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Nanometers
Kinds of Nanometers Terms modified by Nanometers Selected AbstractsGiant Coercive Field of Nanometer- Sized Iron Oxide,ADVANCED MATERIALS, Issue 1 2004J. Jin Nanocrystals of iron oxide in a silica matrix exhibiting a giant Hc value of 2.0,T at room temperature are reported. The nanocomposite was obtained by combining reverse-micelle and sol,gel methods. The nanocrystals of iron oxide are composed of the ,-Fe2O3 phase, with rod-like particles 100,140,nm long and 20,40,nm wide. The Figure shows the hysteresis curve of the nanocrystals. [source] Polyoxometallate als Bausteine für funktionelle NanosystemeANGEWANDTE CHEMIE, Issue 10 2010De-Liang Long Dr. Abstract Die Polyoxometallate (POM), eine Untergruppe der Metalloxide, bilden vielfältige Molekülcluster, die nicht nur außerordentlich vielfältige physikalische Eigenschaften zeigen, sondern auch dynamische Strukturen mit Abmessungen vom Nanometer- bis zum Mikrometermaßstab bilden können. Hier beschreiben wir die neuesten Entwicklungen von der Synthese bis zur Struktur und Funktion von Polyoxometallaten. Wir diskutieren Wege zur Herstellung höchst differenzierter hierarchischer Systeme mit mehreren voneinander unabhängigen Funktionalitäten und geben eine kritische Analyse, aus der auch nichtspezialisierte Leser die wichtigsten Eigenschaften ersehen können. In diesem Zusammenhang schlagen wir auch ein "Periodensystem der Polyoxometallat-Baueinheiten" vor. Schließlich beleuchten wir einige aktuelle Herausforderungen beim Design funktioneller Systeme auf der Basis von POM-Baueinheiten und geben einen Ausblick auf mögliche Anwendungen. [source] Sonochemical synthesis and characterization of ZnO nanorod/Ag nanoparticle compositesCRYSTAL RESEARCH AND TECHNOLOGY, Issue 11 2009Fei Li Abstract A simple sonochemical route for the synthesis of Ag nanoparticles on ZnO nanorods is reported. Ultrasonic irradiation of a mixture of ZnO nanorods, Ag(NH3)2+, and formaldehyde in an aqueous medium yields ZnO nanorod/Ag nanoparticle composites. The powder X-ray diffraction of the ZnO/Ag composites shows additional diffraction peaks corresponding to the face-center-cubic structured Ag crystalline, apart from the signals from the ZnO nanorods. Scanning electron microscopy and transmission electron microscopy images of the ZnO/Ag composites reveal that the ZnO nanorods are coated with Ag nanoparticles with a mean size of several tens nanometer. The absorption band of ZnO/Ag composites is distinctly broadened and red-shifted, indicating the strong interfacial interaction between ZnO nanorods and Ag nanoparticles. This sonochemical method is simple, mild and readily scaled up, affording a simple way for synthesis of other composites. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Nanoparticle-Structured Ligand Framework as Electrode InterfacesELECTROANALYSIS, Issue 1-2 2004Nancy Abstract Nanostructured thin film assemblies derived from metal or oxide nanocrystal cores and functionalized molecular shells provide large surface-to-volume ratio and three-dimensional ligand frameworks. In this article, we report results of an investigation of the nanostructured materials for electroanalysis. Monolayer-capped gold nanoparticles of 2-nm core diameter and carboxylic acid-functionalized alkyl thiols were assembled on electrode surfaces via an exchange-crosslinking-precipitation reaction route, and were studied as a model system. The network assemblies exhibit open frameworks in which the void space forms channels with the nanometer sized cores defining its size and the shell structures defining its chemical specificity. Such nanostructures were exploited to demonstrate the viability of responsive materials for interfacial incorporation and fluxes of ionic species. The nanomaterials were characterized by an array of techniques, including cyclic voltammetry, electrochemical quartz-crystal nanobalance, flow injection analysis, and surface infrared reflection spectroscopy. The current responses and mass loading as a result of the incorporation of ionic species into the nanostructure have been analyzed. The potential application of the nanostructured thin films for electrochemical detection in microfluidic systems is also discussed. [source] Multifunctional FeCo/TiN Multilayer Thin Films with Combined Magnetic and Protective Properties,ADVANCED ENGINEERING MATERIALS, Issue 12 2009Christian Klever Abstract Coatings with thicknesses ranging from a few nanometer up to several micrometer produced by physical vapor deposition (PVD) processes have been established in engineering technologies since the early 1980s. In particular, magnetron sputtered wear resistance coatings are industrially established and capable to enhance tool lifetimes significantly. However, in cases where optical inspection of a coating in use is not possible, an intrinsic sensor function of the film would be beneficial. Therefore, the development of wear resistant coatings with an integrated sensor functionality based on the insertion of a magnetoelastic ferromagnetic phase is suggested. In combination with appropriate read-out electronics such a film system would be ready for online monitoring of the coatings' actual state (e.g., strain, temperature, volume loss). This paper focuses on the development of wear resistance coatings which simultaneously supply beneficial mechanical properties as well as ferromagnetic