| 1. |
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| 2. |
- Andersson, M, et al.
(författare)
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Macroscopic alignment of silver nanoparticles in reverse hexagonal liquid crystalline templates
- 2002
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 2:12, s. 1403-1407
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Tidskriftsartikel (refereegranskat)abstract
- A flexible method of preparing and macroscopically aligning nanoparticles of crystalline silver into millimeter long fibers is presented. The approach utilizes the dual functionality of a reverse hexagonal liquid crystalline template containing a built-in reducing agent facing the aqueous domain. The method is advantageous in that its slow kinetics allows for a thorough introduction of a silver salt into the liquid crystal before the reduction takes place, allowing for an efficient loading of he template and a retained mesoscopic ordering as evidenced by SAXS. It was confirmed by H-1 NMR that the oxyethylene groups of the amphiphilic polymer reduce the silver ions while being oxidized to aldehydes. The silver nanoparticles are uniform in size and in the same size range as the diameter of the aqueous domain of the liquid crystal (3 nm), further supporting that the silver particles form inside the liquid crystal. TEM images confirm the macroscopic alignment of silver nanoparticles into fibrils and the packing of fibrils into millimeter long fibers. The diameter of the fibrils and fibers ranges from 30 nm to several hundreds of micrometers. Electron diffraction analysis of a collection of silver nanoparticles confirms their crystallinity as three diffraction rings could be indexed to the face centered cubic structure of silver. A key to the successful macroscopic alignment of the nanoparticles is that the particles are formed inside the liquid crystal, thus minimizing the need for their diffusion i to and inside the liquid crystal.
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| 3. |
- Björk, Mikael, et al.
(författare)
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Few-electron quantum dots in nanowires
- 2004
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 4:9, s. 1621-1625
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate transport spectroscopy on bottom-up grown few-electron quantum dots in semiconductor nanowires. The dots are defined by InP double barrier heterostructures in InAs nanowires catalytically grown from nanoparticles. By changing the dot size, we can design devices ranging from single-electron transistors to few-electron quantum dots. In the latter case, electrons can be added one by one to the dots from 0 to similar to50 electrons while maintaining an almost constant charging energy, with addition spectra of the devices displaying shell structures as a result of spin and orbital degeneracies. The reduced dimensionality of the nanowire emitter gives rise to pronounced resonant tunneling peaks, where a gate can be used to control the peak positions.
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| 4. |
- Björk, Mikael, et al.
(författare)
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One-dimensional steeplechase for electrons realized
- 2002
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 2:2, s. 87-89
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Tidskriftsartikel (refereegranskat)abstract
- We report growth of one-dimensional semiconductor nanocrystals, nanowhiskers, in which segments of the whisker with different composition are formed, illustrated by InAs whiskers containing segments of InP. Our conditions for growth allow the formation of abrupt interfaces and heterostructure barriers of thickness from a few monolayers to 100s of nanometers, thus creating a one-dimensional landscape along which the electrons move. The crystalline perfection, the quality of the interfaces, and the variation in the lattice constant are demonstrated by high-resolution transmission electron microscopy, and the conduction band off-set of 0.6 eV is deduced from the current due to thermal excitation of electrons over an InP barrier.
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| 5. |
- Jensen, Linus, et al.
(författare)
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Role of surface diffusion in chemical beam epitaxy of InAs nanowires
- 2004
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 4:10, s. 1961-1964
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Tidskriftsartikel (refereegranskat)abstract
- We present growth studies of InAs nanowires nucleated from lithographically positioned Au seeds on InAs (111)B substrates. The nanowires are grown in a chemical beam epitaxy system and exhibit high aspect ratios and high homogeneity in length and width. Investigations of wire growth rate as a function of diameter, density, and time were performed and the results indicate that 80% of the growth is due to In species diffusing from the (111)B substrate surface. Furthermore, we have established that the diffusion length on the {110} wire side surfaces exceeds 10 mum. We also observe a decreasing length growth rate with increasing wire diameter.
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| 6. |
- Kemerink, Martijn, et al.
(författare)
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Relating substitution to single-chain conformation and aggregation in poly(p-phenylene vinylene) films
- 2003
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Ingår i: Nano letters (Print). - : American Chemical Society. - 1530-6984 .- 1530-6992. ; 3:9, s. 1191-1196
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Tidskriftsartikel (refereegranskat)abstract
- The morphology of films of PPV derivatives is studied with molecular (single chain) resolution by phase-imaging scanning force microscopy. It is found that the symmetry of substitution is directly related to surface morphology and aggregation behavior. The molecular resolution in the phase contrast is shown to result from van der Waals interaction between the conjugated backbone of the polymer chains and the metallic tip, and can quantitatively be described by a simple harmonic oscillator model.
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| 7. |
- Lee, SangWook, et al.
(författare)
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A three-terminal carbon nanorelay
- 2004
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Ingår i: Nano letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 4:10, s. 2027-2030
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Tidskriftsartikel (refereegranskat)abstract
- Three-terminal nanorelay structures were fabricated with multiwall carbon nanotubes (MWNTs). The nanotube relays were deflected by applying a gate voltage until contact (mechanical and/or electrical) was made with a drain electrode, thus closing the circuit. It was possible to achieve multiple switching cycles, showing that carbon nanotubes are suitable and practical systems for developing nanoelectromechanical devices of this kind.
