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Sample records for self-assembled nano structured

  1. Templated Self Assemble of Nano-Structures

    SciTech Connect

    Suo, Zhigang

    2013-04-29

    This project will identify and model mechanisms that template the self-assembly of nanostructures. We focus on a class of systems involving a two-phase monolayer of molecules adsorbed on a solid surface. At a suitably elevated temperature, the molecules diffuse on the surface to reduce the combined free energy of mixing, phase boundary, elastic field, and electrostatic field. With no template, the phases may form a pattern of stripes or disks. The feature size is on the order of 1-100 nm, selected to compromise the phase boundary energy and the long-range elastic or electrostatic interaction. Both experimental observations and our theoretical simulations have shown that the pattern resembles a periodic lattice, but has abundant imperfections. To form a perfect periodic pattern, or a designed aperiodic pattern, one must introduce a template to guide the assembly. For example, a coarse-scale pattern, lithographically defined on the substrate, will guide the assembly of the nanoscale pattern. As another example, if the molecules on the substrate surface carry strong electric dipoles, a charged object, placed in the space above the monolayer, will guide the assembly of the molecular dipoles. In particular, the charged object can be a mask with a designed nanoscale topographic pattern. A serial process (e.g., e-beam lithography) is necessary to make the mask, but the pattern transfer to the molecules on the substrate is a parallel process. The technique is potentially a high throughput, low cost process to pattern a monolayer. The monolayer pattern itself may serve as a template to fabricate a functional structure. This project will model fundamental aspects of these processes, including thermodynamics and kinetics of self-assembly, templated self-assembly, and self-assembly on unconventional substrates. It is envisioned that the theory will not only explain the available experimental observations, but also motivate new experiments.

  2. Thermal conductivity of self-assembled nano-structured ZnO bulk ceramics

    SciTech Connect

    Zhao, Yu; Yan, Yongke; Kumar, Ashok; Wang, Hsin; Porter, Wallace D

    2012-01-01

    In this study, we describe the changes in thermal conductivity behavior of ZnO-Al micro- and nano-two-phase self-assembled composites with varying grain sizes. The reduction in thermal conductivity values of micro-composites was limited to {approx}15% for ZnO-4% Al. However, nano-composites exhibited large reduction, by a factor of about three, due to uniform distribution of nano-precipitates (ZnAl2O4) and large grain boundary area. Interestingly, the micro-composites revealed continuous decrease in thermal conductivity with increase in Al substitution while the nano-composites exhibited the lowest magnitudes for 2% Al concentration. Raman spectra indicated that phonon confinement in ZnO-Al nano-composites causes drastic decrease in the value of thermal conductivity.

  3. Formation of self-assembled micro- and nano-domain structures in uniaxial ferroelectrics

    NASA Astrophysics Data System (ADS)

    Shur, V. Ya; Shur, A. G.; Akhmatkhanov, A. R.

    2017-04-01

    We present the experimental study of appearance of domain wall shape instabilities and self-assembled domain structures in uniaxial ferroelectrics lithium niobate and lithium tantalate covered by artificial dielectric layer. The domain structure evolution has been considered as a manifestation of nucleation processes similar to the first order phase transformation. The necessary conditions for formation of self-assembled domain structures including the highly non-equilibrium switching conditions and stability of concave angles were proposed. The formation of the self-assembled domain shape instabilities under application of the uniform external electric field during switching (domain growth) and backswitching (domain shrinkage) has been studied experimentally with these conditions fulfilled. The formation of the bumps at the vortexes of hexagon domain for diameter above 3 - 5 μm with subsequent oriented growth was obtained in stoichiometric lithium tantalate. The formation of quasi-regular fish-bone domain structure has been revealed during spontaneous backswitching in Mg doped lithium niobate. The resulted structure consisted of the narrow residual domains with width from 200 to 500 nm appeared as a result of finger growth to the center of hexagon domain. The obtained decreasing of the number of the residual domains during growth has been attributed to strong electrostatic interaction of domain walls.

  4. Self-Assembled Wiggling Nano-Structures and the Principle of Maximum Entropy Production

    NASA Astrophysics Data System (ADS)

    Belkin, A.; Hubler, A.; Bezryadin, A.

    2015-02-01

    While behavior of equilibrium systems is well understood, evolution of nonequilibrium ones is much less clear. Yet, many researches have suggested that the principle of the maximum entropy production is of key importance in complex systems away from equilibrium. Here, we present a quantitative study of large ensembles of carbon nanotubes suspended in a non-conducting non-polar fluid subject to a strong electric field. Being driven out of equilibrium, the suspension spontaneously organizes into an electrically conducting state under a wide range of parameters. Such self-assembly allows the Joule heating and, therefore, the entropy production in the fluid, to be maximized. Curiously, we find that emerging self-assembled structures can start to wiggle. The wiggling takes place only until the entropy production in the suspension reaches its maximum, at which time the wiggling stops and the structure becomes quasi-stable. Thus, we provide strong evidence that maximum entropy production principle plays an essential role in the evolution of self-organizing systems far from equilibrium.

  5. Self-assembled dual-sided hemispherical nano-dimple-structured broadband antireflection coatings

    NASA Astrophysics Data System (ADS)

    Lin, Cheng-Yen; Lin, Kun-Yi; Tsai, Hui-Ping; He, Yi-Xuan; Yang, Hongta

    2016-11-01

    A non-lithography-based approach is developed in this study for assembling monolayer close-packed hemispherical nano-dimple arrays on both sides of a PET film by a scalable Langmuir-Blodgett technology. The resulting gratings greatly suppress specular reflection and therefore enhance specular transmission for a broad range of visible wavelengths, resulting from a gradual change in the effective refractive index at air/PET interface. The experimental results reveal that the antireflection properties of the as-fabricated coatings are affected by the size of the nano-dimples. Moreover, both optical performances of single-sided and dual-sided nano-dimple-structured coatings have been investigated in this study.

  6. Block copolymer self-assembly fundamentals and applications in formulation of nano-structured fluids

    NASA Astrophysics Data System (ADS)

    Sarkar, Biswajit

    Dispersions of nanoparticles in polymer matrices form hybrid materials that can exhibit superior structural and functional properties and find applications in e.g. thermo-plastics, electronics, polymer electrolytes, catalysis, paint formulations, and drug delivery. Control over the particle location and orientation in the polymeric matrices are essential in order to realize the enhanced mechanical, electrical, and optical properties of the nanohybrids. Block copolymers, composed of two or more different monomers, are promising for controlling particle location and orientation because of their ability to organize into ordered nanostructures. Fundamental questions pertaining to nanoparticle-polymer interfacial interactions remain open and formulate the objectives of our investigation. Particle-polymer enthalpic and entropic interactions control the nanoparticle dispersion in polymer matrices. Synthetic chemical methods for modifying the particle surface in order to control polymer-particle interactions are involved and large scale production is not possible. In the current approach, a physical method is employed to control polymer-particle interactions. The use of commercially available solvents is found to be effective in modifying particle-polymer interfacial interactions. The approach is applicable to a wide range of particle-polymer systems and can thereby enable large scale processing of polymer nanohybrids. The systems of silica nanoparticles dispersed in long-range or short-range self-assembled structures of aqueous poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers (Pluronics) is considered here. The effect of various parameters such as the presence of organic solvents, pH, and particle size on the block copolymer organization and the ensuing particle-polymer interactions are investigated. Favorable surface interactions between the deprotonated silica nanoparticle and PEO-rich domain facilitate particle

  7. Sub-molecular electronic structure of self-assembled metal-organic nano-chains on a noble metal surface

    NASA Astrophysics Data System (ADS)

    Schiffrin, Agustin; Capsoni, Martina; Shaw, Adam; Burke, Sarah

    2014-03-01

    Complexes composed of organic ligands coordinated with transition metal atoms exhibit broad absorption bands from the ultraviolet to the near-infrared. These are the result of the intrinsic molecular electronic properties, which include intra-ligand excitations and metal-to-ligand charge transfer. When adsorbed on a surface, these compounds are relevant for photovoltaic applications. In order to ensure a hierarchical transfer of function from the nano- to the macro-scale, electronic characterization at the single molecule level is essential. We present a low-temperature scanning tunneling spectroscopy study on the local electronic structure of one-dimensional self-assembled metal-organic nanostructures formed on a noble metal surface. The nano-chains consist of terpyridine-based ligands coordinated with iron (Fe) adatoms. We map the local density of electronic states of the system with sub-molecular spatial resolution. Energy-broadened highest-occupied molecular orbitals are dominated by metal states, whereas sharp resonances above Fermi are mainly related to the organic moiety. Coordination between the ligand and Fe induces energy shifts and a break of spatial symmetry of the unoccupied states, pointing to an electron transfer from the metal atom to the terpyridine groups.

  8. Guided Self-Assembly of Nano-Precipitates into Mesocrystals

    PubMed Central

    Liu, H.; Gao, Y.; Xu, Z.; Zhu, Y.M.; Wang, Y.; Nie, J.F.

    2015-01-01

    We show by a combination of computer simulation and experimental characterization guided self-assembly of coherent nano-precipitates into a mesocrystal having a honeycomb structure in bulk materials. The structure consists of different orientation variants of a product phase precipitated out of the parent phase by heterogeneous nucleation on a hexagonal dislocation network. The predicted honeycomb mesocrystal has been confirmed by experimental observations in an Mg-Y-Nd alloy. The structure and lattice parameters of the mesocrystal and the size of the nano-precipitates are readily tuneable, offering ample opportunities to tailor its properties for a wide range of technological applications. PMID:26559002

  9. Guided Self-Assembly of Nano-Precipitates into Mesocrystals

    NASA Astrophysics Data System (ADS)

    Liu, H.; Gao, Y.; Xu, Z.; Zhu, Y. M.; Wang, Y.; Nie, J. F.

    2015-11-01

    We show by a combination of computer simulation and experimental characterization guided self-assembly of coherent nano-precipitates into a mesocrystal having a honeycomb structure in bulk materials. The structure consists of different orientation variants of a product phase precipitated out of the parent phase by heterogeneous nucleation on a hexagonal dislocation network. The predicted honeycomb mesocrystal has been confirmed by experimental observations in an Mg-Y-Nd alloy. The structure and lattice parameters of the mesocrystal and the size of the nano-precipitates are readily tuneable, offering ample opportunities to tailor its properties for a wide range of technological applications.

  10. Self-Assembly of Large-Scale Shape-Controlled DNA Nano-Structures

    DTIC Science & Technology

    2014-12-16

    DNA nanotechnology application: Patterning inorganic oxides using DNA templates 7 5.1.4 Structural DNA nanotechnology application: DNA Foundries...and supported foreign nationals 8 9 Productivity 9 9.1 Refereed journal article 9 9.2 Non-refereed journal article 10 9.3 Workshops and...mask for graphene 22 11.5.3 Structural DNA nanotechnology application: Patterning inorganic oxides using DNA templates 23 11.5.4 Structural DNA

  11. Self Assembled, Ultra-Hydrophobic Micro/Nano-Textured Surfaces

    DTIC Science & Technology

    2007-04-01

    Self Assembled, Ultra-Hydrophobic Micro / Nano -Textured Surfaces by Adam M. Rawlett, Joshua A. Orlicki, Nicole Zander, Afia Karikari, and...5069 ARL-TN-275 April 2007 Self Assembled, Ultra-Hydrophobic Micro / Nano -Textured Surfaces Adam M. Rawlett, Joshua A. Orlicki, and...NUMBER 5b. GRANT NUMBER 4. TITL Self A bled, Ultra-Hydrophobic Micro / Nano -Textured Surfaces 5c. PROGRAM ELEMENT NUMBER E ssem AND SUBTITLE 5d

  12. Elucidating dominant pathways of the nano-particle self-assembly process.

    PubMed

    Zeng, Xiangze; Li, Bin; Qiao, Qin; Zhu, Lizhe; Lu, Zhong-Yuan; Huang, Xuhui

    2016-09-14

    Self-assembly processes play a key role in the fabrication of functional nano-structures with widespread application in drug delivery and micro-reactors. In addition to the thermodynamics, the kinetics of the self-assembled nano-structures also play an important role in determining the formed structures. However, as the self-assembly process is often highly heterogeneous, systematic elucidation of the dominant kinetic pathways of self-assembly is challenging. Here, based on mass flow, we developed a new method for the construction of kinetic network models and applied it to identify the dominant kinetic pathways for the self-assembly of star-like block copolymers. We found that the dominant pathways are controlled by two competing kinetic parameters: the encounter time Te, characterizing the frequency of collision and the transition time Tt for the aggregate morphology change from rod to sphere. Interestingly, two distinct self-assembly mechanisms, diffusion of an individual copolymer into the aggregate core and membrane closure, both appear at different stages (with different values of Tt) of a single self-assembly process. In particular, the diffusion mechanism dominates the middle-sized semi-vesicle formation stage (with large Tt), while the membrane closure mechanism dominates the large-sized vesicle formation stage (with small Tt). Through the rational design of the hydrophibicity of the copolymer, we successfully tuned the transition time Tt and altered the dominant self-assembly pathways.

  13. Nano-Structured Mesoporous Silica Wires with Intra-Wire Lamellae via Evaporation-Induced Self-Assembly in Space-Confined Channels

    SciTech Connect

    Hu, Michael Z.; Shi, Donglu; Blom, Douglas Allen

    2014-04-06

    Evaporation-induced self-assembly (EISA) of silica sol-gel ethanol-water solution mixtures with block-copolymer were studied inside uniform micro/nano channels. Nano-structured mesoporous silica wires, with various intra-wire self-assembly structures including lamellae, were prepared via EISA process but in space-confined channels with the diameter ranging from 50 nm to 200 nm. Membranes made of anodized aluminum oxide (AAO) and track-etched polycarbonate (EPC) were utilized as the arrays of space-confined channels (i.e., 50, 100, and 200-nm EPC and 200-nm AAO) for infiltration and drying of mixture solutions; these substrate membranes were submerged in mixture solutions consisting of a silica precursor, a structure-directing agent, ethanol, and water. After the substrate channels were filled with the solution under vacuum impregnation, the membrane was removed from the solution and dried in air. The silica precursor used was tetra-ethyl othosilicate (TEOS), and the structure-directing agent employed was triblock copolymer Pluronic-123 (P123). It was found that the formation of the mesoporous nanostructures in silica wires within uniform channels were significantly affected by the synthesis conditions including (1) pre-assemble TEOS aging time, (2) the evaporation rate during the vacuum impregnation, and (3) the air-dry temperature. The obtained intra-wire structures, including 2D-hexagonal rods and lamellae, were studied by scanning transmission electron microscopy (STEM). A steric hindrance effect seems to explain well the observed polymer-silica mesophase formation tailored by TEOS aging time. The evaporation effect, air-drying effect, and AAO-vs-EPC substrate effect on the mesoporous structure of the formed silica wires were also presented and discussed.

  14. Nano-imaging enabled via self-assembly

    PubMed Central

    McLeod, Euan; Ozcan, Aydogan

    2014-01-01

    SUMMARY Imaging object details with length scales below approximately 200 nm has been historically difficult for conventional microscope objective lenses because of their inability to resolve features smaller than one-half the optical wavelength. Here we review some of the recent approaches to surpass this limit by harnessing self-assembly as a fabrication mechanism. Self-assembly can be used to form individual nano- and micro-lenses, as well as to form extended arrays of such lenses. These lenses have been shown to enable imaging with resolutions as small as 50 nm half-pitch using visible light, which is well below the Abbe diffraction limit. Furthermore, self-assembled nano-lenses can be used to boost contrast and signal levels from small nano-particles, enabling them to be detected relative to background noise. Finally, alternative nano-imaging applications of self-assembly are discussed, including three-dimensional imaging, enhanced coupling from light-emitting diodes, and the fabrication of contrast agents such as quantum dots and nanoparticles. PMID:25506387

  15. Observation of self-assembled periodic nano-structures induced by femtosecond laser in both ablation and deposition regimes

    NASA Astrophysics Data System (ADS)

    Tang, Mingzhen; Zhang, Haitao; Her, Tsing-Hua

    2008-02-01

    We observed the spontaneous formation of periodic nano-structures in both femtosecond laser ablation and deposition. The former involved 400-nm femtosecond pulses from a 250-KHz regenerated amplified mode-locked Ti:sapphire laser and periodic nanocracks and the nano-structure are in the form of periodic nanocracks in the substrate, the latter applied an 80-MHz mode-locked Ti:sapphire oscillator with pulse energy less than half nanojoule in a laser-induced chemical vapor deposition configuration and tungsten nanogratings grow heterogeneously on top of the substrates. These two observed periodic nanostructures have opposite orientations respecting to laser polarization: the periodic nanocracks are perpendicular to, whereas the deposited tungsten nanogratings are parallel to laser polarization direction. By translating the substrate respecting to the laser focus, both the periodic nanocrack and tungsten nanograting extend to the whole scanning range. The deposited tungsten nanogratings possess excellent uniformity on both the grating period and tooth length. Both the attributes can be tuned precisely by controlling the laser power and scanning speed. Furthermore, we discovered that the teeth of transverse tungsten nanogratings are self aligned along their axial direction during multiple scanning with appropriate offset between scans. We demonstrate the feasibility of fabricating large-area one-dimensional grating by exploiting such unique property. These distinct phenomena of nanocracks and tungsten nanogratings indicate different responsible mechanisms.

  16. Self-assembly in the ferritin nano-cage protein superfamily.

    PubMed

    Zhang, Yu; Orner, Brendan P

    2011-01-01

    Protein self-assembly, through specific, high affinity, and geometrically constraining protein-protein interactions, can control and lead to complex cellular nano-structures. Establishing an understanding of the underlying principles that govern protein self-assembly is not only essential to appreciate the fundamental biological functions of these structures, but could also provide a basis for their enhancement for nano-material applications. The ferritins are a superfamily of well studied proteins that self-assemble into hollow cage-like structures which are ubiquitously found in both prokaryotes and eukaryotes. Structural studies have revealed that many members of the ferritin family can self-assemble into nano-cages of two types. Maxi-ferritins form hollow spheres with octahedral symmetry composed of twenty-four monomers. Mini-ferritins, on the other hand, are tetrahedrally symmetric, hollow assemblies composed of twelve monomers. This review will focus on the structure of members of the ferritin superfamily, the mechanism of ferritin self-assembly and the structure-function relations of these proteins.

  17. Structure and Properties of Nano- and Meso-Scale Materials Prepared by Designed Self-Assembly of Nanoparticles

    NASA Astrophysics Data System (ADS)

    Lukach, Ariella

    The work presented in this thesis explores the homo- and co-assembly process, structural characteristics and properties of nano- and meso-scale, one- and three-dimensional structures composed of nanoscale building blocks. In chapter 3, we developed a method for terminating the colloidal polymerization process of gold nanorods by post-assembly photocrosslinking of polymer ligands. By functionalizing gold nanorods with a hydrophobic polymer containing pendant double bonds, we were able to compartmentalize a hydrophobic photoinitiator. We could then suppress the association ability of the polymer ligands by covalently crosslinking them using photoirradiation. The averaged aggregation number of the polymers could be predicted from the kinetics of molecular step-growth polymerization. Furthermore, we found that following crosslinking, the inert-rod distance reduced, and the nanorod co-linearity increased, both allowing for better electromagnetic coupling between the nanorods. In chapter 4, we further explored the resemblance between colloidal and molecular polymerization reactions by applying strategies from molecular copolymerization to the co-assembly of gold nanorods with different dimensions into random and block copolymer structures (plasmonic copolymers). The approach was extended to the co-assembly of random copolymers of gold and palladium nanorods. We showed that the formation of random copolymers is achieved regardless of the composition, size, or concentration if both co-monomers are present at the beginning of the copolymerization. Block copolymers were prepared by combining one pre-polymer with the second monomer, or two pre-polymers. A kinetic model validated and further expanded the kinetic theories developed for molecular copolymerization reactions. Chapters 5 and 6 explore a bottom-up method to produce composite materials from spherical nanoparticles with different core-composition, surface-characteristics, and concentrations and cellulose nanocrystals

  18. A route to self-assemble suspended DNA nano-complexes

    NASA Astrophysics Data System (ADS)

    Lansac, Yves; Degrouard, Jeril; Renouard, Madalena; Toma, Adriana C.; Livolant, Françoise; Raspaud, Eric

    2016-02-01

    Highly charged polyelectrolytes can self-assemble in presence of condensing agents such as multivalent cations, amphiphilic molecules or proteins of opposite charge. Aside precipitation, the formation of soluble micro- and nano-particles has been reported in multiple systems. However a precise control of experimental conditions needed to achieve the desired structures has been so far hampered by the extreme sensitivity of the samples to formulation pathways. Herein we combine experiments and molecular modelling to investigate the detailed microscopic dynamics and the structure of self-assembled hexagonal bundles made of short dsDNA fragments complexed with small basic proteins. We suggest that inhomogeneous mixing conditions are required to form and stabilize charged self-assembled nano-aggregates in large excess of DNA. Our results should help re-interpreting puzzling behaviors reported for a large class of strongly charged polyelectrolyte systems.

  19. A route to self-assemble suspended DNA nano-complexes

    PubMed Central

    Lansac, Yves; Degrouard, Jeril; Renouard, Madalena; Toma, Adriana C.; Livolant, Françoise; Raspaud, Eric

    2016-01-01

    Highly charged polyelectrolytes can self-assemble in presence of condensing agents such as multivalent cations, amphiphilic molecules or proteins of opposite charge. Aside precipitation, the formation of soluble micro- and nano-particles has been reported in multiple systems. However a precise control of experimental conditions needed to achieve the desired structures has been so far hampered by the extreme sensitivity of the samples to formulation pathways. Herein we combine experiments and molecular modelling to investigate the detailed microscopic dynamics and the structure of self-assembled hexagonal bundles made of short dsDNA fragments complexed with small basic proteins. We suggest that inhomogeneous mixing conditions are required to form and stabilize charged self-assembled nano-aggregates in large excess of DNA. Our results should help re-interpreting puzzling behaviors reported for a large class of strongly charged polyelectrolyte systems. PMID:26912166

  20. Nano-engineering by optically directed self-assembly.

    SciTech Connect

    Furst, Eric; Dunn, Elissa; Park, Jin-Gyu; Brinker, C. Jeffrey; Sainis, Sunil; Merrill, Jason; Dufresne, Eric; Reichert, Matthew D.; Brotherton, Christopher M.; Bogart, Katherine Huderle Andersen; Molecke, Ryan A.; Koehler, Timothy P.; Bell, Nelson Simmons; Grillet, Anne Mary; Gorby, Allen D.; Singh, John; Lele, Pushkar; Mittal, Manish

    2009-09-01

    Lack of robust manufacturing capabilities have limited our ability to make tailored materials with useful optical and thermal properties. For example, traditional methods such as spontaneous self-assembly of spheres cannot generate the complex structures required to produce a full bandgap photonic crystals. The goal of this work was to develop and demonstrate novel methods of directed self-assembly of nanomaterials using optical and electric fields. To achieve this aim, our work employed laser tweezers, a technology that enables non-invasive optical manipulation of particles, from glass microspheres to gold nanoparticles. Laser tweezers were used to create ordered materials with either complex crystal structures or using aspherical building blocks.

  1. Self-assembled Nano-layering at the Adhesive interface.

    PubMed

    Yoshida, Y; Yoshihara, K; Nagaoka, N; Hayakawa, S; Torii, Y; Ogawa, T; Osaka, A; Meerbeek, B Van

    2012-04-01

    According to the 'Adhesion-Decalcification' concept, specific functional monomers within dental adhesives can ionically interact with hydroxyapatite (HAp). Such ionic bonding has been demonstrated for 10-methacryloyloxydecyl dihydrogen phosphate (MDP) to manifest in the form of self-assembled 'nano-layering'. However, it remained to be explored if such nano-layering also occurs on tooth tissue when commercial MDP-containing adhesives (Clearfil SE Bond, Kuraray; Scotchbond Universal, 3M ESPE) were applied following common clinical application protocols. We therefore characterized adhesive-dentin interfaces chemically, using x-ray diffraction (XRD) and energy-dispersive x-ray spectroscopy (EDS), and ultrastructurally, using (scanning) transmission electron microscopy (TEM/STEM). Both adhesives revealed nano-layering at the adhesive interface, not only within the hybrid layer but also, particularly for Clearfil SE Bond (Kuraray), extending into the adhesive layer. Since such self-assembled nano-layering of two 10-MDP molecules, joined by stable MDP-Ca salt formation, must make the adhesive interface more resistant to biodegradation, it may well explain the documented favorable clinical longevity of bonds produced by 10-MDP-based adhesives.

  2. 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

  3. Self-Assembled, Ultra-Hydrophobic Micro/Nano-Textured Surfaces

    DTIC Science & Technology

    2005-08-01

    Self-Assembled, Ultra-Hydrophobic Micro / Nano -Textured Surfaces by Adam M. Rawlett, Joshua A. Orlicki, Afia Karikari, and Tim Long ARL-TR...3547 August 2005 Self-Assembled, Ultra-Hydrophobic Micro / Nano -Textured Surfaces Adam M. Rawlett and Joshua A. Orlicki, Weapons and...AND SUBTITLE Self-Assembled, Ultra-Hydrophobic Micro / Nano -Textured Surfaces 5c. PROGRAM ELEMENT NUMBER 5d. PROJECT NUMBER AH84 5e. TASK NUMBER

  4. Simultaneous Nano- and Microscale Control of Nanofibrous Microspheres Self-Assembled from Star-Shaped Polymers.

    PubMed

    Zhang, Zhanpeng; Marson, Ryan L; Ge, Zhishen; Glotzer, Sharon C; Ma, Peter X

    2015-07-08

    Star-shaped polymers with varying arm numbers and arm lengths are synthesized, and self-assembled into microspheres, which are either smooth or fibrous on the nanoscale, and either nonhollow, hollow, or spongy on the microscale. The molecular architecture and functional groups determine the structure on both length scales. This exciting mechanistic discovery guides simultaneous control of both the nano- and microfeatures of the microspheres.

  5. Self assembled structures for 3D integration

    NASA Astrophysics Data System (ADS)

    Rao, Madhav

    Three dimensional (3D) micro-scale structures attached to a silicon substrate have various applications in microelectronics. However, formation of 3D structures using conventional micro-fabrication techniques are not efficient and require precise control of processing parameters. Self assembly is a method for creating 3D structures that takes advantage of surface area minimization phenomena. Solder based self assembly (SBSA), the subject of this dissertation, uses solder as a facilitator in the formation of 3D structures from 2D patterns. Etching a sacrificial layer underneath a portion of the 2D pattern allows the solder reflow step to pull those areas out of the substrate plane resulting in a folded 3D structure. Initial studies using the SBSA method demonstrated low yields in the formation of five different polyhedra. The failures in folding were primarily attributed to nonuniform solder deposition on the underlying metal pads. The dip soldering method was analyzed and subsequently refined. A modified dip soldering process provided improved yield among the polyhedra. Solder bridging referred as joining of solder deposited on different metal patterns in an entity influenced the folding mechanism. In general, design parameters such as small gap-spacings and thick metal pads were found to favor solder bridging for all patterns studied. Two types of soldering: face and edge soldering were analyzed. Face soldering refers to the application of solder on the entire metal face. Edge soldering indicates application of solder only on the edges of the metal face. Mechanical grinding showed that face soldered SBSA structures were void free and robust in nature. In addition, the face soldered 3D structures provide a consistent heat resistant solder standoff height that serve as attachments in the integration of dissimilar electronic technologies. Face soldered 3D structures were developed on the underlying conducting channel to determine the thermo-electric reliability of

  6. Self-Assembled, Ultra-Hydrophobic Micro/Nano-Textured Surfaces

    DTIC Science & Technology

    2006-11-01

    SELF ASSEMBLED, ULTRA-HYDROPHOBIC MICRO / NANO -TEXTURED SURFACES Adam M. Rawlett,* Joshua A. Orlicki, Nicole Zander U.S. Army Research...These micro / nano -textured surfaces have enhanced the hydrophobicity of the textured polymer when measured by contact angle. This method of pro...REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE Self Assembled, Ultra-Hydrophobic Micro / Nano -Textured Surfaces 5a. CONTRACT NUMBER 5b

  7. Unique nano-domain structures in self-assembled BiFeO₃ and Pb(Zr,Ti)O₃ ferroelectric nanocapacitors.

    PubMed

    Zhang, Fengyuan; Miao, Qing; Tian, Guo; Lu, Zengxing; Zhao, Lina; Fan, Hua; Song, Xiao; Li, Zhongwen; Zeng, M; Gao, Xingsen; Liu, Junming

    2016-01-08

    In this work, self-assembled ferroelectric BiFeO3 (BFO) and Pb(Zr,Ti)O3 (PZT) nanocapacitors were fabricated by a one-step pulsed-laser deposition process. Each individual nanocapacitor consists of a SrRuO3 or LaSrMnO3 bottom electrode layer, an epitaxial ferroelectric middle layer and a self-assembled nanoisland of conductive Bi2O3 or PbO2 as the top nanoelectrode. The nanoelectrodes have a lateral size of 10-100 nm depending on various deposition equivalent thickness. The as-fabricated nanocapacitors exhibit unique so-called anti-domain structures, with opposite polarization orientation to that of the naked ferroelectric films, which can be understood by the different interface built-in-voltages between their neighboring layers. They also show apparent reduced coercive fields and enhanced piezoelectricity compared to the naked films, as revealed by the switching spectroscopy piezoresponse force microscopy (SSPFM) and band-excitation mapping. Besides that, individual addressable polarization writing and erasing properties were also observed in these nanocapacitors and the written domain can maintain stability up to 12 h, which is promising for data storage devices.

  8. Multidimensional Self-Assembled Structures of Alkylated Cellulose Oligomers Synthesized via in Vitro Enzymatic Reactions.

    PubMed

    Yataka, Yusuke; Sawada, Toshiki; Serizawa, Takeshi

    2016-10-04

    The self-assembly of biomolecules into highly ordered nano-to-macroscale structures is essential in the construction of biological tissues and organs. A variety of biomolecular assemblies composed of nucleic acids, peptides, and lipids have been used as molecular building units for self-assembled materials. However, crystalline polysaccharides have rarely been utilized in self-assembled materials. In this study, we describe multidimensional self-assembled structures of alkylated cellulose oligomers synthesized via in vitro enzymatic reactions. We found that the alkyl chain length drastically affected the assembled morphologies and allomorphs of cellulose moieties. The modulation of the intermolecular interactions of cellulose oligomers by alkyl substituents was highly effective at controlling their assembly into multidimensional structures. This study proposes a new potential of crystalline oligosaccharides for structural components of molecular assemblies with controlled morphologies and crystal structures.

  9. Mechanisms of the self-assembly of EAK16-family peptides into fibrillar and globular structures: molecular dynamics simulations from nano- to micro-seconds.

    PubMed

    Emamyari, Soheila; Kargar, Faezeh; Sheikh-Hasani, Vahid; Emadi, Saeed; Fazli, Hossein

    2015-05-01

    The self-assembly of EAK16-family peptides in a bulk solution was studied using a combination of all-atom and coarse-grained molecular dynamics simulations. In addition, specified concentrations of EAK16 peptides were induced to form fibrillary or globular assemblies in vitro. The results show that the combination of all-atom molecular dynamics simulations on the single- and double-chain levels and coarse-grained simulations on the many-chain level predicts the experimental observations reasonably well. At neutral pH conditions, EAK16-I and EAK16-II assemble into fibrillary structures, whereas EAK16-IV aggregates into globular assemblies. Mechanisms of the formation of fibrillar and globular assemblies are described using the simulation results.

  10. Colloidosome like structures: self-assembly of silica microrods

    SciTech Connect

    Datskos, P.; Polizos, G.; Bhandari, M.; Cullen, D. A.; Sharma, J.

    2016-03-07

    Self-assembly of one-dimensional structures is attracting a great deal of interest because assembled structures can provide better properties compared to individual building blocks. We demonstrate silica microrod self-assembly by exploiting Pickering emulsion based strategy. Micron-sized silica rods were synthesized employing previously reported methods based on polyvinylpyrrolidone/ pentanol emulsion droplets. Moreover, rods self-assembled to make structures in the range of z10 40 mm. Smooth rods assembled better than segmented rods. Finally, the assembled structures were bonded by weak van der Waals forces.

  11. Colloidosome like structures: self-assembly of silica microrods

    DOE PAGES

    Datskos, P.; Polizos, G.; Bhandari, M.; ...

    2016-03-07

    Self-assembly of one-dimensional structures is attracting a great deal of interest because assembled structures can provide better properties compared to individual building blocks. We demonstrate silica microrod self-assembly by exploiting Pickering emulsion based strategy. Micron-sized silica rods were synthesized employing previously reported methods based on polyvinylpyrrolidone/ pentanol emulsion droplets. Moreover, rods self-assembled to make structures in the range of z10 40 mm. Smooth rods assembled better than segmented rods. Finally, the assembled structures were bonded by weak van der Waals forces.

  12. Structures Self-Assembled Through Directional Solidification

    NASA Technical Reports Server (NTRS)

    Dynys, Frederick W.; Sayir, Ali

    2005-01-01

    dry plasma etch. The wet chemical etches the silicon away, exposing the TiSi2 rods, whereas plasma etching preferentially etches the Si-TiSi2 interface to form a crater. The porous architectures are applicable to fabricating microdevices or creating templates for part fabrication. The porous rod structure can serve as a platform for fabricating microplasma devices for propulsion or microheat exchangers and for fabricating microfilters for miniatured chemical reactors. Although more work is required, self-assembly from DSE can have a role in microdevice fabrication.

  13. Strain mediated self-assembly of ceramic nano islands

    NASA Astrophysics Data System (ADS)

    Rauscher, Michael

    This dissertation presents the first observations of self-assembled arrays of epitaxial nano islands in ceramic systems, based on RF sputtering and thermal processing of Gadolinia-doped ceria (GDC) thin films on an yttria-stabilized zirconia (YSZ) single crystal substrate. In contrast to the conventional semiconductor nano island self-assembly systems, the island arrays in the GDC-YSZ system provide materials with categorically different physical properties and functionalities, and they exhibit a stronger ordering at a larger characteristic length scale. The initial focus of this study was on the processing and characterization of thin GDC layers on YSZ, which are used in SOFCs as barriers to prevent the reaction of some cathode materials with the YSZ electrolyte. Chapter 3 of this document describes studies on relatively thin (<200 nm) GDC deposits which remained adherent to their substrates during post-deposition processing. The GDC films were amorphous or ultra-fine grained as deposited, with a mixed GDC-YSZ layer at the interface. After annealing at 1150°C, the GDC films were epitaxially oriented on the YSZ substrates, with isolated porosity in their interior. Some of the thick RF-sputtered GDC layers (>300 nm) were found to fail by spalling from the YSZ substrate, leaving behind patches of unspalled film and exposing a sputter-mixed GDC-YSZ surface. Upon annealing, the modified surface spontaneously broke up into two-dimensional arrays of epitaxial islands with sub-micron dimensions, exhibiting order in spacing and alignment. In addition to the classical local effects that drive dewetting processes, the self-assembly of the epitaxial GDC-bearing islands is driven by elastic interactions between them, and these interactions are mediated by the elastically anisotropic underlying YSZ substrate. The stresses in the initial mixed surface layers are modified by two factors: The thermal-expansion mismatch leads to stresses, depending on temperature and heating rates

  14. Self-Assembly of Structures with Addressable Complexity.

    PubMed

    Jacobs, William M; Frenkel, Daan

    2016-03-02

    The self-assembly of structures with "addressable complexity", where every component is distinct and is programmed to occupy a specific location within a target structure, is a promising route to engineering materials with precisely defined morphologies. Because systems with many components are inherently complicated, one might assume that the chances of successful self-assembly are extraordinarily small. Yet recent advances suggest otherwise: addressable structures with hundreds of distinct building blocks have been designed and assembled with nanometer precision. Despite this remarkable success, it is often challenging to optimize a self-assembly reaction to ensure that the intended structure is kinetically accessible. In this Perspective, we focus on the prediction of kinetic pathways for self-assembly and implications for the design of robust experimental protocols. The development of general principles to predict these pathways will enable the engineering of complex materials using a much wider range of building blocks than is currently possible.

  15. Chemical sensitivity of self-assembled porphyrin nano-aggregates.

    PubMed

    Dini, Francesca; Martinelli, Eugenio; Pomarico, Giuseppe; Paolesse, Roberto; Monti, Donato; Filippini, Daniel; D'Amico, Arnaldo; Lundström, Ingemar; Di Natale, Corrado

    2009-02-04

    Nanostructured molecular assemblies may provide additional sensing properties not found in other arrangements of the same basic constituents. Among three-dimensional structures, nanotubes are particularly appealing for applications as chemical sensors, because of the potential inclusion of different guests inside the cavity or the induced modification of the skeletal interaction after analyte binding. Porphyrins are a class of compounds characterized by brilliant sensing properties, appearing also in non-ordered solid-state aggregates. In recent years, it was reported that aggregation of oppositely charged porphyrins led to the formation of self-assembled nanotubes and in this paper their sensing properties, both in solution and in the solid state, have been investigated. The interactions of porphyrin nanotubes with guest molecules have been monitored by following the changes in their UV-vis spectra. The results obtained have been exploited to build up a sensing platform based on a computer screen as a light source and a digital camera as detector. Porphyrin nanostructures exhibited an enhanced sensitivity to different compounds with respect to those shown by single porphyrin subunits. The reason for the increased sensitivity may be likely found in an additional sensing mechanism related to the modulation of the strength of the forces that keep the supramolecular ensemble together.

  16. Silicon based near infrared photodetector using self-assembled organic crystalline nano-pillars

    SciTech Connect

    Ajiki, Yoshiharu E-mail: isao@i.u-tokyo.ac.jp; Kan, Tetsuo; Yahiro, Masayuki; Hamada, Akiko; Adachi, Chihaya; Adachi, Junji; Matsumoto, Kiyoshi; Shimoyama, Isao E-mail: isao@i.u-tokyo.ac.jp

    2016-04-11

    We propose a silicon (Si) based near-infrared photodetector using self-assembled organic crystalline nano-pillars, which were formed on an n-type Si substrate and were covered with an Au thin-film. These structures act as antennas for near-infrared light, resulting in an enhancement of the light absorption on the Au film. Because the Schottky junction is formed between the Au/n-type Si, the electron excited by the absorbed light can be detected as photocurrent. The optical measurement revealed that the nano-pillar structures enhanced the responsivity for the near-infrared light by 89 (14.5 mA/W) and 16 (0.433 mA/W) times compared with those of the photodetector without nano-pillars at the wavelengths of 1.2 and 1.3 μm, respectively. Moreover, no polarization dependency of the responsivity was observed, and the acceptable incident angle ranged from 0° to 30°. These broad responses were likely to be due to the organic nano-pillar structures' having variation in their orientation, which is advantageous for near-infrared detector uses.

  17. Self-assembly and transformation of hybrid nano-objects and nanostructures under equilibrium and non-equilibrium conditions

    NASA Astrophysics Data System (ADS)

    Mann, Stephen

    2009-10-01

    Understanding how chemically derived processes control the construction and organization of matter across extended and multiple length scales is of growing interest in many areas of materials research. Here we review present equilibrium and non-equilibrium self-assembly approaches to the synthetic construction of discrete hybrid (inorganic-organic) nano-objects and higher-level nanostructured networks. We examine a range of synthetic modalities under equilibrium conditions that give rise to integrative self-assembly (supramolecular wrapping, nanoscale incarceration and nanostructure templating) or higher-order self-assembly (programmed/directed aggregation). We contrast these strategies with processes of transformative self-assembly that use self-organizing media, reaction-diffusion systems and coupled mesophases to produce higher-level hybrid structures under non-equilibrium conditions. Key elements of the constructional codes associated with these processes are identified with regard to existing theoretical knowledge, and presented as a heuristic guideline for the rational design of hybrid nano-objects and nanomaterials.

  18. Self-assembly of polymeric microspheres of complex internal structures

    NASA Astrophysics Data System (ADS)

    Fialkowski, Marcin; Bitner, Agnieszka; Grzybowski, Bartosz A.

    2005-01-01

    Self-assembly can easily produce intricate structures that would be difficult to make by conventional fabrication means. Here, self-assembly is used to prepare multicomponent polymeric microspheres of arbitrary internal symmetries. Droplets of liquid prepolymers are printed onto a water-soluble hydrogel, and are allowed to spread and coalesce into composite patches. These patches are then immersed in an isodense liquid, which both compensates the force of gravity and dissolves the gel beneath the polymers. Subsequently, the patches fold into spheres whose internal structures are dictated by the arrangement of the droplets printed onto the surface. The spheres can be solidified either thermally or by ultraviolet radiation. We present a theoretical analysis of droplet spreading, coalescence and folding. Conditions for the stability of the folded microspheres are derived from linear stability analysis. The composite microbeads that we describe are likely to find uses in optics, colloidal self-assembly and controlled-delivery applications.

  19. 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.

  20. Self-assembled domain structures: From micro- to nanoscale

    NASA Astrophysics Data System (ADS)

    Shur, Vladimir; Akhmatkhanov, Andrey; Lobov, Alexey; Turygin, Anton

    2015-06-01

    The recent achievements in studying the self-assembled evolution of micro- and nanoscale domain structures in uniaxial single crystalline ferroelectrics lithium niobate and lithium tantalate have been reviewed. The results obtained by visualization of static domain patterns and kinetics of the domain structure by different methods from common optical microscopy to more sophisticated scanning probe microscopy, scanning electron microscopy and confocal Raman microscopy, have been discussed. The kinetic approach based on various nucleation processes similar to the first-order phase transition was used for explanation of the domain structure evolution scenarios. The main mechanisms of self-assembling for nonequilibrium switching conditions caused by screening ineffectiveness including correlated nucleation, domain growth anisotropy, and domain-domain interaction have been considered. The formation of variety of self-assembled domain patterns such as fractal-type, finger and web structures, broad domain boundaries, and dendrites have been revealed at each of all five stages of domain structure evolution during polarization reversal. The possible applications of self-assembling for micro- and nanodomain engineering were reviewed briefly. The review covers mostly the results published by our research group.

  1. Toughening of epoxies based on self-assembly of nano-sized amphiphilic block copolymer micelles

    NASA Astrophysics Data System (ADS)

    Liu, Jia

    As a part of a larger effort towards the fundamental understanding of mechanical behaviors of polymers toughened by nanoparticles, this dissertation focuses on the structure-property relationship of epoxies modified with nano-sized poly(ethylene-alt-propylene)-b-poly(ethylene oxide) (PEP-PEO) block copolymer (BCP) micelle particles. The amphiphilic BCP toughener was incorporated into a liquid epoxy resin and self-assembled into well-dispersed 15 nm spherical micelle particles. The nano-sized BCP, at 5 wt% loading, can significantly improve the fracture toughness of epoxy (ca. 180% improvement) without reducing modulus at room temperature and exhibits only a slight drop (ca. 5°C) in glass transition temperature (Tg). The toughening mechanisms were found to be BCP micelle nanoparticle cavitation, followed by matrix shear banding, which mainly accounted for the observed remarkable toughening effect. The unexpected "nano-cavitation" phenomenon cannot be predicted by existing physical models. The plausible causes for the observed nano-scale cavitation and other mechanical behaviors may include the unique structural characteristics of BCP micelles and the influence from the surrounding epoxy network, which is significantly modified by the epoxy-miscible PEO block. Other mechanisms, such as crack tip blunting, may also play a role in the toughening. Structure-property relationships of this nano-domain modified polymer are discussed. In addition, other important factors, such as strain rate dependence and matrix crosslink density effect on toughening, have been investigated. This BCP toughening approach and conventional rubber toughening techniques are compared. Insights on the decoupling of modulus, toughness, and Tg for designing high performance thermosetting materials with desirable physical and mechanical properties are discussed.

  2. Self Assembled Structures by Directional Solidification of Eutectics

    NASA Technical Reports Server (NTRS)

    Dynys, Frederick W.; Sayir, Ali

    2004-01-01

    Interest in ordered porous structures has grown because of there unique properties such as photonic bandgaps, high backing packing density and high surface to volume ratio. Inspired by nature, biometric strategies using self assembled organic molecules dominate the development of hierarchical inorganic structures. Directional solidification of eutectics (DSE) also exhibit self assembly characteristics to form hierarchical metallic and inorganic structures. Crystallization of diphasic materials by DSE can produce two dimensional ordered structures consisting of rods or lamella. By selective removal of phases, DSE is capable to fabricate ordered pore arrays or ordered pin arrays. Criteria and limitations to fabricate hierarchical structures will be presented. Porous structures in silicon base alloys and ceramic systems will be reported.

  3. Structure and dynamics of self-assembly

    NASA Astrophysics Data System (ADS)

    van Lengerich, Henrik; James, Richard

    2013-03-01

    We investigate structures that are composed of many identical building blocks. Of particular interest are equilibrium structures where every building block sees the same environment - we call these ``objective structures''. For example, carbon nanotubes and virus capsids are both objective structures. The dynamics of assembly is investigated through experiments and simulations. The experiment consist of a macro-scale shaker containing identical neutrally buoyant magnetic particles. Simulations model the translation and rotation of particles using Langevin dynamics. This kind of modelling is applicable to both our experiment and to molecular assembly.

  4. Ultra thin CVD diamond film deposition by electrostatic self-assembly seeding process with nano-diamond particles.

    PubMed

    Kim, J H; Lee, S K; Kwon, O M; Lim, D S

    2009-07-01

    Ultra thin and smooth nano crystalline diamond films were fabricated with electrostatic self-assembly seeding of explosively synthesized nano-diamond particles. Hard aggregates of nano-diamond particles were crushed by high revolution attrition milling at 1000 RPM to regulate the particle size. Through this process, cationic nano-diamond particles were coated with anionic PSS (poly sodium 4-styrene sulfonate) electrolytes. Anionic Si(100) substrate was coated with cationic PDDA (poly diallyldimethyl ammonium chloride) solution. Si(100)/PDDA/PSS/ND (nano-diamond) layer-by-layer structure was formed as a seeding layer by the simple dipping and rinsing of positively charged substrate into anionic PSS/nano-diamond solution. Throughout the seeding process, neither mechanical damage nor chemical attack was observed on the substrate. Every stage of this preparation was carried out at room temperature and pressure. The effect of attrition milling was determined by changing the milling time from 1 hr to 5 hrs. Through the attritional milling and monolayer formation of the nano-diamond, nucleation density was increased up to 3 x 10(11)/cm2. Typical hot filament chemical vapor deposition system was used to coat the diamond film on the ESA (electrostatic self-assembly) seeded Si(100) substrate. Although typical diamond deposition conditions (90 torr/1% CH4 in H2/800 degrees C) were maintained, ultra thin (< 100 nm) and continuous nano crystalline diamond films were deposited. Regardless of metallic or ceramic substrate, ESND (ESA Seeding of nano-diamond) process is applicable if the substrate has any charge. This simple nano technology based process ensures high thickness uniformity of diamond coating without visible edge effect.

  5. DNA ionogel: Structure and self-assembly.

    PubMed

    Pandey, Pankaj Kumar; Rawat, Kamla; Aswal, V K; Kohlbrecher, J; Bohidar, H B

    2016-12-21

    DNA dissolved in ionic liquid (IL) solution (1-ethyl-3-methylimidazolium chloride, [C2mim][Cl]) showed a transition to the gel phase ([DNA] ≥ 1% (w/v)). The gelation time was 400 s for the 1% [IL] sample which reduced to 260 s for 5% [IL] concentration. Gelation times, obtained from the viscosity and ergodicity breaking from the dynamic structure factor data, were remarkably identical to each other. Correspondingly, the gelation temperature which was ∼60 °C increased to 67 °C with [IL] content. The small angle neutron scattering (SANS) structure factor profile revealed the presence of the following three distinct length scales: (a) mesh size, ξ ≈ 3 ± 0.5 nm for ionogels, and ≈0.73 ± 0.06 nm, for sol; (b) cross-sectional radius of DNA strand, Rc ≈ 1.6 ± 0.1 nm; and (c) the characteristic inter-cluster distance ≈33 ± 5 nm. Physical conformation of the DNA-IL complexes remained close to the Gaussian coil definition. It was observed that without IL, in the sol phase, the system was completely ergodic and did not gel, while on addition of IL a sudden transition to the non-ergodic (arrested) gel phase occurred. This was due to the formation of an amorphous network of DNA-IL complexes preceding gelation. In summary, it is shown that the DNA ionogels can be prepared with a tunable gel strength (27-70 Pa) and gelation temperature (60-67 °C). Further, the relaxation dynamics was found to be hierarchical in IL content of the gel, revealing considerable self-organization.

  6. Nano-defect management in directed self-assembly of block copolymers (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Azuma, Tsukasa; Seino, Yuriko; Sato, Hironobu; Kasahara, Yusuke; Kodera, Katsuyoshi; Jiravanichsakul, Phubes; Hayakawa, Teruaki; Yoshimoto, Kenji; Takenaka, Mikihito

    2017-03-01

    Directed self-assembly (DSA) of block copolymers (BCPs) has been expected to become one of the most promising next generation lithography candidates for sub-15 nm line patterning and sub-20 nm contact hole patterning. In order to provide the DSA lithography to practical use in advanced semiconductor device manufacturing, defect mitigation in the DSA materials and processes is the primary challenge. We need to clarify the defect generation mechanism using in-situ measurement of self-assembling processes of BCPs in cooperation with modeling approaches to attain the DSA defect mitigation. In this work, we thus employed in-situ atomic force microscope (AFM) and grazing-incidence small angle X-ray scattering (GI-SAXS) and investigated development of surface morphology as well as internal structure during annealing processes. Figure 1 shows series of the AFM images of PMAPOSS-b-PTFEMA films during annealing processes. The images clearly show that vitrified sponge-like structure without long-range order in as-spun film transforms into lamellar structure and that the long range order of the lamellar structure increases with annealing temperature. It is well-known that ordering processes of BCPs from disordered state in bulk progress via nucleation and growth. In contrary to the case of bulk, the observed processes seem to be spinodal decomposition. This is because the structure in as-spun film is not the concentration fluctuation of disordered state but the vitrified sponge-like structure. The annealing processes induce order-order transition from non-equilibrium ordered-state to the lamellar structure. The surface tension assists the transition and directs the orientation. Figure 2 shows scattering patterns of (a) vicinity of film top and (b) whole sample of the GI-SAXS. We can find vertically oriented lamellar structure in the vicinity of film top while horizontally oriented lamellar structures in the vicinity of film bottom, indicating that the GI-SAXS measurement can

  7. Polymer magnetic microactuators fabricated with hot embossing and layer-by-layer nano self-assembly.

    PubMed

    Xue, Wei; Cui, Tianhong

    2007-08-01

    Polymer-based magnetic microactuators have been fabricated with hot embossing technique and layer-by-layer (LbL) nano self-assembly. Silicon molds are fabricated with conventional UV lithography and wet etching techniques. Hot embossing is used to transfer the patterns from silicon molds to polymethylmethacrylate (PMMA) sheets. The overall processing time for the pattern transfer is less than 20 min. Low-cost devices with massive and rapid replication can be fabricated. Six layers of magnetic iron oxide (Fe2O3) nanoparticles are LbL self-assembled on the PMMA surface as the magnetically sensitive material. Positive photoresist PR1813 is used as the sacrificial layer to protect the gold electrode on the back side of the membrane. LbL nano self-assembly technique provides a simple method to obtain the magnetic film with low cost, short processing time, simple fabrication steps at room temperature. The volume of the magnetic material can be precisely controlled by the number of nano-assembled iron oxide layers. The mechanical, electrical, and magnetic properties of the microactuator are characterized by a laser interferometer. The natural frequency of the actuator is approximately 151 Hz; and the maximum deflection amplitude is about 34 nm. At all frequencies, the increase of the magnetic field increases the deflection amplitude which is in agreement with the theoretical equation.

  8. Effects of particle self-assembly and structural disjoining pressure on wetting kinetics of nanofluid droplet

    NASA Astrophysics Data System (ADS)

    Lu, Gui; Hu, Han; Duan, Yuanyuan; Sun, Ying

    2013-11-01

    The wettability of nanofluids, fluids containing suspensions of nanometer-sized particles, is of particular interest to microfluidic systems. Previous studies showed that the self-assembly of nanoparticles in the vicinity of the contact line gives rise to a structural disjoining pressure, which greatly affects the wettability of nanofluid droplets of micron size or larger. In this study, dynamic wetting of water nano-droplets containing non-surfactant gold nanoparticles on a gold substrate was studied via molecular dynamics simulations to examine the effects nanoparticle self-assembly. To mimic the effect of structural disjoining pressure, the excess disjoining pressure was calculated for a pure water film on a gold substrate with a smooth surface on one end and ordered nano-pillar structures on the other. The results show that the addition of non-surfactant nanoparticles hinders the nano-second droplet wetting process, attributed to the increases in both surface tension of the nanofluid and friction between nanofluid and substrate. The spreading enhancement of nanofluids due to the presence of structural disjoining pressure as a result of nanoparticle ordering is not the case for this nano-droplet spreading system. NSFC (No. 21176133) and the US National Science Foundation (Grant No. CAREER-0968927 and No. DMR-1104835).

  9. Facile synthesis of self-assembled SnO nano-square sheets and hydrogen absorption characteristics

    SciTech Connect

    Iqbal, M. Zubair; Wang, Fengping; Feng, Ting; Zhao, Hailei; Rafique, M. Yasir; Rafi ud Din; Farooq, M. Hassan; Javed, Qurat ul ain; Khan, Dil Faraz

    2012-11-15

    Graphical abstract: Display Omitted Highlights: ► Self-assembled stannous oxide (SnO) 2D nano-square sheets have been synthesized. ► The average size of the nano-square sheets is about 200–400 nm. ► Direct optical band gap of 3.16 eV was acquired by using Davis–Mott model. ► The hydrogen absorption capacity of as-synthesized material was 1.194 wt.% comparatively good. -- Abstract: Stannous oxide is an important functional material which contributes to a wide range of applications in energy storage and optoelectronic devices. In the present study, the single crystalline self-assembled stannous oxide (SnO) 2D nano-square sheets have been synthesized with template-free hydrothermal growth method. The morphology, composition and structure were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) with selected area electron diffraction (SAED), energy dispersive X-ray (EDX), X-ray diffraction (XRD) and Raman spectroscopy, respectively. FESEM results have illustrated that the size of self-assembled 3D hierarchical polygon-shape structure of SnO is in the range of 8–12 μm and the average size of the nano-square sheets is about 100 nm. X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns have revealed that the prepared SnO nano-square sheets exist in single-crystalline nature. Two Raman modes A{sub 1g} = 211 cm{sup −1} and B{sub 1g} = 113 cm{sup −1} were observed by Raman spectroscopy, which is consistent with nano tetragonal phase SnO. Furthermore, the chemical valence of Sn and relative atomic composition of as-prepared SnO have been confirmed by X-ray photoelectron spectroscopy (XPS). Ultraviolet–visible–near infrared spectrophotometry was used to study the transmittance behavior of SnO nano-structures and direct optical band gap of 3.16 eV was acquired by using Davis–Mott model. The first ever study on

  10. Self-Assembling Organic Micro-/Nano-Pillars on Gold and Glass Surfaces

    PubMed Central

    Ji, Hai-Feng; Ruan, Wenli; Li, Yingying; Ding, Guohua

    2014-01-01

    In this work, we report the formation of a family of organic micro-/nano-pillars prepared from surface-assisted self-assembly processes and factors controlling the growth of the pillars. These acids include cyanuric acid (CA), 1,3,5-benzenetricarboxylic acid (TMA), 1,2,4,5-benzenetetracarboxylic acid (TA) and 3,4,9,10-perylenetetracarboxylic acid (PTA). Aqueous solutions mixed with acids and melamine (M) can be fine-tuned to prepare ordered micro-/nano-pillars on substrates, which can be further optimized for their applications.

  11. 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).

  12. Model for dynamic self-assembled magnetic surface structures.

    SciTech Connect

    Belkin, M.; Glatz, A.; Snezhko, A.; Aranson, I. S.; Materials Science Division; Northwestern Univ.

    2010-07-07

    We propose a first-principles model for the dynamic self-assembly of magnetic structures at a water-air interface reported in earlier experiments. The model is based on the Navier-Stokes equation for liquids in shallow water approximation coupled to Newton equations for interacting magnetic particles suspended at a water-air interface. The model reproduces most of the observed phenomenology, including spontaneous formation of magnetic snakelike structures, generation of large-scale vortex flows, complex ferromagnetic-antiferromagnetic ordering of the snake, and self-propulsion of bead-snake hybrids.

  13. Structure of dioctadecyl L-glutamide-derived lipid self-assembled monolayers on Au(1 1 1) surface

    NASA Astrophysics Data System (ADS)

    Sakurai, Toshihiko; Horikawa, Maki; Chowdhury, Md. Saleh; Takafuji, Makoto; Hachisako, Hiroshi; Kubo, Atsushi; Taniguchi, Isao; Ihara, Hirotaka

    2006-11-01

    An L-glutamic acid-derived lipid with a terminal thiol has been synthesized and its corresponding self-assembled structure on Au(1 1 1) surfaces described. The surface morphology of the lipid self-assembled monolayer (SAM) exhibits nano-order patterning, where the height of the monolayer (approximately 1.5 nm) could be interpreted as due to the monolayer structure estimated from molecular models. The molecular orientation in the monolayer is almost perpendicular to the Au(1 1 1) surface depending on the three-point hydrogen-bonding sites in the molecule.

  14. Molecular and electronic structure of electroactive self-assembled monolayers

    NASA Astrophysics Data System (ADS)

    Méndez De Leo, Lucila P.; de la Llave, Ezequiel; Scherlis, Damián; Williams, Federico J.

    2013-03-01

    Self-assembled monolayers (SAMs) containing electroactive functional groups are excellent model systems for the formation of electronic devices by self-assembly. In particular ferrocene-terminated alkanethiol SAMs have been extensively studied in the past. However, there are still open questions related with their electronic structure including the influence of the ferrocene group in the SAM-induced work function changes of the underlying metal. We have thus carried out a thorough experimental and theoretical investigation in order to determine the molecular and electronic structure of ferrocene-terminated alkanethiol SAMs on Au surfaces. In agreement with previous studies we found that the Fc-containing alkanethiol molecules adsorb forming a thiolate bond with the Au surface with a molecular geometry 30° tilted with respect to the surface normal. Measured surface coverages indicate the formation of a compact monolayer. We found for the first time that the ferrocene group has little influence on the observed work function decrease which is largely determined by the alkanethiol. Furthermore, the ferrocene moiety lies 14 Å above the metal surface covalently bonded to the alkanethiol SAM and its HOMO is located at -1.6 eV below the Fermi level. Our results provide new valuable insight into the molecular and electronic structure of electroactive SAMs which are of fundamental importance in the field of molecular electronics.

  15. Molecular and electronic structure of electroactive self-assembled monolayers.

    PubMed

    Méndez De Leo, Lucila P; de la Llave, Ezequiel; Scherlis, Damián; Williams, Federico J

    2013-03-21

    Self-assembled monolayers (SAMs) containing electroactive functional groups are excellent model systems for the formation of electronic devices by self-assembly. In particular ferrocene-terminated alkanethiol SAMs have been extensively studied in the past. However, there are still open questions related with their electronic structure including the influence of the ferrocene group in the SAM-induced work function changes of the underlying metal. We have thus carried out a thorough experimental and theoretical investigation in order to determine the molecular and electronic structure of ferrocene-terminated alkanethiol SAMs on Au surfaces. In agreement with previous studies we found that the Fc-containing alkanethiol molecules adsorb forming a thiolate bond with the Au surface with a molecular geometry 30° tilted with respect to the surface normal. Measured surface coverages indicate the formation of a compact monolayer. We found for the first time that the ferrocene group has little influence on the observed work function decrease which is largely determined by the alkanethiol. Furthermore, the ferrocene moiety lies 14 Å above the metal surface covalently bonded to the alkanethiol SAM and its HOMO is located at -1.6 eV below the Fermi level. Our results provide new valuable insight into the molecular and electronic structure of electroactive SAMs which are of fundamental importance in the field of molecular electronics.

  16. Self-Assembly of Soft Colloids with Multi-scale Phase-Separated Structures

    NASA Astrophysics Data System (ADS)

    Sosa, Chris; Prud'Homme, Robert K.; Priestley, Rodney D.

    The ability of polymers and block co-polymers to self-assemble into highly-ordered structures in bulk two-dimensional films under specific environmental conditions has allowed in recent years for the fabrication of nano-porous membranes, nano-structured surfaces, and sacrificial templates for the preparation of inorganic nanomaterials with well-defined geometries. Extending these fairly specific fabrication techniques to the creation of similar three-dimensional colloidal structures in bulk solutions, however, has proven quite challenging despite the significant need for heterogeneously-structured colloidal materials in medicine and industry. Here we present a strategy for controlling the structural heterogeneity of soft polymer particles along multiple length scales by inducing the rapid phase-separation of polymer mixtures through a continuous nanoprecipitation process. DOE SCGF Fellowship Program.

  17. Self-Assembly of Soft Colloids with Multi-scale Phase-Separated Structures

    NASA Astrophysics Data System (ADS)

    Sosa, Chris; Prud'Homme, Robert K.; Priestley, Rodney D.

    2015-03-01

    The ability of polymers and block co-polymers to self-assemble into highly-ordered structures in bulk two-dimensional films under specific environmental conditions has allowed in recent years for the fabrication of nano-porous membranes, nano-structured surfaces, and sacrificial templates for the preparation of inorganic nanomaterials with well-defined geometries. Extending these fairly specific fabrication techniques to the creation of similar three-dimensional colloidal structures in bulk solutions, however, has proven quite challenging despite the significant need for heterogeneously-structured colloidal materials in medicine and industry. Here we present a strategy for controlling the structural heterogeneity of soft polymer particles along multiple length scales by inducing the rapid phase-separation of polymer mixtures through a continuous nanoprecipitation process. Supported by the DOE SCGF Fellowship administered under ORAU.

  18. Self-assembled nano-balls released from multistage vector for cancer therapy

    NASA Astrophysics Data System (ADS)

    Qian, Jin; Xia, Xiaojun; Xie, Yan

    2017-03-01

    The efficacy of cancer drugs is often compromised due to the existence of biological barriers such as nonspecific distribution, hemorheological flow limitation and endothelial extravasation, impaired delivery across tumor cell membranes and tissue, and multidrug resistance. To overcome these obstacles, Xu et al developed an injectable nanoparticle generator platform to negotiate with the biological barriers and enable self-assembly of nano-balls in situ in order to maximize drug accumulation inside the tumor tissues and hence the therapeutic efficacy. This perspective aims to elaborate the designing strategy, and discuss the mechanism of action of the new drug and the potential for future development of nanoparticulate drugs.

  19. Toward Single Electron Nanoelectronics Using Self-Assembled DNA Structure.

    PubMed

    Tapio, Kosti; Leppiniemi, Jenni; Shen, Boxuan; Hytönen, Vesa P; Fritzsche, Wolfgang; Toppari, J Jussi

    2016-11-09

    DNA based structures offer an adaptable and robust way to develop customized nanostructures for various purposes in bionanotechnology. One main aim in this field is to develop a DNA nanobreadboard for a controllable attachment of nanoparticles or biomolecules to form specific nanoelectronic devices. Here we conjugate three gold nanoparticles on a defined size TX-tile assembly into a linear pattern to form nanometer scale isolated islands that could be utilized in a room temperature single electron transistor. To demonstrate this, conjugated structures were trapped using dielectrophoresis for current-voltage characterization. After trapping only high resistance behavior was observed. However, after extending the islands by chemical growth of gold, several structures exhibited Coulomb blockade behavior from 4.2 K up to room temperature, which gives a good indication that self-assembled DNA structures could be used for nanoelectronic patterning and single electron devices.

  20. Structural Diversity of Self-Assembled Iridescent Arthropod Biophotonic Nanostructures

    NASA Astrophysics Data System (ADS)

    Saranathan, Vinod Kumar; Prum, Richard O.

    2015-03-01

    Many organisms, especially arthropods, produce vivid interference colors using diverse mesoscopic (100-350 nm) integumentary biophotonic nanostructures that are increasingly being investigated for technological applications. Despite a century of interest, we lack precise structural knowledge of many biophotonic nanostructures and mechanisms controlling their development, when such knowledge can open novel biomimetic routes to facilely self-assemble tunable, multi-functional materials. Here, we use synchrotron small angle X-ray scattering and electron microscopy to characterize the photonic nanostructure of 140 iridescent integumentary scales and setae from 127 species of terrestrial arthropods in 85 genera from 5 orders. We report a rich nanostructural diversity, including triply-periodic bicontinuous networks, close-packed spheres, inverse columnar, perforated lamellar, and disordered sponge-like morphologies, commonly observed as stable phases of amphiphilic surfactants, block copolymer, and lyotropic lipid-water systems. Diverse arthropod lineages appear to have independently evolved to utilize the self-assembly of infolding bilayer membranes to develop biophotonic nanostructures that span the phase-space of amphiphilic morphologies, but at optical length scales.

  1. A simple route for renewable nano-sized arjunolic and asiatic acids and self-assembly of arjuna-bromolactone.

    PubMed

    Bag, Braja G; Dey, Partha P; Dinda, Shaishab K; Sheldrick, William S; Oppel, Iris M

    2008-01-01

    While separating two natural nano-sized triterpenic acids via bromolactonization, we serendipitously discovered that arjuna-bromolactone is an excellent gelator of various organic solvents. A simple and efficient method for the separation of two triterpenic acids and the gelation ability and solid state 1D-helical self-assembly of nano-sized arjuna-bromolactone are reported.

  2. Epitaxial growth of sexi-thiophene and para-hexaphenyl and its implications for the fabrication of self-assembled lasing nano-fibres

    NASA Astrophysics Data System (ADS)

    Simbrunner, Clemens

    2013-05-01

    Over the last few years, epitaxially grown self-assembled organic nano-structures became of increasing interest due to their high potential for implementation within opto-electronic devices. Exemplarily, the epitaxial growth of the rod-like molecules para-hexaphenyl (p-6P) and α-sexi-thiophene (6T) is discussed within this review. Both molecules tend to crystallize in highly asymmetric elongated entities which are also called nano-fibres. It is demonstrated that the obtained needle orientations and morphologies result from a complex interplay between various parameters e.g. substrate surface symmetry, molecular adsorption, crystal structure and contact plane. The interplay and its implications on the fabrication of self-assembled waveguiding nano-fibres and optical resonator structures are discussed and substantiated by a comparison with the reported literature. In further consequence, it is demonstrated that a precise control on the molecular adsorption geometry and the crystal contact plane represents a fundamental key parameter for the fabrication of self-assembled nano-fibres. As both parameters are basically determined by the chosen molecule-substrate material couple, the possible spectrum of molecular building blocks for the fabrication of waveguiding and lasing nano-structures can be predicted by the discussed growth model. A possible expansion of this common valid concept is presented by the utilization of organic-organic heteroepitaxy. Based on the reported p-6P/6T heterostructures which have been fabricated on various substrate surfaces, it is substantiated that the fabrication of organic-organic interfaces can be effectively used to gain control on the molecular adsorption geometry. As the proposed strategy still lacks a precise control of the obtained crystal contact plane, further strategies are discussed which potentially lead to a controlled fabrication of opto-electronic devices based on self-assembled organic nano-structures.

  3. Structural heterogeneities of self-assembled peptide nanomaterials

    NASA Astrophysics Data System (ADS)

    Anthony, Neil R.; Bisignano, Anthony J.; Mehta, Anil K.; Lynn, David G.; Berland, Keith M.

    2012-03-01

    We use Fluorescence Lifetime Imaging Microscopy (FLIM) and Second Harmonic Imaging Microscopy (SHIM) to investigate the fundamental molecular mechanisms responsible for nucleation and growth of amyloidogenic-derived nanomaterials. The nanomaterials are assembled from of Amyloid-β(16-22), specifically Ac-KLVFFAE-NH2, the nucleating core of the Alzheimer's Amyloid-β protein. We describe how FLIM and SHIM can be used to follow different nucleation pathways and to quantify structural heterogeneities within these complex nanomaterials. New evidence suggests that different structures emerge from distinct nucleation pathways and these insights inform our understanding of the peptide self-assembly mechanisms. We discuss these insights in the context of a top down understanding of amyloidogenic diseases, the bottom up control of functional nanomaterials and the discovery of realtime structural indicators for nanofabrication strategies.

  4. A nanoscale bio-inspired light-harvesting system developed from self-assembled alkyl-functionalized metallochlorin nano-aggregates.

    PubMed

    Ocakoglu, Kasim; Joya, Khurram S; Harputlu, Ersan; Tarnowska, Anna; Gryko, Daniel T

    2014-08-21

    Self-assembled supramolecular organization of nano-structured biomimetic light-harvesting modules inside solid-state nano-templates can be exploited to develop excellent light-harvesting materials for artificial photosynthetic devices. We present here a hybrid light-harvesting system mimicking the chlorosomal structures of the natural photosynthetic system using synthetic zinc chlorin units (ZnChl-C6, ZnChl-C12 and ZnChl-C18) that are self-aggregated inside the anodic aluminum oxide (AAO) nano-channel membranes. AAO nano-templates were modified with a TiO2 matrix and functionalized with long hydrophobic chains to facilitate the formation of supramolecular Zn-chlorin aggregates. The transparent Zn-chlorin nano-aggregates inside the alkyl-TiO2 modified AAO nano-channels have a diameter of ∼120 nm in a 60 μm length channel. UV-Vis studies and fluorescence emission spectra further confirm the formation of the supramolecular ZnChl aggregates from monomer molecules inside the alkyl-functionalized nano-channels. Our results prove that the novel and unique method can be used to produce efficient and stable light-harvesting assemblies for effective solar energy capture through transparent and stable nano-channel ceramic materials modified with bio-mimetic molecular self-assembled nano-aggregates.

  5. Thermodynamics and structure of self-assembled networks

    NASA Astrophysics Data System (ADS)

    Zilman, A. G.; Safran, S. A.

    2002-11-01

    We study a generic model of self-assembling chains that can branch and form networks with branching points (junctions) of arbitrary functionality. The physical realizations include physical gels, wormlike micelles, dipolar fluids, and microemulsions. The model maps the partition function of a solution of branched, self-assembling, mutually avoiding clusters onto that of a Heisenberg magnet in the mathematical limit of zero spin components. As for the calculation of thermodynamic properties as well as the scattering structure factor, the mapping rigorously accounts for all possible cluster configurations, except for closed rings. The model is solved in the mean-field approximation. It is found that despite the absence of any specific interaction between the chains, the presence of the junctions induces an effective attraction between the monomers, which in the case of threefold junctions leads to a first-order reentrant phase separation between a dilute phase consisting mainly of single chains, and a dense network, or two network phases. The model is then modified to predict the structural properties at the mean-field level. Independent of the phase separation, we predict a percolation (connectivity) transition at which an infinite network is formed. The percolation transition partially overlaps with the first-order transition, and is a continuous, nonthermodynamic transition that describes a change in the topology of the system. Our treatment that predicts both the thermodynamic phase equilibria as well as the spatial correlations in the system allows us to treat both the phase separation and the percolation threshold within the same framework. The density-density correlation has the usual Ornstein-Zernicke form at low monomer densities. At higher densities, a peak emerges in the structure factor, signifying the onset of medium-range order in the system. Implications of the results for different physical systems are discussed.

  6. Three-Dimensional Structures Self-Assembled from DNA Bricks

    NASA Astrophysics Data System (ADS)

    Ke, Yonggang; Ong, Luvena L.; Shih, William M.; Yin, Peng

    2012-11-01

    We describe a simple and robust method to construct complex three-dimensional (3D) structures by using short synthetic DNA strands that we call “DNA bricks.” In one-step annealing reactions, bricks with hundreds of distinct sequences self-assemble into prescribed 3D shapes. Each 32-nucleotide brick is a modular component; it binds to four local neighbors and can be removed or added independently. Each 8-base pair interaction between bricks defines a voxel with dimensions of 2.5 by 2.5 by 2.7 nanometers, and a master brick collection defines a “molecular canvas” with dimensions of 10 by 10 by 10 voxels. By selecting subsets of bricks from this canvas, we constructed a panel of 102 distinct shapes exhibiting sophisticated surface features, as well as intricate interior cavities and tunnels.

  7. Folding and self-assembly of aromatic and aliphatic urea oligomers: towards connecting structure and function.

    PubMed

    Fischer, Lucile; Guichard, Gilles

    2010-07-21

    Folding and self-assembly of biomacromolecules has inspired the development of discrete, non-natural oligomers that fold and/or self-assemble in a controlled manner. Though aromatic and aliphatic oligoamides remain unmatched for structural diversity and synthetic versatility, oligomers based on amide bond surrogates, such as urea backbones, also demonstrated a propensity for folding and self-assembly. In this Perspective, we review the advances in the design of oligomeric aromatic and aliphatic urea sequences (essentially N,N'-linked) that fold and/or self-assemble. Whenever applicable, the relationship between structure and function will be highlighted.

  8. Self-assembly formation of palm-based esters nano-emulsion: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Abdul Rahman, Mohd. Basyaruddin; Huan, Qiu-Yi; Tejo, Bimo A.; Basri, Mahiran; Salleh, Abu Bakar; Rahman, Raja Noor Zaliha Abdul

    2009-10-01

    Palm-oil esters (POEs) are unsaturated and non-ionic esters that can be prepared by enzymatic synthesis from palm oil. Their nano-emulsion properties possess great potential to act as drug carrier for transdermal drug delivery system. A ratio of 75:5:20 (water/POEs/Span20) was chosen from homogenous region in the phase diagram of our previous experimental work to undergo molecular dynamics simulation. A 15 ns molecular dynamics simulation of nano-emulsion system (water/POEs/Span20) was carried out using OPLS-AA force field. The aggregations of the oil and surfactant molecules are observed throughout the simulation. After 8 ns of simulation, the molecules start to aggregate to form one spherical micelle where the POEs molecules are surrounded by the non-ionic surfactant (Span20) molecules with an average size of 4.2 ± 0.05 nm. The size of the micelle and the ability of palm-based nano-emulsion to self-assemble suggest that this nano-emulsion can potentially use in transdermal drug delivery system.

