ChemPhysChem

Cover image for Vol. 6 Issue 12

December 9, 2005

Volume 6, Issue 12

Pages 2445–2679

    1. Cover Picture: Oxidation of Formic Acid and Carbon Monoxide on Gold Electrodes Studied by Surface-Enhanced Raman Spectroscopy and DFT (ChemPhysChem 12/2005) (page 2445)

      Guillermo L. Beltramo, Tatyana E. Shubina and Marc T. M. Koper

      Article first published online: 6 DEC 2005 | DOI: 10.1002/cphc.200590029

      The cover picture shows an artistic impression of a formate anion adsorbed on a gold electrode, as probed by surface-enhanced Raman spectroscopy (SERS). By a combination of SERS and density functional theory calculations, the surface-bonded formate anion is shown to be the key intermediate in formic acid oxidation on gold electrodes. Formic acid oxidation activity on gold is also compared to the remarkable electro-oxidation properties of gold towards carbon monoxide. Find out more in the Article by Beltramo et al. on p. 2597.

    2. Graphical Abstract: ChemPhysChem 12/2005 (pages 2447–2455)

      Article first published online: 6 DEC 2005 | DOI: 10.1002/cphc.200590030

    3. Single-Molecule Studies on DNA and RNA (pages 2458–2471)

      Karl Otto Greulich

      Article first published online: 6 DEC 2005 | DOI: 10.1002/cphc.200500038

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      Single file: DNA and RNA are molecules with a high degree of individuality, and therefore single-molecule techniques are necessary to understand their properties in sufficient detail (see picture). This Review examines recent techniques for the preparation, handling, and detection of single molecules of nucleic acids, as well as some of the obtained results. These include the construction of nanomachines, such as a walking single-molecule robot and a single-molecule DNA computer.

    4. Inherent Complexities of Trace Detection by Surface-Enhanced Raman Scattering (pages 2473–2484)

      Nicholas P. W. Pieczonka and Ricardo F. Aroca

      Article first published online: 18 NOV 2005 | DOI: 10.1002/cphc.200500112

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      The dark side of SERS: Surface-enhanced Raman scattering (SERS) is a powerful analytical tool (see figure). With the ability to amplify the normally weak Raman signal by up to factors of 1010, this method has been successfully used for single-molecule detection. With this great promise comes a myriad of difficulties. This Minireview attempts to collect in one place many of the confounding issues that arise in SERS experiments.

    5. Electric Field-Induced Chaining of Au/Aniline Polymeric Particle Pairs and TEM Characterization (pages 2485–2488)

      Jianfei Sun, Zhirui Guo, Changling Wang and Ning Gu

      Article first published online: 6 DEC 2005 | DOI: 10.1002/cphc.200500286

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      Peanutlike nano-heterostructures: Chainlike structures of the metal-organic hybrids are formed under an alternating current field without contact to the electrodes. Two quasi-one-dimensional structures are observed by transmission electron microscopy, which are named σ- and π-type chaining. In addition, the novel phenomenon of detached organic and metallic particles, observed at some frequencies, is reported (see picture). This observation arises due to the dielectric difference between the particle pairs.

    6. Improved Hydrogen Storage of TiF3-Doped NaAlH4 (pages 2488–2491)

      Ping Wang, Xiang Dong Kang and Hui Ming Cheng

      Article first published online: 14 NOV 2005 | DOI: 10.1002/cphc.200500207

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      Hydrogen energy systems: For reversible hydrogen storage TiF3 is superior to TiCl3 as a dopant precursor for preparing catalytically enhanced Ti–NaAlH4 systems (see diagram). In addition to the increased hydrogen capacity, the TiF3-doped NaAlH4 exhibits a more pronounced kinetic enhancement than the TiCl3-doped hydride at varied operational conditions.

    7. New Catanionic Triblock Amphiphiles: Supramolecular Organization of a Sugar-Derived Bolaamphiphile Associated with Dicarboxylates (pages 2492–2494)

      Elodie Soussan, Andreea Pasc-Banu, Sabrina Consola, Thomas Labrot, Emile Perez, Muriel Blanzat, Reiko Oda, Christiane Vidal and Isabelle Rico-Lattes

      Article first published online: 18 NOV 2005 | DOI: 10.1002/cphc.200500273

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      Sweet-and-sour mix: A series of catanionic triblock amphiphiles, containing a sugar-based bolaamphiphile associated with dicarboxylates, exhibits structure-dependent supramolecular organization. Spontaneous vesicle formation (see transmission electron micrograph) can be correlated to the catanionic amphiphile arrangement by molecular modeling.

