Graphene-based Composites: Preprations And Fluorescence Properties

Novoselov and Geim has directly observed and characterized the morphology ofa single-layer graphene via a mechanical exfoliation method in2004. Graphene is atwo-dimensional framework of carbon atoms linked together through sp2hybridization in a hexagonal lattice.It has many excellent properties, the carrierdensity at ambient temperature， theoretical specific surface area,thermalconductivity and transmittance reaches1012cm-2,，2630m2g-1，5000Wm-1K-1，97.7%respectively. Scientists has explored versatile approaches to take full advantage of theexcellent properties of graphene,such as chemical vapor deposition,mechanicalexfoliation and reduction of grapheme oxide. The reduction of graphene oxide is a lowcost,mass production method to obtain chemically reduced graphene oxide.Theoxygen-containing functional groups has been introduced during the process,henceundermined the Van der Waals force and generated graphite oxide-An important basicraw material to modify graphene. To date,the method of large scale preparation ofhighly conductive graphene is immature and some scholars offered a variety ofways to synthesize graphene-based composites. Currently,we can combine graphenewith inorganic nanoparticles,organic molecules and polymers,these composites gaverise to a huge family of graphene-based materials. Such materials can be used insensors,supercapacitors,fuel cells and other fields. Graphene-based composites has abig advantage is that by changing the morphology,reduction time and ingredientsmodified on it,people can regulate their performance in some certain aspects.In thispaper,surface modification is employed to regulate the fluorescence properties of graphene.In the second chapter, we described an improved method for the preparation ofgraphite oxides. It was carried out under50°C throughout the reaction and we canalways achieve a bright yellow solution after H2O2has been added to the solutionrather than a brick-red one.XRD,XPS and TGA was engaged to characterizegraphene oxides made by this improved method,result shows that this method canproduce highly oxidized grapheme oxides steadily.In the third chapter,we modified graphene oxide with cinnamamide in a two-stepsynthesis including solvothermal and solution method.After cinnamanide wasintroduced to graphene oxides, the photoisomerization property of cinnamanide leadto an enhancement of photoluminescence performance of graphemeoxides.XPS,TGA,IR and NMR was engaged to confirm that we has successfullymodified graphene oxides with cinnamamide.Fluorescence spectra of cinnamamidemodified graphene oxides excited at325nm suggested that there has been a50%ormore increase of intensity after the composites exposure to300nm ultraviolet lightfor different periods of time.Then we use cucurbit[7]uril to make an ultra-high affinityhost-guest complexes with cinnamamide modified graphene oxides,quenchingoccurred.That may attributed to the inclusion between cucurbit[7]uril andcinnamamide.which impeded the interaction between sp2carbon framework andcinnamamide.In summary,we used an improved method for synthesizing a highly oxidizedgraphite oxide as a raw material and functionally modified graphene oxides withphotosensitive molecular.The molecular is photoresponsive to a certain wavelength oflight,which lead to an enhancement of photoluminescence intensity of chemicallymodified graphene oxides.Finally,we applied cucurbit[7]uril to quench thefluorescence by host-guest interaction.This paper introduces a method to regulatefluorescence properties of graphene oxide and provides a new idea to harness theuseful properties of graphene.