In situ characterisation of calcite growth and inhibition using atomic force microscopy

Real time in situ monitoring of calcite growth and inhibition on the cleavage plane (10 (1) over bar4) is investigated using atomic force microscopy (AFM). Calcite growth and inhibition were studied using a Molecular Imaging microscope in contact mode, equipped with an in situ fluid cell. As has been reported previously, it is observed that calcite growth from aqueous solution is by motion of mono-molecular steps, and dissolution by a combination of step motion and etch pit expansion. The measured step heights were between 2.7 to 3 Angstrom. Our aim is to study the effects of a range of phosphonate-based crystal growth inhibitors of related structure, in order to provide insight into the mechanism of inhibition as a function of the additive structure. Results of this study demonstrate the effect of inhibitors on the growth steps and terraces on the (10 (1) over bar4) surface of calcite in real time. The organic additives bind to the crystal surface, with selective binding to the step edges particularly evident in some cases. In other cases, it appears that the additive acts by binding to the terraces on the crystal surface, resulting in inhibition by coating the surface, Efforts to correlate the observations made by atomic force microscopy with bulk crystallization experiments have been made.