Revisiting structure of silica gels from water glass: An 1H and 29Si MAS and CP-MAS NMR study

Jie Li, Satoshi Hayakawa, Yuki Shirosaki, Akiyoshi Osaka

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The silica gels, derived from water glass solution with pH adjusted at 3.0 and 9.9, were revisited to investigate their constitution, although water glass has been studied for last tens of decades on gelation. Solid-state nuclear magnetic resonance spectroscopy was applied to the nuclei 1H and 29Si, by the use of magic angle spinning (MAS), 1H → 29Si CP-MAS (CP: cross-polarization), and modern techniques such as 2D HETCOR (two dimensional heteronuclear correlation), and variable-contact time CP techniques. Gelation time (tgel) showed U-letter shape dependence on pH. All gels consisted of Qn groups (n: 2, 3, and 4), where Qn stands for a silicate unite [(O1/2)nSi (-O-)4-n] (n: 0-4). The analysis of the 1H → 29Si CP kinetics and 1H-29Si HETCOR spectra elucidated the presence of four kinds of 1H nuclei, i.e., those giving a peak at 6.9 ppm in chemical shift δ: 1H-OSi hydrogen bonded to H2O molecules; one at 4.3 ppm: 1H of adsorbed water molecules, hydrogen-bonded to the silanol groups; one at 1.7 ppm: 1H-OSi confined in the gel lattice, including that forming aggregations like Si-OH/NaO-Si; and one at 4.2 ppm: 1H of water molecules on the outermost hydration layer.

Original languageEnglish
Pages (from-to)135-142
Number of pages8
JournalJournal of Sol-Gel Science and Technology
Volume65
Issue number2
DOIs
Publication statusPublished - Feb 2013

Fingerprint

Magic angle spinning
Silica Gel
Silica gel
silica gel
metal spinning
Nuclear magnetic resonance
Glass
nuclear magnetic resonance
Water
glass
gelation
Gelation
water
Molecules
Hydrogen
Gels
gels
molecules
Silicates
nuclei

Keywords

  • 2-D spectrum
  • Gelation
  • MAS NMR: HETCORE
  • Relaxation time
  • Silicate network
  • Structure model
  • Water glass

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Biomaterials
  • Ceramics and Composites
  • Electronic, Optical and Magnetic Materials
  • Materials Chemistry

Cite this

Revisiting structure of silica gels from water glass : An 1H and 29Si MAS and CP-MAS NMR study. / Li, Jie; Hayakawa, Satoshi; Shirosaki, Yuki; Osaka, Akiyoshi.

In: Journal of Sol-Gel Science and Technology, Vol. 65, No. 2, 02.2013, p. 135-142.

Research output: Contribution to journalArticle

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