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A Combined Solid-State NMR, Dielectric Spectroscopy and Calorimetric Study of Water in Lowly Hydrated MCM-41 Samples

Brodrecht, Martin ; Klotz, Edda ; Lederle, Christina ; Breitzke, Hergen ; Stühn, Bernd ; Vogel, Michael ; Buntkowsky, Gerd (2021):
A Combined Solid-State NMR, Dielectric Spectroscopy and Calorimetric Study of Water in Lowly Hydrated MCM-41 Samples. (Publisher's Version)
In: Zeitschrift für Physikalische Chemie, 232 (7-8), pp. 1003-1015. De Gruyter, ISSN 0942-9352, e-ISSN 2196-7156,
DOI: 10.26083/tuprints-00019681,
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Item Type: Article
Origin: Secondary publication service
Status: Publisher's Version
Title: A Combined Solid-State NMR, Dielectric Spectroscopy and Calorimetric Study of Water in Lowly Hydrated MCM-41 Samples
Language: English
Abstract:

The processes of drying mesoporous silica materials and their refilling with water have been examined by magic-angle spinning (MAS) solid-state NMR, broadband dielectric spectroscopy (BDS), and differential scanning calorimetry (DSC). It is shown that different drying protocols strongly influence the amount and types of hydroxy-species inside the pores. It is found that a very good vacuum (≈10−6 bar) is necessary to remove all H₂O molecules from the silica matrices in order to accurately refill them with very low amounts of water such as e.g. a mono- or submonolayer coverage of the surface. Time-dependent ¹H-NMR-spectra recorded after loading the samples indicate a very specific course of water first existing in a bulk-like form inside the pores and then distributing itself through the pores by hydrogen bonding to surface silanol groups. After assuring accurate sample loading, we were able to investigate lowly hydrated samples of water confined in MCM-41 via DCS and BDS at temperatures below the freezing point of free bulk-water (0°C) and find two non-crystallizing water species with Arrhenius behavior and activation energies of 0.53 eV (51.1 kJ/mol).

Journal or Publication Title: Zeitschrift für Physikalische Chemie
Journal volume: 232
Number: 7-8
Publisher: De Gruyter
Classification DDC: 500 Naturwissenschaften und Mathematik > 540 Chemie
Divisions: 07 Department of Chemistry > Physical Chemistry
Date Deposited: 01 Oct 2021 11:22
Last Modified: 01 Oct 2021 11:22
DOI: 10.26083/tuprints-00019681
Corresponding Links:
URN: urn:nbn:de:tuda-tuprints-196818
Additional Information:

Keywords: broadband dielectric spectroscopy; confinement; solid-state NMR; water; wetting

URI: https://tuprints.ulb.tu-darmstadt.de/id/eprint/19681
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