Small

Cover image for Vol. 2 Issue 6

June 2006

Volume 2, Issue 6

Pages 685–815

    1. Cover Picture: Core/Shell Fluorescent Silica Nanoparticles for Chemical Sensing: Towards Single-Particle Laboratories (Small 6/2006) (page 685)

      Andrew Burns, Prabuddha Sengupta, Tara Zedayko, Barbara Baird and Ulrich Wiesner

      Version of Record online: 25 APR 2006 | DOI: 10.1002/smll.200690023

      The cover picture illustrates quantitative chemical imaging of pH in mast cells facilitated by core/shell silica nanoparticle sensors incorporating two fluorescent dye species. These 70-nm particles maximize the exposure of the sensor dye in the outer silica shell, while sequestering the reference dye within the particle core to minimize perturbations. Ratiometric comparison of the sensor and reference fluorescence allows the pH to be measured down to the single-particle scale. Confocal fluorescence images of the red and green channels are shown superimposed on a bright-field image of the cell under investigation (inset) and were analyzed to yield the false-spectrum image of pH in various intracellular vesicles. For more information, please read the Communication “Core/Shell Fluorescent Silica Nanoparticles for Chemical Sensing: Towards Single-Particle Laboratories” by U. Wiesner and co-workers on page 723 ff.

    2. Semiconductor Nanowires: From Self-Organization to Patterned Growth (pages 700–717)

      Hong Jin Fan, Peter Werner and Margit Zacharias

      Version of Record online: 25 APR 2006 | DOI: 10.1002/smll.200500495

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      News on the wires: Nanowires have been fabricated either via self-organization or controlled assembly. Strategies for position-controlled and nanopatterned growth of semiconductor nanowire arrays are reviewed and discussed in terms of technical simplicity and the potential for larger-scale realization. Issues on nanowire-based devices are also addressed with a brief survey of recent advances.

    3. In Vitro Transcription and Protein Translation from Carbon Nanotube–DNA Assemblies (pages 718–722)

      Kaushal Rege, Gunaranjan Viswanathan, Guangyu Zhu, Aravind Vijayaraghavan, Pulickel M. Ajayan and Jonathan S. Dordick

      Version of Record online: 30 MAR 2006 | DOI: 10.1002/smll.200500465

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      DNA bound to single-walled carbon nanotubes retains its innate functional and structural properties, and therefore, can serve as the genetic template for gene transcription by RNA polymerase catalysis in the formation of mRNA (see figure). This mRNA is also fully functional and is used as the message for in vitro protein synthesis.

    4. Core/Shell Fluorescent Silica Nanoparticles for Chemical Sensing: Towards Single-Particle Laboratories (pages 723–726)

      Andrew Burns, Prabuddha Sengupta, Tara Zedayko, Barbara Baird and Ulrich Wiesner

      Version of Record online: 25 APR 2006 | DOI: 10.1002/smll.200600017

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      A fluorescent chemical sensor based upon a core/shell architecture of silica nanoparticles (see figure) is introduced. By covalent attachment of organic reference dyes within the core and sensor dyes in the outer shell, optimal sensor architectures can be realized. This paves the way for the development of highly functional particles with catalytic or synthetic abilities.

    5. Self-Assembly of Copper Micro/Nanoscale Parallel Wires by Electrodeposition on a Silicon Substrate (pages 727–731)

      Mingzhe Zhang, Guihong Zuo, Zhaocun Zong, Haiyong Cheng, Zhi He, Cunming Yang and Guangtian Zou

      Version of Record online: 29 MAR 2006 | DOI: 10.1002/smll.200500338

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      Arrays of straight copper wires can be deposited onto a silica layer (see image) by controlling the concentration of the CuSO4 electrolyte used. The copper wires are shown to contain nanograins of copper oxide, a consequence of the mechanism of their preparation. Wires with widths varying from 80 to 1200 nm suggest promise for applications in, amongst other realms, magnetic storage devices.

    6. Experimental Evidence of an Octahedron Nucleus in ZnS Tetrapods (pages 732–735)

      Jiangfeng Gong, Shaoguang Yang, Hongbo Huang, Junhong Duan, Hongwei Liu, Xiaoning Zhao, Rong Zhang and Youwei Du

      Version of Record online: 3 APR 2006 | DOI: 10.1002/smll.200500419

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      Four-by-four: ZnS tetrapods were directly synthesized from Zn and S vapors with a stainless steel network as the collecting substrate. Each branch has a triangular cross section connected to form a tetrapod structure (see TEM image). The branches have the wurtzite phase and the core has the zinc blende phase. The results provide direct evidence of the zinc blende octahedron nucleus model.

