Recent Advances in Biological Applications of NaErF<sub>4</sub>-based NIR-Ⅱ Luminescent Nanomaterials

Abstract Compared to the visible and near-infrared- (NIR-) spectral regions the near-infrared- (NIR- 1 000-1 700 nm) window has emerged as a promising frontier in bioimaging due to its greater tissue penetration depth and reduced spontaneous background fluorescence.In recent years significant progress has been made in ap plying Er 3+ -rich systems (NaErF 4 ) as NIR- fluorescent probes in biomedical photonics.These studies not only fo cus on enhancing imaging signal-to-noise ratios and detection sensitivity but also aim to achieve precision imagingguided therapy for tumor regions.This review systematically summarizes the design strategies luminescence mecha nisms and recent advances in the biological applications of NaErF 4 -based NIR- luminescent nanomaterials.Addi tionally the challenges associated with their future translation are discussed. Key words NaErF 4