Enhanced Circularly Polarized Luminescence in Emissive Charge‐Transfer Complexes

Achieving a large dissymmetry factor (g_lum) is a challenge in the field of circularly polarized luminescence (CPL). A chiral charge‐transfer (CT) system consisting of chiral electron donor and achiral electron acceptor shows bright circularly polarized emission with large g_lum value. The chiral emissive CT complexes could be fabricated through various approaches, such as grinding, crystallization, spin coating, and gelatinization, by simply blending chiral donor and achiral acceptor. The structural synergy originating from π–π stacking and strong CT interactions resulted in the long‐range ordered self‐assembly, enabling the formation of supramolecular gels. Benefiting from the large magnetic dipole transition moment in the CT state, the CPL activity of CT complexes exhibited large circular polarization. Our design strategy of the chiral emissive CT complexes is expected to help the development of new molecular engineering strategies for designing highly efficient CPL‐active materials.     

A New Well–Dawson Polyoxometalate Based Compound Containing Helix for Electrochemical Uric Acid Biosensor

A new [Cu₂bix₂] sub-ring modifying Wells–Dawson polyoxometalates (POMs) compound containing, H₁₀[Cu(bix)₂(P₂W₁₈O₆₂)₂](bix)₆·16H₂O (CubixP₂W₁₈) (bix?=?1,4-bis(imidazol-1-ylmethyl)benzene), has been synthesized, characterized and studied as electrochemical biosensor for detecting uric acid (UA) for the first time in the work. Interesting is that CubixP₂W₁₈ contain fascinating left- and right-helical chain. Moreover, the CubixP₂W₁₈ modified glassy carbon electrodes (GCE) shows excellent electrochemical activities and higher selectivity and stabilization toward UA. The linear response range is from 2.5?×?10^?7 M to 6.79?×?10^?4 M and the lower detection limit is as low as 4.97?×?10^?7 M (S/N?=?3). The strategy of employing Wells–Dawson POMs-based sensors provides a new pathway to design new sensor for detecting UA in the field of sensor and medical diagnosis.

     

Mechanically Strong Globular‐Protein‐Based Fibers Obtained Using a Microfluidic Spinning Technique

Proteins used for the formation of light weight and mechanically strong biological fibers are typically composed of folded rigid and unfolded flexible units. In contrast to fibrous proteins, globular proteins are generally not regarded as a good candidate for fiber production due to their intrinsic structural defects. Thus, it is challenging to develop an efficient strategy for the construction of mechanically strong fibers using spherical proteins. Herein, we demonstrate the production of robust protein fibers from bovine serum albumin (BSA) using a microfluidic technique. Remarkably, the toughness of the fibers was up to 143 MJ m^?3, and after post‐stretching treatment, their breaking strength increased to almost 300 MPa due to the induced long‐range ordered structure in the fibers. The performance is comparable to or even higher than that of many recombinant spider silks or regenerated silkworm fibers. Thus, this work opens a new way for making biological fibers with high performance.     

非对称鞍点问题的修正非线性Uzawa算法

该文基于Cao等^[3]的算法, 提出了修正的非线性Uzawa算法来求解大型稀疏非对称鞍点问题, 并对所提算法进行了收敛性分析. 同时, 数值实验验证了所提算法的有效性.     

The evolution of cooperation in spatial groups

Much of human cooperation remains an evolutionary riddle. There is evidence that individuals are often organized into groups in many social situations. Inspired by this observation, we propose a simple model of evolutionary public goods games in which individuals are organized into networked groups. Here, nodes in the network represent groups; the edges, connecting the nodes, refer to the interactions between the groups. Individuals establish public goods games with partners in the same group and migrate among neighboring groups depending on their payoffs and expectations. We show that the paradigmatic public goods social dilemma can be resolved and high cooperation levels are attained in structured groups, even in relatively harsh conditions for cooperation. Further, by means of numerical simulations and mean-field analysis, we arrive at the result: larger average group size and milder cooperation environment would lead to lower cooperation level but higher average payoffs of the entire population. Altogether, these results emphasize that our understanding of cooperation can be enhanced by investigations of how spatial groups of individuals affect the evolution dynamics, which might help in explaining the emergence and evolution of cooperation.     

