Morphology-Controlled Synthesis and Multifunctional Luminescence/MRI/CT Imaging Applications of Octahedral BaGdF5:Eu3+ Phosphors

RE 3+ -activated BaGdF 5 phosphors have broad applications in LED-based fluorescence displays and biological tracing. In this research, various types (GdF 3 :5%Eu 3+ , BaGdF 5 :5%Eu 3+ ) and different morphologies (peanut, octahedron, microsphere) of gadolinium-based fluoride micro/nano-materials with down-shifting luminescence were synthesized via the hydrothermal method. The coordination environments of Gd 3+ , Eu 3+ , Ba 2+ , and F - ions were tuned by systematically varying the reaction time (6–36 h), the initial pH (3–11), and surfactants/chelating agents (CTAB, EDTA-2Na, Na 3 Cit and PVP). The optimal synthesis conditions (36 h, pH=3) were identified through X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. The samples were comprehensively characterized using thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) surface area measurements, Fourier-transform infrared (FT-IR) spectroscopy, and photoluminescence (PL) spectroscopy. The octahedral BaGdF 5 :5%Eu 3+ particles synthesized with CTAB demonstrated good thermal stability and the strongest fluorescence emission intensity at 595 nm, producing an orange-red light with CIE chromaticity coordinates of (0.5141, 0.4845). The luminescence intensity was 2.23 times greater than that of samples prepared with PVP. Moreover, the signal intensity in MRI T 1 -weighted imaging exhibits a positive correlation with Gd 3+ concentration. The composite material containing 2% wt% BaGdF 5 :5% Eu 3+ within the chitin matrix demonstrated optimal performance in CT imaging. Research indicates that the synthesised octahedral BaGdF 5 :5% Eu 3+ compound holds potential applications for down-shifting luminescence and multimodal MRI/CT imaging.