软模板合成有序介孔碳材料

有序介孔碳材料由于其较大的表面积、均一的孔径、良好的热稳定性和化学稳定性,广泛应用于吸附、分离、催化以及能量储存等众多领域。与传统的以硅基介孔材料为硬模板的反向复制方法相比,通过嵌段共聚物和聚合物前驱体之间的有机-有机自组装的软模板法简便易行,已成为合成有序介孔碳材料有效方法。本论文综述了介孔碳材料的软模板合成机制、合成方法、功能化及其应用,对合成技术、结构控制、孔径调控以及形貌控制等方面进行了讨论,并探讨了其在吸附、催化、电极材料等领域的应用。     

Solventless Formation of G‐Quartet Complexes Based on Alkali and Alkaline Earth Salts on Au(111)

Template cations have been extensively employed in the formation, stabilization and regulation of structural polymorphism of G‐quadruplex structures in vitro. However, the direct addition of salts onto solid surfaces, especially under ultra‐high‐vacuum (UHV) conditions, to explore the feasibility and universality of the formation of G‐quartet complexes in a solventless environment has not been reported. By combining UHV‐STM imaging and DFT calculations, we have shown that three different G‐quartet‐M (M: Na/K/Ca) complexes can be obtained on Au(111) using alkali and alkaline earth salts as reactants. We have also identified the driving forces (intra‐quartet hydrogen bonding and electrostatic ionic bonding) for the formation of these complexes and quantified the interactions involved. Our results demonstrate a novel route to fabricate G‐quartet‐related complexes on solid surfaces, providing an alternative feasible way to bring metal elements to surfaces for constructing metal–organic systems.     

Synthesis and characterization of visible light responsive N-TiO2 mixed crystal by a modified hydrothermal process

N doped TiO₂ with anatase and rutile mixed crystal were prepared by using tetrabutyl titanate as the precursor via a modified hydrothermal process and calcination at 320 °C. The microstructure and morphology of samples were characterized by XRD, UV-vis-DRS, FTIR and XPS. The results showed that N-TiO₂ particles were crystallized to anatase and rutile mixed crystal structure; they were presented narrow particle size distribution, and the average particle size was ca. 13.5 nm calculated from XRD results. It was found that the N-doped TiO₂ particles showed strong visible-light absorption and high photocatalytic activity for the mineralization of Rhodamine B under irradiation by visible light (400-500 nm). The high visible-light photocatalytic activity of the obtained N-doped TiO₂ might result from the synergetic effect of nitrogen doping and the mixed lattice structure of N-TiO₂. Possible mechanism of N-TiO₂ mixed crystal formed under hydrothermal conditions was discussed.     

Syntheses,Structures and Photocurrent Response Properties of Two Crystals Based on Tetrathiafulvalene Derivatives

In this paper, two compounds [Zn_2~(2+)(2,6-bis(4'-pyridyl)-TTF)(TPA)_2~(2-)](1) and [Cd~(2+)(2,6(7)-bis(4'-pyridyl)-TTF)(TPA)~(2-)(H_2O)_2](TTF = tetrathiafulvalene, TPA = terephthalic acid)(2) were synthesized by using solvothermal method and characterized by single-crystal X-ray. The purity of the two compounds was confirmed by their PXRD data. We also tested the photocurrent responses of these two compounds, and found they could generate photocurrent signal when exposed to light, but the photocurrent intensity of compound 2 is significantly greater than that of 1. From the crystal structure analysis, the possible reason for this phenomenon is that 2 has a more compact ligand arrangement than 1, leading to a higher carrier density and easier excitation.     

HMD-Net: A Vehicle Hazmat Marker Detection Benchmark

Vehicles carrying hazardous material (hazmat) are severe threats to the safety of highway transportation, and a model that can automatically recognize hazmat markers installed or attached on vehicles is essential for intelligent management systems. However, there is still no public dataset for benchmarking the task of hazmat marker detection. To this end, this paper releases a large-scale vehicle hazmat marker dataset named VisInt-VHM, which includes 10,000 images with a total of 20,023 hazmat markers captured under different environmental conditions from a real-world highway. Meanwhile, we provide an compact hazmat marker detection network named HMD-Net, which utilizes a revised lightweight backbone and is further compressed by channel pruning. As a consequence, the trained-model can be efficiently deployed on a resource-restricted edge device. Experimental results demonstrate that compared with some established methods such as YOLOv3, YOLOv4, their lightweight versions and popular lightweight models, HMD-Net can achieve a better trade-off between the detection accuracy and the inference speed.     

