We describe herein a novel type of monodisperse water-soluble magnetite nanoparticle coated with pheomelanin using an environmentally-friendly approach in aqueous medium. The results indicate superparamagnetic behaviour at room temperature and show improved negative contrast in T2-weighted MRI with a transverse relaxivity of 218 mM(-1) s(-1).
Three novel non-enzymatic sensors based on the modification of a glassy carbon electrode with nanoparticles of Fe 3+ , Cu 2+ or Ni 2+ Prussian blue derivatives (PB) are proposed herein. The Fe 3+ -, Cu 2+ -and Ni 2+ -modified Prussian blue nanoparticles were supported in an environmentally-friendly chemical product known as melanin. The nanomaterials prepared were characterized by transmission electron microscopy (TEM) images, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The drop casting method was used to build the enzymeless sensors, which were able to catalyze the oxidation of hydrogen peroxide at +1.5 V. The calibration curves obtained by amperometry were linear in the range of 0.1 to 13.0 mmol L -1 . Several figures of merit were obtained in order to characterize the analytical electrochemical behavior of the as-prepared sensors. For instance, the detection limits achieved were 0.14, 0.32 and 0.57 µmol L -1 for the melanincapped modified Prussian blue nanoparticle sensor containing respectively Fe 3+ , Cu 2+ and Ni 2+ ions. These values are lower than the detection limits provided by other non-enzymatic sensors. The sensors were applied for the detection of hydrogen peroxide in tooth whitening gel. The results obtained were compared with those of the standard method.Index Terms-Non-enzimatic amperometric sensors, Prussian blue derivatives, nanoparticles, hydrogen peroxide, tooth whitening gel.
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