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