Nanostructure Research Papers - Academia.edu (original) (raw)

Synthesis of nanomaterials by a simple, low cost and in high yield has been a great challenge since the very early development of nanoscience. Various bottom and top down approaches have been developed so far, for the commercial... more

Synthesis of nanomaterials by a simple, low cost and in high yield has been a great challenge since the very early development of nanoscience. Various bottom and top down approaches have been developed so far, for the commercial production of nanomaterials. Among all top down approaches, high energy ball milling, has been widely exploited for the synthesis of various nanomaterials, nanograins, nanoalloy, nanocomposites and nano -quasicrystalline materials. Mechanical alloying techniques have been utilized to produce amorphous and nanocrystalline alloys as well as metal/non-metal nanocomposite materials by milling and post annealing, of elemental or compound powders in an inert atmosphere. Mechanical alloying is a non-equilibrium processing technique in which different elemental powders are milled in an inert atmosphere to create one mixed powder with the same composition as the constituents. In high-energy ball milling, plastic deformation, cold-welding and fracture are predominant factors, in which the deformation leads to a change in particle shape, cold-welding leads to an increase in particle size and fracture leads to decrease in particle size resulting in the formation of fine dispersed alloying particles in the grain-refined soft matrix. By utilizing mechanical milling various kind of aluminium/ nickel/ magnesium/ copper based nanoalloys, wear resistant spray coatings, oxide and carbide strengthened aluminium alloys, and many other nanocomposites have been synthesized in very high yield. The mechanical milling has been utilized for the synthesis of nanomaterials either by milling and post annealing or by mechanical activation and then applying some other process on these activated materials. This review is a systematic view of the basic concept of mechanical milling, historical view and applications of mechanical milling in the synthesis of various nanomaterials, nanosomposites, nnaocarbons and nano quasicrystalline materials.

In the past several years, there has been a trend in the sunscreen/ cosmetics industry to replace micron-sized titanium dioxide (TiO 2) particles with nanoscale materials. The increased use of nanoscale TiO 2 has resulted in questions... more

In the past several years, there has been a trend in the sunscreen/ cosmetics industry to replace micron-sized titanium dioxide (TiO 2) particles with nanoscale materials. The increased use of nanoscale TiO 2 has resulted in questions about these and other nanoproducts. This study examines the effects of using nanoscale TiO 2 on ultraviolet (UV) attenuation in simple to complex sunscreen formulations. UV light attenuation, product stability, and potential damage to the skin barrier were examined with both nanoscale and microscale TiO 2 particles. Results indicate that none of the formulations decreased the barrier function of the skin and the best UV attenuation occurs when the TiO 2 particles are stabilized with a coating and evenly distributed such as with non-agglomerated coated nanoscale materials. This indicates that nanoscale TiO 2 may have better efficacy while lacking toxicity. Ré sumé Au cours des dernières années, nous avons constaté une tendance dans l'industrie solaire/cosmétique pour le remplacement des particules micron-taille de dioxyde de titane (TiO 2) avec des matériaux de nano-échelle. L'utilisation accrue des particules de TiO 2 l'échelle du nanométre a engendré des questions sur tous les produits contenant des matériaux nano-échelle. Cette étude examine les effets de l'utilisation de particule de TiO 2 a l'échelle du nanomètre sur l'atténuation des rayons UV dans les formulations de crème solaire simple et complexe. Nous avons étudié l'atténuation de la luminosité ultraviolet (UV), la stabilité du produit et les effets sur la fonction barrière de la peau, avec les particules de TiO 2 nano-échelle et micro-échelle. Les résultats indiquent que les particules a l'échelle du nanométre, enduits et non-aggloméré, fournissent une excellente atténuation UV, sans diminuer la fonction barrière de la peau. Ceci suggére que les particules de TiO 2 a l'échelle du nanométre ont une meilleure efficacité, sans poser des inquiétudes en ce qui concerne leur securité.

Metal matrix composites with high interface density are produced via severe plastic co-deformation of multiphase alloys. 1–15 Corresponding compounds are first prepared by liquid or powder metallurgy3–12 or through restacking solids of... more

Metal matrix composites with high interface density are produced via severe plastic co-deformation of multiphase alloys. 1–15 Corresponding compounds are first prepared by liquid or powder metallurgy3–12 or through restacking solids of different composition. 2 Subsequent extreme straining, to promote intense microstructure refinement, proceeds by wire drawing, ball milling, accumulative roll bonding, damascene forging, equal channel angular extrusion, friction, or highpressure torsion. 7

The adsorption properties of pyridine on H-ZSM-5 zeolites have been investigated by cluster calculations with the ONIOM scheme and with an embedded-ONIOM scheme. The active site has been modeled with cluster sizes of up to 46 tetrahedra.... more

The adsorption properties of pyridine on H-ZSM-5 zeolites have been investigated by cluster calculations with the ONIOM scheme and with an embedded-ONIOM scheme. The active site has been modeled with cluster sizes of up to 46 tetrahedra. Two different types of pyridine adsorption complexes on the zeolite models are found. If Zeolite is modeled by a small 3T quantum cluster, the adsorption energy of the hydrogen-bonded pyridine complex (Py-Hz), is found to be À18.5 kcal/mol. When a larger cluster or the ONIOM models are employed, the optimized geometries show the formation of pyrdinium cation [PyH + ] bound as an ion-pair complex [PyH + ][Z À ]. The calculated energy of formation for this ion-pair complex is À36.8 kcal/mol in the ONIOM (B3LYP/6-31G(d,p):UFF) model. Both values are considerably lower than the experimentally estimated heat of adsorption of pyridine in ZSM-5 zeolite of À47.6 kcal/mol. Inclusion of the electrostatic effects of the zeolite crystal lattice via the embedded ONIOM model increases the adsorption energy to À44.4 kcal/mol. Performing the quantum-chemical treatment at the MP2/6-31G(d,p) level instead of the B3LYP/6-31G(d,p) leads to a slightly lower adsorption energy to À45.9 kcal/mol. These data suggest that the embedded ONIOM scheme provides an accurate method of studying the interaction of small organic molecules with zeolites.

