The mechanical resonance of a single ZnO nanobelt, induced by an alternative electric field, was studied by in situ transmission electron microscopy. Due to the rectangular cross section of the nanobelt, two fundamental resonance modes have been observed corresponding to two orthogonal transverse vibration directions, showing the versatile applications of nanobelts as nanocantilevers and nanoresonators. The bending modulus of the ZnO nanobelts was measured to be ∼52 GPa and the damping time constant of the resonance in a vacuum of 5×10−8 Torr was ∼1.2 ms and quality factor Q=500.

We present an ab initio investigation of water adsorption on ordered hydroxylated silica surfaces, using the density functional theory within the ultrasoft pseudopotentials and generalized-gradient approximation. The ͑100͒ and ͑111͒ surfaces of the hydroxylated cristobalite are used as substrates to adsorb water clusters and overlayers. Water adsorbs through hydrogen bonds formed between water and surface hydroxyl groups on the ␤͑␣͒-cristobalite ͑100͒ surface. A large enhancement of the hydrogen bonding in the adsorbed water dimer is observed, which can be inferred from the shortened hydrogen-bond ͑H bond͒ length, the vibrational spectra from the molecular dynamics simulation and the redistribution of electron density. At one monolayer ͑ML͒ coverage, a "tessellation ice," with characteristic quadrangular and octagonal hydrogen-bonded water rings, is formed. It has two types of H bonds and can exist on two different adsorption sites with two different OH orderings in a surface supercell. Our study is further extended to the ␤-cristobalite ͑111͒ surface. Based on these studies, we find that the water-silica bond, which comprises several H bonds, is usually stronger than other associative water-surface interactions. The H bonds between water and surface usually differ in strength-and hence, in vibrational spectra-from those between adsorbed water molecules. Because the ͑100͒ and ͑111͒ surfaces sustain different silanol groups ͑geminal and isolated silanols͒, a well-defined twodimensional tessellation ice phase can be observed only on the cristobalite ͑100͒ surface. On ␤-cristobalite ͑111͒ surface, however, isolated water molecules, hydrogen-bonded to the surface hydroxyls, are formed, even at 1 ML coverage.

Soon after the discovery of carbon nanotubes, the ternary system of BCN nanotubes began to attract increasing research interest. [1][2][3] A prime advantage of the BCN nanotubes over their carbon counterparts is the relative simplicity in controlling the tube electronic properties. 2,3 A pristine carbon single-walled nanotube (C-SWNT) may behave either as metal or as semiconductor with varying band gaps, depending sensitively on the tube diameter and chirality whose control remains a formidable challenge for all known synthetic methods. By contrast, the electronic structure of BCN nanotubes is predicted to be controlled largely by their chemistry rather than their geometry, such that the band gap could be tailored over a wide range merely by varying the tube's chemical composition. 2,3 Direct synthesis of the B-and N-doped multi-walled carbon nanotubes (BCN-MWNTs) was first attempted by Stéphan et al. in 1994. 2a Since then, considerable progress has been made in the synthesis of the ternary BCN-MWNTs and/or nanofibers by different means of arc-discharge, laser ablation, and chemical vapor deposition (CVD). 2,4,5 At the same time, theoretical understanding of the structural and electronic properties concerning the BCN nanotubes has also been largely advanced. 3,6 The majority of the theoretical work, however, has been dealing with the SWNT structures rather than MWNTs (or nanofibers). 3,6 There are clearly many fundamental differences between those two systems. 7 Importantly, it is only the SWNTs' structure that would make the study of their intrinsic structural and physical properties easier and more valuable. 3,[6][7][8] In this regard, exploring synthetic methods for producing high-quality ternary BCN-SWNTs is highly desirable, though it seems to be an even more difficult task. Up to now, the only existing example of the ternary BCN-SWNTs synthesis was achieved via an alternative post-growth treatment route, that is, by substitution reaction of the presynthesized pristine C-SWNTs with B 3 O 2 and N 2 at high temperature. 9 As far as the direct synthesis route is concerned, although a few studies showed the possibility of direct doping of C-SWNTs solely with B or N, 10,11 evidences for the presence of the ternary SWNTs simultaneously composed of the B, C, and N elements have not been identified yet.Herein, we report on the direct, large-scale synthesis of ternary BCN-SWNTs via a bias-assisted hot filament CVD (HF-CVD) process. The same HF-CVD system has previously been used in our group to grow turbostratic BCN films and oriented BCN MWNTs. 12 This work is a continuation of our ongoing efforts toward the rational growth of BCN nanostructures. In the present contribution, the BCN-SWNTs' growth by HF-CVD was achieved over the powdery MgO-supported Fe-Mo bimetallic catalyst (denoted as Fe-Mo/MgO), by using CH 4 , B 2 H 6 , and ethylenediamine vapor as the reactant gases. Details of the catalyst preparation and the HF-CVD growth process are presented in the Supporting Information.In Figure 1a, we display the...