Partial reduction of anthracene by cold field emission in liquid in a microreactor with an integrated planar microstructured electrode

We report a novel microreactor with a photolithographically defined integrated electrode containing micro tips that serve as emission points for solvated electrons into liquid n-hexane in a microfluidic channel. The implementation of sharp electrode tips permits to extract electrons from the electrode material at relatively low voltages. The electric field distribution in the gap between a planar patterned platinum microtip array and a planar rectangular counterelectrode is analyzed by a computational model. Cold field emission using these microdevices is experimentally verified, and the partial reduction of anthracene to 9,10-dihydroanthracene, via solvated electrons emitted in solutions with or without ethanol in n-hexane is investigated. It is found that in the current microreactor configuration, the majority of the products are products originating from coupling of ethanol fragments to, and/or oxidation of 9,10-dihydroanthracene at the platinum counterelectrode, leaving no detectable yield of the desired reduction product

ODH @ CNTs – Metal-free Catalytic Alkane Activation

The conversion of alkanes into higher valued olefins by oxidative dehydrogenation (ODH) using supported transition metal oxides is a topic of intense research, however, the yield of alkenes is still too low for industrial application. A completely innovative approach is the metal-free carbon mediated ODH catalysis, which is so far predominantly investigated on the substrate ethylbenzene. After surface modification, commercial multiwalled carbon nano-tubes (CNTs) can be used as stable catalysts also for the activation of alkanes (C2–C4), en-abling alkene yields comparable with supported vanadia catalysts but avoiding the use of toxic transition metal oxides

Genetic Modifiers for the Long-QT Syndrome

Background— Long-QT syndrome is an inherited cardiac channelopathy characterized by delayed repolarization, risk of life-threatening arrhythmia, and significant clinical variability even within families. Three single-nucleotide polymorphisms (SNPs) in the 3′ untranslated region of KCNQ1 were recently suggested to be associated with suppressed gene expression and hence decreased disease severity when located on the same haplotype with a disease-causing KCNQ1 mutation. We sought to replicate this finding in a larger and a genetically more homogeneous population of KCNQ1 mutation carriers. Methods and Results— The 3 SNPs (rs2519184, rs8234, and rs10798) were genotyped in a total of 747 KCNQ1 mutation carriers with A341V, G589D, or IVS7-2A>G mutation. The SNP haplotypes were assigned based on family trees. The SNP allele frequencies and clinical severity differed between the 3 mutation groups. The different SNP haplotypes were neither associated with heart rate–corrected QT interval duration (QTc) nor cardiac events in any of the 3 mutation groups. When the mutation groups were combined, the derived SNP haplotype of rs8234 and rs10798 located on the same haplotype with the mutation was associated with a shorter QTc interval ( P <0.05) and a reduced occurrence of cardiac events ( P <0.01), consistent with the previous finding. However, when the population-specific mutation was controlled for, both associations were no longer evident. Conclusions— 3′ Untranslated region SNPs are not acting as genetic modifiers in a large group of LQT1 patients. The confounding effect of merging a genetically and clinically heterogeneous group of patients needs to be taken into account when studying disease modifiers

Cold field emission in microreactors to perform chemical reactions

Cold field emission in liquids offers the possibility to partially reduce aromatic hydrocarbons without the addition of electrolytes to the solution. A narrow gap (few microns) between electrodes and the creation of sharp tips or needles on the electrode surface give the possibility to generate high electric fields required to emit electrons from the electrode surface. Microtechnology gives the possibility to fabricate microreactors with the above mentioned characteristics. In this study the reaction performances of two different microreactor types are analyzed for partial reduction of anthracene and naphthalene

Cover Picture: Oxidative Dehydrogenation of Ethane over Multiwalled Carbon Nanotubes

The cover picture shows hydrocarbon substrates activated by oxidative dehydrogenation (ODH) using carbon-based catalysts. In their Communication on page 644 ff., B. Frank et al. describe the conversion of ethane to ethylene on surface-modified carbon nanotubes. Due to the high C-H bond strength, harsh reaction conditions are required, in conflict with the oxidation resistance of the carbon catalyst. Surface protection by B2O3 and P2O5 reduces degradation and blocks unselective active sites, as shown by kinetic studies

A new ATR-IR microreactor to study electric field-driven processes

A silicon-based microreactor with a structure that allows in situ characterization by Attenuated Total Internal Reflection Infrared spectroscopy (ATR-IR) of processes driven by an external electric field (E-field) is presented. The microreactor is characterized electrically and spectroscopically. The effects of applying an electric field over a gas or liquid medium in the flow channel of the microreactor are carefully investigated and electrical, mechanical, and optical phenomena which may affect the interpretation of ATR-IR spectroscopic data are discussed. Among these phenomena are heating as a result of the E-field-driven current and the associated phonon generation in the silicon crystal. Experimental IR results under the application of an electrical field are shown for CO2 gas and ammonium ions in aqueous solution. The ability to follow liquid-phase reactions in situ is demonstrate

