Physico-Chemical nanomaterials science

Brominated nanostructured carbons: surface properties and preparation of N-, S-та O-containing sorbents and catalysts
Diyuk V. E.1, Zaderko A. N.1, Grishchenko L. M.1, Vakaliuk A. V.1, Mischanchuk A. V.2, Boldyrieva O. Yu.1, Lisnyak V. V.1,3
1 Faculty of Chemistry, Taras Shevchenko National University of Kyiv, Volodymyrska Street, 64/13, Kyiv 01601, Ukraine.
E-mail: vdiyuk@gmail.com; lisnyak@chem.univ.kiev.ua
2 Chuiko Institute of Surface Chemistry of NAS of Ukraine, General Naumov Street, 17, Kyiv 03164, Ukraine.
3 Preљov Universirty in Preљov, Ul. 17 novembra, 1, Preљov 15 080 01, Slovakia.

Carbon nanomaterials are used to create sensors and electronic devices and are traditionally used as sorbents, carriers, and catalysts. Bromination and the subsequent substitution of bromine are composed in a universal approach for surface functionalization. The purpose of this work is to brominate carbon granular and fibrous nanostructured materials and to study their functional properties. Bromination was carried out with liquid bromine and aqueous Br2 and KBr3 solutions. By direct bromination with KBr3 and elemental Br2, one can obtain the samples containing 0.5–0.7 mmol/g of chemically active bromine. The thermal analysis methods show the staged thermal desorption of bromine, regardless of the carbon nature, bromination method, and bromine content. The use of different brominating agents and different pHs allows the direct introduction of Br- and O-containing functional groups. Increasing the acidity of the reaction mixture leads to the introduction of more (0.75–1.15 mmol/g) bromine. Bromination passed in a neutral or alkaline media results in the formation of predominantly Ph functional groups in an amount of up to 2 mmol/g. The oxidation of the carbon surface almost completely prevents its bromination. Thermal treatment and removal of oxygen-containing groups significantly increase the efficiency of bromination, therefore the surface concentration of active bromine increases by 20–50%. The increase in the surface reactivity is determined by the number of removed oxygen-containing functional groups and does not depend on their nature. A reaction model is proposed that describes the interaction of bromine with a system of isolated and coupled C=C bonds. A part of these bonds can attach bromine, breaking the conjugation, and during desorption, can renew the conjugation, eliminating HBr. Thus, the proposed bromination techniques are effective in creating bromine-containing surface precursors to new surface functionalities.