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Metal halide perovskites have witnessed great success in green, red, and near-infrared light-emitting diodes (LEDs), yet blue LEDs still lag behind. Reducing undesired energetic disorders – broad n-phases and halide segregation – is considered as the most critical strategy to further improve the performances. Here, the study reports a newly designed and synthesized di-ammonium ligand with rigid π-conjugated rings and additional methyl groups to construct Dion–Jacobson (DJ) structure. Augmented coordination from the extra ammonium site and increased effective bulkiness from methyl groups lead to better distribution control over conventional mono-ammonium ligands. This enhances the radiative recombination of blue emissions in the film with homogeneous energy landscape and improved surface morphology, as evidenced by a series of imaging and mapping techniques. As a result, it demonstrates DJ perovskite LEDs (PeLEDs) with peak external quantum efficiencies of ≈4% at 484 nm and ≈11% at 494 nm, which are among the top reported for pure DJ phase-based PeLEDs in the corresponding wavelength regions. The results deepen the understanding of regulating energetic disorders in perovskite materials via molecular engineering.

Comparative analysis of aroma-active compounds in large-leaf yellow tea and rice crust was carried out via headspace solid phase micro-extraction (HS-SPME) combined with gas chromatography-olfactometry-mass spectrometry (GC-O-MS) to elucidate the material basis of the rice crust-like aroma of large-leaf yellow tea. The results revealed that 72 and 45 volatile compounds were identified in large-leaf yellow tea infusion and rice crust, respectively. In total, 15 aroma-active components were found in both large-leaf yellow tea and rice crust. Among them, five pyrazines responsible for a roasted aroma were common to both, which made a key contribution to the characteristic rice crust-like aroma of large-leaf yellow tea. 2-Ethyl-3,5-dimethylpyrazine, 2-ethyl-5-methylpyrazine and 2,6-diethylpyrazine were the key aroma-active components of both large-leaf yellow tea and rice crust. 3,5-Diethyl-2-methylpyrazine was key to the formation of the rice crust-like aroma of large-leaf yellow tea, but contributed little to the characteristic aroma of rice crust. 3-Ethyl-2,5-dimethylpyrazine was key to the formation of the characteristic aroma of rice crust, butt contributed little to the characteristic aroma of large-leaf yellow tea.

Polymers are desirable optoelectronic materials, stemming from their solution processability, tunable electronic properties, and large absorption coefficients. An exciting development is the recent discovery that singlet fission (SF), the conversion of a singlet exciton to a pair of triplet states, can occur along the backbone of an individual conjugated polymer chain. Compared to other intramolecular SF compounds, the nature of the triplet pair state in SF polymers remains poorly understood, hampering the development of new materials with optimized excited state dynamics. Here, we investigate the effect of solvent polarity on the triplet pair dynamics in the SF polymer polybenzodithiophene-thiophene-1,1-dioxide. We use transient emission measurements to study isolated polymer chains in solution and use the change in the solvent polarity to investigate the role of charge transfer character in both the singlet exciton and the triplet pair multiexciton. We identify both singlet fluorescence and direct triplet pair emission, indicating significant symmetry breaking. Surprisingly, the singlet emission peak is relatively insensitive to solvent polarity despite its nominal "charge-transfer" nature. In contrast, the redshift of the triplet pair energy with increasing solvent polarity indicates significant charge transfer character. While the energy separation between singlet and triplet pair states increases with solvent polarity, the overall SF rate constant depends on both the energetic driving force and additional environmental factors. The triplet pair lifetime is directly determined by the solvent effect on its overall energy. The dominant recombination channel is a concerted, radiationless decay process that scales as predicted by a simple energy gap law. [ABSTRACT FROM AUTHOR]

In recent years, environmental pollution and resource waste have become the focus of heated discussion around the world. In order to realize green and sustainable development, the development of green supply chain (GSC) has attracted the attention of many scholars. The research object of this paper is the dual-channel green supply chain (DGSC) composed of online channels and offline channels. The supplier is the leader of the entire DGSC, and it needs to optimize the wholesale price of the product and the level of green investment to maximize its own benefit. In addition, the supplier also needs to establish contracts with network sales platform (NSP) and store sales platform (SSP) to increase the benefit of NSP and SSP, and ultimately increase the benefit level of the entire DGSC. Among them, we constructed a centralized decision (CD) model and a decentralized decision (DD) model, and obtained the optimal pricing, optimal greenness and optimal benefit of the supplier, NSP and SSP under the two models. We found that the benefits of SC members under the DD model are generally lower than those of the CC model. Therefore, we built contracts between the supplier, NSP and SSP to coordinate. Finally, we substituted specific parameters to verify the model. The following conclusions are drawn: (i) When consumers prefer online sales channels, it will positively affect the online sales price, online sales volume and greenness level of DGSC. At the same time, it negatively affects offline sales price and sales volume. (ii) The benefit of DGSC and the benefit of NSP, SSP, and the supplier show a phenomenon of decline first and then increase with respect to consumers' preference for online sales channels. (iii) Under the coordination contract, the subsidy factor positively affects the benefits of the supplier and online and offline wholesale prices, and negatively affects the benefits of online platforms and physical stores. [ABSTRACT FROM AUTHOR]

Introduction: Cognitive training and physical exercise have shown positive effects on delaying progression of mild cognitive impairment (MCI) to dementia. Methods: We explored the enhancing effect from Tai Chi when it was provided with cognitive training for MCI. In the first 12 months, the cognitive training group (CT) had cognitive training, and the mixed group (MixT) had additional Tai Chi training. In the second 12 months, training was only provided for a subgroup of MixT. Results: In the first 12 months, MixT and CT groups were benefited from training. Compared to the CT group, MixT had additional positive effects with reference to baseline. In addition, Compared to short‐time training, prolonged mixed training further delayed decline in global cognition and memory. Functional magnetic resonance imaging showed more increased regional activity in both CT and MixT. Discussion: Tai Chi enhanced cognitive training effects in MCI. Moreover, Tai Chi and cognitive mixed training showed effects on delaying cognitive decline. [ABSTRACT FROM AUTHOR]

The synthesis and structure of atomically precise Au130−xAgx (average x=98) alloy nanoclusters protected by 55 ligands of 4‐tert‐butylbenzenethiolate are reported. This large alloy structure has a decahedral M54 (M=Au/Ag) core. The Au atoms are localized in the truncated Marks decahedron. In the core, a drum of Ag‐rich sites is found, which is enclosed by a Marks decahedral cage of Au‐rich sites. The surface is exclusively Ag−SR; X‐ray absorption fine structure analysis supports the absence of Au−S bonds. The optical absorption spectrum shows a strong peak at 523 nm, seemingly a plasmon peak, but fs spectroscopic analysis indicates its non‐plasmon nature. The non‐metallicity of the Au130−xAgx nanocluster has set up a benchmark to study the transition to metallic state in the size evolution of bimetallic nanoclusters. The localized Au/Ag binary architecture in such a large alloy nanocluster provides atomic‐level insights into the Au−Ag bonds in bimetallic nanoclusters. [ABSTRACT FROM AUTHOR]