ChemPhysChem

Cover image for Vol. 5 Issue 10

October 18, 2004

Volume 5, Issue 10

Pages 1457–1634

    1. Cover Picture: In-Situ Observation of Nanowire Growth from Luminescent CdTe Nanocrystals in a Phosphate Buffer Solution (ChemPhysChem 10/2004) (page 1457)

      Yuri Volkov, Siobhan Mitchell, Nikolai Gaponik, Yurii P. Rakovich, John F. Donegan, Dermot Kelleher and Andrey L. Rogach

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200490051

      The cover picture shows a three-dimensional confocal image of luminescent nanowires self-assembled from CdTe nanocrystals of different sizes and, thus, different emission colors in a standard physiological phosphate-buffered solution. The formation of nanowires was followed in situ, as described in the Communication by Rogach et al. on page 1600.

    2. Graphical Abstract: ChemPhysChem 10/2004 (pages 1459–1466)

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200490052

    3. Molecule-to-Metal Bonds: Electrografting Polymers on Conducting Surfaces (pages 1468–1481)

      Serge Palacin, Christophe Bureau, Julienne Charlier, Guy Deniau, Brigitte Mouanda and Pascal Viel

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200301202

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      No hard graft: Electrografting allows the easy formation of thin polymer films that are covalently bound to an electrode. This Review discusses the mechanism of formation of grafted polymer films and the major applications of this technique. The grafting can also be localized on doped semiconducting surfaces (see micrograph).

    4. Nanotechnology and Single Molecules (pages 1483–1487)

      Christian Eggeling

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400290

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      Single molecules on the move: The fourth international symposium on physics, chemistry and biology with single molecules in Staffelstein, Germany, witnessed many new insights and plans for the future developments of this research field. All kinds of experimental techniques such as scanning tunnelling, atomic force, or optical microscopy are involved. The immense progress in the field of nanotechnology opens up ways for the realization of “nanovisions” such as working nanomotors and molecular optoelectronic devices and circuits (for example, see picture).

    5. Pulsed-Laser Production and Detection of Spin-Polarized Hydrogen Atoms (pages 1489–1494)

      T. Peter Rakitzis*

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400108

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      Photodissociation of HCl: Spin-polarized hydrogen is produced from the pulsed-laser photolysis of HCl using circularly polarized light (see picture). A fluorescence scheme for measuring the hydrogen atom polarization is presented. Together, the pulsed-laser production and detection steps allow to study spin-polarized hydrogen in the nanosecond timescale, which is orders of magnitude faster than that achievable with existing methods.

    6. Protonated Water Clusters: The Third Dimension (pages 1495–1497)

      Ralf Ludwig

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400323

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      Searching in the third dimension. Large protonated water clusters turned out to be cage structures similar to those found in gas hydrates (see graphic). Size-selected water clusters could be probed by infrared spectroscopy. The assignment is supported by quantum mechanical calculations.

    7. The Jahn–Teller Effect of the TiIII Ion in Aqueous Solution: Extended Ab Initio QM/MM Molecular Dynamics Simulations (pages 1499–1506)

      Chinapong Kritayakornupong, Kristof Plankensteiner and Bernd M. Rode

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400019

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      High-speed dynamics: TiIII in aqueous solution displays a very fast dynamical Jahn–Teller effect, which has been observed for the first time by using the new hybrid QM/MM-MD method that combines quantum mechanical calculations with molecular mechanics. Several distorted configurations are assumed by the hexaquo complex on the sub-picosecond scale. The picture shows a snapshot of a configuration with three ligands at elongated “axial” (yellow) positions.

    8. Two-Photon Dissociation Spectroscopy of State-Selected HCl+ and DCl+ Ions (pages 1507–1512)

      Michael Michel and Karl-Michael Weitzel

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400140

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      State-selective spectroscopy: The current work demonstrates that spectra of ions (see picture) are significantly simplified if the formation of ions by resonance-enhanced multiphoton ionization (REMPI) is combined with state-selective fragmentation spectroscopy. The experiments prove that ions are selectively formed, with a narrow quantum-state distribution, by the REMPI process.

    9. Accurate pKa Determination for a Heterogeneous Group of Organic Molecules (pages 1513–1522)

      Marcel Schmidt am Busch and Ernst-Walter Knapp

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400171

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      Protonation in two steps: The authors show that a combination of quantum mechanical density functional vacuum calculations and solution of the Poisson equation reproduces the energetics of gas-phase and solution-phase protonation reactions quantitatively for 26 different organic compounds, over the spectrum of substance classes depicted in the graphic.

