A low-cost assay for hydrogen peroxide using sewage sludge-based carbon nanodots†

In this work, sewage sludge-based carbon nanodots (ss-CNDs) were prepared by a one-pot hydrothermal strategy using sewage sludge as the only raw material. The ss-CNDs showed high peroxidase-like activity. In the presence of hydrogen peroxide (H₂O₂), ss-CNDs catalyze the decomposition of H₂O₂ to form hydroxyl radicals (·OH), which oxidize colorless 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) into green ABTS radicals (ABTS·⁺). From this, a simple and effective method is developed for sewage sludge resource utilization and low-cost H₂O₂ colorimetric detection. The colorimetric sensing system for H₂O₂ offers a satisfactory determination range from 0.05 mM to 10 mM and a detection limit of 9.5 μM for H₂O₂. In addition, this colorimetric assay allows H₂O₂ as low as 0.2 mM to be distinguished with the bare eye. And the developed colorimetric system has potential application in environmental water samples.