3D electron microscopy study of metal particles inside multiwalled carbon nanotubes

The location of palladium nanoparticles on and inside the multiwalled carbon nanotubes channel is presented for the first time using electron tomography (3D TEM). The palladium salt precursor was rapidly sucked inside the nanotube channel by means of capillarity that is favored by the hydrophilic character of the tube wall after acidic treatment at low temperature. Statistical analysis indicates that the palladium particles were well dispersed and the palladium particle size was relatively homogeneous, ranging from 3 to 4 nm regardless of their location within the nanotube, within the resolution limit of the technique for our experimental conditions, i.e., about 2 nm. Three-dimensional TEM analysis also revealed that introduction of foreign elements inside the tube channel is strongly influenced by the diameter of the tube inner channel, i.e., easy filling seems to occur with a tube channel >or=30 nm , whereas with tubes having a smaller channel (<15 nm), almost no filling by capillarity occurred leading to the deposition of the metal particles only on the outer wall of the tube.     

In situ ellipsometric study of copper growth on silicon

Thin copper films are of high interest for interconnect applications. However, optical studies, such as ellipsometry, of metallic thin films are still rare as the measurements are difficult to interpret due to the lack of a transparent range and often island-like growth at very low coverages. We investigated by in situ spectroscopic ellipsometry the growth of thermally evaporated thin copper films on silicon substrates from 0.5 nm to more than 100 nm, a thickness for which bulk-like response is observed. A strong change in the optical response was observed for films thinner than 10 nm as a result of plasmonic effects. The data at each thickness was modeled by employing the effective medium approximation theory. Besides the layer thickness and the void filling fraction, giving the film density, we obtained information about the mean free path of electrons in the thin films and compared it to single crystals. Cu oxidation was studied by deliberately introducing oxygen or air in the chamber, leading to a fast and pronounced change in the optical response. The data analysis provides detailed information on film thickness and quality.     

Microwave synthesis of large few-layer graphene sheets in aqueous solution of ammonia

Few-layer graphene (FLG) sheets with sizes exceeding several micrometers have been synthesized by exfoliation of expanded graphite in aqueous solution of ammonia under microwave irradiation, with an overall yield approaching 8 wt.%. Transmission electron microscopy (in bright-field and dark-field modes) together with electron diffraction patterns and atomic force microscopy confirmed that this graphene material consisted mostly of mono-, bi- or few-layer graphene (less than ten layers). The high degree of surface reduction was confirmed by X-ray photoelectron and infrared spectroscopies. In addition, the high stability of the FLG in the liquid medium facilitates the deposition of the graphene material onto several substrates via low-cost solution-phase processing techniques, opening the way to subsequent applications of the material.      

Synthesis and hydrogen adsorption properties of a new iron based porous metal-organic framework

A new metal-organic framework [Fe₃O(OOC-C₆H₄-COO)₃(H₂O)₃]Cl·(H₂O)_x was synthesized with a specific surface area of 2823 m²/g and a lattice parameter of 88.61 Å. Isostructural with MIL-101, this compound exhibits similar hydrogen adsorption properties, with maximum adsorption capacity of 5.1wt.% H at 77 K. The adsorption enthalpy of hydrogen for MIL-101 and ITIM-1 (MIL-101Fe) at zero coverage was calculated for a wide temperature range of 77 K ÷ 324 K, considering corrections for the variation of hydrogen gas entropy with the temperature. The resulted adsorption enthalpy is 9.4 kJ/mol for MIL-101, in excellent agreement with the value reported in literature from microcalorimetric measurements, and a value of 10.4 kJ/mol at zero coverage was obtained for ITIM-1 (MIL-101Fe).     

High-flux electron beams from laser wakefield accelerators driven by petawatt lasers

Laser wakefield accelerators (LWFAs) are considered to be one of the most competitive next-generation accelerator candidates.In this paper,we will study the potential high-flux electron beam production of an LWFA driven by petawatt-level laser pulses.In our three-dimensional particle-in-cell simulations,an optimal set of parameters gives ～40 nC of charge with 2 PW laser power,thus ～400 kA of instantaneous current if we assume the electron beam duration is 100 fs.This high flux and its secondary radiation are widely applicable in nuclear and QED physics,industrial imaging,medical and biological studies.     

