Preparation Of Graphene Quantum Dot Sensor And Detection Of Perfluorooctanoic Acid

Perfluorooctanoic acid（PFOA）is a kind of perfluorinated compound that is widely used in industrial production and life.It is difficult to degrade in the environment,has high toxicity and carcinogenicity,pollutes the environment and endangers human health.Therefore,a rapid,convenient and highly sensitive method for perfluorooctanoic acid detection is urgently needed.In this paper,a graphene quantum dot fluorescent probe was prepared to detect trace PFOA.（1）Graphene quantum dots（B-GQDs）with high quantum yield and blue fluorescence were rapidly synthesized by hydrothermal method.The optimal preparation conditions were obtained by controlling the heating temperature,heating time and the amount of carbon source.The fluorescence emission peak of the graphene quantum dots in the blue luminescence spectrum was 470 nm.When the heating temperature was set to 180°C,the reaction time was 10 h in a high-pressure reactor,and 1 m L graphene oxide was added,the synthesized B-GQDs had the strongest fluorescence a particle size of 1–1.5 nm and a measurement potential of-11.4 m V.（2）A novel green emission band graphene quantum dots（G-GQDs）with high quantum yield and green fluorescence was prepared by ultraviolet radiation method,and used to detect PFOA.With 10 m L of 1 mg/m L graphene oxide and 1m L of ammonia as raw materials,the green graphene quantum dots（G-GQDs）were prepared under the optimal preparation conditions by heating in a high-pressure reactor for 5 h in an oven at 180°C.Due to the addition of 1 m L ammonia in the reaction,the amino group was introduced,which changed the distribution of GQDs surface and its fluorescence properties.The fluorescence emission peak of G-GQDs was at 530 nm,and the particle size distribution was also in the range of 1-3 nm.The measured potential was-25.8 m V.（3）Graphene quantum dots with red emission band（R-RQDs）were rapidly and simply synthesized by microwave irradiation with R.viridis leaves as raw material.The R-GQDs prepared with high microwave oven power and reaction time of 5 min had the highest fluorescence intensity,the maximum emission wavelength was 630 nm,the particle size distribution was in the range of 1-2 nm,and the measurement potential was 1.02 m V.（4）The detection of perfluorooctanoic acid by graphene quantum dots with three color emission bands was studied.The fluorescence enhancement was more obvious with the increase of perfluorooctanoic acid concentration in R-GQDs,indicating that perfluorooctanoic acid could well quench the fluorescence of G-GQDs and enhance the fluorescence of R-GQDs.The quenching constant was 5176 L/mol,the enhancement constant was 3086 L/mol,and the detection limits were 1×10^-10mol/L.Much higher than the quenching constant of perfluorooctanoic acid on blue quantum dots.In order to effectively evaluate the effect of G-GQDs and R-GQDs as fluorescence sensors on the selective detection of perfluorooctanoic acid,G-GQDs and R-GQDs were used to detect perfluorohexanoic acid（PFHA）,perfluoropentanoic acid（PFPe A）,perfluoropropionic acid（PFPA）and perfluorononanoic acid（PFNA）as comparative experiments.Finally,it was found that in addition to perfluorooctanoic acid,the other four cannot make G-GQDs and R-GQDs undergo significant quenching and enhancement.The quenching constants of G-GQDs were 1191,1109,1238 and 1008 L/mol,respectively,and the enhancement constants of R-GQDs were926,906,2031 and 2391 L/mol,which were far less than the quenching and enhancement constants of perfluorooctanoic acid.In addition,three kinds of graphene quantum dots have good stability and luminescence properties.