Thursday, December 23, 2010

Hot off the presses! Jan 01 UNKNOWN

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Latest Articles Include:

  • Chemistry on a global stage
    - UNKNOWN 6(1):1 (2011)
    Nature Nanotechnology | Editorial Chemistry on a global stage Journal name:Nature NanotechnologyVolume: 6,Page:1Year published:(2011)DOI:doi:10.1038/nnano.2011.276Published online23 December 2010 Read the full article * FREE access with registration Register now * Already have a Nature.com account? Login Additional access options: * Use a document delivery service * Login via Athens * Purchase a site license * Institutional access * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. The International Year of Chemistry gives chemists a chance to raise the profile of their subject. View full text Read the full article * FREE access with registration Register now * Already have a Nature.com account? Login Additional access options: * Use a document delivery service * Login via Athens * Purchase a site license * Institutional access * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. Additional data
  • Science in the service of citizens and consumers
    - UNKNOWN 6(1):3-4 (2011)
    Nature Nanotechnology | Thesis Science in the service of citizens and consumers * Chris Toumey1 Contact Chris Toumey Search for this author in: * NPG journals * PubMed * Google ScholarJournal name:Nature NanotechnologyVolume: 6,Pages:3–4Year published:(2011)DOI:doi:10.1038/nnano.2011.263Published online23 December 2010 Read the full article * Instant access to this article: US$32Buy now * Subscribe to Nature Nanotechnology for full access: SubscribeLogin for existing subscribers Additional access options: * Use a document delivery service * Login via Athens * Purchase a site license * Institutional access * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. A new approach to public knowledge of science focuses on what the public want to know rather than what scientists think they should know. Chris Toumey reports. View full text Subject terms: * Ethical, legal and other societal issues Author information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Affiliations * Chris Toumey is at the University of South Carolina NanoCenter. Toumey@mailbox.sc.edu Read the full article * Instant access to this article: US$32Buy now * Subscribe to Nature Nanotechnology for full access: SubscribeLogin for existing subscribers Additional access options: * Use a document delivery service * Login via Athens * Purchase a site license * Institutional access * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. Additional data
  • Our choice from the recent literature
    - UNKNOWN 6(1):5 (2011)
    Nature Nanotechnology | Research Highlights Our choice from the recent literature Journal name:Nature NanotechnologyVolume: 6,Page:5Year published:(2011)DOI:doi:10.1038/nnano.2011.269Published online23 December 2010 Read the full article * Instant access to this article: US$32Buy now * Subscribe to Nature Nanotechnology for full access: SubscribeLogin for existing subscribers Additional access options: * Use a document delivery service * Login via Athens * Purchase a site license * Institutional access * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. © 2010 ACS Nano Lett. doi:10.1021/nl1033304 (2010) View full text Read the full article * Instant access to this article: US$32Buy now * Subscribe to Nature Nanotechnology for full access: SubscribeLogin for existing subscribers Additional access options: * Use a document delivery service * Login via Athens * Purchase a site license * Institutional access * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. Additional data
  • Scanning tunnelling microscopy: Closing in on molecular junctions
    - UNKNOWN 6(1):7-8 (2011)
    Nature Nanotechnology | News and Views Scanning tunnelling microscopy: Closing in on molecular junctions * Andreas Heinrich1 Contact Andreas Heinrich Search for this author in: * NPG journals * PubMed * Google ScholarJournal name:Nature NanotechnologyVolume: 6,Pages:7–8Year published:(2011)DOI:doi:10.1038/nnano.2011.266Published online23 December 2010 Read the full article * Instant access to this article: US$18Buy now * Subscribe to Nature Nanotechnology for full access: SubscribeLogin for existing subscribers Additional access options: * Use a document delivery service * Login via Athens * Purchase a site license * Institutional access * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. Contacts between a single molecule and a metal electrode can be good or bad depending on the number of metal atoms that are in direct contact with the molecule. View full text Subject terms: * Electronic properties and devices * Surface patterning and imaging Author information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Affiliations * Andreas Heinrich is in the IBM Research Division, Almaden Research Center, San Jose, California 95120, USA. heinrich@almaden.ibm.com Read the full article * Instant access to this article: US$18Buy now * Subscribe to Nature Nanotechnology for full access: SubscribeLogin for existing subscribers Additional access options: * Use a document delivery service * Login via Athens * Purchase a site license * Institutional access * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. Additional data
  • Nanoelectronics: Graphene gets a better gap
    - UNKNOWN 6(1):8-9 (2011)
    Nature Nanotechnology | News and Views Nanoelectronics: Graphene gets a better gap * Stephan Roche1 Contact Stephan Roche Search for this author in: * NPG journals * PubMed * Google ScholarJournal name:Nature NanotechnologyVolume: 6,Pages:8–9Year published:(2011)DOI:doi:10.1038/nnano.2011.262Published online23 December 2010 Read the full article * Instant access to this article: US$18Buy now * Subscribe to Nature Nanotechnology for full access: SubscribeLogin for existing subscribers Additional access options: * Use a document delivery service * Login via Athens * Purchase a site license * Institutional access * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. Graphene nanoribbons with low defect densities and large energy gaps can be fabricated by chemically unzipping carbon nanotubes and annealing the result. View full text Subject terms: * Electronic properties and devices * Synthesis and processing Author information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Affiliations * Stephan Roche is at the Catalan Institute of Nanotechnology (ICN-ICREA) and CIN2, Campus UAB, 08193, Bellaterra, Barcelona, Spain. stephan.roche@icn.cat Read the full article * Instant access to this article: US$18Buy now * Subscribe to Nature Nanotechnology for full access: SubscribeLogin for existing subscribers Additional access options: * Use a document delivery service * Login via Athens * Purchase a site license * Institutional access * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. Additional data
  • Quantum computing: Solid-state spins survive
    - UNKNOWN 6(1):9-11 (2011)
    Nature Nanotechnology | News and Views Quantum computing: Solid-state spins survive * Michael J. Biercuk1 Contact Michael J. Biercuk Search for this author in: * NPG journals * PubMed * Google Scholar * David J. Reilly1 Contact David J. Reilly Search for this author in: * NPG journals * PubMed * Google Scholar * AffiliationsJournal name:Nature NanotechnologyVolume: 6,Pages:9–11Year published:(2011)DOI:doi:10.1038/nnano.2011.261Published online23 December 2010 Read the full article * Instant access to this article: US$18Buy now * Subscribe to Nature Nanotechnology for full access: SubscribeLogin for existing subscribers Additional access options: * Use a document delivery service * Login via Athens * Purchase a site license * Institutional access * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. Quantum-control pulse sequences can suppress errors and significantly extend the lifetimes of spin-based quantum bits in solid-state devices. View full text Subject terms: * Nanomagnetism and spintronics * Quantum information Author information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Affiliations * Michael J. Biercuk and David J. Reilly are in the School of Physics, University of Sydney, New South Wales 2006, Australia. michael.biercuk@sydney.edu.au; david.reilly@sydney.edu.au Read the full article * Instant access to this article: US$18Buy now * Subscribe to Nature Nanotechnology for full access: SubscribeLogin for existing subscribers Additional access options: * Use a document delivery service * Login via Athens * Purchase a site license * Institutional access * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. Additional data
  • Nanobiotechnology: Nanoparticle coronas take shape
    - UNKNOWN 6(1):11-12 (2011)
    Nature Nanotechnology | News and Views Nanobiotechnology: Nanoparticle coronas take shape * Marco P. Monopoli1 Contact Marco P. Monopoli Search for this author in: * NPG journals * PubMed * Google Scholar * Francesca Baldelli Bombelli1 Contact Francesca Baldelli Bombelli Search for this author in: * NPG journals * PubMed * Google Scholar * Kenneth A. Dawson1 Contact Kenneth A. Dawson Search for this author in: * NPG journals * PubMed * Google Scholar * AffiliationsJournal name:Nature NanotechnologyVolume: 6,Pages:11–12Year published:(2011)DOI:doi:10.1038/nnano.2011.267Published online23 December 2010 Read the full article * Instant access to this article: US$18Buy now * Subscribe to Nature Nanotechnology for full access: SubscribeLogin for existing subscribers Additional access options: * Use a document delivery service * Login via Athens * Purchase a site license * Institutional access * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. Understanding the impact of nanomaterials on human health will require more detailed knowledge about the protein corona that surrounds nanoparticles in biological environments. View full text Subject terms: * Nanomedicine * Nanoparticles Author information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Affiliations * Marco P. Monopoli, Francesca Baldelli Bombelli and Kenneth A. Dawson are in the Centre for BioNano Interactions, University College Dublin, Belfield, Dublin 4, Ireland. marco.monopoli@cbni.ucd.ie; francesca.baldelli@cbni.ucd.ie; kenneth.a.dawson@cbni.ucd.ie Read the full article * Instant access to this article: US$18Buy now * Subscribe to Nature Nanotechnology for full access: SubscribeLogin for existing subscribers Additional access options: * Use a document delivery service * Login via Athens * Purchase a site license * Institutional access * British Library Document Supply Centre * Infotrieve * Thompson ISI Document Delivery * You can also request this document from your local library through inter-library loan services. Additional data