Isolation and Characterization of New Microsatellite Markers for the Invasive Softshell Clam, Mya arenaria (L.) (Bivalvia: Myidae)

The invasive softshell clam (Mya arenaria Linnaeus, 1758) is native to the northwestern region of the Atlantic Ocean. This species has been introduced in the northeast Pacific and along the European coasts, due to intense naval transports and aquaculture, and it is now present in all the European seas. In this paper we describe seven new microsatellite loci for Mya arenaria. The isolated loci are polymorphic with a number of alleles per locus between 6 and 14. The observed and expected heterozygosities ranged from 0.417 to 0.951, and from 0.643 to 0.895, with an average of 0.716 and 0.775, respectively. These microsatellite markers should be useful in analyzing this species' genetic diversity, which could explain various processes of its invasion history.     

Hexahistidine‐Tagged Single‐Walled Carbon Nanotubes (His6‐tagSWNTs): A Multifunctional Hard Template for Hierarchical Directed Self‐Assembly and Nanocomposite Construction

While a hexahistidine affinity tag can be introduced at protein termini or internal sites by standard molecular biology procedures for purification, immobilization, or labeling of proteins, here the versatility of this concept is exploited for the chemical preparation of novel hexahistidine‐tagged single‐walled carbon nanotubes (His₆‐tagSWNTs), a novel hard template useful for solubilizing, assembling, processing, and interfacing SWNTs in aqueous conditions. Water‐soluble and exfoliated His₆‐tagSWNTs are prepared and fully characterized. This functional molecular module is able to interact via robust physisorption (π?π stacking) with the sidewall of SWNTs and combines the versatility of small, water‐soluble reporters (His₆) for hierarchical directed self‐assembly (HDSA) and construction of nanocomposites. It is demonstrated that metal coordination bonds with Ni(II) can be used for the supramolecular self assembly of His₆‐tagSWNTs, generating complex reticulated networks and architectures. The His₆‐tagSWNTs hard template nanohybrid is further utilized for directed self‐assembly with silica nanoparticles. The versatility of the novel hybrids opens a new era for the rational design, smart (bio)functionalization, processing, interfacing, and self assembling of carbon nanotubes for the construction of multicomposites and more complex systems with controllable spatial organization and programmable properties for a wide range of applications in biology, nanoelectronics, and catalysis.     

High temperature stability of platinum nanoparticles on few-layer graphene investigated by In Situ high resolution transmission electron microscopy

eterogeneous catalytic reactions involve the use of highly dispersed active phases such as metal, metal oxide, or metal sulphide nanoparticles on thermally stable supports. Fluctuations of the reaction temperature during the reactions can induce sintering of the particles. The stability of such small particles represents a crucial parameter in the development of new families of catalysts with high activity in many fields. Here we report the stability of platinum nanoparticles (2–3 nm) on a few-layer graphene (FLG) surface as studied by in situ high temperature transmission electron microscopy.     

Sinanodonta woodiana (mollusca: bivalvia: unionidae): isolation and characterization of the first microsatellite markers

Sinanodonta woodiana (Lea, 1834) is a large Unionid species with a real invasion success. It colonized Europe, Central America, the Indonesian Islands and recently North America. The species life cycle involves a larval parasitic stage on freshwater fish species which contributes to the spread of the mussel. In this paper we describe, for the first time, eight polymorphic microsatellite loci for the species Sinanodonta woodiana. The genetic screening of individuals confirmed that all loci were highly polymorphic. The number of alleles per locus ranged from 7 to 14 and the observed heterozygosity ranged from 0.650 to 0.950. These loci should prove useful to study the species population genetics which could help to infer important aspects of the invasion process.     

Molecularly imprinted “bulk” copolymers as selective sorbents for gallic acid

We report the synthesis of molecularly imprinted sorbents, selective for gallic acid. The particles were prepared by using acrylic acid, acrylonitrile, and hydroxyethyl methacrylate as functional monomers, whereas ethyleneglycol dimethacrylate and 1,4‐buthanediol dimethacrylate were used as crosslinkers. Preparation and manipulation protocols were adjusted considering template's nature. To highlight the influence of monomer/crosslinker nature upon imprinted particles, the adsorption capacity, the imprinting factor, and the distribution and selectivity coefficients were calculated. An imprinting factor of 3.53 and a selectivity coefficient of 6.86 were found for hydroxyethyl methacrylate/ethylene glycol methacrylate system. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci. 2013