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Dark field microscopy

Wei Wang
Nanomaterials exhibit structural and functional heterogeneity among individual nanoparticles, thus requiring a capability to study single nanoparticles. While electron microscopes often provide static images of their chemical composition, morphology and structure, imaging the chemical activity of single nanoparticles is highly desirable for exploring the structure-activity relationship via a bottom-up strategy, to understand their microscopic reaction mechanisms and kinetics, and to identify a minority subpopulation with extraordinary activity...
March 15, 2018: Chemical Society Reviews
Yohei Ishida, Akihiro Morita, Tomoharu Tokunaga, Tetsu Yonezawa
We herein present the preparation of short, bulky cationic thiolate (thiocholine) protected fluorescent Au nanoclusters via sputter deposition over a liquid polymer matrix. The obtained Au nanoclusters showed near-infrared fluorescence and had an average core diameter of 1.7 ± 0.6 nm, which is too large compared with that of the reported fluorescent Au nanoclusters prepared via chemical means. We revealed the mechanism of formation of this unique material using single-particle electron microscopy, optical measurements, X-ray photoelectron spectroscopy (XPS), and high-performance liquid chromatography fractionations...
March 12, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Tsunetomo Yamada, Takayuki Kojima, Eiji Abe, Satoshi Kameoka, Yumi Murakami, Peter Gille, An Pang Tsai
The atomic structure of a 0.2 atom % Pt-doped complex metallic alloy, monoclinic Al13 Fe4 , was investigated using a single crystal prepared by the Czochralski method. High-angle annular dark-field scanning transmission electron microscopy showed that the Pt atoms were dispersed as single atoms and substituted at Fe sites in Al13 Fe4 . Single-crystal X-ray structural analysis revealed that the Pt atoms preferentially substitute at Fe(1). Unlike those that have been reported, Pt single atoms in the surface layers showed lower activity and selectivity than those of Al2 Pt and bulk Pt for propyne hydrogenation, indicating that the active state of a given single-atom Pt site is strongly dominated by the bonding to surrounding Al atoms...
March 6, 2018: Journal of the American Chemical Society
Aijuan Han, Wenxing Chen, Shaolong Zhang, Maolin Zhang, Yunhu Han, Jian Zhang, Shufang Ji, Lirong Zheng, Yu Wang, Lin Gu, Chen Chen, Qing Peng, Dingsheng Wang, Yadong Li
A novel polymer encapsulation strategy to synthesize metal isolated-single-atomic-site (ISAS) catalysts supported by porous nitrogen-doped carbon nanospheres is reported. First, metal precursors are encapsulated in situ by polymers through polymerization; then, metal ISASs are created within the polymer-derived p-CN nanospheres by controlled pyrolysis at high temperature (200-900 °C). Transmission electron microscopy and N2 sorption results reveal this material to exhibit a nanospheric morphology, a high surface area (≈380 m2 g-1 ), and a porous structure (with micropores and mesopores)...
March 6, 2018: Advanced Materials
Luca Luzzi, Federico Franchi, Annarita Dapoto, Marco Ghisalberti, Roberto Corzani, Daniele Marrelli, Luca Marchetti, Piero Paladini, Sabino Scolletta
Background: In the treatment of malignant pleural mesothelioma the Hyperthermic Intra THOracic Chemotherapy (HITHOC) can improve the efficacy of pleurectomy and decortication with a local cytotoxic effect. However its biological impact in patient's hemodynamic and microcirculatory changes were rarely investigated. Aim of this study is to describe our experience with HITHOC after pleurectomy and decortication evaluating the role of sublingual video-microscopy in assessing the microcirculatory changes in the perioperative period...
January 2018: Journal of Thoracic Disease
A Sett, D Das, D Banerjee, U K Ghorai, N S Das, B Das, K K Chattopadhyay
Zinc oxide (ZnO) nanorods (NRs) wrapped with graphitic carbon nitride (GCN) nanosheet (NS) hybrids have been synthesized by a simple chemical process. The as-prepared samples are characterized by X-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy, Fourier transformed infrared spectroscopy, UV-Vis spectroscopy and photoluminescence spectroscopy. The images obtained from the transmission electron microscopic study and the existence of C-N stretching modes as observed from Fourier transform infrared spectroscopy confirm the successful attachment of GCN NSs onto the ZnO NRs...
