Growth of single crystals in structured templates

Biology provides numerous examples of calcite single crystals with unique morphologies which are completely at odds with the internal lattice structure of the crystal. We have recently demonstrated that similar structures can be produced synthetically, using a suitable mould to template calcite crystal morphologies. We here investigate the generality of templating approaches to produce single crystals with complex morphologies. A variety of contrasting crystals were selected, and precipitated in polymer membranes with sponge-like structures, under a range of growth conditions. The structures of the product crystals were investigated using single crystal X-ray diffraction, and the morphology using scanning electron microscopy. True single crystal or oligocrystalline products were obtained for SrSO4, PbSO4, PbCO3, NaCl and CuSO4.5H2O, demonstrating that calcite is in no way unique in its ability to be moulded into complex morphologies. The principal requirement for templating single crystals is simply that the natural size of the crystal under the given growth conditions must exceed the length scale of the template.