The absorbance, excitation, and emission spectra of Nuc-DAOTA + (10 μM) in PBS (10 mM, pH 7.4) (Figure , ESI) were found similar to the spectra of previously reported diazaoxa- triangulenium hexafluorophosphate derivatives that have absorption and fluorescence maxima around 555 nm and 585 nm, respectively. During pH titration in a PBS (100 mM) + NaCl (100 mM) solution, the absorbance band of Nuc-DAOTA + appeared at 557 nm, corresponds to the dicationic form of the molecule resulting from the protonation of the tertiary amine within the PEG-type chains and is stable up to pH 10.