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Sample records for nanosphere self-assembly initiated

  1. A Solution NMR Investigation into the Early Events of Amelogenin Nanosphere Self-Assembly Initiated with Sodium Chloride or Calcium Chloride†

    PubMed Central

    Buchko, Garry W.; Tarasevich, Barbara J.; Bekhazi, Jacky; Snead, Malcolm L.; Shaw, Wendy J.

    2009-01-01

    Using solution-state NMR spectroscopy, new insights into the early events governing amelogenin supramolecular self-assembly have been identified using sodium chloride and calcium chloride to trigger the association. Two-dimensional 1H–15N HSQC spectra were recorded for 15N- and 13C-labeled murine amelogenin as a function of increasing NaCl and CaCl2 concentration beginning with solution conditions of 2% acetic acid at pH 3.0, where amelogenin was monomeric. Residue specific changes in molecular dynamics, manifested by the reduction in intensity and disappearance of 1H–15N HSQC cross-peaks, were observed with the addition of either salt to the protein. With increasing NaCl concentrations, residues between T21 and R31 near the N-terminus were affected first, suggesting that these residues may initiate amelogenin dimerization, the first step in nanosphere assembly. At higher NaCl concentrations, more residues near the N-terminus (Y12–I51) were affected, and with further additions of NaCl, residues near the C-terminus (L141–T171) began to show a similar change in molecular dynamics. With increasing CaCl2 concentrations, a similar stepwise change in molecular dynamics involving essentially the same set of amelogenin residues was observed. As the concentration of either salt was increased, a concomitant increase in the estimated overall rotational correlation time (τc) was observed, consistent with assembly. Self-assembly into a dimer or trimer was established with dynamic light scattering studies under similar conditions that showed an increase in diameter of the smallest species from 4.1 nm in the absence of salt to ~10 nm in the presence of salt. These results suggest a possible stepwise interaction mechanism, starting with the N-terminus and followed by the C-terminus, leading to amelogenin nanosphere assembly. PMID:19086270

  2. A solution NMR investigation into the early events of amelogenin nanosphere self-assembly initiated with sodium chloride or calcium chloride.

    PubMed

    Buchko, Garry W; Tarasevich, Barbara J; Bekhazi, Jacky; Snead, Malcolm L; Shaw, Wendy J

    2008-12-16

    Using solution-state NMR spectroscopy, new insights into the early events governing amelogenin supramolecular self-assembly have been identified using sodium chloride and calcium chloride to trigger the association. Two-dimensional 1H-15N HSQC spectra were recorded for 15N- and 13C-labeled murine amelogenin as a function of increasing NaCl and CaCl2 concentration beginning with solution conditions of 2% acetic acid at pH 3.0, where amelogenin was monomeric. Residue specific changes in molecular dynamics, manifested by the reduction in intensity and disappearance of 1H-15N HSQC cross-peaks, were observed with the addition of either salt to the protein. With increasing NaCl concentrations, residues between T21 and R31 near the N-terminus were affected first, suggesting that these residues may initiate amelogenin dimerization, the first step in nanosphere assembly. At higher NaCl concentrations, more residues near the N-terminus (Y12-I51) were affected, and with further additions of NaCl, residues near the C-terminus (L141-T171) began to show a similar change in molecular dynamics. With increasing CaCl2 concentrations, a similar stepwise change in molecular dynamics involving essentially the same set of amelogenin residues was observed. As the concentration of either salt was increased, a concomitant increase in the estimated overall rotational correlation time (tau(c)) was observed, consistent with assembly. Self-assembly into a dimer or trimer was established with dynamic light scattering studies under similar conditions that showed an increase in diameter of the smallest species from 4.1 nm in the absence of salt to 10 nm in the presence of salt. These results suggest a possible stepwise interaction mechanism, starting with the N-terminus and followed by the C-terminus, leading to amelogenin nanosphere assembly.

  3. Self-assembled hollow nanospheres strongly enhance photoluminescence.

    PubMed

    Ke, Damei; Zhan, Chuanlang; Xu, Shuangping; Ding, Xunlei; Peng, Aidong; Sun, Jin; He, Shenggui; Li, Alexander D Q; Yao, Jiannian

    2011-07-27

    We report that two molecular building blocks differ only by two protons, yet they form totally different nanostructures. The protonated one self-organized into hollow nanospheres (~200 nm), whereas the one without the protons self-assembled into rectangular plates. Consequently, the geometrically defined nanoassemblies exhibit radically different properties. As self-assembly directing units, protons impart ion-pairing and hydrogen-bonding probabilities. The plate-forming nanosystem fluoresces weakly, probably due to energy transfer among chromophores (Φ < 0.2), but the nanospheres emit strong yellow fluorescence (Φ ≈ 0.58-0.85).

  4. A Solution NMR Investigation into the Early Events of Amelogenin Nanosphere Self-Assembly Initiated with Sodium Chloride or Calcium Chloride

    SciTech Connect

    Buchko, Garry W.; Tarasevich, Barbara J.; Bekhazi, Jacky G.; Snead, Malcolm L.; Shaw, Wendy J.

    2008-12-08

    Using solution-state NMR spectroscopy, new insights into the early intermolecular interactions stabilizing amelogenin supramolecular assembly and the potential role of calcium ions have been discovered. Two-dimensional 1H-15N spectra were recorded for 15N-labeled amelogenin as a function of increasing Ca2+ concentration starting from monomeric conditions. Evidence for protein-protein interactions were observed between residues E18 and E40 in the N-terminus. At higher Ca2+ concentrations there was concurrent involvement of residues in both the N- (Y12-Q56) and the C-terminus (Q144-T171). Neither specific residues nor their stepwise interaction have previously been identified in the initial stages of nanosphere assembly.

  5. One-pot synthesis, optical property and self-assembly of monodisperse silver nanospheres

    SciTech Connect

    Tang Aiwei; Qu Shengchun; Hou Yanbing; Teng Feng; Wang Yongsheng; Wang Zhanguo

    2011-08-15

    High-quality spherical silver (Ag) nanocrystals have been synthesized by using a one-pot approach, in which pre-synthesis of organometallic precursors is not required. This reaction involves the thermolysis of a mixed solution of silver acetate and n-dodecanethiol in a non-coordinating organic solvent. The size of the as-obtained Ag nanospheres can be controlled by adjusting the reaction time, reaction temperature and the amount of silver acetate added. The growth and nucleation process of the resultant Ag nanospheres have been studied by employing UV-vis absorption spectra and transmission electron microscopy (TEM) images. Furthermore, these Ag nanospheres have good self-assembly behaviors, and they are easily self-assembled into two- or three-dimensional superlattice structures due to the bundling and interdigitation of thiolate molecules adsorbed on Ag nanospheres. This one-pot synthetic procedure is simple and highly reproducible, which may be extended to prepare other noble-metal nanocrystals. - Graphical abstract: Different sized and monodisperse silver nanospheres were prepared using a one-pot approach with no pre-synthesis of organometallic precursors, and the silver nanospheres can self-assemble into highly ordered superlattices. Highlights: > Monodisperse silver nanospheres have been synthesized by a one-pot approach. > The synthetic method does not need pre-synthesis of organometallic precursors. > The silver nanospheres can self-assemble into highly ordered superlattices. > This synthetic method can be extended to prepare other metal nanocrystals.

  6. Close-packed monolayer self-assembly of silica nanospheres assisted by infrared irradiation

    NASA Astrophysics Data System (ADS)

    Minh, Nguyen Van; Hue, Nguyen Thi; Lien, Nghiem Thi Ha; Hoang, Chu Manh

    2017-08-01

    In this paper, we report on a fast and cost-effective drop coating technique for the self-assembly of silica nano-spheres from a mono-dispersed colloidal suspension into close-packed monolayer (CMP) on hydrophilic single-crystal silicon substrate. The technique includes the self-assembly of silica nano-spheres on slanted silicon substrate and infrared irradiation during evaporation process of the coated droplet. The influence of the substrate slant angle and infrared irradiation on the formation of silica nano-sphere monolayer is investigated. This achievement is promising for various applications, such as a mask layer for nano-sphere lithography that is employed for producing fundamental elements in photonics, plasmonics, and solar cell. [Figure not available: see fulltext.

  7. Kinetically controlled self-assembly of redox-active ferrocene-diphenylalanine: from nanospheres to nanofibers.

    PubMed

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

    2013-11-22

    Putting metals into organic compounds such as peptides can lead to many new desirable properties. Here we designed a novel bioorganometallic molecule, ferrocene-diphenylalanine (Fc-FF), and investigated its self-assembly behavior. We directly observed a morphological transition from metastable nanospheres to nanofibers, which led to the formation of a self-supporting hydrogel. The strong hydrophobic interaction of the Fc moiety was suggested to have a key role in this kinetically controlled self-assembly process. Moreover, the redox center of the ferrocene group further allowed us to reversibly control the self-assembly behavior of Fc-FF by altering its redox state.

  8. Kinetically controlled self-assembly of redox-active ferrocene-diphenylalanine: from nanospheres to nanofibers

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

    Putting metals into organic compounds such as peptides can lead to many new desirable properties. Here we designed a novel bioorganometallic molecule, ferrocene-diphenylalanine (Fc-FF), and investigated its self-assembly behavior. We directly observed a morphological transition from metastable nanospheres to nanofibers, which led to the formation of a self-supporting hydrogel. The strong hydrophobic interaction of the Fc moiety was suggested to have a key role in this kinetically controlled self-assembly process. Moreover, the redox center of the ferrocene group further allowed us to reversibly control the self-assembly behavior of Fc-FF by altering its redox state.

  9. Amphiphilic Graft Copolymer Nanospheres: From Colloidal Self-Assembly to CO2 Capture Membranes.

    PubMed

    Jeon, Harim; Kim, Dong Jun; Park, Min Su; Ryu, Du Yeol; Kim, Jong Hak

    2016-04-13

    Colloidal nanosphere self-assembly effectively generates ordered nanostructures, prompting tremendous interest in many applications such as photonic crystals and templates for inverse opal fabrication. Here we report the self-assembly of low-cost, graft copolymer nanospheres for CO2 capture membranes. Specifically, poly(dimethylsiloxane)-graft-poly(4-vinylpyridine) (PDMS-g-P4VP) is synthesized via one-pot, free radical dispersion polymerization to give discrete monodisperse nanospheres. These nanospheres comprise a surface-anchored highly permeable PDMS layer and internal CO2-philic P4VP spherical core. Their diameter is controllable below the submicrometer range by varying grafting ratios. The colloidal dispersion forms a long-range, close-packed hexagonal array on a substrate by inclined deposition and convective assembly. The array shows dispersion medium-dependent packing characteristics. A thermodynamic correlation is determined using different solvents to obtain stable PDMS-g-P4VP dispersions and interpreted in terms of Flory-Huggins interaction parameter. As a proof-of-concept, the implementation of these nanospheres into membranes simultaneously enhances the CO2 permeability and CO2/N2 selectivity of PDMS-based transport matrixes. Upon physical aging of the solution, the CO2/N2 selectivity is improved up to 26, one of the highest values for highly permeable PDMS-based polymeric membranes.

  10. 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

  11. Peptide nanospheres self-assembled from a modified β-annulus peptide of Sesbania mosaic virus.

    PubMed

    Matsuura, Kazunori; Mizuguchi, Yusaku; Kimizuka, Nobuo

    2016-11-04

    A novel β-annulus peptide of Sesbania mosaic virus bearing an FKFE sequence at the C terminus was synthesized, and its self-assembling behavior in water was investigated. Dynamic light scattering and transmission electron microscopy showed that the β-annulus peptide bearing an FKFE sequence self-assembled into approximately 30 nm nanospheres in water at pH 3.8, whereas the β-annulus peptide without the FKFE sequence afforded only irregular aggregates. The peptide nanospheres possessed a definite critical aggregation concentration (CAC = 26 μM), above which the size of nanospheres were nearly unaffected by the peptide concentration. The formation of peptide nanospheres was significantly affected by pH; the peptide did not form any assemblies at pH 2.2, whereas larger aggregates were formed at pH 6.4-11.6. © 2015 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 470-475, 2016. © 2015 Wiley Periodicals, Inc.

  12. Initial condition of stochastic self-assembly

    NASA Astrophysics Data System (ADS)

    Davis, Jason K.; Sindi, Suzanne S.

    2016-02-01

    The formation of a stable protein aggregate is regarded as the rate limiting step in the establishment of prion diseases. In these systems, once aggregates reach a critical size the growth process accelerates and thus the waiting time until the appearance of the first critically sized aggregate is a key determinant of disease onset. In addition to prion diseases, aggregation and nucleation is a central step of many physical, chemical, and biological process. Previous studies have examined the first-arrival time at a critical nucleus size during homogeneous self-assembly under the assumption that at time t =0 the system was in the all-monomer state. However, in order to compare to in vivo biological experiments where protein constituents inherited by a newly born cell likely contain intermediate aggregates, other possibilities must be considered. We consider one such possibility by conditioning the unique ergodic size distribution on subcritical aggregate sizes; this least-informed distribution is then used as an initial condition. We make the claim that this initial condition carries fewer assumptions than an all-monomer one and verify that it can yield significantly different averaged waiting times relative to the all-monomer condition under various models of assembly.

  13. Construction of mono- and multilayer colloidal crystals with self-assembled nanospheres.

    PubMed

    Kim, Kwang Hyun; Kang, Bo-Sun; Kim, Min-Cheol; Sohn, Youngjoo; Tae, Ki-Sik; Lee, Hyun-Ju; Kim, Do Kyung

    2013-09-01

    A new self-assembly method for the fabrication of periodic structures using monodispersed polystyrene nanoparticles matrix was developed. The self-assembly could be formed into polystyrene nanoparticles matrix constructed by the face centered cubic (FCC) structure and hexagonally close-packed (HCP) monolayer. The polystyrene nanoparticles have been prepared by emulsion polymerization. Several aspects were investigated by using different techniques: Particle sizer, TEM and DSC etc. In this study, the feasibility of synthesizing nanoparticles of 550 nm polystyrene with a perfect spherical shape and a narrow size distribution was demonstrated. Subsequently, an investigation of the self-assembly of polystyrene nanospheres to built up an opal structure was performed. This arrangement was achieved by gravitational sedimentation under vacuum. The face centered cubic structure was identified by using SEM, thus that the different facet type {100}, {110} and {111} were composed. The self-assembly of monodispersed polystyrene nanoparticles in 2D structure was fabricated in the structure of hexagonally close-packed monolayer.

  14. Self-assembled multifunctional DNA nanospheres for biosensing and drug delivery into specific target cells.

    PubMed

    Bi, Sai; Dong, Ying; Jia, Xiaoqiang; Chen, Min; Zhong, Hua; Ji, Bin

    2015-04-28

    Self-assembly of three dimensional nucleic acid nanostructures is of great significance in nanotechnology, biosensing and biomedicine. Herein we present a novel class of multifunctional and programmable DNA nanostructures, termed nanospheres (NSs), with monodispersity, dense compaction and uniform size (∼ 200 nm) using only four DNAs based on not only Watson-Crick base pair hybridization between single-stranded DNA but also liquid crystallization and dense packing from periodic DNA duplexes. Due to the diversity of the internal structures, the present NSs can easily evolve into other kinds of DNA assemblies, such as DNA spherical structures with a larger size and a rough surface via rolling circle replication (RCR). Importantly, the functional arms incorporated in building units can be readily designed for biosensing and targeted cancer therapy with high payload capacity and excellent biocompatibility. Therefore, the proposed NSs could lead to novel routes for nucleic acid self-assembly, promising versatile applications in biosensing and biomedicine.

  15. Self-assembled multifunctional DNA nanospheres for biosensing and drug delivery into specific target cells

    NASA Astrophysics Data System (ADS)

    Bi, Sai; Dong, Ying; Jia, Xiaoqiang; Chen, Min; Zhong, Hua; Ji, Bin

    2015-04-01

    Self-assembly of three dimensional nucleic acid nanostructures is of great significance in nanotechnology, biosensing and biomedicine. Herein we present a novel class of multifunctional and programmable DNA nanostructures, termed nanospheres (NSs), with monodispersity, dense compaction and uniform size (~200 nm) using only four DNAs based on not only Watson-Crick base pair hybridization between single-stranded DNA but also liquid crystallization and dense packing from periodic DNA duplexes. Due to the diversity of the internal structures, the present NSs can easily evolve into other kinds of DNA assemblies, such as DNA spherical structures with a larger size and a rough surface via rolling circle replication (RCR). Importantly, the functional arms incorporated in building units can be readily designed for biosensing and targeted cancer therapy with high payload capacity and excellent biocompatibility. Therefore, the proposed NSs could lead to novel routes for nucleic acid self-assembly, promising versatile applications in biosensing and biomedicine.Self-assembly of three dimensional nucleic acid nanostructures is of great significance in nanotechnology, biosensing and biomedicine. Herein we present a novel class of multifunctional and programmable DNA nanostructures, termed nanospheres (NSs), with monodispersity, dense compaction and uniform size (~200 nm) using only four DNAs based on not only Watson-Crick base pair hybridization between single-stranded DNA but also liquid crystallization and dense packing from periodic DNA duplexes. Due to the diversity of the internal structures, the present NSs can easily evolve into other kinds of DNA assemblies, such as DNA spherical structures with a larger size and a rough surface via rolling circle replication (RCR). Importantly, the functional arms incorporated in building units can be readily designed for biosensing and targeted cancer therapy with high payload capacity and excellent biocompatibility. Therefore, the

  16. Self-assembly and nanosphere lithography for large-area plasmonic patterns on graphene.

    PubMed

    Lotito, Valeria; Zambelli, Tomaso

    2015-06-01

    Plasmonic structures on graphene can tailor its optical properties, which is essential for sensing and optoelectronic applications, e.g. for the enhancement of photoresponsivity of graphene photodetectors. Control over their structural and, hence, spectral properties can be attained by using electron beam lithography, which is not a viable solution for the definition of patterns over large areas. For the fabrication of large-area plasmonic nanostructures, we propose to use self-assembled monolayers of nanospheres as a mask for metal evaporation and etching processes. An optimized approach based on self-assembly at air/water interface with a properly designed apparatus allows the attainment of monolayers of hexagonally closely packed patterns with high long-range order and large area coverage; special strategies are devised in order to protect graphene against damage resulting from surface treatment and further processing steps such as reactive ion etching, which could potentially impair graphene properties. Therefore we demonstrate that nanosphere lithography is a cost-effective solution to create plasmonic patterns on graphene. Copyright © 2014 Elsevier Inc. All rights reserved.

  17. Electric field enhancement in a self-assembled 2D array of silver nanospheres

    SciTech Connect

    El-Khoury, Patrick Z. E-mail: wayne.hess@pnnl.gov; Gong, Yu; Joly, Alan G.; Abellan, Patricia; Browning, Nigel D.; Hess, Wayne P. E-mail: wayne.hess@pnnl.gov; Khon, Elena; Hu, Dehong; Zamkov, Mikhail; Evans, James E.

    2014-12-07

    We investigate the plasmonic properties of a self-assembled 2D array of Ag nanospheres (average particle diameter/inter-particle separation distance of 9/3.7 nm). The structures of the individual particles and their assemblies are characterized using high-resolution transmission electron microscopy (HR-TEM). The plasmonic response of the nanoparticle network is probed using two-photon photoemission electron microscopy (TP-PEEM). HR-TEM and TP-PEEM statistics reveal the structure and plasmonic response of the network to be homogeneous on average. This translates into a relatively uniform surface-enhanced Raman scattering (SERS) response from biphenyl,4-4{sup ′}-dithiol (BPDT) molecules adsorbed onto different sites of the network. Reproducible, bright, and low-background SERS spectra are recorded and assigned on the basis of density functional theory calculations in which BPDT is chemisorbed onto the vertex of a finite tetrahedral Ag cluster consisting of 20 Ag atoms. A notable agreement between experiment and theory allows us to rigorously account for the observable vibrational states of BPDT in the ∼200–2200 cm{sup −1} region of the spectrum. Finite difference time domain simulations further reveal that physical enhancement factors on the order of 10{sup 6} are attainable at the nanogaps formed between the silver nanospheres in the 2D array. Combined with modest chemical enhancement factors, this study paves the way for reproducible single molecule signals from an easily self-assembled SERS substrate.

  18. Electric Field Enhancement in a Self-Assembled 2D Array of Silver Nanospheres

    SciTech Connect

    El-Khoury, Patrick Z.; Khon, Elena; Gong, Yu; Joly, Alan G.; Abellan, Patricia; Evans, James E.; Browning, Nigel D.; Hu, Dehong; Zamkov, Mikhail; Hess, Wayne P.

    2014-12-07

    We investigate the plasmonic properties of a self-assembled 2D array of Ag nanospheres (average particle diameter/inter-particle separation distance of ~9/~4 nm). The structures of the individual particles and their assemblies are characterized using high-resolution transmission electron microscopy (HR-TEM). The plasmonic response of the nanoparticle network is probed using two-photon photoemission electron microscopy (TP-PEEM). HR-TEM and TP-PEEM statistics reveal the structure and plasmonic response of the network to be homogeneous on average. This translates into a relatively uniform surface-enhanced Raman scattering (SERS) response from biphenyl,4-4’-dithiol (BPDT) molecules adsorbed onto different sites of the network. Bright and background free SERS spectra are recorded, assigned on the basis of density 2 functional theory calculations in which BPDT is chemisorbed onto the vertex of a finitie tetrahedral Ag cluster consisting of 20 Ag atoms. A remarkable agreement between experiment and theory allows us to rigorously account for the observable vibrational states of BPDT in the ~200-2200 cm-1 region of the spectrum. Finite difference time domain simulations further reveal that physical enhancement factors on the order of 106 are attainable at the nanogaps formed between the silver nanospheres in the 2D array. Combined with modest chemical enhancement factors, this study paves the way for reproducible single molecule signals from an easily self-assembled SERS substrate.

  19. Gold(I) catalysis at extreme concentrations inside self-assembled nanospheres.

    PubMed

    Gramage-Doria, Rafael; Hessels, Joeri; Leenders, Stefan H A M; Tröppner, Oliver; Dürr, Maximilian; Ivanović-Burmazović, Ivana; Reek, Joost N H

    2014-12-01

    Homogeneous transition-metal catalysis is a crucial technology for the sustainable preparation of valuable chemicals. The catalyst concentration is usually kept as low as possible, typically at mM or μM levels, and the effect of high catalyst concentration is hardly exploited because of solubility issues and the inherent unfavorable catalyst/substrate ratio. Herein, a self-assembly strategy is reported which leads to local catalyst concentrations ranging from 0.05 M to 1.1 M, inside well-defined nanospheres, whilst the overall catalyst concentration in solution remains at the conventional mM levels. We disclose that only at this high concentration, the gold(I) chloride is reactive and shows high selectivity in intramolecular CO and CC bond-forming cyclization reactions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Tuning the Chirality of Block Copolymers: From Twisted Morphologies to Nanospheres by Self-Assembly.

    PubMed

    Suárez-Suárez, Silvia; Carriedo, Gabino A; Presa Soto, Alejandro

    2015-09-28

    New advances into the chirality effect in the self-assembly of block copolymers (BCPs) have been achieved by tuning the helicity of the chiral-core-forming blocks. The chiral BCPs {[N=P(R)-O2C20H12](200-x)[N=P(OC5H4N)2](x)}-b-[N=PMePh]50 ((R)-O2C20H12 = (R)-1,1'-binaphthyl-2,2'-dioxy, OC5H4N = 4-pyridinoxy (OPy); x = 10, 30, 60, 100 for 3 a-d, respectively), in which the [N=P(OPy)2] units are randomly distributed within the chiral block, have been synthesised. The chiroptical properties of the BCPs ([α]D vs. T and CD) demonstrated that the helicity of the BCP chains may be simply controlled by the relative proportion of the chiral and achiral (i.e., [N=P(R)-O2C20H12] and [N=P(OPy)2], respectively) units. Thus, although 3 a only contained only 5% [N=P(OPy)2] units and exhibited a preferential helical sense, 3 d with 50% of this unit adopted non-preferred helical conformations. This gradual variation of the helicity allowed us to examine the chirality effect on the self-assembly of chiral and helical BCPs (i.e., 3 a-c) and chiral but non-helical BCPs (i.e., 3 d). The very significant influence of the helicity on the self-assembly of these materials resulted in a variety of morphologies that extend from helical nanostructures to pearl-necklace aggregates and nanospheres (i.e., 3 b and 3 d, respectively). We also demonstrate that the presence of pyridine moieties in BCPs 3 a-d allows specific decoration with gold nanoparticles.

  1. Self-assembly directed synthesis of poly(ortho-toluidine)-metal(gold and palladium) composite nanospheres.

    PubMed

    Reddy, Kakarla Raghava; Lee, Kwang-Pill; Gopalan, Anantha Iyenger

    2007-09-01

    Poly(ortho-toluidine) (POT)-gold (Au) and palladium (Pd) composite nanospheres were successfully synthesized by the reaction of o-toluidine with the corresponding metal (Au or Pd) colloidal solution through self-assembly process in the presence of dodecylbenzenesulfonic acid (DBSA), which acts as both a dopant and surfactant, and ammonium peroxydisulfate as an oxidizing agent. The composites (POT-DBSA/Au or Pd) were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, UV-Visible (UV-Vis) spectroscopy, and electrical conductivity measurements. TEM images of the nanocomposites reveal that metal (Au or Pd) nanoparticles were well dispersed on POT spheres. TGA and XRD results show that the composites exhibit high thermal stability and are more crystalline compared with pristine POT. It was found that the electrical conductivity of the POT-DBSA/Au or Pd composites is 2 orders of magnitude higher than that of pristine polymer. Also, the POT-DBSA/Pd composite exhibits magnetic property. The formation mechanism of the POT-DBSA/Au or Pd composite nanosphere is discussed.

  2. Controllable preparation of multishelled NiO hollow nanospheres via layer-by-layer self-assembly for supercapacitor application

    NASA Astrophysics Data System (ADS)

    Yang, Zeheng; Xu, Feifei; Zhang, Weixin; Mei, Zhousheng; Pei, Bo; Zhu, Xiao

    2014-01-01

    In this work, we demonstrate a facile layer-by-layer (LBL) self-assembly method for controllable preparation of single-, double-, and triple-shelled NiO hollow nanospheres by calcining Ni(OH)2/C precursors formed at different stage. It is observed that the external nanoflakes of the NiO hollow nanospheres are inherited from the Ni(OH)2 precursors organized on the surface of carbon spheres via a self-assembly growth process and the inner shells result from the formation of different Ni(OH)2 layers within the carbon spheres during different preparation cycles. Supercapacitive performance of the three types of NiO hollow nanospheres as active electrode materials has been evaluated by cyclic voltammetry (CV) and galvanostatic charge-discharge. The results indicate that double-shelled NiO hollow nanosphere sample with largest surface area (92.99 m2 g-1) exhibits the best electrochemical properties among the three NiO hollow nanosphere samples. It delivers a high capacitance of 612.5 F g-1 at 0.5 A g-1 and demonstrates a superior long-term cyclic stability, with over 90% specific capacitance retention after 1000 charge-discharge cycles. This excellent performance is ascribed to the short diffusion path and large surface area of the unique hollow structure with nanoflake building blocks for bulk accessibility of faradaic reaction.

  3. Macroscopic ordering of polystyrene carboxylate-modified nanospheres self-assembled at the water-air interface.

    PubMed

    Sirotkin, Evgeny; Apweiler, Julius D; Ogrin, Feodor Y

    2010-07-06

    We present results from an experimental study of ordering characteristics in monolayers of polystyrene nanospheres self-assembled at a water-air interface. We demonstrate that the interaction of spheres, governed by the dissemination of surface charge, leads to the formation of macroscopic close-packed ordered areas or "domains" with a well-defined orientation of the lattice axes over areas of 25 mm(2). It was found that by changing the surface chemistry of the spheres it is possible to modify the balance between the attractive and repulsive forces and thus to control the ordering characteristics. We implemented a model that simulates the process of self-assembly and examines the ordering characteristics for layers with different ratio between attractive and repulsive forces. A good qualitative agreement was found between the simulations and experiment. These studies are technologically relevant as a method of producing nanosphere templates for large area patterned materials.

  4. Self-assembly of conjugated polymer on hybrid nanospheres for cellular imaging applications.

    PubMed

    Xia, Bihua; Wang, Xiaoyu; He, Fang; Cui, Qianling; Li, Lidong

    2012-11-01

    A new kind of hybrid core-shell nanosphere was fabricated by combining the in situ formation of Au nanoparticles and covalent cross-linking of biocompatible carboxymethyl starch dialdehyde (CMSD) and chitosan (CTS). When the fluorescent dye poly[9,9'-bis(6″-(N,N,N-trimethylammonium)-hexyl)fluorene-2,7-ylenevinylene-co-alt-1,4-phenylene dibromide] (PFV) was assembled on the surface of the hybrid nanospheres through electrostatic attraction, these biocompatible hybrid nanospheres exhibited metal-enhanced fluorescence effects. The fluorescence intensity of (CTS-Au)@CMSD/PFV hybrid nanosphere is 1.43 times that of CTS-CMSD/PFV hybrid nanospheres lacking Au nanoparticle. In addition, the (CTS-Au)@CMSD/PFV hybrid nanospheres exhibit excellent biodegradability upon exposure to enzymatic aqueous solution and good biocompatibility when cocultured with HeLa cervical carcinoma cells; these advantages make them attractive for cellular imaging and biological analysis and detection.

  5. GREEN AND CONTROLLED SYNTHESIS OF GOLD AND PLATINUM NANOMATERIALS USING VITAMIN B2: DENSITY-ASSISTED SELF-ASSEMBLY OF NANOSPHERES, WIRES AND RODS

    EPA Science Inventory

    For the first time, we report density-assisted self-assembly and efficient synthesis of gold (Au) and platinum (Pt) nanospheres, nanowires and nanorods using vitamin B2 (riboflavin) without employing any special capping or dispersing agent at room temperature; this env...

  6. GREEN AND CONTROLLED SYNTHESIS OF GOLD AND PLATINUM NANOMATERIALS USING VITAMIN B2: DENSITY-ASSISTED SELF-ASSEMBLY OF NANOSPHERES, WIRES AND RODS

    EPA Science Inventory

    For the first time, we report density-assisted self-assembly and efficient synthesis of gold (Au) and platinum (Pt) nanospheres, nanowires and nanorods using vitamin B2 (riboflavin) without employing any special capping or dispersing agent at room temperature; this env...

  7. Porous fluorinated SnO(2) hollow nanospheres: transformative self-assembly and photocatalytic inactivation of bacteria.

    PubMed

    Liu, Shengwei; Huang, Guocheng; Yu, Jiaguo; Ng, Tsz Wai; Yip, Ho Yin; Wong, Po Keung

    2014-02-26

    Highly porous surface fluorinated SnO2 hollow nanospheres (SnO2(F) HNS) were produced in high yield by a hydrothermal treatment of stannous fluoride in the presence of hydrogen peroxide. Two important processes in terms of oriented self-assembly and in situ self-transformation were highlighted for the formation of as-prepared SnO2(F) HNS, which were largely relying on the directing effects of selected specific chemical species in the present synthesis system. Significantly, these SnO2(F) HNS showed considerable activity in photocatalytic inactivation of a surface negatively charged bacterium, Escherichia coli K-12, in aqueous saline solution. The dominant reactive species involved in the inactivation process were also identified.

  8. Self-assembled Multilayers of Silica Nanospheres for Defect Reduction in Non- and Semipolar Gallium Nitride Epitaxial Layers

    PubMed Central

    2015-01-01

    Non- and semipolar GaN have great potential to improve the efficiency of light emitting devices due to much reduced internal electric fields. However, heteroepitaxial GaN growth in these crystal orientations suffers from very high dislocation and stacking faults densities. Here, we report a facile method to obtain low defect density non- and semipolar heteroepitaxial GaN via selective area epitaxy using self-assembled multilayers of silica nanospheres (MSN). Nonpolar (11–20) and semipolar (11–22) GaN layers with high crystal quality have been achieved by epitaxial integration of the MSN and a simple one-step overgrowth process, by which both dislocation and basal plane stacking fault densities can be significantly reduced. The underlying defect reduction mechanisms include epitaxial growth through the MSN covered template, island nucleation via nanogaps in the MSN, and lateral overgrowth and coalescence above the MSN. InGaN/GaN multiple quantum wells structures grown on a nonpolar GaN/MSN template show more than 30-fold increase in the luminescence intensity compared to a control sample without the MSN. This self-assembled MSN technique provides a new platform for epitaxial growth of nitride semiconductors and offers unique opportunities for improving the material quality of GaN grown on other orientations and foreign substrates or heteroepitaxial growth of other lattice-mismatched materials. PMID:27065755

  9. Self-assembled Multilayers of Silica Nanospheres for Defect Reduction in Non- and Semipolar Gallium Nitride Epitaxial Layers.

    PubMed

    Zhu, Tongtong; Ding, Tao; Tang, Fengzai; Han, Yisong; Ali, Muhammad; Badcock, Tom; Kappers, Menno J; Shields, Andrew J; Smoukov, Stoyan K; Oliver, Rachel A

    2016-02-03

    Non- and semipolar GaN have great potential to improve the efficiency of light emitting devices due to much reduced internal electric fields. However, heteroepitaxial GaN growth in these crystal orientations suffers from very high dislocation and stacking faults densities. Here, we report a facile method to obtain low defect density non- and semipolar heteroepitaxial GaN via selective area epitaxy using self-assembled multilayers of silica nanospheres (MSN). Nonpolar (11-20) and semipolar (11-22) GaN layers with high crystal quality have been achieved by epitaxial integration of the MSN and a simple one-step overgrowth process, by which both dislocation and basal plane stacking fault densities can be significantly reduced. The underlying defect reduction mechanisms include epitaxial growth through the MSN covered template, island nucleation via nanogaps in the MSN, and lateral overgrowth and coalescence above the MSN. InGaN/GaN multiple quantum wells structures grown on a nonpolar GaN/MSN template show more than 30-fold increase in the luminescence intensity compared to a control sample without the MSN. This self-assembled MSN technique provides a new platform for epitaxial growth of nitride semiconductors and offers unique opportunities for improving the material quality of GaN grown on other orientations and foreign substrates or heteroepitaxial growth of other lattice-mismatched materials.

  10. Semi-insulating behaviour of self-assembled tin(IV)corrole nanospheres.

    PubMed

    Sinha, Woormileela; Kumar, Mohit; Garai, Antara; Purohit, Chandra Shekhar; Som, Tapobrata; Kar, Sanjib

    2014-09-07

    Three novel tin(iv)corrole complexes have been prepared and characterized by various spectroscopic techniques including single crystal X-ray structural analysis. Packing diagrams of the tin(iv)corroles revealed that corrolato-tin(iv)-chloride molecules are interconnected by intermolecular C-HCl hydrogen bonding interactions. HCl distances are 2.848 Å, 3.051 Å, and 2.915 Å, respectively, for the complexes. In addition, the C-HCl angles are 119.72°, 144.70°, and 147.08°, respectively, for the complexes. It was also observed that in one of the three synthesized complexes dimers were formed, while in the other two cases 1D infinite polymer chains were formed. Well-defined and nicely organized three-dimensional hollow nanospheres (SEM images on silicon wafers) with diameters of ca. 676 nm and 661 nm are obtained in the complexes, forming 1D polymer chains. By applying a thin layer of tin(iv)corrole nanospheres to an ITO surface (AFM height images of ITO films; ∼200 nm in height), a device was fabricated with the following composition: Ag/ITO-coated glass/tin(iv)corrole nanospheres/ITO-coated glass/Ag. The resistivity (ρ) of the nanostructured film was calculated to be ∼2.4 × 10(8) Ω cm, which falls in the range of semi-insulating semiconductors. CAFM current maps at 10 V bias show bright spots with a 10-20 pA intensity and indicate that the nanospheres (∼250 nm in diameter) are the electron-conducting pathway in the device. The semi-insulating behavior arises from the non-facile electron transfer in the HOMOs of the tin(iv)corrole nanospheres.

  11. Linear and nonlinear optical characterization of self-assembled, large-area gold nanosphere metasurfaces with sub-nanometer gaps.

    PubMed

    Fontana, Jake; Maldonado, Melissa; Charipar, Nicholas; Trammell, Scott A; Nita, Rafaela; Naciri, Jawad; Pique, Alberto; Ratna, Banahalli; Gomes, Anderson S L

    2016-11-28

    We created centimeter-scale area metasurfaces consisting of a quasi-hexagonally close packed monolayer of gold nanospheres capped with alkanethiol ligands on glass substrates using a directed self-assembly approach. We experimentally characterized the morphology and the linear and nonlinear optical properties of metasurfaces. We show these metasurfaces, with interparticle gaps of 0.6 nm, are modeled well using a classical (without charge transfer) description. We find a large dispersion of linear refractive index, ranging from values less than vacuum, 0.87 at 600 nm, to Germanium-like values of 4.1 at 880 nm, determined using spectroscopic ellipsometry. Nonlinear optical characterization was carried out using femtosecond Z-scan and we observe saturation behavior of the nonlinear absorption (NLA) and nonlinear refraction (NLR). We find a negative NLR from these metasurfaces two orders of magnitude larger (n2,sat = -7.94x10-9 cm2/W at Isat,n2 = 0.43 GW/cm2) than previous reports on gold nanostructures at similar femtosecond time scales. We also find the magnitude of the NLA comparable to the largest values reported (β2,sat = -0.90x105 cm/GW at Isat,β2 = 0.34 GW/cm2). Precise knowledge of the index of refraction is of crucial importance for emerging dispersion engineering technologies. Furthermore, utilizing this directed self-assembly approach enables the nanometer scale resolution required to develop the unique optical response and simultaneously provides high-throughput for potential device realization.

  12. Magnetization reversal and microstructure in polycrystalline Fe50Pd50 dot arrays by self-assembling of polystyrene nanospheres

    PubMed Central

    Tiberto, Paola; Celegato, Federica; Barrera, Gabriele; Coisson, Marco; Vinai, Franco; Rizzi, Paola

    2016-01-01

    Abstract Nanoscale magnetic materials are the basis of emerging technologies to develop novel magnetoelectronic devices. Self-assembly of polystyrene nanospheres is here used to generate 2D hexagonal dot arrays on Fe50Pd50 thin films. This simple technique allows a wide-area patterning of a magnetic thin film. The role of disorder on functional magnetic properties with respect to conventional lithographic techniques is studied. Structural and magnetic characteristics have been investigated in arrays having different geometry (i.e. dot diameters, inter-dot distances and thickness). The interplay among microstructure and magnetization reversal is discussed. Magnetic measurements reveal a vortex domain configuration in all as-prepared films. The original domain structure changes drastically upon thermal annealing performed to promote the transformation of disordered A1 phase into the ordered, tetragonal L10 phase. First-order reversal magnetization curves have been measured to rule out the role of magnetic interaction among crystalline phases characterized by different magnetic coercivity. PMID:27877896

  13. Multiscale active layer morphologies for organic photovoltaics through self-assembly of nanospheres.

    PubMed

    Gehan, Timothy S; Bag, Monojit; Renna, Lawrence A; Shen, Xiaobo; Algaier, Dana D; Lahti, Paul M; Russell, Thomas P; Venkataraman, Dhandapani

    2014-09-10

    We address here the need for a general strategy to control molecular assembly over multiple length scales. Efficient organic photovoltaics require an active layer comprised of a mesoscale interconnected networks of nanoscale aggregates of semiconductors. We demonstrate a method, using principles of molecular self-assembly and geometric packing, for controlled assembly of semiconductors at the nanoscale and mesoscale. Nanoparticles of poly(3-hexylthiophene) (P3HT) or [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) were fabricated with targeted sizes. Nanoparticles containing a blend of both P3HT and PCBM were also fabricated. The active layer morphology was tuned by the changing particle composition, particle radii, and the ratios of P3HT:PCBM particles. Photovoltaic devices were fabricated from these aqueous nanoparticle dispersions with comparable device performance to typical bulk-heterojunction devices. Our strategy opens a revolutionary pathway to study and tune the active layer morphology systematically while exercising control of the component assembly at multiple length scales.

  14. Efficiency improvement of InGaN light emitting diodes with embedded self-assembled SiO2 nanosphere arrays

    NASA Astrophysics Data System (ADS)

    Zhang, Yonghui; Wei, Tongbo; Wang, Junxi; Fan, Chao; Chen, Yu; Hu, Qiang; Li, Jinmin

    2014-05-01

    In this study, the periodic SiO2 nanosphere nanopatterned sapphire substrate (SiO2-NPSS) was made using self-assembled SiO2 nanosphere monolayer template and inductively coupled plasma (ICP) etching. And the self-assembled SiO2 nanosphere monolayer was directly embedded into the GaN/sapphire interface by nanoscale epitaxial lateral overgrowth (NELOG). For comparison, a common nanopatterned sapphire substrate (C-NPSS) was also made through dry etching with the SiO2 nanospheres used as the mask. Compared with LEDs grown on C-NPSS and flat sapphire substrate (FSS), the external quantum efficiency of LEDs with SiO2 nanopheres (SiO2-NPSS) was increased by 30.7% and 81.9% under a driving current 350 mA. The SiO2-NPSS not only improved the crystalline quality of GaN but also enhanced the light extraction efficiency (LEE) of LED. And the SiO2-NPSS LED also showed more light in vertical direction and more uniform light distribution. By finite-difference time-domain (FDTD) simulation, we confirmed that more light could be reflected from the GaN/SiO2 interface than the GaN/sapphire interface because the refractive index of SiO2 was lower than that of sapphire. Therefore, LED grown on the SiO2-NPSS showed superior light extraction efficiency compared to that on C-NPSS.

  15. Rapid Synthesis of Monodisperse Au Nanospheres through a Laser Irradiation -Induced Shape Conversion, Self-Assembly and Their Electromagnetic Coupling SERS Enhancement

    PubMed Central

    Liu, Dilong; Li, Cuncheng; Zhou, Fei; Zhang, Tao; Zhang, Honghua; Li, Xinyang; Duan, Guotao; Cai, Weiping; Li, Yue

    2015-01-01

    We develop a facile and effective strategy to prepare monodispersed Au spherical nanoparticles by two steps. Large-scale monocrystalline Au nanooctahedra with uniform size were synthesized by a polyol-route and subsequently Au nanoparticles were transformed from octahedron to spherical shape in a liquid under ambient atmosphere by non-focused laser irradiation in very short time. High monodipersed, ultra-smooth gold nanospheres can be obtained by simply optimizing the laser fluence and irradiation time. Photothermal melting-evaporation model was employed to get a better understanding of the morphology transformation for the system of nanosecond pulsed-laser excitation. These Au nanoparticles were fabricated into periodic monolayer arrays by self-assembly utilizing their high monodispersity and perfect spherical shape. Importantly, such Au nanospheres arrays demonstrated very good SERS enhancement related to their periodic structure due to existence of many SERS hot spots between neighboring Au nanospheres caused by the electromagnetic coupling in an array. These gold nanospheres and their self-assembled arrays possess distinct physical and chemical properties. It will make them as an excellent and promising candidate for applying in sensing and spectroscopic enhancement, catalysis, energy, and biology. PMID:25566872

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  17. Theoretical Study of the Initial Stages of Self-Assembly of a Carboxysome’s Facet

    SciTech Connect

    Mahalik, J. P.; Brown, Kirsten A.; Cheng, Xiaolin

    2016-02-24

    Bacterial microcompartments, BMCs, are organelles that exist within wide variety of bacteria and act as nanofactories. Among the different types of known BMCs, the carboxysome has been studied the most. The carboxysome plays an important role in the light-independent part of the photosynthesis process, where its icosahedral-like proteinaceous shell acts as a membrane that controls the transport of metabolites. Although a structural model exists for the carboxysome shell, it remains largely unknown how the shell proteins self-assemble. Understanding the self-assembly process can provide insights into how the shell affects the carboxysome s function and how it can be modified to create new functionalities, such as artificial nanoreactors and artificial protein membranes. Here, we explain a theoretical framework that employs Monte Carlo simulations with a coarse-grain potential that reproduces well the atomistic potential of mean force; employing this framework, we are able to capture the initial stages of the 2D self-assembly of CcmK2 hexamers, a major protein-shell component of the carboxysome's facet. The simulations reveal that CcmK2 hexamers self-assemble into clusters that resemble what was seen experimentally in 2D layers. Further analysis of the simulation results suggests that the 2D self-assembly of carboxysome s facets is driven by a nucleation growth process, which in turn could play an important role in the hierarchical self- assembly of BMC shells in general.

  18. Theoretical Study of the Initial Stages of Self-Assembly of a Carboxysome’s Facet

    DOE PAGES

    Mahalik, J. P.; Brown, Kirsten A.; Cheng, Xiaolin; ...

    2016-02-24

    Bacterial microcompartments, BMCs, are organelles that exist within wide variety of bacteria and act as nanofactories. Among the different types of known BMCs, the carboxysome has been studied the most. The carboxysome plays an important role in the light-independent part of the photosynthesis process, where its icosahedral-like proteinaceous shell acts as a membrane that controls the transport of metabolites. Although a structural model exists for the carboxysome shell, it remains largely unknown how the shell proteins self-assemble. Understanding the self-assembly process can provide insights into how the shell affects the carboxysome s function and how it can be modified tomore » create new functionalities, such as artificial nanoreactors and artificial protein membranes. Here, we explain a theoretical framework that employs Monte Carlo simulations with a coarse-grain potential that reproduces well the atomistic potential of mean force; employing this framework, we are able to capture the initial stages of the 2D self-assembly of CcmK2 hexamers, a major protein-shell component of the carboxysome's facet. The simulations reveal that CcmK2 hexamers self-assemble into clusters that resemble what was seen experimentally in 2D layers. Further analysis of the simulation results suggests that the 2D self-assembly of carboxysome s facets is driven by a nucleation growth process, which in turn could play an important role in the hierarchical self- assembly of BMC shells in general.« less

  19. Triphenylalanine peptides self-assemble into nanospheres and nanorods that are different from the nanovesicles and nanotubes formed by diphenylalanine peptides.

    PubMed

    Guo, Cong; Luo, Yin; Zhou, Ruhong; Wei, Guanghong

    2014-03-07

    Understanding the nature of the self-assembly of peptide nanostructures at the molecular level is critical for rational design of functional bio-nanomaterials. Recent experimental studies have shown that triphenylalanine(FFF)-based peptides can self-assemble into solid plate-like nanostructures and nanospheres, which are different from the hollow nanovesicles and nanotubes formed by diphenylalanine(FF)-based peptides. In spite of extensive studies, the assembly mechanism and the molecular basis for the structural differences between FFF and FF nanostructures remain poorly understood. In this work, we first investigate the assembly process and the structural features of FFF nanostructures using coarse-grained molecular dynamics simulations, and then compare them with FF nanostructures. We find that FFF peptides spontaneously assemble into solid nanometer-sized nanospheres and nanorods with substantial β-sheet contents, consistent with the structural properties of hundred-nanometer-sized FFF nano-plates characterized by FT-IR spectroscopy. Distinct from the formation mechanism of water-filled FF nanovesicles and nanotubes reported in our previous study, intermediate bilayers are not observed during the self-assembly process of FFF nanospheres and nanorods. The peptides in FFF nanostructures are predominantly anti-parallel-aligned, which can form larger sizes of β-sheet-like structures than the FF counterparts. In contrast, FF peptides exhibit lipid-like assembly behavior and assemble into bilayered nanostructures. Furthermore, although the self-assembly of FF and FFF peptides is mostly driven by side chain-side chain (SC-SC) aromatic stacking interactions, the main chain-main chain (MC-MC) interactions also play an important role in the formation of fine structures of the assemblies. The delicate interplay between MC-MC and SC-SC interactions results in the different nanostructures formed by the two peptides. These findings provide new insights into the structure

  20. Bi-Component Nanostructured Arrays of Co Dots Embedded in Ni80Fe20 Antidot Matrix: Synthesis by Self-Assembling of Polystyrene Nanospheres and Magnetic Properties.

    PubMed

    Coïsson, Marco; Celegato, Federica; Barrera, Gabriele; Conta, Gianluca; Magni, Alessandro; Tiberto, Paola

    2017-08-23

    A bi-component nanostructured system composed by a Co dot array embedded in a Ni80Fe20 antidot matrix has been prepared by means of the self-assembling polystyrene nanospheres lithography technique. Reference samples constituted by the sole Co dots or Ni80Fe20 antidots have also been prepared, in order to compare their properties with those of the bi-component material. The coupling between the two ferromagnetic elements has been studied by means of magnetic and magneto-transport measurements. The Ni80Fe20 matrix turned out to affect the vortex nucleation field of the Co dots, which in turn modifies the magneto-resistance behaviour of the system and its spinwave properties.

  1. Light extraction improvement of InGaN light-emitting diodes with large-area highly ordered ITO nanobowls photonic crystal via self-assembled nanosphere lithography

    NASA Astrophysics Data System (ADS)

    Wu, Kui; Zhang, Yiyun; Wei, Tongbo; Lan, Ding; Sun, Bo; Zheng, Haiyang; Lu, Hongxi; Chen, Yu; Wang, Junxi; Luo, Yi; Li, Jinmin

    2013-09-01

    The InGaN multiple quantum well light-emitting diodes (LEDs) with different sizes of indium-tin-oxide (ITO) nanobowl photonic crystal (PhC) structure has been fabricated using self-assembled monolayer nanosphere lithography. The light output power (LOP) of PhC LEDs (at 350 mA) has been enhanced by 63.5% and the emission divergence exhibits a 28.8° reduction compared to conventional LEDs without PhC structure. Current-Voltage curves have shown that these PhC structures on ITO layer will not degrade the LED electrical properties. The finite-difference time-domain simulation (FDTD) has also been performed for light extraction and emission characteristics, which is consistent with the experimental results.

  2. Preparation of high-quality colloidal mask for nanosphere lithography by a combination of air/water interface self-assembly and solvent vapor annealing.

    PubMed

    Yu, Jie; Geng, Chong; Zheng, Lu; Ma, Zhaohui; Tan, Tianya; Wang, Xiaoqing; Yan, Qingfeng; Shen, Dezhong

    2012-08-28

    Nanosphere lithography (NSL) has been regarded as an inexpensive, inherently parallel, high-throughput, materials-general approach to the fabrication of nanoparticle arrays. However, the order of the resulting nanoparticle array is essentially dependent on the quality of the colloidal monolayer mask. Furthermore, the lateral feature size of the nanoparticles created using NSL is coupled with the diameter of the colloidal spheres, which makes it inconvenient for studying the size-dependent properties of nanoparticles. In this work, we demonstrate a facile approach to the fabrication of a large-area, transferrable, high-quality latex colloidal mask for nanosphere lithography. The approach is based on a combination of the air/water interface self-assembly method and the solvent-vapor-annealing technique. It enables the fabrication of colloidal masks with a higher crystalline integrity compared to those produced by other strategies. By manipulating the diameter of the colloidal spheres and precisely tuning the solvent-vapor-annealing process, flexible control of the size, shape, and spacing of the interstice in a colloidal mask can be realized, which may facilitate the broad use of NSL in studying the size-, shape-, and period-dependent optical, magnetic, electronic, and catalytic properties of nanomaterials.

  3. Soft-Templated Self-Assembly of Mesoporous Anatase TiO2/Carbon Composite Nanospheres for High-Performance Lithium Ion Batteries.

    PubMed

    Wu, Ruofei; Shen, Shuiyun; Xia, Guofeng; Zhu, Fengjuan; Lastoskie, Christian; Zhang, Junliang

    2016-08-10

    Mesoporous anatase TiO2/carbon composite nanospheres (designated as meso-ATCCNs) were successfully synthesized via a facile soft-templated self-assembly followed by thermal treatment. Structural and morphological analyses reveal that the as-synthesized meso-ATCCNs are composed of primary TiO2 nanoparticles (∼5 nm), combined with in situ deposited carbon either on the surface or between the primary TiO2 nanoparticles. When cycled in an extended voltage window from 0.01 to 3.0 V, meso-ATCCNs exhibit excellent rate capabilities (413.7, 289.7, and 206.8 mAh g(-1) at 200, 1000, and 3000 mA g(-1), respectively) as well as stable cyclability (90% capacity retention over 500 cycles at 1000 mA g(-1)). Compared with both mesoporous TiO2 nanospheres and bulk TiO2, the superior electrochemical performance of the meso-ATCCNs electrode could be ascribed to a synergetic effect induced by hierarchical structure that includes uniform TiO2 nanoparticles, the presence of hydrothermal carbon derived from phenolic resols, a high surface area, and open mesoporosity.

  4. Cooperative effects of fibronectin matrix assembly and initial cell-substrate adhesion strength in cellular self-assembly.

    PubMed

    Brennan, James R; Hocking, Denise C

    2016-03-01

    The cell-dependent polymerization of intercellular fibronectin fibrils can stimulate cells to self-assemble into multicellular structures. The local physical cues that support fibronectin-mediated cellular self-assembly are largely unknown. Here, fibronectin matrix analogs were used as synthetic adhesive substrates to model cell-matrix fibronectin fibrils having different integrin-binding specificity, affinity, and/or density. We utilized this model to quantitatively assess the relationship between adhesive forces derived from cell-substrate interactions and the ability of fibronectin fibril assembly to induce cellular self-assembly. Results indicate that the strength of initial, rather than mature, cell-substrate attachments correlates with the ability of substrates to support fibronectin-mediated cellular self-assembly. The cellular response to soluble fibronectin was bimodal and independent of the integrin-binding specificity of the substrate; increasing soluble fibronectin levels above a critical threshold increased aggregate cohesion on permissive substrates. Once aggregates formed, continuous fibronectin polymerization was necessary to maintain cohesion. During self-assembly, soluble fibronectin decreased cell-substrate adhesion strength and induced aggregate cohesion via a Rho-dependent mechanism, suggesting that the balance of contractile forces derived from fibronectin fibrils within cell-cell versus cell-substrate adhesions controls self-assembly and aggregate cohesion. Thus, initial cell-substrate attachment strength may provide a quantitative basis with which to build predictive models of fibronectin-mediated microtissue fabrication on a variety of substrates. Cellular self-assembly is a process by which cells and extracellular matrix (ECM) proteins spontaneously organize into three-dimensional (3D) tissues in the absence of external forces. Cellular self-assembly can be initiated in vitro, and represents a potential tool for tissue engineers to

  5. Fabrication of composite thin films with microstructures of honeycomb, foam, and nanosphere arrays through adsorption and self-assembly of block copolymers at the liquid/liquid interface.

    PubMed

    Liu, Yanan; Chen, Lifang; Geng, Yuanyuan; Lee, Yong-Ill; Li, Ying; Hao, Jingcheng; Liu, Hong-Guo

    2013-10-01

    The adsorption and self-organization behaviors of two kinds of block copolymers, polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) and poly(4-vinylpyridine)-block-polystyrene-block-poly(4-vinylpyridine) (P4VP-b-PS-b-P4VP), at planar liquid/liquid interfaces were investigated. A gel film decorating with honeycomb-like microstructures forms at the liquid/liquid interface between PS-b-P4VP chloroform solution and chloroauric acid aqueous solution. However, foam films were developed when the chloroauric acid aqueous solution was replaced by a chloroplatinic acid solution or a silver nitrate solution. Furthermore, a free-standing film containing the ordered arrays of nanospheres appeared at the liquid/liquid interface between P4VP-b-PS-b-P4VP chloroform solution and chloroauric acid aqueous solution. The formation of these microstructures was attributed to the adsorption of polymer molecules, combining with inorganic ions and the self-assembly of the composite species at the interface. The doped metal ions and complex ions were transformed to metal nanoparticles after further treatment. This is a facile and convenient method to prepare polymer/inorganic nanoparticle composites. These results also indicate the great influences of the polymer structures and the inorganic species in the aqueous phases on the self-assembly behaviors of the polymers at the interfaces, the final morphology, and structure of the composites. In addition, the formed thin composite films doped with well-dispersed, homogeneous small noble metal nanoparticles exhibit great and durable catalytic activities for the reduction of 4-nitrophenol (4-NP) by potassium borohydride.

  6. Cooperative Effects of Fibronectin Matrix Assembly and Initial Cell-Substrate Adhesion Strength in Cellular Self-Assembly

    PubMed Central

    Brennan, James R.; Hocking, Denise C.

    2015-01-01

    The cell-dependent polymerization of intercellular fibronectin fibrils can stimulate cells to self-assemble into multicellular structures. The local physical cues that support fibronectin-mediated cellular self-assembly are largely unknown. Here, fibronectin matrix analogs were used as synthetic adhesive substrates to model cell-matrix fibronectin fibrils having different integrin-binding specificity, affinity, and/or density. We utilized this model to quantitatively assess the relationship between adhesive forces derived from cell-substrate interactions and the ability of fibronectin fibril assembly to induce cellular self-assembly. Results indicate that the strength of initial, rather than mature, cell-substrate attachments correlates with the ability of substrates to support fibronectin-mediated cellular self-assembly. The cellular response to soluble fibronectin was bimodal and independent of the integrin-binding specificity of the substrate; increasing soluble fibronectin levels above a critical threshold increased aggregate cohesion on permissive substrates. Once aggregates formed, continuous fibronectin polymerization was necessary to maintain cohesion. During self-assembly, soluble fibronectin decreased cell-substrate adhesion strength and induced aggregate cohesion via a Rho-dependent mechanism, suggesting that the balance of contractile forces derived from fibronectin fibrils within cell-cell versus cell-substrate adhesions controls self-assembly and aggregate cohesion. Thus, initial cell-substrate attachment strength may provide a quantitative basis with which to build predictive models of fibronectin-mediated microtissue fabrication on a variety of substrates. PMID:26712598

  7. Function-Led Design of Aerogels: Self-Assembly of Alloyed PdNi Hollow Nanospheres for Efficient Electrocatalysis.

    PubMed

    Cai, Bin; Wen, Dan; Liu, Wei; Herrmann, Anne-Kristin; Benad, Albrecht; Eychmüller, Alexander

    2015-10-26

    One plausible approach to endow aerogels with specific properties while preserving their other attributes is to fine-tune the building blocks. However, the preparation of metallic aerogels with designated properties, for example catalytically beneficial morphologies and transition-metal doping, still remains a challenge. Here, we report on the first aerogel electrocatalyst composed entirely of alloyed PdNi hollow nanospheres (HNSs) with controllable chemical composition and shell thickness. The combination of transition-metal doping, hollow building blocks, and the three-dimensional network structure make the PdNi HNS aerogels promising electrocatalysts for ethanol oxidation. The mass activity of the Pd83 Ni17 HNS aerogel is 5.6-fold higher than that of the commercial Pd/C catalyst. This work expands the exploitation of the electrocatalysis properties of aerogels through the morphology and composition control of its building blocks. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Effect of curvature on the structural and magnetic properties of Ni film deposited on self-assembled nanospheres

    NASA Astrophysics Data System (ADS)

    Sharma, A.; Tripathi, S.; Gupta, Dileep; Halder, N.; Tripathi, J.

    2016-05-01

    Important experimental findings and their impact on physical properties of Ni thin film are presented with the focus on structural and magnetic property investigations. For this purpose, Ni film (40 nm) was deposited on polystyrene nanospheres (PS, diameter 800 nm) using electron beam evaporation technique simultaneously with a similar reference film on plane Si substrate. The structural properties of the films measured using XRD technique show nanocrystalline growth of Ni on both size PS spheres with an average grain size of ˜ 78 nm, while high crystallinity was observed in the film deposited onto plane Si substrate. A lower coercivity (9 mT) was observed in the Ni/(800 nm) PS as compared to the film deposited on 530 nm PS (23 mT) (our earlier study) and Ni/Si (20 mT). The observed changes in structural and magnetic properties are attributed to the curvature induced modifications at atomic level.

  9. Self-assembly of an amphiphilic macromolecule under spherical confinement: an efficient route to generate hollow nanospheres.

    PubMed

    Glagoleva, A A; Vasilevskaya, V V; Yoshikawa, K; Khokhlov, A R

    2013-12-28

    In general, bio-macromolecules are composed of hydrophilic and hydrophobic moieties and are confined within small cavities, such as cell membranes and intracellular organelles. Here, we studied the self-organization of macromolecules having groups with different affinities to solvents under spherical nano-scale confinement by means of computer modeling. It is shown that depending on the interaction parameters of monomer units composed of side- and main-chain monomer groups along a single linear macromolecule and on cavity size, such amphiphilic polymers undergo the conformational transitions between hollow nanospheres, rod-like and folded cylindrical structures, and a necklace conformation with and without a particular ordering of beads. The diagram of the conformations in the variables the incompatibility parameter of monomer units and the cavity radius is constructed.

  10. Self-assembly of an amphiphilic macromolecule under spherical confinement: An efficient route to generate hollow nanospheres

    NASA Astrophysics Data System (ADS)

    Glagoleva, A. A.; Vasilevskaya, V. V.; Yoshikawa, K.; Khokhlov, A. R.

    2013-12-01

    In general, bio-macromolecules are composed of hydrophilic and hydrophobic moieties and are confined within small cavities, such as cell membranes and intracellular organelles. Here, we studied the self-organization of macromolecules having groups with different affinities to solvents under spherical nano-scale confinement by means of computer modeling. It is shown that depending on the interaction parameters of monomer units composed of side- and main-chain monomer groups along a single linear macromolecule and on cavity size, such amphiphilic polymers undergo the conformational transitions between hollow nanospheres, rod-like and folded cylindrical structures, and a necklace conformation with and without a particular ordering of beads. The diagram of the conformations in the variables the incompatibility parameter of monomer units and the cavity radius is constructed.

  11. Hollow nanospheres based on the self-assembly of alginate-graft-poly(ethylene glycol) and α-cyclodextrin.

    PubMed

    Meng, Xian-Wei; Ha, Wei; Cheng, Cong; Dong, Zhen-Qiang; Ding, Li-Sheng; Li, Bang-Jing; Zhang, Sheng

    2011-12-06

    This article studies the self-assembly of alginate-graft-poly(ethylene glycol) (Alg-g-PEG) and α-cyclodextrin (α-CD) in aqueous solution. It was found that they could form hollow spheres because of the formation of coil-rod Alg-g-PEG/α-CD inclusion complexes. In these Alg-g-PEG/α-CD complexes, the α-CDs are stacked along the PEG side chains to form a rod block, and alginate main chains act as a coil block. More rod-like blocks in Alg-g-PEG/α-CD favor the formation of small assemblies. The assemblies of Alg-g-PEG/α-CD show a dependence on concentration, temperature, pH, and salt concentration. At low concentration (below 0.125%) or high temperature (above 32 °C), Alg-g-PEG/α-CD particles were unstable and disrupted. Increasing the salt or decreasing the pH resulted in the aggregation of Alg-g-mPEG/α-CD particles, as detected by the increase in the recorded hydrodynamic diameter (D(h)). © 2011 American Chemical Society

  12. Initiation of Chondrocyte Self-Assembly Requires an Intact Cytoskeletal Network

    PubMed Central

    Lee, Jennifer K.; Hu, Jerry C.Y.

    2016-01-01

    Self-assembly and self-organization have recently emerged as robust scaffold-free tissue engineering methodologies that can be used to generate various tissues, including cartilage, vessel, and liver. Self-assembly, in particular, is a scaffold-free platform for tissue engineering that does not require the input of exogenous energy to the system. Although self-assembly can generate functional tissues, most notably neocartilage, the mechanisms of self-assembly remain unclear. To study the self-assembling process, we used articular chondrocytes as a model to identify parameters that can affect this process. Specifically, the roles of cell–cell and cell–matrix adhesion molecules, surface-bound collagen, and the actin cytoskeletal network were investigated. Using time-lapse imaging, we analyzed the early stages of chondrocyte self-assembly. Within hours, chondrocytes rapidly coalesced into cell clusters before compacting to form tight cellular structures. Chondrocyte self-assembly was found to depend primarily on integrin function and secondarily on cadherin function. In addition, actin or myosin II inhibitors prevented chondrocyte self-assembly, suggesting that cell adhesion alone is not sufficient, but rather the active contractile actin cytoskeleton is essential for proper chondrocyte self-assembly and the formation of neocartilage. Better understanding of the self-assembly mechanisms allows for the rational modulation of this process toward generating neocartilages with improved properties. These findings are germane to understanding self-assembly, an emerging platform for tissue engineering of a plethora of tissues, especially as these neotissues are poised for translation. PMID:26729374

  13. Effect of curvature on the structural and magnetic properties of Ni film deposited on self-assembled nanospheres

    SciTech Connect

    Sharma, A. Tripathi, S.; Halder, N.; Gupta, Dileep; Tripathi, J.

