Study Of Effect Of Functional Modification On Structural Stability And Elastic Properties Of Graphene Nanoribbons

Since the monolayer graphite was first prepared in the laboratory by the researchers at University of Manchestet in 2004,the research enthusiasm on graphene never fade.The study on the nanocomposites have been mostly focused on carbon-based nano-material in recent years,as from zero-dimensional fullerene,one-dimensional carbon nanotubes to two-dimensional grapheme.The materials have been found successively and their composites have been extensively researched,Especially to reinforce materials,the simulation researches on graphene nanoribbons and their functionalized modifications have become the current research upsurge.As a reinforcement,graphene has received more and more attentions in the preparation of the lightweight,high-strength and high-toughness composites due to its unique electrical,mechanical and thermal properties.However,by the experiments,it is found that that the surface of untreated graphene is inert and so is difficult to make conglutination with reinforcing matrix materials.Especially because the raw graphene in matrix always agglomerates severely,the homogeneous distribution of graphene nanoribbons in a matrix remains a challenge that is commonly encountered in the synthesis of graphene-reinforced nanocomposites.To obtain graphene composites with improved mechanical properties,developing an effective chemical treatment is important to achieve optimum grafting of the functional group in terms of variety,quantity,and location.In this paper,the elastic properties and the structural stability of the grafted armchair graphene nanoribbons and zigzag graphene nanoribbons with different functional groups were studied by using molecular dynamics theory.The simulation results show that the Young’s moduli of graphenes with auto update-grafted hydrogen(-H)are 982 GPa for zigzag and 1046 GPa for armchair graphenes,When the graphenes are grafted with hydroxyl(-OH),amine(–NH2),carboxylic(–COOH),and thiol(–SH)groups,Graphene–OH shows the highest Young’s modulus,followed by graphene–COOH.Among the moduli obtained,those for graphene–NH2 and graphene–SH,which are nearly identical to that of graphene–H,are the lowest.The modulus variations of the zigzag and armchair graphenes with different grafts have similar trends,but the moduli for armchair graphenes are always higher than those for zigzag graphenes.This phenomenon is analyzed on the basis of the radial distribution function,deformation electron density,and chemical bond theory.The results indicate that smaller oxygen-containing functional groups,as well as the C–O or C–C–O bond formations caused by grafted atoms with dangling bonds,could effectively enhance the flexibility of the graphenes while maintaining their stability.The elastic performance of the grafted armchair graphenes is superior to that of the grafted zigzag graphenes.