Home About us Contact
|
Home About us Contact | ||
|
|
||
Nanopores
Terms modified by Nanopores Selected AbstractsCoarse Grained Molecular Dynamics Simulation of Electromechanically-Gated DNA Modified Conical NanoporesELECTROANALYSIS, Issue 3 2008Lajos Höfler Abstract Nanopore-based devices are emerging as tools for single molecule manipulation, characterization and chemical analysis. Single or random arrays of chemically modified nanopores have been established as platforms for selective chemical and biosensing. However, it is little known about the orientation and behavior of surface tethered species in the nanopore environment as function of applied transpore voltages. In this study we report on coarse grained modeling of short (5-, 15-mer) DNA modified conical gold nanopores subjected to electrical field gradients of 5 and 50,mV/nm. An electromechanical gating effect in the single stranded DNA modified conical nanopores is predicted, which is due to the obstruction of the tip entrance by DNA strands oriented by the external electrical field. The magnitude of the rectification effect increases with increasing DNA length and decreasing tip diameter of the conical nanopore. The direction of on/off switching was found to be dependent on the location of the immobilized DNAs on the membrane supporting the nanopore. [source] Multiple Base-Recognition Sites in a Biological Nanopore: Two Heads are Better than One,ANGEWANDTE CHEMIE, Issue 3 2010David Stoddart Die ,-Hämolysin-Nanopore ist ein vielversprechender Sensor für die ultraschnelle Sequenzierung von DNA-Strängen. Mithilfe immobilisierter synthetischer Oligonucleotide wird gezeigt, wie zusätzliche Sequenzinformation erhalten werden können, indem in der Nanopore zwei Erkennungszentren statt nur einem genutzt werden (siehe Bild). [source] Coarse Grained Molecular Dynamics Simulation of Electromechanically-Gated DNA Modified Conical NanoporesELECTROANALYSIS, Issue 3 2008Lajos Höfler Abstract Nanopore-based devices are emerging as tools for single molecule manipulation, characterization and chemical analysis. Single or random arrays of chemically modified nanopores have been established as platforms for selective chemical and biosensing. However, it is little known about the orientation and behavior of surface tethered species in the nanopore environment as function of applied transpore voltages. In this study we report on coarse grained modeling of short (5-, 15-mer) DNA modified conical gold nanopores subjected to electrical field gradients of 5 and 50,mV/nm. An electromechanical gating effect in the single stranded DNA modified conical nanopores is predicted, which is due to the obstruction of the tip entrance by DNA strands oriented by the external electrical field. The magnitude of the rectification effect increases with increasing DNA length and decreasing tip diameter of the conical nanopore. The direction of on/off switching was found to be dependent on the location of the immobilized DNAs on the membrane supporting the nanopore. [source] Sensors: DNA Sensing Using Nanocrystalline Surface-Enhanced Al2O3 Nanopore Sensors (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 8 2010Mater. R. Bashir and co-workers report on page 1266 the development of solid-state Al2O3 nanopore sensors with enhanced surface properties for the real-time detection and analysis of individual DNA molecules. The cover illustrates the extension of coiled double-stranded DNA in the high-field region surrounding a nanocrystalline Al2O3 nanopore, followed by DNA transport. Nanocrystallite nucleation during pore formation helps enhance the single-molecule sensitivity and surface-charge characteristics of these devices and enables the potential fabrication of nanometer-scale metallic contacts in the pore. This technology finds broad application in drug screening, medicine, and bio-nanotechnology. [source] DNA Sensing Using Nanocrystalline Surface-Enhanced Al2O3 Nanopore SensorsADVANCED FUNCTIONAL MATERIALS, Issue 8 2010Bala Murali Venkatesan Abstract A new solid-state, Al2O3 nanopore sensor with enhanced surface properties for the real-time detection and analysis of individual DNA molecules is reported. Nanopore formation using electron-beam-based decomposition transforms the local nanostructure and morphology of the pore from an amorphous, stoichiometric structure (O to Al ratio of 1.5) to a heterophase crystalline network, deficient in O (O to Al ratio of ,0.6). Direct metallization of the pore region is observed during irradiation, thereby permitting the potential fabrication of nanoscale metallic contacts in the pore region with application to nanopore-based DNA sequencing. Dose-dependent phase transformations to purely , and/or ,-phase nanocrystallites are also observed during pore formation, allowing for surface-charge engineering at the nanopore/fluid interface. DNA transport studies reveal an order-of-magnitude reduction in translocation velocities relative to alternate solid-state architectures, accredited to high surface-charge density and the nucleation of charged nanocrystalline domains. The unique surface properties of Al2O3 nanopore sensors make them ideal for the detection and analysis of single-stranded DNA, double-stranded DNA, RNA secondary structures, and small proteins. These nanoscale sensors may also serve as useful tools in studying the mechanisms driving biological processes including DNA,protein interactions and enzyme activity at the single-molecule level. [source] Water flow through nanoporeINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 10 2008Julio Marañón Di Leo Abstract A molecular dynamics simulation of water flow through a prismatic surface of van der Waals particles at 300 K is reported. The application of different pressure gradients to a water produces a large spectrum of average velocities from Poiseuille to turbulent flow. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source] Investigation of p-type macroporous silicon formationPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2005C. Lévy-Clément Abstract Nanopores and macropores can be formed electrochemically on p-type silicon depending on the silicon resistivity and composition of the electrolyte. In order to understand if the structural dimensionality of the porous p-type Si, either nanopore or macropore formation, depends on the electrochemical process at the Si/electrolyte interface, in situ pulsed surface photovoltage (SPV) and photoluminescence (PL) measurements have been undertaken. The SPV and PL studies have been made as a function of the applied current density as well as the electrolyte composition (aqueous or in presence of organic solvent) and the silicon doping density. Main results show that the Si surface is well passivated with preferential formation of ionic species and the Si band bending is around 100 mV, during porous Si formation. It varies slightly with the doping density, but is not affected by the composition of the electrolyte (HF/water and HF/organic solvent). This demonstrates that the chemistry of the electrolyte plays a major role in the formation of macroporous and nanoporous Si, but has still to be determined. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Theoretical Trends of Diffusion and Reaction into Tubular Nano- and Mesoporous Structures: General Physicochemical and Physicomathematical ModelingCHEMISTRY - A EUROPEAN JOURNAL, Issue 18 2008Christian Amatore Prof. Abstract A general and adaptable physicochemical model is presented to evaluate the mass transport within nanopores of mesoporous particles when the mass transport is coupled to heterogeneous kinetics occurring at active sites located onto the nanopore walls surface. The model framework encompasses almost all situations of practical interest in solutions and may be used for characterizing the kinetic rates and constants controlling the system under different sets of experimental conditions. Furthermore, it allows the delineation of simple effective parameters, which should be most useful for optimizing a given material in view of specific applications. For the sake of clarification the simplified model is presented and its results discussed by specializing it for cases where the reactions involve a simple adsorption of a target species on the nanopore immobilized sites as observed for inorganic sponges used in water decontamination. Yet it may easily be extended further to encompass a wider variety of situations where the sites immobilized onto the nanopore walls perform chemical or biochemical transformations as occur in supported catalysis in liquid solution. [source] Coarse Grained Molecular Dynamics Simulation of Electromechanically-Gated DNA Modified Conical NanoporesELECTROANALYSIS, Issue 3 2008Lajos Höfler Abstract Nanopore-based devices are emerging as tools for single molecule manipulation, characterization and chemical analysis. Single or random arrays of chemically modified nanopores have been established as platforms for selective chemical and biosensing. However, it is little known about the orientation and behavior of surface tethered species in the nanopore environment as function of applied transpore voltages. In this study we report on coarse grained modeling of short (5-, 15-mer) DNA modified conical gold nanopores subjected to electrical field gradients of 5 and 50,mV/nm. An electromechanical gating effect in the single stranded DNA modified conical nanopores is predicted, which is due to the obstruction of the tip entrance by DNA strands oriented by the external electrical field. The magnitude of the rectification effect increases with increasing DNA length and decreasing tip diameter of the conical nanopore. The direction of on/off switching was found to be dependent on the location of the immobilized DNAs on the membrane supporting the nanopore. [source] Characterization of Nanopore Electrode Structures as Basis for Amplified Electrochemical AssaysELECTROANALYSIS, Issue 19-20 2006Sebastian Neugebauer Abstract A nanopore electrode structure was fabricated consisting of ensembles of nanopores with separately addressable electrodes at the pore bottoms and the rims. A metal/insulator/metal layer structure allowed for adjusting the spacing between the bottom and rim electrodes to be in the range of