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Sample records for supramolecular self-assembly study

  1. Communication: Self-assembly of a model supramolecular polymer studied by replica exchange with solute tempering

    Science.gov (United States)

    Arefi, Hadi H.; Yamamoto, Takeshi

    2017-12-01

    Conventional molecular-dynamics (cMD) simulation has a well-known limitation in accessible time and length scales, and thus various enhanced sampling techniques have been proposed to alleviate the problem. In this paper, we explore the utility of replica exchange with solute tempering (REST) (i.e., a variant of Hamiltonian replica exchange methods) to simulate the self-assembly of a supramolecular polymer in explicit solvent and compare the performance with temperature-based replica exchange MD (T-REMD) as well as cMD. As a test system, we consider a relatively simple all-atom model of supramolecular polymerization (namely, benzene-1,3,5-tricarboxamides in methylcyclohexane solvent). Our results show that both REST and T-REMD are able to predict highly ordered polymer structures with helical H-bonding patterns, in contrast to cMD which completely fails to obtain such a structure for the present model. At the same time, we have also experienced some technical challenge (i.e., aggregation-dispersion transition and the resulting bottleneck for replica traversal), which is illustrated numerically. Since the computational cost of REST scales more moderately than T-REMD, we expect that REST will be useful for studying the self-assembly of larger systems in solution with enhanced rearrangement of monomers.

  2. Photoluminescence Spectra of Self-Assembling Helical Supramolecular Assemblies: A Theoretical Study

    NARCIS (Netherlands)

    van Dijk, Leon; Kersten, Sander P.; Jonkheijm, Pascal; van der Schoot, Paul; Bobbert, Peter A.

    2008-01-01

    The reversible assembly of helical supramolecular polymers of chiral molecular building blocks is known to be governed by the interplay between mass action and the competition between weakly and strongly bound states of these building blocks. The highly co-operative transition from free monomers at

  3. Controlled Self-Assembly of Photofunctional Supramolecular Nanotubes.

    Science.gov (United States)

    Cohen, Erez; Weissman, Haim; Pinkas, Iddo; Shimoni, Eyal; Rehak, Pavel; Král, Petr; Rybtchinski, Boris

    2018-01-23

    Designing supramolecular nanotubes (SNTs) with distinct dimensions and properties is highly desirable, yet challenging, since structural control strategies are lacking. Furthermore, relatively complex building blocks are often employed in SNT self-assembly. Here, we demonstrate that symmetric bolaamphiphiles having a hydrophobic core comprised of two perylene diimide moieties connected via a bipyridine linker and bearing polyethylene glycol (PEG) side chains can self-assemble into diverse molecular nanotubes. The structure of the nanotubes can be controlled by assembly conditions (solvent composition and temperature) and a PEG chain length. The resulting nanotubes differ both in diameter and cross section geometry, having widths of 3 nm (triangular-like cross-section), 4 nm (rectangular), and 5 nm (hexagonal). Molecular dynamics simulations provide insights into the stability of the tubular superstructures and their initial stages of self-assembly, revealing a key role of oligomerization via side-by-side aromatic interactions between bis-aromatic cores. Probing electronic and photonic properties of the nanotubes revealed extended electron delocalization and photoinduced charge separation that proceeds via symmetry breaking, a photofunction distinctly different from that of the fibers assembled from the same molecules. A high degree of structural control and insights into SNT self-assembly advance design approaches toward functional organic nanomaterials.

  4. Self-Assembled Supramolecular Architectures Lyotropic Liquid Crystals

    CERN Document Server

    Garti, Nissim

    2012-01-01

    This book will describe fundamentals and recent developments in the area of Self-Assembled Supramolecular Architecture and their relevance to the  understanding of the functionality of  membranes  as delivery systems for active ingredients. As the heirarchial architectures determine their performance capabilities, attention will be paid to theoretical and design aspects related to the construction of lyotropic liquid crystals: mesophases such as lamellar, hexagonal, cubic, sponge phase micellosomes. The book will bring to the reader mechanistic aspects, compositional c

  5. Preface: special topic on supramolecular self-assembly at surfaces.

    Science.gov (United States)

    Bartels, Ludwig; Ernst, Karl-Heinz; Gao, Hong-Jun; Thiel, Patricia A

    2015-03-14

    Supramolecular self-assembly at surfaces is one of the most exciting and active fields in Surface Science today. Applications can take advantage of two key properties: (i) versatile pattern formation over a broad length scale and (ii) tunability of electronic structure and transport properties, as well as frontier orbital alignment. It provides a new frontier for Chemical Physics as it uniquely combines the versatility of Organic Synthesis and the Physics of Interfaces. The Journal of Chemical Physics is pleased to publish this Special Topic Issue, showcasing recent advances and new directions.

  6. Self-assembling supramolecular systems of different symmetry formed by wedged macromolecular dendrons

    Energy Technology Data Exchange (ETDEWEB)

    Shcherbina, M. A., E-mail: shcherbina@ispm.ru; Bakirov, A. V. [Russian Academy of Sciences, Institute of Synthetic Polymer Materials (Russian Federation); Yakunin, A. N. [Karpov Institute of Physical Chemistry (Russian Federation); Percec, V. [University of Pennsylvania (United States); Beginn, U. [Universitaet Osnabrueck, Institut fuer Chemie (Germany); Moeller, M. [Institute for Technical and Macromolecular Chemistry (Germany); Chvalun, S. N. [Russian Academy of Sciences, Institute of Synthetic Polymer Materials (Russian Federation)

    2012-03-15

    The main stages of the self-assembling of supramolecular ensembles have been revealed by studying different functional wedged macromolecules: polymethacrylates with tapered side chains based on gallic acid, their macromonomers, and salts of 2,3,4- and 3,4,5-tris(dodecyloxy)benzenesulphonic acid. The first stage is the formation of individual supramolecular aggregates (long cylinders or spherical micelles) due to the weak noncovalent interactions of mesogenic groups and the subsequent ordering in these aggregates, which is accompanied by a decrease in the free energy of the system. Supramolecular aggregates, in turn, form 2D or 3D lattices. The shape of supramolecular aggregates and its change with temperature are delicate functions of the mesogen chemical structure; this circumstance makes it possible to rationally design complex self-assembling systems with the ability to respond smartly to external stimuli. X-ray diffraction analysis allows one to study the structure of supramolecular systems with different degrees of order, determine the type of mesophases formed by these systems, and reveal the phase behavior of the material. Particular attention has been paid to the method for reconstruction of electron density distribution from the relative reflection intensity. The application of a suite of experimental methods, including wide- and small-angle X-ray diffraction, molecular modeling, differential scanning calorimetry, and polarization optical microscopy, allows one to establish the relationship between the shape of the structural unit (molecule or molecular aggregate), the nature of the interaction, and the phase behavior of the material.

  7. Self-assembling supramolecular systems of different symmetry formed by wedged macromolecular dendrons

    Science.gov (United States)

    Shcherbina, M. A.; Bakirov, A. V.; Yakunin, A. N.; Percec, V.; Beginn, U.; Möller, M.; Chvalun, S. N.

    2012-03-01

    The main stages of the self-assembling of supramolecular ensembles have been revealed by studying different functional wedged macromolecules: polymethacrylates with tapered side chains based on gallic acid, their macromonomers, and salts of 2,3,4- and 3,4,5-tris(dodecyloxy)benzenesulphonic acid. The first stage is the formation of individual supramolecular aggregates (long cylinders or spherical micelles) due to the weak noncovalent interactions of mesogenic groups and the subsequent ordering in these aggregates, which is accompanied by a decrease in the free energy of the system. Supramolecular aggregates, in turn, form 2D or 3D lattices. The shape of supramolecular aggregates and its change with temperature are delicate functions of the mesogen chemical structure; this circumstance makes it possible to rationally design complex self-assembling systems with the ability to respond smartly to external stimuli. X-ray diffraction analysis allows one to study the structure of supramolecular systems with different degrees of order, determine the type of mesophases formed by these systems, and reveal the phase behavior of the material. Particular attention has been paid to the method for reconstruction of electron density distribution from the relative reflection intensity. The application of a suite of experimental methods, including wide- and small-angle X-ray diffraction, molecular modeling, differential scanning calorimetry, and polarization optical microscopy, allows one to establish the relationship between the shape of the structural unit (molecule or molecular aggregate), the nature of the interaction, and the phase behavior of the material.

  8. Supramolecular Hydrogels Based on DNA Self-Assembly.

    Science.gov (United States)

    Shao, Yu; Jia, Haoyang; Cao, Tianyang; Liu, Dongsheng

    2017-04-18

    viability in the three-dimensional matrix to several weeks and also provides an easy way to prepare interpenetrating double network materials. In this Account, we outline the stream of hydrogels based on DNA self-assembly and discuss the mechanism that brings outstanding properties to the materials. Unlike most reported hydrogel systems, the all-in-one character of the DNA hydrogel avoids the "cask effect" in the properties. We believe the hydrogel will greatly benefit cell behavior studies especially in the following aspects: (1) stem cell differentiation can be studied with solely tunable mechanical strength of the matrix; (2) the dynamic nature of the network can allow cell migration through the hydrogel, which will help to build a more realistic model to observe the migration of cancer cells in vivo; (3) combination with rapidly developing three-dimension printing technology, the hydrogel will boost the construction of three-dimensional tissues and artificial organs.

  9. Light- and pH Switchable Supramolecular Nanoparticles through Electrostatic Self-Assembly

    Science.gov (United States)

    Groehn, Franziska; Willerich, Immanuel

    2011-03-01

    Supramolecular structures that can respond to external triggers are of high interest for example for nanotechnology or drug delivery. Recently we have introduced an approach to electrostatic self-assembly for the formation of supramolecular particles in solution: polyelectrolytes and multivalent stiff organic counterions build well-defined and stable nano-objects. In addition to electrostatics, secondary interactions between counterions such as pi-pi stacking directs the association. Aggregates with narrow size distribution and varying shape such as spheres, cylinders, vesicles and networks result. PH-responsive assemblies can be repeatedly switched ``on'' and ``off'' through pH. Furthermore, light is an elegant, non-invasive stimulus offering possibilities for new functional nanostructures. By electrostatic self-assembly, supramolecular particles can be built the size of which can be triggered by light. For example, assemblies of dendrimer macroions and divalent azobenzene counterions can respond to light with a size increase from 30 nm to 165 nm radius. Detailed characterization by static and dynamic light scattering, AFM, SANS and zeta-potential measurements as well as thermodynamic studies yield insight into driving forces and structural control in the self-assembly process.

  10. Supramolecular nanoparticles generated by the self-assembly of polyrotaxanes for antitumor drug delivery

    Directory of Open Access Journals (Sweden)

    Liu R

    2012-10-01

    Full Text Available Rong Liu,1,2,* Yusi Lai,1,* Bin He,1 Yuan Li,1 Gang Wang,1 Shuang Chang,1 Zhongwei Gu1 1National Engineering Research Center for Biomaterials, Sichuan University, Chengdu, China; 2Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China*These authors contributed equally to this paperAbstract: A new approach of fabricating supramolecular nanoparticles generated by self-assembly polyrotaxanes for antitumor drug delivery has been reported. Cinnamic-acid-modified poly(ethylene glycol chains were threaded in a-cyclodextrins to form polyrotaxanes. The polyrotaxanes self-assembled supramolecular nanoparticles. The morphology of the nanoparticles was changed from nanovesicle to micelle after the antitumor drug, doxorubicin, was loaded. The release profile of the drug-loaded nanoparticles was investigated, and it was found that the sustaining release time could last for 32 hours. The drug-loaded nanoparticles were co-cultured with mouse 4T1 breast cancer cells with a drug concentration of 10 µg/mL; the cell survival rate was 3.3% after a 72-hour incubation. In an in vivo study of breast cancer in a mouse model, the drug-loaded nanoparticles were injected in the tail veins of mice with a dose of 5 mg/kg body weight. The tumor inhibition rate of drug-loaded nanoparticles was 53%, which was better than that of doxorubicin hydrochloride. The cardiac toxicity of doxorubicin was decreased greatly after the encapsulation into supramolecular polyrotaxane nanoparticles.Keywords: polyrotaxane, self-assembly, nanoparticle, doxorubicin, supermolecular

  11. Effect of H-bonding interactions of water molecules in the self assembly of supramolecular architecture-joint experimental and computational studies

    Science.gov (United States)

    Jassal, Amanpreet Kaur; Kaur, Rajwinder; Islam, Nasarul; Anu; Mudsainiyan, Rahul Kumar

    2017-08-01

    A new {[Cu(4,4‧-BP)2.(H2O)4].2,6-NDC.3(H2O)} complex has been synthesized by refluxing Cu(NO3)2, 2,6-NDC and 4,4‧-BP (1:1:1 ratio) (2,6-NDC = 2,6-Naphthalene Dicarboxylic acid, 4,4‧-BP = 4,4'-bipyridine) in methanol/ammonia mixture and characterized by various spectroscopic techniques. The geometry around Cu2+ ion is typical octahedral in cationic complex, while the deprotonated 2,6-NDC act as a charge balancing counter anionic part. Water molecules (lattice and coordinated) also play important role in the self-assembly by forming Hsbnd bonded supramolecular architecture involving strong inter/intramolecular secondary interactions. The luminescence property and thermogravimetric analyses were also investigated. Both the intermolecular interactions of molecular and crystal structures of this complex were compared and discussed using Hirshfeld surface analysis and 2D-fingerprint plots. Hirshfeld surface analysis indicates that H⋯H, O⋯H and π···π contacts can account for 40.4, 19.3 and 7.7% respectively of the total Hirshfeld surface area. The DFT calculation at the CAM-B3LYP level of theory revealed the existence of three hydrogens binds in the complex. These hydrogen bonds exist between the oxygen atom of ligand and the hydrogen of coordinated water molecules.

  12. Self-assembly of a supramolecular hexagram and a supramolecular pentagram

    Science.gov (United States)

    Jiang, Zhilong; Li, Yiming; Wang, Ming; Song, Bo; Wang, Kun; Sun, Mingyu; Liu, Die; Li, Xiaohong; Yuan, Jie; Chen, Mingzhao; Guo, Yuan; Yang, Xiaoyu; Zhang, Tong; Moorefield, Charles N.; Newkome, George R.; Xu, Bingqian; Li, Xiaopeng; Wang, Pingshan

    2017-05-01

    Five- and six-pointed star structures occur frequently in nature as flowers, snow-flakes, leaves and so on. These star-shaped patterns are also frequently used in both functional and artistic man-made architectures. Here following a stepwise synthesis and self-assembly approach, pentagonal and hexagonal metallosupramolecules possessing star-shaped motifs were prepared based on the careful design of metallo-organic ligands (MOLs). In the MOL design and preparation, robust ruthenium-terpyridyl complexes were employed to construct brominated metallo-organic intermediates, followed by a Suzuki coupling reaction to achieve the required ensemble. Ligand LA (VRu2+X, V=bisterpyridine, X=tetraterpyridine, Ru=Ruthenium) was initially used for the self-assembly of an anticipated hexagram upon reaction with Cd2+ or Fe2+ however, unexpected pentagonal structures were formed, that is, [Cd5LA5]30+ and [Fe5LA5]30+. In our redesign, LB [V(Ru2+X)2] was synthesized and treated with 60° V-shaped bisterpyridine (V) and Cd2+ to create hexagonal hexagram [Cd12V3LB3]36+ along with traces of the triangle [Cd3V3]6+. Finally, a pure supramolecular hexagram [Fe12V3LB3]36+ was successfully isolated in a high yield using Fe2+ with a higher assembly temperature.

  13. Amphiphiles Self-Assembly: Basic Concepts and Future Perspectives of Supramolecular Approaches

    Directory of Open Access Journals (Sweden)

    Domenico Lombardo

    2015-01-01

    Full Text Available Amphiphiles are synthetic or natural molecules with the ability to self-assemble into a wide variety of structures including micelles, vesicles, nanotubes, nanofibers, and lamellae. Self-assembly processes of amphiphiles have been widely used to mimic biological systems, such as assembly of lipids and proteins, while their integrated actions allow the performance of highly specific cellular functions which has paved a way for bottom-up bionanotechnology. While amphiphiles self-assembly has attracted considerable attention for decades due to their extensive applications in material science, drug and gene delivery, recent developments in nanoscience stimulated the combination of the simple approaches of amphiphile assembly with the advanced concept of supramolecular self-assembly for the development of more complex, hierarchical nanostructures. Introduction of stimulus responsive supramolecular amphiphile assembly-disassembly processes provides particularly novel approaches for impacting bionanotechnology applications. Leading examples of these novel self-assembly processes can be found, in fact, in biosystems where assemblies of different amphiphilic macrocomponents and their integrated actions allow the performance of highly specific biological functions. In this perspective, we summarize in this tutorial review the basic concept and recent research on self-assembly of traditional amphiphilic molecules (such as surfactants, amphiphile-like polymers, or lipids and more recent concepts of supramolecular amphiphiles assembly which have become increasingly important in emerging nanotechnology.

  14. Surface-Assisted Self-Assembly Strategies Leading to Supramolecular Hydrogels.

    Science.gov (United States)

    Vigier-Carrière, Cécile; Boulmedais, Fouzia; Schaaf, Pierre; Jierry, Loïc

    2018-02-05

    Localized molecular self-assembly processes leading to the growth of nanostructures exclusively from the surface of a material is one of the great challenges in surface chemistry. In the last decade, several works have been reported on the ability of modified or unmodified surfaces to manage the self-assembly of low-molecular-weight hydrogelators (LMWH) resulting in localized supramolecular hydrogel coatings mainly based on nanofiber architectures. This Minireview highlights all strategies that have emerged recently to initiate and localize LMWH supramolecular hydrogel formation, their related fundamental issues and applications. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Zwitterionic supramolecular nanoparticles: self-assembly and responsive properties

    NARCIS (Netherlands)

    Stoffelen, C.; Huskens, Jurriaan

    2015-01-01

    Supramolecular nanoparticles (SNPs) are of high interest in both nanoscience and molecular diagnostics and therapeutics, because of their reversible and designable properties. To ensure colloidal stabilization and biocompatibility, most reported strategies require the use of hydrophilic long-chain

  16. Supramolecular self-assembly of nonlinear amphiphilic and double hydrophilic block copolymers in aqueous solutions.

    Science.gov (United States)

    Ge, Zhishen; Liu, Shiyong

    2009-09-17

    Supramolecular self-assembly of block copolymers in aqueous solution has received ever-increasing interest over the past few decades due to diverse biological and technological applications in drug delivery, imaging, sensing and catalysis. In addition to relative block lengths, molecular weights and solution conditions, chain architectures of block copolymers can also dramatically affect their self-assembling properties in selective solvents. This feature article mainly focuses on recent developments in the field of supramolecular self-assembly of amphiphilic and double hydrophilic block copolymers (DHBCs) possessing nonlinear chain topologies, including miktoarm star polymers, dendritic-linear block copolymers, cyclic block copolymers and comb-shaped copolymer brushes. Copyright © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Self-assembly of boron-based supramolecular structures

    OpenAIRE

    Christinat, Nicolas

    2008-01-01

    This work describes the synthesis and characterization of boronic acid-based supramolecular structures. Macrocycles, dendritic structures, polymers, rotaxanes, and cages were assembled using four types of reversible reactions. The key point of the strategy is the parallel utilization of two –or more– of these reactions. Initially, aryl and alkylboronic acids were condensed with dihydroxypyridine ligands to give tetrameric or pentameric macrocycles, in which four or five boronate esters are co...

  18. Solid structures of the stepwise self-assembled copillar[5]arene-based supramolecular polymers

    Energy Technology Data Exchange (ETDEWEB)

    Park, Yeon Sil; Hwang, Seong Min; Shin, Jae Yeon; Paek, Kyung Soo [Dept. of Chemistry, Soongsil University, Seoul (Korea, Republic of)

    2016-10-15

    Development of supramolecular polymer has attracted much interest because of their interesting properties such as stimuli-responsiveness, recycling, self-healing and degradability, and their consequential applications. The essential feature of this class of polymers is the self-assembly of discrete monomeric subunits via non-covalent interactions or dynamic covalent bonds. Among the many monomeric subunits, pillar[n]arenes have been ideal building blocks for the fabrication of polymeric supramolecules because of their intrinsic characteristics. The ring-shaped morphologies in supramolecular polymer P are probably due to the tendency of the end-to-end connection in the solid state of long flexible supramolecular chains. The size increase of nano-rings as the stepwise addition increases might be due to the fact that the linear supramolecular polymer P in solution seems to be maintained until the nano-ring formation by solidification.

  19. Supramolecular self-assembling in mesostructured materials through charge tuning in the inorganic phase

    OpenAIRE

    Roca, Manuel; El Haskouri, Jamal; Cabrera Medina, Saúl; Beltrán Porter, Aurelio; Álamo Serrano, Jaime; Beltrán Porter, Daniel; Marcos, María Dolores; Amorós del Toro, Pedro José

    1998-01-01

    Supramolecular self-assembling of organic CTA+ micelles and inorganic [VO(H2O)PO4]n^q-2 2D-anions for the isolation of hexagonal mesostructured materials can be reached by charge tuning in the inorganic phase through the adjustment of the vanadium mean oxidation state. El Haskouri, Jamal, ; Cabrera Medina, Saul, ; Beltran Porter, Aurelio, ; Alamo Serrano, Jaime, ; Beltran Porter, Daniel, ; ...

  20. Covalent defects restrict supramolecular self-assembly of homopolypeptides: case study of β2-fibrils of poly-L-glutamic acid.

    Directory of Open Access Journals (Sweden)

    Aleksandra Fulara

    Full Text Available Poly-L-glutamic acid (PLGA often serves as a model in studies on amyloid fibrils and conformational transitions in proteins, and as a precursor for synthetic biomaterials. Aggregation of PLGA chains and formation of amyloid-like fibrils was shown to continue on higher levels of superstructural self-assembly coinciding with the appearance of so-called β2-sheet conformation manifesting in dramatic redshift of infrared amide I' band below 1600 cm(-1. This spectral hallmark has been attributed to network of bifurcated hydrogen bonds coupling C = O and N-D (N-H groups of the main chains to glutamate side chains. However, other authors reported that, under essentially identical conditions, PLGA forms the conventional in terms of infrared characteristics β1-sheet structure (exciton-split amide I' band with peaks at ca. 1616 and 1683 cm(-1. Here we attempt to shed light on this discrepancy by studying the effect of increasing concentration of intentionally induced defects in PLGA on the tendency to form β1/β2-type aggregates using infrared spectroscopy. We have employed carbodiimide-mediated covalent modification of Glu side chains with n-butylamine (NBA, as well as electrostatics-driven inclusion of polylysine chains, as two different ways to trigger structural defects in PLGA. Our study depicts a clear correlation between concentration of defects in PLGA and increasing tendency to depart from the β2-structure toward the one less demanding in terms of chemical uniformity of side chains: β1-structure. The varying predisposition to form β1- or β2-type aggregates assessed by infrared absorption was compared with the degree of morphological order observed in electron microscopy images. Our results are discussed in the context of latent covalent defects in homopolypeptides (especially with side chains capable of hydrogen-bonding that could obscure their actual propensities to adopt different conformations, and limit applications in the field of

  1. Covalent Defects Restrict Supramolecular Self-Assembly of Homopolypeptides: Case Study of β2-Fibrils of Poly-L-Glutamic Acid

    Science.gov (United States)

    Fulara, Aleksandra; Hernik, Agnieszka; Nieznańska, Hanna; Dzwolak, Wojciech

    2014-01-01

    Poly-L-glutamic acid (PLGA) often serves as a model in studies on amyloid fibrils and conformational transitions in proteins, and as a precursor for synthetic biomaterials. Aggregation of PLGA chains and formation of amyloid-like fibrils was shown to continue on higher levels of superstructural self-assembly coinciding with the appearance of so-called β2-sheet conformation manifesting in dramatic redshift of infrared amide I′ band below 1600 cm−1. This spectral hallmark has been attributed to network of bifurcated hydrogen bonds coupling C = O and N-D (N-H) groups of the main chains to glutamate side chains. However, other authors reported that, under essentially identical conditions, PLGA forms the conventional in terms of infrared characteristics β1-sheet structure (exciton-split amide I′ band with peaks at ca. 1616 and 1683 cm−1). Here we attempt to shed light on this discrepancy by studying the effect of increasing concentration of intentionally induced defects in PLGA on the tendency to form β1/β2-type aggregates using infrared spectroscopy. We have employed carbodiimide-mediated covalent modification of Glu side chains with n-butylamine (NBA), as well as electrostatics-driven inclusion of polylysine chains, as two different ways to trigger structural defects in PLGA. Our study depicts a clear correlation between concentration of defects in PLGA and increasing tendency to depart from the β2-structure toward the one less demanding in terms of chemical uniformity of side chains: β1-structure. The varying predisposition to form β1- or β2-type aggregates assessed by infrared absorption was compared with the degree of morphological order observed in electron microscopy images. Our results are discussed in the context of latent covalent defects in homopolypeptides (especially with side chains capable of hydrogen-bonding) that could obscure their actual propensities to adopt different conformations, and limit applications in the field of synthetic

  2. A novel self-assembly with zinc porphyrin coordination polymer for enhanced photocurrent conversion in supramolecular solar cells

    International Nuclear Information System (INIS)

    Cao, Jing; Liu, Jia-Cheng; Deng, Wen-Ting; Li, Ren-Zhi; Jin, Neng-Zhi

    2013-01-01

    Graphical abstract: An innovative type of self-assembly based on acetohydrazide zinc porphyrin coordination polymer has been prepared in supramolecular solar cells. - Highlights: • A novel assembly with acetohydrazide porphyrin coordination polymer. • The assembly based on porphyrin is prepared as parallel sample. • Coordination polymer-based assembly shows enhanced photoelectronic behavior. • A series of different organic acid ligands as anchoring groups are prepared. - Abstract: In this work, a novel acetohydrazide zinc porphyrin-based coordination polymer (CP)-isonicotinic acid self-assembly by metal-ligand axial coordination to modify the nano-structured TiO 2 electrode surface has been investigated in photoelectrochemical device. Compared to the assembly based on corresponding zinc porphyrin combined with isonicotinic acid by metal-ligand axial coordination, CP-isonicotinic acid assembly exhibits a significantly enhanced photoelectronic behavior. In addition, a series of different organic acid ligands were prepared to probe the impact of their structures on the photoelectronic performances of their corresponding assemblies-sensitized cells. This study affords a novel type of self-assembly to functionalize the nanostructured TiO 2 electrode surface in supramolecular solar cells

  3. A combined experimental and theoretical study of the supramolecular self-assembly of Cu(II) malonate complex assisted by various weak forces and water dimer

    Energy Technology Data Exchange (ETDEWEB)

    Manna, Prankrishna [Department of Chemistry, Jadavpur University, Kolkata 700 032 (India); Ray Choudhury, Somnath [Central Chemical Laboratory, Geological Survey of India, 15 A and B Kyd Street, Kolkata 700 016 (India); Mitra, Monojit [Department of Chemistry, Jadavpur University, Kolkata 700 032 (India); Kumar Seth, Saikat [Department of Physics, M. G. Mahavidyalaya, Bhupatinagar, Purba Medinipur, West Bengal 721 425 (India); Helliwell, Madeleine [School of Chemistry, The University of Manchester, Brunswick Street, Manchester M13 9PL (United Kingdom); Bauzá, Antonio [Departament de Química, Universitat de les Illes Balears, Crta. de Valldemossa km 7.5, 07122 Palma (Baleares) (Spain); Frontera, Antonio, E-mail: toni.frontera@uib.es [Departament de Química, Universitat de les Illes Balears, Crta. de Valldemossa km 7.5, 07122 Palma (Baleares) (Spain); Mukhopadhyay, Subrata, E-mail: smukhopadhyay@chemistry.jdvu.ac.in [Department of Chemistry, Jadavpur University, Kolkata 700 032 (India)

    2014-12-15

    A Cu(II) malonate complex with formula [Cu(C{sub 3}H{sub 2}O{sub 4})(C{sub 6}H{sub 8}N{sub 2})(H{sub 2}O)]{sub 2}·4H{sub 2}O (1) [C{sub 6}H{sub 8}N{sub 2}=2-picolylamine, C{sub 3}H{sub 2}O{sub 4}{sup 2−}=malonate dianion] has been synthesized by mixing the reactants in their stoichiometric proportion and its crystal structure has been determined by single-crystal X-ray diffraction. In 1, monomeric neutral metal malonate units [Cu(C{sub 3}H{sub 2}O{sub 4})(C{sub 6}H{sub 8}N{sub 2})(H{sub 2}O)] are interlinked with each other through hydrogen bonds, weak lone pair⋯π and cuprophilic interactions to generate supramolecular dimers, which in turn further associated through hydrogen bonding to form infinite 1D chains. Water dimers, through series of hydrogen bonds and weak π–stacking forces are found to be responsible for interconnection of 1D chains, which resulted in a 3D network. A density functional (DFT) study of the energetic features of several noncovalent interactions observed in the solid state have been analyzed and characterized using Bader's theory of “atoms-in-molecules”. We also present here Hirshfeld surface analysis to investigate the close intermolecular contacts. - Graphical Abstract: Interplay of weak forces like hydrogen bonding, lone pair⋯π, Cu⋯Cu and π–stacking interactions leading to the formation of supramolecular network in [Cu(C{sub 3}H{sub 2}O{sub 4})(C{sub 6}H{sub 8}N{sub 2})(H{sub 2}O)]{sub 2}·4H{sub 2}O complex. - Highlights: • A complex of Cu(II) with malonate and 2-picolylamine is synthesized and X-ray characterized. • We report a density functional study of the energetic features of several noncovalent interactions • We perform Hirshfeld surface analysis to investigate the close intermolecular contacts.

  4. Self-assembly of P-chiral supramolecular phosphines on rhodium and direct evidence for Rh-catalyst-substrate interactions.

    Science.gov (United States)

    Koshti, Vijay S; Sen, Anirban; Shinde, Dinesh; Chikkali, Samir H

    2017-10-17

    Supramolecular phosphine-derived catalysts are known to provide high enantioselectivity in asymmetric transformations such as hydrogenation, but direct evidence unravelling the role of secondary interactions is largely missing. As a representative case study, the role of hydrogen bonding in asymmetric hydrogenation catalysed by p-chiral supramolecular phosphines is investigated. To establish the nature of hydrogen bonding in the self-assembled Rh-complex, NMR experiments were performed at different concentrations and temperatures. It was found that with increasing concentration of 1-(3-(phenyl(o-tolyl)phosphanyl)phenyl)urea ligand (L1), the NH and NH 2 peaks shift downfield. This indicated the presence of intermolecular hydrogen bonding in L1. This observation was further supported by variable temperature NMR experiments wherein, with decreasing temperature, the NH and NH 2 resonances of L1 shifted downfield. The downfield shift once again suggests the existence of intermolecular hydrogen bonding in L1. In contrast, the chemical shift of NH and NH 2 signals did not significantly change with increasing concentration of the self-assembled Rh-complex (C1). This observation suggested the existence of intramolecular hydrogen bonding in the self-assembled complex. The concentration experiment was further corroborated by variable temperature NMR experiments. No change in the chemical shift of NH 2 resonance could be detected with decreasing temperature, which corroborates the existence of intramolecular hydrogen bonding in C1. In a stoichiometric experiment, C1 was treated with hydrogenation substrate N-acetyldehydrophenylalanine (S2) and the proton NMR was recorded. The NH 2 protons of the self-assembled Rh-complex were found to shift downfield, as compared to untreated parent C1. These observations indicated that there is a hydrogen bonding interaction between the Rh-complex and the substrate. To further attest this hypothesis, NH and NH 2 groups were exchanged with ND

  5. Design and construction of self-assembling supramolecular protein complexes using artificial and fusion proteins as nanoscale building blocks.

    Science.gov (United States)

    Kobayashi, Naoya; Arai, Ryoichi

    2017-08-01

    The central goal of nanobiotechnology is to design and construct novel biomaterials of nanometer sizes. In this short review, we describe recent progress of several approaches for designing and creating artificial self-assembling protein complexes and primarily focus on the following biotechnological strategies for using artificial and fusion proteins as nanoscale building blocks: fusion proteins designed for symmetrical self-assembly; three-dimensional domain-swapped oligomers; self-assembling designed coiled-coil peptide modules; metal-directed self-assembling engineered proteins; computationally designed self-assembling de novo proteins; and self-assembling protein nanobuilding blocks (PN-Blocks) using an intermolecularly folded dimeric de novo protein. These state-of-the-art nanobiotechnologies for designing supramolecular protein complexes will facilitate the development of novel functional nanobiomaterials. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. A Ferrocene-Based Catecholamide Ligand: the Consequences of Ligand Swivel for Directed Supramolecular Self-Assembly

    Energy Technology Data Exchange (ETDEWEB)

    Mugridge, Jeffrey; Fiedler, Dorothea; Raymond, Kenneth

    2010-02-04

    A ferrocene-based biscatecholamide ligand was prepared and investigated for the formation of metal-ligand supramolecular assemblies with different metals. Reaction with Ge(IV) resulted in the formation of a variety of Ge{sub n}L{sub m} coordination complexes, including [Ge{sub 2}L{sub 3}]{sup 4-} and [Ge{sub 2}L{sub 2}({mu}-OMe){sub 2}]{sup 2-}. The ligand's ability to swivel about the ferrocenyl linker and adopt different conformations accounts for formation of many different Ge{sub n}L{sub m} species. This study demonstrates why conformational ligand rigidity is essential in the rational design and directed self-assembly of supramolecular complexes.

  7. Highly stereoselective recognition and deracemization of amino acids by supramolecular self-assembly.

    Science.gov (United States)

    So, Soon Mog; Moozeh, Kimia; Lough, Alan J; Chin, Jik

    2014-01-13

    The highly stereoselective supramolecular self-assembly of α-amino acids with a chiral aldehyde derived from binol and a chiral guanidine derived from diphenylethylenediamine (dpen) to form the imino acid salt is reported. This system can be used to cleanly convert D-amino acids into L-amino acids or vice versa at ambient temperature. It can also be used to synthesize α-deuterated D- or L-amino acids. A crystal structure of the ternary complex together with DFT computation provided detailed insight into the origin of the stereoselective recognition of amino acids. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Supramolecular Self-Assembled Chaos: Polyphenolic Lignin’s Barrier to Cost-Effective Lignocellulosic Biofuels

    Directory of Open Access Journals (Sweden)

    Shawn Matthew Dirk

    2010-11-01

    Full Text Available Phenylpropanoid metabolism yields a mixture of monolignols that undergo chaotic, non-enzymatic reactions such as free radical polymerization and spontaneous self-assembly in order to form the polyphenolic lignin which is a barrier to cost-effective lignocellulosic biofuels. Post-synthesis lignin integration into the plant cell wall is unclear, including how the hydrophobic lignin incorporates into the wall in an initially hydrophilic milieu. Self-assembly, self-organization and aggregation give rise to a complex, 3D network of lignin that displays randomly branched topology and fractal properties. Attempts at isolating lignin, analogous to archaeology, are instantly destructive and non-representative of in planta. Lack of plant ligninases or enzymes that hydrolyze specific bonds in lignin-carbohydrate complexes (LCCs also frustrate a better grasp of lignin. Supramolecular self-assembly, nano-mechanical properties of lignin-lignin, lignin-polysaccharide interactions and association-dissociation kinetics affect biomass deconstruction and thereby cost-effective biofuels production.

  9. Self-assembly of a highly organized, hexameric supramolecular architecture: formation, structure and properties.

    Science.gov (United States)

    Schaeffer, Gaël; Fuhr, Olaf; Fenske, Dieter; Lehn, Jean-Marie

    2014-01-03

    Two derivatives, (3)L and (9)L, of a ditopic, multiply hydrogen-bonding molecule, known for more than a decade, have been found, in the solid state as well as in solvents of low polarity at room temperature, to exist not as monomers, but to undergo a remarkable self-assembly into a complex supramolecular species. The solid-state molecular structure of (3)L, determined by single-crystal X-ray crystallography, revealed that it forms a highly organized hexameric entity (3)L6 with a capsular shape, resulting from the interlocking of two sets of three monomolecular components, linked through hydrogen-bonding interactions. The complicated (1)H NMR spectra observed in o-dichlorobenzene (o-DCB) for (3)L and (9)L are consistent with the presence of a hexamer of D3 symmetry in both cases. DOSY measurements confirm the hexameric constitution in solution. In contrast, in a hydrogen-bond-disrupting solvent, such as DMSO, the (1)H NMR spectra are very simple and consistent with the presence of isolated monomers only. Extensive temperature-dependent (1)H NMR studies in o-DCB showed that the L6 species dissociated progressively into the monomeric unit on increasing th temperature, up to complete dissociation at about 90 °C. The coexistence of the hexamer and the monomer indicated that exchange was slow on the NMR timescale. Remarkably, no species other than hexamer and monomer were detected in the equilibrating mixtures. The relative amounts of each entity showed a reversible sigmoidal variation with temperature, indicating that the assembly proceeded with positive cooperativity. A full thermodynamic analysis has been applied to the data. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Encapsulated-guest rotation in a self-assembled heterocapsule directed toward a supramolecular gyroscope

    Science.gov (United States)

    Kitagawa, Hitomi; Kobori, Yasuhiro; Yamanaka, Masamichi; Yoza, Kenji; Kobayashi, Kenji

    2009-01-01

    The self-assembled heterocapsule 1·2, which is formed by the hydrogen bonds of tetra(4-pyridyl)-cavitand 1 and tetrakis(4-hydroxyphenyl)-cavitand 2, encapsulates 1 molecule of guests such as 1,4-diacetoxybenzene 3a, 1,4-diacetoxy-2,5-dimethylbenzene 3b, 1,4-diacetoxy-2,5-dialkoxybenzenes (3c, OCH3; 3d, OC2H5; 3e, OC3H7; 3f, OC4H9; 3g, OC5H11; 3h, OC6H13; 3i, OC8H17), 1,4-diacetoxy-2,5-difluorobenzene 4a, and 1,4-diacetoxy-2,3-difluorobenzene 4b. The X-ray crystallographic analysis of 3c@(1·2) showed that the acetoxy groups at the 1,4-positions of 3c are oriented toward the 2 aromatic cavity ends of 1·2 and that 3c can rotate along the long axis of 1·2. Thus, the 1·2 (stator) with the encapsulation guest (rotator) behaves as a supramolecular gyroscope. A variable temperature (VT) 1H NMR study in CDCl3 showed that 3a, 3b, 4a, and 4b within 1·2 rotate rapidly even at 218 K, whereas guest rotation is almost inhibited for 3h and 3i even at 323 K. In this respect, 4b with a large dipole moment is a good candidate for the rotator of 1·2. For 3c–3g, the enthalpic (ΔH‡) and entropic (ΔS‡) contributions to the free energy of activation (ΔG‡) for the guest-rotational steric barriers within 1·2 were obtained from Eyring plots based on line-shape analysis of the VT 1H NMR spectra. The value of ΔG‡ increased in the order 3c guest rotation within 1·2. PMID:19416810

  11. Self-assembling graphene-anthraquinone-2-sulphonate supramolecular nanostructures with enhanced energy density for supercapacitors

    Science.gov (United States)

    Gao, Lifang; Gan, Shiyu; Li, Hongyan; Han, Dongxue; Li, Fenghua; Bao, Yu; Niu, Li

    2017-07-01

    Boosting the energy density of capacitive energy storage devices remains a crucial issue for facilitating applications. Herein, we report a graphene-anthraquinone supramolecular nanostructure by self-assembly for supercapacitors. The sulfonated anthraquinone exhibits high water solubility, a π-conjugated structure and redox active features, which not only serve as a spacer to interact with and stabilize graphene but also introduce extra pseudocapacitance contributions. The formed nest-like three-dimensional (3D) nanostructure with further hydrothermal treatment enhances the accessibility of ion transfer and exposes the redox-active quinone groups in the electrolytes. A fabricated all-solid-state flexible symmetric device delivers a high specific capacitance of 398.5 F g-1 at 1 A g-1 (1.5 times higher than graphene), superior energy density (52.24 Wh kg-1 at about 1 kW kg-1) and good stability (82% capacitance retention after 10 000 cycles).

  12. A dynamic combinatorial approach for identifying side groups that stabilize DNA-templated supramolecular self-assemblies.

    Science.gov (United States)

    Paolantoni, Delphine; Cantel, Sonia; Dumy, Pascal; Ulrich, Sébastien

    2015-02-06

    DNA-templated self-assembly is an emerging strategy for generating functional supramolecular systems, which requires the identification of potent multi-point binding ligands. In this line, we recently showed that bis-functionalized guanidinium compounds can interact with ssDNA and generate a supramolecular complex through the recognition of the phosphodiester backbone of DNA. In order to probe the importance of secondary interactions and to identify side groups that stabilize these DNA-templated self-assemblies, we report herein the implementation of a dynamic combinatorial approach. We used an in situ fragment assembly process based on reductive amination and tested various side groups, including amino acids. The results reveal that aromatic and cationic side groups participate in secondary supramolecular interactions that stabilize the complexes formed with ssDNA.

  13. A Dynamic Combinatorial Approach for Identifying Side Groups that Stabilize DNA-Templated Supramolecular Self-Assemblies

    Directory of Open Access Journals (Sweden)

    Delphine Paolantoni

    2015-02-01

    Full Text Available DNA-templated self-assembly is an emerging strategy for generating functional supramolecular systems, which requires the identification of potent multi-point binding ligands. In this line, we recently showed that bis-functionalized guanidinium compounds can interact with ssDNA and generate a supramolecular complex through the recognition of the phosphodiester backbone of DNA. In order to probe the importance of secondary interactions and to identify side groups that stabilize these DNA-templated self-assemblies, we report herein the implementation of a dynamic combinatorial approach. We used an in situ fragment assembly process based on reductive amination and tested various side groups, including amino acids. The results reveal that aromatic and cationic side groups participate in secondary supramolecular interactions that stabilize the complexes formed with ssDNA.

  14. Application of atomic force microscopy to protein anatomy:. Imaging of supramolecular structures of self-assemblies formed from synthetic peptides

    Science.gov (United States)

    Shibata-Seki, T.; Masai, J.; Ogawa, Y.; Sato, K.; Yanagawa, H.

    This paper reports morphological studies of structures of self-assemblies from synthetic peptide fragments with the use of atomic force microscope (AFM) and transmission electron microscope (TEM). Two systems of synthetic peptides have been examined: one is peptides from barnase (a ribonuclease) and the other is those from tau protein (Alzheimer's disease-related protein). The AFM observation was carried out by using a commercially available AFM operated in the tapping mode in air. The general appearance in shape and size of the peptide assemblies in AFM images was essentially similar to that in TEM images, except that the AFM images provide us with fruitful three-dimensional information about the assemblies. For assemblies from barnase peptides, possible formation processes of the supramolecular structures from the corresponding peptide fragment have been proposed on the basis of the AFM images.

  15. Self-assembled materials and supramolecular chemistry within microfluidic environments: from common thermodynamic states to non-equilibrium structures.

    Science.gov (United States)

    Sevim, S; Sorrenti, A; Franco, C; Furukawa, S; Pané, S; deMello, A J; Puigmartí-Luis, J

    2018-05-01

    Self-assembly is a crucial component in the bottom-up fabrication of hierarchical supramolecular structures and advanced functional materials. Control has traditionally relied on the use of encoded building blocks bearing suitable moieties for recognition and interaction, with targeting of the thermodynamic equilibrium state. On the other hand, nature leverages the control of reaction-diffusion processes to create hierarchically organized materials with surprisingly complex biological functions. Indeed, under non-equilibrium conditions (kinetic control), the spatio-temporal command of chemical gradients and reactant mixing during self-assembly (the creation of non-uniform chemical environments for example) can strongly affect the outcome of the self-assembly process. This directly enables a precise control over material properties and functions. In this tutorial review, we show how the unique physical conditions offered by microfluidic technologies can be advantageously used to control the self-assembly of materials and of supramolecular aggregates in solution, making possible the isolation of intermediate states and unprecedented non-equilibrium structures, as well as the emergence of novel functions. Selected examples from the literature will be used to confirm that microfluidic devices are an invaluable toolbox technology for unveiling, understanding and steering self-assembly pathways to desired structures, properties and functions, as well as advanced processing tools for device fabrication and integration.

  16. Self-assembly of a supramolecular square between [Ni(dppe(TOF2] and 4,4'-Bipyridine

    Directory of Open Access Journals (Sweden)

    Paulo Torres

    2013-08-01

    Full Text Available The main interest of this research is to contribute to the development and understanding of supramolecular chemistry and molecular architectures, which are constructed by the self-assembly of supramolecular entities. Therefore, the synthesis and characterization (IR, UV, 1H NMR, 31P, 19F, 1H-1H COSY of a nickel (II supramolecular square [7] was performed through the synthesis between nickel chloride [1] and diphenylphosphinoethane (dppe [2] to form the precursor complex [Ni(dppeCl2] [3]. This was followed by the synthesis of the complex of interest, [Ni(dppe(TOF2] [5], using the precursor and silver trifluoromethanesulfonate (Ag-TOF. Finally, the self-assembly was performed between the complex [1,2-bis(diphenylphosphinoethanebistriflatonickel(II] [Ni(dppe(OSO2CF32] [5] and the organic ligand 4,4'-bipyridine [6], which act as vertex and edge, respectively.According to various analyses, it was found that the self-assembly generated only one supramolecular species; a square is the most probable thermodynamic structure.

  17. Construction of an organelle-like nanodevice via supramolecular self-assembly for robust biocatalysts.

    Science.gov (United States)

    Li, Hongxia; Zheng, Guojun; Zhu, Shaozhou

    2018-02-20

    When using the microbial cell factories for green manufacturing, several important issues need to be addressed such as how to maintain the stability of biocatalysts used in the bioprocess and how to improve the synthetic efficiency of the biological system. One strategy widely used during natural evolution is the creation of organelles which can be used for regional control. This kind of compartmentalization strategy has inspired the design of artificial organelle-like nanodevice for synthetic biology and "green chemistry". Mimicking the natural concept of functional compartments, here we show that the engineered thermostable ketohydroxyglutarate aldolase from Thermotoga maritima could be developed as a general platform for nanoreactor design via supramolecular self-assembly. An industrial biocatalyst-(+)-γ-lactamase was selected as a model catalyst and successful encapsulated in the nanoreactor with high copies. These nanomaterials could easily be synthesized by Escherichia coli by heterologous expression and subsequently self-assembles into the target organelle-like nanoreactors both in vivo and in vitro. By probing their structural characteristics via transmission electronic microscopy and their catalytic activity under diverse conditions, we proved that these nanoreactors could confer a significant benefit to the cargo proteins. The encapsulated protein exhibits significantly improved stability under conditions such as in the presence of organic solvent or proteases, and shows better substrate tolerance than free enzyme. Our biodesign strategy provides new methods to develop new catalytically active protein-nanoreactors and could easily be applied into other biocatalysts. These artificial organelles could have widely application in sustainable catalysis, synthetic biology and could significantly improve the performance of microbial cell factories.

  18. Self-assembly of amphiphilic Janus dendrimers into mechanically robust supramolecular hydrogels for sustained drug release.

    Science.gov (United States)

    Nummelin, Sami; Liljeström, Ville; Saarikoski, Eve; Ropponen, Jarmo; Nykänen, Antti; Linko, Veikko; Seppälä, Jukka; Hirvonen, Jouni; Ikkala, Olli; Bimbo, Luis M; Kostiainen, Mauri A

    2015-10-05

    Compounds that can gelate aqueous solutions offer an intriguing toolbox to create functional hydrogel materials for biomedical applications. Amphiphilic Janus dendrimers with low molecular weights can readily form self-assembled fibers at very low mass proportion (0.2 wt %) to create supramolecular hydrogels (G'≫G'') with outstanding mechanical properties and storage modulus of G'>1000 Pa. The G' value and gel melting temperature can be tuned by modulating the position or number of hydrophobic alkyl chains in the dendrimer structure; thus enabling exquisite control over the mesoscale material properties in these molecular assemblies. The gels are formed within seconds by simple injection of ethanol-solvated dendrimers into an aqueous solution. Cryogenic TEM, small-angle X-ray scattering, and SEM were used to confirm the fibrous structure morphology of the gels. Furthermore, the gels can be efficiently loaded with different bioactive cargo, such as active enzymes, peptides, or small-molecule drugs, to be used for sustained release in drug delivery. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Self-assembling graphene-anthraquinone-2-sulphonate supramolecular nanostructures with enhanced energy density for supercapacitors.

    Science.gov (United States)

    Gao, Lifang; Gan, Shiyu; Li, Hongyan; Han, Dongxue; Li, Fenghua; Bao, Yu; Niu, Li

    2017-07-07

    Boosting the energy density of capacitive energy storage devices remains a crucial issue for facilitating applications. Herein, we report a graphene-anthraquinone supramolecular nanostructure by self-assembly for supercapacitors. The sulfonated anthraquinone exhibits high water solubility, a π-conjugated structure and redox active features, which not only serve as a spacer to interact with and stabilize graphene but also introduce extra pseudocapacitance contributions. The formed nest-like three-dimensional (3D) nanostructure with further hydrothermal treatment enhances the accessibility of ion transfer and exposes the redox-active quinone groups in the electrolytes. A fabricated all-solid-state flexible symmetric device delivers a high specific capacitance of 398.5 F g -1 at 1 A g -1 (1.5 times higher than graphene), superior energy density (52.24 Wh kg -1 at about 1 kW kg -1 ) and good stability (82% capacitance retention after 10 000 cycles).

  20. Supramolecular self-assembly on the B-Si(111)-(√3x√3) R30° surface: From single molecules to multicomponent networks

    Science.gov (United States)

    Makoudi, Younes; Jeannoutot, Judicaël; Palmino, Frank; Chérioux, Frédéric; Copie, Guillaume; Krzeminski, Christophe; Cleri, Fabrizio; Grandidier, Bruno

    2017-09-01

    Understanding the physical and chemical processes in which local interactions lead to ordered structures is of particular relevance to the realization of supramolecular architectures on surfaces. While spectacular patterns have been demonstrated on metal surfaces, there have been fewer studies of the spontaneous organization of supramolecular networks on semiconductor surfaces, where the formation of covalent bonds between organics and adatoms usually hamper the diffusion of molecules and their subsequent interactions with each other. However, the saturation of the dangling bonds at a semiconductor surface is known to make them inert and offers a unique way for the engineering of molecular patterns on these surfaces. This review describes the physicochemical properties of the passivated B-Si(111)-(√3x√3) R30° surface, that enable the self-assembly of molecules into a rich variety of extended and regular structures on silicon. Particular attention is given to computational methods based on multi-scale simulations that allow to rationalize the relative contribution of the dispersion forces involved in the self-assembled networks observed with scanning tunneling microscopy. A summary of state of the art studies, where a fine tuning of the molecular network topology has been achieved, sheds light on new frontiers for exploiting the construction of supramolecular structures on semiconductor surfaces.

  1. From fundamental supramolecular chemistry to self-assembled nanomaterials and medicines and back again - how Sam inspired SAMul.

    Science.gov (United States)

    Smith, David K

    2018-04-26

    This feature article provides a personal insight into the research from my group over the past 10 years. In particular, the article explains how, inspired in 2005 by meeting my now-husband, Sam, who had cystic fibrosis, and who in 2011 went on to have a double lung transplant, I took an active decision to follow a more applied approach to some of our research, attempting to use fundamental supramolecular chemistry to address problems of medical interest. In particular, our strategy uses self-assembly to fabricate biologically-active nanosystems from simple low-molecular-weight building blocks. These systems can bind biological polyanions in highly competitive conditions, allowing us to approach applications in gene delivery and coagulation control. In the process, however, we have also developed new fundamental principles such as self-assembled multivalency (SAMul), temporary 'on-off' multivalency, and adaptive/shape-persistent multivalent binding. By targeting materials with applications in drug formulation and tissue engineering, we have discovered novel self-assembling low-molecular-weight hydrogelators based on the industrially-relevant dibenzylidenesorbitol framework and developed innovative approaches to spatially-resolved gels and functional multicomponent hybrid hydrogels. In this way, taking an application-led approach to research has also delivered significant academic value and conceptual advances. Furthermore, beginning to translate fundamental supramolecular chemistry into real-world applications, starts to demonstrate the power of this approach, and its potential to transform the world around us for the better.

  2. Tunable Affinity and Molecular Architecture Lead to Diverse Self-Assembled Supramolecular Structures in Thin Films.

    Science.gov (United States)

    Hsu, Chih-Hao; Dong, Xue-Hui; Lin, Zhiwei; Ni, Bo; Lu, Pengtao; Jiang, Zhang; Tian, Ding; Shi, An-Chang; Thomas, Edwin L; Cheng, Stephen Z D

    2016-01-26

    The self-assembly behavior of specifically designed giant surfactants is systematically studied in thin films using grazing incidence X-ray scattering and transmission electron microscopy, focusing on the effects of molecular nanoparticle (MNP) functionalities and molecular architectures on nanostructure formation. Two MNPs with different surface functionalities, i.e., hydrophilic carboxylic acid functionalized [60]fullerene (AC60) and omniphobic fluorinated polyhedral oligomeric silsesquioxane (FPOSS), are utilized as the head portions of the giant surfactants. By covalently tethering these functional MNPs onto the end point or junction point of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer, linear and star-like giant surfactants with different molecular architectures are constructed. With fixed length of the PEO block, changing the molecular weight of the PS block leads to the formation of various ordered phases and phase transitions. Due to the distinct affinity, the AC60-based and FPOSS-based giant surfactants form two- or three-component morphologies, respectively. A stretching parameter for the PS block is introduced to characterize the PS chain conformation in the different morphologies. The highly diverse self-assembled nanostructures with high etch resistance between components in small dimensions obtained from the giant surfactant thin films suggest that these macromolecules could provide a promising and robust platform for nanolithography applications.

  3. Towards supramolecular engineering of functional nanomaterials: pre-programming multi-component 2D self-assembly at solid-liquid interfaces.

    Science.gov (United States)

    Ciesielski, Artur; Palma, Carlos-Andres; Bonini, Massimo; Samorì, Paolo

    2010-08-24

    Materials with a pre-programmed order at the supramolecular level can be engineered with a sub-nanometer precision making use of reversible non- covalent interactions. The intrinsic ability of supramolecular materials to recognize and exchange their constituents makes them constitutionally dynamic materials. The tailoring of the materials properties relies on the full control over the self-assembly behavior of molecular modules exposing recognition sites and incorporating functional units. In this review we focus on three classes of weak-interactions to form complex 2D architectures starting from properly designed molecular modules: van der Waals, metallo-ligand and hydrogen bonding. Scanning tunneling microscopy studies will provide evidence with a sub-nanometer resolution, on the formation of responsive multicomponent architectures with controlled geometries and properties. Such endeavor enriches the scientist capability of generating more and more complex smart materials featuring controlled functions and unprecedented properties.

  4. Improved enzyme-mediated synthesis and supramolecular self-assembly of naturally occurring conjugates of beta-sitosterol

    Czech Academy of Sciences Publication Activity Database

    Wimmerová, Martina; Siglerová, Věra; Šaman, David; Šlouf, Miroslav; Kaletová, Eva; Wimmer, Zdeněk

    2017-01-01

    Roč. 117, JAN (2017), s. 38-43 ISSN 0039-128X R&D Projects: GA MŠk LD15012; GA MŠk(CZ) LO1507 Institutional support: RVO:61389030 ; RVO:61388963 ; RVO:61389013 Keywords : glycosides * esterification * resolution * sterols * esters * foods * l. * beta-Sitosterol * Acylated steryl glycoside * Lipase * Ionic liquid * Supramolecular self-assembly * Pharmacological activity Subject RIV: CC - Organic Chemistry; CD - Macromolecular Chemistry (UMCH-V) OBOR OECD: Organic chemistry; Polymer science (UMCH-V); Organic chemistry (UOCHB-X) Impact factor: 2.282, year: 2016

  5. Brønsted Acid-Catalyzed Carbonyl-Olefin Metathesis inside a Self-Assembled Supramolecular Host.

    Science.gov (United States)

    Catti, Lorenzo; Tiefenbacher, Konrad

    2017-12-20

    Carbonyl-olefin metathesis represents a powerful yet underdeveloped method for the formation of carbon-carbon bonds. So far, no Brønsted acid based method for the catalytic carbonyl-olefin metathesis has been described. Herein, a cocatalytic system based on a simple Brønsted acid (HCl) and a self-assembled supramolecular host is presented. The developed system compares well with the current benchmark catalyst for carbonyl-olefin metathesis in terms of substrate scope and yield of isolated product. Control experiments provide strong evidence that the reaction proceeds inside the cavity of the supramolecular host. A mechanistic probe indicates that a stepwise reaction mechanism is likely. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Self assembly of amphiphilic C60 fullerene derivatives into nanoscale supramolecular structures

    Directory of Open Access Journals (Sweden)

    Casscells S Ward

    2007-08-01

    Full Text Available Abstract Background The amphiphilic fullerene monomer (AF-1 consists of a "buckyball" cage to which a Newkome-like dendrimer unit and five lipophilic C12 chains positioned octahedrally to the dendrimer unit are attached. In this study, we report a novel fullerene-based liposome termed 'buckysome' that is water soluble and forms stable spherical nanometer sized vesicles. Cryogenic electron microscopy (Cryo-EM, transmission electron microscopy (TEM, and dynamic light scattering (DLS studies were used to characterize the different supra-molecular structures readily formed from the fullerene monomers under varying pH, aqueous solvents, and preparative conditions. Results Electron microscopy results indicate the formation of bilayer membranes with a width of ~6.5 nm, consistent with previously reported molecular dynamics simulations. Cryo-EM indicates the formation of large (400 nm diameter multilamellar, liposome-like vesicles and unilamellar vesicles in the size range of 50–150 nm diameter. In addition, complex networks of cylindrical, tube-like aggregates with varying lengths and packing densities were observed. Under controlled experimental conditions, high concentrations of spherical vesicles could be formed. In vitro results suggest that these supra-molecular structures impose little to no toxicity. Cytotoxicity of 10–200 μM buckysomes were assessed in various cell lines. Ongoing studies are aimed at understanding cellular internalization of these nanoparticle aggregates. Conclusion In this current study, we have designed a core platform based on a novel amphiphilic fullerene nanostructure, which readily assembles into supra-molecular structures. This delivery vector might provide promising features such as ease of preparation, long-term stability and controlled release.

  7. Two novel self-assemblies of supramolecular solar cells using N-heterocyclic-anchoring porphyrins

    Science.gov (United States)

    Zhang, Qian; Wu, Fang-Yuan; Liu, Jia-Cheng; Li, Ren-Zhi; Jin, Neng-Zhi

    2018-02-01

    Two novel N-substituted anchoring porphyrins (ZnPAtz and ZnPAim) have been devised and synthesized. Moreover, these two anchoring porphyrins were linked to the TiO2 semiconductor through carboxyl groups and then a zinc porphyrin ZnP was bound to the anchoring porphyrin using a zinc-to-ligand axial coordination approach. The different performances of these assemblies were compared with single anchoring porphyrin devices ZnPAtz and ZnPAim. The photoelectric conversion efficiency of the new supramolecular solar cells sensitized by ZnP-ZnPAx (x = tz, im) has been improved. The ZnP-ZnPAtz-based DSSCs provided the highest photovoltaic efficiency (1.86%). Fundamental studies showed that incorporation of these assemblies promote light-harvesting efficiency.

  8. Template-directed supramolecular self-assembly of coordination dumbbells at surfaces.

    Science.gov (United States)

    Lin, Nian; Langner, Alexander; Tait, Steven L; Rajadurai, Chandrasekar; Ruben, Mario; Kern, Klaus

    2007-12-14

    Scanning tunneling microscopy reveals, at single-molecular resolution, how external parameters--substrate morphology and guest addition--re-direct the assembly of dumbbell-shaped coordination supramolecules towards different surface-confined supramolecular organizations.

  9. Self-assembly of a supramolecular, three-dimensional, spoked, bicycle-like wheel.

    Science.gov (United States)

    Lu, Xiaocun; Li, Xiaopeng; Cao, Yan; Schultz, Anthony; Wang, Jin-Liang; Moorefield, Charles N; Wesdemiotis, Chrys; Cheng, Stephen Z D; Newkome, George R

    2013-07-22

    Where there's a wheel, there's a way: The terpyridine-based title system has been synthesized through a facile self-assembly process. Two tris(terpyridine) ligands possessing angles of either 120° or 60° between adjacent tpy units were mixed with a stoichiometric amount of Zn(2+) (2:6:12) to generate the desired coordination-driven bicycle-like wheel (90 % yield). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Design of supramolecular nanomaterials : from molecular recognition to hierarchical self-assembly

    OpenAIRE

    El Idrissi, Mohamed

    2017-01-01

    In the present thesis, are reported new strategies for the design of nanostructures to partly address environmental issues. The work carried out has been divided into three parts: the design of cyclodextrin (CD)-based polymeric materials, the molecular engineering of a pyrene derivative for the formation of self-assembled nanostructures and the design of smart nanocarriers. Considerable efforts have been devoted to the design of molecular receptors capable of specific recognition of a wid...

  11. Hydrogen bonds induced supramolecular self-assembly of azobenzene derivatives on the highly oriented pyrolytic graphite surface

    Science.gov (United States)

    Miao, Xinrui; Cheng, Zhiyu; Ren, Biye; Deng, Wenli

    2012-08-01

    The self-assembly of azobenzene derivatives (CnAzCOOH) with various lengths of peripheral alkyl chains (with carbon number of n = 8, 10, 12, 14, 16) were observed by scanning tunneling microscopy on highly oriented pyrolytic graphite (HOPG) surface. The effect of van der Waals interactions and the intermolecular hydrogen bonding on the two-dimensional self-assembly was systematically studied. No alkyl-chain length effect was observed according to the STM images. All kinds of CnAzCOOH adopting the same pattern self-assembled on the HOPG surface, suggesting the formation of the two-dimensional structures was dominated by the hydrogen bonding of the functional groups. It could be found that two CnAzCOOH molecules formed a hydrogen-bonded dimer with “head-to-head” fashion as expected; however, the dimers organized themselves in the form of relative complex lamellae. Three dimers as a group arranged side by side and formed a well-defined stripe with periodic dislocations due to the registry mechanism of the alkyl chain with the underlying HOPG surface. The hydrogen bonds between the adjacent dimers in one lamella were formed and dominated the self-assembled pattern.

  12. Supramolecular Self-Assembly of a Model Hydrogelator: Characterization of Fiber Formation and Morphology

    Directory of Open Access Journals (Sweden)

    Yuan Gao

    2016-10-01

    Full Text Available Hydrogels are of intense recent interest in connection with biomedical applications ranging from 3-D cell cultures and stem cell differentiation to regenerative medicine, controlled drug delivery, and tissue engineering. This prototypical form of soft matter has many emerging material science applications outside the medical field. The physical processes underlying this type of solidification are incompletely understood, and this limits design efforts aimed at optimizing these materials for applications. We address this general problem by applying multiple techniques (e.g., NMR, dynamic light scattering, small angle neutron scattering, rheological measurements to the case of a peptide derivative hydrogelator (molecule 1, NapFFKYp over a broad range of concentration and temperature to characterize both the formation of individual nanofibers and the fiber network. We believe that a better understanding of the hierarchical self-assembly process and control over the final morphology of this kind of material should have broad significance for biological and medicinal applications utilizing hydrogels.

  13. A versatile strategy towards non-covalent functionalization of graphene by surface-confined supramolecular self-assembly of Janus tectons

    Directory of Open Access Journals (Sweden)

    Ping Du

    2015-03-01

    Full Text Available Two-dimensional (2D, supramolecular self-assembly at surfaces is now well-mastered with several existing examples. However, one remaining challenge to enable future applications in nanoscience is to provide potential functionalities to the physisorbed adlayer. This work reviews a recently developed strategy that addresses this key issue by taking advantage of a new concept, Janus tecton materials. This is a versatile, molecular platform based on the design of three-dimensional (3D building blocks consisting of two faces linked by a cyclophane-type pillar. One face is designed to steer 2D self-assembly onto C(sp2-carbon-based flat surfaces, the other allowing for the desired functionality above the substrate with a well-controlled lateral order. In this way, it is possible to simultaneously obtain a regular, non-covalent paving as well as supramolecular functionalization of graphene, thus opening interesting perspectives for nanoscience applications.

