Advanced Functional Materials

Cover image for Vol. 12 Issue 8

August, 2002

Volume 12, Issue 8

Pages 475–545

    1. Contents: Adv. Funct. Mater. 8/2002 (pages 475–477)

      Article first published online: 29 JUL 2002 | DOI: 10.1002/1616-3028(20020805)12:8<475::AID-ADFM475>3.0.CO;2-G

    2. Advanced Functional Materials: Off to a Great Start (pages 479–481)

      E. Levy

      Article first published online: 29 JUL 2002 | DOI: 10.1002/1616-3028(20020805)12:8<479::AID-ADFM479>3.0.CO;2-0

      There are many indications that Advanced Functional Materials is off to a great start. The journal has grown quickly from 6 issues in 2001 to 12 issues in 2002, and a 20 % page increase is planned for next year to cater for the healthy increase in quality manuscripts that are being submitted to the journal. Some further measures of the success of the journal are discussed in this Editorial and recent innovations that have been implemented to foster the quick development of the journal are presented.

    3. Tuning Photoelectrochemical and Photocatalytic Properties through Electronic Semiconductor–Support Interaction (pages 483–488)

      H. Kisch and H. Weiß

      Article first published online: 29 JUL 2002 | DOI: 10.1002/1616-3028(20020805)12:8<483::AID-ADFM483>3.0.CO;2-K

      Do semiconductor–support interactions influence the bandgap energy? For cadmium sulfide supported on silica it is shown that the bandgap increases with decreasing coverage. Based on experimental data it is concluded that these changes originate from an electronic semiconductor–support interaction (SEMSI) mediated through surface [Si]–O–CdS bonds. The Figure shows a typical redox reaction catalyzed by a semiconductor.

    4. Fabrication of a Class of Nanostructured Materials Using Carbon Nanowalls as the Templates (pages 489–494)

      Y.H. Wu, B.J. Yang, G.C. Han, B.Y. Zong, H.Q. Ni, P. Luo, T.C. Chong, T.S. Low and Z.X. Shen

      Article first published online: 29 JUL 2002 | DOI: 10.1002/1616-3028(20020805)12:8<489::AID-ADFM489>3.0.CO;2-X

      Carbon nanowalls with a thickness of a few nanometers and a lateral size in the micrometer range have been grown on a variety of substrates and have been used as templates for the fabrication of nanostructured materials. The templating of for instance magnetic nanoparticles or semiconducting oxides into 3D structures (see Figure) makes this simple technique advantageous for use in a myriad of applications (see also cover).

    5. The Effect of Surfactants on the Reactivity and Photophysics of Luminescent Nanocrystalline Porous Silicon (pages 495–500)

      C.A. Canaria, M. Huang, Y. Cho, J.L. Heinrich, L.I. Lee, M.J. Shane, R.C. Smith, M.J. Sailor and G.M. Miskelly

      Article first published online: 29 JUL 2002 | DOI: 10.1002/1616-3028(20020805)12:8<495::AID-ADFM495>3.0.CO;2-8

      Dramatic differences are observed in the chemistry and photophysics of nanocrystalline porous Si exposed to surfactants with cationic or anionic headgroups. The cationic surfactant dodecyltrimethylammonium bromide causes irreversible quenching by catalyzing rapid corrosion of the silicon surface, visualized by IR spectroscopy. The anionic surfactant sodium dodecyl sulfonate, on the other hand, physisorbs to the surface and leads to reversible photoluminescence quenching, probably due to local dielectric effects that increase the non-radiative decay rate in porous silicon.

    6. Chemical Solution Deposition of Silver Halide Films (pages 501–505)

      G. Hodes and G. Calzaferri

      Article first published online: 29 JUL 2002 | DOI: 10.1002/1616-3028(20020805)12:8<501::AID-ADFM501>3.0.CO;2-J

      Why have only chalcogenide semiconductors been deposited from chemical solution up to now? Here it is shown that films of the silver halides AgBr and AgI are just as easily generated by in-situ hydrolysis of haloalcohols (e.g., 2-bromo-1-propanol) in the presence of silver ions. For AgCl, the straight reaction of AgNO3 and NaCl yields better films. The Figure shows an AgBr film on a glass substrate.

    7. Novel Heterolayer Organic Light-Emitting Diodes Based on a Conjugated Dendrimer (pages 507–511)

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

      Article first published online: 29 JUL 2002 | DOI: 10.1002/1616-3028(20020805)12:8<507::AID-ADFM507>3.0.CO;2-W

      Two chemically identical layers, except for the presence of a dopant (the electron transport material 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole) in the outer one, characterize a new light-emitting diode based on the dendrimer shown in the Figure. A graded interlayer, instead of a sharp boundary, improves exciton formation and enhances quantum efficiency, at 0.16 % at 600 cd/m2, to three times that of conventional LEDs.