Experimental Study on Wave Characteristics of Stilling Basin with a Negative Step

Stilling basin with a negative step is an important structure in hydraulic systems, because it can avoid atomization and decrease scouring problems. Although stilling basins with a negative step have attracted much attention from researchers, few researchers have focused on the wave characteristics. In this research, an experimental study on the wave characteristics of stilling basins with a negative step was carried out. The wave height, average period, wave probability density and power spectrum along the flow direction of different stilling basins with a negative step were described based on the wave theory, and the results indicate discharge and step height have a significant effect on the wave characteristics. The relationships between the different characteristic wave heights, and the empirical formula for the relative characteristic wave height are obtained. Finally, the dimensionless standard deviation at the end of the stilling basin with a negative step is linearly related to the flow-energy ratio and the relative step height under B-jump.     

Surface Functionalized Magnetic Nanoparticles as a Selective Sorbent for Affinity Fishing of PPAR-γ Ligands from Choerospondias axillaris

Coronary heart disease (CHD), which has developed into one of the major diseases, was reported to be treated by the target of peroxisome proliferators-activate receptor γ (PPAR-γ). As a natural medicine long used in the treatment of CHD, there are few studies on how to screen the target active compounds with high specific activity from Choerospondias axillaris. To advance the pace of research on target-specific active compounds in natural medicines, we have combined magnetic ligand fishing and functionalized nano-microspheres to investigate the active ingredients of PPAR-γ targets in Choerospondias axillaris. The PPAR-γ functionalized magnetic nano-microspheres have been successfully synthesized and characterized by vibrating sample magnetometer (VSM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The specificity, reusability, and reproducibility of the nano-microspheres were investigated with the help of the specific binding of rosiglitazone to PPAR-γ. In addition, the incubation temperature and the pH of the buffer solution in the magnetic ligand fishing were optimized to improve the specific adsorption efficiency of the analytes. Finally, with the aid of ultraperformance liquid chromatography plus Q-Exactive Orbitrap tandem mass spectrometry (UHPLC-Q-Exactive Orbitrap-MS/MS), the 16 active ligands including 9 organic acids, 5 flavonoids, and 2 phenols were found in the ethanolic extracts of Choerospondias axillaris. Therefore, the study can provide a successful precedent for realizing the designated extraction and rapid isolation of target-specific active ingredient groups in the complex mixtures.     

Pyrene分子(小片石墨晶体)的电子传导特性

利用量子理论中基于Green函数的tight-binding方法,对pyrene分子的电子传导和电子流分布进行了理论研究。在考虑到界面耦合和Hopping积分的情况下,得出了电子透射谱和流分布的模拟结果。结果显示透射与电子的能量紧密相关;谱的振荡特征是能级量子化的结果;流分布有着特定的方向,并且在每一个原子点上符合Kirchhoff量子流守恒定律。另外还发现了桥接pyrene分子的正负能开关特性。     

Precise electro-reduction of alkyl halides for radical defluorinative alkylation

Reported here is a precise electro-reduction strategy for radical defluorinative alkylation towards the synthesis of gem-difluoroalkenes from α-trifluoromethylstyrenes. According to the redox-potential difference of the radical precursors, direct or indirect electrolysis is respectively adopted to realize the precise reduction. An easy-to-handle, catalyst-and metal-free condition is developed for the reduction of alkyl radical precursors that are generally easier to be reduced than α-trifluorome...     

Facile Fabrication of 1-Methylimidazole/Cu Nanozyme with Enhanced Laccase Activity for Fast Degradation and Sensitive Detection of Phenol Compounds

Facile construction of functional nanomaterials with laccase-like activity is important in sustainable chemistry since laccase is featured as an efficient and promising catalyst especially for phenolic degradation but still has the challenges of high cost, low activity, poor stability and unsatisfied recyclability. In this paper, we report a simple method to synthesize nanozymes with enhanced laccase-like activity by the self-assembly of copper ions with various imidazole derivatives. In the case of 1-methylimidazole as the ligand, the as-synthesized nanozyme (denoted as Cu-MIM) has the highest yield and best activity among the nanozymes prepared. Compared to laccase, the K_m of Cu-MIM nanozyme to phenol is much lower, and the v_max is 6.8 times higher. In addition, Cu-MIM maintains excellent stability in a variety of harsh environments, such as high pH, high temperature, high salt concentration, organic solvents and long-term storage. Based on the Cu-MIM nanozyme, we established a method for quantitatively detecting phenol concentration through a smartphone, which is believed to have important applications in environmental protection, pollutant detection and other fields.