  • Nanotechnological strategies for engineering complex tissues
    - UNKNOWN 6(1):13-22 (2011)
    Nature Nanotechnology | Review Nanotechnological strategies for engineering complex tissues * Tal Dvir1, 2 Search for this author in: * NPG journals * PubMed * Google Scholar * Brian P. Timko2, 3 Search for this author in: * NPG journals * PubMed * Google Scholar * Daniel S. Kohane2 Search for this author in: * NPG journals * PubMed * Google Scholar * Robert Langer1 Contact Robert Langer Search for this author in: * NPG journals * PubMed * Google Scholar * Affiliations * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Pages:13–22Year published:(2011)DOI:doi:10.1038/nnano.2010.246Published online12 December 2010 Abstract * Abstract * Author information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Tissue engineering aims at developing functional substitutes for damaged tissues and organs. Before transplantation, cells are generally seeded on biomaterial scaffolds that recapitulate the extracellular matrix and provide cells with information that is important for tissue development. Here we review the nanocomposite nature of the extracellular matrix, describe the design considerations for different tissues and discuss the impact of nanostructures on the properties of scaffolds and their uses in monitoring the behaviour of engineered tissues. We also examine the different nanodevices used to trigger certain processes for tissue development, and offer our view on the principal challenges and prospects of applying nanotechnology in tissue engineering. View full text Subject terms: * Nanobiotechnology * Nanomaterials * Nanomedicine Figures at a glance * Figure 1: An example of a tissue engineering concept that involves seeding cells within porous biomaterial scaffolds. , Cells are isolated from the patient and may be cultivated () in vitro on two-dimensional surfaces for efficient expansion. , Next, the cells are seeded in porous scaffolds together with growth factors, small molecules, and micro- and/or nanoparticles. The scaffolds serve as a mechanical support and a shape-determining material, and their porous nature provides high mass transfer and waste removal. , The cell constructs are further cultivated in bioreactors to provide optimal conditions for organization into a functioning tissue. , Once a functioning tissue has been successfully engineered, the construct is transplanted on the defect to restore function. * Figure 2: The information provided to cells by the extracellular matrix (ECM). , ECM fibres provide cells with topographical features that trigger morphogenesis. Adhesion proteins such as fibronectin and laminin located on the fibres interact with the cells through their transmembrane integrin receptors to initiate intracellular signalling cascades, which affect most aspects of cell behaviour. Polysaccharides such as hyaluronic acid and heparan sulphate act as a compression buffer against the stress, or serve as a growth factor depot. , Illustrations of the heart, liver and bone at the level of organ (left) and tissue and cell/matrix interaction (centre), followed by scanning electron micrographs of engineered scaffolds (right). The ECMs of various tissues have different composition and spatial organization of molecules to maintain specific tissue morphologies. For example (), the ECM of muscle tissues, such as the heart, forces the heart cells (cardiomyocytes) to couple mechanically to each other and to form elongated and aligned cell bundles that cre! ate an anisotropic syncytium. Nanogrooved surfaces (SEM image) are suitable matrices for cardiac tissue engineering because they force cardiomyocytes to align. , Cells composing epithelial tissues are polarized and contact three types of surfaces for efficient mass transfer: the ECM, other cells and a lumen. Nanofibres modified with surface molecules can promote cell adhesion and tissue polarity (SEM images). , Bone is a nanocomposite material consisting primarily of a collagen-rich organic matrix and inorganic hydroxyapatite nanocrystallites, which serve as a chelating agent for mineralization of osteoblasts. The scaffold structure (SEM image), stiffness and hydroxyapatite nanopatterning on the surface (inset) can enhance osteoblast spreading and bone tissue formation. SEM images reproduced with permission from: , ref. 56, © 2010 NAS; , ref. 59, © 2009 Elsevier; , ref. 65, © 2010 Elsevier. * Figure 3: Recreating ECM components using nanoscale tools. , ECM nanofibres produced by electrospinning polymeric fibres contain nanoparticles that release epidermal growth factor (green) and bovine serum albumin (red) in parallel. , Self-assembled peptide amphiphile nanofibres. , Alginate scaffolds containing short motifs of ECM adhesion proteins such as RGD encouraged mesenchymal stem cells to spread and attach to the matrix (), whereas on unmodified scaffolds () only cell–cell interactions were seen (collagen fibres, green; nuclei, red). , Epithelial cells respond to nanopatterning by alignment and elongation along the grating axis. , On smooth substrates, cells are mostly rounded. Figures reproduced with permission from: , ref. 28, © 2009 Wiley; , ref. 32, © 2009 AAAS; and , ref. 42, © 2009 Elsevier; and , ref. 48, © 2003 Company of Biologists. * Figure 4: Nanodevices in tissue engineering. , Three-dimensional, free-standing nanowire transistor probe for electrical recording. The probe is composed of a kinked nanowire (yellow arrow) and a flexible substrate material. The device is used to penetrate the membrane of living cells (inset) and measure intracellular signals (lower panel). , Biosensors based on carbon nanotubes are used for the detection of genotoxic analytes, including chemotherapeutic drugs and reactive oxygen species. Upper figure shows a schematic of a sensor made from a DNA and a single-walled carbon nanotube complex bound to a glass surface through a biotin-BSA (orange) and neutravidin (blue) linkage. Lower figures reveal the spectral changes arising from the interaction of the nanotube sensor with (from left to right): a chemotherapeutic agent, hydrogen peroxide, singlet oxygen and hydroxyl radicals (blue curve, before addition of analytes; green curve, after addition of analytes). Figures reproduced with permission from: , ref. 99, © 2010 AAA! S; , 101 © 2010 NPG. Author information * Abstract * Author information Affiliations * Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA * Tal Dvir & * Robert Langer * Laboratory for Biomaterials and Drug Delivery, Department of Anesthesiology, Division of Critical Care Medicine, Children's Hospital Boston, Harvard Medical School, 300 Longwood Avenue, Boston, Massachusetts 02115, USA * Tal Dvir, * Brian P. Timko & * Daniel S. Kohane * Harvard-Massachusetts Institute of Technology Division of Health Sciences and Technology, Cambridge, Massachusetts 02139, USA. * Brian P. Timko Competing financial interests R.L. has a financial interest in Pervasis and Fibrocell Science, Inc. Corresponding author Correspondence to: * Robert Langer Additional data
  • Atomic-scale engineering of electrodes for single-molecule contacts
    - UNKNOWN 6(1):23-27 (2011)
    Nature Nanotechnology | Letter Atomic-scale engineering of electrodes for single-molecule contacts * Guillaume Schull1 Contact Guillaume Schull Search for this author in: * NPG journals * PubMed * Google Scholar * Thomas Frederiksen2 Contact Thomas Frederiksen Search for this author in: * NPG journals * PubMed * Google Scholar * Andrés Arnau2, 3, 4 Search for this author in: * NPG journals * PubMed * Google Scholar * Daniel Sánchez-Portal2, 3 Search for this author in: * NPG journals * PubMed * Google Scholar * Richard Berndt5 Search for this author in: * NPG journals * PubMed * Google Scholar * Affiliations * Contributions * Corresponding authorsJournal name:Nature NanotechnologyVolume: 6,Pages:23–27Year published:(2011)DOI:doi:10.1038/nnano.2010.215Received02 September 2010Accepted07 October 2010Published online14 November 2010 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg The transport of charge through a conducting material depends on the intrinsic ability of the material to conduct current and on the charge injection efficiency at the contacts between the conductor and the electrodes carrying current to and from the material1, 2, 3. According to theoretical considerations4, this concept remains valid down to the limit of single-molecule junctions5. Exploring this limit in experiments requires atomic-scale control of the junction geometry. Here we present a method for probing the current through a single C60 molecule while changing, one by one, the number of atoms in the electrode that are in contact with the molecule. We show quantitatively that the contact geometry has a strong influence on the conductance. We also find a crossover from a regime in which the conductance is limited by charge injection at the contact to a regime in which the conductance is limited by scattering at the molecule. Thus, the concepts of 'good' and 'bad' ! contacts, commonly used in macro- and mesoscopic physics, can also be applied at the molecular scale. View full text Subject terms: * Electronic properties and devices * Surface patterning and imaging Figures at a glance * Figure 1: STM images of atomically engineered electrodes on Cu(111). , Constant-current STM image of CuN clusters on a Cu(111) surface obtained with a copper-terminated STM tip (I = 0.1 nA; sample voltage Vs = 0.1 V). , Image obtained with a C60-terminated STM tip (I = 0.1 nA; Vs = −1.7 V). The CuN clusters work as tips for 'reverse imaging' of the C60 fixed at the tip apex17. The threefold symmetric patterns reveal that one of the hexagons of the C60 cage is facing the surface. Standing waves related to surface states are not visible at this sample voltage. Both images, 18.2 nm × 7.2 nm. * Figure 2: Transport measurements of a single C60 molecule in contact with an increasing number of atoms. , Conductance in units of G0 (on a logarithmic scale) versus distance for a C60 tip approaching a bare Cu(111) surface (black line) and a surface covered with CuN clusters (coloured lines). One of the hexagons of the C60 cage is facing the surface. The distance scale was established from the apparent height of each cluster in STM images recorded at I = 100 pA and Vs = −0.1 V. Hereafter, with the same settings, the STM feedback was opened for collecting conductance data. Crosses mark the experimental contact points defined as the intersection of the contact and transition regimes (dashed grey lines indicate the bare surface data). Insets: geometry (bottom left) and list (right) of the experimental conductances at contact (Gc) derived from the conductance traces. zc is the contact distance. , STM image (I = 100 pA; Vs = 0.1 V; 8.0 × 2.3 nm2) of Cu2 and linear Cu3 recorded with a copper tip. –, STM images (I = 100 pA; Vs = −0.1 V; 8.0 × 2.3 nm2) of the same area recorde! d with a C60 tip. After the image in was recorded, the approach of the C60 tip caused the Cu2 cluster to move ~1.3 nm to the right (), after which the approach of the tip to the linear Cu3 cluster caused it to adopt a more compact configuration (). ,, Simulation showing how a linear Cu3 (, red circles) relaxes into a triangular configuration () as the distance between a C60 tip and the surface is reduced from 18 Å to 17.2 Å. The orange circles represent the Cu(111) surface; the carbon atoms are shown in grey. * Figure 3: Conductances at contact between a single C60 molecule and clusters of copper atoms. , Normalized conductance at contact versus cluster size N. Experimental data from six different molecular tips are shown, as well as theoretical data for two electrode separations around the point of contact (L1 = 17.2 Å and L2 = 18.0 Å, measured between the second-topmost layers). Conductance is normalized to the value for a single C60 molecule in contact with a 16-atom cluster. , Normalized conductance at contact per atom in the cluster versus cluster size N. ,, Calculated PDOS onto the atomic basis orbitals (s, p and d character) of CuN () and C60 () versus energy for seven different cluster sizes and for a separation of L1 = 17.2 Å. Inset to : the PDOS of CuN at the Fermi energy varies linearly with N. * Figure 4: Scattering at the contact between a single C60 molecule and clusters of copper atoms. Visualization of the scattering states at the Fermi energy for different numbers of contacting atoms. The calculated isosurfaces (shown in grey) represent the electron density in the junction at the centre of the Brillouin zone for a sum over the first three (most transmitting) eigenchannels (electron waves coming from below)20. Data were calculated for clusters with N = 1, … , 7 and 16 adatoms at an electrode separation L1 = 17.2 Å (measured between the second-topmost layers). Not all copper atoms in the cluster are visible. The scattering states are only calculated in the region of space defined by the topmost copper surface layers. Author information * Abstract * Author information * Supplementary information Affiliations * Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504 (CNRS – Université de Strasbourg), 67034 Strasbourg, France * Guillaume Schull * Donostia International Physics Center (DIPC), 20018 San Sebastián, Spain * Thomas Frederiksen, * Andrés Arnau & * Daniel Sánchez-Portal * Centro de Fisica de Materiales CSIC-UPV/EHU, Materials Physics Center MPC, 20080 San Sebastián, Spain * Andrés Arnau & * Daniel Sánchez-Portal * Depto. Fisica de Materiales UPV/EHU, Facultad de Quimica, 20080 San Sebastián, Spain * Andrés Arnau * Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany * Richard Berndt Contributions G.S. and R.B. provided the experimental concept. G.S. performed the STM and contact experiments. T.F. performed the first-principles calculations, and analysis was carried out with A.A. and D.S.P. All authors contibuted to the discussion of the results and preparation of the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding authors Correspondence to: * Guillaume Schull or * Thomas Frederiksen Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (890 KB) Supplementary information Additional data
  • Freestanding palladium nanosheets with plasmonic and catalytic properties
    - UNKNOWN 6(1):28-32 (2011)
    Nature Nanotechnology | Letter Freestanding palladium nanosheets with plasmonic and catalytic properties * Xiaoqing Huang1 Search for this author in: * NPG journals * PubMed * Google Scholar * Shaoheng Tang1 Search for this author in: * NPG journals * PubMed * Google Scholar * Xiaoliang Mu1 Search for this author in: * NPG journals * PubMed * Google Scholar * Yan Dai1 Search for this author in: * NPG journals * PubMed * Google Scholar * Guangxu Chen1 Search for this author in: * NPG journals * PubMed * Google Scholar * Zhiyou Zhou1 Search for this author in: * NPG journals * PubMed * Google Scholar * Fangxiong Ruan2 Search for this author in: * NPG journals * PubMed * Google Scholar * Zhilin Yang2 Search for this author in: * NPG journals * PubMed * Google Scholar * Nanfeng Zheng1 Contact Nanfeng Zheng Search for this author in: * NPG journals * PubMed * Google Scholar * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Pages:28–32Year published:(2011)DOI:doi:10.1038/nnano.2010.235Received14 July 2010Accepted29 October 2010Published online05 December 2010 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Ultrathin metal films can exhibit quantum size and surface effects that give rise to unique physical and chemical properties1, 2, 3, 4, 5, 6, 7. Metal films containing just a few layers of atoms can be fabricated on substrates using deposition techniques7, but the production of freestanding ultrathin structures remains a significant challenge. Here we report the facile synthesis of freestanding hexagonal palladium nanosheets that are less than 10 atomic layers thick, using carbon monoxide as a surface confining agent. The as-prepared nanosheets are blue in colour and exhibit a well-defined but tunable surface plasmon resonance peak in the near-infrared region. The combination of photothermal stability and biocompatibility makes palladium nanosheets promising candidates for photothermal therapy. The nanosheets also exhibit electrocatalytic activity for the oxidation of formic acid that is 2.5 times greater than that of commercial palladium black catalyst. View full text Subject terms: * Nanomaterials * Structural properties Figures at a glance * Figure 1: Characterization of ultrathin palladium nanosheets synthesized in the presence of PVP and CTAB in DMF. , TEM image of the palladium nanosheets. Inset: photograph of an ethanol dispersion of the as-prepared palladium nanosheets in a curvette. , HRTEM image of a palladium nanosheet flat lying on the TEM grid. , SAED pattern of a single palladium nanosheet (shown in the inset). , TEM image of the assembly of palladium nanosheets perpendicular to the TEM grid. Inset: thickness distribution of the palladium nanosheets. * Figure 2: TEM images of the palladium nanosheets produced under different reaction conditions. ,, Palladium nanosheets, collected following 0.5 h () and 1.5 h () reactions, using CTAB as the Br− source. ,, Nanosheets collected following 3 h reactions using NaBr () and TBAB () as the Br− source. , Larger nanosheets, grown using the palladium nanosheets in as seed particles. , Edge lengths of samples –. Error bars in are the standard deviations of the edge length distributions. * Figure 3: Optical absorption and photothermal properties of palladium nanosheets. , Absorption spectra of hexagonal palladium nanosheets with average edge lengths of 21, 27, 41 and 51 nm. , Photothermal effect of palladium nanosheets. The temperature versus time plots were recorded for various concentrations of palladium nanosheets (edge length, 41 nm) on irradiation by a 1 W laser. , Viability of healthy liver cells incubated for 48 h with different concentrations of palladium nanosheets. , Viability of human hepatoma cells upon irradiation by an 808 nm laser with a power density of 1.4 W cm−2 for various periods. Before irradiation, the cells were incubated with palladium nanosheets (20 µg ml−1) for 12 h. Cell viabilities were measured by standard MTT assay. ,, Micrographs corresponding to 2 min () and 5 min () irradiation. Dead cells are stained with trypan blue. Error bars in and are the standard deviations of the means of five independent determinations. Scale bars, 50 µm. * Figure 4: Comparison of electrocatalytic properties of palladium nanosheets and palladium black. The CV curves were recorded in an aqueous solution containing 0.5 M H2SO4 and 0.25 M HCOOH at a scan rate of 50 mV s−1. Edge size of palladium nanosheets, 41 nm; palladium black from Aldrich (47 m2 g−1). Author information * Abstract * Author information * Supplementary information Affiliations * State Key Laboratory for Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China * Xiaoqing Huang, * Shaoheng Tang, * Xiaoliang Mu, * Yan Dai, * Guangxu Chen, * Zhiyou Zhou & * Nanfeng Zheng * Department of Physics, Xiamen University, Xiamen 361005, China * Fangxiong Ruan & * Zhilin Yang Contributions X.Q.H. performed the experiments, collected and analysed the data, and wrote the paper. S.H.T. carried out the apoptosis assay and in vitro photothermal therapy tests. X.L.M. was responsible for AFM analysis. Y.D. and G.X.C. helped with synthesis of the materials. Z.Y.Z. helped with the electrochemical and FTIR measurements. F.X.R. and Z.L.Y. carried out the calculations of extinction spectra. N.F.Z. conceived the experiments, planned the synthesis, analysed the results and wrote the paper. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * Nanfeng Zheng Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (3,422 KB) Supplementary information Additional data
  • Vibrational and electronic heating in nanoscale junctions
    - UNKNOWN 6(1):33-38 (2011)
    Nature Nanotechnology | Letter Vibrational and electronic heating in nanoscale junctions * Daniel R. Ward1 Search for this author in: * NPG journals * PubMed * Google Scholar * David A. Corley2 Search for this author in: * NPG journals * PubMed * Google Scholar * James M. Tour2 Search for this author in: * NPG journals * PubMed * Google Scholar * Douglas Natelson1, 3 Contact Douglas Natelson Search for this author in: * NPG journals * PubMed * Google Scholar * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Pages:33–38Year published:(2011)DOI:doi:10.1038/nnano.2010.240Received23 July 2010Accepted08 November 2010Published online12 December 2010 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Understanding and controlling the flow of heat is a major challenge in nanoelectronics. When a junction is driven out of equilibrium by light or the flow of electric charge, the vibrational and electronic degrees of freedom are, in general, no longer described by a single temperature1, 2, 3, 4, 5, 6. Moreover, characterizing the steady-state vibrational and electronic distributions in situ is extremely challenging. Here, we show that surface-enhanced Raman emission may be used to determine the effective temperatures for both the vibrational modes and the electrons in the current in a biased metallic nanoscale junction decorated with molecules7. Molecular vibrations show mode-specific pumping by both optical excitation8 and d.c. current9, with effective temperatures exceeding several hundred kelvin. Anti-Stokes electronic Raman emission10, 11 indicates that the effective electronic temperature at bias voltages of a few hundred millivolts can reach values up to three times the! values measured when there is no current. The precise effective temperatures are model-dependent, but the trends as a function of bias conditions are robust, and allow direct comparisons with theories of nanoscale heating. View full text Subject terms: * Electronic properties and devices Figures at a glance * Figure 1: Measurement overview. , SEM false-colour image of a typical nanogap. , Schematic of electrical and optical measurements. , Waterfall plot showing the Raman response of an OPV3 junction (in CCD counts) as a function of d.c. bias V (y-axis) and Raman shift (x-axis). The anti-Stokes spectrum (left) shows a strong dependence on V, whereas the Stokes spectrum (right) is relatively constant as a function of V. The strong Stokes peak at 520 cm−1 is from the silicon substrate. Note, the false-colour scales for Stokes and anti-Stokes signals are different. , Current (top) and differential conductance (bottom) measured simultaneously as a function of V. * Figure 2: Optically driven vibrational pumping. , Raman response of a dodecanethiol-coated junction (in CCD counts; see false-colour bars) as a function of time (y-axis) and Raman shift (x-axis) under zero bias. Note, the false-colour scales for Stokes and anti-Stokes signals are different. The junction switches stochastically between several stable configurations, each with characteristic spectra that exhibit strong optical pumping of vibrational modes at 1,099 cm−1 (C–C stretch) and 1,475 cm−1 (CH2 or CH3 deformation). , Spectra from specific time slices in . Note that the higher energy peak spectrally diffuses between 1,475 cm−1 and 1,525 cm−1 and the lower energy peak between 1,099 cm−1 and 1,110 cm−1. The temperature of the 1,099 cm−1 mode changes as follows with increasing time: 769 K, 1,722 K, 532 K, 754 K, 512 K and 775 K. The temperature of the 1,475 cm−1 mode changes as follows: 701 K, 815 K, 658 K, 729 K, 648 K and 746 K. Note that at 70 s, a vibration at 1,450 cm−1 is observed at 2,161 K. A! ll temperatures have an uncertainty of ±10 K. , Power dependence of Stokes (black symbols) and anti-Stokes (blue symbols) signal taken from a different device, also showing optical pumping. As expected, in the optical pumping regime the Stokes signal is linear (solid black line) in laser power, whereas the anti-Stokes signal increases quadratically (solid blue line) in laser power. Error bars indicate uncertainty in the signal due to read and shot noise in the CCD. * Figure 3: Electrically driven vibrational pumping. , Effective vibrational temperature as a function of V for two OPV3 modes: 1,317 cm−1 (red) and 1,625 cm−1 (blue). Error bars indicate uncertainty in temperature due to anti-Stokes amplitude measurements. Inset: I–V curve for this device. , Raman response of this device as a function of V (y-axis) and Raman shift (x-axis). Note, the false-colour scales for the Stokes and anti-Stokes signals are different. , Sample Raman spectra at six different bias voltages. The full scale of the anti-Stokes signal is 235 counts; the full scale of the Stokes signal is 10,000 counts. , Effective vibrational temperature as a function of V for three OPV3 modes: 1,815 cm−1 (black), 1,480 cm−1 (red) and 562 cm−1 (blue). Error bars indicate uncertainty in temperature due to anti-Stokes amplitude measurements. Simultaneous optical and electrical vibrational pumping are observed for the 1,810 cm−1 mode as Teff is much greater than 80 K at V = 0. , Raman response of this device as a fu! nction of V (y-axis) and Raman shift (x-axis). Note, the false-colour scales for Stokes and anti-Stokes signals are different. , Sample Raman spectra at six different bias voltages. The full scale of the anti-Stokes signal is 350 counts; the full scale of the Stokes signal is 10,000 counts. * Figure 4: Electronic heating under bias. , Effective temperature (blue; left axis) and dissipated electrical power (red; right axis) versus bias voltage V in a nominally bare device. Error bars are described in the text. Inset: current/voltage curves for this device. Error bars are described in the text. ,, Raman response shown as a Raman signal (in CCD counts) as a function of voltage and Raman shift (), and as the Raman intensity (in CCD counts) as a function of Raman shift () at three different voltages (blue lines); the green lines are best fits to the data given by equation (2). Only the anti-Stokes signals are shown in and . This device shows no molecular Raman peaks, and is considered a 'clean' junction. –, The same data for the OPV3 device used for Figs 1 and 3. The data in ,, demonstrate that bias-driven electronic heating is also detectable in junctions that show optical pumping and bias-driven vibrational heating. Author information * Abstract * Author information * Supplementary information Affiliations * Department of Physics and Astronomy, Rice University, 6100 Main Street, Houston, Texas 77005, USA * Daniel R. Ward & * Douglas Natelson * Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005, USA * David A. Corley & * James M. Tour * Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, Houston, Texas 77005, USA * Douglas Natelson Contributions D.R.W. fabricated the devices, performed all measurements, and analysed the data. D.N. supervised and provided continuous guidance for the experiments and the analysis. D.A.C. synthesized the OPV3 molecules under the supervision of J.M.T. The bulk of the paper was written by D.R.W. and D.N. All authors discussed the results and contributed to manuscript revision. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * Douglas Natelson Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (2,043 KB) Supplementary information Additional data
  • Nanoparticle-induced unfolding of fibrinogen promotes Mac-1 receptor activation and inflammation
    - UNKNOWN 6(1):39-44 (2011)
    Nature Nanotechnology | Letter Nanoparticle-induced unfolding of fibrinogen promotes Mac-1 receptor activation and inflammation * Zhou J. Deng1 Search for this author in: * NPG journals * PubMed * Google Scholar * Mingtao Liang2, 3 Search for this author in: * NPG journals * PubMed * Google Scholar * Michael Monteiro4 Search for this author in: * NPG journals * PubMed * Google Scholar * Istvan Toth2, 3 Search for this author in: * NPG journals * PubMed * Google Scholar * Rodney F. Minchin1 Contact Rodney F. Minchin Search for this author in: * NPG journals * PubMed * Google Scholar * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Pages:39–44Year published:(2011)DOI:doi:10.1038/nnano.2010.250Received23 September 2010Accepted16 November 2010Published online19 December 2010 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg The chemical composition, size, shape and surface characteristics of nanoparticles affect the way proteins bind to these particles, and this in turn influences the way in which nanoparticles interact with cells and tissues1, 2, 3, 4, 5. Nanomaterials bound with proteins can result in physiological and pathological changes, including macrophage uptake1, 6, blood coagulation7, protein aggregation8 and complement activation7, 9, but the mechanisms that lead to these changes remain poorly understood. Here, we show that negatively charged poly(acrylic acid)-conjugated gold nanoparticles bind to and induce unfolding of fibrinogen, which promotes interaction with the integrin receptor, Mac-1. Activation of this receptor increases the NF-κB signalling pathway, resulting in the release of inflammatory cytokines. However, not all nanoparticles that bind to fibrinogen demonstrated this effect. Our results show that the binding of certain nanoparticles to fibrinogen in plasma offers an! alternative mechanism to the more commonly described role of oxidative stress in the inflammatory response to nanomaterials. View full text Subject terms: * Nanomedicine * Nanoparticles Figures at a glance * Figure 1: Fibrinogen is the major human plasma protein bound by PAA–GNP. , SDS–PAGE of human plasma proteins bound to PAA–GNP with diameters of 5, 10 and 20 nm. Three major protein bands were observed at ~65, 55 and 45 kDa. , Unbound fibrinogen following pull-down with PAA–GNP with diameters of ~5 nm (blue) or 20 nm (red). Purified fibrinogen (0.6 µg) was incubated with increasing amounts of PAA–GNP. Inset: unbound fibrinogen is plotted against total surface area for the two nanoparticles. , Crystal structure of fibrinogen. The protein was drawn using Swiss-PdbViewer and coordinates for PDB entry 3GHG. Common domains are shown. Inset: the C-terminus of the γ chain (purple) that interacts with the Mac-1 receptor. , Circular dichroism of fibrinogen in the absence and presence of increasing concentrations of 5 nm PAA–GNP. * Figure 2: Selective binding of fibrinogen/PAA–GNP complexes to Mac-1 receptors. , HL-60 cells are Mac-1-receptor-negative cells, as shown by flow cytometry following labelling with fluorescent CD11b antibodies (upper panel, solid lines) and THP-1 cells are Mac-1-receptor-positive. This was confirmed by plating both HL-60 and THP-1 cells onto immobilized fibrinogen (Supplementary Fig. S4). Lower panel shows binding of fibrinogen alone (open bars) or fibrinogen with 5 nm PAA–GNP (filled bars) to THP-1 cells and HL-60 is shown. Addition of nanoparticles significantly increased the binding to THP-1 cells but not to HL-60 cells. Replacing fibrinogen with albumin abrogated the effect of the nanoparticles. Results are mean ± s.e.m, n = 3; asterisk indicates P < 0.05. , HEK293 cells were transfected with empty vector (EV) or CD11b/CD18 constructs and Mac-1 receptor expression was determined by flow cytometry (upper panels). Lower panel shows binding of fibrinogen alone (open bars) or fibrinogen with 5 nm PAA–GNP (filled bars) is shown. The nanoparticles in! creased fibrinogen binding in Mac-1-receptor-positive cells only. Results are mean ± s.e.m., n = 3; asterisk indicates P < 0.05. , PAA–GNP (20 nm) did not induce fibrinogen binding to THP-1 cells to the same extent as the 5 nm. Binding was performed with an equal surface area (3,900 mm2) for each of the nanoparticles to ensure similar protein binding. , Pre-treatment of THP-1 cells with the P2 peptide significantly reduced the binding of fibrinogen in the presence of 5 nm PAA–GNP (grey bars). Control peptide, H19, showed no inhibitory effects on binding (filled bars). Results are mean ± s.e.m., n = 3. , PAA–GNP (20 nm) induced fibrinogen binding to THP-1 cells when the level of protein binding was reduced. However, no increase in binding was seen under the same conditions in HL-60 cells. Percent binding saturation is shown on the x-axis and was determined from the data shown in Fig. 1b. Results are mean ± s.e.m., n = 3, expressed as a percentage of the control (100! %). , Electrophoretic mobility shift assay, showing the increa! sed nuclear localization of NF-κB in THP-1 cells when exposed to the fibrinogen/PAA–GNP complexes. The open arrow indicates the location of the P65 complex of NF-κB, which was confirmed by a supershift (solid arrow) with anti-P65 antibody (lane 5). * Figure 3: Pro-inflammatory effects of fibrinogen/PAA–GNP complexes. ,, Treatment of THP-1 cells with complexes of fibrinogen (33 µg ml−1) and 5 nm PAA–GNP (100 µg ml−1) induced the secretion of IL-8 () and TNF-α (). Neither fibrinogen alone nor PAA–GNP altered cytokine release. The concentration effect of the complexes on cytokine release is shown in Supplementary Fig. S5. NF-κB pathway inhibitor, Bay 11-7082, inhibited the secretion of both cytokines. Lipopolysaccharide-treated cells were used as a positive control. Results are mean ± s.e.m., n = 3. Single asterisk indicates P < 0.05 compared to control (no treatment). Double asterisk indicates P < 0.05 compared to respective treatments without Bay 11-7082. ,, THP-1 cells treated with 20 nm PAA–GNP bound to excess fibrinogen did not induce IL-8 () or TNF-α () release. Nanoparticles were adjusted to equal total surface area for similar protein binding. ,, Cells treated with 20 nm PAA–GNP bound to a reduced concentration of fibrinogen (10 µg ml−1), which resulted in only ! 33% binding saturation, induced low but significant release of IL-8 () and a more substantial release of TNF-α (). Nanoparticles (5 nm; 30 µg ml−1) bound to 10 µg ml−1 fibrinogen are shown for comparison. Asterisk indicates P < 0.05 compared to nanoparticles alone (respective controls). * Figure 4: Effects of nanoparticle surface characteristics on fibrinogen binding. , Unbound fibrinogen following pull-down with PAA–PDHA–GNP. Purified fibrinogen (0.6 µg) was incubated with 2 µg of each nanoparticle. Only the 100% PAA/0% PDHA–GNP and 80% PAA/20% PDHA–GNP significantly bound fibrinogen. , Binding of fibrinogen to THP-1 cells was only significantly increased with the nanoparticles containing 100% PAA. Results are mean ± s.e.m., n = 3. Asterisk indicates P < 0.05 compared to control (no treatment). , Binding of fibrinogen to nano-metal oxides was determined by ultracentrifugation after mixing 0.6 µg protein with 8 µg nanoparticles. All the metal-oxide nanoparticles bound more than 70% of the fibrinogen. , Binding of the fibrinogen–metal oxide complexes to THP-1 cells was determined. Results are mean ± s.e.m., n = 3. Asterisk indicates P < 0.05 compared to control (no treatment). , Pre-treatment of THP-1 cells with the P2 peptide significantly reduced (P < 0.05) the binding of fibrinogen in the presence of nano-SiO2. Control p! eptide, H19, showed no inhibitory effect on the binding. Results are mean ± s.e.m., n = 3. Author information * Abstract * Author information * Supplementary information Affiliations * School of Biomedical Sciences, University of Queensland, Brisbane 4072, Australia * Zhou J. Deng & * Rodney F. Minchin * School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane 4072, Australia * Mingtao Liang & * Istvan Toth * School of Pharmacy, University of Queensland, Brisbane 4072, Australia * Mingtao Liang & * Istvan Toth * Australian Institute for Bioengineering and Nanotechnology, University of Queensland, Brisbane 4072, Australia * Michael Monteiro Contributions Z.J.D. performed all the biological experiments, assisted in designing the biological experiments and co-wrote the manuscript. M.L. synthesized and characterized the nanoparticles. M.M. and I.T. designed the nanoparticle synthesis procedure. R.F.M. conceived and designed the biological studies and co-wrote the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * Rodney F. Minchin Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (1,298 KB) Supplementary information Additional data
  • Large intrinsic energy bandgaps in annealed nanotube-derived graphene nanoribbons
    - UNKNOWN 6(1):45-50 (2011)
    Nature Nanotechnology | Article Large intrinsic energy bandgaps in annealed nanotube-derived graphene nanoribbons * T. Shimizu1 Search for this author in: * NPG journals * PubMed * Google Scholar * J. Haruyama1 Contact J. Haruyama Search for this author in: * NPG journals * PubMed * Google Scholar * D. C. Marcano2 Search for this author in: * NPG journals * PubMed * Google Scholar * D. V. Kosinkin2 Search for this author in: * NPG journals * PubMed * Google Scholar * J. M. Tour2 Contact J. M. Tour Search for this author in: * NPG journals * PubMed * Google Scholar * K. Hirose3 Search for this author in: * NPG journals * PubMed * Google Scholar * K. Suenaga3 Search for this author in: * NPG journals * PubMed * Google Scholar * Affiliations * Contributions * Corresponding authorsJournal name:Nature NanotechnologyVolume: 6,Pages:45–50Year published:(2011)DOI:doi:10.1038/nnano.2010.249Received14 October 2010Accepted12 November 2010Published online19 December 2010 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg The usefulness of graphene for electronics has been limited because it does not have an energy bandgap. Although graphene nanoribbons have non-zero bandgaps, lithographic fabrication methods introduce defects that decouple the bandgap from electronic properties, compromising performance. Here we report direct measurements of a large intrinsic energy bandgap of ~50 meV in nanoribbons (width, ~100 nm) fabricated by high-temperature hydrogen-annealing of unzipped carbon nanotubes. The thermal energy required to promote a charge to the conduction band (the activation energy) is measured to be seven times greater than in lithographically defined nanoribbons, and is close to the width of the voltage range over which differential conductance is zero (the transport gap). This similarity suggests that the activation energy is in fact the intrinsic energy bandgap. High-resolution transmission electron and Raman microscopy, in combination with an absence of hopping conductance and stoc! hastic charging effects, suggest a low defect density. View full text Subject terms: * Electronic properties and devices * Synthesis and processing Figures at a glance * Figure 1: Characterization of graphene nanoribbons. , Field-emission SEM image of an ensemble of the as-grown nanoribbons, which were dispersed on a silicon oxide substrate in a water droplet containing a suspension of nanoribbons. The nanoribbons are entangled and not sufficiently exfoliated. Insets (right): atomic force microscopy images of individual nanoribbons spread by applying a strong air flow to the droplet (see Methods). Inset (left): height of the nanoribbon measured along the longitudinal direction. The thickness of ~0.8 nm indicates a single-layer nanoribbon. , HRTEM image of the as-grown nanoribbon (no annealing; see Methods), showing a clear hexagonal lattice of graphene with few defects and some oxidized parts. Annealing (see Methods) strongly enhances the quality of the nanoribbons and also results in carrier doping. , Typical Raman spectrum of an annealed bilayer nanoribbon taken with a laser excitation of 532 nm and 0.14 mW incident power at room temperature. The width of the nanoribbon is ~100 nm and the G! /D band ratio is as high as ~2.2. , FET fabricated using a nanoribbon end-bonded by two metal electrodes, which eliminates single-electron charging effects (see Supplementary Section 1). The thickness of the SiO2 layer on the gold/titanium backgate electrode was 300 nm, and the spacing of source and drain electrodes was 500 nm in all samples. * Figure 2: Electronic characteristics of a graphene-nanoribbon FET. , Typical drain current (ISD) versus drain voltage (VSD) relationship for a sample (W = 75 nm and N = 1) at room temperature (inset) and T = 1.5 K (main panel), revealing a strong zero-bias (G0) anomaly with a voltage width of ΔVSD ≈ ± V, even at a backgate voltage (VBG) of ±20 V. ΔVSD was determined from the VSD range for differential conductance (dISD/dVSD) ≈ 0. The temperature dependence of the G0 anomaly does not follow the formula for single-electron charging effect26, 27. This is consistent with end-bonding of the nanoribbon. , Differential conductance (dISD/dVSD) as a function of VBG at T = 1.5 K for the sample in . A transport gap of the backgate voltage of ΔVBG ≈ 1 V is observed. At higher VSD, the gap becomes ambiguous (Fig. 3). In contrast, at lower VSD, the same gap was observed in most cases, although it also becomes ambiguous due to insulating behaviour at values of VBG outside the gap. The energy estimated from this in the single-particle energy spe! ctrum, Δm, is ~70 meV, which is smaller than that for lithographically formed nanoribbons (~100 meV) with the same W. * Figure 3: Source–drain current versus backgate voltage. –, IDS versus VBG in four different nanoribbon FETs. VSD was changed in steps of 1 V. A significant increase in ISD in the −VBG region suggests hole-dominant transport. The ratio of ISD at VBG = –20 V to the minimum ISD strongly depends on VSD, and becomes large for large absolute values of VSD. This suggests the appearance of different states driven by high VSD (such as edge reconstruction; Supplementary Section 7). The transport gap and slight ambipolar feature shown in Fig. 2b remain at low VSD (~1 V) in . (W, width (nm); N, number of layers.). * Figure 4: Temperature dependence of minimum conductance around the charge neutrality point and activation energy. , Arrhenius plot for minimum conductance (Gmin) versus temperature of the samples shown in Fig. 3. Gmin represents the values at the charge neutrality point (VBG ≈ 0–2 V). An Ea of ~50 meV was obtained from the dotted lines, and Gmin ∝ exp(−Ea/2kBT) at high temperatures is mostly independent of W and N, except for the W = 75 nm sample, where Ea increases slightly to ~55 meV. This value is seven times greater than those in lithographically formed nanoribbons and is close to the Δm value (~80%). , Ea and Δm values as a function of W for two different values of N. The trend in is more evident. * Figure 5: Single-electron spectroscopy—half part of a Coulomb diamond measured at T = 1.5 K. The colours represent differential conductance. ΔVBG is 5 mV. The transport gap is represented by the region of 20 × 10−12 S. No stochastic Coulomb diamonds can be observed inside the transport gap (Supplementary Section 1). A transport gap only exists around the charge neutrality point. The measured sample, with W = 80 nm and N = 1, is different from that in Figs 2 and 3. Author information * Abstract * Author information * Supplementary information Affiliations * Faculty of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara, Kanagawa 252-5258, Japan * T. Shimizu & * J. Haruyama * Department of Chemistry and Mechanical Engineering and Materials Science, Rice University, 6100 Main Street, Houston, Texas 77005, USA * D. C. Marcano, * D. V. Kosinkin & * J. M. Tour * Nanotube Research Center, National Institute of Advanced Industrial Science and Technology (AIST), AIST Central 5, Tsukuba, 305-8565, Japan * K. Hirose & * K. Suenaga Contributions J.H., J.M.T. and K.S conceived and designed the experiments. T.S., D.C.M., D.V.K., and K.H. performed the experiments. J.H. analysed the data. J.H. and J.M.T. co-wrote the paper. Competing financial interests The authors declare no competing financial interests. Corresponding authors Correspondence to: * J. Haruyama or * J. M. Tour Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (814 KB) Supplementary information Additional data
  • Single-walled carbon nanotubes as excitonic optical wires
    - UNKNOWN 6(1):51-56 (2011)
    Nature Nanotechnology | Article Single-walled carbon nanotubes as excitonic optical wires * Daniel Y. Joh1, 2, 4 Search for this author in: * NPG journals * PubMed * Google Scholar * Jesse Kinder2, 4 Search for this author in: * NPG journals * PubMed * Google Scholar * Lihong H. Herman1, 4 Search for this author in: * NPG journals * PubMed * Google Scholar * Sang-Yong Ju2 Search for this author in: * NPG journals * PubMed * Google Scholar * Michael A. Segal2 Search for this author in: * NPG journals * PubMed * Google Scholar * Jeffreys N. Johnson2 Search for this author in: * NPG journals * PubMed * Google Scholar * Garnet K.-L. Chan2 Search for this author in: * NPG journals * PubMed * Google Scholar * Jiwoong Park2, 3 Contact Jiwoong Park Search for this author in: * NPG journals * PubMed * Google Scholar * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Pages:51–56Year published:(2011)DOI:doi:10.1038/nnano.2010.248Received25 October 2010Accepted12 November 2010Published online19 December 2010 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Although metallic nanostructures are useful for nanoscale optics, all of their key optical properties are determined by their geometry. This makes it difficult to adjust these properties independently, and can restrict applications. Here we use the absolute intensity of Rayleigh scattering to show that single-walled carbon nanotubes can form ideal optical wires. The spatial distribution of the radiation scattered by the nanotubes is determined by their shape, but the intensity and spectrum of the scattered radiation are determined by exciton dynamics, quantum-dot-like optical resonances and other intrinsic properties. Moreover, the nanotubes display a uniform peak optical conductivity of ~8 e2/h, which we derive using an exciton model, suggesting universal behaviour similar to that observed in nanotube conductance. We further demonstrate a radiative coupling between two distant nanotubes, with potential applications in metamaterials and optical antennas. View full text Subject terms: * Carbon nanotubes and fullerenes * Photonic structures and devices Figures at a glance * Figure 1: Optical scattering from single-walled carbon nanotubes. , Upper panel: schematic illustrating electromagnetic radiation from a long, straight wire. Intensity plot corresponds to the strength of the scattered electric field (Escatt), which decays as 1/√r. Middle panel: schematic of an electronic band diagram for a semiconducting nanotube (where kz represents the azimuthal quantum number). An interband transition from valence to conduction band (red arrow) resulting from optical excitation leads to the formation of an excitonic bound state that dissociates into free particles in lower sub-bands at rate ΓX (dashed blue arrows). Lower panel: optical excitation and exciton formation (e–h) in a nanotube by an electromagnetic plane wave (Eex). The solid arrow indicates the direction of propagation of the incident photons. , Representative spatial Rayleigh image, showing more than 10 nanotubes simultaneously (in false colour, corresponding to strongly scattered wavelengths). , Optical setup schematic. The incident electric field Eex! is linearly polarized and incident at angle θex with respect to the nanotube axis, inducing a surface current I along the nanotube. The scattered light is focused onto a disk or cone around the nanotube axis and is collected with a detection angle θdet = 80.6°. The Fraunhofer image is effectively obtained by removing the tube lens (TL) and placing the CCD immediately after the objective lens (OL) to image the nanotube radiation pattern, as indicated by the dotted blue line (see Supplementary Information). ,, Main panels: radiation behaviour for nanotubes. Spatial Rayleigh images (upper inset) and radiation patterns from Fraunhofer imaging (lower inset) of individual nanotubes when θex = 90° () and when θex ≠ 90 (). * Figure 2: Scattering patterns for periodically spaced nanotube segments. , Colour Rayleigh image before (upper panel) and after (lower panel) cutting. Scale bar, 5 µm. , Rayleigh spectra (normalized to the peak) before and after patterning for the nanotube marked by the symbols in , Schematic illustrating the scattering pattern for periodically spaced (h = pitch distance) linear structures. , Upper panel: Fraunhofer image for a nanotube with h = 2.0 µm after cutting. Lower panel: measured scattering patterns for nanotubes of different pitch sizes after cutting. Asterisks denote side bands depicted in . * Figure 3: Frequency-dependent scattering intensity and optical conductivity of single-walled carbon nanotubes. , Colour Rayleigh images of five nanotubes, together with their corresponding resonant Rayleigh peaks and diameters determined by AFM (height traces shown in red). , Normalized spatial Rayleigh scattering intensity plots for tubes of different diameter (dexp) measured at their respective resonance energies. , √(δscattλ) as a function of dexp, measured for 19 nanotube resonances of various sub-band transitions. Inset: histogram of peak dynamic conductivity |σ|peak in units of G0 (e2/h). , Main panel: calculated plots of Re[σ(ω)], Im[σ(ω)] and |σ(ω)| versus ħω for a representative semiconducting nanotube using the exciton model. Inset: calculated values of |σ|peak for different resonances and nanotube diameters using the exciton model (same symbols as in ). * Figure 4: Radiative coupling between distant single-walled carbon nanotubes. , AFM image of two nanotubes with overlapping spectral resonances centred at 634 nm (λL) and 664 nm (λR) (for nanotubes L and R, respectively). The two nanotubes run parallel to each other over a distance of 10 µm. Corresponding height traces are shown in red. , Main panels: optical coupling (insets show spatial Rayleigh images near the coupling region, denoted by blue lines) recorded at 634 and 664 nm. Re[σ(ω)] represented by solid lines and Im[σ(ω)] by dashed lines. Scale bar, 5 µm. , Rayleigh scattering intensity contour of excitation wavelength versus position for the green cross-sections marked in the inset of for coupled (middle panel) and uncoupled (left and right panels) regions. , Intensity contributions for nanotubes L and R in the uncoupled and coupled regions obtained from Gaussian deconvolution (left inset) of . Inset: calculated values for the observed transition. Arrows indicate the changes in the scattering intensity of tube R before and after intertu! be coupling. Author information * Abstract * Author information * Supplementary information Primary authors * These authors contributed equally to this work * Daniel Y. Joh, * Jesse Kinder & * Lihong H. Herman Affiliations * School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA * Daniel Y. Joh & * Lihong H. Herman * Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA * Daniel Y. Joh, * Jesse Kinder, * Sang-Yong Ju, * Michael A. Segal, * Jeffreys N. Johnson, * Garnet K.-L. Chan & * Jiwoong Park * Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, New York 14853, USA * Jiwoong Park Contributions D.J. and L.H. performed optical measurements and analysed the data. J.K. carried out theoretical calculations. S.-Y.J. and J.J. performed Raman spectroscopy measurements. M.S. carried out nanotube synthesis. G.C. and J.P. supervised the project. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * Jiwoong Park Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (1,061 KB) Supplementary information Additional data
  • Multifunctional carbon-nanotube cellular endoscopes
    - UNKNOWN 6(1):57-64 (2011)
    Nature Nanotechnology | Article Multifunctional carbon-nanotube cellular endoscopes * Riju Singhal1, 5 Search for this author in: * NPG journals * PubMed * Google Scholar * Zulfiya Orynbayeva1, 2, 5 Search for this author in: * NPG journals * PubMed * Google Scholar * Ramalingam Venkat Kalyana Sundaram3, 5 Search for this author in: * NPG journals * PubMed * Google Scholar * Jun Jie Niu1, 5 Search for this author in: * NPG journals * PubMed * Google Scholar * Sayan Bhattacharyya1, 5, 6 Search for this author in: * NPG journals * PubMed * Google Scholar * Elina A. Vitol4, 5 Search for this author in: * NPG journals * PubMed * Google Scholar * Michael G. Schrlau1, 5 Search for this author in: * NPG journals * PubMed * Google Scholar * Elisabeth S. Papazoglou3, 5 Search for this author in: * NPG journals * PubMed * Google Scholar * Gary Friedman4, 5 Contact Gary Friedman Search for this author in: * NPG journals * PubMed * Google Scholar * Yury Gogotsi1, 5 Contact Yury Gogotsi Search for this author in: * NPG journals * PubMed * Google Scholar * Affiliations * Contributions * Corresponding authorsJournal name:Nature NanotechnologyVolume: 6,Pages:57–64Year published:(2011)DOI:doi:10.1038/nnano.2010.241Received31 August 2010Accepted09 November 2010Published online12 December 2010 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Glass micropipettes, atomic force microscope tips and nanoneedles can be used to interrogate cells, but these devices either have conical geometries that can damage cells during penetration or are incapable of continuous fluid handling. Here, we report a carbon-nanotube-based endoscope for interrogating cells, transporting fluids and performing optical and electrochemical diagnostics at the single organelle level. The endoscope, which is made by placing a multiwalled carbon nanotube (length, 50–60 µm) at the tip of a glass pipette, can probe the intracellular environment with a spatial resolution of ~100 nm and can also access organelles without disrupting the cell. When the nanotube is filled with magnetic nanoparticles, the endoscope can be remotely manoeuvered to transport nanoparticles and attolitre volumes of fluids to and from precise locations. Because they are mounted on conventional glass micropipettes, the endoscopes readily fit standard instruments, creating a ! broad range of opportunities for minimally invasive intracellular probing, drug delivery and single-cell surgery. View full text Subject terms: * Carbon nanotubes and fullerenes * Nanobiotechnology * Nanosensors and other devices Figures at a glance * Figure 1: Comparison between cellular endoscopes and glass pipettes. , Schematic showing a conventional glass pipette (left) and a nanotube endoscope (right) interrogating cells. , Schematic of the nanotube endoscope. A multiwalled carbon nanotube is attached to the end of a glass pipette, which is coated with a non-conducting epoxy on the outside and a conducting epoxy on the inside. , A HeLa cell (left) being injected by a 1 µm commercial glass pipette, and a primary rat hepatocyte nucleus (right) being interrogated by a 100 nm nanotube endoscope. ,, Scanning electron micrograph of as-assembled endoscopes with 100 and 50 nm carbon nanotube tips, respectively. Inset in : nanotube tip opening. Epoxy glue seals the glass pipette entrance, and the ends of the nanotube remain open for fluid transfer. , Optical image of a glass pipette with a carbon-nanotube tip (not visible at this magnification). * Figure 2: Mechanical robustness, flexibility and remote manipulation of the nanotube endoscope. ,, Differential interference contrast micrographs showing a 100 nm nanotube tip of the endoscope bending (left) and elastically recovering its shape (right) when pushed against a cell membrane () or a glass slide (). , Sequential optical micrographs of a nanotube tip bending towards a magnetic field (white arrow). Superparamagnetic properties and flexibility of the nanotube tip allow remote magnetic manipulation. * Figure 3: Fluid and particulate flow through the nanotube endoscope. , Optical micrographs showing the transport of an oil-based ferrofluid-fluorescent dye under an applied magnetic field. Inset: schematic of the fluid-filled nanotube endoscope ejecting fluid at its tip. , Optical micrograph showing the flow and alighment of 50 nm polypropylene particles (green spheres) inside a carbon-nanotube tip. ,, Fluorescence () and differential interference contrast () micrographs showing a cell being interrogated with an endoscope filled with FITC-labelled (green) fluorescent polymer nanoparticles. The fluorescence micrograph in shows mitochondria labelled with Mitotracker Orange (red). * Figure 4: Application of nanotube endoscopes for SERS and electrochemistry. , Schematic of a SERS-active endoscope consisting of a nanotube tip decorated with gold nanoparticles. , Transmission electron micrograph of the SERS-active nanotube tip. , Raman spectra recorded when the SERS-active endoscope tip is positioned inside (red spectrum) and outside (black spectrum) a HeLa cell. Inset: optical micrograph showing the corresponding 200-nm-diameter endoscope tip positioned in the cell cytoplasm. , Voltammetric traces obtained using the nanotube endoscope in 100 mM supporting electrolyte alone (circles) and 100 µM (triangles) and 1 mM (squares) potassium ferricyanide. Inset: oxidative current change as a function of potassium ferricyanide concentration. * Figure 5: Intracellular Ca2+ response to mechanical stimulation. ,, Differential interference contrast micrographs showing a 200-nm-tip diameter glass pipette tip () and a 200-nm-diameter endoscope tip () penetrating the cell membrane of a HeLa cell. ,, Pseudo-colour fluorescent images representing the cytosolic Ca2+ concentration corresponding to cell membrane penetration by the glass pipette () and endoscope (). The blue streak (arrow) in represents the aspiration of Ca2+-labelled cytosol into the endoscope after membrane penetration. , Typical Ca2+ response as a function of time upon insertion of a 200-nm-diameter glass pipette (blue trace) and 100-nm-diameter endoscope (red trace). * Figure 6: Effect of probe insertion on the cytoskeleton. ,, Differential interference contrast micrographs showing a HeLa cell before () and after () insertion of a conical glass pipette. ,, Corresponding fluorescent images of actin cytoskeleton before () and after () insertion of a glass pipette. The circled area in shows cytoskeletal destruction. , Differential interference contrast micrograph (,) and the corresponding fluorescent image (,) of the cell before (,) and after (,) insertion of a 100-nm-diameter endoscope. No damage or changes of the cell cytoskeleton were observed after insertion. The dotted circle in shows the point of insertion. Author information * Abstract * Author information * Supplementary information Affiliations * Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104, USA * Riju Singhal, * Zulfiya Orynbayeva, * Jun Jie Niu, * Sayan Bhattacharyya, * Michael G. Schrlau & * Yury Gogotsi * Department of Biochemistry and Molecular Biology, Drexel University, Philadelphia, Pennsylvania 19102, USA * Zulfiya Orynbayeva * School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia, Pennsylvania 19104, USA * Ramalingam Venkat Kalyana Sundaram & * Elisabeth S. Papazoglou * Department of Electrical and Computer Engineering, Drexel University, Philadelphia, Pennsylvania 19104, USA * Elina A. Vitol & * Gary Friedman * A.J. Drexel Nanotechnology Institute, Drexel University, Philadelphia, Pennsylvania 19104, USA * Riju Singhal, * Zulfiya Orynbayeva, * Ramalingam Venkat Kalyana Sundaram, * Jun Jie Niu, * Sayan Bhattacharyya, * Elina A. Vitol, * Michael G. Schrlau, * Elisabeth S. Papazoglou, * Gary Friedman & * Yury Gogotsi * Present address: Department of Chemical Sciences, Indian Institute of Science Education and Research, Kolkata, Mohanpur – 741252, Nadia, W.B., India * Sayan Bhattacharyya Contributions Y.G., G.F., E.P. and M.G.S. conceived the project and planned experiments. R.S. designed and fabricated the cellular endoscopes for all studies. Z.O. performed cell studies. R.S. and R.V.K.S. performed fluid and particulate flow studies. R.V.K.S. and M.G.S. carried out electrochemical studies. J.N., M.G.S. and E.V. performed SERS studies using the endoscopes. S.B. performed fluorescent labelling of the nanotubes. R.S., M.G.S., G.F. and Y.G. organized the manuscript, and all authors contributed to writing the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding authors Correspondence to: * Gary Friedman or * Yury Gogotsi Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (1,417 KB) Supplementary information Additional data
  • Biomagnification of cadmium selenide quantum dots in a simple experimental microbial food chain
    - UNKNOWN 6(1):65-71 (2011)
    Nature Nanotechnology | Article Biomagnification of cadmium selenide quantum dots in a simple experimental microbial food chain * R. Werlin1, 2 Search for this author in: * NPG journals * PubMed * Google Scholar * J. H. Priester2, 3, 4 Search for this author in: * NPG journals * PubMed * Google Scholar * R. E. Mielke2, 3, 4, 5 Search for this author in: * NPG journals * PubMed * Google Scholar * S. Krämer6 Search for this author in: * NPG journals * PubMed * Google Scholar * S. Jackson2, 7 Search for this author in: * NPG journals * PubMed * Google Scholar * P. K. Stoimenov8 Search for this author in: * NPG journals * PubMed * Google Scholar * G. D. Stucky2, 6, 8 Search for this author in: * NPG journals * PubMed * Google Scholar * G. N. Cherr2, 7 Search for this author in: * NPG journals * PubMed * Google Scholar * E. Orias1 Search for this author in: * NPG journals * PubMed * Google Scholar * P. A. Holden2, 3, 4 Contact P. A. Holden Search for this author in: * NPG journals * PubMed * Google Scholar * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Pages:65–71Year published:(2011)DOI:doi:10.1038/nnano.2010.251Received18 August 2010Accepted17 November 2010Published online19 December 2010 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Previous studies have shown that engineered nanomaterials can be transferred from prey to predator, but the ecological impacts of this are mostly unknown. In particular, it is not known if these materials can be biomagnified—a process in which higher concentrations of materials accumulate in organisms higher up in the food chain. Here, we show that bare CdSe quantum dots that have accumulated in Pseudomonas aeruginosa bacteria can be transferred to and biomagnified in the Tetrahymena thermophila protozoa that prey on the bacteria. Cadmium concentrations in the protozoa predator were approximately five times higher than their bacterial prey. Quantum-dot-treated bacteria were differentially toxic to the protozoa, in that they inhibited their own digestion in the protozoan food vacuoles. Because the protozoa did not lyse, largely intact quantum dots remain available to higher trophic levels. The observed biomagnification from bacterial prey is significant because bacteria are! at the base of environmental food webs. Our findings illustrate the potential for biomagnification as an ecological impact of nanomaterials. View full text Subject terms: * Electronic properties and devices * Surface patterning and imaging Figures at a glance * Figure 1: Extent and rate of growth of Tetrahymena varies with Pseudomonas prey treatment. , Tetrahymena population growth (filled symbols) and Pseudomonas population decline (open symbols) for control (triangles), CdSe QD (squares) and cadmium acetate (circles) treatments. Error bars represent standard error of the mean. For the Tetrahymena data, error bars are masked by the symbols. , Tetrahymena population increase for three individual cultures in the QD (squares) and cadmium acetate (circles) treatments. Tetrahymena cells that fed upon cadmium-acetate-grown bacteria stopped growing by 6 h, whereas those that fed on QD-grown bacteria continued to grow slowly for up to 14 h. * Figure 2: Tetrahymena cells after 24 h culture with Pseudomonas. –, Nomarski bright-field optical micrographs of Tetrahymena cells that have preyed on control (no cadmium) (), cadmium-acetate-grown () and CdSe QD-grown () Pseudomonas bacteria. Note the abnormally high accumulation of large food vacuoles (arrow) in . Some Pseudomonas cells can be seen in the media external to the Tetrahymena in all images. * Figure 3: Stunted digestion in Tetrahymena cells preying on CdSe QD-grown, but not cadmium-acetate-grown, Pseudomonas bacteria. –, Dark-field STEM images of Tetrahymena cells that have fed on control Pseudomonas (,), cadmium-acetate-grown bacteria (,) and CdSe QD-grown bacteria (,). ,, are taken at 1 h; is at 16 h, and , are at 24 h. Triangles, Pseudomonas cells; eFV and lFV, early and late food vacuoles; OA, oral apparatus; M and m, macronucleus and micronucleus. In , two eFV packed with undigested Pseudomonas cells are visible near the oral apparatus. Note the abundance of Pseudomonas outside the Tetrahymena cell. In , fine lamellar membranes (arrow) and intact Pseudomonas are seen in mid- to late-stage food vacuoles. A normal mitochondrion is also visible (star). In , the presence of an eFV at 1 h shows that normal phagocytic ingestion has occurred in cadmium acetate-grown Pseudomonas. In , intact Pseudomonas are found outside the Tetrahymena, and amorphous digestion products are seen in the lFV. Bright cadmium spots (arrow) appear throughout. In , eFV shows intact Pseudomonas, and lFV contains ! cellular debris, fine lamellar membranes and QDs (arrows). In , eFV (arrow) shows tightly packed, undigested Pseudomonas surrounded by numerous QDs. The observation of QDs throughout indicates that undigested QDs have crossed the food vacuole membrane. * Figure 4: CD:Se ratios obtained using EDS. Vertical lines represent the ranges of Cd:Se ratios. Boxes are bounded by the 75th and 25th percentiles; intermediate horizontal lines are data medians. The number of observations (100 nm2 spots) is located above each bar. The x-axis labels (left to right) include times relative to the time course of the trophic transfer experiments: as-synthesized CdSe QDs, washed CdSe QD-grown Pseudomonas (Pa) prey, endpoint CdSe QD-grown Pseudomonas outside the predator, endpoint Tetrahymena (Tt) food vacuole (FV) containing undigested CdSe QD-grown Pseudomonas, and endpoint Tetrahymena cytoplasm (CP) outside of food vacuoles (QD treatment). * Figure 5: High-resolution STEM image and EDS of Tetrahymena that has fed on QD-grown Pseudomonas, after 24 h. , High-angle annular dark-field micrograph of an EDS line scan (large inset) performed through one bright spot (putative CdSe QD as in Fig. 3f) in a region interior to a mitochondrion (small rectangle). , Six EDS spectra acquired in 5 nm steps. Spectra 1, 2 and 6 are external to, 3 and 5 are near the edge of, and 4 is internal to the 'bright spot' (~10 nm across) on the line scan axis (inset). Sloping lines drawn in spectra 2–5 provide baselines for judging peak magnitudes. The spectra clearly show an enrichment of cadmium from the edges to the interior of the bright spot, consistent with a QD-type particle. Note that the Se peak overlaps the Os peak, precluding reliable identification of Se enrichment along this scan. * Figure 6: Mass- and volume-based cadmium concentrations show biomagnification in the predator relative to the prey. ,, Cellular cadmium concentrations with standard error bars for CdSe QD (black bars) and cadmium acetate (white bars) treatments plotted as either cadmium mass per cell volume () or cadmium mass per dry cell biomass (). The concentration ratio of the 16 h Tetrahymena to the 0 h Pseudomonas represents the TTF. Volume- and dry mass-based TTFs were, respectively, 4.82 and 5.37 (QD treatment) and 2.97 and 3.54 (cadmium acetate treatment). Ratios greater than 1 reflect cadmium biomagnification during trophic transfer. Author information * Abstract * Author information * Supplementary information Affiliations * Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106-9625, USA * R. Werlin & * E. Orias * UC Center for the Environmental Implications of Nanotechnology (UC CEIN), University of California, Santa Barbara, California 93106-5131, USA * R. Werlin, * J. H. Priester, * R. E. Mielke, * S. Jackson, * G. D. Stucky, * G. N. Cherr & * P. A. Holden * Donald Bren School of Environmental Science and Management, University of California, Santa Barbara, California 93106-5131, USA * J. H. Priester, * R. E. Mielke & * P. A. Holden * Earth Research Institute, University of California, Santa Barbara, California 93106-5131, USA * J. H. Priester, * R. E. Mielke & * P. A. Holden * Jet Propulsion Laboratory, California Institute of Technology – NASA, Planetary Science, Pasadena, California 91109-8099, USA * R. E. Mielke * Department of Materials, University of California, Santa Barbara, California 93106-5050, USA * S. Krämer & * G. D. Stucky * Departments of Environmental Toxicology and Nutrition, Bodega Marine Laboratory, University of California, Davis, Bodega Bay, California 94923-0247, USA * S. Jackson & * G. N. Cherr * Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106-9510, USA * P. K. Stoimenov & * G. D. Stucky Contributions P.A.H., J.H.P., R.W., E.O. and G.D.S. designed the experiment. P.K.S. and G.D.S. synthesized and provided the quantum dots. R.W. and J.H.P. executed the trophic transfer experiments. R.E.M. and S.K. performed the electron microscopy and EDS analyses. G.N.C. and S.J. determined protein carbonyl content. All authors contributed to the writing of the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * P. A. Holden Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (743 KB) Supplementary information Additional data

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