    10. Photon Counting Histogram: One-Photon Excitation (pages 1523–1531)

      Bo Huang, Thomas D. Perroud and Richard N. Zare

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400176

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      Few-molecule spectroscopy: The three-dimensional Gaussian approximation for the confocal observation volume profile is found to be invalid in the photon counting histogram (PCH) analysis for one-photon excitation. A semiempirical approach is introduced to correct this deviation (see picture).

    11. Determination of the Heterogeneous Association Constants of Metal Ions to ω-Mercaptoalkanoic Acids by Using Double-Layer Capacity Measurements (pages 1532–1539)

      Doron Burshtain and Daniel Mandler

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400232

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      Interfacial interactions: The heterogeneous association constant of CdII ions by a self-assembled monolayer was determined by means of double-layer capacity measurements to be much higher than that obtained in homogeneous solutions. The observed difference may be due to a reduced degree of freedom of the ligand and due to a higher charge density at the monolayer–electrolyte interface. The picture is a representation of the monolayer on a gold electrode.

    12. Gaseous Ion Activation Dynamics: The Role of the Bulk Gas in the Racemization of Chiral Oxonium Ions (pages 1540–1546)

      Antonello Filippi and Maurizio Speranza

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400249

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      The dynamics of the inversion of configuration of a family of chiral oxonium ions in gaseous CH3X (X=F,Cl) media was found to be determined by the activation dynamics, which, in turn, depend on the specific vibrational coupling between the normal modes of the transient ion–dipole complexes formed between the chiral oxonium ions and a CH3X molecule (see picture).

    13. Revision of the Dissociation Energies of Mercury Chalcogenides—Unusual Types of Mercury Bonding (pages 1547–1557)

      Michael Filatov and Dieter Cremer

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200301207

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      Mercury chalcogenides HgE (E=O, S, Se) are described to possess rather stable bonds, which is actually difficult to understand in view of the closed-shell electron configuration of the Hg atom in its ground state. Based on ab initio calculations, it is shown that the covalent HgE bond is rather weak, that the ground state of HgE is a triplet rather than a singlet state, and that the experimental bond dissociation energies have been obtained for dimers Hg2E2 (see picture) rather than for true monomers.

    14. Azulene-to-Naphthalene Rearrangement: The Car–Parrinello Metadynamics Method Explores Various Reaction Mechanisms (pages 1558–1568)

      András Stirling, Marcella Iannuzzi, Alessandro Laio and Michele Parrinello

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400063

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      Exploring pathways: The authors present a novel method for examining five possible routes in the rearrangement of azulene to naphthalene (see graphic).

    15. On the Quantum Nature of an Excess Proton in Liquid Hydrogen Fluoride (pages 1569–1576)

      Simone Raugei and Michael L. Klein

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400198

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      Quantum delocalization of charge defects: The role of the excess protons in liquid HF, key to liquid superacid chemistry, has been probed with path integral density functional theory (DFT) based molecular dynamics. Not only does the charge defect strongly perturb the HF chain, but it has also been shown to be delocalized over several HF molecules (see graphic).

    16. Experimental and Theoretical Study of the Photophysics and Structures of Europium Cryptates Incorporating 3,3′-Bi-isoquinoline-2,2′-dioxide (pages 1577–1584)

      Paula Gawryszewska, Oscar L. Malta, Ricardo L. Longo, Fabiana R. Goncalves e Silva, Severino Alves Jr., Krzysztof Mierzwicki, Zbigniew Latajka, Marek Pietraszkiewicz and Janina Legendziewicz

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400036

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      A glowing success: The authors present a detailed experimental and theoretical photophysical study of [Eu⊂(biqO2.2.2)(CF3SO3)](CF3SO3)2⋅CH3CN⋅H2O (Eu⊂1) and two other types of cryptates incorporating three 3,3′-bi-isoquinoline-2,2′-dioxide units. The effect of the different cryptate structures on the emission spectra under different conditions is investigated (see graphic for an energy-level diagram of the different processes).

    17. Visual Observation of Contact-Induced Intercrystalline Migration of Aromatic Species Adsorbed in Zeolites by Fluorescence Microscopy (pages 1585–1591)

      Shuichi Hashimoto and Shinji Yamashita

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400167

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      Mapping migrating molecules: Aromatic molecules were observed by fluorescence microscopy to migrate over time (see picture) between two sets of zeolite crystals.

    18. Monolayers of Zeolite A Containing Luminescent Silver Sulfide Clusters (pages 1593–1596)

      Claudia Leiggener and Gion Calzaferri

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400355

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      Clustered crystals: The authors demonstrate formation of stable zeolite A monolayers on quartz and subsequent “ship-in-a-bottle” synthesis of luminescent silver sulfide clusters. The pictures show the zeolite crystals at various stages of this process.

