Fig. 5.

TEM images of calcium oxalate precipitates formed in titration experiments in the presence of 10 mM citrate at pH 6.2. a TEM image showing particles with dark contrast and well-defined spherical morphology, which are connected with a less dense (lighter contrast) shapeless structure (quenching time: 10,000 s). Scale bar: 500 nm. b General overview (STEM-HAADF image) of dried precipitates formed at 15,000 s. Nanometer-sized crystalline calcium oxalate crystals coexist with rounded nanoparticles that seem to grow by aggregation of smaller nanoparticles. Scale bar: 200 nm. c Detail of b showing the growth of ACO nanoparticles by aggregation or attachment of smaller units. Scale bar: 10 nm