  9. A nano-scale quantum dot photodetector by self-assembly

    NASA Astrophysics Data System (ADS)

    Hegg, Michael C.; Horning, Matthew P.; Lin, Lih Y.

    2005-11-01

    Modern CMOS transistors will not scale well in the next decade due to leakage currents, sources of variation, and platform requirements. To keep the cost per transistor decreasing, and to realize the feasibility of ultra-high density integrated circuits, low power techniques and efficiency optimization are being explored to counter these problems. Parallel to the development of electronic VLSI, using photons as a means of carrying information has been an appealing approach, due to the high speed and broad bandwidth of light, and the elimination of on-chip parasitic and electro-magnetic interference as its electronic counterpart. This paper focuses on photonic integrated circuits to solve the high-density problem, and presents a design for a nano-scale QD optical transducer (QDOT) that will function as a near-field photodetector and that can easily interface into a self- assembled QD integrated circuit (QDIC). The optical transducer consists of a QD between two metal electrodes. The tunneling current between the metal electrodes is mediated by the QD and can be gated by changing the optical signal intensity impinging on the QD. The device can be fabricated via self-assembly using QDs. In this method, a chemistry linker such as DNA or APTES is covalently bound to pre- defined zones on a substrate. The global location of these zones is defined via electron-beam lithography (EBL). Numerical simulations are discussed and ideal characteristics of the device are presented.

  10. Self-assembly, redox activity, and charge transport of functional surface nano-architectures by molecular design

    NASA Astrophysics Data System (ADS)

    Skomski, Daniel

    Surface-assisted molecular self-assembly is a promising strategy to program the structure and chemical state of atoms and molecules in nano-architectures to achieve a specific function. The experiments described in this thesis demonstrate that the design and programming of basic organic components leads to desired characteristics by self-assembly. The fabrication of uniform single-site metal centers at surfaces, important for high selectivity in next-generation catalysts, was accomplished by coordination to redox non-innocent phenanthroline and tetrazine-based ligands. These examples were the first demonstrating tuning of the metal oxidation state in surface coordination architectures through rational ligand design. The molecular-scale coordination architectures were the first formed from chromium and vanadium, and the first from platinum in a non-porphyrin system. The first mixed valence metal-ligand surface structure was fabricated that attained the same ligand coordination number for all metal sites. A new surface reaction method was demonstrated between an inexpensive sodium chloride reagent and carboxylate ligands. High-temperature, molecular-resolution microscopy and spectroscopy of the ordered metal-organic structures demonstrated thermal stability up to 300 °C, the highest molecular-level thermal stability in organic surface nanostructures yet achieved, making such systems potential candidates for moderate-temperature catalytic reactions. Molecular self-assembly was expanded into organic semiconductor thin films. In a two-component, bi-layered system, hydrogen bonding between carboxylates and carboxylic acid-substituted thiophenes was utilized, yielding the first real-space images of phenyl-thiophene stacking. In a one-component system, multiple donor-acceptor pi-pi contacts between phenyltriazole building blocks accomplished assembly of flat-lying molecules from a surface with molecular-scale precision through more than twenty molecular layers. Sufficient

  11. Self-assembled hierarchically structured organic-inorganic composite systems.

    PubMed

    Tritschler, Ulrich; Cölfen, Helmut

    2016-05-13

    Designing bio-inspired, multifunctional organic-inorganic composite materials is one of the most popular current research objectives. Due to the high complexity of biocomposite structures found in nacre and bone, for example, a one-pot scalable and versatile synthesis approach addressing structural key features of biominerals and affording bio-inspired, multifunctional organic-inorganic composites with advanced physical properties is highly challenging. This article reviews recent progress in synthesizing organic-inorganic composite materials via various self-assembly techniques and in this context highlights a recently developed bio-inspired synthesis concept for the fabrication of hierarchically structured, organic-inorganic composite materials. This one-step self-organization concept based on simultaneous liquid crystal formation of anisotropic inorganic nanoparticles and a functional liquid crystalline polymer turned out to be simple, fast, scalable and versatile, leading to various (multi-)functional composite materials, which exhibit hierarchical structuring over several length scales. Consequently, this synthesis approach is relevant for further progress and scientific breakthrough in the research field of bio-inspired and biomimetic materials.

  12. Lipid self-assembled structures for reactivity control in food.

    PubMed

    Sagalowicz, L; Moccand, C; Davidek, T; Ghanbari, R; Martiel, I; Negrini, R; Mezzenga, R; Leser, M E; Blank, I; Michel, M

    2016-07-28

    Lipid self-assembled structures (SASs) have recently gained considerable interest for their potential applications, especially for sustained nutrient release and protein crystallization. An additional property, which is underexploited, is their ability to control chemical reactions in food products. Here, we concentrate on SASs formed by phospholipids (PLs) and monoglycerides (MGs), those compounds being the most natural surfactants and therefore, the best compatible with food products, in view of providing new functionalities through the formation of SASs. In this work, the phase behaviour of these amphiphiles when mixed with oil and water is described and compared. Subsequently, we address the influence of these structures to the oxidation and Maillard-type reactions. Finally, we show that SASs formed by MGs can strongly increase the yield of key aroma impact compounds generated by Maillard-type reactions when compared with the reaction performed in aqueous precursor solutions. Various SASs are compared. In particular, addition of oil to a reversed bicontinuous structure formed by MG leads to a reversed microemulsion, which, considering its low viscosity, is particularly suitable for food products and act as a very efficient reactor system. The influence of oil and precursors on phase behaviour is discussed and related to the efficiency of the Maillard reactions.This article is part of the themed issue 'Soft interfacial materials: from fundamentals to formulation'. © 2016 The Author(s).

  13. Self-assembly of renewable  nano-sized triterpenoids.

    PubMed

    Bag, Braja Gopal; Majumdar, Rakhi

    2017-02-14

    Studies on plant metabolites have gained renewed interest in recent years because these can serve as renewable chemicals for the development of a sustainable society. Among various plant secondary metabolites, terpenoids constitute the major component and triterpenoids are the 30C subset of it. In recent years, triterpenoids have drawn the attention of scientific community due to many of its potential and realized applications in medicine, drug delivery, thermochromic materials, pollutant capture, catalysis, liquid crystals, etc. In this personal review, we have discussed our computational results carried out on sixty representative naturally occurring triterpenoids demonstrating that all the triterpenoids are renewable functional nano-entities. Study of the self-assembly of several triterpenoids such as betulin, betulinic acid, oleanolic acid, glycyrrhetinic acid and arjunolic acid and their derivatives in different liquids have also been discussed. Moreover, the utilization of the resulting supramolecular architectures such as vesicles, spheres, flowers and fibrillar networks of nano- to micrometer dimensions and gels have also been discussed in the perspective of green, renewable and nanos.

  14. Temperature Triggered Structural Transitions in Surfactant organized Self Assemblies

    NASA Astrophysics Data System (ADS)

    Rose, J. Linet; Balamurugan, S.; Sajeevan, Ajin C.; Sreejith, Lisa

    2011-10-01

    Preparation & characterization of tunable fluids is an emerging area with potential application in many fields. Surfactants self assemble in aqueous solution to give a rich variety of phase structures, the size and shape of which can be tuned by additives like salts, alcohols, amines, aromatics etc or external stimuli such as light, temperature etc. The addition of long chain aliphatic alcohol has significant influence on the surfactant aggregation, as it promotes morphological growth of micelles. The cationic surfactant, Cetyl Trimethyl Ammonium Bromide (CTAB) with nonanol in presence of potassium bromide (KBr) shows thermo tunable viscosity behaviour and optical switching behaviour. The solution is visually observed to transform from a turbid and less viscous phase at low temperature to clear and considerably viscous phase at high temperature. Temperature induced changes in turbidity and viscosity are consistent with the transition from vesicle to worm like micelle. It is also worth emphasizing that the transition is thermo reversible, so that vesicles that are disrupted into micelles upon heating can be reformed upon cooling. The thermo tunable transition from turbid to transparent state and the concomitant changes in viscosity are promising for the use in smart windows, monitoring of tumor growth or in other stimuli based application.

  15. Molecular Structure of a Helical ribbon in a Peptide Self-Assembly

    NASA Astrophysics Data System (ADS)

    Hwang, Wonmuk; Marini, Davide; Kamm, Roger D.; Zhang, Shuguang

    2002-03-01

    We have studied the molecular structure of nanometer scale helical ribbons observed during self-assembly of the peptide KFE8 (amino acid sequence: FKFEFKFE) (NanoLetters (2002, in press)). By analyzing the hydrogen bonding patterns between neighboring peptide backbones, we constructed a number of possible β-sheets. Using all possible combinations of these, we built helical ribbons with dimensions close to those found experimentally and performed molecular dynamics simulations to identify the most stable structure. Solvation effects were implemented by the analytic continuum electrostatics (ACE) model developed by Schaefer and Karplus (J. Phys. Chem. 100, 1578 (1996)). By applying electrostatic double layer theory, we incorporated the effect of pH by scaling the amount of charge on the sidechains. Our results suggest that the helical ribbon is comprised of a double β-sheet where the inner and the outer helices have distinct hydrogen bonding patterns. Our approach has general applicability to the study of helices formed by the self-assembly of β-sheet forming peptides with various amino acid sequences.

  16. Structural transformation of peptide amphiphile self-assembly induced by headgroup charge and size regulation

    NASA Astrophysics Data System (ADS)

    Gao, Changrui; Bedzyk, Michael; Olvera, Monica; Kewalramani, Sumit; Palmer, Liam

    The ability to control the nano and the meso-scale architecture of molecular assemblies is one of the major challenges in nanoscience. Significantly, structural transformations of amphiphilic aggregates induced by variations in environmental conditions have attracted attention due to their biotechnological relevance. Here, we study the assembly in aqueous solution for a modular series of peptide amphiphiles with 3, 2 or 1 lysine groups conjugated to a C16 carbon tail (C16K3, C16K2 and C16K1) . This system design allow us to probe how the equilibrium structure of the self-assembly can be tuned by controlling the coupling between steric (via choice of headgroup: K3, K2, or K1) and electrostatic (via solution pH) interactions. Solution small- and wide-angle X-ray scattering (SAXS/WAXS) and transmission electron microscopy (TEM) studies reveal that depending on pH and number of lysines in the lipid headgroup, amphiphiles can assemble into a range of structures: spherical micelles, bilayer ribbons and vesicles. We also perform detailed phase space mapping of pH-and headgroup size dependency of the structures of assembly over 0.1-100 nm length scales via SAXS/WAXS. The experimental results in conjunction with molecular dynamics (MD) simulations deduce quantitative relations between pH-dependent molecular charges, steric constraints and self-assembly morphologies, which is significant for developing experimental routes to obtain assembly structures with specific nano- and meso-scale features through controlled external stimuli.

  17. Structural simulations of nanomaterials self-assembled from ionic macrocycles.

    SciTech Connect

    van Swol, Frank B.; Medforth, Craig John

    2010-10-01

    Recent research at Sandia has discovered a new class of organic binary ionic solids with tunable optical, electronic, and photochemical properties. These nanomaterials, consisting of a novel class of organic binary ionic solids, are currently being developed at Sandia for applications in batteries, supercapacitors, and solar energy technologies. They are composed of self-assembled oligomeric arrays of very large anions and large cations, but their crucial internal arrangement is thus far unknown. This report describes (a) the development of a relevant model of nonconvex particles decorated with ions interacting through short-ranged Yukawa potentials, and (b) the results of initial Monte Carlo simulations of the self-assembly binary ionic solids.

  18. Self-assembly of aromatic α-amino acids into amyloid inspired nano/micro scaled architects.

    PubMed

    Singh, Prabhjot; Brar, Surinder K; Bajaj, Manish; Narang, Nikesh; Mithu, Venus S; Katare, Om P; Wangoo, Nishima; Sharma, Rohit K

    2017-03-01

    In the pursuit for design of novel bio inspired materials, aromatic α-amino acids (phenylalanine, tyrosine, tryptophan and histidine) have been investigated for the generation of well-ordered self-assembled architects such as fibrils, rods, ribbons and twisted nanosheets in varying solvent systems. These nano/micro scaled architects were thoroughly characterized using FE-SEM, confocal microscopy, optical microscopy, (1)H NMR, FTIR, XRD and TGA. These self-assembled architects were histologically stained with Congo red and thioflavin T dyes for investigation of amyloid morphology which revealed that the deposited state of ordered assemblies exhibit specific characteristic of amyloid deposits. The self-assembly of aromatic amino acids was observed to be driven by non-covalent forces such as π-π stacking, van der Waals and electrostatic interaction.

  19. Effect of self-assembly of fullerene nano-particles on lipid membrane.

    PubMed

    Zhang, Saiqun; Mu, Yuguang; Zhang, John Z H; Xu, Weixin

    2013-01-01

    Carbon nanoparticles can penetrate the cell membrane and cause cytotoxicity. The diffusion feature and translocation free energy of fullerene through lipid membranes is well reported. However, the knowledge on self-assembly of fullerenes and resulting effects on lipid membrane is poorly addressed. In this work, the self-assembly of fullerene nanoparticles and the resulting influence on the dioleoylphosphtidylcholine (DOPC) model membrane were studied by using all-atom molecular dynamics simulations with explicit solvents. Our simulation results confirm that gathered small fullerene cluster can invade lipid membrane. Simulations show two pathways: 1) assembly process is completely finished before penetration; 2) assembly process coincides with penetration. Simulation results also demonstrate that in the membrane interior, fullerene clusters tend to stay at the position which is 1.0 nm away from the membrane center. In addition, the diverse microscopic stacking mode (i.e., equilateral triangle, tetrahedral pentahedral, trigonal bipyramid and octahedron) of these small fullerene clusters are well characterized. Thus our simulations provide a detailed high-resolution characterization of the microscopic structures of the small fullerene clusters. Further, we found the gathered small fullerene clusters have significant adverse disturbances to the local structure of the membrane, but no great influence on the global integrity of the lipid membrane, which suggests the prerequisite of high-content fullerene for cytotoxicity.

  20. Effect of Self-Assembly of Fullerene Nano-Particles on Lipid Membrane

    PubMed Central

    Zhang, Saiqun; Mu, Yuguang; Zhang, John Z. H.; Xu, Weixin

    2013-01-01

    Carbon nanoparticles can penetrate the cell membrane and cause cytotoxicity. The diffusion feature and translocation free energy of fullerene through lipid membranes is well reported. However, the knowledge on self-assembly of fullerenes and resulting effects on lipid membrane is poorly addressed. In this work, the self-assembly of fullerene nanoparticles and the resulting influence on the dioleoylphosphtidylcholine (DOPC) model membrane were studied by using all-atom molecular dynamics simulations with explicit solvents. Our simulation results confirm that gathered small fullerene cluster can invade lipid membrane. Simulations show two pathways: 1) assembly process is completely finished before penetration; 2) assembly process coincides with penetration. Simulation results also demonstrate that in the membrane interior, fullerene clusters tend to stay at the position which is 1.0 nm away from the membrane center. In addition, the diverse microscopic stacking mode (i.e., equilateral triangle, tetrahedral pentahedral, trigonal bipyramid and octahedron) of these small fullerene clusters are well characterized. Thus our simulations provide a detailed high-resolution characterization of the microscopic structures of the small fullerene clusters. Further, we found the gathered small fullerene clusters have significant adverse disturbances to the local structure of the membrane, but no great influence on the global integrity of the lipid membrane, which suggests the prerequisite of high-content fullerene for cytotoxicity. PMID:24204827

  1. A nanoscale bio-inspired light-harvesting system developed from self-assembled alkyl-functionalized metallochlorin nano-aggregates

    NASA Astrophysics Data System (ADS)

    Ocakoglu, Kasim; Joya, Khurram S.; Harputlu, Ersan; Tarnowska, Anna; Gryko, Daniel T.

    2014-07-01

    Self-assembled supramolecular organization of nano-structured biomimetic light-harvesting modules inside solid-state nano-templates can be exploited to develop excellent light-harvesting materials for artificial photosynthetic devices. We present here a hybrid light-harvesting system mimicking the chlorosomal structures of the natural photosynthetic system using synthetic zinc chlorin units (ZnChl-C6, ZnChl-C12 and ZnChl-C18) that are self-aggregated inside the anodic aluminum oxide (AAO) nano-channel membranes. AAO nano-templates were modified with a TiO2 matrix and functionalized with long hydrophobic chains to facilitate the formation of supramolecular Zn-chlorin aggregates. The transparent Zn-chlorin nano-aggregates inside the alkyl-TiO2 modified AAO nano-channels have a diameter of ~120 nm in a 60 μm length channel. UV-Vis studies and fluorescence emission spectra further confirm the formation of the supramolecular ZnChl aggregates from monomer molecules inside the alkyl-functionalized nano-channels. Our results prove that the novel and unique method can be used to produce efficient and stable light-harvesting assemblies for effective solar energy capture through transparent and stable nano-channel ceramic materials modified with bio-mimetic molecular self-assembled nano-aggregates.Self-assembled supramolecular organization of nano-structured biomimetic light-harvesting modules inside solid-state nano-templates can be exploited to develop excellent light-harvesting materials for artificial photosynthetic devices. We present here a hybrid light-harvesting system mimicking the chlorosomal structures of the natural photosynthetic system using synthetic zinc chlorin units (ZnChl-C6, ZnChl-C12 and ZnChl-C18) that are self-aggregated inside the anodic aluminum oxide (AAO) nano-channel membranes. AAO nano-templates were modified with a TiO2 matrix and functionalized with long hydrophobic chains to facilitate the formation of supramolecular Zn-chlorin aggregates. The

  2. Electrophoretic dynamics of self-assembling branched DNA structures

    NASA Astrophysics Data System (ADS)

    Heuer, Daniel Milton

    This study advances our understanding of the electrophoretic dynamics of branched biopolymers and explores technologies designed to exploit their unique properties. New self-assembly techniques were developed to create branched DNA for visualization via fluorescence microscopy. Experiments in fixed gel networks reveal a distinct trapping behavior, in contrast with linear topologies. The finding that detection can be achieved by introducing a branch point contributes significantly to the field of separation science and can be exploited to develop new applications. Results obtained in polymer solutions point to identical mobilities for branched and linear topologies, despite large differences in their dynamics. This finding led to a new description of electrophoresis based on non-Newtonian viscoelastic effects in the electric double layer surrounding a charged object. This new theoretical framework presents a new outlook important not only to the electrophoretic physics of nucleic acids, but all charged objects including proteins, colloids, and nanoparticles. To study the behavior of smaller biopolymers, such as restriction fragments and recombination intermediates, a library of symmetrically branched DNA was synthesized followed by characterization in gels. The experimental results contribute a large body of information relating molecular architecture and the dynamics of rigid structures in an electric field. The findings allow us to create new separation technologies based on topology. These contributions can also be utilized in a number of different applications including the study of recombination intermediates and the separation of proteins according to structure. To demonstrate the importance of these findings, a sequence and mutation detection technique was envisioned and applied for genetic analysis. Restriction fragments from mutation "hotspots" in the p53 tumor suppressor gene, known to play a role in cancer development, were analyzed with this technique

  3. Novel multiferroicity in GdMnO3 thin films with self-assembled nano-twinned domains

    PubMed Central

    Li, Xiang; Lu, Chengliang; Dai, Jiyan; Dong, Shuai; Chen, Yan; Hu, Ni; Wu, Guangheng; Liu, Meifeng; Yan, Zhibo; Liu, Jun-Ming

    2014-01-01

    There have been many interests in exploring multiferroic materials with superior ferroelectric and magnetic properties for the purpose of developing multifunctional devices. Fabrication of thin films plays an important role in achieving this purpose, since the multiferroicity can be tuned via strain, dimensionality, and size effect, without varying the chemical composition. Here, we report exotic multiferroic behaviors, including high-TC (~75 K) ferroelectric state, a large spontaneous polarization (~4900 μC/m2) and relatively strong ferromagnetism emerging at ~105 K, in orthorhombic GdMnO3/SrTiO3 (001) thin films with self-assembled nano-scale twin-like domains. We propose a possible ab-plane spiral-spin-order phase to be responsible for the large spontaneous polarization in the films, which can only be stabilized by relatively high magnetic field H > 6 T in the bulk crystals. It is suggested that the nano-scale twin-like domain structure is essential for the high temperature ferroelectricity and ferromagnetism of the thin films. PMID:25387445

  4. A Novel Self-Assembling DNA Nano Chip for Rapid Detection of Human Papillomavirus Genes

    PubMed Central

    Li, Xin; Li, Yanbo; Hong, Li

    2016-01-01

    Rapid detection of tumor-associated DNA such as Human Papillomavirus (HPV) has important clinical value for the early screening of tumors. By attaching oligonucleotides or cDNA onto the chip surface, DNA chip technology provides a rapid method to analyze gene expression. However, challenges remain regarding increasing probe density and improving detection time. To address these challenges, we proposed a DNA chip that was self-assembled from single stranded DNA in combination with high probe density and a rapid detection method. Over 200 probes could be attached to the surface of this 100-nm diameter DNA chip. For detection, the chips were adsorbed onto a mica surface and then incubated for ten minutes with HPV-DNA; the results were directly observable using atomic force microscopy (AFM). This bottom-up fabricated DNA nano chip combined with high probe density and direct AFM detection at the single molecule level will likely have numerous potential clinical applications for gene screening and the early diagnosis of cancer. PMID:27706184

  5. A Novel Self-Assembling DNA Nano Chip for Rapid Detection of Human Papillomavirus Genes.

    PubMed

    Li, Xin; Li, Yanbo; Hong, Li

    2016-01-01

    Rapid detection of tumor-associated DNA such as Human Papillomavirus (HPV) has important clinical value for the early screening of tumors. By attaching oligonucleotides or cDNA onto the chip surface, DNA chip technology provides a rapid method to analyze gene expression. However, challenges remain regarding increasing probe density and improving detection time. To address these challenges, we proposed a DNA chip that was self-assembled from single stranded DNA in combination with high probe density and a rapid detection method. Over 200 probes could be attached to the surface of this 100-nm diameter DNA chip. For detection, the chips were adsorbed onto a mica surface and then incubated for ten minutes with HPV-DNA; the results were directly observable using atomic force microscopy (AFM). This bottom-up fabricated DNA nano chip combined with high probe density and direct AFM detection at the single molecule level will likely have numerous potential clinical applications for gene screening and the early diagnosis of cancer.

  6. Self-Assembling NanoLuc Luciferase Fragments as Probes for Protein Aggregation in Living Cells.

    PubMed

    Zhao, Jia; Nelson, Travis J; Vu, Quyen; Truong, Tiffany; Stains, Cliff I

    2016-01-15

    Given the clear role of protein aggregation in human disease, there is a critical need for assays capable of quantifying protein aggregation in living systems. We hypothesized that the inherently low background and biocompatibility of luminescence signal readouts could provide a potential solution to this problem. Herein, we describe a set of self-assembling NanoLuc luciferase (Nluc) fragments that produce a tunable luminescence readout that is dependent upon the solubility of a target protein fused to the N-terminal Nluc fragment. To demonstrate this approach, we employed this assay in bacteria to assess mutations known to disrupt amyloid-beta (Aβ) aggregation as well as disease-relevant mutations associated with familial Alzheimer's diseases. The luminescence signal from these experiments correlates with the reported aggregation potential of these Aβ mutants and reinforces the increased aggregation potential of disease-relevant mutations in Aβ1-42. To further demonstrate the utility of this approach, we show that the effect of small molecule inhibitors on Aβ aggregation can be monitored using this system. In addition, we demonstrate that aggregation assays can be ported into mammalian cells. Taken together, these results indicate that this platform could be used to rapidly screen for mutations that influence protein aggregation as well as inhibitors of protein aggregation. This method offers a novel, genetically encodable luminescence readout of protein aggregation in living cells.

  7. X-ray Analysis of Self-assembled Nano-Dielectrics

    NASA Astrophysics Data System (ADS)

    Zeng, Li; Turrisi, Riccardo; Emery, Jonathan; Hersam, Mark; Marks, Tobin; Bedzyk, Michael

    Organic thin-film transistors (OTFTs) are viewed as the new generation thin-film transistors (TFT) for future low-cost, printable, flexible electronics. A class of materials called self-assembled nano-dielectrics (SAND) with phosphoric acid-based-electron (PAE) building blocks sandwiched between ultrathin layers of high- k inorganic oxide materials has been synthesized. These materials show exceptional large capacitance, insulating properties, and are also suitable for ambient atmosphere fabrication. The hybrid nature of these materials combines the distinct properties of both the organic and inorganic components and can be incorporated into the low-operating voltage semiconductor-based OTFT. Despite the great performance and flexibility of SANDs, fundamental aspects of dielectric behavior remain unexplored. Particularly, the behaviors of the Br counteranions that exist within PAE building blocks are poorly understood. Therefore, long-period X-ray Standing Wave (LP-XSW), which is a powerful technique sensitive to heavy atom distributions, was used to characterize SAND deposited on synthetic Si/Mo multilayer substrates. The elemental distributions of Br and reference elements were extracted from the analysis of XSW data. These accurate measurements are important for better understanding of counteranions distributions, charge transportation, dipole-semiconductors interactions, and future device modeling and engineering.

  8. Investigating the Self-assembled Structure of Polycyclic Aromatic Hydrocarbons Using Two Dimensional Infrared Spectroscopy

    NASA Astrophysics Data System (ADS)

    Cyran, Jenee D.; Krummel, Amber T.

    Self-assembly mechanisms are required for many biological and material processes, such as chlorophyll in photosynthesis, the tobacco mosaic virus and in the formation of molecular crystals. The self-assembly process can be favorable in the case of formation of nanoparticles for electronic devices. However, self-assembly processes, such as asphaltene nanoaggregation, can be unwarranted. Studying the structure of self-assembled supramolecules is important to understand how to mimic or inhibit the formation of the nanoaggregates. In this research, we studied the monomer and self-assembled structure of two polycyclic aromatic hydrocarbons (PAHs), lumogen orange and violanthrone-79, using two-dimensional infrared spectroscopy (2D IR). The carbonyl stretching and the ring breathing vibrational modes were used as vibrational probes. For violanthrone-79, a local mode basis and an electrostatic coupling model were applied to three nanoaggregate structures; parallel, antiparallel, and 28 degrees rotation. The experimental and simulated 2D IR spectra are best represented by majority of the antiparallel configuration with some angular distribution. For lumogen orange, vibrational cross peaks appear as the concentration is increased from a monomer to a nanoaggregate. The 2D IR cross peaks indicate vibrational coupling, which relates directly to the nanoaggregate structure. Comparison between the self-assembled structure of lumogen orange and violanthrone-79 can determine the role of side chains in the nanoaggregate structure.

  9. Self-assembly of Gemini Surfactant Molecules and the Properties of Nano-confined Water

    NASA Astrophysics Data System (ADS)

    Mantha, Sriteja

    Gemini surfactants are dimeric surfactants, formed by connecting two single tail surfactants with a linker at or near their headgroups. These surfactants in water have tendency to self-assemble into lyotropic liquid crystalline (LLC) morphologies with percolating water channels, which have potential applications as membranes for selective ion transport, controlled release formulations, media for chemical separation and catalysis. Using molecular dynamics simulations, this thesis investigates self-assembly behavior of gemini surfactants and properties of water confined in their LLCs. Length of the linker is known to significantly effect the self-assembly behavior of gemini surfactants in water. Dicarboxylate gemini surfactants with odd number of carbon atoms in the linker are shown to favor bicontinuous cubic (Gyroid) LLC morphologies over hexagonally(H) packed cylinders. On the other hand, surfactants with even number of carbon atoms favor H morphologies at same water content. This thesis suggests that, differences in LLC phase behavior of odd and even gemini surfactants is due to differences in the headgroup/headgroup repulsion caused by inherent conformational preferences of the surfactants. In the LLCs formed by dicarboxylate gemini surfactants, water molecules are under charged confinement. Structure and dynamic properties of water in these confinements depend on width of the water channel and nature of the counterion. Simulation results reported in this thesis suggest that water dynamics is at least an order of magnitude slower than that in bulk water, and decrease in the size of water channel results in further decrease in the dynamic properties. Counterion effect investigated in this thesis suggests that excluded volume effects play a significant role in the dynamics of confined water. Water molecules in surfactant systems with TMA+ as counterion have access to less volume for mobility than the systems with Na+ and K+ as counterion. At high water content

  10. Synthesis of novel 3D SnO flower-like hierarchical architectures self-assembled by nano-leaves and its photocatalysis

    SciTech Connect

    Cui, Yongkui; Wang, Fengping Iqbal, M. Zubair; Wang, Ziya; Li, Yan; Tu, Jianhai

    2015-10-15

    Highlights: • Novel 3D SnO flowers self-assembled by 2D nano-leaves were synthesized by hydrothermal method. • The SnO nano-leaf is of single crystalline nature. • The band gap of 2.59 eV of as-prepared products was obtained. • The as-synthesized material will be a promising photocatalytic material. - Abstract: In this report, the novel 3D SnO flower-like hierarchical architectures self-assembled by 2D SnO nano-leaves are successfully synthesized via template-free hydrothermal approach under facile conditions. The high-resolution transmission electron microscopy results demonstrate that the 2D nano-leaves structure is of single crystalline nature. The band gap 2.59 eV for prepared product is obtained from UV–vis diffuse reflectance spectrum. The photocatalysis of the as prepared SnO for degrading methyl orange (MO) has been studied. A good photocatalytic activity is obtained and the mechanism is discussed in detail. Results indicate that the SnO nanostructures are the potential candidates for photocatalyst applications.

  11. Effect of secondary structure on the self-assembly of amphiphilic molecules: A multiscale simulation study

    NASA Astrophysics Data System (ADS)

    Mondal, Jagannath; Yethiraj, Arun

    2012-02-01

    The self-assembly of amphiphilic molecules is of interest from a fundamental and practical standpoint. There has been recent interest in a class of molecules made from β-amino acids (which contain an additional backbone carbon atom when compared with natural amino acids). Block copolymers of β-peptides, where one block is hydrophobic and the other is hydrophilic, self-assemble into micelles. In this work, we use computer simulations to provide insight into the effect of secondary structure on the self-assembly of these molecules. Atomistic simulations for the free energy of association of a pair of molecules show that a homochiral hydrophobic block promotes self assembly compared to a heterochiral hydrophobic block, consistent with experiment. Simulations of a coarse-grained model show that these molecules spontaneously form spherical micelles.

  12. First self-assembly study of betulinic acid, a renewable nano-sized, 6-6-6-6-5 pentacyclic monohydroxy triterpenic acid.

    PubMed

    Bag, Braja Gopal; Dash, Shib Shankar

    2011-11-01

    Self-assembly of betulinic acid, a renewable nano-sized 6-6-6-6-5 pentacyclic triterpenic acid studied in twenty two organic liquids and alcohol-water mixtures showed that it self-assembled in all the liquids studied affording strong gels in nineteen organic liquids and also in alcohol-water mixtures. Optical and electron microscopy and atomic force microscopy studies revealed fibrillar networks having fibers of nano- to micro-metre cross sections and micrometre lengths.

  13. Biocompatible self-assembly of nano-materials for Bio-MEMS and insect reconnaissance.

    SciTech Connect

    Brozik, Susan Marie; Cesarano, Joseph, III; Brinker, C. Jeffrey; Dunphy, Darren Robert; Sinclair, Michael B.; Manginell, Monica; Ashley, Carlee E.; Timlin, Jerilyn Ann; Werner-Washburne, Margaret C.; Calvert, Paul Davidson; Hartenberger, Tamara N.; Flemming, Jeb Hunter; Baca, Helen Kennicott

    2003-12-01

    This report summarizes the development of new biocompatible self-assembly procedures enabling the immobilization of genetically engineered cells in a compact, self-sustaining, remotely addressable sensor platform. We used evaporation induced self-assembly (EISA) to immobilize cells within periodic silica nanostructures, characterized by unimodal pore sizes and pore connectivity, that can be patterned using ink-jet printing or photo patterning. We constructed cell lines for the expression of fluorescent proteins and induced reporter protein expression in immobilized cells. We investigated the role of the abiotic/biotic interface during cell-mediated self-assembly of synthetic materials.

  14. Synthesis, construction, and evaluation of self-assembled nano-bacitracin A as an efficient antibacterial agent in vitro and in vivo.

    PubMed

    Hong, Wei; Gao, Xiang; Qiu, Peng; Yang, Jie; Qiao, Mingxi; Shi, Hong; Zhang, Dexian; Tian, Chunlian; Niu, Shengli; Liu, Mingchun

    2017-01-01

    Bacitracin A (BA) is an excellent polypeptide antibiotic that is active against gram-positive bacteria without triggering multidrug resistance. However, BA is inactive against gram-negative bacteria because of its inability to cross the outer membrane of these cells, and it has strong nephrotoxicity, thus limiting its clinical applications. Nanoantibiotics can effectively localize antibiotics to the periplasmic space of bacteria while decreasing the adverse effects of antibiotics. In this study, biodegradable hydrophobic copolymers of poly (d,l-lactide-co-glycolide) (PLGA) were attached to the N-termini of BA to design a novel class of self-assembled nano-bacitracin A (nano-BAs), and their potential as antibacterial agents was evaluated in vitro and in vivo. Nano-BAs had a core-shell structure with a mean diameter <150 nm. Impressively, nano-BAs had strong antibacterial properties against both gram-positive and gram-negative bacteria, and the distribution of antibacterial activity as a function of PLGA block length was skewed toward longer PLGA chains. No cytotoxicity against HK-2 cells or human red blood cells (hRBCs) was observed in vitro, suggesting good biocompatibility. A high local density of BA mass on the surface promoted endocytotic cellular uptake, and hydrophobic interactions between the PLGA block and lipopolysaccharide (LPS) facilitated the uptake of nano-BAs, thereby leading to greater antibacterial activities. In addition, Nano-BA5K was found to be effective in vivo, and it served as an anti-infective agent for wound healing. Collectively, this study provides a cost-effective means of developing self-assembling nano-polypeptide antibiotic candidates with a broader antibacterial spectrum and a lower toxicity than commercially available peptide antibiotics, owing to their modification with biodegradable copolymers.

  15. Synthesis, construction, and evaluation of self-assembled nano-bacitracin A as an efficient antibacterial agent in vitro and in vivo

    PubMed Central

    Hong, Wei; Gao, Xiang; Qiu, Peng; Yang, Jie; Qiao, Mingxi; Shi, Hong; Zhang, Dexian; Tian, Chunlian; Niu, Shengli; Liu, Mingchun

    2017-01-01

    Bacitracin A (BA) is an excellent polypeptide antibiotic that is active against gram-positive bacteria without triggering multidrug resistance. However, BA is inactive against gram-negative bacteria because of its inability to cross the outer membrane of these cells, and it has strong nephrotoxicity, thus limiting its clinical applications. Nanoantibiotics can effectively localize antibiotics to the periplasmic space of bacteria while decreasing the adverse effects of antibiotics. In this study, biodegradable hydrophobic copolymers of poly (d,l-lactide-co-glycolide) (PLGA) were attached to the N-termini of BA to design a novel class of self-assembled nano-bacitracin A (nano-BAs), and their potential as antibacterial agents was evaluated in vitro and in vivo. Nano-BAs had a core-shell structure with a mean diameter <150 nm. Impressively, nano-BAs had strong antibacterial properties against both gram-positive and gram-negative bacteria, and the distribution of antibacterial activity as a function of PLGA block length was skewed toward longer PLGA chains. No cytotoxicity against HK-2 cells or human red blood cells (hRBCs) was observed in vitro, suggesting good biocompatibility. A high local density of BA mass on the surface promoted endocytotic cellular uptake, and hydrophobic interactions between the PLGA block and lipopolysaccharide (LPS) facilitated the uptake of nano-BAs, thereby leading to greater antibacterial activities. In addition, Nano-BA5K was found to be effective in vivo, and it served as an anti-infective agent for wound healing. Collectively, this study provides a cost-effective means of developing self-assembling nano-polypeptide antibiotic candidates with a broader antibacterial spectrum and a lower toxicity than commercially available peptide antibiotics, owing to their modification with biodegradable copolymers. PMID:28721045

  16. Synthesis and characterization of DNA fenced, self-assembled SnO2 nano-assemblies for supercapacitor applications.

    PubMed

    Nithiyanantham, U; Ramadoss, Ananthakumar; Kundu, Subrata

    2016-02-28

    Self-assembled, aggregated, chain-like SnO2 nano-assemblies were synthesized at room temperature by a simple wet chemical route within an hour in the presence of DNA as a scaffold. The average size of the SnO2 particles and the chain diameter were controlled by tuning the DNA to Sn(ii) molar ratio and altering the other reaction parameters. A formation and growth mechanism of the SnO2 NPs on DNA is discussed. The SnO2 chain-like assemblies were utilized as potential anode materials in an electrochemical supercapacitor. From the supercapacitor study, it was found that the SnO2 nanomaterials showed different specific capacitance (Cs) values depending on varying chain-like morphologies and the order of Cs values was: chain-like (small size) > chain-like (large size). The highest Cs of 209 F g(-1) at a scan rate of 5 mV s(-1) was observed for SnO2 nano-assemblies having chain-like structure with a smaller size. The long term cycling stability study of a chain-like SnO2 electrode was found to be stable and retained ca. 71% of the initial specific capacitance, even after 5000 cycles. A supercapacitor study revealed that both morphologies can be used as a potential anode material and the best efficiency was observed for small sized chain-like morphology which is due to their higher BET surface area and specific structural orientation. The proposed route, by virtue of its simplicity and being environmentally benign, might become a future promising candidate for further processing, assembly, and practical application of other oxide based nanostructure materials.

  17. Systematic Study on the Self-Assembled Hexagonal Au Voids, Nano-Clusters and Nanoparticles on GaN (0001)

    PubMed Central

    Pandey, Puran; Sui, Mao; Li, Ming-Yu; Zhang, Quanzhen; Kim, Eun-Soo; Lee, Jihoon

    2015-01-01

    Au nano-clusters and nanoparticles (NPs) have been widely utilized in various electronic, optoelectronic, and bio-medical applications due to their great potentials. The size, density and configuration of Au NPs play a vital role in the performance of these devices. In this paper, we present a systematic study on the self-assembled hexagonal Au voids, nano-clusters and NPs fabricated on GaN (0001) by the variation of annealing temperature and deposition amount. At relatively low annealing temperatures between 400 and 600°C, the fabrication of hexagonal shaped Au voids and Au nano-clusters are observed and discussed based on the diffusion limited aggregation model. The size and density of voids and nano-clusters can systematically be controlled. The self-assembled Au NPs are fabricated at comparatively high temperatures from 650 to 800°C based on the Volmer-Weber growth model and also the size and density can be tuned accordingly. The results are symmetrically analyzed and discussed in conjunction with the diffusion theory and thermodynamics by utilizing AFM and SEM images, EDS maps and spectra, FFT power spectra, cross-sectional line-profiles and size and density plots. PMID:26285135

  18. Systematic Study on the Self-Assembled Hexagonal Au Voids, Nano-Clusters and Nanoparticles on GaN (0001).

    PubMed

    Pandey, Puran; Sui, Mao; Li, Ming-Yu; Zhang, Quanzhen; Kim, Eun-Soo; Lee, Jihoon

    2015-01-01

    Au nano-clusters and nanoparticles (NPs) have been widely utilized in various electronic, optoelectronic, and bio-medical applications due to their great potentials. The size, density and configuration of Au NPs play a vital role in the performance of these devices. In this paper, we present a systematic study on the self-assembled hexagonal Au voids, nano-clusters and NPs fabricated on GaN (0001) by the variation of annealing temperature and deposition amount. At relatively low annealing temperatures between 400 and 600°C, the fabrication of hexagonal shaped Au voids and Au nano-clusters are observed and discussed based on the diffusion limited aggregation model. The size and density of voids and nano-clusters can systematically be controlled. The self-assembled Au NPs are fabricated at comparatively high temperatures from 650 to 800°C based on the Volmer-Weber growth model and also the size and density can be tuned accordingly. The results are symmetrically analyzed and discussed in conjunction with the diffusion theory and thermodynamics by utilizing AFM and SEM images, EDS maps and spectra, FFT power spectra, cross-sectional line-profiles and size and density plots.

  19. Self-assembly and structural relaxation in a model ionomer melt

    SciTech Connect

    Goswami, Monojoy; Borreguero, Jose M.; Sumpter, Bobby G.

    2015-02-26

    Molecular dynamics simulations are used to understand the self-assembly and structural relaxation in ionomer melts containing less than 10% degree of ionization on the backbone. We study the self-assembly of charged sites and counterions that show structural ordering and agglomeration with a range of structures that can be achieved by changing the dielectric constant of the medium. The intermediate scattering function shows a decoupling of charge and counterion relaxation at longer length scales for only high dielectric constant and at shorter length scales for all dielectric constants. Finally, the slow structural decay of counterions in the strongly correlated ionomer system closely resembles transport properties of semi-flexible polymers.

  20. Mathematical Models, Analytical Solutions and Numerical Simulations of Self-Assembled Magnetic Colloidal Structures

    NASA Astrophysics Data System (ADS)

    Piet, David L.

    Ferromagnetic microparticles suspended at the interface between immiscible liquids and energized by an external alternating magnetic field show a rich variety of self-assembled structures, from linear snakes to radial asters, elongated wires to spinning chains to less dense clouds of particles called snails. In order to obtain insight into the fundamental physical mechanisms and the overall balance of forces governing self-assembly, we develop a modeling approach based on analytical solutions of the time-averaged Navier-Stokes equations. These analytical expressions for the self-consistent hydrodynamic flows are then employed to modify effective interactions between the particles, which in turn are formulated in terms of the time-averaged quantities. Our method allows effective computational verification of the mechanisms of self-assembly and leads to a testable predictions on the transitions between various self-assembled patterns. In one set of experiments, it was observed that viscosity is the primary driving force that determines whether asters or snakes appear at steady state. In the second set of experiments where hydrodynamics are less critical, the amplitude and frequency of the applied magnetic field determine whether wires, spinners or snails will appear. The ability to better understand what drives self-assembly and how to control which dynamic structures appear is necessary for further development of such structures and their applications.

  1. Hierarchical self-assembly of colloidal magnetic particles into reconfigurable spherical structures.

    PubMed

    Morphew, Daniel; Chakrabarti, Dwaipayan

    2015-05-14

    Colloidal self-assembly has enormous potential as a bottom-up means of structure fabrication. Here we demonstrate hierarchical self-assembly of rationally designed charge-stabilised colloidal magnetic particles into ground state structures that are topologically equivalent to a snub cube and a snub dodecahedron, the only two chiral Archimedean solids, for size-selected clusters. These spherical structures open up in response to an external magnetic field and demonstrate controllable porosity. Such features are critical to their applications as functional materials.

  2. Hierarchical self-assembly of colloidal magnetic particles into reconfigurable spherical structures

    NASA Astrophysics Data System (ADS)

    Morphew, Daniel; Chakrabarti, Dwaipayan

    2015-04-01

    Colloidal self-assembly has enormous potential as a bottom-up means of structure fabrication. Here we demonstrate hierarchical self-assembly of rationally designed charge-stabilised colloidal magnetic particles into ground state structures that are topologically equivalent to a snub cube and a snub dodecahedron, the only two chiral Archimedean solids, for size-selected clusters. These spherical structures open up in response to an external magnetic field and demonstrate controllable porosity. Such features are critical to their applications as functional materials.

  3. Crystal-Structure-Guided Design of Self-Assembling RNA Nanotriangles.

    PubMed

    Boerneke, Mark A; Dibrov, Sergey M; Hermann, Thomas

    2016-03-14

    RNA nanotechnology uses RNA structural motifs to build nanosized architectures that assemble through selective base-pair interactions. Herein, we report the crystal-structure-guided design of highly stable RNA nanotriangles that self-assemble cooperatively from short oligonucleotides. The crystal structure of an 81 nucleotide nanotriangle determined at 2.6 Å resolution reveals the so-far smallest circularly closed nanoobject made entirely of double-stranded RNA. The assembly of the nanotriangle architecture involved RNA corner motifs that were derived from ligand-responsive RNA switches, which offer the opportunity to control self-assembly and dissociation.

  4. Designed post-self-assembly structural and functional modifications of a truncated tetrahedron.

    PubMed

    Zheng, Yao-Rong; Lan, Wen-Jie; Wang, Ming; Cook, Timothy R; Stang, Peter J

    2011-10-26

    Post-self-assembly modifications of a discrete metal-organic supramolecular structure have been developed. Such modifications allow the properties of the self-assembled supramolecular species to be changed in a simple and efficient manner (>90% yield). Initiated by the application of chemical stimuli, the post-self-assembly modifications described herein result in three distinct changes to the supramolecular system: an individual building-block component change, an overall structural modification, and a functional evolution of a [6+4] metal-organic supramolecular structure. The three modifications have been carefully examined by a range of characterization methods, including NMR and UV-vis spectroscopy, electrospray ionization mass spectrometry, pulsed field gradient spin echo NMR measurements, electrochemical analysis, and computational simulations.

  5. Enzyme-mediated self-assembly of highly ordered structures from disordered proteins

    NASA Astrophysics Data System (ADS)

    Athamneh, Ahmad I.; Barone, Justin R.

    2009-10-01

    Wheat gluten is an amorphous storage protein. Trypsin hydrolysis of wheat gluten produced glutamine-rich peptides. Some peptides were able to self-assemble into fibrous structures extrinsic to native wheat gluten. The final material was an in situ formed peptide composite of highly ordered nanometer-sized fibrils and micron-sized fibers embedded in an unassembled peptide matrix. Fourier transform infrared spectroscopic and x-ray diffraction data suggested that the new structures resembled that of cross- β fibrils found in some insect silk and implicated in prion diseases. The largest self-assembled fibers were about 10 µm in diameter with right-handed helicity and appeared to be bundles of smaller nanometer-sized fibrils. Results demonstrated the potential for utilizing natural mechanisms of protein self-assembly to design advanced materials that can provide a wide range of structural and chemical functionality.

  6. Self-assembly of polystyrene nanospheres and its applications as templates for plasmonic structures

    NASA Astrophysics Data System (ADS)

    Chang, Shih-Hsin

    Monodispersed colloidal polystyrene spheres have been self-assembled into various structures as templates for the fabrication of different nanostructures. Two unique self-assembly processes have been developed and systematically investigated. A method to make the multi-layer and mono-layer close-packed structure by means of capillary-convective force has been developed. By directly visualizing the self-assembling process using optical microscopy, a mechanism based on the 2-D crystal formation and 3-D repulsive force model has been proposed to explain the process. A vertical deposition technique to produce nanosphere crystal structure with single orientation on hydrophilic glass substrate has also been developed. Using a lithographically patterned substrate with alternating areas of glass and Au, self-assembled crystal structures can be generated on the hydrophobic Au surface. It has been found that the contact angle of the colloid solution on the substrates controls this self-assembly process. Using self-assembled polystyrene nanosphere crystals as templates, Au nanovoid arrays, in which the voids about several hundreds of nanometer in diameter are embedded in a gold film with a thickness less than the void diameter, have been fabricated by templated electrodeposition. In order to use Au nanovoid arrays as surface enhanced Raman scattering (SERS) sensors on optical fiber tips for in situ and in vivo applications, a new structure has been designed. In such structure, each void has optical openings on both sides of the nanovoid array, one side is mounted to the fiber tip surface for introduction of incident light and collection of scattered light and the other side is for interrogation of analyte molecules in the voids. The effect of structural parameters, including void diameter, Au film thickness, and the bottom hole diameter of the nanovoid arrays on the electric field confinement are investigated using three-dimensional finite difference time domain (FDTD

  7. Effect of Topological Structures on the Self-Assembly Behavior of Supramolecular Amphiphiles.

    PubMed

    Wang, Juan; Wang, Xing; Yang, Fei; Shen, Hong; You, Yezi; Wu, Decheng

    2015-12-29

    Three types of azobenzene-based telechelic guest polymers, PEG-azo, azo-PEG-azo, and PEG-azo4, were synthesized by a facile method. Subsequently, a series supramolecular amphiphiles with three distinct topological structures (hemitelechelic, ditelechelic, and quadritelechelic) were constructed through coupling with host polymer β-cyclodextrin-poly(l-lactide) (β-CD-PLLA) by combined host-guest complexation. Research on the self-assembly behavior of these amphiphiles demonstrated that the variation in self-assembly was tuned by the synergistic interaction of hydrophilicity and the curvature of the polymer chains, and very importantly, the topological structure of amphiphiles demonstrated effective control of the self-assembly behavior.

  8. Polymerization-Induced Self-Assembly of Block Copolymer Nano-objects via RAFT Aqueous Dispersion Polymerization

    PubMed Central

    2014-01-01

    In this Perspective, we discuss the recent development of polymerization-induced self-assembly mediated by reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization. This approach has quickly become a powerful and versatile technique for the synthesis of a wide range of bespoke organic diblock copolymer nano-objects of controllable size, morphology, and surface functionality. Given its potential scalability, such environmentally-friendly formulations are expected to offer many potential applications, such as novel Pickering emulsifiers, efficient microencapsulation vehicles, and sterilizable thermo-responsive hydrogels for the cost-effective long-term storage of mammalian cells. PMID:24968281

  9. Biomimetic Branched Hollow Fibers Templated by Self-assembled Fibrous Polyvinylpyrrolidone (PVP) Structures in Aqueous Solution

    PubMed Central

    Qiu, Penghe; Mao, Chuanbin

    2010-01-01

    Branched hollow fibers are common in nature, but to form artificial fibers with a similar branched hollow structure is still a challenge. We discovered that polyvinylpyrrolidone (PVP) could self-assemble into branched hollow fibers in an aqueous solution after aging the PVP solution for about two weeks. Based on this finding, we demonstrated two approaches by which the self-assembly of PVP into branched hollow fibers could be exploited to template the formation of branched hollow inorganic fibers. First, inorganic material such as silica with high affinity against the PVP could be deposited on the surface of the branched hollow PVP fibers to form branched hollow silica fibers. To extend the application of PVP self-assembly in templating the formation of hollow branched fibers, we then adopted a second approach where the PVP molecules bound to inorganic nanoparticles (using gold nanoparticles as a model) co-self-assemble with the free PVP molecules in an aqueous solution, resulting in the formation of the branched hollow fibers with the nanoparticles embedded in the PVP matrix constituting the walls of the fibers. Heating the resultant fibers above the glass transition temperature of PVP led to the formation of branched hollow gold fibers. Our work suggests that the self-assembly of the PVP molecules in the solution can serve as a general method for directing the formation of branched hollow inorganic fibers. The branched hollow fibers may find potential applications in microfluidics, artificial blood vessel generation, and tissue engineering. PMID:20158250

  10. Biomimetic branched hollow fibers templated by self-assembled fibrous polyvinylpyrrolidone structures in aqueous solution.

    PubMed

    Qiu, Penghe; Mao, Chuanbin

    2010-03-23

    Branched hollow fibers are common in nature, but to form artificial fibers with a similar branched hollow structure is still a challenge. We discovered that polyvinylpyrrolidone (PVP) could self-assemble into branched hollow fibers in an aqueous solution after aging the PVP solution for about two weeks. On the basis of this finding, we demonstrated two approaches by which the self-assembly of PVP into branched hollow fibers could be exploited to template the formation of branched hollow inorganic fibers. First, inorganic material such as silica with high affinity against the PVP could be deposited on the surface of the branched hollow PVP fibers to form branched hollow silica fibers. To extend the application of PVP self-assembly in templating the formation of hollow branched fibers, we then adopted a second approach where the PVP molecules bound to inorganic nanoparticles (using gold nanoparticles as a model) co-self-assemble with the free PVP molecules in an aqueous solution, resulting in the formation of the branched hollow fibers with the nanoparticles embedded in the PVP matrix constituting the walls of the fibers. Heating the resultant fibers above the glass transition temperature of PVP led to the formation of branched hollow gold fibers. Our work suggests that the self-assembly of the PVP molecules in the solution can serve as a general method for directing the formation of branched hollow inorganic fibers. The branched hollow fibers may find potential applications in microfluidics, artificial blood vessel generation, and tissue engineering.

  11. Polarization switching and patterning in self-assembled peptide tubular structures

    NASA Astrophysics Data System (ADS)

    Bdikin, Igor; Bystrov, Vladimir; Delgadillo, Ivonne; Gracio, José; Kopyl, Svitlana; Wojtas, Maciej; Mishina, Elena; Sigov, Alexander; Kholkin, Andrei L.

    2012-04-01

    Self-assembled peptide nanotubes are unique nanoscale objects that have great potential for a multitude of applications, including biosensors, nanotemplates, tissue engineering, biosurfactants, etc. The discovery of strong piezoactivity and polar properties in aromatic dipeptides [A. Kholkin, N. Amdursky, I. Bdikin, E. Gazit, and G. Rosenman, ACS Nano 4, 610 (2010)] opened up a new perspective for their use as biocompatible nanoactuators, nanomotors, and molecular machines. Another, as yet unexplored functional property is the ability to switch polarization and create artificial polarization patterns useful in various electronic and optical applications. In this work, we demonstrate that diphenylalanine peptide nanotubes are indeed electrically switchable if annealed at a temperature of about 150 °C. The new orthorhombic antipolar structure that appears after annealing allows for the existence of a radial polarization component, which is directly probed by piezoresponse force microscopy (PFM) measurements. Observation of the relatively stable polarization patterns and hysteresis loops via PFM testifies to the local reorientation of molecular dipoles in the radial direction. The experimental results are complemented with rigorous molecular calculations and create a solid background of electric-field induced deformation of aromatic rings and corresponding polarization switching in this emergent material.

  12. The structural parameters of self-assembled quantum dots determined from the optical spectra

    NASA Astrophysics Data System (ADS)

    Hong, Boon Hon; Tinkler, Lloyd; Beaumont, Matthew; Rybchenko, Sergey I.; Itskevich, Igor E.; Haywood, Stephanie K.; Hugues, Maxime

    2013-12-01

    Structural parameters of InGaAs/GaAs self-assembled quantum dots (SAQDs), which were grown using In-flush technique, were deduced using optical spectroscopy combined with computer modeling. The results are in excellent agreement with the experimental data obtained from transmission electron microscopy. The developed approach suggests a promising alternative to structural characterization methods for SAQDs.

  13. The structural parameters of self-assembled quantum dots determined from the optical spectra

    SciTech Connect

    Hong, Boon Hon; Beaumont, Matthew; Rybchenko, Sergey I.; Itskevich, Igor E.; Haywood, Stephanie K.; Tinkler, Lloyd; Hugues, Maxime

    2013-12-04

    Structural parameters of InGaAs/GaAs self-assembled quantum dots (SAQDs), which were grown using In-flush technique, were deduced using optical spectroscopy combined with computer modeling. The results are in excellent agreement with the experimental data obtained from transmission electron microscopy. The developed approach suggests a promising alternative to structural characterization methods for SAQDs.

  14. Self-assembly and dynamics of oxide nano-rods on NiAl(110).

    SciTech Connect

    Pierce, John P.; McCarty, Kevin F.

    2004-10-01

    We observe the spontaneous formation of parallel oxide rods upon exposing a clean NiAl(110) surface to oxygen at elevated temperatures (850-1350 K). By following the self-assembly of individual nanorods in real time with low-energy electron microscopy (LEEM), we are able to investigate the processes by which the rods lengthen along their axes and thicken normal to the surface of the substrate. At a fixed temperature and O{sub 2} pressure, the rods lengthen along their axes at a constant rate. The exponential temperature dependence of this rate yields an activation energy for growth of 1.2 {+-} 0.1 eV. The rod growth rates do not change as their ends pass in close proximity (<40 nm) to each other, which suggests that they do not compete for diffusing flux in order to elongate. Both LEEM and scanning tunneling microscopy (STM) studies show that the rods can grow vertically in layer-by-layer fashion. The heights of the rods are extremely bias dependent in STM images, but occur in integer multiples of approximately 2-{angstrom}-thick oxygen-cation layers. As the rods elongate from one substrate terrace to the next, we commonly see sharp changes in their rates of elongation that result from their tendency to gain (lose) atomic layers as they descend (climb) substrate steps. Diffraction analysis and dark-field imaging with LEEM indicate that the rods are crystalline, with a lattice constant that is well matched to that of the substrate along their length. We discuss the factors that lead to the formation of these highly anisotropic structures.

  15. Self-assembled nano- to micron-size fibers from molten R11Ni4In9 intermetallics

    SciTech Connect

    Provino, Alessia; Manfrinetti, Pietro; Gschneidner, Karl A; Dhar, Sudesh K; Schlagel, Deborah L; Lograsso, Thomas A; Miller, Gordon J; Thimmaiah, Srinivasa; Wang, Hui; Russell, Alan M; Becker, Andrew; Mudryk, Yaroslav

    2014-07-01

    A study of the formation of Gd11M4In9 (M = Ni, Pd, Pt) and R11Ni4In9 (R = rare earth) compounds revealed a unique and peculiar property, which is to naturally crystallize in a bundle of self-assembled fibers when cooled from the melt. The fibers, which are nano- to millimeters in cross-section and approximate to 11-40 mm long, grow unidirectionally along a temperature gradient. These compounds adopt the orthorhombic Nd11Pd4In9 structure type (oC48-Cmmm). This structure is layered, with slabs of R atoms alternating with slabs of Ni/In atoms along a short c-axis (much shorter than either the a- or b-axis). The growth direction of the fibers is along the crystallographic c-axis, orthogonal to the a-b plane. Two strong and short In In bonds lie in the a-b plane, which are even shorter than in In metal. Integrated crystal orbital Hamilton population calculations show that the In In bonds create isolated "R8Ni4In9" rods growing along the c-axis, with the In In bonds being part of the rods. This appears to be an important factor explaining the microfibrous nature of these phases. Some physical properties have been measured on the Gd11Ni4In9 homolog. The compound orders ferrimagnetically at T-c approximate to 88 K, and at lower temperatures (46 and 10 K), two other magnetic anomalies were observed, probably due to spin reorientations. As expected from the bonding features, the mechanical, magnetic and electrical properties are strongly anisotropic. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  16. Hydrophobic pharmaceuticals mediated self-assembly of β-cyclodextrin containing hydrophilic copolymers: Novel chemical responsive nano-vehicles for drug delivery

    PubMed Central

    Zhang, Jianxiang; Ellsworth, Kristin; Ma, Peter X

    2010-01-01

    Double hydrophilic copolymers with one polyethylene glycol (PEG) block and one β-cyclodextrin β-CD) flanking block (PEG-b-PCDs) were synthesized through the post-modification of macromolecules. The self-assembly of PEG-b-PCDs in aqueous solutions was initially studied by a fluorescence technique. This measurement together with AFM and TEM characterization demonstrated the formation of nanoparticles in the presence of lipophilic small molecules. The host-guest interaction between the β-CD unit of a host copolymer and the hydrophobic group of a guest molecule was found to be the driving force for the observed self-assembly. This spontaneous assembly upon loading of guest molecules was also observed for hydrophobic drugs with various chemical structures. Relatively high drug loading was achieved by this approach. Desirable encapsulation was also achieved for the hydrophobic drugs that cannot efficiently interact with free β-CD. In vitro release studies suggested that the payload in nano-assemblies could be released in a sustained manner. In addition, both the fluorescence measurement and the in vitro drug release studies suggested that these nano-assemblies mediated by the inclusion complexation exhibited a chemical sensitivity. The release of payload can be accelerated upon the triggering by hydrophobic guest molecules or free β-CD molecules. These results support the potential applications of the synthesized copolymers for the delivery of hydrophobic drugs. PMID:20417674

  17. Self-assembly of nanocomponents into composite structures: derivation and simulation of Langevin equations.

    PubMed

    Pankavich, S; Shreif, Z; Miao, Y; Ortoleva, P

    2009-05-21

    The kinetics of the self-assembly of nanocomponents into a virus, nanocapsule, or other composite structure is analyzed via a multiscale approach. The objective is to achieve predictability and to preserve key atomic-scale features that underlie the formation and stability of the composite structures. We start with an all-atom description, the Liouville equation, and the order parameters characterizing nanoscale features of the system. An equation of Smoluchowski type for the stochastic dynamics of the order parameters is derived from the Liouville equation via a multiscale perturbation technique. The self-assembly of composite structures from nanocomponents with internal atomic structure is analyzed and growth rates are derived. Applications include the assembly of a viral capsid from capsomers, a ribosome from its major subunits, and composite materials from fibers and nanoparticles. Our approach overcomes errors in other coarse-graining methods, which neglect the influence of the nanoscale configuration on the atomistic fluctuations. We account for the effect of order parameters on the statistics of the atomistic fluctuations, which contribute to the entropic and average forces driving order parameter evolution. This approach enables an efficient algorithm for computer simulation of self-assembly, whereas other methods severely limit the timestep due to the separation of diffusional and complexing characteristic times. Given that our approach does not require recalibration with each new application, it provides a way to estimate assembly rates and thereby facilitate the discovery of self-assembly pathways and kinetic dead-end structures.

  18. Self-assembly of nanocomponents into composite structures: Derivation and simulation of Langevin equations

    NASA Astrophysics Data System (ADS)

    Pankavich, S.; Shreif, Z.; Miao, Y.; Ortoleva, P.

    2009-05-01

    The kinetics of the self-assembly of nanocomponents into a virus, nanocapsule, or other composite structure is analyzed via a multiscale approach. The objective is to achieve predictability and to preserve key atomic-scale features that underlie the formation and stability of the composite structures. We start with an all-atom description, the Liouville equation, and the order parameters characterizing nanoscale features of the system. An equation of Smoluchowski type for the stochastic dynamics of the order parameters is derived from the Liouville equation via a multiscale perturbation technique. The self-assembly of composite structures from nanocomponents with internal atomic structure is analyzed and growth rates are derived. Applications include the assembly of a viral capsid from capsomers, a ribosome from its major subunits, and composite materials from fibers and nanoparticles. Our approach overcomes errors in other coarse-graining methods, which neglect the influence of the nanoscale configuration on the atomistic fluctuations. We account for the effect of order parameters on the statistics of the atomistic fluctuations, which contribute to the entropic and average forces driving order parameter evolution. This approach enables an efficient algorithm for computer simulation of self-assembly, whereas other methods severely limit the timestep due to the separation of diffusional and complexing characteristic times. Given that our approach does not require recalibration with each new application, it provides a way to estimate assembly rates and thereby facilitate the discovery of self-assembly pathways and kinetic dead-end structures.

  19. Thermal dewetting with a chemically heterogeneous nano-template for self-assembled L10 FePt nanoparticle arrays

    NASA Astrophysics Data System (ADS)

    Wang, Liang-Wei; Cheng, Chung-Fu; Liao, Jung-Wei; Wang, Chiu-Yen; Wang, Ding-Shuo; Huang, Kuo-Feng; Lin, Tzu-Ying; Ho, Rong-Ming; Chen, Lih-Juann; Lai, Chih-Huang

    2016-02-01

    A design for the fabrication of metallic nanoparticles is presented by thermal dewetting with a chemically heterogeneous nano-template. For the template, we fabricate a nanostructured polystyrene-b-polydimethylsiloxane (PS-b-PDMS) film on a Si|SiO2 substrate, followed by a thermal annealing and reactive ion etching (RIE) process. This gives a template composed of an ordered hexagonal array of SiOC hemispheres emerging in the polystyrene matrix. After the deposition of a FePt film on this template, we utilize the rapid thermal annealing (RTA) process, which provides in-plane stress, to achieve thermal dewetting and structural ordering of FePt simultaneously. Since the template is composed of different composition surfaces with periodically varied morphologies, it offers more tuning knobs to manipulate the nanostructures. We show that both the decrease in the area of the PS matrix and the increase in the strain energy relaxation transfer the dewetted pattern from the randomly distributed nanoparticles into a hexagonal periodic array of L10 FePt nanoparticles. Transmission electron microscopy with the in situ heating stage reveals the evolution of the dewetting process, and confirms that the positions of nanoparticles are aligned with those of the SiOC hemispheres. The nanoparticles formed by this template-dewetting show an average diameter and center-to-center distance of 19.30 +/- 2.09 nm and 39.85 +/- 4.80 nm, respectively. The hexagonal array of FePt nanoparticles reveals a large coercivity of 1.5 T, much larger than the nanoparticles fabricated by top-down approaches. This approach offers an efficient pathway toward self-assembled nanostructures in a wide range of material systems.A design for the fabrication of metallic nanoparticles is presented by thermal dewetting with a chemically heterogeneous nano-template. For the template, we fabricate a nanostructured polystyrene-b-polydimethylsiloxane (PS-b-PDMS) film on a Si|SiO2 substrate, followed by a thermal

  20. Control of Partial Coalescence of Self-Assembled Metal Nano-Particles across Lyotropic Liquid Crystals Templates towards Long Range Meso-Porous Metal Frameworks Design

    PubMed Central

    Dumée, Ludovic F.; Lemoine, Jean-Baptiste; Ancel, Alice; Hameed, Nishar; He, Li; Kong, Lingxue

    2015-01-01

    The formation of purely metallic meso-porous metal thin films by partial interface coalescence of self-assembled metal nano-particles across aqueous solutions of Pluronics triblock lyotropic liquid crystals is demonstrated for the first time. Small angle X-ray scattering was used to study the influence of the thin film composition and processing conditions on the ordered structures. The structural characteristics of the meso-structures formed demonstrated to primarily rely on the lyotropic liquid crystal properties while the nature of the metal nano-particles used as well as the their diameters were found to affect the ordered structure formation. The impact of the annealing temperature on the nano-particle coalescence and efficiency at removing the templating lyotropic liquid crystals was also analysed. It is demonstrated that the lyotropic liquid crystal is rendered slightly less thermally stable, upon mixing with metal nano-particles and that low annealing temperatures are sufficient to form purely metallic frameworks with average pore size distributions smaller than 500 nm and porosity around 45% with potential application in sensing, catalysis, nanoscale heat exchange, and molecular separation. PMID:28347094

  1. Ca(2+)-induced self-assembly of Bombyx mori silk sericin into a nanofibrous network-like protein matrix for directing controlled nucleation of hydroxylapatite nano-needles.

    PubMed

    Yang, Mingying; Zhou, Guanshan; Shuai, Yajun; Wang, Jie; Zhu, Liangjun; Mao, Chuanbin

    2015-03-28

    Bone biomineralization is a well-regulated protein-mediated process where hydroxylapatite (HAP) crystals are nucleated with preferred orientation within self-assembled protein matrix. Mimicking this process is a promising approach to the production of bone-like protein/mineral nanocomposites for bone repair and regeneration. Towards the goal of fabricating such nanocomposites from sericin, a protein spun by Bombyx mori (B.mori) silkworm, and bone mineral HAP, for the first time we investigated the chemical mechanism underpinning the synergistic processes of the conformational change/self-assembly of B.mori sericin ( BS ) as well as the nucleation of HAP on the resultant self-assembled BS matrix. We found that BS , rich in anionic amino acid residues, could bind Ca(2+) ions from the HAP precursor solution through electrostatic attraction. The Ca(2+)binding drove the conformational change of BS from random coils into β-sheets and its concomitant self-assembly into interconnected nanofibrous network-like protein matrix, which initiated the nucleation and growth of HAP crystals. HAP crystals directed by the resultant self-assembled BS matrix grew preferentially along their crystallographic c-axis, leading to the formation of HAP nano-needles. The HAP nano-needles in the self-assembled BS matrix were subsequently aggregated into globules, probably driven by the hydrogen bonding between C=O groups of BS and O-H groups of HAP nano-needles. The present work sheds light on the chemical mechanisms of BS self-assembly and the controlled mineralization directed by the self-assembled matrix. We also found that the resultant nanocomposites could promote the osteogenic differentiation of human bone marrow-derived mesenchymal stem cells. Thus our work also generates a biomimetic approach to bone-like silk protein/mineral nanocomposite scaffolds that can find potential applications in bone repair and regeneration.

  2. Self-assembly of hierarchically ordered structures in DNA nanotube systems

    NASA Astrophysics Data System (ADS)

    Glaser, Martin; Schnauß, Jörg; Tschirner, Teresa; Schmidt, B. U. Sebastian; Moebius-Winkler, Maximilian; Käs, Josef A.; Smith, David M.

    2016-05-01

    The self-assembly of molecular and macromolecular building blocks into organized patterns is a complex process found in diverse systems over a wide range of size and time scales. The formation of star- or aster-like configurations, for example, is a common characteristic in solutions of polymers or other molecules containing multi-scaled, hierarchical assembly processes. This is a recurring phenomenon in numerous pattern-forming systems ranging from cellular constructs to solutions of ferromagnetic colloids or synthetic plastics. To date, however, it has not been possible to systematically parameterize structural properties of the constituent components in order to study their influence on assembled states. Here, we circumvent this limitation by using DNA nanotubes with programmable mechanical properties as our basic building blocks. A small set of DNA oligonucleotides can be chosen to hybridize into micron-length DNA nanotubes with a well-defined circumference and stiffness. The self-assembly of these nanotubes to hierarchically ordered structures is driven by depletion forces caused by the presence of polyethylene glycol. This trait allowed us to investigate self-assembly effects while maintaining a complete decoupling of density, self-association or bundling strength, and stiffness of the nanotubes. Our findings show diverse ranges of emerging structures including heterogeneous networks, aster-like structures, and densely bundled needle-like structures, which compare to configurations found in many other systems. These show a strong dependence not only on concentration and bundling strength, but also on the underlying mechanical properties of the nanotubes. Similar network architectures to those caused by depletion forces in the low-density regime are obtained when an alternative hybridization-based bundling mechanism is employed to induce self-assembly in an isotropic network of pre-formed DNA nanotubes. This emphasizes the universal effect inevitable

  3. Fungal Hydrophobin Proteins Produce Self-Assembling Protein Films with Diverse Structure and Chemical Stability

    PubMed Central

    Lo, Victor C.; Ren, Qin; Pham, Chi L. L.; Morris, Vanessa K.; Kwan, Ann H.; Sunde, Margaret

    2014-01-01

    Hydrophobins are small proteins secreted by fungi and which spontaneously assemble into amphipathic layers at hydrophilic-hydrophobic interfaces. We have examined the self-assembly of the Class I hydrophobins EAS∆15 and DewA, the Class II hydrophobin NC2 and an engineered chimeric hydrophobin. These Class I hydrophobins form layers composed of laterally associated fibrils with an underlying amyloid structure. These two Class I hydrophobins, despite showing significant conformational differences in solution, self-assemble to form fibrillar layers with very similar structures and require a hydrophilic-hydrophobic interface to trigger self-assembly. Addition of additives that influence surface tension can be used to manipulate the fine structure of the protein films. The Class II hydrophobin NC2 forms a mesh-like protein network and the engineered chimeric hydrophobin displays two multimeric forms, depending on assembly conditions. When formed on a graphite surface, the fibrillar EAS∆15 layers are resistant to alcohol, acid and basic washes. In contrast, the NC2 Class II monolayers are dissociated by alcohol treatment but are relatively stable towards acid and base washes. The engineered chimeric Class I/II hydrophobin shows increased stability towards alcohol and acid and base washes. Self-assembled hydrophobin films may have extensive applications in biotechnology where biocompatible; amphipathic coatings facilitate the functionalization of nanomaterials.

  4. Detection and analysis of SERS effect of nano gold by self-assembly chemical plating composite method

    NASA Astrophysics Data System (ADS)

    Wang, Chunyan; Xu, Yi; Zhao, Huazhou; Gang, Chen; Lai, Chunhong; Liao, Xin; Wang, Rong

    2015-10-01

    Surface-enhanced Raman spectroscopy (SERS) as a powerful analytical tool has gained extensive attention. Despite of many efforts have been devoted to design SERS substrates, it still remains a grand challenge for creating a general substrate with high SERS active by a simple, controllable and low-cost way. Herein, we attempt to address this issue by fabricating SERS-active nano gold film based on self-assembly chemical plating composite method. The influence of gold colloid particle size on gold seed distribution density and the influence of the particle size of nano gold films on the SERS activity were investigated in detail. 10-5 M Rhodamine 6G (R6G) was taken as Raman probe molecules and homemade Raman detection microsystem was used as detector. According to the results of SERS detection, the SERS substrate enhancement factors (SSEF) were calculated, and the nano gold film with average particle size of about 55 nm showed the maximum SSEF of 0.93 × 105, which indicated such nano gold films showed excellent SERS activity. Moreover, these nano gold films are all low-cost and easy to prepared. This study provided theoretical and experimental basis for the design and preparation of general SERS substrate.

