A tunable plasmon resonance in gold nanobelts

Plasmonic nanowires with sub-100-nm rectangular cross sections were found to exhibit a strong transverse plasmon peak at visible wavelengths. By correlating atomic force microscopy measurements of individual nanobelts with their dark-field scattering spectra, it is seen that the transverse peak tunes with cross-sectional aspect ratio. Simulations revealed that the scattering plasmonic modes are transverse antisymmetric excitations across the nanobelt width. Unlike larger diameter silver nanowires, these nanobelts exhibit sharp, tunable plasmon resonances similar to those of nanoparticles.     

Synthesis of cation-intercalated titanate nanobelts

Monovalent, bivalent and trivalent cations of Li+, Sn2+, Al3+, Fe3+ with different values of electronegativity were designed as doped-ions to prepare cations-intercalated titanate nanobelts through ex-situ ion-exchange reaction. XRD results revealed that the d200 values of layered TNBs decreased as the following sequence: Li-intercalated TNBs > Al-intercalated TNBs > Fe-intercalated TNBs > Sn-intercalated TNBs. The electronegativity differences between respective doped-cations and oxygen can well explain the trend of the reduction of d200 values for the synthesized layered nanobelts with different cations. The width change of nanobelts depending on intercalated cations showed similar tendency as that of d200 excluding Sn-intercalated case. That is mostly due to the crystallization of SnO2 nanoparticles on the nanobelts. Sn2+ is easily crystallized to form SnO2 nanoparticles on the surface of TNBs and being considered as unfavorable metal dopant for the present intercalation purpose. The reduction of d200 values of the doped TNBs from that of the undoped TNBs confirms the intercalation of the doped cations into layered structure. Such simple electronegativity-difference depending mechanism may be convenient for the designing of metal ion intercalation into octahedral TiO6 layered-oxide materials.     

Optical characterization of ZnO nanobelts

Zinc oxide nanobelts have been synthesized by chemical precipitation technique using zinc acetate as starting material. Scanning electron microscopy observations indicate that the lengths of nanobelts are ranging from a few hundreds of micrometers to a few millimeters. X-Ray Diffraction pattern confirms the würtzite structure. Nitrogen laser is employed here as an excitation source (337.1 nm, 10 ns) for phosphorescence studies. From the decay curves of time resolved laser induced photoluminescence, various optical parameters such as Einstein’s spontaneous and stimulated coefficients, oscillator strength, integrated cross-section and dipole-moment of ZnO nanobelts have been calculated and reported in this paper. Einstein’s spontaneous and stimulated coefficient values obtained from the decay curves indicate the probability of transitions from various traps. Selective excitation of the levels can make ZnO as a best suited laser medium.     

Mechanical properties of ZnS nanobelts

Mechanical properties of ZnS nanobelts were measured at room temperature by direct nanoindentation experiments. It was found that the ZnS nanobelts achieve 79% increase in hardness but 52% decrease in elastic modulus compared to bulk ZnS. The nanobelts were found to exhibit creep under indentation. Indentation cracking was preferred along the belt growth direction. Indentation deformation behavior and fracture mechanisms of the ZnS nanobelts are discussed in conjunction with their crystalline structure, size effect, and surface-to-volume ratio.     

Twinning-induced ZnO bicrystalline nanobelts

ZnO bicrystalline nanobelts induced by three types of twinning have been synthesized by thermal evaporation method. The morphology and microstructure of the ZnO bicrystalline nanobelts have been studied by means of scanning electron microscopy, transmission electron microscopy and high resolution electron microscopy. <21­1­3>/{2­112} twinning-induced ZnO bicrystalline nanobelts are dominant in the product. ZnO bicrystalline nanobelts induced by <011­1­>/{011­2} and <033­2­>/{011­3} twinnings take up low fraction of the product. High oxygen partial pressure favors formation of the ZnO bicrystalline nanobelts.     

Bicrystalline gallium oxide nanobelts

We have synthesized gallium oxide (Ga₂O₃) nanobelts by heating GaN powders in the conventional furnace. The nanobelts exhibited a unique bicrystalline structure that consisted of two single-crystalline monoclinic Ga₂O₃ nanobelts, which split along the twin boundary that exists at the centerline. Energy dispersive X-ray spectroscopy and electron energy loss spectroscopy spectra coincidentally indicated the presence of nitrogen in the Ga₂O₃ nanobelts. Photoluminescence spectra exhibited the visible light emission. We discussed the possible emission mechanisms, including the effect of the nitrogen dopant.     

