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Dark field microscopy

Martin Linck, Peter A Ercius, Jordan S Pierce, Benjamin J McMorran
In the past 15 years, the advent of aberration correction technology in electron microscopy has enabled materials analysis on the atomic scale. This is made possible by precise arrangements of multipole electrodes and magnetic solenoids to compensate the aberrations inherent to any focusing element of an electron microscope. Here, we describe an alternative method to correct for the spherical aberration of the objective lens in scanning transmission electron microscopy (STEM) using a passive, nanofabricated diffractive optical element...
June 12, 2017: Ultramicroscopy
Xueli Wang, Zhiqiang Xie, Huilan Huang, Zhihong Jia, Guang Yang, Lin Gu, Qing Liu
The morphology, composition, and structure of precipitates in an Al-Si-Mg-Hf alloy after heat treatment at 560°C for 20 h were studied by means of C s -corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), energy dispersive X-ray spectrometry (EDS), high-resolution transmission electron microscopy (HRTEM), and first-principle calculations. Precipitates with three kinds of morphologies were observed. The rectangular and square precipitates were predominantly (Si2-x Al x )Hf phases, while the nanobelt-like precipitate is the Si2Hf phase...
June 20, 2017: Microscopy and Microanalysis
M Canillas, B Moreno, E Chinarro, A M Rajnicek
TiO2 is proposed here for the first time as a substrate for neural prostheses that involve electrical stimulation. Several characteristics make TiO2 an attractive material: Its electrochemical behaviour as an insulator prevents surface changes during stimulation. Hydration creates -OH groups at the surface, which aid cell adhesion by interaction with inorganic ions and macromolecules in cell membranes. Its ability to neutralize reactive oxygen and nitrogen species that trigger inflammatory processes confers biocompatibility properties in dark conditions...
October 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
Vitor Brasiliense, Jan Clausmeyer, Alice L Dauphin, Jean-Marc Noël, Pascal Berto, Gilles Tessier, Wolfgang Schuhmann, Frederic Kanoufi
Single particle electrochemistry at a nanoelectrode is explored by dark-field optical microscopy. The analysis of the scattered light allows in situ dynamic monitoring of the electrodeposition of single cobalt nanoparticles down to a radius of 65 nm. Larger sub-micrometer particles are directly sized optically by edges super-localization and the scattered light contains complementary chemical information concerning the particle redox chemistry. This opto-electrochemical approach is used to derive mechanistic insights about electrocatalysis which are not accessible from single particle electrochemistry...
June 19, 2017: Angewandte Chemie
Yoones Kabiri, Adithya N Ananth, Jaco van der Torre, Allard Katan, Jin-Yong Hong, Sairam Malladi, Jing Kong, Henny Zandbergen, Cees Dekker
While graphene may appear to be the ultimate support membrane for transmission electron microscopy (TEM) imaging of DNA nanostructures, very little is known if it poses an advantage over conventional carbon supports in terms of resolution and contrast. Microscopic investigations are carried out on DNA origami nanoplates that are supported onto freestanding graphene, using advanced TEM techniques, including a new dark-field technique that is recently developed in our lab. TEM images of stained and unstained DNA origami are presented with high contrast on both graphene and amorphous carbon membranes...
June 16, 2017: Small
Lin Wei, Yanhong Ma, Xupeng Zhu, Jianghong Xu, Yaxin Wang, Huigao Duan, Lehui Xiao
In this work, with wavelength-resolved dark-field microscopy, the center-of-mass localization information from nanoparticle pairs (i.e., spherical (45 nm in diameter) and rod (45 × 70 nm) shaped gold nanoparticle pairs with different gap distances and orientations) was explored and compared with the results determined by scanning electron microscopy (SEM) measurements. When the gap distance was less than 20 nm, the scattering spectrum of the nanoparticle pair was seriously modulated by the plasmonic coupling effect...
June 15, 2017: Nanoscale
Na Yeon Kim, Hu Young Jeong, Jung Hwa Kim, Gwangwoo Kim, Hyeon Suk Shin, Zonghoon Lee
Transition to a commensurate state changes the local symmetry periodicity on two-dimensional van der Waals superstructures, evoking distinctive properties far beyond individual layers. We investigate the morphology of moiré superstructures of graphene on hexagonal boron nitride (hBN) with a low twist angle (≈0°) through moiré fringe analyses with dark field transmission electron microscopy. The moiré fringes exhibit local variation, suggesting that the interaction between graphene and hBN depends on the stacking configuration and that local transition to the commensurate state occurs through the reduced crystalline mismatch (that is, by lattice stretching and twisting on the graphene lattices)...
