Figure 1.
XRD patterns obtained of co-precipitation products.
Increasing growth times yield larger particles as indicated by narrowing Bragg peaks. Magnetite peak indexing is given in brackets. Unindexed weak peaks are from an internal α-SiO2 standard for sample-detector distance calibration.
Figure 2.
TEM images of magnetite nanoparticles grown for 480 min.
a) Aggregate composed of several particles in the stable single-domain size range and smaller particles. b) HRTEM of edge of the 45 nm marked particle in (a), inset: FFT with indexed reflections, zone axis [-112]. c) large, presumably multi-domain particle, d) HRTEM of particle corner in (c), inset: FFT with indexed reflections, zone axis [001].
Figure 3.
Plot of particle size over growth time for the synthetic particles (black squares, size measured from peak broadening of XRD patterns) and magnetite particle growth within magnetotactic bacteria M. gryphiswaldense (red circles, size measured from TEM images as described in [31], [35]).
Error bars represent standard deviations of the mean particle sizes determined by XRD peak broadening for synthetic samples (black) and standard deviations of crystal size distributions measured by TEM for bacteria (red).
Table 1.
High resolution X-ray diffraction measurements, derived oxidation parameter and average oxidized layer thickness.
Figure 4.
Magnetic properties at 300 K and 5K.
Hysteresis measurements of magnetite with increasing particle size. Note that samples marked with (*) were estimated in µg range.
Table 2.
Summarized properties of the synthesized magnetite particles including the required growth time, the mean grain size as determined by XRD and coercivity at 300 K and 5 K as determined by hysteresis measurements.