Collision synthesis of unique carbon nanomaterials inspired by the Allende meteorite

A simple shock event approach inspired by the Allende meteorite to produce sophisticated carbon nanomaterials is reported. It is demonstrated that unique carbon nanostructures, including carbon nanotubes, carbon onions, and new carbon nanorings are synthesized by high-speed ball-milling of steel balls. The carbon nanorings have diameter of several tens of nanometers. It is considered that the carbon nanomaterials are formed from around the surface of steel balls under local high temperatures induced by the collision energy in ball-milling process.     

Magnetic nanoparticle formulations for DNA and siRNA delivery

Newly synthesized magnetic nanomaterials possess high DNA binding capacity either itself or in the presence of a positively charged lipid-based Metafectene™ reagent or branched polyethylene imine 25 kDa. Polyethylene imine (PEI)-modified nanomaterials are able to deliver nucleic acids in cell culture in duplexes. Magnetofection with triplexes of nanomaterials results in higher transduction efficiencies compared to optimal PEI or Metafectene formulations. 90% transient down-regulation of the target protein in HeLa-green fluorescence protein cells was achieved at short interfering RNA concentrations as low as 8 nM with a formulation of PEI-modified nanoparticles.     

Ultraviolet tip‐enhanced nanoscale Raman imaging

We have constructed an ultraviolet (UV)‐apertureless near‐field scanning optical microscope‐Raman spectroscopy system by using an aluminum tip for the simultaneous measurement of topography and Raman scattering of nanomaterials with high spatial resolution. The topography, Rayleigh scattering image, and tip‐enhanced Raman scattering image of the carbon nanotube film showed that a spatial resolution of around 19 nm was achieved. This spatial resolution of UV‐Raman mapping image exceeds that of previous approaches, which have several hundred nanometers of spatial resolution. Copyright © 2012 John Wiley & Sons, Ltd.     

Short range order heterogeneity on plastic mechanisms in γ-phase nickel-based superalloys

The fine structure of slip lines in the γ-phase of Ni-based superalloy single crystals has been investigated by in situ atomic force microscopy observations of the specimen surface during deformation. For the first time, the dislocation structure is discussed in terms of short range order heterogeneity. A stress-driven unlocking mechanism is observed of dislocation pile-ups scanning the short range order in the bulk material. This is strongly enhanced by the propagation of other pile-ups a few hundreds of nanometers apart. A modelling based on elasticity is proposed and discussed.     

Effect of pulse width and fluence of femtosecond laser on the size of nanobump array

Conical nanobump arrays were generated on gold thin film processed by interfering femtosecond laser. The transition of the height and diameter as functions of fluence and pulse width was investigated. When the fluence was 87 mJ/cm², the height and diameter were not so different at 350 fs or shorter pulse width. They decreased at longer pulse width, and no bump could be generated over 1.6 ps. The results suggest the decrease of size is due to the diffusion of electron to not-excited region, and due to heat conduction to not heated region or substrate, or change of absorbance of laser. At long pulse width of 2.4 ps and relatively higher fluence of 190 mJ/cm², nanobump had liquid-like structure as a stop motion of a water drop.     

Effect of interference pattern on femtosecond laser-induced ripple structure

Combined structures composed of a micron-sized periodic structure and a nano-sized quasi-periodic ripple structure were generated by a single process of multiple shots of an interfering femtosecond laser. The former structure was generated by an interference pattern and controlled by a number of beams. The latter structure was generated by a multiple shot method. As a result, multiple periodic structures were generated. The periodicity of the structures was analyzed by two-dimensional (2D) fast Fourier transform (FFT). The most probable period of ripple structure was downsized to 177 nm by restricting irradiated region by a TM wave interference pattern. The smallest period was 105 nm. The dispersion angle of a ripple decreased to about 50%. The period and direction of the ripples were for a first time controlled by using interference.     

Liquidly process in femtosecond laser processing

Nano-sized water-crown like structure in array was firstly generated on metallic thin film by interfering femtosecond laser processing. We named the structure as “nanocrown”. Ridges are standing on the edge of each ablated hole. The shapes of ridges are spike, nano-waterdrop and bead on column. The radius of the top of a spike was just 7 nm, which is far smaller than that of nanobump generated in the previous work. The self-rising in liquidly process result in the generation of mesoscopic nanostructure with the size between nanohorn or nanotube and micron structures processed by machining or lithography. This is a new surface modification technique in top-down technology.     

Nano-structured surfaces on Ni–Ti generated by multiple shots of interfering femtosecond laser

Combined periodic structures composed of micron-sized periodic structure and nano-sized quasi periodic structure were generated on Ni–Ti target by multiple shots of interfering femtosecond laser beams. The micron-sized structure was generated by the interference pattern of four beams, and the nano-sized quasi period was generated due to the multiple shot effect of femtosecond laser. The structures were investigated in detail by two-dimensional fast Fourier transform (2D-FFT). The power spectra showed small spots and fuzzy spots due to precise period and quasi period, respectively. The most major size of the quasi periodic structure was 580 nm.     