Thin films of nanocrystalline cubic AlN were synthesized by vapor–liquid–solid (VLS) route on Si and fused silica substrates at appropriate conditions. The formation of cubic AlN was confirmed by X-ray diffraction studies. We also... more

Thin films of nanocrystalline cubic AlN were synthesized by vapor–liquid–solid (VLS) route on Si and fused silica substrates at appropriate conditions. The formation of cubic AlN was confirmed by X-ray diffraction studies. We also observed that AuCl3 plays an important role as a catalyst in the synthesis of well crystalline cubic phase of AlN. Energy dispersive analysis of X-rays confirmed

We observe the appearance of Fano resonances in the optical response of plasmonic nanocavities due to the coherent coupling between their superradiant and subradiant plasmon modes. Two reduced-symmetry nanostructures probed via confocal... more

We observe the appearance of Fano resonances in the optical response of plasmonic nanocavities due to the coherent coupling between their superradiant and subradiant plasmon modes. Two reduced-symmetry nanostructures probed via confocal spectroscopy, a dolmen-style slab arrangement and a ring/disk dimer, clearly exhibit the strong polarization and geometry dependence expected for this behavior at the individual nanostructure level, confirmed by full-field electrodynamic analysis of each structure. In each case, multiple Fano resonances occur as structure size is increased.

Over a decade ago, Dresselhaus predicted that low-dimensional systems would one day serve as a route to enhanced thermoelectric performance.In this article, recent results in the thermoelectric properties of nanowires and nanotubes are... more

Over a decade ago, Dresselhaus predicted that low-dimensional systems would one day serve as a route to enhanced thermoelectric performance.In this article, recent results in the thermoelectric properties of nanowires and nanotubes are discussed. Various synthesis techniques will be presented, including chemical vapor deposition for the growth of thermoelectric nanostructures in templated alumina.Electrical transport measurements of carbon nanostructures, such as resistivity and thermopower, have revealed some very interesting thermoelectric properties.Challenges still remain concerning the measurement of individual nanostructures such as nanowires.Much work has been performed on the thermoelectric properties of carbon nanotubes, and these results will be highlighted.In addition, routes for enhanced thermoelectric materials have focused on incorporating nanostructures within the bulk materials.The role of these “hybrid composite structures” based on nanomaterials incorporated into t...

We make a brief review on the effect of silver photodiffusion in Ge-chalcogenide glasses and report some of our recent results in this aspect. Using Raman spectroscopy and X-ray diffraction analysis we demonstrate that the hosting... more

We make a brief review on the effect of silver photodiffusion in Ge-chalcogenide glasses and report some of our recent results in this aspect. Using Raman spectroscopy and X-ray diffraction analysis we demonstrate that the hosting backbone undergoes depletion in chalcogen due to the specific conditions of photodiffusion and the diffusion products are silver chalcogenides. While in the Ge-Se system preliminary binary Ag-chalcogenides are forming, in the Ge-S system formation of Ag 2 GeS 3 is evidenced. This effect is related to the ability of the Ge-S glasses to form ethane-like structure at much lower Ge concentration than the Ge-Se glasses. For this type of structures is known that Ag replaces Ge to form homogeneous material, hence formation of Ag-containing ternary occurs. r

The objective of this review article is to provide a concise discussion of atomistic modeling efforts aimed at understanding the nanoscale behavior and the role of grain boundaries in plasticity of metallic polycrystalline materials.... more

The objective of this review article is to provide a concise discussion of atomistic modeling efforts aimed at understanding the nanoscale behavior and the role of grain boundaries in plasticity of metallic polycrystalline materials. Atomistic simulations of grain boundary behavior during plastic deformation have focused mainly on three distinct configurations: (i) bicrystal models, (ii) columnar nanocrystalline models, and (iii) 3D nanocrystalline models. Bicrystal models facilitate the isolation of specific mechanisms that occur at the grain boundary during plastic deformation, whereas columnar and 3D nanocrystalline models allow for an evaluation of triple junctions and complex stress states characteristic of polycrystalline microstructures. Ultimately, both sets of calculations have merits and are necessary to determine the role of grain boundary structure on material properties. Future directions in grain boundary modeling are discussed, including studies focused on the role of...

Raman spectra of sulfur, selenium and tellurium clusters confined in the large cavities of zeolite A with diameters of -1.4 nm have been studied. It is shown that sulfur is stablilized in the form of Ss rings. Selenium is stabilized in... more

Raman spectra of sulfur, selenium and tellurium clusters confined in the large cavities of zeolite A with diameters of -1.4 nm have been studied. It is shown that sulfur is stablilized in the form of Ss rings. Selenium is stabilized in the form of Se12 and Se8 rings. Se12 rings show dominant bands in the Raman spectra but they are less stable than Se8 rings under laser illumination with a wavelength of 514.5 nm. Tellurium is stabilized iy the form of Te8 rings. Low-frequency strong and broad bands at -40 cm and -29 cm observed in the spectra of zeolite A with sulfur and with selenium, respectively, are attributed to librations of the ring molecules in the zeolite cavities. 0 1998 Published by Elsevier Science Ltd.

