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- Why not zwergo-technology?
- Nat Nanotechnol 6(7):393-394 (2011)
Article preview View full access options Nature Nanotechnology | Thesis Why not zwergo-technology? * Chris Toumey1Journal name:Nature NanotechnologyVolume: 6,Pages:393–394Year published:(2011)DOI:doi:10.1038/nnano.2011.106Published online06 July 2011 The prefix nano, which is based on the Greek word for dwarf, became part of scientific nomenclature in 1960. Chris Toumey explores the role of language and languages in science. Subject terms: * Nanometrology and instrumentation 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 - Compare and contrast as microscopes get up close and personal
- Nat Nanotechnol 6(7):394 (2011)
Nature Nanotechnology | Correction Compare and contrast as microscopes get up close and personal Journal name:Nature NanotechnologyVolume: 6,Page:394Year published:(2011)DOI:doi:10.1038/nnano.2011.83Published online04 May 2011 Article tools * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg In the Thesis 'Compare and contrast as microscopes get up close and personal' (Nature Nanotech.6, 191–193; 2011), in the caption of Fig. 3, 'tunnelling' should have read 'transmission'. This error was corrected in the HTML and PDF versions on 4 May 2011. Additional data - Our choice from the recent literature
- Nat Nanotechnol 6(7):395 (2011)
Article preview View full access options Nature Nanotechnology | Research Highlights Our choice from the recent literature Journal name:Nature NanotechnologyVolume: 6,Page:395Year published:(2011)DOI:doi:10.1038/nnano.2011.113Published online06 July 2011 Science 332, 1407–1410 (2011) © 2011 AAAS The plasmon resonance wavelength of metal nanoparticles such as gold is affected by changes in the particle's immediate environment, and these changes can be measured using scattering or absorption spectroscopy. Moreover, two nanoparticles placed in close proximity can exhibit a shift in resonance wavelength that depends on the separation between them. This effect has been used to make plasmon rulers, which measure nanoscale distances in one dimension and have been employed to study DNA hybridization. Laura Na Liu and colleagues have now created a three-dimensional plasmon ruler from a stack of five gold nanorods. 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. Additional data - Metamaterials: A stamp of quality
- Nat Nanotechnol 6(7):396-397 (2011)
Article preview View full access options Nature Nanotechnology | News and Views Metamaterials: A stamp of quality * Richard D. Averitt1Journal name:Nature NanotechnologyVolume: 6,Pages:396–397Year published:(2011)DOI:doi:10.1038/nnano.2011.109Published online06 July 2011 Transfer printing of negative-index metamaterials with areas of tens of square centimetres onto flexible substrates paves the way for practical, low-cost, large-area exotic optics. Subject terms: * Photonic structures and devices * Surface patterning and imaging * Synthesis and processing 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 * Richard D. Averitt is in the Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA Corresponding author Correspondence to: * Richard D. Averitt Author Details * Richard D. Averitt Contact Richard D. Averitt Search for this author in: * NPG journals * PubMed * Google Scholar Additional data - Nanobiotechnology: Building a basic nanomachine
- Nat Nanotechnol 6(7):397-398 (2011)
Article preview View full access options Nature Nanotechnology | News and Views Nanobiotechnology: Building a basic nanomachine * Tijana Jovanovic-Talisman1 * Anton Zilman2 * Affiliations * Corresponding authorsJournal name:Nature NanotechnologyVolume: 6,Pages:397–398Year published:(2011)DOI:doi:10.1038/nnano.2011.108Published online06 July 2011 Attaching certain protein fragments that are found in the nuclear pore complex onto a solid-state nanopore mimics important aspects of the selective transport of molecules and proteins that occurs in real cells. Subject terms: * Nanobiotechnology 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 * Tijana Jovanovic-Talisman is in the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA * Anton Zilman is in the Department of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada. Corresponding authors Correspondence to: * Tijana Jovanovic-Talisman or * Anton Zilman Author Details * Tijana Jovanovic-Talisman Contact Tijana Jovanovic-Talisman Search for this author in: * NPG journals * PubMed * Google Scholar * Anton Zilman Contact Anton Zilman Search for this author in: * NPG journals * PubMed * Google Scholar Additional data - Scanning probes: Cold-atom microscope shapes up
- Nat Nanotechnol 6(7):399-400 (2011)
Article preview View full access options Nature Nanotechnology | News and Views Scanning probes: Cold-atom microscope shapes up * Christian L. Degen1 * Jonathan P. Home1 * Affiliations * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Pages:399–400Year published:(2011)DOI:doi:10.1038/nnano.2011.107Published online06 July 2011 The ultrasoft 'tip' of the cold-atom scanning probe microscope will offer new possibilities for exploring the interactions between atoms and surfaces. Subject terms: * Nanosensors and other devices * 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 * Christian L. Degen and Jonathan P. Home are in the Department of Physics, ETH Zurich, Switzerland Corresponding author Correspondence to: * Christian L. Degen Author Details * Christian L. Degen Contact Christian L. Degen Search for this author in: * NPG journals * PubMed * Google Scholar * Jonathan P. Home Search for this author in: * NPG journals * PubMed * Google Scholar Additional data - Condensed matter physics: Superconductivity at the double
- Nat Nanotechnol 6(7):400-401 (2011)
Article preview View full access options Nature Nanotechnology | News and Views Condensed matter physics: Superconductivity at the double * Kosmas Prassides1Journal name:Nature NanotechnologyVolume: 6,Pages:400–401Year published:(2011)DOI:doi:10.1038/nnano.2011.104Published online06 July 2011 Electrostatic doping of the transparent insulator potassium tantalate with an electric double-layer transistor has allowed superconductivity to be observed in this material for the first time. Subject terms: * Electronic properties and devices * 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 * Kosmas Prassides is in the Department of Chemistry, Durham University, Durham DH1 3LE, UK Corresponding author Correspondence to: * Kosmas Prassides Author Details * Kosmas Prassides Contact Kosmas Prassides Search for this author in: * NPG journals * PubMed * Google Scholar Additional data - Large-area flexible 3D optical negative index metamaterial formed by nanotransfer printing
- Nat Nanotechnol 6(7):402-407 (2011)
Nature Nanotechnology | Letter Large-area flexible 3D optical negative index metamaterial formed by nanotransfer printing * Debashis Chanda1 * Kazuki Shigeta1 * Sidhartha Gupta1 * Tyler Cain1 * Andrew Carlson1 * Agustin Mihi1 * Alfred J. Baca3 * Gregory R. Bogart4 * Paul Braun1 * John A. Rogers1, 2 * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Pages:402–407Year published:(2011)DOI:doi:10.1038/nnano.2011.82Received18 March 2011Accepted27 April 2011Published online05 June 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Negative-index metamaterials (NIMs) are engineered structures with optical properties that cannot be obtained in naturally occurring materials1, 2, 3. Recent work has demonstrated that focused ion beam4 and layer-by-layer electron-beam lithography5 can be used to pattern the necessary nanoscale features over small areas (hundreds of µm2) for metamaterials with three-dimensional layouts and interesting characteristics, including negative-index behaviour in the optical regime. A key challenge is in the fabrication of such three-dimensional NIMs with sizes and at throughputs necessary for many realistic applications (including lenses, resonators and other photonic components6, 7, 8). We report a simple printing approach capable of forming large-area, high-quality NIMs with three-dimensional, multilayer formats. Here, a silicon wafer with deep, nanoscale patterns of surface relief serves as a reusable stamp. Blanket deposition of alternating layers of silver and magnesium fluor! ide onto such a stamp represents a process for 'inking' it with thick, multilayer assemblies. Transfer printing this ink material onto rigid or flexible substrates completes the fabrication in a high-throughput manner. Experimental measurements and simulation results show that macroscale, three-dimensional NIMs (>75 cm2) nano-manufactured in this way exhibit a strong, negative index of refraction in the near-infrared spectral range, with excellent figures of merit. View full text Subject terms: * Photonic structures and devices * Surface patterning and imaging * Synthesis and processing Figures at a glance * Figure 1: Fabricating 3D NIMs by transfer printing. , Schematic of steps for printing. , Top-view SEM image of a silicon stamp (left; inset, magnified view), tilted view (52°) SEM image of a stack of alternating layers of Ag and MgF2 on a silicon stamp (middle; inset, magnified top view), cross-sectioned by FIB, and a macroscopic optical image of a large (~2.5 × 2.5 cm) printed 3D NIM (right). , Corresponding SEM images of a tilted silicon stamp (left), an eleven-layer Ag/MgF2 stack (middle) and a printed 3D NIM (right: inset, magnified top view). Period P of the structure is 850 nm, and the depth-averaged widths of the ribs in the fishnet along the x- and y-directions are 635 nm (Wx) and 225 nm (Wy), respectively. The thicknesses of the Ag and MgF2 layers are 30 and 50 nm, respectively. * Figure 2: Large-area, printed 3D NIMs in supported and free-standing configurations. , Large-area SEM image of a representative region of a printed 3D NIM. ,, SEM images of cross-sectional (FIB milled) and top views of this structure. , SEM image of a flexible 3D NIM membrane formed by release and subsequent deposition on a solid support. * Figure 3: Macroscale, printed 3D NIMs and demonstration of use in a repetitive 'manufacturing' mode. , Macroscopic optical image of a 10 cm × 10 cm multilayer deposit on a large-area