    19. Diffusion in Protein Crystals—A Computer Simulation (pages 1596–1599)

      Kourosh Malek, Theo Odijk and Marc-Olivier Coppens

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400116

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      Nanoporous protein crystals: Long-time Brownian dynamics simulations provide first insights into electrostatic and steric confinement effects on the mobility of probes in protein crystals. A transition is shown between the dominance of electrostatic effects for small ions and steric confinement for larger ions. The picture shows part of the trajectory of a charged probe through a pore of a lysozyme molecule.

    20. In-Situ Observation of Nanowire Growth from Luminescent CdTe Nanocrystals in a Phosphate Buffer Solution (pages 1600–1602)

      Yuri Volkov, Siobhan Mitchell, Nikolai Gaponik, Yurii P. Rakovich, John F. Donegan, Dermot Kelleher and Andrey L. Rogach

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400330

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      Watching nanowires grow! Self-organization of CdTe nanocrystals into luminescent nanowires (see picture) takes place in a standard physiological phosphate-buffered solution and is completed in several hours, as demonstrated in situ by means of confocal microscopy. Luminescence and Raman spectroscopy data evidence the occurrence of recrystallization processes during the nanowire formation.

    21. Double-System-Size Resonance for Spiking Activity of Coupled Hodgkin–Huxley Neurons (pages 1602–1605)

      Maosheng Wang, Zhonghuai Hou and Houwen Xin

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400255

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      A brainy idea! The collective spiking behavior of a 1D chain of linearly coupled neurons was investigated. As shown in the Figure, the coefficient of variance of the spike train reaches a clear minimum when both the membrane patch size and the number of neurons have optimal values. Such findings might have important applications for information processing in real neural networks.

    22. Anisotropic Translational Diffusion of Single Fluorescent Perylene Molecules in a Nematic Liquid Crystal (pages 1606–1609)

      Tsuyoshi Kawai, Sunao Yoshihara, Yasuhide Iwata, Tuyoshi Fukaminato and Masahiro Irie

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400072

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      A moving story: Translational diffusion (see graphic) of a fluorescent molecule in a nematic liquid crystal was studied with single-molecule fluorescence autocorrelation spectroscopy for the first time. Unique anisotropy in the translational diffusion dynamics was clearly demonstrated at the single-molecule level.

    23. Size-Dependent Spectroscopic Properties and Thermochromic Behavior in Poly(substituted thiophene) Nanoparticles (pages 1609–1615)

      Naonori Kurokawa, Hiroyuki Yoshikawa, Nobuaki Hirota, Kenji Hyodo and Hiroshi Masuhara

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400117

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      Nanoparticles are attractive nanomaterials, since they exhibit unique physical and chemical properties. We have found that poly(substituted thiophene) nanoparticles, ranging in size from several tens to hundreds of nanometers, exhibit size-dependent characteristic spectroscopic properties and thermochromic behavior, which can be explained by distorted polymer conformations in the surface layer (see graphic).

    24. Low-Pressure Organometallic Chemical Vapor Deposition of Indium Nitride on Titanium Dioxide Nanoparticles (pages 1615–1618)

      Jeng-Han Wang and M. C. Lin

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400137

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      Saving for a sunny day: The first thin-film deposition and UV/Vis absorption spectrum of InN-coated TiO2 nanoparticle films is reported. A broad absorption band, which appears in the ≈390–800 nm range (see spectrum) indicates an attractive possibility for solar energy-conversion applications.

    25. A New Cubic Phase Containing DNA and a Surfactant (pages 1619–1623)

      Daragh McLoughlin, Marianne Impéror-Clerc and Dominique Langevin

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400163

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      Encapsulating DNA: A new cubic phase that contains both DNA and a cationic surfactant was discovered. The authors propose a cubic arrangement of surfactant micelles with DNA rods intercalated between several cells (see picture). The results presented here may be important for the development of efficient delivery vectors for genetic material.

    26. Intramolecular Electrostatics: Coulomb's Law at Sub-Nanometers (pages 1623–1629)

      Shan Jin, Dihua Wang, Xianbo Jin and George Z. Chen

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200400234

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      Intramolecular interactions: Two new series of alkyl-linked ferrocene benzoaza[15]crown-5 host molecules have been investigated by means of voltammetric techniques in the absence and presence of HPF6, LiClO4, NaClO4, KPF6, Mg(ClO4)2, or Ba(ClO4)2 in acetonitrile (see picture). Cation binding-induced mean-potential shifts, ΔE1/2, were observed for all ligands, and were found to vary linearly with the reciprocal of the sub-nanometer distance, l, between the centers of the bound cation and ferrocene.

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      Preview: ChemPhysChem 10/2004 (page 1634)

      Article first published online: 14 OCT 2004 | DOI: 10.1002/cphc.200490053

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