| 1. |
- Aili, Daniel, et al.
(författare)
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Polypeptide Folding-Mediated Tuning of the Optical and Structural Properties of Gold Nanoparticle Assemblies
- 2011
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 11:12, s. 5564-5573
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Tidskriftsartikel (refereegranskat)abstract
- Responsive hybrid nanomaterials with well-defined properties are of significant interest for the development of biosensors with additional applications in tissue engineering and drug delivery. Here, we present a detailed characterization using UV-vis spectroscopy and small angle X-ray scattering of a hybrid material comprised of polypeptide-decorated gold nanoparticles with highly controllable assembly properties. The assembly is triggered by a folding-dependent bridging of the particles mediated by the heteroassociation of immobilized helix-loop-helix polypeptides and a complementary nonlinear polypeptide present in solution. The polypeptides are de novo designed to associate and fold into a heterotrimeric complex comprised of two disulfide-linked four-helix bundles. The particles form structured assemblies with a highly defined interparticle gap (4.8 +/- 0.4 nm) that correlates to the size of the folded polypeptides. Transitions in particle aggregation dynamics, mass-fractal dimensions and ordering, as a function of particle size and the concentration of the bridging polypeptide, are observed; these have significant effects on the optical properties of the assemblies. The assembly and ordering of the particles are highly complex processes that are affected by a large number of variables including the number of polypeptides bridging the particles and the particle mobility within the aggregates. A fundamental understanding of these processes is of paramount interest for the development of novel hybrid nanomaterials with tunable structural and optical properties and for the optimization of nanoparticle-based colorimetric biodetection strategies.
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| 2. |
- Alaverdyan, Yury, 1976, et al.
(författare)
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Optical antennas based on coupled nanoholes in thin metal films
- 2007
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Ingår i: Nature Physics. - : Springer Science and Business Media LLC. - 1745-2481 .- 1745-2473. ; 3:12, s. 884-889
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Tidskriftsartikel (refereegranskat)abstract
- The ability to control optical effects at the nanoscale is a challenge that could be of great importance for a range of photonic applications. However, progress requires a deep understanding of the relationship between near-field and far-field properties of the individual elements of the nanostructure, as well as of the role of nano-optical interactions. Here, we show that the strong interaction between nanoholes in optically thin metal films can be used to readily tune their spectral response and visibility. Control of this interaction in short chains of nanoholes enables either amplification or almost total suppression of the scattered light. The phenomena are interpreted in terms of hole coupling mediated via antisymmetric surface plasmon polaritons, which makes the nanohole chains effectively behave as linear wire antennas.
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| 3. |
- Brian, Björn, 1980, et al.
(författare)
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Sensitivity enhancement of nanoplasmonic sensors on low refractive index substrates
- 2009
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 17:3, s. 2015-2023
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Tidskriftsartikel (refereegranskat)abstract
- Metal films perforated by nanoholes constitute a powerful platform for surface plasmon resonance biosensing. We find that the refractive index sensitivity of nanohole arrays increases if their resonance is red-shifted by increasing the separation distance between holes. However, an additional sensitivity enhancement occurs if the nanohole sensors are manufactured on low index substrates, despite the fact such substrates significantly blue-shift the resonance. We find a ∼40% higher bulk refractive index sensitivity for a system of -100 nm holes in 20 nm gold films fabricated on Teflon substrates (n=1.32) compared to the case when conventional glass substrates (n=1.52) are used. A similar improvement is observed for the case when a thin layer of dielectric material is deposited on the samples. These results can be understood by considering the electric field distribution induced by the so-called antisymmetric surface plasmon polariton in the thin gold films.
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| 4. |
- Eskilson, Olof, 1992-, et al.
(författare)
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Self-Assembly of Mechanoplasmonic Bacterial Cellulose-Metal Nanoparticle Composites
- 2020
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Ingår i: Advanced Functional Materials. - : Wiley-VCH Verlagsgesellschaft. - 1616-301X .- 1616-3028. ; 30:40
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposites of metal nanoparticles (NPs) and bacterial nanocellulose (BC) enable fabrication of soft and biocompatible materials for optical, catalytic, electronic, and biomedical applications. Current BC-NP nanocomposites are typically prepared by in situ synthesis of the NPs or electrostatic adsorption of surface functionalized NPs, which limits possibilities to control and tune NP size, shape, concentration, and surface chemistry and influences the properties and performance of the materials. Here a self-assembly strategy is described for fabrication of complex and well-defined BC-NP composites using colloidal gold and silver NPs of different sizes, shapes, and concentrations. The self-assembly process results in nanocomposites with distinct biophysical and optical properties. In addition to antibacterial materials and materials with excellent senor performance, materials with unique mechanoplasmonic properties are developed. The homogenous incorporation of plasmonic gold NPs in the BC enables extensive modulation of the optical properties by mechanical stimuli. Compression gives rise to near-field coupling between adsorbed NPs, resulting in tunable spectral variations and enhanced broadband absorption that amplify both nonlinear optical and thermoplasmonic effects and enables novel biosensing strategies.
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| 5. |
- Gonzalez-Diaz, J. B., et al.
