Dendron-functionalized perylene diimides with carrier-transporting ability for red luminescent materials

This paper presents a series of dendrimers via a convergent synthetic approach with three generations, which contain perylene diimide cores, Fréchet-type poly(aryl ether) dendrons, and carbazole (CZ) or oxadiazole (OXZ) peripheral functional groups. The higher generation dendrimer has an obvious site-isolation or dilution effect of dendrons, which results in a relatively small red-shift of absorption and emission spectra when it forms a solid thin film for applications. The interactions between peripheral units and perylene diimide core in the dendrimers are also studied by steady-state and time-resolved fluorescence spectra under both direct and indirect excitation. The fluorescence data show that there exist two possible mechanisms, Förster energy transfer (FRET) and photo-induced electron transfer (PET), for dendrimers bearing carbazole units. No enhanced core fluorescence is observed because the energy transfer or light-harvesting potential of peripheral carbazole is counteracted by PET. While for dendrimers bearing oxadiazole units, no PET can take place between OXZ and perylene diimide since both of them are high electron affinity. The FRET and higher light-harvesting ability of oxadiazole without PET interfering result in the distinct enhancement of core emission in higher generation dendrimers. DSC results indicate that the incorporation of Fréchet-type poly(aryl ether) dendrons can improve the amorphous property and increase glass transition temperature (T_g). The preliminary EL results with single-layer architectures demonstrate that these dendrimers could be utilized as a promising kind of active red luminescent emitters with carrier-transporting ability. EL emission has the same recombination zone as PL, indicating that the recombination of excitons in fabricated EL devices is not close to cathode or anode vicinity. It is suggested that the site-isolation effect of dendron wedges is attributed to prevent the core luminorphores from approaching electrodes efficiently.     

Conjugated random and alternating 2,3,4,5-tetraphenylsilole-containing polyfluorenes: Synthesis, characterization, strong solution photoluminescence, and light-emitting diodes

A novel series of soluble conjugated random and alternating copolymers derived from 9,9-dioctylfluorene (FO) and 1,1-dimethyl-2,3,4,5-tetraphenylsilole (PSP) were synthesized by Suzuki coupling reactions. The feed ratios of FO to PSP were 95:5, 90:10, 85:15, 70:30, and 50:50. Chemical structures and optoelectronic properties of the copolymers were characterized by elemental analysis, NMR, UV absorption, cyclic voltammetry, photoluminescence (PL), and electroluminescence (EL). The elemental analyses of the copolymers indicated that FO and PSP contents in the copolymers were very close to that of the feed compositions. Unlike the weak PL emission of PSP small molecules in a solution, PFO-PSP solutions could emit strong lights with PL quantum yields between 13 and 30%, indicating that the incorporation of the PSP into the conjugated rigid main chain could greatly restrict the rotations of the phenyl groups of the PSP units even in a solution. Compared with the solution PL, complete PL excitation energy transfer from the PFO segments to the PSP units could be achieved by film PL at lower PSP content. The films of the copolymers exhibited high absolute PL quantum yields between 55 and 84%. EL devices with a configuration of ITO/PEDOT/PFO-PSP/Ba/Al demonstrated that the PSP units could serve as powerful exciton traps, giving exclusively pure green EL emissions. A maximum external quantum efficiency of 1.51% was achieved using the PFO-PSP15 as the emissive layer.     

The preparation of coupled WO3/TiO2 photocatalyst by ball milling

The coupled photocatalyst WO₃/TiO₂ is prepared by ball milling by doping WO₃ into TiO₂ and using H₂O solution as disperser. The coupled photocatalyst WO₃/TiO₂ is characterized by UV–VIS diffuse reflection spectrum, X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and Transmission electron microscopy (TEM). The results show that the optimum percentage of WO₃ doped is 3% and that the photocatalytic activity of the coupled WO₃/TiO₂ photocatalyst is much higher than that of TiO₂ and WO₃–TiO₂ with no ball milling. Compared with TiO₂, the photoexcited wavelength range of the WO₃/TiO₂ photocatalyst red-shifts about 50 nm, and the light absorption intensity is also improved. The crystal phase of TiO₂ is not changed and new crystal phases are not found during the process of ball milling. WO₃ and TiO₂ coupled highly, forming the WO₃/TiO₂ photocatalyst. The increased photocatalytic activity of the coupled photocatalyst may be attributed to the enhance charge separation efficiency and the extend wavelength range of photoexcitation.     

