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Sökning: WFRF:(Höök Fredrik)

  • Resultat 1-10 av 248
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2.
  • Hagman, Henning, 1981, et al. (författare)
  • Plasmon-enhanced four-wave mixing by nanoholes in thin gold films
  • 2014
  • Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 39:4, s. 1001-1004
  • Tidskriftsartikel (refereegranskat)abstract
    • Nonlinear plasmonics opens up for wavelength conversion, reduced interaction/emission volumes, and nonlinear enhancement effects at the nanoscale with many compelling nanophotonic applications foreseen. We investigate nonlinear plasmonic responses of nanoholes in thin gold films by exciting the holes individually with tightly focused laser beams, employing a degenerated pump/probe and Stokes excitation scheme. Excitation of the holes results in efficient generation of both narrowband four-wave mixing (FWM) and broadband multiphoton excited luminescence, blueshifted relative to the excitation beams. Clear enhancements were observed when matching the pump/probe wavelength with the hole plasmon resonance. These observations show that the FWM generation is locally excited by nanoholes and has a resonant behavior primarily governed by the dimensions of the individual holes.
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4.
  • Lubart, Quentin, 1989, et al. (författare)
  • High throughput size-determination and multiplexed fluorescence analysis of single biological particles in a nanofluidic device
  • 2019
  • Ingår i: 23rd International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2019. ; , s. 1420-1421
  • Konferensbidrag (refereegranskat)abstract
    • Biological nanoparticles, such as exosomes and viruses, are responsible for a multitude of important functions, but methods to characterize them on the single particle level are rare. We here present a nanofluidic platform for multi-parametric characterization of biological nanoparticles with high throughput. The device consists of feeding microchannels and an array of ~100 nanochannels where the nanoparticles can be characterized. We determine the size by analyzing the Brownian motion of the particles and quantify their content based on fluorescence imaging of up to three different colors. We successfully benchmark our method against existing techniques, such as Nanoparticle Tracking Analysis (NTA).
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5.
  • Midtvedt, Benjamin, et al. (författare)
  • Fast and Accurate Nanoparticle Characterization Using Deep-Learning-Enhanced Off-Axis Holography
  • 2021
  • Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 15:2, s. 2240-2250
  • Tidskriftsartikel (refereegranskat)abstract
    • Characterization of suspended nanoparticles in their native environment plays a central role in a wide range of fields, from medical diagnostics and nanoparticle-enhanced drug delivery to nanosafety and environmental nanopollution assessment. Standard optical approaches for nanoparticle sizing assess the size via the diffusion constant and, as a consequence, require long trajectories and that the medium has a known and uniform viscosity. However, in most biological applications, only short trajectories are available, while simultaneously, the medium viscosity is unknown and tends to display spatiotemporal variations. In this work, we demonstrate a label-free method to quantify not only size but also refractive index of individual subwavelength particles using 2 orders of magnitude shorter trajectories than required by standard methods and without prior knowledge about the physicochemical properties of the medium. We achieved this by developing a weighted average convolutional neural network to analyze holographic images of single particles, which was successfully applied to distinguish and quantify both size and refractive index of subwavelength silica and polystyrene particles without prior knowledge of solute viscosity or refractive index. We further demonstrate how these features make it possible to temporally resolve aggregation dynamics of 31 nm polystyrene nanoparticles, revealing previously unobserved time-resolved dynamics of the monomer number and fractal dimension of individual subwavelength aggregates.
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6.
  • Midtvedt, Benjamin, et al. (författare)
  • Single-shot self-supervised object detection in microscopy
  • 2022
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 13:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Object detection is a fundamental task in digital microscopy, where machine learning has made great strides in overcoming the limitations of classical approaches. The training of state-of-the-art machine-learning methods almost universally relies on vast amounts of labeled experimental data or the ability to numerically simulate realistic datasets. However, experimental data are often challenging to label and cannot be easily reproduced numerically. Here, we propose a deep-learning method, named LodeSTAR (Localization and detection from Symmetries, Translations And Rotations), that learns to detect microscopic objects with sub-pixel accuracy from a single unlabeled experimental image by exploiting the inherent roto-translational symmetries of this task. We demonstrate that LodeSTAR outperforms traditional methods in terms of accuracy, also when analyzing challenging experimental data containing densely packed cells or noisy backgrounds. Furthermore, by exploiting additional symmetries we show that LodeSTAR can measure other properties, e.g., vertical position and polarizability in holographic microscopy.
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7.
