Template Films Research Articles

Templated polypyrrole electro-polymerization: Self-assembled bundles of bilayer membranes of amphiphiles and their actuation behavior

The electrochemical properties of conducting polymers are highly dependent on the microstructure. We report a method to produce specific microstructures of polypyrrole through electro-polymerization in the presence of the amphiphile N-{11-(2-hydroxyethyldimethylammonium)undecanoyl}- N, N′-dioctyl- l-glutamate, bromide, which forms supramolecular hydrogels with pyrrole in aqueous solution. These hydrogels were used as templates during polypyrrole electro-polymerization to give microstructures composed of the bundles of bilayer membranes. The highly porous nature of these films resulted in electrochemical properties superior to polypyrrole deposited under the same condition without use of an amphiphilic template. Analysis of the scan rate dependence on cyclic voltammogram reveals that the porous templated films facilitate fast diffusion of dopant ions. The actuation properties were also investigated in aqueous solutions containing sodium p-toluene sulfonate electrolyte. The strains displayed by the template polypyrrole films were twice those synthesized without the use of a template.

Disordered mesoporous silica low- k thin films prepared by vapor deposition into a triblock copolymer template film

Mesoporous silica films have been prepared by a vapor phase method using tetraethoxysilane (TEOS) in a batch reactor and in a continuous flow reactor. The TEOS molecules penetrated into a triblock copolymer films and then a triblock copolymer/silica composite structure was formed. A two dimensional grazing-incidence small angle X-ray scattering pattern and field emission scanning electron microscopy images of the films indicated that the films possess ordered and disordered regions. The tortuous pore channels in the wormhole-like disordered structure run parallel to the film surface. The mesostructured triblock copolymer/silica composite films were treated with a trimethylethoxysilane (TMES) vapor before and after calcination. The vapor infiltration treatments effectively improved mechanical strength and hydrothermal stability of the films. The dielectric constant of the TMES-treated mesoporous silica films was reduced into the 1.5–1.7 range.

Cr N x and Cr1−xAlxN as template films for the growth of α-alumina using ac reactive magnetron sputtering

Crystalline alumina thin films were deposited on WC–Co substrates using a reactive inverted cylindrical ac magnetron sputtering technique with a chromium oxide prelayer. The interfacial prelayer of chromium oxide was prepared by controlled oxidation of CrNx and Cr1−xAlxN films deposited previously using the same ac reactive magnetron configured with one Cr and Al target. The oxidation was carried out by annealing CrNx and Cr1−xAlxN films in air at 973 and 1373K, respectively. Scanning electron microscopy and energy dispersive x-ray microanalysis were carried out to investigate the thin film surface morphology and composition. The alumina coatings obtained on oxidized CrNx films (templates) were smooth and consisted primarily of κ and α phases. The diffraction peaks from the γ phase were not observed in any of the alumina coatings. The morphology and phase composition of the alumina coatings on the oxidized Cr1−xAlxN films (templates) were strongly dependent on the aluminum content in the films.

Dual Ion Assist Beam Processing of Magnesium Oxide Template Layers for 2nd Generation Coated Conductors

Ion beam assisted deposition (IBAD) of magnesium oxide (MgO) has been shown to be a viable route for producing biaxially textured template films on flexible polycrystalline metal substrates for high-performance coated conductor development. We have refined the technique of IBAD by using a dual ion assist approach. Dual ion assist beam deposition (DIBAD) of MgO reduces the requirements for substrate surface finishing while maintaining comparable film quality (phi scan full-width at half-maximum values between 7 and 8deg). Furthermore, this adaptation of the IBAD process eliminates the degradation of MgO texture observed in IBAD MgO films deposited on silicon nitride. We have deposited films up to 50 nanometers thick without degradation of the in-plane texture. Increasing the MgO thickness increases the chemical stability of template layer and can eliminate the necessity for subsequent buffer layers or the application of the homoepitaxial MgO layer needed to stabilize the thin, conventional IBAD MgO layer. The initial performance of coated conductors made with DIBAD templates is quite promising.