    2016-05-06

    Important experimental findings and their impact on physical properties of Ni thin film are presented with the focus on structural and magnetic property investigations. For this purpose, Ni film (40 nm) was deposited on polystyrene nanospheres (PS, diameter 800 nm) using electron beam evaporation technique simultaneously with a similar reference film on plane Si substrate. The structural properties of the films measured using XRD technique show nanocrystalline growth of Ni on both size PS spheres with an average grain size of ∼ 78 nm, while high crystallinity was observed in the film deposited onto plane Si substrate. A lower coercivity (9 mT) was observed in the Ni/(800 nm) PS as compared to the film deposited on 530 nm PS (23 mT) (our earlier study) and Ni/Si (20 mT). The observed changes in structural and magnetic properties are attributed to the curvature induced modifications at atomic level.

  14. Nanoscience and technology: An interdisciplinary initiative, self-assembling nanoscale quantum devices

    SciTech Connect

    Doolen, G.; Smith, D.; Mineev, M.

    1996-10-01

    This is the final report of a three-year Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Our objective is to develop the devices, interconnection technologies, and self-assembling systems required for quantum-based information processing that permit ultra-dense integrated circuits and that allow continuation of the on-going silicon VLSI miniaturization process. That process is facing increasing difficulties related to switch performance, heat dissipation, interconnect failure, quantum effect complications, and rapidly escalating manufacturing costs. Our approach is intended to address these concerns and consists of the development of highly parallel stochastic computers utilizing quantum components and self-assembly methods; the development of self-assembling monolayers for use as resists and memory devices; and research on approaches to molecular self-assembly of the precursors to molecular transistors. The work will provide confirmation of principles, is intended to provide near-term results of potential relevance to the commercial sector, and has a range of applications that include high performance computing, biotechnology, and nanoscale chemistry.

  15. Anti-fouling surfaces by combined molecular self-assembly and surface-initiated ATRP for micropatterning active proteins.

    PubMed

    Xiu, K M; Cai, Q; Li, J S; Yang, X P; Yang, W T; Xu, F J

    2012-02-01

    A simple method by combined molecular self assembly and surface-initiated atom transfer radical polymerization (SI-ATRP) was proposed to prepare a biologically inert surface for micropatterning active proteins. The MPEG microdomains having a short terminal poly(ethylene glycol) (PEG) unit were prepared by self assembly of 2-(methyoxy(polyethylenoxy) propyl)trimethoxy silane (MPEG-silane). The remaining local regions or poly(poly(ethylene glycol)methyl ether methacrylate-co-glycidyl methacrylate) (P(PEGMEMA-co-GMA)) microdomains were produced via SI-ATRP of PEGMEMA and GMA comonomers. The epoxy groups of the P(PEGMEMA-co-GMA) microdomains were used directly for covalent coupling of an active protein (human immunoglobulin or IgG) via the ring-opening reaction to produce the IgG-coupled microdomains. The IgG-coupled microdomains interact only and specifically with target anti-IgG, while the other antifouling microregions from self-assembled monolayers with short terminal PEG units effectively prevent specific and non-specific protein fouling. When extended to other active biomolecules, microarrays for specific and non-specific analyte interactions with a high signal-to-noise ratio could be readily tailored.

  16. Constructing Novel Si@SnO2 Core-Shell Heterostructures by Facile Self-Assembly of SnO2 Nanowires on Silicon Hollow Nanospheres for Large, Reversible Lithium Storage.

    PubMed

    Zhou, Zheng-Wei; Liu, Yi-Tao; Xie, Xu-Ming; Ye, Xiong-Ying

    2016-03-23

    Developing an industrially viable silicon anode, featured by the highest theoretical capacity (4200 mA h g(-1)) among common electrode materials, is still a huge challenge because of its large volume expansion during repeated lithiation-delithiation as well as low intrinsic conductivity. Here, we expect to address these inherent deficiencies simultaneously with an interesting hybridization design. A facile self-assembly approach is proposed to decorate silicon hollow nanospheres with SnO2 nanowires. The two building blocks, hand in hand, play a wonderful duet by bridging their appealing functionalities in a complementary way: (1) The silicon hollow nanospheres, in addition to the major role as a superior capacity contributor, also act as a host material (core) to partially accommodate the volume expansion, thus alleviating the capacity fading by providing abundant hollow interiors, void spaces, and surface areas. (2) The SnO2 nanowires serve as a conductive coating (shell) to enable efficient electron transport due to a relatively high conductivity, thereby improving the cyclability of silicon. Compared to other conductive dopants, the SnO2 nanowires with a high theoretical capacity (790 mA h g(-1)) can contribute outstanding electrochemical reaction kinetics, further adding value to the ultimate electrochemical performances. The resulting novel Si@SnO2 core-shell heterostructures exhibit remarkable synergy in large, reversible lithium storage, delivering a reversible capacity as high as 1869 mA h g(-1)@500 mA g(-1) after 100 charging-discharging cycles.

  17. The influence of interparticle correlations and self-assembly on the dynamic initial magnetic susceptibility spectra of ferrofluids

    NASA Astrophysics Data System (ADS)

    Ivanov, A. O.; Kantorovich, S. S.; Elfimova, E. A.; Zverev, V. S.; Sindt, J. O.; Camp, P. J.

    2017-06-01

    Using computer simulations and a mean-field theoretical approach, we study how the growth in dipolar interparticle correlations manifests itself in the frequency-dependent initial magnetic susceptibility of a ferrofluid. Our recently developed theory gives the correct single-particle Debye-theory results in the low-concentration, non-interacting regime; and it yields the exact leading-order contributions from interparticle correlations. The susceptibility spectra are analysed in terms of the low-frequency behaviours of the real and imaginary parts, and the position of the peak in the imaginary part. By comparing the theoretical predictions to the results from Brownian dynamics simulations, it is possible to identify the conditions where correlations are important, but where self-assembly has not developed. We also provide a qualitative explanation for the behaviour of spectra beyond the mean-field limit.

  18. Self-assembled peptide-polyoxometalate hybrid nanospheres: two in one enhances targeted inhibition of amyloid β-peptide aggregation associated with Alzheimer's disease.

    PubMed

    Li, Meng; Xu, Can; Wu, Li; Ren, Jinsong; Wang, Enbo; Qu, Xiaogang

    2013-10-25

    Amyloid fibril formation is a critical step in Alzheimer's disease (AD) pathogenesis. Inhibition of Aβ aggregation has shown promising against AD and has been used in clinic trials. Here, a novel strategy is reported for the self-assembly of polyoxometalate-peptide (POM@P) hybrid particles as bifunctional Aβ inhibitors. The two-in-one bifunctional POM@P nanoparticles show an enhanced inhibition effect on amyloid aggregation in mice cerebrospinal fluid. Incorporating a clinically used Aβ fibril-staining dye, congo red (CR), into the hybrid colloidal spheres, the nanoparticles can also act as an effective fluorescent probe to monitor the inhibition process of POM@P via CR fluorescence change in real time. It is believed that such flexible organic-inorganic hybrid systems may prompt the design of new multifunctional materials for AD treatment. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Selective inhibition of MG-63 osteosarcoma cell proliferation induced by curcumin-loaded self-assembled arginine-rich-RGD nanospheres

    PubMed Central

    Chang, Run; Sun, Linlin; Webster, Thomas J

    2015-01-01

    Osteosarcoma is the most frequent primary malignant form of bone cancer, comprising 30% of all bone cancer cases. The objective of this in vitro study was to develop a treatment against osteosarcoma with higher selectivity toward osteosarcoma cells and lower cytotoxicity toward normal healthy osteoblast cells. Curcumin (or diferuloylmethane) has been found to have antioxidant and anticancer effects by multiple cellular pathways. However, it has lower water solubility and a higher degradation rate in alkaline conditions. In this study, the amphiphilic peptide C18GR7RGDS was used as a curcumin carrier in aqueous solution. This peptide contains a hydrophobic aliphatic tail group leading to their self-assembly by hydrophobic interactions, as well as a hydrophilic head group composed of an arginine-rich and an arginine-glycine-aspartic acid structure. Through characterization by transmission electron microscopy, self-assembled structures of spherical amphiphilic nanoparticles (APNPs) with diameters of 10–20 nm in water and phosphate-buffered saline were observed, but this structure dissociated when the pH value was reduced to 4. Using a method of codissolution with acetic acid and dialysis tubing, the solubility of curcumin was enhanced and a homogeneous solution was formed in the presence of APNPs. Successful encapsulation of curcumin in APNPs was then confirmed by Fourier transform infrared and X-ray diffraction analyses. The cytotoxicity and cellular uptake of the APNP/curcumin complexes on both osteosarcoma and normal osteoblast cell lines were also evaluated by methyl-thiazolyl-tetrazolium assays and confocal fluorescence microscopy. The results showed that the curcumin-loaded APNPs had significant selective cytotoxicity against MG-63 osteosarcoma cells when compared with normal osteoblasts. We have demonstrated for the first time that APNPs can encapsulate hydrophobic curcumin in their hydrophobic cores, and curcumin-loaded APNPs could be an innovative treatment

  20. Self-assembly of lead chalcogenide nanocrystals.

    PubMed

    Quan, Zewei; Valentin-Bromberg, Loriana; Loc, Welley Siu; Fang, Jiye

    2011-05-02

    This review focuses on recent developments in the self-assembly of lead chalcogenide nanocrystals into two- and three-dimensional superstructures. Self-assembly is categorized by the shapes of building blocks, including nanospheres, nanocubes, nano-octahedra, and nanostars. In the section on nanospheres, rapid assemblies of lead chalcogenide-based multicomponent nanocrystals with additional components, such as semiconductors, noble metals, and magnetic nanocrystals, are further highlighted. In situ self-assembly of lead chalcogenide nanocrystals into one-dimensional nanostructures at elevated temperatures is also covered. Each section of this paper highlights examples extracted from recent publications. Finally, relatively novel properties and applications arising from lead chalcogenide superlattices as typical examples are also discussed.

  1. Facile fabrication of dual emissive nanospheres via the self-assembling of CdSe@CdS and zinc phthalocyanine and their application for silver ion detection

    NASA Astrophysics Data System (ADS)

    Liu, Shuning; Liu, Chenchen; Luan, Xinying; Yao, Rui; Feng, Yakai

    2017-09-01

    The far-red/near infrared photoluminescence of zinc phthalocyanines would be strongly quenched once they are aggregated, which will obviously hinder their wide applications in environmental, energy related and biomedical fields. Herein, the ultra-small sized semiconductor quantum dots with core-shell structures (CdSe@CdS) have been firstly synthesized and then assembled with a dendritic zinc phthalocyanine (ZnPc) in the H2O/DMF mixed solvent to obtain monodispersed nanospheres. Finally, it was found that the resultant ethanolic colloids can be employed as a sensitive and specific fluorescent nanoprobe for silver ions discrimination with a limit of detection (LOD) approaching to 10-8 mol/L.

  2. Directed immobilization of protein-coated nanospheres to nanometer-scale patterns fabricated by electron beam lithography of poly(ethylene glycol) self-assembled monolayers.

    PubMed

    Rundqvist, Jonas; Hoh, Jan H; Haviland, David B

    2006-05-23

    Controlling the spatial organization of biomolecules on solid supports with high resolution is important for a wide range of scientific and technological problems. Here we report a study of electron beam lithography (EBL) patterning of a self-assembled monolayer (SAM) of the amide-containing poly(ethylene glycol) (PEG) thiol CH(3)O(CH(2)CH(2)O)(17)NHCO(CH(2))(2)SH on Au and demonstrate the patterning of biomolecular features with dimensions approaching 40 nm. The electron dose dependence of feature size and pattern resolution is studied in detail by atomic force microscopy (AFM), which reveals two distinct patterning mechanisms. At low doses, the pattern formation occurs by SAM ablation in a self-developing process where the feature size is directly dose-dependent. At higher doses, electron beam-induced deposition of material, so-called contamination writing, is seen in the ablated areas of the SAM. The balance between these two mechanisms is shown to depend on the geometry of the pattern. The patterned SAMs were backfilled with fluorescent 40-nm spheres coated with NeutrAvidin. These protein-coated spheres adhered to exposed areas in the SAM with high selectivity. This direct writing approach for patterning bioactive surfaces is a fast and efficient way to produce patterns with a resolution approaching that of single proteins.

  3. Atomic-level elucidation of the initial stages of self-assembled monolayer metallization and nanoparticle formation.

    PubMed

    Keith, John A; Jacob, Timo

    2010-11-02

    The development of high-performance molecular electronics and nanotech applications requires deep understanding of atomic level structural, electronic, and magnetic properties of electrode/molecular interfaces. Recent electrochemical experiments on self-assembled monolayers (SAMs) have identified highly practical means to generate nanoparticles and metal monolayers suspended above substrate surfaces through SAM metallizations. A rational basis why this process is even possible is not yet well-understood. To clarify the initial stages of interface formation during SAM metallization, we used first-principles spin-polarized density functional theory (DFT) calculations to study Pd diffusion on top of 4-mercaptopyridine (4MP) SAMs on Au(111). After distinguishing potential-energy surfaces (PESs) for different spin configurations for transition metal atoms on the SAM, we find adatom diffusion is not possible over the clean 4MP-SAM surface. Pre-adsorption of transition-metal atoms, however, facilitates atomic diffusion that appears to explain multiple reports on experimentally observed island and monolayer formation on top of SAMs. Furthermore, these diffusions most likely occur by moving across low-lying and intersecting PESs of different spin states, opening the possibility of magnetic control over these systems. Vertical diffusion processes were also investigated, and the electrolyte was found to play a key role in preventing metal permeation through the SAM to the substrate.

  4. Monitoring and targeting the initial dimerization stage of amyloid self-assembly.

    PubMed

    Bram, Yaron; Lampel, Ayala; Shaltiel-Karyo, Ronit; Ezer, Anat; Scherzer-Attali, Roni; Segal, Daniel; Gazit, Ehud

    2015-02-09

    Amyloid deposits are pathological hallmark of a large group of human degenerative disorders of unrelated etiologies. While accumulating evidence suggests that early oligomers may account for tissue degeneration, most detection tools do not allow the monitoring of early association events. Here we exploit bimolecular fluorescence complementation analysis to detect and quantify the dimerization of three major amyloidogenic polypeptides; islet amyloid polypeptide, β-amyloid and α-synuclein. The constructed systems provided direct visualization of protein-protein interactions in which only assembled dimers display strong fluorescent signal. Potential inhibitors that interfere with the initial intermolecular interactions of islet amyloid polypeptide were further identified using this system. Moreover, the identified compounds were able to inhibit the aggregation and cytotoxicity of islet amyloid polypeptide, demonstrating the importance of targeting amyloid dimer formation for future drug development. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Modeling the self-assembly of silica-templated nanoparticles in the initial stages of zeolite formation.

    PubMed

    Chien, Szu-Chia; Auerbach, Scott M; Monson, Peter A

    2015-05-05

    The reaction ensemble Monte Carlo method was used to model the self-assembly and structure of silica nanoparticles found in the initial stages of the clear-solution synthesis of the silicalite-1 zeolite. Such nanoparticles, which comprise both silica and organic structure-directing agents (OSDAs), are believed to play a crucial role in the formation of silica nanoporous materials, yet very limited atomic-level structural information is available for these nanoparticles. We have modeled silica monomers as flexible tetrahedra with spring constants fitted in previous work to silica bulk moduli and OSDAs as spheres attracted to anionic silica monomers. We have studied one-step and two-step formation mechanisms, the latter involving the initial association of silica species and OSDAs driven by physical solution forces, followed by silica condensation/hydrolysis reactions simulated with reaction ensemble Monte Carlo. The two-step process with preassociation was found to be crucial for generating nearly spherical nanoparticles; otherwise, without preassociation they exhibited jagged, ramified structures. The two-step nanoparticles were found to exhibit a core-shell structure with mostly silica in the core surrounded by a diffuse shell of OSDAs, in agreement with SANS and SAXS data. The Qn distribution, quantifying silicon atoms bound to n bridging oxygens, found in the simulated nanoparticles is in broad agreement with (29)Si solid-state NMR data on smaller, 2 nm nanoparticle populations. Ring-size distributions from the simulated nanoparticles show that five-membered rings are prevalent when considering OSDA/silica mole fractions (∼0.2) that lead to silicalite-1, in agreement with a previous IR and modeling study. Nanoparticles simulated with higher OSDA concentrations show ring-size distributions shifted to smaller rings, with three-membered silica rings dominating at an OSDA/silica mole fraction of 0.8. Our simulations show no evidence of long-range silicalite-1

  6. Self-assembled SnO2 micro- and nanosphere-based gas sensor thick films from an alkoxide-derived high purity aqueous colloid precursor.

    PubMed

    Kelp, G; Tätte, T; Pikker, S; Mändar, H; Rozhin, A G; Rauwel, P; Vanetsev, A S; Gerst, A; Merisalu, M; Mäeorg, U; Natali, M; Persson, I; Kessler, V G

    2016-04-07

    Tin oxide is considered to be one of the most promising semiconductor oxide materials for use as a gas sensor. However, a simple route for the controllable build-up of nanostructured, sufficiently pure and hierarchical SnO2 structures for gas sensor applications is still a challenge. In the current work, an aqueous SnO2 nanoparticulate precursor sol, which is free of organic contaminants and sorbed ions and is fully stable over time, was prepared in a highly reproducible manner from an alkoxide Sn(OR)4 just by mixing it with a large excess of pure neutral water. The precursor is formed as a separate liquid phase. The structure and purity of the precursor is revealed using XRD, SAXS, EXAFS, HRTEM imaging, FTIR, and XRF analysis. An unconventional approach for the estimation of the particle size based on the quantification of the Sn-Sn contacts in the structure was developed using EXAFS spectroscopy and verified using HRTEM. To construct sensors with a hierarchical 3D structure, we employed an unusual emulsification technique not involving any additives or surfactants, using simply the extraction of the liquid phase, water, with the help of dry butanol under ambient conditions. The originally generated crystalline but yet highly reactive nanoparticles form relatively uniform spheres through self-assembly and solidify instantly. The spheres floating in butanol were left to deposit on the surface of quartz plates bearing sputtered gold electrodes, producing ready-for-use gas sensors in the form of ca. 50 μm thick sphere-based-films. The films were dried for 24 h and calcined at 300 °C in air before use. The gas sensitivity of the structures was tested in the temperature range of 150-400 °C. The materials showed a very quickly emerging and reversible (20-30 times) increase in electrical conductivity as a response to exposure to air containing 100 ppm of H2 or CO and short (10 s) recovery times when the gas flow was stopped.

  7. Self-assembled SnO2 micro- and nanosphere-based gas sensor thick films from an alkoxide-derived high purity aqueous colloid precursor

    NASA Astrophysics Data System (ADS)

    Kelp, G.; Tätte, T.; Pikker, S.; Mändar, H.; Rozhin, A. G.; Rauwel, P.; Vanetsev, A. S.; Gerst, A.; Merisalu, M.; Mäeorg, U.; Natali, M.; Persson, I.; Kessler, V. G.

    2016-03-01

    Tin oxide is considered to be one of the most promising semiconductor oxide materials for use as a gas sensor. However, a simple route for the controllable build-up of nanostructured, sufficiently pure and hierarchical SnO2 structures for gas sensor applications is still a challenge. In the current work, an aqueous SnO2 nanoparticulate precursor sol, which is free of organic contaminants and sorbed ions and is fully stable over time, was prepared in a highly reproducible manner from an alkoxide Sn(OR)4 just by mixing it with a large excess of pure neutral water. The precursor is formed as a separate liquid phase. The structure and purity of the precursor is revealed using XRD, SAXS, EXAFS, HRTEM imaging, FTIR, and XRF analysis. An unconventional approach for the estimation of the particle size based on the quantification of the Sn-Sn contacts in the structure was developed using EXAFS spectroscopy and verified using HRTEM. To construct sensors with a hierarchical 3D structure, we employed an unusual emulsification technique not involving any additives or surfactants, using simply the extraction of the liquid phase, water, with the help of dry butanol under ambient conditions. The originally generated crystalline but yet highly reactive nanoparticles form relatively uniform spheres through self-assembly and solidify instantly. The spheres floating in butanol were left to deposit on the surface of quartz plates bearing sputtered gold electrodes, producing ready-for-use gas sensors in the form of ca. 50 μm thick sphere-based-films. The films were dried for 24 h and calcined at 300 °C in air before use. The gas sensitivity of the structures was tested in the temperature range of 150-400 °C. The materials showed a very quickly emerging and reversible (20-30 times) increase in electrical conductivity as a response to exposure to air containing 100 ppm of H2 or CO and short (10 s) recovery times when the gas flow was stopped.Tin oxide is considered to be one of the

  8. Simulation of metal-ligand self-assembly into spherical complex M6L8.

    PubMed

    Yoneya, Makoto; Yamaguchi, Tomohiko; Sato, Sota; Fujita, Makoto

    2012-09-05

    Molecular dynamics simulations were performed to study the self-assembly of a spherical complex through metal-ligand coordination interactions. M(6)L(8), a nanosphere with six palladium ions and eight pyridine-capped tridentate ligands, was selected as a target system. We successfully observed the spontaneous formation of spherical shaped M(6)L(8) cages over the course of our simulations, starting from random initial placement of the metals and ligands. To simulate spontaneous coordination bond formations and breaks, the cationic dummy atom method was employed to model nonbonded metal-ligand interactions. A coarse-grained solvent model was used to fill the gap between the time scale of the supramolecular self-assembly and that accessible by common molecular dynamics simulation. The simulated formation process occurred in the distinct three-stage (assembly, evolution, fixation) process that is well correlated with the experimental results. We found that the difference of the lifetime (or the ligand exchange rate) between the smaller-sized incomplete clusters and the completed M(6)L(8) nanospheres is crucially important in their supramolecular self-assembly.

  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. 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…

  11. Photovoltaic self-assembly.

    SciTech Connect

    Lavin, Judith; Kemp, Richard Alan; Stewart, Constantine A.

    2010-10-01

    This late-start LDRD was focused on the application of chemical principles of self-assembly on the ordering and placement of photovoltaic cells in a module. The drive for this chemical-based self-assembly stems from the escalating prices in the 'pick-and-place' technology currently used in the MEMS industries as the size of chips decreases. The chemical self-assembly principles are well-known on a molecular scale in other material science systems but to date had not been applied to the assembly of cells in a photovoltaic array or module. We explored several types of chemical-based self-assembly techniques, including gold-thiol interactions, liquid polymer binding, and hydrophobic-hydrophilic interactions designed to array both Si and GaAs PV chips onto a substrate. Additional research was focused on the modification of PV cells in an effort to gain control over the facial directionality of the cells in a solvent-based environment. Despite being a small footprint research project worked on for only a short time, the technical results and scientific accomplishments were significant and could prove to be enabling technology in the disruptive advancement of the microelectronic photovoltaics industry.

  12. Clinical performance of self-assembling peptide P11 -4 in the treatment of initial proximal carious lesions: A practice-based case series.

    PubMed

    Schlee, Markus; Schad, Till; Koch, Jan H; Cattin, Philippe C; Rathe, Florian

    2017-09-03

    The aim of the present study was to investigate the clinical performance of self-assembling peptide P11 -4 on non-cavitated initial proximal carious lesions 12 months after treatment. Twenty-six patients, aged between 18 and 65 years, with 35 carious lesions were included in this practice-based, uncontrolled, prospective case series. The opacity and size of the proximal lesions were evaluated visually at baseline and at day 360 using standardized single-tooth or bite-wing and digital-subtraction radiography. Pairwise evaluation of images was carried out in a randomized and blinded manner with respect to the time point. Twelve months after treatment of the proximal carious lesions, the visual evaluation showed a predominant shift toward regression of the initial lesions. Radiographic assessment yielded regression of the caries in 17 of 28 cases; four of 28 were regarded as unchanged, and seven of 28 lesions showed progression of the carious lesion. Combined assessment of clinical radiographs and digital subtraction radiographs confirmed the radiographic assessment, with 20 of 28 lesions showing total or partial regression, four unchanged, and four progressing. Radiographic and digital subtraction analyses suggest that initial proximal carious lesions can regress after treatment with P11 -4, but additional factors might influence the overall treatment outcome. © 2017 John Wiley & Sons Australia, Ltd.

  13. Adsorption of Amelogenin onto Self-Assembled and Fluoroapatite Surfaces

    SciTech Connect

    Tarasevich, Barbara J.; Lea, Alan S.; Bernt, William; Engelhard, Mark H.; Shaw, Wendy J.

    2009-02-19

    Abstract. The interactions of proteins at surfaces are of great importance to biomineralizaton processes and to the development and function of biomaterials. Amelogenin is a unique biomineralization protein because it self-assembles to form supramolecular structures called “nanospheres,” spherical aggregates of monomers that are 20-60 nm in diameter. Although the nanosphere quaternary structure has been observed in solution, the quaternary structure of amelogenin adsorbed onto surfaces is also of great interest because the surface structure is critical to its function. We report studies of the adsorption of the amelogenin onto self-assembled monolayers (SAMs) with COOH and CH3 end group functionality and single crystal fluoroapatite (FAP). Dynamic light scattering (DLS) experiments showed that the solutions contained nanospheres and aggregates of nanospheres. Protein adsorption onto the various substrates was evidenced by null ellipsometry, x-ray photoelectron spectroscopy (XPS), and external reflectance Fourier transform infrared spectroscopy (ERFTIR). Although only nanospheres were observed in solution, ellipsometry and atomic force microscopy (AFM) indicated that the protein adsorbates were much smaller structures than the original nanospheres, from monomers to small oligomers in size. Monomer adsorption was promoted onto the CH3 surfaces and small oligomer adsorption was promoted onto the COOH and FAP substrates. In some cases, remnants of the original nanospheres adsorbed as multilayers on top of the underlying subnanosphere layers. This work suggests that amelogenin can adsorb by the “shedding” or disassembling of substructures from the nanospheres onto substrates and indicates that amelogenin may have a range of possible quaternary structures depending on whether it is in solution or interacting with surfaces.

  14. Self-assembled monolayer initiated electropolymerization: a route to thin-film materials with enhanced photovoltaic performance.

    PubMed

    Hwang, Euiyong; de Silva, K M Nalin; Seevers, Chad B; Li, Jie-Ren; Garno, Jayne C; Nesterov, Evgueni E

    2008-09-02

    Continuing progress in the field of organic polymer photovoltaic (PV) devices requires the development of new materials with better charge-transport efficiency. To improve this parameter, we have investigated surface-attached bilayer polymer PV thin films prepared starting from a covalently attached monolayer of an electroactive initiator using sequential electropolymerization of dithiophene and its derivatives. These systems were found to show significantly increased photocurrent generation quantum yields as compared to systems made through conventional approaches. In addition, the described PV thin films possess remarkable mechanical, air, and photostability. These properties likely arise from the more uniform and better ordered bulk layer morphologies as well as tighter covalently bonded contacts at the interfacial junctions, contributing to improved charge transport. While more studies on the fundamental reasons behind the discovered phenomenon are currently underway, this information can be readily applied to build more efficient organic polymer photovoltaics.

  15. Self-assembly of nanocomposite materials

    DOEpatents

    Brinker, C. Jeffrey; Sellinger, Alan; Lu, Yunfeng

    2001-01-01

    A method of making a nanocomposite self-assembly is provided where at least one hydrophilic compound, at least one hydrophobic compound, and at least one amphiphilic surfactant are mixed in an aqueous solvent with the solvent subsequently evaporated to form a self-assembled liquid crystalline mesophase material. Upon polymerization of the hydrophilic and hydrophobic compounds, a robust nanocomposite self-assembled material is formed. Importantly, in the reaction mixture, the amphiphilic surfactant has an initial concentration below the critical micelle concentration to allow formation of the liquid-phase micellar mesophase material. A variety of nanocomposite structures can be formed, depending upon the solvent evaporazation process, including layered mesophases, tubular mesophases, and a hierarchical composite coating composed of an isotropic worm-like micellar overlayer bonded to an oriented, nanolaminated underlayer.

  16. Self-assembling segmented coiled tubing

    SciTech Connect

    Raymond, David W.

    2016-09-27

    Self-assembling segmented coiled tubing is a concept that allows the strength of thick-wall rigid pipe, and the flexibility of thin-wall tubing, to be realized in a single design. The primary use is for a drillstring tubular, but it has potential for other applications requiring transmission of mechanical loads (forces and torques) through an initially coiled tubular. The concept uses a spring-loaded spherical `ball-and-socket` type joint to interconnect two or more short, rigid segments of pipe. Use of an optional snap ring allows the joint to be permanently made, in a `self-assembling` manner.

  17. Synthesis of ordered porous graphitic-C3N4 and regularly arranged Ta3N5 nanoparticles by using self-assembled silica nanospheres as a primary template.

    PubMed

    Fukasawa, Yuki; Takanabe, Kazuhiro; Shimojima, Atsushi; Antonietti, Markus; Domen, Kazunari; Okubo, Tatsuya

    2011-01-03

    Uniform-sized silica nanospheres (SNSs) assembled into close-packed structures were used as a primary template for ordered porous graphitic carbon nitride (g-C(3)N(4)), which was subsequently used as a hard template to generate regularly arranged Ta(3)N(5) nanoparticles of well-controlled size. Inverse opal g-C(3)N(4) structures with the uniform pore size of 20-80 nm were synthesized by polymerization of cyanamide and subsequent dissolution of the SNSs with an aqueous HF solution. Back-filling of the C(3)N(4) pores with tantalum precursors, followed by nitridation in an NH(3) flow gave regularly arranged, crystalline Ta(3)N(5) nanoparticles that are connected with each other. The surface areas of the Ta(3)N(5) samples were as high as 60 m(2) g(-1), and their particle size was tunable from 20 to 80 nm, which reflects the pore size of g-C(3)N(4). Polycrystalline hollow nanoparticles of Ta(3)N(5) were also obtained by infiltration of a reduced amount of the tantalum source into the g-C(3)N(4) template. An improved photocatalytic activity for H(2) evolution on the assembly of the Ta(3)N(5) nanoparticles under visible-light irradiation was attained as compared with that on a conventional Ta(3)N(5) bulk material with low surface area.

  18. Multilayer self-assemblies as electronic and optical materials

    SciTech Connect

    Li, D.; Luett, M.; Shi, X.; Fitzsimmons, M.R.

    1997-12-31

    The layer-by-layer growth of film structures consisting of sequential depositions of oppositely charged polymers and macrocycles (ring-shaped molecules) have been constructed using molecular self-assembly techniques. These self-assembled thin films were characterized with X-ray reflectometry, which yielded (1) the average electron density, (2) the average thicknesses, and (3) the roughness of the growth surface of the self-assembled multilayer of macrocycles and polymers. These observations suggest that inorganic-organic interactions play an important role during the initial stages of thin-film growth, but less so as the thin film becomes thicker. Optical absorption techniques were also used to characterize the self-assembled multilayers. Phorphyrin and phthalocyanine derivatives were chosen as one of the building blocks of the self-assembled multilayers because of their interesting optical properties.

  19. Intrinsic defect formation in peptide self-assembly

    NASA Astrophysics Data System (ADS)

    Deng, Li; Zhao, Yurong; Xu, Hai; Wang, Yanting

    2015-07-01

    In contrast to extensively studied defects in traditional materials, we report here a systematic investigation of the formation mechanism of intrinsic defects in self-assembled peptide nanostructures. The Monte Carlo simulations with our simplified dynamic hierarchical model revealed that the symmetry breaking of layer bending mode at the two ends during morphological transformation is responsible for intrinsic defect formation, whose microscopic origin is the mismatch between layer stacking along the side-chain direction and layer growth along the hydrogen bond direction. Moreover, defect formation does not affect the chirality of the self-assembled structure, which is determined by the initial steps of the peptide self-assembly process.

  20. Self-assembly via microfluidics.

    PubMed

    Wang, Lei; Sánchez, Samuel

    2015-12-07

    The self-assembly of amphiphilic building blocks has attracted extensive interest in myriad fields in recent years, due to their great potential in the nanoscale design of functional hybrid materials. Microfluidic techniques provide an intriguing method to control kinetic aspects of the self-assembly of molecular amphiphiles by the facile adjustment of the hydrodynamics of the fluids. Up to now, there have been several reports about one-step direct self-assembly of different building blocks with versatile and multi-shape products without templates, which demonstrated the advantages of microfluidics. These assemblies with different morphologies have great applications in various areas such as cancer therapy, micromotor fabrication, and controlled drug delivery.

  1. Self-assembling amphiphilic peptides†

    PubMed Central

    Dehsorkhi, Ashkan; Castelletto, Valeria; Hamley, Ian W

    2014-01-01

    The self-assembly of several classes of amphiphilic peptides is reviewed, and selected applications are discussed. We discuss recent work on the self-assembly of lipopeptides, surfactant-like peptides and amyloid peptides derived from the amyloid-β peptide. The influence of environmental variables such as pH and temperature on aggregate nanostructure is discussed. Enzyme-induced remodelling due to peptide cleavage and nanostructure control through photocleavage or photo-cross-linking are also considered. Lastly, selected applications of amphiphilic peptides in biomedicine and materials science are outlined. © 2014 The Authors. Journal of Peptide Science published by European Peptide Society and John Wiley & Sons, Ltd. PMID:24729276

  2. 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.

  3. Self-Assembly of Large Amyloid Fibers

    NASA Astrophysics Data System (ADS)

    Ridgley, Devin M.

    Functional amyloids found throughout nature have demonstrated that amyloid fibers are potential industrial biomaterials. This work introduces a new "template plus adder" cooperative mechanism for the spontaneous self-assembly of micrometer sized amyloid fibers. A short hydrophobic template peptide induces a conformation change within a highly alpha-helical adder protein to form beta-sheets that continue to assemble into micrometer sized amyloid fibers. This study utilizes a variety of proteins that have template or adder characteristics which suggests that this mechanism may be employed throughout nature. Depending on the amino acid composition of the proteins used the mixtures form amyloid fibers of a cylindrical ( 10 mum diameter, 2 GPa Young's modulus) or tape (5- 10 mum height, 10-20 mum width and 100-200 MPa Young's modulus) morphology. Processing conditions are altered to manipulate the morphology and structural characteristics of the fibers. Spectroscopy is utilized to identify certain amino acid groups that contribute to the self-assembly process. Aliphatic amino acids (A, I, V and L) are responsible for initiating conformation change of the adder proteins to assemble into amyloid tapes. Additional polyglutamine segments (Q-blocks) within the protein mixtures will form Q hydrogen bonds to reinforce the amyloid structure and form a cylindrical fiber of higher modulus. Atomic force microscopy is utilized to delineate the self-assembly of amyloid tapes and cylindrical fibers from protofibrils (15-30 nm width) to fibers (10-20 mum width) spanning three orders of magnitude. The aliphatic amino acid content of the adder proteins' alpha-helices is a good predictor of high density beta-sheet formation within the protein mixture. Thus, it is possible to predict the propensity of a protein to undergo conformation change into amyloid structures. Finally, Escherichia coli is genetically engineered to express a template protein which self-assembles into large amyloid

  4. Final Report for Grant # DE-FG02-02ER46000 Simulations of Self-Assembly of Tethered Nanoparticle Shape Amphiphiles

    SciTech Connect

    Glotzer, Sharon C.

    2014-08-25

    Self-assembly of nanoparticle building blocks including nanospheres, nanorods, nanocubes, nano plates, nanoprisms, etc., may provide a promising means for manipulating these building blocks into functional and useful materials. One increasingly popular method for self-assembly involves functionalizing nanoparticles and nanostructured molecules with “tethers” of organic polymers or biomolecules with specific or nonspecific interactions to facilitate their assembly. However, there is little theory and little understanding of the general principles underlying self-assembly in these complex materials. Using computer simulation to elucidate the principles of self-assembly and develop a predictive theoretical framework was the central goal of this project.

  5. Mussel-inspired bolaamphiphile sticky self-assemblies for the preparation of magnetic nanoparticles.

    PubMed

    Lee, Chaemyeong; Lee, Sang-Yup

    2015-03-01

    Adopting the strong metal binding moiety of a mussel protein, a novel bolaamphiphile molecule was prepared and applied to the fabrication of magnetic core-shell nanoparticles. The novel bolaamphiphile molecule with 3,4-dihydroxyphenylalanine (DOPA) end groups was synthesized and its self-assembly was used as a template to adsorb metal ions and subsequently to produce magnetic nanoparticles. The DOPA bolaamphiphile molecule self-assembled in aqueous solution to produce nanospherical structures that exposed the catechol moiety of DOPA to the outer surface. The catechol groups adsorbed cobalt and iron ions to create magnetic metal oxide clusters on the self-assembly. Spectroscopic analysis showed that the cobalt and iron ions were coordinated with quinone, an oxidized form of the catechol. Exploiting the strong metal-adsorbing and binding properties of DOPA, dense cobalt oxide and iron oxide shell layers were created on the nanospherical self-assembly to produce magnetic core-shell nanoparticles. This study demonstrated a simple method for creating magnetic metal oxide nanoparticles that exploits the molecular binding forces and self-assembly property of DOPA.

  6. Self-Assembly of Plasmonic Nanoclusters for Optical Metauids

    NASA Astrophysics Data System (ADS)

    Schade, Nicholas Benjamin

    I discuss experimental progress towards developing a material with an isotropic, negative index of refraction at optical frequencies. The simplest way to make such a material is to create a metafluid, or a disordered collection of subwavelength, isotropic electromagnetic resonators. Small clusters of metal particles, such as tetrahedra, serve as these constituents. What is needed are methods for manufacturing these structures with high precision and in sufficient yield that their resonances are identical. Jonathan Fan et al. [Science, 328 (5982), 1135-1138, 2010] demonstrated that colloidal self-assembly is a means of preparing electromagnetic resonators from metal nanoparticles. However, the resonances are sensitive to the separation gaps between particles. Standard synthesis routes for metal nanoparticles yield crystals or nanoshells that are inadequate for metafluids due to polydispersity, faceting, and thermal instabilities. To ensure that the separation gaps and resonances are uniform, more monodisperse spherical particles are needed. An additional challenge is the self-assembly of tetrahedral clusters in high yield from these particles. In self-assembly approaches that others have examined previously, the yield of any particular type of cluster is low. In this dissertation I present solutions to several of these problems, developed in collaboration with my research group and others. We demonstrate that slow chemical etching can transform octahedral gold crystals into ultrasmooth, monodisperse nanospheres. The particles can serve as seeds for the growth of larger octahedra which can in turn be etched. The size of the gold nanospheres can therefore be adjusted as desired. We further show that in colloidal mixtures of two sphere species that strongly bind to one another, the sphere size ratio determines the size distribution of self-assembled clusters. At a critical size ratio, tetrahedral clusters assemble in high yield. We explain the experimentally observed

  7. Hierarchical Self-Assembly of Peptide Amphiphiles: Form and Function at Multiple Length Scales

    NASA Astrophysics Data System (ADS)

    Zha, Runye Helen

    Hierarchical self-assembly, the organization of molecules into supramolecular structures of increasing size and complexity, is a potent tool for materials synthesis and requires understanding the connections of structure across multiple length scales. Herein, self-assembly of peptide amphiphiles (PAs) into nanoscopic and macroscopic materials is explored, and their anti-cancer applications are investigated. First, nanoscale assembly is examined in the context of an anti-angiogenic PA bearing the G-helix motif of maspin, a tumor suppressor protein. Assembly of this maspin-mimetic PA (MMPA) stabilizes the native G-helix conformation and improves binding to endothelial cells. Furthermore, PA nanostructures significantly increase cell adhesion to fibronectin as compared to G-helix peptide alone. Combined with its inhibitory effect on cell migration, MMPA nanostructures thus show anti-angiogenic activity on par with maspin protein in vitro and in vivo. Second, assembly of cationic PAs with hyaluronic acid (HA), an anionic polyelectrolyte, into macroscopic membranes is explored using PAs with identical formal charge but systematically varied self-assembly domains. Results suggest that membrane formation is dictated by the initial moments of component aggregation and is highly sensitive to PA molecular structure via nanoscale assembly. Specifically, PAs with beta-sheet forming residues are nanofibrous and have high surface charge density, leading to robust membranes with aligned-fiber microstructure. PAs without beta-sheet forming residues are nanospherical and have low surface charge density, leading to weak membranes with non-fibrous finger-like microstructure. Lastly, the principles of PA-HA membrane assembly are applied towards development of anti-cancer therapeutic biomaterials. Here, cytotoxic PAs bearing the epitope (KLAKLAKbeta)2 are co-assembled with non-bioactive cationic PA in order to achieve varying nanoscale morphology. These nanostructures are then

  8. Self-Assembled Nanospheres for Encapsulation and Aerosolization of Rifampicin.

    PubMed

    Ishikawa, Aline A; Salazar, Jesus V; Salinas, Magaly; Gaitani, Cristiane M; Nurkiewicz, Timothy; Negrete, George R; Garcia, Carlos D

    2016-01-01

    Rifampicin (RIF) is a benchmark drug for treatment of tuberculosis, but poor bioavailability, prolonged treatment, and pill burden have been linked to therapeutic failure and the development of multidrug resistant strains. To overcome these limitations, this study investigated a method of rifampicin nanoencapsulation and aerosol delivery using a commercial, hand-held nebulizer modified with a nitrogen stream.

  9. Moiré Nanosphere Lithography.

    PubMed

    Chen, Kai; Rajeeva, Bharath Bangalore; Wu, Zilong; Rukavina, Michael; Dao, Thang Duy; Ishii, Satoshi; Aono, Masakazu; Nagao, Tadaaki; Zheng, Yuebing

    2015-06-23

    We have developed moiré nanosphere lithography (M-NSL), which incorporates in-plane rotation between neighboring monolayers, to extend the patterning capability of conventional nanosphere lithography (NSL). NSL, which uses self-assembled layers of monodisperse micro/nanospheres as masks, is a low-cost, scalable nanofabrication technique and has been widely employed to fabricate various nanoparticle arrays. Combination with dry etching and/or angled deposition has greatly enriched the family of nanoparticles NSL can yield. In this work, we introduce a variant of this technique, which uses sequential stacking of polystyrene nanosphere monolayers to form a bilayer crystal instead of conventional spontaneous self-assembly. Sequential stacking leads to the formation of moiré patterns other than the usually observed thermodynamically stable configurations. Subsequent O2 plasma etching results in a variety of complex nanostructures. Using the etched moiré patterns as masks, we have fabricated complementary gold nanostructures and studied their optical properties. We believe this facile technique provides a strategy to fabricate complex nanostructures or metasurfaces.

  10. Self-assembled magnetocapillary swimmers

    NASA Astrophysics Data System (ADS)

    Hubert, Maxime; Lumay, Geoffroy; Weyer, Floriane; Obara, Noriko; Vandewalle, Nicolas

    2013-11-01

    Capillary driven self-assembly consists of suspending small objects at a water-air interface. Due to the effects of wetting, gravity and surface tension, the interface is slightly deformed, inducing a net force between the particles. In the experiments we present, we consider the presence of a vertical magnetic field acting on soft-ferromagnetic particles. Dipole-dipole repulsion competes with capillary attraction such that 2d ordered structures are self-assembling. By adding a secondary horizontal and oscillating magnetic field, periodic deformations of the assembly are induced. Pulsating particle arrangements start to swim, either translating or rotating. The physical mechanisms and geometrical ingredients behind this cooperative locomotion are identified. Furthermore, strategies to control the swimming dynamics are proposed.

  11. Multifunctional self-assembled monolayers

    SciTech Connect

    Zawodzinski, T.; Bar, G.; Rubin, S.; Uribe, F.; Ferrais, J.

    1996-06-01

    This is the final report of at three year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The specific goals of this research project were threefold: to develop multifunctional self-assembled monolayers, to understand the role of monolayer structure on the functioning of such systems, and to apply this knowledge to the development of electrochemical enzyme sensors. An array of molecules that can be used to attach electrochemically active biomolecules to gold surfaces has been synthesized. Several members of a class of electroactive compounds have been characterized and the factors controlling surface modification are beginning to be characterized. Enzymes have been attached to self-assembled molecules arranged on the gold surface, a critical step toward the ultimate goal of this project. Several alternative enzyme attachment strategies to achieve robust enzyme- modified surfaces have been explored. Several means of juxtaposing enzymes and mediators, electroactive compounds through which the enzyme can exchange electrons with the electrode surface, have also been investigated. Finally, the development of sensitive biosensors based on films loaded with nanoscale-supported gold particles that have surface modified with the self-assembled enzyme and mediator have been explored.

  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. Anisotropic Self-Assembly of Citrate-Coated Gold Nanoparticles on Fluidic Liposomes.

    PubMed

    Sugikawa, Kouta; Kadota, Tatsuya; Yasuhara, Kazuma; Ikeda, Atsushi

    2016-03-14

    The behavior of self-assembly processes of nanoscale particles on plasma membranes can reveal mechanisms of important biofunctions and/or intractable diseases. Self-assembly of citrate-coated gold nanoparticles (cAuNPs) on liposomes was investigated. The adsorbed cAuNPs were initially fixed on the liposome surfaces and did not self-assemble below the phospholipid phase transition temperature (Tm ). In contrast, anisotropic cAuNP self-assembly was observed upon heating of the composite above the Tm, where the phospholipids became fluid. The number of self-assembled NPs is conveniently controlled by the initial mixing ratio of cAuNPs and liposomes. Gold nanoparticle protecting agents strongly affected the self-assembly process on the fluidic membrane.

  14. Self-assembly of subwavelength nanostructures with symmetry breaking in solution

    NASA Astrophysics Data System (ADS)

    Tian, Xiang-Dong; Chen, Shu; Zhang, Yue-Jiao; Dong, Jin-Chao; Panneerselvam, Rajapandiyan; Zhang, Yun; Yang, Zhi-Lin; Li, Jian-Feng; Tian, Zhong-Qun

    2016-01-01

    Nanostructures with symmetry breaking can allow the coupling between dark and bright plasmon modes to induce strong Fano resonance. However, it is still a daunting challenge to prepare bottom-up self-assembled subwavelength asymmetric nanostructures with appropriate gaps between the nanostructures especially below 5 nm in solution. Here we present a viable self-assembly method to prepare symmetry-breaking nanostructures consisting of Ag nanocubes and Au nanospheres both with tunable size (90-250 nm for Au nanospheres; 100-160 nm for Ag nanocubes) and meanwhile control the nanogaps through ultrathin silica shells of 1-5 nm thickness. The Raman tag of 4-mercaptobenzoic acid (MBA) assists the self-assembly process and endows the subwavelength asymmetric nanostructures with surface-enhanced Raman scattering (SERS) activity. Moreover, thick silica shells (above 50 nm thickness) can be coated on the self-assembled nanostructures in situ to stabilize the whole nanostructures, paving the way toward bioapplications. Single particle scattering spectroscopy with a 360° polarization resolution is performed on individual Ag nanocube and Au nanosphere dimers, correlated with high-resolution TEM characterization. The asymmetric dimers exhibit strong configuration and polarization dependence Fano resonance properties. Overall, the solution-based self-assembly method reported here is opening up new opportunities to prepare diverse multicomponent nanomaterials with optimal performance.Nanostructures with symmetry breaking can allow the coupling between dark and bright plasmon modes to induce strong Fano resonance. However, it is still a daunting challenge to prepare bottom-up self-assembled subwavelength asymmetric nanostructures with appropriate gaps between the nanostructures especially below 5 nm in solution. Here we present a viable self-assembly method to prepare symmetry-breaking nanostructures consisting of Ag nanocubes and Au nanospheres both with tunable size (90-250 nm

  15. 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.

  16. 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

  17. Self-assembling magnetic "snakes"

    SciTech Connect

    2010-01-01

    Nickel particles float peacefully in a liquid medium until a giant snake seems to swim by and snatch several particles up, adding to its own mass. The self-assembled "snakes" act like biological systems, but they are not alive and are driven by a magnetic field. The research may someday offer some insight into the organization of life itself. Read more at Wired: http://www.wired.com/wiredscience/2009/03/snakes/ Research and video by Alex Snezhko and Igor Aronson, Argonne National Laboratory.

  18. Colloidal self-assembly meets nanofabrication: from two-dimensional colloidal crystals to nanostructure arrays.

    PubMed

    Zhang, Junhu; Li, Yunfeng; Zhang, Xuemin; Yang, Bai

    2010-10-08

    Self-assembly of colloidal microspheres or nanospheres is an effective strategy for fabrication of ordered nanostructures. By combination of colloidal self-assembly with nanofabrication techniques, two-dimensional (2D) colloidal crystals have been employed as masks or templates for evaporation, deposition, etching, and imprinting, etc. These methods are defined as "colloidal lithography", which is now recognized as a facile, inexpensive, and repeatable nanofabrication technique. This paper presents an overview of 2D colloidal crystals and nanostructure arrays fabricated by colloidal lithography. First, different methods for fabricating self-assembled 2D colloidal crystals and complex 2D colloidal crystal structures are summarized. After that, according to the nanofabrication strategy employed in colloidal lithography, related works are reviewed as colloidal-crystal-assisted evaporation, deposition, etching, imprinting, and dewetting, respectively.

  19. Molecular self-assembly at solid surfaces.

    PubMed

    Otero, Roberto; Gallego, José María; de Parga, Amadeo L Vázquez; Martín, Nazario; Miranda, Rodolfo

    2011-11-23

    Self-assembly, the process by which objects initially distributed at random arrange into well-defined patterns exclusively due to their local mutual interactions without external intervention, is generally accepted to be the most promising method for large-scale fabrication of functional nanostructures. In particular, the ordering of molecular building-blocks deposited at solid surfaces is relevant for the performance of many organic electronic and optoelectronic devices, such as organic field-effect transistors (OFETs), organic light-emitting diodes (OLEDs) or photovoltaic solar cells. However, the fundamental knowledge on the nature and strength of the intermolecular and molecule-substrate interactions that govern the ordering of molecular adsorbates is, in many cases, rather scarce. In most cases, the structure and morphology of the organic-metal interface is not known and it is just assumed to be the same as in the bulk, thereby implicitly neglecting the role of the surface on the assembly. However, this approximation is usually not correct, and the evidence gathered over the last decades points towards an active role of the surface in the assembly, leading to self-assembled structures that only in a few occasions can be understood by considering just intermolecular interactions in solid or gas phases. In this work we review several examples from our recent research demonstrating the apparently endless variety of ways in which the surface might affect the assembly of organic adsorbates.

  20. Self-assembled nanostructured metamaterials

    NASA Astrophysics Data System (ADS)

    Ponsinet, Virginie; Baron, Alexandre; Pouget, Emilie; Okazaki, Yutaka; Oda, Reiko; Barois, Philippe

    2017-07-01

    The concept of metamaterials emerged in the years 2000 with the achievement of artificial structures enabling nonconventional propagation of electromagnetic waves, such as negative phase velocity or negative refraction. The electromagnetic response of metamaterials is generally based on the presence of optically resonant elements —or meta-atoms— of sub-wavelength size and well-designed morphology so as to provide the desired electric and magnetic optical properties. Top-down technologies based on lithography techniques have been intensively used to fabricate a variety of efficient electric and magnetic resonators operating from microwave to visible light frequencies. However, the technological limits of the top-down approach are reached in visible light where a huge number of nanometre-sized elements is required. We show here that the bottom-up fabrication route based on the combination of nanochemistry and the self-assembly methods of colloidal physics provide an excellent alternative for the large-scale synthesis of complex meta-atoms, as well as for the fabrication of 2D and 3D samples exhibiting meta-properties in visible light. Contribution to the Focus Issue Self-assemblies of Inorganic and Organic Nanomaterials edited by Marie-Paule Pileni.

  1. Self-assembling RNA square

    SciTech Connect

    Dibrov, Sergey M.; McLean, Jaime; Parsons, Jerod; Hermann, Thomas

    2011-12-22

    The three-dimensional structures of noncoding RNA molecules reveal recurring architectural motifs that have been exploited for the design of artificial RNA nanomaterials. Programmed assembly of RNA nanoobjects from autonomously folding tetraloop-receptor complexes as well as junction motifs has been achieved previously through sequence-directed hybridization of complex sets of long oligonucleotides. Due to size and complexity, structural characterization of artificial RNA nanoobjects has been limited to low-resolution microscopy studies. Here we present the design, construction, and crystal structure determination at 2.2 {angstrom} of the smallest yet square-shaped nanoobject made entirely of double-stranded RNA. The RNA square is comprised of 100 residues and self-assembles from four copies each of two oligonucleotides of 10 and 15 bases length. Despite the high symmetry on the level of secondary structure, the three-dimensional architecture of the square is asymmetric, with all four corners adopting distinct folding patterns. We demonstrate the programmed self-assembly of RNA squares from complex mixtures of corner units and establish a concept to exploit the RNA square as a combinatorial nanoscale platform.

  2. Self-assembled controllable microswimmers

    NASA Astrophysics Data System (ADS)

    Grosjean, Galien; Lagubeau, Guillaume; Darras, Alexis; Lumay, Geoffroy; Hubert, Maxime; Vandewalle, Nicolas

    2015-11-01

    Because they cause a deformation of the interface, floating particles interact. In particular, identical particles attract each other. To counter this attraction, particles possessing a large magnetic moment m-> are used. When m-> is perpendicular to the surface, dipole-dipole interaction is repulsive. This competition of forces can lead to the spontaneous formation of organized structures. By using submillimetric steel spheres for which m-> ~ B-> , interdistances in the system can be precisely tuned. Here, we deform these self-assemblies by adding a horizontal contribution m-> to the magnetic moment. Time reversal symmetry is broken in the system, leading to locomotion at low Reynolds number. Moreover, swimming direction depends on the orientation of field, meaning that swimming trajectories can be finely controlled. A model allows to understand the breaking of symmetry, while a study of the vibration modes gives further informations on the dynamics of this sytem. Because this system forms by self-assembly, it allows miniaturization with applications such as cargo transport or solvent flows. It is highly versatile, being composed of simple passive particles and controlled by magnetic fields.

  3. Chemical reactions directed Peptide self-assembly.

    PubMed

    Rasale, Dnyaneshwar B; Das, Apurba K

    2015-05-13

    Fabrication of self-assembled nanostructures is one of the important aspects in nanoscience and nanotechnology. The study of self-assembled soft materials remains an area of interest due to their potential applications in biomedicine. The versatile properties of soft materials can be tuned using a bottom up approach of small molecules. Peptide based self-assembly has significant impact in biology because of its unique features such as biocompatibility, straight peptide chain and the presence of different side chain functionality. These unique features explore peptides in various self-assembly process. In this review, we briefly introduce chemical reaction-mediated peptide self-assembly. Herein, we have emphasised enzymes, native chemical ligation and photochemical reactions in the exploration of peptide self-assembly.

  4. Chemical Reactions Directed Peptide Self-Assembly

    PubMed Central

    Rasale, Dnyaneshwar B.; Das, Apurba K.

    2015-01-01

    Fabrication of self-assembled nanostructures is one of the important aspects in nanoscience and nanotechnology. The study of self-assembled soft materials remains an area of interest due to their potential applications in biomedicine. The versatile properties of soft materials can be tuned using a bottom up approach of small molecules. Peptide based self-assembly has significant impact in biology because of its unique features such as biocompatibility, straight peptide chain and the presence of different side chain functionality. These unique features explore peptides in various self-assembly process. In this review, we briefly introduce chemical reaction-mediated peptide self-assembly. Herein, we have emphasised enzymes, native chemical ligation and photochemical reactions in the exploration of peptide self-assembly. PMID:25984603

  5. 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.

  6. Evolution of Nanoflowers and Nanospheres of Zinc Bisporphyrinate Tweezers at the Air/water Interface.

    PubMed

    Xie, Fan; Zhuo, Congcong; Hu, Chuanjiang; Liu, Ming Hua

    2017-03-22

    While the sophisticated Langmuir and Langmuir-Blodgett technique facilitates the fabrication of uniform ultrathin monolayer and films, it is also revealed as a powerful tool for the bottom-up constructions of the nanostructures through the air/water interface. In this paper, unique nanoflowers or nanospheres were constructed based on the synthesized m-phthalic diamide-linked Zinc bis-porphyrinate tweezers using the Langmuir and Langmuir-Blodgett (LB) technique. It was found that both the two tweezer type Zinc bisporphyrinates could form stable two-dimensional spreading films at the air/water interface, which could be subsequently transferred onto solid substrates by the vertical lifting method. The atomic force microscope (AFM) revealed that at the initial spreading stage the compound formed flat disk-like domains and then hierarchically evolved into nanoflowers or nanospheres upon compressing the floating film. Such nanostructures have not been reported before and cannot be fabricated using the other self-assembly methods.

  7. Self-assembly of tetrahedral plasmonic nanoclusters for optical metafluids

    NASA Astrophysics Data System (ADS)

    Schade, Nicholas; Manoharan, Vinothan

    2015-03-01

    We direct the assembly of clusters of gold nanospheres that behave as nanoscale electromagnetic resonators. We use spherical gold nanoparticles that are exceptionally smooth, monocrystalline, and monodisperse. These particles exhibit highly reproducible scattering spectra compared with gold colloids that are available commercially. We mix these positively charged particles with negatively charged dielectric particles. The gold particles stick to the dielectric particles permanently and randomly in a process that can be modeled mathematically as ``random parking,'' a type of non-equilibrium self-assembly. By controlling the particles' sizes, stoichiometry, and interactions, we maximize the yield of tetrahedral clusters, the ideal structures for isotropic metamaterials. We measure the optical properties of these structures with dark-field spectroscopy to characterize their suitability as building blocks for a bulk, isotropic, optical metafluid.

  8. Stereochemistry in subcomponent self-assembly.

    PubMed

    Castilla, Ana M; Ramsay, William J; Nitschke, Jonathan R

    2014-07-15

    incorporated in self-assembly reactions to control the stereochemistry of increasingly complex architectures. This strategy has also allowed exploration of the degree to which stereochemical information is propagated through tetrahedral frameworks cooperatively, leading to the observation of stereochemical coupling across more than 2 nm between metal stereocenters and the enantioselective synthesis of a face-capped tetrahedron containing no carbon stereocenters via a stereochemical memory effect. Several studies on the communication of stereochemistry between the configurationally flexible metal centers in tetrahedral metal-organic cages have shed light on the factors governing this process, allowing the synthesis of an asymmetric cage, obtained in racemic form, in which all symmetry elements have been broken. Finally, we discuss how stereochemical diversity leads to structural complexity in the structures prepared through subcomponent self-assembly. Initial use of octahedral metal templates with facial stereochemistry in subcomponent self-assembly, which predictably gave rise to structures of tetrahedral symmetry, was extended to meridional metal centers. These lower-symmetry linkages have allowed the assembly of a series of increasingly intricate 3D architectures of varying functionality. The knowledge gained from investigating different aspects of the stereochemistry of metal-templated assemblies thus not only leads to new means of structural control but also opens pathways toward functions such as stereoselective guest binding and transformation.

  9. Multi-scale modeling for the self-assembly of DNA-functionalized nanoparticle into supperlattice and Wulff polydedra

    NASA Astrophysics Data System (ADS)

    Li, Ting; Auyeung, Evelyn; Mirkin, Chad; Olvera de La Cruz, Monica; Northwestern University Team

    2014-03-01

    Since 1996, DNA hybridization has proven robust for programmable self-assembly of nanoparticles (NPs). Recently, we showed that through a ``slow cooling'' method, DNA functionalized nanospheres or so-called ``programmable atom equivalents'' can assemble into crystals with a specific and uniform habit. Here we perform molecular dynamics simulations on multi-scale models to study and predict the corresponding shapes. Firstly, we use a scale-accurate coarse-grained model with explicit DNA chains to estimate surface energy ratios for different surface orientations, and predict the corresponding Wulff polyhedra based on these values. Secondly, we use a colloidal model in which each DNA coated nanosphere is represented by a single bead to simulate the growth dynamics of the crystals. By this method, we confirm the shape for the body-centered-cubic system to be a (110)-enclosed rhombic dodecahedron. But the face-centered-cubic system does not show any uniform shape yet except triangular features with (111) and (100) facets due to crystallographic defects including twinning and stacking faults. These simulated crystal shapes agrees very well with experiments. Air Force Office of Scientific Research (AFOSR) Multidisciplinary University Research Initiative (MURI) FA9550-11-1-0275.

  10. Functionalization of Recombinant Amelogenin Nanospheres Allows Their Binding to Cellulose Materials.

    PubMed

    Butler, Samuel J; Bülow, Leif; Bonde, Johan

    2016-10-01

    Protein engineering to functionalize the self-assembling enamel matrix protein amelogenin with a cellulose binding domain (CBD) is used. The purpose is to examine the binding of the engineered protein, rh174CBD, to cellulose materials, and the possibility to immobilize self-assembled amelogenin nanospheres on cellulose. rh174CBD assembled to nanospheres ≈35 nm in hydrodynamic diameter, very similar in size to wild type amelogenin (rh174). Uniform particles are formed at pH 10 for both rh174 and rh174CBD, but only rh174CBD nanospheres showes significant binding to cellulose (Avicel). Cellulose binding of rh174CBD is promoted when the protein is self-assembled to nanospheres, compared to being in a monomeric form, suggesting a synergistic effect of the multiple CBDs on the nanospheres. The amount of bound rh174CBD nanospheres reached ≈15 mg/g Avicel, which corresponds to 4.2 to 6.3 × 10(-7) mole/m(2) . By mixing rh174 and rh174CBD, and then inducing self-assembly, composite nanospheres with a high degree of cellulose binding can be formed, despite a lower proportion of rh174CBD. This demonstrates that amelogenin variants like rh174 can be incorporated into the nanospheres, and still retain most of the binding to cellulose. Engineered amelogenin nanoparticles can thus be utilized to construct a range of new cellulose based hybrid materials, e.g. for wound treatment.

  11. 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…

  12. 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.

  13. 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…

  14. Research on Self-Assembling Quantum Dots.

    DTIC Science & Technology

    1995-10-30

    0K. in a second phase of this contract we turned our efforts to the fabrication and studies of self assembled quantum dots . We first demonstrated a...method for producing InAs-GasAs self assembled quantum dots (SAD) using MBE. (AN)

  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. Developmental self-assembly of a DNA tetrahedron.

    PubMed

    Sadowski, John P; Calvert, Colby R; Zhang, David Yu; Pierce, Niles A; Yin, Peng

    2014-04-22

    Kinetically controlled isothermal growth is fundamental to biological development, yet it remains challenging to rationally design molecular systems that self-assemble isothermally into complex geometries via prescribed assembly and disassembly pathways. By exploiting the programmable chemistry of base pairing, sophisticated spatial and temporal control have been demonstrated in DNA self-assembly, but largely as separate pursuits. By integrating temporal with spatial control, here we demonstrate the "developmental" self-assembly of a DNA tetrahedron, where a prescriptive molecular program orchestrates the kinetic pathways by which DNA molecules isothermally self-assemble into a well-defined three-dimensional wireframe geometry. In this reaction, nine DNA reactants initially coexist metastably, but upon catalysis by a DNA initiator molecule, navigate 24 individually characterizable intermediate states via prescribed assembly pathways, organized both in series and in parallel, to arrive at the tetrahedral final product. In contrast to previous work on dynamic DNA nanotechnology, this developmental program coordinates growth of ringed substructures into a three-dimensional wireframe superstructure, taking a step toward the goal of kinetically controlled isothermal growth of complex three-dimensional geometries.

