DNA Nanoribbon-Templated Self-Assembly of Ultrasmall Fluorescent Copper Nanoclusters with Enhanced Luminescence

Fluorescent copper nanoclusters (CuNCs) have been widely used in chemical sensors, biological imaging, and light-emitting devices. However, individual fluorescent CuNCs have limitations in their capabilities arising from poor photostability and weak emission intensities. As one kind of aggregation-induced emission luminogen (AIEgen), the formation of aggregates with high compactness and good order can efficiently improve the emission intensity, stability, and tunability of CuNCs. Here, DNA nanoribbons, containing multiple specific binding sites, serve as a template for in situ synthesis and assembly of ultrasmall CuNCs (0.6 nm). These CuNC self-assemblies exhibit enhanced luminescence and excellent fluorescence stability because of tight and ordered arrangement through DNA nanoribbons templating. Furthermore, the stable and bright CuNC assemblies are demonstrated in the high-sensitivity detection and intracellular fluorescence imaging of biothiols.     

Water-Soluble Polymers with Appending Porphyrins as Bioinspired Catalysts for the Hydrogen Evolution Reaction

Molecular design to improve catalyst performance is significant but challenging. In enzymes, residue groups that are close to reaction centers play critical roles in regulating activities. Using this bioinspired strategy, three water-soluble polymers were designed with appending Co porphyrins and different side-chain groups to mimic enzyme reaction centers and activity-controlling residue groups, respectively. With these polymers, high hydrogen evolution efficiency was achieved in neutral aqueous media for electro- (turnover frequency >2.3×10⁴ s⁻¹) and photocatalysis (turnover number >2.7×10⁴). Porphyrin units are surrounded and protected by polymer chains, and more importantly, the activity can be tuned with different side-chain groups. Therefore, instead of revising molecular structures that is difficult from both design and synthesis points of view, polymers can be used to improve molecular solubility and stability and simultaneously regulate activity by using side-chain groups.     

手性环丙烯构建策略用于对映选择性合成偕二氟亚甲基三元环化合物

作为最小的不饱和环状分子,环丙烯独特的刚性结构和多变的反应活性吸引了化学家的研究兴趣.自1922年Demjanov[1]报道了环丙烯化合物的首例合成以来,现已发展了一系列环丙烯的合成方法.手性环丙烯的合成是通过炔烃和重氮化合物的[2+1]不对称环加成反应.根据底物的不同,这些不对称环加成反应可以分为四类:(a)末端炔烃和单取代重氮化合物的反应,(b)末端炔烃和双取代重氮化合物的反应,(c)非末端炔烃和双取代重氮化合物的反应,(d)非末端炔烃和单取代重氮化合物的反应.在这四类反应中,末端炔烃和单取代重氮化合物的不对称反应相对容易进行.1992年,Doyle和Müller等[2]报道了手性铑催化剂[Rh2(5R-MEPY)4]促进的末端炔烃和重氮醋酸酯之间的不对称环丙烯基化反应(Scheme 1a).随后各种手性催化剂包括[Rh2(OAc)-(DPTI)3][3]、Ir(salen)衍生物[4]和[Co(3,5-diMes-Chen-Phyrin)][5]等被先后报道用于末端炔烃和单取代重氮化合物的不对称[2+1]环加成反应.     

[1,2,4]三唑并[3,4-b][1,3,4]噻二嗪类衍生物的合成及生物活性研究进展

[1,2,4]三唑并[3,4-b][1,3,4]噻二嗪作为极具前景的活性基团,在抗菌、抗肿瘤等方面具有多种药理活性,在药物和化学领域受到了广泛的关注。本文以含三唑并噻二嗪结构化合物的合成及其在抗肿瘤、抗菌等方面的生物活性为依据,对近几年国内外关于[1,2,4]三唑并[3,4-b][1,3,4]噻二嗪类化合物的研究进行分析总结,以期为后续该类新型抗肿瘤化合物的设计合成提供参考。     

基于手机光线传感器为检测器的简易光度计的自组装设计

By using light sensors of the cellphone, we build a simple photometer which can be used in quantitative analysis experiments. We have performed 5 replicate measurements of iron with phenanthroline to verify reproducibility and stability. We find the absorbance of the sample has a good linear relationship with the concentrations of iron with a R² value around 0.999 and the RSD of 2.81%. The result is 4.94 μg·mL^-1 with spectrophotometer and 5.11 μg·mL^-1 with our photometer. The photometer is simple, convenient, accurate and realistic by using a phone as detector, which can replace the traditional spectrophotometer in the laboratory class. The students can enhance their understanding of the structure and principle of spectrophotometer by the DIY photometer experiment.     

Determination of tritium in Li–Pb alloy irradiated by thermal neutrons with quantitatively analyzing the byproduct 4He

The mass of the tritium produced in ⁶Li(n,α)T reaction was obtained by quantitatively analyzing the byproduct ⁴He with mass spectrometer. The self-expending seal method was employed to quantitatively prepare the Li–Pb alloy targets in room temperature. They were irradiated for 2 h in two rabbit irradiation channels in Xi’an pulsed reactor and measured after cooling 15 days. A sample purifying unit was set up to get rid of the hydrogen isotopes to remarkably reduce the interference to helium isotopes when measuring. And the sample disposal platform including purifying unit was testified with simulative gas and nature atmosphere. The targets were melted at 700 °C to release most of the ⁴He atoms which were measured by adding dilution gas ³He. And it was testified that ⁴He had released completely by repetitiously melting the targets. This approach had solved the problem that the tritium couldn’t be accurately determined by directly analyzing it because of non-complete releasing from lithium alloy.     

Phase behavior of amphiphiles at liquid crystals/water interface: A coarse-grained molecular dynamics study

We present a coarse-grained molecular dynamics simulation study of phase behavior of amphiphilic monolayers at the liquid crystal （LC）/water interface. The results revealed that LCs at interface can influence the lateral ordering of amphiphiles. Particularly, the amphiphile tails along with perpendicularly penetrated LCs between tails undergo a two-dimension phase transition from liquid-expanded into a liquid-condensed phase as their area density at interface reaches 0.93. While, the liquid-condensed phase of the monolayer never appears at oil/water interface with isotropic shape oil particles. These findings reveal the penetration of anisotropic LC can promote ordered lateral organization of amphiphiles. Moreover, we find the phase transition point is shifted to lower surface coverage of amphiphiles when the LCs have larger affinity to the amphiphile tails.     

纳秒脉冲下聚合物电树枝引发实验方法

 借鉴直流、交流的研究经验,比较了纳秒脉冲条件下几种不同的电树枝老化实验方法。对单针-板电极和多针-板电极在纳秒脉冲下实验结果的一致性进行考察,结果表明,多针-板电极系统可以在提高实验效率的同时保证结果的准确性。采用步进法和累加法进行了不同频率下聚苯乙烯电树枝引发实验,结果表明:两种方法得到的纳秒脉冲下聚苯乙烯电树枝引发电压-频率特性基本一致,在50~500 Hz范围内,引发电压随频率的升高而降低;在500~800 Hz范围内,引发电压随频率的升高而增加。最后讨论了对于不同脉冲功率装置中绝缘材料老化试验设计的方法。     

Behaviour of silicon ointment for power-cable insulation under external heating

Journal of Thermal Analysis and Calorimetry - The burning process and typical fire parameters of power-cable silicon ointment were explored experimentally using a cone calorimeter, and the effects...