Controlled calcite nucleation on polarized calcite single crystal substrates in the presence of polyacrylic acid

Calcite Crystallization on Polarized Single Calcite Crystal Substrates in the Presence of Poly-Lysine

“…We have discussed, in our previous papers, , a theory regarding nucleation in the presence of an electric field, based on classical nucleation theory and electromagnetic theory and have indicated that the activation energy for nucleation, Δ G *, decreases with an electric field generated by the polarized substrate and the supersaturation of the reactant solution. In addition, discussion on the effect of the electrostatic force density, given by ρ E , where ρ is the charge density of the ion (including its sign, either positive or negative) and E is the electric field due to the polarized substrate, suggests that the surface electric field at the N-surface induced a high concentration of Ca 2+ ions around this surface, while the P-surface exhibited a low concentration; the electrostatic interactions between the CO 3 2– ions and the N- and P-surfaces were neglected because of the relatively low charge density of the CO 3 2– ions.…”

“…The electrical polarization and an experimental system adapted to slow diffusion were the same as those used in previous studies. , A brief overview of the experimental procedure is as follows. The polarization was performed under a DC electric field of 5 kV·cm –1 at 400 °C for 1 h in air.…”

“…CaCO 3 precipitation experiments were performed in the absence of PLys using a 5 mM calcium chloride solution (10 mL) in the presence of differing amounts of PLys (0.5, 1.0, 2.0, and 3.0 mg/10 mL) through slow diffusion of carbon dioxide and ammonia into calcium chloride solutions, based on the gas diffusion method by thermal decomposition of ammonium carbonate. − , PLys was added to the calcium chloride solution before vapor diffusion. Initially, the pH values of the calcium chloride solutions with and without PLys were adjusted to ca.…”

“…Yamashita et al made the discovery that hydroxyapatite (HAp) material can be polarized by applying an external electric field at elevated temperature, and the resulting polarized state can be maintained at room temperature, namely, an electret, and indicated that the growth of HAp was accelerated at the negatively charged surface, but not at the positively charged surface. − We reported that the surface electric fields due to HAp, calcite, and yttria-stabilized zirconia electrets regulated not only the nucleation of the precipitate and but also the subsequent growth on calcite crystallization in the presence of poly acrylic acid (PAA) and poly aspartic acid (PAsp). − We also suggested that the cooperation of PAA or PAsp and the local electric field due to the electrets promoted the formation of calcite thin films with c -axis orientation and acted remarkably on the negatively charged surfaces of these ceramics. On the crystallization of CaCO 3 on polarized calcite single crystal substrates, the presence of PAA favored the formation of calcite thin films that were composed of a large number of prismatic calcite crystals with c -axis orientation, and the presence of PAsp led to the formation of CaCO 3 films with a multiple phase structure with thin-film-like and hemispherical forms which consisted of calcite as the main polymorphic form and aragonite, respectively. − The obtained results indicated that the negatively charged poly amino acids, which contain carboxyl groups that can interact with calcium ions in solution, played an important role in CaCO 3 crystallization. However, the effects of positively charged poly amino acids on CaCO 3 crystallization have not fully been understood.…”

Controlled in Vivo Nacre Formation in Flat Pearls with Hydroxyapatite Bioceramic Nuclei

“…As reported in our previous paper, the surface electric-field strength generated by the polarized substrate (assumed to be a disc) was calculated according to electrostatics. 34 It was indicated that a local electric field uniformly exists in the polarized substrate vicinity. Hence, to study the influence of the electric field due to the polarized HAp pellets on nacreous aragonite formation, we measured the thickness of aragonite tablets in the range of about 20 μm from the interface between the prismatic layers and the nacreous layer.…”