Water dynamics in a mesoporous bioactive glass studied by NMR relaxometry

Abstract : Water confined in a new class of mesoporous bioactive glasses (MBGs) has been studied by NMR relaxometry technique. Two CaO-SiO2-P2O5 materials have been compared: both have the same chemical composition but they have been made with different methods – standard or microfluidic techniques -, inducing different textural properties (surface areas, porous volume, mesoporous arrangement). NMR is known for being particularly well suited for studying fluids embedded in mesostructured porous materials because, in addition of being non-invasive and relatively fast, it allows the characterization of molecules dynamics. In this study, we used NMR relaxometry, which consists in measuring spin relaxation times as a function of the measurement frequency (or equivalently of the static magnetic field B0), in order to determine the dynamics of water molecules embedded in the MBGs. The low field domain (10kHz-10MHz proton Larmor frequency) was investigated with measurements done with a fast field-cycling relaxometer, and the socalled dispersion curves (longitudinal relaxation rate as a function of the measurement frequency) were analyzed in order to have additional insights on the motion of confined water. The frequency dependence of the proton relaxation rate in MBGs was first studied by comparing the relaxation dispersion detected in HOD (residual proton of heavy water) with that in H2O, the proton low-frequency relaxation is thus shown to be mainly due to intramolecular dipolar interactions. Secondly, dispersion curves were recorded as a function of the filling degree and analyzed in the frame of the two-phase fast exchange model: tiny differences in the dynamical behavior of the water inside the two bioglasses (exchange timescale, hydration layers) could be evidenced.
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Poster communications
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https://hal.univ-lorraine.fr/hal-02271927
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Submitted on : Tuesday, August 27, 2019 - 12:44:33 PM
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Abdelkarim Rjiba, Nizar Bchellaoui, Rachida Dorbez-Sridi, El-Eulmi Bendeif, Axel Gansmuller, et al.. Water dynamics in a mesoporous bioactive glass studied by NMR relaxometry. Euromar 2018, Jul 2018, Nantes, France. ⟨hal-02271927⟩

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