Polyurethane (PU) nanocomposites reinforced with magnetic iron oxide nanoparticles and/or dielectric barium titanate nanoparticles fabricated by the surface-initiated-polymerization approach were investigated. The polymer matrix... more

Polyurethane (PU) nanocomposites reinforced with magnetic iron oxide nanoparticles and/or dielectric barium titanate nanoparticles fabricated by the surface-initiated-polymerization approach were investigated. The polymer matrix incorporated with different nanoparticles shows different presenting status surrounding the nanoparticles, i.e., chemical bonding, physical entanglement and bulk polymer chain. The nanoparticles have a different effect on the thermal stability of the polymer nanocomposites. By embedding different functional nanoparticles, unique physical properties were observed, such as enlarged coercivity and larger dielectric constant (real permittivity). The synergistic effect of the binary nanoparticle reinforced PU nanocomposite was explored. The addition of the iron oxide nanoparticles does have some effect on the permittivity. However, little difference was observed in the magnetic properties and permeability after the introduction of the dielectric barium titanate nanoparticle into Fe 2 O 3 /PU nanocomposites. The permeability and permittivity of c-Fe 2 O 3 and BaTiO 3 nanoparticle reinforced PU nanocomposites were investigated with frequencies ranging from 10 MHz to 1 GHz. The predicted microwave properties from Bruggeman's equation were consistent with the measured data, except for the real permittivity of Fe 2 O 3 /BaTiO 3 /PU. The volume average method (VAM) usually used for fiber-reinforced composites with reinforcements in the thickness direction was applied in this nanocomposite system. The predicted real permittivity by VAM was found to be in better agreement with the measured data than that predicted by Bruggeman's equation.

We review recent developments in our group regarding the solution-phase synthesis of one-dimensional nanostructures of metals. The synthetic approaches include solution-liquid-solid growth for nanowires of low-melting-point metals such as... more

We review recent developments in our group regarding the solution-phase synthesis of one-dimensional nanostructures of metals. The synthetic approaches include solution-liquid-solid growth for nanowires of low-melting-point metals such as Pb; seed-directed growth for Ag nanowires, nanobeams, and nanobelts; kinetically controlled growth for Pt nanorods, nanowires, and multipods; and galvanic replacement for nanotubes of Au, Pt, and Pd. Both characterization and mechanistic studies are presented for each nanostructure. Finally, we highlight the electrical and plasmonic properties of these metal nanostructures and discuss their potential applications in nanoscale devices. (1) Xia, Y.; Yang, P.; Sun, Y.; Wu, Y.; Mayers, B.; Gates, B.; Yin, Y.; Kim, F.; Yan, H. Alekseeva, A. V.; Bogatyrev, V. A.; Dykman, L. A.; Khlebtsov, B. N.; Trachuk, L. A.; Melnikov, A. G.; Khlebtsov, N.

Here, we design and develop high-power electric double-layer capacitors (EDLCs) using carbon-based three dimensional (3-D) hybrid nanostructured electrodes. 3-D hybrid nanostructured electrodes consisting of vertically aligned carbon... more

Here, we design and develop high-power electric double-layer capacitors (EDLCs) using carbon-based three dimensional (3-D) hybrid nanostructured electrodes. 3-D hybrid nanostructured electrodes consisting of vertically aligned carbon nanotubes (CNTs) on highly porous carbon nanocups (CNCs) were synthesized by a combination of anodization and chemical vapor deposition techniques. A 3-D electrode-based supercapacitor showed enhanced areal capacitance by accommodating more charges in a given footprint area than that of a conventional CNC-based device.

In polymer electrolyte membrane fuel cells (PEMFCs), because the reaction rate in the cathode is slower than that in the anode, the cathode catalyst layers require more catalyst loading than the anodes [1]. Much research has been focused... more

In polymer electrolyte membrane fuel cells (PEMFCs), because the reaction rate in the cathode is slower than that in the anode, the cathode catalyst layers require more catalyst loading than the anodes [1]. Much research has been focused on improving the catalytic activity in cathodes and simultaneously reducing the amount of Pt supported by carbon black, which is the most commonly used cathode catalyst [2-4]. Recently, carbon nanotubes [5-9], carbon nanohorn [10], and carbon nanofibers [11-13] have been

The paper analyses, at nanoscale levels, the chemical composition and mechanical properties of the anodic oxide films formed on Ti-6Al-4V alloy by galvanostatic polarization at maximum final voltages of 12-100 V. For the investigations... more

The paper analyses, at nanoscale levels, the chemical composition and mechanical properties of the anodic oxide films formed on Ti-6Al-4V alloy by galvanostatic polarization at maximum final voltages of 12-100 V. For the investigations Auger Electron Spectroscopy, Photoelectron Spectroscopy and nanoindentation measurements have been used. The results have shown that anodizing the Ti-6Al-4V alloy produces an oxide film whose thickness depends on the final voltage. The chemical composition is not significantly dependent on the thickness, the film consists of TiO 2 and Al 2 O 3. However, the best insulating properties of the films, determined from the growth parameter nm/V, are achieved with a final voltage between 30 and 65 V. Nanohardness and Young's modulus measurements have shown that the anodic films formed by different voltages exhibit similar mechanical properties which is consistent with the results of the surface analysis.

