Advanced Materials

Cover image for Advanced Materials

November, 2003

Volume 15, Issue 21

Pages 1779–1870

    1. Solar Energy Materials (pages 1789–1803)

      C.G. Granqvist

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/adma.200300378

      Solar energy materials are used for thermal and electrical conversion of solar energy in man-made collectors, as well as for energy-efficient passive design in architecture. They have properties tailored to meet requirements set by the spectral distribution, angle of incidence, and intensity of the electromagnetic radiation prevailing in our natural surroundings. This paper reviews these materials with emphasis on thermal applications of a variety of types.

    2. Alignment of Long DNA Molecules on Templates Generated via Dip-Pen Nanolithography (pages 1805–1809)

      D. Nyamjav and A. Ivanisevic

      Version of Record online: 10 SEP 2003 | DOI: 10.1002/adma.200305342

      A methodology to place and stretch long DNA molecules by coupling dip-pen Nanolithography with molecular combing is presented. Templates were fabricated on SiOx surfaces using a positively charged polymer, poly(allylamine hydrochloride). Upon molecular combing, DNA molecules elongate on the surface (for example, see Figure) and are localized by the presence of the charged lithographically defined structures.

    3. Highly Transparent γ-Fe2O3/Vycor-Glass Magnetic Nanocomposites Exhibiting Faraday Rotation (pages 1809–1812)

      M. Zayat, F. del Monte, M.P. Morales, G. Rosa, H. Guerrero, C.J. Serna and D. Levy

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/adma.200305436

      The preparation and characterization of highly transparent (see Figure) and magnetic nanocomposites exhibiting Faraday rotation is reported. Superparamagnetic behavior results from the confinement of the γ-Fe2O3 nanoparticles within the pores of a Vycor glass. The remarkable Faraday rotation exhibited by the resulting composites opens their application to a wide range of magneto-optical devices.

    4. Substrate-Mediated Electronic Structure and Properties of Sexiphenyl Films (pages 1812–1815)

      J. Ivanco, B. Winter, F.P. Netzer and M.G. Ramsey

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/adma.200304993

      It is shown that for organic film growth, the substrate conditions can lead to large differences in the electronic structure of the films. The significance for organic devices is illustrated with the band alignment of sexiphenyl films on Al(111), which is variable over almost 2 eV; 0.9 eV arising from differences in the planarity of the molecules in the films (see Figure) and up to 1 eV depending on the oxygen content at the interface.

    5. Higher-Order Synthesis of Organoclay Pipes Using Self-Assembled Lipid Templates (pages 1816–1819)

      A.J. Patil, E. Muthusamy, A.M. Seddon and S. Mann

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/adma.200305426

      The template-directed synthesis of helical ribbons and cylindrical micropipes (see Figure) of organically functionalized magnesium phyllosilicate clay is achieved by high fidelity decoration of self-assembled phospholipid tubules. The replicas are produced by electrostatic interactions between the positively charged organoclay precursors and charged lipid headgroups exposed on the surfaces of the organic template.

    6. Contact Printing of Metal Ions onto Carboxylate-Terminated Self-Assembled Monolayers (pages 1819–1823)

      K.-L. Yang, K. Cadwell and N.L. Abbott

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/adma.200305478

      The selective exchange of metals ions between salts inked onto the surfaces of polydimethylsiloxane (PDMS) stamps and sodium carboxylate-terminated monolayers is reported. When Ni(ClO4)2 is inked onto a PDMS stamp and contacted with the monolayer, Ni2+ is transferred onto the surface and Na+ is transferred from the surface to the stamp (see Figure). Patterning of metals ions is demonstrated.

    7. A 4 % Efficient Dye-Sensitized Solar Cell Fabricated from Cathodically Electrosynthesized Composite Titania Films (pages 1823–1825)

      J. Yamamoto, A. Tan, R. Shiratsuchi, S. Hayase, C.R. Chenthamarakshan and K. Rajeshwar

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/adma.200305239

      Cathodically electrosynthesized TiO2 films (see Figure) containing occluded Degussa P-25 titania particles can yield short-circuit current densities as high as 10.5 mA cm–2, an open-circuit photovoltage of 690 mV, a fill factor of 57.3 %, and a photovoltaic efficiency of 4.13 % under simulated air mass 1.5 (100 mW cm–2) sunlight in a dye-sensitized solar cell device.

    8. Pyroelectricity in Highly Stressed Quasi-Amorphous Thin Films (pages 1826–1828)

      V. Lyahovitskaya, I. Zon, Y. Feldman, S.R. Cohen, A.K. Tagantsev and I. Lubomirsky

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/adma.200305346

      Quasi-amorphous BaTiO3 thin films (see Figure) represent a polar ionic solid without spatial periodicity. Most probably, polarity of the quasi-amorphous BaTiO3 is associated with directional ordering of crystal motifs formed in the steep temperature gradient and stabilized by high in-plane mechanical stress. A remarkable characteristic of quasi-amorphous BaTiO3 is expression of strong pyro- and piezoelectric effects in a low dielectric constant material.

    9. Hydrogel Formation via Cell Crosslinking (pages 1828–1832)

      K.Y. Lee, H.J. Kong, R.G. Larson and D.J. Mooney

      Version of Record online: 29 SEP 2003 | DOI: 10.1002/adma.200305406

      It is demonstrated that cells can be utilized as a crosslinker to form network structures from polymers. The properties of these systems can be interpreted with classical network theory. This approach can be useful to determine various parameters related to cell receptor–ligand binding (see Figure), such as the number of bonds, as well as to suggest a unique means to the delivery of cells for therapeutic purposes.

