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

Abstract

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.

Electroluminochromic Materials and Devices Based on Metal Complexes

“…Next, an ELC device wasp repared by attaching the luminescent complex Eu-4 and the viologen derivative to the porousT iO 2 electrode through carboxyl and phosphate groups. [66] Thed evice had excellent performance, such as rapid response time, high switchingl uminescence contrast, and good repeatabilityo fe lectrochemical luminescence modula-tion. The viologen-Eu-4-modified electrode exhibited strong red emission when no voltage was applied.However,the emission was completely quenched at an applied potential bias of À0.8 Vf or only 5s.T he electrode achieved an "on-off"e mission contrast of 81:1 and the emission switch was consistent over 150 cycles,w hich was attributed to the electron transfer between Eu-4 and TiO 2 electrode as well as the electron and energy transfers between Eu-4 and the reduced viologen derivative.…”

“…The response time and repeatability of the luminescence switch were significantly improved. Next, an ELC device was prepared by attaching the luminescent complex Eu‐4 and the viologen derivative to the porous TiO 2 electrode through carboxyl and phosphate groups . The device had excellent performance, such as rapid response time, high switching luminescence contrast, and good repeatability of electrochemical luminescence modulation.…”

Magenta-Blue Electrofluorochromic Device Incorporating Eu(III) Complex, Anthracene Derivative, and Viologen Molecule

“…Owing to these optical properties, Ln(III) complexes have broad application for bioassays/bioimaging, sensors, and display devices [ 32 , 33 , 34 , 35 ]. Previously, we reported electrochemical modulation of both absorption and luminescence using Eu(III) complex, a luminescent Ln(III) complex, as a photoluminescent molecule, and electrochromic viologen derivatives [ 36 , 37 , 38 , 39 ]. By developing an electrochemical device comprising an electrolyte solution dissolving the Eu(III) complex and viologen derivatives, the modulation of luminescence and coloration was demonstrated by the use of electrochromic reaction of viologen derivatives.…”