Template Films Research Articles

PEO– 液晶ブロックコポリマー薄膜の ナノテンプレートプロセスとスマートメンブレンへの展開

A new wave is surging on a long history of microphase-separated nanostructures in block copolymers as the selfassembled nanostructures leading to industrial use as the coming engineered plastics. Emphasis should be placed on both high reproducibility and mass production of these ordered nanostructures through self-assembling nanofabrication processes, expected as one of the powerful counterparts of the top–down–type nanofabrication such as lithography and beam processing. In 2001 we developed highly reliable nanostructured template film, in which newly designed amphiphilic liquid crystalline block copolymers show normally oriented and hexagonally arranged nanocylinder array structures in meter–sized area thin films. This success satisfies the above requirements applicable to industrial use and also guarantees their high regularity as reliable nanotemplates for structural transcription to and hybridization with various kinds of materials such as metal, semiconductors, and so on. Furthermore, we also introduce the fabrication process of free–standing membranes equipped with fully penetrated straight channels by using a series of amphiphilic liquid crystalline block copolymers, which form normally oriented and hexagonally arranged cylindrical domains with a high aspect ratio up to more than 400.

Highly efficient dye sensitized solar cells based on ordered and disordered mesoporous titania thick templated films

Highly efficient DSSCs were achieved by worm-like and grid-like mesoporous thick templated photoanodes prepared by spin and dip coating methods.

Voc from a Morphology Point of View: the Influence of Molecular Orientation on the Open Circuit Voltage of Organic Planar Heterojunction Solar Cells

The film morphology and device performance of planar heterojunction solar cells based on the molecular donor material α-sexithiophene (6T) are investigated. Planar heterojunctions of 6T with two different acceptor molecules, the C60 fullerene and diindenoperylene (DIP), have been prepared. The growth temperature of the 6T bottom layer has been varied between room temperature and 100 °C for each acceptor. By means of X-ray diffraction and X-ray absorption, we show that the crystallinity and the molecular orientation of 6T is influenced by the preparation conditions and that the 6T film templates the growth of the subsequent acceptor layer. These structural changes are accompanied by changes in the characteristic parameters of the corresponding photovoltaic cells. This is most prominently observed as a shift of the open circuit voltage (Voc): In the case of 6T/C60 heterojunctions, Voc decreases from 0.4 to 0.3 V, approximately, if the growth temperature of 6T is increased from room temperature to 100 °C. By...

Ordered Nanomaterial Thin Films via Supported Anodized Alumina Templates

Supported anodized alumina template films with highly ordered porosity are best suited for fabricating large area ordered nanostructures with tunable dimensions and aspect ratios. In this paper we first discuss important issues for the generation of such templates, including required properties of the Al/Ti/Au/Ti thin film heterostructure on a substrate for high quality templates. We then show examples of anisotropic nanostructure films consisting of noble metals using these templates, discuss briefly their optical properties and their applications to molecular detection using surface enhanced Raman spectroscopy. Finally we briefly address the possibility to make nanocomposite films, exemplary shown on a plasmonic-thermochromic nanocomposite of VO2-capped Au-nanorods.

Relationship between crosslinking and ordering kinetics for the fabrication of soft templated (FDU-16) mesoporous carbon thin films

Although the fabrication of mesoporous carbon films through the cooperative assembly of phenolic resin oligomers (resol) and block copolymers is well-established, these methods generally rely upon simply following protocols developed for analogous bulk powders despite growing evidence of significant differences between thin films and bulk powders. Here, we examine the chemical evolution of resol through spectroscopically tracking the methylol content for films with and without a common templating agent (Pluronic F127). At lower temperature (100 °C and 120 °C), the crosslinking rate is not impacted by the presence of the template, while the addition of the Pluronic template decreases the reaction rate at higher temperatures (140 °C and 160 °C). At all conditions examined, the crosslinking kinetics of resol can be fit using the Jander model. in situ grazing incidence small angle X-ray scattering illustrates that the mesostructural evolution is not highly correlated with the chemical changes during crosslinking. With this knowledge, a shortened processing schedule (3 h total) was devised in place of the standard 24 h thermopolymerization without adversely impacting the ordered structure of the mesoporous film and this protocol significantly increases (almost double) the porosity of the film.