    10. Facile Synthesis of Hollow Nickel Submicrometer Spheres (pages 1832–1835)

      J. Bao, Y. Liang, Z. Xu and L. Si

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/adma.200305315

      Hollow Ni spheres with average diameter of ∼370 nm have been prepared via redox reaction of NiSO4 with NaH2PO2 in a cyclohexane–water–polyglycol emulsion system. It is found that the composition of the reaction system has a significant influence on the formation of hollow Ni spheres. A mechanism of formation of the Ni hollow spheres is proposed.

    11. Large-Area Nanowire Arrays of Molybdenum and Molybdenum Oxides: Synthesis and Field Emission Properties (pages 1835–1840)

      J. Zhou, N.-S. Xu, S.-Z. Deng, J. Chen, J.-C. She and Z.-L. Wang

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/adma.200305528

      Well-aligned nanowire arrays of Mo and its oxides have been synthesized. MoO2 nanowire arrays are first synthesized by thermal evaporation in a vacuum chamber. With further treatments in the growth chamber, the above nanowire arrays can be turned into MoO3 nanowire arrays or metallic Mo nanowire arrays (see Figure). The field emission properties of these nanowires are fully investigated.

    12. Unique Single-Crystalline Beta Carbon Nitride Nanorods (pages 1840–1844)

      L.-W. Yin, Y. Bando, M.-S. Li, Y.-X. Liu and Y.-X. Qi

      Version of Record online: 16 SEP 2003 | DOI: 10.1002/adma.200305307

      Growth of single crystal beta carbon nitride (β-C3N4) nanorods (see Figure) has been achieved for the first time through thermal annealing of nanosized carbon nitrides induced by high-energy ball milling under a streaming flow of NH3. Most of the nanorods grow along the [001] direction, and the surfaces are defined by (011) and (010) specific crystallographic planes. A possible growth mechanism of the β-C3N4 nanorods is discussed.

    13. Colloidal PbS Nanocrystals with Size-Tunable Near-Infrared Emission: Observation of Post-Synthesis Self-Narrowing of the Particle Size Distribution (pages 1844–1849)

      M.A. Hines and G.D. Scholes

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/adma.200305395

      The synthesis of nanocrystalline PbS quantum dots using organometallic precursors is reported. The samples exhibit tunable, strong near-infrared photoluminescence. A remarkable spontaneous self-directed narrowing of the particle size distribution is shown to occur after the particles are synthesized and dispersed in organic solvent. The Figure shows the tuning of band-edge exciton absorption features through the near-infrared spectral region according to particle size.

    14. Nanotubes Prepared by Layer-by-Layer Coating of Porous Membrane Templates (pages 1849–1853)

      Z. Liang, A.S. Susha, A. Yu and F. Caruso

      Version of Record online: 10 OCT 2003 | DOI: 10.1002/adma.200305580

      Polyelectrolyte (PE) (see Figure) and PE–nanoparticle hybrid nanotubes are prepared by the layer-by-layer deposition of oppositely charged species into the cylindrical pores of polycarbonate membrane templates. This method affords the preparation of compositionally complex tubes with nanometer-level controllable tube wall thicknesses and enhanced structural stabilities.

    15. Probing of Functionalized Mesoporous Silica Nanoparticles Using Transition Metal Clusters (pages 1853–1857)

      S. Hermans, S. Sadasivan, C.M.G. Judkins, B.F.G. Johnson, S. Mann and D. Khushalani

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/adma.200305350

      Molecular clusters (homo- and bi-metallic) have been used to gain structural information on nanoparticles of mesoporous silica (see Figure). Using scanning transmission electron microscopy, the spatial distribution of clusters has been imaged to determine the accessibility of the mesopores. The clusters are also used as “stains” to determine the exact location and number of functional sites within the substrates.

    16. A Continuous-Flow Microcapillary Reactor for the Preparation of a Size Series of CdSe Nanocrystals (pages 1858–1862)

      B.K.H. Yen, N.E. Stott, K.F. Jensen and M.G. Bawendi

      Version of Record online: 11 SEP 2003 | DOI: 10.1002/adma.200305162

      A microcapillary flow reactor has been used to prepare a size series of colloidal CdSe nanocrystals (NCs). The continuous-flow method (see Figure for schematic) produces samples with size distributions and quantum yields comparable to those prepared in conventional batch processes. The results obtained from the reactor provide insight into the kinetics of nucleation and growth for NC systems.

    17. 1.3 μm to 1.55 μm Tunable Electroluminescence from PbSe Quantum Dots Embedded within an Organic Device (pages 1862–1866)

      J.S. Steckel, S. Coe-Sullivan, V. Bulović and M.G. Bawendi

      Version of Record online: 6 NOV 2003 | DOI: 10.1002/adma.200305449

      Large area (mm2 in size) infrared electroluminescent devices are demonstrated using colloidally grown PbSe quantum dots (QDs) in organic host materials. By changing the QD size the electroluminescence is tuned from λ = 1.33–1.56 μm. The fabrication of this light-emitting device (see Figure) combines the thin film processing techniques available to organic materials with the tunable optical properties of PbSe QDs.