Synthesis and optical characterization of sub-5 nm Terbium oxalate nanocrystals: A novel intense green emitting phosphor

Abstract

Green emitting novel Terbium oxalate decahydrate nanophosphor (Tb2(C2O4)3.10H2O) with particle size in the range 2–4 nm, was synthesized by microwave assisted co-precipitation method. The structure and particle size of the sample were elucidated by X-ray powder diffraction and TEM analysis. The photoluminescence excitation spectra of the terbium oxalate nanophosphor exhibited several peaks in the 200-500 nm range of DUV to visible region with the strongest one at 369 nm in n-UV region and these excitation peaks matches well with the emission peaks of commercially available LED sources. The emission spectra recorded at the representative excitations exhibit intense and sharp green emission (5D4→7F5, at 543 nm) owing to the heavy population of 5D4 level at the expense of 5D3 level of Terbium ion. The decay curve is fitted to single exponential function with a decay time of 0.82 ms. The chromaticity co-ordinate is found to be (0.25, 0.54) and is located in green region with a colour purity of 68%. The experimental observations revealed that the synthesized ultrafine terbium oxalate nanocrystal is a suitable candidate as green emitting phosphor.