Template Films Research Articles

Self-assembly of metal nanocolloids entrapped in Langmuir Blodgett Film templates: Evidence of efficient SERS sensing platforms

Novel SERS active substrates of metallic nanocolloids entrapped in the Langmuir- Blodgett (LB) film matrices of stearic acid, PMMA, DPPC have been reported. The use of organized templates of PMMA and DPPC as SERS sensing platforms are explored for the first time. The efficacies of the as prepared substrates are tested from the SERS spectra of Rhodamine 6G (R6G) and 4-mercapto pyridine (4-MPy) molecules. Gigantic enhancement factors ∼ 10 12 and 10 14 orders of magnitudes have been estimated. The interparticle coupling of the localized surface plasmons in the nanoaggregated domains are tuned by lifting the LB film of PMMA at different surface pressures.

Nanopatterning of Crystalline Transition Metal Oxides by Surface Templated Nucleation on Block Copolymer Mesostructures

While patterning the nucleation of crystalline inorganics at the nanometer length scale via low temperature, aqueous growth methods is highly desirable, it remains synthetically challenging. We report a generalizable approach for fabricating crystalline nanostructured inorganics at temperatures below 60 °C with periodicities on the order of 50 nm. A block copolymer (BCP) of polystyrene-block-poly[(allyl glycidyl ether)-co-(ethylene oxide)] (PS-b-P(AGE-co-EO)) is used to prepare periodically ordered, reactive thin film templates that are functionalized postassembly with an amino acid, cysteine, via thiol–ene click chemistry, exclusively at the sites of the exposed P(AGE-co-EO) domains. These functionalized areas subsequently template the confined crystallization of copper(I) oxide (Cu2O) and zinc oxide (ZnO) with high fidelity, from aqueous solutions at low temperatures. The demonstrated method provides a versatile materials platform to control the growth of nanostructured crystalline materials via the introduction of a plethora of surface functional groups by means of facile thiol–ene click chemistry. The resulting organic substrates can be used to template the growth of multiple different crystalline inorganic materials on surfaces nanostructured via BCP self-assembly.

Fabrication of Microlens Arrays with Controlled Curvature by Micromolding Water Condensing Based Porous Films for Deep Ultraviolet LEDs

Microlens arrays (MLAs) have attracted wide attention due to their crucial applications in optics, optoelectronics, and biochemistry. In this paper, we present a simple and green approach for the economical fabrication of MLAs with controlled curvature based on water condensing. By controlling the input current and working time of initiative cooling and the viscoelasticity of UV-curable polymer, uniform porous films with adjustable morphology were prepared. MLAs with aspect ratios of 1.41, 1.01, and 0.69 were fabricated by micromolding the porous film templates. Furthermore, the fluoropolymer encapsulations with the MLAs were applied for the packaging of deep ultraviolet light-emitting diodes (DUV-LEDs). Consequently, the light output powers of DUV-LEDs are enhanced by 7.1%, 10.2%, and 15.4%, respectively, by using these MLAs at the driving current of 350 mA.

In situ fabrication of cobalt nanoflowers on sulfonated and fluorinated poly (arylene ether ketone-benzimidazole) template film for the electrocatalytic oxidation of glucose

