Advanced Functional Materials

Cover image for Vol. 11 Issue 2

April, 2001

Volume 11, Issue 2

Pages 87–150

    1. Unique Electro-Optical Properties of Liquid Crystals Designed for Molecular Optics (pages 87–94)

      S. T. Lagerwall, A. Dahlgren, P. Jägemalm, P. Rudquist, K. D’havé, H. Pauwels, R. Dabrowski and W. Drzewinski

      Version of Record online: 17 APR 2001 | DOI: 10.1002/1616-3028(200104)11:2<87::AID-ADFM87>3.0.CO;2-E

      By proper molecular design, a new generic class of antiferroelectric materials have been developed and tested. Their optical properties make them unique not only among liquid crystals but among electro-optical materials in general. The design of this generic class, which is called orthoconic, also gives an illustrative example of the physical meaning of the addition of tensorial properties (see Figure).

    2. The Race for the Photonic Chip: Colloidal Crystal Assembly in Silicon Wafers (pages 95–104)

      G. A. Ozin and S. M. Yang

      Version of Record online: 17 APR 2001 | DOI: 10.1002/1616-3028(200104)11:2<95::AID-ADFM95>3.0.CO;2-O

      Recent developments in the creation of 3D photonic crystals and how these have led to in-wafer patterned colloidal crystals are reviewed. Single-crystal micrometer-scale features embedded within a single crystal silicon wafer (see Figure) are shown and discussed. Two processes for growing opal-patterned chips (one based on microfluidic, the other on spin-coating driven self-assembly) are described.

    3. Optically Functional Zeolites: Evaluation of UV and VUV Stimulated Photoluminescence Properties of Ce3+- and Tb3+-doped Zeolite X (pages 105–110)

      T. Jüstel, D. U. Wiechert, C. Lau, D. Sendor and U. Kynast

      Version of Record online: 17 APR 2001 | DOI: 10.1002/1616-3028(200104)11:2<105::AID-ADFM105>3.0.CO;2-J

      The optical properties of Tb3+/Ce3+ doped zeolites are elucidated with emphasis on ultraviolet (UV) and vacuum ultraviolet (VUV) excitation and luminescence. Ce3+-sensitized Tb3+ emission with quantum yields of 85 % may be obtained. The capability of the zeolite host lattice to transfer excitation energy to the sensitizer or rare earth ions may be of immediate interest in applications, such as Xe2* excimer discharge-driven lighting systems, in which the primary VUV radiation needs to be down-converted with high efficiency.

    4. Full-Color Phosphors from Amine-Functionalized Crosslinked Hybrids Lacking Metal Activator Ions (pages 111–115)

      L. D. Carlos, R A. Sá Ferreira, V. De Zea Bermudez and S. J. L. Ribeiro

      Version of Record online: 17 APR 2001 | DOI: 10.1002/1616-3028(200104)11:2<111::AID-ADFM111>3.0.CO;2-V

      Sol–gel derived hybrids that contain –OCH2-CH2– repeat units, which are grafted onto a siliceous backbone by urea and urethane bridges, have been prepared. The white light photoluminescence spectra of these materials result from longer lived emissions that originate in the NH groups of the urea and urethane groups. The real time-dependence of the white-light emission is shown in the Figure.

    5. Water Vapor and Oxygen Degradation Mechanisms in Organic Light Emitting Diodes (pages 116–121)

      M. Schaer, F. Nüesch, D. Berner, W. Leo and L. Zuppiroli

      Version of Record online: 17 APR 2001 | DOI: 10.1002/1616-3028(200104)11:2<116::AID-ADFM116>3.0.CO;2-B

      What exactly degrades organic light emitting diodes (OLEDs)? The authors separately investigate the effect of oxygen, which locally oxidizes both the device cathode and the electro-active layer, and water vapor, which is more detrimental and deteriorates the electrode’s physical structure. The Figure juxtaposes the two mechanisms.

    6. Core–Shell Colloids and Hollow Polyelectrolyte Capsules Based on Diazoresins (pages 122–128)

      I. Pastoriza-Santos, B. Schöler and F. Caruso

      Version of Record online: 17 APR 2001 | DOI: 10.1002/1616-3028(200104)11:2<122::AID-ADFM122>3.0.CO;2-N

      Stable and well-defined hollow polyelectrolyte microcapsules (see Figure and cover picture) are fabricated by the layer-by-layer self-assembly of cross-linkable polyelectrolytes onto colloid particles and subsequently removing the template core. The covalent cross-linked structures provide colloidal materials that exhibit high mechanical stability and that are highly resistant to solvent etching.

    7. Spherical MSU-1 Mesoporous Silica Particles Tuned for HPLC (pages 129–135)

      C. Boissière, M. Kümmel, M. Persin, A. Larbot and E. Prouzet

      Version of Record online: 17 APR 2001 | DOI: 10.1002/1616-3028(200104)11:2<129::AID-ADFM129>3.0.CO;2-W

      The high surface area and low pore size of MSU-1 silica are of advantage for high-performance liquid chromatography (HPLC) applications. Employing MSU-1 as the stationary phase rather than the silica particles normally used, very high resolution between the elution peaks is observed, even between almost identical solutes such as biphenyl and naphthalene (see Figure: dashed line is raw MSU-1 powder, solid line is the same material after ultrasonication).

    8. Limitations in Producing Nanocrystals Using Reverse Micelles as Nanoreactors (pages 136–139)

      D. Ingert and M.-P. Pileni

      Version of Record online: 17 APR 2001 | DOI: 10.1002/1616-3028(200104)11:2<136::AID-ADFM136>3.0.CO;2-3

      The use of reverse micelles to produce nanomaterials is one of the techniques largely employed. The size of the droplet affects the nanocrystal size, whereby the main parameter involved in controlling the size is the structure of the water droplet. The Figure shows the EXAFS results confirming that CdTe nanocrystals with 3.5 nm diameter have the same composition as bulk phase CdTe.

    9. Self-Assembled Monolayers on Gold for the Fabrication of Radioactive Stents (pages 140–146)

      K. J. C. van Bommel, A. Friggeri, D. Mateman, F. A. J. Geurts, K. G. C. van Leerdam, W. Verboom, F. C. J. M. van Veggel and D. N. Reinhoudt

      Version of Record online: 17 APR 2001 | DOI: 10.1002/1616-3028(200104)11:2<140::AID-ADFM140>3.0.CO;2-N

      Radioactive self-assembled monolayers (SAMs) are deposited on gold surfaces for the fabrication of stents, which can be used in the treatment of restenosis. Innovative and easily applicable methods are described and complete studies of the properties of these materials (including stability tests) have been carried out. The two approaches described in this paper present viable possibilities for the delivery of therapeutical doses of local radiation.

    10. Microcontact Printing with Heavyweight Inks (pages 147–150)

      M. Liebau, J. Huskens and D. N. Reinhoudt

      Version of Record online: 17 APR 2001 | DOI: 10.1002/1616-3028(200104)11:2<147::AID-ADFM147>3.0.CO;2-W

      Self-assembled monolayers (SAMs) on gold of thioether derivatives with 1–4 thioether moieties have been used for microcontact printing (see Figure). The quality of the SAMs of thioether adsorbates with three or four thioether moieties, both regarding monolayer order and etch resistance, is comparable to SAMs of decanethiol. The use of these materials prevents the diffusion of the ink, and large areas can be printed reliably.