  • Midtvedt, Daniel, et al. (författare)
  • Size and Refractive Index Determination of Subwavelength Particles and Air Bubbles by Holographic Nanoparticle Tracking Analysis
  • 2020
  • Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 92:2, s. 1908-1915
  • Tidskriftsartikel (refereegranskat)abstract
    • Determination of size and refractive index (RI) of dispersed unlabeled subwavelength particles is of growing interest in several fields, including biotechnology, wastewater monitoring, and nanobubble preparations. Conventionally, the size distribution of such samples is determined via the Brownian motion of the particles, but simultaneous determination of their R1 remains challenging. This work demonstrates nanoparticle tracking analysis (NTA) in an off-axis digital holographic microscope (DHM) enabling determination of both particle size and RI of individual subwavelength particles from the combined information about size and optical phase shift. The potential of the method to separate particle populations is demonstrated by analyzing a mixture of three types of dielectric particles within a narrow size range, where conventional NTA methods based on Brownian motion alone would fail. Using this approach, the phase shift allowed individual populations of dielectric beads overlapping in either size or RI to be clearly distinguished and quantified with respect to these properties. The method was furthermore applied for analysis of surfactant-stabilized micro- and nanobubbles, with RI lower than that of water. Since bubbles induce a phase shift of opposite sign to that of solid particles, they were easily distinguished from similarly sized solid particles made up of undissolved surfactant. Surprisingly, the dependence of the phase shift on bubble size indicates that only those with 0.15-0.20 mu m radius were individual bubbles, whereas larger bubbles were actually clusters of bubbles. This label-free means to quantify multiple parameters of suspended individual submicrometer particles offers a crucial complement to current characterization strategies, suggesting broad applicability for a wide range of nanoparticle systems.
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8.
  • Olsén, Erik, 1994, et al. (författare)
  • Dual-Angle Interferometric Scattering Microscopy for Optical Multiparametric Particle Characterization
  • 2024
  • Ingår i: NANO LETTERS. - 1530-6984 .- 1530-6992. ; 24:6, s. 1874-1881
  • Tidskriftsartikel (refereegranskat)abstract
    • Traditional single-nanoparticle sizing using optical microscopy techniques assesses size via the diffusion constant, which requires suspended particles to be in a medium of known viscosity. However, these assumptions are typically not fulfilled in complex natural sample environments. Here, we introduce dual-angle interferometric scattering microscopy (DAISY), enabling optical quantification of both size and polarizability of individual nanoparticles (radius <170 nm) without requiring a priori information regarding the surrounding media or super-resolution imaging. DAISY achieves this by combining the information contained in concurrently measured forward and backward scattering images through twilight off-axis holography and interferometric scattering (iSCAT). Going beyond particle size and polarizability, single-particle morphology can be deduced from the fact that the hydrodynamic radius relates to the outer particle radius, while the scattering-based size estimate depends on the internal mass distribution of the particles. We demonstrate this by differentiating biomolecular fractal aggregates from spherical particles in fetal bovine serum at the single-particle level.
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10.
  • Vandoolaeghe, Pauline, et al. (författare)
  • Adsorption of cubic liquid crystalline nanoparticles on model membranes
  • 2008
  • Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 4:11, s. 2267-2277
  • Tidskriftsartikel (refereegranskat)abstract
    • The interactions of lipid based cubic liquid crystalline nanoparticles (Cubosome (R)) with surface supported model membranes constituted of dioleylphosphatidylcholine ( DOPC) have been studied in situ by use of ellipsometry, quartz crystal microbalance with dissipation monitoring and neutron reflectivity. The systems investigated were cubic phase dispersions of glycerol monooleate (GMO) stabilised by a non-ionic block copolymer, Pluronic (R) F-127. The interaction between the cubic nanoparticles and the lipid bilayer is a dynamic process where the nanoparticles initially adsorb at the bilayer surface. Interfacial  lipid exchange takes place where GMO is delivered into the bilayer and DOPC is extracted into the nanoparticle (34% loss). A subsequent release of the adsorbates can be triggered when the solution concentration exceeds 0.002 mg ml(-1). The release shows that the attractive interaction between the cubic nanoparticles and lipid bilayer is unstable after sufficient exchange of material takes place.This instability is indicative of a local phase separation at the interface between the bilayer and the nanoparticles, which causes desorption of nanoparticles. Some particles remain attached to the bilayer even hours after the initial interaction. The ability to trigger the release of the nanoparticles through increasing the   solution concentration offers exciting potential in the design of drug delivery aids.
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