properties optimized for online non-contact read-out applications. Multilayer coatings obtained through alternate stacking of magnetron sputtered TiN and FeCo layers with a nominal total thickness of 1000,nm were produced as a model system meeting the above conditions. The bilayer period was varied down to 2.6,nm while the individual layer thickness ratio tTiN/tFeCo was determined by the deposition rates and maintained constant at a value of about 3/1. The films were vacuum annealed ex situ in a static magnetic field subsequent to the deposition. The constitution of the as-deposited and annealed coatings as well as their mechanical (nanohardness, Young's modulus) and magnetic properties (magnetization hysteresis, frequency-dependent permeability) are described. Finally, the suitability of the coatings for the use in remote-interrogable wear sensor applications is briefly discussed. [source] The Optimal Grain Sized Nanocrystalline Ni with High Strength and Good Ductility Fabricated by a Direct Current Electrodeposition,ADVANCED ENGINEERING MATERIALS, Issue 6 2008X. Shen In this work, six pure Ni specimen which mean grain sizes spans a broad range from ultra-fine to nanometer were fabricated by direct current electrodeposition and a coarse grain Ni was obtained by annealing. A gradual transition of the crystallographic preferred orientation of the deposited Ni from (200) texture to isotropic or random orientation with decreasing the mean grain size was revealed by XRD. [source] Interaction of Zoospores of the Green Alga Ulva with Bioinspired Micro- and Nanostructured Surfaces Prepared by Polyelectrolyte Layer-by-Layer Self-AssemblyADVANCED FUNCTIONAL MATERIALS, Issue 12 2010Xinyu Cao Abstract The interaction of spores of Ulva with bioinspired structured surfaces in the nanometer,micrometer size range is investigated using a series of coatings with systematically varying morphology and chemistry, which allows separation of the contributions of morphology and surface chemistry to settlement (attachment) and adhesion strength. Structured surfaces are prepared by layer-by-layer spray-coating deposition of polyelectrolytes. By changing the pH during application of oppositely charged poly(acrylic acid) and polyethylenimine polyelectrolytes, the surface structures are systematically varied, which allows the influence of morphology on the biological response to be determined. In order to discriminate morphological from chemical effects, surfaces are chemically modified with poly(ethylene glycol) and tridecafluoroctyltriethoxysilane. This chemical modification changes the water contact angles while the influence of the morphology is retained. The lowest level of settlement is observed for structures of the order 2,µm. All surfaces are characterized with respect to their wettability, chemical composition, and morphological properties by contact angle measurement, X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy. [source] The loose coupling mechanism in molecular machines of living cellsGENES TO CELLS, Issue 1 2000Fumio Oosawa Living cells have molecular machines for free energy conversion, for example, sliding machines in muscle and other cells, flagellar motors in bacteria, and various ion pumps in cell membranes. They are constructed from protein molecules and work in the nm (nanometer), pN (piconewton) and ms (millisecond) ranges, without inertia. In 1980s, a question was raised of whether the input,output or influx,efflux coupling in these molecular machines is tight or loose, and an idea of loose coupling was proposed. Recently, the long-distance multistep sliding of a single myosin head on an actin filament, coupled with the hydrolysis of one ATP molecule, was observed by Yanagida's group using highly developed techniques of optical microscopy and micromanipulation. This gave direct evidence for the loose coupling between the chemical reaction and the mechanical event in the sliding machine. In this review, I will briefly describe a historical overview of the input,output problem in the molecular machines of living cells. [source] Polyimide Orientation Layers Prepared from Lyotropic Aromatic Poly(Amic Ethyl Ester)s,ADVANCED FUNCTIONAL MATERIALS, Issue 5 2003C. Neuber Abstract The synthesis and characterization of liquid-crystalline precursor polymer solutions[1] for polyimides permit for the first time the preparation of bulk- and surface-oriented polyimide thin films from the nematic lyotropic state by shear. A special shearing technique was developed and optimized to orient viscous solutions into thin films with thicknesses below 100 nm. The films produced were thermally imidized and characterized by polarized light microscopy, as well as polarized FTIR and UV-vis spectroscopy before and after imidization. The dichroic ratios (DRs) before imidization were determined as 5 by FTIR, and 4.5 by UV-vis spectroscopies. After imidization the DRs increased to 14 and 7, respectively. The shear-oriented layers possess a surface profile in the form of striations, which was characterized by mechanical surface scanning and atomic force microscopy (AFM). The profile height was determined in the nanometer range in contrast to the profile distance in the micrometer range, thus the latter is a magnitude larger than the film thickness. To quantify and compare the orientation potential of the obtained orientation layers, cells with a liquid-crystalline host and a dichroic azo dye