Polymer Chain Conformation on Deuterated Polystyrene Nanoparticles Investigated by SANS

We previously reported that grafted polystyrene (PS) chains on silica nanoparticles at a low grafting density show similar conformations to free PS chains in the same solvent, THF (diameter ?50 nm, Colloid.poly.Sci. (2013), 291, 9, 2087–2099). As an extension of our previous study we choose an organic nanoparticle (deuterated polystyrene, dPS) instead of inorganic nanoparticle to see the impact of the substrate material on chain conformation. Additionally, a wider range of molecular weights were prepared to investigate the conformation feature of grafted PS chains more in detail. Small angle neutron scattering (SANS) experiments were performed to characterize PS grafted dPS particles in good solvent condition, with deuterated toluene and deuterated THF as solvent. To get insight into the conformation of the grafted PS layer we apply a scaling law describing the dimension of free PS polymer in good solvent condition to the obtained thickness of the grafted PS layer. We find an overall agreement with the scaling law where the thickness of the grafted PS layer is slightly larger than 2R_g of the free polymer chains in the respective solvent giving hint for semi dilute polymer brush (SDPB) situation.     

Polyvinylimidazole/sol–gel composite as a novel solid‐phase microextraction coating for the determination of halogenated benzenes from aqueous solutions

A polyvinylimidazole/sol–gel composite is proposed as a novel solid‐phase microextraction fiber to extract five halobenzenes from the headspace of aqueous solutions in combination with gas chromatography with mass spectrometry. The prepared fiber was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The obtained results showed that porous polyvinylimidazole/sol–gel composite was chemically deposited on fused silica fiber. The effect of important extraction parameters including extraction temperature, extraction time, and salt content were investigated. The optimum conditions were as follows: extraction temperature 25°C, extraction time 20 min, and salt concentration 30 w/v%. Detection limits and relative standard deviations of the developed method for halogenated benzenes were below 0.1 pg/mL and 15%, respectively. Repeatability of the proposed method, explained by relative standard deviation, varied between 5.48 and 9.15% (n = 5). The limits of detection (S/N = 3) ranged between 0.01 and 0.10 ng/L using gas chromatography with mass spectrometry with selected ion monitoring mode. For real sample analysis, three types of water samples with different matrices (ground, surface, and tap water) were studied. The optimized procedure was applied to extraction and method validation of halogenated benzenes in spiked water samples.     

Cathode catalysts degradation mechanism from liquid electrolyte to membrane electrode assembly

Single-cell and half-cell degradation test procedures were evaluated for carbon-supported Pt/C, PtCo/C and PtNi/C catalysts. Half-cell analyses were employed to understand the effect of the number of cycles and of the scan rate over the cathode catalysts degradation under potential cycling from 0.6 to 1.2 V. The data suggested a time-dependent degradation for all three catalytic systems. Single-cell measurements were used to evaluate the impact of catalyst degradation on fuel cell performance. The measurements in both setups showed similar ECSA and ORR mass activity losses. Specific degradation mechanisms related to Pt dissolution, Pt agglomeration, and transitional metal leaching were quantified and correlated with performance losses.     

生物基化工与材料产业技术的开发与探索

本文阐述了中国石油化工集团公司(中国石化)在生物基化工与材料领域的探索路径和发展战略,介绍了中国石化近年来在生物基单体、生物基材料与可降解材料等领域开展的创新实践及取得的阶段性成果,主要包括乳酸—聚乳酸、丁二酸/二元醇—生物可降解材料、长链二元酸—生物基尼龙以及生物质芳烃—聚对苯二甲酸乙二酯(PET)等技术领域.提出了建立生物基化工与材料科学技术平台、突破关键技术、发展新兴产业等建议.     

ZnO纳米线基MWNTs/PVDF复合热电材料的制备及特性研究

将不同比例的多壁碳管(MWNTs)与聚偏二氟乙烯(PVDF)聚合物混合后,喷涂于n型ZnO半导体纳米线阵列上,制备了一种新型ZnO纳米线基MWNTs/PVDF热电复合材料.与以往采用价格昂贵的p型与n型单壁碳纳米管(SWNTs)与聚合物混合制备的复合热电材料特性相比,这种新型热电复合材料在降低制造成本的同时,利用分散于聚合物中MWNTs的一维电子传输特性及形成的大量界面势垒,加上ZnO半导体纳米线具有的较高载流子密度与迁移率,提高了复合热电材料中电子的输运特性,增加了材料对声子的散射强度.测试发现,在一定的温度梯度下,随着MWNTs添加质量百分比的增加,热电材料的温差电动势和电导率也随之增加,但其Seebeck系数变化量不大.研究表明,这种热电材料有望替代采用p型与n型SWNTs构建的SWNTs/PVDF复合热电材料.研究结果对开发超轻、无毒、廉价、可应用于各种微纳电子领域的新型电源具有重要的参考价值.     

基于磷光材料的低给体比例有机太阳能电池

本文以低比例的磷光材料作为给体,制备了基于MoOx/C60:x%Ir(ppy)3的有机太阳能电池(OPV)器件.其中,C60为高比例的受体材料,金属配合物Ir(ppy)3为低比例的给体材料,MoOx为阳极缓冲层.通过一系列不同Ir(ppy)3比例的OPV器件对比研究,得出了最优器件结构.研究发现,当Ir(ppy)3比例足够小时,器件表现为肖特基势垒,开路电压(VOC)较大,短路电流(JSC)较小;随着Ir(ppy)3比例的增加,VOC逐渐减少,而JSC逐渐增大;当进一步增加Ir(ppy)3比例时,VOC趋于稳定,JSC开始减小.结果显示,5%Ir(ppy)3比例的器件性能最佳,效率达1.7%.为了使器件效率得到进一步提升,本研究组采用吸收光谱范围比C60更宽的C70作为受体材料,使光电转换效率进一步提升至3.0%.     

