engleski

Multiscale study of the cationic surfactants influence on amorphous calcium phosphate precipitation

The influence of monomeric and micellar concentrations of the cationic monomeric, dodecyltrimethylammonium bromide (DTAB) and corresponding dimeric, bis(N, N-dimethyl-N-dodecyl)ethylene-1, 2-diammonium dibromide (12-2-12), surfactants on the formation and transformation of amorphous calcium phosphate (ACP) was investigated. Such a choice of surfactants enabled assessing the influence of different surfactant molecular structure and aggregation states on calcium phosphates (CaPs) precipitation while keeping additive chemistry the same. Combination of microscopy (AFM and TEM) and light scattering techniques (size and zeta potential measurements), enabled for the first time, to follow simultaneously the effect that additive exert at different length scales during CaPs formation in the solution - from Posner’s clusters and ACP particles to crystalline phase. In control system after 10 min reaction time Posner’s clusters, spherical particles and their chain-like aggregates were formed. After 24 h crystalline mixture of octacalcium phosphate (OCP) and calcium deficient apatite was formed. In the presence of surfactants, except DTAB monomers, ACP transformation proceeded via formation of an intermediate phase. OCP crystals grew larger in the presence of surfactant monomers while their growth was completely suppressed by 12-2-12 micelles. Observed effects were ascribed to the difference in molecular structure of DTAB and 12-2-12 monomers and consequently difference in their micellar structure and charge distribution at the micelle/solution interface. Obtained results may have implications for understanding general mechanism of inorganic-organic interactions underlying biomineralization processes, as well as for materials science.

amorphous calcium phosphate ; AFM ; DLS ; TEM ; surfactants ; prenucleation cluster

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