Differential two-signal picosecond-pulse coherent anti-Stokes Raman scattering imaging microscopy by using a dual-mode optical parametric oscillator

We propose and demonstrate a novel differential two-signal technique of coherent anti-Stokes Raman scattering (CARS) imaging microscopy using a picosecond (ps) optical parametric oscillator (OPO). By adjusting a Lyot filter inside the cavity, we operated the OPO oscillating in two stable modes separated by a few nanometers. The CARS images generated by the two modes are separated by a spectrograph behind the microscope setup, and their differential image is directly obtained by balanced lock-in detection. The feasibility of the technique is experimentally verified by imaging micrometer-sized polystyrene beads immersed in water.     

Evolution of nanoscale nonuniformities under deformation of irradiated Plexiglas

The example of Plexiglas irradiated with γ radiation to the dose of D = 330 kGy is used to demonstrate the presence of minor deformation jumps. Deformation levels are determined by deformation jumps values measured by the interferometric technique. These results support the position on the existence of domains from nanometers to tens of nanometers in size within amorphous polymers and allow one to study multilevel organization of the deformation process and determine the influence of external factors on various structures on the nanoscale and above.     

Electronic band structure and optical properties of silicon nanoporous pillar array

Silicon nanoporous pillar array (Si-NPA) is fabricated by hydrothermally etching single crystal silicon (c-Si) wafers in hydrofluoric acid containing ferric nitrate. Microstructure studies disclosed that it is a typical micron/nanometer structural composite system with clear hierarchical structures. The optical parameters of Si-NPA were calculated by general light-absorption theory and Kramers–Kronig relations based on the experimental data of reflectance and the variations compared with the counterparts of c-Si were analyzed. The features of the electronic band structure deduced from the optical measurements strongly indicate that Si-NPA material is a direct-band-gap semiconductor and possesses separated conduction sub-bands which accords with conduction band splitting caused by silicon nanocrystallites several nanometers in size. All these electronic and optical results are due to the quantum confinement effect of the carriers in silicon nanocrystallites.     

Hydrogen bonding and clusters in supercritical methanol–water mixture by neutron diffraction with H/D substitution combined with empirical potential structure refinement modelling

ABSTRACT

Neutron diffraction measurements of H/D isotopic substitution have been performed for seven H/D substituted methanol-water mixtures of 0.3?mol fraction of methanol (x_M) under the supercritical (618?K, 100?MPa) and ambient (298?K, 0.1?MPa) conditions. The seven structure factors obtained were subjected to an empirical potential structure refinement (EPSR) modelling to derive all site-site pair correlation functions, coordination number distributions, spatial density functions, and cluster distributions. Water has a four coordinated structure in the first coordination shell under both ambient and supercritical conditions; however, the spatial density distribution of water molecules in the second coordination shell is delocalised under the supercritical condition. The mean coordination number of all atomic pairs with hydrophilic interactions decreases in the supercritical state. On the other hand, the mean coordination number of interactions between the hydrophobic part of methanol and water molecule is less sensitive to temperature. In the supercritical condition, water clusters with a wide size distribution are generated in a methanol-water mixture as well as in pure water. Since the critical temperature of a methanol-water mixture is lower than that of pure water, it can be concluded that the addition of methanol can generate fragment water clusters at a lower temperature.     

Synchrotron investigations of the specific features in the electron energy spectrum of silicon nanostructures

The Si L _{2, 3} x-ray absorption near-edge structure (XANES) spectra of porous silicon nanomaterials and nanostructures with epitaxial silicon layers doped by erbium or containing germanium quantum dots are measured using synchrotron radiation for the first time. A model of photoluminescence in porous silicon is proposed on the basis of the results obtained. According to this model, the photoluminescence is caused by interband transitions between the energy levels of the crystalline phase and oxide phases covering silicon nanocrystals. The stresses generated in surface silicon nanolayers by Ge quantum dots or clusters with incorporated Er atoms are responsible for the fine structure of the spectra in the energy range of the conduction band edge and can stimulate luminescence in these nanostructures.     

Synthesis of snowflake-like multi-layered ZnO with controllable pore sizes and its photocatalytic property

Snowflake-like multi-layered ZnO with porous structure is synthesized through a facile hydrothermal process and followed by calcinating process. The pore size of the multilayered ZnO is controlled by just regulating the calcination temperature. X-diffraction (XRD) patterns reveal that the precursor obtained by hydrothermal method is zinc hydroxide carbonate (ZnHC)¹, after being calcinated, pure wurtzite ZnO is got. TEM and SEM demonstrate the existence of the porosity and the variation of the pore size (ranges from tens of nanometers to hundreds of nanometers). The photocatalytic property is investigated by Xenon Lamp and sunlight.     

boldmath Broadband water window supercontinuum generation with a ω+3ω/2 multicycle two-colour pulse

We propose a method to generate a high-efficiency broadband water window supercontinuum with a ω+3ω/2 multicycle two-colour pulse. Our results reveal that the 3ω/2 laser pulse can simultaneously modulate the acceleration step and the ionization step, which not only broadens the bandwidth but also enhances the yield of the generated supercontinuum. An ultra-broadband supercontinuum from 290 eV to 555 eV covering the whole water window is generated. Using this method, we expect that an isolated 62-as pulse with a minor pre-pulse can be directly obtained.     

