Search

We present observational evidence that helps classify the non-eclipsing binary system SDSSJ 122405.58+184102.7 as a new member of the SW Sextantis (SW Sex) class. First, from the analysis of the optical light curve, we identify the presence of two periodic signals that develop on different time scales. The first one is the orbital period of 0.167811(1) days (= 4.027464 (3) h) and the second one is the white dwarf spin period of 28.6 minutes. This second period is probably the first evidence for the presence of a magnetic white dwarf in the system. The second evidence is the presence of the HeII λ4886 emission line in its optical spectrum. In this work we interpret the detected periodicities within the context of a magnetic accretion model for SW Sex stars.

In this work, the surface modification of zinc oxide nanoparticles (ZnO-NPs) with 3-glycidyloxy-propyl-trimethoxysilane (GPTMS) was investigated. The ZnO-NPs were synthesized using the physical method of continuous arc discharge in controlled atmosphere (DARC-AC). The surface modification was carried out using a chemical method with constant agitation for 24 h at room temperature. This surface functionalization of zinc oxide nanoparticles (ZnO-NPs-GPTMS) was experimentally confirmed by infrared spectroscopy (FT-IR), TGA, and XRD, and its morphological characterization was performed with SEM. The increase in mechanical bending properties in the two final hybrid materials compared to the base polymers was verified. An average increase of 67% was achieved with a moderate decrease in ductility. In the case of compressive strength, they showed mixed results, maintaining the properties. With respect to thermal properties, it was observed that inorganic reinforcement conferred resistance to degradation on the base material, giving a greater resistance to high temperatures. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

In the last decades, air pollution control has received much attention due to the increase of environmental and health problems. The design of new materials with potential applications in air pollution control systems is a challenge nowadays. In this work, BiOI nanostructured materials were synthesized and used for photocatalytic oxidation of nitric oxide (NO). A microwave-assisted solvothermal method was successfully applied for BiOI synthesis at 126 °C, using ethylene glycol (EG) as a solvent. Several samples were prepared by varying the microwave irradiation time between 5 and 120 min. Resulting materials were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), N2 adsorption-desorption isotherms, diffuse reflectance spectroscopy (DRS) and photoluminescence measurements (PL). The photocatalytic activity of BiOI samples was evaluated in the photo-oxidation reaction of nitric oxide (NO) in gas phase under visible light irradiation. BiOI sample synthesized after 15 min of microwave exposition shows the highest photocatalytic activity, even greater than that obtained when TiO2 Evonik P-25 is used. This nanostructured material was applied into the formulation of two types of materials (ceramic paint and stucco) for its potential use in the construction industry. Preliminary results show that the application of nanostructured BiOI into stucco formulation has a great potential to develop commercial products to remove NO from air.

In this study, the tannins extracted from the Pinus radiata bark were used to develop an active–passive dual paint scheme with intumescent (IN) and fire-resistant (FR) behaviors. The properties of the coating were observed to depend on the concentration of high-molecular-weight tannins (H-MWT) incorporated into the formulation. At high concentrations (13% w/w), the coating exhibits fire-retardant properties due to the generation of a carbonaceous layer, however, at low concentrations (2.5% w/w), it generates an intumescent effect due to the formation of a carbonaceous foam layer. The dual IN–FR scheme was evaluated against fire by flame advance tests, carbonization index, mass loss, and intumescent effect, and was also compared to a commercial coating. The dual scheme presented good mechanical properties with a pull-off adhesion value of 0.76 MPa and an abrasion index of 54.7% at 1000 cycles, when using a coating with a high solid content (&gt, 60%) and the same thickness as those of the commercial coatings. The results of the fire resistance test indicate that the dual scheme generates a protective effect for wood and metal, with an excellent performance that is comparable to that of a commercial intumescent coating.

Thousands of new asteroids are discovered every year and the rate of discovery is by far larger than the determination rate of their physical properties. In 2015 a group of researchers and students of several Mexican institutions have established an observational program to study asteroids photometrically. The program, named Mexican Asteroid Photometry Campaign, is aiming to derive rotation periods of asteroids based on optical photometric observations. Since then four campaigns have been carried out. The results obtained throughout these campaigns, as well as future work, are presented.

