| 1. |
- 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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| 5. |
- Acimovic, Srdjan, 1982, et al.
(författare)
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Antibody−antigen interaction dynamics revealed by analysis of single-molecule equilibrium fluctuations on individual plasmonic nanoparticle biosensors
- 2018
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 12:10, s. 9958-9965
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Tidskriftsartikel (refereegranskat)abstract
- Antibody−antigen interactions are complex events central to immune response, in vivo and in vitro diagnostics, and development of therapeutic substances. We developed an ultrastable single-molecule localized surface plasmon resonance (LSPR) sensing platform optimized for studying antibody−antigen interaction kinetics over very long time scales. The setup allowed us to perform equilibrium fluctuations analysis of the PEG/anti-PEG interaction. By time and frequency domain analysis, we demonstrate that reversible adsorption of monovalently bound anti-PEG antibodies is the dominant factor affecting the LSPR fluctuations. The results suggest that equilibrium fluctuation analysis can be an alternative to established methods for determination of interaction rates. In particular, the methodology is suited to analyze molecular systems whose properties change during the initial interaction phases, for example, due to mass transport limitations or, as demonstrated here, because the effective association rate constant varies with surface concentration of adsorbed molecules.
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| 6. |
- Andrén, Daniel, 1991, et al.
(författare)
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Probing Photothermal Effects on Optically Trapped Gold Nanorods by Simultaneous Plasmon Spectroscopy and Brownian Dynamics Analysis
- 2017
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 11:10, s. 10053-10061
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Tidskriftsartikel (refereegranskat)abstract
- Plasmonic gold nanorods are prime candidates for a variety of biomedical, spectroscopy, data storage, and sensing applications. It was recently shown that gold nanorods optically trapped by a focused circularly polarized laser beam can function as extremely efficient nanoscopic rotary motors. The system holds promise for-applications ranging from nanofluidic flow control and nanorobotics to biomolecular actuation and analysis. However, to fully exploit this potential, one needs to be able to control and understand heating effects associated with laser trapping. We investigated photothermal heating of individual rotating gold nanorods by simultaneously probing their localized surface plasmon resonance spectrum and rotational Brownian dynamics over extended periods of time. The data reveal an extremely slow nanoparticle reshaping process, involving migration of the order of a few hundred atoms per minute, for moderate laser powers and a trapping wavelength close to plasmon resonance. The plasmon spectroscopy and Brownian analysis allows for separate temperature estimates based on the refractive index and the viscosity of the water surrounding a trapped nanorod. We show that both measurements yield similar effective temperatures, which correspond to the actual temperature at a distance of the order 10-15 nm from the particle surface. Our results shed light on photothermal processes on the nanoscale and will be useful in evaluating the applicability and performance of nanorod motors and optically heated nanoparticles for a variety of applications.
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| 7. |
- Fang, Yurui, 1983, et al.
(författare)
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Hot Electron Generation and Cathodoluminescence Nanoscopy of Chiral Split Ring Resonators
- 2016
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 16:8, s. 5183-5190
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Tidskriftsartikel (refereegranskat)abstract
- Three-dimensional chiral plasmonic nanostructures have been shown to be able to dramatically boost photon-spin selective light-matter interactions, potentially leading to novel photonics, molecular spectroscopy, and light-harvesting applications based on circularly polarized light. Here, we show that chiral split-ring gold nanoresonators interfaced to a wide band gap semiconductor exhibit a contrast in hot-electron transfer rate between left-handed and right-handed visible light that essentially mimics the far-field circular dichroism of the structures. We trace down the origin of this effect to the differential excitation of the thinnest part of the split-ring structures using dichroic-sensitive cathodoluminescence imaging with nanometer spatial resolution. The results highlight the intricate interplay between the near-field and far field chiral response of a nanostructure and establishes a clear link to the emerging field of hot carrier plasmonics with numerous potential applications in photocatalysis and solar light harvesting.
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| 8. |
- Fang, Yurui, 1983, et al.