  14. Supramolecular Self-Assembly and Dual-Switch Vapochromic, Vapoluminescent, and Resistive Memory Behaviors of Amphiphilic Platinum(II) Complexes.

    Science.gov (United States)

    Li, Yongguang; Chen, Ling; Ai, Yeye; Hong, Eugene Yau-Hin; Chan, Alan Kwun-Wa; Yam, Vivian Wing-Wah

    2017-10-04

    A series of amphiphilic platinum(II) complexes with tridentate N-donor ligands has been synthesized and characterized. Different supramolecular architectures are constructed using the amphiphilic molecules as the building blocks through the formation of Pt···Pt and π-π stacking interactions in aqueous media. The aggregation-deaggregation-aggregation self-assembly behavior together with obvious spectroscopic changes could be fine-tuned by the addition of THF in aqueous media. More interestingly, one of the complexes is found to show fast response and high selectivity toward alcohol and water vapors with good reversibility, leading to drastic color and luminescence changes, and hence unique dual switching behavior, with the water molecules readily displaced by the alcohol vapor. Rapid writing and erasure have been realized via the control of a jet or a stream of alcohol vapor flow. In addition, it has been employed as active materials in the fabrication of small-molecule solution-processable resistive memory devices, exhibiting stable and promising binary memory performance with threshold voltages of ca. 3.4 V, high ON/OFF ratios of up to 10 5 and long retention times of over 10 4 s. The vapochromic and vapoluminescent materials are demonstrated to have potential applications in chemosensing, logic gates, VOC monitoring, and memory functions.

  15. Self-assembling nanocomposites for protein delivery: supramolecular interactions between PEG-cholane and rh-G-CSF.

    Science.gov (United States)

    Salmaso, Stefano; Bersani, Sara; Mastrotto, Francesca; Tonon, Giancarlo; Schrepfer, Rodolfo; Genovese, Stefano; Caliceti, Paolo

    2012-08-20

    PEG(5 kDa)-cholane, PEG(10 kDa)-cholane and PEG(20 kDa)-cholane self-assembling polymers have been synthesised by the end-functionalisation of 5, 10 and 20 kDa linear amino-terminating monomethoxy-poly(ethylene glycol) (PEG-NH(2)) with 5β-cholanic acid. Spectroscopic studies and isothermal titration calorimetry showed that the CMC of the PEG-cholane derivatives increased from 23.5 ± 1.8 to 60.2 ± 2.4 μM as the PEG molecular weight increased. Similarly, light scattering analysis showed that the micelle size increased from 15.8 ± 4.9 to 23.2 ± 11.1 nm with the PEG molecular weight. Gel permeation studies showed that the polymer bioconjugates associate with recombinant human granulocyte colony stimulating factor (rh-G-CSF) to form supramolecular nanocomposites according to multi-modal association profiles. The protein loadings obtained with PEG(5 kDa)-cholane, PEG(10 kDa)-cholane and PEG(20 kDa)-cholane were 7.4 ± 1.1, 2.7 ± 0.3 and 2.1 ± 0.4% (protein/polymer, w/w %), respectively. Scatchard and Klotz analyses showed that the protein/polymer affinity constant increased and that the number of PEG-cholane molecules associated to rh-G-CSF decreased as the PEG molecular weight increased. Isothermal titration calorimetry confirmed the protein/polymer multi-modal association. Circular dichroism analyses showed that the polymer association alters the secondary structure of the protein. Nevertheless, in vitro studies performed with NFS-60 cells showed that the polymer interaction does not impair the biological activity of the cytokine. In vivo studies performed by intravenous and subcutaneous administrations of rh-G-CSF to rats showed that the association with PEG(5 kDa)-cholane prolongs the body exposure of the protein. After subcutaneous administration, the protein t(max) values obtained with rh-G-CSF and 1:14 and 1:21 rh-G-CSF/PEG(5 kDa)-cholane (w/w ratio) nanocomplexes were 2, 8 and 24h, respectively. The 1:21 (w/w) rh-G-CSF/PEG(5kDa)-cholane formulation

  16. A Case Study of the Likes and Dislikes of DNA and RNA in Self-Assembly.

    Science.gov (United States)

    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.

  17. Influence of Odd and Even Alkyl Chains on Supramolecular Nanoarchitecture via Self-Assembly of Tetraphenylethylene-Based AIEgens

    Directory of Open Access Journals (Sweden)

    Mina Salimimarand

    2017-10-01

    Full Text Available The Tetraphenylethylene (TPE based dumbbell shaped molecules TPE-Pi, TPE-Su, TPE-Az, and TPE-Se were synthesised bearing odd-even alkyl chains containing 7, 8, 9 and 10 carbons respectively. These molecules reveal typical Aggregation Induced Emission (AIE behaviour. The influence of the odd or even alkyl chain length was shown by studying the morphology of self-assembled nanostructures formed in a range of tetrahydrofuran (THF/water solvent systems. For example, with a water fraction of 80%, TPE derivatives with odd alkyl chains (TPE-Pi and TPE-Az self-assembled into nanosphere structures, while TPE-Su with 8 alkyl chains formed microbelts and TPE-Se with 10 alkyl chains aggregated into flower-like superstructures. These TPE derivatives also revealed interesting mechanochromic properties upon grinding, fuming and heating, which reveal the importance of molecular stacking in the crystal structure to the luminescent properties of the aggregates .The mechanochromic properties of TPE-Pi, TPE-Su, and TPE-Az were also demonstrated by the process of grounding, fuming, and heating.

  18. Self-assembly of designed supramolecular magnetic filaments of different shapes

    Energy Technology Data Exchange (ETDEWEB)

    Novak, E.V. [Ural Federal University, Lenin Av. 51, Ekaterinburg (Russian Federation); Rozhkov, D.A., E-mail: d.a.rozhkov@gmail.com [Ural Federal University, Lenin Av. 51, Ekaterinburg (Russian Federation); Sanchez, P.A. [University of Vienna, Sensengasse 8, Vienna (Austria); Kantorovich, S.S. [Ural Federal University, Lenin Av. 51, Ekaterinburg (Russian Federation); University of Vienna, Sensengasse 8, Vienna (Austria)

    2017-06-01

    In the present work we study via molecular dynamics simulations filaments of ring and linear shape. Filaments are made of magnetic nanoparticles, possessing a point dipole in their centres. Particles in filaments are crosslinked in a particular way, so that the deviation of the neighbouring dipoles from the head-to-tail orientation is penalised by the bond. We show how the conformation of a single chain and ring filament changes on cooling for different lengths. We also study filament pairs, by fixing filaments at a certain distance and analysing the impact of inter-filament interaction on the equilibrium configurations. Our study opens a perspective to investigate the dispersions of filaments, both theoretically and numerically, by using effective potentials. - Highlights: • Single filament study. • Magnetic particles crosslinked in chains and rings. • Magnetic filament interactions.

  19. Supramolecular Self-Assembly of Histidine-Capped-Dialkoxy-Anthracene: A Visible Light Triggered Platform for facile siRNA Delivery

    KAUST Repository

    Patil, Sachin

    2016-06-29

    Supramolecular self-assembly of histidine-capped-dialkoxy-anthracene (HDA) results in the formation of light responsive nanostructures.Single-crystal X-ray diffraction analysis of HDA shows two types of hydrogen bonding. The first hydrogen bond is established between the imidazole moieties while the second involves the oxygen atom of one amide group and the hydrogen atom of a second amide group. When protonated in acidic aqueous media, HDA successfully complexes siRNA yielding spherical nanostructures. This biocompatible platform controllably delivers siRNA with high efficacy upon visible light irradiation leading up to 90% of gene silencing in live cells.

  20. Catalytic Deprotection of Acetals In Strongly Basic Solution Usinga Self-Assembled Supramolecular 'Nanozyme'

    Energy Technology Data Exchange (ETDEWEB)

    Pluth, Michael D.; Bergman, Robert G.; Raymond, Kenneth N.

    2007-07-26

    Acetals are among the most commonly used protecting groups for aldehydes and ketones in organic synthesis due to their ease of installation and resistance to cleavage in neutral or basic solution.[1] The common methods for hydrolyzing acetals almost always involve the use of either Broensted acid or Lewis acid catalysts.[2] Usually aqueous acids or organic solutions acidified with organic or inorganic acids have been used for reconversion of the acetal functionality to the corresponding carbonyl group; however, recently a number of reports have documented a variety of strategies for acetal cleavage under mild conditions. These include the use of Lewis acids such as bismuth(III)[3] or cerium(IV),[4, 5] functionalized silica gel, such as silica sulfuric acid[6] or silica-supported pyridinium p-toluene sulfonate,[7] or the use of silicon-based reagents such as TESOTf-2,6-Lutidine.[8] Despite these mild reagents, all of the above conditions require either added acid or overall acidic media. Marko and co-workers recently reported the first example of acetal deprotection under mildly basic conditions using catalytic cerium ammonium nitrate at pH 8 in a water-acetonitrile solution.[5] Also recently, Rao and co-workers described a purely aqueous system at neutral pH for the deprotection of acetals using {beta}-cyclodextrin as the catalyst.[9] Herein, we report the hydrolysis of acetals in strongly basic aqueous solution using a self-assembled supramolecular host as the catalyst. During the last decade, we have used metal-ligand interactions for the formation of well-defined supramolecular assemblies with the stoichiometry M{sub 4}L{sub 6}6 (M = Ga{sup III} (1 refers to K{sub 12}[Ga{sub 4}L{sub 6}]), Al{sup III}, In{sup III}, Fe{sup III}, Ti{sup IV}, or Ge{sup IV}, L = N,N{prime}-bis(2,3-dihydroxybenzoyl)-1,5-diaminonaphthalene) (Figure 1).[10] The metal ions occupy the vertices of the tetrahedron and the bisbidentate catecholamide ligands span the edges. The strong

  1. Improved enzyme-mediated synthesis and supramolecular self-assembly of naturally occurring conjugates of β-sitosterol.

    Science.gov (United States)

    Wimmerová, Martina; Siglerová, Věra; Šaman, David; Šlouf, Miroslav; Kaletová, Eva; Wimmer, Zdeněk

    2017-01-01

    Naturally occurring acylated β-sitosteryl glucosides have been investigated for their novel properties. The synthetic protocol based on the literature data was improved and optimized. The main improvement consists in employing systems of ionic liquids combined with organic solvents in lipase-mediated esterification of (3β)-stigmast-5-en-3-yl β-d-glucopyranoside to get (3β)-stigmast-5-en-3-yl 6-O-acyl-β-d-glucopyranosides. Maximum yields of these products were achieved with Candida antarctica lipase B immobilized on Immobead 150, recombinant from yeast, in absolute THF and in the presence of either ionic liquid [1-butyl-3-methyl imidazolium tetrafluoroborate ([BMIM]BF 4 ) or 1-butyl-3-methyl imidazolium hexafluorophosphate ([BMIM]PF 6 )] employed. Pharmacological activity of (3β)-stigmast-5-en-3-yl 6-O-acyl-β-d-glucopyranosides was studied in tests on MCF7 tumor cell lines; the compounds displayed moderate activity which was higher than the activity of β-sitosterol. Supramolecular characteristics were discovered at (3β)-stigmast-5-en-3-yl 6-O-dodecanoyl-β-d-glucopyranoside that formed supramolecular polymer through multiple H-bonds in a methanol/water system (60/40). Its formation was confirmed by the independent UV-vis measurements during certain time period, by variable temperature DOSY-NMR measurement in deuteriochloroform, and visualized by transmission electron microscopy (TEM) and atomic force microscopy (AFM) showing chiral helical structures and complex superassembly systems based on fibrous supramolecular polymer. In contrary, no such properties have been observed for the other two (3β)-stigmast-5-en-3-yl 6-O-acyl-β-d-glucopyranosides under the given experimental conditions. Copyright © 2016 Elsevier Inc. All rights reserved.

  2. Anandamide and analogous endocannabinoids: a lipid self-assembly study

    Energy Technology Data Exchange (ETDEWEB)

    Sagnella, Sharon M.; Conn, Charlotte E.; Krodkiewska, Irena; Mulet, Xavier; Drummond, Calum J.

    2014-09-24

    Anandamide, the endogenous agonist of the cannabinoid receptors, has been widely studied for its interesting biological and medicinal properties and is recognized as a highly significant lipid signaling molecule within the nervous system. Few studies have, however, examined the effect of the physical conformation of anandamide on its function. The study presented herein has focused on characterizing the self-assembly behaviour of anandamide and four other endocannabinoid analogues of anandamide, viz., 2-arachidonyl glycerol, arachidonyl dopamine, 2-arachidonyl glycerol ether (noladin ether), and o-arachidonyl ethanolamide (virodhamine). Molecular modeling of the five endocannabinoid lipids indicates that the highly unsaturated arachidonyl chain has a preference for a U or J shaped conformation. Thermal phase studies of the neat amphiphiles showed that a glass transition was observed for all of the endocannabinoids at {approx} -110 C with the exception of anandamide, with a second glass transition occurring for 2-arachidonyl glycerol, 2-arachidonyl glycerol ether, and virodhamine (-86 C, -95 C, -46 C respectively). Both anandamide and arachidonyl dopamine displayed a crystal-isotropic melting point (-4.8 and -20.4 C respectively), while a liquid crystal-isotropic melting transition was seen for 2-arachidonyl glycerol (-40.7 C) and 2-arachidonyl glycerol ether (-71.2 C). No additional transitions were observed for virodhamine. Small angle X-ray scattering and cross polarized optical microscopy studies as a function of temperature indicated that in the presence of excess water, both 2-arachidonyl glycerol and anandamide form co-existing Q{sub II}{sup G} (gyroid) and Q{sub II}{sup D} (diamond) bicontinuous cubic phases from 0 C to 20 C, which are kinetically stable over a period of weeks but may not represent true thermodynamic equilibrium. Similarly, 2-arachidonyl glycerol ether acquired an inverse hexagonal (HII) phase in excess water from 0 C to 40 C, while

  3. Design and Sensing Properties of a Self-Assembled Supramolecular Oligomer (Chem. Eur. J. 6/2016)

    DEFF Research Database (Denmark)

    Bähring, Steffen; Martín-Gomis, Luis; Olsen, Gunnar

    2016-01-01

    The controlled self-assembly of electron-rich and electron-deficient components to create a stimulus responsive oligomeric ensemble that functions as a sensor system for nitroaromatic explosives is depicted schematically on the cover. More information can be found in the Full Paper by Á. Sastre...

  4. Hirshfeld surface analyses and crystal structures of supramolecular self-assembly thiourea derivatives directed by non-covalent interactions

    Science.gov (United States)

    Gumus, Ilkay; Solmaz, Ummuhan; Binzet, Gun; Keskin, Ebru; Arslan, Birdal; Arslan, Hakan

    2018-04-01

    The novel N-(bis(3,5-dimethoxybenzyl)carbamothioyl)-4-R-benzamide (R: H, Cl, CH3 and OCH3) compounds have been synthesized and characterized by FT-IR, 1H NMR and 13C NMR spectroscopy. Their crystal structures were also determined by single-crystal X-ray diffraction studies. Hirshfeld surfaces analysis and their associated two dimensional fingerprint plots of compounds were used as theoretical approach to assess driving force for crystal structure formation via the intermolecular interactions in the crystal lattices of synthesized compounds. The study of X-ray single crystal diffraction and Hirshfeld surfaces analysis of the prepared compounds shows that hydrogen bonding and other weaker interactions such as Nsbnd H⋯S, weak Csbnd H⋯S, Csbnd H⋯O, Csbnd H⋯N and Csbnd H···π intermolecular interactions and π-π stacking, among molecules of synthesized compounds participate in a cooperative way to stabilize the supramolecular structures.

  5. Construction of nanostructures for selective lithium ion conduction using self-assembled molecular arrays in supramolecular solids.

    Science.gov (United States)

    Moriya, Makoto

    2017-01-01

    In the development of innovative molecule-based materials, the identification of the structural features in supramolecular solids and the understanding of the correlation between structure and function are important factors. The author investigated the development of supramolecular solid electrolytes by constructing ion conduction paths using a supramolecular hierarchical structure in molecular crystals because the ion conduction path is an attractive key structure due to its ability to generate solid-state ion diffusivity. The obtained molecular crystals exhibited selective lithium ion diffusion via conduction paths consisting of lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) and small molecules such as ether or amine compounds. In the present review, the correlation between the crystal structure and ion conductivity of the obtained molecular crystals is addressed based on the systematic structural control of the ionic conduction paths through the modification of the component molecules. The relationship between the crystal structure and ion conductivity of the molecular crystals provides a guideline for the development of solid electrolytes based on supramolecular solids exhibiting rapid and selective lithium ion conduction.

  6. Novel self-assembling nanogels: stability and lyophilisation studies.

    Science.gov (United States)

    Daoud-Mahammed, S; Couvreur, P; Gref, R

    2007-03-06

    The stability of new supramolecular nanoassemblies (nanogels), based on the association of a hydrophobically modified dextran (MD) and a beta-cyclodextrin polymer (pbetaCD), has been studied by two complementary methods: (i) size measurements and (ii) turbidity experiments using a Turbiscan optical analyser. Nanogels of about 120-150nm were obtained whatever the concentration of the two polymer solutions. At low concentrations, the suspensions presented little mean diameter variations upon storage. However, the concentrated ones tended to destabilize and their mean diameter increased upon time. Size measurements and Turbiscan investigations have demonstrated that destabilization in the MD-pbetaCD nanogel suspension was only due to particle aggregation and/or fusion, as no sedimentation or creaming occurred. The destabilization of MD-pbetaCD suspensions led to the formation of a highly viscous phase, as a final state. Moreover, the two methods have shown that aggregation and/or fusion phenomena were more pronounced in the concentrated MD-pbetaCD suspensions than in the diluted ones. The stability of MD-pbetaCD suspensions could be improved by their storage at 4 degrees C. Finally, freeze-drying was found to be a convenient method for the long-time storage of MD-pbetaCD nanoassemblies.

  7. High-definition self-assemblies driven by the hydrophobic effect: synthesis and properties of a supramolecular nanocapsule.

    Science.gov (United States)

    Liu, Simin; Gibb, Bruce C

    2008-08-28

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

  8. Metal-organic and supramolecular networks driven by 5-chloronicotinic acid: Hydrothermal self-assembly synthesis, structural diversity, luminescent and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Zhu-Qing, E-mail: zqgao2008@163.com [School of Chemical and Biological Engineering, Taiyuan University of Science and Technology, Taiyuan 030021 (China); Li, Hong-Jin [School of Chemical and Biological Engineering, Taiyuan University of Science and Technology, Taiyuan 030021 (China); Gu, Jin-Zhong, E-mail: gujzh@lzu.edu.cn [College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000 (China); Zhang, Qing-Hua [School of Chemical and Biological Engineering, Taiyuan University of Science and Technology, Taiyuan 030021 (China); Kirillov, Alexander M. [Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049–001 Lisbon (Portugal)

    2016-09-15

    Four new crystalline solids, namely [Co{sub 2}(µ{sub 2}-5-Clnic){sub 2}(µ{sub 3}-5-Clnic){sub 2}(µ{sub 2}-H{sub 2}O)]{sub n} (1), [Co(5-Clnic){sub 2}(H{sub 2}O){sub 4}]·2(5-ClnicH) (2), [Pb(µ{sub 2}-5-Clnic){sub 2}(phen)]{sub n} (3), and [Cd(5-Clnic){sub 2}(phen){sub 2}]·3H{sub 2}O (4) were generated by hydrothermal self-assembly methods from the corresponding metal(II) chlorides, 5-chloronicotinic acid (5-ClnicH) as a principal building block, and 1,10-phenanthroline (phen) as an ancillary ligand (optional). All the products 1–4 were characterized by IR spectroscopy, elemental analysis, thermogravimetric (TGA), powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. Their structures range from an intricate 3D metal-organic network 1 with the 3,6T7 topology to a ladder-like 1D coordination polymer 3 with the 2C1 topology, whereas compounds 2 and 4 are the discrete 0D monomers. The structures of 2 and 4 are further extended (0D→2D or 0D→3D) by hydrogen bonds, generating supramolecular networks with the 3,8L18 and ins topologies, respectively. Synthetic aspects, structural features, thermal stability, magnetic (for 1) and luminescent (for 3 and 4) properties were also investigated and discussed. - Graphical abstract: A new series of crystalline solids was self-assembled and fully characterized; their structural, topological, luminescent and magnetic features were investigated. Display Omitted.

  9. Programming protein self assembly with coiled coils

    Science.gov (United States)

    Dietz, Hendrik; Bornschlögl, Thomas; Heym, Roland; König, Frauke; Rief, Matthias

    2007-11-01

    The controlled assembly of protein domains into supramolecular structures will be an important prerequisite for the use of functional proteins in future nanotechnology applications. Coiled coils are multimerization motifs whose dimerization properties can be programmed by amino acid sequence. Here, we report programmed supramolecular self-assembly of protein molecules using coiled coils and directly demonstrate its potential on the single molecule level by AFM force spectroscopy. We flanked two different model proteins, Ig27 from human cardiac titin and green fluorescent protein (GFP), by coiled coil binding partners and studied the capability of these elementary building blocks to self-assemble into linear chains. Simple sterical constraints are shown to control the assembly process, providing evidence that many proteins can be assembled with this method. An application for this technique is the design of polyproteins for single molecule force spectroscopy with an integrated force-calibration standard.

  10. Supramolecular self-assembly of graphene oxide and metal nanoparticles into stacked multilayers by means of a multitasking protein ring.

    Science.gov (United States)

    Ardini, Matteo; Golia, Giordana; Passaretti, Paolo; Cimini, Annamaria; Pitari, Giuseppina; Giansanti, Francesco; Di Leandro, Luana; Ottaviano, Luca; Perrozzi, Francesco; Santucci, Sandro; Morandi, Vittorio; Ortolani, Luca; Christian, Meganne; Treossi, Emanuele; Palermo, Vincenzo; Angelucci, Francesco; Ippoliti, Rodolfo

    2016-03-28

    Graphene oxide (GO) is rapidly emerging worldwide as a breakthrough precursor material for next-generation devices. However, this requires the transition of its two-dimensional layered structure into more accessible three-dimensional (3D) arrays. Peroxiredoxins (Prx) are a family of multitasking redox enzymes, self-assembling into ring-like architectures. Taking advantage of both their symmetric structure and function, 3D reduced GO-based composites are hereby built up. Results reveal that the "double-faced" Prx rings can adhere flat on single GO layers and partially reduce them by their sulfur-containing amino acids, driving their stacking into 3D multi-layer reduced GO-Prx composites. This process occurs in aqueous solution at a very low GO concentration, i.e. 0.2 mg ml(-1). Further, protein engineering allows the Prx ring to be enriched with metal binding sites inside its lumen. This feature is exploited to both capture presynthesized gold nanoparticles and grow in situ palladium nanoparticles paving the way to straightforward and "green" routes to 3D reduced GO-metal composite materials.

  11. Integrative self-assembly of functional hybrid nanoconstructs by inorganic wrapping of single biomolecules, biomolecule arrays and organic supramolecular assemblies.

    Science.gov (United States)

    Patil, Avinash J; Li, Mei; Mann, Stephen

    2013-08-21

    Synthesis of functional hybrid nanoscale objects has been a core focus of the rapidly progressing field of nanomaterials science. In particular, there has been significant interest in the integration of evolutionally optimized biological systems such as proteins, DNA, virus particles and cells with functional inorganic building blocks to construct mesoscopic architectures and nanostructured materials. However, in many cases the fragile nature of the biomolecules seriously constrains their potential applications. As a consequence, there is an on-going quest for the development of novel strategies to modulate the thermal and chemical stabilities, and performance of biomolecules under adverse conditions. This feature article highlights new methods of "inorganic molecular wrapping" of single or multiple protein molecules, individual double-stranded DNA helices, lipid bilayer vesicles and self-assembled organic dye superstructures using inorganic building blocks to produce bio-inorganic nanoconstructs with core-shell type structures. We show that spatial isolation of the functional biological nanostructures as "armour-plated" enzyme molecules or polynucleotide strands not only maintains their intact structure and biochemical properties, but also enables the fabrication of novel hybrid nanomaterials for potential applications in diverse areas of bionanotechnology.

  12. Integrative self-assembly of functional hybrid nanoconstructs by inorganic wrapping of single biomolecules, biomolecule arrays and organic supramolecular assemblies

    Science.gov (United States)

    Patil, Avinash J.; Li, Mei; Mann, Stephen

    2013-07-01

    Synthesis of functional hybrid nanoscale objects has been a core focus of the rapidly progressing field of nanomaterials science. In particular, there has been significant interest in the integration of evolutionally optimized biological systems such as proteins, DNA, virus particles and cells with functional inorganic building blocks to construct mesoscopic architectures and nanostructured materials. However, in many cases the fragile nature of the biomolecules seriously constrains their potential applications. As a consequence, there is an on-going quest for the development of novel strategies to modulate the thermal and chemical stabilities, and performance of biomolecules under adverse conditions. This feature article highlights new methods of ``inorganic molecular wrapping'' of single or multiple protein molecules, individual double-stranded DNA helices, lipid bilayer vesicles and self-assembled organic dye superstructures using inorganic building blocks to produce bio-inorganic nanoconstructs with core-shell type structures. We show that spatial isolation of the functional biological nanostructures as ``armour-plated'' enzyme molecules or polynucleotide strands not only maintains their intact structure and biochemical properties, but also enables the fabrication of novel hybrid nanomaterials for potential applications in diverse areas of bionanotechnology.

  13. Integrated effect of supramolecular self-assembled sandwich-like melamine cyanurate/MoS{sub 2} hybrid sheets on reducing fire hazards of polyamide 6 composites

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Xiaming [State Key Laboratory of Fire Science, University of Science and Technology of China, Anhui 230026 (China); Suzhou Key Laboratory of Urban Public Safety, Suzhou Institute for Advanced Study, University of Science and Technology of China, Suzhou, Jiangsu 215123 (China); Wang, Xin, E-mail: wxcmx@ustc.edu.cn [State Key Laboratory of Fire Science, University of Science and Technology of China, Anhui 230026 (China); Cai, Wei; Hong, Ningning [State Key Laboratory of Fire Science, University of Science and Technology of China, Anhui 230026 (China); Hu, Yuan, E-mail: yuanhu@ustc.edu.cn [State Key Laboratory of Fire Science, University of Science and Technology of China, Anhui 230026 (China); Suzhou Key Laboratory of Urban Public Safety, Suzhou Institute for Advanced Study, University of Science and Technology of China, Suzhou, Jiangsu 215123 (China); Liew, Kim Meow [Suzhou Key Laboratory of Urban Public Safety, Suzhou Institute for Advanced Study, University of Science and Technology of China, Suzhou, Jiangsu 215123 (China); Department of Architectural and Civil Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong)

    2016-12-15

    A novel strategy of using supramolecular self-assembly for preparing sandwich-like melamine cyanurate/MoS{sub 2} sheets as the hybrid flame retardants for polyamide 6 (PA6) is reported for the first time. The introduction of MoS{sub 2} sheets function not only as a template to induce the formation of two-dimensional melamine cyanurate capping layers but also as a synergist to generate integrated flame-retarding effect of hybrid sheets, as well as a high-performance smoke suppressor to reduce fire hazards of PA6 materials. Once incorporating this well-designed structures (4 wt%) into PA6 matrix, there resulted in a remarkable drop (40%) in the peak heat release rate and a 25% reduction in total heat release. Moreover, the smoke production and pyrolysis gaseous products were efficiently suppressed by the addition of sandwich-like hybrid sheets. The integrated functions consisting of inherent flame retarding effect, physical barrier performance and catalytic activity are believed to the crucial guarantee for the reduced fire hazards of PA6 nanocomposites. Furthermore, this novel strategy with facile and scalable features may provide reference for developing various kinds of MoS{sub 2} based hybrid sheets for diverse applications.

  14. Triangles and tetrahedra: metal directed self-assembly of metallo-supramolecular structures incorporating bis-beta-diketonato ligands.

    Science.gov (United States)

    Clegg, Jack K; Lindoy, Leonard F; Moubaraki, Boujema; Murray, Keith S; McMurtrie, John C

    2004-08-21

    The interaction of six aryl-linked bis-beta-diketones, including a new naphthylene linked species, with copper(II), iron(III) and, in one instance gallium(III), has been investigated with the aim of obtaining metallo-supramolecular assemblies exhibiting different geometries. New examples of two assembly types incorporating the above bis-beta-diketones (L) were generated. The first type is represented by a range of molecular triangles of formula [Cu(3)(L-H(2))(3)](solvent)(n) while the second is given by a corresponding selection of less-common neutral molecular tetrahedra of formula [Fe(4)(L-H(2))(6)](solvent)(n) as well as [Ga(4)(L-H(2))(6)].8.5THF.0.5H(2)O; an example of each type has been characterised by X-ray crystallography. A magnetochemical investigation of [Fe(4)(-H(2))(6)].6THF is reported. The susceptibility is Curie like and consistent with very weak coupling occurring between the iron(III) d(5)(high spin) centres. The X-ray structures of two trinuclear copper(II) as well as a tetranuclear iron(III) and a tetranuclear gallium(III) assembly confirm their discrete triangular and tetrahedral geometries, respectively. The structure of the gallium(III) species is closely related to that of the corresponding iron(III) species. The tetrahedral structures provide rare examples of such assemblies encapsulating guest solvent molecules--in each case tetrahydrofuran is incorporated in the central cavity.

  15. Molecular self-assembly in substituted alanine derivatives: XRD, Hirshfeld surfaces and DFT studies

    Science.gov (United States)

    Rajalakshmi, Periasamy; Srinivasan, Navaneethakrishnan; Sivaraman, Gandhi; Razak, Ibrahim Abdul; Rosli, Mohd Mustaqim; Krishnakumar, Rajaputi Venkatraman

    2014-06-01

    The molecular assemblage in the crystal structures of three modified chiral amino acids, two of which are isomeric D- and L-pairs boc-L-benzothienylalanine (BLA), boc-D-benzothienylalanine (BDA) and the other boc-D-naphthylalanine (NDA) differing from this pair very slightly in the chemical modification introduced, is accurately described. The aggregation of amino acid molecules is similar in all the crystals and may be described as a twisted double helical ladder in which two complementary long helical chains formed through O-H⋯O hydrogen bonds are interconnected through the characteristic head-to-tail N-H⋯O hydrogen bonds. Thus the molecular aggregation enabled through classical hydrogen bonds may be regarded as a mimic of the characteristic double helical structure of DNA. Also, precise structural information involving these amino acid molecules with lower symmetry exhibiting higher trigonal symmetry in their self-assembly is expected to throw light on the nature and strength of intermolecular interactions and their role in self-assembly of molecular aggregates, which are crucial in developing new or at least supplement existing crystal engineering strategies. Single crystal X-ray analysis and their electronic structures were calculated at the DFT level with a detailed analysis of Hirshfeld surfaces and fingerprint plots facilitating a comparison of intermolecular interactions in building different supramolecular architectures.

  16. Cross-sectional nanophotoluminescence studies of Stark effects in self-assembled quantum dots

    International Nuclear Information System (INIS)

    Htoon, H.; Keto, J. W.; Baklenov, O.; Holmes, A. L. Jr.; Shih, C. K.

    2000-01-01

    By using a cross-sectional geometry, we show the capability to perform single-dot spectroscopy in self-assembled quantum dots using far-field optics. By using this method, we study the quantum-confined Stark effect in self-assembled quantum dots. For single-stack quantum dots (QDs), we find that the spectra are redshifted with an increase in electric field. For vertically coupled double-stack quantum dots, while most of the QDs are redshifted, some QDs show blueshifted spectra, which can be interpreted as an evidence of coupled QD molecules. (c) 2000 American Institute of Physics

  17. DNA Self-Assembly and Computation Studied with a Coarse-grained Dynamic Bonded Model

    DEFF Research Database (Denmark)

    Svaneborg, Carsten; Fellermann, Harold; Rasmussen, Steen

    2012-01-01

    We utilize a coarse-grained directional dynamic bonding DNA model [C. Svaneborg, Comp. Phys. Comm. (In Press DOI:10.1016/j.cpc.2012.03.005)] to study DNA self-assembly and DNA computation. In our DNA model, a single nucleotide is represented by a single interaction site, and complementary sites can...

  18. Orientation modulation of a synthetic polypeptide in self-assembled monolayers: a TOF-SIMS study.

    Science.gov (United States)

    Leufgen, Kirsten; Mutter, Manfred; Vogel, Horst; Szymczak, Wilfried

    2003-07-23

    Structure and orientation of molecules are key properties of functionalized surfaces. Using time-of-flight secondary ion mass spectrometry (TOF-SIMS), here we investigate how to modulate these parameters upon the immobilization process varying the conditions of self-assembly. The molecule of interest, a template-assembled synthetic protein (TASP), consists of a central peptide ring with orthogonally arranged residues. Thioalkane chains allow the directed self-assembly of the molecule on a gold surface; four serine residues on the opposite side of the ring can be used as anchoring sites for various functional sensing molecules. The TASP conformation and its orientation in self-assembled monolayers (SAMs) play a central role for the accessibility of these serine residues. To study the influence of the self-assembly conditions, two series of samples were prepared. Pure TASP monolayers of different surface densities are compared to mixed TASP/alkanethiol monolayers prepared by sequential adsorption varying sequence and particular incubation times as well as by coadsorption modifying incubation times and TASP/alkanethiol mass ratios. Switching the TASP orientation from a state where the molecules are lying flat on the surface to an upright orientation turned out to be possible by inserting the TASP into a preformed alkanethiol monolayer of an appropriate surface density. This study demonstrates that TOF-SIMS is an excellent tool not only to investigate the surface composition, but also the molecular structure of functionalized surfaces.

  19. Molecular self-assembly advances and applications

    CERN Document Server

    Dequan, Alex Li

    2012-01-01

    In the past several decades, molecular self-assembly has emerged as one of the main themes in chemistry, biology, and materials science. This book compiles and details cutting-edge research in molecular assemblies ranging from self-organized peptide nanostructures and DNA-chromophore foldamers to supramolecular systems and metal-directed assemblies, even to nanocrystal superparticles and self-assembled microdevices

  20. Self-assembly of poly(ionic liquid) (PIL)-based amphiphilic homopolymers into vesicles and supramolecular structures with dyes and silver nanoparticles

    KAUST Repository

    Manojkumar, Kasina

    2017-04-27

    The incorporation of both hydrophilic and hydrophobic segments in homopolymers leads to their self-assembly into nanostructures in selective solvents, owing to their amphiphilic character. Here we report the RAFT polymerization of N-imidazole-3-propylmethacrylamide and the further quaternization of the resulting polymer with different alkyl bromides of a varying chain length, which afforded well-defined polymeric ionic liquids (PILs) 1-4. These PILs are characterized by the presence of both hydrophobic alkyl chains and hydrophilic ionic moieties, allowing their spontaneous self-assembly in water, forming distinct polymeric vesicles (= polymersomes) the size of which can be varied as a function of alkyl chain length. As demonstrated by the dye-encapsulation study, a particular organic-soluble PIL, 3, consisting of a dodecyl side-chain enabled the transfer of the water-soluble Rose Bengal dye, from an aqueous solution to the organic phase. In addition, polymersomes obtained from a PIL (2) featuring butyl side chains were used as templates and polymeric stabilizers of silver nanoparticles (NPs), i.e. leading to AgNP@PIL hybrids, as observed by transmission electron microscopy (TEM). It was found that the extent of functionalization of polymersomes by the Ag-based NPs varied greatly before and after the end-group removal of the PIL. Altogether, this report emphasizes the facile synthesis of amphiphilic homoPILs and their manipulation in water for dye encapsulation and for stabilization of silver NPs.

  1. Self-assembly behaviour of conjugated terthiophene surfactants in water

    NARCIS (Netherlands)

    van Rijn, Patrick; Janeliunas, Dainius; Brizard, Aurelie M.; Stuart, Marc C. A.; Koper, Ger J. M.; Eelkema, Rienk; van Esch, Jan H.

    2011-01-01

    Conjugated self-assembled systems in water are of great interest because of their potential application in biocompatible supramolecular electronics, but so far their supramolecular chemistry remains almost unexplored. Here we present amphiphilic terthiophenes as a general self-assembling platform

  2. Self-assembled chlorophyll a systems as studied by californium-252 plasma desorption mass spectroscopy

    OpenAIRE

    Hunt, J. E.; Macfarlane, R. D.; Katz, J. J.; Dougherty, R. C.

    1980-01-01

    Self-assembled chlorophyll a and pheophytin a systems in thin solid films have been studied by 252Cf plasma desorption mass spectrometry (PDMS). The 252Cf-PDMS spectra of these films show monomer cation and anion molecular ions, ions of molecular aggregates, and positive and negative ion fragmentation patterns arising from the loss of various aliphatic side chains from the chlorin ring. Chlorophyll a films cast from dry carbon tetrachloride solution, in which chlorophyll a is known to occur a...

  3. Self-assembled chlorophyll a systems as studied by californium-252 plasma desorption mass spectroscopy

    Science.gov (United States)

    Hunt, J. E.; Macfarlane, R. D.; Katz, J. J.; Dougherty, R. C.

    1980-01-01

    Self-assembled chlorophyll a and pheophytin a systems in thin solid films have been studied by 252Cf plasma desorption mass spectrometry (PDMS). The 252Cf-PDMS spectra of these films show monomer cation and anion molecular ions, ions of molecular aggregates, and positive and negative ion fragmentation patterns arising from the loss of various aliphatic side chains from the chlorin ring. Chlorophyll a films cast from dry carbon tetrachloride solution, in which chlorophyll a is known to occur as the dimer, produced an abundant dimer ion. The highest degree of chlorophyll a self-assembly was observed in chlorophyll a films cast from n-octane solutions. Oligomer ions extending upwards in size to the heptamer were detected in this system. Images PMID:16592795

  4. Surface Modification of Self-Assembled Graphene Oxide for Cell Culture Studies

    Science.gov (United States)

    Swain, John E., III

    Thin films show great promise for biological applications, from in situ monitoring to pharmaceutical testing. In this study, a graphene oxide (GO) thin film is prepared with the aim to further functionalize the film for pharmaceutical toxicity screening applications. GO was selected due to its capability to be reduced into an optically transparent and electrically conductive thin film. In addition, GO is derived from carbon, a widely abundant element, in contrast to many other thin films that rely on resource-limited precious metals. Special care was taken to select GO and GO film synthesis methods that minimize the amount of organic-based solvents, maintain reactions at atmospheric pressure and moderate temperatures, and are scalable for manufacturing. Chemical oxidation of graphite flakes was carried out via a modified Hummer's Method with a pre-oxidation step. The resulting GO flakes were self-assembled using commercially available 4-sulfocalix[4]arene. Analytical characterizations (e.g., elemental analysis, XRD, FTIR, Raman, SEM, AFM) were performed to evaluate the success of graphite oxidation and formation of the self-assembled thin film. In order to gain a better understanding of the interactions between GO and sulfocalix (SCX), equilibrium conformations of the SCX molecule and truncated GO were calculated using Spartan'16 Parallels. This study demonstrates that the interaction between the GO and the SCX molecule to create a self-assembled thin film is the result of pi-pi stacking, as hypothesized by Sundramoorthy et al. (2015). The self-assembled GO film was successfully deposited on a polyethylene terephthalate (PET) substrate and functionalized with 3-aminopropyl triethoxysilane (APTES), which renders the film capable of further functionalization with proteins for yielding a three-dimensional cell culture or co-culture platform for different applications.

  5. Study of the Gemini Surfactants' Self-Assembly on Graphene Nanosheets: Insights from Molecular Dynamic Simulation.

    Science.gov (United States)

    Poorsargol, M; Sohrabi, B; Dehestani, M

    2018-04-06

    Understanding the mechanism of adsorption and self-assembly of surfactants on graphene is highly important to perform better optimization of the graphene dispersion process. Because of Gemini surfactants' special structure, they have a high charge capacity, high hydrophobicity, and unique self-assembly properties compared to single-chain surfactants. Therefore, Gemini surfactants with their small concentrations are expected to disperse and stabilize graphene nanosheets in aqueous solutions more effectively. We conducted molecular dynamics simulations to study adsorption and self-assembly of single-chain cationic surfactant dodecyltrimethylammonium bromide (C 12 TAB) and its same family Gemini surfactant dimethylene-α,β-bis(dodecyldimethylammonium bromide) ([12-2-12]Br 2 ) on graphene nanosheets. The results showed that assemblies morphology formed on graphene is affected by surfactant structure. We observed that increasing surface coverage, especially for [12-2-12]Br 2 , leads to a transmission in adsorption mechanism and most [12-2-12]Br 2 head groups tend toward the aqueous phase and prevent water molecules from accessing graphene surface. It can be concluded from morphological assessments that [12-2-12]Br 2 is more effective than C 12 TAB in stabilizing graphene aqueous suspensions. Moreover, we investigated the effect of graphene sheet size and Gemini surfactant spacer length on the structure of surfactant assemblies on graphene. The present study results can expand our comprehension of dispersion mechanism of graphene nanosheets by Gemini surfactants.

  6. Structural study of the self-assembled fullerene carboxylates: monoadducts versus bisadducts.

    Science.gov (United States)

    Zhou, Shuiqin; Ouyang, Jianying; Golas, Patricia; Wang, Feng; Pan, Yi

    2005-10-27

    Laser light scattering and transmission electronic microscopy have been used to study the self-assembled structures of mono- and bisadducts of fullerene carboxylic acids in tetrahydrofuran (THF) and their sodium salts in aqueous solutions, respectively. In THF, the self-association of monoadducts of fullerene carboxylic acid (MFCA) produces large but narrowly distributed particles with R(h) approximately 145 nm. The self-aggregates from the bisadducts of fullerene carboxylic acid (BFCA) in THF are relatively small in size (R(h) approximately 80 nm) due to the better solubility. After the ionization of carboxylic acid groups on the C(60) cage in dilute NaOH solutions, these aggregates dissolved and reorganized. The self-assembly of the monoadducts of sodium carboxylate fullerenes (MSCF) produces small solid spherical particles with R(h) approximately 32 nm. The ratio of R(g)/R(h) approximately 0.83 indicates that the particles have a nearly uniform density. The increase in concentrations leads to strong interparticle associations to form rodlike and irregularly shaped large aggregates. In contrast, the self-assembly of bisadducts of sodium carboxylate fullerenes (BSCF) results in hollow shells with mainly two different size scales of R(h) approximately 23 nm and R(h) approximately 104 nm. At high concentrations, the hollow shells associate and melt together to generate three-dimensional networks.

  7. Synergy in supramolecular chemistry

    CERN Document Server

    Nabeshima, Tatsuya

    2014-01-01

    Synergy and Cooperativity in Multi-metal Supramolecular Systems, T. NabeshimaHierarchically Assembled Titanium Helicates, Markus AlbrechtSupramolecular Hosts and Catalysts Formed by Self-assembly of Multinuclear Zinc Complexes in Aqueous Solution, Shin AokiSupramolecular Assemblies Based on Interionic Interactions, H. MaedaSupramolecular Synergy in the Formation and Function of Guanosine Quadruplexes, Jeffery T. DavisOn-Surface Chirality in Porous Self-Assembled Monolayers at Liquid-Solid Interface, Kazukuni Tahar

  8. The Structures of Self-Assembled Monolayer Films of Organosulfur Compounds Adsorbed on Gold Single Crystals: Electron Diffraction Studies.

    Science.gov (United States)

    1988-01-01

    AD-M193 125 THE STRUCTURES OF SELF-RSSENSLED MOMOLAYER FILMS OF 1/1 ORGANOSULFUR COMPOUND..(U) HRlYARD UNJY CAMBRIDGE MASS DEPT OF CHEMISTRY L STRONG...VV L- ___ THE STRUCTURES OF SELF-ASSEMBLED MONOLAYER FILMS OF ORGANOSULFUR COMPOUNDS ADSORBED ON GOLD SINGLE CRYSTALS: ELECTRON DIFFRACTION STUDIES...true sulfide phase. V V ’A. LA8700876 REVISED The Structures of Self-Assembled Monolayer Films of Organosulfur Compounds Adsorbed on Gold Single

  9. A One-Pot Self-Assembly Reaction to Prepare a Supramolecular Palladium(II) Cyclometalated Complex: An Undergraduate Organometallic Laboratory Experiment

    Science.gov (United States)

    Fernandez, Alberto; Lopez-Torres, Margarita; Fernandez, Jesus J.; Vazquez-Garcia, Digna; Vila, Jose M.

    2012-01-01

    A laboratory experiment for students in advanced inorganic chemistry is described. Students prepare palladium(II) cyclometalated complexes. A terdentate [C,N,O] Schiff base ligand is doubly deprotonated upon reaction with palladium(II) acetate in a self-assembly process to give a palladacycle with a characteristic tetranuclear structure. This…

  10. DNA self-assembly on graphene surface studied by SERS mapping

    DEFF Research Database (Denmark)

    Botti, Sabina; Rufoloni, Alessandro; Laurenzi, Susanna

    2016-01-01

    The self-assembly of double-stranded DNA (dsDNA) segments on two variations of graphene surfaces having nano-platelets with different lateral sizes and thicknesses was investigated using surface enhanced Raman spectroscopy (SERS) and electrical impedance spectroscopy (EIS) techniques. Due...... nano-platelets. Results from the EIS analysis supported the SERS findings and confirmed that SERS mapping is a reliable method for a rapid monitoring of the procedures used to interface DNA with graphene surfaces. The present study, linking DNA anchoring morphology to the conductive properties of nano...

  11. Peptide amphiphile self-assembly

    Science.gov (United States)

    Iscen, Aysenur; Schatz, George C.

    2017-08-01

    Self-assembly is a process whereby molecules organize into structures with hierarchical order and complexity, often leading to functional materials. Biomolecules such as peptides, lipids and DNA are frequently involved in self-assembly, and this leads to materials of interest for a wide variety of applications in biomedicine, photonics, electronics, mechanics, etc. The diversity of structures and functions that can be produced provides motivation for developing theoretical models that can be used for a molecular-level description of these materials. Here we overview recently developed computational methods for modeling the self-assembly of peptide amphiphiles (PA) into supramolecular structures that form cylindrical nanoscale fibers using molecular-dynamics simulations. Both all-atom and coarse-grained force field methods are described, and we emphasize how these calculations contribute insight into fiber structure, including the importance of β-sheet formation. We show that the temperature at which self-assembly takes place affects the conformations of PA chains, resulting in cylindrical nanofibers with higher β-sheet content as temperature increases. We also present a new high-density PA model that shows long network formation of β-sheets along the long axis of the fiber, a result that correlates with some experiments. The β-sheet network is mostly helical in nature which helps to maintain strong interactions between the PAs both radially and longitudinally. Contribution to Focus Issue Self-assemblies of Inorganic and Organic Nanomaterials edited by Marie-Paule Pileni.

  12. Macroscopic magnetic Self assembly

    NARCIS (Netherlands)

    Löthman, Per Arvid

    2018-01-01

    Exploring the macroscopic scale's similarities to the microscale is part and parcel of this thesis as reflected in the research question: what can we learn about the microscopic scale by studying the macroscale? Investigations of the environment in which the self-assembly takes place, and the

  13. Supramolecular Langmuir monolayers and multilayered vesicles of self-assembling DNA–lipid surface structures and their further implications in polyelectrolyte-based cell transfections

    Energy Technology Data Exchange (ETDEWEB)

    Demirsoy, Fatma Funda Kaya [Ankara University, The Central Laboratory of The Institute of Biotechnology (Turkey); Eruygur, Nuraniye [Gazi University, Department of Pharmacognosy, Faculty of Pharmacy (Turkey); Süleymanoğlu, Erhan, E-mail: erhans@mail.ru [Gazi University, Department of Pharmaceutical Chemistry, Faculty of Pharmacy (Turkey)

    2015-01-15

    The basic interfacial characteristics of DNA–lipid recognitions have been studied. The complex structures of individual unbound DNA molecules and their binary and ternary complexes with zwitterionic lipids and divalent cations were followed by employing lipid monolayers at the air–liquid interfaces, as well as by performing various microscopic, spectroscopic, and thermodynamic measurements with multilayered vesicles. The pressure-area isotherms depicted that Mg{sup 2+}-ions increase the surface pressure of lipid films and thus give rise to electrostatic and hydrophobic lipid–DNA interactions in terms of DNA adsorption, adhesion, and compaction. These features were further approached by using multilamellar vesicles with a mean diameter of 850 nm, where a metal ion-directed nucleic acid compaction and condensation effects were shown. The data obtained show the effectiveness of Langmuir monolayers and lipid multilayers in studying nucleic acid–lipid recognitions. The data provide with further details and support previous reports on mainly structural features of these recognitions. Biomolecular surface recognition events were presented in direct link with spectral and thermodynamic features of lipid vesicle–polynucleotide complex formations. The results serve to build a theoretical model considering the use of neutral lipids in lipoplex designs as a polyelectrolyte alternatives to the currently employed cytotoxic cationic liposomes. The supramolecular structures formed and their possible roles in interfacial electrostatic and hydrophobic mechanisms of endosomal escape in relevant cell transfection assays are particularly emphasized.

  14. Comparative self-assembly studies and self-sorting of two ...

    Indian Academy of Sciences (India)

    The propensity for self-assembly of NDI-1 was greater due to symmetrical placement of two amide groups on either arms of this chromophore which allowed -stacking in tandem with hydrogen-bonding, while NDI-2 formed thermally more stable self-assembled fibres possibly due to location of two amide groups in close ...

  15. Singlet and triplet energy transfer dynamics in self-assembled axial porphyrin-anthracene complexes: towards supra-molecular structures for photon upconversion.

    Science.gov (United States)

    Gray, Victor; Küçüköz, Betül; Edhborg, Fredrik; Abrahamsson, Maria; Moth-Poulsen, Kasper; Albinsson, Bo

    2018-03-14

    Energy and electron transfer reactions are central to many different processes and research fields, from photosynthesis and solar energy harvesting to biological and medical applications. Herein we report a comprehensive study of the singlet and triplet energy transfer dynamics in porphyrin-anthracene coordination complexes. Seven newly synthesized pyridine functionalized anthracene ligands, five with various bridge lengths and two dendrimer structures containing three and seven anthracene units, were prepared. We found that triplet energy transfer from ruthenium octaethylporphyrin to an axially coordinated anthracene is possible, and is in some cases followed by back triplet energy transfer to the porphyrin. The triplet energy transfer follows an exponential distance dependence with an attenuation factor, β, of 0.64 Å -1 . Further, singlet energy transfer from anthracene to the ruthenium porphyrin appears to follow a R 6 Förster distance dependence. Porphyrin-anthracene complexes are also used as triplet sensitizers for triplet-triplet annihilation (TTA) based photon upconversion, demonstrating their potential for photophysical and photochemical applications. The triplet lifetime of the complex is extended by the anthracene ligands, resulting in a threefold increase in the upconversion efficiency, Φ UC to 4.5%, compared to the corresponding ruthenium porphyrin-pyridine complex. Based on the results herein we discuss the future design of supra-molecular structures for TTA upconversion.

  16. Silk nanofibril self-assembly versus electrospinning.

    Science.gov (United States)

    Humenik, Martin; Lang, Gregor; Scheibel, Thomas

    2018-02-02

    Natural silk fibers represent one of the most advanced blueprints for (bio)polymer scientists, displaying highly optimized mechanical properties due to their hierarchical structures. Biotechnological production of silk proteins and implementation of advanced processing methods enabled harnessing the potential of these biopolymer not just based on the mechanical properties. In addition to fibers, diverse morphologies can be produced, such as nonwoven meshes, films, hydrogels, foams, capsules and particles. Among them, nanoscale fibrils and fibers are particularly interesting concerning medical and technical applications due to their biocompatibility, environmental and mechanical robustness as well as high surface-to-volume ratio. Therefore, we introduce here self-assembly of silk proteins into hierarchically organized structures such as supramolecular nanofibrils and fabricated materials based thereon. As an alternative to self-assembly, we also present electrospinning a technique to produce nanofibers and nanofibrous mats. Accordingly, we introduce a broad range of silk-based dopes, used in self-assembly and electrospinning: natural silk proteins originating from natural spinning glands, natural silk protein solutions reconstituted from fibers, engineered recombinant silk proteins designed from natural blueprints, genetic fusions of recombinant silk proteins with other structural or functional peptides and moieties, as well as hybrids of recombinant silk proteins chemically conjugated with nonproteinaceous biotic or abiotic molecules. We highlight the advantages but also point out drawbacks of each particular production route. The scope includes studies of the natural self-assembly mechanism during natural silk spinning, production of silk fibrils as new nanostructured non-native scaffolds allowing dynamic morphological switches, as well as studying potential applications. This article is categorized under:  Biology-Inspired Nanomaterials

  17. In Situ Atomic Force Microscopy Studies on Nucleation and Self-Assembly of Biogenic and Bio-Inspired Materials

    Directory of Open Access Journals (Sweden)

    Cheng Zeng

    2017-08-01

    Full Text Available Through billions of years of evolution, nature has been able to create highly sophisticated and ordered structures in living systems, including cells, cellular components and viruses. The formation of these structures involves nucleation and self-assembly, which are fundamental physical processes associated with the formation of any ordered structure. It is important to understand how biogenic materials self-assemble into functional and highly ordered structures in order to determine the mechanisms of biological systems, as well as design and produce new classes of materials which are inspired by nature but equipped with better physiochemical properties for our purposes. An ideal tool for the study of nucleation and self-assembly is in situ atomic force microscopy (AFM, which has been widely used in this field and further developed for different applications in recent years. The main aim of this work is to review the latest contributions that have been reported on studies of nucleation and self-assembly of biogenic and bio-inspired materials using in situ AFM. We will address this topic by introducing the background of AFM, and discussing recent in situ AFM studies on nucleation and self-assembly of soft biogenic, soft bioinspired and hard materials.

  18. Self-Assembly, Supramolecular Organization, and Phase Behavior of L-Alanine Alkyl Esters (n = 9-18) and Characterization of Equimolar L-Alanine Lauryl Ester/Lauryl Sulfate Catanionic Complex.

    Science.gov (United States)

    Sivaramakrishna, D; Swamy, Musti J

    2015-09-08

    A homologous series of l-alanine alkyl ester hydrochlorides (AEs) bearing 9-18 C atoms in the alkyl chain have been synthesized and characterized with respect to self-assembly, supramolecular structure, and phase transitions. The CMCs of AEs bearing 11-18 C atoms were found to range between 0.1 and 10 mM. Differential scanning calorimetric (DSC) studies showed that the transition temperatures (Tt), enthalpies (ΔHt) and entropies (ΔSt) of AEs in the dry state exhibit odd-even alternation, with the odd-chain-length compounds having higher Tt values, but the even-chain-length homologues showing higher values of ΔHt and ΔSt. In DSC measurements on hydrated samples, carried out at pH 5.0 and pH 10.0 (where they exist in cationic and neutral forms, respectively), compounds with 13-18 C atoms in the alkyl chain showed sharp gel-to-liquid crystalline phase transitions, and odd-even alternation was not seen in the thermodynamic parameters. The molecular structure, packing properties, and intermolecular interactions of AEs with 9 and 10 C atoms in the alkyl chain were determined by single crystal X-ray diffraction, which showed that the alkyl chains are packed in a tilted interdigitated bilayer format. d-Spacings obtained from powder X-ray diffraction studies exhibited a linear dependence on the alkyl chain length, suggesting that the other AEs also adopt an interdigitated bilayer structure. Turbidimetric, fluorescence spectroscopic, and isothermal titration calorimetric (ITC) studies established that in aqueous dispersions l-alanine lauryl ester hydrochloride (ALE·HCl) and sodium dodecyl sulfate (SDS) form an equimolar complex. Transmission electron microscopic and DSC studies indicate that the complex exists as unilamellar liposomes, which exhibit a sharp phase transition at ∼39 °C. The aggregates were disrupted at high pH, suggesting that the catanionic complex would be useful to develop a base-labile drug delivery system. ITC studies indicated that ALE·HCl forms

  19. Self-assembling peptide-based building blocks in medical applications

    Energy Technology Data Exchange (ETDEWEB)

    Acar, Handan; Srivastava, Samanvaya; Chung, Eun Ji; Schnorenberg, Mathew R.; Barrett, John C.; LaBelle, James L.; Tirrell, Matthew

    2017-02-01

    Peptides and peptide-conjugates, comprising natural and synthetic building blocks, are an increasingly popular class of biomaterials. Self-assembled nanostructures based on peptides and peptide-conjugates offer advantages such as precise selectivity and multifunctionality that can address challenges and limitations in the clinic. In this review article, we discuss recent developments in the design and self-assembly of various nanomaterials based on peptides and peptide-conjugates for medical applications, and categorize them into two themes based on the driving forces of molecular self-assembly. First, we present the self-assembled nanostructures driven by the supramolecular interactions between the peptides, with or without the presence of conjugates. The studies where nanoassembly is driven by the interactions between the conjugates of peptide-conjugates are then presented. Particular emphasis is given to in vivo studies focusing on therapeutics, diagnostics, immune modulation and regenerative medicine. Finally, challenges and future perspectives are presented.

  20. Theoretical study of the morphology of self-assembled amphoteric oxide colloid nanocrystals in weak electrolyte solutions

    Science.gov (United States)

    Alfimov, A. V.; Aryslanova, E. M.; Chivilikhin, S. A.

    2016-08-01

    The present paper is devoted to the theoretical study of the morphology of nanocrystals formed through self-assembly of amphoteric oxide colloidal nanoparticles in weak electrolytes. A mathematical model of multi-particle colloidal interaction was developed within the framework of the Derjaguin, Landau, Verwey, Overbeak (DLVO) theory. This model accounts for the surface charge regulation during the multi-particle interaction and reveals the presence of orientation effects during nanoparticle aggregation. These effects are presumed to affect the morphology of the self-assembled nanocrystals and may present the means of controlling the structure of synthesised nanomaterials.

  1. Self-assembly and flux closure studies of magnetic nanoparticle rings

    DEFF Research Database (Denmark)

    Wei, Alexander; Kasama, Takeshi; Dunin-Borkowski, Rafal E.

    2011-01-01

    Thermoremanent magnetic nanoparticles (MNPs) can self-assemble into rings through dipolar interactions, when dispersed under appropriate conditions. Analysis of individual MNP rings and clusters by off-axis electron holography reveals bistable flux closure (FC) states at ambient temperatures...

  2. Self-assembly of designed coiled coil peptides studied by small-angle X-ray scattering and analytical ultracentrifugation

    DEFF Research Database (Denmark)

    Malik, Leila; Nygaard, Jesper; Christensen, Niels Johan

    2013-01-01

    , they are promising tools for the construction of nanomaterials. Small-angle X-ray scattering (SAXS) has emerged as a new biophysical technique for elucidation of protein topology. Here, we describe a systematic study of the self-assembly of a small ensemble of coiled coil sequences using SAXS and analytical...

  3. Oral insulin delivery by self-assembled chitosan nanoparticles: In vitro and in vivo studies in diabetic animal model

    Energy Technology Data Exchange (ETDEWEB)

    Mukhopadhyay, Piyasi; Sarkar, Kishor [Department of Polymer Science and Technology, 92, A.P.C. Road, Kolkata-700009, University of Calcutta (India); Chakraborty, Mousumi; Bhattacharya, Sourav; Mishra, Roshnara [Department of Physiology, 92, A.P.C. Road, Kolkata-700009, University of Calcutta (India); Kundu, P.P., E-mail: ppk923@yahoo.com [Department of Polymer Science and Technology, 92, A.P.C. Road, Kolkata-700009, University of Calcutta (India)

    2013-01-01

    We have developed self-assembled chitosan/insulin nanoparticles for successful oral insulin delivery. The main purpose of our study is to prepare chitosan/insulin nanoparticles by self-assembly method, to characterize them and to evaluate their efficiency in vivo diabetic model. The size and morphology of the nanoparticles were analyzed by dynamic light scattering (DLS), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The average particle size ranged from 200 to 550 nm, with almost spherical or sub spherical shape. An average insulin encapsulation within the nanoparticles was {approx} 85%. In vitro release study showed that the nanoparticles were also efficient in retaining good amount of insulin in simulated gastric condition, while significant amount of insulin release was noticed in simulated intestinal condition. The oral administrations of chitosan/insulin nanoparticles were effective in lowering the blood glucose level of alloxan-induced diabetic mice. Thus, self-assembled chitosan/insulin nanoparticles show promising effects as potential insulin carrier system in animal models. Highlights: Black-Right-Pointing-Pointer Self-assembled chitosan/insulin nanoparticle preparation. Black-Right-Pointing-Pointer Almost spherical or sub-spherical nanoparticles observed under microscope. Black-Right-Pointing-Pointer Good insulin encapsulation of the nanoparticles. Black-Right-Pointing-Pointer Nanoparticles reduced blood glucose level significantly in diabetic mice.

  4. Hydrazine-mediated construction of nanocrystal self-assembly materials.

    Science.gov (United States)

    Zhou, Ding; Liu, Min; Lin, Min; Bu, Xinyuan; Luo, Xintao; Zhang, Hao; Yang, Bai

    2014-10-28

    Self-assembly is the basic feature of supramolecular chemistry, which permits to integrate and enhance the functionalities of nano-objects. However, the conversion of self-assembled structures to practical materials is still laborious. In this work, on the basis of studying one-pot synthesis, spontaneous assembly, and in situ polymerization of aqueous semiconductor nanocrystals (NCs), NC self-assembly materials are produced and applied to design high performance white light-emitting diode (WLED). In producing self-assembly materials, the additive hydrazine (N2H4) is curial, which acts as the promoter to achieve room-temperature synthesis of aqueous NCs by favoring a reaction-controlled growth, as the polyelectrolyte to weaken inter-NC electrostatic repulsion and therewith facilitate the one-dimensional self-assembly, and in particular as the bifunctional monomers to polymerize with mercapto carboxylic acid-modified NCs via in situ amidation reaction. This strategy is versatile for mercapto carboxylic acid-modified aqueous NCs, for example CdS, CdSe, CdTe, CdSe(x)Te(1-x), and Cd(y)Hg(1-y)Te. Because of the multisite modification with carboxyl, the NCs act as macromonomers, thus producing cross-linked self-assembly materials with excellent thermal, solvent, and photostability. The assembled NCs preserve strong luminescence and avoid unpredictable fluorescent resonance energy transfer, the main problem in design WLED from multiple NC components. These advantages allow the fabrication of NC-based WLED with high color rendering index (86), high luminous efficacy (41 lm/W), and controllable color temperature.