silicon stamp. , 3D NIM printed with such a stamp onto a flexible substrate, in a single step. , Tilted view (~15°) macroscopic optical images of three different 3D NIMs printed using a single stamp. , Corresponding representative small-area SEM views of these three samples. * Figure 4: Experimental measurements and simulation results for transmission/reflection and refractive indices of 3D NIMs. ,, Experimental and FDTD results for transmission (T) and reflection (R) spectra of a three-layer NIM monolayer () and an eleven-layer 3D NIM (). , Transmission spectra collected from five different locations across the entire area of a 8.7 cm × 8.7 cm, eleven-layer 3D NIM. , Corresponding retrieved indices for three and eleven layers showing a negative index of refraction in the NIR band. , FOM of three- and eleven-layer 3D NIM structures. , The 4.48° NIM prism showing negative-phase propagation at λ = 1.95 µm. In all cases, P = 850 nm, depth-averaged Wx = 635 nm and Wy = 225 nm, Ag thickness = 30 nm, MgF2 thickness = 50 nm, and background refractive index ns = 1.2. Author information * Abstract * Author information * Supplementary information Affiliations * Departments of Materials Science and Engineering, Beckman Institute, and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA * Debashis Chanda, * Kazuki Shigeta, * Sidhartha Gupta, * Tyler Cain, * Andrew Carlson, * Agustin Mihi, * Paul Braun & * John A. Rogers * Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA * John A. Rogers * US Navy NAVAIR-NAWCWD, Research and Intelligence Department, Chemistry Branch, China Lake, California 93555, USA * Alfred J. Baca * Sandia National Laboratories, Albuquerque, New Mexico, USA * Gregory R. Bogart Contributions D.C. conceived the idea and designed experiments. J.A.R. provided technical guidance. D.C., K.S. and T.C. performed the experiments. D.C. measured, analysed and simulated the data. G.R.B., S.G., A.M., A.C., A.B. and P.B. contributed materials and analysis tools. D.C. and J.A.R. co-wrote the paper. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * John A. Rogers Author Details * Debashis Chanda Search for this author in: * NPG journals * PubMed * Google Scholar * Kazuki Shigeta Search for this author in: * NPG journals * PubMed * Google Scholar * Sidhartha Gupta Search for this author in: * NPG journals * PubMed * Google Scholar * Tyler Cain Search for this author in: * NPG journals * PubMed * Google Scholar * Andrew Carlson Search for this author in: * NPG journals * PubMed * Google Scholar * Agustin Mihi Search for this author in: * NPG journals * PubMed * Google Scholar * Alfred J. Baca Search for this author in: * NPG journals * PubMed * Google Scholar * Gregory R. Bogart Search for this author in: * NPG journals * PubMed * Google Scholar * Paul Braun Search for this author in: * NPG journals * PubMed * Google Scholar * John A. Rogers Contact John A. Rogers Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (971 KB) Supplementary information Additional data - Discovery of superconductivity in KTaO3 by electrostatic carrier doping
- Nat Nanotechnol 6(7):408-412 (2011)
Nature Nanotechnology | Letter Discovery of superconductivity in KTaO3 by electrostatic carrier doping * K. Ueno1, 2 * S. Nakamura3, 4 * H. Shimotani5 * H. T. Yuan5 * N. Kimura4, 6 * T. Nojima3, 4 * H. Aoki4, 6 * Y. Iwasa5, 7 * M. Kawasaki1, 5, 7 * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Pages:408–412Year published:(2011)DOI:doi:10.1038/nnano.2011.78Received16 February 2011Accepted15 April 2011Published online22 May 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Superconductivity at interfaces has been investigated since the first demonstration of electric-field-tunable superconductivity in ultrathin films in 19601. So far, research on interface superconductivity has focused on materials that are known to be superconductors in bulk1, 2, 3, 4, 5, 6, 7, 8, 9. Here, we show that electrostatic carrier doping can induce superconductivity in KTaO3, a material in which superconductivity has not been observed before10, 11. Taking advantage of the large capacitance of the self-organized electric double layer that forms at the interface between an ionic liquid and KTaO3 (ref. 12), we achieve a charge carrier density that is an order of magnitude larger than the density that can be achieved with conventional chemical doping. Superconductivity emerges in KTaO3 at 50 mK for two-dimensional carrier densities in the range 2.3 × 1014 to 3.7 × 1014 cm−2. The present result clearly shows that electrostatic carrier doping can lead to new states of! matter at nanoscale interfaces. View full text Subject terms: * Electronic properties and devices * Nanomaterials Figures at a glance * Figure 1: Electric double-layer (EDL) transistor. ,, Schematic diagrams () and photograph () of the EDL transistor with an ionic liquid electrolyte, DEME-BF4. DEME+ ions comprise the cations and BF4− ions ore the anions. The device was fabricated on a KTaO3 single crystal. Source, drain and gate electrodes were fabricated on the crystal (black area in the photograph), and the entire surface of the crystal, except for the channel area and electrodes, was covered by separator layer (yellow area in the photograph). A small amount of the ionic liquid was dropped on the crystal so that it covered the channel region (KTaO3 surface) and the gate electrode. , Molecular and crystal structures for the anion, cation and KTaO3. * Figure 2: Characterization of EDL transistors. , Superconducting critical temperature Tc as a function of three-dimensional charge carrier density for chemically doped superconductivity in 11 different material systems (filled symbols), and electrostatically induced superconductivity in two of these (open symbols). The lower panel shows the electronic phases appearing in KTaO3 as a function of carrier density up to the maximum density that can be achieved with chemical doping: much higher densities are possible with EDL transistors (dashed red vertical line). , Sheet resistance RS (on a logarithmic scale) versus temperature T at six different gate voltages VG for an EDL transistor in which the channel is a single crystal of KTaO3. The channel shows metallic conduction for values of VG higher than a threshold of 2.75 V. , Two-dimensional charge carrier density n2D (top) and carrier mobility (bottom) versus T for five values of VG: both n2D and mobility were evaluated by Hall measurements. * Figure 3: Transport properties. , Two-dimensional charge carrier density n2D, deduced from the Hall coefficient at 100 K, versus gate voltage VG for four different EDL transistors in which the channel is a layer of KTaO3. , Mobility at 2 K versus n2D for the same four samples. , Mobility versus three-dimensional carrier density n3D, deduced from the estimated depth distribution of carriers (see Supplementary Information) for the same four samples: note that both axes are logarithmic. Solid and open symbols correspond to the data deduced from the three-dimensional carrier density n3D determined by the Hall coefficient measured at 100 K and 2 K, respectively. Data for chemically doped bulk KTaO3 crystals from ref. 10 are also shown. Chemical doping in KTaO3 cannot access values of n3D in the shaded area. * Figure 4: Superconducting properties. , Sheet resistance RS versus temperature T at gate voltage VG = 5 V in an EDL transistor in which the channel is a layer of KTaO3. The solid line denotes the mid-point of the superconducting transition. , RS versus magnetic field μ0H at 20 mK. , Current I versus differential voltage V at 20 mK, measured in a four-terminal geometry. * Figure 5: Transport properties and critical parameters of superconductivity. , Sheet resistance RS versus temperature T at five values of the gate voltage VG. , Two-dimensional carrier density n2D (top panel), mid-point critical temperature Tcmid (middle panel), critical magnetic field μ0Hc (bottom panel, blue; left axis) and critical current density Jc (bottom panel, green; right axis) as a function of gate voltage VG. Green and grey points in the top panel correspond to data deduced from the Hall coefficient RH at 100 K and 2 K, respectively. The KTaO3 channel remained insulating at VG = 2.5 V, and n2D was close to zero because of the low temperature. The bar for VG = 4 V in the middle panel indicates uncertainty owing to the minimum accessible temperature of 20 mK. Each critical parameter was deduced from the mid-point of the transition. Author information * Abstract * Author information * Supplementary information Affiliations * WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan * K. Ueno & * M. Kawasaki * PRESTO, Japan Science and Technology Agency, Tokyo 102-0075, Japan * K. Ueno * Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan * S. Nakamura & * T. Nojima * Center for Low Temperature Science, Tohoku University, Sendai 980-8577, Japan * S. Nakamura, * N. Kimura, * T. Nojima & * H. Aoki * Quantum-Phase Electronics Center and Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan * H. Shimotani, * H. T. Yuan, * Y. Iwasa & * M. Kawasaki * Department of Physics, Tohoku University, Sendai 980-8578, Japan * N. Kimura & * H. Aoki * CREST, Japan Science and Technology Agency, Tokyo 102-0075, Japan * Y. Iwasa & * M. Kawasaki Contributions K.U. performed planning, sample fabrication, measurements and analysis. S.N., N.K., T.N. and H.A. assisted with cryogenic transport measurements. H.S. and H.T.Y. assisted with planning. Y.I. and M.K. performed planning and analysis. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * M. Kawasaki Author Details * K. Ueno Search for this author in: * NPG journals * PubMed * Google Scholar * S. Nakamura Search for this author in: * NPG journals * PubMed * Google Scholar * H. Shimotani Search for this author in: * NPG journals * PubMed * Google Scholar * H. T. Yuan Search for this author in: * NPG journals * PubMed * Google Scholar * N. Kimura Search for this author in: * NPG journals * PubMed * Google Scholar * T. Nojima Search for this author in: * NPG journals * PubMed * Google Scholar * H. Aoki Search for this author in: * NPG journals * PubMed * Google Scholar * Y. Iwasa Search for this author in: * NPG journals * PubMed * Google Scholar * M. Kawasaki Contact M. Kawasaki Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (1,066 KB) Supplementary information Additional data - Spin–orbit-driven ferromagnetic resonance
