Inorganic salt recrystallization strategy for achieving ultralong room temperature phosphorescence through structural confinement and aluminized reconstruction.

Achieving highly efficient and stable room temperature phosphorescence (RTP) with ultralong lifetime is critical for the multi-purpose applications of phosphorescent materials. In this work, we propose an inorganic salt heating recrystallization strategy to simultaneously improve the lifetime, quantum efficiency, and stability of phosphorescent scandium/leucine microspheres (Sc/Leu-MSs). Inorganic salt-treated Sc/Leu-MSs are obtained by simply heating and drying inorganic salt solution containing Sc/Leu-MSs, which can achieve a maximum lifetime increase of 4.42-times from 208.37 ms (Sc/Leu-MSs) to 920.08 ms (Al2(SO4)3-treated Sc/Leu-MSs), accompanied by a RTP intensity increase up to 24.08-times. The enhancement mechanism of RTP efficiency is attributed to the stabilization of triplet excitons caused by inorganic salt coating that suppresses molecular motion and isolates oxygen on the one hand, and the efficient intersystem crossing promoted by aluminized reconstruction-caused duplex heavy atom effects on the other hand. This study provides new design principle and a facile strategy to construct RTP materials with ultralong lifetime, high phosphorescent quantum efficiency, and high stability for promising applications such as anti-counterfeiting and light emitting diodes.

Cage-Like Sodalite-Type Porous Organic Salts Enabling Luminescent Molecule's Incorporation and Room-temperature Phosphorescence Induction in Air.

Expression of room-temperature phosphorescence (RTP) in organic materials requires complicated molecular design and specific intermolecular interactions, and therefore types of RTP materials are restricted. This work presents cage-like sodalite-type porous organic salts (s-POSs) as host materials for luminescent molecules to induce RTP, using tetrasulfonic acid with an adamantane core and triphenylmethylamines that are modified with substituents in the para-positions of benzene rings (TPMA-X). By adding a representative luminescent molecule (pyrene) to a reaction solution during construction of s-POSs, the molecule is incorporated in a facile manner. s-POSs with a heavy halogen atom (X: Iodine) on the pore surface give heavy atom effects, suppression of thermal vibration, and protection from oxygen, for the incorporated molecule, which induce its RTP even in air. This strategy can be applied to various luminescent molecules, which may lead to the achievement of RTP of various colors.

Preparation of AIE Functional Single-Chain Polymer Nanoparticles and Their Application in H2 O2 Detection through Intermolecular Heavy-Atom Effect.

Single-chain polymer nanoparticles (SCNPs) are soft matter constructed by intrachain crosslinks, with promising prospects in detection and catalysis. Herein, a fluorescent core (SCNPs) with aggregation-induced emission (AIE) is prepared, applying for H2 O2 detection through intermolecular heavy-atom effect. In detail, the SCNPs precursors are synthesized by ring-opening copolymerization. Then the SCNPs are prepared by intramolecularly cross-linking via olefin metathesis. Imitating the structure of AIE dots, SCNPs are encapsulated by H2 O2 -responsive polymers. Probably due to the stable secondary structure of SCNPs, the obtained micelles show stable fluorescence performance. Furthermore, as the heavy-atom, tellurium is introduced into the carriers to construct the heavy-atom effect. In this micelle-based system, the SCNPs act as the fluorescent core, and the stimuli-responsive polymer acts as the carrier and the fluorescent switch. The hydrophilicity of the tellurium-containing segment is affected by the concentration of H2 O2 , resulting in a change in the distance from the SCNPs, which ultimately leads to a change in the fluorescence intensity. Furthermore, tellurium is particularly sensitive to H2 O2 , which can detect low concentrations of H2 O2 . The SCNPs are merged with AIE materials, with the hope of exploring new probe designs.

Boron-, Sulfur- and Nitrogen-Doped Polycyclic Aromatic Hydrocarbon Multiple Resonance Emitters for Narrow-Band Blue Emission.

Two boron-, sulfur- and nitrogen-doped polycyclic aromatic hydrocarbon multiple resonance thermally activated delayed fluorescence emitters with high photoluminescent quantum efficiency (88 %) and rapid reverse intersystem crossing (kRISC = 1.0×105  s-1 ) are designed and synthesized, enabling efficient narrow-band blue electroluminescence at 473 nm with full width at half maximum of 29 nm and maximum external quantum efficiency of 22.0 %, which provides an avenue to expand the structure library for multiple resonance emitters and an approach to regulate their emission properties.

Room-Temperature Phosphorescence Emitters Exhibiting Red to Near-Infrared Emission Derived from Intermolecular Charge-Transfer Triplet States of Naphthalenediimide-Halobenzoate Triad Molecules.

