115 research outputs found
Graphite Nanoeraser
We present here a method for cleaning intermediate-size (5~50nm)
contamination from highly oriented pyrolytic graphite. Electron beam deposition
causes a continuous increase of carbonaceous material on graphene and graphite
surfaces, which is difficult to remove by conventional techniques. Direct
mechanical wiping using a graphite nanoeraser is observed to drastically reduce
the amount of contamination. After the mechanical removal of contamination, the
graphite surfaces were able to self-retract after shearing, indicating that van
der Waals contact bonding is restored. Since contact bonding provides an
indication of a level of cleanliness normally only attainable in a high-quality
clean-room, we discuss potential applications in preparation of ultraclean
surfaces.Comment: 10 pages, two figure
Rotational cooling of molecules using lamps
We investigate theoretically the application of tailored incoherent
far-infrared fields in combination with laser excitation of a single
rovibrational transition for rotational cooling of translationally cold polar
diatomic molecules. The cooling schemes are effective on a timescale shorter
than typical unperturbed trapping times in ion traps and comparable to
obtainable confinement times of neutral molecules.Comment: 5 pages, 2 figure
Molecular Dynamics Simulation of Sympathetic Crystallization of Molecular Ions
It is shown that the translational degrees of freedom of a large variety of
molecules, from light diatomic to heavy organic ones, can be cooled
sympathetically and brought to rest (crystallized) in a linear Paul trap. The
method relies on endowing the molecules with an appropriate positive charge,
storage in a linear radiofrequency trap, and sympathetic cooling. Two
well--known atomic coolant species, and
, are sufficient for cooling the molecular mass range
from 2 to 20,000 amu. The large molecular charge required for simultaneous
trapping of heavy molecules and of the coolant ions can easily be produced
using electrospray ionization. Crystallized molecular ions offer vast
opportunities for novel studies.Comment: Accepted for publication in Phys. Rev.
Deterministic delivery of externally cold and precisely positioned single molecular ions
We present the preparation and deterministic delivery of a selectable number
of externally cold molecular ions. A laser cooled ensemble of Mg^+ ions
subsequently confined in several linear Paul traps inter-connected via a
quadrupole guide serves as a cold bath for a single or up to a few hundred
molecular ions. Sympathetic cooling embeds the molecular ions in the
crystalline structure. MgH^+ ions, that serve as a model system for a large
variety of other possible molecular ions, are cooled down close to the Doppler
limit and are positioned with an accuracy of one micrometer. After the
production process, severely compromising the vacuum conditions, the molecular
ion is efficiently transfered into nearly background-free environment. The
transfer of a molecular ion between different traps as well as the control of
the molecular ions in the traps is demonstrated. Schemes, optimized for the
transfer of a specific number of ions, are realized and their efficiencies are
evaluated. This versatile source applicable for broad charge-to-mass ratios of
externally cold and precisely positioned molecular ions can serve as a
container-free target preparation device well suited for diffraction or
spectroscopic measurements on individual molecular ions at high repetition
rates (kHz).Comment: 11 pages, 8 figure
Simple top-down preparation of magnetic BiGdFeTiO nanoparticles by ultrasonication of multiferroic bulk material
We present a simple technique to synthesize ultrafine nanoparticles directly
from bulk multiferroic perovskite powder. The starting materials, which were
ceramic pellets of the nominal compositions of
BiGdFeTiO (x = 0.00-0.20), were prepared
initially by a solid state reaction technique, then ground into
micrometer-sized powders and mixed with isopropanol or water in an ultrasonic
bath. The particle size was studied as a function of sonication time with
transmission electron microscopic imaging and electron diffraction that
confirmed the formation of a large fraction of single-crystalline nanoparticles
with a mean size of 11-13 nm. A significant improvement in the magnetic
behavior of BiGdFeTiO nanoparticles compared to
their bulk counterparts was observed at room temperature. This sonication
technique may be considered as a simple and promising route to prepare
ultrafine nanoparticles for functional applications.Comment: 7 pages, 5 figure
Dose and energy dependence of mechanical properties of focused electron beam induced pillar deposits from Cu(C5HF6O2)2
Bending and vibration tests performed inside the scanning electron microscope
were used to mechanically characterize high-aspect pillars grown by focused
electron-beam (FEB) induced deposition from the precursor Cu(C5HF6O2)2.
