Tuning Luminescence Properties of Lanthanide Coordination Polymers by Ag@SiO2 Nanoparticles
A series of core-shell Ag@SiO2 nanoparticles with different core diameter and shell thickness have been prepared by a modified-Stöber method. They provide a facile route to tune the luminescence intensities, lifetimes and quantum efficiencies of lanthanide coordination polymers in solid powder state. The coordination polymers [Tb2(p-PTA)3(H2O)2]n, [Tb2(o-PTA)3(H2O)2]n, [Eu2(p-PTA)3(H2O)2]n and [Eu2(o-PTA)3(H2O)2]n (PTA = phthalic acid) are synthesized and subsequently bound to the surface of Ag@SiO2 nanoparticles. The luminescence intensities of the lanthanide complexes are enhanced as high as 10.8 times. The enhancement times depend on the core diameter and shell thickness of Ag@SiO2. Importantly, by simply controlling the ratios between the complexes and nanoparticles, the luminescence intensities, lifetimes and quantum efficiencies of lanthanide complexes can be tuned in wide ranges. Typically, the luminescence lifetime of [Eu2(p-PTA)3(H2O)2]n powder increases from 451 s to 783 s when 300 L Ag@SiO2 solution is added. Meanwhile, the luminescence quantum efficiency of the complex increases from 32.1% to 40.9%. The change of the luminescence properties of the lanthanide coordination polymers can be ascribed to the surface plasmon resonance effect of the Ag@SiO2 nanoparticles as well as the decrease of the nonradiative decay rates of the complexes.