Please use this identifier to cite or link to this item: http://elar.usfeu.ru/handle/123456789/8935
Title: Acid-Base Properties of Nanoconfined Volumes of Anodic Aluminum Oxide Pores by EPR of pH-Sensitive Spin Probes
Authors: Kovaleva, E. G.
Molochnikov, L. S.
Venkatesan, U.
Marek, A.
Stepanova, D. P.
Kozhikhova, K. V.
Mironov, M. A.
Smirnov, A. I.
Issue Date: 2016
Publisher: American Chemical Society
Citation: Kovaleva, E. G. Acid-Base Properties of Nanoconfined Volumes of Anodic Aluminum Oxide Pores by EPR of pH-Sensitive Spin Probes / E. G. Kovaleva, L. S. Molochnikov, U. Venkatesan [et al.] // Journal of Physical Chemistry C. – 2016. – Vol. 120. – Iss. 5. – P. 2703-2711.
Abstract: Anodic aluminum oxide (AAO) ceramic membranes with macroscopically aligned and hexagonally packed nanopore architecture are attractive substrates for forming nanotubular lipid bilayers as well as sorption and catalytic media because of a tunable pore diameter, robust pore structure, and low fabrication cost. Here we employed continuous wave X-band (9 GHz) EPR of two pH-sensitive nitroxide radicals to assess acid-base properties AAO membranes prepared from low-cost commercial grade aluminum and compared those with commercial Anodisc membranes from Whatman, Ltd. The AAO membranes with pore diameters ≥58 ± 8 nm showed essentially the same pH inside the pores, pHint, as the bulk external solution, pHext, over the 0.1-3.0 M range of ionic strength. However, the apparent pKa of nitroxide probes inside the pores deviated from the bulk values for the nanopores of smaller diameters of ca. 29 and 18 nm. Specifically, for the latter nanopores the values of pHint were found to be 0.5-0.8 pH unit lower than the bulk pHext. An increase in acidity of the bulk solution led to a steady decrease of the negative charge on inner surface of the 38 nm nanopores and its recharge from a negative to a positive value at pH 4.7 ± 0.1, corresponding to the point of zero charge (pzc). Overall, the EPR titration method described here could assist in characterization of meso- and nanoporous membranes for catalytic and sorption applications as well as act a support medium for self-assembled biomembrane systems. © 2016 American Chemical Society.
Keywords: ALUMINUM
ANODIC OXIDATION
CERAMIC MEMBRANES
ELECTRON SPIN RESONANCE SPECTROSCOPY
IONIC STRENGTH
LIPID BILAYERS
MEMBRANES
MESOPOROUS MATERIALS
OXIDES
PH SENSORS
PROBES
SUBSTRATES
TITRATION
ACID-BASE PROPERTY
ANODIC ALUMINUM OXIDE
COMMERCIAL GRADE
EXTERNAL SOLUTIONS
FABRICATION COST
NANOPOROUS MEMBRANE
NITROXIDE RADICALS
POINT OF ZERO CHARGE
NANOPORES
URI: http://elar.usfeu.ru/handle/123456789/8935
DOI: 10.1021/acs.jpcc.5b10241
SCOPUS: 2-s2.0-84958092831
WoS: WOS:000370210400025
RSCI: 26831122
Appears in Collections:Научные публикации, проиндексированные в SCOPUS и WoS CC

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