H 2 O 2 ‐Stimulus‐Responsive NIR‐II Imaging Employing an Organic Radical as Resonance Energy Transfer Acceptor for High‐Security Information Encryption

ABSTRACT Optical information encryption technology has emerged as a crucial strategy for ensuring data security. In particular, the integration of second near‐infrared (NIR‐II, 1000–1700 nm) fluorescence imaging and chemical stimulus‐triggered decryption presents a promising approach for constructing high‐security optical encryption systems. Nevertheless, no related encryption materials have been reported due to the absence of efficient strategies for modulating NIR‐II fluorescence. To overcome these limitations, an organic radical composite MPTCar 2+ ‐MPTCar •+ ‐CB[8] was rationally designed to modulate the NIR‐II fluorescence of NaYF 4 :3%Nd rare‐earth nanoparticles (RENPs) through resonance energy transfer (RET), facilitating the fabrication of the high‐security encryption material named RENPs‐MPT +• . This material only generated a fluorescence signal under specific NIR‐II imaging conditions after the H 2 O 2 ‐triggered conversion of the radical back to the parent compound. These dual‐security mechanisms endowed the encryption material with a high‐level security. Moreover, the combination of this material with permanently fluorescent RENPs‐MPT 2+ allowed for the introduction of deceptive pseudo‐information to further enhance encryption security, offering an innovative model for the development of high‐performance advanced optical encryption technologies.