Fig. 4: Confocal microscopy study of the viologen-modified film degradation.

Coherent anti-Stokes Raman scattering (CARS) and confocal fluorescence microscopy a in the absence and b in the presence of KI (0.1 M). A constant potential of −0.1 V vs SHE was applied to the electrodes in the presence of air to generate H₂O₂. CARS images show Raman intensity at 2841 cm⁻¹. Fluorescence was recorded between 500 and 630 nm at 488 nm excitation. The arrows in the CARS images (1.5 and 4 h) highlight the gap between the film and the electrode surface. For all experiments, the GCE (3 mm in diameter) were coated with viologen-modified polymer with a surface coverage of 2.2 mg cm⁻². Electrolyte: phosphate buffer (0.1 M, pH 7). The scale is the same for all images. These images are part of a longer time-resolved measurement available as a video file (Supplementary Movies 1–4).