Images of 0–13 mM H2O2 acquired using an iPhone 4s or 6, a home-built darkbox, and the time-lapse imaging application OSnap! (a) Unprocessed images and (b) images processed in ImageJ by setting the maximum pixel value to 35 using 25 µL aliquots of 0–13 mM H2O2 (0–1 mM final concentration) and 3.9 mM DPA, 3.7 mM imidazole, and 3.1 mM TCPO in 9:1 EtOAc:CH3CN. (c) Unprocessed images and (d) images processed in ImageJ by setting the maximum pixel value to 35 using 25 µL aliquots of 0–13 mM H2O2 (0–1 mM final microwell concentration) and 3.9 mM rubrene, 3.7 mM imidazole, and 3.1 mM TCPO in 9:1 EtOAc:CH3CN. (e) Unprocessed images and (f) images processed in ImageJ by setting the maximum pixel value to 35 using 25 µL aliquots of 0–13 mM H2O2 (0–1 mM final concentration) and 3.9 mM BPEA, 3.7 mM imidazole, and 2.2 mM CCPO in 9:1 EtOAc:CH3CN. Images were acquired 2–3 seconds after addition of H2O2.