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Sample records for assembled polymer nanowires

  1. Direct Assembly of Large Arrays of Oriented Conducting Polymer Nanowires

    SciTech Connect

    Liang, Liang; Liu, Jun; Windisch, Charles F.; Exarhos, Gregory J.; Lin, Yuehe

    2002-10-04

    Although oriented carbon nanotubes, oriented nanowires of metals, semiconductors and oxides have attracted wide attention, there have been few reports on oriented polymer nanostructures such as nanowires. In this paper we report the assembly of large arrays of oriented nanowires through controlled nucleation and growth during a stepwise electrochemical deposition process in which a large number of nuclei were first deposited on the substrate using a large current density. After the initial nucleation, the current density was reduced step by step to grow the oriented nanowires from the nucleation sites created in the first step. A very different morphology was also demonstrated by first depositing a monolayer of close-packed colloidal spheres using a similar step-wise deposition process. As a result, the polymer nanofibers grew from the spheres in a radial fashion and formed the continuous three-dimensional network of nanofibers in the film. The principles of control nucleation and growth in electrochemical deposition investigated in this paper should be applicable to other electrical conducting and electrochemical active materials, including metals and conducting oxides. We also hope the oriented electroactive polymer nanostructure will open the door for new applications, such as miniaturized biosensors.

  2. Single conducting polymer nanowire based conductometric sensors

    NASA Astrophysics Data System (ADS)

    Bangar, Mangesh Ashok

    The detection of toxic chemicals, gases or biological agents at very low concentrations with high sensitivity and selectivity has been subject of immense interest. Sensors employing electrical signal readout as transduction mechanism offer easy, label-free detection of target analyte in real-time. Traditional thin film sensors inherently suffered through loss of sensitivity due to current shunting across the charge depleted/added region upon analyte binding to the sensor surface, due to their large cross sectional area. This limitation was overcome by use of nanostructure such as nanowire/tube as transducer where current shunting during sensing was almost eliminated. Due to their benign chemical/electrochemical fabrication route along with excellent electrical properties and biocompatibility, conducting polymers offer cost-effective alternative over other nanostructures. Biggest obstacle in using these nanostructures is lack of easy, scalable and cost-effective way of assembling these nanostructures on prefabricated micropatterns for device fabrication. In this dissertation, three different approaches have been taken to fabricate individual or array of single conducting polymer (and metal) nanowire based devices and using polymer by itself or after functionalization with appropriate recognition molecule they have been applied for gas and biochemical detection. In the first approach electrochemical fabrication of multisegmented nanowires with middle functional Ppy segment along with ferromagnetic nickel (Ni) and end gold segments for better electrical contact was studied. This multi-layered nanowires were used along with ferromagnetic contact electrode for controlled magnetic assembly of nanowires into devices and were used for ammonia gas sensing. The second approach uses conducting polymer, polypyrrole (Ppy) nanowires using simple electrophoretic alignment and maskless electrodeposition to anchor nanowire which were further functionalized with antibodies against

  3. Aluminum Nanowire Arrays via Directed Assembly

    NASA Astrophysics Data System (ADS)

    Nesbitt, Nathan T.; Merlo, Juan M.; Rose, Aaron H.; Calm, Yitzi M.; D'Imperio, Luke A.; Courtney, Dave T.; Shepard, Steve; Kempa, Krzysztof; Burns, Michael J.; Naughton, Michael J.

    Vertically-oriented metal nanowire arrays are rare. Here, freestanding, vertically-oriented, and lithographically-ordered Al nanowire arrays have been fabricated via directed assembly. The fabrication technique is a variation on the preparation of anodized aluminum oxide (AAO) templates, using nanoimprint lithography (NIL) to direct the formation of pores on an Al film and produce Al nanowires. Near-field scanning optical microscope (NSOM) and conventional optical microscope data of a single nanowire lying on glass and illuminated by a laser spot show evidence of surface plasmons propagating along the nanowire. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. (DGE-1258923).

  4. Polymer-Mediated Self-Assembly of TiO2@Cu2O Core-Shell Nanowire Array for Highly Efficient Photoelectrochemical Water Oxidation.

    PubMed

    Yuan, Weiyong; Yuan, Jia; Xie, Jiale; Li, Chang Ming

    2016-03-01

    Phototoelectrochemical (PEC) water splitting represents a highly promising strategy to convert solar energy to chemical energy in the form of hydrogen, but its performance is severely limited by the water oxidation reaction. We conformally grew an ultrathin and continuous coating of Cu2O on TiO2 nanowire array (NWA) to form a truly core-shell TiO2@Cu2O NWA via a new facile, economical, and scalable polymer-mediated self-assembly approach, in which the polymer serves as a stabilizer, reductant, and linker simultaneously. This heteronanostructure was subsequently directly used as a photoanode for PEC water splitting, showing a photocurrent density of 4.66 mA cm(-2) at 1.23 V vs RHE in 0.5 M Na2SO4 solution and a maximum photoconversion efficiency of 0.71%, both of which are the highest reported for TiO2-based photoanodes measured under the same conditions (neutral conditions and without any sacrificial agent). The superior PEC performance of the TiO2@Cu2O NWA toward water oxidation is primarily due to much enhanced visible light collection and charge separation for high charge carrier density as well as greatly facilitated charge transfer and transport. This work not only offers a novel TiO2@Cu2O core-shell NWA photoanode for highly efficient PEC water oxidation and investigate its enhancement mechanism but also provides scientific insights into the mechanism of the polymer-mediated self-assembly, which can be further extended to fabricate various other core-shell nanoarchitectures for broad applications. PMID:26908094

  5. Synthesis and characterization of nanowire coils of organometallic coordination polymers for controlled cargo release.

    PubMed

    Liang, Guodong; Ni, Huan; Bao, Suping; Zhu, Fangming; Gao, Haiyang; Wu, Qing

    2014-06-12

    Nanowire coils of organometallic coordination polymers have been synthesized for the first time by using the emulsion periphery polymerization technique. An amphiphilic triblock copolymer terminated with inclusion complex of β-cyclodextrin and 4,4'-bipyridine self-assembles into oil-in-water emulsion in a toluene/water mixture. Subsequent coordination of bipyridine with Ni(II) in periphery of emulsions results in the formation of coordination polymer nanowire coils. The nanowire coils are composed of nanowires with diameter of 2 nm. Nanowire coils exhibit enhanced thermal stability in contrast to their parent triblock copolymer. Interestingly, nanowire coils are capable of encapsulating organic cargoes. Encapsulated cargoes can be selectively extracted from nanowire coils without damaging nanowire coils. Nanowire coils are potential candidates for encapsulating and controlled release of organic cargoes. PMID:24842771

  6. Shape-Controlled Deterministic Assembly of Nanowires.

    PubMed

    Zhao, Yunlong; Yao, Jun; Xu, Lin; Mankin, Max N; Zhu, Yinbo; Wu, Hengan; Mai, Liqiang; Zhang, Qingjie; Lieber, Charles M

    2016-04-13

    Large-scale, deterministic assembly of nanowires and nanotubes with rationally controlled geometries could expand the potential applications of one-dimensional nanomaterials in bottom-up integrated nanodevice arrays and circuits. Control of the positions of straight nanowires and nanotubes has been achieved using several assembly methods, although simultaneous control of position and geometry has not been realized. Here, we demonstrate a new concept combining simultaneous assembly and guided shaping to achieve large-scale, high-precision shape controlled deterministic assembly of nanowires. We lithographically pattern U-shaped trenches and then shear transfer nanowires to the patterned substrate wafers, where the trenches serve to define the positions and shapes of transferred nanowires. Studies using semicircular trenches defined by electron-beam lithography yielded U-shaped nanowires with radii of curvature defined by inner surface of the trenches. Wafer-scale deterministic assembly produced U-shaped nanowires for >430,000 sites with a yield of ∼90%. In addition, mechanistic studies and simulations demonstrate that shaping results in primarily elastic deformation of the nanowires and show clearly the diameter-dependent limits achievable for accessible forces. Last, this approach was used to assemble U-shaped three-dimensional nanowire field-effect transistor bioprobe arrays containing 200 individually addressable nanodevices. By combining the strengths of wafer-scale top-down fabrication with diverse and tunable properties of one-dimensional building blocks in novel structural configurations, shape-controlled deterministic nanowire assembly is expected to enable new applications in many areas including nanobioelectronics and nanophotonics. PMID:26999059

  7. Solution assembly of conjugated polymers

    NASA Astrophysics Data System (ADS)

    Bokel, Felicia A.

    This dissertation focuses on the solution-state polymer assembly of conjugated polymers with specific attention to nano- and molecular-scale morphology. Understanding how to control these structures holds potential for applications in polymer-based electronics. Optimization of conjugated polymer morphology was performed with three objectives: 1) segregation of donor and acceptor materials on the nanometer length-scale, 2) achieving molecular-scale ordering in terms of crystallinity within distinct domains, and 3) maximizing the number and quality of well-defined donor/acceptor interfaces. Chapter 1 introduces the development of a mixed solvent method to create crystalline poly(3-hexyl thiophene) (P3HT) fibrils in solution. Chapter 2 describes fibril purification and approaches to robust and functional fibrils, while chapters 3 and 4 demonstrate the formation of hybrid nanocomposite wires of P3HT and cadmium selenide (CdSe) nanoparticles by two methods: 1) co-crystallization of free and P3HT-grafted CdSe for composite nanowires and 2) direct attachment of CdSe nanoparticles at fibril edges to give superhighway structures. These composite structures show great potential in the application of optoelectronic devices, such as the active layer of solar cells. Finally, ultrafast photophysical characterization of these polymers, using time-resolved photoluminescence and transient absorption, was performed to determine the aggregation types present in suspended fibrils and monitor the formation and decay of charged species in fibrils and donor-acceptor systems.

  8. The Self- and Directed Assembly of Nanowires

    NASA Astrophysics Data System (ADS)

    Smith, Benjamin David

    This thesis explores the self- and directed assembly of nanowires. Specifically, we examine the driving forces behind nanowire self-assembly and the macro-structures that are formed. Particle-dense, oriented nanowire structures show promise in the fields of photonics, energy, sensing, catalysis, and electronics. Arrays of spherical particles have already found uses in electronic inks, sensing arrays, and many other commercial applications; but, it is a challenge to create specific arrays of morphologically and/or compositionally anisotropic particles. The following chapters illuminate the interactions that drive the assembly of anisotropic particles in high density solutions in the absence of applied fields or solution drying. Special emphasis is placed on the structures that are formed. The properties of micro- and nanoparticles and their assembly are introduced in Chapter 1. In particular, the properties of shape and material anisotropic particles are highlighted, while challenges in producing desired arrays are discussed. In this thesis, metallic nanowires of increasing complexity were used to examine the self-assembly behavior of both shape and material anisotropic particles. Nanowires were synthesized through templated electrodeposition. In this process, porous alumina membranes served as a template in which metal salts were reduced to form particles. Upon template dissolution, billions of nominally identical particles were released. We specifically focused on segmented, metallic nanowires 2-13 mum in length and 180 to 350 nm in diameter. Since these particles have strong van der Waals (VDWs) attractions, an electrostatically repulsive coating was necessary to prevent aggregation; we used small molecule, DNA, or amorphous silica coatings. Nanowires and their coatings were characterized by electron microscopy. In order to study self-assembly behavior, particle-dense aqueous suspensions were placed within an assembly chamber defined by a silicone spacer. The

  9. Manufacturing a nanowire-based sensing system via flow-guided assembly in a microchannel array template

    NASA Astrophysics Data System (ADS)

    Chen, Juan; Zu, Yingbo; Rajagopalan, Kartik Kumar; Wang, Shengnian

    2015-06-01

    A novel flow-guided assembly approach is presented to accurately align and position nanowire arrays in pre-defined locations with high throughput and large-scale manufacturing capability. In this approach, a polymer solution is first filled in an array of microfluidic channels. Then a gas flow is introduced to blow out most of the solution while pushing a little leftover against the channel wall for assembly into polymer nanowires. In this way, highly ordered nanowires are conveniently aligned in the flow direction and patterned along both sides of the microchannels. In this study, we demonstrated this flow-guided assembly process by producing millimetre-long nanowires across a 5 × 12 mm area in the same orientation and with basic ‘I-shape’, ‘T-shape’, and ‘cross’ patterns. The assembled polymer nanowires were further converted to conductive carbon nanowires through a standard carbonization process. After being integrated into electronic sensors, high sensitivity was found in model protein sensing tests. This new nanowire manufacturing approach is anticipated to open new doors to the fabrication of nanowire-based sensing systems and serve as good manufacturing practice for its simplicity, low cost, alignment reliability, and high throughput.

  10. Assembly and magnetic properties of nickel nanoparticles on silicon nanowires

    SciTech Connect

    Picraux, Samuel T; Manandhar, Pradeep; Nazaretski, E; Thompson, J

    2009-01-01

    The directed assembly of magnetic Ni nanoparticles at the tips of silicon nanowires is reported. Using electrodeposition Ni shells of thickness from 10 to 100 nm were selectively deposited on Au catalytic seeds at the ends of nanowires. Magnetic characterization confirms a low coercivity ({approx}115 Oe) ferromagnetic behavior at 300 K. This approach to multifunctional magnetic-semiconducting nanostructure assembly could be extended to electrodeposition of other materials on the nanowire ends, opening up novel ways of device integration. Such magnetically functionalized nanowires offer a new approach to developing novel highly localized magnetic probes for high resolution magnetic resonance force microscopy.

  11. Sensing properties of assembled Bi2S3 nanowire arrays

    NASA Astrophysics Data System (ADS)

    Kunakova, G.; Meija, R.; Bite, I.; Prikulis, J.; Kosmaca, J.; Varghese, J.; Holmes, J. D.; Erts, Donats

    2015-09-01

    Bismuth sulfide (Bi2S3) nanowires were grown in porous aluminium oxide template and a selective chemical etching was applied to transfer the nanowires to a solution. Well aligned nanowire arrays were assembled on pre-patterned silicon substrates employing dielectrophoresis. Electron beam lithography was used to connect aligned individual nanowires to the common macroelectrode. In order to evaluate the conductometric sensing performance of the Bi2S3 nanowires, current-voltage characteristics were measured at different relative humidity (RH) levels (5-80%) / argon medium. The response of the Bi2S3 nanowires depending of RH is found to be considerably different from those reported for other types of nanowire RH sensor devices.

  12. Kinetic pathways to organized polymer/nanoparticle assemblies

    NASA Astrophysics Data System (ADS)

    Hayward, Ryan

    2012-02-01

    Processes that allow for controlled access to kinetically trapped non-equilibrium states have the potential to significantly expand the range of structures and properties that may be achieved by self-assembly. We will describe several recent examples from our group wherein new types of polymer/nanoparticle assemblies are enabled by designed processing pathways. In the first case, we study the formation of amphiphilic polymer micelles through hydrodynamic instabilities of solvent/water interfaces induced during emulsion processing. We show that this route allows for efficient co-encapsulation of multiple types of hydrophobic nanoparticles within the micelle cores. Second, we consider the influence of nanoparticles on spinodal decomposition of a polymer blend and find that the inclusion of aggregating particles provides a route to kinetically stabilize co-continuous structures through particle gelation in one of the polymer phases. Finally, we show how the structures of hybrid nanoparticle/conjugated polymer nanowires can be tuned using solution-state crystallization.

  13. Fabrication of Si3N4 nanowire membranes: free standing disordered nanopapers and aligned nanowire assemblies

    NASA Astrophysics Data System (ADS)

    Liu, Haitao; Fang, Minghao; Huang, Zhaohui; Huang, Juntong; Liu, Yan-gai; Wu, Xiaowen

    2016-08-01

    Herein, ultralong silicon nitride nanowires were synthesized via a chemical vapor deposition method by using the low-cost quartz and silicon powder as raw materials. Simple processes were used for the fabrication of disordered and ordered nanowire membranes of pure silicon nitride nanowires. The nanowires in the disordered nanopapers are intertwined with each other to form a paper-like structure which exhibit excellent flame retardancy and mechanical properties. Fourier-transform infrared spectroscopy and thermal gravity analysis were employed to characterize the refractory performance of the disordered nanopapers. Highly ordered nanowire membranes were also assembled through a three-phase assembly approach which make the Si3N4 nanowires have potential use in textured ceramics and semiconductor field. Moreover, the surface nanowires can also be modified to be hydrophobic; this characteristic make the as-prepared nanowires have the potential to be assembled by the more effective Langmuir–Blodgett method and also make the disordered nanopapers possess a super-hydrophobic surface.

  14. Electrically Conductive Metal Nanowire Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Luo, Xiaoxiong

    This thesis investigates electrically conductive polymer nanocomposites formulated with metal nanowires for electrostatic discharge and electromagnetic interference shielding. Copper nanowires (CuNWs) of an average length of 1.98 mum and diameter of 25 +/- 4 nm were synthesized. The oxidation reaction of the CuNWs in air can be divided into two stages at weight of 111.2% on TGA curves. The isoconversional activation energies determined by Starink method were used to fit the different master plots. Johnson-Mehl-Avrami (JMA) equation gave the best fit. The surface atoms of the CuNWs are the sites for the random nucleation and the crystallite strain in the CuNWs is the driving force for the growth of nuclei mechanism during the oxidation process. To improve the anti-oxidation properties of the CuNWs, silver was coated onto the surface of the CuNWs in Ag-amine solution. The prepared silver coated CuNWs (AgCuNWs) with silver content of 66.52 wt. %, diameter of 28--33 nm exhibited improved anti-oxidation behavior. The electrical resistivity of the AgCuNW/low density polyethylene (LDPE) nanocomposites is lower than that of the CuNW/LDPE nanocomposites with the same volume percentage of fillers. The nanocomposites formulated with CuNWs and polyethylenes (PEs) were compared to study the different interaction between the CuNWs and the different types of PE matrices. The electrical conductivity of the different PE matrices filled with the same concentrations of CuNWs correlated well with the level of the CuNW dispersion. The intermolecular force and entanglement resulting from the different macromolecular structures such as molecular weight and branching played an important role in the dispersion, electrical properties and rheological behaviour of the CuNW/PE nanocomposites. Ferromagnetic polycrystalline nickel nanowires (NiNWs) were synthesized with uniform diameter of ca. 38 nm and an average length of 2.68 mum. The NiNW linear low density polyethylene (LLDPE

  15. Magnetic field manipulation of nanowires for anisotropic polymer composite synthesis

    NASA Astrophysics Data System (ADS)

    Keshoju, Kusuma

    One-dimensional magnetic nanowires (NWs) have attracted a great deal of attention recently due to their interesting physical properties and applications. This dissertation involves synthesizing magnetic NWs, manipulating NWs under the effect of external magnetic field in various suspensions, and integrating and assembling the NWs in polymer to develop anisotropic nanocomposites. Nickel NWs with high aspect ratio were fabricated in nanoporous alumina membranes by template assisted electrodeposition. Electrodeposition provides the flexibility to control the size, structure, morphology and composition of the NWs. One of the major challenges is to assemble the as-synthesized NWs for the development of polymer nanocomposites and biomedical sensors. In this project, magnetic field was used to assemble NWs by controlling their motion and position in fluids. This is a low-cost, non-contact and easy to scale-up approach. Nanowire rotation in responding to fixed and rotating uniform field in various suspensions has been investigated. Due to strong wire and field interaction, small fields are sufficient to manipulate NWs even in highly viscous fluids. Synchronous rotation of NWs with field has been successfully achieved indicating that NWs can be used as "nano-stir bars". To describe the NW rotation, quantitative model based on the competing magnetic field induced torque and resisting fluid drag torque was developed. As a demonstration of potential applications of the NWs, polymer nanocomposites have been fabricated. Polydimethylsiloxane with low elastic modulus and tensile strength was chosen as the polymer of interest. Based on the magnetic field manipulation, composites with NWs distributed in different orientations (random, longitudinal and transverse) were synthesized. To characterize the nonlinear elastic behavior of the composites, a high resolution strain measurement method using "micro-ruler" was developed. The mechanical and magnetic properties of composite samples

  16. Location deterministic biosensing from quantum-dot-nanowire assemblies.

    PubMed

    Liu, Chao; Kim, Kwanoh; Fan, D L

    2014-08-25

    Semiconductor quantum dots (QDs) with high fluorescent brightness, stability, and tunable sizes, have received considerable interest for imaging, sensing, and delivery of biomolecules. In this research, we demonstrate location deterministic biochemical detection from arrays of QD-nanowire hybrid assemblies. QDs with diameters less than 10 nm are manipulated and precisely positioned on the tips of the assembled Gold (Au) nanowires. The manipulation mechanisms are quantitatively understood as the synergetic effects of dielectrophoretic (DEP) and alternating current electroosmosis (ACEO) due to AC electric fields. The QD-nanowire hybrid sensors operate uniquely by concentrating bioanalytes to QDs on the tips of nanowires before detection, offering much enhanced efficiency and sensitivity, in addition to the position-predictable rationality. This research could result in advances in QD-based biomedical detection and inspires an innovative approach for fabricating various QD-based nanodevices. PMID:25316926

  17. Location deterministic biosensing from quantum-dot-nanowire assemblies

    SciTech Connect

    Liu, Chao; Kim, Kwanoh; Fan, D. L.

    2014-08-25

    Semiconductor quantum dots (QDs) with high fluorescent brightness, stability, and tunable sizes, have received considerable interest for imaging, sensing, and delivery of biomolecules. In this research, we demonstrate location deterministic biochemical detection from arrays of QD-nanowire hybrid assemblies. QDs with diameters less than 10 nm are manipulated and precisely positioned on the tips of the assembled Gold (Au) nanowires. The manipulation mechanisms are quantitatively understood as the synergetic effects of dielectrophoretic (DEP) and alternating current electroosmosis (ACEO) due to AC electric fields. The QD-nanowire hybrid sensors operate uniquely by concentrating bioanalytes to QDs on the tips of nanowires before detection, offering much enhanced efficiency and sensitivity, in addition to the position-predictable rationality. This research could result in advances in QD-based biomedical detection and inspires an innovative approach for fabricating various QD-based nanodevices.

  18. Location deterministic biosensing from quantum-dot-nanowire assemblies

    PubMed Central

    Liu, Chao; Kim, Kwanoh; Fan, D. L.

    2014-01-01

    Semiconductor quantum dots (QDs) with high fluorescent brightness, stability, and tunable sizes, have received considerable interest for imaging, sensing, and delivery of biomolecules. In this research, we demonstrate location deterministic biochemical detection from arrays of QD-nanowire hybrid assemblies. QDs with diameters less than 10 nm are manipulated and precisely positioned on the tips of the assembled Gold (Au) nanowires. The manipulation mechanisms are quantitatively understood as the synergetic effects of dielectrophoretic (DEP) and alternating current electroosmosis (ACEO) due to AC electric fields. The QD-nanowire hybrid sensors operate uniquely by concentrating bioanalytes to QDs on the tips of nanowires before detection, offering much enhanced efficiency and sensitivity, in addition to the position-predictable rationality. This research could result in advances in QD-based biomedical detection and inspires an innovative approach for fabricating various QD-based nanodevices. PMID:25316926

  19. Suspended InAs nanowire Josephson junctions assembled via dielectrophoresis.

    PubMed

    Montemurro, D; Stornaiuolo, D; Massarotti, D; Ercolani, D; Sorba, L; Beltram, F; Tafuri, F; Roddaro, S

    2015-09-25

    We present a novel technique for the realization of suspended Josephson junctions based on InAs semiconductor nanowires. The devices are assembled using a technique of drop-casting guided by dielectrophoresis, which allows one to finely align the nanostructures on top of the electrodes. The proposed architecture removes the interaction between the nanowire and the substrate which is known to influence disorder and the orientation of the Rashba vector. The relevance of this approach in view of the implementation of hybrid Josephson junctions based on semiconducting nanowires coupled with high-temperature superconductors is discussed. PMID:26335273

  20. Suspended InAs nanowire Josephson junctions assembled via dielectrophoresis

    NASA Astrophysics Data System (ADS)

    Montemurro, D.; Stornaiuolo, D.; Massarotti, D.; Ercolani, D.; Sorba, L.; Beltram, F.; Tafuri, F.; Roddaro, S.

    2015-09-01

    We present a novel technique for the realization of suspended Josephson junctions based on InAs semiconductor nanowires. The devices are assembled using a technique of drop-casting guided by dielectrophoresis, which allows one to finely align the nanostructures on top of the electrodes. The proposed architecture removes the interaction between the nanowire and the substrate which is known to influence disorder and the orientation of the Rashba vector. The relevance of this approach in view of the implementation of hybrid Josephson junctions based on semiconducting nanowires coupled with high-temperature superconductors is discussed.

  1. Substrateless Welding of Self-Assembled Silver Nanowires at Air/Water Interface.

    PubMed

    Hu, Hang; Wang, Zhongyong; Ye, Qinxian; He, Jiaqing; Nie, Xiao; He, Gufeng; Song, Chengyi; Shang, Wen; Wu, Jianbo; Tao, Peng; Deng, Tao

    2016-08-10

    Integrating connected silver nanowire networks with flexible polymers has appeared as a popular way to prepare flexible electronics. To reduce the contact resistance and enhance the connectivity between silver nanowires, various welding techniques have been developed. Herein, rather than welding on solid supporting substrates, which often requires complicated transferring operations and also may pose damage to heat-sensitive substrates, we report an alternative approach to prepare easily transferrable conductive networks through welding of self-assembled silver nanowires at the air/water interface using plasmonic heating. The intriguing welding behavior of partially aligned silver nanowires was analyzed with combined experimental observation and theoretical modeling. The underlying water not only physically supports the assembled silver nanowires but also buffers potential overheating during the welding process, thereby enabling effective welding within a broad range of illumination power density and illumination duration. The welded networks could be directly integrated with PDMS substrates to prepare high-performance stable flexible heaters that are stretchable, bendable, and can be easily patterned to explore selective heating applications. PMID:27437907

  2. Size dependence of transition temperature in polymer nanowires.

    PubMed

    Nakanishi, Sana; Yoshikawa, Hirofumi; Shoji, Satoru; Sekkat, Zouheir; Kawata, Satoshi

    2008-03-27

    We studied the effect of changing temperature on the mechanical properties of nanosized poly(methyl methacrylate) wires fabricated by two-photon fabrication. At around room temperature, the nanowires showed a transition temperature where the shear modulus suddenly changed. This transition temperature was observed to decrease more than 40 K by decreasing the radius of the nanowires from 450 to 150 nm. This size is several times larger in nanowires than reported values of polymer thin film thickness showing a depression of the glass transition temperature. PMID:18318534

  3. Preparation of Ag/Cu Janus nanowires: Electrodeposition in track-etched polymer templates

    NASA Astrophysics Data System (ADS)

    Zhu, X. R.; Wang, C. M.; Fu, Q. B.; Jiao, Z.; Wang, W. D.; Qin, G. Y.; Xue, J. M.

    2015-08-01

    Bimetal (Janus) nanowire has been widely used as a promising nanoscale motor. In this paper we present a highly controllable method to fabricate Ag/Cu Janus nanowires using track-etched polymer templates. Ag/Cu Janus nanowires with uniform size and stabilized structure have been successfully fabricated by electrodepositing Ag nanowires, and subsequently Cu nanowires in track-etched polymer templates. The pore size of nanopores prepared by this template is uniform and continuously controlled, so aperture of achieved nanowires are uniform and can be regulated. This polymer template can dissolve inorganic solvents that do not react with the nanowires, making it is easy to release the nanowires into solution. The nanopore shape in the track-etched templates is adjustable (e.g. conical), nanowires with more special shapes could be fabricated. Thus, these features make this simple and inexpensive method very suitable for the preparation of Janus nanowire.

  4. Thermodynamics of the adsorption of flexible polymers on nanowires

    SciTech Connect

    Vogel, Thomas; Gross, Jonathan; Bachmann, Michael

    2015-03-09

    Generalized-ensemble simulations enable the study of complex adsorption scenarios of a coarse-grained model polymer near an attractive nanostring, representing an ultrathin nanowire. We perform canonical and microcanonical statistical analyses to investigate structural transitions of the polymer and discuss their dependence on the temperature and on model parameters such as effective wire thickness and attraction strength. The result is a complete hyperphase diagram of the polymer phases, whose locations and stability are influenced by the effective material properties of the nanowire and the strength of the thermal fluctuations. Major structural polymer phases in the adsorbed state include compact droplets attached to or wrapping around the wire, and tubelike conformations with triangular pattern that resemble ideal boron nanotubes. In conclusion, the classification of the transitions is performed by microcanonical inflection-point analysis.

  5. Thermodynamics of the adsorption of flexible polymers on nanowires

    SciTech Connect

    Vogel, Thomas; Gross, Jonathan; Bachmann, Michael

    2015-03-14

    Generalized-ensemble simulations enable the study of complex adsorption scenarios of a coarse-grained model polymer near an attractive nanostring, representing an ultrathin nanowire. We perform canonical and microcanonical statistical analyses to investigate structural transitions of the polymer and discuss their dependence on the temperature and on model parameters such as effective wire thickness and attraction strength. The result is a complete hyperphase diagram of the polymer phases, whose locations and stability are influenced by the effective material properties of the nanowire and the strength of the thermal fluctuations. Major structural polymer phases in the adsorbed state include compact droplets attached to or wrapping around the wire, and tubelike conformations with triangular pattern that resemble ideal boron nanotubes. The classification of the transitions is performed by microcanonical inflection-point analysis.

  6. Thermodynamics of the adsorption of flexible polymers on nanowires

    DOE PAGESBeta

    Vogel, Thomas; Gross, Jonathan; Bachmann, Michael

    2015-03-09

    Generalized-ensemble simulations enable the study of complex adsorption scenarios of a coarse-grained model polymer near an attractive nanostring, representing an ultrathin nanowire. We perform canonical and microcanonical statistical analyses to investigate structural transitions of the polymer and discuss their dependence on the temperature and on model parameters such as effective wire thickness and attraction strength. The result is a complete hyperphase diagram of the polymer phases, whose locations and stability are influenced by the effective material properties of the nanowire and the strength of the thermal fluctuations. Major structural polymer phases in the adsorbed state include compact droplets attached tomore » or wrapping around the wire, and tubelike conformations with triangular pattern that resemble ideal boron nanotubes. In conclusion, the classification of the transitions is performed by microcanonical inflection-point analysis.« less

  7. Silver nanowire array-polymer composite as thermal interface material

    NASA Astrophysics Data System (ADS)

    Xu, Ju; Munari, Alessio; Dalton, Eric; Mathewson, Alan; Razeeb, Kafil M.

    2009-12-01

    Silver nanowire arrays embedded inside polycarbonate templates are investigated as a viable thermal interface material for electronic cooling applications. The composite shows an average thermal diffusivity value of 1.89×10-5 m2 s-1, which resulted in an intrinsic thermal conductivity of 30.3 W m-1 K-1. The nanowires' protrusion from the film surface enables it to conform to the surface roughness to make a better thermal contact. This resulted in a 61% reduction in thermal impedance when compared with blank polymer. An ˜30 nm Au film on the top of the composite was found to act as a heat spreader, reducing the thermal impedance further by 35%. A contact impedance model was employed to compare the contact impedance of aligned silver nanowire-polymer composites with that of aligned carbon nanotubes, which showed that the Young's modulus of the composite is the defining factor in the overall thermal impedance of these composites.

  8. Metal nanowires from self-assembled protein fibers

    NASA Astrophysics Data System (ADS)

    Parthasarathy, Raghuveer; Lin, Xiao-Min; Jaeger, Heinrich M.; Sawicki, George; Scheibel, Thomas; Lindquist, Susan L.

    2002-03-01

    We present gold and silver nanowires formed by metallization of self-assembled yeast prion proteins. The proteins form 10nm wide, microns long fibers, which we metallize by growth of gold or silver crystals from specific nucleation sites on the genetically engineered fiber surface. This site-specific metal decoration is the first step toward more elaborate functionalization of these biological nanostructures. Deposition of fibers onto substrates with in-plane electrodes will allow electronic transport measurements, correlated with images (TEM and AFM) of the nanowire structure.

  9. Spherulitic assembly of peptide nanowires via spontaneous crystallization.

    PubMed

    Han, Tae Hee

    2014-11-01

    In this work, the hierarchal arrangement of peptide nanowires was achieved via the spontaneous crystallization of peptide molecules. Peptide molecules, which are structural motifs associated with Alzheimer's disease, assembled into one-dimensional nanowires and spontaneously formed two-dimensional peptide spherulites during crystallization of the peptide melt. The assembly behavior of the peptides could be directed by physically confining the soft mold. Furthermore, a hybrid assembly of small functional molecules, such as photoluminescent Alq3, was also achieved. Our approach offers a simple method for achieving spontaneous long-range crystalline order of building blocks approaching macroscopic dimensions and also a facile hybridization strategy to conjugate biomolecules and functional small molecules. PMID:25958606

  10. Bottlebrush Polymers: Synthesis, Rheology, and Self-Assembly

    NASA Astrophysics Data System (ADS)

    Dalsin, Samuel J.

    Bottlebrush polymers are comb-like molecules with a high density of side chains grafted along a central backbone. Due to their unique conformational properties, bottlebrush polymers have become attractive candidates for developing new photonic bandgap materials, nanotubes and nanowires, or drug delivery vehicles, to name a few. This dissertation primarily investigates the rheological properties and self-assembly behavior of bottlebrush polymer molecules made using a variety of different polymerization routes. A considerable portion of the work is directed towards the linear rheology of model, polyolefin-based bottlebrush polymers with independently varied branch and backbone lengths. These studies demonstrate how the tight spacing between branch points effectively precludes backbone entanglement in the polymer melts, but it does not inhibit the formation of entanglements among the branched side chains. Furthermore, the relaxation profiles reveal transient scaling behavior in which the dynamics transition from Zimm-like to Rouse-like at increasing relaxation times. These results highlight the distinct conformational character of bottlebrushes at different length scales. The latter parts of this work report on the self-assembly behavior of bottlebrush diblock polymers composed of atactic polypropylene and polystyrene side chains. The diblock samples are analyzed using small-angle X-ray scattering and atomic force microscopy. Nearly all of the samples display strong segregation between the two blocks, owing to the large molar mass of typical bottlebrush polymers. Consequently, only one experimental sample displays an accessible order-disorder transition temperature. The strong segregation is also shown to affect the ability of large bottlebrush diblocks to readily achieve well-ordered nanostructures by self-assembly. Finally, results of the most symmetric (by volume fraction) diblock samples are compared with predictions of a newly developed self-consistent field

  11. Synthesis of platinum dendrites and nanowires via directed electrochemical nanowire assembly.

    PubMed

    Kawasaki, Jason K; Arnold, Craig B

    2011-02-01

    Directed electrochemical nanowire assembly is a promising high growth rate technique for synthesizing electrically connected nanowires and dendrites at desired locations. Here we demonstrate the directed growth and morphological control of edge-supported platinum nanostructures by applying an alternating electric field across a chloroplatinic acid solution. The dendrite structure is characterized with respect to the driving frequency, amplitude, offset, and salt concentration and is well-explained by classical models. Control over the tip diameter, side branch spacing, and amplitude is demonstrated, opening the door to novel device architectures for sensing and catalytic applications. PMID:21235218

  12. Computational design of co-assembling protein-DNA nanowires

    NASA Astrophysics Data System (ADS)

    Mou, Yun; Yu, Jiun-Yann; Wannier, Timothy M.; Guo, Chin-Lin; Mayo, Stephen L.

    2015-09-01

    Biomolecular self-assemblies are of great interest to nanotechnologists because of their functional versatility and their biocompatibility. Over the past decade, sophisticated single-component nanostructures composed exclusively of nucleic acids, peptides and proteins have been reported, and these nanostructures have been used in a wide range of applications, from drug delivery to molecular computing. Despite these successes, the development of hybrid co-assemblies of nucleic acids and proteins has remained elusive. Here we use computational protein design to create a protein-DNA co-assembling nanomaterial whose assembly is driven via non-covalent interactions. To achieve this, a homodimerization interface is engineered onto the Drosophila Engrailed homeodomain (ENH), allowing the dimerized protein complex to bind to two double-stranded DNA (dsDNA) molecules. By varying the arrangement of protein-binding sites on the dsDNA, an irregular bulk nanoparticle or a nanowire with single-molecule width can be spontaneously formed by mixing the protein and dsDNA building blocks. We characterize the protein-DNA nanowire using fluorescence microscopy, atomic force microscopy and X-ray crystallography, confirming that the nanowire is formed via the proposed mechanism. This work lays the foundation for the development of new classes of protein-DNA hybrid materials. Further applications can be explored by incorporating DNA origami, DNA aptamers and/or peptide epitopes into the protein-DNA framework presented here.

  13. Self-assembled diphenylalanine nanowires for cellular studies and sensor applications.

    PubMed

    Sasso, Luigi; Vedarethinam, Indumathi; Emnéus, Jenny; Svendsen, Winnie E; Castillo-León, Jaime

    2012-04-01

    In this paper we present a series of experiments showing that vertical self-assembled diphenylalanine peptide nanowires (PNWs) are a suitable candidate material for cellular biosensing. We grew HeLa and PC12 cells onto PNW modified gold surfaces and observed no hindrance of cell growth caused by the peptide nanostructures; furthermore we studied the properties of PNWs by investigating their influence on the electrochemical behavior of gold electrodes. The PNWs were functionalized with polypyrrole (PPy) by chemical polymerization, therefore creating conducting peptide/polymer nanowire structures vertically attached to a metal electrode. The electroactivity of such structures was characterized by cyclic voltammetry. The PNW/PPy modified electrodes were finally used as amperometric dopamine sensors, yielding a detection limit of 3,1 microM. PMID:22849068

  14. Designing and building nanowires: directed nanocrystal self-assembly into radically branched and zigzag PbS nanowires

    NASA Astrophysics Data System (ADS)

    Xu, Fan; Ma, Xin; Gerlein, L. Felipe; Cloutier, Sylvain G.

    2011-07-01

    Lead sulfide nanowires with controllable optoelectronic properties would be promising building blocks for various applications. Here, we report the hot colloidal synthesis of radically branched and zigzag nanowires through self-attachment of star-shaped and octahedral nanocrystals in the presence of multiple surfactants. We obtained high-quality single-crystal nanowires with uniform diameter along the entire length, and the size of the nanowire can be tuned by tailoring the reaction parameters. This slow oriented attachment provides a better understanding of the intricacies of this complex nanocrystal assembly process. Meanwhile, these self-assembled nanowire structures have appealing lateral conformations with narrow side arms or highly faceted edges, where strong quantum confinement can occur. Consequently, the single-crystal nanowire structures exhibit strong photoluminescence in the near-infrared region with a large blue-shift compared to the bulk material.

  15. Size dependent nanomechanics of coil spring shaped polymer nanowires.

    PubMed

    Ushiba, Shota; Masui, Kyoko; Taguchi, Natsuo; Hamano, Tomoki; Kawata, Satoshi; Shoji, Satoru

    2015-01-01

    Direct laser writing (DLW) via two-photon polymerization (TPP) has been established as a powerful technique for fabrication and integration of nanoscale components, as it enables the production of three dimensional (3D) micro/nano objects. This technique has indeed led to numerous applications, including micro- and nanoelectromechanical systems (MEMS/NEMS), metamaterials, mechanical metamaterials, and photonic crystals. However, as the feature sizes decrease, an urgent demand has emerged to uncover the mechanics of nanosized polymer materials. Here, we fabricate coil spring shaped polymer nanowires using DLW via two-photon polymerization. We find that even the nanocoil springs follow a linear-response against applied forces, following Hooke's law, as revealed by compression tests using an atomic force microscope. Further, the elasticity of the polymer material is found to become significantly greater as the wire radius is decreased from 550 to 350 nm. Polarized Raman spectroscopy measurements show that polymer chains are aligned in nanowires along the axis, which may be responsible for the size dependence. Our findings provide insight into the nanomechanics of polymer materials fabricated by DLW, which leads to further applications based on nanosized polymer materials. PMID:26612544

  16. Size dependent nanomechanics of coil spring shaped polymer nanowires

    NASA Astrophysics Data System (ADS)

    Ushiba, Shota; Masui, Kyoko; Taguchi, Natsuo; Hamano, Tomoki; Kawata, Satoshi; Shoji, Satoru

    2015-11-01

    Direct laser writing (DLW) via two-photon polymerization (TPP) has been established as a powerful technique for fabrication and integration of nanoscale components, as it enables the production of three dimensional (3D) micro/nano objects. This technique has indeed led to numerous applications, including micro- and nanoelectromechanical systems (MEMS/NEMS), metamaterials, mechanical metamaterials, and photonic crystals. However, as the feature sizes decrease, an urgent demand has emerged to uncover the mechanics of nanosized polymer materials. Here, we fabricate coil spring shaped polymer nanowires using DLW via two-photon polymerization. We find that even the nanocoil springs follow a linear-response against applied forces, following Hooke’s law, as revealed by compression tests using an atomic force microscope. Further, the elasticity of the polymer material is found to become significantly greater as the wire radius is decreased from 550 to 350 nm. Polarized Raman spectroscopy measurements show that polymer chains are aligned in nanowires along the axis, which may be responsible for the size dependence. Our findings provide insight into the nanomechanics of polymer materials fabricated by DLW, which leads to further applications based on nanosized polymer materials.

  17. Size dependent nanomechanics of coil spring shaped polymer nanowires

    PubMed Central

    Ushiba, Shota; Masui, Kyoko; Taguchi, Natsuo; Hamano, Tomoki; Kawata, Satoshi; Shoji, Satoru

    2015-01-01

    Direct laser writing (DLW) via two-photon polymerization (TPP) has been established as a powerful technique for fabrication and integration of nanoscale components, as it enables the production of three dimensional (3D) micro/nano objects. This technique has indeed led to numerous applications, including micro- and nanoelectromechanical systems (MEMS/NEMS), metamaterials, mechanical metamaterials, and photonic crystals. However, as the feature sizes decrease, an urgent demand has emerged to uncover the mechanics of nanosized polymer materials. Here, we fabricate coil spring shaped polymer nanowires using DLW via two-photon polymerization. We find that even the nanocoil springs follow a linear-response against applied forces, following Hooke’s law, as revealed by compression tests using an atomic force microscope. Further, the elasticity of the polymer material is found to become significantly greater as the wire radius is decreased from 550 to 350 nm. Polarized Raman spectroscopy measurements show that polymer chains are aligned in nanowires along the axis, which may be responsible for the size dependence. Our findings provide insight into the nanomechanics of polymer materials fabricated by DLW, which leads to further applications based on nanosized polymer materials. PMID:26612544

  18. Semiconducting nanowires from hairpin-shaped self-assembling sexithiophenes.

    PubMed

    Tsai, Wei-Wen; Tevis, Ian D; Tayi, Alok S; Cui, Honggang; Stupp, Samuel I

    2010-11-18

    Conjugated organic molecules can be designed to self-assemble from solution into nanostructures for functions such as charge transport, light emission, or light harvesting. We report here the design and synthesis of a novel hairpin-shaped self-assembling molecule containing electronically active sexithiophene moieties. In several nonpolar organic solvents, such as toluene or chlorocyclohexane, this compound was found to form organogels composed of nanofibers with uniform diameters of 3.0 (±0.3) nm. NMR analysis and spectroscopic measurements revealed that the self-assembly is driven by π-π interactions of the sexithiophene moieties and hydrogen bonding among the amide groups at the head of the hairpin. Field effect transistors built with this molecule revealed p-type semiconducting behavior and higher hole mobilities when films were cast from solvents that promote self-assembly. We propose that hydrogen bonding and π-π stacking act synergistically to create ordered stacking of sexithiophene moieties, thus providing an efficient pathway for charge carriers within the nanowires. The nanostructures formed exhibit unusually broad absorbance in their UV-vis spectrum, which we attribute to the coexistence of both H and J aggregates from face-to-face π-π stacking of sexithiophene moieties and hierarchical bundling of the nanowires. The large absorption range associated with self-assembly of the hairpin molecules makes them potentially useful in light harvesting for energy applications. PMID:20698523

  19. Energy harvesting performance of piezoelectric ceramic and polymer nanowires

    NASA Astrophysics Data System (ADS)

    Crossley, Sam; Kar-Narayan, Sohini

    2015-08-01

    Energy harvesting from ubiquitous ambient vibrations is attractive for autonomous small-power applications and thus considerable research is focused on piezoelectric materials as they permit direct inter-conversion of mechanical and electrical energy. Nanogenerators (NGs) based on piezoelectric nanowires are particularly attractive due to their sensitivity to small-scale vibrations and may possess superior mechanical-to-electrical conversion efficiency when compared to bulk or thin-film devices of the same material. However, candidate piezoelectric nanowires have hitherto been predominantly analyzed in terms of NG output (i.e. output voltage, output current and output power density). Surprisingly, the corresponding dynamical properties of the NG, including details of how the nanowires are mechanically driven and its impact on performance, have been largely neglected. Here we investigate all realizable NG driving contexts separately involving inertial displacement, applied stress T and applied strain S, highlighting the effect of driving mechanism and frequency on NG performance in each case. We argue that, in the majority of cases, the intrinsic high resonance frequencies of piezoelectric nanowires (∼tens of MHz) present no barrier to high levels of NG performance even at frequencies far below resonance (<1 kHz) typically characteristic of ambient vibrations. In this context, we introduce vibrational energy harvesting (VEH) coefficients ηS and ηT, based on intrinsic materials properties, for comparing piezoelectric NG performance under strain-driven and stress-driven conditions respectively. These figures of merit permit, for the first time, a general comparison of piezoelectric nanowires for NG applications that takes into account the nature of the mechanical excitation. We thus investigate the energy harvesting performance of prototypical piezoelectric ceramic and polymer nanowires. We find that even though ceramic and polymer nanowires have been found, in

  20. Energy harvesting performance of piezoelectric ceramic and polymer nanowires.

    PubMed

    Crossley, Sam; Kar-Narayan, Sohini

    2015-08-28

    Energy harvesting from ubiquitous ambient vibrations is attractive for autonomous small-power applications and thus considerable research is focused on piezoelectric materials as they permit direct inter-conversion of mechanical and electrical energy. Nanogenerators (NGs) based on piezoelectric nanowires are particularly attractive due to their sensitivity to small-scale vibrations and may possess superior mechanical-to-electrical conversion efficiency when compared to bulk or thin-film devices of the same material. However, candidate piezoelectric nanowires have hitherto been predominantly analyzed in terms of NG output (i.e. output voltage, output current and output power density). Surprisingly, the corresponding dynamical properties of the NG, including details of how the nanowires are mechanically driven and its impact on performance, have been largely neglected. Here we investigate all realizable NG driving contexts separately involving inertial displacement, applied stress T and applied strain S, highlighting the effect of driving mechanism and frequency on NG performance in each case. We argue that, in the majority of cases, the intrinsic high resonance frequencies of piezoelectric nanowires (∼tens of MHz) present no barrier to high levels of NG performance even at frequencies far below resonance (<1 kHz) typically characteristic of ambient vibrations. In this context, we introduce vibrational energy harvesting (VEH) coefficients ηS and ηT, based on intrinsic materials properties, for comparing piezoelectric NG performance under strain-driven and stress-driven conditions respectively. These figures of merit permit, for the first time, a general comparison of piezoelectric nanowires for NG applications that takes into account the nature of the mechanical excitation. We thus investigate the energy harvesting performance of prototypical piezoelectric ceramic and polymer nanowires. We find that even though ceramic and polymer nanowires have been found, in

  1. Mechanism of formation of supramolecular DNA-templated polymer nanowires.

    PubMed

    Watson, Scott M D; Galindo, Miguel A; Horrocks, Benjamin R; Houlton, Andrew

    2014-05-01

    Details of the mechanism of formation of supramolecular polymer nanowires by templating on DNA are revealed for the first time using AFM. Overall these data reveal that the smooth, regular, structures produced are rendered by highly dynamic supramolecular transformations occurring over the micrometre scale. In the initial stages of the process a low density of conducting polymer (CP) binds to the DNA as, essentially, spherical particles. Further reaction time produces DNA strands which are more densely packed with particles giving a beads-on-a-string appearance. The particles subsequently undergo dynamic reconfiguration so as to elongate along the template axis and merge to yield the highly regular, smooth morphology of the final nanowire. MD simulations illustrate the early stages of the process showing the binding of globular CP to duplex DNA, while the latter stages can be modeled effectively by a linear thermodynamic description based on the balance between the line energy, which accounts for adhesion of the material to the template, and its surface tension. This model accounts for the phenomena observed in the AFM studies: the relative success of DNA templating of polymers compared to metals; the slow approach to equilibrium; and the observed thinning and 'necking' phenomena as the structures transform from beads-on-a-string to smooth nanowire. PMID:24712548

  2. Development of self-assembling nanowires containing electronically active oligothiophenes

    NASA Astrophysics Data System (ADS)

    Tsai, Wei-Wen

    This dissertation discusses the development of conductive one-dimensional nanowires from self-assembling oligothiophene molecules. Self-assembly has been demonstrated to be a promising alternative approach towards high performance, solution processable, and low-cost organic electronics. One of the many challenges in this field is the control of supramolecular morphologies of ordered structures containing pi-conjugated moieties. This research demonstrated several successful strategies to achieve self assembly of conductive nanowires using synergistic interactions combining pi stacking and hydrogen bonding. The first approach used was to develop a hairpin-shaped sexithiophene molecule, which features two arms of the conjugated structure. The diamidocyclohexyl headgroup of this molecule successfully directs the self-assembly from hydrogen bonding among the amides, forming high-aspect-ratio one-dimensional nanowires with well-defined diameters of 3.0 +/- 0.3 nm. The molecular orientation in the nanostructures promotes formation of sexithiophene H and J aggregates that facilitate efficient charge transport. Organic field-effect transistors were fabricated to reveal improved intrinsic hole mobility from films of the nanostructures, 3.46 x 10-6 cm2V-1s-1, which is one order of magnitude higher than films cast from unassembled molecules. Bulk heterojunction solar cells were developed from this molecule and fullerenes utilizing solution-phase fabrication methods. Intimate mix of the molecule and phenyl-C61-butyric acid methyl ester creates structured interfaces for efficient exciton splitting. The charge carrier mobilities of each material are improved by self-assembly in solution and thermal-energy assisted phase separation.The photovoltaic devices achieved the highest open-circuit voltage of 0.62 V, short-circuit current of 1.79 mA/cm2, fill factor of 35%, and power conversion efficiency of 0.48%. Another strategy to one-dimensional nanowires studied here involved the

  3. Composite Layer-by-Layer (LBL) assembly with inorganic nanoparticles and nanowires.

    PubMed

    Srivastava, Sudhanshu; Kotov, Nicholas A

    2008-12-01

    New assembly techniques are required for creating advanced materials with enough structural flexibility to be tuned for specific applications, and to be practical, the techniques must be implemented at relatively low cost. Layer-by-layer (LBL) assembly is a simple, versatile, and significantly inexpensive approach by which nanocomponents of different groups can be combined to coat both macroscopically flat and non-planar (e.g., colloidal core-shell particles) surfaces. Compared with other available assembly methods, LBL assembly is simpler and more universal and allows more precise thickness control at the nanoscale. LBL can be used to combine a wide variety of species--including nanoparticles (NPs), nanosheets, and nanowires (NWs)--with polymers, thus merging the properties of each type of material. This versatility has led to recent exceptional growth in the use of LBL-generated nanocomposites. This Account will focus on the materials and biological applications of introducing inorganic nanocrystals into polymer thin films. Combining inorganic NPs and NWs with organic polymers allows researchers to manipulate the unique properties in the nanomaterial. We describe the LBL assembly technique for introducing metallic NPs into polymers in order to generate a material with combined optomechanical properties. Similarly, LBL assembly of highly luminescent semiconductor NPs like HgTe or CdTe with poly(diallyldimethylammonium chloride) (PDDA) was used to create uniform optical-quality coatings made on optical fibers and tube interiors. In addition, LBL assembly with inorganic nanosheets or clay molecules is reported for fabricating films with strong mechanical and ion transport properties, and the technique can also be employed to prepare Au/TiO(2) core/sheath NWs. The LBL approach not only will be useful for assembly of inorganic nanocrystals with various polymers but can be further applied to introduce specific functions. We discuss how the expanded use of NWs and

  4. Exploiting polymer single crystals to assemble and functionalize nanomaterials

    NASA Astrophysics Data System (ADS)

    Li, Bing

    Nanomaterials are fundamental building blocks for nanoscience and nanotechnology. They can generally be categorized into three classes: zero-dimensional (0D) (e.g. nanoparticles), one-dimensional (1D) (e.g. carbon nanotubes) and two-dimensional (2D) (e.g. thin films) nanomaterials. Assembly of nanomaterials is the key step to transfer their fascinating mechanical, electronic and optical properties from nano- to micro- or macro-scale. Among all types of assemblies, assembling across different nanomaterial classes is of particular interest. For example, assembling 0D nanoparticles with 1D nanotubes or 2D thin films. These assembled structures have the advantage of possessing properties from both classes of nanomaterials. Functionalization of nanomaterials is important from both scientific and technological points of view. A newly developed field of functionalization is called "patchy particles". Multiple types of functional molecules form different domains on particle surface. Each domain contains only one type of functional molecules. These domains are called patches. These patchy particles are advanced building blocks, which may assemble into useful complex structures. In this thesis, polymer single crystals are exploited to assemble and functionalize nanomaterials. Polymer single crystals have a lamellar structure. Since the thickness of these lamellae is ˜10 nm, polymer single crystals are introduced as a new type of 2D nanomaterials. Different from the traditional 2D nanomaterials such as Langmuir-Blodgett films, self-assembled monolayers and thin films made by Layer-by-Layer technique, these polymer single crystals are free-standing, which means no substrate is needed. Furthermore, the surface of these polymer single crystals can be readily functionalized by crystallizing end-functionalized polymers. Based on the studied polymers, this thesis is divided into two parts. The first part is focused on single crystals of poly(ethylene oxide) (PEO). Thiol

  5. Casting metal nanowires within discrete self-assembled peptide nanotubes.

    PubMed

    Reches, Meital; Gazit, Ehud

    2003-04-25

    Tubular nanostructures are suggested to have a wide range of applications in nanotechnology. We report our observation of the self-assembly of a very short peptide, the Alzheimer's beta-amyloid diphenylalanine structural motif, into discrete and stiff nanotubes. Reduction of ionic silver within the nanotubes, followed by enzymatic degradation of the peptide backbone, resulted in the production of discrete nanowires with a long persistence length. The same dipeptide building block, made of D-phenylalanine, resulted in the production of enzymatically stable nanotubes. PMID:12714741

  6. Casting Metal Nanowires Within Discrete Self-Assembled Peptide Nanotubes

    NASA Astrophysics Data System (ADS)

    Reches, Meital; Gazit, Ehud

    2003-04-01

    Tubular nanostructures are suggested to have a wide range of applications in nanotechnology. We report our observation of the self-assembly of a very short peptide, the Alzheimer's β-amyloid diphenylalanine structural motif, into discrete and stiff nanotubes. Reduction of ionic silver within the nanotubes, followed by enzymatic degradation of the peptide backbone, resulted in the production of discrete nanowires with a long persistence length. The same dipeptide building block, made of D-phenylalanine, resulted in the production of enzymatically stable nanotubes.

  7. Polymer blends for directed self-assembly

    NASA Astrophysics Data System (ADS)

    Namie, Yuuji; Anno, Yusuke; Naruoka, Takehiko; Minegishi, Shinya; Nagai, Tomoki; Hishiro, Yoshi; Yamaguchi, Yoshikazu

    2013-03-01

    The advantage of blend DSA (Directed Self Assembly) is milder anneal condition than PS-b-PMMA BCP DSA materials and availability of conventional instruments. In this paper, blend type DSA was applied for hole patterning. Target patterns were contact hole and oval hole. Polymer phase separation behavior has been studied from the point of χN. In the case of polymer blend, χN needs to be more than 2 to give phase separation. At first the effect of polymer size was studied. When the polymer weight was low, the shrunk hole was not clean because of low χN. Furthermore, the correlation of shrink amount and χN was studied. Higher χN polymer blend system gave higher shrink amount. High χN polymer systems give clear interface, then the intermixing area would be reduced, then the attached polymer blend part became larger. The polymer blend ratio effect was also investigated. The blend ratio was varied for polymer A/ polymer B=70/30-50/50. The shrink amount of oval hole was reduced with increasing the ratio of polymer B. However, the shrink amount ratio of CDY/CDX was almost constant (~3).

  8. Investigation of functionalized silicon nanowires by self-assembled monolayer

    NASA Astrophysics Data System (ADS)

    Hemed, Nofar Mintz; Convertino, Annalisa; Shacham-Diamand, Yosi

    2016-03-01

    The functionalization using self assembled monolayer (SAM) of silicon nanowires (SiNW) fabricated by plasma enhanced chemical vapor deposition (PECVD) is reported here. The SAM is being utilized as the first building block in the functionalization process. The morphology of the SiNW comprises a polycrystalline core wrapped by an hydrogenated amorphous silicon (α-Si:H) shell. Since most of the available methods for SAM verification and characterization are suitable only for flat substrates; therefore, in addition to the SiNW α-Si:H on flat samples were produced in the same system as the SiNWs. First we confirmed the SAM's presence on the flat α-Si:H samples using the following methods: contact angle measurement to determine the change in surface energy; atomic force microscopy (AFM) to determine uniformity and molecular coverage. Spectroscopic ellipsometry and X-ray reflectivity (XRR) were performed to measure SAM layer thickness and density. X-ray photoelectron spectroscopy (XPS) was applied to study the chemical states of the surface. Next, SiNW/SAM were tested by electrochemical impedance spectroscopy (EIS), and the results were compared to α-Si:H/SAM. The SAM electrical coverage on SiNW and α-Si:H was found to be ∼37% and ∼65 ± 3%, respectively. A model, based on transmission line theory for the nanowires is presented to explain the disparity in results between the nanowires and flat surface of the same materials.

  9. Zinc Oxide Nanowire Interphase for Enhanced Lightweight Polymer Fiber Composites

    NASA Technical Reports Server (NTRS)

    Sodano, Henry A.; Brett, Robert

    2011-01-01

    The objective of this work was to increase the interfacial strength between aramid fiber and epoxy matrix. This was achieved by functionalizing the aramid fiber followed by growth of a layer of ZnO nanowires on the fiber surface such that when embedded into the polymer, the load transfer and bonding area could be substantially enhanced. The functionalization procedure developed here created functional carboxylic acid surface groups that chemically interact with the ZnO and thus greatly enhance the strength of the interface between the fiber and the ZnO.

  10. Stirring-assisted assembly of nanowires at liquid-solid interfaces

    NASA Astrophysics Data System (ADS)

    Li, Wen-Ze; Wei, Wei; Chen, Jun-Yi; He, Ji-Xiang; Xue, Sheng-Nan; Zhang, Jing; Liu, Xia; Li, Xiang; Fu, Yu; Jiao, Yong-Hua; Zhang, Kai; Liu, Fuchun; Han, En-Hou

    2013-03-01

    The assembly of Ag nanowires on quartz substrates from suspensions of water and ethylene glycol under stirring has been investigated. The introduction of stirring makes a remarkable difference to the assembly morphology. Firstly, the surface coverage of Ag nanowires is increased by a factor of 4 (in water) and 8 (in ethylene glycol) with stirring. Secondly, the Ag nanowires assembled in the stirred ethylene glycol dispersion were highly aligned. The influence of the surface of substrates, solvents and profile of the nanowires on the alignment has been explored, which indicates that stirring is an efficient way to generate nanowire arrays. This study has revealed the great potential of the stirring-assisted assembly technique in producing structurally controlled nanoarchitectures, opening up new opportunities for manufacturing ordered nanomaterials.

  11. Synthesis and supramolecular assembly of biomimetic polymers

    NASA Astrophysics Data System (ADS)

    Marciel, Amanda Brittany

    A grand challenge in materials chemistry is the synthesis of macromolecules and polymers with precise shapes and architectures. Polymer microstructure and architecture strongly affect the resulting functionality of advanced materials, yet understanding the static and dynamic properties of these complex macromolecules in bulk has been difficult due to their inherit polydispersity. Single molecule studies have provided a wealth of information on linear flexible and semi-flexible polymers in dilute solutions. However, few investigations have focused on industrially relevant complex topologies (e.g., star, comb, hyperbranched polymers) in industrially relevant solution conditions (e.g., semi-dilute, concentrated). Therefore, from this perspective there is a strong need to synthesize precision complex architectures for bulk studies as well as complex architectures compatible with current single molecule techniques to study static and dynamic polymer properties. In this way, we developed a hybrid synthetic strategy to produce branched polymer architectures based on chemically modified DNA. Overall, this approach enables control of backbone length and flexibility, as well as branch grafting density and chemical identity. We utilized a two-step scheme based on enzymatic incorporation of non-natural nucleotides containing bioorthogonal dibenzocyclooctyne (DBCO) functional groups along the main polymer backbone, followed by copper-free "click" chemistry to graft synthetic polymer branches or oligonucleotide branches to the DNA backbone, thereby allowing for the synthesis of a variety of polymer architectures, including three-arm stars, H-polymers, graft block copolymers, and comb polymers for materials assembly and single molecule studies. Bulk materials properties are also affected by industrial processing conditions that alter polymer morphology. Therefore, in an alternative strategy we developed a microfluidic-based approach to assemble highly aligned synthetic

  12. Nanostructured assemblies from amphiphilic ABC multiblock polymers

    NASA Astrophysics Data System (ADS)

    Hillmyer, Marc A.

    2012-02-01

    Amphiphilic AB diblock copolymers containing a water compatible segment can self-assemble in aqueous media to give supramolecular structures that include simple spherical micelles and macromolecular vesicles termed polymersomes. Amphiphilic ABA triblocks with hydrophobic end blocks can adopt analogous structures but can also form gels at high polymer concentrations. The structural and chemical diversity demonstrated in block copolymer micelles and gels makes them attractive for applications ranging from drug delivery to personal care products to nanoreactors. The inclusion of a third block in amphiphilic ABC triblock systems can lead to a much wider array of self-assembled structures that depend not only on composition but also on block sequence, architecture and incompatibility considerations. I will present our recent efforts on tuning micelle and gel structure and behavior using controlled architecture ABC triblocks. The combination of diverse polymer segments into a single macromolecule is a powerful method for development of self-assembled structures with both new form and new function.

  13. Electric-field assisted growth and self-assembly of intrinsic silicon nanowires.

    PubMed

    Englander, Ongi; Christensen, Dane; Kim, Jongbaeg; Lin, Liwei; Morris, Stephen J S

    2005-04-01

    Electric-field assisted growth and self-assembly of intrinsic silicon nanowires, in-situ, is demonstrated. The nanowires are seen to respond to the presence of a localized DC electric field set up between adjacent MEMS structures. The response is expressed in the form of improved nanowire order, alignment, and organization while transcending a gap. This process provides a simple yet reliable method for enhanced control over intrinsic one-dimensional nanostructure placement and handling. PMID:15826112

  14. Controlled assembly of multi-segment nanowires by histidine-tagged peptides

    NASA Astrophysics Data System (ADS)

    Wang, Aijun A.; Lee, Joun; Jenikova, Gabriela; Mulchandani, Ashok; Myung, Nosang V.; Chen, Wilfred

    2006-07-01

    A facile technique was demonstrated for the controlled assembly and alignment of multi-segment nanowires using bioengineered polypeptides. An elastin-like-polypeptide (ELP)-based biopolymer consisting of a hexahistine cluster at each end (His6-ELP-His6) was generated and purified by taking advantage of the reversible phase transition property of ELP. The affinity between the His6 domain of biopolymers and the nickel segment of multi-segment nickel/gold/nickel nanowires was exploited for the directed assembly of nanowires onto peptide-functionalized electrode surfaces. The presence of the ferromagnetic nickel segments on the nanowires allowed the control of directionality by an external magnetic field. Using this method, the directed assembly and positioning of multi-segment nanowires across two microfabricated nickel electrodes in a controlled manner was accomplished with the expected ohmic contact.

  15. Strong carrier lifetime enhancement in GaAs nanowires coated with semiconducting polymer.

    PubMed

    Yong, Chaw Keong; Noori, Keian; Gao, Qiang; Joyce, Hannah J; Tan, H Hoe; Jagadish, Chennupati; Giustino, Feliciano; Johnston, Michael B; Herz, Laura M

    2012-12-12

    The ultrafast charge carrier dynamics in GaAs/conjugated polymer type II heterojunctions are investigated using time-resolved photoluminescence spectroscopy at 10 K. By probing the photoluminescence at the band edge of GaAs, we observe strong carrier lifetime enhancement for nanowires blended with semiconducting polymers. The enhancement is found to depend crucially on the ionization potential of the polymers with respect to the Fermi energy level at the surface of the GaAs nanowires. We attribute these effects to electron doping by the polymer which reduces the unsaturated surface-state density in GaAs. We find that when the surface of nanowires is terminated by native oxide, the electron injection across the interface is greatly reduced and such surface doping is absent. Our results suggest that surface engineering via π-conjugated polymers can substantially improve the carrier lifetime in nanowire hybrid heterojunctions with applications in photovoltaics and nanoscale photodetectors. PMID:23171081

  16. Investigation of fluidic assembly of nanowires using a droplet inside microchannels

    NASA Astrophysics Data System (ADS)

    Salalha, Wael; Zussman, Eyal

    2005-06-01

    Nanowires are common building blocks for the bottom-up assembly of electronic and photonic devices. A significant challenge is to introduce a single nanowire into an oriented assembly in order to express its unique anisotropic properties or to fabricate a nanodevice. In this work we focused on the development of a micrometer length scale approach, based on a fluidic method for alignment and assembling of nanowires. The alignment is achieved by manipulating a droplet composed of a dilute nanowire suspension by creating thermocapillary motion inside a microchannel. Our purpose is to explore the nanowires' alignment mechanism in the middle region between the droplet's front and rear menisci, and their interaction with the free surface and the contact lines. Experimental results show that nanowires which are found in the middle region of the droplet are generally aligned with the flow direction. Nanowires which reach the front meniscus move together with the displacing fluid which undergoes a "rolling" type motion, and are finally adsorbed to the surface of the microchannel. The adsorbed nanowires were found in most cases to align with the droplet's flow direction. However, in certain cases nanowires may become reoriented by the passage of the rear-contact line.

  17. Porous Cu Nanowire Aerosponges from One-Step Assembly and their Applications in Heat Dissipation.

    PubMed

    Jung, Sung Mi; Preston, Daniel J; Jung, Hyun Young; Deng, Zhengtao; Wang, Evelyn N; Kong, Jing

    2016-02-17

    Highly porous metal nanowire aerosponges are produced by direct assembly of the Cu nanowire in situ during their synthesis. Such a method offers not only great simplicity, but also excellent properties such as extremely low densities, high electrical conductivities, and remarkable mechanical properties. Furthermore, these Cu aerosponges exhibit excellent wicking behavior, suggesting their potential for heat-exchange applications in heat pipes. PMID:26635235

  18. Directed Assembly of Biological Polymers

    NASA Astrophysics Data System (ADS)

    Miller, Aline

    2009-03-01

    The self-assembly of polypeptides into beta-sheet rich nanofibrils has attracted considerable attention in recent years to both understand amyloidgenesis and for their potential biomaterials applications. This self-assembly process is generic to all proteins where fibrillation is typically induced under harsh conditions of low pH and/or high temperature, which are of course not suitable for biomaterials applications. Here we will outline the method developed in our laboratory to create thermo-reversible fibrillar hydrogels from aqueous solutions of a series of proteins by adding a reductant. Proteins studied include beta-lactoglobulin, ovalbimum, lysozyme and bovine serum albimum; all contain an increasing number of disulfide bridges that are disrupted by the reductant. Such disruption destabilises the native state of the protein and this allows us to form transparent, self-supporting hydrogels under physiological conditions. The potential to control and manipulate the gel properties, including mechanical strength and structure (fibre diameter and mesh size of hydrogel) has been explored by varying the protein (consequently the number of disulfide bridges), protein concentration, reductant concentration and ionic strength of the matrix. Our results will be presented here and similarities and differences highlighted. Furthermore we will present both our 2- and 3-dimensional cell culture experiments that show the gel matrix promotes both fibroblast and chondrocyte cell spreading, attachment and proliferation; indicating our hydrogels gels are biocompatible and they can provide a viable support for different cell types.

  19. Collaborative Investigations of Supramolecular Polymer Assembly Processes.

    NASA Astrophysics Data System (ADS)

    Wooley, Karen

    2007-03-01

    It is a pleasure to participate in this symposium, honoring Darrin J. Pochan's awarding of the John H. Dillon Medal for advancing our understanding of the physics of assembly and chain conformation of synthetic polypeptides. Assemblies of polypeptides, polysaccharides and polymers of nucleic acids are, of course, complex natural systems that form the bases of life. Over the past three years, we have worked together as a highly interdisciplinary team of investigators, to investigate the self assembly behaviors and resulting morphologies for synthetic amphiphilic block copolymer systems. This presentation will highlight the findings from these collaborative studies, including the importance of the block copolymer composition and topology and the significance of the assembly conditions.

  20. Tailoring Dielectric Properties and Energy Density of Ferroelectric Polymer Nanocomposites by High-k Nanowires.

    PubMed

    Wang, Guanyao; Huang, Xingyi; Jiang, Pingkai

    2015-08-19

    High dielectric constant (k) polymer nanocomposites have shown great potential in dielectric and energy storage applications in the past few decades. The introduction of high-k nanomaterials into ferroelectric polymers has proven to be a promising strategy for the fabrication of high-k nanocomposites. One-dimensional large-aspect-ratio nanowires exhibit superiority in enhancing k values and energy density of polymer nanocomposites in comparison to their spherical counterparts. However, the impact of their intrinsic properties on the dielectric properties of polymer nanocomposites has been seldom investigated. Herein, four kinds of nanowires (Na2Ti3O7, TiO2, BaTiO3, and SrTiO3) with different inherent characteristics are elaborately selected to fabricate high-k ferroelectric polymer nanocomposites. Dopamine functionalization facilitates the excellent dispersion of these nanowires in the ferroelectric polymer matrix because of the strong polymer/nanowire interfacial adhesion. A thorough comparative study on the dielectric properties and energy storage capability of the nanowires-based nanocomposites has been presented. The results reveal that, among the four types of nanowires, BaTiO3 NWs show the best potential in improving the energy storage capability of the proposed nanocomposites, resulting from the most signficant increase of k while retaining the rather low dielectric loss and leakage current. PMID:26225887

  1. Directed Assembly of Nanofilled Polymer Thin Films

    NASA Astrophysics Data System (ADS)

    Karim, Alamgir

    Facile directed self-assembly (DSA) of multicomponent thin films is important for potential technological applications. This requires a fine control of a complex interplay of processing parameters that need to be properly optimized for different organized structures. This talk will discuss some of our recent success towards realizing tunable DSA of soft matter multicomponent systems involving a dispersion of polymer-grafted nanoparticles in block copolymer or homopolymer matrices. DSA methods for such multicomponent films will be discussed. These include the use of zone-annealing with soft-shear to create highly anisotropic nanoparticle arrays, while direct immersion annealing (DIA) has been used to order nanoparticle filled films by dipping the films into controlled solvent quality solvent mixtures. A recently observed phenomena of confinement driven entropic order and phase segregation of polymer grafted nanoparticles in similar and dissimilar polymer matrices in melt state will be discussed. A high density of nano particles of different types ranging from metallic to inorganic to organic were patterned almost exclusively into channels via topographical soft confinement using entropic forces. Enthalpic interactions between the nanoparticle grafted layer and the polymer matrix could be used as a further handle to tune the directed assembly of the nanoparticles. The phenomena will be discussed in terms of confinement parameters, partition coefficient, free energy gain and entropic versus enthalpic interactions.

  2. The fabrication of polycrystalline silver nanowires via self-assembled nanotubes at controlled temperature

    NASA Astrophysics Data System (ADS)

    Liu, Jui-Hsiang; Tsai, Ching-Yi; Chiu, Yi-Hong; Hsieh, Feng-Ming

    2009-01-01

    We report a novel method for the fabrication of silver nanowires under controlled conditions. Silver nanoparticles were synthesized using a surfactant of octanoic acid via a reverse micelle technique. Hollow nanotubes were prepared under various controlled conditions through self-assembly of surfactant clusters of reversed micelles containing silver nanoparticles. These organized nanotubes were used as a structure-directing template for the preparation of silver nanowires. This is a bottom-up technique for the fabrication of silver nanowires. Self-assembled nanotube construction and the cross section of the nanotubes were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. From the results, reasonable schematic representations of the formation of self-assembled nanoparticles and nanowires were proposed. Further sintering treatment at 500 °C burned away the organic compounds and left silver nanowires. The construction of the nanowires was confirmed using SEM, x-ray diffraction (XRD), and energy dispersive x-ray analysis (EDXA). This paper demonstrates that silver nanowires can be fabricated via self-assembled nanoparticles at a controlled low temperature.

  3. The fabrication of polycrystalline silver nanowires via self-assembled nanotubes at controlled temperature.

    PubMed

    Liu, Jui-Hsiang; Tsai, Ching-Yi; Chiu, Yi-Hong; Hsieh, Feng-Ming

    2009-01-21

    We report a novel method for the fabrication of silver nanowires under controlled conditions. Silver nanoparticles were synthesized using a surfactant of octanoic acid via a reverse micelle technique. Hollow nanotubes were prepared under various controlled conditions through self-assembly of surfactant clusters of reversed micelles containing silver nanoparticles. These organized nanotubes were used as a structure-directing template for the preparation of silver nanowires. This is a bottom-up technique for the fabrication of silver nanowires. Self-assembled nanotube construction and the cross section of the nanotubes were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. From the results, reasonable schematic representations of the formation of self-assembled nanoparticles and nanowires were proposed. Further sintering treatment at 500 degrees C burned away the organic compounds and left silver nanowires. The construction of the nanowires was confirmed using SEM, x-ray diffraction (XRD), and energy dispersive x-ray analysis (EDXA). This paper demonstrates that silver nanowires can be fabricated via self-assembled nanoparticles at a controlled low temperature. PMID:19417290

  4. Macroscopic assembly of indefinitely long and parallel nanowires into large area photodetection circuitry.

    PubMed

    Ozgur, Erol; Aktas, Ozan; Kanik, Mehmet; Yaman, Mecit; Bayindir, Mehmet

    2012-05-01

    Integration of nanowires into functional devices with high yields and good reliability turned out to be a lot more challenging and proved to be a critical issue obstructing the wide application of nanowire-based devices and exploitation of their technical promises. Here we demonstrate a relatively easy macrofabrication of a nanowire-based imaging circuitry using a recently developed nanofabrication technique. Extremely long and polymer encapsulated semiconducting nanowire arrays, mass-produced using the iterative thermal drawing, facilitate the integration process; we manually aligned the fibers containing selenium nanowires over a lithographically defined circuitry. Controlled etching of the encapsulating polymer revealed a monolayer of nanowires aligned over an area of 1 cm(2) containing a 10 × 10 pixel array. Each light-sensitive pixel is formed by the contacting hundreds of parallel photoconductive nanowires between two electrodes. Using the pixel array, alphabetic characters were identified by the circuitry to demonstrate its imaging capacity. This new approach makes it possible to devise extremely large nanowire devices on planar, flexible, or curved substrates with diverse functionalities such as thermal sensors, phase change memory, and artificial skin. PMID:22494446

  5. Electrical conductivity studies on individual conjugated polymer nanowires: two-probe and four-probe results.

    PubMed

    Long, Yunze; Duvail, Jeanluc; Li, Mengmeng; Gu, Changzhi; Liu, Zongwen; Ringer, Simon P

    2009-01-01

    Two- and four-probe electrical measurements on individual conjugated polymer nanowires with different diameters ranging from 20 to 190 nm have been performed to study their conductivity and nanocontact resistance. The two-probe results reveal that all the measured polymer nanowires with different diameters are semiconducting. However, the four-probe results show that the measured polymer nanowires with diameters of 190, 95-100, 35-40 and 20-25 nm are lying in the insulating, critical, metallic and insulting regimes of metal-insulator transition, respectively. The 35-40 nm nanowire displays a metal-insulator transition at around 35 K. In addition, it was found that the nanocontact resistance is in the magnitude of 104Ω at room temperature, which is comparable to the intrinsic resistance of the nanowires. These results demonstrate that four-probe electrical measurement is necessary to explore the intrinsic electronic transport properties of isolated nanowires, especially in the case of metallic nanowires, because the metallic nature of the measured nanowires may be coved by the nanocontact resistance that cannot be excluded by a two-probe technique. PMID:20652139

  6. Cationic Antimicrobial Polymers and Their Assemblies

    PubMed Central

    Carmona-Ribeiro, Ana Maria; de Melo Carrasco, Letícia Dias

    2013-01-01

    Cationic compounds are promising candidates for development of antimicrobial agents. Positive charges attached to surfaces, particles, polymers, peptides or bilayers have been used as antimicrobial agents by themselves or in sophisticated formulations. The main positively charged moieties in these natural or synthetic structures are quaternary ammonium groups, resulting in quaternary ammonium compounds (QACs). The advantage of amphiphilic cationic polymers when compared to small amphiphilic molecules is their enhanced microbicidal activity. Besides, many of these polymeric structures also show low toxicity to human cells; a major requirement for biomedical applications. Determination of the specific elements in polymers, which affect their antimicrobial activity, has been previously difficult due to broad molecular weight distributions and random sequences characteristic of radical polymerization. With the advances in polymerization control, selection of well defined polymers and structures are allowing greater insight into their structure-antimicrobial activity relationship. On the other hand, antimicrobial polymers grafted or self-assembled to inert or non inert vehicles can yield hybrid antimicrobial nanostructures or films, which can act as antimicrobials by themselves or deliver bioactive molecules for a variety of applications, such as wound dressing, photodynamic antimicrobial therapy, food packing and preservation and antifouling applications. PMID:23665898

  7. Self-assembly mechanism of Ni nanowires prepared with an external magnetic field.

    PubMed

    Li, Xiaoyu; Wang, Hu; Xie, Kenan; Long, Qin; Lai, Xuefei; Liao, Li

    2015-01-01

    Nickel nanowires with a mean diameter of about 95 nm and lengths of up to 26 μm were prepared by a chemical reduction method in aqueous solution under an external magnetic field. The self-assembly mechanism was investigated in detail. The results indicate that the self-assembly process of Ni nanowires consists of three stages: nucleation and growth, ordered alignment and self-assembly, and deposition on the surface and gaps between the nickel particles. The self-assembly phenomenon occurs only when nickel particles grow to a size of about 60 nm in the reaction system. This critical size, which is proposed for the first time, is very important to comprehend the self-assembly mechanism of Ni nanowires prepared with an external magnetic field. PMID:26665084

  8. Self-assembly mechanism of Ni nanowires prepared with an external magnetic field

    PubMed Central

    Li, Xiaoyu; Wang, Hu; Xie, Kenan; Long, Qin; Lai, Xuefei

    2015-01-01

    Summary Nickel nanowires with a mean diameter of about 95 nm and lengths of up to 26 μm were prepared by a chemical reduction method in aqueous solution under an external magnetic field. The self-assembly mechanism was investigated in detail. The results indicate that the self-assembly process of Ni nanowires consists of three stages: nucleation and growth, ordered alignment and self-assembly, and deposition on the surface and gaps between the nickel particles. The self-assembly phenomenon occurs only when nickel particles grow to a size of about 60 nm in the reaction system. This critical size, which is proposed for the first time, is very important to comprehend the self-assembly mechanism of Ni nanowires prepared with an external magnetic field. PMID:26665084

  9. Self-Assembly of a Functional Oligo(Aniline)-Based Amphiphile into Helical Conductive Nanowires

    PubMed Central

    2015-01-01

    A tetra(aniline)-based cationic amphiphile, TANI-NHC(O)C5H10N(CH3)3+Br– (TANI-PTAB) was synthesized, and its emeraldine base (EB) state was found to self-assemble into nanowires in aqueous solution. The observed self-assembly is described by an isodesmic model, as shown by temperature-dependent UV–vis investigations. Linear dichroism (LD) studies, combined with computational modeling using time-dependent density functional theory (TD-DFT), suggests that TANI-PTAB molecules are ordered in an antiparallel arrangement within nanowires, with the long axis of TANI-PTAB arranged perpendicular to the nanowire long axis. Addition of either S- or R- camphorsulfonic acid (CSA) to TANI-PTAB converted TANI to the emeraldine salt (ES), which retained the ability to form nanowires. Acid doping of TANI-PTAB had a profound effect on the nanowire morphology, as the CSA counterions’ chirality translated into helical twisting of the nanowires, as observed by circular dichroism (CD). Finally, the electrical conductivity of CSA-doped helical nanowire thin films processed from aqueous solution was 2.7 mS cm–1. The conductivity, control over self-assembled 1D structure and water-solubility demonstrate these materials’ promise as processable and addressable functional materials for molecular electronics, redox-controlled materials and sensing. PMID:26496508

  10. Self-assembly of semiconductor organogelator nanowires for photoinduced charge separation.

    PubMed

    Wicklein, André; Ghosh, Suhrit; Sommer, Michael; Würthner, Frank; Thelakkat, Mukundan

    2009-05-26

    We investigated an innovative concept of general validity based on an organogel/polymer system to generate donor-acceptor nanostructures suitable for charge generation and charge transport. An electron conducting (acceptor) perylene bisimide organogelator forms nanowires in suitable solvents during gelation process. This phenomenon was utilized for its self-assembly in an amorphous hole conducting (donor) polymer matrix to realize an interpenetrating donor-acceptor interface with inherent morphological stability. The self-assembly and interface generation were carried out either stepwise or in a single-step. Morphology of the donor-acceptor network in thin films obtained via both routes were studied by a combination of scanning electron microscopy and atomic force microscopy. Additionally, photoinduced charge separation and charge transport in these systems were tested in organic solar cells. Fabrication steps of multilayer organogel/polymer photovoltaic devices were optimized with respect to morphology and surface roughness by introducing additional smoothening layers and charge injection/blocking layers. An inverted cell geometry was used here in which electrons are collected at the bottom electrode and holes at the top electrode. The simultaneous preparation of the interface exhibits almost 3-fold improvement in device characteristics compared to the successive method. The device characteristics under AM1.5 spectral conditions and 100 mW/cm(2) for the simultaneous preparation route are short circuit current J(sc) = 0.28 mA cm(-2), open circuit voltage V(OC) = 390 mV, fill factor FF = 38%, and a power conversion efficiency eta = 0.041%. PMID:19408933

  11. Nanoparticles in Polymers: Assembly, Rheology and Properties

    NASA Astrophysics Data System (ADS)

    Rao, Yuanqiao

    Inorganic nanoparticles have the potential of providing functionalities that are difficult to realize using organic materials; and nanocomposites is an effective mean to impart processibility and construct bulk materials with breakthrough properties. The dispersion and assembly of nanoparticles are critical to both processibility and properties of the resulting product. In this talk, we will discuss several methods to control the hierarchical structure of nanoparticles in polymers and resulting rheological, mechanical and optical properties. In one example, polymer-particle interaction and secondary microstructure were designed to provide a low viscosity composition comprising exfoliated high aspect ratio clay nanoparticles; in another example, the microstructure control through templates was shown to enable unique thermal mechanical and optical properties. Jeff Munro, Stephanie Potisek, Phillip Hustad; all of the Dow Chemical Company are co-authors.

