Kinetics Simulation of Luminol Chemiluminescence Based on Quantitative Analysis of Photons Generated in Electrochemical Oxidation

Abstract

The kinetics of electrogenerated chemiluminescence (ECL) of luminol at a gold electrode in alkaline solution was investigated by measuring the absolute number of photons emitted in an integrating sphere. The ECL efficiency as the ratio of photon to electric charge was 0.0004 in cyclic voltammography and 0.0005 in chronoamperometry. By numerically solving the rate equations based on a diffusion layer model, the observed time profile of the luminescence intensity could be successfully simulated from the oxidation current of luminol in the chronoamperometry. In the simulation, the rate constant for the oxidation of luminol by superoxide radicals in alkaline solution was determined to be 6 × 10(5) M(-1) s(-1). The present methodology and the achievement could be widely applicable to various analytical techniques using chemiluminescence.

Spectroscopic Investigation of the Mechanism of Photocatalysis

“…Reduced oxygen molecules such as superoxide radical (•O 2 − ) and H 2 O 2 can be detected by chemiluminescence with luminol (LH 2 , aminodiazabenzoquinone). The one electron oxidized state of luminol (•L − ) reacts with •O 2 − to form the excited state of 3-aminophthalic acid to emit fluorescence in alkaline solution [7], where •L − is formed from LH 2 by the oxidation with •O 2 − [8]. Since •O 2 − is rather stable in alkaline solution, after the irradiation on photocatalyst was stopped, luminol is injected to measure the amount of •O 2 − by the chemiluminescence intensity.…”

“…The same chemiluminescence was obtained from H 2 O 2 by the reaction with L that is two-electron oxidized state of LH 2 [9]. To measure the amount of H 2 O 2 in solution, after mixing luminol, hemoglobin was added to oxidize luminol, because L is rather unstable [8]. Luminol chemiluminescence method has some problems.…”

Remarkable increase in luminol electrochemiluminescence by sequential electroreduction and electrooxidation

“…[1][2][3][4] ECL has superior advantages over conventional chemiluminescence (CL), such as better reproducibility, lower background signal, and easier temporal and spatial control of ECL reactions. [5][6][7][8][9] ECL has become a very intensively studied and widely used analytical technique, and has been successfully applied in life science, material science, clinical medicine and environmental monitoring, etc. [10][11][12][13][14] Among various ECL systems, luminol ECL is continuously one of the most popular systems.…”

Imaging of chemical kinetics at the water-water interface in a free-flowing liquid flat-jet

“…One of the prime factors that make them interesting tools is the free flow through air or vacuum which permits unobstructed optical access to the liquid and thus enables a wide range of spectroscopic detection that are incompatible with many solid container materials. Recent applications include X-ray photoelectron spectroscopy, 1,[6][7][8][9][10][11][12][13][14] evaporation dynamics, [15][16][17][18][19][20][21] attosecond-pulse generation, 22,23 and liquidgas scattering. 24,24,25 The most common implementation is a single cylindrical jet, obtained by forcing the liquid at a pressure of a few bars through a 10-50 µm-diameter nozzle, which results in a laminar jet with a flow velocity of tens of m/s.…”