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 ions and sensitized their emission. The 3:1 complexes of BDP displayed efficiencies of 18% and 12% for Eu and Tb, respectively. The analogous complexes of BMP had efficiencies of 23% and 18% for Eu and Tb, respectively. Both BDP and BMP were used to cap ZnS nanoparticles (NPs) in a one-pot synthesis, and then Ln ions were added, resulting in systems with metal ions at the surface of the capped NPs. Photoexcitation of the Eu and Tb 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-centered emission. The Eu-containing systems displayed higher efficiencies in the range 0.04-0.23% than the corresponding Tb-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 and Tb, respectively, were observed.