纳米带的研究进展

综述了纳米带的研究进展．重点介绍了纳米带的定义,纳米带的特点,纳米带的制备方法,纳米带的生长机理,并对纳米带的潜在应用做了介绍．     

Morphology-tuned wurtzite-type ZnS nanobelts

Nanometre-sized inorganic dots, wires and belts have a wide range of electrical and optical properties, and variable mechanical stability and phase-transition mechanisms that show a sensitive dependency on size, shape and structure. The optical properties of the semiconductor ZnS in wurtzite structures are considerably enhanced, but the lack of structural stability limits technological applications. Here, we demonstrate that morphology-tuned wurtzite ZnS nanobelts show a particular low-energy surface structure dominated by the +/-[210] surface facets. Experiments and calculations show that the morphology of ZnS nanobelts leads to a very high mechanical stability to approximately 6.8 GPa, and also results in an explosive mechanism for the wurtzite-to-sphalerite phase transformation together with in situ fracture of the nanobelts. ZnS wurtzite nanobelts provide a model that is useful not only for understanding the morphology-tuned stability and transformation mechanism, but also for improving synthesis of metastable nanobelts with quantum effects for electronic and optical devices.     

Raman studies of semiconducting oxide nanobelts

Crystalline nanobelts of ZnO and SnO2 were prepared from a thermal evaporation of oxide powders inside an alumina tube in the absence of catalysts. Typical dimensions of the nanobelt samples ranged from approximately 10 to 100 microns in length, 30 to 300 nm in width, and 6 to 30 nm in thickness. Room temperature Raman spectra were obtained on pressed mats of nanobelt samples and compared with the corresponding spectra of the starting oxide powders and bulk materials. Collectively, our Raman data indicated that the as-prepared nanobelt samples used in this study were oxygen deficient. Upon annealing at 900 degrees C in flowing oxygen for 1 h, the nanobelt samples exhibited Raman features that corresponded to those expected in respective bulk semiconducting oxides. The dimensions of the nanobelts were a bit too large to expect significant quantum size effects on the phonon structure similar to those observed in carbon nanotubes and short-period semiconductor superlattices.     

Water molecule-induced stiffening in ZnO nanobelts

We report the observation of remarkable water molecule-induced stiffening in ZnO nanobelts using atomic force microscopy three-point bending test. It was found that the elastic modulus of ZnO nanobelts could increase significantly from 40 GPa under ambient condition up to 88 GPa at the relative humidity level of 80%. The physical mechanism for this phenomenon was explained in terms of increasing surface stress induced by water molecule adsorption on ZnO nanobelt surface. Our first-principles density functional theory calculations revealed that the water molecules adsorbed on the ZnO surface would attract surface Zn atoms to move outward and hence increase the value of surface stress of ZnO surface.     

Synthesis of single-crystalline bismuth nanobelts and nanosheets

Single-crystalline bismuth nanobelts have been synthesized successfully by solution-phase route, using ethylene glycol as reductant and solvent. It was speculated that the final morphology resulted from the layered structure of rhombohedral bismuth.     

Catalyst-nanostructure interaction and growth of ZnS nanobelts

Details of the vapour-liquid-solid Au droplet catalysed growth of ZnS nanobelts are elucidated in this work. The inclination of the Au droplet after solidification shows that it is indeed in the liquid state during nanobelt growth. Numerous stacking faults are observed when (0001) wurtzite is the side surface of the nanobelt. Compressive stress at the droplet-nanobelt-atmosphere triple interface is the cause of the stacking faults. Sawteeth-like structures are observed on the Zn-terminated polar (0001) side surface only. These surfaces are chemically active, while S-terminated [Formula: see text] surfaces and non-polar surfaces are not. On these active surfaces, autocatalysed vapour-solid growth leads to the formation of the observed sawteeth.     

Large-scale hydrothermal synthesis of SnS2 nanobelts

SnS2 nanobelts were successfully synthesized through a controllable solution-phase hydrothermal method on a large scale. The nanobelts have a very high yield, which is more than 95%, with widths ranging from 100 to 200 nanometers, lengths up to several micrometers and thicknesses ca. 10 nanometers. X-ray diffraction patterns, electronic diffraction, X-ray photoelectron spectra, field emission scanning electron microscopy images, transmission electron microscopy images and high-resolution transmission electron microscopy investigated the phase structures, compositions, and morphologies of SnS2 nanobelts. Dodecanethiol played important roles in the process of SnS2 nanobelts formation and growth. The formation mechanism of SnS2 nanobelts was investigated and discussed on the basis of the experimental results.     

