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Nm Diameter (nm + diameter)
Selected AbstractsHigh-sensitivity detection of oxytetracycline using light scattering agglutination assay with aptasensorELECTROPHORESIS, Issue 18 2010Keesung Kim Abstract We present an aptamer-based biosensor (aptasensor) for rapid and high-sensitive detection of oxytetracycline (OTC) antibiotic in PBS inside a Y-channel PDMS microfluidic device. The detection was made by real-time monitoring of the agglutination assay of ssDNA aptamer-conjugated polystyrene latex microspheres with proximity optical fibers. The agglutination assay was performed with serially diluted OTC antibiotic solutions using highly carboxylated polystyrene particles of 920,nm diameter conjugated with OTC-binding ssDNA aptamer. Proximity optical fibers were used to measure the increase in 45° forward light scattering of the aggregated particles by fixing them around the viewing cell of the device with stable angle and distance to the detector. The detection limit was around 100,ppb for the current aptasensor system with the detection time less than 3,min. [source] Vitrified Silica-Nanofiber Mats as Reinforcements for Epoxy ResinsADVANCED ENGINEERING MATERIALS, Issue 5 2009Oliver Weichold The effects of vitrified, electrospun silica nanofiber mats on the tensile and bending strength (see Figure) of epoxy resins are presented. The mats consist of randomly oriented, amorphous filaments of 600,800,nm diameter. The effects of annealing conditions and surface functionalization on the fiber/matrix adhesion is discussed. The results are compared to those of reference materials. [source] Biomimetic Composites: Protein Localization in Silica Nanospheres Derived via Biomimetic Mineralization (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010Mater. Abstract Lysozyme-templated precipitation of silica synthesized by sol-gel chemistry produces a composite material with antimicrobial properties. This study investigates the structural properties of the composite material that allow for retention of the antimicrobial activity of lysozyme. Scanning (SEM) and transmission (TEM) electron microscopy reveal that the composite has a hierarchical structure composed of quasi-spherical structures (,450 nm diameter), which are in turn composed of closely packed spherical structures of ,8,10 nm in diameter. Using small-angle neutron scattering (SANS) with contrast variation, the scattering signatures of the lysozyme and silica within the composite were separated. It was determined that the lysozyme molecules are spatially correlated in the material and form clusters with colloidal silica particles. The size of the clusters determined by SANS agrees well with the structural architecture observed by TEM. BET analysis revealed that the surface area of the composite is relatively low (4.73 m2/g). However, after removal of the protein by heating to 200 °C, the surface area is increased by ,20%. In addition to demonstrating a well organized sol-gel synthesis which generates a functional material with antimicrobial applications, the analysis and modeling approaches described herein can be used for characterizing a wide range of mesoporous and ultrastructural materials. [source] Protein Localization in Silica Nanospheres Derived via Biomimetic MineralizationADVANCED FUNCTIONAL MATERIALS, Issue 18 2010Mateus B. Cardoso Abstract Lysozyme-templated precipitation of silica synthesized by sol-gel chemistry produces a composite material with antimicrobial properties. This study investigates the structural properties of the composite material that allow for retention of the antimicrobial activity of lysozyme. Scanning (SEM) and transmission (TEM) electron microscopy reveal that the composite has a hierarchical structure composed of quasi-spherical structures (,450 nm diameter), which are in turn composed of closely packed spherical structures of ,8,10 nm in diameter. Using small-angle neutron scattering (SANS) with contrast variation, the scattering signatures of the lysozyme and silica within the composite were separated. It was determined that the lysozyme molecules are spatially correlated in the material and form clusters with colloidal silica particles. The size of the clusters determined by SANS agrees well with the structural architecture observed by TEM. BET analysis revealed that the surface area of the composite is relatively low (4.73 m2/g). However, after removal of the protein by heating to 200 °C, the surface area is increased by ,20%. In addition to demonstrating a well organized sol-gel synthesis which generates a functional material with antimicrobial applications, the analysis and modeling approaches described herein can be used for characterizing a wide range of mesoporous