Preparation And Performances Of Functionalized Graphene-calixarenes Composite Materials

Graphene,excellent two-dimensional carbon material,has attracted more interests for its superior electrical properties,good thermal stability and mechanical properties.Graphene-based materials can be prepared and functionalized easily,so they are the ideal candidate of nanometer matrix for the synthesis of functionalized composites.Calixarenes,as a third-generation supramolecular host compound,are easy to form a variety of derivatives via chemical modification and their cavity sizes are adjustable,they can recognize certain target molecules with high selective identification for their unique supramolecule recognizing ability.Based on the unparalleled performance of graphene and calixarene,the novel graphene-calixarene composites were obtained by grafting the calixarene molecules onto the graphene via esterification and polymerization.The new materials were characterized by a variety of analysis methods.And then they are used as adsorbent and electrode materials for studying their adsorption and electrical properties,respectively.In our present work,the main contents and results are as follows:(1)The results of FT-IR,Raman,SEM,AFM,XPS,TGA and BET show that the calixarene and its derivatives have been successfully grafted onto the surface of graphene oxide.The new composites are rough and porous with higher specific surface area,so they are more suitable to be used as the adsorption material to remove metal ions,which has a wide application prospect.(2)Adsorption of neodymium ions on the new functionalized graphene composites was studied.The results show that these new materials are more efficient for the adsorption of the neodymium ions in aqueous solutions after grafting calixarenes and its derivatives on the surface of graphene oxide and their maximum adsorption capacity has a greater increase compared to the pristine graphene oxidation,of which nine non-covalent functionalized graphene-calixarene composite materials can adsorb neodymium ions with higher efficiency due to their stronger electronegativity of the ester group.The adsorption process of neodymium ions is a spontaneous endothermic reaction process and the adsorption capacity of the composites is the highest at pH 6-7.The process of adsorbing neodymium ions is more suitable for pseudo-second-order kinetics model and Freundlich adsorption isotherm model.It is a dynamic adsorption process which occurs on the non-uniform surface and controlled by chemical adsorption mechanism.The whole process is based on complex complexation reaction occurred between the oxygen-containing functional groups and neodymium ions,and in a way then the affluence degree of the oxygen-containing functional groups determines their adsorption capacity.(3)The novel functionalized graphene-calixarene composites were modified on the surface of glassy carbon electrodes(GCEs)and their electrochemical properties were characterized by cyclic voltammetry(CV).,electrochemical impedance spectroscopy(EIS),differential pulse voltammetry(DPV).The results show that the electrode modified by the novel composite material can selectively recognize target small molecules such as tryptophan,ascorbic acid and dopamine with good response and high sensitivity.The reason is that the modified glassy carbon electrode successfully inherited the excellent electrical conductivity of the graphene oxide and the excellent supramolecular recognition ability of the calixarenes.In particular,the electrical properties of CFGO-S4/GCE,NCF-GO-CDM4 and NCF-GO-CDT4 were better,they were able to efficiently identify dopamine molecules with a detection limit of 0.25,0.01 and 0.012 μM at a signal to noise ratio of 3,respectively,and their current densities were 8.82,4.16 and 5.17 mA mM-1L cm-2,which were expected to be used in biosensors.The results show that the functionalized graphene-calixarene composite has good electrocatalytic activity for hydrogen evolution(HER)and oxygen reduction(ORR)reactions,the reason is that the interaction between the oxygen-containing functional groups on the surface of the materials leads to many lattice defects,which provides a large number of active centers for the reaction,accelerating the electron transport and thus promoting the reaction.In addition,after 20 or more periodic scannings the current signal for the electrode response were not significantly reduced and the relative standard deviation(RSDs)were less than 5%,indicating that the repeatability and stability of the electrode response was better.In summary,these new composites inherit both the advantages of graphene and calixarene,and overcome their shortcomings to a certain extent with better performance.Therefore,they are expected to be widely used in sensors,catalytic,energy storage,electronics,molecular recognition,separation and other fields.