Magnetic Nanoparticle Preparation Methods

Co-precipitation Method Co-precipitation is one of the most conventional procedures to obtain magnetic nanoparticles. Iron oxide nanoparticles as well as mixed oxide particles can be obtained. The key in this method lies in the control of pH during the synthesis procedure. Mixed oxide magnetic nanoparticles can be obtained by co-precipitation of stoichiometric quantities of the ions involved.

Iron oxide magnetic nanoparticles synthesis consists of the mixture of ferric and ferrous salts in 1:2 iron molar ratios. The reaction can occur either at room temperature or at high temperature and the key is the increase of pH by the addition of an alkali. When pH is lower than 11 nucleation of Fe3O4 is facilitated meanwhile at an increase of pH over 11 it undergoes growth of the nucleus.

In general, the reaction needs gas protection to prevent oxidation of Fe(II) to obtain a better performance in the synthesis of magnetite as the final product.

stabilizers such as oleic acid [24], poly(N-vinyl pirrolidone) (PVP) [25], and sodium dodecyl sulfate [23] could be used to make o controlled size and shape nano-magnetite at room temperature and without control on inert atmosphere

Magnetite nanoparticles were synthesized by co-precipitation applying modifications with respect to the traditional methodology [15, 28]. Briefly, 5.4075g of FeCl3.6H2O and 2.8g FeSO4.7H2O (ratio Fe3+/Fe2+= 2/1)were dissolved in 100 ml of distilled water using a magnetic stirrer at room temperature and in absence of inert atmosphere. Different amounts (0– 1.0g) of SDS were added to this solution under stirring. The magnetite precipitation was achieved by raising the pH of the mixture to 12 by addition of different volumes of alkali. The alkali addition was performed at controlled rate to minimize aggregation. The described procedure was carried out in presence and absence of visible light generated by a tungsten lamp. The lamp was placed 10 cm from the reactor with a 90 degrees angle. Finally, the obtained dark solution was decanted using a magnet and the supernatant was extracted. The precipitate was washed several times with distilled water or a mixture ethanol/distilled water 50/50 solution. This procedure was repeated until pH and conductivity reached the levels corresponding to distilled water. The solid was dried in oven at 45◦C overnight under vacuum. The inverted co-precipitation was conducted by adding the Fe2+ /Fe3+ aqueous solution containing the proper amount of SDS to the alkali solution