Interfacial Electrostatic Properties of Hydrated Mesoporous and Nanostructured Alumina Powders by Spin Labeling EPR

Interfacial Electrostatic Properties of Hydrated Mesoporous and Nanostructured Alumina Powders by Spin Labeling EPR Научная публикация

Журнал

Cell Biochemistry and Biophysics
ISSN: 1085-9195 , E-ISSN: 1559-0283

Вых. Данные

Год: 2017, Том: 75, Номер: 2, Страницы: 159-170 Страниц : DOI: 10.1007/s12013-016-0767-0

Ключевые слова

Mesoporous alumina; Phospholipids; Aluminum alkoxides; pH-sensitive nitroxides

Авторы

Kovaleva Elena G. ¹ , Molochnikov Leonid S. ² , Stepanova Darya P. ¹ , Pestov Alexander V. ³ , Trofimov Dmitrii G. ⁴ , Kirilyuk Igor A. ^4,5 , Smirnov Alex I. ⁶

Организации

1	(Данные Web of science) Ural Fed Univ, Inst Chem Engn, 19 Mira St, Ekaterinburg 620002, Russia
2	(Данные Web of science) Ural State Forest Engn Univ, Dept Chem, 37 Siberian Highway, Ekaterinburg 620100, Russia
3	(Данные Web of science) Russian Acad Sci, Mat Organ Lab, I Ya Postovsky Inst Organ Synth, Ural Branch, Akad Skaya S Kovalevskoi 22-20, Ekaterinburg 2220, Russia
4	(Данные Web of science) Russian Acad Sci, Siberian Branch, Inst Organ Chem, Akad Lavrentev Ave 9, Novosibirsk 630090, Russia
5	(Данные Web of science) Novosibirsk State Univ, Pirogova Str 2, Novosibirsk 630090, Russia
6	(Данные Web of science) North Carolina State Univ, Dept Chem, 2620 Yarbrough Dr, Raleigh, NC 27695 USA

Acid-base equilibria and interfacial electrostatic properties of hydrated mesoporous and nanostructured alumina powders are determining factors for the use of these materials in heterogeneous catalysis and as a sorption media for filtration and chromatographic applications including life sciences. Here spin probe electron paramagnetic resonance spectroscopy of pH-sensitive nitroxides was employed to evaluate the surface charge and interfacial acid-base equilibria at the pore surface of mesoporous powders of alpha-Al2O3, gamma-Al2O3, Al2O3 x nH(2)O, and basic gamma-Al2O3 and nanostructured Al2O3 in the form of pristine materials and modified with aluminum-tri-sec-butoxide, hydroxyaluminum glycerate, and several phospholipids. A new pH-sensitive nitroxide probe, 4-dimethylamino-5,5-dimethyl-2-(4-(chloromethyl)phenyl)-2-ethyl-2,5-dihydro-1H-imidazol-1-oxyl hydrochloride semihydrate (nitroxide R1), has been synthesized and characterized. It was found that conditions of preparation of alumina powders exert strikingly large effects on the apparent pK (a) of nitroxides measured from electron paramagnetic resonance titration curves. Specifically, while the electron paramagnetic resonance titrations curves for the nitroxide R1 in mesoporous powders prepared from basic gamma-Al2O3 and Al2O3 x nH(2)O were shifted by Delta pK (a)ae +0.6 and up to ae +1.2 pH units respectively, the shift for gamma-Al2O3 was found to be much higher: Delta pK (a) = +3.5. Assuming approximately the same a dagger pH = 0.5-1.0 arising from a difference in the hydrogen ion activity between the bulk solution phase and that in a confined pore volume, the samples were ranked in the following order of descending magnitude of the effective surface electrostatic potential I<spacing diaeresis>: mesoporous gamma-Al2O3 > Al2O3 x nH(2)O > basic gamma-Al2O3 > alpha-Al2O3. Conditions of the Al2O3 synthesis as well as the surface modification procedures were found to have profound effects on the interfacial electrostatic properties of hydrated samples that are likely related to the nature and concentration of the active sites on the alumina surfaces.

Kovaleva E.G. , Molochnikov L.S. , Stepanova D.P. , Pestov A.V. , Trofimov D.G. , Kirilyuk I.A. , Smirnov A.I.
Interfacial Electrostatic Properties of Hydrated Mesoporous and Nanostructured Alumina Powders by Spin Labeling EPR
Cell Biochemistry and Biophysics. 2017. V.75. N2. P.159-170. DOI: 10.1007/s12013-016-0767-0 WOS Scopus

Опубликована online:	4 нояб. 2016 г.
Опубликована в печати:	1 июн. 2017 г.

Web of science	WOS:000400867700003
Scopus	2-s2.0-84994323104
OpenAlex	W2547861982