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Dark field microscopy

Jian Liu, Nan Jian, Isabel Ornelas, Alexander J Pattison, Tanja Lahtinen, Kirsi Salorinne, Hannu Häkkinen, Richard E Palmer
Monolayer-protected (MP) Au clusters present attractive quantum systems with a range of potential applications e.g. in catalysis. Knowledge of the atomic structure is needed to obtain a full understanding of their intriguing physical and chemical properties. Here we employed aberration-corrected scanning transmission electron microscopy (ac-STEM), combined with multislice simulations, to make a round-robin investigation of the atomic structure of chemically synthesised clusters with nominal composition Au144(SCH2CH2Ph)60 provided by two different research groups...
November 22, 2016: Ultramicroscopy
Jun Zhou, Peng Fei Gao, Hong Zhi Zhang, Gang Lei, Lin Ling Zheng, Hui Liu, Cheng Zhi Huang
Imaging of light scattering plasmonic nanoparticles (PNPs) with the aid of the dark-field microscopy imaging (iDFM) technique has attracted wide attention owing to its high signal-to-noise ratio, but to improve the color resolution and contrast of dark-field microscopy (DFM) images of single light scattering PNPs in a small spectral variation environment is still a challenge. In this study, a new color analytical method for resolving the resolution and contrast in DFM images has been developed and further applied for colorimetric analysis using the digital image processing technique...
March 21, 2017: Nanoscale
L López-Conesa, J M Rebled, D Pesquera, N Dix, F Sánchez, G Herranz, J Fontcuberta, C Magén, M J Casanove, S Estradé, F Peiró
LaNiO3 (LNO) thin films of 14 nm and 35 nm thicknesses grown epitaxially on LaAlO3 (LAO) and (LaAlO3)0.3(Sr2TaAlO6)0.7 (LSAT) substrates are studied using High Resolution Transmission Electron Microscopy (HRTEM) and High Angle Annular Dark Field (HAADF) imaging. The strain state of the films is studied using Geometric Phase Analysis (GPA). Results show the successful in-plane adaptation of the films to the substrates, both in the compressive (LAO) and tensile (LSAT) cases. Through the systematic analysis of HRTEM superstructure contrast modulation along different crystal orientations, localized regions of the monoclinic LaNiO2...
March 20, 2017: Physical Chemistry Chemical Physics: PCCP
R Bhuvaneswari, R John Xavier, M Arumugam
The current study describes a simple, rapid and eco-friendly method for the synthesis of silver nanoparticles (AgNPs) using Excoecaria agallocha (E. agallocha) leaf extract as stabilizer, bioreductant and capping agent. Synthesized AgNPs were characterized by UV-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDX). Generation of AgNPs was initially confirmed with the color change from yellow to dark brown which produces intense absorbance spectra at 440 nm in UV-Vis spectroscopy without any shifting of peaks...
March 2017: Journal of Parasitic Diseases: Official Organ of the Indian Society for Parasitology
Annelies De Wael, Annick De Backer, Lewys Jones, Peter D Nellist, Sandra Van Aert
A hybrid statistics-simulations based method for atom-counting from annular dark field scanning transmission electron microscopy (ADF STEM) images of monotype crystalline nanostructures is presented. Different atom-counting methods already exist for model-like systems. However, the increasing relevance of radiation damage in the study of nanostructures demands a method that allows atom-counting from low dose images with a low signal-to-noise ratio. Therefore, the hybrid method directly includes prior knowledge from image simulations into the existing statistics-based method for atom-counting, and accounts in this manner for possible discrepancies between actual and simulated experimental conditions...
January 25, 2017: Ultramicroscopy
Sigurd Wenner, Lewys Jones, Calin D Marioara, Randi Holmestad
Scanning transmission electron microscopy (STEM) coupled with energy-dispersive X-ray spectroscopy (EDS) is a common technique for chemical mapping in thin samples. Obtaining high-resolution elemental maps in the STEM is jointly dependent on stepping the sharply focused electron probe in a precise raster, on collecting a significant number of characteristic X-rays over time, and on avoiding damage to the sample. In this work, 80kV aberration-corrected STEM-EDS mapping was performed on ordered precipitates in aluminium alloys...
May 2017: Micron: the International Research and Review Journal for Microscopy
Kepeng Song, Kui Du, Hengqiang Ye
Oxide thin films with perovskite structures possess multifunctional properties, while defects in the films usually have significant influences on their physical properties. Here, the atomic structure and chemistry of a[100] dislocation cores in epitaxial La2/3Sr1/3MnO3 films were investigated by aberration-corrected scanning transmission electron microscopy combining with atomically resolved electron energy-loss spectroscopy imaging. The results demonstrated an edge dislocation terminated with Mn columns and significant nonstoichiometry at the dislocation core region...