The aim of this work was to prepare and characterize color-tunable luminescent nanocomposite fibers composed of CdTe quantum dots (CdTe-QDs) and polylactic acid (PLA) via nanoprecipitation. This method provides a simple procedure to incorporate QDs with various emission wavelengths onto nanofibers’ surfaces. A one-pot microwave irradiation method was employed to prepare green- to red-emitting 3-mercaptopropionic acid (MPA)-capped CdTe-QDs with high luminescence. Microfiber PLA membranes were produced via forcespinning. These nanofibers can integrate the luminescent properties of CdTe-QDs and extend their advantages to fiber-based structures. Ultraviolet-visible spectroscopy (UV–vis) and transmission electron microscopy (TEM) were used to characterize the CdTe-QDs. TEM images revealed that the CdTe-QDs were 4 nm in size. The CdTe-QDs’ effect on the microfibers were characterized morphologically via scanning electron microscopy (SEM), which showed that the average diameter of the CdTe-QDs/PLA nanofibers was 3.5 μm. They were optically analyzed by photoluminescence (PL), absorption spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and confocal fluorescence microscopy. FTIR revealed strong interactions between the MAP stabilizing agents and PLA fibers. These preliminary results demonstrate that these microfibers have potential for biological labeling and diagnostics based on their properties.

We investigated the surface modification of zinc oxide nanoparticles (ZnO-NPs) with 3-aminopropyltriethoxysilane (APTES). The ZnO-NPs were synthesized by the physical method of continuous arc discharge in controlled atmosphere (DARC-AC). The surface modification was performed using a chemical method with constant stirring and reflux for 24 h at room temperature. This surface functionalization of the ZnO nanoparticles (funct-ZnO-NPs) was experimentally confirmed by infrared spectroscopy (FT-IR), Raman spectroscopy, TGA, UV–Visible and XRD, while its morphological characterization was performed by HRTEM. Using Raman spectroscopy, it was possible to study the functionalization process after the change, as well as the appearance of new bands of the molecular vibrations produced by the chemical interaction of the surface of the nanoparticles with the silane coupling agent. Comparing the Raman spectra of the ZnO-NPs, APTES and funct-ZnO-NPs, it was observed that the area between 2700 and 3200 cm −1 related to the vibrations of the CH 2 and CH 3 bonds of the APTES molecule. The funct-ZnO-NPs showed a decrease in the peak intensity, which indicates a deactivation of the degrees of freedom of the APTES at the time of the surface functionalization with the ZnO-NPs, suggesting a redistribution of the APTES CH 2 groups, as they interact with the surface of the ZnO-NPs. The APTES molecule is anchored to the surface of the ZnO-NPs via one or two Si-O-Zn bonds and not by three, as is commonly reported. The above finding is attributable to steric impediment of the side groups of the APTES and the strain of the Si-O-Zn bonds that hinders the trivalent interaction with the surface of the nanostructured ZnO. Similarly, the results obtained by Raman were verified and complemented by means of FT-IR due to the presence of bands at specific wavelengths.

This work reports a new method for large scale production of ZnO nanowires (ZnO-NWs) by microwave assisted thermal decomposition (MATD). This method is simple, economical and reproducible; in addition, the production of material exceeds 95% without using preferential growth precursors. The reaction occurs in only 3 min with minimal energy expenditure. ZnO-NWs produced at 1200 W had diameters ranging between 20 and 70 nm and lengths that varied between 1 and 15 µm, were totally crystalline and showed preferential growth in the [001] direction. Using XRD and HRTEM, it was determined that ZnO presented a hexagonal, wurtzite structure. The relationship between graphite and ZnO, the power of the reaction system and the reactor humidity each played an important role in this method and need to be properly controlled to optimize the production of nanowires. The reactor used allowed for the separation of the reaction products; for that reason, the ZnO-NWs produced had a high degree of purity, as determined by XRD. The photocatalytic activity of ZnO-NWs in methyl orange (MO) decreased as the pH increased; this behavior is common in ZnO because basic pH increased the interaction between the MO and ZnO. The synthesis process, growth mechanisms and photocatalytic activity of ZnO-NWs are discussed in this work.