- Nat Nanotechnol 6(7):413-417 (2011)
Nature Nanotechnology | Letter Spin–orbit-driven ferromagnetic resonance * D. Fang1 * H. Kurebayashi1 * J. Wunderlich2, 3 * K. Výborný2, 5 * L. P. Zârbo2 * R. P. Campion4 * A. Casiraghi4 * B. L. Gallagher4 * T. Jungwirth2, 4 * A. J. Ferguson1 * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Pages:413–417Year published:(2011)DOI:doi:10.1038/nnano.2011.68Received28 February 2011Accepted07 April 2011Published online22 May 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Ferromagnetic resonance is the most widely used technique for characterizing ferromagnetic materials1. However, its use is generally restricted to wafer-scale samples or specific micro-magnetic devices, such as spin valves, which have a spatially varying magnetization profile and where ferromagnetic resonance can be induced by an alternating current owing to angular momentum transfer2, 3, 4. Here we introduce a form of ferromagnetic resonance in which an electric current oscillating at microwave frequencies is used to create an effective magnetic field in the magnetic material being probed, which makes it possible to characterize individual nanoscale samples with uniform magnetization profiles. The technique takes advantage of the microscopic non-collinearity of individual electron spins arising from spin–orbit coupling and bulk or structural inversion asymmetry in the band structure of the sample5, 6. We characterize lithographically patterned (Ga,Mn)As and (Ga,Mn)(As,P) ! nanoscale bars, including broadband measurements of resonant damping as a function of frequency, and measurements of anisotropy as a function of bar width and strain. In addition, vector magnetometry on the driving fields reveals contributions with the symmetry of both the Dresselhaus and Rashba spin–orbit interactions. View full text Subject terms: * Electronic properties and devices * Nanomagnetism and spintronics * Nanometrology and instrumentation Figures at a glance * Figure 1: Principle of the experiment and setup. , Precession of the magnetization vector around the total magnetic field tot. is subject to a damping torque τα (yellow arrow) owing to energy dissipation, which causes the magnetic motion to relax towards tot. The driving torque τSO owing to the current-induced effective field counters the effect of damping, and leads to steady-state motion ∂/∂t = −γ × tot (grey arrow). The current density vector is represented by j(t). , SEM image of an 80-nm-wide bar, patterned from the (Ga,Mn)(As,P) wafer. , Schematic of the experimental setup. A microwave frequency current is driven across the nanoscale magnetic bar, which is contacted with Cr/Au bondpads. The d.c. voltage, generated by magnetization precession, is extracted through a bias tee (represented by the capacitor and inductor network attached between the signal generator and sample source). The d.c. connection at the drain also provides a microwave ground, represented by a capacitor. * Figure 2: Spin–orbit-driven ferromagnetic resonance. , Vdc measured at 8, 10 and 12 GHz (symbols) on the 80-nm-wide device. The resonance peaks are clearly observed and can be well described by the solution to the LLG equation (for example equation (32) in ref. 16). Solid lines are the fitted results. The difference in the signal level at different frequencies is caused by the frequency-dependent attenuation of the microwave circuit. , Resonance field Hres as a function of microwave frequency. The red solid line is the fitted results to equation (3). , Frequency dependence of the FMR linewidth ΔH. The data are fitted to a straight line to extract ΔHinhomo and α. , Vdc measured from in-plane rotational scans of the external field 0. The colour scale represents the magnitude of the voltage. ϕ is the angle between the magnetization vector and the [100] crystalline axis. , Angle plot of the resonance field Hres. The red line is a fitting curve to equations (3) and (4) to calculate the magnetic anisotropy. * Figure 3: Characterization of the driving field in both (Ga,Mn)As and (Ga,Mn)(As,P) devices. ,, Amplitudes of the anti-symmetric part of the FMR signal Vasy, measured on a group of 500-nm-wide (Ga,Mn)As bars, patterned along different crystalline directions. The solid lines are fitted results to equation (2). , Plot of the magnitude and direction of the current-induced effective field eff measured on the (Ga,Mn)As nanobars, scaled for a current density j = 1 × 105 A cm−2. , Similar plot for eff measured on the (Ga,Mn)(As,P) devices. ,, Current density dependence of D and R in both (Ga,Mn)As and (Ga,Mn)(As,P) nanobars. A second horizontal scale is included for the electric field, calculated from the device resistance (values given in Methods). * Figure 4: SO-FMR on devices patterned from different materials and with various sizes. , Hres(ϕ) measured from an in-plane rotational scan on a 500-nm-wide (Ga,Mn0.06)As bar (patterned along the [010] axis). The circles are measurement data, and the solid line is the fitted result to equations (3) and (4). , Hres(ϕ) measured on a (Ga,Mn0.06)(As,P0.1) device with identical shape and orientation. , Comparison of the in-plane anisotropy fields Hi between the two samples. , Linewidth ΔH of the FMR signals measured on the 80 nm, 500 nm and 4 µm (Ga,Mn)(As,P) bars. , Comparison of the magnetic anisotropy (in terms of the profiles of Hres) of 80 nm, 500 nm and 4 µm (Ga,Mn)(As,P) bars. Author information * Abstract * Author information * Supplementary information Affiliations * Microelectronics Group, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK * D. Fang, * H. Kurebayashi & * A. J. Ferguson * Institute of Physics ASCR, v.v.i., Cukrovarnická 10, 162 53 Praha 6, Czech Republic * J. Wunderlich, * K. Výborný, * L. P. Zârbo & * T. Jungwirth * Hitachi Cambridge Laboratory, Cambridge CB3 0HE, UK * J. Wunderlich * School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK * R. P. Campion, * A. Casiraghi, * B. L. Gallagher & * T. Jungwirth * Present address: Department of Physics, State University of New York at Buffalo, Buffalo, New York 14260, USA * K. Výborný Contributions D.F. and A.J.F. carried out device fabrication. D.F., H.K., J.W. and A.J.F. conducted experiments and carried out data analysis. K.V., L.P.Z. and T.J. developed the theory. R.P.C., A.C. and B.L.G. provided materials. D.F., A.J.F., T.J., L.P.Z., K.V., H.K. and J.W. all contributed to writing the manuscript. A.J.F. planned the project. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * A. J. Ferguson Author Details * D. Fang Search for this author in: * NPG journals * PubMed * Google Scholar * H. Kurebayashi Search for this author in: * NPG journals * PubMed * Google Scholar * J. Wunderlich Search for this author in: * NPG journals * PubMed * Google Scholar * K. Výborný Search for this author in: * NPG journals * PubMed * Google Scholar * L. P. Zârbo Search for this author in: * NPG journals * PubMed * Google Scholar * R. P. Campion Search for this author in: * NPG journals * PubMed * Google Scholar * A. Casiraghi Search for this author in: * NPG journals * PubMed * Google Scholar * B. L. Gallagher Search for this author in: * NPG journals * PubMed * Google Scholar * T. Jungwirth Search for this author in: * NPG journals * PubMed * Google Scholar * A. J. Ferguson Contact A. J. Ferguson Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (2,311 KB) Supplementary information Additional data - Exchange-coupled magnetic nanoparticles for efficient heat induction
- Nat Nanotechnol 6(7):418-422 (2011)
Nature Nanotechnology | Letter Exchange-coupled magnetic nanoparticles for efficient heat induction * Jae-Hyun Lee1 * Jung-tak Jang1 * Jin-sil Choi1 * Seung Ho Moon1 * Seung-hyun Noh1 * Ji-wook Kim1 * Jin-Gyu Kim2 * Il-Sun Kim3 * Kook In Park3 * Jinwoo Cheon1 * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Pages:418–422Year published:(2011)DOI:doi:10.1038/nnano.2011.95Received07 April 2011Accepted19 May 2011Published online26 June 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg The conversion of electromagnetic energy into heat by nanoparticles has the potential to be a powerful, non-invasive technique for biotechnology applications such as drug release1, 2, 3, disease treatment4, 5, 6 and remote control of single cell functions7, 8, 9, but poor conversion efficiencies have hindered practical applications so far10, 11. In this Letter, we demonstrate a significant increase in the efficiency of magnetic thermal induction by nanoparticles. We take advantage of the exchange coupling between a magnetically hard core and magnetically soft shell to tune the magnetic properties of the nanoparticle and maximize the specific loss power, which is a gauge of the conversion efficiency. The optimized core–shell magnetic nanoparticles have specific loss power values that are an order of magnitude larger than conventional iron-oxide nanoparticles. We also perform an antitumour study in mice, and find that the therapeutic efficacy of these nanoparticles is superi! or to that of a common anticancer drug. View full text Subject terms: * Nanobiotechnology * Nanomagnetism and spintronics * Nanomedicine * Nanometrology and instrumentation Figures at a glance * Figure 1: Experimental setup, measurements and simulations of SLP of magnetic nanoparticles. , Samples are placed in the water-cooled magnetic induction coil with a heat insulator (Styrofoam). , Experimentally observed SLP values of MFe2O4 (M = Mn, Fe, Co) nanoparticles of different sizes (f = 500 kHz, H0 = 37.3 kA m−1). The maximum peak of SLP changes with the size and composition of nanoparticles. Error bars indicate standard deviation (n = 5). , Simulated plot of SLP based on nanoparticle size D and magnetic anisotropy constant K at a magnetization value M of 100 emu g−1. , Simulated plot of SLP based on K and M for 12 nm nanoparticle. SLP of maghemite is indicated by the blue line. Simulations are based on the superparamagnetic characteristics of nanoparticles. * Figure 2: TEM analyses and magnetic measurements of core–shell nanoparticles. ,, TEM image () and