Can a Procedure for the Growth of Single-layer Graphene on Copper be used in Different Chemical Vapor Deposition Reactors?

In the last decade, catalytic chemical vapor deposition (CVD) has been intensively explored for the growth of single-layer graphene (SLG). Despite the scattering of guidelines and procedures, variables such as the surface texture/chemistry of catalyst metal foils, carbon feedstock, and growth process parameters have been well-scrutinized. Still, questions remain on how best to standardize the growth procedure. The possible correlation of procedures between different CVD setups is an example. Here, two thermal CVD reactors were explored to grow graphene on Cu foil. The design of these setups was entirely distinct, one being a “showerhead” cold-wall type, whereas the other represented the popular “tubular” hot-wall type. Upon standardizing the Cu foil surface, it was possible to develop a procedure for cm²-scale SLG growth that differed only by the carrier gas flow rate used in the two reactors.     

Inorganic Sol-Gel Preparation of Medium Sized Microparticles of Li2TiO3 from TiCl4 as Tritium Breeding Material for Fusion Reactors

Microspheres of Li₂TiO₃ were fabricated by a classical, inorganic sol-gel process from commercially available TiCl₄. Elaborated process consists of the following main steps: (1) dissolving of TiCl₄ in concentrated aqueous HCl and addition of LiOH; (2) formation of sol emulsion in 2-ethylhexanol-1 containing the surfactant SPAN-80 (EH); (3) gelation of emulsion drops by extraction of water with partially dehydrated EH; (4) impregnation of gel to Li:Ti molar ratio MR = 2; (5) thermal treatment at 1200°C in order to receive chloride free product. This temperature can be significantly lowered (to 750°C) by dechlorination starting solution TiCl₄ by chemical treatment of the with nitric acid to form of nitrate-stabilized titania sols. Tritium release from sol-gel made Li₂TiO₃ microspheres were found very close to that observed for other traditional materials, however for the first sample process starts slightly earlier.     

Temperature measurements by H2-CARS in the reactive zone of a plasma test reactor for hydrocarbon synthesis

The application of coherent anti-Stokes Raman spectroscopy (CARS) to an electric are test reactor is described in which acetylene synthesis in analogy to the large-scale industrial process is .studied. We report on spatially resolved measurements of H₂-CARS spectra, the comparison with calculated spectra, and the determination of temperatures in the reaction zone.Dedicated to Prof. Rudolf Wienecke on the occasion of his 65 birthday.     

~(13)C代谢通量分析

代谢通量分析(metabolic flux analysis,MFA)是通过确定代谢网络中代谢流分布来表征细胞代谢状态的强有力的工具。鉴于计量学代谢通量分析在处理复杂代谢网络时表现出的局限性,发展了以13C标记实验为基础的13C MFA。本文介绍了13C MFA的原理与方法,总结和评述了13C MFA在实验与数据分析方面的最新进展以及MFA在功能基因组研究中的重要地位,同时对代谢通量分析的发展前景进行了展望。     

Use of non-segmented flow,post-columns reaction detection with miniaturized HPLC systems

Summary The use of non-segmented flow, post-column reaction detection is evaluated for use with miniaturized HPLC. Non-segmented open-tubular reactors with internal diameters 0.1 mm to 0.25 mm and packed-bed reactors with internal diameters of 1 mm, filled with 5 and 10 m particles are evaluated theoretically and experimentally with respect to band broadening and pressure drop characteristics. An integrated system consisting of miniaturized HPLC (1 mm i. d.) columns and compatible hardware is described. An example of the separation of catecholamines is given.     

Rapid measurement of fish freshness indices by an amperometric flow-injection system with a 16-way switching valve and immobilized enzyme reactors

A novel flow-injection system is proposed for the rapid measurement of the fish freshness indices K₁ and K₂: K₁=[([HxR+[Hx])×100/([IMP]+[HxR]+[Hx])] and K₂=[[Hx]×100/([HxR]+[Hx])], where [IMP], [HxR] and [Hx] are inosine-5′-monophosphate, inosine and hypoxanthine concentrations, respectively. For the estimation of index K₁, 5′-nucleotidase immobilized reactor and nucleoside phosphorylase (NP)/xanthine oxidase (XO) coimmobilized reactor were incorporated in series in the flow-injection line made up by a 16-way switching valve with two sample loops. For the estimation of index K₂, NP and XO immobilized reactors were also incorporated in the similar flow-line. Two sample portions passed through the flow-line with different residence times so that two peaks were obtained. The first and second peaks obtained in the K₁-determining system corresponded to the total of HxR and Hx and the total of Hx, HxR and IMP, respectively. Similarly, the first and second peaks obtained in the K₂-determining system corresponded to Hx and the total of Hx and HxR, respectively. Therefore, the indices K₁ and K₂ can be estimated by

