Functionalized Graphene:Preparation And Their Applications

Graphene based on its unique two-dimensional single atomic layer honeycomb lattice structure,poceesses excellent electrical,mechanical and thermal properties for the potential broad applications in supercapacitor,energy storage,sensors,and other fields.Several strategies are developed to synthesize graphene based materials,and chemical reduction of graphene oxide due to the simple operation and large scale preparation has attracted researcher's attention.Graphene oxide and reduced graphene oxide are the improtant derivative products of the functionalized graphene.In this thesis,we focus on the facbrication of functionlized graphene.From pattern to three-dimensional assembly,and to two-dimensional composite,as well as applications of functionalized graphene,several critical issues were systematically investigated.The research contents and main results are summarized as follows:(1)The preparation and application of graphene conductive ink.Giant graphene oxide with layer thinkness of 0.8 nm and lateral size of 50-80 ?m was synthesized using the modified Hummers method.Through the solvent evaporation method,the graphene dispersion was condensed for facbricating graphene oxide ink with different concentrations.Through the tailoring of printing parameters with direct ink writing method and investigation of reduction conditions,the best technical parameters were obtained.The results showed that the graphene oxide ink with concentration of 15 mg/mL,pressure is 70 KPa,linear velocity is 3 mm/s,the lines were printed smoothly and possess the best morphology.When hydroiodic acid as reductant and its concentration is 15%,heated to 95 ?,and then reduced for 3 h,reduced graphene oxide exhibits excellent conductivity.By means of the direct ink writing technology,patterned printing can be realized on the flexible and non-flexible substrates such as polyethylene terephthalate(PET),polydimethylsiloxane(PDMS),and glass.The results will be of great significance for realizing the pattern of graphene materials and its applications in high performance of photoelectric devices.(2)The facbrication and application of three-dimensional graphene aerogel.Graphene aerogel endows three-dimensional deformation morphology and flexibility,which makes it appropriately suitable for the multi-response,multi-functional and high integration flexible wearable electric sensor.A feasible strategy was developed to prepare graphene aerogel by direct ink writing with graphene oxide ink via vacuum freeze-drying method.The effect of graphene oxide ink with different concentrations on porosity,mechanical and stability properties of aerogel was systematically investigated.By the way of direct ink writing,patterned aerogel was obtained;the effect of different number of serpentine lines on aerogel of mechanical sensitive property was investigated.The results show that the aerogel printed with 15 mg/mL graphene oxide ink can form suitable space structure with proper size to prepare sensors with excellent electrical and mechanical properties.The conductivity of graphene aerogel can be varied according to the different degree of deformation;the graphene aerogel sensor with four serpentine lines has more prominent sensitive mechanical properties.When aerogel sensor was attached at figer joints,gesture recognition is successfully achieved by sensing the finger joints for universal gestures,which could be applied to finger motion manipulation auxiliary apparatuses for muscle atrophy and Parkinson's disease patients.(3)The facbrication and application of graphene/Ag NPs hybrid ink.Graphene poceesses excellent flexibility and conductivity because of its intrinsic two-dimensionas structures.However,the excellent properties are usually limited by the aggregation in solution between graphene sheets,due to the strong Vander Waals force.Through adhering metal nanoparticles to a two-dimensional graphene sheet could inhibit the aggregation and decrease the contact resistance of graphene sheets.Ag NPs with the diameter of 150 nm were synthsized using polyols method.And then graphene/Ag NPs hybrid ink was prepared through mechanical stirring.The influence of different hybrid mole proportion for graphene oxide and Ag NPs on the conductivity of printed circuit was investigated.The results show that,after reduction the printed lines with 1:1 mole proportion of graphene oxide:Ag NPs possess the optimal electrical conductivity,the resistivity is 1.12×10-6? m.A simple circuit was printed on PET substrate.When voltage of 9 V was applied,four LED bulbs were lightened.The results will be of great significance for the development of graphene-based conductive inks and printed electronics.