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With various techniques to probe a surface, we studied the decomposition of methanol on Au–Pt bimetallic clusters, of diameter ≤6.0 nm, formed by sequential deposition of Au and Pt evaporated onto thin-film Al2O3/NiAl(100). The surface of the bimetallic clusters comprised both Au and Pt, but the decomposition, through dehydrogenation to CO and scission of the C–O bond, proceeded primarily on the surface Pt. Alloying of Pt with Au altered little the dehydrogenation on the Pt sites. The CO and hydrogen produced from dehydrogenated methanol increased with the extent of Pt sites; the production per surface Pt was comparable to that of Pt clusters. The temperature of the onset of dehydrogenation resembled that of Pt clusters. Little methanol decomposed to CO on the Au sites. Varying the surface structure and composition of the bimetallic clusters affected these properties insignificantly. In contrast to the dehydrogenation, scission of the C–O bond in methanol did not depend exclusively on the concentration of Pt atoms at the surface, given that production of methane from this second channel did not increase with the extent of Pt surface sites. The modified electronic structure of the alloyed Pt controlled the probability of the C–O bond scission. The bimetallic clusters restructured during the reaction such that the Au atoms in the clusters aggregated and decorated the Pt surface, leading to fewer surface Pt and increased mean coordination of surface Au.

The controllable synthesis and growth kinetics of new nanostructures has an enormous impact on the fabrication and application of nanomaterials, and continues to be a central challenge in nanoscience and nanotechnology. On the other hand, sophisticated helical structures have been an attractive subject due to its significance in understanding biological self-assembly and appealing application in nanoscience. Here, we report the synthesis of novel dual-chirality hetero nanoscrews with controllable backbones and circles of SiO2 spiral threads by a single-step method and reveal experimentally its growth kinetics imaging for the first time. The nanoscrews are composed of amorphous SiO2 winds around cone-shaped single crystal β-SiC backbone via linear-to-rotary growth process. Our finding might open a new door to understand the growth process of sophisticated helical nanostructures.

We report a simple, efficient method to in situ grow the Al2O3 coating on the surface of single-crystalline tubular SiC nanostructures with controllable morphology, size and population density. The nanostructures are fabricated by heating evaporation Al powders and C60 on the Si substrates. By varying the reaction temperature, we can conveniently control the size and density of Al2O3 nanoparticles coating. Moreover, the ultrathin Al2O3 coating is also achieved by decreasing the quantity of Al source. The electrical transport measurement from single nanostructure is carried out to further confirm the excellent electrical insulation of ultrathin Al2O3 coating. This result contributes to the development of SiC based-nanodevices, as well as nanocomposites.

ZnO semiconductors at the micro- and nanometre scales are attractive in optical, magnetic, and electronic applications because of their particular features and excellent properties. The whispering gallery mode (WGM) is a general and effective type to amplify the intensity of the luminescence emission, and has gained extensive application in lasing and microcavities. In this contribution, we reported that the smallest whispering gallery optical resonator has been achieved in an individual ZnO nanocone whose diameter gradually reduces from bottom to top in the range of 700 to 50 nm. Using the monochromatic cathodoluminescence (CL) equipment attached at a scanning electron microscopy, we observed the alternating patterns of bright and dark rings from the monochromatic CL image of an individual ZnO nanocone, which is attributed to the WGM-like enhanced luminescence emission when the ZnO nanocone is considered as an optical resonator. The smallest mode number of WGM, N=0, was observed in the ZnO nanocone with a radius of 55 nm for the considered light wavelength of 380 nm, and with a radius of 81 nm for the considered light wavelength of 500 nm, respectively. These results showed that the smallest whispering gallery optical resonator from an individual ZnO nanocone has been fabricated. Experiments are in good agreement with both theoretical predictions and computer simulations based on the finite-difference time domain method with perfectly matched layer boundary conditions. These findings provided valuable information for applications of ZnO micro- and nanostructures in optoelectronic devices.