  5. Process-directed self-assembly of block copolymers: a computer simulation study

    International Nuclear Information System (INIS)

    Müller, Marcus; Sun, De-Wen

    2015-01-01

    The free-energy landscape of self-assembling block copolymer systems is characterized by a multitude of metastable minima and concomitant protracted relaxation times of the morphology. Tailoring rapid changes (quench) of thermodynamic conditions, one can reproducibly trap the ensuing kinetics of self-assembly in a specific metastable state. To this end, it is necessary to (1) control the generation of well-defined, highly unstable states and (2) design the unstable state such that the ensuing spontaneous kinetics of structure formation reaches the desired metastable morphology. This process-directed self-assembly provides an alternative to fine-tuning molecular architecture by synthesis or blending, for instance, in order to fabricate complex network structures. Comparing our simulation results to recently developed free-energy techniques, we highlight the importance of non-equilibrium molecular conformations in the starting state and motivate the significance of the local conservation of density. (paper)

  6. Study of polymorphism using patterned self-assembled monolayers approach on metal substrates

    Science.gov (United States)

    Quiñones, Rosalynn; Brown, Ryanne T.; Searls, Noah; Richards-Waugh, Lauren

    2018-01-01

    Polymorphism is a molecule's ability to possess altered physical crystalline structures and has become an active interest in pharmaceuticals due to its ability to influence a drug's physical and chemical properties. Crystal stability and solubility are crucial in determining a drug's pharmacokinetics and pharmacodynamics. Changes in these properties due to polymorphisms have contributed to recalls and modifications in industrial production. For this study, the effects of surface interactions with pharmaceuticals were examined through surface modification methodology using organic phosphonic and sulfonic acid self-assembled monolayers (SAMs) developed on a nickel or zinc oxide metal substrate. Drugs analyzed included carbamazepine, cimetidine, tolfenamic acid, and flufenamic acid. All drugs were thermodynamically applied to the reformed surface to aid in recrystallization. It was hypothesized and confirmed that intermolecular bonds, especially hydrogen bonds between the SAMs and pharmaceutical drugs, were the force that assisted in polymorph development. The study was successful in revealing multiple forms for each drug, including their commercial form and at least one additional form using micro FT-IR, Raman spectroscopy, and PXRD. Visual comparisons of crystal polymorphisms were performed with IR microscopy.

  7. Molecular dynamics simulations reveal disruptive self-assembly in dynamic peptide libraries.

    Science.gov (United States)

    Sasselli, I R; Moreira, I P; Ulijn, R V; Tuttle, T

    2017-08-09

    There is significant interest in the use of unmodified self-assembling peptides as building blocks for functional, supramolecular biomaterials. Recently, dynamic peptide libraries (DPLs) have been proposed to select self-assembling materials from dynamically exchanging mixtures of dipeptide inputs in the presence of a nonspecific protease enzyme, where peptide sequences are selected and amplified based on their self-assembling tendencies. It was shown that the results of the DPL of mixed sequences (e.g. starting from a mixture of dileucine, L 2 , and diphenylalanine, F 2 ) did not give the same outcome as the separate L 2 and F 2 libraries (which give rise to the formation of F 6 and L 6 ), implying that interactions between these sequences could disrupt the self-assembly. In this study, coarse grained molecular dynamics (CG-MD) simulations are used to understand the DPL results for F 2 , L 2 and mixed libraries. CG-MD simulations demonstrate that interactions between precursors can cause the low formation yield of hexapeptides in the mixtures of dipeptides and show that this ability to disrupt is influenced by the concentration of the different species in the DPL. The disrupting self-assembly effect between the species in the DPL is an important effect to take into account in dynamic combinatorial chemistry as it affects the possible discovery of new materials. This work shows that combined computational and experimental screening can be used complementarily and in combination providing a powerful means to discover new supramolecular peptide nanostructures.

  8. Experimental study of thermophysical properties and nanostructure of self-assembled water/polyalphaolefin nanoemulsion fluids

    Directory of Open Access Journals (Sweden)

    Jiajun Xu

    2015-04-01

    Full Text Available In this study, the nanostructures and thermophysical properties (thermal conductivity, viscosity, and specific heat of one new type of nanostructured heat transfer fluid, water/polyalphaolefin nanoemulsion fluid, are investigated. The water/polyalphaolefin nanoemulsion fluids are thermodynamically stable containing dispersed water nanodroplets formed by self-assembly. It has been found that the nanostructure inside nanoemulsion fluids may affect their thermophysical properties, especially the phase change heat transfer characteristics. The small-angle neutron scattering technique has been used to help identify the nanostructure inside the water/polyalphaolefin nanoemulsion fluids. By using the 3-region Guinier–Porod model, the fitting curve shows that there is a nonlinear variation of the nanodroplets’ size and shape with water’s concentration, which also coincides with the trend of its viscosity and specific heat. On the other hand, the thermal conductivity increases linearly with higher volume fraction of water which, however, appears to be insensitive to the nanostructure change. While the water nanodroplets inside can increase the thermal conductivity of the nanoemulsion fluid by 16%, its effective specific heat can be boosted up to 90% when the water nanodroplets undergo liquid–solid phase change.

  9. Generation of Low-Dimensional Architectures through the Self-Assembly of Pyromellitic Diimide Derivatives.

    Science.gov (United States)

    Musumeci, Chiara; Wałe Sa-Chorab, Monika; Gorczyński, Adam; Markiewicz, Grzegorz; Bogucki, Andrzej; Świetlik, Roman; Hnatejko, Zbigniew; Jankowski, Wojciech; Hoffmann, Marcin; Orgiu, Emanuele; Stefankiewicz, Artur R; Patroniak, Violetta; Ciesielski, Artur; Samorì, Paolo

    2017-04-30

    Small π-conjugated molecules can be designed and synthesized to undergo controlled self-assembly forming low-dimensional architectures, with programmed order at the supramolecular level. Such order is of paramount importance because it defines the property of the obtained material. Here, we have focused our attention to four pyromellitic diimide derivatives exposing different types of side chains. The joint effect of different noncovalent interactions including π-π stacking, H-bonding, and van der Waals forces on the four derivatives yielded different self-assembled architectures. Atomic force microscopy studies, corroborated with infrared and nuclear magnetic resonance spectroscopic measurements, provided complementary multiscale insight into these assemblies.

  10. Porphyrins with directly meso-attached disaccharide moieties: Synthesis, self-assembly and cellular study

    Czech Academy of Sciences Publication Activity Database

    Malachowska, M.; Sperduto, C.; Darmostuk, M.; Monti, D.; Venanzi, M.; Mancini, G.; D'Acunto, C.W.; Králová, Jarmila; Ruml, T.; Wimmer, Zdeněk; Drasar, P.

    2016-01-01

    Roč. 20, č. 7 (2016), s. 773-784 ISSN 1088-4246 Institutional support: RVO:61389030 ; RVO:68378050 Keywords : derivatives * aggregation * steroids * sucrose * porphyrinoids * carbohydrates * self-assembly * cellular localisation * liposomes Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 1.043, year: 2016

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

    DEFF Research Database (Denmark)

    Sasso, Luigi; Vedarethinam, Indumathi; Emnéus, Jenny

    2012-01-01

    In this paper we present a series of experiments showing that vertical self-assembled diphenylalanine peptide nanowires (PNWs) are a suitable candidate material for cellular biosensing. We grew HeLa and PC12 cells onto PNW modified gold surfaces and observed no hindrance of cell growth caused by ...

  12. Molecular Dynamics Study of Alkanethiolate Self-Assembled Monolayer Coated Gold Nanoparticle

    Science.gov (United States)

    2007-06-01

    of Organosulfur Compounds on Au( 111). Implications for Molecular Self-Assembly on Gold 21. Plimpton, S.J., "Fast Parallel Algorithms for Short-Range... Organosulfur Compounds SHAKE Algorithm for Molecular Dynamics." Journal of Adsorbed on Gold Single Crystals: Electron Diffraction Computational Physics, 52

  13. Dynamic light scattering study of self-assembly of HPMA hybrid graft copolymers

    Czech Academy of Sciences Publication Activity Database

    Yang, J.; Wu, J.; Koňák, Čestmír; Kopeček, J.

    2008-01-01

    Roč. 9, č. 2 (2008), s. 510-517 ISSN 1525-7797 R&D Projects: GA AV ČR IAA100500501 Institutional research plan: CEZ:AV0Z40500505 Keywords : self-assembly * hybrid hydrogel system * oppositely charged peptide grafts Subject RIV: CD - Macromolecular Chemistry Impact factor: 4.146, year: 2008

  14. Amphiphilic building blocks for self-assembly: from amphiphiles to supra-amphiphiles.

    Science.gov (United States)

    Wang, Chao; Wang, Zhiqiang; Zhang, Xi

    2012-04-17

    The process of self-assembly spontaneously creates well-defined structures from various chemical building blocks. Self-assembly can include different levels of complexity: it can be as simple as the dimerization of two small building blocks driven by hydrogen bonding or as complicated as a cell membrane, a remarkable supramolecular architecture created by a bilayer of phospholipids embedded with functional proteins. The study of self-assembly in simple systems provides a fundamental understanding of the driving forces and cooperativity behind these processes. Once the rules are understood, these guidelines can facilitate the research of highly complex self-assembly processes. Among the various components for self-assembly, an amphiphilic molecule, which contains both hydrophilic and hydrophobic parts, forms one of the most powerful building blocks. When amphiphiles are dispersed in water, the hydrophilic component of the amphiphile preferentially interacts with the aqueous phase while the hydrophobic portion tends to reside in the air or in the nonpolar solvent. Therefore, the amphiphiles aggregate to form different molecular assemblies based on the repelling and coordinating forces between the hydrophilic and hydrophobic parts of the component molecules and the surrounding medium. In contrast to conventional amphiphiles, supra-amphiphiles are constructed on the basis of noncovalent interactions or dynamic covalent bonds. In supra-amphiphiles, the functional groups can be attached to the amphiphiles by noncovalent synthesis, greatly speeding their construction. The building blocks for supra-amphiphiles can be either small organic molecules or polymers. Advances in the development of supra-amphiphiles will not only enrich the family of conventional amphiphiles that are based on covalent bonds but will also provide a new kind of building block for the preparation of complex self-assemblies. When polymers are used to construct supra-amphiphiles, the resulting

  15. Self-Assembly, Interfacial Nanostructure, and Supramolecular Chirality of the Langmuir-Blodgett Films of Some Schiff Base Derivatives without Alkyl Chain

    Directory of Open Access Journals (Sweden)

    Tifeng Jiao

    2013-01-01

    Full Text Available A special naphthyl-containing Schiff base derivative, N,N′-bis(2-hydroxy-1-naphthylidene-1,2-phenylenediamine, was synthesized, and its coordination with various metal ions in situ at the air/water interface has been investigated. Although the ligand contains no alkyl chain, it can be spread on water surface. When metal ions existed in the subphase, an interfacial coordination between the ligand and different metal ions occurred in the spreading film, while different Nanostructures were fabricated in the monolayers. Interestingly to note that among various metal ions, only the in situ coordination-induced Cu(II-complex film showed supramolecular chirality, although the multilayer films from the ligand or preformed complex are achiral. The chirality of the in situ Cu(II-coordinated Langmuir film was developed due to the special distorted coordination reaction and the spatial limitation at the air/water interface. A possible organization mechanism at the air/water interface was suggested.

  16. UV/Vis Spectroscopy Studies of the Photoisomerization Kinetics in Self-Assembled Azobenzene-Containing Adlayers.

    Science.gov (United States)

    Krekiehn, N R; Müller, M; Jung, U; Ulrich, S; Herges, R; Magnussen, O M

    2015-08-04

    Direct comparative studies of the photoisomerization of azobenzene derivatives in self-assembled adlayers on Au and as free molecules in dichloromethane solution were performed using UV/vis spectroscopy. For all studied systems a highly reversible trans-cis isomerization in the adlayer is observed. Quantitative studies of the absorbance changes and photoisomerization kinetics reveal that in azobenzenes mounted as freestanding vertical groups on the surface via triazatriangulene-based molecular platforms photoswitching is nearly uninhibited by the local environment in the adlayer. The blue-shift of the π-π* transition in adlayers of these molecules is in good agreement with theoretical studies of the effect of excitonic coupling between the molecules. In contrast, in azobenzene-containing thiol self-assembled monolayers the fraction of photoswitching molecules and the photoisomerization kinetics are significantly reduced compared to free molecules in solution.

  17. Spectroscopic imaging studies of nanoscale polarity and mass transport phenomena in self-assembled organic nanotubes.

    Science.gov (United States)

    Xu, Hao; Nagasaka, Shinobu; Kameta, Naohiro; Masuda, Mitsutoshi; Ito, Takashi; Higgins, Daniel A

    2017-08-02

    Synthetic organic nanotubes self-assembled from bolaamphiphile surfactants are now being explored for use as drug delivery vehicles. In this work, several factors important to their implementation in drug delivery are explored. All experiments are performed with the nanotubes immersed in ethanol. First, Nile Red (NR) and a hydroxylated Nile Red derivative (NR-OH) are loaded into the nanotubes and spectroscopic fluorescence imaging methods are used to determine the apparent dielectric constant of their local environment. Both are found in relatively nonpolar environments, with the NR-OH molecules preferring regions of relatively higher dielectric constant compared to NR. Unique two-color imaging fluorescence correlation spectroscopy (imaging FCS) measurements are then used along with the spectroscopic imaging results to deduce the dielectric properties of the environments sensed by mobile and immobile populations of probe molecules. The results reveal that mobile NR molecules pass through less polar regions, likely within the nanotube walls, while immobile NR molecules are found in more polar regions, possibly near the nanotube surfaces. In contrast, mobile and immobile NR-OH molecules are found to locate in environments of similar polarity. The imaging FCS results also provide quantitative data on the apparent diffusion coefficient for each dye. The mean diffusion coefficient for the NR dye was approximately two-fold larger than that of NR-OH. Slower diffusion by the latter could result from its additional hydrogen bonding interactions with polar triglycine, amine, and glucose moieties near the nanotube surfaces. The knowledge gained in these studies will allow for the development of nanotubes that are better engineered for applications in the controlled transport and release of uncharged, dipolar drug molecules.

  18. Studying plasmonic resonance modes of hierarchical self-assembled meta-atoms based on their transfer matrix

    Science.gov (United States)

    Suryadharma, Radius N. S.; Fruhnert, Martin; Fernandez-Corbaton, Ivan; Rockstuhl, Carsten

    2017-07-01

    Hierarchical self-assembled meta-atoms are made from a larger number of suitably arranged metallic nanoparticles. They constitute the basic building blocks for isotropic metamaterials. The properties of these meta-atoms are usually studied upon illumination with a plane wave and by analyzing the multipolar composition of the scattered field. This, however, does not always provide full information. The coupling between multiple meta-atoms is usually not considered, and a physical understanding for the cause of the response is often incomplete. Here we overcome these limitations by performing a spectral eigenvalue analysis of the transfer matrix of isolated and coupled self-assembled meta-atoms. Emphasis is put on using a transfer-matrix formulation in either a local or a global coordinate frame. We show that for the magnetic resonance, coupling to nearest neighbors is weak, suggesting the possibility to preserve the response of the isolated meta-atom upon tight packaging in a metamaterial.

  19. Self-assembled monolayers on gold nanospheres studied by optical second-harmonic generation

    Science.gov (United States)

    Yamaguchi, T.; Kajikawa, K.

    2008-08-01

    Recently plasmonic biosensors consisting of gold nanoparticles have been developed. In order to understand the response of the biosensors, we have investigated how are gold nanospheres immobilized on a surface covered by a self-assembled monolayer (SAM) which is formed by immersion of the substrate in a solution, by use of surface second-harmonic generation (SHG). The surface immobilized gold nanospheres (SIGNs) are supported by a self-assembled monolayer (SAM) of aminoundecanthiol on a gold thin film. The SIGN substrate was immersed in an ethanol solution of hemicyanine-terminated alkanethiol. The capping angles of the hemicyanine SAM with respect to the top of the SIGN were evaluated from polarization dependence of SHG intensity. The SIGNs are not fully covered with the SAM, and the capping angle is found to be approximately 120 degrees.

  20. X-Ray Reflectometry Study of Self-Assembled Ionic Nanolayers

    Directory of Open Access Journals (Sweden)

    Szymon Jasiecki

    2012-01-01

    Full Text Available The self-assembly technique has been applied for the fabrication of thin films including macrocyclic molecules. These multilayered structures, grown by sequential deposition of oppositely charged molecules, were characterised with X-ray reflectometry. The data obtained indicate regular thickness of ion pair layers formed regardless of the number of depositions made as well as the number of ion groups occurring in the molecule. Savitzky-Golay algorithm was used for the calculation of the layer thickness. Formation of self-assembled multilayers (SAMs occurs not only for polymeric structures but also for small ionic compound systems and results from the electrostatic interaction of many strongly dissipated charges on the whole structure of the molecule.

  1. Molecular dynamics studies of PEGylated α-helical coiled coils and their self-assembled micelles.

    Science.gov (United States)

    Woo, Sun Young; Lee, Hwankyu

    2014-07-29

    We performed coarse-grained (CG) molecular dynamics simulations of trimeric α-helical coiled coils grafted with poly(ethylene glycol) (PEG) of different sizes and conjugate positions and the self-assembled micelle of amphiphilic trimers. The CG model for the trimeric coiled coil is verified by comparing the α-helical structure and interhelical distance with those calculated from all-atom simulations. In CG simulations of PEGylated trimers, the end-to-end distances and radii of gyration of PEGs grafted to the sides of peptides become shorter than those of free PEGs in water, which agrees with experiments. This shorter size of the grafted PEGs is also confirmed by calculating the thickness of the PEG layer, which is less than the size of the mushroom. These indicate the adsorption of PEG chains onto coiled coils since hydrophobic residues in the exterior sites of coiled coils tend to be less exposed to water and thus interact with PEGs, leading to the compact conformation of adsorbed PEGs. Simulations of the self-assembly of amphiphilic trimers show that the randomly distributed trimers self-assemble to micelles. The outer radius and hydrodynamic radius of the micelle, which were calculated respectively from radial densities and diffusion coefficients, are ∼7 nm, in agreement with the experimental value of ∼7.5 nm, while the aggregation number of amphiphilic molecules per micelle is lower than the experimentally proposed value. These simulations predict the experimentally measured size of PEGs grafted to the trimeric coiled coils and their self-assembled amphiphilic micelles and suggest that the aggregation number of the micelle may be lower, which needs to be confirmed by experiments.

  2. Photocontrolled reversible self-assembly of dodecamer nitrilase.

    Science.gov (United States)

    Yu, Qiao; Wang, Yong; Zhao, Shengyun; Ren, Yuhong

    2017-01-01

    Naturally photoswitchable proteins act as a powerful tool for the spatial and temporal control of biological processes by inducing the formation of a photodimerizer. In this study, a method for the precise and reversible inducible self-assembly of dodecamer nitrilase in vivo (in Escherichia coli ) and in vitro (in a cell-free solution) was developed by means of the photoswitch-improved light-inducible dimer (iLID) system which could induce protein-protein dimerization. Nitrilase was fused with the photoswitch protein AsLOV2-SsrA to achieve the photocontrolled self-assembly of dodecamer nitrilase. The fusion protein self-assembled into a supramolecular assembly when illuminated at 470 nm. Scanning electron microscopy showed that the assembly formed a circular sheet structure. Self-assembly was also induced by light in E. coli . Dynamic light scattering and turbidity assay experiments showed that the assemblies formed within a few seconds under 470-nm light and completely disassembled within 5 min in the dark. Assembly and disassembly could be maintained for at least five cycles. Both in vitro and in vivo, the assemblies retained 90% of the initial activity of nitrilase and could be reused at least four times in vitro with 90% activity. An efficient method was developed for the photocontrolled assembly and disassembly of dodecamer nitrilase and for scaffold-free reversible self-assembly of multiple oligomeric enzymes in vivo and in vitro, providing new ideas and methods for immobilization of enzyme without carrier.

  3. Molecular modeling of directed self-assembly of block copolymers: Fundamental studies of processing conditions and evolutionary pattern design

    Science.gov (United States)

    Khaira, Gurdaman Singh

    Rapid progress in the semi-conductor industry has pushed for smaller feature sizes on integrated electronic circuits. Current photo-lithographic techniques for nanofabrication have reached their technical limit and are problematic when printing features small enough to meet future industrial requirements. "Bottom-up'' techniques, such as the directed self-assembly (DSA) of block copolymers (BCP), are the primary contenders to compliment current "top-down'' photo-lithography ones. For industrial requirements, the defect density from DSA needs to be less than 1 defect per 10 cm by 10 cm. Knowledge of both material synthesis and the thermodynamics of the self-assembly process are required before optimal operating conditions can be found to produce results adequate for industry. The work present in this thesis is divided into three chapters, each discussing various aspects of DSA as studied via a molecular model that contains the essential physics of BCP self-assembly. Though there are various types of guiding fields that can be used to direct BCPs over large wafer areas with minimum defects, this study focuses only on chemically patterned substrates. The first chapter addresses optimal pattern design by describing a framework where molecular simulations of various complexities are coupled with an advanced optimization technique to find a pattern that directs a target morphology. It demonstrates the first ever study where BCP self-assembly on a patterned substrate is optimized using a three-dimensional description of the block-copolymers. For problems pertaining to DSA, the methodology is shown to converge much faster than the traditional random search approach. The second chapter discusses the metrology of BCP thin films using TEM tomography and X-ray scattering techniques, such as CDSAXS and GISAXS. X-ray scattering has the advantage of being able to quickly probe the average structure of BCP morphologies over large wafer areas; however, deducing the BCP morphology

  4. Chemical reactions directed Peptide self-assembly.

    Science.gov (United States)

    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.

  5. Chemical Reactions Directed Peptide Self-Assembly

    Directory of Open Access Journals (Sweden)

    Dnyaneshwar B. Rasale

    2015-05-01

    Full Text Available 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.

  6. X-ray reflectivity study of the self-assembly of ordered lysozyme films

    International Nuclear Information System (INIS)

    Kayushina, R.L.; Stepina, N.D.; Belyaev, V.V.; Khurgin, Yu.I.

    1996-01-01

    It is shown that the method of self-assembly of multilayer structures can be successfully used to obtain structures including the globular protein lysozyme. A precursor film was obtained by alternating adsorption of polyanions [sodium poly(styrenesulfonate)] and polycations [poly(allylaimine) hydrochoride.] The process of film assembly was controlled by the x-ray reflectivity method. It is shown that the total thickness of a multilayer film increases linearly with the number of layers of polyelectrolyte pairs. The average thickness of the layer of polyelectrolyte pairs was 37 A. The thickness of the adsorbed lysozyme layer was about 45 A, which is consistent with the dimensions of the protein molecule

  7. Self-assembly of silicon nanowires studied by advanced transmission electron microscopy

    Directory of Open Access Journals (Sweden)

    Marta Agati

    2017-02-01

    Full Text Available Scanning transmission electron microscopy (STEM was successfully applied to the analysis of silicon nanowires (SiNWs that were self-assembled during an inductively coupled plasma (ICP process. The ICP-synthesized SiNWs were found to present a Si–SiO2 core–shell structure and length varying from ≈100 nm to 2–3 μm. The shorter SiNWs (maximum length ≈300 nm were generally found to possess a nanoparticle at their tip. STEM energy dispersive X-ray (EDX spectroscopy combined with electron tomography performed on these nanostructures revealed that they contain iron, clearly demonstrating that the short ICP-synthesized SiNWs grew via an iron-catalyzed vapor–liquid–solid (VLS mechanism within the plasma reactor. Both the STEM tomography and STEM-EDX analysis contributed to gain further insight into the self-assembly process. In the long-term, this approach might be used to optimize the synthesis of VLS-grown SiNWs via ICP as a competitive technique to the well-established bottom-up approaches used for the production of thin SiNWs.

  8. Self-assembly of self-assembled molecular triangles

    Indian Academy of Sciences (India)

    (tmeda), 2,2 -bipyridine (bpy), and 1,10-phenanthroline. (phen), etc. The synthesis and dynamic studies of a vari- ety of designed Pd(II) cages are well studied1a−d but the crystal engineering of Pd(II)-based self-assembled coordination cages has been less explored.4 Recently we have been investigating the significance of ...

  9. Synthetic Molecular Machines for Active Self-Assembly: Prototype Algorithms, Designs, and Experimental Study

    Science.gov (United States)

    Dabby, Nadine L.

    Computer science and electrical engineering have been the great success story of the twentieth century. The neat modularity and mapping of a language onto circuits has led to robots on Mars, desktop computers and smartphones. But these devices are not yet able to do some of the things that life takes for granted: repair a scratch, reproduce, regenerate, or grow exponentially fast--all while remaining functional. This thesis explores and develops algorithms, molecular implementations, and theoretical proofs in the context of "active self-assembly" of molecular systems. The long-term vision of active self-assembly is the theoretical and physical implementation of materials that are composed of reconfigurable units with the programmability and adaptability of biology's numerous molecular machines. En route to this goal, we must first find a way to overcome the memory limitations of molecular systems, and to discover the limits of complexity that can be achieved with individual molecules. One of the main thrusts in molecular programming is to use computer science as a tool for figuring out what can be achieved. While molecular systems that are Turing-complete have been demonstrated [Winfree, 1996], these systems still cannot achieve some of the feats biology has achieved. One might think that because a system is Turing-complete, capable of computing "anything," that it can do any arbitrary task. But while it can simulate any digital computational problem, there are many behaviors that are not "computations" in a classical sense, and cannot be directly implemented. Examples include exponential growth and molecular motion relative to a surface. Passive self-assembly systems cannot implement these behaviors because (a) molecular motion relative to a surface requires a source of fuel that is external to the system, and (b) passive systems are too slow to assemble exponentially-fast-growing structures. We call these behaviors "energetically incomplete" programmable

  10. Charge trapping at organic/self-assembly molecule interfaces studied by electrical switching behaviour in a crosspoint structure

    International Nuclear Information System (INIS)

    Li Yun; Pan Lijia; Pu Lin; Shi Yi; Liu Chuan; Tsukagoshi, Kazuhito

    2012-01-01

    Charge trapping at organic/self-assembly molecule (SAM) interfaces is studied by the electrical switching behaviour in a crosspoint structure, where interfacial charge trapping tunes the potential barrier of the SAM layer. The sample with rubrene exhibits the write-once read-many-times memory effect, which is due to the interfacial charges trapped at deep states. On the other hand, the sample with 2-amino-4,5-dicyanoimidazole presents recyclable conduction transition, which results from the trapped charges distributed at shallow states. Moreover, the percentage of the charges trapped at shallow states can be estimated from electrical transition levels. (paper)

  11. Charge trapping at organic/self-assembly molecule interfaces studied by electrical switching behaviour in a crosspoint structure

    Science.gov (United States)

    Li, Yun; Liu, Chuan; Pan, Lijia; Pu, Lin; Tsukagoshi, Kazuhito; Shi, Yi

    2012-01-01

    Charge trapping at organic/self-assembly molecule (SAM) interfaces is studied by the electrical switching behaviour in a crosspoint structure, where interfacial charge trapping tunes the potential barrier of the SAM layer. The sample with rubrene exhibits the write-once read-many-times memory effect, which is due to the interfacial charges trapped at deep states. On the other hand, the sample with 2-amino-4,5-dicyanoimidazole presents recyclable conduction transition, which results from the trapped charges distributed at shallow states. Moreover, the percentage of the charges trapped at shallow states can be estimated from electrical transition levels.

  12. Study of cluster ion emission from self assembled monolayers of alkanethiols under keV ion bombardment

    OpenAIRE

    Arezki, Bahia

    2007-01-01

    This work focuses on the emission processes of metal-organic clusters MmMen, (M is the organic molecule and Me the metal atom) ejected from self assembled monolayers (SAMs) of alkanethiols on gold after keV ion bombardment. These aggregates are often observed upon energetic ion bombardment of strongly bound molecules like SAMs. The explanation of this effect remains elusive, especially for large clusters as those observed in our study. The emission of these clusters is investigated using ToF-...

  13. Study of Alkylthiolate Self-assembled Monolayers on Au(111) Using a Semilocal meta-GGA Density Functional

    DEFF Research Database (Denmark)

    Ferrighi, Lara; Pan, Yun-xiang; Grönbeck, Henrik

    2012-01-01

    We present a density functional theory study of the structure and stability of self-assembled monolayers (SAMs) of alkylthiolate on Au(111) as a function of the alkyl chain length. The most favorable structure of the SAMs involves an RS–Au–SR complex (S being sulfur, R being an alkyl chain) formed...... through sandwiching one Au adatom by two alkylthiolates (RSs). Comparing a generalized gradient (GGA-PBE) and a meta-GGA (MGGA-M06-L) exchange-correlation functional we find that only the meta-GGA functional predicts the experimentally observed attractive intermolecular interactions within the SAMs...

  14. Study of the helium cross-section of unsymmetric disulfide self-assembled monolayers on Au(111)

    Energy Technology Data Exchange (ETDEWEB)

    Albayrak, Erol [Department of Materials and Metallurgical Engineering, Ahi Evran University, Kırşehir 40000 (Turkey); Karabuga, Semistan [Department of Chemistry, Kahramanmaraş Sütçü İmam University, Kahramanmaraş 46030 (Turkey); Bracco, Gianangelo [CNR-IMEM and Department of Physics, University of Genoa, Via Dodecaneso 33, Genoa 16146 (Italy); Danışman, M. Fatih, E-mail: danisman@metu.edu.tr [Department of Chemistry, Middle East Technical University, Ankara 06800 (Turkey)

    2016-12-30

    Highlights: • Unsymmetrtic disulfide (HDD and HOD) self assembled monolayers were grown on Au(111) by supersonic molecular beam deposition. • Helium scattering cross sections for these two different unsymmetric disulfides were determined. • A common low temperature film phase was observed for the studied disulfides. - Abstract: We have investigated the formation of self-assembled monolayers (SAMs) of 11-hydroxyundecyl decyl disulfide (CH{sub 3}-(CH{sub 2}){sub 9}-S-S-(CH{sub 2}){sub 11}-OH, HDD) and 11-hydroxyundecyl octadecyl disulfide (CH{sub 3}-(CH{sub 2}){sub 17}-S-S-(CH{sub 2}){sub 11}-OH, HOD) produced by supersonic molecular beam deposition (SMBD). The study has been carried out by means of helium diffraction at very low film coverage. In this regime helium single molecule cross sections have been estimated in a temperature range between 100 K and 450 K. The results show a different behavior above 300 K that has been interpreted as the starting of mobility with the formation of two thiolate moieties either linked by a gold adatom or distant enough to prevent cross section overlapping. Finally, helium diffraction patterns measured at 80 K for the SAMs grown at 200 K are discussed and the results support the proposed hypothesis of molecular dissociation based on the cross section data.

  15. A comprehensive molecular dynamics study on the self-assembly and properties of SiC based cage structures

    Science.gov (United States)

    Zhang, Congyan; Xin, Zihua; Yu, Ming; Jayanthi, C. S.; Wu, S. Y.; Shanghai University Collaboration

    2014-03-01

    A molecular dynamics study to investigate a plausible way of fabricating SiC based cage structures has been performed. In this work, the existence of the stable SiC based cage nanostructures SimCn with the size up to about 2.05nm in diameter and the compositions n/(n +m) from 0.4 to 0.6 has been demonstrated using an efficient semi-empirical Hamiltonian method (SCED-LCAO) [PRB 74, 15540 (2006)]. The structural properties are analyzed in terms of the composition, the bonding nature, the surface environment, the local strain, and types of ring structures. It is found that the sp2 bonding nature between Si and C atoms and the environmental mediation are two key factors for the self-assembly of the stable SiC based cage structures. In particular, the transition from one stable cage structure to another of similar composition might occur due to the mending process in the self-assembly. The first and second authors acknowledge the support from the NSFC (grant No.: 61176118) and 085 project of Shanghai University (China) for this work.

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

    Directory of Open Access Journals (Sweden)

    Puran Pandey

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

  17. Comparative Study of Electroless Copper Film on Different Self-Assembled Monolayers Modified ABS Substrate

    Directory of Open Access Journals (Sweden)

    Jiushuai Xu

    2014-04-01

    Full Text Available Copper films were grown on (3-Mercaptopropyltrimethoxysilane (MPTMS, (3-Aminopropyltriethoxysilane (APTES and 6-(3-(triethoxysilylpropylamino-1,3,5- triazine-2,4-dithiol monosodium (TES self-assembled monolayers (SAMs modified acrylonitrile-butadiene-styrene (ABS substrate via electroless copper plating. The copper films were examined using scanning electron microscopy (SEM and X-ray diffraction (XRD. Their individual deposition rate and contact angle were also investigated to compare the properties of SAMs and electroless copper films. The results indicated that the formation of copper nuclei on the TES-SAMs modified ABS substrate was faster than those on the MPTMS-SAMs and APTES-SAMs modified ABS substrate. SEM images revealed that the copper film on TES-SAM modified ABS substrate was smooth and uniform, and the density of copper nuclei was much higher. Compared with that of TES-SAMs modified resin, the coverage of copper nuclei on MPTMS and APTES modified ABS substrate was very limited and the copper particle size was too big. The adhesion property test demonstrated that all the SAMs enhanced the interfacial interaction between copper plating and ABS substrate. XRD analysis showed that the copper film deposited on SAM-modified ABS substrate had a structure with Cu(111 preferred orientation, and the copper film deposited on TES-SAMs modified ABS substrate is better than that deposited on MPTMS-SAMs or APTES-SAMs modified ABS resins in electromigrtion resistance.

  18. A thermal stability study of alkane and aromatic thiolate self-assembled monolayers on copper surfaces

    Science.gov (United States)

    Carbonell, L.; Whelan, C. M.; Kinsella, M.; Maex, K.

    2004-07-01

    The thermal stability of 1-decanethiol (C10) and benzenethiol (BT) Self-Assembled Monolayers (SAMs) on metallic and oxidized copper surfaces has been investigated by thermal desorption spectrometry. High quality C10 and BT SAMs exhibit low thermal stabilities on clean copper surfaces with a maximum in decomposition occurring between 100 and 150 ∘C. The decomposition of SAMs follows different mechanisms. For the alkanethiol, a direct interaction between the alkyl group of the thiolate and the metallic copper surface is the dominant pathway for the C-S bond scission. The head group desorbs as oxidized sulfur and this is followed by the desorption of the alkyl fragments of the chain adsorbed on the clean copper surface. In the case of benzenethiol, a simultaneous desorption of the head group as oxidized sulfur and the benzene group occurs. SAM formation on the oxidized copper surface results in complete removal and/or reduction of the CuO layer. Higher SAM surface coverages on the resulting Cu/Cu 2O surface result from the enhanced surface roughness of the substrate. The decomposition mechanisms and thermal stabilities of the C10 and BT SAMs are dependent on the oxidation state of the underlying substrate and the chemical nature of the chain.

  19. Substrate dependent morphologies of self-assembled nanocrystalline manganite films: An atomic force microscopy study

    International Nuclear Information System (INIS)

    Kale, S.N.; Mona, J.; Ganesan, V.; Choudhary, R.J.; Phase, D.M.

    2009-06-01

    Thin films of La 0 .7Sr 0 .3MnO 3 (LSMO) have been deposited on different substrates: Si (001), Al 2 O 3 (AlO) (0001) and LaAlO 3 (LAO) (001), using a pulsed laser deposition system. 100 nm films have been deposited at substrate temperature of 700 deg C and oxygen partial pressure of 400 mTorr. X-Ray diffraction analysis shows a polycrystalline growth of both layers on Si and Al 2 O 3 substrates, while a c-axis oriented growth on LAO substrate. Atomic force microscopy images exhibit interesting island-like morphology of grain size ∼ 250 nm on Si substrate. Similar morphology with much smaller (∼ 150 nm), closely packed islands are seen to grow on AlO substrate. Films on LAO show comparatively a smooth morphology with the grains size less than 100 nm, decorated by characteristic depressions at the grain boundaries. The formation of self-assembled nanostructures can be understood on the basis of film-substrate lattice misfit, strains in the systems and eventual growth of the films to attain energy minimization (author)

  20. Systematic Moiety Variations of Ultrashort Peptides Produce Profound Effects on Self-Assembly, Nanostructure Formation, Hydrogelation, and Phase Transition

    KAUST Repository

    Chan, Kiat Hwa

    2017-10-04

    Self-assembly of small biomolecules is a prevalent phenomenon that is increasingly being recognised to hold the key to building complex structures from simple monomeric units. Small peptides, in particular ultrashort peptides containing up to seven amino acids, for which our laboratory has found many biomedical applications, exhibit immense potential in this regard. For next-generation applications, more intricate control is required over the self-assembly processes. We seek to find out how subtle moiety variation of peptides can affect self-assembly and nanostructure formation. To this end, we have selected a library of 54 tripeptides, derived from systematic moiety variations from seven tripeptides. Our study reveals that subtle structural changes in the tripeptides can exert profound effects on self-assembly, nanostructure formation, hydrogelation, and even phase transition of peptide nanostructures. By comparing the X-ray crystal structures of two tripeptides, acetylated leucine-leucine-glutamic acid (Ac-LLE) and acetylated tyrosine-leucine-aspartic acid (Ac-YLD), we obtained valuable insights into the structural factors that can influence the formation of supramolecular peptide structures. We believe that our results have major implications on the understanding of the factors that affect peptide self-assembly. In addition, our findings can potentially assist current computational efforts to predict and design self-assembling peptide systems for diverse biomedical applications.

  1. Relation between the grafting density of liquid crystal macromolecule and the symmetry of self-assembled bulk phase: coarse-grained molecular dynamics study

    Directory of Open Access Journals (Sweden)

    J.M. Ilnytskyi

    2013-01-01

    Full Text Available I consider a generic coarse-grained model suitable for the study of bulk self-assembly of liquid crystal (LC macromolecules. The cases include LC dendrimers, gold nanoparticles modified by polymer chains with terminating LC groups and oth. The study is focused on the relation between a number of grafted chains, Nch, and the symmetry of the self-assembled bulk phases. Simple space-filling arguments are used first to estimate stability intervals for a rod-like, disc-like and spherulitic conformations in terms of Nch. These are followed by coarse-grained molecular dynamics simulations for both spontaneous and aided self-assembly of LC macromolecules into bulk phases. In spontaneous self-assembly runs, essential coexistence of rod-like and disc-like conformations is observed (via analysis of the histograms for the molecular asphericity in a broad interval of Nch, which prevents formation of defect-free structures. The use of uniaxial and planar aiding fields is found to improve self-assembly into monodomain phases by promoting conformations of respective symmetry. Strong shape-phase relation, observed experimentally, is indicated also by the simulations by the coincidence of the stability intervals for the respective conformations with those for the bulk phases.

  2. Self-assembled nanostructures

    CERN Document Server

    Zhang, Jin Z; Liu, Jun; Chen, Shaowei; Liu, Gang-yu

    2003-01-01

    Nanostructures refer to materials that have relevant dimensions on the nanometer length scales and reside in the mesoscopic regime between isolated atoms and molecules in bulk matter. These materials have unique physical properties that are distinctly different from bulk materials. Self-Assembled Nanostructures provides systematic coverage of basic nanomaterials science including materials assembly and synthesis, characterization, and application. Suitable for both beginners and experts, it balances the chemistry aspects of nanomaterials with physical principles. It also highlights nanomaterial-based architectures including assembled or self-assembled systems. Filled with in-depth discussion of important applications of nano-architectures as well as potential applications ranging from physical to chemical and biological systems, Self-Assembled Nanostructures is the essential reference or text for scientists involved with nanostructures.

  3. Scattering studies of self-assembling processes of polymer blends in spinodal decomposition

    International Nuclear Information System (INIS)

    Hashimoto, Takeji; Takenaka, Mikihito; Jinnai, Hiroshi

    1991-01-01

    Structure self-assembling in the spinodal decomposition (SD) of polymer blends in its late stage has been explored for a near-critical mixture of polybutadiene and polyisoprene by a time-resolved light scattering technique, with a particular emphasis on the time evolution of the interface structure. By analysis of a scaled structure factor F(x, t)triple bond I(q, t)q m (t) 3 over wide ranges of a reduced scattering vector xtriple bondq/q m (t) and time, it was found relevant to divide the late stage of SD into two stages, I and II. Here, I(q, t) denotes the scattered intensity as a function of the scattering vector q and time t. In the intermediate stage preceding the late one, F(x, t) became sharper with its peak at x=1 increasing with t. However, as time elapsed, F(x, t) turned out to be universal for t, first in the range of x smaller than about 2 and then over the entire range of x accessible by the present experiment. The time interval in which the former occurred is defined as late stage I and the one in which the latter was realized is called late stage II. In late stage I, the average thickness of phase-phase interfaces decreases towards an equilibrium value and the time evolution of the interfacial area density, Σ(t) does not scale with q m (t), i.e. the exponents γ and α in the power laws Σ(t)∝t -γ and q m (t)∝t -α do not coincide (actually, α<γ). Late stage II corresponds to the process in which these exponents become equal and the interface thickness reaches equilibrium. Such conditions probably ensure the establishment of a complete dynamical scaling law in the SD process. (orig.)

  4. Suprmolecular chirality of self-assembled systems in solution

    NARCIS (Netherlands)

    Mateos timoneda, Miguel; Crego Calama, Mercedes; Reinhoudt, David

    2004-01-01

    Self-assembly plays an important role in the formation of many (chiral) biological structures, such as DNA, α-helices or ß-sheets of proteins. This process, which is the main tool of Supramolecular Chemistry (i.e. the chemistry of the molecular assemblies and of the intermolecular bonds), starts to

  5. Nanoporous Network Channels from Self-Assembled Triblock Copolymer Supramolecules

    NARCIS (Netherlands)

    du Sart, Gerrit Gobius; Vukovic, Ivana; Vukovic, Zorica; Polushkin, Evgeny; Hiekkataipale, Panu; Ruokolainen, Janne; Loos, Katja; ten Brinke, Gerrit

    2011-01-01

    Supramolecular complexes of a poly(tert-butoxystyrene)-block-polystyrene-block-poly(4-vinylpyridine) triblock copolymers and less than stoichiometric amounts of pentadecylphenol (PDP) are shown to self-assemble into a core-shell gyroid morphology with the core channels formed by the hydrogen-bonded

  6. Interactions of doxorubicin with self-assembled monolayer-modified electrodes: electrochemical, surface plasmon resonance (SPR), and gravimetric studies.

    Science.gov (United States)

    Nieciecka, Dorota; Krysinski, Pawel

    2011-02-01

    We present the results on the partitioning of doxorubicin (DOX), a potent anticancer drug, through the model membrane system, self-assembled monolayers (SAMs) on gold electrodes. The monolayers were formed from alkanethiols of comparable length with different ω-terminal groups facing the aqueous electrolyte: the hydrophobic -CH(3) groups for the case of dodecanethiol SAMs or hydrophilic -OH groups of mercaptoundecanol SAMs. The electrochemical experiments combined with the surface plasmon resonance (SPR) and gravimetric studies show that doxorubicin is likely adsorbed onto the surface of hydrophilic monolayer, while for the case of the hydrophobic one the drug mostly penetrates the monolayer moiety. The adsorption of the drug hinders further penetration of doxorubicin into the monolayer moiety.

  7. Raman study of self-assembled InAs/InP quantum wire stacks with varying spacer thickness

    Science.gov (United States)

    Angelova, T.; Cros, A.; Cantarero, A.; Fuster, D.; González, Y.; González, L.

    2008-08-01

    Self-assembled InAs/InP (001) quantum wire stacks have been investigated by means of Raman scattering. The characteristics of the observed vibrational modes show clear evidence of confinement and atomic intermixing between As and P atoms from the wire and the spacer. The change in the intermixing with spacer layer thickness and growth temperature is investigated. Likewise, the effect of annealing on the exchange of As and P atoms is also studied. Resonance effects in confined and interface phonons are discussed for excitation in the vicinity of the InAs E1 critical point. Finally, the energy of the interface modes is related to the structural characteristics of the wires by comparing the experimental data with a lattice dynamic calculation based on the dielectric continuum model.

  8. Photovoltaic self-assembly.

    Energy Technology Data Exchange (ETDEWEB)

    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.

  9. A real time analysis of the self-assembly process using thermal analysis inside the differential scanning calorimeter instrument.

    Science.gov (United States)

    Roy, Debmalya; Shastri, Babita; Mukhopadhyay, K

    2012-07-12

    The supramolecular assembly of the regioregular poly-3-hexylthiophene (rr-P3HT) in solution has been investigated thoroughly in the past. In the current study, our focus is on the enthalpy of nanofiber formation using thermal analysis techniques by performing the self-assembly process inside the differential scanning calorimetry (DSC) instrument. Thermogravimetric analysis (TGA) was carried out to check the concentration of the solvent during the self-assembly process of P3HT in p-xylene. Ultraviolet visible (UV-vis) spectophotometric technique, small-angle X-ray scattering (SAXS) experiment, atomic force microscopic (AFM), and scanning electron microscopic (SEM) images were used to characterize the different experimental yields generated by cooling the reaction mixture at desired temperatures. Comparison of the morphologies of self-assembled products at different fiber formation temperatures gives us an idea about the possible crystallization parameters which could affect the P3HT nanofiber morphology.

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

    Directory of Open Access Journals (Sweden)

    Charlotte A.E. Hauser

    2011-09-01

    Full Text Available 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.

  11. Self-assembled biomimetic nanoreactors I: Polymeric template

    Science.gov (United States)

    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.

  12. Polymorphism of lipid self-assembly systems

    International Nuclear Information System (INIS)

    Takahashi, Hiroshi

    2002-01-01

    When lipid molecules are dispersed into an aqueous medium, various self-organized structures are formed, depending on conditions (temperature, concentration, etc), in consequence of the amphipathic nature of the molecules. In addition, lipid self-assembly systems exhibit polymorphic phase transition behavior. Since lipids are one of main components of biomembranes, studies on the structure and thermodynamic properties of lipid self-assembly systems are fundamentally important for the consideration of the stability of biomembranes. (author)

  13. On the Origin of the Chiro-Optical Activity in Supramolecular Assemblies: A Quantum Chemical Study of C3 Octopolar Systems.

    Science.gov (United States)

    Nieto-Ortega, Belén; Casado, Juan; López Navarrete, Juan T; Hennrich, Gunter; Ramírez, Francisco J

    2011-10-11

    First-principles quantum chemical approach has been used to understand the origin of the chiro-optical signal induced by the chiral aggregation of an achiral chromophore. The study was focused in predicting the circular dichroism (CD) spectra of different π-stacked columnar oligomers built with C3 star-shape molecular bricks. We studied the influence of the relevant structural self-assembly parameters on the CD spectra (i.e., the number of units, the rotation angle and the intermonomer distance). A detailed analysis was based on the MO topologies and the magnetic and electric transition dipole moments, the vectors which determine the CD intensities, has been conducted. We have rationalized the influence of the various structural factors of supramolecular self-assemblies in connection with the nature of their CD spectroscopic signal, which provides new avenues for structure-spectroscopic relationships.

  14. Simulation study of the effect of differences in block energy and density on the self-assembly of block copolymers

    Science.gov (United States)

    Lawson, Richard A.; Peters, Andrew J.; Nation, Benjamin; Ludovice, Peter J.; Henderson, Clifford L.

    2014-03-01

    Implementation of directed self-assembly (DSA) of block copolymers (BCPs) introduces a series of engineering challenges that have not been completely addressed in previous block copolymer and lithography studies. One of the required innovations for further DSA development and implementation is the accurate simulation of specific block copolymer chemistries and their interactions with interfaces. Many of the BCP simulation tools developed so far have limitations or difficulty in terms of matching many of the common issues found in experimental BCP systems such as polydispersity and different statistical segment lengths. One of the potentially most important issues is the fact that real BCPs often have block energy and/or density asymmetry, meaning that each block has a different homopolymer density and/or cohesive energy density (CED). A simulation of BCP behavior and DSA processes based on molecular dynamics (MD) of coarse-grained polymer chains has been developed that can independently parameterize and control the density and CED of each block to more accurately match the asymmetry found in experimental BCPs. This model was used to study the effect of block asymmetry on the order-disorder transition (ODT), domain scaling, and self-assembly of thin films of BCPs. BCPs whose blocks each have a different density show deviations from the mean-field ODT coexistence curve, exhibiting an order-disorder transition or co-existence curve that is asymmetric with shifts and tilts in the direction of majority highest density block. This impact of density and cohesive energy differences diblock copolymers on their phase behavior can explain some of the unexpected shapes found experimentally in BCP ODT curves. Asymmetry in the BCP block energy or density does not appear to have a significant effect on domain scaling behavior compared to the mean-field estimates. Self-assembly of thin films of BCPs with mismatches in CED shows significant deviations in the expected morphologies

  15. Directed Self-Assembly of Nanodispersions

    Energy Technology Data Exchange (ETDEWEB)

    Furst, Eric M [University of Delaware

    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

  16. Imaging and Quantitation of a Succession of Transient Intermediates Reveal the Reversible Self-Assembly Pathway of a Simple Icosahedral Virus Capsid.

    Science.gov (United States)

    Medrano, María; Fuertes, Miguel Ángel; Valbuena, Alejandro; Carrillo, Pablo J P; Rodríguez-Huete, Alicia; Mateu, Mauricio G

    2016-11-30

    Understanding the fundamental principles underlying supramolecular self-assembly may facilitate many developments, from novel antivirals to self-organized nanodevices. Icosahedral virus particles constitute paradigms to study self-assembly using a combination of theory and experiment. Unfortunately, assembly pathways of the structurally simplest virus capsids, those more accessible to detailed theoretical studies, have been difficult to study experimentally. We have enabled the in vitro self-assembly under close to physiological conditions of one of the simplest virus particles known, the minute virus of mice (MVM) capsid, and experimentally analyzed its pathways of assembly and disassembly. A combination of electron microscopy and high-resolution atomic force microscopy was used to structurally characterize and quantify a succession of transient assembly and disassembly intermediates. The results provided an experiment-based model for the reversible self-assembly pathway of a most simple (T = 1) icosahedral protein shell. During assembly, trimeric capsid building blocks are sequentially added to the growing capsid, with pentamers of building blocks and incomplete capsids missing one building block as conspicuous intermediates. This study provided experimental verification of many features of self-assembly of a simple T = 1 capsid predicted by molecular dynamics simulations. It also demonstrated atomic force microscopy imaging and automated analysis, in combination with electron microscopy, as a powerful single-particle approach to characterize at high resolution and quantify transient intermediates during supramolecular self-assembly/disassembly reactions. Finally, the efficient in vitro self-assembly achieved for the oncotropic, cell nucleus-targeted MVM capsid may facilitate its development as a drug-encapsidating nanoparticle for anticancer targeted drug delivery.

  17. Synthesis, spectroscopy, thermal studies and supramolecular ...

    Indian Academy of Sciences (India)

    TECS

    structures of two new alkali-earth 4-nitrobenzoate complexes containing ... adopt a cis orientation in 2 resulting in different supramolecular structures. Complex 1 .... The compound analysed satisfactorily and exhibited an identical IR spectrum as that of the product from method 1. 2.2 Preparation of anhydrous complexes.

  18. Photooxidation of self-assembled monolayers by exposure to light of wavelength 254 nm: a static SIMS study.

    Science.gov (United States)

    Brewer, Nicholas J; Janusz, Stefan; Critchley, Kevin; Evans, Stephen D; Leggett, Graham J

    2005-06-09

    Self-assembled monolayers (SAMs) of alkanethiols have been photooxidized by exposure to light from a lamp emitting light with a wavelength of 254 nm. The data confirm that SAM oxidation on exposure to UV light sources occurs in the absence of ozone, but also suggest that the mechanism is different from that observed in previous studies using broad-spectrum arc lamps. In particular, for monolayers on both gold and silver, carboxylic acid-terminated SAMs oxidize significantly faster than methyl-terminated SAMs, in contrast to earlier observations for monolayers exposed to light from a mercury arc lamp. The difference in rates of photooxidation for the two classes of monolayer is significantly greater on silver than on gold. These data support our recent suggestion that while methyl-terminated SAMs are able to pack much more closely on silver than on gold, carboxylic acid-terminated thiols are not able to adopt the same close-packed structures, and their rates of photooxidation on silver are similar to, or slightly greater than, those measured for the same adsorbates on gold. Surface potential measurements were made for carboxylic acid- and methyl-terminated SAMs using a Kelvin probe apparatus. It was found that the work functions of carboxylic acid-terminated SAMs are significantly greater than those of methyl-terminated monolayers. It is concluded that these data are consistent with the oxidation reaction being initiated by "hot" electrons generated following the interaction of photons with the metallic substrate.

  19. Study and Optimization of Self-Assembled Polymeric Multilayer Structures with Neutral Red for pH Sensing Applications

    Directory of Open Access Journals (Sweden)

    Javier Goicoechea

    2008-01-01

    Full Text Available The characterization of nanostructured thin films is critical in the design and fabrication of optical sensors. Particularly, this work is a detailed study of the properties of layer-by-layer electrostatic self-assembled multilayer (LbL structures fabricated using poly(allylamine hydrochloride (PAH and Neutral Red (NR as cations, and poly(acrylic acid (PAA as polyanion. These LbL films, due to the colorimetric properties of the NR, are suitable for sensor applications such as pH sensing in the physiological range. In the (PAH+NR/PAA LbL structure, it has been observed a very important influence of the pH of the solutions in the properties of the resultant films. Different techniques such as spectroscopy and atomic force microscopy (AFM are combined to characterize the films, and the results are analyzed showing coherence with previous works. The LbL structure is finally optimized and dramatically improved nanostructured films were fabricated, showing good sensing properties, short response times, and good stability.

  20. Self-assembled monolayers with different chemical group substrates for the study of MCF-7 breast cancer cell line behavior

    International Nuclear Information System (INIS)

    Yan, Hongji; Yin, Yanbin; Li, Yu; Tian, Weiming; Zhang, Song; Nie, Yongzhan; He, Jin; Wang, Xiumei; Cui, Fuzhai; Chen, Xiongbiao

    2013-01-01

    The interactions between cancer cells and the extracellular matrix (ECM) are important with respect to a number of cell behavoirs, yet remain unclear. In this study, self-assembled monolayers with different terminal chemical groups (hydroxyl (-OH), carboxyl (-COOH), animo (-NH 2 ), mercapto (-SH), and methyl (-CH 3 )) were employed as substrates for the culture of MCF-7 cells to examine effects on cell behavior. Cell spreading was investigated by scanning electron microscopy, tallin expression by immunofluorescence, proliferation rate by counting cell numbers, cell cycle by flow cytometry, metabolism by high-performance liquid chromatography and cell migration by live cell imaging. Annexin V-FITC (fluorescein isothiocyanate) and JC-1 assays were performed to determine cell apoptosis and mitochondrial membrane potential, respectively. Our results demonstrate the varied behaviors of MCF-7 cells in response to different chemical groups. Specifically, NH 2 and COOH terminal functional groups promote proliferation, the production of lactic acid and mobility of MCF-7 cells; SH and OH terminal groups enhance the expression and distribution of tallin but result in weak cell proliferation, metabolism, spreading and mobility. These results are meaningful for uncovering the interactions between the ECM and cancer cells; they are potentially useful for designing novel cancer treatment strategies. (paper)

  1. Chirality effects at each amino acid position on tripeptide self-assembly into hydrogel biomaterials

    Science.gov (United States)

    Marchesan, S.; Easton, C. D.; Styan, K. E.; Waddington, L. J.; Kushkaki, F.; Goodall, L.; McLean, K. M.; Forsythe, J. S.; Hartley, P. G.

    2014-04-01

    Hydrogels formed by ultrashort peptides are emerging as cost-effective materials for cell culture. However, l-peptides are labile to proteases, while their d-isomers are thought to not support cell growth as well. In contrast, the self-assembly behaviour and biological performance of heterochiral peptides (i.e., made of both d and l amino acids) are largely unknown. In this study, we evaluate the effects of amino acid chirality on tripeptide self-assembly and hydrogelation at physiological pH, and cytocompatibility in fibroblast cell culture. A series of uncapped hydrophobic tripeptides with all combinations of d, l amino acids was prepared, tested for self-assembly under physiological conditions, and analysed by circular dichroism, FT-IR, cryo-TEM, AFM, and Thioflavin T fluorescence imaging. Amino acid chirality has a profound effect on the peptides' supramolecular behaviour. Only selected isomers form hydrogels, and of amyloid structure, as confirmed by rheology and XRD. Importantly, they are able to maintain the viability and proliferation of fibroblasts in vitro. This study identifies two heterochiral gels that perform well in cell culture and will assist in the design of innovative and cost-effective peptide gel biomaterials.Hydrogels formed by ultrashort peptides are emerging as cost-effective materials for cell culture. However, l-peptides are labile to proteases, while their d-isomers are thought to not support cell growth as well. In contrast, the self-assembly behaviour and biological performance of heterochiral peptides (i.e., made of both d and l amino acids) are largely unknown. In this study, we evaluate the effects of amino acid chirality on tripeptide self-assembly and hydrogelation at physiological pH, and cytocompatibility in fibroblast cell culture. A series of uncapped hydrophobic tripeptides with all combinations of d, l amino acids was prepared, tested for self-assembly under physiological conditions, and analysed by circular dichroism, FT

  2. Self-assembling peptide and protein nanodiscs for studies of membrane proteins

    DEFF Research Database (Denmark)

    Midtgaard, Søren Roi

    investigations of membrane proteins by traditional X-ray crystallography have proved a difficult challenge, and a surprisingly small amount of membrane proteins has been crystalized so far. This implies that development of lipoproteins as a platform for studying membrane proteins is much needed. In this thesis......Particles containing both lipids and proteins (so-called lipoproteins) are vital to study. They are selfassembling particles that, in the human body, are responsible for the transport of lipids and cholesterol. Due to the increasing problems of obesity and related illnesses in the world, obtaining...... for working with lipoprotein particles are their potential in the study membrane proteins. Membrane proteins are responsible for most of the transport in and out of cells and signaling between cells. As an example G-protein coupled receptors, a class of membrane proteins, are the third largest class...

  3. Supramolecular systems chemistry

    NARCIS (Netherlands)

    Mattia, Elio; Otto, Sijbren

    The field of supramolecular chemistry focuses on the non-covalent interactions between molecules that give rise to molecular recognition and self-assembly processes. Since most non-covalent interactions are relatively weak and form and break without significant activation barriers, many

  4. Solvent-driven symmetry of self-assembled nanocrystal superlattices-A computational study

    KAUST Repository

    Kaushik, Ananth P.

    2012-10-29

    The preference of experimentally realistic sized 4-nm facetted nanocrystals (NCs), emulating Pb chalcogenide quantum dots, to spontaneously choose a crystal habit for NC superlattices (Face Centered Cubic (FCC) vs. Body Centered Cubic (BCC)) is investigated using molecular simulation approaches. Molecular dynamics simulations, using united atom force fields, are conducted to simulate systems comprised of cube-octahedral-shaped NCs covered by alkyl ligands, in the absence and presence of experimentally used solvents, toluene and hexane. System sizes in the 400,000-500,000-atom scale followed for nanoseconds are required for this computationally intensive study. The key questions addressed here concern the thermodynamic stability of the superlattice and its preference of symmetry, as we vary the ligand length of the chains, from 9 to 24 CH2 groups, and the choice of solvent. We find that hexane and toluene are "good" solvents for the NCs, which penetrate the ligand corona all the way to the NC surfaces. We determine the free energy difference between FCC and BCC NC superlattice symmetries to determine the system\\'s preference for either geometry, as the ratio of the length of the ligand to the diameter of the NC is varied. We explain these preferences in terms of different mechanisms in play, whose relative strength determines the overall choice of geometry. © 2012 Wiley Periodicals, Inc.

  5. Biocompatible or biodegradable hyperbranched polymers: from self-assembly to cytomimetic applications.

    Science.gov (United States)

    Jin, Haibao; Huang, Wei; Zhu, Xinyuan; Zhou, Yongfeng; Yan, Deyue

    2012-09-21

    Self-assembly of amphiphilic hyperbranched polymers (HBPs) is a newly emerging research area and has attracted increasing attention due to the great advantages in biomedical applications. This tutorial review focuses on the self-assembly of biocompatible or biodegradable amphiphilic HBPs and their cytomimetic applications, and specialities or advantages therein owing to the hyperbranched structure have also been summarized. As shown here, various supramolecular structures including micelles, vesicles, tubes, fibers and films have been prepared through the primary self-assembly processes. The primary self-assemblies can be further assembled into more complex structures through hierachical self-assembly processes. Besides, the hyperbranched polymer vesicles have demonstrated great potential to be used as model membranes to mimic cellular behaviors, such as fusion, fission and cell aggregation. Other biomedical applications of HBPs as well as their self-assemblies are also briefly summarized.

  6. Probing the effects of ligand isomerism in chiral luminescent lanthanide supramolecular self-assemblies: a europium "Trinity Sliotar" study.

    Science.gov (United States)

    Kotova, Oxana; Kitchen, Jonathan A; Lincheneau, Christophe; Peacock, Robert D; Gunnlaugsson, Thorfinnur

    2013-11-25

    "Trinity Sliotar" family: Chiral ligands containing pyridyl and naphthalene moieties were synthesized and characterized. These ligands were successfully used for the synthesis of Eu(III) bundles where chirality of the ligand is successfully transferred onto the lanthanide centre resulting in circularly polarized red luminescence. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Study on the formation of self-assembled monolayers on sol-gel processed hafnium oxide as dielectric layers.

    Science.gov (United States)

    Ting, Guy G; Acton, Orb; Ma, Hong; Ka, Jae Won; Jen, Alex K-Y

    2009-02-17

    High dielectric constant (k) metal oxides such as hafnium oxide (HfO2) have gained significant interest due to their applications in microelectronics. In order to study and control the surface properties of hafnium oxide, self-assembled monolayers (SAMs) of four different long aliphatic molecules with binding groups of phosphonic acid, carboxylic acid, and catechol were formed and characterized. Surface modification was performed to improve the interface between metal oxide and top deposited materials as well as to create suitable dielectric properties, that is, leakage current and capacitance densities, which are important in organic thin film transistors. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, contact angle goniometry, atomic force microscopy (AFM), and simple metal-HfO2-SAM-metal devices were used to characterize the surfaces before and after SAM modification on sol-gel processed hafnium oxide. The alkylphosphonic acid provided the best monolayer formation on sol-gel processed hafnium oxide to generate a well-packed, ultrathin dielectric exhibiting a low leakage current density of 2x10(-8) A/cm2 at an applied voltage of -2.0 V and high capacitance density of 0.55 microF/cm2 at 10 kHz. Dialkylcatechol showed similar characteristics and the potential for using the catechol SAMs to modify HfO2 surfaces. In addition, the integration of this alkylphosphonic acid SAM/hafnium oxide hybrid dielectric into pentacene-based thin film transistors yields low-voltage operation within 1.5 V and improved performance over bare hafnium oxide.

  8. Cathodoluminescence study of excited states and spatial smearing effects in InAs/GaAs self-assembled quantum dots

    International Nuclear Information System (INIS)

    Khatsevich, S.; Madhukar, A.; Rich, D. H.; Kim, Eui-Tae

    2004-01-01

    Full Text:We have examined state-filling and thermal activation of carriers in buried InAs self-assembled quantum dots (SAQDs) with excitation-dependent cathodoluminescence (CL) imaging and spectroscopy. The InAs SAQDs were formed during molecular beam epitaxial growth of InAs on undoped planar GaAs (001). Emission from the excited states was obtained under high electron beam currents, revealing up to three QD excited states in CL spectroscopy. A suppressed relaxation from the first excited state to the ground state at very low excitation densities was observed, demonstrating the presence of a phonon-bottle neck. The dependence of the CL intensity of the ground and the first excited state transitions on excitation density was shown to be linear at all temperatures at low excitation density. This result can be understood by considering that carriers escape and are recaptured as excitons or correlated electron-hole pairs. At sufficiently high excitations, state filling and spatial smearing elects are observed together with a sublinear dependence of the CL intensity on electron beam current. A successive filling of the ground and excited states in adjacent groups of QDs that possess different size distributions is argued to be the cause of the spatial smearing. The intensities of the ground and excited state transitions were analyzed as a function of temperature and excitation to study the thermal activation and reemission of carriers. Thermal quenching of the CL intensity of the QD ground and first excited state transitions at low excitations in 230 to 300 K temperature range is attributed to dissociation and reemission of excitons from the QD states into the WL. At high excitations, significantly reduced activation energies of the ground and excited states are obtained, suggesting that thermal reemission of single holes from QD states into the GaAs barrier is responsible for the observed temperature dependence of the QD luminescence in 230 to 300 K temperature range

  9. Side-chain-controlled self-assembly of polystyrene-polypeptide miktoarm star copolymers

    KAUST Repository

    Junnila, Susanna

    2012-03-27

    We show how the self-assembly of miktoarm star copolymers can be controlled by modifying the side chains of their polypeptide arms, using A 2B and A 2B 2 type polymer/polypeptide hybrids (macromolecular chimeras). Initially synthesized PS 2PBLL and PS 2PBLL 2 (PS, polystyrene; PBLL, poly(ε-tert-butyloxycarbonyl-l-lysine) ) miktoarms were first deprotected to PS 2PLLHCl and PS 2PLLHCl 2 miktoarms (PLLHCl, poly(l-lysine hydrochloride)) and then complexed ionically with sodium dodecyl sulfonate (DS) to give the supramolecular complexes PS 2PLL(DS) and PS 2(PLL(DS)) 2. The solid-state self-assemblies of these six miktoarm systems were studied by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and small- and wide-angle X-ray scattering (SAXS, WAXS). The side chains of the polypeptide arms were observed to have a large effect on the solubility, polypeptide conformation, and self-assembly of the miktoarms. Three main categories were observed: (i) lamellar self-assemblies at the block copolymer length scale with packed layers of α-helices in PS 2PBLL and PS 2PBLL 2; (ii) charge-clustered polypeptide micelles with less-defined conformations in a nonordered lattice within a PS matrix in PS 2PLLHCl and PS 2PLLHCl 2; (iii) lamellar polypeptide-surfactant self-assemblies with β-sheet conformation in PS 2PLL(DS) and PS 2(PLL(DS)) 2 which dominate over the formation of block copolymer scale structures. Differences between the 3- and 4-arm systems illustrate how packing frustration between the coil-like PS arms and rigid polypeptide conformations can be relieved by the right number of arms, leading to differences in the extent of order. © 2012 American Chemical Society.

