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Dark field microscopy

B Dubiel, P Indyka, T Moskalewicz, A Kruk, M Zubko, I Kalemba-Rec, K Berent
A combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and scanning-transmission electron microscopy (STEM) using high-angle annular-dark-field (HAADF) imaging, focussed ion beam- scanning electron microscopy (FIB-SEM) tomography, selected area electron diffraction with beam precession (PED), as well as spatially resolved energy-dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS), was used to investigate topologically close-packed (TCP) phases, occurring in the CMSX-4 superalloy subjected to high temperature annealing and creep deformation...
February 20, 2017: Journal of Microscopy
T K Sharma, M Alazhari, A Heath, K Paine, R M Cooper
AIMS: Characterisation of alkaliphilic Bacillus species for spore production and germination and calcite formation as a prelude to investigate their potential in micro-crack remediation in concrete. METHODS AND RESULTS: Conditions, extent and timing of endospore production was determined by dark field light microscopy; germination induction and kinetics was assessed by combining reduction in optical density with formation of refractile bodies by phase contrast microscopy...
February 15, 2017: Journal of Applied Microbiology
Peiyuan Wang, Yujie Bai, Chi Yao, Xiaomin Li, Lei Zhou, Wenxing Wang, Ahmed Mohamed El-Toni, Jian Zi, Dongyuan Zhao, Lei Shi, Fan Zhang
Cyanide is extremely toxic to organisms but difficult to detect in living biological specimens. Here, we report a new CN(-) sensing platform based on unmodified Au-Ag alloy nanoboxes that etch in the presence of this analyte, yielding a shift in plasmon frequency that correlates with the analyte concentration. Significantly, when combined with dark field microscopy, these particle probes can be used to measure CN(-) concentrations in HeLa cells and in vivo in Zebra fish embryos. The limit of detection (LOD) of the novel method is 1 nM (below the acceptable limit defined by the World Health Organization), and finite-difference time-domain (FDTD) calculations are used to understand the CN(-) induced spectral shifts...
February 8, 2017: Analytical Chemistry
Gang Xu, Yuhua Zhu, Jie Pang
A simple and sensitive method to determinate glucose content was developed based on single plasmonic nanoparticles by conventional dark-field microscopy (DFM). An enzyme-responsive plasmonic Ag/Au bilayer of rods was designed and prepared. Their localized surface plasmon resonance (LSPR) could be tailored by the enzyme reaction of glucose oxidase (GOx) by finely tuning the morphology and plasmonic optical response of the hybrid nanostructure. It was found that the plasmon resonance scattering (PRS) spectra peak (λmax) shifted to longer wavelengths under enzyme reactions, and the degree of the shift were proportional to the content of glucose...
2017: Analytical Sciences: the International Journal of the Japan Society for Analytical Chemistry
Rafael Frederice, Diego Lencione, Marcelo H Gehlen
The combination of a sensitizer and TiO2 nanoparticles forming a photocatalytic material is a central issue in many fields of applied photochemistry. The charge injection of emissive sensitizers into the conduction band of the semiconductor TiO2 may form a photoactive region that becomes dark, or it has a very low emission signal due to the generation of sensitizer radicals. However, by sequential coupling of a selected photoredox dye, such as resazurin, the dark region may become fluorescent at the interfaces where the charge injection has taken place due to the concomitant formation of fluorescent resorufin by cascade electron transfer...
February 10, 2017: Methods and Applications in Fluorescence
Flavio F Contreras-Torres, Andrés Rodríguez-Galván, Carlos E Guerrero-Beltrán, Erick Martínez-Lorán, Eduardo Vázquez-Garza, Nancy Ornelas-Soto, Gerardo García-Rivas
Given the well-known physical properties of graphene oxide (GO), numerous applications for this novel nanomaterial have been recently envisioned to improve the performance of biomedical devices. However, the toxicological assessment of GO, which strongly depends on the used material and the studied cell line, is a fundamental task that needs to be performed prior to its use in biomedical applications. Therefore, the toxicological characterization of GO is still ongoing. This study contributes to this, aiming to synthesize and characterize GO particles and thus investigate their toxic effects in myocardial cells...
April 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
Takumi Igarashi, Zhenxin Zhang, Terufumi Haioka, Nao Iseki, Norihito Hiyoshi, Norihito Sakaguchi, Chisato Kato, Sadafumi Nishihara, Katsuya Inoue, Akira Yamamoto, Hisao Yoshida, Nao Tsunoji, Wataru Ueda, Tsuneji Sano, Masahiro Sadakane
We describe the preparation of ε-Keggin-type cobaltomolybdate-based 3D frameworks with sodium cations, NaH9[ε-Co(II)Mo(V)8Mo(VI)4O40Co(II)2], and their characterization by high-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption fine structure (XAFS) spectroscopy. Atomic-scale HAADF-STEM images of ε-Keggin compounds were obtained for the first time, and positions of Mo and Co were confirmed. Furthermore, clear evidence of the presence of a CoO4 tetrahedron was obtained by X-ray absorption near-edge structure (XANES) analysis...