  17. 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

  18. Liquid Cell Electron Microscopy of Nanoparticle Self-Assembly Driven by Solvent Drying.

    PubMed

    Lee, Won Chul; Kim, Byung Hyo; Choi, Sun; Takeuchi, Shoji; Park, Jungwon

    2017-02-02

    Drying a colloidal solution of nanoparticles is a versatile method to construct self-assembled structures of nanoparticles. However, mechanistic understanding has mostly relied on empirical knowledge obtained from the final structures of self-assembly as relevant processes during solvent drying are likely kinetic and far from equilibrium. Here, we present in situ TEM studies of nanoparticle self-assembly under various conditions, including the concentrations of the initial solution and the types of nanoparticles and substrates. The capability of tracking trajectories of individual nanoparticles enables us to understand the mechanisms of drying-mediated self-assembly at the single-nanoparticle level. Our results consistently show that a solvent boundary primarily affects nanoparticle motions and the resulting self-assembly processes regardless of different conditions. The solvent boundary drives nanoparticles to form two-dimensional assembly mainly through two pathways, transporting scattered nanoparticles by lateral dragging and flattening aggregated nanoparticles by vertical pressing.

  19. 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.

  20. Nanosphere lithography from template-directed colloidal sphere assemblies.

    PubMed

    Yan, Qingfeng; Chen, Ao; Chua, Soo Jin; Zhao, X S

    2006-06-01

    Conventional nanosphere lithography holds the drawbacks of lacking precise control over the shape and architecture of the resultant nanostructures. In this work, nanoimprinting lithography was used to construct various desired patterns on a polymer film coated on a silicon substrate. The patterns were then used as templates to direct the self-assembly of silica colloidal spheres, forming colloidal assemblies with well-controlled sizes, shapes, and structures. Subsequent nanosphere lithography using template-directed colloidal sphere assemblies resulted in complex nanostructures that can not be obtained using the conventional nanosphere lithography method.

  1. 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

  2. Self-Assembly Behavior of Pullulan Abietate

    NASA Astrophysics Data System (ADS)

    Gradwell, Sheila; Esker, Alan; Glasser, Wolgang; Heinze, Thomas

    2003-03-01

    Wood is one of nature's most fascinating biological composites due to its toughness and resistance to fracture properties. These properties stem from the self-assembly of cellulose microfibrils in an amorphous matrix of hemicellulose and lignin. In recent years, science has looked to nature for guidance in preparing synthetic materials with desirable physical properties. In order to study the self-assembly process in wood, a model system composed of a polysaccharide, pullulan abietate, and a biomimetic cellulose substrate prepared by the Langmuir-Blodgett technique has been developed. Interfacial tension and surface plasmon resonance measurements used to study the self-assembly process will be discussed for different pullulan derivatives.

  3. Self-assembling nanoparticles into holographic nanopatterns

    NASA Astrophysics Data System (ADS)

    Lee, Seung-Heon; Diana, Frédéric S.; Badolato, Antonio; Petroff, Pierre M.; Kramer, Edward J.

    2004-05-01

    We demonstrate a method to self-assemble metal nanoparticles into two-dimensional lattices. Monodisperse cobalt nanoparticles were synthesized within inverse micelles of polystyrene-block-poly(2-vinylpyridine) copolymer in toluene. A periodic hole pattern of photoresist (PR) was fabricated on a GaAs substrate by holographic lithography. The nanoparticles as prepared above were self-assembled onto the PR nanopatterns by dip or spin casting. They were selectively positioned in the holes due to the capillary forces related to the pattern geometry. Our study reveals that self-assembled nanoparticles in two-dimensional lattices can be obtained with a controllable number of particles per lattice point.

  4. Computational design of protein self-assembly.

    PubMed

    Norn, Christoffer H; André, Ingemar

    2016-08-01

    Protein self-assembly is extensively used in nature to build functional biomolecules and provides a general approach to design molecular complexes with many intriguing applications. Although computational design of protein-protein interfaces remains difficult, much progress has recently been made in de novo design of protein assemblies with cyclic, helical, cubic, internal and lattice symmetries. Here, we discuss some of the underlying biophysical principles of self-assembly that influence the design problem and highlight methodological advances that have made self-assembly design a fruitful area of protein design.

  5. Dissecting Amelogenin Protein Nanospheres

    PubMed Central

    Bromley, Keith M.; Kiss, Andrew S.; Lokappa, Sowmya Bekshe; Lakshminarayanan, Rajamani; Fan, Daming; Ndao, Moise; Evans, John Spencer; Moradian-Oldak, Janet

    2011-01-01

    Amelogenin self-assembles to form an extracellular protein matrix, which serves as a template for the continuously growing enamel apatite crystals. To gain further insight into the molecular mechanism of amelogenin nanosphere formation, we manipulated the interactions between amelogenin monomers by altering pH, temperature, and protein concentration to create isolated metastable amelogenin oligomers. Recombinant porcine amelogenins (rP172 and rP148) and three different mutants containing only a single tryptophan (Trp161, Trp45, and Trp25) were used. Dynamic light scattering and fluorescence studies demonstrated that oligomers were metastable and in constant equilibrium with monomers. Stable oligomers with an average hydrodynamic radius (RH) of 7.5 nm were observed at pH 5.5 between 4 and 10 mg·ml−1. We did not find any evidence of a significant increase in folding upon self-association of the monomers into oligomers, indicating that they are disordered. Fluorescence experiments with single tryptophan amelogenins revealed that upon oligomerization the C terminus of amelogenin (around residue Trp161) is exposed at the surface of the oligomers, whereas the N-terminal region around Trp25 and Trp45 is involved in protein-protein interaction. The truncated rP148 formed similar but smaller oligomers, suggesting that the C terminus is not critical for amelogenin oligomerization. We propose a model for nanosphere formation via oligomers, and we predict that nanospheres will break up to form oligomers in mildly acidic environments via histidine protonation. We further suggest that oligomeric structures might be functional components during maturation of enamel apatite. PMID:21840988

  6. Sequential self-assembly of DNA functionalized droplets

    DOE PAGES

    Zhang, Yin; McMullen, Angus; Pontani, Lea-Laetitia; ...

    2017-06-16

    Complex structures and devices, both natural and manmade, are often constructed sequentially. From crystallization to embryogenesis, a nucleus or seed is formed and built upon. Sequential assembly allows for initiation, signaling, and logical programming, which are necessary for making enclosed, hierarchical structures. Though biology relies on such schemes, they have not been available in materials science. We demonstrate programmed sequential self-assembly of DNA functionalized emulsions. The droplets are initially inert because the grafted DNA strands are pre-hybridized in pairs. Active strands on initiator droplets then displace one of the paired strands and thus release its complement, which in turn activatesmore » the next droplet in the sequence, akin to living polymerization. This strategy provides time and logic control during the self-assembly process, and offers a new perspective on the synthesis of materials.« less

  7. Defects in the Self-Assembly of Block Copolymers and Their Relevance for Directed Self-Assembly.

    PubMed

    Li, Weihua; Müller, Marcus

    2015-01-01

    Block copolymer self-assembly provides a platform for fabricating dense, ordered nanostructures by encoding information in the chemical architecture of multicomponent macromolecules. Depending on the volume fraction of the components and chain topology, these macromolecules form a variety of spatially periodic microphases in thermodynamic equilibrium. The kinetics of self-assembly, however, often results in initial morphologies with defects, and the subsequent ordering is protracted. Different strategies have been devised to direct the self-assembly of copolymer materials by external fields to align and perfect the self-assembled nanostructures. Understanding and controlling the thermodynamics of defects, their response to external fields, and their dynamics is important because applications in microelectronics either require extremely low defect densities or aim at generating specific defects at predetermined locations to fabricate irregular device-oriented structures for integrated circuits. In this review, we discuss defect morphologies of block copolymers in the bulk and thin films, highlighting (a) analogies to and differences from defects in other crystalline materials, (b) the stability of defects and their dynamics, and (c) the influence of external fields.

  8. 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.

  9. Directed Self-Assembly of Nanodispersions

    SciTech Connect

    Furst, Eric M

    2013-11-15

    Directed self-assembly promises to be the technologically and economically optimal approach to industrial-scale nanotechnology, and will enable the realization of inexpensive, reproducible and active nanostructured materials with tailored photonic, transport and mechanical properties. These new nanomaterials will play a critical role in meeting the 21st century grand challenges of the US, including energy diversity and sustainability, national security and economic competitiveness. The goal of this work was to develop and fundamentally validate methods of directed selfassembly of nanomaterials and nanodispersion processing. The specific aims were: 1. Nanocolloid self-assembly and interactions in AC electric fields. In an effort to reduce the particle sizes used in AC electric field self-assembly to lengthscales, we propose detailed characterizations of field-driven structures and studies of the fundamental underlying particle interactions. We will utilize microscopy and light scattering to assess order-disorder transitions and self-assembled structures under a variety of field and physicochemical conditions. Optical trapping will be used to measure particle interactions. These experiments will be synergetic with calculations of the particle polarizability, enabling us to both validate interactions and predict the order-disorder transition for nanocolloids. 2. Assembly of anisotropic nanocolloids. Particle shape has profound effects on structure and flow behavior of dispersions, and greatly complicates their processing and self-assembly. The methods developed to study the self-assembled structures and underlying particle interactions for dispersions of isotropic nanocolloids will be extended to systems composed of anisotropic particles. This report reviews several key advances that have been made during this project, including, (1) advances in the measurement of particle polarization mechanisms underlying field-directed self-assembly, and (2) progress in the

  10. From Solvolysis to Self-Assembly*

    PubMed Central

    Stang, Peter J.

    2009-01-01

    My sojourn from classical physical-organic chemistry and solvolysis to self-assembly and supramolecular chemistry, over the last forty years, is described. My contributions to unsaturated reactive intermediates, namely vinyl cations and unsaturated carbenes, along with my decade long involvement with polyvalent iodine chemistry, especially alkynyliodonium salts, as well as my more recent research with metal-ligand, coordination driven and directed self-assembly of finite supramolecular ensembles are discussed. PMID:19111062

  11. Self-assembled nanostructured cellulose prepared by a dissolution and regeneration process using phosphoric acid as a solvent.

    PubMed

    Hao, Xiaoxia; Shen, Wei; Chen, Zhigang; Zhu, Jiaming; Feng, Li; Wu, Zongwei; Wang, Peng; Zeng, Xiaoxiong; Wu, Tao

    2015-06-05

    This report describes a "green" method for preparing self-assembled nanostructured cellulose through a dissolution and regeneration process. Cold phosphoric acid is used to dissolve cellulose in order to convert crystalline cellulose into its molecular form. Self-assembly of cellulose molecules into nanostructured cellulose is achieved by using water to regenerate cellulose. By controlling the temperature and time of the phosphoric acid treatment between dissolution and regeneration, the degree of polymerization and the degree of substitution of phosphorous for the regenerated celluloses can be tuned. As a result, cellulose nanofibers or nanospheres can be obtained when the treatment temperature is set to 5 or 50°C, respectively. X-ray analysis shows that the cellulose nanofibers are amorphous and that the cellulose nanospheres are structured similarly to cellulose II with crystallinity indexes between 56 and 73%. Our method offers a "green" process for preparing nanostructured celluloses in high yields. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Tetraphenylethene-based star shaped porphyrins: synthesis, self-assembly, and optical and photophysical study.

    PubMed

    Rananaware, Anushri; Bhosale, Rajesh S; Ohkubo, Kei; Patil, Hemlata; Jones, Lathe A; Jackson, Sam L; Fukuzumi, Shunichi; Bhosale, Sidhanath V; Bhosale, Sheshanath V

    2015-04-17

    Supramolecular self-assembly and self-organization are simple and convenient ways to design and create controlled assemblies with organic molecules, and they have provoked great interest due to their potential applications in various fields, such as electronics, photonics, and light-energy conversion. Herein, we describe the synthesis of two π-conjugated porphyrin molecules bearing tetraphenylethene moieties with high fluorescence quantum yield. Photophysical and electrochemical studies were conducted to understand the physical and redox properties of these new materials, respectively. Furthermore, these derivatives were used to investigate self-assembly via the solvophobic effect. The self-assembled aggregation was performed in nonpolar and polar organic solvents and forms nanospheres and ring-like nanostructures, respectively. The solution based aggregation was studied by means of UV-vis absorption, emission, XRD, and DLS analyses. Self-assembled ring-shape structures were visualized by SEM and TEM imaging. This ring-shape morphology of nanosized macromolecules might be a good candidate for the creation of artificial light-harvesting nanodevices.

  13. Self-assembling holographic biosensors and biocomputers.

    SciTech Connect

    Light, Yooli Kim; Bachand, George David (Sandia National Laboratories, Albuquerque, NM); Schoeniger, Joseph S.; Trent, Amanda M. (Sandia National Laboratories, Albuquerque, NM)

    2006-05-01

    We present concepts for self-assembly of diffractive optics with potential uses in biosensors and biocomputers. The simplest such optics, diffraction gratings, can potentially be made from chemically-stabilized microtubules migrating on nanopatterned tracks of the motor protein kinesin. We discuss the fabrication challenges involved in patterning sub-micron-scale structures with proteins that must be maintained in aqueous buffers to preserve their activity. A novel strategy is presented that employs dry contact printing onto glass-supported amino-silane monolayers of heterobifunctional crosslinkers, followed by solid-state reactions of these cross-linkers, to graft patterns of reactive groups onto the surface. Successive solution-phase addition of cysteine-mutant proteins and amine-reactive polyethylene glycol allows assembly of features onto the printed patterns. We present data from initial experiments showing successful micro- and nanopatterning of lines of single-cysteine mutants of kinesin interleaved with lines of polyethylene, indicating that this strategy can be employed to arrays of features with resolutions suitable for gratings.

  14. Guided self-assembly of nanostructured titanium oxide

    NASA Astrophysics Data System (ADS)

    Wang, Baoxiang; Rozynek, Zbigniew; Fossum, Jon Otto; Knudsen, Kenneth D.; Yu, Yingda

    2012-02-01

    A series of nanostructured titanium oxide particles were synthesized by a simple wet chemical method and characterized by means of small-angle x-ray scattering (SAXS)/wide-angle x-ray scattering (WAXS), atomic force microscope (AFM), scanning electron microscope (SEM), transmission electron microscope (TEM), thermal analysis, and rheometry. Tetrabutyl titanate (TBT) and ethylene glycol (EG) can be combined to form either TiOx nanowires or smooth nanorods, and the molar ratio of TBT:EG determines which of these is obtained. Therefore, TiOx nanorods with a highly rough surface can be obtained by hydrolysis of TBT with the addition of cetyl-trimethyl-ammonium bromide (CTAB) as surfactant in an EG solution. Furthermore, TiOx nanorods with two sharp ends can be obtained by hydrolysis of TBT with the addition of salt (LiCl) in an EG solution. The AFM results show that the TiOx nanorods with rough surfaces are formed by the self-assembly of TiOx nanospheres. The electrorheological (ER) effect was investigated using a suspension of titanium oxide nanowires or nanorods dispersed in silicone oil. Oil suspensions of titanium oxide nanowires or nanorods exhibit a dramatic reorganization when submitted to a strong DC electric field and the particles aggregate to form chain-like structures along the direction of applied electric field. Two-dimensional SAXS images from chains of anisotropically shaped particles exhibit a marked asymmetry in the SAXS patterns, reflecting the preferential self-assembly of the particles in the field. The suspension of rough TiOx nanorods shows stronger ER properties than that of the other nanostructured TiOx particles. We find that the particle surface roughness plays an important role in modification of the dielectric properties and in the enhancement of the ER effect.

  15. 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.

  16. Self assembled nanoparticle aggregates from line focused femtosecond laser ablation.

    PubMed

    Zuhlke, Craig A; Alexander, Dennis R; Bruce, John C; Ianno, Natale J; Kamler, Chad A; Yang, Weiqing

    2010-03-01

    In this paper we present the use of a line focused femtosecond laser beam that is rastered across a 2024 T3 aluminum surface to produce nanoparticles that self assemble into 5-60 micron diameter domed and in some cases sphere-shaped aggregate structures. Each time the laser is rastered over initial aggregates their diameter increases as new layers of nanoparticles self assemble on the surface. The aggregates are thus composed of layers of particles forming discrete layered shells inside of them. When micron size aggregates are removed, using an ultrasonic bath, rings are revealed that have been permanently formed in the sample surface. These rings appear underneath, and extend beyond the physical boundary of the aggregates. The surface is blackened by the formation of these structures and exhibits high light absorption.

  17. Polymerization-Induced Self-Assembly of Galactose-Functionalized Biocompatible Diblock Copolymers for Intracellular Delivery

    PubMed Central

    2013-01-01

    Recent advances in polymer science are enabling substantial progress in nanobiotechnology, particularly in the design of new tools for enhanced understanding of cell biology and for smart drug delivery formulations. Herein, a range of novel galactosylated diblock copolymer nano-objects is prepared directly in concentrated aqueous solution via reversible addition–fragmentation chain transfer polymerization using polymerization-induced self-assembly. The resulting nanospheres, worm-like micelles, or vesicles interact in vitro with galectins as judged by a turbidity assay. In addition, galactosylated vesicles are highly biocompatible and allow intracellular delivery of an encapsulated molecular cargo. PMID:23941545

  18. Self-assembly concepts for multicompartment nanostructures.

    PubMed

    Gröschel, André H; Müller, Axel H E

    2015-07-28

    Compartmentalization is ubiquitous to many biological and artificial systems, be it for the separate storage of incompatible matter or to isolate transport processes. Advancements in the synthesis of sequential block copolymers offer a variety of tools to replicate natural design principles with tailor-made soft matter for the precise spatial separation of functionalities on multiple length scales. Here, we review recent trends in the self-assembly of amphiphilic block copolymers to multicompartment nanostructures (MCNs) under (semi-)dilute conditions, with special emphasis on ABC triblock terpolymers. The intrinsic immiscibility of connected blocks induces short-range repulsion into discrete nano-domains stabilized by a third, soluble block or molecular additive. Polymer blocks can be synthesized from an arsenal of functional monomers directing self-assembly through packing frustration or response to various fields. The mobility in solution further allows the manipulation of self-assembly processes into specific directions by clever choice of environmental conditions. This review focuses on practical concepts that direct self-assembly into predictable nanostructures, while narrowing particle dispersity with respect to size, shape and internal morphology. The growing understanding of underlying self-assembly mechanisms expands the number of experimental concepts providing the means to target and manipulate progressively complex superstructures.

  19. Self-assembly concepts for multicompartment nanostructures

    NASA Astrophysics Data System (ADS)

    Gröschel, André H.; Müller, Axel H. E.

    2015-07-01

    Compartmentalization is ubiquitous to many biological and artificial systems, be it for the separate storage of incompatible matter or to isolate transport processes. Advancements in the synthesis of sequential block copolymers offer a variety of tools to replicate natural design principles with tailor-made soft matter for the precise spatial separation of functionalities on multiple length scales. Here, we review recent trends in the self-assembly of amphiphilic block copolymers to multicompartment nanostructures (MCNs) under (semi-)dilute conditions, with special emphasis on ABC triblock terpolymers. The intrinsic immiscibility of connected blocks induces short-range repulsion into discrete nano-domains stabilized by a third, soluble block or molecular additive. Polymer blocks can be synthesized from an arsenal of functional monomers directing self-assembly through packing frustration or response to various fields. The mobility in solution further allows the manipulation of self-assembly processes into specific directions by clever choice of environmental conditions. This review focuses on practical concepts that direct self-assembly into predictable nanostructures, while narrowing particle dispersity with respect to size, shape and internal morphology. The growing understanding of underlying self-assembly mechanisms expands the number of experimental concepts providing the means to target and manipulate progressively complex superstructures.

  20. Directed self-assembly of performance materials

    NASA Astrophysics Data System (ADS)

    Nealey, Paul

    Directed self-assembly (DSA) is a promising strategy for high-volume cost-effective manufacturing at the nanoscale. Over the past decades, manufacturing techniques have been developed with such remarkable efficiency that it is now possible to engineer complex systems of heterogeneous materials at the scale of a few tens of nanometers. Further evolution of these techniques, however, is faced with difficult challenges not only in feasibility of implementation at scales of 10 nm and below, but also in prohibitively high capital equipment costs. Materials that self-assemble, on the other hand, spontaneously form structures at the mesoscale, but the micrometer areas or volumes over which the materials self-assemble with adequate perfection in structure is incommensurate with the macroscopic dimensions of working devices and systems of devices of industrial relevance. Directed Self-Assembly (DSA) refers to the integration of self-assembling materials with traditional manufacturing processes. Here we will discuss DSA of block copolymers to revolutionize sub 10 nm lithography and the manufacture of integrated circuits and storage media, DSA of ex-situ synthesized nanoparticles for applications in nanophotonics, and DSA of liquid crystals for advanced optics.

  1. S-Layer Protein Self-Assembly

    PubMed Central

    Pum, Dietmar; Toca-Herrera, Jose Luis; Sleytr, Uwe B.

    2013-01-01

    Crystalline S(urface)-layers are the most commonly observed cell surface structures in prokaryotic organisms (bacteria and archaea). S-layers are highly porous protein meshworks with unit cell sizes in the range of 3 to 30 nm, and thicknesses of ~10 nm. One of the key features of S-layer proteins is their intrinsic capability to form self-assembled mono- or double layers in solution, and at interfaces. Basic research on S-layer proteins laid foundation to make use of the unique self-assembly properties of native and, in particular, genetically functionalized S-layer protein lattices, in a broad range of applications in the life and non-life sciences. This contribution briefly summarizes the knowledge about structure, genetics, chemistry, morphogenesis, and function of S-layer proteins and pays particular attention to the self-assembly in solution, and at differently functionalized solid supports. PMID:23354479

  2. Self-assembled gelators for organic electronics.

    PubMed

    Babu, Sukumaran Santhosh; Prasanthkumar, Seelam; Ajayaghosh, Ayyappanpillai

    2012-02-20

    Nature excels at engineering materials by using the principles of chemical synthesis and molecular self-assembly with the help of noncovalent forces. Learning from these phenomena, scientists have been able to create a variety of self-assembled artificial materials of different size, shapes, and properties for wide ranging applications. An area of great interest in this regard is solvent-assisted gel formation with functional organic molecules, thus leading to one-dimensional fibers. Such fibers have improved electronic properties and are potential soft materials for organic electronic devices, particularly in bulk heterojunction solar cells. Described herein is how molecular self-assembly, which was originally proposed as a simple laboratory curiosity, has helped the evolution of a variety of soft functional materials useful for advanced electronic devices such as organic field-effect transistors and organic solar cells. Highlights on some of the recent developments are discussed.

  3. Theory of Programmable Hierarchic Self-Assembly

    NASA Astrophysics Data System (ADS)

    Tkachenko, Alexei V.

    2011-06-01

    We present a theoretical analysis of the inverse problem in self-assembly. A particular scheme is proposed for building an arbitrary desired nanostructure out of self-assembled building blocks (“octopus” nanoparticles). The conditions for robust self-assembly of the target structure are identified. This includes the minimal number of “colors” needed to encode interparticle bonds, which are to be implemented as pairs of complementary DNA sequences. As a part of this analysis, it is demonstrated that a floppy network with thermal fluctuations, in a certain range of coordination numbers ⟨Z⟩, possesses entropic rigidity and can be described as a traditional elastic solid. The onset of the entropic rigidity, ⟨Z⟩=d+1, determines the minimal number of bond types per particle needed to encode the desired structure. Thermodynamic considerations give additional conditions for the implementation of this scheme.

  4. Self-Assembly of Peptides to Nanostructures

    PubMed Central

    Mandal, Dindyal; Shirazi, Amir Nasrolahi; Parang, Keykavous

    2014-01-01

    The formation of well-ordered nanostructures through self-assembly of diverse organic and inorganic building blocks has drawn much attention owing to their potential applications in biology and chemistry. Among all organic building blocks, peptides are one of the most promising platforms due to their biocompatibility, chemical diversity, and resemblance with proteins. Inspired from the protein assembly in biological systems, various self-assembled peptide structures have been constructed using several amino acids and sequences. This review focuses on this emerging area, the recent advances in peptide self-assembly, and formation of different nanostructures, such as tubular, fibers, vesicles, spherical, and rod coil structures. While different peptide nanostructures are discovered, potential applications will be explored in drug delivery, tissue engineering, wound healing, and surfactants. PMID:24756480

  5. Fabrication of ordered nanostructures of sulfide nanocrystal assemblies over self-assembled genetically engineered P22 coat protein.

    PubMed

    Shen, Liming; Bao, Ningzhong; Prevelige, Peter E; Gupta, Arunava

    2010-12-15

    Ordered ZnS and CdS nanocrystal assemblies have been synthesized by a facile bioinspired approach consisting of an initial self-assembly of engineered proteins into spherical biotemplates and a subsequent protein-directed nucleation and growth of ZnS and CdS nanocrystals symmetrically distributed over the self-assembled biotemplates.

  6. Self-assembly of small peptidomimetic cyclophanes.

    PubMed

    Becerril, Jorge; Burguete, M Isabel; Escuder, Beatriu; Galindo, Francisco; Gavara, Raquel; Miravet, Juan F; Luis, Santiago V; Peris, Gabriel

    2004-08-20

    The self-assembly of a series of small peptidomimetic cyclophanes in organic solvents was studied. X-ray diffraction, NMR spectroscopy, and molecular modelling were used to understand the structural features of these self-assembling compounds both at the molecular and supramolecular level. The factors that could influence the formation of gels rather than crystals were studied and a model for the arrangement of molecules in the gel was proposed. Furthermore, scanning electron microscopy revealed that in some cases these compounds undergo a transcription of chirality when going from organogelator to helicoidal gel fibres.

  7. 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.

  8. Self-assembly of chlorophenols in water

    PubMed Central

    Rogalska, Ewa; Rogalski, Marek; Gulik-Krzywicki, Tadeusz; Gulik, Annette; Chipot, Christophe

    1999-01-01

    In saturated solutions of some di- and trichlorophenols, structures with complex morphologies, consisting of thin, transparent sheets often coiling into helices and ultimately twisting into filaments, were observed under the optical microscope. Freeze-fracture electron microscopy, x-ray diffraction, phase diagrams, and molecular modeling were performed to elucidate the observed phenomena. Here, we present evidence that the chlorophenols studied, when interacting with water, self-assemble into bilayers. The fact that some chlorophenols form the same supramolecular structures as those described previously for structurally nonrelated surfactants sheds light on the mechanisms of self-assembly. PMID:10359753

  9. Remote control of self-assembled microswimmers

    PubMed Central

    Grosjean, G.; Lagubeau, G.; Darras, A.; Hubert, M.; Lumay, G.; Vandewalle, N.

    2015-01-01

    Physics governing the locomotion of microorganisms and other microsystems is dominated by viscous damping. An effective swimming strategy involves the non-reciprocal and periodic deformations of the considered body. Here, we show that a magnetocapillary-driven self-assembly, composed of three soft ferromagnetic beads, is able to swim along a liquid-air interface when powered by an external magnetic field. More importantly, we demonstrate that trajectories can be fully controlled, opening ways to explore low Reynolds number swimming. This magnetocapillary system spontaneously forms by self-assembly, allowing miniaturization and other possible applications such as cargo transport or solvent flows. PMID:26538006

  10. Remote control of self-assembled microswimmers

    NASA Astrophysics Data System (ADS)

    Grosjean, G.; Lagubeau, G.; Darras, A.; Hubert, M.; Lumay, G.; Vandewalle, N.

    2015-11-01

    Physics governing the locomotion of microorganisms and other microsystems is dominated by viscous damping. An effective swimming strategy involves the non-reciprocal and periodic deformations of the considered body. Here, we show that a magnetocapillary-driven self-assembly, composed of three soft ferromagnetic beads, is able to swim along a liquid-air interface when powered by an external magnetic field. More importantly, we demonstrate that trajectories can be fully controlled, opening ways to explore low Reynolds number swimming. This magnetocapillary system spontaneously forms by self-assembly, allowing miniaturization and other possible applications such as cargo transport or solvent flows.

  11. Nondeterministic self-assembly with asymmetric interactions

    NASA Astrophysics Data System (ADS)

    Tesoro, S.; Göpfrich, K.; Kartanas, T.; Keyser, U. F.; Ahnert, S. E.

    2016-08-01

    We investigate general properties of nondeterministic self-assembly with asymmetric interactions, using a computational model and DNA tile assembly experiments. By contrasting symmetric and asymmetric interactions we show that the latter can lead to self-limiting cluster growth. Furthermore, by adjusting the relative abundance of self-assembly particles in a two-particle mixture, we are able to tune the final sizes of these clusters. We show that this is a fundamental property of asymmetric interactions, which has potential applications in bioengineering, and provides insights into the study of diseases caused by protein aggregation.

  12. Model-driven optimization of multicomponent self-assembly processes.

    PubMed

    Korevaar, Peter A; Grenier, Christophe; Markvoort, Albert J; Schenning, Albertus P H J; de Greef, Tom F A; Meijer, E W

    2013-10-22

    Here, we report an engineering approach toward multicomponent self-assembly processes by developing a methodology to circumvent spurious, metastable assemblies. The formation of metastable aggregates often hampers self-assembly of molecular building blocks into the desired nanostructures. Strategies are explored to master the pathway complexity and avoid off-pathway aggregates by optimizing the rate of assembly along the correct pathway. We study as a model system the coassembly of two monomers, the R- and S-chiral enantiomers of a π-conjugated oligo(p-phenylene vinylene) derivative. Coassembly kinetics are analyzed by developing a kinetic model, which reveals the initial assembly of metastable structures buffering free monomers and thereby slows the formation of thermodynamically stable assemblies. These metastable assemblies exert greater influence on the thermodynamically favored self-assembly pathway if the ratio between both monomers approaches 1:1, in agreement with experimental results. Moreover, competition by metastable assemblies is highly temperature dependent and hampers the assembly of equilibrium nanostructures most effectively at intermediate temperatures. We demonstrate that the rate of the assembly process may be optimized by tuning the cooling rate. Finally, it is shown by simulation that increasing the driving force for assembly stepwise by changing the solvent composition may circumvent metastable pathways and thereby force the assembly process directly into the correct pathway.

  13. Model-driven optimization of multicomponent self-assembly processes

    PubMed Central

    Korevaar, Peter A.; Grenier, Christophe; Markvoort, Albert J.; Schenning, Albertus P. H. J.; de Greef, Tom F. A.; Meijer, E. W.

    2013-01-01

    Here, we report an engineering approach toward multicomponent self-assembly processes by developing a methodology to circumvent spurious, metastable assemblies. The formation of metastable aggregates often hampers self-assembly of molecular building blocks into the desired nanostructures. Strategies are explored to master the pathway complexity and avoid off-pathway aggregates by optimizing the rate of assembly along the correct pathway. We study as a model system the coassembly of two monomers, the R- and S-chiral enantiomers of a π-conjugated oligo(p-phenylene vinylene) derivative. Coassembly kinetics are analyzed by developing a kinetic model, which reveals the initial assembly of metastable structures buffering free monomers and thereby slows the formation of thermodynamically stable assemblies. These metastable assemblies exert greater influence on the thermodynamically favored self-assembly pathway if the ratio between both monomers approaches 1:1, in agreement with experimental results. Moreover, competition by metastable assemblies is highly temperature dependent and hampers the assembly of equilibrium nanostructures most effectively at intermediate temperatures. We demonstrate that the rate of the assembly process may be optimized by tuning the cooling rate. Finally, it is shown by simulation that increasing the driving force for assembly stepwise by changing the solvent composition may circumvent metastable pathways and thereby force the assembly process directly into the correct pathway. PMID:24101463

  14. Self-assembly of lipopolysaccharide layers on allantoin crystals.

    PubMed

    Vagenende, Vincent; Ching, Tim-Jang; Chua, Rui-Jing; Jiang, Qiu Zhen; Gagnon, Pete

    2014-08-01

    Self-assembly of lipopolysaccharides (LPS) on solid surfaces is important for the study of bacterial membranes, but has not been possible due to technical difficulties and the lack of suitable solid supports. Recently we found that crystals of the natural compound allantoin selectively bind pure LPS with sub-nanomolar affinity. The physicochemical origins of this selectivity and the adsorption mode of LPS on allantoin crystals remain, however, unknown. In this study we present evidence that LPS adsorption on allantoin crystals is initiated through hydrogen-bond attachment of hydrophilic LPS regions. Hydrophobic interactions between alkyl chains of adjacently adsorbed LPS molecules subsequently promote self-assembly of LPS layers. The essential role of hydrogen-bond interactions is corroborated by our finding that allantoin crystals bind to practically any hydrophilic surface chemistry. Binding contributions of hydrophobic interactions between LPS alkyl chains are evidenced by the endothermic nature of the adsorption process and explain why the binding affinity for LPS is several orders of magnitude higher than for proteins (lysozyme, BSA and IgG) and polysaccharides. Self-assembly of LPS layers via hydrogen-bond attachment on allantoin crystals emerges as a novel binding mechanism and could be considered as a practical method for preparing biomimetic membranes on a solid support. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Observation of localized surface plasmons and hybridized surface plasmon polaritons on self-assembled two-dimensional nanocavities.

    PubMed

    Xiong, Qiuyang; Wei, Jue; Mahpeykar, Seyed Milad; Meng, Lingju; Wang, Xihua

    2016-04-01

    Large-area patterning of periodic nanostructures using self-assembled nanospheres is of interest for fabricating low-cost plasmonic substrates, such as two-dimensional (2D) metallic gratings. Surface plasmon polaritons (SPPs) excited on metallic gratings have applications in biosensors, thin-film photovoltaics, photoelectrochemical cells, and photodetectors. Here we fabricated large-area metallic gratings using nanosphere lithography, and the geometry of gratings was controlled by the sphere size and distance between nanospheres. Both forward and backward propagating SPPs were observed using the grating coupling geometry. Furthermore, we reported the first observation of localized surface plasmons (LSPs) on this large-area metallic grating by both simulation and experimental studies. Such an LSP mode was confined in the 2D nanocavities and was not supported by dielectric gratings with the same 2D geometry.

  16. Integrating nanosphere lithography in device fabrication

    NASA Astrophysics Data System (ADS)

    Laurvick, Tod V.; Coutu, Ronald A.; Lake, Robert A.

    2016-03-01

    This paper discusses the integration of nanosphere lithography (NSL) with other fabrication techniques, allowing for nano-scaled features to be realized within larger microelectromechanical system (MEMS) based devices. Nanosphere self-patterning methods have been researched for over three decades, but typically not for use as a lithography process. Only recently has progress been made towards integrating many of the best practices from these publications and determining a process that yields large areas of coverage, with repeatability and enabled a process for precise placement of nanospheres relative to other features. Discussed are two of the more common self-patterning methods used in NSL (i.e. spin-coating and dip coating) as well as a more recently conceived variation of dip coating. Recent work has suggested the repeatability of any method depends on a number of variables, so to better understand how these variables affect the process a series of test vessels were developed and fabricated. Commercially available 3-D printing technology was used to incrementally alter the test vessels allowing for each variable to be investigated individually. With these deposition vessels, NSL can now be used in conjunction with other fabrication steps to integrate features otherwise unattainable through current methods, within the overall fabrication process of larger MEMS devices. Patterned regions in 1800 series photoresist with a thickness of ~700nm are used to capture regions of self-assembled nanospheres. These regions are roughly 2-5 microns in width, and are able to control the placement of 500nm polystyrene spheres by controlling where monolayer self-assembly occurs. The resulting combination of photoresist and nanospheres can then be used with traditional deposition or etch methods to utilize these fine scale features in the overall design.

  17. Large branched self-assembled DNA complexes

    NASA Astrophysics Data System (ADS)

    Tosch, Paul; Wälti, Christoph; Middelberg, Anton P. J.; Davies, A. Giles

    2007-04-01

    Many biological molecules have been demonstrated to self-assemble into complex structures and networks by using their very efficient and selective molecular recognition processes. The use of biological molecules as scaffolds for the construction of functional devices by self-assembling nanoscale complexes onto the scaffolds has recently attracted significant attention and many different applications in this field have emerged. In particular DNA, owing to its inherent sophisticated self-organization and molecular recognition properties, has served widely as a scaffold for various nanotechnological self-assembly applications, with metallic and semiconducting nanoparticles, proteins, macromolecular complexes, inter alia, being assembled onto designed DNA scaffolds. Such scaffolds may typically contain multiple branch-points and comprise a number of DNA molecules selfassembled into the desired configuration. Previously, several studies have used synthetic methods to produce the constituent DNA of the scaffolds, but this typically constrains the size of the complexes. For applications that require larger self-assembling DNA complexes, several tens of nanometers or more, other techniques need to be employed. In this article, we discuss a generic technique to generate large branched DNA macromolecular complexes.

  18. Inverse Problem in Self-assembly

    NASA Astrophysics Data System (ADS)

    Tkachenko, Alexei

    2012-02-01

    By decorating colloids and nanoparticles with DNA, one can introduce highly selective key-lock interactions between them. This leads to a new class of systems and problems in soft condensed matter physics. In particular, this opens a possibility to solve inverse problem in self-assembly: how to build an arbitrary desired structure with the bottom-up approach? I will present a theoretical and computational analysis of the hierarchical strategy in attacking this problem. It involves self-assembly of particular building blocks (``octopus particles''), that in turn would assemble into the target structure. On a conceptual level, our approach combines elements of three different brands of programmable self assembly: DNA nanotechnology, nanoparticle-DNA assemblies and patchy colloids. I will discuss the general design principles, theoretical and practical limitations of this approach, and illustrate them with our simulation results. Our crucial result is that not only it is possible to design a system that has a given nanostructure as a ground state, but one can also program and optimize the kinetic pathway for its self-assembly.

  19. Self-assembled thin film chemical sensors

    SciTech Connect

    Swanson, B.; Li, DeQuan

    1996-11-01

    This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Current chemical sensors suffer from poor molecular specificity, sensitivity, and stability and seldom have the recovery properties needed for real-time monitoring applications. We have employed self-assembly techniques to covalently bond species- selective reagents directly to the surface of the transducer so that analyte/reagent chemistry occurs at the interface between the transducer and the media to be monitored. The use of self-assembling monolayer and -multilayer (SAM) techniques results in stable sensing elements with optimal specificity built in through the use of reagents that have been designed for molecular recognition. Moreover, self-assembly chemistry applied to oxide surfaces allows flexible means of transduction spanning optical, electrochemical, mass-loading, and conduction methods. The work conducted on this project focused on demonstration of the methodology and the application to selected organic vapors (aromatic compounds and halogenated hydrocarbons). We have been able to develop a series of surface acoustic wave (SAW) sensors that are specific for aromatic compounds and halogenated hydrocarbons based on self-assembled thin films of cyclodextrins and calixarenes. Monolayers of seven different cyclodextrins and clixarenes have been attached to SAW transducers and their response to several organic molecules in the vapor phase have been measured. This preliminary data confirms the efficacy of this approach for real- time monitoring of hydrocarbons.

  20. Self-assembling materials for therapeutic delivery✩

    PubMed Central

    Branco, Monica C.; Schneider, Joel P.

    2009-01-01

    A growing number of medications must be administered through parenteral delivery, i.e., intravenous, intramuscular, or subcutaneous injection, to ensure effectiveness of the therapeutic. For some therapeutics, the use of delivery vehicles in conjunction with this delivery mechanism can improve drug efficacy and patient compliance. Macromolecular self-assembly has been exploited recently to engineer materials for the encapsulation and controlled delivery of therapeutics. Self-assembled materials offer the advantages of conventional crosslinked materials normally used for release, but also provide the ability to tailor specific bulk material properties, such as release profiles, at the molecular level via monomer design. As a result, the design of materials from the “bottom up” approach has generated a variety of supramolecular devices for biomedical applications. This review provides an overview of self-assembling molecules, their resultant structures, and their use in therapeutic delivery. It highlights the current progress in the design of polymer- and peptide-based self-assembled materials. PMID:19010748

  1. [INVITED] Self-assembled optical metamaterials

    NASA Astrophysics Data System (ADS)

    Baron, Alexandre; Aradian, Ashod; Ponsinet, Virginie; Barois, Philippe

    2016-08-01

    Self-assembled metamaterials constitute a promising platform to achieving bulk and homogenous optical materials that exhibit unusual effective medium properties. For many years now, the research community has contemplated lithographically fabricated metasurfaces, with extraordinary optical features. However, achieving large volumes at low cost is still a challenge by top-down fabrication. Bottom-up fabrication, that relies both on nanochemistry and self-assembly, is capable of building such materials while greatly reducing the energy footprint in the formulation of the metamaterial. Self-assembled metamaterials have shown that they are capable of reaching unprecedented values of bulkiness and homogeneity figures of merit. This feat is achieved by synthesizing plasmonic nanoresonators (meta-atoms in the sense of artificial polarizable units) and assembling them into a fully three-dimensional matrix through a variety of methods. Furthermore it has been shown that a wide range of material parameters can be tailored by controlling the geometry and composition of the meta-atoms as well as the volume fraction of the nano-objects in the metamaterial. Here we conduct a non-comprehensive review of some of the recent trends in self-assembled optical metamaterials and illustrate these trends with our recent work.

  2. Inertially assisted nanoscale self-assembly.

    PubMed

    Saeedi, E; Marcheselli, C; Shum, A; Parviz, B A

    2010-09-17

    We present a simple and versatile method for integrating submicron objects onto pre-determined locations on a substrate. The method relies on augmenting inertial forces using centrifugal motion and geometric constraints to guide the placement of submicron objects on a substrate with minimal requirements for surface engineering and binding chemistries. Here, we demonstrate the utility of the method for placing gold particles, metal nanorods and inorganic nanocrystals. The method has demonstrated high yield of self-assembly for submicron particles with a variety of shapes and sizes. We have been able to get a near-perfect yield for filling hundreds of traps with nanoparticles in only 20 min. Two hundred nanometer diameter nanorods were self-assembled into an array of 256 traps on the template with 92% yield. 1.4 microm and 300 nm sodium chloride crystals were self-assembled in arrays of 7000 and 576 traps, respectively, with near-perfect yield in filling each site. Due to its convenient set-up and high performance, inertially assisted self-assembly can be easily adopted and used for a variety of integration needs on the submicron scale.

  3. 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.

  4. Self-assembly micro optical filter

    NASA Astrophysics Data System (ADS)

    Zhang, Ping (Cerina); Le, Kevin; Malalur-Nagaraja-Rao, Smitha; Hsu, Lun-Chen; Chiao, J.-C.

    2006-01-01

    Optical communication and sensor industry face critical challenges in manufacturing for system integration. Due to the assembly complexity and integration platform variety, micro optical components require costly alignment and assembly procedures, in which many required manual efforts. Consequently, self-assembly device architectures have become a great interest and could provide major advantages over the conventional optical devices. In this paper, we discussed a self-assembly integration platform for micro optical components. To demonstrate the adaptability and flexibility of the proposed optical device architectures, we chose a commercially available MEMS fabrication foundry service - MUMPs (Multi-User MEMS Process). In this work, polysilicon layers of MUMPS are used as the 3-D structural material for construction of micro component framework and actuators. However, because the polysilicon has high absorption in the visible and near infrared wavelength ranges, it is not suitable for optical interaction. To demonstrate the required optical performance, hybrid integration of materials was proposed and implemented. Organic compound materials were applied on the silicon-based framework to form the required optical interfaces. Organic compounds provide good optical transparency, flexibility to form filters or lens and inexpensive manufacturing procedures. In this paper, we have demonstrated a micro optical filter integrated with self-assembly structures. We will discuss the self-assembly mechanism, optical filter designs, fabrication issues and results.

  5. Drug delivery with nanospherical supramolecular cell penetrating peptide-taxol conjugates containing a high drug loading.

    PubMed

    Tian, Ran; Wang, Huaimin; Niu, Ruifang; Ding, Dan

    2015-09-01

    Supramolecular nanostructures via small molecule self-assembly hold great promise for controlled delivery of hydrophobic anticancer drugs. Particularly, taxol has recently been discovered to possess excellent self-assembly property, which may provide new opportunities to develop a new class of functional supramolecular nanomaterials for drug delivery application. A cell penetrating peptide (CPP)-taxol conjugate (Taxol-CPP) was designed and synthesized. The self-assembling property of Taxol-CPP was investigated and the resultant nanomaterials were well characterized. Subsequently, the cytotoxicity of the Taxol-CPP after self-assembly against HepG2 cancer cells was evaluated. It is found that the Taxol-CPP possesses a high drug loading of 26.4% in each molecule, which is able to self-assemble into supramolecular nanospheres. By taking advantages of the self-assembly ability of taxol, Taxol-CPP supramolecular nanospheres with a mean size of around 130 nm can be obtained, composed of only the functional peptide (CPP) and the drug (taxol). Furthermore, we have demonstrated that the Taxol-CPP nanospheres do not compromise the taxol's potency, which can also be utilized as the carriers for co-delivery of another anticancer drug (doxorubicin). Copyright © 2015 Elsevier Inc. All rights reserved.

  6. Self-assembled nanolaminate coatings (SV)

    SciTech Connect

    Fan, H.

    2012-03-01

    Sandia National Laboratories (Sandia) and Lockheed Martin Aeronautics (LM Aero) are collaborating to develop affordable, self-assembled, nanocomposite coatings and associated fabrication processes that will be tailored to Lockheed Martin product requirements. The purpose of this project is to develop a family of self-assembled coatings with properties tailored to specific performance requirements, such as antireflective (AR) optics, using Sandia-developed self-assembled techniques. The project met its objectives by development of a simple and economic self-assembly processes to fabricate multifunctional coatings. Specifically, materials, functionalization methods, and associated coating processes for single layer and multiple layers coatings have been developed to accomplish high reflective coatings, hydrophobic coatings, and anti-reflective coatings. Associated modeling and simulations have been developed to guide the coating designs for optimum optical performance. The accomplishments result in significant advantages of reduced costs, increased manufacturing freedom/producibility, improved logistics, and the incorporation of new technology solutions not possible with conventional technologies. These self-assembled coatings with tailored properties will significantly address LMC's needs and give LMC a significant competitive lead in new engineered materials. This work complements SNL's LDRD and BES programs aimed at developing multifunctional nanomaterials for microelectronics and optics as well as structure/property investigations of self-assembled nanomaterials. In addition, this project will provide SNL with new opportunities to develop and apply self-assembled nanocomposite optical coatings for use in the wavelength ranges of 3-5 and 8-12 micrometers, ranges of vital importance to military-based sensors and weapons. The SANC technologies will be applied to multiple programs within the LM Company including the F-35, F-22, ADP (Future Strike Bomber, UAV, UCAV

  7. Solvation Effects in Self-Assembled Systems

    SciTech Connect

    Frink, L.J.D.

    1998-11-10

    Many types of self-assembly can be found in nature. They include crystallization, the formation of micelles, and the folding of proteins. Recently there has been much interest in pursuing nano-to-microscopically engineered materials by way of self-assembly on imprinted or templated surfaces. In all of these diverse cases, wetting plays a critical role in the assembly process. Wetting involves the interactions of the substrate or amphiphilic molecule or macromolecule with a solvent. In many self-assembled systems we find that the critical feature of the system is a substrate! or macromolecule with a both hydrophilic and hydrophobic nature. In this paper we discuss the wetting properties of a striped surface where the stripes represent alternating chemical characteristics. We show how the chemical heterogeneity affects the wetting properties of the surface (e.g. the static contact angle), and discuss the length limitations on the soft lithography approach. In this paper, the wetting of a chemically heterogeneous surface is studied using a nonlocal Density Functional Theory (DFT). The results for the heterogeneous surface model we discuss have immediate implications for soft-lithography by self-assembly. It also lends fundamental insight into the mechanisms controlling self-assembly of macromolecules. We present the results of nonlocal 2D DFT calculations on the wetting properties of chemically heterogeneous surfaces. These calculations showed complex density distributions and phase behavior as a result of the heterogeneity. The location of the wetting transition are found to be strongly dependent on the extent and strength of the heterogeneity, and complete wetting was suppressed altogether if the hydrophobic parts of the surface were large enough. In these cases, the condensed nanophase may crystallize if the hydrophilic surface-fluid interactions are strong enough. By exploring the phase space including strength of hydrophilic interactions and extent of chemical

  8. 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

  9. Chemical Functionalization, Self-Assembly, and Applications of Nanomaterials and Nanocomposites

    SciTech Connect

    Jiao, Tifeng; Yan, Xingbin; Balan, Lavinia; Stepanov, Andrey; Chen, Xinqing; Hu, Michael Z.

    2014-01-01

    This special issue addresses the research studies on chemical functionalization, self-assembly, and applications of nanomaterials and nanocomposites. It contains twentyfour articles including two reviews and twenty-two research articles. It is used to create new functional nanomaterials and nanocomposites with a variety of sizes and morphologies such as Zn/Al layered double hydroxide, tin oxide nanowires, FeOOH-modified anion resin, Au nanoclusters silica composite nanospheres, Ti-doped ZnO sol-composite films, TiO2/ZnO composite, graphene oxide nanocomposites, LiFePO4/C nanocomposites, and chitosan nanoparticles. These nanomaterials and nanocomposites have widespread applications in tissue engineering, antitumor, sensors, photoluminescence, electrochemical, and catalytic properties. In addition, this themed issue includes some research articles about self-assembly systems covering organogels and Langmuir films. Furthermore, B. Blasiak et al. performed a literature survey on the recent advances in production, functionalization, toxicity reduction, and application of nanoparticles in cancer diagnosis, treatment, and treatment monitoring. P. Colson et al. performed a literature survey on the recent advances in nanosphere lithography due to its compatibility with wafer-scale processes as well as its potential to manufacture a wide variety of homogeneous one-, two-, or three-dimensional nanostructures.

  10. 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

  11. Ultrasmall peptides self-assemble into diverse nanostructures: morphological evaluation and potential implications.

    PubMed

    Lakshmanan, Anupama; Hauser, Charlotte A E

    2011-01-01

    In this study, we perform a morphological evaluation of the diverse nanostructures formed by varying concentration and amino acid sequence of a unique class of ultrasmall self-assembling peptides. We modified these peptides by replacing the aliphatic amino acid at the C-aliphatic terminus with different aromatic amino acids. We tracked the effect of introducing aromatic residues on self-assembly and morphology of resulting nanostructures. Whereas aliphatic peptides formed long, helical fibers that entangle into meshes and entrap >99.9% water, the modified peptides contrastingly formed short, straight fibers with a flat morphology. No helical fibers were observed for the modified peptides. For the aliphatic peptides at low concentrations, different supramolecular assemblies such as hollow nanospheres and membrane blebs were found. Since the ultrasmall peptides are made of simple, aliphatic amino acids, considered to have existed in the primordial soup, study of these supramolecular assemblies could be relevant to understanding chemical evolution leading to the origin of life on Earth. In particular, we propose a variety of potential applications in bioengineering and nanotechnology for the diverse self-assembled nanostructures.

  12. Ultrasmall Peptides Self-Assemble into Diverse Nanostructures: Morphological Evaluation and Potential Implications

    PubMed Central

    Lakshmanan, Anupama; Hauser, Charlotte A.E.

    2011-01-01

    In this study, we perform a morphological evaluation of the diverse nanostructures formed by varying concentration and amino acid sequence of a unique class of ultrasmall self-assembling peptides. We modified these peptides by replacing the aliphatic amino acid at the C-aliphatic terminus with different aromatic amino acids. We tracked the effect of introducing aromatic residues on self-assembly and morphology of resulting nanostructures. Whereas aliphatic peptides formed long, helical fibers that entangle into meshes and entrap >99.9% water, the modified peptides contrastingly formed short, straight fibers with a flat morphology. No helical fibers were observed for the modified peptides. For the aliphatic peptides at low concentrations, different supramolecular assemblies such as hollow nanospheres and membrane blebs were found. Since the ultrasmall peptides are made of simple, aliphatic amino acids, considered to have existed in the primordial soup, study of these supramolecular assemblies could be relevant to understanding chemical evolution leading to the origin of life on Earth. In particular, we propose a variety of potential applications in bioengineering and nanotechnology for the diverse self-assembled nanostructures. PMID:22016623

  13. A Theoretical and Experimental Study of DNA Self-assembly

    NASA Astrophysics Data System (ADS)

    Chandran, Harish

    providing detailed designs for local molecular computations that involve spatially contiguous molecules arranged on addressable substrates via enzyme-free DNA hybridization reaction cascades. We use the Visual DSD simulation software in conjunction with localized reaction rates obtained from biophysical modeling to create chemical reaction networks of localized hybridization circuits that are then model checked using the PRISM model checking software. We develop a DNA detection system employing the triggered self-assembly of a novel DNA dendritic nanostructure. Detection begins when a specific, single-stranded target DNA strand triggers a hybridization chain reaction between two distinct DNA hairpins. Each hairpin opens and hybridizes up to two copies of the other, and hence each layer of the growing dendritic nanostructure can in principle accommodate an exponentially increasing number of cognate molecules, generating a nanostructure with high molecular weight. We build linear activatable assemblies employing a novel protection/deprotection strategy to strictly enforce the direction of tiling assembly growth to ensure the robustness of the assembly process. Our system consists of two tiles that can form a linear co-polymer. These tiles, which are initially protected such that they do not react with each other, can be activated to form linear co-polymers via the use of a strand displacing enzyme.

  14. Self-assembly between biomacromolecules and lipids

    NASA Astrophysics Data System (ADS)

    Liang, Hongjun

    Anionic DNA and cationic lipsomes can self-assemble into a multi-lamellar structure where two-dimensional (2-D) lipid sheets confine a periodic one-dimensional (1-D) lattice of parallel DNA chains, between which Cd2+ ions can condense, and be subsequently reacted with H 2S to template CdS nanorods with crystallographic control analogous to biomineralization. The strong electrostatic interactions align the templated CdS (002) polar planes parallel to the negatively charged sugar-phosphate DNA backbone, which indicates that molecular details of the DNA molecule are imprinted onto the inorganic crystal structure. The resultant nanorods have (002) planes tilted by ˜60° with respect to the rod axis, in contrast to all known II-VI semiconductor nanorods. Rational design of the biopolymer-membrane templates is possible, as demonstrated by the self-assembly between anionic M13 virus and cationic membrane. The filamentous virus has diameter ˜3x larger but similar surface charge density as DNA, the self-assembled complexes maintain the multi-lamellar structure, but pore sizes are ˜10x larger in area, which can be used to package and organize large functional molecules. Not only the counter-charged objects can self-assemble, the like-charged biopolymer and membrane can also self-assemble with the help of multivalent ions. We have investigated anionic lipid-DNA complexes induced by a range of divalent ions to show how different ion-mediated interactions are expressed in the self-assembled structures, which include two distinct lamellar phases and an inverted hexagonal phase. DNA can be selectively organized into or expelled out of the lamellar phases depending on membrane charge density and counterion concentration. For a subset of ion (Zn2+ etc.) at high enough concentration, 2-D inverted hexagonal phase can be formed where DNA strands are coated with anionic lipid tubes via interaction with Zn2+ ions. We suggest that the effect of ion binding on lipid's spontaneous

  15. Self-assembling membranes and related methods thereof

    DOEpatents

    Capito, Ramille M; Azevedo, Helena S; Stupp, Samuel L

    2013-08-20

    The present invention relates to self-assembling membranes. In particular, the present invention provides self-assembling membranes configured for securing and/or delivering bioactive agents. In some embodiments, the self-assembling membranes are used in the treatment of diseases, and related methods (e.g., diagnostic methods, research methods, drug screening).

  16. Controlling and imaging biomimetic self-assembly

    NASA Astrophysics Data System (ADS)

    Aliprandi, Alessandro; Mauro, Matteo; de Cola, Luisa

    2016-01-01

    The self-assembly of chemical entities represents a very attractive way to create a large variety of ordered functional structures and complex matter. Although much effort has been devoted to the preparation of supramolecular nanostructures based on different chemical building blocks, an understanding of the mechanisms at play and the ability to monitor assembly processes and, in turn, control them are often elusive, which precludes a deep and comprehensive control of the final structures. Here the complex supramolecular landscape of a platinum(II) compound is characterized fully and controlled successfully through a combination of supramolecular and photochemical approaches. The supramolecular assemblies comprise two kinetic assemblies and their thermodynamic counterpart. The monitoring of the different emission properties of the aggregates, used as a fingerprint for each species, allows the real-time visualization of the evolving self-assemblies. The control of multiple supramolecular pathways will help the design of complex systems in and out of their thermodynamic equilibrium.

  17. Controlling and imaging biomimetic self-assembly.

    PubMed

    Aliprandi, Alessandro; Mauro, Matteo; De Cola, Luisa

    2016-01-01

    The self-assembly of chemical entities represents a very attractive way to create a large variety of ordered functional structures and complex matter. Although much effort has been devoted to the preparation of supramolecular nanostructures based on different chemical building blocks, an understanding of the mechanisms at play and the ability to monitor assembly processes and, in turn, control them are often elusive, which precludes a deep and comprehensive control of the final structures. Here the complex supramolecular landscape of a platinum(II) compound is characterized fully and controlled successfully through a combination of supramolecular and photochemical approaches. The supramolecular assemblies comprise two kinetic assemblies and their thermodynamic counterpart. The monitoring of the different emission properties of the aggregates, used as a fingerprint for each species, allows the real-time visualization of the evolving self-assemblies. The control of multiple supramolecular pathways will help the design of complex systems in and out of their thermodynamic equilibrium.

  18. Dissipative self-assembly of vesicular nanoreactors.

    PubMed

    Maiti, Subhabrata; Fortunati, Ilaria; Ferrante, Camilla; Scrimin, Paolo; Prins, Leonard J

    2016-07-01

    Dissipative self-assembly is exploited by nature to control important biological functions, such as cell division, motility and signal transduction. The ability to construct synthetic supramolecular assemblies that require the continuous consumption of energy to remain in the functional state is an essential premise for the design of synthetic systems with lifelike properties. Here, we show a new strategy for the dissipative self-assembly of functional supramolecular structures with high structural complexity. It relies on the transient stabilization of vesicles through noncovalent interactions between the surfactants and adenosine triphosphate (ATP), which acts as the chemical fuel. It is shown that the lifetime of the vesicles can be regulated by controlling the hydrolysis rate of ATP. The vesicles sustain a chemical reaction but only as long as chemical fuel is present to keep the system in the out-of-equilibrium state. The lifetime of the vesicles determines the amount of reaction product produced by the system.

  19. Self-assembled Oniontype Multiferroic Nanostructures

    NASA Astrophysics Data System (ADS)

    Ren, Shenqiang; Briber, Robert M.; Wuttig, Manfred

    2009-03-01

    Spontaneously self-assembled oniontype multiferroic nanostructures based on block copolymers as templating materials are reported. Diblock copolymer containing two different magnetoelectric precursors separately segregated to the two microdomains have been shown to form well-ordered templated lamellar structures. Onion-type multilamellar ordered multiferroic (PZT/CoFe2O4) nanostructures have been induced by room temperature solvent annealing in a magnetic field oriented perpendicular to the plane of the film. The evolution of the onion-like microstructure has been characterized by AFM, MFM, and TEM. The structure retains lamellar periodicity observed at zero field. The onion structure is superparamagnetic above and antiferromagnetic below the blocking temperature. This templating process opens a route for nanometer-scale patterning of magnetic toroids by means of self-assembly on length scales that are difficult to obtain by standard lithography techniques.

  20. Biologically-Based Self-Assembling Hydrogels

    DTIC Science & Technology

    2002-04-01

    Based Self-Assembling Hydrogels Brandon L. Seal and Alyssa Panitch Department of Bioengineering, Arizona State University Tempe, AZ 85287-9709, U.S.A...the ligand from the a- chain of human fibrinogen as well as substrates for factor Xlla (Fa XllIa) (Table f) were synthesized using solid- state Fmoc...chemistry in the Arizona State University Protein Chemistry Laboratory. All peptides were purified with a C4 reverse phase preparatory column on an

  1. Columnar self-assembly of colloidal nanodisks.

    PubMed

    Saunders, Aaron E; Ghezelbash, Ali; Smilgies, Detlef-M; Sigman, Michael B; Korgel, Brian A

    2006-12-01

    The self-assembly of sterically stabilized colloidal copper sulfide nanodisks, 14-20 nm in diameter and 5-7 nm thick, was studied. The nanodisks were observed by electron microscopy and small-angle X-ray scattering to form columnar arrays when evaporated as thin films from concentrated dispersions. These superstructured nanomaterials might give rise to technologically useful properties, such as anisotropic electrical transport and electrorheological and optical properties.

  2. Self-assembled Nanomaterials for Chemotherapeutic Applications

    NASA Astrophysics Data System (ADS)

    Shieh, Aileen

    The self-assembly of short designed peptides into functional nanostructures is becoming a growing interest in a wide range of fields from optoelectronic devices to nanobiotechnology. In the medical field, self-assembled peptides have especially attracted attention with several of its attractive features for applications in drug delivery, tissue regeneration, biological engineering as well as cosmetic industry and also the antibiotics field. We here describe the self-assembly of peptide conjugated with organic chromophore to successfully deliver sequence independent micro RNAs into human non-small cell lung cancer cell lines. The nanofiber used as the delivery vehicle is completely non-toxic and biodegradable, and exhibit enhanced permeability effect for targeting malignant tumors. The transfection efficiency with nanofiber as the delivery vehicle is comparable to that of the commercially available RNAiMAX lipofectamine while the toxicity is significantly lower. We also conjugated the peptide sequence with camptothecin (CPT) and observed the self-assembly of nanotubes for chemotherapeutic applications. The peptide scaffold is non-toxic and biodegradable, and drug loading of CPT is high, which minimizes the issue of systemic toxicity caused by extensive burden from the elimination of drug carriers. In addition, the peptide assembly drastically increases the solubility and stability of CPT under physiological conditions in vitro, while active CPT is gradually released from the peptide chain under the slight acidic tumor cell environment. Cytotoxicity results on human colorectal cancer cells and non-small cell lung cancer cell lines display promising anti-cancer properties compared to the parental CPT drug, which cannot be used clinically due to its poor solubility and lack of stability in physiological conditions. Moreover, the peptide sequence conjugated with 5-fluorouracil formed a hydrogel with promising topical chemotherapeutic applications that also display

  3. 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.

  4. The dynamics of nacre self-assembly

    PubMed Central

    Cartwright, Julyan H.E; Checa, Antonio G

    2006-01-01

    We show how nacre and pearl construction in bivalve and gastropod molluscs can be understood in terms of successive processes of controlled self-assembly from the molecular- to the macro-scale. This dynamics involves the physics of the formation of both solid and liquid crystals and of membranes and fluids to produce a nanostructured hierarchically constructed biological composite of polysaccharides, proteins and mineral, whose mechanical properties far surpass those of its component parts. PMID:17251136

  5. Dynamics of self-assembled droplet etching

    NASA Astrophysics Data System (ADS)

    Heyn, Ch.; Stemmann, A.; Hansen, W.

    2009-10-01

    We study the self-assembled local droplet etching of nanoholes in AlGaAs surfaces with Ga droplets. The data establish an unexpected delay of both the hole drilling process as well as the removal of the liquid material after etching. Furthermore, coarsening by Ostwald ripening is found to reduce the droplet density before drilling. Basing on these findings, we propose a growth, coarsening, drilling, and removal mechanism for the droplet etching process.