  10. Self-assembly of self-assembled molecular triangles

    Indian Academy of Sciences (India)

    While the solution state structure of 1 can be best described as a trinuclear complex, in the solidstate well-fashioned intermolecular - and CH- interactions are observed. Thus, in the solid-state further self-assembly of already self-assembled molecular triangle is witnessed. The triangular panels are arranged in a linear ...

  11. Study of the ability of self-assembled N-vinylcarbazole monolayers to protect copper against corrosion

    Directory of Open Access Journals (Sweden)

    NAI-XING WANG

    2002-10-01

    Full Text Available N-Vinylcarbazole (NVC monolayers were self-assembled on copper surfaces. The electrochemical properties of the copper surfaces modified by NVC self-assembled monolayers (SAMs were investigated using polarization and electrochemical impedance spectroscopic (EIS methods. The polarization measurements indicated that the NVC SAMs could reduce the rates of the anodic and cathodic reaction on the surface of copper electrodes in 0.5 mol dm-3 NaCl solution. The EIS results showed the NVC formed a closely packed film that was able to inhibit copper corrosion. X-Ray photoelectron spectroscopy (XPS analysis of the copper samples and atomic adsorption analysis of the solution showed that the copper surfaces were covered by NVC SAMs, and the adsorption of NVC on the copper surfaces was accompanied with dissolution of Cu into the solution.

  12. NANOSIZE STRUCTURE OF SELF-ASSEMBLY SODIUM DODECYL SULFATE: A STUDY BY SMALL ANGLE NEUTRON SCATTERING (SANS

    Directory of Open Access Journals (Sweden)

    Edy Giri Rachman Putra

    2010-06-01

    Full Text Available Small Angle Neutron Scattering (SANS investigation on the self-assembly sodium dodecyl sulfate (SDS molecules as a function of concentration and additives has been carried out. SANS spectrometer which has been completely installed at the neutron scattering laboratory (NSL BATAN in Serpong, Indonesia has played most important role to determine the growth (size and also the shapes of a micelle structure. In this works we report that spherical micelle structure with a radius of 16.7 Å will transform to ellipsoidal or rod-like micelle structure with the long axis extends up to 50 Å by increasing the concentration of SDS. Similar to that the micelle structures change by addition of salt in SDS micellar solutions.   Keywords: nanostructure, micelle, self-assembly

  13. Self-assembled structures in blends of disordered and lamellar block copolymers: SAXS, SANS and TEM study

    Czech Academy of Sciences Publication Activity Database

    Holoubek, Jaroslav; Baldrian, Josef; Lednický, František; Lal, J.

    2009-01-01

    Roč. 58, č. 1 (2009), s. 81-87 ISSN 0959-8103 R&D Projects: GA AV ČR IAA100500501; GA ČR GESON/06/E005 Institutional research plan: CEZ:AV0Z40500505 Keywords : diblock copolymers * copolymer blends * SANS * SAXS * self-assembly Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.137, year: 2009

  14. Self-assembled nanowire formation during Cu deposition on atomically flat Vse2 surfaces studied by microscopic methods

    International Nuclear Information System (INIS)

    Hollensteiner, S.; Spiecker, E.; Dieker, C.; Jaeger, W.; Adelung, R.; Kipp, L.; Skibowski, M.

    2003-01-01

    Self-assembled metallic nanostructures gain increasing interest in nanotechnologies and might find application in future electronic device fabrication. Upon UHV deposition of copper onto cleaved layered crystals of VSe 2 , self-assembled networks of nanowires and nanoclusters are observed to form and found to be remarkably stable even during storage under ambient conditions and at moderately increased temperatures. Transmission and scanning electron microscopy combined with scanning tunneling and atomic force microscopy have been used to characterize the arrangements, structure and dimensions of the nanostructures and the substrate before metal deposition. On the flat parts of the substrate, self-similar nanowire networks form with wire diameters ranging from 8 to 250 nm and mesh dimensions ranging from 0.35 to 10 μm. The nanowires are preferentially aligned along low-index crystal directions and possess polycrystalline structure. Nanoclusters are formed within the meshes of the nanowire network. A model for the self-assembled growth of nanostructures during metal deposition, which takes into account the electronic charge exchange of adsorbed atoms with the substrate, will be discussed

  15. Tailoring two-dimensional PTCDA-melamine self-assembled architectures at room temperature by tuning molecular ratio

    NARCIS (Netherlands)

    Sun, Xiaonan; Jonkman, Harry T.; Silly, Fabien

    2010-01-01

    Engineering and tuning multi-component supramolecular self-assemblies on surfaces is one of the challenges of nanotechnology. We use scanning tunneling microscopy to investigate the influence of molecular ratio on the self-assembly of PTCDA-melamine structures on Au(111)-(22 x root 3). Our

  16. Self-assembly of novel supramolecular silver(I) compound based on mixed ligands bipy/TST3- H3TST=2,4,6-tris (4-sulfophenylamino)-1,3,5-triazine

    NARCIS (Netherlands)

    Yu, Yunfang; Wei, Yongqin; Broer, Ria; Wu, Kechen

    2007-01-01

    The novel supramolecular silver(I) compound with formula [Ag-6(TST)(2)(bipy)(6)(H2O)(2)](n) center dot 3nH(2)O (1) based on assembly of Ag(I) and mixed ligand bipy/TST3-, bipy = 2,2'-bipyridine, H3TST = 2,4,6-tris(4-sulfophenylamino)-1,3,5-triazine, has been prepared by hydrothermal method. In the

  17. Phosphorylation Modulates Ameloblastin Self-assembly and Ca2+ Binding

    Directory of Open Access Journals (Sweden)

    Øystein Stakkestad

    2017-07-01

    Full Text Available Ameloblastin (AMBN, an important component of the self-assembled enamel extra cellular matrix, contains several in silico predicted phosphorylation sites. However, to what extent these sites actually are phosphorylated and the possible effects of such post-translational modifications are still largely unknown. Here we report on in vitro experiments aimed at investigating what sites in AMBN are phosphorylated by casein kinase 2 (CK2 and protein kinase A (PKA and the impact such phosphorylation has on self-assembly and calcium binding. All predicted sites in AMBN can be phosphorylated by CK2 and/or PKA. The experiments show that phosphorylation, especially in the exon 5 derived part of the molecule, is inversely correlated with AMBN self-assembly. These results support earlier findings suggesting that AMBN self-assembly is mostly dependent on the exon 5 encoded region of the AMBN gene. Phosphorylation was significantly more efficient when the AMBN molecules were in solution and not present as supramolecular assemblies, suggesting that post-translational modification of AMBN must take place before the enamel matrix molecules self-assemble inside the ameloblast cell. Moreover, phosphorylation of exon 5, and the consequent reduction in self-assembly, seem to reduce the calcium binding capacity of AMBN suggesting that post-translational modification of AMBN also can be involved in control of free Ca2+ during enamel extra cellular matrix biomineralization. Finally, it is speculated that phosphorylation can provide a functional crossroad for AMBN either to be phosphorylated and act as monomeric signal molecule during early odontogenesis and bone formation, or escape phosphorylation to be subsequently secreted as supramolecular assemblies that partake in enamel matrix structure and mineralization.

  18. Synthesis and studies of polypeptide materials: Self-assembled block copolypeptide amphiphiles, DNA-condensing block copolypeptides and membrane-interactive random copolypeptides

    Science.gov (United States)

    Wyrsta, Michael Dmytro

    A new class of transition metal initiators for the controlled polymerization of alpha-aminoacid-N-carboxyanhydrides (alpha-NCAs), has been developed by Deming et al. This discovery has allowed for the synthesis of well-defined "protein-like" polymers. Using this chemistry we have made distinct block/random copolypeptides for biomedical applications. Drug delivery, gene delivery, and antimicrobial polymers were the focus of our research efforts. The motivation for the synthesis and study of synthetic polypeptide based materials comes from proteins. Natural proteins are able to adopt a staggeringly large amount of uniquely well-defined folded structures. These structures account for the diversity in properties of proteins. As catalysts (enzymes) natural proteins perform some of the most difficult chemistry with ease and precision at ambient pressures and temperatures. They also exhibit incredible structural properties that directly result from formation of complex hierarchical assemblies. Self-assembling block copolymers were synthesized with various compositions and architectures. In general, di- and tri-block amphiphiles were studied for their self-assembling properties. Both spherical and tubular vesicles were found to assemble from di- and tri-block amphiphiles, respectively. In addition to self-assembly, pH responsiveness was engineered into these amphiphiles by the incorporation of basic residues (lysine) into the hydrophobic block. Another form of self-assembly studied was the condensation of DNA using cationic block copolymers. It was found that cationic block copolymers could condense DNA into compact, ordered, water-soluble aggregates on the nanoscale. These aggregates sufficiently protected DNA from nucleases and yet were susceptible to proteases. These studies form the basis of a gene delivery platform. The ease with which NCAs are polymerized renders them completely amenable to parallel synthetic methods. We have employed this technique to discover new

  19. Linear sweep voltammetric studies on the supramolecular complex ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 121; Issue 2. Linear sweep voltammetric studies on the supramolecular complex of alizarin red S with lysozyme and determination of lysozyme. Wei Sun Na Zhao Xueliang Niu Yan Wang Kui Jiao. Full Papers Volume 121 Issue 2 March 2009 pp 217-223 ...

  20. Linear sweep voltammetric studies on the supramolecular complex ...

    Indian Academy of Sciences (India)

    Administrator

    Linear sweep voltammetric studies on the supramolecular complex of alizarin red S with lysozyme and determination of lysozyme. WEI SUN*, NA ZHAO, XUELIANG NIU, YAN WANG and KUI JIAO. Key Laboratory of Eco-Chemical Engineering of Ministry of Education, College of Chemistry and. Molecular Engineering ...

  1. Experimental Investigation Of Microbially Induced Corrosion Of Test Samples And Effect Of Self-assembled Hydrophobic Monolayers. Exposure Of Test Samples To Continuous Microbial Cultures, Chemical Analysis, And Biochemical Studies

    CERN Document Server

    Laurinavichius, K S

    1998-01-01

    Experimental Investigation Of Microbially Induced Corrosion Of Test Samples And Effect Of Self-assembled Hydrophobic Monolayers. Exposure Of Test Samples To Continuous Microbial Cultures, Chemical Analysis, And Biochemical Studies

  2. Self-Assembly of Discrete Metal Complexes in Aqueous Solution via Block Copolypeptide Amphiphiles

    Directory of Open Access Journals (Sweden)

    Timothy J. Deming

    2013-01-01

    Full Text Available The integration of discrete metal complexes has been attracting significant interest due to the potential of these materials for soft metal-metal interactions and supramolecular assembly. Additionally, block copolypeptide amphiphiles have been investigated concerning their capacity for self-assembly into structures such as nanoparticles, nanosheets and nanofibers. In this study, we combined these two concepts by investigating the self-assembly of discrete metal complexes in aqueous solution using block copolypeptides. Normally, discrete metal complexes such as [Au(CN2]−, when molecularly dispersed in water, cannot interact with one another. Our results demonstrated, however, that the addition of block copolypeptide amphiphiles such as K183L19 to [Au(CN2]− solutions induced one-dimensional integration of the discrete metal complex, resulting in photoluminescence originating from multinuclear complexes with metal-metal interactions. Transmission electron microscopy (TEM showed a fibrous nanostructure with lengths and widths of approximately 100 and 20 nm, respectively, which grew to form advanced nanoarchitectures, including those resembling the weave patterns of Waraji (traditional Japanese straw sandals. This concept of combining block copolypeptide amphiphiles with discrete coordination compounds allows the design of flexible and functional supramolecular coordination systems in water.

  3. Template-directed self-assembly of dynamic covalent capsules with polar interiors.

    Science.gov (United States)

    Galán, Albano; Escudero-Adán, Eduardo C; Ballester, Pablo

    2017-11-01

    Chiral polyimine molecular capsules with polar interiors have been prepared through template covalent dynamic self-assembly. An aryl-extended tetraaldehyde calix[4]pyrrole scaffold was condensed with suitable diamines as linkers using templates for efficient self-assembly. The capsular complexes were characterized in solution, gas phase and the solid-state. Unprecedented transfer of asymmetry was observed from a chiral diamine linker to the resulting supramolecular capsular assembly.

  4. End-to-end self-assembly of gold nanorods in isopropanol solution: experimental and theoretical studies

    Energy Technology Data Exchange (ETDEWEB)

    Gordel, M., E-mail: marta.gordel@pwr.edu.pl [Wrocław University of Technology, Advanced Materials Engineering and Modelling Group, Faculty of Chemistry (Poland); Piela, K., E-mail: katarzyna.piela@pwr.edu.pl [Wrocław University of Technology, Department of Physical and Quantum Chemistry (Poland); Kołkowski, R. [Wrocław University of Technology, Advanced Materials Engineering and Modelling Group, Faculty of Chemistry (Poland); Koźlecki, T. [Wrocław University of Technology, Department of Chemical Engineering, Faculty of Chemistry (Poland); Buckle, M. [CNRS, École Normale Supérieure de Cachan, Laboratoire de Biologie et Pharmacologie Appliquée (France); Samoć, M. [Wrocław University of Technology, Advanced Materials Engineering and Modelling Group, Faculty of Chemistry (Poland)

    2015-12-15

    We describe here a modification of properties of colloidal gold nanorods (NRs) resulting from the chemical treatment used to carry out their transfer into isopropanol (IPA) solution. The NRs acquire a tendency to attach one to another by their ends (end-to-end assembly). We focus on the investigation of the change in position and shape of the longitudinal surface plasmon (l-SPR) band after self-assembly. The experimental results are supported by a theoretical calculation, which rationalizes the dramatic change in optical properties when the NRs are positioned end-to-end at short distances. The detailed spectroscopic characterization performed at the consecutive stages of transfer of the NRs from water into IPA solution revealed the features of the interaction between the polymers used as ligands and their contribution to the final stage, when the NRs were dispersed in IPA solution. The efficient method of aligning the NRs detailed here may facilitate applications of the self-assembled NRs as building blocks for optical materials and biological sensing.Graphical Abstract.

  5. Concentration effects on the dynamics of liquid crystalline self-assembly: time-resolved X-ray scattering studies.

    Science.gov (United States)

    Petri, Marcel; Menzel, Andreas; Bunk, Oliver; Busse, Gerhard; Techert, Simone

    2011-03-24

    A manifold of ordering transitions relevant to chemical and biological systems occur at interfaces from liquids to self-assembled soft solids like membranes or liquid crystals. In the present case, we were interested in understanding the phase transition from the microemulsion phase to the liquid crystal phase in terms of their driving forces, i.e., activation energy and entropy. The purpose of this work was to clarify the influence of concentration effects of the amphiphilic molecules on the nature of these self-assembly processes. By photosensitization of the model system (polyalkylglycolether (C(10)E(4)), water, decane, and cyclohexane) with laser dyes, we could effectively induce and control the phase transition through the absorption of optical photons. The photo transformation conditions were chosen in such a way that the system was in thermal equilibrium. By application of time-resolved photo small-angle X-ray scattering we could monitor the conversion process and demonstrate that the surfactant concentration has a direct impact on the activation energy, which is observable through the length of the induction time.

  6. End-to-end self-assembly of gold nanorods in isopropanol solution: experimental and theoretical studies

    Science.gov (United States)

    Gordel, M.; Piela, K.; Kołkowski, R.; Koźlecki, T.; Buckle, M.; Samoć, M.

    2015-12-01

    We describe here a modification of properties of colloidal gold nanorods (NRs) resulting from the chemical treatment used to carry out their transfer into isopropanol (IPA) solution. The NRs acquire a tendency to attach one to another by their ends (end-to-end assembly). We focus on the investigation of the change in position and shape of the longitudinal surface plasmon (l-SPR) band after self-assembly. The experimental results are supported by a theoretical calculation, which rationalizes the dramatic change in optical properties when the NRs are positioned end-to-end at short distances. The detailed spectroscopic characterization performed at the consecutive stages of transfer of the NRs from water into IPA solution revealed the features of the interaction between the polymers used as ligands and their contribution to the final stage, when the NRs were dispersed in IPA solution. The efficient method of aligning the NRs detailed here may facilitate applications of the self-assembled NRs as building blocks for optical materials and biological sensing.

  7. Self Assembly and Pyroelectric Poling for Organics

    Science.gov (United States)

    2015-07-06

    and semiconducting molecular phosphonic acid (PA) self-assembled monolayers (SAMs) have been developed for applications in organic field-effect...SAM structure and electronic performance of various commonly used organic semiconducting small molecules/polymers. Mechanisms for improving device...Fig. 3). This study represents a major advancement in understanding the mechanisms at play between SAMs and linear organic semiconducting molecules. A

  8. Scanning tunneling microscopy studies of corrosion passivation and nanometer-scale lithography with self-assembled monolayers

    Science.gov (United States)

    Zamborini, Francis Patrick

    The research in this dissertation examines the possible applications of organomercaptan self-assembled monolayers (SAMs) for corrosion passivation and nanometer-scale lithography. We examined linear-chain n-alkanethiol and aromatic SAMs in these studies and used scanning tunneling microscopy (STM) as the main tool for surface characterization. The corrosion passivation properties of n-alkanethiol SAMs were studied on Au in aqueous CN- and Br - solutions and on underpotentially deposited Cu on Au (Au/Cu-UPD) in aqueous HClO4. All SAMs suppress corrosion and shift the potential for corrosion to more positive potentials compared to that on the unmodified metals. We found that corrosion of n-alkanethiol SAM-modified Au begins at defects in the monolayer and the surface morphology depends on the functional end group of the SAM. Corrosion on the unpassivated metal surface begins at high energy sites such as step edges and pits. The chain length and functional end group of SAMs were varied to determine which factors were most important for the best protection against corrosion. We found that corrosion passivation improves with increasing chain length and more hydrophilic functional end groups like OH and COOH protect better than hydrophobic end groups like CH3. The passivation properties of linear-chain SAMs was compared with aromatic SAMs and we found that if they are equally thick and contain the same functional end group, the aromatic SAMs are superior. One goal of this research was to improve the barrier properties of SAMs. We found that depositing a single layer of Cu onto Au before adsorbing the SAM improved its barrier properties dramatically compared to when the SAM was adsorbed directly to the Au. In summary, the corrosion-related studies in this dissertation discuss the corrosion mechanism of SAM-modified metal surfaces, the important factors that determine the passivation properties of SAMs, and a strategy for dramatically improving the barrier properties of

  9. Metal ion controlled self-assembly of a chemically reengineered protein drug studied by small-angle X-ray scattering

    DEFF Research Database (Denmark)

    Jesper, Nygaard; Munch, Henrik K.; Thulstrup, Peter W.

    2012-01-01

    . This protein drug system was designed to form non-native homo-oligomers through selective coordination of two divalent metal ions, Fe(II) and Zn(II), respectively. The insulin type chosen for this study is a variant designed for a reduced tendency toward native dimer formation at physiological concentrations......Precise control of the oligomeric state of proteins is of central importance for biological function and for the properties of biopharmaceutical drugs. Here, the self-assembly of 2,2′-bipyridine conjugated monomeric insulin analogues, induced through coordination to divalent metal ions, was studied...

  10. Multivalency in supramolecular chemistry and nanofabrication

    NARCIS (Netherlands)

    Mulder, A.; Huskens, Jurriaan; Reinhoudt, David

    2004-01-01

    Multivalency is a powerful and versatile self-assembly pathway that confers unique thermodynamic and kinetic behavior onto supramolecular complexes. The diversity of the examples of supramolecular multivalent systems discussed in this perspective shows that the concept of multivalency is a general

  11. Surface sealing using self-assembled monolayers and its effect on metal diffusion in porous low-k dielectrics studied using monoenergetic positron beams

    Energy Technology Data Exchange (ETDEWEB)

    Uedono, Akira, E-mail: uedono.akira.gb@u.tsukuba.ac.jp [Division of Applied Physics, Faculty of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Armini, Silvia; Zhang, Yu [IMEC, Kapeldreef 75, B-3001 Heverlee, Leuven (Belgium); Kakizaki, Takeaki [Division of Applied Physics, Faculty of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Krause-Rehberg, Reinhard [Department of Physics, Martin Luther University Halle, 06099 Halle (Germany); Anwand, Wolfgang; Wagner, Andreas [Institute for Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden (Germany)

    2016-04-15

    Graphical abstract: - Highlights: • Pores with cubic pore side lengths of 1.1 and 3.1 nm coexisted in the low-k film. • For the sample without the SAM sealing process, metal atoms diffused from the top Cu/MnN layer into the OSG film and were trapped by the pores. Almost all pore interiors were covered by those metals. • For the sample damaged by a plasma etch treatment before the SAM sealing process, self-assembled molecules diffused into the OSG film, and they were preferentially trapped by larger pores. - Abstract: Surface sealing effects on the diffusion of metal atoms in porous organosilicate glass (OSG) films were studied by monoenergetic positron beams. For a Cu(5 nm)/MnN(3 nm)/OSG(130 nm) sample fabricated with pore stuffing, C{sub 4}F{sub 8} plasma etch, unstuffing, and a self-assembled monolayer (SAM) sealing process, it was found that pores with cubic pore side lengths of 1.1 and 3.1 nm coexisted in the OSG film. For the sample without the SAM sealing process, metal (Cu and Mn) atoms diffused from the top Cu/MnN layer into the OSG film and were trapped by the pores. As a result, almost all pore interiors were covered with those metals. For the sample damaged by an Ar/C{sub 4}F{sub 8} plasma etch treatment before the SAM sealing process, SAMs diffused into the OSG film, and they were preferentially trapped by larger pores. The cubic pore side length in these pores containing self-assembled molecules was estimated to be 0.7 nm. Through this work, we have demonstrated that monoenergetic positron beams are a powerful tool for characterizing capped porous films and the trapping of atoms and molecules by pores.

  12. Self-assembly of pi-conjugated peptides in aqueous environments leading to energy-transporting bioelectronic nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Tavor, John [Johns Hopkins Univ., Baltimore, MD (United States)

    2016-12-06

    The realization of new supramolecular pi-conjugated organic structures inspired and driven by peptide-based self-assembly will offer a new approach to interface with the biotic environment in a way that will help to meet many DOE-recognized grand challenges. Previously, we developed pi-conjugated peptides that undergo supramolecular self-assembly into one-dimensional (1-D) organic electronic nanomaterials under benign aqueous conditions. The intermolecular interactions among the pi-conjugated organic segments within these nanomaterials lead to defined perturbations of their optoelectronic properties and yield nanoscale conduits that support energy transport within individual nanostructures and throughout bulk macroscopic collections of nanomaterials. Our objectives for future research are to construct and study biomimetic electronic materials for energy-related technology optimized for harsher non-biological environments where peptide-driven self-assembly enhances pi-stacking within nanostructured biomaterials, as detailed in the following specific tasks: (1) synthesis and detailed optoelectronic characterization of new pi-electron units to embed within homogeneous self assembling peptides, (2) molecular and data-driven modeling of the nanomaterial aggregates and their higher-order assemblies, and (3) development of new hierarchical assembly paradigms to organize multiple electronic subunits within the nanomaterials leading to heterogeneous electronic properties (i.e. gradients and localized electric fields). These intertwined research tasks will lead to the continued development and fundamental mechanistic understanding of a powerful bioinspired materials set capable of making connections between nanoscale electronic materials and macroscopic bulk interfaces, be they those of a cell, a protein or a device.

  13. Study on nanocomposite construction based on the multi-functional biotemplate self-assembled by the recombinant TMGMV coat protein for potential biomedical applications.

    Science.gov (United States)

    Song, Lei; Wang, Shiwen; Wang, Haina; Zhang, Hua; Cong, Haolong; Jiang, Xingyu; Tien, Po

    2015-02-01

    Nowadays there is a growing interest in bio-scaffolded nanoarchitectures. Rapid progress in nanobiotechnology and molecular biology has allowed the engineering of inorganic-binding peptides termed as genetically engineered polypeptides for inorganics (GEPIs) into self-assembling biological structures to facilitate the design of novel biomedical or bioimaging devices. Here we introduce a novel nanocomposite comprising a self-assembled protein scaffold based on a recombinant tobacco mild green mosaic tobamovirus (TMGMV) coat protein (CP) and the photocatalytic TiO2 nanoparticles attached to it, which may provide a generic method for materials engineering. A template containing a modified TMGMV CP (mCP) gene, with the first six C-terminal amino acid residues deleted to accommodate more foreign peptides and expressing a site-directed mutation of A123C for bioconjugation utility, and two genetically engineered mutants, Escherichia coli-based P-mCP-Ti7 containing a C-terminal TiO2 GEPI sequence of seven peptides (Ti7) and Hi5 insect cells-derived E-CP-Ti7-His6 C-terminally fused with Ti7+His6 tag were created. Expression vectors and protocols for enriching of the two CP variants were established and the resultant proteins were identified by western blot analysis. Their RNA-free self-assembling structures were analyzed by transmission electron microscopy (TEM) and immuno-gold labeling TEM analysis. Adherence of nanoparticles to the P-mCP-Ti7 induced protein scaffold was visualized by TEM analysis. Also discussed is the Cysteine thiol reactivity in bioconjugation reactions with the maleimide-functionalized porphyrin photosensitizers which can function as clinical photodynamic therapy agents. This study introduced a novel approach to producing an assembly-competent recombinant TMGMV CP, examined its ability to serve as a novel platform for the multivalent display of surface ligands and demonstrated an alternative method for nanodevice synthesis for nanobiotechnological

  14. New Hybrid Nanomaterial Based on Self-Assembly of Cyclodextrins and Cobalt Prussian Blue Analogue Nanocubes

    Science.gov (United States)

    Carvalho, Caio L. C.; Silva, Anna T. B.; Macedo, Lucyano J. A.; Luz, Roberto A. S.; Neto, José M. Moita; Filho, Ubirajara P. Rodrigues; Cantanhêde, Welter

    2015-01-01

    Supramolecular self-assembly has been demonstrated to be a useful approach to developing new functional nanomaterials. In this work, we used a cobalt Prussian blue analogue (PBA, Co3[Co(CN)6]2) compound and a β-cyclodextrin (CD) macrocycle to develop a novel host-guest PBA-CD nanomaterial. The preparation of the functional magnetic material involved the self-assembly of CD molecules onto a PBA surface by a co-precipitation method. According to transmission electronic microscopy results, PBA-CD exhibited a polydisperse structure composed of 3D nanocubes with a mean edge length of 85 nm, which became shorter after CD incorporation. The supramolecular arrangement and structural, crystalline and thermal properties of the hybrid material were studied in detail by vibrational and electronic spectroscopies and X-ray diffraction. The cyclic voltammogram of the hybrid material in a 0.1 mol·L−1 NaCl supporting electrolyte exhibited a quasi-reversible redox process, attributed to Co2+/Co3+ conversion, with an E1/2 value of 0.46 V (vs. SCE), with higher reversibility observed for the system in the presence of CD. The standard rate constants for PBA and PBA-CD were determined to be 0.07 and 0.13 s−1, respectively, which suggests that the interaction between the nanocubes and CD at the supramolecular level improves electron transfer. We expect that the properties observed for the hybrid material make it a potential candidate for (bio)sensing designs with a desirable capability for drug delivery. PMID:26132565

  15. Hydrogen bonded supramolecular materials

    CERN Document Server

    Li, Zhan-Ting

    2015-01-01

    This book is an up-to-date text covering topics in utilizing hydrogen bonding for constructing functional architectures and supramolecular materials. The first chapter addresses the control of photo-induced electron and energy transfer. The second chapter summarizes the formation of nano-porous materials. The following two chapters introduce self-assembled gels, many of which exhibit unique functions. Other chapters cover the advances in supramolecular liquid crystals and the versatility of hydrogen bonding in tuning/improving the properties and performance of materials. This book is designed

  16. Equilibrium and non-equilibrium kinetics of self-assembled surfactant monolayers: a vibrational sum-frequency study of dodecanoate at the fluorite-water interface.

    Science.gov (United States)

    Schrödle, Simon; Richmond, Geraldine L

    2008-04-16

    The adsorption, desorption, and equilibrium monomer exchange processes of sodium dodecanoate at the fluorite(CaF 2)-water interface have been studied. For the first time, we use in situ vibrational sum-frequency spectroscopy (VSFS) to gain insights into the mechanism and kinetics of monolayer self-assembly at the mineral-water interface. By exploiting the nonlinear optical response of the adsorbate, the temporal correlation of headgroup adsorption and alignment of the surfactant's alkyl chain was monitored. Because of the unique surface-specificity of VSFS, changes in the interfacial water structure were also tracked experimentally. The spectra clearly reveal that the structure of interfacial water molecules is severely disturbed at the start of the adsorption process. With the formation of a well-ordered adsorbate layer, it is partially reestablished; however, the molecular orientation and state of coordination is significantly altered. Even at very low surfactant concentrations, overcharging of the mineral surface (i.e., the adsorption of adsorbates past the point of electrostatic equilibrium) was observed. This points out the importance of effects other than electrostatic interactions and it is proposed that cooperative effects of both water structure and surfactant hemimicelle formation at the interface are key factors. The present study also investigates desorption kinetics of partially and fully established monolayers and a statistical model for data analysis is proposed. Additional experiments were performed in the presence of electrolytes and showed that uni- and divalent anions affect the nonequilibrium kinetics of self-assembled monolayers in strikingly different ways.

  17. Self-assembly and bilayer-micelle transition of fatty acids studied by replica-exchange constant pH molecular dynamics

    Science.gov (United States)

    Morrow, Brian H.; Koenig, Peter H.; Shen, Jana K.

    2014-01-01

    Recent interest in the development of surfactant-based nano delivery systems targeting tumor sites has sparked our curiosity to understand the detailed mechanism of the self-assembly and phase transitions of pH-sensitive surfactants. Towards this goal we applied a state-of-the-art simulation technique, continuous constant pH molecular dynamics (CpHMD) with the hybrid-solvent scheme and pH-based replica-exchange protocol, to study de novo self-assembly of 30 and 40 lauric acids, a simple model titratable surfactant. We observed the formation of a gel-state bilayer at low and intermediate pH and a spherical micelle at high pH, with the phase transition starting at 20–30% ionization and completing at 50%. The degree of cooperativity for the transition increases from the 30-mer to the 40-mer. The calculated apparent or bulk pKa value is 7.0 for the 30-mer and 7.5 for the 40-mer. Congruent with experiment, these data demonstrate that CpHMD is capable of accurately modeling large conformational transitions of surfactant systems while allowing simultaneous proton titration of constituent molecules. We suggest that CpHMD simulations may become a useful tool to aid in the design and development of pH-sensitive nanocarriers for a variety of biomedical and technological applications. PMID:24215478

  18. Self-assembling biomolecular catalysts for hydrogen production

    Science.gov (United States)

    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.

  19. Self-assembled anchor layers/polysaccharide coatings on titanium surfaces: a study of functionalization and stability

    Directory of Open Access Journals (Sweden)

    Ognen Pop-Georgievski

    2015-03-01

    Full Text Available Composite materials based on a titanium support and a thin, alginate hydrogel could be used in bone tissue engineering as a scaffold material that provides biologically active molecules. The main objective of this contribution is to characterize the activation and the functionalization of titanium surfaces by the covalent immobilization of anchoring layers of self-assembled bisphosphonate neridronate monolayers and polymer films of 3-aminopropyltriethoxysilane and biomimetic poly(dopamine. These were further used to bind a bio-functional alginate coating. The success of the titanium surface activation, anchoring layer formation and alginate immobilization, as well as the stability upon immersion under physiological-like conditions, are demonstrated by different surface sensitive techniques such as spectroscopic ellipsometry, infrared reflection–absorption spectroscopy and X-ray photoelectron spectroscopy. The changes in morphology and the established continuity of the layers are examined by scanning electron microscopy, surface profilometry and atomic force microscopy. The changes in hydrophilicity after each modification step are further examined by contact angle goniometry.

  20. Self-assembled organic radicals on Au(111) surfaces: a combined ToF-SIMS, STM, and ESR study.

    Science.gov (United States)

    Mannini, Matteo; Sorace, Lorenzo; Gorini, Lapo; Piras, Federica M; Caneschi, Andrea; Magnani, Agnese; Menichetti, Stefano; Gatteschi, Dante

    2007-02-27

    Electron spin resonance (ESR), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and scanning tunneling microscopy (STM) have been used in parallel to characterize the deposition on gold surface of a series of nitronyl nitroxide radicals. These compounds have been specifically synthesized with methyl-thio linking groups suitable to interact with the gold surface to form self-assembled monolayers (SAMs), which can be considered relevant in the research for molecular-based spintronics devices, as suggested in recent papers. The degree of the expected ordering on the surface of these SAMs has been tuned by varying the chemical structure of synthesized radicals. ToF-SIMS has been used to support the evidence of the occurrence of the deposition process. STM has shown the different qualities of the obtained SAMs, with the degree of local order increasing as the degree of freedom of the molecules on the surface is decreased. Finally, ESR has confirmed that the deposition process does not affect the paramagnetic characteristics of radicals and that it affords a complete single-layered coverage of the surface. Further, the absence of angular dependence in the spectra indicates that the small regions of local ordering do not give rise to a long-range order and suggests a quite large mobility of the radical on the surface, probably due to the weak interaction with gold provided by the methyl-thio linking group.

  1. Self-assembly and photopolymerization of a novel quaternary-ammonium functionalized diacetylene on noble metal nanoparticles: A comparative study

    Science.gov (United States)

    Martinez-Espinoza, Maria Isabel; Maccagno, Massimo; Thea, Sergio; Alloisio, Marina

    2018-01-01

    Stable hydrosols of gold and silver nanoparticles coated with the quaternary-ammonium group endowed diacetylene DAAMM (N,N,N-trimethyl-3-(pentacosa-10,12-diynamido)propan-1-ammonium) were obtained through a ligand-exchange reaction leaving the morphology of the pristine cores unmodified. Photopolymerization of the chemisorbed diacetylene shell occurred in both red and blue phases thanks to the presence of internal, H-bondable amide functions in the monomer chain, which are supposed to help the formation of a packed bilayer on the metal surfaces. Multidisciplinary characterization of the polymerized samples, including spectroscopic, morphological and thermal techniques, highlighted that differences occur in the polymerization process on gold and silver nanoparticles under different experimental conditions, suggesting a higher affinity of the trimethylammonium headgroup for gold substrates in acidic media. With respect to the extensively investigated PCDA (pentacosa-10,12-diynoic acid), DAAMM showed reduced capability of photogenerating thick polymer shells, especially in the more delocalized blue form, probably because of the inefficiency of the cationic monomer to form the multi-bilayered architecture typical of the highly-performing, carboxyl-terminated diacetylene. On the other end, the inner cross-linked structure gives to poly(DAAMM)-coated nanohybrids increased stability in water with respect to self-assembled counterparts deriving from saturated cationic surfactants, making them a promising sensing platform for rapid and cost effective assays of real samples.

  2. Quantitative self-assembly prediction yields targeted nanomedicines

    Science.gov (United States)

    Shamay, Yosi; Shah, Janki; Işık, Mehtap; Mizrachi, Aviram; Leibold, Josef; Tschaharganeh, Darjus F.; Roxbury, Daniel; Budhathoki-Uprety, Januka; Nawaly, Karla; Sugarman, James L.; Baut, Emily; Neiman, Michelle R.; Dacek, Megan; Ganesh, Kripa S.; Johnson, Darren C.; Sridharan, Ramya; Chu, Karen L.; Rajasekhar, Vinagolu K.; Lowe, Scott W.; Chodera, John D.; Heller, Daniel A.

    2018-02-01

    Development of targeted nanoparticle drug carriers often requires complex synthetic schemes involving both supramolecular self-assembly and chemical modification. These processes are generally difficult to predict, execute, and control. We describe herein a targeted drug delivery system that is accurately and quantitatively predicted to self-assemble into nanoparticles based on the molecular structures of precursor molecules, which are the drugs themselves. The drugs assemble with the aid of sulfated indocyanines into particles with ultrahigh drug loadings of up to 90%. We devised quantitative structure-nanoparticle assembly prediction (QSNAP) models to identify and validate electrotopological molecular descriptors as highly predictive indicators of nano-assembly and nanoparticle size. The resulting nanoparticles selectively targeted kinase inhibitors to caveolin-1-expressing human colon cancer and autochthonous liver cancer models to yield striking therapeutic effects while avoiding pERK inhibition in healthy skin. This finding enables the computational design of nanomedicines based on quantitative models for drug payload selection.

  3. Hydrogen-Bonded Polymer-Porphyrin Assemblies in Water: Supramolecular Structures for Light Energy Conversion.

    Science.gov (United States)

    Kutz, Anne; Alex, Wiebke; Krieger, Anja; Gröhn, Franziska

    2017-09-01

    In this study, a new type of functional, self-assembled nanostructure formed from porphyrins and polyamidoamine dendrimers based on hydrogen bonding in an aqueous solution is presented. As the aggregates formed are promising candidates for solar-energy conversion, their photocatalytic activity is tested using the model reaction of methyl viologen reduction. The self-assembled structures show significantly increased activity as compared to unassociated porphyrins. Details of interaction forces driving the supramolecular structure formation and regulating catalytic efficiency are fundamentally discussed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Pt–Ru decorated self-assembled TiO2–carbon hybrid nanostructure ...

    Indian Academy of Sciences (India)

    Accordingly, titanium oxide–carbon nanocomposite with mesoporous structure is directly synthesized as a cata- lyst support via supramolecular self-assembly with an in situ crystallization process in order to achieve high surface area. Active sites on such a porous structure would be ea- sily accessible to the reactant leading ...

  5. Self-assembled M2L4 coordination cages : Synthesis and potential applications

    NARCIS (Netherlands)

    Schmidt, Andrea; Casini, Angela; Kuehn, Fritz E.

    2014-01-01

    Metal-mediated self-assemblies of the general formula MxLy (M = metal ion, L = ligand) have emerged as a promising research area of supramolecular chemistry because of their applicability in various fields such as molecular recognition, catalysis and drug delivery. The focus of this review is on

  6. Self-assembly between biomacromolecules and lipids

    Science.gov (United States)

    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

  7. On sulfur core level binding energies in thiol self-assembly and alternative adsorption sites: An experimental and theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Juanjuan [Institut des Sciences Moléculaires d’Orsay, Université-Paris Sud, 91405 Orsay (France); CNRS, UMR 8214, Institut des Sciences Moléculaires d’Orsay, Orsay ISMO, Bâtiment 351, Université Paris Sud, 91405 Orsay (France); Kara, Abdelkader, E-mail: abdelkader.kara@ucf.edu, E-mail: vladimir.esaulov@u-psud.fr [Department of Physics, University of Central Florida, Orlando, Florida 32816 (United States); Pasquali, Luca [Dipartimento di Ingegneria “E. Ferrari,” Università di Modena e Reggio Emilia, Via Vignolese 905, 41125 Modena (Italy); IOM-CNR, s.s. 14, Km. 163.5 in AREA Science Park, 34149 Basovizza, Trieste (Italy); Department of Physics, University of Johannesburg, P.O. Box 524, Auckland Park 2006 (South Africa); Bendounan, Azzedine; Sirotti, Fausto [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, F-91192 Gif-sur-Yvette Cedex (France); Esaulov, Vladimir A., E-mail: abdelkader.kara@ucf.edu, E-mail: vladimir.esaulov@u-psud.fr [Institut des Sciences Moléculaires d’Orsay, Université-Paris Sud, 91405 Orsay (France); CNRS, UMR 8214, Institut des Sciences Moléculaires d’Orsay, Orsay ISMO, Bâtiment 351, Université Paris Sud, 91405 Orsay (France); IOM-CNR, s.s. 14, Km. 163.5 in AREA Science Park, 34149 Basovizza, Trieste (Italy)

    2015-09-14

    Characteristic core level binding energies (CLBEs) are regularly used to infer the modes of molecular adsorption: orientation, organization, and dissociation processes. Here, we focus on a largely debated situation regarding CLBEs in the case of chalcogen atom bearing molecules. For a thiol, this concerns the case when the CLBE of a thiolate sulfur at an adsorption site can be interpreted alternatively as due to atomic adsorption of a S atom, resulting from dissociation. Results of an investigation of the characteristics of thiol self-assembled monolayers (SAMs) obtained by vacuum evaporative adsorption are presented along with core level binding energy calculations. Thiol ended SAMs of 1,4-benzenedimethanethiol (BDMT) obtained by evaporation on Au display an unconventional CLBE structure at about 161.25 eV, which is close to a known CLBE of a S atom on Au. Adsorption and CLBE calculations for sulfur atoms and BDMT molecules are reported and allow delineating trends as a function of chemisorption on hollow, bridge, and atop sites and including the presence of adatoms. These calculations suggest that the 161.25 eV peak is due to an alternative adsorption site, which could be associated to an atop configuration. Therefore, this may be an alternative interpretation, different from the one involving the adsorption of atomic sulfur resulting from the dissociation process of the S–C bond. Calculated differences in S(2p) CLBEs for free BDMT molecules, SH group sulfur on top of the SAM, and disulfide are also reported to clarify possible errors in assignments.

  8. Self-assembly of cyclodextrins

    DEFF Research Database (Denmark)

    Fülöp, Z.; Kurkov, S.V.; Nielsen, T.T.

    2012-01-01

    that increases upon formation of inclusion complexes with lipophilic drugs. However, the stability of such aggregates is not sufficient for parenteral administration. In this review CD polymers and CD containing nanoparticles are categorized, with focus on self-assembled CD nanoparticles. It is described how...

  9. Rapid self-assembly of block copolymers to photonic crystals

    Science.gov (United States)

    Xia, Yan; Sveinbjornsson, Benjamin R; Grubbs, Robert H; Weitekamp, Raymond; Miyake, Garret M; Atwater, Harry A; Piunova, Victoria; Daeffler, Christopher Scot; Hong, Sung Woo; Gu, Weiyin; Russell, Thomas P.

    2016-07-05

    The invention provides a class of copolymers having useful properties, including brush block copolymers, wedge-type block copolymers and hybrid wedge and polymer block copolymers. In an embodiment, for example, block copolymers of the invention incorporate chemically different blocks comprising polymer size chain groups and/or wedge groups that significantly inhibit chain entanglement, thereby enhancing molecular self-assembly processes for generating a range of supramolecular structures, such as periodic nanostructures and microstructures. The present invention also provides useful methods of making and using copolymers, including block copolymers.

  10. Nanoporous network channels from self-assembled triblock copolymer supramolecules.

    Science.gov (United States)

    du Sart, Gerrit Gobius; Vukovic, Ivana; Vukovic, Zorica; Polushkin, Evgeny; Hiekkataipale, Panu; Ruokolainen, Janne; Loos, Katja; ten Brinke, Gerrit

    2011-02-16

    Supramolecular complexes of a poly(tert-butoxystyrene)-block-polystyrene-block-poly(4-vinylpyridine) triblock copolymers and less than stoichiometric amounts of pentadecylphenol (PDP) are shown to self-assemble into a core-shell gyroid morphology with the core channels formed by the hydrogen-bonded P4VP(PDP)complexes. After structure formation, PDP was removed using a simple washing procedure, resulting in well-ordered nanoporous films that were used as templates for nickel plating. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. SUPPORTING INFORMATION Gold nanodots self-assembled ...

    Indian Academy of Sciences (India)

    VICHU

    Figure S1. Catalytic test reactions carried out for different AuNDs catalysts. Figure S2. Catalytic test reactions carried out for AuNDs prepared using different Au concentrations. Figure S3. AFM images of self-assembled AuNDs and bare PADA films. Figure S4. Recycle study of catalytic plate. Figure S5-S16. 1H and 13C NMR ...

  12. Studies on the supramolecular shape memory polyurethane containing pyridine moieties

    Science.gov (United States)

    Shaojun, Chen

    Fabricating smart materials with supramolecular switch is an attractive research topic. In this study, supramolecular polyurethane networks containing pyridine moieties (PUPys) were synthesized from N,N-bis(2-hydroxylethyl)isonicotinamide (BINA), hexamethylene diisocyanate (HDI), 4, 4-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BDO). A series of studies were carried out to investigate the supramolecular structure, morphology and shape memory properties including of thermal-induced shape memory effect and moisture-sensitive shape memory effect. Results show that hydrogen-bonded supramolecular structure and phase separation morphology are formed in the PUPys. The glass transition temperature (Tg) of soft phase is controlled by the hydrogen bonding while the hard phase grows up from amorphous phase to crystalline phase as the BINA content increases. The addition of MDI-BDO promotes the formation of amorphous hard phase. PUPys have high shape fixity and high shape recovery with the recovery temperature of 45 °C-55 °C. To achieve satisfying shape recovery, 30wt% BINA contents are required. The addition of MDI-BDO improves the shape recovery force. In addition, PUPys have high moisture absorption which increases with the increase of temperature, relative humidity, BINA content as well as the decrease of MDI-BDO content. The final shape recovery decreases with the decrease of BINA content significantly and the strain recovery start time, strain recovery time, strain recovery end time and the time length are also short in the higher BINA content PUPys. Moreover, it is found that the low critical value of BINA unit for PUPys having moisture-sensitive SME is still 30wt%. The addition of MDI-BDO improves the moisture-sensitive shape recovery. Finally, it is proposed that the hydrogen bonding present in the pyridine ring serves as "switch" whereas the formed hard phase via hydrogen bonding present in the urethane groups acts as the physical netpoints for the both

  13. Self-assembled monolayers (SAMs) of alkoxycyanobiphenyl thiols on gold--a study of electron transfer reaction using cyclic voltammetry and electrochemical impedance spectroscopy.

    Science.gov (United States)

    Ganesh, V; Pal, Santanu Kumar; Kumar, Sandeep; Lakshminarayanan, V

    2006-04-01

    Self-assembled monolayers (SAMs) of liquid crystalline thiol-terminated alkoxycyanobiphenyl molecules with different alkyl chain lengths on Au surface have been studied for the first time using electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The barrier property of the SAM-modified surfaces was evaluated using two different redox probes, namely potassium ferro/ferri cyanide and hexaammineruthenium(III) chloride. It was found that for short-length alkyl chain thiol (C5) the electron transfer reaction of hexaammineruthenium(III) chloride takes place through tunneling mechanism. In contrast, redox reaction of potassium ferro/ferri cyanide is almost completely blocked by the SAM-modified Au surface. From the impedance data, a surface coverage value of >99.9% was calculated for all the thiol molecules.

  14. Carbohydrates in Supramolecular Chemistry.

    Science.gov (United States)

    Delbianco, Martina; Bharate, Priya; Varela-Aramburu, Silvia; Seeberger, Peter H

    2016-02-24

    Carbohydrates are involved in a variety of biological processes. The ability of sugars to form a large number of hydrogen bonds has made them important components for supramolecular chemistry. We discuss recent advances in the use of carbohydrates in supramolecular chemistry and reveal that carbohydrates are useful building blocks for the stabilization of complex architectures. Systems are presented according to the scaffold that supports the glyco-conjugate: organic macrocycles, dendrimers, nanomaterials, and polymers are considered. Glyco-conjugates can form host-guest complexes, and can self-assemble by using carbohydrate-carbohydrate interactions and other weak interactions such as π-π interactions. Finally, complex supramolecular architectures based on carbohydrate-protein interactions are discussed.

  15. RT Self-assembly of Silica Nanoparticles on Optical Fibres

    DEFF Research Database (Denmark)

    Canning, John; Lindoy, Lachlan; Huyang, George

    2013-01-01

    The room temperature deposition of self-assembling silica nanoparticles onto D-shaped optical fibres x201c;D-fibrex201d;), drawn from milled preforms fabricated by modified chemical vapor deposition, is studied and preliminary results reported here.......The room temperature deposition of self-assembling silica nanoparticles onto D-shaped optical fibres x201c;D-fibrex201d;), drawn from milled preforms fabricated by modified chemical vapor deposition, is studied and preliminary results reported here....

  16. Understanding emergent functions in self-assembled fibrous networks

    Science.gov (United States)

    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.

  17. Promoting self-assembly of collagen-related peptides into various higher-order structures by metal-histidine coordination.

    Science.gov (United States)

    Hsu, Wei; Chen, Yi-Lun; Horng, Jia-Cherng

    2012-02-14

    Collagen is an important and widely used biomaterial and therapeutic. The construction of large-scale collagen structures via the self-assembly of small collagen-related peptides has been extensively studied in the past decade. Here, we report a highly effective and simple means to assemble small synthetic collagen-related peptides into various higher-order structures by utilizing metal-histidine coordination. In this work, two short collagen-related peptides in which histidine residues were incorporated as metal binding sites were designed and chemically synthesized: HG(PPG)(9)GH (X9) and HG(PPG)(4)(PHG)(PPG)(4)GH (PHG). Circular dichroism measurements indicated that these two peptides form only marginally stable collagen triple helices but that their stability can be increased upon the addition of metal ions. Dynamic light scattering analyses, turbidity measurements, TEM, and SEM results demonstrated the metal ion-dependent self-assembly of X9 and PHG into supramolecular structures ranging from various nanofibrils to microscale spherical, laminated, and granulated assemblies. The topology and size of these higher-order structures depends both on the metal ion identity and the location of the binding sites. Most intriguingly, the assembled fibrils show similar D-periodicity to that of natural collagen. Our results demonstrate that metal-histidine coordination can serve as an effective force to induce the self-assembly of unstable collagen-related peptides into higher-order structures.

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

    KAUST Repository

    Ocakoǧlu, Kasim

    2014-01-01

    Self-assembled supramolecular organization of nano-structured biomimetic light-harvesting modules inside solid-state nano-templates can be exploited to develop excellent light-harvesting materials for artificial photosynthetic devices. We present here a hybrid light-harvesting system mimicking the chlorosomal structures of the natural photosynthetic system using synthetic zinc chlorin units (ZnChl-C6, ZnChl-C12 and ZnChl-C 18) that are self-aggregated inside the anodic aluminum oxide (AAO) nano-channel membranes. AAO nano-templates were modified with a TiO2 matrix and functionalized with long hydrophobic chains to facilitate the formation of supramolecular Zn-chlorin aggregates. The transparent Zn-chlorin nano-aggregates inside the alkyl-TiO2 modified AAO nano-channels have a diameter of ∼120 nm in a 60 μm length channel. UV-Vis studies and fluorescence emission spectra further confirm the formation of the supramolecular ZnChl aggregates from monomer molecules inside the alkyl-functionalized nano-channels. Our results prove that the novel and unique method can be used to produce efficient and stable light-harvesting assemblies for effective solar energy capture through transparent and stable nano-channel ceramic materials modified with bio-mimetic molecular self-assembled nano-aggregates. © 2014 the Partner Organisations.

  19. Metallo-supramolecular Architectures based on Multifunctional N-Donor Ligands

    OpenAIRE

    Tanh Jeazet, Harold Brice

    2010-01-01

    Self-assembly processes were used to construct supramolecular architectures based on metal-ligand interactions. The structures formed strongly depend on the used metal ion, the ligand type, the chosen counter ion and solvent as well as on the experimental conditions. The focus of the studies was the design of multifunctional N-donor ligands and the characterization of their complexing and structural properties. This work was divided into three distinct main parts: The bis(2-pyridylimine), the...

  20. A triaxial supramolecular weave

    Science.gov (United States)

    Lewandowska, Urszula; Zajaczkowski, Wojciech; Corra, Stefano; Tanabe, Junki; Borrmann, Ruediger; Benetti, Edmondo M.; Stappert, Sebastian; Watanabe, Kohei; Ochs, Nellie A. K.; Schaeublin, Robin; Li, Chen; Yashima, Eiji; Pisula, Wojciech; Müllen, Klaus; Wennemers, Helma

    2017-11-01

    Despite recent advances in the synthesis of increasingly complex topologies at the molecular level, nano- and microscopic weaves have remained difficult to achieve. Only a few diaxial molecular weaves exist—these were achieved by templation with metals. Here, we present an extended triaxial supramolecular weave that consists of self-assembled organic threads. Each thread is formed by the self-assembly of a building block comprising a rigid oligoproline segment with two perylene-monoimide chromophores spaced at 18 Å. Upon π stacking of the chromophores, threads form that feature alternating up- and down-facing voids at regular distances. These voids accommodate incoming building blocks and establish crossing points through CH-π interactions on further assembly of the threads into a triaxial woven superstructure. The resulting micrometre-scale supramolecular weave proved to be more robust than non-woven self-assemblies of the same building block. The uniform hexagonal pores of the interwoven network were able to host iridium nanoparticles, which may be of interest for practical applications.

  1. Design of novel supramolecular self-assembly creating ...

    Indian Academy of Sciences (India)

    Administrator

    To the best of our knowledge this is the third structure reported in the area of neutral rectangular assembly. The staggered stacking between the 2D sheets makes the structure less intriguing and reducing the cavity size which accommodates two water molecules by O–H… O interaction. Proc. Indian Acad. Sci. (Chem. Sci.) ...

  2. Design of novel supramolecular self-assembly creating ...

    Indian Academy of Sciences (India)

    Administrator

    Metal–organic composite materials with appropriate building blocks which can assemble into structures with specific and desired frameworks are challenging both for their solid state technology and for their chemical architecture. Of special interest is the construction of a microporous network that can exhibit reversible guest ...

  3. Glucosamine-Based Supramolecular Nanotubes for Human Mesenchymal Cell Therapy.

    Science.gov (United States)

    Talloj, Satish Kumar; Cheng, Bill; Weng, Jen-Po; Lin, Hsin-Chieh

    2018-04-23

    Herein, we demonstrate an example of glucosamine-based supramolecular hydrogels that can be used for human mesenchymal cell therapy. We designed and synthesized a series of amino acid derivatives based on a strategy of capping d-glucosamine moiety at the C-terminus and fluorinated benzyl group at the N-terminus. From a systematic study on chemical structures, we discovered that the glucosamine-based supramolecular hydrogel [pentafluorobenzyl (PFB)-F-Glu] self-assembled with one-dimensional nanotubular structures at physiological pH. The self-assembly of a newly discovered PFB-F-Glu motif is attributed to the synergistic effect of π-π stacking and extensive intermolecular hydrogen bonding network in aqueous medium. Notably, PFB-F-Glu nanotubes are proven to be nontoxic to human mesenchymal stem cells (hMSCs) and have been shown to enhance hMSC proliferation while maintaining their pluripotency. Retaining of pluripotency capabilities provides potentially unlimited source of undifferentiated cells for the treatment of future cell therapies. Furthermore, hMSCs cultured on PFB-F-Glu are able to secrete paracrine factors that downregulate profibrotic gene expression in lipopolysaccharide-treated human skin fibroblasts, which demonstrates that PFB-F-Glu nanotubes have the potential to be used for wound healing applications. Overall, this article addresses the importance of chemical design to generate supramolecular biomaterials for stem cell therapy.

  4. Self-assembled nanostructured metamaterials

    Science.gov (United States)

    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.

  5. Supramolecular materials based on hydrogen-bonded polymers

    NARCIS (Netherlands)

    ten Brinke, Gerrit; Ruokolainen, Janne; Ikkala, Olli; Binder, W

    2007-01-01

    Combining supramolecular principles with block copolymer self-assembly offers unique possibilities to create materials with responsive and/or tunable properties. The present chapter focuses on supramolecular materials based on hydrogen bonding and (block co-) polymers. Several cases will be

  6. Solvent induced supramolecular anisotropy in molecular gels

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, Michael A., E-mail: mroger09@uoguelph.ca [Department of Food Science, University of Guelph, Guelph, Ontario, N3C3X9 (Canada); Corradini, Maria G. [Department of Food Science, University of Massachusetts Amherst, Amherst, MA, 01003 (United States); Emge, Thomas [Department of Chemistry and Biochemistry, Rutgers University, New Brunswick, NJ, 08901 (United States)

    2017-06-15

    Herein is the first report of solvent induced anisotropy in 12-hydroxystearic acid self-assembled fibrillar networks. Increasing the chain length of polar solvent, such as nitriles and ketones, tailored the anisotropy of the fibrillar aggregates. 12HSA molecular gels, comprised of alkanes, exhibited an isotropic fibrillar network irrespective of the alkane chain length. In polar solvents, anisotropy, observed using 2D powder x-ray diffraction profiles, is correlated to a fibrillar supramolecular morphologies in long chain nitriles and ketones while sphereulitic crystals are correlated to x-ray diffraction patterns with an isotropic scatter intensity in short chain ketones and nitriles. These changes directly modify the final physical properties of the gels. - Highlights: • 12-HSA self-assembles into crystalline supramolecular morphologies depending on the solvent. • Alkanes, short chain nitriles and ketones led to 12-HSA displaying supramolecular isotropy. • In long chain nitriles and ketones, 12-HSA displays supramolecular anisotropy.

  7. Solvent induced supramolecular anisotropy in molecular gels

    International Nuclear Information System (INIS)

    Rogers, Michael A.; Corradini, Maria G.; Emge, Thomas

    2017-01-01

    Herein is the first report of solvent induced anisotropy in 12-hydroxystearic acid self-assembled fibrillar networks. Increasing the chain length of polar solvent, such as nitriles and ketones, tailored the anisotropy of the fibrillar aggregates. 12HSA molecular gels, comprised of alkanes, exhibited an isotropic fibrillar network irrespective of the alkane chain length. In polar solvents, anisotropy, observed using 2D powder x-ray diffraction profiles, is correlated to a fibrillar supramolecular morphologies in long chain nitriles and ketones while sphereulitic crystals are correlated to x-ray diffraction patterns with an isotropic scatter intensity in short chain ketones and nitriles. These changes directly modify the final physical properties of the gels. - Highlights: • 12-HSA self-assembles into crystalline supramolecular morphologies depending on the solvent. • Alkanes, short chain nitriles and ketones led to 12-HSA displaying supramolecular isotropy. • In long chain nitriles and ketones, 12-HSA displays supramolecular anisotropy.

  8. Time-of-flight-secondary ion mass spectrometry and cyclic voltammetry studies of self-assembly of dodecanethiol on a nanoporous gold surface.

    Science.gov (United States)

    Hafez, Aly M; Huber, Andreas; Wenclawiak, Bernd W

    2013-03-19

    Preparation of a nanoporous gold surface by dealloying (etching) of a 585 gold plate (58.5% Au, 30% Ag, and 11.5% non-noble metals) was studied by applying acidic and thermal treatment of the gold plate. The gold plate surface was studied before and after the etching process using different analytical techniques like field emission scanning electron microscope (FE-SEM) with an energy dispersive X-ray spectroscopy analyzer (EDX), cyclic voltammetry (CV), and time-of-flight-secondary ion mass spectrometry (TOF-SIMS). CV analysis of the gold surface has shown that overnight etching with warm nitric acid increases the surface area 20 times higher than before etching. FE-SEM analysis has shown that a nanoporous gold surface with pore diameter ≤100 nm was obtained. SIMS depth profile analysis and EDX analysis have shown that the nanoporous gold surface was obtained as a result of removing the silver and copper from the first layers of the plate. The nanoporous gold surface was used as a substrate for self-assembly of dodecanethiol and has shown a higher extraction efficiency than the unetched gold alloy.

  9. Study of the synthesis and self-assembly of CO2-philic copolymers with complexing groups: application to decontamination in supercritical CO2 medium

    International Nuclear Information System (INIS)

    Ribaut, T.

    2009-10-01

    In the frame of sustainable development, a priority is to decrease the volume of nuclear wastes. The use of supercritical carbon dioxide (scCO 2 ) could allow to solve this problem. The aim of this study is to extract an ionic or particle cobalt contamination deposited on textile lab coats. The strategy uses CO 2 -philic/CO 2 -phobic copolymers soluble in scCO 2 and containing complexing groups. This approach combines the use of amphiphilic copolymers for steric stabilization of particles, of surfactants able to self-assemble to promote extraction and of ligands. Controlled radical polymerization is used to synthesize fluorinated gradient or block copolymers. Cloud point curves of the copolymers are determined experimentally in scCO 2 . Prediction of polymer/scCO 2 phase diagrams was assessed by Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) modeling. Gradient copolymers appear more advantageous than block copolymers due to their solubility in much milder conditions of pressure and temperature. Small-angle neutron scattering (SANS) allowed us to evidence the pressure-induced aggregation of the gradient copolymers in scCO 2 . Their interface properties were demonstrated: they allow to form water-in-CO 2 microemulsions and to stabilize cobalt hydroxide dispersions in scCO 2 . Lastly, in presence of a very low quantity of water, Co 2+ ions were removed with a rate of 37 % from a cotton/polyester matrix by a gradient copolymer. (author)

  10. Internal Nanoparticle Structure of Temperature-Responsive Self-Assembled PNIPAM-b-PEG-b-PNIPAM Triblock Copolymers in Aqueous Solutions: NMR, SANS, and Light Scattering Studies.

    Science.gov (United States)

    Filippov, Sergey K; Bogomolova, Anna; Kaberov, Leonid; Velychkivska, Nadiia; Starovoytova, Larisa; Cernochova, Zulfiya; Rogers, Sarah E; Lau, Wing Man; Khutoryanskiy, Vitaliy V; Cook, Michael T

    2016-05-31

    In this study, we report detailed information on the internal structure of PNIPAM-b-PEG-b-PNIPAM nanoparticles formed from self-assembly in aqueous solutions upon increase in temperature. NMR spectroscopy, light scattering, and small-angle neutron scattering (SANS) were used to monitor different stages of nanoparticle formation as a function of temperature, providing insight into the fundamental processes involved. The presence of PEG in a copolymer structure significantly affects the formation of nanoparticles, making their transition to occur over a broader temperature range. The crucial parameter that controls the transition is the ratio of PEG/PNIPAM. For pure PNIPAM, the transition is sharp; the higher the PEG/PNIPAM ratio results in a broader transition. This behavior is explained by different mechanisms of PNIPAM block incorporation during nanoparticle formation at different PEG/PNIPAM ratios. Contrast variation experiments using SANS show that the structure of nanoparticles above cloud point temperatures for PNIPAM-b-PEG-b-PNIPAM copolymers is drastically different from the structure of PNIPAM mesoglobules. In contrast with pure PNIPAM mesoglobules, where solidlike particles and chain network with a mesh size of 1-3 nm are present, nanoparticles formed from PNIPAM-b-PEG-b-PNIPAM copolymers have nonuniform structure with "frozen" areas interconnected by single chains in Gaussian conformation. SANS data with deuterated "invisible" PEG blocks imply that PEG is uniformly distributed inside of a nanoparticle. It is kinetically flexible PEG blocks which affect the nanoparticle formation by prevention of PNIPAM microphase separation.