The molten salt electrolytic method for the preparation of nano-structured carbon materials has been subjected to a systematic investigation. It has been confirmed that the electrolysis of molten lithium chloride in the presence of a... more

The molten salt electrolytic method for the preparation of nano-structured carbon materials has been subjected to a systematic investigation. It has been confirmed that the electrolysis of molten lithium chloride in the presence of a graphite cathode generates a carbonaceous product that contains nanostructured constituents like particles, fibres and tubes. It has furthermore been found that the precise composition of the product depends critically on a number of process parameters, namely, type of graphite material, reaction temperature, electrochemical polarisation regime, and reaction time. After careful optimisation of these parameters, it has become possible to achieve a content of nanotubes in the carbonaceous product of approximately 80%. This exceeds by far the results of all previous studies using this approach. The nanotubes synthesised are multi-walled with varying diameters and highly curved, and they occur in the form of aggregates of considerable size.

We demonstrate that interferometric lithography provides a fast, simple approach to the production of patterns in self-assembled monolayers (SAMs) with high resolution over square centimeter areas. As a proof of principle, two-beam... more

We demonstrate that interferometric lithography provides a fast, simple approach to the production of patterns in self-assembled monolayers (SAMs) with high resolution over square centimeter areas. As a proof of principle, two-beam interference patterns, formed using light from a frequency-doubled argon ion laser (244 nm), were used to pattern methyl-terminated SAMs on gold, facilitating the introduction of hydroxyl-terminated adsorbates and yielding patterns of surface free energy with a pitch of ca. 200 nm. The photopatterning of SAMs on Pd has been demonstrated for the first time, with interferometric exposure yielding patterns of surface free energy with similar features sizes to those obtained on gold. Gold nanostructures were formed by exposing SAMs to UV interference patterns and then immersing the samples in an ethanolic solution of mercaptoethylamine, which etched the metal substrate in exposed areas while unoxidized thiols acted as a resist and protected the metal from dissolution. Macroscopically extended gold nanowires were fabricated using single exposures and arrays of 66 nm gold dots at 180 nm centers were formed using orthogonal exposures in a fast, simple process. Exposure of oligo(ethylene glycol)-terminated SAMs to UV light caused photodegradation of the protein-resistant tail groups in a substrate-independent process. In contrast to many protein patterning methods, which utilize multiple steps to control surface binding, this single step process introduced aldehyde functional groups to the SAM surface at exposures as low as 0.3 J cm -2 , significantly less than the exposure required for oxidation of the thiol headgroup. Although interferometric methods rely upon a continuous gradient of exposure, it was possible to fabricate well-defined protein nanostructures by the introduction of aldheyde groups and removal of protein resistance in nanoscopic regions. Macroscopically extended, nanostructured assemblies of streptavidin were formed. Retention of functionality in the patterned materials was demonstrated by binding of biotinylated proteins.

Langevin dynamics treats finite temperature effects in micromagnetics framework by adding a thermal fluctuation field to the local effective field. Several works have addressed that the numerical results depend on the cell size used to... more

Langevin dynamics treats finite temperature effects in micromagnetics framework by adding a thermal fluctuation field to the local effective field. Several works have addressed that the numerical results depend on the cell size used to split the ferromagnetic samples on the nanoscale regime. In this short paper, we analyze a thermally perturbed micromagnetic problem by using an implicit unconditionally stable numerical scheme to integrate the Langevin equation at room temperature. The obtained micromagnetic results for several cell sizes inside the validity range of the micromagnetic formalism, indicate that the addressed cell size dependence could be associated to numerical limitations of the commonly used numerical schemes. r

Gold nanoparticles and their arrays are some of the most studied nanomaterials, with promising applications in many fields such as electronics, optoelectronics, catalysis and biology. In order to protect bare gold nanoparticles from... more

Gold nanoparticles and their arrays are some of the most studied nanomaterials, with promising applications in many fields such as electronics, optoelectronics, catalysis and biology. In order to protect bare gold nanoparticles from aggregation, to manipulate the optical, electronic and catalytic properties of the gold core, as well as to control interfacial properties, the gold nanoparticles are generally capped by an organic layer. Previous studies [C.D. Bain, G.M. Whitesides, J. Am. Chem. Soc. 110 (1988) 3665–3666] have revealed that many phenomena (e.g., wetting, friction and adhesion), are sensitive to the top few angstroms of a surface. The interfacial properties of a gold surface derivatized with a self-assembled monolayer will thus be dictated by the functionalities present on the outer side of the monolayer. The synthesis, functionalization and surface structure of monolayer-protected gold nanoparticles have been intensively studied in recent times [M.-C. Daniel, D. Astruc, Chem. Rev. 104 (2004) 293–346]. In addition, the aggregation and dispersion of colloidal nanoparticles is one of the key issues related to their potential applications. The forces that govern the colloid stability of nanoparticle dispersions, and how to control them, have yet to be fully investigated. Here special attention has been paid to control of colloid stability using external stimuli. In this feature article, the following five areas are reviewed: synthesis and applications of nanostructured particles; formation and structure of self-assembled monolayer protected gold nanoparticles; colloid stability—DLVO and non-DLVO forces; photochemistry, photochromism and pyrimidine; and manipulation of colloid stability with external stimuli.

We consider strain hardening of nanostructured materials and propose a physically based interpretation of their low strain hardening capability in terms of a reduced storage rate of dislocations. The model suggested provides a... more

We consider strain hardening of nanostructured materials and propose a physically based interpretation of their low strain hardening capability in terms of a reduced storage rate of dislocations. The model suggested provides a modification of the Kocks-Mecking-Estrin evolution law for dislocation storage for nanostructured materials and predicts a critical grain size below which the strain hardening rate drops off.

