Effect of pressure on the size of magnetite nanoparticles in the coprecipitation synthesis

The effect of pressure on the size of magnetite nanoparticles synthesized by the coprecipitation technique was studied. It is generally believed that pressure has negligible effects, if any, on liquid and solid reactions. However, in this work it was shown that pressure has a significant effect on the size of magnetite nanoparticles. This could be attributed to the very high surface-to-volume ratio of nanosized particles and to some other physical properties of magnetite, such as supersaturation and surface tension. The increase in the size of the nanoparticles is explained by the change in the Gibbs free energy value during crystallization from a homogeneous supersaturated solution at higher pressures. This phenomenon could find important applications especially in biomedicine where a limitation on the maximum size of the nanoparticles will be desired. (C) 2010 Elsevier B.V. All rights reserved.