Using sulfonated and fluorinated poly (arylene ether ketone) comprising functional strong coordination group benzimidazole (SPAEK-F-BI) as a template film, a novel fabrication method of cobalt nanoflowers (CoNFs) and non-enzymatic glucose electrochemical sensor was developed in this work. After the precursors Co2+ ions were cooperatively bound by sulfonate and imidazole functionalities contained in SPAEK-F-BI film through ion exchange and strong coordination action, cobalt colloid nuclei were formed and grew to flower-like nanostructures by subsequent in-situ electrochemical reduction on SPAEK-F-BI film modified GCE. Characterization of SPAEK-F-BI film and CoNFs/SPAEK-F-BI film on GCE was performed in detail by FT-IR spectroscopy and scanning electron microscopy (SEM) attached with energy dispersive spectroscopy (EDS), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The results of SEM showed that beautiful CoNFs constructed by Co colloid nanosheets with just a few nanometers thickness were well dispersed on uniform SPAEK-F-BI film modified GCE, and the density of CoNFs was mainly influenced by the concentration of the precursor solution CoSO4. The CoNFs/SPAEK-F-BI composite modified electrode exhibited good electrocatalytic activity toward glucose oxidation in 0.1M NaOH solution, and the kinetic parameters of glucose oxidation were determined using chronoamperometry. When it was applied for the determination of glucose by amperometry at a potential of 0.6V versus Ag/AgCl, the linear range from 5μM to 1.14mM and the detection limit of 800nM (S/N = 3) were obtained. Finally, it was successfully employed to detect the glucose in human serum real samples, and the results were agreed closely with those measured in hospital.

Nano-patterned polyelectrolyte multilayers assembled using block copolymer templates: The combined effect of ionic strength and nano-confinement

Polyelectrolyte multilayers gain their importance from their applicability to a wide variety of functional building blocks. The ability to create these multilayers as laterally nano-patterned films, which has only been scarcely investigated so far, augments the functionality of the multilayer and makes it valuable for applications that require nanoscale features or periodic arrangement, such as photonic devices, catalytic surfaces, and biomedical applications. In this study we reveal how the lateral confinement imposed by block copolymer nano-domains in thin film templates affects the assembly of the deposited polyelectrolyte layers at different ionic strengths, and how the combined effects of nano-confinement and ionic strength dictate the final structure of the multilayer. These fundamental insights provide the basis for successful construction of nano-patterned, functional coatings.

Sharpened VO2 Phase Transition via Controlled Release of Epitaxial Strain.

Phase transitions in correlated materials can be manipulated at the nanoscale to yield emergent functional properties, promising new paradigms for nanoelectronics and nanophotonics. Vanadium dioxide (VO2), an archetypal correlated material, exhibits a metal-insulator transition (MIT) above room temperature. At the thicknesses required for heterostructure applications, such as an optical modulator discussed here, the strain state of VO2 largely determines the MIT dynamics critical to the device performance. We develop an approach to control the MIT dynamics in epitaxial VO2 films by employing an intermediate template layer with large lattice mismatch to relieve the interfacial lattice constraints, contrary to conventional thin film epitaxy that favors lattice match between the substrate and the growing film. A combination of phase-field simulation, in situ real-time nanoscale imaging, and electrical measurements reveals robust undisturbed MIT dynamics even at preexisting structural domain boundaries and significantly sharpened MIT in the templated VO2 films. Utilizing the sharp MIT, we demonstrate a fast, electrically switchable optical waveguide. This study offers unconventional design principles for heteroepitaxial correlated materials, as well as novel insight into their nanoscale phase transitions.

Investigation of Carrier Dynamics in Templated Perovskite Films with Different Densities of Nanopores

Carrier dynamics in templated perovskite films with different densities of nanopores were investigated. We employed colloidal solution processing to obtain templated perovskite films with different number densities of nanopores. X-ray diffraction (XRD) and photoluminescence (PL) measurements confirmed that porous structures dominantly influence a fast carrier decay process such as carrier extraction, while PbI2 residuals influence a slow carrier decay process.

The effect of the number of calcination steps on preparing crack free titania thick templated films for use in dye sensitized solar cells

Crack free titania thick templated films were prepared by evaporation-induced self-assembly (EISA) process and spin coating method with different numbers of calcination steps; then, their application in dye sensitized solar cells (DSSC) was investigated. Wormlike meso-layers prepared at different spin speeds were characterized by TEM analysis. The correlation between spin speed and thickness and porosity of the films were investigated using ellipsometry method. The crystallinity and surface area of the films obtained at a repeated thermal treatment method and different temperatures were investigated by XRD and BET techniques. UV–vis spectroscopy and cross-sectional SEM images were also used to characterize the films. Finally, the mesoporous thick films (5.7µm) were used in DSSC devices and their photovoltaic performances were examined. The optimum mesoporous film exhibited an open-circuit voltage (VOC) of 0.729V, short-circuit current density (JSC) of 14.93mAcm−2, fill factor of 0.68 and a power conversion efficiency of 7.35%.

