A study using quantum chemical theory methods on the intrinsic fluorescence emission and the possible emission mechanisms of PAMAM

In recent decades, it has been found and determined that poly-amidoamine (PAMAM) can give fluorescence emission under certain conditions. PAMAMs possess amide, primary amine and tertiary amine groups, which are not typical fluorescence emission groups. The fluorescence emission centers and mechanisms of PAMAM were studied. In this report we used quantum chemical TDDFT methods to calculate the absorption and emission states of the chemical components of PAMAM, which including amide, amide resonance structure imidic acid, amine and ammonium groups. The theory calculations showed that the imidic acid and tertiary ammonium components can give emission. The mechanisms for the formation of the amide resonance structure imidic acid and tertiary ammonium were discussed. The calculation results show that the imidic acid and tertiary ammonium groups are responsible for the fluorescence emission of PAMAM, which might help to explain the intrinsic-fluorescence phenomenon.