  11. Grafting of benzylic amide macrocycles onto acid-terminated self-assembled monolayers studied by XPS, RAIRS, and contact angle measurements

    NARCIS (Netherlands)

    Cecchet, F; Pilling, M; Hevesi, L; Schergna, S; Wong, JKY; Clarkson, GJ; Leigh, DA; Rudolf, P; Wong, Jenny K.Y.; Clarkson, Guy J.

    2003-01-01

    The grafting of benzylic amide macrocycles, the basic units of more complex mechanically interlocked architectures such as catenanes and rotaxanes, was performed via the functionalization of an acid-terminated self-assembled monolayer (SAM) of 11-mercaptoundecanoic acid (11-MUA). Both chemical and

  12. Dynamics of chain exchange between self-assembled diblock copolymer micelles of poly(ethylene oxide)-block-polylactide studied by direct nonradiative excitation energy transfer

    Czech Academy of Sciences Publication Activity Database

    Popelka, Štěpán; Machová, Luďka; Rypáček, František; Špírková, Milena; Štěpánek, M.; Matějíček, P.; Procházka, K.

    2005-01-01

    Roč. 70, č. 11 (2005), s. 1811-1828 ISSN 0010-0765 R&D Projects: GA AV ČR IAA4050202; GA AV ČR IAA400500505 Institutional research plan: CEZ:AV0Z40500505 Keywords : block copolymers * self-assembly * micelles Subject RIV: CD - Macromolecular Chemistry Impact factor: 0.949, year: 2005

  13. Crystalline self-assembly of organic molecules with metal ions at the air-aqueous solution interface. A grazing incidence X-ray scattering study

    DEFF Research Database (Denmark)

    Weissbuch, I.; Buller, R.; Kjær, K.

    2002-01-01

    The advent of intense X-rays from synchrotron sources made possible to probe, at the molecular level, the structural aspects of self-assemblies generated at interfaces. Here we present the two-dimensional (2-D) packing arrangements of two-, three- and multi-component organo-metallic self-assembli......The advent of intense X-rays from synchrotron sources made possible to probe, at the molecular level, the structural aspects of self-assemblies generated at interfaces. Here we present the two-dimensional (2-D) packing arrangements of two-, three- and multi-component organo-metallic self......-assemblies formed via interfacial reaction at the air-aqueous solution interface, as determined by grazing incidence X-ray diffraction (GIRD) and X-ray specular reflectivity techniques. GIXD yields structural information on the crystalline part of the Langmuir film, including the ions and counterions lateral order...... of metal ions bound to the polar head groups of amphipilic molecules; use of bolaamphiphiles to generate oriented thin films with metal ions arranged in periodic layers; delineation of differences in the lateral organization of metal ions at interfaces as induced by racemates and enantiomerically pure...

  14. Self-assembly of patchy colloidal dumbbells.

    Science.gov (United States)

    Avvisati, Guido; Vissers, Teun; Dijkstra, Marjolein

    2015-02-28

    We employ Monte Carlo simulations to investigate the self-assembly of patchy colloidal dumbbells interacting via a modified Kern-Frenkel potential by probing the system concentration and dumbbell shape. We consider dumbbells consisting of one attractive sphere with diameter σ1 and one repulsive sphere with diameter σ2 and center-to-center distance d between the spheres. For three different size ratios, we study the self-assembled structures for different separations l = 2d/(σ1 + σ2) between the two spheres. In particular, we focus on structures that can be assembled from the homogeneous fluid, as these might be of interest in experiments. We use cluster order parameters to classify the shape of the formed structures. When the size of the spheres is almost equal, q = σ2/σ1 = 1.035, we find that, upon increasing l, spherical micelles are transformed to elongated micelles and finally to vesicles and bilayers. For size ratio q = 1.25, we observe a continuously tunable transition from spherical to elongated micelles upon increasing the sphere separation. For size ratio q = 0.95, we find bilayers and vesicles, plus faceted polyhedra and liquid droplets. Our results identify key parameters to create colloidal vesicles with attractive dumbbells in experiments.

  15. Three's company: co-crystallization of a self-assembled S(4) metallacyclophane with two diastereomeric metallacycle intermediates.

    Science.gov (United States)

    Lindquist, Nathan R; Carter, Timothy G; Cangelosi, Virginia M; Zakharov, Lev N; Johnson, Darren W

    2010-05-28

    Three discrete supramolecular self-assembled arsenic(iii) complexes including an unusual S(4)-symmetric tetranuclear [As(4)L(2)Cl(4)] metallacyclophane and two diastereomeric cis/trans-[As(2)LCl(2)] metallacycle intermediates co-crystallize within a single crystal lattice.

  16. DFT computations on: Crystal structure, vibrational studies and optical investigations of a luminescent self-assembled material

    Science.gov (United States)

    Kessentini, A.; Ben Ahmed, A.; Dammak, T.; Belhouchet, M.

    2018-02-01

    The current work undertakes the growth and the physicochemical properties of a novel green-yellow luminescence semi-organic material, the 3-picolylammonium bromide abbreviated (Pico-Br). In this paper, we report the X-ray diffraction measurements which show that the crystal lattice consists of distinct 3-picolylammonium cations and free bromide anions connected via Nsbnd H ⋯ Br and Nsbnd H ⋯ N hydrogen bonds leading to form a two dimensional frameworks. Molecular geometry compared with its optimized counterpart shows that the quantum chemical calculations carried out with density functional method (DFT) well produce the perceived structure by X-ray resolution of the studied material. To provide further insight into the spectroscopic properties, additional characterization of this material have been performed with Raman and infrared studies at room temperature. Theoretical computations have been computed using the (DFT) method at B3LYP/LanL2DZ level of theory implemented within Gaussian 03 program to study the vibrational spectra of the investigated molecule in the ground state. Optical absorption spectrum inspected by UV-visible absorption reveals the appearance of sharp optical gap of 280 nm (4.42 eV) as well as a strong green photoluminescence emission at 550 nm (2.25 eV) is detected on the photoluminescence (PL) spectrum at room temperature. Using the TD/DFT method, HOMO-LUMO energy gap and the Mulliken atomic charges were calculated in order to get an insight into the material. Good agreement between the theoretical results and the experimental ones was predicted.

  17. DFT computations on: Crystal structure, vibrational studies and optical investigations of a luminescent self-assembled material.

    Science.gov (United States)

    Kessentini, A; Ben Ahmed, A; Dammak, T; Belhouchet, M

    2018-02-15

    The current work undertakes the growth and the physicochemical properties of a novel green-yellow luminescence semi-organic material, the 3-picolylammonium bromide abbreviated (Pico-Br). In this paper, we report the X-ray diffraction measurements which show that the crystal lattice consists of distinct 3-picolylammonium cations and free bromide anions connected via NH⋯Br and NH⋯N hydrogen bonds leading to form a two dimensional frameworks. Molecular geometry compared with its optimized counterpart shows that the quantum chemical calculations carried out with density functional method (DFT) well produce the perceived structure by X-ray resolution of the studied material. To provide further insight into the spectroscopic properties, additional characterization of this material have been performed with Raman and infrared studies at room temperature. Theoretical computations have been computed using the (DFT) method at B3LYP/LanL2DZ level of theory implemented within Gaussian 03 program to study the vibrational spectra of the investigated molecule in the ground state. Optical absorption spectrum inspected by UV-visible absorption reveals the appearance of sharp optical gap of 280nm (4.42eV) as well as a strong green photoluminescence emission at 550nm (2.25eV) is detected on the photoluminescence (PL) spectrum at room temperature. Using the TD/DFT method, HOMO-LUMO energy gap and the Mulliken atomic charges were calculated in order to get an insight into the material. Good agreement between the theoretical results and the experimental ones was predicted. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Multi-scale coarse-graining for the study of assembly pathways in DNA-brick self-assembly

    Science.gov (United States)

    Fonseca, Pedro; Romano, Flavio; Schreck, John S.; Ouldridge, Thomas E.; Doye, Jonathan P. K.; Louis, Ard A.

    2018-04-01

    Inspired by recent successes using single-stranded DNA tiles to produce complex structures, we develop a two-step coarse-graining approach that uses detailed thermodynamic calculations with oxDNA, a nucleotide-based model of DNA, to parametrize a coarser kinetic model that can reach the time and length scales needed to study the assembly mechanisms of these structures. We test the model by performing a detailed study of the assembly pathways for a two-dimensional target structure made up of 334 unique strands each of which are 42 nucleotides long. Without adjustable parameters, the model reproduces a critical temperature for the formation of the assembly that is close to the temperature at which assembly first occurs in experiments. Furthermore, the model allows us to investigate in detail the nucleation barriers and the distribution of critical nucleus shapes for the assembly of a single target structure. The assembly intermediates are compact and highly connected (although not maximally so), and classical nucleation theory provides a good fit to the height and shape of the nucleation barrier at temperatures close to where assembly first occurs.

  19. A theoretical and simulation study of the self-assembly of a binary blend of diblock copolymers

    KAUST Repository

    Padmanabhan, Poornima

    2012-01-01

    Pure diblock copolymer melts exhibit a narrow range of conditions at which bicontinuous and cocontinuous phases are stable; such conditions and the morphology of such phases can be tuned by the use of additives. In this work, we have studied a bidisperse system of diblock copolymers using theory and simulation. In particular, we elucidated how a short, lamellar-forming diblock copolymer modifies the phase behavior of a longer, cylinder-forming diblock copolymer. In a narrow range of intermediate compositions, self-consistent field theory predicts the formation of a gyroid phase although particle-based simulations show that three phases compete: the gyroid phase, a disordered cocontinuous phase, and the cylinder phase, all having free energies within error bars of each other. Former experimental studies of a similar system have yielded an unidentified, partially irregular bicontinuous phase, and our simulations suggest that at such conditions the formation of a partially transformed network phase is indeed plausible. Close examination of the spatial distribution of chains reveals that packing frustration (manifested by chain stretching and low density spots) occurs in the majority-block domains of the three competing phases simulated. In all cases, a double interface around the minority-block domains is also detected with the outer one formed by the short chains, and the inner one formed by the longer chains. © 2012 American Institute of Physics.

  20. Comparative Study of Ultrasonication-Induced and Naturally Self-Assembled Silk Fibroin-Wool Keratin Hydrogel Biomaterials

    Directory of Open Access Journals (Sweden)

    Trang Vu

    2016-09-01

    Full Text Available This study reports the formation of biocompatible hydrogels using protein polymers from natural silk cocoon fibroins and sheep wool keratins. Silk fibroin protein contains β-sheet secondary structures, allowing for the formation of physical cross-linkers in the hydrogels. Comparative studies were performed on two groups of samples. In the first group, ultrasonication was used to induce a quick gelation of a protein aqueous solution, enhancing the ability of Bombyx mori silk fibroin chains to quickly entrap the wool keratin protein molecules homogenously. In the second group, silk/keratin mixtures were left at room temperature for days, resulting in naturally-assembled gelled solutions. It was found that silk/wool blended solutions can form hydrogels at different mixing ratios, with perfectly interconnected gel structure when the wool content was less than 30 weight percent (wt % for the first group (ultrasonication, and 10 wt % for the second group (natural gel. Differential scanning calorimetry (DSC and temperature modulated DSC (TMDSC were used to confirm that the fibroin/keratin hydrogel system was well-blended without phase separation. Fourier transform infrared spectroscopy (FTIR was used to investigate the secondary structures of blended protein gels. It was found that intermolecular β-sheet contents significantly increase as the system contains more silk for both groups of samples, resulting in stable crystalline cross-linkers in the blended hydrogel structures. Scanning electron microscopy (SEM and atomic force microscopy (AFM were used to analyze the samples’ characteristic morphology on both micro- and nanoscales, which showed that ultrasonic waves can significantly enhance the cross-linker formation and avoid phase separation between silk and keratin molecules in the blended systems. With the ability to form cross-linkages non-chemically, these silk/wool hydrogels may be economically useful for various biomedical applications

  1. Physical principles for DNA tile self-assembly.

    Science.gov (United States)

    Evans, Constantine G; Winfree, Erik

    2017-06-19

    DNA tiles provide a promising technique for assembling structures with nanoscale resolution through self-assembly by basic interactions rather than top-down assembly of individual structures. Tile systems can be programmed to grow based on logical rules, allowing for a small number of tile types to assemble large, complex assemblies that can retain nanoscale resolution. Such algorithmic systems can even assemble different structures using the same tiles, based on inputs that seed the growth. While programming and theoretical analysis of tile self-assembly often makes use of abstract logical models of growth, experimentally implemented systems are governed by nanoscale physical processes that can lead to very different behavior, more accurately modeled by taking into account the thermodynamics and kinetics of tile attachment and detachment in solution. This review discusses the relationships between more abstract and more physically realistic tile assembly models. A central concern is how consideration of model differences enables the design of tile systems that robustly exhibit the desired abstract behavior in realistic physical models and in experimental implementations. Conversely, we identify situations where self-assembly in abstract models can not be well-approximated by physically realistic models, putting constraints on physical relevance of the abstract models. To facilitate the discussion, we introduce a unified model of tile self-assembly that clarifies the relationships between several well-studied models in the literature. Throughout, we highlight open questions regarding the physical principles for DNA tile self-assembly.

  2. Supramolecular gel electrophoresis of large DNA fragments.

    Science.gov (United States)

    Tazawa, Shohei; Kobayashi, Kazuhiro; Oyoshi, Takanori; Yamanaka, Masamichi

    2017-10-01

    Pulsed-field gel electrophoresis is a frequent technique used to separate exceptionally large DNA fragments. In a typical continuous field electrophoresis, it is challenging to separate DNA fragments larger than 20 kbp because they migrate at a comparable rate. To overcome this challenge, it is necessary to develop a novel matrix for the electrophoresis. Here, we describe the electrophoresis of large DNA fragments up to 166 kbp using a supramolecular gel matrix and a typical continuous field electrophoresis system. C 3 -symmetric tris-urea self-assembled into a supramolecular hydrogel in tris-boric acid-EDTA buffer, a typical buffer for DNA electrophoresis, and the supramolecular hydrogel was used as a matrix for electrophoresis to separate large DNA fragments. Three types of DNA marker, the λ-Hind III digest (2 to 23 kbp), Lambda DNA-Mono Cut Mix (10 to 49 kbp), and Marker 7 GT (10 to 165 kbp), were analyzed in this study. Large DNA fragments of greater than 100 kbp showed distinct mobility using a typical continuous field electrophoresis system. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Hierarchical Formation of Fibrillar and Lamellar Self-Assemblies from Guanosine-Based Motifs

    Directory of Open Access Journals (Sweden)

    Paolo Neviani

    2010-01-01

    Full Text Available Here we investigate the supramolecular polymerizations of two lipophilic guanosine derivatives in chloroform by light scattering technique and TEM experiments. The obtained data reveal the presence of several levels of organization due to the hierarchical self-assembly of the guanosine units in ribbons that in turn aggregate in fibrillar or lamellar soft structures. The elucidation of these structures furnishes an explanation to the physical behaviour of guanosine units which display organogelator properties.

  4. Pt–Ru decorated self-assembled TiO2–carbon hybrid nanostructure ...

    Indian Academy of Sciences (India)

    Porous titanium oxide–carbon hybrid nanostructure (TiO2–C) with a specific surface area of 350 m2/g and an average pore-radius of 21.8 Å is synthesized via supramolecular self-assembly with an in situ crystallization process. Subsequently, TiO2–C supported Pt–Ru electro-catalyst (Pt–Ru/TiO2–C) is obtained and ...

  5. Self-Assembly of Infinite Structures

    Directory of Open Access Journals (Sweden)

    Scott M. Summers

    2009-06-01

    Full Text Available We review some recent results related to the self-assembly of infinite structures in the Tile Assembly Model. These results include impossibility results, as well as novel tile assembly systems in which shapes and patterns that represent various notions of computation self-assemble. Several open questions are also presented and motivated.

  6. Self-assembled nanomaterials for photoacoustic imaging.

    Science.gov (United States)

    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.

  7. A rheo-optical apparatus for real time kinetic studies on shear-induced alignment of self-assembled soft matter with small sample volumes

    Science.gov (United States)

    Laiho, Ari; Ikkala, Olli

    2007-01-01

    In soft materials, self-assembled nanoscale structures can allow new functionalities but a general problem is to align such local structures aiming at monodomain overall order. In order to achieve shear alignment in a controlled manner, a novel type of rheo-optical apparatus has here been developed that allows small sample volumes and in situ monitoring of the alignment process during the shear. Both the amplitude and orientation angles of low level linear birefringence and dichroism are measured while the sample is subjected to large amplitude oscillatory shear flow. The apparatus is based on a commercial rheometer where we have constructed a flow cell that consists of two quartz teeth. The lower tooth can be set in oscillatory motion whereas the upper one is connected to the force transducers of the rheometer. A custom made cylindrical oven allows the operation of the flow cell at elevated temperatures up to 200 °C. Only a small sample volume is needed (from 9 to 25 mm3), which makes the apparatus suitable especially for studying new materials which are usually obtainable only in small quantities. Using this apparatus the flow alignment kinetics of a lamellar polystyrene-b-polyisoprene diblock copolymer is studied during shear under two different conditions which lead to parallel and perpendicular alignment of the lamellae. The open device geometry allows even combined optical/x-ray in situ characterization of the alignment process by combining small-angle x-ray scattering using concepts shown by Polushkin et al. [Macromolecules 36, 1421 (2003)].

  8. Regulating DNA Self-assembly by DNA-Surface Interactions.

    Science.gov (United States)

    Liu, Longfei; Li, Yulin; Wang, Yong; Zheng, Jianwei; Mao, Chengde

    2017-12-14

    DNA self-assembly provides a powerful approach for preparation of nanostructures. It is often studied in bulk solution and involves only DNA-DNA interactions. When confined to surfaces, DNA-surface interactions become an additional, important factor to DNA self-assembly. However, the way in which DNA-surface interactions influence DNA self-assembly is not well studied. In this study, we showed that weak DNA-DNA interactions could be stabilized by DNA-surface interactions to allow large DNA nanostructures to form. In addition, the assembly can be conducted isothermally at room temperature in as little as 5 seconds. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Cyclic voltammetry and scanning electrochemical microscopy studies of methylene blue immobilized on the self-assembled monolayer of n-dodecanethiol

    International Nuclear Information System (INIS)

    Salamifar, Seyed Ehsan; Mehrgardi, Masoud Ayatollahi; Kazemi, Sayed Habib; Mousavi, Mir Fazllollah

    2010-01-01

    Electron transfer (ET) kinetics through n-dodecanethiol (C 12 SH) self-assembled monolayer on gold electrode was studied using cyclic voltammetry (CV), scanning electrochemical microscopy (SECM) and electrochemical impedance spectroscopy (EIS). An SECM model for compensating pinhole contribution, was used to measure the ET kinetics of solution-phase probes of ferrocyanide/ferricyanide (Fe(CN) 6 4-/3- ) and ferrocenemethanol/ferrociniummethanol (FMC 0/+ ) through the C 12 SH monolayer yielding standard tunneling rate constant (k ET 0 ) of (4 ± 1) x 10 -11 and (3 ± 1) x 10 -10 cm s -1 for Fe(CN) 6 4-/3- and FMC 0/+ respectively. Decay tunneling constants (β) of 0.97 and 0.96 A -1 for saturated alkane thiol chains were obtained using Fe(CN) 6 4- and FMC respectively. Also, it was found that methylene blue (MB) molecules are effectively immobilized on the C 12 SH monolayer and can mediate the ET between the solution-phase probes and underlying gold substrate. SECM-mediated model was used to simultaneously measure the bimolecular ET between the solution-phase probes and the monolayer-immobilized MB molecules, as well as tunneling ET between the monolayer-immobilized MB molecules and the underlying gold electrode, allowing the measurement of k BI = (5 ± 1) x 10 6 and (4 ± 2) x 10 7 cm 3 mol -1 s -1 for the bimolecular ET and k ET/MB 0 =(1±0.3)x10 -3 and (7 ± 3) x 10 -2 s -1 for the standard tunneling rate constant of ET using Fe(CN) 6 4-/3- and FMC 0/+ probes respectively.

  10. Geometrical frustration yields fiber formation in self-assembly.

    Science.gov (United States)

    Lenz, Martin; Witten, Thomas A

    2017-11-01

    Controlling the self-assembly of supramolecular structures is vital for living cells, and a central challenge for engineering at the nano- and microscales [1, 2]. Nevertheless, even particles without optimized shapes can robustly form well-defined morphologies. This is the case in numerous medical conditions where normally soluble proteins aggregate into fibers [3, 4]. Beyond the diversity of molecular mechanisms involved [5, 6], we propose that fibers generically arise from the aggregation of irregular particles with short-range interactions. Using a minimal model of ill-fitting, sticky particles, we demonstrate robust fiber formation for a variety of particle shapes and aggregation conditions. Geometrical frustration plays a crucial role in this process, and accounts for the range of parameters in which fibers form as well as for their metastable character.

  11. Geometrical frustration yields fibre formation in self-assembly

    Science.gov (United States)

    Lenz, Martin; Witten, Thomas A.

    2017-11-01

    Controlling the self-assembly of supramolecular structures is vital for living cells, and a central challenge for engineering at the nano- and microscales. Nevertheless, even particles without optimized shapes can robustly form well-defined morphologies. This is the case in numerous medical conditions where normally soluble proteins aggregate into fibres. Beyond the diversity of molecular mechanisms involved, we propose that fibres generically arise from the aggregation of irregular particles with short-range interactions. Using a minimal model of ill-fitting, sticky particles, we demonstrate robust fibre formation for a variety of particle shapes and aggregation conditions. Geometrical frustration plays a crucial role in this process, and accounts for the range of parameters in which fibres form as well as for their metastable character.

  12. Control over the self-assembly and dynamics of metallacarborane nanorotors by the nature of the polymer matrix: a solid-state NMR study

    Czech Academy of Sciences Publication Activity Database

    Brus, Jiří; Zhigunov, Alexander; Czernek, Jiří; Kobera, Libor; Uchman, M.; Matějíček, P.

    2014-01-01

    Roč. 47, č. 18 (2014), s. 6343-6354 ISSN 0024-9297 R&D Projects: GA ČR(CZ) GA14-03636S; GA ČR(CZ) GA14-14608S; GA MŠk(CZ) LD14010 Grant - others:European Commission(XE) MPNS COST Action MP1202 Institutional support: RVO:61389013 Keywords : self -assembly * metallacarboranes * polymers Subject RIV: CD - Macromolecular Chemistry Impact factor: 5.800, year: 2014

  13. Physical principles of filamentous protein self-assembly kinetics

    International Nuclear Information System (INIS)

    Michaels, Thomas C T; Liu, Lucie X; Meisl, Georg; Knowles, Tuomas P J

    2017-01-01

    The polymerization of proteins and peptides into filamentous supramolecular structures is an elementary form of self-organization of key importance to the functioning biological systems, as in the case of actin biofilaments that compose the cellular cytoskeleton. Aberrant filamentous protein self-assembly, however, is associated with undesired effects and severe clinical disorders, such as Alzheimer’s and Parkinson’s diseases, which, at the molecular level, are associated with the formation of certain forms of filamentous protein aggregates known as amyloids. Moreover, due to their unique physicochemical properties, protein filaments are finding extensive applications as biomaterials for nanotechnology. With all these different factors at play, the field of filamentous protein self-assembly has experienced tremendous activity in recent years. A key question in this area has been to elucidate the microscopic mechanisms through which filamentous aggregates emerge from dispersed proteins with the goal of uncovering the underlying physical principles. With the latest developments in the mathematical modeling of protein aggregation kinetics as well as the improvement of the available experimental techniques it is now possible to tackle many of these complex systems and carry out detailed analyses of the underlying microscopic steps involved in protein filament formation. In this paper, we review some classical and modern kinetic theories of protein filament formation, highlighting their use as a general strategy for quantifying the molecular-level mechanisms and transition states involved in these processes. (topical review)

  14. Magnetic self-assembly of small parts

    Science.gov (United States)

    Shetye, Sheetal B.

    Modern society's propensity for miniaturized end-user products is compelling electronic manufacturers to assemble and package different micro-scale, multi-technology components in more efficient and cost-effective manners. As the size of the components gets smaller, issues such as part sticking and alignment precision create challenges that slow the throughput of conventional robotic pick-n-place systems. As an alternative, various self-assembly approaches have been proposed to manipulate micro to millimeter scale components in a parallel fashion without human or robotic intervention. In this dissertation, magnetic self-assembly (MSA) is demonstrated as a highly efficient, completely parallel process for assembly of millimeter scale components. MSA is achieved by integrating permanent micromagnets onto component bonding surfaces using wafer-level microfabrication processes. Embedded bonded powder methods are used for fabrication of the magnets. The magnets are then magnetized using pulse magnetization methods, and the wafers are then singulated to form individual components. When the components are randomly mixed together, self-assembly occurs when the intermagnetic forces overcome the mixing forces. Analytical and finite element methods (FEM) are used to study the force interactions between the micromagnets. The multifunctional aspects of MSA are presented through demonstration of part-to-part and part-to-substrate assembly of 1 mm x 1mm x 0.5 mm silicon components. Part-to-part assembly is demonstrated by batch assembly of free-floating parts in a liquid environment with the assembly yield of different magnetic patterns varying from 88% to 90% in 20 s. Part-to-substrate assembly is demonstrated by assembling an ordered array onto a fixed substrate in a dry environment with the assembly yield varying from 86% to 99%. In both cases, diverse magnetic shapes/patterns are used to control the alignment and angular orientation of the components. A mathematical model is

  15. Surfaces wettability and morphology modulation in a fluorene derivative self-assembly system

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Xinhua, E-mail: caoxhchem@163.com; Gao, Aiping; Zhao, Na; Yuan, Fangyuan; Liu, Chenxi; Li, Ruru

    2016-04-15

    Graphical abstract: - Highlights: • The different structures could be obtained in this self-assembly system. • A water-drop could freely roll on the xerogel film with the sliding angle of 15.0. • The superhydrophobic surface can be obtained via supramolecular self-assembly. - Abstract: A new organogelator based on fluorene derivative (gelator 1) was designed and synthesized. Organogels could be obtained via the self-assembly of the derivative in acetone, toluene, ethyl acetate, hexane, DMSO and petroleum ether. The self-assembly process was thoroughly characterized using field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), UV–vis, FT-IR and the contact angle. Surfaces with different morphologies and wetting properties were formed via the self-assembly of gelator 1 in the six different solvents. Interestingly, a superhydrophobic surface with a contact angle of 150° was obtained from organogel 1 in DMSO and exhibited the lotus-effect. The sliding angle necessary for a water droplet to move on the glass was only 15°. Hydrogen bonding and van der Waals forces were attributed as the main driving forces for gel formation.

  16. Covalent Tethering and Residues with Bulky Hydrophobic Side Chains Enable Self-Assembly of Distinct Amyloid Structures.

    Science.gov (United States)

    Ruiz, Jérémy; Boehringer, Régis; Grogg, Marcel; Raya, Jésus; Schirer, Alicia; Crucifix, Corinne; Hellwig, Petra; Schultz, Patrick; Torbeev, Vladimir

    2016-12-02

    Polymorphism is a common property of amyloid fibers that complicates their detailed structural and functional studies. Here we report experiments illustrating the chemical principles that enable the formation of amyloid polymorphs with distinct stoichiometric composition. Using appropriate covalent tethering we programmed self-assembly of a model peptide corresponding to the [20-41] fragment of human β2-microglobulin into fibers with either trimeric or dimeric amyloid cores. Using a set of biophysical and biochemical methods we demonstrated their distinct structural, morphological, and templating properties. Furthermore, we showed that supramolecular approaches in which the peptide is modified with bulky substituents can also be applied to modulate the formation of different fiber polymorphs. Such strategies, when applied to disease-related peptides and proteins, will greatly help in the evaluation of the biological properties of structurally distinct amyloids. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Self-Assembling Brush Polymers Bearing Multisaccharides.

    Science.gov (United States)

    Lee, Jongchan; Kim, Jin Chul; Lee, Hoyeol; Song, Sungjin; Kim, Heesoo; Ree, Moonhor

    2017-06-01

    Three different series of brush polymers bearing glucosyl, maltosyl, or maltotriosyl moiety at the bristle end are successfully prepared by using cationic ring-opening polymerization and two sequential postmodification reactions. All brush polymers, except for the polymer containing 100 mol% maltotriosyl moiety, demonstrate the formation of multibilayer structure in films, always providing saccharide-enriched surface. These self-assembling features are remarkable, regarding the bulkiness of saccharide moieties and the kink in the bristle due to the triazole linker. The saccharide-enriched film surfaces reveal exceptionally high specific binding affinity to concanavalin A but suppress nonspecific binding of plasma proteins severely. Overall, the brush polymers bearing saccharide moieties of various kinds in this study are highly suitable materials for biomedical applications including biosensors. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Recent Advances in Supramolecular Gels and Catalysis.

    Science.gov (United States)

    Fang, Weiwei; Zhang, Yang; Wu, Jiajie; Liu, Cong; Zhu, Haibo; Tu, Tao

    2018-04-04

    Over the past two decades, supramolecular gels have attracted significant attention from scientists in diverse research fields and have been extensively developed. This review mainly focuses on the significant achievements in supramolecular gels and catalysis. First, by incorporating diverse catalytic sites and active organic functional groups into gelator molecules, supramolecular gels have been considered as a novel matrix for catalysis. In addition, these rationally designed supramolecular gels also provide a variety of templates to access metal nanocomposites, which may function as catalysts and exhibit high activity in diverse catalytic transformations. Finally, as a new kind of biomaterial, supramolecular gels formed in situ by self-assembly triggered by catalytic transformations are also covered herein. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Nanoscale isoindigo-carriers: self-assembly and tunable properties

    Directory of Open Access Journals (Sweden)

    Tatiana N. Pashirova

    2017-02-01

    Full Text Available Over the last decade isoindigo derivatives have attracted much attention due to their high potential in pharmacy and in the chemistry of materials. In addition, isoindigo derivatives can be modified to form supramolecular structures with tunable morphologies for the use in drug delivery. Amphiphilic long-chain dialkylated isoindigos have the ability to form stable solid nanoparticles via a simple nanoprecipitation technique. Their self-assembly was investigated using tensiometry, dynamic light scattering, spectrophotometry, and fluorometry. The critical association concentrations and aggregate sizes were measured. The hydrophilic–lipophilic balance of alkylated isoindigo derivatives strongly influences aggregate morphology. In the case of short-chain dialkylated isoindigo derivatives, supramolecular polymers of 200 to 700 nm were formed. For long-chain dialkylated isoindigo derivatives, micellar aggregates of 100 to 200 nm were observed. Using micellar surfactant water-soluble forms of monosubstituted 1-hexadecylisoindigo as well as 1,1′-dimethylisoindigo were prepared for the first time. The formation of mixed micellar structures of different types in micellar anionic surfactant solutions (sodium dodecyl sulfate was determined. These findings are of practical importance and are of potential interest for the design of drug delivery systems and new nanomaterials.

  20. Structural Determinants of the Supramolecular Organization of G Protein-Coupled Receptors in Bilayers

    NARCIS (Netherlands)

    Periole, Xavier; Knepp, Adam M.; Sakmar, Thomas P.; Marrink, Siewert J.; Huber, Thomas

    2012-01-01

    The G protein-coupled receptor (GPCR) rhodopsin self-assembles into supramolecular structures in native bilayers, but the structural determinants of receptor oligomerization are not known. We carried out multiple self-assembly coarse-grained molecular dynamics (CGMD) simulations of model membranes

  1. Covalently stabilized self-assembled chlorophyll nanorods by olefin metathesis.

    Science.gov (United States)

    Sengupta, Sanchita; Würthner, Frank

    2012-06-11

    A new chlorophyll derivative with peripheral olefinic chains has been synthesised and its self-assembly properties have been studied, revealing formation of well-defined nanorods. These nanorods were stabilized and rigidified by olefin metathesis reaction as confirmed by spectroscopic and microscopic methods.

  2. Critical Self-assembly Concentration of Bolaamphiphilic Peptides ...

    African Journals Online (AJOL)

    The study of the self-assembly properties of peptides and proteins is important for the understanding of molecular recognition processes and for the rational design of functional biomaterials. Novel bolaamphiphilic peptides and peptide hybrids incorporating non-natural aminoacids were designed around a model ...

  3. Self-assembly of gibberellic amide assemblies and their applications in the growth and fabrication of ordered gold nanoparticles

    International Nuclear Information System (INIS)

    Smoak, Evan M; Carlo, Andrew D; Fowles, Catherine C; Banerjee, Ipsita A

    2010-01-01

    Gibberellins are a group of naturally occurring diterpenoid based phytohormones that play a vital role in plant growth and development. In this work, we have studied the self-assembly of gibberellic acid, a phytohormone, which belongs to the family of gibberellins, and designed amide derivatives of gibberellic acid (GA 3 ) for the facile, green synthesis of gold nanoparticles. It was found that the derivatives self-assembled into nanofibers and nanoribbons in aqueous solutions at varying pH. Further, upon incubation with tetrachloroaurate, the self-assembled GA 3 -amide derivatives efficiently nucleated and formed gold nanoparticles when heated to 60 deg. C. Energy dispersive x-ray spectroscopy, transmission electron microscopy and scanning electron microscopy analyses revealed that uniform coatings of gold nanoparticles in the 10-20 nm range were obtained at low pH on the nanowire surfaces without the assistance of additional reducing agents. This simple method for the development of morphology controlled gold nanoparticles using a plant hormone derivative opens doors for a new class of plant biomaterials which can efficiently yield gold nanoparticles in an environmentally friendly manner. The gold encrusted nanowires formed using biomimetic methods may lead on to the formation of conductive nanowires, which may be useful for a wide range of applications such as in optoelectronics and sensors. Further, the spontaneous formation of highly organized nanostructures obtained from plant phytohormone derivatives such as gibberellic acid is of particular interest as it might help in further understanding the supramolecular assembly mechanism of more highly organized biological structures.

  4. A new supramolecular chromium(III) complex: Synthesis, structural determination, optical study, magnetic and antibacterial activity

    Science.gov (United States)

    Dridi, Rihab; Dhieb, Cyrine; Cherni, Saoussen Namouchi; Boudjada, Nassira Chniba; Sadfi Zouaoui, Najla; Zid, Mohamed Faouzi

    2018-01-01

    A new chromium (III) complex 1,5-Naphthyridine Trans-diaquadioxalatochromate (III) dihydrate, had been synthesized by self-assembly of chromium (III) nitrate with oxalic acid and 1,5-Naphthyridine. The complex was characterized by X-ray diffraction, Fourier Transform Infrared spectroscopy, thermogravimetric analysis and UV-Visible spectroscopy. The crystal morphology was carried out using Bravais-Friedel-Donnay-Harker (BFDH) model. Single crystal X-Ray structure determination revealed that the complex posses two crystallographically independent Cr(III) centers. Each Cr(III) has a distorted octahedron geometry involving two axial O atoms from two water molecules and four equatorial O atoms from two oxalate dianions forming trans-[Cr(C2O4)2(H2O)2]- complex anions. The charge compensation is accomplished by the incorporation of 1,5-Naphthyridine cations. Connection between these entities is ensured by means of strong hydrogen bonds giving rise to 3D supramolecular architecture. Hirshfeld surface analysis and the related 2D fingerprint plots were used for decoding plausible intermolecular interactions in the crystal packing. The magnetic properties of the complex had been investigated and discussed in the context of its structure. The antimicrobial activity was evaluated by disc diffusion method highlighting an antagonistic effect of the synthesized complex against Gram-positive and Gram-negative species.

  5. Self-Assembly of Small Molecules for Organic Photovoltaic Applications

    Science.gov (United States)

    Aytun, Taner

    Organic photovoltaic (OPV) solar cells aim to provide efficient, flexible and lightweight photovoltaics (PV) with simple processing and low-cost. Advances in device optimization, structural and molecular design, as well as mechanistic understanding have helped increase device efficiency and performance. Within the framework of active layer optimization, systematically improving bulk heterojunction (BHJ) morphology could improve the power conversion efficiency of OPVs. However, most strategies aimed at improving morphology focus on annealing methods or the use of solvent additives. Rational approaches in supramolecular self-assembly can potentially offer additional control over the morphology of BHJ active layers and lead to improved power conversion efficiencies. In Chapter 2, the author explores the effect of molecular shape on the assembly of electron donating small molecules, and its ensuing effect on OPV performance. Two tripodal 'star-shaped' donor molecules with diketopyrrolopyrrole (DPP) side chains were used to generate solution-processed BHJ OPVs. It was found that the tripod molecules neither aggregate in solution nor form crystalline domains in thin films when a branched alkyl solubilizing group is used. On the other hand, linear alkyl chains promote the formation of one-dimensional (1D) nanowires and crystalline domains as well. This work demonstrated that the one-dimensional assembly of donor molecules enhances the performance of the corresponding solution-processed OPVs by 50%. This is attributed to the reduction of trap states in the 1D nanowires, resulting in a significant increase in the fill factor of the devices. In Chapter 3, experiments are described in which the electron donor is a hairpin-shaped molecule containing a trans-1,2-diamidocyclohexane core and two DPP conjugated segments, and a fullerene derivative as the electron acceptor. Self-assembly of the donor molecule is driven by the synergistic interaction between hydrogen bonds and pi

  6. Hierarchical self-assembly of complex polyhedral microcontainers

    International Nuclear Information System (INIS)

    Filipiak, David J; Leong, Timothy G; Gracias, David H; Azam, Anum

    2009-01-01

    The concept of self-assembly of a two-dimensional (2D) template to a three-dimensional (3D) structure has been suggested as a strategy to enable highly parallel fabrication of complex, patterned microstructures. We have previously studied the surface-tension-based self-assembly of patterned, microscale polyhedral containers (cubes, square pyramids and tetrahedral frusta). In this paper, we describe the observed hierarchical self-assembly of more complex, patterned polyhedral containers in the form of regular dodecahedra and octahedra. The hierarchical design methodology, combined with the use of self-correction mechanisms, was found to greatly reduce the propagation of self-assembly error that occurs in these more complex systems. It is a highly effective way to mass-produce patterned, complex 3D structures on the microscale and could also facilitate encapsulation of cargo in a parallel and cost-effective manner. Furthermore, the behavior that we have observed may be useful in the assembly of complex systems with large numbers of components

  7. The dynamic self-assembly of peptides into nanostructures

    Science.gov (United States)

    Perumal, Shiamalee

    Progress in the new and interdisciplinary field of biophysics holds great promise for new understandings and practical applications. Applying the methods of physics and chemistry to biological systems provides us with a valuable insight into the fundamental processes of life. In this study, the advanced physical techniques of neutron reflection and small-angle neutron scattering are applied to investigate the dynamic self-assembly of peptide systems at the solid-liquid and air-liquid interface, and in bulk solution. The characterisation of various peptides and an in-depth evaluation of their interfacial structural conformations and their outstanding ability to form well-defined nanostructures in aqueous solution will be presented in this thesis. The key adsorption factors of peptide concentration, solution pH, temperature, salt addition, and time were found to have imperative and varying effects on these self-assembled peptide structures. The hydrophobic nature of certain ?-sheet forming peptides resulted in an adsorption where the peptides were predominantly afloat on the surface of water. Point mutations of four other analogously designed peptides were reported to self-assemble into either ?-helix or ?-sheet secondary structures in order of increasing hydrophobicity. Short ionic peptides that had the potential to solubilise and stabilise membrane proteins were also discovered to self-assemble into aqueous solution to form a co-existing mixture of nanotube and nanovesicle structures of varying diversity with an unwavering bilayer wall thickness also consistent with interfacial structural parameters. These self-assembled peptide conformations were of course highly dependent on solution conditions and on the physical properties of the interface.

  8. Self-assembling peptide hydrogels immobilized on silicon surfaces

    International Nuclear Information System (INIS)

    Franchi, Stefano; Battocchio, Chiara; Galluzzi, Martina; Navisse, Emanuele; Zamuner, Annj; Dettin, Monica; Iucci, Giovanna

    2016-01-01

    The hydrogels of self-assembling ionic complementary peptides have collected in the scientific community increasing consensus as mimetics of the extracellular matrix that can offer 3D supports for cell growth or be vehicles for the delivery of stem cells or drugs. Such scaffolds have also been proposed as bone substitutes for small defects as they promote beneficial effects on human osteoblasts. In this context, our research deals with the introduction of a layer of self-assembling peptides on a silicon surface by covalent anchoring and subsequent physisorption. In this work, we present a spectroscopic investigation of the proposed bioactive scaffolds, carried out by surface-sensitive spectroscopic techniques such as XPS (X-ray photoelectron spectroscopy) and RAIRS (Reflection Absorption Infrared Spectroscopy) and by state-of-the-art synchrotron radiation methodologies such as angle dependent NEXAFS (Near Edge X-ray Absorption Fine Structure). XPS studies confirmed the change in the surface composition in agreement with the proposed enrichments, and led to assess the self-assembling peptide chemical stability. NEXAFS spectra, collected in angular dependent mode at the N K-edge, allowed to investigate the self-assembling behavior of the macromolecules, as well as to determine their molecular orientation on the substrate. Furthermore, Infrared Spectroscopy measurements demonstrated that the peptide maintains its secondary structure (β-sheet anti-parallel) after deposition on the silicon surface. The complementary information acquired by means of XPS, NEXAFS and RAIRS lead to hypothesize a “layer-by-layer” arrangement of the immobilized peptides, giving rise to an ordered 3D nanostructure. - Highlights: • A self-assembling peptide (SAP) was covalently immobilized of on a flat silicon surface. • A physisorbed SAP layer was grown on top of the covalently immobilized peptide layer. • Molecular order and orientation of the peptide overlayer on the flat silicon

  9. Composition and method for self-assembly and mineralization of peptide amphiphiles

    Science.gov (United States)

    Stupp, Samuel I [Chicago, IL; Beniash, Elia [Newton, MA; Hartgerink, Jeffrey D [Houston, TX

    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.

  10. Composition and method for self-assembly and mineralization of peptide-amphiphiles

    Science.gov (United States)

    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.

  11. Hierarchised luminescent organic architectures: design, synthesis, self-assembly, self-organisation and functions.

    Science.gov (United States)

    Maggini, Laura; Bonifazi, Davide

    2012-01-07

    This critical review aims at highlighting the prevailing supramolecular approaches employed nowadays in the preparation of luminescent hierarchised materials. Specifically, it has the ambition to illustrate how progresses in the control of the supramolecular interaction toolbox ultimately led to the development of spectacular luminescent nano- and micro-architectures, through a combination of molecular self-assembly and self-organisation processes involving organic π-conjugated molecules. The reader will be guided through a systematic exploration of the most common avenues to prepare and characterise luminescent self-assembled/self-organised materials embedded into one-, two- or three-dimensional networks, accompanied by a critical discussion of their main advantages and limitations. Key representative examples of this research field will be thoroughly described, with a particular focus on those systems displaying potential on the device application scene. Particular attention will be devoted to the design and synthetic approaches aimed at the preparation of the primary π-conjugated molecular modules, the chemical, structural and electronic properties of which dramatically influence the fate and the features of the self-assembled/self-organised material (215 references). This journal is © The Royal Society of Chemistry 2012

  12. Functionalized 2,6-bis-(2-anilinoethynyl) pyridine: Anion-mediated self-assembly and chemosensing

    Science.gov (United States)

    Stimpson, Calden Nathaniel Carroll

    Mimicking the simplicity and efficiency of Nature in the synthesis and design of non-covalent receptors for ions in solution has piqued the interest of the chemical community since the mid 20th century. Until recently most of that focus has been on the binding, sensing, or remediation of inorganic cations instead of their anionic counterparts. With the realization of the role anions play in biological function or dysfunction, the development of selective probes for these highly solvated and elusive targets has become an important goal in the chemical and biological communities. Concurrently the optoelectronic properties of planar extended pi-systems have been exploited in the development of novel light absorbing and emitting organics and carbon-rich materials with tunable optical outputs. While many of these compounds exhibit desirable sensor properties, their insolubility and non-specificity has hindered the inclusion of these materials in probes for biologically relevant substrates. This body of research seeks to combine our knowledge of supramolecular structure-function relationships with novel extended aromatic topologies to yield highly specific probes for anions in competitive media that exhibit discrete, tunable outputs upon interaction with their target substrates. Chapter I provides a brief overview of phenylacetylene topologies as they have been used in supramolecular assemblies and sensor design, with an emphasis on their use in anion-directed complexes. Chapter II focuses on our choice of specific arylethynylpyridine architectures upon which we can build a modular synthetic scheme to access working receptors. Chapter III encompasses the synthesis of urea and sulfonamide derivatives of phenylethynylpyridine and binding studies with these receptors and halide salts in organic media. Chapters IV and V focus upon the optoelectronic properties of these receptors, the tunability of their outputs and how we utilized their behavior in aqueous media to develop

  13. Temperature dependent coordinating self-assembly.

    Science.gov (United States)

    Wang, Yijie; Gao, Xuedong; Xiao, Yunlong; Zhao, Qiang; Yang, Jiang; Yan, Yun; Huang, Jianbin

    2015-04-14

    Self-assemblies dominated by coordination interaction are hardly responsive to thermal stimuli. We show that in case the coordinating mode changes with temperature, the resultant assemblies also exhibit temperature dependence. The self-assemblies are constructed with perylene tetracarboxylate and metal ions. Compounds containing a perylene skeleton often self-assemble into micro-belts, which is also true for the combination of perylene tetracarboxylate and metal ions. However, a unique pinecone structure was observed upon increasing the temperature of the coordinating system. The structural transition is triggered by the change of coordinating mode between the carboxylate group and the metal ion. At low temperature, intermolecular coordination occurs which favours the growth of the coordinating self-assembly along the long axis of the perylene. However, upon the elevation of temperature, the coordination is overwhelmed by intra-molecular mode. This is against the extension of the coordinating assembly due to the loss of connection between neighbouring perylenes. As a result, the pinecone structure is observed. We expect that the cases introduced in this work may inspire the design of structurally controllable temperature-dependent soft materials based on coordinating self-assembly.

  14. Self-assembled nanostructures in oxide ceramics

    Science.gov (United States)

    Ansari, Haris Masood

    Self-assembled nanoislands in the gadolinia-doped ceria (GDC)/ yttria-stabilized zirconia (YSZ) system have recently been discovered. This dissertation is an attempt to study the mechanism by which these nanoislands form. Nanoislands in the GDC/YSZ system form via a strain based mechanism whereby the stress accumulated in the GDC-doped surface layer on the YSZ substrate is relieved by creation of self-assembled nanoislands by a mechanism similar to the ATG instability. Unlike what was previously believed, a modified surface layer is not required prior to annealing, that is, this modification can occur during annealing by surface diffusion of dopants from the GDC sources (distributed on the YSZ surface in either lithographically defined patch or powder form) with simultaneous breakup, which occurs at the hold temperature independent of the subsequent cooling. Additionally, we have developed a simple powder based process of producing nanoislands which bypasses lithography and thin film deposition setups. The versatility of the process is apparent in the fact that it allows us to study the effect of experimental parameters such as soak time, temperature, cooling rate and the effect of powder composition on nanoisland properties in a facile way. With the help of this process, we have shown that nanoislands are not peculiar to Gd containing oxide source materials on YSZ substrates and can also be produced with other source materials such as La2O3, Nd2O3, Sm 2O3, Eu2O3, Tb2O3 and even Y2O3, which is already present in the substrate and hence simplifies the system further. We have extended our work to include YSZ substrates of the (110) surface orientation and have found that instead of nanoisland arrays, we obtain an array of parallel nanobars which have their long axes oriented along the [1-10] direction on the YSZ-(110) surface. STEM EDS performed on both the bars and the nanoislands has revealed that they are solid YSZ-rich solid solutions with the dopant species and

  15. Non-equilibrium supramolecular polymerization.

    Science.gov (United States)

    Sorrenti, Alessandro; Leira-Iglesias, Jorge; Markvoort, Albert J; de Greef, Tom F A; Hermans, Thomas M

    2017-09-18

    Supramolecular polymerization has been traditionally focused on the thermodynamic equilibrium state, where one-dimensional assemblies reside at the global minimum of the Gibbs free energy. The pathway and rate to reach the equilibrium state are irrelevant, and the resulting assemblies remain unchanged over time. In the past decade, the focus has shifted to kinetically trapped (non-dissipative non-equilibrium) structures that heavily depend on the method of preparation (i.e., pathway complexity), and where the assembly rates are of key importance. Kinetic models have greatly improved our understanding of competing pathways, and shown how to steer supramolecular polymerization in the desired direction (i.e., pathway selection). The most recent innovation in the field relies on energy or mass input that is dissipated to keep the system away from the thermodynamic equilibrium (or from other non-dissipative states). This tutorial review aims to provide the reader with a set of tools to identify different types of self-assembled states that have been explored so far. In particular, we aim to clarify the often unclear use of the term "non-equilibrium self-assembly" by subdividing systems into dissipative, and non-dissipative non-equilibrium states. Examples are given for each of the states, with a focus on non-dissipative non-equilibrium states found in one-dimensional supramolecular polymerization.

  16. Solvent Clathrate Driven Dynamic Stereomutation of a Supramolecular Polymer with Molecular Pockets.

    Science.gov (United States)

    Kulkarni, Chidambar; Korevaar, Peter A; Bejagam, Karteek K; Palmans, Anja R A; Meijer, E W; George, Subi J

    2017-10-04

    Control over the helical organization of synthetic supramolecular systems is intensively pursued to manifest chirality in a wide range of applications ranging from electron spin filters to artificial enzymes. Typically, switching the helicity of supramolecular assemblies involves external stimuli or kinetic traps. However, efforts to achieve helix reversal under thermodynamic control and to understand the phenomena at a molecular level are scarce. Here we present a unique example of helix reversal (stereomutation) under thermodynamic control in the self-assembly of a coronene bisimide that has a 3,5-dialkoxy substitution on the imide phenyl groups (CBI-35CH), leading to "molecular pockets" in the assembly. The stereomutation was observed only if the CBI monomer possesses molecular pockets. Detailed chiroptical studies performed in alkane solvents with different molecular structures reveal that solvent molecules intercalate or form clathrates within the molecular pockets of CBI-35CH at low temperature (263 K), thereby triggering the stereomutation. The interplay among the helical assembly, molecular pockets, and solvent molecules is further unraveled by explicit solvent molecular dynamics simulations. Our results demonstrate how the molecular design of self-assembling building blocks can orchestrate the organization of surrounding solvent molecules, which in turn dictates the helical organization of the resulting supramolecular assembly.

  17. Self-assembly of Renewable  Nano-sized Triterpenoids.

    Science.gov (United States)

    Bag, Braja Gopal; Majumdar, Rakhi

    2017-09-01

    Studies on plant metabolites have gained renewed interest in recent years because these can serve as renewable chemicals for the development of a sustainable society. Among various plant secondary metabolites, terpenoids constitute the major component and triterpenoids are the 30C subset of it. In recent years, triterpenoids have drawn the attention of scientific community due to many of its potential and realized applications in medicine, drug delivery, thermochromic materials, pollutant capture, catalysis, liquid crystals, etc. In this personal review, we have discussed our computational results carried out on sixty representative naturally occurring triterpenoids demonstrating that all the triterpenoids are renewable functional nano-entities. Study of the self-assembly of several triterpenoids such as betulin, betulinic acid, oleanolic acid, glycyrrhetinic acid and arjunolic acid and their derivatives in different liquids have also been discussed. Moreover, the utilization of the resulting supramolecular architectures such as vesicles, spheres, flowers and fibrillar networks of nano- to micrometer dimensions and gels have also been discussed in the perspective of green, renewable and nanos. © 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Remote control of self-assembled microswimmers

    Science.gov (United States)

    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.

  19. Self-assembling segmented coiled tubing

    Science.gov (United States)

    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.

  20. Sustained and controlled release of lipophilic drugs from a self-assembling amphiphilic peptide hydrogel

    DEFF Research Database (Denmark)

    Briuglia, Maria-Lucia; Urquhart, Andrew; Lamprou, Dimitrios A.

    2014-01-01

    . In this work, we have investigated the diffusion properties of Pindolol, Quinine and Timolol maleate from RADA16 in PBS and in BSS-PLUS at 37°C. A sustained, controlled, reproducible and efficient drug release has been detected for all the systems, which allows to understand the dependence of release kinetics......Materials which undergo self-assembly to form supramolecular structures can provide alternative strategies to drug loading problems in controlled release application. RADA 16 is a simple and versatile self-assembling peptide with a designed structure formed of two distinct surfaces, one hydrophilic...... and one hydrophobic that are positioned in such a well-ordered fashion allowing precise assembly into a predetermined organization. A "smart" architecture in nanostructures can represent a good opportunity to use RADA16 as a carrier system for hydrophobic drugs solving problems of drugs delivery...

  1. Enabling Light Work in Helical Self-Assembly for Dynamic Amplification of Chirality with Photoreversibility.

    Science.gov (United States)

    Cai, Yunsong; Guo, Zhiqian; Chen, Jianmei; Li, Wenlong; Zhong, Liubiao; Gao, Ya; Jiang, Lin; Chi, Lifeng; Tian, He; Zhu, Wei-Hong

    2016-02-24

    Light-driven transcription and replication are always subordinate to a delicate chirality transfer. Enabling light work in construction of the helical self-assembly with reversible chiral transformation becomes attractive. Herein we demonstrate that a helical hydrogen-bonded self-assembly is reversibly photoswitched between photochromic open and closed forms upon irradiation with alternative UV and visible light, in which molecular chirality is amplified with the formation of helixes at supramolecular level. The characteristics in these superhelixes such as left-handed or right-handed twist and helical length, height, and pitch are revealed by SEM and AFM. The helical photoswitchable nanostructure provides an easily accessible route to an unprecedented photoreversible modulation in morphology, fluorescence, and helicity, with precise assembly/disassembly architectures similar to biological systems such as protein and DNA.

  2. Unfolding a molecular trefoil derived from a zwitterionic metallopeptide to form self-assembled nanostructures

    KAUST Repository

    Zhang, Ye

    2015-02-19

    While used extensively by nature to control the geometry of protein structures, and dynamics of proteins, such as self-organization, hydration forces and ionic interactions received less attention for controlling the behaviour of small molecules. Here we describe the synthesis and characterization of a novel zwitterionic metallopeptide consisting of a cationic core and three distal anionic groups linked by self-assembling peptide motifs. 2D NMR spectra, total correlated spectroscopy and nuclear Overhauser effect spectroscopy, show that the molecule exhibits a three-fold rotational symmetry and adopts a folded conformation in dimethyl sulfoxide due to Coulombic forces. When hydrated in water, the molecule unfolds to act as a self-assembling building block of supramolecular nanostructures. By combining ionic interactions with the unique geometry from metal complex and hydrophobic interactions from simple peptides, we demonstrate a new and effective way to design molecules for smart materials through mimicking a sophisticated biofunctional system using a conformational switch.

  3. Zinc-Triggered Hydrogelation of Self-assembled Small Molecules to Inhibit Bacterial Growth

    Science.gov (United States)

    Xu, Chao; Cai, Yanbin; Ren, Chunhua; Gao, Jie; Hao, Jihui

    2015-01-01

    There is a significant need to develop antibacterial materials that could be applied locally and directly to the places surrounded by large amount of bacteria, in order to address the problems of bacterial antibiotic-resistance or irreversible biofilm formation. Hydrogels are thought to be suitable candidates due to their versatile applications in biomedical field. Among them, small molecular hydrogels have been paid lots of attention because they are easy to design and fabricate and often sensitive to external stimuli. Meanwhile, the antibacterial activity of metal ions are attracting more and more attention because resistance to them are not yet found within bacteria. We therefore designed the zinc ion binding peptide of Nap-GFFYGGGHGRGD, who can self-assemble into hydrogels after binds Zn2+ and inhibit the growth of bacteria due to the excellent antibacterial activity of Zn2+. Upon the addition of zinc ions, solutions containing Nap-GFFYGGGHGRGD transformed into supramolecular hydrogels composed of network of long nano-fibers. Bacterial tests revealed an antibacterial effect of the zinc triggered hydrogels on E. coli. The studied small molecular hydrogel shows great potential in locally addressing bacterial infections.

  4. Self-Assembled Monolayers for Dental Implants

    Directory of Open Access Journals (Sweden)

    Sidónio C. Freitas

    2018-01-01

    Full Text Available Implant-based therapy is a mature approach to recover the health conditions of patients affected by edentulism. Thousands of dental implants are placed each year since their introduction in the 80s. However, implantology faces challenges that require more research strategies such as new support therapies for a world population with a continuous increase of life expectancy, to control periodontal status and new bioactive surfaces for implants. The present review is focused on self-assembled monolayers (SAMs for dental implant materials as a nanoscale-processing approach to modify titanium surfaces. SAMs represent an easy, accurate, and precise approach to modify surface properties. These are stable, well-defined, and well-organized organic structures that allow to control the chemical properties of the interface at the molecular scale. The ability to control the composition and properties of SAMs precisely through synthesis (i.e., the synthetic chemistry of organic compounds with a wide range of functional groups is well established and in general very simple, being commercially available, combined with the simple methods to pattern their functional groups on complex geometry appliances, makes them a good system for fundamental studies regarding the interaction between surfaces, proteins, and cells, as well as to engineering surfaces in order to develop new biomaterials.

  5. From dynamic self-assembly to networked chemical systems.

    Science.gov (United States)

    Grzybowski, Bartosz A; Fitzner, Krzysztof; Paczesny, Jan; Granick, Steve

    2017-09-18

    Although dynamic self-assembly, DySA, is a relatively new area of research, the past decade has brought numerous demonstrations of how various types of components - on scales from (macro)molecular to macroscopic - can be arranged into ordered structures thriving in non-equilibrium, steady states. At the same time, none of these dynamic assemblies has so far proven practically relevant, prompting questions about the field's prospects and ultimate objectives. The main thesis of this Review is that formation of dynamic assemblies cannot be an end in itself - instead, we should think more ambitiously of using such assemblies as control elements (reconfigurable catalysts, nanomachines, etc.) of larger, networked systems directing sequences of chemical reactions or assembly tasks. Such networked systems would be inspired by biology but intended to operate in environments and conditions incompatible with living matter (e.g., in organic solvents, elevated temperatures, etc.). To realize this vision, we need to start considering not only the interactions mediating dynamic self-assembly of individual components, but also how components of different types could coexist and communicate within larger, multicomponent ensembles. Along these lines, the review starts with the discussion of the conceptual foundations of self-assembly in equilibrium and non-equilibrium regimes. It discusses key examples of interactions and phenomena that can provide the basis for various DySA modalities (e.g., those driven by light, magnetic fields, flows, etc.). It then focuses on the recent examples where organization of components in steady states is coupled to other processes taking place in the system (catalysis, formation of dynamic supramolecular materials, control of chirality, etc.). With these examples of functional DySA, we then look forward and consider conditions that must be fulfilled to allow components of multiple types to coexist, function, and communicate with one another within the

  6. From self-assembly fundamental knowledge to nanomedicine developments.

    Science.gov (United States)

    Monduzzi, Maura; Lampis, Sandrina; Murgia, Sergio; Salis, Andrea

    2014-03-01

    This review highlights the key role of NMR techniques in demonstrating the molecular aspects of the self-assembly of surfactant molecules that nowadays constitute the basic knowledge which modern nanoscience relies on. The aim is to provide a tutorial overview. The story of a rigorous scientific approach to understand self-assembly in surfactant systems and biological membranes starts in the early seventies when the progresses of SAXRD and NMR technological facilities allowed to demonstrate the existence of ordered soft matter, and the validity of Tanford approach concerning self-assembly at a molecular level. Particularly, NMR quadrupolar splittings, NMR chemical shift anisotropy, and NMR relaxation of dipolar and quadrupolar nuclei in micellar solutions, microemulsions, and liquid crystals proved the existence of an ordered polar-apolar interface, on the NMR time scale. NMR data, rationalized in terms of the two-step model of relaxation, allowed to quantify the dynamic aspects of the supramolecular aggregates in different soft matter systems. In addition, NMR techniques allowed to obtain important information on counterion binding as well as on size of the aggregate through molecular self-diffusion. Indeed NMR self-diffusion proved without any doubt the existence of bicontinuous microemulsions and bicontinuous cubic liquid crystals, suggested by pioneering and brilliant interpretation of SAXRD investigations. Moreover, NMR self-diffusion played a fundamental role in the understanding of microemulsion and emulsion nanostructures, phase transitions in phase diagrams, and particularly percolation phenomena in microemulsions. Since the nineties, globalization of the knowledge along with many other technical facilities such as electron microscopy, particularly cryo-EM, produced huge progresses in surfactant and colloid science. Actually we refer to nanoscience: bottom up/top down strategies allow to build nanodevices with applications spanning from ICT to food

  7. An improved layer-by-layer self-assembly technique to generate biointerfaces for platelet adhesion studies: Dynamic LbL

    Science.gov (United States)

    Lopez, Juan Manuel

    Layer-by-layer self-assembly (LbL) is a technique that generates engineered nano-scale films, coatings, and particles. These nanoscale films have recently been used in multiple biomedical applications. Concurrently, microfabrication methods and advances in microfluidics are being developed and combined to create "Lab-on-a-Chip" technologies. The potential to perform complex biological assays in vitro as a first-line screening technique before moving on to animal models has made the concept of lab on a chip a valuable research tool. Prior studies in the Biofluids Laboratory at Louisiana Tech have used layer-by-layer and in vitro biological assays to study thrombogenesis in a controlled, repeatable, engineered environment. The reliability of these previously established techniques was unsatisfactory for more complex cases such as chemical and shear stress interactions. The work presented in this dissertation was performed to test the principal assumptions behind the established laboratory methodologies, suggest improvements where needed, and test the impact of these improvements on accuracy and repeatability. The assumptions to be tested were: (1) The fluorescence microscopy (FM) images of acridine orange-tagged platelets accurately provide a measure of percent area of surface covered by platelets; (2) fibrinogen coatings can be accurately controlled, interact with platelets, and do not interfere with the ability to quantify platelet adhesion; and (3) the dependence of platelet adhesion on chemical agents, as measured with the modified methods, generally agrees with results obtained from our previous methods and with known responses of platelets that have been documented in the literature. The distribution of fibrinogen on the final LbL surface generated with the standard, static process (s-LbL) was imaged by tagging the fibrinogen with an anti-fibrinogen antibody bound to fluorescein isothiocyanate (FITC). FITC FM images and acridine orange FM images were taken

  8. Self-assembling bisphosphonates into nanofibers to enhance their inhibitory capacity on bone resorption

    Science.gov (United States)

    Tang, Anming; Qian, Yu; Liu, Shuang; Wang, Weijuan; Xu, Bing; Qin, An; Liang, Gaolin

    2016-05-01

    Osteoporosis (OP) is an important aging-related disease and the effective prevention/treatment of this disease remains challenging. Considering the acidic microenvironment of bone resorption lacunae, herein, we rationally designed two pamidronate (Pami)-derivative and alendronate (Alen)-derivative hydrogelators Pami-D and Alen-D which self-assemble into nanofibers to form supramolecular hydrogels under acidic conditions. Cell viability assay, osteoclastogenesis, osteoclastic gene expression, and in vitro bone resorption results indicated that both Pami-D and Alen-D have better inhibitory effects on osteoclastic formation and bone resorption than Pami and Alen, respectively. We anticipate that our new drugs Pami-D and Alen-D could ``smartly'' self-assemble and locally concentrate the drugs at bone resorption lacunae in vivo and subsequently prevent/treat osteoporosis more efficiently.Osteoporosis (OP) is an important aging-related disease and the effective prevention/treatment of this disease remains challenging. Considering the acidic microenvironment of bone resorption lacunae, herein, we rationally designed two pamidronate (Pami)-derivative and alendronate (Alen)-derivative hydrogelators Pami-D and Alen-D which self-assemble into nanofibers to form supramolecular hydrogels under acidic conditions. Cell viability assay, osteoclastogenesis, osteoclastic gene expression, and in vitro bone resorption results indicated that both Pami-D and Alen-D have better inhibitory effects on osteoclastic formation and bone resorption than Pami and Alen, respectively. We anticipate that our new drugs Pami-D and Alen-D could ``smartly'' self-assemble and locally concentrate the drugs at bone resorption lacunae in vivo and subsequently prevent/treat osteoporosis more efficiently. Electronic supplementary information (ESI) available: Experiment methods and details; syntheses and characterization of Pami-D and Alen-D; HPLC conditions; Fig. S1-S15, Schemes S1 and S2, Tables S1 and S2

  9. Bola-amphiphile self-assembly

    DEFF Research Database (Denmark)

    Svaneborg, Carsten

    2012-01-01

    Bola-amphiphiles are rod-like molecules where both ends of the molecule likes contact with water, while the central part of the molecule dislikes contact with water. What do such molecules do when they are dissolved in water? They self-assemble into micelles. This is a Dissipartive particle...

