Brushes

Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Kinds of Brushes

  • cylindrical brush
  • mixed polymer brush
  • molecular brush
  • polyelectrolyte brush
  • polymer brush
  • spherical polyelectrolyte brush

  • Terms modified by Brushes

  • brush biopsy
  • brush border
  • brush border membrane
  • brush border membrane vesicle
  • brush cell
  • brush cytology
  • brush layer
  • brush polymer

  • Selected Abstracts


    Power Generation and Electrochemical Analysis of Biocathode Microbial Fuel Cell Using Graphite Fibre Brush as Cathode Material

    FUEL CELLS, Issue 5 2009
    S.-J. You
    Abstract To improve cathodic efficiency and sustainability of microbial fuel cell (MFC), graphite fibre brush (GFB) was examined as cathode material for power production in biocatalysed-cathode MFC. Following 133-h mixed culturing of electricity-producing bacteria, the MFC could generate a reproducible voltage of 0.4,V at external resistance (REX) of 100,,. Maximum volumetric power density of 68.4,W,m,3 was obtained at a current density of 178.6,A,m,3. Upon aerobic inoculation of electrochemically active bacteria, charge transfer resistance of the cathode was decreased from 188 to 17,, as indicated by electrochemical impedance spectroscopy (EIS) analysis. Comparing investigations of different cathode materials demonstrated that biocatalysed GFB had better performance in terms of half-cell polarisation, power and Coulombic efficiency (CE) over other tested materials. Additionally, pH deviation of electrolyte in anode and cathode was also observed. This study provides a demonstration of GFB used as biocathode material in MFC for more efficient and sustainable electricity recovery from organic substances. [source]


    Normal and Lateral Deformation of Lyotropically Ordered Polymer Brush

    MACROMOLECULAR THEORY AND SIMULATIONS, Issue 9 2006
    Alexey A. Polotsky
    Abstract Summary: Planar polymer brush formed by semirigid chains of freely jointed rigid segments and immersed into a solvent is considered. Brush collapse induced by deterioration of the solvent quality and its deformation by external normal or lateral force is studied. It is demonstrated that these three different situations can be described in the framework of the common approach. It is shown that the collapse is accompanied by liquid-crystalline (LC) ordering within the brush. The LC transition can be jump-like (the first order) or continuous, depending on the segment's aspect ratio and grafting density. Transition point is investigated in detail, the corresponding phase diagrams are calculated. It is shown that the phase diagrams of a normally deformed brush have different structures, with a narrow ,leg' in the good solvent region for sparsely grafted brush, with two coexistence regions and a triple point, in addition, for shorter segment length or without these features if the chains are densely grafted. For the laterally deformed brush, phase diagrams have similar structures with a critical point in the good solvent regime. Polymer brush subjected to deformation by normal (top) and lateral (bottom) external force. [source]


    Free Energy of a Non-Gaussian Polymer Brush

    MACROMOLECULAR THEORY AND SIMULATIONS, Issue 4 2003
    Victor M. Amoskov
    Abstract An analytical theory describing layers of polymer chains grafted to a planar surface (i.e. polymer brush) is developed. We consider a brush of chains with finite extensibility (or non-Gaussian brush) within the framework of molecular field theory. An analytical solution for free energy of the brush and a few other brush characteristics are obtained and studied. Comparison with other known models of a brush is also made. Chain extensibility E(x, y) for Gaussian model (dashed lines) and BCC model (solid lines) for a few chain end positions y (numbers near curves). [source]


    Poly(2-(dimethylamino)ethyl methacrylate) Brushes with Incorporated Nanoparticles as a SERS Active Sensing Layer

    ADVANCED FUNCTIONAL MATERIALS, Issue 11 2010
    Smrati Gupta
    Abstract A simple, fast, and versatile approach to the fabrication of outstanding surface enhanced Raman spectroscopy (SERS) substrates by exploiting the optical properties of the Ag nanoparticles and functional as well as organizational characteristics of the polymer brushes is reported. First, poly(2-(dimethylamino)ethyl methacrylate) brushes are synthesized directly on glassy carbon by self-initiated photografting and photopolymerization and thoroughly characterized in terms of their thickness, wettability, morphology, and chemical structure by means of ellipsometry, contact angle, AFM, and XPS, respectively. Second, Ag nanoparticles are homogeneously immobilized into the brush layer, resulting in a sensor platform for the detection of organic molecules by SERS. The surface enhancement factor (SEF) as determined by the detection of Rhodamine 6G is calculated as 6,,106. [source]