  6. Self-Assembly of Chiral Plasmonic Nanostructures.

    PubMed

    Lan, Xiang; Wang, Qiangbin

    2016-12-01

    Plasmonic chiroptical effects have attracted significant attention for their widespread potential applications in negative-refractive-index materials, advanced light-polarization filters, and ultrasensitive sensing devices, etc. As compared to top-down fabrication methods, the bottom-up self-assembly strategy provides nanoscale resolution, parallel production, and isotropic optical response, and therefore plays an indispensable role in the fabrication of chiral plasmonic nanostructures. The optical properties of these chiral structures can be predicted based on the near-field coupling of localized surface plasmons in structural components, which offers a route to tune or enhance optical activity by selecting building blocks and designing structural configurations. To date, three main types of chiral plasmonic nanostructures, i.e., chiral "plasmonic molecules", chiral superstructures, and chiral-molecule-metal hybrid complexes, are usually assembled, in which metal nanoparticles with various sizes, shapes, and compositions, and/or chiral molecules are employed as building blocks. Here, recent achievements in the self-assembly of chiral plasmonic nanostructures are highlighted and perspectives on the future directions of chiral plasmonics integrated with bottom-up self-assembly are presented, showing three typical examples, including chiral plasmonic switches, chiral nanoparticles, and chiral metamaterials.

  7. Self-assembly of Artificial Actin Filaments

    NASA Astrophysics Data System (ADS)

    Grosenick, Christopher; Cheng, Shengfeng

    Actin Filaments are long, double-helical biopolymers that make up the cytoskeleton along with microtubules and intermediate filaments. In order to further understand the self-assembly process of these biopolymers, a model to recreate actin filament geometry was developed. A monomer in the shape of a bent rod with vertical and lateral binding sites was designed to assemble into single or double helices. With Molecular Dynamics simulations, a variety of phases were observed to form by varying the strength of the binding sites. Ignoring lateral binding sites, we have found a narrow range of binding strengths that lead to long single helices via various growth pathways. When lateral binding strength is introduced, double helices begin to form. These double helices self-assemble into substantially more stable structures than their single helix counterparts. We have found double helices to form long filaments at about half the vertical binding strength of single helices. Surprisingly, we have found that triple helices occasionally form, indicating the importance of structural regulation in the self-assembly of biopolymers.

  8. Self-assembly of knots and links

    NASA Astrophysics Data System (ADS)

    Orlandini, Enzo; Polles, Guido; Marenduzzo, Davide; Micheletti, Cristian

    2017-03-01

    Guiding the self-assembly of identical building blocks towards complex three-dimensional structures with a set of desired properties is a major goal in material science, chemistry and physics. A particularly challenging problem, especially explored in synthetic chemistry, is that of self-assembling closed structures with a target topology starting by simple geometrical templates. Here we overview and revisit recent advancements, based on stochastic simulations, where the geometry of rigid helical templates with functionalised sticky ends has been designed for self-assembling efficiently and reproducibly into a wide range of three-dimensional closed structures. Notably, these include non trivial topologies of links and knots, including the 819 knot that we had predicted to be highly encodable and that has only recently been obtained experimentally. By appropriately tuning the parameters that define the template shape, we show that, for fixed concentration of templates, the assembly process can be directed towards the formation of specific knotted and linked structures such as the trefoils, pentafoil knots, Hopf and Solomon links. More exotic and unexpected knots and links are also found. Our results should be relevant to the design of new protocols that can both increase and broaden the population of synthetise molecular knots and catenanes.

  9. Self-assembly of polar food lipids.

    PubMed

    Leser, Martin E; Sagalowicz, Laurent; Michel, Martin; Watzke, Heribert J

    2006-11-16

    Polar lipids, such as monoglycerides and phospholipids, are amphiphilic molecules commonly used as processing and stabilization aids in the manufacturing of food products. As all amphiphilic molecules (surfactants, emulsifiers) they show self-assembly phenomena when added into water above a certain concentration (the critical aggregation concentration). The variety of self-assembly structures that can be formed by polar food lipids is as rich as it is for synthetic surfactants: micelles (normal and reverse micelles), microemulsions, and liquid crystalline phases can be formulated using food-grade ingredients. In the present work we will first discuss microemulsion and liquid crystalline phase formation from ingredients commonly used in food industry. In the last section we will focus on three different potential application fields, namely (i) solubilization of poorly water soluble ingredients, (ii) controlled release, and (iii) chemical reactivity. We will show how the interfacial area present in self-assembly structures can be used for (i) the delivery of functional molecules, (ii) controlling the release of functional molecules, and (iii) modulating the chemical reactivity between reactive molecules, such as aromas.

  10. Anisotropic Self-Assembly of Nanoparticle Amphiphiles

    NASA Astrophysics Data System (ADS)

    Kumar, Sanat

    2009-03-01

    It is easy to understand the self-assembly of particles having anisotropic shapes or interactions, such as Co nanoparticles or proteins, into highly extended structures. However, there is no experimentally established strategy for creating anisotropic structures from common spherical nanoparticles. We demonstrate that spherical nanoparticles, uniformly grafted with macromolecules, robustly self-assemble into a range of anisotropic superstructures when they are dispersed in the corresponding homopolymer matrix. This phenomenon is driven by the microphase separation between the inorganic nanoparticles and the (organic) polymeric chains grafted to their surfaces in a fashion similar to block copolymers. This microphase separation driven particle self-assembly provides a unique means of controlling the global nanoparticle dispersion state in polymer nanocomposites. The relationship between the state of particle dispersion and nanocomposite properties can thus be critically examined, and in particular we focus on the mechanical reinforcement afforded when particles are added to polymers. Grafted nanoparticles are thus versatile building blocks for creating tunable and functional particle superstructures with significant practical applications. With Pinar Akcora, Hongjun Liu, Yu Li, Brian Benicewicz, Linda Schadler, Thanos Panagiotopoulos, Jack Douglas, P. Thiyagarajan and Ralph Colby.

  11. Meniscus height controlled convective self-assembly

    NASA Astrophysics Data System (ADS)

    Choudhary, Satyan; Crosby, Alfred

    Convective self-assembly techniques based on the 'coffee-ring effect' allow for the fabrication of materials with structural hierarchy and multi-functionality across a wide range of length scales. The coffee-ring effect describes deposition of non-volatiles at the edge of droplet due to capillary flow and pattern formations due to pinning and de-pinning of meniscus with the solvent evaporation. We demonstrate a novel convective self-assembly method which uses a piezo-actuated bending motion for driving the de-pinning step. In this method, a dilute solution of nanoparticles or polymers is trapped by capillary forces between a blade and substrate. As the blade oscillates with a fixed frequency and amplitude and the substrate translates at a fixed velocity, the height of the capillary meniscus oscillates. The meniscus height controls the contact angle of three phase contact line and at a critical angle de-pinning occurs. The combination of convective flux and continuously changing contact angle drives the assembly of the solute and subsequent de-pinning step, providing a direct means for producing linear assemblies. We demonstrate a new method for convective self-assembly at an accelerated rate when compared to other techniques, with control over deposit dimensions. Army Research Office (W911NF-14-1-0185).

  12. Interparticle Forces Underlying Nanoparticle Self-Assemblies.

    PubMed

    Luo, Dan; Yan, Cong; Wang, Tie

    2015-12-02

    Studies on the self-assembly of nanoparticles have been a hot topic in nanotechnology for decades and still remain relevant for the present and future due to their tunable collective properties as well as their remarkable applications to a wide range of fields. The novel properties of nanoparticle assemblies arise from their internal interactions and assemblies with the desired architecture key to constructing novel nanodevices. Therefore, a comprehensive understanding of the interparticle forces of nanoparticle self-assemblies is a pre-requisite to the design and control of the assembly processes, so as to fabricate the ideal nanomaterial and nanoproducts. Here, different categories of interparticle forces are classified and discussed according to their origins, behaviors and functions during the assembly processes, and the induced collective properties of the corresponding nanoparticle assemblies. Common interparticle forces, such as van der Waals forces, electrostatic interactions, electromagnetic dipole-dipole interactions, hydrogen bonds, solvophonic interactions, and depletion interactions are discussed in detail. In addition, new categories of assembly principles are summarized and introduced. These are termed template-mediated interactions and shape-complementary interactions. A deep understanding of the interactions inside self-assembled nanoparticles, and a broader perspective for the future synthesis and fabrication of these promising nanomaterials is provided.

  13. Symmetry, Equivalence and Self-Assembly

    NASA Astrophysics Data System (ADS)

    Douglas, Jack

    2006-03-01

    Molecular self-assembly at equilibrium is central to the formation of many biological structures and the emulation of this process through the creation of synthetic counterparts offers great promise for nanofabrication. The central problems in this field are an understanding of how the symmetry of the interacting particles encodes the geometrical structure of the organized structure and the nature of the thermodynamic transitions involved. Our approach is inspired by the self-assembly of actin, tubulin and icosahedral structures of plant and animal viruses. We observe chain, membrane,`nanotube' and hollow icosahedron structures using `equivalent' particles exhibiting an interplay between directional (dipolar and multi-polar) interactions and short-range (van der Waals) interactions. Specifically, a dipolar potential (continuous rotational symmetry) gives rise to chain formation, while potentials having discrete rotational symmetries (e.g., square quadrupole or triangular ring of dipoles) led to the self-organization of nanotube and icosahedral structures with some resemblance to tubulin and icosahedral viruses. The simulations are compared to theoretical models of molecular self-assembly, especially in the case of dipolar fluids where the corresponding analytic theory of equilibrium polymerization is well developed. These computations give insights into the design elements required for the development of synthetic systems exhibiting this type of organization.

  14. Engineered Self-Assembly of Plasmonic Nanomaterials

    NASA Astrophysics Data System (ADS)

    Tao, Andrea

    2013-03-01

    A critical need in nanotechnology is the development of new tools and methods to organize, connect, and integrate solid-state nanocomponents. Self-assembly - where components spontaneously organize themselves - can be carried out on a massively parallel scale to construct large-scale architectures using solid-state nanocrystal building blocks. I will present our recent work on the synthesis and self-assembly of nanocrystals for plasmonics, where light is propagated, manipulated, and confined by solid-state components that are smaller than the wavelength of light itself. We show the organization of polymer-grafted metal nanocrystals into hierarchical nanojunction arrays that possess intense ``hot spots'' due to electromagnetic field localization. We also show that doped semiconductor nanocrystals can serve as a new class of plasmonic building blocks, where shape and carrier density can be actively tuned to engineer plasmon resonances. These examples demonstrate that nanocrystals possess unique electromagnetic properties that rival top-down structures, and the potential of self-assembly for fabricating designer plasmonic materials.

  15. Self-assembled biomimetic nanoreactors I: Polymeric template

    NASA Astrophysics Data System (ADS)

    McTaggart, Matt; Malardier-Jugroot, Cecile; Jugroot, Manish

    2015-09-01

    The variety of nanoarchitectures made feasible by the self-assembly of alternating copolymers opens new avenues for biomimicry. Indeed, self-assembled structures allow the development of nanoreactors which combine the efficiency of high surface area metal active centres to the effect of confinement due to the very small cavities generated by the self-assembly process. A novel self-assembly of high molecular weight alternating copolymers is characterized in the present study. The self-assembly is shown to organize into nanosheets, providing a 2 nm hydrophobic cavity with a 1D confinement.

  16. Amphiphilic Janus gold nanoparticles prepared by interface-directed self-assembly: synthesis and self-assembly.

    PubMed

    Liu, Guannan; Tian, Jia; Zhang, Xu; Zhao, Hanying

    2014-09-01

    Materials with Janus structures are attractive for wide applications in materials science. Although extensive efforts in the synthesis of Janus particles have been reported, the synthesis of sub-10 nm Janus nanoparticles is still challenging. Herein, the synthesis of Janus gold nanoparticles (AuNPs) based on interface-directed self-assembly is reported. Polystyrene (PS) colloidal particles with AuNPs on the surface were prepared by interface-directed self-assembly, and the colloidal particles were used as templates for the synthesis of Janus AuNPs. To prepare colloidal particles, thiol-terminated polystyrene (PS-SH) was dissolved in toluene and citrate-stabilized AuNPs were dispersed in aqueous solution. Upon mixing the two solutions, PS-SH chains were grafted to the surface of AuNPs and amphiphilic AuNPs were formed at the liquid-liquid interface. PS colloidal particles decorated with AuNPs on the surfaces were prepared by adding the emulsion to excess methanol. On the surface, AuNPs were partially embedded in the colloidal particles. The outer regions of the AuNPs were exposed to the solution and were functionalized through the grafting of atom-transfer radical polymerization (ATRP) initiator. Poly[2-(dimethamino)ethyl methacrylate] (PDMAEMA) on AuNPs were prepared by surface-initiated ATRP. After centrifugation and dissolving the colloidal particles in tetrahydrofuran (THF), Janus AuNPs with PS and PDMAEMA on two hemispheres were obtained. In acidic pH, Janus AuNPs are amphiphilic and are able to emulsify oil droplets in water; in basic pH, the Janus AuNPs are hydrophobic. In mixtures of THF/methanol at a volume ratio of 1:5, the Janus AuNPs self-assemble into bilayer structures with collapsed PS in the interiors and solvated PDMAEMA at the exteriors of the structures.

  17. Molecular Self-Assembly of Short Aromatic Peptides: From Biology to Nanotechnology and Material Science

    NASA Astrophysics Data System (ADS)

    Gazit, Ehud

    2013-03-01

    The formation of ordered amyloid fibrils is the hallmark of several diseases of unrelated origin. In spite of grave clinical consequence, the mechanism of amyloid formation is not fully understood. We have suggested, based on experimental and bioinformatic analysis, that aromatic interactions may provide energetic contribution as well as order and directionality in the molecular-recognition and self-association processes that lead to the formation of these assemblies. This is in line with the well-known central role of aromatic-stacking interactions in self-assembly processes. Our works on the mechanism of aromatic peptide self-assembly, lead to the discovery that the diphenylalanine recognition motif self-assembles into peptide nanotubes with a remarkable persistence length. Other aromatic homodipeptides could self-assemble in nano-spheres, nano-plates, nano-fibrils and hydrogels with nano-scale order. We demonstrated that the peptide nanostructures have unique chemical, physical and mechanical properties including ultra-rigidity as aramides, semi-conductive, piezoelectric and non-linear optic properties. We also demonstrated the ability to use these peptide nanostructures as casting mold for the fabrication of metallic nano-wires and coaxial nano-cables. The application of the nanostructures was demonstrated in various fields including electrochemical biosensors, tissue engineering, and molecular imaging. Finally, we had developed ways for depositing of the peptide nanostructures and their organization. We had use inkjet technology as well as vapour deposition methods to coat surface and from the peptide ``nano-forests''. We recently demonstrated that even a single phenylalanine amino-acid can form well-ordered fibrilar assemblies.

  18. Bacterial expression of self-assembling peptide hydrogelators

    NASA Astrophysics Data System (ADS)

    Sonmez, Cem

    For tissue regeneration and drug delivery applications, various architectures are explored to serve as biomaterial tools. Via de novo design, functional peptide hydrogel materials have been developed as scaffolds for biomedical applications. The objective of this study is to investigate bacterial expression as an alternative method to chemical synthesis for the recombinant production of self-assembling peptides that can form rigid hydrogels under physiological conditions. The Schneider and Pochan Labs have designed and characterized a 20 amino acid beta-hairpin forming amphiphilic peptide containing a D-residue in its turn region (MAX1). As a result, this peptide must be prepared chemically. Peptide engineering, using the sequence of MAX1 as a template, afforded a small family of peptides for expression (EX peptides) that have different turn sequences consisting of natural amino acids and amenable to bacterial expression. Each sequence was initially chemically synthesized to quickly assess the material properties of its corresponding gel. One model peptide EX1, was chosen to start the bacterial expression studies. DNA constructs facilitating the expression of EX1 were designed in such that the peptide could be expressed with different fusion partners and subsequently cleaved by enzymatic or chemical means to afford the free peptide. Optimization studies were performed to increase the yield of pure peptide that ultimately allowed 50 mg of pure peptide to be harvested from one liter of culture, providing an alternate means to produce this hydrogel-forming peptide. Recombinant production of other self-assembling hairpins with different turn sequences was also successful using this optimized protocol. The studies demonstrate that new beta-hairpin self-assembling peptides that are amenable to bacterial production and form rigid hydrogels at physiological conditions can be designed and produced by fermentation in good yield at significantly reduced cost when compared to

  19. Formation of porous nitrogen-doped carbon-coating MnO nanospheres for advanced reversible lithium storage.

    PubMed

    Zhang, Lingling; Ge, Danhua; Qu, Genlong; Zheng, Junwei; Cao, Xueqin; Gu, Hongwei

    2017-05-04

    Herein, we have developed a facile and effective approach for synthesizing a novel kind of porous nitrogen-doped carbon-coated MnO nanosphere. The porous Mn2O3 nanospheres are initially obtained by the calcination treatment of a coordination self-assembled aggregation precursor (referred to as Mn(OAc)2-C-8). Then, MnO@N-doped carbon composites (MnO@NCs) are obtained by the calcination of the Mn2O3 nanospheres coated with polydopamine (Mn2O3@PDA). The MnO@NCs are evaluated as an anode for lithium ion batteries (LIBs), which exhibit high specific capacity, stable cycling performance (1096.6 mA h g(-1) after 100 cycles at 100 mA g(-1)) and high coulombic efficiency (about 99% over 100 cycles). The unique structure design and synergistic effect not only settle the challenges of low conductivity and poor cycling stability of transition metal oxides but also resolve the imperfection of inferior specific capacity of traditional graphite materials. Importantly, it may provide a commendable conception for developing new-fashioned anode materials to improve the lithium storage capability and electrochemical performance.

  20. Dynamic modeling and scaling of nanostructure formation in the lithographically induced self-assembly and self-construction

    NASA Astrophysics Data System (ADS)

    Wu, Lin; Chou, Stephen Y.

    2003-05-01

    We numerically studied the dynamical formation process and the scaling of the nanostructures in the lithographically induced self-assembly and self-construction of thin polymer films. Our studies show that the period of the self-assembled pillars depends on the ratio between the surface tension force and the electrostatic force. The viscosity of the polymer has no effect on the final pillar shape. When the feature width of the mold is comparable to or smaller than the most unstable disturbance wavelength of the system, the initially self-assembled pillars will merge to form a self-constructed mesa.

  1. Functional membranes via nanoparticle self-assembly.

    PubMed

    Green, Erica; Fullwood, Emily; Selden, Julieann; Zharov, Ilya

    2015-05-07

    This article summarizes a recently developed approach for the preparation of membrane materials by the self-assembly of inorganic, polymeric or hybrid nanoparticles, with the focus on functional membranes possessing permselectivity. Two types of such membranes are discussed, those possessing size and charge selectivity suitable for ultra- and nanofiltration and chemoselective separation, and those possessing proton or lithium transport properties suitable for fuel cell and lithium battery applications, respectively. This article describes the preparation methods of nanoparticle membranes, as well as their mechanical, molecular, and ionic transport properties.

  2. Self-assembly of Random Copolymers

    PubMed Central

    Li, Longyu; Raghupathi, Kishore; Song, Cunfeng; Prasad, Priyaa; Thayumanavan, S.

    2014-01-01

    Self-assembly of random copolymers has attracted considerable attention recently. In this feature article, we highlight the use of random copolymers to prepare nanostructures with different morphologies and to prepare nanomaterials that are responsive to single or multiple stimuli. The synthesis of single-chain nanoparticles and their potential applications from random copolymers are also discussed in some detail. We aim to draw more attention to these easily accessible copolymers, which are likely to play an important role in translational polymer research. PMID:25036552

  3. Self-assembled lipid bilayer materials

    DOEpatents

    Sasaki, Darryl Y.; Waggoner, Tina A.; Last, Julie A.

    2005-11-08

    The present invention is a self-assembling material comprised of stacks of lipid bilayers formed in a columnar structure, where the assembly process is mediated and regulated by chemical recognition events. The material, through the chemical recognition interactions, has a self-regulating system that corrects the radial size of the assembly creating a uniform diameter throughout most of the structure. The materials form and are stable in aqueous solution. These materials are useful as structural elements for the architecture of materials and components in nanotechnology, efficient light harvesting systems for optical sensing, chemical processing centers, and drug delivery vehicles.

  4. Microscale Self-Assembled Electrical Contacts

    DTIC Science & Technology

    2007-09-01

    Capillary forces from a molten alloy can be used to both bond microscale components and make electrical connections between them in a self...melting point, with Sn being the primary component to corrode and react with the underlying base metal. Using a eutectic Sn-Bi alloy and glycerol at...on this Sn-Bi-glycerol system was measured at 1.9 /mΩ-cm2. 15. SUBJECT TERMS Self-assembly, capillary forces, eutectic Bi-Sn solder, packaging 16

  5. Self-assembly of colloidal surfactants

    NASA Astrophysics Data System (ADS)

    Kegel, Willem

    2012-02-01

    We developed colloidal dumbbells with a rough and a smooth part, based on a method reported in Ref. [1]. Specific attraction between the smooth parts occurs upon addition of non-adsorbing polymers of appropriate size. We present the first results in terms of the assemblies that emerge in these systems. [4pt] [1] D.J. Kraft, W.S. Vlug, C.M. van Kats, A. van Blaaderen, A. Imhof and W.K. Kegel, Self-assembly of colloids with liquid protrusions, J. Am. Chem. Soc. 131, 1182, (2009)

  6. Nanoscale spirals by directed self-assembly

    NASA Astrophysics Data System (ADS)

    Choi, Hong Kyoon; Chang, Jae-Byum; Hannon, Adam F.; Yang, Joel K. W.; Berggren, Karl K.; Alexander-Katz, Alfredo; Ross, Caroline A.

    2017-06-01

    Archimedean spiral patterns are formed by the directed self-assembly of diblock copolymer thin films within a circular template. The presence of a notch in the template promotes the formation of a spiral compared to concentric rings, and the notch shape determines the chirality of the spiral. Double spirals occur when the notch width is increased or when there are two notches. The spiral followed an Archimedean form with exponent ≈0.9. Self-consistent field theory reproduces the experimentally observed morphologies and demonstrates the templating of spirals in cylindrical-morphology block copolymer films.

  7. Self-assembly of magnetic biofunctional nanoparticles

    SciTech Connect

    Sun Xiangcheng; Thode, C.J.; Mabry, J.K.; Harrell, J.W.; Nikles, D.E.; Sun, K.; Wang, L.M.

    2005-05-15

    Spherical, ferromagnetic FePt nanoparticles with a particle size of 3 nm were prepared by the simultaneous polyol reduction of Fe(acac){sub 3} and Pt(acac){sub 2} in phenyl ether in the presence of oleic acid and oleylamine. The oleic acid ligands can be replaced with 11-mercaptoundecanoic acid, giving particles that can be dispersed in water. Both x-ray diffraction and transmission electron microscopy indicated that FePt particles were not affected by ligands replacement. Dispersions of the FePt particles with 11-mercaptoundecanoic acid ligands and ammonium counter ions gave self-assembled films consisting of highly ordered hexagonal arrays of particles.

  8. Self-assembly processes in the prebiotic environment

    PubMed Central

    Deamer, David; Singaram, Sara; Rajamani, Sudha; Kompanichenko, Vladimir; Guggenheim, Stephen

    2006-01-01

    An important question guiding research on the origin of life concerns the environmental conditions where molecular systems with the properties of life first appeared on the early Earth. An appropriate site would require liquid water, a source of organic compounds, a source of energy to drive polymerization reactions and a process by which the compounds were sufficiently concentrated to undergo physical and chemical interactions. One such site is a geothermal setting, in which organic compounds interact with mineral surfaces to promote self-assembly and polymerization reactions. Here, we report an initial study of two geothermal sites where mixtures of representative organic solutes (amino acids, nucleobases, a fatty acid and glycerol) and phosphate were mixed with high-temperature water in clay-lined pools. Most of the added organics and phosphate were removed from solution with half-times measured in minutes to a few hours. Analysis of the clay, primarily smectite and kaolin, showed that the organics were adsorbed to the mineral surfaces at the acidic pH of the pools, but could subsequently be released in basic solutions. These results help to constrain the range of possible environments for the origin of life. A site conducive to self-assembly of organic solutes would be an aqueous environment relatively low in ionic solutes, at an intermediate temperature range and neutral pH ranges, in which cyclic concentration of the solutes can occur by transient dry intervals. PMID:17008220

  9. Self-assembly processes in the prebiotic environment.

    PubMed

    Deamer, David; Singaram, Sara; Rajamani, Sudha; Kompanichenko, Vladimir; Guggenheim, Stephen

    2006-10-29

    An important question guiding research on the origin of life concerns the environmental conditions where molecular systems with the properties of life first appeared on the early Earth. An appropriate site would require liquid water, a source of organic compounds, a source of energy to drive polymerization reactions and a process by which the compounds were sufficiently concentrated to undergo physical and chemical interactions. One such site is a geothermal setting, in which organic compounds interact with mineral surfaces to promote self-assembly and polymerization reactions. Here, we report an initial study of two geothermal sites where mixtures of representative organic solutes (amino acids, nucleobases, a fatty acid and glycerol) and phosphate were mixed with high-temperature water in clay-lined pools. Most of the added organics and phosphate were removed from solution with half-times measured in minutes to a few hours. Analysis of the clay, primarily smectite and kaolin, showed that the organics were adsorbed to the mineral surfaces at the acidic pH of the pools, but could subsequently be released in basic solutions. These results help to constrain the range of possible environments for the origin of life. A site conducive to self-assembly of organic solutes would be an aqueous environment relatively low in ionic solutes, at an intermediate temperature range and neutral pH ranges, in which cyclic concentration of the solutes can occur by transient dry intervals.

  10. Mineral Surface Chemistry and Nanoparticle-aggregation Control Membrane Self-Assembly

    PubMed Central

    Sahai, Nita; Kaddour, Hussein; Dalai, Punam; Wang, Ziqiu; Bass, Garrett; Gao, Min

    2017-01-01

    The self-assembly of lipid bilayer membranes to enclose functional biomolecules, thus defining a “protocell,” was a seminal moment in the emergence of life on Earth and likely occurred at the micro-environment of the mineral-water interface. Mineral-lipid interactions are also relevant in biomedical, industrial and technological processes. Yet, no structure-activity relationships (SARs) have been identified to predict lipid self-assembly at mineral surfaces. Here we examined the influence of minerals on the self-assembly and survival of vesicles composed of single chain amphiphiles as model protocell membranes. The apparent critical vesicle concentration (CVC) increased in the presence of positively-charged nanoparticulate minerals at high loadings (mg/mL) suggesting unfavorable membrane self-assembly in such situations. Above the CVC, initial vesicle formation rates were faster in the presence of minerals. Rates were correlated with the mineral’s isoelectric point (IEP) and reactive surface area. The IEP depends on the crystal structure, chemical composition and surface hydration. Thus, membrane self-assembly showed rational dependence on fundamental mineral properties. Once formed, membrane permeability (integrity) was unaffected by minerals. Suggesting that, protocells could have survived on rock surfaces. These SARs may help predict the formation and survival of protocell membranes on early Earth and other rocky planets, and amphiphile-mineral interactions in diverse other phenomena. PMID:28266537

  11. Mineral Surface Chemistry and Nanoparticle-aggregation Control Membrane Self-Assembly

    NASA Astrophysics Data System (ADS)

    Sahai, Nita; Kaddour, Hussein; Dalai, Punam; Wang, Ziqiu; Bass, Garrett; Gao, Min

    2017-03-01

    The self-assembly of lipid bilayer membranes to enclose functional biomolecules, thus defining a “protocell,” was a seminal moment in the emergence of life on Earth and likely occurred at the micro-environment of the mineral-water interface. Mineral-lipid interactions are also relevant in biomedical, industrial and technological processes. Yet, no structure-activity relationships (SARs) have been identified to predict lipid self-assembly at mineral surfaces. Here we examined the influence of minerals on the self-assembly and survival of vesicles composed of single chain amphiphiles as model protocell membranes. The apparent critical vesicle concentration (CVC) increased in the presence of positively-charged nanoparticulate minerals at high loadings (mg/mL) suggesting unfavorable membrane self-assembly in such situations. Above the CVC, initial vesicle formation rates were faster in the presence of minerals. Rates were correlated with the mineral’s isoelectric point (IEP) and reactive surface area. The IEP depends on the crystal structure, chemical composition and surface hydration. Thus, membrane self-assembly showed rational dependence on fundamental mineral properties. Once formed, membrane permeability (integrity) was unaffected by minerals. Suggesting that, protocells could have survived on rock surfaces. These SARs may help predict the formation and survival of protocell membranes on early Earth and other rocky planets, and amphiphile-mineral interactions in diverse other phenomena.

  12. Mineral Surface Chemistry and Nanoparticle-aggregation Control Membrane Self-Assembly.

    PubMed

    Sahai, Nita; Kaddour, Hussein; Dalai, Punam; Wang, Ziqiu; Bass, Garrett; Gao, Min

    2017-03-07

    The self-assembly of lipid bilayer membranes to enclose functional biomolecules, thus defining a "protocell," was a seminal moment in the emergence of life on Earth and likely occurred at the micro-environment of the mineral-water interface. Mineral-lipid interactions are also relevant in biomedical, industrial and technological processes. Yet, no structure-activity relationships (SARs) have been identified to predict lipid self-assembly at mineral surfaces. Here we examined the influence of minerals on the self-assembly and survival of vesicles composed of single chain amphiphiles as model protocell membranes. The apparent critical vesicle concentration (CVC) increased in the presence of positively-charged nanoparticulate minerals at high loadings (mg/mL) suggesting unfavorable membrane self-assembly in such situations. Above the CVC, initial vesicle formation rates were faster in the presence of minerals. Rates were correlated with the mineral's isoelectric point (IEP) and reactive surface area. The IEP depends on the crystal structure, chemical composition and surface hydration. Thus, membrane self-assembly showed rational dependence on fundamental mineral properties. Once formed, membrane permeability (integrity) was unaffected by minerals. Suggesting that, protocells could have survived on rock surfaces. These SARs may help predict the formation and survival of protocell membranes on early Earth and other rocky planets, and amphiphile-mineral interactions in diverse other phenomena.

  13. Hollow Nanospheres Array Fabrication via Nano-Conglutination Technology.

    PubMed

    Zhang, Man; Deng, Qiling; Xia, Liangping; Shi, Lifang; Cao, Axiu; Pang, Hui; Hu, Song

    2015-09-01

    Hollow nanospheres array is a special nanostructure with great applications in photonics, electronics and biochemistry. The nanofabrication technique with high resolution is crucial to nanosciences and nano-technology. This paper presents a novel nonconventional nano-conglutination technology combining polystyrenes spheres (PSs) self-assembly, conglutination and a lift-off process to fabricate the hollow nanospheres array with nanoholes. A self-assembly monolayer of PSs was stuck off from the quartz wafer by the thiol-ene adhesive material, and then the PSs was removed via a lift-off process and the hollow nanospheres embedded into the thiol-ene substrate was obtained. Thiolene polymer is a UV-curable material via "click chemistry" reaction at ambient conditions without the oxygen inhibition, which has excellent chemical and physical properties to be attractive as the adhesive material in nano-conglutination technology. Using the technique, a hollow nanospheres array with the nanoholes at the diameter of 200 nm embedded into the rigid thiol-ene substrate was fabricated, which has great potential to serve as a reaction container, catalyst and surface enhanced Raman scattering substrate.

  14. Quantifying quality in DNA self-assembly

    PubMed Central

    Wagenbauer, Klaus F.; Wachauf, Christian H.; Dietz, Hendrik

    2014-01-01

    Molecular self-assembly with DNA is an attractive route for building nanoscale devices. The development of sophisticated and precise objects with this technique requires detailed experimental feedback on the structure and composition of assembled objects. Here we report a sensitive assay for the quality of assembly. The method relies on measuring the content of unpaired DNA bases in self-assembled DNA objects using a fluorescent de-Bruijn probe for three-base ‘codons’, which enables a comparison with the designed content of unpaired DNA. We use the assay to measure the quality of assembly of several multilayer DNA origami objects and illustrate the use of the assay for the rational refinement of assembly protocols. Our data suggests that large and complex objects like multilayer DNA origami can be made with high strand integration quality up to 99%. Beyond DNA nanotechnology, we speculate that the ability to discriminate unpaired from paired nucleic acids in the same macromolecule may also be useful for analysing cellular nucleic acids. PMID:24751596

  15. Comparison of directed self-assembly integrations

    NASA Astrophysics Data System (ADS)

    Somervell, Mark; Gronheid, Roel; Hooge, Joshua; Nafus, Kathleen; Rincon Delgadillo, Paulina; Thode, Chris; Younkin, Todd; Matsunaga, Koichi; Rathsack, Ben; Scheer, Steven; Nealey, Paul

    2012-03-01

    Directed Self-Assembly (DSA) is gaining momentum as a means for extending optical lithography past its current limits. There are many forms of the technology, and it can be used for creating both line/space and hole patterns.1-3 As with any new technology, adoption of DSA faces several key challenges. These include creation of a new materials infrastructure, fabrication of new processing hardware, and the development of implementable integrations. Above all else, determining the lowest possible defect density remains the industry's most critical concern. Over the past year, our team, working at IMEC, has explored various integrations for making 12-14nm half-pitch line/space arrays. Both grapho- and chemo-epitaxy implementations have been investigated in order to discern which offers the best path to high volume manufacturing. This paper will discuss the manufacturing readiness of the various implementations by comparing the process margin for different DSA processing steps and defect density for the entirety of the flow. As part of this work, we will describe our method for using programmed defectivity on reticle to elucidate the mechanisms that drive self-assembly defectivity on wafer.

  16. Peptide self-assembly: thermodynamics and kinetics.

    PubMed

    Wang, Juan; Liu, Kai; Xing, Ruirui; Yan, Xuehai

    2016-10-21

    Self-assembling systems play a significant role in physiological functions and have therefore attracted tremendous attention due to their great potential for applications in energy, biomedicine and nanotechnology. Peptides, consisting of amino acids, are among the most popular building blocks and programmable molecular motifs. Nanostructures and materials assembled using peptides exhibit important potential for green-life new technology and biomedical applications mostly because of their bio-friendliness and reversibility. The formation of these ordered nanostructures pertains to the synergistic effect of various intermolecular non-covalent interactions, including hydrogen-bonding, π-π stacking, electrostatic, hydrophobic, and van der Waals interactions. Therefore, the self-assembly process is mainly driven by thermodynamics; however, kinetics is also a critical factor in structural modulation and function integration. In this review, we focus on the influence of thermodynamic and kinetic factors on structural assembly and regulation based on different types of peptide building blocks, including aromatic dipeptides, amphiphilic peptides, polypeptides, and amyloid-relevant peptides.

  17. Triggered self-assembly of magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Ye, L.; Pearson, T.; Cordeau, Y.; Mefford, O. T.; Crawford, T. M.

    2016-03-01

    Colloidal magnetic nanoparticles are candidates for application in biology, medicine and nanomanufac-turing. Understanding how these particles interact collectively in fluids, especially how they assemble and aggregate under external magnetic fields, is critical for high quality, safe, and reliable deployment of these particles. Here, by applying magnetic forces that vary strongly over the same length scale as the colloidal stabilizing force and then varying this colloidal repulsion, we can trigger self-assembly of these nanoparticles into parallel line patterns on the surface of a disk drive medium. Localized within nanometers of the medium surface, this effect is strongly dependent on the ionic properties of the colloidal fluid but at a level too small to cause bulk colloidal aggregation. We use real-time optical diffraction to monitor the dynamics of self-assembly, detecting local colloidal changes with greatly enhanced sensitivity compared with conventional light scattering. Simulations predict the triggering but not the dynamics, especially at short measurement times. Beyond using spatially-varying magnetic forces to balance interactions and drive assembly in magnetic nanoparticles, future measurements leveraging the sensitivity of this approach could identify novel colloidal effects that impact real-world applications of these nanoparticles.

  18. Triggered self-assembly of magnetic nanoparticles.

    PubMed

    Ye, L; Pearson, T; Cordeau, Y; Mefford, O T; Crawford, T M

    2016-03-15

    Colloidal magnetic nanoparticles are candidates for application in biology, medicine and nanomanufacturing. Understanding how these particles interact collectively in fluids, especially how they assemble and aggregate under external magnetic fields, is critical for high quality, safe, and reliable deployment of these particles. Here, by applying magnetic forces that vary strongly over the same length scale as the colloidal stabilizing force and then varying this colloidal repulsion, we can trigger self-assembly of these nanoparticles into parallel line patterns on the surface of a disk drive medium. Localized within nanometers of the medium surface, this effect is strongly dependent on the ionic properties of the colloidal fluid but at a level too small to cause bulk colloidal aggregation. We use real-time optical diffraction to monitor the dynamics of self-assembly, detecting local colloidal changes with greatly enhanced sensitivity compared with conventional light scattering. Simulations predict the triggering but not the dynamics, especially at short measurement times. Beyond using spatially-varying magnetic forces to balance interactions and drive assembly in magnetic nanoparticles, future measurements leveraging the sensitivity of this approach could identify novel colloidal effects that impact real-world applications of these nanoparticles.

  19. Geometry and universality in self-assembly

    NASA Astrophysics Data System (ADS)

    Bowick, Mark

    2007-03-01

    I will discuss the use of ideas from geometry and topology in combination with the statistical mechanics of self-assembly to classify the possible types of mesoatoms that can constitute a library of raw materials for making mesomolecules and bulk materials. I will concentrate on mesoatoms made up of an ordered two-dimensional monolayer of particles on the surface of a liquid droplet. Both the shape and the topology of the two-dimensional surface can be varied as well as the architecture of the ordering particles. The topology of the surface and the symmetries of the two-dimensional order severely restrict the possible defect structure of the mesoatom, which in turn fixes its valency. Defective regions are natural places for biological activity, chemical linking, unusual elastic response and aggregation of disorder. Specific examples include crystalline and hexatic order of point particles on the sphere, paraboloid, torus and Gaussian bump, nematic order of nematogens on the sphere and torus, and vector order of polar units on the sphere. The Gaussian curvature of the underlying surface may also lead to new features in the ground state, such as extended defect arrays of various kinds and curvature-driven defect unbinding, all of which may be exploited via engineered or spontaneous self-assembly.

  20. Quantifying quality in DNA self-assembly

    NASA Astrophysics Data System (ADS)

    Wagenbauer, Klaus F.; Wachauf, Christian H.; Dietz, Hendrik

    2014-04-01

    Molecular self-assembly with DNA is an attractive route for building nanoscale devices. The development of sophisticated and precise objects with this technique requires detailed experimental feedback on the structure and composition of assembled objects. Here we report a sensitive assay for the quality of assembly. The method relies on measuring the content of unpaired DNA bases in self-assembled DNA objects using a fluorescent de-Bruijn probe for three-base ‘codons’, which enables a comparison with the designed content of unpaired DNA. We use the assay to measure the quality of assembly of several multilayer DNA origami objects and illustrate the use of the assay for the rational refinement of assembly protocols. Our data suggests that large and complex objects like multilayer DNA origami can be made with high strand integration quality up to 99%. Beyond DNA nanotechnology, we speculate that the ability to discriminate unpaired from paired nucleic acids in the same macromolecule may also be useful for analysing cellular nucleic acids.

  1. Triggered self-assembly of magnetic nanoparticles

    PubMed Central

    Ye, L.; Pearson, T.; Cordeau, Y.; Mefford, O. T.; Crawford, T. M.

    2016-01-01

    Colloidal magnetic nanoparticles are candidates for application in biology, medicine and nanomanufac-turing. Understanding how these particles interact collectively in fluids, especially how they assemble and aggregate under external magnetic fields, is critical for high quality, safe, and reliable deployment of these particles. Here, by applying magnetic forces that vary strongly over the same length scale as the colloidal stabilizing force and then varying this colloidal repulsion, we can trigger self-assembly of these nanoparticles into parallel line patterns on the surface of a disk drive medium. Localized within nanometers of the medium surface, this effect is strongly dependent on the ionic properties of the colloidal fluid but at a level too small to cause bulk colloidal aggregation. We use real-time optical diffraction to monitor the dynamics of self-assembly, detecting local colloidal changes with greatly enhanced sensitivity compared with conventional light scattering. Simulations predict the triggering but not the dynamics, especially at short measurement times. Beyond using spatially-varying magnetic forces to balance interactions and drive assembly in magnetic nanoparticles, future measurements leveraging the sensitivity of this approach could identify novel colloidal effects that impact real-world applications of these nanoparticles. PMID:26975332

  2. 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).

  3. Self-assembled Nanofibrils for Immunomodulation

    NASA Astrophysics Data System (ADS)

    Zhao, Fan

    This thesis has been mainly focused on applying self-assembled nanofibrils as unique depots for controlled release to modulate immune system, with two major chapters on modulation of innate immunity in chapter 2 and adaptive immunity in chapter 3, respectively. There are 5 chapters in the thesis. Chapter 1 gives a detailed review on the discovery, synthesis and application of self-assembled nanofibrils of therapeutic agents (termed as "self-delivery drugs"), including bioactive molecules; Chapter 2 demonstrates the supramolecular hydrogel of chemotactic peptides as a prolonged inflammation model through proper molecular engineering; Chapter 3 reports a suppressive antibody response achieved by encapsulation of antigens by supramolecular hydrogel of glycopeptide; Chapter 4 illustrates an example of supramolecular hydrogel formation of molecules with extremely low solubility, based on the fact that many small organic drugs have poor solubility. Chapter 5 used beta-galatosidase as a model to study glycosidase-instructed supramolecular hydrogel formation, with potential to target cancer cells due to their distinct metabolic profile.

  4. Self-assembled virus-membrane complexes

    NASA Astrophysics Data System (ADS)

    Yang, Lihua; Liang, Hongjun; Angelini, Thomas E.; Butler, John; Coridan, Robert; Tang, Jay X.; Wong, Gerard C. L.

    2004-09-01

    Anionic polyelectrolytes and cationic lipid membranes can self-assemble into lamellar structures ranging from alternating layers of membranes and polyelectrolytes to 'missing layer' superlattice structures. We show that these structural differences can be understood in terms of the surface-charge-density mismatch between the polyelectrolyte and membrane components by examining complexes between cationic membranes and highly charged M13 viruses, a system that allowed us to vary the polyelectrolyte diameter independently of the charge density. Such virus-membrane complexes have pore sizes that are about ten times larger in area than DNA-membrane complexes, and can be used to package and organize large functional molecules; correlated arrays of Ru(bpy)32+ macroionic dyes have been directly observed within the virus-membrane complexes using an electron-density reconstruction. These observations elucidate fundamental design rules for rational control of self-assembled polyelectrolyte-membrane structures, which have applications ranging from non-viral gene therapy to biomolecular templates for nanofabrication.

  5. Self-assembled virus-membrane complexes

    SciTech Connect

    Yang, Lihua; Liang, Hongjun; Angelini, Thomas; Butler, John; Coridan, Robert; Tang, Jay; Wong, Gerard

    2010-11-16

    Anionic polyelectrolytes and cationic lipid membranes can self-assemble into lamellar structures ranging from alternating layers of membranes and polyelectrolytes to 'missing layer' superlattice structures. We show that these structural differences can be understood in terms of the surface-charge-density mismatch between the polyelectrolyte and membrane components by examining complexes between cationic membranes and highly charged M13 viruses, a system that allowed us to vary the polyelectrolyte diameter independently of the charge density. Such virus-membrane complexes have pore sizes that are about ten times larger in area than DNA-membrane complexes, and can be used to package and organize large functional molecules; correlated arrays of Ru(bpy){sub 3}{sup 2+} macroionic dyes have been directly observed within the virus-membrane complexes using an electron-density reconstruction. These observations elucidate fundamental design rules for rational control of self-assembled polyelectrolyte-membrane structures, which have applications ranging from non-viral gene therapy to biomolecular templates for nanofabrication.

  6. Directed Self-Assembly: Expectations and Achievements

    PubMed Central

    2010-01-01

    Nanotechnology has been a revolutionary thrust in recent years of development of science and technology for its broad appeal for employing a novel idea for relevant technological applications in particular and for mass-scale production and marketing as common man commodity in general. An interesting aspect of this emergent technology is that it involves scientific research community and relevant industries alike. Top–down and bottom–up approaches are two broad division of production of nanoscale materials in general. However, both the approaches have their own limits as far as large-scale production and cost involved are concerned. Therefore, novel new techniques are desired to be developed to optimize production and cost. Directed self-assembly seems to be a promising technique in this regard; which can work as a bridge between the top–down and bottom–up approaches. This article reviews how directed self-assembly as a technique has grown up and outlines its future prospects. PMID:20730077

  7. Micropatterning of bioactive self-assembling gels†

    PubMed Central

    Mata, Alvaro; Hsu, Lorraine; Capito, Ramille; Aparicio, Conrado; Henrikson, Karl

    2009-01-01

    Microscale topographical features have been known to affect cell behavior. An important target in this area is to integrate top down techniques with bottom up self-assembly to create three-dimensional (3D) patterned bioactive mimics of extracellular matrices. We report a novel approach toward this goal and demonstrate its use to study the behavior of human mesenchymal stem cells (hMSCs). By incorporating polymerizable acetylene groups in the hydrophobic segment of peptide amphiphiles (PAs), we were able to micro-pattern nanofiber gels of these bioactive materials. PAs containing the cell adhesive epitope arginine–glycine–aspartic acid–serine (RGDS) were allowed to self-assemble within microfabricated molds to create networks of either randomly oriented or aligned ~30 nm diameter nanofiber bundles that were shaped into topographical patterns containing holes, posts, or channels up to 8 μm in height and down to 5 μm in lateral dimensions. When topographical patterns contained nanofibers aligned through flow prior to gelation, the majority of hMSCs aligned in the direction of the nanofibers even in the presence of hole microtextures and more than a third of them maintained this alignment when encountering perpendicular channel microtextures. Interestingly, in topographical patterns with randomly oriented nanofibers, osteoblastic differentiation was enhanced on hole microtextures compared to all other surfaces. PMID:20047022

  8. Coarse-grained simulation reveals key features of HIV-1 capsid self-assembly

    NASA Astrophysics Data System (ADS)

    Grime, John M. A.; Dama, James F.; Ganser-Pornillos, Barbie K.; Woodward, Cora L.; Jensen, Grant J.; Yeager, Mark; Voth, Gregory A.

    2016-05-01

    The maturation of HIV-1 viral particles is essential for viral infectivity. During maturation, many copies of the capsid protein (CA) self-assemble into a capsid shell to enclose the viral RNA. The mechanistic details of the initiation and early stages of capsid assembly remain to be delineated. We present coarse-grained simulations of capsid assembly under various conditions, considering not only capsid lattice self-assembly but also the potential disassembly of capsid upon delivery to the cytoplasm of a target cell. The effects of CA concentration, molecular crowding, and the conformational variability of CA are described, with results indicating that capsid nucleation and growth is a multi-stage process requiring well-defined metastable intermediates. Generation of the mature capsid lattice is sensitive to local conditions, with relatively subtle changes in CA concentration and molecular crowding influencing self-assembly and the ensemble of structural morphologies.

  9. Cyclodextrin directed self-assembly of TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Yoon, Sungkwon; Nichols, William T.

    2013-11-01

    In this paper we study the self-assembly of TiO2 nanoparticles with cyclodextrin molecules into a self-supporting fiber network. We observe the network's macroscopic growth and evolving microstructure as a function of time and relate these to the chemical changes of the solution and the composition of the growing network. From this data we elucidate the steps of the self-assembly process. The TiO2 nanoparticles initiate a photocatalytic reaction that results in a ring breaking and dehydration of the cyclodextrin molecules in solution. This dehydration exposes the hydrophobic regions of the cyclodextrin molecule to the water solution, supplying the force that drives self-assembly. This same hydrophobic force also leads to branch and junction formation between fibers that ultimately build up the self-supporting network structure.

  10. 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.

  11. Coarse-grained simulation reveals key features of HIV-1 capsid self-assembly

    PubMed Central

    Grime, John M. A.; Dama, James F.; Ganser-Pornillos, Barbie K.; Woodward, Cora L.; Jensen, Grant J.; Yeager, Mark; Voth, Gregory A.

    2016-01-01

    The maturation of HIV-1 viral particles is essential for viral infectivity. During maturation, many copies of the capsid protein (CA) self-assemble into a capsid shell to enclose the viral RNA. The mechanistic details of the initiation and early stages of capsid assembly remain to be delineated. We present coarse-grained simulations of capsid assembly under various conditions, considering not only capsid lattice self-assembly but also the potential disassembly of capsid upon delivery to the cytoplasm of a target cell. The effects of CA concentration, molecular crowding, and the conformational variability of CA are described, with results indicating that capsid nucleation and growth is a multi-stage process requiring well-defined metastable intermediates. Generation of the mature capsid lattice is sensitive to local conditions, with relatively subtle changes in CA concentration and molecular crowding influencing self-assembly and the ensemble of structural morphologies. PMID:27174390

  12. Entropic Phase Transitions with Stable Twisted Intermediates of Bio-Inspired Self-Assembly.

    PubMed

    Tao, Kai; Levin, Aviad; Jacoby, Guy; Beck, Roy; Gazit, Ehud

    2016-10-17

    Controlling the hierarchical process and capturing the intermediate stage underlying bio-inspired self-assembly are pivotal for understanding their aggregation mechanism and exploring possible applications. Here, the self-assembly of a designed minimal lipopeptide was characterized, showing it to initially self-assemble to narrow nanotwists, which then ripen to wide nanotwists, and finally transit to hollow nanotubes. The supramolecular phase transitions were revealed to be driven by entropic hydrophobic interactions, rather than by the common mechanism of enthalpy-related contributions. The transformation dynamics were sufficiently slow to enable detection and characterization of each stage, thus inducing the stable and extensive distributions of twisted intermediates. The findings allow an in-depth understanding of the hierarchical self-association of bio-inspired building blocks and provide a new approach for the preparation of superstructures of unique morphologies.

  13. Tunable Self-Assembly of Diblock Copolymers into Colloidal Particles with Triply Periodic Minimal Surfaces.

    PubMed

    Lin, Zhixing; Liu, Shaohua; Mao, Wenting; Tian, Hao; Wang, Nan; Zhang, Ninghe; Tian, Feng; Han, Lu; Feng, Xinliang; Mai, Yiyong

    2017-06-12

    We herein report the tunable self-assembly of simple block copolymers, namely polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymers, into porous cubosomes with inverse Im3‾m or Pn3‾m mesophases of controlled unit cell parameters as well as hexasomes with an inverse hexagonal (p6mm) structure, which have been rarely observed in polymer self-assembly. A new morphological phase diagram was constructed for the solution self-assembly of PS-b-PEO based on the volume fraction of the PS block against the initial copolymer concentration. The formation mechanisms of the cubosomes and hexasomes have also been revealed. This study not only affords a simple system for the controllable preparation and fundamental studies of ordered bicontinuous structures, but also opens up a new avenue towards porous architectures with highly ordered pores. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Amphiphilic self-assembly of semiconductor nanocrystals with heterogeneous compositions

    NASA Astrophysics Data System (ADS)

    Taniguchi, Yuki; Takishita, Takao; Kobayashi, Yusei; Arai, Noriyoshi; Kawai, Tsuyoshi; Nakashima, Takuya

    2017-06-01

    We describe herein that amphiphilic semiconductor nanocrystals (NCs) self-assembled into network structures with heterogeneous compositions. The semiconductor nanorods and tetrapods were subjected to ligand exchange with short-chained water-soluble thiolates, giving an amphiphilic surface pattern with a hydrophilic wall and hydrophobic tips. The amphiphilic NCs self-assembled through hydrophobic effects between tip-surfaces in water. The hydrophobic effect-facilitated self-assembly of NCs was well reproduced by a dissipative particle dynamics simulation. The amphiphilic self-assembly of NCs was demonstrated regardless of NC-shapes and compositions to give semiconductor NC-network structures with heterogeneous compositions. The tandem connection of luminescent core/shell nanorods demonstrated energy transfer between the nanorods in the self-assembly. Contribution to the Focus Issue Self-assemblies of Inorganic and Organic Nanomaterials edited by Marie-Paule Pileni.

  15. Terminal groups control self-assembly of amphiphilic block copolymers in solution

    NASA Astrophysics Data System (ADS)

    Grzelakowski, M.; Kita-Tokarczyk, K.

    2016-03-01

    The terminal groups of amphiphilic block copolymers are shown to control macromolecular self-assembly in aqueous solutions, in the micellar/lamellar region of the phase diagram. At the same concentration and using the same self-assembly conditions, dramatic differences are observed in polymer hydration and the resulting nano-/microstructure for two series of polymers with identical block chemistry and hydrophilic-lipophilic balance (HLB). This suggests a strong contribution from end groups to the hydration as the initial step of the self-assembly process, and could be conveniently used to guide the particle morphology and size. Additionally, for polymers with those head groups which drive vesicular structures, differences in membrane organization affect their physical properties, such as permeability.The terminal groups of amphiphilic block copolymers are shown to control macromolecular self-assembly in aqueous solutions, in the micellar/lamellar region of the phase diagram. At the same concentration and using the same self-assembly conditions, dramatic differences are observed in polymer hydration and the resulting nano-/microstructure for two series of polymers with identical block chemistry and hydrophilic-lipophilic balance (HLB). This suggests a strong contribution from end groups to the hydration as the initial step of the self-assembly process, and could be conveniently used to guide the particle morphology and size. Additionally, for polymers with those head groups which drive vesicular structures, differences in membrane organization affect their physical properties, such as permeability. Electronic supplementary information (ESI) available: Fig. S1: Particle diameters for hydrated NH2-ABA-NH2 polymers with different degrees of functionalization; Fig. S2: TEM characterization of compound micelles from BA-OH polymer after extrusion; Fig. S3: Cryo-TEM and stopped flow characterization of lipid vesicles; Fig. S4 and S5: NMR spectra for ABA and BA polymers

  16. A green-light gain-assisted metamaterial fabricated by self-assembled electrochemical deposition

    NASA Astrophysics Data System (ADS)

    Li, Sa; Gong, Boyi; Cao, Di; Pan, Zhenzhen; Luo, Chunrong; Zhao, Xiaopeng

    2013-10-01

    Based on the fabrication of nanospheres self-assembled and electrochemical deposition, the high-quality double-fishnet metamaterials consisting of Ag-polyvinyl alcohol-Ag nanostructures on an indium tin oxide conductive glass substrate have been prepared, with a resonant pass band in the vicinity of 545-nm green-light wavelength. The active medium Rhodamine B (Rh B) was incorporated into metamaterial structure to overcome the inherent losses, and the experiments demonstrate that the transmission intensity of the sample doped with Rh B is enhanced evidently versus that of the sample without Rh B; this may provide another way towards the fabrication of gain-assisted low-loss visible metamaterials.

  17. Anisotropic nanocolloids: self-assembly, interfacial adsorption, and electrostatic screening

    NASA Astrophysics Data System (ADS)

    de Graaf, J.

    2012-06-01

    we obtained a fascinating richness in crystal structures. For the octahedron we determined the equation of state and we obtained a liquid, a (metastable) body-centred-cubic rotator phase, and a crystal phase. (3.) - Octapod hierarchical self-assembly. We analysed the recently observed hierarchical self-assembly of octapod-shaped nanocrystals (octapods) into three-dimensional (3D) superstructures. We constructed an empirical simulation model capable of reproducing the initial chain-formation step of the self-assembly. The van-der-Waals (vdW) interactions between octapods suspended in an (a)polar medium were obtained by means of a Hamaker-de-Boer-type integration and the nature of these interactions allowed us to justify elements of our empirical model. We used the theoretical vdW calculation, together with the experimental and simulation results, to formulate a mechanism which explained the observed self-assembly in terms of the solvent-dependence and directionality of the octapod-octapod interactions. (4.) - Ionic screening of charged Janus particles. We studied the screening of charged Janus particles in an electrolyte by primitive-model Monte Carlo (MC) simulations for a wide variety of parameters. We also introduced a method to compare these results to the predictions of nonlinear Poisson-Boltzmann (PB) theory. The comparison of MC and PB results allowed us to probe the range of validity of the PB approximation. This range of validity corresponds well to the range that was predicted by field-theoretical studies of homogeneously charged flat surfaces.

  18. Ionic self-assembly for functional hierarchical nanostructured materials.

    PubMed

    Faul, Charl F J

    2014-12-16

    CONSPECTUS: The challenge of constructing soft functional materials over multiple length scales can be addressed by a number of different routes based on the principles of self-assembly, with the judicious use of various noncovalent interactions providing the tools to control such self-assembly processes. It is within the context of this challenge that we have extensively explored the use of an important approach for materials construction over the past decade: exploiting electrostatic interactions in our ionic self-assembly (ISA) method. In this approach, cooperative assembly of carefully chosen charged surfactants and oppositely charged building blocks (or tectons) provides a facile noncovalent route for the rational design and production of functional nanostructured materials. Generally, our research efforts have developed with an initial focus on establishing rules for the construction of novel noncovalent liquid-crystalline (LC) materials. We found that the use of double-tailed surfactant species (especially branched double-tailed surfactants) led to the facile formation of thermotropic (and, in certain cases, lyotropic) phases, as demonstrated by extensive temperature-dependent X-ray and light microscopy investigations. From this core area of activity, research expanded to cover issues beyond simple construction of anisotropic materials, turning to the challenge of inclusion and exploitation of switchable functionality. The use of photoactive azobenzene-containing ISA materials afforded opportunities to exploit both photo-orientation and surface relief grating formation. The preparation of these anisotropic LC materials was of interest, as the aim was the facile production of disposable and low-cost optical components for display applications and data storage. However, the prohibitive cost of the photo-orientation processes hampered further exploitation of these materials. We also expanded our activities to explore ISA of biologically relevant tectons

  19. Self-assembled software and method of overriding software execution

    DOEpatents

    Bouchard, Ann M.; Osbourn, Gordon C.

    2013-01-08

    A computer-implemented software self-assembled system and method for providing an external override and monitoring capability to dynamically self-assembling software containing machines that self-assemble execution sequences and data structures. The method provides an external override machine that can be introduced into a system of self-assembling machines while the machines are executing such that the functionality of the executing software can be changed or paused without stopping the code execution and modifying the existing code. Additionally, a monitoring machine can be introduced without stopping code execution that can monitor specified code execution functions by designated machines and communicate the status to an output device.

  20. DNA tile based self-assembly: building complex nanoarchitectures.

    PubMed

    Lin, Chenxiang; Liu, Yan; Rinker, Sherri; Yan, Hao

    2006-08-11

    DNA tile based self-assembly provides an attractive route to create nanoarchitectures of programmable patterns. It also offers excellent scaffolds for directed self-assembly of nanometer-scale materials, ranging from nanoparticles to proteins, with potential applications in constructing nanoelectronic/nanophotonic devices and protein/ligand nanoarrays. This Review first summarizes the currently available DNA tile toolboxes and further emphasizes recent developments toward self-assembling DNA nanostructures with increasing complexity. Exciting progress using DNA tiles for directed self-assembly of other nanometer scale components is also discussed.

  1. Metal-Directed Protein Self Assembly

    PubMed Central

    SALGADO, ERIC N.; RADFORD, ROBERT J.

    2010-01-01

    CONSPECTUS Proteins are Nature’s premier building blocks for constructing sophisticated nanoscale architectures that carry out complex tasks and chemical transformations. It is estimated that 70–80% of all proteins are permanently oligomeric, that is, they are composed of multiple proteins that are held together in precise spatial organization through non-covalent interactions. While it is of great fundamental interest to understand the physicochemical basis of protein self-assembly, the mastery of protein-protein interactions (PPIs) would also allow access to novel biomaterials using Nature’s favorite and most versatile building block. With this possibility in mind, we have developed a new approach, Metal Directed Protein Self-Assembly (MDPSA), which utilizes the strength, directionality and selectivity of metal-ligand interactions to control PPIs. At its core, MDPSA is inspired by supramolecular coordination chemistry which exploits metal coordination for the self-assembly of small molecules into discrete, more-or-less predictable higher-order structures. Proteins, however, are not exactly small molecules or simple metal ligands: they feature extensive, heterogeneous surfaces that can interact with each other and with metal ions in unpredictable ways. We will start this Account by first describing the challenges of using entire proteins as molecular building blocks. This will be followed by our work on a model protein (cytochrome cb562) to both highlight and overcome those challenges toward establishing some ground rules for MDPSA. Proteins are also Nature’s metal ligands of choice. In MDPSA, once metal ions guide proteins into forming large assemblies, they are by definition embedded within extensive interfaces formed between protein surfaces. These complex surfaces make an inorganic chemist’s life somewhat difficult, yet they also provide a wide platform to modulate the metal coordination environment through distant, non-covalent interactions

  2. Extracellular self-assembly of virus-like particles from secreted recombinant polyoma virus major coat protein.

    PubMed

    Ng, J; Koechlin, O; Ramalho, M; Raman, D; Krauzewicz, N

    2007-12-01

    Mouse polyoma virus major coat protein (VP1) expressed from a recombinant baculovirus is efficiently transported to infected cell nuclei and assembles into protein nanospheres morphologically similar to natural capsids. The nanospheres readily combine with plasmid DNA to form a hybrid gene therapy agent known as virus-like particles (VLPs). To facilitate large-scale production of VLPs free from cellular contaminants, the use of stable Drosophila cell lines expressing either wild-type protein, or VP1 tagged with a secretion signal for targeting to the extracellular medium, was investigated. Both wild-type and tagged VP1 expressed at 2-4 mg VP1/litre of culture. As expected, the wild-type protein self-assembled into VLPs. The tagged VP1 was efficiently secreted to the extracellular medium but was also glycosylated, unlike wild-type VP1. Despite this fact, a small fraction of the recombinant secreted protein assembled into VLP-like structures that had altered disulphide bonding, but were still biologically active. These results demonstrate the considerable tolerance in the nanosphere assembly to structural (i.e. aberrant glycosylation) and environmental (i.e. extracellular medium vs. nuclear milieu) changes. Thus, with modifications to improve nanosphere assembly, the secretion method could be adapted to large-scale preparation of VLPs, providing significant advantages over current methods of production of the vector.

  3. Capillary self-assembly of floating bodies

    NASA Astrophysics Data System (ADS)

    Jung, Sunghwan; Thompson, Paul; Bush, John

    2007-11-01

    We study the self-assembly of bodies supported on the water surface by surface tension. Attractive and repulsive capillary forces exist between menisci of, respectively, the same and opposite signs. In nature, floating objects (e.g. mosquito larvae) thus interact through capillary forces to form coherent packings on the water surface. We here present the results of an experimental investigation of such capillary pattern formation. Thin elliptical metal sheets were designed to have variable shape, flexibility and mass distribution. On the water surface, mono-, bi-, or tri-polar menisci could thus be achieved. The influence of the form of the menisci on the packings arising from the interaction of multiple floaters is explored. Biological applications are discussed.

  4. Self-assembling multimeric nucleic acid constructs

    DOEpatents

    Cantor, Charles R.; Niemeyer, Christof M.; Smith, Cassandra L.; Sano, Takeshi; Hnatowich, Donald J.; Rusckowski, Mary

    1996-01-01

    The invention is directed to constructs and compositions containing multimeric forms of nucleic acid. Multimeric nucleic acids comprise single-stranded nucleic acids attached via biotin to streptavidin and bound with a functional group. These constructs can be utilized in vivo to treat or identify diseased tissue or cells. Repeated administrations of multimeric nucleic acid compositions produce a rapid and specific amplification of nucleic acid constructs and their attached functional groups. For treatment purposes, functional groups may be toxins, radioisotopes, genes or enzymes. Diagnostically, labeled multimeric constructs may be used to identify specific targets in vivo or in vitro. Multimeric nucleic acids may also be used in nanotechnology and to create self-assembling polymeric aggregates such as membranes of defined porosity, microcircuits and many other products.

  5. Self-assembling multimeric nucleic acid constructs

    DOEpatents

    Cantor, Charles R.; Niemeyer, Christof M.; Smith, Cassandra L.; Sano, Takeshi; Hnatowich, Donald J.; Rusckowski, Mary

    1999-10-12

    The invention is directed to constructs and compositions containing multimeric forms of nucleic acid. Multimeric nucleic acids comprise single-stranded nucleic acids attached via biotin to streptavidin and bound with a functional group. These constructs can be utilized in vivo to treat or identify diseased tissue or cells. Repeated administrations of multimeric nucleic acid compositions produce a rapid and specific amplification of nucleic acid constructs and their attached functional groups. For treatment purposes, functional groups may be toxins, radioisotopes, genes or enzymes. Diagnostically, labeled multimeric constructs may be used to identify specific targets in vivo or in vitro. Multimeric nucleic acids may also be used in nanotechnology and to create self-assembling polymeric aggregates such as membranes of defined porosity, microcircuits and many other products.

