PKa determination of graphene-like materials: Validating chemical functionalization

Elisa S. Orth, José G.L. Ferreira, Jéssica E.S. Fonsaca, Sirlon F. Blaskievicz, Sergio H. Domingues, Archi Dasgupta, Mauricio Terrones, Aldo J.G. Zarbin

Research output: Contribution to journalArticlepeer-review

75 Scopus citations


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 (pKaGOSH/GONRSH=6.7) and imidazole (pKaGOIMZ=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.

Original languageEnglish (US)
Pages (from-to)239-244
Number of pages6
JournalJournal of Colloid And Interface Science
StatePublished - Apr 1 2016

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Surfaces, Coatings and Films
  • Colloid and Surface Chemistry


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