  12. Self-assembled GaN nanowires on diamond.

    PubMed

    Schuster, Fabian; Furtmayr, Florian; Zamani, Reza; Magén, Cesar; Morante, Joan R; Arbiol, Jordi; Garrido, Jose A; Stutzmann, Martin

    2012-05-01

    We demonstrate the nucleation of self-assembled, epitaxial GaN nanowires (NWs) on (111) single-crystalline diamond without using a catalyst or buffer layer. The NWs show an excellent crystalline quality of the wurtzite crystal structure with m-plane faceting, a low defect density, and axial growth along the c-axis with N-face polarity, as shown by aberration corrected annular bright-field scanning transmission electron microscopy. X-ray diffraction confirms single domain growth with an in-plane epitaxial relationship of (10 ̅10)(GaN) [parallel] (01 ̅1)(Diamond) as well as some biaxial tensile strain induced by thermal expansion mismatch. In photoluminescence, a strong and sharp excitonic emission reveals excellent optical properties superior to state-of-the-art GaN NWs on silicon substrates. In combination with the high-quality diamond/NW interface, confirmed by high-resolution transmission electron microscopy measurements, these results underline the potential of p-type diamond/n-type nitride heterojunctions for efficient UV optoelectronic devices. PMID:22506554

  13. Synergistic Assembly of Covalent and Supramolecular Polymers.

    PubMed

    Bai, Linyi; Zhao, Yanli

    2016-06-01

    Integrating irreplaceable features of both covalent chemistry and noncovalent interactions into a single entity to maximize the applicability is highly desired. Here, a discovery of this type of hybrid, developed by Stupp and co-workers, is developed, where a synergistic combination of covalent and noncovalent compartments enables them to assemble by each other perfectively. The covalent compartments can grow into polymer chains assisted by a supramolecular compartment. The supramolecular compartments can be reversibly removed and re-formed to reconstitute the hybrid structure. The obtained soft materials can serve as functional platforms for molecular delivery or self-repairing materials. PMID:27076255

  14. Self-assembled nanowire array capacitors: capacitance and interface state profile

    NASA Astrophysics Data System (ADS)

    Li, Qiliang; Xiong, Hao D.; Liang, Xuelei; Zhu, Xiaoxiao; Gu, Diefeng; Ioannou, Dimitris E.; Baumgart, Helmut; Richter, Curt A.

    2014-04-01

    Direct characterization of the capacitance and interface states is very important for understanding the electronic properties of a nanowire transistor. However, the capacitance of a single nanowire is too small to precisely measure. In this work we have fabricated metal-oxide-semiconductor capacitors based on a large array of self-assembled Si nanowires. The capacitance and conductance of the nanowire array capacitors are directly measured and the interface state profile is determined by using the conductance method. We demonstrate that the nanowire array capacitor is an effective platform for studying the electronic properties of nanoscale interfaces. This approach provides a useful and efficient metrology for the study of the physics and device properties of nanoscale metal-oxide-semiconductor structures.

  15. Flow-enabled self-assembly of large-scale aligned nanowires.

    PubMed

    Li, Bo; Zhang, Chuchu; Jiang, Beibei; Han, Wei; Lin, Zhiqun

    2015-03-27

    One-dimensional nanowires enable the realization of optical and electronic nanodevices that may find applications in energy conversion and storage systems. Herein, large-scale aligned DNA nanowires were crafted by flow-enabled self-assembly (FESA). The highly oriented and continuous DNA nanowires were then capitalized on either as a template to form metallic nanowires by exposing DNA nanowires that had been preloaded with metal salts to an oxygen plasma or as a scaffold to direct the positioning and alignment of metal nanoparticles and nanorods. The FESA strategy is simple and easy to implement and thus a promising new method for the low-cost synthesis of large-scale one-dimensional nanostructures for nanodevices. PMID:25689374

  16. Directed organization of gold nanoclusters on silver nanowires: A step forward in heterostructure assembly

    NASA Astrophysics Data System (ADS)

    Sharma, Jadab; Vivek, J. P.; Vijayamohanan, Kunjukrishna P.; Singh, Poonam; Dharmadhikari, C. V.

    2006-05-01

    We investigate the directed assembly of tridecylamine protected gold nanoclusters of 4-5nm size on functionalized silver nanowires of 55-60nm diameter and the electron transfer behavior of this integrated structure using transmission electron microscopy, non-contact atomic force microscopy, and scanning tunneling microscopy/spectroscopy. Linear I-V for bare silver nanowire suggests metallic behavior but high tunnel resistance indicates presence of insulating layer on the surface. Identical I-Vs obtained for isolated gold nanoparticle and heterostructure suggests that electron transport across nanowires in the latter is governed by gold nanoparticles in contrast to expected ballistic or diffusive transport along their length.

  17. Ultrathin W18O49 nanowire assemblies for electrochromic devices.

    PubMed

    Liu, By Jian-Wei; Zheng, Jing; Wang, Jin-Long; Xu, Jie; Li, Hui-Hui; Yu, Shu-Hong

    2013-08-14

    Ordered W18O49 nanowire thin films were fabricated by Langmuir-Blodgett (LB) technique in the presence of poly(vinyl pyrrolidone) coating. The well-organized monolayer of W18O49 nanowires with periodic structures can be readily used as electrochromic sensors, showing reversibly switched electrochromic properties between the negative and positive voltage. Moreover, the electrochromism properties of the W18O49 nanowire films exhibit significant relationship with their thickness. The coloration/bleaching time was around 2 s for the W18O49 nanowire monolayer, which is much faster than the traditional tungsten oxide nanostructures. Moreover, the nanowire devices display excellent stability when color switching continues, which may provide a versatile and promising platform for electrochromism device, smart windows, and other applications. PMID:23869487

  18. Nanowires and Nanostructures That Grow Like Polymer Molecules

    SciTech Connect

    Shaw, Santosh; Cademartiri, Ludovico

    2013-09-20

    Unique properties (e.g., rubber elasticity, viscoelasticity, folding, reptation) determine the utility of polymer molecules and derive from their morphology (i.e., one-dimensional connectivity and large aspect ratios) and flexibility. Crystals do not display similar properties because they have smaller aspect ratios, they are rigid, and they are often too large and heavy to be colloidally stable. We argue, with the support of recent experimental studies, that these limitations are not fundamental and that they might be overcome by growth processes that mimic polymerization. Furthermore, we (i) discuss the similarities between crystallization and polymerization, (ii) critically review the existing experimental evidence of polymer-like growth kinetic and behavior in crystals and nanostructures, and (iii) propose heuristic guidelines for the synthesis of “polymer-like” crystals and assemblies. Understanding these anisotropic materials at the boundary between molecules and solids will determine whether we can confer the unique properties of polymer molecules to crystals, expanding them with topology, dynamics, and information and not just tuning them with size.

  19. Metal-conductive polymer hybrid nanostructures: preparation and electrical properties of palladium-polyimidazole nanowires.

    PubMed

    Al-Hinai, Mariam; Hassanien, Reda; Watson, Scott M D; Wright, Nicholas G; Houlton, Andrew; Horrocks, Benjamin R

    2016-03-01

    A simple, convenient method for the formation of hybrid metal/conductive polymer nanostructures is described. Polyimidazole (PIm) has been templated on λ-DNA via oxidative polymerisation of imidazole using FeCl3 to produce conductive PIm/DNA nanowires. The PIm/DNA nanowires were decorated with Pd (Pd/PIm/DNA) by electroless reduction of PdCl4(-2) with NaBH4 in the presence of PIm/DNA; the choice of imidazole was motivated by the potential Pd(II) binding site at the pyridinic N atom. The formation of PIm/DNA and the presence of metallic Pd on Pd/PIm/DNA nanowires were verified by FTIR, UV-vis and XPS spectroscopy techniques. AFM studies show that the nanowires have diameters in the range 5-45 nm with a slightly greater mean diameter (17.1 ± 0.75 nm) for the Pd-decorated nanowires than the PIm/DNA nanowires (14.5 ± 0.89 nm). After incubation for 24 h in the polymerisation solution, the PIm/DNA nanowires show a smooth, uniform morphology, which is retained after decoration with Pd. Using a combination of scanned conductance microscopy, conductive AFM and two-terminal measurements we show that both types of nanowire are conductive and that it is possible to discriminate different possible mechanisms of transport. The conductivity of the Pd/PIm/DNA nanowires, (0.1-1.4 S cm(-1)), is comparable to the PIm/DNA nanowires (0.37 ± 0.029 S cm(-1)). In addition, the conductance of Pd/PIm/DNA nanowires exhibits Arrhenius behaviour (E(a )= 0.43 ± 0.02 eV) as a function of temperature in contrast to simple Pd/DNA nanowires. These results indicate that although the Pd crystallites on Pd/PIm/DNA nanowires decorate the PIm polymer, the major current pathway is through the polymer rather than the Pd. PMID:26855053

  20. Metal-conductive polymer hybrid nanostructures: preparation and electrical properties of palladium-polyimidazole nanowires

    NASA Astrophysics Data System (ADS)

    Al-Hinai, Mariam; Hassanien, Reda; Watson, Scott M. D.; Wright, Nicholas G.; Houlton, Andrew; Horrocks, Benjamin R.

    2016-03-01

    A simple, convenient method for the formation of hybrid metal/conductive polymer nanostructures is described. Polyimidazole (PIm) has been templated on λ-DNA via oxidative polymerisation of imidazole using FeCl3 to produce conductive PIm/DNA nanowires. The PIm/DNA nanowires were decorated with Pd (Pd/PIm/DNA) by electroless reduction of {{{{PdCl}}}4}2- with NaBH4 in the presence of PIm/DNA; the choice of imidazole was motivated by the potential Pd(II) binding site at the pyridinic N atom. The formation of PIm/DNA and the presence of metallic Pd on Pd/PIm/DNA nanowires were verified by FTIR, UV-vis and XPS spectroscopy techniques. AFM studies show that the nanowires have diameters in the range 5-45 nm with a slightly greater mean diameter (17.1 ± 0.75 nm) for the Pd-decorated nanowires than the PIm/DNA nanowires (14.5 ± 0.89 nm). After incubation for 24 h in the polymerisation solution, the PIm/DNA nanowires show a smooth, uniform morphology, which is retained after decoration with Pd. Using a combination of scanned conductance microscopy, conductive AFM and two-terminal measurements we show that both types of nanowire are conductive and that it is possible to discriminate different possible mechanisms of transport. The conductivity of the Pd/PIm/DNA nanowires, (0.1-1.4 S cm-1), is comparable to the PIm/DNA nanowires (0.37 ± 0.029 S cm-1). In addition, the conductance of Pd/PIm/DNA nanowires exhibits Arrhenius behaviour (E a = 0.43 ± 0.02 eV) as a function of temperature in contrast to simple Pd/DNA nanowires. These results indicate that although the Pd crystallites on Pd/PIm/DNA nanowires decorate the PIm polymer, the major current pathway is through the polymer rather than the Pd.

  1. Evaporation-Induced Self-Assembly of Ultrathin Tungsten Oxide Nanowires over a Large Scale for Ultraviolet Photodetector.

    PubMed

    Cheng, Wei; Niederberger, Markus

    2016-03-15

    Self-assembly of inorganic nanowires on a large scale directly on a substrate represents a great challenge. Starting from colloidally stable dispersions of ultrathin tungsten oxide nanowires, we successfully assemble the nanowires on a centimeter scale on flat or patterned substrates by a simple evaporation-induced self-assembly method. The capillary flow generated during the evaporation is responsible for the assembly of the nanowires. The concentration of the nanowire dispersion has a significant influence on the self-assembly behavior. Well-aligned tungsten oxide nanowire thin films are achieved when the concentration of the dispersion is in the range from 0.5 to 3.0 mg/mL. While at higher concentrations disordered nanowire thin films with cracks are formed, lower concentrations do not result in the formation of a continuous thin film. A macroscopic device based on the self-assembled tungsten oxide nanowires is fabricated, exhibiting good performance for UV light detection. Our results may pave the road for integrating aligned ultrathin semiconductor nanowires into macroscopic devices for optoelectronic applications. PMID:26900019

  2. Polymer chain alignment and transistor properties of nanochannel-templated poly(3-hexylthiophene) nanowires

    NASA Astrophysics Data System (ADS)

    Oh, Seungjun; Hayakawa, Ryoma; Pan, Chengjun; Sugiyasu, Kazunori; Wakayama, Yutaka

    2016-08-01

    Nanowires of semiconducting poly(3-hexylthiophene) (P3HT) were produced by a nanochannel-template technique. Polymer chain alignment in P3HT nanowires was investigated as a function of nanochannel widths (W) and polymer chain lengths (L). We found that the ratio between chain length and channel width (L/W) was a key parameter as regards promoting polymer chain alignment. Clear dichroism was observed in polarized ultraviolet-visible (UV-Vis) absorption spectra only at a ratio of approximately L/W = 2, indicating that the L/W ratio must be optimized to achieve uniaxial chain alignment in the nanochannel direction. We speculate that an appropriate L/W ratio is effective in confining the geometries and conformations of polymer chains. This discussion was supported by theoretical simulations based on molecular dynamics. That is, the geometry of the polymer chains, including the distance and tilting angles of the chains in relation to the nanochannel surface, was dominant in determining the longitudinal alignment along the nanochannels. Thus prepared highly aligned polymer nanowire is advantageous for electrical carrier transport and has great potential for improving the device performance of field-effect transistors. In fact, a one-order improvement in carrier mobility was observed in a P3HT nanowire transistor.

  3. Development of Hierarchical Polymer@Pd Nanowire-Network: Synthesis and Application as Highly Active Recyclable Catalyst and Printable Conductive Ink.

    PubMed

    Mir, Sajjad Husain; Ochiai, Bungo

    2016-06-01

    A facile one-pot approach for preparing hierarchical nanowire-networks of hollow polymer@Pd nanospheres is reported. First, polymer@Pd hollow nanospheres were produced through metal-complexation-induced phase separation with functionalized graft copolymers and subsequent self-assembly of PdNPs. The nanospheres hierarchically assembled into the nanowire-network upon drying. The Pd nanowire-network served as an active catalyst for Mizoroki-Heck and Suzuki-Miyaura coupling reactions. As low as 500 μmol % Pd was sufficient for quantitative reactions, and the origin of the high activity is ascribed to the highly active sites originating from high-index facets, kinks, and coalesced structures. The catalyst can be recycled via simple filtration and washing, maintaining its high activity owing to the micrometer-sized hierarchical structure of the nanomaterial. The polymer@Pd nanosphere also served as a printable conductive ink for a translucent grid pattern with excellent horizontal conductivity (7.5×10(5) S m(-1)). PMID:27551657

  4. Grooved nanowires from self-assembling hairpin molecules for solar cells.

    PubMed

    Tevis, Ian D; Tsai, Wei-Wen; Palmer, Liam C; Aytun, Taner; Stupp, Samuel I

    2012-03-27

    One of the challenges facing bulk heterojunction organic solar cells is obtaining organized films during the phase separation of intimately mixed donor and acceptor components. We report here on the use of hairpin-shaped sexithiophene molecules to generate by self-assembly grooved nanowires as the donor component in bulk heterojunction solar cells. Photovoltaic devices were fabricated via spin-casting to produce by solvent evaporation a percolating network of self-assembled nanowires and fullerene acceptors. Thermal annealing was found to increase power conversion efficiencies by promoting domain growth while still maintaining this percolating network of nanostructures. The benefits of self-assembly and grooved nanowires were examined by building devices from a soluble sexithiophene derivative that does not form one-dimensional structures. In these systems, excessive phase separation caused by thermal annealing leads to the formation of defects and lower device efficiencies. We propose that the unique hairpin shape of the self-assembling molecules allows the nanowires as they form to interact well with the fullerenes in receptor-ligand type configurations at the heterojunction of the two domains, thus enhancing device efficiencies by 23%. PMID:22397738

  5. Synthesis of diphenylalanine/polyaniline core/shell conducting nanowires by peptide self-assembly.

    PubMed

    Ryu, Jungki; Park, Chan Beum

    2009-01-01

    Breaking the mold: Self-assembled peptide nanowires were used as a template for the synthesis of hollow polyaniline (PANI) nanotubes (see scanning electron microscopy images). The thickness and the morphology of the PANI nanostructures could be controlled readily either by varying the reaction time or by applying multiple PANI coatings. PMID:19466726

  6. Carbonaceous Nanowire Supports for Polymer Electrolyte Membrane Fuel Cells

    SciTech Connect

    Garzon, Fernando; Wilson, Mahlon; Banham, Dustin; More, Karren Leslie

    2016-01-01

    Carbohydrate-dye combinations were used to form ionically-linked soft templates for the formation of polypyrrole nanowire networks. High yields of nanostructured products were obtained using small amounts of low-cost carbohydrate and dye template materials, the majority of which remained encapsulated within the nanowires. Varying the concentration and the two-part ratio of the templates influenced the length and diameter of the nanofiber segments within the nanowire network. Pyrolysis of the nanowires yielded carbonaceous fibers containing nitrogen heteroatoms, as well as convoluted graphitic domains, well suited for supporting Pt nanoparticles. The resulting high density of nucleation sites enabled the formation of well dispersed, smaller Pt particles compared to commercial catalysts, despite significantly higher support surface loadings. (C) The Author(s) 2015. Published by ECS.

  7. Carbonaceous nanowire supports for polymer electrolyte membrane fuel cells

    SciTech Connect

    Garzon, Fernando H.; Wilson, Mahlon S.; Banham, Dustin; Ye, Siyu; More, Karren Leslie

    2015-12-03

    Here, carbohydrate-dye combinations were used to form ionically-linked soft templates for the formation of polypyrrole nanowire networks. High yields of nanostructured products were obtained using small amounts of low-cost carbohydrate and dye template materials, the majority of which remained encapsulated within the nanowires. Varying the concentration and the two-part ratio of the templates influenced the length and diameter of the nanofiber segments within the nanowire network. Pyrolysis of the nanowires yielded carbonaceous fibers containing nitrogen heteroatoms, as well as convoluted graphitic domains, well suited for supporting Pt nanoparticles. The resulting high density of nucleation sites enabled the formation of well dispersed, smaller Pt particles compared to commercial catalysts, despite significantly higher support surface loadings.

  8. Carbonaceous nanowire supports for polymer electrolyte membrane fuel cells

    DOE PAGESBeta

    Garzon, Fernando H.; Wilson, Mahlon S.; Banham, Dustin; Ye, Siyu; More, Karren Leslie

    2015-12-03

    Here, carbohydrate-dye combinations were used to form ionically-linked soft templates for the formation of polypyrrole nanowire networks. High yields of nanostructured products were obtained using small amounts of low-cost carbohydrate and dye template materials, the majority of which remained encapsulated within the nanowires. Varying the concentration and the two-part ratio of the templates influenced the length and diameter of the nanofiber segments within the nanowire network. Pyrolysis of the nanowires yielded carbonaceous fibers containing nitrogen heteroatoms, as well as convoluted graphitic domains, well suited for supporting Pt nanoparticles. The resulting high density of nucleation sites enabled the formation of wellmore » dispersed, smaller Pt particles compared to commercial catalysts, despite significantly higher support surface loadings.« less

  9. Nanostructured photovoltaic materials using block polymer assemblies

    NASA Astrophysics Data System (ADS)

    Mastroianni, Sarah Elizabeth

    Despite its potential as an abundant, sustainable alternative to non-renewable energy sources, solar energy currently is underutilized. Photovoltaics, which convert energy from sunlight into electricity, commonly are made from inorganic semiconductor materials that require expensive manufacturing and processing techniques. Alternatively, organic materials can be used to produce flexible and lightweight organic photovoltaic (OPV) devices, which can be prepared using solution-based processing techniques. However, OPV devices are limited by low efficiencies and short lifetimes compared to their inorganic counterparts. In OPV systems, charge carriers are generated in the active layer via the separation of excitons (electron-hole pairs) at interfaces between donor and acceptor materials. Because excitons have a limited diffusion length (˜10 nm), they may recombine before reaching a donor-acceptor interface if domain sizes are large. This exciton recombination can limit device efficiency; thus, the design parameters for improved active layer morphologies include large interfacial areas, small size scales, and continuous conducting pathways. Currently, most OPV devices are prepared by blending donor and acceptor materials in bulk heterojunction (BHJ) devices, often resulting in non-ideal, process-dependent morphologies. Alternatively, the self-assembly of block polymers (BP)s offers a reproducible means to generate nanostructured active layers. The work presented in this dissertation examines the synthetic approaches to preparing BPs containing different electroactive materials: non-conjugated, amorphous poly(vinyl-m-triphenylamine) [PVmTPA] and conjugated poly(3-alkythiophene) [P3AT] p-type materials as well as fullerene-based n-type materials. The synthesis and self-assembly of a model poly(methyl methacrylate)- b-PVmTPA system is presented. This work was extended to synthesize PVmTPA BPs with complementary poly(methyl methacrylate- co-hydroxyethyl methacrylate) [P

  10. A promising routine to fabricate GeSi nanowires via self-assembly on miscut Si (001) substrates

    PubMed Central

    2011-01-01

    Very small and compactly arranged GeSi nanowires could self-assembled on vicinal Si (001) substrates with ~8° off toward ⟨110⟩ during Ge deposition. The nanowires were all oriented along the miscut direction. The small ration of height over width of the nanowire indicated that the nanowires were bordered partly with {1 0 5} facets. These self-assembled small nanowires were remarkably influenced by the growth conditions and the miscut angle of substrates in comparison with large dome-like islands obtained after sufficient Ge deposition. These results proposed that the formation of the nanowire was energetically driven under growth kinetic assistance. Three-dimensionally self-assembled GeSi nanowires were first realized via multilayer Ge growth separated with Si spacers. These GeSi nanowires were readily embedded in Si matrix and compatible with the sophisticated Si technology, which suggested a feasible strategy to fabricate nanowires for fundamental studies and a wide variety of applications. PACS: 81.07.Gf, 81.16.Dn, 68.65.-k, 68.37.Ps PMID:21711814

  11. Self-assembled quantum dots in a nanowire system for quantum photonics.

    PubMed

    Heiss, M; Fontana, Y; Gustafsson, A; Wüst, G; Magen, C; O'Regan, D D; Luo, J W; Ketterer, B; Conesa-Boj, S; Kuhlmann, A V; Houel, J; Russo-Averchi, E; Morante, J R; Cantoni, M; Marzari, N; Arbiol, J; Zunger, A; Warburton, R J; Fontcuberta i Morral, A

    2013-05-01

    Quantum dots embedded within nanowires represent one of the most promising technologies for applications in quantum photonics. Whereas the top-down fabrication of such structures remains a technological challenge, their bottom-up fabrication through self-assembly is a potentially more powerful strategy. However, present approaches often yield quantum dots with large optical linewidths, making reproducibility of their physical properties difficult. We present a versatile quantum-dot-in-nanowire system that reproducibly self-assembles in core-shell GaAs/AlGaAs nanowires. The quantum dots form at the apex of a GaAs/AlGaAs interface, are highly stable, and can be positioned with nanometre precision relative to the nanowire centre. Unusually, their emission is blue-shifted relative to the lowest energy continuum states of the GaAs core. Large-scale electronic structure calculations show that the origin of the optical transitions lies in quantum confinement due to Al-rich barriers. By emitting in the red and self-assembling on silicon substrates, these quantum dots could therefore become building blocks for solid-state lighting devices and third-generation solar cells. PMID:23377293

  12. High temperature self-assembly of Ag nanowires on vicinal Si(001)

    NASA Astrophysics Data System (ADS)

    Roos, K. R.; Roos, K. L.; Horn-von Hoegen, M.; Heringdorf, F.-J. Meyer zu

    2005-04-01

    We have used low energy electron microscopy (LEEM) and photo emission electron microscopy (PEEM) to study the high temperature (620 °C) self-assembly of Ag nanowires on vicinal Si(001), miscut 4° in the [110] direction. After formation of an initial wetting layer, growth of wire-like structures proceeds with subsequent deposition. Simultaneously, compact islands form and the nanowires comprise only a minority of the total Ag deposit. The wires display quasi-one-dimensional behaviour as their length is observed to increase while their width remains constant. The lengths of the wires can be controlled and we have routinely grown wires longer than 100 µm. A kinetically limiting process, wherein mass transport is suppressed in the direction normal to the direction of elongation, is identified as a contributor to the growth of the nanowires.

  13. Chemical nano-gardens: growth of salt nanowires from supramolecular self-assembly gels.

    PubMed

    Daly, Ronan; Kotova, Oxana; Boese, Markus; Gunnlaugsson, Thorfinnur; Boland, John J

    2013-06-25

    In this article, we examine the phenomenon of single-crystal halide salt wire growth at the surface of porous materials. We report the use of a single-step casting technique with a supramolecular self-assembly gel matrix that upon drying leads to the growth of single-crystal halide (e.g., NaCl, KCl, and KI) nanowires with diameters ~130-200 nm. We demonstrate their formation using electron microscopy and electron-dispersive X-ray spectroscopy, showing that the supramolecular gel stabilizes the growth of these wires by facilitating a diffusion-driven base growth mechanism. Critically, we show that standard non-supramolecular gels are unable to facilitate nanowire growth. We further show that these nanowires can be grown by seeding, forming nanocrystal gardens. This study helps understand the possible prefunctionalization of membranes to stimulate ion-specific filters or salt efflorescence suppressors, while also providing a novel route to nanomaterial growth. PMID:23663045

  14. Zinc oxide nanowire-poly(methyl methacrylate) dielectric layers for polymer capacitive pressure sensors.

    PubMed

    Chen, Yan-Sheng; Hsieh, Gen-Wen; Chen, Shih-Ping; Tseng, Pin-Yen; Wang, Cheng-Wei

    2015-01-14

    Polymer capacitive pressure sensors based on a dielectric composite layer of zinc oxide nanowire and poly(methyl methacrylate) show pressure sensitivity in the range of 2.63 × 10(-3) to 9.95 × 10(-3) cm(2) gf(-1). This represents an increase of capacitance change by as much as a factor of 23 over pristine polymer devices. An ultralight load of only 10 mg (corresponding to an applied pressure of ∼0.01 gf cm(-2)) can be clearly recognized, demonstrating remarkable characteristics of these nanowire-polymer capacitive pressure sensors. In addition, optical transmittance of the dielectric composite layer is approximately 90% in the visible wavelength region. Their low processing temperature, transparency, and flexible dielectric film makes them a highly promising means for flexible touching and pressure-sensing applications. PMID:25494204

  15. CONDUCTING-POLYMER NANOWIRE IMMUNOSENSOR ARRAYS FOR MICROBIAL PATHOGENS

    EPA Science Inventory

    The lack of methods for routine rapid and sensitive detection and quantification of specific pathogens has limited the amount of information available on their occurrence in drinking water and other environmental samples. The nanowire biosensor arrays developed in this study w...

  16. Optical devices for ultra-compact photonic integrated circuits based on III-V/polymer nanowires

    NASA Astrophysics Data System (ADS)

    Lauvernier, D.; Garidel, S.; Zegaoui, M.; Vilcot, J. P.; Harari, J.; Magnin, V.; Decoster, D.

    2007-04-01

    We demonstrated the potential application of III-V/polymer nanowires for photonic integrated circuits in a previous paper. Hereby, we report the use of a spot size converter based on 2D reverse nanotaper structure in order to improve the coupling efficiency between the nanowire and optical fiber. A total coupling enhancement of up to a factor 60 has been measured from an 80 nm × 300 nm cross-section tip which feeds an 300 nm-side square nanowire at its both ends. Simultaneously, micro-radius bends have been fabricated to increase the circuit density; for a radius of 5 µm, the 90º bend losses were measured as low as 0.60 dB and 0.80 dB for TE and TM polarizations respectively.

  17. A one-step approach for the fabrication of polymer and metal nanowires.

    PubMed

    Gu, Hongyan; Zhu, Shiping

    2011-07-01

    The fabrication of one-dimensional (1D) polymer and metal nanowires were obtained in a one-step mechanical approach. This approach is based on a controlled chattering process at the cutting edge of an oscillating diamond knife to conduct wavy cutting. Consecutive shallow wavy cuttings at different phases yield uniform ultra-long nanowire products with controlled lateral dimensions in the range of sub-100 nanometers to micrometers. The morphologies and lateral dimensions of the nanowires can be tuned through phase alignment, cutting depth and cutting speed, as demonstrated in this paper through examples of its application to polymethyl methacrylate, aluminum and copper. This facile one-step 'cutting-edge' method is robust, clean, involves no chemicals, and can be readily scaled up with precision machining for long-range and large-area fabrications. PMID:21586814

  18. Directed Assembly of Ultrathin Gold Nanowires over Large Area by Dielectrophoresis.

    PubMed

    Venkatesh, R; Kundu, Subhajit; Pradhan, Avradip; Sai, T Phanindra; Ghosh, Arindam; Ravishankar, N

    2015-08-25

    Ultrathin Au nanowires (∼2 nm diameter) are interesting from a fundamental point of view to study structure and electronic transport and also hold promise in the field of nanoelectronics, particularly for sensing applications. Device fabrication by direct growth on various substrates has been useful in demonstrating some of the potential applications. However, the realization of practical devices requires device fabrication strategies that are fast, inexpensive, and efficient. Herein, we demonstrate directed assembly of ultrathin Au nanowires over large areas across electrodes using ac dielectrophoresis with a mechanistic understanding of the process. On the basis of the voltage and frequency, the wires either align in between or across the contact pads. We exploit this assembly to produce an array of contacting wires for statistical estimation of electrical transport with important implications for future nanoelectronic/sensor applications. PMID:26255906

  19. Fabrication and optical properties of conjugated polymer composited multi-arrays of TiO2 nanowires via sequential electrospinning.

    PubMed

    Shim, Hee-Sang; Kim, Jeong Won; Kim, Won Bae

    2009-08-01

    We report here a simple method of fabricating multi-layered architectures of cross-aligned inorganic nanowires via sequential electrospinning method equipped with a newly devised collector that is able to prepare aligned inorganic nanowires. The multi-layers of aligned TiO2 nanowires can be deposited in a proportional increment of weight with collecting time and reveal a large reduction of electrical resistance by at least 30% compared to a randomly collected TiO2 nanowire structure. The solar cell performance of the cross-aligned TiO2 nanowire layers composited with a conjugated polymer of poly[2-methoxy, 5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV) is significantly enhanced by 70% or greater in the organic-inorganic hybrid photovoltaic devices than that fabricated with the randomly-collected TiO2 nanowire photoanode. PMID:19928140

  20. Zinc oxide nanowire interphase for enhanced interfacial strength in lightweight polymer fiber composites.

    PubMed

    Ehlert, Gregory J; Sodano, Henry A

    2009-08-01

    A novel functionalization method for aramid fibers is developed to enhance the bonding of a ZnO nanowire interphase grown on the fiber surface for interfacial strength enhancement. The nanowire interphase functionally grades the typically discrete interface and reduces the stress concentration between the fiber and matrix. The functionalization process is developed to improve the bonding between the ZnO nanowires and the aramid fiber and is validated through Fourier transform IR and X-ray photoelectron spectroscopy studies. Mechanical testing shows significant improvement in the interfacial shear strength with no decrease in the base fiber strength. This is the only technique found in the literature for the growth of a nanowire interphase on polymer fibers for structural enhancement without degrading the in-plane properties of the bulk composite. Furthermore, it is firmly shown that the functionalization process is a necessary condition for enhanced interfacial strength, demonstrating that ZnO nanowires strongly interact with carboxylic acid functional groups. PMID:20355800

  1. Development of multifunctional fiber reinforced polymer composites through ZnO nanowire arrays

    NASA Astrophysics Data System (ADS)

    Malakooti, Mohammad H.; Patterson, Brendan A.; Hwang, Hyun-Sik; Sodano, Henry A.

    2016-04-01

    Piezoelectric nanowires, in particular zinc oxide (ZnO) nanowires, have been vastly used in the fabrication of electromechanical devices to convert wasted mechanical energy into useful electrical energy. Over recent years, the growth of vertically aligned ZnO nanowires on various structural fibers has led to the development of fiber-based nanostructured energy harvesting devices. However, the development of more realistic energy harvesters that are capable of continuous power generation requires a sufficient mechanical strength to withstand typical structural loading conditions. Yet, a durable, multifunctional material system has not been developed thoroughly enough to generate electrical power without deteriorating the mechanical performance. Here, a hybrid composite energy harvester is fabricated in a hierarchical design that provides both efficient power generating capabilities while enhancing the structural properties of the fiber reinforced polymer composite. Through a simple and low-cost process, a modified aramid fabric with vertically aligned ZnO nanowires grown on the fiber surface is embedded between woven carbon fabrics, which serve as the structural reinforcement as well as the top and the bottom electrodes of the nanowire arrays. The performance of the developed multifunctional composite is characterized through direct vibration excitation and tensile strength examination.

  2. Non-resonant Mie scattering: Emergent optical properties of core-shell polymer nanowires

    PubMed Central

    Khudiyev, Tural; Huseyinoglu, Ersin; Bayindir, Mehmet

    2014-01-01

    We provide the in-depth characterization of light-polymer nanowire interactions in the context of an effective Mie scattering regime associated with low refractive index materials. Properties of this regime sharply contrast with these of resonant Mie scattering, and involve the formation of strictly forward-scattered and coupling-free optical fields in the vicinity of core-shell polymer nanowires. Scattering from these optical fields is shown to be non-resonant in nature and independent from incident polarization. In order to demonstrate the potential utility of this scattering regime in one-dimensional (1D) polymeric nanostructures, we fabricate polycarbonate (PC) - polyvinylidene difluoride (PVDF) core-shell nanowires using a novel iterative thermal drawing process that yields uniform and indefinitely long core-shell nanostructures. These nanowires are successfully engineered for novel nanophotonics applications, including size-dependent structural coloration, efficient light capture on thin-film solar cells, optical nano-sensors with ultrahigh sensitivity and a mask-free photolithography method suitable for the straightforward production of 1D nanopatterns. PMID:24714206

  3. Self-assembled DNA nanostructures and DNA-templated silver nanowires

    NASA Astrophysics Data System (ADS)

    Park, Sung Ha

    DNA-based nanotechnology has been attractive as a novel assembly method for fabricating nanostructures for the last two decades. Artificially designed, self-assembled DNA nanostructures have been reported with various geometrical structures and functionalities: one- and two-dimensional periodically patterned structures, three-dimensional polyhedra, nanomechanical devices, molecular computers, and organization of other functionalized molecules. This thesis describes self-assembled DNA nanostructures and DNA-templated metallic nanowires. One- and two-dimensional periodically patterned superstructures, such as filaments, lattices, nanoribbons, nanotracks, and nanogrids, utilizing newly conceived two distinct DNA motifs---three helix bundles, and the cross-tiles as well as synthetic double-stranded DNA molecules---will be discussed with unique design schemes and characteristics. DNA complexes have been visualized by high-resolution tapping mode atomic force microscopy under buffer. Their dimensions are shown to be in excellent agreement with designed structures. We have also presented fabrication of size-controllable, fully addressable, and precisely programmable DNA-based nanomatrices, consisting of two different cross-tiles using a novel stepwise assembly technique. Especially in design and construction of functionalized electronic nanodevices, properly fabricated DNA lattices can serve as a precisely controllable and programmable scaffold for organizing functionalized nanomaterials. DNA-templated metallic nanowires are an example demonstration of DNA molecules' scaffold capability and have been considered an interesting research subject for the last decade. Until recently, mostly native lambda-DNA molecules have been used as template for fabricating various metallic nanowires, such as silver, gold, palladium, platinum, and copper. In this thesis, we also present fabrication of metallic silver nanowires templated on artificially designed one-dimensional DNA

  4. Simple assembly of long nanowires through substrate stretching

    NASA Astrophysics Data System (ADS)

    Dong, Jianjin; Mohieddin Abukhdeir, Nasser; Goldthorpe, Irene A.

    2015-12-01

    Although nanowire (NW) alignment has been previously investigated, minimizing limitations such as process complexity and NW breakage, as well as quantifying the quality of alignment, have not been sufficiently addressed. A simple, low cost, large-area, and versatile alignment method is reported that is applicable for NWs either grown on a substrate or synthesized in solution. Metal and semiconductor NWs with average lengths of up to 16 μm are aligned through the stretching of polyvinyl alcohol (PVA) films, which compared to other stretching methods results in superior alignment because of the large stretching ratio of PVA. Poly[oxy(methyl-1,2-ethanediyl)] is employed as lubricant to prevent NW breakage. To quantify NW alignment, a simple and effective image processing method is presented. The alignment process results in an order parameter (S) of NW alignment as high as 0.97.

  5. Self-Assembled DNA Templated Nano-wires and Circuits

    NASA Astrophysics Data System (ADS)

    Braun, Erez

    2000-03-01

    The realization that conventional microelectronics is approaching its miniaturization limits has motivated the search for an alternative route based on self-assembled nanometer-scale electronics. We have recently proposed a new approach based on the hybridization of biological and electronic materials (Braun E., Eichen Y., Sivan U. and Ben-Yoseph G., Nature 391, 775 (1998)). The concept relies on a two-step self-assembly process. The inherent molecular recognition capabilities of DNA molecules are first utilized to construct a network that serves as a template for the subsequent assembly of electronic materials into a circuit. The utilization of DNA and its associated enzymatic machinery enables: (a) self-assembly of complex substrates, (b) specific molecular addresses for the localization of electronic materials (e.g., gold colloids) by standard molecular biology techniques, (c) interdevice wiring and (d) bridging the microscopic structures to the macroscopic world. The self-assembly of nanometer scale electronics relies on two complementary developments. First, the ability to convert DNA molecules into thin conductive wires and second, the self-assembly of complex extended DNA templates. Our progress in these two directions will be presented. Regarding the first issue, a physical process resulting in condensation of gold colloids onto DNA molecules enables the assembly of thin gold wires (around 100-200 A wide) having, in principle, unlimited extensions. The second issue is developed in the context of recombinant DNA which allows the self-assembly of precise molecular junctions and networks. Specifically, we use RecA protein, which is the main protein responsible for genetic recombination in E. Coli bacteria, to construct DNA junctions at pre-designed addresses (sequences) on the molecules. The integration of these processes allows advancing nanometer-scale electronics. A realistic fabrication scheme for a room-temperature single-electron transistor

  6. Solution-Processed Donor-Acceptor Polymer Nanowire Network Semiconductors For High-Performance Field-Effect Transistors

    PubMed Central

    Lei, Yanlian; Deng, Ping; Li, Jun; Lin, Ming; Zhu, Furong; Ng, Tsz-Wai; Lee, Chun-Sing; Ong, Beng S.

    2016-01-01

    Organic field-effect transistors (OFETs) represent a low-cost transistor technology for creating next-generation large-area, flexible and ultra-low-cost electronics. Conjugated electron donor-acceptor (D-A) polymers have surfaced as ideal channel semiconductor candidates for OFETs. However, high-molecular weight (MW) D-A polymer semiconductors, which offer high field-effect mobility, generally suffer from processing complications due to limited solubility. Conversely, the readily soluble, low-MW D-A polymers give low mobility. We report herein a facile solution process which transformed a lower-MW, low-mobility diketopyrrolopyrrole-dithienylthieno[3,2-b]thiophene (I) into a high crystalline order and high-mobility semiconductor for OFETs applications. The process involved solution fabrication of a channel semiconductor film from a lower-MW (I) and polystyrene blends. With the help of cooperative shifting motion of polystyrene chain segments, (I) readily self-assembled and crystallized out in the polystyrene matrix as an interpenetrating, nanowire semiconductor network, providing significantly enhanced mobility (over 8 cm2V−1s−1), on/off ratio (107), and other desirable field-effect properties that meet impactful OFET application requirements. PMID:27091315

  7. Solution-Processed Donor-Acceptor Polymer Nanowire Network Semiconductors For High-Performance Field-Effect Transistors

    NASA Astrophysics Data System (ADS)

    Lei, Yanlian; Deng, Ping; Li, Jun; Lin, Ming; Zhu, Furong; Ng, Tsz-Wai; Lee, Chun-Sing; Ong, Beng S.

    2016-04-01

    Organic field-effect transistors (OFETs) represent a low-cost transistor technology for creating next-generation large-area, flexible and ultra-low-cost electronics. Conjugated electron donor-acceptor (D-A) polymers have surfaced as ideal channel semiconductor candidates for OFETs. However, high-molecular weight (MW) D-A polymer semiconductors, which offer high field-effect mobility, generally suffer from processing complications due to limited solubility. Conversely, the readily soluble, low-MW D-A polymers give low mobility. We report herein a facile solution process which transformed a lower-MW, low-mobility diketopyrrolopyrrole-dithienylthieno[3,2-b]thiophene (I) into a high crystalline order and high-mobility semiconductor for OFETs applications. The process involved solution fabrication of a channel semiconductor film from a lower-MW (I) and polystyrene blends. With the help of cooperative shifting motion of polystyrene chain segments, (I) readily self-assembled and crystallized out in the polystyrene matrix as an interpenetrating, nanowire semiconductor network, providing significantly enhanced mobility (over 8 cm2V‑1s‑1), on/off ratio (107), and other desirable field-effect properties that meet impactful OFET application requirements.

  8. Solution-Processed Donor-Acceptor Polymer Nanowire Network Semiconductors For High-Performance Field-Effect Transistors.

    PubMed

    Lei, Yanlian; Deng, Ping; Li, Jun; Lin, Ming; Zhu, Furong; Ng, Tsz-Wai; Lee, Chun-Sing; Ong, Beng S

    2016-01-01

    Organic field-effect transistors (OFETs) represent a low-cost transistor technology for creating next-generation large-area, flexible and ultra-low-cost electronics. Conjugated electron donor-acceptor (D-A) polymers have surfaced as ideal channel semiconductor candidates for OFETs. However, high-molecular weight (MW) D-A polymer semiconductors, which offer high field-effect mobility, generally suffer from processing complications due to limited solubility. Conversely, the readily soluble, low-MW D-A polymers give low mobility. We report herein a facile solution process which transformed a lower-MW, low-mobility diketopyrrolopyrrole-dithienylthieno[3,2-b]thiophene (I) into a high crystalline order and high-mobility semiconductor for OFETs applications. The process involved solution fabrication of a channel semiconductor film from a lower-MW (I) and polystyrene blends. With the help of cooperative shifting motion of polystyrene chain segments, (I) readily self-assembled and crystallized out in the polystyrene matrix as an interpenetrating, nanowire semiconductor network, providing significantly enhanced mobility (over 8 cm(2)V(-1)s(-1)), on/off ratio (10(7)), and other desirable field-effect properties that meet impactful OFET application requirements. PMID:27091315

  9. Suppression of Low-Frequency Electronic Noise in Polymer Nanowire Field-Effect Transistors.

    PubMed

    Lezzi, Francesca; Ferrari, Giorgio; Pennetta, Cecilia; Pisignano, Dario

    2015-11-11

    The authors report on the reduction of low-frequency noise in semiconductor polymer nanowires with respect to thin-films made of the same organic material. Flicker noise is experimentally investigated in polymer nanowires in the range of 10-10(5) Hz by means of field-effect transistor architectures. The noise in the devices is well described by the Hooge empirical model and exhibits an average Hooge constant, which describes the current power spectral density of fluctuations, suppressed by 1-2 orders of magnitude compared to thin-film devices. To explain the Hooge constant reduction, a resistor network model is developed, in which the organic semiconducting nanostructures or films are depicted through a two-dimensional network of resistors with a square-lattice structure, accounting for the different anisotropy and degree of structural disorder of the active nanowires and films. Results from modeling agree well with experimental findings. These results support enhanced structural order through size-confinement in organic nanostructures as effective route to improve the noise performance in polymer electronic devices. PMID:26479330

  10. Nonlinear optical studies of aqueous interfaces, polymers, and nanowires

    NASA Astrophysics Data System (ADS)

    Onorato, Robert Michael

    -transfer-to-solvent band and a Langmuir adsorption model are used to determine the affinity of bromide for both the air/water and dodecanol/water interfaces in the molar concentration regime. The Gibbs free energy of adsorption for the former is determined to be -1.4 kJ/mol with a lower 90% confidence limit of -4.1 kJ/mol. For the dodecanol/water interface the data are best fit with a Gibbs free energy of +8 kJ/mol with an estimated a lower limit of -4 kJ/mol. Adsorption of ions to the air/water interface in the millimolar regime is a particularly interesting phenomenon. In Chapter 4, the affinity of sodium chloride and sodium bromide to the air/water interface is probed by UV-SHG. Both salts exhibit a strong adsorption, with free energies greater than -20 kJ/mol. Interestingly, sodium chloride exhibits a stronger affinity for the interface than does sodium iodide, which was previously studied by Poul Peterson. This is counter to both experimental and theoretical results for higher concentrations. It has been predicted that ion adsorption is dictated by strong and opposing electrostatic and entropic forces. The change in order of ion interfacial affinity can be explained by relatively small changes in these forces at different concentrations and ionic strengths. In Chapters 5 and 6, other work using nonlinear optical techniques is described. Coherent anti-Stokes Raman scattering microscopy is a promising tool for chemically selective imaging based on molecular vibrations. While CARS is currently used as a biological imaging tool, many variations are still being developed, perhaps the most important being multiplex CARS microscopy. Multiplex CARS has the advantage of comparing images based on different molecular vibrations without changing the excitation wavelengths. In Chapter 5, I demonstrate both high spectral and spatial resolution multiplex CARS imaging of polymer films using a simple scheme for chirped CARS with a spectral bandwidth of 300 cm-1. In Chapter 6, the nonlinear optical

  11. Recent advances in large-scale assembly of semiconducting inorganic nanowires and nanofibers for electronics, sensors and photovoltaics.

    PubMed

    Long, Yun-Ze; Yu, Miao; Sun, Bin; Gu, Chang-Zhi; Fan, Zhiyong

    2012-06-21

    Semiconducting inorganic nanowires (NWs), nanotubes and nanofibers have been extensively explored in recent years as potential building blocks for nanoscale electronics, optoelectronics, chemical/biological/optical sensing, and energy harvesting, storage and conversion, etc. Besides the top-down approaches such as conventional lithography technologies, nanowires are commonly grown by the bottom-up approaches such as solution growth, template-guided synthesis, and vapor-liquid-solid process at a relatively low cost. Superior performance has been demonstrated using nanowires devices. However, most of the nanowire devices are limited to the demonstration of single devices, an initial step toward nanoelectronic circuits, not adequate for production on a large scale at low cost. Controlled and uniform assembly of nanowires with high scalability is still one of the major bottleneck challenges towards the materials and device integration for electronics. In this review, we aim to present recent progress toward nanowire device assembly technologies, including flow-assisted alignment, Langmuir-Blodgett assembly, bubble-blown technique, electric/magnetic- field-directed assembly, contact/roll printing, planar growth, bridging method, and electrospinning, etc. And their applications in high-performance, flexible electronics, sensors, photovoltaics, bioelectronic interfaces and nano-resonators are also presented. PMID:22573265

  12. Assembly and performance of silicone polymer waveguides

    NASA Astrophysics Data System (ADS)

    Lostutter, Calob K.; Hodge, Malcolm H.; Marrapode, Thomas R.; Swatowski, Brandon W.; Weidner, W. Ken

    2016-03-01

    We report on the functionality and key performance properties of 50 μm x 50 μm flexible graded index silicone polymer waveguides. The materials show low optical propagation losses of < 0.04 dB/cm @ 850 nm over 1 m lengths as well as stability to 2000 hours 85°C/85% relative humidity and 5 cycles of 260°C solder wave reflow testing. Methods to fabricate large area panels are demonstrated for scaled manufacturing of polymer based optical printed wiring boards. The polymer waveguides are terminated with a passive direct fiber attach method. Fully MPO connectorized waveguide panels are realized and their optical performance properties assessed.

  13. Self-assembling of molecular nanowires for enhancing the conducting properties of discotic liquid crystals

    NASA Astrophysics Data System (ADS)

    Park, Ji Hyun; Kim, Kyung Ho; Takanishi, Yoichi; Yamamoto, Jun; Park, Yung Woo; Kim, Youn Sang; Scalia, Giusy

    2015-08-01

    The self-organization of discotic liquid crystal molecules in columns has enormous interest for soft nanoelectronic applications. A great advantage of discotic liquid crystal is that defects can be self-annealed in contrast to typical organic materials. Through the overlap of molecular orbitals, the aromatic cores assemble into long range ordered one-dimensional structures. Very thin structured films can be obtained by spin-coating from solution and the resulting morphologies are strongly dependent on the interaction between discotics and solvent molecules. Toluene produces films formed by very long nanowires, spontaneously aligned along a common direction and over fairly large areas. These nanostructured films are a result of the interplay between liquid crystal self-organization and solvent driven assembly. The ordered nanowire structures exhibit improvement in the electrical properties compared to misaligned structures and even to pristine HAT5, deposited without the aid of solvent. In this study we show that the toluene-based deposition of discotic liquid crystals is advantageous because it allows a uniform coverage of the substrate, unlike pristine HAT5 but also thanks to the type of induced structures exhibiting one order of magnitude higher conductivity, in the aligned nanowire films, compared to bare HAT5 ones.

  14. Nanowire polarizers by guided self-assembly of block copolymers

    NASA Astrophysics Data System (ADS)

    Roberts, Philip M. S.; Baum, Alexandra; Karamath, James; Evans, Allan; Shibata, Satoshi; Walton, Harry

    2014-01-01

    Wire-grid polarizers (WGPs) are currently limited by their wafer-scale manufacturing methods to sizes of approximately 12 to 18 in. For large-size displays, a new method for the production of large-area WGPs is required. Large-area WGPs were simulated using the finite-difference-time-domain method, and a scaleable method for their production based on a block copolymer (BCP)-nanostructured template was implemented. The nanostructured template is globally aligned through the use of a cylinder-forming liquid crystal (LC) diblock copolymer, which is first aligned on a rubbed polyimide substrate. A surface-relief template is produced using the differential dry etch rates of the cylinder-forming component and LC polymer matrix component of the BCP. The template is metalized to produce a WGP. Polarizers of arbitrary size with polarization efficiency up to 0.6 have been made in close agreement with calculated values for idealized structures. The choice of the cylinder-forming polymer is critical to the degree of alignment of the template, and the thermal stability of the LC polymer matrix is critical to the stability of the template during etching.

  15. Design directed self-assembly of donor-acceptor polymers.

    PubMed

    Marszalek, Tomasz; Li, Mengmeng; Pisula, Wojciech

    2016-09-21

    Donor-acceptor polymers with an alternating array of donor and acceptor moieties have gained particular attention during recent years as active components of organic electronics. By implementation of suitable subunits within the conjugated backbone, these polymers can be made either electron-deficient or -rich. Additionally, their band gap and light absorption can be precisely tuned for improved light-harvesting in solar cells. On the other hand, the polymer design can also be modified to encode the desired supramolecular self-assembly in the solid-state that is essential for an unhindered transport of charge carriers. This review focuses on three major factors playing a role in the assembly of donor-acceptor polymers on surfaces which are (1) nature, geometry and substitution position of solubilizing alkyl side chains, (2) shape of the conjugated polymer defined by the backbone curvature, and (3) molecular weight which determines the conjugation length of the polymer. These factors adjust the fine balance between attractive and repulsive forces and ensure a close polymer packing important for an efficient charge hopping between neighboring chains. On the microscopic scale, an appropriate domain formation with a low density of structural defects in the solution deposited thin film is crucial for the charge transport. The charge carrier transport through such thin films is characterized by field-effect transistors as basic electronic elements. PMID:27440174

  16. Self-assembled metallic nanowire-based vertical organic field-effect transistor.

    PubMed

    Ben-Sasson, Ariel J; Azulai, Daniel; Gilon, Hagit; Facchetti, Antonio; Markovich, Gil; Tessler, Nir

    2015-02-01

    We report on in situ, self-assembly, solution-processing of metallic (Au/Ag) nanowire-based transparent electrodes integrated to vertical organic field-effect transistors (VOFETs). In the VOFET architecture, the nanowires' microstructure facilitates current modulation by the gate across the otherwise shielding sandwiched source electrode. We show N-type VOFETs operation with on/off ratio ∼1 × 10(5) and high current density (>1 mA cm(-2) at VDS = 5 V). The integration of the device design and the transparent electrode deposition methods offers a potential route for all-solution processing-based, large-area, high-efficiency organic electronics. PMID:25602371

  17. Plasmonic nanocomposites: polymer-guided strategies for assembling metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Gao, Bo; Rozin, Matthew J.; Tao, Andrea R.

    2013-06-01

    Noble metal nanoparticles that support localized surface plasmon resonances (LSPRs) have the unique ability to manipulate and confine light at subwavelength dimensions. Utilizing these capabilities in devices and coatings requires the controlled organization of metal nanoparticles into ordered or hierarchical structures. Polymer grafts can be used as assembly-regulating molecules that bind to the nanoparticle surface and guide nanoparticle organization in solution, at interfaces, and within condensed phases. Here, we present an overview of polymer-directed assembly of plasmonic nanoparticles. We discuss how polymer grafts can be used to control short-range nanoparticle interactions that dictate interparticle gap distance and orientation. We also discuss how condensed polymer grafts can be used to control long-range order within condensed nanoparticle-polymer blends. The assembly of shaped plasmonic nanoparticles that have potential applications in enhanced spectroscopy and optical metamaterials is highlighted. We end with a summary of promising new directions toward the fabrication of plasmonic nanocomposites that are responsive and possess three-dimensional order.

  18. Facile preparation of transparent and conductive polymer films based on silver nanowire/polycarbonate nanocomposites

    NASA Astrophysics Data System (ADS)

    Moreno, Ivan; Navascues, Nuria; Arruebo, Manuel; Irusta, Silvia; Santamaria, Jesus

    2013-07-01

    Silver nanowires (AgNW) synthesized by a solvothermal method were incorporated into a polycarbonate matrix by a solution mixing procedure. Films with a thickness around 18 μm were obtained, showing a good distribution of the wires within the polymer matrix. The thermal stability of the polymer matrix increased significantly, with the main decomposition peak shifting up to 74 ° C for an AgNW loading of 4.35 wt%. The percolation threshold was obtained at very low AgNW content (0.04 wt%), and the composite electrical conductivity at the maximum loading (4.35 wt%) was 41.3 Ω cm. Excellent transparency was obtained at the percolation threshold, with negligible reduction in the transmittance of the polymer matrix (from 88.2 to 87.6% at 0.04 wt% loading of AgNW). In addition, the polymer matrix protected the silver nanowires from oxidation, as demonstrated by the XPS analysis.

  19. Facile preparation of transparent and conductive polymer films based on silver nanowire/polycarbonate nanocomposites.

    PubMed

    Moreno, Ivan; Navascues, Nuria; Arruebo, Manuel; Irusta, Silvia; Santamaria, Jesus

    2013-07-12

    Silver nanowires (AgNW) synthesized by a solvothermal method were incorporated into a polycarbonate matrix by a solution mixing procedure. Films with a thickness around 18 μm were obtained, showing a good distribution of the wires within the polymer matrix. The thermal stability of the polymer matrix increased significantly, with the main decomposition peak shifting up to 74 ° C for an AgNW loading of 4.35 wt%. The percolation threshold was obtained at very low AgNW content (0.04 wt%), and the composite electrical conductivity at the maximum loading (4.35 wt%) was 41.3 Ω cm. Excellent transparency was obtained at the percolation threshold, with negligible reduction in the transmittance of the polymer matrix (from 88.2 to 87.6% at 0.04 wt% loading of AgNW). In addition, the polymer matrix protected the silver nanowires from oxidation, as demonstrated by the XPS analysis. PMID:23743565

  20. Supramolecular polymer formed by reversible self-assembly of tetrakisporphyrin

    PubMed Central

    Haino, Takeharu; Fujii, Takashi; Watanabe, Akihide; Takayanagi, Urara

    2009-01-01

    S-shaped tetrakisporphyrin 2 forms supramolecular polymeric assemblies via a complementary affinity of its bisporphyrin units in solution. The self-association constant determined by applying the isodesmic model is >106 L mol−1, which suggests that a sizable polymer forms at millimolar concentrations at room temperature. The electron deficient aromatic guest (TNF) binds within the molecular clefts provided by the bisporphyrin units via a charge-transfer interaction. This guest complexation completely disrupts supramolecular polymeric assembly. The long, fibrous fragments of the polymeric assemblies were characterized by atomic-force microscopy imaging of a film cast on a mica surface. The polymeric assemblies have lengths of >1μm and show a coiled structure with a higher level of organization. The approach discussed in this report concerning the quick preparation of supramolecular polymeric assemblies driven by noncovalent forces sets the stage for the preparation of a previously undescribed class of macromolecular porphyrin architectures. PMID:19289843

  1. Modular, polymer-directed nanoparticle assembly for fabricating metamaterials.

    PubMed

    Laxminarayana, Gurunatha K; Rozin, Matthew; Smith, Stephanie; Tao, Andrea R

    2016-04-12

    We achieve the fabrication of plasmonic meta-atoms by utilizing a novel, modular approach to nanoparticle self-assembly that utilizes polymer templating to control meta-atom size and geometry. Ag nanocubes are deposited and embedded into a polymer thin-film, where the polymer embedding depth is used to dictate which nanocube faces are available for further nanocrystal binding. Horizontal and vertical nanocube dimers were successfully fabricated with remarkably high yield using a bifunctional molecular linker to bind a second nanocube. Surface plasmon coupling can be readily tuned by varying the size, shape, and orientation of the second nanoparticle. We show that meta-atoms can be fabricated to exhibit angle- and polarization-dependent optical properties. This scalable technique for meta-atom assembly can be used to fabricate large-area metasurfaces for polarization- and phase-sensitive applications, such as optical sensing. PMID:26818438

  2. Cationic polymers and their self-assembly for antibacterial applications.

    PubMed

    Deka, Smriti Rekha; Sharma, Ashwani Kumar; Kumar, Pradee

    2015-01-01

    The present article focuses on the amphiphilic cationic polymers as antibacterial agents. These polymers undergo self-assembly in aqueous conditions and impart biological activity by efficiently interacting with the bacterial cell wall, hence, used in preparing chemical disinfectants and biocides. Both cationic charge as well as hydrophobic segments facilitate interactions with the bacterial cell surface and initiate its disruption. The perturbation in transmembrane potential causes leakage of cytosolic contents followed by cell death. Out of two categories of macromolecules, peptide oligomers and cationic polymers, which have extensively been used as antibacterials, we have elaborated on the current advances made in the area of cationic polymer-based (naturally occurring and commonly employed synthetic polymers and their modified analogs) antibacterial agents. The development of polymer-based antibacterials has helped in addressing challenges posed by the drug-resistant bacterial infections. These polymers provide a new platform to combat such infections in the most efficient manner. This review presents concise discussion on the amphiphilic cationic polymers and their modified analogs having low hemolytic activity and excellent antibacterial activity against array of fungi, bacteria and other microorganisms. PMID:25858132

  3. Polymer electrolyte membrane assembly for fuel cells

    NASA Technical Reports Server (NTRS)

    Yen, Shiao-Ping S. (Inventor); Kindler, Andrew (Inventor); Yavrouian, Andre (Inventor); Halpert, Gerald (Inventor)

    2002-01-01

    An electrolyte membrane for use in a fuel cell can contain sulfonated polyphenylether sulfones. The membrane can contain a first sulfonated polyphenylether sulfone and a second sulfonated polyphenylether sulfone, wherein the first sulfonated polyphenylether and the second sulfonated polyphenylether sulfone have equivalent weights greater than about 560, and the first sulfonated polyphenylether and the second sulfonated polyphenylether sulfone also have different equivalent weights. Also, a membrane for use in a fuel cell can contain a sulfonated polyphenylether sulfone and an unsulfonated polyphenylether sulfone. Methods for manufacturing a membrane electrode assemblies for use in fuel cells can include roughening a membrane surface. Electrodes and methods for fabricating such electrodes for use in a chemical fuel cell can include sintering an electrode. Such membranes and electrodes can be assembled into chemical fuel cells.

  4. Polymer electrolyte membrane assembly for fuel cells

    NASA Technical Reports Server (NTRS)

    Yen, Shiao-Ping S. (Inventor); Kindler, Andrew (Inventor); Yavrouian, Andre (Inventor); Halpert, Gerald (Inventor)

    2000-01-01

    An electrolyte membrane for use in a fuel cell can contain sulfonated polyphenylether sulfones. The membrane can contain a first sulfonated polyphenylether sulfone and a second sulfonated polyphenylether sulfone, wherein the first sulfonated polyphenylether and the second sulfonated polyphenylether sulfone have equivalent weights greater than about 560, and the first sulfonated polyphenylether and the second sulfonated polyphenylether sulfone also have different equivalent weights. Also, a membrane for use in a fuel cell can contain a sulfonated polyphenylether sulfone and an unsulfonated polyphenylether sulfone. Methods for manufacturing a membrane electrode assemblies for use in fuel cells can include roughening a membrane surface. Electrodes and methods for fabricating such electrodes for use in a chemical fuel cell can include sintering an electrode. Such membranes and electrodes can be assembled into chemical fuel cells.

  5. Field-effect memory transistors based on arrays of nanowires of a ferroelectric polymer

    NASA Astrophysics Data System (ADS)

    Cai, Ronggang; Kassa, Hailu G.; Marrani, Alessio; van Breemen, Albert J. J. M.; Gelinck, Gerwin H.; Nysten, Bernard; Hu, Zhijun; Jonas, Alain M.

    2015-09-01

    Ferroelectric poly(vinylidene fluoride-co-trifluoroethylene), P(VDF-TrFE), is increasingly used in organic non-volatile memory devices, e.g., in ferroelectric field effect transistors (FeFETs). Here, we report on FeFETs integrating nanoimprinted arrays of P(VDF-TrFE) nanowires. Two previously-unreported architectures are tested, the first one consisting of stacked P(VDF-TrFE) nanowires placed over a continuous semiconducting polymer film; the second one consisting of a nanostriped blend layer wherein the semiconducting and ferroelectric components alternate regularly. The devices exhibit significant reversible memory effects, with operating voltages reduced compared to their continuous film equivalent, and with different possible geometries of the channels of free charge carriers accumulating in the semiconductor.

  6. Excitation of surface plasmons from silver nanowires embedded in polymer nanofibers.

    PubMed

    Li, Juan; Zhang, Weina; Li, Qiuguo; Li, Baojun

    2015-02-21

    We report an excitation of surface plasmons in silver nanowires (AgNWs) which were embedded in flexible polymer nanofibers. Using waveguiding excitation, surface plasmons in AgNWs were excited and propagated. By directing light of 650, 532, and 473 nm wavelengths into the nanofiber, surface plasmons in an embedded single AgNW (average diameter 400 nm, length 4.3 μm) were excited and the corresponding propagation lengths for the three wavelengths are 10.6, 7.7, and 5.1 μm. It was also found that, when a spatially incoherent white light of a halogen lamp with an excitation optical power of 80 μW was coupled into the polymer nanofiber, a surface plasmon mediated interference fringe was observed. In addition, on the basis of surface plasmon excitation, two adjacent AgNWs embedded in the polymer nanofibers were demonstrated to serve as coupled plasmonic waveguides. PMID:25620621

  7. Particle-Directed Assembly of Semiflexible Polymer Chains

    NASA Astrophysics Data System (ADS)

    McGovern, Michael; Dorfman, Kevin; Morse, David

    We use molecular dynamics simulations to investigate several models of semiflexible polymers that exhibit an attractive interaction with spherical particles. The organization of semiflexible polymer chains through attractive interactions with spherical particles occurs in several important processes in nature, such as the winding of DNA around histones and counter-ion condensation of charged polymers. The process is also of technological interest in the packaging of DNA for delivery to cells. In this presentation, we will present data on both the phase behavior and the kinetics of self-assembly as a function of the stiffness of the polymers, the attractive potential between the monomers and the particles, and the relative size of the monomers and particles. Our simulations suggest a transition between globular and rod-like aggregates that changes from a gradual to a sudden transition depending on particle size, and that rod formation is a slow, nucleation dependent process.

  8. Bioreceptor-conducting polymer multilayer assemblies for biosensing

    NASA Astrophysics Data System (ADS)

    Samuelson, Lynne A.; Alva, Shridhara; Kumar, Jayant; Kaplan, David L.; Tripathy, Sukant K.

    1998-04-01

    This research focuses on the organized integration of biological receptors and polymers into thin film architectures for biosensing applications. Layer-by-layer electrostatic adsorption was used for the first time to form alternating protein-conducting polymer multilayers. The light-harvesting, phycobiliproteins and the enzyme, alkaline phosphatase were the bioreceptors investigated and sulfonated polystyrene, poly(diallyl dimethyl ammonium chloride) and a new enzymatically polymerized, water soluble, polyaniline were the polymer counterions used for deposition. Spectroscopic characterization was used to determine both multilayer formation and biosensing function of the final bioreceptor-polymer assemblies. These techniques have proven to be simple, chemically mild, and versatile and are expected to find application in the fabrication of ultrathin films for biosensors, opto- electronic devices and biomedical applications.

  9. The controllable assembly of nanorods, nanowires and microwires of a perylenediimide molecule with photoswitching property

    NASA Astrophysics Data System (ADS)

    Ma, Ying; An, Boxing; Wang, Meng; Shi, Fangxiao; Wang, Qing; Gu, Yaxin; Niu, Wanyang; Fan, Zhaorong; Shang, Yanli; Wang, Dan; Zhao, Cong

    2015-07-01

    By using an electron donor-acceptor molecule that consists of a perylenediimide (PDI) core bonded with two ferrocene (Fc) units, well-defined nanorods, nanowires and microwires of PDI-Fc were formed through simply adjusting the initial concentration of PDI-Fc in dichloromethane or CH2Cl2. Moreover, the two-ended devices based on individual microwire were fabricated. Highly reproducible and sensitive photo response characteristics were demonstrated in the microwire through controlling the white light on and off with different light intensities. The assembly strategy via complementary donors and acceptors is of significance for constructing photoconductive systems and developing novel functional devices.

  10. Structure and Assembly of Polymeric Dots Formed by Conjugated Polymers

    NASA Astrophysics Data System (ADS)

    Osti, Naresh; Ratnaweera, Dilru; Etempawala, Thusitha; Shrestha, Umesh; Perahia, Dvora

    2012-02-01

    Rigid conjugated polymers assume extended conformation in dilute solution and often behave as colloidal suspensions. When forced into a collapsed configuration, they form highly fluorescing particles, or poly-dots, which have demonstrated potential as intracellular imaging markers, as well as building blocks for light harvesting devices. The current work investigates the structure and stability of poly-dots of di-alkyl para polyphenyleneethynylene (PPE) conjugated polymers in solution and follows their assembly at interfaces. Small angle neutron scattering measurements of the poly-dots in water have shown that at low concentrations, stable unimolecular spherical poly-dots are formed with a polydispersity that corresponds to that of the polymer itself. With increasing concentration, yet, below the critical micelle concentration of these rod-like polymers in good solvents, the size and density of the NPs increases, however the spherical symmetry is retained. The nature and length of the substituents affect the internal density and the degree of swelling of the poly dots. Atomic Force Microscopy results show that these PPE poly-dots assemble into arrays with different symmetries, depending on molecular parameters and assembly conditions.

  11. Efficient Multiscale Models of Polymer Assembly.

    PubMed

    Ruiz-Martinez, Alvaro; Bartol, Thomas M; Sejnowski, Terrence J; Tartakovsky, Daniel M

    2016-07-12

    Protein polymerization and bundling play a central role in cell physiology. Predictive modeling of these processes remains an open challenge, especially when the proteins involved become large and their concentrations high. We present an effective kinetics model of filament formation, bundling, and depolymerization after GTP hydrolysis, which involves a relatively small number of species and reactions, and remains robust over a wide range of concentrations and timescales. We apply this general model to study assembly of FtsZ protein, a basic element in the division process of prokaryotic cells such as Escherichia coli, Bacillus subtilis, or Caulobacter crescentus. This analysis demonstrates that our model outperforms its counterparts in terms of both accuracy and computational efficiency. Because our model comprises only 17 ordinary differential equations, its computational cost is orders-of-magnitude smaller than the current alternatives consisting of up to 1000 ordinary differential equations. It also provides, to our knowledge, a new insight into the characteristics and functioning of FtsZ proteins at high concentrations. The simplicity and versatility of our model render it a powerful computational tool, which can be used either as a standalone descriptor of other biopolymers' assembly or as a component in more complete kinetic models. PMID:27410746

  12. Ultralong Ordered Nanowires from the Concerted Self-Assembly of Discotic Liquid Crystal and Solvent Molecules.

    PubMed

    Park, Ji Hyun; Kim, Kyung Ho; Park, Yung Woo; Lagerwall, Jan P F; Scalia, Giusy

    2015-09-01

    The realization of long, aligned molecular wires is a great challenge, and a variety of approaches have been proposed. Interestingly, hexapentyloxytriphenylene (HAT5) discotic liquid crystal molecules, a model system of molecules with flat and aromatic cores, can spontaneously form well-aligned, micrometer long, yet only tens of nanometers thick, nanowires on solid surfaces. We have investigated the formation mechanism of these wires using different solvents with selected characteristics, including chemical structure, boiling point, vapor pressure, and surface tension. When casting from toluene and benzene solutions, atomic force microscopy reveals that the discotics spontaneously form very long and thin wires, self-aligning along a common orientation. If instead dodecane or heptane are used, different and in general thicker structures are obtained. The chemical structure of the solvent appears to have a key role, coupling to the liquid crystal self-assembly by allowing solvent molecules to enter the ordered structure if their design matches the core of HAT5 molecules, thereby guiding the assembly. However, other aspects are also relevant in the assembly, including the nature of the substrate and the rate of solvent evaporation, and these can favor or interfere with the self-assembly into long structures. The use of solvents with aromatic structure is advantageous not only because it affects the geometry of the assembly, promoting long wire formation, but it is also compatible with good quality of the intermolecular order, as suggested by a high anisotropy of the Raman spectra of the nanowires formed from these solvents. Finally, the electrical properties of ordered systems show a clearly higher electrical conductivity compared to the disorganized aggregates. PMID:26079283

  13. Silicon nanowire growth and transistor fabrication by self-assembling "grow-in-place" approach

    NASA Astrophysics Data System (ADS)

    Shan, Yinghui

    Nanowires have attracted much attention recently owing to their ability to serve as critical building blocks for emerging nanotechnologies. Silicon nanowires (SiNWs) are particularly promising because of the central role of silicon in semiconductor industry. SiNWs would allow device fabrication with high density and their high surface to volume ratio offers high sensitivity. In addition, the possible quantum confinement in SiNWs may further enhance device performances and open windows for exploiting fundamental properties. Intense researches have been carried out in SiNW growth and device fabrication. However, there are still challenges in SiNW growth controls, such as size, number, shape, position, orientation, and inter-wire spacings. To make devices from these SiNWs, post-growth processing steps are needed, such as SiNW collecting, picking, positioning, aligning, and assembling. Due to the extremely small size of SiNWs, there are also challenges in SiNW device fabrication. To solve these challenges in both SiNW growth control and device fabrication, we introduced a novel self-assembling "grow-in-place" approach. Our approach combined vapor-liquid-solid (VLS) nanowire growth mechanism and pre-fabricated nanochannel template. The VLS growth mechanism offers the ability of controlling nanowire size and shape by nanochannel templates. The pre-fabricated nanochannel template guides nanowire growth and offers good SiNW growth control. SiNWs and silicon nanoribbons (SiNRs) with different sizes have been successfully grown in our nanochannel templates. Characterizations on their size, shape, composition, and crystallinity of the SiNW/Rs have confirmed that our "grow-in-place" approach offers good controls on crystalline SiNW/Rs size, shape, number, orientation, position, and inter-wire spacing. So our approach solved the challenges in SiNW growth control. Our grow-in-place approach also solved the challenges in SiNW device fabrication. We introduced two versions of

  14. The Assembly of Nanorods in Comb Polymer Supramolecules

    NASA Astrophysics Data System (ADS)

    Mastroianni, Alexander; Thorkelsson, Kari; Luther, Joseph; Alivisatos, Paul; Xu, Ting

    2010-03-01

    Inorganic nanoparticles exhibit a wide range of size-dependent properties and present great promise in technological applications. Fully harnessing this potential requires developing bottom-up strategies to assemble nanoparticles over multiple length scales simultaneously. Nanoparticles have been co-assembled with block copolymers (BCPs). Often this approach requires delicate balance between particle-polymer interactions and entropic penalty associated with polymer chain deformation upon particle incorporation. Recently, we showed that a coil-comb supramolecule formed by non- covalent attachment of small molecule amphiphiles to one block of a BCP can be used to direct nanoparticle assemblies with high precision. The alkyl tail of the small molecules chosen interacts favorably with the native alkyl ligands of a wide variety of inorganic nanoparticles and eliminates the need for particle surface modification. Upon attaching small molecule to one BCP block, the polymer chain stiffens, providing entropic driving force to further direct nanoparticle organization within BCP microdomains. Here, the co-assembly of these supramolecules with nanorods was systematically investigated as a function of small molecule loading, supramolecular morphology, nanorod diameter, and aspect ratio. The presented fundamental studies pave a path toward nanorod-based device fabrication.