Nanocomposites and a composite based on poly(butylene adipate-co-terephthalate) (PBAT) were synthesized using commercial copper nanoparticles (Cu-NPs), copper/cuprous oxide nanoparticles (Cu|Cu2O-NPs), and copper sulfate (CuSO4), respectively. The Cu|Cu2O-NPs were synthesized using chemical reduction and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The synthesis of Cu|Cu2O-NPs yielded a mixture of Cu and Cu2O, with metal Cu having a spherical morphology of approximately 40 nm in diameter and Cu2O with a diameter of 150 nm. To prepare the nanocomposites (NCs) and the composite material (MC), the NPs and the CuSO4 salt were incorporated into the PBAT matrix in concentrations of 1, 3, and 5% p/p via an ex situ method. Fourier transform infrared spectroscopy (FTIR), a tensile test, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and agar diffusion assays were used for structural, thermomechanical, and antimicrobial characterization. Results showed that the reinforcements did not modify the chemical structure of the PBAT and only slightly increased the percentage of crystallization. The mechanical and thermal properties of the PBAT did not change much with the addition of fillers, except for a slight increase in tensile strength and thermal stability, respectively. The agar diffusion antimicrobial assays showed that the NCs and MCs had good inhibitory responses against the nonresistant strains Enterococcus faecalis, Streptococcus mutans, and Staphylococcus aureus. The MCs based on CuSO4 had the highest biocidal effect, even against the resistant bacteria Acinetobacter baumannii. Electronic supplementary material The online version of this article (10.1186/s11671-019-2987-x) contains supplementary material, which is available to authorized users.

We report the study of ZnO nanorods (ZnO-NR) decorated with BiOI nanoplatelets by the simple precipitation of BiOI in aqueous solution containing ZnO-NR powders. Likewise, as a reference for the decoration of ZnO-NR, BiOI thin films were prepared by the SILAR technique on RF magnetron-sputtered ZnO thin films. The scanning electron microscopy analysis showed that BiOI grew on the ZnO-NR surfaces in nanoplatelet shape with an order of magnitude smaller in size, with respect to the platelets observed in BiOI thin films. Analysis by X-ray diffraction exhibited the hexagonal P63mc phase of ZnO and the tetragonal P4nmm crystal phase of BiOI. On the other hand, BiOI thin films are nonuniform and strongly adherent and, besides they exhibited the P4nmm tetragonal crystal structure of BiOI, they have highly preferential orientation along (001) direction (9.66°). Optical characterization of ZnO-NR/BiOI by absorbance showed a widened peak slightly shifted to infrared compared with the ZnO-NR absorbance peak, suggesting the increase of the absorption wavelength ranges from the ultraviolet to visible for ZnO-NR. Similarly, the results of the optical characterization by absorbance, for BiOI thin films, indicated the bandgap energy of the samples was between 1.78 eV and 1.88 eV, values previously reported for BiOI.

Incorporation of SnS as a blocking layer at the interface of TiO2 and CH3NH3PbI3(MAPbI3) perovskite has been investigated. With respect to the control, the inclusion of a 3 nm SnS layer via thermal evaporation leads to an improved power conversion efficiency as well as stability, under similar storage conditions. The highest power conversion efficiency of approx. 13.6% is achieved for the champion cell (average 12%) and stability study over the period of 4 weeks revealed the retention of approximately 85% of its initial efficiency (average 83%). The surface photovoltage spectroscopy (SPV) measurements confirmed that the improvement in the photovoltaic performance is due to the lower photogenerated electron lifetime exhibited by devices with the SnS blocking layer which in turn is attributed to the reduction of trap states at the TiO2-perovskite interface, decreasing the interfacial charge recombination. Electrical impedance spectroscopy (EIS) and photoluminescence (PL) spectroscopy, additionally endorse the reduction of traps and recombination centers.

