A Carbonate Controlled-Addition Method for Amorphous Calcium Carbonate Spheres Stabilized by Poly(acrylic acid)s

Abstract

Stable amorphous calcium carbonate (ACC) composite particle with a size-controlled monodispersed sphere was obtained by a new simple carbonate controlled-addition method by using poly(acrylic acid) (PAA) (Mw = 5000), in which an aqueous ammonium carbonate solution was added into an aqueous solution of PAA and CaCl2 with a different time period. The obtained ACC composite products consist of about 50 wt % of ACC, 30 wt % of PAA, and H2O. Average particle sizes of the ACC spheres increased from (1.8 +/- 0.4) x 102 to (5.5 +/- 1.2) x 102 nm with an increase of the complexation time of the PAA-CaCl2 solution from 3 min to 24 h, respectively. The ACC formed from the complexation time for 3 min was stable for 10 days with gentle stirring as well as 3 months under a quiescent condition in the aqueous solution. Moreover, the ACC was also stable at 400 degrees C. Stability of the amorphous phase decreased with an increase of the complexation time of the PAA-CaCl2 solution. No ACC was obtained when the lower molar mass PAAs (Mw = 1200 and 2100) were used. In the higher molar mass case (Mw = 25 000), a mixture of the amorphous phase and vaterite and calcite crystalline product was produced. The present results demonstrate that the interaction and the reaction kinetics of the PAA-Ca2+-H2O complex play an important role in the mineralization of CaCO3.

Tailoring the shape of amorphous nanomaterials: recent developments and applications

“…Spherical structure is also favorable in terms of surface energy. Nanospheres are the most reported shape of amorphous materials in the last decade (see Table 1), and they can be composed of calcium carbonate (CaCO 3 ) [43][44][45][46][47], silicon (Si) [48][49][50][51][52], metals or their compounds [53][54][55][56][57][58][59][60][61]. CaCO 3 is abundant in the natural world, and a typical model system used to mimic the mineralization process of biominerals [43].…”

“…This rapid process makes it difficult to study the properties of ACC and the mechanism of the mineralization process. Some specific additives, such as organic macromolecules and magnesium ions, have been used to stabilize ACC nanospheres by forming complexes with metal ions [44,46,47]. Huang et al [47] reported a poly(acrylic acid) (PAA)-assisted method to synthesize highly stable, size-controlled monodisperse ACC nanospheres.…”

“…Some specific additives, such as organic macromolecules and magnesium ions, have been used to stabilize ACC nanospheres by forming complexes with metal ions [44,46,47]. Huang et al [47] reported a poly(acrylic acid) (PAA)-assisted method to synthesize highly stable, size-controlled monodisperse ACC nanospheres. They suggested that the amorphous state was induced and stabilized more with higher atomic structure disorder using a shorter complexation time as well as PAA with an medium molar mass rather than PAA with lower or higher molar mass.…”

“…Because of their complex internal structure, the growth of amorphous nanomaterial is usually ruleless, resulting in irregular particles using solution approaches or thin films using deposition techniques as their conventional shape. Over the last decade, inorganic amorphous nanomaterials with a variety of novel shapes, with notable examples including spheres, wires, tubes, fibers, cubes, octahedra, polyhedra, flower-like spheres and arrays, which are summarized in spheres (hollow) CaCO 3 gas-diffusion solution method [43] spheres CaCO 3 solution method [44] spheres CaCO 3 solution method [45] spheres CaCO 3 solution method [46] spheres CaCO 3 solution method [47] spheres Si thermal decomposition [48] spheres Si solution method [49] spheres Si/Ti solution method [50] spheres Si:H thermal decomposition [51] spheres Si:H thermal decomposition [52] spheres Se solution method [53] spheres TiO 2 solution method [54][55][56] spheres (hollow) PbO-TiO 2 sol-gel method [57] spheres Co-B alloy solution method [58] spheres 2 solution method [80] nanoboxes Ni(OH) 2 solution method [81] nanocubes (hollow) Co(OH) 2 solution method [82] nanopolyhedra (hollow) CoS solution method [83] mesopores nanocubes ZnSnO 3 solution method and annealing [84] REVIEWS SCIENCE CHINA Materials Table 1, have been synthesized. In this review, we explain how these exquisite nanostructures can be obtained by a number of innovative methods.…”

Solubility and bioavailability of stabilized amorphous calcium carbonate

“…(6) Several techniques have been reported for the synthesis and stabilization of ACC, (4,7) but all known methods use either toxic materials or various organic polymers to stabilize ACC for more than 3 days. (7)(8)(9)(10)(11) To avoid use of such compounds, a novel method for synthetic production of stabilized ACC using phosphoaminoacids was developed recently (12) and was shown to stabilize ACC for more than 4 months under ambient conditions.…”