Morphosynthesis of framboidal stable vaterite using a salicylic acid-aniline dye as an additive

Abstract

Morphosynthesis and stabilization of pure framboidal vaterite microspheres using a salicylic acid–aniline dye as an additive has been reported in this paper. Formation and stabilization of vaterite crystals could be regulated by changing the dye concentration. Calcite rhombohedra were predominant species when no additive was added. As the concentration of dye was increased vaterite was more pronounced in the solution leading to the formation of pure framboidal vaterite (∼98% at 10 mM dye concentration). The size of these microspheres varied from 0.5 to 4.0 μm. Various instrumental analysis has been incorporated to study the dynamics of phase transformation throughout the process. Detailed analysis of TEM images reveals that vaterite microspheres were in turn aggregates of small vaterite nanospheres. The vaterite microspheres were stable up to a week in solution. The dissolution of the vaterite crystals to calcite was arrested by the presence of the dye at the nucleation process. The stability of the vaterite may be attributed to the strong electrostatic interaction of the Ca ions present on the surface of the crystal with the –COOH group of the dye. This finding opens up a new domain of organic additives to explore.