Figure 1. Morphological progression of calcite nucleated on COOH terminated SAMs.

(a) A schematic of the experimental set-up, where CO₂ and NH₃ diffuse into hanging droplets of CaCl_2(aq), causing amorphous calcium carbonate formation (red dot). An oriented tetrahedron of calcite bounded by planar {104} faces then forms, whose growth leads to the development of an additional facet as a truncation of the long axis. Further growth then results in a transformation to rhombohedral calcite. (b) Schematic images of the tetrahedral growth form, showing the location of the truncation face. (c) Scanning electron microscope images showing the morphological development of the calcite crystals. (d) Winterbottom reconstructions predicting the morphological development of the calcite crystals, where these are of identical volume with stepwise increasing relative interfacial energy of the crystal/SAM (γ_s; 0.1–0.9). Crystal/ water interfacial energy values used were taken from Duffy and colleagues³⁶.