Acidic and Electrosurface Properties of Binary TiO2–SiO2 Xerogels Using EPR of pH-Sensitive Nitroxides

Acidic and Electrosurface Properties of Binary TiO2–SiO2 Xerogels Using EPR of pH-Sensitive Nitroxides Full article

Journal

Gels
ISSN: 2310-2861

Output data

Year: 2021, Volume: 7, Number: 3, Article number : 119, Pages count : DOI: 10.3390/gels7030119

Tags

xerogels characterization; TiO2–SiO2; surface electrostatic potential; electron paramagnetic resonance; pH-sensitive nitroxide radicals; titration curve

Authors

Antonov Denis O. ¹ , Tambasova Daria P. ¹ , Shishmakov Andrey B. ² , Kirilyuk Igor A. ³ , Kovaleva Elena G. ¹

Affiliations

1	Institute of Chemical Engineering, Ural Federal University Named after the First President of Russia B N Yeltsin, Mira St., 19, 620002 Yekaterinburg, Russia
2	Laboratory of Organic Materials, I. Ya. Postovsky Institute of Organic Synthesis, Ural Branch of the Russian Academy of Sciences, Akademicheskaya/S. Kovalevskoy, 22/20, 620990 Ekaterinburg, Russia
3	Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, Akad. Lavrent’ev Av. 9, 630090 Novosibirsk, Russia

The binary xerogels TiO2–SiO2 are widely used as catalysts and their carriers in organic synthesis. Characterization and adjustment of the electrostatic properties of the surface and the local acidity inside the pores, are necessary for the further development of TiO2–SiO2 xerogels applications. This research investigates acid–base equilibria in the pores, and the surface electrostatic potential (SEP) of binary TiO2–SiO2 xerogels, by the EPR of stable pH-sensitive nitroxide radicals. These radicals are small enough to penetrate directly into the pores, and to be adsorbed onto the surface of the material under study. This makes it possible to obtain valuable information on the acidic and electrosurface properties of the studied system. The highest negative surface electrical charge associated with surface electrical potential (SEP) was equal to –196 ± 6 mV. It was induced by the surface of the sample with a 7% TiO2 content. Тhe local acidity inside the pores of this sample was found to be higher, by approximately 1.49 pH units, as compared to that in the external bulk solution.

Antonov D.O. , Tambasova D.P. , Shishmakov A.B. , Kirilyuk I.A. , Kovaleva E.G.
Acidic and Electrosurface Properties of Binary TiO2–SiO2 Xerogels Using EPR of pH-Sensitive Nitroxides
Gels. 2021. V.7. N3. 119 . DOI: 10.3390/gels7030119 WOS Scopus OpenAlex

Submitted:	Jun 25, 2021
Accepted:	Aug 6, 2021
Published print:	Aug 11, 2021

Web of science:	WOS:000699677100001
Scopus:	2-s2.0-85113774726
OpenAlex:	W3188213642

DB	Citing
Scopus	7
Web of science	7
OpenAlex	9