It was found that rhodamine B could induce oscillating chemiluminescence (OCL) from the Ce4+-cata-lyzed Belousov-Zhabotinsky reaction. This new OCL system, i.e., rhodamine B-malonic acid-bromate-Ce(Ⅳ)-sulfuric acid, exhibited two clearly distinguished emission peaks in each oscillation period. The initial concentrations of the reactants strongly influenced the oscillation pattern. For the study of the CL mechanism, a platform for a versatile and simultaneous potential and CL measurement was estab-lished to compare the potential oscillation with the CL oscillation behavior of this system. The CL spectra, UV-visible absorption spectra and time-resolved fluorescence spectra of this OCL system were studied. A possible, simplified mechanism for the OCL is proposed. It is suggested that the generation of the two CL peaks is likely due to the oxidation of the intermediate of rhodamine B by Ce(Ⅳ) and Br2, respectively. This work provided a new method and platform to research the complex chemical oscilla-tions.
The electrochemiluminescence(ECL) behavior of N-(4-aminobutyl)-N-ethylisoluminol(ABEI)-functionalized graphene composite(ABEI-GC) modified on an indium tin oxide(ITO) electrode was studied. ABEI-GC exhibited excellent ECL activity. On this basis, a label-free ECL immunosensor was developed for the sensitive detection of human immunoglobulin G(h Ig G) by using ABEI-GC as the ECL nano-interface via a layer-by-layer assembly technique. ABEI-GC was first assembled onto an ITO electrode. Positively charged chitosan was then electrostatically adsorbed to the modified electrode. Finally, negatively charged antibody-coated gold nanoparticles were attached to the surface to form the ECL immunosensor. In the presence of h Ig G, h Ig G was captured by its antibody. In addition, an ECL signal was detected in the presence of H2O2 when a double potential was applied. The ECL immunosensor for the determination of h Ig G showed a linear range of 1.0×10-13–1.0×10-8 g/mL with a detection limit of 5.0×10-14 g/m L. This immunosensor has high sensitivity, wide linearity and good reproducibility. The superior sensitivity of the proposed ECL immunoassay mainly derives from the incorporation of ABEI-GC, which not only improves the ECL intensity, response speed, and stability, but also provides a large specific surface for high levels of protein loading. This work reveals that ABEI-GC is good nano-interface for the construction of ECL biosensors. Our strategy is promising for protein detection and may open up a new avenue for ultrasensitive label-free immunoassays.