  5. Cooperativity Scale: A Structure-Mechanism Correlation in the Self-Assembly of Benzene-1,3,5-tricarboxamides.

    PubMed

    Kulkarni, Chidambar; Meijer, E W; Palmans, Anja R A

    2017-08-15

    The self-assembly of small and well-defined molecules using noncovalent interactions to generate various nano- and microarchitectures has been extensively studied. Among various architectures, one-dimensional (1-D) nano-objects have garnered significant attention. It has become increasingly evident that a cooperative or nucleation-elongation mechanism of polymerization leads to highly ordered 1-D supramolecular polymers, analogous to shape-persistent biopolymers such as actin. With this in mind, achieving cooperativity in self-assembled structures has been actively pursued with significant success. Only recently, researchers are focusing on the origin of the mechanism at the molecular level in different synthetic systems. Taking a step further, a thorough quantitative structure-mechanism correlation is crucial to control the size, shape, and functions of supramolecular polymers, and this is currently lacking in the literature. Among a plethora of molecules, benzene-1,3,5-tricarboxamides (BTAs) provide a unique combination of important noncovalent interactions such as hydrogen bonding, π-stacking, and hydrophobic interactions, for self-assembly and synthetic ease. Due to the latter, a diverse range of BTA derivatives with all possible structural mutations have been synthesized and studied during the past decade, mainly from our group. With such a large body of experimental results on BTA self-assembly, it is time to embark on a structure-mechanism correlation in this family of molecules, and a first step toward this will form the main focus of this Account. The origin of the cooperative mechanism of self-assembly in BTAs has been ascribed to 3-fold intermolecular hydrogen bonding (HB) between monomers based on density-functional theory (DFT) calculations. The intermolecular hydrogen-bonding interaction forms the central premise of this work, in which we evaluate the effect of different moieties such as alkyl chains, and amino acids, attached to the core amides on

  6. The Role of Secondary Structure in the Entropically Driven Amelogenin Self-Assembly

    PubMed Central

    Lakshminarayanan, Rajamani; Fan, Daming; Du, Chang; Moradian-Oldak, Janet

    2007-01-01

    Amelogenin, the major extracellular enamel matrix protein, plays critical roles in controlling enamel mineralization. This generally hydrophobic protein self-assembles to form nanosphere structures under certain solution conditions. To gain clearer insight into the mechanisms of amelogenin self-assembly, we first investigated the occurrences of secondary structures within its sequence. By applying isothermal titration calorimetry (ITC), we determined the thermodynamic parameters associated with protein-protein interactions and with conformational changes during self-assembly. The recombinant porcine full length (rP172) and a truncated amelogenin lacking the hydrophilic C-terminal (rP148) were used. Circular dichroism (CD) measurements performed at low concentrations (<5 μM) revealed the presence of the polyproline-type II (PPII) conformation in both amelogenins in addition to α-helix and unordered conformations. Structural transition from PPII/unordered to β-sheet was observed for both proteins at higher concentrations (>62.5 μM) and upon self-assembly. ITC measurements indicated that the self-assembly of rP172 and rP148 is entropically driven (+ΔSA) and energetically favorable (−ΔGA). The magnitude of enthalpy (ΔHA) and entropy changes of assembly (ΔSA) were smaller for rP148 than rP172, whereas the Gibbs free energy change of assembly (ΔGA) was not significantly different. It was found that rP172 had higher PPII content than rP148, and the monomer-multimer equilibrium for rP172 was observed in a narrower protein concentration range when compared to rP148. The large positive enthalpy and entropy changes in both cases are attributed to the release of ordered water molecules and the associated entropy gain (due to the hydrophobic effect). These findings suggest that PPII conformation plays an important role in amelogenin self-assembly and that rP172 assembly is more favorable than rP148. The data are direct evidence for the notion that hydrophobic

  7. Self-assembled Materials for Catalysis

    SciTech Connect

    Zhu, Kake; Wang, Donghai; Liu, Jun

    2009-01-01

    The purpose of this review is to highlight developments on self-assembled nanostructured materials (i.e. mesoporous and nanoparticle based materials) and their catalytic applications. Since there are some reviews available for metal-based nanoparticles as catalysts, this review will mainly focus on self-assembled oxide-based catalytic materials. The content includes: (1) Design and synthetic strategy toward self-assembled mesoporous catalysts; (2) Polyoxometalates (POMs) based nanocatalysts; (3) Dendrimers based nanocatalysts; (4) Shaped nanomaterials and catalytic applications. We show that self-assemblies of molecules, crystalline seeds, nano-building blocks into organized mesoscopic structures paved new roads for tailoring porosities of heterogeneous catalysts and catalytic active sites.

  8. Dynamic transformation of self-assembled structures using anisotropic magnetized hydrogel microparticles

    NASA Astrophysics Data System (ADS)

    Yoshida, Satoru; Takinoue, Masahiro; Iwase, Eiji; Onoe, Hiroaki

    2016-08-01

    This paper describes a system through which the self-assembly of anisotropic hydrogel microparticles is achieved, which also enables dynamic transformation of the assembled structures. Using a centrifuge-based microfluidic device, anisotropic hydrogel microparticles encapsulating superparamagnetic materials on one side are fabricated, which respond to a magnetic field. We successfully achieve dynamic assembly using these hydrogel microparticles and realize three different self-assembled structures (single and double pearl chain structures, and close-packed structures), which can be transformed to other structures dynamically via tuning of the precessional magnetic field. We believe that the developed system has potential application as an effective platform for a dynamic cell manipulation and cultivation system, in biomimetic autonomous microrobot organization, and that it can facilitate further understanding of the self-organization and complex systems observed in nature.

  9. Galactosylated Polymer Nano-objects by Polymerization-Induced Self-Assembly, Potential Drug Nanocarriers.

    PubMed

    Semsarilar, Mona; Canton, Irene; Ladmiral, Vincent

    2016-01-01

    Glycopolymer-based nanostructures are invaluable tools to both study biological phenomena and to design future targeted drug delivery systems. Polymerization-induced self-assembly, especially RAFT aqueous dispersion polymerization is a unique method to prepare such polymer nanostructures, as it enables the preparation of very-well-defined morphologies at very high concentrations. Here we describe the implementation of PISA to the synthesis of galactosylated spheres, wormlike micelles and vesicles, and the preliminary results of cell toxicity, cell uptake, and cargo delivering capacity of galactose-decorated vesicles.

  10. Self-assembled germanium nano-clusters on silver(110) [rapid communication

    NASA Astrophysics Data System (ADS)

    Léandri, C.; Oughaddou, H.; Gay, J. M.; Aufray, B.; Le Lay, G.; Bibérian, J. P.; Ranguis, A.; Bunk, O.; Johnson, R. L.

    2004-12-01

    The adsorption of germanium on Ag(1 1 0) has been investigated by scanning tunnelling microscopy (STM), as well as surface X-ray diffraction (SXRD). At 0.5 germanium monolayer (ML) coverage, Low Energy Electron Diffraction (LEED) patterns reveals a sharp c(4 × 2) superstructure. Based on STM images and SXRD measurements, we present an atomic model of the surface structure with Ge atoms forming tetramer nano-clusters perfectly assembled in a two-dimensional array over the silver top layer. The adsorption of the germanium atoms induces a weak perturbation of the Ag surface. Upon comparison with results obtained on the (1 1 1) and (1 0 0) faces, we stress the role played by the relative interactions between silver and germanium on the observed surface structures.

  11. Self-Assembly of Colloidal Particles on Template Structures

    NASA Technical Reports Server (NTRS)

    Yodh, Arjun G.

    2002-01-01

    I will discuss recent experiments from my lab, which use surface templates to induce ordered colloidal structures. Particle assembly driven by entropic depletion, fluid convection, and sedimentation will be described. Confocal microscopy was used to visualize most of these samples.

  12. Nano-self-assembly in manganese-based spinels through solid state process

    NASA Astrophysics Data System (ADS)

    Zhang, Chenglin

    Transition-metal oxides characterized with anisotropic d-orbital electrons are subject to intense discussion in strongly correlated electron systems, ranging from colossal magnetoresistance (CMR) to high temperature superconductivity (HTSC). The orbital degree of freedom often underpins complex physical properties and a variety of extraordinary phenomena while coupling with charge, spin and lattice. In this thesis, we demonstrate a fascinating example of orbital-related physical properties in Mn-based spinels. The strong octahedral preference of Jahn-Teller ions Mn3+ results in simultaneous chemical and structural phase separation into Mn-poor (cubic) and Mn-rich (tetragonal) regions, forming two types of rectangular nanorods with cross section checkerboard-like (CB). Because of the pioneering discovery of checkerboards in the nonmagnetic ZnMnxGa1-xO4, we chose to study two magnetic spinel systems: (1) Mg(MnxFe1-x)O4, where unfortunately only poorly-ordered magnetic nano CBs were observed; and (2) Mn-doped CoFe 2O4, the nano CBs with distinct magnetic properties and tunable sizes achieved here are highly ordered, exhibiting a nearly ideal architecture for the patterned perpendicular recording medium. The evolution of such compositional separation and topological nanoscale ordering is reasonably understood based on a three dimensional (3D) phase-field microelasticity (PFM) model.

  13. In situ monitoring of structural changes during colloidal self-assembly.

    PubMed

    Koh, Yaw Koon; Wong, Chee Cheong

    2006-01-31

    Reflectance spectroscopy is utilized to monitor structural changes during the self-assembly of a monodisperse colloidal system at the meniscus of a sessile drop on an inert substrate. Treating the ordered colloidal structure as a photonic crystal is equivalent to monitoring the changes in the photonic band gap (PBG) as the colloidal system self-assembles heterogeneously into a crystal through solvent evaporation in ambient conditions. Using a modified Bragg's law model of the photonic crystal, we can trace the structural evolution of the self-assembling colloidal system. After a certain induction period, a face-centered cubic (FCC) structure emerges, albeit with a lattice parameter larger than that of a true close-packed structure. This FCC structure is maintained while the lattice parameter shrinks continuously with further increase in the colloidal concentration due to drying. When the structure reaches a lattice parameter 1.09 times the size of that of a true close-packed structure, it undergoes an abrupt decrease in lattice spacing, apparently similar to those reported for lattice-distortive martensitic transformations. This abrupt final lattice shrinkage agrees well with the estimated Debye screening length of the electric double layer of charged colloids and could be the fundamental reason behind the cracking commonly seen in colloidal crystals.

  14. Self-assembly and structural relaxation in a model ionomer melt

    DOE PAGES

    Goswami, Monojoy; Borreguero, Jose M.; Sumpter, Bobby G.

    2015-02-26

    Molecular dynamics simulations are used to understand the self-assembly and structural relaxation in ionomer melts containing less than 10% degree of ionization on the backbone. We study the self-assembly of charged sites and counterions that show structural ordering and agglomeration with a range of structures that can be achieved by changing the dielectric constant of the medium. The intermediate scattering function shows a decoupling of charge and counterion relaxation at longer length scales for only high dielectric constant and at shorter length scales for all dielectric constants. Finally, the slow structural decay of counterions in the strongly correlated ionomer systemmore » closely resembles transport properties of semi-flexible polymers.« less

  15. Influence of chain ordering on frictional properties of self-assembled monolayers (SAMs) in nano-lubrication.

    PubMed

    Cheng, Hefa; Hu, Yuanan

    2012-01-01

    Adhesion of organic films to substrates is important in applications that involve solid surfaces in sliding contact. Although the thickness of self-assembled monolayers (SAMs) is only a few nanometers, they can drastically modify the frictional properties of the underlying substrate, and thus have great potential for serving as boundary lubricants on micro- and nano-scales. This review focuses on the relationship between the structural and compositional properties of SAMs and their frictional response. Adhesion of SAMs to the substrate surface usually occurs through chemisorption of the head groups on the constituent molecules, with molecular interactions such as van der Waals interactions playing important roles in organizing the molecules into surface films, and in controlling their tribological behavior. The durability and wear resistance of SAMs depend on the nature and strength of the binding forces between the head groups and the substrate surfaces, while the adhesion and friction forces are strongly influenced by the interactions of the terminal groups with the counterfaces. Results from both experimental measurements and molecular dynamics simulations consistently indicate that structural ordering of alkyl chains in SAMs reduces their frictional response, and that SAMs formed by molecules with alkyl chains longer than 8 to 10 methylene units are well organized, exhibiting low levels of friction. Less densely packed or more disordered monolayers inherently possess greater numbers of conformational defects at room temperature and present lower barriers to defect creation under the action of a contacting surface, and thus exhibit higher friction. Cross-linking of the spacer chains can reduce the frictional response of disordered films by increasing the chain ordering, but has little impact on SAMs that are already well ordered. On the other hand, introduction of sterically demanding terminal groups and dissimilar molecules reduces molecular ordering in SAMs

  16. Self-assembled coffee-ring colloidal crystals for structurally colored contact lenses.

    PubMed

    Xie, Zhuoying; Li, Linliang; Liu, Panmiao; Zheng, Fuyin; Guo, Liuyang; Zhao, Yuanjin; Jin, Lu; Li, Tingting; Gu, Zhongze

    2015-02-25

    A circlular structural-colored contact lens is reported, which is fabricated by replicating self-assembled colloidal photonic crystal templates. The structural-colored contact lenses not only display variable and brilliant color under light illumination, but also avoid the addition of any colorants to the hydrogel lenses and prevent the potential harm posed by traditional colored contact lenses. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Structural rearrangements in self-assembled surfactant layers at surfaces

    SciTech Connect

    Sushko, Maria L.; Liu, Jun

    2010-03-25

    The transition from compact to extended configuration in ionic surfactant layers under the influence of salt, surfactant surface density and temperature is studied using the classical density functional theory (cDFT). The increase in ionic strength of aqueous salt solution or in surfactant surface density leads to the transition from the hemicylindrical to the perpendicular monolayer configuration of the molecules. Although producing the same structural rearrangement in the surfactant layer the origin of the effect of salt and surface density is different. While the addition of salt increases the out-of-plane attractive interactions with the solvent, the increase in density results in the increase in the in-plane repulsion in surfactant layer. The temperature effects are subtler and are mainly manifested in the reduction of the solution structuring at elevated temperatures.

  18. Self-Assembled Structures of Tubulin and Microtubules Complexed with Oppositely Charged Molecules

    NASA Astrophysics Data System (ADS)

    Case, Ryan; Pfohl, Thomas; Kim, Joon Heon; Lin, Alison; Safinya, Cyrus R.; Miller, Herb P.; Wilson, Les

    2000-03-01

    Tubulin normally polymerizes into hollow cylindrical microtubules, with outer diameters of about 25 nm, in the presence of Mg^2+ ions and GTP at 37^o C. Microtubules can be stabilized with anticancer agents, such as Taxol. We report on synchotron x-ray studies and confocal imaging data that show that tubulin self-assembles in the presence of cationic lipids at room temperature. These complexes form novel structures with length scales up to three times the diameter of microtubules formed under normal conditions. To improve our understanding of these structures, we use x-ray scattering data of self-assembled structures of Taxol-stabilized microtubule - cationic lipid complexes as a comparison. Supported by NSF DMR-9972246, University of California Biotech Research, and Education Program Training Grant 99-14, DFG Pf 375/1-1.

  19. M13 Bacteriophage-Based Self-Assembly Structures and Their Functional Capabilities

    PubMed Central

    Moon, Jong-Sik; Kim, Won-Geun; Kim, Chuntae; Park, Geun-Tae; Heo, Jeong; Yoo, So Y; Oh, Jin-Woo

    2015-01-01

    Controlling the assembly of basic structural building blocks in a systematic and orderly fashion is an emerging issue in various areas of science and engineering such as physics, chemistry, material science, biological engineering, and electrical engineering. The self-assembly technique, among many other kinds of ordering techniques, has several unique advantages and the M13 bacteriophage can be utilized as part of this technique. The M13 bacteriophage (Phage) can easily be modified genetically and chemically to demonstrate specific functions. This allows for its use as a template to determine the homogeneous distribution and percolated network structures of inorganic nanostructures under ambient conditions. Inexpensive and environmentally friendly synthesis can be achieved by using the M13 bacteriophage as a novel functional building block. Here, we discuss recent advances in the application of M13 bacteriophage self-assembly structures and the future of this technology. PMID:26146494

  20. M13 Bacteriophage-Based Self-Assembly Structures and Their Functional Capabilities.

    PubMed

    Moon, Jong-Sik; Kim, Won-Geun; Kim, Chuntae; Park, Geun-Tae; Heo, Jeong; Yoo, So Y; Oh, Jin-Woo

    2015-06-01

    Controlling the assembly of basic structural building blocks in a systematic and orderly fashion is an emerging issue in various areas of science and engineering such as physics, chemistry, material science, biological engineering, and electrical engineering. The self-assembly technique, among many other kinds of ordering techniques, has several unique advantages and the M13 bacteriophage can be utilized as part of this technique. The M13 bacteriophage (Phage) can easily be modified genetically and chemically to demonstrate specific functions. This allows for its use as a template to determine the homogeneous distribution and percolated network structures of inorganic nanostructures under ambient conditions. Inexpensive and environmentally friendly synthesis can be achieved by using the M13 bacteriophage as a novel functional building block. Here, we discuss recent advances in the application of M13 bacteriophage self-assembly structures and the future of this technology.

  1. Complex self-assembly of pyrimido[4,5-d]pyrimidine nucleoside supramolecular structures

    NASA Astrophysics Data System (ADS)

    Zhao, Hang; Guo, Xiurong; He, Shiliang; Zeng, Xin; Zhou, Xinglong; Zhang, Chaoliang; Hu, Jing; Wu, Xiaohua; Xing, Zhihua; Chu, Liangyin; He, Yang; Chen, Qianming

    2014-01-01

    Supramolecular self-assembly is not only one of the chemical roots of biological structure but is also drawing attention in different industrial fields. Here we study the mechanism of the formation of a complex flower-shaped supramolecular structure of pyrimido[4,5-d]pyrimidine nucleosides by dynamic light scattering, scanning electron microscopy, differential scanning calorimetry, nuclear magnetic resonance and X-ray analysis. Upon removing the hydroxyl group of sugars, different flower-shaped superstructures can be produced. These works demonstrate that complex self-assembly can indeed be attained through hierarchical non-covalent interactions of single molecules. Furthermore, chimerical structures built from molecular recognition by these monomers indicate their potential in other fields if combined with other chemical entities.

  2. Rational design of self-assembly pathways for complex multicomponent structures.

    PubMed

    Jacobs, William M; Reinhardt, Aleks; Frenkel, Daan

    2015-05-19

    The field of complex self-assembly is moving toward the design of multiparticle structures consisting of thousands of distinct building blocks. To exploit the potential benefits of structures with such "addressable complexity," we need to understand the factors that optimize the yield and the kinetics of self-assembly. Here we use a simple theoretical method to explain the key features responsible for the unexpected success of DNA-brick experiments, which are currently the only demonstration of reliable self-assembly with such a large number of components. Simulations confirm that our theory accurately predicts the narrow temperature window in which error-free assembly can occur. Even more strikingly, our theory predicts that correct assembly of the complete structure may require a time-dependent experimental protocol. Furthermore, we predict that low coordination numbers result in nonclassical nucleation behavior, which we find to be essential for achieving optimal nucleation kinetics under mild growth conditions. We also show that, rather surprisingly, the use of heterogeneous bond energies improves the nucleation kinetics and in fact appears to be necessary for assembling certain intricate 3D structures. This observation makes it possible to sculpt nucleation pathways by tuning the distribution of interaction strengths. These insights not only suggest how to improve the design of structures based on DNA bricks, but also point the way toward the creation of a much wider class of chemical or colloidal structures with addressable complexity.

  3. DNA Free Energy Landscapes and RNA Nano-Self-Assembly Using Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Frey, Eric William

    There is an important conceptual lesson which has long been appreciated by those who work in biophysics and related interdisciplinary fields. While the extraordinary behavior of biological matter is governed by its detailed atomic structure and random fluctuations, and is therefore difficult to predict, it can nevertheless be understood within simplified frameworks. Such frameworks model the system as consisting of only one or a few components, and model the behavior of the system as the occupation of a single state out of a small number of states available. The emerging widespread application of nanotechnology, such as atomic force microscopy (AFM), has expanded this understanding in eye-opening new levels of detail by enabling nano-scale control, measurement, and visualization of biological molecules. This thesis describes two independent projects, both of which illuminate this understanding using AFM, but which do so from very different perspectives. The organization of this thesis is as follows. Chapter 1 begins with an experimental background and introduction to AFM, and then describes our setup in both single-molecule manipulation and imaging modes. In Chapter 2, we describe the first project, the motivation for which is to extend methods for the experimental determination of the free energy landscape of a molecule. This chapter relies on the analysis of single-molecule manipulation data. Chapter 3 describes the second project, the motivation for which is to create RNA-based nano-structures suitable for future applications in living mammalian cells. This chapter relies mainly on imaging. Chapters 2 and 3 can thus be read and understood separately.

  4. High-Definition Self-Assemblies driven by the Hydrophobic Effect: Synthesis and Properties of a Supramolecular Nano-Capsule

    PubMed Central

    Liu, Simin

    2008-01-01

    High definition self-assemblies, those that possess order at the molecular level, are most commonly made from subunits possessing metals and metal coordination sites, or groups capable of partaking in hydrogen bonding. In other words, enthalpy is the driving force behind the free energy of assembly. The hydrophobic effect engenders the possibility of (nominally) relying not on enthalpy but entropy to drive assembly. Towards this idea, we describe how template molecules can trigger the dimerization of a cavitand in aqueous solution, and in doing so are encapsulated within the resulting capsule. Although not held together by (enthalpically) strong and directional non-covalent forces, these capsules possess considerable thermodynamic and kinetic stability. As a result, they display unusual and even unique properties. We discuss some of these, including the use of the capsule as a nano-scale reaction chamber and how they can bring about the separation of hydrocarbon gases. PMID:18685753

  5. Engineering biological structures of prescribed shape using self-assembling multicellular systems

    PubMed Central

    Jakab, Karoly; Neagu, Adrian; Mironov, Vladimir; Markwald, Roger R.; Forgacs, Gabor

    2004-01-01

    Self-assembly is a fundamental process that drives structural organization in both inanimate and living systems. It is in the course of self-assembly of cells and tissues in early development that the organism and its parts eventually acquire their final shape. Even though developmental patterning through self-assembly is under strict genetic control it is clear that ultimately it is physical mechanisms that bring about the complex structures. Here we show, both experimentally and by using computer simulations, how tissue liquidity can be used to build tissue constructs of prescribed geometry in vitro. Spherical aggregates containing many thousands of cells, which form because of tissue liquidity, were implanted contiguously into biocompatible hydrogels in circular geometry. Depending on the properties of the gel, upon incubation, the aggregates either fused into a toroidal 3D structure or their constituent cells dispersed into the surrounding matrix. The model simulations, which reproduced the experimentally observed shapes, indicate that the control parameter of structure evolution is the aggregate–gel interfacial tension. The model-based analysis also revealed that the observed toroidal structure represents a metastable state of the cellular system, whose lifetime depends on the magnitude of cell–cell and cell–matrix interactions. Thus, these constructs can be made long-lived. We suggest that spherical aggregates composed of organ-specific cells may be used as “bio-ink” in the evolving technology of organ printing. PMID:14981244

  6. Fabrication of cyclodextrins-procainamide supramolecular self-assembly: shape-shifting of nanosheet into microtubular structure.

    PubMed

    Siva, S; Kothai Nayaki, S; Rajendiran, N

    2015-05-20

    Encapsulation behavior of α- and β-cyclodextrins (α-CD, β-CD) with procainamide hydrochloride (PCA) has been investigated by absorption, fluorescence, time-resolved fluorescence, proton nuclear magnetic resonance spectroscopy, scanning electron microscope, Fourier transform-infrared spectroscopy, differential scanning calorimetry, and powder X-ray diffraction techniques. Spectral results revealed that PCA forms 1:2 drug-CD2 inclusion complexes with CDs. Novel supramolecular self-assemblies have been fabricated by inclusion complexation of PCA with α-CD/β-CD and characterized by transmission electron microscope and micro-Raman imaging. The obtained results from transmission electron microscope indicated that PCA/α-CD complex could form nano-sized particles. However, when the macrocyclic ring with six glucose units was switched into seven glucose units, the resultant PCA/β-CD complex could be self-assembled to micro-sized tubular structures. Shape-shifting of 2D nanosheet into 1D microtube by simple rolling mechanism was analyzed. Thermodynamic parameters of inclusion process were determined by Parameter Method 3 calculations.

  7. Multi-stacks of epitaxial GeSn self-assembled dots in Si: Structural analysis

    SciTech Connect

    Oliveira, F.; Fischer, I. A.; Schulze, J.; Benedetti, A.; Cerqueira, M. F.; Vasilevskiy, M. I.; Stefanov, S.; Chiussi, S.

    2015-03-28

    We report on the growth and structural and morphologic characterization of stacked layers of self-assembled GeSn dots grown on Si (100) substrates by molecular beam epitaxy at low substrate temperature T = 350 °C. Samples consist of layers (from 1 up to 10) of Ge{sub 0.96}Sn{sub 0.04} self-assembled dots separated by Si spacer layers, 10 nm thick. Their structural analysis was performed based on transmission electron microscopy, atomic force microscopy, and Raman scattering. We found that up to 4 stacks of dots could be grown with good dot layer homogeneity, making the GeSn dots interesting candidates for optoelectronic device applications.

  8. Polymorphism in Self-Assembled Structures of 9-Anthracene Carboxylic Acid on Ag(111)

    PubMed Central

    Lu, Chao; Wei, Yinying; Zhu, Erkuang; Reutt-Robey, Janice E.; Xu, Bo

    2012-01-01

    Surface self-assembly process of 9-anthracene carboxylic acid (AnCA) on Ag(111) was investigated using STM. Depending on the molecular surface density, four spontaneously formed and one annealed AnCA ordered phases were observed, namely a straight belt phase, a zigzag double-belt phase, two simpler dimer phases, and a kagome phase. The two high-density belt phases possess large unit cells on the scale length of 10 nm, which are seldom observed in molecular self-assembled structures. This structural diversity stems from a complicated competition of different interactions of AnCA molecules on metal surface, including intermolecular and molecular-substrate interactions, as well as the steric demand from high molecular surface density. PMID:22837666

  9. Cluster perturbation theory for the self-assembly of associating fluids into complex structures.

    PubMed

    Marshall, Bennett D

    2014-12-01

    Wertheim's two-density thermodynamic perturbation theory (TPT) has proven to be an indispensable statistical mechanical tool in the description of associating fluids with a single association site. TPT was developed to enforce the monovalence of the hydrogen bond and only recently has been extended to account for divalent association sites. It has been shown through experiment and molecular simulation that certain one-site associating fluids can self-assemble into complex extended supramolecular structures as a result of multiple bonding of association sites. In this paper we reorganize TPT into a form that is more easily applied to complex associated structures. The derived theory is general to all possible self-assemble structures. We obtain the free energy and bonding fractions in a general way in terms of single-cluster partition functions and averages. The new formalism removes any reference to graph theory allowing for the conceptually straightforward application of the two-density formalism to complex self-assembled structures.

  10. Solvent Controlled Structural Transition of KI4K Self-Assemblies: from Nanotubes to Nanofibrils.

    PubMed

    Zhao, Yurong; Deng, Li; Wang, Jiqian; Xu, Hai; Lu, Jian R

    2015-12-01

    The structural modulation of peptide and protein assemblies under well-controlled conditions is of both fundamental and practical significance. In spite of extensive studies, it remains hugely challenging to tune the self-assembled nanostructures in a controllable manner because the self-assembly processes are dictated by various noncovalent interactions and their interplay. We report here how to manipulate the self-assembly of a designed, symmetric amphiphilic peptide (KI4K) via the solvent-controlled structural transition. Structural transition processes were carefully followed by the combination of transmission electronic microscopy (TEM), atomic force microscopy (AFM), circular dichroism (CD), Fourier transform infrared spectroscopy (FTIR), and small angle neutron scattering (SANS). The results show that the introduction of acetonitrile into water significantly affected the hydrophobic interactions among hydrophobic side chains while imposing little impact on the β-sheet hydrogen bonding between peptide backbones. A structural transition occurred from nanotubes to helical/twisted ribbons and then to thin fibrils with the addition of acetonitrile due to the reduced hydrophobic interactions and the consequent weakening of the lateral stacking between KI4K β-sheets. The increased intermolecular electrostatic repulsions among lysine side chain amino groups had little effect on the lateral stacking of KI4K β-sheets due to the molecular symmetry. Complementary molecular dynamic (MD) simulations also indicated the solvation of acetonitrile molecules into the hydrophobic domains weakening the coherence between the neighboring sheets.

  11. Structural ordering of self-assembled clusters with competing interactions: transition from faceted to spherical clusters.

    PubMed

    Galván-Moya, J E; Nelissen, K; Peeters, F M

    2015-01-27

    The self-assembly of nanoparticles into clusters and the effect of the different parameters of the competing interaction potential on it are investigated. For a small number of particles, the structural organization of the clusters is almost unaffected by the attractive part of the potential, and for an intermediate number of particles the configuration strongly depends on the strength of it. The cluster size is controlled by the range of the interaction potential, and the structural arrangement is guided by the strength of the potential: i.e., the self-assembled cluster transforms from a faceted configuration at low strength to a spherical shell-like structure at high strength. Nonmonotonic behavior of the cluster size is found by increasing the interaction range. An approximate analytical expression is obtained that predicts the smallest cluster for a specific set of potential parameters. A Mendeleev-like table is constructed for different values of the strength and range of the attractive part of the potential in order to understand the structural ordering of the ground-state configuration of the self-assembled clusters.

  12. Two-Dimensional Layered Oxide Structures Tailored by Self-Assembled Layer Stacking via Interfacial Strain.

    PubMed

    Zhang, Wenrui; Li, Mingtao; Chen, Aiping; Li, Leigang; Zhu, Yuanyuan; Xia, Zhenhai; Lu, Ping; Boullay, Philippe; Wu, Lijun; Zhu, Yimei; MacManus-Driscoll, Judith L; Jia, Quanxi; Zhou, Honghui; Narayan, Jagdish; Zhang, Xinghang; Wang, Haiyan

    2016-07-06

    Study of layered complex oxides emerge as one of leading topics in fundamental materials science because of the strong interplay among intrinsic charge, spin, orbital, and lattice. As a fundamental basis of heteroepitaxial thin film growth, interfacial strain can be used to design materials that exhibit new phenomena beyond their conventional forms. Here, we report a strain-driven self-assembly of bismuth-based supercell (SC) with a two-dimensional (2D) layered structure. With combined experimental analysis and first-principles calculations, we investigated the full SC structure and elucidated the fundamental growth mechanism achieved by the strain-enabled self-assembled atomic layer stacking. The unique SC structure exhibits room-temperature ferroelectricity, enhanced magnetic responses, and a distinct optical bandgap from the conventional double perovskite structure. This study reveals the important role of interfacial strain modulation and atomic rearrangement in self-assembling a layered singe-phase multiferroic thin film, which opens up a promising avenue in the search for and design of novel 2D layered complex oxides with enormous promise.

  13. Glyconectin glycans as the self-assembling nano-molecular-velcrosystem mediating self-nonself recognition and adhesion implicated in evolution of multicellularity.

    PubMed

    Misevic, Gradimir N; Misevic, Nikola; Popescu, Octavian

    2012-01-01

    The goal of this chapter is to make a specific contribution about glyconectin glycan as the self-assembling nano-molecular-velcro system mediating initial steps of self-nonself recognition and cell adhesion in Porifera, the first descendants of the most simple primordial multicellular organisms. Two original findings will be described: (i) Velcro like concept based on highly polyvalent and specific intermolecular glycan to glycan associations with extremely low affinity of the single binding site and (ii) novel structures of the large and newly emerging family of glyconectin like glycan molecules. The emphasis will be put on the interdisciplinary approach for studying structure to function relationship at the different size scale levels by combining the knowledge and technologies (instrumentation and methods) of physics, chemistry, biology and mathematics. Applying such strategy which is crossing the boundaries of different science disciplines enabled us to develop a new Atomic Force Microscopy (AFM) based nano-bio-technology and perform the first quantitative measurements of intermolecular binding forces at the single molecular level under physiological conditions. We propose that nano-velcro systems of the glyconectin glycans, which are the constituents on the cell surface that are the most exposed to the environment, were responsible for the molecular self-nonself recognition and adhesion processes that underpinned the emergence of multicellular life forms.

  14. Hydrogen bonded helices: Synthesis, crystal structure and self-assembled microtubes

    NASA Astrophysics Data System (ADS)

    Mosae Selvakumar, P.; Suresh, E.; Subramanian, P. S.

    2009-02-01

    Dicarboxylic bola-shaped compounds 1- 3, possessing phthalyl head groups and diol spacers are synthesized and characterized. Keeping phthalyl head group common for all three diester-dicarboxylic acids, the spacer moiety is systematically altered by two and four carbon atoms in 1 and 2, 3, respectively. The flexible spacer moiety ethane-1,2-diol in compound 1 is replaced by cis-but-2-ene-1,4-diol and 1,4-butane diol in 2 and 3, respectively, to study the effect on the morphology of the microcrystal grown on them. Thus compound 2 and 3 though posses four carbon atoms in their respective spacer moiety, they differ by their rigidity. The single crystal X-ray structure obtained for 1, 2 and 3 indicates the formation of self-assembled single stranded helical structure mediated through O-H…O interaction of the end carboxylic acids. Interestingly compound 1 self-assembled into microtubes in ethanol:water solvent mixture. The solvent and the O-H…O; C-H…O interaction combinedly play crucial role in molecular self-assembly process and defines the morphology for 1 into "microtube" whereas 2 and 3 forming "bar" fails to produce such tubular texture though their respective crystal structure shows single stranded helices. The role of weak C-H...O interaction, incorporation of rigid spacer and various other factors such as polarity of the solvents are discussed in detail to explore the difference in the morphology.

  15. A Filled-Honeycomb-Structured Crystal Formed by Self-Assembly of a Janus Polyoxometalate-Silsesquioxane (POM-POSS) Co-Cluster.

    PubMed

    Ma, Chi; Wu, Han; Huang, Zi-Han; Guo, Ruo-Hai; Hu, Min-Biao; Kübel, Christian; Yan, Li-Tang; Wang, Wei

    2015-12-21

    Clusters with diverse structures and functions have been used to create novel cluster-assembled materials (CAMs). Understanding their self-assembly process is a prerequisite to optimize their structure and function. Herein, two kinds of unlike organo-functionalized inorganic clusters are covalently linked by a short organic tether to form a dumbbell-shaped Janus co-cluster. In a mixed solvent of acetonitrile and water, it self-assembles into a crystal with a honeycomb superstructure constructed by hexagonal close-packed cylinders of the smaller cluster and an orderly arranged framework of the larger cluster. Reconstruction of these structural features via coarse-grained molecular simulations demonstrates that the cluster crystallization and the nanoscale phase separation between the two incompatible clusters synergistically result in the unique nano-architecture. Overall, this work opens up new opportunities for generating novel CAMs for advanced future applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Structural and optical properties of self-assembled chains of plasmonic nanocubes

    SciTech Connect

    Klinkova, Anna; Gang, Oleg; Therien-Aubin, Heloise; Ahmed, Aftab; Nykypanchuk, Dmytro; Choueiri, Rachelle M.; Gagnon, Brandon; Muntyanu, Anastasiya; Walker, Gilbert C.; Kumacheva, Eugenia

    2014-10-10

    Solution-based linear self-assembly of metal nanoparticles offers a powerful strategy for creating plasmonic polymers, which, so far, have been formed from spherical nanoparticles and nanorods. Here, we report linear solution-based self-assembly of metal nanocubes (NCs), examine the structural characteristics of the NC chains and demonstrate their advanced optical characteristics. Predominant face-to-face assembly of large NCs coated with short polymer ligands led to a larger volume of hot spots in the chains, a nearly uniform E-field enhancement in the gaps between co-linear NCs and a new coupling mode for NC chains, in comparison with chains of nanospheres with similar dimensions, composition and surface chemistry. The NC chains exhibited a stronger surface enhanced Raman scattering (SERS) signal, in comparison with linear assemblies of nanospheres. The experimental results were in agreement with finite difference time domain (FDTD) simulations.

  17. Structural and optical properties of self-assembled chains of plasmonic nanocubes

    DOE PAGES

    Klinkova, Anna; Gang, Oleg; Therien-Aubin, Heloise; ...

    2014-10-10

    Solution-based linear self-assembly of metal nanoparticles offers a powerful strategy for creating plasmonic polymers, which, so far, have been formed from spherical nanoparticles and nanorods. Here, we report linear solution-based self-assembly of metal nanocubes (NCs), examine the structural characteristics of the NC chains and demonstrate their advanced optical characteristics. Predominant face-to-face assembly of large NCs coated with short polymer ligands led to a larger volume of hot spots in the chains, a nearly uniform E-field enhancement in the gaps between co-linear NCs and a new coupling mode for NC chains, in comparison with chains of nanospheres with similar dimensions, compositionmore » and surface chemistry. The NC chains exhibited a stronger surface enhanced Raman scattering (SERS) signal, in comparison with linear assemblies of nanospheres. The experimental results were in agreement with finite difference time domain (FDTD) simulations.« less

  18. Structure formation in binary mixtures of lipids and detergents: self-assembly and vesicle division.

    PubMed

    Noguchi, Hiroshi

    2013-01-14

    Self-assembly dynamics in binary surfactant mixtures and structure changes of lipid vesicles induced by detergent solution are studied using coarse-grained molecular simulations. Disk-shaped micelles, the bicelles, are stabilized by detergents surrounding the rim of a bilayer disk of lipids. The self-assembled bicelles are considerably smaller than bicelles formed from vesicle rupture, and their size is determined by the concentrations of lipids and detergents and the interactions between the two species. The detergent-adsorption induces spontaneous curvature of the vesicle bilayer and results in vesicle division into two vesicles or vesicle rupture into worm-like micelles. The division occurs mainly via the inverse pathway of the modified stalk model. For large spontaneous curvature of the monolayers of the detergents, a pore is often opened, thereby leading to vesicle division or worm-like micelle formation.

  19. Structure formation in binary mixtures of lipids and detergents: Self-assembly and vesicle division

    NASA Astrophysics Data System (ADS)

    Noguchi, Hiroshi

    2013-01-01

    Self-assembly dynamics in binary surfactant mixtures and structure changes of lipid vesicles induced by detergent solution are studied using coarse-grained molecular simulations. Disk-shaped micelles, the bicelles, are stabilized by detergents surrounding the rim of a bilayer disk of lipids. The self-assembled bicelles are considerably smaller than bicelles formed from vesicle rupture, and their size is determined by the concentrations of lipids and detergents and the interactions between the two species. The detergent-adsorption induces spontaneous curvature of the vesicle bilayer and results in vesicle division into two vesicles or vesicle rupture into worm-like micelles. The division occurs mainly via the inverse pathway of the modified stalk model. For large spontaneous curvature of the monolayers of the detergents, a pore is often opened, thereby leading to vesicle division or worm-like micelle formation.

  20. Programmed Self-Assembly of a Biochemical and Magnetic Scaffold to Trigger and Manipulate Microtubule Structures.

    PubMed

    Ducasse, Rémi; Wang, Wei-An; Navarro, Marina Garcia-Jove; Debons, Nicolas; Colin, Alexandra; Gautier, Jérémie; Guigner, Jean-Michel; Guyot, François; Gueroui, Zoher

    2017-09-12

    Artificial bio-based scaffolds offer broad applications in bioinspired chemistry, nanomedicine, and material science. One current challenge is to understand how the programmed self-assembly of biomolecules at the nanometre level can dictate the emergence of new functional properties at the mesoscopic scale. Here we report a general approach to design genetically encoded protein-based scaffolds with modular biochemical and magnetic functions. By combining chemically induced dimerization strategies and biomineralisation, we engineered ferritin nanocages to nucleate and manipulate microtubule structures upon magnetic actuation. Triggering the self-assembly of engineered ferritins into micrometric scaffolds mimics the function of centrosomes, the microtubule organizing centres of cells, and provides unique magnetic and self-organizing properties. We anticipate that our approach could be transposed to control various biological processes and extend to broader applications in biotechnology or material chemistry.

  1. Polymer Physics Prize Lecture: Self-assemblies of Giant Molecular Shape Amphiphiles as a New Platform for Engineering Structures with Sub-Nanometer Feature Sizes

    NASA Astrophysics Data System (ADS)

    Cheng, Stephen Z. D.

    2013-03-01

    Utilizing nano-building blocks rather than atoms to construct and engineer new structures is a fresh approach to design and develop functional materials for the purpose of transferring and amplifying microscopic functionality to macroscopic materials' property. As one of the important elements of these nano-building blocks, giant molecular shape amphiphiles (GMSAs) provide a latest platform for generating self-assembled ordered structures at nanometer scale, which are stabilized by collective physical bonds (such as collective hydrogen bonding). In this talk, two topics will be focused on. First, composed of functionalized hydrophilic molecular nanoparticles as the heads with rigid shape and fixed volume, and tethered polymer chains as the tails (such as giant molecular surfactants and lipids and other topologies), these GMSAs of various architectures can self-assemble into highly diversified, thermodynamically stable microstructures at sub-10 nm length scale in the bulk, thin film and solution states. Second, GMSAs could also be constructed solely from nanoparticles interconnected via different numbers of the rigid linkages in specific symmetry, simulating the overall shapes of small molecules but with sizes that are one-order of magnitude larger in length and three-order of magnitude larger in volume. Giant crystal structures can then be obtained from this class of ``giant molecules'' via supramolecular crystallization. These findings are not only scientifically intriguing in understanding the physical principles underlying their self-assembly, but also technologically relevant in industrial applications.

  2. Nanoscale self-assembly of starch: Phase relations, formation, and structure

    NASA Astrophysics Data System (ADS)

    Creek, John A.

    This project has been undertaken to develop a fundamental understanding of the spherulitic self-assembly of starch polymers from aqueous solution, both as a model for starch granule initiation in vivo and as a biologically-inspired material with applications in the food and pharmaceutical industries. Botanical starches were observed to form semi-crystalline spherulites from aqueous solution when cooled after a high temperature treatment, and the processes resulting in spherulite formation were investigated. Based on the influence of cooling rate on spherulite formation from a botanical starch, liquid-liquid demixing in competition with crystallization was proposed as the mechanism leading to spherulite formation (summarized in a hypothetical phase diagram). Study of amylose and amylopectin self-assembly demonstrated that the linear polymer plays the primary role in forming spherulites. As a result, the roles of degree of polymerization, concentration, and thermal processing conditions on amylose self-assembly were explored. Thermal properties, final system morphology, and crystalline allomorph were characterized. In all cases the experimental findings supported the proposed phase diagram. Finally, the crystalline nanostructure of the spherulites was probed using atomic force microscopy (AFM), revealing a seemingly universal level of structure in crystalline starch materials. This was compared to an existing model of crystallization for synthetic polymers involving a transitional liquid crystalline-like ordering---a comparison that makes sense in light of the known helical structure of starch.

  3. Drying-Mediated Self-Assembly of Highly Ordered Complex Structures: From Polymers to Nanoparticles

    NASA Astrophysics Data System (ADS)

    Lin, Zhiqun

    2009-03-01

    Drying of a sessile drop containing nonvolatile solutes readily self-assembles into a number of concentric ``coffee rings'' by repetitive ``stick-slip'' motion of the three-phase contact line. However, due mainly to lack of control over the evaporation process of the drop, the challenge remains to use evaporative self-assembly to rationally ``synthesize'' ``coffee rings'' of different shapes and sizes of high regularity and fidelity. Here, we report a facile, robust, and one-step evaporation method for producing in a precisely controllable manner versatile microstructures possessing high regularity, dispensing with the need for lithographic techniques and externally applied fields. Polymer or nanocrystal solutions are confined in a simple geometry comprised of a curved surface placed upon a flat substrate. By changing the shape of the upper surface of the imposed geometry, the controlled, evaporative self-assembly of polymer or nanocrystal solutions yields a variety of complex, intriguing, and well-ordered structures over large areas. As such, this method represents a significant advance in creating regularly organized, complex structures with potential applications in microelectronics, optoelectronics, and biotechnology, among other areas.

  4. Small Angle Neutron Scattering (SANS) Studies on the Structural Evolution of Pyromellitamide Self-assembled Gels

    SciTech Connect

    Scott, Jamieson; Tong, Katie; William, Hamilton; He, Lilin; James, Michael; Thordarson, Pall; Boukhalfa, Sofiane

    2014-10-31

    The kinetics of aggregation of two pyromellitamide gelators; tetrabutyl- (C4) and tetrahexylpyromellitamide (C6), in deuterated cyclohexane has been investigated by small angle neutron scattering (SANS) for up to six days. The purpose of this study was to improve our understanding of how self-assembled gels are formed. Short-term (< 3 hour) time scales revealed multiple phases with the data for the tetrabutylpyromellitamide C4 indicating one dimensional stacking and aggregation corresponding to a multi-fiber braided cluster arrangement that is about 35 Å in diameter. The corresponding tetrahexylpyromellitamide C6 data suggests that the C6 also forms one-dimensional stacks but that these aggregate to a thicker multi-fiber braided cluster that have a diameter of 61.8 Å. Over a longer period of time, the radius, persistence length and contour length all continue to increase in 6 days after cooling. This data suggests that structural changes in self-assembled gels occur over a period exceeding several days and that fairly subtle changes in the structure (e.g. tail-length) can influence the packing of molecules in self-assembled gels on the single-to-few fiber bundle stage.

  5. Small Angle Neutron Scattering (SANS) Studies on the Structural Evolution of Pyromellitamide Self-assembled Gels

    DOE PAGES

    Scott, Jamieson; Tong, Katie; William, Hamilton; ...

    2014-10-31

    The kinetics of aggregation of two pyromellitamide gelators; tetrabutyl- (C4) and tetrahexylpyromellitamide (C6), in deuterated cyclohexane has been investigated by small angle neutron scattering (SANS) for up to six days. The purpose of this study was to improve our understanding of how self-assembled gels are formed. Short-term (< 3 hour) time scales revealed multiple phases with the data for the tetrabutylpyromellitamide C4 indicating one dimensional stacking and aggregation corresponding to a multi-fiber braided cluster arrangement that is about 35 Å in diameter. The corresponding tetrahexylpyromellitamide C6 data suggests that the C6 also forms one-dimensional stacks but that these aggregate tomore » a thicker multi-fiber braided cluster that have a diameter of 61.8 Å. Over a longer period of time, the radius, persistence length and contour length all continue to increase in 6 days after cooling. This data suggests that structural changes in self-assembled gels occur over a period exceeding several days and that fairly subtle changes in the structure (e.g. tail-length) can influence the packing of molecules in self-assembled gels on the single-to-few fiber bundle stage.« less

  6. Structure of biological graded refractive index materials, and possible routes to self-assembly

    NASA Astrophysics Data System (ADS)

    Cai, Jing; Heiney, Paul; Sweeney, Alison

    2014-03-01

    For a camera-like eye, a spherical lens with a radially graded refractive index is required for high-quality image formation. Squids have evolved this lens design, and the index gradient results from variation in the density of protein in the lens from the center (70% packing fraction) to the periphery (2% packing fraction). However, density fluctuations must also remain low in all regions to maintain lens transparency. Squids have achieved this by an evolutionary radiation of the isoforms of one protein, S-crystallin; different protein isoforms are synthesized in different radial positions of the lens. We studied whether these proteins self-assemble into the observed gradient index material. X-ray scattering was performed on both intact lenses and solubilized lens protein. Our results show that protein packing is organized, and that the organization changes with radial position. We identify possible self-assembled routes to the observed structures via the predicted interactions between the proteins. Our study may provide insights into engineering new self-assembling graded refractive index materials.

  7. Structural and thermodynamic analysis of modified nucleosides in self-assembled DNA cross-tiles.

    PubMed

    Hakker, Lauren; Marchi, Alexandria N; Harris, Kimberly A; LaBean, Thomas H; Agris, Paul F

    2014-01-01

    DNA Holliday junctions are important natural strand-exchange structures that form during homologous recombination. Immobile four-arm junctions, analogs to Holliday junctions, have been designed to self-assemble into cross-tile structures by maximizing Watson-Crick base pairing and fixed crossover points. The cross-tiles, self-assembled from base pair recognition between designed single-stranded DNAs, form higher order lattice structures through cohesion of self-associating sticky ends. These cross-tiles have 16 unpaired nucleosides in the central loop at the junction of the four duplex stems. The importance of the centralized unpaired nucleosides to the structure's thermodynamic stability and self-assembly is unknown. Cross-tile DNA nanostructures were designed and constructed from nine single-stranded DNAs with four shell strands, four arms, and a central loop containing 16 unpaired bases. The 16 unpaired bases were either 2'-deoxyribothymidines, 2'-O-methylribouridines, or abasic 1',2'-dideoxyribonucleosides. Thermodynamic profiles and structural base-stacking contributions were assessed using UV absorption spectroscopy during thermal denaturation and circular dichroism spectroscopy, respectively, and the resulting structures were observed by atomic force microscopy. There were surprisingly significant changes in the thermodynamic and structural properties of lattice formation as a result of altering only the 16 unpaired, centralized nucleosides. The 16 unpaired 2'-O-methyluridines were stabilizing and produced uniform tubular structures. In contrast, the abasic nucleosides were destabilizing producing a mixture of structures. These results strongly indicate the importance of a small number of centrally located unpaired nucleosides within the structures. Since minor modifications lead to palpable changes in lattice formation, DNA cross-tiles present an easily manipulated structure convenient for applications in biomedical and biosensing devices.

  8. Structure-property Relationships for Methyl-terminated Alkyl Self-assembled Monolayers

    SciTech Connect

    F DelRio; D Rampulla; C Jaye; G Stan; R Gates; D Fischer; R Cook

    2011-12-31

    Structure-property relationships for methyl-terminated alkyl self-assembled monolayers (SAMs) are developed using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and atomic force microscopy (AFM). NEXAFS C K-edge spectra are used to compute the dichroic ratio, which provides a quantitative measure of the molecular structure. AFM data are analyzed with an elastic adhesive contact model, modified by a first-order elastic perturbation method to include substrate effects, to extract the monolayer mechanical properties. Using this approach, the measured mechanical properties are not influenced by the substrate, which allows universal structure-property relationships to be developed for methyl-terminated alkyl SAMs.

  9. Immobilization of self-assembled pre-dispersed nano-TiO2 onto montmorillonite and its photocatalytic activity.

    PubMed

    Zhang, Tingting; Luo, Yuan; Jia, Bing; Li, Yan; Yuan, Lingling; Yu, Jiang

    2015-06-01

    The immobilization of pre-dispersed TiO2 colloids onto the external surface of the clay mineral montmorillonite (Mt) was accomplished and regulated via a self-assembly method employing the cationic surfactant cetyltrimethylammonium bromide (CTAB). The role of CTAB in the synthesis process was investigated by preparing a series of TiO2-CTAB-Mt composites (TCM) with various CTAB doses. The results indicated that a uniform and continuous TiO2 film was deposited on the external surface of montmorillonite in the composite synthesized with 0.1 wt.% of CTAB, and the TCM nano-composites showed much higher values for specific surface area, average pore size and pore volume than the raw montmorillonite clay. Then, the formed TCM materials were applied in photocatalytic degradation of 2,4-dichlorophenol (2,4-DCP) in aqueous solution. The degradation efficiency reached as high as 94.7%. Based on the degradation intermediates benezoquinone, fumaric acid and oxalic acid identified by LC-MS analysis, a mechanism for the photocatalytic oxidation of 2,4-DCP on TiO2/Mt nano-composites is proposed.

  10. Self-assembled Ag nanoparticle network passivated by a nano-sized ZnO layer for transparent and flexible film heaters

    SciTech Connect

    Seo, Ki-Won; Kim, Han-Ki; Kim, Min-Yi; Chang, Hyo-Sik

    2015-12-15

    We investigated a self-assembled Ag nanoparticle network electrode passivated by a nano-sized ZnO layer for use in high-performance transparent and flexible film heaters (TFFHs). The low temperature atomic layer deposition of a nano-sized ZnO layer effectively filled the uncovered area of Ag network and improved the current spreading in the self-assembled Ag network without a change in the sheet resistance and optical transmittance as well as mechanical flexibility. The time-temperature profiles and heat distribution analysis demonstrate that the performance of the TFTH with the ZnO/Ag network is superior to that of a TFFH with Ag nanowire electrodes. In addition, the TFTHs with ZnO/Ag network exhibited better stability than the TFFH with a bare Ag network due to the effective current spreading through the nano-sized ZnO layer.

  11. Surface Nano-Structuring by Adsorption and Chemical Reactions

    PubMed Central

    Tanaka, Ken-ichi

    2010-01-01

    Nano-structuring of the surface caused by adsorption of molecules or atoms and by the reaction of surface atoms with adsorbed species is reviewed from a chemistry viewpoint. Self-assembly of adsorbed species is markedly influenced by weak mutual interactions and the local strain of the surface induced by the adsorption. Nano-structuring taking place on the surface is well explained by the notion of a quasi-molecule provided by the reaction of surface atoms with adsorbed species. Self-assembly of quasi-molecules by weak internal bonding provides quasi-compounds on a specific surface. Various nano-structuring phenomena are discussed: (i) self-assembly of adsorbed molecules and atoms; (ii) self-assembly of quasi-compounds; (iii) formation of nano-composite surfaces; (iv) controlled growth of nano-materials on composite surfaces. Nano-structuring processes are not always controlled by energetic feasibility, that is, the formation of nano-composite surface and the growth of nano-particles on surfaces are often controlled by the kinetics. The idea of the “kinetic controlled molding” might be valuable to design nano-materials on surfaces. PMID:28883340

  12. Novel 3D nano-antennas of self-assembled zinc oxide on silver nanowires

    NASA Astrophysics Data System (ADS)

    Sanchez, John Eder

    The manipulation of geometrical and structural arrangement of nano-devices, especially nanoantennas (nantennnas), is highly desirable for a precise controlling and monitoring of the multidirectional radiation pattern generated from the active elements on nanoantenna (nantenna) applications. Here we report the epitaxial growing of ZnO nanorods preferentially oriented along the [0001] direction on pentagonal faces (010) of Ag nanowires (Ag/ZnO ). The Ag/ZnO nanosystem, resembling an hierarchal aerial antenna, was obtained using an innovative microwave irradiation process. There, the combination of chemical synthesis along accelerated micro wave irradiation digestion process, allows us to control precisely the morphology and distribution of the Ag/ZnO nanostructure. Because of the high order arrangement exhibited for the nanosystem as well as high rate of reproducibility in the production process, we opted to tested the nanostructures in a set of experiments ranging from the bulk properties down to in-situ nanoscale; in order to gain valuable information from the experiments and with the aim to give a real application to the nanomaterial. In this order, first, we described the far and near electric field generated for the nantenna obtained from electrical radiation patterns resulting from phase map reconstruction using off-axis electron holography. It is important to notice that knowing the properties at nanoscale level, it will give key insight of mechanism through which the metal-semiconductor (Ag-ZnO) behaves in opto-electronic applications. In fact, using electric numerical approximations methods for a finite number of ZnO nanorods on Ag nanowires it was shown that the electric radiation intensities maps match closely the experimental results obtained with electron holography. Additionally, to reinforce the understanding of how the metal-semiconductor (Ag-ZnO) nanostructures could be used as an active element on photo-signal reception/transmitter generation it was

  13. Strip-Pattern-Spheres Self-Assembled from Polypeptide-Based Polymer Mixtures: Structure and Defect Features

    NASA Astrophysics Data System (ADS)

    Zhu, Xingyu; Guan, Zhou; Lin, Jiaping; Cai, Chunhua

    2016-07-01

    We found that poly(γ-benzyl-L-glutamate)-block-poly(ethylene glycol) (PBLG-b-PEG) rod-coil block copolymers and polystyrene (PS) homopolymers can cooperatively self-assemble into nano-spheres with striped patterns on their surfaces (strip-pattern-spheres) in aqueous solution. With assistance of dissipative particle dynamics simulation, it is discovered that the PS homopolymers form a spherical template core and the PBLG-b-PEG block copolymers assemble into striped patterns on the spherical surface. The hydrophobic PBLG rods are packed orderly in the strips, while the hydrophilic PEG blocks stabilize the strip-pattern-spheres in solution. Defects such as dislocations and disclinations can be observed in the striped patterns. Self-assembling temperature and sphere radius are found to affect defect densities in the striped patterns. A possible mechanism is proposed to illustrate how PBLG-b-PEG and PS cooperatively self-assemble into hierarchical spheres with striped patterns on surfaces.

  14. Preparation of a multifunctional verapamil-loaded nano-carrier based on a self-assembling PEGylated prodrug.

    PubMed

    Zhao, Dongping; Liu, Na; Shi, Kemei; Wang, Xiaojuan; Wu, Guolin

    2015-11-01

    In an effort to prove the inherent side effects of doxorubicin (DOX) and potentially revoke the effects of drug resistance exhibited by cancer cells, we have designed a multifunctional DOX-delivery nano-carrier system able to encapsulate the drug resistance reversal agent Verapamil HCl (VRP·HCl). Hydrophilic short-chain polyethylene glycol (i.e., mPEG) was covalently linked to hydrophobic DOX and a benzoic imine linkage was used to form a linear amphiphilic PEGylated prodrug, namely mPEG-b-DOX. In aqueous solution, the amphiphilic PEG-b-DOX is able to self-assemble to form stable nanoparticles with a DOX loading content of approximately 40 wt% and a diameter of ∼ 143 nm. The resulting nanoparticles can simultaneously serve as an anticancer drug conjugate and as a drug carrier system. Here, the hydrophilic VRP could be encapsulated into the nano-carriers via a conventional dialysis method. The loading efficiency in mPEG-b-DOX nano-carrier was determined to be 53.97% and the loading content was found to be 7.71 wt%. The VRP-loaded nano-carriers grew slightly in size, to a diameter of ∼ 177 nm. We found that the release of DOX and VRP was much faster at a lower pH value. The biological activity of the nano-carriers were evaluated in vitro and compared with the DOX-loaded system. In doing so we found that the VRP-loaded nano-carrier features a much higher antitumor activity. Furthermore, the combined-system exhibits a significantly enhanced cytotoxicity with an elevated apoptosis rate observed for MCF-7/ADR used as a cell line in this in vitro study. This combinatory system and promising candidate for applications involving DOX chemotherapy proved to be easy to prepare and could be characterized in terms of biocompatibility, biodegradability, loading capacity, pH responsiveness and reversal of drug resistance. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Structure of self-assembled Mn atom chains on Si(001)

    NASA Astrophysics Data System (ADS)

    Villarreal, Renan; Longobardi, Maria; Koester, Sigrun A.; Kirkham, Christopher J.; Bowler, David; Renner, Christoph

    Mn has been found to self-assemble into atomic chains running perpendicular to the surface dimer reconstruction on Si(001). They differ from other atomic chains by a striking asymmetric appearance in filled state scanning tunneling microscopy (STM) images. This has prompted complicated structural models involving up to three Mn atoms per chain unit. Combining STM, atomic force microscopy and density functional theory we find that a simple necklace-like chain of single Mn atoms reproduces all their prominent features, including their asymmetry not captured by current models. The upshot is a remarkably simpler structure for modelling the electronic and magnetic properties of Mn atom chains on Si(001).

  16. Structure of Self-Assembled Mn Atom Chains on Si(001)

    NASA Astrophysics Data System (ADS)

    Villarreal, R.; Longobardi, M.; Köster, S. A.; Kirkham, Ch. J.; Bowler, D.; Renner, Ch.

    2015-12-01

    Mn has been found to self-assemble into atomic chains running perpendicular to the surface dimer reconstruction on Si(001). They differ from other atomic chains by a striking asymmetric appearance in filled state scanning tunneling microscopy (STM) images. This has prompted complicated structural models involving up to three Mn atoms per chain unit. Combining STM, atomic force microscopy, and density functional theory we find that a simple necklacelike chain of single Mn atoms reproduces all their prominent features, including their asymmetry not captured by current models. The upshot is a remarkably simpler structure for modeling the electronic and magnetic properties of Mn atom chains on Si(001).

  17. Self-assembled ferromagnetic and superparamagnetic structures of hybrid Fe block copolymers

    NASA Astrophysics Data System (ADS)

    Sarantopoulou, E.; Kovač, J.; Pispas, S.; Kobe, S.; Kollia, Z.; Cefalas, A. C.

    2008-10-01

    Self-assembled 2D structures on thin films of block copolymers/Fe hybrid materials were fabricated on Si/Ta substrates, either by wet chemistry or laser irradiation at 157 nm. The polymer exhibits micelle-like structures with average dimensions of 5-10 nm and 30-50 nm for light and chemically reduced films respectively. For the laser processed films, SQUID measurements reveal a ferromagnetic response at 5 K, and 100 Oe coercivity was obtained for 2:1 iron concentration. For chemically reduced films, on the other hand, a superparamagnetic response with near zero coercivity at 5 K was obtained.

  18. Structure and Property Changes in Self-Assembled Lubricin Layers Induced by Calcium Ion Interactions.

    PubMed

    Greene, George W; Thapa, Rajiv; Holt, Stephen A; Wang, Xiaoen; Garvey, Christopher J; Tabor, Rico F

    2017-03-14

    Lubricin (LUB) is a "mucin-like" glycoprotein found in synovial fluids and coating the cartilage surfaces of articular joints, which is now generally accepted as one of the body's primary boundary lubricants and antiadhesive agents. LUB's superior lubrication and antiadhesion are believed to derive from its unique interfacial properties by which LUB molecules adhere to surfaces (and biomolecules, such as hyaluronic acid and collagen) through discrete interactions localized to its two terminal end domains. These regionally specific interactions lead to self-assembly behavior and the formation of a well-ordered "telechelic" polymer brush structure on most substrates. Despite its importance to biological lubrication, detailed knowledge on the LUB's self-assembled brush structure is insufficient and derived mostly from indirect and circumstantial evidence. Neutron reflectometry (NR) was used to directly probe the self-assembled LUB layers, confirming the polymer brush architecture and resolving the degree of hydration and level of surface coverage. While attempting to improve the LUB contrast in the NR measurements, the LUB layers were exposed to a 20 mM solution of CaCl2, which resulted in a significant change in the polymer brush structural parameters consisting of a partial denaturation of the surface-binding end-domain regions, partial dehydration of the internal mucin-domain "loop", and collapse of the outer mucin-domain surface region. A series of atomic force microscopy measurements investigating the LUB layer surface morphology, mechanical properties, and adhesion forces in phosphate-buffered saline and CaCl2 solutions reveal that the structural changes induced by calcium ion interactions also significantly alter key properties, which may have implications to LUB's efficacy as a boundary lubricant and wear protector in the presence of elevated calcium ion concentrations.

  19. Self-Assembled, Iridescent, Crustacean-Mimetic Nanocomposites with Tailored Periodicity and Layered Cuticular Structure.

    PubMed

    Wang, Baochun; Walther, Andreas

    2015-11-24

    Natural high-performance materials inspire the pursuit of ordered hard/soft nanocomposite structures at high fractions of reinforcements and with balanced molecular interactions. Herein, we develop a facile, waterborne self-assembly pathway to mimic the multiscale cuticle structure of the crustacean armor by combining hard reinforcing cellulose nanocrystals (CNCs) with soft poly(vinyl alcohol) (PVA). We show iridescent CNC nanocomposites with cholesteric liquid-crystal structure, in which different helical pitches and photonic band gaps can be realized by varying the CNC/PVA ratio. We further show that multilayered crustacean-mimetic materials with tailored periodicity and layered cuticular structure can be obtained by sequential preparation pathways. The transition from a cholesteric to a disordered structure occurs for a critical polymer concentration. Correspondingly, we find a transition from stiff and strong mechanical behavior to materials with increasing ductility. Crack propagation studies using scanning electron microscopy visualize the different crack growth and toughening mechanisms inside cholesteric nanocomposites as a function of the interstitial polymer content for the first time. Different extents of crack deflection, layered delamination, ligament bridging, and constrained microcracking can be observed. Drawing of highly plasticized films sheds light on the mechanistic details of the transition from a cholesteric/chiral nematic to a nematic structure. The study demonstrates how self-assembly of biobased CNCs in combination with suitable polymers can be used to replicate a hierarchical biological structure and how future design of these ordered multifunctional nanocomposites can be optimized by understanding mechanistic details of deformation and fracture.

  20. Self-Assembled Silica Nano-Composite Polymer Electrolytes: Synthesis, Rheology & Electrochemistry

    SciTech Connect

    Khan, Saad A.: Fedkiw Peter S.; Baker, Gregory L.

    2007-01-24

    The ultimate objectives of this research are to understand the principles underpinning nano-composite polymer electrolytes (CPEs) and facilitate development of novel CPEs that are low-cost, have high conductivities, large Li+ transference numbers, improved electrolyte-electrode interfacial stability, yield long cycle life, exhibit mechanical stability and are easily processable. Our approach is to use nanoparticulate silica fillers to formulate novel composite electrolytes consisting of surface-modified fumed silica nano-particles in polyethylene oxides (PEO) in the presence of lithium salts. We intend to design single-ion conducting silica nanoparticles which provide CPEs with high Li+ transference numbers. We also will develop low-Mw (molecular weight), high-Mw and crosslinked PEO electrolytes with tunable properties in terms of conductivity, transference number, interfacial stability, processability and mechanical strength

  1. Chelating DTPA amphiphiles: ion-tunable self-assembly structures and gadolinium complexes.

    PubMed

    Moghaddam, Minoo J; de Campo, Liliana; Kirby, Nigel; Drummond, Calum J

    2012-10-05

    A series of chelating amphiphiles and their gadolinium (Gd(III)) metal complexes have been synthesized and studied with respect to their neat and lyotropic liquid crystalline phase behavior. These amphiphiles have the ability to form ion-tunable self-assembly nanostructures and their associated Gd(III) complexes have potential as magnetic resonance imaging (MRI) contrast enhancement agents. The amphiphiles are composed of diethylenetriaminepentaacetic acid (DTPA) chelates conjugated to one or two oleyl chain(s) (DTPA-MO and DTPA-BO), or isoprenoid-type chain(s) of phytanyl (DTPA-MP and DTPA-BP). The thermal phase behavior of the neat amphiphiles was examined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and cross polarizing optical microscopy (POM). Self-assembly of neat amphiphiles and their associated Gd complexes, as well as their lyotropic phase behavior in water and sodium acetate solutions of different ionic strengths, were examined by POM and small and wide angle X-ray scattering (SWAXS). All neat amphiphiles exhibited lamellar structures. The non-complexed amphiphiles showed a variety of lyotropic phases depending on the number and nature of the hydrophobic chain in addition to the ionic state of the hydration. Upon hydration with increased Na-acetate concentration and the subtle changes in the effective headgroup size, the interfacial curvature of the amphiphile increased, altering the lyotropic liquid crystalline structures towards higher order mesophases such as the gyroid (Ia3d) bicontinuous cubic phase. The chelation of Gd with the DTPA amphiphiles resulted in lamellar crystalline structures for all the neat amphiphiles. Upon hydration with water, the Gd-complexed mono-conjugates formed micellar or vesicular self-assemblies, whilst the bis-conjugates transformed only partially into lyotropic liquid crystalline mesophases.

  2. Template assisted self-assembly of iron oxide nanoparticles: An x-ray structural analysis

    NASA Astrophysics Data System (ADS)

    Mishra, D.; Zabel, H.; Ulyanov, S. V.; Romanov, V. P.; Uzdin, V. M.

    2014-02-01

    We have fabricated by e-beam lithography periodic arrays of rectangular shaped trenches of different widths into Si substrates. The trenches were filled with iron oxide nanoparticles, 20 nm in diameter, by spin-coating them onto the Si substrate. The trenches have the purpose to assist the self-assembly of the iron oxide nanoparticles. Using x-ray scattering techniques, we have analyzed the structure factor of the trenches before and after filling in order to determine the filling factor. We present a theoretical analysis of the x-ray scattering function within the distorted-wave Born approximation and we present a quantitative comparison between theory and experiment.

  3. Structural Studies of Liquid Surface Self-Assembled Iron Oxide Nanoparticle Monolayers

    NASA Astrophysics Data System (ADS)

    Stanley, Jacob

    The phenomenon of self--assembly has become increasingly relevant due to the role it can play in nanofabrication and the emergence of macro-scale structure. This phenomenon has been seen in a broad range of material systems. For example, iron oxide nanoparticles undergo self-assembly into well-ordered monolayer films of macroscopic size at an air-water interface. It is this system that is the topic of the work herein. The self-assembly process is the result of the van der Waals forces between the constituent particles. For roughly spherical particles the monolayer is a 2D hexagonal close packed lattice. Using a variety of X-Ray scattering techniques including Grazing Incidence X-Ray Diffraction (GID), X-Ray Reflectivity (XR), and Grazing Incidence X-Ray Off-Specular Scattering (GIXOS) the structure of some of the emergent characteristics of these films is studied. Namely, the microscale multilayering that occurs when these films are laterally compressed, exhibits varying morphologies which depend on the size of the constituent particles. Additionally, when these films are formed from bi-dispersed mixtures containing 10 and 20 nm particles, the particles phase separate into well--ordered patches during the self-assembly process. The domain sizes of these phase separated regions are at most a factor of 2-3 times smaller than that of a film comprising only mono-dispersed particles, and their degree of disorder is comparable. Finally, using these iron oxide nanoparticle monolayers as a test system, a novel analysis is demonstrated that allows a direct comparison between Scanning Electron Microscopy (SEM) of ex-situ films and GID measurements of in-situ films: the results demonstrate that structural information comparable to that contained in the GID measurements can be obtained by Fourier transform analysis of the SEM images taken of the film after it has been transferred to a silicon substrate. Furthermore this comparison suggests that the Langmuir-Schaefer method of

  4. Structure and dynamics of optically directed self-assembly of nanoparticles

    PubMed Central

    Roy, Debjit; Mondal, Dipankar; Goswami, Debabrata

    2016-01-01

    Self-assembly of nanoparticles leading to the formation of colloidal clusters often serves as the representative analogue for understanding molecular assembly. Unravelling the in situ structure and dynamics of such clusters in liquid suspensions is highly challenging. Presently colloidal clusters are first isolated from their generating environment and then their structures are probed by light scattering methods. In order to measure the in situ structure and dynamics of colloidal clusters, we have generated them using the high-repetition-rate femtosecond laser pulse optical tweezer. Since the constituent of our dimer, trimer or tetramer clusters are 250 nm radius two-photon resonant fluorophore coated nanospheres under the optical trap, they inherently produce Two-Photon Fluorescence, which undergo intra-nanosphere Fluorescence Energy Transfer. This unique energy transfer signature, in turn, enables us to visualize structures and orientations of these colloidal clusters during the process of their formation and subsequent dynamics in a liquid suspension. We also show that due to shape-birefringence, orientation and structural control of these colloidal clusters are possible as the polarization of the trapping laser is changed from linear to circular. We thus report important progress in sampling the smallest possible aggregates of nanoparticles, dimers, trimers or tetramers, formed early in the self-assembly process. PMID:27006305

  5. Structural and thermodynamic anaylsis of self-assembled DNA cross-tiles

    NASA Astrophysics Data System (ADS)

    Hakker, Lauren

    A thermodynamic and structural analysis of DNA nanostructures was performed, following the replacement of the unpaired thymine bases within a central loop to determine their effect on the self-assembly process. Specifically this study focused on DNA cross-tile nanostructures. Self-assembly of DNA cross-tiles occurs by means of Watson-crick base-pairing interactions between designed single-stranded DNAs from which lattice structures assemble through sticky-end cohesion. These cross-tile structures were constructed from nine single-stranded DNAs and consisted of a central loop containing 16 unpaired thymine bases, four shell strands, and four arms. Modifications were introduced to replace the central unpaired thymine base loop. The modifications used were ribouridine, 2'-O-methyluridine and abasic. The thermodynamic profile and structural base-stacking contributions were assessed using UV thermal denaturation and circular dichroism, respectively. As a result of altering the unpaired region of the tiles, there were significant changes in the thermodynamic and structural properties of the lattice formation. Therefore disrupting normal lattice formation by altering the unpaired central loop allows for a large possibility of uses for cross-tiles, such as designs for biosensing devices.

  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. Numerical simulation of colloidal self-assembly of super-hydrophobic arachnid cerotegument structures.

    PubMed

    Filippov, Alexander É; Wolff, Jonas O; Seiter, Michael; Gorb, Stanislav N

    2017-10-07

    Certain arachnids exhibit complex coatings of their exoskeleton, consisting of globular structures with complex surface features. This, so-called, cerotegument is formed by a multi-component colloidal secretion that self-assembles and cures on the body surface, and leads to high water repellency. Previous ultrastructural studies revealed the involvement of different glandular cells that contribute different components to the secretion mixture, but the overall process of self-assembly into the complex regular structures observed remained highly unclear. Here we study this process from a theoretical point of view, starting from the so-called Tammes-problem. We show that slight changes of simple parameters lead to a variety of morphologies that are highly similar to the ones observed in the species specific cerotegument structures of whip-spiders. These results are not only important for our understanding of the formation of globular hierarchical structures in nature, but also for the fabrication of novel surface coatings by colloidal lithography. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Activity and lifetime of urease immobilized using layer-by-layer nano self-assembly on silicon microchannels.

    PubMed

    Forrest, Scott R; Elmore, Bill B; Palmer, James D

    2005-01-01

    Urease has been immobilized and layered onto the walls of manufactured silicon microchannels. Enzyme immobilization was performed using layer-by-layer nano self-assembly. Alternating layers of oppositely charged polyelectrolytes, with enzyme layers "encased" between them, were deposited onto the walls of the silicon microchannels. The polycations used were polyethylenimine (PEI), polydiallyldimethylammonium (PDDA), and polyallylamine (PAH). The polyanions used were polystyrenesulfonate (PSS) and polyvinylsulfate (PVS). The activity of the immobilized enzyme was tested by pumping a 1 g/L urea solution through the microchannels at various flow rates. Effluent concentration was measured using an ultraviolet/visible spectrometer by monitoring the absorbance of a pH sensitive dye. The architecture of PEI/PSS/PEI/urease/PEI with single and multiple layers of enzyme demonstrated superior performance over the PDDA and PAH architectures. The precursor layer of PEI/PSS demonstrably improved the performance of the reactor. Conversion rates of 70% were achieved at a residence time of 26 s, on d 1 of operation, and >50% at 51 s, on d 15 with a six-layer PEI/urease architecture.

  9. Undesired usage and the robust self-assembly of heterogeneous structures

    NASA Astrophysics Data System (ADS)

    Murugan, Arvind; Zou, James; Brenner, Michael P.

    2015-02-01

    Inspired by multiprotein complexes in biology and recent successes in synthetic DNA tile and colloidal self-assembly, we study the spontaneous assembly of structures made of many kinds of components. The major challenge with achieving high assembly yield is eliminating incomplete or incorrectly bound structures. Here, we find that such undesired structures rapidly degrade yield with increasing structural size and complexity in diverse models of assembly, if component concentrations reflect the composition (that is, stoichiometry) of the desired structure. But this yield catastrophe can be mitigated by using highly non-stoichiometric concentrations. Our results support a general principle of ‘undesired usage’—concentrations of components should be chosen to account for how they are ‘used’ by undesired structures and not just by the desired structure. This principle could improve synthetic assembly methods, but also raises new questions about expression levels of proteins that form biological complexes such as the ribosome.

