title: pKa determination of graphene-like materials: Validating chemical functionalization.
abstract: We report a novel pKa determination for different graphene-like samples: graphene oxide (GO), reduced GO (rGO), graphene nanoribbons (GNR), oxidized GNR (GONR), thiol- and imidazole-functionalized GO (GOSH and GOIMZ, respectively) and thiol-functionalized GONR (GONRSH). Using the specialized computational program BEST7 for treating titration curves, pKas for different functional groups were discriminated (confirmed by infrared spectra) and their composition quantified. Overall, three equilibria were distinguished, two relative to carboxylic acids exhibiting different acidic degrees (pKa1∼4.0 and pKa2∼6.0) and one relative to alcohols (pKa4∼10.0). Upon functionalization on carboxylate sites, thiol (pKa(GOSH/GONRSH)=6.7) and imidazole (pKa(GOIMZ)=6.6) moieties were discerned, followed by a decrease of their carboxylate percentage (compared to the precursors), thus allowing determining the degree of functionalization (48% and 36% of thiol content for GOSH and GONRSH respectively, and 29% of imidazole for GOIMZ). The proposed method is innovative and simpler when compared to the traditional tools usually employed to quantify chemical functionalization.
authors.affiliation: Department of Chemistry, Universidade Federal do Paraná (UFPR), CP 19081, CEP 81531-990, Curitiba, PR, Brazil. Electronic address: elisaorth@ufpr.br.
authors.forename: Elisa S
authors.initials: ES
authors.lastname: Orth
authors.affiliation: Department of Chemistry, Universidade Federal do Paraná (UFPR), CP 19081, CEP 81531-990, Curitiba, PR, Brazil.
authors.forename: José G L
authors.initials: JGL
authors.lastname: Ferreira
authors.affiliation: Department of Chemistry, Universidade Federal do Paraná (UFPR), CP 19081, CEP 81531-990, Curitiba, PR, Brazil.
authors.forename: Jéssica E S
authors.initials: JES
authors.lastname: Fonsaca
authors.affiliation: Department of Chemistry, Universidade Federal do Paraná (UFPR), CP 19081, CEP 81531-990, Curitiba, PR, Brazil.
authors.forename: Sirlon F
authors.initials: SF
authors.lastname: Blaskievicz
authors.affiliation: Graphene and Nano-materials Research Center - Mackgraphe - Graphene and Nanomaterials Research Center, Mackenzie Presbyterian University, 01302-907 São Paulo, Brazil.
authors.forename: Sergio H
authors.initials: SH
authors.lastname: Domingues
authors.affiliation: Department of Chemistry and Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Archi
authors.initials: A
authors.lastname: Dasgupta
authors.affiliation: Department of Physics and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, PA 16802, USA; Department of Chemistry and Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Mauricio
authors.initials: M
authors.lastname: Terrones
authors.affiliation: Department of Chemistry, Universidade Federal do Paraná (UFPR), CP 19081, CEP 81531-990, Curitiba, PR, Brazil.
authors.forename: Aldo J G
authors.initials: AJG
authors.lastname: Zarbin
keywords: Graphene functionalization; Graphene nanoribbon; Titration; pK(a) determination