(författare)
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Plasmonic Au/Co/Au nanosandwiches with enhanced magneto-optical activity
- 2008
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Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 4:2, s. 202-205
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Tidskriftsartikel (refereegranskat)abstract
- A study was conducted to analyzed magneto-optical (MO) activity of thin films prepared by Au/Co/Au trilayers as surface plasmon polaritons. Trilyers exhibit a magnetic-field-induced nonreciprocal effect in the surface plasmon polariton propagation. The Au/Co/Au nanosandwiches, prepared by a self-assembly process, show localized surface plasmon resonances (LSPRs) that affect the optical properties of metallic nanostructures. The fabrication of the nanostructures was performed using colloidal lithography (CL). An atomic force microscopy was used to analyze the structure of thin films. The polar Kerr ellipticity and rotation spectra for an array of nanoparticles with identical dimensions were examined. Metal trilyer films were sputtered onto glass substrates. Results show that nanoparticles can be used for the development of high-sensitive magnetoplasmonic nanosensors with multiplexing capabilities.
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| 6. |
- Guell-Grau, Pau, et al.
(författare)
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Elastic Plasmonic-Enhanced Fabry-Perot Cavities with Ultrasensitive Stretching Tunability
- 2022
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Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 34:7
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Tidskriftsartikel (refereegranskat)abstract
- The emerging stretchable photonics field faces challenges, like the robust integration of optical elements into elastic matrices or the generation of large optomechanical effects. Here, the first stretchable plasmonic-enhanced and wrinkled Fabry-Perot (FP) cavities are demonstrated, which are composed of self-embedded arrays of Au nanostructures at controlled depths into elastomer films. The novel self-embedding process is triggered by the Au nanostructures catalytic activity, which locally increases the polymer curing rate, thereby inducing a mechanical stress that simultaneously pulls the Au nanostructures into the polymer and forms a wrinkled skin layer. This geometry yields unprecedented optomechanical effects produced by the coupling of the broad plasmonic modes of the Au nanostructures and the FP modes, which are modulated by the wrinkled optical cavity. As a result, film stretching induces drastic changes in both the spectral position and intensity of the plasmonic-enhanced FP resonances due to the simultaneous cavity thickness reduction and cavity wrinkle flattening, thus increasing the cavity finesse. These optomechanical effects are exploited to demonstrate new strain-sensing approaches, achieving a strain detection limit of 0.006%, i.e., 16-fold lower than current optical strain-detection schemes.
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| 7. |
- Martinsson, Erik, et al.
(författare)
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Optimizing the Refractive Index Sensitivity of Plasmonically Coupled Gold Nanoparticles
- 2014
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Ingår i: PLASMONICS. - : Springer Verlag (Germany). - 1557-1955 .- 1557-1963. ; 9:4, s. 773-780
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Tidskriftsartikel (refereegranskat)abstract
- The possibility to enhance the local refractive index sensitivity using plasmonic coupling between spherical gold nanoparticles (Au-NPs) has been investigated. A strong and distinct optical coupling between Au-NPs of various sizes was achieved by controlling the interparticle separation using a layer-by-layer assembly of polyelectrolytes. The frequency of the coupled plasmon peak could be tuned by varying either the particle size or the interparticle separation, shown both experimentally and by theoretical simulations. The bulk refractive index (RI) sensitivity for the plasmonic coupling modes was investigated and compared to the RI sensitivity of monolayers of well-separated Au-NPs, and the results clearly demonstrates that the RI sensitivity can be significantly enhanced in plasmonically coupled Au-NPs. The proposed approach is simple and scalable and improves the rather modest RI sensitivity of spherical gold nanoparticles with a factor of 3, providing a new route for fabrication of inexpensive sensors based on plasmonic nanostructures.
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| 8. |
- Martinsson, Erik, et al.
(författare)
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Substrate Effect on the Refractive Index Sensitivity of Silver Nanoparticles
- 2014
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 118:42, s. 24680-24687
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Tidskriftsartikel (refereegranskat)abstract
- The bulk refractive index (RI) sensitivity of dispersed and immobilized silver nanoparticles of three different shapes (spheres, cubes, and plates) is investigated. We demonstrate, both experimentally and theoretically, that the influence of immobilization on the RI sensitivity is highly dependent on the shape of the nanoparticles. A strong correlation is seen between the fraction of the particle surface area in direct contact with the substrate and the decrease in RI sensitivity when the particles are immobilized on a glass substrate. The largest decrease (−36%) is seen for the most sensitive nanoparticles (plates), drastically reducing their advantage over other nanoparticle shapes. The shape-dependent substrate effect is thus an important factor to consider when designing nanoplasmonic sensors based on colloidal noble-metal nanoparticles.
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| 9. |
- Miljkovic, Vladimir, 1982, et al.
(författare)
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Optical Forces in Plasmonic Nanoparticle Dimers
- 2010
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:16, s. 7472-7479
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Tidskriftsartikel (refereegranskat)abstract
- We present calculations of the optical forces between two metal nanospheres forming a hybridized plasmonic chiller. We consider homo- and heterodimers and investigate different plane wave illumination configurations. The forces between the particles are calculated using kill Mie theory combined with the Maxwell stress tensor (MST) formalism, as well as by approximate methods, such as the Lorentz force (LF) approach taken in the dipole limit and calculations based on an optical potential. We show that the simplified calculation schemes can lead to serious errors in the case of strongly interacting particles and low damping. In particular, we find that equilibrium configurations, corresponding to vanishing optical forces, only are possible for homodimers illuminated in the end-fire configuration and for heterodimers, although multipolar effects and clamping radically reduce the repulsive interactions in the latter case.
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| 10. |
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