Metal-catalyzed organosulfur cathodes for rechargeable lithium batteries

Extensive studies were carried out to apply composite materials composed of polyaniline (PAn) and 2,5-dimercapto-1,3,4-thiadiazole (DMcT) to develop cathode materials which exhibit high energy densities. Previous results have established that composites of PAn and DMcT which are coated onto copper substrates exhibit greatly enhanced charge and discharge performance. It is shown that composite materials composed of DMcT, PAn, and Cu ion have the ability to be reversibly charged and discharged at ca. 260 A h per kg-cathode (ca. 830 W h per kg-cathode) for more than 80 cycles. These two results are explored in general in this contribution via investigation of the electron transfer reactions between the components using UV/Vis and investigation of the copper substrate/DMcT chemistry using electrochemical quartz crystal microbalance and phase modulated interferometric microscopy.     

Effects of Co doping on antiferromagnetic structure in

We performed the elastic neutron scattering experiments on the mixed compounds CeRh_1-xCo_xIn₅, and found that doping Co into CeRhIn₅ dramatically changes the antiferromagnetic (AF) structure. The incommensurate AF state with the propagation vector of observed in pure CeRhIn₅ is suppressed with increasing x, and new AF states with an incommensurate and a commensurate modulations simultaneously develop near the AF quantum critical point: x_c0.8. These results suggest that the AF correlations with the q_c and q₁ modulations enhanced in the intermediate Co concentrations may play a crucial role in the evolution of the superconductivity observed above x0.4.     

Rapid controlled hydrolytic degradation of poly(l-lactic acid) by blending with poly(aspartic acid-co-l-lactide)

Although poly(lactic acid) is known as a biodegradable polymer, its hydrolytic degradation is extremely slow, taking years in water and in the human body. In this study the effects of blending oligomeric poly(aspartic acid-co-lactide) (PALs) on the hydrolytic degradation of poly(l-lactic acid) (PLLA) were studied in detail. It was found that the addition of PAL did not accelerate the hydrolysis of the PLLA in air (25 °C, 60% relative humidity), but significantly accelerated it in a phosphate buffer solution. The degradation rate becomes higher for the blends containing PAL with higher molar ratios of lactide to aspartic acid units, [LA]/[Asp], when PLLA/PAL blends prepared with different PALs are compared at the same PAL concentration. TEM results, in which the distribution of PALs with higher [LA]/[Asp] occurs at a smaller scale in blends, imply that higher miscibility of the PAL with PLLA results in higher contact area between the components, thereby accelerating the degradation efficiently.     

纳米铂直接修饰玻碳电极的制备及在半胱氨酸中的电化学行为

采用一步化学原位还原法将球形纳米铂颗粒直接修饰在玻碳电极上,用SEM、EDS和电化学方法对该电极进行表征并与铂片电极、裸玻碳电极进行了对比。结果表明,纳米铂修饰电极的峰电流与扫描速度呈线性关系,纳米铂在电极表面覆盖率为1.28×10-7mol/cm2。循环伏安法研究结果表明纳米铂修饰电极对半胱氨酸的催化氧化作用和铂片电极相比提高了数倍,且峰电位负移了0.3V。在纳米铂修饰的玻碳电极上,半胱氨酸的浓度在1.0×10-7mol/L到1.0×10-5mol/L范围内和催化电流呈线性关系。     

Mössbauer study of paramagnetic-like behavior below the Néel temperature in a random mixture Fe x Mn1−x TiO3 withx<0.3

As a part of studies of the microscopic behavior of spins in a mixed compound with competing exchange interactions Fe _x Mn_1–x TiO₃, the Mössbauer technique has been applied to the samples withx=0.05, 0.10 and 0.20 which establish the antiferromagnetic long-range order at the respectiveT _N's and do not show reentrant transitions at lower temperatures. We have found that in each of the three samples, the paramagnetic doublet superimposes on the magnetically split spectrum belowT _N. The peak intensity of the paramagnetic doublet decreases with decreasing temperature and the paramagnetic doublet becomes undetected as sharp peaks at a temperature aroundT _N/2. However, the spectra observed at temperatures lower thanT _N/2 suggest that the paramagnetic doublet still exists, though it is highly broadened. This is interpreted as that short-range clusters of spins fluctuating rather slowly with time coexist with the spins forming the antiferromagnetic long-range order. We consider that these short-range clusters are responsible for the existence of the paramagnetic component contributing to the magnetization versus temperature curve.     

Photoluminescence and population analysis of single-walled carbon nanotubes produced by CVD and pulsed-laser vaporization methods

Band gap photoluminescence (PL) behaviors of single-walled carbon nanotubes (SWNTs) grown by the methods of chemical vapor deposition and pulsed-laser vaporization are investigated over the wide diameter range (≈0.8–1.4 nm). The peak intensity of the PL signals strongly depends on chirality and the ‘(2n + m) family type’ of SWNTs. Based on the PL results, a population analysis of these SWNTs is conducted by combining the calculated PL yields for each (n, m) tube. The results are directly compared with the histograms of diameter distributions estimated by the transmission electron microscope (TEM) observations to check the validity of the analysis.     

Organic high-spin systems: synthesis, electrochemical and ETSF studies of a series of tetraaryl-meta-phenylenediamines

A series of N,N,N′,N′-tetraaryl-1,3-phenylenediamines with various substituents at the para-position of peripheral rings were designed and synthesized. Electrochemical and novel electron transfer stopped-flow methods were invoked for characterizing the absorption spectra of the corresponding short-lived mono- and dicationic states. Both thermodynamic and kinetic stabilization are required to extend the lifetime of the dicationic states. Useful molecular design rules for stabilizing the dicationic states of N,N,N′,N′-tetraaryl-1,3-phenylenediamines as precursors for positively charged high-spin systems were elucidated.