Increase In Number Of Atoms Research Articles

Repetitively Coupled Chemical Reduction and Galvanic Exchange as a Synthesis Strategy for Expanding Applicable Number of Pt Atoms in Dendrimer-Encapsulated Pt Nanoparticles.

In this study, we report the controllable synthesis of dendrimer-encapsulated Pt nanoparticles (Pt DENs) utilizing repetitively coupled chemical reduction and galvanic exchange reactions. The synthesis strategy allows the expansion of the applicable number of Pt atoms encapsulated inside dendrimers to more than 1000 without being limited by the fixed number of complexation sites for Pt2+ precursor ions in the dendrimers. The synthesis of Pt DENs is achieved in a short period of time (i.e., ∼10 min) simply by the coaddition of appropriate amounts of Cu2+ and Pt2+ precursors into aqueous dendrimer solution and subsequent addition of reducing agents such as BH4-, resulting in fast and selective complexation of Cu2+ with the dendrimers and subsequent chemical reduction of the complexed Cu2+ while uncomplexed Pt2+ precursors remain oxidized. Interestingly, the chemical reduction of Cu2+, leading to the formation of Cu nanoparticles encapsulated inside the dendrimers, is coupled with the galvanic exchange of the Cu nanoparticles with the nearby Pt2+. This coupling repetitively proceeds until all of the added Pt2+ ions form into Pt nanoparticles encapsulated inside the dendrimers. In contrast to the conventional method utilizing direct chemical reduction, this repetitively coupled chemical reduction and galvanic exchange enables a substantial increase in the applicable number of Pt atoms up to 1320 in Pt DENs while maintaining the unique features of DENs.

Systematic Observation of EUV Spectra from Highly Charged Lanthanide Ions in the Large Helical Device

We have systematically observed extreme ultraviolet (EUV) spectra from highly charged ions of nine lanthanide elements with atomic numbers from 60–70 in optically thin plasmas produced in the Large Helical Device (LHD). Discrete spectral features with isolated lines from relatively higher charge states around Cu-like ions are observed under high temperature conditions around 2 keV, while narrowed quasicontinuum features from charge states around Ag-like ions are observed under low temperature conditions below 1 keV. The positions of the lines and the quasicontinuum features systematically move to shorter wavelengths as the atomic number increases. The wavelengths of the main peaks in the quasicontinuum features agree well with those of singlet transitions of Pd-like ions reported previously. We have easily identified discrete spectral lines from Cu-like and Ag-like ions, some of which are experimentally identified for the first time in the LHD. Their wavelengths are compared with theoretical calculations using a GRASP family of atomic codes. The theoretical values are synthesized to the LHD experimental data for the cases of Ag- and Pd-like ions.

Forward Yields of the Secondary Light Nuclei in CC-collisions at Beam Energy 20.5 GeV/n on the Accelerator U-70 in Comparison with Models UrQMD, FTFP-BERT-EMV and QGSP-FTFP-BERT-EMV in the Framework of Geant4

The zero angle production of light nuclei has been studied in CC-interactions at beam energy 20.5 GeV/n on accelerator U-70. The measurements were performed with employing of the beamline no. 22 as spectrometer of secondary particles with verying its rigidity from 10 to 70 GeV/c. We observed secondary protons and deuterons with momenta above kinematic limit of NN-interactions. The measured dependence of forward yields on momentum are compared with the model predictions in the framework of Geant4. The models more or less correctly give positions of maxima of the distributions and their general qualitative dependence on the momentum. But in the quantitative predictions of the yields there are significant differences with the experiment which grow with increase of atomic mass number A.

Li6M(SeO3)4 (M = Co, Ni, and Cd) and Li2Zn(SeO3)2: Selenites with Late Transition-Metal Cations.

