Synthesis of 2,5-disubstituted 1,3,4-oxadiazoles by visible-light-mediated decarboxylation–cyclization of hydrazides and diketones

A visible-light-induced synthesis of 2,5-disubstituted 1,3,4-oxadiazoles from simple diketones and hydrazides with the assistant of the photocatalyst eosin Y catalyzed decarboxylation and cyclization under mild conditions has been discovered. The reaction tolerates a wide range of functional groups and gives a variety of valuable 1,3,4-oxadiazoles in moderate to good yields. Finally, a plausible reaction mechanism was proposed.     

Look fast: Crystallization of conjugated molecules during solution shearing probed in‐situ and in real time by X‐ray scattering

High‐speed solution shearing, in which a drop of dissolved material is spread by a coating knife onto the substrate, has emerged as a versatile, yet simple coating technique to prepare high‐mobility organic thin film transistors. Solution shearing and subsequent drying and crystallization of a thin film of conjugated molecules is probed in situ using microbeam grazing incidence wide‐angle X‐ray scattering (μGIWAXS). We demonstrate the advantages of this approach to study solution based crystal nucleation and growth, and identify casting parameter combinations to cast highly ordered and laterally aligned molecular thin films.

     

Binding affinity of a small molecule to an amorphous polymer in a solvent. Part 1: free energy of binding to a binding site

Crystallization is commonly used in a separation and purification process in the production of a wide range of materials in various industries. In industry, crystallization usually starts with heterogeneous nucleation on a foreign surface. The complicated mechanism of heterogeneous nucleation is not well understood; however, we hypothesize that there might be a possible correlation between binding affinity to a surface and enhancement of nucleation. Recent studies show that amorphous polymers can be used to control crystallization, selectively produce pharmaceutical polymorphs, and discover novel pharmaceutical polymorphs. To investigate the possible correlation between the binding affinity of one molecule to key binding sites (local binding) and heterogeneous nucleation activity as well as the possibility of using this binding affinity to help guide the selection of polymers that promote heterogeneous nucleation, we computed the free energy of binding of aspirin to four nonporous cross-linked polymers in an ethanol-water 38 v% mixture. These cross-linked polymers are poly(4-acryloylmorpholine) (PAM), poly(2-carboxyethyl acrylate) (PCEA), poly(4-hydroxylbutyl acrylate) (PHBA), and polystyrene (PS); all of them were cross-linked with divinylbenzene (DVB). These systems were used because their heterogeneous nucleation activities are available in literature, and the ranking is PAM > PCEA > PHBA ≈ PS. We generated three independent surfaces for each polymer and computed the free energy of binding of aspirin to the best binding site that we found on each surface. The average free energies of binding to the best sites of PAM, PCEA, PHBA, and PS are -20.4 ± 1.0, -16.7 ± 1.0, -14.4 ± 1.1, and -13.6 ± 1.1 kcal/mol, respectively. We found that the trend of the magnitudes of the average free energies of binding to the best sites is PAM > PCEA > PHBA ≈ PS. This trend is very similar to that of heterogeneous nucleation activity. Our results suggest the importance of the free energy of binding to key sites (local binding) and the possibility of using this quantity to help guide the selection of polymers that promote heterogeneous nucleation.     

The nitrogen position effect on the selectivity of diazacrown ethers to metal ion

In this paper, the nitrogen position isomers of diaza-18-crown-6, diaza-15-crown-5, diaza-12-crown-4, and their complexes with Na⁺ ion are studied by the density functional theory. Their stable structures are identified by geometry optimization without strict for their geometry. The binding capability that reflects the selectivity of these diazacrown ethers to metallic ions is estimated by the binding energy. The position effects of nitrogen on the stability of these complexes are also investigated by the explicit natural bond orbital and atoms-in-molecule analysis. It is found that different nitrogen position in crown ring will result in different relative energy. To those diazacrown ethers under consideration, the calculation results show that 1,10-diaza-4,7,13,16-tetraoxacyclooctadecane, 1,4-diaza-7,10,13-trioxacyclopentadecane, and 1,7-diaza-4,10-dioxacyclododecane exhibit higher metal binding selectivity than their corresponding nitrogen position isomers, respectively. Clearly, the position of nitrogen plays an important role in the selectivity of diazacrown ethers to metal ions in the system involved. This work will be help for the material design of ionic recognition and other related fields.     

原位制备SrSb2O6/g-C3N4新型二维异质结用于可见光催化降解四环素的研究

本文采用高温固相原位制备新型二维SrSb2O6/g-C3N4异质结光催化复合材料,并将其用于可见光催化降解四环素.通过XRD和FT-IR谱对其结构进行表征.光催化降解实验表明,异质结复合材料较母体g-C3N4和SrSb2O6而言,光催化效率均得到了提升.其中,异质结样品SSO-CN-2对四环素溶液具有最优的光催化降解效...     