and ultrastructural materials. [source] Interaction of ostreolysin, a cytolytic protein from the edible mushroom Pleurotus ostreatus, with lipid membranes and modulation by lysophospholipidsFEBS JOURNAL, Issue 6 2003Kristina Sep Ostreolysin is a 16-kDa cytolytic protein specifically expressed in primordia and fruiting bodies of the edible mushroom Pleurotus ostreatus. To understand its interaction with lipid membranes, we compared its effects on mammalian cells, on vesicles prepared with either pure lipids or total lipid extracts, and on dispersions of lysophospholipids or fatty acids. At nanomolar concentrations, the protein lysed human, bovine and sheep erythrocytes by a colloid-osmotic mechanism, compatible with the formation of pores of 4 nm diameter, and was cytotoxic to mammalian tumor cells. A search for lipid inhibitors of hemolysis revealed a strong effect of lysophospholipids and fatty acids, occurring below their critical micellar concentration. This effect was distinct from the capacity of ostreolysin to bind to and permeabilize lipid membranes. In fact, permeabilization of vesicles occurred only when they were prepared with lipids extracted from erythrocytes, and not with lipids extracted from P. ostreatus or pure lipid mixtures, even if lysophospholipids or fatty acids were included. Interaction with lipid vesicles, and their permeabilization, correlated with an increase in the intrinsic fluorescence and ,-helical content of the protein, and with aggregation, which were not detected with lysophospholipids. It appears that either an unknown lipid acceptor or a specific lipid complex is required for binding, aggregation and pore formation. The inhibitory effect of lysophospholipids may reflect a regulatory role for these components on the physiological action of ostreolysin and related proteins during fruiting. [source] Physical characterization of plakophilin 1 reconstituted with and without zincFEBS JOURNAL, Issue 14 2000Ilse Hofmann Plakophilin 1 (PKP1) belongs to the arm -repeat protein family which is characterized by the presence of a conserved 42-amino-acid motif. Despite individual members of the family containing a similar type of structural domain, they exhibit diverse cellular functions. PKP1 is ubiquitously expressed in human tissues and, depending on the type of cell, found prominently in the karyoplasm and/or in desmosomes. In surface plasmon resonance detection experiments, we noticed that PKP1 specifically bound zinc but not calcium or magnesium. Therefore we have used circular dichroism spectroscopy, limited proteolysis, analytical ultracentrifugation, electron microscopy and dynamic light scattering to establish the physical properties of recombinant PKP1 depending on the presence or absence of zinc. The , helix content of PKP1 was considerably higher when reconstituted with zinc than without. By atomic absorption spectroscopy 7.3 atoms zinc were shown to be tightly associated with one molecule of wild-type PKP1. The zinc-reconstituted protein formed globular particles of 21.9 ± 8.4 nm diameter, as measured by electron microscopy after glycerol spraying/rotary metal shadowing. In parallel, the average sedimentation coefficient (s20,w) for zinc-containing PKP1 was 41S and its diffusion coefficient, as obtained by dynamic light scattering, 1.48 × 10,7 cm2·s,1. The molecular mass of 2.44 × 106 obtained from s and D yields an average stoichiometry of 30 for the PKP1 oligomer. In contrast, PKP1, reconstituted without zinc, contained no significant amount of zinc, sedimented with 4.6S, and was present in monomeric form as determined by sedimentation equilibrium centrifugation. [source] Photoelectrochemical Study of Nanostructured ZnO Thin Films for Hydrogen Generation from Water SplittingADVANCED FUNCTIONAL MATERIALS, Issue 12 2009Abraham Wolcott Abstract Photoelectrochemical cells based on traditional and nanostructured ZnO thin films are investigated for hydrogen generation from water splitting. The ZnO thin films are fabricated using three different deposition geometries: normal pulsed laser deposition, pulsed laser oblique-angle deposition, and electron-beam glancing-angle deposition. The nanostructured films are characterized by scanning electron microscopy, X-ray diffraction, UV-vis spectroscopy and photoelectrochemical techniques. Normal pulsed laser deposition produces dense thin films with ca. 200,nm grain sizes, while oblique-angle deposition produces nanoplatelets with a fishscale morphology and individual features measuring ca. 900 by 450,nm on average. In contrast, glancing-angle deposition generates a highly porous, interconnected network of spherical nanoparticles of 15,40,nm diameter. Mott-Schottky plots show the flat band potential of pulsed laser deposition, oblique-angle