A series of lithium metal selenites, Li6M(SeO3)4 (M = Co, Ni, and Cd) and Li2Zn(SeO3)2, were synthesized by hydrothermal and solid-state reactions. Li6M(SeO3)4 is composed of Li+ cations, MO6 octahedra, and SeO3 polyhedra, while Li2Zn(SeO3)2 consists of Li+, Zn(Li)O4 tetrahedra, and SeO3 polyhedra. Isostructural Li6Co(SeO3)4 and Li6Ni(SeO3)4 crystallize in the rhombohedral space group R3̅, forming a three-dimensional distorted cubic lattice. Li2Zn(SeO3)2 crystallizes in the orthorhombic space group Pbam and reveals a layered structure in the bc plane. Li6Cd(SeO3)4 revealing a unidimensional structure crystallizes in the polar non-centrosymmetric space group C2, attributed to the parallel alignment of distorted CdO6 octahedra. The direct-current magnetic susceptibility measurements unveil that Li6Co(SeO3)4 is a canted antiferromagnet with TN = 25 K, while Li6Ni(SeO3)4 undergoes an antiferromagnetic transition at TN = 54 K, having a negligible canted moment. The weak ferromagnetism observed in Li6Co(SeO3)4 indicates the significance of spin-orbit coupling, bringing about anisotropic exchange interactions. Li6Cd(SeO3)4 reveals a second harmonic generation (SHG) efficiency of 10 × α-SiO2. Dipole moment calculations on Li6Cd(SeO3)4 indicate that the cooperative interaction of CdO6 and SeO3 is responsible for the observed SHG properties. Band gaps of the compounds are enlarged as atomic number increases. The effect of late transition-metal cations with different coordination numbers on the framework structures and the subsequent physical properties will be also discussed.

A comparative study on the fuel properties of biodiesel from woody essential oil depending on terpene composition

The essential oils from four Korean domestic gymnosperm species (red pine, white pine, cypress, and cedar) were examined in this study to understand the fuel characteristics based on their terpene compositions. The elemental composition, heating value, density at 20 °C, energy density, flash point, and kinematic viscosity at 40 °C of each woody essential oil were analyzed based on their terpene composition. The major elements in all woody essential oils investigated in this study were carbon, hydrogen, and oxygen. The woody essential oils were composed of more than 80% carbon and less than 10% oxygen due to the presence of terpene derivatives (terpene alcohols and terpene acetates). With respect to minor elements, sulfur contents did not satisfy the quality standard (10 ppm). Among the four woody essential oils, both red pine oil and white pine oil showed slightly lower higher heating values (HHVs; 44.09 MJ/kg and 44.13 MJ/kg, respectively) than diesel fuel. There was a negative correlation between oxygen content and HHV. Density was raised by an increase in the average number of carbon atoms and/or the terpene derivative contents and ranged from 0.875 g/mL for red pine oil to 0.924 g/mL for cedar oil. Based on their higher densities than diesel fuel and although they had lower HHVs, higher energy densities (38.59–39.18 MJ/L) were observed, with the exception of cypress oil. All the woody essential oils satisfied the quality standard for flash point (>40 °C). These flash points should consider both the average number of carbon atoms and terpene derivatives. In contrast, the kinematic viscosity of the essential oils was only affected by the number of carbon atoms. Cedar oil (6.1 mm2/s) had the largest kinematic viscosity followed by cypress oil (2.7 mm2/s), white pine oil (1.6 mm2/s), and red pine oil (1.4 mm2/s). By considering all assessed properties, a terpene mixture similar to the essential oil from red pine oil or white pine oil was deemed the most appropriate alternative biodiesel candidate though its viscosity and sulfur content must be improved.

Syntheses, crystal structures and magnetic properties of a series of ZnII2LnIII2 compounds (Ln = Gd, Tb, Dy, Ho and Er): contrasting structural and magnetic features

In the five ZnII2LnIII2 compounds – (i) the TbIII and ErIII analogues show slow relaxation of the magnetization, while the HoIII system and, surprisingly, the DyIII analogue don’t; (ii) the GdIII system shows the MCE; and (iii) interestingly, the Ln–O bond length increases with the increase of atomic number.