Hard templating of symmetric and asymmetric carbon thin films with three-dimensionally ordered mesoporosity.

Sacrificial colloidal crystal templating of porous carbon films of tunable thickness is demonstrated using a facile thin-film assembly and hard-template-based nanoreplication process. Convectively assembled, colloidal crystal films composed of size-tunable silica nanoparticles (ca. 10-50 nm) serve as scalable sacrificial scaffolds for the formation of thickness-tunable, structurally robust, and flexible porous carbon films. Both precursor vapor infiltration (PVI) and precursor immersion/spin-off (PIS) techniques, suitable for replication by various carbon sources (e.g., furfural/oxalic acid, phenol-formaldehyde, resorcinol-formaldehyde, sucrose), result in continuous, crack-free porous replica films. Systematic PVI-based underfilling of the template film or PIS-based complete spin-off of excess carbon replica precursor results in porous carbon films endowed with a symmetric three-dimensionally ordered mesopore (3DOm) topology uniformly distributed across the film thickness. Alternatively, by tuning the nanoparticle crystal film thickness and the degree of overfilling (PVI) or rate of spin-off of the carbon replica precursor (PIS), films bearing an asymmetric structure composed of 3DOm-supported ultrathin carbon layers can be realized. The stability of the silica templates under polymerization and carbonization conditions helps bolster mesopore robustness within the replica films, eliminating uniaxial pore shrinkage upon template sacrifice. The decoupling of the template assembly and its replication enables film formation from a wide range of carbon sources and possibly a further expanded materials palette. Realization of porous carbon films on various substrates without degradation of the mesostructure is enabled by robustness of the coating/replication process to characteristic surface roughness at scales several-fold larger than the template particle size as well as to polymer-mediated film transfer. Among various possible applications, we demonstrate how properties of the symmetric 3DOm films in particular (e.g., high surface area, large pore volume) enable their exploitation as potential low-cost alternatives to costly Pt-based electrodes for dye-sensitized solar cell (DSSC) technologies.

Assembly of quantum dots on peptide nanostructures and their spectroscopic properties

We present a chemical process for the decoration of self-assembled two-dimensional peptide fibrils with two different sizes of CdSe@ZnS core–shell quantum dots (Qdots) capped with trioctylphosphine oxide molecules. The attachment of the semiconducting nanoparticles to the fibrils is directed via disulfide bond between the quantum dot and cysteine aminoacids that are deliberately impeded in the peptide structures. A significant red shift in the emission spectra of the quantum dots is observed and attributed to the synergistic interaction between adjacent nanoparticles arranged on peptide film templates extending over hundreds of nanometers.

Particle lithography-based patterning of polyelectrolyte template films and their application in fabrication of gold/silver nanoparticle assembly

The site-specific deposition of polyelectrolytes (PEs) or PE/noble metallic nanoparticle (NP) composites at nanoscale is highly desirable owing to their diverse applications in nanodevices. Herein, we demonstrated a simple yet effective method to fabricate different types of surface micropatterns with PE/noble metallic NP composites via particle lithography. The positively charged PE of poly(diallyldimethylammonium chloride) and negatively charged NPs of gold/silver (Au/Ag) were used as a model system. The layer-by-layer self-assembly technique was employed as the fabricating strategy. The final nanostructures, consisting of Au NP films with inlaid circular vacant island microarrays or Au NP films with inlaid circular Ag NP island microarrays, were fabricated, respectively. Scanning electron microscopy and atomic force microscopy were used to investigate the structural morphology, microstructure, and the NP growth. Furthermore, the surface-enhanced Raman scattering performance has been obtained based on the as-prepared Au/Ag nanopatterns. Our method displayed an excellent opportunity for the simple and effective production of nanopatterns on the surfaces demonstrating significant advantages in designing novel nanodevices.

Poly(N-isopropylacrylamide)/poly(dopamine) capsules.