March 5, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Rui Yang, Shuwen Liu, Zhenjie Wu, Ying Tan, Shuqing Sun
In this work, we developed a robust and ultrasensitive bio-sensor based on the target-aptamer recognition strategy and microscopic enumeration of gold nanoparticles (AuNPs) using dark field microscopy (DFM). The aptasensor with a core-shell structure consisting of a magnetic bead (MB), aptamer and AuNPs was fabricated by complementary hybridization of the DNA probe on the AuNPs surface to the aptamer coupled to the MB. Upon addition of the target molecule, the strong interaction between the aptamer and the target molecule, thrombin, results in the release of the AuNPs from the MB...
May 15, 2018: Talanta
Niels de Jonge, Andreas Verch, Hendrix Demers
The spatial resolution of aberration-corrected annular dark field scanning transmission electron microscopy was studied as function of the vertical position z within a sample. The samples consisted of gold nanoparticles (AuNPs) positioned in different horizontal layers within aluminum matrices of 0.6 and 1.0 µm thickness. The highest resolution was achieved in the top layer, whereas the resolution was reduced by beam broadening for AuNPs deeper in the sample. To examine the influence of the beam broadening, the intensity profiles of line scans over nanoparticles at a certain vertical location were analyzed...
February 2018: Microscopy and Microanalysis
W J Clough, P R Little, A Hodge, V C Chapman, D K Holz
AIMS: To evaluate a multivalent leptospiral and clostridial vaccine for prevention of renal colonisation and urinary shedding in sheep, following experimental challenge with New Zealand strains of Leptospira borgpetersenii serovar Hardjo type Hardjobovis and Leptospira interrogans serovar Pomona. METHODS: Two separate but similarly designed studies were conducted. In both studies, Romney cross lambs, aged 9-11 weeks, were randomly allocated to a vaccinated group and a control group...
February 19, 2018: New Zealand Veterinary Journal
Margarita Lopez-Fernandez, Maria Romero-González, Alix Günther, Pier L Solari, Mohamed L Merroun
This study presents the effect of aqueous uranium speciation (U-hydroxides and U-hydroxo-carbonates) on the interaction of this radionuclide with the cells of the yeast Rhodotorula mucigilanosa BII-R8. This strain was isolated from Spanish bentonites considered as reference materials for the engineered barrier components of the future deep geological repository of radioactive waste. X-ray absorption and infrared spectroscopy showed that the aqueous uranium speciation has no effect on the uranium binding process by this yeast strain...
February 9, 2018: Chemosphere
Lisa V Brown, Marcelo Davanco, Zhiyuan Sun, Andrey V Kretinin, Yiguo Chen, Joseph Robert Matson, Igor Vurgaftman, Nicholas Sharac, Alexander Giles, Michael M Fogler, Takashi Taniguchi, Kenji Watanabe, Kostya S Novoselov, Stefan A Maier, Andrea Centrone, Joshua D Caldwell
The inherent crystal anisotropy of hexagonal boron nitride (hBN) provides the ability to support hyperbolic phonon polaritons, i.e. polaritons that can propagate with very large wavevectors within the material volume, thereby enabling optical confinement to exceedingly small dimensions. Indeed, previous research has shown that nanometer-scale truncated nanocone hBN cavities, with deep subdiffractional dimensions, support three-dimensionally confined optical modes in the mid-infrared. Due to optical selection rules only a few of the many theoretically predicted modes have been observed experimentally via far-field reflection and scattering-type scanning near-field optical microscopy (s-SNOM)...
February 16, 2018: Nano Letters
Tobias Heil, Gordon J Tatlock
This publication is a systematic investigation of the effect the improvement of dark-reference images has on the resulting bright-field images. For this, data were acquired with three different charge-coupled device cameras attached to two different transmission electron microscopes. Multi-frame acquisitions and methods to correct x-ray noise are introduced and quantified as options to improve the dark-reference images. Furthermore, the influence of x-ray noise on transmission electron microscopy measurements is discussed and observations on its composition are shared...
February 13, 2018: Microscopy
Rui Yan, Seonah Moon, Samuel J Kenny, Ke Xu
As an elegant integration of the spatial and temporal dimensions of single-molecule fluorescence, single-molecule localization microscopy (SMLM) overcomes the diffraction-limited resolution barrier of optical microscopy by localizing single molecules that stochastically switch between fluorescent and dark states over time. While this type of super-resolution microscopy (SRM) technique readily achieves remarkable spatial resolutions of ∼10 nm, it typically provides no spectral information. Meanwhile, current scanning-based single-location approaches for mapping the positions and spectra of single molecules are limited by low throughput and are difficult to apply to densely labeled (bio)samples...
