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Dark field microscopy

Tian Li, Xi Wu, Feng Liu, Na Li
This minireview summarizes analytical methods based on the light-scattering of plasmonic nanoparticles, primarily gold nanoparticles (AuNPs), at the single particle level from recent year publications. Examples are presented to illustrate simple and highly sensitive approaches based on AuNP localized surface plasmon resonance light-scattering with the dark-field microscopy imaging technology.
December 5, 2016: Analyst
Nivedita Chatterjee, Jisu Yang, Dahye Yoon, Suhkmann Kim, Sang-Woo Joo, Jinhee Choi
The present study endeavored to evaluate the comprehensive mechanisms of MWCNT-induced toxicity with particular emphasis on understanding cell specificity in relation to surface functionalization of MWCNT. Following treatment with differentially functionalized (hydroxylation/carboxylation) MWCNT on human bronchial epithelial (BEAS-2B) and human hepatoma (HepG2) cell lines, intracellular uptake, various toxicological end points, global metabolomics profiling and DNA methylation were evaluated. Herein, the comparative in vitro studies ascertained that surface functionalization diminished the toxic potentiality of MWCNT in respect of their pristine counterpart...
November 9, 2016: Biomaterials
Michael Stöger-Pollach, Thomas Schachinger, Kati Biedermann, Volkhard Beyer
In this experimental work we present novel methods to increase the spatial resolution of valence electron energy loss spectrometry (VEELS) investigations below the limit given by the inelastic delocalization. For this purpose we analyse a layer stack consisting of silicon/silicon-oxide/silicon-nitride/silicon-oxide/silicon (SONOS) with varying layer thickness down to the 2nm level. Using a combination of a conical illumination and energy filtered transmission electron microscopy we are able to identify the layers by using low energy losses...
November 22, 2016: Ultramicroscopy
Joran Deschamps, Andreas Rowald, Jonas Ries
Single-molecule localization microscopy (SMLM) relies on the switching of fluorescent molecules between a fluorescent and a dark state to achieve super resolution. This process is inherently dependent on the intensity distribution of the laser light used for both activation from the dark state and excitation of the bright state. Typically, laser light is coupled directly or via a single-mode fiber into the microscope, which leads to a Gaussian intensity profile in total internal reflection (TIR) or epi illumination...
November 28, 2016: Optics Express
Jingxu Zheng, Zhongyuan Luo, Lida Tan, Bin Chen
In the present study, nano-sized cuboid-shaped particles in Mg-Nd-Y are studied by means of Cs-corrected atomic-scale high-angle annular dark-field scanning transmission electron microscopy. The structure of the cuboid-shaped phase is identified to be yttrium (major component) and neodymium atoms in face-centered cubic arrangement without the participation of Mg. The lattice parameter a=5.15 Å. During isothermal aging at 225°C, Mg3(Nd,Y) precipitates adhere to surface (100) planes of the cuboid-shaped particles with the orientation relationship: $[100]_{{{\rm Mg}_{{\rm 3}} {\rm RE}}} \,/\,\,/\,[100]_{{{\rm Cuboid}}} $ and $[310]_{{{\rm Mg}_{{\rm 3}} {\rm RE}}} \,/\,\,/\,[012]_{{{\rm Cuboid}}} $ ...
November 30, 2016: Microscopy and Microanalysis
Joshua Gild, Yuanyao Zhang, Tyler Harrington, Sicong Jiang, Tao Hu, Matthew C Quinn, William M Mellor, Naixie Zhou, Kenneth Vecchio, Jian Luo
Seven equimolar, five-component, metal diborides were fabricated via high-energy ball milling and spark plasma sintering. Six of them, including (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)B2, (Hf0.2Zr0.2Ta0.2Mo0.2Ti0.2)B2, (Hf0.2Zr0.2Mo0.2Nb0.2Ti0.2)B2, (Hf0.2Mo0.2Ta0.2Nb0.2Ti0.2)B2, (Mo0.2Zr0.2Ta0.2Nb0.2Ti0.2)B2, and (Hf0.2Zr0.2Ta0.2Cr0.2Ti0.2)B2, possess virtually one solid-solution boride phase of the hexagonal AlB2 structure. Revised Hume-Rothery size-difference factors are used to rationalize the formation of high-entropy solid solutions in these metal diborides...
November 29, 2016: Scientific Reports
So Young Lee, Ji Won Ha
Bimetallic core-shell gold nanorods are promising multifunctional orientation probes due to the synergetic effect of two different metals, as examined under an optical microscope. Herein, we performed a single particle study to characterize the optical properties of palladium-coated core-shell gold nanorods (Pd-AuNRs) using scattering-based dark-field (DF) and differential interference contrast (DIC) microscopy, and to examine their use as multifunctional orientation probes in biological and physical studies...