Selenium‐Substituted Diketopyrrolopyrrole Polymer for High‐Performance p‐Type Organic Thermoelectric Materials

Development of high‐performance organic thermoelectric (TE) materials is of vital importance for flexible power generation and solid‐cooling applications. Demonstrated here is the significant enhancement in TE performance of selenium‐substituted diketopyrrolopyrrole (DPP) derivatives. Along with strong intermolecular interactions and high Hall mobilities of 1.0–2.3 cm² V^?1 s^?1 in doping‐states for polymers, PDPPSe‐12 exhibits a maximum power factor and ZT of up to 364 μW m^?1 K^?2 and 0.25, respectively. The performance is more than twice that of the sulfur‐based DPP derivative and represents the highest value for p‐type organic thermoelectric materials based on high‐mobility polymers. These results reveal that selenium substitution can serve as a powerful strategy towards rationally designed thermoelectric polymers with state‐of‐the‐art performances.     

Using simulated Tianqin gravitational wave data and electromagnetic wave data to study the coincidence problem and Hubble tension problem

In this study, we used electromagnetic wave data (H0LiCOW, \begin{document}$ H(z) $\end{document}, SNe) and gravitational wave data (Tianqin) to constrain the interacting dark energy (IDE) model and investigate the Hubble tension and coincidence problems. By combining these four types of data (Tianqin+H0LiCOW+SNe+\begin{document}$ H(z) $\end{document}), we obtained the following parameter values with a confidence interval of \begin{document}$ 1\sigma $\end{document}: \begin{document}$ \Omega_m=0.36\pm0.18 $\end{document}, \begin{document}$ \omega_x=-1.29^{+0.61}_{-0.23} $\end{document}, \begin{document}$ \xi=3.15^{+0.36}_{-1.1} $\end{document}, and \begin{document}$H_0=70.04\pm $\end{document}\begin{document}$ 0.42~ {\rm kms}^{-1}{\rm Mpc}^{-1}$\end{document}. According to our results, the best value of \begin{document}$ H_0 $\end{document} shows that the Hubble tension problem can be alleviated to some extent. In addition, the center value of \begin{document}$ \xi+3\omega_x = -0.72^{+2.19}_{-1.19}(1\sigma) $\end{document} indicates that the coincidence problem is slightly alleviated. However, \begin{document}$ \xi+3\omega_x = 0 $\end{document} is still within the \begin{document}$ 1\sigma $\end{document} error range, which indicates that the ΛCDM model is still the model in best agreement with the observational data at present. Finally, we compared the constraint results of the electromagnetic and gravitational waves on the model parameters and found that the constraint effect of electromagnetic wave data on model parameters is better than that of simulated Tianqin gravitational wave data.     

聚苯胺电致变色薄膜的红外发射特性研究

为实现聚苯胺电致变色薄膜红外发射率的大幅度调制,在柔性PET-ITO薄膜基底上恒电位沉积硫酸-磺基水杨酸共掺杂的聚苯胺薄膜.采用扫描电镜和傅立叶红外光谱仪表征了薄膜的形貌和结构,用红外比辐射率测试仪和紫外-可见分光光度计测量薄膜的红外发射率和可见光透过率.在优化电解液浓度配比的基础上,通过建立薄膜红外发射率与方块电阻之间的关系曲线(R-E曲线),深入探讨了影响聚苯胺红外发射特性的关键因素.研究结果表明,在薄膜中聚苯胺厚度和电导率的影响下,红外发射率和方块电阻之间遵循对数函数的变化特征.随着中间态发射率E0的增加,氧化态和还原态的红外发射率呈阶梯状上升,红外发射率调制幅度ΔE先增大后减小,在0.71处达到最大值.同时,红外发射率调节对薄膜的可见光电致变色性能无消极影响,可见光平均透过率之差可达43.8%.     

Characterizing passive coherent population trapping resonance in a cesium vapor cell filled with neon buffer gas

We present a pair of phase-locked lasers with a 9.2-GHz frequency difference through the injection locking of a master laser to the RF-modulation sideband of a slave diode laser. Using this laser system, a coherent population trapping (CPT) signal with a typical linewidth of ～ 182 Hz is obtained in a cesium vapor cell filled with 30 Torr (4kPa) of neon as the buffer gas. We investigate the influence of the partial pressure of the neon buffer gas on the CPT linewidth, amplitude, and frequency shift. The results may offer some references for CPT atomic clocks and CPT atomic magnetometers.