Template Films Research Articles

Nanostructured conducting molecularly imprinted polymer for selective uptake/release of naproxen by the electrochemically controlled sorbent

A conducting molecularly imprinted polymer (CMIP) film, based on polypyrrole, was electrosynthesized for selective uptake/release and determination of naproxen. The film was prepared by incorporation of a template anion (naproxen) during the electropolymerization of pyrrole into a platinum electrode using the cyclic voltammetry method. Overoxidized polypyrrole films with cavities complementary to the template were used as a potential-induced selective recognition element in the solid-phase sorbent. Various important fabricating factors, which control the performance of the CMIP film, were investigated using fluorescence spectroscopy. The measured fluorescence intensities of released solutions were related to the concentrations of naproxen taken up into the films. Several key parameters such as applied potential and time for uptake and release were varied to achieve the optimal sorption procedure. The film template with naproxen exhibited excellent selectivity over some interference. The calibration graphs were linear in the ranges of 5×10−8 to 3×10−7molml−1 and 7×10−6 to 8×10−4molml−1, and the limit of detection was 1×10−8molml−1. The CMIP films, as the electrochemically controlled solid-phase sorbent, were applied for the selective cleanup and quantification of trace amounts of naproxen from physiological samples. Scanning electron microscopy confirmed the nanostructure morphology of the films.

Selective deposition on block copolymer film by thermal evaporation of silver

Selective deposition of Ag onto nanostructured block copolymer film template of poly(ethylene oxide) and poly(methacrylate) with azobenzene mesogen (PEO-b-PMA(Az)) has been done by thermal evaporation technique. A hexagonally arranged pattern or ordered strip structure of the PEO nanocylinders dispersed in the PMA(Az) matrix appears on the pure copolymer film surface after thermal annealing at 140°C or 110°C, respectively. Atomic force microscopy confirms that the deposited Ag atoms prefer to wet PMA(Az) matrix domains on the film surface, and finally aggregate into discrete nanoparticles in both cases. An ordered porous metallic layer is created on the hexagonally patterned copolymer template surface due to the preferential interaction of Ag toward the PMA(Az) phase. Alternatively, ordered array of metallic chains is formed on the template featured with strip structure. While the nominal layer thickness of the deposited Ag is 50nm, the ordered metallic nanostructure disappears, indicating the host copolymer template cannot guide the spatial distribution of the deposited metal any more.

Alumina Template Assistance in Titania Nanotubes Dye-Sensitized Solar Cell ( NT-DSSC) Device Fabrication

In our previous works, we have made alumina template films and used it for nanowire, nanowhisk, and nanosphere fabrication and molecular aggregation studies. In the present paper, we have combined Al2O3 template and titania (TiO2) NT fabrication processes to achieve an Al2O3/TiO2 NT dye-sensitized solar cell (DSSC) devices. The DSSC structure includes glass substrate, transparent conductive film of ITO, Pt particles serving as the counter electrode, Al2O3/TiO2 NT film, dye, and ITO serving as the working electrode, and the electrolyte is injected into the counter-working interface. Al2O3 template was made by anodization and TiO2 NT was made by sol-gel deposition into Al2O3 template. Al2O3 template has a light, transparence, large surface, good mechanical strength, and flexibility, making it a candidate material for DSSC electrode template. TiO2 NT is a semiconductor with an energy gap that matches up very nicely with N3 sensitized dye.

Formation of conductive polyaniline nanoarrays from block copolymer template via electroplating

Nanostructured thin films have drawn extensive attention because of their unique properties resulting from nanoscale features. One of the convenient ways to generate nanostructured thin films is to use pattern with nanoscale texture as a template for the reactions carrying out within the template. In this study, nanoporous thin film template was obtained from the self-assembly of degradable block copolymer, polystyrene-b-poly(l-lactide) (PS-PLLA) with PLLA cylinder nanostructure, at which the PLLA block can be hydrolyzed to form the nanopatterns with cylinder nanopores on conductive substrate (i.e., ITO substrate). The nanoporous PS thin film template was stabilized by modification of substrate using hydroxyl terminated PS so as to enhance the adhesion with substrate for following electroplating process. Combining a pulse electroplating method with the control of micro current, polyanilines can be successfully synthesized within the template to fabricate well-defined of conductive polymer nanoarrays.

