In situ atomic force microscopy investigation of the growth of secondary nuclei produced by contact of different growth faces of potash alum crystals under supersaturated solutions

Abstract

Contact of a potash alum crystal in a supersaturated solution with a solid surface may easily produce many secondary nuclei of the same orientation and crystal structure as the parent crystal contact faces. Previous studies have shown that, if this contact is sufficiently gentle, secondary nuclei may be produced by the transfer of ordered solute molecules without the need for microabrasion of the parent solid. In this investigation, crystal faces of the {1 0 0}, {1 1 0}, and {1 1 1} families were identified in a parent crystal, and gentle contact between these and a solid surface (glass slide) in a slightly supersaturated solution of potash alum produced many secondary nuclei, the external symmetry of which reflected that of the parent face. In situ atomic force microscopy (AFM) measurements were carried out to study the early stages of the growth of these new nuclei. A strong correlation was found between the symmetry of the nuclei produced and that of the parent crystal face. The topographies of the in situ growth of the (1 1 1) face of the parent crystal and those of the very small new nuclei produced were compared.