Vertically aligned carbon nanotube field emitter arrays with Ohmic base contact to silicon by Fe-catalyzed chemical vapor deposition

Abstract In this study, dense arrays of aligned carbon nanotubes are obtained by thermal catalytic chemical vapor deposition, using Fe catalyst dispersed on a thin Ta layer. Alignment of the carbon nanotubes depends on the original Fe layer thickness from which the catalyst dispersion is obtained by thermal treatment prior to the synthesis step, as well as on the synthesis temperature, which in this study was varied between 680 and 740 °C. For the intended application of the nanotubes as field emitters, it is essential that electrical conductivity between the tubes and the substrate is guaranteed. In a novel approach, a noble metal layer, of 100 nm Pt or Au, was applied between the Ta layer and the support, which ensures an Ohmic contact throughout the metal multilayer which connects the silicon substrate with the CNT fibers, because oxidation of Ta at its interface with Si is prevented. For optimized dense arrays of aligned nanotubes with low Ohmic resistance, field emission in nitrogen atmosphere is demonstrated, with field enhancement factors of up to ca. 2000 for nanotubes grown using Fe/Ta catalyst deposited on Au and Pt

Selective defects in channel permeability associated with Cx32 mutations causing X-linked Charcot-Marie-Tooth disease

The X-linked form of Charcot-Marie-Tooth disease (CMTX) is caused by mutations in connexin32 (Cx32), a gap junction protein expressed by Schwann cells where it forms reflexive channels that allow the passage of ions and signaling molecules across the myelin sheath. Although most mutations result in loss of function, several studies have reported that some retain the ability to form homotypic intercellular channels. To gain insight into the molecular defect of three functional CMTX variants, S26L, Δ111-116 and R220stop, we have used several fluorescent tracers of different size and ionic charge to compare their permeation properties to those of wild-type Cx32. Although all mutations allowed the passage of the dye with the smallest molecular mass, they exhibited a clear reduction in the permeability of either one or all of the probes with respect to wild-type channels, as assessed by the percentage of injections showing dye coupling. These data reveal that a lower size cutoff distinguishes these functional CMTX variants from wild-type channels and suggest that this defect may be of pathophysiological relevance. © 2005 Elsevier Inc. All rights reserved.link_to_subscribed_fulltex

Selective defects in channel permeability associated with Cx32 mutations causing X-linked Charcot-Marie-Tooth disease

The X-linked form of Charcot\u2013Marie\u2013Tooth disease (CMTX) is caused by mutations in connexin32 (Cx32), a gap junction protein expressed by Schwann cells where it forms reflexive channels that allow the passage of ions and signaling molecules across the myelin sheath. Although most mutations result in loss of function, several studies have reported that some retain the ability to form homotypic intercellular channels. To gain insight into the molecular defect of three functional CMTX variants, S26L, \u394111\u2013116 and R220stop, we have used several fluorescent tracers of different size and ionic charge to compare their permeation properties to those of wild-type Cx32. Although all mutations allowed the passage of the dye with the smallest molecular mass, they exhibited a clear reduction in the permeability of either one or all of the probes with respect to wild-type channels, as assessed by the percentage of injections showing dye coupling. These data reveal that a lower size cutoff distinguishes these functional CMTX variants from wild-type channels and suggest that this defect may be of pathophysiological relevance

Selective defects in channel permeability associated with Cx32 mutations causing X-linked Charcot-Marie-Tooth disease

The X-linked form of Charcot\u2013Marie\u2013Tooth disease (CMTX) is caused by mutations in connexin32 (Cx32), a gap junction protein expressed by Schwann cells where it forms reflexive channels that allow the passage of ions and signaling molecules across the myelin sheath. Although most mutations result in loss of function, several studies have reported that some retain the ability to form homotypic intercellular channels. To gain insight into the molecular defect of three functional CMTX variants, S26L, D111 \u2013 116 and R220stop, we have used several fluorescent tracers of different size and ionic charge to compare their permeation properties to those of wild-type Cx32. Although all mutations allowed the passage of the dye with the smallest molecular mass, they exhibited a clear reduction in the permeability of either one or all of the probes with respect to wild-type channels, as assessed by the percentage of injections showing dye coupling. These data reveal that a lower size cutoff distinguishes these functional CMTX variants from wild-type channels and suggest that this defect may be of pathophysiological relevance