  15. Aligned and Electrospun Piezoelectric Polymer Fiber Assembly and Scaffold

    NASA Technical Reports Server (NTRS)

    Scott-Carnell, Lisa A. (Inventor); Siochi, Emilie J. (Inventor); Holloway, Nancy M. (Inventor); Leong, Kam W. (Inventor); Kulangara, Karina (Inventor)

    2015-01-01

    A scaffold assembly and related methods of manufacturing and/or using the scaffold for stem cell culture and tissue engineering applications are disclosed which at least partially mimic a native biological environment by providing biochemical, topographical, mechanical and electrical cues by using an electroactive material. The assembly includes at least one layer of substantially aligned, electrospun polymer fiber having an operative connection for individual voltage application. A method of cell tissue engineering and/or stem cell differentiation uses the assembly seeded with a sample of cells suspended in cell culture media, incubates and applies voltage to one or more layers, and thus produces cells and/or a tissue construct. In another aspect, the invention provides a method of manufacturing the assembly including the steps of providing a first pre-electroded substrate surface; electrospinning a first substantially aligned polymer fiber layer onto the first surface; providing a second pre-electroded substrate surface; electrospinning a second substantially aligned polymer fiber layer onto the second surface; and, retaining together the layered surfaces with a clamp and/or an adhesive compound.

  16. Self-Assembly of Emulsion Droplets into Polymer Chains

    NASA Astrophysics Data System (ADS)

    Bargteil, Dylan; McMullen, Angus; Brujic, Jasna

    We experimentally investigate `beads-on-a-string' models of polymers using the spontaneous assembly of emulsion droplets into linear chains. Droplets functionalized with surface-mobile DNA allow for programmable 'monomers' through which we can influence the three-dimensional structure of the assembled 'polymer'. Such model polymers can be used to study conformational changes of polypeptides and the principles governing protein folding. In our system, we find that droplets bind via complementary DNA strands that are recruited into adhesion patches. Recruitment is driven by the DNA hybridization energy, and is limited by the energy cost of surface deformation and the entropy loss of the mobile linkers, yielding adhesion patches of a characteristic size with a given number of linkers. By tuning the initial surface coverage of linkers, we control valency between the droplets to create linear or branched polymer chains. We additionally control the flexibility of the model polymers by varying the salt concentration and study their dynamics between extended and collapsed states. This system opens the possibility of programming stable three-dimensional structures, such as those found within folded proteins.

  17. Differentially photo-crosslinked polymers enable self-assembling microfluidics

    PubMed Central

    Jamal, Mustapha; Zarafshar, Aasiyeh M.; Gracias, David H.

    2012-01-01

    An important feature of naturally self-assembled systems such as leaves and tissues is that they are curved and have embedded fluidic channels that enable the transport of nutrients to, or removal of waste from, specific three-dimensional (3D) regions. Here, we report the self-assembly of photopatterned polymers, and consequently microfluidic devices, into curved geometries. We discovered that differentially photo-crosslinked SU-8 films spontaneously and reversibly curved upon film de-solvation and re-solvation. Photolithographic patterning of the SU-8 films enabled the self-assembly of cylinders, cubes, and bidirectionally folded sheets. We integrated polydimethylsiloxane (PDMS) microfluidic channels with these SU-8 films to self-assemble curved microfluidic networks. PMID:22068594

  18. Field-directed assembly of nanowires: identifying directors, disruptors and indices to maximize the device yield

    NASA Astrophysics Data System (ADS)

    Sam, Mahshid; Moghimian, Nima; Bhiladvala, Rustom B.

    2015-12-01

    Individually-addressable nano-electro-mechanical (NEMS) devices have been used to demonstrate sensitive mass detection to the single-proton level, as well as neutral-particle mass spectrometry. The cost of individually securing or patterning such devices is proportional to their number or the chip area covered. This limits statistical support for new research, as well as paths to the commercial availability of extraordinarily sensitive instruments. Field-directed assembly of synthesized nanowires addresses this problem and shows potential for low-cost, large-area coverage with NEMS devices. For positive dielectrophoresis (pDEP) as the main assembly director, the space of field, geometric and material parameters is large, with combinations that can serve either as directors or disruptors for directed assembly. We seek parameter values to obtain the best yield, by introducing a rational framework to reduce trial-and-error. We show that sorting the disruptors by severity and eliminating those weakly coupled to the director, allows reduction of the parameter space. The remaining disruptors are then represented compactly by dimensionless parameters. In the example protocol chosen, a single dimensionless parameter, the yield index, allows minimization of disruptors by the choice of frequency. Following this, the voltage may be selected to maximize the yield. Using this framework, we obtained 94% pre-clamped and 88% post-clamped yield over 57000 nanowire sites. Organizing the parameter space using a director-disruptor framework, with economy introduced by non-dimensional parameters, provides a path to controllably decrease the effort and cost of manufacturing nanoscale devices. This should help in the commercialization of individually addressable nanodevices.Individually-addressable nano-electro-mechanical (NEMS) devices have been used to demonstrate sensitive mass detection to the single-proton level, as well as neutral-particle mass spectrometry. The cost of

  19. Cross-Linked Conjugated Polymer Fibrils: Robust Nanowires from Functional Polythiophene Diblock Copolymers

    SciTech Connect

    Hammer, Brenton A. G.; Bokel, Felicia A.; Hayward, Ryan C.; Emrick, Todd

    2011-09-27

    A series of poly(3-hexyl thiophene) (P3HT)-based diblock copolymers were prepared and examined in solution for their assembly into fibrils, and post-assembly cross-linking into robust nanowire structures. P3HT-b-poly(3-methanol thiophene) (P3MT), and P3HT-b-poly(3-aminopropyloxymethyl thiophene) (P3AmT) diblock copolymers were synthesized using Grignard metathesis (GRIM) polymerization. Fibrils formed from solution assembly of these copolymers are thus decorated with hydroxyl and amine functionality, and cross-linking is achieved by reaction of diisocyanates with the hydroxyl and amine groups. A variety of cross-linked structures, characterized by transmission electron microscopy (TEM), were produced by this method, including dense fibrillar sheets, fibril bundles, or predominately individual fibrils, depending on the chosen reaction conditions. In solution, the cross-linked fibrils maintained their characteristic vibronic structure in solvents that would normally disrupt (dissolve) the structures.

  20. Mesoporous Silicia Nanowires by Space-Confined Organic-Inorganic Hybrid Self-Assembly

    SciTech Connect

    Lai, Peng

    2007-10-01

    This research focuses on the space-confined self-assembly of P123-silica hybrid solution inside nano-scale channels. Mesoporous silica nanowires with various diameters (10-400nm) were synthesized via sol-gel combined evaporation-induced self-assembly in channels of both anodized aluminum oxide (AAO) and etched polycarbonate (EPC) substrate. Scanning transmission electron microscope (STEM) was utilized to characterize the samples in terms of nanopore size, ordering, and orientation. The mesoporous structures of silica wires formed in EPC channels with diameter less than 400 nm are investigated and reported for the first time. Substrate effect (EPC vs. AAO) and processing condition effect on the morphology of the mesoporous structure of silica wires are presented and discussed. The more ordered and uniform mesoporous structure is preferentially formed in narrower substrate channel confinement. A critical diameter of hard template channels is around 30-50 nm, below which the space confinement effect leads to more uniform nanostructured nanowires, and above which mixed meso-structures usually exist. The formation of various meso-structures of silica wires is sensitive to process conditions.

  1. Templated Self-Assembly of Ultrathin Gold Nanowires by Nanoimprinting for Transparent Flexible Electronics.

    PubMed

    Maurer, Johannes H M; González-García, Lola; Reiser, Beate; Kanelidis, Ioannis; Kraus, Tobias

    2016-05-11

    We fabricated flexible, transparent, and conductive metal grids as transparent conductive materials (TCM) with adjustable properties by direct nanoimprinting of self-assembling colloidal metal nanowires. Ultrathin gold nanowires (diameter below 2 nm) with high mechanical flexibility were confined in a stamp and readily adapted to its features. During drying, the wires self-assembled into dense bundles that percolated throughout the stamp. The high aspect ratio and the bundling yielded continuous, hierarchical superstructures that connected the entire mesh even at low gold contents. A soft sintering step removed the ligand barriers but retained the imprinted structure. The material exhibited high conductivities (sheet resistances down to 29 Ω/sq) and transparencies that could be tuned by changing wire concentration and stamp geometry. We obtained TCMs that are suitable for applications such as touch screens. Mechanical bending tests showed a much higher bending resistance than commercial ITO: conductivity dropped by only 5.6% after 450 bending cycles at a bending radius of 5 mm. PMID:26985790

  2. Oriented assembled TiO2 hierarchical nanowire arrays with fast electron transport properties.

    PubMed

    Sheng, Xia; He, Dongqing; Yang, Jie; Zhu, Kai; Feng, Xinjian

    2014-01-01

    Developing high surface area nanostructured electrodes with rapid charge transport is essential for artificial photosynthesis, solar cells, photocatalysis, and energy storage devices. Substantial research efforts have been recently focused on building one-dimensional (1D) nanoblocks with fast charge transport into three-dimensional (3D) hierarchical architectures. However, except for the enlargement in surface area, there is little experimental evidence of fast electron transport in these 3D nanostructure-based solar cells. In this communication, we report single-crystal-like 3D TiO2 branched nanowire arrays consisting of 1D branch epitaxially grown from the primary trunk. These 3D branched nanoarrays not only demonstrate 71% enlargement in large surface area (compared with 1D nanowire arrays) but also exhibit fast charge transport property (comparable to that in 1D single crystal nanoarrays), leading to 52% improvement in solar conversion efficiency. The orientated 3D assembly strategy reported here can be extended to assemble other metal oxides with one or multiple components and thus represents a critical avenue toward high-performance optoelectronics. PMID:24628675

  3. Co-assembled thin films of Ag nanowires and functional nanoparticles at the liquid-liquid interface by shaking

    NASA Astrophysics Data System (ADS)

    Zhang, Shao-Yi; Liu, Jian-Wei; Zhang, Chuan-Ling; Yu, Shu-Hong

    2013-05-01

    In this paper, we report the fabrication of co-assembled thin films composed of silver nanowires (NWs) and Au nanoparticles (NPs) at the liquid-liquid interface (water-chloroform) by vigorous shaking. The composition of co-assembled thin films can be controlled by adjusting the concentration of the nanosized building blocks. As a versatile interfacial assembly method, other nanoparticles such as Ag2S and Fe3O4 NPs can also be co-assembled with Ag NWs using the same procedure. Meanwhile, the co-assembly state of the obtained Au NPs and Ag NWs makes a significant contribution to the high sensitivity of surface-enhanced Raman scattering (SERS) to model the molecule 3,3'-diethylthiatricarbocyanine iodide (DTTCI). The SERS intensities show high dependence on the molar ratio of Au NPs and Ag NWs and the layer number of the co-assembled thin films. This shaking-assisted liquid-liquid assembly system has been proved to be a facile way for co-assembling nanowires and nanoparticles, and will pave a way for further applications of the macroscopic co-assemblies with novel functionalities.In this paper, we report the fabrication of co-assembled thin films composed of silver nanowires (NWs) and Au nanoparticles (NPs) at the liquid-liquid interface (water-chloroform) by vigorous shaking. The composition of co-assembled thin films can be controlled by adjusting the concentration of the nanosized building blocks. As a versatile interfacial assembly method, other nanoparticles such as Ag2S and Fe3O4 NPs can also be co-assembled with Ag NWs using the same procedure. Meanwhile, the co-assembly state of the obtained Au NPs and Ag NWs makes a significant contribution to the high sensitivity of surface-enhanced Raman scattering (SERS) to model the molecule 3,3'-diethylthiatricarbocyanine iodide (DTTCI). The SERS intensities show high dependence on the molar ratio of Au NPs and Ag NWs and the layer number of the co-assembled thin films. This shaking-assisted liquid-liquid assembly system

  4. Structure and assembly of haptoglobin polymers by electron microscopy.

    PubMed

    Wejman, J C; Hovsepian, D; Wall, J S; Hainfeld, J F; Greer, J

    1984-04-01

    Haptoglobin (Hp) consists of light (L) and heavy (H) chains, the latter of which combine with hemoglobin alpha beta dimers to form a highly stable complex. Human haptoglobin assembles as HL units that occur in two allelic forms; HL1 , which is monovalent, and HL2 , which is divalent. As a result, three phenotypic forms exist in the human population: Hp1-1, the homozygous form in which the monovalent HL1 unit occurs as a dimer; Hp2-2, the homozygous form of the divalent HL2 unit, which gives a series of polymers; and the heterozygous Hp2-1 form, which gives a different series of polymers. We have investigated the structures and assembly properties of these two haptoglobin polymeric series in their complexes with hemoglobin using high-resolution scanning transmission electron microscopy. Polymers of complex are composed of ellipsoidal or bilobal head groups, which are the H alpha beta subunits connected by thin filament-like structures, which are the L chains. Polymers of size up to pentamers can be identified easily by counting the number of head groups in the molecule. Complex 2-1 and complex 2-2 trimers were studied extensively. The differences in detailed morphology show that while the 2-1 trimer is a linear polymer, the 2-2 trimer is a closed circular molecule. The micrograph images suggest that complex 2-2 tetramers and pentamers, and perhaps higher forms may also be cyclic. The structure of the L2 subunit of haptoglobin is shown to be composed of two domains, which may be similar in structure to the single domain of the monovalent L1 chain. The two L2 domains are connected by a hinge that has quite limited flexibility. Using these structural models, assembly characteristics and structural properties of the trimers and tetramers of complex 2-1 and complex 2-2 are described. PMID:6716482

  5. Assembling and properties of the polymer-particle nanostructured materials

    NASA Astrophysics Data System (ADS)

    Sheparovych, Roman

    Complementary properties of the soft and hard matter explain its common encounter in many natural and manmade applications. A combination of flexible organic macromolecules and hard mineral clusters results in new materials far advantageous than its constituents alone. In this work we study assembling of colloidal nanocrystals and polymers into complex nanostructures. Magnetism, surface wettability and adhesion comprise properties of interest for the obtained nanocomposites. Applying a magnetic field induces a reversible 1D ordering of the magnetically susceptible particles. This property was employed in the fabrication of the permanent chains of magnetite nanocrystals (d=15nm). In the assembling process the aligned particles were bound together using polyelectrolyte macromolecules. The basics of the binding process involved an electrostatic interaction between the positively charged polyelectrolyte and the negative surface of the particles (aqueous environment). Adsorption of the polymer molecules onto several adjacent particles in the aligned 1D aggregate results in the formation of the permanent particulate chains. Positive charges of the adsorbed polyelectrolyte molecules stabilize the dispersion of the obtained nanostructures in water. Magnetization measurements revealed that superparamagnetic nanoparticles, being assembled into 1D ordered structures, attain magnetic coercivity. This effect originates from the magnetostatic interaction between the neighboring magnetite nanocrystals. The preferable dipole alignment of the assembled nanoparticles is directed along the chain axis. Another system studied in this project includes polymer-particle responsive surface coatings. Tethered polymer chains and particles bearing different functionalities change surface properties upon restructuring of the composite layer. When the environment favors polymer swelling (good solvent), the polymer chains segregate to the surface and cover the particles. In the opposite case

  6. Assembly and Integration of Nanowires and Graphene for Nanoelectronics and Nanobiotechnology

    NASA Astrophysics Data System (ADS)

    Nam, Sungwoo

    Flexible bottom-up assembly and integration of nanoscale materials with tunable composition and structure could make possible the development and advancement of novel fabrication strategies and unconventional integrated electronics/sensors not previously achievable with top-down approaches. We demonstrate contact-printing assembly and integration of semiconducting nanowires for three-dimensional (3D), multilayer nanowire (NW) electronics and large-scale complementary SiNW biosensor arrays, and monolithic integration of graphene-graphite for flexible bioprobes and integrated graphene electronics. First, we achieved the assembly of highly-ordered NW arrays by contact-printing with well-controlled shear process between growth and target substrates. We show the capability of uniform and patterned automated contact-printing from single chip to a 4-inch wafer scale. We also demonstrate the power of our assembly approach with the creation of 3D NW electronics and large-scale, complementary SiNW biosensor arrays. We show, first, multilayer assembly of semiconducting NWs for 3D, multi-functional electronics, which includes (1) 10 layers of Ge/Si NW field-effect transistor (FET) arrays, (2) two-layer, multi-functional circuits assembled onto flexible plastic substrates and (3) vertically-interconnected complementary metal-oxide-semiconductor (CMOS) circuits based on heterogeneous n-InAs and p-Ge/Si NW FETs with a record high ring oscillation frequency of ca. 110 MHz. Furthermore, we present the assembly and integration of large-scale, complementary SiNW biosensor arrays capable of simultaneous, multi-channel detections with femtomolar sensitivity of prostate-specific antigen (PSA). Second, we report monolithic integration of graphene-graphite to realize flexible, electrically-active nanoprobes, and a single-step synthesis of monolithic graphene-graphite structure to realize the integration of a whole circuit. We demonstrate that monolithically-integrated graphene

  7. Solution assembly behaviors of 3-hexylthiophene polymer based rod-coil graft copolymer

    NASA Astrophysics Data System (ADS)

    Kim, Youngkwon; Kim, Jin-Sung; Kim, Hyeong Jun; Kim, Bumjoon

    Solution assembly of conjugated polymer based block copolymers (BCPs) is an attractive approach for achieving conducting nanowires (NWs) with nanometer-scale cross-sectional dimensions. In particular, conjugated block offers one-dimensional self-growth of crystalline NWs, and secondary block gives rise to stable dispersion of NWs and additional tuning parameter for the structures of NWs. Herein, we developed a series of poly(3-hexylthiophene)-graft-poly(2-vinylpyridine) (P3HT-g-P2VP) rod-coil copolymers with systematically controlled crystallinity by modifying both grafting density and molecular weight (Mn) of coil block, and their solution assembly behaviors were carefully examined. As increasing the volume fraction and grafting density of the secondary blocks, melting temperatures, crystallization temperatures, and the crystallinity were gradually decreased by hindering rod-rod interaction between P3HT backbones, resulting in the formation of short NWs. Furthermore, the length of NMs was relatively shorter for the densely grafted copolymer despite same volume fraction of secondary block. These results suggested that controlling Mn and the number of branched coil block was critical to regulate the crystalline properties and new approach for determining the NWs growth.

  8. Self-Assembly of Globular Protein-Polymer Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    Thomas, C. S.; Olsen, B. D.

    2011-03-01

    The self-assembly of globular protein-polymer diblock copolymers into nanostructured phases is demonstrated as an elegant and simple method for structural control in biocatalysis or bioelectronics. In order to fundamentally investigate self-assembly in these complex block copolymer systems, a red fluorescent protein was expressed in E. coli and site-specifically conjugated to a low polydispersity poly(N-isopropyl acrylamide) (PNIPAM) block using thiol-maleimide coupling to form a well-defined model globular protein-polymer diblock. Functional protein materials are obtained by solvent evaporation and solvent annealing above and below the lower critical solution temperature of PNIPAM in order to access different pathways toward self-assembly. Small angle x-ray scattering and microscopy are used to show that the diblock forms lamellar nanostructures and to explore dependence of nanostructure formation on processing conditions. Circular dichroism and UV-vis show that a large fraction of the protein remains in its folded state after conjugation, and wide angle x-ray scattering demonstrates that diblock copolymer self-assembly changes the protein packing symmetry.

  9. Protein Biosensors Based on Polymer Nanowires, Carbon Nanotubes and Zinc Oxide Nanorods

    PubMed Central

    M., Anish Kumar; Jung, Soyoun; Ji, Taeksoo

    2011-01-01

    The development of biosensors using electrochemical methods is a promising application in the field of biotechnology. High sensitivity sensors for the bio-detection of proteins have been developed using several kinds of nanomaterials. The performance of the sensors depends on the type of nanostructures with which the biomaterials interact. One dimensional (1-D) structures such as nanowires, nanotubes and nanorods are proven to have high potential for bio-applications. In this paper we review these three different kinds of nanostructures that have attracted much attention at recent times with their great performance as biosensors. Materials such as polymers, carbon and zinc oxide have been widely used for the fabrication of nanostructures because of their enhanced performance in terms of sensitivity, biocompatibility, and ease of preparation. Thus we consider polymer nanowires, carbon nanotubes and zinc oxide nanorods for discussion in this paper. We consider three stages in the development of biosensors: (a) fabrication of biomaterials into nanostructures, (b) alignment of the nanostructures and (c) immobilization of proteins. Two different methods by which the biosensors can be developed at each stage for all the three nanostructures are examined. Finally, we conclude by mentioning some of the major challenges faced by many researchers who seek to fabricate biosensors for real time applications. PMID:22163892

  10. Silica coating of polymer nanowires produced via nanoimprint lithography from femtosecond laser machined templates

    NASA Astrophysics Data System (ADS)

    Rajput, Deepak; Costa, Lino; Terekhov, Alexander; Lansford, Kathleen; Hofmeister, William

    2012-03-01

    In this paper we report on the fabrication of regular arrays of silica nanoneedles by deposition of a thin layer of silica on patterned arrays of polymer nanowires (or polymer nanohair). An array of high-aspect-ratio nanoscale diameter holes of depths greater than 10 µm was produced at the surface of a fused silica wafer by an amplified femtosecond laser system operated in single-pulse mode. Cellulose acetate (CA) film was imprinted into the nanoholes and peeled off to form a patterned array of standing CA nanowires, a negative replica of the laser machined nanoholes. The cellulose acetate replica was then coated with silica in a chemical vapor deposition process using silicon tetrachloride vapor at 65 °C. Field emission scanning electron microscopy, focused ion beam sectioning, energy dispersive x-ray analysis and Fourier-transform infrared spectroscopy were used to characterize the silica nanoneedles. Precisely patterned, functionalized arrays of standing silica nanoneedles are useful for a number of applications.

  11. Field-directed assembly of nanowires: identifying directors, disruptors and indices to maximize the device yield.

    PubMed

    Sam, Mahshid; Moghimian, Nima; Bhiladvala, Rustom B

    2016-01-14

    Individually-addressable nano-electro-mechanical (NEMS) devices have been used to demonstrate sensitive mass detection to the single-proton level, as well as neutral-particle mass spectrometry. The cost of individually securing or patterning such devices is proportional to their number or the chip area covered. This limits statistical support for new research, as well as paths to the commercial availability of extraordinarily sensitive instruments. Field-directed assembly of synthesized nanowires addresses this problem and shows potential for low-cost, large-area coverage with NEMS devices. For positive dielectrophoresis (pDEP) as the main assembly director, the space of field, geometric and material parameters is large, with combinations that can serve either as directors or disruptors for directed assembly. We seek parameter values to obtain the best yield, by introducing a rational framework to reduce trial-and-error. We show that sorting the disruptors by severity and eliminating those weakly coupled to the director, allows reduction of the parameter space. The remaining disruptors are then represented compactly by dimensionless parameters. In the example protocol chosen, a single dimensionless parameter, the yield index, allows minimization of disruptors by the choice of frequency. Following this, the voltage may be selected to maximize the yield. Using this framework, we obtained 94% pre-clamped and 88% post-clamped yield over 57000 nanowire sites. Organizing the parameter space using a director-disruptor framework, with economy introduced by non-dimensional parameters, provides a path to controllably decrease the effort and cost of manufacturing nanoscale devices. This should help in the commercialization of individually addressable nanodevices. PMID:26649627

  12. Nanoscale Control of Polymer Assembly on a Synthetic Catalyst-Bilayer System.

    PubMed

    Gorgoll, Ricardo M; Harano, Koji; Nakamura, Eiichi

    2016-08-01

    The use of the interior of self-assembled membrane as a template for polymer synthesis and assembly has long attracted the interest of chemists. However, it is difficult to utilize a lipid membrane as a chemical reactor for controlled assembly for polymers because lipid membrane is easily destabilized by loading of extraneous molecules. We found that a several-nanometer-thick bilayer vesicle made by self-assembly of an organic fullerene amphiphile doped with a metathesis catalyst serves as a nanosized chemical reactor in water, where a polymer is synthesized and assembled, depending on the affinity of the growing polymer to the organic groups on the amphiphile. This catalyst-bilayer system can thus control supramolecular assembly of the ester-functionalized polymer product into different nanoscale structures: a nanoparticle made of a single polymer chain and a nanocapsule made of several tens of polymer chains. PMID:27404736

  13. A facile synthesis of novel nanorod-assembling hollow nanowires of cadmium sulfide/DBTU nanocomposite

    SciTech Connect

    Tang, Yu; Mo, Yan-mei; Yang, Kui; Chen, Tie-shi; Yang, Jun; Zhang, Yuan-ming

    2010-11-15

    Novel nanorod-assembling hollow nanowires of cadmium sulfide/DBTU (N,N'-dibutylthiourea) nanocomposite were synthesized by reacting CdCl{sub 2} with in situ produced H{sub 2}S from reaction of butylamine and carbon disulfide at molar ratio 3:3 of CS{sub 2}:BuNH{sub 2} at 50 {sup o}C. This product was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SEAD), energy dispersive X-ray spectroscopy (EDAX), thermogravimetric (TG), Fourier transform infrared (FTIR) and UV-vis absorption spectra. A plausible mechanism that the extending DBTU molecules in solvent of CS{sub 2} induce the formation of CdS/DBTU nanorods by coordinating with the formed CdS particles, and construct these nanorods to hollow nanowires via molecular interactions is proposed and discussed on the basis of experimental results. Photoluminescence (PL) of CdS/DBTU nanocomposite exhibits increasing emission intensity largely.

  14. Self-assembled nanowire arrays as three-dimensional nanopores for filtration of DNA molecules.

    PubMed

    Rahong, Sakon; Yasui, Takao; Yanagida, Takeshi; Nagashima, Kazuki; Kanai, Masaki; Meng, Gang; He, Yong; Zhuge, Fuwei; Kaji, Noritada; Kawai, Tomoji; Baba, Yoshinobu

    2015-01-01

    Molecular filtration and purification play important roles for biomolecule analysis. However, it is still necessary to improve efficiency and reduce the filtration time. Here, we show self-assembled nanowire arrays as three-dimensional (3D) nanopores embedded in a microfluidic channel for ultrafast DNA filtration. The 3D nanopore structure was formed by a vapor-liquid-solid (VLS) nanowire growth technique, which allowed us to control pore size of the filtration material by varying the number of growth cycles. λ DNA molecules (48.5 kbp) were filtrated from a mixture of T4 DNA (166 kbp) at the entrance of the 3D nanopore structure within 1 s under an applied electric field. Moreover, we observed single DNA molecule migration of T4 and λ DNA molecules to clarify the filtration mechanism. The 3D nanopore structure has simplicity of fabrication, flexibility of pore size control and reusability for biomolecule filtration. Consequently it is an excellent material for biomolecular filtration. PMID:25765268

  15. The controllable assembly of nanorods, nanowires and microwires of a perylenediimide molecule with photoswitching property

    SciTech Connect

    Ma, Ying; An, Boxing; Wang, Meng; Shi, Fangxiao; Wang, Qing; Gu, Yaxin; Niu, Wanyang; Fan, Zhaorong; Shang, Yanli; Wang, Dan; Zhao, Cong

    2015-07-15

    By using an electron donor–acceptor molecule that consists of a perylenediimide (PDI) core bonded with two ferrocene (Fc) units, well-defined nanorods, nanowires and microwires of PDI-Fc were formed through simply adjusting the initial concentration of PDI-Fc in dichloromethane or CH{sub 2}Cl{sub 2}. Moreover, the two-ended devices based on individual microwire were fabricated. Highly reproducible and sensitive photo response characteristics were demonstrated in the microwire through controlling the white light on and off with different light intensities. The assembly strategy via complementary donors and acceptors is of significance for constructing photoconductive systems and developing novel functional devices. - Graphical abstract: The two-ended devices based on individual microwire were fabricated. Highly reproducible and sensitive photo response characteristics were observed by controlling the white light on and off with different light intensities. - Highlights: • An electron donor–acceptor molecule (PDI-Fc) was synthesized. • Well-defined nanorods, nanowires and microwires of PDI-Fc were formed. • The two-ended devices based on individual microwire were fabricated. • Highly reproducible and sensitive photo response characteristics were observed.

  16. Ionic self-assembled wormlike nanowires and their cyclodextrin inclusion-tuned transition.

    PubMed

    Li, Qiuhong; Chen, Xiao; Wang, Xudong; Zhao, Yurong; Ma, Fumin

    2010-08-19

    Wormlike nanowires have been successfully prepared via the ionic self-assembly (ISA) route from the cationic (ferrocenylmethyl)trimethylammonium iodide (FcMI) and the anionic sodium bis(2-ethyl-1-hexyl)sulfosuccinate (AOT). The formed FcM-AOT complexes have been proved to possess a composition of equal molar ratio and show good redox activity also due to the introduction of organic metal ferrocene. These complexes exhibit an ordered hexagonal columnar structure with the lattice spacing D of 2.49 nm. More interestingly, the wormlike nanowires interweave themselves together to form a net-like structure, and some of them are large enough to exhibit a high-order crystal structure. In addition, such an ISA organized aggregate can be changed into vesicles by including the Fc blocks into beta-cyclodextrins to form another supramolecular complex. The supramolecular structure and morphology of the vesicles were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS), respectively. Both the complex fabrication and transition mechanisms are discussed and found to be controlled by the inclusion equilibrium and the cooperative binding of noncovalent interactions, including the electrostatic interactions, pi-pi stacking, and amphiphilic hydrophobic association. PMID:20701373

  17. Simulation Methods for Self-Assembled Polymers and Rings

    NASA Astrophysics Data System (ADS)

    Kindt, James T.

    2003-11-01

    New off-lattice grand canonical Monte Carlo simulation methods have been developed and used to model the equilibrium structure and phase diagrams of equilibrium polymers and rings. A scheme called Polydisperse Insertion, Removal, and Resizing (PDIRR) is used to accelerate the equilibration of the size distribution of self-assembled aggregates. This method allows the insertion or removal of aggregates (e.g., chains) containing an arbitrary number of monomers in a single Monte Carlo move, or the re-sizing of an existing aggregate. For the equilibrium polymer model under semi-dilute conditions, a several-fold increase in equilibration rate compared with single-monomer moves is observed, facilitating the study of the isotropic-nematic transition of semiflexible, self-assembled chains. Combined with the pivot-coupled GCMC method for ring simulation, the PDIRR approach also allows the phenomenological simulation of a polydisperse equilibrium phase of rings, 2-dimensional fluid domains, or flat self-assembled disks in three dimensions.

  18. Polymer adsorption-driven self-assembly of nanostructures.

    PubMed

    Chakraborty, A K; Golumbfskie, A J

    2001-01-01

    Driven by prospective applications, there is much interest in developing materials that can perform specific functions in response to external conditions. One way to design such materials is to create systems which, in response to external inputs, can self-assemble to form structures that are functionally useful. This review focuses on the principles that can be employed to design macromolecules that when presented with an appropriate two-dimensional surface, will self-assemble to form nanostructures that may be functionally useful. We discuss three specific examples: (a) biomimetic recognition between polymers and patterned surfaces. (b) control and manipulation of nanomechanical motion generated by biopolymer adsorption and binding, and (c) creation of patterned nanostructuctures by exposing molten diblock copolymers to patterned surfaces. The discussion serves to illustrate how polymer sequence can be manipulated to affect self-assembly characteristics near adsorbing surfaces. The focus of this review is on theoretical and computational work aimed toward elucidating the principles underlying the phenomena pertinent to the three topics noted above. However, synergistic experiments are also described in the appropriate context. PMID:11326074

  19. Micelle-Induced Self-Assembling Protein Nanowires: Versatile Supramolecular Scaffolds for Designing the Light-Harvesting System.

    PubMed

    Sun, Hongcheng; Zhang, Xiyu; Miao, Lu; Zhao, Linlu; Luo, Quan; Xu, Jiayun; Liu, Junqiu

    2016-01-26

    Organic nanoparticle induced self-assembly of proteins with periodic nanostructures is a promising and burgeoning strategy to develop functional biomimetic nanomaterials. Cricoid proteins afford monodispersed and well-defined hollow centers, and can be used to multivalently interact with geometrically symmetric nanoparticles to form one-dimensional protein nanoarrays. Herein, we report that core-cross-linked micelles can direct cricoid stable protein one (SP1) to self-assembling nanowires through multiple electrostatic interactions. One micelle can act as an organic nanoparticle to interact with two central concaves of SP1 in an opposite orientation to form a sandwich structure, further controlling the assembly direction to supramolecular protein nanowires. The reported versatile supramolecular scaffolds can be optionally manipulated to develop multifunctional integrated or synergistic biomimetic nanomaterials. Artificial light-harvesting nanowires are further developed to mimic the energy transfer process of photosynthetic bacteria for their structural similarity, by means of labeling donor and acceptor chromophores to SP1 rings and spherical micelles, respectively. The absorbing energy can be transferred within the adjacent donors around the ring and shuttling the collected energy to the nearby acceptor chromophore. The artificial light-harvesting nanowires are designed by mimicking the structural characteristic of natural LH-2 complex, which are meaningful in exploring the photosynthesis process in vitro. PMID:26634314

  20. Self-Assembly and Horizontal Orientation Growth of VO2 Nanowires

    PubMed Central

    Cheng, Chun; Guo, Hua; Amini, Abbas; Liu, Kai; Fu, Deyi; Zou, Jian; Song, Haisheng

    2014-01-01

    Single-crystalline vanadium dioxide (VO2) nanostructures have attracted an intense research interest recently because of their unique single-domain metal-insulator phase transition property. Synthesis of these nanostructures in the past was limited in density, alignment, or single-crystallinity. The assembly of VO2 nanowires (NWs) is desirable for a “bottom-up” approach to the engineering of intricate structures using nanoscale building blocks. Here, we report the successful synthesis of horizontally aligned VO2 NWs with a dense growth mode in the [1-100]quartz direction of a polished x-cut quartz surface using a simple vapor transport method. Our strategy of controlled growth of VO2 NWs promisingly paves the way for designing novel metal-insulator transition devices based on VO2 NWs. PMID:24965899

  1. Self-Assembled Collagen-like Peptide Fibers as Templates for Metallic Nanowires

    PubMed Central

    Gottlieb, Daniel; Morin, Stephen A.

    2009-01-01

    Inspired by nature’s ability to fabricate supramolecular nanostructures from the bottom-up, materials scientist have become increasingly interested in the use of biomolecules like DNA, peptides, or proteins as templates for the creation of novel nanostructures and nanomaterials. Although the advantages of self-assembling biomolecular structures clearly lie in their chemical diversity, spatial control, and numerous geometric architectures, it is challenging to elaborate them into functional hybrid inorganic–bionanomaterials without rendering the biomolecular scaffold damaged or dysfunctional. In this study, attachment of gold nanoparticles to collagen-related self-assembling peptides at L-lysine residues incorportated within the peptides sequence and the N-terminus led to metal nanoparticle–decorated fibers. After electroless silver plating, these fibers were completely metalized, creating electrically conductive nanowires under mild conditions while leaving the peptide fiber core intact. This study demonstrates the bottom-up assembly of synthetic peptidic fibers under mild conditions and their potential as templates for other complex inorganic–organic hybrid nanostructures. PMID:20130788

  2. Self-Assembled Collagen-like Peptide Fibers as Templates for Metallic Nanowires.

    PubMed

    Gottlieb, Daniel; Morin, Stephen A; Jin, Song; Raines, Ronald T

    2008-01-01

    Inspired by nature's ability to fabricate supramolecular nanostructures from the bottom-up, materials scientist have become increasingly interested in the use of biomolecules like DNA, peptides, or proteins as templates for the creation of novel nanostructures and nanomaterials. Although the advantages of self-assembling biomolecular structures clearly lie in their chemical diversity, spatial control, and numerous geometric architectures, it is challenging to elaborate them into functional hybrid inorganic-bionanomaterials without rendering the biomolecular scaffold damaged or dysfunctional. In this study, attachment of gold nanoparticles to collagen-related self-assembling peptides at L-lysine residues incorportated within the peptides sequence and the N-terminus led to metal nanoparticle-decorated fibers. After electroless silver plating, these fibers were completely metalized, creating electrically conductive nanowires under mild conditions while leaving the peptide fiber core intact. This study demonstrates the bottom-up assembly of synthetic peptidic fibers under mild conditions and their potential as templates for other complex inorganic-organic hybrid nanostructures. PMID:20130788

  3. Simultaneous Tunable Selection and Self-Assembly of Si Nanowires from Heterogeneous Feedstock.

    PubMed

    Constantinou, Marios; Rigas, Grigorios Panagiotis; Castro, Fernando A; Stolojan, Vlad; Hoettges, Kai F; Hughes, Michael P; Adkins, Emily; Korgel, Brian A; Shkunov, Maxim

    2016-04-26

    Semiconducting nanowires (NWs) are becoming essential nanobuilding blocks for advanced devices from sensors to energy harvesters, however their full technology penetration requires large scale materials synthesis together with efficient NW assembly methods. We demonstrate a scalable one-step solution process for the direct selection, collection, and ordered assembly of silicon NWs with desired electrical properties from a poly disperse collection of NWs obtained from a supercritical fluid-liquid-solid growth process. Dielectrophoresis (DEP) combined with impedance spectroscopy provides a selection mechanism at high signal frequencies (>500 kHz) to isolate NWs with the highest conductivity and lowest defect density. The technique allows simultaneous control of five key parameters in NW assembly: selection of electrical properties, control of NW length, placement in predefined electrode areas, highly preferential orientation along the device channel, and control of NWs deposition density from few to hundreds per device. Direct correlation between DEP signal frequency and deposited NWs conductivity is confirmed by field-effect transistor and conducting AFM data. Fabricated NW transistor devices demonstrate excellent performance with up to 1.6 mA current, 10(6)-10(7) on/off ratio and hole mobility of 50 cm(2) V(-1) s(-1). PMID:27002685

  4. Layer-by-layer assembly of nanowires for three-dimensional, multifunctional electronics.

    PubMed

    Javey, Ali; Nam, SungWoo; Friedman, Robin S; Yan, Hao; Lieber, Charles M

    2007-03-01

    We report a general approach for three-dimensional (3D) multifunctional electronics based on the layer-by-layer assembly of nanowire (NW) building blocks. Using germanium/silicon (Ge/Si) core/shell NWs as a representative example, ten vertically stacked layers of multi-NW field-effect transistors (FETs) were fabricated. Transport measurements demonstrate that the Ge/Si NW FETs have reproducible high-performance device characteristics within a given device layer, that the FET characteristics are not affected by sequential stacking, and importantly, that uniform performance is achieved in sequential layers 1 through 10 of the 3D structure. Five-layer single-NW FET structures were also prepared by printing Ge/Si NWs from lower density growth substrates, and transport measurements showed similar high-performance characteristics for the FETs in layers 1 and 5. In addition, 3D multifunctional circuitry was demonstrated on plastic substrates with sequential layers of inverter logical gates and floating gate memory elements. Notably, electrical characterization studies show stable writing and erasing of the NW floating gate memory elements and demonstrate signal inversion with larger than unity gain for frequencies up to at least 50 MHz. The ability to assemble reproducibly sequential layers of distinct types of NW-based devices coupled with the breadth of NW building blocks should enable the assembly of increasing complex multilayer and multifunctional 3D electronics in the future. PMID:17266383

  5. Self-assembled hydrogels utilizing polymer-nanoparticle interactions

    NASA Astrophysics Data System (ADS)

    Appel, Eric A.; Tibbitt, Mark W.; Webber, Matthew J.; Mattix, Bradley A.; Veiseh, Omid; Langer, Robert

    2015-02-01

    Mouldable hydrogels that flow on applied stress and rapidly self-heal are increasingly utilized as they afford minimally invasive delivery and conformal application. Here we report a new paradigm for the fabrication of self-assembled hydrogels with shear-thinning and self-healing properties employing rationally engineered polymer-nanoparticle (NP) interactions. Biopolymer derivatives are linked together by selective adsorption to NPs. The transient and reversible interactions between biopolymers and NPs enable flow under applied shear stress, followed by rapid self-healing when the stress is relaxed. We develop a physical description of polymer-NP gel formation that is utilized to design biocompatible gels for drug delivery. Owing to the hierarchical structure of the gel, both hydrophilic and hydrophobic drugs can be entrapped and delivered with differential release profiles, both in vitro and in vivo. The work introduces a facile and generalizable class of mouldable hydrogels amenable to a range of biomedical and industrial applications.

  6. Managing Complex Self-Assembly of Multicomponent Polymers

    NASA Astrophysics Data System (ADS)

    Fredrickson, Glenn H.

    2000-03-01

    Polymer blends, composites, and solutions of commercial significance are often characterized by high-dimensional compositional and architectural parameter spaces. Optimizing the properties of these formulations is largely empirical and is frequently limited by restrictions on the number of experiments that can be performed. A new approach is described for implementing self-consistent field theory of multicomponent polymers that facilitates massively parallel screening of large parameter spaces for novel types of self-assembly. This combinatorial-theoretical screening approach is demonstrated on a class of tetrablock copolymers motivated by a collaboration with the Dow Chemical Company. Extensions of the formalism are described that allow for the inclusion of chemical reactions, realistic treatment of diffusion processes, and flow effects. Collaborators: F. Drolet, E. J. Kramer, S. F. Hahn, C. Y. Ryu, E. Flewelling, F. S. Bates

  7. Polymer-template-assisted growth of gold nanowires using a novel flow-stream technique.

    PubMed

    Metwalli, E; Moulin, J-F; Perlich, J; Wang, W; Diethert, A; Roth, S V; Müller-Buschbaum, P

    2009-10-01

    By utilizing a fluidic device, a gold nanoparticle dispersion is cast onto a nanostructured polymer template using solution subjected to hydrodynamic flow. With in situ grazing incidence small-angle X-ray scattering (GISAXS), the progressive gold deposition from a stream of gold solution onto the polymer template of a diblock copolymer with parallel cylinder morphology arranged into powder-like domains is investigated. The continuously flowing solution causes a systematic increase in the X-ray contrast between both of the microphase-separated blocks of the block copolymer film, indicating flow-induced selective gold immobilization on one block. Both in situ GISAXS data and atomic force microscopy of the metal-deposited polymer film prove the 1D coalescence of nanoparticles into continuous nanowires. With additional gold nanoparticle upload by the continuous flow-stream method, the selectivity of the nanoparticle deposition diminishes as a result of the formation of a pseudo uniform gold layer. Consequently, this flow-stream deposition technique introduces an easy alternative method to the vapor deposition technique for surface gold nanopatterning. PMID:19572494

  8. Highly efficient and stable Si nanowires array embedded into transparent polymer for visible light photoelectrochemical cell

    NASA Astrophysics Data System (ADS)

    Wang, Hui; Wang, Jian-Tao; Ou, Xue-Mei; Li, Fan; Zhang, Xiao-Hong

    2014-07-01

    Photoelectrochemical (PEC) cell supports a renewable method for solving current environmental and energy issues by combining solar energy collection and photocatalysis in a single semiconductor photoelectrode. However, it is still challenged by visible light photoelectrodes. The present work reports fabricating highly efficient and stable Si nanowires (SiNWs) array as visible light photoelectrodes. It involves embedding SiNWs arrays into a transparent polymer substrate to build an axial carrier collection geometry. We demonstrated that this strategy could significantly strengthen the chemical stability of SiNWs by largely reducing their surface area. Moreover, this device structure can also enhance visible light absorption efficiency through taking advantage of the highly crystalline structure of vapor-liquid-solid (VLS) grown SiNWs. Thus it can double the photodegradation ability of SiNWs.

  9. Si6H12/Polymer Inks for Electrospinning a-Si Nanowire Lithium Ion Battery Anodes

    SciTech Connect

    Schulz, Douglas L.; Hoey, Justin; Smith, Jeremiah; Elangovan, Arumugasamy; Wu, Xiangfa; Akhatov, Iskander; Payne, Scott; Moore, Jayma; Boudjouk, Philip; Pederson, Larry; Xiao, Jie; Zhang, Jiguang

    2010-08-04

    Amorphous silicon nanowires 'a-SiNWs' have been prepared by electrospinning a liquid silane-based precursor. Cyclohexasilane 'Si6H12' was admixed with poly-methyl methacrylate (PMMA) in toluene giving an ink that was electrospun into the Si6H12/PPMA wires with diameters of 50-2000 nm. Raman spectroscopy revealed that thermal treatment at 350 C transforms this deposit into a-SiNWs. These materials were coated with a thin carbon layer and then tested as half-cells where a reasonable plateau in electrochemical cycling was observed after an initial capacity fade. Additionally, porous a-SiNWs were realized when the thermally decomposable binder polypropylene carbonate/polycyclohexene carbonate was used as the polymer carrier.

  10. Gold nanowired: a linear (Au25)(n) polymer from Au25 molecular clusters.

    PubMed

    De Nardi, Marco; Antonello, Sabrina; Jiang, De-en; Pan, Fangfang; Rissanen, Kari; Ruzzi, Marco; Venzo, Alfonso; Zoleo, Alfonso; Maran, Flavio

    2014-08-26

    Au25(SR)18 has provided fundamental insights into the properties of clusters protected by monolayers of thiolated ligands (SR). Because of its ultrasmall core, 1 nm, Au25(SR)18 displays molecular behavior. We prepared a Au25 cluster capped by n-butanethiolates (SBu), obtained its structure by single-crystal X-ray crystallography, and studied its properties both experimentally and theoretically. Whereas in solution Au25(SBu)18(0) is a paramagnetic molecule, in the crystal it becomes a linear polymer of Au25 clusters connected via single Au-Au bonds and stabilized by proper orientation of clusters and interdigitation of ligands. At low temperature, [Au25(SBu)18(0)]n has a nonmagnetic ground state and can be described as a one-dimensional antiferromagnetic system. These findings provide a breakthrough into the properties and possible solid-state applications of molecular gold nanowires. PMID:25088331

  11. High stability of self-assembled peptide nanowires against thermal, chemical, and proteolytic attacks.

    PubMed

    Ryu, Jungki; Park, Chan Beum

    2010-02-01

    Understanding the self-assembly of peptides into ordered nanostructures is recently getting much attention since it can provide an alternative route for fabricating novel bio-inspired materials. In order to realize the potential of the peptide-based nanofabrication technology, however, more information is needed regarding the integrity or stability of peptide nanostructures under the process conditions encountered in their applications. In this study, we investigated the stability of self-assembled peptide nanowires (PNWs) and nanotubes (PNTs) against thermal, chemical, proteolytic attacks, and their conformational changes upon heat treatment. PNWs and PNTs were grown by the self-assembly of diphenylalanine (Phe-Phe), a peptide building block, on solid substrates at different chemical atmospheres and temperatures. The incubation of diphenylalanine under aniline vapor at 150 degrees C led to the formation of PNWs, while its incubation with water vapor at 25 degrees C produced PNTs. We analyzed the stability of peptide nanostructures using multiple tools, such as electron microscopy, thermal analysis tools, circular dichroism, and Fourier-transform infrared spectroscopy. Our results show that PNWs are highly stable up to 200 degrees C and remain unchanged when incubated in aqueous solutions (from pH 1 to 14) or in various chemical solvents (from polar to non-polar). In contrast, PNTs started to disintegrate even at 100 degrees C and underwent a conformational change at an elevated temperature. When we further studied their resistance to a proteolytic environment, we discovered that PNWs kept their initial structure while PNTs fully disintegrated. We found that the high stability of PNWs originates from their predominant beta-sheet conformation and the conformational change of diphenylalanine nanostructures. Our study suggests that self-assembled PNWs are suitable for future nano-scale applications requiring harsh processing conditions. PMID:19777585

  12. Conducting nanowires built by controlled self-assembly of amyloid fibers and selective metal deposition

    PubMed Central

    Scheibel, Thomas; Parthasarathy, Raghuveer; Sawicki, George; Lin, Xiao-Min; Jaeger, Heinrich; Lindquist, Susan L.

    2003-01-01

    Recent research in the field of nanometer-scale electronics has focused on the operating principles of small-scale devices and schemes to realize useful circuits. In contrast to established “top-down” fabrication techniques, molecular self-assembly is emerging as a “bottom-up” approach for fabricating nanostructured materials. Biological macromolecules, especially proteins, provide many valuable properties, but poor physical stability and poor electrical characteristics have prevented their direct use in electrical circuits. Here we describe the use of self-assembling amyloid protein fibers to construct nanowire elements. Self-assembly of a prion determinant from Saccharomyces cerevisiae, the N-terminal and middle region (NM) of Sup35p, produced 10-nm-wide protein fibers that were stable under a wide variety of harsh physical conditions. Their lengths could be roughly controlled by assembly conditions in the range of 60 nm to several hundred micrometers. A genetically modified NM variant that presents reactive, surface-accessible cysteine residues was used to covalently link NM fibers to colloidal gold particles. These fibers were placed across gold electrodes, and additional metal was deposited by highly specific chemical enhancement of the colloidal gold by reductive deposition of metallic silver and gold from salts. The resulting silver and gold wires were ≈100 nm wide. These biotemplated metal wires demonstrated the conductive properties of a solid metal wire, such as low resistance and ohmic behavior. With such materials it should be possible to harness the extraordinary diversity and specificity of protein functions to nanoscale electrical circuitry. PMID:12672964

  13. Phosphorylcholine substituted polyolefins: New syntheses, solution assemblies, and polymer vesicles

    NASA Astrophysics Data System (ADS)

    Kratz, Katrina A.

    This thesis describes the synthesis and applications of a new series of amphiphilic homopolymers and copolymers consisting of hydrophobic polyolefin backbone and hydrophilic phosphorylcholine (PC) pendant groups. These polymers are synthesized by ring opening metathesis polymerization (ROMP) of a novel PC- cyclooctene monomer, and copolymerization of various functionalized cyclooctene comonomers. Incorporation of different comonomers into the PC-polyolefin backbone affords copolymers with different functionalities, including crosslinkers, fluorophores, and other reactive groups, that tune the range of applications of these polymers, and their hydrophobic/hydrophilic balance. The amphiphilic nature of PC-polyolefins was exploited in oil-water interfacial assembly, providing robust polymer capsules to encapsulate and deliver nanoparticles to damaged regions of a substrate in a project termed `repair-and-go.' In repair-and-go, a flexible microcapsule filled with a solution of nanoparticles probes an imperfection-riddled substrate as it rolls over the surface. The thin capsule wall allows the nanoparticles to escape the capsules and enter into the cracks, driven in part by favorable interactions between the nanoparticle ligands and the cracked surface (i.e., hydrophobic-hydrophobic interactions). The capsules then continue their transport along the surface, filling more cracks and depositing particles into them. The amphiphilic nature of PC-polyolefins was also exploited in aqueous assembly, forming novel polymer vesicles in water. PC-polyolefin vesicles ranged in size from 50 nm to 30 µm. The mechanical properties of PC-polyolefin vesicles were measured by micropipette aspiration techniques, and found to be more robust than conventional liposomes or polymersomes prepared from block copolymers. PC-polyolefin vesicles have potential use in drug delivery; it was found that the cancer drug doxorubicin could be encapsulated efficiently in PC-polyolefin vesicles. In

  14. Integrated chemical and biological systems in nanowire structures towards nano-scale sensors

    NASA Astrophysics Data System (ADS)

    Hernandez, Rose M.

    Nanowires composed of metal and conducting polymers with integrated proteins and chemical systems have been investigated as building blocks for next-generation nano-scale sensors and assemblies. These nanowires were fabricated by combining chemical and electrochemical methods of synthesis of gold and conducting polymers in nanopores of anodized alumina membranes. Polymer nanowires were synthesized from buffer solutions as a mean to promote a biocompatible environment for the incorporation of proteins. A variety of proteins were incorporated into the polymer matrix by entrapment during polymerization that imparted the polymer material with biological functionality. Another class of composite nanowires containing electro-active conducting polymer junctions was developed for applications in chemical sensor arrays. The methodologies described in this thesis provide an inexpensive and straightforward approach to the synthesis of anisotropic nanoparticles incorporating a variety of biological and inorganic species that can be integrated to current microelectronic technologies for the development of nano-scale sensor arrays.

  15. Self-assembled GaN quantum wires on GaN/AlN nanowire templates.

    PubMed

    Arbiol, Jordi; Magen, Cesar; Becker, Pascal; Jacopin, Gwénolé; Chernikov, Alexey; Schäfer, Sören; Furtmayr, Florian; Tchernycheva, Maria; Rigutti, Lorenzo; Teubert, Jörg; Chatterjee, Sangam; Morante, Joan R; Eickhoff, Martin

    2012-12-01

    We present a novel approach for self-assembled growth of GaN quantum wires (QWRs) exhibiting strong confinement in two spatial dimensions. The GaN QWRs are formed by selective nucleation on {112[combining macron]0} (a-plane) facets formed at the six intersections of {11[combining macron]00} (m-plane) sidewalls of AlN/GaN nanowires used as a template. Based on microscopy observations we have developed a 3D model explaining the growth mechanism of QWRs. We show that the QWR formation is governed by self-limited pseudomorphic growth on the side facets of the nanowires (NWs). Quantum confinement in the QWRs is confirmed by the observation of narrow photoluminescence lines originating from individual QWRs with emission energies up to 4.4 eV. Time-resolved photoluminescence studies reveal a short decay time (~120 ps) of the QWR emission. Capping of the QWRs with AlN allows enhancement of the photoluminescence, which is blue-shifted due to compressive strain. The emission energies from single QWRs are modelled assuming a triangular cross-section resulting from self-limited growth on a-plane facets. Comparison with the experimental results yields an average QWR diameter of about 2.7 nm in agreement with structural characterization. The presented results open a new route towards controlled realization of one-dimensional semiconductor quantum structures with a high potential both for fundamental studies and for applications in electronics and in UV light generation. PMID:23100169

  16. Component assembly with shape memory polymer fastener for microrobots

    NASA Astrophysics Data System (ADS)

    Kim, Ji-Suk; Lee, Dae-Young; Koh, Je-Sung; Jung, Gwang-Pil; Cho, Kyu-Jin

    2014-01-01

    Adhesives are generally used for the assembly of microrobots, whereas bolts, screws, or rivets are used for larger robots. Although adhesives are easy to apply, lightweight, and small, they cannot be used for repeated assembly and disassembly of parts. In this paper, we present a novel microfastener composed of a polyurethane-based shape memory polymer (SMP) that is lightweight and small but that is easily detached for disassembly. This was achieved by using the shape recovery and modulus change of the SMP. A sheet of macromolded SMP was laser machined into an I-beam-shaped rivet, and notches were added to the structure to prevent stress concentration. Pull-off tests showed that, as the notch radius increased, the disengagement strength of the rivet fastener decreased and the reusability increased. Through the elastoplastic model, a single SMP rivet was calculated to have maximum disengagement strength of 150 N cm-2 in the elastic range, depending on the notch radius. The fasteners were applied to a jumping microrobot. The legs and body were assembled with ten fasteners, which showed no permanent deformation after impact during jumping movements. The legs were easily replaced with ones of different stiffness by heating the engaged sites to make the fasteners compliant and detachable. The proposed detachable SMP microfasteners are particularly useful for testing the isolated performance of microrobot components to determine the optimal designs for these components.

  17. Patterning of self-assembled monolayers by phase-shifting mask and its applications in large-scale assembly of nanowires

    SciTech Connect

    Gao, Fan; Zhang, Dakuan; Wang, Jianyu; Sheng, Yun; Wang, Xinran; Chen, Kunji; Zhou, Minmin; Yan, Shancheng; Shen, Jiancang; Pan, Lijia; Shi, Yi

    2015-01-26

    A nonselective micropatterning method of self-assembled monolayers (SAMs) based on laser and phase-shifting mask (PSM) is demonstrated. Laser beam is spatially modulated by a PSM, and periodic SAM patterns are generated sequentially through thermal desorption. Patterned wettability is achieved with alternating hydrophilic/hydrophobic stripes on octadecyltrichlorosilane monolayers. The substrate is then used to assemble CdS semiconductor nanowires (NWs) from a solution, obtaining well-aligned NWs in one step. Our results show valuably the application potential of this technique in engineering SAMs for integration of functional devices.

  18. Selective crystallization of conjugated polymers into nanowires from graphene coated surfaces

    NASA Astrophysics Data System (ADS)

    Acevedo-Cartagena, Daniel; Zhu, Jiaxin; Trabanino, Elvira; Pentzer, Emily; Emrick, Todd; Briseño, Alejandro; Nonnenmann, Stephen; Hayward, Ryan

    Solution-based crystallization of conjugated polymers offers a scalable and attractive route to develop hierarchical structures for organic electronic devices, especially solar cells. The introduction of well-defined nucleation sites into metastable supersaturated solutions provides a way to regulate the crystallization behavior, and therefore the morphology of the material. We focus on metastable solutions of poly(3-hexylthiophene) (P3HT) dissolved in mixtures of m-xylene, a marginal solvent, and chlorobenzene, a good solvent. Appropriate levels of supersaturation are identified to suppress homogenous nucleation of crystals at room temperature, while allowing for crystallization on heterogeneous nucleation sites. We show that in these metastable solutions, P3HT selectively crystallizes on graphene-coated surfaces. Through in situ atomic force microscopy, we confirm that nanowires grow vertically in a face-on orientation from highly oriented pyrolytic graphite and graphene. Moreover, this method can be successfully extended to other conjugated polymers with superior electronic properties, such as poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b] thiophene]. Therefore, this method is a promising route to improve the performance of organic electronics.

  19. Self-assembly of supramolecular triarylamine nanowires in mesoporous silica and biocompatible electrodes thereof

    NASA Astrophysics Data System (ADS)

    Licsandru, Erol-Dan; Schneider, Susanne; Tingry, Sophie; Ellis, Thomas; Moulin, Emilie; Maaloum, Mounir; Lehn, Jean-Marie; Barboiu, Mihail; Giuseppone, Nicolas

    2016-03-01

    Biocompatible silica-based mesoporous materials, which present high surface areas combined with uniform distribution of nanopores, can be organized in functional nanopatterns for a number of applications. However, silica is by essence an electrically insulating material which precludes applications for electro-chemical devices. The formation of hybrid electroactive silica nanostructures is thus expected to be of great interest for the design of biocompatible conducting materials such as bioelectrodes. Here we show that we can grow supramolecular stacks of triarylamine molecules in the confined space of oriented mesopores of a silica nanolayer covering a gold electrode. This addressable bottom-up construction is triggered from solution simply by light irradiation. The resulting self-assembled nanowires act as highly conducting electronic pathways crossing the silica layer. They allow very efficient charge transfer from the redox species in solution to the gold surface. We demonstrate the potential of these hybrid constitutional materials by implementing them as biocathodes and by measuring laccase activity that reduces dioxygen to produce water.Biocompatible silica-based mesoporous materials, which present high surface areas combined with uniform distribution of nanopores, can be organized in functional nanopatterns for a number of applications. However, silica is by essence an electrically insulating material which precludes applications for electro-chemical devices. The formation of hybrid electroactive silica nanostructures is thus expected to be of great interest for the design of biocompatible conducting materials such as bioelectrodes. Here we show that we can grow supramolecular stacks of triarylamine molecules in the confined space of oriented mesopores of a silica nanolayer covering a gold electrode. This addressable bottom-up construction is triggered from solution simply by light irradiation. The resulting self-assembled nanowires act as highly conducting

  20. Structure of assemblies of metal nanowires in mesoporous alumina membranes studied by EXAFS, XANES, X-ray diffraction and SAXS.

    PubMed

    Benfield, Robert E; Grandjean, Didier; Dore, John C; Esfahanian, Hamid; Wu, Zhonghua; Kröll, Michael; Geerkens, Marcus; Schmid, Günter

    2004-01-01

    Mesoporous alumina membranes ("anodic aluminium oxide", or "AAO") are made by anodic oxidation of aluminium metal. These membranes contain hexagonal arrays of parallel non-intersecting cylindrical pores perpendicular to the membrane surface. By varying the anodisation voltage, the pore diameters are controllable within the range 5-250 nm. We have used AAO membranes as templates for the electrochemical deposition of metals within the pores to produce nanowires. These represent assemblies of one-dimensional quantum wires with prospective applications in electronic, optoelectronic and magnetic devices. Detailed characterisation of the structures of these nanowire assemblies on a variety of length scales is essential to understand their physical properties and evaluate their possible applications. We have used EXAFS, XANES, WAXS, high energy X-ray diffraction and SAXS to study their structure and bonding. In this paper we report the results of our studies of four different nanowire systems supported in AAO membranes. These are the ferromagnetic metals iron and cobalt, the superconducting metal tin, and the semiconductor gallium nitride. Iron nanowires in pores of diameter over the range 12 nm-72 nm are structurally very similar to bcc bulk iron. They have a strong preferred orientation within the alumina pores. Their XANES shows significant differences from that of bulk iron, showing that the electronic structure of the iron nanowires depends systematically on their diameter. Cobalt nanowires are composed of a mixture of hcp and fcc phases, but the ratio of the two phases does not depend in a simple way on the pore diameter or preparation conditions. In bulk cobalt, the fcc beta-phase is normally stable only at high temperatures. Strong preferred orientation of the c-axis in the pores was found. Tin nanowires in alumina membranes with pores diameters between 12 nm and 72 nm have a tetragonal beta-structure at ambient temperature and also at 80 K. Magnetic

  1. Effects of polymer side chains on the self-assembling of conjugated polymer in thin film

    NASA Astrophysics Data System (ADS)

    Jiang, Yunfei; Wang, Yiqing; Bunz, Uvw H. F.; Perahia, Dvora

    2006-03-01

    Conjugated polymers are inherently semi-conducting and optically active materials, with immense potential applications in organic electro-optical devices. The chemical structure of the polymer including the rigidity of the backbone and the nature of substituents affect their association as well as their electro-optical response. The following work reports the effects of different side chains on the structure and fluorescence of highly conjugated polymer, poly(para phenyleneethynylene) (PPE). When substituted by long polylactide side chains they self-assemble into wires with fingerprint-like arrangement, casting from chloroform solutions on oxidized silicon wafer. With increasing content of poor solvent, the dimension of the structures increased and then crystallized area appeared, as showed in AFM studies. The introducing of the long flexible polymer side chains has significantly reduced the stacking between rigid backbones. This in tern results in a frequency shift in their fluoresces response, indication changes in the electronic levels. Direct measurements of the electronic levels using ATM are currently in progress.

  2. Self-Assembled Hydrogels Utilising Polymer-Nanoparticle Interactions

    PubMed Central

    Appel, Eric A.; Tibbitt, Mark W.; Webber, Matthew J.; Mattix, Bradley A.; Veiseh, Omid

    2015-01-01

    Mouldable hydrogels that flow upon applied stress and rapidly self-heal are increasingly utilised as they afford minimally invasive delivery and conformal application. Here we report a new paradigm for the fabrication of self-assembled hydrogels with shear-thinning and self-healing properties employing rationally engineered polymer-nanoparticle interactions. Biopolymer derivatives are linked together by selective adsorption to nanoparticles. The transient and reversible interactions between biopolymers and nanoparticles enable flow under applied shear stress, followed by rapid self-healing when the stress is relaxed. We develop a physical description of polymer-nanoparticle gel formation that is utilised to design biocompatible gels for minimally-invasive drug delivery. Owing to the hierarchical structure of the gel, both hydrophilic and hydrophobic drugs can be entrapped and delivered with differential release profiles, both in vitro and in vivo. The work introduces a facile and generalizable class of mouldable hydrogels amenable to a range of biomedical and industrial applications. PMID:25695516

  3. Copper(II)-Mediated Self-Assembly of Hairpin Peptides and Templated Synthesis of CuS Nanowires.

    PubMed

    Wang, Chengdong; Sun, Yawei; Wang, Jiqian; Xu, Hai; Lu, Jian R

    2015-09-01

    The self-assembly of peptides and proteins under well-controlled conditions underlies important nanostructuring processes that could be harnessed in practical applications. Herein, the synthesis of a new hairpin peptide containing four histidine residues is reported and the self-assembly process mediated by metal ions is explored. The work involves the combined use of circular dichroism, NMR spectroscopy, UV/Vis spectroscopy, AFM, and TEM to follow the structural and morphological details of the metal-coordination-mediated folding and self-assembly of the peptide. The results indicate that by forming a tetragonal coordination geometry with four histidine residues, copper(II) ions selectively trigger the peptide to fold and then self-assemble into nanofibrils. Furthermore, the copper(II)-bound nanofibrils template the synthesis of CuS nanowires, which display a near-infrared laser-induced thermal effect. PMID:26110265

  4. Enhancing Crystalline Structural Orders of Polymer Semiconductors for Efficient Charge Transport via Polymer-Matrix-Mediated Molecular Self-Assembly.

    PubMed

    Lei, Yanlian; Deng, Ping; Lin, Ming; Zheng, Xuelin; Zhu, Furong; Ong, Beng S

    2016-08-01

    A facile polymer-matrix-mediated molecular self-assembly of polymer semiconductors into highly crystalline orders for efficient charge transport in organic thin-film transistors is demonstrated. Phenomenal enhancements in field-effect mobility of about one order of magnitude and current on/off ratio of two to three orders of magnitude are realized with polyacrylonitrile-incorporated polymer semiconductor compositions via solution deposition. PMID:27168128

  5. Recognition-Mediated Assembly of Quantum Dot Polymer Conjugates with Controlled Morphology

    PubMed Central

    Nandwana, Vikas; Subramani, Chandramouleeswaran; Eymur, Serkan; Yeh, Yi-Cheun; Tonga, Gulen Yesilbag; Tonga, Murat; Jeong, Youngdo; Yang, Boqian; Barnes, Michael D.; Cooke, Graeme; Rotello, Vincent M.

    2011-01-01

    We have demonstrated a polymer mediated “bricks and mortar” method for the self-assembly of quantum dots (QDs). This strategy allows QDs to self-assemble into structured aggregates using complementary three-point hydrogen bonding. The resulting nanocomposites have distinct morphologies and inter-particle distances based on the ratio between QDs and polymer. Time resolved photoluminescence measurements showed that the optical properties of the QDs were retained after self-assembly. PMID:22016664

  6. Design of polymer motifs for nucleic acid recognition and assembly stabilization

    NASA Astrophysics Data System (ADS)

    Zhou, Zhun

    This dissertation describes the synthesis and assembly of bio-functional polymers and the applications of these polymers to drug encapsulation, delivery, and multivalent biomimetic macromolecular recognition between synthetic polymer and nucleic acids. The main content is divided into three parts: (1) polyacidic domains as strongly stabilizing design elements for aqueous phase polyacrylate diblock assembly; (2) small molecule/polymer recognition triggered macromolecular assembly and drug encapsulation; (3) trizaine derivatized polymer as a novel class of "bifacial polymer nucleic acid" (bPoNA) and applications of bPoNA to nanoparticle loading of DNA/RNA, silencing delivery as well as control of aptamer function. Through the studies in part (1) and part (2), it was demonstrated that well-designed polymer motifs are not only able to enhance assemblies driven by non-specific hydrophobic effect, but are also able to direct assemblies based on specific recognitions. In part (3) of this dissertation, this concept was further extended by the design of polyacrylate polymers that are capable of discrete and robust hybridization with nucleic acids. This surprising finding demonstrated both fundamental and practical applications. Overall, these studies provided insights into the rational design elements for improving the bio-functions of synthetic polymers, and significantly expanded the scope of biological applications in which polymers synthesized via controlled radical polymerization may play a role.

  7. Intraband absorption in self-assembled Ge-doped GaN/AlN nanowire heterostructures.

    PubMed

    Beeler, M; Hille, P; Schörmann, J; Teubert, J; de la Mata, M; Arbiol, J; Eickhoff, M; Monroy, E

    2014-03-12

    We report the observation of transverse-magnetic-polarized infrared absorption assigned to the s-p(z) intraband transition in Ge-doped GaN/AlN nanodisks (NDs) in self-assembled GaN nanowires (NWs). The s-p(z) absorption line experiences a blue shift with increasing ND Ge concentration and a red shift with increasing ND thickness. The experimental results in terms of interband and intraband spectroscopy are compared to theoretical calculations of the band diagram and electronic structure of GaN/AlN heterostructured NWs, accounting for their three-dimensional strain distribution and the presence of surface states. From the theoretical analysis, we conclude that the formation of an AlN shell during the heterostructure growth applies a uniaxial compressive strain which blue shifts the interband optical transitions but has little influence on the intraband transitions. The presence of surface states with density levels expected for m-GaN plane charge-deplete the base of the NWs but is insufficient to screen the polarization-induced internal electric field in the heterostructures. Simulations show that the free-carrier screening of the polarization-induced internal electric field in the NDs is critical to predicting the photoluminescence behavior. The intraband transitions, on the other hand, are blue-shifted due to many-body effects, namely, the exchange interaction and depolarization shift, which exceed the red shift induced by carrier screening. PMID:24502703

  8. Self-assembly of supramolecular triarylamine nanowires in mesoporous silica and biocompatible electrodes thereof.

    PubMed

    Licsandru, Erol-Dan; Schneider, Susanne; Tingry, Sophie; Ellis, Thomas; Moulin, Emilie; Maaloum, Mounir; Lehn, Jean-Marie; Barboiu, Mihail; Giuseppone, Nicolas

    2016-03-14

    Biocompatible silica-based mesoporous materials, which present high surface areas combined with uniform distribution of nanopores, can be organized in functional nanopatterns for a number of applications. However, silica is by essence an electrically insulating material which precludes applications for electro-chemical devices. The formation of hybrid electroactive silica nanostructures is thus expected to be of great interest for the design of biocompatible conducting materials such as bioelectrodes. Here we show that we can grow supramolecular stacks of triarylamine molecules in the confined space of oriented mesopores of a silica nanolayer covering a gold electrode. This addressable bottom-up construction is triggered from solution simply by light irradiation. The resulting self-assembled nanowires act as highly conducting electronic pathways crossing the silica layer. They allow very efficient charge transfer from the redox species in solution to the gold surface. We demonstrate the potential of these hybrid constitutional materials by implementing them as biocathodes and by measuring laccase activity that reduces dioxygen to produce water. PMID:26892311

  9. Self-assembly of Nanopatterns on Shape Memory Polymer Substrates

    NASA Astrophysics Data System (ADS)

    Chen, Zhongbi

    Periodic surface nanostructures provide unique acoustic, electronic, optical and mechanical properties, with potential applications to metamaterials, sensors, catalysis, medicine, etc. However, assembling nanometer scale constituents into engineering scale components or devices poses tremendous challenges such as cost reduction and scalability. In this work, we will introduce a novel directed self-assembly method that has the potential to address these challenges by forming unidirectional micro- and nano-wrinkles on engineering scale polymer substrates. The approach utilizes a smart material, shape memory polymer (SMP), as the substrate in a bi-layer thin-film/substrate system. With a specially-designed programming scheme, the SMP substrate can retract in one direction while expand in the perpendicular direction in a heating process. Consequently, the thin film corrugates and the wrinkling patterns are aligned. A parametric study that investigates how the system parameters influence the surface topology will be presented. Besides wrinkles, surface defects that occurred concurrently were also observed. We will present a progressive damage scheme and a microdomain-based model to understand and possibly help preventing the formation of defects. In addition, this work will also address our efforts in shrinking the wrinkle feature size from several microns to the tens of nanometer range. Two methods, through which the minimum wrinkle wavelength was reduced from one micron to 300 nm and further down to 35 nm will be elaborated. Such aligned wrinkles whose wavelength spanning two orders of magnitude from as small as 35 nm to as large as 5 mum will open up avenues for numerous exciting applications. The application of using the self-assembled wrinkled surface as the back-reflector in solar cells to improve the power conversion efficiency will be discussed as a case study. The long-term stability of the wrinkle topology, which is essential to efficiency boost will be

  10. Template directed assembly of nanoelements in viscous polymer environments

    NASA Astrophysics Data System (ADS)

    Modi, Satyamkumar

    Polymer melt-based manufacturing methods, such as injection molding, offer the potential of directly fabricating three-dimensional parts with nanostructured surfaces in a one-step, high-rate, and solventless process. Electrophoretic deposition has the potential to produce in-mold assembly of nanoparticles during injection molding. The process is fast, is cost effective and can be automated. This electrophoretic deposition, however, has been performed from low-viscosity media and polymer melts are far more viscous. This research provided a fundamental understanding of the electrophoretic deposition process in viscous media. Electrophoresis was performed using a model system of carbon black and polystyrene in tetrahydrofuran (THF). Examined were the effects of processing parameters, polystyrene molecular weight, and carbon black charge. The presence of polystyrene did not prevent deposition of carbon black, but deposition rates decreased at shorter deposition times; deposition was not linear with increasing applied voltage; and greater solution concentrations reduced the critical voltages. A comparison of experimental data with Hamaker's model showed that about 1.6% of the available polystyrene was initially deposited with the carbon black. At voltages above the critical voltage, the deposited mass indicated formation of electrically insulating layers on the electrodes. Increases in polystyrene molecular weight reduced the electrophoretic deposition of the carbon black particles due to increases in suspension viscosity and preferential adsorption of the longer polystyrene chains on the carbon black particles. At low deposition times (≤ 5 seconds), only carbon black deposited onto the electrodes. For longer deposition times, polystyrene co-deposited with the carbon black, with the amount of polystyrene increasing with molecular weight and decreasing with greater charge on the polystyrene molecules. The additional of function groups to the carbon black surface

  11. Measuring photoluminescence spectra of self-assembly array nanowire of colloidal CdSe quantum dots using scanning near-field optics microscopy

    NASA Astrophysics Data System (ADS)

    Bai, Zhongchen; Hao, Licai; Zhang, Zhengping; Qin, Shuijie

    2016-05-01

    A novel periodic array CdSe nanowire is prepared on a substrate of the porous titanium dioxide by using a self-assembly method of the colloidal CdSe quantum dots (QDs). The experimental results show that the colloidal CdSe QDs have renewedly assembled on its space scale and direction in process of losing background solvent and form the periodic array nanowire. The main peak wavelength of Photoluminescence (PL) spectra, which is measured by using a 100-nm aperture laser beam spot on a scanning near-field optics microscopy, has shifted 60 nm with compared to the colloidal CdSe QDs. Furthermore, we have measured smaller ordered nanometer structure in thin QDs area as well, a 343-nm periodic nanowire in thick QDs area and the colloidal QDs in edge of well-ordered nanowire.

  12. Temperature-induced reversible self-assembly of diphenylalanine peptide and the structural transition from organogel to crystalline nanowires.

    PubMed

    Huang, Renliang; Wang, Yuefei; Qi, Wei; Su, Rongxin; He, Zhimin

    2014-01-01

    Controlling the self-assembly of diphenylalanine peptide (FF) into various nanoarchitectures has received great amounts of attention in recent years. Here, we report the temperature-induced reversible self-assembly of diphenylalanine peptide to microtubes, nanowires, or organogel in different solvents. We also find that the organogel in isopropanol transforms into crystalline flakes or nanowires when the temperature increases. The reversible self-assembly in polar solvents may be mainly controlled by electronic and aromatic interactions between the FF molecules themselves, which is associated with the dissociation equilibrium and significantly influenced by temperature. We found that the organogel in the isopropanol solvent made a unique transition to crystalline structures, a process that is driven by temperature and may be kinetically controlled. During the heating-cooling process, FF preferentially self-assembles to metastable nanofibers and organogel. They further transform to thermodynamically stable crystal structures via molecular rearrangement after introducing an external energy, such as the increasing temperature used in this study. The strategy demonstrated in this study provides an efficient way to controllably fabricate smart, temperature-responsive peptide nanomaterials and enriches the understanding of the growth mechanism of diphenylalanine peptide nanostructures. PMID:25520600

  13. Temperature-induced reversible self-assembly of diphenylalanine peptide and the structural transition from organogel to crystalline nanowires

    PubMed Central

    2014-01-01

    Controlling the self-assembly of diphenylalanine peptide (FF) into various nanoarchitectures has received great amounts of attention in recent years. Here, we report the temperature-induced reversible self-assembly of diphenylalanine peptide to microtubes, nanowires, or organogel in different solvents. We also find that the organogel in isopropanol transforms into crystalline flakes or nanowires when the temperature increases. The reversible self-assembly in polar solvents may be mainly controlled by electronic and aromatic interactions between the FF molecules themselves, which is associated with the dissociation equilibrium and significantly influenced by temperature. We found that the organogel in the isopropanol solvent made a unique transition to crystalline structures, a process that is driven by temperature and may be kinetically controlled. During the heating-cooling process, FF preferentially self-assembles to metastable nanofibers and organogel. They further transform to thermodynamically stable crystal structures via molecular rearrangement after introducing an external energy, such as the increasing temperature used in this study. The strategy demonstrated in this study provides an efficient way to controllably fabricate smart, temperature-responsive peptide nanomaterials and enriches the understanding of the growth mechanism of diphenylalanine peptide nanostructures. PMID:25520600

  14. Directed assembly of gold nanowires on silicon via reorganization and simultaneous fusion of randomly distributed gold nanoparticles.

    PubMed

    Reinhardt, Hendrik M; Bücker, Kerstin; Hampp, Norbert A

    2015-05-01

    Laser-induced reorganization and simultaneous fusion of nanoparticles is introduced as a versatile concept for pattern formation on surfaces. The process takes advantage of a phenomenon called laser-induced periodic surface structures (LIPSS) which originates from periodically alternating photonic fringe patterns in the near-field of solids. Associated photonic fringe patterns are shown to reorganize randomly distributed gold nanoparticles on a silicon wafer into periodic gold nanostructures. Concomitant melting due to optical heating facilitates the formation of continuous structures such as periodic gold nanowire arrays. Generated patterns can be converted into secondary structures using directed assembly or self-organization. This includes for example the rotation of gold nanowire arrays by arbitrary angles or their fragmentation into arrays of aligned gold nanoparticles. PMID:25969286

  15. Blood-clotting-inspired reversible polymer-colloid composite assembly in flow

    NASA Astrophysics Data System (ADS)

    Chen, Hsieh; Fallah, Mohammad A.; Huck, Volker; Angerer, Jennifer I.; Reininger, Armin J.; Schneider, Stefan W.; Schneider, Matthias F.; Alexander-Katz, Alfredo

    2013-01-01

    Blood clotting is a process by which a haemostatic plug is assembled at the site of injury. The formation of such a plug, which is essentially a (bio)polymer-colloid composite, is believed to be driven by shear flow in its initial phase, and contrary to our intuition, its assembly is enhanced under stronger flowing conditions. Here, inspired by blood clotting, we show that polymer-colloid composite assembly in shear flow is a universal process that can be tailored to obtain different types of aggregates including loose and dense aggregates, as well as hydrodynamically induced ‘log’-type aggregates. The process is highly controllable and reversible, depending mostly on the shear rate and the strength of the polymer-colloidbinding potential. Our results have important implications for the assembly of polymer-colloid composites, an important challenge of immense technological relevance. Furthermore, flow-driven reversible composite formation represents a new paradigm in non-equilibrium self-assembly.

