Nanoporous Cobalt Hexacyanoferrate Nanospheres for\nScreen-Printed H₂O₂ Sensors

Abstract

The\ndevelopment of highly sensitive hydrogen peroxide (H₂O₂) sensors of low cost with high stability is essential\nbecause of the significance of H₂O₂ in biological\nsystems and its practical applications in different fields. The present\nwork concerns the development of a highly sensitive flexible screen-printed\namperometric H₂O₂ sensor. Hexacyanoferrates\nare known to be excellent sensing materials for nonenzymatic electrochemical\nsensing of hydrogen peroxide (H₂O₂), but they\nhave certain limitations such as instability and low sensitivity.\nWe have developed a method for the synthesis of porous cobalt hexacyanoferrate\nnanospheres (CoHCF-NSp’s) (<50 nm size) by using EDTA as\na chelating agent. Increasing the EDTA concentration and heating the\nEDTA complex at 60 °C turned the microspheres of CoHCF into porous\nnanospheres due to the rapid nucleation of CoHCF. The synthesized\nporous nanospheres with high specific surface area and pore volume\nled to much improved electrochemical properties. The porous CoHCF-NSp’s\nwere used for the fabrication of a highly sensitive H₂O₂ sensor. Amperometric characterization of screen-printed sensors\nprepared using the CoHCF nanospheres showed a linear response in the\ndetection range of 0.002–1.13 mM with a detection limit of\n2.1 μM. The sensitivity of the sensor was found to be 329 μA·mM^–1·cm^–2, which is much better\nthan the sensitivities of most of the previously reported H₂O₂ sensors. The fabricated sensors were found to be stable\nat ambient temperature. The sensors were found to be effective in\nthe testing of real samples (lake water and flavored drink).