SU‐FF‐T‐402: The Development of a New Radiochromic Film Protocol for Three‐Dimensional and Beta Dosimetry

Purpose: To develop a film‐specific correction factor for radiochromic film (RCF) when exposed to in a parallel geometry and to use this technique with three‐dimensional and beta dosimetry. Method and Materials: Radiochromic films were placed in a Virtual Water™ phantom at 100 SSD and exposed to radiation using both parallel and orthogonal exposure techniques. The dose rate was determined using an Exradin #a12 ionization chamber at 5 cm depth in the same phantom. Response curves were generated for each technique using a novel film readout protocol employing an i900 Microtek flatbed scanner and localized background subtraction. Several film readout techniques were investigated including transmission and reflective modes. All films were scanned simultaneously using a film template to ensure millimeter alignment for pre‐ and post‐irradiation scans. A correction factor was determined to account for the different response of RCF to parallel and orthogonal exposures. This correction factor was then applied to a parallel exposure to allow comparison with an orthogonal exposure from a NIST‐traceable ophthalmic applicator. The ophthalmic exposure was conducted using a certified technique. Results: The depth dose exposure method resulted in an average over response at depths > 1 cm of 5% and 15% and was proportional to film thickness. Film‐specific correction factors were determined for EBT and HD‐810 radiochromic films. Using these correction factors, the parallel exposure method was within the 3.5% uncertainty of the ophthalmic applicator. An accurate film readout protocol was essential to obtaining precise results and it was determined that the reflective black and white protocol was the most reliable and reproducible. Conclusion: A “many points” calibration method was developed using a single film exposed to in a parallel (on‐edge) geometry. This technique, along with a film‐specific correction factor, allows for improved accuracy when applied to 3D and beta dosimetry.

Ordered Arrays of Au Nanoclusters by TiOx Ultrathin Templates on Pt(111)

Ultrathin ordered films of TiO x (x ≈1) on Pt(111) have been investigated by scanning tunneling microscopy (STM) to test their capability as templates for growing ordered and monodispersed Au nanocluster arrays. The ordered array of parallel black troughs spaced by 1.44 nm, observed in the STM data of the zigzag-like TiO x ultrathin film, was revealed to be a good template for growing a linear array of Au clusters, with a mean size of 1.3 nm and a narrow dispersion. The wagon-wheel-like TiO x film, having a similar chemical composition but without a nanostructured array of defects, does not show templating effects, thus leading to nucleation of disordered and larger Au clusters (mean size of 3.4 nm with a large dispersion). Hence, this work shows that the ordering of the deposited Au nanoclusters is strongly dependent on the actual defectivity of the film. Annealing the Au cluster arrays at high temperature produces drastic changes in the spatial arrangement of the clusters, which has been interpreted as the consequence of the changes in the ultrathin film template.

Application of Al2O3 in the electrosynthesis of polypyrrole with fuzzy morphology—Microtentacle

AbstractPolypyrrole (PPy) thin films were electrochemically polymerized onto the electrode surface. In this study alumina was used as the template and PPy film was prepared by electrochemical polymerization using Al/Al2O3 as the working electrode. Surface morphology of PPy was investigated by scanning electron microscopy (SEM) and the results revealed that the application of the template resulted in PPy with fantastic surface morphology which was called microtentacle and the length of the tentacle could reach 15 µm. The morphology can evidently increase the roughness, thus the surface area of the electrode substrate, and provide an intimate contact with the surrounding brain tissue compared to the hard, stiff metal surface. Relationship between PPy morphology and electrochemical polymerization parameters, such as polymerization time, was investigated. The study provided a fundamental method to prepare a PPy‐modified electrode with high surface area. Potential application of the study is proposed. Copyright © 2007 John Wiley & Sons, Ltd.

Onset of magnetic interface exchange interactions in epitaxially grown Mn/Co(001)

Manganese (Mn) grows in a metastable expanded (c/a > 1) face-centered-tetragonal (fct) phase on thin fct-Co(001) template films. A layer-by-layer growth mode is observed for small Mn thicknesses. Antiferromagnetism (AFM) of fct-Mn is evidenced by the observation of shifted magnetization loops antiparallel to the cooling field direction (negative bias) and enhanced coercive fields for Co/Mn bilayers. At low temperature, magnetic exchange interactions are detected at the Co/Mn interface for nominal Mn thicknesses as low as 1.4 monolayer (ML), indicating the onset of AFM in 2-ML-thick Mn islands. However, between 2- and 5-ML Mn, a positive bias of the magnetization loops is observed in a certain temperature range below the blocking temperature (TB) of the films. This peculiar behavior is explained by the dependence of TB on both the local Mn ML thickness and the Mn island size, leading to a unidirectional coercivity enhancement in a temperature range where both blocked and unblocked regions coexist in the Mn layers.

