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Magnetite (Fe3O4) nanoparticles modified with electroactive Prussian Blue (PB) were first synthesized by a simple chemical method. Transmission electronic microscopy showed that the average size of the sample was about 12 nm, and X-ray powder diffraction, X-ray photoelectron spectroscopy, Fourier-transform IR, and UV−vis spectra showed the spinel structure for the nanoparticles and confirmed the existence of PB on the surface of Fe3O4. Magnetic properties of the sample were investigated by low-field alternating current susceptibility and superconducting quantum interference device measurement; the results indicated that the superparamagnetic properties remain for the sample with almost immeasurable remanence and coercivity at room temperature, while the value of saturation magnetization (Ms) reduces, and the blocking temperature (TB) of PB modified Fe3O4 is around 150 K, lower than that of the pure Fe3O4 nanoparticles, so the interaction between the particles is decreased. More interesting, when at 5 K, the Ms of PB-modified Fe3O4 is greatly larger than that at 300 K and shows ferromagnetic behavior. Furthermore, PB-modified Fe3O4 nanoparticles have been immobilized on the surface of glassy carbon electrode and applied to construct a sensor, it showed two well-defined pairs of redox peaks and a dramatic catalysis for the reduction of H2O2, which might be exploited to develop a new type of biosensor without any mediator.
Zhao et al. (Fri,) studied this question.