Advanced Materials

Cover image for Vol. 13 Issue 4

February, 2001

Volume 13, Issue 4

Pages 227–291

    1. Epitaxy and Molecular Organization on Solid Substrates (pages 227–241)

      D. E. Hooks, T. Fritz and M. D. Ward

      Version of Record online: 22 FEB 2001 | DOI: 10.1002/1521-4095(200102)13:4<227::AID-ADMA227>3.0.CO;2-P

      A classification scheme for epitaxial crystalline overlayers on crystalline substratesis described that is particularly useful for understanding the structure and formation of molecular films. Geometrical lattice match calculations useful for the confirmation and prediction of epitaxial relationships are also presented. The Figure shows the commensurate structure of Cu-Pc on MoS2.

    2. Self-Assembled Hexagonal Nanoarrays of Novel Macrocyclic Oligothiophene-Diacetylenes (pages 243–246)

      E. Mena-Osteritz and P. Bäuerle

      Version of Record online: 22 FEB 2001 | DOI: 10.1002/1521-4095(200102)13:4<243::AID-ADMA243>3.0.CO;2-X

      The self-assembly of macrocyclic conjugated oligothiophene-diacetylenes at the liquid/solid interface is investigated by scanning tunneling microscopy (STM). Well-ordered and stable hexagonal nanoarrays (see Figure) are formed. The molecular parameters of the individual macrocycles determined from the STM images are confirmed by semiempirical calculations (see also cover).

    3. Synthesis of Well-Aligned Diamond Nanocylinders (pages 247–249)

      H. Masuda, T. Yanagishita, K. Yasui, K. Nishio, I. Yagi, T. N. Rao and A. Fujishima

      Version of Record online: 22 FEB 2001 | DOI: 10.1002/1521-4095(200102)13:4<247::AID-ADMA247>3.0.CO;2-H

      Alumina templates are used to assist the deposition of highly ordered polycrystalline diamond nanocylinders (see Figure) and diamond-like carbon nanotubes. The growth of diamond is carried out by microwave plasma-assisted CVD, using acetone as the carbon source. The dimensions of the nanofibers are easily controllable and this technique could be adopted to prepare arrays for various applications.

    4. DNA-Directed Assembly of Gold Nanowires on Complementary Surfaces (pages 249–254)

      J. K. N. Mbindyo, B. D. Reiss, B. R. Martin, C. D. Keating, M. J. Natan and T. E. Mallouk

      Version of Record online: 22 FEB 2001 | DOI: 10.1002/1521-4095(200102)13:4<249::AID-ADMA249>3.0.CO;2-9

      The coverage of Au surfaces with Au nanowires by linking them with DNA offers great prospects for the assembly of wire structures with particular connectivity. This work presents the first example of using DNA hybridization to control the assembly of micrometer-size inorganic particles on surfaces. The Figure shows the optical microscopy image of Au nanowires modified with DNA.

    5. “Supra Crystals” Made of Nanocrystals (pages 254–258)

      A. Courty, C. Fermon and M.-P. Pileni

      Version of Record online: 22 FEB 2001 | DOI: 10.1002/1521-4095(200102)13:4<254::AID-ADMA254>3.0.CO;2-P

      Quantum-dot superlattices provide a new horizon in fundamental physics. The fabrication and characterization of well-defined 3D superlattices made of silver nanocrystals is described in this communication. “Supra crystals” of relatively large sizes could be obtained with very high reproducibility. The picture shows an SEM image at a 45° tilt of the silver nanocrystal aggregates on an HOPG substrate.

    6. Control of Charge Transport and Intermolecular Interaction in Organic Light-Emitting Diodes by Dendrimer Generation (pages 258–261)

      J. M. Lupton, I. D. W. Samuel, R. Beavington, P. L. Burn and H. Bässler

      Version of Record online: 22 FEB 2001 | DOI: 10.1002/1521-4095(200102)13:4<258::AID-ADMA258>3.0.CO;2-9

      A novel family of conjugated dendrimers is used as model compounds to explore the effect of intermolecular interactions on photo-physical and transport properties. The Figure shows the third generation of the dendrimers. The dendrimer generation controls the degree of chromophore interaction, which leads to a unique correlation between the chemical structure of the molecules and the macroscopic device properties (see also inside front cover).

    7. Triangular CdS Nanocrystals: Structural and Optical Studies (pages 261–264)

      N. Pinna, K. Weiss, J. Urban and M.-P. Pileni

      Version of Record online: 22 FEB 2001 | DOI: 10.1002/1521-4095(200102)13:4<261::AID-ADMA261>3.0.CO;2-X

      CdS nanostructures with high crystallinityare widely investigated for their semiconductor properties. This work focuses on the preparation and properties of equilateral-triangular nanocrystals made by colloidal self-assembly. The picture shows the results of high-resolution transmission electron microscopy imaging of a CdS nanostructure prepared by this method.

    8. Nanotube Structure Revealed by High-Resolution X-ray Diffraction (pages 264–267)

      G. Xu, Z.-C. Feng, Z. Popovic, J.-Y. Lin and J. J. Vittal

      Version of Record online: 22 FEB 2001 | DOI: 10.1002/1521-4095(200102)13:4<264::AID-ADMA264>3.0.CO;2-L

      High-resolution X-ray diffraction of high-purity multiwall carbon nanotubes has been performed and unusual diffraction physics was observed. Fourier analysis confirms that the multiwall nanotubes are made of concentric cylinders and that there is a non-uniform distribution of inner tube diameter. The interference effect discussed in this paper is unique for concentric tubes and in contrast to nanotubes that are scroll-like or made up of irregular grains.

