ZnS Nanoparticles Sensitize Luminescence of Capping-Ligand-Bound Lanthanide Ions

2,6-Bis(diethylamide)-4-oxo(3-thiopropane)pyridine (BDP) and 2,6-bis(methyl ester)-4-oxo(3-thiopropane)pyridine (BMP) were synthesized. These compounds chelated Ln^III ions and sensitized their emission. The 3:1 complexes of BDP displayed efficiencies of 18% and 12% for Eu^III and Tb^III, respectively. The analogous complexes of BMP had efficiencies of 23% and 18% for Eu^III and Tb^III, respectively. Both BDP and BMP were used to cap ZnS nanoparticles (NPs) in a one-pot synthesis, and then Ln^III ions were added, resulting in systems with metal ions at the surface of the capped NPs. Photoexcitation of the Eu^III and Tb^III systems through NPs capped with these two ligands, with the carboxylato derivative of BMP [dicarboxylato-4-oxo(3-thiopropane)pyridine] and the nonchromophore 3-mercaptopropionate, resulted in sensitized Ln^III-centered emission. The Eu^III-containing systems displayed higher efficiencies in the range 0.04-0.23% than the corresponding Tb^III-containing systems with efficiencies in the range 0.01-0.15%. The NPs capped with BDP were the exception; in this case, efficiencies of 0.36% and 0.79% for Eu^III and Tb^III, respectively, were observed.