Singling Out the Electrochemiluminescence Profile in Microelectrode Arrays

Among various electrochemical imaging techniques, electrochemiluminescence microscopy (ECLM) stands out as a powerful approach to visualize electrochemical reactions by converting localized reactivity into optical signals. This study investigates ECL light emission spatial distribution in a confined space by using microelectrode arrays (MEAs) fabricated on glassy carbon (GC) and gold (Au) substrates via thermal nanoimprint lithography (TNIL). With the Ru-(bpy)₃ ² ⁺/TPrA system, ECL imaging revealed distinct emission profiles, with Au exhibiting a broader spatial distribution compared to GC under identical geometric conditions. The estimated thickness of the ECL emitting layer (TEL) was significantly larger on Au (∼7 μm) than on GC (∼4 μm), attributed to the interplay between the electrode material and dominant ECL mechanism. Decreasing Ru-(bpy)₃ ² ⁺ concentration resulted in minimal perturbation of the GC ECL profile, consistent with a predominant oxidative-reductive mechanism. In contrast, a significant narrowing of the ECL profile was observed on Au, indicative of a transition from a catalytic to an oxidative-reductive pathway. These observations were corroborated and rationalized by finite element simulations. Our findings demonstrate the capacity to fine-tune the Thickness of the Emission Layer (TEL) and modulate ECL emission through electrode material selection and luminophore concentration. Such precise control has significant implications for the development of highly sensitive and spatially resolved bioanalytical assays, particularly those employing bead-based detection methodologies.