November 29, 2016: Physical Chemistry Chemical Physics: PCCP
Dudekula Althaf Basha, Julian M Rosalie, Hidetoshi Somekawa, Takashi Miyawaki, Alok Singh, Koichi Tsuchiya
Microstructural investigation of extremely strained samples, such as severely plastically deformed (SPD) materials, by using conventional transmission electron microscopy techniques is very challenging due to strong image contrast resulting from the high defect density. In this study, low angle annular dark field (LAADF) imaging mode of scanning transmission electron microscope (STEM) has been applied to study the microstructure of a Mg-3Zn-0.5Y (at%) alloy processed by high pressure torsion (HPT). LAADF imaging advantages for observation of twinning, grain fragmentation, nucleation of recrystallized grains and precipitation on second phase particles in the alloy processed by HPT are highlighted...
2016: Science and Technology of Advanced Materials
Philip-Helge Arnemann, Michael Hessler, Tim Kampmeier, Andrea Morelli, Hugo Karel Van Aken, Martin Westphal, Sebastian Rehberg, Christian Ertmer
BACKGROUND: Life-threatening diseases of critically ill patients are known to derange microcirculation. Automatic analysis of microcirculation would provide a bedside diagnostic tool for microcirculatory disorders and allow immediate therapeutic decisions based upon microcirculation analysis. METHODS: After induction of general anaesthesia and instrumentation for haemodynamic monitoring, haemorrhagic shock was induced in ten female sheep by stepwise blood withdrawal of 3 × 10 mL per kilogram body weight...
December 2016: Intensive Care Medicine Experimental
B D Esser, A J Hauser, R E A Williams, L J Allen, P M Woodward, F Y Yang, D W McComb
Using aberration-corrected high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM), we investigate ordering phenomena in epitaxial thin films of the double perovskite Sr_{2}CrReO_{6}. Experimental and simulated imaging and diffraction are used to identify antiphase domains in the films. Image simulation provides insight into the effects of atomic-scale ordering along the beam direction on HAADF-STEM intensity. We show that probe channeling results in ±20% variation in intensity for a given composition, allowing 3D ordering information to be probed using quantitative STEM...
October 21, 2016: Physical Review Letters
Yazhong Wang, Fei-Ting Huang, Xuan Luo, Bin Gao, Sang-Wook Cheong
Sr3 Sn2 O7 is the first room-temperature ferroelectric Sn insulator with switchable electric polarization. The ferroelastic twin domains are observed using polarized optical microscope. Polarization hysteresis loop clearly demonstrates the ferroelectric property. The intriguing polarization switching kinetics are observed through an in situ poling process using a dark-field transmission electron microscopy technique.
October 31, 2016: Advanced Materials
Jared M Johnson, Soohyun Im, Wolfgang Windl, Jinwoo Hwang
We propose a new scanning transmission electron microscopy (STEM) technique that can realize the three-dimensional (3D) characterization of vacancies, lighter and heavier dopants with high precision. Using multislice STEM imaging and diffraction simulations of β-Ga2O3 and SrTiO3, we show that selecting a small range of low scattering angles can make the contrast of the defect-containing atomic columns substantially more depth-dependent. The origin of the depth-dependence is the de-channeling of electrons due to the existence of a point defect in the atomic column, which creates extra "ripples" at low scattering angles...
October 18, 2016: Ultramicroscopy
Gregg Anthony Duncan, Sharon Gerecht, D Howard Fairbrother, Michael A Bevan
In the optimization of applied biomaterials, measurements of their interactions with cell surfaces are important to understand their influence on specific and nonspecific cell surface adhesion, internalization pathways, and toxicity. In this study, a novel approach using dark field video microscopy with combined real-time particle and cell tracking allows the trajectories of biomaterial-coated colloids to be monitored in relation to their distance from cell perimeters. Dynamic and statistical mechanical analyses enable direct measurement of colloid-cell surface association lifetimes and interaction potentials mediated by biomaterials...
October 27, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Célia Fontana, Steve Crussard, Nathalie Simon-Dufay, Daniel Pialot, Natalia Bomchil, Jean Reyes
Enumeration of Leptospira, the causative agent of leptospirosis, is arduous mainly because of its slow growth rate. Rapid and reliable tools for numbering leptospires are still lacking. The current standard for Leptospira cultures is the count on Petroff-Hausser chamber under dark-field microscopy, but this method remains time-consuming, requires well-trained operators and lacks reproducibility. Here we present the development of a flow-cytometry technique for counting leptospires. We showed that upon addition of fluorescent dyes, necessary to discriminate the bacterial population from debris, several live Leptospira strains could be enumerated at different physiologic states...