Mixing aqueous silver solutions with aqueous leaf aromatic plant extracts from basil, mint, marjoram and peppermint resulted in the synthesis of quasi-spherical silver nanoparticles in a range of size between 2 and 80 nm in diameter as analyzed by analytical high-resolution electron microscopy. The average size could be controlled by applying heat to the initial reaction system at different rates of heating, and by the specific botanical species employed for the reaction. Increasing the rate of heating resulted in a statistically significant decrease in the size of the nanoparticles produced, regardless of the species employed. This fact was more evident in the case of marjoram, which decreased the average diameter from 27 nm at a slow rate of heating to 8 nm at a high rate of heating. With regard to the species, minimum sizes of

Nanostructured TiN thin films were grown by reactive magnetron sputtering deposition on Si (100) substrate at room temperature. The nanostructured TiN thin films were characterized by X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Scanning Tunneling Microscopy (STM), Atomic Force Microscopy (AFM), resistivity and hydrophobicity tests. The nanostructured TiN thin films had an average grain size 4.6 nm, an average roughness of 1.3 nm, a preferential orientation in the [111] direction and also they showed hydrophobicity Type I. Fil: Solis Pomar, F.. Universidad Autónoma de Nuevo León; México Fil: Nápoles, O.. Universidad de La Habana; Cuba Fil: Vázquez Robaina, Odin. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de La Habana; Cuba Fil: Gutierrez Lazos, C.. Universidad Autónoma de Nuevo León; México Fil: Fundora, A.. Universidad de La Habana; Cuba Fil: Colin, Angel. Universidad Autónoma de Nuevo León; México Fil: Pérez Tijerina, E.. Universidad Autónoma de Nuevo León; México Fil: Melendrez, M. F.. Universidad de Concepción; Chile

In this work, we report a highly adherent, and uniform deposition of nanostructured tellurium. The deposition of the nanostructured tellurium was realized by the dripping of a modified solution of NaHTe based on the dissolution of NaBH4 and tellurium powder in an aqueous solution of NH4OH. This method allowed the relatively simple manipulation of tellurium nanostructures under laboratory ambient, without requiring the use of organic stabilizers. Transmission electron microscopy (TEM) was realized on a powder sample obtained by the reaction between H2Te and aqueous solution of NH4OH. TEM analysis indicated that tellurium nanorods and Y-type nanostructures are grown from tellurium nanoparticles, such as in a hydrothermal system. Then, the nanoparticles serve as seeds for the growth of more extended tellurium nanostructures. Electron diffraction and X-ray diffraction analysis showed that depositions have the hexagonal structure of tellurium highly oriented on (101) direction.

In this work, a new method to obtain zinc oxide nanonails (ZnO-NNs) via microwave plasma-assisted chemical vapor deposition (MAP-CVD) is reported. The ZnO-NNs were grown on cobalt seeds using He as the carrier gas. The cobalt seeds were deposited onto alumina at different distances from the substrate to the precursor material via the sputtering technique. The ZnO-NNs were characterized by SEM, TEM, SAED, HRTEM and EDX. NNs growth was uniform on the substrate surface: the stem of these structures ranged between 250 and 450 nm, the cap ranged between 25–150 nm, and the necks ranged between 30–200 nm. The wide distribution of the NNs dimensions was due to the vapor from the thermal decomposition of ZnO, which is richer in gaseous species of Zn than oxygen, leading to the formation of oxygen vacancies. The rich Zn vapor triggers the growth in a different direction to the shank of the cap forming the NNs, which grows in the direction [1010]. Some structural and experimental aspects are discussed in this paper.

We propose a model of antenna-coupled microbolometer to be included in an array for receiving and detecting long wave infrared (LWIR) electromagnetic radiation. The antenna is joined to microstrip bandpass filters thus forming a single metal structure to define the operation frequency band. The antenna and microstrip filters are modeled in aluminum thin film. The microbolometer is modeled with superconducting niobium, all together on a silicon nitride membrane. The squared pixel structure is designed on a support frame of 20 μm in size. Simulation results for this antenna exhibit a frequency range of operation from 27 to 35 THz and is configured for two arrays, one of 10×10 and the other one of 50×50 elements. The device has been simulated by means of the commercial electromagnetic software (HFSS), which is based on the finite elements method. The predicted values for the figures of merit of this microbolometer are as follows: τ=5.8 ns, Rv=5.3×103 V/W, and D⁎ = 2.07×1010 cmHz/W, respectively.