  6. Electrical characterization of self-assembled monolayers

    NASA Astrophysics Data System (ADS)

    Wang, Wenyong

    Electrical characterization of alkanethiol self-assembled monolayers (SAMs) has been performed using a nanometer-scale device structure. Temperature-variable current-voltage measurement is carried out to distinguish between different conduction mechanisms and temperature-independent transport characteristics are observed, revealing that tunneling is the dominant conduction mechanism of alkanethiols. Electronic transport through alkanethiol SAMs is further investigated with the technique of inelastic electron tunneling spectroscopy (IETS). The obtained IETS spectra exhibit characteristic vibrational signatures of the alkane molecules that are used, presenting direct evidence of the presence of molecular species in the device structure. Further investigation on the modulation broadening and thermal broadening of the spectral peaks yield intrinsic linewidths of different vibrational modes, which may give insight into molecular conformation and may prove to be a powerful tool in future molecular transport characterization.

  7. Self Assembly and Elasticity of Nuclear Pasta

    NASA Astrophysics Data System (ADS)

    Caplan, Matthew; Horowitz, Chuck; Berry, Don; da Silva Schneider, Andre

    2015-10-01

    While the outer crust of a neutron star is likely a solid ion lattice, the core consists of uniform nuclear matter at or above saturation density. In between, nuclei adopt exotic non-spherical geometries called ``nuclear pasta'' in order to minimize the nuclear attraction and Coulomb repulsion between protons. These structures have been well studied with both classical and quantum molecular dynamics, and their geometry can be predicted from the density, temperature, and proton fraction. Recent classical molecular dynamics simulations find evidence for a phase transition at T ~ 0 . 5 MeV, where simulations with low proton fractions undergo a solid-liquid phase transition, while simulations with high proton fractions under a glass-rubber phase transition. This is expected to have nontrivial consequences for the elastic properties of the pasta. Additionally, recent observations indicate that the structure of nuclear pasta may be related to structures observed in biophysics, specifically self assembling lipid membranes.

  8. Controlling water evaporation through self-assembly

    PubMed Central

    Roger, Kevin; Liebi, Marianne; Heimdal, Jimmy; Pham, Quoc Dat; Sparr, Emma

    2016-01-01

    Water evaporation concerns all land-living organisms, as ambient air is dryer than their corresponding equilibrium humidity. Contrarily to plants, mammals are covered with a skin that not only hinders evaporation but also maintains its rate at a nearly constant value, independently of air humidity. Here, we show that simple amphiphiles/water systems reproduce this behavior, which suggests a common underlying mechanism originating from responding self-assembly structures. The composition and structure gradients arising from the evaporation process were characterized using optical microscopy, infrared microscopy, and small-angle X-ray scattering. We observed a thin and dry outer phase that responds to changes in air humidity by increasing its thickness as the air becomes dryer, which decreases its permeability to water, thus counterbalancing the increase in the evaporation driving force. This thin and dry outer phase therefore shields the systems from humidity variations. Such a feedback loop achieves a homeostatic regulation of water evaporation. PMID:27573848

  9. Controlling water evaporation through self-assembly.

    PubMed

    Roger, Kevin; Liebi, Marianne; Heimdal, Jimmy; Pham, Quoc Dat; Sparr, Emma

    2016-09-13

    Water evaporation concerns all land-living organisms, as ambient air is dryer than their corresponding equilibrium humidity. Contrarily to plants, mammals are covered with a skin that not only hinders evaporation but also maintains its rate at a nearly constant value, independently of air humidity. Here, we show that simple amphiphiles/water systems reproduce this behavior, which suggests a common underlying mechanism originating from responding self-assembly structures. The composition and structure gradients arising from the evaporation process were characterized using optical microscopy, infrared microscopy, and small-angle X-ray scattering. We observed a thin and dry outer phase that responds to changes in air humidity by increasing its thickness as the air becomes dryer, which decreases its permeability to water, thus counterbalancing the increase in the evaporation driving force. This thin and dry outer phase therefore shields the systems from humidity variations. Such a feedback loop achieves a homeostatic regulation of water evaporation.

  10. Supramolecular self-assemblies as functional nanomaterials

    NASA Astrophysics Data System (ADS)

    Busseron, Eric; Ruff, Yves; Moulin, Emilie; Giuseppone, Nicolas

    2013-07-01

    In this review, we survey the diversity of structures and functions which are encountered in advanced self-assembled nanomaterials. We highlight their flourishing implementations in three active domains of applications: biomedical sciences, information technologies, and environmental sciences. Our main objective is to provide the reader with a concise and straightforward entry to this broad field by selecting the most recent and important research articles, supported by some more comprehensive reviews to introduce each topic. Overall, this compilation illustrates how, based on the rules of supramolecular chemistry, the bottom-up approach to design functional objects at the nanoscale is currently producing highly sophisticated materials oriented towards a growing number of applications with high societal impact.

  11. Pseudotannins self-assembled into antioxidant complexes.

    PubMed

    Cheng, H A; Drinnan, C T; Pleshko, N; Fisher, O Z

    2015-10-21

    Natural tannins are attractive as building blocks for biomaterials due to their antioxidant properties and ability to form interpolymer complexes (IPCs) with other macromolecules. One of the major challenges to tannin usage in biomedical applications is their instability at physiological conditions and a lack of control over the purity and reactivity. Herein, we report the synthesis and characterization of tannin-like polymers with controlled architecture, reactivity, and size. These pseudotannins were synthesized by substituting linear dextran chains with gallic, resorcylic, and protocatechuic pendant groups to mimic the structure of natural hydrolysable tannins. We demonstrate that these novel materials can self-assemble to form reductive and colloidally stable nanoscale and microscale particles. Specifically, the synthesis, turbidity, particle size, antioxidant power, and cell uptake of IPCs derived from pseudotannins and poly(ethylene glycol) was evaluated.

  12. Pseudotannins Self-assembled into Antioxidant Complexes

    PubMed Central

    Cheng, H. A.; Drinnan, C. T.; Pleshko, N.; Fisher, O. Z.

    2015-01-01

    Natural tannins are attractive as building blocks for biomaterials due to their antioxidant properties and ability to form interpolymer complexes (IPCs) with other macromolecules. One of the major challenges to tannin usage in biomedical applications is their instability at physiological conditions and a lack of control over the purity and reactivity. Herein, we report the synthesis and characterization of tannin-like polymers with controlled architecture, reactivity, and size. These pseudotannins were synthesized by substituting linear dextran chains with gallic, resorcylic, and protocatechuic pendant groups to mimic the structure of natural hydrolysable tannins. We demonstrate that these novel materials can self-assemble to form reductive and colloidally stable nanoscale and microscale particles. Specifically, the synthesis, turbidity, particle size, antioxidant power, and cell uptake of IPCs derived from pseudotannins and poly(ethylene glycol) was evaluated. PMID:26313262

  13. Self-assembled magnetic surface swimmers.

    SciTech Connect

    Snezhko, A.; Belkin, M.; Aranson, I. S.; Kwok, W.-K.; Materials Science Division; Illinois Inst. of Tech.

    2009-03-20

    We report studies of novel self-assembled magnetic surface swimmers (magnetic snakes) formed from a dispersion of magnetic microparticles at a liquid-air interface and energized by an alternating magnetic field. We show that under certain conditions the snakes spontaneously break the symmetry of surface flows and turn into self-propelled objects. Parameters of the driving magnetic field tune the propulsion velocity of these snakelike swimmers. We find that the symmetry of the surface flows can also be broken in a controlled fashion by attaching a large bead to a magnetic snake (bead-snake hybrid), transforming it into a self-locomoting entity. The observed phenomena have been successfully described by a phenomenological model based on the amplitude equation for surface waves coupled to a large-scale hydrodynamic mean flow equation.

  14. Self-assembling multimeric nucleic acid constructs

    DOEpatents

    Cantor, C.R.; Niemeyer, C.M.; Smith, C.L.; Sano, Takeshi; Hnatowich, D.J.; Rusckowski, M.

    1996-10-01

    The invention is directed to constructs and compositions containing multimeric forms of nucleic acid. Multimeric nucleic acids comprise single-stranded nucleic acids attached via biotin to streptavidin and bound with a functional group. These constructs can be utilized in vivo to treat or identify diseased tissue or cells. Repeated administrations of multimeric nucleic acid compositions produce a rapid and specific amplification of nucleic acid constructs and their attached functional groups. For treatment purposes, functional groups may be toxins, radioisotopes, genes or enzymes. Diagnostically, labeled multimeric constructs may be used to identify specific targets in vivo or in vitro. Multimeric nucleic acids may also be used in nanotechnology and to create self-assembling polymeric aggregates such as membranes of defined porosity, microcircuits and many other products. 5 figs.

  15. Self-Assembled Magnetic Surface Swimmers

    NASA Astrophysics Data System (ADS)

    Snezhko, A.; Belkin, M.; Aranson, I. S.; Kwok, W.-K.

    2009-03-01

    We report studies of novel self-assembled magnetic surface swimmers (magnetic snakes) formed from a dispersion of magnetic microparticles at a liquid-air interface and energized by an alternating magnetic field. We show that under certain conditions the snakes spontaneously break the symmetry of surface flows and turn into self-propelled objects. Parameters of the driving magnetic field tune the propulsion velocity of these snakelike swimmers. We find that the symmetry of the surface flows can also be broken in a controlled fashion by attaching a large bead to a magnetic snake (bead-snake hybrid), transforming it into a self-locomoting entity. The observed phenomena have been successfully described by a phenomenological model based on the amplitude equation for surface waves coupled to a large-scale hydrodynamic mean flow equation.

  16. Electrodynamic tailoring of self-assembled three-dimensional electrospun constructs

    NASA Astrophysics Data System (ADS)

    Reis, Tiago C.; Correia, Ilídio J.; Aguiar-Ricardo, Ana

    2013-07-01

    The rational design of three-dimensional electrospun constructs (3DECs) can lead to striking topographies and tailored shapes of electrospun materials. This new generation of materials is suppressing some of the current limitations of the usual 2D non-woven electrospun fiber mats, such as small pore sizes or only flat shaped constructs. Herein, we pursued an explanation for the self-assembly of 3DECs based on electrodynamic simulations and experimental validation. We concluded that the self-assembly process is driven by the establishment of attractive electrostatic forces between the positively charged aerial fibers and the already collected ones, which tend to acquire a negatively charged network oriented towards the nozzle. The in situ polarization degree is strengthened by higher amounts of clustered fibers, and therefore the initial high density fibrous regions are the preliminary motifs for the self-assembly mechanism. As such regions increase their in situ polarization electrostatic repulsive forces will appear, favoring a competitive growth of these self-assembled fibrous clusters. Highly polarized regions will evidence higher distances between consecutive micro-assembled fibers (MAFs). Different processing parameters - deposition time, electric field intensity, concentration of polymer solution, environmental temperature and relative humidity - were evaluated in an attempt to control material's design.The rational design of three-dimensional electrospun constructs (3DECs) can lead to striking topographies and tailored shapes of electrospun materials. This new generation of materials is suppressing some of the current limitations of the usual 2D non-woven electrospun fiber mats, such as small pore sizes or only flat shaped constructs. Herein, we pursued an explanation for the self-assembly of 3DECs based on electrodynamic simulations and experimental validation. We concluded that the self-assembly process is driven by the establishment of attractive

  17. Self assembly properties of primitive organic compounds

    NASA Technical Reports Server (NTRS)

    Deamer, D. W.

    1991-01-01

    A central event in the origin of life was the self-assembly of amphiphilic, lipid-like compounds into closed microenvironments. If a primitive macromolecular replicating system could be encapsulated within a vesicular membrane, the components of the system would share the same microenvironment, and the result would be a step toward true cellular function. The goal of our research has been to determine what amphiphilic molecules might plausibly have been available on the early Earth to participate in the formation of such boundary structures. To this end, we have investigated primitive organic mixtures present in carbonaceous meteorites such as the Murchison meteorite, which contains 1-2 percent of its mass in the form of organic carbon compounds. It is likely that such compounds contributed to the inventory of organic carbon on the prebiotic earth, and were available to participate in chemical evolution leading to the emergence of the first cellular life forms. We found that Murchison components extracted into non-polar solvent systems are surface active, a clear indication of amphiphilic character. One acidic fraction self-assembles into vesicular membranes that provide permeability barriers to polar solutes. Other evidence indicates that the membranes are bimolecular layers similar to those formed by contemporary membrane lipids. We conclude that bilayer membrane formation by primitive amphiphiles on the early Earth is feasible. However, only a minor fraction of acidic amphiphiles assembles into bilayers, and the resulting membranes require narrowly defined conditions of pH and ionic composition to be stable. It seems unlikely, therefore, that meteoritic infall was a direct source of membrane amphiphiles. Instead, the hydrocarbon components and their derivatives more probably would provide an organic stock available for chemical evolution. Our current research is directed at possible reactions which would generate substantial quantities of membranogenic

  18. Nanoparticle string formation on self-assembled copolymer films

    NASA Astrophysics Data System (ADS)

    Jenczyk, J.; Woźniak-Budych, M.; Jarek, M.; Grzeszkowiak, M.; Nowaczyk, G.; Jurga, S.

    2017-06-01

    Nanoparticles (NP) string formations on self-assembled copolymeric substrates has been observed. These ;thread of beads; like structures develop via simple colloidal droplet evaporation during meniscus rim withdrawal on polystyrene-block-poly(ethylene oxide) (PS-PEO) copolymer surfaces. It is shown that the process is triggered by the presence of the substrate impurities, which lead to NP aggregate formations serving as string initiation sites. The growth mechanism of these linear structures seems to be capillarity-driven. Moreover, there is an exceptional alignment coupling between NP strips and the block copolymer (BC) domains observed. BC directed NP assembly stems from a gold nanocrystal surface functionalization, which introduces selective affinity for one particular type of BC domain. The presented results reveal a potential fabrication method of NP wires characterized by remarkably low width and thickness comparable with the size of the individual constituent NP.

  19. Aerosol-based self-assembly of nanoparticles into solid or hollow mesospheres.

    PubMed

    Wu, Chunwei; Lee, Donggeun; Zachariah, Michael R

    2010-03-16

    The ability to manipulate miniature object assemblies with well-defined structures in a controllable manner is of both fundamental and applied interests. This article presents general strategies, with nanospheres as building blocks, to engineer mesoscopic spherical architectures via a process of evaporation-driven self-assembly in aerosol droplets. Uniform magnetite iron oxide (Fe(3)O(4), approximately 2.5 nm), silica (SiO(2), approximately 15 nm), and cupric oxide (CuO, approximately 6 nm) nanoparticles were employed for the structural architecture. The method enables microstructural control of the self-assembled mesospheres by tuning the competition between solvent evaporation and solute diffusion within an aerosol droplet. Furthermore, we have demonstrated it is technically feasible to assemble surface-dissimilar binary components, i.e., charge-stabilized hydrophilic SiO(2) and hydrophobic ligand-capped Fe(3)O(4) nanoparticles, into hierarchical composite structures, which could be extended for preparation of more hierarchically textured materials with desired functionalities.

  20. An insight into polymerization-induced self-assembly by dissipative particle dynamics simulation.

    PubMed

    Huang, Feng; Lv, Yisheng; Wang, Liquan; Xu, Pengxiang; Lin, Jiaping; Lin, Shaoliang

    2016-08-14

    Polymerization-induced self-assembly is a one-pot route to produce concentrated dispersions of block copolymer nano-objects. Herein, dissipative particle dynamics simulations with a reaction model were employed to investigate the behaviors of polymerization-induced self-assembly. The polymerization kinetics in the polymerization-induced self-assembly were analyzed by comparing with solution polymerization. It was found that the polymerization rate enhances in the initial stage and decreases in the later stage. In addition, the effects of polymerization rate, length of macromolecular initiators, and concentration on the aggregate morphologies and formation pathway were studied. The polymerization rate and the length of the macromolecular initiators are found to have a marked influence on the pathway of the aggregate formations and the final structures. Morphology diagrams were mapped correspondingly. A comparison between simulation results and experimental findings is also made and an agreement is shown. This work can enrich our knowledge about polymerization-induced self-assembly.

  1. Controlled self-assembly in homopolymer and diblock copolymer

    NASA Astrophysics Data System (ADS)

    Zhuang, Lei

    This thesis work studies the process, mechanism and control of self-assembly in homopolymers and diblock copolymers. These studies are aimed at finding novel patterning methods that can lead to low cost lithography technologies capable of creating micrometer to nanometer patterns over a large area. We first present a new phenomenon called Lithographically-Induced Self-Assembly (LISA) that can create ordered arrays of pillars in a homopolymer film with a mask placed close to its surface. We demonstrate that the shape, size and morphology of the ordered pillar arrays can be controlled with a patterned mask. A model is developed based on the instability in a fluidic film induced by the Coulomb force from charge accumulation in the polymer film and the mask. Experimental results are shown to support the model. We also investigate the behavior of defects that destroy the ordering of the LISA array and propose ways to prevent them. This self-assembly phenomenon is used as a patterning technique to define the active area of an organic light emitting diode (OLED). The device shows significantly improved lifetime due to the restriction of defect growth. Another patterning technology that is closely related to LISA, Lithographically-Induced Self-Construction (LISC), is also introduced. LISC can form mesas of polymer from the initial thin film and they inherit the shape and size of the mask patterns. A model based on the dynamics of LISA pillar formation and mass conservation is presented and provides a guideline for choosing LISC process parameters. In the final part of the thesis, we study a technique to control the orientation of diblock copolymer phase separation in a thin film by applying a pressure on the film through a flat mask. The result is a well-ordered grating pattern of the phase separation with a period of tens of nanometers. The effect of pressure and film thickness on the final pattern is investigated by experiments. We suggest that the increased ordering is

  2. Supramolecular chemistry: Unexplored territory for self-assembly

    NASA Astrophysics Data System (ADS)

    Beuerle, Florian

    2016-12-01

    Cage-like structures can self-assemble from suitable metal ions and organic linkers, but the size of the assemblies was limited. The surprise discovery of a new series of cages opens up fresh horizons for self-assembly. See Letter p.563

  3. Self-assembled Nanomaterials for Hybrid Electronic and Photonic Systems

    DTIC Science & Technology

    2015-05-15

    Self-assembled Nanomaterials for Hybrid Electronic and Photonic Systems This grant studied DNA nanostructures and their applications in a variety of...Number of Papers published in non peer-reviewed journals: Final Report: Self-assembled Nanomaterials for Hybrid Electronic and Photonic Systems Report

  4. Spatiotemporal Control of Supramolecular Self-Assembly and Function.

    PubMed

    Zhan, Jie; Cai, Yanbin; Ji, Shenglu; He, Shuangshuang; Cao, Yi; Ding, Dan; Wang, Ling; Yang, Zhimou

    2017-03-09

    The enzyme-triggered self-assembly of peptides has flourished in controlling the self-assembly kinetics and producing nanostructures that are typically inaccessible by conventional self-assembly pathways. However, the diffusion and nanoscale chemical gradient of self-assembling peptides generated by the enzyme also significantly affect the outcome of self-assembly, which has not been reported yet. In this work, we demonstrated for the first time a spatiotemporal control of enzyme-triggered peptide self-assembly. By simply adjusting the temperature, we could change both the catalytic activity of the enzyme of phosphatase and their aggregation states. The strategy kinetically controls the production rate of self-assembling peptides and spatially controls their distribution in the system, leading to the formation of nanoparticles at 37 °C and nanofibers at 4 °C. The nanofibers showed ∼10 times higher cellular uptake by 3T3 cells than the nanoparticles, thanks to their higher stability and more ordered structures. Using such spatiotemporal control, we could prepare optimized nanoprobes with low background fluorescence, rapid and high cellular uptake, and high sensitivity. We postulate that this strategy would be very useful in general for preparing self-assembled nanomaterials with controllable morphology and function.

  5. Self-Assembly of Optical Molecules with Supramolecular Concepts

    PubMed Central

    Okamoto, Ken; Chithra, Parayalil; Richards, Gary J.; Hill, Jonathan P.; Ariga, Katsuhiko

    2009-01-01

    Fabrication of nano-sized objects is one of the most important issues in nanoscience and nanotechnology. Soft nanomaterials with flexible properties have been given much attention and can be obtained through bottom-up processing from functional molecules, where self-assembly based on supramolecular chemistry and designed assembly have become crucial processes and techniques. Among the various functional molecules, dyes have become important materials in certain areas of nanotechnology and their self-assembling behaviors have been actively researched. In this short review, we briefly introduce recent progress in self-assembly of optical molecules and dyes, based mainly on supramolecular concepts. The introduced examples are classified into four categories: self-assembly of (i) low-molecular-weight dyes and (ii) polymeric dyes and dye self-assembly (iii) in nanoscale architectures and (iv) at surfaces. PMID:19564931

  6. Challenges and breakthroughs in recent research on self-assembly

    PubMed Central

    Ariga, Katsuhiko; Hill, Jonathan P; Lee, Michael V; Vinu, Ajayan; Charvet, Richard; Acharya, Somobrata

    2008-01-01

    The controlled fabrication of nanometer-scale objects is without doubt one of the central issues in current science and technology. However, existing fabrication techniques suffer from several disadvantages including size-restrictions and a general paucity of applicable materials. Because of this, the development of alternative approaches based on supramolecular self-assembly processes is anticipated as a breakthrough methodology. This review article aims to comprehensively summarize the salient aspects of self-assembly through the introduction of the recent challenges and breakthroughs in three categories: (i) types of self-assembly in bulk media; (ii) types of components for self-assembly in bulk media; and (iii) self-assembly at interfaces. PMID:27877935

  7. Osteogenic potential of BMP-2-releasing self-assembled membranes.

    PubMed

    Chung, Eun Ji; Chien, Karen B; Aguado, Brian A; Shah, Ramille N

    2013-12-01

    We report here the use of novel self-assembling collagen-hyaluronic acid (HyA) membranes to deliver bone morphogenetic protein-2 (BMP-2) for orthopedic applications. Prior work has demonstrated that collagen-HyA membranes are formed initially through electrostatic interactions between the oppositely charged collagen and HyA molecules, and that membrane growth is driven by osmotic pressure imbalances between the collagen and HyA solutions. The purpose of this study was to investigate the potential of incorporating charged growth factors such as BMP-2 within the membrane for regenerative medicine applications. Membrane material properties, protein mass loss, and release kinetics of BMP-2, as well as biocompatibility and osteogenic potential in vitro and in vivo using a subcutaneous mouse model were assessed. Scanning electron microscopy and mechanical testing confirmed no loss of structural or mechanical integrity upon BMP-2 incorporation into the membranes. Slow and steady release of the growth factor was demonstrated with 17% of total loaded BMP-2 released over the course of 49 days. To test biocompatibility and osteogenic potential in vitro, human mesenchymal stem cells were cultured on collagen-HyA membranes and showed greater proliferation rates (for up to 28 days) on membranes without BMP-2, but a greater alkaline phosphatase activity and osteocalcin production on membranes releasing BMP-2. In vivo subcutaneous implantation of the membranes showed a minimal immune response with osteoblasts and mineral deposits present in the ectopic site for BMP-2-releasing membranes, further demonstrating the potential of the BMP-2-releasing membranes to induce osteogenic differentiation. This study presents a novel strategy to create self-assembled membranes using two biocompatible molecules that can deliver bioactive agents in a sustained manner to induce a local regenerative response.

  8. RNA self-assembly and RNA nanotechnology.

    PubMed

    Grabow, Wade W; Jaeger, Luc

    2014-06-17

    CONSPECTUS: Nanotechnology's central goal involves the direct control of matter at the molecular nanometer scale to build nanofactories, nanomachines, and other devices for potential applications including electronics, alternative fuels, and medicine. In this regard, the nascent use of nucleic acids as a material to coordinate the precise arrangements of specific molecules marked an important milestone in the relatively recent history of nanotechnology. While DNA served as the pioneer building material in nucleic acid nanotechnology, RNA continues to emerge as viable alternative material with its own distinct advantages for nanoconstruction. Several complementary assembly strategies have been used to build a diverse set of RNA nanostructures having unique structural attributes and the ability to self-assemble in a highly programmable and controlled manner. Of the different strategies, the architectonics approach uniquely endeavors to understand integrated structural RNA architectures through the arrangement of their characteristic structural building blocks. Viewed through this lens, it becomes apparent that nature routinely uses thermodynamically stable, recurrent modular motifs from natural RNA molecules to generate unique and more complex programmable structures. With the design principles found in natural structures, a number of synthetic RNAs have been constructed. The synthetic nanostructures constructed to date have provided, in addition to affording essential insights into RNA design, important platforms to characterize and validate the structural self-folding and assembly properties of RNA modules or building blocks. Furthermore, RNA nanoparticles have shown great promise for applications in nanomedicine and RNA-based therapeutics. Nevertheless, the synthetic RNA architectures achieved thus far consist largely of static, rigid particles that are still far from matching the structural and functional complexity of natural responsive structural elements such

  9. Solvent mediated self-assembly of solids

    SciTech Connect

    De Yoreo, J.; Wilson, W.D.; Palmore, T.

    1997-12-12

    Solvent-mediated crystallization represents a robust approach to self-assembly of nanostructures and microstructures. In organic systems, the relative ease with which the structure of hydrogen- bonded molecules can be manipulated allows for generation of a wide variety of nanoscale crystal structures. In living organisms, control over the micron-to-millimeter form of inorganic crystals is achieved through introduction of bio-organic molecules. The purpose of this proposal is to understand the interplay between solution chemistry, molecular structure, surface chemistry, and the processes of nucleation and crystal growth in solvent-mediated systems, with the goal of developing the atomic and molecular basis of a solvent-mediated self-assembly technology. We will achieve this purpose by: (1) utilizing an atomic force microscopy (AFM) approach that provides in situ, real time imaging during growth from solutions, (2) by modifying kinetic Monte Carlo (KMC) models to include solution-surface kinetics, (3) by introducing quantum chemistry (QC) calculations of the potentials of the relevant chemical species and the near-surface structure of the solution, and (4) by utilizing molecular dynamics (MD) simulations to identify the minimum energy pathways to the solid state. Our work will focus on two systems chosen to address both the manometer and micron-to-millimeter length scales of assembly, the family of 2,5- diketopiperazines (X-DKPs) and the system of CaCO{sub 3} with amino acids. Using AFM, we will record the evolution of surface morphology, critical lengths, step speeds, and step-step interactions as a function of supersaturation and temperature. In the case of the X-DKPs, these measurements will be repeated as the molecular structure of the growth unit is varied. In the case of CaCO{sub 3}, they will be performed as a function of solution chemistry including pH, ionic strength, and amino acid content. In addition, we will measure nucleation rates and orientations of

  10. Hierarchical and helical self-assembly of ADP-ribosyl cyclase into large-scale protein microtubes.

    PubMed

    Liu, Qun; Kriksunov, Irina A; Wang, Zhongwu; Graeff, Richard; Lee, Hon Cheung; Hao, Quan

    2008-11-27

    Proteins are macromolecules with characteristic structures and biological functions. It is extremely challenging to obtain protein microtube structures through self-assembly as proteins are very complex and flexible. Here we present a strategy showing how a specific protein, ADP-ribosyl cyclase, helically self-assembles from monomers into hexagonal nanochains and further to highly ordered crystalline microtubes. The structures of protein nanochains and consequently self-assembled superlattice were determined by X-ray crystallography at 4.5 A resolution and imaged by scanning electron microscopy. The protein initially forms into dimers that have a fixed size of 5.6 nm, and then, helically self-assembles into 35.6 nm long hexagonal nanochains. One such nanochain consists of six dimers (12 monomers) that stack in order by a pseudo P6(1) screw axis. Seven nanochains produce a series of large-scale assemblies, nanorods, forming the building blocks for microrods. A proposed aging process of microrods results in the formation of hollow microstructures. Synthesis and characterization of large scale self-assembled protein microtubes may pave a new pathway, capable of not only understanding the self-assembly dynamics of biological materials, but also directing design and fabrication of multifunctional nanobuilding blocks with particular applications in biomedical engineering.

  11. Large-scale self-assembly of uniform submicron silver sulfide material driven by precise pressure control

    NASA Astrophysics Data System (ADS)

    Qi, Juanjuan; Chen, Ke; Zhang, Shuhao; Yang, Yun; Guo, Lin; Yang, Shihe

    2017-03-01

    The controllable self-assembly of nanosized building blocks into larger specific structures can provide an efficient method of synthesizing novel materials with excellent properties. The self-assembly of nanocrystals by assisted means is becoming an extremely active area of research, because it provides a method of producing large-scale advanced functional materials with potential applications in the areas of energy, electronics, optics, and biologics. In this study, we applied an efficient strategy, namely, the use of ‘pressure control’ to the assembly of silver sulfide (Ag2S) nanospheres with a diameter of approximately 33 nm into large-scale, uniform Ag2S sub-microspheres with a size of about 0.33 μm. More importantly, this strategy realizes the online control of the overall reaction system, including the pressure, reaction time, and temperature, and could also be used to easily fabricate other functional materials on an industrial scale. Moreover, the thermodynamics and kinetics parameters for the thermal decomposition of silver diethyldithiocarbamate (Ag(DDTC)) are also investigated to explore the formation mechanism of the Ag2S nanosized building blocks which can be assembled into uniform sub-micron scale architecture. As a method of producing sub-micron Ag2S particles by means of the pressure-controlled self-assembly of nanoparticles, we foresee this strategy being an efficient and universally applicable option for constructing other new building blocks and assembling novel and large functional micromaterials on an industrial scale.

  12. 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

  13. Large-scale self-assembly of uniform submicron silver sulfide material driven by precise pressure control.

    PubMed

    Qi, Juanjuan; Chen, Ke; Zhang, Shuhao; Yang, Yun; Guo, Lin; Yang, Shihe

    2017-03-10

    The controllable self-assembly of nanosized building blocks into larger specific structures can provide an efficient method of synthesizing novel materials with excellent properties. The self-assembly of nanocrystals by assisted means is becoming an extremely active area of research, because it provides a method of producing large-scale advanced functional materials with potential applications in the areas of energy, electronics, optics, and biologics. In this study, we applied an efficient strategy, namely, the use of 'pressure control' to the assembly of silver sulfide (Ag2S) nanospheres  with a diameter of approximately 33 nm into large-scale, uniform Ag2S sub-microspheres with a size of about 0.33 μm. More importantly, this strategy realizes the online control of the overall reaction system, including the pressure, reaction time, and temperature, and could also be used to easily fabricate other functional materials on an industrial scale. Moreover, the thermodynamics and kinetics parameters for the thermal decomposition of silver diethyldithiocarbamate (Ag(DDTC)) are also investigated to explore the formation mechanism of the Ag2S nanosized building blocks which can be assembled into uniform sub-micron scale architecture. As a method of producing sub-micron Ag2S particles by means of the pressure-controlled self-assembly of nanoparticles, we foresee this strategy being an efficient and universally applicable option for constructing other new building blocks and assembling novel and large functional micromaterials on an industrial scale.

  14. 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

  15. Self-assembly models for lipid mixtures

    NASA Astrophysics Data System (ADS)

    Singh, Divya; Porcar, Lionel; Butler, Paul; Perez-Salas, Ursula

    2006-03-01

    Solutions of mixed long and short (detergent-like) phospholipids referred to as ``bicelle'' mixtures in the literature, are known to form a variety of different morphologies based on their total lipid composition and temperature in a complex phase diagram. Some of these morphologies have been found to orient in a magnetic field, and consequently bicelle mixtures are widely used to study the structure of soluble as well as membrane embedded proteins using NMR. In this work, we report on the low temperature phase of the DMPC and DHPC bicelle mixture, where there is agreement on the discoid structures but where molecular packing models are still being contested. The most widely accepted packing arrangement, first proposed by Vold and Prosser had the lipids completely segregated in the disk: DHPC in the rim and DMPC in the disk. Using data from small angle neutron scattering (SANS) experiments, we show how radius of the planar domain of the disks is governed by the effective molar ratio qeff of lipids in aggregate and not the molar ratio q (q = [DMPC]/[DHPC] ) as has been understood previously. We propose a new quantitative (packing) model and show that in this self assembly scheme, qeff is the real determinant of disk sizes. Based on qeff , a master equation can then scale the radii of disks from mixtures with varying q and total lipid concentration.

  16. Self-assembled biomimetic superhydrophobic hierarchical arrays.

    PubMed

    Yang, Hongta; Dou, Xuan; Fang, Yin; Jiang, Peng

    2013-09-01

    Here, we report a simple and inexpensive bottom-up technology for fabricating superhydrophobic coatings with hierarchical micro-/nano-structures, which are inspired by the binary periodic structure found on the superhydrophobic compound eyes of some insects (e.g., mosquitoes and moths). Binary colloidal arrays consisting of exemplary large (4 and 30 μm) and small (300 nm) silica spheres are first assembled by a scalable Langmuir-Blodgett (LB) technology in a layer-by-layer manner. After surface modification with fluorosilanes, the self-assembled hierarchical particle arrays become superhydrophobic with an apparent water contact angle (CA) larger than 150°. The throughput of the resulting superhydrophobic coatings with hierarchical structures can be significantly improved by templating the binary periodic structures of the LB-assembled colloidal arrays into UV-curable fluoropolymers by a soft lithography approach. Superhydrophobic perfluoroether acrylate hierarchical arrays with large CAs and small CA hysteresis can be faithfully replicated onto various substrates. Both experiments and theoretical calculations based on the Cassie's dewetting model demonstrate the importance of the hierarchical structure in achieving the final superhydrophobic surface states. Copyright © 2013 Elsevier Inc. All rights reserved.

  17. Surfactant mediated polyelectrolyte self-assembly

    SciTech Connect

    Goswami, Monojoy; Borreguero Calvo, Jose M.; Pincus, Phillip A.; Sumpter, Bobby G.

    2015-11-25

    Self-assembly and dynamics of polyelectrolyte (PE) surfactant complex (PES) is investigated using molecular dynamics simulations. The complexation is systematically studied for five different PE backbone charge densities. At a fixed surfactant concentration the PES complexation exhibits pearl-necklace to agglomerated double spherical structures with a PE chain decorating the surfactant micelles. The counterions do not condense on the complex, but are released in the medium with a random distribution. The relaxation dynamics for three different length scales, polymer chain, segmental and monomer, show distinct features of the charge and neutral species; the counterions are fastest followed by the PE chain and surfactants. The surfactant heads and tails have the slowest relaxation due to their restricted movement inside the agglomerated structure. At the shortest length scale, all the charge and neutral species show similar relaxation dynamics confirming Rouse behavior at monomer length scales. Overall, the present study highlights the structure-property relationship for polymer-surfactant complexation. These results will help improve the understanding of PES complex and should aid in the design of better materials for future applications.

  18. Self-Assembled Monolayers with Molecular Gradients

    NASA Astrophysics Data System (ADS)

    Schäferling, Michael; Riepl, Michael; Liedberg, Bo

    In recent years, biosensors and sensor arrays have developed into very important analytical tools, which found applications in many fields such as pharmaceutical (high-throughput) screening, medical diagnosis, or industrial process control. One of the major challenges for material research is the preparation of appropriate sensor surfaces, providing an interface with a high sensitivity and selectivity toward a given analyte. This chapter discusses some straightforward and flexible approaches to study structure and/or composition-function relationships and response characteristics of polymeric and molecular sensor materials. The controlled continuous deposition of self-assembled monolayers (SAMs), e.g. of substituted thiols or silanes, paves the way for the generation of molecular gradients on solid surfaces. These are useful for the preparation of interfaces with spatially controlled chemical composition and/ or physical properties. These tools can help to improve the selectivity and specificity of surfaces for biosensors and biochips. They can also be utilized for the study of fundamental protein adsorption and exchange phenomena.

  19. Surfactant mediated polyelectrolyte self-assembly

    DOE PAGES

    Goswami, Monojoy; Borreguero Calvo, Jose M.; Pincus, Phillip A.; ...

    2015-11-25

    Self-assembly and dynamics of polyelectrolyte (PE) surfactant complex (PES) is investigated using molecular dynamics simulations. The complexation is systematically studied for five different PE backbone charge densities. At a fixed surfactant concentration the PES complexation exhibits pearl-necklace to agglomerated double spherical structures with a PE chain decorating the surfactant micelles. The counterions do not condense on the complex, but are released in the medium with a random distribution. The relaxation dynamics for three different length scales, polymer chain, segmental and monomer, show distinct features of the charge and neutral species; the counterions are fastest followed by the PE chain andmore » surfactants. The surfactant heads and tails have the slowest relaxation due to their restricted movement inside the agglomerated structure. At the shortest length scale, all the charge and neutral species show similar relaxation dynamics confirming Rouse behavior at monomer length scales. Overall, the present study highlights the structure-property relationship for polymer-surfactant complexation. These results will help improve the understanding of PES complex and should aid in the design of better materials for future applications.« less

  20. Self-assembled nanostructures via electrospraying

    NASA Astrophysics Data System (ADS)

    Jayasinghe, S. N.

    2006-07-01

    A concentrated nanoparticulate-based ethylene glycol suspension was prepared and electrosprayed at optimum and stable cone-jet mode conditions. Using laser spectroscopy, the droplets were measured and found to range within ∼0.23-3.8 μm. In parallel to spectroscopy-assisted sizing, a volume equivalence route for estimating droplet sizes was carried out by measuring contact angles and diameters of the deposits. The electrosprayed nanosuspension relics were examined using optical and transmission electron microscopy. These deposits were further characterized using energy-dispersive X-rays and selected area electron diffraction. Simultaneously deposits were formed by a controlled route through needle deposition without the presence of an electric field. The structures formed in this non-electric field driven route are compared with those formed with electric fields. Thus, elucidating electrosprays as a competing nanofabrication route for forming self-assemblies with a wide range of nanomaterials in the nanoscale for top-down based bottom-up assembly of structures.

  1. Electronically Guided Self Assembly within Quantum Corrals

    NASA Astrophysics Data System (ADS)

    Cao, Rongxing; Miao, Bingfeng; Zhong, Zhangfeng; Sun, Liang; You, Biao; Zhang, Wei; Wu, Di; Hu, An; Bader, Samuel; Ding, Haifeng; Center Collaboration; Low Dimensional Magnetism Team

    2013-03-01

    A grand challenge of nanoscience is to master the control of structure and properties in order to go beyond present day functionality. The creation of nanostructures via atom manipulation by means of a scanning probe represents one of the great achievements of the nano era. Here we build on this achievement to self-assemble nanostructures within quantum corrals. We constructed circular and triangular Fe quantum corrals on Ag(111) substrate via STM manipulation and studied the quantum confinement of electronic states and the diffusion of Gd atoms inside the corrals. Statistical results reveal the motion of the Gd atoms forming several individual orbits that are closely related to the local density of states. We experimentally demonstrate that different self-organized Gd atomic structures are formed within 30-nm circular and triangular Fe quantum corrals with a step-by-step guiding process. The findings demonstrate that quantum confinement can be used to engineer atomic structures and atom diffusion. And 30-nm resolution can be reached by means of advanced lithography. Adding quantum engineering to augment it opens new possibilities for local functionality design down to the atomic scale. Work at Nanjing is supported by the State Key Program for Basic Research of China (Grant No. 2010CB923401), NSFC (Grants Nos. 10974087, 10834001, and 11023002) and PAPD.

  2. Dissipative adaptation in driven self-assembly.

    PubMed

    England, Jeremy L

    2015-11-01

    In a collection of assembling particles that is allowed to reach thermal equilibrium, the energy of a given microscopic arrangement and the probability of observing the system in that arrangement obey a simple exponential relationship known as the Boltzmann distribution. Once the same thermally fluctuating particles are driven away from equilibrium by forces that do work on the system over time, however, it becomes significantly more challenging to relate the likelihood of a given outcome to familiar thermodynamic quantities. Nonetheless, it has long been appreciated that developing a sound and general understanding of the thermodynamics of such non-equilibrium scenarios could ultimately enable us to control and imitate the marvellous successes that living things achieve in driven self-assembly. Here, I suggest that such a theoretical understanding may at last be emerging, and trace its development from historic first steps to more recent discoveries. Focusing on these newer results, I propose that they imply a general thermodynamic mechanism for self-organization via dissipation of absorbed work that may be applicable in a broad class of driven many-body systems.

  3. Self-assembly programming of DNA polyominoes.

    PubMed

    Ong, Hui San; Syafiq-Rahim, Mohd; Kasim, Noor Hayaty Abu; Firdaus-Raih, Mohd; Ramlan, Effirul Ikhwan

    2016-10-20

    Fabrication of functional DNA nanostructures operating at a cellular level has been accomplished through molecular programming techniques such as DNA origami and single-stranded tiles (SST). During implementation, restrictive and constraint dependent designs are enforced to ensure conformity is attainable. We propose a concept of DNA polyominoes that promotes flexibility in molecular programming. The fabrication of complex structures is achieved through self-assembly of distinct heterogeneous shapes (i.e., self-organised optimisation among competing DNA basic shapes) with total flexibility during the design and assembly phases. In this study, the plausibility of the approach is validated using the formation of multiple 3×4 DNA network fabricated from five basic DNA shapes with distinct configurations (monomino, tromino and tetrominoes). Computational tools to aid the design of compatible DNA shapes and the structure assembly assessment are presented. The formations of the desired structures were validated using Atomic Force Microscopy (AFM) imagery. Five 3×4 DNA networks were successfully constructed using combinatorics of these five distinct DNA heterogeneous shapes. Our findings revealed that the construction of DNA supra-structures could be achieved using a more natural-like orchestration as compared to the rigid and restrictive conventional approaches adopted previously. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Stochastic self-assembly of incommensurate clusters.

    PubMed

    D'Orsogna, M R; Lakatos, G; Chou, T

    2012-02-28

    Nucleation and molecular aggregation are important processes in numerous physical and biological systems. In many applications, these processes often take place in confined spaces, involving a finite number of particles. Analogous to treatments of stochastic chemical reactions, we examine the classic problem of homogeneous nucleation and self-assembly by deriving and analyzing a fully discrete stochastic master equation. We enumerate the highest probability steady states, and derive exact analytical formulae for quenched and equilibrium mean cluster size distributions. Upon comparison with results obtained from the associated mass-action Becker-Döring equations, we find striking differences between the two corresponding equilibrium mean cluster concentrations. These differences depend primarily on the divisibility of the total available mass by the maximum allowed cluster size, and the remainder. When such mass "incommensurability" arises, a single remainder particle can "emulsify" the system by significantly broadening the equilibrium mean cluster size distribution. This discreteness-induced broadening effect is periodic in the total mass of the system but arises even when the system size is asymptotically large, provided the ratio of the total mass to the maximum cluster size is finite. Ironically, classic mass-action equations are fairly accurate in the coarsening regime, before equilibrium is reached, despite the presence of large stochastic fluctuations found via kinetic Monte-Carlo simulations. Our findings define a new scaling regime in which results from classic mass-action theories are qualitatively inaccurate, even in the limit of large total system size.

  5. Self-Assembly of Tetraphenylalanine Peptides.

    PubMed

    Mayans, Enric; Ballano, Gema; Casanovas, Jordi; Díaz, Angélica; Pérez-Madrigal, Maria M; Estrany, Francesc; Puiggalí, Jordi; Cativiela, Carlos; Alemán, Carlos

    2015-11-16

    Three different tetraphenylalanine (FFFF) based peptides that differ at the N- and C-termini have been synthesized by using standard procedures to study their ability to form different nanoassemblies under a variety of conditions. The FFFF peptide assembles into nanotubes that show more structural imperfections at the surface than those formed by the diphenylalanine (FF) peptide under the same conditions. Periodic DFT calculations (M06L functional) were used to propose a model that consists of three FFFF molecules defining a ring through head-to-tail NH3(+)⋅⋅⋅(-)OOC interactions, which in turn stack to produce deformed channels with internal diameters between 12 and 16 Å. Depending on the experimental conditions used for the peptide incubation, N-fluorenylmethoxycarbonyl (Fmoc) protected FFFF self-assembles into a variety of polymorphs: ultra-thin nanoplates, fibrils, and star-like submicrometric aggregates. DFT calculations indicate that Fmoc-FFFF prefers a parallel rather than an antiparallel β-sheet assembly. Finally, coexisting multiple assemblies (up to three) were observed for Fmoc-FFFF-OBzl (OBzl = benzyl ester), which incorporates aromatic protecting groups at the two peptide terminals. This unusual and noticeable feature is attributed to the fact that the assemblies obtained by combining the Fmoc and OBzl groups contained in the peptide are isoenergetic. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. What promotes derected self assembly (DSA)?

    NASA Astrophysics Data System (ADS)

    Nakagawa, S. T.

    2016-09-01

    A low-energy electron beam (EB) can create self-interstitial atoms (SIA) in a solid and can cause directed self-assembly (DSA), e.g. {3 1 1}SIA platelets in c-Si. The crystalline structure of this planar defect is known from experiment to be made up of SIAs that form well aligned <1 1 0> atomic rows on each (3 1 1) plane. To simulate the experiment we distributed Frenkel pairs (FP) randomly in bulk c-Si. Then making use of a molecular dynamic (MD) simulation, we have reproduced the experimental result, where SIAs are trapped at metastable sites in bulk. With increasing pre-doped FP concentration, the number of SIAs that participate in DSA tends to be increased but soon slightly supressed. On the other hand, when the FP concentration is less than 3%, a cooperative motion of target atoms was characterized from the long-range-order (LRO) parameter. Here we investigated the correlation between DSA and that cooperative motion, by adding a case of intrinsic c-Si. We confirmed that the cooperative motion slightly promote DSA by assisting migration of SIAs toward metastable sites as long as the FP concentration is less than 3%, however, it is essentially independent of DSA.

  7. Electrostatic self-assembly of biomolecules

    NASA Astrophysics Data System (ADS)

    Olvera de La Cruz, Monica

    2015-03-01

    Charged filaments and membranes are natural structures abundant in cell media. In this talk we discuss the assembly of amphiphiles into biocompatible fibers, ribbons and membranes. We describe one- and two-dimensional assemblies that undergo re-entrant transitions in crystalline packing in response to changes in the solution pH and/or salt concentration resulting in different mesoscale morphologies and properties. In the case of one-dimensional structures, we discuss self-assembled amphiphiles into highly charged nanofibers in water that order into two-dimensional crystals. These fibers of about 6 nm cross-sectional diameter form crystalline arrays with inter-fiber spacings of up to 130 nm. Solution concentration and temperature can be adjusted to control the inter-fiber spacings. The addition of salt destroys crystal packing, indicating that electrostatic repulsions are necessary for the observed ordering. We describe the crystallization of bundles of filament networks interacting via long-range repulsions in confinement by a phenomenological model. Two distinct crystallization mechanisms in the short and large screening length regimes are discussed and the phase diagram is obtained. Simulation of large bundles predicts the existence of topological defects among bundled filaments. Crystallization processes driven by electrostatic attractions are also discussed. Funded by Center for Bio-Inspired Energy Science (CBES), which is an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0000989.

  8. Functional Self-Assembled Nanofibers by Electrospinning

    NASA Astrophysics Data System (ADS)

    Greiner, A.; Wendorff, J. H.

    Electrospinning constitutes a unique technique for the production of nanofibers with diameters down to the range of a few nanometers. In strong contrast to conventional fiber producing techniques, it relies on self-assembly processes driven by the Coulomb interactions between charged elements of the fluids to be spun to nanofibers. The transition from a macroscopic fluid object such as a droplet emerging from a die to solid nanofibers is controlled by a set of complex physical instability processes. They give rise to extremely high extensional deformations and strain rates during fiber formation causing among others a high orientational order in the nanofibers as well as enhanced mechanical properties. Electrospinning is predominantly applied to polymer based materials including natural and synthetic polymers, but, more recently, its use has been extended towards the production of metal, ceramic and glass nanofibers exploiting precursor routes. The nanofibers can be functionalized during electrospinning by introducing pores, fractal surfaces, by incorporating functional elements such as catalysts, quantum dots, drugs, enzymes or even bacteria. The production of individual fibers, random nonwovens, or orientationally highly ordered nonwovens is achieved by an appropriate selection of electrode configurations. Broad areas of application exist in Material and Life Sciences for such nanofibers, including not only optoelectronics, sensorics, catalysis, textiles, high efficiency filters, fiber reinforcement but also tissue engineering, drug delivery, and wound healing. The basic electrospinning process has more recently been extended towards compound co-electrospinning and precision deposition electrospinning to further broaden accessible fiber architectures and potential areas of application.

  9. Stochastic self-assembly of incommensurate clusters

    NASA Astrophysics Data System (ADS)

    DÓ Rsogna, Maria; Lakatos, Greg; Chou, Tom

    2013-03-01

    We examine the classic problem of homogeneous nucleation and self-assembly by deriving and analyzing a fully discrete stochastic master equation. We enumerate the highest probability steady-states, and derive exact analytical formulae for quenched and equilibrium mean cluster size distributions. Upon comparison with results obtained from the associated the mass-action Becker-Döring (BD) equations, we find striking differences between the two corresponding equilibrium mean cluster concentrations. These differences depend primarily on the divisibility of the total available mass by the maximum allowed cluster size, and the remainder. When such mass ``incommensurability'' arises, a single remainder particle can ``emulsify'' the system by significantly broadening the equilibrium mean cluster size distribution. This discreteness-induced broadening effect is periodic in the total mass of the system but arises even when the system size is asymptotically large, provided the ratio of the total mass to the maximum cluster size is finite. Our findings define a new scaling regime in which results from classic mass-action theories are qualitatively inaccurate, even in the limit of large total system size. This work supported by NSF DMS-1021818 and DMS-1021850

  10. Stochastic self-assembly of incommensurate clusters

    NASA Astrophysics Data System (ADS)

    D'Orsogna, M. R.; Lakatos, G.; Chou, T.

    2012-02-01

    Nucleation and molecular aggregation are important processes in numerous physical and biological systems. In many applications, these processes often take place in confined spaces, involving a finite number of particles. Analogous to treatments of stochastic chemical reactions, we examine the classic problem of homogeneous nucleation and self-assembly by deriving and analyzing a fully discrete stochastic master equation. We enumerate the highest probability steady states, and derive exact analytical formulae for quenched and equilibrium mean cluster size distributions. Upon comparison with results obtained from the associated mass-action Becker-Döring equations, we find striking differences between the two corresponding equilibrium mean cluster concentrations. These differences depend primarily on the divisibility of the total available mass by the maximum allowed cluster size, and the remainder. When such mass "incommensurability" arises, a single remainder particle can "emulsify" the system by significantly broadening the equilibrium mean cluster size distribution. This discreteness-induced broadening effect is periodic in the total mass of the system but arises even when the system size is asymptotically large, provided the ratio of the total mass to the maximum cluster size is finite. Ironically, classic mass-action equations are fairly accurate in the coarsening regime, before equilibrium is reached, despite the presence of large stochastic fluctuations found via kinetic Monte-Carlo simulations. Our findings define a new scaling regime in which results from classic mass-action theories are qualitatively inaccurate, even in the limit of large total system size.

  11. Self-assembly of smallest magnetic particles

    PubMed Central

    Mehdizadeh Taheri, Sara; Michaelis, Maria; Friedrich, Thomas; Förster, Beate; Drechsler, Markus; Römer, Florian M.; Bösecke, Peter; Narayanan, Theyencheri; Weber, Birgit; Rehberg, Ingo; Rosenfeldt, Sabine; Förster, Stephan

    2015-01-01

    The assembly of tiny magnetic particles in external magnetic fields is important for many applications ranging from data storage to medical technologies. The development of ever smaller magnetic structures is restricted by a size limit, where the particles are just barely magnetic. For such particles we report the discovery of a kind of solution assembly hitherto unobserved, to our knowledge. The fact that the assembly occurs in solution is very relevant for applications, where magnetic nanoparticles are either solution-processed or are used in liquid biological environments. Induced by an external magnetic field, nanocubes spontaneously assemble into 1D chains, 2D monolayer sheets, and large 3D cuboids with almost perfect internal ordering. The self-assembly of the nanocubes can be elucidated considering the dipole–dipole interaction of small superparamagnetic particles. Complex 3D geometrical arrangements of the nanodipoles are obtained under the assumption that the orientation of magnetization is freely adjustable within the superlattice and tends to minimize the binding energy. On that basis the magnetic moment of the cuboids can be explained. PMID:26554000

  12. Controlling Self-Assembly of Engineered Peptides on Graphite by Rational Mutation

    PubMed Central

    So, Christopher R.; Hayamizu, Yuhei; Yazici, Hilal; Gresswell, Carolyn; Khatayevich, Dmitriy; Tamerler, Candan; Sarikaya, Mehmet

    2012-01-01

    Self-assembly of proteins on surfaces is utilized in many fields to integrate intricate biological structures and diverse functions with engineered materials. Controlling proteins at bio-solid interfaces relies on establishing key correlations between their primary sequences and resulting spatial organizations on substrates. Protein self-assembly, however, remains an engineering challenge. As a novel approach, we demonstrate here that short dodecapeptides selected by phage display are capable of self-assembly on graphite and form long-range ordered biomolecular nanostructures. Using atomic force microscopy and contact angle studies, we identify three amino-acid domains along the primary sequence that steer peptide ordering and lead to nanostructures with uniformly displayed residues. The peptides are further engineered via simple mutations to control fundamental interfacial processes, including initial binding, surface aggregation and growth kinetics, and intermolecular interactions. Tailoring short peptides via their primary sequence offers versatile control over molecular self-assembly, resulting in well-defined surface properties essential in building engineered, chemically rich, bio-solid interfaces. PMID:22233341

  13. Facile preparation of luminescent and intelligent gold nanodots based on supramolecular self-assembly

    NASA Astrophysics Data System (ADS)

    Shi, Yunfeng; Li, Sujuan; Zhou, Yahui; Zhai, Qingpan; Hu, Mengyue; Cai, Fensha; Du, Jimin; Liang, Jiamiao; Zhu, Xinyuan

    2012-12-01

    A new strategy for preparing luminescent and intelligent gold nanodots based on supramolecular self-assembly is described in this paper. The supramolecular self-assembly was initiated through electrostatic interactions and ion pairing between palmitic acid and hyperbranched poly(ethylenimine). The resulting structures not only have the dynamic reversible properties of supramolecules but also possess torispherical and highly branched architectures. Thus they can be regarded as a new kind of ideal nanoreactor for preparing intelligent Au nanodots. By preparing Au nanodots within this kind of supramolecular self-assembly, the environmental sensitivity of intelligent polymers and the optical, electrical properties of Au nanodots can be combined, endowing the Au nanodots with intelligence. In this paper, a supramolecular self-assembly process based on dendritic poly(ethylenimine) and palmitic acid was designed and then applied to prepare fluorescent and size-controlled Au nanodots. The pH response of Au nanodots embodied by phase transfer from oil phase to water phase was also investigated.

  14. Aqueous Self-Assembly of Y-Shaped Amphiphilic Block Copolymers into Giant Vesicles.

    PubMed

    Li, Hanping; Jin, Yong; Fan, Baozhu; Lai, Shuangquan; Sun, Xiaopeng; Qi, Rui

    2017-02-06

    The preparation and aqueous self-assembly of newly Y-shaped amphiphilic block polyurethane (PUG) copolymers are reported here. These amphiphilic copolymers, designed to have two hydrophilic poly(ethylene oxide) (PEO) tails and one hydrophobic alkyl tail via a two-step coupling reaction, can self-assemble into giant unilamellar vesicles (GUVs) (diameter ≥ 1000 nm) with a direct dissolution method in aqueous solution, depending on their Y-shaped structures and initial concentrations. More interesting, the copolymers can self-assemble into various distinct nano-/microstructures, such as spherical micelles, small vesicles, and GUVs, with the increase of their concentrations. The traditional preparation methods of GUVs generally need conventional amphiphilic molecules and additional complicated conditions, such as alternating electrical field, buffer solution, or organic solvent. Therefore, the self-assembly of Y-shaped PUGs with a direct dissolution method in aqueous solution demonstrated in this study supplies a new clue to fabricate GUVs based on the geometric design of amphiphilic polymers.

  15. Enzyme-assisted self-assembly under thermodynamic control

    NASA Astrophysics Data System (ADS)

    Williams, Richard J.; Smith, Andrew M.; Collins, Richard; Hodson, Nigel; Das, Apurba K.; Ulijn, Rein V.

    2009-01-01

    The production of functional molecular architectures through self-assembly is commonplace in biology, but despite advances, it is still a major challenge to achieve similar complexity in the laboratory. Self-assembled structures that are reproducible and virtually defect free are of interest for applications in three-dimensional cell culture, templating, biosensing and supramolecular electronics. Here, we report the use of reversible enzyme-catalysed reactions to drive self-assembly. In this approach, the self-assembly of aromatic short peptide derivatives provides a driving force that enables a protease enzyme to produce building blocks in a reversible and spatially confined manner. We demonstrate that this system combines three features: (i) self-correction-fully reversible self-assembly under thermodynamic control; (ii) component-selection-the ability to amplify the most stable molecular self-assembly structures in dynamic combinatorial libraries; and (iii) spatiotemporal confinement of nucleation and structure growth. Enzyme-assisted self-assembly therefore provides control in bottom-up fabrication of nanomaterials that could ultimately lead to functional nanostructures with enhanced complexities and fewer defects.

  16. Self-assembled single-crystal silicon circuits on plastic.

    PubMed

    Stauth, Sean A; Parviz, Babak A

    2006-09-19

    We demonstrate the use of self-assembly for the integration of freestanding micrometer-scale components, including single-crystal, silicon field-effect transistors (FETs) and diffusion resistors, onto flexible plastic substrates. Preferential self-assembly of multiple microcomponent types onto a common platform is achieved through complementary shape recognition and aided by capillary, fluidic, and gravitational forces. We outline a microfabrication process that yields single-crystal, silicon FETs in a freestanding, powder-like collection for use with self-assembly. Demonstrations of self-assembled FETs on plastic include logic inverters and measured electron mobility of 592 cm2/V-s. Finally, we extend the self-assembly process to substrates each containing 10,000 binding sites and realize 97% self-assembly yield within 25 min for 100-microm-sized elements. High-yield self-assembly of micrometer-scale functional devices as outlined here provides a powerful approach for production of macroelectronic systems.

  17. Self-Assembly and Crystallization of Conjugated Block Copolymers

    NASA Astrophysics Data System (ADS)

    Davidson, Emily Catherine

    melting regimes are identified. A structural model of the conjugated block melting process is proposed, consisting of (I) excluded-chain relaxation followed by (II) chain inter-digitation during melt-recrystallization, and finally (III) complete melting independent of the initial crystallization conditions. These detailed studies of the impact of processing conditions suggest that crystallization processes coupled to temperature-dependent diffusion and nucleation are critical for determining the final crystalline state in confinement. They also suggest that, surprisingly, improvement in conjugated polymer crystallinity may correspond to a more compact structure along the chain dimension. Throughout this dissertation, we consider how key parameters governing structure formation impact self-assembly and crystallization. In particular, we consider the driving forces for crystallization versus microphase separation, the impact of conformational asymmetry, the drive for extended chain crystallites, and finally the role of detailed crystallization processes. The findings presented here demonstrate the biases introduced by conjugated polymers for the self-assembly and crystallization of such systems, and suggest design rules for the targeted creation of block copolymers containing high-performing conjugated polymers. (Abstract shortened by ProQuest.).

  18. The structure evolution of colloidal aggregates composed of monodisperse silica nanospheres.

    PubMed

    Sun, Wei; Chen, Sheng-Li; Zhu, Huili; Xu, Mingri; Wang, Aijun

    2017-09-15

    In this work, colloidal aggregates, such as higher-order clusters with polyhedral geometry, supraparticles with intermediate packing ordering, different inner structured supraballs with face-centered cubic ordering were produced through self-assembly of different quantities of monodisperse silica nanospheres in water-in-oil emulsion droplets which were formed by ultrasonic dispersion of silica nanospheres suspension into different solvents. The structure evolution of colloidal aggregates as a function of the number of constituent silica nanospheres was studied in this article. It was found that the inner structures of colloidal aggregates would be changed with increasing of the number of constituent silica nanospheres in different solvents. In the case of n-octanol being as solvent, the supraparticles were the transition structure for higher-order clusters into supraballs with hollow structure, while in silicone oil, the supraparticles were the transition structure for higher-order clusters into solid structured supraballs. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. One-step synthesis of monodisperse AuNPs@PANI composite nanospheres as recyclable catalysts for 4-nitrophenol reduction

    NASA Astrophysics Data System (ADS)

    Li, Runming; Li, Zhiyuan; Wu, Qiang; Li, Dongfeng; Shi, Jiahua; Chen, Yuewen; Yu, Shuling; Ding, Tao; Qiao, Congzhen

    2016-06-01

    Oxidative polymerization of aniline was carried out in ethanol using chloroauric acid (HAuCl4) as the oxidant. Simultaneous reduction of HAuCl4 and formation of gold nanoparticles (AuNPs) and polyaniline (PANI) composite nanospheres (AuNPs@PANI nanospheres) were achieved without using any templates or structure-directing agents. The composite nanospheres are uniformly distributed with an average diameter of about 400 nm, in which the ultrafine AuNPs with size of about 2-4 nm were evenly embedded in the PANI matrix which acted as the dispersing agent and stabilizer of AuNPs. In addition, the catalytic performance of these composite nanospheres towards the reduction of 4-nitrophenol in the presence of NaBH4 was studied. Furthermore, the possible formation mechanism and catalytic mechanism of the self-assembled AuNPs@PANI nanospheres were also discussed.

  20. 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.

  1. Functional self-assembled lipidic systems derived from renewable resources.

    PubMed

    Silverman, Julian R; Samateh, Malick; John, George

    2016-01-01

    Self-assembled lipidic amphiphile systems can create a variety of multi-functional soft materials with value-added properties. When employing natural reagents and following biocatalytic syntheses, self-assembling monomers may be inherently designed for degradation, making them potential alternatives to conventional and persistent polymers. By using non-covalent forces, self-assembled amphiphiles can form nanotubes, fibers, and other stimuli responsive architectures prime for further applied research and incorporation into commercial products. By viewing these lipid derivatives under a lens of green principles, there is the hope that in developing a structure-function relationship and functional smart materials that research may remain safe, economic, and efficient.

  2. Magnetic manipulation of self-assembled colloidal asters.

    SciTech Connect

    Snezhko, A.; Aranson, I. S.

    2011-09-01

    Self-assembled materials must actively consume energy and remain out of equilibrium to support structural complexity and functional diversity. Here we show that a magnetic colloidal suspension confined at the interface between two immiscible liquids and energized by an alternating magnetic field dynamically self-assembles into localized asters and arrays of asters, which exhibit locomotion and shape change. By controlling a small external magnetic field applied parallel to the interface, we show that asters can capture, transport, and position target microparticles. The ability to manipulate colloidal structures is crucial for the further development of self-assembled microrobots

  3. Magnetic manipulation of self-assembled colloidal asters

    NASA Astrophysics Data System (ADS)

    Snezhko, Alexey; Aranson, Igor S.

    2011-09-01

    Self-assembled materials must actively consume energy and remain out of equilibrium to support structural complexity and functional diversity. Here we show that a magnetic colloidal suspension confined at the interface between two immiscible liquids and energized by an alternating magnetic field dynamically self-assembles into localized asters and arrays of asters, which exhibit locomotion and shape change. By controlling a small external magnetic field applied parallel to the interface, we show that asters can capture, transport, and position target microparticles. The ability to manipulate colloidal structures is crucial for the further development of self-assembled microrobots.

  4. 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.

