| 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. |
- Aissaoui, Nesrine, 1983, et al.
(författare)
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FRET enhancement close to gold nanoparticles positioned in DNA origami constructs
- 2017
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Ingår i: Nanoscale. - Cambridge, United Kingdom : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 9:2, s. 673-683
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Tidskriftsartikel (refereegranskat)abstract
- Here we investigate the energy transfer rates of a Förster resonance energy transfer (FRET) pair positioned in close proximity to a 5 nm gold nanoparticle (AuNP) on a DNA origami construct. We study the distance dependence of the FRET rate by varying the location of the donor molecule, D, relative to the AuNP while maintaining a fixed location of the acceptor molecule, A. The presence of the AuNP induces an alteration in the spontaneous emission of the donor (including radiative and non-radiative rates) which is strongly dependent on the distance between the donor and AuNP surface. Simultaneously, the energy transfer rates are enhanced at shorter D-A (and D-AuNP) distances. Overall, in addition to the direct influence of the acceptor and AuNP on the donor decay there is also a significant increase in decay rate not explained by the sum of the two interactions. This leads to enhanced energy transfer between donor and acceptor in the presence of a 5 nm AuNP. We also demonstrate that the transfer rate in the three "particle" geometry (D + A + AuNP) depends approximately linearly on the transfer rate in the donor-AuNP system, suggesting the possibility to control FRET process with electric field induced by 5 nm AuNPs close to the donor fluorophore. It is concluded that DNA origami is a very versatile platform for studying interactions between molecules and plasmonic nanoparticles in general and FRET enhancement in particular.
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| 3. |
- Bodvard, Kristofer, 1981, et al.
(författare)
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Light-sensing via hydrogen peroxide and a peroxiredoxin
- 2017
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Yeast lacks dedicated photoreceptors; however, blue light still causes pronounced oscillations of the transcription factor Msn2 into and out of the nucleus. Here we show that this poorly understood phenomenon is initiated by a peroxisomal oxidase, which converts light into a hydrogen peroxide (H2O2) signal that is sensed by the peroxiredoxin Tsa1 and transduced to thioredoxin, to counteract PKA-dependent Msn2 phosphorylation. Upon H2O2, the nuclear retention of PKA catalytic subunits, which contributes to delayed Msn2 nuclear concentration, is antagonized in a Tsa1-dependent manner. Conversely, peroxiredoxin hyperoxidation interrupts the H2O2 signal and drives Msn2 oscillations by superimposing on PKA feedback regulation. Our data identify a mechanism by which light could be sensed in all cells lacking dedicated photoreceptors. In particular, the use of H2O2 as a second messenger in signalling is common to Msn2 oscillations and to light-induced entrainment of circadian rhythms and suggests conserved roles for peroxiredoxins in endogenous rhythms.
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| 4. |
- Fang, Yurui, 1983, et al.
(författare)
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Plasmon Enhanced Internal Photoemission in Antenna-Spacer-Mirror Based Au/TiO2 Nanostructures
- 2015
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 15:6, s. 4059-4065
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Tidskriftsartikel (refereegranskat)abstract
- Emission of photoexcited hot electrons from plasmonic metal nanostructures to semiconductors is key to a number of proposed nanophotonics technologies for Solar harvesting, water splitting, photocatalysis, and a variety of optical sensing and photodetector applications. Favorable materials and catalytic properties make systems based on gold and TiO2 particularly interesting, but the internal photo emission efficiency for visible light is low because of the wide bandgap of the semiconductor. We investigated the incident photon-to-electron conversion efficiency of thin TiO2 films decorated with Au nanodisk antennas in an electrochemical circuit and found that incorporation of a Au mirror beneath the semiconductor amplified the photoresponse for light with wavelength lambda = 500-950 nm by a factor 2-10 compared to identical structures lacking the mirror component. Classical electrodynamics simulations showed that the enhancement effect is caused by a favorable interplay between localized surface plasmon excitations and cavity modes that together amplify the light absorption in the Au/TiO2 interface. The experimentally determined internal quantum efficiency for hot electron transfer decreases monotonically with wavelength, similar to the probability for interband excitations with energy higher than the Schottky barrier obtained from a density functional theory band structure simulation of a thin Au/TiO2 slab.
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| 5. |
- 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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| 6. |
- Jiao, Yang, 1985, et al.
(författare)
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Schottky barrier formation and band bending revealed by first- principles calculations
- 2015
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 5, s. Art. no. 11374-
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Tidskriftsartikel (refereegranskat)abstract
- The formation of a Schottky barrier at the metal-semiconductor interface is widely utilised in semiconductor devices. With the emerging of novel Schottky barrier based nanoelectronics, a further microscopic understanding of this interface is in high demand. Here we provide an atomistic insight into potential barrier formation and band bending by ab initio simulations and model analysis of a prototype Schottky diode, i.e., niobium doped rutile titania in contact with gold (Au/Nb:TiO2). The local Schottky barrier height is found to vary between 0 and 1.26 eV depending on the position of the dopant. The band bending is caused by a dopant induced dipole field between the interface and the dopant site, whereas the pristine Au/TiO2 interface does not show any band bending. These findings open the possibility for atomic scale optimisation of the Schottky barrier and light harvesting in metal-semiconductor nanostructures.
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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. |
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| 9. |
- 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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| 10. |
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