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. 2014 Oct;10(7):1529–1538. doi: 10.1016/j.nano.2013.12.011

Figure 2.

Figure 2

Structural characterization of the ferrihydrite. (A-D), High-angle annular dark-field, aberration-corrected, scanning transmission electron microscopy (HAADF-STEM) images of tartrate-modified ferrihydrite in tryptophan (A, B) or adipate buffer (C), and of synthetic (unmodified) ferrihydrite (D). Scale bars are 50 nm (A and C) or 2 nm (B and D). (E) X-ray diffraction patterns of synthetic ferrihydrite (black) and tartrate-modified ferrihydrite (red). Both patterns have peaks characteristic of ferrihydrite, with the synthetic ferrihydrite peaks centred at 35° and 62° 2θ (2.6 Å and 1.5 Å, respectively) and the tartrate-modified ferrihydrite peaks centered at 33° and 61° 2θ (2.7 Å and 1.5 Å, respectively), indicating expansion of the ferrihydrite lattice. Sodium tartrate is shown in green. Synthetic ferrihydrite was precipitated from an Fe(III) chloride solution and tartrate-modified ferrihydrite from an Fe(III) chloride solution in the presence of tartrate and tryptophan buffer (Fe/tartrate/tryptophan = 1:0.5:0.375). Excess ligand and buffer were removed from the modified material by ultrafiltration and washing prior to drying as described in Methods.