Fig. 2. (A) ECL mechanism of a SEES. (B) Dependence of the ECL intensity on the applied external voltage. (C) ECL profiles of three consecutive measurements using a SEES at 2.0 V, 3.0 V and 4.0 V, respectively. The photomultiplier tube (PMT) voltage was set at 400 V. “Turn-on” means that the external power source is turned on to induce ECL; “Turn-off” means that the external power source is turned off. (D) ECL emission images taken using a smartphone at different external voltages. 0.1 M carbonate buffer, pH 11.0; c (luminol), 1.0 mM; c (H₂O₂), 1.0 mM.