Embedded exponential-type low-regularity integrators for KdV equation under rough data

BIT Numerical Mathematics - In this paper, we introduce a novel class of embedded exponential-type low-regularity integrators (ELRIs) for solving the KdV equation and establish their optimal...     

Tuning Emission Wavelength of Polymorphous Crystal via Controllable Alkyl Chain Stacking and Its Vapor- and Thermo-Responsive Fluorescence

Tuning fluorescence colour of solid-state materials has become a topic of increasing interest for both fundamental mechanism study and practical applications such as sensors, optical recording and security printing. In this work, a fluorescent colour tuneable molecule BA-C16 is rationally designed and facilely synthesized by attaching flexible long alkyl chains to 2-hydroxybenzophenone azine ( BA ), which shows both aggregation-induced emission (AIE) and excited-state intramolecular proton transfer (ESIPT) characteristics. Compared to BA , the simple introduction of long alkyl chains in BA-C16 leads to an emission wavelength redshift from 542 to 558 nm. This strategy of extending emission wavelength is rarely reported, and is ascribed to the enlarged through-space π-conjugation between interplanar molecules in the aggregate of BA-C16 . Three crystals of BA-C16 are obtained with green, yellowish green and yellow emission. According to characterization by X-ray crystallography, X-ray powder diffraction and differential scanning calorimetry, alkyl chains play an important role in inducing different stacking modes of the three crystals, which further leads to polymorph-dependent fluorescence colour. BA-C16 exhibits tuneable solid-state fluorescence upon vapor fumigation, or annealing based on a transition between a “near-monomer” crystalline state and a “dimer” crystalline state. BA-C16 is further applied for rewritable fluorescence printing tuned by vapor- and thermal-treatment.     

传输线方程的高精度龙格−库塔数值求解方法

提出了一种求解传输线方程的高精度龙格-库塔(RK)方法。此方法在空间上采取高阶泰勒展开,提高了对空间微分的近似精度,减少了数值色散所带来的误差。与传统的时域有限差分法(FDTD)方法相比,在每波长采样数相同时,RK方法的计算精度更高。同时,根据Taylor模型,对外界平面波激励源进行离散,成功利用RK方法对外部场激励传输线进行求解,扩大了龙格-库塔方法在求解传输线方程时的应用范围。通过编程对平面波辐照下无限大地平面上的单导体与双导体的算例分别应用FDTD方法与RK方法进行了计算,验证了RK方法的正确性。结果表明同等计算条件下RK方法的计算精度更高。     

Co-Assembly between Fmoc Diphenylalanine and Diphenylalanine within a 3D Fibrous Viscous Network Confers Atypical Curvature and Branching

Supramolecular polymer co-assembly is a useful approach to modulate peptide nanostructures. However, the co-assembly scenario where one of the peptide building blocks simultaneously forms a hydrogel is yet to be studied. Herein, we investigate the co-assembly formation of diphenylalanine (FF), and Fmoc-diphenylalanine (FmocFF) within the 3D network of FmocFF hydrogel. The overlapping peptide sequence between the two building blocks leads to their co-assembly within the gel state modulating the nature of the FF crystals. We observe the formation of branched microcrystalline aggregates with an atypical curvature, in contrast to the FF assemblies obtained from aqueous solution. Optical microscopy reveal the sigmoidal kinetic growth profile of these aggregates. Microfluidics and ToF-SIMS experiments exhibit the presence of co-assembled structures of FF and FmocFF in the crystalline aggregates. Molecular dynamics simulation was used to decipher the mechanism of co-assembly formation.     

Cooperative effect of Fe and Ti species over Fe–Ti–Ox catalysts on the catalytic hydrolysis performance of hydrogen cyanide

FeO_x, TiO₂, and Fe–Ti–O_x catalysts were synthesized and used in the catalytic hydrolysis of hydrogen cyanide (HCN). Nearly 100% HCN conversion was achieved at 250 °C over the Fe–Ti–O_x catalyst. TiO₂ rutile was detected over TiO₂, but not over Fe–Ti–O_x, which suggested that the interaction between Fe and Ti species could inhibit the TiO₂ phase transition. Furthermore, the interaction between Fe and Ti species over Fe–Ti–O_x could promote the selectivity of NH₃ and CO. The mechanism of hydrolysis of HCN over FeO_x, TiO₂, and Fe–Ti–O_x can be given as follows: HCN + H₂O → methanamide → ammonium formate → formic acid → H₂O + CO.     

