Colorimetric hydrogen peroxide and glucose sensors based on the destruction of micelle-protected iron(ii) complex probes

In this study, we present a facile and inexpensive colorimetric sensor for hydrogen peroxide (H2O2) and glucose based on the formation of an Fe3+ complex assisted by the Fenton reaction in a micellar medium. The mechanism of the sensor is based on the Fenton reaction occurring between the added H2O2 and ferrous ion (Fe2+) probe, which was stabilized by complexing with dithizone (Dz) before forming a micelle with the non-ionic surfactant Triton X-114 (TX-114). The extremely reactive hydroxyl radical (˙OH), the by-product of the Fenton reaction, exhibited much stronger oxidizing ability than H2O2, and thus strongly oxidized the stabilized Fe2+ ion, thereby accelerating the spectrophotometric response of the Fe3+ ion after coordinating with the thiocyanate ion (SCN−). The obtained absorbance of the Fe3+ and SCN− complex was related to the concentration of H2O2. Under the optimal condition, the micelle probe of Fe2+ exhibited good stability, without transforming to Fe3+ within 24 h. The sensor achieved an LOD of 5 μM and provided a linear range of 10 μM-4.0 mM for H2O2 determination. When coupled with glucose oxidase to generate a biosensing system, glucose was changed to H2O2 and could be measured down to 10 μM within a linear range of 10 μM-4.0 mM. The interferences naturally found in human blood plasma at the physiological level had no obvious effects on the glucose biosensor. According to the comparison with the hexokinase-spectrophotometric method used by hospitals, the results obtained from the proposed method for glucose measurements in human plasma samples were in good agreement (p > 0.05). This indicated the enormous potential of combining the Fenton reaction and micellar system-stabilized metal ion complex probes to design sensors for the alternative detection of H2O2 and glucose.