  10. Stabilization of Self-Assembled Alumina Mesophases

    NARCIS (Netherlands)

    Perez, Lidia Lopez; Perdriau, Sebastien; ten Brink, Gert; Kooi, Bart J.; Heeres, Hero Jan; Melian-Cabrera, Ignacio

    2013-01-01

    An efficient route to stabilize alumina mesophases derived from evaporation-induced self-assembly is reported after investigating various aspects in-depth: influence of the solvent (EtOH, s-BuOH, and t-BuOH) on the textural and structural properties of the mesophases based on aluminum

  11. Self-assembled nanogaps for molecular electronics

    International Nuclear Information System (INIS)

    Tang Qingxin; Tong Yanhong; Jain, Titoo; Hassenkam, Tue; Moth-Poulsen, Kasper; Bjoernholm, Thomas; Wan Qing

    2009-01-01

    A nanogap for molecular devices was realized using solution-based self-assembly. Gold nanorods were assembled to gold nanoparticle-coated conducting SnO 2 :Sb nanowires via thiol end-capped oligo(phenylenevinylene)s (OPVs). The molecular gap was easily created by the rigid molecule itself during self-assembly and the gap length was determined by the molecule length. The gold nanorods and gold nanoparticles, respectively covalently bonded at the two ends of the molecule, had very small dimensions, e.g. a width of ∼20 nm, and hence were expected to minimize the screening effect. The ultra-long conducting SnO 2 :Sb nanowires provided the bridge to connect one of the electrodes of the molecular device (gold nanoparticle) to the external circuit. The tip of the atomic force microscope (AFM) was contacted onto the other electrode (gold nanorod) for the electrical measurement of the OPV device. The conductance measurement confirmed that the self-assembly of the molecules and the subsequent self-assembly of the gold nanorods was a feasible method for the fabrication of the nanogap of the molecular devices.

  12. Self-assembly of patchy colloidal dumbbells

    NARCIS (Netherlands)

    Avvisati, Guido; Vissers, Teun; Dijkstra, Marjolein

    2015-01-01

    We employ Monte Carlo simulations to investigate the self-assembly of patchy colloidal dumbbells interacting via a modified Kern-Frenkel potential by probing the system concentration and dumbbell shape. We consider dumbbells consisting of one attractive sphere with diameter sigma(1) and one

  13. Self-assembled nanogaps for molecular electronics

    DEFF Research Database (Denmark)

    Tang, Qingxin; Tong, Yanhong; Jain, Titoo

    2009-01-01

    A nanogap for molecular devices was realized using solution-based self-assembly. Gold nanorods were assembled to gold nanoparticle-coated conducting SnO2:Sb nanowires via thiol end-capped oligo(phenylenevinylene)s (OPVs). The molecular gap was easily created by the rigid molecule itself during self...

  14. Bioinspired synthesis and self-assembly of hybrid organic–inorganic nanomaterials

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Honghu [Iowa State Univ., Ames, IA (United States)

    2016-12-17

    Nature is replete with complex organic–inorganic hierarchical materials of diverse yet specific functions. These materials are intricately designed under physiological conditions through biomineralization and biological self-assembly processes. Tremendous efforts have been devoted to investigating mechanisms of such biomineralization and biological self-assembly processes as well as gaining inspiration to develop biomimetic methods for synthesis and self-assembly of functional nanomaterials. In this work, we focus on the bioinspired synthesis and self-assembly of functional inorganic nanomaterials templated by specialized macromolecules including proteins, DNA and polymers. The in vitro biomineralization process of the magnetite biomineralizing protein Mms6 has been investigated using small-angle X-ray scattering. Templated by Mms6, complex magnetic nanomaterials can be synthesized on surfaces and in the bulk. DNA and synthetic polymers have been exploited to construct macroscopic two- and three-dimensional (2D and 3D) superlattices of gold nanocrystals. Employing X-ray scattering and spectroscopy techniques, the self-assembled structures and the self-assembly mechanisms have been studied, and theoretical models have been developed. Our results show that specialized macromolecules including proteins, DNA and polymers act as effective templates for synthesis and self-assembly of nanomaterials. These bottom-up approaches provide promising routes to fabricate hybrid organic–inorganic nanomaterials with rationally designed hierarchical structures, targeting specific functions.

  15. Self-assembled nanolaminate coatings (SV)

    Energy Technology Data Exchange (ETDEWEB)

    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

  16. Switching surface chemistry with supramolecular machines.

    Energy Technology Data Exchange (ETDEWEB)

    Dunbar, Timothy D.; Kelly, Michael James; Jeppesen, Jan O. (University of California, Los Angeles, CA); Bunker, Bruce Conrad; Matzke, Carolyn M.; Stoddart, J. Fraser; Huber, Dale L.; Kushmerick, James G.; Flood, Amar H. (University of California, Los Angeles, CA); Perkins, Julie (University of California, Los Angeles, CA); Cao, Jianguo (University of California, Los Angeles, CA)

    2005-07-01

    Tethered supramolecular machines represent a new class of active self-assembled monolayers in which molecular configurations can be reversibly programmed using electrochemical stimuli. We are using these machines to address the chemistry of substrate surfaces for integrated microfluidic systems. Interactions between the tethered tetracationic cyclophane host cyclobis(paraquat-p-phenylene) and dissolved {pi}-electron-rich guest molecules, such as tetrathiafulvalene, have been reversibly switched by oxidative electrochemistry. The results demonstrate that surface-bound supramolecular machines can be programmed to adsorb or release appropriately designed solution species for manipulating surface chemistry.

  17. The self-assembly mechanism of the Lindqvist anion [W6O19]2- in aqueous solution: a density functional theory study.

    Science.gov (United States)

    Lang, Zhong-Ling; Guan, Wei; Yan, Li-Kai; Wen, Shi-Zheng; Su, Zhong-Min; Hao, Li-Zhu

    2012-10-07

    The formation mechanism is always a fundamental and confused issue for polyoxometalate chemistry. Two formation mechanisms (M1 and M2) of the Lindqvist anion [W(6)O(19)](2-) have been adopted to investigate it's self-assembly reaction pathways at a density functional theory (DFT) level. The potential energy surfaces reveal that both the mechanisms are thermodynamically favorable and overall barrierless at room temperature, but M2 is slightly dominant to M1. The formation of the pentanuclear species [W(5)O(16)](2-) and [W(5)O(15)(OH)](-) are recognized as the rate-determining steps in the whole assembly polymerization processes. These two steps involve the highest energy barriers with 30.48 kcal mol(-1) and 28.90 kcal mol(-1), respectively, for M1 and M2. [W(4)O(13)](2-) and [W(4)O(12)(OH)](-) are proved to be the most stable building blocks. In addition, DFT results reveal that the formation of [W(3)O(10)](2-) experiences a lower barrier along the chain channel.

  18. Preparation and phase behaviour of surface-active pharmaceuticals: self-assembly of DNA and surfactants with membranes. Differential adiabatic scanning microcalorimetric study.

    Science.gov (United States)

    Süleymanoğlu, Erhan

    2005-08-01

    Some energetics issues relevant to preparation and surface characterization of zwitterionic phospholipid-DNA self-assemblies, as alternative models of the currently used problematic lipoplexes are presented. Nucleic acid compaction capacities of Mg(2+) and N-alkyl-N,N,N-trimetylammonium ions (C(n)TMA, n=12) were compared, with regard to surface interaction with unilamellar vesicles. Differential adiabatic scanning microcalorimetric measurements of synthetic phosphatidylcholine liposomes and calf thymus DNA and their ternary complexes with Mg(2+) and C(12)TMA, were employed for deduction of the thermodynamic model describing their structural transitions. Small monodisperce and highly stable complexes are established after precompaction of DNA with detergent, followed by addition of liposomes. In contrast, divalent metal cation-mediated aggregation of vesicles either leads to heterogeneous multilamellar DNA-lipid arrangements, or to DNA-induced bilayer destabilization and lipid fusion. Possible dependence of the cellular internalization and gene transfection efficiency on the structure and physicochemical properties of DNA-Mg(2+)-liposomes or DNA-cationic surfactant-liposome systems is emphasized by proposing the structure of their molecular self-organizations with further implications in gene transfer research.

  19. Adsorption and Fibrillization of Islet Amyloid Polypeptide at Self-Assembled Monolayers Studied by QCM-D, AFM, and PM-IRRAS.

    Science.gov (United States)

    Hajiraissi, Roozbeh; Hanke, Marcel; Yang, Yu; Duderija, Belma; Gonzalez Orive, Alejandro; Grundmeier, Guido; Keller, Adrian

    2018-03-20

    Aggregation and fibrillization of human islet amyloid polypeptide (hIAPP) plays an important role in the development of type 2 diabetes mellitus. Understanding the interaction of hIAPP with interfaces such as cell membranes at a molecular level therefore represents an important step toward new therapies. Here, we investigate the fibrillization of hIAPP at different self-assembled alkanethiol monolayers (SAMs) by quartz crystal microbalance with dissipation monitoring (QCM-D), atomic force microscopy (AFM), and polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). We find that hydrophobic interactions with the CH 3 -terminated SAM tend to retard hIAPP fibrillization compared to the carboxylic acid-terminated SAM where attractive electrostatic interactions lead to the formation of a three-dimensional network of interwoven fibrils. At the hydroxyl- and amino-terminated SAMs, fibrillization appears to be governed by hydrogen bonding between the peptide and the terminating groups which may even overcome electrostatic repulsion. These results thus provide fundamental insights into the molecular mechanisms governing amyloid assembly at interfaces.

  20. Use of self assembled monolayers at variable coverage to control interface bonding in a model study of interfacial fracture: Pure shear loading

    Energy Technology Data Exchange (ETDEWEB)

    KENT,MICHAEL S.; YIM,HYUN; MATHESON,AARON J.; COGDILL,C.; NELSON,GERALD C.; REEDY JR.,EARL DAVID

    2000-05-16

    The relationships between fundamental interfacial interactions, energy dissipation mechanisms, and fracture stress or fracture toughness in a glassy thermoset/inorganic solid joint are not well understood. This subject is addressed with a model system involving an epoxy adhesive on a polished silicon wafer containing its native oxide. The proportions of physical and chemical interactions at the interface, and the in-plane distribution, are varied using self-assembling monolayers of octadecyltrichlorosilane (ODTS). The epoxy interacts strongly with the bare silicon oxide surface, but forms only a very weak interface with the methylated tails of the ODTS monolayer. The fracture stress is examined as a function of ODTS coverage in the napkin-ring (pure shear) loading geometry. The relationship between fracture stress and ODTS coverage is catastrophic, with a large change in fracture stress occurring over a narrow range of ODTS coverage. This transition in fracture stress does not correspond to a wetting transition of the epoxy. Rather, the transition in fracture stress corresponds to the onset of deformation in the epoxy, or the transition from brittle to ductile fracture. The authors postulate that the transition in fracture stress occurs when the local stress that the interface can support becomes comparable to the yield stress of the epoxy. The fracture results are independent of whether the ODTS deposition occurs by island growth (T{sub dep} = 10 C) or by homogeneous growth (T{sub dep} = 24 C).

  1. Synthesis, structure, and magnetic studies on self-assembled BiFeO3-CoFe2O4 nanocomposite thin films

    Science.gov (United States)

    Muralidharan, R.; Dix, N.; Skumryev, V.; Varela, M.; Sánchez, F.; Fontcuberta, J.

    2008-04-01

    Self-assembled (0.65)BiFeO3-(0.35)CoFe2O4 (BFO-CFO) nanostructures were deposited on SrTiO3 (001) and (111) substrates by pulsed laser deposition at various temperatures from 500to800°C. The crystal phases and the lattice strain for the two different substrate orientations have been determined and compared. The films grow epitaxial on both substrates but separation of the spinel and perovskite crystallites, without parasitic phases, is only obtained for growth temperatures of around 600-650°C. The BFO crystallites are out-of-plane expanded on STO(001), whereas they are almost relaxed on (111). In contrast, CFO crystallites grow out-of-plane compressed on both substrates. The asymmetric behavior of the cell parameters of CFO and BFO is discussed on the basis of the role of the epitaxial stress caused by the substrate and the spinel-perovskite interfacial stress. It is concluded that interfacial stress dominates the elastic properties of CFO crystallites and thus it may play a fundamental on the interface magnetoelectric coupling in these nanocomposites.

  2. Combining supramolecular chemistry with biology.

    Science.gov (United States)

    Uhlenheuer, Dana A; Petkau, Katja; Brunsveld, Luc

    2010-08-01

    Supramolecular chemistry has primarily found its inspiration in biological molecules, such as proteins and lipids, and their interactions. Currently the supramolecular assembly of designed compounds can be controlled to great extent. This provides the opportunity to combine these synthetic supramolecular elements with biomolecules for the study of biological phenomena. This tutorial review focuses on the possibilities of the marriage of synthetic supramolecular architectures and biological systems. It highlights that synthetic supramolecular elements are for example ideal platforms for the recognition and modulation of proteins and cells. The unique features of synthetic supramolecular systems with control over size, shape, valency, and interaction strength allow the generation of structures fitting the demands to approach the biological problems at hand. Supramolecular chemistry has come full circle, studying the biology and its molecules which initially inspired its conception.

  3. Morphology-tunable and photoresponsive properties in a self-assembled two-component gel system.

    Science.gov (United States)

    Zhou, Yifeng; Xu, Miao; Yi, Tao; Xiao, Shuzhang; Zhou, Zhiguo; Li, Fuyou; Huang, Chunhui

    2007-01-02

    Photoresponsive C3-symmetrical trisurea self-assembling building blocks containing three azobenzene groups (LC10 and LC4) at the rim were designed and synthesized. By introducing a trisamide gelator (G18), which can self-aggregate through hydrogen bonds of acylamino moieties to form a fibrous network, the mixture of LC10 (or LC4) and G18 forms an organogel with coral-like supramolecular structure from 1,4-dioxane. The cooperation of hydrogen bonding and the hydrophobic diversity between these components are the main contributions to the specific superstructure. The two-component gel exhibits reversible photoisomerization from trans to cis transition without breakage of the gel state.

  4. Electrostatic Force Microscopy of Self Assembled Peptide Structures

    DEFF Research Database (Denmark)

    Clausen, Casper Hyttel; Dimaki, Maria; Pantagos, Spyros P.

    2011-01-01

    In this report electrostatic force microscopy (EFM) is used to study different peptide self-assembled structures, such as tubes and particles. It is shown that not only geometrical information can be obtained using EFM, but also information about the composition of different structures. In partic...... compared to the radius of the AFM tip used. Finally, an agreement between the detected signal and the structure of the hollow peptide tubes is demonstrated....

  5. DNA-Based Self-Assembly of Fluorescent Nanodiamonds.

    Science.gov (United States)

    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.

  6. Self-assembly of inorganic nanoparticles: Ab ovo

    Science.gov (United States)

    Kotov, Nicholas A.

    2017-09-01

    There are numerous remarkable studies related to the self-organization of polymers, coordination compounds, microscale particles, biomolecules, macroscale particles, surfactants, and reactive molecules on surfaces. The focus of this paper is on the self-organization of nanoscale inorganic particles or simply nanoparticles (NPs). Although there are fascinating and profound discoveries made with other self-assembling structures, the ones involving NPs deserve particular attention because they (a) are omnipresent in Nature; (b) have relevance to numerous disciplines (physics, chemistry, biology, astronomy, Earth sciences, and others); (c) embrace most of the features, geometries, and intricacies observed for the self-organization of other chemical species; (d) offer new tools for studies of self-organization phenomena; and (e) have a large economic impact, extending from energy and construction industries, to optoelectronics, biomedical technologies, and food safety. Despite the overall success of the field it is necessary to step back from its multiple ongoing research venues and consider two questions: What is self-assembly of nanoparticles? and Why do we need to study it? The reason to bring them up is to achieve greater scientific depth in the understanding of these omnipresent phenomena and, perhaps, deepen their multifaceted impact. Contribution to the Focus Issue Self-assemblies of Inorganic and Organic Nanomaterials edited by Marie-Paule Pileni.

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

    Science.gov (United States)

    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.

  8. Dispersion of nanoparticulate suspensions using self-assembled surfactant aggregates

    Science.gov (United States)

    Singh, Pankaj Kumar

    The dispersion of particles is critical for several industrial applications such as paints, inks, coatings, and cosmetics. Several emerging applications such as abrasives for precision polishing, and drug delivery systems are increasingly relying on nanoparticulates to achieve the desired performance. In the case of nanoparticles, the dispersion becomes more challenging because of the lack of fundamental understanding of dispersant adsorption and interparticle force prediction. Additionally, many of these processes use severe processing environments such as high normal forces (>100 mN/m), high shear forces (>10,000 s -1), and high ionic strengths (>0.1 M). Under such processing conditions, traditionally used dispersants based on electrostatics, and steric force repulsion mechanism may not be adequate. Hence, the development of optimally performing dispersants requires a fundamental understanding of the dispersion mechanism at the atomic/molecular scale. This study explores the use of self-assembled surfactant aggregates at the solid-liquid interface for dispersing nanoparticles in severe processing environments. Surfactant molecules can provide a feasible alternative to polymeric or inorganic dispersants for stabilizing ultrafine particles. The barrier to aggregation in the presence of surfactant molecules was measured using atomic force microscopy. The barrier heights correlated to suspension stability. To understand the mechanism for nanoparticulate suspension stability in the presence of surfactant films, the interface was characterized using zeta potential, contact angle, adsorption, and FT-IR (adsorbed surfactant film structure measurements). The effect of solution conditions such as pH and ionic strength on the suspension stability, and the self-assembled surfactant films was also investigated. It was determined that a transition from a random to an ordered orientation of the surfactant molecules at the interface was responsible for stability of

  9. Self-assembled discrete molecules for sensing nitroaromatics.

    Science.gov (United States)

    Shanmugaraju, Sankarasekaran; Mukherjee, Partha Sarathi

    2015-04-27

    Efficient sensing of trace amount nitroaromatic (NAC) explosives has become a major research focus in recent time due to concerns over national security as well as their role as environment pollutants. NO2 -containing electron-deficient aromatic compounds, such as picric acid (PA), trinitrotoluene (TNT), and dinitrotoluene (DNT), are the common constituents of many commercially available chemical explosives. In this article, we have summarized our recent developments on the rational design of electron-rich self-assembled discrete molecular sensors and their efficacy in sensing nitroaromatics both in solution as well as in vapor phase. Several π-electron-rich fluorescent metallacycles (squares, rectangles, and tweezers/pincers) and metallacages (trigonal and tetragonal prisms) have been synthesized by means of metal-ligand coordination-bonding interactions, with enough internal space to accommodate electron-deficient nitroaromatics at the molecular level by multiple supramolecular interactions. Such interactions subsequently result in the detectable fluorescence quenching of sensors even in the presence of trace quantities of nitroaromatics. The fascinating sensing characteristics of molecular architectures discussed in this article may enable future development of improved sensors for nitroaromatic explosives. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Physical characterization and in vivo pharmacokinetic study of self-assembling amphotericin B-loaded lecithin-based mixed polymeric micelles

    Directory of Open Access Journals (Sweden)

    Chen YC

    2015-12-01

    Full Text Available Ying-Chen Chen,* Chia-Yu Su,* Hua-Jun Jhan, Hsiu-O Ho, Ming-Thau Sheu School of Pharmacy, College of Pharmacy, Taipei Medical University, Taipei, Taiwan *These authors contributed equally to this work Abstract: To alleviate the inherent problems of amphotericin B (AmB, such as poor water solubility and nephrotoxicity, a novel self-assembling mixed polymeric micelle delivery system based on lecithin and combined with amphiphilic polymers, Pluronic®, Kolliphor®, d-alpha tocopheryl polyethylene glycol succinate, and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-methoxy(poly(ethylene glycol-2000 (DSPE-PEG2K was developed. An optimal formulation (Ambicelles composed of AmB:lecithin:DSPE-PEG2K in a 1:1:10 weight ratio was obtained. The particle size, polydispersion index, drug encapsulation efficiency, and drug loading were 187.20±10.55 nm, 0.51±0.017, 90.14%, and 7.51%, respectively, and the solubility was increased from 0.001 to 5 mg/mL. Compared with that of Fungizone®, the bioavailability of Ambicelles administered intravenously and orally increased 2.18- and 1.50-fold, respectively. Regarding the in vitro cytotoxicity, Ambicelles had a higher cell viability than free AmB solution or Fungizone® did. With pretreatment of 50 µg/mL ethanolic extract of Taiwanofungus camphoratus followed by AmB to HT29 colon cancer cells, the 50% inhibitory concentration of AmB solution was 12 µg/mL, whereas that of Ambicelles was 1 µg/mL, indicating that Ambicelles exerted a greater synergistic anticancer effect. Keywords: amphotericin B, micelle, amphiphilic polymer, lecithin, DSPE-PEG

  11. A Novel Strategy for Synthesis of Gold Nanoparticle Self Assemblies

    NARCIS (Netherlands)

    Verma, Jyoti; Lal, Sumit; van Veen, Henk A.; van Noorden, Cornelis J. F.

    2014-01-01

    Gold nanoparticle self assemblies are one-dimensional structures of gold nanoparticles. Gold nanoparticle self assemblies exhibit unique physical properties and find applications in the development of biosensors. Methodologies currently available for lab-scale and commercial synthesis of gold

  12. Intraligand Charge Transfer Sensitization on Self-Assembled Europium Tetrahedral Cage Leads to Dual-Selective Luminescent Sensing toward Anion and Cation.

    Science.gov (United States)

    Liu, Cui-Lian; Zhang, Rui-Ling; Lin, Chen-Sheng; Zhou, Li-Peng; Cai, Li-Xuan; Kong, Jin-Tao; Yang, Song-Qiu; Han, Ke-Li; Sun, Qing-Fu

    2017-09-13

    Luminescent supramolecular lanthanide edifices have many potential applications in biology, environments, and materials science. However, it is still a big challenge to improve the luminescent performance of multinuclear lanthanide assemblies in contrast to their mononuclear counterparts. Herein, we demonstrate that combination of intraligand charge transfer (ILCT) sensitization and coordination-driven self-assembly gives birth to bright Eu III tetrahedral cages with a record emission quantum yield of 23.1%. The ILCT sensitization mechanism has been unambiguously confirmed by both time-dependent density functional theory calculation and femtosecond transient absorption studies. Meanwhile, dual-responsive sensing toward both anions and cations has been demonstrated making use of the ILCT transition on the ligand. Without introduction of additional recognition units, high sensitivity and selectivity are revealed for the cage in both turn-off luminescent sensing toward I - and turn-on sensing toward Cu 2+ . This study offers important design principles for the future development of luminescent lanthanide molecular materials.

  13. Supramolecular structures constructed from three novel rare earth ...

    Indian Academy of Sciences (India)

    Three complexes assembled into 3D frameworks based on C-H··· O, O-H··· O hydrogen bond linkages. Keywords. Rare earth metal complex; crystal structure; hydrogen bonds; 3D supramolecular structure. 1. Introduction. The self-assembly of supramolecules via non-covalent bonds is currently an interesting topic of ...

  14. Ternary self-assemblies in water

    DEFF Research Database (Denmark)

    Hill, Leila R.; Blackburn, Octavia A.; Jones, Michael W.

    2013-01-01

    The self-assembly of higher order structures in water is realised by using the association of 1,3-biscarboxylates to binuclear meta-xylyl bridged DO3A complexes. Two dinicotinate binding sites are placed at a right-angle in a rhenium complex, which is shown to form a 1 : 2 complex with α,α'-bis(E......The self-assembly of higher order structures in water is realised by using the association of 1,3-biscarboxylates to binuclear meta-xylyl bridged DO3A complexes. Two dinicotinate binding sites are placed at a right-angle in a rhenium complex, which is shown to form a 1 : 2 complex with α...

  15. Self-assembling membranes and related methods thereof

    Science.gov (United States)

    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. Self-assembled granular towers

    Science.gov (United States)

    Pacheco-Vazquez, Felipe; Moreau, Florian; Vandewalle, Nicolas; Dorbolo, Stephan; GroupResearch; Applications in Statistical Physics Team

    2013-03-01

    When some water is added to sand, cohesion among the grains is induced. In fact, only 1% of liquid volume respect to the total pore space of the sand is necessary to built impressive sandcastles. Inspired on this experience, the mechanical properties of wet piles and sand columns have been widely studied during the last years. However, most of these studies only consider wet materials with less than 35% of liquid volume. Here we report the spontaneous formation of granular towers produced when dry sand is poured on a highly wet sand bed: The impacting grains stick on the wet grains due to instantaneous liquid bridges created during the impact. The grains become wet by the capillary ascension of water and the process continues, giving rise to stable narrow sand towers. Actually, the towers can reach the maximum theoretical limit of stability predicted by previous models, only expected for low liquid volumes. The authors would like to thank FNRS and Conacyt Mexico for financial support. FPV is a beneficiary of a movility grant from BELSPO/Marie Curie and the University of Liege.

  17. Self-assembled Nanomaterials for Chemotherapeutic Applications

    Science.gov (United States)

    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

  18. Self-assembly of polar food lipids.

    Science.gov (United States)

    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.

  19. Self-Assembly of Nanoparticle Surfactants

    Science.gov (United States)

    Lombardo, Michael T.

    Self-assembly utilizes non-covalent forces to organize smaller building blocks into larger, organized structures. Nanoparticles are one type of building block and have gained interest recently due to their unique optical and electrical properties which have proved useful in fields such as energy, catalysis, and advanced materials. There are several techniques currently used to self-assemble nanoparticles, each with its own set of benefits and drawbacks. Here, we address the limited number of techniques in non-polar solvents by introducing a method utilizing amphiphilic gold nanoparticles. Grafted polymer chains provide steric stabilization while small hydrophilic molecules induce assembly through short range attractive forces. The properties of these self-assembled structures are found to be dependent on the polymer and small molecules surface concentrations and chemistries. These particles act as nanoparticle surfactants and can effectively stabilize oil-water interfaces, such as in an emulsion. In addition to the work in organic solvent, similar amphiphilic particles in aqueous media are shown to effectively stabilize oil-in-water emulsions that show promise as photoacoustic/ultrasound theranostic agents.

  20. Application of self-consistent field theory to self-assembled bilayer membranes

    International Nuclear Information System (INIS)

    Zhang Ping-Wen; Shi An-Chang

    2015-01-01

    Bilayer membranes self-assembled from amphiphilic molecules such as lipids, surfactants, and block copolymers are ubiquitous in biological and physiochemical systems. The shape and structure of bilayer membranes depend crucially on their mechanical properties such as surface tension, bending moduli, and line tension. Understanding how the molecular properties of the amphiphiles determine the structure and mechanics of the self-assembled bilayers requires a molecularly detailed theoretical framework. The self-consistent field theory provides such a theoretical framework, which is capable of accurately predicting the mechanical parameters of self-assembled bilayer membranes. In this mini review we summarize the formulation of the self-consistent field theory, as exemplified by a model system composed of flexible amphiphilic chains dissolved in hydrophilic polymeric solvents, and its application to the study of self-assembled bilayer membranes. (topical review)

  1. Self-assembly and headgroup effect in nanostructured organogels via cationic amphiphile-graphene oxide composites.

    Directory of Open Access Journals (Sweden)

    Tifeng Jiao

    Full Text Available Self-assembly of hierarchical graphene oxide (GO-based nanomaterials with novel functions has received a great deal of attentions. In this study, nanostructured organogels based on cationic amphiphile-GO composites were prepared. The gelation behaviors of amphiphile-GO composites in organic solvents can be regulated by changing the headgroups of amphiphiles. Ammonium substituted headgroup in molecular structures in present self-assembled composites is more favorable for the gelation in comparison to pyridinium headgroup. A possible mechanism for headgroup effects on self-assembly and as-prepared nanostructures is proposed. It is believed that the present amphiphile-GO self-assembled system will provide an alternative platform for the design of new GO nanomaterials and soft matters.

  2. Distinct self-assembly of dithiol monolayers on Au(1 1 1) in water and hexane

    Science.gov (United States)

    Sharif, Aisyah M.; Laffir, Fathima R.; Buckley, D. Noel; Silien, Christophe

    2014-09-01

    The self-assembly of 1,4-benzenedimethanethiol on Au(1 1 1), at low concentration in water and in hexane which are respectively polar and non-polar solvent, has been studied by scanning tunneling microscopy (STM). The data reveal that, on clean Au(1 1 1), a complete and ordered self-assembled monolayer (SAM) of lying-down dithiols can form within a few seconds in water. While in hexane the adsorption is initially impeded by the rapid growth of an ordered hexane film that is gradually replaced by disordered domains of dithiol until completion of a saturated monolayer. Complemented by X-ray photoelectron spectroscopy measurements, the STM images resolve the progression of the self-assembly in both these polar and non-polar solvent, and highlight how the self-assembly depends on the trio solvent, dithiol, and substrate.

  3. Self-assembled peptide-based nanostructures: Smart nanomaterials toward targeted drug delivery.

    Science.gov (United States)

    Habibi, Neda; Kamaly, Nazila; Memic, Adnan; Shafiee, Hadi

    2016-02-01

    Self-assembly of peptides can yield an array of well-defined nanostructures that are highly attractive nanomaterials for many biomedical applications such as drug delivery. Some of the advantages of self-assembled peptide nanostructures over other delivery platforms include their chemical diversity, biocompatibility, high loading capacity for both hydrophobic and hydrophilic drugs, and their ability to target molecular recognition sites. Furthermore, these self-assembled nanostructures could be designed with novel peptide motifs, making them stimuli-responsive and achieving triggered drug delivery at disease sites. The goal of this work is to present a comprehensive review of the most recent studies on self-assembled peptides with a focus on their "smart" activity for formation of targeted and responsive drug-delivery carriers.

  4. Combustion and self-assembly of nanoenergetic materials

    Science.gov (United States)

    Malchi, Jonathan Yaniv

    The recent worldwide interest in nanotechnology spans a wide variety of scientific fields such as electronics, biology, materials science and medicine. Because of their extremely small dimensions, nanoparticles demonstrate properties different from matter at larger scales. Understanding these unusual properties and utilizing them for macroscale devices is an overall goal for nanotechnology. Moreover, manipulating these small particles into organized structures is crucial for taking full advantage of what nanotechnology has to offer, however it has proven to be a difficult task. Recent work utilizing electrostatic forces shows great potential for the self-assembly of nanoparticles into organized two-dimensional and three-dimensional structures. Overall, this work examines how nanotechnology and self-assembly can benefit the field of energetic materials. Because of aluminum's high energy density and low cost, it has been used in the field of energetic materials for several decades. In order to achieve sufficient energy release rates, aluminum is typically manufactured as a powder having spherical particles with diameters on the micron scale. It is well-known that decreasing the original particle diameter of a fuel particle will increase the burning time and, thus, energy release rate. Therefore, aluminum particles have recently been made to have diameters on the nanoscale, and shown to be advantageous for several applications. The combustion of nanoaluminum (nAl) in various systems is the primary focus of this study. A progression of experiments is used to analyze the combustion of nAl: (1) a fully heterogeneous flame spread system, (2) a semi-homogeneous sonicated thermite system and (3) a quasi-homogeneous self-assembled thermite system. The flame spread experiment physically separates the nAl from the gaseous oxidizer allowing for a well-understood convective, diffusive, reactive system to be analyzed. Because of the simplicity of the experimental setup, variables

  5. Morphological Evolution of Self-Assembled Structures Induced by the Molecular Architecture of Supra-Amphiphiles.

    Science.gov (United States)

    Wang, Juan; Li, Boxuan; Wang, Xing; Yang, Fei; Shen, Hong; Wu, Decheng

    2016-12-27

    A series of telechelic supramolecular amphiphiles [POSS-Azo 8 @(β-CD-PDMAEMA) 1→8 ] was accomplished by orthogonally coupling the multiarm host polymer β-cyclodextrin-poly(dimethylaminoethyl methacrylate) (β-CD-PDMAEMA) with an octatelechelic guest molecule azobenzene modified-polyhedral oligomeric silsesquioxanes (POSS-Azo 8 ) under different host-guest ratios. These telechelic supramolecular amphiphiles possess a rigid core and flexible corona. Increasing the multiarm host polymer coupled onto the rigid POSS core made the molecular architecture tend to be symmetrical and spherical. POSS-Azo 8 @[β-CD-PDMAEMA] 1→8 could self-assemble into diverse morphologies evolving from spherical micelles, wormlike micelles, and branched aggregates to bowl-shaped vesicles. Distinct from the traditional linear amphiphilic polymers, we discovered that the self-assembly of POSS-Azo 8 @[β-CD-PDMAEMA] 1→8 was dominantly regulated by their molecular architectures instead of hydrophilicity, which has also been verified using computer simulation results.

  6. Synthesis and Characterization of Stimuli Responsive Block Copolymers, Self-Assembly Behavior and Applications

    Energy Technology Data Exchange (ETDEWEB)

    Determan, Michael Duane [Iowa State Univ., Ames, IA (United States)

    2005-12-17

    The central theme of this thesis work is to develop new block copolymer materials for biomedical applications. While there are many reports of stimuli-responsive amphiphilic [19-21] and crosslinked hydrogel materials [22], the development of an in situ gel forming, pH responsive pentablock copolymer is a novel contribution to the field, Figure 1.1 is a sketch of an ABCBA pentablock copolymer. The A blocks are cationic tertiary amine methacrylates blocked to a central Pluronic F127 triblock copolymer. In addition to the prerequisite synthetic and macromolecular characterization of these new materials, the self-assembled supramolecular structures formed by the pentablock were experimentally evaluated. This synthesis and characterization process serves to elucidate the important structure property relationships of these novel materials, The pH and temperature responsive behavior of the pentablock copolymer were explored especially with consideration towards injectable drug delivery applications. Future synthesis work will focus on enhancing and tuning the cell specific targeting of DNA/pentablock copolymer polyplexes. The specific goals of this research are: (1) Develop a synthetic route for gel forming pentablock block copolymers with pH and temperature sensitive properties. Synthesis of these novel copolymers is accomplished with ATRP, yielding low polydispersity and control of the block copolymer architecture. Well defined macromolecular characteristics are required to tailor the phase behavior of these materials. (2) Characterize relationship between the size and shape of pentablock copolymer micelles and gel structure and the pH and temperature of the copolymer solutions with SAXS, SANS and CryoTEM. (3) Evaluate the temperature and pH induced phase separation and macroscopic self-assembly phenomenon of the pentablock copolymer. (4) Utilize the knowledge gained from first three goals to design and formulate drug delivery formulations based on the multi

  7. Self assembly of rectangular shapes on concentration programming and probabilistic tile assembly models.

    Science.gov (United States)

    Kundeti, Vamsi; Rajasekaran, Sanguthevar

    2012-06-01

    Efficient tile sets for self assembling rectilinear shapes is of critical importance in algorithmic self assembly. A lower bound on the tile complexity of any deterministic self assembly system for an n × n square is [Formula: see text] (inferred from the Kolmogrov complexity). Deterministic self assembly systems with an optimal tile complexity have been designed for squares and related shapes in the past. However designing [Formula: see text] unique tiles specific to a shape is still an intensive task in the laboratory. On the other hand copies of a tile can be made rapidly using PCR (polymerase chain reaction) experiments. This led to the study of self assembly on tile concentration programming models. We present two major results in this paper on the concentration programming model. First we show how to self assemble rectangles with a fixed aspect ratio ( α:β ), with high probability, using Θ( α + β ) tiles. This result is much stronger than the existing results by Kao et al. (Randomized self-assembly for approximate shapes, LNCS, vol 5125. Springer, Heidelberg, 2008) and Doty (Randomized self-assembly for exact shapes. In: proceedings of the 50th annual IEEE symposium on foundations of computer science (FOCS), IEEE, Atlanta. pp 85-94, 2009)-which can only self assembly squares and rely on tiles which perform binary arithmetic. On the other hand, our result is based on a technique called staircase sampling . This technique eliminates the need for sub-tiles which perform binary arithmetic, reduces the constant in the asymptotic bound, and eliminates the need for approximate frames (Kao et al. Randomized self-assembly for approximate shapes, LNCS, vol 5125. Springer, Heidelberg, 2008). Our second result applies staircase sampling on the equimolar concentration programming model (The tile complexity of linear assemblies. In: proceedings of the 36th international colloquium automata, languages and programming: Part I on ICALP '09, Springer-Verlag, pp 235

  8. Nanostructure to microstructure self-assembly of aliphatic polyurethanes: the effect on mechanical properties.

    Science.gov (United States)

    Mishra, Abhinay; Aswal, Vinod K; Maiti, Pralay

    2010-04-29

    We report the step by step self-assembly from nanostructure to microstructure (bottom-up approach through X-ray diffraction (1.6 nm), small angle neutron scattering (SANS) (11.6 nm), atomic force microscopy (70 nm smaller crystallite from enlarged image and 450 nm greater crystallites), and polarizing optical microscope (2 microm)) of aliphatic polyurethanes (PU) in contrast to aromatic polyurethanes depending on hard segment content (HSC). Polyurethanes of 10 to 80% HSC have been synthesized by using appropriate amount of polyol and chain extender. The effect of self-assembled patterns on mechanical properties both in solid and liquid state has been established exhibiting structure-property relationship of supramolecular polyurethanes. The crystallinity enhances but the degradation temperature decreases with increasing HSC. The characteristic length (measure of gap between lamellar crystallites), as revealed from SANS, gradually decreases with increasing HSC suggesting compactness of the crystallites through extensive hydrogen bonding. The Young's modulus increases with increasing HSC with a percolation threshold of hard segment (50%) while the toughness improves up to 30% HSC followed by gradual decrease in presence of bigger crystallites which promote brittle fracture. The origin of self-assembly in aliphatic PUs has been demonstrated through electronic structure calculations to form a loop structure with minimum intermolecular distance (2.2 A) while that distance is quite large in aromatic polyurethanes (4.6 A) that cannot form hydrogen bonds. The unique splintering of domain structure and its subsequent reformation under dynamic shear experiment has been established.

  9. Disassembly of Bacterial Biofilms by the Self-Assembled Glycolipids Derived from Renewable Resources.

    Science.gov (United States)

    Prasad, Yadavali Siva; Miryala, Sandeep; Lalitha, Krishnamoorthy; Ranjitha, K; Barbhaiwala, Shehnaz; Sridharan, Vellaisamy; Maheswari, C Uma; Srinandan, C S; Nagarajan, Subbiah

    2017-11-22

    More than 80% of chronic infections of bacteria are caused by biofilms. It is also a long-term survival strategy of the pathogens in a nonhost environment. Several amphiphilic molecules have been used in the past to potentially disrupt biofilms; however, the involvement of multistep synthesis, complicated purification and poor yield still remains a major problem. Herein, we report a facile synthesis of glycolipid based surfactant from renewable feedstocks in good yield. The nature of carbohydrate unit present in glycolipid influence the ring chain tautomerism, which resulted in the existence of either cyclic structure or both cyclic and acyclic structures. Interestingly, these glycolipids self-assemble into gel in highly hydrophobic solvents and vegetable oils, and displayed foam formation in water. The potential application of these self-assembled glycolipids to disrupt preformed biofilm was examined against various pathogens. It was observed that glycolipid 6a disrupts Staphylococcus aureus and Listeria monocytogenes biofilm, while the compound 6c was effective in disassembling uropathogenic E. coli and Salmonella enterica Typhimurium biofilms. Altogether, the supramolecular self-assembled materials, either as gel or as surfactant solution could be potentially used for surface cleansing in hospital environments or the food processing industries to effectively reduce pathogenic biofilms.

  10. Nanoscale protein arrays of rich morphologies via self-assembly on chemically treated diblock copolymer surfaces

    International Nuclear Information System (INIS)

    Song Sheng; Milchak, Marissa; Zhou Hebing; Lee, Thomas; Hanscom, Mark; Hahm, Jong-in

    2013-01-01

    Well-controlled assembly of proteins on supramolecular templates of block copolymers can be extremely useful for high-throughput biodetection. We report the adsorption and assembly characteristics of a model antibody protein to various polystyrene-block-poly(4-vinylpyridine) templates whose distinctive nanoscale structures are obtained through time-regulated exposure to chloroform vapor. The strong adsorption preference of the protein to the polystyrene segment in the diblock copolymer templates leads to an easily predictable, controllable, rich set of nanoscale protein morphologies through self-assembly. We also demonstrate that the chemical identities of various subareas within individual nanostructures can be readily elucidated by investigating the corresponding protein adsorption behavior on each chemically distinct area of the template. In our approach, a rich set of intricate nanoscale morphologies of protein arrays that cannot be easily attained through other means can be generated straightforwardly via self-assembly of proteins on chemically treated diblock copolymer surfaces, without the use of clean-room-based fabrication tools. Our approach provides much-needed flexibility and versatility for the use of block copolymer-based protein arrays in biodetection. The ease of fabrication in producing well-defined and self-assembled templates can contribute to a high degree of versatility and simplicity in acquiring an intricate nanoscale geometry and spatial distribution of proteins in arrays. These advantages can be extremely beneficial both for fundamental research and biomedical detection, especially in the areas of solid-state-based, high-throughput protein sensing. (paper)

  11. All-Atom Multiscale Molecular Dynamics Theory and Simulation of Self-Assembly, Energy Transfer and Structural Transition in Nanosystems

    Science.gov (United States)

    Espinosa Duran, John Michael

    The study of nanosystems and their emergent properties requires the development of multiscale computational models, theories and methods that preserve atomic and femtosecond resolution, to reveal details that cannot be resolved experimentally today. Considering this, three long time scale phenomena were studied using molecular dynamics and multiscale methods: self-assembly of organic molecules on graphite, energy transfer in nanosystems, and structural transition in vault nanoparticles. Molecular dynamics simulations of the self-assembly of alkoxybenzonitriles with different tail lengths on graphite were performed to learn about intermolecular interactions and phases exhibited by self-organized materials. This is important for the design of ordered self-assembled organic photovoltaic materials with greater efficiency than the disordered blends. Simulations revealed surface dynamical behaviors that cannot be resolved experimentally today due to the lack of spatiotemporal resolution. Atom-resolved structures predicted by simulations agreed with scanning tunneling microscopy images and unit cell measurements. Then, a multiscale theory based on the energy density as a field variable is developed to study energy transfer in nanoscale systems. For applications like photothermal microscopy or cancer phototherapy is required to understand how the energy is transferred to/from nanosystems. This multiscale theory could be applied in this context and here is tested for cubic nanoparticles immersed in water for energy being transferred to/from the nanoparticle. The theory predicts the energy transfer dynamics and reveals phenomena that cannot be described by current phenomenological theories. Finally, temperature-triggered structural transitions were revealed for vault nanoparticles using molecular dynamics and multiscale simulations. Vault is a football-shaped supramolecular assembly very distinct from the commonly observed icosahedral viruses. It has very promising

  12. Graphene controlled H- and J-stacking of perylene dyes into highly stable supramolecular nanostructures for enhanced photocurrent generation

    DEFF Research Database (Denmark)

    Gan, Shiyu; Zhong, Lijie; Engelbrekt, Christian

    2014-01-01

    We report a new method for controlling H- and J-stacking in supramolecular self-assembly. Graphene nanosheets act as structure inducers to direct the self-assembly of a versatile organic dye, perylene into two distinct types of functional nanostructures, i.e. one-dimensional nanotubes via J-stack......-junction solar cells.......We report a new method for controlling H- and J-stacking in supramolecular self-assembly. Graphene nanosheets act as structure inducers to direct the self-assembly of a versatile organic dye, perylene into two distinct types of functional nanostructures, i.e. one-dimensional nanotubes via J......-stacking and two-dimensional branched nanobuds through H-stacking. Graphene integrated supramolecular nanocomposites are highly stable and show significant enhancement of photocurrent generation in these two configurations of photosensing devices, i.e. solid-state optoelectronic constructs and liquid...

  13. pH-Dependent In-Cell Self-Assembly of Peptide Inhibitors Increases the Anti-Prion Activity While Decreasing the Cytotoxicity.

    Science.gov (United States)

    Waqas, Muhammad; Jeong, Woo-Jin; Lee, Young-Joo; Kim, Dae-Hwan; Ryou, Chongsuk; Lim, Yong-Beom

    2017-03-13

    The first step in the conventional approach to self-assembled biomaterials is to develop well-defined nanostructures in vitro, which is followed by disruption of the preformed nanostructures at the inside of the cell to achieve bioactivity. Here, we propose an inverse strategy to develop in-cell gain-of-function self-assembled nanostructures. In this approach, the supramolecular building blocks exist in a unimolecular/unordered state in vitro or at the outside of the cell and assemble into well-defined nanostructures after cell internalization. We used block copolypeptides of an oligoarginine and a self-assembling peptide as building blocks and investigated correlations among the nanostructural state, antiprion bioactivity, and cytotoxicity. The optimal bioactivity (i.e., the highest antiprion activity and lowest cytotoxicity) was obtained when the building blocks existed in a unimolecular/unordered state in vitro and during the cell internalization process, exerting minimal cytotoxic damage to cell membranes, and were subsequently converted into high-charge-density vesicles in the low pH endosome/lysosomes in vivo, thus, resulting in the significantly enhanced antiprion activity. In particular, the in-cell self-assembly concept presents a feasible approach to developing therapeutics against protein misfolding diseases. In general, the in-cell self-assembly provides a novel inverse methodology to supramolecular bionanomaterials.

  14. Analysis of supramolecular surface nanostructures using secondary ion mass spectrometry (poster)

    International Nuclear Information System (INIS)

    Halaszova, S.; Velic, D.

    2013-01-01

    Our system consists of host molecules β-cyclodextrin (C 42 H 70 O 35 ), of implemented Iron nanoparticles (guest). Whole supramolecular complex is placed on a gold substrate. In our project we work with monotiolated β-cyclodextrin (C 42 H 70 O 34 S), consisting of seven α-D-1-4 glucopyranose units. Cyclodextrins have been selected deliberately because of their ability to form inclusion complexes .They are also capable of forming structures similar to self-assembly monolayers. To study the formation of these supramolecular surface nanostructures mass secondary ion spectrometry is used. With this technique fragmentation of monotiolated β-cyclodextrin and the presence of the supramolecular complex on a gold surface can be examined. The observed fragments of monotiolated cyclodextrines films can be divided into three groups: Au X H Y S Z , fragments originating from cyclodextrin molecules associated with Au. Fragments as (C 42 H 70 O 34 S)Na + , (C 42 H 70 O 35 )Na + and (AuC 42 H 69 O 34 S)Na + were identified as well as fragments thereof in cationized form with K + . The main objective of the project is a detailed study and preparation of supramolecular nanostructures consisting of complex guest-host monotiolated β-cyclodextrin host-iron), and a gold substrate. (Authors)

  15. Exploiting Biocatalysis in the Synthesis of Supramolecular Polymers

    Science.gov (United States)

    Roy, Sangita; Ulijn, Rein V.

    This chapter details the exploitation of biocatalysis in generating supramolecular polymers. This approach provides highly dynamic supramolecular structures, inspired by biological polymeric systems found in the intra- and extracellular space. The molecular design of the self-assembling precursors is discussed in terms of enzyme recognition, molecular switching mechanisms and non-covalent interactions that drive the supramolecular polymerisation process, with an emphasis on aromatic peptide amphiphiles. We discuss a number of unique features of these systems, including spatiotemporal control of nucleation and growth of supramolecular polymers and the possibility of kinetically controlling mechanical properties. Fully reversible systems that operate under thermodynamic control allow for defect correction and selection of the most stable structures from mixtures of monomers. Finally, a number of potential applications of enzymatic supramolecular polymerisations are discussed in the context of biomedicine and nanotechnology.

  16. Structures of self-assembled amphiphilic peptide-heterodimers: effects of concentration, pH, temperature and ionic strength

    KAUST Repository

    Luo, Zhongli

    2010-01-01

    The amphiphilic double-tail peptides AXG were studied regarding secondary structure and self-assembly in aqueous solution. The two tails A = Ala 6 and G = Gly6 are connected by a central pair X of hydrophilic residues, X being two aspartic acids in ADG, two lysines in AKG and two arginines in ARG. The peptide AD (Ala6Asp) served as a single-tail reference. The secondary structure of the four peptides was characterized by circular dichroism spectroscopy under a wide range of peptide concentrations (0.01-0.8 mM), temperatures (20-98 °C), pHs (4-9.5) and ionic strengths. In salt-free water both ADG and AD form a β-sheet type of structure at high concentration, low pH and low temperature, in a peptide-peptide driven assembly of individual peptides. The transition has a two-state character for ADG but not for AD, which indicates that the added tail in ADG makes the assembly more cooperative. By comparison the secondary structures of AKG and ARG are comparatively stable over the large range of conditions covered. According to dynamic light scattering the two-tail peptides form supra-molecular aggregates in water, but high-resolution AFM-imaging indicate that ordered (self-assembled) structures are only formed when salt (0.1 M NaCl) is added. Since the CD-studies indicate that the NaCl has only a minor effect on the peptide secondary structure we propose that the main role of the added salt is to screen the electrostatic repulsion between the peptide building blocks. According to the AFM images ADG and AKG support a correlation between nanofibers and a β-sheet or unordered secondary structure, whereas ARG forms fibers in spite of lacking β-sheet structure. Since the AKG and ARG double-tail peptides self-assemble into distinct nanostructures while their secondary structures are resistant to environment factors, these new peptides show potential as robust building blocks for nano-materials in various medical and nanobiotechnical applications. © 2010 The Royal Society

  17. Supramolecular polymers

    National Research Council Canada - National Science Library

    Ciferri, A

    2000-01-01

    ... to the new class of self-assembled polymers that undergo reversible growth by the formation of noncovalent bonds. This class (Part II) is wider than expected: not only mainchain assemblies of hydrogen-bonded repeating units, but also planar organization of S-layer proteins, micellar and related three-dimensional structures of blo...

  18. Self-assembled nanostructures of oligopyridine molecules.

    Science.gov (United States)

    Ziener, Ulrich

    2008-11-27

    The high potential of self-assembly processes of molecular building blocks is reflected in the vast variety of different functional nanostructures reported in the literature. The constituting units must fulfill several requirements like synthetic accessibility, presence of functional groups for appropriate intermolecular interactions and depending on the type of self-assembly processsignificant chemical and thermal stability. It is shown that oligopyridines are versatile building blocks for two- and three-dimensional (2D and 3D) self-assembly. They can be employed for building up different architectures like gridlike metal complexes in solution. By the appropriate tailoring of the heterocycles, further metal coordinating and/or hydrogen bonding capabilities to the heteroaromatic molecules can be added. Thus, the above-mentioned architectures can be extended in one-step processes to larger entities, or in a hierarchical fashion to infinite assemblies in the solid state, respectively. Besides the organizational properties of small molecules in solution, 2D assemblies on surfaces offer certain advantages over 3D arrays. By precise tailoring of the molecular structures, the intermolecular interactions can be fine-tuned expressed by a large variety of resulting 2D patterns. Oligopyridines prove to be ideal candidates for 2D assemblies on graphite and metal sufaces, respectively, expressing highly ordered structures. A slight structural variation in the periphery of the molecules leads to strongly changed 2D packing motifs based on weak hydrogen bonding interactions. Such 2D assemblies can be exploited for building up host-guest networks which are attractive candidates for manipulation experiments on the single-molecule level. Thus, "erasing" and "writing" processes by the scanning tunneling microscopy (STM) tip at the liquid/solid interface are shown. The 2D networks are also employed for performing coordination chemistry experiments at surfaces.

  19. Self-assembly of colloidal surfactants

    Science.gov (United States)

    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)

  20. Self-assembled silicon oxide nanojunctions

    International Nuclear Information System (INIS)

    Lin, L W; Tang, Y H; Chen, C S

    2009-01-01

    Novel silicon oxide nanojunction structures with various shapes, such as X type, Y type, T type, ringlike and treelike, are fabricated in a self-assembled manner by the hydrothermal method without any metallic catalyst. In the silicon oxide nanojunctions, both the silicon oxide nanowire part and the junction part consist of the same chemical composition, forming homogeneous homojunctions and being made suitable for application in nanoscale optoelectronics devices. The formation of silicon oxide nanojunctions may be influenced by the surrounding environment in the reaction kettle, growth space among the silicon oxide nanowires and the weight of SiO droplets at the growth tip.

  1. Supramolecular Chemistry

    Indian Academy of Sciences (India)

    antigen interactions. working in different areas such as chemical science, biological science, physical science, material science and so on. On the whole, supramolecular chemistry focuses on two over- lapping areas, 'supramolecules' and ...

  2. Self-assembling peptides form nanodiscs that stabilize membrane proteins

    DEFF Research Database (Denmark)

    Midtgaard, Søren Roi; Pedersen, Martin Cramer; Kirkensgaard, Jacob Judas Kain

    2014-01-01

    New methods to handle membrane bound proteins, e.g. G-protein coupled receptors (GPCRs), are highly desirable. Recently, apoliprotein A1 (ApoA1) based lipoprotein particles have emerged as a new platform for studying membrane proteins, and it has been shown that they can self-assemble in combinat......New methods to handle membrane bound proteins, e.g. G-protein coupled receptors (GPCRs), are highly desirable. Recently, apoliprotein A1 (ApoA1) based lipoprotein particles have emerged as a new platform for studying membrane proteins, and it has been shown that they can self...

  3. Construction and Systematical Symmetric Studies of a Series of Supramolecular Clusters with Binary or Ternary Ammonium Triphenylacetates.

    Science.gov (United States)

    Sasaki, Toshiyuki; Ida, Yoko; Yuge, Tetsuharu; Yamamoto, Atsushi; Hisaki, Ichiro; Tohnai, Norimitsu; Miyata, Mikiji

    2016-02-15

    Functions of clusters in nano or sub-nano scale significantly depend on not only kinds of their components but also arrangements, or symmetry, of their components. Therefore, the arrangements in the clusters have been precisely characterized, especially for metal complexes. Contrary to this, characterizations of molecular arrangements in supramolecular clusters composed of organic molecules are limited to a few cases. This is because construction of the supramolecular clusters, especially obtaining a series of the supramolecular clusters, is difficult due to low stability of non-covalent bonds compare to covalent bonds. From this viewpoint, utilization of organic salts is one of the most useful strategies. A series of the supramolecules could be constructed by combinations of a specific organic molecule with various counter ions. Especially, primary ammonium carboxylates are suitable as typical examples of supramolecules because various kinds of carboxylic acids and primary amines are commercially available, and it is easy to change their combinations. Previously, it was demonstrated that primary ammonium triphenylacetates using various kinds of primary amines specifically construct supramolecular clusters, which are composed of four ammoniums and four triphenylacetates assembled by charge-assisted hydrogen bonds, in crystals obtained from non-polar solvents. This study demonstrates an application of the specific construction of the supramolecular clusters as a strategy to conduct systematical symmetric study for clarification of correlations between molecular arrangements in supramolecules and kinds and numbers of their components. In the same way with binary salts composed of triphenylacetates and one kind of primary ammoniums, ternary organic salts composed of triphenylacetates and two kinds of ammoniums construct the supramolecular clusters, affording a series of the supramolecular clusters with various kinds and numbers of the components.

  4. Self-Assembled Pyridine-Dipyrrolate Cages.

    Science.gov (United States)

    Zhang, Huacheng; Lee, Juhoon; Lammer, Aaron D; Chi, Xiaodong; Brewster, James T; Lynch, Vincent M; Li, Hao; Zhang, Zhan; Sessler, Jonathan L

    2016-04-06

    An inherently nonlinear pyridine dipyrrolate ligand, namely 2,6-bis(3,4-diethyl-5-carboxy-1H-pyrrol-2yl)pyridine (compound 1), is able to distinguish between different zinc(II) cation sources, namely Zn(acac)2 and Zn(OAc)2, respectively. This differentiation is manifest both in terms of the observed fluorescent behavior in mixed organic media and the reaction chemistry. Treatment of 1 with Zn(acac)2 gives rise to a cage dimer, cage-1, wherein two molecules of compound 1 act as double bridging units to connect two individual cage subunits. As inferred from X-ray crystallographic studies, this cage system consists of discrete zinc dimers with hydroxide bridges that, with the assistance of bound DMF solvent molecules, serve to fix the geometry and orientation of the pyridine dipyrrolate building blocks. When a different zinc source, Zn(OAc)2, is used to carry out an ostensibly similar complexation reaction with compound 1, an acetate-bridged 1D abacus-like cage polymer is obtained as inferred from X-ray diffraction analysis. This extended solid state structure, cage-2, contains individual zinc dimer cage submits and appears stabilized by solvent molecules (DMF) and the counteranion (acetate). Rod-like assemblies are also observed by DLS and SEM. This construct, in contrast to cage-1, proved fluorescent in mixed organic media. The structure of the ligand itself (i.e., in the absence of Zn(II)) was confirmed by X-ray crystallographic analysis and was found to assemble into a supramolecular polymer. Conversion to a dimer form was seen upon the addition of TBAOAc. On the basis of the metric parameters, the structures seen in the solid state are stabilized via hydrogen bonding interactions involving solvent molecules.

  5. Acceleration of Amide Bond Rotation by Encapsulation in the Hydrophobic Interior of a Water-Soluble Supramolecular Assembly

    Energy Technology Data Exchange (ETDEWEB)

    Pluth, Michael D.; Bergman, Robert G.; Raymond, Kenneth N.

    2008-04-08

    The hydrophobic interior cavity of a self-assembled supramolecular assembly exploits the hydrophobic effect for the encapsulation of tertiary amides. Variable temperature 1H NMR experiments reveal that the free energy barrier for rotation around the C-N amide bond is lowered by up to 3.6 kcal/mol upon encapsulation. The hydrophobic cavity of the assembly is able to stabilize the less polar transition state of the amide rotation process. Carbon-13 labeling studies showed that the {sup 13}C NMR carbonyl resonance increases with temperature for the encapsulated amides which suggests that the assembly is able to favor a twisted for of the amide.

  6. Understanding the self-assembly of TCNQ on Cu(111)

    DEFF Research Database (Denmark)

    Stradi, Daniele; Borca, Bogdana; Barja, Sara

    2016-01-01

    The structure of self-assembled monolayers of 7,7',8,8'-tetracyano-p-quinodimethane (TCNQ) adsorbed on Cu(111) has been studied using a combination of scanning tunnelling microscopy (STM) experiments and density functional theory (DFT) calculations. We show that the polymorphism of the self...... perpendicular to the other. Conversely, when the substrate is held at room temperature during deposition and slightly annealed afterwards, a more complex structure with five molecules per unit cell is formed. DFT calculations complement the experimental results by revealing that the building blocks of the two...

  7. Self-assembled manganese oxide structures through direct oxidation

    KAUST Repository

    Zhao, Chao

    2012-12-01

    The morphology and phase of self-assembled manganese oxides during different stages of thermal oxidation were studied. Very interesting morphological patterns of Mn oxide films were observed. At the initial oxidation stage, the surface was characterized by the formation of ring-shaped patterns. As the oxidation proceeded to the intermediate stage, concentric plates formed to relax the compressive stress. Our experimental results gave a clear picture of the evolution of the structures. We also examined the properties of the structures. © 2012 Elsevier B.V.

  8. Homochiral Evolution in Self-Assembled Chiral Polymers and Block Copolymers.

    Science.gov (United States)

    Wen, Tao; Wang, Hsiao-Fang; Li, Ming-Chia; Ho, Rong-Ming

    2017-04-18

    The significance of chirality transfer is not only involved in biological systems, such as the origin of homochiral structures in life but also in man-made chemicals and materials. How the chiral bias transfers from molecular level (molecular chirality) to helical chain (conformational chirality) and then to helical superstructure or phase (hierarchical chirality) from self-assembly is vital for the chemical and biological processes in nature, such as communication, replication, and enzyme catalysis. In this Account, we summarize the methodologies for the examination of homochiral evolution at different length scales based on our recent studies with respect to the self-assembly of chiral polymers and chiral block copolymers (BCPs*). A helical (H*) phase to distinguish its P622 symmetry from that of normal hexagonally packed cylinder phase was discovered in the self-assembly of BCPs* due to the chirality effect on BCP self-assembly. Enantiomeric polylactide-containing BCPs*, polystyrene-b-poly(l-lactide) (PS-PLLA) and polystyrene-b-poly(d-lactide) (PS-PDLA), were synthesized for the examination of homochiral evolution. The optical activity (molecular chirality) of constituted chiral repeating unit in the chiral polylactide is detected by electronic circular dichroism (ECD) whereas the conformational chirality of helical polylactide chain can be explicitly determined by vibrational circular dichroism (VCD). The H* phases of the self-assembled polylactide-containing BCPs* can be directly visualized by 3D transmission electron microscopy (3D TEM) technique at which the handedness (hierarchical chirality) of the helical nanostructure is thus determined. The results from the ECD, VCD, and 3D TEM for the investigated chirality at different length scales suggest the homochiral evolution in the self-assembly of the BCPs*. For chiral polylactides, twisted lamellae in crystalline banded spherulite can be formed by dense packing scheme and effective interactions upon helical

  9. Quantifying quality in DNA self-assembly

    Science.gov (United States)

    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

  10. Supramolecular assembled three-dimensional graphene hybrids: Synthesis and applications in supercapacitors

    Energy Technology Data Exchange (ETDEWEB)

    Ni, Lubin [College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, Jiangsu (China); Zhang, Wang [College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, Jiangsu (China); Graduate School of Convergence Science and Technology, Seoul National University, Seoul, 151-742 (Korea, Republic of); Wu, Zhen; Sun, Chunyu; Cai, Yin; Yang, Guang; Chen, Ming [College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, Jiangsu (China); Piao, Yuanzhe, E-mail: parkat9@snu.ac.kr [Graduate School of Convergence Science and Technology, Seoul National University, Seoul, 151-742 (Korea, Republic of); Diao, Guowang, E-mail: gwdiao@yzu.edu.cn [College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, Jiangsu (China)

    2017-02-28

    Graphical abstract: Supramolecular assembled three-dimensdional graphene-based architectures were built by host-guest interactions of β-cyclodextrin polymers(β-CDPs) with adamantine end-capped poly(ethylene oxide) polymer linker (PEG-AD), exhibit significantly improved electrochemical performances of supercapacitor in terms of high specific capacitance, remarkable rate capability, and excellent cycling stability compared to pristine reduced graphene oxide. - Highlights: • Supramolecular assembled three-Dimensional (3D) graphene was first fabricated by host-guest interactions of β-CDPs with PEG-AD linkers. • The incorporation of PEG-AD linker into rGO sheets can provide efficient 3D electron transfer pathways and ion diffusion channels. • The 3D self-assembled graphene exhibits high specific capacitance, remarkable rate capability, and excellent cycling stability. • This study shed new lights to design 3D self-assembled graphene materials and their urgent applications in energy storage. - Abstract: Graphene-based materials have received worldwide attention in the focus of forefront energy storage investigations. Currently, the design of novel three-dimensional (3D) graphene structures with high energy capability, superior electron and ion conductivity, and robust mechanical flexibility is still a great challenge. Herein, we have successfully demonstrated a novel approach to fabricate 3D assembled graphene through the supramolecular interactions of β-cyclodextrin polymers (β-CDP) with an adamantine end-capped poly(ethylene oxide) polymer linker (PEG-AD). The incorporation of PEG-AD linker into rGO sheets increased the interlayer spacing of rGO sheets to form 3D graphene materials, which can provide efficient 3D electron transfer pathways and ion diffusion channels, and facilitate the infiltration of gel electrolyte. The as-prepared 3D self-assembled graphene materials exhibit significantly improved electrochemical performances of supercapacitor in terms

  11. Supramolecular assembled three-dimensional graphene hybrids: Synthesis and applications in supercapacitors

    International Nuclear Information System (INIS)

    Ni, Lubin; Zhang, Wang; Wu, Zhen; Sun, Chunyu; Cai, Yin; Yang, Guang; Chen, Ming; Piao, Yuanzhe; Diao, Guowang

    2017-01-01

    Graphical abstract: Supramolecular assembled three-dimensdional graphene-based architectures were built by host-guest interactions of β-cyclodextrin polymers(β-CDPs) with adamantine end-capped poly(ethylene oxide) polymer linker (PEG-AD), exhibit significantly improved electrochemical performances of supercapacitor in terms of high specific capacitance, remarkable rate capability, and excellent cycling stability compared to pristine reduced graphene oxide. - Highlights: • Supramolecular assembled three-Dimensional (3D) graphene was first fabricated by host-guest interactions of β-CDPs with PEG-AD linkers. • The incorporation of PEG-AD linker into rGO sheets can provide efficient 3D electron transfer pathways and ion diffusion channels. • The 3D self-assembled graphene exhibits high specific capacitance, remarkable rate capability, and excellent cycling stability. • This study shed new lights to design 3D self-assembled graphene materials and their urgent applications in energy storage. - Abstract: Graphene-based materials have received worldwide attention in the focus of forefront energy storage investigations. Currently, the design of novel three-dimensional (3D) graphene structures with high energy capability, superior electron and ion conductivity, and robust mechanical flexibility is still a great challenge. Herein, we have successfully demonstrated a novel approach to fabricate 3D assembled graphene through the supramolecular interactions of β-cyclodextrin polymers (β-CDP) with an adamantine end-capped poly(ethylene oxide) polymer linker (PEG-AD). The incorporation of PEG-AD linker into rGO sheets increased the interlayer spacing of rGO sheets to form 3D graphene materials, which can provide efficient 3D electron transfer pathways and ion diffusion channels, and facilitate the infiltration of gel electrolyte. The as-prepared 3D self-assembled graphene materials exhibit significantly improved electrochemical performances of supercapacitor in terms

  12. Self-assembly, Self-organization, Nanotechnology and vitalism

    OpenAIRE

    Bensaude Vincent, Bernadette

    2009-01-01

    International audience; Over the past decades, self-assembly has attracted a lot of research attention and transformed the relations between chemistry, materials science and biology. The paper explores the impact of the current interest in self-assembly techniques on the traditional debate over the nature of life. The first section describes three different research programs of self-assembly in nanotechnology in order to characterize their metaphysical implications: -1- Hybridization ( using ...