MgO polyhedral nanocages and nanocrystals, synthesized by non-catalytic simple thermal evaporation process, were used to fabricate high-sensitive amperometric glucose biosensor which showed a high and reproducible sensitivity of 31.6 lA... more

MgO polyhedral nanocages and nanocrystals, synthesized by non-catalytic simple thermal evaporation process, were used to fabricate high-sensitive amperometric glucose biosensor which showed a high and reproducible sensitivity of 31.6 lA lM À1 cm À2 with a response time less than 5 s, linear dynamic range from 1.0 to 9.0 lM and correlation coefficient of R = 0.9993. The detection limit of fabricated biosensor (based on S/N ratio = 3) was estimated to be 68.3 ± 0.02 nM. To the best of our knowledge, this is the first report which demonstrates the use of MgO nanostructures for the fabrication of glucose biosensor; hence, this work opens a new way to utilize MgO nanostructures as an efficient electron mediator to fabricate efficient glucose biosensors.

We have developed a polyaniline/carboxy-functionalized multiwalled carbon nanotube (PAn/MWCNTCOOH) nanocomposite by blending the emeraldine base form of polyaniline (PAn) and carboxy-functionalized multiwalled carbon nanotubes (MWCNT) in... more

We have developed a polyaniline/carboxy-functionalized multiwalled carbon nanotube (PAn/MWCNTCOOH) nanocomposite by blending the emeraldine base form of polyaniline (PAn) and carboxy-functionalized multiwalled carbon nanotubes (MWCNT) in dried dimethyl sulfoxide (DMSO) at room temperature. The conductivity of the resulting PAn/MWCNTCOOH was 3.6 × 10 −3 S cm −1 , mainly as a result of the protonation of the PAn with the carboxyl group and the radical cations of the MWCNT fragments. Horseradish peroxidase (HRP) was immobilized within the PAn/MWCNTCOOH nanocomposite modified Au (PAn/MWCNTCOOH/Au) electrode to form HRP/PAn/MWCNTCOOH/Au for use as a hydrogen peroxide (H 2 O 2 ) sensor. The adsorption between the negatively charged PAn/MWCNTCOOH nanocomposite and the positively charged HRP resulted in a very good sensitivity to H 2 O 2 and an increased electrochemically catalytical current during cyclic voltammetry. The HRP/PAn/MWCNTCOOH/Au electrode exhibited a broad linear response range for H 2 O 2 concentrations (86 M-10 mM). This sensor exhibited good sensitivity (194.9 A mM −1 cm −2 ), a fast response time (2.9 s), and good reproducibility and stability at an applied potential of −0.35 V. The construction of the enzymatic sensor demonstrated the potential application of PAn/MWCNTCOOH nanocomposites for the detection of H 2 O 2 with high performance and excellent stability.

Silicon nanostructures are dispersed into an organic solvent and the third order optical properties of the system are studied by z-scan technique under 1064 nm and 532 nm excitations. The experiment results show that the silicon... more

Silicon nanostructures are dispersed into an organic solvent and the third order optical properties of the system are studied by z-scan technique under 1064 nm and 532 nm excitations. The experiment results show that the silicon nanostructures exhibit self-focus and saturable absorption with both excitation wavelengths. Nonlinear absorption results suggest that a new optical bleaching band exists under 532 nm excitation, and a two-step mechanism is tentatively put forward to explain the saturable absorption under 1064 nm excitation.

Several novel hierarchical ZnO nanostructures have been successfully prepared in mixed solvents of ethylene glycol (EG)-water via a facile microwave-assisted method. By only change of the heating parameters of the microwave oven, ZnO... more

Several novel hierarchical ZnO nanostructures have been successfully prepared in mixed solvents of ethylene glycol (EG)-water via a facile microwave-assisted method. By only change of the heating parameters of the microwave oven, ZnO nanostructures with straw-bundle-like, wide chrysanthemum-like, and oat-arista-like morphologies and microspheres were obtained. The products were characterized by means of X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and room-temperature photoluminescence spectrometry (PLS). The possible mechanisms for the growth of these hierarchical ZnO nanostructures were tentatively proposed.

We report the structural and optical properties of nanocrystalline thin films of vanadium oxide prepared via evaporation technique on amorphous glass substrates. The crystallinity of the films was studied using X-ray diffraction and... more

We report the structural and optical properties of nanocrystalline thin films of vanadium oxide prepared via evaporation technique on amorphous glass substrates. The crystallinity of the films was studied using X-ray diffraction and surface morphology of the films was studied using scanning electron microscopy and atomic force microscopy. Deposition temperature was found to have a great impact on the optical and structural properties of these films. The films deposited at room temperature show homogeneous, uniform and smooth texture but were amorphous in nature. These films remain amorphous even after postannealing at 300°C. On the other hand the films deposited at substrate temperature T S N 200°C were well textured and c-axis oriented with good crystalline properties. Moreover colour of the films changes from pale yellow to light brown to black corresponding to deposition at room temperature, 300°C and 500°C respectively. The investigation revealed that nanocrystalline V 2 O 5 films with preferred 001 orientation and with crystalline size of 17.67 nm can be grown with a layered structure onto amorphous glass substrates at temperature as low as 300°C. The photograph of V 2 O 5 films deposited at room temperature taken by scanning electron microscopy shows regular dot like features of nm size.