Supported by finite element (FE) analysis the Young's modulus was determined
from load-deflection measurements using cantilever-based force sensing and the
material density from additional resonance vibration analysis. The pillar
material consisted of a carbonaceous (C, O, F, H containing) matrix which
embeds 5...10 at. % Cu deposited at 5 keV and 20 keV primary electron energy
and 100 pA beam current, depending on primary electron energy. Young's moduli
of the FEB deposits increased from 17+/-6 GPa to 25+/-8 GPa with increasing
electron dose. The density of the carbonaceous matrix shows a dependence on the
primary electron energy: 1.2+/-0.3 g cm-3 (5 keV) and 2.2+/-0.5 g cm-3 (20
keV). At a given primary energy a correlation with the irradiation dose is
found. Quality factors determined from the phase relation at resonance of the
fundamental pillar vibration mode were in the range of 150 to 600 and
correlated to the deposited irradiation energy.Comment: 17 pages, 9 figures, 2 table
FIB-SEM imaging of carbon nanotubes in mouse lung tissue
Ultrastructural characterisation is important for understanding carbon nanotube (CNT) toxicity and how the CNTs interact with cells and tissues. The standard method for this involves using transmission electron microscopy (TEM). However, in particular, the sample preparation, using a microtome to cut thin sample sections for TEM, can be challenging for investigation of regions with agglomerations of large and stiff CNTs because the CNTs cut with difficulty. As a consequence, the sectioning diamond knife may be damaged and the uncut CNTs are left protruding from the embedded block surface excluding them from TEM analysis. To provide an alternative to ultramicrotomy and subsequent TEM imaging, we studied focused ion beam scanning electron microscopy (FIB-SEM) of CNTs in the lungs of mice, and we evaluated the applicability of the method compared to TEM. FIB-SEM can provide serial section volume imaging not easily obtained with TEM, but it is time-consuming to locate CNTs in the tissue. We demonstrate that protruding CNTs after ultramicrotomy can be used to locate the region of interest, and we present FIB-SEM images of CNTs in lung tissue. FIB-SEM imaging was applied to lung tissue from mice which had been intratracheally instilled with two different multiwalled CNTs; one being short and thin, and the other longer and thicker. FIB-SEM was found to be most suitable for detection of the large CNTs (Ø ca. 70 nm), and to be well suited for studying CNT agglomerates in biological samples which is challenging using standard TEM techniques. [Figure: see text] ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00216-013-7566-x) contains supplementary material, which is available to authorized users
Magnetic and Photoluminescent Sensors Based on Metal-Organic Frameworks Built up from 2-aminoisonicotinate
Red Guipuzcoana de Ciencia, Tecnologia e Innovacion
OF218/2018
University of Basque Country
GIU 17/13
Basque Government
IT1005-16
IT1291-19
IT1310-19
Junta de Andalucia
FQM-394
Spanish Ministry of Science, Innovation and Universities (MCIU/AEI/FEDER, UE)
PGC2018-102052-A-C22
PGC2018-102052-B-C21
MAT2016-75883-C2-1-P
European Union (EU)
ESFIn this work, three isostructural metal-organic frameworks based on frst row transition metal ions
and 2-aminoisonicotinate (2ain) ligands, namely, {[M(μ-2ain)2]·DMF}n [MII=Co (1), Ni (2), Zn (3)], are
evaluated for their sensing capacity of various solvents and metal ions by monitoring the modulation
of their magnetic and photoluminescence properties. The crystal structure consists of an open
diamond-like topological 3D framework that leaves huge voids, which allows crystallizing two-fold
interpenetrated architecture that still retains large porosity. Magnetic measurements performed on 1
reveal the occurrence of feld-induced spin-glass behaviour characterized by a frequency-independent
relaxation. Solvent-exchange experiments lead successfully to the replacement of lattice molecules by
DMSO and MeOH, which, on its part, show dominating SIM behaviour with low blocking temperatures
but substantially high energy barriers for the reversal of the magnetization. Photoluminescence studied
at variable temperature on compound 3 show its capacity to provide bright blue emission under UV
excitation, which proceeds through a ligand-centred charge transfer mechanism as confrmed by timedependent DFT calculations. Turn-of and/or shift of the emission is observed for suspensions of 3 in
diferent solvents and aqueous solutions containing metal ions
Time-Dependent Subcellular Distribution and Effects of Carbon Nanotubes in Lungs of Mice
BACKGROUND AND METHODS:Pulmonary deposited carbon nanotubes (CNTs) are cleared very slowly from the lung, but there is limited information on how CNTs interact with the lung tissue over time. To address this, three different multiwalled CNTs were intratracheally instilled into female C57BL/6 mice: one short (850 nm) and tangled, and two longer (4 μm and 5.7 μm) and thicker. We assessed the cellular interaction with these CNTs using transmission electron microscopy (TEM) 1, 3 and 28 days after instillation. RESULTS:TEM analysis revealed that the three CNTs followed the same overall progression pattern over time. Initially, CNTs were taken up either by a diffusion mechanism or via endocytosis. Then CNTs were agglomerated in vesicles in macrophages. Lastly, at 28 days post-exposure, evidence suggesting CNT escape from vesicle enclosures were found. The longer and thicker CNTs more often perturbed and escaped vesicular enclosures in macrophages compared to the smaller CNTs. Bronchoalveolar lavage (BAL) showed that the CNT exposure induced both an eosinophil influx and also eosinophilic crystalline pneumonia. CONCLUSION:Two very different types of multiwalled CNTs had very similar pattern of cellular interactions in lung tissue, with the longer and thicker CNTs resulting in more severe effects in terms of eosinophil influx and incidence of eosinophilic crystalline pneumonia (ECP)
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