    8. Mechanism of Regular Pattern Formation in Reactive Dewetting (pages 2495–2498)

      Steven Lenhert, Michael Gleiche, Harald Fuchs and Lifeng Chi

      Article first published online: 6 DEC 2005 | DOI: 10.1002/cphc.200500276

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      Regularly striped patterns of various dimensions and directions can emerge from the Langmuir–Blodgett transfer of phospholipids onto hydrophilic substrates under the appropriate conditions (see optical micrographs; bar=5 μm). The authors quantitatively measure the dependence of the pattern dimensions on the transfer velocity and the surface pressure. A mechanism for pattern formation, based on the local curvature of the monolayer-covered liquid–vapour interface in the vicinity of the three-phase contact line, is presented.

    9. Bismuth–Copper Vanadate BiCu2VO6 as a Novel Photocatalyst for Efficient Visible-Light-Driven Oxygen Evolution (pages 2499–2502)

      Haimei Liu, Ryuhei Nakamura and Yoshihiro Nakato

      Article first published online: 6 DEC 2005 | DOI: 10.1002/cphc.200500278

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      A novel narrow-band photocatalyst, BiCu2VO6, was successfully synthesized by modulating the band structure of the semiconductor. BiCu2VO6 exhibits higher activity for O2 evolution under visible-light illumination. The picture shows the incident photon-to-current efficiency (IPCE) for a BiCu2VO6 particulate thin-film electrode (▪).

    10. Model for the Conductivity of Ionic Liquids Based on an Infinite Dilution of Holes (pages 2502–2505)

      Andrew P. Abbott

      Article first published online: 31 OCT 2005 | DOI: 10.1002/cphc.200500283

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      Charge transport in an ambient-temperature ionic liquid is limited by the mobility of suitably sized voids into which ions can migrate (see figure). This allows conductivity data to be simply analyzed by using the Stokes–Einstein equation. The mechanism of charge transport is contrasted with that in high-temperature molten salts, which is different from that in low-temperature systems.

    11. Chemical Synthesis and Optical Properties of Size-Selected CdSe Tetrapod-Shaped Nanocrystals (pages 2505–2507)

      Mona B. Mohamed, Dino Tonti, Awos Al Salman and Majed Chergui

      Article first published online: 18 NOV 2005 | DOI: 10.1002/cphc.200500445

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      Control of size and shape: The high-yield chemical synthesis of size-selected CdSe tetrapods (see microstructure pictures) is presented. This method is based on nucleation of nanodots with a zinc-blende lattice structure and growth of the arms with a wurtzite structure on the four [111] facets of the dots. Absorption, emission and photoluminescence excitation spectra are presented and discussed.

    12. Kinetic and DFT Studies on the Photoinduced Desorption of Sulfur from Gold Nanoparticles Loaded on Titanium Dioxide (pages 2508–2512)

      Tomokazu Kiyonaga, Tomohiro Mitsui, Tetsuro Soejima, Seishiro Ito, Hiroaki Tada, Tetsuro Kawahara, Tomoki Akita, Koji Tanaka and Hisayoshi Kobayashi

      Article first published online: 14 NOV 2005 | DOI: 10.1002/cphc.200500201

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      Cleaning poisoned gold catalysts: Kinetic analysis of the photoinduced desorption of sulfur from gold nanoparticles loaded on TiO2 particles in water revealed that the rate constant increases with increasing pH. Photoelectrochemical measurements and DFT calculations led to the conclusion that this reaction results from an upward shift in the Fermi energy of gold nanoparticles by irradiation. The picture shows a high-resolution TEM image of an Au nanoparticle on TiO2.

    13. Influence of Coadsorbates on the NO Dissociation on a Rhodium(311) Surface (pages 2513–2521)

      Oliver R. Inderwildi, Dirk Lebiedz, Olaf Deutschmann and Jürgen Warnatz

      Article first published online: 18 NOV 2005 | DOI: 10.1002/cphc.200500222

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      Exhaust-gas aftertreatment: NO dissociation on the stepped Rh(311) surface is investigated and the influence of oxygen precoverage on this reaction is examined by density functional calculations (see picture). The results are discussed in terms of an NOx-dissociation exhaust-gas catalyst system proposed by Nakatsuji, which removes nitrogen oxides in excess oxygen.