An Open Pit Nanofluidic Tool: Localized Chemistry Assisted by Mesoporous Thin Film Infiltration.

Nanofluidics based on nanoscopic porous structures has emerged as the next evolutionary milestone in the construction of versatile nanodevices with unprecedented applications. However, the straightforward development of nanofluidically interconnected systems is crucial for the production of practical devices. Here, we demonstrate that spontaneous infiltration into supramolecularly templated mesoporous oxide films at the edge of a sessile drop in open air can be used to connect pairs of landmarks. The liquids from the drops can then join through the nanoporous network to guide a localized chemical reaction at the nanofluid-front interface. This method, here named "open-pit" nanofluidics, allows mixing reagents from nanofluidically connected droplet reservoirs that can be used as reactors to conduct reactions and precipitation processes. From the fundamental point of view, the work contributes to unveiling subtle phenomena during spontaneous infiltration of fluids in bodies with nanoscale dimensions such as the front broadening effect and the oscillatory behavior of the infiltration-evaporation front. The approach has distinctive advantages such as easy fabrication, low cost, and facility of scaling up for future development of ultrasensitive detection, controlled nanomaterial synthesis, and novel patterning methods.

Mesoporous metal-oxide-semiconductor capacitors detect intra-porous fluid changes

Real-time measurements of fluidic phenomena inside nano/mesoporous films offer an alternative way to study fundamental processes, as well as to explore novel applications. Most current techniques use optical measurement methods or microgravimetric approaches. Here it is shown that a metal-oxide-semiconductor (MOS) capacitor can be used to detect fluidic transport inside mesoporous networks. The MOS stack, which consists of two contacts (Cu and silicon) separated by a supramolecularly templated mesoporous oxide film to form a MOS capacitor, detects fluid changes that can be quantified from an effective permittivity model of mesoporous structures interacting with a fluid. The device was used to monitor liquids infiltration and subsequent evaporation in both titania and silica mesoporous films. It was observed how the evaporation dynamics significantly depends on film characteristics and fluid properties.

Template Effects of Tetrakis(thiadiazole)Porphyrazine to the Structures of Phthalocyanine Thin Films

Molecular templating is an attractive method to improve the crystallinity of organic thin films and control the molecular orientations in them. Here, we report on the templating effects of an organic n-type semiconductor, tetrakis(thiadiazole)porphyrazine (H2TTDPz), on the structure and optical absorption of a p-type semiconductor, copper phthalocyanine (CuPc). X-ray diffraction measurements for the double layer thin films, CuPc/H2TTDPz, indicate a flat-on structure of CuPc, which is copied by the structure of the H2TTDPz thin films, in spite of that the CuPc thin films usually form edge-on type thin films. The optical absorption measurements show new low-energy transitions in the templated CuPc films.

Homoepitaxy of Crystalline Rubrene Thin Films.

The smooth surface of crystalline rubrene films formed through an abrupt heating process provides a valuable platform to study organic homoepitaxy. By varying growth rate and substrate temperature, we are able to manipulate the onset of a transition from layer-by-layer to island growth modes, while the crystalline thin films maintain a remarkably smooth surface (less than 2.3 nm root-mean-square roughness) even with thick (80 nm) adlayers. We also uncover evidence of point and line defect formation in these films, indicating that homoepitaxy under our conditions is not at equilibrium or strain-free. Point defects that are resolved as screw dislocations can be eliminated under closer-to-equilibrium conditions, whereas we are not able to eliminate the formation of line defects within our experimental constraints at adlayer thicknesses above ∼25 nm. We are, however, able to eliminate these line defects by growing on a bulk single crystal of rubrene, indicating that the line defects are a result of strain built into the thin film template. We utilize electron backscatter diffraction, which is a first for organics, to investigate the origin of these line defects and find that they preferentially occur parallel to the (002) plane, which is in agreement with expectations based on calculated surface energies of various rubrene crystal facets. By combining the benefits of crystallinity, low surface roughness, and thickness-tunability, this system provides an important study of attributes valuable to high-performance organic electronic devices.