  5. Magnetic manipulation of self-assembled colloidal asters.

    PubMed

    Snezhko, Alexey; Aranson, Igor S

    2011-08-07

    Self-assembled materials must actively consume energy and remain out of equilibrium to support structural complexity and functional diversity. Here we show that a magnetic colloidal suspension confined at the interface between two immiscible liquids and energized by an alternating magnetic field dynamically self-assembles into localized asters and arrays of asters, which exhibit locomotion and shape change. By controlling a small external magnetic field applied parallel to the interface, we show that asters can capture, transport, and position target microparticles. The ability to manipulate colloidal structures is crucial for the further development of self-assembled microrobots.

  6. Dynamic self-assembly of 'living' polymeric chains

    NASA Astrophysics Data System (ADS)

    Deng, Binghui; Shi, Yunfeng

    2017-01-01

    We report a dynamic self-assembly system of 'living' polymeric chains sustained by chemistry using reactive molecular dynamics simulations. The linear polymeric chains consist of self-assembled nanoparticles connected by metastable linker molecules. As such, the polymeric chains, once assembled, undergo spontaneous dissociation driven by thermodynamics. However, with a continuous supply of linker molecules and the stored chemical energy therein, the polymeric chains can survive and maintain a steady state averaged chain length. These dynamically self-assembled polymeric chains are analogous to biological systems that both are thermodynamically metastable, yet dynamically stable upon continuous influx of matter and energy.

  7. Self-assembly in block polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Yang, Shuang; Vishnyakov, Aleksey; Neimark, Alexander V.

    2011-02-01

    The self-consistent field theory (SCFT) complemented with the Poisson-Boltzmann equation is employed to explore self-assembly of polyelectrolyte copolymers composed of charged blocks A and neutral blocks B. We have extended SCFT to dissociating triblock copolymers and demonstrated our approach on three characteristic examples: (1) diblock copolymer (AB) melt, (2) symmetric triblock copolymer (ABA) melt, (3) triblock copolymer (ABA) solution with added electrolyte. For copolymer melts, we varied the composition (that is, the total fraction of A-segments in the system) and the charge density on A blocks and calculated the phase diagram that contains ordered mesophases of lamellar, gyroid, hexagonal, and bcc symmetries, as well as the uniform disordered phase. The phase diagram of charged block copolymer melts in the charge density - system composition coordinates is similar to the classical phase diagram of neutral block copolymer melts, where the composition and the Flory mismatch interaction parameter χ _{AB} are used as variables. We found that the transitions between the polyelectrolyte mesophases with the increase of charge density occur in the same sequence, from lamellar to gyroid to hexagonal to bcc to disordered morphologies, as the mesophase transitions for neutral diblocks with the decrease of χ _{AB}. In a certain range of compositions, the phase diagram for charged triblock copolymers exhibits unexpected features, allowing for transitions from hexagonal to gyroid to lamellar mesophases as the charge density increases. Triblock polyelectrolyte solutions were studied by varying the charge density and solvent concentration at a fixed copolymer composition. Transitions from lamellar to gyroid and gyroid to hexagonal morphologies were observed at lower polymer concentrations than the respective transitions in the similar neutral copolymer, indicating a substantial influence of the charge density on phase behavior.

  8. Functionalized fullerenes in self-assembled monolayers.

    PubMed

    Gimenez-Lopez, Maria del Carmen; Räisänen, Minna T; Chamberlain, Thomas W; Weber, Uli; Lebedeva, Maria; Rance, Graham A; Briggs, G Andrew D; Pettifor, David; Burlakov, Victor; Buck, Manfred; Khlobystov, Andrei N

    2011-09-06

    Anisotropy of intermolecular and molecule-substrate interactions holds the key to controlling the arrangement of fullerenes into 2D self-assembled monolayers (SAMs). The chemical reactivity of fullerenes allows functionalization of the carbon cages with sulfur-containing groups, thiols and thioethers, which facilitates the reliable adsorption of these molecules on gold substrates. A series of structurally related molecules, eight of which are new fullerene compounds, allows systematic investigation of the structural and functional parameters defining the geometry of fullerene SAMs. Scanning tunnelling microscopy (STM) measurements reveal that the chemical nature of the anchoring group appears to be crucial for the long-range order in fullerenes: the assembly of thiol-functionalized fullerenes is governed by strong molecule-surface interactions, which prohibit formation of ordered molecular arrays, while thioether-functionalized fullerenes, which have a weaker interaction with the surface than the thiols, form a variety of ordered 2D molecular arrays owing to noncovalent intermolecular interactions. A linear row of fullerene molecules is a recurring structural feature of the ordered SAMs, but the relative alignment and the spacing between the fullerene rows is strongly dependent on the size and shape of the spacer group linking the fullerene cage and the anchoring group. Careful control of the chemical functionality on the carbon cages enables positioning of fullerenes into at least four different packing arrangements, none of which have been observed before. Our new strategy for the controlled arrangement of fullerenes on surfaces at the molecular level will advance the development of practical applications for these nanomaterials. © 2011 American Chemical Society

  9. Self assembly: An approach to terascale integration

    SciTech Connect

    Singer, S.

    1993-09-01

    Surely one of the most remarkable accomplishments of modern times has been the miniaturization of electronic components, starting with discrete transistors and leading to Very Large Scale Integrated (VLSI) Circuits which will soon contain almost 100 million components in a few square centimeters. It led to an information processing industry that fuels almost every aspect of industrial societies and that has brought manifold benefits to their citizens. Although continuation of the miniaturization process is likely to produce even greater benefits, many experts are concerned that extrapolation of traditional silicon VLSI techniques will meet with increasingly severe difficulties. Some of these are fundamental in nature, e. g., granularity and fluctuations in semiconductors and interconnects and proximity effects such as tunneling. The first major difficulty to be encountered will be a rising cost of products due to increased complexity and difficulty of manufacturing and assembly. Such difficulties are likely to be seen in about 10 years when minimum component sizes are expected to decrease below 0.15--0.2 {mu}m. If alternatives to present VLSI techniques are to be available when needed, work on them must start now. At Los Alamos, we are exploring the feasibility of ultrasmall wires and switches that self-assemble themselves into computing elements and circuits. Their operation is based on the quantum properties of nanometer scale molecular clusters. This paper will describe our efforts in the development of these components and will summarize our work in four areas: (1) the development of conducting molecular wires, (2) conducting nanoparticle wires and switches based on the Coulomb Blockade principle, (3) the development of advanced architectures that benefit from the use of such components and that significantly advance the art of high performance computing, and (4) the development of novel methods for attaining sub-Angstrom 3-D non-destructive imaging.

  10. Lutetium(III)-dependent self-assembly study of ciliate Euplotes octocarinatus centrin.

    PubMed

    Duan, Lian; Zhao, Ya-Qin; Wang, Zhi-Jun; Li, Guo-Ting; Liang, Ai-Hua; Yang, Bin-Sheng

    2008-02-01

    Ciliate Euplotes octocarinatus centrin (EoCen) is a member of the EF-hand superfamily of calcium-binding proteins, which often associated with the centrosomes and basal bodies. To explore the possible structural role of EoCen, we initiated a physicochemical study of the self-assembly properties of the purified protein in vitro. The native PAGE results indicate that only the integral protein shows multimers in the presence of Lu(3+). The dependence of Lu(3+) induced self-assembly of EoCen on various chemical and physical factors, including temperature, protein concentration, ionic strength and pH, was characterized using resonance light scattering (RLS). Control experiments with different metal ions suggest that Ca(2+) and Lu(3+) bindings to the N-terminal domain of EoCen are all positive to the self-assembly of the protein, and Lu(3+) exhibits the stronger effect, however, Mg(2+) alone cannot take the same effect. The experiments of 2-ptoluidinylnaphthalene-6-sulfonate (TNS) binding and ionic strength demonstrate that the lutetium(III)-dependent self-assembly is closely related to the exposure of hydrophobic cavity. Control experiment on pH value with EoCen and the fragments of it, N-terminal domain of EoCen (N-EoCen), indicates that the electrostatic effect is of small tendency to be served as the main driving force in the self-assembly of EoCen. The specific oligomerization form of the protein was exhibited by cross-linking experiment.

  11. Self-assembled peptide nanostructures for functional materials

    NASA Astrophysics Data System (ADS)

    Sardan Ekiz, Melis; Cinar, Goksu; Aref Khalily, Mohammad; Guler, Mustafa O.

    2016-10-01

    Nature is an important inspirational source for scientists, and presents complex and elegant examples of adaptive and intelligent systems created by self-assembly. Significant effort has been devoted to understanding these sophisticated systems. The self-assembly process enables us to create supramolecular nanostructures with high order and complexity, and peptide-based self-assembling building blocks can serve as suitable platforms to construct nanostructures showing diverse features and applications. In this review, peptide-based supramolecular assemblies will be discussed in terms of their synthesis, design, characterization and application. Peptide nanostructures are categorized based on their chemical and physical properties and will be examined by rationalizing the influence of peptide design on the resulting morphology and the methods employed to characterize these high order complex systems. Moreover, the application of self-assembled peptide nanomaterials as functional materials in information technologies and environmental sciences will be reviewed by providing examples from recently published high-impact studies.

  12. Understanding emergent functions in self-assembled fibrous networks

    NASA Astrophysics Data System (ADS)

    Sinko, Robert; Keten, Sinan

    2015-09-01

    Understanding self-assembly processes of nanoscale building blocks and characterizing their properties are both imperative for designing new hierarchical, network materials for a wide range of structural, optoelectrical, and transport applications. Although the characterization and choices of these material building blocks have been well studied, our understanding of how to precisely program a specific morphology through self-assembly still must be significantly advanced. In the recent study by Xie et al (2015 Nanotechnology 26 205602), the self-assembly of end-functionalized nanofibres is investigated using a coarse-grained molecular model and offers fundamental insight into how to control the structural morphology of nanofibrous networks. Varying nanoscale networks are observed when the molecular interaction strength is changed and the findings suggest that self-assembly through the tuning of molecular interactions is a key strategy for designing nanostructured networks with specific topologies.

  13. Directed self-assembly of proteins into discrete radial patterns

    PubMed Central

    Thakur, Garima; Prashanthi, Kovur; Thundat, Thomas

    2013-01-01

    Unlike physical patterning of materials at nanometer scale, manipulating soft matter such as biomolecules into patterns is still in its infancy. Self-assembled monolayer (SAM) with surface density gradient has the capability to drive biomolecules in specific directions to create hierarchical and discrete structures. Here, we report on a two-step process of self-assembly of the human serum albumin (HSA) protein into discrete ring structures based on density gradient of SAM. The methodology involves first creating a 2-dimensional (2D) polyethylene glycol (PEG) islands with responsive carboxyl functionalities. Incubation of proteins on such pre-patterned surfaces results in direct self-assembly of protein molecules around PEG islands. Immobilization and adsorption of protein on such structures over time evolve into the self-assembled patterns. PMID:23719678

  14. Ionic liquids as amphiphile self-assembly media.

    PubMed

    Greaves, Tamar L; Drummond, Calum J

    2008-08-01

    In recent years, the number of non-aqueous solvents which mediate hydrocarbon-solvent interactions and promote the self-assembly of amphiphiles has been markedly increased by the reporting of over 30 ionic liquids which possess this previously unusual solvent characteristic. This new situation allows a different exploration of the molecular "solvophobic effect" and tests the current understanding of amphiphile self-assembly. Interestingly, both protic and aprotic ionic liquids support amphiphile self-assembly, indicating that it is not required for the solvents to be able to form a hydrogen bonded network. Here, the use of ionic liquids as amphiphile self-assembly media is reviewed, including micelle and liquid crystalline mesophase formation, their use as a solvent phase in microemulsions and emulsions, and the emerging field of nanostructured inorganic materials synthesis. Surfactants, lipids and block co-polymers are the focus amphiphile classes in this critical review (174 references).

  15. Directed flexibility: self-assembly of a supramolecular tetrahedron.

    PubMed

    Ludlow, James M; Xie, Tingzheng; Guo, Zaihong; Guo, Kai; Saunders, Mary Jane; Moorefield, Charles N; Wesdemiotis, Chrys; Newkome, George R

    2015-03-04

    Self-assembly of a tribenzo-27-crown-9 ether functionalized with six terpyridines generated (85%) an expanded tetrahedral structure comprised of four independent triangular surfaces interlinked by crown ether vertices.

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

    PubMed Central

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

    2012-01-01

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

  17. Predicting self-assembled patterns on spheres with multicomponent coatings.

    PubMed

    Edlund, Erik; Lindgren, Oskar; Jacobi, Martin Nilsson

    2014-05-07

    Patchy colloids are promising candidates for building blocks in directed self-assembly, but large scale synthesis of colloids with controlled surface patterns remains challenging. One potential fabrication method is to self-assemble the surface patterns themselves, allowing complex morphologies to organize spontaneously. For this approach to be competitive, prediction and control of the pattern formation process are necessary. However, structure formation in many-body systems is fundamentally hard to understand, and new theoretical methods are needed. Here we present a theory for self-assembling pattern formation in multi-component systems on the surfaces of colloidal particles, formulated as an analytic technique that predicts morphologies directly from the interactions in an effective model. As a demonstration we formulate an isotropic model of alkanethiols on gold, a suggested system for directed self-assembly, and predict its morphologies and transitions as a function of the interaction parameters.

  18. Modeling the Kinetics of Open Self-Assembly.

    PubMed

    Verdier, Timothée; Foret, Lionel; Castelnovo, Martin

    2016-07-07

    In this work, we explore theoretically the kinetics of molecular self-assembly in the presence of constant monomer flux as an input, and a maximal size. The proposed model is supposed to reproduce the dynamics of viral self-assembly for enveloped virus. It turns out that the kinetics of open self-assembly is rather quantitatively different from the kinetics of similar closed assembly. In particular, our results show that the convergence toward the stationary state is reached through assembly waves. Interestingly, we show that the production of complete clusters is much more efficient in the presence of a constant input flux, rather than providing all monomers at the beginning of the self-assembly.

  19. Converting molecular information of redox coenzymes via self-assembly.

    PubMed

    Morikawa, Masa-aki; Kimizuka, Nobuo

    2012-11-21

    β-Nicotinamide adenine dinucleotide (NAD(+)) and its reduced form NADH specifically interact with a cyanine dye in aqueous media, giving distinct spectral and nanostructural characteristics to which molecular information of constituent coenzymes are converted via self-assembly.

  20. Self-assembly of biofunctional polymer on graphene nanoribbons.

    PubMed

    Reuven, Darkeyah G; Suggs, Kelvin; Williams, Michael D; Wang, Xiao-Qian

    2012-02-28

    Graphene's adhesive properties owing to inherent van der Waals interactions become increasingly relevant in the nanoscale regime. Polymer self-assembly via graphene-mediated noncovalent interactions offers a powerful tool for the creation of anisotropic nanopatterned systems. Here, we report the supramolecular self-assembly of biofunctional-modified poly(2-methoxystyrene) on graphene nanoribbons prepared by unzipping multiwalled carbon nanotubes. This approach promotes the glycol-modified polymer to self-assemble into structured nanopatterns with preserved bioactivity. The self-assembly is attributed to enhanced van der Waals interactions and the associated charge transfer from polymer to graphene. These findings demonstrate that the assembly yields a prospective route to novel nanomaterial systems.

  1. 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.

  2. Activity-assisted self-assembly of colloidal particles

    NASA Astrophysics Data System (ADS)

    Mallory, S. A.; Cacciuto, A.

    2016-08-01

    We outline a basic strategy of how self-propulsion can be used to improve the yield of a typical colloidal self-assembly process. The success of this approach is predicated on the thoughtful design of the colloidal building block as well as how self-propulsion is endowed to the particle. As long as a set of criteria are satisfied, it is possible to significantly increase the rate of self-assembly, and greatly expand the window in parameter space where self-assembly can occur. In addition, we show that by tuning the relative on-off time of the self-propelling force it is possible to modulate the effective speed of the colloids allowing for further optimization of the self-assembly process.

  3. 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

  4. 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.

  5. Self-assembled tunable networks of sticky colloidal particles

    DOEpatents

    Demortiere, Arnaud; Snezhko, Oleksiy Alexey; Sapozhnikov, Maksim; Becker, Nicholas G.; Proslier, Thomas; Aronson, Igor S.

    2017-07-18

    Self-assembled tunable networks of microscopic polymer fibers ranging from wavy colloidal "fur" to highly interconnected networks are created from polymer systems and an applied electric field. The networks emerge via dynamic self-assembly in an alternating (ac) electric field from a non-aqueous suspension of "sticky" polymeric colloidal particles with a controlled degree of polymerization. The resulting architectures are tuned by the frequency and amplitude of the electric field and surface properties of the particles.

  6. Self-assembled nanotubes from single fluorescent amino acid

    NASA Astrophysics Data System (ADS)

    Babar, Dipak Gorakh; Sarkar, Sabyasachi

    2017-03-01

    Self-assembly of biomolecules has gained increasing attention as it generates various supramolecular structural assemblies having potential applications principally in biomedical sciences. Here, we show that amino acid like tryptophan or tyrosine readily aggregates as nanotubes via a simple self-assembly process. These were characterized by FTIR, scanning electron microscopy, and by fluorescence microscopy. Nanotubes prepared from tryptophan are having 200 nm inner diameter and those from tyrosine are having the same around 50 nm diameter.

  7. Optimal control of electrostatic self-assembly of binary monolayers

    NASA Astrophysics Data System (ADS)

    Shestopalov, N. V.; Henkelman, G.; Powell, C. T.; Rodin, G. J.

    2009-05-01

    A simple macroscopic model is used to determine an optimal annealing schedule for self-assembly of binary monolayers of spherical particles. The model assumes that a single rate-controlling mechanism is responsible for the formation of spatially ordered structures and that its rate follows an Arrhenius form. The optimal schedule is derived in an analytical form using classical optimization methods. Molecular dynamics simulations of the self-assembly demonstrate that the proposed schedule outperforms other schedules commonly used for simulated annealing.

  8. Electronic polymers and DNA self-assembled in nanowire transistors.

    PubMed

    Hamedi, Mahiar; Elfwing, Anders; Gabrielsson, Roger; Inganäs, Olle

    2013-02-11

    Aqueous self-assembly of DNA and molecular electronic materials can lead to the creation of innumerable copies of identical devices, and inherently programmed complex nanocircuits. Here self-assembly of a water soluble and highly conducting polymer PEDOT-S with DNA in aqueous conditions is shown. Orientation and assembly of the conducting DNA/PEDOT-S complex into electrochemical DNA nanowire transistors is demonstrated.

  9. AFM characterization of spin coated carboxylated polystyrene nanospheres/xyloglucan layers on mica and silicon.

    PubMed

    Lubambo, Adriana F; Lucyszyn, Neoli; Petzhold, Cesar L; Sierakowski, Maria-R; Schreiner, Wido H; Saul, Cyro K

    2013-03-01

    Self-assembled nano-arrays have a potential application as solid-phase diagnostics in many biomedical devices. The easiness of its production is directly connected to manufacture cost reduction. In this work, we present self-assembled structures starting from spin coated thin films of carboxylated polystyrene (PSC) and xyloglucan (XG) mixtures on both mica and silicon substrates. AFM images showed PSC nanospheres on top of a homogeneous layer of XG, for both substrates. The average nanosphere diameter fluctuated for a constant speed and it was likely to be independent of the component proportions on the mixture within a range of 30-50% (v/v) PSC. It was also observed that the largest diameters were found at the center of the sample and the smallest at the border. The detected nanospheres were also more numerous at the border. This behavior presents a similarity to spin coated colloidal dispersions. We observed that the average nanosphere diameter on mica substrates was bigger than the nanosphere diameters obtained on top of silicon substrates, under the same conditions. This result seems to be possibly connected to different mixture-surface interactions.

  10. DYNAMIC SHEAR-INFLUENCED COLLAGEN SELF-ASSEMBLY

    PubMed Central

    Saeidi, Nima; Sander, Edward A.

    2011-01-01

    The ability to influence the direction of polymerization of a self-assembling biomolecular system has the potential to generate materials with extremely high anisotropy. In biological systems where highly-oriented cellular populations give rise to aligned and often load-bearing tissue such organized molecular scaffolds could aid in the contact guidance of cells for engineered tissue constructs (e.g cornea and tendon). In this investigation we examine the detailed dynamics of pepsin-extracted type I bovine collagen assembly on a glass surface under the influence of flow between two plates. Differential Interference Contrast (DIC) imaging (60x-1.4NA) with focal plane stabilization was used to resolve and track the growth of collagen aggregates on borosilicate glass for 4 different shear rates (500, 80, 20, and 9 s-1). The detailed morphology of the collagen fibrils/aggregates was examined using Quick Freeze Deep Etch electron microscopy. Nucleation of fibrils on the glass was observed to occur rapidly (~2 min) followed by continued growth of the fibrils. The growth rates were dependent on flow in a complex manner with the highest rate of axial growth (0.1 microns/sec) occurring at a shear rate of 9 s-1. The lowest growth rate occurred at the highest shear. Fibrils were observed to both branch and join during the experiments. The best alignment of fibrils was observed at intermediate shear rates of 20 and 80s-1. However, the investigation revealed that fibril directional growth was not stable. At high shear rates, fibrils would often turn downstream forming what we term “hooks” which are likely the combined result of monomer interaction with the initial collagen layer or “mat” and the high shear rate. Further, QFDE examination of fibril morphology demonstrated that the assembled fibrillar structure did not possess native D-periodicity. Instead, fibrils comprised a collection of generally aligned, monomers which were self-assembled to form a fibril

  11. Electric Field Controlled Self-Assembly of Hierarchically Ordered Membranes

    PubMed Central

    Velichko, Yuri S.; Mantei, Jason R.; Bitton, Ronit; Carvajal, Daniel; Shull, Kenneth R.; Stupp, Samuel I.

    2012-01-01

    Self-assembly in the presence of external forces is an adaptive, directed organization of molecular components under nonequilibrium conditions. While forces may be generated as a result of spontaneous interactions among components of a system, intervention with external forces can significantly alter the final outcome of self-assembly. Superimposing these intrinsic and extrinsic forces provides greater degrees of freedom to control the structure and function of self-assembling materials. In this work we investigate the role of electric fields during the dynamic self-assembly of a negatively charged polyelectrolyte and a positively charged peptide amphiphile in water leading to the formation of an ordered membrane. In the absence of electric fields, contact between the two solutions of oppositely charged molecules triggers the growth of closed membranes with vertically oriented fibrils that encapsulate the polyelectrolyte solution. This process of self-assembly is intrinsically driven by excess osmotic pressure of counterions, and the electric field is found to modify the kinetics of membrane formation, and also its morphology and properties. Depending on the strength and orientation of the field we observe a significant increase or decrease of up to nearly 100% in membrane thickness, as well as the controlled rotation of nanofiber growth direction by 90 degrees, resulting in a significant increase in mechanical stiffness. These results suggest the possibility of using electric fields to control structure in self-assembly processes involving diffusion of oppositely charged molecules. PMID:23166533

  12. Effect of polymerization on hierarchical self-assembly into nanosheets.

    PubMed

    Ikeda, Taichi

    2015-01-20

    The oligomers consisting of phenyl-capped bithiophene and tetra(ethylene glycol)s linked by azide-alkyne Huisgen cycloaddition were synthesized. The relationship between the degree of polymerization and self-assembling ability was investigated in o-dichlorobenzene and dimethyl sulfoxide. From the absorption spectrum, it was confirmed that the critical degree of polymerization (CDP) for thiophene unit aggregation was 4. The morphology of the aggregated product was observed by atomic force microscopy. The oligomers 4mer and 5mer could not self-assemble into well-defined structures due to the weak driving force for the self-assembly. In the cases of 6mer and 7mer, aggregates with nonwell-defined and nanosheet structures coexisted. In the cases of 8mer and 9mer, the nanosheet was the main product. The critical point between 7mer and 8mer could be confirmed by different aggregation behaviors in the cooling process of the solution (nonsigmoidal and sigmoidal). In the cases of 8mer and 9mer, polymer folding prior to intermolecular self-assembly, which was supported by sigmoidal aggregation behavior, leads to the nanosheet formation. On the contrary, shorter oligomers than 8mer experience intermolecular aggregation prior to intramolecular polymer folding, which was supported by the nonsigmoidal aggregation behavior. This is the first report to prove the existence of CDP for folded polymer nanosheet formation which requires hierarchical self-assembly, i.e., polymer folding followed by intermolecular self-assembly.

  13. DNA-based self-assembly for functional nanomaterials.

    PubMed

    Wang, Zhen-Gang; Ding, Baoquan

    2013-07-26

    The unprecedented development of DNA nanotechnology has caused DNA self-assembly to attract close attention in many disciplines. In this research news article, the employment of DNA self-assembly in the fields of materials science and nanotechnology is described. DNA self-assembly can be used to prepare bulk-scale hydrogels and 3D macroscopic crystals with nanoscale internal structures, to induce the crystallization of nanoparticles, to template the fabrication of organic conductive nanomaterials, and to act as drug delivery vehicles for therapeutic agents. The properties and functions are fully tunable because of the designability and specificity of DNA assembly. Moreover, because of the intrinsic dynamics, DNA self-assembly can act as a program switch and can efficiently control stimuli responsiveness. We highlight the power of DNA self-assembly in the preparation and function regulation of materials, aiming to motivate future multidisciplinary and interdisciplinary research. Finally, we describe some of the challenges currently faced by DNA assembly that may affect the functional evolution of such materials, and we provide our insights into the future directions of several DNA self-assembly-based nanomaterials.

  14. Albumin binds self-assembling dyes as specific polymolecular ligands.

    PubMed

    Stopa, Barbara; Rybarska, Janina; Drozd, Anna; Konieczny, Leszek; Król, Marcin; Lisowski, Marek; Piekarska, Barbara; Roterman, Irena; Spólnik, Paweł; Zemanek, Grzegorz

    2006-12-15

    Self-assembling dyes with a structure related to Congo red (e.g. Evans blue) form polymolecular complexes with albumin. The dyes, which are lacking a self-assembling property (Trypan blue, ANS) bind as single molecules. The supramolecular character of dye ligands bound to albumin was demonstrated by indicating the complexation of dye molecules outnumbering the binding sites in albumin and by measuring the hydrodynamic radius of albumin which is growing upon complexation of self-assembling dye in contrast to dyes lacking this property. The self-assembled character of Congo red was also proved using it as a carrier introducing to albumin the intercalated nonbonding foreign compounds. Supramolecular, ordered character of the dye in the complex with albumin was also revealed by finding that self-assembling dyes become chiral upon complexation. Congo red complexation makes albumin less resistant to low pH as concluded from the facilitated N-F transition, observed in studies based on the measurement of hydrodynamic radius. This particular interference with protein stability and the specific changes in digestion resulted from binding of Congo red suggest that the self-assembled dye penetrates the central crevice of albumin.

  15. Impregnation of tubular self-assemblies into dextran hydrogels.

    PubMed

    Sun, Guoming; Chu, Chih-Chang

    2010-02-16

    Amine groups are the building units of proteins. The incorporation of amine groups into polyethylene glycol diacrylate (PEGDA) hydrogel through dextran-allyl isocyanate-ethylamine (Dex-AE) enhances sustained protein release by introducing effective interactions. To investigate such an interaction effect and to improve protein release, we impregnated self-assembled tubular structures from dextran-bromoethylamine (Dex-BH) and dextran-chloroacetic acid (Dex-CA) into Dex-AE/PEGDA hydrogel. The morphology data obtained from scanning electron microscopy (SEM) reveal that pure PEGDA hydrogel had no effect on the distribution of the self-assembled tubules; the introduction of Dex-AE brought about the dispersion of these tubules, and an increase in Dex-AE content led to more evenly distributed structures. Moreover, the implantation of the self-assembled tubules had no distinct effect on the swelling capacity of the hybrid self-assembly embedded hydrogels. The in vitro albumin release study was carried out in a pH 7.4 buffer solution; the results show that the implantation of the self-assembly into the hydrogels reduced the burst release and prolonged the protein release time. These findings demonstrate that the impregnation of tubular self-assembly into hydrogel makes the hybrid hydrogel an excellent protein delivery system.

  16. Design strategies for self-assembly of discrete targets

    SciTech Connect

    Madge, Jim; Miller, Mark A.

    2015-07-28

    Both biological and artificial self-assembly processes can take place by a range of different schemes, from the successive addition of identical building blocks to hierarchical sequences of intermediates, all the way to the fully addressable limit in which each component is unique. In this paper, we introduce an idealized model of cubic particles with patterned faces that allows self-assembly strategies to be compared and tested. We consider a simple octameric target, starting with the minimal requirements for successful self-assembly and comparing the benefits and limitations of more sophisticated hierarchical and addressable schemes. Simulations are performed using a hybrid dynamical Monte Carlo protocol that allows self-assembling clusters to rearrange internally while still providing Stokes-Einstein-like diffusion of aggregates of different sizes. Our simulations explicitly capture the thermodynamic, dynamic, and steric challenges typically faced by self-assembly processes, including competition between multiple partially completed structures. Self-assembly pathways are extracted from the simulation trajectories by a fully extendable scheme for identifying structural fragments, which are then assembled into history diagrams for successfully completed target structures. For the simple target, a one-component assembly scheme is most efficient and robust overall, but hierarchical and addressable strategies can have an advantage under some conditions if high yield is a priority.

  17. Absorption enhancement in nanostructured silicon fabricated by self-assembled nanosphere lithography

    NASA Astrophysics Data System (ADS)

    Li, Qiang; Gao, Jinsong; Li, Zizheng; Yang, Haigui; Liu, Hai; Wang, Xiaoyi; Li, Yudong

    2017-08-01

    In this work, we give a detailed experimental and theoretical analysis of a nano cone array on silicon wafer, which can greatly enhance the absorption compared with the polished silicon. The experimental absorptance can reach 98.7% in the wavelength ranging from 400 nm to 1100 nm. The mechanism of absorption enhancement is attributed to the nano cone array that can suppress the reflection by building a grade index from air to silicon surface. Moreover, an ultrathin 13 nm thickness gold film was sputtered on the nano cone array, by which surface plasmon can be excited and the absorption in the near-infrared region can be greatly enhanced. We also give a deep comprehending on the physics mechanism of such high absorption. This kind of nano cone array can be fabricated by a simple and low-cost colloidal sphere lithography and reactive ion etching, which makes it a more appropriate candidate for photovoltaics, spectroscopy, photodetectors, sensor, especially for the silicon-based application in the near-infrared region.

  18. Tunable two dimensional protein patterns through self-assembly nanosphere template

    NASA Astrophysics Data System (ADS)

    Li, Zhishi; Ruan, Weidong; Shen, Shanshan; Wang, Haiyang; Guo, Zhinan; Xue, Xiangxin; Mao, Zhu; Ji, Wei; Wang, Xu; Song, Wei; Zhao, Bing

    2012-10-01

    By the aim of constructing surfaces for multi-component and multifunctional bioassay, a microsphere lithography technique was employed to control the surface morphology. Two kinds of protein molecules (antibodies) were used as building blocks. As a result, dual-component biocompatible surfaces with alternate immunoglobulin micropatterns were fabricated. The employed antibodies included human Immunoglobulin G (IgG) and rabbit IgG, which composed nanometer scale surface arrays on the surfaces. The antibodies were identified specially by immunoreactions with labeled antigens of fluorescein isothiocyanate (FITC)-antihuman IgG and tetramethylrhodamine-5-(and 6)-isothiocyanate (TRITC)-antirabbit IgG. The immune responses were confirmed by confocal fluorescence (FL) microscopy. A study on the sensitivity and quantification was done by using surface-enhanced resonance Raman scattering (SERRS) spectroscopy. The obtained SERRS spectra showed satisfactory resolution in the multi-component detection objects. No interference was observed from inner- or interactions of detecting molecules. The detection limits for both of the antigens reached to as low as 1 ng/mL, which was comparable to FL method. Meanwhile, a good linear relationship between SERRS peak intensity and the logarithm of antigens' concentrations (from 1 ng/mL to 1 mg/mL) were observed. The results demonstrated that SERRS is a very promising detection technique for multi-component immunoassay, and has great potential applications in biotechnology and biochemistry.

  19. Self-assembled magnetic nanospheres with three-dimensional magnetic vortex

    SciTech Connect

    Kim, Min-Kwan; Dhak, Prasanta; Lee, Ha-Youn; Lee, Jae-Hyeok; Yoo, Myoung-Woo; Lee, Jehyun; Kim, Sang-Koog; Jin, Kyoungsuk; Chu, Arim; Nam, Ki Tae; Kim, Miyoung; Park, Hyun Soon; Aizawa, Shinji; Tanigaki, Toshiaki; Shindo, Daisuke

    2014-12-08

    We report the electron holography images of spin configurations in peculiar assemblies of soft magnetic nanoparticles in single-, double-, triple-, or quadruple-sphere geometrical arrangements, in which each particle has a three-dimensional (3D) magnetic-vortex structure. Micromagnetic numerical calculations reveal that the uniqueness of the nanoparticles' 3D vortex structure plays a crucial role in their assembly, especially in terms of the contrasting contributions of the exchange and dipolar interactions to their binding energies. The results represent physical insights into the assembly of 3D-vortex-structure magnetic nanoparticles in different geometrical configurations and offer a practical means of controlling those assemblies.

  20. Clamped Hybridization Chain Reactions for the Self-Assembly of Patterned DNA Hydrogels.

    PubMed

    Wang, Jianbang; Chao, Jie; Liu, Huajie; Su, Shao; Wang, Lianhui; Huang, Wei; Willner, Itamar; Fan, Chunhai

    2017-02-13

    DNA hydrogels hold great potential for biological and biomedical applications owing to their programmable nature and macroscopic sizes. However, most previous studies involve spontaneous and homogenous gelation procedures in solution, which often lack precise control. A clamped hybridization chain reaction (C-HCR)-based strategy has been developed to guide DNA self-assembly to form macroscopic hydrogels. Analogous to catalysts in chemical synthesis or seeds in crystal growth, we introduced DNA initiators to induce the gelation process, including crosslinked self-assembly and clamped hybridization in three dimensions with spatial and temporal control. The formed hydrogels show superior mechanical properties. The use of printed, surface-confined DNA initiators was also demonstrated for fabricating 2D hydrogel patterns without relying on external confinements. This simple method can be used to construct DNA hydrogels with defined geometry, composition, and order for various bioapplications.

  1. Born-Haber cycle for monolayer self-assembly at the liquid-solid interface: assessing the enthalpic driving force.

    PubMed

    Song, Wentao; Martsinovich, Natalia; Heckl, Wolfgang M; Lackinger, Markus

    2013-10-02

    The driving force for self-assembly is the associated gain in free energy with decisive contributions from both enthalpy and entropy differences between final and initial state. For monolayer self-assembly at the liquid-solid interface, solute molecules are initially dissolved in the liquid phase and then become incorporated into an adsorbed monolayer. In this work, we present an adapted Born-Haber cycle for obtaining precise enthalpy values for self-assembly at the liquid-solid interface, a key ingredient for a profound thermodynamic understanding of this process. By choosing terephthalic acid as a model system, it is demonstrated that all required enthalpy differences between well-defined reference states can be independently and consistently assessed by both experimental and theoretical methods, giving in the end a reliable value of the overall enthalpy gain for self-assembly of interfacial monolayers. A quantitative comparison of enthalpy gain and entropy cost reveals essential contributions from solvation and dewetting, which lower the entropic cost and render monolayer self-assembly a thermodynamically favored process.

  2. 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.

  3. Kinetics of Surface-Driven Self-Assembly and Fatigue-Induced Disassembly of a Virus-Based Nanocoating.

    PubMed

    Valbuena, Alejandro; Mateu, Mauricio G

    2017-02-28

    Self-assembling protein layers provide a "bottom-up" approach for precisely organizing functional elements at the nanoscale over a large solid surface area. The design of protein sheets with architecture and physical properties suitable for nanotechnological applications may be greatly facilitated by a thorough understanding of the principles that underlie their self-assembly and disassembly. In a previous study, the hexagonal lattice formed by the capsid protein (CA) of human immunodeficiency virus (HIV) was self-assembled as a monomolecular layer directly onto a solid substrate, and its mechanical properties and dynamics at equilibrium were analyzed by atomic force microscopy. Here, we use atomic force microscopy to analyze the kinetics of self-assembly of the planar CA lattice on a substrate and of its disassembly, either spontaneous or induced by materials fatigue. Both self-assembly and disassembly of the CA layer are cooperative reactions that proceed until a phase equilibrium is reached. Self-assembly requires a critical protein concentration and is initiated by formation of nucleation points on the substrate, followed by lattice growth and eventual merging of CA patches into a continuous monolayer. Disassembly of the CA layer showed hysteresis and appears to proceed only after large enough defects (nucleation points) are formed in the lattice, whose number is largely increased by inducing materials fatigue that depends on mechanical load and its frequency. Implications of the kinetic results obtained for a better understanding of self-assembly and disassembly of the HIV capsid and protein-based two-dimensional nanomaterials and the design of anti-HIV drugs targeting (dis)assembly and biocompatible nanocoatings are discussed. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  4. Synthesis of nanocrystals and nanocrystal self-assembly

    NASA Astrophysics Data System (ADS)

    Chen, Zhuoying

    Chapter 1. A general introduction is presented on nanomaterials and nanoscience. Nanoparticles are discussed with respect to their structure and properties. Ferroelectric materials and nanoparticles in particular are highlighted, especially in the case of the barium titanate, and their potential applications are discussed. Different nanocrystal synthetic techniques are discussed. Nanoparticle superlattices, the novel "meta-materials" built from self-assembly at the nanoscale, are introduced. The formation of nanoparticle superlattices and the importance and interest of synthesizing these nanostructures is discussed. Chapter 2. Advanced applications for high k dielectric and ferroelectric materials in the electronics industry continues to demand an understanding of the underlying physics in decreasing dimensions into the nanoscale. The first part of this chapter presents the synthesis, processing, and electrical characterization of nanostructured thin films (thickness ˜100 nm) of barium titanate BaTiO3 built from uniform nanoparticles (<20 nm in diameter) in diameter. Essential to our approach is an understanding of the nanoparticle as a building block, combined with an ability to integrate them into thin films that have uniform and characteristic electrical properties. We observe the BaTiO3 nanocrystals crystallize with evidence of tetragonality. Electric field dependent polarization measurements show spontaneous polarization and hysteresis, indicating ferroelectric behavior for the BaTiO 3 nanocrystalline films with grain sizes in the range of 10--30 nm. Dielectric measurements of the films show dielectic constants in the range of 85--90 over the 1 kHz--100 kHz, with low loss. We present nanocrystals as initial building blocks for the preparation of thin films which exhibit uniform nanostructured morphologies and grain sizes. In the second part of this chapter, a nonhydrolytic alcoholysis route to study the preparation of well-crystallized size-tunable BaTiO3

  5. Self-Assembling Peptide Amphiphiles for Targeted Drug Delivery

    NASA Astrophysics Data System (ADS)

    Moyer, Tyson

    The systemic delivery of therapeutics is currently limited by off-target side effects and poor drug uptake into the cells that need to be treated. One way to circumvent these issues is to target the delivery and release of therapeutics to the desired location while limiting systemic toxicity. Using self-assembling peptide amphiphiles (PAs), this work has investigated supramolecular nanostructures for the development of targeted therapies. Specifically, the research has focused on the interrelationships between presentation of targeting moeities and the control of nanostructure morphology in the context of systemic delivery for targeting cancer and vascular injuries. The self-assembly region of the PA was systematically altered to achieve control of nanostructure widths, from 100 nm to 10 nm, by the addition of valine-glutamic acid dimers into the chemical structure, subsequently increasing the degree of nanostructure twist. For the targeting of tumors, a homing PA was synthesized to include a dimeric, cyclic peptide sequence known to target the cancer-specific, death receptor 5 (DR5) and initiate apoptosis through the oligomerization of DR5. This PA presented a multivalent display of DR5-binding peptides, resulting in improved binding affinity measured by surface plasmon resonance. The DR5-targeting PA also showed enhanced efficacy in both in vitro and in vivo tumor models relative to non-targeted controls. Alternative modifications to the PA-based antitumor therapies included the use of a cytotoxic, membrane-lytic PA coassembled with a pegylated PA, which showed enhanced biodistribution and in vivo activity after coassembly. The functionalization of the hydrophobic core was also accomplished through the encapsulation of the chemotherapy camptothecin, which was shown to be an effective treatment in vivo. Additionally, a targeted PA nanostructure was designed to bind to the site of vascular intervention by targeting collagen IV. Following balloon angioplasty

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

    PubMed

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

    2015-01-01

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

  7. Single spins in self-assembled quantum dots.

    PubMed

    Warburton, Richard J

    2013-06-01

    Self-assembled quantum dots have excellent photonic properties. For instance, a single quantum dot is a high-brightness, narrow-linewidth source of single photons. Furthermore, the environment of a single quantum dot can be tailored relatively easily using semiconductor heterostructure and post-growth processing techniques, enabling electrical control of the quantum dot charge and control over the photonic modes with which the quantum dot interacts. A single electron or hole trapped inside a quantum dot has spintronics applications. Although the spin dephasing is rather rapid, a single spin can be manipulated using optical techniques on subnanosecond timescales. Optical experiments are also providing new insights into old issues, such as the central spin problem. This Review provides a snapshot of this active field, with some indications for the future. It covers the basic materials and optical properties of single quantum dots, techniques for initializing, manipulating and reading out single spin qubits, and the mechanisms that limit the electron-spin and hole-spin coherence.

  8. Electric Field Driven Self-Assembly of Colloidal Rods

    NASA Astrophysics Data System (ADS)

    Juarez, Jaime; Chaudhary, Kundan; Chen, Qian; Granick, Steve; Lewis, Jennifer

    2012-02-01

    The ability to assemble anisotropic colloidal building blocks into ordered configurations is of both scientific and technological importance. We are studying how electric field-induced interactions guide the self-assembly of these blocks into well aligned microstructures. Specifically, we present observations of the assembly of colloidal silica rods (L/D ˜ 4) within planar electrode cells as a function of different electric field parameters. Results from video microscopy and image analysis demonstrate that aligned microstructures form due to the competition between equilibrium interactions of induced dipoles and non-equilibrium processes (i.e., electro-osmosis). Under the appropriate electric field conditions (˜ kHZ AC fields), aligned colloidal rod fluids form over large areas on the electrode surface. The superposition of a DC electric field to this aligned colloidal rod fluid initiates their condensation into a vertically oriented crystalline phase. Ongoing work is now focused on exploring how temporal changes to electric fields influence colloidal rod dynamics and, hence, the assembly kinetics of aligned colloidal monolayers.

  9. Directed self-assembly cut mask assignment for unidirectional design

    NASA Astrophysics Data System (ADS)

    Ou, Jiaojiao; Yu, Bei; Gao, Jhih-Rong; Pan, David Z.

    2015-07-01

    Recently, directed self-assembly (DSA) has emerged as a promising lithography solution for cut manufacturing. We perform a comprehensive study on the DSA aware mask optimization problem to provide a DSA friendly design on cut layers. We first formulate the problem as an integer linear programming (ILP) to assign cuts to different guiding templates, targeting both conflict minimization and line-end extension minimization. As ILP may not be scalable for very large size problems, we then propose two speed-up strategies. The first one is to decompose the initial problem into smaller ones and solve them separately, followed by solution merging without much loss of quality. The second one is using the set cover algorithm to decide the DSA guiding pattern assignment, and then legalize the template placement. Our approaches can be naturally extended to handle arbitrary DSA guiding template patterns with complicated shapes. Experimental results show that our methodologies can significantly improve the DSA friendly, i.e., both the unresolved pattern number and the line-end extensions can be reduced.

  10. Self-assemblies of 5'-cholesteryl-ethyl-phosphoryl zidovudine.

    PubMed

    Du, Lina; Jia, Junwei; Ge, Pingju; Jin, Yiguang

    2016-12-01

    Anti-HIV prodrugs are recently focused on due to their ability of self-assembly, macrophage targeting, and enhanced antiviral effects. Here, an amphiphilic prodrug of zidovudine, an anti-HIV nucleoside analogue, 5'-cholesteryl-ethyl-phosphoryl zidovudine (CEPZ) was synthesized. CEPZ showed some unique physicochemical properties. The solubility of CEPZ in the noncompetitive solvents chloroform and tetrahydrofuran (THF) was very high based on the hydrogen bonds between zidovudine groups, though CEPZ was sparing soluble in alcohols and almost insoluble in water. The typical amphiphilic property of CEPZ was demonstrated according to the Langmuir monolayers at the air/water interface. The LogP of CEPZ was high to 13.78, indicating the high hydrophobicity of amphiphilic CEPZ similar to phospholipids. Homogenous and stable self-assemblies were formed with the mean size of 128.7nm and the zeta potential of -35.4mV after injecting the CEPZ-in-THF solution into water. Hydrophobic interaction between the cholesteryl moieties of CEPZ could drive molecular self-assembly and lead to the formation of spherical vesicles. CEPZ self-assemblies showed strong stability even under high temperature and gravity probably due to the high surface charge. CEPZ was very slowly degraded in neutral solutions (e.g., pH 7.4), but fast in acid solutions (e.g., pH 5.0) and some tissue homogenates. CEPZ was quickly eliminated from the circulation and distributed into the mononuclear phagocyte system (MPS) including the liver, spleen and lung after bolus intravenous administration of CEPZ self-assemblies to mice. The MPS targeting effect of CEPZ self-assemblies makes them become a promising self-assembled drug delivery system to eradicate the HIV hidden in the macrophages.

  11. Self-assembled tethered bimolecular lipid membranes.

    PubMed

    Sinner, Eva-Kathrin; Ritz, Sandra; Naumann, Renate; Schiller, Stefan; Knoll, Wolfgang

    2009-01-01

    This chapter describes some of the strategies developed in our group for designing, constructing and structurally and functionally characterizing tethered bimolecular lipid membranes (tBLM). We introduce this platform as a novel model membrane system that complements the existing ones, for example, Langmuir monolayers, vesicular liposomal dispersions and bimolecular ("black") lipid membranes. Moreover, it offers the additional advantage of allowing for studies of the influence of membrane structure and order on the function of integral proteins, for example, on how the composition and organization of lipids in a mixed membrane influence the ion translocation activity of integral channel proteins. The first strategy that we introduce concerns the preparation of tethered monolayers by the self-assembly of telechelics. Their molecular architecture with a headgroup, a spacer unit (the "tether") and the amphiphile that mimics the lipid molecule allows them to bind specifically to the solid support thus forming the proximal layer of the final architecture. After fusion of vesicles that could contain reconstituted proteins from a liposomal dispersion in contact to this monolayer the tethered bimolecular lipid membrane is obtained. This can then be characterized by a broad range of surface analytical techniques, including surface plasmon spectroscopies, the quartz crystal microbalance, fluorescence and IR spectroscopies, and electrochemical techniques, to mention a few. It is shown that this concept allows for the construction of tethered lipid bilayers with outstanding electrical properties including resistivities in excess of 10 MOmega cm2. A modified strategy uses the assembly of peptides as spacers that couple covalently via their engineered sulfhydryl or lipoic acid groups at the N-terminus to the employed gold substrate, while their C-terminus is being activated afterward for the coupling of, for example, dimyristoylphosphatidylethanol amine (DMPE) lipid molecules

  12. Investigate the Effect of Thawing Process on the Self-Assembly of Silk Protein for Tissue Applications.

    PubMed

    Nguyen, Hiep Thi; Luong, Hien Thu; Nguyen, Hai Dai; Tran, Hien Anh; Huynh, Khon Chan; Vo, Toi Van

    2017-01-01

    Biological self-assembly is a process in which building blocks autonomously organize to form stable supermolecules of higher order and complexity through domination of weak, noncovalent interactions. For silk protein, the effect of high incubating temperature on the induction of secondary structure and self-assembly was well investigated. However, the effect of freezing and thawing on silk solution has not been studied. The present work aimed to investigate a new all-aqueous process to form 3D porous silk fibroin matrices using a freezing-assisted self-assembly method. This study proposes an experimental investigation and optimization of environmental parameters for the self-assembly process such as freezing temperature, thawing process, and concentration of silk solution. The optical images demonstrated the possibility and potential of -80ST48 treatment to initialize the self-assembly of silk fibroin as well as controllably fabricate a porous scaffold. Moreover, the micrograph images illustrate the assembly of silk protein chain in 7 days under the treatment of -80ST48 process. The surface morphology characterization proved that this method could control the pore size of porous scaffolds by control of the concentration of silk solution. The animal test showed the support of silk scaffold for cell adhesion and proliferation, as well as the cell migration process in the 3D implantable scaffold.

  13. Label-free optical characterization methods for detecting amine silanization-driven gold nanoparticle self-assembly.

    PubMed

    Roy, Shibsekhar; Dixit, Chandra K; Woolley, Robert; O'Kennedy, Richard; McDonagh, Colette

    2011-09-06

    Fluorescence lifetime correlation spectroscopy (FLCS) is presented as a single-step label-free detection method for probing the amine silanization-driven spontaneous 3D self-assembly of freestanding gold nanoparticles (GNPs) in solution. Unlike the conventional methods of studying self-assembly, for example, UV-vis spectroscopy and electron microscopy, FLCS utilizes the intrinsic gold fluorescence. The significance of this approach is to amalgamate the measurement of optical and hydrodynamic size properties simultaneously to achieve a more coherent description of the self-assembly pathway. GNP self-assembly has two-stage kinetics. Electrostatic interaction drives the initial amine silanization, and this is followed by siloxane bond formation between hydrolyzed ethoxy groups of GNP-attached APTES, resulting in the formation of micrometer-sized superstructures. The self-assembly has resulted in a 5-fold increase in the fluorescence lifetime (FL), and the FLCS study has shown an 8- to 10-fold increase in the diffusion coefficient using the pure diffusion model. This result is consistent with the transmission electron microscopy (TEM) observation, which shows a few hundred fold increase in the diameter due to assembly formation by the GNPs.

  14. Investigate the Effect of Thawing Process on the Self-Assembly of Silk Protein for Tissue Applications

    PubMed Central

    Tran, Hien Anh; Huynh, Khon Chan; Vo, Toi Van

    2017-01-01

    Biological self-assembly is a process in which building blocks autonomously organize to form stable supermolecules of higher order and complexity through domination of weak, noncovalent interactions. For silk protein, the effect of high incubating temperature on the induction of secondary structure and self-assembly was well investigated. However, the effect of freezing and thawing on silk solution has not been studied. The present work aimed to investigate a new all-aqueous process to form 3D porous silk fibroin matrices using a freezing-assisted self-assembly method. This study proposes an experimental investigation and optimization of environmental parameters for the self-assembly process such as freezing temperature, thawing process, and concentration of silk solution. The optical images demonstrated the possibility and potential of −80ST48 treatment to initialize the self-assembly of silk fibroin as well as controllably fabricate a porous scaffold. Moreover, the micrograph images illustrate the assembly of silk protein chain in 7 days under the treatment of −80ST48 process. The surface morphology characterization proved that this method could control the pore size of porous scaffolds by control of the concentration of silk solution. The animal test showed the support of silk scaffold for cell adhesion and proliferation, as well as the cell migration process in the 3D implantable scaffold. PMID:28367442

  15. Supramolecular star polymers. Increased molecular weight with decreased polydispersity through self-assembly.

    PubMed

    Todd, Eric M; Zimmerman, Steven C

    2007-11-28

    A ditopic structure containing two heterocyclic DeAP units and programmed to self-assemble is used as an initiation unit for the synthesis of polylactide and polystyrene. The resultant polymers self-assemble into higher molecular weight structures with a lower molecular weight distribution. The largest discrete nanoscale polymeric assembly is proposed to be a hexameric star with a molecular weight of ca. 92.7 kDa. All polymeric assemblies generally exhibit PDI values of 1.3 to 1.5, which are lower than the PDI value of the corresponding polymeric arms. A hexameric assembly is stabilized by 30 hydrogen bonds, including six AADD.DDAA contacts. The hexameric star is formed under conditions that are at least partially controlled by kinetics.

  16. Self-assembly enhances the strength of fibers made from vimentin intermediate filament proteins.

    PubMed

    Pinto, Nicole; Yang, Fei-Chi; Negishi, Atsuko; Rheinstädter, Maikel C; Gillis, Todd E; Fudge, Douglas S

    2014-02-10

    Hagfish slime threads were recently established as a promising biomimetic model for efforts to produce ecofriendly alternatives to petroleum polymers. Initial attempts to make fibers from solubilized slime thread proteins fell short of achieving the outstanding mechanics of native slime threads. Here we tested the hypothesis that the high strength and toughness of slime threads arise from the ability of constituent intermediate filaments to undergo a stress-induced α-to-β transition. To do this, we made fibers from human vimentin proteins that were first allowed to self-assemble into 10 nm intermediate filaments. Fibers made from assembled vimentin hydrogels underwent an α-to-β transition when strained and exhibited improved mechanical performance. Our data demonstrate that it is possible to make materials from intermediate filament hydrogels and that mimicking the secondary structure of native hagfish slime threads using intermediate filament self-assembly is a promising strategy for improving the mechanical performance of biomimetic protein materials.

  17. Morphology evolution of MoS2: From monodisperse nanoparticles to self-assembled nanobelts

    NASA Astrophysics Data System (ADS)

    Yu, Ting; Luo, Xingfang; Han, Shuming; Cao, Yingjie; Yuan, Cailei; Yang, Yong; Li, Qinliang

    2016-02-01

    The MoS2 nanobelts were successfully synthesized on SiO2/Si substrates using a vapor phase sulfurization process. Atomic force microscopy (AFM) techniques are employed to comprehensively study the morphology evolution of MoS2 from monodisperse nanoparticles to self-assembled nanobelts on the SiO2/Si substrates. A possible three-step morphology evolution process, which includes initial nucleation process, self-assembly process, and subsequent crystal growth process (Ostwald ripening), is proposed to explain the formation of MoS2. Moreover, MoS2 nanobelts are characterized by Raman spectroscopy and photo-luminescence (PL). These results provide the possibility to develop an easier-to-cooperate and morphology-controllable approach to fabricate novel architectures.

  18. Two-dimensional nanoparticle self-assembly using plasma-induced Ostwald ripening.

    PubMed

    Tang, J; Photopoulos, P; Tserepi, A; Tsoukalas, D

    2011-06-10

    In this work, a novel Ag nanoparticle self-assembly process based on plasma-induced two-dimensional Ostwald ripening is demonstrated. Ag nanoparticles are deposited on p-doped Si substrates using a DC magnetron sputtering process. With the assistance of O(2)/Ar plasma treatment, different sizes and patterns of Ag nanoparticles are formed, due to the Ostwald ripening. The evolution of plasma-induced nanoparticle ripening is studied and a clear increase in particle size and a decrease in particle density are observed with increasing plasma treatment. From the experiments, it is concluded that the initial nanoparticle density and the plasma gas mixture (Ar/O(2) ratio) are important factors that affect the ripening process. The proposed plasma-directed Ag nanoparticle self-assembly provides a rapid method of tailoring the nanoparticle distribution on substrates, with potential applications in the fields of solar cells, biosensors, and catalysis.

  19. DC electric field induced phase array self-assembly of Au nanoparticles

    NASA Astrophysics Data System (ADS)

    Yadavali, S.; Sachan, R.; Dyck, O.; Kalyanaraman, R.

    2014-11-01

    In this work we report the discovery of phase array self-assembly, a new way to spontaneously make periodic arrangements of metal nanoparticles. An initially random arrangement of gold (Au) or silver (Ag) nanoparticles on SiO2/Si substrates was irradiated with linearly polarized (P) laser light in the presence of a dc electric (E) field applied to the insulating substrate. For E fields parallel to the laser polarization (E \\parallel P), the resulting periodic ordering was single-crystal like with extremely low defect density and covered large macroscopic areas. The E field appears to be modifying the phase between radiation scattered by the individual nanoparticles thus leading to enhanced interference effects. While phase array behavior is widely known in antenna technology, this is the first evidence that it can also aid in nanoscale self-assembly. These results provide a simple way to produce periodic metal nanoparticles over large areas.

  20. Flexible minerals: self-assembled calcite spicules with extreme bending strength.

    PubMed

    Natalio, Filipe; Corrales, Tomas P; Panthöfer, Martin; Schollmeyer, Dieter; Lieberwirth, Ingo; Müller, Werner E G; Kappl, Michael; Butt, Hans-Jürgen; Tremel, Wolfgang

    2013-03-15

    Silicatein-α is responsible for the biomineralization of silicates in sponges. We used silicatein-α to guide the self-assembly of calcite "spicules" similar to the spicules of the calcareous sponge Sycon sp. The self-assembled spicules, 10 to 300 micrometers (μm) in length and 5 to 10 μm in diameter, are composed of aligned calcite nanocrystals. The spicules are initially amorphous but transform into calcite within months, exhibiting unusual growth along [100]. They scatter x-rays like twinned calcite crystals. Whereas natural spicules evidence brittle failure, the synthetic spicules show an elastic response, which greatly enhances bending strength. This remarkable feature is linked to a high protein content. With nano-thermogravimetric analysis, we measured the organic content of a single spicule to be 10 to 16%. In addition, the spicules exhibit waveguiding properties even when they are bent.

  1. One-step electrodeposition of self-assembled colloidal particles: a novel strategy for biomedical coating.

    PubMed

    Sun, Jiadi; Liu, Xiaoya; Meng, Long; Wei, Wei; Zheng, Yufeng

    2014-09-23

    A novel biomedical coating was prepared from self-assembled colloidal particles through direct electrodeposition. The particles, which are photo-cross-linkable and nanoscaled with a high specific surface area, were obtained via self-assembly of amphiphilic poly(γ-glutamic acid)-g-7-amino-4-methylcoumarin (γ-PGA-g-AMC). The size, morphology, and surface charge of the resulting colloidal particles and their dependence on pH, initial concentrations, and UV irradiation were successfully studied. A nanostructured coating was formed in situ on the surface of magnesium alloys by electrodeposition of colloidal particles. The composition, morphology, and phase of the coating were monitored using Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and X-ray diffraction. The corrosion test showed that the formation of the nanostructured coating on magnesium alloys effectively improved their initial anticorrosion properties. More importantly, the corrosion resistance was further enhanced by chemical photo-cross-linking. In addition, the low cytotoxicity of the coated samples was confirmed by MTT assay against NIH-3T3 normal cells. The contribution of our work lies in the creation of a novel strategy to fabricate a biomedical coating in view of the versatility of self-assembled colloidal particles and the controllability of the electrodeposition process. It is believed that our work provides new ideas and reliable data to design novel functional biomedical coatings.

  2. Self-assembly morphology effects on the crystallization of semicrystalline block copolymer thin film

    NASA Astrophysics Data System (ADS)

    Wei, Yuhan; Pan, Caiyuan; Li, Binyao; Han, Yanchun

    2007-03-01

    Self-assembly morphology effects on the crystalline behavior of asymmetric semicrystalline block copolymer polystyrene-block-poly(L-lactic acid) thin film were investigated. Firstly, a series of distinctive self-assembly aggregates, from spherical to ellipsoid and rhombic lamellar micelles (two different kinds of rhombic micelles, defined as rhomb 1 and rhomb 2) was prepared by means of promoting the solvent selectivity. Then, the effects of these self-assembly aggregates on crystallization at the early stage of film evolution were investigated by in situ hot stage atomic force microscopy. Heterogeneous nucleation initiated from the spherical micelles and dendrites with flat on crystals appeared with increasing temperature. At high temperature, protruding structures were observed due to the thickening of the flat-on crystals and finally more thermodynamically stable crystallization formed. Annealing the rhombic lamellar micelles resulted in different phenomena. Turtle-shell-like crystalline structure initiated from the periphery of the rhombic micelle 1 and spread over the whole film surface in the presence of mostly noncrystalline domain interior. Erosion and small hole appeared at the surface of the rhombic lamellar micelle 2; no crystallization like that in rhomb 1 occurred. It indicated that the chain-folding degree was different in these two micelles, which resulted in different annealing behaviors.

  3. Interface-induced disassembly of a self-assembled two-component nanoparticle system.

    PubMed

    Gao, Yan; Duc, Le T; Ali, Affira; Liang, Beverly; Liang, Jenn-Tai; Dhar, Prajnaparamita

    2013-03-19

    We present a study of static and dynamic interfacial properties of self-assembled polyelectrolyte complex nanoparticles (size 110-120 nm) containing entrapped surfactant molecules at a fluid/fluid interface. Surface tension vs time measurements of an aqueous solution of these polyelectrolyte complex nanoparticles (PCNs) show a concentration-dependent biphasic adsorption to the air/water interface while interfacial microrheology data show a concentration-dependent initial increase in the surface viscosity (up to 10(-7) N·m/s), followed by a sharp decrease (10(-9) N·m/s). Direct visualization of the air/water interface shows disappearance of particles from the interface over time. On the basis of these observations, we propose that the PCNs at fluid/fluid interfaces exist in two states: initial accumulation of PCNs at the air/water interface as nanoparticles, followed by interface induced disassembly of the accumulated PCNs into their components. The lack of change in particle size, charge, and viscosity of the bulk aqueous solution of PCNs with time indicates that this disintegration of the self-assembled PCNs is an interfacial phenomenon. Changes in energy encountered by the PCNs at the interface lead to instability of the self-assembled system and dissociation into its components. Such systems can be used for applications requiring directed delivery and triggered release of entrapped surfactants or macromolecules at fluid/fluid interfaces.

  4. Hydrogels constructed via self-assembly of beta-hairpin molecules

    NASA Astrophysics Data System (ADS)

    Ozbas, Bulent

    There is a recent and growing interest in hydrogel materials that are formed via peptide self-assembly for tissue engineering applications. Peptide based materials are excellent candidates for diverse applications in biomedical field due to their responsive behavior and complex self-assembled structures. However, there is very limited information on the self-assembly and resultant network and mechanical properties of these types of hydrogels. The main goal of this dissertation is to investigate the self-assembly mechanism and viscoelastic properties of hydrogels that can be altered by changing solution conditions as well as the primary structure of the peptide. These hydrogels are formed via intramolecular folding and consequent self-assembly of 20 amino acid long beta-hairpin peptide molecules (Max1). The peptide molecules are locally amphiphilic with two linear strands of alternating hydrophobic valine and hydrophilic lysine amino acids connected with a Dproline-LProline turn sequence. Circular dichroism and FTIR spectroscopy show that at physiological conditions peptides are unfolded in the absence of salt. By raising the ionic strength of the solution electrostatic interactions between charged lysines are screened and the peptide arms are forced into a beta-sheet secondary structure stabilized by the turn sequence. These folded molecules intermolecularly assemble via hydrophobic collapse and hydrogen bonding into a three dimensional network. Folding and self-assembly of these molecules can also be triggered by increasing temperature and/or pH of the peptide solution. In addition, the random-coil to beta-sheet transition of the beta-hairpin peptides is pH and, with proper changes in the peptide sequence, thermally reversible. Rheological measurements demonstrate that the resultant supramolecular structure forms an elastic material, whose structure, and thus modulus, can be tuned by magnitude of the stimulus. Hydrogels recover their initial viscoelastic

  5. Supracolloidal reconfigurable polyhedra via hierarchical self-assembly.

    PubMed

    Morphew, Daniel; Chakrabarti, Dwaipayan

    2016-12-06

    Enclosed three-dimensional structures with hollow interiors have been attractive targets for the self-assembly of building blocks across different length scales. Colloidal self-assembly, in particular, has enormous potential as a bottom-up means of structure fabrication exploiting a priori designed building blocks because of the scope for tuning interparticle interactions. Here we use computer simulation study to demonstrate the self-assembly of designer charge-stabilised colloidal magnetic particles into a series of supracolloidal polyhedra, each displaying a remarkable two-level structural hierarchy. The parameter space for design supports thermodynamically stable polyhedra of very different morphologies, namely tubular and hollow spheroidal structures, involving the formation of subunits of four-fold and three-fold rotational symmetry, respectively. The spheroidal polyhedra are chiral, despite having a high degree of rotational symmetry. The dominant pathways for self-assembly into these polyhedra reveal two distinct mechanisms - a growth mechanism via sequential attachment of the subunits for a tubular structure and a staged or hierarchical pathway for a spheroidal polyhedron. These supracolloidal architectures open up in response to an external magnetic field. Our results suggest design rules for synthetic reconfigurable containers at the microscale exploiting a hierarchical self-assembly scheme.

