Fluorescence quenching and luminescence sensitization in complexes of Tb3+ and Eu3+ with humic substances.
Intrinsic fluorescence quenching of humic substances (HS) and the sensitization of Ln3+ luminescence (Ln3+ = Tb3+, Eu3+) in HS complexes were investigated. Both measurements yielded complementary information on the complexation of metals by HS. Large differences between fulvic acids (FA) and humic acids (HA) were found. From time-resolved luminescence measurements it is concluded that a combination of energy transfer and energy back transfer between HS and Ln3+ is responsible for the observed luminescence decay characteristics. In the case of Eu3+, an additional participation of charge-transfer states is suggested. A new concept for the evaluation of the sensitized luminescence decays of Ln3+ was adapted.
Kumke
Michael U
MU
Institute of Chemistry, University of Potsdam, Karl-Liebknecht-Strasse 24-25, 14476 Potsdam, Germany. kumke@chem.uni-potsdam.de
Eidner
Sascha
S
Krüger
Tobias
T
D000818:Animals; D001578:Benzopyrans / Q000032:analysis; D001665:Binding Sites; D002412:Cations; D005063:Europium / Q000737:chemistry*; D005453:Fluorescence; D006812:Humic Substances / Q000032:analysis*; D007700:Kinetics; D049449:Luminescence; D013050:Spectrometry, Fluorescence / Q000379:methods; D013725:Terbium / Q000737:chemistry*
D001578:Benzopyrans; D002412:Cations; D006812:Humic Substances; D013725:Terbium; D005063:Europium; C005023:fulvic acid