Synthesis of Biocompatible Liquid Crystal Elastomer Foams as Cell Scaffolds for 3D Spatial Cell Cultures.

Here, we present a step-by-step preparation of a 3D, biodegradable, foam-like cell scaffold. These scaffolds were prepared by cross-linking star block co-polymers featuring cholesterol units as side-chain pendant groups, resulting in smectic-A (SmA) liquid crystal elastomers (LCEs). Foam-like scaffolds, prepared using metal templates, feature interconnected microchannels, making them suitable as 3D cell culture scaffolds. The combined properties of the regular structure of the metal foam and of the elastomer result in a 3D cell scaffold that promotes not only higher cell proliferation compared to conventional porous templated films, but also better management of mass transport (i.e., nutrients, gases, waste, etc.). The nature of the metal template allows for the easy manipulation of foam shapes (i.e., rolls or films) and for the preparation of scaffolds of different pore sizes for different cell studies while preserving the interconnected porous nature of the template. The etching process does not affect the chemistry of the elastomers, preserving their biocompatible and biodegradable nature. We show that these smectic LCEs, when grown for extensive time periods, enable the study of clinically relevant and complex tissue constructs while promoting the growth and proliferation of cells.

Templating effects of tetrakis(thiadiazole)porphyrazine on the structure and optical properties of copper phthalocyanine thin films

Molecular templating is an attractive method to improve the crystallinity and control the molecular orientations of organic thin films. Here, we report on the templating effects of an organic [Formula: see text]-type semiconductor, tetrakis(thiadiazole)porphyrazine (H2TTDPz), on the structure and optical absorption of a [Formula: see text]-type semiconductor, copper phthalocyanine (CuPc). X-ray diffraction measurements for the double layer thin films, CuPc/H2TTDPz, indicate a face-on orientation of CuPc, which is replicating the structure of the H2TTDPz thin films, even though the CuPc thin films usually form edge-on-type thin films. The optical absorption measurements show new low-energy transitions in the templated CuPc films.

Hydrophilicity Reinforced Adhesion of Anodic Alumina Oxide Template Films to Conducting Substrates for Facile Fabrication of Highly Ordered Nanorod Arrays.

Arrays of ordered nanorods are of special interest in many fields. However, it remains challenging to obtain such arrays on conducting substrates in a facile manner. In this article, we report the fabrication of highly ordered and vertically standing nanorod arrays of both metals and semiconductors on Au films and indium tin oxide glass substrates without an additional layering. In this approach, following the simple hydrophilic treatment of an anodic aluminum oxide (AAO) membrane and conducting substrates, the AAO membrane was transferred onto the modified substrates with excellent adhesion. Subsequently, nanorod arrays of various materials were electrodeposited on the conducting substrates directly. This method avoids any expensive and tedious lithographic and ion milling process, which provides a simple yet robust route to the fabrication of arrays of 1D materials with high aspect ratio on conducting substrates, which shall pave the way for many practical applications in a range of fields.

Solid state microwave synthesis of highly crystalline ordered mesoporous hausmannite Mn3O4films

Microwave calcination of ordered micelle templated manganese carbonate films leads to highly crystalline, ordered mesoporous manganese oxide, while similar temperatures in a furnace lead to disordered, amorphous manganese oxide.