Study of the electrochemical performance of VO2+/VO2 + redox couple in sulfamic acid for vanadium redox flow battery

The present work was performed in order to evaluate sulfamic acid as the supporting electrolyte for VO²⁺/VO₂ ⁺ redox couple in vanadium redox flow battery. The oxidation process of VO²⁺ has similar electrochemical kinetics compared with the reduction process of VO₂ ⁺. The exchange current density and standard rate constant of VO²⁺/VO₂ ⁺ redox reaction on a graphite electrode in sulfamic acid are determined as 7.6?×?10^?4 A cm^?2 and 7.9?×?10^?5 cm s^?1, respectively. The energy efficiency of the cell employing sulfamic acid as supporting electrolyte in the positive side can reach 75.87 %, which is adequate for redox flow battery applied in energy storage. The addition of NH₄ ⁺ to the positive electrolyte can enhance the electrochemical performance of the cell, with larger discharge capacity and energy efficiency. The preliminary exploration shows that the vanadium sulfamate electrolyte is promising for vanadium redox flow battery and is worthy of further study.     

Self-assembly Induced Enhanced Electrochemiluminescence of Copper Nanoclusters Using DNA Nanoribbon Templates

Copper nanoclusters (CuNCs) are attractive electrochemiluminescence (ECL) emitters as Cu is comparatively inexpensive, nontoxic, and highly abundant. However, their ECL yield is relatively low. Herein, we report that orderly self-assembly of CuNCs using DNA nanoribbon as the template (DNR/CuNCs) conferred the CuNCs with improved ECL properties compared with individual CuNCs in both annihilation and co-reactant processes. The DNR/CuNCs resulted in a high ECL yield of 46.8 % in K₂S₂O₈, which was ≈68 times higher than that of individual CuNCs. This strategy was successfully extended to other ECL emitters, such as gold nanoclusters and the Ru(bpy)₃²⁺/TPrA system. Furthermore, as an application of DNR/CuNCs, a DNR/CuNC-based ECL biosensor with higher sensitivity was constructed for dopamine determination (two orders of magnitude lower than that previously reported), showing that DNR/CuNCs have a potential for application in ECL bioanalysis as a new type of superior luminophore candidate.     

Helical Nanostructures: Chirality Transfer and a Photodriven Transformation from Superhelix to Nanokebab

Photosensitive cinnamic acid conjugated glutamides were designed to demonstrate photocontrolled hierarchical chirality transfer and switching in self‐assembled systems. In methanol, the cinnamic acid derivatives self‐assembled into superhelices, which could be switched into nanokebabs upon UV irradiation. These two nanostructures showed opposite helicity. The chiral nanostructures could further convey their chirality to achiral fluorescent molecules and result in the emission of circularly polarized luminescence (CPL). Remarkably, the CPL followed the helicity of the chiral nanostructure rather than the inherent molecular chirality. Photodriven dimerization of the cinnamic moiety lead to a significant change in molecular packing and subsequent switching of the helicity of the formed nanostructures.     

Numerical study on evolution of subharmonic varicose low-speed streaks in turbulent channel flow

The evolution of two spanwise-aligned low-speed streaks in a wall turbulent flow, triggered by the instability of the subharmonic varicose (SV) mode, is studied by a direct numerical simulation (DNS) method in a small spatial-periodic channel. The results show that the SV low-speed streaks are self-sustained at the early stage, and then transform into subharmonic sinuous (SS) low-speed streaks. Initially, the streamwise vortex sheets are formed by shearing, and then evolve into zigzag vortex sheets due to the mutual induction. As the intensification of the SV low-speed streaks becomes prominent, the tilted streamwise vortex tubes and the V-like streamwise vortex tubes can be formed simultaneously by increasing \( + \frac{{\partial u}}{{\partial x}}\). When the SV low-speed streaks break down, new zigzag streamwise vortices will be generated, thus giving birth to the next sustaining cycle of the SV low-speed streaks. When the second breakdown happens, new secondary V-like streamwise vortices instead of zigzag streamwise vortices will be generated. Because of the sweep motion of the fluid induced by the secondary V-like streamwise vortices, each decayed low-speed streak can be divided into two parts, and each part combines with the part of another streak, finally leading to the formation of SS low-speed streaks.     

1.5 J high-beam-quality Nd:LuAG ceramic active mirror laser amplifier

A 1.5 J Nd:LuAG ceramic active mirror laser amplifier with a high beam quality is demonstrated in which a 0.8%(atomic fraction)Nd-doped Nd:LuAG ceramic disk with a diameter of 64 mm and a thickness of 5.5 mm is used as a laser gain medium.A maximum single-pass small-signal gain of 2.59 is measured when the pump energy is 11.5 J,with an injected seed energy of 0.4 J;a maximum output energy of 1.5 J is obtained at the repetition rate of 10 Hz.A far-field beam spot 1.25 times the diffraction limit(DL)is achieved by using a stimulated Brillouin scattering phase conjugation mirror(SBS-PCM)for wavefront correction.