SiC@Al2O3 core-shell epitaxial nanowires have been synthesized via one-step process by simply heating evaporating Al source and C source on silicon substrate. Energy dispersive X-ray spectroscopy and transmission electron microscopy analysis of as-fabricated samples indicate that the core-shell nanowires consist of single-crystalline β-SiC core and thin cubic γ-Al2O3 shell. Epitaxial relationship is also observed between SiC core and Al2O3 shell. The corresponding growth model is proposed to describe the growth process of the core-shell epitaxial nanowires. Moreover, field emission measurement reveals the core-shell epitaxial nanowires have the excellent field emission property with low threshold electric field of 13.8 V μm−1.

Single crystalline one-dimensional (1-D) β-SiC nanostructures were synthesized by the CVD (chemical vapor deposition) method using single crystal silicon wafers and detonation soot as the raw materials. The phase, morphology, crystal structure, and defects of the products were characterized by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. Within a 2 h reaction time, the morphology of the SiC nanostructures can be tuned to nanowires, hexagonal columns and nanopyramids by simply altering the reaction temperature from 1250 °C, 1300 °C to 1350 °C, respectively. Based on the VLS mechanism, we propose a model to explain the novel behavior of the temperature-dependent morphology considering the relationships between catalytic droplets and nucleation.

Nowadays, the development of nano-synthesis has turned to controllable design for specific demands in micro-nano device application, to be integrated into functional units more conveniently with low-cost and efficiency principles. In this case, an appropriate approach for directly obtaining horizontally aligned nanowires in a large scale would be of great significance in future micro-nano device integration. Here, on the HOPG surface, we managed to achieve this. The approach is versatile to various kinds of materials. Horizontally aligned nanowires of Al-C based materials, such as Al4C3 and Al4O4C, were achieved. All of the nanowires exhibit a high degree ordered alignments and possess super aspect ratios with uniform widths of about 100 nm and lengths on the millimeter level. We believe the assembly mechanism lies in a step-edge induced ordered growth process, through which quaternary Al-Si-O-C nanoball alignment could also be obtained. It is expected that this method could be beneficial to adjust many useful materials for micro device integration in the future.

Metal W is employed as an efficient catalyst to grow AlN nanowires. High-density nanowires have been synthesized with a W catalyst cap at the tip. Transmission electron microscopy further reveals that the W-catalyzed AlN nanowires have an unusual [1 0 1] growth direction. The growth process of the nanowires has been studied by adjusting the experimental conditions and a growth kinetics model is proposed to describe the growth process of the W-catalyzed AlN nanowires. In addition, the surface wettability of a nanowire film is also observed and the sample shows smart wetting behavior. First, the as-grown sample exhibits a self-dewetting property with a water CA (contact angle) spontaneous transition from initial superhydrophilicity to final superhydrophobicity in the air. Then, the superhydrophilic surface can be recovered by illumination with UV light. The surface oxidation state of the catalyst may be responsible for the transition of the wettability.

2H-SiC–α-Al2O3 epitaxial heterostructures in a 1-D nanosystem were achieved via a simple CVD (chemical vapor deposition) process. Detailed structural characterizations and elemental analyses were carried out using methods such as elemental mapping, EELS (electron energy loss spectroscopy), XPS (X-ray photoelectron spectroscopy) and Raman spectroscopy, which identified the amounts of Al atoms that occupied the Si sites in the SiC lattice and that a small quantity of oxygen atoms were found on the SiC side. The carbon atoms dissolve in the Al2O3 crystal, substituting the oxygen elements, and there is only a small amount of Si in the Al2O3 part. These results supply a comprehensive understanding about the interface and information about the atoms that diffuse between 2H-SiC and α-Al2O3. We hope that this work contributes to the design of SiC–Al2O3 based epitaxial heterostructures.

The Al–O–C–N system is known as a kind of Al2O3-based ceramic material with various different chemical compositions and structures. Considering its superior physical and mechanical properties, the corresponding one-dimensional Al–O–C–N system may have huge potential applications in future nanodevices. Herein, for the first time, two types of ultralong one-dimensional Al3CON nanostructures, nanowires and bicrystalline nanobelts, were simultaneously synthesized by asimple CVD process. The products were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy as well as energy dispersive X-ray spectrometry. Corresponding property studies were carried out to explore the potential applications of the products. The force measurement based on a single nanostructure was performed by using an atomic force microscope (AFM) and the nanostructure showed high strength with a Young's modulus of 251 GPa. Semiconductor characteristics were also observed by electrical measurement at room temperature, which may be attributed to the doping and/or native defects. In addition, the Al3CON nanostructures showed deep-ultraviolet photoconductivity, in which the conductance increases only when illuminated with 254 nm light rather than 365 nm light.

