Surface enhanced electrochemiluminescence with mesoporous gold: Understanding the electrochemical and optical effects

Surface enhanced electrochemiluminescence (SEECL) is a promising optical biosensing technique for ultrasensitive molecular detection in clinical diagnostics. Herein we show that mesoporous gold (mesoAu) is an appropriate substrate for SEECL. The mesoAu electrode was fabricated with electrodeposition using polystyrene-block-polyethylene oxide (PS-b-PEO) on silicon substrate. The electrode was characterized by scanning-electron microscopy (SEM), X-ray photo-electron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), nitrogen adsorption isotherm and X-ray diffraction (XRD), respectively. Spectroelectrochemical studies were performed by cyclic voltammetry (CV) and i-t amperometry, using a known ECL probe of tris-2-2'-bipyridyl ruthenium [Ru(bpy)3]2+. It was found that the enhancement was closely related to the pore size, with a maximum ratio of ~80 when the diameter of the pore was tuned to ~50 nm. By measuring the double-layer capacitance current of the non-faradic region at different scan rates, it was shown that enhancements due to electrochemical effects and optical coupling could be studied separately. This work suggests that SEECL with mesoAu is a combination of effects of electrochemical, optical and mass transport. It indicates the careful design of the sensing interface is crucial to obtain optimal analytical performance with mesoAu enabled SEECL bioassays.