high-resolution TEM image () of 15 nm CoFe2O4@MnFe2O4, showing the narrow size distribution and single crystallinity. –, EELS mapped images: Co mapped image (), Fe mapped image (), Mn mapped image () and overlay image of – (). , Co, Fe and Mn line-scanned EELS profiles of a nanoparticle. EELS images and line-scan profiles confirm the CoFe2O4 core and MnFe2O4 shell. , Schematic drawing of core–shell nanoparticle with an exchange-coupled magnetism, and M–H curve of 15 nm CoFe2O4@MnFe2O4, 15 nm MnFe2O4 and 9 nm CoFe2O4 nanoparticles measured at 5 K using a SQUID magnetometer. The magnetization curve of the core–shell nanoparticle (red curve) shows the hard–soft exchange-coupled magnetism with a smooth hysteresis curve. Inset: M–H curve of CoFe2O4@MnFe2O4 at 300 K, showing its superparamagnetic nature with zero coercivity. * Figure 3: SLP comparison of magnetic nanoparticles. , Schematic of 15 nm CoFe2O4@MnFe2O4 nanoparticle and its SLP value in comparison with the values for its components (9 nm CoFe2O4 and 15 nm MnFe2O4). ,, SLP values of single-component magnetic nanoparticles (Feridex and MFe2O4; M = Mn, Fe and Co) () and various combinations of core–shell nanoparticles (CoFe2O4@MnFe2O4, CoFe2O4@Fe3O4, MnFe2O4@CoFe2O4, Fe3O4@CoFe2O4, Zn0.4Co0.6Fe2O4@Zn0.4Mn0.6Fe2O4) (). SLP values range from 100 to 450 W g−1 for single-component magnetic nanoparticles, and values for core–shell nanoparticles range from 1,000 to 4,000 W g−1 (f = 500 kHz, H0 = 37.3 kA m−1). Error bars indicate standard deviation (n = 5). * Figure 4: In vivo hyperthermia treatment of cancer. , Schematics of magnetic in vivo hyperthermia treatment in a mouse. Magnetic nanoparticles were directly injected into the tumour of a mouse and an a.c. magnetic field was applied. , Nude mice xenografted with cancer cells (U87MG) before treatment (upper row, dotted circle) and 18 days after treatment (lower row) with untreated control, CoFe2O4@MnFe2O4 hyperthermia, Feridex hyperthermia and doxorubicin, respectively. The same amounts (75 µg) of nanoparticles and doxorubicin were injected into the tumour (tumour volume, 100 mm3, n = 3). , Plot of tumour volume (V/Vinitial) versus days after treatment with core–shell nanoparticle hyperthermia, doxorubicin, Feridex hyperthermia, a.c. field only, core–shell nanoparticles only and untreated control. In the doxorubicin-treated group, tumour growth slowed initially, but then regrew after 18 days. In the group treated with core–shell nanoparticles hyperthermia, the tumour was clearly eliminated in 18 days. The suppression of ! tumour growth was not observed for the groups of Feridex hyperthermia, a.c. field only, core–shell nanoparticles only and the untreated control. , Immunofluorescence histological images of the tumour region after hyperthermia treatment with core–shell nanoparticles (upper image) and the control tumour region (lower image). , Plot of dose dependency on tumour volume measured 18 days after the treatment. For core–shell nanoparticle hyperthermia and doxorubicin treatments, doses of 75 µg and 300 µg, respectively, were needed to completely eliminate a tumour with a volume of 100 mm3. For Feridex hyperthermia, even a 1,200 µg nanoparticle dose did not adequately suppress tumour growth. Error bars in ,, indicate standard deviation (n = 5). Author information * Abstract * Author information * Supplementary information Affiliations * Department of Chemistry, Yonsei University, Seoul, 120-749, Korea * Jae-Hyun Lee, * Jung-tak Jang, * Jin-sil Choi, * Seung Ho Moon, * Seung-hyun Noh, * Ji-wook Kim & * Jinwoo Cheon * Division of Electron Microscopic Research, Korea Basic Science Institute, Daejeon, 305-333, Korea * Jin-Gyu Kim * Department of Pediatrics and BK 21, Yonsei University College of Medicine, Seoul, 120-752, Korea * Il-Sun Kim & * Kook In Park Contributions J.C. conceived and designed the experiment. J-H.L, J-t.J., S.H.M., J-G.K. and S-h.N. performed syntheses, characterizations and property measurements of the nanoparticles. J-s.C., I-S.K. and K.I.P. performed in vivo experiments. J-H.L., J-w.K. and J.C. wrote the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * Jinwoo Cheon Author Details * Jae-Hyun Lee Search for this author in: * NPG journals * PubMed * Google Scholar * Jung-tak Jang Search for this author in: * NPG journals * PubMed * Google Scholar * Jin-sil Choi Search for this author in: * NPG journals * PubMed * Google Scholar * Seung Ho Moon Search for this author in: * NPG journals * PubMed * Google Scholar * Seung-hyun Noh Search for this author in: * NPG journals * PubMed * Google Scholar * Ji-wook Kim Search for this author in: * NPG journals * PubMed * Google Scholar * Jin-Gyu Kim Search for this author in: * NPG journals * PubMed * Google Scholar * Il-Sun Kim Search for this author in: * NPG journals * PubMed * Google Scholar * Kook In Park Search for this author in: * NPG journals * PubMed * Google Scholar * Jinwoo Cheon Contact Jinwoo Cheon Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (1,062 KB) Supplementary information Additional data - Tunable subradiant lattice plasmons by out-of-plane dipolar interactions
- Nat Nanotechnol 6(7):423-427 (2011)
Nature Nanotechnology | Letter Tunable subradiant lattice plasmons by out-of-plane dipolar interactions * Wei Zhou1 * Teri W. Odom1, 2 * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Pages:423–427Year published:(2011)DOI:doi:10.1038/nnano.2011.72Received28 February 2011Accepted11 April 2011Published online15 May 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Plasmonic nanostructures concentrate optical fields into nanoscale volumes1, 2, which is useful for plasmonic nanolasers3, 4, surface enhanced Raman spectroscopy5, 6 and white-light generation7. However, the short lifetimes of the emissive plasmons correspond to a rapid depletion of the plasmon energy, preventing further enhancement of local optical fields. Dark (subradiant) plasmons8, 9, 10, 11, 12 have longer lifetimes, but their resonant wavelengths cannot be tuned over a broad wavelength range without changing the overall geometry of the nanostructures. Also, fabrication of the nanostructures cannot be readily scaled because their complex shapes have subwavelength dimensions. Here, we report a new type of subradiant plasmon with a narrow (~5 nm) resonant linewidth that can be easily tuned by changing the height of large (>100 nm) gold nanoparticles arranged in a two-dimensional array. At resonance, strong coupling between out-of-plane nanoparticle dipolar moments suppres! ses radiative decay, trapping light in the plane of the array and strongly localizing optical fields on each nanoparticle. This new mechanism can open up applications for subradiant plasmons because height-controlled nanoparticle arrays can be manufactured over wafer-scale areas on a variety of substrates. View full text Subject terms: * Nanoparticles * Photonic structures and devices Figures at a glance * Figure 1: Template-stripping nanofabrication technique used to produce two-dimensional arrays of large nanoparticles with variable heights over wafer-scale areas. , Scheme for fabricating two-dimensional arrays of large (>100 nm) gold nanoparticles. , Top-down and cross-sectional (inset) scanning electron microscopy (SEM) images of a gold nanoparticle array embedded in a PU matrix. , Optical micrograph of a gold nanoparticle array on a flexible, polyethylene film (patterned area, >18 cm2; nanoparticle array parameters, h = 100 nm, d = 160 nm, a0 = 400 nm). PR, photoresist. * Figure 2: Out-of-plane lattice plasmon resonances can be tuned by controlling the height of nanoparticles. ,, Measured reflectance and transmittance spectra of gold two-dimensional nanoparticle arrays with heights of h = 65, 100, 120 and 170 nm under TM-polarized light () and TE-polarized light (). The incident excitation plane was aligned along the high-symmetry lattice direction. Incident angle, θ = 15°. The individual spectra have been displaced by 10% for clarity. * Figure 3: Strongly coupled two-dimensional nanoparticle arrays exhibit a continuously tunable Fano-like profile. ,, Measured () and FDTD simulations () of angle-dependent transmittance and reflectance spectra of gold two-dimensional nanoparticle arrays (h = 100 nm, d = 160 nm) under TM-polarized light. * Figure 4: Local hot spots on strongly coupled nanoparticles are orders of magnitude higher than those on isolated nanoparticles with the same size and shape. –, FDTD-simulated extinction (black line), scattering (red line) and absorption (blue line) cross-sections and electric field intensity distribution maps for a single nanoparticle at λ = 850 nm (–) and a two-dimensional nanoparticle array at λ = 758 nm (–; h = 100 nm, d = 160 nm, a0 = 400 nm). NP, nanoparticle. * Figure 5: Far-field and near-field optical properties of strongly coupled two-dimensional nanoparticle arrays are correlated. , Measured (solid lines) and simulated (dashed lines) out-of-plane lattice plasmon wavelengths (λout) and peak absorption cross-sections (σabs) as a function of θ. The grey line indicates the (1,0) Rayleigh anomaly (RA(1,0)) with n = 1.52 and a0 = 400 nm. , Local field intensity (|loc|2) and average field intensity (|ave|2) of strongly coupled nanoparticle arrays as a function of θ. Author information * Abstract * Author information * Supplementary information Affiliations * Department of Materials Science and Engineering, Northwestern University, 2220 Campus Drive, Evanston, Illinois 60208, USA * Wei Zhou & * Teri W. Odom * Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois, 60208, USA * Teri W. Odom Contributions T.W.O. and W.Z. conceived and designed the experiments. W.Z. performed the experiments, fabricated samples and performed numerical simulations. W.Z. and T.W.O. analysed the data and co-wrote the paper. Both authors discussed the results and commented on the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * Teri W. Odom Author Details * Wei Zhou Search for this author in: * NPG journals * PubMed * Google Scholar * Teri W. Odom Contact Teri W. Odom Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (1,680 KB) Supplementary information Additional data - Detecting single viruses and nanoparticles using whispering gallery microlasers
