Diffusion of dissolved ions from wet silica sol–gel monoliths: Implications for biological encapsulation
| Autor: | Roger L. Ely, Benjamin A. Glassy, Alexandre F. T. Yokochi, Catherine J. Page, David J. Dickson, Bethany Lassetter |
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| Rok vydání: | 2013 |
| Předmět: |
Aqueous solution
Chromatography Siloxanes Syneresis Hydrated silica Silica gel chemistry.chemical_element Surfaces and Interfaces General Medicine Silanes Silicon Dioxide Fick's laws of diffusion Diffusion Nickel chemistry.chemical_compound Colloid and Surface Chemistry chemistry Chemical engineering Methyl orange Physical and Theoretical Chemistry Gels Biotechnology Sol-gel |
| Zdroj: | Colloids and Surfaces B: Biointerfaces. 102:611-619 |
| ISSN: | 0927-7765 |
| Popis: | Divalent nickel (Ni 2+ ), Cu(II)EDTA, methyl orange, and dichromate were used to investigate diffusion from hydrated silica sol–gel monoliths. The objective was to examine diffusion of compounds on a size regime relevant to supporting biological components encapsulated within silica gel prepared in a biologically compatible process space with no post-gelation treatments. With an initial sample set, gels prepared from tetraethoxysilane were explored in a factorial design with Ni 2+ as the tracer, varying water content during hydrolysis, acid catalyst present during hydrolysis, and the final concentration of silica. A second sample set explored diffusion of all four tracers in gels prepared with aqueous silica precursors and a variety of organically modified siloxanes. Excluding six outliers which displayed significant syneresis, the mean diffusion constant ( D gel ) across the entire process space of sample set 1 was 2.42 × 10 −10 m 2 s −1 ; approximately 24% of the diffusion coefficient of Ni 2+ in unconfined aqueous solution. In sample set 2, the tracer size and not gel hydrophobicity was the primary determinant of changes in diffusion rates. A strong linear inverse correlation was found between tracer size and the magnitude of D gel . Based on correlation with the tracers used in this investigation, the characteristic 1-h diffusion distance for carbonate species relevant to supporting active phototrophic organisms was approximately 1.5 mm. These results support the notion that silica sol–gel formulations may be optimized for a given biological entity of interest with manageable impact to the diffusion of small ions and molecules. |
| Databáze: | OpenAIRE |
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