about 200,nm. Pore diameters varied between 200 and 800,nm. The electrochemical properties of this electrode structure and its perspectives for applications in bioelectronics were studied using cyclic voltammetry and chronoamperometry along with high-resolution scanning electrochemical microscopy (SECM) in constant-distance mode. It was possible to visualize the electrochemical activity of a single nanometric electrode using high-resolution SECM in a combination of sample-generation-tip-collection mode and positive feedback mode. The SECM images suggested an influence of the unbiased rim electrode on redox amplification which was used as a basis for evaluating the feasibility of current amplification by means of redox cycling between the bottom and rim electrodes. Amplification factors superior to those obtained with interdigitated array electrodes could be demonstrated. [source] Arrays of Electroplated Multilayered Co/Cu Nanowires with Controlled Magnetic AnisotropyADVANCED ENGINEERING MATERIALS, Issue 12 2005R. Pirota The controlled production of arrays of nanowires exhibiting outstanding characteristics is recently attracting much interest owing to their applications in a number of emerging technologies related with multifunctional biosensor applications, controlled optomagnetic response, magnetic storage, magnetotransport, or catalytic performance. While nanolitography methodes require sophisticated experimental facilities, an alternative technique that makes use of much simpler conventional anodization and electrodeposition methods in the fabrication of metallic nanowires arrays is increasingly employed. This method allows the preparation of arrays of highly-ordered nanopores induced by anodisation, and its filling with metallic elements by electrodepositon. [source] Porous Structures: In situ Porous Structures: A Unique Polymer Erosion Mechanism in Biodegradable Dipeptide-Based Polyphosphazene and Polyester Blends Producing Matrices for Regenerative Engineering (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Mater. Abstract Synthetic biodegradable polymers serve as temporary substrates that accommodate cell infiltration and tissue in-growth in regenerative medicine. To allow tissue in-growth and nutrient transport, traditional three-dimensional (3D) scaffolds must be prefabricated with an interconnected porous structure. Here we demonstrated for the first time a unique polymer erosion process through which polymer matrices evolve from a solid coherent film to an assemblage of microspheres with an interconnected 3D porous structure. This polymer system was developed on the highly versatile platform of polyphosphazene-polyester blends. Co-substituting a polyphosphazene backbone with both hydrophilic glycylglycine dipeptide and hydrophobic 4-phenylphenoxy group generated a polymer with strong hydrogen bonding capacity. Rapid hydrolysis of the polyester component permitted the formation of 3D void space filled with self-assembled polyphosphazene spheres. Characterization of such self-assembled porous structures revealed macropores (10,100 ,m) between spheres as well as micro- and nanopores on the sphere surface. A similar degradation pattern was confirmed in vivo using a rat subcutaneous implantation model. 12 weeks of implantation resulted in an interconnected porous structure with 82,87% porosity. Cell infiltration and collagen tissue in-growth between microspheres observed by histology confirmed the formation of an in situ 3D interconnected porous structure. It was determined that the in situ porous structure resulted from unique hydrogen bonding in the blend promoting a three-stage degradation mechanism. The robust tissue in-growth of this dynamic pore forming scaffold attests to the utility of this system as a new strategy in regenerative medicine for developing solid matrices that balance degradation with tissue formation. [source] In situ Porous Structures: A Unique Polymer Erosion Mechanism in Biodegradable Dipeptide-Based Polyphosphazene and Polyester Blends Producing Matrices for Regenerative EngineeringADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Meng Deng Abstract Synthetic biodegradable polymers serve as temporary substrates that accommodate cell infiltration and tissue in-growth in regenerative medicine. To allow tissue in-growth and nutrient transport, traditional three-dimensional (3D) scaffolds must be prefabricated with an interconnected porous structure. Here a unique polymer erosion process through which polymer matrices evolve from a solid coherent film to an assemblage of microspheres with an interconnected 3D porous structure is demonstrated for the first time. This polymer system is developed on the highly versatile platform of polyphosphazene-polyester blends. Co-substituting a polyphosphazene backbone with both hydrophilic glycylglycine dipeptide and hydrophobic 4-phenylphenoxy group generates a polymer with strong hydrogen bonding capacity. Rapid hydrolysis of the polyester component permits the formation of 3D void space filled with self-assembled polyphosphazene spheres. Characterization of such self-assembled porous structures reveals macropores (10,100 ,m) between spheres as well as micro- and nanopores on the sphere surface. A similar degradation pattern is confirmed In vivo using a rat subcutaneous implantation model. 