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| 8. |
- Lorén, Anders, 1974, et al.
(författare)
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Self-assembled monolayer coating for normalization of surface enhanced Raman spectra
- 2004
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 4:2, s. 309-312
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that the use of a self-assembled monolayer, consisting of a thiol derivative of Dabcyl, can be used to normalize surface enhanced Raman signals (SERS) with respect to varying enhancement. Chaotic assemblies of gold nanoparticles exhibit large spatial variation in enhancement. Our work shows that in such a system the signals from the reporting molecules in the SAM co-vary with the signal from the analyte solution. With this knowledge, a normalization procedure was used to increase the precision of the analyte signal by 1 order of magnitude, to 8-13%, fully acceptable for quantitative work.
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| 9. |
- Mårtensson, Thomas, et al.
(författare)
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Epitaxial III-V nanowires on silicon
- 2004
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 4:10, s. 1987-1990
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Tidskriftsartikel (refereegranskat)abstract
- We present results of ideal epitaxial nucleation and growth of III-V semiconductor nanowires on silicon substrates. This addresses the long-time challenge of integrating high performance III-V semiconductors with mainstream Si technology. Efficient room-temperature generation of light on silicon is demonstrated by the incorporation of double heterostructure segments in such nanowires. We expect that advanced heterostructure devices, such as resonant tunneling diodes, superiattice device structures, and heterostructure photonic devices for on-chip communication, could now become available as complementary device technologies for integration with silicon.
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| 10. |
- Mårtensson, Thomas, et al.
(författare)
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Nanowire arrays defined by nanoimprint lithography
- 2004
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 4:4, s. 699-702
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate the use of nanoimprint lithography to define arrays of vertical InP nanowires. Each nanowire is individually seeded from a catalyzing gold particle and then grown via vapor-liquid-solid growth in a metal-organic vapor phase epitaxy system. The diameter and position of each nanowire can be controlled to create engineered arrays, demonstrated with a hexagonal photonic crystal pattern. This combination of nanoimprint and self-assembly of nanostructures is attractive for photonics and electronics, as well as in life sciences.
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| 11. |
- Persson, Martin, et al.
(författare)
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Electronic structure of [100]-oriented free-standing semiconductor nanowires
- 2004
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 4:12, s. 2409-2414
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Tidskriftsartikel (refereegranskat)abstract
- We report on a theoretical study of the electronic structure of [100]-oriented free-standing III-V semiconductor nanowires with quadratic (square wire) and rectangular (nanobelt) cross-sections based on an atomistic tight-binding approach. It is shown that at the same cross-section aspect ratio, the characteristics of the band structure and state wave functions of the nanowires in the vicinity of the band edges are insensitive to variation of the lateral size, although the band energies show a strong dependence on the lateral size. It is also shown that the effective mass of the conduction bands of the nanowires is systematically enhanced with decrease of the nanowire size, and k(.)p analysis generally overestimates the effective mass enhancement.
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| 12. |
- Prikulis, Juris, 1973, et al.
(författare)
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Optical spectroscopy of single trapped metal nanoparticles in solution
- 2004
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 4:1, s. 115-118
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Tidskriftsartikel (refereegranskat)abstract
- We present a simple method for the optical manipulation and spectroscopy of colloidal silver nanoparticles in aqueous solution using optical tweezers combined with dark-field microscopy. Because of their localized plasmon resonances, single trapped metal nanoparticles can be used as efficient near-field optical probes, with potential applicability in surface-enhanced spectroscopy, near-field microscopy, and biochemical sensing schemes. As a proof of principle, we study the near-field optical interaction between a trapped and an immobilized Ag nanoparticle.
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| 13. |
- Unge, Mikael, et al.
(författare)
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Electron Localization in DNA
- 2003
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 3:10, s. 1417-1420
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Tidskriftsartikel (refereegranskat)abstract
- Electron localization lengths in different DNA sequences have been calculated numerically using the transfer matrix method. It is shown that electronic states associated with guanine can reach fairly long localization lengths in disordered guanine-cytosine double strands if both intra- and interstrand π−π interactions are considered. For DNA sequences containing all four bases, the electronic states become localized to very few base pairs. In particular, the human chromosome 22 and λ-DNA, both with approximately equal concentrations of the four bases, show insulating behavior.
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| 14. |
- Zhang, Fengling, et al.
(författare)
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Conducting Polymer Nanowires and Nanodots Made with Soft Lithography
- 2002
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 2:12, s. 1373-1377
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Tidskriftsartikel (refereegranskat)abstract
- The conducting polymer poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT-PSS) was patterned by micromolding in capillaries (MIMIC), in the form of nanowires on a glass or a Si wafer. The periods of the molded nanowires were 833 or 278 nm. By applying force on top of the stamp during MIMIC, the height of these nanowires could be changed. An alternative method of preparing structured surfaces is the liquid embossing technique, used to pattern polymers deposited from dispersion. Nanowires (278 nm) and 2-D nanodots on semiconducting polymer (poly(3-(2'-methoxy-5'-octyphenyl) thiophene)) POMeOPT were also achieved by another soft lithography technique-soft-embossing. The possibility to pattern both semiconducting and metallic conjugated polymers from aqueous solutions or organic solvents on a submicron level makes it possible to use these materials in flexible optoelectronic devices where light propagation and electronic paths are defined by patterning.
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| 15. |
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