  16. Performance improvement in flexible polymer solar cells based on modified silver nanowire electrode

    NASA Astrophysics Data System (ADS)

    Wang, Danbei; Zhou, Weixin; Liu, Huan; Ma, Yanwen; Zhang, Hongmei

    2016-08-01

    In this work, an efficient flexible polymer solar cell was achieved by controlling the UV-ozone treatment time of silver nanowires (Ag NWs) used in the electrode and combined with other modification materials. Through optimizing the time of UV-ozone treatment, it is shown that Ag NWs electrode treated by UV-ozone for 10 s improves the power conversion efficiency (PCE) of the device based on the blend of poly(3-hexylthiophene)(P3HT): [6,6]-phenyl C61-butyric acid methyl ester (PC61BM) from 0.76% to 1.34%. After treatment by UV-ozone, Ag NWs electrodes exhibit several promising characteristics, including high optical transparency, low sheet resistance and superior surface work function. As a consequence, the performance of devices utilizing 10 s UV-ozone-treated Ag NWs with PEDOT:PSS or MoO3 as composite anode showed higher PCEs of 2.77% (2.73%) compared with that for Ag NW electrodes without UV-ozone treatment. In addition, a PCE of 5.97% in flexible polymer solar cells based on poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b0]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl](PBDTTT-EFT):[6, 6]-phenyl C71-butyric acid methyl ester (PC71BM) as a photoactive layer was obtained.

  17. Highly efficient flexible optoelectronic devices using metal nanowire-conducting polymer composite transparent electrode

    NASA Astrophysics Data System (ADS)

    Jung, Eui Dae; Nam, Yun Seok; Seo, Houn; Lee, Bo Ram; Yu, Jae Choul; Lee, Sang Yun; Kim, Ju-Young; Park, Jang-Ung; Song, Myoung Hoon

    2015-09-01

    Here, we report a comprehensive analysis of the electrical, optical, mechanical, and surface morphological properties of composite nanostrutures based on silver nanowires (AgNW) and PEDOT:PSS conducting polymer for the use as flexible and transparent electrodes. Compared to ITO or the single material of AgNW or PEDOT:PSS, the AgNW/PEDOT:PSS composite electrode showed high electrical conductivity with a low sheet resistance of 26.8 Ω/sq at 91% transmittance (at 550 nm), improves surface smoothness, and enhances mechanical properties assisted by an amphiphilic fluoro-surfactant. The polymeric light-emitting diodes (PLEDs) and organic solar cells (OSCs) using the AgNW/PEDOT:PSS composite electrode showed higher device performances than those with AgNW and PEDOT:PSS electrodes and excellent flexibility under bending test. These results indicates that the AgNW/PEDOT:PSS composite presented is a good candidate as next-generation transparent elelctrodes for applications into flexible optoelectronic devices. [Figure not available: see fulltext.

  18. Self-Assembled Polymer Light-Emitting Devices

    NASA Astrophysics Data System (ADS)

    Rubner, Michael

    1996-03-01

    A new layer-by-layer process involving the alternate spontaneous adsorption of oppositely charged polymers onto substrate surfaces has been utilized to fabricate a number of novel thin film multilayer heterostructures with electrical and optical properties that can be tuned at the molecular level. Using this process, we have fabricated large area, thin film light emitting devices based on multilayer heterostructures of poly(p-phenylene vinylene) (PPV) and various polyanions. The nature of the polyanion used to assemble the PPV multilayers was found to dramatically influence the emission wavelength, intensity and charge transport capabilities of the thin films. Active layer thicknesses ranging from as thin as 8 nm to about 150 nm were readily prepared using this new technique. Light emitting devices with high luminance levels (>500 cd/m2 in the range of 5-12 volts) and tunable emission wavelengths have been created through the use of multi-bilayer "slab" systems that are used to control the charge injection and transport characteristics of the device. Since this is a molecular layer-by-layer fabrication technique, it is also possible to readily manipulate the nature of the polymer/electrode interfaces present in these devices. We have found, for example, that the addition of a 3 nm thick insulating layer at the PPV/aluminum interface improves device efficiency by as much as a factor of five. Details concerning the behavior of these new devices and the mechanisms of charge injection and transport operating in these new multilayer thin films will be discussed.

  19. Sn-Seeded GaAs Nanowires as Self-Assembled Radial p–n Junctions

    PubMed Central

    2015-01-01

    The widespread use of Au as a seed particle in the fabrication of semiconductor nanowires presents a fundamental limitation to the potential incorporation of such nanostructures into electronic devices. Although several other growth techniques have been demonstrated, the use of alternative seed particle metals remains an underexplored but potentially very promising way to influence the properties of the resulting nanowires while simultaneously avoiding gold. In this Letter, we demonstrate the use of Sn as a seed particle metal for GaAs nanowires grown by metal–organic vapor phase epitaxy. We show that vertically aligned and stacking defect-free GaAs nanowires can be grown with very high yield. The resulting nanowires exhibit Esaki diode behavior, attributed to very high n-doping of the nanowire core with Sn, and simultaneous C-doping of the radial overgrowth. These results demonstrate that the use of alternative seed particle metals is a potentially important area to explore for developing nanowire materials with controlled material properties. PMID:25989532

  20. Self-assembly based nanometer-scale patterning for nanowire growth

    NASA Astrophysics Data System (ADS)

    Chandramohan, Abhishek; Sibirev, Nikolai; Dubrovskii, Vladimir G.; Mendis, Budhika; Petty, Mike C.; Gallant, Andrew J.; Zeze, Dagou A.

    2015-08-01

    Periodic nanostructure arrays have been ubiquitously exploited lately due to their properties and prospective applications in production of templates for self-induced and gold (Au)-catalysed nanowires (NWs), because this approach is relatively cheap, time-efficient and do not require electron beam lithography. The technique consists creating nanoholes in SiO2 to expose the silicon Si (111) beneath where self-induced NWs can nucleate, while nanodots deposited onto the Si (111) surface serve as catalyst seeds. For Au-catalysed NWs, a monolayer of self-assembled polystyrene nanospheres (PNS 300nm) was created on a 2 inch Si wafer by spin coating and later etched for a short time before a very thin Au-catalyst layer was deposited. In turn, for self-induced, PNS monolayer was created onto a SiO2-Si substrate. A longer etch was required to reduce PNS diameter significantly to leave relatively larger spacing where chromium is blanket deposited. PNS were lifted off by sonicating the samples in toluene produce the periodic arrays of nanodots and nanoholes, respectively. The underlying SiO2 was etched further through the nanoholes to uncover the Si below. 200 nm holes and 30-70 nm dots were demonstrated through the bespoke methods. The patterned substrates served as master templates, subsequently copied using polydimethylsiloxane (PDMS) to produce a flexible stamp for nanoimprint lithography. A bilayer resist lift off process was developed to print the replicated nanodots or nanoholes on large-area substrates onto which III-V NWs can be grown.

  1. Self-assembly of cadmium metasilicate nanowires as a broadband optical limiter

    NASA Astrophysics Data System (ADS)

    Zheng, Chan; Dai, Chongchong; Huang, Li; Li, Wei; Chen, Wenzhe

    2016-04-01

    Cadmium metasilicate nanowires (CdSiO3 NWs) have been synthesized through a facile, eco-friendly, low-cost water-ethanol mixed-solution hydrothermal route. The transmission electron microscopy measurements of as-prepared samples indicate that the CdSiO3 NWs with diameters in the range of 10-60 nm and lengths of more than 1 μm were constructed by self-assembly of 5-10-nm CdSiO3 nanoparticles with good crystallinity. The monoclinic phase formation of the sample is studied in detail by X-ray diffraction, Fourier-transform infrared spectroscopy, and thermo gravimetric analysis. The results indicate that a pure monoclinic phase of CdSiO3 can be obtained by a hydrothermal route without further calcinations and SiO4 tetrahedra were the main constituents of the CdSiO3 NWs. The nanosecond optical limiting (OL) effects were characterized by using an open-aperture (OA) Z-scan technique with 4-ns laser pulses at both 532 and 1064 nm. Theses CdSiO3 NWs displayed an excellent OL performance at 532 and 1064 nm, which was better than carbon nanotubes, a benchmark optical limiter. Input-fluence dependent scattering measurements suggested than nonlinear scattering played an important role in the observed optical limiting behavior in CdSiO3 NWs at 532 and 1064 nm. More significantly, the NLO performance in CdSiO3 NWs incorporated solid silica gel glass has been improved in comparison to those dispersed in water. The unique structure and excellent OL property render these CdSiO3 NWs competitors in the realms of optical limiting applications.

  2. Temporal and Triggered Evolution of Host-Guest Characteristics in Amphiphilic Polymer Assemblies.

    PubMed

    Rangadurai, Poornima; Molla, Mijanur Rahaman; Prasad, Priyaa; Caissy, Matthew; Thayumanavan, S

    2016-06-22

    An amphiphilic polymer with cleavable side chain and main chain functional groups has been designed and synthesized. Specific cleavage of either of its functional groups was found to have an effect on the morphology of the assembly. Degradation of the main chain is shown to cause morphology of the supramolecular assembly to evolve with time from a micelle-like assembly to a vesicular assembly. On the other hand, stimulus-induced cleavage of the side chains causes these nanoassemblies to disassemble. These temporal (main chain) and triggered (side chain) degradation processes have implications in the design of degradable polymers as supramolecular scaffolds for biological applications. PMID:27258854

  3. Continuous monitoring of structural dynamics in polymer assemblies

    NASA Astrophysics Data System (ADS)

    Guzman Sepulveda, Jose Rafael; Deng, Jinan; Fang, Jiyu; Dogariu, Aristide

    Due to their flexibility, optical methods are preferred approaches for monitoring the dynamics and mechanical properties of scattering systems such as polymer solutions, colloidal suspensions, and complex media in general. In particular, their potential noninvasiveness is critical for the passive assessment of dynamic processes. Practical implementations however suffer sometimes from limitations due to effects such as multiple scattering or strong attenuation. Here we introduce an optical technique that overcomes some of these limitations and permits accessing the dynamics of complex colloidal systems under realistic conditions and inherent external influences. This interferometric technique operates based on the coherence-gated isolation of single scattering and allows for the spatially-resolved evaluation of the system's dynamics in optically isolated picoliter-sized volumes. This effective isolation permits a fully passive characterization of nonstationary dynamic processes in complex systems including aggregation and self-assembling, sedimentation, structural evolution and phase transitions, interface dynamics, and dynamics in inhomogeneous or stratified solvents. CREOL, The College of Optics and Photonics.

  4. Membrane electrode assemblies for unitised regenerative polymer electrolyte fuel cells

    NASA Astrophysics Data System (ADS)

    Wittstadt, U.; Wagner, E.; Jungmann, T.

    Membrane electrode assemblies for regenerative polymer electrolyte fuel cells were made by hot pressing and sputtering. The different MEAs are examined in fuel cell and water electrolysis mode at different pressure and temperature conditions. Polarisation curves and ac impedance spectra are used to investigate the influence of the changes in coating technique. The hydrogen gas permeation through the membrane is determined by analysing the produced oxygen in electrolysis mode. The analysis shows, that better performances in both process directions can be achieved with an additional layer of sputtered platinum on the oxygen electrode. Thus, the electrochemical round-trip efficiency can be improved by more than 4%. Treating the oxygen electrode with PTFE solution shows better performance in fuel cell and less performance in electrolysis mode. The increase of the round-trip efficiency is negligible. A layer sputtered directly on the membrane shows good impermeability, and hence results in high voltages at low current densities. The mass transportation is apparently constricted. The gas diffusion layer on the oxygen electrode, in this case a titanium foam, leads to flooding of the cell in fuel cell mode. Stable operation is achieved after pretreatment of the GDL with a PTFE solution.

  5. A Nonconventional Approach to Patterned Nanoarrays of DNA Strands for Template-Assisted Assembly of Polyfluorene Nanowires.

    PubMed

    Bae, Dong Geun; Jeong, Ji-Eun; Kang, Seok Hee; Byun, Myunghwan; Han, Dong-Wook; Lin, Zhiqun; Woo, Han Young; Hong, Suck Won

    2016-08-01

    DNA molecules have been widely recognized as promising building blocks for constructing functional nanostructures with two main features, that is, self-assembly and rich chemical functionality. The intrinsic feature size of DNA makes it attractive for creating versatile nanostructures. Moreover, the ease of access to tune the surface of DNA by chemical functionalization offers numerous opportunities for many applications. Herein, a simple yet robust strategy is developed to yield the self-assembly of DNA by exploiting controlled evaporative assembly of DNA solution in a unique confined geometry. Intriguingly, depending on the concentration of DNA solution, highly aligned nanostructured fibrillar-like arrays and well-positioned concentric ring-like superstructures composed of DNAs are formed. Subsequently, the ring-like negatively charged DNA superstructures are employed as template to produce conductive organic nanowires on a silicon substrate by complexing with a positively charged conjugated polyelectrolyte poly[9,9-bis(6'-N,N,N-trimethylammoniumhexyl)fluorene dibromide] (PF2) through the strong electrostatic interaction. Finally, a monolithic integration of aligned arrays of DNA-templated PF2 nanowires to yield two DNA/PF2-based devices is demonstrated. It is envisioned that this strategy can be readily extended to pattern other biomolecules and may render a broad range of potential applications from the nucleotide sequence and hybridization as recognition events to transducing elements in chemical sensors. PMID:27351291

  6. Bundling of GaAs nanowires: a case of adhesion-induced self-assembly of nanowires.

    PubMed

    Carapezzi, Stefania; Priante, Giacomo; Grillo, Vincenzo; Montès, Laurent; Rubini, Silvia; Cavallini, Anna

    2014-09-23

    The origin of deflections of semiconductor nanowires (NWs) induced by an electron beam in scanning electron microscopy has been subject to different interpretations. Similarly, the subsequent clumping together of NWs into bundles is frequently observed, but no interpretation has yet been advanced. Here we present results on the bundling of NWs following the intentional bending by an electron beam. Furthermore, we extend the concept of lateral collapse, usually applied to fibrillar architectures mimicking the adhesiveness of natural surfaces (the so-called Gecko effect), to analyze the mechanism of the NW bundle formation. We demonstrate how the geometry of the NW arrays and the mechanical properties of the composing materials govern bundling and how these parameters should be taken into account in the design of NW arrays both for avoiding vertical misalignment when detrimental and for achieving patterning of NW arrays into nanoarchitectures. PMID:25162379

  7. Nanohelices from planar polymer self-assembled in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Fu, Hongjin; Xu, Shuqiong; Li, Yunfang

    2016-07-01

    The polymer possessing with planar structure can be activated and guided to encapsulate the inner space of SWNT and form a helix through van der Waals interaction and the π-π stacking effect between the polymer and the inner surface of SWNT. The SWNT size, the nanostructure and flexibility of polymer chain are all determine the final structures. The basic interaction between the polymer and the nanotubes is investigated, and the condition and mechanism of the helix-forming are explained particularly. Hybrid polymers improve the ability of the helix formation. This study provides scientific basis for fabricating helical polymers encapsulated in SWNTs and eventually on their applications in various areas.

  8. Dynamics of nanoparticle assembly from disjointed images of nanoparticle-polymer composites

    NASA Astrophysics Data System (ADS)

    Murthy, Chaitanya R.; Gao, Bo; Tao, Andrea R.; Arya, Gaurav

    2016-02-01

    Understanding how nanoparticles (NPs) diffuse, stick, and assemble into larger structures within polymers is key to the design and fabrication of NP-polymer composites. Here we describe an approach for inferring the dynamic parameters of NP assembly from spatially and temporally disjointed images of composites. The approach involves iterative adjustment of the parameters of a kinetic model of assembly until the computed size statistics of NP clusters match those obtained from high-throughput analysis of the experimental images. Application of this approach to the assembly of shaped, metal NPs in polymer films suggests that NP structures grow via a cluster-cluster aggregation mechanism, where NPs and their clusters diffuse with approximately Stokes-Einstein diffusivity and stick to other NPs or clusters with a probability that depends strongly on the size and shape of the NPs and the molecular weight of the polymer.

  9. Nanoscale neuroelectrode modification via sub-20 nm silicon nanowires through self-assembly of block copolymers.

    PubMed

    Mokarian-Tabari, Parvaneh; Vallejo-Giraldo, Catalina; Fernandez-Yague, Marc; Cummins, Cian; Morris, Michael A; Biggs, Manus J P

    2015-02-01

    Neuroprosthetic technologies for therapeutic neuromodulation have seen major advances in recent years but these advances have been impeded due to electrode failure or a temporal deterioration in the device recording or electrical stimulation potential. This deterioration is attributed to an intrinsic host tissue response, namely glial scarring or gliosis, which prevents the injured neurons from sprouting, drives neurite processes away from the neuroelectrode and increases signal impedance by increasing the distance between the electrode and its target neurons. To address this problem, there is a clinical need to reduce tissue encapsulation of the electrodes in situ and improve long-term neuroelectrode function. Nanotopographical modification has emerged as a potent methodology for the disruption of protein adsorption and cellular adhesion in vitro. This study investigates the use of block copolymer self-assembly technique for the generation of sub-20 nm nanowire features on silicon substrates. Critically, these nanostructures were observed to significantly reduce electrical impedance and increase conductivity. Human neuroblastoma SH-SY5Y cells cultured on nanowire substrates for up to 14 days were associated with enhanced focal adhesion reinforcement and a reduction in proliferation. We conclude that nanowire surface modulation may offer significant potential as an electrode functionalization strategy. PMID:25677116

  10. Epitaxial self-assembly of binary molecular components into branched nanowire heterostructures for photonic applications.

    PubMed

    Kong, Qinghua; Liao, Qing; Xu, Zhenzhen; Wang, Xuedong; Yao, Jiannian; Fu, Hongbing

    2014-02-12

    We report a sequential epitaxial growth to prepare organic branched nanowire heterostructures (BNwHs) consisting of a microribbon trunk of 1,4-dimethoxy-2,5-di[4'-(cyano)styryl]benzene (COPV) with multiple nanowire branches of 2,4,5-triphenylimidazole (TPI) in a one-pot solution synthesis. The synthesis involves a seeded-growth process, where COPV microribbons are grown first as a trunk followed by a seeded-growth of TPI nanowire branches at the pregrown trunk surfaces. Selected area electron diffraction characterizations reveal that multiple hydrogen-bonding interactions between TPI and COPV components play an essential role in the epitaxial growth as a result of the structural matching between COPV and TPI crystals. A multichannel optical router was successfully realized on the basis of the passive waveguides of COPV green photoluminescence (PL) along TPI nanowire branches in a single organic BNwH. PMID:24446808

  11. Fabrication of Pt nanoparticle incorporated polymer nanowires by high energy ion and electron beam irradiation

    NASA Astrophysics Data System (ADS)

    Tsukuda, Satoshi; Takahasi, Ryouta; Seki, Shu; Sugimoto, Masaki; Idesaki, Akira; Yoshikawa, Masahito; Tanaka, Shun-Ichiro

    2016-01-01

    Polyvinylpyrrolidone (PVP)-Pt nanoparticles (NPs) hybrid nanowires were fabricated by high energy ion beam irradiation to PVP thin films including H2PtCl6. Single ion hitting caused crosslinking reactions of PVP and reduction of Pt ions within local cylindrical area along an ion trajectory (ion track); therefore, the PVP nanowires including Pt NPs were formed and isolated on Si substrate after wet-development procedure. The number of Pt NPs was easily controlled by the mixed ratio of PVP and H2PtCl6. However, increasing the amount of H2PtCl6 led to decreasing the radial size and separation of the hybrid nanowires during the wet-development. Additional electron beam irradiation after ion beam improved separation of the nanowires and controlled radial sizes due to an increase in the density of crosslinking points inner the nanowires.

  12. Co-assembly of polymer covered cyclic peptide nanotubes and block copolymer in thin films

    NASA Astrophysics Data System (ADS)

    Zhang, Chen; Lazzara, Thomas; Li, Changyi; Helmes, Brett; Xu, Ting

    2013-03-01

    Nanotubular structures have gained prevalent interest for their unique hollow structures and high aspect ratio and their potential applications ranging from molecular separation to nanocomposite membranes. We used nanotube forming cyclic peptide (CP) as the structural motif and studied the self-assembly of polymer conjugated CPs in block copolymer (BCP) matrix in thin films. The co-assembly process is mainly driven by thermodynamic quantities, namely Flory-Huggins polymer-polymer interactions that governs the interaction between CP and BCP, interfacial interactions that affects polymer chain orientation, and thin film commensurability. In addition, due to the dynamic nature of the nanotube formation, the co-assembly process is also pathway-dependent. Thus, processing conditions are critical in co-assembling CP nanotubes and BCP in thin films. Our result shows that the initial aggregation state of polymer covered CP nanotubes determines the pathway the system takes and hence the final morphology of the films. The co-assembly of polymer-conjugated CPs and BCPs demonstrates the feasibility of assembling 1D nanotubes in supramolecular thin films and opens up a new avenue for the generation of novel nanotubular structures.

  13. Particles Bridge the Gap -- Relevance of Polymer Graft Architecture on the Properties of Particle Brush Assemblies

    NASA Astrophysics Data System (ADS)

    Bockstaller, Michael

    2011-03-01

    Current interest in the assembly of ligand-coated nanoparticles into 2D and 3D array structures is driven by the opportunities for novel material technologies that derive from the interactions within nanoparticle superlattice structures. A common challenge in the solution-based assembly of particle superlattice structures is the propensity of hard-sphere type particle assemblies to crack formation and brittle fracture during solvent evaporation. Recent progress in controlled radical polymerization offers novel opportunities for polymer-stabilized particle systems (particle brushes) as building blocks of particle superlattice structures. This contribution will discuss synthetic strategies to realize particle brush systems with well defined polymer graft-architecture in the dense or semi-dilute brush regime and discuss the effect of polymer grafting on the structure formation and cohesive interactions in particle brush assemblies. In particular, it will be demonstrated chain entanglements between surface-grafted chains give rise to fracture through polymer-like crazing thus dramatically increasing the toughness and flexibility of the particle assembly. The modulus and toughness of polymer nanocomposites synthesized by self-assembly of particle brush systems will be shown to exceed those of ``conventional'' particle-filled polymer composites -- a result that will be interpreted as a consequence of the particular conformational constraints of surface grafted chains. The author acknowledges financial support by AFOSR and DTRA.

  14. Layer-by-layer assembly synthesis of ZnO/SnO{sub 2} composite nanowire arrays as high-performance anode for lithium-ion batteries

    SciTech Connect

    Wang, Jiazheng; Du, Ning; Zhang, Hui; Yu, Jingxue; Yang, Deren

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer SnO{sub 2} nanoparticles was deposited on ZnO nanoarrays through layer-by-layer assembly. Black-Right-Pointing-Pointer The composite nanowire arrays show improved performance as anode for Li-ion battery. Black-Right-Pointing-Pointer Improved performance was attributed to the combining advantages of each ingredient. -- Abstract: A layer-by-layer approach has been developed to synthesize ZnO/SnO{sub 2} composite nanowire arrays on copper substrate. ZnO nanowire arrays have been first prepared on copper substrate through seed-assisted method, and then, the surface of ZnO nanowires have been modified by the polyelectrolyte. After oxidation-reduction reaction, SnO{sub 2} layer has been deposited onto the surface of ZnO nanowires. The as-synthesized ZnO/SnO{sub 2} composite nanowire arrays have been applied as anode for lithium-ion batteries, which show high reversible capacity and good cycling stability compared to pure ZnO nanowire arrays and SnO{sub 2} nanoparticles. It is believed that the improved performance may be attributed to the high capacity of SnO{sub 2} and the good cycling stability of the array structure on current collector.

  15. The cluster-assembled nanowires based on M12N12 (M = Al and Ga) clusters as potential gas sensors for CO, NO, and NO2 detection.

    PubMed

    Yong, Yongliang; Jiang, Huai; Li, Xiaohong; Lv, Shijie; Cao, Jingxiao

    2016-08-01

    The advances in cluster-assembled materials where clusters serve as building blocks have opened new opportunities to develop ever more sensitive gas sensors. Here, using density functional theory calculations, the structural and electronic properties of cluster-assembled nanowires based on M12N12 (M = Al and Ga) clusters and their application as gas sensors have been investigated. Our results show that the nanowires can be produced via the coalescence of stable M12N12 fullerene-like clusters. The M12N12-based nanowires have semiconducting electrical properties with direct energy gaps, and are particularly stable at room temperature for long enough to allow for their characterization and applications. Furthermore, we found that the CO, NO, and NO2 molecules are chemisorbed on the M12N12-based nanowires with reasonable adsorption energies and apparent charge transfer. The electronic properties of the M12N12-based nanowires present dramatic changes after the adsorption of the CO, NO, and NO2 molecules, especially their electric conductivity. However, the adsorption of NO2 on the Al12N12-based nanowire is too strong, indicating an impractical recovery time as NO2 sensors. In addition to this, due to reasonable adsorption energies, apparent charge transfer, change in the electric conductivity, and the short recovery time, the Al12N12-based nanowire should be a good CO and NO sensor with quick response as well as short recovery time, while the Ga12N12-based nanowire should be a promising gas sensor for CO, NO, and NO2 detection. PMID:27424739

  16. Chemical Sensing with Nanowires

    NASA Astrophysics Data System (ADS)

    Penner, Reginald M.

    2012-07-01

    Transformational advances in the performance of nanowire-based chemical sensors and biosensors have been achieved over the past two to three years. These advances have arisen from a better understanding of the mechanisms of transduction operating in these devices, innovations in nanowire fabrication, and improved methods for incorporating receptors into or onto nanowires. Nanowire-based biosensors have detected DNA in undiluted physiological saline. For silicon nanowire nucleic acid sensors, higher sensitivities have been obtained by eliminating the passivating oxide layer on the nanowire surface and by substituting uncharged protein nucleic acids for DNA as the capture strands. Biosensors for peptide and protein cancer markers, based on both semiconductor nanowires and nanowires of conductive polymers, have detected these targets at physiologically relevant concentrations in both blood plasma and whole blood. Nanowire chemical sensors have also detected several gases at the parts-per-million level. This review discusses these and other recent advances, concentrating on work published in the past three years.

  17. In situ probing and integration of single self-assembled quantum dots-in-nanowires for quantum photonics

    NASA Astrophysics Data System (ADS)

    Zha, Guo-Wei; Shang, Xiang-Jun; Ni, Hai-Qiao; Yu, Ying; Xu, Jian-Xing; Wei, Si-Hang; Ma, Ben; Zhang, Li-Chun; Niu, Zhi-Chuan

    2015-09-01

    The realization of fiber-output single photon sources is necessary for quantum photonics. Here we present in situ probing and integration of single self-assembled quantum dots (QDs)-in-nanowires. Single self-assembled AlGaAs QDs were synthesized in GaAs/AlGaAs core-shell nanowires by molecular beam epitaxy and characterized by optical excitation in both micro-PL and fiber-integrating set-up. Cascaded biexciton-exciton emission with a saturation signal of 1000 counts per second at nitrogen temperature is achieved through the fiber-integrating setup, which makes single mode fibers an ideal candidate for single photons sources and paves the way for the realization of ‘all fiber’ devices. Numerical calculations were carried out to illustrate the collection efficiency and polarized photoluminescence characteristics. Extraction efficiencies as high as 70% over a broadband emission are reported and increase by a factor of about seven in comparison with air extraction, due to the larger refractive index of the fiber core.

  18. Electric-Field-Assisted Assembly of Polymer-Tethered Gold Nanorods in Cylindrical Nanopores.

    PubMed

    Wang, Ke; Jin, Seon-Mi; Xu, Jiangping; Liang, Ruijing; Shezad, Khurram; Xue, Zhigang; Xie, Xiaolin; Lee, Eunji; Zhu, Jintao

    2016-05-24

    In this report, we demonstrate the confined assembly of polymer-tethered gold nanorods in anodic aluminum oxide (AAO) channels with the assistance of electric field (EF). Various interesting hybrid assemblies, such as single-, double-, triple-, or quadruple-helix, linear, and hexagonally packed structures are obtained by adjusting pore size in AAO channels, ligand length, and EF orientation. Correspondingly, surface plasmonic property of the assemblies can thus be tuned. This strategy, by coupling of external-field and cylindrically confined assembly, is believed to be a promising approach for generating ordered hybrid assemblies with hierarchical structures, which may find potential applications in photoelectric devices, biosensors, and data storage devices. PMID:27054687

  19. Supramolecular polymer assembly in aqueous solution arising from cyclodextrin host-guest complexation.

    PubMed

    Wang, Jie; Qiu, Zhiqiang; Wang, Yiming; Li, Li; Guo, Xuhong; Pham, Duc-Truc; Lincoln, Stephen F; Prud'homme, Robert K

    2016-01-01

    The employment of cyclodextrin host-guest complexation to construct supramolecular assemblies with an emphasis on polymer networks is reviewed. The main driving force for this supramolecular assembly is host-guest complexation between cyclodextrin hosts and guest groups either of which may be discrete molecular species or substituents on a polymer backbone. The effects of such complexation on properties at the molecular and macroscopic levels are discussed. It is shown that cyclodextrin complexation may be used to design functional polymer materials with tailorable properties, especially for photo-, pH-, thermo- and redox-responsiveness and self-healing. PMID:26877808

  20. Supramolecular polymer assembly in aqueous solution arising from cyclodextrin host–guest complexation

    PubMed Central

    Wang, Jie; Qiu, Zhiqiang; Wang, Yiming; Li, Li; Pham, Duc-Truc; Prud’homme, Robert K

    2016-01-01

    Summary The employment of cyclodextrin host–guest complexation to construct supramolecular assemblies with an emphasis on polymer networks is reviewed. The main driving force for this supramolecular assembly is host–guest complexation between cyclodextrin hosts and guest groups either of which may be discrete molecular species or substituents on a polymer backbone. The effects of such complexation on properties at the molecular and macroscopic levels are discussed. It is shown that cyclodextrin complexation may be used to design functional polymer materials with tailorable properties, especially for photo-, pH-, thermo- and redox-responsiveness and self-healing. PMID:26877808

  1. Langevin dynamics simulation of polymer-assisted virus-like assembly

    NASA Astrophysics Data System (ADS)

    Mahalik, J. P.; Muthukumar, M.

    2012-04-01

    Starting from a coarse grained representation of the building units of the minute virus of mice and a flexible polyelectrolyte molecule, we have explored the mechanism of assembly into icosahedral structures with the help of Langevin dynamics simulations and the parallel tempering technique. Regular icosahedra with appropriate symmetry form only in a narrow range of temperature and polymer length. Within this region of parameters where successful assembly would proceed, we have systematically investigated the growth kinetics. The assembly of icosahedra is found to follow the classical nucleation and growth mechanism in the absence of the polymer, with the three regimes of nucleation, linear growth, and slowing down in the later stage. The calculated average nucleation time obeys the laws expected from the classical nucleation theory. The linear growth rate is found to obey the laws of secondary nucleation as in the case of lamellar growth in polymer crystallization. The same mechanism is seen in the simulations of the assembly of icosahedra in the presence of the polymer as well. The polymer reduces the nucleation barrier significantly by enhancing the local concentration of subunits via adsorbing them on their backbone. The details of growth in the presence of the polymer are also found to be consistent with the classical nucleation theory, despite the smallness of the assembled structures.

  2. Particle-directed assembly of semiflexible polymer chains.

    PubMed

    McGovern, Michael; Dorfman, Kevin D; Morse, David C

    2016-07-20

    We use Langevin dynamics simulations to study aggregation of semiflexible polymers driven by attractions between polymers and spherical particles. We consider a simple model with purely repulsive polymer/polymer and particle/particle interactions but attractive polymer/particle interactions. We find a rich "phase diagram" that contains several different types of globular and rod-like aggregates with either liquid-like or crystalline structure for the particle positions. Systems that exhibit rod-like aggregates with crystalline internal order exhibit a discontinuous rod-globule transition, while systems with liquid-like internal order exhibit a smooth crossover between isotropic and elongated aggregates with increasing chain stiffness. Polymers in elongated liquid-like aggregates often adopt helical configurations that wind around the axis of the aggregate. PMID:27378073

  3. Nanohelices from planar polymer self-assembled in carbon nanotubes

    PubMed Central

    Fu, Hongjin; Xu, Shuqiong; Li, Yunfang

    2016-01-01

    The polymer possessing with planar structure can be activated and guided to encapsulate the inner space of SWNT and form a helix through van der Waals interaction and the π-π stacking effect between the polymer and the inner surface of SWNT. The SWNT size, the nanostructure and flexibility of polymer chain are all determine the final structures. The basic interaction between the polymer and the nanotubes is investigated, and the condition and mechanism of the helix-forming are explained particularly. Hybrid polymers improve the ability of the helix formation. This study provides scientific basis for fabricating helical polymers encapsulated in SWNTs and eventually on their applications in various areas. PMID:27440493

  4. Nanohelices from planar polymer self-assembled in carbon nanotubes.

    PubMed

    Fu, Hongjin; Xu, Shuqiong; Li, Yunfang

    2016-01-01

    The polymer possessing with planar structure can be activated and guided to encapsulate the inner space of SWNT and form a helix through van der Waals interaction and the π-π stacking effect between the polymer and the inner surface of SWNT. The SWNT size, the nanostructure and flexibility of polymer chain are all determine the final structures. The basic interaction between the polymer and the nanotubes is investigated, and the condition and mechanism of the helix-forming are explained particularly. Hybrid polymers improve the ability of the helix formation. This study provides scientific basis for fabricating helical polymers encapsulated in SWNTs and eventually on their applications in various areas. PMID:27440493

  5. Controlled Sequestration of DNA Intercalated Drug by Polymer-Surfactant Supramolecular Assemblies.

    PubMed

    Mora, Aruna K; Singh, Prabhat K; Nath, Sukhendu

    2016-05-01

    Triblock copolymer and surfactant based supramolecular assemblies have been used for the controlled sequestration of the DNA intercalator. The triblock copolymer micelles do not affect the molecules that are intercalated in the DNA. However, on addition of charged surfactant to the triblock copolymer micellar solution, sequestration of the intercalated molecules from DNA to the polymer-surfactant supramolecular assemblies takes place. Such sequestration of the intercalated molecules in the polymer-surfactant supramolecular assemblies has been explained on the basis of the charged surface formed in the polymer micelles due to the addition of surfactants. Sequestration of the intercalated molecules from the DNA to the polymer-surfactant supramolecular assemblies has been monitored through the ground state absorption, steady state, and time-resolved emission measurements. It is shown that the extent of sequestration of the intercalated molecules can be finely tuned by tuning the concentration of the surfactant in the triblock copolymer solution. Quantitative sequestration of the intercalated molecules by the supramolecular assemblies has been achieved. Such controlled sequestration of the DNA intercalated molecules by polymer-surfactant supramolecular assemblies can be used to study the binding of drug with DNA and may be useful in applications like detoxification in the case of drug overdose. PMID:27077791

  6. Patterned polymer nanowire arrays as an effective protein immobilizer for biosensing and HIV detection

    NASA Astrophysics Data System (ADS)

    Shen, Yue; Liu, Yingyi; Zhu, Guang; Fang, Hao; Huang, Yunhui; Jiang, Xingyu; Wang, Zhong L.

    2012-12-01

    We report an array of polymeric nanowires for effectively immobilizing biomolecules on biochips owing to the large surface area. The nanowires were fabricated in predesigned patterns using an inductively coupled plasma (ICP) etching process. Microfluidic biochips integrated using the substrates with arrays of nanowires and polydimethylsiloxane channels have been demonstrated to be effective for detecting antigens, and a detection limit of antigens at 0.2 μg mL-1 has been achieved, which is improved by a factor of 50 compared to that based on flat substrates without the nanowires. In addition, the high sensitivity for clinical detection of human immunodeficiency virus (HIV) antibody has also been demonstrated, showing a 20 times enhancement in fluorescent signal intensity between the samples with positive and negative HIV.

  7. Patterned polymer nanowire arrays as an effective protein immobilizer for biosensing and HIV detection.

    PubMed

    Shen, Yue; Liu, Yingyi; Zhu, Guang; Fang, Hao; Huang, Yunhui; Jiang, Xingyu; Wang, Zhong L

    2013-01-21

    We report an array of polymeric nanowires for effectively immobilizing biomolecules on biochips owing to the large surface area. The nanowires were fabricated in predesigned patterns using an inductively coupled plasma (ICP) etching process. Microfluidic biochips integrated using the substrates with arrays of nanowires and polydimethylsiloxane channels have been demonstrated to be effective for detecting antigens, and a detection limit of antigens at 0.2 μg mL(-1) has been achieved, which is improved by a factor of 50 compared to that based on flat substrates without the nanowires. In addition, the high sensitivity for clinical detection of human immunodeficiency virus (HIV) antibody has also been demonstrated, showing a 20 times enhancement in fluorescent signal intensity between the samples with positive and negative HIV. PMID:23223639

  8. Self-assembled ZnO agave-like nanowires and anomalous superhydrophobicity

    NASA Astrophysics Data System (ADS)

    Yang, Y. H.; Li, Z. Y.; Wang, B.; Wang, C. X.; Chen, D. H.; Yang, G. W.

    2005-09-01

    Thin films of ZnO agave-like nanowires were prepared on amorphous carbon thin layers on silicon substrates using thermal chemical vapour transport and condensation without any metal catalysts. The unusual superhydrophobicity of the fabricated surface was measured; the water contact angle reaches 151.1°. On the basis of experimental and theoretical analyses, it appears likely that the biomimetic microcomposite and nanocomposite surfaces of the prepared thin films of ZnO agave-like nanowires are responsible for the excellent superhydrophobicity.

  9. Host-Guest Binding-Site-Tunable Self-Assembly of Stimuli-Responsive Supramolecular Polymers.

    PubMed

    Yao, Hao; Qi, Miao; Liu, Yuyang; Tian, Wei

    2016-06-13

    Despite the remarkable progress made in controllable self-assembly of stimuli-responsive supramolecular polymers (SSPs), a basic issue that has not been consideration to date is the essential binding site. The noncovalent binding sites, which connect the building blocks and endow supramolecular polymers with their ability to respond to stimuli, are expected to strongly affect the self-assembly of SSPs. Herein, the design and synthesis of a dual-stimuli thermo- and photoresponsive Y-shaped supramolecular polymer (SSP2) with two adjacent β-cyclodextrin/azobenzene (β-CD/Azo) binding sites, and another SSP (SSP1) with similar building blocks, but only one β-CD/Azo binding site as a control, are described. Upon gradually increasing the polymer solution temperature or irradiating with UV light, SSP2 self-assemblies with a higher binding-site distribution density; exhibits a flower-like morphology, smaller size, and more stable dynamic aggregation process; and greater controllability for drug-release behavior than those observed with SSP1 self-assemblies. The host-guest binding-site-tunable self-assembly was attributed to the positive cooperativity generated among adjacent binding sites on the surfaces of SSP2 self-assemblies. This work is beneficial for precisely controlling the structural parameters and controlled release function of SSP self-assemblies. PMID:27167577

  10. Dynamic assembly of polymer nanotube networks via kinesin powered microtubule filaments

    NASA Astrophysics Data System (ADS)

    Paxton, Walter F.; Bouxsein, Nathan F.; Henderson, Ian M.; Gomez, Andrew; Bachand, George D.

    2015-06-01

    We describe for the first time how biological nanomotors may be used to actively self-assemble mesoscale networks composed of diblock copolymer nanotubes. The collective force generated by multiple kinesin nanomotors acting on a microtubule filament is large enough to overcome the energy barrier required to extract nanotubes from polymer vesicles comprised of poly(ethylene oxide-b-butadiene) in spite of the higher force requirements relative to extracting nanotubes from lipid vesicles. Nevertheless, large-scale polymer networks were dynamically assembled by the motors. These networks displayed enhanced robustness, persisting more than 24 h post-assembly (compared to 4-5 h for corresponding lipid networks). The transport of materials in and on the polymer membranes differs substantially from the transport on analogous lipid networks. Specifically, our data suggest that polymer mobility in nanotubular structures is considerably different from planar or 3D structures, and is stunted by 1D confinement of the polymer subunits. Moreover, quantum dots adsorbed onto polymer nanotubes are completely immobile, which is related to this 1D confinement effect and is in stark contrast to the highly fluid transport observed on lipid tubules.We describe for the first time how biological nanomotors may be used to actively self-assemble mesoscale networks composed of diblock copolymer nanotubes. The collective force generated by multiple kinesin nanomotors acting on a microtubule filament is large enough to overcome the energy barrier required to extract nanotubes from polymer vesicles comprised of poly(ethylene oxide-b-butadiene) in spite of the higher force requirements relative to extracting nanotubes from lipid vesicles. Nevertheless, large-scale polymer networks were dynamically assembled by the motors. These networks displayed enhanced robustness, persisting more than 24 h post-assembly (compared to 4-5 h for corresponding lipid networks). The transport of materials in and on

  11. Templating Organic Semi- conductors via Self-Assembly of Polymer Colloids

    NASA Astrophysics Data System (ADS)

    Mezzenga, Raffaele; Ruokolainen, Janne; Fredrickson, Glenn H.; Kramer, Edward J.; Moses, Daniel; Heeger, Alan J.; Ikkala, Olli

    2003-03-01

    A route for producing semiconducting polymer blends is demonstrated in which a doped pi-conjugated polymer is forced into a three-dimensionally continuous minor phase by the self-assembly of colloidal particles and block copolymers. The resulting cellular morphology can be viewed as a high-internal phase polymeric emulsion. Compared with traditional blending procedures, this process reduces the percolation threshold for electrical conductivity by a factor of 10, increases the conductivity by several orders of magnitude, and simultaneously improves thermal stability. Following this route, new applications can be envisaged for semiconducting polymer blends that require only minimal concentrations of doped pi-conjugated polymer.

  12. Formation and properties of surface-anchored polymer assemblies with tunable physico-chemical characteristics

    NASA Astrophysics Data System (ADS)

    Wu, Tao

    We describe two new methodologies leading to the formation of novel surface-anchored polymer assemblies on solid substrates. While the main goal is to understand the fundamentals pertaining to the preparation and properties of the surface-bound polymer assemblies (including neutral and chargeable polymers), several examples also are mentioned throughout the Thesis that point out to practical applications of such structures. The first method is based on generating assemblies comprising anchored polymers with a gradual variation of grafting densities on solid substrates. These structures are prepared by first covering the substrate with a molecular gradient of the polymerization initiator, followed by polymerization from these substrate-bound initiator centers ("grafting from"). We apply this technique to prepare grafting density gradients of poly(acryl amide) (PAAm) and poly(acrylic acid) (PAA) on silica-covered substrates. We show that using the grafting density gradient geometry, the characteristics of surface-anchored polymers in both the low grafting density ("mushroom") regime as well as the high grafting density ("brush") regime can be accessed conveniently on a single sample. We use a battery of experimental methods, including Fourier transform infrared spectroscopy (FTIR), Near-edge absorption fine structure spectroscopy (NEXAFS), contact angle, ellipsometry, to study the characteristics of the surface-bound polymer layers. We also probe the scaling laws of neutral polymer as a function of grafting density, and for weak polyelectrolyte, in addition to the grafting density, we study the affect of solution ionic strength and pH values. In the second novel method, which we coined as "mechanically assisted polymer assembly" (MAPA), we form surface anchored polymers by "grafting from" polymerization initiators deposited on elastic surfaces that have been previously extended uniaxially by a certain length increment, Deltax. Upon releasing the strain in the

  13. Solution-state polymer assemblies influence BCS class II drug dissolution and supersaturation maintenance.

    PubMed

    Dalsin, Molly C; Tale, Swapnil; Reineke, Theresa M

    2014-02-10

    Spray dried dispersions (SDDs), solid dispersions of polymer excipients and active pharmaceuticals, are important to the field of oral drug delivery for improving active stability, bioavailability, and efficacy. Herein, we examine the influence of solution-state polymer assemblies on amorphous spray-dried dispersion (SDD) performance with two BCS II model drugs, phenytoin and probucol. These drugs were spray dried with 4 model polymer excipients consisting of poly(ethylene-alt-propylene) (PEP), N,N,-dimethylacrylamide (DMA), or 2-methacrylamido glucopyranose (MAG): amphiphilic diblock ter- and copolymers, PEP-P(DMA-grad-MAG) and PEP-PDMA, and their respective hydrophilic analogues, P(DMA-grad-MAG) and PDMA. Selective and nonselective solvents for the hydrophilic block of the diblock ter- and copolymers were used to induce or repress solution-state assemblies prior to spray drying. Prespray dried solution-state assemblies of these four polymers were probed with dynamic light scattering (DLS) and showed differences in solution assembly size and structure (free polymer versus aggregates versus micelles). Solid-state structures of spray dried dispersions (SDDs) showed a single glass transition event implying a homogeneous mixture of drug/polymer. Crystallization temperatures and enthalpies indicated that the drugs interact mostly with the DMA-containing portions of the polymers. Scanning electron microscopy was used to determine SDD particle size and morphology for the various polymer-drug pairings. In vitro dissolution tests showed excellent performance for one system, spray-dried PEP-PDMA micelles with probucol. Dissolution structures were investigated through DLS to determine drug-polymer aggregates that lead to enhanced SDD performance. Forced aggregation of the polymer into regular micelle structures was found to be a critical factor to increase the dissolution rate and supersaturation maintenance of SDDs, and may be an attractive platform to exploit in excipient

  14. Towards controlled polymer brushes via a self-assembly-assisted-grafting-to approach

    PubMed Central

    Zhou, Tian; Qi, Hao; Han, Lin; Barbash, Dmitri; Li, Christopher Y.

    2016-01-01

    Precise synthesis of polymer brushes to modify the surface of nanoparticles and nanodevices for targeted applications has been one of the major focuses in the community for decades. Here we report a self-assembly-assisted-grafting-to approach to synthesize polymer brushes on flat substrates. In this method, polymers are pre-assembled into two-dimensional polymer single crystals (PSCs) with functional groups on the surface. Chemically coupling the PSCs onto solid substrates leads to the formation of polymer brushes. Exquisite control of the chain folding in PSCs allows us to obtain polymer brushes with well-defined grafting density, tethering points and brush conformation. Extremely high grafting density (2.12 chains per nm2) has been achieved in the synthesized single-tethered polymer brushes. Moreover, polymer loop brushes have been successfully obtained using oddly folded PSCs from telechelic chains. Our approach combines some of the important advantages of conventional ‘grafting-to' and ‘grafting-from' methods, and is promising for tailored synthesis of polymer brushes. PMID:27009369

  15. Towards controlled polymer brushes via a self-assembly-assisted-grafting-to approach

    NASA Astrophysics Data System (ADS)

    Zhou, Tian; Qi, Hao; Han, Lin; Barbash, Dmitri; Li, Christopher Y.

    2016-03-01

    Precise synthesis of polymer brushes to modify the surface of nanoparticles and nanodevices for targeted applications has been one of the major focuses in the community for decades. Here we report a self-assembly-assisted-grafting-to approach to synthesize polymer brushes on flat substrates. In this method, polymers are pre-assembled into two-dimensional polymer single crystals (PSCs) with functional groups on the surface. Chemically coupling the PSCs onto solid substrates leads to the formation of polymer brushes. Exquisite control of the chain folding in PSCs allows us to obtain polymer brushes with well-defined grafting density, tethering points and brush conformation. Extremely high grafting density (2.12 chains per nm2) has been achieved in the synthesized single-tethered polymer brushes. Moreover, polymer loop brushes have been successfully obtained using oddly folded PSCs from telechelic chains. Our approach combines some of the important advantages of conventional `grafting-to' and `grafting-from' methods, and is promising for tailored synthesis of polymer brushes.

  16. Synthesis and characterization of self-assembling water-soluble polymers

    SciTech Connect

    Hogen-Esch, T.E.; Amis, E.J.

    1992-05-01

    The synthesis is proposed of water-soluble vinyl and other polymers capable of self-assembly through hydrophobic bonding of pendent fluorocarbon and other hydrophobic groups. The self-assembly process will be studied by viscometry and dynamic viscoelasticity, and by static and dynamic light scattering. These investigations are aimed at identifying the structural features of polymers that are important in enhancing the viscosity of aqueous polymer solutions at very low polymer concentrations (< 1,000 ppm). The authors also initiate small angle neutron scattering (SANS) measurements aimed at the determination of the size of the fluorocarbon-containing hydrophobic aggregates. They will be interested in the degree of self assembly as a function of the type and length of the hydrophobic groups and of the type and length of the flexible spacer group linking the hydrophobic to the polymer backbone. The nature of the hydrophilic chain will also be of interest. Thus, they investigate a number of hydrophilic comonomers such as acrylamide, N-vinylpyrrolidone and anionic or cationic vinyl monomers. Surface interactions of these interesting copolymers will be studied by adsorption onto appropriate modified latex spheres. Finally, they propose to explore the synthesis of water-soluble polymers capable of self assembly through interactions of pendent polyanions and polycations.

  17. Meso-scale Modeling of Self-assembly of Polymer-Grafted Nanoparticles

    NASA Astrophysics Data System (ADS)

    Mancini, Derrick; Deshmukh, Sanket; Sankaranarayanan, Subramanian

    2015-03-01

    We develop meso-scale models to explore the self-assembly behavior of polymer-grafted nanoparticles. Specifically, we study nanoparticles with grafts of the thermo-sensitive polymer poly(N-isopropylacrylamide) (PNIPAM), which undergoes a coil-to-globule transition across the LCST at around 305 K. The atomic-scale mechanism of the coil-to-globule transition of polymers grafted nanoparticles and their interactions (agglomeration, assembly behavior) with other particles that are in its vicinity is poorly understood, yet knowledge about these interactions would enable designing novel self-assembled materials with well-defined structural and dynamical properties. Additionally, the effects of chemical nature, geometry, and morphology of the nanoparticle surface on the conformational transition of thermo-sensitive polymers is also unknown. We report on 1) development of all-atom models of polymer-grafted nanoparticles to conduct MD simulations at atomic-levels and 2) perform mesoscopic scaling of the conformational dynamics resulting from the atomistic simulations with the aid of coarse-grained or meso-scale models of PNIPAM and its composites. Coarse-grained simulations allow modeling of larger assemblies of polymer-grafted nanoparticles over longer time scales. This research used resources of the Center for Nanoscale Materials and the Argonne Leadership Computing Facility at Argonne National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract DE-AC02-06CH11357.

  18. Self-assembly of Open-Shell-containing Block Polymer Thin Films

    NASA Astrophysics Data System (ADS)

    Boudouris, Bryan; Rostro, Lizbeth; Baradwaj, Aditya; Laster, Jennifer

    Radical polymers, where a stable open-shell group is present on each repeat unit of a non-conjugated macromolecular backbone, are emerging as promising materials in organic electronic and magnetic applications. As such, designing molecular motifs that allow for the self-assemble of these open-shell species into nanostructured domains could be beneficial in a host of next-generation flexible electronic applications. In addition, the relatively flexible nature of their macromolecular backbone and ability to conduct charge in the amorphous state offer distinct advantages regarding their self-assembly relative to block polymers based on conjugated semiconducting polymers. Here, we demonstrate the controlled synthesis and self-assembly of diblock copolymers containing radical polymer moieties. In fact, we show that A-B diblock copolymers, where the A moiety contains nitroxide radical functionalities and the B moiety is a closed-shell, low glass transition temperature polymer, self-assemble into ordered structures with domain spacing values that are consistent with common coil-coil diblock copolymers (d = 30 nm). In this way, we present a means by which to readily generate electronically-active macromolecules that self-assemble into nanostructured thin films with controlled morphologies over long ranges.

  19. Understanding Molecular Interactions within Chemically Selective Layered Polymer Assemblies

    SciTech Connect

    Gary J. Blanchard

    2009-06-30

    This work focuses on two broad issues. These are (1) the molecular origin of the chemical selectivity achieved with ultrathin polymer multilayers, and (2) how the viscoelastic properties of the polymer layers are affected by exposure to solvent and analytes. These issues are inter-related, and to understand them we need to design experiments that probe both the energetic and kinetic aspects of interfacial adsorption processes. This project focuses on controling the chemical structure, thickness, morphology and sequential ordering of polymer layers bound to interfaces using maleimide-vinyl ether and closely related alternating copolymerization chemistry and efficient covalent cross-linking reactions that allow for layer-by-layer polymer deposition. This chemistry has been developed during the funding cycle of this Grant. We have measure the equilibrium constants for interactions between specific layers within the polymer interfaces and size-controlled, surface-functionalized gold nanoparticles. The ability to control both size and functionality of gold nanoparticle model analytes allows us to evaluate the average “pore size” that characterizes our polymer films. We have measured the “bulk” viscosity and shear modulus of the ultrathin polymer films as a function of solvent overlayer identity using quartz crystal microbalance complex impedance measurements. We have measured microscopic viscosity at specific locations within the layered polymer interfaces with time-resolved fluorescence lifetime and depolarization techniques. We combine polymer, cross-linking and nanoparticle synthetic expertise with a host of characterization techniques, including QCM gravimetry and complex impedance analysis, steady state and time-resolved spectroscopies.

  20. Thermally Induced Charge Reversal of Layer-by-Layer Assembled Single-Component Polymer Films.

    PubMed

    Richardson, Joseph J; Tardy, Blaise L; Ejima, Hirotaka; Guo, Junling; Cui, Jiwei; Liang, Kang; Choi, Gwan H; Yoo, Pil J; De Geest, Bruno G; Caruso, Frank

    2016-03-23

    Temperature can be harnessed to engineer unique properties for materials useful in various contexts and has been shown to affect the layer-by-layer (LbL) assembly of polymer thin films and cause physical changes in preassembled polymer thin films. Herein we demonstrate that exposure to relatively low temperatures (≤ 100 °C) can induce physicochemical changes in cationic polymer thin films. The surface charge of polymer films containing primary and secondary amines reverses after heating (from positive to negative), and different characterization techniques are used to show that the change in surface charge is related to oxidation of the polymer that specifically occurs in the thin film state. This charge reversal allows for single-polymer LbL assembly to be performed with poly(allylamine) hydrochloride (PAH) through alternating heat/deposition steps. Furthermore, the negative charge induced by heating reduces the fouling and cell-association of PAH-coated planar and particulate substrates, respectively. This study highlights a unique property of thin films which is relevant to LbL assembly and biofouling and is of interest for the future development of thin polymer films for biomedical systems. PMID:26953514

  1. Highly sensitive broadband flexible photodetectors based on a blend film with zinc octaethylporphyrin long nanowires embedded in an insulating polymer

    NASA Astrophysics Data System (ADS)

    Yang, Jia-Mei; Wang, Feng-Xia; Pan, Ge-Bo

    2016-01-01

    Blend films with long nanowires of zinc octaethylporphyrin (ZnOEP) embedded in an insulating polymer of poly(methyl methacrylate) (PMMA) have been successfully fabricated by a one-step spin-coating process. Concerning photoactive blends based on small-molecule semiconductors, this is quite a novel strategy and allows us to greatly reduce the issues related to low device performance, such as phase-separation, poor connectivity of the semiconducting layer, and higher densities of interfacial defects. Intensive studies on the correlation between the film morphology and device performance have revealed that excellent photodetector performance is derived from efficient charge transport and good connectivity observed in highly crystalline, interconnected ZnOEP nanowires embedded in an insulating PMMA matrix. To the best of our knowledge, this is the first demonstration of a blend-film-based organic photodetector, which exhibits high sensitivity, high stability, high Ion/Ioff ratio, excellent mechanical flexibility, and a broadband responsivity region extending up to 1050 nm. The unique characteristics of facile fabrication, high sensitivity, excellent mechanical stability, and broadband responsivity can make the blend film of ZnOEP and PMMA promising in large-area flexible photodetectors.Blend films with long nanowires of zinc octaethylporphyrin (ZnOEP) embedded in an insulating polymer of poly(methyl methacrylate) (PMMA) have been successfully fabricated by a one-step spin-coating process. Concerning photoactive blends based on small-molecule semiconductors, this is quite a novel strategy and allows us to greatly reduce the issues related to low device performance, such as phase-separation, poor connectivity of the semiconducting layer, and higher densities of interfacial defects. Intensive studies on the correlation between the film morphology and device performance have revealed that excellent photodetector performance is derived from efficient charge transport and

  2. All-in-one assembly based on 3D-intertangled and cross-jointed architectures of Si/Cu 1D-nanowires for lithium ion batteries

    PubMed Central

    Hwang, Chihyun; Kim, Tae-Hee; Cho, Yoon-Gyo; Kim, Jieun; Song, Hyun-Kon

    2015-01-01

    All-in-one assemblies of separator, electrode and current collector (SECA) for lithium ion batteries are presented by using 1D nanowires of Si and Cu (nwSi and nwCu). Even without binders, integrity of SECA is secured via structural joints based on ductility of Cu as well as entanglement of nwSi and nwCu. By controlling the ratio of the nanowires, the number of contact points and voids accommodating volume expansion of Si active material are tunable. Zero volume expansion and high energy density are simultaneously achievable by the architecture. PMID:25720334

  3. Stabilization of 2D assemblies of silver nanoparticles by spin-coating polymers

    NASA Astrophysics Data System (ADS)

    Hu, Longyu; Pfirman, Aubrie; Chumanov, George

    2015-12-01

    Silver nanoparticles self-assembled on poly(4-vinylpyridine) modified surfaces were spin-coated with poly(methyl methacrylate), poly(butyl methacrylate) and polystyrene from anisole and toluene solutions. The polymers filled the space between the particles thereby providing stabilization of the assemblies against particle aggregation when dried or chemically modified. The polymers did not coat the top surface of the nanoparticles offering the chemical accessibility to the metal surface. This was confirmed by converting the stabilized nanoparticles into silver sulfide and gold clusters. Etching the nanoparticles resulted in crater-like polymeric structures with the cavities extending down to the underlying substrate. Electrochemical reduction of silver inside the craters was performed. The approach can be extended to other nanoparticle assemblies and polymers.

  4. Bioinspired assemblies of plant cell wall polymers unravel the affinity properties of carbohydrate-binding modules.

    PubMed

    Paës, Gabriel; von Schantz, Laura; Ohlin, Mats

    2015-09-01

    Lignocellulose-acting enzymes play a central role in the biorefinery of plant biomass to make fuels, chemicals and materials. These enzymes are often appended to carbohydrate binding modules (CBMs) that promote substrate targeting. When used in plant materials, which are complex assemblies of polymers, the binding properties of CBMs can be difficult to understand and predict, thus limiting the efficiency of enzymes. In order to gain more information on the binding properties of CBMs, some bioinspired model assemblies that contain some of the polymers and covalent interactions found in the plant cell walls have been designed. The mobility of three engineered CBMs has been investigated by FRAP in these assemblies, while varying the parameters related to the polymer concentration, the physical state of assemblies and the oligomerization state of CBMs. The features controlling the mobility of the CBMs in the assemblies have been quantified and hierarchized. We demonstrate that the parameters can have additional or opposite effects on mobility, depending on the CBM tested. We also find evidence of a relationship between the mobility of CBMs and their binding strength. Overall, bioinspired assemblies are able to reveal the unique features of affinity of CBMs. In particular, the results show that oligomerization of CBMs and the presence of ferulic acid motifs in the assemblies play an important role in the binding affinity of CBMs. Thus we propose that these features should be finely tuned when CBMs are used in plant cell walls to optimise bioprocesses. PMID:26189625

  5. One-step synthesis and patterning of aligned polymer nanowires on a substrate

    DOEpatents

    Wang Zhong L.; Wang, Xudong; Morber, Jenny R.; Liu, Jin

    2011-11-08

    In a method of making a polymer structure on a substrate a layer of a first polymer, having a horizontal top surface, is applied to a surface of the substrate. An area of the top surface of the polymer is manipulated to create an uneven feature that is plasma etched to remove a first portion from the layer of the first polymer thereby leaving the polymer structure extending therefrom. A light emitting structure includes a conductive substrate from which an elongated nanostructure of a first polymer extends. A second polymer coating is disposed about the nanostructure and includes a second polymer, which includes a material such that a band gap exists between the second polymer coating and the elongated nanostructure. A conductive material coats the second polymer coating. The light emitting structure emits light when a voltage is applied between the conductive substrate and the conductive coating.

  6. First-principles study of the geometry of Ag nanowires growing on a self-assembled Bi nanoline

    NASA Astrophysics Data System (ADS)

    Koga, H.; Ohno, T.

    2007-09-01

    Epitaxial Ag nanowires on a self-assembled Bi nanoline on the Si(001) surface are examined for their geometry and energetic stability at the level of the generalized-gradient approximation. The orientations examined are Ag(001)[100], Ag(110)[100], Ag(111)[110], and Ag(001)[110], where the indices refer to the plane and the direction parallel to the Si(001) surface and the Bi nanoline, respectively. The wires are found to have mostly bulklike structure, except that Ag(001) monolayers undergo extensive reconstruction. The calculated electronic band structure indicates that the Ag wires are metallic wires. Particularly stable among the wires are the Ag(111) wires, having a coincident site lattice interface with the Bi nanoline. The energetic stability generally improves with thickness, indicating that Ag grows through three-dimensional nucleation on the Bi nanoline.

  7. Crystal Phase Transformation in Self-Assembled InAs Nanowire Junctions on Patterned Si Substrates.

    PubMed

    Rieger, Torsten; Rosenbach, Daniel; Vakulov, Daniil; Heedt, Sebastian; Schäpers, Thomas; Grützmacher, Detlev; Lepsa, Mihail Ion

    2016-03-01

    We demonstrate the growth and structural characteristics of InAs nanowire junctions evidencing a transformation of the crystalline structure. The junctions are obtained without the use of catalyst particles. Morphological investigations of the junctions reveal three structures having an L-, T-, and X-shape. The formation mechanisms of these structures have been identified. The NW junctions reveal large sections of zinc blende crystal structure free of extended defects, despite the high stacking fault density obtained in individual InAs nanowires. This segment of zinc blende crystal structure in the junction is associated with a crystal phase transformation involving sets of Shockley partial dislocations; the transformation takes place solely in the crystal phase. A model is developed to demonstrate that only the zinc blende phase with the same orientation as the substrate can result in monocrystalline junctions. The suitability of the junctions to be used in nanoelectronic devices is confirmed by room-temperature electrical experiments. PMID:26881450

  8. Controlling the adhesion of conducting polymer films with patterned self-assembled monolayers

    SciTech Connect

    Rozsnyai, L.F.; Wrighton, M.S.

    1996-02-01

    A photosensitive self-assembled monolayer (SAM) is selectively irradiated to fabricate a pattern on an Au electrode, and a thin film of aniline or 3-methylthiophene is deposited on it by electopolymerization. Adhesion of the polymer films can be controlled by the monolayer terminal group. Applying tape to the sample and peeling it away selectively removes the conducting polymer film to the tape in a near-micron resolution pattern. 14 refs., 1 fig.

  9. Healable capacitive touch screen sensors based on transparent composite electrodes comprising silver nanowires and a furan/maleimide diels-alder cycloaddition polymer.

    PubMed

    Li, Junpeng; Liang, Jiajie; Li, Lu; Ren, Fengbo; Hu, Wei; Li, Juan; Qi, Shuhua; Pei, Qibing

    2014-12-23

    A healable transparent capacitive touch screen sensor has been fabricated based on a healable silver nanowire-polymer composite electrode. The composite electrode features a layer of silver nanowire percolation network embedded into the surface layer of a polymer substrate comprising an ultrathin soldering polymer layer to confine the nanowires to the surface of a healable Diels-Alder cycloaddition copolymer and to attain low contact resistance between the nanowires. The composite electrode has a figure-of-merit sheet resistance of 18 Ω/sq with 80% transmittance at 550 nm. A surface crack cut on the conductive surface with 18 Ω is healed by heating at 100 °C, and the sheet resistance recovers to 21 Ω in 6 min. A healable touch screen sensor with an array of 8×8 capacitive sensing points is prepared by stacking two composite films patterned with 8 rows and 8 columns of coupling electrodes at 90° angle. After deliberate damage, the coupling electrodes recover touch sensing function upon heating at 80 °C for 30 s. A capacitive touch screen based on Arduino is demonstrated capable of performing quick recovery from malfunction caused by a razor blade cutting. After four cycles of cutting and healing, the sensor array remains functional. PMID:25486240

  10. Self-assembled growth of GaN nanowires on amorphous Al x O y : from nucleation to the formation of dense nanowire ensembles.

    PubMed

    Sobanska, M; Fernández-Garrido, S; Zytkiewicz, Z R; Tchutchulashvili, G; Gieraltowska, S; Brandt, O; Geelhaar, L

    2016-08-12

    We present a comprehensive description of the self-assembled nucleation and growth of GaN nanowires (NWs) by plasma-assisted molecular beam epitaxy on amorphous Al x O y buffers (a-Al x O y ) prepared by atomic layer deposition. The results are compared with those obtained on nitridated Si(111). Using line-of-sight quadrupole mass spectrometry, we analyze in situ the incorporation of Ga starting from the incubation and nucleation stages till the formation of the final nanowire ensemble and observe qualitatively the same time dependence for the two types of substrates. However, on a-Al x O y the incubation time is shorter and the nucleation faster than on nitridated Si. Moreover, on a-Al x O y we observe a novel effect of decrease in incorporated Ga flux for long growth durations which we explain by coalescence of NWs leading to reduction of the GaN surface area where Ga may reside. Dedicated samples are used to analyze the evolution of surface morphology. In particular, no GaN nuclei are detected when growth is interrupted during the incubation stage. Moreover, for a-Al x O y , the same shape transition from spherical cap-shaped GaN crystallites to the NW-like geometry is found as it is known for nitridated Si. However, while the critical radius for this transition is only slightly larger for a-Al x O y than for nitridated Si, the critical height is more than six times larger for a-Al x O y . Finally, we observe that in fully developed NW ensembles, the substrate no longer influences growth kinetics and the same N-limited axial growth rate is measured on both substrates. We conclude that the same nucleation and growth processes take place on a-Al x O y as on nitridated Si and that these processes are of a general nature. Quantitatively, nucleation proceeds somewhat differently, which indicates the influence of the substrate, but once shadowing limits growth processes to the upper part of the NW ensemble, they are not affected anymore by the type of substrate. PMID

  11. Self-assembled growth of GaN nanowires on amorphous Al x O y : from nucleation to the formation of dense nanowire ensembles

    NASA Astrophysics Data System (ADS)

    Sobanska, M.; Fernández-Garrido, S.; Zytkiewicz, Z. R.; Tchutchulashvili, G.; Gieraltowska, S.; Brandt, O.; Geelhaar, L.

    2016-08-01

    We present a comprehensive description of the self-assembled nucleation and growth of GaN nanowires (NWs) by plasma-assisted molecular beam epitaxy on amorphous Al x O y buffers (a-Al x O y ) prepared by atomic layer deposition. The results are compared with those obtained on nitridated Si(111). Using line-of-sight quadrupole mass spectrometry, we analyze in situ the incorporation of Ga starting from the incubation and nucleation stages till the formation of the final nanowire ensemble and observe qualitatively the same time dependence for the two types of substrates. However, on a-Al x O y the incubation time is shorter and the nucleation faster than on nitridated Si. Moreover, on a-Al x O y we observe a novel effect of decrease in incorporated Ga flux for long growth durations which we explain by coalescence of NWs leading to reduction of the GaN surface area where Ga may reside. Dedicated samples are used to analyze the evolution of surface morphology. In particular, no GaN nuclei are detected when growth is interrupted during the incubation stage. Moreover, for a-Al x O y , the same shape transition from spherical cap-shaped GaN crystallites to the NW-like geometry is found as it is known for nitridated Si. However, while the critical radius for this transition is only slightly larger for a-Al x O y than for nitridated Si, the critical height is more than six times larger for a-Al x O y . Finally, we observe that in fully developed NW ensembles, the substrate no longer influences growth kinetics and the same N-limited axial growth rate is measured on both substrates. We conclude that the same nucleation and growth processes take place on a-Al x O y as on nitridated Si and that these processes are of a general nature. Quantitatively, nucleation proceeds somewhat differently, which indicates the influence of the substrate, but once shadowing limits growth processes to the upper part of the NW ensemble, they are not affected anymore by the type of substrate.

  12. Self-assembled and highly selective sensors based on air-bridge-structured nanowire junction arrays.

    PubMed

    Park, Won Jeong; Choi, Kyung Jin; Kim, Myung Hwa; Koo, Bon Hyeong; Lee, Jong-Lam; Baik, Jeong Min

    2013-08-14

    We describe a strategy for creating an air-bridge-structured nanowire junction array platform that capable of reliably discriminating between three gases (hydrogen, carbon monoxide, and nitrogen dioxide) in air. Alternatively driven dual nanowire species of ZnO and CuO with the average diameter of ∼30 nm on a single substrate are used and decorated with metallic nanoparticles to form two-dimensional microarray, which do not need to consider the post fabrications. Each individual nanowires in the array form n-n, p-p, and p-n junctions at the micro/nanoscale on single substrate and the junctions act as electrical conducting path for carriers. The adsorption of gas molecules to the surface changes the potential barrier height formed at the junctions and the carrier transport inside the straight semiconductors, which provide the ability of a given sensor array to differentiate among the junctions. The sensors were tested for their ability to distinguish three gases (H2, CO, and NO2), which they were able to do unequivocally when the data was classified using linear discriminant analysis. PMID:23841667

  13. Under-Liquid Self-Assembly of Submerged Buoyant Polymer Particles.

    PubMed

    Multanen, Victor; Pogreb, Roman; Bormashenko, Yelena; Shulzinger, Evgeny; Whyman, Gene; Frenkel, Mark; Bormashenko, Edward

    2016-06-14

    The self-assembly of submerged cold-plasma-treated polyethylene beads (PBs) is reported. The plasma-treated immersed millimetrically sized PBs formed well-ordered 2D quasicrystalline structures. The submerged floating of "light" (buoyant) PBs is possible because of the energy gain achieved by the wetting of the high-energy plasma-treated polymer surface prevailing over the energy loss due to the upward climb of the liquid over the beads. The capillary "immersion" attraction force is responsible for the observed self-assembly. The observed 2D quasicrystalline structures demonstrate "dislocations" and "point defects". The mechanical vibration of self-assembled rafts built of PBs leads to the healing of point defects. The immersion capillary lateral force governs the self-assembly, whereas the elastic force is responsible for the repulsion of polymer beads. PMID:27193509

  14. The magnetic assembly of polymer colloids in a ferrofluid and its display applications.

    PubMed

    Liu, Jing; Mao, Yiwu; Ge, Jianping

    2012-03-01

    Nonmagnetic polymer colloids have been assembled into colloidal photonic crystals in a ferrofluid by applying an external magnetic field based on the dipole-dipole interactions of "magnetic holes". The photonic crystal disassembles immediately when the magnetic field is removed. The mechanism of assembly can be explained by two simultaneous processes: phase separation and colloidal assembly. In this work, increasing the size of the building blocks still produces colorful photonic crystals due to their 2nd order diffraction. With a larger building block, the magnetic response between the polymer colloids is greatly enhanced so that an instant and reversible assembly/disassembly can be realized in a much weaker magnetic field and lower ferrofluid concentration. Based on these investigations, a magnetically controlled photonic display unit has been fabricated, which works in a weak magnetic field, has stable reflection signals and possesses fast and reversible on/off switching of reflections. PMID:22297654

  15. Dynamic assembly of polymer nanotube networks via kinesin powered microtubule filaments

    SciTech Connect

    Paxton, Walter F.; Bachand, George D.; Gomez, Andrew; Henderson, Ian M.; Bouxsein, Nathan F.

    2015-04-24

    In this study, we describe for the first time how biological nanomotors may be used to actively self-assemble mesoscale networks composed of diblock copolymer nanotubes. The collective force generated by multiple kinesin nanomotors acting on a microtubule filament is large enough to overcome the energy barrier required to extract nanotubes from polymer vesicles comprised of poly(ethylene oxide-b-butadiene) in spite of the higher force requirements relative to extracting nanotubes from lipid vesicles. Nevertheless, large-scale polymer networks were dynamically assembled by the motors. These networks displayed enhanced robustness, persisting more than 24 h post-assembly (compared to 4–5 h for corresponding lipid networks). The transport of materials in and on the polymer membranes differs substantially from the transport on analogous lipid networks. Specifically, our data suggest that polymer mobility in nanotubular structures is considerably different from planar or 3D structures, and is stunted by 1D confinement of the polymer subunits. Moreover, quantum dots adsorbed onto polymer nanotubes are completely immobile, which is related to this 1D confinement effect and is in stark contrast to the highly fluid transport observed on lipid tubules.

  16. Dynamic assembly of polymer nanotube networks via kinesin powered microtubule filaments

    DOE PAGESBeta

    Paxton, Walter F.; Bachand, George D.; Gomez, Andrew; Henderson, Ian M.; Bouxsein, Nathan F.

    2015-04-24

    In this study, we describe for the first time how biological nanomotors may be used to actively self-assemble mesoscale networks composed of diblock copolymer nanotubes. The collective force generated by multiple kinesin nanomotors acting on a microtubule filament is large enough to overcome the energy barrier required to extract nanotubes from polymer vesicles comprised of poly(ethylene oxide-b-butadiene) in spite of the higher force requirements relative to extracting nanotubes from lipid vesicles. Nevertheless, large-scale polymer networks were dynamically assembled by the motors. These networks displayed enhanced robustness, persisting more than 24 h post-assembly (compared to 4–5 h for corresponding lipid networks).more » The transport of materials in and on the polymer membranes differs substantially from the transport on analogous lipid networks. Specifically, our data suggest that polymer mobility in nanotubular structures is considerably different from planar or 3D structures, and is stunted by 1D confinement of the polymer subunits. Moreover, quantum dots adsorbed onto polymer nanotubes are completely immobile, which is related to this 1D confinement effect and is in stark contrast to the highly fluid transport observed on lipid tubules.« less

  17. Fully solution-processed semitransparent organic solar cells with a silver nanowire cathode and a conducting polymer anode.

    PubMed

    Yim, Jong Hyuk; Joe, Sung-yoon; Pang, Christina; Lee, Kyung Moon; Jeong, Huiseong; Park, Ji-Yong; Ahn, Yeong Hwan; de Mello, John C; Lee, Soonil

    2014-03-25

    We report the fabrication of efficient indium-tin-oxide-free organic solar cells based on poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM). All layers of the devices from the lowermost silver nanowire cathode to the uppermost conducting polymer anode are deposited from solution and processed at plastic-compatible temperatures<200 °C. Owing to the absence of an opaque metal electrode, the devices are semitransparent with potential applications in power-generating windows and tandem-cells. The measured power conversion efficiencies (PCEs) of 2.3 and 2.0% under cathode- and anode-side illumination, respectively, match previously reported PCE values for equivalent semitransparent organic solar cells using indium tin oxide. PMID:24533638

  18. Electrostatically Directed Self-Assembly of Ultrathin Supramolecular Polymer Microcapsules

    PubMed Central

    Parker, Richard M; Zhang, Jing; Zheng, Yu; Coulston, Roger J; Smith, Clive A; Salmon, Andrew R; Yu, Ziyi; Scherman, Oren A; Abell, Chris

    2015-01-01

    Supramolecular self-assembly offers routes to challenging architectures on the molecular and macroscopic scale. Coupled with microfluidics it has been used to make microcapsules—where a 2D sheet is shaped in 3D, encapsulating the volume within. In this paper, a versatile methodology to direct the accumulation of capsule-forming components to the droplet interface using electrostatic interactions is described. In this approach, charged copolymers are selectively partitioned to the microdroplet interface by a complementary charged surfactant for subsequent supramolecular cross-linking via cucurbit[8]uril. This dynamic assembly process is employed to selectively form both hollow, ultrathin microcapsules and solid microparticles from a single solution. The ability to dictate the distribution of a mixture of charged copolymers within the microdroplet, as demonstrated by the single-step fabrication of distinct core–shell microcapsules, gives access to a new generation of innovative self-assembled constructs. PMID:26213532

  19. Highly Ordered Single Crystalline Nanowire Array Assembled Three-Dimensional Nb3O7(OH) and Nb2O5 Superstructures for Energy Storage and Conversion Applications.

    PubMed

    Zhang, Haimin; Wang, Yun; Liu, Porun; Chou, Shu Lei; Wang, Jia Zhao; Liu, Hongwei; Wang, Guozhong; Zhao, Huijun

    2016-01-26

    Three-dimensional (3D) metal oxide superstructures have demonstrated great potentials for structure-dependent energy storage and conversion applications. Here, we reported a facile hydrothermal method for direct growth of highly ordered single crystalline nanowire array assembled 3D orthorhombic Nb3O7(OH) superstructures and their subsequent thermal transformation into monoclinic Nb2O5 with well preserved 3D nanowire superstructures. The performance of resultant 3D Nb3O7(OH) and Nb2O5 superstructures differed remarkably when used for energy conversion and storage applications. The thermally converted Nb2O5 superstructures as anode material of lithium-ion batteries (LiBs) showed higher capacity and excellent cycling stability compared to the Nb3O7(OH) superstructures, while directly hydrothermal grown Nb3O7(OH) nanowire superstructure film on FTO substrate as photoanode of dye-sensitized solar cells (DSSCs) without the need for further calcination exhibited an overall light conversion efficiency of 6.38%, higher than that (5.87%) of DSSCs made from the thermally converted Nb2O5 film. The high energy application performance of the niobium-based nanowire superstructures with different chemical compositions can be attributed to their large surface area, superior electron transport property, and high light utilization efficiency resulting from a 3D superstructure, high crystallinity, and large sizes. The formation process of 3D nanowire superstructures before and after thermal treatment was investigated and discussed based on our theoretical and experimental results. PMID:26579783

  20. Assembly of optical fibers for the connection of polymer-based waveguide

    NASA Astrophysics Data System (ADS)

    Ansel, Yannick; Grau, Daniel; Holzki, Markus; Kraus, Silvio; Neumann, Frank; Reinhard, Carsten; Schmitz, Felix

    2003-03-01

    This paper describes the realization of polymer-based optical structures and the assembly and packaging strategy to connect optical fiber ribbons to the waveguides. For that a low cost fabrication process using the SU-8TM thick photo-resist is presented. This process consists in the deposition of two photo-structurized resist layers filled up with epoxy glue realising the core waveguide. For the assembly, a new modular vacuum gripper was realised and installed on an automatic pick and place assembly robot to mount precisely and efficiently the optical fibers in the optical structures. First results have shown acceptable optical propagation loss for the complete test structure.

