A Viologen-Eu(III)-Modified TiO2 Electrode for Electroswitchable Luminescence and Coloration

A europium(III) [Eu(III)] complex and a viologen derivative were covalently immobilized on a porous titanium(IV) dioxide (TiO2) electrode by the interaction of carboxyl and phosphate groups with the surface, demonstrating electrochemically induced photoluminescence and coloration switching. The modulation of emission and coloration using the functional Eu(III)-viologen modified TiO2 electrode was achieved by an electrochemical reaction between TiO2 and the viologen derivative. Luminescence control was induced via electron and energy transfer from the Eu(III) complex to TiO2 and the linked viologen derivative. The dual functional electrode showed a high on-off emission contrast (81:1), short response time (off: 2.5 s at -0.8 V, on: 5 s at 0 V), and high stability (over 150 cycles) for both emission and coloration control.