  10. Large-scale self-assembled epitaxial growth of highly-ordered three-dimensional micro/nano single-crystalline PbSe pyramid arrays by selective chemical bath deposition

    NASA Astrophysics Data System (ADS)

    Qiu, Jijun; Weng, Binbin; Li, Lin; Li, Xiaomin; Shi, Zhisheng

    2015-05-01

    Highly ordered three-dimensional micro- and nano- PbSe pyramid arrays were synthesized by using selective epitaxial self-assembled chemical bath deposition method. Each pyramid consists of a very sharp (111) tip with six smooth equivalent {100} facets. Every (100) facet forms an angle of about 54.7° with respect to the (111) facet. The structural features including pyramidal size and period could be precisely tailored by pre-patterned Au mask and etching time. Pyramids are self-assembled on the confined positions by the dual functions of one-dimensional and two-dimensional oriented attachment mechanisms along [110] directions on the (111) surface, following the Gibbs-Curie-Wulff minimum energy principle. This method could effectively create large, bottom-up 3D pyramidal surface patterns in a cost-effective and time-saving manner, which has potential applications in infrared photoconductors, solar cells and light emitting enhancement for display, etc.

  11. Electroactive self-assembled monolayers of unique geometric structures by using rigid norbornylogous bridges.

    PubMed

    Darwish, Nadim; Eggers, Paul K; Da Silva, Paulo; Zhang, Yi; Tong, Yujin; Ye, Shen; Gooding, J Justin; Paddon-Row, Michael N

    2012-01-02

    Herein, we describe the synthesis of straight (S) and L-shaped (L) norbornylogous bridges (NBs) with an anthraquinone moiety at the distal end as the redox-active head group and two thiol feet at the proximal end, by which the molecules assemble on gold surfaces. The NB molecules were shown to form self-assembled monolayers (SAMs) with a well-behaved surface redox process. The SAMs were characterized by using in situ IR spectroscopy, cyclic voltammetry, scanning tunnelling microscopy and electrochemical impedance spectroscopy. The surface selection rules associated with the IR band intensities allowed the estimation of the position of the anthraquinone moiety with respect to the surface and the tilt of the bridge with respect to the surface normal, both in pure and diluted monolayers. It is shown that the S- and L-NBs hold the plane of the anthraquinone moiety close to the surface normal or the surface tangent, respectively. Neither NB molecule changes its orientation if spaced by diluents on the surface. The difference in the structure of the S- and L-NB SAMs provides a suitable framework for the investigation of factors that govern electron transfer of anthraquinone moieties across self-assembled monolayers with limited structural ambiguity, as compared with the commonly used structurally flexible alkanethiol monolayers.

  12. A Structural Model for a Self-Assembled Nanotube Provides Insight into Its Exciton Dynamics

    PubMed Central

    2016-01-01

    The design and synthesis of functional self-assembled nanostructures is frequently an empirical process fraught with critical knowledge gaps about atomic-level structure in these noncovalent systems. Here, we report a structural model for a semiconductor nanotube formed via the self-assembly of naphthalenediimide-lysine (NDI-Lys) building blocks determined using experimental 13C–13C and 13C–15N distance restraints from solid-state nuclear magnetic resonance supplemented by electron microscopy and X-ray powder diffraction data. The structural model reveals a two-dimensional-crystal-like architecture of stacked monolayer rings each containing ∼50 NDI-Lys molecules, with significant π-stacking interactions occurring both within the confines of the ring and along the long axis of the tube. Excited-state delocalization and energy transfer are simulated for the nanotube based on time-dependent density functional theory and an incoherent hopping model. Remarkably, these calculations reveal efficient energy migration from the excitonic bright state, which is in agreement with the rapid energy transfer within NDI-Lys nanotubes observed previously using fluorescence spectroscopy. PMID:26120375

  13. Infrared light-induced protein crystallization. Structuring of protein interfacial water and periodic self-assembly

    NASA Astrophysics Data System (ADS)

    Kowacz, Magdalena; Marchel, Mateusz; Juknaité, Lina; Esperança, José M. S. S.; Romão, Maria João; Carvalho, Ana Luísa; Rebelo, Luís Paulo N.

    2017-01-01

    We show that a physical trigger, a non-ionizing infrared (IR) radiation at wavelengths strongly absorbed by liquid water, can be used to induce and kinetically control protein (periodic) self-assembly in solution. This phenomenon is explained by considering the effect of IR light on the structuring of protein interfacial water. Our results indicate that the IR radiation can promote enhanced mutual correlations of water molecules in the protein hydration shell. We report on the radiation-induced increase in both the strength and cooperativeness of H-bonds. The presence of a structured dipolar hydration layer can lead to attractive interactions between like-charged biomacromolecules in solution (and crystal nucleation events). Furthermore, our study suggests that enveloping the protein within a layer of structured solvent (an effect enhanced by IR light) can prevent the protein non-specific aggregation favoring periodic self-assembly. Recognizing the ability to affect protein-water interactions by means of IR radiation may have important implications for biological and bio-inspired systems.

  14. Bio-inspired Structural Colors from Deposition of Synthetic Melanin Nanoparticles by Evaporative Self-assembly

    NASA Astrophysics Data System (ADS)

    Xiao, Ming; Li, Yiwen; Deheyn, Dimitri; Yue, Xiujun; Gianneschi, Nathan; Shawkey, Matthew; Dhinojwala, Ali

    2015-03-01

    Melanin, a ubiquitous black or brown pigment in the animal kingdom, is a unique but poorly understood biomaterial. Many bird feathers contain melanosomes (melanin-containing organelles), which pack into ordered nanostructures, like multilayer or two-dimensional photonic crystal structures, to produce structural colors. To understand the optical properties of melanin and how melanosomes assemble into certain structures to produce colors, we prepared synthetic melanin (polydopamine) particles with variable sizes and aspect ratios. We have characterized the absorption and refractive index of the synthetic melanin particles. We have also shown that we can use an evaporative process to self-assemble melanin films with a wide range of colors. The colors obtained using this technique is modeled using a thin-film interference model and the optical properties of the synthetic melanin nanoparticles. Our results on self-assembly of synthetic melanin nanoparticles provide an explanation as why the use of melanosomes to produce colors is prevalent in the animal kingdom. National science foundation, air force office of scientific research, human frontier science program.

  15. Magnetically Self-Assembled Colloidal Three-Dimensional Structures as Cell Growth Scaffold.

    PubMed

    Kokot, Gašper; Zemljič Jokhadar, Špela; Batista, Urška; Babič, Dušan

    2015-09-08

    Understanding the chemical and physical conditions for cell growth is important from biological and medical aspects. Many tissues and cell types (e.g., epithelial cells and neurons) naturally grow on surfaces that span in three-dimensions and offer structural or mechanical support. The scaffold surface has to promote adhesion and cell proliferation as well as support their weight and retain its structural integrity. Here, we present a flexible method that uses self-assembly of micrometer superparamagnetic particles to produce appropriate scaffold surfaces with controllable general appearance in three dimensions, such as oriented membranes, branched structure, or void network. As a proof of principle, the Chinese hamster ovary epithelial cell line was successfully grown for several days on inclined membranes. Robustness of the oriented membrane architecture was probed with optical tweezers. We measured the magnetic force holding one particle in a self-assembled upright hexagonal sheet and modeled it as a sum of pair interaction forces between spatially arrested static dipoles.

  16. Self-assembled supramolecular nano vesicles for safe and highly efficient gene delivery to solid tumors

    PubMed Central

    Li, Wei; Li, Huafei; Li, Jinfeng; Wang, Huajing; Zhao, He; Zhang, Li; Xia, Yu; Ye, Zengwei; Gao, Jie; Dai, Jianxin; Wang, Hao; Guo, Yajun

    2012-01-01

    The main obstacles for cationic polyplexes in gene delivery are in vivo instability and low solid-tumor accumulation. Safe vectors with high transfection efficiency and in vivo tumor accumulation are therefore highly desirable. In this study, the amphiphilic block copolymer poly(n-butyl methacrylate)-b-poly(N-acryloylmorpholine) was synthesized by reversible addition–fragmentation chain-transfer (RAFT) radical polymerization. The corresponding well-defined vesicles with narrow size distribution were tailored by finely regulating the packing parameter (β) of copolymer (1/2 < β < 1). Compared with traditional “gold-standard” polycation (polyethylenimine, 25 kDa), plasmid DNA condensing efficiency, DNase I degradation protection, and cellular uptake were improved by the supramolecular nano vesicles. In addition, the plasmid DNA transferring efficiency in 10% fetal bovine serum medium was enlarged five times to that of polyethylenimine in renal tubular epithelial and human hepatocellular carcinoma cell lines. This improved in vitro transfection was mainly attributed to the densely packed bilayer. This stealth polyplex showed high serum stability via entropic repulsion, which further protected the polyplex from being destroyed during sterilization. As indicated by the IVIS® Lumina II Imaging System (Caliper Life Sciences, Hopkinton, MA) 24 hours post-intravenous administration, intra-tumor accumulation of the stealth polyplex was clearly promoted. This study successfully circumvented the traditional dilemma of efficient gene transfection at a high nitrogen-from-polyethylenimine to phosphate-from-DNA ratio that is accompanied with site cytotoxicity and low stability. As such, these simply tailored noncytotoxic nano vesicles show significant potential for use in practical gene therapy. PMID:22977303

  17. Structure of a designed protein cage that self-assembles into a highly porous cube

    SciTech Connect

    Lai, Yen-Ting; Reading, Eamonn; Hura, Greg L.; Tsai, Kuang-Lei; Laganowsky, Arthur; Asturias, Francisco J.; Tainer, John A.; Robinson, Carol V.; Yeates, Todd O.

    2014-11-10

    Natural proteins can be versatile building blocks for multimeric, self-assembling structures. Yet, creating protein-based assemblies with specific geometries and chemical properties remains challenging. Highly porous materials represent particularly interesting targets for designed assembly. Here we utilize a strategy of fusing two natural protein oligomers using a continuous alpha-helical linker to design a novel protein that self assembles into a 750 kDa, 225 Å diameter, cube-shaped cage with large openings into a 130 Å diameter inner cavity. A crystal structure of the cage showed atomic level agreement with the designed model, while electron microscopy, native mass spectrometry, and small angle x-ray scattering revealed alternate assembly forms in solution. These studies show that accurate design of large porous assemblies with specific shapes is feasible, while further specificity improvements will likely require limiting flexibility to select against alternative forms. Finally, these results provide a foundation for the design of advanced materials with applications in bionanotechnology, nanomedicine and material sciences.

  18. Two-Dimensional Layered Oxide Structures Tailored by Self-Assembled Layer Stacking via Interfacial Strain

    SciTech Connect

    Zhang, Wenrui; Li, Mingtao; Chen, Aiping; Li, Leigang; Zhu, Yuanyuan; Xia, Zhenhai; Lu, Ping; Boullay, Philippe; Wu, Lijun; Zhu, Yimei; MacManus-Driscoll, Judith L.; Jia, Quanxi; Zhou, Honghui; Narayan, Jagdish; Zhang, Xinghang; Wang, Haiyan

    2016-06-13

    Two-dimensional (2D) nanostructures emerge as one of leading topics in fundamental materials science and could enable next generation nanoelectronic devices. Beyond graphene and molybdenum disulphide, layered complex oxides are another large group of promising 2D candidates because of their strong interplay of intrinsic charge, spin, orbital and lattice. As a fundamental basis of heteroepitaxial thin film growth, interfacial strain can be used to design materials exhibiting new phenomena beyond their conventional form. Here we report the strain-driven self-assembly of Bismuth-based supercells (SC) with a 2D layered structure, and elucidate the fundamental growth mechanism with combined experimental tools and first-principles calculations. The study revealed that the new layered structures were formed by the strain-enabled self-assembled atomic layer stacking, i.e., alternative growth of Bi2O2 layer and [Fe0.5Mn0.5]O6 layer. The strain-driven approach is further demonstrated in other SC candidate systems with promising room-temperature multiferroic properties. This well-integrated theoretical and experimental study inspired by the Materials Genome Initiatives opens up a new avenue in searching and designing novel 2D layered complex oxides with enormous promises.

  19. Structure of a designed protein cage that self-assembles into a highly porous cube

    NASA Astrophysics Data System (ADS)

    Lai, Yen-Ting; Reading, Eamonn; Hura, Greg L.; Tsai, Kuang-Lei; Laganowsky, Arthur; Asturias, Francisco J.; Tainer, John A.; Robinson, Carol V.; Yeates, Todd O.

    2014-12-01

    Natural proteins can be versatile building blocks for multimeric, self-assembling structures. Yet, creating protein-based assemblies with specific geometries and chemical properties remains challenging. Highly porous materials represent particularly interesting targets for designed assembly. Here, we utilize a strategy of fusing two natural protein oligomers using a continuous alpha-helical linker to design a novel protein that self assembles into a 750 kDa, 225 Å diameter, cube-shaped cage with large openings into a 130 Å diameter inner cavity. A crystal structure of the cage showed atomic-level agreement with the designed model, while electron microscopy, native mass spectrometry and small angle X-ray scattering revealed alternative assembly forms in solution. These studies show that accurate design of large porous assemblies with specific shapes is feasible, while further specificity improvements will probably require limiting flexibility to select against alternative forms. These results provide a foundation for the design of advanced materials with applications in bionanotechnology, nanomedicine and material sciences.

  20. Two-Dimensional Layered Oxide Structures Tailored by Self-Assembled Layer Stacking via Interfacial Strain

    SciTech Connect

    Zhang, Wenrui; Li, Mingtao; Chen, Aiping; Li, Leigang; Zhu, Yuanyuan; Xia, Zhenhai; Lu, Ping; Boullay, Philippe; Wu, Lijun; Zhu, Yimei; MacManus-Driscoll, Judith L.; Jia, Quanxi; Zhou, Honghui; Narayan, Jagdish; Zhang, Xinghang; Wang, Haiyan

    2016-06-13

    Two-dimensional (2D) nanostructures emerge as one of leading topics in fundamental materials science and could enable next generation nanoelectronic devices. Beyond graphene and molybdenum disulphide, layered complex oxides are another large group of promising 2D candidates because of their strong interplay of intrinsic charge, spin, orbital and lattice. As a fundamental basis of heteroepitaxial thin film growth, interfacial strain can be used to design materials exhibiting new phenomena beyond their conventional form. Here we report the strain-driven self-assembly of Bismuth-based supercells (SC) with a 2D layered structure, and elucidate the fundamental growth mechanism with combined experimental tools and first-principles calculations. The study revealed that the new layered structures were formed by the strain-enabled self-assembled atomic layer stacking, i.e., alternative growth of Bi2O2 layer and [Fe0.5Mn0.5]O6 layer. The strain-driven approach is further demonstrated in other SC candidate systems with promising room-temperature multiferroic properties. This well-integrated theoretical and experimental study inspired by the Materials Genome Initiatives opens up a new avenue in searching and designing novel 2D layered complex oxides with enormous promises.

  1. Two-Dimensional Layered Oxide Structures Tailored by Self-Assembled Layer Stacking via Interfacial Strain

    DOE PAGES

    Zhang, Wenrui; Li, Mingtao; Chen, Aiping; ...

    2016-06-13

    Two-dimensional (2D) nanostructures emerge as one of leading topics in fundamental materials science and could enable next generation nanoelectronic devices. Beyond graphene and molybdenum disulphide, layered complex oxides are another large group of promising 2D candidates because of their strong interplay of intrinsic charge, spin, orbital and lattice. As a fundamental basis of heteroepitaxial thin film growth, interfacial strain can be used to design materials exhibiting new phenomena beyond their conventional form. Here we report the strain-driven self-assembly of Bismuth-based supercells (SC) with a 2D layered structure, and elucidate the fundamental growth mechanism with combined experimental tools and first-principles calculations.more » The study revealed that the new layered structures were formed by the strain-enabled self-assembled atomic layer stacking, i.e., alternative growth of Bi2O2 layer and [Fe0.5Mn0.5]O6 layer. The strain-driven approach is further demonstrated in other SC candidate systems with promising room-temperature multiferroic properties. This well-integrated theoretical and experimental study inspired by the Materials Genome Initiatives opens up a new avenue in searching and designing novel 2D layered complex oxides with enormous promises.« less

  2. Structure of a designed protein cage that self-assembles into a highly porous cube

    DOE PAGES

    Lai, Yen-Ting; Reading, Eamonn; Hura, Greg L.; ...

    2014-11-10

    Natural proteins can be versatile building blocks for multimeric, self-assembling structures. Yet, creating protein-based assemblies with specific geometries and chemical properties remains challenging. Highly porous materials represent particularly interesting targets for designed assembly. Here we utilize a strategy of fusing two natural protein oligomers using a continuous alpha-helical linker to design a novel protein that self assembles into a 750 kDa, 225 Å diameter, cube-shaped cage with large openings into a 130 Å diameter inner cavity. A crystal structure of the cage showed atomic level agreement with the designed model, while electron microscopy, native mass spectrometry, and small angle x-raymore » scattering revealed alternate assembly forms in solution. These studies show that accurate design of large porous assemblies with specific shapes is feasible, while further specificity improvements will likely require limiting flexibility to select against alternative forms. Finally, these results provide a foundation for the design of advanced materials with applications in bionanotechnology, nanomedicine and material sciences.« less

  3. Self-organized hierarchical structures in polymer surfaces: self-assembled nanostructures within breath figures.

    PubMed

    Muñoz-Bonilla, Alexandra; Ibarboure, Emmanuel; Papon, Eric; Rodriguez-Hernandez, Juan

    2009-06-02

    Herein we report the preparation of hierarchically micro- and nanostructured polymer surfaces in block copolymer/homopolymer blends. The structural order at different length scales was obtained combining two methodologies, e.g., the breath figures method to produce porous microstructures ("top-down" approach) with block copolymer self-assembly to induce microphase separation at the nanometer length scale ("bottom-up" approach). The interplay of the breath figure formation during the spin-coating and self-assembly of the triblock copolymer allowed the preparation of polymer surfaces having micrometer-sized cavities decorated with nanostructured block copolymers. The system described herein possesses unique characteristics. First, the surface chemical composition can be varied by a surface rearrangement upon annealing either to dry or humid air. Moreover, surface rearrangement is accompanied with structural changes, i.e. both topography and nanostructuration can be reversibly modified upon annealing. In terms of topograghy, a transition between holes and hills was obtained upon soft annealing to water vapor and can be recovered upon annealing to dry air. Finally, the pore nanostructure can be modulated from a micellar array to a lamellar phase when the film is exposed either to air or to tetrahydrofuran vapor.

  4. Structure of a Designed Protein Cage that Self-Assembles into a Highly Porous Cube

    PubMed Central

    Lai, Yen-Ting; Reading, Eamonn; Hura, Greg L.; Tsai, Kuang-Lei; Laganowsky, Arthur; Asturias, Francisco J.; Tainer, John A.; Robinson, Carol V.

    2014-01-01

    Natural proteins can be versatile building blocks for multimeric, self-assembling structures. Yet, creating protein-based assemblies with specific geometries and chemical properties remains challenging. Highly porous materials represent particularly interesting targets for designed assembly. Here we utilize a strategy of fusing two natural protein oligomers using a continuous alpha-helical linker to design a novel protein that self assembles into a 750 kDa, 225 Å diameter, cube-shaped cage with large openings into a 130 Å diameter inner cavity. A crystal structure of the cage showed atomic level agreement with the designed model, while electron microscopy, native mass spectrometry, and small angle x-ray scattering revealed alternate assembly forms in solution. These studies show that accurate design of large porous assemblies with specific shapes is feasible, while further specificity improvements will likely require limiting flexibility to select against alternative forms. These results provide a foundation for the design of advanced materials with applications in bionanotechnology, nanomedicine and material sciences. PMID:25411884

  5. Self-assembly of synthetic hydroxyapatite nanorods into an enamel prism-like structure.

    PubMed

    Chen, Haifeng; Clarkson, Brian H; Sun, Kai; Mansfield, John F

    2005-08-01

    The application of surfactants as reverse micelles or microemulsions for the synthesis and self-assembly of nanoscale structures is one of the most widely adopted methods in nanotechnology. These synthesized nanostructure assemblies sometimes have an ordered arrangement. The aim of this research was to take advantage of these latest developments in the area of nanotechnology to mimic the natural biomineralization process to create the hardest tissue in the human body, dental enamel. This is the outermost layer of the teeth and consists of enamel prisms, highly organized micro-architectural units of nanorod-like calcium hydroxyapatite (HA) crystals arranged roughly parallel to each other. In particular, we have synthesized and modified the hydroxyapatite nanorods surface with monolayers of surfactants to create specific surface characteristics which will allow the nanorods to self-assemble into an enamel prism-like structure at a water/air interface. The size of the synthetic hydroxyapatite nanorods can be controlled and we have synthesized nanorods similar in size to both human and rat enamel. The prepared nanorod assemblies were examined using transmission electron microscopy (TEM) and atomic force microscopy (AFM). The specific Langmuir-Blodgett films were shown to be comprised of enamel prism-like nanorod assemblies with a Ca/P ratio between 1.6 and 1.7.

  6. Self-Assembled DNA Structures for Molecular Force Measurement: A Magnetically Actuated Approach

    NASA Astrophysics Data System (ADS)

    Armstrong, M.; Lauback, S.; Miller, C.; Peace, C.; Castro, C.; Sooryakumar, R.

    2015-03-01

    Understanding molecular forces is important to comprehend many of the underlying properties of molecular machines and biological processes. The relevant forces in these cases often lie in the picoNewton range, and thus experiments on individual biomolecules must integrate techniques capable of measuring such forces. A mechanical system to measure molecular forces associated with interacting DNA strands is being developed by using self-assembled DNA nanostructures and super-paramagnetic beads. The DNA nanostructure consists of single-stranded DNA molecules which can be folded into a precise compact geometry using hundreds of short oligonucleotides, i.e., staples, via programmed molecular self-assembly. These nanostructures can be polymerized into micron-scale filaments. By functionalizing the filament ends with bispecific conjugate staples, the structure can be attached to a surface as well as labeled with magnetic beads in order to apply a force on the system. External magnetic fields provide the means to maneuver and manipulate the magnetically labeled DNA structures. Preliminary findings associated with the DNA constructs and their manipulation lay the groundwork to establish real-time control of DNA nanodevices with micromanipulation.

  7. Controlled evaporative self-assembly of confined microfluids: A route to complex ordered structures

    NASA Astrophysics Data System (ADS)

    Byun, Myunghwan

    The evaporative self-assembly of nonvolatile solutes such as polymers, nanocrystals, and carbon nanotubes has been widely recognized as a non-lithographic means of producing a diverse range of intriguing complex structures. Due to the spatial variation of evaporative flux and possible convection, however, these non-equilibrium dissipative structures (e.g., fingering patterns and polygonal network structures) are often irregularly and stochastically organized. Yet for many applications in microelectronics, data storage devices, and biotechnology, it is highly desirable to achieve surface patterns having a well-controlled spatial arrangement. To date, only a few elegant studies have centered on precise control over the evaporation process to produce ordered structures. In a remarked comparison with conventional lithography techniques, surface patterning by controlled solvent evaporation is simple and cost-effective, offering a lithography- and external field-free means to organize nonvolatile materials into ordered microscopic structures over large surface areas. The ability to engineer an evaporative self-assembly process that yields a wide range of complex, self-organizing structures over large areas offers tremendous potential for applications in electronics, optoelectronics, and bio- or chemical sensors. We developed a facile, robust tool for evaporating polymer, nanoparticle, or DNA solutions in curve-on-flat geometries to create versatile, highly regular microstructures, including hierarchically structured polymer blend rings, conjugated polymer "snake-skins", block copolymer stripes, and punch-hole-like meshes, biomolecular microring arrays, etc. The mechanism of structure formation was elucidated both experimentally and theoretically. Our method further enhances current fabrication approaches to creating highly ordered structures in a simple and cost-effective manner, envisioning the potential to be tailored for use in photonics, optoelectronics, microfluidic

  8. Double hydrogen bond mediating self-assembly structure of cyanides on metal surface

    NASA Astrophysics Data System (ADS)

    Wang, Zhongping; Xiang, Feifei; Lu, Yan; Wei, Sheng; Li, Chao; Liu, Xiaoqing; Liu, Lacheng; Wang, Li

    2016-10-01

    Cyanides with different numbers of -C≡N, 1,2,4,5-Tetracyanobenzene (TCNB) and 2,3-Dicyanonaphthalene (2,3-DCN) deposited on Ag(111) and Ag(110) surfaces, have been investigated by room temperature scanning tunneling microscopy (RTSTM), respectively. High resolution STM images show double hydrogen bond is the main driving force to form variety of self-assembly structures, indicating the double hydrogen bond affects the electron distribution of cyanides and leads to a more stable structure with lower energy. In addition, the difference between Ag(111) and Ag(110) surfaces in their lattice structure induces a bigger assembly structural change of 2,3-DCN than that of 1,2,4,5-TCNB, which confirms the fact that the opposite double hydrogen bond formation formed by 1,2,4,5-TCNB is more stable than the neighboring double hydrogen bond formation formed by molecule 2,3-DCN.

  9. Chemically and mechanically isolated nanocellulose and their self-assembled structures.

    PubMed

    Jiang, Feng; Hsieh, You-Lo

    2013-06-05

    Cellulose nanocrystals (CNCs) and nanofibrils (CNFs) have been isolated from pure rice straw cellulose via sulfuric acid hydrolysis, mechanical blending and TEMPO-mediated oxidation to 16.9%, 12% and 19.7% yields, respectively. Sulfuric acid hydrolysis produced highly crystalline (up to 90.7% CrI) rod-like (3.96-6.74 nm wide, 116.6-166 nm long) CNCs with similarly negative surface charges (-67 to -57 mV) and sulfate contents but decreasing yields and dimensions with longer hydrolysis time. Mechanical defibrillated CNFs were 82.5% crystalline and bimodally distributed in sizes (2.7 nm wide and 100-200 nm long; 8.5 nm wide and micrometers long). TEMPO mediated oxidation liberated the most uniform, finest (1.7 nm) and micrometer long, but least crystalline (64.4% CrI) CNFs. These nanocellulose self-assembled into submicron (153-440 nm wide) fibers of highly crystalline (up to 90.9% CrI) cellulose Iβ structure upon rapid freezing (-196 °C) and freeze-drying. The self-assembling behaviors were analyzed based on nanocellulose dimensions, specific surfaces and surface chemistries. Copyright © 2013 Elsevier Ltd. All rights reserved.

  10. Directed self-assembly of large scaffold-free multi-cellular honeycomb structures.

    PubMed

    Tejavibulya, Nalin; Youssef, Jacquelyn; Bao, Brian; Ferruccio, Toni-Marie; Morgan, Jeffrey R

    2011-09-01

    A significant challenge to the field of biofabrication is the rapid construction of large three-dimensional (3D) living tissues and organs. Multi-cellular spheroids have been used as building blocks. In this paper, we create large multi-cellular honeycomb building blocks using directed self-assembly, whereby cell-to-cell adhesion, in the context of the shape and obstacles of a micro-mold, drives the formation of a 3D structure. Computer-aided design, rapid prototyping and replica molding were used to fabricate honeycomb-shaped micro-molds. Nonadhesive hydrogels cast from these micro-molds were equilibrated in the cell culture medium and seeded with two types of mammalian cells. The cells settled into the honeycomb recess were unable to attach to the nonadhesive hydrogel and so cell-to-cell adhesion drove the self-assembly of a large multi-cellular honeycomb within 24 h. Distinct morphological changes occurred to the honeycomb and its cells indicating the presence of significant cell-mediated tension. Unlike the spheroid, whose size is constrained by a critical diffusion distance needed to maintain cell viability, the overall size of the honeycomb is not limited. The rapid production of the honeycomb building unit, with its multiple rings of high-density cells and open lumen spaces, offers interesting new possibilities for biofabrication strategies.

  11. Sequence-dependent structural changes in a self-assembling DNA oligonucleotide.

    PubMed

    Saoji, Maithili; Paukstelis, Paul J

    2015-12-01

    DNA has proved to be a remarkable molecule for the construction of sophisticated two-dimensional and three-dimensional architectures because of its programmability and structural predictability provided by complementary Watson-Crick base pairing. DNA oligonucleotides can, however, exhibit a great deal of local structural diversity. DNA conformation is strongly linked to both environmental conditions and the nucleobase identities inherent in the oligonucleotide sequence, but the exact relationship between sequence and local structure is not completely understood. This study examines how a single-nucleotide addition to a class of self-assembling DNA 13-mers leads to a significantly different overall structure under identical crystallization conditions. The DNA 13-mers self-assemble in the presence of Mg(2+) through a combination of Watson-Crick and noncanonical base-pairing interactions. The crystal structures described here show that all of the predicted Watson-Crick base pairs are present, with the major difference being a significant rearrangement of noncanonical base pairs. This includes the formation of a sheared A-G base pair, a junction of strands formed from base-triple interactions, and tertiary interactions that generate structural features similar to tandem sheared G-A base pairs. The adoption of this alternate noncanonical structure is dependent in part on the sequence in the Watson-Crick duplex region. These results provide important new insights into the sequence-structure relationship of short DNA oligonucleotides and demonstrate a unique interplay between Watson-Crick and noncanonical base pairs that is responsible for crystallization fate.

  12. Investigating the Structure-Property Relationships of Aqueous Self-Assembled Materials

    NASA Astrophysics Data System (ADS)

    Krogstad, Daniel Vincent

    The components of all living organisms are formed through aqueous self-assembly of organic and inorganic materials through physical interactions including hydrophobic, electrostatic, and hydrogen bonding. In this dissertation, these physical interactions were exploited to develop nanostructured materials for a range of applications. Peptide amphiphiles (PAs) self-assemble into varying structures depending on the physical interactions of the peptides and tails. PA aggregation was investigated by cryo-TEM to provide insight on the effects of varying parameters, including the number and length of the lipid tails as well as the number, length, charge, hydrophobicity, and the hydrogen bonding ability of the peptides. It was determined that cylindrical micelles are most commonly formed, and that specific criteria must be met in order to form spherical micelles, nanoribbons, vesicles or less ordered aggregates. Controlling the aggregated structure is necessary for many applications---particularly in therapeutics. Additionally, two-headed PAs were designed to act as a catalyst and template for biomimetic mineralization to control the formation of inorganic nanomaterials. Finally, injectable hydrogels made from ABA triblock copolymers were synthesized with the A blocks being functionalized with either guanidinium or sulfonate groups. These oppositely charged polyelectrolyte endblocks formed complex coacervate domains, which served as physical crosslinks in the hydrogel network. The mechanical properties, the network structure, the nature of the coacervate domain and the kinetics of hydrogel formation were investigated as a function of polymer concentration, salt concentration, pH and stoichiometry with rheometry, SAXS and SANS. It was shown that the mechanical properties of the hydrogels was highly dependent on the structural organization of the coacervate domains and that the properties could be tuned with polymer and salt concentration. Polymer and salt concentration were

  13. Magnetic and structural properties of electrochemically self-assembled Fe1-xCox nanowires.

    PubMed

    Menon, L; Bandyopadhyay, S; Liu, Y; Zeng, H; Sellmyer, D J

    2001-06-01

    Fe1-xCox (0 < or = x < or = 1) nanowires have been self-assembled by electrodeposition in porous alumina films. The crystal structure is bee at the Fe end. With increased addition of Co, the crystal structure remains bcc until about 67% addition of Co. At the Co end, the structure is a mixture of hcp and fcc. Magnetic studies show very high coercivities for the Fe-Co alloys in the bcc phase. For Fe0.67Co0.33 nanowires of diameter 9 nm, the coercivity is about 2900 Oe, whereas for Fe0.33Co0.67 nanowires, it is about 2850 Oe. Temperature and size dependence of magnetic properties show no indication of superparamagnetic effects down to wire diameters of 9 nm.

  14. Bio-Inspired Structural Colors Produced via Self-Assembly of Synthetic Melanin Nanoparticles.

    PubMed

    Xiao, Ming; Li, Yiwen; Allen, Michael C; Deheyn, Dimitri D; Yue, Xiujun; Zhao, Jiuzhou; Gianneschi, Nathan C; Shawkey, Matthew D; Dhinojwala, Ali

    2015-05-26

    Structural colors arising from interactions of light with submicron scale periodic structures have been found in many species across all taxa, serving multiple biological functions including sexual signaling, camouflage, and aposematism. Directly inspired by the extensive use of self-assembled melanosomes to produce colors in avian feathers, we set out to synthesize and assemble polydopamine-based synthetic melanin nanoparticles in an effort to fabricate colored films. We have quantitatively demonstrated that synthetic melanin nanoparticles have a high refractive index and broad absorption spanning across the UV-visible range, similar to natural melanins. Utilizing a thin-film interference model, we demonstrated the coloration mechanism of deposited films and showed that the unique optical properties of synthetic melanin nanoparticles provide advantages for structural colors over other polymeric nanoparticles (i.e., polystyrene colloidal particles).

  15. Cryogenic Electron Microscopy Studies: Structure and Formation of Self-assembled Nanostructures in Solution

    NASA Astrophysics Data System (ADS)

    Lee, Han Seung

    Cryogenic electron microscopy (Cryo-EM) techniques are among the most powerful to characterize self-assembling soft materials (colloids, polymers, and microemulsions, etc.) at the nanometer scale, without any need for implicit models or assumptions about the structure. We can even visualize structure under dynamic conditions, capturing each stage of development. In this thesis, cryo-EM has been used to investigate the formation and structure of a variety of self-assembling soft materials. Visualization is complemented by small angle X-ray scattering (SAXS), dynamic light scattering, and conductivity measurements. In each case, cryo-EM provides new insights, not otherwise available, into the nanostructure development. Self-assembly phenomena at the molecular level are critical to the performance of tremendous number of applied systems ranging from personal care products to industrial products. To evaluate these self-assembled materials, multiple characterization techniques are required. We investigated aggregation behavior of cesium dodecyl sulfate (CsDS) ionic surfactant in aqueous solution. Coupled with the real space data from cryogenic transmission electron microscopy (Cryo-TEM) and the inverse space data from SAXS, the experimental result of CsDS in aqueous solution gave a new insight in CsDS micellar structures and their development as a function of concentration. Cryo-TEM showed the presence of the liquid-like hydrocarbon core in the CsDS micelles and relatively thick shell structures at a low CsDS concentration. The core-shell sphere structure micelle shifted to core-shell cylindrical micelle structure at high concentration. The morphology and structure of paclitaxel silicate (PTX) prodrug, encapsulated with amphiphilic poly(ethylene glycol)-b-poly(lactic-co-glycolic acid) diblock copolymers were studied. The six different silicate PTX prodrug candidates were characterized with cryo-TEM. Direct imaging with cryo-TEM illustrated structure of prodrug

  16. Crystalline structures and misfit strain inside Er silicide nanocrystals self-assembled on Si(001) substrates.

    PubMed

    Ding, Tao; Wu, Yueqin; Song, Junqiang; Li, Juan; Huang, Han; Zou, Jin; Cai, Qun

    2011-06-17

    The morphology and crystalline structure of Er silicide nanocrystals self-assembled on the Si(001) substrate were investigated using scanning tunneling microscopy (STM) and transmission electron microscopy (TEM). It was found that the nanowires and nanorods formed at 630 °C has dominant hexagonal AlB(2)-type structure, while inside the nanoislands self-organized at 800 °C the tetragonal ThSi(2)-type structure is prevalent. The lattice analysis via cross-sectional high-resolution TEM demonstrated that internal misfit strain plays an important role in controlling the growth of nanocrystals. With the relaxation of strain, the nanoislands could evolve from a pyramid-like shape into a truncated-hut-like shape.

  17. Reversible Self-Assembly of Hydrophilic Inorganic Polyelectrolytes into Highly Conservative, Vesicle-like Structures

    NASA Astrophysics Data System (ADS)

    Kistler, Melissa; Bhatt, Anish; Liu, Guang; Liu, Tianbo

    2007-03-01

    The hydrophilic polyoxometalate (POM) macroanions are inorganic polyelectrolytes which offer a direct connection between simple ions and organic polyelectrolytes. POM solutions are perfect model systems for studying polyelectrolyte solutions because they are identical in size, shape, mass and charges, with easily tunable charge density. Many types of POM macroanions are highly soluble but undergo reversible self-assembly to form uniform, stable, soft, single-layer vesicle-like ``blackberry'' structures containing >1000 individual POMs in dilute solutions. The driving force of the blackberry formation is likely counterion-mediated attraction (like-charge attraction). The blackberry size can be accurately controlled by solvent quality, or the charge density on macroions. Many unexpected phenomena have been observed in these novel systems. Blackberry structures may be analogous to virus shell structures formed by capsid proteins. References: Nature, 2003, 426, 59; JACS, 2002, 124, 10942; 2003, 125, 312; 2004, 126, 16690; 2005, 127, 6942; 2006, 128, 10103.

  18. Regulated self-assembly of epitaxial silicon-germanium quantum structures and their properties

    NASA Astrophysics Data System (ADS)

    Vandervelde, Thomas Edwin

    Most proposed next generation architectures use quantum dots (QDs) in their design. Current lithography techniques either do not have the resolution required or are too time intensive for practical creation of these architectures. This has led many to suggest that the answer lies in self-assembly of QDs. Many unresolved issues, however, remain before we can implement this concept. The four areas of research discussed in this dissertation improve the fundamental understanding of processes involved in self-assembly. Once we had established that our system was producing the highest quality samples, we were able to say with confidence that the structures we observed were due to intrinsic phenomena, and not the result of contamination. In addition, because the existing standard curves lacked the sensitivity associated with modern analytical equipment, we employed more exploratory techniques (i.e. combinatorial epitaxy) to establish base growth conditions and define the evolution of structures. The examination of various growth conditions yielded the discovery of quantum fortresses (QFs), a novel, self-assembled, Quantum Cellular Automata (QCA)-like structure. We mapped the possible conditions under which these QFs form to gain a further understanding of their evolution. Additionally, we electrically tested their ability to act as SETs and quantum mechanically calculated growth conditions that result in those QFs that would best function as a QCA unit cell. To form a QCA circuit, QFs need to align in specific configurations. We investigated the fundamentals of a new technique to direct QF alignment. We demonstrated that FIB-mediated disruption of 1/10th ML or less is sufficient to guide island formation through the creation of preferential binding sites and denuded zones. In addition, we investigated the effect of altering growth conditions on the ability of large-scale features to align QDs. We also examined the ability of QDs to self-order into superlattice structures

  19. Self-Assembling Nano-Architectures Created from a Protein Nano-Building Block Using an Intermolecularly Folded Dimeric de Novo Protein.

    PubMed

    Kobayashi, Naoya; Yanase, Keiichi; Sato, Takaaki; Unzai, Satoru; Hecht, Michael H; Arai, Ryoichi

    2015-09-09

    The design of novel proteins that self-assemble into supramolecular complexes is an important step in the development of synthetic biology and nanotechnology. Recently, we described the three-dimensional structure of WA20, a de novo protein that forms an intermolecularly folded dimeric 4-helix bundle (PDB code 3VJF ). To harness the unusual intertwined structure of WA20 for the self-assembly of supramolecular nanostructures, we created a protein nanobuilding block (PN-Block), called WA20-foldon, by fusing the dimeric structure of WA20 to the trimeric foldon domain of fibritin from bacteriophage T4. The WA20-foldon fusion protein was expressed in the soluble fraction in Escherichia coli, purified, and shown to form several homooligomeric forms. The stable oligomeric forms were further purified and characterized by a range of biophysical techniques. Size exclusion chromatography, multiangle light scattering, analytical ultracentrifugation, and small-angle X-ray scattering (SAXS) analyses indicate that the small (S form), middle (M form), and large (L form) forms of the WA20-foldon oligomers exist as hexamer (6-mer), dodecamer (12-mer), and octadecamer (18-mer), respectively. These findings suggest that the oligomers in multiples of 6-mer are stably formed by fusing the interdigitated dimer of WA20 with the trimer of foldon domain. Pair-distance distribution functions obtained from the Fourier inversion of the SAXS data suggest that the S and M forms have barrel- and tetrahedron-like shapes, respectively. These results demonstrate that the de novo WA20-foldon is an effective building block for the creation of self-assembling artificial nanoarchitectures.

  20. Intermolecular hydrogen bonded and self-assembled β-pleated sheet structures of β-sulfidocarbonyls

    NASA Astrophysics Data System (ADS)

    Hussain, Sahid; Das, Gopal; Chaudhuri, Mihir K.

    2007-06-01

    The three crystal structures of β-sulfidocarbonyls 1, 2 and 3 synthesized from the reaction of acryl amide with cystiene, 1,2-dithiol and 1,3-dithiols, respectively, in water catalyzed by borax, have been determined at 273 K. The characteristic features of the structures are self-assembly through intermolecular hydrogen bonding leading to infinite chains of molecules in one direction, in addition to the stacking of layers of such molecular chains in the perpendicular direction ultimately giving rise to β-pleated sheets of 3D molecular network involving N-H⋯O, C-H⋯O and C-H⋯S bonding in the crystal lattice.

  1. Directed self-assembly of quantum structures by nanomechanical stamping using probe tips.

    PubMed

    Taylor, Curtis; Marega, Euclydes; Stach, Eric A; Salamo, Gregory; Hussey, Lindsay; Muñoz, Martin; Malshe, Ajay

    2008-01-09

    We demonstrate that nanomechanically stamped substrates can be used as templates to pattern and direct the self-assembly of epitaxial quantum structures such as quantum dots. Diamond probe tips are used to indent or stamp the surface of GaAs(100) to create nanoscale volumes of dislocation-mediated deformation, which alter the growth surface strain. These strained sites act to bias nucleation, hence allowing for selective growth of InAs quantum dots. Patterns of quantum dots are observed to form above the underlying nanostamped template. The strain state of the patterned structures is characterized by micro-Raman spectroscopy. The potential of using nanoprobe tips as a quantum dot nanofabrication technology are discussed.

  2. Thermally-nucleated self-assembly of water and alcohol into stable structures at hydrophobic interfaces.

    PubMed

    Voïtchovsky, Kislon; Giofrè, Daniele; José Segura, Juan; Stellacci, Francesco; Ceriotti, Michele

    2016-10-07

    At the interface with solids, the mobility of liquid molecules tends to be reduced compared with bulk, often resulting in increased local order due to interactions with the surface of the solid. At room temperature, liquids such as water and methanol can form solvation structures, but the molecules remain highly mobile, thus preventing the formation of long-lived supramolecular assemblies. Here we show that mixtures of water with methanol can form a novel type of interfaces with hydrophobic solids. Combining in situ atomic force microscopy and multiscale molecular dynamics simulations, we identify solid-like two-dimensional interfacial structures that nucleate thermally, and are held together by an extended network of hydrogen bonds. On graphite, nucleation occurs above ∼35 °C, resulting in robust, multilayered nanoscopic patterns. Our findings could have an impact on many fields where water-alcohol mixtures play an important role such as fuel cells, chemical synthesis, self-assembly, catalysis and surface treatments.

  3. Thermally-nucleated self-assembly of water and alcohol into stable structures at hydrophobic interfaces

    NASA Astrophysics Data System (ADS)

    Voïtchovsky, Kislon; Giofrè, Daniele; José Segura, Juan; Stellacci, Francesco; Ceriotti, Michele

    2016-10-01

    At the interface with solids, the mobility of liquid molecules tends to be reduced compared with bulk, often resulting in increased local order due to interactions with the surface of the solid. At room temperature, liquids such as water and methanol can form solvation structures, but the molecules remain highly mobile, thus preventing the formation of long-lived supramolecular assemblies. Here we show that mixtures of water with methanol can form a novel type of interfaces with hydrophobic solids. Combining in situ atomic force microscopy and multiscale molecular dynamics simulations, we identify solid-like two-dimensional interfacial structures that nucleate thermally, and are held together by an extended network of hydrogen bonds. On graphite, nucleation occurs above ~35 °C, resulting in robust, multilayered nanoscopic patterns. Our findings could have an impact on many fields where water-alcohol mixtures play an important role such as fuel cells, chemical synthesis, self-assembly, catalysis and surface treatments.

  4. Self-assembled periodic sub-wavelength structures by femtosecond laser direct writing.

    PubMed

    Yang, Weijia; Bricchi, Erica; Kazansky, Peter G; Bovatsek, James; Arai, Alan Y

    2006-10-16

    Self-assembled, sub-wavelength periodic structures are induced in fused silica by a tightly focused, linearly polarized, femtosecond laser beam. Two different types of periodic structures, the main one with period (Lambda(E)) in the direction of the laser beam polarization and the second with period (Lambda(k)) in the direction of the light propagation, are identified from the cross-sectional images of the modified regions using scanning electron microscopy. We demonstrate the spatial coherence of these nanogratings in the plane perpendicular to the beam propagation direction. The range of effective pulse energy which could produce nanogratings narrows when the pulse repetition rate of writing laser increases. The period Lambda(E) is proportional to the wavelength of the writing laser and period Lambda(k) in the head of the modified region remains approximately the wavelength of light in fused silica.

  5. Structural investigations of self-assembled monolayers for organic electronics: results from X-ray reflectivity.

    PubMed

    Khassanov, Artoem; Steinrück, Hans-Georg; Schmaltz, Thomas; Magerl, Andreas; Halik, Marcus

    2015-07-21

    Self-assembled monolayers (SAMs) have been established as crucial interlayers and electronically active layers in organic electronic devices, such as organic light emitting diodes (OLEDs), organic photovoltaics (OPVs), organic thin film transistors (OTFTs), and nonvolatile memories (NVMs). The use of self-assembling functionalized organic molecules is beneficial due to mainly three advantages compared with common thin film deposition approaches. (1) Molecular self-assembly occurs with surface selectivity, determined by the interaction between the functional anchor group of the organic molecules and the target surface. (2) The film thickness of the resulting layers is perfectly controllable on the angstrom scale, due to the self-terminating film formation to only a single molecular layer. And finally, (3) the wide variability in the chemical structure of such molecules enables different SAM functionalities for devices, ranging from electrical insulation to charge storage to charge transport. The SAM approach can be further expanded by employing several functionalized molecules to create mixed SAMs with consequently mixed properties. The function of SAMs in devices depends not only on the chemical structure of the molecules but also on their final arrangement and orientation on the surface. A reliable and nondestructive in-depth characterization of SAMs on nonconductive oxide surfaces is still challenging because of the very small thickness and the impracticality of methods such as scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). In this Account, we illustrate how X-ray reflectivity (XRR) provides analytical access to major questions of SAM composition, morphology, and even formation by means of investigations of pure and mixed SAMs based on phosphonic acids (PAs) of various chain structures on flat alumina (AlOx) surfaces. XRR is an analytical method that provides access to spatially averaged structural depth profiles over a relatively

  6. Synthesis, electrochemistry, STM investigation of oligothiophene self-assemblies with superior structural order and electronic properties

    NASA Astrophysics Data System (ADS)

    Kuo, Cheng-Yu; Liu, Yinghao; Yarotski, Dmitry; Li, Hao; Xu, Ping; Yen, Hung-Ju; Tretiak, Sergei; Wang, Hsing-Lin

    2016-12-01

    Three oligothiophene (terthiophene, tetrathiophene and pentathiophene) derivatives are synthesized and their monolayer self-assemblies on gold (Au) are prepared via Au-S covalent bond. Our UV-Vis experimental characterization of solution reveals the dependence of the optical properties on the conjugation length of the oligothiophenes, which compares well with Time-Dependent Density Functional Theory (TDDFT) simulations of spectra of individual chromophores. Photoluminescent spectra of thin films show pronounced red shifts compared to that of solutions, suggesting strong inter-oligomer interactions. The comparative studies of cyclic voltammograms of tetrathiophene from solution, cast film and self-assembled monolayer (SAM) indicate presence of one, two, and three oxidized species in these samples, respectively, suggesting a very strong electronic coupling between tetrathiophene molecules in the SAM. Scanning tunneling microscopy (STM) imaging of SAMs of the tetrathiophene on an atomically flat Au surface exhibits formation of monolayer assemblies with molecular order, and the molecular packing appears to show an overlay of oligothiophene molecules on top of another one. In contrast, the trimer and pentamer images show only aggregated species lacking long-range order on the molecular level. Such trends in going from disordered-ordered-disordered monolayer assemblies are mainly due to a delicate balance between inter-chromophore π-π couplings, hydrophobic interaction and the propensity to form Au-S covalent bond. Such hypothesis has been validated by our computational results suggesting different interaction patterns of oligothiophenes with odd numbered and even numbered thiophene repeat units placed in a dimer configuration. Observed correlations between oligomer geometry and structural order of monolayer assembly elucidate important structure-property relationships and have implications for these molecular structures in organic optoelectronic devices and energy

  7. Molecular structure of self-assembled chiral nanoribbons and nanotubules revealed in the hydrated state.

    PubMed

    Oda, Reiko; Artzner, Franck; Laguerre, Michel; Huc, Ivan

    2008-11-05

    A detailed molecular organization of racemic 16-2-16 tartrate self-assembled multi-bilayer ribbons in the hydrated state is proposed where 16-2-16 amphiphiles, tartrate ions, and water molecules are all accurately positioned by comparing experimental X-ray powder diffraction and diffraction patterns derived from modeling studies. X-ray diffuse scattering studies show that molecular organization is not fundamentally altered when comparing the flat ribbons of the racemate to chirally twisted or helical ribbons of the pure tartrate enantiomer. Essential features of the three-dimensional molecular organizations of these structures include interdigitation of alkyl chains within each bilayer and well-defined networks of ionic and hydrogen bonds between cations, anions, and water molecules between bilayers. The detailed study of diffraction patterns also indicated that the gemini headgroups are oriented parallel to the long edge of the ribbons. The structure thus possesses a high cohesion and good crystallinity, and for the first time, we could relate the packing of the chiral molecules to the expression of the chirality at a mesoscopic scale. The organization of the ribbons at the molecular level sheds light on a number of their macroscopic features. Among these are the reason why enantiomerically pure 16-2-16 tartrate forms ribbons that consist of exactly two bilayers, and a plausible mechanism by which a chirally twisted or helical shape may emerge from the packing of chiral tartrate ions. Importantly, the distinction between commonly observed helical and twisted morphologies could be related to a subtle symmetry breaking. These results demonstrate that accurately solving the molecular structure of self-assembled soft materials--a process rarely achieved--is within reach, that it is a valid approach to correlate molecular parameters to macroscopic properties, and thus that it offers opportunities to modulate properties through molecular design.

  8. Combinatorial and topological modeling of cluster self-assembly of the crystal structure of zeolites

    NASA Astrophysics Data System (ADS)

    Ilyushin, G. D.; Blatov, V. A.

    2015-07-01

    Combinatorial and topological modeling of packings of symmetrically connected polyhedral T12 clusters (hexagonal prisms), which are most widespread in crystal structures of zeolites, has been performed. Packings of T12 clusters are periodic 1D chains (11 types) and 2D microlayers (15 types). 2D microlayers that can be involved in the self-assembly of 3D zeolite structures described by tetracoordinated T nets are selected. Computer methods (the ToposPro program package) have been used to establish a correspondence with zeolites CHA (Chabazite, Ca6(H2O)40Al12Si24O72), AEI (AlPO-18, Al24P24O96), SAV ((C18H42N6)2(H2O)7Mg5Al19P24O96), KFI (Na30(H2O)98Al30Si66O192), GME (Gmelinite, (Ca,Na)4(H2O)24Al8Si16O48), AFX (SAPO-56, H3Al23Si5P20O96), and AFT (AlPO-52, Al36P36O144) for 7 out of 11 obtained models of 3D frameworks. Modeling of 3D polytypes of the GME (1L type)- AFX (2L type)- AFT (3L type) family has resulted in a new 3L polytype with the following crystallographic parameters: a =13.75 Å, c = 30.00 Å, V = 4912.0 Å3, sp. gr. P m2 (no. 187). It is established that the 2D self-assembly of known zeolite structures is accompanied by pairwise binding of all (T12 + T12) clusters with the formation of 4C rings, and the number of bonds between complementary chains during the formation of microlayers is maximum. Three types of obtained frameworks, which have no analogs among zeolites, exhibit low chain connectivity during microlayer formation in all cases.

  9. Self assembling proteins

    DOEpatents

    Yeates, Todd O.; Padilla, Jennifer; Colovos, Chris

    2004-06-29

    Novel fusion proteins capable of self-assembling into regular structures, as well as nucleic acids encoding the same, are provided. The subject fusion proteins comprise at least two oligomerization domains rigidly linked together, e.g. through an alpha helical linking group. Also provided are regular structures comprising a plurality of self-assembled fusion proteins of the subject invention, and methods for producing the same. The subject fusion proteins find use in the preparation of a variety of nanostructures, where such structures include: cages, shells, double-layer rings, two-dimensional layers, three-dimensional crystals, filaments, and tubes.

  10. Hierarchical self-assembly of suspended branched colloidal nanocrystals into superlattice structures.

    PubMed

    Miszta, Karol; de Graaf, Joost; Bertoni, Giovanni; Dorfs, Dirk; Brescia, Rosaria; Marras, Sergio; Ceseracciu, Luca; Cingolani, Roberto; van Roij, René; Dijkstra, Marjolein; Manna, Liberato

    2011-09-25

    Self-assembly of molecular units into complex and functional superstructures is ubiquitous in biology. The number of superstructures realized by self-assembly of man-made nanoscale units is also growing. However, assemblies of colloidal inorganic nanocrystals are still at an elementary level, not only because of the simplicity of the shape of the nanocrystal building blocks and their interactions, but also because of the poor control over these parameters in the fabrication of more elaborate nanocrystals. Here, we show how monodisperse colloidal octapod-shaped nanocrystals self-assemble, in a suitable solution environment, on two sequential levels. First, linear chains of interlocked octapods are formed, and subsequently the chains spontaneously self-assemble into three-dimensional superstructures. Remarkably, all the instructions for the hierarchical self-assembly are encoded in the octapod shape. The mechanical strength of these superstructures is improved by welding the constituent nanocrystals together.

  11. Template assisted self-assembly of iron oxide nanoparticles: An x-ray structural analysis

    SciTech Connect

    Mishra, D.; Zabel, H.; Ulyanov, S. V.; Romanov, V. P.; Uzdin, V. M.

    2014-02-07

    We have fabricated by e-beam lithography periodic arrays of rectangular shaped trenches of different widths into Si substrates. The trenches were filled with iron oxide nanoparticles, 20 nm in diameter, by spin-coating them onto the Si substrate. The trenches have the purpose to assist the self-assembly of the iron oxide nanoparticles. Using x-ray scattering techniques, we have analyzed the structure factor of the trenches before and after filling in order to determine the filling factor. We present a theoretical analysis of the x-ray scattering function within the distorted-wave Born approximation and we present a quantitative comparison between theory and experiment.

  12. Structurally homogeneous nanosheets from self-assembly of a collagen-mimetic peptide.

    PubMed

    Jiang, Tao; Xu, Chunfu; Zuo, Xiaobing; Conticello, Vincent P

    2014-08-04

    A collagen-mimetic peptide, NSIII, has been designed with three sequential blocks having positive, neutral, and negative charges, respectively. The non-canonical imino acid, (2S,4S)-4-aminoproline (amp), was used to specify the positive charges at the Xaa positions of (Xaa-Yaa-Gly) triads in the N-terminal domain of NSIII. Peptide NSIII underwent self-assembly from aqueous solution to form a highly homogeneous population of nanosheets. Two-dimensional crystalline sheets formed in which the length of the peptide defined the height of the sheets. These results contrasted with prior results on a similar multi-domain collagen-mimetic polypeptides in which the sheets had highly polydisperse distribution of sizes in the (x/y)- and (z)-dimensions. The structural differences between the two nanosheet assemblies were interpreted in terms of the relative stereoelectronic effects of the different aminoproline derivatives on the local triple helical conformation of the peptides.

  13. Directed self-assembly, genomic assembly complexity and the formation of biological structure, or, what are the genes for nacre?

    PubMed

    Cartwright, Julyan H E

    2016-03-13

    Biology uses dynamical mechanisms of self-organization and self-assembly of materials, but it also choreographs and directs these processes. The difference between abiotic self-assembly and a biological process is rather like the difference between setting up and running an experiment to make a material remotely compared with doing it in one's own laboratory: with a remote experiment-say on the International Space Station-everything must be set up beforehand to let the experiment run 'hands off', but in the laboratory one can intervene at any point in a 'hands-on' approach. It is clear that the latter process, of directed self-assembly, can allow much more complicated experiments and produce far more complex structures than self-assembly alone. This control over self-assembly in biology is exercised at certain key waypoints along a trajectory and the process may be quantified in terms of the genomic assembly complexity of a biomaterial. © 2016 The Author(s).

  14. Collagen I Self-Assembly: Revealing the Developing Structures that Generate Turbidity

    PubMed Central

    Zhu, Jieling; Kaufman, Laura J.

    2014-01-01

    Type I collagen gels are routinely used in biophysical studies and bioengineering applications. The structural and mechanical properties of these fibrillar matrices depend on the conditions under which collagen fibrillogenesis proceeds, and developing a fuller understanding of this process will enhance control over gel properties. Turbidity measurements have long been the method of choice for monitoring developing gels, whereas imaging methods are regularly used to visualize fully developed gels. In this study, turbidity and confocal reflectance microscopy (CRM) were simultaneously employed to track collagen fibrillogenesis and reconcile the information reported by the two techniques, with confocal fluorescence microscopy (CFM) used to supplement information about early events in fibrillogenesis. Time-lapse images of 0.5 mg/ml, 1.0 mg/ml, and 2.0 mg/ml acid-solubilized collagen I gels forming at 27°C, 32°C, and 37°C were collected. It was found that in situ turbidity measured in a scanning transmittance configuration was interchangeable with traditional turbidity measurements using a spectrophotometer. CRM and CFM were employed to reveal the structures responsible for the turbidity that develops during collagen self-assembly. Information from CRM and transmittance images was collapsed into straightforward single variables; total intensity in CRM images tracked turbidity development closely for all collagen gels investigated, and the two techniques were similarly sensitive to fibril number and dimension. Complementary CRM, CFM, and in situ turbidity measurements revealed that fibril and network formation occurred before substantial turbidity was present, and the majority of increasing turbidity during collagen self-assembly was due to increasing fibril thickness. PMID:24739181

  15. Transformation of self-assembly of a TTF derivative at the 1-phenyloctane/HOPG interface studied by STM--from a nanoporous network to a linear structure

    NASA Astrophysics Data System (ADS)

    Xu, Jing; Xiao, Xunwen; Deng, Ke; Zeng, Qingdao

    2016-01-01

    The self-assembly of a tetrathiafulvalene (TTF) derivative (EDTTF) and a 1,3,5-tris(10-carboxydecyloxy)-benzene (TCDB) heterobilayer nanostructure at the 1-phenyloctane/HOPG interface under ambient conditions has been studied by scanning tunneling microscopy (STM). EDTTF and TCDB could co-assemble into a brand new hexagonal network with one of the largest nano-cavities. Finally, the nanoporous network would transform into a more stable linear structure. Density functional theory (DFT) calculations have been performed to reveal the formation mechanism.The self-assembly of a tetrathiafulvalene (TTF) derivative (EDTTF) and a 1,3,5-tris(10-carboxydecyloxy)-benzene (TCDB) heterobilayer nanostructure at the 1-phenyloctane/HOPG interface under ambient conditions has been studied by scanning tunneling microscopy (STM). EDTTF and TCDB could co-assemble into a brand new hexagonal network with one of the largest nano-cavities. Finally, the nanoporous network would transform into a more stable linear structure. Density functional theory (DFT) calculations have been performed to reveal the formation mechanism. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07345f

  16. Structure-property relationships in self-assembling peptide hydrogels, homopolypeptides and polysaccharides

    NASA Astrophysics Data System (ADS)

    Hule, Rohan A.

    The main objective of this dissertation is to investigate quantitative structure-property relationships in a variety of molecular systems including de novo designed peptides, peptide amphiphiles, polysaccharides and high molecular weight polypeptides. Peptide molecules consisting of 20 amino acids were designed to undergo thermally triggered intramolecular folding into asymmetric beta-hairpins and intermolecular self-assembly via a strand swapping mechanism into physically crosslinked fibrillar hydrogels. The self-assembly mechanism was confirmed by multiple characterization techniques such as circular dichroism and FITR spectroscopy, atomic force and transmission electron microscopy and small angle neutron scattering. Three distinct fibrillar nanostructures, i.e. non-twisted, twisted and laminated were produced, depending on the degree of strand asymmetry and peptide registry. Differences in the fibrillar morphology have a direct consequence on the mechanical properties of the hydrogels, with the laminated hydrogels exhibiting a significantly higher elastic modulus as compared to the twisted or non-twisted fibrillar hydrogels. SANS and cryo-TEM data reveal that the self-assembled fibrils form networks that are fractal in nature. Models employed to elucidate the fractal behavior can relate changes in the correlation lengths, low q (network), and high q (fibrillar) fractal exponents to the distinct fibrillar nanomorphology. The fractal dimension of the networks varies significantly, from a mass to a surface fractal and can be directly related to the local fibrillar morphology and changes in the peptide concentration. Transitions in the fractal behavior seen in the high q regime can be attributed to self-assembly kinetics. An identical model can be used to establish a direct correlation between the bulk properties and changes in both, the network density and underlying morphology, of a modified peptide-based hydrogel. As in the case of asymmetric peptides, changes in

  17. Template-directed hierarchical self-assembly of graphene based hybrid structure for electrochemical biosensing.

    PubMed

    Parlak, Onur; Tiwari, Atul; Turner, Anthony P F; Tiwari, Ashutosh

    2013-11-15

    A template-directed self-assembly approach, using functionalised graphene as a fundamental building block to obtain a hierarchically ordered graphene-enzyme-nanoparticle bioelectrode for electrochemical biosensing, is reported. An anionic surfactant was used to prepare a responsive, functional interface and direct the assembly on the surface of the graphene template. The surfactant molecules altered the electrostatic charges of graphene, thereby providing a convenient template-directed assembly approach to a free-standing planar sheet of sp(2) carbons. Cholesterol oxidase and cholesterol esterase were assembled on the surface of graphene by intermolecular attractive forces while gold nanoparticles are incorporated into the hetero-assembly to enhance the electro-bio-catalytic activity. Hydrogen peroxide and cholesterol were used as two representative analytes to demonstrate the electrochemical sensing performance of the graphene-based hybrid structure. The bioelectrode exhibited a linear response to H2O2 from 0.01 to 14 mM, with a detection limit of 25 nM (S/N=3). The amperometric response with cholesterol had a linear range from 0.05 to 0.35 mM, sensitivity of 3.14 µA/µM/cm(2) and a detection limit of 0.05 µM. The apparent Michaelis-Menten constant (Km(app)) was calculated to be 1.22 mM. This promising approach provides a novel methodology for template-directed bio-self-assembly over planar sp(2) carbons of a graphene sheet and furnishes the basis for fabrication of ultra-sensitive and efficient electrochemical biosensors. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. STRUCTURE AND ELECTRONIC PROPERTIES OF SELF-ASSEMBLED MACROCYCLE AND POLYMER MULTILAYERS

    SciTech Connect

    L. S. LI; A. D. Q. LI

    2001-05-01

    Our results from optical absorption and surface external reflection FTIR reveal that we can grow self-assembled multilayers consisting of electron acceptors like OHBP and donors like NiPc. In order to investigate the evolution of the surface physical properties of self-assembled multilayers, we applied Kelvin probe techniques and surface photovoltage spectroscopy to monitor the growth of self-assembled OHBP and NiPc systems. Kelvin probe results indicate that the surface electronic potential is very sensitive to the presence of self-assembled molecular layers on surfaces. We find that there is an approximately constant gap of 350 meV between the surface work function of OHBP and NiPc terminated self-assembled multilayers. In other words, the surface work function or surface electronic potentials is a periodic function of the terminating layer, oscillating between {approximately}450 mV for OHBP layers and {approximately}100 mV for NiPc layers. On the other hand, the photo-induced effects can be also correlated to the terminating layer of the OHBP-NiPc system. This shows that the self-assembled layers also control the photo-induced effects to some extent. Over the whole excitation spectrum (300-710 nm), the photo-induced band bending change oscillates between two values mostly governed by the properties of the terminating layer of the self-assembled systems.

  19. Self-assembly of 3D prestressed tensegrity structures from DNA

    PubMed Central

    Liedl, Tim; Högberg, Björn; Tytell, Jessica; Ingber, Donald E.; Shih, William M.

    2010-01-01

    Tensegrity or tensional integrity is a property of a structure that relies on a balance between components that are either in pure compression or in pure tension for its stability [1,2]. Tensegrity structures exhibit extremely high strength-to-weight ratios and great resilience, and are therefore widely used in engineering, robotics and architecture [3,4]. Here we report nanoscale, prestressed, three-dimensional tensegrity structures in which rigid bundles of DNA double helices resist compressive forces exerted by segments of single-stranded DNA that act as tension-bearing cables. Our DNA tensegrity structures can self-assemble against forces up to 14 pN, which is twice the stall force of powerful molecular motors such as kinesin or myosin [5,6]. The forces generated by this molecular prestressing mechanism can be employed to bend the DNA bundles or to actuate the entire structure through enzymatic cleavage at specific sites. In addition to being building blocks for nanostructures, tensile structural elements made of single-stranded DNA could be used to study molecular forces, cellular mechanotransduction, and other fundamental biological processes. PMID:20562873

  20. Prediction of Electric Field Effects on Defect-Free Self-Assembled Nano-Patterning of Block Copolymer.

    PubMed

    Kim, Sang-Kon

    2016-03-01

    For future semiconductor device scaling, self-assembly, directed self-assembly (DSA) of block copolymers (BCPs), is a promising method with simplified processing conditions; however, critical challenge is defect control for fine pattern. Electric field is a method for the defect control. In this paper, for electric field effects to jog defects, the electric field induced self-assembled patterns is modeled and simulated by using the Monte Carlo method of dielectric polymers, the self-consistent-field theory (SCFT), and the Navier-Stokes equation. Electric field effects are quantified by using defect degree. Defective patterns are forced to undergo a phase transition to lamellar phase under electric field. For the high electric field, the excess free energy for the defect-free state becomes small. Simulation results can help to optimize electric field and process time in terms of defect area.

  1. Design of Nanostructured Biological Materials Through Self-Assembly of Peptides and Proteins

    DTIC Science & Technology

    2002-01-01

    impact in the coming decades. Engineering principles for micro - and nano -fabrication can be learned by understanding molecular self-assembly...range of applications in nano -biotechnology. Addresses Center for Biomedical Engineering, 56-341 Massachusetts Institute of Technology, 77...acids form stacked nanotubes that can insert into membranes and change their properties. These nano porous structures have potential anti-bacterial

  2. Strong Electro-Optic Effect and Spontaneous Domain Formation in Self-Assembled Peptide Structures.

    PubMed

    Gilboa, Barak; Lafargue, Clément; Handelman, Amir; Shimon, Linda J W; Rosenman, Gil; Zyss, Joseph; Ellenbogen, Tal

    2017-09-01

    Short peptides made from repeating units of phenylalanine self-assemble into a remarkable variety of micro- and nanostructures including tubes, tapes, spheres, and fibrils. These bio-organic structures are found to possess striking mechanical, electrical, and optical properties, which are rarely seen in organic materials, and are therefore shown useful for diverse applications including regenerative medicine, targeted drug delivery, and biocompatible fluorescent probes. Consequently, finding new optical properties in these materials can significantly advance their practical use, for example, by allowing new ways to visualize, manipulate, and utilize them in new, in vivo, sensing applications. Here, by leveraging a unique electro-optic phase microscopy technique, combined with traditional structural analysis, it is measured in di- and triphenylalanine peptide structures a surprisingly large electro-optic response of the same order as the best performing inorganic crystals. In addition, spontaneous domain formation is observed in triphenylalanine tapes, and the origin of their electro-optic activity is unveiled to be related to a porous triclinic structure, with extensive antiparallel beta-sheet arrangement. The strong electro-optic response of these porous peptide structures with the capability of hosting guest molecules opens the door to create new biocompatible, environmental friendly functional materials for electro-optic applications, including biomedical imaging, sensing, and optical manipulation.

  3. Delayed volatile compound release properties of self-assembly structures in emulsions.

    PubMed

    Phan, Van-Anh; Liao, Yong-Cheng; Antille, Nicolas; Sagalowicz, Laurent; Robert, Fabien; Godinot, Nicolas

    2008-02-13

    Temporal release and retention of aroma compounds from structured emulsions (where unsaturated monoglycerides are added to the oil) and conventional oil-in-water emulsions were studied using in vitro dynamic headspace analysis by proton-transfer reaction mass spectrometry and static headspace analysis by gas chromatography-mass spectrometry. Under dynamic conditions, the structured emulsion exhibited delayed release compared to the oil-in-water emulsion containing the same lipid content of 5%. The time to maximum concentration T max of amphiphilic and lipophilic aroma compounds increased by a factor of 1.2 (for 3 E-hexenal) to 1.9 (for octanal). The aroma release profile of the 5% lipid structured emulsion was close to that obtained for the oil-in-water emulsion containing 10% lipid. Under static conditions, the 5% lipid structured emulsion retained more of the most lipophilic aroma compounds than its counterpart 5% oil-in-water nonstructured emulsion. The present study provides potential solutions for modulating aroma release profiles of reduced-fat foods by self-assembly structures.

  4. Electric-Field-Directed Self-Assembly of Active Enzyme-Nanoparticle Structures

    PubMed Central

    Hsiao, Alexander P.; Heller, Michael J.

    2012-01-01

    A method is presented for the electric-field-directed self-assembly of higher-order structures composed of alternating layers of biotin nanoparticles and streptavidin-/avidin-conjugated enzymes carried out on a microelectrode array device. Enzymes included in the study were glucose oxidase (GOx), horseradish peroxidase (HRP), and alkaline phosphatase (AP); all of which could be used to form a light-emitting microscale glucose sensor. Directed assembly included fabricating multilayer structures with 200 nm or 40 nm GOx-avidin-biotin nanoparticles, with AP-streptavidin-biotin nanoparticles, and with HRP-streptavidin-biotin nanoparticles. Multilayered structures were also fabricated with alternate layering of HRP-streptavidin-biotin nanoparticles and GOx-avidin-biotin nanoparticles. Results showed that enzymatic activity was retained after the assembly process, indicating that substrates could still diffuse into the structures and that the electric-field-based fabrication process itself did not cause any significant loss of enzyme activity. These methods provide a solution to overcome the cumbersome passive layer-by-layer assembly methods to efficiently fabricate higher-order active biological and chemical hybrid structures that can be useful for creating novel biosensors and drug delivery nanostructures, as well as for diagnostic applications. PMID:22500078

  5. Electric-field-directed self-assembly of active enzyme-nanoparticle structures.

    PubMed

    Hsiao, Alexander P; Heller, Michael J

    2012-01-01

    A method is presented for the electric-field-directed self-assembly of higher-order structures composed of alternating layers of biotin nanoparticles and streptavidin-/avidin-conjugated enzymes carried out on a microelectrode array device. Enzymes included in the study were glucose oxidase (GOx), horseradish peroxidase (HRP), and alkaline phosphatase (AP); all of which could be used to form a light-emitting microscale glucose sensor. Directed assembly included fabricating multilayer structures with 200 nm or 40 nm GOx-avidin-biotin nanoparticles, with AP-streptavidin-biotin nanoparticles, and with HRP-streptavidin-biotin nanoparticles. Multilayered structures were also fabricated with alternate layering of HRP-streptavidin-biotin nanoparticles and GOx-avidin-biotin nanoparticles. Results showed that enzymatic activity was retained after the assembly process, indicating that substrates could still diffuse into the structures and that the electric-field-based fabrication process itself did not cause any significant loss of enzyme activity. These methods provide a solution to overcome the cumbersome passive layer-by-layer assembly methods to efficiently fabricate higher-order active biological and chemical hybrid structures that can be useful for creating novel biosensors and drug delivery nanostructures, as well as for diagnostic applications.

  6. Ternary blend polymer solar cells with self-assembled structure for enhancing power conversion efficiency

    NASA Astrophysics Data System (ADS)

    Yang, Zhenhua; Li, Hongfei; Nam, Chang-Yong; Kisslinger, Kim; Satija, Sushil; Rafailovich, Miriam

    Bulk heterojunction (BHJ) polymer solar cells are an area of intense interest due to their advantages such as mechanical flexibility. The active layer is typically spin coated from the solution of polythiophene derivatives (donor) and fullerenes (acceptor) and interconnected domains are formed because of phase separation. However, the power conversion efficiency (PCE) of BHJ solar cell is restricted by the disordered inner structures in the active layer, donor or acceptor domains isolated from electrodes. Here we report a self-assembled columnar structure formed by phase separation between (PCDTBT) and polystyrene (PS) for the active layer morphology optimization. The BHJ solar cell device based on this structure is promising for exhibiting higher performance due to the shorter carrier transportation pathway and larger interfacial area between donor and acceptor. The surface morphology is investigated with atomic force microscopy (AFM) and the columnar structure is studied by investigation of cross-section of the blend thin film of PCDTBT and PS under the transmission electron microscopy (TEM). The different morphological structures formed via phase segregation are correlated with the performance of the BHJ solar cells.

  7. Self-assembly Columnar Structure in Active Layer of Bulk Heterojunction Solar Cell

    NASA Astrophysics Data System (ADS)

    Pan, Cheng; Segui, Jennifer; Yu, Yingjie; Li, Hongfei; Akgun, Bulent; Satijia, Sushil. K.; Gersappe, Dilip; Nam, Chang-Yong; Rafailovich, Miriam

    2012-02-01

    Bulk Heterojunction (BHJ) polymer solar cells are an area of intense interest due to their flexibility and relatively low cost. However, due to the disordered inner structure in active layer, the power conversion efficiency of BHJ solar cell is relatively low. Our research provides the method to produce ordered self-assembly columnar structure within active layer of bulk heterojunction (BHJ) solar cell by introducing polystyrene (PS) into the active layer. The blend thin film of polystyrene, poly (3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) at different ratio are spin coated on substrate and annealed in vacuum oven for certain time. Atomic force microscopy (AFM) images show uniform phase segregation on the surface of polymer blend thin film and highly ordered columnar structure is then proven by etching the film with ion sputtering. TEM cross-section technology is also used to investigate the column structure. Neutron reflectometry was taken to establish the confinement of PCBM at the interface of PS and P3HT. The different morphological structures formed via phase segregation will be correlated with the performance of the PEV cells to be fabricated at the BNL-CFN.

