Carbon Nitride Quantum Dots Enhancing the Anodic Electrochemiluminescence of Ruthenium(II) Tris(2,2′-bipyridyl) via Inhibiting the Oxygen Evolution Reaction

Abstract

Although electrochemiluminescence (ECL) has been developed significantly in the past few decades, ECL efficiency in aqueous solutions remains quite low. Determination of the energy losses and development of new ECL-enhancing strategies are still of great value. In this work, we discovered a detrimental nonradiation relaxation pathway by a concurrent oxygen evolution reaction (OER) process in a well-known ruthenium­(II) tris­(2,2′-bipyridyl) (Ru­(bpy)3 2+) aqueous ECL system due to similar surface-sensitive characteristics, and for the first time, a chemical strategy was developed by which carbon nitride quantum dots (CNQDs) could inhibit the surface OER process, alleviate the energy losses by nonradiation relaxation, and enhance the anodic ECL of Ru­(bpy)3 2+. In the Ru­(bpy)3 2+/CNQD system, CNQDs could enhance the anodic ECL of Ru­(bpy)3 2+ in a nitrogen stream (10-fold) and ambient air (161-fold). The luminous and nitrogen-rich CNQDs were also confirmed not to serve as ECL luminophores, anodic coreactants, or donor/acceptors in ECL. The coreactant-free Ru­(bpy)3 2+/CNQD system possesses several advantages over the common coreactant ECL system, such as low dosage (100 μg/mL CNQDs), favorable regeneration capacity, etc. As an example, ECL on–off detection of dopamine utilizing the Ru­(bpy)3 2+/CNQD system was also developed to show prospects in ECL sensing. Besides, CNQDs were introduced into the classical Ru­(bpy)3 2+/C2O4 2– coreactant ECL system, leading to suppressed OER and improved ECL signal. Overall, the proposed new ECL-enhancing strategy is promising for applicable ECL sensing, could be extended to other ECL luminophores with high oxidation potential, and enables an in-depth understanding of the ECL process and mechanism.

Insights into enhanced electrochemiluminescence of a multiresonance thermally activated delayed fluorescence molecule

“…[15][16][17][18][19] For example, [Ru(bpy) 3 ] 2+ , the most widely employed ECLphore, is usually used as the gold standard to determine relative ECL efficiency. [19][20][21][22] However, the absolute ECL efficiency of [Ru(bpy) 3 ] 2+ is still quite low (0.0019% in a potentiodynamic process or ~5% at a rotating disk-ring electrode), reflecting its low photoluminescence quantum yield (ɸ PL = 9.5% in degassed MeCN). 21,22 The low quantum efficiency of many ECL materials significantly limits their use in practical applications.…”

A flexible and bright surface-enhanced electrochemiluminescence film constructed from efficient aggregation-induced emission luminogens for biomolecular sensing

“…The LOD is determined to be 3.16 × 10 −16 M, by far lower than those of materials in previous reports (Table S1, ESI†). 40–53 The high sensitivity is attributed to the high ECL intensity of the film. Moreover, the large surface area of the film facilitates the diffusion of DA, leading to superior sensitivity.…”

Light Scattering and Luminophore Enrichment-Enhanced Electrochemiluminescence by a 2D Porous Ru@SiO2 Nanoparticle Membrane and Its Application in Ultrasensitive Detection of Prostate-Specific Antigen

“…The impact of scan rates on current was also studied as shown in Figure S3, which displayed that the maximal current values increased linearly with the square root of scan rate (ν 1/2 ), from which we can conclude that the electrochemical process was a diffusion-controlled process. In addition, since the oxygen evolution reaction occurs near the potential window of the ECL reaction, the maximal current values might contain the current of the oxygen evolution reaction, which makes the weak oxidation peak at ∼1.05 V hard to be observed at a high scanning rate. A multicycle ECL intensity variation test of the Ru@SiO 2 -NM (Figure S4) displayed that Ru­(bpy) 3 2+ molecules were released from the electrode surface to the bulk solution gradually; at the beginning, the Ru­(bpy) 3 2+ molecules diffuse quickly into the bulk solution due to the large concentration gradient, but the diffusion process slows down with the decrease in the concentration gradient.…”