  6. Self-Assembly for the Synthesis of Functional Biomaterials

    PubMed Central

    Stephanopoulos, Nicholas; Ortony, Julia H.; Stupp, Samuel I.

    2012-01-01

    The use of self-assembly for the construction of functional biomaterials is a highly promising and exciting area of research, with great potential for the treatment of injury or disease. By using multiple noncovalent interactions, coded into the molecular design of the constituent components, self-assembly allows for the construction of complex, adaptable, and highly tunable materials with potent biological effects. This review describes some of the seminal advances in the use of self-assembly to make novel systems for regenerative medicine and biology. Materials based on peptides, proteins, DNA, or hybrids thereof have found application in the treatment of a wide range of injuries and diseases, and this review outlines the design principles and practical applications of these systems. Most of the examples covered focus on the synthesis of hydrogels for the scaffolding or transplantation of cells, with an emphasis on the biological, mechanical, and structural properties of the resulting materials. In addition, we will discuss the distinct advantages conferred by self-assembly (compared with traditional covalent materials), and present some of the challenges and opportunities for the next generation of self-assembled biomaterials. PMID:23457423

  7. Acylpyrazolones: Synthesis, self-assembly and lanthanide metal ion separation

    NASA Astrophysics Data System (ADS)

    Yang, Jun

    The central hypothesis that nanoscale self-assemblies can provide excellent metal ion recognition has been substantiated by employing acylpyrazolones and trivalent lanthanide metal ions as model systems. Several novel acylpyrazolones and their amphiphilic analogs have been designed, synthesized, and characterized. Their lanthanide metal ion recognition efficacies have been demonstrated through baseline separations of a mixture of light, middle, and heavy lanthanide metal ions by employing them in the aqueous mobile phase of high performance liquid chromatography (HPLC) with octadecylsilanized silica (ODS) as the stationary phase. The complex separation mechanism is influenced by the structures of acylpyrazolone and amphiphilic moieties, and spontaneous self-assembly of the ligand in the aqueous and on the stationary phases. Transmission electron microscopy (TEM) studies of the ligand self-assemblies in the aqueous phase in the absence and presence of lanthanide metal ions reveal spherical, dendritic, and linear (nanofibers, nanorods, and nanotubes) nanoscale structures. Such structures have also been observed when chloromethylated acylpyrazolones are stimulated to self-assemble by a base in nonaqueous solvents and when silica nanoparticles derivatized with them spontaneously self-assemble in aqueous and nonaqueous solvents.

  8. 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.

  9. 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.

  10. Mechanism of crystalline self-assembly in aqueous medium: a combined cryo-TEM/kinetic study.

    PubMed

    Tidhar, Yaron; Weissman, Haim; Tworowski, Dmitry; Rybtchinski, Boris

    2014-08-11

    Understanding the crystallization of organic molecules is a long-standing challenge. Herein, a mechanistic study on the self-assembly of crystalline arrays in aqueous solution is presented. The crystalline arrays are assembled from perylene diimide (PDI) amphiphiles bearing a chiral N-acetyltyrosine side group connected to the PDI aromatic core. A kinetic study of the crystallization process was performed using circular dichroism spectroscopy combined with time-resolved cryogenic transmission electron microscopy (cryo-TEM) imaging of key points along the reaction coordinate, and molecular dynamics simulation of the initial stages of the assembly. The study reveals a complex self-assembly process starting from the formation of amorphous aggregates that are transformed into crystalline material through a nucleation-growth process. Activation parameters indicate the key role of desolvation along the assembly pathway. The insights from the kinetic study correlate well with the structural data from cryo-TEM imaging. Overall, the study reveals four stages of crystalline self-assembly: 1) collapse into amorphous aggregates; 2) nucleation as partial ordering; 3) crystal growth; and 4) fusion of smaller crystalline aggregates into large crystals. These studies indicate that the assembly process proceeds according to a two-step crystallization model, whereby initially formed amorphous material is reorganized into an ordered system. This process follows Ostwald's rule of stages, evolving through a series of intermediate phases prior to forming the final structure, thus providing an insight into the crystalline self-assembly process in aqueous medium. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Well-Defined Protein/Peptide-Polymer Conjugates by Aqueous Cu-LRP: Synthesis and Controlled Self-Assembly.

    PubMed

    Zhang, Qiang; Li, Muxiu; Zhu, Chongyu; Nurumbetov, Gabit; Li, Zaidong; Wilson, Paul; Kempe, Kristian; Haddleton, David M

    2015-07-29

    The synthesis of well-defined protein/peptide-polymer conjugates with interesting self-assembly behavior via single electron transfer living radical polymerization in water is described. A range of protein/peptides with different physical and chemical properties have been modified to macroinitiators and optimized polymerization conditions ensure successful polymerization from soluble, insoluble, and dispersed protein/peptide molecules or protein aggregates. This powerful strategy tolerates a range of functional monomers and mediates efficient homo or block copolymerization to generate hydrophilic polymers with controlled molecular weight (MW) and narrow MW distribution. The polymerizations from bovine insulin macroinitiators follow surface-initiated "grafting from" polymerization mechanism and may involve a series of self-assembly and disassembly processes. Synthesized insulin-polymer conjugates form spheres in water, and the self-assembly behavior could be controlled via thermal control, carbohydrate-protein interaction, and protein denaturation.

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

    NASA Astrophysics Data System (ADS)

    Lwoya, Baraka; Albert, Julie

    2015-03-01

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

  13. Self-Assembly of Nanoclusters into Mono-, Few-, and Multilayered Sheets via Dipole-Induced Asymmetric van der Waals Attraction.

    PubMed

    Wu, Zhennan; Liu, Jiale; Li, Yanchun; Cheng, Ziyi; Li, Tingting; Zhang, Hao; Lu, Zhongyuan; Yang, Bai

    2015-06-23

    Two-dimensional (2D) nanomaterials possessing regular layered structures and versatile chemical composition are highly expected in many applications. Despite the importance of van der Waals (vdW) attraction in constructing and maintaining layered structures, the origin of 2D anisotropy is not fully understood, yet. Here, we report the 2D self-assembly of ligand-capped Au15 nanoclusters into mono-, few-, and multilayered sheets in colloidal solution. Both the experimental results and computer simulation reveal that the 2D self-assembly is initiated by 1D dipolar attraction common in nanometer-sized objects. The dense 1D attachment of Au15 leads to a redistribution of the surface ligands, thus generating asymmetric vdW attraction. The deliberate control of the coordination of dipolar and vdW attraction further allows to manipulate the thickness and morphologies of 2D self-assembly architectures.

  14. Cooperative thermodynamic control of selectivity in the self-assembly of rare earth metal-ligand helices.

    PubMed

    Johnson, Amber M; Young, Michael C; Zhang, Xing; Julian, Ryan R; Hooley, Richard J

    2013-11-27

    Metal-selective self-assembly with rare-earth cations is possible with suitable rigid, symmetrical bis-tridentate ligands. Kinetically controlled formation is initially observed, with smaller cations preferentially incorporated. Over time, the more thermodynamically favorable complexes with larger metals are formed. This thermodynamic control is a cooperative supramolecular phenomenon and only occurs upon multiple-metal-based self-assembly: single-metal ML3 analogues do not show reversible selectivity. The selectivity is dependent on small variations in lanthanide ionic radius and occurs despite identical coordination-ligand coordination geometries and minor size differences in the rare-earth metals.

  15. Core-shell self-assembly triggered via a thiol-disulfide exchange reaction for reduced glutathione detection and single cells monitoring

    PubMed Central

    Zhang, Zhen; Jiao, Yuting; Wang, Yuanyuan; Zhang, Shusheng

    2016-01-01

    A novel core-shell DNA self-assembly catalyzed by thiol-disulfide exchange reactions was proposed, which could realize GSH-initiated hybridization chain reaction (HCR) for signal amplification and molecules gathering. Significantly, these self-assembled products via electrostatic interaction could accumulate into prominent and clustered fluorescence-bright spots in single cancer cells for reduced glutathione monitoring, which will effectively drive cell monitoring into a new era. PMID:27412605

  16. Guided and magnetic self-assembly of tunable magnetoceptive gels

    NASA Astrophysics Data System (ADS)

    Tasoglu, S.; Yu, C. H.; Gungordu, H. I.; Guven, S.; Vural, T.; Demirci, U.

    2014-09-01

    Self-assembly of components into complex functional patterns at microscale is common in nature, and used increasingly in numerous disciplines such as optoelectronics, microfabrication, sensors, tissue engineering and computation. Here, we describe the use of stable radicals to guide the self-assembly of magnetically tunable gels, which we call ‘magnetoceptive’ materials at the scale of hundreds of microns to a millimeter, each can be programmed by shape and composition, into heterogeneous complex structures. Using paramagnetism of free radicals as a driving mechanism, complex heterogeneous structures are built in the magnetic field generated by permanent magnets. The overall magnetic signature of final structure is erased via an antioxidant vitamin E, subsequent to guided self-assembly. We demonstrate unique capabilities of radicals and antioxidants in fabrication of soft systems with heterogeneity in material properties, such as porosity, elastic modulus and mass density; then in bottom-up tissue engineering and finally, levitational and selective assembly of microcomponents.

  17. Dynamic self-assembly of microscale rotors and swimmers

    NASA Astrophysics Data System (ADS)

    Davies Wykes, Megan; Palacci, Jeremie; Adachi, Takuji; Ristroph, Leif; Liu, Yanpeng; Zhong, Xiao; Zhang, Jun; Ward, Michael; Shelley, Michael

    2015-11-01

    Self-assembly is a process found throughout nature and is often dynamic, requiring fuel to occur. Artificial examples are valuable both as aids to understanding biological systems and for developing manufacturing techniques for micron-scale machines. We will describe the behaviour of micron-scale rods, constructed of three equal length segments of gold, platinum and gold (Au-Pt-Au). When placed in a solution of hydrogen peroxide fuel, these are expected to create an extensile-like flow in the surrounding fluid. These immotile rods self-assemble into structures that exhibit the two fundamental types of motion: rotation and translation, in the form of steadily rotating stacks and T-shaped swimmers. This is a rare example of an artificial system where dynamic and reversible self-assembly results in ordered structures which exhibit emergent motility.

  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. Actinide Sequestration Using Self-Assembled Monolayers on Mesoporous Supports

    SciTech Connect

    Fryxell, Glen E.; Lin, Yuehe; Fiskum, Sandra K.; Birnbaum, Jerome C.; Wu, Hong; Kemner, K. M.; Kelly, Shelley

    2005-03-01

    Surfactant templated synthesis of mesoporous ceramics provides a versatile foundation upon which to create high efficiency environmental sorbents. These nanoporous ceramic oxides condense a huge amount of surface area into a very small volume. The ceramic oxide interface is receptive to surface functionalization through molecular self-assembly. The marriage of mesoporous ceramics with self-assembled monolayer chemistry creates a powerful new class of environmental sorbent materials called self-assembled monolayers on mesoporous supports (SAMMS). These SAMMS materials are highly efficient sorbents, whose interfacial chemistry can be fine-tuned to selectively sequester a specific target species, such as heavy metals, tetrahedral oxometallate anions and radionuclides. Details addressing the design, synthesis and characterization of SAMMS materials specifically designed to sequester actinides, of central importance to the environmental clean-up necessary after 40 years of weapons grade plutonium production, as well as evaluation of their binding affinities and kinetics are presented.

  20. Production of self-assembling biomaterials for tissue engineering

    PubMed Central

    Kyle, Stuart; Aggeli, Amalia; Ingham, Eileen; McPherson, Michael J.

    2009-01-01

    Self-assembling peptide-based biomaterials are being developed for use as 3D tissue engineering scaffolds and for therapeutic drug-release applications. Chemical synthesis provides custom-made peptides in small quantities, but production approaches based upon transgenic organisms might be more cost-effective for large-scale peptide production. Long lead times for developing appropriate animal clones or plant lines and potential negative public opinion are obstacles to these routes. Microbes, particularly safe organisms used in the food industry, offer a more rapid route to the large-scale production of recombinant self-assembling biomaterials. In this review, recent advances and challenges in the recombinant production of collagen, elastin and de novo designed self-assembling peptides are discussed. PMID:19497631

  1. Production of self-assembling biomaterials for tissue engineering.

    PubMed

    Kyle, Stuart; Aggeli, Amalia; Ingham, Eileen; McPherson, Michael J

    2009-07-01

    Self-assembling peptide-based biomaterials are being developed for use as 3D tissue engineering scaffolds and for therapeutic drug-release applications. Chemical synthesis provides custom-made peptides in small quantities, but production approaches based upon transgenic organisms might be more cost-effective for large-scale peptide production. Long lead times for developing appropriate animal clones or plant lines and potential negative public opinion are obstacles to these routes. Microbes, particularly safe organisms used in the food industry, offer a more rapid route to the large-scale production of recombinant self-assembling biomaterials. In this review, recent advances and challenges in the recombinant production of collagen, elastin and de novo designed self-assembling peptides are discussed.

  2. Guided and magnetic self-assembly of tunable magnetoceptive gels.

    PubMed

    Tasoglu, S; Yu, C H; Gungordu, H I; Guven, S; Vural, T; Demirci, U

    2014-09-01

    Self-assembly of components into complex functional patterns at microscale is common in nature, and used increasingly in numerous disciplines such as optoelectronics, microfabrication, sensors, tissue engineering and computation. Here, we describe the use of stable radicals to guide the self-assembly of magnetically tunable gels, which we call 'magnetoceptive' materials at the scale of hundreds of microns to a millimeter, each can be programmed by shape and composition, into heterogeneous complex structures. Using paramagnetism of free radicals as a driving mechanism, complex heterogeneous structures are built in the magnetic field generated by permanent magnets. The overall magnetic signature of final structure is erased via an antioxidant vitamin E, subsequent to guided self-assembly. We demonstrate unique capabilities of radicals and antioxidants in fabrication of soft systems with heterogeneity in material properties, such as porosity, elastic modulus and mass density; then in bottom-up tissue engineering and finally, levitational and selective assembly of microcomponents.

  3. Self-assembled liposomal nanoparticles in photodynamic therapy

    PubMed Central

    Sadasivam, Magesh; Avci, Pinar; Gupta, Gaurav K.; Lakshmanan, Shanmugamurthy; Chandran, Rakkiyappan; Huang, Ying-Ying; Kumar, Raj; Hamblin, Michael R.

    2013-01-01

    Photodynamic therapy (PDT) employs the combination of non-toxic photosensitizers (PS) together with harmless visible light of the appropriate wavelength to produce reactive oxygen species that kill unwanted cells. Because many PS are hydrophobic molecules prone to aggregation, numerous drug delivery vehicles have been tested to solubilize these molecules, render them biocompatible and enhance the ease of administration after intravenous injection. The recent rise in nanotechnology has markedly expanded the range of these nanoparticulate delivery vehicles beyond the well-established liposomes and micelles. Self-assembled nanoparticles are formed by judicious choice of monomer building blocks that spontaneously form a well-oriented 3-dimensional structure that incorporates the PS when subjected to the appropriate conditions. This self-assembly process is governed by a subtle interplay of forces on the molecular level. This review will cover the state of the art in the preparation and use of self-assembled liposomal nanoparticles within the context of PDT. PMID:24348377

  4. Self-assembly of tunable protein suprastructures from recombinant oleosin

    PubMed Central

    Vargo, Kevin B.; Parthasarathy, Ranganath; Hammer, Daniel A.

    2012-01-01

    Using recombinant amphiphilic proteins to self-assemble suprastructures would allow precise control over surfactant chemistry and the facile incorporation of biological functionality. We used cryo-TEM to confirm self-assembled structures from recombinantly produced mutants of the naturally occurring sunflower protein, oleosin. We studied the phase behavior of protein self-assembly as a function of solution ionic strength and protein hydrophilic fraction, observing nanometric fibers, sheets, and vesicles. Vesicle membrane thickness correlated with increasing hydrophilic fraction for a fixed hydrophobic domain length. The existence of a bilayer membrane was corroborated in giant vesicles through the localized encapsulation of hydrophobic Nile red and hydrophilic calcein. Circular dichroism revealed that changes in nanostructural morphology in this family of mutants was unrelated to changes in secondary structure. Ultimately, we envision the use of recombinant techniques to introduce novel functionality into these materials for biological applications. PMID:22753512

  5. Guided and magnetic self-assembly of tunable magnetoceptive gels

    PubMed Central

    Tasoglu, S.; Yu, C.H.; Gungordu, H.I.; Guven, S.; Vural, T.; Demirci, U.

    2014-01-01

    Self-assembly of components into complex functional patterns at microscale is common in nature, and used increasingly in numerous disciplines such as optoelectronics, microfabrication, sensors, tissue engineering and computation. Here, we describe the use of stable radicals to guide the self-assembly of magnetically tunable gels, which we call ‘magnetoceptive’ materials at the scale of hundreds of microns to a millimeter, each can be programmed by shape and composition, into heterogeneous complex structures. Using paramagnetism of free radicals as a driving mechanism, complex heterogeneous structures are built in the magnetic field generated by permanent magnets. The overall magnetic signature of final structure is erased via an antioxidant vitamin E, subsequent to guided self-assembly. We demonstrate unique capabilities of radicals and antioxidants in fabrication of soft systems with heterogeneity in material properties, such as porosity, elastic modulus and mass density; then in bottom-up tissue engineering and finally, levitational and selective assembly of microcomponents. PMID:25175148

  6. Dynamic self-assembly of coordination polymers in aqueous solution.

    PubMed

    Li, Wen; Kim, Yongju; Li, Jingfang; Lee, Myongsoo

    2014-08-07

    The construction of supramolecular polymers has been intensively pursued because the nanostructures formed through weak non-covalent interactions can be triggered by external stimuli leading to smart materials and sensors. Self-assemblies of coordination polymers consisting of metal ions and organic ligands in aqueous solution also provide particular contributions in this area. The main motivation for developing those coordination polymers originates from the value-added combination between metal ions and ligands. This review highlights the recent progress of the dynamic self-assembly of coordination polymers that result from the sophisticated molecular design, towards fabricating stimuli-responsive systems and bio-related materials. Dynamic structural changes and switchable physical properties triggered by various stimuli are summarized. Finally, the outlook for aqueous nanostructures originated from the dynamic self-assembly of coordination polymers is also presented.

  7. Self-Assemblies of Acicular Hollow Fe/C Nanostructures.

    PubMed

    Li, Wangchang; Qiao, Xiaojing; Li, Mingyu; Zheng, Qiuyu; Ren, Qingguo; Zhu, Y Q; Peng, H X

    2015-08-01

    Self-assemblies of acicular hollow Fe/C structures were synthesized using D-glucose monohydrate and ferric chloride as precursors by a simple hydrothermal process followed by carbonization at 800 °C. The self-assembled structures with an overall diameter of 15~20 µm composed of radially formed hollow needles from a central core with an average diameter of ca. 1 µm and a length up to 10 µm. The end of the needles was revealed to be a awl shape with a hollow structure formed during the self-assembly process and the subsequent heat treatment. The hollow structure was probably caused by the Kirkendall effect at 800 °C. The materials exhibit ferromagnetic characteristic with saturation magnetization (Ms), remanent magnetization (Mr), and coercivity (Hc) of 22.2 emu/g, 3 emu/g, and 151.22 Oe, respectively, with Ms much lower than that of Fe3O4.

  8. Self-Assembly of DNA-coated colloids

    NASA Astrophysics Data System (ADS)

    Pine, David

    DNA-coated particles have emerged as a powerful tool for programming the self-assembly of colloids and nanoparticles. The power of this approach lies in the highly specific molecular recognition properties of DNA and in the thermal reversibility of the interactions between DNA strands attached to different particles. These two properties taken together can, in principle, direct the bottom-up self-assembly of different materials into almost any desired structure. Here we discuss the self-assembly of single and multi-component crystals of DNA-coated colloids. This work is supported by the Army Research Office under MURI Grant Award Number W911NF-10-1-0518 and the MRSEC Program of the NSF under Award Number DMR-1420073.

  9. Functional self-assembled lipidic systems derived from renewable resources

    PubMed Central

    Silverman, Julian R.; Samateh, Malick; John, George

    2015-01-01

    Self-assembled lipidic amphiphile systems can create a variety of multi-functional soft materials with value-added properties. When employing natural reagents and following biocatalytic syntheses, self-assembling monomers may be inherently designed for degradation, making them potential alternatives to conventional and persistent polymers. By using non-covalent forces, self-assembled amphiphiles can form nanotubes, fibers, and other stimuli responsive architectures prime for further applied research and incorporation into commercial products. By viewing these lipid derivatives under a lens of green principles, there is the hope that in developing a structure–function relationship and functional smart materials that research may remain safe, economic, and efficient. PMID:26766923

  10. Self-Assembly in Biosilicification and Biotemplated Silica Materials

    PubMed Central

    Fernandes, Francisco M.; Coradin, Thibaud; Aimé, Carole

    2014-01-01

    During evolution, living organisms have learned to design biomolecules exhibiting self-assembly properties to build-up materials with complex organizations. This is particularly evidenced by the delicate siliceous structures of diatoms and sponges. These structures have been considered as inspiration sources for the preparation of nanoscale and nanostructured silica-based materials templated by the self-assembled natural or biomimetic molecules. These templates range from short peptides to large viruses, leading to biohybrid objects with a wide variety of dimensions, shapes and organization. A more recent strategy based on the integration of biological self-assembly as the driving force of silica nanoparticles organization offers new perspectives to elaborate highly-tunable, biofunctional nanocomposites. PMID:28344249

  11. Equation of State for Phospholipid Self-Assembly.

    PubMed

    Marsh, Derek

    2016-01-05

    Phospholipid self-assembly is the basis of biomembrane stability. The entropy of transfer from water to self-assembled micelles of lysophosphatidylcholines and diacyl phosphatidylcholines with different chain lengths converges to a common value at a temperature of 44°C. The corresponding enthalpies of transfer converge at ∼-18°C. An equation of state for the free energy of self-assembly formulated from this thermodynamic data depends on the heat capacity of transfer as the sole parameter needed to specify a particular lipid. For lipids lacking calorimetric data, measurement of the critical micelle concentration at a single temperature suffices to define an effective heat capacity according to the model. Agreement with the experimental temperature dependence of the critical micelle concentration is then good. The predictive powers should extend also to amphiphile partitioning and the kinetics of lipid-monomer transfer.

  12. Investigating collagen self-assembly with optical tweezers microrheology

    NASA Astrophysics Data System (ADS)

    Forde, Nancy; Shayegan, Marjan; Altindal, Tuba

    Collagen is the fundamental structural protein in vertebrates. Assembled from individual triple-helical proteins to make strong fibres, collagen is a beautiful example of a hierarchical self-assembling system. Using optical tweezers to perform microrheology measurements, we explore the dynamics of interactions between collagens responsible for their self-assembly and examine the development of heterogeneous mechanics during assembly into fibrillar gels. Telopeptides, short non-helical regions that flank the triple helix, have long been known to facilitate fibril self-assembly. We find that their removal not only slows down fibril nucleation but also results in a significant frequency-dependent reduction in the elastic modulus of collagens in solution. We interpret these results in terms of a model in which telopeptides facilitate transient intermolecular interactions, which enhance network connectivity in solution and lead to more rapid assembly in fibril-forming conditions. Current address: Department of Physics, McGill University.

  13. Nanoscale forces and their uses in self-assembly.

    PubMed

    Bishop, Kyle J M; Wilmer, Christopher E; Soh, Siowling; Grzybowski, Bartosz A

    2009-07-01

    The ability to assemble nanoscopic components into larger structures and materials depends crucially on the ability to understand in quantitative detail and subsequently "engineer" the interparticle interactions. This Review provides a critical examination of the various interparticle forces (van der Waals, electrostatic, magnetic, molecular, and entropic) that can be used in nanoscale self-assembly. For each type of interaction, the magnitude and the length scale are discussed, as well as the scaling with particle size and interparticle distance. In all cases, the discussion emphasizes characteristics unique to the nanoscale. These theoretical considerations are accompanied by examples of recent experimental systems, in which specific interaction types were used to drive nanoscopic self-assembly. Overall, this Review aims to provide a comprehensive yet easily accessible resource of nanoscale-specific interparticle forces that can be implemented in models or simulations of self-assembly processes at this scale.

  14. Self-Assembly in Biosilicification and Biotemplated Silica Materials.

    PubMed

    Fernandes, Francisco M; Coradin, Thibaud; Aimé, Carole

    2014-09-04

    During evolution, living organisms have learned to design biomolecules exhibiting self-assembly properties to build-up materials with complex organizations. This is particularly evidenced by the delicate siliceous structures of diatoms and sponges. These structures have been considered as inspiration sources for the preparation of nanoscale and nanostructured silica-based materials templated by the self-assembled natural or biomimetic molecules. These templates range from short peptides to large viruses, leading to biohybrid objects with a wide variety of dimensions, shapes and organization. A more recent strategy based on the integration of biological self-assembly as the driving force of silica nanoparticles organization offers new perspectives to elaborate highly-tunable, biofunctional nanocomposites.

  15. Equation of State for Phospholipid Self-Assembly

    PubMed Central

    Marsh, Derek

    2016-01-01

    Phospholipid self-assembly is the basis of biomembrane stability. The entropy of transfer from water to self-assembled micelles of lysophosphatidylcholines and diacyl phosphatidylcholines with different chain lengths converges to a common value at a temperature of 44°C. The corresponding enthalpies of transfer converge at ∼−18°C. An equation of state for the free energy of self-assembly formulated from this thermodynamic data depends on the heat capacity of transfer as the sole parameter needed to specify a particular lipid. For lipids lacking calorimetric data, measurement of the critical micelle concentration at a single temperature suffices to define an effective heat capacity according to the model. Agreement with the experimental temperature dependence of the critical micelle concentration is then good. The predictive powers should extend also to amphiphile partitioning and the kinetics of lipid-monomer transfer. PMID:26745421

  16. Associative Pattern Recognition Through Macro-molecular Self-Assembly

    NASA Astrophysics Data System (ADS)

    Zhong, Weishun; Schwab, David J.; Murugan, Arvind

    2017-05-01

    We show that macro-molecular self-assembly can recognize and classify high-dimensional patterns in the concentrations of N distinct molecular species. Similar to associative neural networks, the recognition here leverages dynamical attractors to recognize and reconstruct partially corrupted patterns. Traditional parameters of pattern recognition theory, such as sparsity, fidelity, and capacity are related to physical parameters, such as nucleation barriers, interaction range, and non-equilibrium assembly forces. Notably, we find that self-assembly bears greater similarity to continuous attractor neural networks, such as place cell networks that store spatial memories, rather than discrete memory networks. This relationship suggests that features and trade-offs seen here are not tied to details of self-assembly or neural network models but are instead intrinsic to associative pattern recognition carried out through short-ranged interactions.

  17. Self-assembled tunable networks of sticky colloidal particles

    NASA Astrophysics Data System (ADS)

    Demortière, Arnaud; Snezhko, Alexey; Sapozhnikov, Maksim V.; Becker, Nicholas; Proslier, Thomas; Aranson, Igor S.

    2014-01-01

    Surfaces decorated with dense arrays of microscopic fibres exhibit unique materials properties, including superhydrophobicity and low friction. Nature relies on ‘hairy’ surfaces to protect blood capillaries from wear and infection (endothelial glycocalyx). Here we report on the discovery of self-assembled tunable networks of microscopic polymer fibres ranging from wavy colloidal ‘fur’ to highly interconnected networks. The networks emerge via dynamic self-assembly in an alternating electric field from a non-aqueous suspension of ‘sticky’ polymeric colloidal particles with a controlled degree of polymerization. The resulting architectures are tuned by the frequency and amplitude of the electric field and surface properties of the particles. We demonstrate, using atomic layer deposition, that the networks can serve as a template for a transparent conductor. These self-assembled tunable materials are promising candidates for large surface area electrodes in batteries and organic photovoltaic cells, as well as for microfluidic sensors and filters.

  18. Actinide sequestration using self-assembled monolayers on mesoporous supports.

    PubMed

    Fryxell, Glen E; Lin, Yuehe; Fiskum, Sandy; Birnbaum, Jerome C; Wu, Hong; Kemner, Ken; Kelly, Shelley

    2005-03-01

    Surfactant templated synthesis of mesoporous ceramics provides a versatile foundation upon which to create high efficiency environmental sorbents. These nanoporous ceramic oxides condense a huge amount of surface area into a very small volume. The ceramic oxide interface is receptive to surface functionalization through molecular self-assembly. The marriage of mesoporous ceramics with self-assembled monolayer chemistry creates a powerful new class of environmental sorbent materials called self-assembled monolayers on mesoporous supports (SAMMS). These SAMMS materials are highly efficient sorbents whose interfacial chemistry can be fine-tuned to selectively sequester a specific target species, such as heavy metals, tetrahedral oxometalate anions, and radionuclides. Details addressing the design, synthesis, and characterization of SAMMS materials specifically designed to sequester actinides, of central importance to the environmental cleanup necessary after 40 years of weapons-grade plutonium production, as well as evaluation of their binding affinities and kinetics are presented.

  19. Hydrodynamic Self-Assembly of Topographical Patterns on Soft Materials

    SciTech Connect

    Kumar, Satish

    2016-01-06

    The objective of this project is to use theoretical tools to explore fundamentally new ways of creating and controlling surface topography on soft materials (e.g., polymeric liquids, gels, colloidal suspensions) that make use of principles from hydrodynamics and self-assembly. Surface topography is known to have a significant impact on the optical, adhesive, and wetting properties of materials, so improved fundamental understanding of how to create and control it will help enable the tailoring of these properties to desired specifications. Self-assembly is the spontaneous organization of an ordered structure, and hydrodynamics often plays an important role in the self-assembly of soft materials. This research supported through this project has led to the discovery of a number of novel phenomena that are described in published journal articles. In this way, the research significantly adds to the fundamental understanding of the topics investigated.

  20. Intercalators as molecular chaperones in DNA self-assembly.

    PubMed

    Greschner, Andrea A; Bujold, Katherine E; Sleiman, Hanadi F

    2013-07-31

    DNA intercalation has found many diagnostic and therapeutic applications. Here, we propose the use of simple DNA intercalators, such as ethidium bromide, as tools to facilitate the error-free self-assembly of DNA nanostructures. We show that ethidium bromide can influence DNA self-assembly, decrease the formation of oligomeric side products, and cause libraries of multiple equilibrating structures to converge into a single product. Using a variety of 2D- and 3D-DNA systems, we demonstrate that intercalators present a powerful alternative for the adjustment of strand-end alignment, favor the formation of fully duplexed "closed" structures, and create an environment where the smallest, most stable structure is formed. A new 3D-DNA motif, the ninja star, was self-assembled in quantitative yield with this method. Moreover, ethidium bromide can be readily removed using isoamyl alcohol extractions combined with intercalator-specific spin columns, thereby yielding the desired ready-to-use DNA structure.

  1. Scanning tunneling microscopy studies of mixed self-assembled monolayers

    NASA Astrophysics Data System (ADS)

    Raigoza, Annette Fernandez

    This thesis examines the formation of multicomponent self-assembled mono-layers (SAMs) on the Au(111) surface using scanning tunneling microscopy. Two methods, sequential adsorption and coadsorption, are used to create these mixed SAMs. In the sequential adsorption experiments, a clean Au(111)-on-mica sub-strate is exposed to the first molecular species and then this adsorbate-covered sample is exposed to the second molecular species. Alternately, in the coadsorption experiments, a gold surface is exposed to both adsorbates simultaneously. Exposing a coronene- or dithiocarbamate-covered surface to excess thiol in the vapor phase results in a drastic restructuring of the initial surface. This is primarily driven by the kinetics of the octanethiol monolayer formation process, but the extent to which this happens is dependent on the molecule-molecule and molecule-surface interactions of the adsorbate due to the initial coverage and order of the monolayer. An octanethiolate monolayer is also substantially modified when immersed in a solution containing dithiocarbamate (DTC). Defects in the octanethiol monolayer are prime sites for molecular exchange. A surplus of DTC in the solution drives substitution that can lead to the complete removal of thiol from the surface. When a Au(111) surface is exposed to solutions containing both octanethiol and dithiocarbamate (DTC), both molecular species compete for available ad- sorption sites. At equal octanethiol-to-DTC ratios, molecular exchange hinders octanethiol monolayer formation. Higher octanethiol concentration in solution results in the incorporation of thiol into the resulting monolayer, with a strong dependence on the chain length of the DTC molecules.

  2. Controlled evaporative self-assembly of poly(acrylic acid) in a confined geometry for fabricating patterned polymer brushes.

    PubMed

    Men, Yonghong; Xiao, Peng; Chen, Jing; Fu, Jun; Huang, Youju; Zhang, Jiawei; Xie, Zhengchao; Wang, Wenqin; Chen, Tao

    2014-04-29

    A simple yet robust approach was exploited to fabricate large-scaled patterned polymer brushes by combining controlled evaporative self-assembly (CESA) in a confined geometry and self-initiated photografting and photopolymerization (SIPGP). Our method was carried out without any sophisticated instruments, free of lithography, overcoming current difficulties in fabricating polymer patterns by using complex instruments.

  3. 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.

  4. Emerin self-assembly mechanism: role of the LEM domain.

    PubMed

    Samson, Camille; Celli, Florian; Hendriks, Kitty; Zinke, Maximilian; Essawy, Nada; Herrada, Isaline; Arteni, Ana-Andreea; Theillet, François-Xavier; Alpha-Bazin, Béatrice; Armengaud, Jean; Coirault, Catherine; Lange, Adam; Zinn-Justin, Sophie

    2017-01-01

    At the nuclear envelope, the inner nuclear membrane protein emerin contributes to the interface between the nucleoskeleton and the chromatin. Emerin is an essential actor of the nuclear response to a mechanical signal. Genetic defects in emerin cause Emery-Dreifuss muscular dystrophy. It was proposed that emerin oligomerization regulates nucleoskeleton binding, and impaired oligomerization contributes to the loss of function of emerin disease-causing mutants. We here report the first structural characterization of emerin oligomers. We identified an N-terminal emerin region from amino acid 1 to amino acid 132 that is necessary and sufficient for formation of long curvilinear filaments. In emerin monomer, this region contains a globular LEM domain and a fragment that is intrinsically disordered. Solid-state nuclear magnetic resonance analysis identifies the LEM β-fragment as part of the oligomeric structural core. However, the LEM domain alone does not self-assemble into filaments. Additional residues forming a β-structure are observed within the filaments that could correspond to the unstructured region in emerin monomer. We show that the delK37 mutation causing muscular dystrophy triggers LEM domain unfolding and increases emerin self-assembly rate. Similarly, inserting a disulfide bridge that stabilizes the LEM folded state impairs emerin N-terminal region self-assembly, whereas reducing this disulfide bridge triggers self-assembly. We conclude that the LEM domain, responsible for binding to the chromatin protein BAF, undergoes a conformational change during self-assembly of emerin N-terminal region. The consequences of these structural rearrangement and self-assembly events on emerin binding properties are discussed. © 2016 The Authors Journal compilation © 2016 FEBS.

  5. Recombinant self-assembling peptides as biomaterials for tissue engineering

    PubMed Central

    Kyle, Stuart; Aggeli, Amalia; Ingham, Eileen; McPherson, Michael J.

    2010-01-01

    Synthetic nanostructures based on self-assembling systems that aim to mimic natural extracellular matrix are now being used as substrates in tissue engineering applications. Peptides are excellent starting materials for the self-assembly process as they can be readily synthesised both chemically and biologically. P11-4 is an 11 amino acid peptide that undergoes triggered self-assembly to form a self-supporting hydrogel. It exists as unimers of random coil conformations in water above pH 7.5 but at low pH adopts an antiparallel β-sheet conformation. It also self-assembles under physiological conditions in a concentration-dependent manner. Here we describe an unimer P11-4 production system and the use of a simple site-directed mutagenesis approach to generate a series of other P11-family peptide expression vectors. We have developed an efficient purification strategy for these peptide biomaterials using a simple procedure involving chemical cleavage with cyanogen bromide then repeated filtration, lyophilisation and wash steps. We report peptide-fusion protein yields of ca. 4.64 g/L and we believe the highest reported recovery of a recombinant self-assembling peptide at 203 mg/L of pure recombinant P11-4. This peptide forms a self-supporting hydrogel under physiological conditions with essentially identical physico-chemical properties to the chemically synthesised peptide. Critically it also displays excellent cytocompatibility when tested with primary human dermal fibroblasts. This study demonstrates that high levels of a series of recombinant self-assembling peptides can be purified using a simple process for applications as scaffolds in tissue engineering. PMID:20932572

  6. Probing peptide amphiphile self-assembly in blood serum.

    PubMed

    Ghosh, Arijit; Buettner, Christian J; Manos, Aaron A; Wallace, Ashley J; Tweedle, Michael F; Goldberger, Joshua E

    2014-12-08

    There has been recent interest in designing smart diagnostic or therapeutic self-assembling peptide or polymeric materials that can selectively undergo morphological transitions to accumulate at a disease site in response to specific stimuli. Developing approaches to probe these self-assembly transitions in environments that accurately amalgamate the diverse plethora of proteins, biomolecules, and salts of blood is essential for creating systems that function in vivo. Here, we have developed a fluorescence anisotropy approach to probe the pH-dependent self-assembly transition of peptide amphiphile (PA) molecules that transform from spherical micelles at pH 7.4 to nanofibers under more acidic pH's in blood serum. By mixing small concentrations of a Ru(bipy)3(2+)-tagged PA with a Gd(DO3A)-tagged PA having the same lipid-peptide sequence, we showed that the pH dependence of self-assembly is minimally affected and can be monitored in mouse blood serum. These PA vehicles can be designed to transition from spherical micelles to nanofibers in the pH range 7.0-7.4 in pure serum. In contrast to the typical notion of serum albumin absorbing isolated surfactant molecules and disrupting self-assembly, our experiments showed that albumin does not bind these anionic PAs and instead promotes nanofibers due to a molecular crowding effect. Finally, we created a medium that replicates the transition pH in serum to within 0.08 pH units and allows probing self-assembly behavior using conventional spectroscopic techniques without conflicting protein signals, thus simplifying the development pathway from test tube to in vivo experimentation for stimuli-responsive materials.

  7. Interfacial and mechanical properties of self-assembling systems

    NASA Astrophysics Data System (ADS)

    Carvajal, Daniel

    Self-assembly is a fascinating phenomena where interactions between small subunits allow them to aggregate and form complex structures that can span many length scales. These self-assembled structures are especially important in biology where they are necessary for life as we know it. This dissertation is a study of three very different self-assembling systems, all of which have important connections to biology and biological systems. Drop shape analysis was used to study the interfacial assembly of amphiphilic block copolymers at the oil/water interface. When biologically functionalyzed copolymers are used, this system can serve as a model for receptor-ligand interactions that are used by cells to perform many activities, such as interact with their surroundings. The physical properties of a self-assembling membrane system were quantified using membrane inflation and swelling experiments. These types of membranes may have important applications in medicine such as drug eluting (growth factor eluting) scaffolds to aid in wound healing. The factors affecting the properties of bis(leucine) oxalamide gels were also explored. We believe that this particular system will serve as an appropriate model for biological gels that are made up of fiber-like and/or rod-like structures. During the course of the research presented in this dissertation, many new techniques were developed specifically to allow/aid the study of these distinct self-assembling systems. For example, numerical methods were used to predict drop stability for drop shape analysis experiments and the methods used to create reproducibly create self-assembling membranes were developed specifically for this purpose. The development of these new techniques is an integral part of the thesis and should aid future students who work on these projects. A number ongoing projects and interesting research directions for each one of the projects is also presented.

  8. Biomimetic Remineralization of Carious Lesions by Self-Assembling Peptide.

    PubMed

    Kind, L; Stevanovic, S; Wuttig, S; Wimberger, S; Hofer, J; Müller, B; Pieles, U

    2017-07-01

    Caries is the most common disease in the world. Great efforts have been undertaken for prevention and to identify a regenerative treatment solution for dental caries. Self-assembling β-sheet forming peptides have previously shown to form 3-dimensional fiber networks supporting tissue regeneration. In particular, the self-assembling peptide P11-4 has shown potential in the treatment and prevention of dental caries. It has previously been shown that application of monomeric P11-4 solution to early carious lesions can increase net mineral gain by forming de novo hydroxyapatite crystals. The hypothesis for the mode of action was that monomeric self-assembling peptide P11-4 diffuses into the subsurface lesion body and assembles therein into higher order fibrils, facilitating mineralization of the subsurface volume by mimicking the natural biomineralization of the tooth enamel, and it remains within the lesion body as a scaffold built-in by the newly formed hydroxyapatite. The aim of the present study was to investigate the mechanism of action of the self-assembling peptide P11-4 supporting mineralization of carious enamel. By various analytical methods, it could be shown that the self-assembling peptide P11-4 diffuses into the subsurface lesion, assembles into higher formed aggregates throughout the whole volume of the lesion, and supports nucleation of de novo hydroxyapatite nanocrystals and consequently results in increased mineral density within the subsurface carious lesion. The results showed that the application of self-assembling peptide P11-4 can facilitate the subsurface regeneration of the enamel lesion by supporting de novo mineralization in a similar mode of action as has been shown for the natural formation of dental enamel.

  9. 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

  10. Dynamic Self-assembly of Non-Brownian Spheres.

    NASA Astrophysics Data System (ADS)

    Salazar, J. Marcos; Simon, J. Marc; Ruiz-Suárez, J. Carlos; Peñuñuri, Francisco; Carvente, Osvaldo

    2017-06-01

    Granular self-assembly of confined non-Brownian spheres under gravity is studied by Molecular Dynamics simulations. Starting from a disordered phase, dry or cohesive spheres organize, by vibrational annealing into BCT or FCC structures, respectively. During the self-assembling process, isothermal and isodense points are observed. The existence of such points indicates that both granular temperature and packing fraction undergo an inversion process. Around the isothermal point, a sudden growth of beads having the maximum coordination number takes place. We show by a density fluctuation analysis that a transition form a disordered phase to a crystalline structure may be associated to a first-order transition.

  11. Self-assembly of colloidal pyramids in magnetic fields.

    PubMed

    Helseth, L E

    2005-08-02

    We study routes toward the construction of 2D colloidal pyramids. We find that magnetic beads may self-assemble into pyramids near a nonmagnetic 1D boundary as long as the number of beads in the pyramid does not exceed 10. We have also found that a strong magnetic field gradient could act as a boundary, thus assisting the self-assembly of magnetic colloids in water, and have observed the formation of stable microscopic pyramids within a certain magnetic field range. Our results indicate that colloidal pyramids can be formed in a number of ways by utilizing external fields.

  12. Scanning tunneling microscopy of self-assembled viral nanostructures

    NASA Astrophysics Data System (ADS)

    Anacleto, Benjamin; Steinsultz, Nat; Sharma, Prashant

    2010-03-01

    We use scanning tunneling microscopy to investigate self-assembled monolayers of M13 bacteriophages on graphite surface. The bacteriophages we use have gold binding peptide motifs on their outer protein coat (˜1μm long, ˜10 nm diameter) allowing us to self-assemble gold nanoparticles on graphite. Using scanning tunneling microscopy we are able to resolve sub-molecular structure of the protein coat of M13 bacteriophage. Scanning tunneling spectroscopy allows us to study the binding of gold nanoparticles to the peptide motif on the bacteriophage.

  13. 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.

  14. Designing isotropic interactions for self-assembly of complex lattices.

    PubMed

    Edlund, E; Lindgren, O; Jacobi, M Nilsson

    2011-08-19

    We present a direct method for solving the inverse problem of designing isotropic potentials that cause self-assembly into target lattices. Each potential is constructed by matching its energy spectrum to the reciprocal representation of the lattice to guarantee that the desired structure is a ground state. We use the method to self-assemble complex lattices not previously achieved with isotropic potentials, such as a snub square tiling and the kagome lattice. The latter is especially interesting because it provides the crucial geometric frustration in several proposed spin liquids. © 2011 American Physical Society

  15. Self-Assembled Hydrogel Nanoparticles for Drug Delivery Applications

    PubMed Central

    Gonçalves, Catarina; Pereira, Paula; Gama, Miguel

    2010-01-01

    Hydrogel nanoparticles—also referred to as polymeric nanogels or macromolecular micelles—are emerging as promising drug carriers for therapeutic applications. These nanostructures hold versatility and properties suitable for the delivery of bioactive molecules, namely of biopharmaceuticals. This article reviews the latest developments in the use of self-assembled polymeric nanogels for drug delivery applications, including small molecular weight drugs, proteins, peptides, oligosaccharides, vaccines and nucleic acids. The materials and techniques used in the development of self-assembling nanogels are also described.

  16. Leveraging symmetry to predict self-assembly of multiple polymers

    NASA Astrophysics Data System (ADS)

    Lin, Milo M.

    2017-09-01

    Protein self-assembly is fundamental to biological function and disease. Experimentally, the atomic-level structure is difficult to obtain and the assembly mechanism is poorly understood. The large number of possible states accessible to such systems limits computational prediction. Here, I introduce a new computational approach that enforces conformational symmetry, whereby all chains in the system adopt the same conformation. Using this approach on a 2D lattice, a designed multi-chain conformation is found more than four orders of magnitude faster than existing approaches. Furthermore, the free energy landscape can be efficiently computed, showing potential for enabling atomistic prediction of protein self-assembly.

  17. DNA biosensors based on self-assembled carbon nanotubes.

    PubMed

    Wang, S G; Wang, Ruili; Sellin, P J; Zhang, Qing

    2004-12-24

    DNA biosensors based on self-assembled multi-walled carbon nanotubes (MWNTs) were described in this paper, in which the probe DNA oligonucleotides were immobilized by forming covalent amide bonds between carboxyl groups at the nanotubes and amino groups at the ends of the DNA oligonucleotides. Hybridization between the probe and target DNA oligonucleotides was confirmed by the changes in the voltammetric peak of the indicator of methylene blue. Our results demonstrate that the DNA biosensors based on self-assembled MWNTs had a higher hybridization efficiency compared to those based on random MWNTs. In addition, the developed DNA biosensors also had a high selectivity of hybridization detection.

  18. Thermally triggered self-assembly of folded proteins into vesicles.

    PubMed

    Park, Won Min; Champion, Julie A

    2014-12-31

    We report thermally triggered self-assembly of folded proteins into vesicles that incorporates globular proteins as building blocks. Leucine zipper coiled coils were combined with either globular proteins or elastin-like polypeptides as recombinant fusion proteins, which form "rod-coil" and "globule-rod-coil" protein complex amphiphiles. In aqueous solution, they self-assembled into hollow vesicles via temperature-responsive inverse phase transition. The characteristic of the protein vesicle membranes enables preferential encapsulation of simultaneously formed protein coacervate. Furthermore, the type of encapsulated cargo extends to small molecules and nanoparticles. Our approach offers a versatile strategy to create protein vesicles as vehicles with biological functionality.

  19. Self-assembly patterning of organic molecules on a surface

    DOEpatents

    Pan, Minghu; Fuentes-Cabrera, Miguel; Maksymovych, Petro; Sumpter, Bobby G.; Li, Qing

    2017-04-04

    The embodiments disclosed herein include all-electron control over a chemical attachment and the subsequent self-assembly of an organic molecule into a well-ordered three-dimensional monolayer on a metal surface. The ordering or assembly of the organic molecule may be through electron excitation. Hot-electron and hot-hole excitation enables tethering of the organic molecule to a metal substrate, such as an alkyne group to a gold surface. All-electron reactions may allow a direct control over the size and shape of the self-assembly, defect structures and the reverse process of molecular disassembly from single molecular level to mesoscopic scale.

  20. Backfilled, self-assembled monolayers and methods of making same

    DOEpatents

    Fryxell, Glen E [Kennewick, WA; Zemanian, Thomas S [Richland, WA; Addleman, R Shane [Benton City, WA; Aardahl, Christopher L [Sequim, WA; Zheng, Feng [Richland, WA; Busche, Brad [Raleigh, NC; Egorov, Oleg B [West Richland, WA

    2009-06-30

    Backfilled, self-assembled monolayers and methods of making the same are disclosed. The self-assembled monolayer comprises at least one functional organosilane species and a substantially random dispersion of at least one backfilling organosilane species among the functional organosilane species, wherein the functional and backfilling organosilane species have been sequentially deposited on a substrate. The method comprises depositing sequentially a first organosilane species followed by a backfilling organosilane species, and employing a relaxation agent before or during deposition of the backfilling organosilane species, wherein the first and backfilling organosilane species are substantially randomly dispersed on a substrate.

  1. Self-Assembly of Octopus Nanoparticles into Pre-Programmed Finite Clusters

    NASA Astrophysics Data System (ADS)

    Halverson, Jonathan; Tkachenko, Alexei

    2012-02-01

    The precise control of the spatial arrangement of nanoparticles (NP) is often required to take full advantage of their novel optical and electronic properties. NPs have been shown to self-assemble into crystalline structures using either patchy surface regions or complementary DNA strands to direct the assembly. Due to a lack of specificity of the interactions these methods lead to only a limited number of structures. An emerging approach is to bind ssDNA at specific sites on the particle surface making so-called octopus NPs. Using octopus NPs we investigate the inverse problem of the self-assembly of finite clusters. That is, for a given target cluster (e.g., arranging the NPs on the vertices of a dodecahedron) what are the minimum number of complementary DNA strands needed for the robust self-assembly of the cluster from an initially homogeneous NP solution? Based on the results of Brownian dynamics simulations we have compiled a set of design rules for various target clusters including cubes, pyramids, dodecahedrons and truncated icosahedrons. Our approach leads to control over the kinetic pathway and has demonstrated nearly perfect yield of the target.

  2. Composition and method for self-assembly and mineralization of peptide amphiphiles

    DOEpatents

    Stupp, Samuel I.; Beniash, Elia; Hartgerink, Jeffrey D.

    2009-06-30

    The present invention is directed to a composition useful for making homogeneously mineralized self assembled peptide-amphiphile nanofibers and nanofiber gels. The composition is generally a solution comprised of a positively or negatively charged peptide-amphiphile and a like signed ion from the mineral. Mixing this solution with a second solution containing a dissolved counter-ion of the mineral and/or a second oppositely charged peptide amphiphile, results in the rapid self assembly of the peptide-amphiphiles into a nanofiber gel and templated mineralization of the ions. Templated mineralization of the initially dissolved mineral cations and anions in the mixture occurs with preferential orientation of the mineral crystals along the fiber surfaces within the nanofiber gel. One advantage of the present invention is that it results in homogenous growth of the mineral throughout the nanofiber gel. Another advantage of the present invention is that the nanofiber gel formation and mineralization reactions occur in a single mixing step and under substantially neutral or physiological pH conditions. These homogeneous nanostructured composite materials are useful for medical applications especially the regeneration of damaged bone in mammals. This invention is directed to the synthesis of peptide-amphiphiles with more than one amphiphilic moment and to supramolecular compositions comprised of such multi-dimensional peptide-amphiphiles. Supramolecular compositions can be formed by self assembly of multi-dimensional peptide-amphiphiles by mixing them with a solution comprising a monovalent cation.

  3. Composition and method for self-assembly and mineralization of peptide-amphiphiles

    DOEpatents

    Stupp, Samuel I [Chicago, IL; Beniash, Elia [Newton, MA; Hartgerink, Jeffrey D [Pearland, TX

    2012-02-28

    The present invention is directed to a composition useful for making homogeneously mineralized self assembled peptide-amphiphile nanofibers and nanofiber gels. The composition is generally a solution comprised of a positively or negatively charged peptide-amphiphile and a like signed ion from the mineral. Mixing this solution with a second solution containing a dissolved counter-ion of the mineral and/or a second oppositely charged peptide amphiphile, results in the rapid self assembly of the peptide-amphiphiles into a nanofiber gel and templated mineralization of the ions. Templated mineralization of the initially dissolved mineral cations and anions in the mixture occurs with preferential orientation of the mineral crystals along the fiber surfaces within the nanofiber gel. One advantage of the present invention is that it results in homogenous growth of the mineral throughout the nanofiber gel. Another advantage of the present invention is that the nanofiber gel formation and mineralization reactions occur in a single mixing step and under substantially neutral or physiological pH conditions. These homogeneous nanostructured composite materials are useful for medical applications especially the regeneration of damaged bone in mammals. This invention is directed to the synthesis of peptide-amphiphiles with more than one amphiphilic moment and to supramolecular compositions comprised of such multi-dimensional peptide-amphiphiles. Supramolecular compositions can be formed by self assembly of multi-dimensional peptide-amphiphiles by mixing them with a solution comprising a monovalent cation.

  4. Integrating DNA-strand-displacement circuitry with self-assembly of spherical nucleic acids.

    PubMed

    Yao, Dongbao; Song, Tingjie; Sun, Xianbao; Xiao, Shiyan; Huang, Fujian; Liang, Haojun

    2015-11-11

    Programmable and algorithmic behaviors of DNA molecules allow one to control the structures of DNA-assembled materials with nanometer precision and to construct complex networks with digital and analog behaviors. Here we developed a way of integrating a DNA-strand-displacement circuit with self-assembly of spherical nucleic acids, wherein a single DNA strand was used to initiate and catalyze the operation of upstream circuits to release a single strand that subsequently triggers self-assembly of spherical nucleic acids in downstream circuits, realizing a programmable kinetic control of self-assembly of spherical nucleic acids. Through utilizing this method, single-nucleotide polymorphisms or indels occurring at different positions of a sequence of oligonucleotide were unambiguously discriminated. We provide here a sophisticated way of combining the DNA-strand-displacement-based characteristic of DNA with the distinct assembly properties of inorganic nanoparticles, which may find broad potential applications in the fabrication of a wide range of complex multicomponent devices and architectures.

  5. 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.

  6. Multiscale directed self-assembly of composite microgels in complex electric fields.

    PubMed

    Crassous, Jérôme J; Demirörs, Ahmet F

    2016-12-21

    This study explored the application of localized electric fields for reversible directed self-assembly of colloidal particles in 3 dimensions. Electric field microgradients, arising from the use of micro-patterned electrodes, were utilized to direct the localization and self-assembly of polarizable (charged) particles resulting from a combination of dielectrophoretic and multipolar forces. Deionized dispersions of spherical and ellipsoidal core-shell microgels were employed for investigating their assembly under an external alternating electric field. We demonstrated that the frequency of the field allowed for an exquisite control over the localization of the particles and their self-assembled structures near the electrodes. We extended this approach to concentrated binary dispersions consisting of polarizable and less polarizable composite microgels. Furthermore, we utilized the thermosensitivity of the microgels to adjust the effective volume fraction and the dynamics of the system, which provided the possibility to dynamically "solidify" the assembly of the field-responsive particles by a temperature quench from their initial fluid state into an arrested crystalline state. Reversible solidification enables us to re-write/reconstruct various 3 dimensional assemblies by varying the applied field frequency.

  7. Covalently Connected Polymer-Protein Nanostructures Fabricated by a Reactive Self-Assembly Approach.

    PubMed

    Ju, Yuanyuan; Xing, Cheng; Wu, Dongxia; Wu, Yunfang; Wang, Lianyong; Zhao, Hanying

    2017-03-08

    The synthesis of polymer-protein nanostructures opens up a new avenue for the development of new biomaterials. In this research, covalently connected polymer-protein nanostructures were fabricated through a reactive self-assembly approach. Poly(tert-butyl methacrylate-co-pyridyl disulfide methacrylamide) (PtBMA-co-PPDSMA) was synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization. Covalently connected nanostructures (CCNs) with hydrophobic polymer cores and hydrophilic protein coronae were prepared by adding solutions of PtBMA-co-PPDSMA/DMF to aqueous solutions of bovine serum albumin (BSA). The thiol-disulfide exchange reaction between pyridyl disulfide groups on the polymer chains and thiol groups on the protein molecules plays a key role in the fabrication of CCNs. The self-assembly process was investigated by dynamic light scattering (DLS) and stopped-flow techniques. DLS results indicated that the sizes of the CCNs were determined by the initial polymer concentration, the BSA concentration, and the average number of thiol groups on BSA molecules. TEM and sodium dodecyl sulfate polyacrylamide gel electrophoresis were used to analyze the nanostructures. Far-UV circular dichroism results demonstrated that the original folded conformations of BSA molecules were basically maintained in the reactive self-assembly process. Compared with native BSA, the secondary structure and conformation change of coronal BSA induced by urea or thermal treatment were remarkably suppressed. The cytotoxicity assays demonstrated that the CCNs were essentially nontoxic to Hela and COS-7 cells.

  8. Surface-enhanced Raman spectroscopy substrate based on Ag-coated self-assembled polystyrene spheres

    NASA Astrophysics Data System (ADS)

    Mikac, Lara; Ivanda, Mile; Gotić, Marijan; Janicki, Vesna; Zorc, Hrvoje; Janči, Tibor; Vidaček, Sanja

    2017-10-01

    The silver (Ag) films were deposited on the monodispersed polystyrene spheres that were drop-coated on hydrophilic glass substrates in order to form a self-assembled 2D monolayer. Thus prepared Ag films over polystyrene nanospheres (AgFONs) were used to record the surface-enhanced Raman scattering (SERS) spectra of rhodamine 6G (R6G) and pyridine (λex = 514.5 nm). AgFONs were prepared by depositing 120, 180 and 240 nm thick Ag layer on the 1000 nm polystyrene spheres and 80, 120, 160 and 200 nm thick Ag layer on the 350 nm spheres as well as on their mixture (350 + 1000 nm). The silver was deposited by electron beam evaporation technique. The best enhancement of the Raman signal for both test molecules was obtained using 180 nm Ag film deposited on the 1000 nm spheres and using 80 nm Ag film deposited on the 350 nm polystyrene spheres. The lowest detectable concentrations of R6G and pyridine were 10-9 mol L-1 and 1.2 × 10-3 mol L-1, respectively. This study has shown that AgFONs could be regarded as good and reproducible SERS substrate for analytical detection of various organic molecules.

  9. Fluorescent polystyrene photonic crystals self-assembled with water-soluble conjugated polyrotaxanes

    NASA Astrophysics Data System (ADS)

    Di Stasio, Francesco; Berti, Luca; McDonnell, Shane O.; Robbiano, Valentina; Anderson, Harry L.; Comoretto, Davide; Cacialli, Franco

    2013-10-01

    We demonstrate control of the photoluminescence spectra and decay rates of water-soluble green-emitting conjugated polyrotaxanes by incorporating them in polystyrene opals with a stop-band spectrally tuned on the rotaxane emission (405-650 nm). We observe a suppression of the luminescence within the photonic stop-band and a corresponding enhancement of the high-energy edge (405-447 nm). Time-resolved measurements reveal a wavelength-dependent modification of the emission lifetime, which is shortened at the high-energy edge (by ˜11%, in the range 405-447 nm), but elongated within the stop-band (by ˜13%, in the range 448-482 nm). We assign both effects to the modification of the density of photonic states induced by the photonic crystal band structure. We propose the growth of fluorescent composite photonic crystals from blends of "solvent-compatible" non-covalently bonded nanosphere-polymer systems as a general method for achieving a uniform distribution of polymeric dopants in three-dimensional self-assembling photonic structures.

  10. Direct Synthesis of Controlled-Size Nanospheres inside Nanocavities of Self-Organized Photopolymerizing Soft Oxometalates [PW12 O40 ]n (n=1100-7500).

    PubMed

    Das, Kousik; Roy, Soumyajit

    2015-09-01

    The unusual self-assembly of {(BMIm)2 (DMIm)[PW12 O40 ]}n (n=1100-7500) (BMIm=1-butyl-3-methylimidazolium, DMIm=3,3'-dimethyl-1,1'-diimidazolium) soft oxometalates (SOMs) with controlled size and a hollow nanocavity was exploited for the photochemical synthesis of polymeric nanospheres within the nanocavity of the SOM. The SOM vesicle has been characterized by using several techniques, including dynamic light scattering (DLS), static light scattering (SLS), attenuated total reflection (ATR) IR spectroscopy, Raman spectroscopy, microscopy, and zeta-potential analysis. The self-assembly and stabilization of this soft-oxometalate vesicle has been shown by means of counter-ion condensation. The immediate implication of such stabilization-the variation of the dielectric constant with the hydrodynamic radius of the vesicle-has been used to synthesize vesicles of controlled size. Such vesicles of varying size have been used as templates for polymerization reactions that produce polymeric spheres of controlled size. Direct evidence shows that the SOM behaves as a model heterogeneous catalytic system. Such surfactant- and initiator-free photochemical synthetic routes for obtaining uniform latex spheres could be used in the making of optical bandgap materials, inverse opals, and paints. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. A switchable self-assembling and disassembling chiral system based on a porphyrin-substituted phenylalanine–phenylalanine motif

    PubMed Central

    Charalambidis, Georgios; Georgilis, Evangelos; Panda, Manas K.; Anson, Christopher E.; Powell, Annie K.; Doyle, Stephen; Moss, David; Jochum, Tobias; Horton, Peter N.; Coles, Simon J.; Linares, Mathieu; Beljonne, David; Naubron, Jean-Valère; Conradt, Jonas; Kalt, Heinz; Mitraki, Anna; Coutsolelos, Athanassios G.; Balaban, Teodor Silviu

    2016-01-01

    Artificial light-harvesting systems have until now not been able to self-assemble into structures with a large photon capture cross-section that upon a stimulus reversibly can switch into an inactive state. Here we describe a simple and robust FLFL-dipeptide construct to which a meso-tetraphenylporphyrin has been appended and which self-assembles to fibrils, platelets or nanospheres depending on the solvent composition. The fibrils, functioning as quenched antennas, give intense excitonic couplets in the electronic circular dichroism spectra which are mirror imaged if the unnatural FDFD-analogue is used. By slightly increasing the solvent polarity, these light-harvesting fibres disassemble to spherical structures with silent electronic circular dichroism spectra but which fluoresce. Upon further dilution with the nonpolar solvent, the intense Cotton effects are recovered, thus proving a reversible switching. A single crystal X-ray structure shows a head-to-head arrangement of porphyrins that explains both their excitonic coupling and quenched fluorescence. PMID:27582363

  12. A switchable self-assembling and disassembling chiral system based on a porphyrin-substituted phenylalanine-phenylalanine motif.

    PubMed

    Charalambidis, Georgios; Georgilis, Evangelos; Panda, Manas K; Anson, Christopher E; Powell, Annie K; Doyle, Stephen; Moss, David; Jochum, Tobias; Horton, Peter N; Coles, Simon J; Linares, Mathieu; Beljonne, David; Naubron, Jean-Valère; Conradt, Jonas; Kalt, Heinz; Mitraki, Anna; Coutsolelos, Athanassios G; Balaban, Teodor Silviu

    2016-09-01

    Artificial light-harvesting systems have until now not been able to self-assemble into structures with a large photon capture cross-section that upon a stimulus reversibly can switch into an inactive state. Here we describe a simple and robust FLFL-dipeptide construct to which a meso-tetraphenylporphyrin has been appended and which self-assembles to fibrils, platelets or nanospheres depending on the solvent composition. The fibrils, functioning as quenched antennas, give intense excitonic couplets in the electronic circular dichroism spectra which are mirror imaged if the unnatural FDFD-analogue is used. By slightly increasing the solvent polarity, these light-harvesting fibres disassemble to spherical structures with silent electronic circular dichroism spectra but which fluoresce. Upon further dilution with the nonpolar solvent, the intense Cotton effects are recovered, thus proving a reversible switching. A single crystal X-ray structure shows a head-to-head arrangement of porphyrins that explains both their excitonic coupling and quenched fluorescence.

