Novel fluorescent derivatives of generation 0 polyamidoamine (PAMAM), comprising 1,8-naphthalimide units have been synthesized. Their basic photophysical properties in organic solvents of different polarity have been determined and discussed. A 4-N,N-dimethylaminoethylene-1,8-naphthalimide, labelled PAMAM, has been synthesized with designed fluorescent intensity and high sensitiveness to the presence of protons or transition metal cations. This sensitiveness has been ascribed to a photo-induced electron transfer from the amino groups of the central PAMAM core and the terminal amino groups of dialkylamino moieties to the electron-deficient component in 1,8-naphthalimide.