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Real Time measurement of nanosized magnetite synthesis

With a custom made magnetic susceptometer and a custom made mixing unit, we can follow – at a well below sub second pace – the actual chemical reaction between an iron salt solution and a base where superparamagnetic nanosized magnetite particles are synthesized. A major finding is that the reaction with ammonia is orders of magnitude faster than with sodium hydroxide, although ammonia is a much weaker base. A puzzling observation nobody has volunteered to explain.

The mixer with the two syrings in the background, and the vial in the susceptometer to the left in the foreground.
Comparison of magnetic responses from rapid mixing (RM) and slow mixing (SM) of iron solutions with ammonia as precipitation medium. In-phase susceptibility is to the left scale, and the out-of-phase susceptibility is to the right scale. Iron ion concentration was 0.1 M and 2 M ammonia.

Collaboration with Richard Olsson, Fiber & Polymer Dept., KTH

V. Ström, R. T. Olsson och K. V. Rao, "Real-time monitoring of the evolution of magnetism during precipitation of superparamagnetic nanoparticles for bioscience applications," Journal of Materials Chemistry, vol. 20, no. 20, s. 4168-4175, 2010