Improving Electroluminescence Efficiency by Linear Polar Host Capable of Promoting Horizontal Dipole Orientation for Dopant.

In doped organic light-emitting diodes (OLEDs), the host materials play an important role in emitting layers. Most studies about host materials mainly focus on their energy levels and carrier transport behaviors, while less attention is paid to their influence on the dipole orientation of dopants, which closely associate with the light out-coupling efficiency (ηout ) of the device. Herein, a linear polar host material (l-CzTRZ) consisting of carbazole donor, triazine acceptor, and the conjugated para-terphenyl skeleton is developed and its crystal and electronic structures, thermal and electrochemical stabilities, optical property, and carrier transport ability are investigated. l-CzTRZ prefers ordered horizontal orientation and favors electron transport in neat film. More importantly, it can promote horizontal dipole orientation for the dopants via dipole-dipole interaction, furnishing an excellent horizontal dipole ratio of 91.5% and thus a high ηout of 43% for the phosphorescent dopant (PO-01-TB). Consequently, the OLED with l-CzTRZ host and PO-01-TB dopant attains state-of-the-art electroluminescence efficiencies of 135.5 cd A-1 , 135.7 lm W-1 and 41.3%, with a small roll-off of 9.7% at 5000 cd m-2 luminance. The presented significant impact of the host on the dipole orientation of the dopant shall enlighten the design of host materials to improve OLED performance.

A biological luminescent metal-organic framework with high fluorescence quantum yield for the selective detection of amino acids and monosaccharides.

The biological luminescent metal-organic framework (bio-LMOF), (Me2NH2)2[Zn6O(Ade)4(TCPPE)2] (1) {H4TCPPE = tetrakis[4-(4-carboxyphenyl)phenyl]ethene, Ade = adenine} was successfully designed and synthesized under hydrothermal conditions, with two channels of different sizes. The absolute fluorescence quantum yields of complex 1 and activated 1 are up to 77.6% and 85.9%, respectively. Activated 1 exhibits outstanding water stability and excellent selective luminescence sensing for amino acids and monosaccharides. The fluorescence quenching efficiencies of activated 1 towards L-Nph and D-Nga are 86.35% and 91.60%, respectively. Besides, activated 1 also displays highly quenching responses to L-Nph and D-Nga at fairly low concentrations, and the limits of detection for L-Nph and D-Nga are estimated to be 0.149 ppm and 1.612 ppm, respectively. Meanwhile, in multiple cycling experiments, activated 1 still has excellent cycling stability. These phenomena indicate that activated 1 can be utilized as a fast responsive biological luminescent sensor, which is a rare example for bio-LMOFs.

Circularly Polarized Luminescence of Achiral Metal-Organic Colloids and Guest Molecules in a Vortex Field.

Recently, scientists have reported a range of chiral fluorescence materials or chiral composites that can emit circularly polarized luminescence. Herein, two achiral metal-organic colloidal solutions were studied, showing active circularly polarized luminescence, which is observed in vortex stirring. The absolute values for glum are 0.05 and 0.03 and the plus or minus sign of glum depends on the colloidal structure and stirring direction, which make the property easy to manipulate. Further, the host-guest interaction study suggests both electrostatic interactions and coordination bonding may influence the chiroptical property from the colloidal solution to the guest molecule. Rhodamine 6G and its carboxylic acid derivative exhibit good quantum yields and acceptable glum values in the colloidal solution.

Nitrogen-Rich Tetraphenylethene-Based Luminescent Metal-Organic Framework for Efficient Detection of Carcinogens.

The introduction of nitrogen-rich functional groups into a luminescent metal-organic framework (LMOF) can enhance its fluorescent sensing ability. In this work, we designed and synthesized a triazole-containing tetracarboxyl-substituted tetraphenylethene (TPE) ligand, tetrakis[4-(4-carboxyphenyl)(1H-1,2,3-triazol-4,1-diyl)phenyl]ethene (H4TCPTAPE), featuring a prominent aggregation-induced emission (AIE). A highly porous TPE-based LMOF [Zn3(TCPTAPE)(H2O)2(OH)2] (1) with large pores was successfully obtained via solvothermal assembly of the H4TCPTAPE ligand and Zn(II) ions, which showed a high fluorescence quantum yield of 54%. The activated 1 could selectively and sensitively detect aristolochic acid I with a high fluorescence quenching efficiency of 96% and a low detection limit of 1.02 µM, indicating that it has a potential application as a luminescence-based chemical sensor for carcinogens.

Tetraphenylethene-Based Luminescent Metal-Organic Framework for Effective Differentiation of cis/trans Isomers.

Luminescent metal-organic frameworks (LMOFs) that can effectively differentiate cis/trans isomers are rarely reported. Herein, we report a novel non-interpenetrated pillared-layered LMOF [Zn(HIPA)(BPyTPE)] (1) (BPyTPE = (E)-1,2-diphenyl-1,2-bis(4-(pyridin-4-yl)phenyl)ethene; HIPA = (5-hydroxyisophthalic acid)) with a high fluorescence quantum yield of 90.1%. The activated 1 exhibits high thermal stability and strong fluorescence in a methanol suspension. The fluorescence of activated 1 can be much more efficiently quenched by trans-dimethyl-2-butenedioate and trans-2-butene-1,4-diol than cis-dimethyl-2-butenedioate and cis-2-butene-1,4-diol, which enables it to differentiate these cis/trans isomers. This interesting LMOF could be a new type of fluorescence sensor to effectively detect cis/trans isomers.

Type I photosensitizers based on phosphindole oxide for photodynamic therapy: apoptosis and autophagy induced by endoplasmic reticulum stress.

Photodynamic therapy (PDT) is considered a pioneering and effective modality for cancer treatment, but it is still facing challenges of hypoxic tumors. Recently, Type I PDT, as an effective strategy to address this issue, has drawn considerable attention. Few reports are available on the capability for Type I reactive oxygen species (ROS) generation of purely organic photosensitizers (PSs). Herein, we report two new Type I PSs, α-TPA-PIO and ß-TPA-PIO, from phosphindole oxide-based isomers with efficient Type I ROS generation abilities. A detailed study on photophysical and photochemical mechanisms is conducted to shed light on the molecular design of PSs based on the Type I mechanism. The in vitro results demonstrate that these two PSs can selectively accumulate in a neutral lipid region, particularly in the endoplasmic reticulum (ER), of cells and efficiently induce ER-stress mediated apoptosis and autophagy in PDT. In vivo models indicate that ß-TPA-PIO successfully achieves remarkable tumor ablation. The ROS-based ER stress triggered by ß-TPA-PIO-mediated PDT has high potential as a precursor of the immunostimulatory effect for immunotherapy. This work presents a comprehensive protocol for Type I-based purely organic PSs and highlights the significance of considering the working mechanism in the design of PSs for the optimization of cancer treatment protocols.

Reaction-based chiroptical sensing of ClO- using circularly polarized luminescence via self-assembly organogel.

By covalent combination of a chiral amino acid, lipid, and achiral phenothiazine derivative, a reaction-based chiroptical probe, PTZ-D, was obtained. PTZ-D could self-assemble into a chiral organogel realizing the chirality transformation from a chiral amino acid to a self-assembled system and displaying unprecedented chiroptical monitoring of ClO- with switchable CPL signals.