    Electrochemical Nanotransistor from Mixed-Polymer Brushes

    ADVANCED MATERIALS, Issue 16 2010
    Tsz Kin Tam
    Reversible switching of the electrode interface between OFF/ON states is achieved by electrochemically triggered reorganization of a nanostructured polymer brush associated with the interface. The switching process is accomplished by local interfacial pH changes allowing operation in buffered biological environments (see figure). The fabricated device mimics the performance of switching electronic devices such as transistors. [source]


    Polymer Brushes with Nanometer-Scale Gradients

    ADVANCED MATERIALS, Issue 46 2009
    Christian Schuh
    Surfaces with steep height or composition gradients at the nanometer scale are synthesized from self-asssembled photoinitiator monolayers. The monolayers are prestructured by interference lithography followed by brush growth. Through step-and-repeat processes, surfaces with nano meter-scale composition gradients are obtained. [source]


    Engineered Polymer Brushes by Carbon Templating

    ADVANCED MATERIALS, Issue 28 2009
    Marin Steenackers
    A general method for the fabrication of stable polymer brushes of programmable three-dimensional shapes and different chemical functions is presented. The carbon templating method allows the functionalization of a broad variety of substrates without the need of a specific surface chemistry. As an example, the AFM scan of complex polymer brush structures on a bare GaAs substrate is shown. [source]


    In Pursuit of Zero: Polymer Brushes that Resist the Adsorption of Proteins

    ADVANCED MATERIALS, Issue 23 2009
    Angus Hucknall
    Abstract Protein resistant or "non-fouling" surfaces are of great interest for a variety of biomedical and biotechnology applications. This article briefly reviews the development of protein resistant surfaces, followed by recent research on a new methodology to fabricate non-fouling surfaces by surface-initiated polymerization. We show that polymer brushes synthesized by surface-initiated polymerization that present short oligo(ethylene glycol) side chains are exceptionally resistant to protein adsorption and cell adhesion. The importance of the protein and cell resistance conferred by these polymer brushes is illustrated by their use as substrates for the fabrication of antibody microarrays that exhibit femtomolar limits of detection in complex fluids such as serum and blood with relaxed requirements for intermediate wash steps. This example highlights the important point that the reduction in background noise afforded by protein-resistant surfaces can greatly simplify the development of ultrasensitive heterogeneous, surface-based clinical and proteomic assays with increased sensitivity and utility. [source]


    Simple Fabrication of Antibody Microarrays on Nonfouling Polymer Brushes with Femtomolar Sensitivity for Protein Analytes in Serum and Blood

    ADVANCED MATERIALS, Issue 19 2009
    Angus Hucknall
    A multianalyte antibody array that is spotted on a poly(oligo(ethylene glycol) methacrylate) brush 100,nm thick, grown on glass via surface-initiated atom transfer radical polymerization, has femtomolar limit-of-detection (LOD) of cytokines in serum and whole blood, and a dynamic range of six orders of magnitude for a range of protein analytes. [source]


    Self-Cleaning and Anti-Fog Surfaces via Stimuli-Responsive Polymer Brushes,

    ADVANCED MATERIALS, Issue 22 2007
    A. Howarter
    The wetting character of surfactant based polymer brushes is examined. The unique ability for the brush surfaces to be both hydrophilic and oleophobic rendered self-cleaning materials. [source]


    Facile Synthesis of Spherical Polyelectrolyte Brushes as Carriers for Conducting Polymers to be Used in Plastic Electronics

    MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 18 2009
    Jianjun Wang
    Abstract A two-step method for the preparation of spherical polyelectrolyte brushes (SPBs) has been developed. Copolymerization of styrene and divinyl benzene at the particle surface resulted in a large number of accessible vinyl groups. These vinyl groups reacted with sodium styrene sulfonate to give SPBs. The SPBs were used as carriers for conducting polymers resulting in redispersible conducting inks with good film forming properties. Direct current (DC) conductivity of the polypyrrole (PPy) loaded samples showed a percolating behavior as probed by impedance spectroscopy. Finally, device performance of organic light-emitting diodes based on the conducting thin films assembled from the PPy loaded particles was tested. [source]


    Double-Grafted Cylindrical Brushes: Synthesis and Characterization of Poly(lauryl methacrylate) Brushes

    MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 15 2007
    Youyong Xu
    Abstract Double-grafted cylindrical brushes with poly(lauryl methacrylate) (PLMA) as the side chains were synthesized using the grafting-from strategy via atom transfer radical polymerization (ATRP). The polyinitiator poly[2-(2-bromoisobutyryloxy)ethyl methacrylate] (PBIEM) with ,=,240 and 1,500 served as the backbone. The PLMA side chains of the brushes carry long alkyl chains. GPC and 1H NMR measurements confirmed the successful formation of the PLMA cylindrical brushes. The side chains were cleaved from the cylindrical brushes by transesterification. GPC and 1H NMR results indicate that the initiating efficiency of the bromoester groups on the backbone for the bulky monomer was in the range of 0.34,,,f,,,0.67. Static and dynamic light scattering show that the ratio of the radius of gyration to the hydrodynamic radius, Rg/Rh, is in the range of 1.2,1.3, indicating that the LMA cylindrical brushes are semiflexible in solution. Atomic force microscopy (AFM) measurements show that short PLMA brushes exhibit a spherical morphology while the long brushes exhibit a worm-like structure. DSC displayed melting peaks at around ,30,C, indicating the alkyl side chains of the PLMA chains in the double-grafted cylindrical brushes are crystallizable. [source]


    Solution Behavior of Temperature-Responsive Molecular Brushes Prepared by ATRP

    MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2007
    Joanna Pietrasik
    Abstract Molecular brushes, with side chains consisting of two copolymers: 2-(dimethylamino)ethyl methacrylate with methyl methacrylate, and N,N -dimethylacrylamide with butyl acrylate were prepared by grafting-from via atom transfer radical polymerization (ATRP). Poly(2-(2-bromoisobutyryloxy)ethyl methacrylate) and poly(2-(2-bromopropionyloxy)ethyl methacrylate) were used as macroinitiators. Dynamic light scattering (DLS) studies were performed for aqueous solutions of molecular brushes below and above the lower critical solution temperature (LCST), and an unusual concentration-dependent LCST was observed. Due to the compact structure of molecular brushes, intramolecular collapse can occur when the average distance between molecules is much larger than the hydrodynamic dimensions of the individual macromolecules. However, if the concentration of the solution of molecular brushes is increased to the level in which the separation distance is comparable with the brush hydrodynamic dimensions, intermolecular aggregation occurs, as typically observed for solutions of linear polymers. [source]


    Supramolecular Structures Generated by Spherical Polyelectrolyte Brushes and their Application in Catalysis

    MACROMOLECULAR RAPID COMMUNICATIONS, Issue 9-10 2009
    Yan Lu
    Abstract We survey recent studies on composite particles made from spherical polyelectrolyte brushes (SPB) and catalytically active nanoparticles or enzymes. SPB consist of a solid core (diameter: ca. 100 nm) onto which long chains of anionic or cationic polyelectrolyte (PE) are densely grafted ("PE brush"). Immersed in water the PE layer affixed to the colloidal core will swell due to the enormous osmotic pressure of the confined counterions ("osmotic brush"). This confinement of the counterions can be used to generate metal nanoparticles on the surface of the SPB. Moreover, enzymes can be immobilized within the PE layer. In both cases, the resulting composite particles are stable against coagulation and can be easily handled and filtered off. The catalytic activity of both systems is largely preserved in case of the enzymes, in case of the metal nanoparticles it is even enhanced. Thus, the SPB present an excellent carrier system for applications in catalysis. [source]


