Wong, Alan, Howes, A. P., Parkinson, B. G., Anupõld, Tiit, Samoson, Ago, Holland, Diane and Dupree, Ray (2009) High-resolution O-17 double-rotation NMR characterization of ring and non-ring oxygen in vitreous B2O3. Physical Chemistry Chemical Physics, Vol.11 (No.32). pp. 7061-7068. doi:10.1039/b906501f

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Abstract

The application of double rotation (DOR) NMR to crystalline materials (both inorganic and organic) has made tremendous strides in providing site-specific information about materials in recent years. However O-17 DOR has yet to demonstrate its potential in disordered materials such as glasses. In the present study, we have successfully recorded high resolution O-17 DOR spectra of vitreous B2O3 (v-B2O3), a highly effective glass-forming oxide of considerable technological importance. Two distinct oxygen sites are resolved and a complete set of O-17 NMR parameters were determined from the DOR spectra. These were assigned to oxygen atoms in the planar boroxol ring [B3O6] and in the non-boroxol [BO3] groups which share oxygen with the ring boron atoms. This assignment was based on the similarity of all of their O-17 parameters with those found by DFT calculation for caesium enneaborate, Cs2O center dot 9B(2)O(3), which has two boroxol rings in its structure. The boroxol ring oxygens have a more positive chemical shift, a larger shift anisotropy and a smaller electric field gradient than non ring oxygens (O-R: delta(iso) = 100 +/- 1 ppm, span = 180 +/- 20 ppm, skew = -0.4 +/- 0.1, P-q = 5.0 +/- 0.2 MHz; O-NR: delta(iso) = 86 +/- 1 ppm, span = 100 +/- 20 ppm, skew = 0.1 +/- 0.1, P-q = 5.7 +/- 0.2 MHz). The relative proportions of the two sites in v-B2O3 are similar to 1 : 1, as expected if all three boron atoms in the boroxol ring are each connected to one oxygen in a linking [BO3] group and there are very few [BO3]-[BO3] linkages. We see no evidence for a third oxygen site such as has been reported in an earlier study of v-B2O3. This work demonstrates the potential of O-17 DOR to provide site-specific information in disordered materials.

Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry Q Science > QC Physics
Divisions:	Faculty of Science > Physics
Journal or Publication Title:	Physical Chemistry Chemical Physics
Publisher:	Royal Society of Chemistry
ISSN:	1463-9076
Official Date:	2009
Dates:	Date Event 2009 Published
Volume:	Vol.11
Number:	No.32
Number of Pages:	8
Page Range:	pp. 7061-7068
DOI:	10.1039/b906501f
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Funder:	Engineering and Physical Sciences Research Council (EPSRC), Biotechnology and Biological Sciences Research Council (Great Britain) (BBSRC), University of Warwick, Estonian Science Foundation

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