- Nat Nanotechnol 6(7):428-432 (2011)
Nature Nanotechnology | Letter Detecting single viruses and nanoparticles using whispering gallery microlasers * Lina He1 * Şahin Kaya Özdemir1 * Jiangang Zhu1 * Woosung Kim1 * Lan Yang1 * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Pages:428–432Year published:(2011)DOI:doi:10.1038/nnano.2011.99Received26 April 2011Accepted24 May 2011Published online26 June 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg There is a strong demand for portable systems that can detect and characterize individual pathogens and other nanoscale objects without the use of labels, for applications in human health, homeland security, environmental monitoring and diagnostics1, 2, 3, 4, 5, 6. However, most nanoscale objects of interest have low polarizabilities due to their small size and low refractive index contrast with the surrounding medium. This leads to weak light–matter interactions, and thus makes the label-free detection of single nanoparticles very difficult. Micro- and nano-photonic devices have emerged as highly sensitive platforms for such applications, because the combination of high quality factor Q and small mode volume V leads to significantly enhanced light–matter interactions7, 8, 9, 10, 11, 12, 13, 14, 15. For example, whispering gallery mode microresonators have been used to detect and characterize single influenza virions10 and polystyrene nanoparticles with a radius of 30 nm! (ref. 12) by measuring in the transmission spectrum either the resonance shift10 or mode splitting12 induced by the nanoscale objects. Increasing Q leads to a narrower resonance linewidth, which makes it possible to resolve smaller changes in the transmission spectrum, and thus leads to improved performance. Here, we report a whispering gallery mode microlaser-based real-time and label-free detection method that can detect individual 15-nm-radius polystyrene nanoparticles, 10-nm gold nanoparticles and influenza A virions in air, and 30 nm polystyrene nanoparticles in water. Our approach relies on measuring changes in the beat note that is produced when an ultra-narrow emission line from a whispering gallery mode microlaser is split into two modes by a nanoscale object, and these two modes then interfere. The ultimate detection limit is set by the laser linewidth, which can be made much narrower than the resonance linewidth of any passive resonator16, 17. This means that mi! crolaser sensors have the potential to detect objects that are! too small to be detected by passive resonator sensors18. View full text Subject terms: * Nanoparticles * Nanosensors and other devices * Photonic structures and devices Figures at a glance * Figure 1: Heterodyne detection of single nano-objects using frequency splitting in a microlaser. , Schematic of the experimental setup. The pump light and split lasing modes are separated using a wavelength division multiplexer (WDM). The split lasing modes are mixed in a photodetector (PD), leading to a heterodyne beat note signal. A nozzle continuously delivers viral or synthetic nanoparticles onto a toroid-shaped microlaser12, which translates changes in polarizability into changes in frequency splitting. Inset: Top and side views of the WGM microresonator with resonant modes along the periphery traced by up-converted green light emitted by Er3+ ions. , Schematics showing how the lasing spectrum (middle column) and the beat note signal (right column) change as nanoparticles (blue spheres) bind to the microlaser (left column). (i) Before nanoparticles arrive there is a single laser mode and the laser intensity is constant. (ii) The lasing mode splits into two modes when the first nanoparticle binds, leading to a beat note with a frequency that is equal to the differen! ce in frequency between the two modes. (iii) The lasing spectrum and the frequency of the beat note change again when a second nanoparticle binds. (iv) Environmental noise such as temperature fluctuations changes the lasing spectrum, but the beat note signal does not change because both modes are shifted equally, making this detection scheme resistant to environmental noises21. * Figure 2: Detecting virions and nanoparticles. , Discrete changes in this plot of beat frequency versus time correspond to InfA virions binding to the WGM microlaser. Red circles denote individual virus-binding events. Inset: scanning electron micrograph of two InfA virions on the microlaser. ,, Beat frequency versus time for PS nanoparticles with a radius of 15 nm () and gold nanoparticles with a radius of 10 nm () binding to the microlaser. The red lines are drawn at the mean of the measured beat frequencies for each binding event. * Figure 3: Estimating particle size with an ensemble measurement. ,, Beat frequency versus time for gold nanoparticles with radii of 15 nm () and 25 nm () randomly deposited one by one onto the microlaser. Red lines represent the mean of the measured beat frequencies for each binding event. , Histograms showing the size of changes in beat frequency for 15 nm (blue) and 25 nm (red) nanoparticles. Changes in the range ±100 kHz are rejected as they are biased with the beat frequency fluctuation noise. The total numbers of binding events detected are 397 for the 15 nm nanoparticles and 419 for the 25 nm nanoparticles. The measured standard deviations of the histograms are 0.383 MHz for the 15 nm nanoparticles and 1.344 MHz for the 25 nm nanoparticles. All data (a total of 816 events) are measured using the same microlaser and the same lasing mode, implying that small nanoparticles do not cause significant change in the linewidth of the lasing modes. * Figure 4: Simultaneous multiwavelength detection of nanoparticles using a single microlaser. , Typical spectrum of a two-mode microlaser. The pump wavelength is λp = 1,443 nm, and the two lasing lines have wavelengths λs1 = 1,549 nm and λs2 = 1,562 nm. , Typical beat note signal for a two-mode microlaser (top) and its fast Fourier transform (FFT; bottom). The right peak in the FFT spectrum is due to splitting of the λs1 laser mode, and the left peak is due to splitting of the λs2 laser mode. , False-colour plot showing the magnitude of the FFT spectrum (in dB) as a function of time as gold nanoparticles with radii of 50 nm are continuously deposited onto the microlaser. The heights of discrete jumps in the two beat frequencies are different for the same binding event. , Close-up of the region inside the black-dashed rectangle in . Red circles mark a particle binding event that is clearly detected by one laser mode, but undetected by the other mode. * Figure 5: Detection of nanoparticles in water using frequency splitting in a microlaser. , Lasing spectrum (optical power versus wavelength) of a ytterbium-doped microtoroid laser in water. Laser emission occurs at 1,029 nm when the pump wavelength is 971.5 nm. , Changes in beat frequency with time after a suspension containing PS nanoparticles (radius, 30 nm) is injected into the chamber. The red lines are drawn at the mean of the measured beat frequencies for each binding event. , Top view of the microlaser in water. A nanoparticle bound to the ring of the microlaser can be seen because it scatters red light that has been coupled into the microlaser. The white light at the top is due to the illuminating light from the microscope. The white dotted lines denote the boundary of the microlaser and the fibre taper, and the red arrows show the direction of light propagation in the fibre taper. Author information * Abstract * Author information * Supplementary information Affiliations * Department of Electrical and Systems Engineering, Washington University in St. Louis, Missouri 63130, USA * Lina He, * Şahin Kaya Özdemir, * Jiangang Zhu, * Woosung Kim & * Lan Yang Contributions L.H., S.K.O., J.Z. and L.Y. designed the experimental concept. L.H. and J.Z. performed the experiments in air. L.H. and W.K. performed the experiments in water. L.H. and S.K.O. contributed to the theoretical work. L.Y. supervised the project. All authors contributed to the discussion of the results and the preparation of the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * Lan Yang Author Details * Lina He Search for this author in: * NPG journals * PubMed * Google Scholar * Şahin Kaya Özdemir Search for this author in: * NPG journals * PubMed * Google Scholar * Jiangang Zhu Search for this author in: * NPG journals * PubMed * Google Scholar * Woosung Kim Search for this author in: * NPG journals * PubMed * Google Scholar * Lan Yang Contact Lan Yang Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (2,409 KB) Supplementary information Additional data - Single-molecule transport across an individual biomimetic nuclear pore complex
- Nat Nanotechnol 6(7):433-438 (2011)
