Controlling Relative Fundamental Crystal Growth Rates in Silicalite:  AFM Observation

Abstract

A detailed atomic force microscopy study has been performed on the open-framework, microporous material silicalite. Emphasis has been placed on determining the effect of supersaturation on the crystal growth process. The relative rates of fundamental crystal growth processes can be substantially altered by tuning the supersaturation. In this manner, it is possible to, for instance, switch on and off surface nucleation while retaining terrace spreading. This offers a potential mechanism by which it might be possible to control important crystal aspects such as defect density and intergrowths.

Evolution of Surface Morphology with Introduction of Stacking Faults in Zeolites

“…Such layer-by-layer growth of pentasil sheets has been observed in other preparations of silicalite. [19,20] In the present case, we also observed the directional nature in the layers itself with slower growth in the [001] direction, resulting in an elongated c dimension. The other pure end member of the intergrowth series, MEL silicalite-2, formed ovate-shaped crystals of dimensions of about.…”

“…[10][11][12][13] AFM is particularly advantageous in that it can be used either to look at crystal surfaces following synthesis (ex-situ) or in solution during growth (in-situ). AFM investigations of natural zeolites [14][15][16] and synthetic zeolites such as zeolite A, [17,18] silicalite-1, [19,20] zeolite Y [21] and zeolite L [22] have indicated a layer-by-layer growth mechanism, in which the particles add to the terrace edges, forming kinks followed by expansion of the terrace and simultaneous surface nucleation. The surface structure of silicalite-1 prepared using two different templates, that is, the tetrapropylammonium ion (TPA) and trimeric TPA, have also been elucidated by employing HRTEM and AFM techniques.…”

Nanoscale Control of Homoepitaxial Growth on a Two‐Dimensional Zeolite

“…[8][9][10][11] Recent advances in the synthesis of core-shell zeolite catalysts, [12] two-dimensional (2D) and hierarchical zeolites, [13][14][15] exfoliated zeolite nano-sheets, [16,17] and thin zeolite films, [18,19] suggest that nanometer level control of zeolite crystal growth is desirable. However, studies of zeolite crystallization are limited to conventional crystals [20,21] and nanoscale growth events have not been resolved. Herein, growth of a 2D zeolite with nanometer resolution is presented.…”

Super‐Resolution Reactivity Mapping of Nanostructured Catalyst Particles

“…AFM has proven that this growth process is prone to defect incorporation, and this results in irregularities in the developing crystal edge. [30,35,36] In summary, the new NASCA microscopy approach records organic reactivity maps of catalysts at small length scales similar to those of electron, scanning probe, or X-ray microscopy, which rather give inorganic or structural information. This labeling-free scheme is based on conversion of single fluorogenic molecules on the true active sites, and has a generic character as it is broadly applicable, even in biological samples.…”