Preparation Of Graphene-like Materials And Its Application In The Detection Of Environmental Small Molecule Contaminants

Following graphene materials,a number of new graphene materials have gradually entered the field of view,Such graphene-like compounds include transition metal dichalcogenide compounds,topological insulators and graphene quantum dots.In this dissertation,Bi₂Se₃ and GQDs are mainly used as research objects.The sensitivity and rapid detection of bisphenol A,mercury ion and ferric ion were realized by electrochemical detection method and fluorescence detection method,respectively.The detailed work is as follows:1.The electrochemical sensor of bisphenol A was successfully constructed by using a conductive polymer film composed of bismuth selenide and gold nanoparticles/chitosan modified the glassy carbon electrode.The preparation of bismuth selenide itself is a laminar structure of graphene materials,with a higher surfaceareaandbetterconductivityandcatalyticactivity.Gold nanoparticles/chitosan suspensions also have good conductivity,adsorption and catalysis,and the combination of them promotes the transmission of electrons and enhances the catalytic oxidation of the sensor.Under the optimized experimental conditions,the detection of bisphenol A was completed using the prepared sensor.The linear relationship between the concentration of bisphenol A and the measured current intensity is linear with a linear range of 5.0×10^-77 mol·L^-11 to 4.0×10^-66 mol·L^-1,and the lower limit of detection is 1.3×10^-7mol·L^-1?S/N=3?.The sensor has a simple preparation process,rapid response,and good selectivity,and can be used to realize rapid and sensitive detection of bisphenol A.2.Using citric acid as a carbon source and ammonia as a nitrogen source,nitrogen-doped N-GQDs were successfully synthesized by hydrothermal method.The N-GQDs have good fluorescence properties and quantum yield,and have good water solubility and uniform size?average diameter of 3.1 nm?.Because there are many functional groups on the surface of N-GQDs?such as carboxyl group,amino group,etc?,it is easy to react with Hg²⁺,which makes the fluorescence quenched.After adding glutathione?GSH?,it is easy to remove Hg²⁺from the surface of N-GQDs.The formation of a more stable Hg-S bond,so the fluorescence will increase,this experiment constructed two fluorescent probes to complete the detection of Hg²⁺and GSH selectivity.Under optimized experimental conditions,the fluorescence sensor of N-GQDs has good selectivity and high sensitivity to Hg²⁺,and the Hg²⁺concentration is in the range of 1.0×10^-77 mol·L^-11 to 3.0×10^-55 mol·L^-1,the fluorescence intensity and Hg²⁺concentration showed a very good linear relationship,the correlation coefficient reached R²=0.9914,and the detection limit was 2.2×10^-8mol·L^-1?S/N=3?.The linear range of GSH measured by N-GQDs-Hg²⁺system was5.0×10^-66 mol·L^-11 to 3.0×10^-55 mol·L^-1,and the linear correlation coefficient was R²=0.9987.The detection limit was 1.02×10^-6mol·L^-1?S/N=3?.3.Using citric acid as a reaction carbon source and thiourea as a reactive sulfur and nitrogen source,sulfur-nitrogen co-doped graphene quantum dots were prepared by one-step hydrothermal synthesis.The morphology of N,S-GQDs is spherical,with uniform size distribution and an average particle size of 2.9 nm.Because Fe³⁺is easy to specifically bond with phenolic hydroxyl groups on the surface of N,S-GQDs,the doping of N and S increases the surface electron density of N,S-GQDs,which promotes electron transfer and makes N,S-GQDs fluorescence quenching and a fluorescence sensor that selectively detects Fe³⁺was constructed.The linear range of Fe³⁺measured by fluorescence quenching method was 1.0×10^-77 mol·L^-11.0×10^-6mol·L^-1,and the correlation coefficient was R²=0.9952.The detection limit was1.8×10^-88 mol·L^-1?S/N=3?.