  13. Supramolecular chemistry-general principles and selected examples from anion recognition and metallosupramolecular chemistry.

    Science.gov (United States)

    Albrecht, Markus

    2007-12-01

    This review gives an introduction into supramolecular chemistry describing in the first part general principles, focusing on terms like noncovalent interaction, molecular recognition, self-assembly, and supramolecular function. In the second part those will be illustrated by simple examples from our laboratories. Supramolecular chemistry is the science that bridges the gap between the world of molecules and nanotechnology. In supramolecular chemistry noncovalent interactions occur between molecular building blocks, which by molecular recognition and self-assembly form (functional) supramolecular entities. It is also termed the "chemistry of the noncovalent bond." Molecular recognition is based on geometrical complementarity based on the "key-and-lock" principle with nonshape-dependent effects, e.g., solvatization, being also highly influential. Self-assembly leads to the formation of well-defined aggregates. Hereby the overall structure of the target ensemble is controlled by the symmetry features of the certain building blocks. Finally, the aggregates can possess special properties or supramolecular functions, which are only found in the ensemble but not in the participating molecules. This review gives an introduction on supramolecular chemistry and illustrates the fundamental principles by recent examples from our group.

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

    Science.gov (United States)

    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.

  15. Self-assembly of colloids with magnetic caps

    Energy Technology Data Exchange (ETDEWEB)

    Novak, E.V., E-mail: ekaterina.novak@urfu.ru [Ural Federal University, Lenin Av. 51, Ekaterinburg (Russian Federation); Kantorovich, S.S. [Ural Federal University, Lenin Av. 51, Ekaterinburg (Russian Federation); University of Vienna, Sensengasse 8, Vienna (Austria)

    2017-06-01

    In our earlier work (Steinbach et al., 2016 ) we investigated a homogeneous system of magnetically capped colloidal particles that self-assembled via two structural patterns of different symmetry. The particles could form a compact, equilateral triangle with a three-fold rotational symmetry and zero dipole moment and a staggered chain with mirror symmetry with a net magnetisation perpendicular to the chain. The system exhibited a bistability already in clusters of three particles. Based on observations of a real magnetic particles system, analytical calculations and molecular dynamics simulations, it has been shown that the bistability is a result of an anisotropic magnetisation distribution with rotational symmetry inside the particles. The present study is a logical extension of the above research and forms a preparatory stage for the study of a self-assembly of such magnetic particles under the influence of an external magnetic field. Since the magnetic field is only an additive contribution to the total ground state energy, we can study the interparticle interaction energies of candidate ground state structures based on the field-free terms. - Highlights: • Analytical calculations of the energies of ground state candidates for colloids with magnetic caps. • Computer simulations confirmed the theoretical model. • The structural transition between ground states was found.

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

    Science.gov (United States)

    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

  17. Designing self-assembling 3D structures of microcapsules

    Science.gov (United States)

    Li, Like; Shum, Henry; Shklyaev, Oleg; Yashin, Victor; Balazs, Anna

    Self-assembly of complex, three-dimensional structures is commonly achieved by biological cells but difficult to realize in synthetic systems with micron-scale or larger components. Some previous modeling studies have considered only the planar self-assembly of microcapsules on a substrate. In this work, nanoparticles released from the capsules bind to the substrate and to the shells of nearby capsules. The non-uniform nanoparticle deposition on a capsule's surface leads to adhesion gradients, which drive the capsules to effectively ``climb'' on top of one another and self-organize in the vertical direction. We determine conditions that favor this structural organization. In particular, we study how the vertical structuring depends on the background fluid flow, the topography of the microcapsules and the underlying surface, the capsule-capsule interaction and that between the capsules and the substrate. The findings can provide design rules for the autonomous creation of novel nanocomposites, where the layers are formed from nanoparticle-containing and nanoparticle-decorated microcapsules.

  18. Self-assembly of dodecaphenyl POSS thin films

    Science.gov (United States)

    Handke, Bartosz; Klita, Łukasz; Niemiec, Wiktor

    2017-12-01

    The self-assembly abilities of Dodecaphenyl Polyhedral Oligomeric Silsesquioxane thin films on Si(1 0 0) surfaces were studied. Due to their thermal properties - relatively low sublimation temperature and preservation of molecular structure - cage type silsesquioxanes are ideal material for the preparation of a thin films by Physical Vapor Deposition. The Ultra-High Vacuum environment and the deposition precision of the PVD method enable the study of early stages of thin film growth and its molecular organization. X-ray Reflectivity and Atomic Force Microscopy measurements allow to pursuit size-effects in the structure of thin films with thickness ranges from less than a single molecular layer up to several tens of layers. Thermal treatment of the thin films triggered phase change: from a poorly ordered polycrystalline film into a well-ordered multilayer structure. Self-assembly of the layers is the effect of the π-stacking of phenyl rings, which force molecules to arrange in a superlattice, forming stacks of alternating organic-inorganic layers.

  19. Hierarchical Self-Assembly of Light Guided Spinning Microgears

    Science.gov (United States)

    Aubret, Antoine; Youssef, Mena; Sacanna, Stefano; Palacci, Jeremie; Sacanna Group, NYU Team

    2017-11-01

    In this work, we demonstrate the self-assembly of microgears obtained from the guided construction of tailored self-propelled particles used as primary building blocks. The experiment relies on our control of phoretic phenomena: the migration of particles in a solute gradient. We activate a photocatalytic material, the hematite, and trigger the decomposition of hydrogen peroxide to set concentration gradient. We use this effect to engineer phototactic swimmers, attracted to the region of high illumination. We guide the swimmers to form robust and highly persistent microgears. They interact with each other through hydrodynamics and diffusiophoretically through the chemical clouds of fuel consumption. Multiple rotors are studied and we specifically address the dynamics of two rotors. We show that the microgears move collectively or synchronize thanks to the interaction of their chemical clouds. Increasing the number of microrotors (N = 2 - 7), we form an active crystal which can rotate, re-organize, change shape, and exhibit phase synchronization between its individual components. Such crystal made of non-equilibrium rotating gears at the microscale is unique. Our study paves the way for better understanding and control of emergent phenomena in collection of active spinning particles. It is a promising avenue for the creation of cutting-edge materials using emergent behavior from hierarchical self-assembly to unveil untapped functionalities. This work is supported by NSF CAREER DMR 1554724.

  20. Controlling water evaporation through self-assembly.

    Science.gov (United States)

    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.

  1. Shape Restoration by Active Self-Assembly

    Directory of Open Access Journals (Sweden)

    D. Arbuckle

    2005-01-01

    Full Text Available Shape restoration is defined as the problem of constructing a desired, or goal, solid shape Sg by growing an initial solid Si, which is a subset of the goal but is otherwise unknown. This definition attempts to capture abstractly a situation that often arises in the physical world when a solid object loses its desired shape due to wear and tear, corrosion or other phenomena. For example, if the top of the femur becomes distorted, the hip joint no longer functions properly and may have to be replaced surgically. Growing it in place back to its original shape would be an attractive alternative to replacement. This paper presents a solution to the shape restoration problem by using autonomous assembly agents (robots that self-assemble to fill the volume between Sg and Si. If the robots have very small dimension (micro or nano, the desired shape is approximated with high accuracy. The assembly agents initially execute a random walk. When two robots meet, they may exchange a small number of messages. The robot behavior is controlled by a finite state machine with a small number of states. Communication contact models chemical communication, which is likely to be the medium of choice for robots at the nanoscale, while small state and small messages are limitations that also are expected of nanorobots. Simulations presented here show that swarms of such robots organize themselves to achieve shape restoration by using distributed algorithms. This is one more example of an interesting geometric problem that can be solved by the Active Self-Assembly paradigm introduced in previous papers by the authors.

  2. Combined atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and quartz crystal microbalance (QCM) studies of glucose oxidase (GOx) immobilised onto self-assembled monolayer on the gold film

    International Nuclear Information System (INIS)

    Losic, D.; Shapter, J.; Gooding, J.; Erokin, P.; Short, K.

    1999-01-01

    In fabrication of biosensors, self-assembled monolayers (SAM) are an attractive method of immobilising enzymes at electrode surface since it allows precise control over the amount and spatial distribution of the immobilized enzyme. The covalent attachment of glucose oxidase (GOx) to a carboxylic terminated SAM chemisorbed onto gold films was achieved via carbodiimide activation of the carboxylic acids to a reactive intermediate susceptible to nucleophilic attack by amines on free lysine chains of the enzyme. Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and quartz crystal microbalance (QCM) measurements were used for characterisation of GOx modified gold surfaces. Tapping mode AFM studies have revealed that GOx molecules form slightly disordered arrays of pentagonal or hexagonal clusters. Observed features of immobilised GOx are distributed as a submonolayer on the SAM surface which has allowed visualisation of native and unfolded enzyme structure. The presence of the SAM and enzyme on the gold surface was detected by XPS spectroscopy. Spectra show typical peaks for the C 1s, O 1s and N 1s regions. A kinetic study of the adsorption of GOx onto activated SAM using in-situ QCM allowed determination the amount of immobilised GOx on the layer and consequently the optimal immobilisation conditions. Performance parameters of the biosensor such as sensitivity to glucose concentration as a function of enzyme loading were evaluated amperometrically using the redox mediator p-benzoquinone

  3. Interfacial rheological properties of self-assembling biopolymer microcapsules.

    Science.gov (United States)

    Xie, Kaili; de Loubens, Clément; Dubreuil, Frédéric; Gunes, Deniz Z; Jaeger, Marc; Léonetti, Marc

    2017-09-20

    Tuning the mechanical properties of microcapsules through a cost-efficient route of fabrication is still a challenge. The traditional method of layer-by-layer assembly of microcapsules allows building a tailored composite multi-layer membrane but is technically complex as it requires numerous steps. The objective of this article is to characterize the interfacial rheological properties of self-assembling biopolymer microcapsules that were obtained in one single facile step. This thorough study provides new insights into the mechanics of these weakly cohesive membranes. Firstly, suspensions of water-in-oil microcapsules were formed in microfluidic junctions by self-assembly of two oppositely charged polyelectrolytes, namely chitosan (water soluble) and phosphatidic fatty acid (oil soluble). In this way, composite membranes of tunable thickness (between 40 and 900 nm measured by AFM) were formed at water/oil interfaces in a single step by changing the composition. Secondly, microcapsules were mechanically characterized by stretching them up to break-up in an extensional flow chamber which extends the relevance and convenience of the hydrodynamic method to weakly cohesive membranes. Finally, we show that the design of microcapsules can be 'engineered' in an extensive way since they present a wealth of interfacial rheological properties in terms of elasticity, plasticity and yield stress whose magnitudes can be controlled by the composition. These behaviors are explained by the variation of the membrane thickness with the physico-chemical parameters of the process.

  4. Self-assembled rosette nanotubes encapsulate and slowly release dexamethasone

    Directory of Open Access Journals (Sweden)

    Chen Y

    2011-05-01

    Full Text Available Yupeng Chen1,2, Shang Song2, Zhimin Yan3, Hicham Fenniri3, Thomas J Webster2,41Department of Chemistry, Brown University, Providence, RI, USA; 2School of Engineering, Brown University, Providence, RI, USA; 3National Institute for Nanotechnology and Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada; 4Department of Orthopedics, Brown University, Providence, RI, USAAbstract: Rosette nanotubes (RNTs are novel, self-assembled, biomimetic, synthetic drug delivery materials suitable for numerous medical applications. Because of their amphiphilic character and hollow architecture, RNTs can be used to encapsulate and deliver hydrophobic drugs otherwise difficult to deliver in biological systems. Another advantage of using RNTs for drug delivery is their biocompatibility, low cytotoxicity, and their ability to engender a favorable, biologically-inspired environment for cell adhesion and growth. In this study, a method to incorporate dexamethasone (DEX, an inflammatory and a bone growth promoting steroid into RNTs was developed. The drug-loaded RNTs were characterized using diffusion ordered nuclear magnetic resonance spectroscopy (DOSY NMR and UV-Vis spectroscopy. Results showed for the first time that DEX can be easily and quickly encapsulated into RNTs and released to promote osteoblast (bone-forming cell functions over long periods of time. As a result, RNTs are presented as a novel material for the targeted delivery of hydrophobic drugs otherwise difficult to deliver.Keywords: nanotubes, drug delivery, self-assembly, physiological conditions

  5. Synthesis and self-assembly of complex hollow materials

    KAUST Repository

    Zeng, Hua Chun

    2011-01-01

    Hollow materials with interiors or voids and pores are a class of lightweight nanostructured matters that promise many future technological applications, and they have received significant research attention in recent years. On the basis of well-known physicochemical phenomena and principles, for example, several solution-based protocols have been developed for the general preparation of these complex materials under mild reaction conditions. This article is thus a short introductory review on the synthetic aspects of this field of development. The synthetic methodologies can be broadly divided into three major categories: (i) template-assisted synthesis, (ii) self-assembly with primary building blocks, and (iii) induced matter relocations. In most cases, both synthesis and self-assembly are involved in the above processes. Further combinations of these methodologies appear to be very important, as they will allow one to prepare functional materials at a higher level of complexity and precision. The synthetic strategies are introduced through some simple case studies with schematic illustrations. Salient features of the methods developed have been summarized, and some urgent issues of this field have also been indicated. © 2011 The Royal Society of Chemistry.

  6. Aqueous Two Phase System Assisted Self-Assembled PLGA Microparticles

    Science.gov (United States)

    Yeredla, Nitish; Kojima, Taisuke; Yang, Yi; Takayama, Shuichi; Kanapathipillai, Mathumai

    2016-06-01

    Here, we produce poly(lactide-co-glycolide) (PLGA) based microparticles with varying morphologies, and temperature responsive properties utilizing a Pluronic F127/dextran aqueous two-phase system (ATPS) assisted self-assembly. The PLGA polymer, when emulsified in Pluronic F127/dextran ATPS, forms unique microparticle structures due to ATPS guided-self assembly. Depending on the PLGA concentration, the particles either formed a core-shell or a composite microparticle structure. The microparticles facilitate the simultaneous incorporation of both hydrophobic and hydrophilic molecules, due to their amphiphilic macromolecule composition. Further, due to the lower critical solution temperature (LCST) properties of Pluronic F127, the particles exhibit temperature responsiveness. The ATPS based microparticle formation demonstrated in this study, serves as a novel platform for PLGA/polymer based tunable micro/nano particle and polymersome development. The unique properties may be useful in applications such as theranostics, synthesis of complex structure particles, bioreaction/mineralization at the two-phase interface, and bioseparations.

  7. Distinct self-assembly of dithiol monolayers on Au(1 1 1) in water and hexane

    Energy Technology Data Exchange (ETDEWEB)

    Sharif, Aisyah M. [Department of Physics and Energy, University of Limerick (Ireland); Materials and Surface Science Institute, University of Limerick (Ireland); Laffir, Fathima R. [Materials and Surface Science Institute, University of Limerick (Ireland); Buckley, D. Noel [Department of Physics and Energy, University of Limerick (Ireland); Materials and Surface Science Institute, University of Limerick (Ireland); Silien, Christophe, E-mail: christophe.silien@ul.ie [Department of Physics and Energy, University of Limerick (Ireland); Materials and Surface Science Institute, University of Limerick (Ireland)

    2014-09-30

    Highlights: • The self-assembly of 1,4-benzenedimethanethiol in water and in hexane is studied. • The initial phase of assembly is revealed for each solvent using STM and XPS. • Water stabilizes an ordered lying-down phase. • Hexane coadsorbs with benzenedimethanethiol and promotes standing-up absorption. - Abstract: The self-assembly of 1,4-benzenedimethanethiol on Au(1 1 1), at low concentration in water and in hexane which are respectively polar and non-polar solvent, has been studied by scanning tunneling microscopy (STM). The data reveal that, on clean Au(1 1 1), a complete and ordered self-assembled monolayer (SAM) of lying-down dithiols can form within a few seconds in water. While in hexane the adsorption is initially impeded by the rapid growth of an ordered hexane film that is gradually replaced by disordered domains of dithiol until completion of a saturated monolayer. Complemented by X-ray photoelectron spectroscopy measurements, the STM images resolve the progression of the self-assembly in both these polar and non-polar solvent, and highlight how the self-assembly depends on the trio solvent, dithiol, and substrate.

  8. Multifunctional Self-Assembled Monolayers for Organic Field-Effect Transistors

    Science.gov (United States)

    Cernetic, Nathan

    Organic field effect transistors (OFETs) have the potential to reach commercialization for a wide variety of applications such as active matrix display circuitry, chemical and biological sensing, radio-frequency identification devices and flexible electronics. In order to be commercially competitive with already at-market amorphous silicon devices, OFETs need to approach similar performance levels. Significant progress has been made in developing high performance organic semiconductors and dielectric materials. Additionally, a common route to improve the performance metric of OFETs is via interface modification at the critical dielectric/semiconductor and electrode/semiconductor interface which often play a significant role in charge transport properties. These metal oxide interfaces are typically modified with rationally designed multifunctional self-assembled monolayers. As means toward improving the performance metrics of OFETs, rationally designed multifunctional self-assembled monolayers are used to explore the relationship between surface energy, SAM order, and SAM dipole on OFET performance. The studies presented within are (1) development of a multifunctional SAM capable of simultaneously modifying dielectric and metal surface while maintaining compatibility with solution processed techniques (2) exploration of the relationship between SAM dipole and anchor group on graphene transistors, and (3) development of self-assembled monolayer field-effect transistor in which the traditional thick organic semiconductor is replaced by a rationally designed self-assembled monolayer semiconductor. The findings presented within represent advancement in the understanding of the influence of self-assembled monolayers on OFETs as well as progress towards rationally designed monolayer transistors.

  9. Thermoreversible Morphology and Conductivity of a Conjugated Polymer Network Embedded in Block Copolymer Self-Assemblies.

    Science.gov (United States)

    Han, Youngkyu; Carrillo, Jan-Michael Y; Zhang, Zhe; Li, Yunchao; Hong, Kunlun; Sumpter, Bobby G; Ohl, Michael; Paranthaman, Mariappan Parans; Smith, Gregory S; Do, Changwoo

    2016-09-01

    Self-assembly of block copolymers provides numerous opportunities to create functional materials, utilizing self-assembled microdomains with a variety of morphology and periodic architectures as templates for functional nanofillers. Here new progress is reported toward the fabrication of thermally responsive and electrically conductive polymeric self-assemblies made from a water-soluble poly(thiophene) derivative with short poly(ethylene oxide) side chains and Pluronic L62 block copolymer solution in water. The structural and electrical properties of conjugated polymer-embedded self-assembled architectures are investigated by combining small-angle neutron and X-ray scattering, coarse-grained molecular dynamics simulations, and impedance spectroscopy. The L62 solution template organizes the conjugated polymers by stably incorporating them into the hydrophilic domains thus inhibiting aggregation. The changing morphology of L62 during the micellar-to-lamellar phase transition defines the embedded conjugated polymer network. As a result, the conductivity is strongly coupled to the structural change of the templating L62 phase and exhibits thermally reversible behavior with no signs of quenching of the conductivity at high temperature. This study shows promise for enabling more flexibility in processing and utilizing water-soluble conjugated polymers in aqueous solutions for self-assembly based fabrication of stimuli-responsive nanostructures and sensory materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Beta-Sheet-Forming, Self-Assembled Peptide Nanomaterials towards Optical, Energy, and Healthcare Applications.

    Science.gov (United States)

    Kim, Sungjin; Kim, Jae Hong; Lee, Joon Seok; Park, Chan Beum

    2015-08-12

    Peptide self-assembly is an attractive route for the synthesis of intricate organic nanostructures that possess remarkable structural variety and biocompatibility. Recent studies on peptide-based, self-assembled materials have expanded beyond the construction of high-order architectures; they are now reporting new functional materials that have application in the emerging fields such as artificial photosynthesis and rechargeable batteries. Nevertheless, there have been few reviews particularly concentrating on such versatile, emerging applications. Herein, recent advances in the synthesis of self-assembled peptide nanomaterials (e.g., cross β-sheet-based amyloid nanostructures, peptide amphiphiles) are selectively reviewed and their new applications in diverse, interdisciplinary fields are described, ranging from optics and energy storage/conversion to healthcare. The applications of peptide-based self-assembled materials in unconventional fields are also highlighted, such as photoluminescent peptide nanostructures, artificial photosynthetic peptide nanomaterials, and lithium-ion battery components. The relation of such functional materials to the rapidly progressing biomedical applications of peptide self-assembly, which include biosensors/chips and regenerative medicine, are discussed. The combination of strategies shown in these applications would further promote the discovery of novel, functional, small materials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. pH-Responsive Self-Assembly of Polysaccharide through a Rugged Energy Landscape.

    Science.gov (United States)

    Morrow, Brian H; Payne, Gregory F; Shen, Jana

    2015-10-14

    Self-assembling polysaccharides can form complex networks with structures and properties highly dependent on the sequence of triggering cues. Controlling the emergence of such networks provides an opportunity to create soft matter with unique features; however, it requires a detailed understanding of the subtle balance between the attractive and repulsive forces that drives the stimuli-induced self-assembly. Here we employ all-atom molecular dynamics simulations on the order of 100 ns to study the mechanisms of the pH-responsive gelation of the weakly basic aminopolysaccharide chitosan. We find that low pH induces a sharp transition from gel to soluble state, analogous to pH-dependent folding of proteins, while at neutral and high pH self-assembly occurs via a rugged energy landscape, reminiscent of RNA folding. A surprising role of salt is to lubricate the conformational search for the thermodynamically stable states. Although our simulations represent the early events in the self-assembly process of chitosan, which may take seconds or minutes to complete, the atomically detailed insights are consistent with recent experimental observations and provide a basis for understanding how environmental conditions modulate the structure and mechanical properties of the self-assembled polysaccharide systems. The ability to control structure and properties via modification of process conditions will aid in the technological efforts to create complex soft matter with applications ranging from bioelectronics to regenerative medicine.

  12. Self-Assembly of Magnetic Colloids in Soft Confinement

    NARCIS (Netherlands)

    Liu, P.

    2016-01-01

    The central theme in this thesis is the effect of the soft confinements consisting of molecular microtubes and fluid interfaces, on the self-assembly of colloids. We have specially focused on the synthesis of magnetic colloids and the magnetic responses of self-assembled structures including

  13. Electrostatic Self-Assembly of Polysaccharides into Nanofibers

    DEFF Research Database (Denmark)

    Mendes, Ana Carina Loureiro; Strohmenger, Timm; Goycoolea, Francisco

    2017-01-01

    components were tested and observed to affect the diameter, which ranged from 100 to 500 nm, and morphology of the self-assembled nanofibers. The release of diclofenac, as model drug, from self-assembled xanthan-chitosan nanofibers was demonstrated, suggesting that these nanostructures can be used...

  14. Self-assembled nanofiber coatings for controlling cell responses

    NARCIS (Netherlands)

    Barros, Raquel C.; Gelens, Edith; Bulten, Erna; Tuin, Annemarie; de Jong, Menno R; Kuijer, Roel; van Kooten, Theo G

    Nanofibers are thought to enhance cell adhesion, growth, and function. We demonstrate that the choice of building blocks in self-assembling nanofiber systems can be used to control cell behavior. The use of 2 D-coated, self-assembled nanofibers in controlling lens epithelial cells, fibroblasts, and

  15. Different carboxylic acid homodimers in self-assemblies of adducts ...

    Indian Academy of Sciences (India)

    H2cpa) observed inthe self-assemblies of salts or cocrystals of H2cpa with nitrogen containing compounds are discussed. Pyridiniumsalt of the H2cpa is a self-assembly of Hcpa with the pyridinium cation. The assembly is a combinationof ...

  16. Tetrahymena dynamin-related protein 6 self-assembles ...

    Indian Academy of Sciences (India)

    Usha P Kar

    2017-12-30

    Dec 30, 2017 ... We discuss the self-assembly structure of Drp6 and explain the basis for lack of membrane-stimulated GTPase activity. Keywords. Drp6; dynamin; GTPase activity; membrane remodelling; self-assembly; Tetrahymena. 1. Introduction. The Tetrahymena dynamin-related protein 6 (Drp6) localizes.

  17. An Approach to Self-Assembling Swarm Robots Using Multitree Genetic Programming

    Directory of Open Access Journals (Sweden)

    Jong-Hyun Lee

    2013-01-01

    Full Text Available In recent days, self-assembling swarm robots have been studied by a number of researchers due to their advantages such as high efficiency, stability, and scalability. However, there are still critical issues in applying them to practical problems in the real world. The main objective of this study is to develop a novel self-assembling swarm robot algorithm that overcomes the limitations of existing approaches. To this end, multitree genetic programming is newly designed to efficiently discover a set of patterns necessary to carry out the mission of the self-assembling swarm robots. The obtained patterns are then incorporated into their corresponding robot modules. The computational experiments prove the effectiveness of the proposed approach.

  18. An approach to self-assembling swarm robots using multitree genetic programming.

    Science.gov (United States)

    Lee, Jong-Hyun; Ahn, Chang Wook; An, Jinung

    2013-01-01

    In recent days, self-assembling swarm robots have been studied by a number of researchers due to their advantages such as high efficiency, stability, and scalability. However, there are still critical issues in applying them to practical problems in the real world. The main objective of this study is to develop a novel self-assembling swarm robot algorithm that overcomes the limitations of existing approaches. To this end, multitree genetic programming is newly designed to efficiently discover a set of patterns necessary to carry out the mission of the self-assembling swarm robots. The obtained patterns are then incorporated into their corresponding robot modules. The computational experiments prove the effectiveness of the proposed approach.

  19. A novel self-assembling peptide with UV-responsive properties.

    Science.gov (United States)

    Wei, Ran; Jin, Cheng-Cheng; Quan, Jing; Nie, Hua-li; Zhu, Li-Min

    2014-03-01

    A novel heptapeptide comprising Ile-Gln-Ser-Pro-His-Phe-Phe (IQSPHFF) identified and found to undergo self-assembly into microparticles in solution. To understand the effects of ultraviolet (UV) irradiation on the self-assembly process, IQSPHFF solutions were exposed to the UV light of 365 nm at room temperature. This exposure was found to have a profound effect on the morphology of the self-assembled aggregates, converting the microparticles to nanorod shapes. Circular dichroism and FTIR studies indicated distinct structural differences in the arrangements of the peptide moieties before and after UV irradiation. However, Mass spectrum analysis and high performance liquid chromatography of the peptide molecules before and after UV irradiation demonstrated that the chemical structure of IQSPHFF was not changed. UV-visible spectroscopy and fluorescence spectroscopy studies showed that the absorption peak both increased after UV irradiation. Overall, our data show that the heptapeptide with UV-responsive properties. Copyright © 2013 Wiley Periodicals, Inc.

  20. Exploring single chain amphiphile self-assembly and their possible roles in light transduction

    DEFF Research Database (Denmark)

    Monnard, Pierre-Alain

    2011-01-01

    amphiphiles on the early Earth seems reasonably well-documented either by exo-terrestrial delivery or endogeneous syntheses, a fact that singles them out as potential building blocks of primitive membranes. These studies have highlighted two important aspects of the self-assembly of single chain amphiphiles......Self-assembled structures of single-chain amphiphiles have been used as hosts for biochemical, and chemical reactions. Their use as models for protocells (i.e., precursors to the first biological cells) has been extensively researched by various groups because the availability of single chain...... source studied to date can supply one single type of amphiphile at concentrations conducive to self-assembly. Mixtures of single-chain amphiphiles were therefore proposed to better model primitive membranes and potentially enhance their structural integrity1-3. Recently, we have established that complex...

  1. Hierarchical self-assembly of two-length-scale multiblock copolymers

    International Nuclear Information System (INIS)

    Brinke, Gerrit ten; Loos, Katja; Vukovic, Ivana; Du Sart, Gerrit Gobius

    2011-01-01

    The self-assembly in diblock copolymer-based supramolecules, obtained by hydrogen bonding short side chains to one of the blocks, as well as in two-length-scale linear terpolymers results in hierarchical structure formation. The orientation of the different domains, e.g. layers in the case of a lamellar-in-lamellar structure, is determined by the molecular architecture, graft-like versus linear, and the relative magnitude of the interactions involved. In both cases parallel and perpendicular arrangements have been observed. The comb-shaped supramolecules approach is ideally suited for the preparation of nanoporous structures. A bicontinuous morphology with the supramolecular comb block forming the channels was finally achieved by extending the original approach to suitable triblock copolymer-based supramolecules.

  2. Self-assemblies of magnetic nanoparticles and di-block copolymers: Magnetic micelles and vesicles

    International Nuclear Information System (INIS)

    Lecommandoux, S.; Sandre, O.; Checot, F.; Rodriguez-Hernandez, J.; Perzynski, R.

    2006-01-01

    Magnetic nanocomposites are obtained by the self-assembly in water of polypeptide-based di-block copolymers polybutadiene-b-poly(glutamic acid) combined with hydrophobic γ-Fe 2 O 3 nanoparticles. These hybrid supramolecular objects are either-(3D) spherical micelles filled with a hydrophobic ferrofluid at a concentration as high as 45 vol% or-hollow vesicles with a (2D) magnetic membrane. In this last case, the organic amphiphile copolymers are able to confine the hydrophobic nanoparticles within the thin layer of polybutadiene blocks. We probe these objects by atomic force microscopy, by small-angle neutron scattering (SANS) and by light scattering. Furthermore, anisotropic SANS data bring the experimental evidence of the capability to modify the shape of the mineralized membranes in response to a magnetic field intensity as low as 290 G

  3. Enantioselective Light Harvesting with Perylenediimide Guests on Self-Assembled Chiral Naphthalenediimide Nanofibers.

    Science.gov (United States)

    Sethy, Ramarani; Kumar, Jatish; Métivier, Rémi; Louis, Marine; Nakatani, Keitaro; Mecheri, Nila Mohan Thazhe; Subhakumari, Akhila; Thomas, K George; Kawai, Tsuyoshi; Nakashima, Takuya

    2017-11-20

    Self-assembling molecular systems often display amplified chirality compared to the monomeric state, which makes the molecular recognition more sensitive to chiral analytes. Herein, we report the almost absolute enantioselective recognition of a chiral perylenediimide (PDI) molecule by chiral supramolecular nanofibers of a bichromophoric naphthalenediimide (NDI) derivative. The chiral recognition was evaluated through the Förster resonance energy transfer (FRET) from the NDI-based host nanofibers to the guest PDI molecules. The excitation energy was successfully transferred to the guest molecule through efficient energy migration along the host nanofiber, thus demonstrating the light-harvesting capability of these hybrid systems. Furthermore, circularly polarized luminescence (CPL) was enantioselectively sensitized by the guest molecule as the wavelength band and sign of the CPL signal were switched in response to the chiral guest molecule. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. RNA self-assembly and RNA nanotechnology.

    Science.gov (United States)

    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

  5. Solvent mediated self-assembly of solids

    Energy Technology Data Exchange (ETDEWEB)

    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

  6. Solid state nanofibers based on self-assemblies : from cleaving from self-assemblies to multilevel hierarchical constructs

    NARCIS (Netherlands)

    Ikkala, Olli; Ras, Robin H. A.; Houbenov, Nikolay; Ruokolainen, Janne; Paakko, Marjo; Laine, Janne; Leskela, Markku; Berglund, Lars A.; Lindstrom, Tom; ten Brinke, Gerrit; Iatrou, Hermis; Hadjichristidis, Nikos; Faul, Charl F. J.; Pääkkö, Marjo; Leskelä, Markku; Lindström, Tom

    2009-01-01

    Self-assemblies and their hierarchies are useful to construct soft materials with structures at different length scales and to tune the materials properties for various functions. Here we address routes for solid nanofibers based on different forms of self-assemblies. On the other hand, we discuss

  7. A multifunctional supramolecular hydrogel: preparation, properties and molecular assembly.

    Science.gov (United States)

    Wang, Lin; Shi, Xuefeng; Wu, Yaqian; Zhang, Jian; Zhu, Yuejun; Wang, Jinben

    2018-01-24

    A novel supramolecular hydrogel was designed and constructed by molecular self-assembly of a cationic gemini surfactant, 1,3-bis(N,N-dimethyl-N-cetylammonium)-2-propylacrylate dibromide (AGC 16 ), and an anionic aromatic compound, trisodium 1,3,6-naphthalenetrisulfonate (NTS). Owing to its unique structure, the hydrogel (abbreviated as AGC 16 /NTS) has the potential to be used as a multifunctional drug delivery system. The structure and properties of AGC 16 /NTS were characterized by rheological measurements, differential scanning calorimetry, variable-temperature 1 H nuclear magnetic resonance, ultraviolet-visible spectroscopy, variable-temperature fluorescence emission spectroscopy, cryogenic scanning electron microscopy, transmission electron microscopy and X-ray diffraction methods. The rheological and DSC analysis results revealed that the gel AGC 16 /NTS was formed below 57 °C. It was found from UV-vis, fluorescence and 1 H NMR spectroscopy characterization that aromatic π-π stacking and hydrophobic forces were indispensable to the formation of AGC 16 /NTS. The Cryo-SEM and TEM observation results indicated that gelators AGC 16 and NTS self-assembled into one-dimensional fibers which further tightly intertwined to form a three-dimensional network structure. Based on the spectroscopic data and X-ray diffraction measurement results, a self-assembly model was proposed, helping to further understand the molecular self-assembly mechanism of AGC 16 /NTS. It was also found that the electrostatic force, hydrophobic force and π-π interaction were the three main driving forces for the gelation. The multiple non-covalent interactions between AGC 16 and NTS endowed the hydrogel with excellent performance when the hydrogel was used as a carrier for drug delivery, due to multiple micro-domains within the same gel system. We further investigated the encapsulation and releasing properties of the hydrogel, using the hydrophobic model drug curcumin (Cur) and the model

  8. Self-Assembled Binary Nanoscale Systems: Multioutput Model with LFER-Covariance Perturbation Theory and an Experimental-Computational Study of NaGDC-DDAB Micelles.

    Science.gov (United States)

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

    2015-11-10

    Studies of the self-aggregation of binary systems are of both theoretical and practical importance. They provide an opportunity to investigate the influence of the molecular structure of the hydrophobe on the nonideality of mixing. On the other hand, linear free energy relationship (LFER) models, such as Hansch's equations, may be used to predict the properties of chemical compounds such as drugs or surfactants. However, the task becomes more difficult once we want to predict simultaneaously the effect over multiple output properties of binary systems of perturbations under multiple input experimental boundary conditions (b(j)). As a consequence, we need computational chemistry or chemoinformatics models that may help us to predict different properties of the autoaggregation process of mixed surfactants under multiple conditions. In this work, we have developed the first model that combines perturbation theory (PT) and LFER ideas. The model uses as input covariance PT operators (CPTOs). CPTOs are calculated as the difference between covariance ΔCov((i)μ(k)) functions before and after multiple perturbations in the binary system. In turn, covariances calculated as the product of two Box-Jenkins operators (BJO) operators. BJOs are used to measure the deviation of the structure of different chemical compounds from a set of molecules measured under a given subset of experimental conditions. The best CPT-LFER model found predicted the effects of 25,000 perturbations over 9 different properties of binary systems. We also reported experimental studies of different experimental properties of the binary system formed by sodium glycodeoxycholate and didodecyldimethylammonium bromide (NaGDC-DDAB). Last, we used our CPT-LFER model to carry out a 1000 data point simulation of the properties of the NaGDC-DDAB system under different conditions not studied experimentally.

  9. In situ study of self-assembled GaN nanowires nucleation on Si(111) by plasma-assisted molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Hestroffer, K.; Daudin, B. [CEA-CNRS Group (Nanophysique et Semiconducteurs), Universite Joseph Fourier and CEA Grenoble, INAC, SP2M, 17 rue des Martyrs, 38054 Grenoble (France); Leclere, C.; Renevier, H. [Laboratoire des Materiaux et du Genie Physique, Grenoble INP--MINATEC, 3 parvis L. Neel, 38016 Grenoble (France); Cantelli, V. [' ' Nanostructures et Rayonnement Synchrotron' ' Group, CEA Grenoble, INAC, SP2M, 17 rue des Martyrs, 38054 Grenoble (France); Fondation Nanosciences, 23 rue des Martyrs, 38000 Grenoble (France); Bougerol, C. [CEA-CNRS Group, ' ' Nanophysique et Semiconducteurs' ' , Institut Neel, CNRS and Universite Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9 (France)

    2012-05-21

    Nucleation of GaN nanowires grown by plasma-assisted molecular beam epitaxy is studied through a combination of two in situ tools: grazing incidence x-ray diffraction and reflection high energy electron diffraction. Growth on bare Si(111) and on AlN/Si(111) is compared. A significantly larger delay at nucleation is observed for nanowires grown on bare Si(111). The difference in the nucleation delay is correlated to a dissimilarity of chemical reactivity between Al and Ga with nitrided Si(111).

  10. Characterization of self-assembled electrodes based on Au-Pt nanoparticles for PEMFC application

    Energy Technology Data Exchange (ETDEWEB)

    Valenzuela, E. [Politecnica Univ. de Chiapas, Tuxtla Gutierrez, Chiapas (Mexico). Energia y Sustentabilidad; Sebastian, P.J. [Politecnica Univ. de Chiapas, Chiapas (Mexico). Energia y Sustentabilidad; Centro de Investigacion en Energia, UNAM, Morelos (Mexico); Gamboa, S.A. [Centro de Investigacion en Energia, UNAM, Morelos (Mexico); Pal, U. [Inst. de Fisica, Universidad Autonoma de Puebla Univ., Puebla (Mexico). Inst. de Fisica; Gonzalez, I. [Autonoma Metropolitana Univ. (Mexico). Dept. de Quimica

    2008-07-01

    This paper reported on a study in which membrane electrode assemblies (MEAs) were fabricated by depositing Au, Pt and AuPt nanoparticles on Nafion 115 membrane for use in a proton exchange membrane fuel cell (PEMFC). A Rotating Disc Electrode (RDE) was used to measure the nanoparticle catalyst activity. After deposition of the nanoparticles on the membrane, the surface was studied by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The membrane proton conduction process was studied by Electrochemical Impedance Spectroscopy (EIS) with the 4 probe technique. The MEAs fabricated with Nafion/Metal membranes were evaluated in a PEMFC under standard conditions. Colloidal solutions were used to prepare self-assembled electrodes with nanoparticles deposited on Nafion membrane. The particles deposited on Nafion showed good stability and had homogeneous distribution along the membrane surface. The impedance results revealed an increase in the membrane proton resistance of the self-assembled electrodes compared to unmodified Nafion. The Au-Pt nanoparticles were obtained by chemical reduction. The nanoparticle size in the three systems was about 2 nm. The self-assembled electrodes performed well in standard conditions. The optimum colloidal concentration and immersion time must be determined in order to obtain good catalytic activity and high membrane conductance. The self-assembled Nafion/AuPt had the best open circuit potential (887 mV). The Au and Pt self-assemblies showed a similar performance in terms of maximum power and maximum current density. The performance of the Nafion/Au self-assembly was influenced more by ohmic losses, particularly in the membrane. The maximum power generation was obtained at 0.35 V. The mass transport losses increased after this value, thereby affecting the efficiency of the PEMFC. 2 figs.

  11. Enhanced oral absorption of 20(S-protopanaxadiol by self-assembled liquid crystalline nanoparticles containing piperine: in vitro and in vivo studies

    Directory of Open Access Journals (Sweden)

    Jin X

    2013-02-01

    Full Text Available Xin Jin,1,2 Zhen-hai Zhang,1 E Sun,1 Xiao-bin Tan,1 Song-lin Li,3 Xu-dong Cheng,4 Ming You,4 Xiao-bin Jia11Key Laboratory of New Drug Delivery System of Chinese Materia Medica, Jiangsu Provincial Academy of Chinese Medicine, Nanjing, People's Republic of China; 2College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, People's Republic of China; 3Department of Pharmaceutical Analysis and Metabolomics, Jiangsu Province Academy of Traditional Chinese Medicine, Nanjing, People's Republic of China; 4ALG Bioscience Co, Ltd, Suzhou, People's Republic of ChinaBackground: 20(S-protopanaxadiol (PPD, similar to several other anticancer agents, has low oral absorption and is extensively metabolized. These factors limit the use of PPD for treatment of human diseases.Methods: In this study, we used cubic nanoparticles containing piperine to improve the oral bioavailability of PPD and to enhance its absorption and inhibit its metabolism. Cubic nanoparticles loaded with PPD and piperine were prepared by fragmentation of glyceryl monoolein (GMO/poloxamer 407 bulk cubic gel and verified using transmission electron microscopy and differential scanning calorimetry. We evaluated the in vitro release of PPD from these nanoparticles and its absorption across the Caco-2 cell monolayer model, and subsequently, we examined the bioavailability and metabolism of PPD and its nanoparticles in vivo.Results: The in vitro release of PPD from these nanoparticles was less than 5% at 12 hours. PPD-cubosome and PPD-cubosome loaded with piperine (molar ratio PPD/piperine, 1:3 increased the apical to basolateral permeability values of PPD across the Caco-2 cell monolayer from 53% to 64%, respectively. In addition, the results of a pharmacokinetic study in rats showed that the relative bioavailabilities of PPD-cubosome [area under concentration–time curve (AUC0–∞ ] and PPD-cubosome containing piperine (AUC0–∞ compared to that of raw PPD (AUC0–∞ were 166

  12. Aerosolized droplet mediated self-assembly of photosynthetic pigment analogues and deposition onto substrates.

    Science.gov (United States)

    Shah, Vivek B; Biswas, Pratim

    2014-02-25

    Self-assembled photosynthetic molecules have a high extinction coefficient and a broad absorption in the infrared region, and these properties can be used to improve the efficiency of solar cells. We have developed a single-step method for the self-assembly of synthetic chlorin molecules (analogues of native bacteriochlorophylls) in aerosolized droplets, containing a single solvent and two solvents, to synthesize biomimetic light-harvesting structures. In the single-solvent approach, assembly is promoted by a concentration-driven process due to evaporation of the solvent. The peak absorbance of Zn(II) 3-(1-hydroxyethyl)-10-phenyl-13(1)-oxophorbine (1) in methanol shifted from 646 nm to 725 nm (∼ 80 nm shift) after assembly, which is comparable to the shift observed in the naturally occurring assembly of bacteriochlorophyll c. Although assembly is thermodynamically favorable, the kinetics of self-assembly play an important role, and this was demonstrated by varying the initial concentration of the pigment monomer. To overcome kinetic limitations, a two-solvent approach using a volatile solvent (tetrahydrofuran) in which the dye is soluble and a less volatile solvent (ethanol) in which the dye is sparingly soluble was demonstrated to be effective. The effect of molecular structure is demonstrated by spraying the sterically hindered Zn(II) 3-(1-hydroxyethyl)-10-mesityl-13(1)-oxophorbine (2), which is an analogue of 1, under similar conditions. The results illustrate a valuable and facile aerosol-based method for the formation of films of supramolecular assemblies.

  13. On the solution self-assembly of nanocolloidal brushes: insights from simulations

    International Nuclear Information System (INIS)

    Striolo, Alberto

    2008-01-01

    The synthesis of novel nanoparticles with exceptional properties continues to stimulate the search for advanced applications in fields as diverse as solar energy harvesting and polymer reinforcement. It is widely recognized that to practically exploit the promised benefits it is necessary to guide the assembly of the various nanoparticles into well-defined supra-molecular structures. Towards this goal, we report Monte Carlo simulation results for the self-assembly of spherical nanoparticles in implicit solvent. The nanoparticles interact solely via dispersive interactions, modeled as square-well potentials. To control the morphology of the self-assembled aggregates, side chains are grafted on specific locations on the nanoparticle surface (i.e., on the equator, on the tropics, on the entire tropical region, or uniformly on the nanoparticle surface). The results are discussed in terms of average cluster size, probability of observing aggregates of given size, and aggregate radius of gyration and asphericity as a function of the aggregate size. The parameters of interest are the solution conditions and the nanoparticle volume fraction (always in the dilute regime). As shown in previous reports (e.g., Striolo 2007 Small 3 628), the nanoparticles form insoluble agglomerates in the absence of the side chains. When the side chains are long and uniformly distributed on the nanoparticles, these remain individually dispersed in solution. More importantly, when the side chains are grafted on selected locations on the nanoparticles, these self-assemble, yielding structures composed of up to 7-10 nanoparticles. The number of grafted side chains is the parameter that predominantly determines the average aggregate size, while the aggregate morphology can be tuned by appropriately controlling the distribution and length of the grafted side chains.

  14. Topological Self-Assembly of Highly Symmetric Lanthanide Clusters: A Magnetic Study of Exchange-Coupling "Fingerprints" in Giant Gadolinium(III) Cages.

    Science.gov (United States)

    Qin, Lei; Zhou, Guo-Jun; Yu, You-Zhu; Nojiri, Hiroyuki; Schröder, Christian; Winpenny, Richard E P; Zheng, Yan-Zhen

    2017-11-15

    The creation of a perfect hollow nanoscopic sphere of metal centers is clearly an unrealizable synthetic challenge. It is, however, an inspirational challenge from the viewpoint of chemical architecture and also as finite molecular species may provide unique microscopic insight into the origin and onset of phenomena such as topological spin-frustration effects found in infinite 2D and 3D systems. Herein, we report a series of high-symmetry gadolinium(III) (S = 7/2) polyhedra, Gd 20 , Gd 32 , Gd 50 , and Gd 60 , to test an approach based on assembling polymetallic fragments that contain different polygons. Structural analysis reveals that the Gd 20 cage resembles a dodecahedron; the vertices of the Gd 32 polyhedron exactly reveal symmetry O h ; Gd 50 displays an unprecedented polyhedron in which an icosidodecahedron Gd 30 core is encapsulated by an outer Gd 20 dodecahedral shell with approximate I h symmetry; and the Gd 60 shows a truncated octahedron geometry. Experimental and theoretical magnetic studies show that this series produces the expected antiferromagnetic interaction that can be modeled based on classical spins at the Gd sites. From the magnetization analyses, we can roughly correlate the derivative bands to the Gd-O-Gd angles. Such a magneto-structural correlation may be used as "fingerprints" to identify these cages.

  15. Self-assembly of crystalline nanotubes from monodisperse amphiphilic diblock copolypeptoid tiles.

    Science.gov (United States)

    Sun, Jing; Jiang, Xi; Lund, Reidar; Downing, Kenneth H; Balsara, Nitash P; Zuckermann, Ronald N

    2016-04-12

    The folding and assembly of sequence-defined polymers into precisely ordered nanostructures promises a class of well-defined biomimetic architectures with specific function. Amphiphilic diblock copolymers are known to self-assemble in water to form a variety of nanostructured morphologies including spheres, disks, cylinders, and vesicles. In all of these cases, the predominant driving force for assembly is the formation of a hydrophobic core that excludes water, whereas the hydrophilic blocks are solvated and extend into the aqueous phase. However, such polymer systems typically have broad molar mass distributions and lack the purity and sequence-defined structure often associated with biologically derived polymers. Here, we demonstrate that purified, monodisperse amphiphilic diblock copolypeptoids, with chemically distinct domains that are congruent in size and shape, can behave like molecular tile units that spontaneously assemble into hollow, crystalline nanotubes in water. The nanotubes consist of stacked, porous crystalline rings, and are held together primarily by side-chain van der Waals interactions. The peptoid nanotubes form without a central hydrophobic core, chirality, a hydrogen bond network, and electrostatic or π-π interactions. These results demonstrate the remarkable structure-directing influence of n-alkane and ethyleneoxy side chains in polymer self-assembly. More broadly, this work suggests that flexible, low-molecular-weight sequence-defined polymers can serve as molecular tile units that can assemble into precision supramolecular architectures.

  16. Ultrashort cationic naphthalene-derived self-assembled peptides as antimicrobial nanomaterials.

    Science.gov (United States)

    Laverty, Garry; McCloskey, Alice P; Gilmore, Brendan F; Jones, David S; Zhou, Jie; Xu, Bing

    2014-09-08

    Self-assembling dipeptides conjugated to naphthalene show considerable promise as nanomaterial structures, biomaterials, and drug delivery devices. Biomaterial infections are responsible for high rates of patient mortality and morbidity. The presence of biofilm bacteria, which thrive on implant surfaces, are a huge burden on healthcare budgets, as they are highly resistant to current therapeutic strategies. Ultrashort cationic self-assembled peptides represent a highly innovative and cost-effective strategy to form antibacterial nanomaterials. Lysine conjugated variants display the greatest potency with 2% w/v NapFFKK hydrogels significantly reducing the viable Staphylococcus epidermidis biofilm by 94%. Reducing the size of the R-group methylene chain on cationic moieties resulted in reduction of antibiofilm activity. The primary amine of the protruding R-group tail may not be as readily available to interact with negatively charged bacterial membranes. Cryo-SEM, FTIR, CD spectroscopy, and oscillatory rheology provided evidence of supramolecular hydrogel formation at physiological pH (pH 7.4). Cytotoxicity assays against murine fibroblast (NCTC 929) cell lines confirmed the gels possessed reduced cytotoxicity relative to bacterial cells, with limited hemolysis upon exposure to equine erythrocytes. The results presented in this paper highlight the significant potential of ultrashort cationic naphthalene peptides as future biomaterials.

  17. Self-assembling of calcium salt of the new DNA base 5-carboxylcytosine

    Energy Technology Data Exchange (ETDEWEB)

    Irrera, Simona [Department of Chemistry, SAPIENZA University of Rome, Piazzale A. Moro 5, 00185 Rome (Italy); Department of Chemistry, University College London, 20 Grodon Street, WC1H0AJ London (United Kingdom); Ruiz-Hernandez, Sergio E. [School of Chemistry, Cardiff University Main Building, Park Place, CF103AT Cardiff (United Kingdom); Reggente, Melania [Department of Basic and Applied Sciences for Engineering, SAPIENZA University of Rome, Via A. Scarpa 16, 00161 Rome (Italy); Passeri, Daniele, E-mail: daniele.passeri@uniroma1.it [Department of Basic and Applied Sciences for Engineering, SAPIENZA University of Rome, Via A. Scarpa 16, 00161 Rome (Italy); Natali, Marco [Department of Basic and Applied Sciences for Engineering, SAPIENZA University of Rome, Via A. Scarpa 16, 00161 Rome (Italy); Gala, Fabrizio [Department of Basic and Applied Sciences for Engineering, SAPIENZA University of Rome, Via A. Scarpa 16, 00161 Rome (Italy); Department of Medical-Surgical, Techno-Biomedical Sciences and Translational Medicine of SAPIENZA University of Rome, Sant’Andrea Hospital, Rome (Italy); Zollo, Giuseppe [Department of Basic and Applied Sciences for Engineering, SAPIENZA University of Rome, Via A. Scarpa 16, 00161 Rome (Italy); Rossi, Marco [Department of Basic and Applied Sciences for Engineering, SAPIENZA University of Rome, Via A. Scarpa 16, 00161 Rome (Italy); Research Center for Nanotechnology applied to Engineering of SAPIENZA University of Rome (CNIS), Piazzale A. Moro 5, 00185 Rome (Italy); Portalone, Gustavo, E-mail: gustavo.portalone@uniroma1.it [Department of Chemistry, SAPIENZA University of Rome, Piazzale A. Moro 5, 00185 Rome (Italy)

    2017-06-15

    Highlights: • Ca salt of 5-carboxylcytosine has been deposited on HOPG substrate. • Molecules self-assembled in monolayers and filaments. • Height of the features were measured by atomic force microscopy. • Ab-initio calculations confirmed the AFM results. - Abstract: Supramolecular architectures involving DNA bases can have a strong impact in several fields such as nanomedicine and nanodevice manufacturing. To date, in addition to the four canonical nucleobases (adenine, thymine, guanine and cytosine), four other forms of cytosine modified at the 5 position have been identified in DNA. Among these four new cytosine derivatives, 5-carboxylcytosine has been recently discovered in mammalian stem cell DNA, and proposed as the final product of the oxidative epigenetic demethylation pathway on the 5 position of cytosine. In this work, a calcium salt of 5-carboxylcytosine has been synthesized and deposited on graphite surface, where it forms self-assembled features as long range monolayers and up to one micron long filaments. These structures have been analyzed in details combining different theoretical and experimental approaches: X-ray single-crystal diffraction data were used to simulate the molecule-graphite interaction, first using molecular dynamics and then refining the results using density functional theory (DFT); finally, data obtained with DFT were used to rationalize atomic force microscopy (AFM) results.

  18. Understanding recognition and self-assembly in biology using the chemist's toolbox. Insight into medicinal chemistry.

    Science.gov (United States)

    Quirolo, Z B; Benedini, L A; Sequeira, M A; Herrera, M G; Veuthey, T V; Dodero, V I

    2014-01-01

    Medicinal chemistry is intimately connected with basic science such as organic synthesis, chemical biology and biophysical chemistry among other disciplines. The reason of such connections is due to the power of organic synthesis to provide designed molecules; chemical biology to give tools to discover biological and/or pathological pathways and biophysical chemistry which provides the techniques to characterize and the theoretical background to understand molecular behaviour. The present review provides some selective examples of these research areas. Initially, template dsDNA organic synthesis and the spatio-temporal control of transcription are presenting following by the supramolecular entities used in drug delivery, such as liposomes and liquid crystal among others. Finally, peptides and protein self-assembly is connected with biomaterials and as an important event in the balance between health and disease. The final aim of the present review is to show the power of chemical tools not only for the synthesis of new molecules but also to improve our understanding of recognition and self-assembly in the biological context.

  19. Programming Self-Assembly of DNA Origami Honeycomb Two-Dimensional Lattices and Plasmonic Metamaterials.

    Science.gov (United States)

    Wang, Pengfei; Gaitanaros, Stavros; Lee, Seungwoo; Bathe, Mark; Shih, William M; Ke, Yonggang

    2016-06-22

    Scaffolded DNA origami has proven to be a versatile method for generating functional nanostructures with prescribed sub-100 nm shapes. Programming DNA-origami tiles to form large-scale 2D lattices that span hundreds of nanometers to the micrometer scale could provide an enabling platform for diverse applications ranging from metamaterials to surface-based biophysical assays. Toward this end, here we design a family of hexagonal DNA-origami tiles using computer-aided design and demonstrate successful self-assembly of micrometer-scale 2D honeycomb lattices and tubes by controlling their geometric and mechanical properties including their interconnecting strands. Our results offer insight into programmed self-assembly of low-defect supra-molecular DNA-origami 2D lattices and tubes. In addition, we demonstrate that these DNA-origami hexagon tiles and honeycomb lattices are versatile platforms for assembling optical metamaterials via programmable spatial arrangement of gold nanoparticles (AuNPs) into cluster and superlattice geometries.

  20. Electrostatic self-assembly of biomolecules

    Science.gov (United States)

    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.

  1. Self-assembling holographic biosensors and biocomputers.

    Energy Technology Data Exchange (ETDEWEB)

    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.

  2. Self-assembled biomimetic superhydrophobic hierarchical arrays.

    Science.gov (United States)

    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.

  3. Functional Self-Assembled Nanofibers by Electrospinning

    Science.gov (United States)

    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.

  4. Principles Governing the Self Assembly of Polypeptide Nanoparticles

    Science.gov (United States)

    Wahome, Newton

    Self assembling systems on the nanometer scale afford the advantage of being able to control submicron level events. In this study, we focus on the self-assembling polypeptide nanoparticles (SAPN). The SAPN scaffold is made up of oligomerizing domains that align along the principle rotational axes of icosahedral symmetry. By aligning them along these axes, a particle with spherical geometry can be achieved. This particle can be utilized as a vaccine, as a drug delivery vehicle, or as a biomedical imaging device. This research will try to answer why the SAPN self-assembles into distinct molecular weight ranges while mostly maintaining a spherical morphology. The first means will be theoretical and computational, where we will utilize a mathematical formalism to find out how the packing of SAPN's monomeric units can occur within symmetric space. Then molecular dynamics will be run within this symmetric space to test the per amino acid residue susceptibility of SAPN towards becoming polymorphic in nature. Means for examining the aggregation propensity of SAPN will be also be tested. Specifically, the relationship of different sequences of SAPN with pH will be elucidated. Co-assembly of SAPN to reduce the surface density of an aggregation prone epitope will be tested. Also, aggregation reduction consisting of the exchange of an anionic denaturant with a positively charged suppressor in order to mitigate a priori peptide association and misfolding, will also be attempted. SAPN has been shown to be an immunogenic platform for the presentation of pathogen derived antigens. We will attempt to show the efficacy of presenting an antigen from HIV-1 which is structurally restrained to best match the native conformation on the virus. Immunological studies will be performed to test the effect of this approach, as well testing the antigenicity of the nanoparticle in the absence of adjuvant. Finally, the antigen presenting nanoparticles will undergo formulation testing, to measure

  5. Dynamic simulations of many-body electrostatic self-assembly

    Science.gov (United States)

    Lindgren, Eric B.; Stamm, Benjamin; Maday, Yvon; Besley, Elena; Stace, A. J.

    2018-03-01

    Two experimental studies relating to electrostatic self-assembly have been the subject of dynamic computer simulations, where the consequences of changing the charge and the dielectric constant of the materials concerned have been explored. One series of calculations relates to experiments on the assembly of polymer particles that have been subjected to tribocharging and the simulations successfully reproduce many of the observed patterns of behaviour. A second study explores events observed following collisions between single particles and small clusters composed of charged particles derived from a metal oxide composite. As before, observations recorded during the course of the experiments are reproduced by the calculations. One study in particular reveals how particle polarizability can influence the assembly process. This article is part of the theme issue `Modern theoretical chemistry'.

  6. Self-assembled peptide nanotubes as an etching material for the rapid fabrication of silicon wires

    DEFF Research Database (Denmark)

    Larsen, Martin Benjamin Barbour Spanget; Andersen, Karsten Brandt; Svendsen, Winnie Edith

    2011-01-01

    This study has evaluated self-assembled peptide nanotubes (PNTS) and nanowires (PNWS) as etching mask materials for the rapid and low-cost fabrication of silicon wires using reactive ion etching (RIE). The self-assembled peptide structures were fabricated under mild conditions and positioned on c...... characterization by SEM and I-V measurements. Additionally, the fabricated silicon structures were functionalized with fluorescent molecules via a biotin-streptavidin interaction in order to probe their potential in the development of biosensing devices....

  7. Self-Assembling Organic Nanopores as Synthetic Transmembrane Channels with Tunable Functions

    Science.gov (United States)

    Wei, Xiaoxi

    A long-standing goal in the area of supramolecular self-assembly involves the development of synthetic ion/water channels capable of mimicking the mass-transport characteristics of biological channels and pores. Few examples of artificial transmembrane channels with large lumen, high conductivity and selectivity are known. A review of pronounced biological transmembrane protein channels and some representative synthetic models have been provided in Chapter 1, followed by our discovery and initial investigation of shape-persistent oligoamide and phenylene ethynylene macrocycles as synthetic ion/water channels. In Chapter 2, the systematic structural modification of oligoamide macrocycles 1, the so-called first-generation of these shape-persistent macrocycles, has led to third-generation macrocycles 3. The third generation was found to exhibit unprecedented, strong intermolecular association in both the solid state and solution via multiple techniques including X-ray diffraction (XRD), SEM, and 1H NMR. Fluorescence spectroscopy paired with dynamic light scattering (DLS) revealed that macrocycles 3 can assemble into a singly dispersed nanotubular structure in solution. The resultant self-assembling pores consisting of 3 were examined by HPTS-LUVs assays and BLM studies (Chapter 3) and found to form cation-selective (PK+/PCl- = 69:1) transmembrane ion channels with large conductance (200 ˜ 2000 pS for alkali cations) and high stability with open times reaching to 103 seconds. Tuning the aggregation state of macrocycles by choosing an appropriate polar solvent mixture (i.e., 3:1, THF:DMF, v/v) and concentration led to the formation of ion channels with well-defined square top behavior. A parallel study using DLS to examine the size of aggregates was used in conjunction with channel activity assays (LUVs/BLM) to reveal the effects of the aggregation state on channel activity. Empirical evidence now clearly indicates that a preassembled state, perhaps that of a

  8. Applications of molecular self-assembly in tissue engineering

    Science.gov (United States)

    Harrington, Daniel Anton

    This thesis studied the application of three self-assembling molecular systems, as potential biomaterials for tissue engineering applications. Cholesteryl-(L-lactic acid)n molecules form thermotropic liquid crystals, which could be coated onto the inner and outer pores of biodegradable PLLA scaffolds, while retaining the lamellar order of the neat material. Primary bovine chondrocytes were cultured on these structures, demonstrating improved attachment and extended retention of phenotype on the C-LA-coated scaffolds. No difference in fibronectin adsorption to C-LA and PLLA surfaces was observed, suggesting a strong role for cholesterol in influencing cell phenotype. A family of peptide-amphiphiles, bearing the "RGD" adhesion sequence from fibronectin, was also assessed in the contexts of cartilage and bladder repair. These molecules self-assemble into one-dimensional fibers, with diameters of 6--8 nm, and lengths of 500 nm or greater. Chondrocytes were seeded and cultured on covalently-crosslinked PA gels and embedded within calcium-triggered PA gels. Cells became dormant over time, but remained viable, suggesting an inappropriate display of the adhesion sequence to cells. A family of "branched" PA molecules with lysine dendron headgroups was designed, in an effort to increase the spatial separation between molecules in the assembled state, and to theoretically improve epitope accessibility. These molecules coated reliably onto PGA fiber scaffolds, and dramatically increased the attachment of human bladder smooth muscle cells, possibly through better epitope display or electrostatic attraction. They also formed strong gels with several negatively-charged biologically-relevant macromolecules. In a third system, amphiphilic segmented dendrimers based on phenylene vinylene and L-lysine entered cells through an endocytic pathway with no discernible toxic effect on cell proliferation or morphology. These amphiphiles formed complex aggregates in aqueous solution, likely

  9. Sulfonation of alkyl phenyl ether self-assembled monolayers.

    Science.gov (United States)

    Katash, Irit; Luo, Xianglin; Sukenik, Chaim N

    2010-02-02

    The sulfonation of phenyl ether decorated self-assembled monolayers (SAMs) was studied with an eye toward creating surfaces with a particularly high negative charge density based on a close-packed array of phenyl rings with more than one sulfonic acid group per molecule. The product distribution and kinetics of this process were studied by ultraviolet, infrared, and photoelectron spectroscopies and by monitoring changes in the thickness and wetting properties of the SAM. The sulfonation chemistry could be effected without undermining monolayer integrity and the isomer distribution of ortho- and para-monosulfonated material, along with the percentages of mono- and disulfonated molecules could be established throughout the process. As doubly sulfonated molecules appeared, the reaction slowed drastically. Ultimately, sulfonation stops completely with approximately 60% of the molecules disulfonated and 20% each of the two monosulfonated isomers. This striking constraint on monolayer reactivity and the relationship between the surface chemistry and variations in SAM structure are discussed.