Structural and electronic properties of Cu2Q and CuQ (Q = O, S, Se, and Te) studied by first-principles calculations

In order to explore the similarity, difference, and tendency of binary copper-based chalcogenides, the crystal structure, electronic structure, and optical properties of eight compounds of Cu2Q and CuQ (Q = O, S, Se, and Te) have been calculated by density functional theory with HSE06 method. According to the calculated results, the electronic structure and optical properties of Cu2Q and CuQ present certain similarities and tendencies, with the increase of atomic number of Q elements: the interactions between Cu–Q, Cu–Cu, and Q–Q are gradually enhancing; the value of band gap is gradually decreasing, due to the down-shifting of Cu–4p states; the covalent feature of Cu atoms is gradually strengthening, while their ionic feature is gradually weakening; the absorption coefficient in the visible-light region is also increasing. On the other hand, some differences can be found, owing to the different crystal structure and component, for example: CuO presents the characteristics of multi-band gap, which is very favorable to absorb infrared-light; the electron transfer in CuQ is stronger than that in Cu2Q; the absorption peaks and intensity are very strong in the ultraviolet-light region and infrared-light region. The findings in the present work will help to understand the underlying physical mechanism of binary copper-based chalcogenides, and available to design novel copper-based chalcogenides photo-electronics materials and devices.

Energy dependence of radiation interaction parameters of some organic compounds

Gamma rays interact with a material through photoelectric absorption, Compton scattering, Rayleigh scattering and Pair production in the intermediate energy range. The probability of occurrence of a particular type of process depends on the energy of incident gamma rays, atomic number of the material, scattering angle and geometrical conditions. Various radiological parameters for organic compounds, namely ethylene glycol (C2H6O2), propylene glycol (C3H8O2), glycerin (C3H8O3), isoamyl alcohol (C5H12O), butanone (C4H8O), acetophenone (C8H8O2), cyclohexanone (C6H10O), furfural (C5H4O2), benzaldehyde (C7H6O), cinnamaldehyde (C9H8O), glutaraldehyde (C5H8O2), aniline (C6H7N), benzyl amine (C6H7N), nitrobenzene (C6H5NO2), ethyl benzene (C8H10), ethyl formate (C3H6O2) and water (H2O) are presented at 81, 122, 356 and 511keV energies employing NaI(Tl) scintillation detector in narrow-beam transmission geometry. The radiation interaction parameters such as mass attenuation, molar extinction and mass energy absorption coefficients, half value layer, total atomic and effective electronic cross-sections and CT number have been evaluated for these organic compounds. The general trend of values of mass attenuation coefficients, half value layer, molar extinction coefficients, total atomic and effective electronic cross-sections and mass energy absorption coefficients shows a decrease with increase in incident gamma photon energy. The values of CT number are found to increases linearly with increase of effective atomic number (Zeff). The variation in CT number around Zeff ≈ 3.3 shows the peak like structure with respect to water and the correlation between CT number and linear attenuation coefficient is about 0.99. Appropriate equations are fitted to these experimentally determined parameters for the organic compounds at incident photon energy ranging from 81keV to 511keV used in the present study. Experimental values are compared with the theoretical data obtained using WinXcom software package, and are found in good agreement.

From Zinc Clusters to One-Dimensional Crystals on Quasi-Free Sustained Substrates

By using the Amsterdam density functional (ADF) program based on first-principles, we have in detail investigated the Zn n (n = 2–20) clusters, several series of stacked structures, and the growth mechanism of zinc nanorods on silicone oil surfaces, which are isotropic, and can be generally considered as quasi-free sustained substrates. For the Zn n (n = 2–20) clusters, some new ground-state structures are found. The additional boundary atoms can enhance the stability of the stacked structures containing unit cells. The structures from the transverse array of the unit cells on (002) crystal plane are more stable than those stacked along the [002] direction as atomic number increases. The transverse arrayed structures can grow along the [002] direction. However, there is an atomic dislocation between the (002) crystal planes. In fact, the dislocation forms its one side surface of (101). By means of a single point SCF calculation in the ADF program, the adsorption energies per atom on the (101) and (002) crystal planes are calculated. According to the Boltzmann distribution probability law, the adsorption probability on the (101) plane is larger than that on the (002) plane, and the ratio between them is about 24–900. This shows that the Zn nanorods grow preferentially along the [110] direction on the (101) planes. These are in good agreement with our experimental findings.

