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Dark field microscopy

Jiya M George, Millicent Magogotya, Melissa A Vetten, Antoinette V Buys, Mary Gulumian
The suitability of 4 in vitro assays, commonly used for mutagenicity and genotoxicity assessment, was investigated in relation to treatment with 14 nm citrate-stabilized gold nanoparticles (AuNPs). Specifically, the Ames test was conducted without metabolic activation, where no mutagenic effects were observed. High resolution transmission electron microscopy and Cytoviva dark-field image analysis showed that AuNPs did not enter the bacterial cells, thus confirming the unreliability of the Ames test for nanoparticle mutagenicity studies...
January 20, 2017: Toxicological Sciences: An Official Journal of the Society of Toxicology
Aurelien Crut, Paolo Maioli, Fabrice Vallee, Natalia Del Fatti
Single-particle optical investigations have greatly improved our understanding of the fundamental properties of nano-objects, avoiding the spurious inhomogeneous effects that affect ensemble experiments. Correlation with high-resolution imaging techniques providing morphological information (e.g., electron microscopy) allows a quantitative interpretation of the optical measurements by means of analytical models and numerical simulations. In this topical review, we first briefly recall the principles underlying some of the most commonly used single-particle optical techniques: near-field, dark-field, spatial modulation and photothermal microscopies/spectroscopies...
January 17, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Tarun C Narayan, Fariah Hayee, Andrea Baldi, Ai Leen Koh, Robert Sinclair, Jennifer A Dionne
Many energy storage materials undergo large volume changes during charging and discharging. The resulting stresses often lead to defect formation in the bulk, but less so in nanosized systems. Here, we capture in real time the mechanism of one such transformation-the hydrogenation of single-crystalline palladium nanocubes from 15 to 80 nm-to better understand the reason for this durability. First, using environmental scanning transmission electron microscopy, we monitor the hydrogen absorption process in real time with 3 nm resolution...
January 16, 2017: Nature Communications
R H L Haeren, H Vink, J Staals, M A M J van Zandvoort, J Dings, J J van Overbeeke, G Hoogland, K Rijkers, O E M G Schijns
INTRODUCTION: Adequate functioning of the blood-brain barrier (BBB) is important for brain homoeostasis and normal neuronal function. Disruption of the BBB has been described in several neurological diseases. Recent reports suggest that an increased permeability of the BBB also contributes to increased seizure susceptibility in patients with epilepsy. The endothelial glycocalyx is coating the luminal side of the endothelium and can be considered as the first barrier of the BBB. We hypothesise that an altered glycocalyx thickness plays a role in the aetiology of temporal lobe epilepsy (TLE), the most common type of epilepsy...
January 5, 2017: BMJ Open
Pengfei Zhan, Palash K Dutta, Pengfei Wang, Gang Song, Mingjie Dai, Shu-Xia Zhao, Zhen-Gang Wang, Peng Yin, Wei Zhang, Baoquan Ding, Yonggang Ke
Distinct electromagnetic properties can emerge from the three-dimensional (3D) configuration of a plasmonic nanostructure. Furthermore, the reconfiguration of a dynamic plasmonic nanostructure, driven by physical or chemical stimuli, may generate a tailored plasmonic response. In this work, we constructed a 3D reconfigurable plasmonic nanostructure with controllable, reversible conformational transformation using bottom-up DNA self-assembly. Three gold nanorods (AuNRs) were positioned onto a reconfigurable DNA origami tripod...
January 9, 2017: ACS Nano
Antonio M Mio, Stefania M S Privitera, Valeria Bragaglia, Fabrizio Arciprete, Corrado Bongiorno, Raffaella Calarco, Emanuele Rimini
The thermal and electrical properties of phase change materials, mainly GeSbTe alloys, in the crystalline state strongly depend on their phase and on the associated degree of order. The switching of Ge atoms in superlattice structures with trigonal phase has been recently proposed to develop memories with reduced switching energy, in which two differently ordered crystalline phases are the logic states. A detailed knowledge of the stacking plane sequence, of the local composition and of the vacancy distribution is therefore crucial in order to understand the underlying mechanism of phase transformations in the crystalline state and to evaluate the retention properties...
