The magnetic and structural properties of hydrothermal-synthesized single-crystal Sn1-xFexO2 nanograins

The crystal structure and magnetic properties of Sn1-xFexO2 nanograins synthesized by simple hydrothermal method using SnCl4 center dot 5H(2)O and FeCl3 center dot 6H(2)O as raw materials are studied. No secondary phase was found in the XRD spectrum. The linear change of lattice volume for different Fe content strongly supports that the Fe3+ substitutes Sn4+ in SnO2 lattice. A Raman and IR spectra study indicated that the Fe incorporates into the SnO2 lattice. Both ferromagnetic and paramagnetic signals are detected in the Mossbauer spectra. The Sn1-xFexO2 (x <= 0.10) samples show room-temperature ferromagnetism (RTFM) and the saturation magnetization increased with increasing Fe percent. Fe ions present three kinds of magnetic behaviors including paramagnetic, ferromagnetic, and antiferromagnetic in the samples observed by investigation of the M-H and M-T curves. The weak RTFM was due to only a fraction of Fe ions contributing to magnetic-order coupling mediated by oxygen vacancy.

Synthesis and electrical properties of new solid state. Electrolyte materials Ce5.2RE0.8MoO15-delta

A series of solid state electrolytes, Ce-5.2 RE0.8 MoO15-delta (RE = Y, La, Sm, Gd, Dy, Ho, Er), were synthesized by sol-gel method. Their structures and electrical conductivities were characterized by X-ray Diffraction (XRD), Raman and X-ray Photoelectron Spectroscopy (XPS) and AC impedance spectroscopy, respectively. The results show that the concentrations of oxygen vacancy increased with increasing x and their conductivity were improved. And the cell parameters increase as the radius of RE3+ increases. Because the ionic radius of doped Dy3+ (0.0908 nm) is closed to that of Ce4+ (0.0920 nm), their oxide has minimal cell elastic straining between RE3+ and oxygen vacancy, and the system has the least association enthalpy, thus the oxide Ce-5.2 Dy-0.8 MoO15-delta exhibits a higher conductivity (7.02 x 10(-3) S/cm) and lower activation energy (1.056 eV) compared to the other doped compounds.

Synthesis, characterization and electrical properties of solid state electrolyte materials La2-xCaxMo1.7W0.3O9-delta (0 <= x <= 0.2)

The new compounds La2-xCaxMo1.7W0.3O9-delta (0 <= x <= 0.2) in which La3+ substituted with Ca2+ were synthesized by dry-chemistry techniques based on the oxygen Ionic conductor La2Mo1.7W0.3O9. The new series were characterized by X-ray Diffraction (XRD), Raman and X-ray Photoelectron Spectroscopy (XPS) and the electrical conductivity of samples were investigated by AC impedance spectroscopy. The lattice parameters were reduced due to the smaller atomic radius of the Ca2+ compared with that of the La3+. Furthermore, Additional oxygen vacancies were introduced into La2Mo1.7W0.3O9 lattice by substitution, and then the oxygen ionic conductivity was increased. At 550 degrees C, the conductivity increased 89.9%, that is, from 0.79 x 10(-4) S center dot cm(-1) (x=0) to 1.5 X 10(-4)S center dot cm(-1) (x=0.16, 0.2).

Hydrothermal synthesis, structure characterization of a new mixed Mo/V metal-oxygen cluster compound: [Co(phen)(3)](2)[HPMo4V (Mo4V6IV)-V-VI M2O44]center dot 4H(2)O, (M=0.78Mo(V)+0.22V(IV))

A new polyoxometalate [Co(phen)(3)](2)[HPMo4V Mo-4(VI) V-6(IV) M2O44]center dot 4H(2)O (M = 0.78Mo(V)+ 0.22V(IV)) 1 was hydrothermally synthesized and characterized by IR, elemental analyses, X-ray photoelectron spectrum, ESR and single crystal X-ray diffraction. The title compound is in the triclinic space group P (1) over bar with a = 12.0953(7) angstrom, b = 14.0182(6) angstrom, c = 14.6468(7) angstrom, V=2402.55(18) angstrom(3), alpha = 105.134(2), beta = 91.841(3), gamma = 91.401(2), Z = 1, and R-1 (wR(2)) = 0.0617 (0.1701). The compound was prepared from tetra-capped pseudo-Kepin with phosphorus-centered polyoxoanions [PMo8V6M2O44](5-) , [Co(phen)(3)](2+) cations and linked through hydrogen bonds and pi-pi stacking interaction into three-dimensional supramolecular framework. Astudy of the magnetic properties of 1 demonstrates that it exhibits antiferromagnetic coupling interactions.

