A near-infrared (NIR-I) fluorescent photoswitchable nanoparticle system was successfully developed based on a photochromic diarylethene (DAE) derivative linked to a novel aggregation-induced emission (AIE) fluorophore, DPAFTQ. The resulting dyad 1 exhibits exceptional fluorescence switching performance with high contrast and full reversibility in the NIR-I region (650–1000 nm). This achievement stems from an amplified fluorescence quenching mechanism enabled by intermolecular energy transfer within densely packed nanoparticles. In solution, the intramolecular Förster resonance energy transfer (FRET) efficiency between the DPAFTQ fluorophore and the closed-ring DAE unit is limited due to poor spectral overlap, resulting in only moderate fluorescence quenching (~40% at photostationary state).Cytokeratin 8/18 Antibody Autophagy However, when assembled into nanoparticles, the fluorescence intensity drops nearly to zero upon UV irradiation, achieving a >90% quenching ratio.SF3A3 Antibody Autophagy This dramatic enhancement is attributed to the AIE effect, which suppresses non-radiative decay pathways in the aggregated state, thereby increasing the fluorescence quantum yield of the donor.PMID:34690065 In the NP environment, the close proximity of multiple DAE units allows each closed-ring DAE molecule to act as an efficient energy acceptor for numerous neighboring fluorophores, leading to highly effective intermolecular energy transfer. Theoretical calculations confirm that the Förster radius (R₀) increases from 16.6 Å in solution to 24.6 Å in the nanoparticle state, significantly boosting FRET efficiency from 38% to 87%. Time-resolved fluorescence measurements further support this mechanism, showing rapid quenching kinetics consistent with energy migration across the nanoparticle matrix. Single-particle fluorescence microscopy demonstrates that individual dyad 1 nanoparticles undergo complete ON-OFF switching cycles under alternating UV (390 nm) and visible (632 nm) light, with no observable degradation after ten cycles. The system maintains excellent stability and repeatability in both liquid suspension and solid-state deposition. These findings highlight the power of combining AIEgens with photochromic systems in nanostructured formats to overcome intrinsic limitations of molecular-level FRET. This strategy opens new avenues for designing advanced NIR fluorescent switches for applications in bioimaging, optical data storage, and nanoscale sensing. The work exemplifies how supramolecular organization can amplify functional responses beyond what is achievable in isolated molecules.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com