Color-tunable hypersensitive temperature sensor based on metal organic framework doped with Eu3+ and Dy3+ via phonon-assisted energy transfer

In this work, catena-[(μ-benzene-1,3,5-tricarboxylato)-(1,10-phenanthroline)-(N,N-dimethylformamide)-gadolinium(iii)-N,N-dimethylformamide solvate] (denoted as Gd-MOF) co-doped with Eu3+ and Dy3+ was successfully synthesized. The entire X-ray diffraction peaks of the sample match well with the Gd-MOF phase. A detailed characterization by inductively coupled plasma mass spectrometry (ICP-MS) shows that the actual concentration is basically consistent with the design concentration. The temperature sensing properties of Gd-MOF:Eu3+,Dy3+ were analyzed by temperature-dependent fluorescence spectra from 213 to 453 K. As temperature rises, the emission color of Gd-MOF:Eu3+,Dy3+ changes from yellow to red. The relative sensitivity reaches a maximum of 5.87%/K at 383 K in the Gd-MOF:1%Eu3+,30%Dy3+ sample. The high relative sensitivity of this MOF is due to the phonon-assisted energy transfer from Dy3+ to Eu3+, which is proved via fluorescence decay curves and fluorescence spectra. The major route of this energy transfer is 4F9/2(Dy3+) →5D1(Eu3+).