Electrochemical design of ultrathin platinum-coated gold nanoparticle monolayer films as a novel nanostructured electrocatalyst for oxygen reduction

The deliberate tailoring of nanostructured metallic catalysts at the monolayer-level is an ongoing challenge and could lead to new electronic and catalytic properties, since surface-catalyzed reactions are extremely sensitive to the atomic-level details of the catalytic surface. In this article, we present a novel electrochemical strategy to nanoparticle-based catalyst design using the recently developed underpotential deposition (UPD) redox replacement technique. A single UPD Cu replacement with Pt2+ yielded a uniform Pt layer on colloid gold surfaces. The ultrathin (nominally monolayer-level) Pt coating of the novel nanostructured particles was confirmed by cyclic voltammetry and X-ray photoelectron spectra (XPS). The present results demonstrate that ultrathin Pt coating effects efficiently and behaves as the nanostructured monometallic Pt for electrocatalytic oxygen reduction, and also shows size-dependent, tunable electrocatalytic ability. The as-prepared ultrathin Pt-coated Au nanoparticle monolayer electrodes reduce O-2 predominantly by four electrons to H2O, as confirmed by the rotating ring-disk electrode (RRDE) technique.

Morphology and structure of poly(di-n-butylsilane) single crystals prepared by controlling kinetic process of solvent evaporation

The silicon backbone conformation in poly(di-n-butylsilane) (PDBS) has been shown to be a 7/3 helix at ambient conditions, which is in marked contrast to the near-planar conformation of its homologous polymers with side chain lengths of one to three or six to eight carbon atoms. In this work, both the 7/3 helical and near-planar chain conformations are achieved by controlling the solvent evaporation rate around room temperature. The chain conformation and crystal structure obtained in this method have been correlated to the crystal morphology by wide-angle X-ray diffraction, transmission electron microscopy, electron diffraction, optical microscopy, atomic force microscopy, and UV absorption spectrum. The lath-shaped single crystals obtained at 12 degreesC correspond to an orthorhombic form with near-planar chain conformation whereas the lozenge-shaped single crystals obtained at 30 degreesC (in coexistence with the lath-shaped crystals) are orthohexagonal with a 7/3 helix.

Probing the kinetics of single molecule protein folding

We propose an approach to integrate the theory, simulations, and experiments in protein-folding kinetics. This is realized by measuring the mean and high-order moments of the first-passage time and its associated distribution. The full kinetics is revealed in the current theoretical framework through these measurements. In the experiments, information about the statistical properties of first-passage times can be obtained from the kinetic folding trajectories of single molecule experiments ( for example, fluorescence). Theoretical/simulation and experimental approaches can be directly related. We study in particular the temperature-varying kinetics to probe the underlying structure of the folding energy landscape. At high temperatures, exponential kinetics is observed; there are multiple parallel kinetic paths leading to the native state. At intermediate temperatures, nonexponential kinetics appears, revealing the nature of the distribution of local traps on the landscape and, as a result, discrete kinetic paths emerge. At very low temperatures, exponential kinetics is again observed; the dynamics on the underlying landscape is dominated by a single barrier.

Highly enhanced luminescence from single-crystalline C-60 center dot 1m-xylene nanorods

Single-crystalline C-60 center dot 1m-xylene nanorods with a hexagonal structure were successfully synthesized by evaporating a C-60 solution in m-xylene at room temperature. The ratio of the length to the diameter of the nanorods can be controlled in the range of approximate to 10 to over 1000 for different applications. The photoluminescence (PL) intensity of the nanorods is about 2 orders of magnitude higher than that for pristine C-60 crystals in air. Both UV and Raman results indicate that there is no charge transfer between C-60 and m-xylene. It was found that the interaction between C-60 and m-xylene molecules is of the van der Waals type. This interaction reduces the icosahedral symmetry of C-60 molecule and induces strong PL from the solvate nanorods.

Single-molecule dynamics reveals cooperative binding-folding in protein recognition

The study of associations between two biomolecules is the key to understanding molecular function and recognition. Molecular function is often thought to be determined by underlying structures. Here, combining a single-molecule study of protein binding with an energy-landscape-inspired microscopic model, we found strong evidence that biomolecular recognition is determined by flexibilities in addition to structures. Our model is based on coarse-grained molecular dynamics on the residue level with the energy function biased toward the native binding structure ( the Go model). With our model, the underlying free-energy landscape of the binding can be explored. There are two distinct conformational states at the free-energy minimum, one with partial folding of CBD itself and significant interface binding of CBD to Cdc42, and the other with native folding of CBD itself and native interface binding of CBD to Cdc42. This shows that the binding process proceeds with a significant interface binding of CBD with Cdc42 first, without a complete folding of CBD itself, and that binding and folding are then coupled to reach the native binding state.

Synthesis and crystal structure of bis (tert-butyl-cyclopentadienyl)erbium ethoxide, (t-BuCp)(2)ErOEt

The formation of ( t-BuCp)(2)ErOEt was discussed. Its single-crystal structure was determined by X-ray diffraction. The crystal is monoclinic, P2(1)/c space group, a = 1.0191(2), b = 1.6203(5), c = 1.2118(3) nm, beta = 102. 960( 10)degrees, V = 1.9500 (nm(3)), Z = 2, D-c = 1.566 mg . m(-3), R = 0.0450, R-w = 0.1363. The complex is monomeric and solvent-free in the solid state. The erbium ion is coordinated by two tert-butyl-cyclopentadienyl rings and one oxygen atom of ethoxy group to form a seven-coordinated complex.