  8. PREFACE: IUMRS-ICA 2008 Symposium, Sessions 'X. Applications of Synchrotron Radiation and Neutron Beam to Soft Matter Science' and 'Y. Frontier of Polymeric Nano-Soft-Materials - Precision Polymer Synthesis, Self-assembling and Their Functionalization'

    NASA Astrophysics Data System (ADS)

    Takahara, Atsushi; Kawahara, Seiichi

    2009-09-01

    Tashiro (Toyota Technological Institute) Professor Kazuo Sakurai(Kitakyushu University) Professor Keiji Tanaka (Kyushu University) Dr Sono Sasaki (JASRI/Spring-8) Professor Naoya Torikai (KENS) Professor Moonhor Ree (POSTECH) Professor Kookheon Char (Seoul National University) Professor Charles C Han (CAS) Professor Atsushi Takahara(Kyushu University) Frontier of Polymeric Nano-Soft-Materials, Precision Polymer Synthesis, Self-assembling and Their Functionalization (Symposium Y of IUMRS-ICA2008) Seiichi Kawahara, Rong-Ming Ho, Hiroshi Jinnai, Masami Kamigaito, Takashi Miyata, Hiroshi Morita, Hideyuki Otsuka, Daewon Sohn, Keiji Tanaka It is our great pleasure and honor to publish peer-reviewed papers, presented in Symposium Y 'Frontier of Polymeric Nano-Soft-Materials Precision Polymer Synthesis, Self-assembling and Their Functionalization' at the International Union of Materials Research Societies International Conference in Asia 2008 (IUMRS-ICA2008), which was held on 9-13 December 2008, at Nagoya Congress Center, Nagoya, Japan. 'Polymeric nano-soft-materials' are novel outcomes based on a recent innovative evolution in polymer science, i.e. precision polymer synthesis, self-assembling and functionalization of multi-component systems. The materials are expected to exhibit specific functions and unique properties due to their hierarchic morphologies brought either by naturally-generated ordering or by artificial manipulation of the systems, e.g., crystallization and phase-separation. The emerging precision synthesis has brought out new types of polymers with well-controlled primary structures. Furthermore, the surface and interface of the material are recognized to play an important role in the outstanding mechanical, electrical and optical properties, which are required for medical and engineering applications. In order to understand structure-property relationships in the nano-soft-materials, it is indispensable to develop novel characterization techniques. Symposium Y

  9. Self-assembly and structure of directly imaged inorganic-anion monolayers on a gold nanoparticle.

    PubMed

    Wang, Yifeng; Neyman, Alevtina; Arkhangelsky, Elizabeth; Gitis, Vitaly; Meshi, Louisa; Weinstock, Ira A

    2009-12-02

    Cryogenic "trapping" was used to obtain the first TEM images of self-assembled monolayers of inorganic anions on a gold nanoparticle. This unique structural information makes it possible to study the formation of a protecting-ligand shell at an unprecedented level of detail. The protecting ligands are polyoxometalates (POMs; alpha-X(n+)W(12)O(40)((8-n)-), X(n+) = Al(3+) and "2H(+)", and alpha-X(n+)W(11)O(39)((12-n)-), X(n+) = P(5+), Si(4+), and Al(3+)) with large negative charges for association with the gold surface and W atoms (Z = 74) for TEM imaging. The POM-anion shells were obtained by ligand exchange from citrate-protected 13.8 nm gold nanoparticles. Replacement of the organic (citrate) by inorganic (tungsten-oxide) ligand shells results in substantial changes in the surface plasmon resonance (SPR). By correlating cryo-TEM images with changes in the SPR, degrees of surface coverage were reliably quantified by UV-visible spectroscopy. Then, the kinetics and thermodynamics of ligand-shell formation were investigated by systematically varying POM structure and charge. Rates of POM association with the gold surface ("nucleation") are inhibited by the electric-potential barrier of the citrate-stabilized particles, while binding affinities increase linearly with the charges (from 5- to 9-) of structurally different POM anions, suggesting that no single orientation ("lattice matching") is required for monolayer self-assembly. Time-dependent cryo-TEM images reveal that monolayer growth occurs via "islands", a mechanism that points to cation-mediated attraction between bound POMs. Complete ligand shells comprised of 330 molecules of alpha-AlW(11)O(39)(9-) (1) possess small net charges (29e from zeta-potential measurements) and short Debye lengths (kappa(-1) = 1.0 nm), which indicate that approximately 99% of the 2970 K(+) counter cations lie within ca. 1.5 nm (approximately 3 hydrated K(+) ion diameters) from the outer surface of the POM shell. Energetic analysis of

  10. The structural coloration of textile materials using self-assembled silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Gao, Weihong; Rigout, Muriel; Owens, Huw

    2017-09-01

    The work presented investigates how to produce structural colours on textile materials by applying a surface coating of silica nanoparticles (SNPs). Uniform SNPs with particle diameters in a controlled micron size range (207-350 nm) were synthesized using a Stöber-based solvent varying (SV) method which has been reported previously. Photonic crystals (PCs) were formed on the surface of a piece of textile fabric through a process of natural sedimentation self-assembly of the colloidal suspension containing uniform SNPs. Due to the uniformity and a particular diameter range of the prepared SNPs, structural colours were observed from the fabric surface due to the Bragg diffraction of white light with the ordered structure of the silica PCs. By varying the mean particle diameter, a wide range of spectral colours from red to blue were obtained. The comparison of structural colours on fabrics and on glasses suggests that a smooth substrate is critical when producing materials with high colour intensity and spatial uniformity. This work suggested a promising approach to colour textile materials without the need for traditional dyes and/or pigments. [Figure not available: see fulltext.

  11. Structure and self-assembly of the calcium binding matrix protein of human metapneumovirus.

    PubMed

    Leyrat, Cedric; Renner, Max; Harlos, Karl; Huiskonen, Juha T; Grimes, Jonathan M

    2014-01-07

    The matrix protein (M) of paramyxoviruses plays a key role in determining virion morphology by directing viral assembly and budding. Here, we report the crystal structure of the human metapneumovirus M at 2.8 Å resolution in its native dimeric state. The structure reveals the presence of a high-affinity Ca²⁺ binding site. Molecular dynamics simulations (MDS) predict a secondary lower-affinity site that correlates well with data from fluorescence-based thermal shift assays. By combining small-angle X-ray scattering with MDS and ensemble analysis, we captured the structure and dynamics of M in solution. Our analysis reveals a large positively charged patch on the protein surface that is involved in membrane interaction. Structural analysis of DOPC-induced polymerization of M into helical filaments using electron microscopy leads to a model of M self-assembly. The conservation of the Ca²⁺ binding sites suggests a role for calcium in the replication and morphogenesis of pneumoviruses.

  12. Biological and polymeric self-assembled hybrid systems: structure and properties of thylakoid/polyelectrolyte complexes.

    PubMed

    Dementiev, A A; Baikov, A A; Ptushenko, V V; Khomutov, G B; Tikhonov, A N

    2005-06-15

    A novel hybrid system composed of biological components and synthetic polymer, thylakoid/polycation complex, has been formed and studied. Effects of complex formation on the structure, electrostatics and functioning of thylakoid membranes have been examined. Thylakoids from bean leaves were used to form complexes with polycation polyallylamine hydrochloride (PAAH) in two systems: (i) thylakoid/polycation complexes formed in an aqueous bulk phase, and (ii) immobilized thylakoid/polycation planar complexes. Immobilized on a solid substrate surface, thylakoid/polycation complexes were prepared using layer-by-layer stepwise alternate adsorption technique, i.e., via the sequential alternate adsorption of thylakoids and polycation molecules. The morphology of built up structures was investigated by scanning electron microscopy. Light-induced electron transport in chloroplasts was studied by the electron paramagnetic resonance (EPR) method. Spin probe technique was employed to study the structural and electrostatic characteristics of thylakoid membranes. We have found that efficiency of light-induced electron transport in thylakoid membranes and membrane structure were not changed noticeably by PAAH binding to thylakoids in a wide range of PAAH concentrations. The data obtained indicate the physiologically-soft character of polycation interactions with thylakoid membranes and demonstrate effectiveness of interfacial self-assembly approach to fabrication of complex planar functional nanostructures from biological components and synthetic polymers.

  13. Two-dimensional self-assembly of 1-pyrylphosphonic acid: transfer of stacks on structured surface.

    PubMed

    Yip, Hin-Lap; Ma, Hong; Jen, Alex K-Y; Dong, Jianchun; Parviz, Babak A

    2006-05-03

    Strong hydrogen bonding and pi-pi stacking between 1-pyrylphosphonic acid (PYPA) molecules were exploited to create self-assembled two-dimensional supramolecular structures. Polycrystalline films of these laminate crystalline PYPA bilayers were easily deposited onto the solid supports through a simple spin-coating technique. Atomic force microscopy (AFM), scanning tunneling microscopy (STM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV-vis absorption, and fluorescence spectroscopy reveal that processing parameters, such as solvent, concentration, and surface of the substrate, are critical factors in determining the final morphology of the stacked film. Robust laminate structures could be obtained only when short alkyl chain protic solvents (methanol or ethanol) and a nonhydrophobic substrate surface were used. Polycrystalline films were formed through the nucleation and growth of PYPA molecules into laminate structures at the air/solvent interface before they land on the substrate during the spin-coating process. These films possess good mechanical properties and were easily transferred onto a SiO2/Si substrate that was patterned with Au electrodes without breaking their crystalline structures. The successful transfer of the laminate crystals allows us to probe their electrical properties through a field effect transistor device. A gating effect on the charge transport of the stacked films indicates that PYPA laminate crystal possesses p-typed semiconductor characteristics.

  14. Modeling Protein Self Assembly

    ERIC Educational Resources Information Center

    Baker, William P.; Jones, Carleton Buck; Hull, Elizabeth

    2004-01-01

    Understanding the structure and function of proteins is an important part of the standards-based science curriculum. Proteins serve vital roles within the cell and malfunctions in protein self assembly are implicated in degenerative diseases. Experience indicates that this topic is a difficult one for many students. We have found that the concept…

  15. Immobilization of biomaterials to nano-assembled films (self-assembled monolayers, Langmuir-Blodgett films, and layer-by-layer assemblies) and their related functions.

    PubMed

    Ariga, Katsuhiko; Nakanishi, Takashi; Michinobu, Tsuyoshi

    2006-08-01

    For utilization of highly sophisticated functions of biomaterials in nano-scale functional systems, immobilization of biomaterials on artificial devices such as electrodes via thin film technology is one of the most powerful strategies. In this review, we focus on three major organic ultrathin films, self-assembled monolayers (SAM), Langmuir-Blodgett (LB) films, and layer-by-layer (LBL) assemblies, and from the viewpoints of biomaterial immobilization, typical examples and recent progresses in these film technologies are described. The SAM method allows facile contact between biomaterials and man-made devices, and well used for bio-related sensors. In addition, recent micro-fabrication techniques such as micro-contact printing and dip-pen nanolithography were successfully applied to preparation of biomaterial patterning. A monolayer at the air-water interface, which is a unit structure of LB films, provides a unique environment for recognition of aqueous biomaterials. Recognition and immobilization of various biomaterials including nucleotides, nucleic acid bases, amino acids, sugars, and peptides were widely investigated. The LB film can be also used for immobilization of enzymes in an ultrathin film on an electrode, resulting in sensor application. The LBL assembling method is available for wide range of biomaterials and provides great freedom in designs of layered structures. These advantages are reflected in preparation of thin-film bio-reactors where multiple kinds of enzymes sequentially operate. LBL assemblies were also utilized for sensors and drug delivery systems. This kind of assembling structures can be prepared on micro-size particle and very useful for preparation of hollow capsules with biological functions.

  16. Engineering novel mesoscopic structures using DNA-programmed colloidal self-assembly

    NASA Astrophysics Data System (ADS)

    Kim, Anthony Ji

    Controlling interactions between colloidal suspensions has been a fascinating challenge both experimentally and theoretically. Three-dimensional colloidal crystals assembled from monodisperse colloidal particles have generated a significant interest because of their potential application as photonic band gap materials (PBG), chemical sensors, optical filters, and switches. DNA-mediated colloidal assembly offers a unique tool for controlling the range and magnitude of interparticle interaction to promote novel crystal formation. We try to delimit those conditions under which the DNA-mediated interaction gives rise to well-ordered 3-D colloidal crystals, as well as to discuss the applications, optimization, and ultimate limitations of such DNA-mediated particle self-assembly. There are many unknowns regarding the expected colloidal phase diagram and the strength and kinetics of the DNA-mediated interaction, as well as the nonspecific interactions between colloids with different surface chemistries. We start with the simplest case of one-component system, where every colloid has a DNA-mediated attraction to every other, since the phase behavior and kinetics of one-component dispersions is well understood from previous studies. We determine and model the temperature and DNA-density dependence of the self-assembly phase diagram and kinetics. We find that crystals only form with the sterically stabilized DNA-particles in a rather narrow range of temperatures and have acceptably fast nucleation and growth in a small range of grafted-DNA density. In addition, the phase behavior of binary alloy solid solutions is studied using the same sterically stabilized colloidal particles. A competition between DNA single-base mismatches is used to create energy penalties for the substitution of a few KBTs'. The minority species substitute into the crystal lattice when the pair interaction difference is a fraction of a K BT, however, they exclude from the growing crystal when the pair

  17. Strip-Pattern-Spheres Self-Assembled from Polypeptide-Based Polymer Mixtures: Structure and Defect Features

    PubMed Central

    Zhu, Xingyu; Guan, Zhou; Lin, Jiaping; Cai, Chunhua

    2016-01-01

    We found that poly(γ-benzyl-L-glutamate)-block-poly(ethylene glycol) (PBLG-b-PEG) rod-coil block copolymers and polystyrene (PS) homopolymers can cooperatively self-assemble into nano-spheres with striped patterns on their surfaces (strip-pattern-spheres) in aqueous solution. With assistance of dissipative particle dynamics simulation, it is discovered that the PS homopolymers form a spherical template core and the PBLG-b-PEG block copolymers assemble into striped patterns on the spherical surface. The hydrophobic PBLG rods are packed orderly in the strips, while the hydrophilic PEG blocks stabilize the strip-pattern-spheres in solution. Defects such as dislocations and disclinations can be observed in the striped patterns. Self-assembling temperature and sphere radius are found to affect defect densities in the striped patterns. A possible mechanism is proposed to illustrate how PBLG-b-PEG and PS cooperatively self-assemble into hierarchical spheres with striped patterns on surfaces. PMID:27418116

  18. 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.

  19. 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

  20. Three dimensional tubular structure self-assembled by vascular mesenchymal cells at stiffness interfaces of hydrogels.

    PubMed

    Zhu, Xiaolu; Gojgini, Shiva; Chen, Ting-Hsuan; Teng, Fang; Fei, Peng; Dong, Siyan; Segura, Tatiana; Ho, Chih-Ming

    2016-10-01

    In this study, we report a rational and robust methodology to construct three dimensional (3D) tubular-structures solely by self-assembly of vascular mesenchymal cells (VMCs). Using the cell-laden hyaluronic acid hydrogel surrounded by cell-free gel with a higher stiffness, VMCs spontaneously migrated across the interface and assembled into 3D tubes, which composes of numerous cells. Based on turing instability which describes the reaction-diffusion processes of inhibitors and activators, this result of 3D tubular structure formation agrees with theoretical predictions from simulations of the reaction-diffusion of morphogens and cells under the initial conditions of patterned cell-laden hydrogel. We showed that this combination of theoretical prediction and experiments is able to produce multi-cellular 3D tubes with desired dimensions and determinate orientation in hydrogel mimicking the 3D features of tubular tissue. This work provides a reliable methodology for creating tubular structures with controllable sizes inside the 3D hydrogel through multi-cellular self-organization. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  1. Self-assembling peptide and protein amyloids: from structure to tailored function in nanotechnology.

    PubMed

    Wei, Gang; Su, Zhiqiang; Reynolds, Nicholas P; Arosio, Paolo; Hamley, Ian W; Gazit, Ehud; Mezzenga, Raffaele

    2017-07-31

    Self-assembled peptide and protein amyloid nanostructures have traditionally been considered only as pathological aggregates implicated in human neurodegenerative diseases. In more recent times, these nanostructures have found interesting applications as advanced materials in biomedicine, tissue engineering, renewable energy, environmental science, nanotechnology and material science, to name only a few fields. In all these applications, the final function depends on: (i) the specific mechanisms of protein aggregation, (ii) the hierarchical structure of the protein and peptide amyloids from the atomistic to mesoscopic length scales and (iii) the physical properties of the amyloids in the context of their surrounding environment (biological or artificial). In this review, we will discuss recent progress made in the field of functional and artificial amyloids and highlight connections between protein/peptide folding, unfolding and aggregation mechanisms, with the resulting amyloid structure and functionality. We also highlight current advances in the design and synthesis of amyloid-based biological and functional materials and identify new potential fields in which amyloid-based structures promise new breakthroughs.

  2. Self-Assembled Structures of Benzoic Acid on Au(111) Surface

    NASA Astrophysics Data System (ADS)

    Vu, Thu-Hien; Wandlowski, Thomas

    2017-02-01

    Electrochemical scanning tunneling microscopy combined with cyclic voltammetry were employed to explore the self-assembly of benzoic acid (BA) on a Au(111) substrate surface in a 0.1-M HClO4 solution. At the negatively charged surface, BA molecules form two highly ordered physisorbed adlayers with their phenyl rings parallel to the substrate surface. High-resolution scanning tunneling microscopy images reveal the packing arrangement and internal molecular structures. The striped pattern and zigzag structure of the BA adlayers are composed of parallel rows of dimers, in which two BA molecules are bound through a pair of O-H···O hydrogen bonds. Increasing the electrode potential further to positive charge densities of Au(111) leads to the desorption of the physisorbed hydrogen-bonded networks and the formation of a chemisorbed adlayer. BA molecules change their orientation from planar to upright fashion, which is accompanied by the deprotonation of the carboxyl group. Furthermore, potential-induced formation and dissolution of BA adlayers were also investigated. Structural transitions between the various types of ordered adlayers occur according to a nucleation and growth mechanism.

  3. Self-Assembled Structures of Benzoic Acid on Au(111) Surface

    NASA Astrophysics Data System (ADS)

    Vu, Thu-Hien; Wandlowski, Thomas

    2017-06-01

    Electrochemical scanning tunneling microscopy combined with cyclic voltammetry were employed to explore the self-assembly of benzoic acid (BA) on a Au(111) substrate surface in a 0.1-M HClO4 solution. At the negatively charged surface, BA molecules form two highly ordered physisorbed adlayers with their phenyl rings parallel to the substrate surface. High-resolution scanning tunneling microscopy images reveal the packing arrangement and internal molecular structures. The striped pattern and zigzag structure of the BA adlayers are composed of parallel rows of dimers, in which two BA molecules are bound through a pair of O-H···O hydrogen bonds. Increasing the electrode potential further to positive charge densities of Au(111) leads to the desorption of the physisorbed hydrogen-bonded networks and the formation of a chemisorbed adlayer. BA molecules change their orientation from planar to upright fashion, which is accompanied by the deprotonation of the carboxyl group. Furthermore, potential-induced formation and dissolution of BA adlayers were also investigated. Structural transitions between the various types of ordered adlayers occur according to a nucleation and growth mechanism.

  4. Self-assembly of "Mickey Mouse" shaped colloids into tube-like structures: experiments and simulations.

    PubMed

    Wolters, Joost R; Avvisati, Guido; Hagemans, Fabian; Vissers, Teun; Kraft, Daniela J; Dijkstra, Marjolein; Kegel, Willem K

    2015-02-14

    The self-assembly of anisotropic patchy particles with a triangular shape was studied by experiments and computer simulations. The colloidal particles were synthesized in a two-step seeded emulsion polymerization process, and consist of a central smooth lobe connected to two rough lobes at an angle of ∼90°, resembling the shape of a "Mickey Mouse" head. Due to the difference in overlap volume, adding an appropriate depletant induces an attractive interaction between the smooth lobes of the colloids only, while the two rough lobes act as steric constraints. The essentially planar geometry of the Mickey Mouse particles is a first geometric deviation of dumbbell shaped patchy particles. This new geometry enables the formation of one-dimensional tube-like structures rather than spherical, essentially zero-dimensional micelles. At sufficiently strong attractions, we indeed find tube-like structures with the sticky lobes at the core and the non-sticky lobes pointing out as steric constraints that limit the growth to one direction, providing the tubes with a well-defined diameter but variable length both in experiments and simulations. In the simulations, we found that the internal structure of the tubular fragments could either be straight or twisted into so-called Bernal spirals.

  5. Nano-scale characterization of binary self-assembled monolayers under an ambient condition with STM and TERS.

    PubMed

    Horimoto, Noriko N; Tomizawa, Shigeru; Fujita, Yasuhiko; Kajimoto, Shinji; Fukumura, Hiroshi

    2014-09-07

    Gold surfaces were modified by benzyl-mercaptan (BM) and then partly replaced with benzenethiol (BT), which formed binary self-assembled monolayers (SAM). Initially BT randomly replaced BM in the monolayer, but at long exchange times >15 nm radius domains were observed with specific relative composition of BT and BM.

  6. Structure and property relations of macromolecular self-assemblies at interfaces

    NASA Astrophysics Data System (ADS)

    Yang, Zhihao

    Hydrophilic polymer chains, poly(ethylene glycol) (PEG), are attached to glass surfaces by silylation of the silanol groups on glass surfaces with the omega-(methoxyl terminated PEG) trimethoxysilanes. These tethered polymer chains resemble the self-assembled monolayers (SAMs) of PEG, which exhibit excellent biocompatibility and provide a model system for studying the interactions of proteins with polymer surfaces. The low molecular weight PEGs tend to extend, forming a brush-like monolayer, whereas the longer polymer chains tend to interpenetrate each other, forming a mushroom-like PEG monolayer at the interface. Interactions between a plasma protein, bovine serum albumin, and the PEG-SAMs are investigated in terms of protein adsorption and diffusion on the surfaces by the technique of fluorescence recovery after photobleaching (FRAP). The diffusion and aggregation behaviors of the protein on the two monolayers are found to be quite different despite the similarities in adsorption and desorption behaviors. The results are analyzed with a hypothesis of the hydrated surface dynamics. A method of covalently bonding phospholipid molecules to silica substrates followed by loading with free phospholipids is demonstrated to form well organized and stable phospholipid self-assembled monolayers. Surfaces of such SAMs structurally mimic the aqueous sides of phospholipid bilayer membranes. The dynamics of phospholipids and an adsorbed protein, lipase, in the SAMs are probed with FRAP, in terms of lateral diffusion of both phospholipids and protein molecules. The esterase activity of lipase on the SAM surfaces is confirmed by the hydrolysis reaction of a substrate, umbelliferone stearate, showing such lipid SAMs posess biomembrane functionality in terms of interfacial activation of the membranous enzymes. Dynamics of polyethylene oxide and polypropylene oxide tri-block copolymers, PEO-PPO-PEO and PPO-PEO-PPO, at the air/water interface upon thermal stimulation is studied by

  7. Self-assembly and structural-functional flexibility of oxygenic photosynthetic machineries: personal perspectives.

    PubMed

    Garab, Győző

    2016-01-01

    This short review, with a bit of historical aspect and a strong personal bias and emphases on open questions, is focusing on the (macro-)organization and structural-functional flexibilities of the photosynthetic apparatus of oxygenic photosynthetic organisms at different levels of the structural complexity-selected problems that have attracted most my attention in the past years and decades. These include (i) the anisotropic organization of the pigment-protein complexes and photosynthetic membranes-a basic organizing principle of living matter, which can, and probably should be adopted to intelligent materials; (ii) the organization of protein complexes into chiral macrodomains, large self-assembling highly organized but structurally flexible entities with unique spectroscopic fingerprints-structures, where, important, high-level regulatory functions appear to 'reside'; (iii) a novel, dissipation-assisted mechanism of structural changes, based on a thermo-optic effect: ultrafast thermal transients in the close vicinity of dissipation of unused excitation energy, which is capable of inducing elementary structural changes; it makes plants capable of responding to excess excitation with reaction rates proportional to the overexcitation above the light-saturation of photosynthesis; (iv) the 3D ultrastructure of the granum-stroma thylakoid membrane assembly and other multilamellar membrane systems, and their remodelings-associated with regulatory mechanisms; (v) the molecular organization and structural-functional plasticity of the main light-harvesting complex of plants, in relation to their crystal structure and different in vivo and in vitro states; and (vi) the enigmatic role of non-bilayer lipids and lipid phases in the bilayer thylakoid membrane-warranting its high protein content and contributing to its structural flexibility.

  8. Self-assembly of conjugated oligomers and polymers at the interface: structure and properties.

    PubMed

    Xu, Lirong; Yang, Liu; Lei, Shengbin

    2012-08-07

    In this review, we give a brief account on the recent scanning tunneling microscopy investigation of interfacial structures and properties of π-conjugated semiconducting oligomers and polymers, either at the solid-air (including solid-vacuum) or at the solid-liquid interface. The structural aspects of the self-assembly of both oligomers and polymers are highlighted. Conjugated oligomers can form well ordered supramolecular assemblies either at the air-solid or liquid-solid interface, thanks to the relatively high mobility and structural uniformity in comparison with polymers. The backbone structure, substitution of side chains and functional groups can affect the assembling behavior significantly, which offers the opportunity to tune the supramolecular structure of these conjugated oligomers at the interface. For conjugated polymers, the large molecular weight limits the mobility on the surface and the distribution in size also prevents the formation of long range ordered supramolecular assembly. The submolecular resolution obtained on the assembling monolayers enables a detailed investigation of the chain folding at the interface, both the structural details and the effect on electronic properties. Besides the ability in studying the assembling structures at the interfaces, STM also provides a reasonable way to evaluate the distribution of the molecular weight of conjugated polymers by statistic of the contour length of the adsorbed polymer chains. Both conjugated oligomers and polymers can form composite assemblies with other materials. The ordered assembly of oligomers can act as a template to controllably disperse other molecules such as coronene or fullerene. These investigations open a new avenue to fine tune the assembling structure at the interface and in turn the properties of the composite materials. To summarize scanning tunneling microscopy has demonstrated its surprising ability in the investigation of the assembling structures and properties of

  9. Self-assembled nano-architecture liquid crystalline particles as a promising carrier for progesterone transdermal delivery.

    PubMed

    Elgindy, Nazik A; Mehanna, Mohammed M; Mohyeldin, Salma M

    2016-03-30

    The study aims to elaborate novel self-assembled liquid crystalline nanoparticles (LCNPs) for management of hormonal disturbances following non-invasive progesterone transdermal delivery. Fabrication and optimization of progesteroneloaded LCNPs for transdermal delivery were assessed via a quality by design approach based on 2(3) full factorial design. The design includes the functional relationships between independent processing variables and dependent responses of particle size, polydispersity index, zeta potential, cumulative drug released after 24h and ex-vivo transdermal steady flux. The developed nanocarrier was subjected to TEM (transmission electron microscope) for morphological elucidation and stability study within a period of three months at different storage temperatures. The cubic phase of LCNPs was successfully prepared using glyceryl monooleate (GMO) via the emulsification technique. Based on the factorial design, the independent operating variables significantly affected the five dependent responses. The cubosomes hydrodynamic diameters were in the nanometric range (101-386 nm) with narrow particle size distribution, high negative zeta potential ≥-30 mV and entrapment efficiency ≥94%. The LCNPs succeeded in sustaining progesterone release for almost 24h, following a non-fickian transport of drug diffusion mechanism. Ex-vivo study revealed a significant enhancement up to 6 folds in the transdermal permeation of progesterone-loaded LCNPs compared to its aqueous suspension. The optimized LCNPs exhibited a high physical stability while retaining the cubic structure for at least three months. Quality by design approach successfully accomplished a predictable mathematical model permitting the development of novel LCNPs for transdermal delivery of progesterone with the benefit of reducing its oral route side effects.

  10. Post-directed-self-assembly membrane fabrication for in situ analysis of block copolymer structures

    NASA Astrophysics Data System (ADS)

    Ren, J.; Ocola, L. E.; Divan, R.; Czaplewski, D. A.; Segal-Peretz, T.; Xiong, S.; Kline, R. J.; Arges, C. G.; Nealey, P. F.

    2016-10-01

    Full characterization of the three-dimensional structures resulting from the directed self-assembly (DSA) of block copolymers (BCP) remains a difficult challenge. Transmission electron microscope (TEM) tomography and resonant soft x-ray scattering have emerged as powerful and complementary methods for through-film characterization; both techniques require samples to be prepared on specialized membrane substrates. Here we report a generalizable process to implement BCP DSA with density multiplication on silicon nitride membranes. A key feature of the process developed here is that it does not introduce any artefacts or damage to the polymer assemblies as DSA is performed prior to back-etched membrane formation. Because most research and applications of BCP lithography are based on silicon substrates, process variations introduced by implementing DSA on a silicon nitride/silicon stack versus silicon were identified and mitigated. Using full-wafers, membranes were fabricated with different sizes and layouts to enable both TEM and x-ray characterization. Finally, both techniques were used to characterize structures resulting from the DSA of lamella-forming BCP with density multiplication.

  11. Self-assembled micro-organogels for 3D printing silicone structures

    PubMed Central

    O’Bryan, Christopher S.; Bhattacharjee, Tapomoy; Hart, Samuel; Kabb, Christopher P.; Schulze, Kyle D.; Chilakala, Indrasena; Sumerlin, Brent S.; Sawyer, W. Gregory; Angelini, Thomas E.

    2017-01-01

    The widespread prevalence of commercial products made from microgels illustrates the immense practical value of harnessing the jamming transition; there are countless ways to use soft, solid materials that fluidize and become solid again with small variations in applied stress. The traditional routes of microgel synthesis produce materials that predominantly swell in aqueous solvents or, less often, in aggressive organic solvents, constraining ways that these exceptionally useful materials can be used. For example, aqueous microgels have been used as the foundation of three-dimensional (3D) bioprinting applications, yet the incompatibility of available microgels with nonpolar liquids, such as oils, limits their use in 3D printing with oil-based materials, such as silicone. We present a method to make micro-organogels swollen in mineral oil, using block copolymer self-assembly. The rheological properties of this micro-organogel material can be tuned, leveraging the jamming transition to facilitate its use in 3D printing of silicone structures. We find that the minimum printed feature size can be controlled by the yield stress of the micro-organogel medium, enabling the fabrication of numerous complex silicone structures, including branched perfusable networks and functional fluid pumps. PMID:28508071

  12. Post-directed-self-assembly membrane fabrication for in situ analysis of block copolymer structures.

    PubMed

    Ren, J; Ocola, L E; Divan, R; Czaplewski, D A; Segal-Peretz, T; Xiong, S; Kline, R J; Arges, C G; Nealey, P F

    2016-09-23

    Full characterization of the three-dimensional structures resulting from the directed self-assembly (DSA) of block copolymers (BCP) remains a difficult challenge. Transmission electron microscope (TEM) tomography and resonant soft x-ray scattering have emerged as powerful and complementary methods for through-film characterization; both techniques require samples to be prepared on specialized membrane substrates. Here we report a generalizable process to implement BCP DSA with density multiplication on silicon nitride membranes. A key feature of the process developed here is that it does not introduce any artefacts or damage to the polymer assemblies as DSA is performed prior to back-etched membrane formation. Because most research and applications of BCP lithography are based on silicon substrates, process variations introduced by implementing DSA on a silicon nitride/silicon stack versus silicon were identified and mitigated. Using full-wafers, membranes were fabricated with different sizes and layouts to enable both TEM and x-ray characterization. Finally, both techniques were used to characterize structures resulting from the DSA of lamella-forming BCP with density multiplication.

  13. Structural and Electronic Properties of Aromatic Isocyanide Self-Assembled Monolayers on Au(111) Surface

    NASA Astrophysics Data System (ADS)

    Li, Yan; Galli, Giulia

    2007-03-01

    The search for molecular assemblies with interesting transport properties for molecular electronic devices is an active field of research. Isocyanide self-assembled monolayers (SAMs) have received some attention lately, as they may provide a better π-network for electron transport than other molecular SAMs such as benzenethiols. We have studied the structural and electronic properties of the interface between a gold surface and an aromatic isocyanide SAM, using density-functional theory in the GGA-PBE approximation. Our calculations predict a herringbone arrangement at high coverage, instead of the conventional structure with (√3x√3)R30^o periodicity. The most favorable geometry is however found at low coverage, where the interaction between molecules is negligible and the barriers between differently tilted geometries are small compared to room temperature. These results explain the disordered patterns recently observed in room temperature STM measurements and point at possible difficulties in using isocyanide SAMs for molecular devices. Our calculations also give insight into the alignment of the molecular energy levels with respect to the Fermi energy of the metal substrate, and the charge redistribution at the interface, which provide essential guide for understanding and predicting transport properties of these SAMs, in case ordering can be achieved.

  14. Thermally-nucleated self-assembly of water and alcohol into stable structures at hydrophobic interfaces

    PubMed Central

    Voïtchovsky, Kislon; Giofrè, Daniele; José Segura, Juan; Stellacci, Francesco; Ceriotti, Michele

    2016-01-01

    At the interface with solids, the mobility of liquid molecules tends to be reduced compared with bulk, often resulting in increased local order due to interactions with the surface of the solid. At room temperature, liquids such as water and methanol can form solvation structures, but the molecules remain highly mobile, thus preventing the formation of long-lived supramolecular assemblies. Here we show that mixtures of water with methanol can form a novel type of interfaces with hydrophobic solids. Combining in situ atomic force microscopy and multiscale molecular dynamics simulations, we identify solid-like two-dimensional interfacial structures that nucleate thermally, and are held together by an extended network of hydrogen bonds. On graphite, nucleation occurs above ∼35 °C, resulting in robust, multilayered nanoscopic patterns. Our findings could have an impact on many fields where water-alcohol mixtures play an important role such as fuel cells, chemical synthesis, self-assembly, catalysis and surface treatments. PMID:27713413

  15. Formation mechanism for hexagonal-structured self-assemblies of nanocrystalline titania templated by cetyltrimethylammonium bromide.

    PubMed

    Sakai, Toshio; Yano, Hanae; Ohno, Mitsuru; Shibata, Hirobumi; Torigoe, Kanjiro; Utsumi, Shigenori; Sakamoto, Kazutami; Koshikawa, Naokiyo; Adachi, Satoshi; Sakai, Hideki; Abe, Masahiko

    2008-01-01

    Hexagonal-structured self-assemblies of nanocrystalline (anatase) titania templated by cetyltrimethylammonium bromide (C(16)H(33)N(CH(3))(3)Br; CTAB) (Hex-ncTiO(2)/CTAB Nanoskeleton) were formed after mixing of aqueous solutions containing CTAB spherical micelles and titanium oxysulfate acid hydrate (TiOSO(4).xH(2)SO(4).xH(2)O) as a titania precursor in the absence of any other additives. Formation mechanism of the Hex-ncTiO(2)/CTAB Nanoskeleton was examined in terms of the reaction temperature, titania precursor/CTAB mixing ratio, surfactant type, electrostatic interaction, micelle formation and molecular component. We found that crystal growth of crystalline (anatase) titania (polymorphic crystallization) was promoted with higher temperature and lower titania precursor content in aqueous solutions. In addition, we revealed that the crystalline (anatase) titania was formed in polycation, poly(allylamine hydrochloride ([CH(2)CH(CH(2)NH(2))HCl](n); PAH), and formamide (HCONH(2)) solutions. On the other hand, no titania formation was observed in anionic systems such as sodium dodecyl sulfate (CH(3)(CH(2))(11)OSO(3)Na; SDS) and poly(sodium 4-styrenesulfonate ([C(8)H(7)SO(3)Na](n); PSSS). This indicates that hydrolysis reaction of the titania precursor is initiated by not only cations but also nitrogen atoms in molecules and polymers. Hexagonally structure was formed in only cationic surfactant micellar solutions but not in polycation solutions and formamide.

  16. Laser printing hierarchical structures with the aid of controlled capillary-driven self-assembly

    PubMed Central

    Hu, Yanlei; Lao, Zhaoxin; Cumming, Benjamin P.; Wu, Dong; Li, Jiawen; Liang, Haiyi; Chu, Jiaru; Huang, Wenhao; Gu, Min

    2015-01-01

    Capillary force is often regarded as detrimental because it may cause undesired distortion or even destruction to micro/nanostructures during a fabrication process, and thus many efforts have been made to eliminate its negative effects. From a different perspective, capillary force can be artfully used to construct specific complex architectures. Here, we propose a laser printing capillary-assisted self-assembly strategy for fabricating regular periodic structures. Microscale pillars are first produced by localized femtosecond laser polymerization and are subsequently assembled into periodic hierarchical architectures with the assistance of controlled capillary forces in an evaporating liquid. Spatial arrangements, pillar heights, and evaporation processes are readily tuned to achieve designable ordered assemblies with various geometries. Reversibility of the assembly is also revealed by breaking the balance between the intermolecular force and the elastic standing force. We further demonstrate the functionality of the hierarchical structures as a nontrivial tool for the selective trapping and releasing of microparticles, opening up a potential for the development of in situ transportation systems for microobjects. PMID:26038541

  17. Molecular simulation studies of the structure of phosphorylcholine self-assembled monolayers

    NASA Astrophysics Data System (ADS)

    Zheng, Jie; He, Yi; Chen, Shengfu; Li, Lingyan; Bernards, Matthew T.; Jiang, Shaoyi

    2006-11-01

    We report a study of the structure of phosphorylcholine self-assembled monolayers (PC-SAMs) on Au(111) surfaces using both molecular mechanics (MM) and molecular dynamics (MD) simulation techniques. The lattice structure (i.e., packing densities and patterns) of the PC chains was determined first, by examining the packing energies of different structures by MM simulations in an implicit solvent. The chain orientation (i.e., antiparallel and parallel arrangements of the PC head groups) was then evaluated. The initial azimuthal angles of the PC chains were also adjusted to ensure that the optimal lattice structure was found. Finally, the two most probable lattice structures were solvated with explicit water molecules and their energies were compared after 1.5ns of MD simulations to verify the optimal structures obtained from MM. We found that the optimal lattice structure of the PC-SAM corresponds to a √7×√7 R19° lattice structure (i.e., surface coverage of 50.4Å2/molecule) with a parallel arrangement of the head groups. The corresponding thickness of the optimal PC-SAM is 13.4Å which is in agreement with that from experiments. The head groups of the PC chains are aligned on the surface in such a way that their dipole components are minimized. The P →N vector of the head groups forms an angle of 82° with respect to the surface normal. The tilt direction of molecular chains was observed to be towards their next nearest neighbor.

  18. Pressure effects on structures formed by entropically driven self-assembly: illustration for denaturation of proteins.

    PubMed

    Yoshidome, Takashi; Harano, Yuichi; Kinoshita, Masahiro

    2009-01-01

    We propose a general framework of pressure effects on the structures formed by the self-assembly of solute molecules immersed in solvent. The integral equation theory combined with the morphometric approach is employed for a hard-body model system. Our picture is that protein folding and ordered association of proteins are driven by the solvent entropy: At low pressures, the structures almost minimizing the excluded volume (EV) generated for solvent particles are stabilized. Such structures appear to be even more stabilized at high pressures. However, it is experimentally known that the native structure of a protein is unfolded, and ordered aggregates such as amyloid fibrils and actin filaments are dissociated by applying high pressures. This initially puzzling result can also be elucidated in terms of the solvent entropy. A clue to the basic mechanism is in the phenomenon that, when a large hard-sphere solute is immersed in small hard spheres forming the solvent, the small hard spheres are enriched near the solute and this enrichment becomes greater as the pressure increases. We argue that "attraction" is entropically provided between the solute surface and solvent particles, and the attraction becomes higher with rising pressure. Due to this effect, at high pressures, the structures possessing the largest possible solvent-accessible surface area together with sufficiently small EV become more stable in terms of the solvent entropy. To illustrate this concept, we perform an analysis of pressure denaturation of three different proteins. It is shown that only the structures that have the characteristics described above exhibit interesting behavior. They first become more destabilized relative to the native structure as the pressure increases, but beyond a threshold pressure the relative instability begins to decrease and they eventually become more stable than the native structure.

  19. Functional architectures based on self-assembly of bio-inspired dipeptides: Structure modulation and its photoelectronic applications.

    PubMed

    Chen, Chengjun; Liu, Kai; Li, Junbai; Yan, Xuehai

    2015-11-01

    Getting inspiration from nature and further developing functional architectures provides an effective way to design innovative materials and systems. Among bio-inspired materials, dipeptides and its self-assembled architectures with functionalities have recently been the subject of intensive studies. However, there is still a great challenge to explore its applications likely due to the lack of effective adaptation of their self-assembled structures as well as a lack of understanding of the self-assembly mechanisms. In this context, taking diphenylalanine (FF, a core recognition motif for molecular self-assembly of the Alzheimer's β-amyloid polypeptides) as a model of bio-inspired dipeptides, recent strategies on modulation of dipeptide-based architectures were introduced with regard to both covalent (architectures modulation by coupling functional groups) and non-covalent ways (controlled architectures by different assembly pathways). Then, applications are highlighted in some newly emerging fields of innovative photoelectronic devices and materials, such as artificial photosynthetic systems for renewable solar energy storage and renewable optical waveguiding materials for optoelectronic devices. At last, the challenges and future perspectives of these bio-inspired dipeptides are also addressed.

  20. [4 + 2] cycloaddition reaction to approach diazatwistpentacenes: synthesis, structures, physical properties, and self-assembly.

    PubMed

    Li, Junbo; Li, Peizhou; Wu, Jiansheng; Gao, Junkuo; Xiong, Wei-Wei; Zhang, Guodong; Zhao, Yanli; Zhang, Qichun

    2014-05-16

    Three novel diazatwistpentacenes (1,4,6,13-tetraphenyl-7:8,11:12-bisbenzo-2,3-diazatwistpentacene (1, IUPAC name: 9,11,14,16-tetraphenyl-1,6-dihydrobenzo[8,9]triphenyleno[2,3-g]phthalazine); 1,4-di(pyridin-2-yl)-6,13-diphenyl-7:8,11:12-bisbenzo-2,3-diazatwistpentacene (2, IUPAC name: 9,16-diphenyl-11,14-di(pyridin-2-yl)-1,6-dihydrobenzo[8,9]triphenyleno[2,3-g]phthalazine); and 1,4-di(thien-2-yl)-6,13-diphenyl-7:8,11:12-bisbenzo-2,3-diazatwistpentacene (3, IUPAC name: 9,16-diphenyl-11,14-di(thien-2-yl)-1,6-dihydrobenzo[8,9]triphenyleno[2,3-g]phthalazine)) have been successfully synthesized through [4 + 2] cycloaddition reaction involving in situ arynes as dienophiles and substituted 1,2,4,5-tetrazines as dienes. Their structures have been determined by single-crystal X-ray diffraction, confirming that all compounds have twisted configurations with torsion angles between the pyrene unit and the 2,3-diazaanthrance part as high as 21.52° (for 1), 24.74° (for 2), and 21.14° (for 3). The optical bandgaps for all compounds corroborate the values derived from CV. The calculation done by DFT shows that the HOMO-LUMO bandgaps are in good agreement with experimental data. Interestingly, the substituted groups (phenyl, pyridyl, thienyl) in the 1,4-positions did affect their self-assembly and the optical properties of as-resulted nanostructures. Under the same conditions, compounds 1-3 could self-assemble into different morphologies such as microrods (for 1), nanoprisms (for 2), and nanobelts (for 3). Moreover, the UV-vis absorption and emission spectra of as-prepared nanostructures were largely red-shifted, indicating J-type aggregation for all materials. Surprisingly, both 1 and 2 showed aggregation-induced emission (AIE) effect, while compound 3 showed aggregation-caused quenching (ACQ) effect. Our method to approach novel twisted azaacenes through [4 + 2] reaction could offer a new tool to develop unusual twisted conjugated materials for future optoelectronic

  1. Nanopropulsion by biocatalytic self-assembly.

    PubMed

    Leckie, Joy; Hope, Alexander; Hughes, Meghan; Debnath, Sisir; Fleming, Scott; Wark, Alastair W; Ulijn, Rein V; Haw, Mark D

    2014-09-23

    A number of organisms and organelles are capable of self-propulsion at the micro- and nanoscales. Production of simple man-made mimics of biological transportation systems may prove relevant to achieving movement in artificial cells and nano/micronscale robotics that may be of biological and nanotechnological importance. We demonstrate the propulsion of particles based on catalytically controlled molecular self-assembly and fiber formation at the particle surface. Specifically, phosphatase enzymes (acting as the engine) are conjugated to a quantum dot (the vehicle), and are subsequently exposed to micellar aggregates (fuel) that upon biocatalytic dephosphorylation undergo fibrillar self-assembly, which in turn causes propulsion. The motion of individual enzyme/quantum dot conjugates is followed directly using fluorescence microscopy. While overall movement remains random, the enzyme-conjugates exhibit significantly faster transport in the presence of the fiber forming system, compared to controls without fuel, a non-self-assembling substrate, or a substrate which assembles into spherical, rather than fibrous structures upon enzymatic dephosphorylation. When increasing the concentration of the fiber-forming fuel, the speed of the conjugates increases compared to non-self-assembling substrate, although directionality remains random.

  2. Self-Assembled Multilayer Structure and Enhanced Thermochromic Performance of Spinodally Decomposed TiO2-VO2 Thin Film.

    PubMed

    Sun, Guangyao; Zhou, Huaijuan; Cao, Xun; Li, Rong; Tazawa, Masato; Okada, Masahisa; Jin, Ping

    2016-03-23

    Composite films of VO2-TiO2 were deposited on sapphire (11-20) substrate by cosputtering method. Self-assembled well-ordered multilayer structure with alternating Ti- and V-rich epitaxial thin layer was obtained by thermal annealing via a spinodal decomposition mechanism. The structured thermochromic films demonstrate superior optical modulation upon phase transition, with significantly reduced transition temperature. The results provide a facile and novel approach to fabricate smart structures with excellent performance.

  3. Self-assembly of amido-ended hyperbranched polyester films with a highly ordered dendritic structure.

    PubMed

    Zhang, Daohong; Xu, Zhicai; Li, Junna; Chen, Sufang; Cheng, Juan; Zhang, Aiqing; Chen, Shenghui; Miao, Menghe

    2014-09-24

    Self-assemblies fabricated from dendrimers and amphiphilic polymers have demonstrated remarkable performances and a wide range of applications. Direct self-assembly of hyperbranched polymers into highly ordered macrostructures with heat-resistance remains a big challenge due to the weak amphiphilicity of the polymers. Here, we report the self-assembly of amphiphilic amido-ended hyperbranched polyester (HTDA-2) into millimeter-size dendritic films using combined hydrogen bond interaction and solvent induction. The self-assembly process and mechanism have been studied. Hydrogen bond interaction between amido-ended groups assists the aggregation of inner and outer chains of the HTDA-2, resulting in phase separation and micelle formation. Some micelles attach to and grow on the glass substrate like seedlings. Other micelles move to the seedlings and connect with their branches via solvent induction and hydrogen bond interaction, leading to the fabrication of highly ordered crystalline dendritic films that show high heat-resistance. HTDA-2 can further self-assemble into sheet crystals on the dendritic films.

  4. Controlled self-assembly of PbS nanoparticles into macrostar-like hierarchical structures

    SciTech Connect

    Li, Guowei; Li, Changsheng; Tang, Hua; Cao, Kesheng; Chen, Juan

    2011-07-15

    Graphical abstract: The aggregation and rotation of nanoparticles to adopt parallel orientations in three dimensions was indirectly illustrated by TEM and HRTEM images. Highlights: {yields} Macrostar-like PbS hierarchical structures was successfully synthesized by a simple hydrothermal method and mesostars were assembled from the PbS nanocube building blocks with edge lengths of about 100 nm. {yields} Ostwald-ripening-assisted oriented attachment is believed to play a key role in the growth behavior of novel 3D structures. {yields} Optical properties indicating few defects on the surface of the PbS structure and exhibit large blue-shifts compared to bulk PbS. -- Abstract: The synthesis of macrostar-like PbS hierarchical structures by a simple hydrothermal method at 180 {sup o}C for 24 h is proven successful with the assistance of a new surfactant called tetrabutylammonium bromide (TBAB). The as-obtained product is characterized by means of X-ray powder diffraction, field emission scanning electron microscopy, energy dispersive spectrometry, high resolution transmission electron microscopy, and selected area electron diffraction. The presence of TBAB and NaF plays an important role in the formation of PbS macrostructures. Ostwald-ripening-assisted oriented attachment is believed to play a key role in the growth behavior of novel 3D structures. As such, a possible self-assembly mechanism is proposed to explain the formation of the said structures. The present study aims to introduce new insights into understanding the formation process of such unique hierarchical superstructures.

  5. Cerium ion doping into self-assembled Ge using three-dimensional dot structure

    NASA Astrophysics Data System (ADS)

    Miyata, Yusuke; Ueno, Kazuya; Yoshimura, Takashi; Ashida, Atsushi; Fujimura, Norifumi

    2017-06-01

    Rare earth element, Ce, doped Ge (Ge:Ce) three-dimensional crystal is fabricated on Si (001) via a solid source low-temperature molecular beam epitaxy. Ce affects the formation of the self-assembled Ge dot, including its structure, initial growth and the density because of the self-limited process to suppress the total energy contained in the surface, the interface and bulk stress. Owing to the compressive strain from Si substrate, the out-of-plane lattice parameters of Ge:Ce dots are larger than that of bulk Ge, while in-plane lattice constants are smaller. Based on the lattice constant change and the full width at half maximum of the Raman peaks found as a function of Ce concentration, the solid solubility limit of Ce in the substitutional sites of Ge is as high as 0.7 at%. The magnitude of Raman shift does not depend upon Ce concentration, which suggests the growth or incorporation of Ge:Ce dots on Si (001) is limited by the stress.

  6. Bioadhesive lipid compositions: self-assembly structures, functionality, and medical applications.

    PubMed

    Barauskas, Justas; Christerson, Lars; Wadsäter, Maria; Lindström, Fredrick; Lindqvist, Anna-Karin; Tiberg, Fredrik

    2014-03-03

    Lipid-based liquid crystalline compositions of phospholipids and diglycerides have unique bioadhesive properties with several medical applications, as exemplified by a lipid-based medical device indicated for management and relief of intraoral pain. The present paper describes the relation between self-assembly properties of phosphatidyl choline (PC) and glycerol dioleate (GDO) mixtures in the presence of aqueous fluids and functional attributes of the system, including: film formation and bioadhesion, intraoral coverage, acceptance by patients, and potential as a drug delivery system. The phase behavior of PC/GDO was characterized using synchrotron small-angle X-ray scattering. Functional properties, including the presence of study formulations at intraoral surfaces, ease of attachment, taste, and degree of and intraoral pain, were assessed in a crossover clinical pilot study in head and neck cancer patients. An optimum in functional properties was indicated for formulations with a PC/GDO weight ratio of about 35/65, where the lipids form a reversed cubic liquid crystalline micellar phase structure (Fd3m space group) over the relevant temperature range (25-40 °C).

  7. Structure and Order of Phosphonic Acid-Based Self-Assembled Monolayers on Si(100)

    PubMed Central

    Dubey, Manish; Weidner, Tobias; Gamble, Lara J.; Castner, David G.

    2010-01-01

    Organophosphonic acid self-assembled monolayers (SAMs) on oxide surfaces have recently seen increased use in electrical and biological sensor applications. The reliability and reproducibility of these sensors require good molecular organization in these SAMs. In this regard, packing, order and alignment in the SAMs is important, as it influences the electron transport measurements. In this study, we examine the order of hydroxyl- and methyl- terminated phosphonate films deposited onto silicon oxide surfaces by the tethering by aggregation and growth method using complementary, state-of-art surface characterization tools. Near edge x-ray absorption fine structure (NEXAFS) spectroscopy and in situ sum frequency generation (SFG) spectroscopy are used to study the order of the phosphonate SAMs in vacuum and under aqueous conditions, respectively. X-ray photoelectron spectroscopy and time of flight secondary ion mass spectrometry results show that these samples form chemically intact monolayer phosphonate films. NEXAFS and SFG spectroscopy showed that molecular order exists in the octadecylphosphonic acid and 11-hydroxyundecylphosphonic acid SAMs. The chain tilt angles in these SAMs were approximately 37° and 45°, respectively. PMID:20735054

  8. Antibacterial and water purification activities of self-assembled honeycomb structure of aerosol deposited titania film.

    PubMed

    Park, Jung-Jae; Lee, Jong-Gun; Kim, Do-Yeon; Hong, Joo-Hyun; Kim, Jae-Jin; Hong, Seungkwan; Yoon, Sam S

    2012-11-20

    A simple and rapid room-temperature aerosol deposition method was used to fabricate TiO(2) films for photokilling/photdegradation applications. TiO(2) particles were accelerated to supersonic speeds and fractured upon impacting a glass substrate to form a functional thin film, a process known as aerosol deposition. After deposition, the films were annealed at various temperatures, and their photokilling/photodegradation performances following ultraviolet (UV) exposure were evaluated by counting the number of surviving bacterial colonies, and by a methylene blue decolorization test. The photocatalytic performances of all TiO(2) films were obtained under weak UV exposure (0.6 mW/cm(2)). The film density, crystalline phase, and surface roughness (morphology) were measured by scanning electron microscopy, X-ray diffraction, UV-visible spectroscopy, and atomic force microscopy. The unique, self-assembled honeycomb structure of the aerosol deposited films contributed to the increase in surface area because of extreme roughness, which enhances the photokilling and photodegradation performance. Nonannealed films yielded the best photocatalytic performance due to their small crystalline sizes and large surface areas due to increased surface roughness.

  9. Graphene film doped with silver nanoparticles: self-assembly formation, structural characterizations, antibacterial ability, and biocompatibility.

    PubMed

    Zhang, Panpan; Wang, Haixia; Zhang, Xiaoyuan; Xu, Wei; Li, Yang; Li, Qing; Wei, Gang; Su, Zhiqiang

    2015-06-01

    Graphene and silver nanoparticles (AgNPs) are important building blocks for the synthesis of functional nanomaterials for bio-related applications. Here, we report a facile strategy to decorate AgNPs onto reduced graphene oxide (RGO) by the simultaneous reduction of silver ions and graphene oxide nanosheets within one system, and further to fabricate a dimension-adjustable RGO/AgNP multi-layered film by a thermal-driven self-assembly process. The structures of the fabricated RGO/AgNP hybrid films were identified by UV-visible spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and transmission electron microscopy. The thickness of the fabricated RGO/AgNP film was further measured by scanning electron microscopy. The hydrophilicity of the RGO/AgNP films was tested by contact angle measurement. Antibacterial and cell culture experiments based on the fabricated RGO/AgNP films indicate that this kind of hybrid film exhibits excellent antibacterial activity and high biocompatibility. A potential antibacterial mechanism of the fabricated RGO/AgNP hybrid film was proposed.

  10. Thermal dewetting with a chemically heterogeneous nano-template for self-assembled L1(0) FePt nanoparticle arrays.

    PubMed

    Wang, Liang-Wei; Cheng, Chung-Fu; Liao, Jung-Wei; Wang, Chiu-Yen; Wang, Ding-Shuo; Huang, Kuo-Feng; Lin, Tzu-Ying; Ho, Rong-Ming; Chen, Lih-Juann; Lai, Chih-Huang

    2016-02-21

    A design for the fabrication of metallic nanoparticles is presented by thermal dewetting with a chemically heterogeneous nano-template. For the template, we fabricate a nanostructured polystyrene-b-polydimethylsiloxane (PS-b-PDMS) film on a Si|SiO2 substrate, followed by a thermal annealing and reactive ion etching (RIE) process. This gives a template composed of an ordered hexagonal array of SiOC hemispheres emerging in the polystyrene matrix. After the deposition of a FePt film on this template, we utilize the rapid thermal annealing (RTA) process, which provides in-plane stress, to achieve thermal dewetting and structural ordering of FePt simultaneously. Since the template is composed of different composition surfaces with periodically varied morphologies, it offers more tuning knobs to manipulate the nanostructures. We show that both the decrease in the area of the PS matrix and the increase in the strain energy relaxation transfer the dewetted pattern from the randomly distributed nanoparticles into a hexagonal periodic array of L10 FePt nanoparticles. Transmission electron microscopy with the in situ heating stage reveals the evolution of the dewetting process, and confirms that the positions of nanoparticles are aligned with those of the SiOC hemispheres. The nanoparticles formed by this template-dewetting show an average diameter and center-to-center distance of 19.30 ± 2.09 nm and 39.85 ± 4.80 nm, respectively. The hexagonal array of FePt nanoparticles reveals a large coercivity of 1.5 T, much larger than the nanoparticles fabricated by top-down approaches. This approach offers an efficient pathway toward self-assembled nanostructures in a wide range of material systems.

  11. In Situ Electrochemical Synthesis and Deposition of Discotic Hexa-peri-hexabenzocoronene Molecules on Electrodes: Self-Assembled Structure, Redox Properties, and Application for Supercapacitor.

    PubMed

    Qin, Leiqiang; Zhang, Yunan; Wu, Xiaoyan; Nian, Li; Xie, Zengqi; Liu, Linlin; Ma, Yuguang

    2015-07-01

    Discotic hexa-peri-hexabenzocoronene (HBC) molecules are synthesized by electrochemical cyclodehydrogenation reaction and in situ self-assembled to π-electronic, discrete nanofibular objects with an average diameter about 70 nm, which are deposited directly onto the electrode. The nanofibers consist of columnar arrays of the π-stacked HBC molecules and the intercolumnar distance is determined to be 1.19 nm by X-ray diffraction, which corresponds well to the distance of 1.1 nm observed by high-resolution transmitting electron microscopy. The diameter of the molecular columns matches the size of the discotic HBC molecule indicating face-to-face π-stacking of HBC units in the column. The HBC nanofibers on electrode are redox active, and the nanosized columnar structures provide a huge surface area, which is a great benefit for the charging/discharging process, delivering excellent capacitance of 155 F g(-1) . The described electrochemical deposition method shows great advantage for self-assembling the family of insoluble and structurally designable graphene-like nano materials, which constitutes an important step toward molecular electronics.

  12. Self-Assembly of SbCl3 and 1,4-Dioxane: Cubic Structure Connected by Very Weak Bonds

    NASA Astrophysics Data System (ADS)

    Kua, Jeremy; Daly, Rowena C.; Tomlin, Keaton M.; Duin, Adri C. T. Van; Brill, Thomas B.; Beal, Royce W.; Rheingold, Arnold L.

    2009-09-01

    The self-assembly of SbCl3 and 1,4-dioxane in a 2:3 ratio leads to an interpenetrating extended cubic structure from X-ray crystallography. The structure is held together by very weak Sb-O bonds (˜7 kcal/mol each), which still maintain strong directionality. Parameterization and subsequent simulation of the system using a reactive force field (ReaxFF) gives us insight into the key interactions necessary for self-assembly from a completely random configuration of molecules into the experimentally observed cubic structure. We explain why the porous structure (with no interpenetration of lattices) is not observed, and we trace the important intermediate substructures formed en route to the crystal.

  13. Self-assembly of SbCl3 and 1,4-dioxane: cubic structure connected by very weak bonds.

    PubMed

    Kua, Jeremy; Daly, Rowena C; Tomlin, Keaton M; van Duin, Adri C T; Brill, Thomas B; Beal, Royce W; Rheingold, Arnold L

    2009-10-22

    The self-assembly of SbCl(3) and 1,4-dioxane in a 2:3 ratio leads to an interpenetrating extended cubic structure from X-ray crystallography. The structure is held together by very weak Sb-O bonds ( approximately 7 kcal/mol each), which still maintain strong directionality. Parameterization and subsequent simulation of the system using a reactive force field (ReaxFF) gives us insight into the key interactions necessary for self-assembly from a completely random configuration of molecules into the experimentally observed cubic structure. We explain why the porous structure (with no interpenetration of lattices) is not observed, and we trace the important intermediate substructures formed en route to the crystal.

  14. Self-assembly of silica colloidal crystal thin films with tuneable structural colours over a wide visible spectrum

    NASA Astrophysics Data System (ADS)

    Gao, Weihong; Rigout, Muriel; Owens, Huw

    2016-09-01

    Colloidal crystal (CC) thin films that produce structural colours over a wide visible spectrum have been self-assembled from silica nanoparticles (SNPs) using a natural sedimentation method. A series of colloidal suspensions containing uniform SNPs (207-350 nm) were prepared using the Stöber method. The prepared silica suspensions were directly subjected to natural sedimentation at an elevated temperature. The SNPs were deposited under the force of gravity and self-assembled into an ordered array. The solid CC thin films produced structural colours over a wide visible spectrum from red to violet. Visual inspection and colorimetric measurements indicated that the structural colour of the CC thin film is tuneable by varying the SNPs diameters and the viewing angles. The closely packed face-centred cubic (fcc) structure of the CC thin film was confirmed using SEM imaging and was in agreement with the intense colour observed from the film surface.

  15. High-Resolution Structure of a Self-Assembly-Competent Form of a Hydrophobic Peptide Captured in a Soluble [beta]-Sheet Scaffold

    SciTech Connect

    Makabe, Koki; Biancalana, Matthew; Yan, Shude; Tereshko, Valentina; Gawlak, Grzegorz; Miller-Auer, Hélène; Meredith, Stephen C.; Koide, Shohei

    2010-02-08

    {beta}-Rich self-assembly is a major structural class of polypeptides, but still little is known about its atomic structures and biophysical properties. Major impediments for structural and biophysical studies of peptide self-assemblies include their insolubility and heterogeneous composition. We have developed a model system, termed peptide self-assembly mimic (PSAM), based on the single-layer {beta}-sheet of Borrelia outer surface protein A. PSAM allows for the capture of a defined number of self-assembly-like peptide repeats within a water-soluble protein, making structural and energetic studies possible. In this work, we extend our PSAM approach to a highly hydrophobic peptide sequence. We show that a penta-Ile peptide (Ile{sub 5}), which is insoluble and forms {beta}-rich self-assemblies in aqueous solution, can be captured within the PSAM scaffold in a form capable of self-assembly. The 1.1-{angstrom} crystal structure revealed that the Ile{sub 5} stretch forms a highly regular {beta}-strand within this flat {beta}-sheet. Self-assembly models built with multiple copies of the crystal structure of the Ile5 peptide segment showed no steric conflict, indicating that this conformation represents an assembly-competent form. The PSAM retained high conformational stability, suggesting that the flat {beta}-strand of the Ile{sub 5} stretch primed for self-assembly is a low-energy conformation of the Ile{sub 5} stretch and rationalizing its high propensity for self-assembly. The ability of the PSAM to 'solubilize' an otherwise insoluble peptide stretch suggests the potential of the PSAM approach to the characterization of self-assembling peptides.

  16. Crystal structure of a self-assembling lipopeptide detergent at 1.20 Å

    SciTech Connect

    Ho, Dona N.; Pomroy, Neil C.; Cuesta-Seijo, Jose A.; Prive, Gilbert G.

    2008-10-21

    Lipopeptide detergents (LPDs) are a new class of amphiphile designed specifically for the structural study of integral membrane proteins. The LPD monomer consists of a 25-residue peptide with fatty acyl chains linked to side chains located at positions 2 and 24 of the peptide. LPDs are designed to form {alpha}-helices that self-assemble into cylindrical micelles, providing a more natural interior acyl chain packing environment relative to traditional detergents. We have determined the crystal structure of LPD-12, an LPD coupled to two dodecanoic acids, to a resolution of 1.20 {angstrom}. The LPD-12 monomers adopt the target conformation and associate into cylindrical octamers as expected. Pairs of helices are strongly associated as Alacoil-type antiparallel dimers, and four of these dimers interact through much looser contacts into assemblies with approximate D{sub 2} symmetry. The aligned helices form a cylindrical shell with a hydrophilic exterior that protects an interior hydrophobic cavity containing the 16 LPD acyl chains. Over 90% of the methylene/methyl groups from the acylated side chains are visible in the micelle interiors, and {approx}90% of these adopt trans dihedral angle conformations. Dodecylmaltoside (DDM) was required for the crystallization of LPD-12, and we find 10-24 ordered DDM molecules associated with each LPD assembly, resulting in an overall micelle molecular weight of {approx}30 kDa. The structures confirm the major design objectives of the LPD framework, and reveal unexpected features that will be helpful in the engineering additional versions of lipopeptide amphiphiles.

  17. Analysis of Secondary Structure and Self-Assembly of Amelogenin by Variable Temperature Circular Dichroism and Isothermal Titration Calorimetry

    PubMed Central

    Lakshminarayanan, Rajamani; Yoon, Il; Hegde, Balachandra G.; Daming, Fan; Du, Chang; Moradian-Oldak, Janet

    2009-01-01

    Amelogenin is a proline-rich enamel matrix protein known to play an important role in the oriented growth of enamel crystals. Amelogenin self-assembles to form nanospheres and higher order structures mediated by hydrophobic interactions. This study aims to obtain a better insight into the relationship between primary-secondary structure and self-assembly of amelogenin by applying computational and biophysical methods. Variable temperature circular dichroism studies indicated that under physiological pH recombinant full-length porcine amelogenin contains unordered structures in equilibrium with polyproline type II (PPII) structure, the latter being more populated at lower temperatures. Increasing the concentration of rP172 resulted in the promotion of folding to an ordered β-structured assembly. Isothermal titration calorimetry dilution studies revealed that, at all temperatures, self-assembly is entropically driven due to the hydrophobic effect and the molar heat of assembly (ΔHA) decreases with temperature. Using a computational approach, a profile of domains in the amino acid sequence that have a high propensity to assemble and to have PPII structures has been identified. We conclude that the assembly properties of amelogenin are due to complementarity between the hydrophobic and PPII helix prone regions. PMID:19274734

  18. Self-assembly of poly(lauryl methacrylate)-b-poly(benzyl methacrylate) nano-objects synthesised by ATRP and their temperature-responsive dispersion properties.

    PubMed

    Obeng, Melody; Milani, Amir H; Musa, Muhamad S; Cui, Zhengxing; Fielding, Lee A; Farrand, Louise; Goulding, Mark; Saunders, Brian R

    2017-03-15

    Self-assembling poly(lauryl methacrylate)-b-poly(benzyl methacrylate) (PLMAx-PBzMAy) diblock copolymers were synthesised for the first time using solution atom transfer radical polymerisation (ATRP). The PLMA degree of polymerisation (x) was fixed at 14 and the PBzMA degree of polymerisation (y) was varied from 34 to 74. Post-polymerisation transfer of this new series of diblock copolymers from chloroform into n-dodecane (a poor solvent for PBzMA) resulted in self-assembly of polymeric nano-objects. The morphologies for the latter (spheres, worms and vesicles) were controlled by y. The observed morphologies generally agreed with those reported for related PLMAx-PBzMAy diblock copolymers (x ≥ 16) prepared by polymerisation induced self-assembly (PISA) via reversible addition-fragmentation chain transfer (RAFT) polymerisation (Fielding et al., J. Am. Chem. Soc., 2014, 136, 5790). However, a number of differences were observed such as de-gelation behaviour and the phase boundary positions compared to those expected from Fielding et al. Variable-temperature dynamic light scattering studies for the PLMA14-PBzMA34 spheres revealed that the aggregation number was unaffected by a temperature increase over the range of 20-90 °C, which differed markedly from the behaviour observed for PLMA14-PBzMA64 worms. This difference is a new observation with mechanistic importance for the worm-to-sphere breakdown mechanism. We show that concentrated PLMA14-PBzMAy dispersions (20% w/w) in n-dodecane can be prepared using post-polymerisation transfer. The dispersion with a mixed spherical and worm-like copolymer phase exhibited reversible de-gelation when heated. Surprisingly, the dispersions containing only the worm phase remained as gels (which were white) at temperatures up to 90 °C. Our new ATRP approach for preparing temperature-responsive non-aqueous nano-object dispersions presented here decoupled chain growth and self-assembly and will apply to other copolymer dispersions.

  19. Self-assembly drugs: from micelles to nanomedicine.

    PubMed

    Messina, Paula V; Besada-Porto, Jose Miguel; Ruso, Juan M

    2014-03-01

    Self-assembly has fascinated many scientists over the past few decades. Rapid advances and widespread interest in the study of this subject has led to the synthesis of an ever-increasing number of elegant and intricate functional structures with sizes that approach nano- and mesoscopic dimensions. Today, it has grown into a mature field of modern science whose interfaces with many disciplines have provided invaluable opportunities for crossing boundaries for scientists seeking to design novel molecular materials exhibiting unusual properties, and for researchers investigating the structure and function of biomolecules. Consequently, self-assembly transcends the traditional divisional boundaries of science and represents a highly interdisciplinary field including nanotechnology and nanomedicine. Basically, self-assembly focuses on a wide range of discrete molecules or molecular assemblies and uses physical transformations to achieve its goals. In this Review, we present a comprehensive overview of the advances in the field of drug self-assembly and discuss in detail the synthesis, self-assembly behavior, and physical properties as well as applications. We refer the reader to past reviews dealing with colloidal molecules and colloidal self-assembly. In the first part, we will discuss, compare, and link the various bioinformatic procedures: Molecular Dynamics and Quantitative Structure Activity Relationship. The second section deals with the self-assembly behavior in more detail, in which we focus on several experimental techniques, selected according to the depth of knowledge obtained. The last part will review the advances in drug-protein assembly. Nature provides many examples of proteins that form their substrate binding sites by bringing together the component pieces in a process of self-assembly. We will focus in the understanding of physical properties and applications developing thereof.

  20. Evolving systems: Control and stability inheritance in self-assembling structures

    NASA Astrophysics Data System (ADS)

    Frost, Susan A.

    We propose a new framework called Evolving Systems to describe the autonomous self-assembly of actively controlled dynamical subsystems into an Evolved System with a higher purpose. We introduce Evolving Systems and explore the essential topics of the control and stability properties for such systems. The Evolving Systems framework developed in this thesis provides a scalable, modular architecture to model and analyze the subsystem components, their connections to other components, and the Evolved System. Autonomous assembly of large, complex structures in space is one application of Evolving Systems. Future space missions will entail systems where the scale, complexity, and distance preclude astronaut assistance due to the inherent risks and costs. These considerations suggest the need for a framework and methods to advance the state of the art of autonomous assembly of complex systems. A critical requirement for autonomously assembled structures is that they remain stable during and after mating. The important topic of stability in Evolving Systems is the primary focus of this research. We introduce the key component controller design approach to maintain stability in Evolving Systems. One key component from the Evolving System is augmented with additional local control to achieve the goal of ensuring system stability during assembly. The other components of the Evolving System are left unchanged, enabling modular system design and reuse of components. We present simulation results demonstrating the successful use of these methods to maintain stability in illustrative examples. Aerospace systems are difficult and costly to model, due to their complexity and their uncertain operating environments. The adaptive key component controller we present is well suited to poorly modeled systems because its gains adapt to the sensed system outputs. We develop an impedance-admittance formulation of the contact dynamics between components of an Evolving System to obtain

  1. Green-fuel-mediated synthesis of self-assembled NiO nano-sticks for dual applications—photocatalytic activity on Rose Bengal dye and antimicrobial action on bacterial strains

    NASA Astrophysics Data System (ADS)

    Iyyappa Rajan, P.; Vijaya, J. Judith; Jesudoss, S. K.; Kaviyarasu, K.; Kennedy, L. John; Jothiramalingam, R.; Al-Lohedan, Hamad A.; Vaali-Mohammed, Mansoor-Ali

    2017-08-01

    With aim of promoting the employability of green fuels in the synthesis of nano-scaled materials with new kinds of morphologies for multiple applications, successful synthesis of self-assembled NiO nano-sticks was achieved through a 100% green-fuel-mediated hot-plate combustion reaction. The synthesized NiO nano-sticks show excellent photocatalytic activity on Rose Bengal dye and superior antibacterial potential towards both Gram-positive and Gram-negative bacteria.

  2. Artificial leaf structures as a UV detector formed by the self-assembly of ZnO nanoparticles.

    PubMed

    Wang, Fei; Zhao, Dongxu; Guo, Zhen; Liu, Lei; Zhang, Zhenzhong; Shen, Dezhen

    2013-04-07

    Artificial leaf structures have been fabricated by the self-assembly of ZnO nanoparticles. A hydrothermal method was used to synthesize the nanoparticles. The self-assembly patterns showed asymmetric dendritic morphologies, larger surface-to-volume ratios, a broad absorption band and high resistance. A non-equilibrium two-stage-formation process included diffusion limited aggregation, and the phase-field model was introduced to explain the formation mechanism of the pattern. A high-performance ultraviolet detector was fabricated on the artificial leaf structures, which showed that the current under the irradiation of a UV lamp (1.21 mW cm(-2)) was about 10(4) times greater than in the dark. The various and functional properties of the pattern show us the vast prospects of potential applications for light harvesting systems and other optical-electric devices.

