Using first principles calculations, we report for the first time that large nearly neutral aromatic molecules, such as naphthalene and anthracene, and small charge-transfer aromatic molecules, such as TCNQ and DDQ, interact more strongly with metallic single-wall carbon nanotubes (SWNTs) versus their semiconducting counterparts as the molecular orientation of DDQ is taken into account. Hence two new mechanisms for separating metallic and semiconducting SWNTs via noncovalent pi-pi stacking or charge-transfer interaction are suggested.

Iron nanoparticles are highly desirable for their potential applications in magnetic and catalytic industry. However, their shape-controlled fabrication is still an important challenge. Here we successfully synthesized icosahedral face-centered cubic (fcc) Fe nanoparticles with size of 5-13 nm by a specifically designed thermodynamic governed synthetic route, which is facile but highly efficient and reproducible. With the aberration-corrected transmission electron microscopy (TEM), the unique icosahedral structure's pseudo-2-fold, 3-fold, and pseudo-5-fold axes were directly observed for the first time and verified by computer simulation, which reveals that nanoparticles' orientations have a large impact on HRTEM images at ultrahigh resolution. It is expected that as-synthesized Fe nanoparticles with sharp corners and edges would be beneficial for tailoring chemical and physical properties at the nanoscale.

By using first principles calculations, we show that fine tuning of both p- and n-type doping can be realized on single-wall carbon nanotubes (SWNTs) by tuning the electron affinity or ionization potential of the organic and organometallic molecules encapsulated inside SWNTs. This novel type of SWNT-based material offers great promise for molecular electronics because of its air stability, synthetic simplicity and the abundance of organic and organometallic molecules.

By means of variable-composition evolutionary algorithm coupled with density functional theory and in combination with aberration-corrected high-resolution transmission electron microscopy experiments, we have studied and characterized the composition, structure and hardness properties of WB3+x (x < 0.5). We provide robust evidence for the occurrence of stoichiometric WB3 and non-stoichiometric WB3+x both crystallizing in the metastable hP 16 (P 63/mmc) structure. No signs for the formation of the highly debated WB4 (both hP 20 and hP 10) phases were found. Our results rationalize the seemingly contradictory high-pressure experimental findings and suggest that the interstitial boron atom is located in the tungsten layer and vertically interconnect with four boron atoms, thus forming a typical three-center boron net with the upper and lower boron layers in a three-dimensional covalent network, which thereby strengthen the hardness.PACS numbers: 71.20. Lp, 71.23.Ft, 61.43.Bn Typical ultrahard or superhard materials [1-3] (i.e., diamond, c-B 2 CN, c-BN, γ-B 28 [4,5] and most recently synthesized nanotwinned c-BN [6]) would require threedimensional (3D) bonding networks commonly consisting of high densities of strong covalent bonds, atomic constituents and valence electrons as well as nano-scale grains. Currently, the most powerful way to yield the high densities of these factors is the synthesis under high pressure conditions. However, in recent years transition metal borides (OsB 2 , ReB 2 , CrB 4 , and FeB 4 , etc [7][8][9][10][11][12][13][14][15]) have attracted extensive interests because of superior mechanical properties and ambient-condition synthesis without the need of high pressure, although their hardness is not as hard as superhardness.Among those borides, the W-B system has attracted particular attention since the report [16] Given the fact that the theoretically proposed hP 16-WB 3 [21-23] is thermodynamically and mechanically stable, and its XRD pattern matches well the experimentally observed ones [17,19], there seems no reason to suspect the reliability of its composition and structure. However, it is highly surprising that four recent high-pressure experimental findings of this phase [16,[28][29][30] yielded conflicting tendency of the pressure dependence normalized c/a ratio. The more striking fact is that none of them agrees with the theoretically derived pressure-dependent c/a ratio [31] of hP 16-WB 3 . Therefore, this tungsten boride still needs further clarification.Within this context, by combining first-principles calculations [32,33] (unless otherwise mentioned, all calculations have been performed with the Perdew-BurkeErnzerh generalized gradient approximation (GGA-type PBE) [34]), variable-composition evolutionary algorithm search as implemented recently in USPEX [35,36] and the aberration-corrected images of high resolution transmission electron microscopy (Ac-HRTEM) (method details refers to Supporting information), we have confirmed the existence of WB 3+x (x < 0.5) (including the ...

Ru nanoclusters on Ni/Ni(OH)2 nanoparticles supported on carbon (Ru/Ni/Ni(OH)2/C) were successfully prepared and characterized. Ru/Ni/Ni(OH)2/C exhibited an unprecedented catalytic activity for naphthalene hydrogenation at room temperature due to synergetic catalysis.

Hydroxide-supported atomic structures, particularly single atoms, offer a wide scope for active microenvironmental tuning to enhance catalytic performance, but little has been explored on the electronic synergy between mono- and...

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Highly ordered ultrafine nanostructures (feature size <10 nm) have been successfully fabricated with single-nanometre precision using a convergent electron beam (CEB) in a high-resolution transmission electron microscope (HRTEM). This approach can be widely applied to inorganic solid-state materials including insulators, semiconductors and metals. The feature size can be precisely controlled by the probe size and the irradiation time. The formation mechanism of nanostructures fabricated by CEB has been discussed in terms of knock-on damage and the beam heating effect. On the basis of the experimental results of electron energy-loss spectroscopy (EELS), finite element thermal analysis reveals that the heating effect of the high-energy electron beam is negligible in inorganic solid-state materials, and the sculpting of nanostructures is predominated by the knock-on damage or ionization of high-energy electrons.