H2O2 Ratiometric Electrochemical Sensors Based on Nanospheres Derived from Ferrocence-Modified Covalent Organic Frameworks

A uniform nanosphere derived from ferrocence-modified covalent-organic frameworks (COFETTA-TPAL-Fc(COOH)2) with 200 nm in diameter was prepared by dehydration condensation reaction between 4,4′,4′,4′- (ethane-1,1,2,2-tetrayl) tetraaniline and terephthalaldehyde in the presence of electroactive Fc(COOH)2. The Fc(COOH)2 was embedded into the layers of COFETTA-TPAL to result in the formation of nanospheres, which increased the specific surface area of the available COFETTA-TPAL to provide more active sites due to the increase in interlayer distance. The Fc(COOH)2 could interact with H2O2 which might undergo self-disproportionation process to produce O2 and be reduced into H2O simultaneously, whereas the generated O2 was directly reduced into H2O by COFETTA-TPAL. The reduction peak current of the generated O2 at −0.5 V (j–0.5 V) was gradually enhanced, whereas that of Fc(COOH)2 around 0.45 V (j0.45 V) was decreased with continuous adding of H2O2. Thus, the COFETTA-TPAL-Fc(COOH)2 nanospheres were used to fabricate a “on–off” nonenzymatic H2O2 ratiometric electrochemical sensor. The proposed “on–off” ratiometric electrochemical sensor showed good performance with a wide linear range of 1.1–500 μM, high sensitivity of 0.009 μM–1, and lower detection limit of 0.33 μM. The work would offer insights for design and preparation of electroactive COF and accelerate the practical application of COF in electroanalysis.