deposition, and glancing-angle deposition samples to be ,0.29, ,0.28 and +0.20,V, respectively. Generation of photocurrent is observed at anodic potentials and no limiting photocurrents were observed with applied potentials up to 1.3,V for all photoelectrochemical cells. The effective photon-to-hydrogen efficiency is found to be 0.1%, 0.2% and 0.6% for pulsed laser deposition, oblique-angle deposition and glancing-angle deposition samples, respectively. The photoelectrochemical properties of the three types of films are understood to be a function of porosity, crystal defect concentration, charge transport properties and space charge layer characteristics. [source] Beam to String Transition of Vibrating Carbon Nanotubes Under Axial TensionADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Xianlong Wei Abstract State-of-the-art nanoelectromechanical systems have been demonstrated in recent years using carbon nanotube (CNT) based devices, where the vibration of CNTs is tuned by tension induced through external electrical fields. However, the vibration properties of CNTs under axial tension have not been quantitatively determined in experiments. Here, a novel in situ method for precise and simultaneous measurement of the resonance frequency, the axial tension applied to individual CNTs and the tube geometry is demonstrated. A gradual beam-to-string transition from multi-walled CNTs to single-walled CNTs is observed with the crossover from bending rigidity dominant regime to extensional rigidity dominant regime occur much larger than that expected by previous theoretical work. Both the tube resonance frequency under tension and transition of vibration behavior from beam to string are surprisingly well fitted by the continuum beam theory. In the limit of a string, the vibration of a CNT is independent of its own stiffness, and a force sensitivity as large as 0.25,MHz (pN),1 is demonstrated using a 2.2,nm diameter single-walled CNT. These results will allow for the designs of CNT resonators with tailored properties. [source] Inkjet Printing of Luminescent CdTe Nanocrystal,Polymer Composites,ADVANCED FUNCTIONAL MATERIALS, Issue 1 2007E. Tekin Abstract Inkjet printing is used to produce well-defined patterns of dots (with diameters of ca.,120,,m) that are composed of luminescent CdTe nanocrystals (NCs) embedded within a poly(vinylalcohol) (PVA) matrix. Addition of ethylene glycol (1,2,vol,%) to the aqueous solution of CdTe NCs suppresses the well-known ring-formation effect in inkjet printing leading to exceptionally uniform dots. Atomic force microscopy characterization reveals that in the CdTe NC films the particle,particle interaction could be prevented using inert PVA as a matrix. Combinatorial libraries of CdTe NC,PVA composites with variable NC sizes and polymer/NC ratios are prepared using inkjet printing. These libraries are subsequently characterized using a UV/fluorescence plate reader to determine their luminescent properties. Energy transfer from green-light-emitting to red-light-emitting CdTe NCs in the composite containing green- (2.6,nm diameter) and red-emitting (3.5,nm diameter) NCs are demonstrated. [source] Surfactant-Assisted Synthesis of Alumina with Hierarchical NanoporesADVANCED FUNCTIONAL MATERIALS, Issue 1 2003W. Deng Abstract Using surfactant-assisted synthesis, aluminas with hierarchical nanopores are produced. The hierarchical structures are composed of mesopores of 4 nm diameter, and macropores with diameters of about 300 nm. The structures were found to be stable to the thermal removal of the surfactant. Synthesis factors affecting the appearance of the hierarchically structured alumina material are presented. A potential mechanism for the formation of the uniquely structured aluminas is proposed. [source] Diffusion of Adhesion Layer Metals Controls Nanoscale Memristive SwitchingADVANCED MATERIALS, Issue 36 2010J. Joshua Yang Thermal diffusion of Ti through Pt electrode forms Ti atom channels of 1 nm diameter along Pt grain boundaries, seeding switching centers and controlling nanoscale memristive switching. The image shows EFTEM maps of Ti overlaid on HRTEM images for a Si/SiO2 100 nm/Ti 5nm/Pt 15 nm sample in-situ annealed in ultrahigh vacuum at 250 °C for 1 hour. [source] Self-Assembly of Ordered Semiconductor Nanoholes by Ion Beam SputteringADVANCED MATERIALS, Issue 28 2009Qiangmin Wei Periodic nanohole arrays are formed on a Ge substrate by self-assembly using focused ion beam sputtering at normal incidence with an energy of 5,keV. The figure shows an SEM image of a hexagonally ordered hole domain that has hexagonally ordered quantum dots,20,nm diameter and 3,nm height,around each hole The structured Ge has high surface area and a considerably blue-shifted energy