Properties And Reduce Process Of Graphene Oxide With The Controllable PH Value

As an important derivative of graphene, graphene oxide (GO) is widely employedas the starting material to prepare graphene-based materials and can be assembled intomacroassembly of graphene, such as2D membrane and3D bulk materials.. Thus, theunderstanding and controlling of the structure and properties of GO is urgentlyrequired for the research and application of graphene. In this study, it is demonstratedthat the size and surface chemistry of GO can be precisely turned by adjusting the pHvalue of the GO hydrosol. Besides, the graphene oxide membranes (GOM) withdifferent structure and surface chemistry are successfully self-assembled at theliquid/air interface starting from GO hydrosols of different pH value. A sysmeticaldiscussion of the effect of pH on the reduction process of graphene oxide membranesis also proposed based on our results.Tuning the pH value of GO hydrosol can realize the sieving of the lateral size ofGO and their electrochemical behavior can be optimized with controllable surfacechemistry. Protonation or deprotonation of GONs may occur in GO hydrosol withdifferent pH value, and the oxygen-containing functional groups could bedeoxygenated and reduced simultaneously. Specifically, the GO hydrosol with pHvalue9exhibites the highest electrochemical activity.GOM with well-defined structure and controllable surface chemistry is prepared bya liquid/air interface self-assembly method. The–O-C=O on the edges of GONwould react with OH-firstly and then the epoxy groups would react with the excessOH-, which lead to the evolution of structure and surface chemistry of GOM withvarious pH values.GO and GOM exhibit good electrochemical sensing behaviors. The GO modifiedglassy carbon electrode (GCE) shows a good electrochemical detection behavior toH2O2with a minimum detection limit of29.28μmol/L, and the GOM modified GCEdisplay a good detection behavior to pH value of environment with a response curvesof V=0.05pH+0.05(V means the oxidation peak potential of the electrode).Graphene membranes, whose structure are well maintained, can be obtained byreducing the GOMs with HI, hydrazine hydrate steam or heat treatment at300℃.During the reduction process, pH value of parent GO hydrosol can induce the selective removal of the oxygen-containing functional groups of GOMs. For GOMprepared from the GO hydrosol under acidic condition, the–OH groups of areremoved prior to other groups, while in the case of GOM prepared under basiccondition, the–COOH are removed effectively. It is demonstrated that HI is a highlyeffective reductant to reduce GO prepared under acidic condition, and the resultingreduced GOM possesses fast electron transport rate and excellent mechanicalproperties. The reduced GOM shows promising applications in the fileds of flexibletransparent conductive film.