Polymer capsules are an interesting concept considered in nanobiotechnology. Approaches that facilitate their assembly remain sought after. Poly(dopamine) (PDA) has been considered and successfully applied in this context. We recently demonstrated that PDA could be copolymerized with different types of poly(N-isopropylacrylamide) (pNiPAAm) to assemble mixed films on planar substrates. Herein, we transferred this approach onto colloidal substrates and characterized the film thickness depending on the film composition and template particles size. While the membrane of capsules assembled using 5 μm template particles exhibited strong dependency on the film composition, smaller templates led to capsules with similar membrane thickness. We then compared the permeability of different capsules using fluorescently labeled dextran and fluorescein. We found that the permeability of capsules was heavily dependent on the polymer composition and the template particle size. These fundamental findings contribute to the potential of these capsules, assembled in one-step, for biomedical applications.

Autonomous bottom-up fabrication of three-dimensional nano/microcellulose honeycomb structures, directed by bacterial nanobuilder

We investigated the autonomous bottom-up fabrication of three-dimensional honeycomb cellulose structures, using Gluconacetobacter xylinus as a bacterial nanoengine, on cellulose honeycomb templates prepared by casting water-in-oil emulsions on glass substrates (Kasai and Kondo, Macromol. Biosci., 4, 17-21, 2004). The template film had a unique molecular orientation state along the honeycomb frames, but was non-crystalline. When G.xylinus, used as a nanofiber-producing bacterium, was incubated on the honeycomb scaffold in a culture medium, it secreted cellulose nanofibers only on the upper surface of the honeycomb frame. The movement was regulated by a selective interaction between the synthesized nanofiber and the surface of the honeycomb frames of the template. The relationship between directed deposition of synthesized nanofibers and ordered fabrication from the nano- to the micro-scale could provide a novel bottom-up methodology, using bacteria, for the design of three-dimensional honeycomb structures as functional materials with nano/micro hierarchical structures, with low energy consumption.

Epitaxial Cu(001) films grown on a Cr/Ag/Fe/GaAs(001) buffer system

We present a procedure to prepare single-crystalline, high-purity Cu(001) films (templates) suitable as substrates for subsequent epitaxial thin-film growth. The template films were grown in a dedicated molecular-beam epitaxy system on a Cr/Ag/Fe/GaAs(001) buffer layer system. Low-energy electron diffraction and X-ray diffraction were applied to determine the surface orientation and the epitaxial relationship between all layers of the stack. Post-annealing at moderate temperatures enhances the quality of the film as shown by low-energy electron diffraction and atomic force microscopy. X-ray photoemission and Auger electron spectroscopy confirm that no atoms of the buffer layers diffuse into the Cu film during the initial preparation and the post-annealing treatment. The completed Cu(001) template system can be exposed to air and afterwards refurbished by Ar+-ion bombardment and annealing, enabling the transfer between vacuum systems. The procedure provides suitable conductive thin film templates for studies of epitaxial thin films, e.g. on the magnetic and magnetotransport properties of Co and Ni based films and multilayers.

Titanium Carbide and Titanium Nitride-Based Nanocomposites as Efficient Catalysts for the Co2+/Co3+ Redox Couple in Dye-Sensitized Solar Cells

Two different kinds of nanocomposites were developed by electrochemical deposition of poly(3,4-ethylenedioxythiophene) (PEDOT) into porous hard template films of TiC or TiN nanoparticles, in order to evaluate their use as alternative catalysts in dye-sensitized solar cells (DSSC) utilizing a Co2+/Co3+ polypyridyl redox mediator. Cyclic voltammograms indicate that both types of nanocomposite show comparable catalytic activity to platinum-coated electrodes. However, electrochemical impedance spectroscopy (EIS) reveals that electron transfer resistances are significantly reduced with the porous nanocomposite electrodes (<1 Ω), to about an order of magnitude lower than those observed for the Pt coated electrode. As a result, DSSCs with the composite counter electrodes achieved equivalent or higher photovoltaic conversion efficiencies compared to cells with pristine PEDOT or Pt coated electrodes. In particular, the highest efficiency (8.26%) was achieved with a DSSC using a TiN-PEDOT counter electrode.