gap. [source] Water-Soluble Silicon Quantum Dots with Wavelength-Tunable PhotoluminescenceADVANCED MATERIALS, Issue 6 2009Zhenhui Kang H-terminated Si quantum dots (Si QDs) with 3,nm diameter are converted to water-soluble uniform-sized Si QDs after controlled oxidation in an EtOH/H2O2 solution. These dots present Si/SiOxHy core/shell nanostructures, and can be finely tuned to emit light in seven different colors due to the quantum size effect in the Si cores, exhibiting excellent photocatalytic activity in the visible range. [source] DNA-Based Self-Sorting of Nanoparticles on Gold Surfaces,ADVANCED MATERIALS, Issue 15 2007U. Plutowski Site-selective deposition of nanoparticles onto surfaces is desirable for the fabrication of nanoscale devices. For nanoparticles with vastly different numbers of DNA chains on their surfaces, multivalent binding of short-sequence motifs and nonspecific adsorption complicate sequence-specific immobilization from mixtures. A new nanoparticle coating method that suppresses salt-induced aggregation and undesirable binding events is reported. Size-selective sorting of gold nanoparticles up to 60,nm diameter onto nanopatterned surfaces is shown (see figure). [source] Growth and Optical Properties of Highly Uniform and Periodic InGaN Nanostructures,ADVANCED MATERIALS, Issue 13 2007P. Chen InGaN nanodot arrays with improved optical properties, attributed to the strong localization of photogenerated carriers in the size-homogeneous nanodots, grown by nanoscale selective area epitaxy (NSAE) on electron-beam lithographically patterned templates are presented. The figure shows an array of 60,nm diameter cone-shaped InGaN nanodots with 200,nm spacing, and a single nanodot (inset). [source] Comparison of cytotoxic and inflammatory responses of photoluminescent silicon nanoparticles with silicon micron-sized particles in RAW 264.7 macrophagesJOURNAL OF APPLIED TOXICOLOGY, Issue 1 2009Jonghoon Choi Abstract Photoluminescent silicon nanoparticles have a bright and stable fluorescence and are promising candidates for bio-imaging, cell staining and drug delivery. With increasing development of nanotechnology applications for biomedicine, an understanding of the potential toxicity of nanoparticles is needed to assess safety concerns for clinical applications. The objective of this study was to compare biological responses of silicon nanoparticles (SNs, 3 nm diameter) with silicon microparticles (SMs, ,100,3000 nm diameter) in cultured murine macrophages (RAW 264.7) using standard protocols for assessing cytotoxicity/cell viability and inflammatory responses developed for micron-sized particles. SNs and SMs were exposed to macrophages with and without addition of endotoxin lipopolysaccharide (LPS), a positive inducer of tumor necrosis factor-alpha (TNF- ,), interleukin 6 (IL-6), and nitric oxide (NO). Cytotoxicity was assayed using the dye exclusion and MTT assays. Cell supernatants were assayed for production TNF- ,, IL-6 and NO. SNs at concentrations ,20 µg ml,1 exhibited no cytotoxicity or inflammatory responses; however, SNs and SMs >20 and 200 µg ml,1, respectively, increased cytotoxicity compared with controls. SMs induced concentration-related increases in TNF- , and IL-6 production; in contrast, the production of these cytokines was shown to decrease with increasing concentrations of SNs. NO production was not induced by SNs or SMs alone. Fluorescence microscopy demonstrated that SNs were associated with the macrophages, either internalized or attached to cell membranes. In conclusion, evaluating differences in biological responses for nanoparticles compared with microparticles of the same material may help improve tests to assess biological responses of nanoparticles that may be used in biomedical applications. Copyright © 2008 John Wiley & Sons, Ltd. [source] Regulation of implant surface cell adhesion: characterization and quantification of S-phase primary osteoblast adhesions on biomimetic nanoscale substratesJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 2 2007Manus J.P. Biggs Abstract Integration of an orthopedic prosthesis for bone repair must be associated with osseointegration and implant fixation, an ideal that can be approached via topographical modification of the implant/bone interface. It is thought that osteoblasts use cellular extensions to gather spatial information of the topographical surroundings prior to adhesion formation and cellular flattening. Focal adhesions (FAs) are dynamic structures associated with the actin cytoskeleton that form adhesion plaques of clustered integrin receptors that function in coupling the cell cytoskeleton to the extracellular matrix (ECM). FAs contain structural and signalling molecules crucial to cell adhesion and survival. To investigate