Chiral Twin-Electrodes for Amplifying the Faradaic Current of Enantiomers via Redox Cycling

Redox cycling (RC) is often used to amplify the faradaic current associated with the electrochemical transformation of redox-active species. For a given concentration, this allows a considerable increase in sensitivity and an improvement in the detection limit of analytical devices. However, all previous reports have focused only on the detection of achiral molecules, e.g., ferrocene derivatives. In this contribution, we report an original setup composed of two metal electrodes encoded with chiral features, facing each other to form a microchannel. The presence of the same chiral feature on the two parallel-oriented electrodes enables the preferential cyclic transformation of a specific enantiomer. It will be more easily oxidized at the anode with the right chirality and can subsequently diffuse across the microchannel to be reduced back into the starting enantiomer at a cathode with an identical chiral feature. As a function of the width of the microchannel, this cycle is repeated multiple times, significantly enhancing the overall current in terms of chiral recognition. Herein, we illustrate this fundamental concept with mesoporous Pt-Ir alloy electrodes, imprinted with either L-DOPA or D-DOPA as transducers constituting the microchannel. The latter allows an amplification of the analytical signal of DOPA as a model compound by more than one order of magnitude and with an enantiodiscrimination efficiency reaching 90%. Thus, the proposed strategy opens up very interesting perspectives for chiral-sensing applications.