Why were alternating-current-driven electrochemiluminescence properties from Ru(bpy)₃²⁺ dramatically improved by the addition of titanium dioxide nanoparticles?

Abstract

Electrochemiluminescence (ECL) is a phenomenon in which light is emitted from the excited state of a redox-active material generated by electrochemical reactions. Among light-emitting devices, ECL devices have various advantages in terms of structure and ease of fabrication, and therefore, they are expected to be next-generation emitting devices. In this study, we introduced rutile-type titanium dioxide nanoparticles (TiO2 NPs) in a Ru(ii)-complex-based electrolyte to improve the emission properties of an alternating current (AC)-driven ECL device. The properties of the ECL device with TiO2 NPs were greatly improved (emission luminescence, 165 cd m(-2); half-life time, 1000 s) compared to a previously reported AC-driven ECL device without nanoparticles. To determine how TiO2 NPs helped in achieving high emission luminescence and long-term stability, we measured the optical and electrochemical properties of the Ru(bpy)3(2+)-based ECL solution in detail. The PL intensity of Ru(bpy)3(2+) was increased by adding TiO2 NPs, which indicated that the suppression of non-radiative quenching of the complex's excited states could improve the ECL intensity. With respect to the enhanced stability, electron transfers between Ru(bpy)3(2+) and TiO2 were suggested by detailed electrochemical measurements. These electron transfers occurred from the reduced Ru(bpy)3(2+) species to the TiO2, and subsequently, from the TiO2 to the oxidized Ru(bpy)3(2+) species. Such electron transfers are thought to improve the balance of the redox reactions in the ECL device, leading to long-term stability.

Balancing the Concentrations of Redox Species to Improve Electrochemiluminescence by Tailoring the Symmetry of the AC Voltage

“…Recently, Tsuneyasu et al extracted the collection efficiency of Ru(bpy) 3 * 1 + and Ru(bpy) 3 * 3 + from RRDE experiments in a PC solution. [24] As a result, a lower collection efficiency of Ru(bpy) 3 * 1 + was observed, which implies relatively poorer stability of Ru(bpy) 3 * 1 + , similar to our findings in CV experiments.…”

Ultrafast Response in AC-Driven Electrochemiluminescent Cell Using Electrochemically Active DNA/Ru(bpy)3 2+ Hybrid Film with Mesoscopic Structures

“…As just discribed, the AC-driven, DNA/Ru(bpy) 3 2+ hybrid film-based ECL device showed extremely fast turn-on response compared to the solution-based device, even though its maximum emission intensity was relatively lower. The maximum luminance in the hybrid film based ECL device was still smaller than that in solution based ECL device (~120 cd/m 2 at 50 Hz 22 ). One of the reasons is because effective electrode area for redox reaction on DNA/Ru(bpy) 3 2+ -modified electrode was smaller than that on conventional flat ITO electrode.…”

Reflective‐Emissive Representation by Combining Ru(II)‐Complex‐Based Electrochemiluminescence and Localized‐Surface‐Plasmon‐Resonance‐Based Electrochromism

“…; this agrees with the results of previous studies. [12] During the emissive state, the device did not change transmittance because of the fast consecutive reactions of oxidation and reduction. Additionally, we carried out the switching test of the DMD device, switching between the transparent, mirror, and emissive states by the sequential application of the following biases: −2.3 V DC voltage (350 s), +1.0 V DC voltage (350 s), and ±3.0 V, 50 Hz AC voltage (5 s).…”