Advanced Materials

Cover image for Advanced Materials

July, 2004

Volume 16, Issue 14

Pages 1143–1230

    1. Electrospinning of Nanofibers: Reinventing the Wheel? (pages 1151–1170)

      D. Li and Y. Xia

      Version of Record online: 2 AUG 2004 | DOI: 10.1002/adma.200400719

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      Current research activities on the electrospinning of nanofibers (see Figure, right) are comprehensively reviewed. After a brief discussion of setups (see Figure, left), the mechanisms and theoretical models for electrospinning are presented, followed by approaches for controlling the diameter, morphology, composition, secondary structure, and spatial alignment. Some potential applications of the remarkable features of electrospun fibers are also highlighted.

    2. Dramatic Enhancements in Toughness of Polyvinylidene Fluoride Nanocomposites via Nanoclay-Directed Crystal Structure and Morphology (pages 1173–1177)

      D. Shah, P. Maiti, E. Gunn, D. F. Schmidt, D. D. Jiang, C. A. Batt and E. P. Giannelis

      Version of Record online: 2 AUG 2004 | DOI: 10.1002/adma.200306355

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      The first instance of a remarkable enhancement in toughness and stiffness of a poly(vinylidene fluoride) nanocomposite compared to the pristine polymer is reported (see Figure). The enhanced toughness is attributed to structural and morphological changes induced by the nanoparticles, as well as their increased mobility compared to micrometer-size fillers, which contributes to a new energy dissipation mechanism during deformation.

    3. Molecular-Level Insulation: An Approach to Controlling Interfacial Charge Transfer (pages 1177–1181)

      S. A. Haque, J. S. Park, M. Srinivasarao and J. R. Durrant

      Version of Record online: 2 AUG 2004 | DOI: 10.1002/adma.200400327

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      A novel approach to the attachment of molecular dyes to nanocrystalline TiO2 electrodes (see Figure) is reported. Cyclodextrin encapsulation of an organic dye is shown to result in strong binding to the metal oxide electrode. The encapsulation furthermore results in a well-defined spatial separation of the organic dye from the electrode surface, allowing the photogeneration of a long-lived charge-separated state.

    4. Inorganic–Biomolecular Hybrid Nanomaterials as a Genetic Molecular Code System (pages 1181–1184)

      J.-H. Choy, J.-M. Oh, M. Park, K.-M. Sohn and J.-W. Kim

      Version of Record online: 2 AUG 2004 | DOI: 10.1002/adma.200400027

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      A molecular-level coding method utilizing DNA base pairs as code units has been systemized. The system consists of four steps: encoding, encrypting, decrypting and decoding (see Figure), which are realized by tailor-made nanohybrids (DNA–layered double hydroxide (LDH) and polypyrrole–maghemite). The nanohybrids give solutions to the inherent problems which hamper DNA molecular code systems; stability in encrypting and rapidity in analysis.

    5. Membrane Photolithography: Direct Micropatterning and Manipulation of Fluid Phospholipid Membranes in the Aqueous Phase Using Deep-UV Light (pages 1184–1189)

      C. K. Yee, M. L. Amweg and A. N. Parikh

      Version of Record online: 29 JUN 2004 | DOI: 10.1002/adma.200306498

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      A wet photolithography approach using light-activated, localized, oxidative chemistry can directly pattern fluid phospholipid bilayers submerged in aqueous phases. Targeted incorporation of secondary components within pattern voids (see Figure) allows many membrane dynamical processes to be probed and optically defined arrays of holes, functional membrane microdomains, and proteins embedded in a lipidic background can be designed.

    6. (Ti,Sn)O2 Solid Solution Self-Aligned into “Sandwich” Array on Grafted Modification Collagen Matrix (pages 1189–1192)

      Y. Cao, Y. M. Zhou, Y. Shan, H. X. Ju, X. J. Xue and Z. H. Wu

      Version of Record online: 2 AUG 2004 | DOI: 10.1002/adma.200400028

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      A versatile self-assembly process for preparing nanoscale “sandwich” layer arrays(see Figure) by incorporating bimetal solid solutions into a biological system is reported. Collagen was used as the biological scaffold, and also to control the growth of various metal nanocrystals in an exact arrangement, using two uniform interactions of both hydrogen bonding and covalent bonding between the biomatrix and the nanocrystals.

    7. Theoretical Characterization and Design of End-Substituted Distyrylbenzenes as Excitation Shuttles in One-Dimensional Channels (pages 1193–1197)

      J. C. Sancho-García, L. Poulsen, J. Gierschner, R. Martínez-Alvárez, E. Hennebicq, M. Hanack, H.-J. Egelhaaf, D. Oelkrug, D. Beljonne, J.-L. Brédas and J. Cornil

      Version of Record online: 2 AUG 2004 | DOI: 10.1002/adma.200400354

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      Quantum-chemical calculations have been performed to characterize the potentiality of recently synthesized end-substituted oligophenylenevinylenes (OPVs) as excitation shuttles and to design more efficient derivatives. The approach provides quantitative estimates of the parameters controlling the exciton transfer rates and strategies to promote directional energy transfer.

    8. Formation of TiO2 and ZrO2 Nanotubes Using Atomic Layer Deposition with Ultraprecise Control of the Wall Thickness (pages 1197–1200)

      H. Shin, D.-K. Jeong, J. Lee, M. M. Sung and J. Kim

      Version of Record online: 5 JUL 2004 | DOI: 10.1002/adma.200306296

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      Nanotubes of TiO2 and ZrO2 (see Figure) with diameters of ca. 30–200 nm have been successfully fabricated by atomic layer deposition in a one-step process utilizing nanoporous membranes (commercial polycarbonate filters) as templates. Sub-angstrom wall thickness control and high aspect ratios can be achieved by this method.

