Detection of hydrogen peroxide using an optical fiber-based sensing probe

A sensing probe for hydrogen peroxide (H2O2) in solution at low concentrations has been developed by deposition of Prussian blue dye in a multi-layer structure of polyelectrolytes onto the tip of a multi-mode optical fiber. The sensing mechanism of this optrode (optical electrode) relies on the oxidation of Prussian white (reduced form of Prussian blue) in the presence of hydrogen peroxide. The sensing capabilities of the probe can be recovered by ex situ reduction of Prussian blue to Prussian white using ascorbic acid. A first set of experiments yielded a linear-log relationship between the peak intensity of the reflected light and the concentration of hydrogen peroxide. The intensity of the light, relative to the intensity at immersion, showed an inverse exponential dependency on the time required to reach the saturation for each H2O2 solution tested. Subsequent experiments in which the sensing probe was exposed to H2O2 solutions with different concentrations, showed that only the time-dependent behavior of the intensity of the light remained. Furthermore, the response time for the intensity to reach 63% of its peak value was found to be linearly dependent on the concentration of the H2O2 in a log–log scale. Reproducible results were for H2O2 concentrations ranging from 10 μmol L−1 up to the maximum concentration tested of 1 mmol L−1. This range of concentrations makes this sensing probe suitable for the remote detection of H2O2 as a by-product of biological reactions and electrochemical reactions in polymer electrolyte membrane fuel cells.