In situ preparation of free-standing nanoporous alumina template for polybithiophenenanotube arrays with a concourse base

Vertically aligned polybithiophene nanotube arrays with a concourse base werefabricated by using a free-standing nanoporous alumina template, which wasprepared in situ on conductive substrates. A well defined 20 nm gap between thenanoporous template and the substrate provided substantial space, that allowsfor the formation of a concourse base and improved wetting of the electrolyteon the template film. As a result, the uniformity of the nanotube arrays andthe adhesion of the nanotubes to substrates were improved significantly. Withthe concourse base, the prepared nanotube array has an estimated density of3 × 1010 cm−2, accounting for the occupation ratio of nearly 100% to the nanochannels in aluminatemplates, and the prepared polybithiophene nanotubes are capable of standing alone at anaspect ratio of 5 without any tilt.

Formation of robust, free-standing nanostructured membranes from catanionic surfactant mixtures and hydrophilic polymers

A new type of surfactant templated polymer film, which spontaneously forms at the air/water interface into micron-thick structures, was prepared from a water-soluble polymer and a catanionic surfactant mixture; the film is stable, highly ordered and robust, requiring no cross-linking agents to fix the structure.

Direct electrodeposition of highly ordered magnetic nickel nanowires on silicon wafer

Highly ordered nickel nanowire (50 and 12 nm in diameter) arrays were successfully deposited into the nanoporous alumina template film on a gold-coated silicon wafer. The electrodeposited nickel nanowires have a preferred (220) fibre texture, that is the [110] direction parallel to the wire axis. With electropolishing, nanoporous alumina template with ordered and uniform pores was prepared by anodisation. By complete removal of the barrier layer and careful control of electrodeposition procedures, nearly 100% pore filling of uniform nanowires can be directly deposited onto the Au-coated silicon substrate, therefore no pattern transfer is necessary and incorporation of these nanowires into silicon-based devices is readily possible

Growth of Vertically Aligned Carbon Nanofibers from Nickel Nanodot Arrays Produced from Diblock Copolymer Thin Film Templates

Diblock copolymers of polystyrene and poly(methyl methacrylate) are utilized in a thin film to create a nanoscale template, which is used to deposit a nanoscale array of nickel nanodots. Systematic experiments show that this process must be optimized to successfully transfer the order of the diblock copolymer template to the resultant nickel nanodot array. It is found that the amount of nickel deposited dramatically impacts the fidelity of the final nanodot array, with a thickness ratio for copolymer:metal of 8:1 found to be optimal. The results also indicate that the method by which the surface is neutralized for the diblock domain alignment impacts the amount of nickel nanodots that remain on the surface after template removal. Finally, the nanoscale array of nickel nanodots is utilized to successfully grow vertically aligned carbon nanofibers from 18 nm and 40 nm diameter nickel dots.

Honeycomb-like architecture produced by living bacteria, Gluconacetobacter xylinus

Bacterial cellulose (BC)-producing bacterium, Gluconacetobacter xylinus (ATCC53582), was found to move along linear microgrooves of a stripe-patterned cellulosic scaffold. On the basis of this finding, fabrication of honeycomb-patterned BC was attempted by controlling the bacterial movement using a agarose film scaffold with honeycomb-patterned grooves (concave type). The patterned agarose film was prepared by three steps. The first was transcription of a honeycomb-patterned polycaprolactone film template with polydimethyl siloxane. When the bacteria were cultured on the scaffold under atmospheric conditions, only bacterial proliferation was observed. Honeycomb-patterned BC was obtained when cultured under a humid CO 2 atmosphere. Electron diffraction and polarized microscopic observation showed that the patterned BC comprised of the well defined cellulose Iα microfibrils. As another attempt to fabricate honeycomb-patterned BC, the bacteria were cultured on the patterned cellulose and agarose film with convex type of honeycomb. This culture yielded no honeycomb-patterned BC. Therefore, concave type honeycomb scaffold is more suitable to fabricate honeycomb-patterned BC.

Sensitive slab optical waveguides composed of mesoporous metal-oxide thin films on the tin-diffused layers of float glass substrates

The application of uniform transparent mesoporous thin films for waveguide-based optical chemical and biological sensors could result in ultrahigh sensitivity due to a great increase in the depth of interaction between evanescent wave and analyte molecules adsorbed within the mesoporous film. For this purpose, we designed a low-loss, prism-coupling-compatible slab optical waveguide that can be prepared by deposition of sol-gel surfactant templated mesoporous metal-oxide thin films on the tin-diffused glass layers being intrinsic to float glass slides. In this study, mesoporous WO3 and SnO2 thin films were fabricated and the resulting elements were demonstrated to keep the waveguiding capability and to allow for in situ detection of molecular adsorption within the mesoporous film by single-beam polarimetric interferometry. Induced changes in the phase difference between the fundamental transverse electric and magnetic modes were detected by two methods: (a) monitoring of an interference fringe on the waveguide surface and (b) detection of the light emitting from the prism coupler.