12 weeks of implantation results in an interconnected porous structure with 82,87% porosity. Cell infiltration and collagen tissue in-growth between microspheres observed by histology confirms the formation of an in situ 3D interconnected porous structure. It is determined that the in situ porous structure results from unique hydrogen bonding in the blend promoting a three-stage degradation mechanism. The robust tissue in-growth of this dynamic pore forming scaffold attests to the utility of this system as a new strategy in regenerative medicine for developing solid matrices that balance degradation with tissue formation. [source] Spontaneous Current Oscillations during Hard Anodization of Aluminum under Potentiostatic ConditionsADVANCED FUNCTIONAL MATERIALS, Issue 1 2010Woo Lee Abstract Nanoporous anodic aluminum oxide is prepared by hard anodization of aluminum under potentiostatic conditions using 0.3,M H2C2O4. Under unstirred electrolyte condition, spontaneous current oscillations are observed. The amplitude and period of these current oscillations are observed to increase with anodization time. As a consequence of the oscillatory behavior, the resulting anodic alumina exhibits modulated pore structures, in which the diameter contrast and the length of pore modulation increase with the amplitude and the period of current oscillations, respectively, and the current peak profile determines the internal geometry of oxide nanopores. The mechanism responsible for the oscillatory behavior is suggested to be a diffusion-controlled anodic oxidation of aluminum. [source] Polystyrene Arrays: Non-Close-Packed Crystals from Self-Assembled Polystyrene Spheres by Isotropic Plasma Etching: Adding Flexibility to Colloid Lithography (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Mater. Hexagonally ordered arrays of non-close-packed spherical polystyrene (PS) particles are prepared by A. Plettl et al. on page 3279, and exhibit precisely controlled diameters and interparticle distances. An isotropic low-temperature plasma-etching process is applied to extended monolayers of PS colloids deposited onto hydrophilic silicon. These non-close-packed PS arrays are used as masks for the fabrication of arrays of cylindrical nanopores by reactive ion etching. [source] Non-Close-Packed Crystals from Self-Assembled Polystyrene Spheres by Isotropic Plasma Etching: Adding Flexibility to Colloid LithographyADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Alfred Plettl Abstract Hexagonally ordered arrays of non-close-packed nanoscaled spherical polystyrene (PS) particles are prepared exhibiting precisely controlled diameters and interparticle distances. For this purpose, a newly developed isotropic plasma etching process is applied to extended monolayers of PS colloids (starting diameters <300,nm) deposited onto hydrophilic silicon. Accurate size, shape, and smoothness control of such particles is accomplished by etching at low temperatures (,150,°C) with small rates not usually available in standard reactive ion etching equipment. The applicability of such PS arrays as masks for subsequent pattern transfer is demonstrated by fabricating arrays of cylindrical nanopores into Si. [source] Highly Stable Nickel Hexacyanoferrate Nanotubes for Electrically Switched Ion Exchange,ADVANCED FUNCTIONAL MATERIALS, Issue 15 2007W. Chen Abstract Nickel hexacyanoferrate (NiHCF) nanotubes are fabricated by an electrokinetic method based on the distinct surface properties of porous anodic alumina. By this method, nanotubes can be formed rapidly with the morphologies faithfully replicating the nanopores in the template. The prepared nanotubes were carefully characterized using SEM and TEM. Results from IR, UV, EDX, and electrochemical measurements show that the NiHCF nanotubes exist only in the form of K2Ni[Fe(CN)6]. Because of this single composition and unique nanostructure, NiHCF nanotubes show excellently stable cesium-selective ion-exchange ability. The capacity for electrodes modified with NiHCF nanotubes after 500,potential cycles retains 95.3,% of its initial value. Even after 1500 and 3000 cycles, the NiHCF nanotubes still retain 92.2,% and 82.9,%, respectively, of their ion-exchange capacity. [source] Preparation, Bioactivity, and Drug Release of Hierarchical Nanoporous Bioactive Glass Ultrathin FibersADVANCED MATERIALS, Issue 6 2010Youliang Hong Hierarchical nanoporous bioactive glass ultrathin fibers with different pore diameters from 1.5-nm micropores up to 65-nm macropores are synthesized using P123,PEO co-templates and an electrospinning technique (see image). Experiments demonstrate that the prepared bioactive glass fibers are highly homogenous and bioactive and their nanopores can control drug release well. [source] Vertically Aligned Nanowires on Flexible Silicone using a Supported Alumina Template prepared by Pulsed AnodizationADVANCED MATERIALS, Issue 40 2009Stefan Mátéfi-Tempfli Carpets of vertically