Abstract: A strong fluorescence emission from poly(amido amine)(PAMAM) dendrimers with different terminal groups(amine-terminated and carboxylate-terminated) was studied under different conditions by varing experimental parameters such as temperature,concentration and pH value.The intrinsic fluorescence of PAMAM dendrimer is due to an n→π^* transition from the amido groups throughout the dendritic structure and the close spherical structure of PAMAM.The fluorescence intensity increased fast at lower pH or lower temperature,linear with respect to dendrimer concentration when the dendrimer solution is dilute but depart from the linear relationship at higher concentration and higher dendrimer generations.The mechanism was studied carefully.First,it was reasonable that photoinduced electron transfer(PET) between fluorescence-emitting moiety and tertiary amine groups was prevented,or even eliminated when tertiary amine groups were protonated with H⁺ protons at lower pH,thus fluorescence intensity increased sharply accordingly.Also,the deactivation of luminescence was raised with increasing temperature.Further more,a critical concentration existed over which fluorescence intensity did not increased with linear relationship with increasing concentration because of concentration extinction effects.Oil latent fingerprints deposited on tinfoil surface treated with dendrimer solution emitted blue photoluminescence under ultraviolet excitation of 365 nm from an UV LED in the dark.Fingerprint was successfully detected with good resolving rate.

Key words: fluorescence emission, photoluminescence, poly(amido amine) dendrimer, fingerprint, forensic science