(420s) The Effects of Synthesis Method on the Physical and Chemical Properties of Iron Oxide Nanoparticles

The method by which dextran coated iron oxide nanoparticles are synthesized greatly affects the physical and chemical properties of the nanoparticles. To study this, dextran coated iron oxide nanoparticles were synthesized via four different synthesis methods, which varied the timing of ammonium hydroxide and dextran addition to the iron salt solution in the formation of iron oxide nanoparticles. The four synthesis methods were two-step, semi-two-step, simultaneous semi-two-step, and one-step reactions. The one-step reaction was then synthesized using different amounts of dextran. The nanoparticles were characterized for size, stability, coating percent, crystallinity/crystal size, and AMF heating properties.  In the two-step synthesis, the iron oxide nanoparticles were formed and washed prior to coating with dextran. The semi-two-step first formed the iron oxide nanoparticles via addition of ammonium hydroxide prior to dextran coating but without a washing step in between. For the simultaneous semi-two-step method, the dextran and ammonium hydroxide solutions were injected simultaneously into the iron salt solution, and finally, the one-step reaction formed the iron oxide nanoparticles in the presence of dextran.

The physical and chemical properties of the dextran coated iron oxide nanoparticles were characterized for each synthesis method. The variability between the methods as well as the variability within each synthesis method was evaluated. The two-step method resulted in nanoparticles with high crystallinity and good heating properties. However, the stability in PBS over time was lower than the other synthesis methods due to the larger size and less dextran coating on the surface of the nanoparticles. The other extreme, the one-step method, resulted in highly stable nanoparticles due to a smaller hydrodynamic diameter, but these particles lacked the heating properties of the other synthesis methods. This is most likely due to the high viscosity of the dextran solution present during the nanoparticle formation. When the viscosity of the solution was reduced by decreasing the dextran amount to 1 gram, the heating properties dramatically increased, but the size and stability of the nanoparticles was compromised. The other two synthesis methods resulted in the physical and chemical properties of the iron oxide nanoparticles being somewhere in between the two-step and one-step methods. The semi-two step synthesis was found to have the most batch-to-batch variability due to the separate injections of ammonium hydroxide and dextran into the reaction vessel. The simultaneous semi-two-step had reduced batch-to-batch variability as well as adequate heating properties, size, and stability. Overall, this study demonstrated how the synthesis method of dextran coated iron oxide nanoparticles directly affects the chemical and physical properties of the nanoparticles. Additionally, each method led to a different amount of variability in the properties of the nanoparticles.