engleski

Biomimetic precipitation of nanostructured colloidal calcite particles by enzyme-catalyzed reaction in the presence of magnesium ions

A novel, bioinspired precipitation process, effectuated through the decomposition of urea by catalytically active Canavalia ensiformis urease (urea amidohydrolase ; EC 3.5.1.5), in a solution of calcium and magnesium salts was used to precipitate uniform submicron-size, nanostructured calcium carbonate particles. The structure and morphology of the precipitates were investigated using scanning and transmission electron microscopy and X-ray diffraction. Their surface properties were investigated by electrophoretic mobilities and specific surface area measurements. These precipitates were formed through initial generation of a nanometer-scale, amorphous, metastable precursor phase, which, on aging, transforms into nanosize crystalline calcite and aggregates into nearly spherical nanostructured calcite particles. The presence of magnesium ions in combination with urease macromolecules was found to affect the nucleation process and inhibited the growth of the initially formed nanoparticles in solution. This nonclassical formation of calcite colloids, described as the biomimetic nanoscale aggregation route, supports the recently reaffirmed mechanism according to which carbonate colloids are produced through aggregation of preformed nanosize particles.

aggregation; biomimetic; calcite; enzyme; nanoparticles; precipitation

Article is published on-line: ASAP Cryst. Growth Des., ASAP Article, 10.1021/cg070195n Web Release Date: December 20, 2007