Impact of Homopolymer Pore Expander on the Morphology of Mesoporous Carbon Films Using Organic–Organic Self-Assembly

Soft templated mesoporous carbon films (ca. 60 nm thick) are fabricated by the cooperative assembly of poly(styrene-block-ethylene oxide) (PS-b-PEO) with phenolic resin, where the pore sizes are tuned by the addition of polystyrene oligomers (hPS) to this self-assembling system. Significant differences in the morphology and pore expansion are found for the thin films in comparison to previously reported bulk powders using a similar system. The film porosity is nearly independent of swelling agent content for addition of up to 10 wt % hPS; this limited effect is attributed to surface segregation of the hPS on the basis of wetting considerations, which decreases the effective concentration of hPS in the hydrophobic domains. The templated synthesis yields a relatively narrow pore size distribution for 10 wt % hPS. Elliptical pores are formed due to the uniaxial contraction that occurs during carbonization...

Highly Controlled Dip-Coating Deposition of fct FePt Nanoparticles from Layered Salt Precursor into Nanostructured Thin Films: An Easy Way To Tune Magnetic and Optical Properties

Nanostructured titania films containing hard magnetic FePt nanoparticles were obtained through impregnation and postannealing of salt layered precursor [Fe(H2O)6][PtCl6] nanocrystals. The impregnation was performed by a highly controlled dip-coating process into ethanol based solutions of the salt precursor. The bimetallic salt nanocrystals were formed upon evaporation of the solvent into the cavities of TiO2 template films. The salt was transformed into the hard magnetic fct phase by annealing in reductive atmosphere at 400 °C a particularly low conversion temperature compared with those reported for other synthesis approaches. Two different titania templates were considered. In the first case, the impregnation of 3D mesoporous films was investigated in order to determine the influence of the deposition parameters on the amount of FePt nanoparticles embedded and the final optical and magnetic properties of the layers. In the second case, this approach was further extended to 2D heterogeneous nanoperforated films. The nanoparticles were selectively deposited into the perforations thanks to a prior functionalization of the titania template by the formation of hydrophobic/hydrophilic distinct domains. Interestingly, the coalescence between the magnetic particles was found to be limited due to the low conversion temperature. This procedure of positioning particles onto a 2D nanostructured support constitutes an easy and versatile bottom-up approach toward magnetic arrays with potential application in magnetic data storage devices.

Transformations and enhanced long-range ordering of mesoporous phenolic resin templated by poly(ethylene oxide-b-ε-caprolactone) block copolymers blended with star poly(ethylene oxide)-functionalized silsesquioxane (POSS)

In this study, we prepared ordered mesoporous phenolic resins templated by poly(ethylene oxide)-b-(e-caprolactone) (PEO-b-PCL) diblock copolymers blended with a star PEO octa-functionalized polyhedral oligomeric silsesquioxane (PEO-POSS) homopolymer. Increasing the PEO-POSS content, and thereby increasing the PEO-to-PCL ratio in the template film, allowed us to tune and enhance the long-range order of the mesoporous phenolic resin. The increased pore size and the more ordered structure were accompanied by a narrower pore size distribution. In addition, we observed an ordered-to-ordered mesophase transition, from a bicontinuous gyroid to a hexagonally packed cylinder structure, upon blending with the star PEO-POSS homopolymer. We anticipate that this approach could be extended to the preparation of other large-pore, long-range-ordered mesoporous materials, such as silica and other metal oxides.

Sustained Protection for Transparent Electrodes in Touch Panels and Smart Windows: Template Assisted Encapsulation of Fluorinated Silanes in Sol-Gel Silica Films for Sustained Hydrophobic-Oleophobic Functionality

ABSTRACTHydrophobic-oleophobic coatings are often used to provide the transparent electrodes in devices like touch panels and smart windows with protection from fingerprints and other contaminants which may degrade electronic and optical performance. Conventional fluorosilane monolayers or co-condensed films are often surface-enriched with fluorinated moieties due to the thermodynamic drive of these components to migrate to low-surface energy interfaces. Consequently, these conventional coatings may be strongly non-wetting and have low-surface energy when pristine, but upon wear and exposure of the bulk subsurface regions, the films are much less functional. This work explores the use of surfactant templated sol-gel silica films as scaffolds for encapsulating surface-segregating functional organic moieties as a mesoscopically dispersed phase with the goal of imparting sustained functionality. The results show that surfactant template concentration may be used to tune the dispersion of the fluorosilane-rich phase within the silica film in order to allow worn and exposed internal surfaces to maintain much of the original functionality of the pristine top surface.

