Probing sol-gel matrices microenvironments by PGSE HR-MAS NMR
Copyright © 2016 John Wiley & Sons, Ltd.
| Veröffentlicht in: | Magnetic resonance in chemistry : MRC. - 1985. - 55(2017), 5 vom: 18. Mai, Seite 452-463 |
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| Format: | Online-Aufsatz |
| Sprache: | English |
| Veröffentlicht: |
2017
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| Zugriff auf das übergeordnete Werk: | Magnetic resonance in chemistry : MRC |
| Schlagworte: | Journal Article high-resolution magic angle spinning nuclear magnetic resonance pulsed-field gradient sol-gel matrices Acetonitriles Hexanes Pentanols Silanes Solvents mehr... |
| Zusammenfassung: | Copyright © 2016 John Wiley & Sons, Ltd. We applied Pulsed Gradient Spin Echo diffusion with high-resolution magic angle spinning NMR to study sol-gel matrices used to encapsulate enzymes for biocatalysis (TMOS/MTMS and TMOS/BTMS) to gain insight into the local chemical microenvironment. Transport properties of solvents with different polarities (1-pentanol, acetonitrile and n-hexane) were studied through their apparent self-diffusion coefficients. The spin echo attenuation of the solvents shows two distinct diffusion domains, one with fast diffusion (Dfast ) associated with interparticle diffusion and another with slow diffusion (Dslow ) corresponding to the displacement inside the pores within the sol-gel particles. The analysis of the root mean square displacements at different diffusion times showed that the Dfast domain has a free diffusion regime in both matrices (the root mean square displacement is linearly dependent of the diffusion time), while the Dslow domain shows a different regime that depends on the matrix. We investigated the exchange regime between the two diffusion sites. In both matrices, n-hexane was in intermediate exchange between diffusion domains, while the polar solvents were in slow exchange in TMOS/BTMS and in intermediate exchange in TMOS/MTMS. Data were fitted for TMOS/BTMS with the Kärger model, and the physical parameters were obtained. The results add to the evidence that the pores are a hydrophobic environment but that the presence of some free hydrophilic groups inside the pore, as observed in the TMOS/BTMS, has a key role in slowing down the exchange of polar solvents and that this is relevant to explain previously reported enzyme activity in these materials. Copyright © 2016 John Wiley & Sons, Ltd |
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| Beschreibung: | Date Completed 11.04.2018 Date Revised 11.04.2018 published: Print-Electronic Citation Status MEDLINE |
| ISSN: | 1097-458X |
| DOI: | 10.1002/mrc.4427 |