    7. Enhanced Secondary Electron Emission from Group III Nitride/ZnO Coaxial Nanorod Heterostructures (pages 736–740)

      Shu Ping Lau, Lei Huang, Siu Fung Yu, Huiying Yang, Jin Kyoung Yoo, Sung Jin An and Gyu-Chul Yi

      Version of Record online: 7 APR 2006 | DOI: 10.1002/smll.200500424

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      Needle work: AlN/ZnO and GaN/ZnO coaxial nanoneedle heterostructures (see TEM image) have a higher secondary electron emission (SEE) yield (σ) than thin films of AlN and GaN deposited on Si substrates. The dependence of the SEE on the incidence angle of the beam indicates that these heterostructures do not follow the power law. The σ value of the heterostructures is enhanced by the inherited nanostructure from the ZnO nanoneedle template.

    8. Quantum Dots on Gold: Electrodes For Photoswitchable Cytochrome c Electrochemistry (pages 741–743)

      Christian Stoll, Stefan Kudera, Wolfgang J. Parak and Fred Lisdat

      Version of Record online: 24 MAR 2006 | DOI: 10.1002/smll.200500441

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      A photoswitchable arrangement for direct electrochemistry of the redox protein cytochrome c can result from the application of CdSe/ZnS quantum dots on gold electrodes. “On/off” responses can be realized through photoexcitation of the quantum dots. Electrode illumination resulted in stepwise heterogeneous electron transfer from the electrode via the semiconductor particles to the heme proteins (see figure).

    9. Local Secondary-Electron Emission Spectra via Scanning Probe Energy Loss Spectroscopy (pages 744–746)

      Jinlong Yin, Adriano Pulisciano and Richard E. Palmer

      Version of Record online: 3 APR 2006 | DOI: 10.1002/smll.200500491

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      The magic of SPELS: Scanning probe energy loss spectroscopy (SPELS) can be viewed as a hybrid (see figure) between scanning tunneling microscopy (STM) and electron energy loss spectroscopy (EELS). As the spatial resolution of SPELS is in the 10-nm regime, the way is opened to true nanometer-scale band-structure measurements.

    10. Facile One-Pot Synthesis of Luminescent, Water-Soluble, and Biocompatible Glutathione-Coated CdTe Nanocrystals (pages 747–751)

      Huifeng Qian, Chaoqing Dong, Jifang Weng and Jicun Ren

      Version of Record online: 7 APR 2006 | DOI: 10.1002/smll.200500530

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      A shining example: We report a facile strategy to synthesize highly luminescent, water-soluble, and biocompatible CdTe nanocrystals by using the biomolecule glutathione as a stabilizer. The highest quantum yield obtained was above 60 % and their size-dependent emission ranged from 480 to 650 nm. The nanocrystals could be coupled with antibodies to prepare fluorescent probes for cell imaging (see figure).

    11. Solid-State Synthesis of Well-Defined Carbon Nanocapsules from Organometallic Precursors (pages 752–755)

      Dheeraj Jain, Andreas Winkel and René Wilhelm

      Version of Record online: 30 MAR 2006 | DOI: 10.1002/smll.200600004

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      To cap it all… The pyrolysis of a [CpFe(arene)]PF6 complex yielded new carbon nanocapsules in near-quantitative yield (see TEM image); the capsules contain an Fe–P composite material. The results show that the structure of the obtained material is highly dependent on the complex used in the pyrolysis experiments, and that pyrolyis parameters have to be carefully chosen in order to obtain the nanocapsules in pure form.

    12. Structural Effects of Iron Oxide Nanoparticles and Iron Ions on the Hydrothermal Carbonization of Starch and Rice Carbohydrates (pages 756–759)

      Xianjin Cui, Markus Antonietti and Shu-Hong Yu

      Version of Record online: 30 MAR 2006 | DOI: 10.1002/smll.200600047

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      A carbohydrate diet: Free iron ions and Fe2O3 nanoparticles have been employed to direct the hydrothermal carbonization of starch and rice under mild conditions (≤200 °C). Well-defined carbon nanostructures with various forms (see figure) can be conveniently synthesized in gram-scale quantities from these highly abundant starting materials.

    13. Patterning of Chemical Gradients with Submicrometer Resolution Using Edge-Spreading Lithography (pages 760–765)

      Matthias Geissler, Preeti Chalsani, Neil S. Cameron and Teodor Veres

      Version of Record online: 25 APR 2006 | DOI: 10.1002/smll.200600064

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      Edge-spreading lithography is used to assemble mercaptohexadecanoic acid (MHA) and octadecanethiol (ODT) molecules into gradient monolayer ring patterns on a Au substrate. Co-diffusion of both thiols over the surface of immobilized silica beads introduces a partial separation of the two species. Self-assembled monolayers (SAMs) with a gradient structure emerge from the edges of each bead on the Au substrate, as revealed by lateral force microscopy and the template-assisted assembly of nanoparticles (see picture).

