| During the past decade, inspired by the biomineralization exploited by living organisms, our understanding of crystallization has jumped to a new level—nonclassical crystallization. This concept contains a number of novel steps such as amorphous precursors, oriented attachment, and mesoscopic transformation. Nonclassical crystallization could be applied as an effective strategy for controlled synthesis of inorganic materials with complex morphologies and ordered superstructures. In this dissertation, we stated our recent work about nonclassical crystallization processes. The main results are summarized as the following:1. Amorphous calcium carbonate stabilized by a flexible biomimetic polymer inspired by marine musselsOrganisms make use of amorphous materials as a certain precursor to form insoluble complex biominerals in the presence of various organic matrices. In this chapter, we demonstrate that amorphous calcium carbonate (ACC) nanoparticles can be highly stabilized by a polymerized dopamine (DA), a biomimetic molecule inspired by adhesive proteins in mussels. The cross-linking polydopamine (PDA, a mussel mimicking polymer) flexible chains are adhesively associated with the ACC particles to form ACC@PDA core-shell spheres. We are able to modulate the thickness of PDA shells in the range of a few to several tens of nanometers by adjusting the additive DA amount. The thickness of this mussel mimicking PDA shell significantly influences the stability of ACC nanoparticles, the thicker the PDA shell is, the more stable the ACC core is. The obtained ACC-PDA hybrid particles have high stability, partly because the complexing interaction of Ca2+ions with PDA and encapsulating PDA networks inhibit ACC dissolution and retard subsequent Ostwald ripening; partly because the PDA coating builds isolated confinement spaces for ACC that prevents contacting and merging of ACC particles which further restrains possible solid-phase transformation. Notably, the protecting effects of PDA endow the obtained ACC-PDA composite powder with enough stability to exist for at least one year in the solid state.2. Calcium carbonate heterostructured microspheres with calcite equatorial loops and vaterite spherical coresHere, we describe a successful achievement for synthetic calcium carbonate heterostructured microspheres with calcite equatorial loops and vaterite spherical cores by adding two different functional additives. A reasonable mechanism based on the nonclassical particle-mediated crystallization of calcium carbonate is proposed, demonstrating the individual and cooperative effects of a polymer (poly(sodium4-styrenesulfonate), PSS) and small acidic molecules (folic acid, FA) on the formation of heterostructures at different reaction stages. It is expected to develop our system to be a model for investigating the combination of kinetics and thermodynamics in crystallization processes.3. Template-free facile solution synthesis and optical properties of ZnO mesocrystalsThere have been many examples in preparing complex inorganic materials through biomimetic mineralization, however, it remains a challenge for materials scientists to synthesize highly ordered superstructures with controlled shape and size in the absence of templates. Here, novel ZnO mesocrystal microspheres have been prepared on a large scale by a facile solution-based method without addition of templates. The mesocrystal forms via a nonclassical crystallization pathway involving an oriented aggregation of nanoplatelets building blocks. The intrinsic dipole interactions between the individual hexagonal nanoplatelets act as the driving force. Because there is not any template additives in the reaction system; the organic solvent of butanol may play an important role in the growth of the crystals and result in the final spherical mesocrystal morphology. Interestingly, the as-synthesized ZnO mesocrystals exhibit strong yellow emission centred at560nm and the yellow emission can be clearly visualized under portable UV light. |
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