Dibutyltin Dimethoxide‐Catalyzed Cyano Transfer to Aldehydes and Imines

A novel reaction involving cyano transfer from benzophenone cyanohydrin to aldehydes and imines was realized by using dibutyltin dimethoxide as a catalyst. Various cyanohydrins and α‐amino nitriles were obtained in moderate to high yields by this reaction. Ketimines also showed remarkable reactivity as cyano acceptors under conventional reaction conditions. This catalytic reaction was further applied to a three‐component condensation reaction of aldehydes, aniline, and benzophenone cyanohydrin in the presence of Drierite^®.     

Chiral discrimination between alanine enantiomers by field effect transistor with a homocysteine monolayer-modified gate

The application of field effect transistor (FET) to chiral discrimination was investigated. An Au film vapor-deposited on a self-assembled monolayer (SAM) of (3-mercaptopropyl)trimethoxysilane, which was formed on the SiO₂ gate of FET as an adhesive and insulating layer, stabilizes the drain current-gate voltage (I_d-V_g) property of FET. The modification by homocysteine (Hcy) SAM on the surface of Au-coated gate makes it possible for the FET to distinguish between the enantiomers of alanine (Ala). Namely, after the sequential addition of Ala and Cu(II) to a K₂SO₄ solution in this system, it was confirmed that the lateral shift of I_d-V_g curves for the FET corresponded to the chirality of Ala. With the l-Hcy SAM-modified gate, a notable negative shift was observed for l-Ala, whereas the shift observed with d-Ala was much smaller. In contrast, opposite results were obtained with d-Hcy SAM. Results of quartz crystal microbalance measurement suggested that such an FET response was originated from the enantioselective formation of diastereomeric Cu complexes with Ala molecules on the Hcy SAM. This system was demonstrated to respond quantitatively to one enantiomeric form of Ala in mixed solutions of two enantiomers as well as in pure enantiomeric solutions.     

Contamination and moisture absorption effects on the mechanical properties of catalyst coated membranes in PEM fuel cells

Mechanical degradation of the catalyst coated membrane (CCM), which contains a perfluorosulfonic acid (PFSA) proton transport layer, can significantly deteriorate the performance of proton exchange membrane (PEM) fuel cells. We initially report on the adhesive and cohesive fracture properties of CCMs and show that failure occurs cohesively in the catalyst layer (CL). We then investigate the effects of foreign cations and chloride contamination and moisture absorption on the mechanical properties of CCMs. The fracture resistance of contaminated CCMs is significantly reduced and the time dependent growth of cracks in the CLs in moist air environments occurs at lower crack driving force thresholds. The deterioration in fracture resistance of the CCMs after foreign cation contamination is related to cation interaction with the molecular structure of PFSA polymer. The harmful effect of chloride contamination is attributed to chloride blocking on the surface of catalyst Pt particles, which tends to weaken the catalyst-polymer interface and induces crack initiation and subsequent propagation with lower energy. The accelerated time dependent crack growth at higher humidity is explained by the role of water molecules on weakening ionic interactions and the intermolecular strength of the PFSA polymer.     

Purification and high-resolution top-down mass spectrometric characterization of human salivary α-amylase

Human salivary α-amylase (HSAMY) is a major component of salivary secretions, possessing multiple important biological functions. Here we have established three methods to purify HSAMY in human saliva for comprehensive characterization of HSAMY by high-resolution top-down mass spectrometry (MS). Among the three purification methods, the affinity method based on the enzyme-substrate specific interaction between amylase and glycogen is preferred, providing the highest purity HSAMY with high reproducibility. Subsequently, we employed Fourier transform ion cyclotron resonance MS to analyze the purified HSAMY. The predominant form of α-amylase purified from saliva of various races and genders is nonglycosylated with the same molecular weight of 55,881.2, which is 1885.8 lower than the calculated value based on the DNA-predicted sequence. High-resolution MS revealed the truncation of the first 15 N-terminal amino acids (-1858.96) and the subsequent formation of pyroglutamic acid at the new N-terminus Gln (-17.03). More importantly, five disulfide bonds in HSAMY were identified (-10.08) and effectively localized by tandem MS in conjunction with complete and partial reduction by tris (2-carboxyethyl) phosphine. Overall, this study demonstrates that top-down MS combined with affinity purification and partial reduction is a powerful method for rapid purification and complete characterization of large proteins with complex and overlapping disulfide bond patterns.     

Graphene quantum dots derived from carbon fibers

Graphene quantum dots (GQDs), which are edge-bound nanometer-size graphene pieces, have fascinating optical and electronic properties. These have been synthesized either by nanolithography or from starting materials such as graphene oxide (GO) by the chemical breakdown of their extended planar structure, both of which are multistep tedious processes. Here, we report that during the acid treatment and chemical exfoliation of traditional pitch-based carbon fibers, that are both cheap and commercially available, the stacked graphitic submicrometer domains of the fibers are easily broken down, leading to the creation of GQDs with different size distribution in scalable amounts. The as-produced GQDs, in the size range of 1-4 nm, show two-dimensional morphology, most of which present zigzag edge structure, and are 1-3 atomic layers thick. The photoluminescence of the GQDs can be tailored through varying the size of the GQDs by changing process parameters. Due to the luminescence stability, nanosecond lifetime, biocompatibility, low toxicity, and high water solubility, these GQDs are demonstrated to be excellent probes for high contrast bioimaging and biosensing applications.     