the effects of ordered nanotopographies on osteoblast adhesion formation, primary human osteoblasts (HOBs) were cultured on experimental substrates possessing a defined array of nanoscale pits. Nickel shims of controlled nanopit dimension and configuration were fabricated by electron beam lithography and transferred to polycarbonate (PC) discs via injection molding. Nanopits measuring 120 nm diameter and 100 nm in depth with 300 nm center,center spacing were fabricated in three unique geometric conformations: square, hexagonal, and near-square (300 nm spaced pits in square pattern, but with ±50 nm disorder). Immunofluorescent labeling of vinculin allowed HOB adhesion complexes to be visualized and quantified by image software. Perhipheral adhesions as well as those within the perinuclear region were observed, and adhesion length and number were seen to vary on nanopit substrates relative to smooth PC. S-phase cells on experimental substrates were identified with bromodeoxyuridine (BrdU) immunofluorescent detection, allowing adhesion quantification to be conducted on a uniform flattened population of cells within the S-phase of the cell cycle. Findings of this study demonstrate the disruptive effects of ordered nanopits on adhesion formation and the role the conformation of nanofeatures plays in modulating these effects. Highly ordered arrays of nanopits resulted in decreased adhesion formation and a reduction in adhesion length, while introducing a degree of controlled disorder present in near-square arrays, was shown to increase focal adhesion formation and size. HOBs were also shown to be affected morphologicaly by the presence and conformation of nanopits. Ordered arrays affected cellular spreading, and induced an elongated cellular phenotype, indicative of increased motility, while near-square nanopit symmetries induced HOB spreading. It is postulated that nanopits affect osteoblast,substrate adhesion by directly or indirectly affecting adhesion complex formation, a phenomenon dependent on nanopit dimension and conformation. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:273,282, 2007 [source] The Encapsulation of Bleomycin Within Chitosan Based Polymeric Vesicles Does Not Alter its BiodistributionJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 4 2000J. SLUDDEN Polymeric vesicles have recently been developed from an amphiphilic chitosan derivative,palmitoyl glycol chitosan. Their potential as a drug delivery system was evaluated using the anti-cancer compound bleomycin as a model drug. Palmitoyl glycol chitosan (GCP41) was synthesised by conjugation of palmitoyl groups to glycol chitosan. Bleomycin-containing vesicles (669 nm diameter) were prepared from a mixture of GCP41 and cholesterol by remote loading. The vesicles were imaged by freeze-fracture electron microscopy and their in-vitro stability tested. Incubation of the larger vesicles with plasma in-vitro led to a reduction of mean size by 49%, a reaction not seen with control sorbitan monostearate niosomes (215 nm in size). They also showed a higher initial drug release (1 h), but GCP41 and sorbitan monostearate vesicles retained 62% and 63% of the encapsulated drug after 24 h, respectively. The biodistribution of smaller vesicles (290 nm) prepared by extrusion through a 200-nm filter was also studied in male Balb/c mice. Encapsulation of bleomycin into polymeric vesicles did not significantly alter the pharmacokinetics of biodistribution of bleomycin in male Balb/c mice although plasma and kidney levels were slightly increased. It is concluded that the extruded GCP41 vesicles break down in plasma in-vivo and hence are unlikely to offer any therapeutic advantage over the free drug. [source] Nanosized CdSe Particles Synthesized by an Air Pressure Solution Process Using Ethylene-Glycol-Based SolventJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2010Tao Wang Nanosized CdSe particles were synthesized at a temperature of 115°,175°C by a solution method with air pressure condition. Ethylene glycol (EG) was used as the main solvent and sodium selenite and cadmium nitrate-tetrahydrate as inorganic sources. The influence of refluxing temperature and time on growth morphology and crystallization was investigated by transmission electron microscope, high-resolution transmission electron microscope, and X-ray diffraction. The chemical reaction was deducted based on X-ray photoelectron spectra. The optical absorption property was measured by UV-vis. The CdSe nanoparticles synthesized through this EG solvent system was single wurtzite crystallization and had a nanoscale size below 15 nm diameter with a narrow size distribution. The reduction of Se4+,Se0,Se2,and the disproportionation of Se0 occurred during the synthetic process and dominated