Hot electron-induced electrogenerated chemiluminescence of Ru(bpy)(3)(2+) chelate at oxide covered aluminum electrodes

Ruthenium(II) tris-(2,2'-bipyridine) chelate exhibits strong electrogenerat ed chemiluminescence during cathodic pulse polarization of oxide-covered al uminum electrodes in aqueous solutions. The present method is based on a tu nnel emission of hot electrons into an aqueous electrolyte solution. The me thod allows the detection of ruthenium(II) tris-(2,2'-bipyridine) and its d erivatives below nanomolar concentration levels and yields linear log-log c alibration plots spanning several orders of magnitude of concentration. Thi s method allows simultaneous excitation of derivatives of ruthenium(II) tri s-(2,2'-bipyridine) and Tb(III)-chelates. The former label compounds have a luminescence lifetime of the order of microseconds, while the latter compo unds generally have a luminescence lifetime of around 2 ms. Thus, the combi ned use of these labels easily provides the basis for two-parameter bioaffi nity assays by either using wavelength or time discrimination or their comb ination.