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This article focuses on mesocrystals and morphology change of CaCO3 crystals in the presence of a polyelectrolyte additive. Crystallization control is one of the most important techniques of preparation, purification, and application of solid substances, making it an intensely studied field. Besides conventional crystallization, there are also nonclassical pathways of crystallization via colloidal intermediates and mesoscale transformation, in which crystalline structures are constructed and/or transformed from larger units instead of single ions. The authors present a simple system of calcite paired with polystyrene sulfonate, which undergoes mesocrystal formation. Appropriate concentration adjustment of both partners allows broad, systematic variation of the mesocrystal morphology that demonstrates long-range interactions. Moreover, the authors reports that selective coding of nanocrystal surfaces by polymers can not only lead to mesocrystals exposing unusual crystal faces in their superstructure, but also can form self-assembled structures with changed symmetry.

The principle of polymer-controlled crystallization of inorganic materials has been successfully transferred to functional aromatic organic dyes, in this instance 3,4,9,10-perylenetetracarboxylic acid potassium salt (PTCAPS), after its single-crystal structure was determined. The cationic double hydrophilic block copolymer poly(ethylene glycol)-block-branched-poly(ethyleneimine) (PEG-b-PEI) was used as the polymer additive to modify the crystallization of PTCAPS. Ultralong hierarchically structured PTCAPS microbelts with constant width and thickness of each individual belt have been fabricated. The belts are a mesocrystalline assembly of primary nanoparticles with high-energy anionic {001} faces stabilized by polymer complexation. Polarization microscopy, X-ray diffraction, optical absorption spectra, and fluorescence spectra indicate the favorable orientation of the 1D microbelts in the close-stacking direction and reveal a specific 1 D superstructure fluorescence. Electrical conductivity measurements performed on a single nanobelt disclose in the doped state a remarkably high electronic conductivity and further demonstrate extended, wirelike π-π interactions along the [020] long axis of the belts. Together with the very large length of the belts and their organic-organic hybrid nanostructure, this makes these organic wires potentially interesting for the field of nano-/micro-optoelectronics. [ABSTRACT FROM AUTHOR]

Biomineralization occurs in aqueous environments. Despite the ubiquity and relevance of CaCO 3 biomineralization, the role of water in the biomineralization process has remained elusive. Here, we demonstrate that water reorganization accompanies CaCO 3 biomineralization for sea urchin spine generation in a model system. Using surface-specific vibrational spectroscopy, we probe the water at the interface of the spine-associated protein during CaCO 3 mineralization. Our results show that, while the protein structure remains unchanged, the structure of interfacial water is perturbed differently in the presence of both Ca 2+ and CO 3 2- compared to the addition of only Ca 2+ . This difference is attributed to the condensation of prenucleation mineral species. Our findings are consistent with a nonclassical mineralization pathway for sea urchin spine generation and highlight the importance of protein hydration in biomineralization.