  13. A switchable self-assembling and disassembling chiral system based on a porphyrin-substituted phenylalanine-phenylalanine motif

    NASA Astrophysics Data System (ADS)

    Charalambidis, Georgios; Georgilis, Evangelos; Panda, Manas K.; Anson, Christopher E.; Powell, Annie K.; Doyle, Stephen; Moss, David; Jochum, Tobias; Horton, Peter N.; Coles, Simon J.; Linares, Mathieu; Beljonne, David; Naubron, Jean-Valère; Conradt, Jonas; Kalt, Heinz; Mitraki, Anna; Coutsolelos, Athanassios G.; Balaban, Teodor Silviu

    2016-09-01

    Artificial light-harvesting systems have until now not been able to self-assemble into structures with a large photon capture cross-section that upon a stimulus reversibly can switch into an inactive state. Here we describe a simple and robust FLFL-dipeptide construct to which a meso-tetraphenylporphyrin has been appended and which self-assembles to fibrils, platelets or nanospheres depending on the solvent composition. The fibrils, functioning as quenched antennas, give intense excitonic couplets in the electronic circular dichroism spectra which are mirror imaged if the unnatural FDFD-analogue is used. By slightly increasing the solvent polarity, these light-harvesting fibres disassemble to spherical structures with silent electronic circular dichroism spectra but which fluoresce. Upon further dilution with the nonpolar solvent, the intense Cotton effects are recovered, thus proving a reversible switching. A single crystal X-ray structure shows a head-to-head arrangement of porphyrins that explains both their excitonic coupling and quenched fluorescence.

  14. Solvatochromism, Reversible Chromism and Self-Assembly Effects of Heteroatom-Assisted Aggregation-Induced Enhanced Emission (AIEE) Compounds.

    PubMed

    Niu, Caixia; You, Ying; Zhao, Liu; He, Dacheng; Na, Na; Ouyang, Jin

    2015-09-28

    Two compounds, 9,10-bis[2-(quinolyl)vinyl]anthracene (BQVA) and 9,10-bis[2-(naphthalen-2-yl)vinyl]anthracene (BNVA), have been synthesised and investigated. Both of them have aggregation-induced enhanced emission (AIEE) properties. Heteroatom-assisted BQVA shows solvatochromism, reversible chromism properties and self-assembly effects. When increasing the solvent polarities, the green solution of BQVA turns to orange with a redshift of the fluorescence emission wavelengths from λ=527 to 565 nm. Notably, BQVA exhibits reversible chromism properties, including mechano- and thermochromism. The as-prepared BQVA powders show green fluorescence (λem=525 nm) and the colour can turn into orange (λem=573 nm) after grinding. Interestingly, the orange colour can return at high temperature. Based on these reversible chromism properties, a simple and convenient erasable board has been designed. Different from BQVA, non-heteroatom-assisted BNVA has no clear chromic processes. The results obtained from XRD, differential scanning calorimetry, single-crystal analysis and theoretical calculations indicate that the chromic processes depend on the heteroatoms in BQVA. Additionally, BQVA also exhibits excellent self-assembly effects in different solvents. Homogeneous nanospheres are formed in mixtures of tetrahydrofuran and water, which are then doped into silica nanoparticles and treated with 3-aminopropyltriethoxysilane to give amino-functionalised nanoparticles (BQVA-AFNPs). The BQVAAFNPs could be used to stain protein markers in polyacrylamide gel electrophoresis.

  15. Redox control of GPx catalytic activity through mediating self-assembly of Fmoc-phenylalanine selenide into switchable supramolecular architectures.

    PubMed

    Huang, Zupeng; Luo, Quan; Guan, Shuwen; Gao, Jianxiong; Wang, Yongguo; Zhang, Bo; Wang, Liang; Xu, Jiayun; Dong, Zeyuan; Liu, Junqiu

    2014-12-28

    Artificial enzymes capable of achieving tunable catalytic activity through stimuli control of enzymatic structure transition are of significance in biosensor and biomedicine research. Herein we report a novel smart glutathione peroxidise (GPx) mimic with modulatory catalytic activity based on redox-induced supramolecular self-assembly. First, an amphiphilic Fmoc-phenylalanine-based selenide was designed and synthesized, which can self-assemble into nanospheres (NSs) in aqueous solution. The NSs demonstrate extremely low GPx activity. Upon the oxidation of hydroperoxides (ROOH), the selenide can be quickly transformed into the selenoxide form. The change of the molecular structure induces complete morphology transition of the self-assemblies from NSs to nanotubes (NTs), resulting in great enhancement in the GPx catalytic activity. Under the reduction of GSH, the selenoxide can be further reversibly reduced back into the selenide; therefore the reversible switch between the NSs and NTs can be successfully accomplished. The relationship between the catalytic activity and enzymatic structure was also investigated. The dual response nature makes this mimic play roles of both a sensor and a GPx enzyme at the same time, which can auto-detect the signal of ROOH and then auto-change its activity to achieve quick or slow/no scavenging of ROOH. The dynamic balance of ROOH is vital in organisms, in which an appropriate amount of ROOH does benefit to the metabolism, whereas surplus ROOH can cause oxidative damage of the cell instead and this smart mimic is of remarkable significance. We expect that such a mimic can be developed into an effective antioxidant drug and provide a new platform for the construction of intelligent artificial enzymes with multiple desirable properties.

  16. Increase in stability of cellulase immobilized on functionalized magnetic nanospheres

    NASA Astrophysics Data System (ADS)

    Zhang, Wenjuan; Qiu, Jianhui; Feng, Huixia; Zang, Limin; Sakai, Eiichi

    2015-02-01

    Functionalized magnetic nanospheres were prepared by co-condensation of tetraethylorthosilicate with three different amino-silanes: 3-(2-aminoethylamino propyl)-triethoxysilane (AEAPTES), 3-(2-aminoethylamino propyl)-trimethoxysilane (AEAPTMES) and 3-aminopropyltriethoxysilane (APTES). Then three functionalized magnetic nanospheres were used as supports for immobilization of cellulase. The three functionalized magnetic nanospheres with core-shell morphologies exhibited higher capacity for cellulase immobilization than unfunctionalized magnetic nanospheres. The increasing of surface charge of functionalized magnetic nanospheres leads to an enhancement of the capacity of cellulase immobilization. Particularly, AEAPTMES with methoxy groups was favored to be hydrolyzed and grafted on unfunctionalized magnetic nanospheres than the others. AEAPTMES functionalized magnetic nanospheres with the highest zeta potential (29 mV) exhibited 87% activity recovery and the maximum amount of immobilized cellulase was 112 mg/g support at concentration of initial cellulase of 8 mg/mL. Immobilized cellulase on AEAPTMES functionalized magnetic nanospheres had higher temperature stability and broader pH stability than other immobilized cellulases and free cellulase. In particular, it can be used in about 40 °C, demonstrating the potential of biofuel production using this immobilized cellulase.

  17. 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

  18. Morphological Control of Anisotropic Self-Assemblies from Alternating Poly(p-dioxanone)-poly(ethylene glycol) Multiblock Copolymer Depending on the Combination Effect of Crystallization and Micellization.

    PubMed

    Wang, Mei-Jia; Wang, Hao; Chen, Si-Chong; Chen, Cheng; Liu, Ya

    2015-06-30

    A novel and facile method was developed for morphological controlling of self-assemblies prepared by crystallization induced self-assembly of crystalline-coil copolymer depending on the combination effect of crystallization and micellization. The morphological evolution of the self-assemblies of alternating poly(p-dioxanone)-block-poly(ethylene glycol) (PPDO-PEG) multiblock copolymer prepared by different solvent mixing methods in aqueous solution were investigated. "Chrysanthemum"-like and "star anise"-like self-assemblies were obtained at different rates of solvent mixing. The results suggested gradually change in solvent quality (slowly dropping water into DMF solution) leaded to a hierarchical micellization-crystallization process of core-forming PPDO blocks, and flake-like particles were formed at the initial stage of crystallization. Meanwhile, crystallization induced micellization process occurred when solvent quality changed drastically. Shuttle-like particles, which have much smaller size than those of flake-like particles, were formed at the initial stage of crystallization when quickly injecting water into DMF solution of the copolymer. Therefore, owing to the different changing rate of solvent quality, which may result in different combination effect of crystallization and micellization during self-assembly of the copolymer, PPDO-PEG self-assemblies with different hierarchical morphology in nano scale could be obtained.

  19. Self-assembly from milli- to nanoscales: methods and applications

    PubMed Central

    Mastrangeli, M; Abbasi, S; Varel, C; Van Hoof, C; Celis, J-P; Böhringer, K F

    2009-01-01

    The design and fabrication techniques for microelectromechanical systems (MEMS) and nanodevices are progressing rapidly. However, due to material and process flow incompatibilities in the fabrication of sensors, actuators and electronic circuitry, a final packaging step is often necessary to integrate all components of a heterogeneous microsystem on a common substrate. Robotic pick-and-place, although accurate and reliable at larger scales, is a serial process that downscales unfavorably due to stiction problems, fragility and sheer number of components. Self-assembly, on the other hand, is parallel and can be used for device sizes ranging from millimeters to nanometers. In this review, the state-of-the-art in methods and applications for self-assembly is reviewed. Methods for assembling three-dimensional (3D) MEMS structures out of two-dimensional (2D) ones are described. The use of capillary forces for folding 2D plates into 3D structures, as well as assembling parts onto a common substrate or aggregating parts to each other into 2D or 3D structures, is discussed. Shape matching and guided assembly by magnetic forces and electric fields are also reviewed. Finally, colloidal self-assembly and DNA-based self-assembly, mainly used at the nanoscale, are surveyed, and aspects of theoretical modeling of stochastic assembly processes are discussed. PMID:20209016

  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. 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.

  2. Self-assembling biomolecular catalysts for hydrogen production

    NASA Astrophysics Data System (ADS)

    Jordan, Paul C.; Patterson, Dustin P.; Saboda, Kendall N.; Edwards, Ethan J.; Miettinen, Heini M.; Basu, Gautam; Thielges, Megan C.; Douglas, Trevor

    2016-02-01

    The chemistry of highly evolved protein-based compartments has inspired the design of new catalytically active materials that self-assemble from biological components. A frontier of this biodesign is the potential to contribute new catalytic systems for the production of sustainable fuels, such as hydrogen. Here, we show the encapsulation and protection of an active hydrogen-producing and oxygen-tolerant [NiFe]-hydrogenase, sequestered within the capsid of the bacteriophage P22 through directed self-assembly. We co-opted Escherichia coli for biomolecular synthesis and assembly of this nanomaterial by expressing and maturing the EcHyd-1 hydrogenase prior to expression of the P22 coat protein, which subsequently self assembles. By probing the infrared spectroscopic signatures and catalytic activity of the engineered material, we demonstrate that the capsid provides stability and protection to the hydrogenase cargo. These results illustrate how combining biological function with directed supramolecular self-assembly can be used to create new materials for sustainable catalysis.

  3. Entropy-driven self-assembly of dimers

    NASA Astrophysics Data System (ADS)

    Nakamura, Issei; Shi, An-Chang

    2008-03-01

    Supramolecular self-assembly is an important phenomenon with applications ranging from chemical synthesis to biological systems. Although the driving force of assembly is the weak non-covalent intermolecular interaction such as hydrogen bonding and dispersion force, the self-assembly is a result from balancing the enthalpic and entropic contributions. In general, the disassembled/disordered phase is expected as temperature is raised because of the entropic gain from the components of the aggregate. However, it has been observed that the self-assembled/ordered phase can be promoted with increasing temperature. This implies that the self-assembly is driven by entropy. In order to provide a better understanding of this entropy-driven transition, we have studied a statistical mechanical model for the aggregation of macromolecular dimers immersed in solvents. The model demonstrates that solvent molecules absorbed on the surface of the solute are released with increasing temperature, leading to an increase of the total entropy of the system. Consequently, the cooperative stability of the dimeric state is induced. The thermodynamic features of this transition are analyzed.

  4. Soft self-assembled nanoparticles with temperature-dependent properties

    NASA Astrophysics Data System (ADS)

    Rovigatti, Lorenzo; Capone, Barbara; Likos, Christos N.

    2016-02-01

    The fabrication of versatile building blocks that reliably self-assemble into desired ordered and disordered phases is amongst the hottest topics in contemporary materials science. To this end, microscopic units of varying complexity, aimed at assembling the target phases, have been thought, designed, investigated and built. Such a path usually requires laborious fabrication techniques, especially when specific functionalisation of the building blocks is required. Telechelic star polymers, i.e., star polymers made of a number of f di-block copolymers consisting of solvophobic and solvophilic monomers grafted on a central anchoring point, spontaneously self-assemble into soft patchy particles featuring attractive spots (patches) on the surface. Here we show that the tunability of such a system can be widely extended by controlling the physical and chemical parameters of the solution. Indeed, under fixed external conditions the self-assembly behaviour depends only on the number of arms and on the ratio of solvophobic to solvophilic monomers. However, changes in temperature and/or solvent quality make it possible to reliably change the number and size of the attractive patches. This allows the steering of the mesoscopic self-assembly behaviour without modifying the microscopic constituents. Interestingly, we also demonstrate that diverse combinations of the parameters can generate stars with the same number of patches but different radial and angular stiffness. This mechanism could provide a neat way of further fine-tuning the elastic properties of the supramolecular network without changing its topology.

  5. Molecular Recognition Directed Self-Assembly of Supramolecular Architectures

    DTIC Science & Technology

    1994-06-30

    chemistry. The ability of these supramolecular architectures to form liquid crystalline phases is determined by the shape of the self-assembled...be discussed. In the case of TMV-like supramolecular architectures a comparison between various supramolecdr (generated via H-bonding, ionic and...molecular, macromolecular and supramolecular chemistry. The ability of these supramolecular architectures to form liquid crystalline phases is determined

  6. Photocontrol over cooperative porphyrin self-assembly with phenylazopyridine ligands.

    PubMed

    Hirose, Takashi; Helmich, Floris; Meijer, E W

    2013-01-02

    The cooperative self-assembly of chiral zinc porphyrins is regulated by a photoresponsive phenylazopyridine ligand. Porphyrin stacks depolymerize into dimers upon axial ligation and the strength of the coordination is regulated by its photoinduced isomerization, which shows more than 95 % conversion ratio for both photostationary states.

  7. Controlled self-assembly of hydrophobic quantum dots through silanization.

    PubMed

    Yang, Ping; Ando, Masanori; Murase, Norio

    2011-09-01

    We demonstrate the formation of one-, two-, and three-dimensional nanocomposites through the self-assembly of silanized CdSe/ZnS quantum dots (QDs) by using a controlled sol-gel process. The self-assembly behavior of the QDs was created when partially hydrolyzed silicon alkoxide monomers replaced hydrophobic ligands on the QDs. We examined systematically self-assembly conditions such as solvent components and QD sizes in order to elucidate the formation mechanism of various QD nanocomposites. The QD nanocomposites were assembled in water phase or on the interface of water and oil phase in emulsions. The partially hydrolyzed silicon alkoxides act as intermolecules to assemble the QDs. The QD nanocomposites with well-defined solid or hollow spherical, fiber-like, sheet-like, and pearl-like morphologies were prepared by adjusting the experimental conditions. The high photoluminescence efficiency of the prepared QD nanocomposites suggests partially hydrolyzed silicon alkoxides reduced the surface deterioration of QDs during self-assembly. These techniques are applicable to other hydrophobic QDs for fabricating complex QD nanocomposites.

  8. pH-directed self-assembling helical peptide conformation

    USDA-ARS?s Scientific Manuscript database

    The beta-sheet and alpha-helix peptide conformation are two of the most fundamentally ordered secondary structures found in proteins and peptides. They also give rise to self-assembling motifs that form macromolecular channels and nanostructures. Through design these conformations can yield enhance...

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

  10. 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

  11. 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.

  12. Self-assembling multidomain peptide fibers with aromatic cores

    USDA-ARS?s Scientific Manuscript database

    Self-assembling multidomain peptides have been shown to have desirable properties, such as the ability to form hydrogels that rapidly recover following shear-thinning and the potential to be tailored by amino acid selection to vary their elasticity and encapsulate and deliver proteins and cells. Her...

  13. Probabilistic Analysis of Pattern Formation in Monotonic Self-Assembly

    PubMed Central

    Moore, Tyler G.; Garzon, Max H.; Deaton, Russell J.

    2015-01-01

    Inspired by biological systems, self-assembly aims to construct complex structures. It functions through piece-wise, local interactions among component parts and has the potential to produce novel materials and devices at the nanoscale. Algorithmic self-assembly models the product of self-assembly as the output of some computational process, and attempts to control the process of assembly algorithmically. Though providing fundamental insights, these computational models have yet to fully account for the randomness that is inherent in experimental realizations, which tend to be based on trial and error methods. In order to develop a method of analysis that addresses experimental parameters, such as error and yield, this work focuses on the capability of assembly systems to produce a pre-determined set of target patterns, either accurately or perhaps only approximately. Self-assembly systems that assemble patterns that are similar to the targets in a significant percentage are “strong” assemblers. In addition, assemblers should predominantly produce target patterns, with a small percentage of errors or junk. These definitions approximate notions of yield and purity in chemistry and manufacturing. By combining these definitions, a criterion for efficient assembly is developed that can be used to compare the ability of different assembly systems to produce a given target set. Efficiency is a composite measure of the accuracy and purity of an assembler. Typical examples in algorithmic assembly are assessed in the context of these metrics. In addition to validating the method, they also provide some insight that might be used to guide experimentation. Finally, some general results are established that, for efficient assembly, imply that every target pattern is guaranteed to be assembled with a minimum common positive probability, regardless of its size, and that a trichotomy exists to characterize the global behavior of typical efficient, monotonic self-assembly

  14. Building polyhedra by self-assembly: theory and experiment.

    PubMed

    Kaplan, Ryan; Klobušický, Joseph; Pandey, Shivendra; Gracias, David H; Menon, Govind

    2014-01-01

    We investigate the utility of a mathematical framework based on discrete geometry to model biological and synthetic self-assembly. Our primary biological example is the self-assembly of icosahedral viruses; our synthetic example is surface-tension-driven self-folding polyhedra. In both instances, the process of self-assembly is modeled by decomposing the polyhedron into a set of partially formed intermediate states. The set of all intermediates is called the configuration space, pathways of assembly are modeled as paths in the configuration space, and the kinetics and yield of assembly are modeled by rate equations, Markov chains, or cost functions on the configuration space. We review an interesting interplay between biological function and mathematical structure in viruses in light of this framework. We discuss in particular: (i) tiling theory as a coarse-grained description of all-atom models; (ii) the building game-a growth model for the formation of polyhedra; and (iii) the application of these models to the self-assembly of the bacteriophage MS2. We then use a similar framework to model self-folding polyhedra. We use a discrete folding algorithm to compute a configuration space that idealizes surface-tension-driven self-folding and analyze pathways of assembly and dominant intermediates. These computations are then compared with experimental observations of a self-folding dodecahedron with side 300 μm. In both models, despite a combinatorial explosion in the size of the configuration space, a few pathways and intermediates dominate self-assembly. For self-folding polyhedra, the dominant intermediates have fewer degrees of freedom than comparable intermediates, and are thus more rigid. The concentration of assembly pathways on a few intermediates with distinguished geometric properties is biologically and physically important, and suggests deeper mathematical structure.

  15. Probabilistic Analysis of Pattern Formation in Monotonic Self-Assembly.

    PubMed

    Moore, Tyler G; Garzon, Max H; Deaton, Russell J

    2015-01-01

    Inspired by biological systems, self-assembly aims to construct complex structures. It functions through piece-wise, local interactions among component parts and has the potential to produce novel materials and devices at the nanoscale. Algorithmic self-assembly models the product of self-assembly as the output of some computational process, and attempts to control the process of assembly algorithmically. Though providing fundamental insights, these computational models have yet to fully account for the randomness that is inherent in experimental realizations, which tend to be based on trial and error methods. In order to develop a method of analysis that addresses experimental parameters, such as error and yield, this work focuses on the capability of assembly systems to produce a pre-determined set of target patterns, either accurately or perhaps only approximately. Self-assembly systems that assemble patterns that are similar to the targets in a significant percentage are "strong" assemblers. In addition, assemblers should predominantly produce target patterns, with a small percentage of errors or junk. These definitions approximate notions of yield and purity in chemistry and manufacturing. By combining these definitions, a criterion for efficient assembly is developed that can be used to compare the ability of different assembly systems to produce a given target set. Efficiency is a composite measure of the accuracy and purity of an assembler. Typical examples in algorithmic assembly are assessed in the context of these metrics. In addition to validating the method, they also provide some insight that might be used to guide experimentation. Finally, some general results are established that, for efficient assembly, imply that every target pattern is guaranteed to be assembled with a minimum common positive probability, regardless of its size, and that a trichotomy exists to characterize the global behavior of typical efficient, monotonic self-assembly systems

  16. Polyelectrolyte - mediated adsorption of amelogenin monomers and nanospheres forming mono- or multi-layers

    PubMed Central

    Gergely, Csilla; Szalontai, Balázs; Moradian-Oldak, Janet; Cuisinier, Frédéric J.G.

    2008-01-01

    We have applied optical waveguide lightmode spectroscopy combined with streaming potential measurements and Fourier transformed infrared spectroscopy to investigate adsorption of amelogenin nanospheres onto polyelectrolytes. The long term objective was to better understand the chemical nature of these assemblies and to gain further insight into the molecular mechanisms involved during self-assembly. It was found that monolayers of monomers and negatively charged nanospheres of a recombinant amelogenin (rM179) irreversibly adsorbed onto a positively charged polyelectrolyte multilayer films. Based on measurements performed at different temperatures it was demonstrated that intermolecular interactions for the formation of nanospheres were not affected by their adsorption onto polyelectrolytes. Consecutive adsorption of nanospheres resulting in the formation of multilayer structures was possible by using cationic poly(L-lysine) as mediators. N-Acetyl-D-Glucosamine (GlcNac) did not disturb the nanosphere-assembled protein’s structure and it only affected the adsorption of monomeric amelogenin. Infrared spectroscopy of adsorbed amelogenin revealed conformational differences between the monomeric and assembled forms of rM179. While there was a considerable amount of α-helices in the monomers, β-turn and β-sheet structures dominated the assembled proteins. Our work constitutes the first report on a structurally controlled in-vitro buildup of an rM179 nanosphere monolayer-based matrix. Our data support the notion that amelogenin self-assembly is mostly driven by hydrophobic interactions and that amelogenin/PEM interactions are dominated by electrostatic forces. We suggest that similar forces can govern amelogenin interactions with non-amelogenins or the mineral phase during enamel biomineralization. PMID:17579474

  17. Lag periods during the self-assembly of {Mo(72)Fe(30)} macroions: connection to the virus capsid formation process.

    PubMed

    Zhang, Jie; Li, Dong; Liu, Guang; Glover, Kerney Jebrell; Liu, Tianbo

    2009-10-28

    The kinetic properties of the self-assembly of hydrophilic Keplerate-type polyoxometalate (POM) {Mo(72)Fe(30)} macroanions into single-layer, vesicle-like blackberry structures in solutions were monitored by the static and dynamic laser light scattering techniques. In the presence of additional electrolytes, an obvious lag period at the initial stage of self-assembly was observed, followed by a fast increase of the scattered intensity. The whole kinetic curve is sigmoidal with a lag phase. A two-step nucleation-growth mechanism is proposed to explain this lag phase: the {Mo(72)Fe(30)} macroanions slowly associate into oligomers (mostly dimers), which are the thermodynamically unfavorable intermediates, at the initial stage; once the oligomers reach a critical concentration, the blackberry formation process is accelerated. Analytical ultracentrifugation (AUC) was used to confirm the oligomeric state in {Mo(72)Fe(30)} solution during the lag period. The length of the lag period is dependent on temperature, ionic strength, and the valent states of the additional salts, as well as the solvent content. The kinetics (including the lag period) of the blackberry formation of the {Mo(72)Fe(30)} macroanions show similarities to the self-assembly of virus capsid proteins (which are also soluble macroions) into spherical capsid shells, suggesting possible connections between the self-assembly behaviors of inorganic species and biological macromolecules.

  18. Mapping magnetic fields of Fe{sub 3}O{sub 4} nanosphere assemblies by electron holography

    SciTech Connect

    He Kai; Cumings, John; Ma Feixiang; Xu Chengyan

    2013-05-07

    Crystalline Fe{sub 3}O{sub 4} nanospheres with averaged diameters of 150 nm have been synthesized by a facile solvothermal method and characterized using transmission electron microscopy and electron holography. The nanospheres can self-assemble into either chain-like or ring-like shapes with sizes of a few micrometers, where large magnetic moments are found for individual particles at the remanent state and lead to strong fringing field in vicinity of the assemblies. Magnetic dipolar moments can be aligned both within and out of the sample plane, with a typical length scale on the order of 500 nm.

  19. The impact of substrate interaction in directed self-assembly of symmetric diblock copolymer thin films

    NASA Astrophysics Data System (ADS)

    Seidel, Robert

    ) and size of process window. It also introduces an analysis technique for evaluating assembly kinetics with an emphasis on defect annihilation. The fifth chapter seeks to identify more thoroughly the root causes of LER in BCP line/space DSA by investigating a number of factors. The sixth and final full chapter describes initial success in the effort to extend the concepts of BCP DSA on patterned planar substrates to flexible or three-dimensional substrates (for roll-to-roll applications) by using functional layer-by-layer deposited films. Our final conclusion touches on the ideas of nucleation of self-assembled BCP structures and how they relate to kinetic pathways and timescales of assembly.

  20. Hierarchical self-assembly: Self-organized nanostructures in a nematically ordered matrix of self-assembled polymeric chains

    NASA Astrophysics Data System (ADS)

    Mubeena, Shaikh; Chatterji, Apratim

    2015-03-01

    We report many different nanostructures which are formed when model nanoparticles of different sizes (diameter σn) are allowed to aggregate in a background matrix of semiflexible self-assembled polymeric wormlike micellar chains. The different nanostructures are formed by the dynamical arrest of phase-separating mixtures of micellar monomers and nanoparticles. The different morphologies obtained are the result of an interplay of the available free volume, the elastic energy of deformation of polymers, the density (chemical potential) of the nanoparticles in the polymer matrix, and, of course, the ratio of the size of self-assembling nanoparticles and self-avoidance diameter of polymeric chains. We have used a hybrid semi-grand-canonical Monte Carlo simulation scheme to obtain the (nonequilibrium) phase diagram of the self-assembled nanostructures. We observe rodlike structures of nanoparticles which get self-assembled in the gaps between the nematically ordered chains, as well as percolating gel-like network of conjoined nanotubes. We also find a totally unexpected interlocked crystalline phase of nanoparticles and monomers, in which each crystal plane of nanoparticles is separated by planes of perfectly organized polymer chains. We identified the condition which leads to such interlocked crystal structure. We suggest experimental possibilities of how the results presented in this paper could be used to obtain different nanostructures in the laboratory.

  1. Hierarchical self-assembly: Self-organized nanostructures in a nematically ordered matrix of self-assembled polymeric chains.

    PubMed

    Mubeena, Shaikh; Chatterji, Apratim

    2015-03-01

    We report many different nanostructures which are formed when model nanoparticles of different sizes (diameter σn) are allowed to aggregate in a background matrix of semiflexible self-assembled polymeric wormlike micellar chains. The different nanostructures are formed by the dynamical arrest of phase-separating mixtures of micellar monomers and nanoparticles. The different morphologies obtained are the result of an interplay of the available free volume, the elastic energy of deformation of polymers, the density (chemical potential) of the nanoparticles in the polymer matrix, and, of course, the ratio of the size of self-assembling nanoparticles and self-avoidance diameter of polymeric chains. We have used a hybrid semi-grand-canonical Monte Carlo simulation scheme to obtain the (nonequilibrium) phase diagram of the self-assembled nanostructures. We observe rodlike structures of nanoparticles which get self-assembled in the gaps between the nematically ordered chains, as well as percolating gel-like network of conjoined nanotubes. We also find a totally unexpected interlocked crystalline phase of nanoparticles and monomers, in which each crystal plane of nanoparticles is separated by planes of perfectly organized polymer chains. We identified the condition which leads to such interlocked crystal structure. We suggest experimental possibilities of how the results presented in this paper could be used to obtain different nanostructures in the laboratory.

  2. 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.

  3. A Case Study of the Likes and Dislikes of DNA and RNA in Self-Assembly.

    PubMed

    Zuo, Hua; Wu, Siyu; Li, Mo; Li, Yulin; Jiang, Wen; Mao, Chengde

    2015-12-07

    Programmed self-assembly of nucleic acids (DNA and RNA) is an active research area as it promises a general approach for nanoconstruction. Whereas DNA self-assembly has been extensively studied, RNA self-assembly lags much behind. One strategy to boost RNA self-assembly is to adapt the methods of DNA self-assembly for RNA self-assembly because of the chemical and structural similarities of DNA and RNA. However, these two types of molecules are still significantly different. To enable the rational design of RNA self-assembly, a thorough examination of their likes and dislikes in programmed self-assembly is needed. The current work begins to address this task. It was found that similar, two-stranded motifs of RNA and DNA lead to similar, but clearly different nanostructures. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. MOF-derived self-assembled ZnO/Co3O4 nanocomposite clusters as high-performance anodes for lithium-ion batteries.

    PubMed

    Zhu, Dequan; Zheng, Fangcai; Xu, Shihao; Zhang, Yuanguang; Chen, Qianwang

    2015-10-14

    Although different kinds of metal oxide nanoparticles are extensively investigated as anode materials for lithium-ion batteries (LIBs), their cycle life and energy/power density are still not suitable for commercial applications. Metal oxides have a large storage capacity, but they suffer from low electrical conductivity and severe volume change during the charge/discharge process. Herein, we present a facile route to prepare self-assembled ZnO/Co3O4 nanocomposite clusters through calcination of preformed Prussian Blue Analogue (PBA) Zn3[Co(CN)6]2 nanospheres. These self-assembled ZnO/Co3O4 nanocomposite clusters exhibit superior lithium storage capabilities with good cycling properties. A reversible capacity of 957 mA h g(-1) was retained at a current density of 100 mA g(-1) up to 100 cycles. The enhanced electrochemical performance of the ZnO/Co3O4 nanocomposite anode can be ascribed to the rational design of the self-assembled cluster structures and the synergetic effect of two-component functional nanoparticle systems.

  5. Self-organization in coordination-driven self-assembly.

    PubMed

    Northrop, Brian H; Zheng, Yao-Rong; Chi, Ki-Whan; Stang, Peter J

    2009-10-20

    Self-assembly allows for the preparation of highly complex molecular and supramolecular systems from relatively simple starting materials. Typically, self-assembled supramolecules are constructed by combining complementary pairs of two highly symmetric molecular components, thus limiting the chances of forming unwanted side products. Combining asymmetric molecular components or multiple complementary sets of molecules in one complex mixture can produce myriad different ordered and disordered supramolecular assemblies. Alternatively, spontaneous self-organization phenomena can promote the formation of specific product(s) out of a collection of multiple possibilities. Self-organization processes are common throughout much of nature and are especially common in biological systems. Recently, researchers have studied self-organized self-assembly in purely synthetic systems. This Account describes our investigations of self-organization in the coordination-driven self-assembly of platinum(II)-based metallosupramolecules. The modularity of the coordination-driven approach to self-assembly has allowed us to systematically study a wide variety of different factors that can control the extent of supramolecular self-organization. In particular, we have evaluated the effects of the symmetry and polarity of ambidentate donor subunits, differences in geometrical parameters (e.g., the size, angularity, and dimensionality) of Pt(II)-based acceptors and organic donors, the influence of temperature and solvent, and the effects of intermolecular steric interactions and hydrophobic interactions on self-organization. Our studies have shown that the extent of self-organization in the coordination-driven self-assembly of both 2D polygons and 3D polyhedra ranges from no organization (a statistical mixture of multiple products) to amplified organization (wherein a particular product or products are favored over others) and all the way to the absolute self-organization of discrete

  6. Self-Organization in Coordination-Driven Self-Assembly

    PubMed Central

    Northrop, Brian H.; Zheng, Yao-Rong; Chi, Ki-Whan; Stang, Peter J.

    2009-01-01

    Conspectus Self-assembly allows for the preparation of highly complex molecular and supramolecular systems from relatively simple starting materials. Typically, self-assembled supramolecules are constructed by combining complementary pairs of two highly symmetric molecular components, thus limiting the chances of forming unwanted side products. Combining asymmetric molecular components or multiple complementary sets of molecules in one complex mixture can produce myriad different ordered and disordered supramolecular assemblies. Alternatively, spontaneous self-organization phenomena can promote the formation of specific product(s) out of a collection of multiple possibilities. Self-organization processes are common throughout much of nature and are especially common in biological systems. Recently, researchers have studied self-organized self-assembly in purely synthetic systems. This Account describes our investigations of self-organization in the coordination-driven self-assembly of platinum(II)-based metallosupramolecules. The modularity of the coordination-driven approach to self-assembly has allowed us to systematically study a wide variety of different factors that can control the extent of supramolecular self-organization. In particular, we have evaluated the effects of the symmetry and polarity of ambidentate donor subunits, differences in geometrical parameters (e.g. the size, angularity, and dimensionality) of Pt(II)-based acceptors and organic donors, the influence of temperature and solvent, and the effects of intermolecular steric interactions and hydrophobic interactions on self-organization. Our studies have shown that the extent of self-organization in the coordination-driven self-assembly of both 2D polygons and 3D polyhedra ranges from no organization (a statistical mixture of multiple products), to amplified organization (wherein a particular product or products are favored over others), and all the way to the absolute self-organization of

  7. Orthogonal self-assembly in folding block copolymers.

    PubMed

    Hosono, Nobuhiko; Gillissen, Martijn A J; Li, Yuanchao; Sheiko, Sergei S; Palmans, Anja R A; Meijer, E W

    2013-01-09

    We herein report the synthesis and characterization of ABA triblock copolymers that contain two complementary association motifs and fold into single-chain polymeric nanoparticles (SCPNs) via orthogonal self-assembly. The copolymers were prepared using atom-transfer radical polymerization (ATRP) and possess different pendant functional groups in the A and B blocks (alcohols in the A block and acetylenes in the B block). After postfunctionalization, the A block contains o-nitrobenzyl-protected 2-ureidopyrimidinone (UPy) moieties and the B block benzene-1,3,5-tricarboxamide (BTA) moieties. While the protected UPy groups dimerize after photoinduced deprotection of the o-nitrobenzyl group, the BTA moieties self-assemble into helical aggregates when temperature is reduced. In a two-step thermal/photoirradiation treatment under dilute conditions, the ABA block copolymer forms both BTA-based helical aggregates and UPy dimers intramolecularly. The sequential association of the two self-assembling motifs results in single-chain folding of the polymer, affording nanometer-sized particles with a compartmentalized interior. Variable-temperature NMR studies showed that the BTA and UPy self-assembly steps take place orthogonally (i.e., without mutual interference) in dilute solution. In addition, monitoring of the intramolecular self-assembly of BTA moieties into helical aggregates by circular dichroism spectroscopy showed that the stability of the aggregates is almost independent of UPy dimerization. Size-exclusion chromatography (SEC) and small-angle X-ray scattering analysis provided evidence of significant reductions in the hydrodynamic volume and radius of gyration, respectively, after photoinduced deprotection of the UPy groups; a 30-60% reduction in the size of the polymer chains was observed using SEC in CHCl(3). Molecular imaging by atomic force microscopy (AFM) corroborated significant contraction of individual polymer chains due to intramolecular association of the

  8. Predicting supramolecular self-assembly on reconstructed metal surfaces

    NASA Astrophysics Data System (ADS)

    Roussel, Thomas J.; Barrena, Esther; Ocal, Carmen; Faraudo, Jordi

    2014-06-01

    The prediction of supramolecular self-assembly onto solid surfaces is still challenging in many situations of interest for nanoscience. In particular, no previous simulation approach has been capable to simulate large self-assembly patterns of organic molecules over reconstructed surfaces (which have periodicities over large distances) due to the large number of surface atoms and adsorbing molecules involved. Using a novel simulation technique, we report here large scale simulations of the self-assembly patterns of an organic molecule (DIP) over different reconstructions of the Au(111) surface. We show that on particular reconstructions, the molecule-molecule interactions are enhanced in a way that long-range order is promoted. Also, the presence of a distortion in a reconstructed surface pattern not only induces the presence of long-range order but also is able to drive the organization of DIP into two coexisting homochiral domains, in quantitative agreement with STM experiments. On the other hand, only short range order is obtained in other reconstructions of the Au(111) surface. The simulation strategy opens interesting perspectives to tune the supramolecular structure by simulation design and surface engineering if choosing the right molecular building blocks and stabilising the chosen reconstruction pattern.The prediction of supramolecular self-assembly onto solid surfaces is still challenging in many situations of interest for nanoscience. In particular, no previous simulation approach has been capable to simulate large self-assembly patterns of organic molecules over reconstructed surfaces (which have periodicities over large distances) due to the large number of surface atoms and adsorbing molecules involved. Using a novel simulation technique, we report here large scale simulations of the self-assembly patterns of an organic molecule (DIP) over different reconstructions of the Au(111) surface. We show that on particular reconstructions, the molecule

  9. Recent Advances on Carbon Nanospheres. Synthetic Routes and Applications

    DOE PAGES

    Zhang, Pengfei; Qiao, Zhenan; Dai, Sheng

    2015-01-01

    Carbon-based materials are the most popular material types in both fundamental research and industrial applications, partly because of their well-controlled nano-morphologies. In the past two decades, we have witnessed a number of breakthroughs in carbon research: fullerenes, carbon nanotubes, and more recently graphene. Nowadays, carbon nanospheres are attracting more and more attention worldwide due to their excellent performance in various fields: drug delivery, heterogeneous catalysis, encapsulation of support and electrode materials. Actually, spherical carbon is an old material, whereas controlling carbon spheres in the nanometer range is a recent story. In the past 5 years, it has become possible tomore » precisely control the particle size, surface area, pore size, chemical composition, and dispersity of carbon nanospheres. Toward this end, a number of synthetic strategies are emerging, such as hydrothermal carbonization of biomass-based resources, extended Stöber synthesis, and organic–organic self-assembly via different binding methods. In this feature article, we summarize recent routes for carbon nanospheres and briefly touch on their applications to shed light on the potential of this field. Throughout this article, a special emphasis is placed on the possible modulation of spherical structures at the nanoscale, and we wish to inspire many more designs and applications of carbon nanostructures in the near future.« less

  10. Recent Advances on Carbon Nanospheres. Synthetic Routes and Applications

    SciTech Connect

    Zhang, Pengfei; Qiao, Zhenan; Dai, Sheng

    2015-01-01

    Carbon-based materials are the most popular material types in both fundamental research and industrial applications, partly because of their well-controlled nano-morphologies. In the past two decades, we have witnessed a number of breakthroughs in carbon research: fullerenes, carbon nanotubes, and more recently graphene. Nowadays, carbon nanospheres are attracting more and more attention worldwide due to their excellent performance in various fields: drug delivery, heterogeneous catalysis, encapsulation of support and electrode materials. Actually, spherical carbon is an old material, whereas controlling carbon spheres in the nanometer range is a recent story. In the past 5 years, it has become possible to precisely control the particle size, surface area, pore size, chemical composition, and dispersity of carbon nanospheres. Toward this end, a number of synthetic strategies are emerging, such as hydrothermal carbonization of biomass-based resources, extended Stöber synthesis, and organic–organic self-assembly via different binding methods. In this feature article, we summarize recent routes for carbon nanospheres and briefly touch on their applications to shed light on the potential of this field. Throughout this article, a special emphasis is placed on the possible modulation of spherical structures at the nanoscale, and we wish to inspire many more designs and applications of carbon nanostructures in the near future.

  11. Anion-exchange nanospheres as titration reagents for anionic analytes.

    PubMed

    Zhai, Jingying; Xie, Xiaojiang; Bakker, Eric

    2015-08-18

    We present here anion-exchange nanospheres as novel titration reagents for anions. The nanospheres contain a lipophilic cation for which the counterion is initially Cl(-). Ion exchange takes place between Cl(-) in the nanospheres and a more lipophilic anion in the sample, such as ClO4(-) and NO3(-). Consecutive titration in the same sample solution for ClO4(-) and NO3(-) were demonstrated. As an application, the concentration of NO3(-) in spinach was successfully determined using this method.

  12. Stoichiometric Control of DNA-Grafted Colloid Self-Assembly

    NASA Astrophysics Data System (ADS)

    Vo, Thi; Venkatasubramanian, Venkat; Kumar, Sanat; Srinivasan, Babji; Pal, Suchetan; Zhang, Yugang; Gang, Oleg

    There have been recent surges of interest in understanding the self-assembly of DNA-grafted colloids into different crystallographic lattices, namely CsCl, AlB2, Cr3Si, and Cs6C60. Conventional approaches view the number of grafted linkers and effective size of each colloid as the major governing design parameters. It is generally assumed that the mixed stoichiometries need to match those defined by the target structures in order to obtain the desired lattice. Thus, contributions from stoichiometry are considered secondary and its exact effects on lattice formation remains an open question. Theoretical extensions to the popular complementary contact model show that the equilibrium lattice structure can be tuned through direct control of stoichiometry. Our results are also validated through experimental observations of the equilibrium crystal morphologies at differing stoichiometric ratios. These findings strongly suggest that stoichiometry is a new handle that can be used to control DNA-grafted colloidal self-assembly.

  13. Self-assembling enzymes and the origins of the cytoskeleton.

    PubMed

    Barry, Rachael M; Gitai, Zemer

    2011-12-01

    The bacterial cytoskeleton is composed of a complex and diverse group of proteins that self-assemble into linear filaments. These filaments support and organize cellular architecture and provide a dynamic network controlling transport and localization within the cell. Here, we review recent discoveries related to a newly appreciated class of self-assembling proteins that expand our view of the bacterial cytoskeleton and provide potential explanations for its evolutionary origins. Specifically, several types of metabolic enzymes can form structures similar to established cytoskeletal filaments and, in some cases, these structures have been repurposed for structural uses independent of their normal roles. The behaviors of these enzymes suggest that some modern cytoskeletal proteins may have evolved from dual-role proteins with catalytic and structural functions. Copyright © 2011 Elsevier Ltd. All rights reserved.

  14. Chemical optimization of self-assembled carbon nanotube transistors.

    PubMed

    Auvray, Stéphane; Derycke, Vincent; Goffman, Marcelo; Filoramo, Arianna; Jost, Oliver; Bourgoin, Jean-Philippe

    2005-03-01

    We present the improvement of carbon nanotube field effects transistors (CNTFETs) performances by chemical tuning of the nanotube/substrate and nanotube/electrode interfaces. Our work is based on a method of selective placement of individual single walled carbon nanotubes (SWNTs) by patterned aminosilane monolayer and its use for the fabrication of self-assembled nanotube transistors. This method brings a relevant solution to the problem of systematic connection of self-organized nanotubes. The aminosilane monolayer reactivity can be used to improve carrier injection and doping level of the SWNT. We show that the Schottky barrier height at the nanotube/metal interface can be diminished in a continuous fashion down to an almost ohmic contact through these chemical treatments. Moreover, sensitivity to 20 ppb of triethylamine is demonstrated for self-assembled CNTFETs, thus opening new prospects for gas sensors taking advantages of the chemical functionality of the aminosilane used for assembling the CNTFETs.

  15. 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.

  16. 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.

  17. 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.

  18. Biomolecular decision-making process for self assembly.

    SciTech Connect

    Osbourn, Gordon Cecil

    2005-01-01

    The brain is often identified with decision-making processes in the biological world. In fact, single cells, single macromolecules (proteins) and populations of molecules also make simple decisions. These decision processes are essential to survival and to the biological self-assembly and self-repair processes that we seek to emulate. How do these tiny systems make effective decisions? How do they make decisions in concert with a cooperative network of other molecules or cells? How can we emulate the decision-making behaviors of small-scale biological systems to program and self-assemble microsystems? This LDRD supported research to answer these questions. Our work included modeling and simulation of protein populations to help us understand, mimic, and categorize molecular decision-making mechanisms that nonequilibrium systems can exhibit. This work is an early step towards mimicking such nanoscale and microscale biomolecular decision-making processes in inorganic systems.

  19. Protein-directed self-assembly of a fullerene crystal

    NASA Astrophysics Data System (ADS)

    Kim, Kook-Han; Ko, Dong-Kyun; Kim, Yong-Tae; Kim, Nam Hyeong; Paul, Jaydeep; Zhang, Shao-Qing; Murray, Christopher B.; Acharya, Rudresh; Degrado, William F.; Kim, Yong Ho; Grigoryan, Gevorg

    2016-04-01

    Learning to engineer self-assembly would enable the precise organization of molecules by design to create matter with tailored properties. Here we demonstrate that proteins can direct the self-assembly of buckminsterfullerene (C60) into ordered superstructures. A previously engineered tetrameric helical bundle binds C60 in solution, rendering it water soluble. Two tetramers associate with one C60, promoting further organization revealed in a 1.67-Å crystal structure. Fullerene groups occupy periodic lattice sites, sandwiched between two Tyr residues from adjacent tetramers. Strikingly, the assembly exhibits high charge conductance, whereas both the protein-alone crystal and amorphous C60 are electrically insulating. The affinity of C60 for its crystal-binding site is estimated to be in the nanomolar range, with lattices of known protein crystals geometrically compatible with incorporating the motif. Taken together, these findings suggest a new means of organizing fullerene molecules into a rich variety of lattices to generate new properties by design.

  20. Protein-directed self-assembly of a fullerene crystal.

    PubMed

    Kim, Kook-Han; Ko, Dong-Kyun; Kim, Yong-Tae; Kim, Nam Hyeong; Paul, Jaydeep; Zhang, Shao-Qing; Murray, Christopher B; Acharya, Rudresh; DeGrado, William F; Kim, Yong Ho; Grigoryan, Gevorg

    2016-04-26

    Learning to engineer self-assembly would enable the precise organization of molecules by design to create matter with tailored properties. Here we demonstrate that proteins can direct the self-assembly of buckminsterfullerene (C60) into ordered superstructures. A previously engineered tetrameric helical bundle binds C60 in solution, rendering it water soluble. Two tetramers associate with one C60, promoting further organization revealed in a 1.67-Å crystal structure. Fullerene groups occupy periodic lattice sites, sandwiched between two Tyr residues from adjacent tetramers. Strikingly, the assembly exhibits high charge conductance, whereas both the protein-alone crystal and amorphous C60 are electrically insulating. The affinity of C60 for its crystal-binding site is estimated to be in the nanomolar range, with lattices of known protein crystals geometrically compatible with incorporating the motif. Taken together, these findings suggest a new means of organizing fullerene molecules into a rich variety of lattices to generate new properties by design.

  1. DNA Self-assembly and Computer System Fabrication

    NASA Astrophysics Data System (ADS)

    Dwyer, Chris

    2006-11-01

    The migration of circuit fabrication technology from the microscale to the nanoscale has generated a great deal of interest in how the fundamental physical limitations of materials will change the way computer systems are engineered. The changing relationships between performance, defects, and cost have motivated research into so-called disruptive or exotic technologies and draws inspiration from systems found in biology. Advances in DNA self-assembly have demonstrated versatile and programmable methods for the synthesis of complex nanostructures suitable for logic circuitry. Several recent advances in programmable DNA self-assembly and the theory and design of DNA nanostructures for computing will be presented. The advantages of this technology go beyond the simple scaling of device feature sizes (sub-20nm) to enable new modes of computation that are otherwise impractical with conventional technologies. A brief survey of several computer architectures that take advantage of this new technology will also be presented.

  2. Self-assembly of amorphous calcium carbonate microlens arrays.

    PubMed

    Lee, Kyubock; Wagermaier, Wolfgang; Masic, Admir; Kommareddy, Krishna P; Bennet, Mathieu; Manjubala, Inderchand; Lee, Seung-Woo; Park, Seung B; Cölfen, Helmut; Fratzl, Peter

    2012-03-06

    Biological materials are often based on simple constituents and grown by the principle of self-assembly under ambient conditions. In particular, biomineralization approaches exploit efficient pathways of inorganic material synthesis. There is still a large gap between the complexity of natural systems and the practical utilization of bioinspired formation mechanisms. Here we describe a simple self-assembly route leading to a CaCO(3) microlens array, somewhat reminiscent of the brittlestars' microlenses, with uniform size and focal length, by using a minimum number of components and equipment at ambient conditions. The formation mechanism of the amorphous CaCO(3) microlens arrays was elucidated by confocal Raman spectroscopic imaging to be a two-step growth process mediated by the organic surfactant. CaCO(3) microlens arrays are easy to fabricate, biocompatible and functional in amorphous or more stable crystalline forms. This shows that advanced optical materials can be generated by a simple mineral precipitation.

  3. Self-assembled Chiral Nanostructure as Scaffold for Asymmetric Reaction.

    PubMed

    Jiang, Jian; Ouyang, Guanghui; Zhang, Li; Liu, Minghua

    2017-03-25

    Asymmetric reaction is one of the most important reactions in organic synthesis. While large amount of efficient molecular catalysts have been developed and applied, supramolecular and nanostructured catalysts have been attracting recent interest. In this mini review, we focused on the self-assembled chiral nanostructures and reviewed their possibility and feasibility as the enantioselective catalyst. The design concept and the requirement of the chiral scaffold as the catalysts are discussed. Based on the chirality and catalytic performance of the building molecules and the supramolecular nanostructures, the nanocatalyst is divided into chiral nanostructure driven (CND) and chiral nanostructure enhanced (CNE) enantioselective catalysts. Then, several typical self-assembled chiral nanostructures such as nanocage, nanotube, nanorod, micelles and vesicles are selected as the chiral scaffold and their catalytic behaviors for the asymmetric reactions were demonstrated. Finally, the future development of the field is also outlooked.

  4. DNA-Based Self-Assembly of Fluorescent Nanodiamonds.

    PubMed

    Zhang, Tao; Neumann, Andre; Lindlau, Jessica; Wu, Yuzhou; Pramanik, Goutam; Naydenov, Boris; Jelezko, Fedor; Schüder, Florian; Huber, Sebastian; Huber, Marinus; Stehr, Florian; Högele, Alexander; Weil, Tanja; Liedl, Tim

    2015-08-12

    As a step toward deterministic and scalable assembly of ordered spin arrays we here demonstrate a bottom-up approach to position fluorescent nanodiamonds (NDs) with nanometer precision on DNA origami structures. We have realized a reliable and broadly applicable surface modification strategy that results in DNA-functionalized and perfectly dispersed NDs that were then self-assembled in predefined geometries. With optical studies we show that the fluorescence properties of the nitrogen-vacancy color centers in NDs are preserved during surface modification and DNA assembly. As this method allows the nanoscale arrangement of fluorescent NDs together with other optically active components in complex geometries, applications based on self-assembled spin lattices or plasmon-enhanced spin sensors as well as improved fluorescent labeling for bioimaging could be envisioned.

  5. Thermomechanical Response of Self-Assembled Nanoparticle Membranes.

    PubMed

    Wang, Yifan; Chan, Henry; Narayanan, Badri; McBride, Sean P; Sankaranarayanan, Subramanian K R S; Lin, Xiao-Min; Jaeger, Heinrich M

    2017-08-22

    Monolayers composed of colloidal nanoparticles, with a thickness of less than 10 nm, have remarkable mechanical moduli and can suspend over micrometer-sized holes to form free-standing membranes. In this paper, we discuss experiments and coarse-grained molecular dynamics simulations characterizing the thermomechanical properties of these self-assembled nanoparticle membranes. These membranes remain strong and resilient up to temperatures much higher than previous simulation predictions and exhibit an unexpected hysteretic behavior during the first heating-cooling cycle. We show this hysteretic behavior can be explained by an asymmetric ligand configuration from the self-assembly process and can be controlled by changing the ligand coverage or cross-linking the ligand molecules. Finally, we show the screening effect of water molecules on the ligand interactions can strongly affect the moduli and thermomechanical behavior.

  6. Self-assembly of double helical nanostructures inside carbon nanotubes.

    PubMed

    Lv, Cheng; Xue, Qingzhong; Shan, Meixia; Jing, Nuannuan; Ling, Cuicui; Zhou, Xiaoyan; Jiao, Zhiyong; Xing, Wei; Yan, Zifeng

    2013-05-21

    We use molecular dynamics (MD) simulations to show that a DNA-like double helix of two poly(acetylene) (PA) chains can form inside single-walled carbon nanotubes (SWNTs). The computational results indicate that SWNTs can activate and guide the self-assembly of polymer chains, allowing them to adopt a helical configuration in a SWNT through the combined action of the van der Waals potential well and the π-π stacking interaction between the polymer and the inner surface of SWNTs. Meanwhile both the SWNT size and polymer chain stiffness determine the outcome of the nanostructure. Furthermore, we also found that water clusters encourage the self-assembly of PA helical structures in the tube. This molecular model may lead to a better understanding of the formation of a double helix biological molecule inside SWNTs. Alternatively, it could form the basis of a novel nanoscale material by utilizing the 'empty' spaces of SWNTs.

  7. Self-assembly of nanomaterials at fluid interfaces.

    PubMed

    Toor, Anju; Feng, Tao; Russell, Thomas P

    2016-05-01

    Recent developments in the field of the self-assembly of nanoscale materials such as nanoparticles, nanorods and nanosheets at liquid/liquid interfaces are reviewed. Self-assembly behavior of both biological and synthetic particles is discussed. For biological nanoparticles, the nanoparticle assembly at fluid interfaces provides a simple route for directing nanoparticles into 2D or 3D constructs with hierarchical ordering. The interfacial assembly of single-walled carbon nanotubes (SWCNTs) at liquid interfaces would play a key role in applications such as nanotube fractionation, flexible electronic thin-film fabrication and synthesis of porous SWCNT/polymer composites foams. Liquids can be structured by the jamming of nanoparticle surfactants at fluid interfaces. By controlling the interfacial packing of nanoparticle surfactants using external triggers, a new class of materials can be generated that combines the desirable characteristics of fluids such as rapid transport of energy carriers with the structural stability of a solid.

  8. Design of Self-Assembling Protein-Polymer Conjugates.

    PubMed

    Carter, Nathan A; Geng, Xi; Grove, Tijana Z

    Protein-polymer conjugates are of particular interest for nanobiotechnology applications because of the various and complementary roles that each component may play in composite hybrid-materials. This chapter focuses on the design principles and applications of self-assembling protein-polymer conjugate materials. We address the general design methodology, from both synthetic and genetic perspective, conjugation strategies, protein vs. polymer driven self-assembly and finally, emerging applications for conjugate materials. By marrying proteins and polymers into conjugated bio-hybrid materials, materials scientists, chemists, and biologists alike, have at their fingertips a vast toolkit for material design. These inherently hierarchical structures give rise to useful patterning, mechanical and transport properties that may help realize new, more efficient materials for energy generation, catalysis, nanorobots, etc.

  9. Self-assembly of flagellin on Au(111) surfaces.

    PubMed

    González Orive, Alejandro; Pissinis, Diego E; Diaz, Carolina; Miñán, Alejandro; Benítez, Guillermo A; Rubert, Aldo; Daza Millone, Antonieta; Rumbo, Martin; Hernández Creus, Alberto; Salvarezza, Roberto C; Schilardi, Patricia L

    2014-11-01

    The adsorption of flagellin monomers from Pseudomonas fluorescens on Au(111) has been studied by Atomic Force Microscopy (AFM), Scanning Tunneling Microscopy (STM), X-ray Photoelectron Spectroscopy (XPS), Surface Plasmon Resonance (SPR), and electrochemical techniques. Results show that flagellin monomers spontaneously self-assemble forming a monolayer thick protein film bounded to the Au surface by the more hydrophobic subunit and exposed to the environment the hydrophilic subunit. The films are conductive and allow allocation of electrochemically active cytochrome C. The self-assembled films could be used as biological platforms to build 3D complex molecular structures on planar metal surfaces and to functionalize metal nanoparticles. Copyright © 2014 Elsevier Inc. All rights reserved.

  10. Stable doping of carbon nanotubes via molecular self assembly

    SciTech Connect

    Lee, B.; Chen, Y.; Podzorov, V.; Cook, A.; Zakhidov, A.

    2014-10-14

    We report a novel method for stable doping of carbon nanotubes (CNT) based on methods of molecular self assembly. A conformal growth of a self-assembled monolayer of fluoroalkyl trichloro-silane (FTS) at CNT surfaces results in a strong increase of the sheet conductivity of CNT electrodes by 60–300%, depending on the CNT chirality and composition. The charge carrier mobility of undoped partially aligned CNT films was independently estimated in a field-effect transistor geometry (~100 cm²V⁻¹s⁻¹). The hole density induced by the FTS monolayer in CNT sheets is estimated to be ~1.8 ×10¹⁴cm⁻². We also show that FTS doping of CNT anodes greatly improves the performance of organic solar cells. This large and stable doping effect, easily achieved in large-area samples, makes this approach very attractive for applications of CNTs in transparent and flexible electronics.

  11. Self-assembling enzymes and the origins of the cytoskeleton

    PubMed Central

    Barry, Rachael; Gitai, Zemer

    2011-01-01

    The bacterial cytoskeleton is composed of a complex and diverse group of proteins that self-assemble into linear filaments. These filaments support and organize cellular architecture and provide a dynamic network controlling transport and localization within the cell. Here, we review recent discoveries related to a newly appreciated class of self-assembling proteins that expand our view of the bacterial cytoskeleton and provide potential explanations for its evolutionary origins. Specifically, several types of metabolic enzymes can form structures similar to established cytoskeletal filaments and, in some cases, these structures have been repurposed for structural uses independent of their normal role. The behaviors of these enzymes suggest that some modern cytoskeletal proteins may have evolved from dual-role proteins with catalytic and structural functions. PMID:22014508

  12. Self-assembled architectures from biohybrid triblock copolymers.

    PubMed

    Reynhout, Irene C; Cornelissen, Jeroen J L M; Nolte, Roeland J M

    2007-02-28

    The synthesis and self-assembly behavior of biohybrid ABC triblock copolymers consisting of a synthetic diblock, polystyrene-b-polyethylene glycol (PSm-b-PEG113), where m is varied, and a hemeprotein, myoglobin (Mb) or horse radish peroxidase (HRP), is described. The synthetic diblock copolymer is first functionalized with the heme cofactor and subsequently reconstituted with the apoprotein or the apoenzyme to yield the protein-containing ABC triblock copolymer. The obtained amphiphilic block copolymers self-assemble in aqueous solution into a large variety of aggregate structures. Depending on the protein and the polystyrene block length, micellar rods, vesicles, toroids, figure eight structures, octopus structures, and spheres with a lamellar surface are formed.

  13. 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.

  14. Self-reproduction of nanoparticles through synergistic self-assembly.

    PubMed

    Ikeda, Keisuke; Nakano, Minoru

    2015-01-01

    We describe a self-reproduction mechanism of nanometer-sized particles (i.e., nanodiscs) through chemical ligation of the precursors and self-assembly of the building blocks. The ligation reaction was accelerated on lipid bilayer surfaces, and the products spontaneously assembled into nanodiscs with lipid molecules. With the increase in the number of nanodiscs, a rapid proliferation of the nanodiscs occurred through the spatial rearrangements of the molecules between the pre-existing nanodiscs and the unreacted materials, rather than template- or complex-enhanced ligation of the precursors. The subsequent process of surface-enhanced ligation of integrated precursors matured the nanoparticles into identical copies of the pre-existing assembly. Our study showed that the synergistic self-assembly mechanism probably underlie the self-replication principles for heterogeneous multimolecular systems.

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

    PubMed Central

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

    2015-01-01

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

  16. An information-bearing seed for nucleating algorithmic self-assembly.

    PubMed

    Barish, Robert D; Schulman, Rebecca; Rothemund, Paul W K; Winfree, Erik

    2009-04-14

    Self-assembly creates natural mineral, chemical, and biological structures of great complexity. Often, the same starting materials have the potential to form an infinite variety of distinct structures; information in a seed molecule can determine which form is grown as well as where and when. These phenomena can be exploited to program the growth of complex supramolecular structures, as demonstrated by the algorithmic self-assembly of DNA tiles. However, the lack of effective seeds has limited the reliability and yield of algorithmic crystals. Here, we present a programmable DNA origami seed that can display up to 32 distinct binding sites and demonstrate the use of seeds to nucleate three types of algorithmic crystals. In the simplest case, the starting materials are a set of tiles that can form crystalline ribbons of any width; the seed directs assembly of a chosen width with >90% yield. Increased structural diversity is obtained by using tiles that copy a binary string from layer to layer; the seed specifies the initial string and triggers growth under near-optimal conditions where the bit copying error rate is <0.2%. Increased structural complexity is achieved by using tiles that generate a binary counting pattern; the seed specifies the initial value for the counter. Self-assembly proceeds in a one-pot annealing reaction involving up to 300 DNA strands containing >17 kb of sequence information. In sum, this work demonstrates how DNA origami seeds enable the easy, high-yield, low-error-rate growth of algorithmic crystals as a route toward programmable bottom-up fabrication.

  17. Sequential programmable self-assembly: Role of cooperative interactions

    DOE PAGES

    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 convenientmore » 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.« less

  18. Self-Assembling Protein Materials for Metal Nanoparticle Templation

    DTIC Science & Technology

    2015-05-01

    form nanoporous , durable frameworks upon which cells can be conditioned to grow.8,99,100 The remarkable feature of synthetic protein materials is... Materials for Metal Nanoparticle Templation The views, opinions and/or findings contained in this report are those of the author(s) and should not contrued...Polytechnic Institute of New York University Brooklyn, NY 11201 -3840 ABSTRACT Self-assembling Protein Materials for Metal Nanoparticle Templation Report Title

  19. Controlling guest-host interactions in self-assembled materials

    NASA Astrophysics Data System (ADS)

    Steinbeck, Christian Alexander

    Aqueous solutions of self-assembling macromolecules can be found in many industrial formulations, as well as in many living organisms. Regardless of the specific system, the self-assembling macromolecules are rarely found in the absence of other solutes or guest species. Such components may include fragrance molecules incorporated into block-copolymer micelles for use in detergents, dyes included in micellar precursor solutions for the synthesis of mesostructured silica-block copolymer composites, or specifically designed additives for controlling protein folding and activity. A detailed understanding of the structures and dynamic molecular interactions among the various species in solution and their influences on macromolecule aggregation and phase behaviors is of paramount importance for designing systems with improved properties and performance. Unambiguous measurements of the loci of interaction and solubilization of small molecule species (e.g., dyes or surfactants) within self-assembling block-copolymer species or proteins in aqueous solutions have been established. This has been achieved by exploiting powerful correlative multidimensional nuclear magnetic resonance (NMR) spectroscopy techniques, including pulsed-field-gradient diffusion measurements, which provide detailed molecular insights into a variety of heterogeneous self-assembled systems. Furthermore, these insights and measurements enable the solution conditions to be established that permit the control and release of such guest molecules from association with macromolecular carrier species into the surrounding solution. Specifically, the use of temperature to control the distribution of porphyrin guest-species in a block-copolymer host and the light-dependent folding and unfolding of bovine serum albumin through varying interactions with an azo-benzene functionalized surfactant are demonstrated. In the absence of long-range order in these complex systems, advanced NMR spectroscopy methods provide

  20. Molecular Recognition Directed Self-Assembly of Supramolecular Polymers

    DTIC Science & Technology

    1994-06-30

    SUPRAMOLECULAR POLYMERS by V. Percec, J. Heck, G. Johansson, D. Tomazos, M. Kawasumi and G. Ungar Published in the J. Macromol. SOi: Part A: Pure...W.asetaqIom OC JOS0l 4 TITE AN SUBITLES. FUNDING NUMBERS Molecular Recognition Directed Self-Assembly of Suprainolecular Polymers N00014-89--J-1828 6. AUTHOR(S...comparison between various supramolecular (generated via H-bonding, iions) and molecular " polymer backbones" will be made. The present limitations