2002 Volume 75 Issue 11 Pages 2541-2546
The precipitation of CaCO3 in the absence or the presence of the G4.5 PAMAM dendrimer was carried out by a “carbonate diffusion method”. Formation of crystalline CaCO3 at different feed ratios of the G4.5 dendrimer to calcium ions was studied with the concentration of calcium ions kept at 0.1 M. Although calcite was predominantly formed at the concentration of the G4.5 PAMAM dendrimer corresponding to 2.65 mM of –COONa, the crystal phase of the obtained CaCO3 at the higher concentration of the G4.5 PAMAM dendrimer at 5.3 mM consisted entirely of vaterite. As the concentration of –COONa increased from 5.3 to 10.6 mM, the particle sizes of the spherical vaterites were reduced from 8.7 ± 1.0 to 5.2 ± 3.0 μm determined by SEM observation. The crystal phase of the obtained CaCO3 in the absence of any additives was a mixture of calcite and vaterite. Although vaterite was predominantly formed by the G4.5 dendrimer, relatively high amounts of calcite were observed in the case of the G3.5 and G1.5 dendrimers. These results suggest that the G4.5 dendrimer more effectively induces vaterite formation compared with the earlier generation of the dendrimers.
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