Nature Nanotechnology | Letter Single-molecule transport across an individual biomimetic nuclear pore complex * Stefan W. Kowalczyk1 * Larisa Kapinos2 * Timothy R. Blosser1 * Tomás Magalhães1 * Pauline van Nies1 * Roderick Y. H. Lim2 * Cees Dekker1 * Affiliations * Contributions * Corresponding authorsJournal name:Nature NanotechnologyVolume: 6,Pages:433–438Year published:(2011)DOI:doi:10.1038/nnano.2011.88Received15 February 2011Accepted17 May 2011Published online19 June 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Nuclear pore complexes regulate the selective exchange of RNA and proteins across the nuclear envelope in eukaryotic cells1. Biomimetic strategies offer new opportunities to investigate this remarkable transport phenomenon2. Here, we show selective transport of proteins across individual biomimetic nuclear pore complexes at the single-molecule level. Each biomimetic complex is constructed by covalently tethering either Nup98 or Nup153 (phenylalanine-glycine (FG) nucleoporins) to a solid-state nanopore3. Individual translocation events are monitored using ionic current measurements with sub-millisecond temporal resolution. Transport receptors (Impβ) proceed with a dwell time of ~2.5 ms for both Nup98- and Nup153-coated pores, whereas the passage of non-specific proteins is strongly inhibited with different degrees of selectivity. For pores up to ~25 nm in diameter, Nups form a dense and low-conducting barrier, whereas they adopt a more open structure in larger pores. Our bio! mimetic nuclear pore complex provides a quantitative platform for studying nucleocytoplasmic transport phenomena at the single-molecule level in vitro. View full text Subject terms: * Nanobiotechnology Figures at a glance * Figure 1: Biomimetic NPC. , Side-view schematic showing the device consisting of a 20 nm thin, free-standing silicon nitride window (blue layer) embedded in a silicon wafer (light green). A nanopore is drilled using a highly focused electron beam (yellow). , Sketch showing the experimental concept. The biomimetic NPC is engineered by attaching FG-Nups to a solid-state nanopore, and transport of Impβ is measured by monitoring the trans-pore current. , TEM images of the same nanopore with a diameter of 20 nm (top) or 40 nm (bottom) before (left) and after (right) coating with Nup98. , Example of a current–voltage (I–V) curve before (red) and after (blue) coating a 40 nm nanopore with Nup98, showing an increased resistance due to the coating. * Figure 2: Conductance measurements and models. , Measured conductance versus pore diameter for bare pores (black points), Nup98-coated (green) and Nup153-coated (inset, red) pores. For all pores, the pore conductance decreases upon coating. Coloured lines are linear fits of two models (see text). Model 2 (solid lines) is found to fit the data much better than model 1 (dashed lines). –, Schematics showing small- and large-pore regimes for models 1 and 2, as discussed in the text. Fitting to model 2 yields a Nup layer thickness tNup98 = 15 ± 1 nm and tNup153 = 8 ± 1 nm along the circumference of the pore for Nup98 and Nup153, respectively. * Figure 3: Single-molecule translocation events. , Representative ion current trace before and after addition of Impβ in a bare pore. Downward spikes appear in the current trace upon addition of Impβ. Each spike is a single-molecule event. The lower panel shows zoom-ins on a number of events. , As in , but for a Nup98-coated pore. , Scatter diagram for Impβ translocation in a bare (red) and Nup98-modified (black) pore, where each point represents an individual event. Event amplitudes are similar (~0.6 nS), but the dwell times differ by more than an order of magnitude (~200 µs versus ~3 ms). , Scatter diagram for BSA translocation through bare (green) and Nup98 pores (black). , As in , but for a Nup153 pore. , As in , but for a Nup153-modified pore. * Figure 4: Event frequencies through bare and Nup-modified pores, showing NPC-like selectivity. Average number of events per second for BSA through a bare pore (green), Impβ through a bare pore (red), BSA through a Nup98-coated pore (blue), Impβ through a Nup98-coated pore (black), and finally BSA through a Nup153-coated pore (blue) and Impβ through a Nup153-coated pore (black). Pore diameter is 42–46 nm in all cases. The passage of BSA through the Nup-modified pore is significantly inhibited in Nup-coated pores, whereas that of Impβ is not; that is, these pores display the hallmark of NPC selectivity. * Figure 5: Nanopore array. , TEM image of a nanopore array consisting of 61 pores with diameters of 43 ± 3 nm. , TIRF image of individual Alexa488-labelled fluorescent Impβ proteins that were translocated through the Nup98-coated nanopore array of to the trans chamber and subsequently immobilized onto a cover slide (see text). The inset shows a control image of buffer only, for exactly the same TIRF conditions. Author information * Abstract * Author information * Supplementary information Affiliations * Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands * Stefan W. Kowalczyk, * Timothy R. Blosser, * Tomás Magalhães, * Pauline van Nies & * Cees Dekker * Biozentrum and the Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland * Larisa Kapinos & * Roderick Y. H. Lim Contributions S.W.K., R.Y.H.L. and C.D. devised the experiments. L.K. cloned, purified and labelled proteins and carried out SPR analysis. S.W.K., T.R.B., T.M. and P.V.N. carried out the experiments and analysed data. S.W.K., R.Y.H.L. and C.D. wrote the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding authors Correspondence to: * Roderick Y. H. Lim or * Cees Dekker Author Details * Stefan W. Kowalczyk Search for this author in: * NPG journals * PubMed * Google Scholar * Larisa Kapinos Search for this author in: * NPG journals * PubMed * Google Scholar * Timothy R. Blosser Search for this author in: * NPG journals * PubMed * Google Scholar * Tomás Magalhães Search for this author in: * NPG journals * PubMed * Google Scholar * Pauline van Nies Search for this author in: * NPG journals * PubMed * Google Scholar * Roderick Y. H. Lim Contact Roderick Y. H. Lim Search for this author in: * NPG journals * PubMed * Google Scholar * Cees Dekker Contact Cees Dekker Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (4,997 KB) Supplementary information Additional data - Bi- and trilayer graphene solutions
- Nat Nanotechnol 6(7):439-445 (2011)
Nature Nanotechnology | Article Bi- and trilayer graphene solutions * Chih-Jen Shih1 * Aravind Vijayaraghavan1, 2 * Rajasekar Krishnan1 * Richa Sharma1 * Jae-Hee Han1, 3 * Moon-Ho Ham1 * Zhong Jin1 * Shangchao Lin1, 4 * Geraldine L.C. Paulus1 * Nigel Forest Reuel1 * Qing Hua Wang1 * Daniel Blankschtein1 * Michael S. Strano1 * Affiliations * Contributions * Corresponding authorJournal name:Nature NanotechnologyVolume: 6,Pages:439–445Year published:(2011)DOI:doi:10.1038/nnano.2011.94Received15 April 2011Accepted19 May 2011Published online26 June 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Bilayer and trilayer graphene with controlled stacking is emerging as one of the most promising candidates for post-silicon nanoelectronics. However, it is not yet possible to produce large quantities of bilayer or trilayer graphene with controlled stacking, as is required for many applications. Here, we demonstrate a solution-phase technique for the production of large-area, bilayer or trilayer graphene from graphite, with controlled stacking. The ionic compounds iodine chloride (ICl) or iodine bromide (IBr) intercalate the graphite starting material at every second or third layer, creating second- or third-stage controlled graphite intercolation compounds, respectively. The resulting solution dispersions are specifically enriched with bilayer or trilayer graphene, respectively. Because the process requires only mild sonication, it produces graphene flakes with areas as large as 50 µm2. Moreover, the electronic properties of the flakes are superior to those achieved with o! ther solution-based methods; for example, unannealed samples have resistivities as low as ~1 kΩ and hole mobilities as high as ~400 cm2 V–1 s–1. The solution-based process is expected to allow high-throughput production, functionalization, and the transfer of samples to arbitrary substrates. View full text Subject terms: * Electronic properties and devices * Nanomaterials * Synthesis and processing Figures at a glance * Figure 1: Graphene dispersions from ionic graphite intercalation compounds (GIC). , Three-dimensional computer-generated molecular models (carbon, grey; iodine, red; bromine, yellow; chlorine, cyan) of HOPG (top), IBr Stage-3 GIC (middle) and ICl Stage-2 GIC (bottom). , Comparison of XRD patterns of HOPG, IBr Stage-3 GIC, ICl Stage-2 GIC, IBr Stage-3 expanded graphite (EG) and ICl Stage-2 EG. For IBr Stage-3 GIC, an additional three peaks appear between two of the three main peaks corresponding to the (0 0 2), (0 0 4) and (0 0 6) planes in HOPG, which is a clear signature of Stage-3 GIC (the intercalant layer inserts between every three graphite layers). Analogous XRD patterns also apply to the ICl Stage-2 GIC. Both Stage-3 and Stage-2 expanded graphites show much weaker (0 0 4) peaks than the HOPG, while the (0 0 6) peak becomes unobservable. , Photographs of HOPG (top), Stage-3 GIC (middle) and Stage-3 EG (bottom) (the HOPG and GIC materials are held up with tweezers with the edges toward the viewer). , Photographs of HOPG (top), Stage-2 GIC (middle), a! nd Stage-2 EG (bottom). , Photograph of steps involved in forming suspensions of EGs in 2 wt% sodium cholate aqueous solution. As-prepared Stage-3 (i) and Stage-2 (ii) expanded materials floating on the solution, followed by 30 min homogenization (iii) and 10 min sonication (iv). (v) Clear and grey graphene solutions after 2,000 r.p.m. centrifugation. * Figure 2: On-chip separation method based on graphene size, using the 'coffee-ring effect'. , Schematic of the separation process. (i) A droplet of graphene dispersion on the SiO2 substrate with contact angle θ1. (ii) Because the evaporation rate is greatest at the drop edge, some graphene flakes deposit along the edge of the drop at the beginning. The presence of these flakes facilitates pinning of the contact line at the drop edge. (iii) The outward capillary flow of liquid is induced from the bulk of the drop, and the contact angle θ2 becomes gradually smaller. (iv) The liquid flow carries graphene flakes out towards the edge of the drop, which results in the formation of a 'coffee ring'. (v) By controlling the rate of evaporation, all small flakes collect together to form the coffee ring, and particularly large flakes are found inside the coffee ring. (vi) When the contact angle θ2 becomes too small, the contact line moves back and a smaller droplet forms with contact angle θ1 again. , Low- (left) and high- (right) magnification images of a matrix of sm! all graphene solution droplets (50 nl each) on a SiO2 wafer, spaced by 4 mm, using a microprinter. Bright dots are associated with surfactant residues after drying. , Low- (left) and high- (right) magnification images of the 'coffee ring'. * Figure 3: Characterization of graphene flakes. ,, Raman spectra (excitation wavelength λ = 633 nm) for graphene flakes with different numbers of stacked layers. Note that for multilayer graphene flakes, the D-peaks (1,340 cm−1, ) are absent, but for the relatively smaller monolayer graphene flake, the weak D-peak arises due to edge effects. 