Synthesis of hydroxyapatite nanoparticles in ultrasonic precipitation

Nanocrystalline hydroxyapatite (HAp) was prepared by a precipitation method with aid of ultrasonic irradiation using Ca(NO₃)₂ and NH₄H₂PO₄ as source material and carbamide (NH₂CONH₂) as precipitator. The crystallization and morphology of the prepared nanoparticles were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The mechanism and kinetics of the nano-hydroxyapatite were considered in particular, and the influence of the temperature and time on the HAp formation rate was also investigated. The results show that the needle-like HAp crystalline was prepared by the ultrasonic precipitation process. The HAp content increases with the preparation temperature and time. The adding of carbamide is helpful for formation of HAp nanoparticles. An Arrhenius relationship was found between the HAp formation rate and the temperature, and an apparent activation energy of 59.9 kJ/mol was obtained by calculation.     

氮掺杂纳米TiO_2改性涂料及其抗菌性能

将自制的氮掺杂锐钛矿型纳米二氧化钛光催化剂作为功能性组分,加入耐光催化氧化的硅丙乳胶涂料中,制备出一种新型光催化功能性建筑涂料,实现了可见光光催化效应。使用紫外-可见光吸收光谱研究该功能性涂料对紫外线的吸收能力;采用菌落计数法研究该涂料在可见光照射下对金黄色葡萄球菌的杀灭性能。同时分析了纳米粉体种类、引入量及方式对涂料紫外线的吸收性能和抗菌性能的影响。     

大庆石化公司聚烯烃树脂生产现状及发展

介绍了大庆石化公司现有聚烯烃装置的生产状况及聚烯烃新产品的开发．并从工艺角度与国内外同类装置进行了分析对比。最后简要介绍了大庆石化公司未来聚烯烃项目的发展规划。     

A highly efficient Cu/ZnO/Al2O3 catalyst via gel-coprecipitation of oxalate precursors for low-temperature steam reforming of methanol

The impact of preparation methods on the structure and catalytic behavior of Cu/ZnO/Al₂O₃ catalysts for H₂ production from steam reforming of methanol (SRM) has been reported. The results show that the nanostructured Cu/ZnO/Al₂O₃ catalyst obtained by a novel gel-coprecipitation of oxalate precursors has a high specific surface area and high component dispersion, exhibiting much higher activity in the SRM reaction as compared to the catalysts prepared by conventional coprecipitation techniques. It is suggested that the superior catalytic performance of the oxalate gel-coprecipitation-derived Cu/ZnO/Al₂O₃ catalyst could be attributed to the generation of “catalytically active” copper material with a much higher metallic copper specific surface as well as a stronger Cu–Zn interaction due to an easier incorporation of zinc species into CuC₂O₄ · x H₂O precursors as a consequence of isomorphous substitution between copper and zinc in the oxalate gel-precursors.     

丙烯酸树脂复鞣剂在兔皮制革中的应用

本文叙述了丙烯酸树脂复鞣剂的性能,阐释了ART—Ⅰ和ART—Ⅱ复鞣兔皮手套革的工艺操作及其注意的问题。     

棉杆烧碱—蒽醌法半化学浆分级利用抄造箱纸板的研究

棉杆半化学浆分级利用的试验研究表明:筛选出一定量的长纤维作为面层,其余部分作为芯层,抄造360g/m~2的箱纸板,可以明显地改善耐折度和挺度。棉杆半化学浆采用木浆挂面层生产纸板,以15％的木浆挂面层、5％的木浆混入棉杆浆中作芯层为佳,采用这种配比可以提高纸板的耐破度、挺度和环压强度。     

考虑阻尼影响时结构自由振动的计算方法

本文讨论计及阻尼影响时多自由度和无限自由度结构体系自由振动的计算方法,导出了一整套计算公式和一些有意义的结论。