    Synthesis of Polymer Brushes Using Atom Transfer Radical Polymerization

    MACROMOLECULAR RAPID COMMUNICATIONS, Issue 18 2003
    Jeffrey Pyun
    Abstract Atom transfer radical polymerization (ATRP) is a robust method for the preparation of well-defined (co)polymers. This process has also enabled the preparation of a wide range of polymer brushes where (co)polymers are covalently attached to either curved or flat surfaces. In this review, the general methodology for the synthesis of polymer brushes from flat surfaces, polymers and colloids is summarized focusing on reports using ATRP. Additionally, the morphology of ultrathin films from polymer brushes is discussed using atomic force microscopy (AFM) and other techniques to confirm the formation of nanoscale structure and organization. Formation of polymer brushes by ATRP. [source]


    Grafting Polymer Brushes from Glass Fibers by Surface-Initiated ATRP

    MACROMOLECULAR REACTION ENGINEERING, Issue 3-4 2010
    Hongwen Zhang
    Abstract Grafting of PMMA and/or PS brushes from the surface of glass fibers by SI-ATRP has been investigated in order to achieve a controlled surface structure of the matrix. The surface composition and morphology of the modified glass fibers were analyzed by FTIR, XPS, TGA, and SEM. The results indicated that the surface composition and morphology were improved by grafting polymer after modification. The modified glass fibers were composed of an organic tube and an inorganic core. The organic content on the surface of modified glass fibers was high. GPC data of free polymer showed that the SI-ATRP from the surface of bromine-bound glass fibers proceeded in a controlled/"living" manner. [source]


    Numerical Self-Consistent Field Theory of Cylindrical Polyelectrolyte Brushes

    MACROMOLECULAR THEORY AND SIMULATIONS, Issue 3 2009
    Li-Jian Qu
    Abstract A single cylindrical polyelectrolyte brush is studied by self-consistent field (SCF) theory and the results compared with predictions from scaling theory. It is shown that the SCF theory results give the general trends as well as insight into the crossover regions between different regimes. The density profiles of the polyions and small ions indicate that the systems are locally electroneutral. The salted brush bears characteristics similar to those of a neutral brush. Counter-intuitively, the chains are not uniformly stretched in the osmotic regime. The free-end monomers shift to the outer region and an exclusion zone appears and grows with decreasing of salt concentration. [source]


    Dissipative Particle Dynamics Simulations of Polymer Brushes: Comparison with Molecular Dynamics Simulations

    MACROMOLECULAR THEORY AND SIMULATIONS, Issue 9 2006
    Sandeep Pal
    Abstract Summary: The structure of polymer brushes is investigated by dissipative particle dynamics (DPD) simulations that include explicit solvent particles. With an appropriate choice of the DPD interaction parameters , we obtain good agreement with previous molecular dynamics (MD) results where the good solvent behavior has been modeled by an effective Lennard,Jones potential. The present results confirm that DPD simulation techniques can be applied for large length scale simulations of polymer brushes. A relation between the different length scales and is established. Polymer brush at a solid,liquid interface. [source]


    Structure of Polymer Brushes in Cylindrical Tubes: A Molecular Dynamics Simulation

    MACROMOLECULAR THEORY AND SIMULATIONS, Issue 7 2006
    Dimitar I. Dimitrov
    Abstract Summary: Molecular dynamics simulations of a coarse-grained bead-spring model of flexible macromolecules tethered with one end to the surface of a cylindrical pore are presented. Chain length N and grafting density , are varied over a wide range and the crossover from "mushroom" to "brush" behavior is studied for three pore diameters. The monomer density profile and the distribution of the free chain ends are computed and compared to the corresponding model of polymer brushes at flat substrates. It is found that there exists a regime of N and , for large enough pore diameter where the brush height in the pore exceeds the brush height on the flat substrate, while for large enough N and , (and small enough pore diameters) the opposite behavior occurs, i.e. the brush is compressed by confinement. These findings are used to discuss the corresponding theories on polymer brushes at concave substrates. Snapshot picture of a brush grafted inside of a cylinder, for , , displaying different chains in distinct colors in order to be able to distinguish them. Top shows a side view of the cylinder, and the lower part a view of the cross-section. Note that the particles forming the cylindrical wall are not displayed. [source]


    Corrigendum: Scanning Electron Microscopy Investigation of Molecular Transport and Reactivity within Polymer Brushes