    9. Facile Route to Silver Nanotubes (pages 1200–1203)

      L. Qu, G. Shi, X. Wu and B. Fan

      Version of Record online: 2 AUG 2004 | DOI: 10.1002/adma.200400044

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      Many novel applications of silver become possible if silver nanotubes can be produced reliably and easily. A simple, template-assisted procedure is reported here. The Figure shows a scanning electron microscopy image of one of the silver nanotubes, which was broken by ultrasonic vibration, demonstrating that the nanostructure is indeed a hollow nanotube and showing that the nanotube is formed of (crystalline) nanoparticles.

    10. Colloidal Clusters of Silica or Polymer Microspheres (pages 1204–1208)

      G.-R. Yi, V. N. Manoharan, E. Michel, M. T. Elsesser, S.-M. Yang and D. J. Pine

      Version of Record online: 2 AUG 2004 | DOI: 10.1002/adma.200306638

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      An emulsion encapsulation and shrinkage technique for producing large quantities of colloidally stable clusters of microspheres (see Figure) is demonstrated. In spite of differences in particle properties and interactions, the sequence of cluster packings remains the same for three different systems, suggesting that the sphere-packing process can be successfully applied to a wide range of colloidal materials.

    11. Solvent-Induced Self-Assembly of a Meta-Linked Conjugated Polyelectrolyte. Helix Formation, Guest Intercalation, and Amplified Quenching (pages 1208–1212)

      C. Tan, M. R. Pinto, M. E. Kose, I. Ghiviriga and K. S. Schanze

      Version of Record online: 2 AUG 2004 | DOI: 10.1002/adma.200306711

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      A water-soluble meta-linked poly(phenylene ethynylene) is shown to fold into a helical conformation in water. The helix is stabilized by solvophobic forces and π-stacking interactions. The metallo-intercalator complex Ru(dppz)(phen)22+ binds to the helical polymer via intercalation and the complex is highly luminescent when it is bound to the polymer (see Figure).

    12. Synthesis of Hierarchical Titanium Carbide from Titania-Coated Cellulose Paper (pages 1212–1215)

      Y. Shin, X. S. Li, C. Wang, J. R. Coleman and G. J. Exarhos

      Version of Record online: 2 AUG 2004 | DOI: 10.1002/adma.200306661

      Cellulose paper and an aqueous-based, inexpensive TiO2 precursor, Tyzor-LA, have been used to prepare TiC via carbothermal reduction in an Ar flow. The hierarchical cellulose structures were completely maintained upon the agglomeration of 10–50 nm TiC nanoparticles. The lattice parameter of TiC increased with increasing reaction temperature, while the oxygen content in the sample decreased and showed minimal oxygen impurity at 1500 °C (0.24 wt.-%).

    13. Mesoporous Single-Crystal ZnO Nanowires Epitaxially Sheathed with Zn2SiO4 (pages 1215–1218)

      X. D. Wang, C. J. Summers and Z. L. Wang

      Version of Record online: 19 MAY 2004 | DOI: 10.1002/adma.200306505

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      High-porosity, single-crystal ZnO nanowires have been synthesized for the first time using a solid–vapor process on a Si substrate. The thermal decomposition of ZnO and the formation of a Zn2SiO4 network on the nanowire surface are the keys for forming the high-porosity interior. The structures exhibit a very high surface-to-volume ratio and are expected to have high absorptive capacity and chemical selectivity that could be used for filter and sensor systems.

    14. Efficient Fabrication of Carbon Nanotube Point Electron Sources by Dielectrophoresis (pages 1219–1222)

      J. Zhang, J. Tang, G. Yang, Q. Qiu, L.-C. Qin and O. Zhou

      Version of Record online: 2 AUG 2004 | DOI: 10.1002/adma.200400124

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      Carbon nanotube tips (see Figure) with controllable length, diameter, and orientation have been fabricated by the dielectrophoresis process. They are capable of delivering high and stable electron-field-emission currents of 3–5 μA (105 A cm–2). The emitters can potentially be used as the field-emission electron sources for precision vacuum electronic instruments such as electron microscopes.

    15. Cerium Compound Nanowires and Nanorings Templated by Mixed Organic Molecules (pages 1222–1226)

      M. Yada, S. Sakai, T. Torikai, T. Watari, S. Furuta and H. Katsuki

      Version of Record online: 2 AUG 2004 | DOI: 10.1002/adma.200306546

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      Cerium compound nanowires and nanorings with a layered nanostructure (see Figure), templated by AOT (bis(2-ethylhexyl)sulfosuccinate) anions and alkyl alcohol, have been synthesized. Nanowires form in the presence of NaAOT or NaAOT and butyl alcohol. Nanorings form in the presence of NaAOT and octyl alcohol or NaAOT and dodecyl alcohol.

    16. Facile Fabrication of Nanocellular Block Copolymer Thin Films Using Supercritical Carbon Dioxide (pages 1226–1229)

      L. Li, H. Yokoyama, T. Nemoto and K. Sugiyama

      Version of Record online: 2 AUG 2004 | DOI: 10.1002/adma.200400264

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      A novel, facile, and reproducible method of fabricating nanocells in thin films (see Figure) has been developed using a fluorinated block copolymer with a supercritical carbon dioxide (scCO2) soluble block as a template. The nanocells have an average spacing of 34 nm and a number density of 9 × 1010 cm–2. The size of nanocellular structures is readily tunable by changing the saturation pressure of scCO2.