  1. A pillar[5]arene-fused cryptand: from orthogonal self-assembly to supramolecular polymer.

    PubMed

    Wang, Qi; Cheng, Ming; Zhao, Yue; Wu, Lin; Jiang, Juli; Wang, Leyong; Pan, Yi

    2015-02-28

    A pillar[5]arene-fused cryptand with two different cavities was synthesized successfully. It was found that the novel tricyclic host could associate with two different guest species in an orthogonal manner. And based on this orthogonal self-assembly of two host-guest interactions, a novel type of supramolecular polymer was constructed easily and conveniently. PMID:25636005

  2. Liposome-containing polymer films and colloidal assemblies towards biomedical applications

    NASA Astrophysics Data System (ADS)

    Teo, Boon M.; Hosta-Rigau, Leticia; Lynge, Martin E.; Städler, Brigitte

    2014-05-01

    Liposomes are important components for biomedical applications. Their unique architecture and versatile nature have made them useful carriers for the delivery of therapeutic cargo. The scope of this minireview is to highlight recent developments of biomimetic liposome-based multicompartmentalized assemblies of polymer thin films and colloidal carriers, and to outline a selection of recent applications of these materials in bionanotechnology.

  3. Efficient self-assembly in water of long noncovalent polymers by nucleobase analogues.

    PubMed

    Cafferty, Brian J; Gállego, Isaac; Chen, Michael C; Farley, Katherine I; Eritja, Ramon; Hud, Nicholas V

    2013-02-20

    Molecular self-assembly is widely appreciated to result from a delicate balance between several noncovalent interactions and solvation effects. However, current design approaches for achieving self-assembly in water with small, synthetic molecules do not consider all aspects of the hydrophobic effect, in particular the requirement of surface areas greater than 1 nm(2) for an appreciable free energy of hydration. With the concept of a minimum hydrophobic surface area in mind, we designed a system that achieves highly cooperative self-assembly in water. Two weakly interacting low-molecular-weight monomers (cyanuric acid and a modified triaminopyrimidine) are shown to form extremely long supramolecular polymer assemblies that retain water solubility. The complete absence of intermediate assemblies means that the observed equilibrium is between free monomers and supramolecular assemblies. These observations are in excellent agreement with literature values for the free energy of nucleic acid base interactions as well as the calculated free energy penalty for the exposure of hydrophobic structures in water. The results of our study have implications for the design of new self-assembling structures and hydrogel-forming molecules and may provide insights into the origin of the first RNA-like polymers. PMID:23394182

  4. Tuning the Assembly of Spherical Nanoparticles in Semicrystalline Polymers

    NASA Astrophysics Data System (ADS)

    Zhao, Dan; Jestin, Jacques; Zhao, Longxi; Kumar, Sanat K.; Mohammadkhani, Mohammad; Benicewicz, Brian C.

    We propose a simple, novel strategy to controlling nanoparticle (NPs) dispersion states in a semi-crystalline polymer matrix exploiting the kinetics of polymer crystallization. The system consists of poly(methyl methacrylate) grafted spherical silica NPs and poly(ethylene oxide) matrices, which are thermodynamically miscible in the melt. We first show that no remarkable change was observed in the spatial dispersion of NPs upon fast crystallization. However, for slow crystallization, both TEM and X-ray/neutron scattering reveal that the system starts to be organized in a ``layer-by-layer'' architecture, where the NPs are aligned in the amorphous phases intercalated by the crystalline lamellar phases. More importantly, we have found that the resulting ``sheet-like'' NP morphology gives rise to a 2-fold increase in the storage modulus but without compromising the fracture toughness of the neat polymer. These results open pathways for creating in-situ biomimetic hierarchical structures with improved mechanical properties through a simple, single-step crystallization processing, which could lead to new applications for this largest class of commercially relevant polymeric materials.

  5. Ultrathin Nanotube/Nanowire Electrodes by Spin-Spray Layer-by-Layer Assembly: A Concept for Transparent Energy Storage.

    PubMed

    Gittleson, Forrest S; Hwang, Daniel; Ryu, Won-Hee; Hashmi, Sara M; Hwang, Jonathan; Goh, Tenghooi; Taylor, André D

    2015-10-27

    Fully integrated transparent devices require versatile architectures for energy storage, yet typical battery electrodes are thick (20-100 μm) and composed of optically absorbent materials. Reducing the length scale of active materials, assembling them with a controllable method and minimizing electrode thickness should bring transparent batteries closer to reality. In this work, the rapid and controllable spin-spray layer-by-layer (SSLbL) method is used to generate high quality networks of 1D nanomaterials: single-walled carbon nanotubes (SWNT) and vanadium pentoxide (V2O5) nanowires for anode and cathode electrodes, respectively. These ultrathin films, deposited with ∼2 nm/bilayer precision are transparent when deposited on a transparent substrate (>87% transmittance) and electrochemically active in Li-ion cells. SSLbL-assembled ultrathin SWNT anodes and V2O5 cathodes exhibit reversible lithiation capacities of 23 and 7 μAh/cm(2), respectively at a current density of 5 μA/cm(2). When these electrodes are combined in a full cell, they retain ∼5 μAh/cm(2) capacity over 100 cycles, equivalent to the prelithiation capacity of the limiting V2O5 cathode. The SSLbL technique employed here to generate functional thin films is uniquely suited to the generation of transparent electrodes and offers a compelling path to realize the potential of fully integrated transparent devices. PMID:26344174

  6. Halogen-bonded mesogens direct polymer self-assemblies up to millimetre length scale

    PubMed Central

    Houbenov, Nikolay; Milani, Roberto; Poutanen, Mikko; Haataja, Johannes; Dichiarante, Valentina; Sainio, Jani; Ruokolainen, Janne; Resnati, Giuseppe; Metrangolo, Pierangelo; Ikkala, Olli

    2014-01-01

    Aligning polymeric nanostructures up to macroscale in facile ways remains a challenge in materials science and technology. Here we show polymeric self-assemblies where nanoscale organization guides the macroscopic alignment up to millimetre scale. The concept is shown by halogen bonding mesogenic 1-iodoperfluoroalkanes to a star-shaped ethyleneglycol-based polymer, having chloride end-groups. The mesogens segregate and stack parallel into aligned domains. This leads to layers at ~10 nm periodicity. Combination of directionality of halogen bonding, mesogen parallel stacking and minimization of interfacial curvature translates into an overall alignment in bulk and films up to millimetre scale. Upon heating, novel supramolecular halogen-bonded polymeric liquid crystallinity is also shown. As many polymers present sites capable of receiving halogen bonding, we suggest generic potential of this strategy for aligning polymer self-assemblies. PMID:24893843

  7. Alignment of human cardiomyocytes on laser patterned biphasic core/shell nanowire assemblies

    NASA Astrophysics Data System (ADS)

    Kiefer, Karin; Lee, Juseok; Haidar, Ayman; Martinez Miró, Marina; Akkan, Cagri Kaan; Veith, Michael; Cenk Aktas, Oral; Abdul-Khaliq, Hashim

    2014-12-01

    The management of end stage heart failure patients is only possible by heart transplantation or by the implantation of artificial hearts as a bridge for later transplantation. However, these therapeutic strategies are limited by a lack of donor hearts and by the associated complications, such as coagulation and infection, due to the used artificial mechanical circulatory assist devices. Therefore, new strategies for myocardial regenerative approaches are under extensive research to produce contractile myocardial tissue in the future to replace non-contractile myocardial ischemic and scarred tissue. Different approaches, such as cell transplantation, have been studied intensively. Although successful approaches have been observed, there are still limitations to the application. It is envisaged that myocardial tissue engineering can be used to help replace infarcted non-contractile tissue. The developed tissue should later mimic the aligned fibrillar structure of the extracellular matrix and provide important guidance cues for the survival, function and the needed orientation of cardiomyocytes. Nanostructured surfaces have been tested to provide a guided direction that cells can follow. In the present study, the cellular adhesion/alignment of human cardiomyocytes and the biocompatibility have been investigated after cultivation on different laser-patterned nanowires compared with unmodified nanowires. As a result, the nanostructured surfaces possessed good biocompatibility before and after laser modification. The laser-induced scalability of the pattern enabled the growth and orientation of the adhered myocardial tissue. Such approaches may be used to modify the surface of potential scaffolds to develop myocardial contractile tissue in the future.

  8. Electrochemically Directed Self-Assembly and Conjugated Polymer Semiconductors for Organic Electronic Applications

    NASA Astrophysics Data System (ADS)

    Pillai, Rajesh Gopalakrishna

    2011-07-01

    The research work presented in this thesis investigates the mechanistic details of conventional as well as electrochemically directed self-assembly of alkylthiosulfates and explores the use of conjugated semiconducting polymers for organic electronic applications. Here, the significance of the use of conjugated polymers is twofold; first, to explore their applications in nanoelectronics and second, the possibility of using them as a top contact on the self-assembled monolayers (SAMs) for molecular electronic applications. Throughout this work, deposition of the organic materials was performed on prefabricated device structures that required no further lithographic or metal deposition steps after modification of the electrodes with the organic molecules. Self-assembly of alkylthiosulfates on gold are reported to form monolayers identical to those formed from the corresponding alkanethiols. However, these self-assembly processes follow more complex mechanisms of monolayer formation than originally recognized. Studies on the mechanism of alkylthiosulfate chemisorption on gold shows that the self-assembly process is influenced by electrolyte and solvent. Plausible mechanisms have been proposed for the role of trace water in the solvent on conventional as well as electrochemically assisted self-assembly of alkylthiosulfates on gold. Electroanalytical and spectroscopic techniques have been used to explore the mechanistic details of electrochemically directed self-assembly of alkylthiosulfates on gold. It has been found that the self-assembly process is dynamic under electrochemical conditions and the heterogeneous electron transfer process between the organosulfur compound and gold is mediated through gold surface oxide and accompanied by corrosion. Conducting polymers are serious candidates for organic electronic applications since their properties can be controlled by the manipulation of molecular architecture. Unique electronic properties of conjugated polypyrrole

  9. Assessment of Polarity in GaN Self-Assembled Nanowires by Electrical Force Microscopy.

    PubMed

    Minj, A; Cros, A; Garro, N; Colchero, J; Auzelle, T; Daudin, B

    2015-10-14

    In this work, we demonstrate the capabilities of atomic force microscopies (AFMs) for the nondestructive determination of the polarity of GaN nanowires (NWs). Three complementary AFMs are analyzed here: Kelvin probe force microscopy (KPFM), light-assisted KPFM, and piezo-force microscopy (PFM). These techniques allow us to assess the polarity of individual NWs over an area of tens of μm(2) and provide statistics on the polarity of the ensemble with an accuracy hardly reachable by other methods. The precise quantitative analysis of the tip-sample interaction by multidimensional spectroscopic measurements, combined with advanced data analysis, has allowed the separate characterization of electrostatic and van der Waals forces as a function of tip-sample distance. Besides their polarity, the net surface charge density of individual NWs was estimated. PMID:26380860

  10. Synthesis of Discrete Alkyl-Silica Hybrid Nanowires and Their Assembly into Nanostructured Superhydrophobic Membranes.

    PubMed

    Yi, Deliang; Xu, Chenglong; Tang, Ruidie; Zhang, Xuehua; Caruso, Frank; Wang, Yajun

    2016-07-11

    We report the synthesis of highly flexible and mechanically robust hybrid silica nanowires (NWs) which can be used as novel building blocks to construct superhydrophobic functional materials with three-dimensional macroporous networks. The hybrid silica NWs, with an average diameter of 80 nm and tunable length of up to 12 μm, are prepared by anisotropic deposition of the hydrolyzed tetraethylorthosilicate in water/n-pentanol emulsions. A mechanistic investigation reveals that the trimethoxy(octadecyl)silane introduced to the water-oil interface in the synthesis plays key roles in stabilizing the water droplets to sub-100 nm and also growing a layer of octadecyl groups on the NW surface. This work opens a solution-based route for the one-pot preparation of monodisperse, hydrophobic silica NWs and represents an important step toward the bottom-up construction of 3D superhydrophobic materials and macroporous membranes. PMID:27278242

  11. Self-Assembly into Strands in Amphiphilic Polymer Brushes.

    PubMed

    Larin, Daniil E; Lazutin, Alexei A; Govorun, Elena N; Vasilevskaya, Valentina V

    2016-07-12

    The self-assembly of amphiphilic macromolecules end-grafted to a plane surface is studied using mean-field theory and computer simulations. Chain backbones are built from hydrophobic groups, whereas side groups are hydrophilic. The brush is immersed in a solvent, which can be good or poor, but on average is not far from θ conditions. It is demonstrated that the strong amphiphilicity of macromolecules at a monomer unit level leads to their self-assembly into a system of strands with a 2D hexagonal order in a cross-section parallel to the grafting plane. The structure period is determined by the length of side groups. In theory, this effect is explained by the orientation of strongly amphiphilic monomer units at a strand/solvent boundary that leads to an effective negative contribution to the surface tension. Computer simulations with molecular dynamics (MD) are used for a detailed study of the local brush structure. The aggregation number of strands grows with the increase of the grafting density and side group length. PMID:27267357

  12. Effect of polymer brushes on the Self Assembly of 3D Poly(Styrene-Methylmethacrylate) thin films

    NASA Astrophysics Data System (ADS)

    Lwoya, Baraka; Albert, Julie

    2015-03-01

    It would be instrumental to understand the self-assembly capabilities of polymers especially given their industrial capabilities of templating and membrane application .The ability of block copolymers to self assemble into different morphologies is determined by several factor including type of polymer blocks, volume fraction, substrate preference to a polymer and chain architecture . In this paper Poly(Styrene-Methylmethacrylate) (PS-PMMA) was chosen was chosen to further understand the effect polymer brushes on the substrate had on the self assembly of 3D structured PS-PMMA spin coated thin films (30-150 nm). The polymer brushes were grown using surface initiated atomic transfer radical polymerization (SI-ATRP) with the optimal chain length being confirmed by gel permeation chromatography. By using ellipsometer and contact angle measurement the uniformity of the polymer brushes are characterized, while the morphology of the spin coated thin films after thermal annealing would be characterized using atomic force microscopy (AFM).

  13. Directed Self-assembly of Nanoparticles at the Polymer Surface by Highly Compressible Supercritical Carbon Dioxide

    SciTech Connect

    M Asada; P Gin; M Endoh; S Satija; T Taniguchi; T Koga

    2011-12-31

    We report a versatile route for self-assembly of polymer-soluble nanoparticles at the polymer surface using highly compressible supercritical carbon dioxide (scCO{sub 2}). Polystyrene and poly(methyl methacrylate)-based nanocomposite thin films with functionalized polyhedral oligomeric silsesquioxane and phenyl C{sub 61} butyric acid methyl ester nanoparticles were prepared on Si substrates and exposed to scCO{sub 2} at different pressures under the isothermal condition of 36 C. The resultant structures could be then preserved by the vitrification process of the glassy polymers via quick pressure quench to atmospheric pressure and subsequently characterized by using various surface sensitive experimental techniques in air. We found that the surface segregation of these nanoparticles is induced in the close vicinity of P = 8.2 MPa where the excess absorption of the fluid into the polymers maximizes. However, when the film thickness becomes less than about 4R{sub g} thick (where R{sub g} is the radius of polymer gyration), the uniform dispersion of the nanoparticles is favorable instead even at the same CO{sub 2} conditions. We clarify that the phase transition is correlated with the emergence of a concentration gradient of the fluid at the polymer/CO{sub 2} interface and is a general phenomenon for different polymer-nanoparticle interactions.

  14. Self-assembly of polymers in confined geometrics.

    SciTech Connect

    Curro, John G.; Ye, Yuan; McCoy, John Dwane

    2003-10-01

    Athermal, tethered chains are modeled with Density Functional (DFT) theory for both the explicit solvent and continuum solvent cases. The structure of DFT is shown to reduce to Self-Consistent-Field (SCF) theory in the incompressible limit where there is symmetry between solvent and monomer, and to Single-Chain-Mean-Field (SCMF) theory in the continuum solvent limit. We show that by careful selection of the reference and ideal systems in DFT theory, self-consistent numerical solutions can be obtained, thereby avoiding the single chain Monte Carlo simulation in SCMF theory. On long length scales, excellent agreement is seen between the simplified DFT theory and Molecular Dynamics simulations of both continuum solvents and explicit-molecule solvents. In order to describe the structure of the polymer and solvent near the surface it is necessary to include compressibility effects and the nonlocality of the field.

  15. A general route to nanocrystal kebabs periodically assembled on stretched flexible polymer shish

    PubMed Central

    Xu, Hui; Xu, Yuci; Pang, Xinchang; He, Yanjie; Jung, Jaehan; Xia, Haiping; Lin, Zhiqun

    2015-01-01

    Assembling nanoparticles into one-dimensional (1D) nanostructures with precisely controlled size and shape renders the exploration of new properties and construction of 1D miniaturized devices possible. The physical properties of such nanostructures depend heavily on the size, chemical composition, and surface chemistry of nanoparticle constituents, as well as the close proximity of adjacent nanoparticles within the 1D nanostructure. Chemical synthesis provides an intriguing alternative means of creating 1D nanostructures composed of self-assembled nanoparticles in terms of material diversity, size controllability, shape regularity, and low-cost production. However, this is an area where progress has been slower. We report an unconventional yet general strategy to craft an exciting variety of 1D nanonecklace-like nanostructures comprising uniform functional nanodiscs periodically assembled along a stretched flexible polymer chain by capitalizing on judiciously designed amphiphilic worm-like diblock copolymers as nanoreactors. These nanostructures can be regarded as organic-inorganic shish-kebabs, in which nanodisc kebabs are periodically situated on a stretched polymer shish. Simulations based on self-consistent field theory reveal that the formation of organic-inorganic shish-kebabs is guided by the self-assembled elongated star-like diblock copolymer constituents constrained on the highly stretched polymer chain. PMID:26601151

  16. Polymer-mediated nanorod self-assembly predicted by dissipative particle dynamics simulations.

    PubMed

    Khani, Shaghayegh; Jamali, Safa; Boromand, Arman; Hore, Michael J A; Maia, Joao

    2015-09-14

    Self-assembly of nanoparticles in polymer matrices is an interesting and growing subject in the field of nanoscience and technology. We report herein on modelling studies of the self-assembly and phase behavior of nanorods in a homopolymer matrix, with the specific goal of evaluating the role of deterministic entropic and enthalpic factors that control the aggregation/dispersion in such systems. Grafting polymer brushes from the nanorods is one approach to control/impact their self-assembly capabilities within a polymer matrix. From an energetic point of view, miscible interactions between the brush and the matrix are required for achieving a better dispersibility; however, grafting density and brush length are the two important parameters in dictating the morphology. Unlike in previous computational studies, the present Dissipative Particle Dynamics (DPD) simulation framework is able to both predict dispersion or aggregation of nanorods and determine the self-assembled structure, allowing for the determination of a phase diagram, which takes all of these factors into account. Three types of morphologies are predicted: dispersion, aggregation and partial aggregation. Moreover, favorable enthalpic interactions between the brush and the matrix are found to be essential for expanding the window for achieving a well-dispersed morphology. A three-dimensional phase diagram is mapped on which all the afore-mentioned parameters are taken into account. Additionally, in the case of immiscibility between brushes and the matrix, simulations predict the formation of some new and tunable structures. PMID:26235000

  17. Amphiphilic invertible polymers: Self-assembly into functional materials driven by environment polarity

    NASA Astrophysics Data System (ADS)

    Hevus, Ivan

    Stimuli-responsive polymers adapt to environmental changes by adjusting their chain conformation in a fast and reversible way. Responsive polymeric materials have already found use in electronics, coatings industry, personal care, and bio-related areas. The current work aims at the development of novel responsive functional polymeric materials by manipulating environment-dependent self-assembly of a new class of responsive macromolecules strategically designed in this study,—amphiphilic invertible polymers (AIPs). Environment-dependent micellization and self-assembly of three different synthesized AIP types based on poly(ethylene glycol) as a hydrophilic fragment and varying hydrophobic constituents was demonstrated in polar and nonpolar solvents, as well as on the surfaces and interfaces. With increasing concentration, AIP micelles self-assemble into invertible micellar assemblies composed of hydrophilic and hydrophobic domains. Polarity-responsive properties of AIPs make invertible micellar assemblies functional in polar and nonpolar media including at interfaces. Thus, invertible micellar assemblies solubilize poorly soluble substances in their interior in polar and nonpolar solvents. In a polar aqueous medium, a novel stimuli-responsive mechanism of drug release based on response of AIP-based drug delivery system to polarity change upon contact with the target cell has been established using invertible micellar assemblies loaded with curcumin, a phytochemical drug. In a nonpolar medium, invertible micellar assemblies were applied simultaneously as nanoreactors and stabilizers for size-controlled synthesis of silver nanoparticles stable in both polar and nonpolar media. The developed amphiphilic nanosilver was subsequently used as seeds to promote anisotropic growth of CdSe semiconductor nanoparticles that have potential in different applications ranging from physics to medicine. Amphiphilic invertible polymers were shown to adsorb on the surface of silica

  18. Controlling self-assembly of DNA-polymer conjugates for applications in imaging and drug delivery.

    PubMed

    Peterson, Amberlyn M; Heemstra, Jennifer M

    2015-01-01

    Amphiphilic supramolecular structures such as micelles and vesicles can be formed through phase-driven self-assembly of monomer units having discrete hydrophilic and hydrophobic blocks. These structures show great promise for use in medical and biological applications, and incorporating DNA as the hydrophilic block of the amphiphilic monomers enables the creation of assemblies that also take advantage of the unique information storage and molecular recognition capabilities of DNA. Recently, significant advances have been made in the synthesis of DNA-polymer conjugates (DPCs), controlling the morphology of DPC assemblies by altering monomer structure, and probing the effect of assembly on DNA stability and hybridization. Together, these investigations have laid the framework for using DPCs in drug delivery, cellular imaging, and other applications in materials science and chemistry. PMID:25327363

  19. Ordered silicon nanowire arrays prepared by an improved nanospheres self-assembly in combination with Ag-assisted wet chemical etching

    NASA Astrophysics Data System (ADS)

    Jia, Guobin; Westphalen, Jasper; Drexler, Jan; Plentz, Jonathan; Dellith, Jan; Dellith, Andrea; Andrä, Gudrun; Falk, Fritz

    2016-04-01

    An improved Langmuir-Blodgett self-assembly process combined with Ag-assisted wet chemical etching for the preparation of ordered silicon nanowire arrays is presented in this paper. The new process is independent of the surface conditions (hydrophilic or hydrophobic) of the substrate, allowing for depositing a monolayer of closely packed polystyrene nanospheres onto any flat surface. A full control of the morphology of the silicon nanowire is achieved. Furthermore, it is observed that the formation of porous-Si at the tips of the nanowires is closely related to the release of Ag nanoparticles from the Ag mask during the etching, which subsequently redeposit on the surface initially free of Ag, and these Ag nanoparticles catalyze the etching of the tips and lead to the porous-Si formation. This finding will help to improve the resulting nano- and microstructures to get them free of pores, and renders it a promising technology for low-cost high throughput fabrication of specific optical devices, photonic crystals, sensors, MEMS, and NEMS by substituting the costly BOSCH process. It is shown that ordered nanowire arrays free of porous structures can be produced if all sources of Ag nanoparticles are excluded, and structures with aspect ratio more than 100 can be produced.

  20. Microwave synthesis of branched silver nanowires and their use as fillers for high thermal conductivity polymer composites

    NASA Astrophysics Data System (ADS)

    Seshadri, Indira; Esquenazi, Gibran L.; Cardinal, Thomas; Borca-Tasciuc, Theodorian; Ramanath, Ganpati

    2016-04-01

    We report a rapid synthesis approach to obtain branched Ag nanowires by microwave-stimulated polyvinylpyrrolidone-directed polyol-reduction of silver nitrate. Microwave exposure results in micrometer-long nanowires passivated with polyvinylpyrrolidone. Cooling the reaction mixture by interrupting microwave exposure promotes nanocrystal nucleation at low-surfactant coverage sites. The nascent nuclei grow into nanowire branches upon further microwave exposure. Dispersions of low fractions of the branched nanowires in polydimethylsiloxane yield up to 60% higher thermal conductivity than that obtained using unbranched nanowire fillers. Our findings should be useful for realizing nanocomposites with tailored thermal transport properties for applications.

  1. Microwave synthesis of branched silver nanowires and their use as fillers for high thermal conductivity polymer composites.

    PubMed

    Seshadri, Indira; Esquenazi, Gibran L; Cardinal, Thomas; Borca-Tasciuc, Theodorian; Ramanath, Ganpati

    2016-04-29

    We report a rapid synthesis approach to obtain branched Ag nanowires by microwave-stimulated polyvinylpyrrolidone-directed polyol-reduction of silver nitrate. Microwave exposure results in micrometer-long nanowires passivated with polyvinylpyrrolidone. Cooling the reaction mixture by interrupting microwave exposure promotes nanocrystal nucleation at low-surfactant coverage sites. The nascent nuclei grow into nanowire branches upon further microwave exposure. Dispersions of low fractions of the branched nanowires in polydimethylsiloxane yield up to 60% higher thermal conductivity than that obtained using unbranched nanowire fillers. Our findings should be useful for realizing nanocomposites with tailored thermal transport properties for applications. PMID:26965359

  2. Quantum dots arrangement and energy transfer control via charge-transfer complex achieved on poly(phenylene ethynylene)/schizophyllan nanowires.

    PubMed

    Shiraki, Tomohiro; Haraguchi, Shuichi; Tsuchiya, Youichi; Shinkai, Seiji

    2009-09-01

    Assemblies of organic and inorganic compounds in the nanoscale region have contributed to the development of novel functional materials toward future applications, including sensors and opto-electronics. We succeed in fabricating hybrid nanowires composed of a conjugated polymer and semiconductor quantum dots (QDs) by a supramolecular assembly technique. The 1-D fashion of the nanowire structure is obtained by the polymer wrapping of cationic poly(phenylene ethynylene) (PPE) with helix-forming polysaccharide schizophyllan (SPG). The electrostatic interaction between cationic PPE and anionic QDs affords the nanowires decorated with QDs. Upon addition of an acceptor molecule, tetranitrofluorenone (TNF), the charge-transfer (CT) complex between PPE and TNF is formed, resulting in energy transfer from the QDs to PPE arising from the induced spectral overlap. Furthermore, the employment of the conjugated polymer allows highly sensitive quenching of the QD's emission by raising the transmission efficiency to the CT complexed electron deficient sites along the polymer backbone. PMID:19629958

  3. Formation of gold nanoparticle assemblies in responsive polymer brushes

    NASA Astrophysics Data System (ADS)

    Christau, Stephanie; von Klitzing, Regine; Genzer, Jan

    2014-03-01

    The modification of surfaces by means of polymer brushes has become an active area of research during the past few years due to numerous potential applications of such systems in nano- and biotechnology. The structure and conformation of a brush depends on external stimuli such as pH, temperature or solvent type and can be manipulated by varying these attributes. This stimulus-response can be exploited for the development of smart surfaces and for sensor applications. Furthermore, brushes can be used as 3D matrices for immobilization of nanoparticles. In this study, responsive brushes are used as a matrix for the attachment of gold nanoparticles (AuNPs); this hybrid system exhibits intriguing optical properties due to the surface plasmon resonance of the AuNPs. We address the effect of some system parameters such as synthetic procedure, brush thickness, brush grafting density, particle size and particle incubation time on the characteristics of the resultant particle-impregnated brushes. We also discuss the spatial distribution of the AuNPs inside the brush with regard to the particle size, brush density and brush molecular weight.

  4. Surfactant self-assembly in oppositely charged polymer networks. Theory.

    PubMed

    Hansson, Per

    2009-10-01

    The interaction of ionic surfactants with polyion networks of opposite charge in an aqueous environment is analyzed theoretically by applying a recent theory of surfactant ion-polyion complex salts (J. Colloid. Int. Sci. 2009, 332, 183). The theory takes into account attractive and repulsive polyion-mediated interactions between the micelles, the deformation of the polymer network, the mixing of micelles, polyion chains, and simple ions with water, and the hydrophobic free energy at the micelle surface. The theory is used to calculate binding isotherms, swelling isotherms, surfactant aggregation numbers, compositions of complexes,and phase structure under various conditions. Factors controlling the gel volume transition and conditions for core/shell phase coexistence are investigated in detail, as well as the influence of salt. In particular, the interplay between electrostatic and elastic interactions is highlighted. Results from theory are compared with experimental data reported in the literature. The agreement is found to be semiquantitative or qualitative. The theory explains both the discrete volume transition observed in systems where the surfactant is in excess over the polyion and the core/shell phase coexistence in systems where the polyion is in excess. PMID:19728696

  5. High-performance ambipolar self-assembled Au/Ag nanowire based vertical quantum dot field effect transistor.

    PubMed

    Song, Xiaoxian; Zhang, Yating; Zhang, Haiting; Yu, Yu; Cao, Mingxuan; Che, Yongli; Wang, Jianlong; Dai, Haitao; Yang, Junbo; Ding, Xin; Yao, Jianquan

    2016-10-01

    Most lateral PbSe quantum dot field effect transistors (QD FETs) show a low on current/off current (I on/I off) ratio in charge transport measurements. A new strategy to provide generally better performance is to design PbSe QD FETs with vertical architecture, in which the structure parameters can be tuned flexibly. Here, we fabricated a novel room-temperature operated vertical quantum dot field effect transistor with a channel of 580 nm, where self-assembled Au/Ag nanowires served as source transparent electrodes and PbSe quantum dots as active channels. Through investigating the electrical characterization, the ambipolar device exhibited excellent characteristics with a high I on/I off current ratio of about 1 × 10(5) and a low sub-threshold slope (0.26 V/decade) in the p-type regime. The all-solution processing vertical architecture provides a convenient way for low cost, large-area integration of the device. PMID:27578613

  6. Polymer directed self-assembly of pH-responsive antioxidant nanoparticles.

    PubMed

    Tang, Christina; Amin, Devang; Messersmith, Phillip B; Anthony, John E; Prud'homme, Robert K

    2015-03-31

    We have developed pH-responsive, multifunctional nanoparticles based on encapsulation of an antioxidant, tannic acid (TA), using flash nanoprecipitation, a polymer directed self-assembly method. Formation of insoluble coordination complexes of tannic acid and iron during mixing drives nanoparticle assembly. Tuning the core material to polymer ratio, the size of the nanoparticles can be readily tuned between 50 and 265 nm. The resulting nanoparticle is pH-responsive, i.e., stable at pH 7.4 and soluble under acidic conditions due to the nature of the coordination complex. Further, the coordination complex can be coprecipitated with other hydrophobic materials such as therapeutics or imaging agents. For example, coprecipitation with a hydrophobic fluorescent dye creates fluorescent nanoparticles. In vitro, the nanoparticles have low cytotoxicity and show antioxidant activity. Therefore, these particles may facilitate intracellular delivery of antioxidants. PMID:25760226

  7. Polymer Directed Self-Assembly of pH-Responsive Antioxidant Nanoparticles

    PubMed Central

    Tang, Christina; Amin, Devang; Messersmith, Phillip B.; Anthony, John E.; Prud’homme, Robert K.

    2015-01-01

    We have developed pH-responsive, multifunctional nanoparticles based on encapsulation of an antioxidant, tannic acid (TA), using Flash NanoPrecipitation, a polymer directed self-assembly method. Formation of insoluble coordination complexes of tannic acid and iron during mixing drives nanoparticle assembly. Tuning the core material to polymer ratio, the size of the nanoparticles can be readily tuned between 50 and 265 nm. The resulting nanoparticle is pH-responsive, i.e. stable at pH 7.4 and soluble under acidic conditions due to the nature of the coordination complex. Further, the coordination complex can be coprecipitated with other hydrophobic materials such as therapeutics or imaging agents. For example, coprecipitation with a hydrophobic fluorescent dye creates fluorescent nanoparticles. In vitro, the nanoparticles have low cytotoxicity show antioxidant activity. Therefore, these particles may facilitate intracellular delivery of antioxidants. PMID:25760226

  8. Assembly of polythiophenes on responsive polymer microgels for the highly selective detection of ammonia gas

    DOE PAGESBeta

    Chang, Aiping; Peng, Yahui; Li, Zezhou; Yu, Xiang; Hong, Kunlun; Zhou, Shuiqin; Wu, Weitai

    2016-04-05

    For this study, a class of smart composite materials based on the assembly of conjugated polymers on responsive polymer microgels has been prepared. We have chosen poly(3-((2-(2-methoxyethoxy)ethoxy)methyl)-thiophene) as the model conjugated polymer and an ammonia-responsive microgel of phenoxazinium-functionalized poly(N-isopropylacrylamide-co-propargyl acrylate) as the model template. Under this design, the composite materials can combine the electrical conductivity of the conjugated polymers and the ammonia recognisability of the ammonia-responsive polymer microgels; the cooperation of these properties allows the reversible control of electrical conductivity by ammonia gas. Those composite materials can not only adapt to ammonia gas, but also convert changes in the concentrationmore » of ammonia into conductance, allowing the electrical detection of ammonia gas with high selectivity. This makes the composite materials different from the conductive polymer platforms reported previously, which may also respond to non-ammonia gases and the response induced by non-ammonia gases is close to that induced by ammonia gas. Using these composite materials as sensing materials for the electrical detection of ammonia gas, the detection limit can reach as low as 1.1 ppb. Finally, these features enable their use for the electrical detection of ammonia in breath.« less

  9. Polymer Grafted Nanoparticle Assemblies: From Optical to Mechanical Performance through Clusters, Monolayers and Monoliths

    NASA Astrophysics Data System (ADS)

    Vaia, Richard

    Solution or melt-based fabrication of large area, matrix-free, ordered assemblies of polymer grafted nanoparticles (PGN) will enable additive manufacturing of novel membrane, electronic, and photonic elements. Due to the single component nature of these hybrids, aggregation and phase separation common in blended polymer nanocomposites are avoided. Architecturally, PGNs combine characteristics of colloids, brushes and high molecular weight polymers. Thus the processing-structure-property relationship of the entangled PGN assembly is unique from analogous condensed nano-structures, such as ligand stabilized nanoparticles, hard-sphere colloids, star macromolecules and linear chain - nanoparticle blends. Here in, we will discuss the intermediate character of PGNs with respect to deformability, physical aging, and rapid fabrication of stable, large-area, ordered PGN monolayers. For example, processing via flow coating follows that of classic colloids; however local structure and order within the PGN assembly is determined by the canopy architecture and substrate interactions. From this insight, large-area (cm2), highly-ordered, monolayer polystyrene-Au nanoparticle films that are resistant to de-wetting can be fabricated on substrates with high interface energy (80 mN/m) within seconds using flow-coating and a volatile solvent (THF). Overall these findings imply intriguing parallels between PGN assemblies and other mesoscale ordered polymeric systems including hard-soft block copolymers and semi-crystalline polymers. With the appropriate corona architecture, PGNs afford opportunities to design high inorganic fraction hybrids that retain processibility and enable the creation of films and fibers for next generation optoelectronic applications. Aknowledgement: Justin Che, Christopher A. Grabowski, Yang Jiao, Ming-Siao Hsiao, Kyoungweon Park, Lawrence Drummy.

  10. Directed Self-Assembly of Block Copolymers for High Breakdown Strength Polymer Film Capacitors.

    PubMed

    Samant, Saumil P; Grabowski, Christopher A; Kisslinger, Kim; Yager, Kevin G; Yuan, Guangcui; Satija, Sushil K; Durstock, Michael F; Raghavan, Dharmaraj; Karim, Alamgir

    2016-03-01

    Emerging needs for fast charge/discharge yet high-power, lightweight, and flexible electronics requires the use of polymer-film-based solid-state capacitors with high energy densities. Fast charge/discharge rates of film capacitors on the order of microseconds are not achievable with slower charging conventional batteries, supercapacitors and related hybrid technologies. However, the current energy densities of polymer film capacitors fall short of rising demand, and could be significantly enhanced by increasing the breakdown strength (EBD) and dielectric permittivity (εr) of the polymer films. Co-extruded two-homopolymer component multilayered films have demonstrated much promise in this regard showing higher EBD over that of component polymers. Multilayered films can also help incorporate functional features besides energy storage, such as enhanced optical, mechanical, thermal and barrier properties. In this work, we report accomplishing multilayer, multicomponent block copolymer dielectric films (BCDF) with soft-shear driven highly oriented self-assembled lamellar diblock copolymers (BCP) as a novel application of this important class of self-assembling materials. Results of a model PS-b-PMMA system show ∼50% enhancement in EBD of self-assembled multilayer lamellar BCP films compared to unordered as-cast films, indicating that the breakdown is highly sensitive to the nanostructure of the BCP. The enhancement in EBD is attributed to the "barrier effect", where the multiple interfaces between the lamellae block components act as barriers to the dielectric breakdown through the film. The increase in EBD corresponds to more than doubling the energy storage capacity using a straightforward directed self-assembly strategy. This approach opens a new nanomaterial paradigm for designing high energy density dielectric materials. PMID:26942835

  11. Synthesis and Assembly of Dipolar Heterostructured Tetrapods: Colloidal Polymers with "Giant tert-butyl" Groups.

    PubMed

    Pavlopoulos, Nicholas G; Dubose, Jeffrey T; Pinna, Nicola; Willinger, Marc-Georg; Char, Kookheon; Pyun, Jeffrey

    2016-01-26

    We report on the first synthesis of a heterostructured semiconductor tetrapod from CdSe@CdS that carries a single dipolar nanoparticle tip from a core-shell colloid of Au@Co. A four-step colloidal total synthesis was developed, where the key step in the synthesis was the selective deposition of a single AuNP tip onto a CdSe@CdS tetrapod under UV-irradiation. Synthetic accessibility to this dipolar heterostructured tetrapod enabled the use of these as colloidal monomers to form colloidal polymers that carry the semiconductor tetrapod as a side chain group attached to the CoNP colloidal polymer main chain. The current report details a number of novel discoveries on the selective synthesis of an asymmetric heterostructured tetrapod that is capable of 1D dipolar assembly into colloidal polymers that carry tetrapods as side chain groups that mimic "giant tert-butyl groups". PMID:26696128

  12. Precision polymers and 3D DNA nanostructures: emergent assemblies from new parameter space.

    PubMed

    Serpell, Christopher J; Edwardson, Thomas G W; Chidchob, Pongphak; Carneiro, Karina M M; Sleiman, Hanadi F

    2014-11-01

    Polymer self-assembly and DNA nanotechnology have both proved to be powerful nanoscale techniques. To date, most attempts to merge the fields have been limited to placing linear DNA segments within a polydisperse block copolymer. Here we show that, by using hydrophobic polymers of a precisely predetermined length conjugated to DNA strands, and addressable 3D DNA prisms, we are able to effect the formation of unprecedented monodisperse quantized superstructures. The structure and properties of larger micelles-of-prisms were probed in depth, revealing their ability to participate in controlled release of their constituent nanostructures, and template light-harvesting energy transfer cascades, mediated through both the addressability of DNA and the controlled aggregation of the polymers. PMID:25325677

  13. Kinetic Assembly of Near-IR Active Gold Nanoclusters using Weakly Adsorbing Polymers to Control Size

    PubMed Central

    Tam, Jasmine M.; Murthy, Avinash K.; Ingram, Davis R.; Nguyen, Robin; Sokolov, Konstantin V.; Johnston, Keith P.

    2013-01-01

    Clusters of metal nanoparticles with an overall size less than 100 nm and high metal loadings for strong optical functionality, are of interest in various fields including microelectronics, sensors, optoelectronics and biomedical imaging and therapeutics. Herein we assemble ~5 nm gold particles into clusters with controlled size, as small as 30 nm and up to 100 nm, which contain only small amounts of polymeric stabilizers. The assembly is kinetically controlled with weakly adsorbing polymers, PLA(2K)-b-PEG(10K)-b-PLA(2K) or PEG (MW = 3350), by manipulating electrostatic, van der Waals (VDW), steric, and depletion forces. The cluster size and optical properties are tuned as a function of particle volume fractions and polymer/gold ratios to modulate the interparticle interactions. The close spacing between the constituent gold nanoparticles and high gold loadings (80–85% w/w gold) produce a strong absorbance cross section of ~9×10−15 m2 in the NIR at 700 nm. This morphology results from VDW and depletion attractive interactions that exclude the weakly adsorbed polymeric stabilizer from the cluster interior. The generality of this kinetic assembly platform is demonstrated for gold nanoparticles with a range of surface charges from highly negative to neutral, with the two different polymers. PMID:20361735

  14. Polymer-Carbon Nanotube Composite Films at the Oil/Water Interface: Assembly and Properties

    NASA Astrophysics Data System (ADS)

    Hoagland, David; Feng, Tao; Russell, Thomas P.

    2015-03-01

    Efficient carbon nanotube assembly at the oil/water interface was achieved by dissolving cationic polymers in the oil phase and oxidized nanotubes in the water phase, the two components spontaneously forming salt bridges to produce a composite interfacial film of nanoscopic thickness. As seen by pendant drop tensiometry, parameters such as carbon nanotube and polymer concentration, pH, polymer molecular weight, and degree of nanotube oxidation all affect assembly strongly, with measured trends to be described and explained. The frequency-dependent elastic and viscous moduli of films in dilation were characterized by interfacial pendant drop rheology. Structural (fast, minutes) and adsorption/desorption (slow, tens of minutes) relaxations were both noted, and at frequencies intermediate to the two, almost insensitive to assembly parameters, the films displayed expected behaviors for 2D critical gels, i.e., at the crossover between fluid and solid. Tan(delta) was frequency-independent over one to two decades of frequency, and the modulus of linear stress relaxation was a power law in time. Films wrinkled by larger (nonlinear) strains recovered over the structural relaxation time. Support: NSF-sponsored UMass MRSEC and the US DoE Office of Basic Energy Science through Contract DE-FG02-04ER46126.

  15. Supramolecular self-assembly of amphiphilic hyperbranched polymers at all scales and dimensions: progress, characteristics and perspectives.

    PubMed

    Zhou, Yongfeng; Yan, Deyue

    2009-03-14

    This feature article describes the supramolecular self-assembly of hyperbranched polymers (HBPs), including the progress, unique characteristics and future perspectives. HBPs are irregular in molecular structure compared with that of linear block copolymers and dendrimers. However, similar to these well-defined polymer tectons, HBPs have displayed great potential to be excellent precursors in solution self-assembly, interfacial self-assembly and hybrid self-assembly. Many impressive supramolecular aggregates and hybrids at all scales and dimensions, such as macroscopic tubes, micro- or nano-vesicles, fibers, spherical micelles and honeycomb films, have been generated. In addition, HBPs also demonstrate unique characteristics or advantages in supramolecular self-assembly behaviours, including controllable morphologies and structures, special properties, characteristic self-assembly mechanism and facile functionalization process. Although still being at the early stage, self-assembly of HBPs has provided a new avenue for the development of supramolecular chemistry. PMID:19240868

  16. Carrier Transport Enhancement in Conjugated Polymers through Interfacial Self-Assembly of Solution-State Aggregates.

    PubMed

    Zhao, Kui; Khan, Hadayat Ullah; Li, Ruipeng; Hu, Hanlin; Amassian, Aram

    2016-08-01

    We demonstrate that local and long-range orders of poly(3-hexylthiophene) (P3HT) semicrystalline films can be synergistically improved by combining chemical functionalization of the substrate with solution-state disentanglement and preaggregation of P3HT in a θ solvent, leading to a very significant enhancement of the field effect carrier mobility. The preaggregation and surface functionalization effects combine to enhance the carrier mobility nearly 100-fold as compared with standard film preparation by spin-coating, and nearly 10-fold increase over the benefits of preaggregation alone. In situ quartz crystal microbalance with dissipation (QCM-D) experiments reveal enhanced deposition of preaggregates on surfaces modified with an alkyl-terminated self-assembled monolayer (SAM) in comparison to unaggregated polymer chains in the same conditions. Additional measurements reveal the combined preaggregation and surface functionalization significantly enhances local order of the conjugated polymer through planarization and extension of the conjugated backbone of the polymer which clearly translate to significant improvements of carrier transport at the semiconductor-dielectric interface in organic thin film transistors. This study points to opportunities in combining complementary routes, such as well-known preaggregation with substrate chemical functionalization, to enhance the polymer self-assembly and improve its interfacial order with benefits for transport properties. PMID:27410517

  17. Molecular junctions of self-assembled monolayers with conducting polymer contacts.

    PubMed

    Neuhausen, Alexander B; Hosseini, Ali; Sulpizio, Joseph A; Chidsey, Christopher E D; Goldhaber-Gordon, David

    2012-11-27

    We present a method to fabricate individually addressable junctions of self-assembled monolayers (SAMs) that builds on previous studies which have shown that soft conductive polymer top contacts virtually eliminate shorts through the SAMs. We demonstrate devices with nanoscale lateral dimensions, representing an order of magnitude reduction in device area, with high yield and relatively low device-to-device variation, improving several features of previous soft contact devices. The devices are formed in pores in an inorganic dielectric layer with features defined by e-beam lithography and dry etching. We replace the aqueous PEDOT:PSS conductive polymer used in prior devices with Aedotron P, a low-viscosity, amphiphilic polymer, allowing incorporation of self-assembled monolayers with either hydrophobic or hydrophilic termination with the same junction geometry and materials. We demonstrate the adaptability of this new design by presenting transport measurements on SAMs composed of alkanethiols with methyl, thiol, carboxyl, and azide terminations. We establish that the observed room-temperature tunnel barrier is primarily a function of monolayer thickness, independent of the terminal group's hydrophilicity. Finally, we investigate the temperature dependence of transport and show that the low-temperature behavior is based on the energy distribution of sites from which carriers can tunnel between the polymer and gold contacts, as described by a model of variable-range hopping transport in a disordered conductor. PMID:23035989

  18. Modeling the Assembly of Polymer-Grafted Nanoparticles at Oil-Water Interfaces.

    PubMed

    Yong, Xin

    2015-10-27

    Using dissipative particle dynamics (DPD), I model the interfacial adsorption and self-assembly of polymer-grafted nanoparticles at a planar oil-water interface. The amphiphilic core-shell nanoparticles irreversibly adsorb to the interface and create a monolayer covering the interface. The polymer chains of the adsorbed nanoparticles are significantly deformed by surface tension to conform to the interface. I quantitatively characterize the properties of the particle-laden interface and the structure of the monolayer in detail at different surface coverages. I observe that the monolayer of particles grafted with long polymer chains undergoes an intriguing liquid-crystalline-amorphous phase transition in which the relationship between the monolayer structure and the surface tension/pressure of the interface is elucidated. Moreover, my results indicate that the amorphous state at high surface coverage is induced by the anisotropic distribution of the randomly grafted chains on each particle core, which leads to noncircular in-plane morphology formed under excluded volume effects. These studies provide a fundamental understanding of the interfacial behavior of polymer-grafted nanoparticles for achieving complete control of the adsorption and subsequent self-assembly. PMID:26439456

  19. Design and Fabrication of Molecular Assemblies of Conductive Polymers

    NASA Astrophysics Data System (ADS)

    Cheung, Josephine Ho-Wah

    Two new methods of fabricating multilayer Langmuir -Blodgett (LB) thin films of electrically conductive polyaniline and a novel method of constructing molecular assemblies of polyaniline via the spontaneous adsorption (SA) technique were developed. Quantitative transmission/reflection Fourier transform infrared spectroscopy, polarized ultraviolet -visible spectroscopy and X-ray diffraction techniques were used to examine the structure and composition of multilayer thin films. In the structural study of LB films fabricated from 3-octadecyl pyrrole (3-ODP), 3-octadecanoyl pyrrole (3-ODOP) and polypyrrole/3-ODOP (PPY/3-ODOP), the level of order and orientation were found to be affected by the intermolecular and intramolecular interactions between molecules. For the manipulation of polyaniline using the LB technique, stable and easily transferrable LB monolayers were formed at the air-water interface by mixing polyaniline in its emeraldine-base form (PANb) with two processing aids. Films fabricated from the PANb/StA mixture were found to be phase separated with domains of polyaniline and stearic acid while those from the PANb/PI blend were found to be miscible. Both polyaniline LB films were rendered conductive by doping with 1 M HCl or HCl vapor. Multilayer polyaniline films were also constructed via a SA process. The multilayer buildup of doped polyaniline and sulfonated polystyrene (PANi/SPS) is facilitated by the electrostatic attraction between the delocalized positive -charged defects along the PANi backbone and the negative charges present in the ionizable pendant sulfonic acid groups of the SPS. Uniform multilayer thin films with thicknesses between 20 A and 100 A were constructed on different surfaces with complex topologies. Conductivities in the level of 0.1-1 S/cm were achieved by doping the multilayer PANi/SPS films with 1 M HCl. This level of conductivity was achieved by films with as few as 4 layers of PANi/SPS, that is, films with thicknesses of about

  20. Depletion forces drive polymer-like self-assembly in vibrofluidized granular materials†

    PubMed Central

    Nossal, Ralph

    2011-01-01

    Ranging from nano- to granular-scales, control of particle assembly can be achieved by limiting the available free space, for example by increasing the concentration of particles (“crowding”) or through their restriction to 2D environments. It is unclear, however, if self-assembly principles governing thermally-equilibrated molecules can also apply to mechanically-excited macroscopic particles in non-equilibrium steady-state. Here we show that low densities of vibrofluidized steel rods, when crowded by high densities of spheres and confined to quasi-2D planes, can self-assemble into linear polymer-like structures. Our 2D Monte Carlo simulations show similar finite sized aggregates in thermally equilibrated binary mixtures. Using theory and simulations, we demonstrate how depletion interactions create oriented “binding” forces between rigid rods to form these “living polymers.” Unlike rod-sphere mixtures in 3D that can demonstrate well-defined equilibrium phases, our mixtures confined to 2D lack these transitions because lower dimensionality favors the formation of linear aggregates, thus suppressing a true phase transition. The qualitative and quantitative agreement between equilibrium and granular patterning for these mixtures suggests that entropy maximization is the determining driving force for bundling. Furthermore, this study uncovers a previously unknown patterning behavior at both the granular and nanoscales, and may provide insights into the role of crowding at interfaces in molecular assembly. PMID:22039392

  1. Silicon Nanowire Devices

    NASA Astrophysics Data System (ADS)

    Kamins, Theodore

    2006-03-01

    Metal-catalyzed, self-assembled, one-dimensional semiconductor nanowires are being considered as possible device elements to augment and supplant conventional electronics and to extend the use of CMOS beyond the physical and economic limits of conventional technology. Such nanowires can create nanostructures without the complexity and cost of extremely fine scale lithography. The well-known and controllable properties of silicon make silicon nanowires especially attractive. Easy integration with conventional electronics will aid their acceptance and incorporation. For example, connections can be formed to both ends of a nanowire by growing it laterally from a vertical surface formed by etching the top silicon layer of a silicon-on-insulator structure into isolated electrodes. Field-effect structures are one class of devices that can be readily built in silicon nanowires. Because the ratio of surface to volume in a thin nanowire is high, conduction through the nanowire is very sensitive to surface conditions, making it effective as the channel of a field-effect transistor or as the transducing element of a gas or chemical sensor. As the nanowire diameter decreases, a greater fraction of the mobile charge can be modulated by a given external charge, increasing the sensitivity. Having the gate of a nanowire transistor completely surround the nanowire also enhances the sensitivity. For a field-effect sensor to be effective, the charge must be physically close to the nanowire so that the majority of the compensating charge is induced in the nanowire and so that ions in solution do not screen the charge. Because only induced charge is being sensed, a coating that selectively binds the target species should be added to the nanowire surface to distinguish between different species in the analyte. The nanowire work at Hewlett-Packard Laboratories was supported in part by the Defense Advanced Research Projects Agency.

  2. Self-Assembly of Differently Shaped Protein-Polymer Conjugates through Modification of the Bioconjugation Site.

    PubMed

    Huang, Aaron; Olsen, Bradley D

    2016-08-01

    Self-assembly of protein-polymer block copolymers is an attractive route for preparing biocatalytic materials. To clarify the effect of bioconjugate shape on self-assembly without changing the chemical details of either block, four different conjugation sites are selected on the surface of the model globular protein mCherry at residues 3, 108, 131, and 222 to alter the colloidal shape of the bioconjugate. All four mCherry-b-poly(N-isopropylacrylamide) bioconjugates show qualitatively similar phase diagrams, indicating that self-assembly is robust with respect to changes in conjugation site. However, protein orientation has an effect on the location of the order-disorder transition concentration, and the stability of the disordered micellar phase is shown to be different for each conjugate. Differences in domain spacing also suggest changes in protein orientation within the lamellae. PMID:27322114

  3. Solvent-responsive self-assembly of amphiphilic invertible polymers determined with SANS.

    PubMed

    Kudina, Olena; Kohut, Ananiy; Tarnavchyk, Ihor; Hevus, Ivan; Voronov, Andriy

    2014-04-01

    Amphiphilic invertible polymers (AIPs) are a new class of macromolecules that self-assemble into micellar structures and rapidly change structure in response to changes in solvent polarity. Using small-angle neutron scattering (SANS) data, we obtained a quantitative description of the invertible micellar assemblies (IMAs). The detailed composition and size of the assemblies (including the effect of temperature) were measured in aqueous and toluene polymer solutions. The results show that the invertible macromolecules self-assemble into cylindrical core-shell micellar structures. The composition of the IMAs in aqueous and toluene solutions was used to reveal the inversion mechanism by changing the polarity of the medium. Our experiments demonstrate that AIP unimers self-assemble into IMAs in aqueous solution, predominantly through interactions between the hydrophobic moieties of macromolecules. The hydrophobic effect (or solvophobic interaction) is the major driving force for self-assembly. When the polarity of the environment is changed from polar to nonpolar, poly(ethylene glycol) (PEG) and aliphatic dicarboxylic acid fragments of AIP macromolecules tend to replace each other in the core and the shell of the IMAs. However, neither the interior nor the exterior of the IMAs consists of fragments of a single component of the macromolecule. In aqueous solution, with the temperature increasing from 15 to 35 °C, the IMAs' mixed core from aliphatic dicarboxylic acid and PEG moieties and PEG-based shell change the structure. As a result of the progressive dehydration of the macromolecules, the hydration level (water content) in the micellar core decreases at 25 °C, followed by dehydrated PEG fragments entering the interior of the IMAs when the temperature increases to 35 °C. PMID:24606021

  4. A reticulate superhydrophobic self-assembly structure prepared by ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Gong, Maogang; Xu, Xiaoliang; Yang, Zhou; Liu, Yuanyue; Lv, Haifei; Lv, Liu

    2009-04-01

    A simple hydrothermal self-assembly method was adopted to grow a newly reported superhydrophobic reticulate ZnO film with papillary nodes. The formation mechanism has also been explained by the tension junction model. This structure can extremely enhance the dewettability for the surface modification with low-surface-energy materials such as long chain fluorinated organic compounds. The surfaces of the ZnO thin film were superhydrophobic with a contact angle (CA) of 170° ± 1°, while the sliding angle (SA) is 2°. The samples were characterized by field emission scanning electron microscopy (FESEM).

  5. Development of Self-Assembled Nanoscale Templates via Microphase Separation Induced by Polymer Brushes

    NASA Astrophysics Data System (ADS)

    Chu, Elza

    Phase separation in soft matter has been the crucial element in generating hybrid materials, such as polymer blends and mixed polymer brushes. This dissertation discusses two methods of developing self-assembled nanoscale templates via microphase separation induced by polymer brush synthesis. This work introduces a novel soft substrate approach with renewable grafting sites where polyacrylamide is "grafted through" chitosan soft substrates. The mechanism of grafting leads to ordered arrays of filament-like nanostructures spanning the chitosan-air interface. Additionally, the chemical composition of the filaments allows for post-chemical modification to change the physical properties of the filaments, and subsequently tailor surfaces for specific application. Unlike traditional materials, multi-functional or "smart" materials, such as binary polymer brushes (BPB) are capable of spontaneously changing the spatial distribution of functional groups and morphology at the surface upon external stimuli. Although promising in principle, the limited range of available complementary polymers with common non-selective solvents confines the diversity of usable materials and restricts any further advancement in the field. This dissertation also covers the fabrication and characterization of responsive nanoscale polystyrene templates or "mosaic" brushes that are capable of changing interfacial composition upon exposure to varying solvent qualities. Using a "mosaic" brush template is a unique approach that allows the fabrication of strongly immiscible polymer BPB without the need for a common solvent. The synthesis of such BPB is exemplified by two strongly immiscible polymers, i.e. polystyrene (polar) and polyacrylamide (non-polar), where polyacrylamide brush is "graft through" a Si-substrate modified with the polystyrene collapsed "mosaic" brush. The surface exhibits solvent-triggered responses, as well as application potential for anti-biofouling.

  6. Electronic structure of self-assembled Si nanowires on Ag(110) surfaces

    NASA Astrophysics Data System (ADS)

    Ohta, Taisuke; Rotenberg, Eli; Horn, Karsten

    2006-03-01

    Much attention has recently been paid to the physics of one- dimensional (1-D) systems, since exotic properties are predicted from basic theoretical consideration. However, it is not easy to realize such one-dimensional systems experimentally. Recently, Leandri et al.[1] have reported the growth of self-assembled 1D linear structures of silicon on Ag(110), perfectly aligned along [-110] direction and 16å wide. We have investigated the electronic structure of such self-assembled Si “nanowires” using angle resolved photoemission spectroscopy. The Si 2p core level line shows two narrow components in agreement with earlier work [1]. Silicon-induced features in the valence band region are observed, most clearly within the band gap of the Ag s-p states. The silicon-induced band exhibits a sizeable dispersion only in the direction along the linear structure, i.e. the [- 110] azimuth of the Ag(110) substrate. Details of the experimentally observed bands will be presented and related to the atomic structure within the 1D structure and its arrangement on the silver substrate. T.O. acknowledges financial support from Max Planck Society. Experiments were performed at the Advanced Light Source, Lawrence Berkeley National Laboratory operated by the U.S. DOE under Contract No. DE-AC03-76SF00098. [1] C. Leandri et al., Self-aligned silicon quantum wires on Ag (110), Surface Science 574 (2005) L9 L15

  7. Factors Influencing the Growth of Pt Nanowires via Chemical Self-Assembly and their Fuel Cell Performance.

    PubMed

    Meng, Hui; Zhan, Yunfeng; Zeng, Dongrong; Zhang, Xiaoxue; Zhang, Guoqing; Jaouen, Frédéric

    2015-07-15

    This work reports a detailed investigation of the template-free synthesis of Pt nanowires via the chemical reduction of Pt salt precursors with formic-acid. The results indicate that both the oxidation state of Pt in the salt and the pH value of the aqueous solution comprising the platinum salt and formic acid are critical factors for the formation of Pt nanowires. Nanowires are obtained from platinum atoms in a +IV oxidation state, with ligating chloride anions (H2 PtCl6 and K2 PtCl6 ) or nonligating chloride anions (PtCl4 ). Increasing the pH of the aqueous Pt salt and HCOOH solution leads to a drastic reduction of the nanowires' length between pH 3 and 4.5. A mechanism involving formate as a reducing agent and formic acid as a structure directing agent explains these results. The Pt nanowires are stable up to 200 °C; therefore, these nanowires are suitable for use as catalysts in proton-exchange-membrane fuel cell. The optimized synthesis conditions are then selected for investigating the kinetics of the oxygen reduction reaction (ORR) of such nanowires in a fuel cell. The ORR mass activity of the Pt nanowires is 130 A g(-1) Pt at 0.9 V iR-free potential; significantly higher than that of two commercial Pt/C catalysts tested in the same conditions. The higher mass activity is explained based on a higher surface specific activity. Accelerated degradation tests indicate that Pt nanowires supported on carbon are as stable as Pt nanoparticles supported on carbon. PMID:25682734

  8. Multiarmed star-like platinum nanowires with multienzyme assembly for direct electronic determination of carcinoembryoninc antigen in serum.

    PubMed

    Su, Biling; Tang, Dianping; Tang, Juan; Cui, Yuling; Chen, Guonan

    2011-12-15

    A new electrochemical immunoassay strategy for direct detection of carcinoembryoninc antigen (CEA) in serum was developed by using multiarmed star-like platinum nanowires (PtNWs) with biomolecular assembly as signal tags on an anti-CEA-functionalized graphene sensing platform. Initially, the PtNWs were synthesized via a wet chemical method, and then the synthesized PtNWs were used for the co-immobilization of CEA and horseradish peroxidase (HRP). Compared with platinum nanoparticles, the prepared PtNWs could provide a large room for the conjugation of HRP and CEA. With a competitive-type immunoassay format, the assay was performed in two types of supporting electrolytes including new born cattle serum (NBCS) and acetate buffer solution (ABS, pH 5.5), respectively. Similar detection limit (LOD) of 5.0 pg mL(-1) vs. 1.0 pg mL(-1) but narrower dynamic working linear range of 0.01-60 ng mL(-1) vs. 0.002-80 ng mL(-1) was obtained toward CEA standards in the NBCS compared to the ABS. The intra-assay coefficients of variation (CVs) were 4.3%, 8.6%, and 6.2% at 0.05, 10, and 40 ng mL(-1) CEA, respectively, while the inter-assay CVs were 7.6%, 10.5%, and 8.9% at the above-mentioned levels, respectively. In addition, the selectivity and stability of the electrochemical immunosensor were acceptable. Importantly, the developed method was used to assay clinical serum specimens, receiving a good relation with those obtained from the referenced method. PMID:21982336

  9. Nanowire mesh solar fuels generator

    DOEpatents

    Yang, Peidong; Chan, Candace; Sun, Jianwei; Liu, Bin

    2016-05-24

    This disclosure provides systems, methods, and apparatus related to a nanowire mesh solar fuels generator. In one aspect, a nanowire mesh solar fuels generator includes (1) a photoanode configured to perform water oxidation and (2) a photocathode configured to perform water reduction. The photocathode is in electrical contact with the photoanode. The photoanode may include a high surface area network of photoanode nanowires. The photocathode may include a high surface area network of photocathode nanowires. In some embodiments, the nanowire mesh solar fuels generator may include an ion conductive polymer infiltrating the photoanode and the photocathode in the region where the photocathode is in electrical contact with the photoanode.

  10. Lithium-doped zinc oxide nanowires-polymer composite for high performance flexible piezoelectric nanogenerator.

    PubMed

    Shin, Sung-Ho; Kim, Young-Hwan; Lee, Min Hyung; Jung, Joo-Yun; Seol, Jae Hun; Nah, Junghyo

    2014-10-28

    We present a method to develop high performance flexible piezoelectric nanogenerators (NGs) by employing Li-doped ZnO nanowires (NWs). We synthesized Li-doped ZnO NWs and adopted them to replace intrinsic ZnO NWs with a relatively low piezoelectric coefficient. When we exploited the ferroelectric phase transition induced in Li-doped ZnO NWs, the performance of the NGs was significantly improved and the NG fabrication process was greatly simplified. In addition, our approach can be easily expanded for large-scale NG fabrication. Consequently, the NGs fabricated by our simple method exhibit the excelling output voltage and current, which are stable and reproducible during periodic bending/releasing measurement over extended cycles. In addition, output voltage and current up to ∼ 180 V and ∼ 50 μA, respectively, were obtained in the large-scale NG. The approach introduced here extends the performance limits of ZnO-based NGs and their potentials in practical applications. PMID:25265473

  11. The influence of self-assembly behavior of nanoparticles on the dielectric polymer composites

    SciTech Connect

    Lu, Xin; Li, Weiping Wang, Tingting; Jiang, Long; Luo, Laihui; Hua, Dayin; Zhu, Yuejin

    2013-11-15

    To clearify the influence of the distribution of the conductive nanoparticles on the dielectric properties of the corresponding polymer composites, the microstructure and dielectric character of the composites based on the oleic acid modified ferroferric oxide and polyvinylidene fluoride (PVDF) polymer have been studied experimentally. It is found that these composites exhibit a normal percolative phase transition over the filler content from insulator to conductor, consistent with the classical percolation theory. However, when the percentage of fillers is at a certain value which is below the percolation threshold, these nanoparticles can assemble into a special porous structure in the PVDF matrix, associated with the enhancement of dielectric constant at low frequency. In addition, the controllable dispersion of conducting nanoparticles in a polymer matrix can prevent premature agglomeration at low filling fractions and avoid the appearance of anomalously early percolation. Therefore, the self-assembly behavior of nanoparticles can be beneficial to preparation of the high dielectric constant and low loss composites for the application of electric energy storage.

  12. Self-assembled multilayers of electroactive polymers: From highly conducting transparent thin films to light emitting diodes

    SciTech Connect

    Fou, A.; Onitsuka, O.; Ferreira, M.

    1995-12-01

    Layer-by-layer self-assembly has recently emerged as a most versatile means of processing conjugated polymers into ultrathin films with unprecedented control over thicknesses and molecular architectures. Multilayer heterostructures have been designed and fabricated from various combinations of conjugated polyions, p-type conducting polymers, sulfonated fullerenes, conjugated polymer precursors, molecular dyes, and a variety of nonconjugated polyions to study properties unique to the supramolecular organizations created. In this paper, we use layer-by-layer self-assembly to fabricate extremely thin, highly conductive films of p-doped conjugated polymers such as polypyrrole and polyaniline. Also complex multilayer heterostructures based on polyphenylene vinylene (PPV) are fabricated to study the intermolecular interactions between the PPV and other components of the film which give rise to {open_quotes}tunable{close_quotes} photoluminescence behavior. Finally, thin film light-emitting devices based on self-assembled PPV active layers are presented.

  13. Decoupling Substrate Surface Interactions in Block Polymer Thin Film Self-Assembly

    NASA Astrophysics Data System (ADS)

    Shelton, Cameron; Epps, Thomas

    2015-03-01

    Understanding the impact of the major factors that affect block polymer (BP) thin film self-assembly is necessary to control nanostructure ordering, orientation, and defect density. In this work, we systematically studied the influence of the substrate surface energy, one of the most significant parameters directing self-assembly, on wetting behavior, through-film interactions, and substrate surface field propagation. Notably, we determined the applicability of decoupled surface energy components (dispersive and polar interactions) as opposed to total surface energy, using a suite of chlorosilane monolayers and UV-ozone degradation to create a library of total, dispersive, and polar surface energy effects. Our experimental results combined with surface chemistry literature indicated repulsive total surface energy interactions are the dominant force at the substrate-polymer interface, whereas attractive decoupled surface energy interactions become significant past the contacting layer. This work represents a thorough analysis of a vital force affecting BP self-assembly as well as a blueprint for the generalized design of substrate surfaces that achieve target BP nanostructure orientations for nanolithography, templating, and nanoporous membrane applications.

  14. Soft Polymer Magnetic Nanocomposites: Microstructure Patterning by Magnetophoretic Transport and Self-Assembly.

    PubMed

    Ghosh, Suvojit; Puri, Ishwar K

    2013-01-01

    A method to produce and pattern magnetic microstructure in a soft-polymer matrix is demonstrated. An externally applied magnetic field is used to influence the dynamics of magnetophoretic transport and dipolar self-assembly of magnetic nanoparticle clusters in the liquid precursor of poly-dimethylsiloxane (PDMS). Magnetic nanoparticles agglomerate by an interplay of van der Waals forces and dipolar interactions to form anisotropic clusters. These clusters are concentrated on a substrate by magnetophoresis, wherein they self-organize by dipolar interactions to form microscopic filaments. The polymer is cured in the presence of the magnetic field to preserve the microstructure shape. The externally applied magnetic field and its gradient are the two main control variables of interest when considering magnetic control during nanoparticle self-assembly. Their influence on microstructure geometry is investigated through correlations with the height of a characteristic self-assembled filament, fraction of the substrate area covered by the microstructure and its shape anisotropy. These relations enable a priori design. PMID:25383088

  15. Hierarchical assembly of Ti(IV)/Sn(II) co-doped SnO₂ nanosheets along sacrificial titanate nanowires: synthesis, characterization and electrochemical properties.

    PubMed

    Wang, Hongkang; Xi, Liujiang; Tucek, Jiri; Zhan, Yawen; Hung, Tak Fu; Kershaw, Stephen V; Zboril, Radek; Chung, C Y; Rogach, Andrey L

    2013-10-01

    Hierarchical assembly of Ti(IV)/Sn(II)-doped SnO₂ nanosheets along titanate nanowires serving as both sacrificial templates and a Ti(IV) source is demonstrated, using SnCl2 as a tin precursor and Sn(II) dopants and NaF as the morphology controlling agent. Excess fluoride inhibits the hydrolysis of SnCl2, promoting heterogeneous nucleation of Sn(II)-doped SnO₂ on the titanate nanowires due to the insufficient oxidization of Sn(II) to Sn(IV). Simultaneously, titanate nanowires are dissolved forming Ti(4+) species under the etching effect of in situ generated HF resulting in spontaneous Ti(4+) ion doping of SnO₂ nanosheets formed under hydrothermal conditions. Compositional analysis indicates that Ti(4+) ions are incorporated by substitution of Sn sites at a high level (16-18 at.%), with uniform distribution and no phase separation. Mössbauer spectroscopy quantified the relative content of Sn(II) and Sn(IV) in both Sn(II)-doped and Ti(IV)/Sn(II) co-doped SnO₂ samples. Electrochemical properties were investigated as an anode material in lithium ion batteries, demonstrating that Ti-doped SnO₂ nanosheets show improved cycle performance, which is attributed to the alleviation of inherent volume expansion of the SnO₂-based anode materials by substituting part of Sn sites with Ti dopants. PMID:23904051

  16. Germanium doping of self-assembled GaN nanowires grown by plasma-assisted molecular beam epitaxy

    SciTech Connect

    Schörmann, Jörg; Hille, Pascal; Schäfer, Markus; Müßener, Jan; Becker, Pascal; Klar, Peter J.; Hofmann, Detlev M.; Teubert, Jörg; Eickhoff, Martin; Kleine-Boymann, Matthias; Rohnke, Marcus; Mata, Maria de la; Arbiol, Jordi

    2013-09-14

    Germanium doping of GaN nanowires grown by plasma-assisted molecular beam epitaxy on Si(111) substrates is studied. Time of flight secondary ion mass spectrometry measurements reveal a constant Ge-concentration along the growth axis. A linear relationship between the applied Ge-flux and the resulting ensemble Ge-concentration with a maximum content of 3.3×10{sup 20} cm{sup −3} is extracted from energy dispersive X-ray spectroscopy measurements and confirmed by a systematic increase of the conductivity with Ge-concentration in single nanowire measurements. Photoluminescence analysis of nanowire ensembles and single nanowires reveals an exciton localization energy of 9.5 meV at the neutral Ge-donor. A Ge-related emission band at energies above 3.475 eV is found that is assigned to a Burstein-Moss shift of the excitonic emission.

  17. Polymer-directed synthesis and magnetic property of nanoparticles-assembled BiFeO{sub 3} microrods

    SciTech Connect

    Zhang Lei; Cao Xiaofeng; Ma Yingli; Chen Xuetai; Xue Ziling

    2010-08-15

    Nanoparticles-assembled BiFeO{sub 3} microrods were successfully prepared via a polymer-directed solvothermal route. The phase and morphology of the products were characterized by powder X-ray diffraction (XRD), energy dispersive spectrometry (EDS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), FT-IR spectroscopy and scanning electron microscopy (SEM). Experiments indicated that the linking effect originated from the interactions between polymer molecules could direct the self-assembly of building blocks into one-dimensional nanoparticles-assembled BiFeO{sub 3} microrods. Some factors influencing the morphologies of the products were systematically investigated and a possible mechanism of the formation of the microrods was suggested. Moreover, the magnetic properties of the products were studied. - Graphical abstract: Nanoparticles-assembled BiFeO{sub 3} microrods were successfully prepared via a polymer-directed solvothermal route and characterized by XRD, EDS, FT-IR, ICP-AES and SEM.

  18. General strategy for self-assembly of highly oriented nanocrystalline semiconducting polymers with high mobility.

    PubMed

    Luo, Chan; Kyaw, Aung Ko Ko; Perez, Louis A; Patel, Shrayesh; Wang, Ming; Grimm, Bruno; Bazan, Guillermo C; Kramer, Edward J; Heeger, Alan J

    2014-05-14

    Solution processable semiconducting polymers with excellent film forming capacity and mechanical flexibility are considered among the most progressive alternatives to conventional inorganic semiconductors. However, the random packing of polymer chains and the disorder of the polymer matrix typically result in low charge transport mobilities (10(-5)-10(-2) cm(2) V(-1) s(-1)). These low mobilities compromise their performance and development. Here, we present a strategy, by utilizing capillary action, to mediate polymer chain self-assembly and unidirectional alignment on nanogrooved substrates. We designed a sandwich tunnel system separated by functionalized glass spacers to induce capillary action for controlling the polymer nanostructure, crystallinity, and charge transport. Using capillary action, we demonstrate saturation mobilities with average values of 21.3 and 18.5 cm(2) V(-1 )s(-1) on two different semiconducting polymers at a transistor channel length of 80 μm. These values are limited by the source-drain contact resistance, Rc. Using a longer channel length of 140 μm where the contact resistance is less important, we measured μh = 36.3 cm(2) v(-1) s(-1). Extrapolating to infinite channel length where Rc is unimportant, the intrinsic mobility for poly[4-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b']dithiophen-2-yl)-alt-[1,2,5]thiadiazolo[3,4-c]pyridine] (Mn = 140 kDa) at this degree of chain alignment and structural order is μh ≈ 47 cm(2 )v(-1) s(-1). Our results create a promising pathway toward high performance, solution processable, and low-cost organic electronics. PMID:24712578

  19. Self-assembled and etched cones on laser ablated polymer surfaces

    NASA Astrophysics Data System (ADS)

    Murthy, N. S.; Prabhu, R. D.; Martin, J. J.; Zhou, L.; Headrick, R. L.

    2006-07-01

    At least two different routes lead to conical structures on laser ablated polymer surfaces. These were investigated by studying laser ablation on the surfaces of different classes of polymers. Cones appeared readily in strongly absorbing polymers such as poly(ethylene terephthalate) (PET) and polyimide (PI), but only within narrow laser parameters in nylon 6, and rarely in poly(chlorotrifluoroethylene), the last two being weak ultraviolet (UV) absorbers. Self-assembled, close-packed cones occurred in PET, in which heat generated due to absorbed laser energy creates a thin, chemically stable, viscoelastic, highly compliant layer (above the glass transition temperature). Surface structure in such polymers evolves from nodules through donuts into ripples and finally to cones as the energy deposited per unit area on the surface (total fluence) is increased using a combination of single pulse fluence and number of pulses. A phase transition from a ripple phase to a cone phase is thought to occur as the thickness of the viscoelastic surface layer increases above a critical value. Cones began to appear from almost the beginning of the irradiation process at random locations in PI, a polymer whose surface irreversibly turns into a hard solid upon exposure to either or both UV and heat. It is proposed that the radiation hardened spots serve as nuclei, a cone "grows" out of this as the material surrounding this nuclei is ablated. The initial sparse occurrence of cones in PI-like polymers, and the increase in their number density with total fluence until the surface is densely packed with cones can be explained by a nucleation and growth model.

  20. Observation of the Chiral and Achiral Hexatic Phases of Self-assembled Micellar polymers.

    PubMed

    Pal, Antara; Kamal, Md Arif; Raghunathan, V A

    2016-01-01

    We report the discovery of a thermodynamically stable line hexatic (N + 6) phase in a three-dimensional (3D) system made up of self-assembled polymer-like micelles of amphiphilic molecules. The experimentally observed phase transition sequence nematic (N)  N + 6  two-dimensional hexagonal (2D-H) is in good agreement with the theoretical predictions. Further, the present study also brings to light the effect of chirality on the N + 6 phase. In the chiral N + 6 phase the bond-orientational order within each "polymer" bundle is found to be twisted about an axis parallel to the average polymer direction. This structure is consistent with the theoretically envisaged Moiré state, thereby providing the first experimental demonstration of the Moiré structure. In addition to confirming the predictions of fundamental theories of two-dimensional melting, these results are relevant in a variety of situations in chemistry, physics and biology, where parallel packing of polymer-like objects are encountered. PMID:27577927

  1. EDITORIAL: Nanowires Nanowires

    NASA Astrophysics Data System (ADS)

    Jagadish, Chennupati

    2010-02-01

    Nanowires are considered as building blocks for the next generation of electronics, photonics, sensors and energy applications. One-dimensional nanostructures offer unique opportunities to control the density of states of semiconductors, and in turn their electronic and optical properties. Nanowires allow the growth of axial heterostructures without the constraints of lattice mismatch. This provides flexibility to create heterostructures of a broad range of materials and allows integration of compound semiconductor based optoelectronic devices with silicon based microelectronics. Nanowires are widely studied and the number of papers published in the field is growing exponentially with time. Already nanowire lasers, nanowire transistors, nanowire light emitting diodes, nanowire sensors and nanowire solar cells have been demonstrated. This special issue on semiconductor nanowires features 17 invited papers from leading experts in the field. In this special issue, the synthesis and growth of semiconductor nanowires of a broad range of materials have been addressed. Both axial and radial heterostructures and their structural properties have been discussed. Electrical transport properties of nanowires have been presented, as well as optical properties and carrier dynamics in a range of nanowires and nanowire heterostructures. Devices such as nanowire lasers and nanowire sensors have also been discussed. I would like to thank the Editorial Board of the journal for suggesting this special issue and inviting me to serve as the Guest Editor. Sincere thanks are due to all the authors for their contributions to this special issue. I am grateful to the reviewers and editorial staff at Semiconductor Science and Technology and the Institute of Physics Publishing for their excellent efforts. Special thanks are due to Dr Claire Bedrock for coordinating this special issue.