Monoclinic FeMoO 4 nanorods have been prepared by the hydrothermal method in an acid aqueous solution. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrum, X-ray photoelectron spectra and... more

Monoclinic FeMoO 4 nanorods have been prepared by the hydrothermal method in an acid aqueous solution. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrum, X-ray photoelectron spectra and differential scanning calorimetry are used to characterize the structure, morphology and composition of the sample. The FeMoO 4 nanorods exhibit a ferromagnetic property at room temperature with the coercivity of 31.1 Oe and remnant magnetization of 4.09 × 10 −3 emu/g, respectively.

We present the controlled solution-phase synthesis of several sheet-or rod-like bismuth oxides, BiOCl, Bi 12 O 17 Cl 2 , a-Bi 2 O 3 and (BiO) 2 CO 3 , by adjusting growth parameters such as reaction temperature, mole ratios of reactants,... more

We present the controlled solution-phase synthesis of several sheet-or rod-like bismuth oxides, BiOCl, Bi 12 O 17 Cl 2 , a-Bi 2 O 3 and (BiO) 2 CO 3 , by adjusting growth parameters such as reaction temperature, mole ratios of reactants, and the base used. BiOCl, Bi 12 O 17 Cl 2 , and a-Bi 2 O 3 could be prepared from BiCl 3 and NaOH, whereas (BiO) 2 CO 3 was prepared from BiCl 3 and urea. BiOCl and Bi 12 O 17 Cl 2 could also be prepared from BiCl 3 and ammonia. The a-Bi 2 O 3 sample exhibited strong emission at room temperature.

This paper expands our previous numerical studies predicting the optical properties of highly ordered mesoporous thin films from two-dimensional (2D) nanostructures with cylindrical pores to threedimensional (3D) structures with spherical... more

This paper expands our previous numerical studies predicting the optical properties of highly ordered mesoporous thin films from two-dimensional (2D) nanostructures with cylindrical pores to threedimensional (3D) structures with spherical pores. Simple, face centered, and body centered cubic lattices of spherical pores and hexagonal lattice of cylindrical pores were considered along with various pore diameters and porosities. The transmittance and reflectance were numerically computed by solving 3D Maxwell's equations for transverse electric and transverse magnetic polarized waves normally incident on the mesoporous thin films. The effective optical properties of the films were determined by an inverse method. Reflectance of 3D cubic mesoporous thin films was found to be independent of polarization, pore diameter, and film morphology and depended only on film thickness and porosity. By contrast, reflectance of 2D hexagonal mesoporous films with cylindrical pores depended on pore shape and polarization. The unpolarized reflectance of 2D hexagonal mesoporous films with cylindrical pores was identical to that of 3D cubic mesoporous films with the same porosity and thickness. The effective refractive and absorption indices of 3D films show good agreement with predictions by the 3D Maxwell-Garnett and nonsymmetric Bruggeman effective medium approximations, respectively.

The gate oxide reliability and the electrical behavior of FinFETs are directly related to the surface characteristics of the fin vertical sidewalls. The surface roughness of the fin sidewalls is one of the most important structural... more

The gate oxide reliability and the electrical behavior of FinFETs are directly related to the surface characteristics of the fin vertical sidewalls. The surface roughness of the fin sidewalls is one of the most important structural parameters to be monitored in order to optimize the fin patterning and postetch treatments. Because of the nanometer-scale dimensions of the fins and the vertical orientation of the sidewall surface, their roughness measurement is a serious challenge. In this paper, we describe a simple and effective method for measuring the sidewall morphology of silicon fins by conventional atomic force microscopy. The present methodology has been employed to analyze fins as etched by reactive ion etching and fins repaired by sacrificial oxidation. The results show that sacrificial oxidation not only reduces the roughness of the sidewalls, but also rounds the top corners of silicon fins. The present method can also be applied to characterize sidewall roughness of other nanostructures and materials such as the polysilicon gate of transistors or nanoelectromechanical beams.

High-quality, nano-sized clusters of TiS 2 have been grown successfully inside inverse micellar cages and their optical properties studied. The clusters exhibit large blueshifts in the optical-absorption features with decreasing cluster... more

High-quality, nano-sized clusters of TiS 2 have been grown successfully inside inverse micellar cages and their optical properties studied. The clusters exhibit large blueshifts in the optical-absorption features with decreasing cluster size due to quantum confinement, affording control of the absorption thresholds and a demonstration of the crossover from band-like to molecule-like spectra as the size of the clusters becomes smaller than that of the exciton in the bulk. Crown

A systematic engineering study on continuous synthesis of bismuth metal nanoparticles by vapor condensation in tube ows is presented. Simulations of aerosol nucleation, condensation and coagulation are cast in a design diagram format to... more

A systematic engineering study on continuous synthesis of bismuth metal nanoparticles by vapor condensation in tube ows is presented. Simulations of aerosol nucleation, condensation and coagulation are cast in a design diagram format to guide experimental studies on the e ect of process parameters on product nanoparticle characteristics. Flow visualization, tracer gas analysis and computational uid dynamics are used to unravel the e ect of particle residence time distribution on product morphology during evaluation of alternate quenching designs for the metal vapor. Bismuth nanoparticles of average diameter 12-37 nm, as determined by nitrogen adsorption and X-ray di raction, were made by controlling the quenching gas ow rate, carrier gas ow rate and process pressure. ?

