Aggregation-induced dual-color luminogen with enhanced chiroptical property

Science China Chemistry -     

Resonance Raman spectroscopy and theoretical study on the photodissociation dynamics of diuron in S2 state

Resonance Raman spectra (RRs) and quantum chemical calculations were used to investigate the photodissociation dynamics of diuron in S₂ state. The RRs indicate that the photorelaxation dynamics for the S₀ → S₂ excited state is predominantly along nine motions: the ring C = C stretch vibration ν₁₂ (1593 cm⁻¹), Ph–N–H wag ν₁₄ (1517 cm⁻¹), CO–N(CH₃)₂ stretch ν₂₃ (1365 cm⁻¹)_, CCH wag in plane/ring C = C stretch ν₂₄ (1297 cm⁻¹)_, ring CH rock in plane/ring deformation ν₂₇ (1233 cm⁻¹), CCH wag in plane ν₂₉ (1151 cm⁻¹), Ph–Cl (para) stretch ν₃₅ (1028 cm⁻¹), Ph–N–H wag ν₃₇ (913 cm⁻¹) and ring breath ν₄₄ (685 cm⁻¹). Dissociation by Ph–Cl (para) cleavage at S₂ state directly or relaxation to T₂ state by internal conversion (S₂ → S₁) and intersystem crossing (S₁/T₂) is expected by ~250 nm irradiation based on the RRS, complete active space self‐consistent field, configuration interaction singles and time‐dependent density functional theory calculations. Copyright © 2012 John Wiley & Sons, Ltd.     

Quinolactacin Biosynthesis Involves Non-Ribosomal-Peptide-Synthetase-Catalyzed Dieckmann Condensation to Form the Quinolone-γ-lactam Hybrid

Quinolactacins are novel fungal alkaloids that feature a quinolone-γ-lactam hybrid, which is a potential pharmacophore for the treatment of cancer and Alzheimer's disease. Herein, we report the identification of the quinolactacin A2 biosynthetic gene cluster and elucidate the enzymatic basis for the formation of the quinolone-γ-lactam structure. We reveal an unusual β-keto acid (N-methyl-2-aminobenzoylacetate) precursor that is derived from the primary metabolite l -kynurenine via methylation, oxidative decarboxylation, and amide hydrolysis reactions. In vitro assays reveal two single-module non-ribosomal peptide synthetases (NRPs) that incorporate the β-keto acid and l -isoleucine, followed by Dieckmann condensation, to form the quinolone-γ-lactam. Notably, the bioconversion from l -kynurenine to the β-keto acid is a unique strategy employed by nature to decouple R*-domain-containing NRPS from the polyketide synthase (PKS) machinery, expanding the paradigm for the biosynthesis of quinolone-γ-lactam natural products via Dieckmann condensation.     

Fractal analysis for effective thermal conductivity of random fibrous porous materials

In this Letter, a fractal series-parallel model, which included numerous capillary channels both parallel and perpendicular to the heat flow direction, was established to predict the effective thermal conductivity of fibrous porous material (FPM). The prediction results from the proposed model are compared with calculated values from other theoretical models and experimental data.     

Carbon Quantum Dots with Near-Unity Quantum Yield Bandgap Emission for Electroluminescent Light-Emitting Diodes

Carbon quantum dots (CQDs) feature bright and tunable photoluminescence, solution processability, and low toxicity, showing great potential in optoelectronics. However, the large-scale synthesis of CQDs with near-unity photoluminescence quantum yield (PLQY) has not been achieved so far. In this study, we perform radical-assisted synthesis of hexagon-shaped CQDs (H-CQDs) delivering near-unity PLQY (96 %). Experimental and theoretical analyses revealed that the large vertically oriented transition dipole moment of H-CQDs originating from high symmetry results in nearly 100 % PLQY. The H-CQDs also exhibited a high electron mobility of up to 0.07 cm² V⁻¹ s⁻¹. These properties enable the H-CQD-based light-emitting diodes with a high external quantum efficiency of 4.6 % and a record maximum brightness of over 11 000 cd m⁻². This study represents a significant advance that CQDs-based electroluminescent device can be utilized for potential display and lighting applications.     

高层建筑结构分析与设计软件系统BSAD

本文着重介绍作者最近研究开发的高层建筑结构分析与设计软件系统（ＢＳＡＤ）的主要功能和特点．ＢＳＡＤ适用于由一维杆元和二维壳元组成的任何空间和任意平面的多层及高层建筑结构分析和设计，具有很强的通用性和适用性，分析能力不受特别限制．本系统还配有功能丰富的数据前后处理．     

Facile synthesis of hierarchical core-shell Fe3O4@MgAl-LDH@Au as magnetically recyclable catalysts for catalytic oxidation of alcohols

A novel core-shell structural Fe(3)O(4)@MgAl-LDH@Au nanocatalyst was simply synthesized via supporting Au nanoparticles on the MgAl-LDH surface of Fe(3)O(4)@MgAl-LDH nanospheres. The catalyst exhibited excellent activity for the oxidation of 1-phenylethanol, and can be effectively recovered by using an external magnetic field.     

加速溶剂萃取-超高效液相色谱-串联质谱快速测定棉花中残留的8种脱叶剂

采用加速溶剂萃取结合超高效液相色谱-串联质谱(UPLC-MS/MS)技术,建立了一种快速提取和测定棉花中8种脱叶剂(噻苯隆、脱叶磷、甲基苯噻隆、脱落酸、氟酮唑草酯、敌草隆、百草枯、嘧草硫醚)的分析方法。样品经提取、浓缩,乙腈-水溶液(1:9, v/v)溶解,采用Acquity UPLC^® HSS T3柱(50 mm×2.1 mm, 1.8 μ m)分离,以乙腈-0.05%(v/v)甲酸水溶液为流动相,梯度洗脱,电喷雾正离子模式多反应监测,外标法定量。该方法在0.01~0.3 mg/L范围内线性关系良好(r >0.99),在添加含量水平为0.1、0.5、1.0 mg/kg时,平均回收率范围为(84.18±8.04)%~(95.99±6.76)%,相对标准偏差(RSD)为7.04%~10.60%,方法检出限(LOD)为0.8~29 μ g/kg,方法定量限(LOQ)为2.5~96 μ g/kg。该方法操作简便、快捷、灵敏、准确,适合棉花中8种脱叶剂的确证和定量测定。     

Relative rates and approximate rate constants for inter- and intramolecular hydrogen transfer reactions of polymer-bound radicals

Measurements of relative rates and rate constants for inter- and intramolecular hydrogen transfer reactions of polymer-bound radicals are reported. The relative rate of reaction of resin-bound primary alkyl radical with tributyltin hydride is about 2 times slower than that of the benchmark reaction in solution. The data do not reveal whether this is due to a reduced rate constant or a lower concentration of tin hydride in the resin phase. Yet the difference between solid and solution reactions is small enough to be neglected, and it appears that rate constants measured in solution can be applied directly to resin-bound radicals. A resin-bound aryl radical abstracts a hydrogen atom rapidly (k = 3 x 10(6) s(-1)) from its own polymer backbone and linker, and a simplified view of the resin as a "solvent" is suggested for predicting such effects with other polymers and linkers. Rapid cyclizations of resin-bound aryl radicals will be possible, but slower cyclizations and most bimolecular reactions will be difficult due to the competing polymer/linker hydrogen transfer.