Electrostatic interplay: The interaction triangle of polyamines, silicic acid, and phosphate studied through turbidity measurements, silicomolybdic acid test, and ²⁹Si NMR spectroscopy

Abstract

SummaryThe discovery of long-chain polyamines as biomolecules that are tightly associated to biosilica in diatom cell walls has inspired numerous in vitro studies aiming to characterize polyamine–silica interactions. The determination of these interactions at the molecular level is of fundamental interest on one hand for the understanding of cell wall biogenesis in diatoms and on the other hand for designing bioinspired materials synthesis approaches. The present contribution deals with the influence of amines and polyamines upon the initial self-assembly processes taking place during polyamine-mediated silica formation in solution. The influence of phosphate upon these processes is studied. For this purpose, sodium metasilicate solutions containing additives such as polyallylamine, allylamine and others in the presence/absence of phosphate were investigated. The analyses are based mainly on turbidity measurements yielding information about the early aggregation steps which finally give rise to the formation and precipitation of silica.

Interactions of Long-Chain Polyamines with Silica Studied by Molecular Dynamics Simulations and Solid-State NMR Spectroscopy

“…Figure 2 shows the results of 13 C{ 29 Si} and 15 N{ 29 Si} REDOR experiments on the silica/LCPA nanocomposites (xerogels) containing the selectively 13 C-and 15 N-labeled LCPAs (cf. Figure 1).…”

“…25 Recent experiments focused on cooperative effects between phosphopeptides and LCPA. 28,29 A direct interaction of LCPAs with the silica phase was already observed by 13 C{ 29 Si} rotational echo double resonance (REDOR) NMR spectroscopy for the diatom species Thalassiosira pseudonana. 30 Generally, solid-state NMR spectroscopy is well suited to characterize interface interactions and to determine the spatial organization of molecules with respect to the surface.…”

“…Moreover, these defined LCPAs (cf. Figure 1) could be selectively isotope-labeled with 13 C and 15 N at different positions.…”

“…Here, we exploit a combined approach involving classical molecular dynamics (MD) simulations and 13 C{ 29 Si} and 15 N{ 29 Si} REDOR NMR spectroscopy to describe polyamine− silica interactions. The NMR-derived structural features can be used to validate simulation results.…”

Mimicking Biosintering: The Identification of Highly Condensed Surfaces in Bioinspired Silica Materials

“…In order to take advantage of these interactions, the use of organic additives or templates has been studied extensively for several fully artificial or biologically inspired templated material systems. Taking the case of amorphous silica (a technologically important material with US$4 billion per annum market), surfactant molecules have been widely investigated to direct long-range, ordered porosity in the materials. , Separately, combining the mild and sustainable synthesis conditions of natural silica with the scalability of industrial silica, “bioinspired silica” (BIS) materials have been synthesized using a variety of small molecules or polymers with biomolecule-like moieties to direct their growth. − …”