Intrinsic Redox-Responsive NIR-II Lanthanide Luminescent Nanoprobes Enabled by Phonon-Assisted Cooperative Quenching for Reversible Redox Imaging In Vivo.

Abstract

Lanthanide nanoparticles (LnNPs) are photostable second near-infrared window (NIR-II) emitters well suited to long-term redox imaging. However, responsive LnNP nanoprobes generally require surface-installed molecular recognition components to transduce chemical changes into luminescence signals, which may introduce additional functionalization complexity and compromise long-term signal reliability. Here, we identify a redox-regulated phonon-assisted cooperative quenching (PACQ) phenomenon in NaCeF4:Nd, where Ce(III)/Ce(IV) conversion modulates Nd(III) emission through lattice-mediated interactions. To elucidate this intrinsic response, a model NaLuF4@NaCeF4:Nd architecture was constructed to expose the NaCeF4:Nd shell and reveal the underlying PACQ mechanism. Oxidation-induced changes in Ce electronic configuration and local lattice environment weaken Ce-mediated quenching and restore NIR-II Nd(III) emission. Based on this mechanism, we further develop a ratiometric NaErF4:Yb@NaLuF4@NaCeF4:Nd nanoprobe (RPACQ), where the Er(III) emission provides a stable internal reference. RPACQ exhibits reversible H2O2/glutathione responses, with second-scale activation, concentration-dependent ratiometric responses in vitro, and excellent photostability. In a cerebral ischemia-reperfusion injury (CIRI) model, RPACQ provides proof-of-concept for in vivo redox imaging. Collectively, this work establishes an intrinsic lanthanide nanoparticle strategy for reversible NIR-II luminescence regulation without external molecular reporters, potentially opening new avenues for engineering responsive lanthanide nanomaterials.

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