Nanometer size effects in nucleation, growth and characterization of templated CdS nanocrystal assemblies

We report on the oriented nucleation of CdS nanocrystals on well-defined polydiacetylene Langmuir film templates. Nucleation on the red phase of polydiacetylene resulted in ordered linear arrays of CdS nanocrystals that are aligned with respect to the template. High resolution transmission electron microscopy showed crystalline particles of ~5 to 8 nm size. Selected area electron diffraction micrographs showed spot patterns which are attributed to the well-defined orientations of both polymorphs: the cubic zinc blende and the hexagonal wurtzite polymorphs of CdS. We present a unique growth mechanism where oriented nucleation of CdS on the polydiacetylene template initially takes place in the zinc blende phase. Beyond a certain size threshold, growth proceeds in the more stable wurtzite phase. This transformation keeps the stacking direction of the close packed planes, while altering only their stacking sequence. Notably, size-confinement effects were observed in electron diffraction patterns from the wurtzite phase. These effects originated from off-axis planes that do not fulfill the Bragg conditions, yet their elongated Bragg rods intersect with the Ewald sphere, giving rise to unexpected reflections.

Nanostructured electrocatalysts immobilised on electrode surfaces and organic film templates

AbstractThe development of new electrocatalysts with the aim of enhancing the rate of electrochemical reactions has been a long-term goal of electrochemists. In part, this is due to the great importance of electrocatalysts in energy generation and environmental concerns. In this review, various methods of the preparation of nanostructured electrocatalysts and their applications after attachment to the electrode surface are described. Diazonium chemistry has been extensively used for the preparation and attachment of nanostructured electrocatalysts and this review thus describes the recent developments and applications of this chemistry in electrocatalysis. The preparation of nanostructured electrocatalysts including grafted molecular films and metal nanoparticles physically adsorbed on electrode surfaces and those attached to the surface by molecular links using diazonium chemistry is reviewed. Two methods for the attachment of nanoparticles by simple physical adsorption and by electrochemical deposition on molecular films are described and the electrochemical response of nanostructured electrocatalysts for some of the most common electrochemical reactions is discussed.

Silver Immobilization on Honeycomb-patterned Polyvinypyrrolidone thin Films via an Electroless Process

Honeycomb-patterned polyvinypyrrolidone (PVP) thin films coated with nanometer-sized silver particles were prepared using honeycomb-patterned polystyrene (PS) template films fabricated by casting a polystyrene solution under humid condition. Silver was first metallized on the patterned PS films via silver nitrate () reduction using tetrathiafulvalene (TTF) and a small amount of PVP as the reductant and dispersing agent, respectively. The effects of , TTF, and PVP solution concentrations during the reduction process in acetonitrile were determined to obtain a uniform silver-coated honeycomb-patterned PS film. Second, the silver-metallized patterned porous PS films were filled with high PVP concentration solutions via the spincoating process. Silver-coated patterned PVP films were obtained by peeling off the PVP layer from the template PS film after drying. The results show that the honeycomb-patterned PVP films uniformly coated with silver particles are conveniently obtained using the silver-coated patterned PS template, although the direct fabrication of these films using water droplets under humid conditions was not feasible because of the water solubility of PVP.

Read/write characteristics of a new type of bit-patterned-media using nano-patterned glassy alloy

The paper reports a feasibility study of new type bit-patterned-media using a nano-patterned glassy alloy template for ultra-high density hard disk applications. The prototype bit-patterned-media was prepared using a nano-hole array pattern fabricated on a Pd-based glassy alloy thin film and a Co/Pd multilayered film filled in the nano-holes. The prepared prototype bit-patterned-media had a smooth surface and isolated Co/Pd multilayer magnetic dots, where the average dot diameter, the average dot pitch and the average dot height were 30, 60 and 19nm, respectively. MFM (magnetic force microscope) observation revealed that each dot was magnetized in a perpendicular direction and the magnetization could reverse when an opposite magnetic field was applied. Static read/write tester measurements showed that repeated writing and reading on isolated magnetic dots were possible in combination with conventional magnetic heads and high-accuracy positioning technologies. The present study indicates that the new type of bit-patterned-media composed of nano-hole arrays fabricated on glassy alloy film template and Co/Pd multilayer magnetic dots are promising for applications to next generation ultra-high density hard disk drives.