Features of proteolytic properties of tetraphenylporphyrin complex with lanthanide group metals

Demetallation of metalloporphyrin molecules is one of the essential degradation reactions in photosynthesis. The effect of metalloporphyrin nature on removal of central metals from tetraphenylporphyrin complexes based on lanthanide group metals (Dy, Er, Lu, Ho) has been studied. pH values, at which the metal ions leave the metalloporphyrin complex were established using two-phase spectrophotometric titration with potentiometric pH-control. The pH values decrease with the increase of atomic numbers of lanthanide groups, as well as with increase of 4f–electrons.The reaction of an extra ligand exchange for the hydroxide ion was studied. For Dy-, Er- and Ho-tetraphenylporphyrin complexes one particle of extra ligand coordinates with one porphyrin complex. A complex with dimeric particles can be formed for the system of Lu-tetraphenylporphyrin. Constants of the ion exchange reactions were calculated. SynopsisThe effect of metalloporphyrin nature on removal of central metals from tetraphenylporphyrin complexes based on lanthanide group metals (Dy, Er, Lu, Ho) has been studied. The heterophase reaction of ion-selective electrodes were calculated, as well as the reaction of an extra ligand exchange for the hydroxide ion.

Influence of Breit interaction on the linear polarization of radiation following electron impact excitation of B-like ions

SynopsisThe influences of Breit interaction on the total cross section and linear polarization of highly charged Ca15+, Xe49+, and W69+ ions in the electron impact excitation process are calculated by fully relativistic distorted-wave program REIE06. It is found that the influence of Breit interaction on the linear polarization is more obvious with the increase of atomic number Z.

Electronic transport properties of lead nanowires**Project supported by the National Natural Science Foundation of China (Grant No. 51671114) and the Special Funding in the Project of the Taishan Scholar Construction Engineering and National Key Research Program of China (Grant No. 2016YFB0300501).

Lead nanowire occupies a very important position in an electronic device. In this study, a genetic algorithm (GA) method has been used to simulate the Pb nanowire. The result shows that Pb nanowires are a multishell cylinder. Each shell consists of atomic rows wound up helically side by side. The quantum electron transport properties of these structures are calculated based on the non-equilibrium Green function (NEGF) combined with the density functional theory (DFT), which indicate that electronic transport ability increases gradually with the atomic number increase. In addition, the thickest nanowire shows excellent electron transport performance. It possesses great transmission at the Fermi level due to the strongest delocalization of the electronic state. The results provide valuable information on the relationship between the transport properties of nanowires and their diameter.

Preparation of Double Carboxylic Corn Stalk Gels and Their Adsorption Properties Towards Rare Earths (III)

A novel biosorbent, corn stalk gels with double carboxylic groups synthesized by two oxidation steps (the double carboxylic groups modified adsorbent is abbreviated as DCCS-2), was prepared, characterized, and applied for the recovery of rare earths (III) from the nitric media. For the whole lanthanides, it exhibits a distinct “tetrad effect” with the increase of atomic numbers. Taking Nd(III) as a representative element, the adsorption capacity, kinetics, selectivity and mechanism were investigated. Thermodynamics and kinetic fittings were found to abide by Langmuir and pseudo-second-order rate equations and the corresponding parameters were calculated. The maximum adsorption capacity was calculated to be 2.44 mol/kg at 298 K for DCCS-2. Results showed that the double carboxylic groups played an important role for improving the adsorption capacity, e.g. the adsorption capacity of Nd(III) by DCCS-2 increased to 53.5 times compared to the raw corn stalk. Furthermore, DCCS-2 also shows a good selectivity between Nd(III) and many non-rare earth metal ions. The cation exchange is proposed to be the possible adsorption mechanism.

