| 1. |
- Hakonen, Aron, 1970, et al.
(författare)
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Detection of nerve gases using surface-enhanced Raman scattering substrates with high droplet adhesion
- 2016
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 8:3, s. 1305-1308
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Tidskriftsartikel (refereegranskat)abstract
- Threats from chemical warfare agents, commonly known as nerve gases, constitute a serious security issue of increasing global concern because of surging terrorist activity worldwide. However, nerve gases are difficult to detect using current analytical tools and outside dedicated laboratories. Here we demonstrate that surface-enhanced Raman scattering (SERS) can be used for sensitive detection of femtomol quantities of two nerve gases, VX and Tabun, using a handheld Raman device and SERS substrates consisting of flexible gold-covered Si nanopillars. The substrate surface exhibits high droplet adhesion and nanopillar clustering due to elasto-capillary forces, resulting in enrichment of target molecules in plasmonic hot-spots with high Raman enhancement. The results may pave the way for strategic life-saving SERS detection of chemical warfare agents in the field.
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| 2. |
- Verre, Ruggero, 1985, et al.
(författare)
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Quasi-isotropic Surface Plasmon Polariton Generation through Near-Field Coupling to a Penrose Pattern of Silver Nanoparticles
- 2014
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 8:9, s. 9286-9294
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Tidskriftsartikel (refereegranskat)abstract
- Quasicrystals are structures that possess long-range order without being periodic. We investigate the unique characteristics of a photonic quasicrystal that consists of plasmonic Ag nanodisks arranged in a Penrose pattern. The quasicrystal scatters light in a complex but spectacular diffraction pattern that can be directly imaged in the back focal plane of an optical microscope, allowing us to assess the excitation efficiency of the various diffraction modes. Furthermore, surface plasmon polaritons can be launched almost isotropically through near-field grating coupling when the quasicrystal is positioned close to a homogeneous silver surface. We characterize the dispersion relation of the different excited plasmon modes by reflection measurements and simulations. It is demonstrated that the quasicrystal in-coupling efficiency is strongly enhanced compared to a nanopartide array with the same particle density but only short-range lateral order. We envision that the system can be useful for a number of advanced light harvesting and optoelectronic applications.
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| 3. |
- Chen, Si, 1985, et al.
(författare)
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Plasmon-Enhanced Colorimetric ELISA with Single Molecule Sensitivity
- 2011
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 11:4, s. 1826-1830
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Tidskriftsartikel (refereegranskat)abstract
- Robust but ultrasensitive biosensors with a capability of detecting low abundance biomarkers could revolutionize clinical diagnostics and enable early detection of cancer, neurological diseases, and infections. We utilized a combination of localized surface plasmon resonance (LSPR) refractive index sensing and the well-known enzyme-linked immunosorbent assay to develop a simple colorimetric biosensing methodology with single molecule sensitivity. The technique is based on spectral imaging of a large number of isolated gold nanoparticles. Each particle binds a variable number of horseradish peroxidase (HRP) enzyme molecules that catalyze a localized precipitation reaction at the particle surface. The enzymatic reaction dramatically amplifies the shift of the LSPR scattering maximum, lambda(max), and makes it possible to detect the presence of only one or a few HRP molecules per particle.
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| 4. |
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| 5. |
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| 6. |
- Hakonen, Aron, 1970, et al.
(författare)
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Dimer-on-mirror SERS substrates with attogram sensitivity fabricated by colloidal lithography.
- 2015
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 7:21
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Tidskriftsartikel (refereegranskat)abstract
- Nanoplasmonic substrates with optimized field-enhancement properties are a key component in the continued development of surface-enhanced Raman scattering (SERS) molecular analysis but are challenging to produce inexpensively in large scale. We used a facile and cost-effective bottom-up technique, colloidal hole-mask lithography, to produce macroscopic dimer-on-mirror gold nanostructures. The optimized structures exhibit excellent SERS performance, as exemplified by detection of 2.5 and 50 attograms of BPE, a common SERS probe, using Raman microscopy and a simple handheld device, respectively. The corresponding Raman enhancement factor is of the order 10(11), which compares favourably to previously reported record performance values.
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| 7. |
- Ogier, Robin, 1987, et al.
(författare)
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Continuous-Gradient Plasmonic Nanostructures Fabricated by Evaporation on a Partially Exposed Rotating Substrate
- 2016
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 28:23, s. 4658-4664
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Tidskriftsartikel (refereegranskat)abstract
- Evaporation on a partially exposed rotating substrate (PERS) was used to generate continuous and precise gradients in nanoscale structure parameters. All materials (gold, chromium, alumina, and silver) were deposited in an electron beam evaporation system with stage rotation and tilt possibilities. All evaporations were performed at a high vacuum. To fabricate nanostructures on a glass substrates by HCL, the substrate was first spin-coated with a layer of 950 PMMA and wetted with a poly(diallyldimethylammonium chloride) (PDDA) solution. Negatively charged PS beads were then drop casted and self-assembled on the surface. A thin layer of metal (gold or chromium) was evaporated to act as a mask. The beads were removed by tape stripping, resulting in a mask with holes arranged in a pattern determined by the colloidal particles. The PMMA situated underneath the holes in the film was removed by oxygen plasma etching. Due to the continuous characteristic of the gradients, high precision in the geometric parameters of fabricated nanostructures can be achieved.
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| 8. |
- Ogier, Robin, 1987, et al.
(författare)
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Macroscopic Layers of Chiral Plasmonic Nanoparticle Oligomers from Colloidal Lithography
- 2014
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Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 1:10, s. 1074-1081
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Tidskriftsartikel (refereegranskat)abstract
- Optical near-field coupling between closely spaced plasmonic metal nanoparticles is important to a range of nanophotonic applications of high contemporary interest, including surface-enhanced molecular spectroscopy, nanooptical sensing, and various novel light-harvesting concepts. Here we report on monolayers of chiral heterotrimers and heterotetramers composed of closely spaced silver and/or gold nanodisks of different heights fabricated through facile hole-mask colloidal lithography. These quasi-three-dimensional oligomers are interesting for applications because they exhibit "hot" gaps and crevices of nanometric dimensions, a pronounced circular dichroism, and optical chirality in the visible to near-infrared wavelength range, and they can be produced in large ensembles (>109) of identical orientation. We analyze the optical properties of the samples based on simulation results and find that the circular dichroism is due to strong near-field coupling and intricate phase retardation effects originating in the three-dimensional character of the individual oligomers.
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| 9. |
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| 10. |
- Ogier, Robin, 1987, et al.
(författare)
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Near-Complete Photon Spin Selectivity in a Metasurface of Anisotropic Plasmonic Antennas
- 2015
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Ingår i: Physical Review X. - : American Physical Society. - 2160-3308. ; 5:4
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Tidskriftsartikel (refereegranskat)abstract
- Simple chiroptically active metamaterials are difficult to realize in practice but could pave the way for a range of important applications, such as sensitive optical biosensors, asymmetric catalysis, and novel polarization manipulation devices. We show that a metasurface based on a random arrangement of anisotropic but aligned gold nanoparticles can exhibit an almost perfect selectivity towards incident photon spin for evanescent excitation with visible to near-infrared light. The experimentally attained reflection contrast between left- and right-handed circularly polarized light peaks at similar to 90%, in excellent agreement with analytical theory. These results are important for the development of future photonic and plasmonic polarization-based technologies.
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