The adsorption of dyes by crystals

Abstract

Explanations of the crystal habit modifying powers of certain dyes have usually depended on the adsorption, by means specified or unspecified, of the dye molecules by the growing crystal. The present work has confirmed the importance of dye adsorption in crystal habit modification phenomena. Studies of modified crystals in which dye adsorptions, followed by overgrowth of the dye molecules, have occurred to give pleochroic dye inclusions have indicated, however, that adsorption is not necessarily on the habit modified plane. More frequently it is perpendicular to the modified face of the crystal, which is very reasonable if modern views on the layerwise growth processes of crystal faces are accepted.It was assumed that the polar groups of dye molecules were responsible for the adsorption of dyes by growing crystals, and a considerable weight of evidence has been obtained to support the view that adsorption is due to a close similarity in pattern between the polar groups in a dye molecule and the ions of a crystal plane. The type of crystal c PXIS FIG. 1.

Crystallization at Inorganic-organic Interfaces: Biominerals and Biomimetic Synthesis

“…Some progress has been made, mainly in the field of organic solid-state chemistry (3,4), in which the key structural and stereochemical factors associated with nucleation and crystal morphology can be more readily identified than in systems that are characterized by ionic bonding. The application of a molecular approach to inorganic materials has been essentially restricted to the geometric (epitaxial) models proposed many years ago by Whetstone (5) and Buckley (6) that were developed to explain the interaction of additives with specific crystal faces. Inorganic interfaces involved in oriented overgrowth have been treated from a similar perspective, and unit cell matching of closepacked structures can account for oriented nucleation, provided that the substrate and overgrowth have relatively simple lattice symmetries.…”

Crystal Design of Calcium Carbonate Microparticles Using Double-Hydrophilic Block Copolymers

“…It was speculated that these double-hydrophilic block copolymers, due to their strong interaction with inorganic surfaces, also have the potential to control the growth of inorganic crystallites, such as those of calcium carbonate or hydroxyapatite, by acting as a template during nucleation and growth. This process is called “crystal design/engineering” − and was pioneered by Buckley, Raistrick, and Whetstone; − it enables, in principle, a direct handling of the size, the shape, and the crystal structure of the material (in cases where more than one modification exists). In the case of CaCO 3 , successful control of the modification of crystals grown under Langmuir monolayers could be achieved.…”

The crystal habit modification of inorganic salts with dyes. Part 1.—General considerations

“…This leads to the very important conclusion, when applied to the observed habit modifications of ammonium nitrate IV with Acid Magenta or trisulphonated p-rosaniline, that the Acid Magenta molecules are all situated in parallel planes perpendicular or almost perpendicular to the habit-modified plane. 11 If the inference that at1 dye molecules may be adsorbed on planes perpendicular (or nearly so) to the habit-modified plane of the crystal is accepted, it is possible to explain modified crystal growth in conformity with the newest ideas on normal growth, which postulate the spreading of continuous layers over the faces from continuously renewed nuciei,l2 which may in some cases be spiral dislocations. 13 If crystal faces grow by the spreading thereover of layers 10-1000 A thick rather than by continuous deposition on the plane, it is evident that to retard the growth of a crystal face it is necessary to reduce the rate of spreading of the layers.…”