Palladium-Catalyzed Cascade Reaction in Water to Imidazo[1,2-a]pyridazines as Switchable DSEgens,AIEgens, and ACQgens**

Dual-state emission (DSE) luminophores exhibit strong emissions in both solution and solid states, filling the gaps between aggregation-induced emissions (AIE) and aggregation-caused quenching (ACQ). However, limited design concepts and complicated synthetic strategies restrict the discovery of novel DSE molecules. Developing efficient and green methodologies to access novel DSE scaffolds via rational design remains highly desirable. In this work, we report a water-promoted Pd-catalyzed cascade reaction for the synthesis of multi-substituted imidazo[1,2-a]pyridazine derivatives with DSE properties. The intramolecular interactions of the neighboring benzene rings restrict molecular motion, leading to emissions in the solid state (quantum yield: 11 %), and the newly constructed core structure of imidazo[1,2-a]pyridazine ensures considerable planarity, allowing for emissions in solution. Further removal of the neighboring phenyl groups resulted in ACQgens, while additional methyl groups led to AIEgens. Subsequent live cell imaging investigations suggested that the novel DSEgens could serve as specific lipid droplet (LD) probes in a wide concentration range.     

Interstitial water and the formation of low barrier hydrogen bonds: A computational model study

The B3LYP/D95+(d,p) analysis of the uncharged low barrier hydrogen bond (LBHB) between 4‐methyl‐1H‐imidazole (Mim) and acetic acid (HAc) shows that uncharged LBHBs can be formed either by adding three water molecules around the cluster or by placing the Mim–HAc pair in a dielectric environment created by a polarizable continuum model with a permittivity larger than 20.7. The permittivity of environment around uncharged LBHB can be lowered significantly by including water molecules into the system. A Mim–HAc LBHB stabilized with one water molecule observed in diethyl ether (ε = 4.34), with two water molecules in toluene (ε = 2.38), and with three water molecules in vacuo (ε = 1). Solvation models with different numbers of water molecules predict average differences in the proton affinities of the hydrogen bonded bases (ΔPA) for stable uncharged LBHB systems in vacuo to be 91.5 kcal/mol being different from the ΔPA values close to zero in charge‐assisted LBHB systems. The results clearly indicate that small amounts of interstitial water molecules at the active site of enzymes do not preclude the existence of LBHBs in biological catalysis. Our results also show that interstitial water molecules provide a useful clue in the search for uncharged LBHBs in an enzymatic environment and the number of water molecules can be used as a relative measure for the polarity around the direct environment of LBHBs. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

青藏铁路多年冻土区工程复杂性分析

青藏铁路穿越550km多年冻土区,多年冻土地温、冻土类型以及沿线生态环境等存在较大的差异,使多年冻土区工程较为复杂。因此本文提出了冻土工程复杂性概念,建立冻土工程复杂性评价模型,并利用GIS平台对青藏铁路沿线唐古拉山越岭地段工程复杂性进行了分析和研究。研究结果表明,青藏铁路穿越的唐古拉山越岭地段工程复杂性相对较小,而青藏公路的工程复杂性相对较大。这表明了青藏公路沿线冻土工程比青藏铁路沿线更为复杂,在各种因素的影响下,青藏公路路基稳定性变化比青藏铁路更加复杂。     

Materials doping through sol–gel chemistry: a little something can make a big difference

Several examples of sol–gel preparation of doped materials are taken to illustrate the various situations where the doping elements are responsible for the main function of the material or govern its structure. Other examples are used to illustrate that sometimes unexpected effects can be observed like structural modification and the appearance of new properties. Rare earth doped scintillators demonstrate higher homogeneity for materials prepared via sol–gel chemistry when compared with classical solid state reaction. The XRD study of rare earth doped orthoborates shows that doping can affect the vaterite to calcite phase transition observed in these compounds. A Raman spectroscopic study has been performed on doped silica xerogels and it has been shown that doping ions can modify greatly the densification process in these amorphous materials. Finally, it has been evidenced that sol–gel chemistry allows the preparation of bioactive ceramics with enhanced properties. In particular Zn-doped HAP with anti inflammatory properties has been prepared and Sr-doped bioactive glasses have demonstrated superior in-vitro bioactivity as evidenced by PIXE-RBS study.     

Oscillatory stability of quantum droplets in $\text{}{ \mathcal P }{ \mathcal T }$-symmetric optical lattice

We study stability and collisions of quantum droplets (QDs) forming in a binary bosonic condensate trapped in parity-time (${ \mathcal P }{ \mathcal T }$)-symmetric optical lattices. It is found that the stability of QDs in the ${ \mathcal P }{ \mathcal T }$-symmetric system depends strongly on the values of the imaginary part W₀ of the ${ \mathcal P }{ \mathcal T }$-symmetric optical lattices, self-repulsion strength g, and the condensate norm N. As expected, the ${ \mathcal P }{ \mathcal T }$-symmetric QDs are entirely unstable in the broken ${ \mathcal P }{ \mathcal T }$-symmetric phase. However, the ${ \mathcal P }{ \mathcal T }$-symmetric QDs exhibit oscillatory stability with the increase of N and g in the unbroken ${ \mathcal P }{ \mathcal T }$-symmetric phase. Finally, collisions between ${ \mathcal P }{ \mathcal T }$-symmetric QDs are considered. The collisions of droplets with unequal norms are completely different from that in free space. Besides, a stable ${ \mathcal P }{ \mathcal T }$-symmetric QDs collides with an unstable ones tend to merge into breathers after the collision.     

不同维度ZnO能带结构和电子态密度的研究

本文采用基于密度泛函理论的第一性原理计算方法来研究不同维度ZnO的能带结构和电子态密度.参考实验上的ZnO晶格参数构建不同维度的ZnO模型并进行结构优化后再计算能带结构和电子态密度.研究结果表明二维和三维ZnO都属于直接带隙半导体且二维ZnO的禁带宽度大于三维ZnO;从三维变到二维,ZnO的电子局域化程度变高且Zn 3d轨道电子从能量较低的能级向能量较高的能级跃迁.本文的研究展示了二维和三维ZnO能带结构和电子态密度的异同,为二维ZnO基的器件研究提供了一定的理论参考价值.     

掺碲硒化镓晶体的光学性能(英文)

采用水平区熔法生长了碲(Te)掺杂浓度(质量百分比)分别为0.05%,0.1%,0.5%,1%,2%的硒化镓(GaSe)晶体,并分别对掺杂浓度为0.01%,0.07%,0.38%,0.67%,2.07%的GaSe∶Te晶体的光学性能进行了表征。首次研究了GaSe∶Te晶体中刚性层声子模式的转换。吸收光谱测试结果表明:当Te掺杂浓度小于0.38%时,振动中心位于0.59 THz附近的E'(2)刚性模式吸收峰强度可达最大值,这一过程与GaSe∶Te晶体光学性能的提高密切相关。但Te掺杂浓度的进一步提高会导致E'(2)刚性模式吸收峰强度逐渐减弱,当Te掺杂浓度为1%时,E'(2)刚性模式吸收峰基本消失。这两个过程与GaSe∶Te晶体光学质量的下降密切相关。因此,E'(2)刚性模式吸收强度达到最高时对应的掺杂浓度即是GaSe∶Te晶体中Te的最佳掺杂浓度,光整流产生太赫兹过程证实了此结论的正确性。