| 1. |
- Dahlin, Andreas, 1980, et al.
(författare)
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Electrochemical plasmonic sensors
- 2012
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 402:5, s. 1773-1784
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Forskningsöversikt (refereegranskat)abstract
- The enormous progress of nanotechnology during the last decade has made it possible to fabricate a great variety of nanostructures. On the nanoscale, metals exhibit special electrical and optical properties, which can be utilized for novel applications. In particular, plasmonic sensors including both the established technique of surface plasmon resonance and more recent nanoplasmonic sensors, have recently attracted much attention. However, some of the simplest and most successful sensors, such as the glucose biosensor, are based on electrical readout. In this review we describe the implementation of electrochemistry with plasmonic nanostructures for combined electrical and optical signal transduction. We highlight results from different types of metallic nanostructures such as nanoparticles, nanowires, nanoholes or simply films of nanoscale thickness. We briefly give an overview of their optical properties and discuss implementation of electrochemical methods. In particular, we review studies on how electrochemical potentials influence the plasmon resonances in different nanostructures, as this type of fundamental understanding is necessary for successful combination of the methods. Although several combined platforms exist, many are not yet in use as sensors partly because of the complicated effects from electrochemical potentials on plasmon resonances. Yet, there are clearly promising aspects of these sensor combinations and we conclude this review by discussing the advantages of synchronized electrical and optical readout, illustrating the versatility of these technologies.
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| 2. |
- Dahlin, Andreas, 1980, et al.
(författare)
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Plasmonic Nanopores in Metal-Insulator-Metal Films
- 2014
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Ingår i: Advanced Optical Materials. - : Wiley. - 2195-1071. ; 2:6, s. 556-564
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Tidskriftsartikel (refereegranskat)abstract
- A novel type of plasmonic nanopore array in a metal-insulator-metal thin film is presented. The optical properties of this structure are described using a generic theoretical framework for surface waves in a coupled multilayer system. The characteristic spacing (short-range order) of the pores enables grating-type coupling to hybridized surface plasmons, with stronger coupling to some modes than others. The nature of the optical resonances and their excitation mechanisms can be conceptually understood from a charge distribution argument. The experimental results are further verified by numerical simulations, which also enable visualization of the near field. This study illustrates the surface plasmon characteristics (sensitive to periodicity) of the extinction maximum in the asymmetric spectral resonance induced by aperture arrays, while the transmission maximum corresponds to a resonance of localized character (sensitive to pore shape). Finally, the use of these nanopores for sensing applications through changes in the refractive index is evaluated.
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| 3. |
- Ikenoya, Y., et al.
(författare)
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Optical Resonances in Short-Range Ordered Nanoholes in Ultrathin Aluminum/Aluminum Nitride Multilayers
- 2013
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:12, s. 6373-6382
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Tidskriftsartikel (refereegranskat)abstract
- Nanoholes with short-range ordering were fabricated in ultrathin aluminum/aluminum nitride multilayer films where each layer is as thin as a few nanometers. Optical resonances of the trilayer system with a single metallic layer and five-layer system with two metallic layers were successfully tuned in the visible-near-infrared (vis/NIR) range. The resonance wavelength as well as the width can be predicted and designed by solving the dispersion relation and comparing with the lateral dimension of the short-range ordering. To solve the dispersion relation, we developed a general formulation for multilayer systems. The thermal stability of the fabricated nanoholes in ultrathin multilayers was also tested by vacuum annealing the samples up to 400 degrees C. While no structural change of the nanohole or the multilayer surface has been observed, the optical property showed almost no change in the resonance confirming no structural change but emergence of the interband transition!
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| 4. |
- Junesch, Juliane, 1987, et al.
(författare)
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Location-specific nanoplasmonic sensing of biomolecular binding to lipid membranes with negative curvature
- 2015
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 7:37, s. 15080-15085
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Tidskriftsartikel (refereegranskat)abstract
- The biochemical processes of cell membranes are sensitive to the geometry of the lipid bilayer. We show how plasmonic "nanowells" provide label-free real-time analysis of molecules on membranes with detection of preferential binding at negative curvature. It is demonstrated that norovirus accumulate in invaginations due to multivalent interactions with glycosphingolipids.
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| 5. |
- Junesch, Juliane, 1987, et al.
(författare)
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Optical Properties of Nanohole Arrays in Metal-Dielectric Double Films Prepared by Mask-on-Metal Colloidal Lithography
- 2012
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 6:11, s. 10405-10415
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Tidskriftsartikel (refereegranskat)abstract
- We present the fabrication and optical characterization of plasmonic nanostructures consisting of nanohole arrays in two thin films, a metal and a dielectric. A novel method called mask-on-metal colloidal lithography is used to prepare high aspect ratio holes, providing efficient mass fabrication of stable structures with close to vertical walls and without the need for an adhesion layer under the metal. Our approach for understanding the transmission properties is based on solving the dispersions of. the guided modes supported by the two films and calculating the Influence from interference. The methodology is generic and can be extended to multilayered films. In particular, the influence from coupling to waveguide modes is discussed. We show that by rational design of structural dimensions It Is possible to study only bonding surface plasmons and the associated hole transmission maximum. Further, numerical simulations with the multiple multipole program provide good agreement with experimental data and enable visualization of the asymmetric near field distribution in the nanohole arrays, which is focused to the interior of the "nanowells". The refractometric sensitivity Is evaluated-experimentally both by liquid bulk changes and surface adsorption. We demonstrate how the localized mode provides reasonably good sensitivity in terms of resonance shift to molecular binding inside-the voids. Importantly, high resolution sensing can be accomplished also for the surface plasmon mode, despite its extremely low figure of merit. This is accomplished by monitoring the coupling efficiency of light to plasmons instead of conventional sensing which is based on changes in plasmon energy We suggest that these nanohole structures can be used for studying molecular transport through nanopores and the behavior of molecules confined in volumes of approximately one attoliter.
