The Luminescence of Controllable Lanthanide-based Coordination Polymers and the Properties as Thermometer

Two different structures lanthanide-based coordination polymers (Ln(2)(hbdc)(3)(H2O)(8)center dot 6H(2)O)(infinity) (Ln-1) and (Ln(2)(hbdc)(3)(H2O)(8)center dot 2H(2)O)infinity (Ln-2) have been synthesized by changing the adding order of reactants, and TbEu-1, TbEu-2 and GdTbEu-2 (90% Gd3+) were further synthesized. The luminance was analyzed and the temperature-dependent luminescence spectrum was measured. All the luminescent spectra were recorded at solid state. The luminance was ranked as GdTbEu-2>TbEu-2>TbEu-1. For TbEu-2, the value of intermetallic energy transfer efficiency is 67%, after the dilution of 90% Gd3+, this value significantly decreased to 57%. The introduction of cheap Gd3+ and the transformation of the structure enable GdTbEu-2 to achieve temperature sensing between 100 K and 250 K. Compared with unregulated TbEu-1, the range of temperature sensing was doubled, the absolute sensitivity (S-ab) and relative sensitivity (S-re) increased by 22 and 3 times, respectively. This phenomenon could be caused by the fact that, the intermetallic distance is larger than 1 nm after Gd3+ dilution, which weakens the intermetallic energy transfer effect, and the less free water molecule thermal motion of structure 2. A series of Sm2xEu2-2x-2 (0.1 <= x <= 0.9) were further synthesized, showing both visible and near-infrared luminescence, especially Sm3+ displaying excellent spectral gradation in the near-infrared region. This work provides an idea and basis for regulating doping luminescence thermometer and near-infrared temperature sensors. [GRAPHICS] .