ChemPhysChem

Cover image for ChemPhysChem

November 14, 2003

Volume 4, Issue 11

Pages 1141–1270

    1. Cover Picture: QM/MM Car-Parrinello Molecular Dynamics Study of the Solvent Effects on the Ground State and on the First Excited Singlet State of Acetone in Water (ChemPhysChem 11/2003) (page 1141)

      Ute F. Röhrig, Irmgard Frank, Jürg Hutter, Alessandro Laio, Joost VandeVondele and Ursula Rothlisberger

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200390112

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    3. Aligned Nanotubes (pages 1150–1169)

      Liming Dai, Ajeeta Patil, Xiaoyi Gong, Zhixin Guo, Luqi Liu, Yong Liu and Daoben Zhu

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200300770

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      State-of-the-nanoart: For many applications involving nanotubes, they often need to be aligned and/or patterned at micro-/nanoscales (see graphic). Judicious application of various micro-/nanofabrication techniques has led to the development of many sophisticated structures of aligned nanotubes of practical significance. This review provides a status summary of recent progress in the synthesis and micro-/nanofabrication of aligned carbon and noncarbon nanotubes.

    4. Nanotubes à la Carte: Wetting of Porous Templates (pages 1171–1176)

      Martin Steinhart, Joachim H. Wendorff and Ralf B. Wehrspohn

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200300733

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      Any polymeric liquid can be formed into nanotubes? It can! The wetting of porous templates by polymeric melts or solutions is a powerful approach for fabricating and customizing nanotubes (see picture). It extends the range of processable materials, for example, to high-performance polymers or multicomponent mixtures. Coupling this process with controlled phase transitions allows the generation of specific morphologies within the nanotube walls.

    5. QM/MM Car-Parrinello Molecular Dynamics Study of the Solvent Effects on the Ground State and on the First Excited Singlet State of Acetone in Water (pages 1177–1182)

      Ute F. Röhrig, Irmgard Frank, Jürg Hutter, Alessandro Laio, Joost VandeVondele and Ursula Rothlisberger

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200300650

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      Exciting acetone: The graphic shows a detail of the simulation cell of one acetone molecule solvated in water. The authors calculate the absorption and fluorescence spectra of acetone with a hybrid Car–Parrinello quantum mechanical/molecular mechanical approach and compare the results to the calculated gas-phase spectra and experimental data.

    6. Topological and Electron-Transfer Properties of Yeast Cytochrome c Adsorbed on Bare Gold Electrodes (pages 1183–1188)

      Beatrice Bonanni, Dario Alliata, Anna Rita Bizzarri and Salvatore Cannistraro

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200300784

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      Yeast cytochrome c on gold: Almost complete coverage with yeast cytochrome c was attained by self-chemisorption on bare gold electrodes through the free sulfur-containing group Cys102 (see picture). A combination of in situ atomic force microscopy and scanning tunnelling microscopy revealed single molecules firmly bound to gold, with retention of their morphological characteristics. Cyclic voltammetry indicated that the electrode surface is functionalised with electroactive protein molecules, with a redox midpoint potential in good agreement with the formal potential.

    7. A Combined Atomic Force Microscopy and Molecular Dynamics Simulation Study on a Plastocyanin Mutant Chemisorbed on a Gold Surface (pages 1189–1195)

      Anna Rita Bizzarri, Beatrice Bonanni, Giulio Costantini and Salvatore Cannistraro

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200300792

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      Protein dynamics on gold: A mutant of copper plastocyanin, covalently bound to an Au(111) surface through an engineered disulfide bridge (see picture), has been investigated in aqueous medium by atomic force microscopy (AFM) and, for the first time, by molecular dynamics (MD) simulations. The combined approach involving the two techniques offers new possibilities for deeper understanding of the dynamics and morphology of chemisorbed proteins.

    8. A High-speed Atomic Force Microscope for Studying Biological Macromolecules in Action (pages 1196–1202)

      Toshio Ando, Noriyuki Kodera, Yasuyuki Naito, Tatsuya Kinoshita, Ken'ya Furuta and Yoko Y. Toyoshima

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200300795

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      Molecular movements movie. The nanometer-scale dynamic movement of individual myosin V molecules (see picture) was captured in real time by a high-speed atomic force microscope (AFM). The AFM was designed to include a number of optimized components including feedback manipulation, high scanner bandwidths and stability, Q-control, and small cantilevers.

