Skip to Content
Merck
  • Local environments of boron heteroatoms in non-crystalline layered borosilicates.

Local environments of boron heteroatoms in non-crystalline layered borosilicates.

Physical chemistry chemical physics : PCCP (2015-08-01)
Mounesha N Garaga, Ming-Feng Hsieh, Zalfa Nour, Michael Deschamps, Dominique Massiot, Bradley F Chmelka, Sylvian Cadars
ABSTRACT

Boron heteroatom distributions are shown to be significantly different in two closely related layered borosilicates synthesized with subtly different alkylammonium surfactant species. The complicated order and disorder near framework boron sites in both borosilicates were characterized at the molecular level by using a combination of multi-dimensional solid-state nuclear magnetic resonance (NMR) spectroscopy techniques and first-principles calculations. Specifically, two-dimensional (2D) solid-state J-mediated (through-bond) (11)B{(29)Si} NMR analyses provide direct and local information on framework boron sites that are covalently bonded to silicon sites through bridging oxygen atoms. The resolution and identification of correlated signals from distinct (11)B-O-(29)Si site pairs reveal distinct distributions of boron heteroatoms in layered borosilicate frameworks synthesized with the different C16H33N(+)Me3 and C16H33N(+)Me2Et structure-directing surfactant species. The analyses establish that boron atoms are distributed non-selectively among different types of silicon sites in the layered C16H33N(+)Me3-directed borosilicate framework, whereas boron atoms are preferentially incorporated into incompletely condensed Q(3)-type sites in the C16H33N(+)Me2Et-directed borosilicate material. Interestingly, framework boron species appear to induce framework condensation of their next-nearest-neighbor silicon sites in the C16H33N(+)Me3-directed borosilicate. By comparison, the incorporation of boron atoms is found to preserve the topology of the C16H33N(+)Me2Et-directed borosilicate frameworks. The differences in boron site distributions and local boron-induced structural transformations for the two surfactant-directed borosilicates appear to be due to different extents of cross-linking of the siliceous frameworks. The molecular-level insights are supported by density functional theory (DFT) calculations, which show the distinct influences of boron atoms on the C16H33N(+)Me3- and C16H33N(+)Me2Et-directed borosilicate frameworks, consistent with the experimental observations.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Nitric-14N acid solution, ~10 N in H2O, 99.99 atom % 14N
Sigma-Aldrich
Tetramethylammonium hydroxide solution, 10 wt. % in H2O
Sigma-Aldrich
Tetramethylammonium hydroxide solution, 25 wt. % in methanol
Sigma-Aldrich
Boric acid-11B, ≥99 atom % 11B
Sigma-Aldrich
Tetramethylammonium hydroxide solution, ACS reagent
Sigma-Aldrich
Ethylhexadecyldimethylammonium bromide, ≥98% (non-aqueous titration)
Sigma-Aldrich
Tetramethylammonium hydroxide solution, 25 wt. % in H2O
Sigma-Aldrich
Nitric acid, ACS reagent, ≥90.0%
Sigma-Aldrich
Nitric acid, SAJ first grade, 65.0-66.0%, density: 1.40
Sigma-Aldrich
Nitric acid, 1 M
Sigma-Aldrich
Nitric acid, 0.1 M
Sigma-Aldrich
Boric acid, SAJ first grade, ≥99.5%
Sigma-Aldrich
Boric acid, 99.97% trace metals basis
Sigma-Aldrich
Nitric acid, 70%, purified by redistillation, ≥99.999% trace metals basis
Sigma-Aldrich
Hexadecyltrimethylammonium bromide, BioUltra, for molecular biology, ≥99.0% (AT)
Sigma-Aldrich
Boric acid, 99.999% trace metals basis
Sigma-Aldrich
Hexadecyltrimethylammonium bromide, ≥98%
Sigma-Aldrich
Hexadecyltrimethylammonium bromide, BioXtra, ≥99%
Sigma-Aldrich
Hexadecyltrimethylammonium bromide, for molecular biology, ≥99%
Sigma-Aldrich
Boric acid, BioReagent, for molecular biology, suitable for cell culture, suitable for plant cell culture, ≥99.5%
Sigma-Aldrich
Boric acid, suitable for electrophoresis, ≥99.5%
Sigma-Aldrich
Boric acid, tablet, 1 g boric acid per tablet
Sigma-Aldrich
Boric acid, BioXtra, ≥99.5%
Sigma-Aldrich
Boric acid, BioUltra, for molecular biology, ≥99.5% (T)
SAFC
Hexadecyltrimethylammonium bromide, USP/NF