Nonenzymatic Amperometric Sensors for Hydrogen Peroxide Based on Melanin-Capped Fe3+-, Cu2+-, or Ni2+-Modified Prussian Blue Nanoparticles

Three novel nonenzymatic sensors based on the modification of a glassy carbon electrode with nanoparticles of Fe³⁺, Cu²⁺, or Ni²⁺ Prussian blue (PB) derivatives are proposed herein. The Fe³⁺-, Cu²⁺-, and Ni²⁺-modified PB nanoparticles were supported in an environmentally friendly chemical product known as melanin. The nanomaterials prepared were characterized by transmission electron microscopy images, electrochemical impedance spectroscopy, and cyclic voltammetry. The drop casting method was used to build the enzymeless sensors, which were able to catalyze the oxidation of hydrogen peroxide (H2O2) at +1.5 V. The calibration curves obtained by amperometry were linear in the range of 0.1-13 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 melanin-capped modified PB nanoparticle sensor containing, respectively, Fe³⁺, Cu²⁺, and Ni²⁺ ions. These values are lower than the detection limits provided by other nonenzymatic sensors. The sensors were applied for the detection of H₂O₂ in tooth whitening gel. The results obtained were compared with those of the standard method.