1D oriented attachment of calcite nanocrystals: Formation of single-crystalline rods through collision

The oriented attachment of calcite, which is a main component of biominerals, was experimentally demonstrated in an aqueous system at ambient temperatures. Calcite nanoblocks ∼50 nm in size were prepared by carbonation of Ca(OH)₂. One-dimensional (1D) alignment of the calcite nanoblocks was induced at ambient temperatures under a basic condition (pH ∼ 12), and single-crystalline rods over 1 m were then formed through elongation in the c direction. The oriented attachment of the nanoscale building blocks was enhanced by increasing the collision frequency with stirring of the system, but was halted under a neutral pH condition with further carbonation. The controllable non-classical growth mode of calcium carbonate nanocrystals would provide significant information for biogenic and biomimetic mineralization in aqueous solutions.