Electrofluorescence switching of tetrazine-modified TiO₂ nanoparticles

Highly fluorescent tetrazine-modified TiO₂ nanoparticles were prepared by the reaction of triethoxysilane-appended chloroalkoxy tetrazine (ESTZ) with TiO₂ nanoparticles through a condensation reaction between the surface hydroxyl groups of an electrode and the silane anchor group of ESTZ. The prepared electrodes were used as robust fluorescent layers for electrochemical fluorescence switching (electrofluorochromism) applications in the presence of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) as a charge balancing mediator. The stable charge balancing mediator, TEMPO, in the electrolyte was found to be essential to reduce the intrinsic electron transport resistance of TiO₂ in order to achieve reversible electrofluorescence switching. Furthermore it facilitated a fully reversible electrochemical reaction and provided a sufficient charge balance, which allowed us to realize semiconductor-based electrofluorescence switching with an on/off ratio of 4.0 and cyclability greater than 100 cycles.