Cathodic electrochemiluminescence of luminol in aqueous solutions based on C-doped oxide covered titanium electrode

In the present work, a novel sensor for luminol electrochemiluminescence (ECL) was constructed on the base of a C-doped titanium oxide amorphous semiconductor electrode. The morphology, structural and electrochemical properties of the electrode was characterized by X-Ray diffraction, X-Ray photoelectron spectroscopy and electrochemical methods. The ECL behavior of luminol excited by hot electrons injected from C-doped oxide film-covered electrodes in aqueous medium has been investigated in B-R buffer solution (pH = 9) when linear sweep cyclic voltammetry (CV) was applied. Two ECL peaks were observed at -1.0 V (vs. Ag/AgCl, reduction process) and -0.75 V (vs. Ag/AgCl, oxidation process). The possible mechanism was discussed. The C-doped Ti oxide electrode shows excellent properties for sensitive determination of luminol with good reproducibility and stability. The linear response of luminol was in the range of 1 x 10-8 to 9 x 10-8 mol/L with the detection limit of 3 x 10-9 mol/L (S/N = 3). Since luminol is one of the most useful ECL probe, many bioactive compounds which can be labeled by luminol are able to be detected by using the proposed method.