In this work we describe a novel method for the fabrication of a regular and uniform array of Cu nanowires into anodic alumina membranes. It is based on galvanic contact between the metal sputtered film covering the bottom of template and... more

In this work we describe a novel method for the fabrication of a regular and uniform array of Cu nanowires into anodic alumina membranes. It is based on galvanic contact between the metal sputtered film covering the bottom of template and a less noble metal. The growth rate was estimated as function of the immersion time. Nanowires with aspect ratio from 12 to 286 were obtained by adjusting the deposition time. Copper nanowires were found to be polycrystalline with an average crystalline size of about 40 nm. This procedure can be applied for the preparation of a wide range of metallic nanostructures and it can be easily scaled up for industrial processing.

Nanostructured materials are believed to play a fundamental role in orthopedic research because bone itself has a structural hierarchy at the first level in the nanometer regime. Here, we report on titanium oxide (TiO 2 ) surface... more

Nanostructured materials are believed to play a fundamental role in orthopedic research because bone itself has a structural hierarchy at the first level in the nanometer regime. Here, we report on titanium oxide (TiO 2 ) surface nanostructures utilized for orthopedic implant considerations. Specifically, the effects of TiO 2 nanotube surfaces for bone regeneration will be discussed. This unique 3D tube shaped nanostructure created by electrochemical anodization has profound effects on osteogenic cells and is stimulating new avenues for orthopedic material surface designs. There is a growing body of data elucidating the benefits of using TiO 2 nanotubes for enhanced orthopedic implant surfaces. The current trends discussed within foreshadow the great potential of TiO 2 nanotubes for clinical use.

An overview of recent advances in the synthesis of nanoparticles by flame aerosol processes is given. In flame processes with gaseous precursors emphasis is placed on reactant mixing and composition, additives, and external electric... more

An overview of recent advances in the synthesis of nanoparticles by flame aerosol processes is given. In flame processes with gaseous precursors emphasis is placed on reactant mixing and composition, additives, and external electric fields for control of product characteristics. Thermophoretic sampling can monitor the formation and growth of nanoparticles, while the corresponding temperature history can be obtained by non-intrusive Fourier transform infrared spectroscopy. Furthermore, synthesis of composite nanoparticles for various applications is addressed such as in reinforcement or catalysis as well as for scale-up from 1 to 700 g/h of silica-carbon nanostructured particles. In flame processes with liquid precursors using the so-called flame spray pyrolysis (FSP), emphasis is placed on reactant and fuel composition. The FSP processes are quite attractive as they can employ a wide array of precursors, so a broad spectrum of new nanosized powders can be synthesized. Computational fluid dynamics (CFD) in combination with gas-phase particle formation models offer unique possibilities for improvement and possible new designs for flame reactors. Figure 6. NO-conversion as a function of catalysis temperature for a flamemade (diamonds) and wet-chemistry-made (circles) vanadia coated titania catalyst (courtesy of W. J. Stark, ETHZ). Keynote Ó WILEY-VCH Verlag GmbH, D-69469 Weinheim, 2001 0930-7516/01/0606-0590 $ 17.50+.50/0 Chem. Eng. Technol. 24 (2001) 6 Figure 8. Average primary particle diameter obtained by nitrogen adsorption (BET) as a function of airflow rate with (circles) and without (triangles) secondary air entrainment at production rates of 300 g/h in the reactor of Figure 7. Keynote Ó WILEY-VCH Verlag GmbH, D-69469 Weinheim, 2001 0930-7516/01/0606-0592 $ 17.50+.50/0 Chem. Eng. Technol. 24 (2001) 6 Figure 11. Specific surface area of SiO 2 particles made by FSP for 0.1 molar HMDSO/organic fuel solution as a function of dispersion gas (oxygen) flow rate using ethanol (diamonds) and iso-octane (circles) as solvent.

Transition metal oxides (TMOs) are a fascinating class of materials due to their wide rangingelectronic, chemical and mechanical properties. Additionally, they are gaining increasing attention for theirthermoelectric (TE) properties due... more

Transition metal oxides (TMOs) are a fascinating class of materials due to their wide rangingelectronic, chemical and mechanical properties. Additionally, they are gaining increasing attention for theirthermoelectric (TE) properties due to their high temperature stability,tunable electronic and phonon transport properties and well established synthesis techniques.In this article, we review TETMOs at cryogenic, ambient and high temperatures.

Carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) represent a novel class of low-dimensional materials. All these graphene-based nanostructures are expected to display the extraordinary electronic, thermal and mechanical properties... more

Carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) represent a novel class of low-dimensional materials. All these graphene-based nanostructures are expected to display the extraordinary electronic, thermal and mechanical properties of graphene and are thus promising candidates for a wide range of nanoscience and nanotechnology applications. In this paper, the electronic and quantum transport properties of these carbon nanomaterials are reviewed. Although these systems share the similar graphene electronic structure, confinement effects are playing a crucial role. Indeed, the lateral confinement of charge carriers could create an energy gap near the charge neutrality point, depending on the width of the ribbon, the nanotube diameter, the stacking of the carbon layers regarding the different crystallographic orientations involved. After reviewing the transport properties of defect-free systems, doping and topological defects (including edge disorder) are also proposed as tools to taylor the quantum conductance in these materials. Their unusual electronic and transport properties promote these carbon nanomaterials as promising candidates for new building blocks in a future carbon-based nanoelectronics, thus opening alternatives to present silicon-based electronics devices.

