Yb ³⁺ Energy Relay in Stratified Lanthanide Nanoparticles Enables Multidimensional NIR‐II Lifetime Imaging

ABSTRACT The second near‐infrared window (NIR‐II, 1000–2000 nm) provides an ideal window for multichannel photoluminescence lifetime imaging (mPLI) because of its exceptional tissue penetration depth and minimal scattering. However, the inevitable spectral crosstalk that is caused by the broad and overlapping emissions of traditional luminescent materials (e.g., organic dyes and quantum dots) has restricted the scalability of mPLI channels. Herein, we developed a series of Ln 3+ ‐doped (Ln = Nd, Er, Tm, or Ho) stratified nanoparticles (Ln‐SNPs) that enable highly efficient multiwavelength NIR‐II luminescence. These nanoparticles can be further engineered into concentration‐mediated Yb 3+ energy relay nanoparticles to enable the precise tuning of the luminescence lifetime across the 1060–2050 nm range, thereby expanding the NIR‐II imaging channels in mPLI. Notably, the engineered Tm‐SNPs exhibit optimized downshifting emission at ∼1850 nm (NIR‐IIc subwindow) with distinguishable luminescence lifetimes that span three orders of magnitude at similar emission intensities. This advancement establishes a powerful toolkit for multidimensional information encryption and multiplexed bioimaging applications.