Photoluminescence of Visible and NIR-Emitting Lanthanide-Doped Bismuth-Organic Materials

A bismuth-organic compound containing 2,2':6'2-terpyridine (terpy) and 2-thiophenecarboxylate (TC), of the general formula (terpy)Bi(kappa(2)-TC)(3) center dot 0.47H(2)O (BiOM-1), has been synthesized under hydrothermal conditions. Addition of a lanthanide nitrate solution to the reaction mixture led to statistical replacement of the bismuth centers, and yielded isomorphous lanthanide containing compounds Bi(1-x)Ln(x)OM-1 (Ln = Nd, Sm, Eu, Tb, Dy, Er, and Yb) that showed bismuth and/or ligand sensitized lanthanide-centered emission, and the first example of NIR emission from a lanthanide doped BiOM. The structure was determined by single-crystal X-ray diffraction, and the level and uniformity of lanthanide ion incorporation into the bismuth host was determined by ICP-OES and electron microprobe analysis. For the visible emitters, lifetime data and quantum yields are presented. A high efficiency of sensitization was calculated for the europium analog (50.1%), showing significant improvement over previously reported europium thiophenecarboxylates. These novel materials may provide strategies to address concerns over the long-term sustainability of the rare earth elements, especially relating to optical devices.