Solvothermal synthesis of Eu ³⁺ doped Sr ₂ BiF ₇ nanoparticles with long excited state lifetime for examining latent fingerprints

Lanthanide-doped luminescent nanomaterials have a wide variety of applications in the fields of anti-counterfeiting, solar cells, sensors, photocatalysis, forensic science, bio-imaging, and therapy, etc. This is the first time that europium doped strontium bismuth fluoride (Sr₂BiF₇:<i>x</i>% Eu³⁺, 0 ⩽<i>x</i>⩽ 20) luminescent nanoparticles (NPs) have been synthesized by solvothermal approach at 160 °C and applied for latent fingerprint (LFP) identification. The NPs have a fluorite structure with crystallite size of ∼25 nm. The surface morphology of samples exhibited aggregated spherical particles. These NPs exhibit a strong magenta color under 395 nm and a bluish-white color under 365 nm UV light because of f-f transitions of Eu³⁺and s-p transition of Bi³⁺, respectively. Optimum emission has been observed for SBF: 10% Eu³⁺with an excited state lifetime of 7.03 ms with a calculated quantum yield of 88%. On various surfaces, SBF: Eu³⁺(10%) nano-phosphor is used to develop LFPs that have great sensitivity, selectivity, good contrast, and minimal background interference. According to the results, the new phosphor has a lot of potential for use in forensic applications in real time.