Abstract
From biomineralization to synthesis, organic additives provide an effective means of controlling crystallization processes. There is growing evidence that these additives are often occluded within the crystal lattice. 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 is 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.
Highlights
The incorporation of guest species within host materials is an attractive route to the formation of new functional materials and promises the opportunity to tailor the properties of composites at the nanoscale level[1]
Our study uses confocal fluorescence microscopy (CFM) to demonstrate that organic additives can occlude within calcite in specific zones, while fluorescence spectroscopy and fluorescence-lifetime imaging microscopy (FLIM) reveal the existence of different local environments within the crystals
Calcium carbonate was precipitated in the presence of three fluorescent dyes (Supplementary Fig. 1)
Summary
The incorporation of guest species within host materials is an attractive route to the formation of new functional materials and promises the opportunity to tailor the properties of composites at the nanoscale level[1]. Foreign ions with appropriate size and charge can be exchanged for ions of the parent lattice, and judicious selection of the dopant can create a material with new optical, magnetic and electronic properties This strategy can be extended to the doping of single crystals with a wide range of species, providing a versatile method for tailoring properties. Having established the occlusion of individual dyes within calcite, we extend our study to create a functional material—white fluorescent calcite—through the simultaneous incorporation of red, blue and green fluorescent dyes, which together yield a fluorescence cascade This one-pot synthesis provides a low-cost and versatile method for generating a biocompatible, fluorescent material whose output can be tuned as required, and where the host crystal ensures greater photostability by protecting the occluded dyes from fluorescence quenchers, humidity and oxidation
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