Solvothermal synthesis and luminescent properties of hierarchical flowerlike ZnAl2O4:Ho3+ microstructures

Hierarchical microstructures of ZnAl2O4:Ho3+ (0.25-5 mol %) nanophosphors (NPs) were synthesized via solvothermal route using Epigallocatechin gallate (EGCG) as a bio-surfactant. The effect of EGCG concentration on the morphology was studied in detail. The Powder X-ray diffraction (PXRD) studies confirm the cubic phase of the samples. The photoluminescence (PL) emission spectra exhibit peaks at similar to 540, 553 and 666 nm were due to transitions F-5(4)-> I-5(8), S-5(2) -> I-5(8) and F-5(5) -> I-5(8) of Ho3+ ions, respectively. Thermoluminescence (TL) properties of ZnAl2O4: Ho3+ (0.25-5 mol %) NPs were studied after exposure of Co-60 gamma-rays at a warming rate of 6 degrees Cs-1. The TL intensity was found to increase with gamma-dose. The kinetic parameters have been determined using Chen's method from the deconvoluted glow curve. The CIE Chromaticity co-ordinates of all the prepared phosphors were located in the blue region. The above results clearly evident that the optimized Ho3+ activated ZnAl2O4 NPs was a promising single phased phosphor for WLED's and dosimetry applications.