2D Raman spectra () corresponding to specific numbers of stacked layers of our graphene flakes show the same features observed using the Scotch-tape method on the same substrate. , HRTEM images of the edges of bilayer (left) and trilayer (right) graphene flakes. , TEM image of a representative multilayer graphene flake (area, ~50 µm2). ,, Representative AFM images of bilayer () and ~3–4-layer graphene flakes (). * Figure 4: Evidence for layer- and size-controlled graphene dispersions from different GICs. Distributions for number of stacked layers and the area of graphene flakes inside 'coffee rings' from IBr Stage-3 () and ICl Stage-2 () GICs. Regions occupied by graphene solutions produced from direct exfoliation of natural graphite24, 27 are also shown for comparison. , Schematic describing the exfoliation process of a 9-layer graphite lattice into 8- and 1-layer products with rate constant k8,1 for a Stage-2 EG system. , Calculated concentrations of mono- (blue curve), bi- (red curve) and tri- (green curve) layer graphene dispersions as a function of dimensionless time using graphite with all interlayer bond strengths equal. , Calculated concentrations for Stage-3 EG with every third interlayer bonds weaker. Adjacent graph shows the predicted time (vertical line) corresponding to the experimentally observed layer distribution for Stage-3 solutions. , Calculated concentrations for Stage-2 EG with every third interlayer bond weaker. Adjacent graph shows the predicted ti! me (vertical line) corresponding to the experimentally observed layer distribution for Stage-2 solutions. * Figure 5: Electronic characteristics of bilayer and ~3–4-layer graphene devices in the presence of a perpendicular electric field at room temperature. , Low-magnification image of our fabricated top-gate (TG) device on a specific graphene flake. , 2D resistivities and hole mobilities for several unannealed FET devices using our bilayer- or trilayer-enriched graphene dispersions. Reported values corresponding to micromechanically exfoliated bi- and trilayer graphene52, CVD bilayer graphene10 and reduced graphene oxide18, 51, 53, 54 are also shown for comparison. ,, Transfer currents () and 2D resistivity () as functions of top-gate voltage (VTG) and bottom-gate voltage (VBG) of a representative ~3–4-layer graphene device. ,, Transfer currents () and 2D resistivity () as functions of VTG and VBG of a representative bilayer graphene device. Author information * Abstract * Author information * Supplementary information Affiliations * Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA * Chih-Jen Shih, * Aravind Vijayaraghavan, * Rajasekar Krishnan, * Richa Sharma, * Jae-Hee Han, * Moon-Ho Ham, * Zhong Jin, * Shangchao Lin, * Geraldine L.C. Paulus, * Nigel Forest Reuel, * Qing Hua Wang, * Daniel Blankschtein & * Michael S. Strano * School of Computer Science, The University of Manchester, Manchester M13 9PL, UK * Aravind Vijayaraghavan * Department of Energy IT, Kyungwon University, Seongnam, Gyeonggi-do 461-701, South Korea * Jae-Hee Han * Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA * Shangchao Lin Contributions C.J.S, A.V., R.K. and M.S.S. conceived and designed the dispersion experiments. C.J.S. and R.K. implemented the dispersion method. C.J.S., A.V., R.S., G.P. and M.H.H. fabricated FET devices. C.J.S. and M.S.S. developed the mathematical model. A.V., R.S., Z.J. and J.H.H. performed the TEM and AFM analysis. C.J.S. performed the XRD and Raman analysis. Q.H.W., S.L. and N.F.R. did additional experiments for revising the manuscript. C.J.S., D.B. and M.S.S. wrote the manuscript with input from A.V. All authors discussed the results and commented on the manuscript. Competing financial interests The authors declare no competing financial interests. Corresponding author Correspondence to: * Michael S. Strano Author Details * Chih-Jen Shih Search for this author in: * NPG journals * PubMed * Google Scholar * Aravind Vijayaraghavan Search for this author in: * NPG journals * PubMed * Google Scholar * Rajasekar Krishnan Search for this author in: * NPG journals * PubMed * Google Scholar * Richa Sharma Search for this author in: * NPG journals * PubMed * Google Scholar * Jae-Hee Han Search for this author in: * NPG journals * PubMed * Google Scholar * Moon-Ho Ham Search for this author in: * NPG journals * PubMed * Google Scholar * Zhong Jin Search for this author in: * NPG journals * PubMed * Google Scholar * Shangchao Lin Search for this author in: * NPG journals * PubMed * Google Scholar * Geraldine L.C. Paulus Search for this author in: * NPG journals * PubMed * Google Scholar * Nigel Forest Reuel Search for this author in: * NPG journals * PubMed * Google Scholar * Qing Hua Wang Search for this author in: * NPG journals * PubMed * Google Scholar * Daniel Blankschtein 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 Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (8,330 KB) Supplementary information Additional data - Cold-atom scanning probe microscopy
- Nat Nanotechnol 6(7):446-451 (2011)
Nature Nanotechnology | Article Cold-atom scanning probe microscopy * M. Gierling1 * P. Schneeweiss1 * G. Visanescu1 * P. Federsel1 * M. Häffner1 * D. P. Kern1 * T. E. Judd1 * A. Günther1 * J. Fortágh1 * Affiliations * Contributions * Corresponding authorsJournal name:Nature NanotechnologyVolume: 6,Pages:446–451Year published:(2011)DOI:doi:10.1038/nnano.2011.80Received29 March 2011Accepted21 April 2011Published online29 May 2011 Abstract * Abstract * Author information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg Scanning probe microscopes are widely used to study surfaces with atomic resolution in many areas of nanoscience. Ultracold atomic gases trapped in electromagnetic potentials can be used to study electromagnetic interactions between the atoms and nearby surfaces in chip-based systems. Here we demonstrate a new type of scanning probe microscope that combines these two areas of research by using an ultracold gas as the tip in a scanning probe microscope. This cold-atom scanning probe microscope offers a large scanning volume, an ultrasoft tip of well-defined shape and high purity, and sensitivity to electromagnetic forces (including dispersion forces near nanostructured surfaces). We use the cold-atom scanning probe microscope to non-destructively measure the position and height of carbon nanotube structures and individual free-standing nanotubes. Cooling the atoms in the gas to form a Bose–Einstein condensate increases the resolution of the device. View full text Subject terms: * Nanosensors and other devices * Surface patterning and imaging Figures at a glance * Figure 1: Cold-atom SPM. An ultracold atom cloud (shown in yellow) is confined in a magnetic trap and scanned above a surface in a three-dimensional volume. By measuring the loss of atoms from the cloud (contact mode) or changes in the centre-of-mass oscillation of the cloud (dynamic mode), the topography of the surface is determined. * Figure 2: Magnetic conveyor belt for nanopositioning the cold-atom probe tips near nanostructures. , The carrier chip contains a full set of miniaturized electromagnets (defined by microfabricated wire patterns) for trapping and excitation-free transport of atom clouds over a surface area of 20 mm2 and a variable height up to 500 µm above the carrier chip surface. Current-driven conductors on the front (R1, R2, R3) and rear side (A1–A8) of a sapphire substrate generate magnetic traps for ultracold atoms. The position of the magnetic trap is scanned by changing the current in the conductors12. Nanostructures under study are implemented on the nanochip, which is attached to the surface of the conveyor belt. ,, SEM images of vertically grown carbon nanotube test structures: a carpet of nanotubes () and a free-standing nanotube surrounded by lines of nanotubes (). * Figure 3: Contact mode. , The cold-atom tip (red cloud) is moved downwards until it is a distance d from the carrier chip, and is then moved upwards, and the number of atoms remaining in the cloud is recorded. This process is repeated for different values of d and at different positions in the x–y plane. , Fraction of atoms remaining in the cloud versus d for the four different positions shown in . Measurements at position A are used to determine the height of the nanochip surface; measurements at B1 and B2 are used to locate the edge of a carpet of carbon nanotubes that has been grown on the nanochip. Measurements at C are used to determine the height of the nanotube carpet. At the edge of the nanotube carpet, the atom cloud only partly overlaps with the nanotubes. Equation (2) can be used to determine the overlap parameter p. Inset: p versus position in the x-direction: the edge of the nanotube carpet is the position at which p drops to 0.5. * Figure 4: Cold-atom SPM image of nanostructures. , Image of a single carbon nanotube surrounded by lines of nanotubes taken with a BEC (see SEM image in Fig. 2c). , Lateral scan in the y-direction across the position of the nanotube, comparing the resolution of the BEC (red dots) and the thermal cloud (grey circles) probe tips. * Figure 5: Measuring the length of a single nanotube in contact mode. The fraction of atoms remaining in the cloud as a function of the distance d from the carrier chip for the two positions A and B shown in the inset. (The nanotube is the black vertical line at position B.) The length is derived from the displacement Δ of the two curves. * Figure 6: Measuring the lateral position of a single nanotube in dynamic mode. ,, A BEC can be excited so that it oscillates in the magnetic trap. If the frequency () and amplitude () of the oscillations are plotted as a function of position in the y-direction as the condensate is scanned above a vertical nanotube, it is possible to determine the position of the nanotube, which is y = 0 in this case. Error bars indicate the 95% confidence level of the determined amplitude and frequency. Author information * Abstract * Author information Affiliations * CQ Center for Collective Quantum Phenomena and their Applications, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany * M. Gierling, * P. Schneeweiss, * G. Visanescu, * P. Federsel, * M. Häffner, * D. P. Kern, * T. E. Judd, * A. Günther & * J. Fortágh Contributions A.G. and J.F. contributed to the experimental idea and supervised the project. M.G., P.S., A.G. and J.F. designed and set up the experiment. G.V., M.H. and D.P.K. fabricated the nano structures. M.G., P.S. and P.F. performed the experiments. M.G., P.S., T.E.J., A.G. and J.F. analysed the data. All authors discussed the results. Competing financial interests The authors declare no competing financial interests. Corresponding authors Correspondence to: * A. Günther or * J. Fortágh Author Details * M. Gierling Search for this author in: * NPG journals * PubMed * Google Scholar * P. Schneeweiss Search for this author in: * NPG journals * PubMed * Google Scholar * G. Visanescu Search for this author in: * NPG journals * PubMed * Google Scholar * P. Federsel Search for this author in: * NPG journals * PubMed * Google Scholar * M. Häffner Search for this author in: * NPG journals * PubMed * Google Scholar * D. P. Kern Search for this author in: * NPG journals * PubMed * Google Scholar * T. E. Judd Search for this author in: * NPG journals * PubMed * Google Scholar * A. Günther Contact A. Günther Search for this author in: * NPG journals * PubMed * Google Scholar * J. Fortágh Contact J. Fortágh Search for this author in: * NPG journals * PubMed * Google Scholar Additional data - Highly uniform and reproducible surface-enhanced Raman scattering from DNA-tailorable nanoparticles with 1-nm interior gap
