To elucidate low-dimensional effects on thermoelectric materials, bismuth telluride film and nanowires array were fabricated by potentiostatically electrodeposition. Both materials are slightly Te-rich, n-type Bi2Te3, exhibiting preferred orientation in rhombohedral strcture. For both the Seebeck coefficient S ≈ −70 μV/K at 300 K decreases linearly with decreasing temperature, showing a diffusive nature of current flow. The temperature dependence of resistivity (=1/σ) of nanowires obtained from the data of a nanowires array and a single-nanowire reveals a better electric conductivity than that of the bulk. By coupling temperature-dependent thermal diffusivity and heat capacity data with a modified effective medium theory, a thermal conductivity κ of 0.75 W/(m K) was obtained at 300 K. The ZT was calculated to be 0.45 at 300 K and 0.9 at 350 K for Bi2Te3 nanowires.

The strategy for shape control of alloy FePt nanocrystal was studied systematically. By the careful adjustments of reaction parameters in a solution reaction, surfactant-facet bindings on the growth seed were controlled delicately. FePt octapod, cuboctahedron, truncated cube, and nanocube were successfully prepared from cuboctahedral seed and examined by high-resolution transmission electron microscopy. The formations of FePt nanostructures were mainly attributed to the differences in the growth rate between the {111} and {100} planes of cuboctahedral seeds. The magnetic measurements showed that the order of volume, V (nanocube) >V (octapod) >V (cuboctahedron) obviously reflected the order of saturated magnetization (M s ), M s (nanocube) >M s (octapod) >M s (cuboctahedron) . Furthermore, the measurements of octapod exhibited the highest coercivity and blocking temperature because of its higher surface to volume ratio and more structural facets.

The packing structures and packing effects on excitation energies of thiophene, terthiophene, sexithiophene, and duodecithiophene are studied by employing the molecular dynamic (MD) simulations and the TDDFT/ 6-311++G** calculations. It has been demonstrated by MD simulations that (1) when going from short to long chain systems, the packing structure prefers to be in the π-stacked form and (2) the effective conjugation lengths, ECLs, of terthiophene, sexithiophene, and duodecithiophene chains are 2, 3, and 4, respectively. Accordingly, the comprehensive effects of the interchain distance, R, and ECL on excitation energy can be estimated by a simple formula. The calculated excitation energies of the packing oligothiophenes are in agreement with the experimental data with the average deviation of 0.12 eV.

Unraveling the conformation of membrane-bound viral fusion peptides is essential for understanding how those peptides destabilize the bilayer topology of lipids that is important for virus-cell membrane fusion. Here, molecular dynamics (MD) simulations were performed to investigate the conformation of the 20 amino acids long fusion peptide of influenza hemagglutinin of strain X31 bound to a dimyristoyl phosphatidylcholine (DMPC) bilayer. The simulations revealed that the peptide adopts a kinked conformation, in agreement with the NMR structures of a related peptide in detergent micelles. The peptide is located at the amphipathic interface between the headgroups and hydrocarbon chains of the lipid by an energetically favorable arrangement: The hydrophobic side chains of the peptides are embedded into the hydrophobic region and the hydrophilic side chains are in the headgroup region. The N-terminus of the peptide is localized close to the amphipathic interface. The molecular dynamics simulations also revealed that the peptide affects the surrounding bilayer structure. The average hydrophobic thickness of the lipid phase close to the N-terminus is reduced in comparison with the average hydrophobic thickness of a pure dimyristoyl phosphatidylcholine bilayer.

No abstract

Structural parameters and electronic band gaps of dense TiO(2) polymorphs, i.e., alpha-PbO(2), baddeleyite, fluorite, and cotunnite types of structures, were calculated using a first-principles density functional method with local-density approximation. The ambient phases, i.e., rutile and anatase, with known theoretical and experimental data were used to ensure the validity of the calculations. The fluorite-type TiO(2) turned out to have the narrowest band gap, 1.08 or 2.18 eV after applying a very approximate band gap correction, due to highly symmetrical TiO(8) polyhedra with Ti(3d) and O(2p) orbitals in the most mixed state. Ti with eight coordinated oxygens, as feasible under high pressure or residual stress, may have potential applications as a visible-light-responsive photocatalyst.

For nominal 3 and 9 nm FePt nanoparticles coated with oleylamine/oleic acid and having a face-centred-cubic (fcc) structure, temperature variations (5–300 K) of magnetization M, ac susceptibility χ′ and χ″ for the frequency range fm = 0.1–1000 Hz and electron magnetic resonance (EMR) spectra at 9.28 GHz are reported. X-ray diffraction of the samples shows fcc structure with a lattice constant a = 3.84 Å and TEM characterization yields log-normal distributions of the particle sizes with average D = 3.15(0.16) nm and D = 8.70(0.12) nm for the 3 nm and 9 nm samples, respectively. M versus T data for the zero-field-cooled and field-cooled modes yield a blocking temperature TB = 15 K (85 K) for the 3 nm (9 nm) samples whereas the hysteresis loops at 5 K yield a coercivity Hc = 0 Oe (1.4 kOe). Analysis of the data of TB at different fm determined from the peaks in χ″ in ac susceptibility and the temperature variation of the EMR spectra are used to determine the following parameters of the Vogel–Fulcher relaxation for the 3 nm (9 nm) samples respectively: the attempt frequency fo = 8 × 1010 Hz (2 × 1012 Hz); inter-particle interaction temperature To = 3 K (33 K) and anisotropy Ka = 1.96 × 106 ergs cm−3 (4.3 × 105 ergs cm−3). The use of the above parameters for the calculations of the optimum size for magnetic hyperthermia is analysed and discussed.

No abstract