Surface Modified Iron Oxide Nanoparticles as Fe Source Precursor to Induce the Formation of Prussian Blue Nanocubes

Nano-sized Prussian blue (PB) cubes were synthesized at room temperature by simply stirring the mixture of surface modified iron oxide nanoparticles (IONPs) and potassium ferrocyanide in an aqueous acid solution. The nanocubes were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The influence of different molecules modified on the surface of IONPs on the cube formation was discussed. The surface modification with dimercaptosuccinic acid (DMSA), 3-aminopropyltriethoxysilane (APTS) and citric acid (CA) all displayed a key role in the formation precess of PB nanocubes, but which could not be formed as bare IONPs or Fe3+ were used as precursor. Combined with the reaction process tracing with UV-vis absorption spectroscopy and TEM, a possible kinetically controlled growth mechanism was proposed where slower formation rate of amorphous PB due to very low release rate of Fe ions from the surface modified IONPs and subsequent recrystallization are responsible for the obtained PB nanocubes. The peroxidase-like catalytic activity of the synthesized nanocubes was investigated and catalysis was found to follow Michaelis-Menten kinetics. The potential of using such PB nanocubes as an effective MRI contrast agent was also demonstrated.