Non-classical crystallization

The particle-mediated non-classical crystallization path makes crystallization more independent of ion products or molecular solubility. It can occur without pH or osmotic pressure changes, and opens new strategies for crystal morphogenesis. This is possible because the precursor particles can be formed independently and can be transported to the mineraUzation site so 

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H. Colfen and M. Antonietti, Mesocrystals and Non Classical Crystallization, John Wiley Sons, Chichester, U.K., 2008. 

Keywords Bio-inspired mineralization - Double hydrophilic block copolymers Mesocrystals Non-classical crystallization Oriented attachment Self-assembly... 

Non-classical crystallization often involves self-assembly of preformed nanoparticles to an ordered superstructure, which then can fuse to a single crystal. These pathways are outlined in Fig. 1 and discussed below in more detail... 

Fig.5 Classical (a) vs. non-classical crystallization (b,c). a Crystallization of hydroxyapatite (HAP) fibers from block copolymer aggregates [108], where the block copolymers adsorb to all faces parallel to the HAP c-growth axis resulting in whisker structures with occasional branches (see arrows). b,c Formation of single crystalline and defect-free BaS04 (210) oriented fiber bundles by the process of oriented attachment in experiments described in [109-111], Figure reproduced from [112] with kind permission of Editorial Universitaria, Universidad de Chile, Santiago, Chile...

Niederberger M, Colfen H (2006) Oriented attachment and mesocrystals Non-classical crystallization mechanisms based on nanoparticle assembly. PCCP 8(28) 3271-3287. doi 10. 1039 604589h... 

In 1978, Bryan [11] reported on crystal structure precursors of liquid crystalline phases and their implications for the molecular arrangement in the mesophase. In this work he presented classical nematogenic precursors, where the molecules in the crystalline state form imbricated packing, and non-classical ones with cross-sheet structures. The crystalline-nematic phase transition was called displacive. The displacive type of transition involves comparatively limited displacements of the molecules from the positions which they occupy with respect to their nearest neighbours in the crystal. In most cases, smectic precursors form layered structures. The crystalline-smectic phase transition was called reconstitutive because the molecular arrangement in the crystalline state must alter in a more pronounced fashion in order to achieve the mesophase arrangement [12]. 

Granasy L. and James P.F. (1999) Non-classical theory of crystal nucleation application to oxide glasses review. J. Non-Cryst. Solids 253, 210-230. 

Optical activity in solution, unlike the same effect in crystals, is an isotropic effect. This interaction between a polarized photon and a molecule therefore implicates a chiral factor that is independent of direction, such as the molecular wave function, and in particular, its complex phase. It is a non-classical factor and hence cannot be attributed directly to a classical three-dimensional structure. In a crystal where optical activity arises from three-dimensional... 

Another area in which multinuclear metal complexes play a technologically useful role is that of non-linear optics. A recent novel instance based on, and which is interpreted elegantly within, classical crystal- and ligand-field theory, is that in which near-infrared visible light upconversion has been demonstrated in a tri-nuclear d-f-d metal complex cluster, consisting of Er(III) ions, sandwiched between pairs of Cr(III) ions ([(CrErCr)Ll3] ", ... 

Sear, R.P. The non-classical nucleation of crystals microscopic mechanisms and applications to molecular crystals, ice and calcium carbonate. Int. Mater. Rev. 57, 328-356 (2012)... 

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