3D Visualisation of Additive Occlusion and Tunable Full-Spectrum Fluorescence in Calcite

From biomineralization to synthesis, organic additives provide an effective means of controlling crystallisation processes. There is growing evidence that these additives are often occluded within the crystal lattice, where this promises an elegant means of creating nanocomposites and tuning physical properties. Here, we use the incorporation of sulfonated fluorescent dyes to gain new understanding of additive occlusion in calcite (CaCO3), and to link morphological changes to occlusion mechanisms. We demonstrate that these additives are incorporated within specific zones, as defined by the growth conditions, and show how occlusion can govern changes in crystal shape. Fluorescence spectroscopy and lifetime imaging microscopy also show that the dyes experience unique local environments within different zones. Our strategy was then extended to simultaneously incorporate mixtures of dyes, whose fluorescence cascade creates calcite nanoparticles that fluoresce white. This offers a simple strategy for generating biocompatible and stable fluorescent nanoparticles whose output can be tuned as required.