aligned nanowires on flexible substrates are successfully realized by a template method. Applying special pulsed anodization conditions, defect-free nanoporous alumina structures supported on polydimethylsiloxane (PDMS), a flexible silicone elastomer, are created. By using this template with nanopores ending on a conducting underlayer, a high-density nanowire array can be simply grown by direct DC-electrodeposition on the top of the silicone rubber. [source] Highly Sensitive, Mechanically Stable Nanopore Sensors for DNA AnalysisADVANCED MATERIALS, Issue 27 2009Bala Murali Venkatesan Highly sensitive, mechanically robust Al2O3 nanopores are fabricated and characterized. These sensors allow for size control with sub-nanometer precision, chemical modification, and exhibit superior noise performance and increased lifetime over their solid-state counterparts. This new class of nanopore sensor is used in dsDNA studies and finds broad application in bio-nanotechnology. [source] Template-Free Tuning of Nanopores in Carbonaceous Polymers through Ionothermal SynthesisADVANCED MATERIALS, Issue 8 2009Pierre Kuhn Template-free tuning of nanopores in highly porous carbonaceous polymers can be achieved through polymerization of dicyanobiphenyl at high temperatures in a ZnCl2 melt. [source] Synthesis and Surface Engineering of Complex Nanostructures by Atomic Layer Deposition,ADVANCED MATERIALS, Issue 21 2007M. Knez Abstract Atomic layer deposition (ALD) has recently become the method of choice for the semiconductor industry to conformally process extremely thin insulating layers (high- k oxides) onto large-area silicon substrates. ALD is also a key technology for the surface modification of complex nanostructured materials. After briefly introducing ALD, this Review will focus on the various aspects of nanomaterials and their processing by ALD, including nanopores, nanowires and -tubes, nanopatterning and nanolaminates as well as low-temperature ALD for organic nanostructures and biomaterials. Finally, selected examples will be given of device applications, illustrating recent innovative approaches of how ALD can be used in nanotechnology. [source] Synthesis of Vertical High-Density Epitaxial Si(100) Nanowire Arrays on a Si(100) Substrate Using an Anodic Aluminum Oxide Template,ADVANCED MATERIALS, Issue 7 2007T. Shimizu Growth of vertical epitaxial Si(100) nanowires on Si(100) substrates is demonstrated (see figure) using a combination of an anodic aluminum oxide template, catalytic Au particles embedded in nanopores directly on the Si substrate by using electroless deposition, and vapor,liquid,solid growth using SiH4. HF acid treatment of the porous alumina template is important to realize a direct contact between deposited Au in the AAO nanopores and the Si substrate. [source] Ordered Whiskerlike Polyaniline Grown on the Surface of Mesoporous Carbon and Its Electrochemical Capacitance Performance,ADVANCED MATERIALS, Issue 19 2006Y.-G. Wang Supercapacitor electrode materials must exhibit high specific capacitance and high-rate charge,discharge ability. The ordered whiskerlike polyaniline (PANI) reported here, which was synthesized in situ on the surface of mesoporous carbon by a novel process, is demonstrated to have these properties thanks to its ordered nanometer-sized "thorns" (see figure) and the V-shaped nanopores between them. [source] Identification of single photoswitchable molecules in nanopores of silica xerogels using powder diffractionJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5-1 2010Antonio Cervellino Single photoswitchable molecules of (CN3H6)2[Fe(CN)5NO] (GuNP) are embedded into nanopores of an SiO2 xerogel. It is shown that it is possible to identify the structural motif (`fingerprint') of the embedded complex by analyzing neutron powder diffraction data in a limited Q range (Q < 37,nm,1) using the Debye approach. The structural study reveals that the pores are occupied by GuNP monomers with a fill factor of 60,80%. The mutual arrangement of the anion and cations in the GuNP monomer is slightly changed (,1% elongation), while the bond lengths within the anion and cation are changed by less than 0.2% with respect to the single-crystalline form of GuNP. [source] Synchrotron X-ray reflectivity studies of nanoporous organosilicate thin films with low dielectric constantsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2007Weontae Oh Quantitative, non-destructive X-ray reflectivity analysis using synchrotron radiation sources was successfully performed on nanoporous dielectric thin films prepared by thermal processing of blend films of a thermally curable polymethylsilsesquioxane dielectric precursor and a thermally labile triethoxysilyl-terminated six-arm poly(,-caprolactone) porogen in various compositions. In addition, thermogravimetric analysis and transmission electron microscopy analysis were carried out. These measurements provided important structural information about the nanoporous films. The thermal process used in this study was found to cause the porogen molecules to undergo efficiently sacrificial thermal degradation, generating closed, spherical