Impact of Dopant Concentration on the Structural, Morphological, and Spectroscopic Characteristics of Eu3+-doped Sr10(PO4)6F2 Nanomaterials, Including Temperature-Dependent Emission

Luminescent materials with desirable properties are in constant demand for lighting applications and as probes in bioimaging. In this study, we successfully synthesized nanosized strontium fluorapatite (SrFAp) powders doped with varying concentrations of Eu3+ ions via the hydrothermal method, targeting applications in lighting and bioimaging probes. Our focus was on understanding the impact of annealing temperature and dopant concentration on structural purity, particle morphology, photoluminescence, dopant ion occupancy, and temperature-dependent emission characteristics. The materials emit red light, with the most intense transition being 5D0 → 7F2. The asymmetry parameter (R) determination and CIE color coordinates provided insights into the spectroscopic attributes. Emission spectra were measured and discussed at four distinct excitation lines. Lower-energy excitation wavelengths, deemed favorable for organisms, make these materials particularly suitable for bioimaging applications. While the most intense emission occurred under 393 nm excitation, emissions were also detected at 464.5 nm and 525 nm, suggesting alternative excitation wavelengths better suited for bioimaging. Additionally, we conducted extensive studies to assess the effect of ambient temperature on the emission intensity of SrFAp materials doped with 1 mol% Eu3+ ions. Thermal quenching of luminescence was observed in both as prepared and annealed materials, providing insights into the temperature-dependent behaviour of the emission properties.