Preparation And Sensing Applications Of Functionalized Graphene Quantum Dots

In recent years,with the increasingly serious environmental pollution problem,it has affected the health of human beings and environmental ecology.Therefore,it is urgent to develop green,novel and multi-performance materials for testing.As one of the most common and basic elements in inorganic and organic materials,carbon plays an important role in academic and industrial society.At the same time,another problem is water pollution.With the increase of pollution of drinking water resources（such as groundwater and surface water）,how to detect and deal with it is a great challenge.Due to the application of graphene in various energy sources and environments,graphene has attracted much attention in recent years.Graphene quantum dots（GQDs）,as a unique zero-dimensional（0D）carbon nanomaterial,have attracted great interest in the past few years due to their excellent electronic and physical chemical properties,quantum correlation and edge effect.As a new type of quantum dot material,it has the characteristics of low toxicity,good solubility,good chemical inertia,stable luminescence and good surface morphology,and has been widely used in ion detection,biological imaging,electrochemiluminescence,sensors and so on.However,in the existing research,there are few studies on the one-step hydrothermal synthesis of functionalized GQDs with green materials and their direct use to detect molecules in the environment and biology.In this paper,a new preparation method of functionalized GQDs was established based on the green synthesis method,and its application in detecting molecules in environmental organisms was further discussed.The main contents of this paper include:In the first chapter,we briefly expounded the overview,basic properties,preparation methods and applications of GQDs in biological and environmental detection,and discussed the research content and significance of this paper.In chapter 2,we introduce in detail the simple preparation method and corresponding characterization of new functionalized graphene quantum dots prepared by green materials used in this paper,which provides a basis for the next practical detection application.In chapter 3,based on the fluorescence quenching effect of 6-mercaptopurine（6-MP）on GQDs,we constructed a new optical sensor for the detection of 6-MP.Based on the internal filtration effect between 6-MP and GQDs,the fluorescence of GQDs can be quenched.The concentration of 6-MP shows a good linear relationship with its fluorescence quenching efficiency in the range of 0-60μM,and the detection limit is 0.05μM.Through the change of fluorescence intensity in the system,we have realized the quantitative detection of 6-MP in human urine.In chapter 4,based on the fluorescence"off-on"system of Fe³⁺and catechol to N-GQDs,a simple and sensitive fluorescence sensor was constructed for the detection of catechol.Fe³⁺has strong oxidation and can quench the fluorescence of N-GQDs,and the detection limit is 0.07μM.Catechol,as a pollutant in the natural environment,is more likely to react with Fe³⁺to form a complex,which leads to fluorescence recovery of the system.The detection range is 0-24μM and the detection limit is 0.18μM.Through the change of fluorescence intensity of the system,we realized the quantitative detection of Fe³⁺ and catechol in water samples.