Engineering Crystal Modifiers: Bridging Classical and Nonclassical Crystallization

Abstract

The use of growth modifiers in natural, biological, and synthetic crystallization is a ubiquitous strategy for controlling growth and achieving desired physicochemical properties. For crystals that grow classically (i.e., monomer-by-monomer addition), theories of crystallization are well established and the field of growth modification is rather mature, although many questions remain regarding the molecular driving forces of modifier–crystal interactions. A new frontier in crystallization is the application of classical methods to tailor materials that grow nonclassically (i.e., growth by the addition of species more complex than monomers). A recent surge of interest and activity in this field has been driven by mounting evidence of both inorganic and organic materials that grow via nonclassical pathways. In these systems, the challenge of elucidating the mechanism(s) of crystallization is underscored by a diversity of growth units that far outnumber those available for classical routes. In this Perspective, we discuss growth modification in nonclassical crystallization, including examples in the literature, the challenges associated with elucidating the modes of modifier action, and to what degree classical theories can be applied to these complex problems as a means of establishing versatile blueprints for crystal engineering.

The mechanisms of crystal growth inhibition by organic and inorganic inhibitors

“…To include these species in the microkinetic growth model 7 in a thermodynamically consistent manner requires the knowledge of the solution speciation. The formation of ion pairs has been suggested as a potential growth inhibition mechanism 24 , significantly affecting growth by decreasing the saturation index (SI). We therefore performed a full geochemical speciation calculation with PHREEQC 25 for each experimental data point.…”

Diagnosing the Internal Architecture of Zeolite Ferrierite

“…This is equivalent to the step height measured by AFM, and a schematic of this layer‐by‐layer growth mechanism is shown in Figure d. Growth in this dimension is much slower than growth in the directions of the 8‐ and 10‐MRs, which is reflected in the plate‐like morphology of the crystals. These regular terraces are consistent with a classical crystal growth mechanism where crystals grow via the addition of monomers in solution, which is an interesting finding as zeolites are known to grow by both classical and non‐classical mechanisms . However, the classical growth mechanism may only apply towards the end of zeolite crystallization as we did not probe the initial stages of crystallization when a non‐classical mechanism may apply.…”

Time‐Resolved Dynamics of Struvite Crystallization: Insights from the Macroscopic to Molecular Scale

“…Growth modifiers ranging from ions and small molecules to large macromolecules can impact crystal growth by altering supersaturation (i.e. forming modifier‐solute complexes), physically blocking solute attachment by binding to crystal surfaces, or disrupting the local environment around crystal–solute interfaces . Prior studies of modifiers in other systems, such as antimalarials used to avert hematin crystallization and acids used to treat calcium oxalate kidney stones, have been shown to inhibit crystallization through preferential binding to crystal surfaces.…”