  3. Self-assembly and the Formation of Structure in Granular Materials

    NASA Astrophysics Data System (ADS)

    Behringer, Robert

    2015-03-01

    Particle systems self-assemble in ways that are sensitive to their environments. Proteins fold, polymers crosslink, and molecular systems form crystals. Granular materials, unlike proteins, polymers or molecules, are not sensitive to temperature, and will only form new structures when they are driven. This raises the question of how a granular state depends on the preparation protocol, and an even more basic question of what is needed to specify a granular state. I will focus on granular systems near jamming, where key state variables include the density and stresses. Systems of frictionless grains follow the Liu-Nagel1 scenario of jamming, with a lowest packing fraction, ϕJ, such that any system with ϕ <ϕJ is unjammed, and all isotopic states (shear stress τ = 0) are jammed for ϕ >ϕJ . For frictional grains the picture changes. For a given ϕ in the range ϕS < ϕ <ϕJ , it is possible to have stress-free (unjammed) states, highly anisotropic fragile states, and robustly jammed states. The fragile and strongly jammed states form spontaneously in response to shear. By inference, ϕ is not a state variable, but recent experiments2 indicate that the non-rattler fraction, fNR is. In ϕS < ϕ <ϕJ , the system response is inherently non-linear; under cyclic shear, the system self-organizes to new steady states via a process that resembles thermal activation, with shear stress replacing energy3. The activation is provided by shear strain. We observe similar relaxation under cyclic compression. An important question is, what is (are) the organizing principle(s) which govern jamming by shear, and systematic reorganization under cyclic driving. NSF grants DMR1206351 and DMS1248071, NASA grant NNX10AU10G, and ARO grant W911NF-1-11-0110

  4. Secondary Structures of Ubiquitin Ions Soft-Landed onto Self-Assembled Monolayer Surfaces

    SciTech Connect

    Hu, Qichi; Laskin, Julia

    2016-06-09

    The secondary structures of multiply charged ubiquitin ions soft-landed onto self-assembled monolayer (SAM) surfaces were studied using in situ infrared reflection-absorption spectroscopy (IRRAS). Two charge states of ubiquitin, 5+ and 13+, were mass selected separately from a mixture of different charge states produced by electrospray ionization (ESI). The low 5+ charge state represents a native-like folded state of ubiquitin, while the high 13+ charge state assumes an extended, almost linear conformation. Each of the two charge states was soft-landed onto a CH3- and COOH-terminated SAM of alkylthiols on gold (HSAM and COOH-SAM). HSAM is a hydrophobic surface known to stabilize helical conformations of soft-landed protonated peptides, whereas COOH-SAM is a hydrophilic surface that preferentially stabilizes β-sheet conformations. IRRAS spectra of the soft-landed ubiquitin ions were acquired as a function of time during and after ion soft-landing. Similar to smaller peptide ions, helical conformations of ubiquitin are found to be more abundant on HSAM, while the relative abundance of β-sheet conformations increases on COOH-SAM. The initial charge state of ubiquitin also has a pronounced effect on its conformation on the surface. Specifically, on both surfaces, a higher relative abundance of helical conformations and lower relative abundance of β-sheet conformations is observed for the 13+ charge state compared to the 5+ charge state. Time-resolved experiments indicate that the α-helical band in the spectrum of the 13+ charge state slowly increases with time on the HSAM surface and decreases in the spectrum of the 13+ charge state on COOH-SAM. These results further support the preference of the hydrophobic HSAM surface toward helical conformations and demonstrate that soft-landed protein ions may undergo slow conformational changes during and after deposition.

  5. Tolerance to structural disorder and tunable mechanical behavior in self-assembled superlattices of polymer-grafted nanocrystals

    PubMed Central

    Ye, Xingchen; Koshy, David M.; Vachhani, Shraddha; Hosemann, Peter; Alivisatos, A. Paul

    2017-01-01

    Large, freestanding membranes with remarkably high elastic modulus (>10 GPa) have been fabricated through the self-assembly of ligand-stabilized inorganic nanocrystals, even though these nanocrystals are connected only by soft organic ligands (e.g., dodecanethiol or DNA) that are not cross-linked or entangled. Recent developments in the synthesis of polymer-grafted nanocrystals have greatly expanded the library of accessible superlattice architectures, which allows superlattice mechanical behavior to be linked to specific structural features. Here, colloidal self-assembly is used to organize polystyrene-grafted Au nanocrystals at a fluid interface to form ordered solids with sub-10-nm periodic features. Thin-film buckling and nanoindentation are used to evaluate the mechanical behavior of polymer-grafted nanocrystal superlattices while exploring the role of polymer structural conformation, nanocrystal packing, and superlattice dimensions. Superlattices containing 3–20 vol % Au are found to have an elastic modulus of ∼6–19 GPa, and hardness of ∼120–170 MPa. We find that rapidly self-assembled superlattices have the highest elastic modulus, despite containing significant structural defects. Polymer extension, interdigitation, and grafting density are determined to be critical parameters that govern superlattice elastic and plastic deformation. PMID:28242704

  6. Surface Patterning of Benzene Carboxylic Acids on Graphite: Influence of structure, solvent, and concentration on molecular self-assembly

    NASA Astrophysics Data System (ADS)

    Florio, Gina; Stiso, Kimberly; Campanelli, Joseph; Dessources, Kimberly; Folkes, Trudi

    2012-02-01

    Scanning tunneling microscopy (STM) was used to investigate the molecular self-assembly of four different benzene carboxylic acid derivatives at the liquid/graphite interface: pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid), trimellitic acid (1,2,4-benzenetricarboxylic acid), trimesic acid (1,3,5-benzenetricarboxylic acid), and 1,3,5-benzenetriacetic acid. A range of two dimensional networks are observed that depend sensitively on the number of carboxylic acids present, the nature of the solvent, and the solution concentration. We will describe our recent efforts to determine (a) the preferential two-dimensional structure(s) for each benzene carboxylic acid at the liquid/graphite interface, (b) the thermodynamic and kinetic factors influencing self-assembly (or lack thereof), (c) the role solvent plays in the assembly, (e) the effect of in situ versus ex situ dilution on surface packing density, and (f) the temporal evolution of the self-assembled monolayer. Results of computational analysis of analog molecules and model monolayer films will also be presented to aid assignment of network structures and to provide a qualitative picture of surface adsorption and network formation.

  7. Tolerance to structural disorder and tunable mechanical behavior in self-assembled superlattices of polymer-grafted nanocrystals

    NASA Astrophysics Data System (ADS)

    Gu, X. Wendy; Ye, Xingchen; Koshy, David M.; Vachhani, Shraddha; Hosemann, Peter; Alivisatos, A. Paul

    2017-03-01

    Large, freestanding membranes with remarkably high elastic modulus (>10 GPa) have been fabricated through the self-assembly of ligand-stabilized inorganic nanocrystals, even though these nanocrystals are connected only by soft organic ligands (e.g., dodecanethiol or DNA) that are not cross-linked or entangled. Recent developments in the synthesis of polymer-grafted nanocrystals have greatly expanded the library of accessible superlattice architectures, which allows superlattice mechanical behavior to be linked to specific structural features. Here, colloidal self-assembly is used to organize polystyrene-grafted Au nanocrystals at a fluid interface to form ordered solids with sub-10-nm periodic features. Thin-film buckling and nanoindentation are used to evaluate the mechanical behavior of polymer-grafted nanocrystal superlattices while exploring the role of polymer structural conformation, nanocrystal packing, and superlattice dimensions. Superlattices containing 3-20 vol % Au are found to have an elastic modulus of ˜6-19 GPa, and hardness of ˜120-170 MPa. We find that rapidly self-assembled superlattices have the highest elastic modulus, despite containing significant structural defects. Polymer extension, interdigitation, and grafting density are determined to be critical parameters that govern superlattice elastic and plastic deformation.

  8. Controlling the self-assembly structure of magnetic nanoparticles and amphiphilic block-copolymers: from micelles to vesicles.

    PubMed

    Hickey, Robert J; Haynes, Alyssa S; Kikkawa, James M; Park, So-Jung

    2011-02-09

    We report how to control the self-assembly of magnetic nanoparticles and a prototypical amphiphilic block-copolymer composed of poly(acrylic acid) and polystyrene (PAA-b-PS). Three distinct structures were obtained by controlling the solvent-nanoparticle and polymer-nanoparticle interactions: (1) polymersomes densely packed with nanoparticles (magneto-polymersomes), (2) core-shell type polymer assemblies where nanoparticles are radially arranged at the interface between the polymer core and the shell (magneto-core shell), and (3) polymer micelles where nanoparticles are homogeneously incorporated (magneto-micelles). Importantly, we show that the incorporation of nanoparticles drastically affects the self-assembly structure of block-copolymers by modifying the relative volume ratio between the hydrophobic block and the hydrophilic block. As a consequence, the self-assembly of micelle-forming block-copolymers typically produces magneto-polymersomes instead of magneto-micelles. On the other hand, vesicle-forming polymers tend to form magneto-micelles due to the solubilization of nanoparticles in polymer assemblies. The nanoparticle-polymer interaction also controls the nanoparticle arrangement in the polymer matrix. In N,N-dimethylformamide (DMF) where PS is not well-solvated, nanoparticles segregate from PS and form unique radial assemblies. In tetrahydrofuran (THF), which is a good solvent for both nanoparticles and PS, nanoparticles are homogeneously distributed in the polymer matrix. Furthermore, we demonstrated that the morphology of nanoparticle-encapsulating polymer assemblies significantly affects their magnetic relaxation properties, emphasizing the importance of the self-assembly structure and nanoparticle arrangement as well as the size of the assemblies.

  9. Self-assembly in an evaporating nanofluid droplet: rapid transformation of nanorods into 3D fibre network structures.

    PubMed

    Wu, H; Chen, L X; Zeng, X Q; Ren, T H; Briscoe, Wuge H

    2014-08-07

    Upon evaporation, ZnO nanorods in a nanofluid droplet undergo rapid and spontaneous chemical and morphological transformation into centimetre-long Zn(OH)2 fibres, via a mechanism very different from that for coffee rings. We show that the detailed nanostructure and micromorphology in the residual thin film depend intricately on the ambient moisture, nanofluid solvent composition and substrate surface chemistry. Upon thermal annealing, these Zn(OH)2 fibres readily undergo further chemical and morphological transformation, forming nanoporous fibres with the pore size tuneable by temperature. Our results point to a simple route for generating a self-assembled 3D structure with ultralong and nanoporous ZnO/Zn(OH)2 fibres/belts, and may also be of interest to the fields of evaporation controlled dynamic self-assembly, non-equilibrium crystallisation, and flow and fingering instabilities in nanofluids.

  10. Controlled Self-Assembly of Cyclophane Amphiphiles: From 1D Nanofibers to Ultrathin 2D Topological Structures

    SciTech Connect

    Cai, Zhengxu; Li, Lianwei; Lo, Wai-Yip; Zhao, Donglin; Wu, Qinghe; Zhang, Na; Su, Yu-An; Chen, Wei; Yu, Luping

    2016-07-05

    A novel series of amphiphilic TC-PEG molecules were designed and synthesized based on the orthogonal cyclophane unit. These molecules were able to self-assemble from 1D nanofibers and nanobelts to 2D ultrathin nanosheets (3 nm thick) in a controlled way by tuning the length of PEG side chains. The special structure of the cyclophane moiety allowed control in construction of nanostructures through programmed noncovalent interactions (hydrophobic hydrophilic interaction and pi-pi interaction). The self-assembled nanostructures were characterized by combining real space imaging (TEM, SEM, and AFM) and reciprocal space scattering (GIWAXS) techniques. This unique supramolecular system may provide a new strategy for the design of materials with tunable nanomorphology and functionality.

  11. One-dimensional zinc ferrite nano-chains synthesis by chemical self-assembly assistant by magnetic field

    NASA Astrophysics Data System (ADS)

    Kou, Zhaoxia; Zhang, Wen; Wang, Yukun; Johnny Wong, Ping Kwan; Huang, Haibo; Ji, Cheng; Yue, Jinjin; Zhang, Dong; Zhai, Ya; Zhai, Hongru

    2014-05-01

    A series of zinc ferrite chains have been synthesized successfully by using the self-assembly method in different synthesizing magnetic fields. The particle chains are arranged in order on the Si substrate under the assistant magnetic field. The zinc ferrite chains show various length-to-radius aspect ratio, saturation magnetization Ms, remanent magnetization Mr, and coercivity Hc in the corresponding synthesizing magnetic fields. Using X-ray magnetic circular dichroism, the Zn substitution mechanism in the ferrite chains has been analyzed and discussed.

  12. Self-Assembled Polymeric Ionic Liquid-Functionalized Cellulose Nano-crystals: Constructing 3D Ion-conducting Channels Within Ionic Liquid-based Composite Polymer Electrolytes.

    PubMed

    Shi, Qing Xuan; Xia, Qing; Xiang, Xiao; Ye, Yun Sheng; Peng, Hai Yan; Xue, Zhi Gang; Xie, Xiao Lin; Mai, Yiu-Wing

    2017-09-04

    Composite polymeric and ionic liquid (IL) electrolytes are some of the most promising electrolyte systems for safer battery technology. Although much effort has been directed towards enhancing the transport properties of polymer electrolytes (PEs) through nanoscopic modification by incorporating nano-fillers, it is still difficult to construct ideal ion conducting networks. Here, a novel class of three-dimensional self-assembled polymeric ionic liquid (PIL)-functionalized cellulose nano-crystals (CNC) confining ILs in surface-grafted PIL polymer chains, able to form colloidal crystal polymer electrolytes (CCPE), is reported. The high-strength CNC nano-fibers, decorated with PIL polymer chains, can spontaneously form three-dimensional interpenetrating nano-network scaffolds capable of supporting electrolytes with continuously connected ion conducting networks with IL being concentrated in conducting domains. These new CCPE have exceptional ionic conductivities, low activation energies (close to bulk IL electrolyte with dissolved Li salt), high Li(+) transport numbers, low interface resistances and improved interface compatibilities. Furthermore, the CCPE displays good electrochemical properties and a good battery performance. This approach offers a route to leak-free, non-flammable and high ionic conductivity solid-state PE in energy conversion devices. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Hierarchical structures based on self-assembling beta-hairpin peptides and their application as biomaterials and hybrid materials

    NASA Astrophysics Data System (ADS)

    Altunbas, Aysegul

    Self-assembly represents a robust and powerful paradigm for the bottom-up construction of nanostructures. Self-assembled peptide hydrogels are emerging as promising routes to novel multifunctional materials. The 20 amino acid MAX1and MAX8 peptides self-assemble into a three dimensional network of entangled, branched fibrils rich in beta-sheet secondary structure with a high density of lysine groups exposed on the fibril-surfaces. These hydrogels form self-supporting structures that shear thin upon application of shear and then immediately recover to a solid hydrogel upon cessation of shear which facilitates the local delivery of the hydrogel into a site in vivo. Templated condensation of silica precursors on self-assembled nanoscale peptide fibrils with various surface functionalities can be used to mimic biosilicification. This template-defined approach towards biomineralization was utilized for the controlled fabrication of 3D hybrid nanostructures. We report a study on the structure-property relationship of self-assembled peptide hydrogels where mineralization of individual fibrils through sol-gel chemistry was achieved. The nanostructure and consequent mechanical characteristics of these hybrid networks can be modulated by changing the stoichiometric parameters of the sol-gel process. Construction of such organic-inorganic hybrid networks by sol-gel processing of self-assembled peptide hydrogels has improved mechanical properties and resulted in materials with ˜ 3 orders of magnitude higher stiffness. The physical characterization of the hybrid networks via electron microscopy and small angle scattering is detailed and correlated with changes in the network mechanical behavior. The resultant high fidelity templating process suggests that the peptide substrate can be used to template the coating of other functional inorganic materials. Self-assembling peptide hydrogels encapsulating an anti-tumorigenic drug, curcumin, have been prepared and demonstrated to be

  14. Structure and interactions in biomaterials based on membrane-biopolymer self-assembly

    NASA Astrophysics Data System (ADS)

    Koltover, Ilya

    Physical and chemical properties of artificial pure lipid membranes have been extensively studied during the last two decades and are relatively well understood. However, most real membrane systems of biological and biotechnological importance incorporate macromolecules either embedded into the membranes or absorbed onto their surfaces. We have investigated three classes of self-assembled membrane-biopolymer biomaterials: (i) Structure, interactions and stability of the two-dimensional crystals of the integral membrane protein bacteriorhodopsin (bR). We have conducted a synchrotron x-ray diffraction study of oriented bR multilayers. The important findings were as follows: (1) the protein 2D lattice exhibited diffraction patterns characteristic of a 2D solid with power-law decay of in-plane positional correlations, which allowed to measure the elastic constants of protein crystal; (2) The crystal melting temperature was a function of the multilayer hydration, reflecting the effect of inter-membrane repulsion on the stability of protein lattice; (3) Preparation of nearly perfect (mosaicity < 0.04° ) multilayers of fused bR membranes permitted, for the first time, application of powerful interface-sensitive x-ray scattering techniques to a membrane-protein system. (ii) Interactions between the particles chemically attached or absorbed onto the surfaces of flexible giant phospholipid vesicles. Using video-enhanced light microscopy we have observed a membrane-distortion induced attraction between the particles with the interaction range of the order of particle diameter. Fluid membranes decorated with many particles exhibited: (i) a finite-sized two-dimensional closed packed aggregates and (ii) a one-dimensional ring-like aggregates. (iii) Structure, stability and interactions in the cationic lipid-DNA complexes. Cationic liposomes complexed with DNA are among the most promising synthetic non-viral carriers of DNA vectors currently used in gene therapy applications. We

  15. Layer-by-layer self-assembly of micro-capsules for the magnetic activation of semi-permeable nano-shells

    NASA Astrophysics Data System (ADS)

    Prouty, Malcolm D.

    2007-12-01

    Layer-by-layer (LbL) self-assembly has demonstrated broad perspectives for encapsulating, and the controllable delivery, of drugs. The nano-scale polymer layers have the capability of material protection. Magnetic nanoparticles have great potential to be applied with LbL technology to achieve both "focusing" of the encapsulated drugs to a specific location followed by "switching" them on to release the encapsulated drugs. In this work, Phor21-betaCG(ala), dextran, and dexamethasone were used as model drugs. Encapsulation of these drugs with layer-by-layer self-assembly formed biolnano robotic capsules for controlled delivery and drug release. Silica nanoparticles coated with polyelectrolyte layers of sodium carboxymethyl cellulose (CMC) or gelatin B, along with an oppositely charged peptide drug (Phor2l-betaCG(ala)), were prepared using LbL self-assembly and confirmed using QCM and zeta potential measurements. The peptide drug was assembled as a component of the multilayer walls. The release kinetics of the embedded peptide were determined. Up to 18% of the embedded Phor21-betaCG(ala) was released from the CMC multilayers over a period of 28 hours. The release was based on physiological conditions, and an external control mechanism using magnetic nanoparticles needed to be developed. Magnetic permeability control experiments were setup by applying LbL self-assembly on MnCO3 micro-cores to fabricate polyelectrolyte microcapsules embedded with superparamagnetic gold coated cobalt (Co Au) nanoparticles. An alternating magnetic field was applied to the microcapsules to check for changes in permeability. Permeability experiments were achieved by adding fluorescein isothiocyanate (FITC) labeled dextran to the microcapsule solution. Before an alternating magnetic field was applied, the capsules remained impermeable to the FITC-dextran; however, after an alternating magnetic field was applied for 30 minutes, approximately 99% of the capsules were filled with FITC

  16. Water-Regulated Self-Assembly Structure Transformation and Gelation Behavior Prediction Based on a Hydrazide Derivative.

    PubMed

    Li, Yajie; Ran, Xia; Li, Qiuyue; Gao, Qiongqiong; Guo, Lijun

    2016-08-05

    Herein, we report the water-regulated supramolecular self-assembly structure transformation and the predictability of the gelation ability based on an azobenzene derivative bearing a hydrazide group, namely, N-(3,4,5-tributoxyphenyl)-N'-4-[(4-hydroxyphenyl)azophenyl] benzohydrazide (BNB-t4). The regulation effects are demonstrated in the morphological transformation from spherical to lamellar particles then back to spherical in different solvent ratios of n-propanol/water. The self-assembly behavior of BNB-t4 was characterized by minimum gelation concentration, microstructure, thermal, and mechanical stabilities. From the spectroscopy studies, it is suggested that gel formation of BNB-t4 is mainly driven by intermolecular hydrogen bonding, accompanied with the contribution from π-π stacking as well as hydrophobic interactions. The successfully established correlation between the self-assembly behavior and solubility parameters yields a facile way to predict the gelation performance of other molecules in other single or mixed solvents.

  17. DNA origami: a quantum leap for self-assembly of complex structures.

    PubMed

    Tørring, Thomas; Voigt, Niels V; Nangreave, Jeanette; Yan, Hao; Gothelf, Kurt V

    2011-12-01

    The spatially controlled positioning of functional materials by self-assembly is one of the fundamental visions of nanotechnology. Major steps towards this goal have been achieved using DNA as a programmable building block. This tutorial review will focus on one of the most promising methods: DNA origami. The basic design principles, organization of a variety of functional materials and recent implementation of DNA robotics are discussed together with future challenges and opportunities.

  18. Self-assembled quantum dot structures in a hexagonal nanowire for quantum photonics.

    PubMed

    Yu, Ying; Dou, Xiu-Ming; Wei, Bin; Zha, Guo-Wei; Shang, Xiang-Jun; Wang, Li; Su, Dan; Xu, Jian-Xing; Wang, Hai-Yan; Ni, Hai-Qiao; Sun, Bao-Quan; Ji, Yuan; Han, Xiao-Dong; Niu, Zhi-Chuan

    2014-05-01

    Two types of quantum nanostructures based on self-assembled GaAs quantumdots embedded into GaAs/AlGaAs hexagonal nanowire systems are reported, opening a new avenue to the fabrication of highly efficient single-photon sources, as well as the design of novel quantum optics experiments and robust quantum optoelectronic devices operating at higher temperature, which are required for practical quantum photonics applications.

  19. [Molecular Dynamics of Self-assembling and Rheology of Superhelical Structure of Protofiber of Spider Web].

    PubMed

    Shaitan, K V; Orshanskiy, I A

    2015-01-01

    In this study we suggested a dynamics simulation for the formation of protofiber of spider web nanofiber. It was shown that a bundle of parallel polyalanine β-strands of sufficient length is arranged through self-assembly into a stable right-handed super helix. By numerical analysis we investigated the rheological properties and provided in nonlinear regime a generalization of the model of Singer for description of the rheological behaviour of super helix.

  20. Organic molecules deposited on graphene: A computational investigation of self-assembly and electronic structure

    SciTech Connect

    Oliveira, I. S. S. de; Miwa, R. H.

    2015-01-28

    We use ab initio simulations to investigate the adsorption and the self-assembly processes of tetracyanoquinodimethane (TCNQ), tetrafluoro-tetracyanoquinodimethane (F4-TCNQ), and tetrasodium 1,3,6,8-pyrenetetrasulfonic acid (TPA) on the graphene surface. We find that there are no chemical bonds at the molecule–graphene interface, even at the presence of grain boundaries on the graphene surface. The molecules bond to graphene through van der Waals interactions. In addition to the molecule–graphene interaction, we performed a detailed study of the role played by the (lateral) molecule–molecule interaction in the formation of the, experimentally verified, self-assembled layers of TCNQ and TPA on graphene. Regarding the electronic properties, we calculate the electronic charge transfer from the graphene sheet to the TCNQ and F4-TCNQ molecules, leading to a p-doping of graphene. Meanwhile, such charge transfer is reduced by an order of magnitude for TPA molecules on graphene. In this case, it is not expected a significant doping process upon the formation of self-assembled layer of TPA molecules on the graphene sheet.

  1. Self-assembly of triangular amphiphiles into diverse nano/microstructures and release behavior of the hollow sphere.

    PubMed

    Lv, Kai; Zhang, Li; Liu, Minghua

    2014-08-12

    Amphiphilic triangular derivatives containing imine bond have been designed and used as building blocks for the construction of soft colloidal materials. The acylhydrazone derivative was found to form various nano/microstructures in different solvents. The microspheres, flower-like, and hollow spheres were formed in the polar solvents, while organogels with microporous structures were formed in nonpolar solvents. However, the simple Schiff base amphiphile without amide group did not form any ordered structures in the tested solvents. Therefore, besides the π-π stacking between the aromatic core and the van der Waals interactions between the alkyl chains, the hydrogen bonding between the acylhydrazone moieties played an important role in promoting the formation of various organized structures. More interestingly, the hollow sphere structure which was formed in THF could be used to encapsulate and release the rhodamine B. It was found that rhodamine B was encapsulated within their interiors under neutral conditions and released in an acidic condition due to the breakage of the imine bond.

  2. Evaluating the link between self-assembled mesophase structure and drug release.

    PubMed

    Phan, Stephanie; Fong, Wye-Khay; Kirby, Nigel; Hanley, Tracey; Boyd, Ben J

    2011-12-12

    Lipid-based liquid crystalline materials are of increasing interest for use as drug delivery systems. The intricate nanostructure of the reversed bicontinuous cubic (V(2)) and inverse hexagonal (H(2)) liquid crystal matrices have been shown to provide diffusion controlled release of actives of varying size and polarity. In this study, we extend the understanding of release to other self-assembled phases, the micellar cubic phase (I(2)) and inverse micelles (L(2)). The systems are comparable as they were all prepared from the one lipid, glyceryl monooleate (GMO), which sequentially forms all four phases with increasing hexadecane (HD) content in excess water. Phase identity was confirmed by small angle X-ray scattering (SAXS). SAXS data indicated that four mesophases were formed with increasing HD content at 25°C: V(2) phase (Pn3m space group) formed at 0-4% (w/w) HD, H(2) phase formed at 4-25% (w/w) HD, I(2) phase (Fd3m space group) formed at 25-40% (w/w) HD and finally L(2) phase formed at >40% (w/w) HD. Analogous compositions using phytantriol rather than GMO as the core lipid did not produce the I(2) phase, with only V(2) to H(2) to L(2) transitions being apparent with increasing HD concentration. In order to relate the liquid crystal phase structure to drug release rate, in vitro release tests were conducted by incorporating radio-labelled glucose as a model hydrophilic drug into the four GMO-based mesophases. It was found that the drug release followed first-order diffusion kinetics and was fastest from V(2) followed by L(2), H(2), and I(2). Drug release was shown to be significantly faster from bicontinuous cubic phase than the other mesophases, indicating that the state of the water compartments, whether open or closed, has a great influence on the rate of drug release. It is envisioned that liquid crystalline mesophases with slower release characteristics will more likely have potential applications as sustained release drug delivery systems, and hence

  3. Self-Assembled Formation of Well-Aligned Cu-Te Nano-Rods on Heavily Cu-Doped ZnTe Thin Films

    NASA Astrophysics Data System (ADS)

    Liang, Jing; Cheng, Man Kit; Lai, Ying Hoi; Wei, Guanglu; Yang, Sean Derman; Wang, Gan; Ho, Sut Kam; Tam, Kam Weng; Sou, Iam Keong

    2016-11-01

    Cu doping of ZnTe, which is an important semiconductor for various optoelectronic applications, has been successfully achieved previously by several techniques. However, besides its electrical transport characteristics, other physical and chemical properties of heavily Cu-doped ZnTe have not been reported. We found an interesting self-assembled formation of crystalline well-aligned Cu-Te nano-rods near the surface of heavily Cu-doped ZnTe thin films grown via the molecular beam epitaxy technique. A phenomenological growth model is presented based on the observed crystallographic morphology and measured chemical composition of the nano-rods using various imaging and chemical analysis techniques. When substitutional doping reaches its limit, the extra Cu atoms favor an up-migration toward the surface, leading to a one-dimensional surface modulation and formation of Cu-Te nano-rods, which explain unusual observations on the reflection high energy electron diffraction patterns and apparent resistivity of these thin films. This study provides an insight into some unexpected chemical reactions involved in the heavily Cu-doped ZnTe thin films, which may be applied to other material systems that contain a dopant having strong reactivity with the host matrix.

  4. Nano-Engineered Electrochemical Sensors for Monitoring of Toxic Metals in Groundwater: Development of Novel Square Wave Anodic Stripping Voltammetry Electrodes Using Self Assembled Monolayers on Mesoporous Supports

    DTIC Science & Technology

    2007-03-15

    in Groundwater Development Of Novel Square Wave Anodic Stripping Voltammetry Electrodes Using Self Assembled Monolayers On Mesoporous Supports...Sensors for Monitoring of Toxic Metals in Groundwater Development Of Novel Square Wave Anodic Stripping Voltammetry Electrodes Using Self Assembled... Square Wave Anodic Stripping Voltammetry Electrodes Using Self Assembled onolayers On Mesoporous Supports SI-1267 95440Zemanian, Thomas S., and Lin

  5. Self-Assembly of Crystalline Structures of Magnetic Core-Shell Nanoparticles for Fabrication of Nanostructured Materials.

    PubMed

    Xue, Xiaozheng; Wang, Jianchao; Furlani, Edward P

    2015-10-14

    A theoretical study is presented of the template-assisted formation of crystalline superstructures of magnetic-dielectric core-shell particles. The templates produce highly localized gradient fields and a corresponding magnetic force that guides the assembly with nanoscale precision in particle placement. The process is studied using two distinct and complementary computational models that predict the dynamics and energy of the particles, respectively. Both mono- and polydisperse colloids are studied, and the analysis demonstrates for the first time that although the particles self-assemble into ordered crystalline superstructures, the particle formation is not unique. There is a Brownian motion-induced degeneracy in the process wherein various distinct, energetically comparable crystalline structures can form for a given template geometry. The models predict the formation of hexagonal close packed (HCP) and face centered cubic (FCC) structures as well as mixed phase structures due to in-plane stacking disorders, which is consistent with experimental observations. The polydisperse particle structures are less uniform than the monodisperse particle structures because of the irregular packing of different-sized particles. A comparison of self-assembly using soft- and hard-magnetic templates is also presented, the former being magnetized in a uniform field. This analysis shows that soft-magnetic templates enable an order-of-magnitude more rapid assembly and much higher spatial resolution in particle placement than their hard-magnetic counterparts. The self-assembly method discussed is versatile and broadly applies to arbitrary template geometries and multilayered and multifunctional mono- and polydisperse core-shell particles that have at least one magnetic component. As such, the method holds potential for the bottom-up fabrication of functional nanostructured materials for a broad range of applications. This work provides unprecedented insight into the assembly

  6. Harnessing Surface Dislocation Networks for Molecular Self-Assembly

    NASA Astrophysics Data System (ADS)

    Pohl, Karsten

    2009-03-01

    The controlled fabrication of functional wafer-based nano-arrays is one of the ultimate quests in current nanotechnologies. Well-ordered misfit dislocation networks of ultrathin metal films are viable candidates for the growth of two- dimensional ordered cluster arrays in the nanometer regime. Such bottom-up processes can be very complex, involving collective effects from a large number of atoms. Unraveling the fundamental forces that drive these self-assembly processes requires detailed experimental information at the atomic level of large ensembles of hundreds to thousands of atoms. The combination of variable temperature measurements from our home-built STM correlated with 2D Frenkel-Kontorova models based on first-principle interaction parameters is used to explain how uniform arrays can form with the strain in the thin film as the driving force responsible for the surface self-assembly process. This process is generally applicable to assemble many molecular species thus opening avenues towards complex self-assembled structures based on a lock-and-key type approach. Moreover, when increasing the molecular coverage and/or decreasing the strain in the thin film the intermolecular interactions will eventually dominate the elastic effects and dictate the self-assembly process via molecular structure and functionality. We will show that controlling this delicate balance leads to a richness of structures, ranging from disperse ordered arrays of molecular clusters to patterned self-assembled monolayers (SAMs) of functionalized fullerenes and methanethiol.

  7. Self-assembled formation and transformation of In/CdZnTe(110) nano-rings into camel-humps

    SciTech Connect

    Cohen-Taguri, G.; Ruzin, A.; Goldfarb, I.

    2012-05-21

    We used in situ scanning tunneling microscopy to monitor in real time the formation of nano-rings at the molecular beam epitaxially grown In/CdZnTe(110) surface, and Auger electron spectroscopy to explore the corresponding compositional changes. In-diffusion of In and segregation of Cd to the surface in course of annealing lead to a formation of elliptically distorted nano-rings, elongated along the fast [110] diffusion direction. Exacerbated diffusion anisotropy in the liquid state, at temperatures above the melting point of In, further distorts the nano-rings into a camel-hump shape.

  8. Fabrication of hierarchical hybrid structures using bio-enabled layer-by-layer self-assembly.

    PubMed

    Hnilova, Marketa; Karaca, Banu Taktak; Park, James; Jia, Carol; Wilson, Brandon R; Sarikaya, Mehmet; Tamerler, Candan

    2012-05-01

    Development of versatile and flexible assembly systems for fabrication of functional hybrid nanomaterials with well-defined hierarchical and spatial organization is of a significant importance in practical nanobiotechnology applications. Here we demonstrate a bio-enabled self-assembly technique for fabrication of multi-layered protein and nanometallic assemblies utilizing a modular gold-binding (AuBP1) fusion tag. To accomplish the bottom-up assembly we first genetically fused the AuBP1 peptide sequence to the C'-terminus of maltose-binding protein (MBP) using two different linkers to produce MBP-AuBP1 hetero-functional constructs. Using various spectroscopic techniques, surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR), we verified the exceptional binding and self-assembly characteristics of AuBP1 peptide. The AuBP1 peptide tag can direct the organization of recombinant MBP protein on various gold surfaces through an efficient control of the organic-inorganic interface at the molecular level. Furthermore using a combination of soft-lithography, self-assembly techniques and advanced AuBP1 peptide tag technology, we produced spatially and hierarchically controlled protein multi-layered assemblies on gold nanoparticle arrays with high molecular packing density and pattering efficiency in simple, reproducible steps. This model system offers layer-by-layer assembly capability based on specific AuBP1 peptide tag and constitutes novel biological routes for biofabrication of various protein arrays, plasmon-active nanometallic assemblies and devices with controlled organization, packing density and architecture.

  9. Sequential programmable self-assembly: Role of cooperative interactions

    NASA Astrophysics Data System (ADS)

    Halverson, Jonathan D.; Tkachenko, Alexei V.

    2016-03-01

    We propose a general strategy of "sequential programmable self-assembly" that enables a bottom-up design of arbitrary multi-particle architectures on nano- and microscales. We show that a naive realization of this scheme, based on the pairwise additive interactions between particles, has fundamental limitations that lead to a relatively high error rate. This can be overcome by using cooperative interparticle binding. The cooperativity is a well known feature of many biochemical processes, responsible, e.g., for signaling and regulations in living systems. Here we propose to utilize a similar strategy for high precision self-assembly, and show that DNA-mediated interactions provide a convenient platform for its implementation. In particular, we outline a specific design of a DNA-based complex which we call "DNA spider," that acts as a smart interparticle linker and provides a built-in cooperativity of binding. We demonstrate versatility of the sequential self-assembly based on spider-functionalized particles by designing several mesostructures of increasing complexity and simulating their assembly process. This includes a number of finite and repeating structures, in particular, the so-called tetrahelix and its several derivatives. Due to its generality, this approach allows one to design and successfully self-assemble virtually any structure made of a "GEOMAG" magnetic construction toy, out of nanoparticles. According to our results, once the binding cooperativity is strong enough, the sequential self-assembly becomes essentially error-free.

  10. Structure and dehydration of layered perovskite niobate with bilayer hydrates prepared by exfoliation/self-assembly process

    SciTech Connect

    Chen Yufeng; Zhao Xinhua; Ma Hui; Ma Shulan; Huang Gailing; Makita, Yoji; Bai Xuedong; Yang Xiaojing

    2008-07-15

    The crystals of an H-form niobate of HCa{sub 2}Nb{sub 3}O{sub 10}.xH{sub 2}O (x=0.5) being tetragonal symmetry (space group P4/mbm) with unit cell parameters a=5.4521(6) and c=14.414(2) A were exfoliated into nanosheets with the triple-layered perovskite structure. The colloid suspension of the nanosheets was put into dialysis membrane tubing and allowed self-assembly in a dilute KCl solution. By this method, a novel layered K-form niobate KCa{sub 2}Nb{sub 3}O{sub 10}.xH{sub 2}O (x=1.3, typically) with bilayer hydrates in the interlayer was produced. The Rieveld refinement and transmission electron microscope (TEM)/selected-area electron diffraction (SAED) observation indicated that the orientations of the a-/b-axis of each nanosheet as well as the c-axis are uniform, and the self-assembled compound had the same symmetry, tetragonal (P4/mbm) with a=5.453(2) and c=16.876(5) A, as the H-form precursor; the exfoliation/self-assembly process does not markedly affect the two-dimensional lattice of the layer. The large basal spacing resulted from the interlayer K{sup +} ions solvated by two layers of water molecules. The interlayer bilayers-water was gradually changed to monolayer when the temperatures higher than 100 deg. C, and all the water molecules lost when over 600 deg. C. Accompanying the dehydration, the crystal structure transformed from tetragonal to orthorhombic symmetry. Water molecules may take an important role for the layer layered compound to adjust the unit cell to tetragonal symmetry. - Graphical abstract: The structure of layered perovskite niobate KCa{sub 2}Nb{sub 3}O{sub 10}.xH{sub 2}O (x=1.3) having a bilayers-hydrates interlayer, obtained via the exfoliation of an H-form precursor and the self-assembly of Ca{sub 2}Nb{sub 3}O{sub 10}{sup -} nanosheets, was first discussed in detail and determined to be tetragonal symmetry (P4/mbm). The dehydration resulted in the structural transformation to orthorhombic structure.

  11. The plating of rat scar myofibroblasts on matrigel unmasks a novel phenotype; the self assembly of lumen-like structures.

    PubMed

    El-Helou, Viviane; Gosselin, Hugues; Villeneuve, Louis; Calderone, Angelino

    2012-07-01

    During tissue healing, the primary role of myofibroblasts involves the synthesis and deposition of collagen. However, it has also been reported that selective populations of myofibroblasts can acquire the phenotype and/or differentiate to other cells types. The present study tested the hypothesis that myofibroblasts isolated from the scar of the ischemically damaged rat heart can recapitulate an endothelial cell-like response when plated in a permissive in vitro environment. Scar myofibroblasts, neonatal and adult ventricular fibroblasts express smooth muscle α-actin, collagen α(1) type 1 and a panel of pro-fibrotic and pro-angiogenic peptide growth factor mRNAs. Myofibroblasts plated alone on matrigel led to the self assembly of lumen-like structures whereas neonatal and adult rat ventricular fibroblasts were unresponsive. Myofibroblasts labeled with the fluorescent cell tracker CM-DiI were injected in the viable myocardium of 3-day post-myocardial infarcted Sprague-Dawley rats and sacrificed 7 days later. Injected CM-DiI-labeled myofibroblasts were detected predominantly in the peri-infarct/infarct region, highlighting their migration to the damaged region. However, engrafted myofibroblasts in the peri-infarct/infarct region were unable to adopt an endothelial cell-like phenotype or lead to the de novo formation of CM-DiI-labeled blood vessels. The non-permissive nature of the infarct region may be attributed at least in part to the presence of growth-promoting stimuli as TGF-β and the β-adrenergic agonist isoproterenol inhibited the self assembly of lumen-like structures by myofibroblasts. Thus, when plated in a permissive in vitro environment, scar myofibroblasts can self assemble and form lumen-like structures providing an additional novel phenotype distinguishing this population from normal ventricular fibroblasts. Copyright © 2012 Wiley Periodicals, Inc.

  12. Self-assembly of octadecyltrichlorosilane: Surface structures formed using different protocols of particle lithography

    PubMed Central

    Saner, ChaMarra K; Lusker, Kathie L; LeJeune, Zorabel M; Serem, Wilson K

    2012-01-01

    Summary Particle lithography offers generic capabilities for the high-throughput fabrication of nanopatterns from organosilane self-assembled monolayers, which offers the opportunity to study surface-based chemical reactions at the molecular level. Nanopatterns of octadecyltrichlorosilane (OTS) were prepared on surfaces of Si(111) using designed protocols of particle lithography combined with either vapor deposition, immersion, or contact printing. Changing the physical approaches for applying molecules to masked surfaces produced OTS nanostructures with different shapes and heights. Ring nanostructures, nanodots and uncovered pores of OTS were prepared using three protocols, with OTS surface coverage ranging from 10% to 85%. Thickness measurements from AFM cursor profiles were used to evaluate the orientation and density of the OTS nanostructures. Differences in the thickness and morphology of the OTS nanostructures are disclosed based on atomic force microscopy (AFM) images. Images of OTS nanostructures prepared on Si(111) that were generated by the different approaches provide insight into the self-assembly mechanism of OTS, and particularly into the role of water and solvents in hydrolysis and silanation. PMID:22428102

  13. Hierarchical Structure from the Self-Assembly of Giant Gemini Surfactants in Condensed State

    NASA Astrophysics Data System (ADS)

    Su, Hao; Wang, Zhao; Li, Yiwen; Cheng, Stephen

    2013-03-01

    In the past a few years, a new class of amphiphiles with both asymmetrical shapes and interactions named ``shape amphiphiles'' has been significantly intensified. Recently, a new kind of shape amphiphiles called ``Giant Gemini Surfactants'' consisting of two hydrophilic carboxylic acid-functionalized polyhedral oligomeric silsesquioxane (APOSS) heads and two hydrophobic polystyrene (PS) tails covalently linked via rigid spacers (p-phenylene versus biphenylene) has been successful behavior of giant gemini surfactants. We currently continue to investigate the spacer effects on the self-assembly behaviors of giant gemini surfactants in condensed state by utilizing DCS, SAXS and TEM. Preliminary results showed that giant gemini surfactants with different spacers have diverse phase behaviors. As we use the same 3.2k PS chains, the giant gemini surfactant with p-phenylene spacer showed double gyroid morphology, while the one with biphenylene spacer revealed cylindrical morphology. This study expands the scope of giant gemini surfactants and contributes a lot to the basic physical principles in self-assembly behavior.

  14. Tunable Affinity and Molecular Architecture Lead to Diverse Self-Assembled Supramolecular Structures in Thin Films

    SciTech Connect

    Hsu, Chin-Hao; Dong, Xuehui; Lin, Zhiwei; Ni, Bo; Lu, Pengatao; Jiang, Zhang; Tian, Ding; Cheng, Stephen Z.D.

    2016-01-01

    The self-assembly behaviors of specifically designed giant surfactants are systematically studied in thin films using grazing incident X-ray and transmission electron microscopy (TEM), focusing on the effects of head surface functionalities and molecular architectures on nanostructure formation. Two molecular nanoparticles (MNPs) with different affinities, i.e., hydrophilic carboxylic acid functionalized [60]fullerene (AC60) and omniphobic fluorinated polyhedral oligomeric silsesquioxane (FPOSS), are utilized as heads of the giant surfactants. By covalently tethering these functional MNPs onto the chain end or the junction point of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer, linear and star-like giant surfactants possess distinct molecular architectures are constructed. With fixed length of the PEO block, the molecular weight change of the PS block originates the phase formation and transition. Due to the distinct affinity, the AC60-based giant surfactants form two-component morphologies, while three-component morphologies are found in the FPOSS-based ones. A PS block stretching parameter is introduced to characterize the PS chain conformation in different morphologies. The highly diverse self-assembly behaviors and the tunable dimensions in thin films suggest the giant surfactants could be a promising and robust platform for nanolithography applications.

  15. Structural, Viscoelastic, and Electrochemical Characteristics of Self-Assembled Amphiphilic Comblike Copolymers in Aqueous Solutions.

    PubMed

    Talantikite, Malika; Aoudia, Kahina; Benyahia, Lazhar; Chaal, Lila; Chassenieux, Christophe; Deslouis, Claude; Gaillard, Cédric; Saidani, Boualem

    2017-02-02

    Self-assembly in aqueous solutions of an amphiphilic comblike polyelectrolyte (80C12) that consists of a polystyrene (PS) backbone onto which quaternary ammonium pendant moieties have been grafted has been investigated by light scattering and cryo-transmission electron microscopy measurements in the presence of KCl and methylviologen dication (MV(2+)) under conditions mimicking those for electrochemical measurements. Polymer chains self-assemble within branched cylindrical micelles that display viscoelastic properties, characterized by a relaxation time of 4 s. To tune this time, 80C12 was mixed with a polyoxyethylene nonionic surfactant (Brij C12E10). Relatively increasing the amount of the latter leads to a decrease in the relaxation time of the 80C12 solution. Correlatively, electrochemical experiments with a rotating disk electrode show a transition of the mass transport rate, which deviates from the classical Newtonian behavior in the same velocity domain. This result generalizes what has been already observed with solutions of linear polymers of high molecular weight and wormlike micelles based on surfactants subjected to elongational deformations. Moreover, the critical times derived from rheological and electrochemical experiments display the same trend.

  16. Programmable Crafting of Hierarchically Structured Block Copolymer/Nanoparticles (and Nanorods) via Flow Enabled Self-Assembly

    NASA Astrophysics Data System (ADS)

    Lin, Zhiqun; Li, Bo; Han, Wei

    2014-03-01

    Hierarchical assembly of diblock copolymer/nanocrystals (e.g., Au and CdSe nanoparticles and nanorods) was successfully crafted into parallel stripes by flow enabled self-assembly (FESA). They were precisely and programmably patterned at desired position on the substrate. Remarkably, a minimum spacing between two adjacent stripes was observed and a model was proposed to understand the relationship between the width of stripes and the minimum spacing. FESA of diblock copolymer/nanocrystals is a lithography-free method and facile to implement, offering opportunities for creating functional hierarchically structured materials and devices. We gratefully acknowledge support from NSF CBET 1159048 and 1332780.

  17. Self-assembling iron oxyhydroxide/oxide tubular structures: laboratory-grown and field examples from Rio Tinto.

    PubMed

    Barge, Laura M; Cardoso, Silvana S S; Cartwright, Julyan H E; Doloboff, Ivria J; Flores, Erika; Macías-Sánchez, Elena; Sainz-Díaz, C Ignacio; Sobrón, Pablo

    2016-11-01

    Rio Tinto in southern Spain has become of increasing astrobiological significance, in particular for its similarity to environments on early Mars. We present evidence of tubular structures from sampled terraces in the stream bed at the source of the river, as well as ancient, now dry, terraces. This is the first reported finding of tubular structures in this particular environment. We propose that some of these structures could be formed through self-assembly via an abiotic mechanism involving templated precipitation around a fluid jet, a similar mechanism to that commonly found in so-called chemical gardens. Laboratory experiments simulating the formation of self-assembling iron oxyhydroxide tubes via chemical garden/chemobrionic processes form similar structures. Fluid-mechanical scaling analysis demonstrates that the proposed mechanism is plausible. Although the formation of tube structures is not itself a biosignature, the iron mineral oxidation gradients across the tube walls in laboratory and field examples may yield information about energy gradients and potentially habitable environments.

  18. Self-assembling iron oxyhydroxide/oxide tubular structures: laboratory-grown and field examples from Rio Tinto

    NASA Astrophysics Data System (ADS)

    Barge, Laura M.; Cardoso, Silvana S. S.; Cartwright, Julyan H. E.; Doloboff, Ivria J.; Flores, Erika; Macías-Sánchez, Elena; Sainz-Díaz, C. Ignacio; Sobrón, Pablo

    2016-11-01

    Rio Tinto in southern Spain has become of increasing astrobiological significance, in particular for its similarity to environments on early Mars. We present evidence of tubular structures from sampled terraces in the stream bed at the source of the river, as well as ancient, now dry, terraces. This is the first reported finding of tubular structures in this particular environment. We propose that some of these structures could be formed through self-assembly via an abiotic mechanism involving templated precipitation around a fluid jet, a similar mechanism to that commonly found in so-called chemical gardens. Laboratory experiments simulating the formation of self-assembling iron oxyhydroxide tubes via chemical garden/chemobrionic processes form similar structures. Fluid-mechanical scaling analysis demonstrates that the proposed mechanism is plausible. Although the formation of tube structures is not itself a biosignature, the iron mineral oxidation gradients across the tube walls in laboratory and field examples may yield information about energy gradients and potentially habitable environments.

  19. Growth, structural, and optical properties of self-assembled (In,Ga)as quantum posts on GaAs.

    PubMed

    He, J; Krenner, H J; Pryor, C; Zhang, J P; Wu, Y; Allen, D G; Morris, C M; Sherwin, M S; Petroff, P M

    2007-03-01

    Self-assembled quantum dots embedded in semiconductor heterostructures have proved to be a rich system for exploring the physics of three dimensionally confined charges and excitons. We present here a novel structure, which allows adjusting the level of confinement between 3D and 2D for electrons and holes, respectively. The quantum post consists of a quantum dot connected to a short quantum wire. The molecular beam epitaxy deposition of these self-assembled structures is discussed, and their structural and chemical compositions are presented. Their optical properties measured by photoluminescence are compared to an eight-band strain-dependent k.p model incorporating detailed structure and alloy composition. The calculations show electron delocalization in the quantum wire part of the quantum post and hole localization in the strain-induced regions at the ends of the quantum post. The quantum post offers the possibility of controlling the dipole moment in the structure and opens up new means for tuning the intra-subband transitions by controlling its dimensions.

  20. Surface coating of siRNA-peptidomimetic nano-self-assemblies with anionic lipid bilayers: enhanced gene silencing and reduced adverse effects in vitro

    NASA Astrophysics Data System (ADS)

    Zeng, Xianghui; de Groot, Anne Marit; Sijts, Alice J. A. M.; Broere, Femke; Oude Blenke, Erik; Colombo, Stefano; van Eden, Willem; Franzyk, Henrik; Nielsen, Hanne Mørck; Foged, Camilla

    2015-11-01

    Cationic vectors have demonstrated the potential to facilitate intracellular delivery of therapeutic oligonucleotides. However, enhanced transfection efficiency is usually associated with adverse effects, which also proves to be a challenge for vectors based on cationic peptides. In this study a series of proteolytically stable palmitoylated α-peptide/β-peptoid peptidomimetics with a systematically varied number of repeating lysine and homoarginine residues was shown to self-assemble with small interfering RNA (siRNA). The resulting well-defined nanocomplexes were coated with anionic lipids giving rise to net anionic liposomes. These complexes and the corresponding liposomes were optimized towards efficient gene silencing and low adverse effects. The optimal anionic liposomes mediated a high silencing effect, which was comparable to that of the control (cationic Lipofectamine 2000), and did not display any noticeable cytotoxicity and immunogenicity in vitro. In contrast, the corresponding nanocomplexes mediated a reduced silencing effect with a more narrow safety window. The surface coating with anionic lipid bilayers led to partial decomplexation of the siRNA-peptidomimetic nanocomplex core of the liposomes, which facilitated siRNA release. Additionally, the optimal anionic liposomes showed efficient intracellular uptake and endosomal escape. Therefore, these findings suggest that a more efficacious and safe formulation can be achieved by surface coating of the siRNA-peptidomimetic nano-self-assemblies with anionic lipid bilayers.Cationic vectors have demonstrated the potential to facilitate intracellular delivery of therapeutic oligonucleotides. However, enhanced transfection efficiency is usually associated with adverse effects, which also proves to be a challenge for vectors based on cationic peptides. In this study a series of proteolytically stable palmitoylated α-peptide/β-peptoid peptidomimetics with a systematically varied number of repeating lysine

  1. Directed self-assembly of high-chi block copolymer for nano fabrication of bit patterned media via solvent annealing

    NASA Astrophysics Data System (ADS)

    Xiong, Shisheng; Chapuis, Yves-Andre; Wan, Lei; Gao, He; Li, Xiao; Ruiz, Ricardo; Nealey, Paul F.

    2016-10-01

    We report the formation of nanoimprint master templates that can be used for the fabrication of bit patterned media (BPM). The template was formed by directed self-assembly, with solvent annealing, of a symmetric ABA triblock copolymer to form perpendicularly oriented lamellae on chemical patterns. We used a high-χ block copolymer, poly(2-vinyl pyridine)-block-polystyrene-block-poly(2-vinyl pyridine) to achieve smaller feature sizes than are possible with polystyrene-block-poly(methyl methacrylate). The work shows that triblock copolymers can provide a large processing window in terms of pitch commensurability. Using block-selective infiltration (atomic layer deposition with sequential long soaking/purge cycles), an alumina composite with high etch resistance was specifically incorporated into the polar and hydrophilic P2VP domains. Subsequently, the surface pattern was successfully transferred into underlying Si substrates by etching with a fluorine-containing plasma to create a nanoimprint master. The line/space pattern of the nanoimprint master met the BPM fabrication requirement of defectivity <10-3. For demonstration purposes, the nanoimprint master was used to imprint a replica pattern of photoresist on a quartz wafer.

  2. Biodegradable nano-micro carrier systems for sustained pulmonary drug delivery: (I) Self-assembled nanoparticles encapsulated in respirable/swellable semi-IPN microspheres

    PubMed Central

    El-Sherbiny, I. M.; Smyth, H. D. C.

    2012-01-01

    Design of appropriate inhaled carriers with adequate aerodynamic properties, drug release, biodegradation and evasion of macrophage uptake is a major challenge for controlled release pulmonary drug delivery. In this study, PEG graft copolymerized onto N-phthaloyl chitosan (NPHCs) was synthesized then characterized using FTIR, EA, DSC and 2D-XRD. The resulting PEG-g-NPHCs copolymers were self-assembled into drug loaded nanoparticles and encapsulated in respirable/swellable sodium alginate semi-IPN hydrogel microspheres as novel biodegradable carriers for controlled release pulmonary drug delivery. The developed nano-/microspheres carrier systems were formed via spray drying followed by ionotropic crosslinking in mild aqueous medium. The size of the developed self-assembled nanoparticles and the microspheres was measured using dynamic light scattering and laser diffraction, respectively. Morphology, moisture content, in-vitro biodegradation and dynamic swelling studies were also investigated for the developed carriers. A model protein was entrapped and the in-vitro release profiles were determined in PBS, pH 7.4 at 37°C. A dry powder aerosolization study was conducted using a Next Generation Impactor (NGI). The developed microspheres had suitable aerodynamic diameters (1.02–2.63 μm) and an excellent fine particle fraction, FPF of 31.52%. The microspheres showed also a very fast initial swelling within the first 2 min and started to enzymatically degrade within the first two hours. Moreover, the microspheres entrapped up 90% of the model drug and showed promising in-vitro sustained release profiles as compared to the control formulation. PMID:20580794

  3. Self-assembly synthesis of 3D graphene-encapsulated hierarchical Fe3O4 nano-flower architecture with high lithium storage capacity and excellent rate capability

    NASA Astrophysics Data System (ADS)

    Ma, Yating; Huang, Jian; Lin, Liang; Xie, Qingshui; Yan, Mengyu; Qu, Baihua; Wang, Laisen; Mai, Liqiang; Peng, Dong-Liang

    2017-10-01

    Graphene-encapsulated hierarchical metal oxides architectures can efficiently combine the merits of graphene and hierarchical metal oxides, which are deemed as the potential anode material candidates for the next-generation lithium-ion batteries due to the synergistic effect between them. Herein, a cationic surfactant induced self-assembly method is developed to construct 3D Fe3O4@reduction graphene oxide (H-Fe3O4@RGO) hybrid architecture in which hierarchical Fe3O4 nano-flowers (H-Fe3O4) are intimately encapsulated by 3D graphene network. Each H-Fe3O4 particle is constituted of rod-shaped skeletons surrounded by petal-like nano-flakes that are made up of enormous nanoparticles. When tested as the anode material in lithium-ion batteries, a high reversible capacity of 2270 mA h g-1 after 460 cycles is achieved under a current density of 0.5 A g-1. More impressively, even tested at a large current density of 10 A g-1, a decent reversible capacity of 490 mA h g-1 can be retained, which is still higher than the theoretical capacity of traditional graphite anode, demonstrating the remarkable lithium storage properties. The reasons for the excellent electrochemical performance of H-Fe3O4@RGO electrode have been discussed in detail.

  4. Large Area Fabrication of Moth-Eye Antireflection Structures Using Self-Assembled Nanoparticles in Combination with Nanoimprinting

    NASA Astrophysics Data System (ADS)

    Tsutomu Nakanishi,; Toshiro Hiraoka,; Akira Fujimoto,; Takeshi Okino,; Shinobu Sugimura,; Takuya Shimada,; Koji Asakawa,

    2010-07-01

    A moth-eye structure, which suppresses the reflection on a surface, was fabricated on the entire surface of a large silicon wafer by the formation of a self-assembled particle monolayer as a dry-etch mask formed by our embedded particle monolayer (EPM) method. We optimized the shape of moth-eye structures by optical calculation and improved the fabrication procedure to allow formation over a large area. As a result, we succeeded in fabricating a moth-eye structure on the entire surface of a 12-in. silicon wafer and the surface reflectance was reduced to less than 0.8% in the visible light range. A large nickel mold, which is able to transfer the pattern to an 8-in. display, could be formed using the 12-in. silicon substrate as a master. A moth-eye film was fabricated by UV nanoimprinting using the nickel mold and the high antireflection performance was confirmed. The fabrication cost of the moth-eye structure over a large area would be markedly reduced by the use of the self-assembly technique in combination with nanoimprinting.

  5. The effect of cation structure on the mesophase architecture of self-assembled and polymerized imidazolium-based ionic liquids.

    SciTech Connect

    Batra, D.; Seifert, S.; Firestone, M. A.; Materials Science Division

    2007-01-01

    The binary phase behavior of a series of imidazolium-based ionic liquids (ILs) has been investigated. In particular, the effect of two structural modifications of the imidazolium cation, alkyl chain length, and the introduction of a polymerizable acryloyl group at the alkyl chain terminus, has been studied using small angle X-ray scattering. Upon increasing water content, the non-polymerizable IL, 1-decyl-3-methylimidazolium chloride, adopts mesophase structures of predominately two-dimensional (2D) hexagonal symmetry, including structures intermediate in character between lamellae and 2D hexagonal micelles. Introduction of a photopolymerizable acryloyl functional group to form 1-(10-(acryloyloxy)decyl)-3-methylimidazolium chloride produces a rod-coil IL cation that yields self-assembled mesophases in which the formation of tetragonal morphologies is favored. Covalent linking of the IL cations by UV-induced polymerization converts the lyotropic mesophase into three-dimensional biocontinuous chemical gels. Reducing the alkyl chain length, as in the polymerizable IL cation 1-(8-(acryloyloxy)octyl)-3-methylimidazolium chloride, severely reduces the self-assembled mesophase order, and triggers the formation of only weakly ordered one-dimensional lamellar structures.

  6. Particle-based simulations of bilayer membranes: self-assembly, structural analysis, and shock-wave damage

    NASA Astrophysics Data System (ADS)

    Steinhauser, Martin O.; Schindler, Tanja

    2017-01-01

    We report on the results of particle-based, coarse-grained molecular dynamics simulations of amphiphilic lipid molecules in aqueous environment where the membrane structures at equilibrium are subsequently exposed to strong shock waves, and their damage is analyzed. The lipid molecules self-assemble from unbiased random initial configurations to form stable bilayer membranes, including closed vesicles. During self-assembly of lipid molecules, we observe several stages of clustering, starting with many small clusters of lipids, gradually merging together to finally form one single bilayer membrane. We find that the clustering of lipids sensitively depends on the hydrophobic interaction h_c of the lipid tails in our model and on temperature T of the system. The self-assembled bilayer membranes are quantitatively analyzed at equilibrium with respect to their degree of order and their local structure. We also show that—by analyzing the membrane fluctuations and using a linearized theory— we obtain area compression moduli K_A and bending stiffnesses κ _B for our bilayer membranes which are within the experimental range of in vivo and in vitro measurements of biological membranes. We also discuss the density profile and the pair correlation function of our model membranes at equilibrium which has not been done in previous studies of particle-based membrane models. Furthermore, we present a detailed phase diagram of our lipid model that exhibits a sol-gel transition between quasi-solid and fluid domains, and domains where no self-assembly of lipids occurs. In addition, we present in the phase diagram the conditions for temperature T and hydrophobicity h_c of the lipid tails of our model to form closed vesicles. The stable bilayer membranes obtained at equilibrium are then subjected to strong shock waves in a shock tube setup, and we investigate the damage in the membranes due to their interaction with shock waves. Here, we find a transition from self

  7. Self-assembled structures and excellent surface properties of a novel anionic phosphate diester surfactant derived from natural rosin acids.

    PubMed

    Li, Juan; Lin, Hai-Xia; Chen, Xiao-Yu; Zhu, Jun-Rong; Yang, Ming-Sheng; Yang, Jun; Han, Chun-Rui

    2017-01-15

    A novel anionic rosin-based phosphate diester sodium (DDPDS) was successfully synthesized from raw dehydroabietic acid, a natural raw material, via four-step reactions: acylation, esterification, phosphorylation and neutralization. Nuclear magnetic resonance ((13)C NMR) and Fourier transform infrared spectroscopy (FT-IR) were used to characterize the structure of target products. The aggregation behaviors in aqueous-ethanol solution and surface properties of DDPDS and its mixed systems were investigated by transmission electron microscopy (TEM), automatic tensiometer and contact angle measuring instrument. The results showed that DDPDS had high surface activity, unexpected emulsification and excellent wettability. The critical micelle concentration (CMC) of 1.35g∗L(-1), the minimum surface tension (γcmc) of 31.75mN∗m(-1), emulsifying power of 153s and the minimum contact angle of 13.4° were determined for DDPDS. Spherical vesicles with diameter about 50nm and 5μm were self-assembled respectively in aqueous-ethanol solution when DDPDS concentration is about 1 CMC and 5 CMC. Two surfactant ionic self-assembly systems were constructed by mixing DDPDS with sodium dodecylbenzenesulfonate (SDBS) and cetyltrimethylammonium bromide (CTAB), which forms 40nm and 20nm spherical micelles in 1 CMC aqueous-ethanol solution. Possible formation mechanisms of surfactant ionic self-assembly systems on a combination of ionic interactions between DDPDS and SDBS or CTAB are discussed. It was found that there were an obvious synergistic effect of foam stability in DDPDS/SDBS mixed system and an obvious synergistic effect of foam capability in DDPDS/CTAB mixed system.

  8. Effect of Structure and Disorder on the Charge Transport in Defined Self-Assembled Monolayers of Organic Semiconductors.

    PubMed

    Schmaltz, Thomas; Gothe, Bastian; Krause, Andreas; Leitherer, Susanne; Steinrück, Hans-Georg; Thoss, Michael; Clark, Timothy; Halik, Marcus

    2017-09-26

    Self-assembled monolayer field-effect transistors (SAMFETs) are not only a promising type of organic electronic device but also allow detailed analyses of structure-property correlations. The influence of the morphology on the charge transport is particularly pronounced, due to the confined monolayer of 2D-π-stacked organic semiconductor molecules. The morphology, in turn, is governed by relatively weak van-der-Waals interactions and is thus prone to dynamic structural fluctuations. Accordingly, combining electronic and physical characterization and time-averaged X-ray analyses with the dynamic information available at atomic resolution from simulations allows us to characterize self-assembled monolayer (SAM) based devices in great detail. For this purpose, we have constructed transistors based on SAMs of two molecules that consist of the organic p-type semiconductor benzothieno[3,2-b][1]benzothiophene (BTBT), linked to a C11 or C12 alkylphosphonic acid. Both molecules form ordered SAMs; however, our experiments show that the size of the crystalline domains and the charge-transport properties vary considerably in the two systems. These findings were confirmed by molecular dynamics (MD) simulations and semiempirical molecular-orbital electronic-structure calculations, performed on snapshots from the MD simulations at different times, revealing, in atomistic detail, how the charge transport in organic semiconductors is influenced and limited by dynamic disorder.

  9. Inkjet-printed thiol self-assembled monolayer structures on gold: quality control and microarray electrode fabrication.

    PubMed

    Rianasari, Ina; Walder, Lorenz; Burchardt, Malte; Zawisza, Izabella; Wittstock, Gunther

    2008-08-19

    Laterally structured, self-assembled monolayers (SAMs) of different thiols (HS-R-X, R = (CH 2) 3-16, X = -CH 3, -COOH, -NH 2) on gold have been prepared by inkjet printing. The printer is a modified, low-cost desktop printer (Epson Stylus Photo R200), the ink is a 1 mM solution of the thiol in ethanol/glycerol (6:1). The quality of inkjet-printed large area SAMs obtained in this study is between that of a layer self-assembled from a thiol solution and that obtained by soft lithography, according to cyclic voltammetry, electrochemical impedance spectroscopy, scanning electrochemical microscopy (SECM), and polarization-modulated Fourier transform infrared reflection-absorption spectroscopy (PM IRRAS). For the first time, simultaneous printing of two different thiols in a single print job as an alternative to sequential printing and backfilling is demonstrated. The smallest structures consisting of conductive disks of 40 microm diameter were analyzed as single spots by SECM and as random array electrodes with different average disk-disk distance. Conductive band electrodes with variable bandwidth (300 microm to 1 cm) are presented, as well as a pH switchable band structure. As compared to stamping, inkjet printing allows for simultaneous multiple thiol printing in a single print job with the resolution limited only by the droplet size and the precision of the translation stage.

  10. Coalescence of silver nanoparticles at room temperature: unusual crystal structure transformation and dendrite formation induced by self-assembly.

    PubMed

    Grouchko, Michael; Popov, Inna; Uvarov, Vladimir; Magdassi, Shlomo; Kamyshny, Alexander

    2009-02-17

    It was found that during the evaporation of water from a droplet of a silver nanoparticles dispersion a self-assembly process leads to the coalescence of the nanoparticles at room temperature and eventually results in a 3D, micrometer-sized dendrite. Direct in situ HR-TEM observation of coalescence events of individual nanoparticles revealed that during this process a transformation of the nanoparticles' crystal structure takes place, from the common fcc silver structure to the unusual hcp structure. It was found that even-though a majority of the nanoparticles in the dispersion have the fcc structure the obtained dendrites are characterized by the hcp structure, reflecting the crystal structure transformation due to the coalescence process.

  11. 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.

  12. Fabricating Nanoporous Silica Structure on D-Fibres through Room Temperature Self-Assembly

    PubMed Central

    Canning, John; Moura, Lucas; Lindoy, Lachlan; Cook, Kevin; Crossley, Maxwell J.; Luo, Yanhua; Peng, Gang-Ding; Glavind, Lars; Huyang, George; Naqshbandi, Masood; Kristensen, Martin; Martelli, Cicero; Town, Graham

    2014-01-01

    The room temperature deposition of self-assembling silica nanoparticles onto D-shaped optical fibres (“D-fibre”), drawn from milled preforms fabricated by modified chemical vapour deposition (MCVD), is studied. Vertical dip-and-withdraw produces tapered layers, with one end thicker (surface coverage >0.85) than the other, whilst horizontal dip-and-withdraw produces much more uniform layers over the core region. The propagation of induced fracturing over the core region during drying is overcome using a simple protrusion of the inner cladding. Thick coatings are discernible through thin film interference colouring, but thinner coatings require scanning electron microscopy (SEM) imaging. Here, we show that fluorescence imaging, using Rhodamine B, in this example, can provide some qualitative and speedy assessment of coverage. PMID:28788571

  13. Structural and magnetic properties of self-assembled cobalt on porous silicon; experimental and micromagnetic investigations

    NASA Astrophysics Data System (ADS)

    Saidani, M.; Belkacem, W.; Bessais, L.; Mliki, N.

    2017-08-01

    In this paper, we report on self-assembled Co nanoparticles deposited in and on porous silicon (PS) matrix by using UHV evaporation. Four samples were prepared by varying the Co deposited thickness (t = 3, 5, 7 and 10 nm). All samples have been investigated by means of Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Physical Properties Measurement System (PPMS). The increase of t has induced an increase of the nanoparticle diameter from 3 nm to about 150 nm. Referring to the magnetic characterizations, this increase has been followed by a single to multi-domain transition. Therefore, this has been evidenced by a switching from superparamagnetism to purely ferromagnetism accompanied by a change in the magnetic reversal dynamics. Thus, by performing micromagnetic calculation, we have shown that a transition from the uniform rotation to vortex state occurs at a critical diameter of about 55 nm.

  14. Fabricating Nanoporous Silica Structure on D-Fibres through Room Temperature Self-Assembly.

    PubMed

    Canning, John; Moura, Lucas; Lindoy, Lachlan; Cook, Kevin; Crossley, Maxwell J; Luo, Yanhua; Peng, Gang-Ding; Glavind, Lars; Huyang, George; Naqshbandi, Masood; Kristensen, Martin; Martelli, Cicero; Town, Graham

    2014-03-19

    The room temperature deposition of self-assembling silica nanoparticles onto D-shaped optical fibres ("D-fibre"), drawn from milled preforms fabricated by modified chemical vapour deposition (MCVD), is studied. Vertical dip-and-withdraw produces tapered layers, with one end thicker (surface coverage >0.85) than the other, whilst horizontal dip-and-withdraw produces much more uniform layers over the core region. The propagation of induced fracturing over the core region during drying is overcome using a simple protrusion of the inner cladding. Thick coatings are discernible through thin film interference colouring, but thinner coatings require scanning electron microscopy (SEM) imaging. Here, we show that fluorescence imaging, using Rhodamine B, in this example, can provide some qualitative and speedy assessment of coverage.

  15. Self-assembled micro-structured sensors for food safety in paper based food packaging.

    PubMed

    Hakovirta, M; Aksoy, B; Hakovirta, J

    2015-08-01

    Natural self-assembled microstructured particles (diatomaceous earth) were used to develop a gas sensor paper with detection mechanism based on visible and distinct color changes of the sensor paper when exposed to volatile basic nitrogen compounds. The coating formulation for paper was prepared by applying diatomites, polyvinyl alcohol (PVOH), and pH sensitive dyes on acidic paper substrate. The surface coating was designed to allow a maximum gas flow through the diatomite sensors. The produced sensor paper was tested for sensitivity using different ammonia concentrations and we observed a sensitivity lower limit at 63 ppm. As a comparison, the results show comparable sensitivity levels to carbon nanotube based sensor technologies reported in literature.

  16. Block copolymer strands with internal microphase separation structure via self-assembly at the air-water interface.

    PubMed

    Price, Eric W; Guo, Yunyong; Wang, C-W; Moffitt, Matthew G

    2009-06-02

    Block copolymer microphase separation in the bulk is coupled to amphiphilic block copolymer self-assembly at the air-water interface to yield hierarchical Langmuir-Blodgett (LB) structures combining organization at the meso- and nanoscales. A blend of polystyrene-b-poly(ethylene oxide) (PS-b-PEO) (Mn=141K, 11.4 wt % PEO) and polystyrene-b-poly(butadiene) (PS-b-PB) (Mn=31.9K, 28.5 wt % PB) containing a PS-b-PB weight fraction of f=0.75 was deposited at the air-water interface, resulting in the spontaneous generation of aggregates with multiscale organization, including nanoscale cylinders in mesoscale strands, via evaporation of the spreading solvent. The resulting features were characterized in LB films via AFM and TEM and at the air-water interface via Langmuir compression isotherms. Blends containing lower PS-b-PB contents formed mesoscale aggregate morphologies of continents and strands (f=0.50) or mesoscale continents with holes (f=0.25), but without the internal nanoscale organization found in the f=0.75 blend. The interfacial self-assembly of pure PS-b-PB at the air-water interface (f=1) yielded taller and more irregularly shaped aggregates than blends containing PS-b-PEO, indicating the integral role of the amphiphilic copolymer in regulating the mesoscale organization of the hierarchically structured features.

  17. Modeling and characterization of molecular structures in self assembled and Langmuir-Blodgett films for controlled fabrication

    SciTech Connect

    Cesarano, J. III

    1997-10-01

    Self Assembled (SA) thin films and Langmuir-Blodgett (LB) thin films are emerging technologies for the development of chemical and bio-chemical sensors, electrooptic films, second harmonic generators (frequency doublers), templates for biomimetic growth etc. One of the goals of this project was to extend Sandia`s characterization techniques and molecular modeling capabilities for these complex two-dimensional geometries with the objective of improving the control of the fabrication of these structures for specific applications. Achieving this requires understanding both the structure throughout the thickness of the films and the in-plane lattice of the amphiphilic molecules. To meet these objectives they used atomic force microscopy (AFM), X-ray reflectivity, and molecular modeling. While developing these capabilities, three different materials systems were fabricated and characterized: (1) Self Assembled Monolayers (SAMs) of octadecyltrichlorosilane (OTS) and LB films of arachidic acid on silicon wafers; (2) SAMs on PZT substrates; and (3) electrochemical deposition of CdS on LB film templates.

  18. α-Helical Structures Drive Early Stages of Self-Assembly of Amyloidogenic Amyloid Polypeptide Aggregate Formation in Membranes

    PubMed Central

    Pannuzzo, Martina; Raudino, Antonio; Milardi, Danilo; La Rosa, Carmelo; Karttunen, Mikko

    2013-01-01

    The human islet amyloid polypeptide (hIAPP) is the primary component in the toxic islet amyloid deposits in type-2 diabetes. hIAPP self-assembles to aggregates that permeabilize membranes and constitutes amyloid plaques. Uncovering the mechanisms of amyloid self-assembly is the key to understanding amyloid toxicity and treatment. Although structurally similar, hIAPP's rat counterpart, the rat islet amyloid polypeptide (rIAPP), is non-toxic. It has been a puzzle why these peptides behave so differently. We combined multiscale modelling and theory to explain the drastically different dynamics of hIAPP and rIAPP: The differences stem from electrostatic dipolar interactions. hIAPP forms pentameric aggregates with the hydrophobic residues facing the membrane core and stabilizing water-conducting pores. We give predictions for pore sizes, the number of hIAPP peptides, and aggregate morphology. We show the importance of curvature-induced stress at the early stages of hIAPP assembly and the α-helical structures over β-sheets. This agrees with recent fluorescence spectroscopy experiments. PMID:24071712

  19. Designing DNA-grafted particles that self-assemble into desired crystalline structures using the genetic algorithm.

    PubMed

    Srinivasan, Babji; Vo, Thi; Zhang, Yugang; Gang, Oleg; Kumar, Sanat; Venkatasubramanian, Venkat

    2013-11-12

    In conventional research, colloidal particles grafted with single-stranded DNA are allowed to self-assemble, and then the resulting crystal structures are determined. Although this Edisonian approach is useful for a posteriori understanding of the factors governing assembly, it does not allow one to a priori design ssDNA-grafted colloids that will assemble into desired structures. Here we address precisely this design issue, and present an experimentally validated evolutionary optimization methodology that is not only able to reproduce the original phase diagram detailing regions of known crystals, but is also able to elucidate several previously unobserved structures. Although experimental validation of these structures requires further work, our early success encourages us to propose that this genetic algorithm-based methodology is a promising and rational materials-design paradigm with broad potential applications.

