Voltammetric Study and Modeling of the Electrochemical Oxidation Process and the Adsorption Effects of Luminol and Luminol Derivatives on Glassy Carbon Electrodes

Abstract

Luminol is one of the most widely used electrochemiluminescence (ECL) reagents, yet the detailed mechanism and kinetics of the electrochemical oxidation of luminol remain unclear. We propose a model that describes the electrochemical oxidation of luminol as multiple electron transfer reactions followed by an irreversible chemical reaction, and we applied a finite element method simulation to analyze the electron transfer kinetics in alkaline solutions. Although negligible at higher pH values, the adsorption of luminol on the glassy carbon electrode became noticeable in a solution with pH = 12. Additionally, various types of adsorption behaviors were observed for luminol derivatives and analogues, indicating that the molecular structure affected not only the oxidation but also the adsorption process. The adsorption effect was analyzed through a model with a Langmuir isotherm to show that the saturated surface concentration as well as the reaction kinetics increased with decreasing pH, suggesting a competition for the active sites between the molecule and OH–. Moreover, we show that the ECL intensity could be boosted through the adsorption effect by collecting the ECL intensity generated through the electrochemical oxidation of luminol and a luminol analogue, L012, in a solution with pH = 13. In contrast with luminol, a significant adsorption effect was observed for L012 at pH = 13, and the ECL intensity was enhanced by the adsorbed species, especially at higher scan rates. The magnitude of the enhancement of the ECL intensity matched well with the simulation using our model.

The Implications of Coupling an Electron Transfer Mediated Oxidation with a Proton Coupled Electron Transfer Reduction in Hybrid Water Electrolysis

“…This study demonstrates the advantage of mediated hybrid water electrolysis, through the combination of a protoncoupled electron transfer (PCET) process, the hydrogen evolution reaction (HER) at the cathodic side, and a singe-electron transfer (ET) process at the anodic side, with (2,2,6,6-tetramethyl-1-piperidin-1-yl)oxyl (TEMPO)-mediated benzylamine oxidation as a case study. Although the reaction is diffusion-limited [27] (Figure S8) and there is a miscibility limit of benzylamine in alkaline solutions with high ionic strength, this TEMPO-mediated benzylamine oxidation can be performed with reasonably Scheme 2. Possible pathways for benzylamine oxidation.…”

“…This study demonstrates the advantage of mediated hybrid water electrolysis, through the combination of a proton‐coupled electron transfer (PCET) process, the hydrogen evolution reaction (HER) at the cathodic side, and a singe‐electron transfer (ET) process at the anodic side, with (2,2,6,6‐tetramethyl‐1‐piperidin‐1‐yl)oxyl (TEMPO)‐mediated benzylamine oxidation as a case study. Although the reaction is diffusion‐limited [27] (Figure S8) and there is a miscibility limit of benzylamine in alkaline solutions with high ionic strength, this TEMPO‐mediated benzylamine oxidation can be performed with reasonably high current density (≈100 mA cm −2 ) using a suitable high specific surface area electrode without an interference from oxygen evolution for at least 3 cycles of recyclability (Figures S9 and S10). This pH‐independent electrocatalytic oxidation permits the operation of the hybrid water‐splitting cell at a low cell potential ( E cell <1 V), below the thermodynamic potential of water oxidation at neutral pH conditions.…”

Screening-Capture-Integrated Electrochemiluminescent Aptasensor Based on Mesoporous Silica Nanochannels for the Ultrasensitive Detection of Deoxynivalenol in Wheat

“…29 However, as an ECL emitter, luminol has a strong adsorption capacity and can easily cause pore contamination, which significantly affects experimental results. 31,32 Compared to luminol, Ru(bpy) 3 2+ has a weak adsorption capacity and stable luminescence ability. 33,34 Therefore, the use of Ru(bpy) 3…”

“…Mi et al used Apts and cardiac troponin I (target) to plug the nanopores on MSFs, thereby preventing luminol in the electrolyte from reaching the ITO surface, resulting in altered ECL signaling . However, as an ECL emitter, luminol has a strong adsorption capacity and can easily cause pore contamination, which significantly affects experimental results. , Compared to luminol, Ru­(bpy) 3 2+ has a weak adsorption capacity and stable luminescence ability. , Therefore, the use of Ru­(bpy) 3 2+ as an emitter is preferred in the construction of MSF-type ECL sensors.…”

A novel DNA-quantum dot nanostructure electrochemiluminescence aptamer sensor by chain reaction amplification for rapid detection of trace Cd2+

“…Recently, quantum dots (QDs) have shown great potential in various ECL sensors due to their excellent optical properties. 13,14 However, the ECL intensity of QDs is still slightly lower than those of conventional luminescent reagents such as luminol 15 and Ru(bpy) 3 2+ , 16 making efficient signal amplification a critical area of focus. Currently, several enzyme-free DNA amplification circuits, including the hybridization chain reaction (HCR), 17 rolling cycle amplification (RCA), 18 and loop-mediated isothermal amplification (LAMP), 19 have been developed as promising candidates for molecular diagnostics in small samples.…”