Light Emitting Rare Earth Doped K₃GdF₆:Eu³⁺ for Spectral Mapping/Imaging Studies

Herein, we report a strategy to synthesize an Eu3+ doped single-phase monoclinic K3GdF6 double perovskite via a solid-state route with an average crystallite size of 18 ± 2.00 nm. Characterization methods such as X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and spectroscopic techniques provided a thorough understanding of the material's atomic and molecular-level structural, morphological, and functional properties. The photoluminescence study of K3GdF6:5% Eu3+ under different excitations such as 273, 393, 405, and 464 nm showed a hypersensitive, intense red emission at 613 nm and orange emission at 590 nm, which is a necessary parameter for high contrast imaging, particularly for overcoming autofluorescent background. The usage of K3GdF6:5% Eu3+ for spectral mapping and imaging has been specifically demonstrated through spatial photoluminescence mapping under 405 nm laser excitation. Moreover, the optical studies substantiated the occurrence of quantum cutting in K3GdF6:Eu3+ through systematic energy transfer between Gd3+ and Eu3+. Interestingly, in addition to optical attributes, the double perovskite showed superparamagnetic behavior at low temperature (2 K) with an average saturation magnetization of 96.86 emu/g. Through an exhaustive investigation of its optical and superparamagnetic properties, the synthesized double perovskite has been demonstrated to be a feasible choice for bioimaging (including optical and MRI), multiplexing detection, sensing, and other optical technologies.