[en] Isolated single-walled carbon nanotubes (SWNTs), SWNT bundles, and ropes (or strands) show a structural self-similar characteristic. By calculating the Hausdorff dimension, it was found that their self-similar organization leads to surface fractality and the value of the surface dimension (D_s) depends on self-similar patterns. Experimentally, D_s obtained by nitrogen adsorption measurements at 77.3 K and by the small-angle x-ray scattering technique in our study proved our calculation that the surface dimension of SWNTs is nonintegral, 2< D_s<3, which indicates that the surface of SWNTs is fractal. According to our calculation and analysis, the fractality is determined by the self-similar arrangement of SWNTs, but the value of D_s is also influenced by the effect of finite length and irregular aggregation of real SWNT samples

[en] Electrochromic materials have shown great application prospects in electronic display and information storage. In this work, we synthesized MoO₃@PEDOT coaxial heterostructure nanobelts by a simple and green in situ polymerization method and investigated their electrochromic properties. This MoO₃@PEDOT nanobelts take internal MoO₃ nanobelts as mechanical support and growth templates to make the externally PEDOT covered uniformly on the outside. This unique 1D nano-structure has large surface area, provides large number of accessible electroactive sites for high color contrast. It was found that the electrochromic composite films prepared by spin coating MoO₃@PEDOT coaxial heterostructure nanobelts on ITO exhibited a high contrast of 31.8%, and colored efficiency up to 86.57 cm²·C⁻¹. It turned out the MoO₃@PEDOT coaxial heterostructure nanobelts can improve PEDOT electrochromic properties greatly and will be a suitable choice for smart window application. (paper)

[en] Highlights: • BCNx membranes with high oxygen permeation flux were prepared. • Oxygen permeability of BCNx membranes is stable at 900 °C. • Phase transition is governed by oxygen partial pressure and temperature. • Degradation mechanism of BCNx membrane is suggested. - Abstract: BaCo_1_−_xNb_xO_3_−_δ (BCNx, x = 0.1–0.2) membranes were synthesized through conventional solid-phase reactions. The introduction of niobium facilitates the formation of the cubic perovskite structure and decreases oxygen nonstoichiometry. BCNx membranes possess higher oxygen permeation flux compared with BaCo_0_._7Fe_0_._2Nb_0_._1O_3_−_δ membrane at the same condition. A stable permeation flux as high as 2.61 ml cm"−"2 min"−"1 is obtained through BaCo_0_._9Nb_0_._1O_3_−_δ membrane at 900 °C under the Air/He gradient. Long-time permeation study shows that the oxygen fluxes of BCNx membranes are stable at 900 °C but degrade slowly with time at 850 °C. XRD and TG–DSC results indicate that the degradation behavior occured at 850 °C is due to the phase transition from the cubic perovskite to monoclinic or orthorhombic structure, which is governed by the oxygen partial pressure and temperature. The oxidation of cobalt ion is considered to be the nature for the phase transition, which makes the tolerance factor increasing and results in structural destabilization

[en] The d-orbital contribution from the transition metal centers of phthalocyanine brings difficulties to understand the role of the organic ligands and their molecular frontier orbitals when it adsorbs on oxide surfaces. Here we use zinc phthalocyanine (ZnPc)/TiO₂(110) as a model system where the zinc d-orbitals are located deep below the organic orbitals leaving room for a detailed study of the interaction between the organic ligand and the substrate. A charge depletion from the highest occupied molecular orbital is observed, and a consequent shift of N1s and C1s to higher binding energy in photoelectron spectroscopy (PES). A detailed comparison of peak shifts in PES and near-edge X-ray absorption fine structure spectroscopy illustrates a slightly uneven charge distribution within the molecular plane and an inhomogeneous charge transfer screening between the center and periphery of the organic ligand: faster in the periphery and slower at the center, which is different from other metal phthalocyanine, e.g., FePc/TiO₂. Our results indicate that the metal center can substantially influence the electronic properties of the organic ligand at the interface by introducing an additional charge transfer channel to the inner molecular part.

[en] Standard enthalpies of formation (Δ_f H⁰) of finite-length (5, 5) single-walled carbon nanotubes (SWNTs) are calculated with the framework of density functional theory. Approximate expressions of (Δ_f H⁰) have been proposed for both H-terminated and C30-capped (5, 5) SWNTs, based upon which the calculated values of (Δ_f H⁰) have been reproduced within several kilocalories per mole. It is also found that standard enthalpies of formation contributed by per carbon, Δ_f H⁰(C), oscillate with the increment of the cluster size, suggesting the dependence of the relative stability on the axial length.

