Thermal analysis of polysiloxanes, aromatic polyimide and their blends

Low molecular weight poly(dimethylsiloxane) and poly(methylphenylsiloxane) were synthesized and blended with polyimide (PI) at its precursor poly(amic acid) stage. FTIR analysis has proven the retention of polysiloxanes in polyimide after the ultimate curing of blends. Differential scanning calorimetric analysis was performed on polysiloxanes to elucidate the structures present in polymers while thermogravimetric analysis (TGA) was performed on polysiloxanes, polyimide as well as their blends to evaluate the thermal stability and to analyze the effect of polysiloxane incorporation in blends. Blends have shown synergistic improvement as compared to neat polyimide.     

铱配合物在磷光化学传感器中的应用

由于在生物领域和物联网领域的广泛应用,化学传感器在近期发展迅速.相比于纯有机分子的荧光化学传感器,基于重金属配合物的磷光化学传感器由于发光寿命长,斯托克斯位移大等优点越来越引起人们的广泛关注.重金属铱配合物三线态寿命短,发光效率高而且配合物的发射波长容易受配体的改变而发生变化,因此成为最好的磷光传感器材料之一.本文介绍了铱配合物在磷光化学传感器领域中的应用,具体包括:阳离子传感器、阴离子传感器、氧分子传感器、氨基酸传感器、pH传感器等,并指出了相比于其它磷光化学传感器,基于铱配合物的磷光化学传感器的优势以及目前所存在的问题,最后,对基于铱配合物的磷光化学传感器的研究和发展方向进行了展望.     

Mg、Ti离子复合掺杂改性磷酸铁锂正极材料及其电池性能

在氮气气氛下采用高温固相方法, 合成了Mg、Ti 离子复合掺杂改性的锂离子电池正极材料(Li_0.98Mg_0.01)(Fe_0.98Ti_0.01)PO₄/C, 并通过粉末X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和充放电循环对材料进行性能表征. 测试结果表明, 复合离子掺杂可显著改善材料的电化学性能, 模拟电池在0.2C和1C倍率下的放电比容量分别为154.7 和146.9 mAh·g^-1. 以此复合掺杂样品为正极材料组装60 Ah动力电池, 其3C倍率放电容量仍保持为1C倍率放电容量的100%; 低温0 和-20 °C测试条件下, 动力电池放电容量分别保持为常温初始放电容量的89.7%和63.1%; 在常温1C/1C充放电条件下, 经过2000次循环后, 电池容量依然保持为初始放电容量的89%, 显示出优良的倍率放电性能和循环性能. 研究结果表明, Mg、Ti 离子复合掺杂改性的磷酸铁锂正极材料及其电池具有优良的放电性能和循环稳定性, 可广泛应用于电动(或混合动力)汽车和储能电池系统.     

Luminescent energy transfer between cadmium telluride nanoparticle and lanthanide(III) chelate in competitive bioaffinity assays of biotin and estradiol

Fluorescence resonance energy transfer has been studied between lanthanide(III) chelates as donors and protein-coupled CdTe semiconductor nanoparticles as acceptors. Wide excitation spectra and large Stokes shift of semiconductor nanoparticles and timeresolved fluorescence detection were shown to provide a combination for successful energy transfer assay. Different intrinsically fluorescent europium(III) and terbium(III) chelates coupled to single biotin molecules were studied for optimal energy transfer with streptavidin labeled semiconductor nanoparticles. No significant differences between the studied chelates were observed. The strength of the methodology was demonstrated in a clinically relevant competitive and separation-free immunoassay of estradiol, where subnanomolar limit of detection was achieved with the coefficient of variation 2-11%. The data suggested that relatively short distance was needed to obtain adequate energy transfer. Therefore, biomolecules were coupled onto the semiconductor nanoparticles without any spacers.     

不同基质中s1p1组态的能级

研究了s1p1组态能级位置及能级劈裂同基质的关系. 结果表明, Sn2+的A、B、C带能级和In+、Tl+的A、B带能级位置同基质的环境因子he呈线性关系, 能级能量随he的增大而减小, 给出了相应的经验公式, 并计算了In+和Tl+自由离子的A、B带能级能量. 计算结果同实验数据十分吻合, 最大的偏差来自Tl+的B带, 偏差率仅为-7.34%. 随基质he的增大, 高能级能量比低能级下降得更快, A、B和C带间的能级间距相应变小. 通过对比发现: Sn2+、In+、Tl+的A、B带能级对基质的敏感性存在较大差异, Sn2+能级能量受基质变化影响最大, In+的能级能量随基质变化最小. 更为重要的是, 发现随着he的增大, Sn2+、In+和Tl+的A、B和C带能级劈裂相应变小, 甚至不再劈裂, 很好地解释了光谱现象.     

Solar-Driven Artificial Carbon Cycle

Constituting the artificial carbon cycle,for example,through recycling CO₂ and converting CH₄ to value-added fuels and chemicals with solar energy,offers a sustainable future for humankind to tackle the global environmental issues and energy crisis.However,significant bottlenecks remain in such photocatalytic conversion,mainly related to the reaction activity and product selectivity.Herein,we share our efforts and systematic research progress on addressing the double bottlenecks for achieving solar-driven artificial carbon cycle,with specifically focusing on the photocatalytic CO₂ and CH₄ conversion.We further elucidate the common fundamentals behind various designed photocatalytic materials systems.Toward future development,we highlight the opportunities and challenges in the research field.     