The effect of three different molecular weights of a triblock copolymer nonionic surfactant composed of poly(ethylene oxide) and poly(propylene oxide) have been investigated on the zeta potential, stability and rheology of a commercial... more

The effect of three different molecular weights of a triblock copolymer nonionic surfactant composed of poly(ethylene oxide) and poly(propylene oxide) have been investigated on the zeta potential, stability and rheology of a commercial nanosuspension of 3 mol% yttria stabilised zirconia (3YSZ). Whilst the surfactants showed some evidence of being adsorbed onto the nanoparticle surfaces, it was in insufficient quantities to achieve complete coverage and measurement of the total organic carbon content suggested that the bulk of the surfactants remained in the liquid medium. As a result, there was only a small effect on the zeta potential. Nevertheless, the stability of the suspension was not affected up to solids contents as high as 54 wt%. Whilst the viscosity of the nanosuspension increased slightly with increasing surfactant concentration due to the presence of the polymer molecules, for the lowest molecular weight surfactant the effect was relatively small. Finally, it was observed that if the ionic strength of the suspension was reduced via the removal of free electrolytes in the suspension by dialysis, the viscosity decreased significantly. The reverse behaviour was also observed when extra NH 4 Cl electrolyte was added to the nanosuspension.

The interest in research on inorganic colloidal nanoparticles has moved to more complex structures, such as anisotropically shaped particles and branched objects. Recently, schemes for the synthesis of heterostructures have also been... more

The interest in research on inorganic colloidal nanoparticles has moved to more complex structures, such as anisotropically shaped particles and branched objects. Recently, schemes for the synthesis of heterostructures have also been presented. In this article we discuss the synthesis conditions for spherical and branched nanoparticles. The influence of parameters as temperature and composition of the mixture of surfactants on the shape of the growing particles is discussed. Also, an overview on different approaches for the formation of heterostructures is presented briefly. r

Metal oxide gas sensors are predominant solid-state gas detecting devices for domestic, commercial and industrial applications, which have many advantages such as low cost, easy production, and compact size. However, the performance of... more

Metal oxide gas sensors are predominant solid-state gas detecting devices for domestic, commercial and industrial applications, which have many advantages such as low cost, easy production, and compact size. However, the performance of such sensors is significantly influenced by the morphology and structure of sensing materials, resulting in a great obstacle for gas sensors based on bulk materials or dense films to achieve highly-sensitive properties. Lots of metal oxide nanostructures have been developed to improve the gas sensing properties such as sensitivity, selectivity, response speed, and so on. Here, we provide a brief overview of metal oxide nanostructures and their gas sensing properties from the aspects of particle size, morphology and doping. When the particle size of metal oxide is close to or less than double thickness of the space-charge layer, the sensitivity of the sensor will increase remarkably, which would be called "small size effect", yet small size of metal oxide nanoparticles will be compactly sintered together during the film coating process which is disadvantage for gas diffusion in them. In view of those reasons, nanostructures with many kinds of shapes such as porous nanotubes, porous nanospheres and so on have been investigated, that not only possessed large surface area and relatively mass reactive sites, but also formed relatively loose film

Nanorobotics encompasses the design, fabrication, and programming of robots with overall dimensions below a few micrometers, and the programmable assembly of nanoscale objects. Nanorobots are quintessential nanoelectromechanical systems... more

Nanorobotics encompasses the design, fabrication, and programming of robots with overall dimensions below a few micrometers, and the programmable assembly of nanoscale objects. Nanorobots are quintessential nanoelectromechanical systems (NEMS) and raise all the important issues that must be addressed in NEMS design: sensing, actuation, control, communications, power, and interfacing across spatial scales and between the organic/inorganic and biotic/abiotic realms. Nanorobots are expected to have revolutionary applications in such areas as environmental monitoring and health care. This paper begins by discussing nanorobot construction, which is still at an embryonic stage. The emphasis is on nanomachines, an area which has seen a spate of rapid progress over the last few years. Nanoactuators will be essential components of future NEMS.

of non-ideal magnetic nanostructures which contain both FM and superparamagnetic (SPM) regions. This is an essential ingredient in explaining the high saturation field of GMR commonly observed in ED multilayer films. In addition to the... more

of non-ideal magnetic nanostructures which contain both FM and superparamagnetic (SPM) regions. This is an essential ingredient in explaining the high saturation field of GMR commonly observed in ED multilayer films. In addition to the GMR magnitude, this is another characteristic decisively influencing the magnetic field sensitivity, a key feature concerning applications in sensor devices. The controversial results reported for the spacer layer thickness dependence of GMR in ED multilayer films will also be discussed. It is pointed out that the still inferior GMR characteristics of ED multilayer films can be to a large extent ascribed to microstructural features leading to the appearance of SPM regions, pinholes in the spacer layers and probably not sufficiently perfect interfaces between the FM and NM layers. The origin of the latter deficiency is not yet well understood although it is clearly one of the main causes of a weak interlayer coupling (if there is any coupling at all) and, thus, a small degree of antiparallel alignment leading to a reduced GMR effect. Works will also be described in which attempts were made to produce ED multilayer films with view on possible applications in GMR sensor devices. Finally, problems will be identified which should still be solved in order to make the properties of ED multilayer films attractive for GMR applications.

We review recent advances on the theory of spin qubits in nanostructures. We focus on four selected topics. First, we show how to form spin qubits in the new and promising material graphene. Afterwards, we discuss spin relaxation and... more

We review recent advances on the theory of spin qubits in nanostructures. We focus on four selected topics. First, we show how to form spin qubits in the new and promising material graphene. Afterwards, we discuss spin relaxation and decoherence in quantum dots.