January 4, 2017: Nanotechnology
A Khoo, N Sahoo, S Krishnan, P Diagaradjane
PURPOSE: In recent years, proton beam radiation therapy (PBRT) has gained significant attention in the treatment of tumors in anatomically complex locations. However, the therapeutic benefit of PBRT is limited by a relative biological effectiveness (RBE) of just 1.1. The purpose of this study is to evaluate whether this limitation can be overcome by artificially enhancing the RBE using molecular-targeted gold nanorods (GNRs). METHODS: Molecular-targeting of GNRs was accomplished using Cetuximab (antibody specific to epidermal growth factor receptor that is over-expressed in tumors) conjugated GNRs (cGNRs) and their binding affinity to Head and Neck cancer cells was confirmed using dark field microscopy and Transmission Electron Microscopy (TEM)...
June 2016: Medical Physics
Suzanne Slack, Quan Zeng, Cory Outwater, George W Sundin
Fire blight, caused by the pathogen Erwinia amylovora (Burrill) Winslow et al, is the most devastating bacterial disease of pome fruits in North America and worldwide. The primary method of dispersal for E. amylovora is through ooze, a mass of exopolysaccharides and bacterial cells that is exuded as droplets from infected host tissue. During the 2013 and 2014 field seasons, 317 ooze droplets were collected from field-inoculated apple trees. Populations of E. amylovora in ooze droplets were 108 colony forming units per microliter on average (cfu/µl)...
January 3, 2017: Phytopathology
Xiaojing Su, Hongqiang Li, Xuejun Lai, Lin Zhang, Tao Liang, Yuchun Feng, Xingrong Zeng
Functional surfaces for reversibly switchable wettability and oil-water separation have attracted much interest with pushing forward an immense influence on fundamental research and industrial application in recent years. This article proposed a facile method to fabricate superhydrophobic surfaces on steel substrates via electroless replacement deposition of copper sulfate (CuSO4) and UV curing of vinyl-terminated polydimethylsiloxane (PDMS). PDMS-based superhydrophobic surfaces exhibited water contact angle (WCA) close to 160° and water sliding angle (WSA) lower than 5°, preserving outstanding chemical stability that maintained superhydrophobicity immersing in different aqueous solutions with pH values from 1 to 13 for 12 h...
January 11, 2017: ACS Applied Materials & Interfaces
Mansour Nazari, Ali Najafi
BACKGROUND: Endemic relapsing fever remains under diagnosed in our area according to a low index of suspicion among clinicians, as well as its difficult diagnosis. The goal of this study was to present the epidemiological aspects of the disease in western Iran. METHODS: In this analytical-descriptive cross-sectional study, the epidemiological and clinical aspects of relapsing fever were investigated in Hamadan Province, western Iran from 1999 to 2013. A confirmed patient was defined as a person who had both febrile illness and detected spirochetes by Wright-Giemsa or dark-field microscopy in a peripheral blood smear...
December 2016: Journal of Arthropod-borne Diseases
Zhichao Zhong, Bart Goris, Remco Schoenmakers, Sara Bals, K Joost Batenburg
A three-dimensional (3D) chemical characterization of nanomaterials can be obtained using tomography based on high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) or energy dispersive X-ray spectroscopy (EDS) STEM. These two complementary techniques have both advantages and disadvantages. The Z-contrast images have good image quality but lack robustness in the compositional analysis, while the elemental maps give more element-specific information, but at a low signal-to-noise ratio and a longer exposure time...
December 11, 2016: Ultramicroscopy
U Bangert, A Stewart, E O'Connell, E Courtney, Q Ramasse, D Kepatsoglou, H Hofsäss, J Amani, J-S Tu, B Kardynal
Functionalisation of two-dimensional (2-D) materials via low energy ion implantation could open possibilities for fabrication of devices based on such materials. Nanoscale patterning and/or electronically doping can thus be achieved, compatible with large scale integrated semiconductor technologies. Using atomic resolution High Angle Annular Dark Field (HAADF) scanning transmission electron microscopy supported by image simulation, we show that sites and chemical nature of individual implants/ dopants in graphene, as well as impurities in hBN, can uniquely and directly be identified on grounds of their position and their image intensity in accordance with predictions from Z-contrast theories...
December 11, 2016: Ultramicroscopy
James E Wittig, James Bentley, Lawrence F Allard
In situ high-resolution electron microscopy was used to reveal information at the atomic level for the disordered-to-ordered phase transformation of equiatomic FePt nanoparticles that can exhibit outstanding magnetic properties after transforming from disordered face-centered-cubic into the tetragonal L10 ordered structure. High-angle annular dark-field imaging in the scanning transmission electron microscope provided sufficient contrast between the Fe and Pt atoms to readily monitor the ordering of the atoms during in situ heating experiments...
