Green Preparation Of Graphene Quantum Dots And Its Biological And Catalytic Applications

Graphene quantum dots(GQDs)is a new type of nano-carbon materials.Because of its excellent properties and potential applications in biology,catalysis,energy and other fields,it has received extensive attention.In this thesis,the green preparation of GQDs and its applications in biology and catalysis have been researched and explored.The specific content is as follows:1.Using biomass materials(such as soluble starch,cotton cellulose and dextran)as precursors,a series of GQDs were prepared through a green hydrothermal method.At the same time,for the first time,azo dye pollutants Orange II(AO7)and Reactive Red 2(RR2)were used as raw materials to successfully prepare GQDs with excellent fluorescence properties.The microscopic morphology,molecular structure and fluorescence properties of GQDs were characterized.The research results show that GQDs has stable photoluminescence(PL)performance and good water solubility;GQDs can emit green or blue fluorescence under 365nm ultraviolet light irradiation,and is expected to be better used in biological cell imaging and chemical catalysis,etc.field.2.Through the cytotoxicity test(MTT method),it was found that the prepared GQDs had lower cytotoxicity and better biocompatibility.At the same time,because GQDs has good photoluminescence(PL)performance and water solubility,it has been successfully applied to biological cell imaging.The research results show that under different excitation channels,the stained cells present a clearer outline than the bright field.3.GQDs prepared with soluble starch and dextran can be used as deoxidizers to reduce Au³⁺to Au⁰ and stabilize Au NPs.At the same time,the microscopic morphology,crystal structure and element valence of Au NPs@GQDs were characterized.The research results show that GQDs has weak reducibility,Au NPs is wrapped by GQDs,forming a core-shell structure,and the prepared Au NPs has good crystallinity.Then,the catalytic activity of the catalyst in the reduction of p-nitrophenol(4-NP)to p-aminophenol(4-AP)was further explored.The research results show that the catalytic activity of Au NPs has a size effect,and Au NPs-5 with the smallest particle size(13.4 nm)exhibits the best catalytic activity,with a k_app of 9.3×10^-3.4.GQDs has a surface that is easy to functionalize,making it can be used as an excellent carrier for transition metal nanoparticles(TMNPs).Therefore,this work further explored the application of TMNPs@GQDs in catalyzing the hydrolysis of borohydrides to produce hydrogen.The results of the study show that GQDs wrapped on the surface of TMNPs avoid catalyst aggregation and act as a dispersant-like function.In addition,Rh NPs,Pt NPs and Ru NPs stabilized by GQDs exhibit excellent catalytic activity in a variety of hydrogen storage materials.Among them,4×10^-4 mmol of Pt NPs catalyze the hydrolysis of B₂(OH)₄ to produce hydrogen,TOFs value is 4603 mol _H2·mol^-1_cat·min^-1,4×10^-3 mmol of Rh NPs catalyze the hydrolysis of AB and Na BH₄ to produce hydrogen,TOFs are 656 and 217 mol _H2·mol^-1_cat·min^-1,respectively.