A slight decrease in the absorbance intensity along with red shift (~2 nm) in the maxima was observed at pH 11.5, suggested the formation of a free amine through deprotonation (Figure , ESI). Upon excitation at 520 nm, Nuc-DAOTA + showed high intensity emission band at 590 nm (φf = 0.27), with high stability particularly in the pH range of 4.0 to 8.0 (pH range of various subcellular organelles) and the average fluorescence lifetime remained stable around ~16 ns in the entire range (Figure and S2c, ESI). It demonstrates that the probe can retain high stability, even in complex cellular environments of varying pH during bioimaging studies of live cells.