Preparation of mesoporous silica templated metal nanowire films on foamed nickel substrates

A method has been developed for the formation of high surface area nanowire films on planar and three-dimensional metal electrodes. These nanowire films are formed via electrodeposition into a mesoporous silica film. The mesoporous silica films are formed by a sol–gel process using Pluronic tri-block copolymers to template mesopore formation on both planar and three-dimensional metal electrodes. Surface area increases of up to 120-fold have been observed in electrodes containing a templated film when compared to the same types of electrodes without the templated film.

Polymorph Farming of Acetaminophen and Sulfathiazole on a Chip

The aim of this paper is to understand at a given temperature (1) the role of template films, the droplet volume of a saturated sulfathiazole aqueous solution and the solvent on polymorph screening of sulfathiazole on a silicon wafer, and (2) the effect of template films on the acetaminophen crystal face at the template-crystal interface. Template Effect: Spun cast template films of non-annealed chitosan and annealed chitosan at 140 degrees C on silicon wafers were prepared. A 0.01-cm(3) saturated sulfathiazole aqueous solution droplets were deposited on both kinds of chitosan film. Sulfathiazole crystals were produced on those films by evaporation at 25 degrees C. Volume Effect: Different droplet volumes of a saturated sulfathiazole aqueous solution ranging from 0.01 to 0.14 to 2.7 cm(3) were deposited on non-annealed chitosan films. Sulfathiazole crystals were generated on those films by evaporation at 25 degrees C. Solvent Effect: 0.01 cm(3) saturated sulfathiazole methanol solution droplets were deposited on non-annealed chitosan films and sulfathiazole crystals were formed on those films by evaporation at 25 degrees C. The formation pathways of different sulfathiazole crystal polymorphs of the above mentioned effects were analyzed and verified by systematic studies. Template-crystal Interfacial Study: Millimeter-sized acetaminophen crystals were successfully grown on non-annealed chlorosulfonated poly(ethylene) (PE-Chl) and chitosan template films by cooling the saturated acetaminophen aqueous solution from 50 to 25 degrees C in which those template films were immersed. The bonding energies for specific carbons collected by electron spectroscopy for chemical analysis (ESCA) at the acetaminophen crystal surface, together with the molecular interactions between acetaminophen and PE-Chl and between acetaminophen and chitosan in separately prepared solid dispersion film samples detected by Fourier transformed infrared (FTIR) spectroscopy, proved to be useful for identifying the crystal face of acetaminophen essential for its specific intermolecular interactions at the template-crystal interface. Thermodynamically metastable sulfathiazole Form I crystals were reproducibly obtained on the non-annealed chitosan films whereas the stable sulfathiazole Form III crystals were repeatedly formed on the annealed chitosan films. Droplet volumes and solvents were also found responsible for the polymorphic outcome of sulfathiazole in the kinetically driven area of two overlapping metastable zones from two competing polymorphs of Form I and Form III. Thermodynamically stable sulfathiazole Form III crystals were formed on the non-annealed chitosan films instead when the droplet volumes of a saturated sulfathiazole aqueous solution were increased from 0.01 to 0.14 cm(3) and 2.7 cm(3). When the solvent was changed from water to methanol, the thermodynamically stable sulfathiazole Form III crystals were again observed on the non-annealed chitosan films even from the 0.01 cm(3) saturated sulfathiazole methanol solution droplets. Template surfaces were thought to provide specific functional groups to either change the energy barrier for the nuclei formation of the thermodynamically metastable Form I or alter the droplet contact angle and the droplet surface area which was related to the droplet evaporation time. The evaporation time determines the amount of time available for the polymorphic transformation from Form I to Form III. Apparently, droplet volumes could also determine the amount of time needed to reach supersaturation and the amount of time available for a polymorphic transformation from Form I to Form III. In addition, the molecular conformation and viscosity of solvents such as methanol might alter the original nucleation kinetics in water and lead to a more rapid polymorphic transformation from Form I to Form III. Template films of PE-Chl and chitosan were found to be critical for determining the face of a millimeter-sized acetaminophen crystal at the template-crystal interface. The idea of performing polymorph screening on the template film deposited on a chip has opened up a new doorway to examine the roles of: (1) various kinds of drug carrier in the form of a template film, (2) the droplet volume of a saturated solution, and (3) the type of solvent used, in polymorphic control. Growing millimeter-sized crystals directly on the chip of template has also provided a convenient technology enabling platform for examining the crystal-template interface by solid-state characterization techniques such as ESCA.

