Active sites of Cu-ZSM-5 for the decomposition of acrylonitrile

The catalytic decomposition of acrylonitrile (AN) over Cu-ZSM-5 prepared with various Cu loadings was investigated. AN conversion, during which the nitrogen atoms in AN were mainly converted to N₂, increased as Cu loading increased. N₂ selectivities as high as 90–95% were attained. X-ray diffraction measurements (XRD) and temperature-programmed reduction by H₂ (H₂-TPR) showed the existence of bulk CuO in Cu-ZSM-5 with a Cu loading of 6.4 wt% and the existence of highly dispersed CuO in Cu-ZSM-5 with a Cu loading of 3.3 wt%. Electron spin resonance measurements revealed that Cu-ZSM-5 contains three forms of isolated Cu²⁺ ions (square-planar, square-pyramidal, and distorted square-pyramidal). The H₂-TPR results suggested that in Cu-ZSM-5 with a Cu loading of 2.9 wt% and below, Cu⁺ existed even after oxidizing pretreatment. The activity of AN decomposition over Cu/SiO₂ suggested that CuO could form N₂, but, independent of the CuO dispersion, nitrogen oxides (NO_x) were formed above 350 °C. Cu⁺ and the square-pyramidal and distorted square-pyramidal forms of Cu²⁺ showed low activity for AN decomposition. Temperature-programmed desorption of NH₃ suggested that N₂ formation from NH₃ proceeded on Cu²⁺, resulting in the formation of Cu⁺. The Cu⁺ ions were oxidized to Cu²⁺ at around 300 °C. Thus, high N₂ selectivity over Cu-ZSM-5 with a wide range of temperature was probably attained by the reaction over the square-planar Cu²⁺, which can be reversibly reduced and oxidized.     

Multi-walled carbon nanotube-reinforced copper nanocomposite coating fabricated by low-pressure cold spray process

Multi-walled carbon nanotube (MWCNT)-reinforced copper (Cu) nanocomposite coatings were successfully deposited on aluminum (Al) substrate by a cold spraying process at a low pressure. The microstructure and the Raman spectrum of the low-pressure-cold-sprayed MWCNT–Cu nanocomposite coating showed that the MWCNTs maintained their tube structure in the Cu matrix, even though structural damage to the MWCNTs increased slightly. MWCNT–Cu nanocomposite-coated Al exhibits higher thermal diffusivity than pure-Cu-coated Al with a comparable hardness. The higher thermal diffusivity of the MWCNT–Cu coating could be explained by the dispersion of MWCNTs within the clean and closed CNT/Cu interfaces, which were achieved with the aid of compressive stress during the cold spraying.     

Synthesis of a photoimmobilizable histidine polymer for surface modification

A novel photoreactive polymer with histidine polar groups was synthesized through the copolymerization of two types of methacrylic acid, one carrying histidine groups and the other carrying azidoaniline groups. The polymer was photoimmobilized on polyester disks for surface modification. The effect of the surface modification on the hydrophilic and biofouling properties was investigated. Static contact angle measurements showed that the polymeric surface was modified to be comparatively hydrophilic in the polymer‐immobilized region. Micropattern immobilization was carried out with a photolithographic method. Atomic force microscopy measurements showed that the polymer was formed on the disks in response to ultraviolet irradiation. Protein adsorption was reduced on the polymer‐immobilized regions, and in those regions, spreading and adhesion of mammalian cells were reduced in comparison with that in nonimmobilized regions. In conclusion, a novel histidine‐containing polymer was photoreactively immobilized on a conventional polymer surface, and it had reduced interaction with proteins and cells. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

An Improved Method for Preparing Dimethyl Disulfide Adducts for GC/MS Analysis

Dimethyl disulfide (DMDS) adducts are prepared from fatty acid methyl esters to locate the double-bond position in monoenoic fatty acids by gas chromatography/mass spectrometry. We improved our original procedure for preparing DMDS adducts with a simple device that can be made in any laboratory using a glass pipette and silica based packing material, Extelut NT.     

