Cover image for ChemPhysChem

October 17, 2003

Volume 4, Issue 10

Pages 1033–1138

    1. Cover Picture: Experimental Detection of the H2NO3 Radical (ChemPhysChem 10/2003) (page 1033)

      Fulvio Cacace, Giulia de Petris and Anna Troiani

      Version of Record online: 7 OCT 2003 | DOI: 10.1002/cphc.200390107

    2. Oxygen Vacancy: The Invisible Agent on Oxide Surfaces (pages 1041–1047)

      Gianfranco Pacchioni

      Version of Record online: 7 OCT 2003 | DOI: 10.1002/cphc.200300835

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      Pretty vacant. Oxide surfaces are continuously finding new applications in advanced technologies such as corrosion protection, thermal coating, catalysis, sensors, microelectronics, magnetic properties, etc. A understanding of the microscopic properties of oxide surfaces is closely related to the identification of the surface defects. Oxygen vacancies (see bright spots in picture) are particularly important defects but also very difficult to characterize. Recent advances in the use of STM allows one to follow the dynamics of the migration of oxygen vacancies on an oxide surface. Starting from a recent example of application of dynamic STM to TiO2, the role of oxygen vacancies on the chemistry of oxide surfaces is highlighted.

    3. Structural Forces near Phase Transitions of Liquid Crystals (pages 1049–1056)

      Klemen Kočevar and Igor Muševič

      Version of Record online: 7 OCT 2003 | DOI: 10.1002/cphc.200300787

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      Don't be phased! Structural forces of liquid crystals have been measured at temperatures close to their phase transitions, until now a difficult feat. This achievement is thanks to a new type of extremely sensitive AFM experiment developed by the authors. A molecular layer of these liquid crystal molecules, adsorbed on a glass/surfactant surface (see picture), was studied in this way.

    4. Electric-Field-Induced Capillary Attraction between Like-Charged Particles at Liquid Interfaces (pages 1057–1058)

      Dominique Langevin

      Version of Record online: 7 OCT 2003 | DOI: 10.1002/cphc.200300722

      Birds of a feather, flock together. In a recent paper in Nature, Nikolaides and co-workers discuss the much debated issue of capillary attraction between like-charged particles at liquid interfaces. They show quite convincingly that dipolar electric fields induce surface charges that distort the interface; the dipolar interaction causes repulsion, while the interfacial distortion causes capillary attraction. The behaviour observed has broad implications for interfacial and colloid chemistry, when charged particles are present at fluid interfaces.

    5. Locating Dynamic Species with X-ray Crystallography and NMR Spectroscopy: Acetone in p-tert-Butylcalix[4]arene (pages 1059–1064)

      Konstantin A. Udachin, Gary D. Enright, Christopher I. Ratcliffe and John A. Ripmeester

      Version of Record online: 7 OCT 2003 | DOI: 10.1002/cphc.200300710

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      Filling cavities with acetone: Because of extensive dynamic disorder, X-ray crystallography and solid-state NMR spectroscopy must be used together to show that the carbonyl group in the acetone–p-tert-butylcalix[4]arene compound is excluded from the calixarene cavity (see figure).

    6. Micelle and Solvent Relaxation in Aqueous Sodium Dodecylsulfate Solutions (pages 1065–1072)

      Patrick Fernandez, Simon Schrödle, Richard Buchner and Werner Kunz

      Version of Record online: 7 OCT 2003 | DOI: 10.1002/cphc.200300725

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      Relaxing bubble bath: The hydration of micelles as well as the dynamics of bound counterions is still difficult to investigate and many open questions remain. This contribution shows that precise dielectric relaxation measurements, which simultaneously detect contributions specific to the micelles and to the solvent (see figure), yield reliable information on both topics that directly complements results obtained with other techniques.

    7. Anchoring Fe Ions to Amorphous and Crystalline Oxides: A Means To Tune the Degree of Fe Coordination (pages 1073–1078)

      Gloria Berlier, Francesca Bonino, Adriano Zecchina, Silvia Bordiga and Carlo Lamberti

      Version of Record online: 7 OCT 2003 | DOI: 10.1002/cphc.200300769

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      Tunable coordinative unsaturation: In situ IR spectroscopy (see picture; IR spectra of NO dosed at room temperature for PNO decreasing from 15 Torr (••••) to 10−3 Torr (- - - -) on Fe/SiO2 activated at 773 K) was used to identify the different [Fe2+(NO)n] (n=1, 2, 3) complexes formed by NO adsorption on Fe hosted at the surface of different inorganic oxidic supports. It was shown that, depending on the nature of the support and on the activation temperature, the degree of Fe coordination can be tuned. These observations could be a useful guideline for understanding the effect of the support and conditions on the catalytic activity of Fe-MFI zeolite catalysts in selective oxidation reactions.

