Magnetite (Fe 3 O 4 ) 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, Fouriertransform IR, and UV-vis spectra showed the spinel structure for the nanoparticles and confirmed the existence of PB on the surface of Fe 3 O 4 . Magnetic properties of the sample were investigated by lowfield 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 (T B ) of PB modified Fe 3 O 4 is around 150 K, lower than that of the pure Fe 3 O 4 nanoparticles, so the interaction between the particles is decreased. More interesting, when at 5 K, the Ms of PB-modified Fe 3 O 4 is greatly larger than that at 300 K and shows ferromagnetic behavior. Furthermore, PB-modified Fe 3 O 4 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 H 2 O 2 , which might be exploited to develop a new type of biosensor without any mediator.

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Ionic liquid surfactants are a class of ionic liquids (ILs), which can form micelles in the aqueous solution. In this paper, we demonstrate a novel extracting system based on the use of IL surfactants in ultrasonic-assisted extraction followed by HPLC analysis. No organic solvents were used in the extraction, making this method environmentally friendly and more attractive than the conventional organic solvent-based extraction methods. As an example, this method was applied to determine tanshinones in Chinese herbal medicine Salvia miltiorrhiza bunge. The effect of the carbon chain length of the IL cation, as well as other influencing factors on ultrasonic-assisted extraction, was investigated in detail. Under the optimized conditions, satisfactory extraction efficiency was achieved with the recoveries ranging from 87.5 to 107.6%, and the RSDs were lower than 6%. This work shows a promising prospect of the IL surfactants in the extraction of active ingredients from herbs.