October 23, 2016: Journal of Microbiological Methods
H E du Plessis, J P R de Villiers, A Tuling, E J Olivier
Supported cobalt Fischer-Tropsch catalysts are characteristically nanoparticulate and the reduced SiC supported catalyst was found to contain both HCP and FCC polymorphs. This is reflected in the powder XRD patterns and generally there is a poor fit between the experimental and calculated diffractograms. This was ascribed to small crystallite sizes and the occurrence of disorder, manifested as peak broadening and peak shifts. Selected area electron diffraction data of suitably oriented cobalt catalyst grains on silicon carbide supports show non-periodic disorder in the zone axis orientations that contain the common (001) (HCP) and (111) (FCC) reciprocal lattice planes...
October 25, 2016: Physical Chemistry Chemical Physics: PCCP
Ferdous Ara, Zhi Kun Qi, Jie Hou, Tadahiro Komeda, Keiichi Katoh, Masahiro Yamashita
In this article, we investigate a single molecule magnet bis(phthalocyaninato)terbium(iii) (TbPc2) molecule film by using low temperature STM. In order to investigate the effect of molecule-substrate interaction on the electronic and spin properties of the adsorbed molecule, we tune the molecule-substrate coupling by switching the substrate between Au(111) and Ag(111), the latter of which provides stronger interaction with the molecule than the former. Despite the enhanced chemical reactivity of the Ag(111) surface compared with Au(111), a well-organized pseudo-square film is formed...
October 25, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Akio Hayashi, Hiromi Ota, Xavier López, Norihito Hiyoshi, Nao Tsunoji, Tsuneji Sano, Masahiro Sadakane
Dipotassium cation (K(+))-encapsulated Preyssler-type phosphotungstate, [P5W30O110K2](13-), was prepared by heating monobismuth (Bi(3+))-encapsulated Preyssler-type phosphotungstate, [P5W30O110Bi(H2O)](12-), in acetate buffer in the presence of an excess amount of potassium cations. Characterization of the isolated potassium salt, K13[P5W30O110K2] (1a), and its acid form, H13[P5W30O110K2] (1b), by single crystal X-ray structure analysis, (31)P and (183)W nuclear magnetic resonance (NMR), Fourier transform infrared (FT-IR) spectroscopy, cyclic voltammetry (CV), high-resolution electrospray ionization mass spectroscopy (HR-ESI-MS), and elemental analysis revealed that two potassium cations are encapsulated in the Preyssler-type phosphotungstate molecule with formal D5h symmetry, which is the first example of a Preyssler-type compound with two encapsulated cations...
October 24, 2016: Inorganic Chemistry
Keiko Tawa, Shohei Yamamura, Chisato Sasakawa, Izumi Shibata, Masatoshi Kataoka
Plasmonic chip was applied to the live cancer cell imaging. The epithelial cell adhesion molecule (EpCAM) is a surface marker that can be used to classify breast cancer cell lines into distinct differentiation states. EpCAM and the nuclei of two kinds of living breast cancer cells, MDA-MB231 and MCF-7, were stained with allophycocyanin (APC)-labeled anti-EpCAM antibody and 4,6-diamidino-2-phenylindole (DAPI), respectively, and the cells were scattered on either a plasmonic chip (metal-coated wavelength-scale grating substrate) or a control glass slide...
October 18, 2016: ACS Applied Materials & Interfaces
Eva Bladt, Relinde J A van Dijk-Moes, Joep Peters, Federico Montanarella, Celso de Mello Donegá, Daniël Vanmaekelbergh, Sara Bals
Hetero-nanocrystals consisting of a CdSe core and a giant CdS shell have shown remarkable optical properties which are promising for applications in opto-electrical devices. Since these properties sensitively depend on the size and shape, a morphological characterization is of high interest. Here, we present a High Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM) study of CdSe (core) / CdS (giant shell) hetero-nanocrystals. Electron tomography reveals that the nanocrystals have a bullet shape, either ending in a tip or a small dip, and that the CdSe core is positioned closer to the tip (or dip) than to the hexagonal base...
October 14, 2016: Journal of the American Chemical Society
Akihiro Suzuki, Kei Shimomura, Makoto Hirose, Nicolas Burdet, Yukio Takahashi
The phase shift of light or electrons in objects is now necessary for probing weak-phase objects such as unstained biological specimens. Optical microscopy (OM) and transmission electron microscopy (TEM) have been used to observe weak-phase objects. However, conventional OM has low spatial resolution and TEM is limited to thin specimens. Here, we report on the development of dark-field X-ray ptychography, which combines X-ray ptychography and X-ray in-line holography, to observe weak-phase objects with a phase resolution better than 0...
October 13, 2016: Scientific Reports
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