The phase transition process from VO(2) (B) to VO(2) (A) was first observed through a mild hydrothermal approach, using hybrid density functional theory (DFT) calculations and crystallographic VO(2) topology analysis. All theoretical analyses reveal that VO(2) (A) is a thermodynamically stable phase and has a lower formation energy compared with the metastable VO(2) (B). For the first time, X-ray absorption spectroscopy (XAS) of the V L-edge and O K-edge was performed on different VO(2) phases, and the differences in the electronic structure of the two polymorphic forms provide further experimental evidence of the more stable VO(2) (A). Consequently, transformation from VO(2) (B) to VO(2) (A) is much easier to be realized from a dynamical point of view. Notably, the transformation of VO(2) (B) into VO(2) (A) show the sequence VO(2) (B)-high-temperature VO(2) (A(H)) phase-low-temperature VO(2) (A) phase, which was achieved by hydrothermal treatment, respectively. Also, an alternative synthesis route was proposed based on the above hydrothermal transformation, and VO(2) (A) was successfully prepared via the simple one-step hydrothermal method by hydrolysis of VO(acac)(2) (acac = acetylacetonate). Therefore, VO(2) nanostructures with controlled phase compositions can be obtained in high yields. Through elucidating the structural evolution in the crystallographic shear mechanism, we can easily guide the design of other metal oxide nanostructures with controllable phases.

Low-lying icosahedral (I(h)) B(12)-containing structures of B(80) are explored, and a number of core-shell isomers are found to have lower energy than the previous predicted B(80) fullerene. The structural transformation of boron clusters from tubular structure to core-shell structure may occur at a critical size less than B(80).

{1̄11} faceted Ni3S2 with an asymmetric zigzag structure is elaborately designed and fabricated, which exhibits remarkable electrocatalytic performance for the HER and OER.

To explore the possible existence of boron clusters without carbon analogs, we study B(84) cluster as a prototypical system by ab initio calculations. Structures of several isomer forms of B(84) are optimized. Among these isomers, a group of amorphous (disordered) structures are found to be the most stable. Different from the high-symmetry isomers, the amorphous B(84) clusters are more stable than the fullerene B(80) in terms of cohesive energy per atom. These amorphous structures can be distinguished from other high-symmetry structures experimentally via, for example, infrared spectra. The radial and angular distribution functions of amorphous B(84) structures are more diffuse than those of high-symmetry structures. On the basis of these findings, we propose that amorphous structures may be generic for boron and dominate boron clusters in a range of cluster scale.

Graphene molecules, hexafluorotribenzo[a,g,m]coronene with ncarbon alkyl chains (FTBC-Cn, n ‫؍‬ 4, 6, 8, 12) and Janus-type ''double-concave'' conformation, are used to fabricate self-assembly on highly oriented pyrolytic graphite surface. The structural dependence of the self-assemblies with molecular conformation and alkyl chain is investigated by scanning tunneling microscopy and density functional theory calculation. An interesting reverse face ''up-down'' way is observed in FTBC-C4 assembly due to the existence of hydrogen bonds. With the increase of the alkyl chain length and consequently stronger van der Waals interaction, the molecules no longer take alternating ''up-down'' orientation in their self-assembly and organize into various adlayers with lamellar, hexagonal honeycomb, and pseudohoneycomb structures based on the balance between intermolecular and molecule-substrate interactions. The results demonstrate that the featured ''double-concave'' molecules are available block for designing graphene nanopattern. From the results of scanning tunneling spectroscopy measurement, it is found that the electronic property of the featured graphene molecules is preserved when they are adsorbed on solid surface.graphene molecule ͉ Janus-type double-concave conformation ͉ scanning tunneling microscopy ͉ self-assembly A graphene molecules is composed of fused aromatic sets and is regarded as graphite subunit. After the success in theoretical prediction and experimental realization of graphene, graphene type molecules attract a great deal of interest (1-4). Their unique structures provide them promising potentials in micro/nano electronic devices (5-7). Continuous effort in chemical synthesis of graphene type molecules has produced various graphene molecules with the structures and properties beyond simple graphene. For example, polycyclic aromatic hydrocarbons (PAHs) compounds belong to a class of important functional graphene molecules (7,8). PAHs and their derivatives contain 2D subsections of graphene and show significant advantages, such as good solubility and ability to bear different chemical functionalities in their periphery with various electronic properties. These graphene molecules are promising candidates as building block for nanodevices through self-assembled architectures on 2D solid surfaces (9, 10).As a powerful tool for nanoscience and nanotechnology, scanning probe microscopy, in particular, scanning tunneling microscopy (STM) studies have produced images of the molecular self-assembly of graphene molecules at atomic/submolecular resolution, providing molecular understanding of intermolecular interactions and origin of their physical/chemical properties (11)(12)(13)(14). Because of their chemical structures, most of PAHs have a planar conformation and are inclined to form well-defined long-range self-assemblies on various substrates, such as gold and highly oriented pyrolytic graphite (HOPG). For examples, an alkyl-substituted PAH with D 2h symmetry and 78 carbon atoms in the aromatic core can se...