Enhancement of thermoelectric properties of D-A conjugated polymer through constructing random copolymers with more electronic donors

Developing new D-A conjugated polymer system for thermoelectric (TE) application is highly desirable. Herein, a series of random copolymers by incorporating 3,4-ethylenedioxythiophene (EDOT) electron rich units into a diketopyrrolopyrrole (DPP) D-A conjugated polymer were designed and synthesized. Compared to the alternating conjugated copolymer PDPP-3T, the HOMO level of the random copolymers are increased as part of the electron deficiency acceptor DPP units in the polymer chain were superseded by electron rich EDOT, which could contribute to effective p-doping. Moreover, through incorporating EDOT to construct random copolymers, it can also induce an orientation change from face-on dominated to edge-on dominated orientation as well as enhance the packing of copolymer chains, which is beneficial to the charge transport. Under same doping condition, the electrical conductivities of the doped polymers increase and the Seebeck coefficient decrease as the increasing of EDOT content, resulting in an optimized power factor of 6.4 μW m⁻¹ K⁻² for the random polymer with EDOT content of 40% which is four times higher than that of alternating conjugated copolymer PDPP-3T. These results demonstrated that constructing random copolymers by incorporating more electronic donors into D-A conjugated polymers may be a promising strategy for developing TE conjugated polymers.     

Two-dimensional Supramolecular Polymers Based on Selectively Recognized Aromatic Cation-π and Donor-Acceptor Motifs for Photocatalytic Hydrogen Evolution

Two-dimensional (2D) organic polymers have recently received considerable interest, especially those whose architectures are held together via supramolecular engineering. However, current approaches toward supramolecular 2D structures usually suffer from mutual interference of noncovalent interactions and lack of intrinsic functions. Herein, we report well-regulated 2D supramolecular polymers (2DSPs) through an aromatics-selective recognition strategy of cation-π and donor-acceptor (D-A) motifs, which are derived from C₄-symmetric cationic monomers and electron-withdrawing molecules. By subtly designing the strength and direction of noncovalent driving forces, the mutual interference between cation-π and D-A interactions is effectively avoided, enabling the construction of 2DSPs in aqueous solution. On this basis, the resultant 2DSPs possess boosted photocatalytic hydrogen evolution activity at a rate of 600 μmol g⁻¹ h⁻¹, which is mainly ascribed to the specific stacking mode of cation-π/D-A motifs and the ordered 2D structures.     

Sc,Ti,V修饰B/N掺杂单缺陷石墨烯的储氢研究

3d过渡金属修饰是改善石墨烯储氢性能的最有效途径, 但仍存在金属团聚和H₂解离导致难以脱附的问题. 提出了B/N掺杂单缺陷石墨烯(BMG/NMG)的策略来避免以上两个问题. 密度泛函理论计算结果表明, N掺杂可以使Sc, Ti, V与石墨烯的结合能提高3~4倍, B掺杂可以将Sc与石墨烯的结合能提高3倍. Sc/BMG和Sc/NMG吸附的第一个H₂不会解离. Sc/BMG中Sc吸附5个H₂, 平均氢分子结合能为-0.18～-0.43 eV, 并且可以通过在同侧锚定多个Sc原子形成Sc/C₃B₂五元环增加H₂吸附位点. Sc/NMG中每个Sc吸附6个H₂, 平均氢分子结合能为-0.17～-0.29 eV, 还可以通过在异侧修饰形成Sc/N₃/Sc单元进一步提高储氢能力. 研究结果将为设计基于3d过渡金属修饰碳材料的储氢材料提供理论基础.     

基于学科素养论证分析2020年高考全国卷Ⅰ物理压轴题

2020年高考物理试题依托高考评价体系,结合物理学科特点,考试内容以学科素养考查为导向,即以物理观念、科学思维、科学探究、科学态度与责任的物理学科素养为导向,注重对核心物理概念和规律的考查,引导学生夯实学习发展的基础,促进中学重视培养学生的基础知识、基本技能以及提升学生的基本素养.基于物理学科素养,论证分析2020年高考全国理综卷Ⅰ物理压轴计算题,助力培养学生科学思维.