Magnetic nanoparticles are of great importance for both technical and medical applications. Our focus is on the production and application of magnetite-based nanoparticles.
For the preparation of these nanoparticles we use the following wet chemical methods:
- Partial oxidation of Fe(II) salts under alkaline conditions1
- Co-precipitation of Fe(II) and Fe(III) in the stoichiometric ratio2
The precipitation according to method (1) is carried out under in situ pH measurements and the pH-time graph is used as a parameter to control the particle size. With this method we are able to produce magnetite nanoparticles in the following size ranges:
- 15-35 nm (Ø 25 nm),
- 30-70 nm (Ø 40 nm),
- 40-90 nm (Ø 70 nm) and
- 70-150 nm (Ø 120 nm)
The preparation of the superparamagnetic nanoparticles with mean core diameter < 16 nm is carried out according to method (2) under a constant pH. Here we use the position of the precipitation pH in comparison to the charge zero point of the surface tension (PZC) to selectively influence the particle size and particle distribution.
1 T. Sugimoto and E. Matijevic, Journal of Colloid and Interface Science 74 (1980)1, 227-243
2 L. Vayssieres, E. et al., Journal of Colloid and Interface Science 205 (1998) 205-212
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