Advanced Functional Materials

Cover image for Advanced Functional Materials

November, 2003

Volume 13, Issue 11

Pages 827–898

    1. Solid-State Photovoltaic Thin Films using TiO2, Organic Dyes, and Layer-by-Layer Polyelectrolyte Nanocomposites (pages 831–839)

      H. Tokuhisa and P.T. Hammond

      Version of Record online: 5 NOV 2003 | DOI: 10.1002/adfm.200304404

      Micro- and nanometer-scale patterned TiO2 electrode (see Figure) and layer-by-layer polyelectrolyte multilayer/oligoethylene glycol dicarboxylic acid (OEGDA) composite films were applied to dye-sensitized photovoltaic devices. Significant improvement of the photovoltaic performance was achieved by both the use of OEGDA and the patterning of the TiO2 electrode.

    2. AlxGa1–xN—A New Material System for Biosensors (pages 841–846)

      G. Steinhoff, O. Purrucker, M. Tanaka, M. Stutzmann and M. Eickhoff

      Version of Record online: 5 NOV 2003 | DOI: 10.1002/adfm.200304397

      The applicability of group III nitrides for the fabrication of biosensors is demonstrated (the Figure shows a schematic of a biosensor based on an transparent heterostructure field-effect transistor (FET) as the readout device for selective ion transport across a lipid membrane). Ion-sensitive AlGaN/GaN heterostructure FETs show high pH sensitivity and low drift. The device surfaces are chemically robust and non-toxic to living cells.

    3. Positively Thermo-Sensitive Monodisperse Core–Shell Microspheres (pages 847–852)

      X.-C. Xiao, L.-Y. Chu, W.-M. Chen, S. Wang and Y. Li

      Version of Record online: 5 NOV 2003 | DOI: 10.1002/adfm.200304513

      A novel family of highly monodisperse, thermo-sensitive core–shell hydrogel microspheres is reported. They show positively thermo-responsive volume phase transition characteristics, i.e., the particle swelling is induced by an increase rather than a decrease in temperature, with tunable swelling kinetics. A schematic of the proposed swelling mechanism and the preparation procedure is shown in the Figure.

    4. Micellar Nanoreactors—Preparation and Characterization of Hexagonally Ordered Arrays of Metallic Nanodots (pages 853–861)

      G. Kästle, H.-G. Boyen, F. Weigl, G. Lengl, T. Herzog, P. Ziemann, S. Riethmüller, O. Mayer, C. Hartmann, J.P. Spatz, M. Möller, M. Ozawa, F. Banhart, M.G. Garnier and P. Oelhafen

      Version of Record online: 5 NOV 2003 | DOI: 10.1002/adfm.200304332

      Formation of arrays of metallic nanodots by a new, versatile, bottom-up approach is described. Spherical reverse micelles are loaded with a metal salt and then deposited onto a smooth substrate, exploiting their self-assembly into an ordered array. Exposure to an oxygen or hydrogen plasma is demonstrated to reduce the salt to the corresponding metal and simultaneously remove the polymer matrix without destroying the order. The Figure shows a gold nanoparticle array formed in this way.

    5. Synthesis, Characterization, and Nonlinear Optical Study of Metalloporphyrins (pages 863–867)

      K. McEwan, K. Lewis, G.-Y. Yang, L.-L. Chng, Y.-W. Lee, W.-P. Lau and K.-S. Lai

      Version of Record online: 5 NOV 2003 | DOI: 10.1002/adfm.200304288

      It is well known that the nonlinear optical response of porphyrin molecules depends strongly on the molecular structure. In general, molecular modifications aimed at improving the excited-state absorption also change the ground-state absorption. Here it is shown that it is possible to dramatically increase the triplet excited-state absorption of tetra-phenyl porphyrins (see Structure, right) at 532 nm without changing their linear optical properties.

    6. Long-Range, Entangled Carbon Nanotube Networks in Polycarbonate (pages 868–872)

      S. Singh, Y. Pei, R. Miller and P.R. Sundararajan

      Version of Record online: 5 NOV 2003 | DOI: 10.1002/adfm.200304411

      The natural entanglement properties of carbon nanotubes (CNTs) enable the formation of a widespread network of CNTs (see Figure) within a polycarbonate matrix using simple solution mixing. The Young's modulus of this uniformly transparent binary composite is shown to reach a maximum at a CNT concentration approaching the theoretically estimated percolation limit. (See also cover.)

    7. Atomic Layer Deposition of TiO2 Thin Films on Mixed Self-Assembled Monolayers Studied as a Function of Surface Free Energy (pages 873–876)

      J.P. Lee, Y.J. Jang and M.M. Sung

      Version of Record online: 5 NOV 2003 | DOI: 10.1002/adfm.200304445

      The influence of the surface free energies of the Si substrates on the growth modes of TiO2 thin films has been studied. The TiO2 thin films are grown on mixed self-assembled monolayer-coated Si substrates (see Figure) by atomic layer deposition. A decrease in surface free energy is shown to cause the three-dimensional growth mode to dominate over the two-dimensional one observed at high surface free energies.

    8. Anomalous Spin Transition Observed in Bis(2,6-bis(pyrazol-3-yl)pyridine)iron(II) Thiocyanate Dihydrate (pages 877–882)

      A. Bhattacharjee, V. Ksenofontov, K.H. Sugiyarto, H.A. Goodwin and P. Gütlich

      Version of Record online: 5 NOV 2003 | DOI: 10.1002/adfm.200304356

      Bis(2,6-bis(pyrazol-3-yl)pyridine)iron(II) thiocyanate dihydrate undergoes a two-step singlet (1A1) ⇄ quintet (5T2) transition in which both steps are associated with large thermal hysteresis (see Figure). Thermal cycling of the sample results in its conversion to a second phase, which displays a single-step transition with a very narrow hysteresis loop. This second phase slowly reverts to the initial phase on standing at 300 K.

    9. Anthracene-Containing Binaphthol Chromophores for Light-Emitting Diode (LED) Fabrication (pages 883–886)

      H. Benmansour, T. Shioya, Y. Sato and G.C. Bazan

      Version of Record online: 5 NOV 2003 | DOI: 10.1002/adfm.200304456

      The synthesis and use in efficient light-emitting diodes of non-crystalline anthracene-containing binaphthol chromophores (see Figure) are reported. The size of the alkoxy groups on the binaphthol framework is shown to control not only the glass-transistion temperature, but also the electronic communication between the chromophore units, such that shorter alkoxy groups result in increased charged mobilities in the fabricated devices.

    10. Synthesis of Optically Complex Core–Shell Colloidal Suspensions: Pathways to Multiplexed Biological Screening (pages 887–896)

      G.A. Lawrie, B.J. Battersby and M. Trau

      Version of Record online: 5 NOV 2003 | DOI: 10.1002/adfm.200304390

      Fluorescent dyes have been synthesized as concentric shells around a core silica particle with silica spacer shells between each dye shell to separate different fluorophores (see Figure, left; top: micrograph; bottom: scheme). The resulting particles possess complex optical signatures (see Figure, right). These particles have the potential to be used as solid supports for directed split-and-mix synthesis and subsequent screening of biomolecule libraries.