Cyanographene and Graphene Acid: Emerging Derivatives Enabling High-Yield and Selective Functionalization of Graphene

Abstract

Efficient and selective methods for covalent derivatization of graphene are needed because they enable tuning of graphene’s surface and electronic properties, thus expanding its application potential. However, existing approaches based mainly on chemistry of graphene and graphene oxide achieve only limited level of functionalization due to chemical inertness of the surface and nonselective simultaneous attachment of different functional groups, respectively. Here we present a conceptually different route based on synthesis of cyanographene via the controllable substitution and defluorination of fluorographene. The highly conductive and hydrophilic cyanographene allows exploiting the complex chemistry of −CN groups toward a broad scale of graphene derivatives with very high functionalization degree. The consequent hydrolysis of cyanographene results in graphene acid, a 2D carboxylic acid with pKa of 5.2, showing excellent biocompatibility, conductivity and dispersibility in water and 3D supramolecular assemblies after drying. Further, the carboxyl groups enable simple, tailored and widely accessible 2D chemistry onto graphene, as demonstrated via the covalent conjugation with a diamine, an aminothiol and an aminoalcohol. The developed methodology represents the most controllable, universal and easy to use approach toward a broad set of 2D materials through consequent chemistries on cyanographene and on the prepared carboxy-, amino-, sulphydryl-, and hydroxy- graphenes.

Highly selective covalent organic functionalization of epitaxial graphene

“…At this point, it is important to mention that alternative efficient functionalization routes in a wet-environment starting from cyano- and fluoro-graphene towards graphene covalently modified with thio-, cyano- or carboxy-groups have been recently proposed4647 These strategies lead to development of a broad family of graphene derivatives with organics through consequent chemistries and, together with our present study, enable a selective and controllable way to develop advanced 2D-heterostructures. Among all the potential applications we can envisage those requiring high selectivity, as those related to bio-sensing or bio-field-effect transistors10212728.…”

Cyanographene and Graphene Acid: The Functional Group of Graphene Derivative Determines the Application in Electrochemical Sensing and Capacitors

“…Graphene acid (17.2 mg ml −1 ) and cyanographene (25.5 mg ml −1 ) in deionized water were received from the Regional Centre of Advanced Technologies and Materials (RCPTM), Faculty of Science, Palacký University, Olomouc, according to the previously reported procedure . Ascorbic acid, uric acid, potassium chloride, sodium chloride, sodium phosphate dibasic dihydrate, potassium phosphate monobasic, sodium sulphate were purchased from Sigma‐Aldrich (Singapore).…”

“…Some recent efforts to address this issue have avoided using graphene oxide altogether, making use of alternative precursors that show a well‐defined stoichiometry in their initial states such as graphane and fluorographene ,. Bakandritsos and co‐workers recently introduced two well‐defined graphene derivatives produced via chemistry of fluorographene, i. e. cyanographene (G−CN, having nitrile groups covalently bonded to graphene lattice carbons) and graphene acid (G−COOH, with carboxyl groups covalently grafted onto graphene lattice) . G−CN was synthesized from fluorographene via reductive defluorination by reacting NaCN in DMF.…”

“…The nitrile groups on the G−CN were then selectively converted to carboxyl groups by subjecting G−CN to acid hydrolysis with 20 % HNO 3 , without introducing other oxygen‐bearing functionalities. Based on infra‐red and X‐ray photoelectron spectroscopy (XPS), combined with thermogravimetric analysis the functionalization degrees (FD) of the materials were 15 % for G−CN and 13 % for G−COOH (FD represents the percentage of graphene lattice carbons which are covalently bonded with the reported functional groups) . Energy dispersive spectroscopy (EDS) elemental mapping documented that both graphene derivatives are densely and homogenously covered by the respective functional groups.…”

A Simple and Scalable Method for the Preparation of Magnetite/Graphene Oxide Nanocomposites under Mild Conditions

“…Graphene oxide (GO) is the most prominent host of magnetic nanoparticle (MNP) composites because its properties make it advantageous for large-scale production. Owing to their polar and ionisable surface sites [6], GO particles and their functionalized derivatives [7,8] are easily processable in aqueous media, which favors the interaction of the lamellar host with the simplest, water-soluble iron salts (e.g., FeSO 4 or FeCl 3 ) and complexes as precursors [9][10][11][12]. Graphenebased composites are then obtained by transformation of GO to reduced graphene oxide (RGO).…”