Nitric Acid Stabilized Superparamagnetic Iron Oxide Nanoparticles Studied with X-Rays

SUPPORTING INFORMATION

Nitric acid stabilized superparamagnetic iron oxide nanoparticles studied with X-rays

S1: Fit parameters for modeling the imaginary part of FT EXAFS of the experimental spectra (paper figure 3):

Parameters and fit results for the Fe EXAFS: Fits performed in the R space in the range 1 to 4 Å. The lattice distortion parameter Δr was set constant in all fits at 0. Aocta and Atetra are the amplitude parameters for the octahedral and tetrahedral sites, respectively. ΔE0 is the energy correction factor; experimental condition may have an influence on the factor in particular. σ2O and σ2Fe are the DW factors for each of the elements. Single scattering paths used in the fits -- for the octahedral symmetry: (1) Fe2-O, Ndeg = 6, Reff = 2.0602; (2) Fe2-Fe2, Ndeg= 6, Reff = 2.9684 Å; (3) Fe2-Fe1, Ndeg= 6, Reff = 3.4807 Å; (4) Fe2-O, Ndeg= 2, Reff = 3.5671 Å; (5) Fe2-O, Ndeg= 2, Reff = 3.6588 Å -- for the tetrahedral symmetry: (1) Fe1-O, Ndeg = 4, Reff = 1.8861 Å; (2) Fe1-Fe2, Ndeg= 12, Reff = 3.4807 Å; (3) Fe1-O, Ndeg= 12, Reff = 3.4933 Å; (4) Fe1-Fe1, Ndeg= 4, Reff = 3.6355 Å; (Ndeg – path degeneracy, Reff – half path length; effective range)

Table S1: Parameters and fit results for the Fe EXAFS

Aocta / Atetra / ΔE0 (eV) / σ2O (Å2) / σ2Fe (Å2) / Reduced χ2
Fe3O4 / 1st shell / 0.36(6) / 0.22(5) / -12.6(7) / 0.0035(9) / 0.0044(9) / 673.17
2nd shell / 0.36* / 0.22*
SAMPLE 1 / 1st shell / 0.21(3) / 0.25(2) / -5.7(5) / 0.0035** / 0.0044** / 239.24
2nd shell / 0.24(3) / 0.11(3)
SAMPLE 2 / 1st shell / 0.15(3) / 0.17(2) / -5.6(7) / 0.0035** / 0.0044** / 197.97
2nd shell / 0.14(3) / 0.07(3)

* 1st and 2nd shell fitted with the same amplitude parameter

** value from bulk Fe3O4 kept constant