Controlling thickness in hexagonal polymer templated mesoporous silica films

Many templated mesoporous silica films are synthesized through a solution phase co-assembly process involving association of surfactants or block-copolymers with silica precursors that is driven by the evaporation of solvent. During the film formation, a liquid crystal type structure with well-defined nanometer scale periodicity is formed and then made rigid by condensation of the silica precursors. For a variety of applications there is an interest in controlling the film thickness. The objective of this investigation is to find systematic rules that determine film thickness in hexagonal SBA-15 type silica/polymer composite materials. We find that despite the complex self-organization in these materials, all thickness data can be fit with classic models for evaporation induced deposition in dip-coated films. The models relate film thickness, pull rate, solution viscosity, and solution density. The thickness data can be modeled with no adjustable parameters over more than an order of magnitude thickness range.

Development of IBAD/PLD process for long length Y-123 conductors in Fujikura

Long length manufacturing approach of YBa2Cu3O7−x (Y-123) conductor was performed using ion-beam-assisted-deposition (IBAD) and pulsed-laser-deposition (PLD) process in Fujikura Ltd. A new set of reel-to-reel IBAD system was designed using 110cm×15cm assisting ion source. The planer distribution of in-plane texture (Δϕ) for Gd2Zr2O7 template films were studied in large deposition area of 100cm×25cm. The throughput of 5.5m/h with Δϕ of 15° was obtained for Gd2Zr2O7 films grown on 10mm wide tapes. Long Y-123/CeO2/Gd2Zr2O7/Hastelloy tapes were produced by using reel-to-reel vacuum apparatuses of IBAD and PLD. Ic of 153A, and 88A were obtained in end-to-end of a 104m long tape, and a 217m long one, respectively. Ic of 360A was obtained in a short sample with Y-123 thickness of 2.0μm. A cryo-cooled 5-turn×4-layer small solenoid coil with inner diameter of 60mm was demonstrated using a Y-123 conductor formed by IBAD/PLD method. No severe heat spot was generated even the transporting current exceeded the coil Ic value of 355A at 20K.

Template induced chiral ordering in nematic liquid crystalline materials: A deuterium nuclear magnetic resonance study

Glancing angle deposition is used to create porous liquid crystal alignment layers with high aspect-ratio, three-dimensional features. We use solid-state deuterium nuclear magnetic resonance to determine the alignment of alpha deuterated 4′-pentyl-4-cyanobiphenyl in a 3.2μm thick SiO2 film comprised of independent, helical structures. Comparing measured spectra with models, we determine that the liquid crystalline molecules exhibit chiral ordering dictated by the features of the template films. In the plane of deposition the liquid crystalline molecules tilt away from the substrate normal at an average angle of 51°, which is commensurate with the helical features of the chiral template.

Thermal Stability of Poly(o-Methoxyaniline) Layer-by-Layer Films Investigated by Neutron Reflectivity and UV-VIS Spectroscopy

Neutron reflectivity measurements were used to investigate the thermal stability of layer-by-layer (LBL) films of poly(o-methoxyaniline) (POMA), which was probed by increasing the temperature up to 80 degrees C of a D2O solution in contact with the LBL films. The study was made possible by adsorbing POMA layers on a PEI/(PSS/PAH)5/PSS LBL film template, leading to less rough POMA layers in comparison with the POMA/poly(vinylsulfonic acid sodium salt) (PVS) LBL films adsorbed directly on glass and silicon substrates. While the latter yielded almost fringeless neutron reflectivity curves due to the large roughness, the fitting of the data for POMA films adsorbed onto the template film and UV-vis measurements indicated that the topmost layer is affected for films heated in solution up to 80 degrees C. This is essentially the same thermal stability of LBL films from the template films made with conventional polyelectrolytes. A decrease in thickness of approximately 10 A was inferred when the solution temperature increased from 25 degrees C to 80 degrees C, which was maintained when the sample was cooled back to 25 degrees C. This decrease, observed for solutions of pH 3 and pH 8, is consistent with thermally-stimulated desorption and was corroborated by UV-VIS absorption experiments. The unexpected stability of the POMA layer at pH 8 is attributed to the layer-by-layer structure of the films that allows POMA to remain doped, in its salt emeraldine form, even at high pH.