the chemical reaction. [source] Synthesis and Characterization of Mixed-Metal Oxide Nanopowders Along the CoOx,Al2O3 Tie Line Using Liquid-Feed Flame Spray PyrolysisJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2006Jose Azurdia We report here the use of liquid-feed flame spray pyrolysis (LF-FSP) to produce a series of nanopowders along the CoOx,Al2O3 tie line. The process is a general aerosol combustion synthesis route to a wide range of lightly agglomerated oxide nanopowders. The materials reported here were produced by aerosolizing ethanol solutions of alumatrane [Al(OCH2CH2)3N] and a cobalt precursor, made by reacting Co(NO3)2·6H2O crystals with propionic acid. The compositions of the as-produced nanopowders were controlled by selecting the appropriate ratios of the precursors. Nine samples with compositions (CoO)y(Al2O3)1,y, y=0,1 along the CoOx,Al2O3 tie line were prepared and studied. The resulting nanopowders were characterized by X-ray fluorescence, BET, scanning electron microscopy, high-resolution transmission electron micrographs, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and FTIR. The powders typically consist of single-crystal particles <40 nm diameter and specific surface areas (SSAs) of 20,60 m2/g. XRD studies show a gradual change in powder patterns from ,-Al2O3 to Co3O4. The cobalt aluminate spinel phase is observed at stoichiometries (21 and 37 mol%) not seen in published phase diagrams, likely because LF-FSP processing involves a quench of >1000°C in microseconds frequently leading to kinetic rather than thermodynamic products. Likewise, the appearance of Co3O4 rather than CoO as the end member in the tie line is thought to be a consequence of the process conditions. TGA studies combined with diffuse reflectance FTIR spectroscopic studies indicate that both physi- and chemi-sorbed H2O are the principal surface species present in the as-processed nanopowders. The only sample that differs is Co3O4, which has some carbonate species present that are detected and confirmed by a sharp mass loss event at ,250°C. The thermal behavior of the high cobalt content samples differs greatly from the low cobalt content samples. The latter behave like most LF-FSP-derived nanopowders exhibiting typical 1%,4% mass losses over the 1400°C range due mostly to loss of water and some CO2. The high cobalt content samples exhibit a sharp mass loss event that can be attributed to the decomposition of Co3O4 to CoO. [source] Photoluminescence effects on gold nano- particles modified by short single stranded DNA moleculesMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 4 2009O. Kysil Gold-Nanopartikel; Einzelstrang DNA; sichtbare Photolumineszenz; Photosensor Abstract The concept for a function of gold nanoparticle photosensor based on gold nanoparticle optical properties, depending on the size and architecture of their self , assemblies, is revised from the studies of modified by short ssDNA (5.4 nm length) selected gold nanoparticle (8.6 nm diameter) assembling in biosuspensions. Biosensing effect, collective photoluminescence in visible range of different size 2D, 3D assemblies from these nanoparticles, is revealed due to their controlled assembling in biosuspesions, dependent on ssDNA conformation, that changes gold core capping and therefore a force of interparticle interaction. Nanophotosensor is characterized by intensive photoluminescence maxima in two regions of visible range for tested biosuspensions due to detected difference in the self - assemblies' architecture of gold nanoparticles with different gold core capping by the ssDNA molecules. The emission maxima are 4.2x103 pps and 4.1x104 pps in (525,780) nm and (780,920) nm regions mainly for 2D assemblies as nanowires and 3D assemblies as circle holms, correspondently, in DNA buffer suspensions with different biomolecules. The results are explained addressing photoluminescence of gold nanoparticle assemblies to system of discrete electron states in valence and conductivity bands for gold nanoparticle model. Photolumineszenz-Effekt auf Gold Nanopartikel vermittelt durch kurze Einzelstrang DNA Moleküle Das Konzept für die Funktion der Goldpartikel Nanophotosensoren basiert auf den optischen Eigenschaften der Gold Nanopartikel abhängig von der Größe und Architektur ihrer ,Self-Assemblies", und wird auf Basis von Studien von kurzen ssDNA (5.4 nm Länge) mit ausgewählten sich in Biosuspensionen versammelnden Gold Nanopartikeln (8.6 nm Durchmesser) revidiert. Der Biosensoreffekt, sichtbar durch die gesammelte Photolumineszenz im sichtbaren Spektrum von verschieden großen 2D und 3D-Aggregaten von diesen Nanopartikeln, wird wegen ihrer kontrollierten Ansammlung in Biosuspensionen, welche in Abhängigkeit zu den kurzen ssDNA Konformation, dem