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Differentiating and characterizing geminal silanols in silicas by 29Si NMR spectroscopy.

Authors
Murray-DK
Source
J Colloid and Interface Sci 2010 Dec; 352(1):163-170
NIOSHTIC No.
20037710
Abstract
Single and geminal hydroxyl species in silicas have been characterized using solid-state (29)Si NMR spectroscopy. Differentiating hydroxyl types is important in understanding their roles in chemical toxicity mechanisms for inhaled crystalline silicas responsible for silicosis. (1)H-(29)Si cross polarization NMR spectroscopy has been employed to obtain (29)Si NMR chemical shift data and signal accrual and relaxation characteristics. Spectral deconvolution is used to examine relative single and geminal hydroxyl resonance areas for a series of representative silicas and silica gels. Silicon-containing materials examined include 1878a quartz, and 1879a cristobalite from the National Institute for Science and Technology, kaolin, and several widely used respirable silicas and silica gels. Geminal hydroxyls were observed in every case, with relative resonance areas accounting for 21-65% of total hydroxyl signals. Factors affecting relative areas measured as a function of contact time, relaxation, and surface area are discussed. Subsequent (29)Si and (31)P NMR studies of a silica coated with various sodium hydrogen phosphates show preferential single silanol-phosphate interaction for basic phosphates, and oligomerization products for acidic phosphates. Geminal hydroxyl resonance areas displayed significant error (4-17%) for low surface area silicas, limiting this method to studies exhibiting major changes in chemical or spectroscopic properties.
Keywords
Analytical-processes; Silica-dusts; Quartz-dust; Respirable-dust; Author Keywords: Silica; Silanols; NMR spectroscopy
Contact
David K. Murray, National Institute for Occupational Health and Safety, 1095 Willowdale Road, M/S 3030, Morgantown, WV 26505, United States
CODEN
JCISA5
CAS No.
14808-60-7; 14464-46-1; 1332-58-7
Publication Date
20101201
Document Type
Journal Article
Email Address
DMurray@cdc.gov
Fiscal Year
2011
NTIS Accession No.
NTIS Price
Issue of Publication
1
ISSN
0021-9797
NIOSH Division
HELD
Source Name
Journal of Colloid and Interface Science
State
WV
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