    8. Understanding Dark Spot Formation and Growth in Organic Light-Emitting Devices by Controlling Pinhole Size and Shape (pages 513–518)

      S.F. Lim, W. Wang and S.J. Chua

      Article first published online: 29 JUL 2002 | DOI: 10.1002/1616-3028(20020805)12:8<513::AID-ADFM513>3.0.CO;2-7

      Dark spots are detrimental to the performance of organic light-emitting diodes. This study on their formation and growth reveals that pinholes on the protective layer create pathways for water or oxygen diffusion into the devices. This diffusion process controls the dark spot growth rate (see Figure). The pinhole size dependence illustrates that the pinhole perimeter (not the area) determines the growth rate.

    9. Photoinduced Electron Transfer in Heterosupramolecular Assemblies of TiO2 Nanoparticles and Terthiophene Carboxylic Acid in Apolar Solvents (pages 519–525)

      W.J.E. Beek and R.A.J. Janssen

      Article first published online: 29 JUL 2002 | DOI: 10.1002/1616-3028(20020805)12:8<519::AID-ADFM519>3.0.CO;2-K

      Monodisperse stearic acid coated titanium dioxide nanoparticles (< 3 nm) have been prepared and characterized, and the fluorescence of these supramolecular assemblies (see Figure) has been monitored. The fluorescence of the terthiophene moiety of the heterosupramolecular system is observed to be completely quenched due to a photoinduced electron transfer from terthiophene to titanium dioxide.

    10. Silsesquioxane Resins as High-Performance Solution Processible Dielectric Materials for Organic Transistor Applications (pages 526–531)

      Z. Bao, V. Kuck, J.A. Rogers and M.A. Paczkowski

      Article first published online: 29 JUL 2002 | DOI: 10.1002/1616-3028(20020805)12:8<526::AID-ADFM526>3.0.CO;2-S

      Silsesquioxane dielectric materials have successfully been implemented in organic field-effect transistors (FETs) deposited on robust, plastic substrates. Performances comparable to those found with silicon substrates having SiO2 as the active dielectric layer have been achieved with six p- and n-channel organic semiconductors. The Figure shows an electrophoretic display with a microcontact-printed silsesquioxane dielectric layer.

    11. Nanostructured Surfaces by Deposition of Metal Nanoparticles by Means of Spray Techniques (pages 532–536)

      F. Schulz, S. Franzka and G. Schmid

      Article first published online: 29 JUL 2002 | DOI: 10.1002/1616-3028(20020805)12:8<532::AID-ADFM532>3.0.CO;2-3

      Electrospray and pneumatic dispersion techniques are highly effective for the deposition of pre-formed metal nanoparticles from solution on a variety of substrates as microdroplets, which contain just a few particles each. By subsequent or simultaneous ligand removal with an oxygen plasma, particles strongly adherent to the substrate are obtained. The Figure shows an AFM image of 20–50 nm Pd particles on a Ti surface.

    12. Amplified Spontaneous Emission in Close-Packed Films of Semiconductor Nanocrystals Using Picosecond Excitation (pages 537–540)

      C.E. Finlayson, D.M. Russell, C.M. Ramsdale, D.S. Ginger, C. Silva and N.C. Greenham

      Article first published online: 29 JUL 2002 | DOI: 10.1002/1616-3028(20020805)12:8<537::AID-ADFM537>3.0.CO;2-K

      Stable line-narrowed emission under 100 ps excitation is obtained from close-packed thin films of (CdSe)ZnS core–shell nanocrystals due to waveguide-assisted amplified spontaneous emission at both 77 K and room temperature. In this material, a nanocrystal blend with a bimodal size distribution, the line-narrowing effect appears to be greatly assisted by Förster energy transfer. However, no evidence is obtained for lasing from planar microcavity structures incorporating these films at intensities up to 1 mJ/cm2. The latter result is consistent with the analysis of gain lengths and cavity losses presented.

    13. Biomimetic Crystallization of Calcium Carbonate Spherules with Controlled Surface Structures and Sizes by Double-Hydrophilic Block Copolymers (pages 541–545)

      S.-H. Yu, H. Cölfen, J. Hartmann and M. Antonietti

      Article first published online: 29 JUL 2002 | DOI: 10.1002/1616-3028(20020805)12:8<541::AID-ADFM541>3.0.CO;2-3

      Large CaCO3 spherules (see Figure) with controlled surface structures and sizes can be easily fabricated through a slow gas–liquid diffusion reaction at room temperature by using double-hydrophilic block copolymers (DHBCs) as crystal modifiers. The spherules have high potential as chromatography column packing materials due to their multiple calcite faces and huge size.