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| 6. |
- MacKenzie, R., et al.
(författare)
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Simultaneous electrical and plasmonic monitoring of potential induced ion adsorption on metal nanowire arrays
- 2013
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 5:11, s. 4966-4975
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Tidskriftsartikel (refereegranskat)abstract
- Simultaneous LSPR and electronic sensing of potential induced ion adsorption onto gold nanowire arrays is presented. The formation of a Stern layer upon applying an electrochemical potential generated a complex optical response. Simulation of a lossy atomic layer on the nanowire array using the Multiple Multipole Program (MMP) corresponded very well to the experimentally observed peak position, intensity, and radius of curvature changes. Additionally, a significant voltage-dependent change in the resistance of the gold nanowire array was observed during the controlled formation of the electrical double layer. The results demonstrated that an applied electrochemical potential induces measurable changes in the optical and electrical properties of the gold nanowire surface. This is the first demonstration of combined plasmonic and nanowire resistance-based sensing of a surface process in the literature.
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| 7. |
- Malekian, Bita, 1986, et al.
(författare)
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Optical properties of plasmonic nanopore arrays prepared by electron beam and colloidal lithography
- 2019
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Ingår i: Nanoscale Advances. - : Royal Society of Chemistry (RSC). - 2516-0230. ; 1:11, s. 4282-4289
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Tidskriftsartikel (refereegranskat)abstract
- Solid state nanopores are central structures for many applications. To date, much effort has been spent on controlled fabrication of single nanopores, while relatively little work has focused on large scale fabrication of arrays of nanopores. In this work we show wafer-scale fabrication of plasmonic nanopores in 50 nm thick silicon nitride membranes with one or two 30 nm gold films, using electron beam lithography with a negative resist or a new version of colloidal lithography. Both approaches offer good control of pore diameter (even below 100 nm) and with high yield (>90%) of intact membranes. Colloidal lithography has the advantage of parallel patterning without expensive equipment. Despite its serial nature, electron beam lithography provides high throughput and can make arbitrary array patterns. Importantly, both methods prevent metal from ending up on the membrane pore sidewalls. The new fabrication methods make it possible to compare the optical properties of structurally identical plasmonic nanopore arrays with either long-range order (e-beam) or short-range order (colloidal). The resonance features in the extinction spectrum are very similar for both structures when the pitch is the same as the characteristic spacing in the self-assembled colloidal pattern. Long-range ordering slightly enhances the magnitude of the extinction maximum and blueshift the transmission maximum by tens of nm. Upon reducing the diameter in long-range ordered arrays, the resonance is reduced in magnitude and the transmission maximum is further blue shifted, just like for short-range ordered arrays. These effects are well explained by interpreting the spectra as Fano interference between the grating-type excitation of propagating surface plasmons and the broad transmission via individual pores in the metal film. Furthermore, we find that only the short-range ordered arrays scatter light, which we attribute to the highly limited effective period in the short-range ordered system and the corresponding lack of coherent suppression of scattering by interference effects.
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| 8. |
- Sannomiya, T., et al.
(författare)
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Coupling of plasmonic nanopore pairs: facing dipoles attract each other
- 2016
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Ingår i: Light: Science and Applications. - : Springer Science and Business Media LLC. - 2047-7538 .- 2095-5545. ; 5:9
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Tidskriftsartikel (refereegranskat)abstract
- Control of the optical properties of nano-plasmonic structures is essential for next-generation optical circuits and high-throughput biosensing platforms. Realization of such nano-optical devices requires optical couplings of various nanostructured elements and field confinement at the nanoscale. In particular, symmetric coupling modes, also referred to as dark modes, have recently received considerable attention because these modes can confine light energy to small spaces. Although the coupling behavior of plasmonic nanoparticles has been relatively well studied, couplings of inverse structures, that is, holes and pores, remain partially unexplored. Even for the most fundamental coupling system of two dipolar holes, comparison of the symmetric and anti-symmetric coupling modes has not been performed. Here we present, for the first time, a systematic study of the symmetric and anti-symmetric coupling of nanopore pairs using cathodoluminescence by scanning transmission electron microscopy and electromagnetic simulation. The symmetric coupling mode, approximated as a pair of facing dipoles, is observed at a lower energy than that of the anti-symmetric coupling mode, indicating that the facing dipoles attract each other. The anti-symmetric coupling mode splits into the inner-and outer-edge localized modes as the coupling distance decreases. These coupling behaviors cannot be fully explained as inverses of coupled disks. Symmetric and anti-symmetric coupling modes are also observed in a short-range ordered pore array, where one pore supports multiple local resonance modes, depending on the distance to the neighboring pore. Accessibility to the observed symmetric modes by far field is also discussed, which is important for nanophotonic device applications.
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