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Morphological Control (morphological + control)

Distribution by Scientific Domains
Polymers and Materials Science90%

Selected Abstracts

Preparation of High-Performance Conductive Polymer Fibers through Morphological Control of Networks Formed by Nanofillers

ADVANCED FUNCTIONAL MATERIALS, Issue 9 2010
Hua Deng
Abstract A general method is described to prepare high-performance conductive polymer fibers or tapes. In this method, bicomponent tapes/fibers containing two layers of conductive polymer composites (CPCs) filled with multiwall carbon nanotubes (MWNT) or carbon black (CB) based on a lower-melting-temperature polymer and an unfilled polymer core with higher melting temperature are fabricated by a melt-based process. Morphological control of the conductive network formed by nanofillers is realized by solid-state drawing and annealing. Information on the morphological and electrical change of the highly oriented conductive nanofiller network in CPC bicomponent tapes during relaxation, melting, and crystallization of the polymer matrix is reported for the first time. The conductivity of these polypropylene tapes can be as high as 275,S,m,1 with tensile strengths of around 500,MPa. To the best of the authors' knowledge, it is the most conductive, high-strength polymer fiber produced by melt-processing reported in literature, despite the fact that only ,5,wt.% of MWNTs are used in the outer layers of the tape and the overall MWNT content in the bicomponent tape can be much lower (typically ,0.5,wt.%). Their applications could include sensing, smart textiles, electrodes for flexible solar cells, and electromagnetic interference (EMI) shielding. Furthermore, a modeling approach was used to study the relaxation process of highly oriented conductive networks formed by carbon nanofillers. [source]

Alkyl-Chain-Length-Independent Hole Mobility via Morphological Control with Poly(3-alkylthiophene) Nanofibers

ADVANCED FUNCTIONAL MATERIALS, Issue 5 2010
Wibren D. Oosterbaan
Abstract The field-effect transistor (FET) and diode characteristics of poly(3-alkylthiophene) (P3AT) nanofiber layers deposited from nanofiber dispersions are presented and compared with those of layers deposited from molecularly dissolved polymer solutions in chlorobenzene. The P3AT n -alkyl-side-chain length was varied from 4 to 9 carbon atoms. The hole mobilities are correlated with the interface and bulk morphology of the layers as determined by UV,vis spectroscopy, transmission electron microscopy (TEM) with selected area electron diffraction (SAED), atomic force microscopy (AFM), and polarized carbon K -edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The latter technique reveals the average polymer orientation in the accumulation region of the FET at the interface with the SiO2 gate dielectric. The previously observed alkyl-chain-length-dependence of the FET mobility in P3AT films results from differences in molecular ordering and orientation at the dielectric/semiconductor interface, and it is concluded that side-chain length does not determine the intrinsic mobility of P3ATs, but rather the alkyl chain length of P3ATs influences FET diode mobility only through changes in interfacial bulk ordering in solution processed films. [source]

Morphological Control of Single-Crystalline Silicon Nanowire Arrays near Room Temperature,

ADVANCED MATERIALS, Issue 20 2008
Chia-Yun Chen
Control of the orientation, diameter, and length of silicon nanowires (SiNWs) is achieved in large-scale single-crystalline SiNW arrays fabricated by a statistical electroless metal deposition technique. Taguchi methods are employed to optimize the diameter control and to understand the influence of all processing factors on the growth. The ,100, directions are found to be the preferred crystallographic orientation of the growing SiNWs (see figure). [source]

Organic Nanomaterials: Morphological Control for Charge Stabilization and Charge Transport

CHEMISTRY - AN ASIAN JOURNAL, Issue 6 2009
P. Pramod Dr.
Abstract How grows it? Organic nanostructured materials have been projected as active components in optoelectronic devices. Recent efforts in manipulating the morphology of organic nanomaterials, particularly on their size and shape, are summarized in this Focus Review. Potential application of organic nanostructured materials in charge stabilization and transporting are also discussed. Chromophoric systems with proper recognition motifs can organize into well-defined arrays forming supramolecular assemblies and further into nanoscopic materials. The optical and electrical properties of organic nanomaterials depend upon the stacking modes of organic molecules and also on the kind of interaction between different chromophore units (such as H- and J- type aggregates). These types of aggregates can dramatically alter the opto-electronic properties of organic nanostructures. Hence efforts are currently directed towards manipulating the morphology of organic nanomaterials, particularly on their size and shape by adopting different techniques and these aspects are discussed. Recent studies have shown that such nanostructures are extremely important in the development of optoelectronic systems such as photovoltaic devices. This Focus Review also discusses the potential application of organic nanomaterials in charge stabilization and transport. [source]

Preparation of High-Performance Conductive Polymer Fibers through Morphological Control of Networks Formed by Nanofillers

