Sustainable Bio‐Extract Mediated Synthesis of ZnCr ₂ O ₄ :Dy ³⁺ Nanophosphors for High‐Performanc

Dy ³⁺ ‐doped ZnCr ₂ O ₄ nanophosphors (1–9 mol%) were prepared by green solution combustion route, wherein Punica granatum peel extract served as bio‐derived fuel and surfactant, enabling controlled nucleation and crystallite growth under sustainable reaction conditions. PXRD analysis confirmed the crystallization of a phase‐pure spinel ZnCr ₂ O ₄ lattice, exhibiting well‐defined diffraction peaks characteristic of a highly ordered crystalline structure, while diffuse reflectance spectroscopy (DRS) revealed a Dy ³⁺ ‐induced modulation of the optical bandgap between 1.44 and 1.54 eV. FTIR spectroscopy exhibited characteristic Zn–O and Cr–O lattice vibrations, with band shifts attributable to Dy ³⁺ substitution. FESEM analysis confirmed the formation of densely aggregated rod‐like nanostructures, whereas HRTEM elucidated the presence of highly crystalline domains with an average particle size of ~40 nm and a distinct lattice fringe spacing of 0.29 nm, corresponding to the (220) crystallographic plane of the spinel phase. Under 351 nm excitation, photoluminescence spectra displayed sharp Dy ³⁺ emissions spanning the blue, yellow, and red regions, producing a balanced white‐light output. The optimized Dy ³⁺ ‐doped ZnCr ₂ O ₄ phosphor exhibited superior photometric performance, achieving quantum efficiency of 76%, a chromatic purity of 73%, and a correlated color temperature (CCT) of 5964 K, signifying its emission within the cool‐white region of the visible spectrum.