caa a22 4500 605545596 CHVBK 20210128100936.0 cr unu---uuuuu 210128e20151201xx s 000 0 eng 10.1007/s00723-015-0704-1 doi (NATIONALLICENCE)springer-10.1007/s00723-015-0704-1 Electrosurface Properties of Nanostructured Silica Assessed by EPR of Molecular pH Labels [Elektronische Daten] [Elena Kovaleva, Leonid Molochnikov, Victoria Osipova, Darya Stepanova, Vladimir Reznikov] Three techniques of spin labeling have been applied to nanostructured SiO2 and have been tested by electron paramagnetic resonance spectroscopy of pH-sensitive nitroxide radicals (NRs). The best technique was based on preliminary interaction of the pH-sensitive NR bromomethyl-2,2,3,5,5-pentamethylimidazoline-1-oxyl with aminopropyltriethoxy-silane (APTES) in the presence of trioctylamine and further treatment of the nanostructured SiO2 with the hydrolyzed product and acetic anhydride. It was found that there are two types of location of the pH-sensitive NRs (spin labels) on the surface of nanostructured silica. The spin labels of the first type located near the surface of nanostructured SiO2 ("slow-motional” NR) have been used to measure near-surface electrical potential at the site of NR N-O• fragment location, q equal to −90mV. The NR molecules of the second type which were positioned well far from the nanostructured SiO2 surface ("fast-motional” NRs) were employed to establish the regularities of mutual changes in the NR form and nanoparticle surface charge with variations in pH of external bulk solution (pHext). The pH-sensitive NRs covalently attached to the SiO2 surface were successfully employed for the study of surface charge in the drying process with a rise of temperature up to 375K. A negative surface charge was shown to decrease due to reducing an ionization degree of the surface silanol groups. This process was found to be reversible at re-adsorption of water molecules. Springer-Verlag Wien, 2015 Kovaleva Elena Department of Technology for Organic Synthesis, Institute of Chemical Engineering, Ural Federal University, Mira St., 19, 620002, Yekaterinburg, Russia aut Molochnikov Leonid Department of Chemistry, Ural State Forest Engineering University, Siberian Highway, 37, 620100, Yekaterinburg, Russia aut Osipova Victoria Laboratory of Organic Materials, Institute of Organic Synthesis, Ural Branch of the Russian Academy of Sciences, Sofia Kovalevskaya St., 20, Yekaterinburg, Russia aut Stepanova Darya Department of Technology for Organic Synthesis, Institute of Chemical Engineering, Ural Federal University, Mira St., 19, 620002, Yekaterinburg, Russia aut Reznikov Vladimir Laboratory of Nitroxide Radicals, Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, Akad. Lavrent'ev Av., 9, 630090, Novosibirsk, Russia aut Applied Magnetic Resonance Springer Vienna 46/12(2015-12-01), 1367-1382 0937-9347 46:12<1367 2015 46 723 https://doi.org/10.1007/s00723-015-0704-1 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00723-015-0704-1 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Kovaleva Elena Department of Technology for Organic Synthesis, Institute of Chemical Engineering, Ural Federal University, Mira St., 19, 620002, Yekaterinburg, Russia aut NATIONALLICENCE 700 1- Molochnikov Leonid Department of Chemistry, Ural State Forest Engineering University, Siberian Highway, 37, 620100, Yekaterinburg, Russia aut NATIONALLICENCE 700 1- Osipova Victoria Laboratory of Organic Materials, Institute of Organic Synthesis, Ural Branch of the Russian Academy of Sciences, Sofia Kovalevskaya St., 20, Yekaterinburg, Russia aut NATIONALLICENCE 700 1- Stepanova Darya Department of Technology for Organic Synthesis, Institute of Chemical Engineering, Ural Federal University, Mira St., 19, 620002, Yekaterinburg, Russia aut NATIONALLICENCE 700 1- Reznikov Vladimir Laboratory of Nitroxide Radicals, Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, Akad. Lavrent'ev Av., 9, 630090, Novosibirsk, Russia aut NATIONALLICENCE 773 0- Applied Magnetic Resonance Springer Vienna 46/12(2015-12-01), 1367-1382 0937-9347 46:12<1367 2015 46 723