The Role of Functionalization in the Applications of Carbon Materials: An Overview

Abstract

The carbon-based materials (CbMs) refer to a class of substances in which the carbon atoms can assume different hybridization states (sp 1 , sp 2 , sp 3 ) leading to different allotropic structures -. In these substances, the carbon atoms can form robust covalent bonds with other carbon atoms or with a vast class of metallic and non-metallic elements, giving rise to an enormous number of compounds from small molecules to long chains to solids. This is one of the reasons why the carbon chemistry is at the basis of the organic chemistry and the biochemistry from which life on earth was born. In this context, the surface chemistry assumes a substantial role dictating the physical and chemical properties of the carbon-based materials. Different functionalities are obtained by bonding carbon atoms with heteroatoms (mainly oxygen, nitrogen, sulfur) determining a certain reactivity of the compound which otherwise is rather weak. This holds for classic materials such as the diamond, the graphite, the carbon black and the porous carbon but functionalization is widely applied also to the carbon nanostructures which came at play mainly in the last two decades. As a matter of fact, nowadays, in addition to fabrication of nano and porous structures, the functionalization of CbMs is at the basis of a number of applications as catalysis, energy conversion, sensing, biomedicine, adsorption etc. This work is dedicated to the modification of the surface chemistry reviewing the different approaches also considering the different macro and nano allotropic forms of carbon.C 2019, 5, 84 3 of 45 narrow graphite-like interconnected layers. This leads to a closed pore rigid structure that is chemically inert, hard but brittle [48][49][50].Due to the highly resistant, conductive, and inert network, glassy carbons are utilized in a series of rather different applications. They are utilized as electrodes in solid state batteries and in industrial harsh chemical processes where also high temperatures are involved such as crystallization of CaF2, CdS and ZnS. Glassy carbon can be utilized to manufacture high temperature furnace elements. Due to the chemical inertness, glassy carbons are utilized also in fabrication of protheses. Porous carbon and carbon black are much softer. Generally, in industrial applications important is the extension of the surface which is exposed to the external environment. The porous carbon is characterized by a high specific surface area enhancing the interaction with the external medium. Although it possesses a lower conductivity with respect to glassy carbon, the high porosity and the presence of active sites makes it a good material to fabricate electrodes for applications in electrochemistry [51][52][53] and bioelectrodes for sensing and stimulation [54,55].The same holds for the carbon black mainly utilized as additive in rubbers and polymers to improve their mechanical properties, or as a pigment [56] although new potentialities have been recently envisaged [57].Common to all the forms of carbon which are bri...

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Click Chemistry Enabling Covalent and Non-Covalent Modifications of Graphene with (Poly)saccharides

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