    14. From Colloidal Co/CoO Core/Shell Nanoparticles to Arrays of Metallic Nanomagnets: Surface Modification and Magnetic Properties (pages 2522–2526)

      Ulf Wiedwald, Kai Fauth, Markus Heßler, Hans-Gerd Boyen, Frank Weigl, Michael Hilgendorff, Michael Giersig, Gisela Schütz, Paul Ziemann and Michael Farle

      Article first published online: 4 NOV 2005 | DOI: 10.1002/cphc.200500148

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      Cobalt nanomagnets are formed when Co/CoO core/shell nanoparticles are exposed to a mild reactive hydrogen plasma. In the particle monolayer, agglomeration does not occur during this process. X-ray absorption and magnetic circular dichroism proved ideally suited to monitor the process and to study nanoparticle magnetism in detail. In the picture, the magnetization loop of the metallic magnets is superimposed on a transmission electron microscopy image of their Co/CoO precursor.

    15. Adsorption of Amyloid β-Peptide at Polymer Surfaces: A Neutron Reflectivity Study (pages 2527–2534)

      Sandra Rocha, Rumen Krastev, Andreas F. Thünemann, M. Carmo Pereira, Helmuth Möhwald and Gerald Brezesinski

      Article first published online: 14 NOV 2005 | DOI: 10.1002/cphc.200500158

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      Neutron reflectometry studies at solid–liquid interfaces have shown that amyloid β-peptide (1–40) adsorbs on positively charged hydrophilic films (and readily on hydrophobic surfaces), whereas no adsorption layer was detected on hydrophilic noncharged and negatively charged films, as indicated in the graphic. This study shows that amyloid fibril formation may be driven by interactions with the surface.

    16. Absolute Configuration of C76 from Optical Rotatory Dispersion (pages 2535–2540)

      Prasad L. Polavarapu, Jiangtao He, Jeanne Crassous and Kenneth Ruud

      Article first published online: 4 NOV 2005 | DOI: 10.1002/cphc.200500171

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      Theoretical predictions of electronic circular dichroism (ECD) and optical rotatory dispersion (ORD) for (fC)-C76 were obtained using Hartree–Fock as well as density functional theory. The experimental ORD for C76 (see picture) was derived from the experimental ECD spectrum using Kramers–Kronig transform. The predicted and experimental ECD spectra are in good agreement. Similarly, the predicted and experimental ORD patterns are in good agreement. These data lead to the establishment of the absolute configuration of C76 in terms of the optical rotation as (+)589-(fC)-C76.

    17. σ–π Energy Separation in Homodesmotic Reactions (pages 2541–2551)

      Georg Hohlneicher, Lars Packschies and Johannes Weber

      Article first published online: 31 OCT 2005 | DOI: 10.1002/cphc.200500180

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      The aromatic stabilization energy (ASE) is partitioned into σ and π contributions for homodesmotic reactions. When an isointeractional reaction (see picture) is used to determine the ASE of benzene, the electron–electron, nuclear–nuclear, and nuclear–electron contributions to the potential energy become smaller than those reported previously, and change their sign. The distinction between intrinsic and extrinsic aromaticity is unnecessary.

    18. Aromaticity Analysis of Lithium Cation/ π Complexes of Aromatic Systems (pages 2552–2561)

      Mireia Güell, Jordi Poater, Josep M. Luis, Otilia Mó, Manuel Yáñez and Miquel Solà

      Article first published online: 18 NOV 2005 | DOI: 10.1002/cphc.200500216

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      Changes in local aromaticity of aromatic rings on complexation with lithium cations are discussed for a series of polycyclic aromatic hydrocarbons (e.g., coronene, see picture) by using, as probes of aromaticity, the para-delocalization index (PDI), the aromatic fluctuation index (FLU), the harmonic oscillator model of aromaticity index (HOMA), and the nucleus-independent chemical shift (NICS).