  20. Designing DNA-grafted particles that self-assemble into desired crystalline structures using the genetic algorithm

    PubMed Central

    Srinivasan, Babji; Vo, Thi; Zhang, Yugang; Gang, Oleg; Kumar, Sanat; Venkatasubramanian, Venkat

    2013-01-01

    In conventional research, colloidal particles grafted with single-stranded DNA are allowed to self-assemble, and then the resulting crystal structures are determined. Although this Edisonian approach is useful for a posteriori understanding of the factors governing assembly, it does not allow one to a priori design ssDNA-grafted colloids that will assemble into desired structures. Here we address precisely this design issue, and present an experimentally validated evolutionary optimization methodology that is not only able to reproduce the original phase diagram detailing regions of known crystals, but is also able to elucidate several previously unobserved structures. Although experimental validation of these structures requires further work, our early success encourages us to propose that this genetic algorithm–based methodology is a promising and rational materials-design paradigm with broad potential applications. PMID:24167286

  1. Interface electronic structures of reversible double-docking self-assembled monolayers on an Au(111) surface

    PubMed Central

    Zhang, Tian; Ma, Zhongyun; Wang, Linjun; Xi, Jinyang; Shuai, Zhigang

    2014-01-01

    Double-docking self-assembled monolayers (DDSAMs), namely self-assembled monolayers (SAMs) formed by molecules possessing two docking groups, provide great flexibility to tune the work function of metal electrodes and the tunnelling barrier between metal electrodes and the SAMs, and thus offer promising applications in both organic and molecular electronics. Based on the dispersion-corrected density functional theory (DFT) in comparison with conventional DFT, we carry out a systematic investigation on the dual configurations of a series of DDSAMs on an Au(111) surface. Through analysing the interface electronic structures, we obtain the relationship between single molecular properties and the SAM-induced work-function modification as well as the level alignment between the metal Fermi level and molecular frontier states. The two possible conformations of one type of DDSAM on a metal surface reveal a strong difference in the work-function modification and the electron/hole tunnelling barriers. Fermi-level pinning is found to be a key factor to understand the interface electronic properties. PMID:24615153

  2. Cationic amphiphilic drugs self-assemble to the core-shell interface of PEGylated phospholipid micelles and stabilize micellar structure.

    PubMed

    Wang, Jing; Xing, Xueqing; Fang, Xiaocui; Zhou, Chang; Huang, Feng; Wu, Zhonghua; Lou, Jizhong; Liang, Wei

    2013-10-13

    Since polymeric micelles are promising and have potential in drug delivery systems, people have become more interested in studying the compatibility of polymeric carriers and drugs, which might help them to simplify the preparation method and increase the micellar stability. In this article, we report that cationic amphiphilic drugs can be easily encapsulated into PEGylated phospholipid (PEG-PE) micelles by self-assembly method and that they show high encapsulation efficiency, controllable drug release and better micellar stability than empty micelles. The representative drugs are doxorubicin and vinorelbine. However, gemcitabine and topotecan are not suitable for PEG-PE micelles due to lack of positive charge or hydrophobicity. Using a series of experiments and molecular modelling, we figured out the assembly mechanism, structure and stability of drug-loaded micelles, and the location of drugs in micelles. Integrating the above information, we explain the effect of the predominant force between drugs and polymers on the assembly mechanism and drug release behaviour. Furthermore, we discuss the importance of pKa and to evaluate the compatibility of drugs with PEG-PE in self-assembly preparation method. In summary, this work provides a scientific understanding for the reasonable designing of PEG-PE micelle-based drug encapsulation and might enlighten the future study on drug-polymer compatibility for other polymeric micelles.

  3. Self-Assembled Multi-Component Catenanes: Structural Insights into an Adaptable Class of Molecular Receptors and [2]-Catenanes

    DTIC Science & Technology

    2012-06-11

    SECURITY CLASSIFICATION OF: Under acidic conditions (50 equiv TFA), combinations of hydrazide A-B monomers self assemble into octameric [2...conditions (50 equiv TFA), combinations of hydrazide A-B monomers self assemble into octameric [2] -catenanes with high selectivity for [132]2, where 1...Under acidic conditions (50 equiv of TFA), combinations of hydrazide A-B monomers self-assemble into octameric [2]-catenanes with high selectivity

  4. All-Atom Multiscale Molecular Dynamics Theory and Simulation of Self-Assembly, Energy Transfer and Structural Transition in Nanosystems

    NASA Astrophysics Data System (ADS)

    Espinosa Duran, John Michael

    The study of nanosystems and their emergent properties requires the development of multiscale computational models, theories and methods that preserve atomic and femtosecond resolution, to reveal details that cannot be resolved experimentally today. Considering this, three long time scale phenomena were studied using molecular dynamics and multiscale methods: self-assembly of organic molecules on graphite, energy transfer in nanosystems, and structural transition in vault nanoparticles. Molecular dynamics simulations of the self-assembly of alkoxybenzonitriles with different tail lengths on graphite were performed to learn about intermolecular interactions and phases exhibited by self-organized materials. This is important for the design of ordered self-assembled organic photovoltaic materials with greater efficiency than the disordered blends. Simulations revealed surface dynamical behaviors that cannot be resolved experimentally today due to the lack of spatiotemporal resolution. Atom-resolved structures predicted by simulations agreed with scanning tunneling microscopy images and unit cell measurements. Then, a multiscale theory based on the energy density as a field variable is developed to study energy transfer in nanoscale systems. For applications like photothermal microscopy or cancer phototherapy is required to understand how the energy is transferred to/from nanosystems. This multiscale theory could be applied in this context and here is tested for cubic nanoparticles immersed in water for energy being transferred to/from the nanoparticle. The theory predicts the energy transfer dynamics and reveals phenomena that cannot be described by current phenomenological theories. Finally, temperature-triggered structural transitions were revealed for vault nanoparticles using molecular dynamics and multiscale simulations. Vault is a football-shaped supramolecular assembly very distinct from the commonly observed icosahedral viruses. It has very promising

  5. Self-assembly and gelation of poly(aryl ether) dendrons containing hydrazide units: factors controlling the formation of helical structures.

    PubMed

    Malakar, Partha; Prasad, Edamana

    2015-03-23

    Self-assembly of AB2 and AB3 type low molecular weight poly(aryl ether) dendrons that contain hydrazide units were used to investigate mechanistic aspects of helical structure formation during self-assembly. The results suggest that there are three important aspects that control helical structure formation in such systems with acyl hydrazide/hydrazone linkage: i) J-type aggregation, ii) the hydrogen-bond donor/acceptor ability of the solvent, and iii) the dielectric constant of the solvent. The monomer units self-assemble to form dimer structures through hydrogen-bonding and further assembly of the hydrogen-bonded dimers leads to macroscopic chirality in the present case. Dimer formation was confirmed by NMR spectroscopy and by mass spectrometry. The self-assembly in the system was driven by hydrogen-bonding and π-π stacking interactions. The morphology of the aggregates formed was examined by scanning electron microscopy, and the analysis suggests that aprotic solvent systems facilitate helical fibre formation, whereas introduction of protic solvents results in the formation of flat ribbons. This detailed mechanistic study suggests that the self-assembly follows a nucleation-elongation model to form helical structures, rather than the isodesmic model.

  6. Understanding the structure, dynamics, and mass transport properties of self assembling peptide hydrogels for injectable, drug delivery applications

    NASA Astrophysics Data System (ADS)

    Branco, Monica Cristina

    hydrogels as a function of peptide sequence and concentration. Changes in nanoscale dynamics and structure inherently lead to substantial differences in bulk properties, such as the elastic modulus and network mesh size. Learning how the material properties of the gels influence the transport rate of therapeutics through the hydrogel is essential to the development of delivery vehicles. The remainder of the thesis focuses on correlating the mesh sizes of MAX1 and MAX8 gels to the diffusion and mass transport properties of model dextran and protein probes. Here, work is centered on how peptide charge and concentration, as well as probe structure, in particular hydrodynamic diameter and charge, dictate the temporal release of model probes from the peptide hydrogels. Experiments include self diffusion studies and bulk release experiments with model dextrans and proteins from gels before and after syringe delivery. Overall, this thesis will demonstrate the importance of understanding material properties from the nanoscale up to the macroscale for application based design. With this approach, better and specific development of self-assembling peptide materials can be achieved, allowing for the rational engineering of peptide sequences to form hydrogels appropriate for specific drug delivery applications.

  7. Spontaneous stepwise self-assembly of a polyoxometalate-organic hybrid into catalytically active one-dimensional anisotropic structures.

    PubMed

    Yin, Panchao; Bayaguud, Aruuhan; Cheng, Peng; Haso, Fadi; Hu, Lang; Wang, Joy; Vezenov, Dmitri; Winans, Randall E; Hao, Jian; Li, Tao; Wei, Yongge; Liu, Tianbo

    2014-07-28

    An inorganic-organic hybrid surfactant with a hexavanadate cluster as the polar head group was designed and observed to assemble into micelle structures, which further spontaneously coagulate into a 1D anisotropic structure in aqueous solutions. Such a hierarchical self-assembly process is driven by the cooperation of varied noncovalent interactions, including hydrophobic, electrostatic, and hydrogen-bonding interactions. The hydrophobic interaction drives the quick formation of the micelle structure; electrostatic interactions involving counterions leads to the further coagulation of the micelles into larger assemblies. This process is similar to the crystallization process, but the specific counterions and the directional hydrogen bonding lead to the 1D growth of the final assemblies. Since most of the hexavanadates are exposed to the surface, the 1D assembly with nanoscale thickness is a highly efficient heterogeneous catalyst for the oxidation of organic sulfides with appreciable recyclability. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Structural and optical properties of titanium functionalized periodic mesostructured organosilica framework via evaporation-induced self-assembly method.

    PubMed

    Abdul Wahab, M; He, Chaobin

    2013-04-01

    We describe an evaporation-induced self-assembly method for incorporating Ti into framework of ethane-bridged periodic mesoporous organosilica (PMO). The X-ray diffraction (XRD), transmission electron microscopy (TEM), solid-state 29Si and 13C nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and UV-vis spectroscopy were used to elucidate the optical and structural properties of Ti-incorporated PMO materials. The degree of mesopore ordering and the structural properties were found to be dependent on the loading of Ti into the framework of PMO materials, as confirmed by XRD, and surface structural properties. UV-vis spectra also support the incorporation of Ti into framework of PMO. TEM analyses suggested the formation of mesopores for the pure PMO and Ti-incorporated PMO samples. The solid-state NMR and FT-IR spectra have confirmed the presence of organic fragment in the final PMO framework.

  9. Covalent Tethering and Residues with Bulky Hydrophobic Side Chains Enable Self-Assembly of Distinct Amyloid Structures.

    PubMed

    Ruiz, Jérémy; Boehringer, Régis; Grogg, Marcel; Raya, Jésus; Schirer, Alicia; Crucifix, Corinne; Hellwig, Petra; Schultz, Patrick; Torbeev, Vladimir

    2016-12-02

    Polymorphism is a common property of amyloid fibers that complicates their detailed structural and functional studies. Here we report experiments illustrating the chemical principles that enable the formation of amyloid polymorphs with distinct stoichiometric composition. Using appropriate covalent tethering we programmed self-assembly of a model peptide corresponding to the [20-41] fragment of human β2-microglobulin into fibers with either trimeric or dimeric amyloid cores. Using a set of biophysical and biochemical methods we demonstrated their distinct structural, morphological, and templating properties. Furthermore, we showed that supramolecular approaches in which the peptide is modified with bulky substituents can also be applied to modulate the formation of different fiber polymorphs. Such strategies, when applied to disease-related peptides and proteins, will greatly help in the evaluation of the biological properties of structurally distinct amyloids.

  10. 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).

  11. Ultraporous superhydrophobic gas-permeable nano-layers by scalable solvent-free one-step self-assembly

    NASA Astrophysics Data System (ADS)

    Liu, Guanyu; Wong, William S. Y.; Nasiri, Noushin; Tricoli, Antonio

    2016-03-01

    Superhydrophobic materials with excellent humidity tolerance, high porosity and light transmittance are being investigated for numerous applications including moisture-sensitive catalysts and perovskite solar cells. Here, we report the one-step solvent-free synthesis of ultraporous superhydrophobic nano-layers by the on-the-fly functionalization of nanoparticle aerosols. Short exposure of surfaces to hot Mn3O4, ZnO and TiO2 aerosols results in ultraporous nanoparticle networks with repulsive dewetting state approaching ideal Cassie-Baxter superhydrophobicity. In addition to showcasing sliding angles of ca. 0° and very low contact angle hysteresis of 3° +/- 2°, these optimal nano-layers have up to 98% porosity and pore size of several micrometres, a key feature to enable efficient penetration of gases to the substrate surface. The stability of this ultraporous superhydrophobic morphology is demonstrated by rapidly applying Moses effect-functionality to substrates that parts water up to 5 mm high. This scalable synthesis method offers a flexible and rapid approach for the production of numerous moisture-resistant devices including gas sensors, catalysts and perovskite solar cells.Superhydrophobic materials with excellent humidity tolerance, high porosity and light transmittance are being investigated for numerous applications including moisture-sensitive catalysts and perovskite solar cells. Here, we report the one-step solvent-free synthesis of ultraporous superhydrophobic nano-layers by the on-the-fly functionalization of nanoparticle aerosols. Short exposure of surfaces to hot Mn3O4, ZnO and TiO2 aerosols results in ultraporous nanoparticle networks with repulsive dewetting state approaching ideal Cassie-Baxter superhydrophobicity. In addition to showcasing sliding angles of ca. 0° and very low contact angle hysteresis of 3° +/- 2°, these optimal nano-layers have up to 98% porosity and pore size of several micrometres, a key feature to enable efficient

  12. Ultraporous superhydrophobic gas-permeable nano-layers by scalable solvent-free one-step self-assembly.

    PubMed

    Liu, Guanyu; Wong, William S Y; Nasiri, Noushin; Tricoli, Antonio

    2016-03-21

    Superhydrophobic materials with excellent humidity tolerance, high porosity and light transmittance are being investigated for numerous applications including moisture-sensitive catalysts and perovskite solar cells. Here, we report the one-step solvent-free synthesis of ultraporous superhydrophobic nano-layers by the on-the-fly functionalization of nanoparticle aerosols. Short exposure of surfaces to hot Mn3O4, ZnO and TiO2 aerosols results in ultraporous nanoparticle networks with repulsive dewetting state approaching ideal Cassie-Baxter superhydrophobicity. In addition to showcasing sliding angles of ca. 0° and very low contact angle hysteresis of 3° ± 2°, these optimal nano-layers have up to 98% porosity and pore size of several micrometres, a key feature to enable efficient penetration of gases to the substrate surface. The stability of this ultraporous superhydrophobic morphology is demonstrated by rapidly applying Moses effect-functionality to substrates that parts water up to 5 mm high. This scalable synthesis method offers a flexible and rapid approach for the production of numerous moisture-resistant devices including gas sensors, catalysts and perovskite solar cells.

  13. Self-assembly of Spinel Nano-crystals into Mesoporous Spheres as Bi-functionally Active Oxygen Reduction and Evolution Electrocatalysts.

    PubMed

    Lee, Dong Un; Li, Jingde; Park, Moon Gyu; Seo, Min Ho; Ahn, Wook; Stadelmann, Ian; Ricardez-Sandoval, Luis; Chen, Zhongwei

    2017-03-29

    The present work introduces spinel oxide nano-crystals self-assembled into mesoporous spheres that are bi-functionally active towards catalyzing both oxygen reduction reaction (ORR), and oxygen evolution reaction (OER). The electrochemical evaluation reveals that (Ni,Co)3O4 demonstrates significantly positive shifted ORR on-set and half-wave potentials (-0.127 and -0.292 V vs. SCE, respectively), while Co3O4 results in a negative shifted OER potential (0.65 V vs. SCE) measured at 10 mA cm-2. Based on the DFT analysis, the potential at which all oxygen intermediate reactions proceed spontaneously is the highest for (Ni,Co)3O4 (U = 0.66 eV) during ORR, while it is the lowest for Co3O4 (U = 2.09 eV) during OER. The high ORR activity of (Ni,Co)3O4 is attributed to the enhanced electrical conductivity of the spinel lattice, while the high OER activity of Co3O4 is attributed to relatively weak adsorption energy promoting rapid release of evolved oxygen.

  14. Lattice model for self-assembly with application to the formation of cytoskeletal-like structures

    NASA Astrophysics Data System (ADS)

    Stewman, Shannon F.; Dinner, Aaron R.

    2007-07-01

    We introduce a stochastic approach for self-assembly in systems far from equilibrium. The building blocks are represented by a lattice of discrete variables (Potts-like spins), and physically meaningful mechanisms are obtained by restricting transitions through spatially local rules based on experimental data. We use the method to study nucleation of filopodia-like bundles in a system consisting of purified actin, fascin, actin-related protein 2/3 , and beads coated with Wiskott-Aldrich syndrome protein. Consistent with previous speculation based on static experimental images, we find that bundles derive from Λ -precursor-like patterns of spins on the lattice. The ratcheting of the actin network relative to the surface that represents beads plays an important role in determining the number and orientation of bundles due to the fact that branching is the primary means for generating barbed ends pointed in directions that allow rapid filament growth. By enabling the de novo formation of coexisting morphologies without the computational cost of explicit representation of proteins, the approach introduced complements earlier models of cytoskeletal behavior in vitro and in vivo.

  15. Structure and Morphology of Helicenes: New Nanostructured Materials Spontaneously Self-Assembling into Isolated Fibers

    NASA Astrophysics Data System (ADS)

    Lovinger, A. J.; Nuckolls, C.; Katz, T. J.

    1998-03-01

    A non-racemic aromatic molecule (a helicene) was recently designed and synthesized that spontaneously self-assembles into unique helical columnar aggregates. (Nuckolls, C.; Katz, T. J.; Castellanos, L. J. Am. Chem. Soc. 1996, 118, 3767) These aggregates exhibit remarkable properties, one of which is an enormous optical rotatory ability leading to a record specific rotation at 589 nm of 1400 degrees/mm (or alpha-sub-D of 170,000 degrees). Another property, observed when the material is cooled from the melt, is spontaneous and thermally reversible self-organization into isolated macroscopic liquid-crystalline fibers. The fibers have diameters of ca. 0.1-10 micrometers and can be of unlimited length. Transmission electron microscopy shows that these fibers are comprised of lamellae 50-200 nm wide, each only ca. 10 nm thick. Analyses by X-ray and electron diffraction demonstrate that the molecules are organized in hexagonally packed columns. Polarized light microscopy reveals that the columns are stacked so that their axes parallel the axes of the fibers. In ultra-thin films the alkyl side-chains organize themselves further as in crystalline alkanes.

  16. Structural phase transition in self-assembled 1,10' phenanthroline monolayer on Au(111)

    NASA Astrophysics Data System (ADS)

    Cunha, F.; Jin, Q.; Tao, N. J.; Li, C. Z.

    1997-11-01

    The self-assembly of 1,10' phenanthroline (phen) on Au(111) from aqueous solutions has been studied as a function of the substrate potential with in situ scanning tunneling microscopy (STM). The phen molecules adsorb spontaneously onto the substrate with a preference to decorate the reconstruction stripes of Au(111). The adsorbed molecules stand vertically with their nitrogen atoms facing the Au(111) and stack, like rolls of coins, into polymer-like chains. At high potentials, the chains pack closely in parallel and form an ordered monolayer. Decreasing the potential to a critical value, the chains become randomly oriented via a reversible order-disorder phase transition that resembles the nematic-isotropic transition in liquid crystal materials. High resolution images reveal each phen molecule as two blobs located at the two nitrogen atoms, indicating that the coupling between the nitrogen atoms and Au(111) is responsible for the tunneling current probed by STM. The phen monolayer contains pits with a depth of about one Au layer, which may be attributed to surface stress induced by the strong adsorption of the phen molecules on the surface.

  17. Scaling analysis of self-assembled structures and related morphological information in epitaxial growth

    NASA Astrophysics Data System (ADS)

    Blel, Sonia; Hamouda, Ajmi B. H.; Mahjoub, Brahim; Hoggan, Philip; Oujia, Brahim

    2017-02-01

    Using kinetic Monte-Carlo simulations, we have performed a qualitative and quantitative study of the homo-epitaxial growth for two materials Cu and Ag. Based on their dynamic scaling properties, a relationship between the resultant growth morphology and its computed scaling exponents is found to play a key role in the surface self-assembled at long time (hundreds of monolayer) and also at early time (sub-monolayer regime) of growth. Then, the effect of next-nearest-neighbor (NNN) interactions on the scaling exponents, as well as the surface morphology, is discussed. NNN interactions are found to affect the scaling exponents in the case of Cu rather than Ag. We also show that the higher the local roughness, the best 1-D nanostructures are obtained; which is confirmed by the measurement of filling rate of nanowires at step-edge on vicinal surfaces. Our results were compared to the available experimental and theoretical results and seem advantageous for a better understanding of the growth dynamics.

  18. Structure Prediction of Self-Assembled Dye Aggregates from Cryogenic Transmission Electron Microscopy, Molecular Mechanics, and Theory of Optical Spectra

    PubMed Central

    2016-01-01

    Cryogenic transmission electron microscopy (cryo-TEM) studies suggest that TTBC molecules self-assemble in aqueous solution to form single-walled tubes with a diameter of about 35 Å. In order to reveal the arrangement and mutual orientations of the individual molecules in the tube, we combine information from crystal structure data of this dye with a calculation of linear absorbance and linear dichroism spectra and molecular dynamics simulations. We start with wrapping crystal planes in different directions to obtain tubes of suitable diameter. This set of tube models is evaluated by comparing the resulting optical spectra with experimental data. The tubes that can explain the spectra are investigated further by molecular dynamics simulations, including explicit solvent molecules. From the trajectories of the most stable tube models, the short-range ordering of the dye molecules is extracted and the optimization of the structure is iteratively completed. The final structural model is a tube of rings with 6-fold rotational symmetry, where neighboring rings are rotated by 30° and the transition dipole moments of the chromophores form an angle of 74° with respect to the symmetry axis of the tube. This model is in agreement with cryo-TEM images and can explain the optical spectra, consisting of a sharp red-shifted J-band that is polarized parallel to to the symmetry axis of the tube and a broad blue-shifted H-band polarized perpendicular to this axis. The general structure of the homogeneous spectrum of this hybrid HJ-aggregate is described by an analytical model that explains the difference in redistribution of oscillator strength inside the vibrational manifolds of the J- and H-bands and the relative intensities and excitation energies of those bands. In addition to the particular system investigated here, the present methodology can be expected to aid the structure prediction for a wide range of self-assembled dye aggregates. PMID:27642380

  19. Structure Prediction of Self-Assembled Dye Aggregates from Cryogenic Transmission Electron Microscopy, Molecular Mechanics, and Theory of Optical Spectra.

    PubMed

    Friedl, Christian; Renger, Thomas; Berlepsch, Hans V; Ludwig, Kai; Schmidt Am Busch, Marcel; Megow, Jörg

    2016-09-01

    Cryogenic transmission electron microscopy (cryo-TEM) studies suggest that TTBC molecules self-assemble in aqueous solution to form single-walled tubes with a diameter of about 35 Å. In order to reveal the arrangement and mutual orientations of the individual molecules in the tube, we combine information from crystal structure data of this dye with a calculation of linear absorbance and linear dichroism spectra and molecular dynamics simulations. We start with wrapping crystal planes in different directions to obtain tubes of suitable diameter. This set of tube models is evaluated by comparing the resulting optical spectra with experimental data. The tubes that can explain the spectra are investigated further by molecular dynamics simulations, including explicit solvent molecules. From the trajectories of the most stable tube models, the short-range ordering of the dye molecules is extracted and the optimization of the structure is iteratively completed. The final structural model is a tube of rings with 6-fold rotational symmetry, where neighboring rings are rotated by 30° and the transition dipole moments of the chromophores form an angle of 74° with respect to the symmetry axis of the tube. This model is in agreement with cryo-TEM images and can explain the optical spectra, consisting of a sharp red-shifted J-band that is polarized parallel to to the symmetry axis of the tube and a broad blue-shifted H-band polarized perpendicular to this axis. The general structure of the homogeneous spectrum of this hybrid HJ-aggregate is described by an analytical model that explains the difference in redistribution of oscillator strength inside the vibrational manifolds of the J- and H-bands and the relative intensities and excitation energies of those bands. In addition to the particular system investigated here, the present methodology can be expected to aid the structure prediction for a wide range of self-assembled dye aggregates.

  20. Self-assembly of multilevel branched rutile-type TiO2 structures via oriented lateral and twin attachment

    PubMed Central

    Jordan, Vanja; Javornik, Uroš; Plavec, Janez; Podgornik, Aleš; Rečnik, Aleksander

    2016-01-01

    Recent breakthrough of novel hierarchic materials, orchestrated through oriented attachment of crystal subunits, opened questions on what is the mechanism of their self-assembly. Using rutile-type TiO2, synthesized by hydrothermal reaction of Ti(IV)-butoxide in highly acidic aqueous medium, we uncovered the key processes controlling this nonclassical crystallization process. Formation of complex branched mesocrystals of rutile is accomplished by oriented assembly of precipitated fibers along the two low-energy planes, i.e. {110} and {101}, resulting in lateral attachment and twinning. Phase analysis of amorphous material enclosed in pockets between imperfectly assembled rutile fibers clearly shows harmonic ordering resembling that of the adjacent rutile structure. To our understanding this may be the first experimental evidence indicating the presence of electromagnetic force-fields that convey critical structural information through which oriented attachment of nanocrystals is made possible. PMID:27063110

  1. Self-Assembly of Silver Nanowire Ring Structures Driven by the Compressive Force of a Liquid Droplet.

    PubMed

    Seong, Baekhoon; Park, Hyun Sung; Chae, Ilkyeong; Lee, Hyungdong; Wang, Xiaofeng; Jang, Hyung-Seok; Jung, Jaehyuck; Lee, Changgu; Lin, Liwei; Byun, Doyoung

    2017-04-11

    In a nanowire dispersed in liquid droplets, the interplay between the surface tension of the liquid and the elasticity of the nanowire determines the final morphology of the bent or buckled nanowire. Here, we investigate the fabrication of a silver nanowire ring generated as the nanowire encapsulated inside of fine droplets. We used a hybrid aerodynamic and electrostatic atomization method to ensure the generation of droplets with scalable size in the necessary regime for ring formation. We analytically calculate the compressive force of the droplet driven by surface tension as the key mechanism for the self-assembly of ring structures. Thus, for potential large-scale manufacturing, the droplet size provides a convenient parameter to control the realization of ring structures from nanowires.

  2. Lanthanum induced B-to-Z transition in self-assembled Y-shaped branched DNA structure

    NASA Astrophysics Data System (ADS)

    Nayak, Ashok K.; Mishra, Aseem; Jena, Bhabani S.; Mishra, Barada K.; Subudhi, Umakanta

    2016-05-01

    Controlled conversion of right-handed B-DNA to left-handed Z-DNA is one of the greatest conformational transitions in biology. Recently, the B-Z transition has been explored from nanotechnological points of view and used as the driving machinery of many nanomechanical devices. Using a combination of CD spectroscopy, fluorescence spectroscopy, and PAGE, we demonstrate that low concentration of lanthanum chloride can mediate B-to-Z transition in self-assembled Y-shaped branched DNA (bDNA) structure. The transition is sensitive to the sequence and structure of the bDNA. Thermal melting and competitive dye binding experiments suggest that La3+ ions are loaded to the major and minor grooves of DNA and stabilize the Z-conformation. Our studies also show that EDTA and EtBr play an active role in reversing the transition from Z-to-B DNA.

  3. Mesosized Crystal-like Structure of Hexagonally Packed Hollow Hoops by Solution Self-Assembly of Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    Zhang, Lifeng; Bartels, Carl; Yu, Yisong; Shen, Hongwei; Eisenberg, Adi

    1997-12-01

    Mesosize crystal-like aggregates with an internal structure of hexagonally packed hollow hoops (HHH) in a polystyrene matrix have been prepared in solution by self-assembly of asymmetric polystyrene-b-poly(acrylic acid) diblock copolymers. Most of the aggregates are cylindrical or in the shape of truncated cones. The external surface of the aggregates and the internal surface of the hollow hoops are lines with short poly(acrylic acid) chains. The hoop morphology is imposed because the end-capping energy of a rod on this size scale is more important than the curvature energy. A strong interdependence between the external shape and the internal structure in these mesosize particles is demonstrated.

  4. Theoretical Modelling of Self-Assembly of Molecular Networks

    NASA Astrophysics Data System (ADS)

    Mura, Manuela; Martsinovich, Natalia; Kantorovich, Lev

    2008-03-01

    The phenomenon of self-assembly of atomic and molecular superstructures on crystal surfaces has attracted an increasing interest in nanotechnology. Self-organised nano-templates where the self-assembled monolayer traps other molecules with selected functional properties, can be used as building blocks for larger nanoscale structures. These superstructures can form chiral domains ranging from 1D chains to 2D monolayers. In particular, there have been many scanning tunneling microscopy (STM)studies of self-assembly of melamine, perylene tetra-carboxylic di-imide(PTCDI) or perylene tetra-carboxylic di-anhydride (PTCDA) molecules on the Au(111). STM images of these networks do not reveal the exact details of the intermolecular bonding and process of network growth. It is therefore the task of theory to determine the exact atomic structure of these networks. We present a theoretical study of self-assembly of molecular networks based on different molecules by using a systematic approach to build molecular superstructures. The energies of these structures are calculated using the density-functional theory SIESTA code. The theoretically predicted monolayer structures are in very good agreement with the results of STM measurements.

  5. Fabrication of volcano-shaped nano-patterned sapphire substrates using colloidal self-assembly and wet chemical etching.

    PubMed

    Geng, Chong; Zheng, Lu; Fang, Huajing; Yan, Qingfeng; Wei, Tongbo; Hao, Zhibiao; Wang, Xiaoqing; Shen, Dezhong

    2013-08-23

    Patterned sapphire substrates (PSS) have been widely used to enhance the light output power in GaN-based light emitting diodes. The shape and feature size of the pattern in a PSS affect its enhancement efficiency to a great degree. In this work we demonstrate the nanoscale fabrication of volcano-shaped PSS using a wet chemical etching approach in combination with a colloidal monolayer templating strategy. Detailed analysis by scanning electron microscopy reveals that the unique pattern shape is a result of the different corrosion-resistant abilities of silica masks of different effective heights during wet chemical etching. The formation of silica etching masks of different effective heights has been ascribed to the silica precursor solution in the interstice of the colloidal monolayer template being distributed unevenly after infiltration. In the subsequent wet chemical etching process, the active reaction sites altered as etching duration was prolonged, resulting in the formation of volcano-shaped nano-patterned sapphire substrates.

  6. A new family of multiferrocene complexes with enhanced control of structure and stoichiometry via coordination-driven self-assembly and their electrochemistry.

    PubMed

    Yang, Hai-Bo; Ghosh, Koushik; Zhao, Yue; Northrop, Brian H; Lyndon, Matthew M; Muddiman, David C; White, Henry S; Stang, Peter J

    2008-01-23

    The design and synthesis of a new family of multiferrocene complexes with enhanced control of structure and stoichimetry via coordination-driven self-assembly is described. Insight into the structure and electronic properties of all supramolecules was obtained by electrochemical studies. The collective results provide an enhanced understanding of the influence of structural factors on the electrochemistry of multifunctional electroactive supramolecular architectures.

  7. Theranostic self-assembly structure of gold nanoparticles for NIR photothermal therapy and X-Ray computed tomography imaging.

    PubMed

    Deng, Heng; Zhong, Yanqi; Du, Meihong; Liu, Qinjun; Fan, Zhanming; Dai, Fengying; Zhang, Xin

    2014-01-01

    The controllable self-assembly of amphiphilic mixed polymers grafted gold nanoparitcles (AuNPs) leads to strong interparticle plasmonic coupling, which can be tuned to the near-infrared (NIR) region for enhanced photothermal therapy (PTT). In this study, an improved thiolation method was adopted for ATRP and ROP polymer to obtain amphiphilic brushes of PMEO2MA-SH and PCL-SH. By anchoring PCL-SH and PMEO2MA-SH onto the 14 nm AuNPs, a smart hybrid building block for self-assembly was obtained. Increasing the PCL/PMEO2MA chain ratio from 0.8:1, 2:1 and 3:1 to 7:1, the structure of gold assemblies (GAs) was observed to transfer from vesicle to large compound micelle (LCM). Contributed to the special dense packed structure of gold nanoparticles in LCM, the absorption spectrometry of gold nanoparticles drastically red-shifted from 520 nm to 830 nm, which endowed the GAs remarkable NIR photothermal conversion ability. In addition, gold has high X-ray absorption coefficient which qualifies gold nanomaterial a potential CT contrast agent Herein, we obtain a novel gold assembly structure which can be utilized as potential photothermal therapeutic and CT contrast agents. In vitro and In vivo studies testified the excellent treatment efficacy of optimum GAs as a PTT and CT contrast agent. In vitro degradation test, MTT assay and histology study indicated that GAs was a safe, low toxic reagent with good biodegradability. Therefore, the optimum GAs with strong NIR absorption and high X-ray absorption coefficient could be used as a theranostic agent and the formation of novel gold large compound micelle might offers a new theory foundation for engineering design and synthesis of polymer grafted AuNPs for biomedical applications.

  8. Theranostic Self-Assembly Structure of Gold Nanoparticles for NIR Photothermal Therapy and X-Ray Computed Tomography Imaging

    PubMed Central

    Deng, Heng; Zhong, Yanqi; Du, Meihong; Liu, Qinjun; Fan, Zhanming; Dai, Fengying; Zhang, Xin

    2014-01-01

    The controllable self-assembly of amphiphilic mixed polymers grafted gold nanoparitcles (AuNPs) leads to strong interparticle plasmonic coupling, which can be tuned to the near-infrared (NIR) region for enhanced photothermal therapy (PTT). In this study, an improved thiolation method was adopted for ATRP and ROP polymer to obtain amphiphilic brushes of PMEO2MA-SH and PCL-SH. By anchoring PCL-SH and PMEO2MA-SH onto the 14 nm AuNPs, a smart hybrid building block for self-assembly was obtained. Increasing the PCL/PMEO2MA chain ratio from 0.8:1, 2:1 and 3:1 to 7:1, the structure of gold assemblies (GAs) was observed to transfer from vesicle to large compound micelle (LCM). Contributed to the special dense packed structure of gold nanoparticles in LCM, the absorption spectrometry of gold nanoparticles drastically red-shifted from 520 nm to 830 nm, which endowed the GAs remarkable NIR photothermal conversion ability. In addition, gold has high X-ray absorption coefficient which qualifies gold nanomaterial a potential CT contrast agent Herein, we obtain a novel gold assembly structure which can be utilized as potential photothermal therapeutic and CT contrast agents. In vitro and In vivo studies testified the excellent treatment efficacy of optimum GAs as a PTT and CT contrast agent. In vitro degradation test, MTT assay and histology study indicated that GAs was a safe, low toxic reagent with good biodegradability. Therefore, the optimum GAs with strong NIR absorption and high X-ray absorption coefficient could be used as a theranostic agent and the formation of novel gold large compound micelle might offers a new theory foundation for engineering design and synthesis of polymer grafted AuNPs for biomedical applications. PMID:25057315

  9. A Decentralized Approach to the Formulation of Hypotheses: A Hierarchical Structural Model for a Prion Self-Assembled System

    NASA Astrophysics Data System (ADS)

    Wang, Mingyang; Zhang, Feifei; Song, Chao; Shi, Pengfei; Zhu, Jin

    2016-07-01

    Innovation in hypotheses is a key transformative driver for scientific development. The conventional centralized hypothesis formulation approach, where a dominant hypothesis is typically derived from a primary phenomenon, can, inevitably, impose restriction on the range of conceivable experiments and legitimate hypotheses, and ultimately impede understanding of the system of interest. We report herein the proposal of a decentralized approach for the formulation of hypotheses, through initial preconception-free phenomenon accumulation and subsequent reticular logical reasoning processes. The two-step approach can provide an unbiased, panoramic view of the system and as such should enable the generation of a set of more coherent and therefore plausible hypotheses. As a proof-of-concept demonstration of the utility of this open-ended approach, a hierarchical model has been developed for a prion self-assembled system, allowing insight into hitherto elusive static and dynamic features associated with this intriguing structure.

  10. Molecular and electronic structure of osmium complexes confined to Au(111) surfaces using a self-assembled molecular bridge.

    PubMed

    de la Llave, Ezequiel; Herrera, Santiago E; Adam, Catherine; Méndez De Leo, Lucila P; Calvo, Ernesto J; Williams, Federico J

    2015-11-14

    The molecular and electronic structure of Os(II) complexes covalently bonded to self-assembled monolayers (SAMs) on Au(111) surfaces was studied by means of polarization modulation infrared reflection absorption spectroscopy, photoelectron spectroscopies, scanning tunneling microscopy, scanning tunneling spectroscopy, and density functional theory calculations. Attachment of the Os complex to the SAM proceeds via an amide covalent bond with the SAM alkyl chain 40° tilted with respect to the surface normal and a total thickness of 26 Å. The highest occupied molecular orbital of the Os complex is mainly based on the Os(II) center located 2.2 eV below the Fermi edge and the LUMO molecular orbital is mainly based on the bipyridine ligands located 1.5 eV above the Fermi edge.

  11. A Decentralized Approach to the Formulation of Hypotheses: A Hierarchical Structural Model for a Prion Self-Assembled System

    PubMed Central

    Wang, Mingyang; Zhang, Feifei; Song, Chao; Shi, Pengfei; Zhu, Jin

    2016-01-01

    Innovation in hypotheses is a key transformative driver for scientific development. The conventional centralized hypothesis formulation approach, where a dominant hypothesis is typically derived from a primary phenomenon, can, inevitably, impose restriction on the range of conceivable experiments and legitimate hypotheses, and ultimately impede understanding of the system of interest. We report herein the proposal of a decentralized approach for the formulation of hypotheses, through initial preconception-free phenomenon accumulation and subsequent reticular logical reasoning processes. The two-step approach can provide an unbiased, panoramic view of the system and as such should enable the generation of a set of more coherent and therefore plausible hypotheses. As a proof-of-concept demonstration of the utility of this open-ended approach, a hierarchical model has been developed for a prion self-assembled system, allowing insight into hitherto elusive static and dynamic features associated with this intriguing structure. PMID:27464832

  12. Molecular and electronic structure of osmium complexes confined to Au(111) surfaces using a self-assembled molecular bridge

    SciTech Connect

    Llave, Ezequiel de la; Herrera, Santiago E.; Adam, Catherine; Méndez De Leo, Lucila P.; Calvo, Ernesto J.; Williams, Federico J.

    2015-11-14

    The molecular and electronic structure of Os(II) complexes covalently bonded to self-assembled monolayers (SAMs) on Au(111) surfaces was studied by means of polarization modulation infrared reflection absorption spectroscopy, photoelectron spectroscopies, scanning tunneling microscopy, scanning tunneling spectroscopy, and density functional theory calculations. Attachment of the Os complex to the SAM proceeds via an amide covalent bond with the SAM alkyl chain 40° tilted with respect to the surface normal and a total thickness of 26 Å. The highest occupied molecular orbital of the Os complex is mainly based on the Os(II) center located 2.2 eV below the Fermi edge and the LUMO molecular orbital is mainly based on the bipyridine ligands located 1.5 eV above the Fermi edge.

  13. Adsorption and self-assembled structures of sexithiophene on the Si(111)-√(3)×√(3)-Ag surface

    SciTech Connect

    Yokoyama, Takashi Kawasaki, Mitsunori; Asari, Tomotaka; Ohno, Shinya; Tanaka, Masatoshi; Yoshimoto, Yoshihide

    2015-05-28

    The adsorption and self-assembled structures of α-sexithiophene (α-6T) have been investigated on a Si(111)-Ag surface using scanning tunneling microscopy (STM), low-energy electron diffraction, and density functional theory calculations. The adsorbed α-6T molecules are arranged into unidirectional molecular rows with a side-by-side orientation. The molecular rows reveal three kinds of appearances in the filled-state STM images, which reflect the distinct adsorption sites. From tunneling spectroscopy, we find that the filled-state STM images of α-6T should be influenced by the surface states of Si(111)-Ag. At one monolayer coverage, sequentially ordering of the triple molecular rows results in the close-packed arrangement of the α-6T overlayer.

  14. Improvements in the characterization of the crystalline structure of acid-terminated alkanethiol self-assembled monolayers on Au(111).

    PubMed

    Mendoza, Sandra M; Arfaoui, Imad; Zanarini, Simone; Paolucci, Francesco; Rudolf, Petra

    2007-01-16

    We report a study of acid-terminated self-assembled monolayers of alkanethiols of different length, 11-mercaptoundecanoic acid (11-MUA) and 16-mercaptohexadecanoic acid (16-MHDA), on Au(111). Scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and contact angle techniques were used for characterization, and the results were compared with those obtained from n-alkanethiols of similar chain length, providing a detailed description of the two-dimensional crystalline structure. Molecular resolution STM images show that 11-MUA forms a dense-packed monolayer arranged in a (square root 3 x square root 3)R30 degrees structure with a c(2 x 4) superlattice, where the simple hexagonal phase, the c(2 x 4) superlattice, and nonordered areas coexist. 16-MHDA assembles in a uniform monolayer with similar morphology to that of 11-MUA, but molecular resolution could not be reached in STM due to both the hydrophilicity of the acid groups and the poor conductivity of the thick monolayer. Nevertheless, the monolayer thicknesses estimated by XPS and electrochemistry and the highly blocking character of the film observed by electrochemistry as well as the low water contact angle are consistent with 16-MHDA molecules forming a compact monolayer on the Au(111) substrate with fully extended alkyl chains and acid groups pointing away from the surface. The results obtained for 16-MHDA were reproducible under different preparation conditions such as the addition or omission of acetic acid to the ethanolic solution. Contrary to other reports, we demonstrate that ordered acid-terminated self-assembled monolayers are obtained with the same preparation conditions as those of the methyl-terminated ones, without any additional treatment.

  15. Development of self-assembled molecular structures on polymeric surfaces and their applications as ultrasonically responsive barrier coatings for on-demand, pulsatile drug delivery

    NASA Astrophysics Data System (ADS)

    Kwok, Connie Sau-Kuen

    Nature in the form of DNA, proteins, and cells has the remarkable ability to interact with its environment by processing biological information through specific molecular recognition at the interface. As such, materials that are capable of triggering an appropriate biological response need to be engineered at the biomaterial surface. Chemically and structurally well-defined self-assembled monolayers (SAMs), biomimetics of the lipid bilayer in cell membranes, have been created and studied mostly on rigid metallic surfaces. This dissertation is motivated by the lack of methods to generate a molecularly designed surface for biomedical polymers and thus provides an enabling technology to engineer a polymeric surface precisely at a molecular and cellular level. To take this innovation one step further, we demonstrated that such self-assembled molecular structure coated on drug-containing polymeric devices could act as a stimulus-responsive barrier for controlled drug delivery. A simple, one-step procedure for generating ordered, crystalline methylene chains on polymeric surfaces via urethane linkages was successfully developed. The self-assemblies and molecular structures of these crystalline methylene chains are comparable to the SAM model surfaces, as evidenced by various surface characterization techniques (XPS, TOF-SIMS, and FTIR-ATR). For the first time, these self-assembled molecular structures are shown to function collectively as an ultrasound-responsive barrier membrane for pulsatile drug delivery, including delivery of low-molecular-weight ciprofloxacin and high-molecular-weight insulin. Encouraging results, based on the insulin-activated deoxyglucose uptakes in adipocytes, indicate that the released insulin remained biologically active. Both chemical and acoustic analyses suggest that the ultrasound-assisted release mechanism is primarily induced by transient cavitation, which causes temporary disruption of the self-assembled overlayer, and thus allows

  16. Synthesis, Characterization, and Secondary Structure Determination of a Silk-Inspired, Self-Assembling Peptide: A Laboratory Exercise for Organic and Biochemistry Courses

    ERIC Educational Resources Information Center

    Albin, Tyler J.; Fry, Melany M.; Murphy, Amanda R.

    2014-01-01

    This laboratory experiment gives upper-division organic or biochemistry undergraduate students a comprehensive look at the synthesis, chemical characterization, self-assembly, and secondary structure determination of small, N-acylated peptides inspired by the protein structure of silkworm silk. All experiments can be completed in one 4 h lab…

  17. Synthesis, Characterization, and Secondary Structure Determination of a Silk-Inspired, Self-Assembling Peptide: A Laboratory Exercise for Organic and Biochemistry Courses

    ERIC Educational Resources Information Center

    Albin, Tyler J.; Fry, Melany M.; Murphy, Amanda R.

    2014-01-01

    This laboratory experiment gives upper-division organic or biochemistry undergraduate students a comprehensive look at the synthesis, chemical characterization, self-assembly, and secondary structure determination of small, N-acylated peptides inspired by the protein structure of silkworm silk. All experiments can be completed in one 4 h lab…

  18. Self-Assemblies of novel molecules, VECAR

    NASA Astrophysics Data System (ADS)

    Shrestha, Bijay; Kim, Hye-Young; Lee, Soojin; Novak, Brian; Moldovan, Dorel

    2015-03-01

    VECAR is a newly synthesized molecule, which is an amphiphilic antioxidant molecule that consists of two molecular groups, vitamin-E and Carnosine, linked by a hydrocarbon chain. The hydrocarbon chain is hydrophobic and both vitamin-E and Carnosine ends are hydrophilic. In the synthesis process, the length of the hydrophobic chain of VECAR molecules can vary from the shortest (n =0) to the longest (n =18), where n indicates the number of carbon atoms in the chain. We conducted MD simulation studies of self-assembly of VECAR molecules in water using GROMACS on LONI HPC resources. Our study shows that there is a strong correlation between the shape and atomistic structure of the self-assembled nano-structures (SANs) and the chain-length (n) of VECAR molecules. We will report the results of data analyses including the atomistic structure of each SANs and the dynamic and energetic mechanisms of their formation as function of time. In summary, both VECAR molecules of chain-length n =18 and 9 form worm-like micelles, which may be used as a drug delivery system. This research is supported by the Louisiana Board of Regents-RCS Grant (LEQSF(2012-15)-RD-A-19).

  19. Preparation and Cross-Linking of All-Acrylamide Diblock Copolymer Nano-Objects via Polymerization-Induced Self-Assembly in Aqueous Solution

    PubMed Central

    2017-01-01

    Various carboxylic acid-functionalized poly(N,N-dimethylacrylamide) (PDMAC) macromolecular chain transfer agents (macro-CTAs) were chain-extended with diacetone acrylamide (DAAM) by reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization at 70 °C and 20% w/w solids to produce a series of PDMAC–PDAAM diblock copolymer nano-objects via polymerization-induced self-assembly (PISA). TEM studies indicate that a PDMAC macro-CTA with a mean degree of polymerization (DP) of 68 or higher results in the formation of well-defined spherical nanoparticles with mean diameters ranging from 40 to 150 nm. In contrast, either highly anisotropic worms or polydisperse vesicles are formed when relatively short macro-CTAs (DP = 40–58) are used. A phase diagram was constructed to enable accurate targeting of pure copolymer morphologies. Dynamic light scattering (DLS) and aqueous electrophoresis studies indicated that in most cases these PDMAC–PDAAM nano-objects are surprisingly resistant to changes in either solution pH or temperature. However, PDMAC40–PDAAM99 worms do undergo partial dissociation to form a mixture of relatively short worms and spheres on adjusting the solution pH from pH 2–3 to around pH 9 at 20 °C. Moreover, a change in copolymer morphology from worms to a mixture of short worms and vesicles was observed by DLS and TEM on heating this worm dispersion to 50 °C. Postpolymerization cross-linking of concentrated aqueous dispersions of PDMAC–PDAAM spheres, worms, or vesicles was performed at ambient temperature using adipic acid dihydrazide (ADH), which reacts with the hydrophobic ketone-functionalized PDAAM chains. The formation of hydrazone groups was monitored by FT-IR spectroscopy and afforded covalently stabilized nano-objects that remained intact on exposure to methanol, which is a good solvent for both blocks. Rheological studies indicated that the cross-linked worms formed a stronger gel compared to linear precursor

  20. Sequential programmable self-assembly: Role of cooperative interactions

    SciTech Connect

    Jonathan D. Halverson; Tkachenko, Alexei V.

    2016-03-04

    Here, we propose a general strategy of “sequential programmable self-assembly” that enables a bottom-up design of arbitrary multi-particle architectures on nano- and microscales. We show that a naive realization of this scheme, based on the pairwise additive interactions between particles, has fundamental limitations that lead to a relatively high error rate. This can be overcome by using cooperative interparticle binding. The cooperativity is a well known feature of many biochemical processes, responsible, e.g., for signaling and regulations in living systems. Here we propose to utilize a similar strategy for high precision self-assembly, and show that DNA-mediated interactions provide a convenient platform for its implementation. In particular, we outline a specific design of a DNA-based complex which we call “DNA spider,” that acts as a smart interparticle linker and provides a built-in cooperativity of binding. We demonstrate versatility of the sequential self-assembly based on spider-functionalized particles by designing several mesostructures of increasing complexity and simulating their assembly process. This includes a number of finite and repeating structures, in particular, the so-called tetrahelix and its several derivatives. Due to its generality, this approach allows one to design and successfully self-assemble virtually any structure made of a “GEOMAG” magnetic construction toy, out of nanoparticles. According to our results, once the binding cooperativity is strong enough, the sequential self-assembly becomes essentially error-free.

  1. Supramolecular self-assembled polynuclear complexes from tritopic, tetratopic, and pentatopic ligands: structural, magnetic and surface studies.

    PubMed

    Dey, Subrata K; Abedin, Tareque S M; Dawe, Louise N; Tandon, Santokh S; Collins, Julie L; Thompson, Laurence K; Postnikov, Andrei V; Alam, Mohammad S; Müller, Paul

    2007-09-17

    Polymetallic, highly organized molecular architectures can be created by "bottom-up" self-assembly methods using ligands with appropriately programmed coordination information. Ligands based on 2,6-picolyldihydrazone (tritopic and pentatopic) and 3,6-pyridazinedihydrazone (tetratopic) cores, with tridentate coordination pockets, are highly specific and lead to the efficient self-assembly of square [3 x 3] Mn9, [4 x 4] Mn16, and [5 x 5] Mn25 nanoscale grids. Subtle changes in the tritopic ligand composition to include bulky end groups can lead to a rectangular 3 x [1 x 3] Mn9 grid, while changing the central pyridazine to a more sterically demanding pyrazole leads to simple dinuclear copper complexes, despite the potential for binding four metal ions. The creation of all bidentate sites in a tetratopic pyridazine ligand leads to a dramatically different spiral Mn4 strand. Single-crystal X-ray structural data show metallic connectivity through both mu-O and mu-NN bridges, which leads to dominant intramolecular antiferromagnetic spin exchange in all cases. Surface depositions of the Mn9, Mn16, and Mn25 square grid molecules on graphite (HOPG) have been examined using STM/CITS imagery (scanning tunneling microscopy/current imaging tunneling spectroscopy), where tunneling through the metal d-orbital-based HOMO levels reveals the metal ion positions. CITS imagery of the grids clearly shows the presence of 9, 16, and 25 manganese ions in the expected square grid arrangements, highlighting the importance and power of this technique in establishing the molecular nature of the surface adsorbed species. Nanoscale, electronically functional, polymetallic assemblies of this sort, created by such a bottom-up synthetic approach, constitute important components for advanced molecule-based materials.

  2. Self-Assembly: How Nature Builds

    ERIC Educational Resources Information Center

    Jones, M. Gail; Falvo, Michael R.; Broadwell, Bethany; Dotger, Sharon

    2006-01-01

    Self-assembly or spontaneous assembly is a process in which materials build themselves without assistance. This process plays a central role in the construction of biological structures and materials such as cells, viruses, and bone, and also in abiotic processes like phase transitions and crystal formation. The principles of self-assembly help…

  3. Self-Assembly: How Nature Builds

    ERIC Educational Resources Information Center

    Jones, M. Gail; Falvo, Michael R.; Broadwell, Bethany; Dotger, Sharon

    2006-01-01

    Self-assembly or spontaneous assembly is a process in which materials build themselves without assistance. This process plays a central role in the construction of biological structures and materials such as cells, viruses, and bone, and also in abiotic processes like phase transitions and crystal formation. The principles of self-assembly help…

  4. Self-assembly of hyperbranched polymers and its biomedical applications.

    PubMed

    Zhou, Yongfeng; Huang, Wei; Liu, Jinyao; Zhu, Xinyuan; Yan, Deyue

    2010-11-02

    Hyperbranched polymers (HBPs) are highly branched macromolecules with a three-dimensional dendritic architecture. Due to their unique topological structure and interesting physical/chemical properties, HBPs have attracted wide attention from both academia and industry. In this paper, the recent developments in HBP self-assembly and their biomedical applications have been comprehensively reviewed. Many delicate supramolecular structures from zero-dimension (0D) to three-dimension (3D), such as micelles, fibers, tubes, vesicles, membranes, large compound vesicles and physical gels, have been prepared through the solution or interfacial self-assembly of amphiphilic HBPs. In addition, these supramolecular structures have shown promising applications in the biomedical areas including drug delivery, protein purification/detection/delivery, gene transfection, antibacterial/antifouling materials and cytomimetic chemistry. Such developments promote the interdiscipline researches among surpramolecular chemistry, biomedical chemistry, nano-technology and functional materials.

  5. Structure determination of a bio-inspired self-assembled light-harvesting antenna by solid-state NMR and molecular modeling.

    PubMed

    Pandit, Anjali; Ocakoglu, Kasim; Buda, Francesco; van Marle, Thomas; Holzwarth, Alfred R; de Groot, Huub J M

    2013-09-26

    The molecular stacking of an artificial light-harvesting antenna self-assembled from 3(1)-aminofunctionalized zinc-chlorins was determined by solid-state NMR in combination with quantum-chemical and molecular-mechanics modeling. A library of trial molecular stacking arrangements was generated based on available structural data for natural and semisynthetic homologues of the Zn-chlorins. NMR assignments obtained for the monomer in solution were validated for self-assembled aggregates and refined with (1)H-(13)C heteronuclear correlation spectroscopy data collected from samples with (13)C at natural abundance. Solid-state ring-current shifts for the (1)H provided spatial constraints to determine the molecular overlap. This procedure allows for a discrimination between different self-assembled structures and a classification of the stacking mode in terms of electric dipole alignment and π-π interactions, parameters that determine the functional properties of light-harvesting assemblies and conducting nanowires. The combination with quantum-mechanical modeling then allowed building a low-resolution packing model in silico from molecular stacks. The method allows for moderate disorder and residual polymorphism at the stack or molecular level and is generally applicable to determine molecular packing structures of aromatic molecules with structural asymmetry, such as is commonly provided by functionalized side chains that serve to tune the self-assembly process.

  6. Selection of conformational states in self-assembled surface structures formed from an oligo(naphthylene-ethynylene) 3-bit binary switch

    NASA Astrophysics Data System (ADS)

    Ning, Y.; Cramer, J. R.; Nuermaimaiti, A.; Svane, K.; Yu, M.; Lægsgaard, E.; Besenbacher, F.; Xue, Q.-K.; Ma, X.; Hammer, B.; Gothelf, K. V.; Linderoth, T. R.

    2015-03-01

    Supra-molecular self-assembly on surfaces often involves molecular conformational flexibility which may act to enrich the variation and complexity of the structures formed. However, systematic and explicit investigations of how molecular conformational states are selected in surface self-assembly processes are relatively scarce. Here, we use a combination of high-resolution scanning tunneling microscopy and Density Functional Theory (DFT) calculations to investigate self-assembly for a custom-designed molecule capable of assuming eight distinct surface conformations (four enantiomeric pairs). The conformations result from binary positions of n = 3 naphtalene units on a linear oligo(naphthylene-ethynylene) backbone. On Au(111), inter-molecular interactions involving carboxyl and bulky tert-butyl-phenyl functional groups induce the molecules to form two ordered phases with brick-wall and lamella structure, respectively. These structures each involve molecules in two conformational states, and there is a clear separation between the conformers involved in the two types of structures. On Cu(111), individual molecules isolated by carboxylate-substrate binding show a distribution involving all possible conformational states. Together these observations imply selection and adaptation of conformational states upon molecular self-assembly. From DFT modeling and statistical analysis of the molecular conformations, the observed selection of conformational states is attributed to steric interaction between the naphthalene units. The present study enhances our understanding of how ordering and selection of molecular conformations is controlled by intermolecular interactions in a complex situation with many distinct conformational states for the participating molecules.

  7. Self-assembled 3D ZnO porous structures with exposed reactive {0001} facets and their enhanced gas sensitivity.

    PubMed

    Chang, Jin; Ahmad, Muhammad Z; Wlodarski, Wojtek; Waclawik, Eric R

    2013-07-02

    Complex three-dimensional structures comprised of porous ZnO plates were synthesized in a controlled fashion by hydrothermal methods. Through subtle changes to reaction conditions, the ZnO structures could be self-assembled from 20 nm thick nanosheets into grass-like and flower-like structures which led to the exposure of high proportions of ZnO {0001} crystal facets for both these materials. The measured surface area of the flower-like and the grass, or platelet-like ZnO samples were 72.8 and 52.4 m2∙g-1, respectively. Gas sensing results demonstrated that the porous, flower-like ZnO structures exhibited enhanced sensing performance towards NO2 gas compared with either grass-like ZnO or commercially sourced ZnO nanoparticle samples. The porous, flower-like ZnO structures provided a high surface area which enhanced the ZnO gas sensor response. X-ray photoelectron spectroscopy characterization revealed that flower-like ZnO samples possessed a higher percentage of oxygen vacancies than the other ZnO sample-types, which also contributed to their excellent gas sensing performance.

  8. Self-assembly of polydimethylsiloxane structures from 2D to 3D for bio-hybrid actuation.

    PubMed

    Vannozzi, L; Ricotti, L; Cianchetti, M; Bearzi, C; Gargioli, C; Rizzi, R; Dario, P; Menciassi, A

    2015-08-20

    This work aims to demonstrate the feasibility of a novel approach for the development of 3D self-assembled polydimethylsiloxane structures, to be used as engineered flexible matrices for bio-hybrid actuation. We described the fabrication of engineered bilayers, organized in a 3D architecture by means of a stress-induced rolling membrane technique. Such structures were provided with ad hoc surface topographies, for both cell alignment and cell survival after membrane rolling. We reported the results of advanced finite element model simulations, predicting the system behavior in terms of overall contraction, induced by the contractile activity of muscle cells seeded on the membrane. Then, we tested in vitro the structure with primary cardiomyocytes to evaluate the real bio-actuator contraction, thus validating the simulation results. At a later stage, we provided the samples with a stable fibronectin coating, by covalently binding the protein on the polymer surface, thus enabling long-term cultures with C2C12 skeletal muscle cells, a more controllable cell type. These tests revealed cell viability and alignment on the rolled structures, but also the ability of cells to differentiate and to form multinucleated and oriented myotubes on the polymer surface, also supported by a fibroblast feeder layer. Our results highlighted the possibility of developing 3D rolled PDMS structures, characterized by different mechanical properties, as novel bio-hybrid actuators.

  9. Self-Assembled 3D ZnO Porous Structures with Exposed Reactive {0001} Facets and Their Enhanced Gas Sensitivity

    PubMed Central

    Chang, Jin; Ahmad, Muhammad Z.; Wlodarski, Wojtek; Waclawik, Eric R.

    2013-01-01

    Complex three-dimensional structures comprised of porous ZnO plates were synthesized in a controlled fashion by hydrothermal methods. Through subtle changes to reaction conditions, the ZnO structures could be self-assembled from 20 nm thick nanosheets into grass-like and flower-like structures which led to the exposure of high proportions of ZnO {0001} crystal facets for both these materials. The measured surface area of the flower-like and the grass, or platelet-like ZnO samples were 72.8 and 52.4 m2·g−1, respectively. Gas sensing results demonstrated that the porous, flower-like ZnO structures exhibited enhanced sensing performance towards NO2 gas compared with either grass-like ZnO or commercially sourced ZnO nanoparticle samples. The porous, flower-like ZnO structures provided a high surface area which enhanced the ZnO gas sensor response. X-ray photoelectron spectroscopy characterization revealed that flower-like ZnO samples possessed a higher percentage of oxygen vacancies than the other ZnO sample-types, which also contributed to their excellent gas sensing performance. PMID:23820747

  10. Colloidal gold nanoparticle formation derived from self-assembled supramolecular structure of cyclodextrin/Au salt complex.

    PubMed

    Chung, Jae Woo; Guo, Yunlong; Priestley, Rodney D; Kwak, Seung-Yeop

    2011-04-01

    We present a novel procedure for the formation of colloidal gold nanoparticles (AuNPs) derived from the supramolecular self-assembled structure of a cyclodextrin (CD)/Au salt complex (SCA) without the necessity for additional reducing or stabilizing agents. The SCA served as a solid template for the formation of gold seeds by solid-state thermal treatment within the confining environment of the α-CD, i.e., the matrix of the SCA. Subsequently, thermally treated SCA, denoted as T-SCA, was placed (without further treatment) into an aqueous medium and gold seeds were nucleated for the formation of α-CD-stabilized AuNPs at room temperature. The surface topology of SCA, as revealed by field-emission scanning electron microscopy (FE-SEM), consisted of flaky plate-like structures. Wide angle X-ray diffraction (WXRD) revealed that the surface topology of SCA resulted from a transformation in the crystalline structure of α-CD from the cage-type to the hexagonally ordered channel-type. The structure transformation on the surface of SCA was attributed to the nucleated self-assembly of surface α-CD molecules by Au salt. From combined FE-SEM, energy-dispersed X-ray spectroscopy (EDXS), WXRD and differential scanning calorimetry (DSC) results, it was concluded that the thermal treatment of SCA led to the formation of gold seeds, attributed to the reduction and aggregation of some Au salt molecules, confined within the interface between the cage-type and channel type structure of the SCA. After placement of T-SCA into an aqueous solution, the growth and stabilization of AuNPs by α-CD were verified by UV-vis spectroscopy. The formation of AuNPs, by this novel method, can be considered a one step seed-mediated growth process. The resulting AuNPs are spherical in morphology, narrowly size distributed and possesses excellent stability. Furthermore, the AuNPs size is tunable by simply controlling water content during nanoparticle growth.

  11. Superhydrophobic Behavior on Nano-structured Surfaces

    NASA Astrophysics Data System (ADS)

    Schaeffer, Daniel

    2008-05-01

    Superhydrophobic behavior is observed in natural occurrences and has been thoroughly studied over the past few years. Water repellant properties on uniform arrays of vertically aligned nano-cones were investigated to determine the highest achievable contact angle (a measure of water drop repellency), which is measured from the reference plane on which the water drop sits to the tangent line of the point at which the drop makes contact with the reference plane. At low aspect ratios (height vs. width of the nano-cones), surface tension pulls the water into the nano-cone array, resulting in a wetted surface. Higher aspect ratios reverse the effect of the surface tension, resulting in a larger contact angle that causes water drops to roll off the surface. Fiber drawing, bundling, and redrawing are used to produce the structured array glass composite surface. Triple-drawn fibers are fused together, annealed, and sliced into thin wafers. The surface of the composite glass is etched to form nano-cones through a differential etching process and then coated with a fluorinated self-assembled monolayer (SAM). Cone aspect ratios can be varied through changes in the chemistry and concentration of the etching acid solution. Superhydrophobic behavior occurs at contact angles >150 and it is predicted and measured that optimal behavior is achieved when the aspect ratio is 4:1, which displays contact angles >=175 .

  12. Invited paper: Sintering mechanism of vapor self-assembled multilayer (VSAM) coated Cu nano particles for application in Cu nano ink

    NASA Astrophysics Data System (ADS)

    Haque, Md. Mominul; Park, Shinyoung; Her, Jaehak; Park, Joong-Hak; Lee, Caroline Sunyong

    2011-09-01

    Oxidation preventive Cu nano ink was prepared using a vapor self-assembed multi-layer coating method (VSAMs). These particles were prepared using 100 nm Cu nano particles coated with 1-octanethiol under ultrahigh vacuum condition with octanol used as a solvent. Octanol-based non-oxidized 10% (wt.) nano ink was well-dispersed without any surfactant. The conductive ink had good dispersion and remains stable for more than 6 weeks. It also has a low viscosity rating of 8.3 cPs. In addition, 5 μL of copper nano ink was dropped into a 1 cm × 1 cm glass substrate to form a copper pattern. The copper pattern was then sintered at 350°C in a tube furnace in a H2 gas atmosphere. The resistivity of the film using the fabricated ink was determined to be 5.8 × 10-6 Ωcm. The results show that the non-oxidized oxidation-preventive copper nano ink is suitable for ink-jet printing.

  13. A NiMoS flower-like structure with self-assembled nanosheets as high-performance hydrodesulfurization catalysts

    NASA Astrophysics Data System (ADS)

    Lai, Weikun; Chen, Zhou; Zhu, Jianping; Yang, Lefu; Zheng, Jinbao; Yi, Xiaodong; Fang, Weiping

    2016-02-01

    Uniform 3D NiMoS nanoflowers with self-assembled nanosheets were successfully synthesized via a simple hydrothermal growth method using cheap and nontoxic elemental sulfur as sulfur sources. The structure and morphology of the nanomaterials were characterized by SEM, TEM, XRD, Raman and XPS analyses, revealing that the NiMoS nanoflowers were composed of ultrathin nanosheets with a thickness of approximately 6-12 nm. The HRTEM results indicate that the curve/short MoS2 slabs on the nanosheets possess the characteristics of dislocations, distortions and discontinuity, which suggests a defect-rich structure, resulting in the exposure of additional Ni-Mo-S edge sites. The obtained NiMoS nanoflowers exhibited an excellent activity for thiophene hydrodesulfurization (HDS) and 4,6-dimethyldibenzothiophene deep HDS due to their high density of active sites. The outstanding HDS performance suggests that these NiMoS composites with a unique flower-like nanostructure could be useful as promising catalysts for deep desulfurization of fuel oils.Uniform 3D NiMoS nanoflowers with self-assembled nanosheets were successfully synthesized via a simple hydrothermal growth method using cheap and nontoxic elemental sulfur as sulfur sources. The structure and morphology of the nanomaterials were characterized by SEM, TEM, XRD, Raman and XPS analyses, revealing that the NiMoS nanoflowers were composed of ultrathin nanosheets with a thickness of approximately 6-12 nm. The HRTEM results indicate that the curve/short MoS2 slabs on the nanosheets possess the characteristics of dislocations, distortions and discontinuity, which suggests a defect-rich structure, resulting in the exposure of additional Ni-Mo-S edge sites. The obtained NiMoS nanoflowers exhibited an excellent activity for thiophene hydrodesulfurization (HDS) and 4,6-dimethyldibenzothiophene deep HDS due to their high density of active sites. The outstanding HDS performance suggests that these NiMoS composites with a unique flower

  14. Self-assembled nanomaterials for photoacoustic imaging

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Yang, Pei-Pei; Zhao, Xiao-Xiao; Wang, Hao

    2016-01-01

    In recent years, extensive endeavors have been paid to construct functional self-assembled nanomaterials for various applications such as catalysis, separation, energy and biomedicines. To date, different strategies have been developed for preparing nanomaterials with diversified structures and functionalities via fine tuning of self-assembled building blocks. In terms of biomedical applications, bioimaging technologies are urgently calling for high-efficient probes/contrast agents for high-performance bioimaging. Photoacoustic (PA) imaging is an emerging whole-body imaging modality offering high spatial resolution, deep penetration and high contrast in vivo. The self-assembled nanomaterials show high stability in vivo, specific tolerance to sterilization and prolonged half-life stability and desirable targeting properties, which is a kind of promising PA contrast agents for biomedical imaging. Herein, we focus on summarizing recent advances in smart self-assembled nanomaterials with NIR absorption as PA contrast agents for biomedical imaging. According to the preparation strategy of the contrast agents, the self-assembled nanomaterials are categorized into two groups, i.e., the ex situ and in situ self-assembled nanomaterials. The driving forces, assembly modes and regulation of PA properties of self-assembled nanomaterials and their applications for long-term imaging, enzyme activity detection and aggregation-induced retention (AIR) effect for diagnosis and therapy are emphasized. Finally, we conclude with an outlook towards future developments of self-assembled nanomaterials for PA imaging.

  15. Self-assembled nanomaterials for photoacoustic imaging.

    PubMed

    Wang, Lei; Yang, Pei-Pei; Zhao, Xiao-Xiao; Wang, Hao

    2016-02-07

    In recent years, extensive endeavors have been paid to construct functional self-assembled nanomaterials for various applications such as catalysis, separation, energy and biomedicines. To date, different strategies have been developed for preparing nanomaterials with diversified structures and functionalities via fine tuning of self-assembled building blocks. In terms of biomedical applications, bioimaging technologies are urgently calling for high-efficient probes/contrast agents for high-performance bioimaging. Photoacoustic (PA) imaging is an emerging whole-body imaging modality offering high spatial resolution, deep penetration and high contrast in vivo. The self-assembled nanomaterials show high stability in vivo, specific tolerance to sterilization and prolonged half-life stability and desirable targeting properties, which is a kind of promising PA contrast agents for biomedical imaging. Herein, we focus on summarizing recent advances in smart self-assembled nanomaterials with NIR absorption as PA contrast agents for biomedical imaging. According to the preparation strategy of the contrast agents, the self-assembled nanomaterials are categorized into two groups, i.e., the ex situ and in situ self-assembled nanomaterials. The driving forces, assembly modes and regulation of PA properties of self-assembled nanomaterials and their applications for long-term imaging, enzyme activity detection and aggregation-induced retention (AIR) effect for diagnosis and therapy are emphasized. Finally, we conclude with an outlook towards future developments of self-assembled nanomaterials for PA imaging.

  16. Self-assembled potential bio nanocarriers for drug delivery.

    PubMed

    Akter, Nasima; Radiman, Shahidan; Mohamed, Faizal; Reza, Mohammad Imam Hasan

    2013-07-01

    Self-assembled nanocarriers attract increasing attention due to their wide application in various practical fields; among them, one of the most focused fields is drug delivery. Appropriate selection of surfactant is the basis for preparing a successful nanocarrier. Until now, from phospholipid to synthetic surfactants, many surfactants have been used to explore a suitable drug delivery vehicle for the complex in-vivo environment. Among all, bio surfactants are found to be more suitable due to their bio-origin, less-toxicity, biodegradability, cheaper rate and above all, their versatile molecular structures. This molecular property enables them to self assemble into fascinating structures. Moreover, binding DNA, enhancing pH sensitivity and stability allows novelty over their synthetic counterparts and phospholipid. This review paper focuses on the properties and applications of bio-nano-carriers for drug delivery. Micelle, microemulsion, and vesicle are the three nanocarriers which are discussed herein.

  17. Self-assembled photonic crystals for a chemical sensing

    NASA Astrophysics Data System (ADS)

    Bourdillon, C.; Gam Derouich, S.; Daney de Marcillac, W.; Coolen, L.; Maître, A.; Mangeney, C.; Schwob, C.

    2016-03-01

    As they allow the control of light propagation, photonic crystals find many fields of application. Among them, self-assembled 3D-photonic crystals are ordered at the nanometric scale over centrimetric areas. Furthermore, self-assembly allows the design of complexes structures leading, for example, to the controlled disruption of the crystal periodicity (called defect) and the appearance of permitted optical frequency bands within the photonic bandgap. Light frequencies included in the corresponding passband are then localized in the defect allowing manipulation of nano-emitters fluorescence. We present the fabrication and the optical characterization of a heterostructure composed of a sputtered silica layer sandwiched between two silica opals. We show by photoluminescence measurements than this structure strongly modifies the transmitted fluorescence of nanocrystals.

  18. Ionic Liquid Surfactant Mediated Structural Transitions and Self-Assembly of Bovine Serum Albumin in Aqueous Media: Effect of Functionalization of Ionic Liquid Surfactants.

    PubMed

    Singh, Gurbir; Kang, Tejwant Singh

    2015-08-20

    The self-assembly of globular protein bovine serum albumin (BSA) has been investigated in aqueous solutions of ionic liquid surfactants (ILSs), 1-dodecyl-3-methyl imidazolium chloride, [C12mim][Cl], and its amide, [C12Amim][Cl], and ester, [C12Emim][Cl], functionalized counterparts. Dynamic light scattering (DLS) has provided insights into the alterations in hydrodynamic radii (D(h)) of BSA as a function of concentration of ILSs establishing the presence of different types of BSA-ILS complexes in different concentration regimes of ILSs. Isothermal titration calorimetry (ITC) has been exploited to quantify the ILSs interacting with BSA in dilute concentration regime of ILSs. The zeta-potential measurements shed light on changes in the charged state of BSA. The morphology of various self-assembled structures of BSA in different concentration regimes of ILSs have been explored using confocal laser scanning microscopy (CLSM) and scanning electron microscopy. The structural variations in ILSs have been found to produce remarkable effect on the nature and morphology of self-assembled structures of BSA. The presence of nonfunctionalized [C12mim][Cl] IL at all investigated concentrations has led to the formation of unordered large self-assembled structures of BSA. On the other hand, in specific concentration regimes, ordered self-assembled structures such as long rods and right-handedly twisted helical amyloid fibers have been observed in the presence of functionalized [C12Amim][Cl] and [C12Emim][Cl] ILSs, respectively. The nature of the formed helical fibers as amyloid ones has been confirmed using FTIR spectroscopy. Steady-state fluorescence and circular dichroism (CD) spectroscopy have provided insights into folding and unfolding of BSA as fashioned by interactions with ILSs in different concentration regimes supporting the observations made from other studies.

  19. 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

  20. Biomolecule-assisted hydrothermal synthesis and self-assembly of Bi2Te3 nanostring-cluster hierarchical structure.

    PubMed

    Mi, Jian-Li; Lock, Nina; Sun, Ting; Christensen, Mogens; Søndergaard, Martin; Hald, Peter; Hng, Huey H; Ma, Jan; Iversen, Bo B

    2010-05-25

    A simple biomolecule-assisted hydrothermal approach has been developed for the fabrication of Bi(2)Te(3) thermoelectric nanomaterials. The product has a nanostring-cluster hierarchical structure which is composed of ordered and aligned platelet-like crystals. The platelets are approximately 100 nm in diameter and only approximately 10 nm thick even though a high reaction temperature of 220 degrees C and a long reaction time of 24 h were applied to prepare the sample. The growth of the Bi(2)Te(3) hierarchical structure appears to be a self-assembly process. Initially, Te nanorods are formed using alginic acid as both reductant and template. Subsequently, Bi(2)Te(3) grows in a certain direction on the surface of the Te rods, resulting in the nanostring structure. The nanostrings further recombine side-by-side with each other to achieve the ordered nanostring clusters. The particle size and morphology can be controlled by adjusting the concentration of NaOH, which plays a crucial role on the formation mechanism of Bi(2)Te(3). An even smaller polycrystalline Bi(2)Te(3) superstructure composed of polycrystalline nanorods with some nanoplatelets attached to the nanorods is achieved at lower NaOH concentration. The room temperature thermoelectric properties have been evaluated with an average Seebeck coefficient of -172 microV K(-1), an electrical resistivity of 1.97 x 10(-3) Omegam, and a thermal conductivity of 0.29 W m(-1) K(-1).