Nanoscale shuffling in a template-assisted self-assembly of binary colloidal particles

We have fabricated a square lattice array of sub-micrometer fluorescent (red and green) polystyrene particles. The particles were each embedded into small pits fabricated on a silicon substrate by electron beam lithography, through the drying process of an aqueous suspension containing equal amounts of the two species. We indexed 0 and 1 for each red and green particle, respectively, and then obtained a one-dimensional bit sequence by the successive reading of the indices in a predetermined manner. We evaluated the randomness of the bit sequence by using the improved FIPS 140-2 statistical test suite. Consequently, we found that the bit sequences do not have any non-randomness. The particle array was obtained by a very simple process, i.e., the drying of a suspension, but the particle distribution pattern was definitely unpredictable and irreproducible, and the number of possible patterns was tremendously large. The signal--i.e., the color of the particle--does not deteriorate within a practical timescale under various conditions, such as in an electric field, in a magnetic field, in air or water, on a solid matrix, and so on, which means that a small tip with the particle pattern can be installed in miscellaneous object, including electronic products, plastic credit cards, currency bills, and so on. Therefore, this particle array is applicable to a nanoscale identification tag or a one-time pad encryption tip.     

Preparation of amorphous TiS x thin film electrodes by the PLD method and their application to all-solid-state lithium secondary batteries

Titanium sulfide thin film electrodes were prepared by the pulsed laser deposition method using a KrF excimer laser. Thin films of various compositions were prepared under several deposition conditions such as Ar gas pressure, laser fluence, and target-substrate distance. The thickness of the titanium sulfide thin film prepared under Ar gas pressure of 0.01 Pa, the pulse energy of 200 mJ/pulse, and the distance of 5 cm between the target and the substrate was ca. 400 nm. The films prepared at room temperature showed no peaks in the XRD pattern and no periodic lattice fringe in high-resolution transmission electron microscopic images, suggesting that they were amorphous. An all-solid-state cell using a TiS_4.0 thin film electrode formed on a pelletized Li₂S–P₂S₅ glass–ceramic electrolyte showed the reversible capacity of 543 mAh g⁻¹, which was higher than that of a cell using a TiS_1.7 film. The former solid-state cell retained higher capacity for 20 cycles at room temperature.     

TEM-EDS with Breakthroughs in 3D Wiring and High-Speed Processing

We have been improving our TEM-EDS for elemental microanalysis after a successful achievement of a high energy resolution (7.8?eV at 1.7?keV) using a TES microcalorimeter. The improvements fall into a 3D superconductive wiring and a high-speed processing (～3,000?cps). We are implementing a 10-ch TES array for higher count rate and a broader dynamic range. The shape of a probe needs to be a small polygonal rod with an approximate size of 1?cm×1?cm×10?cm, and hence the placing and wiring of the TES array and read-out circuits at the cryogenic stage were very demanding. We overcame those difficulties by 3D photolithography and electrodeposition. With these new technologies, we developed the OFC probe with solder-plated 3D wiring, and successfully observed a superconductivity at the temperature of liquid helium. As a required count rate per channel is ～300?cps, the overall system count rate is ～3,000?cps, which is incomparably higher than before. In the last model, we used an embedded system to process waveforms from a 4-ch 14-bit 1?MS/s ADC due to a small signal bandwidth, but this time we parallelized three identical ADCs and transfer raw waveforms by Ethernet lines to a host to achieve the required system count rate.     

单向碳/环氧和玻纤/环氧复合材料扭转疲劳性能

提出碳/环氧复合材料作为柔性梁材料的可行性。对相同树脂基体的单向碳纤维复合材料和玻璃纤维/环氧复合材料的扭转疲劳性能进行研究。碳纤维复合材料的初始扭转刚度几乎与玻璃纤维复合材料相同。采用有限元计算的扭转刚度与试验结果吻合:扭转刚度主要受控于材料的剪切刚度。通过控制正弦波扭转的角度,进行了恒定受拉轴向荷载下的扭转疲劳试验。尽管根据循环次数降低了扭矩和扭转刚度振幅,无论是碳纤维还是玻璃纤维复合材料都没出现严重的破坏现象。X-射线CT的检查结果以及有限元计算的结果显示:主要是沿着纤维方向裂缝扩展引起扭转刚度的退化,碳纤维扭转疲劳寿命高于玻璃纤维复合材料。因此,根据扭转刚度和张拉-扭转疲劳性能,证实碳纤维具有很好的性能,可作为柔性梁的抗扭材料。