as guest were prepared. Interesting for this class of rod-like polyimides is that layers, which were cast from low concentration isotropic solutions and rubbed, exhibited an almost doubled DR of 15 compared to analogously prepared alignment layers based on commercial flexible polyimide systems (DR,=,8). [source] Local Electrochemical Functionality in Energy Storage Materials and Devices by Scanning Probe Microscopies: Status and PerspectivesADVANCED MATERIALS, Issue 35 2010Sergei V. Kalinin Abstract Energy storage and conversion systems are an integral component of emerging green technologies, including mobile electronic devices, automotive, and storage components of solar and wind energy economics. Despite the rapidly expanding manufacturing capabilities and wealth of phenomenological information on the macroscopic device behaviors, the microscopic mechanisms underpinning battery and fuel cell operations in the nanometer,micrometer range are virtually unknown. This lack of information is due to the dearth of experimental techniques capable of addressing elementary mechanisms involved in battery operation, including electronic and ion transport, vacancy injection, and interfacial reactions, on the nanometer scale. In this article, a brief overview of scanning probe microscopy (SPM) methods addressing nanoscale electrochemical functionalities is provided and compared with macroscopic electrochemical methods. Future applications of emergent SPM methods, including near field optical, electromechanical, microwave, and thermal probes and combined SPM-(S)TEM (scanning transmission electron microscopy) methods in energy storage and conversion materials are discussed. [source] Multiple Functionalities of Polyelectrolyte Multilayer Films: New Biomedical ApplicationsADVANCED MATERIALS, Issue 4 2010Thomas Boudou Abstract The design of advanced functional materials with nanometer- and micrometer-scale control over their properties is of considerable interest for both fundamental and applied studies because of the many potential applications for these materials in the fields of biomedical materials, tissue engineering, and regenerative medicine. The layer-by-layer deposition technique introduced in the early 1990s by Decher, Moehwald, and Lvov is a versatile technique, which has attracted an increasing number of researchers in recent years due to its wide range of advantages for biomedical applications: ease of preparation under "mild" conditions compatible with physiological media, capability of incorporating bioactive molecules, extra-cellular matrix components and biopolymers in the films, tunable mechanical properties, and spatio-temporal control over film organization. The last few years have seen a significant increase in reports exploring the possibilities offered by diffusing molecules into films to control their internal structures or design "reservoirs," as well as control their mechanical properties. Such properties, associated with the chemical properties of films, are particularly important for designing biomedical devices that contain bioactive molecules. In this review, we highlight recent work on designing and controlling film properties at the nanometer and micrometer scales with a view to developing new biomaterial coatings, tissue engineered constructs that could mimic in vivo cellular microenvironments, and stem cell "niches." [source] From quantum chemistry and the classical theory of polar liquids to continuum approximations in molecular mechanics calculations,INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 5 2005Sergio A. Hassan Abstract Biological macromolecules and other polymers belong to the class of mesoscopic systems, with characteristic length scale of the order of a nanometer. Although microscopic models would be the preferred choice in theoretical calculations, their use in computer simulations becomes prohibitive for large systems or long simulation times. On the other hand, the use of purely macroscopic models in the mesoscopic domain may introduce artifacts, with effects that are difficult to assess and that may compromise the reliability of the calculations. Here is proposed an approach with the aim of minimizing the empirical nature of continuum approximations of solvent effects within the scope of molecular mechanics (MM) approximations in mesoscopic systems. Using quantum chemical methods, the potential generated by the molecular electron density is first decomposed in a multicenter-multipole expansion around predetermined centers. The monopole and dipole terms of the expansion at each site create electric fields that polarize the surrounding aqueous medium whose dielectric properties can be described by the classical theory of polar liquids. Debye's theory allows a derivation of the dielectric profiles created around isolated point charges and dipoles that can incorporate Onsager reaction field corrections. A superposition of screened Coulomb potentials obtained from this theory makes possible a simple derivation of a formal expression for the total electrostatic energy and the polar component of the solvation energy of the system. A discussion is presented on the physical meaning of the model parameters, their transferability, and their convergence to calculable quantities in the limit of simple systems. The performance of this continuum approximation in computer calculations of amino acids in the context of an atomistic force field is discussed. Applications of a continuum model based on screened Coulomb potentials in multinanosecond simulations of peptides and proteins are briefly reviewed. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [source] Investigation of bone and cartilage by synchrotron scanning-SAXS and -WAXD with micrometer spatial resolutionJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3-1 2000Biological materials such as bone or wood are hierarchically structured to optimize mechanical and other properties. Several methods and experimental techniques are usually needed to study these materials on different length scales. We developed a device for small angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD), optimized for position resolved investigations of bone sections using synchrotron radiation. Thin samples can be scanned with 20 µm steps, acquiring two-dimensional SAXS or WAXD patterns at every point. The system was tested by performing one-dimensional scans across bone cartilage interfaces, revealing information about size, shape and orientation of nanometer sized mineral particles as well as about crystal type and texture of these particles. [source] Dispersion of nanoscale BaTiO3 suspensions by a combination of chemical and mechanical grinding/mixing processesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Kuo-Liang Ying Abstract The colloidal stability of aqueous nanometer- and micrometer-scale barium titanate (BaTiO3) utilizing poly (methacrylic acid) (PMAA-Na) and polyacrylamide/(,- N,N -dimethyl- N -acryloyloxyethyl)ammonium ethanate (PDAAE) was investigated. In addition to chemical dispersants, the effects of mechanical milling using either conventional ball milling or nanogrinding/-mixing on the dispersion of BaTiO3 suspensions were also studied. Characterization of the particle size distribution (d50), viscosity, and morphology of BaTiO3 particles in the suspensions revealed that a sole chemical dispersant or mechanical milling was insufficient to achieve nanometer-scale dispersion. The best dispersion results were obtained with a combination of PMAA-Na dispersant and nanogrinding/-mixing, which could provide sufficient electronic repulsive force and shear force to disperse the 80-nm BaTiO3 powders uniformly in the aqueous suspension. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Preparation and applications of novel fluoroalkyl end-capped sulfonic acid oligomers,silica gel polymer hybridsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Kazuo Sasazawa Abstract Fluoroalkyl end-capped 2-methacryloxyethanesulfonic acid homo-oligomer [RF,(MES)n,RF] and 2-methacryloxyethanesulfonic acid,N,N -dimethylacrylamide co-oligomers [RF,(MES)x,(DMAA)y,RF] reacted with tetraethoxysilane (TEOS) under acidic conditions to afford RF,(MES)n,RF homo-oligomer,SiO2 polymer hybrid and RF,(MES)x,(DMAA)y,RF co-oligomer,SiO2 polymer hybrid, respectively. Thermogravimetric,mass spectra showed that the thermal stability of RF,(MES)n,RF homo-oligomer,SiO2 polymer hybrid was superior to that of traditionally well-known perfluorinated ion exchange polymers such as Nafion 112 (TR). The sol solutions of the fluorinated co-oligomer,SiO2 polymer hybrid were applied to the surface modification of glass to exhibit not only a strong oleophobicity imparted by fluorine but also a good hydrophilicity on the glass surface. On the other hand, RF,(MES)x,(DMAA)y,RF co-oligomer reacted with TEOS in the presence of a variety of silica nanoparticles (mean diameters: 11,95 nm) under alkaline conditions to afford fluoroalkyl end-capped oligomers,silica nanoparticles (mean diameters: 32,173 nm) with a good dispersibility and stability in methanol. Similarly, a variety of fluorinated oligomers containing sulfo groups,silica nanoparticles were prepared by the homo- and co-oligomerizations of fluoroalkanoyl peroxides with 2-methacryloxyethane sulfonic acid (MES) and comonomers such as N,N -dimethylacrylamide (DMAA) and acryloylmorpholine (ACMO) in the presence of silica nanoparticles. Interestingly, these isolated fluorinated particle powders were found to afford nanometer size-controlled colloidal particles with a good redispersibility and stability in aqueous and organic media such as methanol. These fluorinated nanoparticles containing sulfo groups were also applied to an excellent heterogeneous catalyst for Bronsted acid-catalyzed transformations. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 110,117, 2007 [source] Preparation of LiMn2O4 powders via spray pyrolysis and fluidized bed hybrid systemAICHE JOURNAL, Issue 7 2006Izumi Taniguchi Abstract A novel technique has been developed to directly produce fine ceramic powders from liquid solution using a spray pyrolysis and fluidized bed hybrid system. Using this technique, the preparation of lithium manganese oxides LiMn2O4, which are the most promising cathode materials for lithium-ion batteries, has been carried out for various superficial gas velocities U0 = 0.30-0.91 m/s, static bed heights Ls = 50-150 mm, and medium particle sizes dpm,g = 294-498 ,m. The resulting powders had spherical nanostructured particles that comprised primary particles with a few tens of nanometer in size, and they exhibited a pure cubic spinel structure without any impurities in the XRD patterns. Moreover, the as-prepared powders showed better crystallinity and smaller specific surface area than those by conventional spray pyrolysis. The effects of process parameters on powder properties, such as specific surface area and crystallinity, were investigated for a wide range of superficial gas velocities and static bed heights. An as-prepared sample was used as cathode active materials for lithium-ion batteries and the cell performance has been investigated. Test experiments in the electrochemical cell Li/1M LiClO4 in PC/LiMn2O4 demonstrated that the sample prepared by the present technique was superior to that by the conventional spray pyrolysis and solid-state reaction method. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Accuracy of scale conceptions in science: Mental maneuverings across many orders of spatial magnitudeJOURNAL OF RESEARCH IN SCIENCE TEACHING, Issue 10 2006Thomas R. Tretter The use of unifying themes that span the various branches of science is recommended to enhance curricular coherence in science instruction. Conceptions of spatial scale are one such unifying theme. This research explored the accuracy of spatial scale conceptions of science phenomena across a spectrum of 215 participants: fifth grade, seventh grade, ninth grade, twelfth grade, and doctoral students in science. Conceptions spanning sizes from one nanometer to one billion meters were investigated through use of written assessments and individual interviews. Results showed that accuracy of conceptions at small scale were not symmetrical with respect to conceptions at large scale. Large scale accuracy tended to decline in a smooth, uniform fashion as the scale increased, whereas small scale accuracy displayed a discontinuity at the microscopic level. To conceptually interact with scales far removed from human scale, experts used strategies of mentally jumping to a new scale-world. Experts tended not to transition smoothly between the differently scaled worlds but rather to make a discontinuous leap, maintaining abstract linkages between the worlds via mathematics. Implications of these findings for curriculum development and classroom instruction are discussed. © 2006 Wiley Periodicals, Inc. J Res Sci Teach 43: 1061,1085, 2006 [source] Evaluating the In Vitro and In Vivo Efficacy of Nano-Structured Polymers for Bladder Tissue Replacement ApplicationsMACROMOLECULAR BIOSCIENCE, Issue 5 2007Megan Pattison Abstract Bladder cancers requiring radical cystectomy, along with congenital and acquired disorders which result in obstruction of the bladder, necessitate surgical measures (including augmentation); such diagnoses bring a clinical need for effective bladder replacement implant designs. Many recent approaches for the design of soft tissue replacement materials have relied on the use of synthetic polymeric substances; unfortunately, the optimal soft tissue implant material is yet to be found. This may, in part, be because current polymeric formulations fail to sufficiently biomimic the neighboring bladder tissue. This study took a brand new approach in designing the next generation of tissue-engineered bladder constructs through the use of nanotechnology, or materials with nanometer (less than 100 nm) surface features. Results provided evidence that nano-structured polymeric scaffolds (specifically, PLGA and PU) created using chemical etching techniques are capable of enhancing the human bladder smooth muscle cell adhesion, proliferation, and the production of extracellular matrix (ECM) proteins. Preliminary in vivo results also speak to the usefulness of such nano-structured materials. In combination, these findings suggest that nano-dimensional PLGA and PU scaffolds are promising replacement materials for the human bladder wall. [source] Biodegradable Polylactide and Its Nanocomposites: Opening a New Dimension for Plastics and CompositesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 14 2003Suprakas Sinha Ray Abstract The academic and industrial aspects of the preparation, characterization, mechanical and materials properties, crystallization behavior, melt rheology, and foam processing of pure polylactide (PLA) and PLA/layered silicate nanocomposites are described in this feature article. Recently, these materials have attracted considerable interest in polymer science research. PLA is linear aliphatic thermoplastic polyester and is made from agricultural products. Hectorite and montmorillonite are among the most commonly used smectite-type layered silicates for the preparation of nanocomposites. Smectites are a valuable mineral class for industrial applications because of their high cation exchange capacities, surface area, surface reactivity, adsorptive properties, and, in the case of hectorite, high viscosity, and transparency in solution. In their pristine form, they are hydrophilic in nature, and this property makes them very difficult to disperse into a polymer matrix. The most common way to overcome this difficulty is to replace interlayer cations with quaternized ammonium or phosphonium cations, preferably with long alkyl chains. In general, polymer/layered silicate nanocomposites are of three different types: (1) intercalated nanocomposites, in which insertion of polymer chains into the layered silicate structure occurs in a crystallographically regular fashion, regardless of polymer to layered silicate ratio, with a repeat distance of few nanometer; (2) flocculated nanocomposites, in which intercalated and stacked silicate layers are sometimes flocculated due to the hydroxylated edge,edge