    9. Self-Assembly of Monodispersed Spherical Colloids into Complex Aggregates with Well-Defined Sizes, Shapes, and Structures (pages 267–271)

      Y. Yin and Y. Xia

      Version of Record online: 22 FEB 2001 | DOI: 10.1002/1521-4095(200102)13:4<267::AID-ADMA267>3.0.CO;2-9

      The self-assembly of polystyrene beads into a variety of polygonal and polyhedral clusters is reported. The Figure shows a schematic illustration of the procedure used to form these well-defined clusters under physical confinement. These aggregates will be useful as new types of building blocks in hierarchical self-assembly to generate mesostructured, 3D systems of high complexity.

    10. Preparation and Characterization of Micrometer-Sized “Egg Shells” (pages 271–274)

      Y. Lu, Y. Yin and Y. Xia

      Version of Record online: 22 FEB 2001 | DOI: 10.1002/1521-4095(200102)13:4<271::AID-ADMA271>3.0.CO;2-T

      Ellipsoidal mesoscale “egg shells” (see Figure) have been prepared by a template-directed synthesis using a sol-gel precursor. TiO2 shells of micrometer sizes should have a great potential as containers in microencapsulation and their ellipsoidal shape should provide them with a range of interesting optical, mechanical, and hydrodynamic properties.

    11. Thermoresponsive Glasses: Temperature-Controlled Rapid Swelling and Deswelling of Silica-Based Sol–Gels (pages 274–276)

      M. S. Rao and B. C. Dave

      Version of Record online: 22 FEB 2001 | DOI: 10.1002/1521-4095(200102)13:4<274::AID-ADMA274>3.0.CO;2-H

      A novel silica sol-gel that swells or shrinks rapidly by changing its hydration state upon temperature variation is described. The swelling–deswelling (see Figure) is reversible and the kinetics of the bulk transition are fast. The effects of preparation technique and structural variation on the thermal shrinkage properties are discussed.

    12. Colloidal Isopressing: A New Shape-Forming Method (pages 276–280)

      B. C. Yu and F. F. Lange

      Version of Record online: 22 FEB 2001 | DOI: 10.1002/1521-4095(200102)13:4<276::AID-ADMA276>3.0.CO;2-9

      Colloidal isopressing of ceramic powders has been introduced as a novel method to form ceramic components from colloidal suspensions. This new shaping method minimizes the need for post-processing machining as the shape and contours imparted by the mold are retained during drying and densification. The versatility of the process and the availability of the equipment needed for this technique ensure that colloidal isopressing can be applied to the fabrication of a wide variety of materials.

    13. One-Dimensional Quantum Confinement in Electrodeposited PbS Nanocrystalline Semiconductors (pages 280–283)

      K. K. Nanda and S. N. Sahu

      Version of Record online: 22 FEB 2001 | DOI: 10.1002/1521-4095(200102)13:4<280::AID-ADMA280>3.0.CO;2-T

      The optical properties of lead sulfide semiconducting nanoparticulate thin films with pancake-like structures are controlled by the lowest dimension of the particles, which is a consequence of 1D quantum confinement. Optical absorption and photoluminescence spectra of the nanoparticles (see Figure) reveal that their bandgap does not change with temperature in contrast to bulk lead sulfide.

    14. Simple Synthesis of MoS2 and WS2 Nanotubes (pages 283–286)

      M. Nath, A. Govindaraj and C. N. R. Rao

      Version of Record online: 22 FEB 2001 | DOI: 10.1002/1521-4095(200102)13:4<283::AID-ADMA283>3.0.CO;2-H

      Trisulfide molybdenum complexes have been employed to produce nanotubes by simple heating in a stream of hydrogen. Bamboo-like stacking (see Figure) was observed, suggesting that the stimulus for the growth of MoS2 nanotubes is similar to that of their carbon equivalents. The wide experience gained with trisulfide complexes directs this technique towards the preparation of other layered sulfide nanotubes, although other precursors are also shown to be successful.

    15. Creating Highly Ordered Metal, Alloy, and Semiconductor Macrostructures by Electrodeposition, Ion Spraying, and Laser Spraying (pages 286–289)

      Q. Luo, Z. Liu, L. Li, S. Xie, J. Kong and D. Zhao

      Version of Record online: 22 FEB 2001 | DOI: 10.1002/1521-4095(200102)13:4<286::AID-ADMA286>3.0.CO;2-5

      The combination of colloid template technology with deposition and spraying techniques leads to the fabrication of highly ordered porous macrostructures. It is shown that 3D structures with variable macropore size can be fabricated. In addition, long-range 2D macroporous semiconductor films (see Figure for a Si film created by laser spraying), which are otherwise difficult to obtain, could be created.

    16. Silica–Maghemite Nanocomposites (pages 289–291)

      A. Bourlinos, A. Simopoulos, D. Petridis, H. Okumura and G. Hadjipanayis

      Version of Record online: 22 FEB 2001 | DOI: 10.1002/1521-4095(200102)13:4<289::AID-ADMA289>3.0.CO;2-U

      The use of silica–maghemite nanocomposites in magnetic refrigerators or various catalytic reactions has now been given a boost by the simple synthesis of maghemite nanoparticles that are supported on silicon oxide. The composition of the magnetic particles on the surface can easily be varied and it is shown that the particles are highly dispersed (see Figure).