Scheelite like NaTb(WO 4 ) 2 nanoparticles: Green fluorescence and in vitro cell imaging applications.

This study highlights the investigation of the green fluorescence in NaTb(WO4)2 materials (NaTbW Bulk and NaTbW Nano) synthesized via template free hydrothermal method as a function of particle size and morphology. Herein, we demonstrated the biocompatibility and intracellular green fluorescence of NaTbW Nano samples using HeLa cells for cell imaging applications. Powder X-ray diffraction studies showed that the as synthesized NaTbW Bulk and NaTbW Nano crystallize in the Scheelite like tetragonal crystal system with the I41/a space group. The reaction pH and solvent is observed to play a critical role in determining particle size, shape and morphology of these luminescent materials. Furthermore, size dependent optical properties were systematically studied by diffuse reflectance, steady state photoluminescence; time resolved fluorescence lifetime and quantum yield measurements. Both the materials have shown bright green fluorescence upon UV excitation as a function of particle size. Remarkable high quantum yield of NaTbW Bulk indicated its greater luminescence efficiency and the closer CIE coordinates to the commercial green illuminant suggested their potential use in solid state display systems. On the other hand the observed biocompatibility of NaTbW Nano particles towards mammalian cancer HeLa cells, Staphylococcus aureus, Escherichia coli and the intracellular green fluorescence rightly proved its functionality as active bio-probes. Thus, our work summarize the potential use of these Scheelite like NaTb(WO4)2 material for solid state display and bio-imaging applications.