    14. Adverse Effects of Citrate/Gold Nanoparticles on Human Dermal Fibroblasts (pages 766–773)

      Nadine Pernodet, Xiaohua Fang, Yuan Sun, Asya Bakhtina, Aditi Ramakrishnan, Jonathan Sokolov, Abraham Ulman and Miriam Rafailovich

      Version of Record online: 25 APR 2006 | DOI: 10.1002/smll.200500492

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      Gold is bad for you! Concerns are rising about future health problems due to the lack of safety regulations in nanoscale engineering. The effects of citrate/gold nanoparticles at different concentrations and exposure times on human dermal fibroblasts were studied (see confocal microscope image). The results suggest that the internal activities of the cell have been damaged.

    15. Crystallographic Order in Multi-Walled Carbon Nanotubes Synthesized in the Presence of Nitrogen (pages 774–784)

      Caterina Ducati, Krzystof Koziol, Steffi Friedrichs, Timothy J. V. Yates, Milo S. Shaffer, Paul A. Midgley and Alan H. Windle

      Version of Record online: 7 APR 2006 | DOI: 10.1002/smll.200500513

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      Made to order: Multi-walled carbon nanotubes synthesized by chemical vapor deposition from toluene/diazine have a high degree of internal order. The structure, defects, and morphology of the nanotubes were analyzed by advanced electron microscopy techniques. Bamboo- and weblike structures are formed (see energy-filtered TEM image). Nitrogen, which seems to be responsible for the dramatic structural order, segregates preferentially within the core of the nanotubes.

      Corrected by:

      Corrigendum: Crystallographic Order in Multi-Walled Carbon Nanotubes Synthesized in the Presence of Nitrogen

      Vol. 4, Issue 3, 306, Version of Record online: 26 FEB 2008

    16. Methotrexate-Immobilized Poly(ethylene glycol) Magnetic Nanoparticles for MR Imaging and Drug Delivery (pages 785–792)

      Nathan Kohler, Conroy Sun, Alex Fichtenholtz, Jonathan Gunn, Chen Fang and Miqin Zhang

      Version of Record online: 25 APR 2006 | DOI: 10.1002/smll.200600009

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      Iron oxide nanoparticles immobilized with methotrexate, a widely used anti-cancer drug, are seen in the cellular cytoplasm of a 9L cell under TEM (left). The internalization of the nanoparticle conjugates by 9L cells is also identified with MR phantom imaging by negative-contrast enhancement (right). The electron diffraction pattern confirms that the nanoparticles retain their crystalline structure after 144 h in the cell.

    17. The Stability and Functionality of Chemically Crosslinked Microtubules (pages 793–803)

      Andrew K. Boal, Hernesto Tellez, Susan B. Rivera, Nicholas E. Miller, George D. Bachand and Bruce C. Bunker

      Version of Record online: 25 APR 2006 | DOI: 10.1002/smll.200500381

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      Tube connections: A variety of bifunctional crosslinking agents that target amine residues (for example, sebacic acid bis(N-succinimidyl) ester, see structure) have been explored for stabilizing microtubules. The formation of intertubulin crosslinks produces crosslinked microtubules (see figure) with structural and functional lifetimes that can be up to four times as long as those achieved with taxol stabilization.

    18. Room-Temperature Ferromagnetism in Doped Face-Centered Cubic Fe Nanoparticles (pages 804–809)

      Bingqing Wei, Mutsuhiro Shima, Ranjit Pati, Saroj K. Nayak, David J. Singh, Renzhi Ma, Yubao Li, Yoshio Bando, Saburo Nasu and Pulickel M. Ajayan

      Version of Record online: 7 APR 2006 | DOI: 10.1002/smll.200500436

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      About face: Fe–C alloys and face-centered cubic (fcc) Fe are not ferromagnetic under ambient conditions, but ferromagnetism has been observed in elongated nanoparticles of fcc Fe formed inside carbon nanotubes (see figure). The magnetic moment and hyperfine fields in 57Fe Mössbauer spectroscopy are explained by C atoms at octahedral interstitial sites in an expanded fcc Fe lattice.

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      Preview: Small 6/2006 (page 815)

      Version of Record online: 25 APR 2006 | DOI: 10.1002/smll.200690026

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