Core/shell microcapsules consisting of Fe3O4 microparticles coated with nitrogen-doped mesoporous carbon for voltammetric sensing of hydrogen peroxide

The authors describe the preparation of core/shell composites consisting of Fe3O4 microparticles coated with nitrogen-doped mesoporous carbon. Synthesis was accomplished by simultaneous reduction of template α-Fe2O3 and pyrolysis of a nitrogen-containing poly(ionic liquids). The mesoporous composites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffractometry and adsorption/desorption isotherms. The characterizations prove successful formation of an Fe3O4 core and an outer shell (coating) consisting of nitrogen-doped mesoporous carbon. The material was placed on a glassy carbon electrode and synergistic catalytic effect of of N-doping, the mesoporous, core/shell structure and two types of active sites properties between Fe3O4 core and nitrogen-doped mesoporous carbon shell is shown to result in superior electrochemical activity towards the reduction of hydrogen peroxide. Figures of merit include (a) a sensitivity of 77.1 μA mM−1 cm−2; (b) a linear response over the 50 μM to 33 mM H2O2 concentration range, (c) a 5.9 μM detection limit of (at an S/N ratio of 3), and (d) a low working voltage of −0.4 V (vs. saturated calomel electrode) which makes the method more selective.