微乳液技术制备纳米材料

微乳液是表面活性剂、油相和水相形成的热力学稳定的各向同性的单分散体系,其分散质点为纳量级,它为纳米材料的制备提供理想的模板和微环境,介绍微乳液制备纳米材料的方法和影响因素以及微乳液法制备催化剂、超导体、半导体及磁性等材料的研究进展。     

Acute toxicities of six manufactured nanomaterial suspensions to Daphnia magna

The rapid growth of nanotechnology is stimulating research on the potential environmental impacts of manufactured nanomaterials (MNMs). This paper summarizes a comprehensive study on the 48-h acute toxicity of water suspensions of six MNMs (i.e., ZnO, TiO₂, Al₂O₃, C₆₀, SWCNTs, and MWCNTs) to Daphnia magna, using immobilization and mortality as toxicological endpoints. The results show that the acute toxicities of all MNMs tested are dose dependent. The EC₅₀ values for immobilization ranged from 0.622 mg/L (ZnO NPs) to 114.357 mg/L (Al₂O₃ NPs), while the LC₅₀ values for mortality ranged from 1.511 mg/L (ZnO NPs) to 162.392 mg/L (Al₂O₃ NPs). In these tests, TiO₂, Al₂O₃, and carbon-based nanomaterials were more toxic than their bulk counterparts. Moreover, D. magna were found to ingest nanomaterials from the test solutions through feeding behaviors, which indicates that the potential ecotoxicities and environmental health effects of these MNMs cannot be neglected.     

Feasibility of an optical experimental method for the sizing of primary spherules in sub-micron agglomerates by polarized light scattering

The possibility of inferring by a non-invasive experimental method the size of primary particles (spherules), which constitute the agglomerated soot generated in an ethylene–air diffusion flame, is investigated. In contrast to the predictions from the Mie theory for isolated spheres, experimental evidence is provided here about the fact that the size of spherules (some tens of nanometers), which stick together to form agglomerates (some hundreds of nanometers), can be recognized from polarization ratio measurements. Validation of the proposed scattering technique is obtained by first performing standard measurements of the primary particle size by SEM analysis of soot samples taken on quartz inserted directly in the flame along the burner axis. Then, the polarization ratio P(θ)≡σ_HH/σ_VV of scattered light is measured at the same locations and for the same flame conditions for different polar scattering angles θ. As major result, evidence is provided of a linear relationship existing between the primary sizes, obtained independently by SEM analysis, and the measurements of the polarization ratio P(90°). Finally, a procedure is reported and applied to retrieve the absolute spherule size from the direct observation of the transition between the power-law and Porod’s scattering regimes, which correspond to the domains of long-range (fractal) and short-range (not fractal) interactions between primary particles, respectively. Received: 24 February 1999 / Final version: 6 December 1999 / Published online: 1 March 2000     

Stimulated four-photon mixing and efficient polychromatic visible light generation in SiO2−based single-mode optical fibers pumped at 1.319 μm

Abstract

The generation of near-infrared and intense visible light through stimulated multi-wave mixing processes in single-mode silica-based optical fibers pumped by a Q-switched and mode-locked Nd:YAG laser operated at 1.319 μm is described. The experimental results show that intense infrared light around 1.2 μm is produced via selp-hase-matched four-photon mixing at the minimum group velocity dispersion region of pure SiO₂?core and P₂O₅?doped silica fibers. In the visible spectral region, from 580 nm to 600 nm, 20 W peak power 100-ps pulses were generated by pumping single spans of single-mode P₂O₅?doped and undoped SiO₂?core fibers with 1.319-μm laser pulses. The signal light generated in such fibers propagated in the LP₀₂ fiber mode and exhibited a threshold power that depended upon the fiber length and a critical length that was power dependent. Also, it exhibited an asymmetrical spectrum of a few nanometers bandwidth, with a long tail toward high frequencies. For GeO₂?doped silica-based fibers, a multiple-wavelength visible signal propagating in several high-order fiber modes was generated.     

Step-profile measurement by backpropagation of multiple-wavelength optical fields

Multiple-wavelength optical fields on a detecting plane of an interferometer are generated from the interference signals detected for an object surface. The generated optical fields are backpropagated along the optical axis. An optical field along the optical axis is reconstructed by summing the backpropagated fields over the multiple wavelengths. The intensity and phase distributions of the reconstructed optical field provide the position of the object surface with an accuracy of a few nanometers.