Electrogenerated Chemiluminescence. 66. The Role of Direct Coreactant Oxidation in the Ruthenium Tris(2,2‘)bipyridyl/Tripropylamine System and the Effect of Halide Ions on the Emission Intensity

Abstract

We describe the electrogenerated chemiluminescence (ECL) processes of the Ru(bpy)3(2+) (bpy = 2,2'-bipyridyl)/ tripropylamine (TPrA) system at glassy carbon, platinum, and gold electrodes. The electrochemical behavior of TPrA on different electrode materials and its influence on the ECL process are demonstrated. At glassy carbon electrodes, the direct oxidation of TPrA began at approximately 0.6 V vs SCE and exhibited a broad irreversible anodic peak. Two ECL waves were observed, one in the potential region more negative than 1.0 V vs SCE and one at more positive potentials. The first ECL process apparently occurs without the electrogeneration of Ru(bpy)3(3+), in contrast to that of the second ECL wave. At Pt and Au electrodes, however, the formation of surface oxides significantly blocked the direct oxidation of TPrA. An ECL wave below 1.0 V did not appear at Pt and was very weak at gold. The ECL peaks at potentials of 1.1-1.2 V were also much weaker than those observed at the glassy carbon electrode. These results showed that the direct oxidation of TPrA played an important role in the ECL processes. Therefore, the enhancement of the TPrA oxidation current might lead to an increase in the ECL intensity. Small amounts of halide species were found to inhibit the growth of surface oxides on Pt and gold electrodes and led to an obvious increase of TPrA oxidation current. The anodic dissolution of gold in halide-containing solution was also important in activating the gold electrode surface. The electrochemical catalytic effect of bromide further promoted the oxidation of TPrA. A halide effect on ECL at Pt and Au electrodes was also evident. The most effective enhancement of ECL was observed at Au electrode in a bromide-containing solution. This effect was also found in an commercial flow-through instrument (IGEN) and provided a simple way to improve the detection sensitivity at low concentrations of Ru(bpy)3(2+).

Simple Electrochemiluminescence Sensor Based on Nafion-Graphene-Ru(bpy)32+Modified Electrode for the Ultrasensitive Detection of Tetrodotoxin

“…The homogeneous catalytic reaction between TPA and electrogenerated Ru(bpy) 3 3+ plays the dominant role in the ECL process, so the influence of scan rate on the ECL intensity is attributed to the chemical kinetics of the ECL system and the rate of TPA diffusion to the electrode surface. 15,29,31 Fig. 6B reveals that the highest ECL intensity obtained when scan rate is 0.10 V · s −1 .…”

“…27 The pH of the detection solution mainly affects the efficiency of Ru(bpy) 3 2+ electrooxidation, which was in agreement with the usually optimum pH value of 7.0-8.0. [28][29][30] The ECL response is attributed to protonation of the TPA at low pH, and then depend on formation of excited state Ru(bpy) 3 2+ * . Fig.…”

Quenching of the Electrochemiluminescence of Tris(2,2′-bipyridine)-ruthenium(II) by Sodium Diphenylamine-4-sulfonate

“…1a, a typical ECL intensity-potential curve for the Ru(bpy)3 2+ /TPrA system with 1.0 mM Ru(bpy)3 2+ and 0.05 M TPrA is presented. Two ECL peaks were observed while sweeping the potential from 0 to 1.5 V. The first peak began to appear at about 0.85 V, and reached the maximum at about 0.95 V. This peak can be described as follow: 17,18 TPrA -e → TPrA· + ,…”

“…25 and 0.05 M TPrA, a scan was made between 0 and 1.5 V, with a current increase beginning at 0.7 V and reaching its peak potential at about 1.1 V, signaling the direct oxidation of TPrA. 18 Compared without SDS in the mixed solution (Fig. 4a), a new oxidative peak was observed at about 0.67 V in the presence of SDS.…”

Cuvette‐Based Electrogenerated Chemiluminescence Detection System for the Assessment of Polymerizable Ruthenium Luminophores

“…[5] Ru While mechanistically far more complex, this system has the advantage of producing ECL through two simultaneous heterogeneous oxidations that are accessible at the same potential. [6] This feature of the coreactant mechanism combined with the intrinsic advantages of ECL (e. g. increased analyte selectivity, low background signal, simplified optics requirements, and no need for a light-based excitation source), has developed ECL into a highly attractive luminescence methodology for analytical assays. [7] ECL instrumentation can be summarized as an electrochemical cell designed to orient the photodetector directly to the source of ECL emission, most often the working electrode face.…”