Peptizing Mechanism at the Molecular Level of Laponite Nanoclay Gels

Abstract

In the presence of additives such as etidronic acid (1-hydroxyethane-1,1-diphosphonic acid, HEDP), a process of peptizing of Laponite clay gels takes place. The peptizing process at the molecular level was directly revealed by P andH high-resolution magic-angle sample spinning (HRMAS) NMR spectroscopy. Two NMR spectral components were detected and assigned to free etidronic acid and bound to the Laponite disk edges. Furthermore, with increase of temperature the ratio of bound-to-free etidronic acid increases. This thermal activation process could be explained by the increase in electrical polarization of the hydroxyl group at the edges and by the exfoliation of the tactoids that leads to more access to the additive molecules to the electrical charges of platelet edges. P HRNMR spectroscopy on sodium fluorohectorite with an aspect ratio of ∼750 shows a reduction of the bound etidronic acid molecules. Transmission electron microscopy (TEM), field-emission scanning microscopy (FESEM), UV-vis spectrophotometry, dynamic light scattering (DLS), and zeta potential results support the proposed peptizing mechanisms.

Collagen-Laponite Nanoclay Hydrogels for Tumor Spheroid Growth

“…Figure shows the Laponite dispersion. The stock dilution in water at 1% w:v (Figure A) showed the presence of platelets of grouped clays, as reported before . The results of directly mixing the stock solution with collagen involved clay and collagen fiber aggregation.…”

“…The stock dilution in water at 1% w:v ( Figure 2 A) showed the presence of platelets of grouped clays, as reported before. 31 The results of directly mixing the stock solution with collagen involved clay and collagen fiber aggregation. Thus, the stock solution was subsequently diluted in culture medium at 0.1% w:v as commented in subsection 2.2 .…”

Highly Stable Phosphonate‐Based MOFs with Engineered Bandgaps for Efficient Photocatalytic Hydrogen Production

“…Remarkably, compared to pure TiO 2 (Figures S5 and S6, Supporting Information), the Ti 2p core level for TiPNW shows a negative shift, which can be attributed to the electron‐donative effect of the hydroxyl group. [ 17,20,36,37 ] This is an evidence for the influence of organic substituents on the electronic structure of the metal centers. The aforementioned results suggest that no phase separation occurred during the synthesis, and the organophosphonic units can efficiently cross‐link Ti‐oxo clusters to generate an extensive metal–organic framework (Figure S7, Supporting Information).…”

“…[ 35 ] In the 1 H MAS‐NMR spectrum (Figure 2d), the two sharp signals at 1.5 and 4.2 ppm correspond to the hydrogen in COH and terminal CH 3 , respectively. [ 36 ] Due to 49 Ti's low natural abundance, small gyromagnetic ratios, and low intrinsic detection sensitivity, double frequency sweep (DFS) enhanced 49 Ti MAS‐NMR technique was conducted to produce a higher signal‐to‐noise instead of conventional MAS‐NMR. The DFS‐enhanced MAS‐NMR spectrum of TiPNW shows the absence of anatase TiO 2 signal and the inherent feature of six‐coordinated Ti atoms (Figure S4, Supporting Information).…”

Collagen-Laponite Nanoclay Hydrogels for Tumor Spheroid Growth

“…The stock dilution in water at 1% w:v (Figure 2A) showed the presence of platelets of grouped clays, as reported before. 31 The results of directly mixing the stock solution with collagen involved clay and collagen fiber aggregation. Thus, the stock solution was subsequently diluted in culture medium at 0.1% w:v as commented in subsection 2.2.…”