    19. The Trigonal Bipyramidal MN3M Species: A New Kind of Aromatic Complex Containing a Multiple-Fold Aromatic N3 Subunit (pages 2562–2569)

      Ying Li, Zhi-Ru Li, Di Wu, Wei Chen and Chia-Chung Sun

      Article first published online: 14 NOV 2005 | DOI: 10.1002/cphc.200500292

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      Ring the changes: The triangular N33− ring and a series of trigonal bipyramidal MN3M (M=Be, B, Mg, Al, Ca) species have negative nucleus-independent chemical shift values. All the species have three aromatic six-electron systems (π, σp, and σs) and exhibit threefold aromaticity. The picture shows the nine valence molecular orbitals of the N33− ring. CaN3Ca can be considered as a new superalkali species.

    20. Probing the Water Coordination of Protein-Targeted MRI Contrast Agents by Pulsed ENDOR Spectroscopy (pages 2570–2577)

      Stephan G. Zech, Wei-Chuan Sun, Vincent Jacques, Peter Caravan, Andrei V. Astashkin and Arnold M. Raitsimring

      Article first published online: 18 NOV 2005 | DOI: 10.1002/cphc.200500250

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      Electron–nuclear double resonance (ENDOR) spectroscopy is used for the direct determination of water coordination numbers and proton–metal distances of gadolinium-based magnetic resonance imaging (MRI) contrast agents. It is shown that the water hydration number q of a complex in aqueous solution can be significantly different to when the complex is noncovalently bound to a protein (see picture; HSA= human serum albumin).

    21. In Situ 1H NMR Study on the Trioctylphosphine Oxide Capping of Colloidal InP Nanocrystals (pages 2578–2584)

      Zeger Hens, Iwan Moreels and Jose C. Martins

      Article first published online: 31 OCT 2005 | DOI: 10.1002/cphc.200500182

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      A powerful technique: Diffusion 1H NMR spectroscopy can be used to selectively observe and identify spectral features arising from molecules adsorbed on a colloidal particle, specifically, trioctylphosphine oxide adsorbed on colloidal InP nanocrystals (TOPO@InP). In this study, the average number of TOPO molecules per nanocrystal could be quantified and the TOPO/pyridine capping exchange could be demonstrated (see figure).

    22. Radiolysis of Confined Water: Hydrogen Production at a High Dose Rate (pages 2585–2596)

      Sophie Le Caër, Patricia Rotureau, Francine Brunet, Thibault Charpentier, Guillaume Blain, Jean Philippe Renault and Jean-Claude Mialocq

      Article first published online: 14 NOV 2005 | DOI: 10.1002/cphc.200500185

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      Trapped in a glass: The production of dihydrogen in mesoporous materials by water radiolysis under high dose rate irradiation (1.7 Gy ns−1 for a 10-MeV electron beam) was investigated. The H2 production is presented in the figure for glasses of different pore sizes: 8 (▪), 25 (•), 50 (▴), 300 nm (▾), and it reflects the radiolysis of nanoconfined water.

    23. Oxidation of Formic Acid and Carbon Monoxide on Gold Electrodes Studied by Surface-Enhanced Raman Spectroscopy and DFT (pages 2597–2606)

      Guillermo L. Beltramo, Tatyana E. Shubina and Marc T. M. Koper

      Article first published online: 6 DEC 2005 | DOI: 10.1002/cphc.200500198

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      Gold electrocatalysis: Studying the electro-oxidation of carbon monoxide and formic acid on gold by a combination of electrochemistry, surface-enhanced Raman spectroscopy, and DFT calculations led to the conclusion that they involve different intermediates, namely, carboxyhydroxyl and the formate anion, respectively. The activity of gold towards CO and HCOOH oxidation is explained by the ability of gold to stabilize these intermediates. The picture shows the calculated most stable geometry of the formate anion on the Au(110) surface.

    24. The Photochemistry of Lipoic Acid: Photoionization and Observation of a Triplet Excited State of a Disulfide (pages 2607–2618)

      Götz Bucher, Changyuan Lu and Wolfram Sander

      Article first published online: 6 DEC 2005 | DOI: 10.1002/cphc.200500211

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      Laser flash photolysis of lipoic acid can result in the detection of very different transient species, depending on the experimental conditions (see scheme). On excitation in acetonitrile solution (λexc=355 nm), a triplet excited state is observed. Short-wavelength laser irradiation (λexc=266 nm) of an aqueous solution of lipoic acid, on the other hand, results in radical ions that undergo typical reactions such as quenching by oxygen or β-carotene.

