Fig. 2.

Calcite crystals precipitated in the presence of GP and 14 nm GP-NPs. a, b Optical micrographs of crystals precipitated at [Ca²⁺] = 20 mM in the presence of a 0.05 wt% GP-functionalised 14 nm NPs and b 0.1 wt% of GP only. c, d SEM images of an FIB cross-section of calcite crystals containing GP-NPs. d is a high-magnification image of c. e TEM bright field image and SAED pattern of a crystal, showing that the host calcite is a single crystal. f Cryo-electron tomogram of a crystal containing 13 wt% Au showing the uniform distribution of the NPs within the host crystal.