Interaction of the excited singlet state of 1,4- and 1,8-dimethoxynaphthalene with some organic compounds: A fluorescence-quenching study

Summary The fluoroescence quenching of 1,4-dimethoxynaphthalene (1) and 1,8-dimethoxynaphthalene (2) by tetraphenylporpyrin (3), 9,10-diphenylanthracene (4), and 3-cyano-4-phenyl-6-(p-tolyl)-pyridin-2-one (5) has been studied in chloroform solution. The quenching occursvia a resonance energy transfer mechanism. The rate constant for the energy transfer (k _ET) of donor2 is slower than that of1 by the same acceptors, indicating that the steric effect dominates the ionization potential effect in all systems. The calculated critical transfer distances (R ₀) are 17–72 Å. In contrast, charge transfer is the predominant pathway of electronic deexcitation in the fluorescence quenching of donors1 and2 by 7,7,8,8-tetracyanoquinone-dimethane (6) in chloroform. The roles of temperature and geometrical structure of the donors on the efficiency of fluorescence quenching of1 and2 by acceptor6 have also been studied.

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Wechselwirkung des angeregten Singlett-Zustands von 1,4- und 1,8-Dimethoxynaphthalin mit einigen organischen Verbindungen: eine Untersuchung zur Fluoreszenzlöschung

Zusammenfassung Die Löschung der Fluoreszenz von 1,4-Dimethoxynaphthalin (1) und 1,8-Dimethoxynaphthalin (2) durch Tetraphenylporphyrin (3), 9,10-Diphenylanthracen (4) und 3-Cyano-4-phenyl-6-(p-tolyl)-pyridin-2-on (5) in Chloroform wurde untersucht. Die Löschung verläuft über einen Resonanzenergietransfermechanismus. Die Geschwindigkeitskonstante für den Energietransfer (k _ET) ist bei gleichem Akzeptor für den Donor2 niedriger als für1. Daraus läßt sich schließen, daß in allen untersuchten Systemen der sterische Effekt über den Effekt des Ionisierungspotentials dominiert. Die berechneten kritischen Transferdistanzen betragen 17–72 Å. Im Gegensatz zu diesen Beobachtungen verläuft der vorherrschende Relaxationsmechanismus bei der Fluoreszenzlöschung von1 und2 durch 7,7,8,8-Tetracyanochinon-dimethan (6) über einencharge-transfer-Prozeß. Die Einflüsse von Temperatur und Geometrie der Verbindungen auf die Effizienz der Fluoreszenzlöschung von1 und2 durch den Akzeptor6 wurden ebenfalls untersucht.

     

Interaction of dispersed phase with concentration polarization

The effect of a dispersed phase in reducing the concentration polarization in a membrane tube has been studied. The presence of a dispersed phase seems to have an effect in controlling the size of eddy formation and the rate of energy dissipation in the fluid medium. The role of eddy length and the energy dissipation rate on the mass transfer coefficient is discussed. Theoretical results obtained for the mass transfer coefficient and for the concentration polarization in the case of gelatin ultrafiltration are compared with the existing experimental results. The theoretical predictions seem to be in good agreement with the experimentally observed results.     

Quinones for redox flow batteries

Quinones are electroactive species that have shown great promise for redox flow batteries due to the ability to tune their properties and to act as both negative and positive electrolytes. The following review outlines highlights of work in the last couple of years working to provide materials with higher stability, solubility, and performance. Developments toward stable negolytes have provided opportunities for potential commercial opportunities when paired with alternate chemistries. However, the stability of quinones in high potential electrolytes is still not sufficient and the number of potential quinones limited.     

Design and Construction of 3D Porous Na3V2(PO4)3/C as High Performance Cathode for Sodium Ion Batteries

An easy and delicate approach using cheap carbon source as conductive materials to construct 3D sequential porous structural Na3V2(PO4)3/C(NVP/C)with high performance for cathode materials of sodium ion battery is highly desired.In this paper,the NVP/C with 3D sequential porous structure is constructed by a delicate approach named as“cooking porridge”including evaporation and calcination stages.Especially,during evaporation,the viscosity of NVP/C precursor is optimized by controlling the adding quantity of citric acid,thus leading to a 3D sequential porous structure with a high specific surface area.Furthermore,the NVP/C with a 3D sequential porous structure enables the electrolyte to interior easily,providing more active sites for redox reaction and shortening the diffusion path of electron and sodium ion.Therefore,benefited from its unique structure,as cathode material of sodium ion batteries,the 3D sequential porous structural NVP/C exhibits high specific capacities(115.7,88.9 and 74.4 mA·h/g at current rates of 1,20 and 50 C,respectively)and excellent cycling stability(107.5 and 80.4 mA·h/g are remained at a current density of 1 C after 500 cycles and at a current density of 20 C after 2200 cycles,respectively).