Synchrotron Powder Diffraction Study of Radiation Damage in Langmuir Blodgett Nanotemplate Crystallised Protein

Polycrystalline samples of lysozyme were prepared with and without a Langmuir-Blodgett (LB) thin film template via both the hanging drop method and batch crystallisation. Powder diffraction methods are used to compare these samples and to measure their resistance to radiation damage at room temperature. The X-ray induced amorphisation of the samples was followed as a function of time and it was shown that diffraction does not entirely disappear even at very long exposure times. Two distinct kinetic timescales are evident suggesting that early and late stage processes are quite different. Radiation damage was also shown to be localized in the sample in the region where the beam impinges.

Sol-Gel Derived ZnO Nanorod Templated TiO&lt;sub&gt;2&lt;/sub&gt; Nanotube Synthesis for Natural Dye Sensitized Solar Cell

Natural dye sensitized solar cells (nDSSC) mostly suffer from low solar cell performance, that vertically aligned nanotube TiO2 as the photoanode is expected to increase the performance by providing higher surface area and direct electron transport. Nanostructured TiO2 films have been fabricated on glass substrates employing ZnO nanorod films as the template. First, vertically oriented ZnO nanorod on a glass substrate was prepared hydrothermally. Then, sol-gel dip-coating technique was used to deposit TiO2. The template films were dip-coated into sols of titanium tetraisopropoxide-ethanol-diethanol ammine with withdrawing rate of 2 cm/min for three- (Ti3) and seven-times (Ti7). After drying at 100 °C for 10 min, the films were calcined at 550 °C for 1h and washed with HCl 3% (v/v). The films were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). It is observed that different coating cycles resulted in different film morphologies. Nanotube TiO2 with diameter of ~50 nm was identified for Ti3, while Ti7 displayed sheet-like structure. The diffraction patterns confirmed the presence of only anatase crystalline phase with crystallite size of 10.3 nm (Ti3) and 21.7 nm (Ti7). The dye absorption was red-shifted indicating dye monomeric adsorption on TiO2 via chelation. Enhanced absorption of anthocyanin dye extracted from pericarps of mangosteen (Garcinia mangostana l.) fruit on TiO2 nanotube compared to TiO2 nanoparticle (P25) was observed leading to improved photovoltaic performance of the constructed nDSSC.

Protein-responsive polymers for point-of-care detection of cardiac biomarker

This work describes a novel use for the polymeric film, poly(o-aminophenol) (PAP) that was made responsive to a specific protein. This was achieved through templated electropolymerization of aminophenol (AP) in the presence of protein. The procedure involved adsorbing protein on the electrode surface and thereafter electroploymerizing the aminophenol. Proteins embedded at the outer surface of the polymeric film were digested by proteinase K and then washed away thereby creating vacant sites. The capacity of the template film to specifically rebind protein was tested with myoglobin (Myo), a cardiac biomarker for ischemia. The films acted as biomimetic artificial antibodies and were produced on a gold (Au) screen printed electrode (SPE), as a step towards disposable sensors to enable point-of-care applications.Raman spectroscopy was used to follow the surface modification of the Au-SPE. The ability of the material to rebind Myo was measured by electrochemical techniques, namely electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV). The devices displayed linear responses to Myo in EIS and SWV assays down to 4.0 and 3.5μg/mL, respectively, with detection limits of 1.5 and 0.8μg/mL. Good selectivity was observed in the presence of troponin T (TnT) and creatine kinase (CKMB) in SWV assays, and accurate results were obtained in applications to spiked serum. The sensor described in this work is a potential tool for screening Myo in point-of-care due to the simplicity of fabrication, disposability, short time response, low cost, good sensitivity and selectivity.

Granular nanostructures and magnetic characteristics of FePt-TiO2/FePt-C stacked granular films

To realize a granular film composed of L10-FePt grains with high uniaxial magnetic anisotropy energy, Ku, and segregants for heat-assisted magnetic recording, the FePt-TiO2/FePt-C stacked film was investigated. The FePt-TiO2/FePt-C stacked film has well-isolated granular structure with average grain size of 6.7 nm because the FePt-TiO2 film follows the FePt-C template film in microstructural growth. However, the Ku value is quite low for total thickness of 9 nm: 5 × 106 erg/cm3. Exploration of the thickness dependence of L10-FePt(001) peaks in XRD spectra and cross-sectional TEM images suggest that degradation of the L10 ordering appears near the middle of the FePt-TiO2 layer. The EDX-STEM mapping reveals that Ti atoms exist within the FePt grains in addition to the grain boundary. This indicates the possibility that TiO2 tends to be incorporated into the FePt grains and that it prevents L10-ordering of the FePt grains along the normal-to-plane direction.