This work presents results of the optical and structural characterization of oleic acid-stabilized cadmium telluride nanocrystals (CdTe-NC) synthesized by an organometallic route. After being cleaned, the CdTe-NC were dispersed in toluene to obtain an ink-like dispersion, which was drop-cast on glass substrate to deposit a thin film. The CdTe-NC colloidal dispersion as well as the CdTe drop-cast thin films were characterized with regard to the optical and structural properties. TEM analysis indicates that the CdTe-NC have a nearly spherical shape (3.5 nm as mean size). Electron diffraction and XRD diffraction analyses indicated the bulk-CdTe face-centered cubic structure for CdTe-NC. An additional diffraction line corresponding to the octahedral Cd3P2 was also detected as a secondary phase, which probably originates by reacting free cadmium ions with trioctylphosphine (the tellurium reducing agent). The Raman spectrum exhibits two broad bands centered at 141.6 and 162.3 cm−1, which could be associated to the TO and LO modes of cubic CdTe nanocrystals, respectively. Additional peaks located in the 222 to 324 cm−1 range, agree fairly well with the wavenumbers reported for TO modes of octahedral Cd3P2.

In this work, we study the synthesis of monodispersed Fe nanoparticles (Fe-NPs)in situfunctionalized with oleic acid. The nanoparticles were self-assembled by inert gas condensation (IGC) technique by using magnetron-sputtering process. Structural characterization of Fe-NPs was performed by transmission electron microscopy (TEM). Particle size control was carried out through the following parameters: (i) condensation zone length, (ii) magnetron power, and (iii) gas flow (Ar and He). Typically the nanoparticles generated by IGC showed diameters which ranged from ~0.7 to 20 nm. Mass spectroscopy of Fe-NPs in the deposition system allowed the study ofin situnanoparticle formation, through a quadrupole mass filter (QMF) that one can use together with a mass filter. When the deposition system works without quadrupole mass filter, the particle diameter distribution is around +/−20%. When the quadrupole is in line, then the distribution can be reduced to around +/−2%.

In this work cadmium telluride quantum dots (CdTeQDs) were prepared via one-pot synthesis microwave assisted. Afterwards, CdTeQDs/silica (SiO2)/nigrosine (nigro)/poly (styrene co-methyl methacrylate) (PSCMM) fluorescent nanocomposite (CSNP) powders were prepared via ultrasonic treatment and post drying at 60 °C. The samples were characterized by UV–vis absorbance, x-ray diffraction (XRD) and transmission electron microscopy (TEM). Finally, successful printing tests were performed on security paper at 130 °C. These results show the potential of this nanocomposite to be used as security toner. This printing toner configuration is reported for first time.

CdSe nanowires (CdSe-NWs) at large scale were obtained through a simple and clean method. The reaction was carried out without complexing agents which often facilitate the preferential nanostructure growth. In this work, CdSe-NWs with lineal and zigzag shape around 40 and 130 nm in diameter with a wurtzite-type structure were synthesized. Quantitative EDX analysis indicated the stoichiometric formation of CdSe, while both HRTEM and HAADF-STEM analysis ruled out the presence of other phases such as CdO or nanotubes formation, respectively. Diameter and length of the nanowires varied with the reaction time and temperature. This synthesis method makes the nanostructures purification process easier and also is non-toxic and its high conversion make it an efficient method for obtaining CdSe-NWs.

In the present manuscript we present the feasibility of two different routes to obtain metal nanoparticles: (1) inert gas deposition technique (IGC) and (2) chemical routes. These two routes can enable the production of metal nanoparticles with a well-controlled size and shape distribution. In addition, Co/Au and Pd/Au nanoparticles have been deposited on three different grids with the aim of studying the coalescence of the different metals. The as-synthesized materials, that initially were forming isolated, core–shell, were sintered by thermal treatment (Co/Au) or by strong electron beam irradiation and the subsequent characterization was carried out in situ in an aberration corrected STEM.

