2.2. Preparation of iron oxide magnetic nano- particles
The iron MNPs were synthesized in aqueous solution using a
modified version of the co- precipitation method previously reported [9].
De- ionized water was de- aerated by sparging with nitrogen for 15
minutes. 4.4 g of FeCl3.6H2O and 1.98 g of FeCl 2.4H2O were dissolved in
61 mL of the de- aerated water while the solution was continuously
sparged with nitrogen (Airgas) to agitate the mixture and to prevent the
oxidation of Fe+2 ions. After the complete dissolution of the iron
compounds, sparging was maintained for an additional 30 minutes. The
solution was then ultra - sonicated while the space above the solution was
continuously purged with nitrogen. 143 mL of 0.7 M NH4OH was then
added drop wise to the above Fe ion solution and the basified solution
was then ultra - sonicated for an additional 10 minutes. During the slow
addition of NH4OH, it was noticed that the solution color changed from brown to dark brown and then to black. The black iron oxide product was found to be strongly magnetic. To isolate the MNP product, the black particles were separated from liquid with the use of a magnet bar, and were washed with absolute ethanol. The rinsing and separation process was repeated three times. The final product was dried in vacuum overnight.