Small

Cover image for Vol. 2 Issue 7

July 2006

Volume 2, Issue 7

Pages 817–927

    1. Cover Picture: A Simple Miniaturization Protocol to Produce Multicomponent Micro- and Nanostructures (Small 7/2006) (page 817)

      Zhenqian Ouyang, Li Tan, Maozi Liu, Onkar S. Judge, Xiaodong Zhang, Hai Li, Jun Hu, Timothy E. Patten and Gang-yu Liu

      Version of Record online: 24 MAY 2006 | DOI: 10.1002/smll.200690027

      The cover picture illustrates a new method of nanolithography, stepwise contraction and adsorption nanolithography (SCAN), that should in principle be able to extend the advantages of multicomponent microfabrication into smaller dimensions, as well as to reach the spatial precision afforded by scanning probe lithography. The left column depicts the balloon analogy of SCAN, in which the writing “small” on the balloon is miniaturized upon deflation. The right column presents a laser confocal micrograph of a two-component array (red and green fluorescent dyes) generated after one and five SCAN cycles (top and bottom, respectively) in 2D reduction. Scale bars are 500 and 50 μm, respectively. For more information, please read the Communication “A Simple Miniaturization Protocol to Produce Multicomponent Micro- and Nanostructures” by G.-y. Liu and co-workers on page 884 ff.

    2. Surface-Tension-Driven Patterning: Combining Tailored Physical Self-Organization with Microfabrication Methods (pages 832–834)

      Kahp Y. Suh

      Version of Record online: 5 MAY 2006 | DOI: 10.1002/smll.200600121

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      Small features: One of the great current challenges is to find new techniques that reliably further reduce the scale at which patterns can be reproduced for the electronics industry, amongst others. A recent study provides a major advance in controlling surface-tension-driven self-organization in combination with a traditional microfabrication method to produce regularly spaced line patterns in an evaporating thin film through guided evaporation and dewetting (see figure).

    3. NaNaX 2: A Conference Devoted to “Nanoscience with Nanocrystals” (pages 836–838)

      Wolfgang J. Parak

      Version of Record online: 5 MAY 2006 | DOI: 10.1002/smll.200600089

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      Focus on nanocrystals: Earlier this year, the second in a series of conferences on “Nanoscience with Nanocrystals” (NaNaX 2) took place at the wonderful alpine venue of Grenoble-Autrans (see picture). A wide variety of discussion surrounding nanocrystal synthesis, characterization, functionalization, and (bio)application epitomized the importance and potential that exists for these materials in future technologies.

    4. Microchip Technology for Automated and Parallel Patch-Clamp Recording (pages 840–846)

      Andrea Brüggemann, Sonja Stoelzle, Michael George, Jan C. Behrends and Niels Fertig

      Version of Record online: 24 MAY 2006 | DOI: 10.1002/smll.200600083

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      Biomedical advances: Ion channels, which mediate the flow of current within cells, play a significant role in our physiology, and are important drug targets. The patch-clamp technique is the preferred method of study for ion channels but is experimentally demanding. This Concept article looks at how microchip technology is providing new techniques for high-throughput drug screening on ion channels (the picture shows the “patchliner”, an instrument employing the new technology).

    5. Nanopatterned Polymer Brushes by Combining AFM Anodization Lithography with Ring-Opening Metathesis Polymerization in the Liquid and Vapor Phase (pages 848–853)

      Woo-Kyung Lee, Kenneth C. Caster, Jeonghan Kim and Stefan Zauscher

      Version of Record online: 24 MAY 2006 | DOI: 10.1002/smll.200500470

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      Nanopatterned polymer structures are fabricated on SiO2 by combining AFM anodization nanolithography (see upper figure) with surface-initiated ring-opening metathesis polymerization (ROMP, lower figure). This process offers a powerful set of tools for the fabrication of highly functional polymer brushes. The simplicity and speed of anodization lithography promises its massively parallel implementation using anodization stamps. The fabrication approach is universal and can easily be adapted to other surface initiated polymerizations.

    6. Fabrication of Jingle-Bell-Shaped Core–Shell Nanoparticulate Films and Molecular-Size-Responsive Photoluminescence Quenching of Cadmium Sulfide Cores (pages 854–858)

      Kentaro Iwasaki, Tsukasa Torimoto, Tamaki Shibayama, Tomohiro Nishikawa and Bunsho Ohtani

      Version of Record online: 5 MAY 2006 | DOI: 10.1002/smll.200500512

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      Size-selective photoetching of multilayered films of SiO2-coated CdS nanoparticles induces a blue shift in their diffuse reflectance spectra, indicating the formation of jingle-bell-shaped CdS/SiO2 core–shell nanoparticles in the film (see figure). Photoluminescence quenching of the as-photoetched films is attributed to the molecular-size-selective penetration of the quencher from the bulk solution to the void space through the pores of the SiO2 shell.