The fabrication of ZnO (80 nm) thin film was achieved by hybrid atomic layer deposition (ALD) to prevent the reaction between the reactants and conductive layer of the substrates. ZnO nanorods (ZnO-NRs) growth over the substrates was performed by wet chemical procedure in which Zn(NO3)2 and hexamethylenetetramine were used as the precursors. HR-TEM, SAED, FE-SEM, X-ray diffraction (XRD), and UV–Vis spectroscopy were employed to characterize the ZnO-NRs samples on the substrates. XRD and HR-TEM analyses confirmed that the ZnO nanorod structure is hexagonal wurtzite type with growth in the [0001] direction. Length and thickness of the ZnO-NRs ranged between 45 and 90 nm and 480 and 600 nm, respectively. It was observed that the growth rate of NRs in [0001] direction is 10 times higher than in [1000] direction. The growth mechanism and resulted dimensions of nanorods are function of the synthesis parameters (in hybrid ALD process) such as reaction time, temperature, precursor molar ratio, and thickness of ZnO film.

Zinc Oxide nanowires (ZnO-NWs) were grown by vapor-liquid-solid (VLS) through chemical vapor deposition (CVD) with Au/Pd nanoparticles (Au/Pd-NPs) as catalyst. (Au/Pd)-NPs of 5 nm were synthesized by inert gas condensation technique (IGC), deposited on silicon substrates and characterized by atomic force microscopy (AFM). The substrate with the catalytic seeds was introduced in the reaction system where the ZnO-NWs were grown under different conditions such as: system pressure, position of the substrates with respect to the precursor material source, growth time and temperature. The nanostructures obtained were characterized by scanning electron microscopy (SEM), energy dispersed x-ray spectroscopy (EDX), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The growth parameters and the effect of catalyst nanoparticles coalescence on the ZnO-NWs dimensions is also discussed in this work.

In the present work, the study of semiconducting Ce(1-x)MXO2 (M=Ru, In) solid-solutions nanostructures with application to gas sensors is addressed. Nanostructured powers were prepared by means of the sol-gel route. The electrical resistance of obtained materials under different conditions of time, concentration and temperature in CO presence was tested. These systems were characterized using x-ray diffraction, SEM microscopy and surface area measurements. The solid solutions demonstrated good sensorial response at low temperatures, as well as fast response as a function of time. Our results show that these novel materials can be potentially applied as gas sensors.

We study the assembling of small gold clusters subject to collisions and close contact coalescence by using molecular dynamics simulations to simulate events that occur typically in the sputtering process of synthesis. Our results support the notion that the kinetics of coalescence processes strongly determine the geometry and structure of the final particle. While impact velocities, relative orientations, and the initial shape of the interacting particles are unlikely to strictly determine the structural details of the newly formed particle, we found that high initial temperatures and/or impact velocities increase the probability of appearance of icosahedral-like structures, Wulff polyhedra are likely to be formed as a product of the interactions between nanospheres, while the appearance of fcc particles of approximately cuboctahedral shape is mainly due to the interaction between icosahedra.

In this work nanostructured PbS thin films were deposited on glass substrates at room temperature by radio frequency sputtering technique varying the power from 50 to 150 W while the other parameters were kept constant (Argon flow at 80 sccm for 30 min). It was observed by x-ray diffraction that they have a preferential growth in the (200) direction. Through atomic force microscopy (AFM) it was proved that the films present a nanostructured growth, with particle size between 6 and 8 nm. So it can be said that nanostructured thin films of PbS have been obtained by physical methods at room temperature for future application in solar cells.

The design and optical characterization by UV–vis transmittance of ultrathin low-emissivity (low-e) windows by reactive sputtering are reported. Two heterostructures on a glass substrate were considered for the low-e windows. The first heterostructure is Si3N4/TiO2/ZnO/Ag/SnO2/Si3N4 and the second is Si3N4/Ag/Si3N4. The transmittance and reflectance of these heterostructures were simulated to determine the required thickness of each layer. The first heterostructure exhibited maximum transmittance of 85% at 550 nm, slightly higher than the one determined by simulation and less than 50% transmittance in the near-infrared region (900 nm). The second heterostructure exhibited transmittance greater than 86% at 550 nm and