The alkylation of biphenyl over three-dimensional large pore zeolites: The influence of zeolite structure and alkylating agent on the selectivity for 4,4′-dialkylbiphenyl

Catalytic properties of three-dimensional zeolites, Y (FAU), Beta (BEA), and CIT-1 (CON) zeolites were examined in the alkylation, isopropylation, sec-butylation, and tert-butylation, of biphenyl (BP), and compared to those of H-mordenite (MOR). The selectivities for 4,4′-dialkylbiphenyl (4,4′-DABP) varied with the types of zeolite and of alkylating agent. FAU, BEA, and CON gave only low selectivities for 4,4′-diisopropylbiphenyl (4,4′-DIPB) in the isopropylation, and predominant isomers were bulky and thermodynamically unstable 2,x′-DIPB (2,2′-, 2,3′-, and 2,4′-) at lower temperatures, and bulky and thermodynamically stable 3,4′- and 3,3′-DIPB at higher temperatures: this is quite different from catalytic features over MOR, which gave 4,4′-DIPB with high selectivities at moderate temperatures. These results suggest that FAU, BEA, and CON have no shape-selective nature in the isopropylation, and that the reaction is principally controlled kinetically at lower temperatures, and thermodynamically at higher temperatures. The sec-butylation gave similar results to the isopropylation. Although the selectivities for 4,4′-di-sec-butylbiphenyl (4,4′-DSBB) were higher than those in the isopropylation, predominant isomers were 2,x′-DSBB (2,2′-, 2,3′-, and 2,4′-) at lower temperatures, and 3,4′- and 3,3′-DSBB at higher temperatures. The tert-butylation gave 4,4′-di-tert-butylbiphenyl (4,4′-DTBB) in moderate to high selectivities over all zeolites at moderate temperatures: the selectivity for 4,4′-DTBB was higher than 80% over BEA and CON; however, it still remained at 50% over FAU. FAU channels with super cages are too large for selective formation of 4,4′-DTBB.

From these results, it is concluded that the selectivity for 4,4′-DABP in the alkylation over MOR, FAU, BEA, and CON is determined by the exclusion of bulky isomers at their transition states, and that the exclusion is caused by the steric restriction at the transition states of bulky isomers by the zeolite channels.     

Synthesis and application of fluorescein- and biotin-labeled molecular probes for the chemokine receptor CXCR4

The design, synthesis, and bioevaluation of fluorescence- and biotin-labeled CXCR4 antagonists are described. The modification of D-Lys8 at an epsilon-amino group in the peptide antagonist Ac-TZ14011 derived from polyphemusin II had no significant influence on the potent binding of the peptide to the CXCR4 receptor. The application of the labeled peptides in flow cytometry and confocal microscopy studies demonstrated the selectivity of their binding to the CXCR4 receptor, but not to CXCR7, which was recently reported to be another receptor for stromal cell-derived factor 1 (SDF-1)/CXCL12.     

Oligodeoxynucleotides containing 3-bromo-3-deazaadenine and 7-bromo-7-deazaadenine 2'-deoxynucleosides as chemical probes to investigate DNA-protein interactions

We describe the design and proof of concept of a pair of chemical probes for investigating DNA-protein interactions-specifically, the incorporation of 7-bromo-7-deazaadenine and 3-bromo-3-deazaadenine 2'-deoxynucleosides (Br(7)C(7)dA and Br(3)C(3)dA) into oligodeoxynucleotides (ODNs)-and their utility. Whereas the bromo substituent of the Br(7)C(7)dA unit in an ODN duplex acts sterically to inhibit binding with NF-kappaB, which interacts with the duplex in its major groove, the bromo substituent of the Br(3)C(3)dA unit acts sterically to inhibit binding with RNase H, which interacts with the duplex in its minor groove. In addition, the utilization of ODNs containing 7-deazaadenine and 3-deazaadenine 2'-deoxynucleosides (C(7)dA and C(3)dA), together with the pair of chemical probes, afforded valuable information on the requirement for nitrogen atoms located in either the major or minor grooves. Accordingly, we were able to show the utility of ODNs containing Br(7)C(7)dA, Br(3)C(3)dA, C(7)dA, and C(3)dA for the investigation of DNA-protein interactions.     