May 2017: Micron: the International Research and Review Journal for Microscopy
Takashi Ogawa, Geun Won Gang, Minh Thu Thieu, Hyuksang Kwon, Sang Jung Ahn, Tai Hwan Ha, Boklae Cho
Utilization of graphene-supporting films and low-voltage scanning transmission electron microscopy (LV-STEM) in scanning electron microscopy (SEM) is shown to be an effective means of observing unstained nanobio materials. Insulin amyloid fibrils, which are implicated as a cause of type II diabetes, are formed in vitro and observed without staining at room temperature. An in-lens cold field-emission SEM, equipped with an additional homemade STEM detector, provides dark field (DF)-STEM images in the low energy range of 5-30keV, together with secondary electron (SE) images...
May 2017: Micron: the International Research and Review Journal for Microscopy
Urszula Zajączkowska, Peter W Barlow
• Orbital movement of the Moon generates a system of gravitational fields which periodically alters the gravitational force on Earth. This lunar tidal acceleration (Etide) is known to act as an external environmental factor affecting many growth and developmental phenomena in plants. Our study has focused on the lunar tidal influence on stem elongation growth, nutations, and leaf movements of peppermint. • Plants were continuously recorded by time-lapse photography under constant illumination as well in constant illumination following five days of alternating dark-light cycles...
March 3, 2017: Plant Biology
Huashan Li, Shanshan Wang, Hidetake Sawada, Grace G D Han, Thomas Samuels, Christopher S Allen, Angus I Kirkland, Jeffrey C Grossman, Jamie H Warner
We have studied atomic level interactions between single Pt atoms and the surface of monolayer MoS2 using aberration-corrected annular dark field scanning transmission electron microscopy at an accelerating voltage of 60 kV. Strong contrast from single Pt atoms on the atomically resolved monolayer MoS2 lattice enables their exact position to be determined with respect to the MoS2 lattice, revealing stable binding sites. In regions of MoS2 free from surface contamination, the Pt atoms are localized in S vacancy sites and exhibit dynamic hopping to nearby vacancy sites driven by the energy supplied by the electron beam...
March 3, 2017: ACS Nano
Geun Wan Kim, So Young Lee, Ji Won Ha
Bimetallic core-shell gold nanorods (AuNRs) are promising multifunctional orientation probes that can be employed in biological and physical studies. This paper presents the optical properties of single AuNRs coated with palladium (Pd) and platinum (Pt) under scattering-based dark-field (DF) microscopy. Strong longitudinal plasmon damping was observed for the bimetallic AuNRs due to Pd and Pt metals on the AuNR surface. Despite the strong plasmon damping, the bimetallic AuNRs yielded characteristic doughnut-shaped scattering patterns under defocused DF microscopy...
March 13, 2017: Analyst
Magnus Nord, Per Erik Vullum, Ian MacLaren, Thomas Tybell, Randi Holmestad
Scanning transmission electron microscopy (STEM) data with atomic resolution can contain a large amount of information about the structure of a crystalline material. Often, this information is hard to extract, due to the large number of atomic columns and large differences in intensity from sublattices consisting of different elements. In this work, we present a free and open source software tool for analysing both the position and shapes of atomic columns in STEM-images, using 2-D elliptical Gaussian distributions...
2017: Advanced Structural and Chemical Imaging
William M Brewer, Yan Xin, Chris Hatem, David R Diercks, Van Q Truong, Kevin S Jones
This paper reports on the unusual diffusion behavior of Ge during oxidation of a multilayer Si/SiGe fin. It is observed that oxidation surprisingly results in the formation of vertically stacked Si nanowires encapsulated in defect free epitaxial strained SixGe1-x. High angle annular dark field scanning transmission electron microscopy (HAADF-STEM) shows that extremely enhanced diffusion of Ge occurs along the vertical Si/SiO2 oxidizing interface and is responsible for the encapsulation process. Further oxidation fully encapsulates the Si layers in defect free single crystal SixGe1-x (x up to 0...
March 1, 2017: Nano Letters
Hong Zhi Zhang, Rong Sheng Li, Peng Fei Gao, Ni Wang, Gang Lei, Cheng Zhi Huang, Jian Wang
Gold nanorods (GNRs) have opened up promising applications based on their reshaping, due to the fact that a tiny change in shape or size could directly lead to optical changes. Herein, we report chemical reshaping of GNRs induced by the coupling reaction between Au, ferric chloride and thiourea. In the coupling reaction, Fe(3+) oxidizes the GNRs to yield Au(i), which complexes with the thiourea ligand, lowering the Gibbs free energy of the gold species and promoting the reaction equilibrium to enable the chemical reshaping of the GNRs...
February 28, 2017: Nanoscale
Michelle Cua, Edward Haojiang Zhou, Changhuei Yang
Optical microscopy in complex, inhomogeneous media is challenging due to the presence of multiply scattered light that limits the depths at which diffraction-limited resolution can be achieved. One way to circumvent the degradation in resolution is to use speckle- correlation-based imaging (SCI) techniques, which permit imaging of objects inside scattering media at diffraction-limited resolution. However, SCI methods are currently limited to imaging sparsely tagged objects in a dark-field scenario. In this work, we demonstrate the ability to image hidden, moving objects in a bright-field scenario...
February 20, 2017: Optics Express
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
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