Small Al and Ga clusters trapped inside the Bucky-ball (C60) — A DFT study

In the present paper, we have done a systematic study of structural and electronic properties of endohedrally doped C[Formula: see text] with Al and Ga atoms using density functional theory (DFT) with the help of Spanish initiative for electronic simulation with thousands of atoms (SIESTA) package in the generalized gradient approximation (GGA). The parameters calculated are binding energy/dopant atom, vertical ionization potential (VIP), vertical electron affinity (VEA), HOMO–LUMO gap and charge transfer. The stabilized ground state structures of Al[Formula: see text]@C[Formula: see text] ([Formula: see text]–10) and Ga[Formula: see text]@C[Formula: see text] ([Formula: see text]–10) show that a maximum of nine Al or Ga atoms can be encapsulated in C[Formula: see text] without distorting the cage significantly. Mulliken charge analysis shows an electron transfer from the metal dopant to the cage surface, except for Al[Formula: see text] ([Formula: see text]–10). The endohedral metal clusters adopt a more compact shape when inside C[Formula: see text], compared to its free-state configuration and its symmetry. The study of HOMO–LUMO gap reveals that the gap decreases with the increase in number of dopant atoms inside C[Formula: see text].

Comprehensive study on physical, elastic and shielding properties of ternary BaO-Bi2O3-P2O5 glasses as a potent radiation shielding material

Recent research studies have been carrying out to characterize the structural, elastic and shielding properties of novel ternary BaO-Bi2O3-P2O5 glasses. The glass series having composition BaO·(50−x) Bi2O3·50P2O5 (10≤x≤40wt%) were prepared by conventional melt-quenching technique and the variation in density (ρ), molar volume (Vm), X-ray diffraction (XRD) and ultrasonic velocities has also been studied and correlated with the structural modifications in the glasses. The shielding parameters, effective atomic numbers, half value layers, and exposure buildup factor values have been computed using WinXCom program and G-P fitting method. The variations of shielding parameters were discussed for the effect of Bi2O3 addition into the glasses. The density, ultrasonic velocity and the calculated elastic moduli are found to be composition dependent and discussed in terms of Bi2O3 modifiers. The replacement of BaO by Bi2O3 causes an increase in effective atomic number, while the half value layer and the exposure buildup factor are decreased. This indicates that the increment in the content of Bi2O3 improves the gamma ray shielding characteristics.

A theoretical investigation on doping superalkali for triggering considerable nonlinear optical properties of Si12 C12 nanostructure.

In this work, we designed a series of superalkali-doped Si12 C12 nanocage M3 O@Si12 C12 (M = Li, Na, K) with donor-acceptor framework. Density functional theory calculations demonstrated that the HOMO-LUMO gap of the complexes conspicuously narrowed with increase of atomic number of the alkali metal, the value decreased from 5.452 eV of pure Si12 C12 nanocage to 3.750, 2.984, and 2.634 eV of Li3 O@Si12 C12 , Na3 O@Si12 C12 , and K3 O@Si12 C12 , respectively. This finding shows that the pristine Si12 C12 cluster could be transformed to n-type semiconductor by introduction of the superalkali M3 O. We also showed that the superalkali doping remarkably enhanced the first hyperpolarizability of Si12 C12 . Among the studied systems, K3 O@Si12 C12 not only has the narrowest gap but also has the strongest nonlinear optical (NLO) properties, its first hyperpolarizability reached as high as 21695 a.u. The striking results presented in this work will be beneficial for potential applications of the Si12 C12 -based nanostructure in the electronic nanodevices and high-performance NLO materials. © 2017 Wiley Periodicals, Inc.

Opacity effects on soft X-ray spectra from highly charged lanthanide ions in laser-produced plasmas

We have observed soft X-ray spectra from highly charged ions of seven different lanthanide elements with atomic numbers ranging from 60 to 70 in laser-produced plasmas (LPPs) using CO2 and Nd:YAG laser systems, the wavelengths of which are 10.6μm and 1.064μm, respectively. The spectral feature drastically changes between the two types of LPPs due primarily to the difference in opacity. Narrowband quasicontinuum features arising from n=4–4 transitions, the centre wavelength of which systematically moves to shorter wavelength as the atomic number (Z) increases, are observed in the CO2 LPPs, accompanied by sharp peaks coinciding with the strongest resonance lines of Pd-like ions for lower Z elements. In contrast, the quasicontinuum bands are broader and smoother in the Nd:YAG LPPs, appearing with bands of n=4–5 transitions on the shorter wavelength side. The results are also discussed based on comparisons with atomic structure calculations for ions with outermost 4d and 4f subshells.