    8. Excited-State Proton-Relay Dynamics of 7-Hydroxyquinoline Embedded in a Solid Matrix of Poly(2-hydroxyethyl methacrylate) (pages 1079–1083)

      Oh-Hoon Kwon, Hyungie Doo, Young-Shin Lee and Du-Jeon Jang

      Version of Record online: 7 OCT 2003 | DOI: 10.1002/cphc.200300779

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      Proton transfer in polymer matrices: Excited 7-hydroxyquinoline embedded in a solid matrix of poly(2-hydroxyethyl methacrylate) undergoes efficient proton relay to form its keto tautomer with a mechanism that depends on the torsional conformation and microscopic environment of the molecule at the moment of excitation. Thus, the bridged cis form undergoes immediate proton transfer, the unbridged cis form must first be bridged by the alcoholic side groups of the polymer, and the trans form must undergo torsional transformation to give the cis form (see picture).

    9. A Theoretical Study of the UV/Visible Absorption and Emission Solvatochromic Properties of Solvent-Sensitive Dyes (pages 1084–1094)

      Wen-Ge Han, Tiqing Liu, Fahmi Himo, Alexei Toutchkine, Donald Bashford, Klaus M. Hahn and Louis Noodleman

      Version of Record online: 7 OCT 2003 | DOI: 10.1002/cphc.200300801

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      Light thrown on dyes: Using their currently established density-functional vertical self-consistent reaction field (VSCRF) solvation model, incorporating the conductor-like screening model (COSMO) and the self-consistent reaction field (SCRF) methods, the authors have studied the solvatochromic shifts of both the absorption and emission bands of four solvent-sensitive dyes: S-TBA merocyanine, Abdel-Halim's merocyanine, the rigidified aminocoumarin C153, and Nile red (see picture). All trends of the blue or red shifts were correctly predicted compared to the experimental observations.

    10. Nanoscopic Structure of a Metallo-supramolecular Polyelectrolyte–Amphiphile Complex, Elucidated by X-ray Scattering and Molecular Modeling (pages 1095–1100)

      Annette Meister, Günter Förster, Andreas F. Thünemann and Dirk G. Kurth

      Version of Record online: 7 OCT 2003 | DOI: 10.1002/cphc.200300702

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      Supramolecular sandwich. A mesophase with a hierarchical architecture consisting of alternating strata of interdigitated amphiphiles and metallo-supramolecular rods (see schematic picture) is formed by self-assembly of FeII ions, a bis-terpyridine, and an amphiphile. The final structure of this semiordered material was obtained by an iterative modeling procedure starting from the approximate structure derived from X-ray scattering data.

    11. Photoinduced Reduction of Silver inside Microscale Polyelectrolyte Capsules (pages 1101–1103)

      Dmitry G. Shchukin, Igor L. Radtchenko and Gleb B. Sukhorukov

      Version of Record online: 7 OCT 2003 | DOI: 10.1002/cphc.200300740

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      Every cloud has a silver lining. The use of poly(styrene sulfonate)/poly(allylamine hydrochloride) (PSS/PAH) polyelectrolyte capsules as microreactors is described for the photochemical synthesis of nanosized silver particles, exclusively, inside a restricted volume of capsule (see graphic). The formed Ag nanoparticles are not aggregated and have an average diameter of 8 nm. The resulting Ag-filled polyelectrolyte capsules can find applications as catalytic microreactors and medical agents.

    12. Silicon-on-Insulator Based Thin-Film Resistor for Chemical and Biological Sensor Applications (pages 1104–1106)

      Michael G. Nikolaides, Stephan Rauschenbach, Sebastian Luber, Karin Buchholz, Marc Tornow, Gerhard Abstreiter and Andreas R. Bausch

      Version of Record online: 7 OCT 2003 | DOI: 10.1002/cphc.200300785

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      Low lysine levels: The authors present a device (see picture) based on silicon-on-insulator (SOI) substrates that enables the detection of poly-L-lysine at concentrations of only 1 nM (80 ng mL−1).

    13. Influence of Molecular Arrangement in Self-Assembled Monolayers on Adhesion Forces Measured by Chemical Force Microscopy (pages 1107–1111)

      Anne-Sophie Duwez, Ulrich Jonas and Hubert Klein

      Version of Record online: 7 OCT 2003 | DOI: 10.1002/cphc.200300743

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      Is it chemistry or physics? Chemical force microscopy (CFM), which combines atomic force microscopy with chemical sensitivity, was used to discriminate between CH3-terminated monolayers obtained from thiol, chlorosilane, or methoxysilane precursors (see diagram). The authors show that, besides surface chemistry and mechanical properties, other parameters can contribute strongly to the measured adhesion forces in water and thus determine the contrast observed by CFM.