    CHEMPHYSCHEM, Issue 9 2010
    Tarik Matrab Dr.
    No abstract is available for this article. [source]


    Controlled Grafting of Poly(methyl methacrylate) Brushes on Poly(vinylidene fluoride) Powders by Surface-initiated Atom Transfer Radical Polymerization

    CHINESE JOURNAL OF CHEMISTRY, Issue 2 2009
    Zhaoqi TANG
    Abstract Controlled grafting of well-defined polymer brushes of methyl methacrylate (MMA) on the poly(vinylidene fluoride) (PVDF) powders was carried out by the surface-initiated atom transfer radical polymerization (ATRP). The ATRP initiator was anchored on the PVDF surface by alkaline treatment, followed by UV-induced bromination; then methyl methacrylate (MMA) was grafted onto the brominated PVDF by the ATRP technique. The chemical composition changes of PVDF were characterized by Fourier transform-infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). FT-IR and XPS results clearly indicated the successful graft of poly(methyl methacrylate) onto the PVDF surface. [source]


    Mechanical removal of necrotic periodontal ligament by either Robinson bristle brush with pumice or scalpel blade.

    DENTAL TRAUMATOLOGY, Issue 6 2007
    Histomorphometric analysis, scanning electron microscopy
    Abstract,,, One of the important factors accounting for successful delayed replantation of avulsed teeth is seemingly the type of root surface treatment. Removal of necrotic cemental periodontal ligament remnants may prevent the occurrence of external root resorption, which is the major cause of loss of teeth replanted in such conditions. The purpose of this study was to compare the efficacy of two mechanical techniques for removal of root-adhered periodontal ligament. Preservation or removal of the cementum layer concomitantly with these procedures was also assessed. Forty-five roots of healthy premolars extracted for orthodontic purposes were selected. After extraction, the teeth were kept dry at room temperature for 1 h and then immersed in saline for rehydration for an additional 10 min. Thereafter, the roots were assigned to three groups, as follows: group 1 (control) - the cemental periodontal ligament was preserved; group 2 - removal of the periodontal ligament by scraping root surface with a scalpel blade (SBS); group 3 - periodontal ligament remnants were removed using a Robinson bristle brush at low-speed with pumice/water slurry (RBP). The specimens were analysed histomorphometrically and examined by scanning electron microscopy. The quantitative and qualitative analyses of the results showed that the RBP technique was significantly more effective than the SBS technique for removal of the periodontal ligament remnants adhered to root surface. Both techniques preserved the cementum layer. [source]


    Dentin surface treatment using a non-thermal argon plasma brush for interfacial bonding improvement in composite restoration

    EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 5 2010
    Andy C. Ritts
    Ritts AC, Li H, Yu Q, Xu C, Yao X, Hong L, Wang Y. Dentin surface treatment using a non-thermal argon plasma brush for interfacial bonding improvement in composite restoration. Eur J Oral Sci 2010; 118: 510,516. 2010 Eur J Oral Sci The objective of this study was to investigate the treatment effects of non-thermal atmospheric gas plasmas on dentin surfaces used for composite restoration. Extracted unerupted human third molars were prepared by removing the crowns and etching the exposed dentin surfaces with 35% phosphoric acid gel. The dentin surfaces were treated using a non-thermal atmospheric argon plasma brush for various periods of time. The molecular changes of the dentin surfaces were analyzed using Fourier transform infrared spectrophotometry/attenuated total reflectance (FTIR/ATR), and an increase in the amount of carbonyl groups was detected on plasma-treated dentin surfaces. Adper Single Bond Plus adhesive and Filtek Z250 dental composite were applied as directed. To evaluate the dentin/composite interfacial bonding, the teeth thus prepared were sectioned into micro-bars and analyzed using tensile testing. Student,Newman,Keuls tests showed that the bonding strength of the composite restoration to peripheral dentin was significantly increased (by 64%) after 30 s of plasma treatment. However, the bonding strength to plasma-treated inner dentin did not show any improvement. It was found that plasma treatment of the peripheral dentin surface for up to 100 s resulted in an increase in the interfacial bonding strength, while prolonged plasma treatment of dentin surfaces (e.g. 5 min) resulted in a decrease in the interfacial bonding strength. [source]


