COVID-19 Pandemic and International Students' Mental Health in China: Age, Gender, Chronic Health Condition and Having Infected Relative as Risk Factors.

International students in China were among the first group of individuals to be affected by the COVID-19 pandemic. However, the pandemic's impact on their mental health is underexplored. This study-utilizing web-based survey data (N = 381), presents preliminary reports using ANOVA and MIMIC analytic approaches.

Spiral Donor Design Strategy for Blue Thermally Activated Delayed Fluorescence Emitters.

Thermally activated delayed fluorescence (TADF) emitters with a spiral donor show tremendous potential toward high-level efficient blue organic light-emitting diodes (OLEDs). However, the underlying design strategy of the spiral donor used for blue TADF emitters remains unclear. As a consequence, researchers often do "try and error" work in the development of new functional spiral donor fragments, making it slow and inefficient.

J-Aggregation Enhances the Electroluminescence Performance of a Sky-Blue Thermally Activated Delayed-Fluorescence Emitter in Nondoped Organic Light-Emitting Diodes.

A pivotal thermally activated delayed-fluorescence (TADF) emitter, DspiroAc-TRZ, was developed, and it exhibits greatly enhanced electroluminescence performance in nondoped organic light-emitting diodes (OLEDs) owing to the concurrent manipulation of aggregation behavior and monomolecular structure. The delicate non-planar packing pattern in the DspiroAc-TRZ crystal can not only lead to highly efficient solid-state luminescence but also form a loose intermolecular packing pattern, greatly decreasing the HOMO or LUMO overlaps in dimers and shortening the triplet exciton diffusion length. In addition, the rigid donor and acceptor moieties in DspiroAc-TRZ can rigidify the molecular backbone, resulting in a tiny geometric vibrational relaxation in the excited state.

Nondoped Red Fluorophores with Hybridized Local and Charge-Transfer State for High-Performance Fluorescent White Organic Light-Emitting Diodes.

Two red fluorophores (TPABTPA and TPABCHO) with hybridized local and charge-transfer properties were systematically studied. TPABTPA and TPABCHO enabled nondoped organic light-emitting diodes (OLEDs) with excellent external quantum efficiency (EQE) of 11.1% and 5.

The luminescence properties of CsPbMBr perovskite nanocrystals transformed from CsPbBr mediated by various divalent bromide MBr salts.

A novel high concentration doping method based on the transformation from CsPbBr nanocrystals (NCs), which reacted with divalent metal bromide MBr, to CsPbMBr NCs was developed. Two types of M and Zn which cannot emit light and Mn and Eu which can be used as the luminous centres, were chosen to trigger the transformation of CsPbBr NCs to CsPbMBr NCs. CsPbZnBr NCs maintained high photoluminescence quantum yields (PLQY) (>75%) and had good dispersion in hexane without obvious dissolution or agglomeration after two weeks.

Adamantane-Substituted Acridine Donor for Blue Dual Fluorescence and Efficient Organic Light-Emitting Diodes.

To date, blue dual fluorescence emission (DFE) has not been realized because of the limited choice of chemical moieties and severe geometric deformation of the DFE emitters leading to strong intramolecular charge transfer (ICT) with a large Stokes shift in excited states. Herein, an emitter (1'r,5'R,7'S)-10-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-10H-spiro [acridine-9,2'-adamantane] (a-DMAc-TRZ) containing a novel adamantane-substituted acridine donor is reported, which exhibits unusual blue DFE. The introduction of the rigid and bulky adamantane moiety not only suppressed the geometry relaxation in excited state, but also induced the formation of quasi-axial conformer (QAC) and quasi-equatorial conformer (QEC) geometries, leading to deep-blue conventional fluorescence and sky-blue thermally activated delayed fluorescence (TADF).

White-light emission from a single heavy atom-free molecule with room temperature phosphorescence, mechanochromism and thermochromism.

Two heavy atom-free luminophores (SHBt and SDBt) with simple molecular structures have been synthesized Suzuki coupling reactions in which both display white-light emission with prompt fluorescence and room temperature phosphorescence (RTP) in the solid state. The impressive RTP of the luminophores is produced by a synergistic effect of the strong intermolecular hydrogen bonding in addition to the spin-orbit coupling of the sulfonyl oxygen atoms and the moderate singlet-triplet energy gaps (Δ). These factors facilitate the intersystem crossing (ISC) process to generate triplet excitons in which the molecular conformations become immobilized to effectively suppress radiationless decay.

Achieving very bright mechanoluminescence from purely organic luminophores with aggregation-induced emission by crystal design.

Although bright organic mechanoluminescence (ML) has been observed for a few luminophores with aggregation-induced emission (AIE), details of the positive effect of AIE on ML performance remain unclear and a feasible design principle for AIE-ML compounds has not yet been presented. Herein, an effective strategy for the molecular design of efficient AIE-ML materials is demonstrated, based on tetraphenylethene (TPE) building blocks with formyl substituents, which yield non-centrosymmetric crystal structures with prominent piezoelectric properties for molecular excitation combined with AIE features for intense emission. Following this approach, three AIE-active compounds have been developed and are found to show unique ML characteristics.

Structure-Performance Investigation of Thioxanthone Derivatives for Developing Color Tunable Highly Efficient Thermally Activated Delayed Fluorescence Emitters.

Thioxanthone derivatives consisting of undecorated carbazole as an electron donor and thioxanthone (TXO) or 9H-thioxanthen-9-one-S,S-dioxide (SOXO) as an electron acceptor in a donor-acceptor (D-A) or donor-acceptor-donor (D-A-D) structure were developed as thermally activated delayed fluorescence emitters to fabricate highly efficient fluorescent organic light emitting diodes. Their emission color was successfully tuned from blue to yellow by changing the sulfur atom valence state of the thioxanthone unit to tune intramolecular charge transfer effect. Their thermal, electrochemical, photophysical, and electroluminescent properties, and theoretical calculations were systematically investigated to illustrate the molecular structure and property relationships.

Achieving remarkable mechanochromism and white-light emission with thermally activated delayed fluorescence through the molecular heredity principle.

Achieving high contrast mechanochromism (Δ > 100 nm) and white-light emission under mild conditions from a single compound with a simple structure is a great challenge. Herein, we report a novel dual-emissive compound, namely SCP, with an asymmetric molecular structure that fully inherits the photophysical properties of the parent molecules SC and SP. SCP shows high contrast, linearly tunable mechanochromism and bright white-light emission arising from a combination of traditional fluorescence and thermally activated delayed fluorescence (TADF).

Intermolecular Electronic Coupling of Organic Units for Efficient Persistent Room-Temperature Phosphorescence.

Although persistent room-temperature phosphorescence (RTP) emission has been observed for a few pure crystalline organic molecules, there is no consistent mechanism and no universal design strategy for organic persistent RTP (pRTP) materials. A new mechanism for pRTP is presented, based on combining the advantages of different excited-state configurations in coupled intermolecular units, which may be applicable to a wide range of organic molecules. By following this mechanism, we have developed a successful design strategy to obtain bright pRTP by utilizing a heavy halogen atom to further increase the intersystem crossing rate of the coupled units.