QCM sensing of a chemical nerve agent analog via electropolymerized molecularly imprinted polythiophene films

AbstractThe highly selective and sensitive detection of a chemical nerve agent analog pinacolyl methylphosphonate (PMP) was demonstrated using an electrochemically molecularly imprinted polymer (MIP) polythiophene film onto a quartz crystal microbalance (QCM) transducer surface. The fabrication and optimization of the sensor film was monitored by in situ electrochemistry‐QCM (EC‐QCM) measurements, which determined the change in mass and simultaneous change in redox properties of the polymer film. The film deposition, template loading, and template removal were evidenced by a combination of surface characterization techniques such as the attenuated total reflection infrared spectroscopy and high‐resolution X‐ray photoelectron spectroscopy. The fabricated MIP film demonstrated a limit of detection and a limit of quantification of ∼60 and ∼197 μM, respectively. The linear sensing range is between 125 and 250 μM concentration of PMP. Finally, theoretical modeling (AM1 semiempirical quantum calculations) studies revealed that a stable prepolymerization complex is formed in solution with the existence of H‐bonding interactions using the 2:1 monomer‐to‐template ratio. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Rectifying Behavior of Aligned ZnO Nanorods on Mg<sub>0.3</sub>Zn<sub>0.7</sub>O Thin Film Template

Rectifying behavior more than 3 orders of aligned zinc oxide (ZnO) nanorods grown on Mg0.3Zn0.7O thin film template using chemical bath deposition method was observed, giving a barrier height of 0.75 eV, and the ideality factor achieved was almost 6, which was analyzed using thermionic emission theory. Field emission scanning electron microscope (FESEM) images revealed that the grown ZnO was in hexagonal shape, uniformly distributed and in vertically aligned form. The crystallinity of the sample being studied using X-ray diffraction (XRD), where the highest peak was found at (002) phase, confirming that high crytallinity of ZnO was attained. The effect of metal/semiconductor junction between metal and aligned ZnO nanorods was discussed in further details.

Influence of the nature of the polycation on the adsorption kinetics and on exchange processes in polyelectrolyte multilayer films

The deposition of polyelectrolyte multilayer films (PEMs) appears more and more as a versatile tool to functionalize a broad range of materials with coatings having controlled thicknesses and properties. To increase the control over the properties of such coatings, a good knowledge of their deposition mechanism is required. Since Cohen Stuart et al. (Langmuir 18 (2002) 5607–5612) showed that the adsorption of one polyelectrolyte could induce desorption of polyelectrolyte complexes instead of regular deposition, more and more findings highlight peculiarities in the deposition of such films. Herein we demonstrate that the association of sodium polyphosphate (PSP) as the polyanion and either poly(-L-lysine hydrobromide) (PLL) or poly(allylamine chloride) (PAH) as the polycations may lead to non-monotonous film deposition as a function of time. Complementary, films containing PSP and PLL can be obtained from a (PLL–HA)n template films after the exchange of HA (hyaluronic acid) from the sacrificial template by PSP from the solution. This exchange is accompanied by pronounced film erosion. However, when starting from a (PAH–HA)n template, the film erosion and exchange due to the contact with PSP is by far less pronounced, nevertheless the film morphology changes. These findings show that the nature of the polycation used to deposit the PEM film may have a profound influence of the film’s response to a competing polyanion.

Nanostructured conducting molecularly imprinted polymer for selective extraction of salicylate from urine and serum samples by electrochemically controlled solid-phase micro-extraction

Overoxidized polypyrrole (OPPy) films templated with salicylate (SA) have been utilized as conducting molecular imprinted polymers (CMIPs) for potential-induced selective solid-phase micro-extraction processes. Various important fabrication factors for controlling the performance of the OPPy films have been investigated using fluorescence spectrometry. Several key parameters such as applied potential for uptake, release, pH of uptake and release solution were varied to achieve the optimum micro-extraction procedure. The film template with SA exhibited excellent selectivity over some interference. The calibration graphs were linear in the ranges of 5 × 10 −8 to 5 × 10 −4 and 1.2 × 10 −6 to 5 × 10 −4 mol mL −1 and the detection limit was 4 × 10 −8 mol L −1. The OPPy film as the solid-phase micro-extraction absorbent has been applied for the selective clean-up and quantification of trace amounts of SA from physiological samples. The results of scanning electron microscopy (SEM) have confirmed the nano-structure morphologies of the films.