February 14, 2018: Accounts of Chemical Research
Fernando Menegatti de Melo, Sabrina da Nobrega Almeida, Noemi Saori Uezu, Carlos Alberto Ospina Ramirez, Antonio Domingues Dos Santos, Henrique Eisi Toma
The extraction of dysprosium (Dy3+) ions from aqueous solution was carried out successfully, using magnetite (Fe3O4) nanoparticles functionalized with diethylenetriaminepentaacetic acid (MagNP@DTPA). The process was monitored by energy dispersive X-ray fluorescence spectroscopy, as a function of concentration, proceeding according to a Langmuir isotherm with an equilibrium constant of 2.57 × 10-3 g(MagNP) L-1 and a saturation limit of 63.2 mgDy/gMagNP. The presence of paramagnetic Dy3+ ions attached to the superparamagnetic nanoparticles led to an overall decrease of magnetization...
June 1, 2018: Journal of Nanoscience and Nanotechnology
Quanchen Feng, Shu Zhao, Dongsheng He, Shubo Tian, Lin Gu, Xiaodong Wen, Chen Chen, Qing Peng, Dingsheng Wang, Yadong Li
Strain engineering has been a powerful strategy to finely tune the catalytic property of materials. We report a tensile-strained 2-3-atomic-layer Pt on intermetallic Pt3Ga (AL-Pt/Pt3Ga) as an active electrocatalysts for methanol oxidation reaction (MOR). Atomic-resolution high-angle annular dark-field scanning transmission electron microscopy characterization showed that the AL-Pt possessed a 3.2% tensile strain along the [001] direc-tion while had a negligible strain along the [100]/[010] direction. For MOR, this tensile strained AL-Pt electrocatalyst showed obviously higher specific activity (7...
February 12, 2018: Journal of the American Chemical Society
Valeria Rodríguez-Fajardo, Vanesa Sanz, Ignacio de Miguel, Johann Berthelot, Srdjan S Aćimović, Rafael Porcar-Guezenec, Romain Quidant
Noble metal nanoparticles (NPs) supporting localized surface plasmon resonances are widely used in the context of biotechnology as optical and absorption contrast agents with great potential applicability to both diagnostics and less invasive therapies. In this framework, it is crucial to have access to simple and reliable microscopy techniques to monitor the NPs that have internalized into cells. While dark field (DF) microscopy takes advantage of the enhanced NP scattering at their plasmon resonance, its use in cells is limited by the large scattering background from the internal cell compartments...
February 12, 2018: Nanoscale
Linda Turner, Howard C Berg
We describe labeling of bacteria with amino-specific or sulfhydryl-specific Alexa Fluor dyes, methods that allow visualization of flagellar filaments, even in swimming cells. Bacterial flagellar filaments are long (~10 μm), but of small diameter (~20 nm), and their rotation rates are high (>100 Hz), so visualization is difficult. Dark-field microscopy works well with isolated filaments, but visualization in situ is hampered by light scattered from cell bodies, which obscures short filaments or the proximal ends of long filaments...
2018: Methods in Molecular Biology
T Nagy-Simon, M Potara, A-M Craciun, E Licarete, S Astilean
Due to the good transparency of the human tissue in the biological spectral window, near-infrared (NIR)-dye loaded nanosystems enable more effective light-activated therapy and better contrast imaging with major impact on nanomedicine. Herein, we prepare Pluronic coated gold nanoparticles incorporating the hydrophobic NIR dye, IR780 iodide (GNP-Plu-IR780) to provide water-solubility and stability and demonstrate the proficiency of combining photodynamic and photothermal therapeutic activity with surface-enhanced resonance Raman scattering (SERRS) imaging facility...
February 3, 2018: Journal of Colloid and Interface Science
Emrah Yücelen, Ivan Lazić, Eric G T Bosch
Using state of the art scanning transmission electron microscopy (STEM) it is nowadays possible to directly image single atomic columns at sub-Å resolution. In standard (high angle) annular dark field STEM ((HA)ADF-STEM), however, light elements are usually invisible when imaged together with heavier elements in one image. Here we demonstrate the capability of the recently introduced Integrated Differential Phase Contrast STEM (iDPC-STEM) technique to image both light and heavy atoms in a thin sample at sub-Å resolution...
February 8, 2018: Scientific Reports
Paula Zamora-Perez, Dionysia Tsoutsi, Ruixue Xu, Pilar Rivera Gil
We review how the hyperspectral dark field analysis gives us quantitative insights into the manner that different nanoscale materials interact with their environment and how this relationship is directly expressed in an optical readout. We engage classification tools to identify dominant spectral signatures within a scene or to qualitatively characterize nanoparticles individually or in populations based on their composition and morphology. Moreover, we follow up the morphological evolution of nanoparticles over time and in different biological environments to better understand and establish a link between the observed nanoparticles' changes and cellular behaviors...
February 6, 2018: Materials
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