  2. Unconventional multiple ring structure formation from evaporation-induced self-assembly of polymers.

    PubMed

    Bi, Wuguo; Wu, Xiangyang; Yeow, Edwin K L

    2012-07-31

    The formation of multiring deposits of poly(2-vinylpyridine) (P2VP) from the evaporation of a P2VP-(2,6-lutidine + water) drop on a glass substrate does not conform to the conventional pinning-depinning mechanism. Instead, ringlike deposits are formed when the droplet undergoes several cycles of spreading and receding where, for each spreading event, a P2VP ridge is formed at the contact line when the polymer flows toward the outward advancing edge. The complex interplay between an outward solutal-Marangoni flow due to a higher concentration of the polymer at the contact line and an inward solvent-Marangoni flow arising from the differences in volatilities and surface tensions of the pure solvent components plays an important role in enhancing the droplet spreading rate. The newly discovered surface patterning mechanism has important implications in the development of novel techniques for inducing self-assembly of functional materials from evaporating drops. PMID:22747256

  3. Assembly of poly(dopamine) films mixed with a nonionic polymer.

    PubMed

    Zhang, Yan; Thingholm, Bo; Goldie, Kenneth N; Ogaki, Ryosuke; Städler, Brigitte

    2012-12-21

    Poly(dopamine) (PDA) coatings have recently attracted considerable interest for a variety of applications. Here, we investigate the film deposition of dopamine mixed with a nonionic polymer (i.e., poly(ethylene glycol) (PEG), poly(vinyl alcohol) (PVA), and poly(N-vinyl pyrrolidone) (PVP)) onto silica substrates using X-ray photoelectron spectroscopy and quartz crystal microbalance. Furthermore, we assess the possibility of coating silica colloids to yield polymer capsules and liposomes with these mixtures. We found that mixed PDA/PEG and PDA/PVA films are deposited without the need for a covalent linker such as an amine or thiol. We also discovered the first material, namely, PVP, that can suppress PDA film assembly. These fundamental findings give further insight into PDA film properties and contribute to establish PDA as a widely applicable coating. PMID:23205620

  4. Optically induced mode splitting in self-assembled, high quality-factor conjugated polymer microcavities

    PubMed Central

    Braam, Daniel; Kushida, Soh; Niemöller, Robert; Prinz, Günther M.; Saito, Hitoshi; Kanbara, Takaki; Kuwabara, Junpei; Yamamoto, Yohei; Lorke, Axel

    2016-01-01

    We investigate the whispering gallery modes (WGMs) of self-assembled single microspheres. They consist of a recently developed highly fluorescent π-conjugated copolymer and exhibit excellent optical properties with Q-factors up to 104. Under continuous laser irradiation, we observe a splitting of the highly degenerate spherical WGMs into a multiplet of lines. Comparison with the calculated spectral response of a weakly distorted sphere shows that the optical excitation induces a change of the optical path length in the microcavity so that it resembles a prolate spheroid. The separation of the lines is given by the ellipticity and the azimuthal mode number. Measurements in various gaseous environments suggest that the distortion is caused by light induced oxidation of the polymer. Our findings show that photooxidation can be a beneficial mechanism for in-situ tuning of optically active polymer structures. PMID:26781838

  5. Telechelic Star Polymers as Self-Assembling Units from the Molecular to the Macroscopic Scale

    NASA Astrophysics Data System (ADS)

    Capone, Barbara; Coluzza, Ivan; LoVerso, Federica; Likos, Christos N.; Blaak, Ronald

    2012-12-01

    By means of multiscale molecular simulations, we show that telechelic-star polymers are a simple, robust, and tunable system, which hierarchically self-assembles into soft-patchy particles and mechanically stabilizes selected, open crystalline structures. The self-aggregating patchy behavior can be fully controlled by the number of arms per star and by the fraction of attractive monomeric units at the free ends of the arms. Such self-assembled soft-patchy particles while forming, upon augmenting density, gel-like percolating networks, preserve properties as particle size, number, and arrangement of patches per particle. In particular, we demonstrate that the flexibility inherent in the soft-patchy particles brings forward a novel mechanism that leads to the mechanical stability of diamond and simple cubic crystals over a wide range of densities, and for molecular sizes ranging from about 10 nm up to the micrometer scale.

  6. Polymer surface interacts with calcium in aqueous media to induce stem cell assembly.

    PubMed

    Hung, Kun-Che; Hsu, Shan-Hui

    2015-10-28

    Bioinspired surface with functional group rearrangement abilities are highly desirable for designing functional materials. Calcium ion (Ca(2+) ) is a pivotal life element and the ion transport is tightly regulated through calcium channels. It is demonstrated here that Ca(2+) can be transported by polymer surface to induce cell assembly. A series of polyurethane materials is synthesized with different abilities to rearrange the surface functional groups in response to aqueous environment. It is observed that surface recruitment of carboxyl and amino groups from the bulk material can interact with Ca(2+) and facilitate its translocation from aqueous media into cells. The surface rearrangement of functional group triggers the calcium trafficking and turns on signals involving cell merging and assembly. This observation provides an insight on adjusting material-calcium interaction to design nature-inspired smart interfaces to induce cell organization and tissue regeneration. PMID:26332827

  7. Molecular assembled self-doped polyaniline interlayer for application in polymer light-emitting diode.

    PubMed

    Yang, Chien-Hsin; Chih, Yi-Kai

    2006-10-01

    Self-doped polyaniline (SPANI) ultrathin films were prepared by using a self-assembly process consisting of a self-doping monomer (o-aminobenzenesulfonic acid, SAN) and aniline (AN). SAN-AN copolymerization and film formation were simultaneously performed in aqueous solution. An immersing self-assembly method was developed to build up a SPANI nanofilm on an ITO glass, providing a hole injection layer in a double-layer electroluminescence (EL) device ITO/SPANI nanofilm//MEH-PV//Ca/Al. This device produces an orange EL as compared with a single-layer EL device of ITO//MEH-PV//Ca/Al. A double-layer device demonstrates that a SPANI film is capable of transporting holes in a polymer light-emitting diode (PLED). PMID:17004799

  8. Self-Assembling Peptide-Polymer Hydrogels Designed From the Coiled Coil Region of Fibrin

    PubMed Central

    Jing, Peng; Rudra, Jai S.; Herr, Andrew B.; Collier, Joel H.

    2010-01-01

    Biomaterials constructed from self-assembling peptides, peptide derivatives, and peptide-polymer conjugates are receiving increasing attention as defined matrices for tissue engineering, controlled therapeutic release, and in vitro cell expansion, but many are constructed from peptide structures not typically found in the human extracellular matrix. Here we report a self-assembling biomaterial constructed from a designed peptide inspired by the coiled coil domain of human fibrin, the major protein constituent of blood clots and the provisional scaffold of wound healing. Targeted substitutions were made in the residues forming the interface between coiled coil strands for a 37-amino acid peptide from human fibrinogen to stabilize the coiled coil peptide bundle, while the solvent-exposed residues were left unchanged to provide a surface similar to that of the native protein. This peptide, which self-assembled into coiled coil dimers and tetramers, was then used to produce triblock peptide-PEG-peptide bioconjugates that self-assembled into viscoelastic hydrogel biomaterials. PMID:18712921

  9. Self-assembly of DNA origami particles in suspension of non-absorbing depleting polymers

    NASA Astrophysics Data System (ADS)

    Siavashpouri, Mahsa; Zakhary, Mark; Wachauf, Christian; Dietz, Hendrik; Dogic, Zvonimir

    2015-03-01

    The connection between the macroscopic properties of a liquid crystalline material and the microscopic features of the constituent molecules is the essential theme that permeates the field of liquid crystals. Previous studies have shown that monodisperse rod-like colloids such as filamentous bacteriophage self-assemble into 1D twisted ribbons in presence of attractive interactions mediated by non-absorbing polymers. The microscopic properties of the colloidal particles play an important role in determining the physical properties of these mesoscopic assemblages. Using structural DNA nanotechnology, we present the design and structure of DNA origami six-helix bundles with tunable microscopic properties, which can be used as a new building block for the self-assembly of rod-like colloidal particles. We demonstrate that formation of higher order structures from the assembly of colloidal rods is universal. By tuning the chirality, aspect ratio and flexibility of the DNA origami particles we can control the physical properties of the entire self-assembled structures.

  10. Processing-Dependent Self-Assembly of Protein-Polymer Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    Thomas, C. S.; Xu, L.; Olsen, B. D.

    2012-02-01

    Self-assembly of globular protein-polymer diblock copolymers is a novel method for nanopatterning protein-based materials which maintains a high fraction of protein activity as well as the folded protein structure. By subjecting these copolymers to different processing conditions, long range ordering and the fraction of active protein can be controlled. Here, self-assembly of model mCherry-b-poly(N-isopropyl acrylamide) (PNIPAM) block copolymers is induced by water evaporation from dilute aqueous solutions of conjugate material, and followed by solvent annealing of the resulting nanostructures. Different pathways towards self-assembly are accessed by orthogonally manipulating the solvent quality for each block of the copolymer using temperature and pH. Small-angle scattering and transmission electron microscopy show nanostructure depends heavily on PNIPAM coil fraction and solvent annealing condition, with solution self-assembly reflected in the solid state structure under certain conditions. Protein structure is unaffected by the processing pathway, while protein activity levels in the nanodomains depend strongly on processing conditions and can retain up to 80% of the initial activity.

  11. Facile Directed Assembly of Hollow Polymer Nanocapsules within Spontaneously Formed Catanionic Surfactant Vesicles

    SciTech Connect

    Kim, Mariya D.; Dergunov, Sergey; Richter, Andrew; Durbin, Jeffrey; Shmakov, Sergey; Jia, Ying; Kenbeilova, Saltanat; Orazbekuly, Yerbolat; Kengpeiil, Aigerim; Lindner, Erno; Pingali, Sai Venkatesh; Urban, Volker S; Weigand, Steven; Pinkhassik, Eugene

    2014-01-01

    Surfactant vesicles containing monomers in the interior of the bilayer were used to template hollow polymer nanocapsules. This study investigated the formation of surfactant/monomer assemblies by two loading methods, concurrent loading and diffusion loading. The assembly process and the resulting aggregates were investigated with dynamic light scattering, small angle neutron scattering, and small-angle X-ray scattering. Acrylic monomers formed vesicles with a mixture of cationic and anionic surfactants in a broad range of surfactant ratios. Regions with predominant formation of vesicles were broader for compositions containing acrylic monomers compared with blank surfactants. This observation supports the stabilization of the vesicular structure by acrylic monomers. Diffusion loading produced monomer-loaded vesicles unless vesicles were composed from surfactants at the ratios close to the boundary of a vesicular phase region on a phase diagram. Both concurrent-loaded and diffusion-loaded surfactant/monomer vesicles produced hollow polymer nanocapsules upon the polymerization of monomers in the bilayer followed by removal of surfactant scaffolds.

  12. Efficiency optimization in ionically self-assembled thin film polymer light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Marciu, Daniela; Miller, M.; Ritter, A. L.; Murray, M. A.; Neyman, Patrick J.; Graupner, Wilhelm; Heflin, James R.; Wang, Hong; Gibson, Harry W.; Davis, Rick M.

    2000-04-01

    We present detailed studies of polymer light emitting diodes fabricated from ionically self-assembled monolayer thin films. The ionically self-assembled monolayer (ISAM) films are created with a new thin film fabrication technique that allows detailed structural and thickness control at the molecular level. The ISAM fabrication method simply involves the dipping of a charged substrate alternately into polycationic and polyanionic aqueous solutions at room temperature. Importantly, the ISAM technique yields exceptionally homogeneous, large area films with excellent control of total film thickness. Our studies concentrate on improving the performance of ISAM light emitting diodes that include poly(para-phenylene vinylene) (PPV). The individual thickness of each monolayer and the interpenetration of adjacent layers can be precisely manipulated through the parameters of the electrolyte solutions. The effects of the pH and ionic strength of the immersion solutions, the total film thickness, and the PPV thermal conversion parameters on the photoluminescence and electroluminescence yields have been systematically studied. Through the ISAM process we can also deposit well-defined thicknesses of different polymers at the indium tin oxide and aluminum electrode interfaces. The interface layers are found to affect the electroluminescence efficiency.

  13. Phospholipid—polymer amphiphile hybrid assemblies and their interaction with macrophages

    PubMed Central

    Panneerselvam, Karthiga; Lynge, Martin E.; Riber, Camilla Frich; Mena-Hernando, Sofia; Smith, Anton A. A.; Goldie, Kenneth N.; Zelikin, Alexander N.; Städler, Brigitte

    2015-01-01

    Recently, the combination of lipids and block copolymers has become an alternative to liposomes and polymersomes as nano-sized drug carriers. We synthesize novel block copolymers consisting of poly(cholesteryl acrylate) as the hydrophobic core and poly(N-isopropylacrylamide) (PNIPAAm) as the hydrophilic extensions. Their successful phospholipid-assisted assembly into vesicles is demonstrated using the evaporation-hydration method. The preserved thermo-responsive property of the lipid-polymer hybrids is shown by a temperature dependent adsorption behaviour of the vesicles to poly(l lysine) coated surfaces. As expected, the vesicle adsorption is found to be higher at elevated temperatures. The cellular uptake efficiency of hybrids is assessed using macrophages with applied shear stress. The amount of adhering macrophages is affected by the time and level of applied shear stress. Further, it is found that shorter PNIPAAm extensions lead to higher uptake of the assemblies by the macrophages with applied shear stress. No inherent cytotoxicity is observed at the tested conditions. Taken together, this first example of responsive lipid-polymer hybrids, and their positive biological evaluation makes them promising nano-sized drug carrier candidates. PMID:26339330

  14. Ultrathin self-assembled anionic polymer membranes for superfast size-selective separation.

    PubMed

    Deng, Chao; Zhang, Qiu Gen; Han, Guang Lu; Gong, Yi; Zhu, Ai Mei; Liu, Qing Lin

    2013-11-21

    Nanoporous membranes with superior separation performance have become more crucial with increasing concerns in functional nanomaterials. Here novel ultrahigh permeable nanoporous membranes have been fabricated on macroporous supports by self-assembly of anionic polymer on copper hydroxide nanostrand templates in organic solution. This facile approach has a great potential for the fabrication of ultrathin anionic polymer membranes as a general method. The as-fabricated self-assembled membranes have a mean pore size of 5-12 nm and an adjustable thickness as low as 85 nm. They allow superfast permeation of water, and exhibit excellent size-selective separation properties and good fouling resistance for negatively-charged solutes during filtration. The 85 nm thick membrane has an ultrahigh water flux (3306 l m(-2) h(-1) bar(-1)) that is an order of magnitude larger than commercial membranes, and can highly efficiently separate 5 and 15 nm gold nanoparticles from their mixtures. The newly developed nanoporous membranes have a wide application in separation and purification of biomacromolecules and nanoparticles. PMID:24072040

  15. A self-assembled polymeric micellar immunomodulator for cancer treatment based on cationic amphiphilic polymers.

    PubMed

    Yim, Hyeona; Park, Wooram; Kim, Dongin; Fahmy, Tarek M; Na, Kun

    2014-12-01

    Here, we report a self-assembled polymeric micellar immunomodulator (SPI) for enhanced cancer treatment based on cationic amphiphilic polymers. To obtain the cationic amphiphilic polymer, the hydrophobic all-trans-retinoic acid (ATRA) was conjugated with a hydrophilic low-molecular-weight PEI (LowPEI, Mn = 1.8 kDa). The ATRA-LowPEI conjugates could self-assemble in aqueous media, forming micelles with a strong positive charge (∼+40 mV) and particle sizes of ~70 nm. Compared to conventional therapeutic agents (e.g., cisplatin), the SPI exhibited enhanced anti-cancer activity regardless of drug resistance. After mechanistic in vitro cell death studies, we revealed that the mechanical disruptive force generated by the cationic charge of SPI primarily induced necrotic cell death. Furthermore, the organelle fragments induced by the necrotic cell death triggered antitumoral immune responses. Therefore, SPI induced synergistic effects of the cationic charge-induced necrosis and antitumoral immune responses could produce an effective cancer treatment. In addition, the SPI was shielded by hyaluronic acid (HA/SPI complex) to enhance its tumor selectivity in vivo. Finally, the HA/SPI complex accumulated selectively into tumor sites after systemic administration into tumor-bearing mice, exhibiting effective antitumoral effects without systemic toxicity. Therefore, this technology holds great potential for translation into a clinical cancer treatment. PMID:25239044

  16. Phospholipid-polymer amphiphile hybrid assemblies and their interaction with macrophages.

    PubMed

    Panneerselvam, Karthiga; Lynge, Martin E; Riber, Camilla Frich; Mena-Hernando, Sofia; Smith, Anton A A; Goldie, Kenneth N; Zelikin, Alexander N; Städler, Brigitte

    2015-09-01

    Recently, the combination of lipids and block copolymers has become an alternative to liposomes and polymersomes as nano-sized drug carriers. We synthesize novel block copolymers consisting of poly(cholesteryl acrylate) as the hydrophobic core and poly(N-isopropylacrylamide) (PNIPAAm) as the hydrophilic extensions. Their successful phospholipid-assisted assembly into vesicles is demonstrated using the evaporation-hydration method. The preserved thermo-responsive property of the lipid-polymer hybrids is shown by a temperature dependent adsorption behaviour of the vesicles to poly(l lysine) coated surfaces. As expected, the vesicle adsorption is found to be higher at elevated temperatures. The cellular uptake efficiency of hybrids is assessed using macrophages with applied shear stress. The amount of adhering macrophages is affected by the time and level of applied shear stress. Further, it is found that shorter PNIPAAm extensions lead to higher uptake of the assemblies by the macrophages with applied shear stress. No inherent cytotoxicity is observed at the tested conditions. Taken together, this first example of responsive lipid-polymer hybrids, and their positive biological evaluation makes them promising nano-sized drug carrier candidates. PMID:26339330

  17. Polymer GARD: computer simulation of covalent bond formation in reproducing molecular assemblies.

    PubMed

    Shenhav, Barak; Bar-Even, Arren; Kafri, Ran; Lancet, Doron

    2005-04-01

    The basic Graded Autocatalysis Replication Domain (GARD) model consists of a repertoire of small molecules, typically amphiphiles, which join and leave a non-covalent micelle-like assembly. Its replication behavior is due to occasional fission, followed by a homeostatic growth process governed by the assembly's composition. Limitations of the basic GARD model are its small finite molecular repertoire and the lack of a clear path from a 'monomer world' towards polymer-based living entities. We have now devised an extension of the model (polymer GARD or P-GARD), where a monomer-based GARD serves as a 'scaffold' for oligomer formation, as a result of internal chemical rules. We tested this concept with computer simulations of a simple case of monovalent monomers, whereby more complex molecules (dimers) are formed internally, in a manner resembling biosynthetic metabolism. We have observed events of dimer 'take-over' - the formation of compositionally stable, replication-prone quasi stationary states (composomes) that have appreciable dimer content. The appearance of novel metabolism-like networks obeys a time-dependent power law, reminiscent of evolution under punctuated equilibrium. A simulation under constant population conditions shows the dynamics of takeover and extinction of different composomes, leading to the generation of different population distributions. The P-GARD model offers a scenario whereby biopolymer formation may be a result of rather than a prerequisite for early life-like processes. PMID:16010993

  18. Well-Defined Protein/Peptide-Polymer Conjugates by Aqueous Cu-LRP: Synthesis and Controlled Self-Assembly.

    PubMed

    Zhang, Qiang; Li, Muxiu; Zhu, Chongyu; Nurumbetov, Gabit; Li, Zaidong; Wilson, Paul; Kempe, Kristian; Haddleton, David M

    2015-07-29

    The synthesis of well-defined protein/peptide-polymer conjugates with interesting self-assembly behavior via single electron transfer living radical polymerization in water is described. A range of protein/peptides with different physical and chemical properties have been modified to macroinitiators and optimized polymerization conditions ensure successful polymerization from soluble, insoluble, and dispersed protein/peptide molecules or protein aggregates. This powerful strategy tolerates a range of functional monomers and mediates efficient homo or block copolymerization to generate hydrophilic polymers with controlled molecular weight (MW) and narrow MW distribution. The polymerizations from bovine insulin macroinitiators follow surface-initiated "grafting from" polymerization mechanism and may involve a series of self-assembly and disassembly processes. Synthesized insulin-polymer conjugates form spheres in water, and the self-assembly behavior could be controlled via thermal control, carbohydrate-protein interaction, and protein denaturation. PMID:26149497

  19. Observation of the Chiral and Achiral Hexatic Phases of Self-assembled Micellar polymers

    PubMed Central

    Pal, Antara; Kamal, Md. Arif; Raghunathan, V. A.

    2016-01-01

    We report the discovery of a thermodynamically stable line hexatic (N + 6) phase in a three-dimensional (3D) system made up of self-assembled polymer-like micelles of amphiphilic molecules. The experimentally observed phase transition sequence nematic (N)  N + 6  two-dimensional hexagonal (2D-H) is in good agreement with the theoretical predictions. Further, the present study also brings to light the effect of chirality on the N + 6 phase. In the chiral N + 6 phase the bond-orientational order within each “polymer” bundle is found to be twisted about an axis parallel to the average polymer direction. This structure is consistent with the theoretically envisaged Moiré state, thereby providing the first experimental demonstration of the Moiré structure. In addition to confirming the predictions of fundamental theories of two-dimensional melting, these results are relevant in a variety of situations in chemistry, physics and biology, where parallel packing of polymer-like objects are encountered. PMID:27577927

  20. Development of block co-polymers as self-assembling templates for patterned media.

    SciTech Connect

    Warke, V.; Bakker, M. G.; Hong, K.; Mays, J.; Britt, P.; Li, X.; Wang, J.; X-Ray Science Division; Univ. of Alabama; ORNL

    2006-01-01

    Block copolymers that self-organize are of interest as templates for patterned media, as they potentially provide a low cost fabrication route. Poly(styrene)-Poly(methylmethacrylate) block co-polymers (PS-b-PMMA) of appropriate block length and PS to PMMA ratio self-assemble into a 2-D hexagonal phase in which the PS majority phase is continuous and surrounds cylinders of the minority, PMMA phase. For application of this phase to patterned media it is necessary that the cylinders of the minority phase be oriented perpendicular to the substrate surface. This can be achieved by a number of methods, including appropriate choice of substrate and use of a random co-polymer underlayer. Appropriate substrates include H-terminated silicon, some carbon coatings and some ITO glasses. Use of an acetic acid wash causes the minority PMMA component can be induced to be rearranged, giving rise to pores perpendicular to the substrate. Electrodeposition of a metal into the pores produces a hardmask which can be used with ion-milling to transfer the block co-polymer pattern onto a magnetic thin film.

  1. Enhancing the Thermal Conductance of Polymer and Sapphire Interface via Self-Assembled Monolayer.

    PubMed

    Zheng, Kun; Sun, Fangyuan; Zhu, Jie; Ma, Yongmei; Li, Xiaobo; Tang, Dawei; Wang, Fosong; Wang, Xiaojia

    2016-08-23

    Interfacial thermal conductance (ITC) receives enormous consideration because of its significance in determining thermal performance of hybrid materials, such as polymer based nanocomposites. In this study, the ITC between sapphire and polystyrene (PS) was systematically investigated by time domain thermoreflectance (TDTR) method. Silane based self-assembled monolayers (SAMs) with varying end groups, -NH2, -Cl, -SH and -H, were introduced into sapphire/PS interface, and their effects on ITC were investigated. The ITC was found to be enhanced up by a factor of 7 through functionalizing the sapphire surface with SAM, which ends with a chloride group (-Cl). The results show that the enhancement of the thermal transport across the SAM-functionalized interface comes from both strong covalent bonding between sapphire and silane-based SAM, and the high compatibility between the SAM and PS. Among the SAMs studied in this work, we found that the ITC almost linearly depends on solubility parameters, which could be the dominant factor influencing on the ITC compared with wettability and adhesion. The SAMs serve as an intermediate layer that bridges the sapphire and PS. Such a feature can be applied to ceramic-polymer immiscible interfaces by functionalizing the ceramic surface with molecules that are miscible with the polymer materials. This research provides guidance on the design of critical-heat transfer materials such as composites and nanofluids for thermal management. PMID:27501117

  2. Dispersion and self-assembly of nanospheres and nanorods in polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Deshmukh, Ranjan Deepak

    2007-12-01

    Polymer nanocomposites are hybrid nanomaterials in which electrical, opto-electronic, magnetic, mechanical and other properties can be precisely tuned by choosing an appropriate combination of nanoparticle (NP) and polymer. This dissertation explores in-situ and ex-situ routes to disperse metal NP in polymers as well as the fundamental thermodynamic and dynamic principles underlying the NP dispersion in polymers. "In-situ" silver NP are prepared by the thermal decomposition of an organometallic precursor (1,1,1,5,5,5-hexafluoroacetylacetonato)silver(I) or (AgHFA) in homopolymer poly(methyl methactyalate), PMMA and block copolymer poly(MMA-b-styrene), PS-b-PMMA films. A range of complementary characterization techniques including Rutherford backscattering spectrometry (RBS), scanning force microscopy (SFM), transmission electron microscopy (TEM), and UV-visible spectroscopy are used to characterize the polymer nanocomposites. The in-situ formed "spherical" silver NP are observed to segregate to the surface and the substrate regions in PMMA and PS-b-PMMA films. By showing that the precursor organizes into aggregates in as-cast films, our experiments uncover the mechanism of NP segregation. Upon annealing, diffusion of the precursor to the surface and substrate occurs concurrently with NP formation resulting in enrichment of Ag at both interfaces. In PS-b-PMMA films, the Ag NP form during the self-assembly of the block copolymer. At the surface, NP organize into well-defined arrays that are guided by the PMMA domains. For the first time, our experiments also show that the kinetics of block copolymer reorganization is slowed down by the incorporation of NP. This dissertation also explores the self-assembly of "ex-situ" synthesized NP with aspect ratio > 1, namely gold nanorods functionalized with poly(ethylene glycol), PEG. After solvent annealing PS-b-PMMA with 5-vol% Au, the nanorods are selectively located and confined in the "lamellar" PMMA domains due to favorable

  3. Fabrication of DNA nanowires by orthogonal self-assembly and DNA intercalation on a Au patterned Si/SiO2 surface.

    PubMed

    Kobayashi, Katsuaki; Tonegawa, Naoya; Fujii, Sho; Hikida, Jiro; Nozoye, Hisakazu; Tsutsui, Ken; Wada, Yasuo; Chikira, Makoto; Haga, Masa-Aki

    2008-11-18

    A novel Ru complex bearing both an acridine group and anchoring phosphonate groups was immobilized on a surface in order to capture double-stranded DNAs (dsDNAs) from solution. At low surface coverage, the atomic force microscopy (AFM) image revealed the "molecular dot" morphology with the height of the Ru complex ( approximately 2.5 nm) on a mica surface, indicating that four phosphonate anchor groups keep the Ru complex in an upright orientation on the surface. Using a dynamic molecular combing method, the DNA capture efficiency of the Ru complex on a mica surface was examined in terms of the effects of the number of molecular dots and surface hydrophobicity. The immobilized surface could capture DNAs; however, the optimal number of molecular dots on the surface as well as the optimal pull-up speed exist to obtain the extended dsDNAs on the surface. Applying this optimal condition to a Au-patterned Si/SiO 2 (Au/SiO 2) surface, the Au electrode was selectively covered with the Ru complex by orthogonal self-assembly of 4-mercaptbutylphosphonic acid (MBPA), followed by the formation of a Zr (4+)-phosphonate layer and the Ru complex. At the same time, the remaining SiO 2 surface was covered with octylphosphonic acid (OPA) by self-assembly. The selective immobilization of the Ru complex only on the Au electrode was identified by time-of-flight secondary-ion mass spectrometry (TOF-SIMS) imaging on the chemically modified Au/SiO 2 surface. The construction of DNA nanowires on the Au/SiO 2 patterned surface was accomplished by the molecular combing method of the selective immobilized Ru complex on Au electrodes. These interconnected nanowires between Au electrodes were used as a scaffold for the modification of Pd nanoparticles on the DNA. Furthermore, Cu metallization was achieved by electroless plating of Cu metal on a priming of Pd nanoparticles on the Pd-covered DNA nanowires. The resulting Cu nanowires showed a metallic behavior with relatively high resistance. PMID

  4. Self-Assembly Directed Organization of Nanodiamond During Ionic Liquid Crystalline Polymer Formation.

    PubMed

    Ringstrand, Bryan S; Seifert, Sönke; Podlesak, David W; Firestone, Millicent A

    2016-07-01

    The UV-initiated free radical polymerization of a lyotropic mesophase prepared by co-assembly of an aqueous mixture of an ionic liquid (IL) monomer, 3-decyl-1-vinylimidazolium chloride, in a dimethyl sulfoxide dispersion of an IL-monomer nanodiamond conjugate yields a well-ordered 2D hexagonally structured network-polymer composite. The IL monomer is covalently bound to carboxylated detonation diamond via ester-linked 3-decyl-1-vinylimidazolium bromide. Successful preparation of the amphiphile-functionalized nanodiamond is determined by ATR/FT-IR, thermogravimetric analysis, and small-angle X-ray scattering (SAXS). Mesophase and composite structure are evaluated by SAXS, revealing a columnar architecture composed of amphiphilic ionic liquid cylinders containing solvent-rich cores. Self-assembly directed site localization of the nanodiamond positions the particles in the alkyl chain continuum upon polymerization. The composite reversibly swells in ethanol allowing structural variation and modulation of the nanoparticle internal packing arrangement. This work demonstrates that through careful molecular design, self-organization and site-directed assembly of nanodiamond into chemically distinct regions of a nanostructured organogel can be achieved. PMID:27197942

  5. Solution-processed low dimensional nanomaterials with self-assembled polymers for flexible photo-electronic devices (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Park, Cheolmin

    2015-09-01

    Self assembly driven by complicated but systematic hierarchical interactions offers a qualified alternative for fabricating functional micron or nanometer scale pattern structures that have been potentially useful for various organic and nanotechnological devices. Self assembled nanostructures generated from synthetic polymer systems such as controlled polymer blends, semi-crystalline polymers and block copolymers have gained a great attention not only because of the variety of nanostructures they can evolve but also because of the controllability of these structures by external stimuli. In this presentation, various novel photo-electronic materials and devices are introduced based on the solution-processed low dimensional nanomaterials such as networked carbon nanotubes (CNTs), reduced graphene oxides (rGOs) and 2 dimensional transition metal dichalcogenides (TMDs) with self assembled polymers including field effect transistor, electroluminescent device, non-volatile memory and photodetector. For instance, a nanocomposite of networked CNTs and a fluorescent polymer turned out an efficient field induced electroluminescent layer under alternating current (AC) as a potential candidate for next generation displays and lightings. Furthermore, scalable and simple strategies employed for fabricating rGO as well as TMD nanohybrid films allowed for high performance and mechanically flexible non-volatile resistive polymer memory devices and broad band photo-detectors, respectively.

  6. Supramolecular Engineering of Hierarchically Self-Assembled, Bioinspired, Cholesteric Nanocomposites Formed by Cellulose Nanocrystals and Polymers.

    PubMed

    Zhu, Baolei; Merindol, Remi; Benitez, Alejandro J; Wang, Baochun; Walther, Andreas

    2016-05-01

    Natural composites are hierarchically structured by combination of ordered colloidal and molecular length scales. They inspire future, biomimetic, and lightweight nanocomposites, in which extraordinary mechanical properties are in reach by understanding and mastering hierarchical structure formation as tools to engineer multiscale deformation mechanisms. Here we describe a hierarchically self-assembled, cholesteric nanocomposite with well-defined colloid-based helical structure and supramolecular hydrogen bonds engineered on the molecular level in the polymer matrix. We use reversible addition-fragmentation transfer polymerization to synthesize well-defined hydrophilic, nonionic polymers with a varying functionalization density of 4-fold hydrogen-bonding ureidopyrimidinone (UPy) motifs. We show that these copolymers can be coassembled with cellulose nanocrystals (CNC), a sustainable, stiff, rod-like reinforcement, to give ordered cholesteric phases with characteristic photonic stop bands. The dimensions of the helical pitch are controlled by the ratio of polymer/CNC, confirming a smooth integration into the colloidal structure. With respect to the effect of the supramolecular motifs, we demonstrate that those regulate the swelling when exposing the biomimetic hybrids to water, and they allow engineering the photonic response. Moreover, the amount of hydrogen bonds and the polymer fraction are decisive in defining the mechanical properties. An Ashby plot comparing previous ordered CNC-based nanocomposites with our new hierarchical ones reveals that molecular engineering allows us to span an unprecedented mechanical property range from highest inelastic deformation (strain up to ∼13%) to highest stiffness (E ∼ 15 GPa) and combinations of both. We envisage that further rational design of the molecular interactions will provide efficient tools for enhancing the multifunctional property profiles of such bioinspired nanocomposites. PMID:27067311

  7. Hierarchical assembly of Ti(iv)/Sn(ii) co-doped SnO2 nanosheets along sacrificial titanate nanowires: synthesis, characterization and electrochemical properties

    NASA Astrophysics Data System (ADS)

    Wang, Hongkang; Xi, Liujiang; Tucek, Jiri; Zhan, Yawen; Hung, Tak Fu; Kershaw, Stephen V.; Zboril, Radek; Chung, C. Y.; Rogach, Andrey L.

    2013-09-01

    Hierarchical assembly of Ti(iv)/Sn(ii)-doped SnO2 nanosheets along titanate nanowires serving as both sacrificial templates and a Ti(iv) source is demonstrated, using SnCl2 as a tin precursor and Sn(ii) dopants and NaF as the morphology controlling agent. Excess fluoride inhibits the hydrolysis of SnCl2, promoting heterogeneous nucleation of Sn(ii)-doped SnO2 on the titanate nanowires due to the insufficient oxidization of Sn(ii) to Sn(iv). Simultaneously, titanate nanowires are dissolved forming Ti4+ species under the etching effect of in situ generated HF resulting in spontaneous Ti4+ ion doping of SnO2 nanosheets formed under hydrothermal conditions. Compositional analysis indicates that Ti4+ ions are incorporated by substitution of Sn sites at a high level (16-18 at.%), with uniform distribution and no phase separation. Mössbauer spectroscopy quantified the relative content of Sn(ii) and Sn(iv) in both Sn(ii)-doped and Ti(iv)/Sn(ii) co-doped SnO2 samples. Electrochemical properties were investigated as an anode material in lithium ion batteries, demonstrating that Ti-doped SnO2 nanosheets show improved cycle performance, which is attributed to the alleviation of inherent volume expansion of the SnO2-based anode materials by substituting part of Sn sites with Ti dopants.Hierarchical assembly of Ti(iv)/Sn(ii)-doped SnO2 nanosheets along titanate nanowires serving as both sacrificial templates and a Ti(iv) source is demonstrated, using SnCl2 as a tin precursor and Sn(ii) dopants and NaF as the morphology controlling agent. Excess fluoride inhibits the hydrolysis of SnCl2, promoting heterogeneous nucleation of Sn(ii)-doped SnO2 on the titanate nanowires due to the insufficient oxidization of Sn(ii) to Sn(iv). Simultaneously, titanate nanowires are dissolved forming Ti4+ species under the etching effect of in situ generated HF resulting in spontaneous Ti4+ ion doping of SnO2 nanosheets formed under hydrothermal conditions. Compositional analysis indicates that Ti4

  8. Polymer Crosslinked 3-D Assemblies of Nanoparticles: Mechanically Strong Lightweight Porous Materials

    NASA Technical Reports Server (NTRS)

    Leventis, Nicholas

    2005-01-01

    In analogy to supramolecular assemblies, which are pursued because of properties above and beyond those of the individual molecules, self-standing monolithic three-dimensional assemblies of nanoparticles also have unique properties attributed to their structure. For example, ultra low-density 3-D assemblies of silica nanoparticles, known as silica aerogels, are characterized by large internal void space, high surface area and very low thermal conductivity. Aerogels, however, are also extremely fragile materials, limiting their application to a few specialized environments, e.g., in nuclear reactors as Cerenkov radiation detectors, in space (refer to NASA's Stardust Program) and aboard certain planetary vehicles (thermal insulators on Mars Rovers in 1997 and 2004). The fragility problem is traced to well-defined weak points in the aerogel skeletal framework, the interparticle necks. Using the surface functionality of the nanoparticle building blocks as a focal point, we have directed attachment of a conformal polymer coating over the entire framework, rendering all necks wider. Thus, although the bulk density may increase only by 3x, the mesoporosity (pores in the range 2-50 nm) remains unchanged, while the strength of the material increases by up to 300... Having addressed the fragility problem, aerogels are now robust materials, and a variety of applications, ranging from thermal/acoustic insulators to catalyst supports, to platform for sensors, and dielectrics are all within reach. Our approach employs molecular science to manipulate nanoscopic matter for achieving useful macroscopic properties, and in our view it resides at the core of what defines nanotechnology. In that spirit, this technology is expandable in three directions. Thus, we have already crosslinked successfully amine-modified silica, and we anticipate that more rich chemistry will be realized by been creative with the nanoparticle surface modifiers. On the other hand, although we do not expect

  9. Conformational assembly and biological properties of collagen mimetic peptides and their thermally responsive polymer conjugates

    NASA Astrophysics Data System (ADS)

    Krishna, Ohm Divyam

    2011-12-01

    Collagens are one of the most abundant proteins found in body tissues and organs, endowing structural integrity, mechanical strength, and multiple biological functions. Destabilized collagen inside human body leads to various degenerative diseases (ex. osteoarthritis) and ageing. This has continued to motivate the design of synthetic peptides and bio-synthetic polypeptides to closely mimic the native collagens in terms of triple helix structure and stability, potential for higher order assembly, and biological properties. However, the widespread application of de novo collagens has been limited in part by the need for hydroxylated proline in the formation of stable triple helical structures. To address this continued need, a hydroxyproline-free, thermally stable collagen-mimetic peptide (CLP-Cys) was rationally designed via the incorporation of electrostatically stabilized amino acid triplets. CLP-Cys was synthesized via solid phase peptide synthesis. The formation and stability of the triple helical structure were indicated via circular dichroism (CD) experiments and confirmed via differential scanning calorimetry (DSC) results. CLP-Cys also self-assembled into nano-rods and micro-fibrils, as evidenced via a combination of dynamic light scattering and transmission electron microscopy. Given the high thermal stability and its propensity for higher-order assembly, CLP-Cys was further functionalized at both the ends with a thermally responsive polymer, poly(diethylene glycol methyl ether methacrylate), (PDEGMEMA) to synthesize a biohybrid triblock copolymer. The CD results indicated that the triple helical form is retained, the thermal unfolding is sustained and helix to coil transition is reversible in the triblock hybrid context. The LCST of PDEGMEMA homopolymer (26 °C) is increased (to 35 °C) upon conjugation to the hydrophilic collagen peptide domain. Further, a combination of static light scattering, Cryo-SEM, TEM and confocal microscopy elucidated that the

  10. Electrochemically Grown Single Nanowire Sensors

    NASA Technical Reports Server (NTRS)

    Yun, Minhee; Lee, Choonsup; Vasquez, Richard P.; Penner, Reginald; Bangar, Mangesh; Mulchandani, Ashok; Myung, Nosang V.

    2004-01-01

    We report a fabrication technique that is potentially capable of producing arrays of individually addressable nanowire sensors with controlled dimensions, positions, alignments, and chemical compositions. The concept has been demonstrated with electrodeposition of palladium wires with 75 nm to 350 nm widths. We have also fabricated single and double conducting polymer nanowires (polyaniline and polypyrrole) with 100nm and 200nm widths using electrochemical direct growth. Using single Pd nanowires, we have also demonstrated hydrogen sensing. It is envisioned that these are the first steps towards nanowire sensor arrays capable of simultaneously detecting multiple chemical species.

  11. Graft-through Synthesis and Assembly of Janus Bottlebrush Polymers from A-Branch-B Diblock Macromonomers.

    PubMed

    Kawamoto, Ken; Zhong, Mingjiang; Gadelrab, Karim R; Cheng, Li-Chen; Ross, Caroline A; Alexander-Katz, Alfredo; Johnson, Jeremiah A

    2016-09-14

    We report the synthesis of Janus bottlebrush block copolymers by graft-through polymerization of branched diblock macromonomers. Self-assembly of the bottlebrushes was characterized by small-angle X-ray scattering, atomic force microscopy, and scanning electron microscopy. Phase separation and packing models of the bottlebrushes were computed, and their self-assembly behavior was corroborated experimentally in bulk and in thin films. Lamellar, hexagonal cylinder, and gyroid phases were observed and modeled. The A-branch-B Janus bottlebrush structure provides several unique advantages in the context of bottlebrush polymer assembly, including access to the first examples of gyroid phases. PMID:27580971

  12. Solution-phase self-assembly of complementary halogen bonding polymers.

    PubMed

    Vanderkooy, Alan; Taylor, Mark S

    2015-04-22

    Noncovalent halogen bonding interactions are explored as a driving force for solution phase macromolecular self-assembly. Conditions for controlled radical polymerization of an iodoperfluoroarene-bearing methacrylate halogen bond donor were identified. An increase in association constant relative to monomeric species was observed for the interaction between halogen bond donor and acceptor polymers in solution. When the polymeric donor was combined with a block copolymer bearing halogen bond-accepting amine groups, higher-order structures were obtained in both organic solvent and in water. Transmission electron microscopy, dynamic light scattering and nuclear magnetic resonance spectroscopic data are consistent with structures having cores composed of the interacting halogen bond donor and acceptor segments. PMID:25867188

  13. Ion current behaviors of mesoporous zeolite-polymer composite nanochannels prepared by water-assisted self-assembly.

    PubMed

    Zhang, Wenjuan; Meng, Zheyi; Zhai, Jin; Heng, Liping

    2014-04-01

    Inspired by the asymmetry of biological ion channels in structure and composition, we designed a novel type of artificial asymmetric nanochannels based on mesoporous zeolite (MCM-41) and polyimide (PI) by water-assisted self-assembly. Meanwhile, we studied ionic current behaviors and rectifying characteristics of the mesoporous zeolite-polymer composite nanochannels. PMID:24394328

  14. Formation of a polymer particle monolayer by continuous self-assembly from a colloidal solution.

    PubMed

    Kim, Soohyun; Choi, Hee-Dok; Kim, Il-Doo; Lee, Jong-Chan; Rhee, Bum Ku; Lim, Jung Ah; Hong, Jae-Min

    2012-02-15

    The preparation of two-dimensional monolayers of polymer particles over a large area was demonstrated via a facile solution process. Polymer microspheres were continuously self-assembled into a close-packed monolayer from a colloidal solution confined between two plates such that the top plate was carefully dragged at a constant velocity in the direction opposite that of the monolayer growth. In situ direct observation of the particle movement during the coating process confirmed that particle transport was directed toward the contact line of the solution meniscus by evaporation-induced convective flow. Sliding of the top plate apparently effectively counterbalanced the convective flow to provide the particles with a contact line for growth of a monolayer particle array. The influence of particle concentration, sliding speed of the top plate, and surface wettability of the bottom substrate were investigated and optimized. Monolayer particle arrays were successfully demonstrated as a template for the preparation of ZnO films with ordered hollow hemispherical structures. This approach is applicable to the fabrication of ordered structures of monodispersed particles composed of various materials over large areas. PMID:22169181

  15. Novel surface treatment materials for aligning block-co-polymer in directed self-assembly processes

    NASA Astrophysics Data System (ADS)

    Someya, Yasunobu; Wakayama, Hiroyuki; Endo, Takafumi; Sakamoto, Rikimaru

    2014-03-01

    Directed Self-Assembly (DSA) process is one of the attractive processes for creating the very fine pitch pattern. Especially, the contact hole shrink processes with block-co-polymer (BCP) or polymer blend materials were attractive processes for creating very small size hole patterns with better CD uniformity compare to general photo-lithography patterning. In general contact hole shrink process, the pattern of Spin-on Carbon Hardmask (SOC) or the photo Resist pattern created by Negative-Tone Development (NTD) process were selected for guide patterns. Since the alignment property of BCP was affected by the surface of these guide materials, it is important to control the surface condition of guide in order to obtain good shrunk contact hole patterns. In this study, we will report the surface treatment materials to control the surface condition of guide patterns such as SOC or NTD resist to achieve the better contact hole shrink performance. These materials were attached to guide pattern surface and controlled the surface energy.

  16. Assembling semiconducting molecules by covalent attachment to a lamellar crystalline polymer substrate

    PubMed Central

    Machatschek, Rainhard; Ortmann, Patrick; Reiter, Renate; Mecking, Stefan

    2016-01-01

    Summary We have investigated the potential of polymers containing precisely spaced side-branches for thin film applications, particularly in the context of organic electronics. Upon crystallization, the side-branches were excluded from the crystalline core of a lamellar crystal. Thus, the surfaces of these crystals were covered by side-branches. By using carboxyl groups as side-branches, which allow for chemical reactions, we could functionalize the crystal with semiconducting molecules. Here, we compare properties of crystals differing in size: small nanocrystals and large single crystals. By assembling nanocrystals on a Langmuir trough, large areas could be covered by monolayers consisting of randomly arranged nanocrystals. Alternatively, we used a method based on local supersaturation to grow large area single crystals of the precisely side-branched polymer from solution. Attachment of the semiconducting molecules to the lamellar surface of large single crystals was possible, however, only after an appropriate annealing procedure. As a function of the duration of the grafting process, the morphology of the resulting layer of semiconducting molecules changed from patchy to compact. PMID:27335767

  17. Exciton and polaron interactions in self-assembled conjugated polymer aggregates

    NASA Astrophysics Data System (ADS)

    Grey, John K.; Thomas, Alan K.; Gao, Jian

    2015-08-01

    We study exciton coupling and interconversion between neutral and charged states of different spin in pi-stacked conjugated polymer aggregates. Rigorous self-assembly approaches are used to prepare aggregate nanofibers that permit reliable control of polymer chain conformational and packing (intra- and interchain) order within these structures. Exciton coupling can be tuned between the H- and J-aggregate limits, which has important implications for determining the fates of excitons and polarons. Single molecule intensity modulation spectroscopy was performed on individual nanofibers and large quenching depths of emissive singlet excitons by triplets are found in J-aggregate type structures. We propose that high intrachain order leads to exciton delocalization that effectively lowers singlet-triplet energy splittings thus increasing triplet yields. Exciton-polaron and polaron-polaron interactions are next investigated in both H- and J-type nanofibers where polarons are injected by charge transfer doping. We find that the enhanced intrachain order of J-aggregates enables efficient intrachain polaron transport and leads to significantly larger doping efficiencies than less ordered H-aggregates. As polaron densities increase, signatures of spin-spin interactions between polarons on adjacent chains become appreciable leading to the formation of a spinless bipolaron. Overall, these studies demonstrate the potential for controlling and directing exciton and polaron interactions via tuning of subtle intra- and interchain ordering characteristics of aggregates, which could benefit various polymeric optoelectronic applications.

  18. Polymer Gard: Computer Simulation of Covalent Bond Formation in Reproducing Molecular Assemblies

    NASA Astrophysics Data System (ADS)

    Shenhav, Barak; Bar-Even, Arren; Kafri, Ran; Lancet, Doron

    2005-04-01

    The basic Graded Autocatalysis Replication Domain (GARD) model consists of a repertoire of small molecules, typically amphiphiles, which join and leave a non-covalent micelle-like assembly. Its replication behavior is due to occasional fission, followed by a homeostatic growth process governed by the assembly’ s composition. Limitations of the basic GARD model are its small finite molecular repertoire and the lack of a clear path from a ‘monomer world’ towards polymer-based living entities.We have now devised an extension of the model (polymer GARD or P-GARD), where a monomer-based GARD serves as a ‘scaffold’ for oligomer formation, as a result of internal chemical rules. We tested this concept with computer simulations of a simple case of monovalent monomers, whereby more complex molecules (dimers) are formed internally, in a manner resembling biosynthetic metabolism. We have observed events of dimer ‘take-over’ the formation of compositionally stable, replication-prone quasi stationary states (composomes) that have appreciable dimer content. The appearance of novel metabolism-like networks obeys a time-dependent power law, reminiscent of evolution under punctuated equilibrium. A simulation under constant population conditions shows the dynamics of takeover and extinction of different composomes, leading to the generation of different population distributions. The P-GARD model offers a scenario whereby biopolymer formation may be a result of rather than a prerequisite for early life-like processes.

  19. A laser microwelding method for assembly of polymer based microfluidic devices

    NASA Astrophysics Data System (ADS)

    Jiang, Xin; Chandrasekar, Soni; Wang, Changhai

    2015-03-01

    This paper presents the development of a laser microwelding method for assembly and packaging of polymer based microfluidic devices. In this approach a diode laser was used to weld two poly(methyl methacrylate) (PMMA) substrates together at the interface using a thin film metal spot based intermediate layer design as a localized absorber. A broad laser beam with a top-hat profile was used to carry out the laser microwelding work. The effects of laser power and processing time on the resultant heated affected zone (HAZ) and the melted zone were investigated. For large area welding, a 2×2 array of thin film metal spots were used to investigate the effect of separation between the spots on the resultant interfacial bond between the two polymer substrates. For comparison, a large area titanium film with a comparable size to that of the 2×2 array was also studied. The results show that the discrete film pattern based design is better than a single large area film in order to reduce the effect of substrate distortion resulting from the higher temperature rise associated with the latter. The tensile strength of the laser welded joints was determined to be about 6 MPa for a sample produced using the 2×2 array of circular titanium spot pattern design. The laser microwelding method has been demonstrated successfully in leak-free encapsulation of a microfluidic channel.

  20. Exploiting Supramolecular Interactions for the Intramolecular Folding of Side-Chain Functionalized Polymers and Assembly of Anisotropic Colloids

    NASA Astrophysics Data System (ADS)

    Romulus, Joy

    The overarching goal presented in this thesis is the self-assembly of synthetic systems into higher ordered structures utilizing supramolecular chemistry. Noncovalent interactions including charge-transfer and hydrogen bonding as well as DNA hybridization are exploited to induce the assembly of polymers and colloids into well-defined architectures. This strategy provides a tunable handle on materials bulk properties that can be adjusted by simply changing variables such as temperature and solvent. A brief overview of design principles for the supramolecular assembly of side-chain functionalized polymers is presented. The polymerization technique selected was living ring-opening metathesis polymerization (ROMP), thus affording control over molecular weight and molecular weight distributions. ROMP also allowed for the incorporation of functional groups that were used to assemble the polymers into ordered structures. Charge-transfer motifs were exploited and shown to drive the assembly of random and alternating copolymers via intramolecular side-chain interactions. Incorporation of complementary hydrogen bonding motifs was shown to guide the single-chain folding of a multifunctional triblock copolymer into sheet-like structures. Precision over the size, shape, and monomer sequence were identified as key elements for efficient self-assembly. The self-assembly of colloids using DNA hybridization was also investigated. Previously, the majority of colloid-based research relied upon the self-assembly of spherical isotropic particles into closed-packed arrangements. In contrast, anisotropic particles may allow for the realization of open structures. By expanding upon a method to permanently cross-link DNA strands incubated on a colloidal surface, a new strategy to engineer patchy particles is described. These functional DNA-coated patches are demonstrated to direct particle assembly. The self-assembly of polymer and colloidal systems utilizing noncovalent interactions

  1. Interfacial assembly of protein-polymer nano-conjugates into stimulus-responsive biomimetic protocells.

    PubMed

    Huang, Xin; Li, Mei; Green, David C; Williams, David S; Patil, Avinash J; Mann, Stephen

    2013-01-01

    The mechanism of spontaneous assembly of microscale compartments is a central question for the origin of life, and has technological repercussions in diverse areas such as materials science, catalysis, biotechnology and biomedicine. Such compartments need to be semi-permeable, structurally robust and capable of housing assemblages of functional components for internalized chemical transformations. In principle, proteins should be ideal building blocks for the construction of membrane-bound compartments but protein vesicles with cell-like properties are extremely rare. Here we present an approach to the interfacial assembly of protein-based micro-compartments (proteinosomes) that are delineated by a semi-permeable, stimulus-responsive, enzymatically active, elastic membrane consisting of a closely packed monolayer of conjugated protein-polymer building blocks. The proteinosomes can be dispersed in oil or water, thermally cycled to temperatures of 70 °C, and partially dried and re-inflated without loss of structural integrity. As a consequence, they exhibit protocellular properties such as guest molecule encapsulation, selective permeability, gene-directed protein synthesis and membrane-gated internalized enzyme catalysis. PMID:23896993

  2. Self-Assembling Nanoparticles of Amphiphilic Polymers for In Vitro and In Vivo FRET Imaging.

    PubMed

    Garcia-Amorós, Jaume; Tang, Sicheng; Zhang, Yang; Thapaliya, Ek Raj; Raymo, Françisco M

    2016-01-01

    Self-assembling nanoparticles of amphiphilic polymers are viable delivery vehicles for transporting hydrophobic molecules across hydrophilic media. Noncovalent contacts between the hydrophobic domains of their macromolecular components are responsible for their formation and for providing a nonpolar environment for the encapsulated guests. However, such interactions are reversible and, as a result, these supramolecular hosts can dissociate into their constituents amphiphiles to release the encapsulated cargo. Operating principles to probe the integrity of the nanocarriers and the dynamic exchange of their components are, therefore, essential to monitor the fate of these supramolecular assemblies in biological media. The co-encapsulation of complementary chromophores within their nonpolar interior offers the opportunity to assess their stability on the basis of energy transfer and fluorescence measurements. Indeed, the exchange of excitation energy between the entrapped chromophores can only occur if the nanoparticles retain their integrity to maintain donors and acceptors in close proximity. In fact, energy-transfer schemes are becoming invaluable protocols to elucidate the transport properties of these fascinating supramolecular constructs in a diversity of biological preparations and can facilitate the identification of strategies to deliver contrast agents and/or drugs to target locations in living organisms for potential diagnostic and/or therapeutic applications. PMID:26589505

  3. Self-assembled nanoscale coordination polymers with trigger release properties for effective anticancer therapy

    NASA Astrophysics Data System (ADS)

    Liu, Demin; Poon, Christopher; Lu, Kuangda; He, Chunbai; Lin, Wenbin

    2014-06-01

    Nanoscale coordination polymers (NCPs) are self-assembled from metal ions and organic bridging ligands, and can overcome many drawbacks of existing drug delivery systems by virtue of tunable compositions, sizes and shapes, high drug loadings, ease of surface modification and intrinsic biodegradability. Here we report the self-assembly of zinc bisphosphonate NCPs that carry 48±3 wt% cisplatin prodrug and 45±5 wt% oxaliplatin prodrug. In vivo pharmacokinetic studies in mice show minimal uptake of pegylated NCPs by the mononuclear phagocyte system and excellent blood circulation half-lives of 16.4±2.9 and 12.0±3.9 h for the NCPs carrying cisplatin and oxaliplatin, respectively. In all tumour xenograft models evaluated, including CT26 colon cancer, H460 lung cancer and AsPC-1 pancreatic cancer, pegylated NCPs show superior potency and efficacy compared with free drugs. As the first example of using NCPs as nanotherapeutics with enhanced antitumour activities, this study establishes NCPs as a promising drug delivery platform for cancer therapy.

  4. Assembly and Characterization of Well Defined High Molecular Weight Poly(p-phenylene) Polymer Brushes

    SciTech Connect

    Alonzo Calderon, Jose E; Kilbey, II, S Michael; Ankner, John Francis; Britt, Phillip F; Chen, Jihua; Dadmun, Mark D; Deng, Suxiang; Hong, Kunlun; Mays, Jimmy; Messman, Jamie M; Sumpter, Bobby; Swader, Onome A; Yu, Xiang; Bredas, Jean-Luc E; Malagoli, Massimo

    2011-01-01

    The assembly and characterization of well-defined, end-tethered poly(p-phenylene) (PPP) brushes having high molecular weight, low polydispersity and high 1,4-stereoregularity are presented. The PPP brushes are formed using a precursor route that relies on either self-assembly or spin coating of high molecular weight (degrees of polymerizations 54, 146, and 238) end-functionalized poly(1,3-cyclohexadiene) (PCHD) chains from benzene solutions onto silicon or quartz substrates, followed by aromatization of the end-attached PCHD chains on the surface. The approach allows the thickness (grafting density) of the brushes to be easily varied. The dry brushes before and after aromatization are characterized by ellipsometry, atomic force microscopy, grazing angle attenuated total reflectance Fourier transform infrared spectroscopy, and UV-Vis spectroscopy. The properties of the PPP brushes are compared with those of films made using oligo-paraphenylenes and with ab initio density functional theory simulations of optical properties. Our results suggest conversion to fully aromatized, end-tethered PPP polymer brushes having effective conjugation lengths of 5 phenyl units.

  5. Long-term biostability of self-assembling protein polymers in the absence of covalent crosslinking.

    PubMed

    Sallach, Rory E; Cui, Wanxing; Balderrama, Fanor; Martinez, Adam W; Wen, Jing; Haller, Carolyn A; Taylor, Jeannette V; Wright, Elizabeth R; Long, Robert C; Chaikof, Elliot L

    2010-02-01

    Unless chemically crosslinked, matrix proteins, such as collagen or silk, display a limited lifetime in vivo with significant degradation observed over a period of weeks. Likewise, amphiphilic peptides, lipopeptides, or glycolipids that self-assemble through hydrophobic interactions to form thin films, fiber networks, or vesicles do not demonstrate in vivo biostability beyond a few days. We report herein that a self-assembling, recombinant elastin-mimetic triblock copolymer elicited minimal inflammatory response and displayed robust in vivo stability for periods exceeding 1 year, in the absence of either chemical or ionic crosslinking. Specifically, neither a significant inflammatory response nor calcification was observed upon implantation of test materials into the peritoneal cavity or subcutaneous space of a mouse model. Moreover, serial quantitative magnetic resonance imaging, evaluation of pre- and post-explant ultrastructure by cryo-high resolution scanning electron microscopy, and an examination of implant mechanical responses revealed substantial preservation of form, material architecture, and biomechanical properties, providing convincing evidence of a non-chemically or ionically crosslinked protein polymer system that exhibits long-term stability in vivo. PMID:19854505

  6. Self-assembled nanoscale coordination polymers with trigger release properties for effective anticancer therapy

    PubMed Central

    Liu, Demin; Poon, Christopher; Lu, Kuangda; He, Chunbai; Lin, Wenbin

    2014-01-01

    Nanoscale coordination polymers (NCPs) are self-assembled from metal ions and organic bridging ligands, and can overcome many drawbacks of existing drug delivery systems by virtue of tunable compositions, sizes, and shapes; high drug loadings; ease of surface modification; and intrinsic biodegradability. Here we report the self-assembly of zinc bisphosphonate NCPs that carry 48±3 wt% cisplatin prodrug and 45±5 wt% oxaliplatin prodrug. In vivo pharmacokinetic studies in mice show minimal uptake of pegylated NCPs by the mononuclear phagocyte system and excellent blood circulation half-lives of 16.4±2.9 and 12.0±3.9 h for the NCPs carrying cisplatin and oxaliplatin, respectively. In all tumor xenograft models evaluated, including CT26 colon cancer, H460 lung cancer, and AsPC-1 pancreatic cancer, pegylated NCPs show superior potency and efficacy compared to free drugs. As the first example of using NCPs as nanotherapeutics with enhanced antitumor activities, this study establishes NCPs as a promising drug delivery platform for cancer therapy. PMID:24964370

  7. Directed Self-Assembly of Block Copolymers in Thin Films on Polymer Nano-Stripes

    NASA Astrophysics Data System (ADS)

    Lee, Dong-Eun; Kang, Ho-Jong; Lee, Dong Hyun; Nano Functional Materials Lab. Team

    In this study, we report directed self-assembly (DSA) of block copolymers in thin films on nano-stripes of polymers. Unique nano-stripes of poly(tetrafluoro ethylene) (PTFE) having ~20 nm of amplitude and ~200 nm of pitch were simply generated by physically rubbing a PTFE bar on various substrates like Si wafers, glass, and polyimide due to its low friction coefficient and high wear rate. The resulting nano-stripes were extremely oriented along the rubbing direction. Then, various asymmetric polystyrene-block-poly(2-vinylpyridine) copolymers (PS- b-P2VP) were directly self-assembled on the nano-stripes of PTFE by solvent-annealing in vapor of tetrahydrofuran (THF). As a result, PS- b-P2VP exhibited extremely ordered P2VP cylinders oriented normal to the surface in large area on the underlying nano-stripes of PTFE. In addition, as utilizing the BCPs as templates, hexagonal arrays of metal nanoparticles were generated in large area for further application. BCP thin films and arrays of metal nanoparticles were characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM).

  8. Polymer-graphene oxide quadlayer thin-film assemblies with improved gas barrier.

    PubMed

    Tzeng, Ping; Stevens, Bart; Devlaming, Ian; Grunlan, Jaime C

    2015-06-01

    Layer-by-layer assembly was used to create quadlayers (QLs) of chitosan (CH), poly(acrylic acid) (PAA), CH, and graphene oxide (GO). Electron microscopy confirmed GO coverage over the film and a highly ordered nanobrick wall structure. By varying pH deviation between CH and PAA, a thick and interdiffused polymer matrix was created because of the altered chain conformation. A 5 CH (pH 5.5)/PAA (pH 3)/CH (pH 5.5)/GO QL assembly (48 nm) exhibits very low oxygen permeability (3.9 × 10(-20) cm(3) cm cm(-2) Pa(-1) s(-1)) that matches SiOx barrier coatings. In an effort to maintain barrier performance under high humidity, GO was thermally reduced to increase hydrophobicity of the film. This reduction step increased H2/CO2 selectivity of a 5 QL film from 5 to 215, exceeding Robeson's upper bound limit. This unique water-based multilayer nanocoating is very promising for a variety of gas purification and packaging applications. PMID:25970136

  9. Self-Assembled Dehydro[24]annulene Monolayers at the Liquid/Solid Interface: Toward On-Surface Synthesis of Tubular π-Conjugated Nanowires.

    PubMed

    Suzuki, Mitsuharu; Guo, Zhaoqi; Tahara, Kazukuni; Kotyk, Juliet F Khosrowabadi; Nguyen, Huan; Gotoda, Jun; Iritani, Kohei; Rubin, Yves; Tobe, Yoshito

    2016-06-01

    We have studied the self-assembly behavior of dehydro[24]annulene (D24A) derivatives 1, 2a-2d, and 3a-3c at the liquid/solid interface using scanning tunneling microscopy (STM). Both the relative placement and the nature of the four D24A substituents strongly influence the self-assembly pattern. Overall, the eight D24A derivatives examined in this study display seven types of 2D packing patterns. The D24A derivatives 1, 2a, and 3a have either two or four stearate groups and adopt face-on configurations of their macrocyclic cores with respect to the highly oriented pyrolytic graphite (HOPG) surface. Their 2D packing pattern is determined by the interchain spacings and number of stearate substituents. The D24A derivatives 2b-2d and 3b-3c bear hydrogen-bonding carbamate groups to further strengthen intermolecular interactions. Face-on patterns were also observed for most of these compounds, while an unstable edge-on self-assembly was observed in the case of 2b at room temperature. Stable edge-on self-assemblies of D24A derivatives were sought for this work as an important stepping stone to achieving the on-surface topochemical polymerization of these carbon-rich macrocycles into tubular π-conjugated nanowires. The overall factors determining the 2D packing patterns of D24As at the liquid/solid interface are discussed on the basis of theoretical simulations, providing useful guidelines for controlling the self-assembly pattern of future D24A macrocycles. PMID:27183003

  10. An automated spin-assisted approach for molecular layer-by-layer assembly of crosslinked polymer thin films

    SciTech Connect

    Chan, Edwin P.; Chung, Jun Young; Stafford, Christopher M.; Lee, Jung-Hyun

    2012-11-15

    We present the design of an automated spin-coater that facilitates fabrication of polymer films based on molecular layer-by-layer (mLbL) assembly. Specifically, we demonstrate the synthesis of ultrathin crosslinked fully-aromatic polyamide (PA) films that are chemically identical to polymer membranes used in water desalination applications as measured by X-ray photoelectron spectroscopy. X-ray reflectivity measurements indicate that the automated mLbL assembly creates films with a constant film growth rate and minimal roughness compared with the traditional interfacial polymerization of PA. This automated spin-coater improves the scalability and sample-to-sample consistency by reducing human involvement in the mLbL assembly.

  11. Improved performance of nanowire-quantum-dot-polymer solar cells by chemical treatment of the quantum dot with ligand and solvent materials

    NASA Astrophysics Data System (ADS)

    Nadarajah, A.; Smith, T.; Könenkamp, R.

    2012-12-01

    We report a nanowire-quantum-dot-polymer solar cell consisting of a chemically treated CdSe quantum dot film deposited on n-type ZnO nanowires. The electron and hole collecting contacts are a fluorine-doped tin-oxide/zinc oxide layer and a P3HT/Au layer. This device architecture allows for enhanced light absorption and an efficient collection of photogenerated carriers. A detailed analysis of the chemical treatment of the quantum dots, their deposition, and the necessary annealing processes are discussed. We find that the surface treatment of CdSe quantum dots with pyridine, and the use of 1,2-ethanedithiol (EDT) ligands, critically improves the device performance. Annealing at 380 °C for 2 h is found to cause a structural conversion of the CdSe from its initial isolated quantum dot arrangement into a polycrystalline film with excellent surface conformality, thereby resulting in a further enhancement of device performance. Moreover, long-term annealing of 24 h leads to additional increases in device efficiency. Our best conversion efficiency reached for this type of cell is 3.4% under 85 mW cm-2 illumination.

  12. Reliability of high strain ionomeric polymer transducers fabricated using the direct assembly process

    NASA Astrophysics Data System (ADS)

    Akle, Barbar; Nawshin, Saila; Leo, Donald

    2007-04-01

    Ionomeric polymer transducers have received considerable attention in the past several years. These actuators, sometimes referred to as artificial muscles, have the ability to generate large bending strain and moderate stress at low applied voltages. As sensors, ionic polymer transducers generate an electric response due to mechanical strain. Typically, ionic polymer transducers are composed of Nafion-117 membranes with platinum electrodes and are saturated with water diluents. Recently the authors have developed a novel fabrication technique called the direct assembly process (DAP), which allowed improved control of the electrode morphology and composition. The DAP consists of spraying two high surface area metal-ionomer electrodes on a Nafion membrane. The benefits of the DAP process over previous methods is the ability to control the thickness of the electrode, the ability to control the composition of the electrode layer of the transducer, and the ability for it to be used with a wide variety of diluents. In past work we have demonstrated that platinum, ruthenium dioxide, and single-walled carbon nanotubes can be used as electrode material with diluents such as water, formamide, and ionic liquids. In this work we will present a reliability study of transducers fabricated using the DAP. Water-hydrated transducers dehydrate and stop moving within 5 min while operating in air under the application of ± 2 V. Ionic liquid based transducers are demonstrated to operate in air for over 400 000 cycles with little loss in performance, and are reliable up to 1 million cycles with a performance loss of less than 43%. The main source of degradation is the adhesion of the conductive surface to the high surface area electrode. This is enhanced in this study by using a PUU linking polymer that has good adhesion properties to gold. Large voltage and large strain are proven to decrease the life of the transducer. Formamide based samples are stable for 3 days under a 1 V

  13. Superhydrophobic Thin Films Fabricated by Reactive Layer-by-Layer Assembly of Azlactone-Functionalized Polymers

    PubMed Central

    Buck, Maren E.; Schwartz, Sarina C.

    2010-01-01

    We report an approach to the fabrication of superhydrophobic thin films that is based on the ‘reactive’ layer-by-layer assembly of azlactone-containing polymer multilayers. We demonstrate that films fabricated from alternating layers of the azlactone functionalized polymer poly(2-vinyl-4,4-dimethylazlactone) (PVDMA) and poly(ethyleneimine) (PEI) exhibit micro- and nanoscale surface features that result in water contact angles in excess of 150º. Our results reveal that the formation of these surface features is (i) dependent upon film thickness (i.e., the number of layers of PEI and PVDMA deposited) and (ii) that it is influenced strongly by the presence (or absence) of cyclic azlactone-functionalized oligomers that can form upon storage of the 2-vinyl-4,4-dimethylazlactone (VDMA) used to synthesize PVDMA. For example, films fabricated using polymers synthesized in the presence of these oligomers exhibited rough, textured surfaces and superhydrophobic behavior (i.e., advancing contact angles in excess of 150º). In contrast, films fabricated from PVDMA polymerized in the absence of this oligomer (e.g., using freshly distilled monomer) were smooth and only moderately hydrophobic (i.e., advancing contact angles of ~75º). The addition of authentic, independently synthesized oligomer to samples of distilled VDMA at specified and controlled concentrations permitted reproducible fabrication of superhydrophobic thin films on the surfaces of a variety of different substrates. The surfaces of these films were demonstrated to be superhydrophobic immediately after fabrication, but they became hydrophilic after exposure to water for six days. Additional experiments demonstrated that it was possible to stabilize and prolong the superhydrophobic properties of these films (e.g., advancing contact angles in excess of 150° even after complete submersion in water for at least six weeks) by exploiting the reactivity of residual azlactones to functionalize the surfaces of the

  14. Development and study of high-Tc superconductor conductive polymer assemblies

    NASA Astrophysics Data System (ADS)

    Schougaard, Steen Brian

    2002-01-01

    This dissertation presents the development and study of organic polymeric conductor/High-Tc superconductor bilayers, for exploration of the superconductor proximity effect. A major obstacle to this research is the instability of the High-Tc superconductor towards H2O and CO2 as it is necessary to create hybrid structures where the two conductors have intimate contact. For this reason, a study of the corrosion characteristics of the RBa2Cu3O 7 (R=Y, Eu, Nd) series was undertaken. In this study, R=Nd was shown to have enhanced corrosion resistance. In an effort to develop chemical processing methods that allow for the production of intimate contact between the cuprate superconductor and the conductive polymer systems, a study of alkyl amine adsorbed onto the surface of the superconductor is presented. In the electrochemical part of the study, alkyl amine ferrocene adsorbed onto the surface revealed that the amines are strongly adhered to the superconductor while still allowing electrons to pass from the superconductor to the ferrocene moiety. The self-assembled monolayer (SAM) structure of CF3(CF2)3(CH2) 11NH2 atop the superconductor was elucidated by employing several techniques, including atomic scale atomic force microscopy (AFM). A novel multistep bilayer sample preparation protocol is presented involving thin film fabrication by pulsed laser deposition (PLD), patterning by shadow mask ablation, sample thinning by scanning probe and electropolymerization of the polymer. Scanning probe thinning yields a smooth superconductor surface, a known superconductor thickness, and if a blocking layer is employed prior to thinning, the localization of polymer growth. Studies of the response of a bilayer structure of Y0.6Ca 0.4Ba1.6La0.4 Cu3O7/poly pyrrole to polymer redox cycling showed a semi-reversible suppression of transition temperature qualitatively consistent with a combination of corrosion and superconductor proximity effect. Quantitative analysis in the framework of

  15. Nanowire sensors and arrays for chemical/biomolecule detection

    NASA Technical Reports Server (NTRS)

    Yun, Minhee; Lee, Choonsup; Vasquez, Richard P.; Ramanathan, K.; Bangar, M. A.; Chen, W.; Mulchandan, A.; Myung, N. V.

    2005-01-01

    We report electrochemical growth of single nanowire based sensors using e-beam patterned electrolyte channels, potentially enabling the controlled fabrication of individually addressable high density arrays. The electrodeposition technique results in nanowires with controlled dimensions, positions, alignments, and chemical compositions. Using this technique, we have fabricated single palladium nanowires with diameters ranging between 75 nm and 300 nm and conducting polymer nanowires (polypyrrole and polyaniline) with diameters between 100 nm and 200 nm. Using these single nanowires, we have successfully demonstrated gas sensing with Pd nanowires and pH sensing with polypirrole nanowires.

  16. Nanowires: A Nonconventional Approach to Patterned Nanoarrays of DNA Strands for Template-Assisted Assembly of Polyfluorene Nanowires (Small 31/2016).

    PubMed

    Bae, Dong Geun; Jeong, Ji-Eun; Kang, Seok Hee; Byun, Myunghwan; Han, Dong-Wook; Lin, Zhiqun; Woo, Han Young; Hong, Suck Won

    2016-08-01

    A simple yet robust strategy is developed to yield the self-assembly of DNA by exploiting controlled stick-slip motions and "coffee ring" effect of DNA solutions in a unique confined geometry, as H. Y. Woo, S. W. Hong, and co-workers report on page 4254. A number of highly ordered concentric ring-like superstructures composed of DNA are spontaneously formed, which can be employed as a "template" to tightly organize cationic conjugated polyelectrolytes alongside the DNA strands. PMID:27510363

  17. Simultaneous nano- and micro-scale control of nanofibrous microspheres self-assembled from star-shaped polymers

    PubMed Central

    Zhang, Zhanpeng; Marson, Ryan L.; Ge, Zhishen; Glotzer, Sharon C.; Ma, Peter X.

    2015-01-01

    The mechanism underlying the multi-scale self-assembly of star-shaped polymers into non-hollow, hollow, and spongy nanofibrous microspheres is reported. Star-shaped poly(L-lactic acid) polymers with varying arm-numbers and arm-lengths are synthesized, dissolved in tetrahydrofuran, emulsified in glycerol, and thermally-induced to phase separate, resulting in microspheres that are either smooth or fibrous on the nano-scale, and either non-hollow, hollow, or spongy on the micro-scale. Molecular architecture and the hydroxyl density are shown to control assembly and morphology at both nano- and micro-scales. Nanofibers form only when the arm length is sufficiently long, while an increase in hydroxyl density causes the microspheres to change from non-hollow to hollow to spongy. We demonstrate via both experiments of capping or doubling the hydroxyl end groups and dissipative particle dynamics simulations that the affinity of hydroxyl to glycerol is critical to stabilizing the micro-scale structure. A “phase diagram” was constructed for the six types of microspheres in relation to the molecular structures of the star-shaped polymers. The proposed mechanism explains how star-shaped polymers self-assemble into various microspheres, and guides us to simultaneously control both nano- and micro-features of the microspheres. PMID:26009995

  18. Thermo-reversible morphology and conductivity of a conjugated polymer network embedded in polymeric self-assembly

    NASA Astrophysics Data System (ADS)

    Han, Youngkyu; Carrillo, Jan-Michael Y.; Zhang, Zhe; Li, Yunchao; Hong, Kunlun; Sumpter, Bobby G.; Ohl, Michael; Paranthaman, Mariappan Parans; Smith, Gregory S.; Do, Changwoo

    Self-assembly of block copolymers provides opportunities to create nano hybrid materials, utilizing self-assembled micro-domains with a variety of morphology and periodic architectures as templates for functional nano-fillers. Here we report new progress towards the fabrication of a thermally responsive conducting polymer self-assembly made from a water-soluble poly(thiophene) derivative with short PEO side chains and Pluronic L62 solution in water. The structural and electrical properties of conjugated polymer-embedded nanostructures were investigated by combining SANS, SAXS, CGMD simulations, and impedance spectroscopy. The L62 solution template organizes the conjugated polymers by stably incorporating them into the hydrophilic domains thus inhibiting aggregation. The changing morphology of L62 during the micellar-to-lamellar phase transition defines the embedded conjugated polymer network. The conductivity is strongly coupled to the structural change of the templating L62 phase and exhibits thermally reversible behavior with no signs of quenching of the conductivity at high temperature. The research was sponsored by the Scientific User Facilities Division, Office of BES, U.S. DOE and Laboratory Directed Research and Development Program of ORNL, managed by UT-Battelle, LLC.

  19. Surface-Directed Assembly of Sequence-Defined Synthetic Polymers into Networks of Hexagonally Patterned Nanoribbons with Controlled Functionalities.

    PubMed

    Chen, Chun-Long; Zuckermann, Ronald N; DeYoreo, James J

    2016-05-24

    The exquisite self-assembly of proteins and peptides in nature into highly ordered functional materials has inspired innovative approaches to the design and synthesis of biomimetic materials. While sequence-defined polymers hold great promise to mimic proteins and peptides for functions, controlled assembly of them on surfaces still remains underdeveloped. Here, we report the assembly of 12-mer peptoids containing alternating acidic and aromatic monomers into networks of hexagonally patterned nanoribbons on mica surfaces. Ca(2+)-carboxylate coordination creates peptoid-peptoid and peptoid-mica interactions that control self-assembly. In situ atomic force microscopy (AFM) shows that peptoids first assemble into discrete nanoparticles; these particles then transform into hexagonally patterned nanoribbons on mica surfaces. AFM-based dynamic force spectroscopy studies show that peptoid-mica interactions are much stronger than peptoid-peptoid interactions, illuminating the driving forces for mica-directed peptoid assembly. We further demonstrate the display of functional domains at the N-terminus of assembling peptoids to produce extended networks with similar hierarchical structures. This research demonstrates that surface-directed peptoid assembly can be used as a robust platform to develop biomimetic coating materials for applications. PMID:27136277

  20. RF/Microwave properties and applications of directly assembled nanotubes and nanowires: LDRD project 102662 final report.

    SciTech Connect

    Mayer, Theresa (The Pennyslvania State University, University Park, PA 16802); Vallett, Aaron (The Pennyslvania State University, University Park, PA 16802); Lee, Mark; Shaner, Eric Arthur; Jones, Frank E.; Talin, Albert Alec; Highstrete, Clark

    2006-11-01

    LDRD Project 102662 provided support to pursue experiments aimed at measuring the basic electrodynamic response and possible applications of carbon nanotubes and silicon nanowires at radiofrequency to microwave frequencies, approximately 0.01 to 50 GHz. Under this project, a method was developed to integrate these nanomaterials onto high-frequency compatible co-planar waveguides. The complex reflection and transmission coefficients of the nanomaterials was studied as a function of frequency. From these data, the high-frequency loss characteristics of the nanomaterials were deduced. These data are useful to predict frequency dependence and power dissipation characteristics in new rf/microwave devices incorporating new nanomaterials.

