was successfully applied to detect copper ions in tap water.In the chapter 3,phenyl-doped graphitic carbon nitride(OPDCN)nanosheets with green fluorescence were prepared by the copolymerization of urea with trimesic acid and then by a chemical oxidation and ultrasonic exfoliated process.OPDCN nanosheets showed good dispersibility with positive charge.The diameter of the nanosheets was about 100 nm,and the thickness was below 10 nm.The fluorescent intensity of OPDCN nanosheets were quenched with the increase of pH.By taking advantage of OPDCN nanosheets as fluorescent probe,E.coli.BL21(DE3)was imaged in muti-chunnel by a laser confocal fluorescent microscope,in weak acid(pH 4),neutral(pH 7)and alkalescent(pH 8)PBS buffer,respectively.