Ultrasonic-assisted synthesis of Au nanobelts and nanowires

Au one-dimensional (1D) nanostructures, including nanobelts and nanowires, have been synthesized in an ethylene glycol (EG)/polyvinylpyrrolidone (PVP) system by a simple and convenient seed-mediated growth method. The nanobelts and nanowires have aspect ratios up to 600, a length distribution ranging from several to tens of microns, and an average width of 100 nm. In this method, we used an ultrasonic process to promote the formation of Au seeds, which largely determines the morphology of final product. Additionally, we have found that the ultrasonic process significantly increases the fabrication yield of 1D nanostructures. Further experimental results show strong polarization dependence of Surface-Enhanced Raman Scattering (SERS) on a single Au 1D nanostructure. This convenient, versatile and low-cost synthesis method can be applied to 1D nanostructures composed from a range of materials, making it widely applicable to many areas of modern science and technology.     

Synthesis of BaTi2O5 nanobelts

BaTi₂O₅ nanobelts with 60–100 nm in thickness, 200–300 nm in width, and several micrometers in length have been successfully synthesized through a two-step hydrothermal reaction. Sodium titanate nanobelts are synthesized via the reaction of titania nanoparticles and NaOH aqueous solution at 180 °C for 24 h. After the reaction, resulting sodium titanate nanobelts are ion-exchanged with barium ions and then treated at 180 °C for 60 h under alkaline condition, BaTi₂O₅ nanobelts are formed. The morphologies and crystal structures of sodium titanate and BaTi₂O₅ nanobelts are characterized by field-emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM) and X-ray powder diffractometer (XRD), respectively.     

单晶银纳米带的合成与机理分析

采用甲苯作为还原剂,水热条件下还原生成宽度为20nm左右,长度1～2μm单晶银纳米带.甲苯与银离子形成的配位聚合物的线状结构导致了银纳米结构的取向生长,是形成银纳米带的关键因素.     

Coordination polymer nanobelts for nucleic acid detection

Herein, coordination polymer nanobelts (CPNBs) were prepared rapidly and on a large scale, by directly mixing aqueous AgNO(3) solution and an ethanol solution of 4, 4'-bipyridine at room temperature. The application of such CPNBs as a fluorescent sensing platform for nucleic acid detection was further explored. CPNB is a π-rich structure, the strong π-π stacking interactions between unpaired DNA bases and CPNB leads to adsorption of fluorescently labeled single-stranded DNA (ssDNA) accompanied by 66% fluorescence quenching. However, the presence of target ssDNA will hybridize with the probe. The resultant helix cannot be adsorbed by CPNB due to its rigid conformation and the absence of unpaired DNA bases. Thus, a significant fluorescence enhancement, 73% fluorescence recovery, was observed in DNA detection as long as the target exists. The present system has excellent sensitivity; a substantial fluorescence enhancement was observed when the concentration of the target was as low as 5 nM. It also exhibits outstanding discrimination ability down to a single-base mismatch.     

Microemulsion-based synthesis of BaCO3 nanobelts and nanorods

The BaCO₃ nanorods and nanobelts were successfully synthesized in CTAB/cyclohexane/H₂O and NP₁₀/cyclohexane/H₂O microemulsion. The samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and infrared spectroscopy (IR). The possible mechanisms for the formation of BaCO₃ samples in series of microemulsion systems were discussed. Various comparison experiments show that several experimental parameters, such as the concentration of surfactant and reactant, and solvent hydrothermal treatment play important roles in the morphological control of BaCO₃ nanostructures.     

Sn掺杂ZnO纳米带的制备及其光致发光性能研究

采用热蒸发法制备了单晶Sn掺杂ZnO纳米带,其中Sn的掺杂含量约为5%(原子分数).X射线衍射(XRD)结果表明Sn掺杂ZnO纳米带为单相纤锌矿结构.X射线光电子能谱(XPS)表明样品中Sn的价态为4+.样品的室温光致发光谱(PL)在445.8nm处存在较强的蓝光发射峰,对其发光机制进行了分析.