February 20, 2017: Inorganic Chemistry
Sungi Kim, Jeong-Eun Park, Woosung Hwang, Jinyoung Seo, Young-Kwang Lee, Jae-Ho Hwang, Jwa-Min Nam
Multiplexed real-time analysis on multiple interacting molecules and particles is needed to obtain information on binding patterns between multiple ligands and receptors, specificity of bond formations and interacting pairs in a complex medi-um, often found in chemical and biological systems, and difference in binding affinity and kinetics for different binding pairs in one solution. In particular, multiplexed profiling of microRNA (miRNA) in a reliable, quantitative manner is of great demand for the use of miRNA in cell biology, biosensing and clinical diagnostic applications, and accurate diagnosis of cancers with miRNA is not possible without detecting multiple miRNA sequences in a highly specific manner...
February 9, 2017: Journal of the American Chemical Society
Shen Hu, Edward L Lin, Ali K Hamze, Agham Posadas, HsinWei Wu, David J Smith, Alexander A Demkov, John G Ekerdt
Using in situ X-ray photoelectron spectroscopy, reflection high-energy electron diffraction, and density functional theory, we analyzed the surface core level shifts and surface structure during the initial growth of ABO3 perovskites on Ge (001) by atomic layer deposition, where A = Ba, Sr and B = Ti, Hf, Zr. We find that the initial dosing of the barium- or strontium-bis(triisopropylcyclopentadienyl) precursors on a clean Ge surface produces a surface phase that has the same chemical and structural properties as the 0...
February 7, 2017: Journal of Chemical Physics
L León Félix, J A H Coaquira, M A R Martínez, G F Goya, J Mantilla, M H Sousa, L de Los Santos Valladares, C H W Barnes, P C Morais
We present a systematic study of core-shell Au/Fe3O4 nanoparticles produced by thermal decomposition under mild conditions. The morphology and crystal structure of the nanoparticles revealed the presence of Au core of d = (6.9 ± 1.0) nm surrounded by Fe3O4 shell with a thickness of ~3.5 nm, epitaxially grown onto the Au core surface. The Au/Fe3O4 core-shell structure was demonstrated by high angle annular dark field scanning transmission electron microscopy analysis. The magnetite shell grown on top of the Au nanoparticle displayed a thermal blocking state at temperatures below TB = 59 K and a relaxed state well above TB...
February 6, 2017: Scientific Reports
Cyril Hnatovsky, Dan Grobnic, David Coulas, Michael Barnes, Stephen J Mihailov
Periodic planar nanostructures are found in Type II-IR Bragg gratings produced in SMF-28 fiber by side-illuminating it with infrared femtosecond-laser pulses through a phase mask. The planar nanostructures are aligned perpendicular to the laser polarization, as demonstrated using scanning electron microscopy analysis of cleaved fiber samples. Dark field optical microscopy is employed for real-time monitoring of structural changes occurring inside the fiber during the inscription process.
February 1, 2017: Optics Letters
Yen-Cheng Chen, Robert M Dickson
Modulation and optical control of photoswitchable fluorescent protein (PS-FP) dark state lifetimes drastically improves sensitivity and selectivity in fluorescence imaging. The dark state population of PS-FPs generates an out-of-phase fluorescence component relative to the sinusoidally modulated 488 nm laser excitation. Because this apparent phase advanced emission results from slow recovery to the fluorescent manifold, we hasten recovery and, therefore, modulation frequency by varying coillumination intensity at 405 nm...
February 16, 2017: Journal of Physical Chemistry Letters
Gang Lei, Peng Fei Gao, Tong Yang, Jun Zhou, Hong Zhi Zhang, Shan Shan Sun, Ming Xuan Gao, Cheng Zhi Huang
Understanding photoinduced electron transfer (PET) mechanism is vital to improving the photoelectric conversion efficiency for solar energy materials and photosensitization systems. Herein we visually demonstrated the PET process by real-time monitoring the photoinduced chemical transformation (PICT) of para-aminothiophenol (p-ATP), an important SERS signal molecule, to 4,4'-dimercaptoazobenzene (DMAB) on single silver nanoparticles (AgNPs) with a localized surface plasmon resonance (LSPR) spectroscopy coupled dark-field microscopy...
January 24, 2017: ACS Nano
Z Liu, T Epicier, Y Lefkir, G Vitrant, N Destouches
Measuring with a high accuracy the size distribution of small metallic nanoparticles loaded in a mesoporous metal oxide matrix is of particular interest for many studies related to new generations of interesting metamaterials. Transmission electron microscopy (TEM) is a powerful tool to determine the nature and morphology of very small particles, but their reliable and automatic identification in an inhomogeneous environment where the nanoparticle/background contrast locally varies is not straightforward. Here, we present how a quantitative analysis of high-angle annular dark field scanning TEM (HAADF STEM) images, accounting for the chemical sensitivity of the technique, can improve the accuracy of semiautomatic segmentation methods based on morphological processing to calculate size histograms...
January 24, 2017: Journal of 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
Aurélien Crut, Paolo Maioli, Fabrice Vallée, 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...
March 29, 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
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