Synthesis And Application Of Functionalized Graphene Oxide

Graphene, with carbon atoms packed into2D honeycomb lattice monolayer, is the baiscbuilding block of the other dimensionalities carbon materials. Graphene has attracted great interestowing to its unique electrical, optical, mechanical physical properties, which facilitates a wide rangeof applications in optoelectronic field. Graphene oxide, resulting from the chemical exfoliation ofthe original graphite, has been a precursor of the graphene considering its low cost and scalableproduction. In addition, graphene oxide is solution processable and easy to chemical modifiedcontributing to the abundant oxygen groups, which enrich the types of the graphene oxide andexplore more applications for graphene materials. Therefore, in this dissertation, the works focus onthe functionalization of graphene oxide and study the electronic performance of functionalizedgraphene.Firstly, the controlled reduce of graphene oxide has been conducted and study its effect onelectronic performance. There are various kind of oxygen groups on graphene oxide sheet. But thedifferent reduced methods retained the different types and quanity of oxygen groups, which leads tolarge distinctive physical performance. So, it is significant to study the controlled reduction ofgraphene oxide and comparing the different performance before and after reduction. Based on thisconsideration, the graphene oxide has been chemical selective decarboxylation without changingthe amount of the other oxygen groups via the typically Ag-catalyst decarboxylation. The retainedoxygen groups keep the good dispersibility of reduced graphene oxide. The selective reduced of thegraphene oxide is applied as charge capture layer in field effect transistor memory via solutionprocess. Its semiconductor device exhibits the excellent performance with larger memory widowand better stability in transistor memory when compared with that of graphene oxide.Secondly，the amphiphilic graphene has been prepared. Graphene oxide has good dispersibilityin water for the rich oxygen groups, but it is so hard to dispersion in organic solvent and itsconductivity is so poor that it is limited in the application of polymer composites. In order toovercome the above mentioned drawbacks, the macromolecule or the polymer has been grafted tothe graphene oxide following by the reduction. The prepared graphene shows so strong amphophilicability that can be used in polymer composites. However, the prepared graphene usually dispersedin organic solvent but not in water. And also, the most solvents for the reaction of graphene oxideare organic solvent, which usually has a complex operation and does harm to the environment. 5,6-diaminopyrazine-2,3-dicarbonitrile has been used as a functional reagent to cyano react to thegraphene oxide in the water solvent with the catalyst of polyphosphate, then the functionalizedgraphene oxide was reduced by N2H4. The cyano groups of prepared amphiphilic graphene preventthe aggregation of the reduced graphene and make it well dispersed in water, methanol andN,N-dimethylformamide four months without deposition, which makes it a promising application inthe polymer composites.Finally, the organic radical compound has been linkaged to the graphene sheet and treating it as theanode materials of the lithium ion battery. The strong interaction between the organic radical andthe graphene sheet prevents the organic radical dissolution in electrolyte. At the same time, thesynergetic effect of the graphene and the organic radical in lithium storage, together with the largesurface area and good conductivity of graphene results in the excellent performance in lithiunsotorge. It shows the ultrahigh capacity(the capacity of the lithium is1080mAh g-1after400cycles), long time cycle stability and the good rate perormance (The capacities can sustain as highas387,385,173, and177mAh g-1at the rate of400,800,2000and5000mA g-1charging/discharging current density after625,1317,4190,5000cycles). cycle stability of thelithium ion battery has been improved because the strong linkage prevent the dissolution of theorganic radical into the electrolyte during the charge and discharge process. The large surface areaand the good conductivity of graphene combined with the electrochemical active group of organicradical, which is more than3times of graphite. This material enrich the types of graphene materialsfor the application of the anode of lithium ion battery.