- Nat Nanotechnol 6(7):452-460 (2011)
Nature Nanotechnology | Article Highly uniform and reproducible surface-enhanced Raman scattering from DNA-tailorable nanoparticles with 1-nm interior gap * Dong-Kwon Lim1, 5 * Ki-Seok Jeon2, 5 * Jae-Ho Hwang1 * Hyoki Kim3 * Sunghoon Kwon3, 4 * Yung Doug Suh2 * Jwa-Min Nam1 * Affiliations * Contributions * Corresponding authorsJournal name:Nature NanotechnologyVolume: 6,Pages:452–460Year published:(2011)DOI:doi:10.1038/nnano.2011.79Received09 March 2011Accepted21 April 2011Published online29 May 2011 Abstract * Abstract * Author information * Supplementary information Article tools * Full text * Print * Email * Download PDF * Download citation * Order reprints * Rights and permissions * Share/bookmark * Connotea * CiteULike * Facebook * Twitter * Delicious * Digg An ideal surface-enhanced Raman scattering (SERS) nanostructure for sensing and imaging applications should induce a high signal enhancement, generate a reproducible and uniform response, and should be easy to synthesize. Many SERS-active nanostructures have been investigated, but they suffer from poor reproducibility of the SERS-active sites, and the wide distribution of their enhancement factor values results in an unquantifiable SERS signal. Here, we show that DNA on gold nanoparticles facilitates the formation of well-defined gold nanobridged nanogap particles (Au-NNP) that generate a highly stable and reproducible SERS signal. The uniform and hollow gap (~1 nm) between the gold core and gold shell can be precisely loaded with a quantifiable amount of Raman dyes. SERS signals generated by Au-NNPs showed a linear dependence on probe concentration (R2 > 0.98) and were sensitive down to 10 fM concentrations. Single-particle nano-Raman mapping analysis revealed that >90% of ! Au-NNPs had enhancement factors greater than 1.0 × 108, which is sufficient for single-molecule detection, and the values were narrowly distributed between 1.0 × 108 and 5.0 × 109. View full text Subject terms: * Nanoparticles Figures at a glance * Figure 1: Surface DNA-mediated synthesis and characterization of DNA-anchored nanobridged nanogap particles. , Synthetic scheme for the gold nanobridged nanogap particles (Au-NNPs) using DNA-modified gold nanoparticles as templates. , UV-vis spectra for the probes. Inset: gradual change in the colour of the solution as the reaction proceeds from seeds (DNA-AuNPs) to intermediates 1, 2 and 3 and product 4. , HRTEM images of intermediate (panels 1–3) and Au-NNPs (panels 4 and 5). Nanobridges within the Au-NNP are indicated by red arrows in panel 5, and element line mapping and the ~1.2 nm gap in the Au-NNP structure are shown in panel 6. , Comparison between multimeric inter-nanogap structure that has a less uniform, multiple point gap junctions (left) and monomeric interior-nanogap structure with a more uniform surface gap junction (right). * Figure 2: Three-dimensional finite-element calculation of Au-NNP and silica-insulated concentric structure. , Calculated near-field electromagnetic field distribution of the Au-NNP. In this calculation, we assume that the gap is filled with DNA and Raman reporter molecules and the area surrounding the particle is filled with water. , Near-field calculation of a silica-insulated (1.2 nm) Au–Au core–gap–shell nanoparticle having the same dimensions as in the structure in . , Comparison of the line electromagnetic field distribution profile along the centre-horizontal line at an incident wavelength of 633 nm (red line, Au-NNP; blue line, silica-insulated core–shell nanoparticle; black line, non-bridged gold nanogap particle). , Incident wavelength dependence of the Au-NNP (solid bars) and silica-insulated core–shell structure (striped bars). * Figure 3: Excitation wavelength and dye position dependence of SERS of Au-NNPs in solution. , SERS spectra of three different incident wavelengths (red line, 633 nm; blue line, 785 nm; black line, 514 nm) for ROX-oligonucleotide-modified Au-NNPs(ROXgap) in solution. –, Time-dependent Raman profiles of Au-NNP(ROXgap) (), Au-NNP(ROXinner) () and Au-NNP(ROXouter) (). All spectra (–) were acquired with a 633 nm excitation laser, at 300 µW, and for a 10 s exposure for a single spectrum for 100 s, with the same particle concentration (0.5 nM). * Figure 4: Comparison of Raman signal intensity as a function of the number of Raman dye molecules in the nanogap of the Au-NNPs and gold shell thickness. , SERS spectra taken from the Au-NNP(ROXgap)n solutions (0.5 nM) with different numbers of ROX-oligonucleotides in the nanogap (n = 1, 8, 45 and 100). , SERS intensity plot at two fingerprint peaks (1,504 and 1,645 cm−1) as a function of the number of ROX-oligonucleotides per particle. , Measured SERS intensity as a function of gold shell thickness and calculated results (blue line). Error bars in and are standard deviations from three independent measurements. All spectra were taken with a 633 nm excitation laser, 10 s exposure for a single spectrum, 300 µW laser power with the same Au-NPP concentration (0.5 nM). * Figure 5: Solution-based Raman intensity plots for two different Au-NNP structures as a function of probe concentration. , Comparison of Raman intensity in solution of Cy3-modified AuNPs and Au-NNPs. , Raman signal change for Au-NNP(Cy3)100 probe concentrations of 1.9–250 pM at three different fingerprint peaks. , Comparison of Raman intensity in solutions of 4,4′dipyridy(44DP)-saturated AuNPs and Au-NNPs. , Raman signal change as a function of probe concentration for the Au-NNP(4,4′-dipyridyl)saturated probes in solution state. Error bars are standard deviations from three independently measured results. All spectra were taken with a 633 nm excitation laser, 10 s exposure, one-time accumulation except for 10 fM concentration in (10 times accumulation used for clear identification), and 10 mW laser power at the sample (Renishaw inVia Raman microscope, ×20 objective lens with NA = 0.40, Leica). * Figure 6: Large-scale AFM-correlated single-particle nano-Raman mapping analysis on the Au-NNPs and SERS enhancement factor distributions. , Instrument setup for AFM-correlated nano-Raman spectroscopy and precise tip-matching procedures for accurate single-particle addressing (see text and Supplementary Information for more details). –, Representative AFM images of Au-NNPs in different positions. –, Distribution diagrams of the measured electromagnetic enhancement factors at 1,190 cm−1 (), 1,460 cm−1 () and 1,580 cm−1 (). All measurements for EF calculations were performed with a 633 nm excitation laser, 10 s exposure, 650 µW laser power and ×100 objective lens. Author information * Abstract * Author information * Supplementary information Primary authors * These authors contributed equally to this work * Dong-Kwon Lim & * Ki-Seok Jeon Affiliations * Department of Chemistry, Seoul National University, Seoul, 151-747, South Korea * Dong-Kwon Lim, * Jae-Ho Hwang & * Jwa-Min Nam * Laboratory for Advanced Molecular Probing (LAMP), NanoBio Fusion Research Center, Korea Research Institute of Chemical Technology, DaeJeon, 305-600, South Korea * Ki-Seok Jeon & * Yung Doug Suh * School of Electrical Engineering and Computer Science * Hyoki Kim & * Sunghoon Kwon * Inter-University Semiconductor Research Center (ISRC), Seoul National University, Seoul 151-744, South Korea * Sunghoon Kwon Contributions J-M.N., D-K.L. and Y.D.S. conceived the initial idea. J-M.N. designed synthetic schemes for the Au-NNPs, and D-K.L. and J-M.N. synthesized and characterized Au-NNPs with partial contributions from J-H.H. K-S.J. and D-K.L. obtained Raman spectra and AFM images under the guidance of Y.D.S. and J-M.N. Y.D.S. designed single-particle nano-Raman mapping experiments, and K-S.J. and D-K.L. carried out the single-particle measurements. K-S.J. calculated the EFs. H.K. and S.K. carried out three-dimensional finite-element method calculations. J-M.N., D-K.L. and Y.D.S. wrote the article with partial contributions from K-S.J., J-H.H., H.K. and S.K. Competing financial interests The authors declare no competing financial interests. Corresponding authors Correspondence to: * Yung Doug Suh or * Jwa-Min Nam Author Details * Dong-Kwon Lim Search for this author in: * NPG journals * PubMed * Google Scholar * Ki-Seok Jeon Search for this author in: * NPG journals * PubMed * Google Scholar * Jae-Ho Hwang Search for this author in: * NPG journals * PubMed * Google Scholar * Hyoki Kim Search for this author in: * NPG journals * PubMed * Google Scholar * Sunghoon Kwon Search for this author in: * NPG journals * PubMed * Google Scholar * Yung Doug Suh Contact Yung Doug Suh Search for this author in: * NPG journals * PubMed * Google Scholar * Jwa-Min Nam Contact Jwa-Min Nam Search for this author in: * NPG journals * PubMed * Google Scholar Supplementary information * Abstract * Author information * Supplementary information PDF files * Supplementary information (1,761 KB) Supplementary information Additional data
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