Facile fabrication of nanostructured Pd–Fe bimetallic thin films and their electrodechlorination activity

A series of nanostructured Pd–Fe bimetallic thin films with the performance of fast and high-efficiency electrochemical reductive dechlorination were directly formed on glassy carbon electrodes (GCEs) through galvanic replacement of partial Fe 0 nanoparticles by Pd(II) ions. The composition and morphology of such Pd–Fe thin films are strongly dependent on the sacrificial Fe film templates fabricated by a template-free, double-potential step electrodeposition technique. The size, shape and morphology of the Fe nanoparticles that constitute the Fe thin films can be controlled well by adjusting the concentration of Fe 2+ ions in electrolyte solutions. Due to the good synergistic effect between Pd and Fe, the as-prepared Pd–Fe thin films with the novel microstructure display a high reactivity towards the electrochemical reductive dechlorination of carbon tetrachloride (CT), which closely related to the composition of Pd–Fe thin films, applied potential and temperature. The dechlorination reaction of CT complied with pseudo-first-order kinetics.

Advanced titania buffer layer architectures prepared by chemical solution deposition

Chemical solution deposition (CSD) was used to grow high-quality (100) oriented films ofSrTiO3 (STO)on CSD CaTiO3 (CTO), Ba0.1Ca0.9TiO3 (BCT) and STO seed and template layers. These template films bridge the lattice misfitbetween STO and the nickel–tungsten (NiW) substrate, assisting in dense growth oftextured STO. Additional niobium (Nb) doping of the STO buffer layer reduces oxygendiffusion which is necessary to avoid undesired oxidation of the NiW. The investigatedtemplates offer suitable alternatives to established standard buffer systems likeLa2Zr2O7 (LZO)and CeO2 for coated conductors.

Thermal Conductivity of Highly-Ordered Mesoporous Titania Thin Films from 30 to 320 K

This paper reports the cross-plane thermal conductivity of highly ordered amorphous and crystalline templated mesoporous titania thin films measured by the 3ω method from 30 to 320 K. Both sol–gel and nanocrystal-based films were synthesized by evaporation-induced self-assembly, with average porosity of 30% and 35%, respectively. The pore diameter ranged from 14 to 25 nm. The size of crystalline domains in polycrystalline mesoporous films was 12–13 nm, while the nanocrystals in the nanocrystal-based film were 9 nm in diameter. At high temperatures, the thermal conductivity of amorphous dense and mesoporous films showed similar trends with respect to temperature. This was attributed to the fact that the presence of pores had a purely geometrical effect by reducing the cross-sectional area through which heat can diffuse. By contrast, the thermal conductivity of polycrystalline dense and mesoporous films behaves differently with temperature due to phonon scattering by pores and crystalline nanosize domains. In addition, at low temperatures, the presence of pores caused the thermal conductivity of mesoporous films to be less temperature dependent than their dense counterparts. Despite its crystallinity, the thermal conductivity of the nanocrystal-based film was about 40% less than that of the polycrystalline mesoporous films. This was mainly attributed to its larger porosity, smaller crystal size, and strong phonon scattering at the poorly interconnected nanocrystal boundaries. These results suggest various ways to control the thermal conductivity of mesoporous materials for various applications.

Influence of distorted electric field distribution on microstructure formation in the electrohydrodynamic patterning process

Electrohydrodynamic (EHD) patterning is a process for electrically duplicating a micrometer- or submicrometer-scale pattern of a template onto a thin polymer film on a substrate by applying an electric potential between the template and substrate as an electrode pair. Simulations of the electrohydrodynamic patterning process that have been reported have been based on a linear and analytical formulation assuming an ideal template shape and process setup for mathematical simplification. However, the EHD process, involving coupling of electrostatic and hydrodynamic fields, tends to be strongly nonlinear in practice. Consequently, even a small deviation (represented by nonuniformity in the height of template microstructures or nonuniform gap between template and polymer film, for example) can lead to deviation of the duplicated pattern from the pattern expected under ideal process conditions. This article presents a numerical method for simulating this electrically induced microstructuring process based on nonlinear EHD theory and arbitrary Lagrangian-Eulerian (ALE) finite element formulation. The dynamic evolution of the microstructure obtained for nonuniform height of the template pattern and a nonuniform gap between the template and polymer film shows that a small deviation tends to lead to considerable distortion in the electrical field during growth of the polymer pattern, resulting in irregularity in the duplicated microstructures. The numerical analysis also demonstrates how the polymer structure irregularity can be alleviated by reduced electric potential and reduced average gap between the template and polymer surface.