Crystal growth in nanoporous framework materials

Abstract

Future applications of nanoporous materials will be in opto-electronic devices, magnetic and chemical sensors, shape-selective and bio-catalysis, structural materials and nuclear waste management. Crucially, in all such applications, an understanding of crystal growth to the same depth as has been achieved in semiconductor technology is needed. Therefore, defects, intergrowths, dopants and isomorphous substitution must be controlled, and crystal habit and size (e.g. single crystal films) must be fabricated with precision. These goals elude the community because of lack of understanding of crystal growth processes. Modern microscopy techniques including AFM, ultra-high resolution SEM and HREM coupled with theoretical calculations are beginning to reveal the details of these growth processes yielding the important thermodynamic data crucial to effect synthetic control such as: controlling defects; controlling intergrowths: introducing chirality; modifying surface access; altering diffusion pathways; controlling crystal habit; synthesising templated materials cheaply in order to render them economically viable; controlling crystal size for instance as single crystal films. In this paper we will discuss recent results including: the details of surface alteration processes in nanoporous materials, measured in situ, under different chemical environments and the ability to switch processes on and off by the control of growth conditions. Further we illustrate an approach to theoretically model the crystal growth in such complex systems which ultimately delivers activation energies for fundamental growth processes.

Concluding Remarks : Crystal growth and nucleation: tracking precursors to polymorphs

“…The implementation of instrumental techniques, apparent in Faraday Discussion 95, has been a very strong feature of Discussion 136, with an unprecedented variety in evidence and a trend towards multi-technique studies. [16][17][18] Strikingly, the techniques have addressed the solution as much as, if not more than, the surface, and the importance of solution entities and precursors in determining the outcome of crystallisation has been an important theme. This aspect has been seen in studies of molecular materials, 16,19 where spectroscopic techniques have afforded detailed information on molecular interactions in solution.…”

Crystal Shape Engineering

“…99 Additionally, Piana et al have developed a kinetic Monte Carlo scheme and have applied it to the growth of urea crystals from water. 100 A similar scheme was followed by Anderson et al 101 to predict the shape of hydrothermally synthesized zeolite A crystals. These simulation techniques have both advantages and drawbacks compared to the modeling methods described in §5.1 for problems ranging from fundamental discovery to product and process development.…”

Anatomy of screw dislocations in nanoporous SAPO-18 as revealed by atomic force microscopy

“…Interestingly, zeolite A crystals 15 showed similar etch pits but since these crystals were never investigated by in situ methods it is unknown whether these are also spiral dissolution pits. In situ AFM revealed that these etch pits are tight spiral dissolution pits.…”

“…This is an unusual phenomenon and to our knowledge never reported previously. Interestingly, zeolite A crystals 15 showed similar etch pits but since these crystals were never investigated by in situ methods it is unknown whether these are also spiral dissolution pits. Monte Carlo simulations show that during dissolution conditions spiral dissolution pits can be generated.…”