Room-temperature phosphorescence (RTP) emitters have attracted significant attention. However, purely organic RTP emitters in red to near-infrared region have not been properly investigated. In this study, a series of naphthalenediimide-halobenzoate-linked molecules are synthesized, one of which exhibits efficient RTP properties, showing red to near-infrared emission in solid and aqueous dispersion. Spectroscopic studies and single-crystal X-ray diffraction analysis have shown that the difference in the stacking modes of compounds affects the optical properties, and the formation of intermolecular charge-transfer complexes of naphthalenediimide-halobenzoate moiety results in a bathochromic shift of absorption and RTP properties. The time-dependent density functional theory calculations showed that the formation of charge-transfer triplet states and the external heavy atom effect of the halogen atom enhance the intersystem crossing between excited singlet and triplet states.

Modulating Room-Temperature Phosphorescence-To-Phosphorescence Mechanochromism by Halogen Exchange.

Modulating the stimulus-responsiveness of a luminescent crystal is challenging owing to the complex interdependent nature of its controlling factors, such as molecular structure, molecular conformation, crystal packing, optical properties, and amorphization behavior. Herein, we demonstrate a halogen-exchange approach that disentangles this problem, thereby realizing the modulation of room-temperature phosphorescence-to-phosphorescence mechanochromism. Replacing the bromine atoms in a brominated thienyl diketone with chlorine atoms afforded isostructural crystals; i.e., molecules with different halogen atoms exhibited the same molecular conformation and crystal packing. Consequently, amorphization behavior toward mechanical stimulation was also the same, and the phosphorescence of amorphous states originated from the same conformer of each diketone. In contrast, the phosphorescence properties of each conformer were modulated differently, which is ascribable to heavy atom effects, resulting in the modulation of the mechanochromism. Thus, halogen exchange is a promising approach for modulating the stimulus-responsive photofunctions of crystals involving spin-forbidden processes.

Highly Stable and Multifunctional Aza-BODIPY-Based Phototherapeutic Agent for Anticancer Treatment.

Phototherapy, as an important class of noninvasive tumor treatment methods, has attracted extensive research interest. Although a large amount of the near-infrared (NIR) phototherapeutic agents have been reported, the low efficiency, complicated structures, tedious synthetic procedures, and poor photostability limit their practical applications. To solve these problems, herein, a donor-acceptor-donor (D-A-D) type organic phototherapeutic agent (B-3) based on NIR aza-boron-dipyrromethene (aza-BODIPY) dye has been constructed, which shows the enhanced photothermal conversion efficiency and high singlet oxygen generation ability by simultaneously utilizing intramolecular photoinduced electron transfer (IPET) mechanism and heavy atom effects. After facile encapsulation of B-3 by amphiphilic DSPE-mPEG5000 and F108, the formed nanoparticles (B-3 NPs) exhibit the excellent photothermal stabilities and reactive oxygen and nitrogen species (RONS) resistance compared with indocyanine green (ICG) proved for theranostic application. Noteworthily, the B-3 NPs can remain outstanding photothermal conversion efficiency (η = 43.0%) as well as continuous singlet oxygen generation ability upon irradiation under a single-wavelength light. Importantly, B-3 NPs can effectively eliminate the tumors with no recurrence via synergistic photothermal/photodynamic therapy under mild condition. The exploration elaborates the photothermal conversion mechanism of small organic compounds and provides a guidance to develop excellent multifunctional NIR phototherapeutic agents for the promising clinical applications.

Halogenated Aza-BODIPY for Imaging-Guided Synergistic Photodynamic and Photothermal Tumor Therapy.

It is always a huge challenge to develop novel near-infrared (NIR) phototherapeutic agents suitable for imaging-guided cancer therapy. In order to clarify the positive heavy atom effects on the photodynamic and photothermal efficiencies of phototherapeutic agents, a series of chlorine-, bromide-, or iodine-substituted aza-BODIPYs (B2, B3, and B4, respectively) are designed and synthesized. Among them, B4 exhibits both excellent photodynamic and photothermal effects (singlet oxygen yield of B4 is 1.57 times more than that of B3) and excellent photothermal effects (1.3 °C higher than that of B3). Then, nanoparticles of B4 (IABNs) with excellent biocompatibility are prepared by coating hydrophobic B4 with hydrophilic polymer DSPE-mPEG5000 . IABN exhibits high photostability, excellent biocompatibility, and low dark toxicity both in vivo and in vitro. Furthermore, IABN shows the enhanced photodynamic effect and high photothermal conversion efficiency (34.8%). In addition, the strong fluorescence emission of IABN makes it suitable for fluorescence imaging-guided tumor therapy in vivo. Finally, IABN has successfully healed the Hela tumor-bearing mice under NIR fluorescence imaging- and photothermal imaging-guided synergistic photothermal and photodynamic therapy with low side effects, demonstrating that it is promising for future clinical applications.