Structural and spectroscopic investigations on the quenching free luminescence of europium oxalate nanocrystals.

The structural features leading to the intense quenching free luminescence exhibited by europium oxalate nanocrystals, poly[[hexaaquatri-μ2-oxalato-dieuropium] 4.34-hydrate], {[Eu2(C2O4)3(H2O)6]·4.34H2O}n, is the focal point of this report. Europium oxalate nanocrystals were synthesized by a simple microwave-assisted co-precipitation method. Powder X-ray diffraction analysis revealed the monoclinic structure of the nanocrystals and the phase purity. The morphology and particle size were examined by transmission electron microscopy (TEM) analysis. Luminescence measurements on a series of samples of La2-xEux(C2O4)3·10H2O, with x varying in the range 0.1 to 2, established the quenching free nature exhibited by the europium oxalate nanocrystals. A single-crystal structure analysis was carried out and the quenching free luminescence is explained on the basis of the crystal structure. A detailed photoluminescence characterization was carried out using excitation and emission studies, decay analysis, and CIE coordinate and colour purity evaluation. The various spectroscopic parameters were evaluated by Judd-Ofelt theoretical analysis and the results are discussed on the basis of the crystal structure analysis.