Photodynamic therapy is arising as a noninvasive treatment modality for cancer and other diseases. One of the key factors to determine the therapeutic function is the efficiency of photosensitizers (PSs). Opposed to traditional PSs, which show quenched fluorescence and reduced singlet oxygen production in the aggregate state, PSs with aggregation-induced emission (AIE) exhibit enhanced fluorescence and strong photosensitization ability in nanoparticles. Here, the design principles of AIE PSs and their biomedical applications are discussed in detail, starting with a summary of traditional PSs, followed by a comparison between traditional and AIE PSs to highlight the various design strategies and unique features of the latter. Subsequently, the applications of AIE PSs in photodynamic cancer cell ablation, bacteria killing, and image-guided therapy are discussed using charged AIE PSs, AIE PS molecular probes, and AIE PS nanoparticles as examples. These studies have demonstrated the great potential of AIE PSs as effective theranostic agents to treat tumor or bacterial infection. This review hopefully will spur more research interest in AIE PSs for future translational research.

Photosensitizers with Aggregation-Induced Emission: Materials and Biomedical Applications

Authenticating products and documents with security inks is vital to global commerce, security and health. Lanthanide complexes are widely used in luminescent security inks owing to their unique and robust photophysical properties. Lanthanide complexes can also be engineered to undergo circularly polarized luminescence (CPL), which encodes chiral molecular fingerprints in luminescence spectra that cannot be decoded by conventional optical measurements. However, chiral CPL signals have not yet been exploited as an extra security layer in advanced security inks. This Review introduces CPL and related concepts that are necessary to appreciate the challenges and potential of lanthanide-based, CPL-active security inks. We describe recent advances in CPL analysis and read-out technologies that have expedited CPL-active security ink applications. Further, we provide a systematic meta-analysis of strongly CPL-active Euiii, Tbiii, Smiii, Ybiii, Cmiii, Dyiii and Criii complexes, discussing the suitability of their photophysical properties and highlighting promising candidates. We conclude by providing key recommendations for the development and advancement of the field. Several transition-metal and lanthanide complexes undergo circularly polarized luminescence. This Review describes design principles for the complexes and instruments used to measure them, including in the context of security inks.

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Circularly polarized lanthanide luminescence for advanced security inks

1,8-Naphthalimide, as one of the classical dyes and fluorophores, has been widely used in analytical chemistry, materials chemistry, and biochemistry fields because of its excellent characteristic photostability, good structural flexibility, high fluorescence quantum yield, and large Stokes shift. This review mainly focuses on 1,8-naphthalimide and its derivatives in ion detection, molecular recognition, material applications, and bioimaging in the past five years. Simultaneously, we hope to develop more powerful fluorescent chemosensors for broad and exciting applications in the future.

1,8-Naphthalimide-based fluorescent chemosensors: recent advances and perspectives

Enantiopure molecules based on macrocyclic architecture are unique for applications in enantioselective host-guest recognition, chiral sensing and asymmetric catalysis. Taking advantage of the chiral transfer from the intrinsically planar chirality of pillar[5]arenes, we herein present an efficient and straightforward approach to achieve early examples of highly luminescent chiral systems (P5NN and P5BN). The optical resolution of their enantiomers has been carried out via preparative chiral HPLC, which was ascribed to the molecular functionalization of pillar[5]arenes with π-conjugated, sterically bulky triarylamine (Ar3 N) as an electron donor and triarylborane (Ar3 B) as an acceptor. This crucial design enabled investigations of the chiroptical properties, including circular dichroism (CD) and circularly polarized luminescence (CPL) in the solid state. The intramolecular charge transfer (ICT) nature in P5BN afforded an interesting thermochromic shift of the emission over a wide temperature range.

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Planar Chiral Organoboranes with Thermoresponsive Emission and Circularly Polarized Luminescence: Integration of Pillar[5]arenes with Boron Chemistry

Pillararene-based AIEgens: research progress and appealing applications

Herein, we report on an unusual light-emitting behavior of the homo- and copillar[5]arenes (MeP5, EtP5, PrP5, BuP5, DBuP5 and DBP5) with combinations of alkoxy functionalities. Our investigations revealed that the emission of these pillar[5]arenes was highly enhanced in the aggregate state. This turn-on fluorescence could be ascribed to the well-known aggregation-induced-emission (AIE) mechanism, which was confirmed by SEM imaging and the dynamic light scattering (DLS) technique. The current work may open another avenue to the chemistry of pillararenes as new AIEgen macrocycles for luminescence sensing of guest species including organic molecules, and metal ions as herein tested for Fe(III).

Pillar[5]arenes: a new class of AIEgen macrocycles used for luminescence sensing of Fe3+ ions

We first describe two examples of highly luminescent organoboranes (NP5BN1 and NP5BN2) with dual chirality that were achieved by molecular functionalization of planar chiral pillar[5]arenes with naphthyls. Sufficiently strong steric effects are imposed by triarylamine (Ar3N) and triarylborane (Ar3B) moieties and further enhanced by the proximity of the chiral building blocks, leading to the isolation of multiple enantiomers via chiral high-performance liquid chromatography. The intramolecular charge transfer from N-donor to B-acceptor across both chiral subunits enabled the circularly polarized luminescence and thermally robust colorimetric responses in their emissions. Furthermore, their remarkable host-guest chemistry was allowed at no expense in the pursuit of advanced chiroptical properties using pillar[5]arene-based supramolecular scaffolds.

Pillar[5]arene-Based Dual Chiral Organoboranes with Allowed Host-Guest Chemistry and Circularly Polarized Luminescence.

We have developed a new family of luminescent materials featuring through-space charge transfer from electron donors to acceptors that are electronically separated by triptycene. Most of these mole...

Triptycene-Based Luminescent Materials in Homoconjugated Charge-Transfer Systems: Synthesis, Electronic Structures, AIE Activity, and Highly Tunable Emissions.

Songhe Zhang

Papers

Planar Chiral Organoboranes with Thermoresponsive Emission and Circularly Polarized Luminescence: Integration of Pillar[5]arenes with Boron Chemistry

Pillar[5]arenes: a new class of AIEgen macrocycles used for luminescence sensing of Fe3+ ions

Pillar[5]arene-Based Dual Chiral Organoboranes with Allowed Host-Guest Chemistry and Circularly Polarized Luminescence.

Triptycene-Based Luminescent Materials in Homoconjugated Charge-Transfer Systems: Synthesis, Electronic Structures, AIE Activity, and Highly Tunable Emissions.

Synthesis, Characterization, and Photophysical Properties of Triptycene-Based Chiral Organoboranes