Coating of Y2O3 : Eu3+ particles with alumina by a humid solid state reaction at room temperature

Humid solid state reaction at room temperature was utilized for the first time to coat Y2O3 : Eu3+ particles with alumina. The particles were studied with an X-ray photoelectron spectrometer (XPS), a scanning electron microscope (SEM), and an energy dispersive spectrometer (EDS). XPS results show that the yttrium and europium contents are decreased and that the aluminum content is the highest except for that of oxygen after coating. SEM and EDS results show that particles are coated with a thin shell of alumina.

Single-crystal X-ray structure and properties of K-10[Ni-4(H2O)(2)(AsW9O34)(2)]center dot 4H(2)O

The rational synthesis and the structural and magnetic characterization of a nickel cluster are presented. The compound comprises a rhomblike Ni4O16 group encapsulated between two-heptadentate tungstoarsenate ligands [AsW9O34](9-). The crystal structure of K-10[Ni-4(H2O)(2)(AsW9O34)(2)](.)4H(2)O was solved in monoclinic, P2(1)/n symmetry, with a = 12.258(3) Angstrom, b = 21.232(4) Angstrom, c = 15.837(3) Angstrom, beta = 92.05(3)degrees, V = 4119.1(14) Angstrom(3), Z = 2, and R = 0.0862. The crystal structure of the Ni(II) derivative was compared with that of the Cu(II), Zn(II), Co(II) and Mn(II) derivatives. The Ni4O14(H2O)(2) unit in the compound shows no Jahn-Teller distortion. On the other hand, the Ni(II) derivative shows ferromagnetic exchange interactions within the Ni4O16 group (J = 7.8 cm(-1), J' = 13.7 cm(-1)) and an S = 4 ground state, the highest spin state reported in a heteropoly complex. Its redox electrochemistry has been studied in acid buffer solutions using cyclic voltammetry. It exhibited two steps of one-electron redox waves attributed to redox processes of the tungsten-oxo framework. The new catalyst showed an electrocatalytic effect on the reduction of NO2-.

Investigating mechanical response of single chain polystyrene particles by scanning probe techniques

Single chain polystyrene particles were obtained by dilute solution casting method. The sample with both single chain polystyrene particles and multi-chain (more than 1000 molecular chains) polystyrene particles was obtained by a little more concentrate solution. Force modulation technique showed that single chain polystyrene particles were softer than multichain polystyrene particles. On the other hand, nanoindentation experiments on multi-chain particles and bulk polystyrene manifested that the elastic modulus of multi-chain polystyrene particles was very close to that of bulk polystyrene. Therefore, it was concluded that single chain polystyrene particles were softer than bulk polystyrene,which indicated that the density of intrachain entanglement points in the single chain polystyrene particles was not as large as that of the interchain entanglement points in the bulk state.

The single crystal-like banded textures in the films of a thermotropic liquid crystalline poly(aryl ether ketone) containing a lateral chloro group

The banded textures in the films of a thermotropic liquid crystalline poly(aryl ether ketone) containing a lateral chloro group have been studied by means of transmission electron microscopy(TEM), electron diffraction(ED) and atomic force microscopy (AFM). The crystallization-induced Landed texture without external shear can be formed when the thin films were annealed at the temperature range(320-330 degrees C) of the liquid crystalline state from the melt, The results show that the banded regions have high orientation of single crystal based on the orthorhombic packing and the growing direction of the Lands is along the b axis of the crystals, This kind of single crystal-like bands is due to the different orientation of the packing molecular chains, The molecular chains of the dark bands in the bright field electron micrograph are perpendicular to the film plane, while the ones of the bright Lands are tilt along the b axis with the tilt angle upto +/-20 degrees.

A new dinuclear molybdenum(V)-sulfur complex containing citrate ligand: synthesis and characterization of K2.5Na2NH4[Mo2O2S2(cit)(2)].5H(2)O

The complex, K2.5Na2NH4[Mo2O2S2(cit)(2)]. 5H(2)O (1), was obtained by crystallization from a solution of (NH4)(2)MoS4, potassium citrate (K(3)cit) and hydroxyl sodium in methanol and water under an atmosphere of pure nitrogen at ambient temperature. The crystals are triclinic, space group , a = 7.376 (3)Angstrom, b = 14.620 (2) Angstrom, c = 14.661 (1) Angstrom, alpha = 71.10 (1)degrees, beta = 81.77 (1)degrees, gamma = 78.27(2)degrees, R = 0.0584 for 2545 observed (I > 2 sigma (I)) reflections. Single crystal structure analysis reveals that citrate ligand coordinated to molybdenum atom through two carboxylato oxygens and one deprotonated hydroxyl oxygen together with two bridging sulfur atoms and a terminal oxygen atom completes distorted coordination octahedron around each molybdenum atom. Principal dimensions are: Mo = O-t, 1.707 Angstrom (av); Mo-S-b, 2.341 Angstrom (av); Mo-O-(hydroxyl), 2.021 Angstrom (av); Mo-O(alpha-carboxyl), 2.1290 Angstrom (av) and Mo-O(beta-carboxyl), 2.268(av) Angstrom. IR spectrum is in agreement with the structure.