A novel efficient lead-free near-infrared emission Re4+-doped double perovskite for dental caries medical imaging

Near-infrared (NIR) two-dimensional (2D) imaging techniques show remarkable potential for diagnosing dental caries by virtue of the high transparency of tooth enamel in specific NIR light. Vacancy-ordered double perovskite Cs 2 HfCl 6 is a promising candidate for modern light sources for biomedical use due to its low phonon energy and unique optical properties. Re 4+ -doped Cs 2 HfCl 6 produces outstanding NIR emission with ultra-high quantum efficiency (IQE = 91.88 %) over a large spectral range from 700 to 1700 nm. The effect of phonons on emission peak splitting and broadening was investigated using in situ luminescence spectroscopy at different temperatures. Its excellent anti-thermal quenching property (92 % @ 420 K) makes it ideal for use in NIR phosphor-converted light-emitting diodes (NIR pc-LEDs). The fabricated Cs 2 HfCl 6 :Re 4+ @pc-LEDs were validated as a light source for dual-mode NIR caries imaging (transillumination and reflection modes) depending on the ≈1300 nm NIR emission. NIR imaging has greater potential for caries imaging than conventional visual, tactile, and radiographic methods of caries detection, as it allows for the safe and accurate monitoring and diagnosis of enamel lesion occurrence and extent. This study enriches the mentality of designing NIR-emitting materials and opens new avenues for future research on novel NIR-emitting materials for medical imaging.