Manipulating Energy Transfer in Multilayer Lanthanide‐Based Nanoparticles for Enhanced NIR‐II Luminescence and Lifetime Tuning

Lanthanide‐based multilayer nanoparticles exhibiting near‐infrared II (NIR‐II, 1,000–1,700 nm) emissions have garnered significant interest for diverse frontier optical applications. However, precisely manipulating emissions simultaneously in intensity and lifetime remains challenging. This study proposes a conceptual model of tuning interfacial energy transfer (IET) in a core–shell–shell nanostructure to spatiotemporally control Er 3+ downconversion luminescence and lifetime. Nanoscale manipulation of the interfacial interactions between Er and Yb sublattices enhances downconversion. Additionally, increasing the thickness of Yb 3+ interlayer effectively modulates the Nd‐Yb‐Er energy transfer pathway, simultaneously 8.2‐fold of suppressing emission intensity and 1.8‐fold prolonging luminescence lifetime. This strategy enables multifunctional tuning of optical properties through combined steady‐state excitation and time‐gated detection, offering new opportunities for photonic applications such as high‐security optical anti‐counterfeiting.