Ändern der monomolekularen Bedeckungsschicht des Goldkerns und somit durch eine Kraft der Teilchen-Wechselwirkung offenbart. Der Nanophotosensor ist durch zwei intensive Photolumineszenz-Maxima im Bereich des sichtbaren Spektrums für derart geprüfte Biosuspensionen wegen des meßbaren Unterschieds in der Selbstanordnung von Gold Nanopartikeln mit dem verschiedenen Goldkernbedeckungen durch die ssDNA Stränge charakterisiert: Emissionsmaxima liegen bei 4.2x103 pps und 4.1x104 pps in den Wellenlängenbereichen von (525,780) nm und (780,920) nm, jeweils hauptsächlich für 2D-Aggregate als Nanodrähte und 3D-Aggregate in kreisförmiger Anordnung in DNA-Puffersuspendierungen mit verschiedenen Biomolekülen. Die Ergebnisse werden Mithilfe der Adressierung der Photolumineszenz von Gold Nanopartikel-Aggregaten zu System von getrennten Elektronzuständen in Valenz und Leitungsbändern entsprechend den Gold Nanopartikel-Modellen erklärt. [source] Innovative process flow to achieve carbon nanotube based interconnectsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2008J. C. Coiffic Abstract We have achieved down to 140 nm diameter carbon nanotube via interconnects with both new single and dual damascene processes on 200 mm silicon wafers. High density 5 × 1010 nanotube/cm2 is obtained. The validity of these two new processes has been checked by performing electrical measurements. At high bias, a low resistance of 20 , has been reached for a 300 nm diameter via interconnect. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Enhanced control of porous silicon morphology from macropore to mesopore formationPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2005Huimin Ouyang Abstract Porous silicon (PSi) is a versatile material that possesses a wide range of morphologies. There are two main types of microstructures that are widely used and well studied: branchy mesoporous silicon with pore sizes from 10 nm to 50 nm and classical macroporous silicon with pore sizes from 500 nm to 20 µm. Much less work has been done on structures with intermediate pore sizes from 100 nm to 300 nm. Applications such as immunoassays biosensing can greatly benefit from the intermediate morphology due to the larger pore openings compared to mesopores, and increased internal surface compared to classical macropores. In this work we demonstrate well-defined macropore of 150 nm diameter in average and precise control of the porous silicon morphology transition from smooth macropores to branchy mesopores on one substrate with one electrolyte. A multilayer structure (microcavity) consisting of both mesopores and macropores is presented. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Excitation relaxation in copper selenide nanowiresPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2009Gediminas Ju Abstract Ultrafast nonequilibrium charge carrier relaxation in highly ordered Cu2,xSe nanowires of 8 nm, 13 nm and 25 nm diameter was investigated by means of femtosecond pump,probe absorption spectroscopy. Transient absorption bleaching was observed in the region of the near infrared absorption band, whereas an induced absorption dominated at higher energies. The transient absorption kinetics is almost independent of the excitation and probe wavelength and shows a biexpoenetial charge carrier recombination with the excitation intensity dependent decay rates. The initial ultrafast relaxation, which gets slower at higher excitation intensities, is followed by the slower decay component emerging at high intensities. These relaxation peculiarities are discussed in terms of recombination enhancement by intragap states, and relaxation kinetics is described by a theoretical model of two concurrent relaxation channels involving deep and shallow impurity levels. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Identification and transmission of Piper yellow mottle virus and Cucumber mosaic virus infecting black pepper (Piper nigrum) in Sri LankaPLANT PATHOLOGY, Issue 5 2002D. P. P. De Silva Sri Lankan black pepper with symptoms of yellow mottle disease contained a mixture of viruses: Piper yellow mottle virus (PYMV) particles (30 × 130 nm), Cucumber mosaic virus (CMV, 30 nm diameter isometric particles), and unidentified, isometric virus-like particles (30 nm diameter). An effective purification procedure is described for PYMV. Immunosorbent and conventional electron microscopy successfully detected badnavirus particles only when at least partially purified extracts were used. PYMV was confirmed as the cause of the disease, with the other two viruses apparently playing no part in producing symptoms. PYMV was transmitted by grafting, by the insect vectors citrus mealy bug (Planococcus citri) and black pepper lace bug (Diconocoris distanti), but not by