Preparation of Yolk‐Shell and Filled Co9S8 Microspheres and Comparison of their Electrochemical Properties

In this study, we report the first preparation of phase‐pure Co₉S₈ yolk–shell microspheres in a facile two‐step process and their improved electrochemical properties. Yolk–shell Co₃O₄ precursor microspheres are initially obtained by spray pyrolysis and are subsequently transformed into Co₉S₈ yolk–shell microspheres by simple sulfidation in the presence of thiourea as a sulfur source at 350 °C under a reducing atmosphere. For comparison, filled Co₉S₈ microspheres were also prepared using the same procedure but in the absence of sucrose during the spray pyrolysis. The prepared yolk–shell Co₉S₈ microspheres exhibited a Brunauer–Emmett–Teller (BET) specific surface area of 18 m² g^?1 with a mean pore size of 16 nm. The yolk–shell Co₉S₈ microspheres have initial discharge and charge capacities of 1008 and 767 mA h g^?1 at a current density of 1000 mA g^?1, respectively, while the filled Co₉S₈ microspheres have initial discharge and charge capacities of 838 and 638 mA h g^?1, respectively. After 100 cycles, the discharge capacities of the yolk–shell and filled microspheres are 634 and 434 mA h g^?1, respectively, and the corresponding capacity retentions after the first cycle are 82 % and 66 %.     

A Theoretical Study on the Structure,Intramolecular Interactions,and Detonation Performance of Hydrazinium Dinitramide

The structures of hydrazinium dinitramide (HDN) in the gas phase and in aqueous solution have been studied at different levels of theory by using quantum chemistry. The intramolecular hydrogen‐bond interactions in HDN were studied by employing the quantum theory of atoms in molecules (QTAIM), as well as those in ammonium dinitramide (ADN), hydrazinium nitroformate (HNF), and ammonium nitroformate (ANF) for comparison. The results showed that HDN possessed the strongest hydrogen bonds, with the largest hydrogen‐bond energy (?47.95 kJ mol^?1) and the largest total hydrogen‐bond energy (?60.29 kJ mol^?1). In addition, the charge transfer between the cation and the anion, the binding energy, the energy difference between the frontier orbitals, and the second‐order perturbation energy of HDN were all the largest among the investigated compounds. These strongest intramolecular interactions accounted for the highest decomposition temperature of HDN among all four compounds. The IR spectra in the gas phase and in aqueous solution were very different and showed the significant influence of the solvent. The UV spectrum showed the strongest absorption at about 253 nm. An orbital‐interaction diagram demonstrated that the transition of electrons mainly happened inside the anion of HDN. The detonation velocity (D=8.34 km s^?1) and detonation pressure (P=30.18 GPa) of HDN were both higher than those of ADN (D=7.55 km s^?1 and P=24.83 GPa). The composite explosive HDN/CL‐20 with the weight ratio w_CL?20/w_HDN=0.388:0.612 showed the best performance (D=9.36 km s^?1, P=39.82 GPa), which was close to that of CL‐20 (D=9.73 km s^?1, P=45.19 GPa) and slightly better than that of the composite explosive ADN/CL‐20 (w_CL?20/w_ADN=0.298:0.702, D=9.34 km s^?1, P=39.63 GPa).     

Clickable SBA‐15 to Screen Functional Groups for Adsorption of Antibiotics

Pharmaceutical antibiotics, as emerging contaminants, are usually composed of several functional groups that endow them with the ability to interact with adsorbents through different interactions. This makes the preparation of adsorbents tedious and time‐consuming to screen appropriate functionalized materials. Herein, we describe the synthesis of clickable SBA‐15 and demonstrate its feasibility as a screening material for the adsorption of antibiotics based on similar adsorption trends on materials with similar functional groups obtained by a click reaction and cocondensation/grafting methods.     

Carbon‐Coated LiTi2(PO4)3: An Ideal Insertion Host for Lithium‐Ion and Sodium‐Ion Batteries

We report the extraordinary performance of carbon‐coated sodium super ion conductor (NASICON)‐type LiTi₂(PO₄)₃ as an ideal host matrix for reversible insertion of both Li and Na ions. The NASICON‐type compound was prepared by means of a Pechini‐type polymerizable complex method and was subsequently carbon coated. Several characterization techniques such as XRD, thermogravimetric analysis (TGA), field‐emission (FE) SEM, TEM, and Raman analysis were used to study the physicochemical properties. Both guest species underwent a two‐phase insertion mechanism during the charge/discharge process that was clearly evidenced from galvanostatic and cyclic voltammetric studies. Unlike that of Li (≈1.5 moles of Li), Na insertion exhibits better reversibility (≈1.59 moles of Na) while experiencing a slightly higher capacity fade (≈8 % higher than Li) and polarization (780 mV) than Li. However, excellent rate capability profiles were noted for Na insertion relative to its counterpart Li. Overall, the Na insertion properties were found to be superior relative to Li insertion, which makes carbon‐coated NASICON‐type LiTi₂(PO₄)₃ hosts attractive for the development of next‐generation batteries.