interactions between the silicate layers; (3) exfoliated nanocomposites, in which individual silicate layers are uniformly distributed in the polymer matrix by average distances that totally depend on the layered silicate loading. This new family of composite materials frequently exhibits remarkable improvements in its material properties when compared with those of virgin PLA. Improved properties can include a high storage modulus both in the solid and melt states, increased flexural properties, a decrease in gas permeability, increased heat distortion temperature, an increase in the rate of biodegradability of pure PLA, and so forth. Illustration of the biodegradability of PLA and various nanocomposites. [source] Effect of loaded TiO2 nanofiller on heteropolyacid-impregnated PVDF polymer electrolyte for the performance of dye-sensitized solar cellsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 2 2009Sambandam Anandan Abstract In order to improve the performance of the dye-sensitized solar cells based on polymer electrolytes, heteropolyacid impregnated polyvinylidene fluoride (PVDF) with loaded TiO2 nanofiller were prepared to mainly impede the back electron transfer processes. The prepared polymer electrolytes were well characterized before using them in solar cells. The SEM image confirms that the prepared polymer electrolytes have extended porosity with intersecting cavities of few nanometer in size. The functioning of the solar cells fabricated was monitored and the current,voltage characteristics were measured. The observed long term stability of the fabricated solar cells may be due to the redox couple mobility of the polymer chain increases upon addition of titania nanofiller. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Crystallographically oriented high resolution lithography of graphene nanoribbons by STM lithographyPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2010G. Dobrik Abstract Due to its exciting physical properties and sheet-like geometry graphene is in the focus of attention both from the point of view of basic science and of potential applications. In order to fully exploit the advantage of the sheet-like geometry very high resolution, crystallographicaly controlled lithography has to be used. Graphene is a zero gap semiconductor, so that a field effect transistor (FET) will not have an "off" state unless a forbidden gap is created. Such a gap can be produced confining the electronic wave functions by etching narrow graphene nanoribbons (GNRs) typically of a few nanometers in width and with well defined crystallographic orientation. We developed the first lithographic method able to achieve GNRs that have both nanometer widths and well defined crystallographic orientation. The lithographic process is carried out by the local oxidation of the sample surface under the tip of a scanning tunneling microscopy (STM). Crystallographic orientation is defined by acquiring atomic resolution images of the surface to be patterned. The cutting of trenches with controlled depth and of a few nanometer in width, folding and manipulation of single graphene layers is demonstrated. The narrowest GNR cut by our method is of 2.5,nm width, scanning tunneling spectroscopy (STS) showed that it has a gap of 0.5,eV, comparable to that of germanium, which allows room temperature operation of graphene nanodevices. [source] Carrier transport in nanodevices: revisiting the Boltzmann and Wigner distribution functionsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2009Fons Brosens Abstract In principle, transport of charged carriers in nanometer sized solid-state devices can be fully characterized once the non-equilibrium distribution function describing the carrier ensemble is known. In this light, we have revisited the Boltzmann and the Wigner distribution functions and the framework in which they emerge from the classical respectively quantum mechanical Liouville equation. We have assessed the method of the characteristic curves as a potential workhorse to solve the time dependent Boltzmann equation for carriers propagating through spatially non-uniform systems, such as nanodevices. In order to validate the proposed solution strategy, we numerically solve the Boltzmann equation for a one-dimensional conductor mimicking the basic features of a biased low-dimensional transistor operating in the on-state. Finally, we propose a computational scheme capable of extending the benefits of the above mentioned solution strategy when it comes to solve the Wigner,Liouville equation. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Nanoporous oxides of refractory metals: fabrication and propertiesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2008S. K. Lazarouk Abstract A new approach to fabrication of nanoporous oxides of refractory metals is presented. It is based on the magnetron co-sputtering of aluminum and refractory metal (titanium, niobium or tungsten) followed by porous electrochemical anodization of the composite film and selective etching of alumina. The nanoporous oxide films with a thickness up to 5 µm were fabricated and studied. The porosity of the oxide films characterized by the surface area of 230 , 460 m2/cm3 can betuned by the aluminum content in the as-deposited composite films. The pore diameters are found to be varied in nanometer and subnanometer ranges. The parameters of porous titania within porous alumina matrix for different titanium concentrations are presented. The fabricated porous composite oxide films are characterized by the refractive index in the range from 1.45 to 1.77. The dielectric permeability for these films is found to be varied from 6.7 to 24. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Nanotechnology advances in controlled drug delivery systemsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2008C. Kiparissides Abstract Nanotechnology advances in drug delivery deal with the development of synthetic nanometer sized targeted delivery systems for therapeutic agents of increased complexity, and biologically active drug products. Therapeutic systems in this class are up to a million times larger than classical drugs like aspirin. Being larger there is more scope for diversity and complexity, which makes their protection much more challenging and their delivery more difficult. Their increased complexity however, gives these systems the unique power to tackle more challenging diseases. Targeted delivery systems can have multiple functions, a key one being their ability to recognize specific molecules which can be located either on the membrane of target cells, or in specific compartments within the cell. A challenging objective of targeted drug delivery is the development of innovative multidisciplinary approaches for the design, synthesis and functionalization of novel nanocarriers for targeted delivery of protein/peptide (P/P) drugs via oral, pulmonary and nasal administration routes as well as the fabrication of "smart" miniaturized drug delivery devices able to release a variety of drugs on demand. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis and applications of novel fluoroalkyl end-capped cooligomers containing diphenylacetylene segments: a new approach to the surface arrangement of diphenylacetylene segments on the traditional organic polymerPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 3 2010Masaki Mugisawa Abstract Fluoroalkyl end-capped cooligomers containing diphenylacetylene segments [RF -(DPMA)x -(Co-M)y - RF] were prepared by reaction of fluoroalkanoyl peroxide with 4-(phenylethynyl)phenyl methacrylate (DPMA) and radical polymerizable comonomers such as N,N -dimethylacrylamide (DMAA) and acryloylmorpholine (ACMO) under very mild conditions. Fluorinated cooligomers containing diphenylacetylene segments thus obtained exhibited a good solubility in a variety of organic solvents. These fluorinated cooligomers were also applied to the surface modification of traditional organic polymers such as poly(methyl methacrylate) (PMMA) to exhibit not only a good surface active property imparted by fluorine but also a fluorescent characteristic related to diphenylacetylene segments on their surface. In addition, these fluorinated cooligomers could form the nanometer size-controlled fluorinated molecular aggregates in chloroform. Interestingly, some benzenes and biphenyl (BP) derivatives could interact with these fluorinated oligomeric aggregates as guest molecules, and in particular 2-chloro-5-nitrobenzotrifluoride (CNB) was most effective for enhancing the fluorescent intensity of these guest molecules. Copyright © 2009 John Wiley & Sons, Ltd. [source] Preparation and applications of novel cross-linked fluoroalkyl end-capped oligomeric nanocomposites possessing aromatic siloxane segments as core unitsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 12 2009Yuki Goto Abstract Fluoroalkyl end-capped N,N -dimethylacrylamide oligomer and N -(1,1-dimethyl-3-oxobutyl)acrylamide oligomer were reacted with phenylene- and biphenylene-bridged ethoxysilanes under alkaline conditions to yield cross-linked fluoroalkyl end-capped oligomeric composites possessing aromatic siloxane segments as core units. These isolated fluorinated composite powders were found to be nanometer size-controlled fine particles with a good dispersibility and stability in water and organic solvents. Nitrogen adsorption,desorption isotherms confirmed the presence of micropores in these nanocomposites; the micropore size estimated by the HK method was 0.7,0.8,nm. Interestingly, fluorinated nanocomposites possessing a higher micropore volume ratio were found to exhibit a selective encapsulation ability of fullerene into their composite cores. These fluorinated nanocomposites were also applied to the surface modification of poly(methyl methacrylate) film, resulting in a good oleophobicity imparted by fluorine on the surface. In addition, fluorescence emission was visibly observed only from the modified PMMA film surface treated with fluorinated nanocomposites possessing biphenylene units when irradiated by light. Copyright © 2009 John Wiley & Sons, Ltd. [source] Preparation of a variety of fluoroalkyl end-capped N -(1,1-dimethyl-3-oxobutyl)acrylamide oligomer/silica nanocomposites possessing no weight loss characteristic at 800°CPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 7 2008Hideo Sawada Abstract A variety of fluoroalkyl end-capped N -(1,1-dimethyl-3-oxobutyl)acrylamide oligomer [RF -(DOBAA)n - RF]/silica nanocomposites, in which the oligomer contents are 18,96%, were prepared by reactions of the corresponding fluorinated oligomer with tetraethoxysilane and silica nanoparticles under alkaline conditions. Each fluorinated oligomer/silica composite thus obtained is nanometer size-controlled very fine particles (22,68,nm) possessing a good dispersibility