June 22, 2017: ACS Nano
Pascal Neibecker, Michael Leitner, Muna Kushaim, Torben Boll, Dalaver Anjum, Tala'at Al-Kassab, Ferdinand Haider
The precipitation mechanism of the δ' (Al3Li) phase in Al-Li alloys has been controversially discussed in recent decades, specifically with respect to a conjectured congruent ordering process. However, kinetics in the Al-Li system does not allow to resolve the intermediate stages of precipitation and hence to experimentally clarify this issue. In this paper, we are revisiting the subject in ternary Al-Cu-Li alloys with pronouncedly slower kinetics, employing Transmission Electron Microscopy, High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy, Differential Scanning Calorimetry and Atom Probe Tomography...
June 12, 2017: Scientific Reports
N Gauquelin, K H W van den Bos, A Béché, F F Krause, I Lobato, S Lazar, A Rosenauer, S Van Aert, J Verbeeck
Nowadays, aberration corrected transmission electron microscopy (TEM) is a popular method to characterise nanomaterials at the atomic scale. Here, atomically resolved images of nanomaterials are acquired, where the contrast depends on the illumination, imaging and detector conditions of the microscope. Visualization of light elements is possible when using low angle annular dark field (LAADF) STEM, annular bright field (ABF) STEM, integrated differential phase contrast (iDPC) STEM, negative spherical aberration imaging (NCSI) and imaging STEM (ISTEM)...
June 3, 2017: Ultramicroscopy
Schindra Kumar Ray, Dipesh Dhakal, Ramesh Prasad Pandey, Soo Wohn Lee
Silver loaded and Er(3+)/Yb(3+) doped BaMoO4 octahedron microcrystals were fabricated by microwave hydrothermal process. The synthesized samples were characterized by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray spectroscopy (EDS), and Ultraviolet-visible diffuse reflection spectroscopy (UV-Vis DRS). The antibacterial application of samples were investigated by visible light irradiation and disk-diffusion method towards representative Gram-negative pathogen (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive pathogen (methicillin resistant Staphylococcus aureus)...
September 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
Timea Nagy-Simon, Andra-Sorina Tatar, Ana-Maria Craciun, Adriana Vulpoi, Maria-Ancuta Jurj, Adrian Florea, Ciprian Tomuleasa, Ioana Berindan-Neagoe, Simion Astilean, Sanda Boca
In this Research Article, we propose a new class of contrast agents for the detection and multimodal imaging of CD19(+) cancer lymphoblasts. The agents are based on NIR responsive hollow gold-silver nanospheres conjugated with antiCD19 monoclonal antibodies and marked with Nile Blue (NB) SERS active molecules (HNS-NB-PEG-antiCD19). Proof of concept experiments on specificity of the complex for the investigated cells was achieved by transmission electron microscopy (TEM). The microspectroscopic investigations via dark field (DF), surface-enhanced Raman spectroscopy (SERS), and two-photon excited fluorescence lifetime imaging microscopy (TPE-FLIM) corroborate with TEM and demonstrate successful and preferential internalization of the antibody-nanocomplex...
June 15, 2017: ACS Applied Materials & Interfaces
C Hamngren Blomqvist, T Gebäck, A Altskär, A-M Hermansson, S Gustafsson, N Lorén, E Olsson
We have used Electron Tomography (ET) to reveal the detailed three-dimensional structure of particulate hydrogels, a material category common in e.g. controlled release, food science, battery and biomedical applications. A full understanding of the transport properties of these gels requires knowledge about the pore structure and in particular the interconnectivity in three dimensions, since the transport takes the path of lowest resistance. The image series for ET were recorded using High-Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM)...
September 2017: Micron: the International Research and Review Journal for Microscopy
Laura Talamini, Martina B Violatto, Qi Cai, Marco P Monopoli, Karsten Kantner, Željka Krpetić, André Perez-Potti, Jennifer Cookman, David Garry, Camila P Silveira, Luca Boselli, Beatriz Pelaz, Tommaso Serchi, Sébastien Cambier, Arno C Gutleb, Neus Feliu, Yan Yan, Mario Salmona, Wolfgang J Parak, Kenneth A Dawson, Paolo Bigini
The transport and the delivery of drugs through nanocarriers is a great challenge of pharmacology. Since the production of liposomes to reduce the toxicity of doxorubicin in patients, a plethora of nanomaterials have been produced and characterized. Although it is widely known that elementary properties of nanomaterials influence their in vivo kinetics, such interaction is often poorly investigated in many preclinical studies. The present study aims to evaluate the actual effect of size and shape on the biodistribution of a set of gold nanoparticles (GNPs) after intravenous administration in mice...
June 27, 2017: ACS Nano
Xin Qin, Shuwen Fang, Lei Zhao, Penghui Shi, Jinchen Fan, Yulin Min, Qunjie Xu, Weifeng Yao
Cobalt super-microparticles anchored on nitrogen-doped graphene (Co-NG) were prepared using an inexpensive method and were tested for heterogeneous oxidation of aniline with peroxymonosulfate (PMS) in aqueous solutions. The crystal structure, morphology, and textural properties of Co-NG hybrids were investigated by various characterization techniques, such as X-ray diffraction, Raman spectroscopy, dark-field scanning transmission electron microscopy and X-ray photoelectron spectroscopy. Electron paramagnetic resonance and classical quenching tests were conducted to investigate the mechanism of PMS activation and aniline oxidation...