nanopores in the dielectric film. The resultant nanoporous films exhibited a homogeneous, well defined structure with a thin skin layer and low surface roughness. In particular, no skin layer was formed in the porous film imprinted using a porogen loading of 30,wt%. The film porosities ranged from 0 to 33.8% over the porogen loading range of 0,30,wt%. [source] Structural characterization of undoped and Sb-doped SnO2 thin films fired at different temperaturesJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3-1 2003Alessandro P. Rizzato SnO2 thin films were obtained by the sol-gel method starting from inorganic precursor solutions. In this work, we compare the structure of undoped and Sb-doped SnO2 films prepared by dip-coating. The films were deposited on quartz substrates and then fired at different temperatures ranging from 383 up to 1173 K. The density and the thickness of the films were determined by X-ray reflectivity (XRR) and their porous nanostructure was characterized by grazing-incidence small angle X-ray scattering (GISAXS). XRR results corresponding to undoped and Sb-doped samples indicate a monotonous decrease in film thickness when they are fired at increasing temperatures. At same time, the apparent density of undoped samples exhibits a progressive increase while for Sb-doped films it remains invariant up to 973 K and then increases for T = 1173 K. Anisotropic GISAXS patterns of both films, Sb-doped and undoped, fired above 573 K indicate the presence of elongated pores with their major axis perpendicular to the film surface. For all firing temperatures the nanopores in doped samples are larger than in undoped ones. This suggests that Sb-doping favours the pore growth hindering the film densification. At the highest firing temperature (1173 K) this effect is reversed. [source] Diffusion through ordered force fields in nanopores represented by Smoluchowski equationAICHE JOURNAL, Issue 6 2009Fu Yang Wang Abstract The classical Einstein or Fick diffusion equation was developed in random force fields. When the equation is applied to gas transport through coal, significant discrepancies are observed between experimental and simulation results. The explanation may be that the random force field assumption is violated. In this article, we analyze molecular transport driven by both random and ordered (directional) forces in nanopores. When applied to CO2 transport through cone-shaped carbon nano-tubes (CNTs) and Li+ doped graphite pores, computational results show that directional force fields may significantly affect porous media flow. Directional forces may be generated by potential gradients arising from a range of non-uniform characteristics, such as variations in the pore-sizes and in local surface compositions. On the basis of the simulation and experimental results, the Smoluchowski and Fokker-Planck equations, which account for the directional force fields, are recommended for diffusion through ordered force fields in nanopores. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Orientation of Syndiotactic Polystyrene Crystallized in Cylindrical NanoporesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 3 2009Hui Wu Abstract Syndiotactic polystyrene (sPS) nanorods with different diameters have been prepared by using anodic aluminum oxide templates, and the orientation of the sPS crystals in the nanorods has been investigated by FT-IR spectroscopy. It is found that the c axis of the ,, crystals preferentially oriented perpendicular to the axis of the nanorod, and the degree of orientation is lower as the diameter of the nanorod decreases. This unexpected result is attributed to nuclei formed at the surface of the nanopores and their subsequent growth, in addition to the preferential growth compatible with the pore direction by the nuclei formed in the bulk film and in the nanorods. [source] Simulated Annealing Study of Self-Assembly of Symmetric ABA Triblock Copolymers Confined in Cylindrical NanoporesMACROMOLECULAR THEORY AND SIMULATIONS, Issue 2-3 2008Zheng Wang Abstract We report a simulated annealing study of the self-assembly of symmetric lamella-forming ABA triblock copolymers confined in cylindrical nanopores. We systematically examine the dependence of the self-assembled morphologies and structural parameters on the degree of confinement and the strength of the surface preference. We find that the confined morphologies for the symmetric ABA triblocks with fA,=,1/2 are similar to those for the symmetric or nearly symmetric AB diblock copolymers under the same confinement. We also find that different structural parameters can reflect different information. The predicted bridging fraction value for the bulk phase is in good agreement with previously established values, whereas the predicted values for the confined morphologies change with both the degree of confinement and the strength of the surface preference. We further explore the self-assembling process by examining the morphology and various ensemble-averaged thermodynamic quantities and structure parameters as a function of the reduced temperature. [source] | |||||||||||||||||||||||||||||||