  1. Cobalt oxide 2D nano-assemblies from infinite coordination polymer precursors mediated by a multidentate pyridyl ligand.

    PubMed

    Li, Guo-Rong; Xie, Chen-Chao; Shen, Zhu-Rui; Chang, Ze; Bu, Xian-He

    2016-05-01

    In this work, the construction of Co3O4 two dimensional (2D) nano-assemblies utilizing infinite coordination polymers (ICPs) as precursors was investigated, aiming at the morphology targeted fabrication and utilization of 2D materials. Based on the successful modulation of morphology, a rose-like Co based ICP precursor was obtained, which was further transformed into porous Co3O4 nanoflake assemblies with a well-preserved 2D morphology and a large surface area. The mechanism of the morphology modulation was illustrated by systematic investigation, which demonstrated the crucial role of a modulating agent in the formation of 2D nano-assemblies. In addition, the cobalt oxide 2D nano-assemblies are fabricated into a lithium anode combined with graphene, and the remarkable capacity and stability (900 mA h g(-1) after 50 cycles) of the resulting Co3O4/G nanocomposite indicates its potential in lithium battery applications. PMID:27064264

  2. Fabrication of interdigitated micropatterns of self-assembled polymer nanofilms containing cell-adhesive materials.

    PubMed

    Shaikh Mohammed, Javeed; Decoster, Mark A; McShane, Michael J

    2006-03-14

    Micropatterns of different biomaterials with micro- and nanoscale features and defined spatial arrangement on a single substrate are useful tools for studying cellular-level interactions, and recent reports have highlighted the strong influence of scaffold compliance in determining cell behavior. In this paper, a simple yet versatile and precise patterning technique for the fabrication of interdigitated micropatterns of nanocomposite multilayer coatings on a single substrate is demonstrated through a combination of lithography and layer-by-layer (LbL) assembly processes, termed polymer surface micromachining (PSM). The first nanofilm pattern is constructed using lithography, followed by LbL multilayer assembly and lift-off, and the process is repeated with optical alignment to obtain interdigitated patterns on the same substrate. Thus, the method is analogous to surface micromachining, except that the deposition materials are polymers and biological materials that are used to produce multilayer nanocomposite structures. A key feature of the multilayers is the capability to tune properties such as stiffness by appropriate selection of materials, deposition conditions, and postdeposition treatments. Two- and four-component systems on glass coverslips are presented to demonstrate the versatility of the approach to construct precisely defined, homogeneous nanofilm patterns. In addition, an example of a complex system used as a testbed for in vitro cell adhesion and growth is provided: micropatterns of poly(sodium 4-styrenesulfonate)/poly-L-lysine hydrobromide (PSS/PLL) and secreted phospholipase A(2)/poly(ethyleneimine) (sPLA(2)/PEI) multilayers. The interdigitated square nanofilm array patterns were obtained on a single coverslip with poly(diallyldimethylammonium chloride) (PDDA) as a cell-repellent background. Cell culture experiments show that cortical neurons respond and bind specifically to the sPLA(2) micropatterns in competition with PLL micropatterns. The

  3. Hierarchical Polymer-Carbon Nanotube Hybrid Mesostructures by Crystallization-Driven Self-Assembly.

    PubMed

    Jia, Lin; Petretic, Amy; Molev, Gregory; Guerin, Gerald; Manners, Ian; Winnik, Mitchell A

    2015-11-24

    Multistep crystallization-driven self-assembly has great potential to enable the construction of sophisticated hybrid mesostructures. During the assembly procedure, each step modifies the properties of the overall structure. Here, we demonstrate the flexibility and efficiency of this approach by preparing polymer-carbon nanotube (CNT) hybrid mesostructures. We started by growing polyferrocenyldimethylsilane (PFS) homopolymer crystals onto multiwalled CNTs. This first step facilitated the redispersion of the coated CNTs in both polar (2-propanol) and nonpolar (decane) solvents. In the second step of hybrid construction, a unimer solution of a PFS block copolymer was added into the PFS-CNT solution. The PFS coating on the CNT initiated the growth of elongated micelles, resulting in structures that resembled hairy caterpillars. PFS-b-P2VP (P2VP = poly-2-vinylpyridine) micelles were grown from the surface of PFS-CNT hybrids in 2-propanol, and PFS-b-PI (PI = polyisoprene) micelles were grown from these hybrids in decane. These micelles, by transmission electron microscopy were seen to have an unusual wavy kinked structure, very different from the uniform smooth structures normally formed by both block copolymers. For hybrids with PFS-b-PI micelles, cross-linking of the micelle coronas locked the whole structure in place and allowed us to use the partial oxidation of PFS components to grow metal nanoparticles in the core of these micelles. We finally investigated the influence of the corona-forming block used to grow the micelles on the wettability of films made from these mesostructures. Films formed with CNT hybrids grafted with PFS-b-PI micelles were superhydrophobic (contact angle, 152°). In contrast, the surface of the films was much more hydrophilic (contact angle, 54°) when they were prepared from CNT hybrids grafted with PFS-b-P2VP micelles. PMID:26418346

  4. Morphology-tunable assembly of periodically aligned Si nanowire and radial pn junction arrays for solar cell applications

    NASA Astrophysics Data System (ADS)

    Li, Xiaocheng; Liang, Kun; Tay, Beng Kang; Teo, Edwin H. T.

    2012-06-01

    Large-area periodically aligned Si nanowire (PASiNW) arrays have been fabricated on Si substrates via a templated catalytic chemical etching process. The diameter, length, packing density, and even the shape of Si nanowires (SiNWs) could be precisely controlled and tuned. A local coupling redox mechanism involving the reduction of H2O2 on silver particles and the dissolution of Si is responsible for formation of SiNWs. With the as-prepared SiNWs as templates, three kinds of PASiNW radial pn junction structures were fabricated on Si substrates via a solid-state phosphorous diffusion strategy and their applications in solar cells were also explored. The PASiNW radial pn junction-based solar cell with big diameter and interspace shows the highest power conversion efficiency (PCE) of 4.10% among the three kinds of devices. Further optimization, including surface passivation and electrode contact, is still needed for the higher efficiency PASiNW radial pn junction-based solar cells in the future.

  5. Pulse electrodeposition and electrochemical quartz crystal microbalance techniques for high perpendicular magnetic anisotropy cobalt nanowire arrays

    NASA Astrophysics Data System (ADS)

    Ursache, Andrei; Goldbach, James T.; Russell, Thomas P.; Tuominen, Mark T.

    2005-05-01

    This research is focused on the development of pulse electrodeposition techniques to fabricate a high-density array of vertically oriented, high-magnetic anisotropy cobalt nanowires using a porous polymer film template. This type of array is a competitive candidate for future perpendicular magnetic media capable of storage densities exceeding 1Terabit/in.2 The polymer template, derived from a self-assembling P(S-b-MMA) diblock copolymer film, provides precise control over the nanowire diameter (15nm) and interwire spacing (24nm), whereas nanowire length (typically 50to1000nm) is controlled accurately with the aid of real-time electrochemical quartz crystal monitoring. Pulse and pulse-reversed electrodeposition techniques, as compared to dc, are shown to significantly enhance the perpendicular magnetic anisotropy of the magnetic nanowire array and ultimately result in coercivity as large as 2.7kOe at 300K. Magnetic and structural characterizations suggest that these properties arise from an improved degree of magnetocrystalline anisotropy (due to c-axis oriented crystal growth and improvements in crystal quality) that strongly supplements the basic shape anisotropy of the nanowires. Low temperature magnetometry is used to investigate exchange bias effects due to the incorporation of CoO antiferromagnetic impurities during the electrodeposition process and subsequent Co oxidation in air.

  6. Pulse electrodeposition and electrochemical quartz crystal microbalance techniques for high perpendicular magnetic anisotropy cobalt nanowire arrays

    SciTech Connect

    Ursache, Andrei; Goldbach, James T.; Russell, Thomas P.; Tuominen, Mark T.

    2005-05-15

    This research is focused on the development of pulse electrodeposition techniques to fabricate a high-density array of vertically oriented, high-magnetic anisotropy cobalt nanowires using a porous polymer film template. This type of array is a competitive candidate for future perpendicular magnetic media capable of storage densities exceeding 1 Terabit/in.{sup 2} The polymer template, derived from a self-assembling P(S-b-MMA) diblock copolymer film, provides precise control over the nanowire diameter (15 nm) and interwire spacing (24 nm), whereas nanowire length (typically 50 to 1000 nm) is controlled accurately with the aid of real-time electrochemical quartz crystal monitoring. Pulse and pulse-reversed electrodeposition techniques, as compared to dc, are shown to significantly enhance the perpendicular magnetic anisotropy of the magnetic nanowire array and ultimately result in coercivity as large as 2.7 kOe at 300 K. Magnetic and structural characterizations suggest that these properties arise from an improved degree of magnetocrystalline anisotropy (due to c-axis oriented crystal growth and improvements in crystal quality) that strongly supplements the basic shape anisotropy of the nanowires. Low temperature magnetometry is used to investigate exchange bias effects due to the incorporation of CoO antiferromagnetic impurities during the electrodeposition process and subsequent Co oxidation in air.

  7. Nanoparticle/Polymer assembled microcapsules with pH sensing property.

    PubMed

    Zhang, Pan; Song, Xiaoxue; Tong, Weijun; Gao, Changyou

    2014-10-01

    The dual-labeled microcapsules via nanoparticle/polymer assembly based on polyamine-salt aggregates can be fabricated for the ratiometric intracellular pH sensing. After deposition of SiO2 nanoparticles on the poly(allylamine hydrochloride)/multivalent anionic salt aggregates followed by silicic acid treatment, the generated microcapsules are stable in a wide pH range (3.0 ∼ 8.0). pH sensitive dye and pH insensitive dye are simultaneously labeled on the capsules, which enable the ratiometric pH sensing. Due to the rough and positively charged surface, the microcapsules can be internalized by several kinds of cells naturally. Real-time measurement of intracellular pH in several living cells shows that the capsules are all located in acidic organelles after being taken up. Furthermore, the negatively charged DNA and dyes can be easily encapsulated into the capsules via charge interaction. The microcapsules with combination of localized pH sensing and drug loading abilities have many advantages, such as following the real-time transportation and processing of the carriers in cells. PMID:25081194

  8. Responsive Hydrogels and Ion Gels by Self-Assembly of ABA and ABC Triblock Polymers

    NASA Astrophysics Data System (ADS)

    Lodge, Timothy

    2014-03-01

    Gels - polymeric networks swollen with a substantial amount of solvent - represent a fascinating class of soft materials, with wide-ranging applications in fields as diverse as biomedicine, pharmaceutics, personal care products, foods, sensors, actuators, flexible electronics, oil recovery, and adhesives. Physical gels are held together by non-covalent interactions, which may be as specific as hydrogen bonds, or as general as solvophobic association of insoluble blocks. Among the attractive features of physical gels are reversibility, stimuli-responsiveness, and tunability of macroscopic properties. In this talk two classes of physical gels will be highlighted. In one, the ability of ABC block terpolymers to form novel structures will be demonstrated, where blocks A and C are mutually immiscible and solvophobic, while B is solvophilic. In particular, the formation of gels by sequential association (first A, then C) leads to a remarkably sharp gelation transition, at a relatively low polymer concentration, compared to analogous gels formed from ABA systems. In the second class, gels formed by self-assembly of a variety of ABA systems in ionic liquids will be described, and in particular how gelation can be controlled through factors such as block chemistry, temperature, choice of ionic liquid, and application of light.

  9. Expanded experimental parameter space of semiflexible polymer assemblies through programmable nanomaterials

    NASA Astrophysics Data System (ADS)

    Smith, David; Schuldt, Carsten; Lorenz, Jessica; Tschirner, Teresa; Moebius-Winkler, Maximilian; Kaes, Josef; Glaser, Martin; Haendler, Tina; Schnauss, Joerg

    2015-03-01

    Biologically evolved materials are often used as inspiration in the development of new materials as well as examinations into the underlying physical principles governing their behavior. For instance, the biopolymer constituents of the highly dynamic cellular cytoskeleton such as actin have inspired a deep understanding of soft polymer-based materials. However, the molecular toolbox provided by biological systems has been evolutionarily optimized to carry out the necessary functions of cells, and the inability modify basic properties such as biopolymer stiffness hinders a meticulous examination of parameter space. Using actin as inspiration, we circumvent these limitations using model systems assembled from programmable materials such as DNA. Nanorods with comparable, but controllable dimensions and mechanical properties as actin can be constructed from small sets of specially designed DNA strands. In entangled gels, these allow us to systematically determine the dependence of network mechanical properties on parameters such as persistence length and crosslink strength. At higher concentrations in the presence of local attractive forces, we see a transition to highly-ordered bundled and ``aster'' phases similar to those previously characterized in systems of actin or microtubules.

  10. Effect of nanoparticle polydispersity on the self-assembly of polymer tethered nanospheres.

    PubMed

    Phillips, Carolyn L; Glotzer, Sharon C

    2012-09-14

    Recent simulations predict that aggregating nanospheres functionalized with polymer "tethers" can self-assemble to form a cylinder, perforated lamellae, lamellae, and even the double gyroid phase, which are phases also seen in block copolymer and surfactant systems. Nanoparticle size polydispersity is likely to be a characteristic of these systems. If too high, polydispersity may destabilize a phase. Using multiple thermodynamic paths to explore the phase diagram as a function of temperature and polydispersity, we explore the effect of nanosphere size polydispersity on the phase diagram. We show that in the portions of the phase diagram characterized by an icosahedral local nanoparticle packing motif, a low amount of polydispersity lowers the energy and a large amount of polydispersity raises the energy of the system by disrupting the icosahedral packing. In general, regions of the phase diagram characterized by liquid-like icosahedral packing have high terminal polydispersities from 15% to more than 30%. In the regions of the phase diagram characterized by crystalline local packing, polydispersity raises the energy of the system and induces a phase transition from crystalline to liquid-like ordering within the nanosphere rich regions of the microphase. We find the bilayer crystalline lamellae phase has a terminal polydispersity of 6%, but may still be partially crystalline up to 12%. PMID:22979884

  11. Molecular self-assembly of conducting polymer by Conducting Probe Technique in Atomic Force Microscope

    NASA Astrophysics Data System (ADS)

    Yamamoto, Shin-ichi; Ogawa, Kazufumi

    2007-04-01

    A polypyrrole derivative monolayer was investigated for the application as a wire. First, a pyrrole derivative monolayer was prepared by chemically adsorbing (self-assembling) monolayer (CAM) of 6-pyrrolylhexyl-12,12,12-trichloro-12- siladodecanoate (PEN) on a glass substrate. Then, the monolayer was polymerized in the presence of pure water by electrooxidation. The surface characterization of the molecular interaction was investigated by measuring the properties of CAMs attached to the glass substrate in the lateral direction. We formed PEN having polypyrrolyl groups, using Pt-patterned electrodes on glass surfaces and measured the conductance under a small bias voltage, using a conductive cantilever of atomic force microscopy (AFM). The polypyrrole derivative monolayer thus synthesized was covalently bonded to the glass substrate and showed conductivity as high as 3.05..103 S/cm after electro-oxidized. The method of preparing a conductive polymer monolayer by the combining chemical adsorption and electro-oxidation leads to a lot molecular wire to perpendicular to the Pt electrodes, and it is one of the key technologies for molecular devices.

  12. Covalent layer-by-layer assembly of hyperbranched polymers on alginate microcapsulesto impart stability and permselectivity.

    PubMed

    Gattás-Asfura, Km; Valdes, M; Celik, E; Stabler, Cl

    2014-12-14

    The microencapsulation of cells has shown promise as a therapeutic vehicle for the treatment of a wide variety of diseases. While alginate microcapsules provide an ideal cell encapsulation material, polycations coatings are commonly employed to enhance stability and impart permselectivity. In this study, functionalized hyperbranched alginate and dendrimer polymers were used to generate discreet nanoscale coatings onto alginate microbeads via covalent layer-by-layer assembly. The bioorthogonal Staudinger ligation scheme was used to chemoselectively crosslink azide functionalized hyperbranched alginate (alginate-hN3) to methyl-2-diphenylphosphino-terephthalate (MDT) linked PAMAM dendrimer (PAMAM-MDT). Covalent layer-by-layer deposition of PAMAM-MDT/alginate-hN3 coatings onto alginate microbeads resulted in highly stable coatings, even after the inner alginate gel was liquefied to form microcapsules. The permselectivity of the coated microcapsules could be manipulated via the charge density of the PAMAM, the number of layers deposited, and the length of the functional arms. The cytocompatibility of the resulting PAMAM-MDT/alginate-hN3 coating was evaluated using a beta cell line, with no significant detrimental response observed. The biocompatibility of the coatings in vivo was also found comparable to uncoated alginate beads. The remarkable stability and versatile nature of these coatings provides an appealing option for bioencapsulation and the release of therapeutic agents. PMID:25478165

  13. Lithium-ion polymer cells assembled with a reactive composite separator containing vinyl-functionalized SiO2 particles

    NASA Astrophysics Data System (ADS)

    Yoo, Ji-Hyun; Shin, Won-Kyung; Koo, Sang Man; Kim, Dong-Won

    2015-11-01

    Vinyl-functionalized SiO2 particles of different sizes are synthesized and coated onto both sides of a polyethylene separator to prepare a reactive composite separator for lithium-ion polymer cells. The SiO2-coated composite separators exhibit excellent thermal stability due to the presence of heat-resistant silica particles. By using these reactive composite separators and a gel electrolyte precursor, lithium-ion polymer cells composed of a graphite negative electrode and a LiNi1/3Co1/3Mn1/3O2 positive electrode are assembled by in-situ chemical cross-linking, and their cycling performance is evaluated. The cells assembled with a reactive composite separator exhibit superior cycling performance to cell prepared with a conventional polyethylene separator due to the strong interfacial adhesion between the electrodes and separator, as well as suppression of deleterious reactions during cycling.

  14. Purification and processing of carbon nanotubes using self-assembly and selective interaction with a semiconjugated polymer

    NASA Astrophysics Data System (ADS)

    Fournet, Patrick; McCarthy, Brendan; Dalton, Alan B.; Coleman, Jonathan N.; Murphy, Robert J.; Stephan, Christophe; Lefrant, Serge; Bernier, Patrick; Byrne, Hugh J.; Blau, Werner J.

    2001-12-01

    A new route for nanotube-based applications in molecular electronics was developed. Individual polymer strands were assembled onto single-walled carbon nanotubes (SWNT) and multi-walled carbon nanotubes (MWNT) by mechanical agitation. The SWNT hybrid systems have been characterized by electron microscopy (TEM, STM), optical absorption and Raman spectroscopy and a fully nondestructive technique, using electron paramagnetic resonance (EPR), has been developed to estimate the purity of MWNT soot and hybrids. It is demonstrated that solutions of the polymer are capable of suspending nanotubes indefinitely while the majority of the accompanying amorphous graphite precipitates out of solution. Electron microscopy and Raman scattering indicate that through an intercalation process, the ropes of SWNT are destroyed, resulting in individual nanotubes being well dispersed within the polymer matrix. Moreover, Raman and absorption studies suggest that the polymer interacts preferentially with nanotubes of specific diameters or a range of diameters. STM studies showed that the chiral angle of the underlying nanotube is reflected in the polymer coating, demonstrating that the lattice structure of the SWNT templates the ordering in the coating. This could lead to design of specific polymer architectures for selection of desired chiral angles, and hence specific electronic properties.

  15. Nanowire sensors for multiplexed detection of biomolecules

    PubMed Central

    He, Bo; Morrow, Thomas J; Keating, Christine D

    2009-01-01

    Nanowire-based detection strategies provide promising new routes to bioanalysis that could one day revolutionize the healthcare industry. This review covers recent developments in nanowire sensors for multiplexed detection of biomolecules such as nucleic acids and proteins. We focus on encoded nanowire suspension arrays and semiconductor nanowire-based field-effect transistors. Nanowire assembly and integration with microchip technology is emphasized as a key step toward the ultimate goal of multiplexed detection at the point of care using portable, low power, electronic biosensor chips. PMID:18804551

  16. Self-Assembly of Telechelic Tyrosine End-Capped PEO and Poly(alanine) Polymers in Aqueous Solution.

    PubMed

    Kirkham, Steven; Castelletto, Valeria; Hamley, Ian William; Reza, Mehedi; Ruokolainen, Janne; Hermida-Merino, Daniel; Bilalis, Panayiotis; Iatrou, Hermis

    2016-03-14

    The self-assembly in aqueous solution of three novel telechelic conjugates comprising a central hydrophilic polymer and short (trimeric or pentameric) tyrosine end-caps has been investigated. Two of the conjugates have a central poly(oxyethylene) (polyethylene oxide, PEO) central block with different molar masses. The other conjugate has a central poly(L-alanine) (PAla) sequence in a purely amino-acid based conjugate. All three conjugates self-assemble into β-sheet based fibrillar structures, although the fibrillar morphology revealed by cryogenic-TEM is distinct for the three polymers--in particular the Tyr5-PEO6k-Tyr5 forms a population of short straight fibrils in contrast to the more diffuse fibril aggregates observed for Tyr5-PEO2k-Tyr5 and Tyr3-PAla-Tyr3. Hydrogel formation was not observed for these samples (in contrast to prior work on related systems) up to quite high concentrations, showing that it is possible to prepare solutions of peptide-polymer-peptide conjugates with hydrophobic end-caps without conformational constraints associated with hydrogelation. The Tyr5-PEO6k-Tyr5 shows significant PEO crystallization upon drying in contrast to the Tyr5-PEO2k-Tyr5 conjugate. Our findings point to the remarkable ability of short hydrophobic peptide end groups to modulate the self-assembly properties of polymers in solution in model peptide-capped "associative polymers". Retention of fluidity at high conjugate concentration may be valuable in potential future applications of these conjugates as bioresponsive or biocompatible materials, for example exploiting the enzyme-responsiveness of the tyrosine end-groups. PMID:26867986

  17. Enantioselective assembly of amphipathic chiral polymer and racemic chiral small molecules during preparation of micro-scale polymer vesicles.

    PubMed

    Wang, Yingjue; Zhuang, Yiwei; Gao, Jiangang; Zou, Gang; Zhang, Qijin

    2016-03-14

    Enantioselective assembly is observed during preparation of vesicles from a solution mixture of an amphipathic block copolymer bearing pendent chiral l- or d-phenylalanine groups in hydrophobic segments and racemic chiral small molecules. Primary experimental results reveal that racemic chiral small molecules have been enantioselectively encapsulated into the hydrophobic shells of assembled vesicles with homochiral bilayer membrane structure, showing reverse CD signals compared with the original vesicles. A further study shows that the enantiomeric excess obtained through the enantioselective assembly is directly dependent on the molecular weight of the hydrophobic chiral chain segments, implying both the hydrophobic interaction and chirality are key points during the assembly of vesicles. Other factors, such as hydrogen-bonding interactions and π-π stacking interaction, are also found to be responsible for the enantioselective assembly phenomenon during the formation of the vesicles. PMID:26853976

  18. Strong enhancement of optical absorbance from ionic self-assembled multilayer thin films of nanocluster Pt and polymer dye

    NASA Astrophysics Data System (ADS)

    Liu, Yanjing; Claus, Richard O.

    1999-01-01

    The observation of unusually enhanced optical absorbance spectra of ionic self assembled multilayer (ISAM) thin films composed of alternating layers of Pt nanoclusters (<1 nm dimension) and polymer dye is reported. The first bilayer absorbance is found to be considerably larger than that of several succeeding bilayers even though there is no difference in composition for each bilayer. A layer-by-layer-dependent redshift in maximum wavelength position due to the strong coupling of metals and polymer molecules is observed. The saturation absorption is obtained for the first time when the required thickness of the ISAM film is deposited. The large and unusual enhancement effects are attributed to both the charge-transfer mechanism and very large local fields and collective phenomena near the surface of the small metal clusters/electrolytes and at the interfaces between the cluster/polymer multilayers.

  19. Self-Assembled ROS-Sensitive Polymer-Peptide Therapeutics Incorporating Built-in Reporters for Evaluation of Treatment Efficacy.

    PubMed

    Qiao, Zeng-Ying; Zhao, Wen-Jing; Cong, Yong; Zhang, Di; Hu, Zhiyuan; Duan, Zhong-Yu; Wang, Hao

    2016-05-01

    One of the major challenges in current cancer therapy is to maximize therapeutic effect and evaluate tumor progression under the scheduled treatment protocol. To address these challenges, we synthesized the cytotoxic peptide (KLAKLAK)2 (named KLAK) conjugated amphiphilic poly(β-thioester)s copolymers (H-P-K) composed of reactive oxygen species (ROS) sensitive backbones and hydrophilic polyethylene glycol (PEG) side chains. H-P-K could self-assemble into micelle-like nanoparticles by hydrophobic interaction with copolymer backbones as cores and PEG and KLAK as shells. The assembled polymer-peptide nanoparticles remarkably improved cellular internalization and accumulation of therapeutic KLAK in cells. Compared to free KLAK peptide, the antitumor activity of H-P-K was significantly enhanced up to ∼400 times, suggesting the effectiveness of the nanoscaled polymer-peptide conjugation as biopharmaceuticals. The higher antitumor activity of nanoparticles was attributed to the efficient disruption of mitochondrial membranes and subsequent excessive ROS production in cells. To realize the ROS monitoring and treatment evaluation, we encapsulated squaraine (SQ) dyes as built-in reporters in ROS-sensitive H-P-K micelles. The overgenerated ROS around mitochondria stimulated the swelling of nanoparticles and subsequent release of SQ, which formed H-aggregates and significantly increased the photoacoustic (PA) signal. We believed that this self-assembled polymer-peptide nanotherapeutics incorporating built-in reporters has great potential for high antitumor performance and in situ treatment evaluation. PMID:27023216

  20. Silver nanowire percolation network soldered with graphene oxide at room temperature and its application for fully stretchable polymer light-emitting diodes.

    PubMed

    Liang, Jiajie; Li, Lu; Tong, Kwing; Ren, Zhi; Hu, Wei; Niu, Xiaofan; Chen, Yongsheng; Pei, Qibing

    2014-02-25

    Transparent conductive electrodes with high surface conductivity, high transmittance in the visible wavelength range, and mechanical compliance are one of the major challenges in the fabrication of stretchable optoelectronic devices. We report the preparation of a transparent conductive electrode (TCE) based on a silver nanowire (AgNW) percolation network modified with graphene oxide (GO). The monatomic thickness, mechanical flexibility, and strong bonding with AgNWs enable the GO sheets to wrap around and solder the AgNW junctions and thus dramatically reduce the inter-nanowire contact resistance without heat treatment or high force pressing. The GO-soldered AgNW network has a figure-of-merit sheet resistance of 14 ohm/sq with 88% transmittance at 550 nm. Its storage stability is improved compared to a conventional high-temperature annealed AgNW network. The GO-soldered AgNW network on polyethylene terephthalate films was processed from solutions using a drawdown machine at room temperature. When bent to 4 mm radius, its sheet resistance was increased by only 2-3% after 12,000 bending cycles. GO solder can also improve the stretchability of the AgNW network. Composite TCE fabricated by inlaying a GO-soldered AgNW network in the surface layer of polyurethane acrylate films is stretchable, by greater than 100% linear strain without losing electrical conductivity. Fully stretchable white polymer light-emitting diodes (PLEDs) were fabricated for the first time, employing the stretchable TCE as both the anode and cathode. The PLED can survive after 100 stretching cycles between 0 and 40% strain and can be stretched up to 130% linear strain at room temperature. PMID:24471886

  1. Understanding the Structure of Reversible Coordination Polymers Based on Europium in Electrostatic Assemblies Using Time-Resolved Luminescence.

    PubMed

    Xu, Limin; Xie, Mengqi; Huang, Jianbin; Yan, Yun

    2016-06-14

    In situ characterization of the structure of reversible coordination polymers remains a challenge because of their dynamic and concentration-responsive nature. It is especially difficult to determine these structures in their self-assemblies where their degree of polymerization responds to the local concentration. In this paper, we report on the structure of reversible lanthanide coordination polymers in electrostatic assemblies using time-resolved luminescence (TRL) measurement. The reversible coordinating system is composed of the bifunctional ligand 1,11-bis(2,6-dicarboxypyridin-4-yloxy)-3,6,9-trioxaundecane (L2EO4) and europium ion Eu(3+). Upon mixing with the positively charged diblock copolymer poly(2-vinylpyridine)-b-poly(ethylene oxide) (P2VP41-b-PEO205), electrostatic polyion micelles are formed and the negatively charged L2EO4-Eu coordination complex simultaneously transforms into coordination "polymers" in the micellar core. By virtue of the water-sensitive luminescence of Eu(3+), we are able to obtain the structural information of the L2EO4-Eu coordination polymers before and after the formation of polyion micelles. Upon analyzing the fluorescence decay curves of Eu(3+) before and after micellization, the fraction of Eu(3+) fully coordinated with L2EO4 is found to increase from 32 to 83%, which verifies the occurrence of chain extension of the L2EO4-Eu coordination polymers in the micellar core. Our work provides a qualitative picture for the structure change of reversible coordination polymers, which allows us to look into these "invisible" structures. PMID:27228142

  2. Self-assembly and glass-formation in a lattice model of telechelic polymer melts: Influence of stiffness of the sticky bonds.

    PubMed

    Xu, Wen-Sheng; Freed, Karl F

    2016-06-01

    Telechelic polymers are chain macromolecules that may self-assemble through the association of their two mono-functional end groups (called "stickers"). A deep understanding of the relation between microscopic molecular details and the macroscopic physical properties of telechelic polymers is important in guiding the rational design of telechelic polymer materials with desired properties. The lattice cluster theory (LCT) for strongly interacting, self-assembling telechelic polymers provides a theoretical tool that enables establishing the connections between important microscopic molecular details of self-assembling polymers and their bulk thermodynamics. The original LCT for self-assembly of telechelic polymers considers a model of fully flexible linear chains [J. Dudowicz and K. F. Freed, J. Chem. Phys. 136, 064902 (2012)], while our recent work introduces a significant improvement to the LCT by including a description of chain semiflexibility for the bonds within each individual telechelic chain [W.-S. Xu and K. F. Freed, J. Chem. Phys. 143, 024901 (2015)], but the physically associative (or called "sticky") bonds between the ends of the telechelics are left as fully flexible. Motivated by the ubiquitous presence of steric constraints on the association of real telechelic polymers that impart an additional degree of bond stiffness (or rigidity), the present paper further extends the LCT to permit the sticky bonds to be semiflexible but to have a stiffness differing from that within each telechelic chain. An analytical expression for the Helmholtz free energy is provided for this model of linear telechelic polymer melts, and illustrative calculations demonstrate the significant influence of the stiffness of the sticky bonds on the self-assembly and thermodynamics of telechelic polymers. A brief discussion is also provided for the impact of self-assembly on glass-formation by combining the LCT description for this extended model of telechelic polymers with the

  3. Enhanced near-infrared photoresponse of organic phototransistors based on single-component donor-acceptor conjugated polymer nanowires

    NASA Astrophysics Data System (ADS)

    Zhu, Min; Lv, Shenchen; Wang, Qinghe; Zhang, Guobing; Lu, Hongbo; Qiu, Longzhen

    2016-03-01

    Single-component near-infrared phototransistors based on ambipolar organic semiconductor nanowires have been investigated and compared with their corresponding thin-film counterparts. The nanowire organic phototransistors (NW-OPTs) showed photocurrent/dark-current ratios and photoresponsivities as high as 1.3 × 104 and 440 mA W-1 for the p-type channel, and 3.3 × 104 and 70 mA W-1 for the n-type channel, respectively, upon near-infrared illumination with an intensity of 47.1 mW cm-2. These were much higher values compared to their thin-film counterparts. The enhancement of the near-infrared photoresponse could be attributed to the larger trap density originating from the semiconductor/insulator interface and the semiconductor/air interface. The performance of NW-OPTs was demonstrated to open up new possibilities to improve the near-infrared photoresponse of single-component devices.Single-component near-infrared phototransistors based on ambipolar organic semiconductor nanowires have been investigated and compared with their corresponding thin-film counterparts. The nanowire organic phototransistors (NW-OPTs) showed photocurrent/dark-current ratios and photoresponsivities as high as 1.3 × 104 and 440 mA W-1 for the p-type channel, and 3.3 × 104 and 70 mA W-1 for the n-type channel, respectively, upon near-infrared illumination with an intensity of 47.1 mW cm-2. These were much higher values compared to their thin-film counterparts. The enhancement of the near-infrared photoresponse could be attributed to the larger trap density originating from the semiconductor/insulator interface and the semiconductor/air interface. The performance of NW-OPTs was demonstrated to open up new possibilities to improve the near-infrared photoresponse of single-component devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr09003b

  4. Solid-State Nanostructured Materials from Self-Assembly of a Globular Protein-Polymer Diblock Copolymer

    PubMed Central

    Thomas, Carla S.; Glassman, Matthew J.; Olsen, Bradley D.

    2014-01-01

    Self-assembly of three-dimensional solid-state nanostructures containing approximately 33% by weight globular protein is demonstrated using a globular protein-polymer diblock copolymer, providing a route to direct nanopatterning of proteins for use in bioelectronic and biocatalytic materials. A mutant red fluorescent protein, mCherryS131C, was prepared by incorporation of a unique cysteine residue and site-specifically conjugated to end-functionalized poly(N-isopropylacrylamide) through thiol-maleimide coupling to form a well-defined model protein-polymer block copolymer. The block copolymer was self-assembled into bulk nanostructures by solvent evaporation from concentrated solutions. Small-angle X-ray scattering and transmission electron microscopy illustrated the formation of highly disordered lamellae or hexagonally perforated lamellae depending upon the selectivity of the solvent during evaporation. Solvent annealing of bulk samples resulted in a transition towards lamellar nanostructures with mCherry packed in a bilayer configuration and a large improvement in long range ordering. Wide-angle X-ray scattering indicated that mCherry did not crystallize within the block copolymer nanodomains and that the β-sheet spacing was not affected by self-assembly. Circular dichroism showed no change in protein secondary structure after self-assembly, while UV-vis spectroscopy indicated approximately 35% of the chromophore remained optically active. PMID:21696135

  5. Patterned Fabrication of Zinc Oxide Nanowire Arrays

    NASA Astrophysics Data System (ADS)

    Khan, Sahar; Lamson, Thomas; Xu, Huizhong

    Zinc oxide nanowires possess desirable mechanical, thermodynamic, electrical, and optical properties. Although the hydrothermal growth process can be applied in tolerable growth conditions, the dimension and density of nanowires has a complex dependence on substrate pre-treatment, precursor concentrations, and growth conditions. Precise control of the geometry and density of nanowires as well as the location of nanowires would allow for the fabrication of useful nanowaveguide devices. In this work, we used electron beam lithography to pattern hole arrays in a polymer layer on gold-coated glass substrates and synthesized zinc oxide nanowires inside these holes. Arrays of nanowires with diameters ranging from 50 nm to 140 nm and various spacings were obtained. The transmission of light through these zinc oxide nanowire arrays in a silver film was also studied. This research was supported by the Seed Grant Program of St. John's University and the National Science Foundation under Grant No. CBET-0953645.

  6. Structure and Electronic Properties of Polymer Chains and Graphene Nanoribbon Formed by Molecular Self-Assembly on Au(111)

    NASA Astrophysics Data System (ADS)

    Ma, Chuanxu; Fuentes-Cabrera, Miguel A.; Sumpter, Bobby G.; Hong, Kunlun; Li, An-Ping; Xiao, Zhongcan; Lu, Wenchang; Bernholc, J.

    Graphene nanoribbons (GNRs) with bandgaps are promising building blocks for ultra-fast electronics. Bottom-up synthesis of GNRs from aromatic hydrocarbon molecules has been proven to be an effective way to control GNR's width with atomically precise edge structures. Using scanning tunneling microscopy (STM), we study the formation of both linear polymer chains and narrow GNRs in the bottom-up self-assembly process with the DBBA molecules as the precursor on Au(111). The linear polymer chains are formed after the deposition of DBBA and 200 °C annealing for 30 min. The polymers can be converted to 7-AGNRs (seven-carbon wide armchair GNRs) after 400 °C annealing. Interestingly, second-layer polymer is seen to survive on the GNRs during the annealing process. This result indicates that the Au(111) substrate plays an important role in the dehydrogenation process and the formation of GNRs, which is confirmed by our DFT calculations. Electronically, the polymers show a bandgap of 3.4 eV, much larger than that of GNRs. After annealing at 500 °C for 30 min, wider GNRs can form: 14-AGNR, 21-AGNR. The 7-AGNR shows a typical edge state at -1.1 eV, while for 14-AGNR it is at -1.35 eV. Moreover, junctions of GNRs with different widths can be formed with pronounced boundary states.

  7. Electrostatic Assembly of Polymers and Nanoparticles at Liquid-Liquid Interfaces

    NASA Astrophysics Data System (ADS)

    Hoagland, David

    The electrostatic attraction between charged solutes on opposite sides of the interface between immiscible liquids offers an efficient route to the self-assembly of two-dimensional films. As implemented by us, a hydrophobic polymer with amine end(s) or block(s) is presented in an oil phase, and a negatively charged nanoparticle is presented in an aqueous phase; both solutes are insoluble in the opposite phase but efficiently driven to the liquid-liquid interface by mutual electrostatically attraction to the solute in the opposite phase. Depending on experimental conditions (salt concentration, pH, solute concentrations, etc.), a continuous, nanoscopically thin composite film builds at the oil-water interface over the timescale of minutes, often accompanied by a dramatic reduction of interfacial tension akin to that observed for a surfactant. Film formation and properties by the new route will be discussed, as principally probed through pendant drop interfacial tensiometry and pendant drop interfacial rheometry. Components of model system are toluene-dissolved amine end-capped polystyrene and water-dispersed acid-treated carbon nanotubes or citrate-treated gold nanospheres. Film structures are complicated, as are crucial electrostatic interactions near the interface. With amine end-capped polystyrene partnered with acid-treated carbon nanotubes, high pH (above 5) and high polystyrene molecular weight (above 5000 g/mol) strongly hinder film formation. These films, which are liquid-like, show two viscoelastic relaxations, a fast relaxation (about 10 s) associated with polystyrene chain rearrangements (slightly impacted by carbon nanotube association) and a slow relaxation (about 20 min) associated with polystyrene adsorption/desorption; at intermediate times (or frequencies), the two-dimensional storage and loss moduli follow approximately the same power law dependences. Support by NSF through the Univ. of Massachusetts MRSEC.

  8. Role of block copolymer adsorption versus bimodal grafting on nanoparticle self-assembly in polymer nanocomposites.

    PubMed

    Zhao, Dan; Di Nicola, Matteo; Khani, Mohammad M; Jestin, Jacques; Benicewicz, Brian C; Kumar, Sanat K

    2016-09-14

    We compare the self-assembly of silica nanoparticles (NPs) with physically adsorbed polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) copolymers (BCP) against NPs with grafted bimodal (BM) brushes comprised of long, sparsely grafted PS chains and a short dense carpet of P2VP chains. As with grafted NPs, the dispersion state of the BCP NPs can be facilely tuned in PS matrices by varying the PS coverage on the NP surface or by changes in the ratio of the PS graft to matrix chain lengths. Surprisingly, the BCP NPs are remarkably better dispersed than the NPs tethered with bimodal brushes at comparable PS grafting densities. We postulate that this difference arises because of two factors inherent in the synthesis of the NPs: In the case of the BCP NPs the adsorption process is analogous to the chains being "grafted to" the NP surface, while the BM case corresponds to "grafting from" the surface. We have shown that the "grafted from" protocol yields patchy NPs even if the graft points are uniformly placed on each particle. This phenomenon, which is caused by chain conformation fluctuations, is exacerbated by the distribution function associated with the (small) number of grafts per particle. In contrast, in the case of BCP adsorption, each NP is more uniformly coated by a P2VP monolayer driven by the strongly favorable P2VP-silica interactions. Since each P2VP block is connected to a PS chain we conjecture that these adsorbed systems are closer to the limit of spatially uniform sparse brush coverage than the chemically grafted case. We finally show that the better NP dispersion resulting from BCP adsorption leads to larger mechanical reinforcement than those achieved with BM particles. These results emphasize that physical adsorption of BCPs is a simple, effective and practically promising strategy to direct NP dispersion in a chemically unfavorable polymer matrix. PMID:27502154

  9. Multifunctional metal-polymer nanoagglomerates from single-pass aerosol self-assembly.

    PubMed

    Byeon, Jeong Hoon

    2016-01-01

    In this study, gold (Au)-iron (Fe) nanoagglomerates were capped by a polymer mixture (PM) consisting of poly(lactide-co-glycolic acid), protamine sulfate, and poly-l-lysine via floating self-assembly in a single-pass aerosol configuration as multibiofunctional nanoplatforms. The Au-Fe nanoagglomerates were directly injected into PM droplets (PM dissolved in dichloromethane) in a collison atomizer and subsequently heat-treated to liberate the solvent from the droplets, resulting in the formation of PM-capped Au-Fe nanoagglomerates. Measured in vitro, the cytotoxicities of the nanoagglomerates (>98.5% cell viability) showed no significant differences compared with PM particles alone (>98.8%), thus implying that the nanoagglomerates are suitable for further testing of biofunctionalities. Measurements of gene delivery performance revealed that the incorporation of the Au-Fe nanoagglomerates enhanced the gene delivery performance (3.2 × 10(6) RLU mg(-1)) of the PM particles alone (2.1 × 10(6) RLU mg(-1)), which may have been caused by the PM structural change from a spherical to a hairy structure (i.e., the change followed the agglomerated backbone). Combining the X-ray-absorbing ability of Au and the magnetic property of Fe led to magnetic resonance (MR)-computed tomography (CT) contrast ability in a phantom; and the signal intensities [which reached 64 s(-1) T2-relaxation in MR and 194 Hounsfield units (HUs) in CT at 6.0 mg mL(-1)] depended on particle concentration (0.5-6.0 mg mL(-1)). PMID:27507668

  10. Multifunctional metal-polymer nanoagglomerates from single-pass aerosol self-assembly

    NASA Astrophysics Data System (ADS)

    Byeon, Jeong Hoon

    2016-08-01

    In this study, gold (Au)-iron (Fe) nanoagglomerates were capped by a polymer mixture (PM) consisting of poly(lactide-co-glycolic acid), protamine sulfate, and poly-l-lysine via floating self-assembly in a single-pass aerosol configuration as multibiofunctional nanoplatforms. The Au-Fe nanoagglomerates were directly injected into PM droplets (PM dissolved in dichloromethane) in a collison atomizer and subsequently heat-treated to liberate the solvent from the droplets, resulting in the formation of PM-capped Au-Fe nanoagglomerates. Measured in vitro, the cytotoxicities of the nanoagglomerates (>98.5% cell viability) showed no significant differences compared with PM particles alone (>98.8%), thus implying that the nanoagglomerates are suitable for further testing of biofunctionalities. Measurements of gene delivery performance revealed that the incorporation of the Au-Fe nanoagglomerates enhanced the gene delivery performance (3.2 × 106 RLU mg‑1) of the PM particles alone (2.1 × 106 RLU mg‑1), which may have been caused by the PM structural change from a spherical to a hairy structure (i.e., the change followed the agglomerated backbone). Combining the X-ray-absorbing ability of Au and the magnetic property of Fe led to magnetic resonance (MR)-computed tomography (CT) contrast ability in a phantom; and the signal intensities [which reached 64 s‑1 T2-relaxation in MR and 194 Hounsfield units (HUs) in CT at 6.0 mg mL‑1] depended on particle concentration (0.5–6.0 mg mL‑1).

  11. Multifunctional metal-polymer nanoagglomerates from single-pass aerosol self-assembly

    PubMed Central

    Byeon, Jeong Hoon

    2016-01-01

    In this study, gold (Au)-iron (Fe) nanoagglomerates were capped by a polymer mixture (PM) consisting of poly(lactide-co-glycolic acid), protamine sulfate, and poly-l-lysine via floating self-assembly in a single-pass aerosol configuration as multibiofunctional nanoplatforms. The Au-Fe nanoagglomerates were directly injected into PM droplets (PM dissolved in dichloromethane) in a collison atomizer and subsequently heat-treated to liberate the solvent from the droplets, resulting in the formation of PM-capped Au-Fe nanoagglomerates. Measured in vitro, the cytotoxicities of the nanoagglomerates (>98.5% cell viability) showed no significant differences compared with PM particles alone (>98.8%), thus implying that the nanoagglomerates are suitable for further testing of biofunctionalities. Measurements of gene delivery performance revealed that the incorporation of the Au-Fe nanoagglomerates enhanced the gene delivery performance (3.2 × 106 RLU mg−1) of the PM particles alone (2.1 × 106 RLU mg−1), which may have been caused by the PM structural change from a spherical to a hairy structure (i.e., the change followed the agglomerated backbone). Combining the X-ray-absorbing ability of Au and the magnetic property of Fe led to magnetic resonance (MR)-computed tomography (CT) contrast ability in a phantom; and the signal intensities [which reached 64 s−1 T2-relaxation in MR and 194 Hounsfield units (HUs) in CT at 6.0 mg mL−1] depended on particle concentration (0.5–6.0 mg mL−1). PMID:27507668

  12. Boosting the Open Circuit Voltage and Fill Factor of QDSSCs Using Hierarchically Assembled ITO@Cu2S Nanowire Array Counter Electrodes.

    PubMed

    Jiang, Yan; Yu, Bin-Bin; Liu, Jie; Li, Zhi-Hua; Sun, Jian-Kun; Zhong, Xin-Hua; Hu, Jin-Song; Song, Wei-Guo; Wan, Li-Jun

    2015-05-13

    The key challenges in enhancing the power conversion efficiency (PCE) of a quantum dot-sensitized solar cell (QDSSC) are efficiently achieving charge separation at the photoanode and improving the charge transfer, which is limited by the interface between the electrolyte and the counter electrode (CE). Here, hierarchically assembled ITO@Cu2S nanowire arrays with conductive single-crystalline ITO cores and Cu2S nanocrystal shells were designed as efficient QDSSCs CEs. These arrays not only provided an efficient three-dimensional charge transport network but also allowed for the effective deposition of more Cu2S nanocrystals as active sites to catalyze the electrolyte reaction. This design considerably reduced the sheet and charge transfer resistance of the CE, thus decreasing the series resistance and increasing the shunt resistance of the QDSSC. As a result, QDSSCs with this CE exhibited an unprecedentedly high Voc of 0.688 V, a fill factor of 58.39%, and a PCE of 6.12%, which is 21.2% higher than that of the conventional brass/Cu2S CE. PMID:25929671

  13. Water-soluble, luminescent ZnTe quantum dots: supersaturation-controlled synthesis and self-assembly into nanoballs, nanonecklaces and nanowires.

    PubMed

    Patra, Sovan Kumar; Bhushan, Bhavya; Priyam, Amiya

    2016-03-01

    A supersaturation-controlled aqueous synthesis route has been developed for ZnTe quantum dots (QDs) with high monodispersity, size tunability, stability, band-edge luminescence (full-width at half-maximum (FWHM) 10-12 nm) and negligibly small Stokes' shift (2-4 nm). The degree of supersaturation of the initial reaction mixture was varied by increasing the reagent concentration, but keeping the molar ratio Zn(2+) : thioglycolic acid : Te(2-) constant at 1 : 2.5 : 0.5. For a 10× increase in supersaturation, the photoluminescence (PL) peak underwent a 50 nm blue shift from 330 to 280 nm at pH 6. The effect was more pronounced at pH 12, where the PL peak blue-shifted by 100 nm from 327 to 227 nm. Concomitantly, the FWHM was also reduced to a low value of 10 nm, indicating high monodispersity. For a 10× change in supersaturation, the particle size decreased by 63% (from 2.2 to 0.8 nm) at pH 12, whereas it changed by 19% (from 2.1 to 1.7 nm) at pH 6. High-resolution transmission electron microscopy and selected area electron diffraction data further revealed that the QDs synthesized at higher supersaturation had a better crystallinity. These QDs exhibited the unique property of undergoing isotropic and anisotropic self-assembly, which resulted in a blue shift and a red shift in the absorption and PL spectra, respectively. Isotropic assembly into spherical nanoballs (100 nm diameter, 1 nm inter-QD separation) occurred when the QDs were stored at pH 12 for 3 weeks at room temperature. The nanoballs further self-assembled into a 'pearl necklace' arrangement. On the partial removal of the capping agents, the QDs self-organized anisotropically into nanowires (1.3 μm long and 4.6 nm in diameter). The self-assembled nanostructures showed exciton-exciton coupling and excellent PL properties, which may be useful in enhanced optoelectronics, photovoltaics and biochemical sensing. PMID:26830257

  14. A density functional study of silver clusters on a stepped graphite surface: formation of self-assembled nano-wires.

    PubMed

    Singh, Akansha; Sen, Prasenjit

    2015-05-21

    Adsorption and diffusion of silver adatoms and clusters containing up to eight atoms on an HOPG substrate with an armchair step are studied using density functional methods. Step edges act as attractive sinks for adatoms and clusters. The diffusion barrier of an Ag adatom along the step edge is much larger than that on a clean terrace. At zero temperature, Ag clusters either distort or dissociate by forming covalent bonds with the edge C atoms. At 600 K, Ag5 and Ag8 clusters diffuse to the step edges, and then break up so as to maximize Ag-C bonds. The Ag atoms try to form a nanowire structure along the step edge. At such high temperatures, diffusion of clusters along the step edge involves diffusion of individual Ag atoms not bonded to the edge C atoms. Assumption of complete immobility of clusters trapped at step edges in the Gates-Robins model is not valid at high temperatures in this particular system. PMID:25903308

  15. Sandwiched assembly of ZnO nanowires between graphene layers for a self-powered and fast responsive ultraviolet photodetector.

    PubMed

    Boruah, Buddha Deka; Mukherjee, Anwesha; Misra, Abha

    2016-03-01

    A heterostructure of graphene and zinc oxide (ZnO) nanowires (NWs) is fabricated by sandwiching an array of ZnO NWs between two graphene layers for an ultraviolet (UV) photodetector. This unique structure allows NWs to be in direct contact with the graphene layers, minimizing the effect of the substrate or metal electrodes. In this device, graphene layers act as highly conducting electrodes with a high mobility of the generated charge carriers. An excellent sensitivity is demonstrated towards UV illumination, with a reversible photoresponse even for a short period of UV illumination. Response and recovery times of a few milliseconds demonstrated a much faster photoresponse than most of the conventional ZnO nanostructure-based photodetectors. It is shown that the generation of a built-in electric field between the interface of graphene and ZnO NWs effectively contributes to the separation of photogenerated electron-hole pairs for photocurrent generation without applying any external bias. Upon application of external bias voltage, the electric field further increases the drift velocity of photogenerated electrons by reducing the charge recombination rates, and results in an enhancement of the photocurrent. Therefore, the graphene-based heterostructure (G/ZnO NW/G) opens avenues to constructing a novel heterostructure with a combination of two functionally dissimilar materials. PMID:26857833

  16. Sandwiched assembly of ZnO nanowires between graphene layers for a self-powered and fast responsive ultraviolet photodetector

    NASA Astrophysics Data System (ADS)

    Deka Boruah, Buddha; Mukherjee, Anwesha; Misra, Abha

    2016-03-01

    A heterostructure of graphene and zinc oxide (ZnO) nanowires (NWs) is fabricated by sandwiching an array of ZnO NWs between two graphene layers for an ultraviolet (UV) photodetector. This unique structure allows NWs to be in direct contact with the graphene layers, minimizing the effect of the substrate or metal electrodes. In this device, graphene layers act as highly conducting electrodes with a high mobility of the generated charge carriers. An excellent sensitivity is demonstrated towards UV illumination, with a reversible photoresponse even for a short period of UV illumination. Response and recovery times of a few milliseconds demonstrated a much faster photoresponse than most of the conventional ZnO nanostructure-based photodetectors. It is shown that the generation of a built-in electric field between the interface of graphene and ZnO NWs effectively contributes to the separation of photogenerated electron-hole pairs for photocurrent generation without applying any external bias. Upon application of external bias voltage, the electric field further increases the drift velocity of photogenerated electrons by reducing the charge recombination rates, and results in an enhancement of the photocurrent. Therefore, the graphene-based heterostructure (G/ZnO NW/G) opens avenues to constructing a novel heterostructure with a combination of two functionally dissimilar materials.

  17. A supramolecular Janus hyperbranched polymer and its photoresponsive self-assembly of vesicles with narrow size distribution.

    PubMed

    Liu, Yong; Yu, Chunyang; Jin, Haibao; Jiang, Binbin; Zhu, Xinyuan; Zhou, Yongfeng; Lu, Zhongyuan; Yan, Deyue

    2013-03-27

    Herein, we report a novel Janus particle and supramolecular block copolymer consisting of two chemically distinct hyperbranched polymers, which is coined as Janus hyperbranched polymer. It is constructed by the noncovalent coupling between a hydrophobic hyperbranched poly(3-ethyl-3-oxetanemethanol) with an apex of an azobenzene (AZO) group and a hydrophilic hyperbranched polyglycerol with an apex of a β-cyclodextrin (CD) group through the specific AZO/CD host-guest interactions. Such an amphiphilic supramolecular polymer resembles a tree together with its root very well in the architecture and can further self-assemble into unilamellar bilayer vesicles with narrow size distribution, which disassembles reversibly under the irradiation of UV light due to the trans-to-cis isomerization of the AZO groups. In addition, the obtained vesicles could further aggregate into colloidal crystal-like close-packed arrays under freeze-drying conditions. The dynamics and mechanism for the self-assembly of vesicles as well as the bilayer structure have been disclosed by a dissipative particle dynamics simulation. PMID:23464832

  18. A structural basis for the assembly and functions of a viral polymer that inactivates multiple tumor suppressors

    PubMed Central

    Ou, Horng D.; Kwiatkowski, Witek; Deerinck, Thomas J.; Noske, Andrew; Blain, Katie Y.; Land, Hannah S.; Soria, Conrado; Powers, Colin J.; May, Andrew P.; Shu, Xiaokun; Tsien, Roger Y.; Fitzpatrick, James A.J.; Long, Jeff A.; Ellisman, Mark H.; Choe, Senyon; O’Shea, Clodagh C.

    2013-01-01

    Summary The evolution of minimal DNA tumor virus’ genomes has selected for small oncoproteins that hijack critical cellular protein interaction networks. The structural basis for the dominant interactions of adenovirus oncoproteins has remained elusive as no full-length structures have been solved. Adenovirus E4-ORF3 forms a nuclear scaffold and simultaneously inactivates p53, PML, TRIM24 and MRE11/RAD50/NBS1 (MRN) tumor suppressors. We identify oligomerization mutants and solve the crystal structure of an E4-ORF3 dimer. The structure of E4-ORF3 is unrelated to known polymers or oncogenes. E4-ORF3 dimers have a central β-core and co-assemble in multiple configurations by exchanging their C-terminal tails. The resulting polymers are disordered weaves of linear and branched oligomer threads that form a 3D network that partitions the nucleus. The assembly of E4-ORF3 creates avidity driven interactions with PML and an emergent MRN binding interface. This study unveils an elegant solution whereby a small domain forms a multivalent polymer to disrupt multiple protein complexes. PMID:23063122

  19. Investigating the energy harvesting capabilities of a hybrid ZnO nanowires/carbon fiber polymer composite beam.

    PubMed

    Masghouni, N; Burton, J; Philen, M K; Al-Haik, M

    2015-03-01

    Hybrid piezoelectric composite structures that are able to convert mechanical energy into electricity have gained growing attention in the past few years. In this work, an energy harvesting composite beam is developed by growing piezoelectric zinc oxide nanowires on the surface of carbon fiber prior to forming structural composites. The piezoelectric behavior of the composite beam was demonstrated under different vibration sources such as water bath sonicator and permanent magnet vibration shaker. The beam was excited at its fundamental natural frequency (43.2 Hz) and the open circuit voltage and the short circuit current were measured to be 3.1 mV and 23 nA, respectively. Upon connecting an optimal resistor (1.2 kΩ) in series with the beam a maximum power output 2.5 nW was achieved. PMID:25670370

  20. Fabrication of metallic nanowires and nanoribbons using laser interference lithography and shadow lithography

    SciTech Connect

    Park, Joong- Mok; Nalwa, Kanwar Singh; Leung, Wai; Constant, Kristen; Chaudhary, Sumit; Ho, Kai-Ming

    2010-04-30

    Ordered and free-standing metallic nanowires were fabricated by e-beam deposition on patterned polymer templates made by interference lithography. The dimensions of the nanowires can be controlled through adjustment of deposition conditions and polymer templates. Grain size, polarized optical transmission and electrical resistivity were measured with ordered and free-standing nanowires.

  1. Blown-Bubble Assembly and in Situ Fabrication of Sausage-like Graphene Nanotubes Containing Copper Nanoblocks.

    PubMed

    Wu, Shiting; Yang, Long; Zou, Mingchu; Yang, Yanbing; Du, Mingde; Xu, Wenjing; Yang, Liusi; Fang, Ying; Cao, Anyuan

    2016-08-10

    We use a blown-bubble method to assemble Cu nanowires and in situ fabricate graphene-based one-dimensional heterostructures, including versatile sausage-like configurations consisting of multilayer graphene nanotubes (GNTs) filled by single or periodically arranged Cu nanoblocks (CuNBs). This is done by first assembling Cu nanowires among a polymer-based blown-bubble film (BBF) and then growing graphene onto the nanowire substrate using the polymer matrix as a solid carbon source by chemical-vapor deposition. The formation of sausage-like GNT@CuNB nanostructures is due to the partial melting and breaking of embedded Cu nanowires during graphene growth, which is uniquely related to our BBF process. We show that the GNT skin significantly slows the oxidation process of CuNBs compared with that of bare Cu nanowires, and the presence of stuffed CuNBs also reduces the linear resistance along the GNTs. The large-scale assembled graphene-based heterostructures achieved by our BBF method may have potential applications in heterojunction electronic devices and high-stability transparent conductive electrodes. PMID:27414282

  2. DNA-programmed modular assembly of cyclic and linear nanoarrays for the synthesis of two-dimensional conducting polymers.

    PubMed

    Chen, Wen; Schuster, Gary B

    2012-01-18

    Nanometer-scale arrays of conducting polymers were prepared on scaffolds of self-assembling DNA modules. A series of DNA oligomers was prepared, each containing six 2,5-bis(2-thienyl)pyrrole (SNS) monomer units linked covalently to N4 atoms of alternating cytosines placed between leading and trailing 12-nucleobase recognition sequences. These DNA modules were encoded so the recognition sequences would uniquely associate through Watson-Crick assembly to form closed-cycle or linear arrays of aligned SNS monomers. The melting behavior and electrophoretic migration of these assemblies showed cooperative formation of multicomponent arrays containing two to five DNA modules (i.e., 12-30 SNS monomers). The treatment of these arrays with horseradish peroxidase and H(2)O(2) resulted in oxidative polymerization of the SNS monomers with concomitant ligation of the DNA modules. The resulting cyclic and linear arrays exhibited chemical and optical properties typical of conducting thiophene-like polymers, with a red-end absorption beyond 1250 nm. AFM images of the cyclic array containing 18 SNS units revealed highly regular 10 nm diameter objects. PMID:22242713

  3. Gold-coated silicon nanowire-graphene core-shell composite film as a polymer binder-free anode for rechargeable lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Kim, Han-Jung; Lee, Sang Eon; Lee, Jihye; Jung, Joo-Yun; Lee, Eung-Sug; Choi, Jun-Hyuk; Jung, Jun-Ho; Oh, Minsub; Hyun, Seungmin; Choi, Dae-Geun

    2014-07-01

    We designed and fabricated a gold (Au)-coated silicon nanowires/graphene (Au-SiNWs/G) hybrid composite as a polymer binder-free anode for rechargeable lithium-ion batteries (LIBs). A large amount of SiNWs for LIB anode materials can be prepared by metal-assisted chemical etching (MaCE) process. The Au-SiNWs/G composite film on current collector was obtained by vacuum filtration using an anodic aluminum oxide (AAO) membrane and hot pressing method. Our experimental results show that the Au-SiNWs/G composite has a stable reversible capacity of about 1520 mA h/g which was maintained for 20 cycles. The Au-SiNWs/G composite anode showed much better cycling performance than SiNWs/polyvinylidene fluoride (PVDF)/Super-P, SiNWs/G composite, and pure SiNWs anodes. The improved electrochemical properties of the Au-SiNWs/G composite anode material is mainly ascribed to the composite's porous network structure.

  4. Harnessing the instabilities of soft matter: Dynamically tuning of wetting, assembly and pattern transformation in polymer microstructures

    NASA Astrophysics Data System (ADS)

    Zhang, Ying

    2008-10-01

    In this dissertation, we have investigated the fabrication, mechanical instability and applications of two kinds of polymer micro/nano-structures: high-aspect-ratio (HAR) polymer pillar arrays, and periodic porous elastomer membranes. For HAR polymer pillar arrays, we demonstrated the fabrication of high-aspect-ratio (up to 18) polymer micropillars with different shapes and dimensions by replica molding. Capillary force lithography (CFL) is also demonstrated as a simple and flexible method to fabricate microstructures with controlled aspect ratios. Meanwhile, by introducing conventional photoresist SU-8, CFL is successfully coupled with photolithography and used to create hierarchical 2D or 3D structures, which greatly expand the capability of current capillary force lithography. The mechanical stability of HAR structures with varied materials and different aspect ratio, density and shape were also studied and the results show that the adhesive forces from environment are the major cause of structure collapsing. When HAR polymer pillars are subjected to different solvents treatment, both capillary force and solvent swelling need to be considered to completely understand the structure instability. On HAR micropillar array, thermoresponsive polymer brushes, poly ( N-isopropylacrylamide) (PNIPAAm), were selectively grafted at different locations for dynamically tuning surface wetting or pattern assembly. When the temperature changed from 40°C to 20°, depending on the location of polymer brushes, different wetting transitions, either from a composite solid/air state (Cassie state) to a composite solid/liquid state (Hemi-wicking state) or a transition between two Cassie states were observed. Meanwhile, the dynamically tuning of water contact angle enables us to control capillary drying force and thus harness pattern collapse to create superlattice micropatterns. For periodic porous elastomer membrane, a novel pattern transformation effect is discovered due to the

  5. Biocompatible polyester macroligands: new subunits for the assembly of star-shaped polymers with luminescent and cleavable metal cores.

    PubMed

    Corbin, P S; Webb, M P; McAlvin, J E; Fraser, C L

    2001-01-01

    The synthesis of a series of star-shaped, biocompatible polyesters--polylactides (PLAs), polycaprolactones (PCLs), and various copolymer analogues--with either labile iron(II) tris-bipyridyl or luminescent ruthenium(II) tris-bipyridyl cores is described. These polymers were readily assembled by a convergent, metal-template-assisted approach that entailed the synthesis of bipyridine (bpy) ligands incorporating PLA- and PCL-containing arms and subsequent chelation of the "macroligands" to iron(II) or ruthenium(II). Specifically, the polyester macroligands bpyPLA(2) and bpyPCL(2) were prepared by a stannous octoate catalyzed ring-opening polymerization of DL- or L-lactide and epsilon-caprolactone, using bis(hydroxymethyl)-2,2'-bipyridine as the initiator. Copolymers bpy(PCL-PLA)(2) and bpy(PLA-PCL)(2) were generated in an analogous manner using bpyPLA(2) and bpyPCL(2) as macroinitiators. Polymers with narrow molecular weight distributions and with molecular weights close to values expected based upon monomer/initiator loading were produced. The macroligands were subsequently chelated to iron(II) to afford six-armed, iron-core star polymers, which were characterized by UV-vis and (1)H NMR spectroscopy. Estimated chelation efficiencies for formation of the star polymers (M(n) calcd: 20-240 kDa) were high, as determined by UV-vis spectral analysis. Within the molecular weight range investigated, differential scanning calorimetry and thermogravimetric analysis revealed that the small amounts of metal in the polyester stars and differences in polymer architecture had little effect on the thermal properties of the PLA/PCL materials. However, thin films of the red-violet colored iron-core stars exhibited reversible, thermochromic bleaching. Solutions and films of the polymers also responded (with color loss) to a variety of chemical stimuli (e.g., acid, base, peroxides, ammonia), thus revealing potential for use in diverse sensing applications. Likewise, the polyester

  6. Direct laser fabrication of nanowires on semiconductor surfaces

    NASA Astrophysics Data System (ADS)

    Haghizadeh, Anahita; Yang, Haeyeon

    2016-03-01

    Periodic nanowires are observed from (001) orientation of Si and GaAs when the surfaces are irradiated interferentially by high power laser pulses. These nanowires are self-assembled and can be strain-free while their period is consistent with interference period. The nanowire morphologies are studied by atomic force microscopy. The observed period between nanowires depends on the wavelengths used and interference angle. The nanowire width increases with laser intensity. The narrowest nanowires observed have the width smaller than 20 nm, which is more than 10 times smaller than the interference period.

  7. Honeycomb-shaped coordination polymers based on the self-assembly of long flexible ligands and alkaline-earth ions

    NASA Astrophysics Data System (ADS)

    Lian, Chen; Liu, Liu; Guo, Xu; Long, Yinshuang; Jia, Shanshan; Li, Huanhuan; Yang, Lirong

    2016-01-01

    Two novel coordination polymers, namely, [Ca(NCP)2]∞ (I) and [Sr(NCP)2]∞ (II) were synthesized under hydrothermal conditions based on 2-(4-carboxyphenyl)imidazo(4,5-f)-(1,10)phenanthroline (HNCP) and characterized by elemental analysis, infrared spectrometry, X-ray powder diffraction and single crystal X-ray diffraction. Findings indicate that I and II are isomorphous and isostructural, containing the unit of M(NCP-)4 (M=Ca(II) and Sr(II)), based on which to assemble into three-dimensional (3D) porous 4-fold interpenetration honeycomb-shaped neutral coordination polymers (CPs). Between the adjacent lamellar structures in I and II, there exist π-π interactions between the pyridine rings belonging to phenanthroline of NCP- which stabilize the frameworks. Both I and II display stronger fluorescence emissions as well as high thermal stability.

  8. Recent Advances in Gas Barrier Thin Films via Layer-by-Layer Assembly of Polymers and Platelets.

    PubMed

    Priolo, Morgan A; Holder, Kevin M; Guin, Tyler; Grunlan, Jaime C

    2015-05-01

    Layer-by-layer (LbL) assembly has emerged as the leading non-vacuum technology for the fabrication of transparent, super gas barrier films. The super gas barrier performance of LbL deposited films has been demonstrated in numerous studies, with a variety of polyelectrolytes, to rival that of metal and metal oxide-based barrier films. This Feature Article is a mini-review of LbL-based multilayer thin films with a 'nanobrick wall' microstructure comprising polymeric mortar and nano-platelet bricks that impart high gas barrier to otherwise permeable polymer substrates. These transparent, water-based thin films exhibit oxygen transmission rates below 5 × 10(-3) cm(3) m(-2) day(-1) atm(-1) and lower permeability than any other barrier material reported. In an effort to put this technology in the proper context, incumbent technologies such as metallized plastics, metal oxides, and flake-filled polymers are briefly reviewed. PMID:25800245

  9. Role of redox centre in charge transport investigated by novel self-assembled conjugated polymer molecular junctions

    NASA Astrophysics Data System (ADS)

    Wang, Zongrui; Dong, Huanli; Li, Tao; Hviid, Rune; Zou, Ye; Wei, Zhongming; Fu, Xiaolong; Wang, Erjing; Zhen, Yonggang; Nørgaard, Kasper; Laursen, Bo W.; Hu, Wenping

    2015-06-01

    Molecular electronics describes a field that seeks to implement electronic components made of molecular building blocks. To date, few studies have used conjugated polymers in molecular junctions despite the fact that they potentially transport charge more efficiently than the extensively investigated small-molecular systems. Here we report a novel type of molecular tunnelling junction exploring the use of conjugated polymers, which are self-assembled into ultrathin films in a distinguishable `planar' manner from the traditional vertically oriented small-molecule monolayers. Electrical measurements on the junctions reveal molecular-specific characteristics of the polymeric molecules in comparison with less conjugated small molecules. More significantly, we decorate redox-active functionality into polymeric backbones, demonstrating a key role of redox centre in the modulation of charge transport behaviour via energy level engineering and external stimuli, and implying the potential of employing tailor-made polymeric components as alternatives to small molecules for future molecular-scale electronics.

  10. Non-equilibrium self-assembly of metals on diblock copolymer templates

    NASA Astrophysics Data System (ADS)

    Lopes, Ward Antone

    Typically, the most perfectly ordered, self-assembled structures correspond to equilibrium states of the system. Here, I show that a high degree of order can arise out of strongly non-equilibrium conditions. I report on a systematic study of non-equilibrium aspects of the decoration of diblock copolymer ultrathin films by evaporated metals. I observe two distinct behaviors for selectively decorating the diblock copolymer: either the metal decorates the diblock copolymer template with nanoparticles or the metal decorates the template with nanowires. Remarkably, these nanowires remain stable under non-equilibrium conditions. I focus on results obtained with evaporated gold and silver on asymmetric polystyrene-b-polymethylmethacrylate (PS-b-PMMA). Gold and a number of other metals (indium, tin, lead, bismuth, aluminum) decorate the diblock copolymer with chains of nanoparticles and don't form wires. Silver forms chains of nanoparticles at low coverage (<30 A), but at high coverage (>100 A), silver forms nanowires. One can understand the formation of the chains of nanoparticles by understanding the equilibrium state of the system (metal + polymer). The silver nanowires, however, are highly non-equilibrium structures. To understand their formation, I modeled the self-assembly of the nanowires with a Monte Carlo simulation. This Monte Carlo simulation qualitatively agrees with the formation of the silver nanowires and their relaxation to equilibrium upon moderate heating.

  11. Redox-Robust Pentamethylferrocene Polymers and Supramolecular Polymers, and Controlled Self-Assembly of Pentamethylferricenium Polymer-Embedded Ag, AgI, and Au Nanoparticles.

    PubMed

    Gu, Haibin; Ciganda, Roberto; Castel, Patricia; Vax, Amélie; Gregurec, Danijela; Irigoyen, Joseba; Moya, Sergio; Salmon, Lionel; Zhao, Pengxiang; Ruiz, Jaime; Hernández, Ricardo; Astruc, Didier

    2015-12-01

    We report the first pentamethylferrocene (PMF) polymers and the redox chemistry of their robust polycationic pentamethylferricenium (PMFium) analogues. The PMF polymers were synthesized by ring-opening metathesis polymerization (ROMP) of a PMF-containing norbornene derivative by using the third-generation Grubbs ruthenium metathesis catalyst. Cyclic voltammetry studies allowed us to determine confidently the number of monomer units in the polymers through the Bard-Anson method. Stoichiometric oxidation by using ferricenium hexafluorophosphate quantitatively and instantaneously provided fully stable (even in aerobic solutions) blue d(5) Fe(III) metallopolymers. Alternatively, oxidation of the PMF-containing polymers was conducted by reactions with Ag(I) or Au(III) , to give PMFium polymer-embedded Ag and Au nanoparticles (NPs). In the presence of I2 , oxidation by using Ag(I) gave polymer-embedded Ag/AgI NPs and AgNPs at the surface of AgI NPs. Oxidation by using Au(III) also produced an Au(I) intermediate that was trapped and characterized. Engineered single-electron transfer reactions of these redox-robust nanomaterial precursors appear to be a new way to control their formation, size, and environment in a supramolecular way. PMID:26494439

  12. Influence of polymer aging on reliability indices of a typical printed-circuit assembly of radioelectronic equipment

    NASA Astrophysics Data System (ADS)

    Kuznetsov, G. V.; Kravchenko, E. V.

    2007-09-01

    Mathematical modeling of nonlinear nonstationary temperature fields of a typical printed-circuit assembly of radioelectronic equipment has been performed in a three-dimensional formulation with account for the convective and radiative heat exchange with the environment. On the basis of the data of the numerical experiment the “aging” (degradation) indices of polymer materials under prolonged thermal action have been determined. It has been established that the reliability of an object modeled with account for the real temperature fields is five times lower compared to the realization of normalized thermal conditions.

  13. Polymer complexes. LVII. Supramolecular assemblies of novel polymer complexes of dioxouranium(VI) with some substituted allyl azo dye compounds

    NASA Astrophysics Data System (ADS)

    Diab, M. A.; El-Sonbati, A. Z.; El-Bindary, A. A.; Balboula, M. Z.

    2013-05-01

    A novel method to synthesize some dioxouranium(VI) polymer complexes of the general formula [UO2(Ln)2(OAc)2] (where HLn = azo allyl rhodanine). The structure of the novel mononuclear dioxoutranium(VI) polymer complexes was characterized using elemental analysis, spectral (electronic, infrared, 1H &13C NMR) studies, magnetic susceptibility measurements and thermal analysis. The molar conductivities show that all the polymer complexes are non-electrolytes. The IR showed that the ligand HLn act as bidentate neutral through carbonyl group and imine group nitrogen atom forming thereby a six-membered chelating ring and concomitant formation of an intramolecular hydrogen bond. The υ3 frequency of UO2+2 has been shown to be an excellent molecular probe for studying the coordinating power of the ligands. The values of υ3 of the prepared complexes containing UO2+2 were successfully used to calculate the force constant, FUO (10-8 N/Å) and the bond length RUO (Å) of the Usbnd O bond. A strategy based upon both theoretical and experimental investigations has been adopted. The theoretical aspects are described in terms of the well-known theory of 5d-4f transitions. Wilson's, matrix method, Badger's formula, and Jones and El-Sonbati equations were used to calculate the Usbnd O bond distances from the values of the stretching and interaction force constants. The most probable correlation between Usbnd O force constant to Usbnd O bond distance were satisfactorily discussed in term of Badger's rule and the equations suggested by Jones and El-Sonbati. The effect of Hammet constant is also discussed.

  14. Tube-graft-Sheet Nano-Objects Created by A Stepwise Self-Assembly of Polymer-Polyoxometalate Hybrids.

    PubMed

    Tang, Jing; Li, Xue-Ying; Wu, Han; Ren, Li-Jun; Zhang, Yu-Qi; Yao, Hai-Xia; Hu, Min-Biao; Wang, Wei

    2016-01-19

    In this work, we report the preparation of complex nano-objects by means of a stepwise self-assembly of two polymer-polyoxometalate hybrids (PPHs) in solution. The PPHs are designed and synthesized by tethering two linear poly(ε-caprolactone)s (PCL) of different molecular weights (MW) on a complex of a Wells-Dawson-type polyoxometalate (POM) cluster and its countraions. The higher MW PCL-POM self-assembled into nanosheets, while the lower MW PCL-POM assembled into nanotubes just by altering the ratio of water in the DMF-water mixed solvent system. The two nano-objects have a similar membrane structure in which a PCL layer is sandwiched by the two POM-based complex layers. The PCL layer in the nanosheets is semicrystalline, while the PCL layer in the nanotubes is amorphous. We further exploited this MW-dependence to self-assemble the nanotubes on the nanosheet edges to create complex tube-graft-sheet nano-objects. We found that the nanotubes nucleate on the four {110} faces of the PCL crystal and then further grow along the crystallographic b-axis of the PCL crystal. Our findings offer hope for the further development of nano-objects with increasing complexity. PMID:26710830

  15. Annealing-free, flexible silver nanowire-polymer composite electrodes via a continuous two-step spray-coating method.

    PubMed

    Choi, Dong Yun; Kang, Hyun Wook; Sung, Hyung Jin; Kim, Sang Soo

    2013-02-01

    For the realization of high-efficiency flexible optoelectronic devices, transparent electrodes should be fabricated through a low-temperature process and have the crucial feature of low surface roughness. In this paper, we demonstrated a two-step spray-coating method for producing large-scale, smooth and flexible silver nanowire (AgNW)-poly3,4-ethylenedioxythiophene:polystyrenesulfonate (PEDOT:PSS) composite electrodes. Without the high-temperature annealing process, the conductivity of the composite film was improved via the lamination of highly conductive PEDOT:PSS modified by dimethyl sulfoxide (DMSO). Under the room temperature process condition, we fabricated the AgNW-PEDOT:PSS composite film showing an 84.3% mean optical transmittance with a 10.76 Ω sq(-1) sheet resistance. The figure of merit Φ(TC) was higher than that obtained from the indium tin oxide (ITO) films. The sheet resistance of the composite film slightly increased less than 5.3% during 200 cycles of tensile and compression folding, displaying good electromechanical flexibility for use in flexible optoelectronic applications. PMID:23241687

  16. A label-free cyclic assembly of G-quadruplex nanowires for cascade amplification detection of T4 polynucleotide kinase activity and inhibition.

    PubMed

    Shi, Zhilu; Zhang, Xiafei; Cheng, Rui; Li, Baoxin; Jin, Yan

    2015-09-01

    Several fluorescence methods have been developed for sensitive detection of PNK activity based on signal amplification techniques, but they need fluorescently labeled DNA probes and superabundant assistant enzymes. We have addressed these limitations and report here a label-free and enzyme-free amplification strategy for sensitively and specifically studying PNK activity and inhibition via hybridization chain reaction (HCR). First, the phosphorylation of hairpin DNA H1 by T4 PNK makes it be specifically digested by lambda exonuclease (λ exo) from 5' to 3' direction to generate a single-stranded initiator which can successively open hairpins H2 and H3 to trigger an autonomous assembly of long DNA nanowires. Meanwhile, an intermolecular G-quadruplex is formed between H2 and H3, thereby providing fluorescence enhancement of N-methyl mesoporphyrin IX (NMM) which is a highly quadruplex-selective fluorophore. So, the PNK activity can be facilely and sensitively detected by using NMM as a signal probe which provides a low background signal to improve the overall sensitivity, resulting in the detection limit of 3.37 × 10(-4) U mL(-1). More importantly, its successful application for detecting PNK activity in a complex biological matrix and studying the inhibition effects of PNK inhibitors demonstrated that it provides a promising platform for screening PNK inhibitors as well as detecting PNK activity. Therefore, it is a highly sensitive, specific, reliable and cost-effective strategy which shows great potential for biological process research, drug discovery, and clinical diagnostics. PMID:26215375

  17. Interfacial Rheology of Hydrogen-Bonded Polymer Multilayers Assembled at Liquid Interfaces: Influence of Anchoring Energy and Hydrophobic Interactions.