Evaluation of hydrogen absorption behaviour during acid etching for surface modification of commercial pure Ti, Ti-6Al-4V and Ni-Ti superelastic alloys

The hydrogen absorption behaviour during acid etching for the surface modification of commercial pure Ti, Ti-6Al-4V and Ni-Ti superelastic alloys has been investigated on the basis of the surface morphology, electrochemical behaviour and hydrogen thermal desorption analysis. To simulate the conventional acid etching for the improvement of the biocompatibility of Ti alloys, the specimens are immersed in 1 M HCl, 1 M H₂SO₄ or 0.5 M HCl + 0.5 M H₂SO₄ aqueous solution at 60 °C. Upon immersion, commercial pure Ti absorbs substantial amounts of hydrogen irrespective of the type of solution. In H₂SO₄ or HCl + H₂SO₄ solutions, the hydrogen absorption occurs for a short time (10 min). For Ti-6Al-4V alloy, no hydrogen absorption is observed in HCl solution, whereas hydrogen absorption occurs in other solutions. For Ni-Ti superelastic alloy, the amount of absorbed hydrogen is large, resulting in the pronounced degradation of the mechanical properties of the alloy even for an immersion time of 10 min, irrespective of the type of solution. The hydrogen absorption behaviour is not necessarily consistent with the morphologies of the surface subjected to corrosion and the shift of the corrosion potential. The hydrogen thermal desorption behaviour of commercial pure Ti and Ni-Ti superelastic alloy are sensitively changed by acid etching conditions. The present results suggest that the evaluation of hydrogen absorption is needed for each condition of acid etching, and that the conventional acid etching often leads to hydrogen embrittlement.     

Investigation of laser consolidation process for metal powder by two-color pyrometer and high-speed video camera

This paper deals with the measurement of surface temperature on metal powder during the laser consolidation process with two-color pyrometer. Additionally, the aspect of selective laser sintering (SLS) and selective laser melting (SLM) of metal powder is visualized with high speed video camera. As a result, the surface temperature during the laser irradiation was ranged 1520–1810 °C and the consolidation phenomena was classified according to the melting point of metal powder. The metal powder at the heating process cohered intermittently to the melt pool although the laser beam was continuously irradiated to the powder surface.     

Synthesis of deoxy(thiosulfato)chitin as the precursor for noncatalytic photoinduced graft copolymerization

Photoinduced graft copolymerization of vinyl monomers onto deoxy(thiosulfato)chitin (S₂O₃–chitin) has been studied. Chitin was first tosylated and subsequently transformed into S₂O₃–chitin. S₂O₃–chitin has good solubility over tosyl–chitin. Graft copolymerization of S₂O₃–chitin proceeded very easily by ultraviolet irradiation without catalyst. Photolysis of S₂O₃ groups was confirmed by infrared spectra. But the photolysis occurred only in quartz, not in a Pyrex tube. Methyl methacrylate (MMA) and acrylonitrile showed good grafting activities. In the case of acrylic acid and acryl amide, homopolymer formation was predominant, and the degree of grafting was low. We chose the MMA monomer for further information. The grafting rate of S₂O₃–chitin using MMA was much faster than those of chitin and O‐acetyl–chitin. Under the appropriate conditions, the degree of grafting reached 600% only in 2 h, and the grafting efficiency was over 75% in any monomer concentration. But addition of DMSO into the polymerization system decreased the degree of grafting. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 189–195, 1999