Ratiometric electrochemical sensing and biosensing based on multiple redox-active state COFDHTA-TTA

Here, a covalent organic framework with multiple redox-active state synthesized by amine-aldehyde condensation reaction between 4,4', 4 '''-(1,3,5-triazine-2,4,6-triyl) trianiline and 2,5-dihydroxy terethaldehyde (COFDHTA-TTA) was used as novel electrochemical sensing and biosensing platform at first time. The COFDHTA-TTA was demonstrated to be two-dimensional nanosheets with highly ordered conjugated structure and uniform mesopores about 3.67 nm. Electrochemical studies revealed that a ratiometric electrochemical sensor could be constructed by using COFDHTA-TTA itself as electroactive materials to determine hydrogen peroxide (H2O2) and pH level based on both current and potential signals. The single electrochemical sensor could monitor H2O2 concentration from 5.66 mu M to 400 mu M and pH level ranging from 11.0 to 3.0. Considering that the COFDHTA-TTA had good catalytic activity for oxygen reduction reaction in 0.2M PBS (pH=7.0), glucose oxidase was further loaded on COFDHTA-TTA via its nanosized pores and abundant active sites originated from N-doped skeleton, and the glucose biosensor exhibited good performances for glucose detection from 1.26 mu M to 6.0mM at -0.30 V, as well as from 0.60 mu M to 6.0mM at -0.53 V. The work provided good examples to construct electrochemical sensors based on redox-active COF.