December 11, 2016: Ultramicroscopy
Caspar Haverkamp, Katja Höflich, Sara Jäckle, Anna Manzoni, Silke Christiansen
Electron beam induced deposition (EBID) currently provides the only direct writing technique for truly three-dimensional nanostructures with geometrical features below 50 nm. Unfortunately, the depositions from metal-organic precursors suffer from a substantial carbon content. This hinders many applications, especially in plasmonics where the metallic nature of the geometric surfaces is mandatory. To overcome this problem a post-deposition treatment with oxygen plasma at room temperature was investigated for the purification of gold containing EBID structures...
February 3, 2017: Nanotechnology
Mark P Oxley, Andrew R Lupini, Stephen J Pennycook
The last two decades have seen dramatic advances in the resolution of the electron microscope brought about by the successful correction of lens aberrations that previously limited resolution for most of its history. We briefly review these advances, the achievement of sub-Ångstrom resolution and the ability to identify individual atoms, their bonding configurations and even their dynamics and diffusion pathways. We then present a review of the basic physics of electron scattering, lens aberrations and their correction, and an approximate imaging theory for thin crystals which provides physical insight into the various different imaging modes...
December 23, 2016: Reports on Progress in Physics
Tao Xie, Chao Jing, Yi-Tao Long
Plasmonic nanoparticles, especially Au and Ag, exhibit unique and tuneable optical properties due to their localized surface plasmon resonance, which have been widely applied in cell imaging, biocatalysis and biosensing. Notably, dark-field microscopy enables the observation of the scattering spectra of single nanoparticles and therefore has been intensively used in the construction of various nanosensors. In this mini review, we will briefly introduce the recent applications of plasmonic nanoparticles based on dark-field microscopy...
December 22, 2016: Analyst
Daniel Knez, Philipp Thaler, Alexander Volk, Gerald Kothleitner, Wolfgang E Ernst, Ferdinand Hofer
We report the transformation of nickel clusters into NiO rings by an electron beam induced nanoscale Kirkendall effect. High-purity nickel clusters consisting of a few thousand atoms have been used as precursors and were synthesized with the superfluid helium droplet technique. Aberration-corrected, analytical scanning transmission electron microscopy was applied to oxidise and simultaneously analyse the nanostructures. The transient dynamics of the oxidation could be documented by time lapse series using high-angle annular dark-field imaging and electron energy-loss spectroscopy...
December 13, 2016: Ultramicroscopy
Sandeep K Mishra, S Kannan
Accurate imaging of the structural and functional state of biological targets is a critical task. To amend paucities associated with individual imaging, there is high interest to develop a multifunctional theranostic devices for cancer diagnosis and therapy. Herein, chitosan coated silver/dysprosium bimetallic nanoparticles (BNPs) were synthesized through a green chemistry route and characterization results inferred that the BNPs are crystalline, spherical, and of size ∼10 nm. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray photoelectron spectroscopy (XPS) confirm the reduced metallic states of Ag and Dy in nanoparticles...
December 27, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Hyung Cheoul Shim, Donghan Kim, Dongwook Shin, Seungmin Hyun, Chang-Su Woo, Taehwan Yu, Jae-Pyoung Ahn
Lithium-rich layered oxides show promise as high-energy harvesting materials due to their large capacities. However, questions remain regarding the large irreversible loss in capacities for the first charge-discharge cycle due to oxygen removal in lattices related to layered Li2MnO3. Herein we present detailed studies on Li-rich Mn-based layered oxides of 0.4Li2MnO3-0.6LiNi1/3Co1/3Mn1/3O2 (Li-rich NCM) electrochemically activated between 2.5 V and 4.3 or 4.7 V vs. Li(+)/Li. Electron energy loss spectroscopy (EELS) and X-ray absorption spectroscopy (XAS) revealed unusual manganese reduction after the first charge up to a high voltage of 4...
January 4, 2017: Physical Chemistry Chemical Physics: PCCP
Mathias Auer, Dexian Ye
The surface orientation of metal nanoparticles is critical to their physical and chemical properties. This study aims on the understanding of the effect of surface orientation as well as heterogeneous epitaxy of metal nanoparticles at an interface between two materials with a large lattice mismatch. Silver nanoparticles of different diameters were grown on arrays of calcium fluoride (CaF2) nanorods using oblique angle deposition as a model system for this study. Scanning electron microscopy and transmission electron microscopy (TEM) imaging were used to verify that the nanoparticles were selectively grown on the desired {111} facets of the nanorod tips...
January 20, 2017: Nanotechnology
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