    7. Preparation of Monodisperse, Submicrometer Carbon Spheres by Pyrolysis of Melamine–Formaldehyde Resin (pages 859–863)

      Bettina Friedel and Siegmund Greulich-Weber

      Version of Record online: 24 MAY 2006 | DOI: 10.1002/smll.200500516

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      Tiny black pearls: Monodisperse, smooth carbon spheres (100–1000 nm in diameter) are prepared via the synthesis and subsequent carbonization of micrometer-sized particles of melamine–formaldehyde resin (see SEM image). The gradual transition of the copolymer to carbon results in uniform shrinkage without deformation of the spheres. These spheres provide an alternative in applications where polymeric or silica particles are unsuitable.

    8. Dendrite-Like Self-Assembly of Magnetite Nanoparticles on Porous Silicon (pages 864–869)

      Sivakumar Balakrishnan, Yurii K. Gun'ko, Tatiana S. Perova, Robert A. Moore, Munuswamy Venkatesan, Alexios P. Douvalis and Paul Bourke

      Version of Record online: 9 MAY 2006 | DOI: 10.1002/smll.200500521

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      Self-organization of nanoparticles into hierarchical assemblies is very important for the development of “bottom-up” approaches in nanotechnology. Porous silicon can be used as a substrate to prepare fractal-like magnetite nanoparticle assemblies, which add a new dimension to nanoscale spin electronics as each small portion of the fractal can be viewed as a reduced-scale replica of the whole (see figure).

    9. pH-Selective Synthesis of Monodisperse Nanoparticles and 3D Dendritic Nanoclusters of CTAB-Stabilized Platinum for Electrocatalytic O2 Reduction (pages 870–873)

      M. Habib Ullah, Won-Sub Chung, Il Kim and Chang-Sik Ha

      Version of Record online: 4 MAY 2006 | DOI: 10.1002/smll.200600071

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      Playing the platinum card: Monodisperse Pt nanoparticles and 3D dendritic Pt nanoclusters (see image), stabilized by cetyltrimethylammonium bromide, were synthesized selectively at pH values of ≈7 and ≈1.7, respectively. Both Pt species, which can be immobilized electrochemically onto glassy carbon electrodes, possess excellent catalytic activity toward the reduction of O2.

    10. Cation-Controlled Aqueous Dispersions of Alginic-Acid-Wrapped Multi-Walled Carbon Nanotubes (pages 874–878)

      Yu Liu, Peng Liang, Heng-Yi Zhang and Dong-Sheng Guo

      Version of Record online: 5 MAY 2006 | DOI: 10.1002/smll.200600099

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      It′s a wrap! Alginic acid can efficiently solubilize multi-walled carbon nanotubes (MWCNTs) in aqueous solution (see figure). The addition of cations to the alginic-acid-wrapped MWCNTs results in their precipitation from aqueous solution. However, subsequent treatment with EDTA selectively redispersed those MWCNTs that were precipitated with Zn2+, Ni2+, Co2+, Pb2+, La3+, and Eu3+ ions in water.

    11. A Strategy for the Synthesis of Transition-Metal Nanoparticles and their Transfer between Liquid Phases (pages 879–883)

      Dongbin Zhao, Zhaofu Fei, Wee Han Ang and Paul J. Dyson

      Version of Record online: 24 MAY 2006 | DOI: 10.1002/smll.200500317

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      Phasing out: Nanoparticles can be stabilized by an ionic liquid polymer (ILP) composed of imidazolium units incorporating a hydrophobic benzyl group. The resulting gold, platinum, and palladium nanoparticles can be efficiently transferred from water to ionic liquids by exchange of the chloride anion of the ILP with the anion of the ionic liquid (see picture).

    12. A Simple Miniaturization Protocol to Produce Multicomponent Micro- and Nanostructures (pages 884–887)

      Zhenqian Ouyang, Li Tan, Maozi Liu, Onkar S. Judge, Xiaodong Zhang, Hai Li, Jun Hu, Timothy E. Patten and Gang-yu Liu

      Version of Record online: 9 MAY 2006 | DOI: 10.1002/smll.200500420

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      Small gets smaller! The figure shows a balloon analogy of stepwise contraction and adsorption nanolithography (SCAN) and a laser confocal fluorescence micrograph of a two-component array (red and green fluorescent dyes) generated after the first (above) and fifth (below) cycles of SCAN (scale bars: 500 and 50 μm, respectively). In principle, SCAN should be able to extend the advantages of microfabrication into the nanometer domain.