Close-packing WC as a kind of metallic carbide, possessing good conductivity, high melting point and superior hardness, has numerous intrinsic properties that deserve to be investigated and then explored for use in micro or nano devices in the photoelectronics field. One of the main reasons why WC has not been considered much is that low-dimensional structures such as nanowires and nanowalls are hard to prepare. Here, we developed a novel method to overcome a series of difficulties in the growth of low-dimensional WC nanostructures and managed to apply eutectic solidification in W–Al–C solution to synthesize a high-quality WC nanowall forest and nanowires on a large scale. The experiment was carried out in a high-vacuum (∼10−4 Pa) chemical vapor deposition system pumped by a turbo molecular pump. We expect that it can be applied as a universal route to prepare low-dimensional nanostructures for refractory metals compound.

Ceramic Al4C3 nanowalls were fabricated through a VS mechanism via a chemical vapor deposition (CVD) method. XRD (X-ray diffraction), Raman spectra, SEM (scanning electron micrograph) and TEM (transmission electron micrograph) methods were employed to characterize the product. The synthesized 2-D nanostructures are confirmed to be polycrystalline R-Al4C3 with a Al2O3 sheath outside the nanosheet. Field emission (FE) measurements show that the turn-on field (where the emission current reaches 10 μA cm−2) of the as-prepared sample is 6.0–7.0 V μm−1. According to several comparative experiments, we propose an atmosphere-controlled nanowall growth mechanism from self-assembling templates under a low-pressure environment to explain the growth process.

Large scale and uniform SiO2 nanowires have been successfully fabricated in a high-frequency induction furnace via a Ge-catalyzed vapor liquid solid (VLS) mechanism. The nanowires were characterized by scanning electron microscopy, transmission electron microscopy, XRD and Raman spectroscopy. The results show that the as-synthesized SiO2 nanowires have an amorphous structure with diameters of 20–50 nm, and lengths up to tens of micrometres. The room-temperature photoluminescence measurement of the products show that they have a blue emission band at 420 nm, reveal that the high yield, and ultralong SiO2 nanowires might have potential applications in the future optoelectronic devices. Furthermore, the growth mechanism of the SiO2 nanowires is discussed.

Although nanomaterials investigations have been carried over the recent decades, researchers still face a fundamental challenge: how to control the phase, size and shape of nanocrystals in the synthesis of nanomaterials, i.e., how to achieve the transformation from nanocrytsal synthesis to functional nanostructure fabrication. For this issue, we, in this review, introduce recent developments in laser ablation in liquid (LAL) for the synthesis and fabrication of novel nanostructures with metastable phases and shapes. Laser ablation of solid targets in liquid has actually opened a door toward to synthesize nanocrystals and fabricate nanostructures due to these advantages as follows: (i) LAL is a chemically "simple and clean" synthesis due to the process with reduced byproduct formation, simpler starting materials, no need for catalyst, etc. (ii) Under ambient conditions, not extreme temperature and pressure, a variety of metastable phases that may not usually be attainable, can be generated by mild preparation methods. (iii) New phase formation involves in both liquid and solid upon LAL, which allows researchers to choose and combine interesting solid target and liquid to synthesize nanocrystals and fabricate nanostructures of new compounds for purpose of fundamental research and potential applications. (iv) The phase, size and shape of the synthesized nanocrystals can be readily controlled by tuning laser parameters and applying assistances such as inorganic salts or electrical field upon LAL. For example, we have synthesized the micro- and nanocubes of carbon with C(8)-like structures by the inorganic salts assisted LAL, and the micro- and nanocubes and spindles of GeO(2) by the electrical field assisted LAL. Additionally, we have developed a new technique to fabricate functional nanopatterns on the basis of the pulsed-laser deposition in liquid. Accordingly, LAL could greatly extend its application in fabrication of functional nanostructures in the future.