Wetting characteristic of nanoporous aluminum oxide films

Nanoporous aluminium oxide film template has been widely used over the last decade for development of numerous functional nanostructures such as nano sensors and nanophotonic devices. In this study, the nanoporous aluminum oxide film on silicon substrates were prepared from a 500 nm-thick aluminum film by low-temperature anodization process in a mixed solution of phosphoric and oxalic acids at different anodization voltage (10-50 Voltage). The morphology and wettability of nonporous aluminum oxide films were investigated by field emission scanning electron microscope and contact angle measurement, respectively. The result shown that the interpore of AAO template increase with anodization voltage increases. In addition, the wettability of the template depends on the pore size on the film surface.

Ultrasonic spray pyrolysis as a processing route for templated electrochromic tungsten oxide films

Mesoporous tungsten oxide films have been reported via numerous processing routes namely dip-coating, spin-coating, electrodeposition etc. and different porous architectures have been emerged. However, the templating strategy becomes more challenging when associated with the more industrially compelling spraying methods. The confined environement of the droplets, the temperature gradient during the droplets trajectory along with the relatively high substrate temperature might severely alter the delicate kinetics of the mesophase process.In this publication, we attest that templating can be effectively combined with the Ultrasonic Spray Pyrolysis method by a careful control of the deposition conditions. The emerging films are structurally characterized in the presence and absence of a surfactant over a temperature range (100 °C-390 °C) in order to determine the optimal deposition temperature. Smooth, uniform films are obtained at lower deposition temperatures (100 °C and 190 °C) and only in the presence of a surfactant. Therefore, surfactants are essentially acting as both wetting and templating agents at the same time. Finally, we emphasize on the role of porosity on enhancing the electrochromic properties of the films. Noticeably improved optical contrast (59 vs. 4%), coloration efficiency (40 vs. 6 cm2.C−1) and capacity (20 vs. 5 mC cm−2) is observed for the porous films compared to their dense counterparts.

Orientation Control of Selected Organic Semiconductor Crystals Achieved by Monolayer Graphene Templates

Crystal orientation in organic thin films is one of the key parameters that determine absorption cross‐section, interfacial energetics and excitonic states, and free charge properties. In this work, monolayer graphene is used to direct the crystal orientation of selected planar organic molecules. Lying‐down orientation with π‐stacking normal to the surface is achieved with graphene templating. The absorption spectra of the graphene‐templated films are correlated to molecular orientation. The same set of absorption features with or without graphene suggests that no vibronic states are forbidden or newly introduced. However, the light absorption with graphene templating is enhanced due to the altered relative orientation between the transition dipole moment of the constituent molecules and the electric field of incident light. The energy level of the highest occupied molecular orbital (HOMO) of graphene templated p‐type films is observed at a deeper‐lying value (relative to vacuum) compared to untemplated diindenoperylene films grown on indium tin oxide. In contrast, the HOMO energy levels of graphene templated n‐type films are observed at higher‐lying energy levels (relative to vacuum) compared to the respective untemplated films due to surface dipoles. Such a change can potentially increase the theoretical V oc expected for photovoltaic devices incorporating these templated films.

Titanium particle incorporation in block copolymer templates

Abstract Template-directed formation of titanium structures on block copolymer templates has been recently reported [1]. Here, the incorporation of titanium in a thin film template is studied. We show that the surface free energy contrast in microphase-separated polystyrene-block-polyethylene oxide templates is not limited to the template film surface, but directs the assembly of titanium atoms in the template thin film. The details of the self-assembly of titanium particles on the block copolymer nanostructured surface and inside the 3D film structure are studied with selected amounts of titanium. Evaporated titanium preferentially wets the polystyrene block of the block copolymer film and diffuses inside the film, conserving the block copolymer nanostructure. Increasing deposition leads to the formation of a mesoporous titanium layer on the block copolymer film, which reproduces that of the underlying template, in this particular case with a thickness of 12 nm and a periodic pore-to-pore distance of 35 nm. The formation of a mesoporous titanium layer prevents from further titanium diffusion inside the block copolymer film. The combination of the X-ray scattering techniques presented here provides sufficient sensitivity to follow the titanium formation in the three dimensional network of the block copolymer films.