In-situ photoelectron spectroscopy with online activity measurement for catalysis research

We report Ambient pressure X-ray Photoelectron Spectroscopy Endstation with an integrated chemical analytical system that consists of a residual gas analyzer in the 2nd differential pumping stage and a new low-reactive sample holder heating assembly. This system has a linear response to the reaction chamber gas pressure. The sample heating assembly also has a low dark reaction rate up to 400 °C for H₂ and CO oxidation. We expect this chemical analytical system will expand our capabilities in conducting in-operando catalysis research.     

Influence of aluminum doping in Li–Co–Ti ferrite

The crystallographic and magnetic properties of low aluminum doped lithium cobalt titanium ferrites, Li_0.5Co_0.2Ti_0.2Al_xFe_2.1−xO₄(0.0≤x≤0.5), in the scope of spinel structure and ferrimagnetic property were investigated. Ferrites were doped with aluminum in the range of 0.0–0.5 and were synthesized by using the conventional ceramic methods. Using X-ray diffraction and Mössbauer spectroscopy, we confirmed the formation of crystallized particles. All of the samples showed a single phase with a spinel structure, and the lattice parameters linearly decreased as the doped aluminum content was increased. The particle size of the samples also decreased as the doped aluminum content increased. Until x=0.4 in Li_0.5Co_0.2Ti_0.2Al_xFe_2.1−xO₄, the Mössbauer spectra could be fitted with two Zeeman sextets, which is the typical spinel ferrite spectra of Fe³⁺ with A- and B-sites. However, for x=0.5, the Mössbauer spectrum could be fitted with two Zeeman sextets and one doublet. From the variation of the Mössbauer parameters and the absorption area ratio, the cation distributions were determined. The magnetic behavior of the samples showed that an increase in the aluminum contents led to a decrease in the saturation magnetization, whereas the coercivity decreased until x=0.4 and then increased. The minimum coercivity was 52.4 Oe at x=0.4 in Li_0.5Co_0.2Ti_0.2Al_xFe_2.1−xO₄.     

Study of SU-8 to make a Ni master-mold: Adhesion, sidewall profile, and removal

For disposable microfluidic devices, easy and inexpensive fabrication is essential. Consequently, replication of microfluidic devices, using injection molding or hot embossing, from a master-mold is widely used. However, the conventional master-mold fabrication technique is unsatisfactory in terms of time and costs. In this regard, direct Ni growth (electroplating) from a back plate is promising when the photoresist is well-defined. Here, we demonstrate the use of SU-8 as a photoresist to define the Ni-growth region. We accomplish this application by focusing on the adhesion, the sidewall profile, and the removal of SU-8: the adhesion is enhanced by controlling the exposure dose, the soft-baking time, and by choosing the adhesion-promoting layer; the sidewall profile is regulated by selecting the intensity of each exposed wavelength, showing an aspect ratio of up to 20.9; and, easy removal is achieved by choosing a proper photoresist-stripper. Using the master-mold fabricated by this method, we test the mechanical stability of the features according to the aspect ratio and length; in the hot embossing process, the features are stable in the aspect ratio of up to 5.8 at a length of 200 microm. In addition, the plastic devices fabricated from this method are applied to the passive stop valves, showing a capillary pressure (-0.2 to -7.2 kPa).     

Regioselective and diastereoselective amination of polybenzyl ethers using chlorosulfonyl isocyanate: total syntheses of 1,4-dideoxy-1,4-imino-D-arabinitol and (-)-lentiginosine

The total syntheses of DAB1 (1) and (-)-lentiginosine (2) were concisely accomplished from D-lyxose via regioselective and diastereoselective NHCbz introduction using CSI, chemoselective removal of the Cbz protection, and ring-closing metathesis as key steps.     

ψ-混合序列加权和的完全收敛性

研究Ψ-混合序列加权和的完全收敛性,证明了一般双下标加权系数的加权部分和的完全收敛性,改进了杨善朝的结果.     

Sodium hydrogen nitrilo­tri­acetate dihydrate

In the title compound, Na⁺·C₆H₈NO₆^?·2H₂O, the sodium ion is coordinated in a distorted octahedral manner by two carboxyl­ate O atoms and two water O atoms. Each of these water mol­ecules bridges two adjacent Na ions, resulting in two four‐membered rings of the type Na–O–Na–O.     

紫精类化合物分子聚集体材料的界面组装

紫精类化合物具有良好的电化学活性,并且在发生氧化还原反应时伴有颜色的变化,在膜修饰电极、电致变色材料和分子器件的研制等方面受到广泛的关注。紫精中的烷基链非常易于进行化学修饰,因而比较适合于通过自下而上的分子自组装技术制备多功能的分子和纳米材料。本文综述了利用Langmuir-Blodgett法、自组装法和层层组装法制备紫精分子聚集体材料的研究进展,并讨论了分子聚集体薄膜中紫精的结构、电致变色、电化学氧化还原特性及其在研制超分子器件方面的应用。     

Phase behaviors of partially ionized hydrogels in aqueous salt solutions: Applicability of the modified double‐lattice model

We investigated the effect of charge densities of the gel network and ionic strength of solution on swelling behaviors of ionized gels. We used the modified double‐lattice model, Flory–Erman's elastic model, and the ideal Donnan theory to describe swelling behaviors of the electrolyte bounded hydrogels. Energy parameters (?/k, δ?/k) were obtained from fitting liquid–liquid equilibria data of the linear poly‐N‐isopropylacrylamide/water system and two adjustable model parameters obtained from a nonelectrolyte hydrogel system. Calculated values agreed with experimental data for the given systems. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2333–2338, 2002     

The investigation on the electronic structures of hybrid GNR-ZnO

To investigate the modification of graphene for a good semiconductor performance, the model of graphene nanoribbon (GNR) and the model of hybrid GNR-ZnO are presented, respectively. The electronic structures such as band structure, density of electronic states (DOS) are investigated by using first-principles calculations based on density functional theory. The results show that the ZnO has direct contribution to the formation of valence band with the composites, which changes the properties of graphene; the adsorption of ZnO nanostructure has an impressive impact on the graphene nanoribbon, which causes the band gap of the composite to become narrower than that of intrinsic graphene nanoribbon. In terms of the graphene nanoribbon, its differentiation of 2p state weakens gradually from the marginal zone to the central region. The mechanism of electronic structure of the graphene nanoribbon and hybrid GNR-ZnO is also discussed to give a further explanation for the change. The results provide a potential way to improve the properties of intrinsic graphene and enhance the controllability of graphene-based materials structure.     

Direct top–down fabrication of nanoscale electrodes for organic semiconductors using fluoropolymer resists

We report the use of a fluoropolymer resist for the damage-free e-beam lithographic patterning of organic semiconductors. The same material is also shown to be suitable as an orthogonal electron beam resist for the patterning of top-contact electrodes on organic thin films. We demonstrate this by characterizing pentacene field-effect transistors with feature sizes as small as 100 nm and compare the performance of bottom- and top-contacted devices.