    9. Magneto-Optical Studies of HgTe/HgxCd1−xTe(S) Core–Shell Nanocrystals (pages 1203–1210)

      Leonid Fradkin, Lidia Langof, Efrat Lifshitz, Andrey Rogach, Nikolai Gaponik, Horst Weller and Alex Eychmüller

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200300809

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      Caps have merit: The authors describe the synthesis and magneto-optical characterization of HgTe nanocrystals covered with alloyed shells, shown schematically in the picture. These shells have the following merits: 1) Adjustment of the shell potential barrier by variation of the shell chemical composition and thickness; 2) adaptation of core–shell crystal match by the variation of the shell chemical composition.

    10. Electrochemical Probing of Photochemical Reactions Inside Femtolitre Droplets Confined to Electrodes (pages 1211–1215)

      Jay D. Wadhawan, Andrew J. Wain and Richard G. Compton

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200300845

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      Lights on, power on: Photoelectrochemical studies have been performed on femtolitre-volume droplets of redox-active, photosensitive compounds immobilised on an electrode substrate (see graphic). Two chemical systems demonstrate potentials in synthetic and analytical or in photosynthetic applications, that is, in the development of solar cells based on photosynthesis.

    11. Radical Ions from 3,3′′′,3′′′″-Tris(butylsulfanyl)-2,2′:5′,2″:5″,2′′′,5′′′,2′′′′:5′′′′,2′′′″-sexithiophene: An Experimental and Theoretical Study of the p- and n-Doped Oligomer (pages 1216–1225)

      Angelo Alberti, Barbara Ballarin, Maurizio Guerra, Dante Macciantelli, Adele Mucci, Francesca Parenti, Luisa Schenetti, Renato Seeber and Chiara Zanardi

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200300888

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      A chameleonic oligomer: Spectroscopic (NMR, EPR, UV/Vis-NIR), electrochemical, spectroelectrochemical and theoretical (DFT) studies show that the sexithiophene 1 (see picture), though not blocked in the terminal α positions, can exist in at least five different oxidation states, that is, a neutral species, a radical cation, a dication, a radical anion and a dianion.

    12. Optimal Spectrum Estimation in Statistical Mechanics (pages 1227–1230)

      Ralph A. Wheeler and Haitao Dong

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200300750

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      Better than a Fourier transform? More accurate and more flexible, principal component analysis is introduced as an alternative to Fourier transforming correlation functions to calculate condensed-phase spectra (see picture). Analytical proof and numerical tests illustrate the potential of principal mode analysis for calculating optimal vibrational spectra from quantum-mechanical/molecular-mechanical trajectories. In principal, the method is also appropriate for calculating other spectra and for analyzing Monte Carlo simulations or experimental data.

    13. Organization of Water Layers at Hydrophilic Interfaces (pages 1231–1233)

      Marc C. Gurau, Gibum Kim, Soon-Mi Lim, Fernando Albertorio, Helen C. Fleisher and Paul S. Cremer

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200300838

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      Difference in the vibes! The effect of divalent metal-cation absorption on the structure of water at aqueous interfaces was explored in the presence of deprotonated fatty acid monolayers. Vibrational spectra were obtained from charged monolayers in the presence of Zn2+ and Mg2+ ions using vibrational sum frequency spectroscopy (see graphic). The differing modes of coordination by the two cations to the carboxylate headgroups led to significantly different water structures at the interfaces.

    14. Additivity Effects in the Reactivities of Bimetallic Cluster Ions PtmAun+ (pages 1233–1237)

      Konrad Koszinowski, Detlef Schröder and Helmut Schwarz

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200300840

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      All that glitters…The gas-phase reactions of the bimetallic cluster ions PtmAun+ (m+n≤4) with dioxygen and methane are investigated. The platinum-rich cluster ions undergo degradation processes and dehydrogenation reactions, which are also known for pure Ptm+ clusters. In contrast, the gold-rich cluster ions are found to be unreactive, similar to the corresponding Aum+ clusters. This distinct trend in reactivity (see graphic) is correlated with the systems' electronic properties changing as a function of cluster composition.

