During the photocatalytic reactions, the NCs precipitated within tens of minutes of light irradiation, suggesting that the initial surface ligands of the NCs were desorbed or deteriorated by light irradiation. The XRD pattern and peak width of the precipitates indicated that the diameter of CdS NCs remained constant despite the photochemical reactions (Supplementary Fig. ). Fourier transform infrared (FTIR) spectra show that MPA was replaced with other organic molecules probably ascribed to TEOA and its photoproducts (Supplementary Fig. ). These results indicate that organic molecules on the surface of NCs dynamically change upon visible light, whereas NCs more or less retain their sizes. The precipitated CdS NCs could be reused to decompose PFOS over more than 12 cycles, although the overall deF% gradually decreased (Fig. ). Each cycle involved (1) N2 bubbling of the reaction solution for 30 min, (2) irradiation of 405-nm LED light for 12 h, (3) centrifugation and decantation of the supernatant, and (4) addition of 1.0 mL of the aqueous solution containing PFOS (1.2 × 10 -6 mol) and TEOA (1.3 × 10 -4 mol). The ratio of CdS NC and PFOS per cycle was 1:122.2, with each PFOS molecule containing 17 C-F bonds. The turnover number of C-F bond dissociation per CdS NC was calculated to be 1.72 × 10 3 from the line exploration. The concentration of cadmium (II) ions dissolved in the solution was 3 ppm after the 1 st cycle, and varied between 6-46 ppm (the average was 13 ppm except for outliers) depending on the experimental conditions (Supplementary Fig. ), which corresponds to 1-7% of the remained CdS NCs. The large deviation of the Cd concentration may be due to insufficient deoxygenation procedures because molecular oxygen promotes photocorrosion. The slight photocorrosion is consistent with the gradual decrease in the overall deF% by repeating the photocatalytic reactions.