Self-grown NiO hexagonal platelets with abundant oxygen vacancies were facilely fabricated, which demonstrated ultrahigh specific capacitance and good rate capability.

Results are presented for the triple differential (e, 2e) cross sections in helium in the region encompassing the (2s2)1S, (2s2p)3P, (2p2)1D and (2s2p)1P resonances at an incident energy of 94.6 eV for a scattered electron angle of 30 degrees and for ejected-electron scattering angles in the-range -25 to -135 degrees . The measured coincidence ejected-electron spectra are compared against those calculated in an equivalent local form of the distorted-wave impulse approximation with the resonant scattering amplitudes being evaluated by a six-state momentum-space coupled channels method. In each case the calculation is folded with the experimental energy resolution. The data are analysed in terms of the Shore-Balashov parametrization to obtain the direct (e, 2e) cross section fr and the resonance parameters ar and br for the (2s2)1S, (2p2)1D and (2s2p)1P resonances as a function of ejected-electron momentum. These derived parameters are compared against the results of a calculation where configuration interaction expansions for the resonances and helium ground state, which employed hydrogenic and multiconfiguration Hartree-Fock orbitals, respectively, were used. Here the distorted-wave Born approximation was employed for the (e, 2e) cross section calculation. The calculated parameters agree quite well with the experimental results with both indicating strong correlations between the resonance amplitudes and the direct ionization amplitudes, Finally we report and discuss our results of an experimental investigation into post-collision interaction effects for the present kinematical conditions.

Electron impact mass spectra have been recorded for helium nanodroplets containing water clusters. In addition to identification of both H + ͑H 2 O͒ n and ͑H 2 O͒ n + ions in the gas phase, additional peaks are observed which are assigned to He͑H 2 O͒ n + clusters for up to n = 27. No clusters are detected with more than one helium atom attached. The interpretation of these findings is that quenching of ͑H 2 O͒ n + by the surrounding helium can cool the cluster to the point where not only is fragmentation to H + ͑H 2 O͒ m ͑where m ഛ n −1͒ avoided, but also, in some cases, a helium atom can remain attached to the cluster ion as it escapes into the gas phase. Ab initio calculations suggest that the first step after ionization is the rapid formation of distinct H 3 O + and OH units within the ͑H 2 O͒ n + cluster. To explain the formation and survival of He͑H 2 O͒ n + clusters through to detection, the H 3 O + is assumed to be located at the surface of the cluster with a dangling O-H bond to which a single helium atom can attach via a charge-induced dipole interaction. This study suggests that, like H + ͑H 2 O͒ n ions, the preferential location for the positive charge in large ͑H 2 O͒ n + clusters is on the surface rather than as a solvated ion in the interior of the cluster.