    15. Electronic and Geometrical Structures of Cyclopropanes: Linear Correlation of Ionization Energies with C[BOND]C Bond Lengths in Monosubstituted Cyclopropanes (pages 1237–1240)

      Paul Rademacher

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200300841

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      A DFT study of monosubstituted cyclopropanes: For substituted cyclopropanes a linear relationship applies for the difference of the ionization potentials related to the Walsh orbitals ωS and ωA (see picture), and the difference between the vicinal and distal C[BOND]C bond lengths. The data of some substituents do not fit this simple correlation and probably require a more extended treatment.

    16. Direct Voltammetric Evidence for a Reducing Agent Generated from the Electrochemical Oxidation of Tripropylamine for Electrochemiluminescence of Ruthenium Tris(bipyridine) Complexes? (pages 1241–1243)

      Ming Zhou, Jürgen Heinze, Kai Borgwarth and Chander P. Grover

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200300875

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      Electrochemical lighting? A redox-active substance was found to be a product of the electrochemical oxidation of tripropylamine (see picture). With regard to the strong reducing ability of the reduced form of the substance, the chemical nature of the species is discussed with respect to the tripropylamine free radical, which is believed to participate in the formation of the luminescent excited state of [Ru(bpy)3]2+ in both acetonitrile and aqueous solutions. The findings may help understand the complicated anodic oxidation mechanism of trialkylamines, which is crucial to the generation of electrochemiluminescence of [Ru(bpy)3]2+.

    17. Time-Resolved Second Harmonic Generation Near-Field Scanning Optical Microscopy (pages 1243–1247)

      Richard D. Schaller, Justin C. Johnson and Richard J. Saykally

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200300907

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      Time and space—with high resolution: Time-resolved second harmonic generation (TRSHG) signals produced via photoexcitation of carriers in ZnSe exhibit different relaxation rates depending upon carrier proximity to an interface; these rates can be controlled via one- versus two-photon excitation. When combined with near-field scanning optical microscopy (NSOM; see graphic), which can provide <100 nm spatial resolution, TRSHG measurements show carrier relaxation rates that are more typical of relaxation in proximity to an interface, owing to the shallow depth of field that is characteristic of NSOM measurements.

    18. Low Temperature Conductance Measurements of Self-Assembled Monolayers of 1,4-Phenylene Diisocyanide (pages 1247–1252)

      Christian J.-F. Dupraz, Udo Beierlein and Jörg P. Kotthaus

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200300706

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      A monolayer sandwich. Electron-transport measurements were carried out in self-assembled monolayers of 1,4-phenylene diisocyanide using two different approaches; in one of the approaches, a single monolayer was sandwiched between two small gold contacts by use of nanolithographical and evaporation techniques (see picture). Conductance measurements at low temperature show discrete structures for both types of samples which are interpreted as arising from quantum transport through molecular ensembles.

    19. Conductance Properties of Stilbenoid Molecules (pages 1252–1256)

      Rafael Gutiérrez, Frank Grossmann and Rüdiger Schmidt

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200300768

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      Electronic transport on the molecular scale is a rapidly developing field. Carbon-based molecular devices are a special class with many potential applications. The graphic shows schematically a stilbene molecule connected via polyene chains of variable length to carbon nanotubes which act as electrodes. Electron transport through this system is theoretically investigated by combining a density-functional based approach with the Landauer formalism.

    20. Theoretical Measurements of Conductance in an (AT)12 DNA Molecule (pages 1256–1260)

      Tomofumi Tada, Masakazu Kondo and Kazunari Yoshizawa

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200300811

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      Electrical conduction through a DNA molecule is significantly dependent on the mode of connection with metallic leads (see picture). A variation of conductance of seven orders of magnitude is found with the Landauer formulation in an (AT)12 DNA molecule. The DNA molecule behaves as a semiconductor when bases are connected to the gold lead, whereas it is insulating when nucleic acids are connected.

    21. Stationary Small and Large Amplitude Patterns during Bulk CO Electrooxidation on Platinum (pages 1260–1263)

      Antoine Bonnefont, Hamilton Varela and Katharina Krischer

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200300874

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      Reaction patterns at electrode surfaces: In low-conducting electrolytes the electrochemical oxidation of CO on Pt electrodes spontaneously forms stationary potential and adsorbate patterns in space. The figure shows such a potential pattern on a ring-shaped (quasi one-dimensional) electrode.

    22. Preview: ChemPhysChem 11/2003 (page 1270)

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/cphc.200390118

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