    14. The Case of the Disappearing Monolayer: Alkylsilane Monolayer Formation, Oxidation, and Subsequent Transparency to Scanning Tunneling Microscopy (pages 1111–1114)

      Kevin S. Schneider, Thomas M. Owens, Daniel R. Fosnacht, Bradford G. Orr and Mark M. Banaszak Holl

      Version of Record online: 7 OCT 2003 | DOI: 10.1002/cphc.200300851

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      An invisible monolayer? Oxidation of an octylsilane monolayer (see graphic) chemisorbed onto Au(111) yields two surprising results. The 23×equation image Au surface reconstruction typical of a clean gold surface forms underneath the siloxane monolayer. In addition, the physisorbed alkylsiloxane monolayer is transparent to scanning tunneling microscopy imaging.

    15. Assembling Nanometer Nickel Particles into Ordered Arrays (pages 1114–1117)

      Sheng-Bin Lei, Chen Wang, Shu-Xia Yin, Li-Jun Wan and Chun-Li Bai

      Version of Record online: 7 OCT 2003 | DOI: 10.1002/cphc.200300667

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      Encapsulated nickel nanofibres: Ultrasmall 1-dodecanethiol-capped nickel clusters were synthesized by a modified Schiffrin reaction. The mean outer diameter of the particles is 3.2 nm. X-ray photoelectron spectroscopy and X-ray diffraction results indicate that the core is composed of metallic nickel, not nickel oxide. This monolayer-protected Ni cluster (Ni-MPC) can be assembled along the template of C12SH and alkane lamellae into ordered nanofibers (see figure.)

    16. Functional Polymeric Micelles Formed from a Novel Cationic Star Block Copolymer (pages 1118–1121)

      Ren-Hua Jin

      Version of Record online: 7 OCT 2003 | DOI: 10.1002/cphc.200300823

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      Flowers made from stars: A star polymer, which consists of a porphyrin center to which four arms with cationic poly(ethyleneimine) (PEI) and hydrophobic poly(phenyloxazoline) (PPOZ) segments were attached, was synthesized and shown to form micelles in both aqueous and organic media (see picture). In aqueous media, the star formed a micelle in which a hydrophobic PPOZ core was surrounded by cationic corona PEI. The porphyrin moieties enclosed in the micellar core can effectively communicate with an ionic substrate enriched in the cationic corona. In organic media, the star gave a flowerlike micelle in which the ionomer segment PEI assembled to form a core and the nonionic PPOZ segments formed a looplike corona coating the core.

    17. Photon Counting Histogram for One-Photon Excitation (pages 1121–1123)

      Thomas D. Perroud, Bo Huang, Mark I. Wallace and Richard N. Zare

      Version of Record online: 7 OCT 2003 | DOI: 10.1002/cphc.200300824

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      An advance that counts! A method is presented for analyzing single-molecule behavior using one-photon excitation of fluorescence. It is based on the photon counting histogram (PCH) procedure that has enjoyed much success for two-photon excitation, but has not previously been applied to one-photon excitation. This corrected PCH model is able to resolve fluorescent species with different degrees of brightness, for example, a mixture of tetramethylrhodamine-5′-maleimide and Cy3-maleimide (see graph). Because one-photon excitation is often much easier to do than two-photon excitation, this method has the potential to be widely used and represents an important advance in the field of single-molecule spectroscopy.

    18. Multifrequency Photochromic Recording and Nondestructive Readout using IR Light (pages 1124–1127)

      Kingo Uchida, Masaaki Saito, Akinori Murakami, Shinichiro Nakamura and Masahiro Irie

      Version of Record online: 7 OCT 2003 | DOI: 10.1002/cphc.200300718

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      Light works. The multifrequency recording of an image and the nondestructive readout using IR light on a polymer film containing two photochromic diarylethene derivatives were successively carried out. The image was recorded using two UV light wavelengths, and monitored nondestructively by using IR light at two different wavelengths (1590 cm-1, upper image; 1550 cm-1, lower image). Different images could be read out at the different wavelengths.

    19. Experimental Detection of the H2NO3 Radical (pages 1128–1131)

      Fulvio Cacace, Giulia de Petris and Anna Troiani

      Version of Record online: 7 OCT 2003 | DOI: 10.1002/cphc.200300849

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      It's in the air. The authors detected by neutralization–reionization mass spectrometry the nitrogen hydroxide oxide 3, which is relevant to atmospheric chemistry and a key intermediate in the NO32− reduction, as a gaseous radical species with a lifetime of 1 μs. The charged precursor utilized was the high-energy isomer 2 from the protonation of HNO3, whereas the more stable isomer 1 dissociates upon neutralization.

    20. Preview: ChemPhysChem 10/2003 (page 1138)

      Version of Record online: 7 OCT 2003 | DOI: 10.1002/cphc.200390110