  1. Hydrogen bonding strength of diblock copolymers affects the self-assembled structures with octa-functionalized phenol POSS nanoparticles.

    PubMed

    Lu, Yi-Syuan; Yu, Chia-Yu; Lin, Yung-Chih; Kuo, Shiao-Wei

    2016-02-28

    In this study, the influence of the functional groups by the diblock copolymers of poly(styrene-b-4-vinylpyridine) (PS-b-P4VP), poly(styrene-b-2-vinylpyridine) (PS-b-P2VP), and poly(styrene-b-methyl methacrylate) (PS-b-PMMA) on their blends with octa-functionalized phenol polyhedral oligomeric silsesquioxane (OP-POSS) nanoparticles (NPs) was investigated. The relative hydrogen bonding strengths in these blends follow the order PS-b-P4VP/OP-POSS > PS-b-P2VP/OP-POSS > PS-b-PMMA/OP-POSS based on the Kwei equation from differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopic analyses. Small-angle X-ray scattering and transmission electron microscopic analyses show that the morphologies of the self-assembly structures are strongly dependent on the hydrogen bonding strength at relatively higher OP-POSS content. The PS-b-P4VP/OP-POSS hybrid complex system with the strongest hydrogen bonds shows the order-order transition from lamellae to cylinders and finally to body-centered cubic spheres upon increasing OP-POSS content. However, PS-b-P2VP/OP-POSS and PS-b-PMMA/OP-POSS hybrid complex systems, having relatively weaker hydrogen bonds, transformed from lamellae to cylinder structures at lower OP-POSS content (<50 wt%), but formed disordered structures at relatively high OP-POSS contents (>50 wt%).

  2. Synergistic toughening of hard, nacre-mimetic MoSi2 coatings by self-assembled hierarchical structure

    NASA Astrophysics Data System (ADS)

    Xu, Jiang; Zhao, Xiaoli; Munroe, Paul; Xie, Zonghan

    2014-02-01

    Like many other intermetallic materials, MoSi2 coatings are typically hard, but prone to catastrophic failure due to their low toughness at ambient temperature. In this paper, a self-assembled hierarchical structure that closely resembles that of nacre (i.e., mother of pearl) was developed in a MoSi2-based coating through a simple, yet cost-effective, depostion technique. The newly formed coating is tough and can withstand multiple indentations at high loads. Key design features responsible for this remarkable outcome were identified. They include a functionally graded multilayer featuring elastic modulus oscillation, varying sublayer thickness and a columnar structure that are able to attenuate stress concentrations; interlocking boundaries between adjacent sublayers that improve the bonding and arrest the cracks; a transitional layer that bridges the coating and substrate and facilitates load transfer. Moreover, the contributions of six important structural characteristics to damage resistance are quantified using finite elemnet analysis and in an additive manner (i.e., from low- to high-level complexity). The in-situ toughened coating is envisaged to enhance the mechanical performance and extend the lifespan of metal components used in safety-critical applications.

  3. Synergistic toughening of hard, nacre-mimetic MoSi2 coatings by self-assembled hierarchical structure.

    PubMed

    Xu, Jiang; Zhao, Xiaoli; Munroe, Paul; Xie, Zonghan

    2014-02-28

    Like many other intermetallic materials, MoSi2 coatings are typically hard, but prone to catastrophic failure due to their low toughness at ambient temperature. In this paper, a self-assembled hierarchical structure that closely resembles that of nacre (i.e., mother of pearl) was developed in a MoSi2-based coating through a simple, yet cost-effective, depostion technique. The newly formed coating is tough and can withstand multiple indentations at high loads. Key design features responsible for this remarkable outcome were identified. They include a functionally graded multilayer featuring elastic modulus oscillation, varying sublayer thickness and a columnar structure that are able to attenuate stress concentrations; interlocking boundaries between adjacent sublayers that improve the bonding and arrest the cracks; a transitional layer that bridges the coating and substrate and facilitates load transfer. Moreover, the contributions of six important structural characteristics to damage resistance are quantified using finite elemnet analysis and in an additive manner (i.e., from low- to high-level complexity). The in-situ toughened coating is envisaged to enhance the mechanical performance and extend the lifespan of metal components used in safety-critical applications.

  4. Synergistic toughening of hard, nacre-mimetic MoSi2 coatings by self-assembled hierarchical structure

    PubMed Central

    Xu, Jiang; Zhao, Xiaoli; Munroe, Paul; Xie, Zonghan

    2014-01-01

    Like many other intermetallic materials, MoSi2 coatings are typically hard, but prone to catastrophic failure due to their low toughness at ambient temperature. In this paper, a self-assembled hierarchical structure that closely resembles that of nacre (i.e., mother of pearl) was developed in a MoSi2-based coating through a simple, yet cost-effective, depostion technique. The newly formed coating is tough and can withstand multiple indentations at high loads. Key design features responsible for this remarkable outcome were identified. They include a functionally graded multilayer featuring elastic modulus oscillation, varying sublayer thickness and a columnar structure that are able to attenuate stress concentrations; interlocking boundaries between adjacent sublayers that improve the bonding and arrest the cracks; a transitional layer that bridges the coating and substrate and facilitates load transfer. Moreover, the contributions of six important structural characteristics to damage resistance are quantified using finite elemnet analysis and in an additive manner (i.e., from low- to high-level complexity). The in-situ toughened coating is envisaged to enhance the mechanical performance and extend the lifespan of metal components used in safety-critical applications. PMID:24577416

  5. Disassembly of the self-assembled, double-ring structure of proteasome α7 homo-tetradecamer by α6.

    PubMed

    Ishii, Kentaro; Noda, Masanori; Yagi, Hirokazu; Thammaporn, Ratsupa; Seetaha, Supaporn; Satoh, Tadashi; Kato, Koichi; Uchiyama, Susumu

    2015-12-14

    The 20S core particle of the eukaryotic proteasome is composed of two α- and two β-rings, each of which is a hetero-heptamer composed of seven homologous but distinct subunits. Although formation of the eukaryotic proteasome is a highly ordered process assisted by assembly chaperones, α7, an α-ring component, has the unique property of self-assembling into a homo-tetradecamer. We used biophysical methods to characterize the oligomeric states of this proteasome subunit and its interaction with α6, which makes direct contacts with α7 in the proteasome α-ring. We determined a crystal structure of the α7 tetradecamer, which has a double-ring structure. Sedimentation velocity analytical ultracentrifugation and mass spectrometric analysis under non-denaturing conditions revealed that α7 exclusively exists as homo-tetradecamer in solution and that its double-ring structure is disassembled upon the addition of α6, resulting in a 1:7 hetero-octameric α6-α7 complex. Our findings suggest that proteasome formation involves the disassembly of non-native oligomers, which are assembly intermediates.

  6. Frictional characteristics of nano-scale mesoporous SiO2 thin film formed by sol-gel and self-assembly method.

    PubMed

    Lee, Gyu-Sun; Shin, Yun-Ha; Kim, Ji-Man; Kim, Tae-Sung; Lee, Young-Ze

    2009-12-01

    The pores on the surface function as an outlet for wear particles and enhance the storage of lubricants, which improves lubrication effectiveness. Mesoporous SiO2 thin films were formed by the sol-gel and self-assembly methods to have a porous structure. One of the important issues in the manufacturing of the films involves the control of the porous structure to ensure proper mechanical properties. Mesoporous materials were manufactured with two surfactants, Pluronid Polyol (F127) and Cetyltrimethylammonium Bromide (CTABr). The pores were then exposed on the surface by chemical mechanical polishing (CMP) and plasma-etching. Ball-on-disk tests with mesoporous SiO2 thin films on glass specimens were conducted. The results show that the friction coefficient and wear volume of a specimen with F127, which has a 8 nm pore size, are far lower than those of CTABr, which has a 3 nm pore size at both the dry condition and at boundary lubricated condition. This proves a significant dependency of friction and wear on pore size of mesoporous SiO2 thin films.

  7. Thermodynamic versus kinetic control in self-assembly of zero-, one-, quasi-two-, and two-dimensional metal-organic coordination structures

    SciTech Connect

    Lin, Tao; Wu, Qi; Shi, Ziliang; Lin, Nian; Liu, Jun; Liu, Pei Nian

    2015-03-14

    Four types of metal-organic structures exhibiting specific dimensionality were studied using scanning tunneling microscopy and Monte Carlo simulations. The four structures were self-assembled out of specifically designed molecular building blocks via the same coordination motif on an Au(111) surface. We found that the four structures behaved differently in response to thermal annealing treatments: The two-dimensional structure was under thermodynamic control while the structures of lower dimension were under kinetic control. Monte Carlo simulations revealed that the self-assembly pathways of the four structures are associated with the characteristic features of their specific heat. These findings provide insights into how the dimensionality of supramolecular coordination structures affects their thermodynamic properties.

  8. Hierarchical Self-Assembled Structures from POSS-Containing Block Copolymers Synthesized by Living Anionic Polymerization

    SciTech Connect

    Hirai, Tomoyasu; Leolukman, Melvina; Jin, Sangwoo; Goseki, Raita; Ishida, Yoshihito; Kakimoto, Masa-aki; Hayakawa, Teruaki; Ree, Moonhor; Gopalan, Padma

    2010-03-16

    Two kinds of polyhedral oligomeric silsesquioxane (POSS)-containing block copolymers (BCPs), namely PS-b-PMAPOSS and PMMA-b-PMAPOSS, were synthesized by living anionic polymerization. A wide range of molecular weights were obtained with a very narrow polydispersity index of less than 1.09. The bulk samples prepared by slow evaporation from a polymer solution in chloroform exhibit well-defined microphase-separated structures with long-range order. Thermal annealing induced hierarchical structures consisting of a smaller length scale ordered crystalline POSS domains within the larger microphase-separated structures. We report detailed structural characterization of these hierarchical structures in bulk and thin films by transmission electron microscopy and grazing incidence wide-angle X-ray scattering (GIWAXS). On the basis of this structural analysis, we propose a model for the formation of an orthorhombic lattice structure through the aggregation of POSS segments which formed a helix-like structure.

  9. Square Wave Voltammetry of TNT at Gold Electrodes Modified with Self-Assembled Monolayers Containing Aromatic Structures

    PubMed Central

    Trammell, Scott A.; Zabetakis, Dan; Moore, Martin; Verbarg, Jasenka; Stenger, David A.

    2014-01-01

    Square wave voltammetry for the reduction of 2,4,6-trinitrotoluene (TNT) was measured in 100 mM potassium phosphate buffer (pH 8) at gold electrodes modified with self-assembled monolayers (SAMs) containing either an alkane thiol or aromatic ring thiol structures. At 15 Hz, the electrochemical sensitivity (µA/ppm) was similar for all SAMs tested. However, at 60 Hz, the SAMs containing aromatic structures had a greater sensitivity than the alkane thiol SAM. In fact, the alkane thiol SAM had a decrease in sensitivity at the higher frequency. When comparing the electrochemical response between simulations and experimental data, a general trend was observed in which most of the SAMs had similar heterogeneous rate constants within experimental error for the reduction of TNT. This most likely describes a rate limiting step for the reduction of TNT. However, in the case of the alkane SAM at higher frequency, the decrease in sensitivity suggests that the rate limiting step in this case may be electron tunneling through the SAM. Our results show that SAMs containing aromatic rings increased the sensitivity for the reduction of TNT when higher frequencies were employed and at the same time suppressed the electrochemical reduction of dissolved oxygen. PMID:25549081

  10. Self-assembled structures of anionic hydrophobically modified polyacrylamide with star-shaped trimeric and hexameric quaternary ammonium surfactants.

    PubMed

    Fan, Yaxun; Wu, Chunxian; Wang, Meina; Wang, Yilin; Thomas, Robert K

    2014-06-17

    The self-assembly of a 1% hydrophobically modified and 30% hydrolyzed polyacrylamide (C12PAM) with cationic star-shaped oligomeric surfactants has been investigated by isothermal titration microcalorimetry, turbidimetry, ζ potential, scanning electron microscopy, and (1)H NMR techniques. The oligomeric surfactants are composed of quaternary dodecyldimethylammonium ions with three or six hydrophobic chains connected by a polyamine spacer at the headgroup level, abbreviated as DTAD and PAHB, respectively. DTAD/C12PAM and PAHB/C12PAM mixed systems undergo the same aggregate transitions with increases in surfactant concentration from soluble networklike aggregates to precipitated denser and more cross-linked structures and then to soluble spherical aggregates. The networklike aggregates are generated at very low surfactant concentration. However, at the corresponding surfactant concentration without C12PAM, DTAD cannot form aggregates and PAHB forms only networklike aggregates with a very loose structure. The strong electrostatic and hydrophobic interaction of DTAD and PAHB with C12PAM and the hydrophobic interaction between the alkyl chains of DTAD and PAHB themselves evidently promote the formation of networklike aggregates. As the surfactant concentration increases, cationic surfactants become excessive. The molecular configuration is changed by the stronger hydrophobic association among the DTAD and PAHB molecules and the enhanced electrostatic repulsion between the mixed aggregates. Thus, the networklike aggregates transfer to spherical aggregates.

  11. Structural Stability and Phase Transitions of Octanethiol Self-Assembled Monolayers on Au(111) in Ultrahigh Vacuum.

    PubMed

    Lee, Nam-Suk; Cho, Gyoujin; Shin, Hoon-Kyu; Noh, Jaegeun

    2016-06-01

    To understand the structural stability of as-prepared octanethiol (OT) self-assembled monolayers (SAMs) with a fully covered c(4 x 2) phase on Au(111) in ultrahigh vacuum (UHV) conditions of 3 x 10(-7) Pa at room temperature, we examined OT SAM samples obtained as a function of storage period using scanning tunneling microscopy (STM). STM imaging revealed that phase transition of OT SAMs after storage in UHV for 3 days occurs from the c(4 x 2) phase to the mixed phase containing ordered c(4 x 2) and disordered phases. It was also observed that the disordered phase was mainly located at around vacancy islands and near step edges of Au(111) terraces, implying that desorption of OT molecules chemisorbed on Au(111) in UHV occurs more quickly in these regions compared with in the closely packed and ordered domains. After a longer storage in UHV for 6 days, OT SAMs with the c(4 x 2) phase were changed to the disordered phase containing a partially ordered domain with a row structure. From this study, we clearly demonstrated that OT molecules in SAMs on Au(111) are desorbed spontaneously in UHV at room temperature, resulting in the formation of disordered and row phases.

  12. Excitation spectra of photoluminescence and its kinetics in structures with self-assembled Ge:Si nanoislands

    SciTech Connect

    Yablonskiy, A. N. Baidakova, N. A. Novikov, A. V.; Lobanov, D. N.; Shaleev, M. V.

    2015-11-15

    The spectral and time characteristics of photoluminescence associated with the radiative recombination of charge carriers in SiGe/Si(001) multilayer structures with self-assembled Ge:Si islands are investigated. The time dependences of the photoluminescence of Ge:Si islands in a wide range of delay times after the pump pulse are considered at various optical-excitation levels. The photoluminescence-excitation spectra from Ge(Si) islands in the SiGe/Si(001) structures are investigated in the region of band-to-band and subband optical pumping corresponding to various time components in the photoluminescence-relaxation kinetics. A significant difference in the shape of the excitation spectra is revealed for fast (0–100 μs) and slow (100 μs–50 ms) components of the photoluminescence signal from the islands. The significant dependence of the photoluminescence-excitation spectra of Ge(Si)/Si(001) islands on the optical-pump power is shown to be associated with the prolonged diffusion of nonequilibrium charge carriers from bulk-silicon layers to Ge:Si islands at high excitation levels.

  13. Hierarchical self-assembly of 'hard-soft' Janus particles into colloidal molecules and larger supracolloidal structures.

    PubMed

    Skelhon, Thomas S; Chen, Yunhua; Bon, Stefan A F

    2014-10-21

    Here we report the self-assembly of 'hard-soft' micron-sized Janus particles into clusters in aqueous media. The assembly process is induced by the desorption of a polymeric stabiliser from the particles, that is polyvinylpyrrolidone (PVP). Upon contact through collision and coalescence of the soft polymeric lobes, the newly formed clusters adopt a minimized surface area to volume ratio, thereby forming distinct microscopic supracolloidal analogues of simple molecular valance shell electron pair repulsion (VSEPR) space-fill structures. To explain this behaviour, the colloidal stability of our particle suspensions were studied with and without an adsorbed steric surfactant. Simulations of expected cluster morphology, compared with those from cryo-SEM analysis support the mechanism of assembly driven by surface area minimization in the case of soft-soft interactions. Altering the soft lobe size with respect to the hard lobe indicates a moderate effect on number of primary particles per cluster. Additionally, higher order structures of clusters containing a number of primary particles exceeding what is possible for a 'solid' core cluster are observed. As such, we also investigated the formation of suprastructures using a high number of 'hard-soft' Janus particles and verified their effective Pickering stabilization of air bubbles.

  14. Colloidal stability of self-assembled monolayer-coated gold nanoparticles: the effects of surface compositional and structural heterogeneity.

    PubMed

    Huang, Rixiang; Carney, Randy P; Stellacci, Francesco; Lau, Boris L T

    2013-09-17

    Surface heterogeneity plays an important role in controlling colloidal phenomena. This study investigated the self-aggregation and bacterial adsorption of self-assembled monolayer coated gold nanoparticles (AuNPs) with different surface compositional and structural heterogeneity. Evaluation was performed on AuNPs coated with (1) one ligand with charged terminals (MUS), (2) two homogeneously distributed ligands with respectively charged and nonpolar terminals (brOT) and (3) two ligands with respectively charged and nonpolar terminals with stripe-like distribution (OT). The brOT particles have less negative electrophoretic mobility (EPM) values, smaller critical coagulation concentration (CCC) and larger adsorption rate on Escherichia coli than that of AuNPs with homogeneously charged groups, in good agreement with DLVO predictions. Although the ligand composition on the surface of AuNPs is the same, OT particles have less negative EPM values and faster rate of bacterial adsorption, but much larger CCC compared to brOT. The deviation of OT particles from brOT and MUS in their self-aggregation behavior reflects the effects of surface heterogeneity on electrical double layer structures at the interface. Results from the present study demonstrated that, besides chemical composition, organization of ligands on particle surface is important in determining their colloidal stability.

  15. Theory of fine structure of correlated exciton states in self-assembled semiconductor quantum dots in a magnetic field

    NASA Astrophysics Data System (ADS)

    Trojnar, Anna H.; Kadantsev, Eugene S.; Korkusiński, Marek; Hawrylak, Pawel

    2011-12-01

    A theory of the fine structure of correlated exciton states in self-assembled parabolic semiconductor quantum dots in a magnetic field perpendicular to the quantum dot plane is presented. The correlated exciton wave function is expanded in configurations consisting of products of electron and heavy-hole 2D harmonic oscillator states (HO) in a magnetic field and the electron spin Sz=±1/2 and a heavy-hole spin τz=±3/2 states. Analytical expressions for the short- and long-range electron-hole exchange Coulomb interaction matrix elements are derived in the HO and spin basis for arbitrary magnetic field. This allows the incorporation of short- and long-range electron-hole exchange, direct electron-hole interaction, and quantum dot anisotropy in the exact diagonalization of the exciton Hamiltonian. The fine structure of ground and excited correlated exciton states as a function of a number of confined shells, quantum dot anisotropy, and magnetic field is obtained using exact diagonalization of the many-body Hamiltonian. The effects of correlations are shown to significantly affect the energy splitting of the two bright exciton states.

  16. Investigation of the structural anisotropy in a self-assembling glycinate layer on Cu(100) by scanning tunneling microscopy and density functional theory calculations

    NASA Astrophysics Data System (ADS)

    Kuzmin, Mikhail; Lahtonen, Kimmo; Vuori, Leena; Sánchez-de-Armas, Rocío; Hirsimäki, Mika; Valden, Mika

    2017-07-01

    Self-assembling organic molecule-metal interfaces exhibiting free-electron like (FEL) states offers an attractive bottom-up approach to fabricating materials for molecular electronics. Accomplishing this, however, requires detailed understanding of the fundamental driving mechanisms behind the self-assembly process. For instance, it is still unresolved as to why the adsorption of glycine ([NH2(CH2)COOH]) on isotropic Cu(100) single crystal surface leads, via deprotonation and self-assembly, to a glycinate ([NH2(CH2)COO-]) layer that exhibits anisotropic FEL behavior. Here, we report on bias-dependent scanning tunneling microscopy (STM) experiments and density functional theory (DFT) calculations for glycine adsorption on Cu(100) single crystal surface. We find that after physical vapor deposition (PVD) of glycine on Cu(100), glycinate self-assembles into an overlayer exhibiting c(2 × 4) and p(2 × 4) symmetries with non-identical adsorption sites. Our findings underscore the intricacy of electrical conductivity in nanomolecular organic overlayers and the critical role the structural anisotropy at molecule-metal interface plays in the fabrication of materials for molecular electronics.

  17. A Global Scale Scenario for Prebiotic Chemistry: Silica-Based Self-Assembled Mineral Structures and Formamide.

    PubMed

    Saladino, Raffaele; Botta, Giorgia; Bizzarri, Bruno Mattia; Di Mauro, Ernesto; Garcia Ruiz, Juan Manuel

    2016-05-17

    The pathway from simple abiotically made organic compounds to the molecular bricks of life, as we know it, is unknown. The most efficient geological abiotic route to organic compounds results from the aqueous dissolution of olivine, a reaction known as serpentinization (Sleep, N.H., et al. (2004) Proc. Natl. Acad. Sci. USA 101, 12818-12822). In addition to molecular hydrogen and a reducing environment, serpentinization reactions lead to high-pH alkaline brines that can become easily enriched in silica. Under these chemical conditions, the formation of self-assembled nanocrystalline mineral composites, namely silica/carbonate biomorphs and metal silicate hydrate (MSH) tubular membranes (silica gardens), is unavoidable (Kellermeier, M., et al. In Methods in Enzymology, Research Methods in Biomineralization Science (De Yoreo, J., Ed.) Vol. 532, pp 225-256, Academic Press, Burlington, MA). The osmotically driven membranous structures have remarkable catalytic properties that could be operating in the reducing organic-rich chemical pot in which they form. Among one-carbon compounds, formamide (NH2CHO) has been shown to trigger the formation of complex prebiotic molecules under mineral-driven catalytic conditions (Saladino, R., et al. (2001) Biorganic & Medicinal Chemistry, 9, 1249-1253), proton irradiation (Saladino, R., et al. (2015) Proc. Natl. Acad. Sci. USA, 112, 2746-2755), and laser-induced dielectric breakdown (Ferus, M., et al. (2015) Proc Natl Acad Sci USA, 112, 657-662). Here, we show that MSH membranes are catalysts for the condensation of NH2CHO, yielding prebiotically relevant compounds, including carboxylic acids, amino acids, and nucleobases. Membranes formed by the reaction of alkaline (pH 12) sodium silicate solutions with MgSO4 and Fe2(SO4)3·9H2O show the highest efficiency, while reactions with CuCl2·2H2O, ZnCl2, FeCl2·4H2O, and MnCl2·4H2O showed lower reactivities. The collections of compounds forming inside and outside the tubular membrane are

  18. A Global Scale Scenario for Prebiotic Chemistry: Silica-Based Self-Assembled Mineral Structures and Formamide

    PubMed Central

    2016-01-01

    The pathway from simple abiotically made organic compounds to the molecular bricks of life, as we know it, is unknown. The most efficient geological abiotic route to organic compounds results from the aqueous dissolution of olivine, a reaction known as serpentinization (Sleep, N.H., et al. (2004) Proc. Natl. Acad. Sci. USA 101, 12818–12822). In addition to molecular hydrogen and a reducing environment, serpentinization reactions lead to high-pH alkaline brines that can become easily enriched in silica. Under these chemical conditions, the formation of self-assembled nanocrystalline mineral composites, namely silica/carbonate biomorphs and metal silicate hydrate (MSH) tubular membranes (silica gardens), is unavoidable (Kellermeier, M., et al. In Methods in Enzymology, Research Methods in Biomineralization Science (De Yoreo, J., Ed.) Vol. 532, pp 225–256, Academic Press, Burlington, MA). The osmotically driven membranous structures have remarkable catalytic properties that could be operating in the reducing organic-rich chemical pot in which they form. Among one-carbon compounds, formamide (NH2CHO) has been shown to trigger the formation of complex prebiotic molecules under mineral-driven catalytic conditions (Saladino, R., et al. (2001) Biorganic & Medicinal Chemistry, 9, 1249–1253), proton irradiation (Saladino, R., et al. (2015) Proc. Natl. Acad. Sci. USA, 112, 2746–2755), and laser-induced dielectric breakdown (Ferus, M., et al. (2015) Proc Natl Acad Sci USA, 112, 657–662). Here, we show that MSH membranes are catalysts for the condensation of NH2CHO, yielding prebiotically relevant compounds, including carboxylic acids, amino acids, and nucleobases. Membranes formed by the reaction of alkaline (pH 12) sodium silicate solutions with MgSO4 and Fe2(SO4)3·9H2O show the highest efficiency, while reactions with CuCl2·2H2O, ZnCl2, FeCl2·4H2O, and MnCl2·4H2O showed lower reactivities. The collections of compounds forming inside and outside the tubular

  19. Fabrication and Optical Properties of Strain-free Self-assembled Mesoscopic GaAs Structures.

    PubMed

    da Silva, Saimon Filipe Covre; Mardegan, Thayná; de Araújo, Sidnei Ramis; Ramirez, Carlos Alberto Ospina; Kiravittaya, Suwit; Couto, Odilon D D; Iikawa, Fernando; Deneke, Christoph

    2017-12-01

    We use a combined process of Ga-assisted deoxidation and local droplet etching to fabricate unstrained mesoscopic GaAs/AlGaAs structures exhibiting a high shape anisotropy with a length up to 1.2 μm and a width of 150 nm. We demonstrate good controllability over size and morphology of the mesoscopic structures by tuning the growth parameters. Our growth method yields structures, which are coupled to a surrounding quantum well and present unique optical emission features. Microscopic and optical analysis of single structures allows us to demonstrate that single structure emission originates from two different confinement regions, which are spectrally separated and show sharp excitonic lines. Photoluminescence is detected up to room temperature making the structures the ideal candidates for strain-free light emitting/detecting devices.

  20. Size limits of self-assembled colloidal structures made using specific interactions

    PubMed Central

    Zeravcic, Zorana; Brenner, Michael P.

    2014-01-01

    We establish size limitations for assembling structures of controlled size and shape out of colloidal particles with short-ranged interactions. Through simulations we show that structures with highly variable shapes made out of dozens of particles can form with high yield, as long as each particle in the structure binds only to the particles in their local environment. To understand this, we identify the excited states that compete with the ground-state structure and demonstrate that these excited states have a completely topological characterization, valid when the interparticle interactions are short-ranged. This allows complete enumeration of the energy landscape and gives bounds on how large a colloidal structure can assemble with high yield. For large structures the yield can be significant, even with hundreds of particles. PMID:25349380

  1. Fabrication and Optical Properties of Strain-free Self-assembled Mesoscopic GaAs Structures

    NASA Astrophysics Data System (ADS)

    da Silva, Saimon Filipe Covre; Mardegan, Thayná; de Araújo, Sidnei Ramis; Ramirez, Carlos Alberto Ospina; Kiravittaya, Suwit; Couto, Odilon D. D.; Iikawa, Fernando; Deneke, Christoph

    2017-01-01

    We use a combined process of Ga-assisted deoxidation and local droplet etching to fabricate unstrained mesoscopic GaAs/AlGaAs structures exhibiting a high shape anisotropy with a length up to 1.2 μm and a width of 150 nm. We demonstrate good controllability over size and morphology of the mesoscopic structures by tuning the growth parameters. Our growth method yields structures, which are coupled to a surrounding quantum well and present unique optical emission features. Microscopic and optical analysis of single structures allows us to demonstrate that single structure emission originates from two different confinement regions, which are spectrally separated and show sharp excitonic lines. Photoluminescence is detected up to room temperature making the structures the ideal candidates for strain-free light emitting/detecting devices.

  2. Self-Assembly of Biomolecular Soft Matter

    PubMed Central

    Zha, R. Helen; Palmer, Liam C.; Cui, Honggang; Bitton, Ronit

    2014-01-01

    Self-assembly programmed by molecular structure and guided dynamically by energy dissipation is a ubiquitous phenomenon in biological systems that build functional structures from the nanoscale to macroscopic dimensions. This paper describes examples of one-dimensional self-assembly of peptide amphiphiles and the consequent biological functions that emerge in these systems. We also discuss here hierarchical self-assembly of supramolecular peptide nanostructures and polysaccharides, and some new results are reported on supramolecular crystals formed by highly charged peptide amphiphiles. Reflecting on presentations at this Faraday Discussion, the paper ends with a discussion of some of the future opportunities and challenges of the field. PMID:24611266

  3. Self-assembled structures and pKa value of oleic acid in systems of biological relevance.

    PubMed

    Salentinig, Stefan; Sagalowicz, Laurent; Glatter, Otto

    2010-07-20

    In the human digestion process, triglycerides are hydrolyzed by lipases to monoglycerides and the corresponding fatty acids. Here we report the self-assembly of structures in biologically relevant, emulsified oleic acid-monoolein mixtures at various pH values and oleic acid concentrations. Small-angle X-ray scattering, cryogenic transmission electron microscopy, and dynamic light scattering were used to investigate the structures formed, and to follow their transitions while these factors were varied. The addition of oleic acid to monoolein-based cubosomes was found to increase the critical packing parameter in the system. Structural transitions from bicontinuous cubosomes through hexosomes and micellar cubosomes (Fd3m symmetry) to emulsified microemulsions occur with increasing oleic acid concentration. At sufficiently high oleic acid concentration, the internal particle structure was also found to strongly depend on the pH of the aqueous phase: transformations from emulsified microemulsion through micellar cubosomes, hexosomes, and bicontinuous cubosomes to vesicles can be observed as a function of increasing pH. The reversible transition from liquid crystals to vesicles occurs at intestinal pH values (between pH 7 and 8). The hydrodynamic radius of the particles decreases from around 120 nm for internally structured particles to around 60 nm for vesicles. All transitions with pH are reversible. Finally, the apparent pK(a) for oleic acid in monoolein could be determined from the change of structure with pH. This value is within the physiological pH range of the intestine and depends somewhat on composition.

  4. Multi-component coordination-driven self-assembly: construction of alkyl-based structures and molecular modelling.

    PubMed

    Pollock, J Bryant; Cook, Timothy R; Schneider, Gregory L; Stang, Peter J

    2013-10-01

    The design of supramolecular coordination complexes (SCCs) is typically predicated on the use of rigid molecular building blocks through which the structural outcome is determined based on the number and orientation of labile coordination sites on metal acceptors, and the angularity of the ligand donors that are to bridge these nodes. Three-component systems extend the complexity of self-assembly by utilizing two different Lewis base donors in concert with a metal that favors a heteroligated coordination environment. The thermodynamic preference for heteroligation provides a new design principle to the formation of SCCs, wherein multicomponent architectures need not employ only rigid donors. Herein, we exploit the self-selection processes of bis(phosphine) Pt(II) metal centers which favor mixed Pt(pyridyl)(carboxylate) coordination spheres over their homoligated counterparts, specifically using alkyl-based dicarboxylate ligands instead of traditionally rigid phenyl, alkenyl, or ethynyl variants. Using this mode of assembly, flexible-based 2D and 3D SCCs containing long alkyl chains were synthesized and characterized. Density functional theory (DFT) and natural population analysis (NPA) calculations were performed on model systems to probe the thermodynamic preference for heteroligated coordination spheres in the experimental systems. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Synthesis, structures, and solid state self-assemblies of formyl and acetyl substituted triptycenes and their derivatives.

    PubMed

    Li, Peng-Fei; Chen, Chuan-Feng

    2012-10-19

    Starting from triptycene, 2-, (2,6- or 2,7-)di-, and (2,6,14- or 2,7,14-)triformyl or acetyl substituted triptycenes were selectively synthesized. The derivatization of the formyl or acetyl substituted triptycenes was then investigated. Consequently, it was found that the formyl-substituted triptycenes could be transformed into cyano substituted triptycene derivatives by the aldoxime formation and dehydration. Acetoxyl- and acetamino-substituted triptycenes were synthesized by Baeyer-Villiger oxidation of acetyl-substituted triptycenes and Beckmann rearrangement of acetyl-oxime triptycenes, respectively. Deacetylation of triacetaminotriptycene provided an alternative way to the synthesis of triaminotriptycene. In addition, 2-ethynyltriptycene could be conveniently synthesized by Corey-Fuchs reaction of 2-formyltriptycene, and 1,3,5-tritriptycenebenzene was obtained in high yield by the dehydration cyclotrimerization of 2-acetyltriptycene. The different functionalized triptycene derivatives and their regioisomers were well characterized by the FT-IR, (1)H NMR, (13)C NMR, MS spectra, and single crystal X-ray analyses. Moreover, it was also found that 2,6,14-triacetaminotriptycene with the three amide groups paralleled to their connected aromatic rings could self-assemble into a 2D layer with porous structure, and further 3D microporous architecture by the hydrogen-bond network in the solid state.

  6. Atomically thick Pt-Cu nanosheets: self-assembled sandwich and nanoring-like structures.

    PubMed

    Saleem, Faisal; Xu, Biao; Ni, Bing; Liu, Huiling; Nosheen, Farhat; Li, Haoyi; Wang, Xun

    2015-03-25

    Atomically thick and flexible Pt-Cu alloy nanosheets are prepared and loaded with either Pd or Pt to produce sandwich structures or nanoring-like nanosheet structures, respectively. Core-shell alloy nanoparticles containing Rh, Ir, and Ru are also prepared. All of these structures exhibit superior specific and mass activities for the oxidation of formic acid for fuel cells for portable electronic devices as compared to commercial Pd/C catalyst. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Self-assembly of diblock copolymer confined in an array-structure space

    SciTech Connect

    He, Xuehao E-mail: hjliang@ustc.edu.cn; Zou, Zhixiang; Kan, Di; Liang, Haojun E-mail: hjliang@ustc.edu.cn

    2015-03-14

    The combination of top-down and bottom-up technologies is an effective method to create the novel nanostructures with long range order in the field of advanced materials manufacture. In this work, we employed a polymeric self-consistent field theory to investigate the pattern formation of diblock copolymer in a 2D confinement system designed by filling pillar arrays with various 2D shapes such as squares, rectangles, and triangles. Our simulation shows that in such confinement system, the microphase structure of diblock copolymer strongly depends on the pitch, shape, size, and rotation of the pillar as well as the surface field of confinement. The array structures can not only induce the formation of new phase patterns but also control the location and orientation of pattern structures. Finally, several methods to tune the commensuration and frustration of array-structure confinement are proposed and examined.

  8. Facile Preparation of Hierarchical Structures Using Crystallization-Kinetics Driven Self-Assembly.

    PubMed

    Cai, Jinguang; Lv, Chao; Watanabe, Akira

    2015-08-26

    Hierarchical structures (HSs) constructed by nanoparticle-based building blocks possess not only the properties of the primary building blocks but also collective properties of the assemblies. Here we report the facile preparation of hierarchical Ag nanoparticles/polyhedral oligomeric silsequioxane molecule (POSS) hybrid branched structures within tens of seconds by using spin-coating and doctor-blade methods. An assembly mechanism mainly controlled by POSS-crystallization kinetics and space resistance of Ag nanoparticles toward the diffusion of POSS molecules was tentatively proposed. It was demonstrated as a universal method for the preparation of hierarchical hybrid branched structures on arbitrary substrates, as well as by using other different POSS and inorganic nanoparticles. As a demonstration, Ag hierarchical structures obtained by heat treatment exhibit excellent SERS performance with enhancement factors as high as on the order of 10(7), making them promising sensors for the detection of trace amount of analyte adsorbed on the surface. Two-dimensional SERS mapping was also demonstrated by using a direct imaging system with high mapping speed and high resolution. Moreover, the substrates with Ag hierarchical structures were used as a SERS sensor for in situ detection due to the excellent SERS performance and stability of the structures.

  9. A terminally protected dipeptide: from crystal structure and self-assembly, through co-assembly with carbon-based materials, to a ternary catalyst for reduction chemistry in water.

    PubMed

    Mazzier, Daniela; Carraro, Francesco; Crisma, Marco; Rancan, Marzio; Toniolo, Claudio; Moretto, Alessandro

    2016-01-07

    A terminally protected, hydrophobic dipeptide Boc-L-Cys(Me)-L-Leu-OMe (1) was synthesized and its 3D-structure was determined by single crystal X-ray diffraction analysis. This peptide is able to hierarchically self-assemble in a variety of superstructures, including hollow rods, ranging from the nano- to the macroscale, and organogels. In addition, 1 is able to drive fullerene (C60) or multiwalled carbon nanotubes (MWCNTs) in an organogel by co-assembling with them. A hybrid 1-C60–MWCNT organogel was prepared and converted (through a high vacuum-drying process) into a robust, high-volume, water insoluble, solid material where C60 is well dispersed over the entire superstructure. This ternary material was successfully tested as a catalyst for: (i) the reduction reaction of water-soluble azo compounds mediated by NaBH4 and UV-light with an overall performance remarkably better than that provided by C60 alone, and (ii) the NaBH4-mediated reduction of benzoic acid to benzyl alcohol. Our results suggest that the self-assembly properties of 1 might be related to the occurrence in its single crystal structure of a sixfold screw axis, a feature shared by most of the linear peptides known so far to give rise to nanotubes.

  10. Self-assembled strained GeSiSn nanoscale structures grown by MBE on Si(100)

    NASA Astrophysics Data System (ADS)

    Nikiforov, A. I.; Timofeev, V. A.; Tuktamyshev, A. R.; Yakimov, A. I.; Mashanov, V. I.; Gutakovskii, A. K.

    2017-01-01

    Gradual relaxation of elastic deformations in a silicon layer at the growth of a covering layer on strained layers was established. The dependence of the thickness of a silicon film, where full elastic strain relaxation occurs, on the germanium layer thickness was determined. The dependence of the critical thickness of 2D-3D transition of temperature and composition of the GeSiSn film on Si(100) was studied. Regularities of the formation of multilayer structures on quantum wells comprising pseudomorphous GeSiSn layers without relaxed buffer layers but creating the structures directly on Si. A possibility of synthesizing multilayer structures by molecular beam epitaxy was shown, and the crystal lattice constants using the high-resolution transmission electron microscopy were determined. Based on multilayer GeSiSn/Si structures the p-i-n-diodes, which demonstrated the photoresponse increasing by several orders of magnitude compared to the Sn-free structures at an increase in the Sn content, were created.

  11. Protein self-assembly via supramolecular strategies.

    PubMed

    Bai, Yushi; Luo, Quan; Liu, Junqiu

    2016-05-21

    Proteins, as the elemental basis of living organisms, mostly execute their biological tasks in the form of supramolecular self-assemblies with subtle architectures, dynamic interactions and versatile functionalities. Inspired by the structural harmony and functional beauty of natural protein self-assemblies to fabricate sophisticated yet highly ordered protein superstructures represents an adventure in the pursuit of nature's supreme wisdom. In this review, we focus on building protein self-assembly systems based on supramolecular strategies and classify recent progress by the types of utilized supramolecular driving forces. Especially, the design strategy, structure control and the thermodynamic/kinetic regulation of the self-assemblies, which will in turn provide insights into the natural biological self-assembly mechanism, are highlighted. In addition, recently, this research field is starting to extend its interest beyond constructing complex morphologies towards the potential applications of the self-assembly systems; several attempts to design functional protein complexes are also discussed. As such, we hope that this review will provide a panoramic sketch of the field and draw a roadmap towards the ultimate construction of advanced protein self-assemblies that even can serve as analogues of their natural counterparts.

  12. Self-assembled plasmonic metamaterials

    NASA Astrophysics Data System (ADS)

    Mühlig, Stefan; Cunningham, Alastair; Dintinger, José; Scharf, Toralf; Bürgi, Thomas; Lederer, Falk; Rockstuhl, Carsten

    2013-07-01

    Nowadays for the sake of convenience most plasmonic nanostructures are fabricated by top-down nanofabrication technologies. This offers great degrees of freedom to tailor the geometry with unprecedented precision. However, it often causes disadvantages as well. The structures available are usually planar and periodically arranged. Therefore, bulk plasmonic structures are difficult to fabricate and the periodic arrangement causes undesired effects, e.g., strong spatial dispersion is observed in metamaterials. These limitations can be mitigated by relying on bottom-up nanofabrication technologies. There, self-assembly methods and techniques from the field of colloidal nanochemistry are used to build complex functional unit cells in solution from an ensemble of simple building blocks, i.e., in most cases plasmonic nanoparticles. Achievable structures are characterized by a high degree of nominal order only on a short-range scale. The precise spatial arrangement across larger dimensions is not possible in most cases; leading essentially to amorphous structures. Such self-assembled nanostructures require novel analytical means to describe their properties, innovative designs of functional elements that possess a desired near- and far-field response, and entail genuine nanofabrication and characterization techniques. Eventually, novel applications have to be perceived that are adapted to the specifics of the self-assembled nanostructures. This review shall document recent progress in this field of research. Emphasis is put on bottom-up amorphous metamaterials. We document the state-of-the-art but also critically assess the problems that have to be overcome.

  13. Selective self-assembly of hexameric homo- and heteropolymetallic lanthanide wheels: synthesis, structure, and photophysical studies.

    PubMed

    Chen, Xiao-Yan; Bretonnière, Yann; Pécaut, Jacques; Imbert, Daniel; Bünzli, Jean-Claude; Mazzanti, Marinella

    2007-02-05

    A rational approach to the formation of pure heteropolymetallic lanthanide complexes that uses a two-step assembly strategy and exploits the different size requirements of the two metals included in the final structure is described. The investigation of the assembly of [LnL2](Otf) (L = 2,2':6',2' '-terpyridine-6-carboxylate) complexes into hexametallic rings hosting an additional hexacoordinated lanthanide cation was crucial for the development of this strategy. The formation and size of the cyclic assembly are controlled by the ionic radius and by the coordination number of the lanthanides. The rather high luminescence quantum yield of the heptaeuropium complex (25%) indicates that the ring structure is well adapted to include highly luminescent lanthanide complexes in nanosized architecture. The use of a stepwise synthetic strategy leads to the selective assembly of large heteropolymetallic rings. The addition of a smaller lanthanide ion to the [EuL2](Otf) complex in anhydrous acetonitrile leads selectively to heterometallic species with the Eu ions located on the peripheral sites and the smaller ion occupying only the central site. The high selectivity is the result of the different size requirements of the two metal sites present in the cyclic structure. The heterometallic structure of the isolated [Lu subset (EuL2)6](Otf)9 complex was confirmed by X-ray diffraction and by high resolution solid-state photophysical studies. The described synthetic approach allowed us to obtain the first example of selective assembly of two different lanthanide ions in a large polymetallic structure characterized in solution and in the solid state and will make the isolation of planned dimetallic combinations presenting different lanthanide emitters in the peripheral sites possible.

  14. Micro-Masonry: Construction of 3D Structures by Mesoscale Self-Assembly

    PubMed Central

    Fernandez, Javier G.; Khademhosseini, Ali

    2010-01-01

    A general method for construction of three dimensional structures by directed assembly of microscale polymeric sub-units is presented. Shape-controlled microgels are directed to assemble into different shapes by limiting their movement onto a molded substrate. The capillary forces, resulting from the presence of a liquid polymer, assemble the microgels in close contact with the rest of the units and with the free surface, the latter imposing the final geometry of the resulting construct. The result is a freestanding structure composed of one or multiple layers of sub-units assembled in a tightly packed conformation. The applicability of the technique for the construction of scaffolds with cell-laden sub-units is demonstrated. In addition, scaffolds formed by the sequential aggregation of sub-units are produced. PMID:20440697

  15. Adamantane-based oxacyclophanes containing pyrazines: synthesis, crystal structure, and self-assembly behavior.

    PubMed

    Tominaga, Masahide; Kunitomi, Nobuto; Katagiri, Kosuke; Itoh, Tsutomu

    2015-02-20

    Two adamantane-based oxacyclophanes were synthesized by the SNAr reaction of bis-phenol derivatives based on adamantane with 2,6-dichloropyrazine. Their crystal structures had distorted or twisted 1,3-alternate conformations. The oxacyclophanes indicated no formation of spherical aggregates in acetone. However, addition of water into the solution caused the generation of hollow spherical aggregates with a multilayer membrane. Over time, the hollow spheres were induced into fibrous and network assemblies, which were eventually transformed into single crystals.

  16. Self-assembly of metal-organic coordination structures on surfaces

    NASA Astrophysics Data System (ADS)

    Dong, Lei; Gao, Zi'Ang; Lin, Nian

    2016-08-01

    Metal-organic coordination structures are materials comprising reticular metal centers and organic linkers in which the two constituents bind with each other via metal-ligand coordination interaction. The underlying chemistry is more than a century old but has attracted tremendous attention in the last two decades owing to the rapidly development of metal-organic (or porous coordination) frameworks. These metal-coordination materials exhibit extraordinarily versatile topologies and many potential applications. Since 2002, this traditionally three-dimensional chemistry has been extended to two-dimensional space, that is, to synthesize metal-organic coordination structures directly on solid surfaces. This endeavor has made possible a wide range of so-called surface-confined metal-organic networks (SMONs) whose topology, composition, property and function can be tailored by applying the principle of rational design. The coordination chemistry manifests unique characteristics at the surfaces, and in turn the surfaces provide additional control for design structures and properties that are inaccessible in three-dimensional space. In this review, our goal is to comprehensively cover the progress made in the last 15 years in this rapidly developing field. The review summarizes (1) the experimental and theoretical techniques used in this field including scanning tunneling microscopy and spectroscopy, low-energy electron diffraction, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, density functional theory, and Monte Carlo and kinetic Monte Carlo simulation; (2) molecular ligands, metal atoms, substrates, and coordination motifs utilized for synthesizing SMON; (3) representative SMON structures with different topologies ranging from finite-size discrete clusters to one-dimensional chains, two-dimensional periodical frameworks and random networks; and (4) the properties and potential applications of SMONs. We conclude the review with some perspectives.

  17. Spontaneous self-assembly of engineered armadillo repeat protein fragments into a folded structure.

    PubMed

    Watson, Randall P; Christen, Martin T; Ewald, Christina; Bumbak, Fabian; Reichen, Christian; Mihajlovic, Maja; Schmidt, Elena; Güntert, Peter; Caflisch, Amedeo; Plückthun, Andreas; Zerbe, Oliver

    2014-07-08

    Repeat proteins are built of modules, each of which constitutes a structural motif. We have investigated whether fragments of a designed consensus armadillo repeat protein (ArmRP) recognize each other. We examined a split ArmRP consisting of an N-capping repeat (denoted Y), three internal repeats (M), and a C-capping repeat (A). We demonstrate that the C-terminal MA fragment adopts a fold similar to the corresponding part of the entire protein. In contrast, the N-terminal YM2 fragment constitutes a molten globule. The two fragments form a 1:1 YM2:MA complex with a nanomolar dissociation constant essentially identical to the crystal structure of the continuous YM3A protein. Molecular dynamics simulations show that the complex is structurally stable over a 1 μs timescale and reveal the importance of hydrophobic contacts across the interface. We propose that the existence of a stable complex recapitulates possible intermediates in the early evolution of these repeat proteins.

  18. Self-assembly of multi-stranded RNA motifs into lattices and tubular structures

    DOE PAGES

    Stewart, Jaimie Marie; Subramanian, Hari K. K.; Franco, Elisa

    2017-02-16

    Rational design of nucleic acidmolecules yields selfassembling scaffolds with increasing complexity, size and functionality. It is an open question whether design methods tailored to build DNA nanostructures can be adapted to build RNA nanostructures with comparable features. We demonstrate the formation of RNA lattices and tubular assemblies from double crossover (DX) tiles, a canonical motif in DNA nanotechnology. Tubular structures can exceed 1 m in length, suggesting that this DX motif can produce very robust lattices. Some of these tubes spontaneously form with left-handed chirality. We obtain assemblies by using two methods: a protocol where gel-extracted RNA strands are slowlymore » annealed, and a one-pot transcription and anneal procedure. We then identify the tile nick position as a structural requirement for lattice formation. These results demonstrate that stable RNA structures can be obtained with design tools imported from DNA nanotechnology. These large assemblies could be potentially integrated with a variety of functional RNA motifs for drug or nanoparticle delivery, or for colocalization of cellular components.« less

  19. Synchronous One-Pot (SOP) synthesis of hybrid structures: metal nanoparticles in self-assemblies of amphiphilic calix[6]biscrowns.

    PubMed

    Liang, Qing; Li, Changxi; Chen, Guosong; Jiang, Ming

    2012-10-01

    In this paper, we present a novel strategy, named Synchronous One-Pot (SOP) synthesis, to prepare gold nanoparticles (AuNPs) with a diameter of 2nm incorporated in self-assembled organic spheres with a diameter around 60nm (denoted as NPAs). Merits of this method include: (1) self-assembly of the organic component (calix[6]biscrown TAC) into spheres and the reduction of chloroauric acid (HAuCl(4)) take place simultaneously; (2) preparation combining UV irradiation and formaldehyde addition reduces the size and homogenizes the distribution of the resultant AuNPs within the TAC spheres. (3) Obtained material NPA gives attractive catalytic property to hydrogenation reaction.

  20. The structure of monomeric components of self-assembling CXCR4 antagonists determines the architecture of resulting nanostructures

    NASA Astrophysics Data System (ADS)

    Lee, Youngshim; Chen, Yuhong; Tarasova, Nadya I.; Gaponenko, Vadim

    2011-12-01

    Self-assembling peptides play increasingly important roles in the development of novel materials and drug delivery vehicles. Understanding mechanisms governing the assembly of nanoarchitectures is essential for the generation of peptide-based nanodevices. We find that a cone-shaped derivative of the second transmembrane domain of CXCR4 receptor, x4-2-6 self-assembles into nanospheres, while a related cylindrical peptide, x4-2-9 forms fibrils. Stronger intermolecular interactions in nanospheres than in fibrils result in slow rates of particle disassembly and protection against proteolytic degradation.

  1. Computing by molecular self-assembly.

    PubMed

    Jonoska, Nataša; Seeman, Nadrian C

    2012-08-06

    The paper reviews two computing models by DNA self-assembly whose proof of principal have recently been experimentally confirmed. The first model incorporates DNA nano-devices and triple crossover DNA molecules to algorithmically arrange non-DNA species. This is achieved by simulating a finite-state automaton with output where golden nanoparticles are assembled to read-out the result. In the second model, a complex DNA molecule representing a graph emerges as a solution of a computational problem. This supports the idea that in molecular self-assembly computing, it may be necessary to develop the notion of shape processing besides the classical approach through symbol processing.

  2. Assessing the utility of infrared spectroscopy as a structural diagnostic tool for β-sheets in self-assembling aromatic peptide amphiphiles.

    PubMed

    Fleming, Scott; Frederix, Pim W J M; Ramos Sasselli, Iván; Hunt, Neil T; Ulijn, Rein V; Tuttle, Tell

    2013-07-30

    β-Sheets are a commonly found structural motif in self-assembling aromatic peptide amphiphiles, and their characteristic "amide I" infrared (IR) absorption bands are routinely used to support the formation of supramolecular structure. In this paper, we assess the utility of IR spectroscopy as a structural diagnostic tool for this class of self-assembling systems. Using 9-fluorene-methyloxycarbonyl dialanine (Fmoc-AA) and the analogous 9-fluorene-methylcarbonyl dialanine (Fmc-AA) as examples, we show that the origin of the band around 1680-1695 cm(-1) in Fourier transform infrared (FTIR) spectra, which was previously assigned to an antiparallel β-sheet conformation, is in fact absorption of the stacked carbamate group in Fmoc-peptides. IR spectra from (13)C-labeled samples support our conclusions. In addition, DFT frequency calculations on small stacks of aromatic peptides help to rationalize these results in terms of the individual vibrational modes.

  3. Role of solution structure in self-assembly of conjugated block copolymer thin films

    DOE PAGES

    Brady, Michael A.; Ku, Sung -Yu; Perez, Louis A.; ...

    2016-10-24

    Conjugated block copolymers provide a pathway to achieve thermally stable nanostructured thin films for organic solar cells. We characterized the structural evolution of poly(3-hexylthiophene)-block-poly(diketopyrrolopyrrole–terthiophene) (P3HT-b-DPPT-T) from solution to nanostructured thin films. Aggregation of the DPPT-T block of P3HT-b-DPPT-T was found in solution by small-angle X-ray scattering with the P3HT block remaining well-solvated. The nanostructure in thin films was determined using a combination of wide and small-angle X-ray scattering techniques as a function of processing conditions. The structure in solution controlled the initial nanostructure in spin-cast thin films, allowing subsequent thermal annealing processes to further improve the ordering. In contrast tomore » the results for thin films, nanostructural ordering was not observed in the bulk samples by small-angle X-ray scattering. Finally, these results suggest the importance of controlling solvent induced aggregation in forming nanostructured thin films of conjugated block copolymers.« less

  4. Dissipative particle dynamics study on self-assembled platycodin structures: the potential biocarriers for drug delivery.

    PubMed

    Dai, Xingxing; Ding, Haiou; Yin, Qianqian; Wan, Guang; Shi, Xinyuan; Qiao, Yanjiang

    2015-04-01

    Platycodin, as a kind of plant based biosurfactants, are saponins which derived from the root of Platycodon grandiflorum A. DC. It has been confirmed that platycodin have the potential to enhance the solubility of hydrophobic drugs and function as the drug carrier, which depends on their micellization over critical micelle concentration (CMC) in aqueous solutions. With the purpose of investigating the effects of influencing factors on the micellization behavior of platycodin and obtaining the phase behavior details at a mesoscopic level, dissipative particle dynamics (DPD) simulations method has been adopted in this study. The simulations reveal that a rich variety of aggregates morphologies will appear with changes of structure or the concentration of saponins, including spherical, ellipse and oblate micelles and vesicles, multilamellar vesicles (MLVs), multicompartment vesicles (MCMs), tubular and necklace-like micelle. They can be formed spontaneously from a randomly generated initial state and the result has been represented in the phase diagrams. Furthermore, deeper explorations have been done on the concentration-dependent structure variation of spherical vesicles as well as the formation mechanism of MLVs. This work provides insight into the solubilization system formed by platycodin, and may serve as guidance for further development and application in pharmaceutical field of platycodin and other saponins.

  5. Role of solution structure in self-assembly of conjugated block copolymer thin films

    SciTech Connect

    Brady, Michael A.; Ku, Sung -Yu; Perez, Louis A.; Cochran, Justin E.; Schmidt, Kristin; Weiss, Thomas M.; Toney, Michael F.; Ade, Harald; Hexemer, Alexander; Wang, Cheng; Hawker, Craig J.; Kramer, Edward J.; Chabinyc, Michael L.

    2016-10-24

    Conjugated block copolymers provide a pathway to achieve thermally stable nanostructured thin films for organic solar cells. We characterized the structural evolution of poly(3-hexylthiophene)-block-poly(diketopyrrolopyrrole–terthiophene) (P3HT-b-DPPT-T) from solution to nanostructured thin films. Aggregation of the DPPT-T block of P3HT-b-DPPT-T was found in solution by small-angle X-ray scattering with the P3HT block remaining well-solvated. The nanostructure in thin films was determined using a combination of wide and small-angle X-ray scattering techniques as a function of processing conditions. The structure in solution controlled the initial nanostructure in spin-cast thin films, allowing subsequent thermal annealing processes to further improve the ordering. In contrast to the results for thin films, nanostructural ordering was not observed in the bulk samples by small-angle X-ray scattering. Finally, these results suggest the importance of controlling solvent induced aggregation in forming nanostructured thin films of conjugated block copolymers.

  6. Role of solution structure in self-assembly of conjugated block copolymer thin films

    DOE PAGES

    Brady, Michael A.; Ku, Sung -Yu; Perez, Louis A.; ...

    2016-10-24

    Conjugated block copolymers provide a pathway to achieve thermally stable nanostructured thin films for organic solar cells. We characterized the structural evolution of poly(3-hexylthiophene)-block-poly(diketopyrrolopyrrole–terthiophene) (P3HT-b-DPPT-T) from solution to nanostructured thin films. Aggregation of the DPPT-T block of P3HT-b-DPPT-T was found in solution by small-angle X-ray scattering with the P3HT block remaining well-solvated. The nanostructure in thin films was determined using a combination of wide and small-angle X-ray scattering techniques as a function of processing conditions. The structure in solution controlled the initial nanostructure in spin-cast thin films, allowing subsequent thermal annealing processes to further improve the ordering. In contrast tomore » the results for thin films, nanostructural ordering was not observed in the bulk samples by small-angle X-ray scattering. Finally, these results suggest the importance of controlling solvent induced aggregation in forming nanostructured thin films of conjugated block copolymers.« less

  7. Investigating phase separation and structural coloration of self-assembled ternary polymer thin films

    NASA Astrophysics Data System (ADS)

    Vohra, Varun; Galeotti, Francesco; Giovanella, Umberto; Anzai, Takuya; Kozma, Erika; Botta, Chiara

    2016-09-01

    Poly(3-hexylthiophene-2,5-diyl) (P3HT) can generate nanoporous structures with variable pore diameters ranging from 150 to 600 nm from spin-coated blends with polystyrene (PS). In the present study, we observe the effect of the addition of polymethylmethacrylate (PMMA) to P3HT:PS blends to increase the pore-to-pore dimensions up to the micrometer scale. The phase separation in the ternary blend can be directly visualized by replacing the commercial (non-emissive) PS with a boron-dipyrromethene functionalized PS to distinctively locate the red-emitting P3HT and the green-emitting PS phases. In particular, in the ternary blend with high PMMA contents, we observe that PS acts as a compatibilizing agent at the interface between the P3HT and PMMA phases. After selective removal of the PS and PMMA phases using acetone, we demonstrate that, in these P3HT structured thin films, iridescence can be observed as they exhibit angle dependent reflectivity which is further emphasized when covered with a thin metal layer. The metal covered nanostructured P3HT films display bright color switching properties with blue and red emission at low and high reflection angles, respectively.

  8. Aqueous-based spinning of fibers from self-assembling structural proteins.

    PubMed

    Arcidiacono, Steven; Welsh, Elizabeth A; Soares, Jason W

    2013-01-01

    There has been long-standing interest in generating fibers from structural proteins and a great deal of work has been done in attempting to mimic dragline spider silk. Dragline silk balances stiffness, strength, extensibility, and high energy to break. Mimicking these properties through aqueous-based spinning of recombinant silk protein is a significant challenge; however, an approach has been developed that facilitates the formation of fibers approaching the mechanical properties seen with natural dragline silk. Due to the multitude of solution, spinning and post-spinning variables one has to consider, the method entails a multivariate approach to protein solution processing and fiber spinning. Optimization to maximize mechanical integrity of the fibers is performed by correlating the solution and spinning variables to mechanical properties and using this information for subsequent fiber spinning studies. Here, the method is described in detail and emphasizes the lessons learned during the iterative variable analysis process, which can be used as a basis for aqueous-based fiber spinning of other structural proteins.

  9. Plasma modification of self-assembled structures of CoTMPP molecules

    NASA Astrophysics Data System (ADS)

    Savastenko, N. A.; Brüser, V.

    2011-02-01

    Plasma-treated cobalt metalloporphyrins have recently been proposed as electrocatalysts for the oxygen and oxygen peroxide reduction reaction. Whereas the effects of plasma treatment on the elemental composition of the surface of catalysts have been investigated, the effects of plasma treatment on the morphology of catalysts have not yet been studied. In this study, plasma modified nanosized structures of cobalt tetramethoxyphenylporphyrin (CoTMPP) molecules arising from the deposition of a porphyrin solution on an a-C:H film are investigated using an atomic force microscope (AFM). Additionally, the effects of plasma treatment on the structure of porphyrin molecules are studied by using ultra violet visible (UV-vis) absorption analysis. The investigations reveal the morphological changes which accompany the transformation of CoTMPP into the final catalytic material. First, the large CoTMPP aggregates are split into smaller ones. Second, the CoTMPP layer appears to be sublimated after plasma treatment. Sublimated CoTMPP molecules can be decomposed by plasma and after redeposition can form catalytic active fragments.

  10. Bile acid-derived mono- and diketals--synthesis, structural characterization and self-assembling properties.

    PubMed

    Ikonen, Satu; Nonappa; Valkonen, Arto; Juvonen, Raija; Salo, Hannu; Kolehmainen, Erkki

    2010-06-21

    Three oxo-derivatives of bile acid methyl esters have been used as starting compounds in the preparation of novel bile acid monoketals with 1,2-benzenediol (catechol) and 2,3-naphthalenediol, as well as mono- and diketals with pentaerythritol. Monoketals of pentaerythritol showed a tendency to form thermoreversible gels in many aromatic solvents and the methyl lithocholate derivative proved to be a supergelator able to form a gel with t-butylbenzene at a concentration as low as 0.5% w/v. Whereas the naphthalenediol ketals formed film-type materials in the studied solvents, the catechol ketals underwent rapid crystallization into X-ray quality single crystals. Single crystal X-ray structures of the catechol ketals have been determined. The monoketal obtained from methyl-3,7,12-trioxo-5beta-cholan-24-oate (dehydrocholate) revealed to have an unusual packing pattern in its solid state compared to other bile acid derivatives reported in the literature. The synthesis of diketals from pentaerythritol furnished a mixture of two diastereomers which, in the case of the methyl lithocholate derivative, have been separated and the X-ray crystal structure of one isomer resolved.

  11. Role of solution structure in self-assembly of conjugated block copolymer thin films

    SciTech Connect

    Brady, Michael A.; Ku, Sung -Yu; Perez, Louis A.; Cochran, Justin E.; Schmidt, Kristin; Weiss, Thomas M.; Toney, Michael F.; Ade, Harald; Hexemer, Alexander; Wang, Cheng; Hawker, Craig J.; Kramer, Edward J.; Chabinyc, Michael L.

    2016-10-24

    Conjugated block copolymers provide a pathway to achieve thermally stable nanostructured thin films for organic solar cells. We characterized the structural evolution of poly(3-hexylthiophene)-block-poly(diketopyrrolopyrrole–terthiophene) (P3HT-b-DPPT-T) from solution to nanostructured thin films. Aggregation of the DPPT-T block of P3HT-b-DPPT-T was found in solution by small-angle X-ray scattering with the P3HT block remaining well-solvated. The nanostructure in thin films was determined using a combination of wide and small-angle X-ray scattering techniques as a function of processing conditions. The structure in solution controlled the initial nanostructure in spin-cast thin films, allowing subsequent thermal annealing processes to further improve the ordering. In contrast to the results for thin films, nanostructural ordering was not observed in the bulk samples by small-angle X-ray scattering. Finally, these results suggest the importance of controlling solvent induced aggregation in forming nanostructured thin films of conjugated block copolymers.

  12. Some Structural Observations of Self-Assembling, Fibrillar Gels Composed of Two-Directional Bolaform Arborols

    SciTech Connect

    Sun, J.

    2005-01-12

    Arborols are dumbbell shaped molecules (bolaform amphiphiles) in which a hydrophobic spacer separates two hydrophilic end groups. They are a valuable model for naturally occurring fibers, such as actin or amyloid. Applications to materials science can be envisioned. On cooling from warm aqueous or methanolic solutions, arborols spontaneously assemble into long fibers. When the solutions are above a certain concentration that depends on the hydrophilic/hydrophobic balance, this leads to thermally reversible gels stabilized by a mechanism that is poorly understood. With the help of wide angle X-ray scattering, details of the arborol fiber and gel structure were obtained on wet gels. The characteristic dimensions of the fibers vary in a sensible fashion with the molecular specifics. Solvent character appears to affect the average domain length of arborols stacked into fibers. Fluorescently labeled arborols were prepared. The label does not prevent incorporation into the fibrillar structure, rendering fibril bundles visible in wet gels. Bundles are visible in concentrated gels, but not in less concentrated sols. These results are consistent with observations of dried arborols using atomic force microscopy and with previously published freeze-fracture electron microscopy and small angle X-ray scattering experiments on dried gels.

  13. Micro-structured inverted pyramid texturization of Si inspired by self-assembled Cu nanoparticles.

    PubMed

    Wang, Yan; Liu, Yaoping; Yang, Lixia; Chen, Wei; Du, Xiaolong; Kuznetsov, Andrej

    2017-01-05

    A superior micron-sized inverted pyramid structure has been successfully achieved by one-step copper nanoparticles assisted chemical etching in Si/Cu(NO3)2/HF/H2O2 solution for light trapping in silicon solar cells. The detailed mechanisms of such a novel method have been systematically demonstrated. The charge transfer during the reaction has been revealed by the simplified energy band diagram of the system as well. In order to form micro-structured inverted pyramids, the generation and dissolution of Cu nanoparticles should keep in balance during the reaction, which depends on the concentration of the etchant, the doping type and the doping level of the silicon substrate. With the investigation of the intrinsic properties of the silicon substrate, the etching rate is found out as a combined result of the electron concentration and the defect density of the substrate, as well as the potential barrier on the interface of Si/Cu nanoparticles. Furthermore, the anisotropic nature of Cu assisted chemical etching has also been investigated.

  14. Advances in Nanostructured Materials via Templated Sol-Gel Structure Control and Self-Assembly

    NASA Astrophysics Data System (ADS)

    Rudisill, Stephen G.

    This dissertation describes a body of work focused on understanding and improving morphology control of nanoporous structures via their aqueous chemistry. Synthesis of materials was carried out primarily using the Pechini process with metal nitrates and colloidal crystal templates. CeO2 and CeO 2-derived compounds were used for a substantial portion of the dissertation as they are useful for thermochemical cycling experiments. Templated CeO 2 shows a tenfold improvement over an untemplated material as well as a nanoparticle powder under lab-scale thermochemical cycling experiments. The Pechini process itself was then investigated as a means to obtain greater structural control over colloidal crystal templated materials. The process was demonstrated to involve phase separation, which allowed for the production of microspheres and bicontinuous networks of templated CeO 2-based solids. Microspheres produced were between 1--3 microm in size, with polydispersity less than 15%. Further experimentation demonstrated that this phase separation methodology was generalizable to Fe2O 3 and Mn3O4, though higher polydispersities were obtained for these materials. The final research project accomplished in this dissertation involves a method to produce ordered collagen fibrils through the incorporation of nanocrystalline cellulose during fibrillogenesis. Results were verified via scanning electron microscopy and a mechanism was proposed based on infrared spectroscopy results indicating a decrease in collagen-collagen hydrogen bonding.

  15. Structure, Function, Self-Assembly and Origin of Simple Membrane Proteins

    NASA Technical Reports Server (NTRS)

    Pohorille, Andrew

    2003-01-01

    Integral membrane proteins perform such essential cellular functions as transport of ions, nutrients and waste products across cell walls, transduction of environmental signals, regulation of cell fusion, recognition of other cells, energy capture and its conversion into high-energy compounds. In fact, 30-40% of genes in modem organisms codes for membrane proteins. Although contemporary membrane proteins or their functional assemblies can be quite complex, their transmembrane fragments are usually remarkably simple. The most common structural motif for these fragments is a bundle of alpha-helices, but occasionally it could be a beta-barrel. In a series of molecular dynamics computer simulations we investigated self-organizing properties of simple membrane proteins based on these structural motifs. Specifically, we studied folding and insertion into membranes of short, nonpolar or amphiphatic peptides. We also investigated glycophorin A, a peptide that forms sequence-specific dimers, and a transmembrane aggregate of four identical alpha-helices that forms an efficient and selective voltage-gated proton channel was investigated. Many peptides are attracted to water-membrane interfaces. Once at the interface, nonpolar peptides spontaneously fold to a-helices. Whenever the sequence permits, peptides that contain both polar and nonpolar amino also adopt helical structures, in which polar and nonpolar amino acid side chains are immersed in water and membrane, respectively. Specific identity of side chains is less important. Helical peptides at the interface could insert into the membrane and adopt a transmembrane conformation. However, insertion of a single helix is unfavorable because polar groups in the peptide become completely dehydrated upon insertion. The unfavorable free energy of insertion can be regained by spontaneous association of peptides in the membrane. The first step in this process is the formation of dimers, although the most common are aggregates of 4

  16. Structure, Function, Self-Assembly and Origin of Simple Membrane Proteins

    NASA Technical Reports Server (NTRS)

    Pohorille, Andrew

    2003-01-01

    Integral membrane proteins perform such essential cellular functions as transport of ions, nutrients and waste products across cell walls, transduction of environmental signals, regulation of cell fusion, recognition of other cells, energy capture and its conversion into high-energy compounds. In fact, 30-40% of genes in modem organisms codes for membrane proteins. Although contemporary membrane proteins or their functional assemblies can be quite complex, their transmembrane fragments are usually remarkably simple. The most common structural motif for these fragments is a bundle of alpha-helices, but occasionally it could be a beta-barrel. In a series of molecular dynamics computer simulations we investigated self-organizing properties of simple membrane proteins based on these structural motifs. Specifically, we studied folding and insertion into membranes of short, nonpolar or amphiphatic peptides. We also investigated glycophorin A, a peptide that forms sequence-specific dimers, and a transmembrane aggregate of four identical alpha-helices that forms an efficient and selective voltage-gated proton channel was investigated. Many peptides are attracted to water-membrane interfaces. Once at the interface, nonpolar peptides spontaneously fold to a-helices. Whenever the sequence permits, peptides that contain both polar and nonpolar amino also adopt helical structures, in which polar and nonpolar amino acid side chains are immersed in water and membrane, respectively. Specific identity of side chains is less important. Helical peptides at the interface could insert into the membrane and adopt a transmembrane conformation. However, insertion of a single helix is unfavorable because polar groups in the peptide become completely dehydrated upon insertion. The unfavorable free energy of insertion can be regained by spontaneous association of peptides in the membrane. The first step in this process is the formation of dimers, although the most common are aggregates of 4

  17. Tandem SAM Domain Structure of Human Caskin1: A Presynaptic, Self-Assembling Scaffold for CASK

    SciTech Connect

    Stafford, Ryan L.; Hinde, Elizabeth; Knight, Mary Jane; Pennella, Mario A.; Ear, Jason; Digman, Michelle A.; Gratton, Enrico; Bowie, James U.

    2012-02-07

    The synaptic scaffolding proteins CASK and Caskin1 are part of the fibrous mesh of proteins that organize the active zones of neural synapses. CASK binds to a region of Caskin1 called the CASK interaction domain (CID). Adjacent to the CID, Caskin1 contains two tandem sterile a motif (SAM) domains. Many SAM domains form polymers so they are good candidates for forming the fibrous structures seen in the active zone. We show here that the SAM domains of Caskin1 form a new type of SAM helical polymer. The Caskin1 polymer interface exhibits a remarkable segregation of charged residues, resulting in a high sensitivity to ionic strength in vitro. The Caskin1 polymers can be decorated with CASK proteins, illustrating how these proteins may work together to organize the cytomatrix in active zones.

  18. Structural control of gold nanoparticles self-assemblies by layer-by-layer process.

    PubMed

    Machado, Giovanna; Feil, Adriano F; Migowski, Pedro; Rossi, Liane; Giovanela, Marcelo; Crespo, Janaina da S; Miotti, Leonardo; Sortica, Maurício A; Grande, Pedro L; Pereira, Marcelo B; Correia, Ricardo R B

    2011-04-01

    This work presents a novel way to introduce gold nanoparticles (Au NPs) in a multilayer polymer produced by the layer-by-layer (LbL) assembling technique. The technique chosen shows that, depending on the pH used, different morphological structures can be obtained from monolayer or bilayer Au NPs. The MEIS and RBS techniques allowed for the modelling of the interface polymer-NPs, as well as the understanding of the interaction of LbL system, when adjusting the pH in weak polyelectrolytes. The process reveals that the optical properties of multilayer systems could be fine-tuned by controlling the addition of metallic nanoparticles, which could also modify specific polarization responses.

  19. Self-Assembly of AB Diblock Copolymer Confined in a Soft Nano-Droplet: A Combination Study by Monte Carlo Simulation and Experiment.

    PubMed

    Yan, Nan; Zhu, Yutian; Jiang, Wei

    2016-11-23

    The self-assembly of AB-type diblock copolymers confined in a three-dimensional (3D) soft nanodroplet is investigated by the combination of Monte Carlo simulation and experiment. The influences of two critical factors, i.e., confinement degree of the imposed confinement space and the interfacial interaction between each individual block and boundary interface, on the 3D soft confined self-assembly are examined systematically. The simulation results reveal that block copolymer chains become more and more folded as the confinement degree (it can be monitored by the ratio of D/L, where L is the length of polymer chain and D is the reduced diameter of the final polymeric particle) is enhanced, causing a series of morphological transitions. Based on the simulation prediction, we perform the corresponding experiments by the 3D confined self-assembly of both symmetric and asymmetric block copolymers within the emulsion droplets. The experimental results well reproduce the confinement degree induced morphological transitions predicted by the simulations, such as the transition from segmented pupa-like particle to hamburger particle and the transition from raspberry-like particle to triangle-like particle, and then to hamburger particle. The current study implies that self-assembled nanostructures under 3D soft confinement can be simply controlled by tuning the confinement degree and interfacial property, i.e., the ratio of D/L and the interfacial interaction between each individual block and boundary interface.

  20. Self-assembled magnetocapillary swimmers

    NASA Astrophysics Data System (ADS)

    Hubert, Maxime