A new 4-bromo-1,8-naphthalimide-labelled polyamidoamine (PAMAM) dendrimer from zero generation has been synthesised and characterised. Its functional characteristics, determined in acetonitrile solvent are discussed. The ability of the dendrimer to detect metal cations has been evaluated in acetonitrile by monitoring the quenching of the fluorescence intensity. Different metal cations have been tested Co(2+), Ni(2+), Cu(2+) and Fe(3+) for the purpose. The results have shown clearly that only Fe(3+) could be efficiently detected using the dendrimer.