Bimetallic nanoparticles of AuPd were synthesized using the inert gas condensation technique, where the material is sputtered from a target and the particles are formed in an inert condensation zone. Throughout the synthesis process and jointly with the control of the atmosphere conditions, the region after the condensation chamber was kept at a fixed temperature, and several experimental runs were performed at 700 and 1000 °C. The synthesis conditions were set to produce particles of 5 nm of diameter, and almost all of the resulting nanoparticles were icosahedral in shape with small deviations from the mean size. We analyzed the particles by high-angle annular dark field and bright field scanning electron microscopy imaging with a resolution high enough to acquire atomic detail and to measure the distance between planes. From the micrographs and their fast Fourier transform patterns, we found that the lattice detail depends on the thermal treatment with larger lattice fringe displacements in the particles produced at 700 °C. Electron energy loss spectroscopy analysis in one and two dimensions shows that irrespective of the temperature the particles keep their icosahedral shape, and both chemical species are distributed nonuniformly all over the volume of the particles, but without forming core-shell structures.

Formation of NiCr nanorings out of 2-3 nm NiCr nanoparticles prepared by DC magnetron sputtering with inert gas condensation is reported. An RF quadrupole mass filter has been used to get the particle size distribution and control the particle size in the plasma stream of grown material. The depositions are made on silicon substrates at room temperature under a helium and argon atmosphere of varying composition. By optimizing the He-Ar composition, magnetron power and the condensation zone, the particle size distribution is narrowed. Magnetic characterization determines that every single nanoparticle possesses a single magnetic domain that influenced their arrangement on the substrate. These arrangements were particularly in ring like structures. Particles join together while being deposited to form rings with a ~100 nm diameter. Particle density and agglomeration phenomena depend on the substrate’s time of exposure to the NiCr nanoparticle source coming from the target.

High resolution transmission electron microscopy analysis of two‐layered graphene yielded Moire patterns induced by Pt atoms/clusters located at the top of one of the layers, which induced rotation between planes. The rotations measures varied between three and five degrees. Theoretical analysis was performed using an extended Huckel tight‐binding scheme on two‐layered graphene with either containing two‐carbon atom vacancies or with two Pt atoms, with a cluster of 6 Pt atoms or with a cluster of 13 Pt atoms located at the top of one of the graphene layers. In most of the cases, the system remains semimetallic, except when a cluster of 6 Pt atoms was located on the surface of one of the graphene layers. For this case, the system behaves as a semiconductor with an energy gap Eg ∼ 0.05 eV. Furthermore, energy bands as well as total and projected. Density of States were evaluated for each case in order to provide more information on the electronic behavior on the material under investigation.

Silver tetrahedral nanoparticles (NP) were synthesized using the inert gas condensation technique. We performed morphological and optical characterization of the nanoparticles (NPs) using atomic force microscopy (AFM), mass spectroscopy (MS), and UV-visible spectroscopy. The Ag NPs were produced by modified magnetron sputtering, followed by thermalization and condensation in a high pressure zone. Along the synthesis process, the size of the NPs was controlled through the handling of the gas flow (Ar and He), the magnetron power, and the length of the aggregation zone. We optimized the synthesis parameters to obtain a peak on the size distribution of Ag NPs around of 5 nm (as measured with AFM and MS). The AFM measurements show that the particles have tetrahedral shape, with a fair correspondence with a 2925-atoms ideal tetrahedron. We performed a set of Molecular Dynamics (MD) calculations using the Embedded Atom potential model to simulate the dynamics of particles with different shapes, obtaining that, at sizes close to that of the particles produced experimentally, the tetrahedra may be as energetically stable as cuboctahedra of roughly the same size, and that their melting point is below but close to that of the bulk. We also found that both the size and shape of the nanoparticles determine the shift of the UV-visible absorption spectrum. Finally, we observed the formation of atomic islands above the faces of the Ag tetrahedral NPs, in agreement with the results obtained from the MD simulations.

