Unlocking\nBright and Switchable Dimeric Singlet Oxygen\nElectrochemiluminescence by Surface Engineering

Visible\nelectrochemiluminescence (ECL) of singlet oxygen (<sup>1</sup>O<sub>2</sub>) from the dimeric <sup>1</sup>Δ<sub>g</sub> state is\na versatile and cost-efficient tool for sensing and imaging\nin various application fields such as biochemistry, pharmaceuticals,\nand material science. However, its implementation is hindered by weak\nemission and complex generation mechanisms. In this work, we enable\na bright and switchable dimeric <sup>1</sup>O<sub>2</sub> ECL through\nfacile yet effective surface engineering strategies on a screen-printed\ncarbon electrode in aqueous media. Specifically, we complement a stepwise\npotential procedure with a pre-cathodic process to switch on the anodic <sup>1</sup>O<sub>2</sub> ECL and unravel how the <i>in situ</i> electrochemical pretreatments remarkably amplify the ECL intensity\nby modifying the surface oxygenates and promoting the <sup>1</sup>O<sub>2</sub>-generating reactions. Additionally, <i>ex situ</i> oxygen plasma treatment on the electrode surface, which switches\noff the <sup>1</sup>O<sub>2</sub> ECL, further demonstrates the surface\nspecificity of the <sup>1</sup>O<sub>2</sub> ECL from another perspective.\nLeveraging these surface strategies, we establish a sensing capability\nof the <sup>1</sup>O<sub>2</sub> ECL system with high sensitivity\nand selectivity toward tertiary amines. This work paves the way for\ntranslating a laboratory-scale <sup>1</sup>O<sub>2</sub>-ECL system\nto portable and patternable sensing, imaging, and display applications.