(författare)
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Photoemission Enhancement of Plasmonic Hot Electrons by Au Antenna-Sensitizer Complexes
- 2024
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Ingår i: ACS Nano. - 1936-086X .- 1936-0851. ; 18:4, s. 3397-3404
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Tidskriftsartikel (refereegranskat)abstract
- The photoemission of surface plasmon decay-produced hot electrons is usually of very low efficiencies, hindering the practical utilization of such nonequilibrium charge carriers in harvesting photons with less energy than the semiconductor band gap for more efficient solar energy collection and photodetection. However, it has been demonstrated that the photoemission efficiency of small metal clusters increases as the particle size decreases. Recent studies have also shown that the photoemission efficiency of surface plasmon-yielded hot carriers can be intrinsically improved through proper material construction. In this paper, we report that the photoemission efficiency of hot electrons on the Au nanodisk-cluster complex/TiO2 interface can be dramatically enhanced under optical nanoantenna-sensitizer design. Such an enhancement is dominantly attributed to three factors. First, the large plasmonic nanodisk antennas provide a significantly enhanced optical near field, which largely increases light absorption in the small Au clusters that are acting as hot electron injection sensitizers. Second, the sub-3 nm size of the Au clusters facilitates the collection of delocalized spreading charges by the semiconductor. Third, the hybrid interface and molecule-like energy level of the Au cluster result in a much longer lifetime of excited electrons. Our results provide a promising approach for the effective harvesting of solar energy with plasmonic antenna-sensitizer complexes.
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| 9. |
- Hajizadeh Chavari, Faegheh, 1982, et al.
(författare)
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Brownian fluctuations of an optically rotated nanorod
- 2017
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Ingår i: Optica. - : The Optical Society. - 2334-2536. ; 4:7, s. 746-751
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Tidskriftsartikel (refereegranskat)abstract
- Gold nanorods can be optically trapped in aqueous solution and forced to rotate at kilohertz rates by circularly polarized laser light. This enables detailed investigations of local environmental parameters and processes, such as medium viscosity and nanoparticle-molecule reactions. Future applications may include nanoactuation and single-cell analysis. However, the influence of photothermal heating on the nanoparticle dynamics needs to be better understood in order to realize widespread and quantitative use. Here we analyze the hot Brownian motion of a rotating gold nanorod trapped in two dimensions by an optical tweezers using experiments and stochastic simulations. We show that, for typical settings, the effective rotational and translational Brownian temperatures are drastically different, being closer to the nanorod surface temperature and ambient temperature, respectively. Further, we show that translational dynamics can have a non-negligible influence on the rotational fluctuations due to the small size of a nanorod in comparison to the focal spot. These results are crucial for the development of gold nanorods into generic and quantitative optomechanical sensor and actuator elements.
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| 10. |
- Shao, Lei, 1987, et al.
(författare)
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Gold Nanorod Rotary Motors Driven by Resonant Light Scattering
- 2015
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 9:12, s. 12542-12551
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Tidskriftsartikel (refereegranskat)abstract
- Efficient and robust artificial nanomotors could provide a variety of exciting possibilities for applications in physics, biology and chemistry, including nanoelectromechanical systems, biochemical sensing, and drug delivery. However, the application of current man-made nanomotors is limited by their sophisticated fabrication techniques, low mechanical output power and severe environmental requirements, making their performance far below that of natural biomotors. Here we show that single-crystal gold nanorods can be rotated extremely fast in aqueous solutions through optical torques dominated by plasmonic resonant scattering of circularly polarized laser light with power as low as a few mW. The nanorods are trapped in 2D against a glass surface, and their rotational dynamics is highly dependent on their surface plasmon resonance properties. They can be kept continuously rotating for hours with limited photothermal side effects and they can be applied for detection of molecular binding with high sensitivity. Because of their biocompatibility, mechanical and thermal stability, and record rotation speeds reaching up to 42 kHz (2.5 million revolutions per minute), these rotary nanomotors could advance technologies to meet a wide range of future nanomechanical and biomedical needs in fields such as nanorobotics, nanosurgery, DNA manipulation and nano/microfluidic flow control.
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