Elemental affinity for siderite found in a Japanese paddy subsoil

ABSTRACTSiderite (FeCO3), a type of carbonate mineral, is very occasionally recognized as a nodule in anoxic soils and sediments. During siderite formation, elements are expected to be accumulated or excluded between siderite and bulk soil. Therefore, we verified the affinity of 40 elements for siderite found in the gley horizon of a smectite-rich paddy field in northeastern Japan from the elemental concentration of the soil and the siderite dissolved in 2.88 mol L−1 hydrochloric acid (10% HCl). The concentration ratio of the target element of the soil to the siderite was expressed by the product of the dimensionless R0 value and ratio of titanium (Ti) concentration of the soil to the siderite (Csiderite /Csoil) = R0 (Tisiderite /Tisoil). The affinity of each element for the siderite was analyzed by comparing the R0 values. In comparison with Ti used as the reference element, P, Cr, Co and Mo were accumulated (R0 > 1.0), and alkali metals, such as Li, Na and K, and chalcophile elements, such as Cu, Zn, Cd and Pb, tended to be equal or excluded from the siderite (R0 ≦1.0). Of the group 2 elements, Ca, Sr and Ba were accumulated, while Mg was excluded. The affinity of Mn for siderite exceeded that of Fe as the main component of the siderite, which reflects the fact that siderite was formed in a fresh water condition. The siderite size did not influence the elemental affinity. Observation of micromorphology using a scanning electron microscope showed that the siderite nodules were aggregations of siderite particles and clays, suggesting that the siderite grew by taking in clay around it. The rare earth element (REE) distribution pattern showed a tendency not to increase linearly but to increase with forming a concave curve at the intervals of the four elements with the increase of atomic number (i.e. tetrad effects). Although these findings are from the lower horizons of anoxic soils, the elemental affinity for siderite of this study is useful in order to elucidate the complex elemental dynamics in the anoxic environment.

Study on Chemical Mechanical Polishing Performances of Sapphire Wafer (0001) Using Silica-Based Slurry

In this paper, the chemical mechanical polishing (CMP) mechanism of silica-based slurry on sapphire wafer was analyzed. The influences of size and abrasive concentration of silica-based slurry on the material removal rate (MRR) of (0001) sapphire wafer were investigated, respectively. Furthermore, the effect of chemical agents on MRR was mainly studied. It was found that most alkali metal salts and halogen salts except for fluoride salts can be used as polishing promoting agents to increase MRR. The promotion effect of monovalence cations to MRR decreases with the increase of atomic number. The MRR strongly relies on the kind of alkaline agents used in slurries. During the process of sapphire CMP, no chelating reaction occurred when the chelating agent was added to the silica-based slurry. The double-polished sapphire wafer has a transmittance of 86% to visible light and can be used as the optical window for the screen of smart mobile phones and so on.

The mechanical and thermodynamic properties of Heusler compounds Ni2XAl (X = Sc, Ti, V) under pressure and temperature: A first-principles study

The effect of pressure on structural and mechanical properties as well as the temperature dependence of thermodynamic properties, such as enthalpies of formation, elastic moduli, anisotropy, heat capacity and thermal expansion coefficient et al., of Ni2XAl (X=Sc, Ti, V) Heusler compounds are investigated implementing first-principles calculations. The influence of pressure on lattice parameters decreases as the increase of atomic number X (Sc, Ti, V). The Ni2XAl (X=Sc, Ti, V) show mechanically stable, ductility and anisotropy in 0–50GPa, and appropriate pressure can improve their mechanical properties because the bulk modulus B, shear modulus G, Young's modulus E, G/B and microhardness H almost linearly increase with pressure. The influence of pressure on B, G, E and H gradually decreases as the order of Ni2ScAl>Ni2TiAl>Ni2VAl, while it has an inverse effect on ductility and anisotropy. In addition, the resistance to volume deformation of NiAl alloys can be improved by second-phase strengthening with Ni2VAl and Ni2TiAl precipitates. Finally, the temperature and pressure dependences of bulk modulus, Debye temperature, heat capacity as well as thermal expansion coefficient of these compounds are elucidated using the quasi-harmonic Debye model. It is inverse for the effect of temperature and pressure on thermodynamic parameters.