    PubMed

    Le Tirilly, Sandrine; Tregouët, Corentin; Reyssat, Mathilde; Bône, Stéphane; Geffroy, Cédric; Fuller, Gerald; Pantoustier, Nadège; Perrin, Patrick; Monteux, Cécile

    2016-06-21

    We study the 2D rheological properties of hydrogen-bonded polymer multilayers assembled directly at dodecane-water and air-water interfaces using pendant drop/bubble dilation and the double-wall ring method for interfacial shear. We use poly(vinylpyrrolidone) (PVP) as a proton acceptor and a series of polyacrylic acids as proton donors. The PAA series of chains with varying hydrophobicity was fashioned from poly(acrylic acid), (PAA), polymethacrylic acid (PMAA), and a homemade hydrophobically modified polymer. The latter consisted of a PAA backbone covalently grafted with C12 moieties at 1% mol (referred to as PAA-1C12). Replacing PAA with the more hydrophobic PMAA provides a route for combining hydrogen bonding and hydrophobic interactions to increase the strength and/or the number of links connecting the polyacid chains to PVP. This systematic replacement allows for control of the ability of the monomer units inside the absorbed polymer layer to reorganize as the interface is sheared or compressed. Consequently, the interplay of hydrogen bonding and hydrophobic interactions leads to control of the resistance of the polymer multilayers to both shear and dilation. Using PAA-1C12 as the first layer improves the anchoring energy of a few monomers of the chain without changing the strength of the monomer-monomer contact in the complex layer. In this way, the layer does not resist shear but resists compression. This strategy provides the means for using hydrophobicity to control the interfacial dynamics of the complexes adsorbed at the interface of the bubbles and droplets that either elongate or buckle upon compression. Moreover, we demonstrate the pH responsiveness of these interfacial multilayers by adding aliquots of NaOH to the acidic water subphase surrounding the bubbles and droplets. Subsequent pH changes can eventually break the polymer complex, providing opportunities for encapsulation/release applications. PMID:27176147

  18. Co-assembly of Zn(SPh){sub 2} and organic linkers into helical and zig-zag polymer chains

    SciTech Connect

    Liu Yi; Yu Lingmin; Loo, Say Chye Joachim; Blair, Richard G.; Zhang Qichun

    2012-07-15

    Two novel one-dimensional coordination polymers, single helicate [Zn(SPh){sub 2}(TPyTA)(EG)]{sub n} (EG=ethylene glycol) (1) and zig-zag structure [Zn(SPh){sub 2}(BPyVB)]{sub n} (2), were synthesized under solvothermal conditions at 150 Degree-Sign C or room temperature by the co-assembly of Zn(SPh){sub 2} and organic linkers such as 2,4,6-tri(4-pyridyl)-1,3,5-triazine (TPyTA) and 1,3-bis(trans-4-pyridylvinyl)benzene (BPyVB). X-ray crystallography study reveals that both polymers 1 and 2 crystallize in space group P2{sub 1}/c of the monoclinic system. The solid-state UV-vis absorption spectra show that 1 and 2 have maxium absorption onsets at 400 nm and 420 nm, respectively. TGA analysis indicates that 1 and 2 are stable up to 110 Degree-Sign C and 210 Degree-Sign C. - Graphical abstract: Two novel one-dimensional coordination polymers, single helicate [Zn(SPh){sub 2}(TPyTA)(EG)]{sub n} (1) and zig-zag structure [Zn(SPh){sub 2}(BPyVB)]{sub n} (2), were synthesized. Solid-state UV-vis absorptions show that 1 and 2 have maxium absorption onsets at 400 nm and 420 nm, respectively. TGA analysis indicates that 1 and 2 are stable up to 110 Degree-Sign C and 210 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Two novel one-dimensional coordination polymers have been synthesized. Black-Right-Pointing-Pointer TPyTA results in helical structures in 1 while BPyVB leads to zig-zag chains in 2. Black-Right-Pointing-Pointer Solid-state UV-vis absorption spectra and TGA analysis of the title polymers were studied.

  19. Surfactant-Templated Mesoporous Metal Oxide Nanowires

    DOE PAGESBeta

    Luo, Hongmei; Lin, Qianglu; Baber, Stacy; Naalla, Mahesh

    2010-01-01

    We demore » monstrate two approaches to prepare mesoporous metal oxide nanowires by surfactant assembly and nanoconfinement via sol-gel or electrochemical deposition. For example, mesoporous Ta 2 O 5 and zeolite nanowires are prepared by block copolymer Pluronic 123-templated sol-gel method, and mesoporous ZnO nanowires are prepared by electrodeposition in presence of anionic surfactant sodium dodecyl sulfate (SDS) surfactant, in porous membranes. The morphologies of porous nanowires are studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses.« less

  20. Optimization and Characterization of Self-assembled Triblock Polymer Membranes with Chemically-Tunable Pore Walls for Nanofiltration Applications

    NASA Astrophysics Data System (ADS)

    Sargent, Jessica; Mulvenna, Ryan; Prato, Rafael; Weidman, Jacob; Phillip, William; Boudouris, Bryan

    2015-03-01

    The field of block polymer-based membranes for separation applications has grown considerably in the past several years. However, decreasing the domain sizes of these membranes to below 5 nm has proven to be a challenge in many instances. Here, we demonstrate that a triblock polymer, polyisoprene- b-polystyrene- b-poly(tert-butyl methacrylate) (PI-PS-PtBMA), can be utilized to form nanoporous membranes capable of high flux and high selectivity based on both size and chemical composition. By controlling the synthesis, solution self-assembly, and non-solvent induced phase separation of these polymers, a scalable fabrication process can produce thin-film membranes that feature monodisperse pores approaching 1 nm in diameter, tunable pore-wall chemistry, good mechanical stability, and chlorine degradation resistance. The PtBMA functionality can further be converted to a number of side chain functionalities through simple coupling chemistry to produce membranes with specific chemical and structural characteristics tailored to meet the needs of various applications. In particular, these membranes provide a promising, inexpensive platform for chlorine degradation and fouling-resistant membranes for water purification that can be produced on an industrial scale.

  1. Heparin as a Bundler in a Self-Assembled Fibrous Network of Functionalized Protein-Based Polymers.

    PubMed

    Włodarczyk-Biegun, Małgorzata K; Slingerland, Cornelis J; Werten, Marc W T; van Hees, Ilse A; de Wolf, Frits A; de Vries, Renko; Stuart, Martien A Cohen; Kamperman, Marleen

    2016-06-13

    Nature shows excellent control over the mechanics of fibrous hydrogels by assembling protein fibers into bundles of well-defined dimensions. Yet, obtaining artificial materials displaying controlled bundling remains a challenge. Here, we developed genetically engineered protein-based polymers functionalized with heparin-binding KRSR domains and show controlled bundling using heparin as a binder. The protein polymer forms fibers upon increasing the pH to physiological values and at higher concentrations fibrous gels. We show that addition of heparin to the protein polymer with incorporated KRSR domains, induces bundling, which results in faster gel formation and stiffer gels. The interactions are expected to be primarily electrostatic and fiber bundling has an optimum when the positive charges of KRSR are approximately in balance with the negative charges of the heparin. Our study suggests that, generally, a straightforward method to control the properties of fibrous gels is to prepare a fiber former with specific binding domains and then simply adding an appropriate amount of binder. PMID:27129090

  2. Conductive polymer nanocomposites with hierarchical multi-scale structures via self-assembly of carbon-nanotubes on graphene on polymer-microspheres.

    PubMed

    Tang, Changyu; Long, Gucheng; Hu, Xin; Wong, Ka-wai; Lau, Woon-ming; Fan, Meikun; Mei, Jun; Xu, Tao; Wang, Bin; Hui, David

    2014-07-21

    A novel and highly conductive 3-dimensional (3D) hierarchical multi-scale structure is formed by a new, simple, facile, and water-based method that enables practical production of conductive carbon nanofiller/polymer composites. More specifically, the π-π interaction between CNTs and graphene oxide (GO) is exploited to disperse conductive but non-polar CNTs with amphiphilic GO sheets to form a stable aqueous colloidal solution. Aqueous-dispersible latex-polystyrene microspheres are then added to enable the self-assembly processes of anchoring CNTs on GO and wrapping microspheres with GO-stabilized CNTs for the formation of an intriguing 3D hierarchical multi-scale structure. During this process, GO is reduced to conductive reduced-graphene oxide (RGO). The resultant RGO sheets act as "nano-walls" to prevent CNTs from randomly diffusing into the polymer bulk during thermal pressing of RGO-CNT/microspheres, which results in the formation of a 3D foam-like network of RGO-CNTs with high quality. The resultant composite with such a structure gives an ultra-low percolation threshold (0.03 vol% RGO-CNTs) and a reasonably high conductivity (153 S m(-1) at 4 vol% RGO-CNTs), which could satisfy various applications requiring both transparency and electrical conduction characteristics (e.g. transparent antistatic coatings, capacitive touch-screens, and transparent electronic devices). PMID:24791273

  3. Polymer-facilitated low temperature fusing of spray-coated silver nanowire networks as transparent top and bottom electrodes in small molecule organic photovoltaics (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Selzer, Franz; Weiß, Nelli; Kneppe, David; Bormann, Ludwig; Sachse, Christoph; Gaponik, Nikolai; Eychmüller, Alexander; Leo, Karl; Müller-Meskamp, Lars

    2015-10-01

    Networks of silver nanowires (AgNWs) are promising candidates for transparent conducting electrodes in organic photovoltaics (OPV), as they achieve similar performance as the commonly used indium tin oxide (ITO) at lower cost and increased flexibility. The initial sheet resistance (Rs) of AgNW electrodes typically needs to be reduced by a post-annealing step (90 min@200 °C), being detrimental for processing on polymeric substrates. We present novel low temperature-based methods to integrate AgNWs in organic small molecule-based photovoltaics, either as transparent and highly conductive bottom-electrode or, for the first time, as spray-coated AgNW top-electrode. The bottom-electrodes are prepared by organic matrix assisted low-temperature fusing. Here, selected polymers are coated below the AgNWs to increase the interaction between NWs and substrate. In comparison to networks without these polymeric sublayers, the Rs is reduced by two orders of magnitude. AgNW top-electrodes are realized by dispersing modified high-quality AgNWs in inert solvents, which do not damage small molecule layers. Accordingly, our AgNW dispersion can be spray-coated onto all kind of OPV devices. Both bottom- and top-electrodes show a Rs of <11 Ω/ at >87 % transparency directly after spray-coating at very low substrate temperatures of <80 °C. We also demonstrate the implementation of our AgNW electrodes in organic solar cells. The corresponding devices show almost identical performance compared to organic solar cells exploiting ITO as bottom or thermally evaporated thin-metal as top-electrode.

  4. Self-assembly of silk-elastinlike protein polymers into three-dimensional scaffolds for biomedical applications

    NASA Astrophysics Data System (ADS)

    Zeng, Like

    Production of brand new protein-based materials with precise control over the amino acid sequences at single residue level has been made possible by genetic engineering, through which artificial genes can be developed that encode protein-based materials with desired features. As an example, silk-elastinlike protein polymers (SELPs), composed of tandem repeats of amino acid sequence motifs from Bombyx mori (silkworm) silk and mammalian elastin, have been produced in this approach. SELPs have been studied extensively in the past two decades, however, the fundamental mechanism governing the self-assembly process to date still remains largely unresolved. Further, regardless of the unprecedented success when exploited in areas including drug delivery, gene therapy, and tissue augmentation, SELPs scaffolds as a three-dimensional cell culture model system are complicated by the inability of SELPs to provide the embedded tissue cells with appropriate biochemical stimuli essential for cell survival and function. In this dissertation, it is reported that the self-assembly of silk-elastinlike protein polymers (SELPs) into nanofibers in aqueous solutions can be modulated by tuning the curing temperature, the size of the silk blocks, and the charge of the elastin blocks. A core-sheath model was proposed for nanofiber formation, with the silk blocks in the cores and the hydrated elastin blocks in the sheaths. The folding of the silk blocks into stable cores -- affected by the size of the silk blocks and the charge of the elastin blocks -- plays a critical role in the assembly of silk-elastin nanofibers. The assembled nanofibers further form nanofiber clusters on the microscale, and the nanofiber clusters then coalesce into nanofiber micro-assemblies, interconnection of which eventually leads to the formation of three-dimensional scaffolds with distinct nanoscale and microscale features. SELP-Collagen hybrid scaffolds were also fabricated to enable independent control over the

  5. Steric hindrance regulated supramolecular assembly between β-cyclodextrin polymer and pyrene for alkaline phosphatase fluorescent sensing

    NASA Astrophysics Data System (ADS)

    Song, Chunxia; Yang, Xiaohai; Wang, Kemin; Wang, Qing; Liu, Jianbo; Huang, Jin; Zhou, Maogui; Guo, Xiaochen

    2016-03-01

    We herein report a strategy for sensitive alkaline phosphatase (ALP) fluorescent sensing based on steric hindrance regulated supramolecular assembly between β-cyclodextrin polymer (polyβ-CD) and pyrene. The fluorescence of pyrene was enhanced more than 10 times through supramolecular assembly with polyβ-CD. The 5‧-phosphorylated dsDNA probe with pyrene attached on the 3‧-terminal could be cleaved by λ exonuclease (λ exo), yielding pyrene attached on mononucleotides. Pyrene attached on mononucleotides could easily enter the cavity of polyβ-CD, resulting in fluorescence enhancement. When ALP was introduced, it could remove 5‧-phosphate groups from dsDNA and then prevented the cleavage of dsDNA. Pyrene attached on dsDNA was difficult to enter the cavity of polyβ-CD because of steric hindrance, resulting in an inconspicuous fluorescence enhancement. Owing to the excellent fluorescence enhancement during steric hindrance regulated supramolecular assembly, excellent performance of the assay method was achieved for ALP with a detection limit of 0.04 U mL- 1. The detection limit was superior or comparable with the reported methods. Besides, this method was simple in design, avoiding double-labeling of probe.

  6. Novel Polymer Nanocomposites Resulted from Melt Processing of Polystyrene-Based Substrates Coated with Layer-by-Layer Assemblies

    NASA Astrophysics Data System (ADS)

    Soltani, Iman; Spontak, Richard J.

    The novel polymer nanocomposites (PNCs) prepared through two steps of coating polystyrene-based substrates with layer-by-layer (LBL) deposition of montmorillonite and alternative polyelectrolyte layers of polyethyleneimine and polyethylene terephthalate ionomer, followed by their cyclic melt pressing, demonstrated particular morphologies. Transmission electron microscopy images at high magnification scales showed the occurrence of swollen intercalation and flocculated exfoliations of clay platelets, down to a few nanometer thickness, inside and sometimes out of LBL assemblies crushed portions. In fact, intercalation and exfoliation of clay platelets, established in LBL assemblies, increased by shear applied through their repetitive melt pressing. Additionally, x-ray diffractometry traces confirmed the aforementioned increase in clay intercalation. These high aspect ratio LBL assemblies portions formed highly tortuous labyrinths, which may work as scavenging centers to promote barrier properties of the PNCs against transport of gases like oxygen and carbon dioxide. It is despite spontaneously low interaction between hydrophobic styrenic groups and almost hydrophilic natural clay and moderate efficiency of cyclic pressing for providing intensive shear stress on samples.

  7. Polymers.

    ERIC Educational Resources Information Center

    Tucker, David C.

    1986-01-01

    Presents an open-ended experiment which has students exploring polymer chemistry and reverse osmosis. This activity involves construction of a polymer membrane, use of it in a simple osmosis experiment, and application of its principles in solving a science-technology-society problem. (ML)

  8. Synthesis of silver nanowires using hydrothermal technique for flexible transparent electrode application

    NASA Astrophysics Data System (ADS)

    Vijila, C. V. Mary; Rahman, K. K. Arsina; Parvathy, N. S.; Jayaraj, M. K.

    2016-05-01

    Transparent conducting films are becoming increasingly interesting because of their applications in electronics industry such as their use in solar energy applications. In this work silver nanowires were synthesized using solvothermal method by reducing silver nitrate and adding sodium chloride for assembling silver into nanowires. Absorption spectra of nanowires in the form of a dispersion in deionized water, AFM and SEM images confirm the nanowire formation. Solution of nanowire was coated over PET films to obtain transparent conducting films.

  9. Ferritin-Polymer Conjugates: Grafting Chemistry and Integration into Nanoscale Assemblies

    SciTech Connect

    Y Hu; D Samanta; S Parelkar; S Hong; Q Wang; T Russell; T Emrick

    2011-12-31

    Controlled free radical polymerization chemistry is used to graft polymer chains to the corona of horse spleen ferritin (HSF) nanocages. Specifically, poly(methacryloyloxyethyl phosphorylcholine) (polyMPC) and poly(PEG methacrylate) (polyPEGMA) chains are grafted onto the nanocages by atom transfer radical polymerization (ATRP), in which the molecular weight of the polymer grafts is controlled by the monomer-to-initiator feed ratio. PolyMPC and polyPEGMA-grafted ferritin show a generally suppressed inclusion into diblock copolymer films relative to native ferritin, and the polymer coating is seen to mask the ferritin nanocages from antibody recognition. The solubility of polyPEGMA-coated ferritin in organic solvents enables its processing with polystyrene-block-poly(ethylene oxide) copolymers, and selective integration into the PEO domains of microphase-separated copolymer structures.

  10. Self-assembled breath figure arrays of conjugated conducting polymers for photovoltaic application

    NASA Astrophysics Data System (ADS)

    Routh, Prahlad Kumar; Venkatesh, T. A.; Cotlet, Mircea

    2014-03-01

    Ordered microporous polymer structures have potential application in catalysis, surface engineering and optoelectronics. The Breath Figure Technique (BFT) is a simple method of producing such ordered microporous structures. In this study BFT was applied to a series of commercial conjugated polymer polythiophene derivatives with varying side chain length (n =6,8,10,12). An in-depth study of processing parameters has been carried with the aim of controlling the morphology of the honeycomb film over large, PV relevant areas. Structural and spectroscopic characterization of honeycomb films were performed using Scanning Electron Microscopy (SEM), X-ray scattering, Fluorescence Lifetime Imaging (FLIM) and Spectroscopy. Blends of these polymers with a fullerene derivative, PCBM, were also subjected to BFT and characterized with similar methods to assess their potential use as active layers in PV solar cells. Center for Functional Nanomaterials, Brookhaven National Laboratory.

  11. Doxorubicin-loaded aromatic imine-contained amphiphilic branched star polymer micelles: synthesis, self-assembly, and drug delivery

    PubMed Central

    Qiu, Liang; Hong, Chun-Yan; Pan, Cai-Yuan

    2015-01-01

    Redox-and pH-sensitive branched star polymers (BSPs), BP(DMAEMA-co-MAEBA-co-DTDMA)(PMAIGP)ns, have been successively prepared by two steps of reversible addition–fragmentation chain transfer (RAFT) polymerization. The first step is RAFT polymerization of 2-(N,N-dimethylaminoethyl)methacrylate (DMAEMA) and p-(methacryloxyethoxy) benzaldehyde (MAEBA) in the presence of divinyl monomer, 2,2′-dithiodiethoxyl dimethacrylate (DTDMA). The resultant branched polymers were used as a macro-RAFT agent in the subsequent RAFT polymerization. After hydrolysis of the BSPs to form BP(DMAEMA-co-MAEBA-co-DTDMA)(PMAGP)ns (BSP-H), the anticancer drug doxorubicin (DOX) was covalently linked to branched polymer chains by reaction of primary amine of DOX and aldehyde groups in the polymer chains. Their compositions, structures, molecular weights, and molecular weight distributions were respectively characterized by nuclear magnetic resonance spectra and gel permeation chromatography measurements. The DOX-loaded micelles were fabricated by self-assembly of DOX-containing BSPs in water, which were characterized by transmission electron microscopy and dynamic light scattering. Aromatic imine linkage is stable in neutral water, but is acid-labile; controlled release of DOX from the BSP-H-DOX micelles was realized at pH values of 5 and 6, and at higher acidic solution, fast release of DOX was observed. In vitro cytotoxicity experiment results revealed low cytotoxicity of the BSPs and release of DOX from micelles in HepG2 and HeLa cells. Confocal laser fluorescence microscopy observations showed that DOX-loaded micelles have specific interaction with HepG2 cells. Thus, this type of BSP micelle is an efficient drug delivery system. PMID:26056444

  12. Doxorubicin-loaded aromatic imine-contained amphiphilic branched star polymer micelles: synthesis, self-assembly, and drug delivery.

    PubMed

    Qiu, Liang; Hong, Chun-Yan; Pan, Cai-Yuan

    2015-01-01

    Redox-and pH-sensitive branched star polymers (BSPs), BP(DMAEMA-co-MAEBA-co-DTDMA)(PMAIGP)(n)s, have been successively prepared by two steps of reversible addition-fragmentation chain transfer (RAFT) polymerization. The first step is RAFT polymerization of 2-(N,N-dimethylaminoethyl)methacrylate (DMAEMA) and p-(methacryloxyethoxy) benzaldehyde (MAEBA) in the presence of divinyl monomer, 2,2'-dithiodiethoxyl dimethacrylate (DTDMA). The resultant branched polymers were used as a macro-RAFT agent in the subsequent RAFT polymerization. After hydrolysis of the BSPs to form BP(DMAEMA-co-MAEBA-co-DTDMA)(PMAGP)(n)s (BSP-H), the anticancer drug doxorubicin (DOX) was covalently linked to branched polymer chains by reaction of primary amine of DOX and aldehyde groups in the polymer chains. Their compositions, structures, molecular weights, and molecular weight distributions were respectively characterized by nuclear magnetic resonance spectra and gel permeation chromatography measurements. The DOX-loaded micelles were fabricated by self-assembly of DOX-containing BSPs in water, which were characterized by transmission electron microscopy and dynamic light scattering. Aromatic imine linkage is stable in neutral water, but is acid-labile; controlled release of DOX from the BSP-H-DOX micelles was realized at pH values of 5 and 6, and at higher acidic solution, fast release of DOX was observed. In vitro cytotoxicity experiment results revealed low cytotoxicity of the BSPs and release of DOX from micelles in HepG2 and HeLa cells. Confocal laser fluorescence microscopy observations showed that DOX-loaded micelles have specific interaction with HepG2 cells. Thus, this type of BSP micelle is an efficient drug delivery system. PMID:26056444

  13. The first biantennary bacterial secondary cell wall polymer and its influence on S-layer glycoprotein assembly.

    PubMed Central

    Steindl, Christian; Schäffer, Christina; Wugeditsch, Thomas; Graninger, Michael; Matecko, Irena; Müller, Norbert; Messner, Paul

    2002-01-01

    -layer glycoprotein in vitro. Initial crystallization experiments performed with the soluble S-layer glycoprotein revealed that the assembly property could be restored upon dissociation of the polymer by the addition of poly(ethylene glycols). The formed two-dimensional crystalline S-layer self-assembly products exhibited the same lattice symmetry as observed on intact bacterial cells. PMID:12201818

  14. Supramolecular polymers with tunable topologies via hierarchical coordination-driven self-assembly and hydrogen bonding interfaces

    PubMed Central

    Yan, Xuzhou; Li, Shijun; Pollock, James Bryant; Cook, Timothy R.; Chen, Jianzhuang; Zhang, Yanyan; Ji, Xiaofan; Yu, Yihua; Huang, Feihe; Stang, Peter J.

    2013-01-01

    A powerful strategy to obtain complex supramolecular materials is the bottom-up construction of noncovalently bound materials by hierarchical self-assembly. This assembly process involves stepwise, uniform increases to the architectural complexity of a substrate, starting from discrete precursors and growing in dimensionality through controlled reactivity to a final product. Herein, two orthogonal processes are exploited: coordination-driven self-assembly and hydrogen bonding. The former relies on the predictable formation of metal–ligand bonds wherein the directionalities of the rigid precursors used determines the structural outcome. The latter uses 2-ureido-4-pyrimidinone interfaces that are structurally robust by virtue of the quadruple hydrogen bonding that can occur between subunits. By combining these two processes into a single system, it is possible to generate hierarchical materials that preserve the attractive tunability associated with discrete supramolecular coordination complexes. For instance, the synthesis of a one-dimensional chain comprising linked metalla-rhomboids is readily adapted to a 2D cross-linked hexagonal network by simply selecting a different metal acceptor precursor as an assembly component. The specific interactions between subunits, in this case platinum(II)-pyridyl bonds and the quadruple H-bonding of ureidopyrimidinone, are unchanged, establishing a unique strategy to obtain supramolecular polymers with marked topological differences with minimal synthetic redesign. In addition, the structural rigidity imposed by the inclusion of the platinum metallacycles serves to minimize the formation of cyclic oligomers, increasing the efficacy of formation and improving the properties of the resultant materials. Furthermore, this study taps the potential of organoplatinum(II) metallacycles in materials science. PMID:24019475

  15. Freestanding and Reactive Thin Films Fabricated by Covalent Layer-by-Layer Assembly and Subsequent Lift-Off of Azlactone-Containing Polymer Multilayers

    PubMed Central

    Buck, Maren E.

    2010-01-01

    We report an approach to the fabrication of freestanding and amine-reactive thin films that is based on the reactive layer-by-layer assembly and subsequent lift-off of azlactone-containing polymer multilayers. We demonstrate that covalently crosslinked multilayers fabricated using the azlactone-functionalized polymer poly(2-vinyl-4,4-dimethylazlactone) (PVDMA) and a primary amine-containing polymer [poly(ethyleneimine) (PEI)] can be delaminated from planar glass and silicon surfaces by immersion in mildly acidic aqueous environments to yield flexible freestanding membranes. These freestanding membranes are robust and can withstand exposure to strong acid, strong base, or incubation in high ionic strength solutions that typically lead to the disruption and erosion of polymer multilayers assembled by reversible weak interactions (e.g., ‘polyelectrolyte multilayers’ assembled by electrostatic interactions or hydrogen bonding). We demonstrate further that these PEI/PVDMA assemblies contain residual reactive azlactone functionality that can be exploited to chemically modify the films (either directly after fabrication or after they have been lifted off of the substrates on which they were fabricated) using a variety of amine-functionalized small molecules. These freestanding membranes can also be transferred readily onto other objects (for example, onto the surfaces of planar substrates containing holes or pores) to fabricate suspended polymer membranes and other film-functionalized interfaces. In addition to planar, two-dimensional freestanding films, this approach can be used to fabricate and isolate three-dimensional freestanding membranes (e.g., curved films or tubes) by layer-by-layer assembly on, and subsequent lift-off from, the surfaces of topologically complex substrates (e.g., the curved ends of glass tubing, etc.). The results of this investigation, when combined, suggest the basis of methods for the fabrication of stable, chemically-reactive, and

  16. Self-assembly of a three-dimensional fibrous polymer sponge by electrospinning.

    PubMed

    Sun, Bin; Long, Yun-Ze; Yu, Fang; Li, Meng-Meng; Zhang, Hong-Di; Li, Wen-Jing; Xu, Tian-Xiang

    2012-03-21

    In this paper, we report a quick approach to self-assemble three-dimensional (3D) spongiform nanofiber stacks via electrospinning, which usually fabricates 2D non-woven fiber mats. Through controlling experimental conditions, cone-like polystyrene fiber stacks can be self-assembled on aluminum foil within 30 min. The stacks are able to reach a height of more than 10 cm. Moreover, conversion between the 3D fiber stack and 2D thin film can be controlled. The formation mechanism of the self-assembled fiber stacks and the influence of experimental conditions have also been explored. The 3D fiber stacks may be promising for applications in many fields such as tissue engineering, electrodes of battery, and filtration, etc. PMID:22344309

  17. Self-assembly of a three-dimensional fibrous polymer sponge by electrospinning

    NASA Astrophysics Data System (ADS)

    Sun, Bin; Long, Yun-Ze; Yu, Fang; Li, Meng-Meng; Zhang, Hong-Di; Li, Wen-Jing; Xu, Tian-Xiang

    2012-03-01

    In this paper, we report a quick approach to self-assemble three-dimensional (3D) spongiform nanofiber stacks via electrospinning, which usually fabricates 2D non-woven fiber mats. Through controlling experimental conditions, cone-like polystyrene fiber stacks can be self-assembled on aluminum foil within 30 min. The stacks are able to reach a height of more than 10 cm. Moreover, conversion between the 3D fiber stack and 2D thin film can be controlled. The formation mechanism of the self-assembled fiber stacks and the influence of experimental conditions have also been explored. The 3D fiber stacks may be promising for applications in many fields such as tissue engineering, electrodes of battery, and filtration, etc.

  18. Toward a chemiresistive ammonia (NH3) gas sensor based on viral-templated gold nanoparticles embedded in polypyrrole nanowires

    NASA Astrophysics Data System (ADS)

    Yan, Yiran; Zhang, Miluo; Su, Heng Chia; Myung, Nosang V.; Haberer, Elaine D.

    2014-08-01

    Preliminary studies toward the assembly of a gold-polypyrrole (PPy) peapod-like chemiresistive ammonia (NH3) gas sensors are presented. The proposed synthesis process will use electropolymerization to embed gold nanoparticles in polypyrrole nanowires. Viral-templating of gold nanoparticles and PPy electrodeposition via cyclic voltammetry are the focus of this investigation. A gold-binding M13 bacteriophage was used as a bio-template to assemble continuous chains of gold nanoparticles on interdigitated Pt working electrodes. The dimensions of the resulting nanowire-like structures were examined and the electrical resistance measured. PPy films were electropolymerized using an interdigitated planar, Pt electrode integrated counter and reference electrode. Morphological characterization of the polymer films was completed.

  19. Enhanced Electron Extraction Capability of Polymer Solar Cells via Employing Electrostatically Self-Assembled Molecule on Cathode Interfacial Layer.

    PubMed

    Li, Zhiqi; Zhang, Xinyuan; Liu, Chunyu; Zhang, Zhihui; Li, Jinfeng; Shen, Liang; Guo, Wenbin; Ruan, Shengping

    2016-03-01

    In this paper, high-performance inverted polymer solar cells (PSCs) with a modified cathode buffer layer, titanium dioxide:polyethylenimine (TiO2:PEI), are demonstrated. The TiO2-O-PEI transport layer was fabricated by electrostatically self-assembled monolayers (ESAM) of PEI molecules. Protonated amine functional groups of PEI can combine protons (H(+)) hydrolyzing from its aqueous solution. Also, PEI could produce ESAM on the surface of hydroxylated TiO2 because of its cationic characteristics. The incorporation of the TiO2-O-PEI layer enhances the photocurrent and power conversion efficiency (PCE) due to the improved interfacial electron transport and extraction of the TiO2-O-PEI surface and the increased light absorption of the active layer. The enhanced PCE, low-cost materials, and solution process of TiO2-O-PEI buffer layers provide a promising method for highly efficient PSCs. PMID:26955888

  20. Honeycomb-patterned fluorescent films fabricated by self-assembly of surfactant-assisted porphyrin/polymer composites.

    PubMed

    Fan, Dawei; Xia, Xiulong; Ma, Hongmin; Du, Bin; Wei, Qin

    2013-07-15

    A novel honeycomb-patterned fluorescent film was fabricated by self-assembly of polystyrene (PS)/poly(ethylene glycol) (PEG)/meso-tetra (N-methy-4-pyridyl) porphinetetratosylate (TMPyP) blend system, at the assistance of diisooctyl sodium sulfosuccinate (AOT). Ordered microporous PS/PEG/TMPyP/AOT blend films were prepared by the breath figure method. The condensed water droplets acted as the sacrificial templates, which were stabilized by strong hygroscopic PEG and amphiphilic surfactant AOT. Relative humidity and evaporation conditions considered as critical factors were investigated to control the morphologies of the films. The introduction of surfactant AOT greatly promoted the dissolution of the TMPyP in PS/PEG polymer solution according to the UV-vis spectra data, which led to the fluorescence enhancement of ordered porous blend films. The unique "internal ring" structures were formed during phase separation and confirmed by scanning electron microscopy images and fluorescence micrographs. PMID:23660019

  1. Comb polymer architecture and particle size effects on the behavior of biphasic nanoparticle inks for direct-write assembly

    NASA Astrophysics Data System (ADS)

    Yoshikawa, Jun

    Biphasic nanoparticle mixtures composed of attractive and repulsive colloidal species enable the direct-write assembly of 3D structures with much finer features than those produced by pure colloidal gels. These mixtures rely on the use of comb polymer dispersants to render one particle population stable, while the other population is attractive. In this thesis, we systematically investigate the effects of comb polymer architecture and particle size ratio on the behavior of biphasic nanoparticle inks with the overarching aim of further advancing the direct-write assembly of 3D colloidal structures. We first investigated the effects of both pure polyelectrolytes, poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA), and comb polymer dispersants composed of a PMAA backbone with methoxy-poly(ethylene oxide) (mPEO) teeth of varying molecular weights on the stability of barium titanate (BaTiO 3) suspensions. While each dispersant imparts stability to BaTiO 3 nanoparticles at low ionic strength (< 0.01 M), only the PMAA-mPEO comb polymer with the longest teeth (MWteeth = 2000) provides stability at higher ionic strengths over a broad range of particle sizes and counterion valencies. These results provide guidelines for tailoring the molecular architecture and functionality of comb polymer dispersants for optimal stabilization of the repulsive particle population within the biphasic inks. Next, particle size effects on the rheological properties of biphasic nanoparticle suspensions are studied. Shear elastic modulus, shear yield stress, and compressive yield stress are measured for mixtures of varying total volume fraction, attractive-to-repulsive volume fraction, and particle size ratio between attractive and repulsive species. Our observations indicate that the repulsive particles hinder the formation of the attractive gel network. The time required for shear elastic modulus to approach a steady-state value increases with the fraction of repulsive species

  2. Block copolymer assembly on nanoscale patterns of polymer brushes formed by electrohydrodynamic jet printing.

    PubMed

    Onses, M Serdar; Ramírez-Hernández, Abelardo; Hur, Su-Mi; Sutanto, Erick; Williamson, Lance; Alleyne, Andrew G; Nealey, Paul F; de Pablo, Juan J; Rogers, John A

    2014-07-22

    Fundamental understanding of the self-assembly of domains in block copolymers (BCPs) and capabilities in control of these processes are important for their use as nanoscale templates in various applications. This paper focuses on the self-assembly of spin-cast and printed poly(styrene-block-methyl methacrylate) BCPs on patterned surface wetting layers formed by electrohydrodynamic jet printing of random copolymer brushes. Here, end-grafted brushes that present groups of styrene and methyl methacrylate in geometries with nanoscale resolution deterministically define the morphologies of BCP nanostructures. The materials and methods can also be integrated with lithographically defined templates for directed self-assembly of BCPs at multiple length scales. The results provide not only engineering routes to controlled formation of complex patterns but also vehicles for experimental and simulation studies of the effects of chemical transitions on the processes of self-assembly. In particular, we show that the methodology developed here provides the means to explore exotic phenomena displayed by the wetting behavior of BCPs, where 3-D soft confinement, chain elasticity, interfacial energies, and substrate's surface energy cooperate to yield nonclassical wetting behavior. PMID:24882265

  3. Cooperative Self-Assembly Transfer from Hierarchical Supramolecular Polymers to Gold Nanoparticles.

    PubMed

    Coelho, João Paulo; Tardajos, Gloria; Stepanenko, Vladimir; Rödle, Alexander; Fernández, Gustavo; Guerrero-Martínez, Andrés

    2015-11-24

    The transfer of information encoded by molecular subcomponents is a key phenomenon that regulates the biological inheritance in living organisms, yet there is a lack of understanding of related transfer mechanisms at the supramolecular level in artificial multicomponent systems. Our contribution to tackle this challenge has focused on the design of a thiolated π-conjugated linking unit, whose hierarchical, cooperative self-assembly in nonpolar media can be efficiently transferred from the molecular to the nanoscopic level, thereby enabling the reversible self-assembly of gold nanoparticle (AuNP) clusters. The transfer of supramolecular information by the linking π-system can only take place when a specific cooperative nucleation-elongation mechanism is operative, whereas low-ordered noncooperative assemblies formed below a critical concentration do not suffice to extend the order to the AuNP level. To the best of our knowledge, our approach has allowed for the first time a deep analysis of the hierarchy levels and thermodynamics involved in the self-assembly of AuNPs. PMID:26493583

  4. Reversible morphology transitions of supramolecular polymer self-assemblies for switch-controlled drug release.

    PubMed

    Zhang, Haitao; Fan, Xiaodong; Suo, Rongtian; Li, Hui; Yang, Zhen; Zhang, Wanbin; Bai, Yang; Yao, Hao; Tian, Wei

    2015-10-28

    A novel method for switch-controlled drug release was developed through the reversible morphology transitions of supramolecular branched copolymer self-assemblies. The reversible transitions from vesicles to nanoparticles were successfully achieved by alternating UV and visible light irradiation to obtain morphology-controlled drug release in a switch mode. PMID:26343347

  5. Conductive polymer nanocomposites with hierarchical multi-scale structures via self-assembly of carbon-nanotubes on graphene on polymer-microspheres

    NASA Astrophysics Data System (ADS)

    Tang, Changyu; Long, Gucheng; Hu, Xin; Wong, Ka-Wai; Lau, Woon-Ming; Fan, Meikun; Mei, Jun; Xu, Tao; Wang, Bin; Hui, David

    2014-06-01

    A novel and highly conductive 3-dimensional (3D) hierarchical multi-scale structure is formed by a new, simple, facile, and water-based method that enables practical production of conductive carbon nanofiller/polymer composites. More specifically, the π-π interaction between CNTs and graphene oxide (GO) is exploited to disperse conductive but non-polar CNTs with amphiphilic GO sheets to form a stable aqueous colloidal solution. Aqueous-dispersible latex-polystyrene microspheres are then added to enable the self-assembly processes of anchoring CNTs on GO and wrapping microspheres with GO-stabilized CNTs for the formation of an intriguing 3D hierarchical multi-scale structure. During this process, GO is reduced to conductive reduced-graphene oxide (RGO). The resultant RGO sheets act as ``nano-walls'' to prevent CNTs from randomly diffusing into the polymer bulk during thermal pressing of RGO-CNT/microspheres, which results in the formation of a 3D foam-like network of RGO-CNTs with high quality. The resultant composite with such a structure gives an ultra-low percolation threshold (0.03 vol% RGO-CNTs) and a reasonably high conductivity (153 S m-1 at 4 vol% RGO-CNTs), which could satisfy various applications requiring both transparency and electrical conduction characteristics (e.g. transparent antistatic coatings, capacitive touch-screens, and transparent electronic devices).A novel and highly conductive 3-dimensional (3D) hierarchical multi-scale structure is formed by a new, simple, facile, and water-based method that enables practical production of conductive carbon nanofiller/polymer composites. More specifically, the π-π interaction between CNTs and graphene oxide (GO) is exploited to disperse conductive but non-polar CNTs with amphiphilic GO sheets to form a stable aqueous colloidal solution. Aqueous-dispersible latex-polystyrene microspheres are then added to enable the self-assembly processes of anchoring CNTs on GO and wrapping microspheres with GO

  6. Current-dependent anisotropic conductivity of locally assembled silver nanoparticles in hybrid polymer films.

    PubMed

    Goel, Pooja; Vinokur, Rostislav; Weichold, Oliver

    2010-12-15

    The electrical behaviour of hybrid poly(ethylene terephthalate) films containing localised, percolating networks of silver nanoparticles separated by pure polymer is studied. The films resemble an array of parallel wires in the submicron range and, thus, exhibit anisotropic conductivity. In the high-conductivity direction at low amplitudes, the films show Ohmic behaviour, while at moderate voltage, non-linearity and a decreasing resistance is observed. The samples were found to heat up during the measurements and the deviation from Ohm's law coincides with the Tg of the polymer. Microstructural analysis of the samples revealed an irreversible agglomeration of the particles at moderate voltages leading to the formation of filaments with higher metallic character than the random particle network. PMID:20843521

  7. Fabrication of self-assembled monolayers (SAMs) and inorganic micropattern on flexible polymer substrate.

    PubMed

    Xiang, Junhui; Zhu, Peixin; Masuda, Yoshitake; Koumoto, Kunihito

    2004-04-13

    By grafting (aminopropyl)triethoxysilane (APTES) as the buffer layer on poly(ethylene terephthalate) (PET) surface, the SAMs ofoctadecyltrichlorosilane (OTS), phenyltrichlorosilane (PTCS), vinyltrichlorosilane (VTCS), andp-tolyltrichlorosilane (TTCS) were fabricated on the flexible polymer substrate. The properties of SAMs were accurately controlled by adjusting the immersing time of substrates in the solutions and the concentration of the solutions. The SAMs acted as templates, and TiO2 micropattern was successfully deposited on OTS, TTCS, and PTCS SAMs. PMID:15875858

  8. H2O2-treated actin: assembly and polymer interactions with cross-linking proteins.

    PubMed Central

    DalleDonne, I; Milzani, A; Colombo, R

    1995-01-01

    During inflammation, hydrogen peroxide, produced by polymorphonuclear leukocytes, provokes cell death mainly by disarranging filamentous (polymerized) actin (F-actin). To show the molecular mechanism(s) by which hydrogen peroxide could alter actin dynamics, we analyzed the ability of H2O2-treated actin samples to polymerize as well as the suitability of actin polymers (from oxidized monomers) to interact with cross-linking proteins. H2O2-treated monomeric (globular) actin (G-actin) shows an altered time course of polymerization. The increase in the lag phase and the lowering in both the polymerization rate and the polymerization extent have been evidenced. Furthermore, steady-state actin polymers, from oxidized monomers, are more fragmented than control polymers. This seems to be ascribable to the enhanced fragility of oxidized filaments rather than to the increase in the nucleation activity, which markedly falls. These facts; along with the unsuitability of actin polymers from oxidized monomers to interact with both filamin and alpha-actinin, suggest that hydrogen peroxide influences actin dynamics mainly by changing the F-actin structure. H2O2, via the oxidation of actin thiols (in particular, the sulfhydryl group of Cys-374), likely alters the actin C-terminus, influencing both subunit/subunit interactions and the spatial structure of the binding sites for cross-linking proteins in F-actin. We suggest that most of the effects of hydrogen peroxide on actin could be explained in the light of the "structural connectivity," demonstrated previously in actin. Images FIGURE 3 FIGURE 9 PMID:8599677

  9. Self-Assembly of Temperature-Responsive Protein-Polymer Bioconjugates.

    PubMed

    Moatsou, Dafni; Li, Jian; Ranji, Arnaz; Pitto-Barry, Anaïs; Ntai, Ioanna; Jewett, Michael C; O'Reilly, Rachel K

    2015-09-16

    We report a simple temperature-responsive bioconjugate system comprising superfolder green fluorescent protein (sfGFP) decorated with poly[(oligo ethylene glycol) methyl ether methacrylate] (PEGMA) polymers. We used amber suppression to site-specifically incorporate the non-canonical azide-functional amino acid p-azidophenylalanine (pAzF) into sfGFP at different positions. The azide moiety on modified sfGFP was then coupled using copper-catalyzed "click" chemistry with the alkyne terminus of a PEGMA synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. The protein in the resulting bioconjugate was found to remain functionally active (i.e., fluorescent) after conjugation. Turbidity measurements revealed that the point of attachment of the polymer onto the protein scaffold has an impact on the thermoresponsive behavior of the resultant bioconjugate. Furthermore, small-angle X-ray scattering analysis showed the wrapping of the polymer around the protein in a temperature-dependent fashion. Our work demonstrates that standard genetic manipulation combined with an expanded genetic code provides an easy way to construct functional hybrid biomaterials where the location of the conjugation site on the protein plays an important role in determining material properties. We anticipate that our approach could be generalized for the synthesis of complex functional materials with precisely defined domain orientation, connectivity, and composition. PMID:26083370

  10. Conducting Polymer Nanostructures and Nanocomposites with Carbon Nanotubes: Hierarchical Assembly by Molecular Electrochemistry, Growth Aspects and Property Characterization.

    PubMed

    Gupta, Sanju; Price, Carson; Heintzman, Eli

    2016-01-01

    Conducting (or π-conjugated) polymers are promising materials for preparing supramolecular nano-structures and nanocomposites. We report controlled nanostructure syntheses of polypyrrole (PPy) and poylaniline (PANi) via electropolymerization (i.e., in-situ electrochemical anodic oxidation). The density, shape, caliber and thickness of self-assembled PPy micro-containers are regulated by electrochemical potential window for H2 bubbles and number of cyclic voltammetric (potentiodynamic) scans. Likewise, we employed amperometry, chronopotentiometry and potentiodynamic modes using hydrochloric acid as oxidizing agent to prepare PANi nanoparticles and nanotubules. We present our findings from the viewpoint of molecular electrochemistry with growth kinetic aspects yielding mechanistic details (initially forming dimers and oligomers as nucleating agents followed by polymer growth). Also targeted is forming nanocomposites with functionalized single- and multi-walled carbon nanotubes (FSWCNTs and FMWCNTs) as reinforced agent to optimize structural and functional properties. All of these novel nanomaterials are characterized using a range of complementary techniques to establish microscopic structure-property-function relationship. PMID:27398466

  11. Effect of Small Molecule Osmolytes on the Self-Assembly and Functionality of Globular Protein-Polymer Diblock Copolymers

    SciTech Connect

    Thomas, Carla S.; Xu, Liza; Olsen, Bradley D.

    2013-12-05

    Blending the small molecule osmolytes glycerol and trehalose with the model globular protein–polymer block copolymer mCherry-b-poly(N-isopropyl acrylamide) (mCherry-b-PNIPAM) is demonstrated to improve protein functionality in self-assembled nanostructures. The incorporation of either additive into block copolymers results in functionality retention in the solid state of 80 and 100% for PNIPAM volume fractions of 40 and 55%, respectively. This represents a large improvement over the 50–60% functionality observed in the absence of any additive. Furthermore, glycerol decreases the thermal stability of block copolymer films by 15–20 °C, while trehalose results in an improvement in the thermal stability by 15–20 °C. These results suggest that hydrogen bond replacement is responsible for the retention of protein function but suppression or enhancement of thermal motion based on the glass transition of the osmolyte primarily determines thermal stability. While both osmolytes are observed to have a disordering effect on the nanostructure morphology with increasing concentration, this effect is less pronounced in materials with a larger polymer volume fraction. Glycerol preferentially localizes in the protein domains and swells the nanostructures, inducing disordering or a change in morphology depending on the PNIPAM coil fraction. In contrast, trehalose is observed to macrophase separate from the block copolymer, which results in nanodomains becoming more disordered without changing significantly in size.

  12. Polymer-templated electrodeposition of Ag nanosheets assemblies array as reproducible surface-enhanced Raman scattering substrate.

    PubMed

    Liu, Sisi; Xu, Zhimou; Sun, Tangyou; Zhao, Wenning; Wu, Xinghui; Ma, Zhichao; Zhang, Xueming; He, Jian; Chen, Cunhua

    2014-06-01

    Position-configurable, reproducible, vertically aligned nanosheets assemblies (ANAs) arrays are fabricated by polymer-templated electrodeposition method at room temperature. Here, nanoimprint lithography is utilized to fabricate polymer template on the fluorine-doped tin oxide substrate for the purpose of evenly tuning the location of Ag nanostructures. Subsequently, vertically aligned ANAs can be achieved at the bottom of each hole via electrodeposition in a mixed aqueous solution of AgNO3 and citric acid. To obtain uniform ANAs array, we have systematically investigated the factors that influenced the electrodeposition. It was found that the formation of uniform ANAs arrays is strongly depended on the seeding layer, citric acid concentration, electrodeposition potential and time. The as-synthesized ANAs array exhibited a remarkable SERS activity and Raman signal reproducibility to rhodamine 6G, a concentration down to 10(-13) M can be identified. Our results revealed that the ANAs array is a highly desirable candidate as the reliable enhancer for high performance SERS analysis. PMID:24738437

  13. Self-assembled tin-doped ZnO nanowire and nanoplate structures grown by thermal treatment of ZnS powder

    NASA Astrophysics Data System (ADS)

    Ortega, Y.; Fernández, P.; Piqueras, J.

    2009-05-01

    Sintering of a ZnS-SnO 2 mixture under argon flow leads to the growth of columnar nanoplate arrays as well as arrays of nanowires, nanorods and nanoplates with six-fold symmetry. The six-fold nanoplate structures correspond to a more advanced stage of growth than the nanowire structures. Cathodoluminescence (CL) in the scanning electron microscope (SEM) shows that the structures contain Sn, but the amount of this element is normally under the detection limit of X-ray energy-dispersive spectroscopy (EDS). The formation of branches in the hierarchical structures depends on the presence of Sn and on defects in the mixture powder.

  14. Effects of molecular geometry on the self-assembly of giant polymer-dendron conjugates in condensed state.

    PubMed

    Dong, Xue-Hui; Lu, Xiaocun; Ni, Bo; Chen, Ziran; Yue, Kan; Li, Yiwen; Rong, Lixia; Koga, Tadanori; Hsiao, Benjamin S; Newkome, George R; Shi, An-Chang; Zhang, Wen-Bin; Cheng, Stephen Z D

    2014-05-14

    A series of giant polymer-dendron conjugates with a dendron head and a linear polymer tail were synthesized via"click" chemistry between azide-functionalized polystyrene (PS(N), N: degree-of-polymerization) and t-butyl protected, alkyne-functionalized second generation dendron (tD), followed by a deprotection process to generate a dendron termini possessing nine carboxylic acid groups. The molecular structures were confirmed by nuclear magnetic resonance, size-exclusion chromatographic analyses, and matrix-assisted laser desorption ionization time-of-flight mass spectra. These well-defined conjugates can serve as a model system to study the effects of the molecular geometries on the self-assembly behaviour, as compared with their linear analogues. Four phase morphologies found in flexible linear diblock copolymer systems, including lamellae, bicontinuous double gyroids, hexagonal packed cylinders, and body-centred cubic packed spheres, were observed in this series of conjugates based on the results of small angle X-ray scattering and transmission electron microscopy. All of the domain sizes in these phase separated structures were around or less than 10 nm. A 'half' phase diagram was constructed based on the experimental results. The geometrical effect was found not only to enhance the immiscibility between the PS(N) tail and dendron head, but also systematically shift all of the phase boundaries towards higher volume fractions of the PS(N) tails, resulting in an asymmetrical phase diagram. This study may provide a pathway to the construction of ordered patterns of sub-10 nm feature size using polymer-dendron conjugates. PMID:24718376

  15. Directed self-assembly of diblock copolymers in cylindrical confinement: effect of underfilling and air-polymer interactions on configurations

    NASA Astrophysics Data System (ADS)

    Carpenter, Corinne L.; Delaney, Kris T.; Laachi, Nabil; Fredrickson, Glenn H.

    2015-03-01

    Directed self-assembly (DSA) of block copolymers has attracted attention for its use as a simple, cost- effective patterning tool for creating vertical interconnect access (VIA) channels in nanoelectronic devices.1, 2 This technique supplements existing lithographic technologies to allow for the creation of high-resolution cylindrical holes whose diameter and placement can be precisely controlled. In this study, we use self-consistent field theory (SCFT) simulations to investigate the equilibrium configurations of under-filled DSA systems with air-polymer interactions. We report on a series of SCFT simulations of our three species (PMMA-b-PS diblock and air) model in cylindrical confinement to explore the role of template diameter, under-fill fraction (i.e. volume fraction of air), air-polymer surface interaction and polymer-side wall/substrate interactions on equilibrium morphologies in an under-filled template with a free top surface. We identify parameters and system configurations where a meniscus appears and explore cases with PMMA-attractive, PS-attractive, and all-neutral walls to understand the effects of wall properties on meniscus geometry and DSA morphology. An important outcome is an understanding of the parameters that control the contact angle of the meniscus with the wall, as it is one of the simplest quantitative measures of the meniscus shape. Ultimately, we seek to identify DSA formulations, templates, and surface treatments with predictable central cylinder diameter and a shallow contact angle, as these factors would facilitate broad process windows and ease of manufacturing.

  16. Morphology control of polymer: Fullerene solar cells by nanoparticle self-assembly

    NASA Astrophysics Data System (ADS)

    Zhang, Wenluan

    During the past two decades, research in the field of polymer based solar cells has attracted great effort due to their simple processing, mechanical flexibility and potential low cost. A standard polymer solar cell is based on the concept of a bulk-heterojunction composed of a conducting polymer as the electron donor and a fullerene derivative as the electron acceptor. Since the exciton lifetime is limited, this places extra emphasis on control of the morphology to obtain improved device performance. In this thesis, detailed characterization and novel morphological design of polymer solar cells was studied, in addition, preliminary efforts to transfer laboratory scale methods to industrialized device fabrication was made. Magnetic contrast neutron reflectivity was used to study the vertical concentration distribution of fullerene nanoparticles within poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2- b]thiophene (pBTTT) thin film. Due to the wide space between the side chains of polymer, these fullerene nanoparticles intercalate between them creating a stable co-crystal structure. Therefore, a high volume fraction of fullerene was needed to obtain optimal device performance as phase separated conductive pathways are required and resulted in a homogeneous fullerene concentration profile through the film. Small angle neutron scattering was used to find there is amorphous fullerene even at lower concentration since it was previously believed that all fullerene formed a co-crystal. These fullerene molecules evolve into approximately 15 nm sized agglomerates at higher concentrations to improve electron transport. Unfortunately, thermal annealing gives these agglomerates mobility to form micrometer sized crystals and reduce the device performance. In standard poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PCMBM) solar cells, a higher concentration of PCBM at the cathode interface is desired due to the band alignment structure. This was

  17. Hierarchical self-assembly of telechelic star polymers: from soft patchy particles to gels and diamond crystals

    NASA Astrophysics Data System (ADS)

    Capone, Barbara; Coluzza, Ivan; Blaak, Ronald; Lo Verso, Federica; Likos, Christos N.

    2013-09-01

    The design of self-assembling materials in the nanometer scale focuses on the fabrication of a class of organic and inorganic subcomponents that can be reliably produced on a large scale and tailored according to their vast applications for, e.g. electronics, therapeutic vectors and diagnostic imaging agent carriers, or photonics. In a recent publication (Capone et al 2012 Phys. Rev. Lett. 109 238301), diblock copolymer stars have been shown to be a novel system, which is able to hierarchically self-assemble first into soft patchy particles and thereafter into more complex structures, such as the diamond and cubic crystal. The self-aggregating single star patchy behavior is preserved from extremely low up to high densities. Its main control parameters are related to the architecture of the building blocks, which are the number of arms (functionality) and the fraction of attractive end-monomers. By employing a variety of computational and theoretical tools, ranging from the microscopic to the mesoscopic, coarse-grained level in a systematic fashion, we investigate the crossover between the formation of microstructure versus macroscopic phase separation, as well as the formation of gels and networks in these systems. We finally show that telechelic star polymers can be used as building blocks for the fabrication of open crystal structures, such as the diamond or the simple-cubic lattice, taking advantage of the strong correlation between single-particle patchiness and lattice coordination at finite densities.

  18. Responsive supramolecular polymer metallogel constructed by orthogonal coordination-driven self-assembly and host/guest interactions.

    PubMed

    Yan, Xuzhou; Cook, Timothy R; Pollock, J Bryant; Wei, Peifa; Zhang, Yanyan; Yu, Yihua; Huang, Feihe; Stang, Peter J

    2014-03-26

    An emerging strategy for the fabrication of advanced supramolecular materials is the use of hierarchical self-assembly techniques wherein multiple orthogonal interactions between molecular precursors can produce new species with attractive properties. Herein, we unify the spontaneous formation of metal-ligand bonds with the host/guest chemistry of crown ethers to deliver a 3D supramolecular polymer network (SPN). Specifically, we have prepared a highly directional dipyridyl donor decorated with a benzo-21-crown-7 moiety that undergoes coordination-driven self-assembly with a complementary organoplatinum acceptor to furnish hexagonal metallacycles. These hexagons subsequently polymerize into a supramolecular network upon the addition of a bisammonium salt due to the formation of [2]pseudorotaxane linkages between the crown ether and ammonium moieties. At high concentrations, the resulting 3D SPN becomes a gel comprising many cross-linked metallohexagons. Notably, thermo- and cation-induced gel-sol transitions are found to be completely reversible, reflecting the dynamic and tunable nature of such supramolecular materials. As such, these results demonstrate the structural complexity that can be obtained when carefully controlling multiple interactions in a hierarchical fashion, in this case coordination and host/guest chemistry, and the interesting dynamic properties associated with the materials thus obtained. PMID:24621148

  19. The Effect of Small Molecule Additives on the Self-Assembly and Functionality of Protein-Polymer Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    Thomas, Carla; Xu, Liza; Olsen, Bradley

    2013-03-01

    Self-assembly of globular protein-polymer block copolymers into well-defined nanostructures provides a route towards the manufacture of protein-based materials which maintains protein fold and function. The model material mCherry-b-poly(N-isopropyl acrylamide) forms self-assembled nanostructures from aqueous solutions via solvent evaporation. To improve retention of protein functionality when dehydrated, small molecules such as trehalose and glycerol are added in solution prior to solvent removal. With as little as 10 wt% additive, improvements in retained functionality of 20-60% are observed in the solid-state as compared to samples in which no additive is present. Higher additive levels (up to 50%) continue to show improvement until approximately 100% of the protein function is retained. These large gains are hypothesized to originate from the ability of the additives to replace hydrogen bonds normally fulfilled by water. The addition of trehalose in the bulk material also improves the thermal stability of the protein by 15-20 °C, while glycerol decreases the thermal stability. Materials containing up to 50% additives remain microphase separated, and, upon incorporation of additives, nanostructure domain spacing tends to increase, accompanied by order-order transitions.

  20. Multi-shape memory polymers achieved by the spatio-assembly of 3D printable thermoplastic building blocks.

    PubMed

    Li, Hongze; Gao, Xiang; Luo, Yingwu

    2016-04-01

    Multi-shape memory polymers were prepared by the macroscale spatio-assembly of building blocks in this work. The building blocks were methyl acrylate-co-styrene (MA-co-St) copolymers, which have the St-block-(St-random-MA)-block-St tri-block chain sequence. This design ensures that their transition temperatures can be adjusted over a wide range by varying the composition of the middle block. The two St blocks at the chain ends can generate a crosslink network in the final device to achieve strong bonding force between building blocks and the shape memory capacity. Due to their thermoplastic properties, 3D printing was employed for the spatio-assembly to build devices. This method is capable of introducing many transition phases into one device and preparing complicated shapes via 3D printing. The device can perform a complex action via a series of shape changes. Besides, this method can avoid the difficult programing of a series of temporary shapes. The control of intermediate temporary shapes was realized via programing the shapes and locations of building blocks in the final device. PMID:26924759

  1. Oil-in-Oil Emulsions Stabilized by Asymmetric Polymersomes Formed by AC + BC Block Polymer Co-Assembly.

    PubMed

    Asano, Itaru; So, Soonyong; Lodge, Timothy P

    2016-04-13

    We demonstrate a facile route to asymmetric polymersomes by blending AC and BC block copolymers in oil-in-oil emulsions containing polystyrene (PS) and polybutadiene (PB) in chloroform (CHCl3). Polymersomes were prepared by mixing polystyrene-b-poly(ethylene oxide) (SO) and polybutadiene-b-poly(ethylene oxide) (BO) in the oil-in-oil emulsion, where the droplets and continuous phase are PS- and PB-rich, respectively. The polymersome structure was directly visualized using dye-labeled SO and BO with confocal fluorescence microscopy; SO and BO with a high O block fraction co-assemble to produce asymmetric polymersomes. As the O block is insoluble in both PS and PB, we infer that the detailed structure of the polymersomes is a bilayer in which the S and B blocks face the PS-inner and PB-outer phases, respectively, while the common O blocks form the core membrane. This structure is only observed for sufficiently long O blocks. It is remarkable that although all the polymers are soluble in CHCl3, such elaborate structures are created by straightforward co-assembly. These asymmetric polymersomes should provide robust bilayer membranes around emulsion droplets, leading to stable nanoscopic dispersions of two fluids. PMID:27046136

  2. Towards a comprehensive insight into efficient hydrogen production by self-assembled Ru(bpy)3(2+)-polymer-Pt artificial photosystems.

    PubMed

    Lin, Huan; Liu, Dan; Long, Jinlin; Zhang, Zizhong; Zhuang, Huaqiang; Zheng, Yi; Wang, Xuxu

    2015-04-28

    The role of polymers in artificial photosystems has been studied in detail. The photosystems were composed of tris(2,2'-bipyridyl) ruthenium(II) chloride as a photosensitizer (PS), colloidal Pt stabilized by polymer as a hydrogen-evolving catalyst and sodium ascorbate as an electron donor, without the addition of a traditional molecular electron mediator. Comprehensive insights into the production of hydrogen on irradiation with visible light were achieved. Several polymers, including neutral polyvinyl pyrrolidone, anionic poly(sodium 4-styrene sulfonate) and poly(acrylic acid) not only stabilized the nanoparticles, but were also effective in the production of hydrogen. Under the optimum conditions, an outstanding apparent quantum efficiency of 12.8% for the evolution of hydrogen was achieved. The formation of self-assembled and spatially separated donor-acceptor complexes via the non-covalent intermolecular interaction between PS and the polymer-Pt was pivotal in the efficient conversion of solar energy to hydrogen fuel. Important details of the photo-induced electron and energy transfer processes in the self-assembled artificial photosystems were determined by nanosecond transient absorption spectrometry and time-resolved fluorescence spectrometry. The initial step in the photo-catalytic production of hydrogen was a reductive quenching of the triplet excited state of the PS by sodium ascorbate, leading to a reduced form of PS, which could then be quickly quenched by the polymer. The rate-determining step was the electron transfer from PS to the catalyst via the polymer bridge. PMID:25811660

  3. Highly ordered self-assembling polymer/clay nanocomposite barrier film.

    PubMed

    Cook, Ray; Chen, Yihong; Beall, Gary W

    2015-05-27

    Efforts to mimic complex-structured biologically based materials such as abalone shell have occupied substantial research time and effort in science and engineering. The majority of the efforts involve tedious and expensive techniques and processes. Layer-by-layer (LBL) is one such technique that can produce materials with quite unique physical properties, approaching, and in some cases surpassing, those seen in nature. The LBL technique, however, is quite tedious and difficult to implement commercially. We report here the discovery of an organic/inorganic spontaneous self-assembling system that forms a highly structured nanocomposite. The driving force behind this self-assembly appears to be entropy. This discovery should open up completely new avenues to designing hierarchical composites and structures. The films have been studied by X-ray diffraction and the barrier properties for oxygen diffusion measured. PMID:25946617

  4. Compaction and multiple chain assembly of DNA with the cationic polymer poly(aluminum chloride) (PAC).

    PubMed

    Matsuzawa, Yukiko; Kanbe, Toshio; Yoshikawa, Kenichi

    2004-07-20

    Assembly of DNA molecules by the addition of poly(aluminum chloride) (PAC) was studied. In the absence of PAC, electron microscopy indicated the formation of elongated coiled DNA molecules. In the presence of PAC, multiple doughnut-like structures, 8-15 nm thick, formed and fused together. When salt was added, the doughnut-like structures tended to be thinner and the morphology of the fused doughnuts became irregular. We obtained a view of a single DNA structure by fluorescent microscopy, which revealed that individual DNA molecules undergo a discrete transition from an elongated to compacted state with an increase in PAC concentration. Electron microscopic observation showed that a regular doughnut is the typical structure seen under low salt conditions. At high salt concentrations, the doughnut shape deformed, yielding results similar to those produced by the salt effect on DNA assembly at high DNA concentrations. PMID:15248734

  5. Polymer/Perovskite-type nanoparticle multilayers with multielectric properties prepared from ligand addition-induced layer-by-layer assembly.

    PubMed

    Kim, Younghoon; Kook, Kyungyun; Hwang, Sun Kak; Park, Cheolmin; Cho, Jinhan

    2014-03-25

    We introduce an adsorption mechanism for a layer-by-layer (LbL) assembly (i.e., a ligand addition-induced LbL assembly) and demonstrate that the (polymer/perovskite nanoparticle (NP))n nanocomposite films based on the ligand addition LbL exhibit ferroelectric and resistive switching properties. Oleic acid (OA)-stabilized BaTiO3 NPs (OA-BTO NPs) with a size of approximately 8 nm were LbL-assembled with amine-functionalized dendrimers (NH2-dendrimers) using the high affinity between NH2 moieties and Ti ions. The ferroelectric properties of the (NH2-dendrimer/OA-BTO NP)n multilayers were generated by the Ti disorder in the OA-BTO NP unit cell despite the use of sub-10 nm OA-BTO NPs (i.e., OA-BTO NPs), which are near the critical size for ferroelectric properties. Additionally, the (NH2-dendrimer/OA-BTO NP)n multilayers sandwiched between the bottom (platinum) and top (silver or tungsten) electrodes exhibited a resistive switching memory at a relatively low operating voltage below 2 V with a switching speed of approximately 100 ns and an ON/OFF current ratio of approximately 10(4). Furthermore, the ferroelectric and resistive switching properties could be further improved by controlling the bilayer number (n). We believe that our approach can provide a basis for designing and exploiting multifunctional memory electronics based on a variety of perovskite NPs with ferroelectric properties. PMID:24571293

  6. Conductive Nanowires Templated by Molecular Brushes.

    PubMed

    Raguzin, Ivan; Stamm, Manfred; Ionov, Leonid

    2015-10-21

    In this paper, we report the fabrication of conductive nanowires using polymer bottle brushes as templates. In our approach, we synthesized poly(2-dimethylamino)ethyl methacrylate methyl iodide quaternary salt brushes by two-step atom transfer radical polymerization, loaded them with palladium salt, and reduced them in order to form metallic nanowires with average lengths and widths of 300 and 20 nm, respectively. The obtained nanowires were deposited between conductive gold pads and were connected to them by sputtering of additional pads to form an electric circuit. We connected the nanowires in an electric circuit and demonstrated that the conductivity of these nanowires is around 100 S·m(-1). PMID:26418290

  7. Quartz resonator assembling with TSV interposer using polymer sealing or metal bonding

    PubMed Central

    2014-01-01

    This paper presents one wafer level packaging approach of quartz resonator based on through-silicon via (TSV) interposer with metal or polymer bonding sealing of frequency components. The proposed silicon-based package of quartz resonator adopts several three-dimensional (3D) core technologies, such as Cu TSVs, sealing bonding, and wafer thinning. It is different from conventional quartz resonator using ceramic-based package. With evaluation of mechanical structure design and package performances, this quartz resonator with advanced silicon-based package shows great manufacturability and excellent performance to replace traditional metal lid with ceramic-based interposer fabrication approach. PMID:25324705

  8. Interplay between polymer chain conformation and nanoparticle assembly in model industrial silica/rubber nanocomposites.

    PubMed

    Bouty, Adrien; Petitjean, Laurent; Chatard, Julien; Matmour, Rachid; Degrandcourt, Christophe; Schweins, Ralf; Meneau, Florian; Kwasńiewski, Paweł; Boué, François; Couty, Marc; Jestin, Jacques

    2016-04-12

    The question of the influence of nanoparticles (NPs) on chain dimensions in polymer nanocomposites (PNCs) has been treated mainly through the fundamental way using theoretical or simulation tools and experiments on well-defined model PNCs. Here we present the first experimental study on the influence of NPs on the polymer chain conformation for PNCs designed to be as close as possible to industrial systems employed in the tire industry. PNCs are silica nanoparticles dispersed in a styrene-butadiene-rubber (SBR) matrix whose NP dispersion can be managed by NP loading with interfacial coatings or coupling additives usually employed in the manufacturing mixing process. We associated specific chain (d) labeling, and the so-called zero average contrast (ZAC) method, with SANS, in situ SANS and SAXS/TEM experiments to extract the polymer chain scattering signal at rest for non-cross linked and under stretching for cross-linked PNCs. NP loading, individual clusters or connected networks, as well as the influence of the type, the quantity of interfacial agent and the influence of the elongation rate have been evaluated on the chain conformation and on its related deformation. We clearly distinguish the situations where the silica is perfectly matched from those with unperfected matching by direct comparison of SANS and SAXS structure factors. Whatever the silica matching situation, the additive type and quantity and the filler content, there is no significant change in the polymer dimension for NP loading up to 15% v/v within a range of 5%. One can see an extra scattering contribution at low Q, as often encountered, enhanced for non-perfect silica matching but also visible for perfect filler matching. This contribution can be qualitatively attributed to specific h or d chain adsorption on the NP surface inside the NP cluster that modifies the average scattering neutron contrast of the silica cluster. Under elongation, NPs act as additional cross-linking junctions

  9. Quartz resonator assembling with TSV interposer using polymer sealing or metal bonding.

    PubMed

    Shih, Jian-Yu; Chen, Yen-Chi; Chiu, Chih-Hung; Lo, Chung-Lun; Chang, Chi-Chung; Chen, Kuan-Neng

    2014-01-01

    This paper presents one wafer level packaging approach of quartz resonator based on through-silicon via (TSV) interposer with metal or polymer bonding sealing of frequency components. The proposed silicon-based package of quartz resonator adopts several three-dimensional (3D) core technologies, such as Cu TSVs, sealing bonding, and wafer thinning. It is different from conventional quartz resonator using ceramic-based package. With evaluation of mechanical structure design and package performances, this quartz resonator with advanced silicon-based package shows great manufacturability and excellent performance to replace traditional metal lid with ceramic-based interposer fabrication approach. PMID:25324705

  10. Template-free fabrication of Ag nanowire arrays/Al2O3 assembly with flexible collective longitudinal-mode resonance and ultrafast nonlinear optical response

    NASA Astrophysics Data System (ADS)

    Hui, Shuai; Gao, Junhua; Wu, Xingzhi; Li, Zhongguo; Zou, Yousheng; Song, Yinglin; Cao, Hongtao

    2016-06-01

    We utilized a co-sputtering technique without any templates, featuring growing and etching synchronously, to delicately fabricate dense and ultrafine Ag nanowire arrays/alumina matrix composite films. Both the diameter and separation distance of the Ag nanowire arrays in the composites are not only within the scope of sub-10 nm but also tunable, which is very hard to accomplish for the conventional optical lithography- or template-based method. It is exhibited that the collective longitudinal plasmon resonance of the composite films, covering a wide range from visible to the near infrared region, is extremely sensitive to the geometrical parameters of the Ag nanowires, owing to the strong plasmonic coupling among neighboring nanowires. The experimental observations were also theoretically supported by the near-field electromagnetic numerical simulation. More interestingly, the fabricated composite films demonstrated ultrafast nonlinear optical response in the visible light region under femtosecond laser excitation, possessing a short relaxation time of 1.45 ps for the longitudinal mode (L mode) resonance. These results indicate that the proposed composite films as a building block with exotic optical properties could provide an opportunity to construct integrated nanodevices for plasmonic optical applications.

  11. Controllable deformation of silicon nanowires with strain up to 24%

    SciTech Connect

    Walavalkar, Sameer S.; Homyk, Andrew P.; Henry, M. David; Scherer, Axel

    2010-06-15

    Fabricated silicon nanostructures demonstrate mechanical properties unlike their macroscopic counterparts. Here we use a force mediating polymer to controllably and reversibly deform silicon nanowires. This technique is demonstrated on multiple nanowire configurations, which undergo deformation without noticeable macroscopic damage after the polymer is removed. Calculations estimate a maximum of nearly 24% strain induced in 30 nm diameter pillars. The use of an electron activated polymer allows retention of the strained configuration without any external input. As a further illustration of this technique, we demonstrate nanoscale tweezing by capturing 300 nm alumina beads using circular arrays of these silicon nanowires.

  12. Nanowire Lasers

    NASA Astrophysics Data System (ADS)

    Couteau, C.; Larrue, A.; Wilhelm, C.; Soci, C.

    2015-05-01

    We review principles and trends in the use of semiconductor nanowires as gain media for stimulated emission and lasing. Semiconductor nanowires have recently been widely studied for use in integrated optoelectronic devices, such as light-emitting diodes (LEDs), solar cells, and transistors. Intensive research has also been conducted in the use of nanowires for subwavelength laser systems that take advantage of their quasione- dimensional (1D) nature, flexibility in material choice and combination, and intrinsic optoelectronic properties. First, we provide an overview on using quasi-1D nanowire systems to realize subwavelength lasers with efficient, directional, and low-threshold emission. We then describe the state of the art for nanowire lasers in terms of materials, geometry, andwavelength tunability.Next,we present the basics of lasing in semiconductor nanowires, define the key parameters for stimulated emission, and introduce the properties of nanowires. We then review advanced nanowire laser designs from the literature. Finally, we present interesting perspectives for low-threshold nanoscale light sources and optical interconnects. We intend to illustrate the potential of nanolasers inmany applications, such as nanophotonic devices that integrate electronics and photonics for next-generation optoelectronic devices. For instance, these building blocks for nanoscale photonics can be used for data storage and biomedical applications when coupled to on-chip characterization tools. These nanoscale monochromatic laser light sources promise breakthroughs in nanophotonics, as they can operate at room temperature, can potentially be electrically driven, and can yield a better understanding of intrinsic nanomaterial properties and surface-state effects in lowdimensional semiconductor systems.

  13. Coordination polymers assembled from semirigid fluorene-based ligand: A couple of enantiomers

    NASA Astrophysics Data System (ADS)

    Li, Liang; Wang, Zihao; Chen, Qiang; Zhou, Xinhui; yang, Tao; Zhao, Qiang; Huang, Wei

    2015-11-01

    A couple of Mg(II)-based coordination polymer enantiomers [MgL(DMF)(H2O)3]n (R-MgL and S-MgL), and a Zn(II)-based coordination polymer [ZnL(DMF)]n (ZnL) have been synthesized by the solvothermal reactions between the achiral ligand 4,4‧-(9,9-dimethyl-9H-fluorene-2,7-diyl)dibenzoic acid (H2L) and the corresponding metal salts. The MgL was obtained as the racemic conglomerate from the one pot reaction. The single crystal X-ray structural analyses reveal that MgL crystallize in the chiral space group P21 and possesses the right- or left-handed homochiral 1D Mg-O-C helical chain. The ZnL crystallize in the non-centrosymmetrical space group Aba2 and possesses the 2D network comprised of 1D Zn-O-C meso-helical chains and ligands. The MgL and ZnL complexes exhibit strong coordination-perturbed ligand-centered blue emissions when excited at 320 nm. Their second-order nonlinear optical effects and thermal properties have also been studied.

  14. Structural diversity in binary superlattices self-assembled from polymer-grafted nanocrystals

    PubMed Central

    Ye, Xingchen; Zhu, Chenhui; Ercius, Peter; Raja, Shilpa N.; He, Bo; Jones, Matthew R.; Hauwiller, Matthew R.; Liu, Yi; Xu, Ting; Alivisatos, A. Paul

    2015-01-01

    Multicomponent nanocrystal superlattices represent an interesting class of material that derives emergent properties from mesoscale structure, yet their programmability can be limited by the alkyl-chain-based ligands decorating the surfaces of the constituent nanocrystals. Polymeric ligands offer distinct advantages, as they allow for more precise tuning of the effective size and ‘interaction softness' through changes to the polymer's molecular weight, chemical nature, architecture, persistence length and surrounding solvent. Here we show the formation of 10 different binary nanocrystal superlattices (BNSLs) with both two- and three-dimensional order through independent adjustment of the core size of spherical nanocrystals and the molecular weight of densely grafted polystyrene ligands. These polymer-brush-based ligands introduce new energetic contributions to the interparticle potential that stabilizes various BNSL phases across a range of length scales and interparticle spacings. Our study opens the door for nanocrystals to become modular elements in the design of functional particle brush solids with controlled nanoscale interfaces and mesostructures. PMID:26628256

  15. Computational Insight into Solvent Effects on Conformation and Assembly of Structured Ionic Polymer

    NASA Astrophysics Data System (ADS)

    Senanayake, Manjula; Aryal, Dipak; Perahia, Dvora; Grest, Gary

    Structured ionomers are in the core of numerous current and potential new applications including clean energy, water purification membranes and sensors. The ability to facilitate ions and solvents transport is a key to their function and is controlled by their structure. One effective path for structural control is tuning their conformation by solvent interactions. Here, the confirmation and association of an ABCBA co-polymer where C is a randomly sulfonated polystyrene with sulfonation fractions f = 0 to 0.55, B is poly (ethylene-r-propylene), and A is poly (t-butyl styrene), in n-propanol are studied by molecular dynamic simulation. In contrast to the collapsed conformation of the ionizable block in hydrophobic solvents, we find that it remains swollen. Similar to hydrophobic solutions the co-polymers aggregate to form an ionizable core surrounded by extended hydrophobic chains. In contrast to the ``locked-in'' ionizable segments observed in cyclohexane/heptane, here the ionic clusters remain dynamic. Supported in part by DOE Grant No. DE-SC007908.

  16. Lithographically patterned nanowire electrodeposition

    NASA Astrophysics Data System (ADS)

    Xiang, Chengxiang

    Lithographically patterned nanowire electrodeposition (LPNE) is a new method for fabricating polycrystalline metal nanowires using electrodeposition. In LPNE, a sacrificial metal (M1 = silver or nickel) layer, 5 - 100 nm in thickness, is first vapor deposited onto a glass, oxidized silicon, or Kapton polymer film. A photoresist (PR) layer is then deposited, photopatterned, and the exposed Ag or Ni is removed by wet etching. The etching duration is adjusted to produce an undercut ≈300 nm in width at the edges of the exposed PR. This undercut produces a horizontal trench with a precisely defined height equal to the thickness of theM1 layer. Within this trench, a nanowire of metal M2 is electrodeposited (M2 = gold, platinum, palladium, or bismuth). Finally the PR layer and M1 layer are removed. The nanowire height and width can be independently controlled down to minimum dimensions of 5 nm (h) and 11 nm (w), for example, in the case of platinum. These nanowires can be 1 cm in total length. We measure the temperature-dependent resistance of 100 um sections of Au and Pd wires in order to estimate