    Effect of stannous fluoride toothpaste on erosion-like lesions: an in vivo study

    EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 3 2006
    Alix Young
    It has recently been shown that stannous fluoride (SnF2), in the form of aqueous solutions and as toothpaste, can reduce the dissolution of enamel in erosive acids in vitro and in situ. The aim of this study was to compare the effect of toothpastes containing SnF2 or NaF on enamel dissolution using an in vivo model. Four healthy anterior teeth in each subject (n = 20) were exposed to diluted citric acid (100 mmol l,1 or 10 mmol l,1) applied using a peristaltic pump (5 ml @7 ml min,1) and the acid was collected in a test tube before and after application of the respective toothpastes (etch I and etch II). Toothpaste was applied to the labial surfaces with a soft brush (four applications, each of 1-min duration), with gentle water rinsing between applications. Each subject had one pair of teeth treated with each of the test toothpastes. Enamel dissolution was examined by assessment of calcium content in the citric acid applied before and after the treatment with toothpaste. The results indicate that the SnF2 toothpaste markedly reduced the dissolution of teeth in vivo (etch II < etch I), whereas the NaF toothpaste provided no protection (etch II > etch I). Toothpaste appears to be an acceptable vehicle for SnF2 and maintains the dissolution-reducing effect exhibited by aqueous solutions of this fluoride salt. [source]


    A Molecular Brush Approach to Enhance Quantum Yield and Suppress Nonspecific Interactions of Conjugated Polyelectrolyte for Targeted Far-Red/Near-Infrared Fluorescence Cell Imaging

    ADVANCED FUNCTIONAL MATERIALS, Issue 17 2010
    Kan-Yi Pu
    Abstract A red-fluorescent conjugated polyelectrolyte (CPE, P2) is grafted with dense poly(ethylene glycol) (PEG) chains via click chemistry and subsequently modified with folic acid to form a molecular brush based cellular probe (P4). P4 self-assembles into a core,shell nanostructure in aqueous medium with an average size of 130 nm measured by laser light scattering. As compared to P2, P4 possesses not only a substantially higher quantum yield (11%), but also reduced nonspecific interactions with biomolecules in aqueous medium due to the shielding effect of PEG. In conjunction with its high photostability and low cytotoxicity, utilization of P4 as a far-red/near-infrared cellular probe allows for effective visualization and discrimination of MCF-7 cancer cells from NIH-3T3 normal cells in a high contrast, selective, and nonviral manner. This study thus demonstrates a flexible molecular brush approach to overcome the intrinsic drawbacks of CPEs for advanced bioimaging applications. [source]


    A Molecular Brush Approach to Enhance Quantum Yield and Suppress Nonspecific Interactions of Conjugated Polyelectrolyte for Targeted Far-Red/Near-Infrared Fluorescence Cell Imaging

    ADVANCED FUNCTIONAL MATERIALS, Issue 17 2010
    Kan-Yi Pu
    Abstract A red-fluorescent conjugated polyelectrolyte (CPE, P2) is grafted with dense poly(ethylene glycol) (PEG) chains via click chemistry and subsequently modified with folic acid to form a molecular brush based cellular probe (P4). P4 self-assembles into a core,shell nanostructure in aqueous medium with an average size of 130 nm measured by laser light scattering. As compared to P2, P4 possesses not only a substantially higher quantum yield (11%), but also reduced nonspecific interactions with biomolecules in aqueous medium due to the shielding effect of PEG. In conjunction with its high photostability and low cytotoxicity, utilization of P4 as a far-red/near-infrared cellular probe allows for effective visualization and discrimination of MCF-7 cancer cells from NIH-3T3 normal cells in a high contrast, selective, and nonviral manner. This study thus demonstrates a flexible molecular brush approach to overcome the intrinsic drawbacks of CPEs for advanced bioimaging applications. [source]


    Synthetic Hydrophilic Materials with Tunable Strength and a Range of Hydrophobic Interactions,

