Electrosurface Properties of Nanostructured Silica Assessed by EPR of Molecular pH Labels


Тип публикации: статья из журнала

Год издания: 2015

Идентификатор DOI: 10.1007/s00723-015-0704-1

Ключевые слова: Electron spectroscopy, Magnetic resonance, Molecules, Paramagnetic resonance, pH sensors, Silica, Surface charge, Adsorption of water, Electrical potential, Electron paramagnetic resonance spectroscopy, Electrosurface properties, Hydrolyzed products, Nanoparticle surface charge, Nanostructured silica, Negative surface charges, Electron spin resonance spectroscopy

Аннотация: 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 aminopropylПоказать полностьюtriethoxy-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 ?90 mV. 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 375 K. 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. © 2015, Springer-Verlag Wien.

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Журнал: Applied Magnetic Resonance

Выпуск журнала: Vol. 46, Is. 12

Номера страниц: 1367-1382


  • Kovaleva E.G. (Department of Technology for Organic Synthesis, Institute of Chemical Engineering, Ural Federal University, Mira St., 19, Yekaterinburg, Russian Federation)
  • Molochnikov L.S. (Department of Chemistry, Ural State Forest Engineering University, Siberian Highway, 37, Yekaterinburg, Russian Federation)
  • Osipova V.A. (Laboratory of Organic Materials, Institute of Organic Synthesis, Ural Branch of the Russian Academy of Sciences, Sofia Kovalevskaya St., 20, Yekaterinburg, Russian Federation)
  • Stepanova D.P. (Department of Technology for Organic Synthesis, Institute of Chemical Engineering, Ural Federal University, Mira St., 19, Yekaterinburg, Russian Federation)
  • Reznikov V.A. (Laboratory of Nitroxide Radicals, Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, Akad. Lavrent’ev Av., 9, Novosibirsk, Russian Federation)

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