May 25, 2017: Science of the Total Environment
M Alania, A De Backer, I Lobato, F F Krause, D Van Dyck, A Rosenauer, S Van Aert
In this paper, we investigate how precise atoms of a small nanocluster can ultimately be located in three dimensions (3D) from a tilt series of images acquired using annular dark field (ADF) scanning transmission electron microscopy (STEM). Therefore, we derive an expression for the statistical precision with which the 3D atomic position coordinates can be estimated in a quantitative analysis. Evaluating this statistical precision as a function of the microscope settings also allows us to derive the optimal experimental design...
December 15, 2016: Ultramicroscopy
Daniele Pullini, Mauro Francesco Sgroi, Agnes Mahmoud, Nicolas Gauquelin, Lorenzo Maschio, Anna Maria Ferrari, Rik Groenen, Cas Damen, Guus Rijnders, Karel Hendrik Wouter van den Bos, Sandra Van Aert, Johan Verbeeck
Heterostructures formed by La0.7Sr0.3MnO3/ZnO (LSMO/ZnO) interfaces exhibit extremely interesting electronic properties making them promising candidates for novel oxide p-n junctions, with multifunctional features. In this work, the structure of the interface is studied through a combined experimental/theoretical approach. Heterostructures were grown epitaxially and homogeneously on 4″ silicon wafers, characterized by advanced electron microscopy imaging and spectroscopy and simulated by ab initio density functional theory calculations...
June 21, 2017: ACS Applied Materials & Interfaces
Monika Tomczyk, Daniel G Stroppa, Ian M Reaney, Paula M Vilarinho
BiFeO3 (BFO) thin films were grown by chemical solution deposition on a range of electrodes to determine their role in controlling the phase formation and microstructure of the films. The crystallization on oxide electrodes followed the sequence: amorphous → Bi2O2(CO3) → perovskite, while those on Pt crystallized directly from the amorphous phase. IrO2 electrodes promoted perovskite phase formation at the lowest temperature and LaNiO3 additionally induced local epitaxial growth. All compositions exhibited fully coherent Fe-rich precipitates within the grain interior of the perovskite matrix, whereas the incoherent Bi2Fe4O9 second phase was also observed at the grain boundaries of BFO grown on Pt electrodes...
June 7, 2017: Physical Chemistry Chemical Physics: PCCP
Xu Wang, Lin-Ying Du, Meng Du, Chao Ma, Jie Zeng, Chun-Jiang Jia, Rui Si
A low-concentration cobalt (∼6 at%) and manganese (∼3 at%) bimetallic oxide catalyst supported on ceria nanorods (CoMnOx/CeO2), as well as its related single metal oxide counterparts (CoOx/CeO2 and MnOx/CeO2) was synthesized via a deposition-precipitation approach. The fresh samples after air-calcination at 400 °C were tested under the reaction conditions of CO oxidation, and showed the following order of reactivity: CoMnOx/CeO2 > CoOx/CeO2 > MnOx/CeO2. X-ray diffraction (XRD) and transmission electron microscopy (TEM) data identified that the structure of the CeO2 support was maintained during deposition of metal (Co, Mn) ions while the corresponding vis-Raman spectra verified that more oxygen vacancies were created after deposition-precipitation than those in pure ceria nanorods...
June 7, 2017: Physical Chemistry Chemical Physics: PCCP
A I Grudyanov, O N Tkacheva, A T Khatagov
The study included 55 patients (24 men and 31 women aged 30-70 years) with chronic periodontal disease and atherosclerosis of brachiocephalic arteries (BCA). Patients in group 1 received only conservative treatment for periodontal disease, while in group 2 both conservative and surgical treatment were performed. The values were evaluated at baseline and 6 months after treatment. Capillaroscopy and laser Doppler flowmetry showed an improvement in periodontal regional vascular network. The level of IL-6 decreased by 3...
2017: Stomatologii︠a︡
Y Daiko, J Schmidt, G Kawamura, S Romeis, D Segets, Y Iwamoto, W Peukert
Surface defects of ZnO nanoparticles were induced via mechanical stressing using a Turbula shaker mixer and a planetary ball mill, and the possibilities for surface modification and functionalization of the ZnO nanoparticles were exemplified by sulfur doping of activated ZnO. Raman spectroscopy reveals that the formation of oxygen vacancies (VO) does not only occur under high stressing conditions in a planetary ball mill but even upon rather 'mild stressing' in the shaker mixer. The temporal evolution of the vacancy concentration in ZnO stressed under different conditions can be described by a model that accounts for stress number and vacancy diffusion with diffusion coefficients of VO of 3...
May 31, 2017: Physical Chemistry Chemical Physics: PCCP
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