and stability in a variety of solvents including water. Interestingly, the weight loss of RF -(DOBAA)n -RF/silica nanocomposites, in which the oligomer contents are 18,72%, were not observed at all even at 800°C, as well as the original silica nanoparticles, although the corresponding sub-micrometer size-controlled RF - (DOBAA)n -RF/silica composites (particle size: 359,nm) decomposed completely at 800°C to afford the weight loss in proportion to the content of RF -(DOBAA)n -RF oligomer in composites. On the other hand, a slight weight loss of RF -(DOBAA)n -RF/silica nanocomposites, in which the oligomer contents are 75,94%, was observed at 800°C compared to that of the original silica nanoparticles. Copyright © 2008 John Wiley & Sons, Ltd. [source] Spectroscopic detection and evaluation of morphologic and biochemical changes in early human oral carcinoma,CANCER, Issue 7 2003Markus G. Müller Ph.D. Abstract BACKGROUND Understanding the development and progression of head and neck squamous cell carcinoma is key in the quest for the early diagnosis and prevention of this type of malignancy. The current study correlated early biochemical and histologic changes in oral tissue with spectral features in fluorescence, reflectance, and light scattering spectra acquired in vivo to diagnose early stages of oral malignancies. METHODS A total of 91 tissue sites from 15 patients with varying degrees of malignancy (normal, dysplastic, and cancerous sites) and 8 healthy volunteers were analyzed with 3 spectroscopic techniques. Direct biochemical information regarding oral tissue native fluorophores was obtained with intrinsic fluorescence spectroscopy by fitting a linear combination of collagen and the reduced form of nicotinamide adenine dinucleotide (NADH) fluorescence spectra to the intrinsic tissue fluorescence spectra excited with 337 nanometer (nm) and 358-nm laser light. Diffuse reflectance spectroscopy was used to provide information regarding tissue absorption and structure, such as hemoglobin concentration and stroma density, by measuring the wavelength-dependent absorption and scattering coefficients. By subtracting the diffusely reflected component from the measured reflectance, light scattering spectroscopy (LSS) information resulting from single backscattering from epithelial cell nuclei was obtained. LSS provides information concerning the size distribution of cell nuclei. RESULTS These optically extracted tissue parameters provide biochemical or structural information in vivo without the need for tissue excision, and can be used to diagnose tissue abnormalities. By combining the information provided by the three techniques, a method known as trimodal spectroscopy, a sensitivity and specificity of 96% and 96%, respectively, in distinguishing cancerous/dysplastic (mild, moderate, and severe) from normal tissue was achieved. In addition, the authors were able to distinguish dysplastic from cancerous tissue with a sensitivity of 64% and a specificity of 90%. CONCLUSIONS The results of the current study demonstrated that Trimodal spectroscopy is a highly sensitive and specific technique with which to diagnose tissue abnormalities. Cancer 2003;97:1681,92. © 2003 American Cancer Society. DOI 10.1002/cncr.11255 [source] Nanoparticle Production with Stirred-Media Mills: Opportunities and LimitsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2010C. Knieke Abstract Nanoparticles can be produced by wet grinding in stirred-media mills. In the lower nanometer range a true grinding limit exists, where the transferred energy from the grinding media is no longer sufficient to induce further breakage of the particles even after stressing events with high stress energies. Variations in process conditions lead to the conclusion that the grinding limit is hardly affected by most of the investigated process parameters. However, at high solids concentrations and/or small particle sizes, a drastic increase in suspension viscosity occurs, which leads to a dampening of the grinding media motion and to a reduction in the transferred stress energy. Hence, the rheological behavior can limit the grinding process, and a viscous dampening-related grinding limit can be reached prior to the true grinding limit. [source] Ion and pH Sensing with Colloidal Nanoparticles: Influence of Surface Charge on Sensing and Colloidal PropertiesCHEMPHYSCHEM, Issue 3 2010Feng Zhang Dr. Abstract Ion sensors based on colloidal nanoparticles (NPs), either as actively ion-sensing NPs or as nanoscale carrier systems for organic ion-sensing fluorescent chelators typically require a charged surface in order to be colloidally stable. We demonstrate that this surface charge significantly impacts the ion binding and affects the read-out. Sensor read-out should be thus not determined by the bulk ion concentration, but by the local ion concentration in the nano-environment of the NP surface. We present a conclusive model corroborated by experimental data that reproduces the strong distance-dependence of the effect. The experimental data are based on the capability of tuning the distance of a pH-sensitive fluorophore to the surface of NPs in the nanometer (nm) range. This in turn allows for modification of the effective acid dissociation constant value (its logarithmic form, pKa) of analyte-sensitive fluorophores by tuning their distance to the underlying colloidal NPs. [source] | |||||||||||||||||||||||||||||||||||||