    13. Self-Organization of Anodic Nanotubes on Two Size Scales (pages 888–891)

      Hiroaki Tsuchiya, Jan M. Macak, Andrei Ghicov and Patrik Schmuki

      Version of Record online: 24 MAY 2006 | DOI: 10.1002/smll.200600035

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      Close-packed tubes: The right choice of metal alloy substrate combined with an adapted anodization can result in self-organized, uniformly aligned nanotubes in two discrete size ranges as is shown in this communication. Using this technique, mixed-oxide nanotubes with novel shapes (see figure) have been obtained.

    14. Nanotemplated Crystallization of Organic Molecules (pages 892–897)

      Jérôme Plain, Antoine Pallandre, Bernard Nysten and Alain M. Jonas

      Version of Record online: 9 MAY 2006 | DOI: 10.1002/smll.200600059

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      Crystal clear: The growth of organic crystals was templated down to 60 nm by chemical nanopatterns, providing access to polycrystalline nanosquares and nanolines. Also, depending on the attractive or repulsive nature of the background of the nanopatterns, crystal nucleation occurred either at the edges of the nanofeatures or 50–70 nm away from them, respectively, giving rise to the formation of crystalline nanocorrals for short crystallization times (see figure).

    15. Incorporating CdTe Nanocrystals into Polystyrene Microspheres: Towards Robust Fluorescent Beads (pages 898–901)

      Yunhua Yang, Zhongkai Wen, Yuping Dong and Mingyuan Gao

      Version of Record online: 24 MAY 2006 | DOI: 10.1002/smll.200600086

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      On the Q-dots: Fluorescent polystyrene beads loaded with CdTe quantum dots exhibit excellent pH-independent fluorescence and antisolvent properties (see figure). The beads, which were prepared by miniemulsion polymerization using polymerizable surfactants as both an emulsifier and a phase-transfer agent, offer excellent photostability to the contained CdTe quantum dots due to the hydrophobic nature and compact structure of the polystyrene matrix.

    16. Critical Oxide Thickness for Efficient Single-Walled Carbon Nanotube Growth on Silicon Using Thin SiO2 Diffusion Barriers (pages 902–909)

      Jason M. Simmons, Beth M. Nichols, Matthew S. Marcus, Olivia M. Castellini, Robert J. Hamers and Mark A. Eriksson

      Version of Record online: 9 MAY 2006 | DOI: 10.1002/smll.200600095

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      The growth of single-walled carbon nanotubes on silicon substrates is inhibited by catalyst poisoning by the formation of a noncatalytic silicide (see figure, top left), however ultrathin SiO2 layers can be used to enable high-yield nanotube growth. Due to the high growth temperature, diffusion of an Fe or Ni catalyst through the oxide layer leads to a minimum required oxide thickness. A 4-nm SiO2 layer permits nanotube growth (bottom), however a 3-nm oxide layer does not (top right).

    17. Simple Method for the Stretching and Alignment of Single Adsorbed Synthetic Polycations (pages 910–916)

      Vera Bocharova, Anton Kiriy, Manfred Stamm, Francois Stoffelbach, Robert Jérôme and Christophe Detrembleur

      Version of Record online: 4 MAY 2006 | DOI: 10.1002/smll.200500490

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      Chain letter: The chains of isolated positively charged macromolecules deposited onto mica surfaces by spin-coating exhibit alignment in their length and conformation in the presence of octylamine; such changes can be directly measured by atomic force microscopy (see figure), and lead to direct measurement of the contour length and molar mass of the macromolecules.

    18. Thermosensitive Y-Shaped Micelles of Poly(oleic acid-Y-N-isopropylacrylamide) for Drug Delivery (pages 917–923)

      Yong-Yong Li, Xian-Zheng Zhang, Gwang-Chol Kim, Han Cheng, Si-Xue Cheng and Ren-Xi Zhuo

      Version of Record online: 9 MAY 2006 | DOI: 10.1002/smll.200600041

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      Why the answer is Y… A Y-shaped copolymer P(OA-Y-NIPAAm) comprised of two hydrophobic poly(oleic acid) segments and one hydrophilic poly(N-isopropylacrylamide) segment was designed and synthesized to prepare thermosensitive nanospheric micelles via self-assembly in aqueous solution (see figure). The P(OA-Y-NIPAAm) micelles demonstrate excellent controlled drug-release properties with good temperature sensitivity. Cytotoxicity studies show that the Y-shaped copolymers exhibit good biocompatibility.

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      Preview: Small 7/2006 (page 927)

      Version of Record online: 24 MAY 2006 | DOI: 10.1002/smll.200690030

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