To further evaluate the decomposition rate, we follow the progress of the HP-NCs decomposition in the kinetics spectra measured for the 3345 G peak. Reduction in the peak intensity is related to a decreased amount of the generated radicals, and a shift of the peak indicates a change in the shape of the EPR spectra. The EPR spectra before and after the kinetics analyses are presented in Figure . We find that the decomposition of CsPbBr3 NCs starts after ~3 min of illumination, and after 18 min, the number of radicals reduces to about 7 % for both solutions (Figure ).