      Corrected by:

      Corrigendum: The Photochemistry of Lipoic Acid: Photoionization and Observation of a Triplet Excited State of a Disulfide

      Vol. 7, Issue 1, 14, Article first published online: 11 JAN 2006

    25. Synchrotron Radiation Circular Dichroism Spectroscopy of Ribose and Deoxyribose Sugars, Adenosine, AMP and dAMP Nucleotides (pages 2619–2624)

      Steen Brøndsted Nielsen, Tapas Chakraborty and Søren Vrønning Hoffmann

      Article first published online: 4 NOV 2005 | DOI: 10.1002/cphc.200500236

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      Circular dichroism of RNA and DNA building blocks in aqueous solution was investigated in the vacuum ultraviolet region with synchrotron radiation. Two isodichroic points were found for d-(−)-ribose by changing the temperature (see picture), which allowed three electronic transitions to be identified and assigned. Moreover, increasing the temperature led to a new, weak band that was tentatively assigned to the open-chain form of the sugar, in equilibrium with the two pyranose forms (inset).

    26. DFT Study of Fullerene Dimers (pages 2625–2632)

      Angela Bihlmeier, Claire C. M. Samson and Wim Klopper

      Article first published online: 14 NOV 2005 | DOI: 10.1002/cphc.200500285

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      Dimers of fullerenes C50to C58: The possibility of polymer formation via [2+2] reactions is investigated for the fullerenes Cn (n=50, 52, 54, 56, 58, 60) in their most stable configuration by density functional theory. The reactive sites that lead to the most stable dimers are identified; further reactions at these sites may yield fullerene oligomers. C50 has five reactive sites, and a hexamer with D5h symmetry (see figure) is obtained if these sites form bonds.

    27. Insights into the Role of the Liquid–Liquid Interface in Biphasic Reactions: The Reaction of Vitamin B12s(aq) with Vicinal Dibromides(oil) (pages 2633–2639)

      Trevor J. Davies, A. Christopher Garner, Stephen G. Davies and Richard G. Compton

      Article first published online: 31 OCT 2005 | DOI: 10.1002/cphc.200500372

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      An active interface! What role, if any, does the liquid–liquid interface play in biphasic reactions? The authors investigate the role of the liquid–liquid interface in the reaction between vitamin B12s and vicinal dibromides using a combination of cyclic voltammetry with electrosynthesis. They find evidence for restricted bond rotation at the liquid–liquid interface.

    28. Comparison of Stochastic Optimization Methods for All-Atom Folding of the Trp-Cage Protein (pages 2640–2646)

      Alexander Schug, Thomas Herges, Abhinav Verma, Kyu Hwan Lee and Wolfgang Wenzel

      Article first published online: 6 DEC 2005 | DOI: 10.1002/cphc.200500213

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      A protein is folded with the stochastic tunneling method, a modified parallel tempering method, and the basin-hopping technique. The picture shows an overlay of the native and folded structures of the 20 amino acid trp-cage protein. All three methods correctly predict the native conformation, and their relative efficiency is discussed.

    29. Patterns with High Rhythmicity Levels in Multicomponent Liesegang Systems (pages 2647–2653)

      Maysam Msharrafieh and Rabih Sultan

      Article first published online: 4 NOV 2005 | DOI: 10.1002/cphc.200500199

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      Band analysis: Liesegang precipitate patterns with a highly periodic structure marked by the succession of group multiplets with an ascending number of bands (from singlets to doublets to triplets to quadruplets, consistently, see figure) have been observed in the presence of a third cation (Mg2+) added to Co2+ and Ni2+ as the latter are precipitated by NH4OH diffusing into the gel solutions. Concentration and diffusive (space/time) bifurcations (the latter at high [Mg2+]0) have been obtained.

    30. You have free access to this content
      Preview: ChemPhysChem 12/2005 (page 2660)

      Article first published online: 6 DEC 2005 | DOI: 10.1002/cphc.200590031

    31. Author Index (ChemPhysChem 2005) (pages 2663–2679)

      Article first published online: 6 DEC 2005 | DOI: 10.1002/cphc.200590032

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