A set of AlN films were deposited by reactive direct current (DC) magnetron sputtering. Films were analyzed with X-ray diffraction and Auger Electron Spectroscopy (AES). There is a correlation between deposition parameters and crystal growth. Depending on the deposition parameters, films can present a hexagonal würzite (P6mm) or cubic zinc-blend (Fm3m) microstructure. Oxygen appears to induce on films a degree of amorphous growth and a distortion of the lattice parameters. For the film with cubic microstructure, AES transitions detected near the surface level at 56 eV and 66 eV were attributed to aluminum-oxide ( Al xOy), AlN , and metallic Al .

Gold/Palladium nanoparticles were fabricated by inert-gas condensation on a sputtering reactor. With this method, by controlling both the atmosphere on the condensation chamber and the magnetron power, it was possible to produce nanoparticles with a high degree of monodispersity in size. The structure and size of the Au/Pd nanoparticles were determined by mass spectroscopy, and confirmed by atomic force microscopy and electron transmission microscopy measurements. The chemical composition was analyzed by X-ray microanalysis. From these measurements we confirmed that with the sputtering technique we are able to produce particles of 1, 3, and 5 nm on size, depending on the choice of the synthesis conditions. From TEM measurements made both in the regular HREM, as well as in STEM-HAADF mode, we found that the particles are icosahedral in shape, and the micrographs show no evidence of a core-shell structure, in contrast to what is observed in the case of nanoparticles prepared by chemical synthesis.

The defect structure of bimetallic nanoparticles differs from that of particles made of a single atomic species. Using high resolution TEM imaging along with molecular dynamics simulations, it is possible to investigate the nature and features of these defects. The definition of a local order parameter allows one to locate regions with different kinds of stacking on the simulated nanoparticles and thus to make a direct comparison with the experimental observations.

We performed a study on bimetallic Au/Pd nanoparticles using aberration corrected electron microscopy along with molecular dynamics simulations to investigate the features of specific atomic sites at the surface, which can be related to the high catalytic activity properties of the particles. The calculations mimic the growth of nanoparticles through a cooling process from a molten solid to a crystalline structure at room temperature. We found that the final structure for the alloy particles is neither a cuboctahedral nor an icosahedral, but a complex structure that has a very rough surface and unique isolated Pd sites surrounded by Au atoms. We also found that there is predominance of three specific Pd sites at the surface, which can be directly related to the catalytic activity of the nanoparticles.

A technique to study several regions of plasma produced by laser ablation in a single laser pulse is presented. The technique is based on a field spectrograph, an instrument where the image of the plasma is captured with a number of fibers in a user defined array, and then projected into the one-dimensional slit of a spectrograph. With this instrument, we can obtain the spectra of a discrete number of regions in the plume and reconstruct the image of the plasma at different wavelengths. Several examples of interest in the field of pulsed laser deposition are given.

To date, 17 circumbinary planets have been discovered. In this paper, we focus our attention on the stability of the Kepler circumbinary planetary systems with only one planet, i.e. Kepler-16, Kepler-34, Kepler-35, Kepler-38, Kepler-64 and Kepler-413. In addition to their intrinsic interest, the study of such systems is an opportunity to test our understanding of planetary system formation and evolution around binaries. The investigation is done by means of numerical simulations. We perform numerical integrations of the full equations of motion of each system with the aim of checking the stability of the planetary orbit. The investigation of the stability of the above systems consists of three numerical experiments. In the first one we perform a long term (1Gyr) numerical integration of the nominal solution of the six Kepler systems under investigation. In the second experiment, we look for the critical semimajor axis of the six planetary orbits, and finally, in the third experiment, we construct two dimensional stability maps on the eccentricity-pericentre distance plane. Additionally, using numerical integrations of the nominal solutions we checked if this solutions were close to the exact resonance., Comment: 11 pages, 11 figure

Solving the statistical equilibrium equations we find line intensity ratios of C III, N III, O III, Si III, and Al III in the visible and ultraviolet range, that are sensitive to electron density and/or temperature in the regime commonly found in pulsed laser deposition. For thin film deposition, the plasma density is between 1012 and 1018 cm−3 and the temperature is close to 104 K. Our results are consistent with experimental data on Al II and Al III, previously reported in the literature. These line intensity ratios are a promising tool to diagnose the physical state of plasmas generated through laser ablation in thin film deposition techniques.