Unlocking Bright and Switchable Dimeric Singlet Oxygen Electrochemiluminescence by Surface Engineering

Visible electrochemiluminescence (ECL) of singlet oxygen (¹O₂) from the dimeric ¹Δ_g state is a versatile and cost-efficient tool for sensing and imaging in various application fields such as biochemistry, pharmaceuticals, and material science. However, its implementation is hindered by weak emission and complex generation mechanisms. In this work, we enable a bright and switchable dimeric ¹O₂ ECL through facile yet effective surface engineering strategies on a screen-printed carbon electrode in aqueous media. Specifically, we complement a stepwise potential procedure with a pre-cathodic process to switch on the anodic ¹O₂ ECL and unravel how the in situ electrochemical pretreatments remarkably amplify the ECL intensity by modifying the surface oxygenates and promoting the ¹O₂-generating reactions. Additionally, ex situ oxygen plasma treatment on the electrode surface, which switches off the ¹O₂ ECL, further demonstrates the surface specificity of the ¹O₂ ECL from another perspective. Leveraging these surface strategies, we establish a sensing capability of the ¹O₂ ECL system with high sensitivity and selectivity toward tertiary amines. This work paves the way for translating a laboratory-scale ¹O₂-ECL system to portable and patternable sensing, imaging, and display applications.