Versatile control over size and spacing of small mesopores in metal oxide films and catalytic coatings via templating with hyperbranched core–multishell polymers

Controlling the pore structure of metal oxide films and supported catalysts is an essential requirement for tuning their functionality and long-term stability. Typical synthesis concepts such as “Evaporation Induced Self Assembly” rely on micelle formation and self assembly. These processes are dynamic in nature and therefore strongly influenced by even slight variations in the synthesis conditions. Moreover, the synthesis of very small mesopores (2–5 nm) and independent control over the thickness of pore walls are very difficult to realize with micelle-based approaches. In this contribution, we present a novel approach for the synthesis of mesoporous metal oxide films and catalytic coatings with ordered porosity that decouples template formation and film deposition by use of hyperbranched core–multishell polymers as templates. The approach enables independent control of pore size, wall thickness and the content of catalytically active metal particles. Moreover, dual templating with a combination of hyperbranched core–multishell polymers and micelles provides facile access to hierarchical bimodal porosity. The developed approach is illustrated by synthesizing one of the most common metal oxides (TiO2) and a typical supported catalyst (PdNP/TiO2). Superior catalyst performance is shown for the gas-phase hydrogenation of butadiene. The concept provides a versatile and general platform for the rational optimization of catalysts based e.g. on computational prediction of optimal pore structures and catalyst compositions.

Large area, flexible ordered mesoporous carbon films from soft templating on polymer substrates

Mesoporous carbon films are generally fabricated on rigid substrates that act to provide mechanical stability. Here, instead of utilizing rigid substrates, a thin sheet of polyimide (Kapton) is utilized as the substrate to enable continuous production of sheets of soft templated mesoporous carbon films. The mesoporous carbon film is well adhered to the carbonized Kapton. Although mesoporous carbon is generally considered brittle, carbonization of the coated polyimide yields a tough flexible sheet that can be gently bent or even cut to the desired shape. Characterization with transmission electron microscopy, small angle X-ray scattering and N2 sorption (B.E.T.) confirms the presence of ordered mesopores that conform to expected structures based upon analogous powders. A simple demonstration of the flexible mesoporous carbons as electrodes for aqueous supercapacitors illustrates that the carbonized Kapton can act as the current collector without significant degradation in performance based on the estimated mass of the active mesoporous carbon film at low rates. The fabrication of ordered mesoporous carbon on Kapton provides a facile route to large area, robust high surface area, conductive materials that could be used for a wide variety of electrochemical applications, especially as sensors.

Au-NR/VO2-NP nanocomposites supported on glass substrates: microstructure and optical properties

On-glass-substrate gold nanorods (Au-NRs) are processed via electrodeposition into anodized alumina template films that were fabricated using an Al/Au/Ti film stack on glass. The Au-NRs are capped with VO2 nanoparticles obtained from sputtered vanadium caps. The nanostructure arrays show intense plasmon resonance and are thermochromic with VO2 size dependent transition temperature.

Electrochemically controlled solid phase microextraction of ibuprofen based on nanostructure conducting molecular imprinted polypyrrole and selective analysis in biological and formulation samples using ion mobility spectrometry

The present work describes a combination of conducting molecularly imprinted solid phase microextraction with electrochemistry for a sample clean-up and selective determination of ibuprofen (IBP) by ion mobility spectrometry (IMS). Overoxidized polypyrrole film template with IBP was utilized as a conducting molecular imprinted polymer (CMIP) for potential-induced highly selective solid-phase microextraction processes. Several parameters such as uptake and release potential, uptake and release time were investigated to achieve the optimum microextraction procedure. The calibration graph was linear in the ranges of 5–100 and 100–1000 μg L−1, the limit of detection was 2.5 μg L−1 and RSD% (n = 5) was lower than 6%. The proposed method was applied for a successful clean-up and quantification of trace amounts of IBP in biological and formulation samples.