To take into account only the contribution of DBCO in the samples, we subtracted the spectra of the NPs control at different times from the sample spectra. Using the extinction coefficient of DBCO at 308 nm (ε = 12000 L • cm -1 • mol -1 ) and the optical path of cuvette l, the absorbance A of the control samples and the corrected sample were recalculated to concentration: