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Latest Articles Include:

• Molecular golems
  - Nat Nanotechnol 7(1):1-2 (2012)
  Article preview View full access options Nature Nanotechnology | Thesis Molecular golems * Chris Toumey1Journal name:Nature NanotechnologyVolume: 7,Pages:1–2Year published:(2012)DOI:doi:10.1038/nnano.2011.239Published online28 December 2011 The golem stories of Jewish history can provide a framework for thinking about some of the ethical questions involved in nanotechnology and nanomedicine, as explains. Subject terms: * Ethical, legal and other societal issues Article preview Read the full article * Instant access to this article: US$32 Buy now * Subscribe to Nature Nanotechnology for full access: Subscribe * Personal subscribers: Log in Additional access options: * Login via Athens * Login via your Institution * Purchase a site license * Use a document delivery service * 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. Author information Article tools * Print * Email * 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 Corresponding author Correspondence to: * Chris Toumey Author Details * Chris Toumey Contact Chris Toumey Search for this author in: * NPG journals * PubMed * Google Scholar Additional data
• Our choice from the recent literature
  - Nat Nanotechnol 7(1):3 (2012)
  Article preview View full access options Nature Nanotechnology | Research Highlights Our choice from the recent literature Journal name:Nature NanotechnologyVolume: 7,Page:3Year published:(2012)DOI:doi:10.1038/nnano.2011.244Published online28 December 2011 Appl. Phys. Lett. 99, 203109 (2011) © 2011 AIP Electron beams are typically plane waves. This means that the beam phase is identical for all points in a plane perpendicular to the beam direction. The phase of an electron vortex beam, on the other hand, describes a spiral. As a result, vortex beams carry orbital angular moment and magnetic moment, which leads to unique interactions with matter. Jo Verbeeck of the University of Antwerp and colleagues from Austria, the Netherlands and Canada have now demonstrated an electron vortex beam with a diameter of less than 1.2 Å. Article preview Read the full article * Instant access to this article: US$32 Buy now * Subscribe to Nature Nanotechnology for full access: Subscribe * Personal subscribers: Log in Additional access options: * Login via Athens * Login via your Institution * Purchase a site license * Use a document delivery service * 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. Author information Article tools * Print * Email * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Additional data
• Molecular electronics: Flipping a single proton switch
  - Nat Nanotechnol 7(1):5-6 (2012)
  Article preview View full access options Nature Nanotechnology | News and Views Molecular electronics: Flipping a single proton switch * Peter Liljeroth1Journal name:Nature NanotechnologyVolume: 7,Pages:5–6Year published:(2012)DOI:doi:10.1038/nnano.2011.242Published online28 December 2011 A four-level conductance switch can be created by using a scanning tunnelling microscope to remove a hydrogen atom from the central cavity of a porphyrin molecule. Subject terms: * Molecular machines and motors * Surface patterning and imaging Article preview Read the full article * Instant access to this article: US$18 Buy now * Subscribe to Nature Nanotechnology for full access: Subscribe * Personal subscribers: Log in Additional access options: * Login via Athens * Login via your Institution * Purchase a site license * Use a document delivery service * 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. Author information Article tools * Print * Email * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Affiliations * Peter Liljeroth is at the Department of Applied Physics, Aalto University School of Science, PO Box 15100, 00076 Aalto, Finland Corresponding author Correspondence to: * Peter Liljeroth Author Details * Peter Liljeroth Contact Peter Liljeroth Search for this author in: * NPG journals * PubMed * Google Scholar Additional data
• Nanofluidics: Neither shaken nor stirred
  - Nat Nanotechnol 7(1):6-7 (2012)
  Article preview View full access options Nature Nanotechnology | News and Views Nanofluidics: Neither shaken nor stirred * Aldo Jesorka1 * Owe Orwar1, 2 * Affiliations * Corresponding authorJournal name:Nature NanotechnologyVolume: 7,Pages:6–7Year published:(2012)DOI:doi:10.1038/nnano.2011.236Published online28 December 2011 Bioinspired nanoreactor arrays can be used to controllably mix subattolitre volumes of liquids. Subject terms: * Nanofluidics * Nanomaterials Article preview Read the full article * Instant access to this article: US$18 Buy now * Subscribe to Nature Nanotechnology for full access: Subscribe * Personal subscribers: Log in Additional access options: * Login via Athens * Login via your Institution * Purchase a site license * Use a document delivery service * 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. Author information Article tools * Print * Email * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Affiliations * Department of Chemical and Biological Engineering, Chalmers University of Technology, 41296 Göteborg, Sweden * Aldo Jesorka & * Owe Orwar * Sanofi-Aventis R&D, 91385 Chilly-Mazarin Cedex, France * Owe Orwar Corresponding author Correspondence to: * Owe Orwar Author Details * Aldo Jesorka Search for this author in: * NPG journals * PubMed * Google Scholar * Owe Orwar Contact Owe Orwar Search for this author in: * NPG journals * PubMed * Google Scholar Additional data
• Nanoimaging: Image contrast using time
  - Nat Nanotechnol 7(1):8-9 (2012)
  Article preview View full access options Nature Nanotechnology | News and Views Nanoimaging: Image contrast using time * Kevin Tvrdy1 * Michael S. Strano1 * Affiliations * Corresponding authorJournal name:Nature NanotechnologyVolume: 7,Pages:8–9Year published:(2012)DOI:doi:10.1038/nnano.2011.241Published online28 December 2011 Laser-based imaging can distinguish between semiconducting and metallic nanotubes in vitro and in vivo, offering a way to study the interactions of carbon nanostructures in biological systems without the use of labels. Subject terms: * Carbon nanotubes and fullerenes * Surface patterning and imaging Article preview Read the full article * Instant access to this article: US$18 Buy now * Subscribe to Nature Nanotechnology for full access: Subscribe * Personal subscribers: Log in Additional access options: * Login via Athens * Login via your Institution * Purchase a site license * Use a document delivery service * 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. Author information Article tools * Print * Email * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Affiliations * Kevin Tvrdy and Michael S. Strano are in the Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA Corresponding author Correspondence to: * Michael S. Strano Author Details * Kevin Tvrdy Search for this author in: * NPG journals * PubMed * Google Scholar * Michael S. Strano Contact Michael S. Strano Search for this author in: * NPG journals * PubMed * Google Scholar Additional data
• Bionanoscience: Nanoparticles in the life of a cell
  - Nat Nanotechnol 7(1):9-10 (2012)
  Article preview View full access options Nature Nanotechnology | News and Views Bionanoscience: Nanoparticles in the life of a cell * Huw Summers1Journal name:Nature NanotechnologyVolume: 7,Pages:9–10Year published:(2012)DOI:doi:10.1038/nnano.2011.207Published online06 November 2011 The cycle of cell birth, growth and division can affect the uptake and dilution of nanoparticles in cells, suggesting that the evolution of nanoparticle dose within a cell population is linked to the life cycle of cells. Subject terms: * Nanomedicine * Nanoparticles * Environmental, health and safety issues Article preview Read the full article * Instant access to this article: US$18 Buy now * Subscribe to Nature Nanotechnology for full access: Subscribe * Personal subscribers: Log in Additional access options: * Login via Athens * Login via your Institution * Purchase a site license * Use a document delivery service * 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. Author information Article tools * Print * Email * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Affiliations * Huw Summers is in the Centre for Nanohealth, College of Engineering, Swansea University, Singleton Park, Swansea SA2 8PP, UK Corresponding author Correspondence to: * Huw Summers Author Details * Huw Summers Contact Huw Summers Search for this author in: * NPG journals * PubMed * Google Scholar Additional data
• The properties and applications of nanodiamonds
  - Nat Nanotechnol 7(1):11-23 (2012)
  Nature Nanotechnology | Review The properties and applications of nanodiamonds * Vadym N. Mochalin1 * Olga Shenderova2 * Dean Ho3, 4 * Yury Gogotsi1 * Affiliations * Corresponding authorJournal name:Nature NanotechnologyVolume: 7,Pages:11–23Year published:(2012)DOI:doi:10.1038/nnano.2011.209Published online18 December 2011 Abstract * Abstract * Author information Article tools * Full text * Print * Email * pdf options * download pdf * view interactive pdfpowered by ReadCube * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Nanodiamonds have excellent mechanical and optical properties, high surface areas and tunable surface structures. They are also non-toxic, which makes them well suited to biomedical applications. Here we review the synthesis, structure, properties, surface chemistry and phase transformations of individual nanodiamonds and clusters of nanodiamonds. In particular we discuss the rational control of the mechanical, chemical, electronic and optical properties of nanodiamonds through surface doping, interior doping and the introduction of functional groups. These little gems have a wide range of potential applications in tribology, drug delivery, bioimaging and tissue engineering, and also as protein mimics and a filler material for nanocomposites. View full text Subject terms: * Nanomaterials * Nanomedicine * Synthesis and processing Figures at a glance * Figure 1: Detonation synthesis of nanodiamonds. , To synthesize nanodiamonds, explosives with a negative oxygen balance (for example a mix of 60 wt% TNT (C6H2(NO2)3CH3) and 40 wt% hexogen (C3H6N6O6)) are detonated in a closed metallic chamber in an atmosphere of N2, CO2 and liquid or solid H2O. After detonation, diamond-containing soot is collected from the bottom and the walls of the chamber. , Phase diagram showing that the most stable phase of carbon is graphite at low pressures, and diamond at high pressures, with both phases melting when at temperatures above 4,500 K (with the precise melting temperature for each phase depending on the pressure). The phase diagrams for nanoscale carbon are similar, but the liquid phase is found at lower temperatures38, 39. During detonation, the pressure and temperature rise instantaneously, reaching the Jouguet point (point A), which falls within the region of liquid carbon clusters of 1–2 nm in size for many explosives. As the temperature and pressure decrease along the isentrope! (red line), carbon atoms condense into nanoclusters, which further coalesce into larger liquid droplets and crystallize39. When the pressure drops below the diamond–graphite equilibrium line, the growth of diamond is replaced by the formation of graphite. , Schematic of the detonation wave propagation showing (I) the front of the shock wave caused by the explosion; (II) the zone of chemical reaction in which the explosive molecules decompose; (III) the Chapman–Jouguet plane (where P and T correspond to point A in Fig. 1b, indicating the conditions when reaction and energy release are essentially complete); (IV) the expanding detonation products; (V) the formation of carbon nanoclusters; (VI) the coagulation into liquid nanodroplets; and (VII) the crystallization, growth and agglomeration of nanodiamonds39. * Figure 2: Structure of a single nanodiamond particle. , Schematic model illustrating the structure of a single ~5-nm nanodiamond after oxidative purification. The diamond core is covered by a layer of surface functional groups, which stabilize the particle by terminating the dangling bonds. The surface can also be stabilized by the conversion of sp3 carbon to sp2 carbon. A section of the particle has been cut along the amber dashed lines and removed to illustrate the inner diamond structure of the particle. , Close-up views of two regions of the nanodiamond shown in . The sp2 carbon (shown in black) forms chains and graphitic patches (). The majority of surface atoms are terminated with oxygen-containing groups (; oxygen atoms are shown in red, nitrogen in blue). Some hydrocarbon chains (green, lower left of ) and hydrogen terminations (hydrogen atoms are shown in white) are also seen. , Each nanodiamond is made up of a highly ordered diamond core. Some nanodiamonds are faceted, such as the one shown in this transmission electr! on micrograph, whereas most have a rounded shape, as shown in . The inset is a fast Fourier transform of the micrograph, which confirms that this nanodiamond has a highly ordered diamond core. Panel , reproduced with permission from ref. 19, © 2011 ACS. * Figure 3: Raman spectroscopy and structure of nanodiamond. Electron micrographs showing detonation soot (bottom), purified nanodiamond (middle) and oxidized nanodiamond (top). The diamond cores in detonation soot seem to be completely covered by graphitic shells, and this is confirmed by the Raman spectrum (black line), which is dominated by the G-band of graphitic carbon at 1,590 cm−1 and has no diamond peak. Purified nanodiamonds are partially covered by a thin layer of graphite, so a diamond peak can be seen at 1,328 cm−1 in the Raman spectrum (blue line). This thin layer of graphite is completely removed by oxidation in air, so the Raman spectrum of oxidized nanodiamonds has an even stronger diamond peak (red line). The diamond peak in the Raman spectrum of purified and air oxidized nanodiamond (inset ) is a combination of peaks originating from larger (I) and smaller (II) coherence scattering domains. The phonon confinement model84 gives a good fit (blue line) to experimental data (open circles). The broad feature at 1,500�! ��1,800 cm−1 in the spectrum of air oxidized nanodiamond (inset ) originates from surface functional groups and adsorbed molecules, with some contribution from sp2 carbon atoms. The Raman spectra were recorded following excitation by an ultraviolet laser (325 nm). * Figure 4: Optical properties of nanodiamonds. , De-aggregation by salt-assisted dry milling reduces the size of diamond particles from ~1 μm to less than 10 nm (), and makes suspensions of the particles both darker and more transparent (). The changes in colour are not related to the presence of graphitic carbon56. , Photonic structures formed by centrifugation of suspensions of nanodiamonds in deionized water. , Covalently attaching ODA to nanodiamonds changes their optical properties. ND–ODA absorbs and re-emits light over a wide range of wavelengths, as can be seen in these excitation (purple) and emission (blue) spectra (). Moreover, and in contrast to non-functionalized nanodiamond, ND–ODA is strongly blue fluorescent when illuminated with ultraviolet light (). , ND–ODA can be used for bio-imaging, as illustrated by this confocal micrograph of the fluorescent scaffold made of ND–ODA–PLLA with 7F2 osteoblasts grown on it (see main text for details). Panel , reproduced with permission from ref. 62, © 2008! IOP. * Figure 5: Surface modification. Precise control over surface chemistry requires a sample of purified nanodiamond with only one kind of functional group attached to its surface. Nanodiamond terminated with carboxylic groups (ND–COOH; green region) is a common starting material (and is made by air oxidation or ozone treatment of nanodiamond, followed by treatment in aqueous HCl to hydrolyse anhydrides and remove metal impurities). The surface of ND–COOH can be modified by high-temperature gas treatments (red) or ambient-temperature wet chemistry techniques (blue). Heating in NH3, for example, can result in the formation of a variety of different surface groups including NH2, C–O–H, C≡N and groups containing C=N (refs 9, 48). Heating in Cl2 produces acylchlorides, and F2 treatment forms C–F groups (not shown)67, 137, 138. Treatment in H2 completely reduces C=O to C–O–H and forms additional C–H groups. Hydroxyl (OH) groups may be removed at higher temperatures or with longer hydrogenation tim! es, or by treatment in hydrogen plasma66. Annealing in N2, Ar or vacuum completely removes the functional groups and converts the nanodiamonds into graphitic carbon nano-onions139, 140. A wide range of surface groups and functionalized nanodiamonds can also be produced using wet chemistry treatments. * Figure 6: Advanced atomic-level composite design with nanodiamond. , Three examples of the interfaces between nanodiamond and different matrices. Nanodiamond can bind to SiC through C–Si bonds between the surface of the nanodiamond and the Si atoms in the SiC to produce ND–SiC (left). Carboxylic groups present on the nanodiamond surface can form salts by ion exchange reactions with different metal ions, such as Cu2+ (middle; ref. 141). Metal ions can be later reduced, forming an atomically thin metal layer around the particle. These metallized particles can be used as a means to disperse nanodiamonds in metals that do not wet carbon, and also to produce wear-resistant ND–Cu sliding contacts. Nanodiamonds with surface carboxylic groups can be functionalized through covalent attachment of ODA by amide bond formation (right). , Stress–strain curves for six ND–ODA–PLLA composites that contain different amounts of ND–ODA11. The Young's modulus of a given composite is proportional to the slope of its stress–strain curve. , Aminate! d nanodiamond, produced through covalent attachment of ethylenediamine to carboxylic groups on the surface of the nanodiamond, can replace traditional epoxy curing agents (amines) in reaction with epoxy resin. This results in the covalent incorporation of the nanodiamond into the epoxy polymer network at a molecular level, improving the mechanical properties of the polymer matrix14. * Figure 7: Nanodiamonds and drug delivery. , DNA can be electrostatically attached to nanodiamonds by first covering negatively charged carboxylated nanodiamonds with positively charged PEI800 molecules. A similar electrostatic binding strategy has been used to attach siRNA and doxorubicin (Dox) to nanodiamond104. , Schematic representation of a proposed mechanism for ND–Dox complexes interacting with a cell. 1, Endocytosis of the ND–drug complexes. 2, Diffusion of free drug molecules across the cell membrane. 3, ABC transporter proteins efflux free drug molecules out of the cell, whereas ND–drug complexes are able to remain inside the cell and deliver a steady, lethal dose of the drug to the tumour. , Photographs of breast-cancer tumours after treatment with ND–Dox (top), Dox (middle) and a control (PBS; bottom). Two representative tumours are shown in each case. The large size of the tumours excised after long-term treatment with Dox or PBS illustrates a reduced ability of Dox to inhibit tumour growth owing! to the extreme resistance of the 4T1 breast cancer to chemotherapy. In contrast, treatment with ND–Dox clearly reduces the size of the tumours. Figure reproduced with permission from: , ref. 127, © 2009 ACS; , ref. 142, © 2011 AAAS; , ref. 104, © 2011 AAAS. Author information * Abstract * Author information Affiliations * Department of Materials Science and Engineering and A. J. Drexel Nanotechnology Institute, Drexel University, Philadelphia, Pennsylvania 19104, USA * Vadym N. Mochalin & * Yury Gogotsi * International Technology Center, Raleigh, North Carolina 27617, USA * Olga Shenderova * Departments of Biomedical and Mechanical Engineering, Northwestern University, Evanston, Illinois 60208, USA * Dean Ho * Institute for BioNanotechnology in Medicine (IBNAM) and Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, Illinois 60611, USA * Dean Ho Corresponding author Correspondence to: * Yury Gogotsi Author Details * Vadym N. Mochalin Search for this author in: * NPG journals * PubMed * Google Scholar * Olga Shenderova Search for this author in: * NPG journals * PubMed * Google Scholar * Dean Ho Search for this author in: * NPG journals * PubMed * Google Scholar * Yury Gogotsi Contact Yury Gogotsi Search for this author in: * NPG journals * PubMed * Google Scholar Additional data
• Synthetically programmable nanoparticle superlattices using a hollow three-dimensional spacer approach
  - Nat Nanotechnol 7(1):24-28 (2012)
  Nature Nanotechnology | Letter Synthetically programmable nanoparticle superlattices using a hollow three-dimensional spacer approach * Evelyn Auyeung1, 2, 5 * Joshua I. Cutler2, 3, 5 * Robert J. Macfarlane2, 3 * Matthew R. Jones1, 2 * Jinsong Wu4 * George Liu4 * Ke Zhang2, 3 * Kyle D. Osberg1, 2 * Chad A. Mirkin1, 2, 3 * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 7,Pages:24–28Year published:(2012)DOI:doi:10.1038/nnano.2011.222Received14 July 2011Accepted14 November 2011Published online11 December 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * pdf options * download pdf * view interactive pdfpowered by ReadCube * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Crystalline nanoparticle arrays and superlattices with well-defined geometries can be synthesized by using appropriate electrostatic1, 2, 3, hydrogen-bonding4, 5 or biological recognition interactions6, 7, 8, 9, 10, 11. Although superlattices with many distinct geometries can be produced using these approaches, the library of achievable lattices could be increased by developing a strategy that allows some of the nanoparticles within a binary lattice to be replaced with 'spacer' entities that are constructed to mimic the behaviour of the nanoparticles they replace, even though they do not contain an inorganic core. The inclusion of these spacer entities within a known binary superlattice would effectively delete one set of nanoparticles without affecting the positions of the other set. Here, we show how hollow DNA nanostructures can be used as 'three-dimensional spacers' within nanoparticle superlattices assembled through programmable DNA interactions7, 11, 12, 13, 14! , 15, 16. We show that this strategy can be used to form superlattices with five distinct symmetries, including one that has never before been observed in any crystalline material. View full text Subject terms: * Molecular self-assembly * Synthesis and processing Figures at a glance * Figure 1: Use of a three-dimensional spacer in DNA-programmable crystallization of gold nanoparticles. , Schematic of the synthesis of three-dimensional spacer particles by crosslinking alkyne-modified DNA on the gold nanoparticle surface and subsequent dissolution of the gold nanoparticle template to create hollow particles (shown in grey). ,, Assembly using a non-self-complementary binary DNA linker system (red and blue strands) results in a bcc lattice when only SNA–AuNPs are used (), and in a simple cubic lattice when a spacer particle is used (). The shaded region surrounding the gold nanoparticle and spacer particles denotes the crosslinked layer between the DNA binding region and the gold (or hollow) core. * Figure 2: SAXS data for seven distinct gold nanoparticle superlattices and 'lattice X'. –, One- and two-dimensional X-ray scattering patterns (left and bottom right of each panel) and schematic unit cell (top right; crosslinked shell omitted) showing the formation of the following superlattices: bcc (); simple cubic (); AB2 (isostructural with AlB2) (); simple hexagonal (); graphite-type (); AB6 (isostructural with Cs6C60) (); bcc (); 'lattice X' (). Five of the seven lattices (,,,,) are made using a mixture of gold and hollow SNA particles. Red traces are the experimentally obtained scattering patterns and the black peaks are the theoretical scattering for each respective lattice. Higher reflections were not indexed for the purpose of clarity. * Figure 3: SAXS data for cubic lattices made from nanoparticles of different sizes. SAXS data with indexed reflections corresponding to a simple cubic lattice made from 5 nm gold nanoparticles (grey line), 10 nm gold nanoparticles (black) and 20 nm gold nanoparticles (red). A hollow SNA particle is incorporated into the centre of each unit cell. Crosslinked shells in the schematic unit cells are omitted for clarity. Lines between particles denote edges of the unit cell, not direct connections between gold nanoparticles. * Figure 4: TEM images of the AB6-type lattices. , AB6-type lattice formed from 20 nm and 10 nm gold nanoparticles. , A bcc lattice formed from 20 nm gold nanoparticles and 10 nm hollow SNA spacers. , Lattice X structure formed from 20 nm hollow SNA spacers and 10 nm gold nanoparticles. All scale bars, 200 nm. Lattice projections shown in the insets are outlined in the TEM images. A three-dimensional reconstruction of a thin (~100 nm) section of the lattice in was obtained from electron tomography. , Representative snapshot of TEM images obtained in the tilt series, where the hole was used as a reference point for alignment (scale bar, 200 nm). ,, Snapshots from the reconstructed lattice along the [100] zone axis () and [111] zone axis () of a bcc lattice. Insets: perfect bcc lattice along each respective zone axis. A unit cell in each reconstructed lattice is outlined in red for clarity. Author information * Abstract * Author information * Supplementary information Primary authors * These authors contributed equally to this work * Evelyn Auyeung & * Joshua I. Cutler Affiliations * Department of Materials Science and Engineering, Evanston, Illinois 60208-3113, USA * Evelyn Auyeung, * Matthew R. Jones, * Kyle D. Osberg & * Chad A. Mirkin * International Institute for Nanotechnology, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA * Evelyn Auyeung, * Joshua I. Cutler, * Robert J. Macfarlane, * Matthew R. Jones, * Ke Zhang, * Kyle D. Osberg & * Chad A. Mirkin * Department of Chemistry, Evanston, Illinois 60208-3113, USA * Joshua I. Cutler, * Robert J. Macfarlane, * Ke Zhang & * Chad A. Mirkin * Electron Probe Instrumentation Center, Northwestern University, Evanston, Illinois 60208-3113, USA * Jinsong Wu & * George Liu Contributions E.A. and J.I.C. designed the experiments, prepared the materials, collected and analysed the data, and wrote the manuscript. R.J.M. designed the experiments and collected and analysed the data. M.R.J. collected and analysed the data. J.W. and G.L. analysed data for the tomography experiments. K.Z. and K.D.O. designed the experiments. C.A.M. designed the experiments and wrote the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * Chad A. Mirkin Author Details * Evelyn Auyeung Search for this author in: * NPG journals * PubMed * Google Scholar * Joshua I. Cutler Search for this author in: * NPG journals * PubMed * Google Scholar * Robert J. Macfarlane Search for this author in: * NPG journals * PubMed * Google Scholar * Matthew R. Jones Search for this author in: * NPG journals * PubMed * Google Scholar * Jinsong Wu Search for this author in: * NPG journals * PubMed * Google Scholar * George Liu Search for this author in: * NPG journals * PubMed * Google Scholar * Ke Zhang Search for this author in: * NPG journals * PubMed * Google Scholar * Kyle D. Osberg Search for this author in: * NPG journals * PubMed * Google Scholar * Chad A. Mirkin Contact Chad A. Mirkin Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (3,504 KB) Supplementary information Movies * Supplementary information (2,399 KB) Supplementary movie 1 * Supplementary information (2,308 KB) Supplementary movie 2 * Supplementary information (3,189 KB) Supplementary movie 3 Additional data
• Direct visualization of large-area graphene domains and boundaries by optical birefringency
  - Nat Nanotechnol 7(1):29-34 (2012)
  Nature Nanotechnology | Letter Direct visualization of large-area graphene domains and boundaries by optical birefringency * Dae Woo Kim1, 3 * Yun Ho Kim1, 2, 3 * Hyeon Su Jeong1 * Hee-Tae Jung1 * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 7,Pages:29–34Year published:(2012)DOI:doi:10.1038/nnano.2011.198Received12 September 2011Accepted13 October 2011Published online20 November 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * pdf options * download pdf * view interactive pdfpowered by ReadCube * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg The boundaries between domains in single-layer graphene1, 2, 3, 4 strongly influence its electronic properties5, 6, 7, 8, 9, 10, 11, 12. However, existing approaches for domain visualization, which are based on microscopy and spectroscopy2, 12, 13, 14, 15, 16, are only effective for domains that are less than a few micrometres in size. Here, we report a simple method for the visualization of arbitrarily large graphene domains by imaging the birefringence of a graphene surface covered with nematic liquid crystals. The method relies on a correspondence between the orientation of the liquid crystals and that of the underlying graphene, which we use to determine the boundaries of macroscopic domains. View full text Subject terms: * Electronic properties and devices * Molecular self-assembly * Nanometrology and instrumentation * Structural properties * Surface patterning and imaging * Synthesis and processing Figures at a glance * Figure 1: Schematic of 4-n-alkyl-4′-cyanobiphenyl (nCB) liquid crystals on graphene and TEM image of the graphene film and its domain boundary. , Liquid-crystal film on graphene transferred to various substrates. Graphene was transferred onto glass or SiO2/Si substrates. Bottom: Schematic of liquid crystal film, graphene and substrate, and molecular structure of nematic () liquid-crystal materials and the thermal transition temperature. , The graphene film was transferred on a holey carbon grid (optical microscopy (OM) image) and SAED patterns were taken from square regions; these indicate good long-range order. , Magnified image of the graphene film; a sharp and single hexagonal SAED pattern was obtained from the bright region. * Figure 2: Optical visibility of the domain boundaries of graphene using aligned liquid-crystal material (5CB) and birefringent colour transition while rotating the sample. , POM images of liquid crystal-coated graphene films on a SiO2/Si substrate. Although the domains or boundaries of the graphene are not observable without liquid crystal (inset, optical microscopy), the POM image shows graphene domains and boundaries on the SiO2/Si substrate. was spin-coated on the same sample, which was then heated to 40 °C and subsequently cooled to room temperature. , Liquid-crystal molecules have different orientations depending on the graphene domain, resulting in various birefringent colours. , When the sample in was rotated 30° in a clockwise direction, the greenish region (indicated by the red dashed circle) became dark, because the optical axis of the liquid-crystal molecules anchored on the graphene domain were now parallel to the polarizer direction. Reddish regions in (indicated by the yellow dashed circle) became white as the sample was rotated. ,, Schematic illustrations of and as liquid-crystal molecules are rotated (by rotation of the samp! le stage), resulting in a colour change. P, polarizer; A, analyser. * Figure 3: Schematic of liquid crystal alignment on the surface of the graphene. The alkyl chains of occupy alternate positions on the hexagons within the graphene surface. Graphene grown on the surface of the copper foil has multiple domains with different lattice orientations. The alignment directions of liquid-crystal molecules differ in accordance with the graphene domains. Red arrows indicate the aligned director field of the liquid crystal. Short yellow lines indicate liquid-crystal molecules lying (or planar anchoring) on the graphene film. * Figure 4: Thermal and electric-field recovery of liquid-crystal molecules (5CB) on graphene. , Liquid-crystal molecules aligned on the graphene. , Above the isotropic transition temperature (40 °C), the transmitted intensity of the polarized light is quite low, with the dark colour therefore representing the isotropic state. , As the sample is cooled, liquid-crystal molecules become re-aligned. , In an electric field (2 V µm−1), liquid-crystal molecules undergo a transition that results in a vertically aligned structure of the molecules. When the electric field is removed, the liquid-crystal molecules again become aligned. The inset in Fig. 4e shows a conoscopic interference pattern. * Figure 5: Relationships between copper domains and graphene domains. , Optical image of copper domains after graphene growth. To mark the selected region, gold (40 nm) was evaporated using an electron-beam evaporator. , POM image of graphene with liquid crystals; graphene has been transferred from the copper region of to the glass substrate. , Extracted boundaries of copper domains in overlapped on the POM image of . The shape and size of the graphene domains match those of the copper domains relatively well. Author information * Abstract * Author information * Supplementary information Primary authors * These authors contributed equally to this work * Dae Woo Kim & * Yun Ho Kim Affiliations * National Research Lab, for Organic Opto-Electronic Materials, Department of Chemical and Biomolecular Eng. (BK-21), Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea * Dae Woo Kim, * Yun Ho Kim, * Hyeon Su Jeong & * Hee-Tae Jung * Department of Biomedical Engineering, Washington University in St Louis, 1 Brookings Drive, St Louis, Missouri 63130, USA * Yun Ho Kim Contributions D.W.K., Y.H.K., H.S.J. and H-T.J. wrote the paper. D.W.K., Y.H.K. and H-T.J. conceived and directed the research. D.W.K. prepared graphene and carried out characterization using electron microscopy. D.W.K., Y.H.K. and H.S.J. carried out liquid-crystal cell experiments and interpreted liquid-crystal alignment on the graphene. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * Hee-Tae Jung Author Details * Dae Woo Kim Search for this author in: * NPG journals * PubMed * Google Scholar * Yun Ho Kim Search for this author in: * NPG journals * PubMed * Google Scholar * Hyeon Su Jeong Search for this author in: * NPG journals * PubMed * Google Scholar * Hee-Tae Jung Contact Hee-Tae Jung Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (955 KB) Supplementary information Additional data
• Mechanically controlled molecular orbital alignment in single molecule junctions
  - Nat Nanotechnol 7(1):35-40 (2012)
  Nature Nanotechnology | Letter Mechanically controlled molecular orbital alignment in single molecule junctions * Christopher Bruot1 * Joshua Hihath1, 2 * Nongjian Tao1 * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 7,Pages:35–40Year published:(2012)DOI:doi:10.1038/nnano.2011.212Received20 September 2011Accepted31 October 2011Published online04 December 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * pdf options * download pdf * view interactive pdfpowered by ReadCube * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Research in molecular electronics often involves the demonstration of devices that are analogous to conventional semiconductor devices, such as transistors and diodes1, but it is also possible to perform experiments that have no parallels in conventional electronics. For example, by applying a mechanical force to a molecule bridged between two electrodes, a device known as a molecular junction, it is possible to exploit the interplay between the electrical and mechanical properties of the molecule to control charge transport through the junction2, 3, 4, 5, 6, 7, 8. 1,4′-Benzenedithiol is the most widely studied molecule in molecular electronics9, 10, 11, 12, 13, 14, 15, 16, 17, 18, and it was shown recently that the molecular orbitals can be gated by an applied electric field11. Here, we report how the electromechanical properties of a 1,4′-benzenedithiol molecular junction change as the junction is stretched and compressed. Counterintuitively, the conductance increases ! by more than an order of magnitude during stretching, and then decreases again as the junction is compressed. Based on simultaneously recorded current–voltage and conductance–voltage characteristics, and inelastic electron tunnelling spectroscopy, we attribute this finding to a strain-induced shift of the highest occupied molecular orbital towards the Fermi level of the electrodes, leading to a resonant enhancement of the conductance. These results, which are in agreement with the predictions of theoretical models14, 15, 16, 17, 19, 20, also clarify the origins of the long-standing discrepancy between the calculated and measured conductance values of 1,4′-benzenedithiol, which often differ by orders of magnitude21. View full text Subject terms: * Electronic properties and devices Figures at a glance * Figure 1: Changes in conductance of BDT due to stretching. , Schematic of a molecular junction (top). Schematic energy diagram (bottom) showing how the energy of the HOMO changes relative to EF of the electrodes as electrode separation increases. , Characteristic conductance histograms at room temperature (black) and 4.2 K (red). Histograms offset for clarity. ,, Plots of conductance (in units of G0) versus electrode displacement measured at 4.2 K. For some junctions the conductance increases with displacement (), whereas for others the conductance–displacement curves are either flat or bowl-shaped (). Different colours in and represent different junctions, and the traces have been offset for clarity. * Figure 2: Differential conductance and IETS of BDT junctions as a result of stretching and compressing. , Plot of conductance G versus electrode displacement for a junction during repeated stretching and compressing at 4.2 K. , Differential conductance curves (G versus V) for positions 1–8 in . The curves show clear, reversible changes in asymmetry as the mechanical force changes. , IET spectra (d2I/dV2 versus V) also show reversible changes. Both the G–V curves and the IET spectra are offset for clarity. ,, Plots of rectification ratio at V = 0.2 V () and peak height ratio for the ±14 mV mode () versus electrode displacement. Red curves are fits to guide the eye. See Supplementary Information for all G–V curves and IET spectra for this junction, including the assignment of vibration modes to the observed peaks. * Figure 3: Conductance switching behaviour of two BDT junctions. , Plot of conductance G versus electrode displacement showing switching and increasing conductance behaviour. , Differential conductance (G–V) curves at the four different positions indicated in : the curve at position 3 is clearly more symmetric than at position 2. ,, IET spectra at positions 1 and 2 () and 3 and 4 () in , showing that changes in the conductance lead to changes in the intensity and shape of the peaks. IET spectra are plotted on the same scale and are offset for clarity. , Plot of conductance versus displacement for a different junction, showing the conductance first decreasing and then increasing after a switching event. , G–V curves from positions 1 and 2 in . All measurements performed at 4.2 K. * Figure 4: Exploring the energy levels of a molecular junction. , Plot of conductance versus electrode displacement of a BDT junction at 4.2 K recorded with the junction being stretched and compressed much faster than the plots shown in Figs 2 and 3. The conductance decreases when the junction is compressed, and then increases to a relatively high value when the junction is stretched. , Plots of current I versus bias voltage V at the three positions indicated in , recorded with V being swept much faster than the plots shown in Figs 2 and 3. Thin lines are fits to the data. , Plots of ln(I/V2) versus 1/V for three different values of the displacement (based on fits to the I–V curves in ). The height of the barrier that electrons have to tunnel through is determined by the transition voltage, which is the voltage corresponding to the minimum of each plot (indicated by arrows). The height of the barrier decreases as the molecule is stretched. Author information * Abstract * Author information * Supplementary information Affiliations * Center for Bioelectronics and Biosensors, Biodesign Institute, School of Electrical, Energy and Computer Engineering, Arizona State University; Tempe, Arizona 85287-5801, USA * Christopher Bruot, * Joshua Hihath & * Nongjian Tao * Department of Electrical and Computer Engineering, University of California Davis, Davis, California 95616, USA * Joshua Hihath Contributions N.J.T. conceived the experiment. C.B. and J.H. performed the experiment and analysed the data. C.B., J.H. and N.J.T. co-wrote the paper. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * Nongjian Tao Author Details * Christopher Bruot Search for this author in: * NPG journals * PubMed * Google Scholar * Joshua Hihath Search for this author in: * NPG journals * PubMed * Google Scholar * Nongjian Tao Contact Nongjian Tao Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (1,746 KB) Supplementary information Additional data
• A surface-anchored molecular four-level conductance switch based on single proton transfer
  - Nat Nanotechnol 7(1):41-46 (2012)
  Nature Nanotechnology | Letter A surface-anchored molecular four-level conductance switch based on single proton transfer * Willi Auwärter1, 2 * Knud Seufert1, 2 * Felix Bischoff1 * David Ecija1 * Saranyan Vijayaraghavan1 * Sushobhan Joshi1 * Florian Klappenberger1 * Niveditha Samudrala1 * Johannes V. Barth1 * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 7,Pages:41–46Year published:(2012)DOI:doi:10.1038/nnano.2011.211Received13 June 2011Accepted31 October 2011Published online11 December 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * pdf options * download pdf * view interactive pdfpowered by ReadCube * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg The development of a variety of nanoscale applications1, 2 requires the fabrication and control of atomic3, 4, 5 or molecular switches6, 7 that can be reversibly operated by light8, a short-range force9, 10, electric current11, 12 or other external stimuli13, 14, 15. For such molecules to be used as electronic components, they should be directly coupled to a metallic support and the switching unit should be easily connected to other molecular species without suppressing switching performance. Here, we show that a free-base tetraphenyl-porphyrin molecule, which is anchored to a silver surface, can function as a molecular conductance switch. The saddle-shaped molecule has two hydrogen atoms in its inner cavity that can be flipped between two states with different local conductance levels using the electron current through the tip of a scanning tunnelling microscope. Moreover, by deliberately removing one of the hydrogens, a four-level conductance switch can be created. The res! ulting device, which could be controllably integrated into the surrounding nanoscale environment, relies on the transfer of a single proton and therefore contains the smallest possible atomistic switching unit. View full text Subject terms: * Molecular machines and motors * Surface patterning and imaging Figures at a glance * Figure 1: Double proton transfer in 2H-TPP on Ag(111). , Pseudo three-dimensional rendering of a high-resolution STM image of 2H-TPP adsorbed on Ag(111). , Corresponding model consistent with the NEXAFS data (cf. Supplementary Fig. S1) highlights the saddle-shaped deformation resulting in two inequivalent pairs of pyrrole rings (α-pyr, marked in orange, and κ-pyr) , STM image of configuration Hα (I = 0.1 nA, U = −0.2 V). , Model highlighting the saddle-shaped deformation and the position of the hydrogen pair in configuration Hα. , STM image of configuration Hκ (I = 0.1 nA, U = −0.2 V). , Model of configuration Hκ. , Spatial dependence of the switching rate displayed with colour-coded dots (recorded at −1.6 V and 2 nA). The highest rates (yellow markers) are observed above the α-pyr. , Current versus time trace recorded at −1.9 V at the position indicated in . A switching between two current levels representing the high (h) and low (l) conductance states is clearly discernible. * Figure 2: Sequential deprotonation of 2H-TPP on Ag(111). , STM image of 2H-TPP (I = 0.2 nA, U = −0.2 V). , STM image of 1H-TPP. , STM image of 0-TPP. –, Tentative models illustrating the 2H-TPP, singly deprotonated 1H-TPP and fully deprotonated 0H-TPP species. , I(t) trace recorded at the centre of 2H-TPP at 1.9 V. The sudden decrease in current represents the single deprotonation to 1H-TPP. * Figure 3: Visualization of the four proton positions in 1H-TPP on Ag(111). –, STM images (–) of the same 1H-TPP molecule in four configurations representing the hydrogen positions schematically shown in corresponding models – (I = 0.2 nA, U = −0.2 V). , Current trace recorded in a slightly asymmetric position on a κ-pyr position (marked by the dot in ). The four conductance levels are clearly discernible (I = 0.4 nA, U = −1.6 V). * Figure 4: Current dependence of switching rate S for 2H-TPP and 1H-TPP recorded on an α-pyr position. , S increases linearly with tunnelling current I, pointing to a one-electron process driving proton transfer. Every single data point represents one I(t) spectrum where the current is averaged over the whole spectrum. The absolute rate depends on tip geometry (see Supplementary Information). The tip used for this experiment yields a rate S2H-TPP of 3.0 ± 0.1 s−1 nA−1 at a constant voltage of −1.6 V. , Comparison of S for 2H-TPP and 1H-TPP for five molecules. The blue line represents the normalized fits for the 2H-TPP species. Normalization to one average rate for 2H-TPP was performed to ease the comparison to 1H-TPP as the absolute rates for 2H-TPP vary from molecule to molecule. The green and red lines show the corresponding rates for the same molecules measured with an identical tip after the first deprotonation. Although the rates are generally similar for 2H-TPP and 1H-TPP, the ratio S1H-TPP/S2H-TPP varies between 0.76 (dark green) and 1.36 (dark red). * Figure 5: Voltage dependence of the switching rate S for 2H-TPP and 1H-TPP excited on an α-pyr position. , Voltage dependences measured at constant currents of 0.5, 2 and 4 nA, respectively, showing a threshold for switching of ~500 mV followed by a sharp increase with similar slope for both polarities (all data points were normalized to 1 at −1.5 V using scaling factors of 0.28 and 0.13, respectively). , Characteristic scanning tunnelling spectra recorded above an α-pyr position of 2H-TPP representing the local density of states, which is clearly asymmetric for both polarities. The broad feature around 700 mV is identified as the LUMO, whereas no occupied resonance is observed at negative bias voltages. The discontinuities observed at elevated voltages of both polarities are effects of proton transfer. , Scheme sketching the stepwise proton transfer via a cis-like intermediate state for 2H-TPP (the phenyl groups are omitted for clarity; see text for discussion). The macrocycle deformation on adsorption potentially lifts the degeneracy of both trans-configurations. Author information * Abstract * Author information * Supplementary information Primary authors * These authors contributed equally to this work * Willi Auwärter & * Knud Seufert Affiliations * Physik Department E20, Technische Universität München, D-85748 Garching, Germany * Willi Auwärter, * Knud Seufert, * Felix Bischoff, * David Ecija, * Saranyan Vijayaraghavan, * Sushobhan Joshi, * Florian Klappenberger, * Niveditha Samudrala & * Johannes V. Barth Contributions K.S., W.A., F.B., D.E., S.V., S.J. and N.S. performed the STM experiments and analysed and interpreted the experimental data. F.K. supported the data analysis and contributed to the NEXAFS experiments. W.A., K.S. and J.V.B conceived the studies and co-wrote the paper. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * Willi Auwärter Author Details * Willi Auwärter Contact Willi Auwärter Search for this author in: * NPG journals * PubMed * Google Scholar * Knud Seufert Search for this author in: * NPG journals * PubMed * Google Scholar * Felix Bischoff Search for this author in: * NPG journals * PubMed * Google Scholar * David Ecija Search for this author in: * NPG journals * PubMed * Google Scholar * Saranyan Vijayaraghavan Search for this author in: * NPG journals * PubMed * Google Scholar * Sushobhan Joshi Search for this author in: * NPG journals * PubMed * Google Scholar * Florian Klappenberger Search for this author in: * NPG journals * PubMed * Google Scholar * Niveditha Samudrala Search for this author in: * NPG journals * PubMed * Google Scholar * Johannes V. Barth Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (1,179 KB) Supplementary information Additional data
• Hole spin relaxation in Ge–Si core–shell nanowire qubits
  - Nat Nanotechnol 7(1):47-50 (2012)
  Nature Nanotechnology | Letter Hole spin relaxation in Ge–Si core–shell nanowire qubits * Yongjie Hu1, 2, 4 * Ferdinand Kuemmeth2 * Charles M. Lieber1, 3 * Charles M. Marcus2 * Affiliations * Contributions * Corresponding authorsJournal name:Nature NanotechnologyVolume: 7,Pages:47–50Year published:(2012)DOI:doi:10.1038/nnano.2011.234Received30 September 2011Accepted21 November 2011Published online18 December 2011 Abstract * Abstract * Author information Article tools * Full text * Print * Email * pdf options * download pdf * view interactive pdfpowered by ReadCube * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Controlling decoherence is the biggest challenge in efforts to develop quantum information hardware1, 2, 3. Single electron spins in gallium arsenide are a leading candidate among implementations of solid-state quantum bits, but their strong coupling to nuclear spins produces high decoherence rates4, 5, 6. Group IV semiconductors, on the other hand, have relatively low nuclear spin densities, making them an attractive platform for spin quantum bits. However, device fabrication remains a challenge, particularly with respect to the control of materials and interfaces7. Here, we demonstrate state preparation, pulsed gate control and charge-sensing spin readout of hole spins confined in a Ge–Si core–shell nanowire. With fast gating, we measure T1 spin relaxation times of up to 0.6 ms in coupled quantum dots at zero magnetic field. Relaxation time increases as the magnetic field is reduced, which is consistent with a spin–orbit mechanism that is usually masked by hyperfine ! contributions. View full text Subject terms: * Electronic properties and devices * Quantum information Figures at a glance * Figure 1: Spin qubit device based on a Ge–Si heterostructure nanowire. Scanning electron micrograph (with false colour) of a Ge–Si nanowire (horizontal) contacted by four palladium contacts (Sdd, Ddd, Ss, Ds, grey) and covered by a HfO2 gate dielectric layer. Top gates L, M and R (blue) induce a double quantum dot on the left device. Plunger gates LP and RP (orange) change the chemical potential of each dot independently, and side gates EL and ER (purple) improve electrical contact to the nanowire. A single quantum dot on the right half of the nanowire (isolated by chemical etching between Ddd and Ds) is capacitively coupled to a floating gate (green) and a tuning gate (yellow), and senses the charge state of the double dot. Inset: transmission electron microscope image of a typical nanowire with a single-crystal germanium core and an epitaxial silicon shell. * Figure 2: Zeeman splitting of confined holes in a single quantum dot. , Differential conductance gdd as a function of source–drain bias VSD and gate voltage VLP. Bright features with VSD > 0 correspond to discrete quantum states of N + 1 holes (N = even) in a single dot formed between gates L and M. , Slices of gdd along dashed lines in (VLP ≈ 655 mV) reveals Zeeman splitting of the N + 1 ground state for a magnetic field of B = 5 T. , Zeeman splitting ΔEZ versus B and a linear fit (dashed line) yield a g-factor of 1.02 ± 0.05. * Figure 3: Hole-spin doublets in a Ge–Si double dot. , Differential conductance dgs/dVL through the sensor dot versus B in the absence of current through the double quantum dot (source–drain bias = 0). Peaks in dgs/dVL versus VL indicate ground-state transitions when holes are removed from the left dot. , B dependence of reduced Coulomb spacings, , where VN are the peak ordinates (emphasized black dotted lines in ). , Data of plotted with guide lines g = 1.0 assuming a gate coupling efficiency α = 0.37 extracted from the single dot device in Fig. 2. * Figure 4: Pulsed gate measurements of spin relaxation times. , Sensor conductance gS near a spin-blocked charge transition between the left and right dot. Spin-to-charge conversion results in pulse triangles that fade away with increasing measurement time τM. Here, N and M indicate an odd number of holes in the left and right dots (denoted (1,1) in the main text). , Visibility I(τM) measured at the centre of the pulse triangle versus τM at different magnetic fields. The fitting curves (solid lines) give T1 = 0.6, 0.3 and 0.2 ms at B = 0 (red), 0.1 (blue) and 1 T (green), respectively. Inset: blue arrows visualize the T1 pulse sequence in gate voltage space when the measurement point is held in the centre of the pulse triangle. Author information * Abstract * Author information Affiliations * Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA * Yongjie Hu & * Charles M. Lieber * Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA * Yongjie Hu, * Ferdinand Kuemmeth & * Charles M. Marcus * School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA * Charles M. Lieber * Present address: Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA * Yongjie Hu Contributions Y.H. and F.K. performed the experiments. Y.H. prepared the materials and fabricated the devices. Y.H., F.K., C.M.L. and C.M.M. analysed the data and co-wrote the paper. All authors discussed the results and commented on the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding authors Correspondence to: * Charles M. Lieber or * Charles M. Marcus Author Details * Yongjie Hu Search for this author in: * NPG journals * PubMed * Google Scholar * Ferdinand Kuemmeth Search for this author in: * NPG journals * PubMed * Google Scholar * Charles M. Lieber Contact Charles M. Lieber Search for this author in: * NPG journals * PubMed * Google Scholar * Charles M. Marcus Contact Charles M. Marcus Search for this author in: * NPG journals * PubMed * Google Scholar Additional data
• Mixing subattolitre volumes in a quantitative and highly parallel manner with soft matter nanofluidics
  - Nat Nanotechnol 7(1):51-55 (2012)
  Nature Nanotechnology | Letter Mixing subattolitre volumes in a quantitative and highly parallel manner with soft matter nanofluidics * Sune M. Christensen1, 2, 3, 4 * Pierre-Yves Bolinger1, 2, 4 * Nikos S. Hatzakis1, 2, 3 * Michael W. Mortensen1, 2 * Dimitrios Stamou1, 2, 3 * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 7,Pages:51–55Year published:(2012)DOI:doi:10.1038/nnano.2011.185Received01 August 2011Accepted27 September 2011Published online30 October 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * pdf options * download pdf * view interactive pdfpowered by ReadCube * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Handling and mixing ultrasmall volumes of reactants in parallel can increase the throughput1, 2 and complexity3 of screening assays while simultaneously reducing reagent consumption1. Microfabricated silicon and plastic can provide reliable fluidic devices4, 5, 6, 7, 8, but cannot typically handle total volumes smaller than ~1 × 10–12 l. Self-assembled soft matter nanocontainers9, 10, 11, 12, 13, 14, 15, 16 can in principle significantly improve miniaturization and biocompatibility, but exploiting their full potential is a challenge due to their small dimensions17. Here, we show that small unilamellar lipid vesicles can be used to mix volumes as small as 1 × 10–19 l in a reproducible and highly parallelized fashion. The self-enclosed nanoreactors are functionalized with lipids of opposite charge to achieve reliable fusion. Single vesicles encapsulating one set of reactants are immobilized on a glass surface and then fused with diffusing vesicles of opposite charge that! carry a complementary set of reactants. We find that ~85% of the ~1 × 106 cm–2 surface-tethered nanoreactors undergo non-deterministic fusion, which is leakage-free in all cases, and the system allows up to three to four consecutive mixing events per nanoreactor. View full text Subject terms: * Nanofluidics * Nanomaterials Figures at a glance * Figure 1: Mixing of subattolitre volumes by fusion of SUVs of opposite charge. , Target SUV reactors containing alkaline phosphatase were immobilized at a PLL-g-PEG/PLL-g-PEG-biotin functionalized glass surface via biotin–neutravidin coupling. Fusion of cargo SUV reactors carrying FDP with the targets caused mixing of enzyme and substrate, thus triggering a biochemical reaction within the confined volumes of the surface-tethered reactors. , Histograms of reactor volumes for populations extruded with 50 nm and 400 nm filters, respectively. , The scheme in monitored by confocal microscopy of Texas Red-DHPE in the target reactor membrane (top), DiD in the cargo reactor membrane (middle) and fluorescein produced from the enzymatic reaction (bottom). Scale bar, 5 µm. A threshold was applied to the images to improve visualization. , Fusion monitored by FRET following lipid mixing. In this experiment target reactors were labelled with DiI (energy acceptor) and cargo reactors with DiO (energy donor). Lipid mixing upon fusion of a reactor pair gave rise to a! n abrupt increase in acceptor fluorescence with a corresponding FRET efficiency above the threshold for lipid mixing (dashed line). , Enzymatic production of fluorescein on fusion of a single reactor pair. Traces show the fluorescence intensity of the cargo reactor membrane label (DiD) and fluorescein. * Figure 2: Characterization of operational performance of the platform. , Scheme showing delivery of FDP to target reactors loaded with alkaline phosphatase (AP). , Volume histograms of all target reactors (N = 1,972) and reactors exhibiting product formation (on average 88%) for the AP–FDP system after 10 min incubation with cargo reactors. The black curve shows the percentage of successful product formation events as a function of reactor volume. The graph includes data from two independent experiments. , Scheme showing reaction experiment with membrane-activated lipase TLL. , Average density of reaction events for three enzyme–substrate systems. AR, Amplex Red. The numbers of fusion events used to calculate reaction densities were 1,676 (AP–FDP), 134 (TLL–CFDA), 42 (HRP–AR). , Leakage assay. , Time traces of the three labels corresponding to a single fusion event characterized by quenching of the donor (target reactor, DiI) and simultaneous increase in acceptor (cargo reactor, DiD) fluorescence. The steady signal of the lumen report! er, A488, demonstrates that the reactor remained sealed during the fusion process. , FRET efficiency trace corresponding to the fusion event in . , Histogram of retained A488 fluorescence quantified from single fusion events such as the one shown in . The retained percentage of A488 was obtained from the average A488 intensity before and after reactor fusion. Fitting the data with a normal distribution showed that the reactors retained 100 ± 1% (s.d.) of the encapsulated fluorophores. * Figure 3: Consecutive mixing events triggered in single target reactors. , Scheme showing repetitive fusion of cargo reactors to a single target. , Time course demonstrating two consecutive product formation events in a single target reactor (horizontal bars have been added to guide the eye). , Lipid mixing traces of cargo and target reactor fluorescence for a target accepting several events. The spikes in donor fluorescence between the labelled events correspond to cargo reactors diffusing in the vicinity of the target without fusing. , Accumulated fusion counts for all target reactors on the surface. Author information * Abstract * Author information * Supplementary information Primary authors * These authors contributed equally to this work * Sune M. Christensen & * Pierre-Yves Bolinger Affiliations * Bionanotechnology and Nanomedicine Laboratory, Department of Neuroscience and Pharmacology, University of Copenhagen, 2100 Copenhagen, Denmark * Sune M. Christensen, * Pierre-Yves Bolinger, * Nikos S. Hatzakis, * Michael W. Mortensen & * Dimitrios Stamou * Nano-Science Center, University of Copenhagen, 2100 Copenhagen, Denmark * Sune M. Christensen, * Pierre-Yves Bolinger, * Nikos S. Hatzakis, * Michael W. Mortensen & * Dimitrios Stamou * Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen, 2100 Copenhagen, Denmark * Sune M. Christensen, * Nikos S. Hatzakis & * Dimitrios Stamou Contributions D.S. designed and supervised the project. S.M.C. and P-Y.B. conducted most experiments and data analysis and contributed equally to this work. S.M.C. and D.S. wrote the paper. All authors helped design experiments, discussed the results and commented on the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * Dimitrios Stamou Author Details * Sune M. Christensen Search for this author in: * NPG journals * PubMed * Google Scholar * Pierre-Yves Bolinger Search for this author in: * NPG journals * PubMed * Google Scholar * Nikos S. Hatzakis Search for this author in: * NPG journals * PubMed * Google Scholar * Michael W. Mortensen Search for this author in: * NPG journals * PubMed * Google Scholar * Dimitrios Stamou Contact Dimitrios Stamou Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (767 KB) Supplementary information Additional data
• Label-free imaging of semiconducting and metallic carbon nanotubes in cells and mice using transient absorption microscopy
  - Nat Nanotechnol 7(1):56-61 (2012)
  Nature Nanotechnology | Letter Label-free imaging of semiconducting and metallic carbon nanotubes in cells and mice using transient absorption microscopy * Ling Tong1 * Yuxiang Liu2 * Bridget D. Dolash3 * Yookyung Jung4 * Mikhail N. Slipchenko2 * Donald E. Bergstrom3, 5 * Ji-Xin Cheng1, 2, 5 * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 7,Pages:56–61Year published:(2012)DOI:doi:10.1038/nnano.2011.210Received02 September 2011Accepted31 October 2011Published online04 December 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * pdf options * download pdf * view interactive pdfpowered by ReadCube * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg As interest in the potential biomedical applications of carbon nanotubes increases1, there is a need for methods that can image nanotubes in live cells, tissues and animals. Although techniques such as Raman2, 3, 4, photoacoustic5 and near-infrared photoluminescence imaging6, 7, 8, 9, 10 have been used to visualize nanotubes in biological environments, these techniques are limited because nanotubes provide only weak photoluminescence and low Raman scattering and it remains difficult to image both semiconducting and metallic nanotubes at the same time. Here, we show that transient absorption microscopy offers a label-free method to image both semiconducting and metallic single-walled carbon nanotubes in vitro and in vivo, in real time, with submicrometre resolution. By using appropriate near-infrared excitation wavelengths, we detect strong transient absorption signals with opposite phases from semiconducting and metallic nanotubes. Our method separates background signals gen! erated by red blood cells and this allows us to follow the movement of both types of nanotubes inside cells and in the blood circulation and organs of mice without any significant damaging effects. View full text Subject terms: * Surface patterning and imaging Figures at a glance * Figure 1: Semiconducting and metallic nanotubes exhibit strong transient absorption signals with opposite phases. , Extinction spectra of pure S-SWNT (left), pure M-SWNT (middle) and DNA-wrapped nanotubes (DNA-SWNT) (right) solutions. E11M, first optical transition of M-SWNTs; E22S, second optical transition of S-SWNTs. , Transient absorption images of pure S-SWNTs (left), pure M-SWNTs (middle) and DNA-SWNTs (right) in the in-phase channel. S-SWNTs and M-SWNTs showed positive and negative contrast, respectively. Scale bars, 2 µm. For all transient absorption images, pump and probe beams were at 707 nm and 885 nm, respectively. The laser power after the objective was 0.7 mW for the pump beam and 1.3 mW for the probe beam. , Raman spectra from pure S-SWNTs (left), pure M-SWNTs (middle) and DNA-SWNTs (right). * Figure 2: Comparison of transient absorption and AFM images of the same nanotube sample show that transient absorption microscopy can detect M-SWNTs and S-SWNTs in a chirality-insensitive manner. –, Transient absorption image (,) and AFM image () of pure S-SWNTs in the same area. –, Transient absorption image (,) and AFM image () of pure M-SWNTs in the same area. The pump and probe polarization directions are vertical in and and horizontal in and , as indicated by two-headed arrows above the transient absorption images. Nanotubes that are detected by transient absorption images are labelled with arrows on both the transient absorption and AFM images. In total, 21 of 25 S-SWNTs (84%) and 15 of 17 M-SWNTs (88%) seen in the AFM image were shown in the transient absorption image, respectively. Scale bars, 1 µm. Laser power post-objective was 0.7 mW for the pump beam and 1.3 mW for the probe beam. ,, Height analyses along the blue dotted lines in and , respectively, show individual nanotubes, not bundles. * Figure 3: Cellular uptake and intracellular trafficking of DNA-SWNTs monitored in real time by transient absorption microscopy. , Transient absorption image of DNA-SWNTs internalized by CHO cells after 24 h incubation. , Time-lapse images showing the fusion process for two nanotubes (indicated by white circle). , Time-lapse images showing the transport of a nanotube (indicated by white circle) back to the cell surface. The yellow line outlines the cell. Grey, transmission of cells; green, S-SWNTs; red, M-SWNTs. Scale bars, 5 µm. Pump, 707 nm; probe, 885 nm. The laser power post-objective was 1 mW for the pump beam and 1.6 mW for the probe beam. * Figure 4: Imaging of RBCs and F127-wrapped SWNTs (F127-SWNTs) circulating in the blood vessels of a mouse earlobe. , Thermal lens signals from isolated RBCs at different z-positions with z = 0 µm as the middle plane of a RBC. Pump, 707 nm; probe, 885 nm. , Phase of thermal lens signals from a RBC as a function of focus position. , In-phase channel signal (X), quadrature channel signal (Y) and amplitude of the thermal lens signal (R = (X2 + Y2)1/2) from a RBC as a function of focus position. ,, Intravital thermal lens imaging of RBCs in the blood vessel inside the earlobe of a mouse injected with pure saline when the pump beam is at 707 nm () and 790 nm (). The probe beam was fixed at 885 nm for both cases. Images were taken by line scanning (x–t scanning, 132 pixels per line). , Intravital imaging of F127-SWNTs in the blood vessel inside the earlobe of a mouse by line scanning (x–t scanning, 105 pixels per line). In-phase channel: transient absorption signals from F127-SWNTs. Quadrature channel: thermal lens signals from RBCs. Pump and probe beams were at 790 nm and 885 nm, respecti! vely. Laser power post-objective was 16 mW for both beams. Scale bars (–), 3 µm. , Intensity profile showing three peaks corresponding to the three dots in . * Figure 5: F127-SWNTs in different organs of treated mice are visualized by transient absorption microscopy at the cellular level. , Image of F127-SWNTs in liver tissue with Kupffer cells labelled with ED-1 antibody. Green, S-SWNTs; red, M-SWNTs; blue, two-photon fluorescent signal from antibody. , A zoom-in image of nanotubes in a Kupffer cell in the liver. , Image of normal liver tissue without nanotubes. , Image of nanotubes in spleen tissue. Grey, transmission of tissue. Scale bars, 5 µm. Pump, 707 nm; probe, 885 nm. Laser power post-objective was 1.0 mW for the pump beam and 1.6 mW for the probe beam. Author information * Abstract * Author information * Supplementary information Affiliations * Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA * Ling Tong & * Ji-Xin Cheng * Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana 47907, USA * Yuxiang Liu, * Mikhail N. Slipchenko & * Ji-Xin Cheng * Department of Medical Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907, USA * Bridget D. Dolash & * Donald E. Bergstrom * Department of Physics, Purdue University, West Lafayette, Indiana 47907, USA * Yookyung Jung * Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA * Donald E. Bergstrom & * Ji-Xin Cheng Contributions L.T. and J.X.C. conceived and designed the experiments. L.T. and Y.L. performed the experiments. L.T. and Y.L. analysed the data. B.D.D., Y.J., M.N.S. and D.E.B. contributed materials and analysis tools. L.T. and J.X.C. co-wrote the paper. All authors discussed the results and commented on the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * Ji-Xin Cheng Author Details * Ling Tong Search for this author in: * NPG journals * PubMed * Google Scholar * Yuxiang Liu Search for this author in: * NPG journals * PubMed * Google Scholar * Bridget D. Dolash Search for this author in: * NPG journals * PubMed * Google Scholar * Yookyung Jung Search for this author in: * NPG journals * PubMed * Google Scholar * Mikhail N. Slipchenko Search for this author in: * NPG journals * PubMed * Google Scholar * Donald E. Bergstrom Search for this author in: * NPG journals * PubMed * Google Scholar * Ji-Xin Cheng Contact Ji-Xin Cheng Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (4,809 KB) Supplementary information Movies * Supplementary information (1,017 KB) Supplementary movie 1 * Supplementary information (457 KB) Supplementary movie 2 * Supplementary information (1,442 KB) Supplementary movie 3 Additional data
• Role of cell cycle on the cellular uptake and dilution of nanoparticles in a cell population
  - Nat Nanotechnol 7(1):62-68 (2012)
  Nature Nanotechnology | Letter Role of cell cycle on the cellular uptake and dilution of nanoparticles in a cell population * Jong Ah Kim1 * Christoffer Åberg1 * Anna Salvati1 * Kenneth A. Dawson1 * Affiliations * Contributions * Corresponding authorsJournal name:Nature NanotechnologyVolume: 7,Pages:62–68Year published:(2012)DOI:doi:10.1038/nnano.2011.191Received07 July 2011Accepted04 October 2011Published online06 November 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * pdf options * download pdf * view interactive pdfpowered by ReadCube * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Nanoparticles are considered a primary vehicle for targeted therapies because they can pass biological barriers and enter and distribute within cells by energy-dependent pathways1, 2, 3. So far, most studies have shown that nanoparticle properties, such as size4, 5, 6 and surface7, 8, can influence how cells internalize nanoparticles. Here, we show that uptake of nanoparticles by cells is also influenced by their cell cycle phase. Although cells in different phases of the cell cycle were found to internalize nanoparticles at similar rates, after 24 h the concentration of nanoparticles in the cells could be ranked according to the different phases: G2/M > S > G0/G1. Nanoparticles that are internalized by cells are not exported from cells but are split between daughter cells when the parent cell divides. Our results suggest that future studies on nanoparticle uptake should consider the cell cycle, because, in a cell population, the dose of internalized nanoparticles in each ce! ll varies as the cell advances through the cell cycle. View full text Subject terms: * Nanoparticles * Nanomedicine * Environmental, health and safety issues Figures at a glance * Figure 1: The cell cycle and its role in nanoparticle uptake. , The cell cycle, which is a series of events that lead to cell division and replication, consists of four phases: G1, S, G2 and M. Cells in the different phases are distinguished by blue, pink and green nuclei for the G1, S and G2/M phases, respectively. The cell cycle commences with the G1 phase, during which the cell increases its size. During the S phase the cell synthesizes DNA, and in the G2 phase it prepares for cell division, which occurs during the M phase. The two daughter cells then enter the G1 phase. , A cell culture contains a mixture of cells in different phases of their cell cycle, simultaneously undergoing progression and cell division. , Nanoparticle uptake in a cycling cell. The yellow-green circles represent the nanoparticles, which, inside cells, accumulate in the lysosomes, represented by the oval compartment. When the cell divides, the internalized nanoparticles are split between the two daughter cells. Figure not to scale. * Figure 2: Internalization of nanoparticles and ranking of the concentration of nanoparticles in the cells. A549 cells were exposed to 40 nm yellow-green PS-COOH (25 µg ml−1 in cMEM) for up to 72 h before imaging and flow cytometry measurements. , Confocal images after 5, 24 and 72 h of exposure show nanoparticles accumulated in the lysosomes. Blue, nuclei (DAPI); red, lysosomes (LAMP1 antibody); green, nanoparticles. , Mean cell fluorescence intensity obtained by flow cytometry as a function of time shows a linear increase due to particle uptake, but plateaus after one day due to cell division. Error bars are standard deviation over three replicates. ,, A549 cells were exposed to similar nanoparticles for up to 28 h before flow cytometry measurements. Mean fluorescence intensity as a function of exposure time () and flow cytometry distributions of cell fluorescence intensity after 2, 12 and 28 h of exposure to nanoparticles () for all cells and cells in the G0/G1, S and G2/M phases (defined in Supplementary Fig. S5). The results and the scheme show that the intracellular conce! ntration of nanoparticles is ranked according to the cell cycle phases: G2/M > S > G0/G1. ,, Numerical simulation corresponding to data in and , respectively, showing good agreement with experimental results. * Figure 3: Nanoparticle export is negligible. A549 cells were exposed to 40 nm yellow-green PS-COOH (25 µg ml−1 in cMEM) for 4 h, then the S-phase cells were EdU-labelled for 30 min and cells grown further in nanoparticle-free media, before cell fluorescence measurement by flow cytometry. , EdU–DNA double-scatter plots 0, 5 and 8 h after EdU-labelling. (For full time course see Supplementary Fig. S10.) The indicated regions show EdU-labelled cells after division ('After division') and all other cells ('Complement'). , Fraction of divided EdU-labelled cells, showing excellent agreement with the prediction from the corresponding numerical simulation (solid line). , Mean cell fluorescence of all cells, divided EdU-labelled cells and their complement. The solid line is a fit to the result expected due to cell division alone. Dashed lines are horizontal fits. The good agreement indicates that export is negligible and the internalized nanoparticle load decreases only as a result of cell division. * Figure 4: Nanoparticle uptake rates during the different phases of the cell cycle. Independent uptake experiments of 40 nm yellow-green PS-COOH nanoparticles (25 µg ml−1 in cMEM) were performed on A549 cells 2, 6 and 12 h after EdU-labelling, at which times many EdU-positive cells are in the S, G2/M and G0/G1 phases, respectively (Supplementary Fig. S12). The presented values are the means of the cell fluorescence intensity of cells in the S, G2/M and G0/G1 phases (as defined in Supplementary Fig. S13) obtained by flow cytometry. Error bars represent the standard deviation of three replicates. Solid lines are linear fits performed to determine the uptake rates. The results show that the uptake rate is comparable for all phases of the cell cycle. * Figure 5: Nanoparticle uptake in synchronized cell cultures. , DNA histograms (obtained by propidium iodide staining) of non-synchronized A549 cells, a population enriched in G0/G1 phase by serum deprivation ('synchronized'), and populations synchronized by the same procedure and subsequently exposed to nanoparticle-free cMEM (for 6 and 24 h) to revert the synchronization and restart cell cycle progression ('restarted'). , Mean cell fluorescence intensity obtained by flow cytometry after exposure to nanoparticles (40 nm yellow-green PS-COOH 25 µg ml−1 in cMEM) in synchronized and non-synchronized A549 cells (with the same starting cell number). Error bars represent standard deviation of three independent replicates. The results show similar nanoparticle uptake during the first 5 h of exposure, but over 24 h the synchronized cells accumulate more nanoparticles. Author information * Abstract * Author information * Supplementary information Affiliations * Centre for BioNano Interactions, School of Chemistry and Chemical Biology and Conway Institute for Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland * Jong Ah Kim, * Christoffer Åberg, * Anna Salvati & * Kenneth A. Dawson Contributions J.A.K. performed experiments, analysed and interpreted data, and wrote the paper. C.Å. developed the numerical simulations and analytical tools, analysed and interpreted data, and wrote the paper. A.S. supervised the experimental work, analysed and interpreted data, and wrote the paper. K.A.D. interpreted data and wrote the paper. Competing financial interests The authors declare no competing financial interests. Corresponding authors Correspondence to: * Kenneth A. Dawson or * Anna Salvati Author Details * Jong Ah Kim Search for this author in: * NPG journals * PubMed * Google Scholar * Christoffer Åberg Search for this author in: * NPG journals * PubMed * Google Scholar * Anna Salvati Contact Anna Salvati Search for this author in: * NPG journals * PubMed * Google Scholar * Kenneth A. Dawson Contact Kenneth A. Dawson Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (3,852 KB) Supplementary information Other * Supplementary information (368 KB) Supplementary information Additional data
• One- and two-dimensional photonic crystal microcavities in single crystal diamond
  - Nat Nanotechnol 7(1):69-74 (2012)
  Nature Nanotechnology | Article One- and two-dimensional photonic crystal microcavities in single crystal diamond * Janine Riedrich-Möller1 * Laura Kipfstuhl1 * Christian Hepp1 * Elke Neu1 * Christoph Pauly2 * Frank Mücklich2 * Armin Baur3 * Michael Wandt3 * Sandra Wolff4 * Martin Fischer5 * Stefan Gsell5 * Matthias Schreck5 * Christoph Becher1 * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 7,Pages:69–74Year published:(2012)DOI:doi:10.1038/nnano.2011.190Received09 August 2011Accepted30 September 2011Published online13 November 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * pdf options * download pdf * view interactive pdfpowered by ReadCube * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Diamond is an attractive material for photonic quantum technologies because its colour centres have a number of outstanding properties, including bright single photon emission and long spin coherence times. To take advantage of these properties it is favourable to directly fabricate optical microcavities in high-quality diamond samples. Such microcavities could be used to control the photons emitted by the colour centres or to couple widely separated spins. Here, we present a method for the fabrication of one- and two-dimensional photonic crystal microcavities with quality factors of up to 700 in single crystal diamond. Using a post-processing etching technique, we tune the cavity modes into resonance with the zero phonon line of an ensemble of silicon-vacancy colour centres, and we measure an intensity enhancement factor of 2.8. The controlled coupling of colour centres to photonic crystal microcavities could pave the way to larger-scale photonic quantum devices based on si! ngle crystal diamond. View full text Subject terms: * Photonic structures and devices * Synthesis and processing Figures at a glance * Figure 1: SEM images of two-dimensional and one-dimensional fabricated PhC cavities. , SEM image of the fabricated M7 cavity with lattice constant a ≈ 275 nm and radii R ≈ 85 nm. , Close-up of the cavity centre. , Cross-sectional image (tilt angle, 52°). A thin platinum layer was deposited on the PhC to allow for a straight cut through the diamond membrane using FIB. From the cross-sectional image, a diamond film thickness of 300 nm can be inferred. The sidewalls of the milled air holes exhibit a tilt angle of ~6°. ,, Top () and side () views of the fabricated one-dimensional nanobeam cavity with a pitch:width:height ratio of 2:3:3 (a ≈ 200 nm). The hole radii monotonically decrease from R ≈ 83 nm at the cavity centre to R ≈ 72 nm at the waveguide edge. , Close-up of the one-dimensional waveguide–cavity. * Figure 2: Photoluminescence spectra. ,, Experimental photoluminescence spectra of an M7 cavity () and a nanobeam cavity () are shown in black, and the reference spectra of the unstructured membrane are shown in grey. The intensity of the reference spectra is scaled to account for the smaller collection efficiency from unpatterned areas of the sample (see Supplementary Information). Coloured curves show the simulated cavity modes for different symmetric boundary conditions. Ex and Ey mode profiles for fundamental mode e1 and various higher-order modes are shown above. The spectrum of the M7 cavity () shows several cavity modes close to the SiV centre zero phonon line at λ = 738 nm (yellow area). The simulated spectrum (coloured curves, arbitrary amplitude) of an ideal M7 cavity with R = 0.31a and h = 1.1a matches the experimental results very well. The spectrum of the nanobeam cavity () shows three cavity modes close to the design wavelength λ = 637 nm of the NV− centre zero phonon line. The calculated modes! (coloured curves, arbitrary amplitude) of an ideal nanobeam cavity with h = w = 1.5a and radii that decrease from R = 0.42a at the cavity centre to R = 0.37a at the structure edge, agree very well with the experimental measurement. ,, Polarization analysis of an M7 cavity () and a nanobeam cavity (). Photoluminescence spectra taken without a polarizer are shown in black. The even modes are pronounced for a polarizer oriented in the y-direction (red curves), whereas the odd modes are prominent for polarizer oriented along the x-axis (blue curves). * Figure 3: Cavity tuning. , Cavity spectrum taken before the first oxidation step (black) and after one, two, three and four oxidation steps (coloured curves). When the cavity mode o2 (marked by *) is tuned into resonance with the emission line of SiV centres, the intensity of the zero phonon line (the peak in the yellow region) is clearly enhanced. , Wavelengths for various cavity modes are blueshifted by 3 nm on average per oxidation step. The four lines at the bottom show higher-order modes (e4, o3, o4, o5; not labelled for clarity). In total, the cavity modes are tuned up to 15 nm. , Quality factors of the fundamental cavity modes show no significant degradation following tuning. Author information * Abstract * Author information * Supplementary information Affiliations * Universität des Saarlandes, Fachrichtung 7.2 (Experimentalphysik), 66123 Saarbrücken, Germany * Janine Riedrich-Möller, * Laura Kipfstuhl, * Christian Hepp, * Elke Neu & * Christoph Becher * Universität des Saarlandes, Fachrichtung 8.4 (Materialwissenschaft und Werkstofftechnik), 66123 Saarbrücken, Germany * Christoph Pauly & * Frank Mücklich * University of Freiburg, Department of Microsystems Engineering (IMTEK), Cleanroom Service Center, 79110 Freiburg, Germany * Armin Baur & * Michael Wandt * TU Kaiserslautern, Nano + Bio Center, 67653 Kaiserslautern, Germany * Sandra Wolff * Universität Augsburg, Lehrstuhl für Experimentalphysik IV, 86159 Augsburg, Germany * Martin Fischer, * Stefan Gsell & * Matthias Schreck Contributions J.R-M. and L.K. fabricated the photonic crystals, performed the experiments and carried out the numerical modelling of the structures. M.F., S.G. and M.S. developed the CVD growth process for the diamond films on iridium buffer layers. A.B. and M.W. prepared the diamond membrane. J.R-M. and S.W. thinned the diamond film. C.P., J.R-M., L.K. and F.M. performed FIB milling. C.H. and E.N. contributed experimental tools and helped with the photoluminescence measurements and interpretation of data. C.B. conceived and designed the experiments. J.R-M. and C.B. wrote the manuscript. All authors discussed the results and commented on the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * Christoph Becher Author Details * Janine Riedrich-Möller Search for this author in: * NPG journals * PubMed * Google Scholar * Laura Kipfstuhl Search for this author in: * NPG journals * PubMed * Google Scholar * Christian Hepp Search for this author in: * NPG journals * PubMed * Google Scholar * Elke Neu Search for this author in: * NPG journals * PubMed * Google Scholar * Christoph Pauly Search for this author in: * NPG journals * PubMed * Google Scholar * Frank Mücklich Search for this author in: * NPG journals * PubMed * Google Scholar * Armin Baur Search for this author in: * NPG journals * PubMed * Google Scholar * Michael Wandt Search for this author in: * NPG journals * PubMed * Google Scholar * Sandra Wolff Search for this author in: * NPG journals * PubMed * Google Scholar * Martin Fischer Search for this author in: * NPG journals * PubMed * Google Scholar * Stefan Gsell Search for this author in: * NPG journals * PubMed * Google Scholar * Matthias Schreck Search for this author in: * NPG journals * PubMed * Google Scholar * Christoph Becher Contact Christoph Becher Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (3,964 KB) Supplementary information Additional data
• Electrically tuned spin–orbit interaction in an InAs self-assembled quantum dot
  - Nat Nanotechnol 7(1):75 (2012)
  Nature Nanotechnology | Corrigendum Electrically tuned spin–orbit interaction in an InAs self-assembled quantum dot * Y. Kanai * R. S. Deacon * S. Takahashi * A. Oiwa * K. Yoshida * K. Shibata * K. Hirakawa * Y. Tokura * S. TaruchaJournal name:Nature NanotechnologyVolume: 7,Page:75Year published:(2012)DOI:doi:10.1038/nnano.2011.228Published online28 December 2011 Article tools * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Nature Nanotechnology6, 511–516 (2011); published online 24 July 2011; corrected after print 22 November 2011. In the version of this Letter originally published, in the discussion of Fig. 5c on page 514, the fitting function should have been Δ = A|cos(θ − θ0 ± π/2)| + B, and the offsets of θ0 should have been −30 ± 4° and −39 ± 5° for Vsg = −0.5 V and 1.0 V, respectively. These errors have been corrected in the HTML and PDF versions of the Letter. Author information Author Details * Y. Kanai Search for this author in: * NPG journals * PubMed * Google Scholar * R. S. Deacon Search for this author in: * NPG journals * PubMed * Google Scholar * S. Takahashi Search for this author in: * NPG journals * PubMed * Google Scholar * A. Oiwa Search for this author in: * NPG journals * PubMed * Google Scholar * K. Yoshida Search for this author in: * NPG journals * PubMed * Google Scholar * K. Shibata Search for this author in: * NPG journals * PubMed * Google Scholar * K. Hirakawa Search for this author in: * NPG journals * PubMed * Google Scholar * Y. Tokura Search for this author in: * NPG journals * PubMed * Google Scholar * S. Tarucha Search for this author in: * NPG journals * PubMed * Google Scholar Additional data