Fluorogens with aggregation-induced emission (AIEgens) are promising optical agents for cellular and vascular imaging. AIEgens with bright emission in the far-red and near-infrared (NIR) regions are highly desirable, but the traditional strategies, i.e., introducing donor–acceptor (D–A) structures into AIEgens, generally lead to fluorogens with photoluminescence that is vulnerable to the polarity of the surrounding environment. In addition, because of the intrinsic rotor structure, AIEgens usually show absorption in the short-wavelength region, which is not optimized for imaging applications. In this contribution, we report binary organic nanoparticles (NPs) with tunable emission and high quantum efficiency in the red and far-red regions. By increasing the intermolecular distance, the obtained NPs offered enhanced luminescence quantum yields from 0.01 to 0.23 and increased three-photon excitation (3PE) cross sections, enabling high-quality and deep brain vascular imaging on an 8-week-old BALB/C mouse with up to 1.68 mm upon excitation at 1610 nm.

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In recent years, with increasing demands for in vivo fluorescence imaging and photodynamic therapy, light in the second near‐infrared window (NIR‐II; 1000–1700 nm) has attracted tremendous interest because it offers numerous merits, including deep penetration, minimal phototoxicity, diminished tissue autofluorescence, and reduced tissue absorption and scattering. Among the diverse types of nanoparticles, organic nanoprobes with aggregation‐induced emission (AIE) characteristics have emerged as a better option owing to their ultra‐brightness, excellent photostability, low cytotoxicity, and tailorable optical properties. Recent efforts in the AIE realm have revealed advancements in molecular design for long wavelength absorption and multiphoton excitation, which efficiently modulate the working optical region to the NIR‐II region. In this review, the current status of AIE nanoprobes in the NIR‐II window is summarized. Starting with molecular design strategies, recent efforts in fluorescence imaging and photodynamic therapy are then discussed. Finally, perspectives and challenges in this newly emerging field are given. This review hopes to encourage more innovative ideas in material design and biomedical applications for promoting AIE nanoprobes for future clinical translation.

Gene therapy has shown great potential in the treatment of many diseases by constructing or downregulating the expression of certain genes. The development of gene vectors as a vehicle for...

Multi-photon theranostics, involving the absorption of two or three photons by luminogens, has come to occupy an important place in biomedical research, with its ability to allow real-time observation/treatment of dynamic structures in living cells and organisms. Luminogens with aggregation-induced emission characteristics are recognized as perfect candidates for multi-photon agents, owing to their flexibility of design, resistance to photobleaching, robust stability, and reduced cytotoxicity. Hence, in recent years, significant breakthroughs in design and application of such luminogens have been reported. In this review, we summarize the latest advances in molecular guidelines and photophysical process control for developing luminogens with large multi-photon action cross section. Special attention is paid to how the molecular structure and intermolecular interactions influence the intramolecular charge transfer, and how new strategies have been developed to advance the multi-photon imaging and therapeutic performance. With this review, we hope to encourage further exploitation of luminogens with aggregation-induced emission characteristics to advance multi-photon theranostics.