Edge Functionalized Graphene Layers for (Ultra) High Exfoliation in Carbon Papers and Aerogels in the Presence of Chitosan

Abstract

Ultra-high exfoliation in water of a nanosized graphite (HSAG) was obtained thanks to the synergy between a graphene layer edge functionalized with hydroxy groups and a polymer such as chitosan (CS). The edge functionalization of graphene layers was performed with a serinol derivative containing a pyrrole ring, serinol pyrrole (SP). The adduct between CS and HSAG functionalized with SP was formed simply with a mortar and pestle, then preparing water dispersions stable for months in the presence of acetic acid. Simple casting of such dispersions on a glass support led to carbon papers. Aerogels were prepared through the freeze-dry procedure. Exfoliation was observed in both these families of composites and ultra-high exfoliation was documented in aerogels swollen in water. Carbon papers and aerogels were stable for months in solvents in a wide range of solubility parameter and in a pretty wide range of pH. By considering that a moderately functionalized nanographite was straightforwardly exfoliated in water in the presence of one of the most abundant biobased polymers, the obtained results pave the way for the simple and sustainable preparation of graphene-based nanocomposites. HSAG–SP/CS adducts were characterized by wide angle X-ray diffraction (WAXD), scanning and transmission electron microscopy (SEM, TEM and HRTEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Thermal stability of the composites was studied by thermogravimetric analysis (TGA) and their direct electrical conductivity with the four-point probe method.

Arsenate Removal from Aqueous Media Using Chitosan-Magnetite Hydrogel by Batch and Fixed-Bed Columns

“…The signal at 287.6 eV was assigned to the C=O bonds of the acetylated portion of chitosan ( Figure 3 a). The signal at 286.1 eV was assigned to C–O and C–N, while the signal at 284.8 eV corresponded to C–C and C–H bonds [ 34 , 35 , 36 ]. The fourth signal at 283.4 eV is attributed to signals of carbon adsorbed on magnetite [ 37 ].…”

Controlled Size Reduction of Liquid Exfoliated Graphene Micro-Sheets via Tip Sonication

“…The thus-produced and characterized graphene inks could be of interest for multiple applications where the size of the flakes and their defect identities are relevant, from solution-processed thin layers and devices to composites. They could even represent starting materials for selective chemical functionalization strategies [23][24][25] aimed at specific sites on the sheets [26,27], such as the edges or the holes in the basal plane formed after the most aggressive treatments.…”

Bionanocomposites based on a covalent network of chitosan and edge functionalized graphene layers

“…Definitely, cationic CS favorably interacts with aromatic substrates such as the graphene layers, as already demonstrated. 27,28 However, the key aspect of this work is the establishment of a covalent bond between the layer and CS, thanks to the reaction between the amino and the CHO groups. It can be thus summarized that preparation of bionanocomposites was performed in an acidic media in order to: (i) protonate the amines and to induce the cation-π interaction between the polymer and the graphene layers; (ii) catalyze the condensation reaction between the amine and the carbonyl and induce the formation of the imine functional group.…”

“…18 They are also used for preparing membranes with a lamellar structure for methanol dehydration, 19 for the adsorption of substances such as tetracycline, 20 dyes, 21 organic liquids, 22 lead 23 and water contaminants, 24 for the catalytic reduction of oxygen in an iron and cobalt based system, 25 and for the preparation of high performance supercapacitors. 26 Among the CS/G nanocomposites, CS/G based hydrogels, 21 aerogels, 22,24,27,28 and carbon papers 27,28 are the subject of increasing research activities. Aerogels 29 are indeed a unique class of materials with incredible lightness: typical average density is about 0.020 g/cm 3 .…”

“…[42][43][44][45] Indeed, to have unperturbed graphene layers, the selective edge functionalization is a preferred approach. 46 Carbon papers and aerogels were prepared 28 with graphene layers edge functionalized with 2-(2,5-dimethyl-1H-pyrrol-1-yl) propane-1,3-diol (SP), a PyC from serinol as the primary amine. The reported outcome 28 was the complete exfoliation of the graphitic aggregates, thanks to the synergy between the cation-pi interaction of the cationic chitosan (from acidic solution) with the aromatic carbon substrate and the water compatibility of the graphene layers.…”