mechanical inoculation or through seeds. The CMV isolate was transmitted to indicator plants by mechanical inoculation and by the vector Aphis gossypii, but not by Myzus persicae; but neither mechanical nor insect transmission of CMV to black pepper was successful. A sensitive polymerase chain reaction assay was developed to detect PYMV in black pepper. [source] Effect of Nano-Aluminum and Fumed Silica Particles on Deflagration and Detonation of NitromethanePROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 5 2009Justin Abstract The heterogeneous interaction between nitromethane (NM), particles of nanoscale aluminum (38 and 80,nm diameter), and fumed silica is examined in terms of the deflagration and detonation characteristics. Burning rates are quantified as functions of pressure using an optical pressure vessel up to 14.2,MPa, while detonation structure is characterized in terms of failure diameter. Nitromethane is gelled using fumed silica (CAB-O-SIL®), as well as by the nanoaluminum particles themselves. Use of nanoaluminum particles with fumed silica slightly increases burning rates compared to the use of larger diameter Al particles; however distinct increases in burning rates are found when CAB-O-SIL is removed and replaced with more energetic aluminum nanoparticles, whose high surface area allows them to also act as the gellant. Mixtures including fumed silica yield a reduced burning rate pressure exponent compared to neat NM, while mixtures of aluminum particles alone show a significant increase. Failure diameters of mixture detonations are found to vary significantly as a function of 38,nm aluminum particle loading, reducing more than 50% from that of neat nitromethane with 12.5% (by mass) aluminum loading. Failure diameter results indicate a relative minimum with respect to particle separation (% loading) which is not observed in other heterogeneous mixtures. [source] In situ ESR study of gold supported on NaY zeoliteASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009Z. Qu Abstract Electron spin resonance (ESR) spectroscopy was used to study the anchoring of a Au complex and gold nanoparticles in NaY type zeolites. The complex of Au(II) with two nitrogen atoms of two ethylenediamine ligands [giso = 2.053, A (Au) = 16.4 G, A (N) = 15.0 G.] in the supercage of the zeolite and conduction electron spin resonance (CESR) of gold particles with 1.56-nm diameter (g = 2.064) were observed. Their formation and stability were related with the gold concentration and the pre-treatment conditions. The small gold particles stabilized in the supercage of zeolite were formed in the samples with low gold concentration after oxygen pre-treatment. The confinement in the zeolite pores obviously prevents the Au(II) complex bound to two nitrogen ligands from undergoing disproportionation. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Ultrastructure of ulvan: A polysaccharide from green seaweedsBIOPOLYMERS, Issue 8 2009Audrey Robic Abstract Ultrastructural analysis of the gel forming green seaweed sulfated polysaccharide ulvan revealed a spherical-based morphology (10,18 nm diameter) more or less aggregated in aqueous solution. At pH 13 in TBAOH (tetrabutyl ammonium hydroxyde) or NaOH, ulvan formed an open gel-like structure or a continuous film by fusion or coalescence of bead-like structures, while in acidic pH conditions, ulvan appeared as dispersed beads. Low concentrations of sodium chloride, copper or boric acid induced the formation of aggregates. These results highlight the hydrophobic and aggregative behavior of ulvan that are discussed in regard to the peculiar gel formation and the low intrinsic viscosity of the polysaccharide in aqueous solution. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 652,664, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Magneto-transport studies of single ferromagnetic nanowirePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2007Y. Rheem Abstract The magnetotransport properites of individual ferromagnetic nanowires (e.g. Ni, Co23Ni77, Ni85Fe15) with 200 nm diameters were investigated. The ferromagnetic nanowires were successfully electrodeposited within an anodized alumina by controlling solution composition, temperature, and current density. Using a magnetic assembly technique, single nanowire was successfully bridged across microfabricated gold elecrodes. The temperature coefficient of resistance for ferromagnetic nanowires was lower than the bulk because of a larger residual resistance from increased electrical scattering in one-dimensional structures. The ferromagnetic nanowires showed typical anisotropic magnetoresistance where the magnetoresistance ratio was lower than bulk values. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||||||||