[en] Graphical abstract: The homogeneously grafted PEDOT/MWCNTs containing numerous whorl fingerprint-like open ends endows with excellent electrochemical performances. Highlights: ► A ternary phase system with the surfactant AOT is utilized to efficiently solve the problem of the aggregation of MWCNTs. ► The homogenously grafted PEDOT/MWCNTs composite is synthesized by in situ chemical polymerization in the ternary phase system. ► The core–shell nanotubes contain many whorl fingerprint-like open ends that are greatly favorable for the transportation of the electrons and ions. ► The energy density of grafted PEDOT/MWCNTs has been enhanced by a factor of four comparing to that of native MWCNTs. ► The grafted PEDOT/MWCNTs composite manifests better cycle durability than both the constituents. - Abstract: The homogenously grafted composite of poly (3,4-ethylenedioxythiophene)/multiwalled carbon nanotubes (PEDOT/MWCNTs) is synthesized by in situ chemical polymerization in a ternary phase system. When carbon nanotubes are dispersed in this system containing sodium bis(2-ethylhexyl) sulfosuccinate (AOT), the surfactant AOT can efficiently hinter the aggregation of MWCNTs by absorbing and arranging regularly on the MWCNT surface. It is greatly advantageous to the stabilization of MWCNTs, which leads to the equally grafted composite. Its morphology was observed by scanning and transmission electron microscopes. Especially, the core–shell nanotubes contain many whorl fingerprint-like open ends that are efficiently favorable for the transportation of the electrons and ions. Such grafted PEDOT/MWCNTs composite nanotubes manifest enhanced electrochemical performances. We investigate the application of PEDOT/MWCNTs as a high-property supercapacitor and test its capacitive performance by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The energy density of grafted composite, 11.3 Wh kg⁻¹, has been enhanced by a factor of four comparing to that of native MWCNTs. Besides, the composite also presents better cycle durability after 1000 cycles. This composite will be a good candidate for the applications on supercapacitors.

[en] The electronic structure of ZnPc, from sub-monolayers to thick films, on bare and iodated Pt(111) is studied by means of X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and scanning tunneling microscopy. Our results suggest that at low coverage ZnPc lies almost parallel to the Pt(111) substrate, in a non-planar configuration induced by Zn-Pt attraction, leading to an inhomogeneous charge distribution within the molecule and an inhomogeneous charge transfer to the molecule. ZnPc does not form a complete monolayer on the Pt surface, due to a surface-mediated intermolecular repulsion. At higher coverage ZnPc adopts a tilted geometry, due to a reduced molecule-substrate interaction. Our photoemission results illustrate that ZnPc is practically decoupled from Pt, already from the second layer. Pre-deposition of iodine on Pt hinders the Zn-Pt attraction, leading to a non-distorted first layer ZnPc in contact with Pt(111)-I(√3×√3) or Pt(111)-I(√7×√7), and a more homogeneous charge distribution and charge transfer at the interface. On increased ZnPc thickness iodine is dissolved in the organic film where it acts as an electron acceptor dopant

[en] Graphical abstract: The novel 3D flowerlike nanomaterial demonstrates high capacitive property on energy storage application. -- Highlights: • 3D conducting polymer are firstly reported as supercapacitor electrode materials. • 3D flowerlike morphology is favorable for electrons and ions transport. • 3D flowerlike PEDOT/MnO₂ manifests much better cycle durability. • Sythesis approach of PEDOT/MnO₂ may give rise to 3D new materials. • Quite small size MnO₂ nanoparticles are well dispersed on conducting matrix. -- Abstract: The electrochemical performances of 3D flowerlike PEDOT are characterized by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. It shows high specific capacitance of 111 F g⁻¹, which is greatly higher than that of 1D PEDOT nanofibers we reported before. In addition, on the basis of this PEDOT matrix, 3D flowerlike PEDOT/MnO₂ composite is synthesized by a two-step approach as a high-property supercapacitor electrode material. Scanning and transmission electron microscopy show that 3D PEDOT matrix is kept well and decorated well by MnO₂ nanoparticles (2–5 nm). And the capacitive performances are tested as well. The specific capacitance of this composite can highly reach around 183 F g⁻¹, and retain more than 90% of the original value after 1000 consecutive charge/discharge cycles. These results indicate that the 3D flowerlike PEDOT/MnO₂ composite possesses a synergy effect of complementary properties of both components, which results in higher specific capacitance and better stability

[en] Highlights: • Much smaller and uniform TiO₂ nanoparticles are achieved during solvothermal process with ethylene glycol as solvent. • MgH₂-70TiO₂@rGO composite starts to release hydrogen at 240 °C. • Encapsulation structure and multivalent titanium compounds lead to the enhanced hydrogen storage properties. -- Abstract: In this paper, we synthesized graphene-supported TiO₂ nanoparticles (TiO₂@rGO) via solvothermal method with different solvents. The combined effect of ethylene glycol (EG) and graphene makes fine, uniform TiO₂ nanoparticles during solvothermal process. The effects of milling time and TiO₂ content on hydrogen storage performance of MgH₂ were investigated systematically. The MgH₂-70TiO₂@rGO-EG composite milled for 10 h starts to release hydrogen at 240 °C. The composite can desorb 6.0 wt% hydrogen within 6 min at 300 °C, while it can absorb 5.9 wt% hydrogen within 2 min at 200 °C. XPS and TEM results indicate that Mg encapsulated with catalyst as well as Ti⁴⁺ partially reduced to Ti²⁺ can make more intimate contacts and promote the charge transfer, which are responsible for the good de-/hydrogenation kinetics performance of MgH₂.

[en] Electron beam-induced nanoinstabilities of pristine double-walled carbon nanotubes (DWCNTs) of two different configurations, one fixed at both ends and another fixed at only one end, were in-situ investigated in transmission electron microscope at room temperature. It was observed that the DWCNT fixed at both ends shrank in its diameter uniformly. Meanwhile, the DWCNT fixed at only one end intriguingly shrank preferentially from its free cap end along its axial direction whereas its diameter shrinkage was offset. A mechanism of “diffusion” along with “evaporation” at room temperature which is driven by the nanocurvature of the DWCNTs, and the athermal activation induced by the electron beam was proposed to elucidate the observed phenomena. The effect of the interlayer interaction of the DWCNTs was also discussed.