where i₁ and i₂ present the peak current of the first and second peaks, respectively, and f the ratio of the peak currents of the first and second peaks for a Hx standard solution. A sea bream was selected as a model fish and it was stored at 4 °C after death. A good correlation was found between the index K₁ and the storage time over a period of 400 h, with a correlation coefficient of 0.992, but no correlation between the index K₂ and the storage time. The measurements could be performed at a rate of 22 samples per hour with satisfactory precision (0.6–1.2% R.S.D.), without calibration for each species, accurate weighing of fish meat and any interferences in fish meat.     

Molecular reactors and machines: applications, potential, and limitations

Molecular reactors are miniature vessels for the assembly of reactants at the molecular level, in order to change the nature of chemical transformations. It seems probable that those that will find most immediate applications are those that change product ratios or give products which would not readily form in the absence of the reactors, and thereby afford easy access to materials that are otherwise difficult to obtain. Molecular machines consist of interrelated parts with separate functions and perform some kind of work, at the molecular level. Practical examples are likely to be relatively uncomplicated and not based on individual functions of single-molecule devices. Instead they will probably rely on extensive redundancy of the molecular components and their interactions and reactions, as well as of the machines themselves.     

Composite poly(dimethylsiloxane)/glass microfluidic system with an immobilized enzymatic particle-bed reactor and sequential sample injection for chemiluminescence determinations

A three-layer poly(dimethylsiloxane) (PDMS)/glass microfluidic system for performing on-chip solid-phase enzymatic reaction and chemiluminescence (CL) reaction was used for the determination of glucose as a model analyte. A novel method for the immobilization of controlled-pore-glass based reactive particles on PDMS microreactor beds was developed, producing an on-chip solid-phase reactor that featured large reactive surface and low flow impedance. Efficient mixing of reagent/sample/carrier streams was achieved by incorporating chaotic mixer structures in the microfluidic channels. A conventional sequential injection (SI) system was adapted for direct coupling with the microfluidic system, and combined with hydrostatic delivery of reagents to achieve efficient and reproducible sample introduction at 10 μl levels. A detection limit of 10 μM glucose (3σ), and a precision of 3.1% RSD (n=7, 0.2 mM glucose) were obtained using the SI-microfluidic-CL system integrated with a glucose oxidase (GOD) reactor. Carryover was <5% at a throughput of 20 samples/h.     

Condensed Mode Cooling of Ethylene Polymerization in Fluidized Bed Reactors

This review gives an overview of the evolution of the technology of condensed mode cooling, primarily for the case of ethylene polymerization on supported catalysts in fluidized bed reactors. It is well known that this mode of heat removal is quite effective in allowing polyolefin manufacturers to increase significantly production rates. What is perhaps less well understood are all of the issues that, in addition to the effect of the latent heat of vaporization of injected liquid components, also have an impact on the rate of production and behavior of the reactor. However, the liquid components injected into the reactor can vaporize rapidly under full‐scale conditions, leaving behind several heavy components (with respect to ethylene) that have numerous effects on how the particles behave, on the reaction rate, and on fluidization, fouling, and other parameters related to reactor and process performance.     

A Cyclodextrin Molecular Reactor for the Regioselective Synthesis of 1,5-disubstituted-1,2,3-triazoles

6^A-Deoxy-6^A-propynamido-β-cyclodextrin reacts with 4-tert-butylphenyl azide in aqueous solution, to form the 5-(aminocarbonyl)-substituted triazole in preference to the 4-(aminocarbonyl)-substituted analogue, in a ratio of 25:1. The cyclodextrin moiety templates the reaction through the formation of a host-guest complex of the dipole with the dipolarophile, controlling the regioselectivity of cycloaddition. In a control reaction under similar conditions, with propiolamide instead of the cyclodextrin derivative, 5- and 4-(aminocarbonyl)-1-(4-tert-butylphenyl)-1,2,3-triazole were formed in a ratio of 1:4. As well as reversing the regioselectivity, the cyclodextrin substituent increases the rate of cycloaddition, by at least two orders of magnitude for the reaction to give the 5-substituted cycloadduct. Even the rate of formation of the 4-substituted cycloadduct is increased by a factor of two. Less marked effects are observed with phenyl azide and 4-tert-butylbenzyl azide as dipoles.