ADVANCED FUNCTIONAL MATERIALS, Issue 9 2010
Hua Deng
Abstract A general method is described to prepare high-performance conductive polymer fibers or tapes. In this method, bicomponent tapes/fibers containing two layers of conductive polymer composites (CPCs) filled with multiwall carbon nanotubes (MWNT) or carbon black (CB) based on a lower-melting-temperature polymer and an unfilled polymer core with higher melting temperature are fabricated by a melt-based process. Morphological control of the conductive network formed by nanofillers is realized by solid-state drawing and annealing. Information on the morphological and electrical change of the highly oriented conductive nanofiller network in CPC bicomponent tapes during relaxation, melting, and crystallization of the polymer matrix is reported for the first time. The conductivity of these polypropylene tapes can be as high as 275,S,m,1 with tensile strengths of around 500,MPa. To the best of the authors' knowledge, it is the most conductive, high-strength polymer fiber produced by melt-processing reported in literature, despite the fact that only ,5,wt.% of MWNTs are used in the outer layers of the tape and the overall MWNT content in the bicomponent tape can be much lower (typically ,0.5,wt.%). Their applications could include sensing, smart textiles, electrodes for flexible solar cells, and electromagnetic interference (EMI) shielding. Furthermore, a modeling approach was used to study the relaxation process of highly oriented conductive networks formed by carbon nanofillers. [source]

Tuning the Composition and Nanostructure of Pt/Ir Films via Anodized Aluminum Oxide Templated Atomic Layer Deposition

ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010
David J. Comstock
Abstract Nanostructured metal films have been widely studied for their roles in sensing, catalysis, and energy storage. In this work, the synthesis of compositionally controlled and nanostructured Pt/Ir films by atomic layer deposition (ALD) into porous anodized aluminum oxide templates is demonstrated. Templated ALD provides advantages over alternative synthesis techniques, including improved film uniformity and conformality as well as atomic-scale control over morphology and composition. Nanostructured Pt ALD films are demonstrated with morphological control provided by the Pt precursor exposure time and the number of ALD cycles. With these approaches, Pt films with enhanced surface areas, as characterized by roughness factors as large as 310, are reproducibly synthesized. Additionally, nanostructured PtIr alloy films of controlled composition and morphology are demonstrated by templated ALD, with compositions varying systematically from pure Pt to pure Ir. Lastly, the application of nanostructured Pt films to electrochemical sensing applications is demonstrated by the non-enzymatic sensing of glucose. [source]

Tuning the Composition and Nanostructure of Pt/Ir Films via Anodized Aluminum Oxide Templated Atomic Layer Deposition

ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010
David J. Comstock
Abstract Nanostructured metal films have been widely studied for their roles in sensing, catalysis, and energy storage. In this work, the synthesis of compositionally controlled and nanostructured Pt/Ir films by atomic layer deposition (ALD) into porous anodized aluminum oxide templates is demonstrated. Templated ALD provides advantages over alternative synthesis techniques, including improved film uniformity and conformality as well as atomic-scale control over morphology and composition. Nanostructured Pt ALD films are demonstrated with morphological control provided by the Pt precursor exposure time and the number of ALD cycles. With these approaches, Pt films with enhanced surface areas, as characterized by roughness factors as large as 310, are reproducibly synthesized. Additionally, nanostructured PtIr alloy films of controlled composition and morphology are demonstrated by templated ALD, with compositions varying systematically from pure Pt to pure Ir. Lastly, the application of nanostructured Pt films to electrochemical sensing applications is demonstrated by the non-enzymatic sensing of glucose. [source]

The Role of OTS Density on Pentacene and C60 Nucleation, Thin Film Growth, and Transistor Performance

ADVANCED FUNCTIONAL MATERIALS, Issue 12 2009
Ajay Virkar
Abstract In organic thin film transistors (OTFTs), charge transport occurs in the first few monolayers of the semiconductor near the semiconductor/dielectric interface. Previous work has investigated the roles of dielectric surface energy, roughness, and chemical functionality on performance. However, large discrepancies in performance, even with apparently identical surface treatments, indicate that additional surface parameters must be identified and controlled in order to optimize OTFTs. Here, a crystalline, dense octadecylsilane (OTS) surface modification layer is found that promotes two-dimensional semiconductor growth. Higher mobility is consistently achieved for films deposited on crystalline OTS compared to on disordered OTS, with mobilities as high as 5.3 and 2.3,cm2,V,1,s,1 for C60 and pentacene, respectively. This is a significant step toward morphological control of organic semiconductors which is directly linked to their thin film charge carrier transport. [source]

Formation of Network and Cellular Structures by Viscoelastic Phase Separation

ADVANCED MATERIALS, Issue 18 2009
Hajime Tanaka
Abstract Network (sponge) and cellular structures are often seen in various types of materials. Materials with such structures are generally characterized by light weight and high mechanical strength. The usefulness of such materials is highlighted, for example, by the remarkable material properties of bone tissue, which often has a highly porous structure. In artificial materials, plastic and metallic foams and breads have such structures. Here, we describe a physical principle for producing network and cellular structures using phase separation, and its potential applications to the morphological control of materials spanning from soft to hard matter. [source]

Gold Nanoparticle-Hybridized "Nano-Sponge" Polymer Coatings to Enhance the Reliability and Sensitivity of Biosensors

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 13 2009
Hyung-Jun Jeong
Abstract We have created a new functional biosensor coating composed of polyelectrolyte multilayers containing gold nanoparticles. This gold-hybridized polyelectrolyte multilayer film possesses a stable nanoporous structure under physiological conditions. Antibody molecules were successfully conjugated onto the gold nanoparticles within the film. This functional coating successfully extinguished false signals from non-specific binding of proteins and cells and also provided highly enhanced detection sensitivity. Furthermore, the drastic differences in protein and cellular adhesion properties between a chip coated with the nanoporous PEM film and a bare chip demonstrate that morphological control of biological interactions on chip surfaces is possible. [source]