Designer crystals: Single crystals with complex morphologies

Biological systems are capable of remarkable control over crystal growth, producing morphologically complex single crystals with curved surfaces. We have previously demonstrated that crystals with identical morphological complexities can be produced synthetically using templating routes. This article provides a detailed investigation into the mechanism of this process, studying the relationship between the chemical environment provided by the template and the structure of the templated particles produced. A range of crystals were precipitated within the confines of macroporous polymer templates whose surface chemistries were varied by oxidation with an oxygen plasma, by modification with adsorbed polyelectrolytes, or by electroless deposition of a thin layer of gold and subsequent functionalization with omega-terminated self-assembled monolayers. The surface chemistry of the template was shown to play a crucial role in determining the structure of templated calcite particles, such that only non-charged surfaces directed the formation of single-crystal particles and polycrystalline particles being produced with negatively charged surfaces. Control of crystal morphologies is clearly fundamental to the development of many new functional materials and devices. This work therefore demonstrates how a templating methodology can provide a general and highly controllable route to synthesizing crystalline materials with defined morphologies and structures.