Confined Electrochemiluminescence Generation at Ultra-High-Density Gold Microwell Electrodes

Abstract

Electrochemiluminescence (ECL) imaging analysis based on the ultra-high-density microwell electrode array (UMEA) has been successfully used in biosensing and diagnostics, while the studies of ECL generation mechanisms with spatial resolution remain scarce. Herein we fabricate a gold-coated polydimethylsiloxane (PDMS) UMEA using electroless deposition method for the visualization of ECL reaction process at the single microwell level in conjunction with using microscopic ECL imaging technique, demonstrating that the microwell gold walls are indeed capable of enhancing the ECL generation. For the classical ECL system involving tris(2,2′-bipyridyl)ruthenium (Ru(bpy)32+) and tri-n-propylamine (TPrA), the ECL image of a single microwell appears as a surface-confined ring, indicating the ECL intensity generated inside the well is much stronger than that on the top surface of UMEA. Moreover, at a low concentration of Ru(bpy)32+, the ECL image remains to be ring-shaped with the increase of exposure time, because of the limited lifetime of TPrA radical cations TPrA+•. In combination with the theoretical simulation, the ring-shaped ECL image is resolved to originate from the superposition effect of the mass diffusion fields at both microwell wall and bottom surfaces.

Deciphering the Mechanisms of Electrochemiluminescence by Spatially Resolved Measurements

“…. Similar evolution of the ECL pattern for Ru(bpy) 3 2+ /TPrA system was also observed using a gold microwell electrode array [58] …”

Enhanced Electrochemiluminescence in a Microwell Bipolar Electrode Array Prepared with an Optical Fiber Bundle

“…Figure 3B shows a similar tendency that ECL intensity increase rapidly from the periphery to the center of the fiber core. Such bell-like ECL produced with MBEA differs from the one in the cylindrical microwell, [29] which only ring-like ECL can be obtained at low concentration of [Ru(bpy) 3 ] 2 + . Indeed, the junction of sidewall and button of the microwell create the overlapped diffusion fields, where the electro-generated species can diffuse from both radical and longitudinal directions.…”

“…The mixed diffusion at the junction facilitate the ECL reactions. [29] But in our case, the parabolic-shaped button of the microwell may create the overlapped diffusion field in the center of the button that leads to a different ECL behavior. Moreover, when increasing the concentration of [Ru(bpy) 3 ] 2 + up to 500 μM, the ECL image presents much stronger ECL emission (Figure 3C), and the light emission transmitted through each optical fiber became less distinct.…”

“…[18,19,21,23] Very recently, ECL imaging was applied to study the light emission generated in MEA and reveal the related ECL mechanism. [29] Nonetheless, most of MEAs used in ECL serve as the working electrode in the traditional threeelectrode system. The use of these MEAs in BE-ECL might cause the obvious variation of polarization potential in each microwell or the difficulty of ECL measurement in closed proximity to microwells depending on the placement direction to external electric field.…”

From glow-sticks to sensors: single-electrode electrochemical detection for paper-based devices

“…25 While the most used luminophores are based on the use of luminol 26 or RuIJbpy) 3 2+ , 27 a variety of metallic complexes and polyaromatic hydrocarbons have also been reported. 25,28 It is also important to consider that ECL has been coupled with traditional electrochemical approaches such as amperometry [29][30][31] as well as bipolar systems. 6,21,26,[32][33][34] While not strictly considered a bipolar system, ECL can also be integrated with much simpler electrochemical systems that use a single, resistive electrode 33 to drive a potential drop across the detection cell.…”