A molecular-scale understanding of crystal growth is critical to the development of important materials such as pharmaceuticals, semiconductors and catalysts. Only recently has this been possible with the advent of atomic force microscopy that permits observation of nanoscopic features on solid surfaces under a liquid or solution environment. This allows in situ measurement of important chemical transformations such as crystal growth and dissolution. Further, the microscope can access not only an accurate height measurement of surface topography, important to deduce structural elements, but also the forces involved during nanoscopic processes. We have discovered that it is possible to use these features to "illuminate" critical nanoscopic chemical events at crystal surfaces and at the same time extract the associated energies and unstitch the details of the stepwise mechanism of growth and dissolution. This approach has been developed using nanoporous crystals of the heterogeneous catalyst zeolite L; however, in principle the approach could be adapted to many crystal growth problems.

Microporous zincophosphate sodalite crystal growth has been studied in situ by atomic force microscopy. This simple model system permits an in depth investigation of some of the axioms governing crystal growth of nanoporous framework solids in general. In particular, this work reveals the importance of considering the growth of a framework material as the growth of a dense phase material where the framework structure, nonframework cations, and hydrogen-bonded water must all be considered. The roles of the different components of the structure, including the role of strict framework ordering, are disentangled, and all of the growth features, both crystal habit and nanoscopic surface structure, are explained according to a simple set of rules. The work describes, for the first time, both ideal growth and growth leading to defect structures on all of the principal facets of the sodalite structure. Also, the discovery of the presence of anisotropic friction on a framework material is described.

The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractThe nanoscopic details of the crystal growth of zeolite A in the presence of the organic modifiers diethanolmaine (DEA) and triethanolamine (TEA) has been determined using a combination of atomic force microscopy (AFM) and high-resolution scanning electron microscopy (HRSEM) coupled with Monte Carlo simulations. Crystallization of zeolite A in the presence of TEA was faster than when the growing solution contained DEA. In addition the morphology of the final zeolite A crystals depended on the type of organic molecule, with TEA producing crystals bound only by {100} facets and DEA leading to the formation of relatively large {110} faces. These features can be explained in terms of the relative Si/Al in the growing medium and its control due to the different affinity of the organic molecules toAl. In addition, synthesis performed at 90 °C showed the appearance of {211} facets. Careful review of the HRSEM and AFM images, in addition to comparison with the MC simulations reveal that these are in fact pseudo-facets, product of the slow dissolution of the metastable zeolite A crystals. This proves that the final habit of the LTA crystals can be governed by very small changes of saturation of the growing medium and a control of this paremeter can prove advantageous when designing crystals for industrial applications.