Oriented Attachment of Calcite Nanocrystals: Formation of Single-Crystalline Configurations as 3D Bundles via Lateral Stacking of 1D Chains

The formation of single-crystalline configurations by the oriented attachment of calcite was experimentally demonstrated as 3D bundles in a nonaqueous system. In the initial stage, 1D short chains elongated in the <i>c</i> direction were formed through the primary oriented attachment of calcite nanoblocks ∼30 nm in diameter. The 3D bundles were then produced through subsequent side-by-side oriented attachment of the 1D chains in the progressive stage. Finally, micrometer-sized single-crystalline architectures were constructed via large-scale oriented attachment of the nanoscale building blocks with a decrease in repulsion force due to the surface charge

Evolution of Calcite Nanocrystals through Oriented Attachment and Fragmentation: Multistep Pathway Involving Bottom-Up and Break-Down Stages

A nonclassical multistep pathway involving bottom-up and break-down stages for the evolution of calcite nanograins ∼50 nm in size was demonstrated in a basic aqueous system. Calcite nanofibrils ∼10 nm wide were produced as the initial crystalline phase via amorphous calcium carbonate through ion-by-ion assembly by the carbonation of Ca­(OH)₂ at a high pH of ∼13. Bundles ∼50 nm in diameter were then formed by the subsequent oriented attachment of the nanofibrils. Monodispersed calcite nanograins were finally obtained through spontaneous fragmentation of the fibrous forms via a decrease in pH by further carbonation

Enhancement of coercivity of self-assembled stacking of ferrimagnetic and antiferromagnetic nanocubes

The coercivity of magnetic nanoparticles is enhanced by the exchange coupling effect at the interface of ferrimagnetic and antiferromagnetic self-assembled monolayers. Antiferromagnetic Co3O4 nanocubes were regularly stacked on an ordered monolayer of ferrimagnetic Fe3O4 nanocubes by layer-by-layer manipulation using evaporation-driven self-assembly. The ordered arrangements of the ferrimagnetic and antiferromagnetic nanocubes are effective for the enhancement of the ferromagnetic character.publishe