    ADVANCED FUNCTIONAL MATERIALS, Issue 14 2010
    Olha Hoy
    Abstract The ability to vary, adjust, and control hydrophobic interactions is crucial in manipulating interactions between biological objects and the surface of synthetic materials in aqueous environment. To this end a grafted polymer layer (multi-component mixed polymer brush) is synthesized that is capable of reversibly exposing nanometer-sized hydrophobic fragments at its hydrophilic surface and of tuning, turning on, and turning off the hydrophobic interactions. The reversible switching occurs in response to changes in the environment and alters the strength and range of attractive interactions between the layer and hydrophobic or amphiphilic probes in water. The grafted layer retains its overall hydrophilicity, while local hydrophobic forces enable the grafted layer to sense and attract the hydrophobic domains of protein molecules dissolved in the aqueous environment. The hydrophobic interactions between the material and a hydrophobic probe are investigated using atomic force microscopy measurements and a long-range attractive and contact-adhesive interaction between the material and the probe is observed, which is controlled by environmental conditions. Switching of the layer exterior is also confirmed via protein adsorption measurements. [source]


    Power Generation and Electrochemical Analysis of Biocathode Microbial Fuel Cell Using Graphite Fibre Brush as Cathode Material

    FUEL CELLS, Issue 5 2009
    S.-J. You
    Abstract To improve cathodic efficiency and sustainability of microbial fuel cell (MFC), graphite fibre brush (GFB) was examined as cathode material for power production in biocatalysed-cathode MFC. Following 133-h mixed culturing of electricity-producing bacteria, the MFC could generate a reproducible voltage of 0.4,V at external resistance (REX) of 100,,. Maximum volumetric power density of 68.4,W,m,3 was obtained at a current density of 178.6,A,m,3. Upon aerobic inoculation of electrochemically active bacteria, charge transfer resistance of the cathode was decreased from 188 to 17,, as indicated by electrochemical impedance spectroscopy (EIS) analysis. Comparing investigations of different cathode materials demonstrated that biocatalysed GFB had better performance in terms of half-cell polarisation, power and Coulombic efficiency (CE) over other tested materials. Additionally, pH deviation of electrolyte in anode and cathode was also observed. This study provides a demonstration of GFB used as biocathode material in MFC for more efficient and sustainable electricity recovery from organic substances. [source]


    Battery Drivable Organic Single-Crystalline Transistors Based on Surface Grafting Ultrathin Polymer Dielectric

    ADVANCED FUNCTIONAL MATERIALS, Issue 18 2009
    Liqiang Li
    Abstract High-performance and battery drivable organic single-crystalline transistors with operational voltages,,,2.0,V are demonstrated using high-quality copper phthalocyanine (CuPc) single-crystalline nanoribbons and ultrathin polymer nanodielectrics. The ultrathin polymer nanodielectric is synthesized by grafting a ca. 10,nm poly(methyl methacrylate) (PMMA) brush on a silicon surface via surface-initiated atom-transfer radical polymerization (SI-ATRP). This surface-grafted nanodielectric exhibits a large capacitance, excellent insulating property, and good compatibility with organic semiconductors. The realization of a low operational voltage for battery driving at high performance, together with the merits of surface grafting of a nanodielectric, as well as the mechanical flexibility of the organic nanoribbon, suggests a bright future for use of these transistors in low-cost and flexible circuits. [source]


    Organic Thin Film Transistors with Polymer Brush Gate Dielectrics Synthesized by Atom Transfer Radical Polymerization

    ADVANCED FUNCTIONAL MATERIALS, Issue 1 2008
    C. Pinto
    Abstract Low operating voltage is an important requirement that must be met for industrial adoption of organic field-effect transistors (OFETs). We report here solution fabricated polymer brush gate insulators with good uniformity, low surface roughness and high capacitance. These ultra thin polymer films, synthesized by atom transfer radical polymerization (ATRP), were used to fabricate low voltage OFETs with both evaporated pentacene and solution deposited poly(3-hexylthiophene). The semiconductor-dielectric interfaces in these systems were studied with a variety of methods including scanning force microscopy, grazing incidence X-ray diffraction and neutron reflectometry. These studies highlighted key differences between the surfaces of brush and spun cast polymethyl methacrylate (PMMA) films. [source]