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3D visualization of additive occlusion and tunable full-spectrum fluorescence in calcite

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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.

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Changing GREEN distribution with changing initial [Dye].(a,f) Representative SEM micrographs of GREEN/calcite composites grown from different conditions (a–e=[Ca2+]=[HCO3−]=3.5 mM and [GREEN]=0.01 mM; f–j=[Ca2+]=[HCO3−]=3.5 mM and [GREEN]=0.2 mM). (b,g) Three-dimensional (3D) representation of composites as imaged by CFM, with approximate faces labelled, and growth sectors coloured in green. (c,h) Confocal fluorescence micrographs of composites from the same conditions. (d,i) Orthogonal views images (XY, YZ and XZ) of composites obtained from z-stacked confocal micrographs effectively detailing the distribution of dye in 3D (z+ direction is away from the substrate, XY is the imaging plane). Colour scale: blue (low intensity) to red (high intensity); black, no signal; white, detector saturation. (e,j) Image analyses in the form of line profiles (e) and intensity histograms (j) corresponding to lines or regions as denoted on orthogonal view images in (d,i), respectively. Scale bars, 20 μm (a,f,c,h).
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f3: Changing GREEN distribution with changing initial [Dye].(a,f) Representative SEM micrographs of GREEN/calcite composites grown from different conditions (a–e=[Ca2+]=[HCO3−]=3.5 mM and [GREEN]=0.01 mM; f–j=[Ca2+]=[HCO3−]=3.5 mM and [GREEN]=0.2 mM). (b,g) Three-dimensional (3D) representation of composites as imaged by CFM, with approximate faces labelled, and growth sectors coloured in green. (c,h) Confocal fluorescence micrographs of composites from the same conditions. (d,i) Orthogonal views images (XY, YZ and XZ) of composites obtained from z-stacked confocal micrographs effectively detailing the distribution of dye in 3D (z+ direction is away from the substrate, XY is the imaging plane). Colour scale: blue (low intensity) to red (high intensity); black, no signal; white, detector saturation. (e,j) Image analyses in the form of line profiles (e) and intensity histograms (j) corresponding to lines or regions as denoted on orthogonal view images in (d,i), respectively. Scale bars, 20 μm (a,f,c,h).

Mentions: The crystals precipitated at [Ca2+]=[HCO3−]=3.5 mM, by comparison, showed quite different morphologies and dye distributions. While the crystals formed at [Ca2+]=5 mM varied little in morphology or dye distribution with the initial concentration of GREEN (Supplementary Fig. 3), the crystals formed at [Ca2+]=3.5 mM were sensitive to the dye concentration and showed edge truncations and the emergence of new, roughened faces with increasing concentration of GREEN (Fig. 1k–o). CFM showed that the dye occlusion followed a Maltese cross motif whose arms expanded in width with increasing [GREEN] (Fig. 3). The fluorescence intensity was very low in the growth sectors beneath the mirror-smooth {104} faces, and was concentrated in growth sectors terminated by rough facets. Such occupancy of symmetry-related sectors is indicative of inter-sectoral zoning24. Modelling of the morphologies of these crystals using the programme WinXMorph suggested that the new faces were approximately parallel to {110} and {018} faces3031.


3D visualization of additive occlusion and tunable full-spectrum fluorescence in calcite
Changing GREEN distribution with changing initial [Dye].(a,f) Representative SEM micrographs of GREEN/calcite composites grown from different conditions (a–e=[Ca2+]=[HCO3−]=3.5 mM and [GREEN]=0.01 mM; f–j=[Ca2+]=[HCO3−]=3.5 mM and [GREEN]=0.2 mM). (b,g) Three-dimensional (3D) representation of composites as imaged by CFM, with approximate faces labelled, and growth sectors coloured in green. (c,h) Confocal fluorescence micrographs of composites from the same conditions. (d,i) Orthogonal views images (XY, YZ and XZ) of composites obtained from z-stacked confocal micrographs effectively detailing the distribution of dye in 3D (z+ direction is away from the substrate, XY is the imaging plane). Colour scale: blue (low intensity) to red (high intensity); black, no signal; white, detector saturation. (e,j) Image analyses in the form of line profiles (e) and intensity histograms (j) corresponding to lines or regions as denoted on orthogonal view images in (d,i), respectively. Scale bars, 20 μm (a,f,c,h).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC5120221&req=5

f3: Changing GREEN distribution with changing initial [Dye].(a,f) Representative SEM micrographs of GREEN/calcite composites grown from different conditions (a–e=[Ca2+]=[HCO3−]=3.5 mM and [GREEN]=0.01 mM; f–j=[Ca2+]=[HCO3−]=3.5 mM and [GREEN]=0.2 mM). (b,g) Three-dimensional (3D) representation of composites as imaged by CFM, with approximate faces labelled, and growth sectors coloured in green. (c,h) Confocal fluorescence micrographs of composites from the same conditions. (d,i) Orthogonal views images (XY, YZ and XZ) of composites obtained from z-stacked confocal micrographs effectively detailing the distribution of dye in 3D (z+ direction is away from the substrate, XY is the imaging plane). Colour scale: blue (low intensity) to red (high intensity); black, no signal; white, detector saturation. (e,j) Image analyses in the form of line profiles (e) and intensity histograms (j) corresponding to lines or regions as denoted on orthogonal view images in (d,i), respectively. Scale bars, 20 μm (a,f,c,h).
Mentions: The crystals precipitated at [Ca2+]=[HCO3−]=3.5 mM, by comparison, showed quite different morphologies and dye distributions. While the crystals formed at [Ca2+]=5 mM varied little in morphology or dye distribution with the initial concentration of GREEN (Supplementary Fig. 3), the crystals formed at [Ca2+]=3.5 mM were sensitive to the dye concentration and showed edge truncations and the emergence of new, roughened faces with increasing concentration of GREEN (Fig. 1k–o). CFM showed that the dye occlusion followed a Maltese cross motif whose arms expanded in width with increasing [GREEN] (Fig. 3). The fluorescence intensity was very low in the growth sectors beneath the mirror-smooth {104} faces, and was concentrated in growth sectors terminated by rough facets. Such occupancy of symmetry-related sectors is indicative of inter-sectoral zoning24. Modelling of the morphologies of these crystals using the programme WinXMorph suggested that the new faces were approximately parallel to {110} and {018} faces3031.

View Article: PubMed Central - PubMed

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.

No MeSH data available.


Related in: MedlinePlus