  10. Probing the surface microstructure of layer-by-layer self-assembly chitosan/poly(L-glutamic acid) multilayers: A grazing-incidence small-angle X-ray scattering study

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Nie; Yang, Chunming, E-mail: yangchunming@sinap.ac.cn; Wang, Yuzhu; Zhao, Binyu; Bian, Fenggang; Li, Xiuhong; Wang, Jie, E-mail: wangjie@sinap.ac.cn

    2016-01-01

    This study characterized the surface structure of layer-by-layer self-assembly chitosan/poly(L-glutamic acid) multilayers through grazing-incidence small-angle X-ray scattering (GISAXS), X-ray reflectivity (XRR), and atomic force microscopy (AFM). A weakly long-period ordered structure along the in-plane direction was firstly observed in the polyelectrolyte multilayer by the GISAXS technique. This structure can be attributed to the specific domains on the film surface. In the domain, nanodroplets that were formed by polyelectrolyte molecules were orderly arranged along the free surface of the films. This ordered structure gradually disappeared with the increasing bilayer number because of the complex merging behavior of nanodroplets into large islands. Furthermore, resonant diffuse scattering became evident in the GISAXS patterns as the number of bilayers in the polyelectrolyte multilayer was increased. Notably, the lateral cutoff length of resonant diffuse scattering for these polyelectrolyte films was comparable with the long-period value of the ordered nanodroplets in the polyelectrolyte multilayer. Therefore, the nanodroplets could be considered as a basic transmission unit for structure propagation from the inner interface to the film surface. It suggests that the surface structure with length scale larger than the size of nanodroplets was partially complicated from the interface structure near the substrate, but surface structure smaller than the cutoff length was mainly depended on the conformation of nanodroplets. - Highlights: • The growth of ordered nanodroplets in PEMs was characterized by the GISAXS technique. • The basic transmission units for structure propagation within PEMs were nanodroplets. • High-performance of wave-guiding devices prepared by PEMs was predicted.

  11. Communication: Programmable self-assembly of thin-shell mesostructures

    Science.gov (United States)

    Halverson, Jonathan D.; Tkachenko, Alexei V.

    2017-10-01

    We study numerically the possibility of programmable self-assembly of various thin-shell architectures. They include clusters isomorphic to fullerenes C20 and C60, finite and infinite sheets, tube-shaped and toroidal mesostructures. Our approach is based on the recently introduced directionally functionalized nanoparticle platform, for which we employ a hybrid technique of Brownian dynamics with stochastic bond formation. By combining a number of strategies, we were able to achieve a near-perfect yield of the desired structures with a reduced "alphabet" of building blocks. Among those strategies are the following: the use of bending rigidity of the interparticle bond as a control parameter, programming the morphology with a seed architecture, use of chirality-preserving symmetries for reduction of the particle alphabet, and the hierarchic approach.

  12. Magnetic ToF GISANS on self-assembled nanoparticles

    Science.gov (United States)

    Glavic, Artur; Josten, Elisabeth; Petracic, Oleg; Lauter, Valeria

    2013-03-01

    Nanoparticle superlattices can be considered as novel type of materials with controllable electronic, optical and magnetic properties. Their building blocks are nanoparticles (or ``nanocrystals'') from a metallic, metal-oxide, or semiconducting material or hybrid between different materials. Using self-assembling techniques it is possible to create a large amount of highly ordered 3D structures, which we have investigated for their structural and magnetic properties. The lateral ordering is quantified using electron microscopy and grazing incidence small angle X-ray scattering (GISAXS). The macroscopic magnetic behavior and correlations are investigated by superconducting quantum interference device (SQUID) magnetometry. Utilizing the time of flight (ToF) magnetism reflectometer at SNS the magnetic correlations have been studied with polarized GISANS and PNR. This research at ORNL's Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.

  13. Modelling the self-assembly of virus capsids

    Science.gov (United States)

    Johnston, Iain G.; Louis, Ard A.; Doye, Jonathan P. K.

    2010-03-01

    We use computer simulations to study a model, first proposed by Wales (2005 Phil. Trans. R. Soc. A 363 357), for the reversible and monodisperse self-assembly of simple icosahedral virus capsid structures. The success and efficiency of assembly as a function of thermodynamic and geometric factors can be qualitatively related to the potential energy landscape structure of the assembling system. Even though the model is strongly coarse-grained, it exhibits a number of features also observed in experiments, such as sigmoidal assembly dynamics, hysteresis in capsid formation and numerous kinetic traps. We also investigate the effect of macromolecular crowding on the assembly dynamics. Crowding agents generally reduce capsid yields at optimal conditions for non-crowded assembly, but may increase yields for parameter regimes away from the optimum. Finally, we generalize the model to a larger triangulation number T = 3, and observe assembly dynamics more complex than that seen for the original T = 1 model.

  14. Circuits and programmable self-assembling DNA structures

    OpenAIRE

    Carbone, Alessandra; Seeman, Nadrian C.

    2002-01-01

    Self-assembly is beginning to be seen as a practical vehicle for computation. We investigate how basic ideas on tiling can be applied to the assembly and evaluation of circuits. We suggest that these procedures can be realized on the molecular scale through the medium of self-assembled DNA tiles. One layer of self-assembled DNA tiles will be used as the program or circuit that leads to the computation of a particular Boolean expression. This layer templates the assembly of tiles, and their as...

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

    Science.gov (United States)

    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.

  16. Magnetic manipulation of self-assembled colloidal asters.

    Energy Technology Data Exchange (ETDEWEB)

    Snezhko, A.; Aranson, I. S. (Materials Science Division)

    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

  17. A redox responsive, fluorescent supramolecular metallohydrogel consists of nanofibers with single-molecule width

    KAUST Repository

    Zhang, Ye

    2013-04-03

    The integration of a tripeptide derivative, which is a versatile self-assembly motif, with a ruthenium(II)tris(bipyridine) complex affords the first supramolecular metallo-hydrogelator that not only self assembles in water to form a hydrogel but also exhibits gel-sol transition upon oxidation of the metal center. Surprisingly, the incorporation of the metal complex in the hydrogelator results in the nanofibers, formed by the self-assembly of the hydrogelator in water, to have the width of a single molecule of the hydrogelator. These results illustrate that metal complexes, besides being able to impart rich optical, electronic, redox, or magnetic properties to supramolecular hydrogels, also offer a unique geometrical control to prearrange the self-assembly motif prior to self-assembling. The use of metal complexes to modulate the dimensionality of intermolecular interactions may also help elucidate the interactions of the molecular nanofibers with other molecules, thus facilitating the development of supramolecular hydrogel materials for a wide range of applications. © 2013 American Chemical Society.

  18. Mixed carboranethiol self-assembled monolayers on gold surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Yavuz, Adem [Micro and Nanotechnology Department, Graduate School of Natural and Applied Science, Middle East Technical University, Ankara 06800 (Turkey); Sohrabnia, Nima [Department of Chemistry, Middle East Technical University, Ankara 06800 (Turkey); Yilmaz, Ayşen [Micro and Nanotechnology Department, Graduate School of Natural and Applied Science, Middle East Technical University, Ankara 06800 (Turkey); Department of Chemistry, Middle East Technical University, Ankara 06800 (Turkey); Danışman, M. Fatih, E-mail: danisman@metu.edu.tr [Micro and Nanotechnology Department, Graduate School of Natural and Applied Science, Middle East Technical University, Ankara 06800 (Turkey); Department of Chemistry, Middle East Technical University, Ankara 06800 (Turkey)

    2017-08-15

    Highlights: • M1 binds to the gold surface preferentially when co-deposited with M9 or O1. • Contact angles show similar trends regardless of the gold substrate roughness. • Contact angles were lower, with higher hysteresis, on template stripped gold. • Mixed carboranethiol SAMs have similar morphological properties regardless of mixing ratio. - Abstract: Carboranethiol self-assembled monolayers on metal surfaces have been shown to be very convenient systems for surface engineering. Here we have studied pure and mixed self-assembled monolayers (SAMs) of three different carboranethiol (CT) isomers on gold surfaces. The isomers were chosen with dipole moments pointing parallel to (m-1-carboranethiol, M1), out of (m-9-carboranethiol, M9) and into (o-1-carboranethiol, O1) the surface plane, in order to investigate the effect of dipole moment orientation on the film properties. In addition, influence of the substrate surface morphology on the film properties was also studied by using flame annealed (FA) and template stripped (TS) gold surfaces. Contact angle measurements indicate that in M1/M9 and M1/O1 mixed SAMs, M1 is the dominant species on the surface even for low M1 ratio in the growth solution. Whereas for O1/M9 mixed SAMs no clear evidence could be observed indicating dominance of one of the species over the other one. Though contact angle values were lower and hysteresis values were higher for SAMs grown on TS gold surfaces, the trends in the behavior of the contact angles with changing mixing ratio were identical for SAMs grown on both substrates. Atomic force microscopy images of the SAMs on TS gold surfaces indicate that the films have similar morphological properties regardless of mixing ratio.

  19. Self-assembly of F16ZnPc thin films and F16ZnPc-ZnPc heterostructures on deactivated Si surfaces studied by scanning tunneling microscopy

    Science.gov (United States)

    Tan, Andrew; Wagner, Sean; Zhang, Pengpeng

    2017-02-01

    Using scanning tunneling microscopy, we show that hexadecafluorinated zinc phthalocyanine (F16ZnPc) molecules form two morphologically different self-assembled structures that both display point-on-line coincident epitaxial registration with the deactivated Si(111)-B √{3 }×√{3 } surface. The packing motif in these structures suggests that fluorination of conjugated organic molecules can lead to stronger molecule-substrate interaction, π-π intermolecular interaction, and side-to-side intermolecular repulsion. The delicate balance and interplay between these interactions determine the self-assembly behavior of fluorinated molecules. Furthermore, we demonstrate the formation of vertically and laterally stacked F16ZnPc-ZnPc heterojunctions, allowing for future spectroscopy investigation of molecular electronic structures and charge transfer behavior at organic-organic hetero-interfaces.

  20. Growth of rat dorsal root ganglion neurons on a novel self-assembling scaffold containing IKVAV sequence

    Energy Technology Data Exchange (ETDEWEB)

    Zou Zhenwei; Zheng Qixin [Department of Orthopaedics, Union Hospital, Tongji Medical college of Huazhong University of science and technology, Wuhan, 430022 (China); Wu Yongchao, E-mail: wuyongchao@hotmail.com [Department of Orthopaedics, Union Hospital, Tongji Medical college of Huazhong University of science and technology, Wuhan, 430022 (China); Song Yulin; Wu Bin [Department of Orthopaedics, Union Hospital, Tongji Medical college of Huazhong University of science and technology, Wuhan, 430022 (China)

    2009-08-31

    The potential benefits of self-assembly in synthesizing materials for the treatment of both peripheral and central nervous system disorders are tremendous. In this study, we synthesized peptide-amphiphile (PA) molecules containing IKVAV sequence and induced self-assembly of the PA solutions in vitro to form nanofiber gels. Then, we tested the characterization of gels by transmission electron microscopy and demonstrated the biocompatibility of this gel towards rat dorsal root ganglion neurons. The nanofiber gel was formed by self-assembly of IKVAV PA molecules, which was triggered by metal ions. The fibers were 7-8 nm in diameter and with lengths of hundreds of nanometers. Gels were shown to be non-toxic to neurons and able to promote neurons adhesion and neurite sprouting. The results indicated that the self-assembling scaffold containing IKVAV sequence had excellent biocompatibility with adult sensory neurons and could be useful in nerve tissue engineering.

  1. Growth of rat dorsal root ganglion neurons on a novel self-assembling scaffold containing IKVAV sequence

    International Nuclear Information System (INIS)

    Zou Zhenwei; Zheng Qixin; Wu Yongchao; Song Yulin; Wu Bin

    2009-01-01

    The potential benefits of self-assembly in synthesizing materials for the treatment of both peripheral and central nervous system disorders are tremendous. In this study, we synthesized peptide-amphiphile (PA) molecules containing IKVAV sequence and induced self-assembly of the PA solutions in vitro to form nanofiber gels. Then, we tested the characterization of gels by transmission electron microscopy and demonstrated the biocompatibility of this gel towards rat dorsal root ganglion neurons. The nanofiber gel was formed by self-assembly of IKVAV PA molecules, which was triggered by metal ions. The fibers were 7-8 nm in diameter and with lengths of hundreds of nanometers. Gels were shown to be non-toxic to neurons and able to promote neurons adhesion and neurite sprouting. The results indicated that the self-assembling scaffold containing IKVAV sequence had excellent biocompatibility with adult sensory neurons and could be useful in nerve tissue engineering.

  2. Scanning tunneling microscopy, Fourier transform infrared spectroscopy, and electrochemical characterization of 2-naphthalenethiol self-assembled monolayers on the Au surface: a study of bridge-mediated electron transfer in Ru(NH3)6(2+)/Ru(NH3)6(3+) redox reactions.

    Science.gov (United States)

    Ganesh, V; Lakshminarayanan, V

    2005-09-01

    We have studied the structure, adsorption kinetics, and barrier properties of self-assembled monolayers of 2-naphthalenethiol on Au using electrochemical techniques, grazing-angle Fourier transform infrared (FTIR) spectroscopy, and scanning tunneling microscopy (STM). The results of cyclic voltammetric and impedance measurements using redox probes show that 2-naphthalenethiol on Au forms a stable and reproducible, but moderately blocking, monolayer. Annealing of the self-assembled monolayer (SAM)-modified surface at 72 +/- 2 degrees C remarkably improves the blocking property of the monolayer of 2-naphthalenethiol on Au. From the study of kinetics of SAM formation, we find that the self-assembly follows Langmuir adsorption isotherm. Our STM and FTIR results show that the molecules are adsorbed with the naphthalene ring tilted from the surface normal by forming a square root 3 x 3 R30 degrees overlayer structure. From our studies, we conclude that the electron-transfer reaction of ferro/ferricyanide in the freshly formed monolayer occurs predominantly through the pinholes and defects present in the monolayer. However, in the case of thermally annealed specimen, although the ferro/ferricyanide reaction is almost completely blocked, the electron-transfer reaction of hexaammineruthenium(III) chloride is not significantly inhibited. It is proposed that the electron-transfer reaction in the case of the ruthenium redox couple takes place by a tunneling mechanism through the high-electron-density aromatic naphthalene ring acting as a bridge between the monolayer-modified electrode and the ruthenium complex.

  3. Fabrication of bioinspired nanostructured materials via colloidal self-assembly

    Science.gov (United States)

    Huang, Wei-Han

    Through millions of years of evolution, nature creates unique structures and materials that exhibit remarkable performance on mechanicals, opticals, and physical properties. For instance, nacre (mother of pearl), bone and tooth show excellent combination of strong minerals and elastic proteins as reinforced materials. Structured butterfly's wing and moth's eye can selectively reflect light or absorb light without dyes. Lotus leaf and cicada's wing are superhydrophobic to prevent water accumulation. The principles of particular biological capabilities, attributed to the highly sophisticated structures with complex hierarchical designs, have been extensively studied. Recently, a large variety of novel materials have been enabled by natural-inspired designs and nanotechnologies. These advanced materials will have huge impact on practical applications. We have utilized bottom-up approaches to fabricate nacre-like nanocomposites with "brick and mortar" structures. First, we used self-assembly processes, including convective self-assembly, dip-coating, and electrophoretic deposition to form well oriented layer structure of synthesized gibbsite (aluminum hydroxide) nanoplatelets. Low viscous monomer was permeated into layered nanoplatelets and followed by photo-curing. Gibbsite-polymer composite displays 2 times higher tensile strength and 3 times higher modulus when compared with pure polymer. More improvement occurred when surface-modified gibbsite platelets were cross-linked with the polymer matrix. We observed ˜4 times higher strength and nearly 1 order of magnitude higher modulus than pure polymer. To further improve the mechanical strength and toughness of inorganicorganic nanocomposites, we exploited ultrastrong graphene oxide (GO), a single atom thick hexagonal carbon sheet with pendant oxidation groups. GO nanocomposite is made by co-filtrating GO/polyvinyl alcohol suspension on 0.2 im pore-sized membrane. It shows ˜2 times higher strength and ˜15 times higher

  4. Self-assembled ordered carbon-nanotube arrays and membranes.

    Energy Technology Data Exchange (ETDEWEB)

    Overmyer, Donald L.; Siegal, Michael P.; Yelton, William Graham

    2004-11-01

    Imagine free-standing flexible membranes with highly-aligned arrays of carbon nanotubes (CNTs) running through their thickness. Perhaps with both ends of the CNTs open for highly controlled nanofiltration? Or CNTs at heights uniformly above a polymer membrane for a flexible array of nanoelectrodes or field-emitters? How about CNT films with incredible amounts of accessible surface area for analyte adsorption? These self-assembled crystalline nanotubes consist of multiple layers of graphene sheets rolled into concentric cylinders. Tube diameters (3-300 nm), inner-bore diameters (2-15 nm), and lengths (nanometers - microns) are controlled to tailor physical, mechanical, and chemical properties. We proposed to explore growth and characterize nanotube arrays to help determine their exciting functionality for Sandia applications. Thermal chemical vapor deposition growth in a furnace nucleates from a metal catalyst. Ordered arrays grow using templates from self-assembled hexagonal arrays of nanopores in anodized-aluminum oxide. Polymeric-binders can mechanically hold the CNTs in place for polishing, lift-off, and membrane formation. The stiffness, electrical and thermal conductivities of CNTs make them ideally suited for a wide-variety of possible applications. Large-area, highly-accessible gas-adsorbing carbon surfaces, superb cold-cathode field-emission, and unique nanoscale geometries can lead to advanced microsensors using analyte adsorption, arrays of functionalized nanoelectrodes for enhanced electrochemical detection of biological/explosive compounds, or mass-ionizers for gas-phase detection. Materials studies involving membrane formation may lead to exciting breakthroughs in nanofiltration/nanochromatography for the separation of chemical and biological agents. With controlled nanofilter sizes, ultrafiltration will be viable to separate and preconcentrate viruses and many strains of bacteria for 'down-stream' analysis.

  5. Supramolecular Layer-by-Layer Assembly of 3D Multicomponent Nanostructures via Multivalent Molecular Recognition

    NARCIS (Netherlands)

    Ling, X.Y.; Phang, In Yee; Reinhoudt, David; Vancso, Gyula J.; Huskens, Jurriaan

    2008-01-01

    The supramolecular layer-by-layer assembly of 3D multicomponent nanostructures of nanoparticles is demonstrated. Nanoimprint lithography (NIL) was used as the patterning tool for making patterned β-cyclodextrin (CD) self-assembled monolayers (SAMs) and for the confinement of nanoparticles on the

  6. Spontaneous Self-Assembly of Fully Protected Ester 1:1 [α/α-Nα-Bn-hydrazino] Pseudodipeptides into a Twisted Parallel β-Sheet in the Crystal State.

    Science.gov (United States)

    Romero, Eugénie; Moussodia, Ralph-Olivier; Kriznik, Alexandre; Wenger, Emmanuel; Acherar, Samir; Jamart-Grégoire, Brigitte

    2016-10-07

    Previous studies have demonstrated that amidic α/β-pseudodipeptides, 1:1 [α/α-N α -Bn-hydrazino], have the ability to fold via a succession of γ-turn (C 7 pseudocycle) and hydrazinoturn in CDCl 3 solution, their amide terminals enabling the formation of an intramolecular H-bond network. Despite their lack of a primary amide terminals allowing the formation of the hydrazinoturn, their ester counterparts 1-4 were proven to self-assemble into C 6 and C 7 pseudocycles by intramolecular H-bonds in solution state and into an uncommon twisted parallel β-sheet through intermolecular H-bonding in the crystal state to form a supramolecular helix, with eight molecules needed to complete a full 360° rotation. Such self-organization (with eight molecules) has only been observed in a specific α/α-pseudodipeptide, depsipeptide (Boc-Leu-Lac-OEt). Relying on IR absorption, NMR, X-ray diffraction, and CD analyses, the aim of this study was to demonstrate that stereoisomers of ester 1:1 [α/α-N α -Bn-hydrazino] pseudodipeptides 1-4 are able to self-assemble into this β-helical structure. The absolute configuration of the asymmetric C α -atom of the α-amino acid residue influences the left- or right-handed twist without changing the pitch of the formed helix.

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

    Science.gov (United States)

    Brennan, James R; Hocking, Denise C

    2016-03-01

    organize cells into modular building blocks for artificial tissue fabrication. Fibronectin is an ECM protein that plays a key role in tissue formation during embryonic development. Additionally, the cell-mediated process of converting soluble fibronectin into insoluble, ECM-associated fibrils has been shown to initiate cellular self-assembly in vitro. In this study, we examine the relationship between the strength of cell-substrate adhesions and the ability of fibronectin fibril assembly to induce cellular self-assembly. Our results indicate that substrate composition and density play cooperative roles with cell-mediated fibronectin matrix assembly to control the transition of cells from 2D monolayers into 3D multicellular aggregates. Results of this study provide a quantitative approach to build predictive models of cellular self-assembly, as well as a simple cell-culture platform to produce biomimetic units for modular tissue engineering. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  8. 3D Printing Polymers with Supramolecular Functionality for Biological Applications.

    Science.gov (United States)

    Pekkanen, Allison M; Mondschein, Ryan J; Williams, Christopher B; Long, Timothy E

    2017-09-11

    Supramolecular chemistry continues to experience widespread growth, as fine-tuned chemical structures lead to well-defined bulk materials. Previous literature described the roles of hydrogen bonding, ionic aggregation, guest/host interactions, and π-π stacking to tune mechanical, viscoelastic, and processing performance. The versatility of reversible interactions enables the more facile manufacturing of molded parts with tailored hierarchical structures such as tissue engineered scaffolds for biological applications. Recently, supramolecular polymers and additive manufacturing processes merged to provide parts with control of the molecular, macromolecular, and feature length scales. Additive manufacturing, or 3D printing, generates customizable constructs desirable for many applications, and the introduction of supramolecular interactions will potentially increase production speed, offer a tunable surface structure for controlling cell/scaffold interactions, and impart desired mechanical properties through reinforcing interlayer adhesion and introducing gradients or self-assembled structures. This review details the synthesis and characterization of supramolecular polymers suitable for additive manufacture and biomedical applications as well as the use of supramolecular polymers in additive manufacturing for drug delivery and complex tissue scaffold formation. The effect of supramolecular assembly and its dynamic behavior offers potential for controlling the anisotropy of the printed objects with exquisite geometrical control. The potential for supramolecular polymers to generate well-defined parts, hierarchical structures, and scaffolds with gradient properties/tuned surfaces provides an avenue for developing next-generation biomedical devices and tissue scaffolds.

  9. Self-assembled nanoparticles of cholesterol-modified O-carboxymethyl chitosan as a novel carrier for paclitaxel

    International Nuclear Information System (INIS)

    Wang Yinsong; Li Rongshan; Wang Yumei; Zhao Jing; Jiang Qian; Liu Linglong; Zhang Qiqing

    2008-01-01

    Self-assembled nanoparticles of cholesterol-modified O-carboxymethyl chitosan (CCMC) were prepared to be used as a novel carrier for paclitaxel (PTX) in this study. CCMC-6.9 was synthesized by the covalent conjugation of cholesterol to O-carboxymethyl chitosan with the succinyl linkage and the degree of substitution (DS) of the cholesterol moiety was 6.9%. CCMC-6.9 formed self-assembled nanoparticles with a size of 209.5 nm in aqueous media. Paclitaxel-loaded CCMC-6.9 self-assembled nanoparticles were prepared using a dialysis method and their characteristics were analyzed by dynamic laser light scattering (LLS), transmission electron microscopy (TEM) and ultraviolet spectroscopy (UV). PTX-loaded CCMC-6.9 self-assembled nanoparticles were almost spherical in shape and their size increased from 245.6 to 355.3 nm with PTX-loading content increasing from 18.7% to 34.9%. In vitro release of PTX from CCMC-6.9 self-assembled nanoparticles was carried out by the dynamic dialysis method. PTX continuously released in phosphate buffered saline (PBS) solutions for 84 h at 37 deg. C and its release was sensitive to the pH of the release media. The biodistribution of PTX-loaded CCMC-6.9 self-assembled nanoparticles was studied in female Balb/c mice. Compared with PTX in the solution of Cremophor EL (polyethoxylated castor oil)/ethanol (PTX-Cre), CCMC-6.9 self-assembled nanoparticles significantly increased the uptake of PTX in plasma, liver and spleen, but decreased the uptake in heart and kidney. These results suggest that CCMC-6.9 self-assembled nanoparticles can effectively solubilize PTX and modify its tissue biodistribution, which may be advantageous in enhancing the therapeutic index and reducing the toxicity of PTX

  10. Self-Assembling Wireless Autonomous Reconfigurable Modules (SWARM) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Payload Systems Inc. and the MIT Space Systems Laboratory propose Self-assembling, Wireless, Autonomous, Reconfigurable Modules (SWARM) as an innovative approach to...

  11. Self-Assembling Wireless Autonomous Reconfigurable Modules (SWARM), Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Payload Systems Inc. and the MIT Space Systems Laboratory propose Self-assembling, Wireless, Autonomous, Reconfigurable Modules (SWARM) as an innovative approach to...

  12. Self-Assembled Nanostructured Health Monitoring Sensors, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of the proposed NASA SBIR program is to design, fabricate and evaluate the performance of self-assembled nanostructured sensors for the health...

  13. Self-Assembling Wireless Autonomous Reconfigurable Modules (SWARM), Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Payload Systems Inc. and the MIT Space Systems Laboratory propose Self-assembling, Wireless, Autonomous, Reconfigurable Modules (SWARM) as an innovative approach to...

  14. Primordial and Modern Self Assembling Peptides: Synthesis and Characterization

    Science.gov (United States)

    Cusumano, Stephen

    The creation and analysis of self-assembling peptides has become a recent research trend due to the wide range of applications and usages. Modern self-assembling such as lanreotide, which is an established anti-cancer drug in the pharmaceutical industry, can be synthetically made. More primitive peptides, such as those discovered to be present in the famous Miller experiment, which replicated the primordial earth atmosphere, are representative of a different aspect of self-assembling peptides. If these novel peptides are found to self-assemble, this will give researchers new insight on how primitive cells first formed on this planet to give rise to life. Using the established nanotube structure of lanreotide, TEM protocols were developed to obtain similar high quality TEM images of primitive peptides, to observe if any structures have begun to form.

  15. Multiresponsive self-assembled liquid crystals with azobenzene groups.

    Science.gov (United States)

    Xu, Miao; Chen, Liqin; Zhou, Yifeng; Yi, Tao; Li, Fuyou; Huang, Chunhui

    2008-10-15

    An optical and electric field-responsive self-assembled complex containing nitril azobenzene groups and 1,3,5-triazine-2,4-diamine was obtained and characterized. Both the azobenzene precursor and the complex form a liquid-crystalline phase in a certain temperature range. The transition temperature from crystalline phase to liquid-crystalline mesophase was obviously decreased in the complex by the self-assembling. The self-assembled liquid crystals revealed good response to both stimuli of light irradiation and electric field, and the induced molecular orientation could be held even after the removal of the stimuli. The structural and mechanical investigation proved that the formation of hydrogen bonds and assembly-induced molecular dipolar change contributed to the multiresponding action. This kind of self-assembled complex thus has potential applications in imaging and data storage.

  16. The btp [2,6-bis(1,2,3-triazol-4-yl)pyridine] binding motif: a new versatile terdentate ligand for supramolecular and coordination chemistry.

    Science.gov (United States)

    Byrne, Joseph P; Kitchen, Jonathan A; Gunnlaugsson, Thorfinnur

    2014-08-07

    Ligands containing the btp [2,6-bis(1,2,3-triazol-4-yl)pyridine] motif have appeared with increasing regularity over the last decade. This class of ligands, formed in a one pot ‘click’ reaction, has been studied for various purposes, such as for generating d and f metal coordination complexes and supramolecular self-assemblies, and in the formation of dendritic and polymeric networks, etc. This review article introduces btp as a novel and highly versatile terdentate building block with huge potential in inorganic supramolecular chemistry. We will focus on the coordination chemistry of btp ligands with a wide range of metals, and how it compares with other classical pyridyl and polypyridyl based ligands, and then present a selection of applications including use in catalysis, enzyme inhibition, photochemistry, molecular logic and materials, e.g. polymers, dendrimers and gels. The photovoltaic potential of triazolium derivatives of btp and its interactions with anions will also be discussed.

  17. Synthesis and Characterization of thermo/pH-responsive Supramolecular G-Quadruplexes for the Construction of Supramolecular Hacky Sacks for Biorelevant Applications

    Science.gov (United States)

    Negron Rios, Luis M.

    The impact of size, shape, and distribution of lipophilic regions on the surfaces of nanoscopic objects that are amphiphilic or patchy (such as proteins) are yet to be fully understood. One of the reasons for this is the lack of an appropriate model systems in which to probe this question. Our group has previously reported 2'-deoxyguanosine (8ArG) derivatives that self-assemble in aqueous media into discrete supramolecular hexadecamers that show the lower critical solution temperature (LCST) phenomenon. The LCST phenomenon is a convenient and rigorous strategy to measure the hydrophobicity of a system. Although these SGQs are potentially attractive for biomedical applications like drug-delivery, the narrow window of physiological temperatures complicates their implementation. This moved us to redesign the constituent 8ArG subunits to incorporate imidazole moieties that would lead to pH-responsive SGQs, working isothermally. Upon reaching a threshold temperature (Lower Critical Solution Temperature, LCST) at pH 7, these dual-responsive SGQs further self-assemble to form nano/micro hydrogel globules that we called them supramolecular hacky sacks (SHS). However, we can isolate kinetically stable versions of these SHS by lowering the ionic strength of the medium (i.e., from the molar to the millimolar range) in a process that we term "fixing the SHS", in which these SHS maintain their integrity (size and shape) and stability without the requirement of crosslinking agents. After structural characterization and in vitro studies of SHS, we performed encapsulation studies of DOX, rhodamine, dsDNA (F26T), thrombin binding aptamer (TBA) and dextran (3 kDa) Texas Red conjugate. Then we performed in vivo studies of cell internalization and drug delivery with neuroblastoma SY-SH5Y. The performed studies will bring new approaches for the development of new biotechnology for fundamental applications and the emerging of novel therapeutic agents for biomedical applications.

  18. Dimensional Control and Morphological Transformations of Supramolecular Polymeric Nanofibers Based on Cofacially-Stacked Planar Amphiphilic Platinum(II) Complexes.

    Science.gov (United States)

    Robinson, Matthew E; Nazemi, Ali; Lunn, David J; Hayward, Dominic W; Boott, Charlotte E; Hsiao, Ming-Siao; Harniman, Robert L; Davis, Sean A; Whittell, George R; Richardson, Robert M; De Cola, Luisa; Manners, Ian

    2017-09-26

    Square-planar platinum(II) complexes often stack cofacially to yield supramolecular fiber-like structures with interesting photophysical properties. However, control over fiber dimensions and the resulting colloidal stability is limited. We report the self-assembly of amphiphilic Pt(II) complexes with solubilizing ancillary ligands based on polyethylene glycol [PEG n , where n = 16, 12, 7]. The complex with the longest solubilizing PEG ligand, Pt-PEG 16 , self-assembled to form polydisperse one-dimensional (1D) nanofibers (diameters fibers of length up to ca. 400 nm. The fiber lengths were dependent on the Pt-PEG 16 complex to seed mass ratio in a manner analogous to a living covalent polymerization of molecular monomers. Moreover, the fiber lengths were unchanged in solution after 1 week and were therefore "static" with respect to interfiber exchange processes on this time scale. In contrast, similarly formed near-uniform fibers of Pt-PEG 12 exhibited dynamic behavior that led to broadening of the length distribution within 48 h. After aging for 4 weeks in solution, Pt-PEG 12 fibers partially evolved into 2D platelets. Furthermore, self-assembly of Pt-PEG 7 yielded only transient fibers which rapidly evolved into 2D platelets. On addition of further fiber-forming Pt complex (Pt-PEG 16 ), the platelets formed assemblies via the growth of fibers selectively from their short edges. Our studies demonstrate that when interfiber dynamic exchange is suppressed, dimensional control and hierarchical structure formation are possible for supramolecular polymers through the use of kinetically controlled seeded growth methods.

  19. Supramolecular polymers for organocatalysis in water.

    Science.gov (United States)

    Neumann, Laura N; Baker, Matthew B; Leenders, Christianus M A; Voets, Ilja K; Lafleur, René P M; Palmans, Anja R A; Meijer, E W

    2015-07-28

    A water-soluble benzene-1,3,5-tricarboxamide (BTA) derivative that self-assembles into one-dimensional, helical, supramolecular polymers is functionalised at the periphery with one L-proline moiety. In water, the BTA-derivative forms micrometre long supramolecular polymers, which are stabilised by hydrophobic interactions and directional hydrogen bonds. Furthermore, we co-assemble a catalytically inactive, but structurally similar, BTA with the L-proline functionalised BTA to create co-polymers. This allows us to assess how the density of the L-proline units along the supramolecular polymer affects its activity and selectivity. Both the supramolecular polymers and co-polymers show high activity and selectivity as catalysts for the aldol reaction in water when using p-nitrobenzaldehyde and cyclohexanone as the substrates for the aldol reaction. After optimisation of the reaction conditions, a consistent conversion of 92 ± 7%, deanti of 92 ± 3%, and eeanti of 97 ± 1% are obtained with a concentration of L-proline as low as 1 mol%.

  20. Trigger sequence can influence final morphology in the self-assembly of asymmetric telechelic polymers

    NARCIS (Netherlands)

    Kumar, A.; Lowe, C.P.; Cohen Stuart, M.A.; Bolhuis, P.G.

    2016-01-01

    We report on a numerical study of polymer network formation of asymmetric biomimetic telechelic polymers with two reactive ends based on a self-assembling collagen, elastin or silk-like polypeptide sequence. The two reactive ends of the polymer can be activated independently using physicochemical

  1. Trigger sequence can influence final morphology in the self-assembly of asymmetric telechelic polymers

    NARCIS (Netherlands)

    Kumar, Aatish; Lowe, C.P.; Cohen Stuart, M.A.; Bolhuis, P.G.

    2016-01-01

    We report on a numerical study of polymer network formation of asymmetric biomimetic telechelic polymers with two reactive ends based on a self-assembling collagen, elastin or silk-like polypeptide sequence. The two reactive ends of the polymer can be activated independently using physicochemical

  2. Electron tunneling through alkanedithiol self-assembled monolayers in large-area molecular junctions

    NARCIS (Netherlands)

    Akkerman, Hylke B.; Naber, Ronald C. G.; Jongbloed, Bert; van Hal, Paul A.; Blom, Paul W. M.; de Leeuw, Dago M.; de Boer, Bert

    2007-01-01

    The electrical transport through self-assembled monolayers of alkanedithiols was studied in large-area molecular junctions and described by the Simmons model [Simmons JIG (1963) J Appi Phys 34:1793-1803 and 2581-2590] for tunneling through a practical barrier, i.e., a rectangular barrier with the

  3. Optical constants and self-assembly of phenylene ethynylene oligomer monolayers

    DEFF Research Database (Denmark)

    Marx, E.; Walzer, Karsten; Less, R.J.

    2004-01-01

    This paper studies the self-assembly on gold surfaces of 1,4-ethynylphenyl-4'-ethynylphenyl-2'-nitro-1-benzenedithiolate (EP2NO(2)), a substituted phenylene ethynylene trimer with applications in molecular electronics. We develop an ellipsometric technique to measure the optical constants...

  4. Conformation and intermolecular interactions of SA2 peptides self-assembled into vesicles.

    NARCIS (Netherlands)

    van Hell, A.J.; Klymchenko, A.; Burgers, P.P.; Moret, E.E.; Jiskoot, W.; Hennink, W.E.; Crommelin, D.J.A.; Mastrobattista, E.

    2010-01-01

    Previously we have shown that the recombinantly produced SA2 amphiphilic oligopeptide (Ac-Ala-Ala-Val-Val-Leu-Leu-Leu-Trp-Glu-Glu-COOH) self-assembles into nanovesicles (van Hell et al. 2007). In this study, the intermolecular interactions that contribute to the formation of such peptide vesicles

  5. The SC3 hydrophobin self-assembles into a membrane with distinct mass transfer properties

    NARCIS (Netherlands)

    Wang, [No Value; Shi, FX; Wosten, HAB; Hektor, H; Poolman, B; Robillard, GT; Wang, X.; Shi, Fuxin

    Hydrophobins are a class of small proteins that fulfill a wide spectrum of functions in fungal growth and development. They do so by self-assembling into an amphipathic membrane at hydrophilic-hydrophobic interfaces. The SC3 hydrophobin of Schizophyllum commune is the best-studied hydrophobin. It

  6. Self-assembling behaviour of Pt nanoparticles onto surface of TiO2 ...

    Indian Academy of Sciences (India)

    In the present study, self-assembling behaviour of guest nanoparticles (platinum) onto the surface of host support (titanium dioxide) during photodeposition process as a function of solution pH has been explored in detail by means of transmission electron microscope (TEM). The photocatalytic activity of the resulting ...

  7. Self-Assembled Student Interactions in Undergraduate General Chemistry Clicker Classrooms

    Science.gov (United States)

    MacArthur, James R.; Jones, Loretta

    2013-01-01

    Student interviews, focus groups, and classroom observations were used in an exploratory study of the nature of student interactions in a large (300+ students) general chemistry course taught with clickers. These data suggest that students are self-assembling their learning environment: choosing ways in which to interact with one another during…

  8. Self-assembly of small-molecule fumaramides allows transmembrane chloride channel formation.

    Science.gov (United States)

    Roy, Arundhati; Gautam, Amitosh; Malla, Javid Ahmad; Sarkar, Sohini; Mukherjee, Arnab; Talukdar, Pinaki

    2018-02-20

    This study reports the formation of self-assembled transmembrane anion channels by small-molecule fumaramides. Such artificial ion channel formation was confirmed by ion transport across liposomes and by planar bilayer conductance measurements. The geometry-optimized model of the channel and Cl - ion selectivity within the channel lumen was also illustrated.

  9. Electrochemical and structural characterization of self-assembled thiol monolayers on gold

    NARCIS (Netherlands)

    Sondag-Huethorst, J.A.M.

    1994-01-01

    Self-assembled alkanethiol monolayers on gold are used as model systems in a fundamental study of the potential-dependent wetting and of the galvanic metal deposition. For using such monolayers as model systems, well-defined and ordered monolayers are required. In order to control the

  10. Controlled, bio-inspired self-assembly of cellulose-based chiral reflectors

    NARCIS (Netherlands)

    Dumanli, Ahu Gumrah; Kamita, Gen; Landman, Jasper; van der Kooij, Hanne; Glover, Beverley J.; Baumberg, Jeremy J.; Steiner, Ullrich; Vignolini, Silvia

    The self-assembly process of photonic structures made of cellulose nanocrystals is studied in detail by locally monitoring and controlling water evaporation. Three different stages during the evaporation process are identified. Spectroscopy quantifies the amount of disorder in the fabricated

  11. Rapid, Brushless Self-assembly of a PS-b-PDMS Block Copolymer for Nanolithography

    DEFF Research Database (Denmark)

    Rasappa, Sozaraj; Schulte, Lars; Borah, Dipu

    2014-01-01

    by grafting of a brush layer that renders the surface energy neutral relative to the constituent blocks. We provide here a first study on rapid, low temperature self-assembly of PS-b-PDMS (polystyrene-block-polydimethylsiloxane) on silicon substrates without a brush layer. We show that it forms line...

  12. Study of Silicon Nitrate and Tin Dioxide carbon nanotube composite as lithium-ion battery anode, gas sensor and the self-assembly of carbon nanotubes on copper substrates

    Science.gov (United States)

    Hernandez-Lugo, Dionne M.

    Carbon nanotubes since their discovery have been used for many applications. They are predicted to reinforce novel composite materials because of their structural perfection, excellent mechanical properties and low density. CNT can be made into nanowires of different materials or as part of a composite making them beneficial for the incorporation into electrochemical devices. Carbon nanotubes in this study were gown directly on a copper substrate employing hot filament chemical vapor deposition (HFCVD). Bamboo-like carbon nanotubes were made into electrodes reducing the use of inactive materials on the development of working electrodes for electrochemical application. This BCNT were tested as lithium-ion battery anodes assembled together with high capacity materials such as Silicon and Tin Oxide (4200mAh/g and 782 mAh/g). On this study BCNT served as a conductive matrix as well as buffer matrix for the volume expansion brought by cycling silicon and tin oxide. The composite structural properties enhance the surface-to-volume ratio of the electrode demonstrating a desirable electrochemical performance for a lithium-ion battery anode. As a gas sensor electrode CNT was assembled with tin-oxide directly on a copper substrate for the detection of ethanol, methanol, ammonia and H2S. CNT gave a higher surface area and a conductive matrix aiding to the sensing capabilities of the SnO2 increasing the effectiveness of the matrix material for gas detection. Copper is known to produce CNT with a disturb structure. To develop an electrode on copper with well-ordered CNT other techniques need to be used. One way to do this is by chemical modification of the copper substrate with a molecule able to react with the carbon nanotube. For the attachment of well-ordered carbon nanotubes such as SWCNT a self-assembly monolayer technique is chosen. On this study 4-aminothiophenol served as the linker between the copper substrate and the carbon nanotubes. This study let to chemically

  13. Dynamic stability of nano-fibers self-assembled from short amphiphilic A6D peptides

    Science.gov (United States)

    Nikoofard, Narges; Maghsoodi, Fahimeh

    2018-04-01

    Self-assembly of A6D amphiphilic peptides in explicit water is studied by using coarse-grained molecular dynamics simulations. It is observed that the self-assembly of randomly distributed A6D peptides leads to the formation of a network of nano-fibers. Two other simulations with cylindrical nano-fibers as the initial configuration show the dynamic stability of the self-assembled nano-fibers. As a striking feature, notable fluctuations occur along the axes of the nano-fibers. Depending on the number of peptides per unit length of the nano-fiber, flat-shaped bulges or spiral shapes along the nano-fiber axis are observed at the fluctuations. Analysis of the particle distribution around the nano-fiber indicates that the hydrophobic core and the hydrophilic shell of the nano-structure are preserved in both simulations. The size of the deformations and their correlation times are different in the two simulations. This study gives new insights into the dynamics of the self-assembled nano-structures of short amphiphilic peptides.

  14. Fabrication of supramolecular star-shaped amphiphilic copolymers for ROS-triggered drug release.

    Science.gov (United States)

    Zuo, Cai; Peng, Jinlei; Cong, Yong; Dai, Xianyin; Zhang, Xiaolong; Zhao, Sijie; Zhang, Xianshuo; Ma, Liwei; Wang, Baoyan; Wei, Hua

    2018-03-15

    Star-shaped copolymers with branched structures can form unimolecular micelles with better stability than the micelles self-assembled from conventional linear copolymers. However, the synthesis of star-shaped copolymers with precisely controlled degree of branching (DB) suffers from complicated sequential polymerizations and multi-step purification procedures, as well as repeated optimizations of polymer compositions. The use of a supramolecular host-guest pair as the block junction would significantly simplify the preparation. Moreover, the star-shaped copolymer-based unimolecular micelle provides an elegant solution to the tradeoff between extracellular stability and intracellular high therapeutic efficacy if the association/dissociation of the supramolecular host-guest joint can be triggered by the biologically relevant stimuli. For this purpose, in this study, a panel of supramolecular star-shaped amphiphilic block copolymers with 9, 12, and 18 arms were designed and fabricated by host-guest complexations between the ring-opening polymerization (ROP)-synthesized star-shaped poly(ε-caprolactone) (PCL) with 3, 4, and 6 arms end-capped with ferrocene (Fc) (PCL-Fc) and the atom transfer radical polymerization (ATRP)-produced 3-arm poly(oligo ethylene glycol) methacrylates (POEGMA) with different degrees of polymerization (DPs) of 24, 30, 47 initiated by β-cyclodextrin (β-CD) (3Br-β-CD-POEGMA). The effect of DB and polymer composition on the self-assembled properties of the five star-shaped copolymers was investigated by dynamic light scattering (DLS), transmission electron microscopy (TEM), and fluorescence spectrometery. Interestingly, the micelles self-assembled from 12-arm star-shaped copolymers exhibited greater stability than the 9- and 18-arm formulations. The potential of the resulting supramolecular star-shaped amphiphilic copolymers as drug carriers was evaluated by an in vitro drug release study, which confirmed the ROS-triggered accelerated drug

  15. The effect of Au amount on size uniformity of self-assembled Au nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Chen, S-H; Wang, D-C; Chen, G-Y; Chen, K-Y [Graduate School of Engineering Science and Technology, National Yunlin University of Science and Technology, Taiwan (China)

    2008-03-15

    The self-assembled fabrication of nanostructure, a dreaming approach in the area of fabrication engineering, is the ultimate goal of this research. A finding was proved through previous research that the size of the self-assembled gold nanoparticles could be controlled with the mole ratio between AuCl{sub 4}{sup -} and thiol. In this study, the moles of Au were fixed, only the moles of thiol were adjusted. Five different mole ratios of Au/S with their effect on size uniformity were investigated. The mole ratios were 1:1/16, 1:1/8, 1:1, 1:8, 1:16, respectively. The size distributions of the gold nanoparticles were analyzed by Mac-View analysis software. HR-TEM was used to derive images of self-assembled gold nanoparticles. The result reached was also the higher the mole ratio between AuCl{sub 4}{sup -} and thiol the bigger the self-assembled gold nanoparticles. Under the condition of moles of Au fixed, the most homogeneous nanoparticles in size distribution derived with the mole ratio of 1:1/8 between AuCl{sub 4}{sup -} and thiol. The obtained nanoparticles could be used, for example, in uniform surface nanofabrication, leading to the fabrication of ordered array of quantum dots.

  16. In-capillary self-assembly and proteolytic cleavage of polyhistidine peptide capped quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jianhao; Li, Jingyan; Li, Jinchen; Liu, Feifei [School of Pharmaceutical Engineering and Life Science, Changzhou University, Changzhou, Jiangsu, 213164 (China); Zhou, Xiang; Yao, Yi [Changzhou Qianhong Bio-pharma Co. Ltd, Changzhou 213164, Jiangsu (China); Wang, Cheli [School of Pharmaceutical Engineering and Life Science, Changzhou University, Changzhou, Jiangsu, 213164 (China); Qiu, Lin, E-mail: linqiupjj@gmail.com [School of Pharmaceutical Engineering and Life Science, Changzhou University, Changzhou, Jiangsu, 213164 (China); Jiang, Pengju, E-mail: pengju.jiang@gmail.com [School of Pharmaceutical Engineering and Life Science, Changzhou University, Changzhou, Jiangsu, 213164 (China); State Key Laboratory of Pharmaceutical Biotechnology, Nanjing, Jiangsu (China)

    2015-10-01

    A new method using fluorescence coupled capillary electrophoresis (CE-FL) for monitoring self-assembly and proteolytic cleavage of hexahistidine peptide capped quantum dots (QDs) inside a capillary has been developed in this report. QDs and the ATTO 590-labeled hexahistidine peptide (H6-ATTO) were injected into a capillary, sequentially. Their self-assembly inside the capillary was driven by a metal-affinity force which yielded a new fluorescence signal due to Förster resonance energy transfer (FRET). The highly efficient separation of fluorescent complexes and the FRET process were analyzed using CE-FL. The self-assembly of QDs and biomolecules was found to effectively take place inside the capillary. The kinetics of the assembly was monitored by CE-FL, and the approach was extended to the study of proteolytic cleavage of surface conjugated peptides. Being the first in-depth analysis of in-capillary nanoparticle–biomolecule assembly, the novel approach reported here provides inspiration to the development of QD-based FRET probes for biomedical applications. - Highlights: • We examined the self-assembly QDs with H6-ATTO inside a capillary. • We prove CE-FL to be a powerful method to resolve QDs-H6-ATTO complex. • We achieve chromatographic separation of QDs-H6-ATTO complex. • We discovered a novel strategy for the online detection of thrombin. • This technique integrated “injection, mixing, reaction, separation and detection”.

  17. Self-Assembly of Telechelic Tyrosine End-Capped PEO Star Polymers in Aqueous Solution.

    Science.gov (United States)

    Edwards-Gayle, Charlotte J C; Greco, Francesca; Hamley, Ian W; Rambo, Robert P; Reza, Mehedi; Ruokolainen, Janne; Skoulas, Dimitrios; Iatrou, Hermis

    2018-01-08

    We investigate the self-assembly of two telechelic star polymer-peptide conjugates based on poly(ethylene oxide) (PEO) four-arm star polymers capped with oligotyrosine. The conjugates were prepared via N-carboxy anhydride-mediated ring-opening polymerization from PEO star polymer macroinitiators. Self-assembly occurs above a critical aggregation concentration determined via fluorescence probe assays. Peptide conformation was examined using circular dichroism spectroscopy. The structure of self-assembled aggregates was probed using small-angle X-ray scattering and cryogenic transmission electron microscopy. In contrast to previous studies on linear telechelic PEO-oligotyrosine conjugates that show self-assembly into β-sheet fibrils, the star architecture suppresses fibril formation and micelles are generally observed instead, a small population of fibrils only being observed upon pH adjustment. Hydrogelation is also suppressed by the polymer star architecture. These peptide-functionalized star polymer solutions are cytocompatible at sufficiently low concentration. These systems present tyrosine at high density and may be useful in the development of future enzyme or pH-responsive biomaterials.

  18. Monosaccharides as Versatile Units for Water-Soluble Supramolecular Polymers.

    Science.gov (United States)

    Leenders, Christianus M A; Jansen, Gijs; Frissen, Martijn M M; Lafleur, René P M; Voets, Ilja K; Palmans, Anja R A; Meijer, E W

    2016-03-18

    We introduce monosaccharides as versatile water-soluble units to compatibilise supramolecular polymers based on the benzene-1,3,5-tricarboxamide (BTA) moiety with water. A library of monosaccharide-based BTAs is evaluated, varying the length of the alkyl chain (hexyl, octyl, decyl and dodecyl) separating the BTA and saccharide units, as well as the saccharide units (α-glucose, β-glucose, α-mannose and α-galactose). In all cases, the monosaccharides impart excellent water compatibility. The length of the alkyl chain is the determining factor to obtain either long, one-dimensional supramolecular polymers (dodecyl spacer), small aggregates (decyl spacer) or molecularly dissolved (octyl and hexyl) BTAs in water. For the BTAs comprising a dodecyl spacer, our results suggest that a cooperative self-assembly process is operative and that the introduction of different monosaccharides does not significantly change the self- assembly behaviour. Finally, we investigate the potential of post-assembly functionalisation of the formed supramolecular polymers by taking advantage of dynamic covalent bond formation between the monosaccharides and benzoxaboroles. We observe that the supramolecular polymers readily react with a fluorescent benzoxaborole derivative permitting imaging of these dynamic complexes by confocal fluorescence microscopy. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Dynamics of dissipative self-assembly of particles interacting through oscillatory forces.

    Science.gov (United States)

    Tagliazucchi, M; Szleifer, I

    2016-01-01

    Dissipative self-assembly is the formation of ordered structures far from equilibrium, which continuously uptake energy and dissipate it into the environment. Due to its dynamical nature, dissipative self-assembly can lead to new phenomena and possibilities of self-organization that are unavailable to equilibrium systems. Understanding the dynamics of dissipative self-assembly is required in order to direct the assembly to structures of interest. In the present work, Brownian dynamics simulations and analytical theory were used to study the dynamics of self-assembly of a mixture of particles coated with weak acids and bases under continuous oscillations of the pH. The pH of the system modulates the charge of the particles and, therefore, the interparticle forces oscillate in time. This system produces a variety of self-assembled structures, including colloidal molecules, fibers and different types of crystalline lattices. The most important conclusions of our study are: (i) in the limit of fast oscillations, the whole dynamics (and not only those at the non-equilibrium steady state) of a system of particles interacting through time-oscillating interparticle forces can be described by an effective potential that is the time average of the time-dependent potential over one oscillation period; (ii) the oscillation period is critical to determine the order of the system. In some cases the order is favored by very fast oscillations while in others small oscillation frequencies increase the order. In the latter case, it is shown that slow oscillations remove kinetic traps and, thus, allow the system to evolve towards the most stable non-equilibrium steady state.

  20. Synthesis of nanocrystals and nanocrystal self-assembly

    Science.gov (United States)

    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 (alcohols were used to study the effect of size and morphological control over the nanocrystals. Techniques including X-ray diffraction, transmission electron microscopy, selected area electron diffraction, and high-resolution electron microscopy are used to examine crystallinity and morphology. Chapter 3. By investigating the self-assembly of cadmium selenide-gold (CdSe-Au) nanoparticle mixtures by transmission electron microscopy after solvent evaporation, the effect of solvents in the formation process of CdSe-Au binary nanoparticle superlattices (BNSLs) was studied. 1-dodecanethiol was found to be critical in generating conditions necessary for superlattice formation, prior to the other factors that likely determine structure, highlighting the dual role of this organic polar molecule as both ligand and high boiling point/crystallization solvent. The influence of thiol was investigated under various concentrations (and also

  1. From ring-in-ring to sphere-in-sphere: self-assembly of discrete 2D and 3D architectures with increasing stability.

    Science.gov (United States)

    Sun, Bin; Wang, Ming; Lou, Zhichao; Huang, Mingjun; Xu, Chenglong; Li, Xiaohong; Chen, Li-Jun; Yu, Yihua; Davis, Grant L; Xu, Bingqian; Yang, Hai-Bo; Li, Xiaopeng

    2015-02-04

    Directed by increasing the density of coordination sites (DOCS) to increase the stability of assemblies, discrete 2D ring-in-rings and 3D sphere-in-sphere were designed and self-assembled by one tetratopic pyridyl-based ligand with 180° diplatinum(II) acceptors and naked Pd(II), respectively. The high DOCS resulted by multitopic ligand provided more geometric constraints to form discrete structures with high stability. Compared to reported supramolecular hexagons and polyhedra by ditotpic ligands, the self-assembly of such giant architectures using multitopic ligands with all rigid backbone emphasized the structural integrity with precise preorganization of entire architecture, and required elaborate synthetic operations for ligand preparation. In-depth structural characterization was conducted to support desired structures, including multinuclear NMR ((1)H, (31)P, and (13)C) analysis, 2D NMR spectroscopy (COSY and NOESY), diffusion-ordered NMR spectroscopy (DOSY), multidimensional mass spectrometry, TEM and AFM. Furthermore, a quantitative definition of DOCS was proposed to compare 2D and 3D structures and correlate the DOCS and stability of assemblies in a quantitative manner. Finally, ring-in-rings in DMSO or DMF could undergo hierarchical self-assembly into the ordered nanostructures and generated translucent supramolecular metallogels.

  2. Development of New Supramolecular Lyotropic Liquid Crystals and Their Application as Alignment Media for Organic Compounds.

    Science.gov (United States)

    Leyendecker, Martin; Meyer, Nils-Christopher; Thiele, Christina M

    2017-09-11

    Most alignment media for the residual dipolar coupling (RDC) based molecular structure determination of small organic compounds consist of rod-like polymers dissolved in organic solvents or of swollen cross-linked polymer gels. Thus far, the synthesis of polymer-based alignment media has been a challenging process, which is often followed by a time-consuming sample preparation. We herein propose the use of non-polymeric alignment media based on benzenetricarboxamides (BTAs), which self-assemble into rod-like supramolecules. Our newly found supramolecular lyotropic liquid crystals (LLCs) are studied in terms of their LLC properties and their suitability as alignment media in NMR spectroscopy. Scalable enantiodifferentiating properties are introduced through a sergeant-and-soldier principle by blending achiral with chiral substituted BTAs. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-02-08

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

  4. Self-Assembly for the Synthesis of Functional Biomaterials.

    Science.gov (United States)

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

    2013-02-01

    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.

  5. Sequential programmable self-assembly: Role of cooperative interactions

    Science.gov (United States)

    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.

  6. Molecular self-assembly for biological investigations and nanoscale lithography

    Science.gov (United States)

    Cheunkar, Sarawut

    Small, diffusible molecules when recognized by their binding partners, such as proteins and antibodies, trigger enzymatic activity, cell communication, and immune response. Progress in analytical methods enabling detection, characterization, and visualization of biological dynamics at the molecular level will advance our exploration of complex biological systems. In this dissertation, analytical platforms were fabricated to capture membrane-associated receptors, which are essential proteins in cell signaling pathways. The neurotransmitter serotonin and its biological precursor were immobilized on gold substrates coated with self-assembled monolayers (SAMs) of oligo(ethylene glycol)alkanethiols and their reactive derivatives. The SAM-coated substrates present the biologically selective affinity of immobilized molecules to target native membrane-associated receptors. These substrates were also tested for biospecificity using antibodies. In addition, small-molecule-functionalized platforms, expressing neurotransmitter pharmacophores, were employed to examine kinetic interactions between G-protein-coupled receptors and their associated neurotransmitters. The binding interactions were monitored using a quartz crystal microbalance equipped with liquid-flow injection. The interaction kinetics of G-protein-coupled serotonin 1A receptor and 5-hydroxytyptophan-functionalized surfaces were studied in a real-time, label-free environment. Key binding parameters, such as equilibrium dissociation constants, binding rate constants, and dissociative half-life, were extracted. These parameters are critical for understanding and comparing biomolecular interactions in modern biomedical research. By integrating self-assembly, surface functionalization, and nanofabrication, small-molecule microarrays were created for high-throughput screening. A hybrid soft-lithography, called microcontact insertion printing, was used to pattern small molecules at the dilute scales necessary for highly

  7. Self assembling nanocomposites for protein delivery: supramolecular interactions of soluble polymers with protein drugs.

    Science.gov (United States)

    Salmaso, Stefano; Caliceti, Paolo

    2013-01-02

    Translation of therapeutic proteins to pharmaceutical products is often encumbered by their inadequate physicochemical and biopharmaceutical properties, namely low stability and poor bioavailability. Over the last decades, several academic and industrial research programs have been focused on development of biocompatible polymers to produce appropriate formulations that provide for enhanced therapeutic performance. According to their physicochemical properties, polymers have been exploited to obtain a variety of formulations including biodegradable microparticles, 3-dimensional hydrogels, bioconjugates and soluble nanocomposites. Several soluble polymers bearing charges or hydrophobic moieties along the macromolecular backbone have been found to physically associate with proteins to form soluble nanocomplexes. Physical complexation is deemed a valuable alternative tool to the chemical bioconjugation. Soluble protein/polymer nanocomplexes formed by physical specific or unspecific interactions have been found in fact to possess peculiar physicochemical, and biopharmaceutical properties. Accordingly, soluble polymeric systems have been developed to increase the protein stability, enhance the bioavailability, promote the absorption across the biological barriers, and prolong the protein residence in the bloodstream. Furthermore, a few polymers have been found to favour the protein internalisation into cells or boost their immunogenic potential by acting as immunoadjuvant in vaccination protocols. Copyright © 2011 Elsevier B.V. All rights reserved.

  8. Protonation of Lipids Impacts the Supramolecular and Biological Properties of Their Self-Assembly

    Czech Academy of Sciences Publication Activity Database

    Breton, M.; Berret, J.; F.; Bourgaux, C.; Kral, Teresa; Hof, Martin; Pichon, Ch.; Bessodes, M.; Scherman, D.; Mignet, N.

    2011-01-01

    Roč. 27, č. 20 (2011), s. 12336-12345 ISSN 0743-7463 R&D Projects: GA AV ČR IAA400400621; GA MŠk(CZ) LC06063 Institutional research plan: CEZ:AV0Z40400503 Keywords : fluorescence correlation spectroscopy * angle neutron - scattering * bilayer thickness Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.186, year: 2011

  9. Rheology of Supramolecular Polymers

    DEFF Research Database (Denmark)

    Shabbir, Aamir

    efficient processes or biomedical areas. Design and development of supramolecular polymers using ionic, hydrogen bonding or transition metal complexes with tailored properties requires deep understanding of dynamics both in linear and non-linear deformations. While linear rheology is important to understand...... the dynamics under equilibrium conditions, extensional rheology is relevant during the processing or in the usage of polymers utilizing supramolecular associations for example, acrylic based pressure sensitive adhesives are subjected to extensional deformations during the peeling where strain hardening......) hydrogen bonding polymers, and (b) ionic bonding polymers (hereafter termed as ionomers). We study linear and non-linear rheology fora model system of entangled pure poly(n-butyl acrylate), PnBA, homopolymer andfour poly(acrylic acid), PnBA-PAA, copolymers with varying AA side groups synthesizedvia...

  10. Associative Pattern Recognition Through Macro-molecular Self-Assembly

    Science.gov (United States)

    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.

  11. Synthesis and Self-Assembly of Triangulenium Salts

    DEFF Research Database (Denmark)

    Shi, Dong

    . The formed vesicles showed excellent stability standing over for 7 month at ambient lab conditions or upon heated up to 70 °C as monitored by dynamic light scattering (DLS) method. Chapter 4 reportes the dynamic air–water interfaces catalyzed self-assembly of insoluble aminotriangulenium salts into Stable......–water interfaces and lateral compression of the monolayer results in the collapsing toward the formation of bilayer nanosheets. The nanosheets showed excellent stability after standing over 10 months stocked in a close vial at ambient conditions due to the ionic atmosphere surrounding its charged surfaces...... in the self-assembly of the synthetic amphiphilic triangulenium salt in aqueous media. In this chapter, self-assembled nanotubes, nanorribbons and nanorods are presented and collusions II are made based on the experimental observations. The following chapter 6 repots the chain length effect on the self...

  12. Directed self-assembly of DNA tiles into complex nanocages.

    Science.gov (United States)

    Tian, Cheng; Li, Xiang; Liu, Zhiyu; Jiang, Wen; Wang, Guansong; Mao, Chengde

    2014-07-28

    Tile-based self-assembly is a powerful method in DNA nanotechnology and has produced a wide range of well-defined nanostructures. But the resulting structures are relatively simple. Increasing the structural complexity and the scope of the accessible structures is an outstanding challenge in molecular self-assembly. A strategy to partially address this problem by introducing flexibility into assembling DNA tiles and employing directing agents to control the self-assembly process is presented. To demonstrate this strategy, a range of DNA nanocages have been rationally designed and constructed. Many of them can not be assembled otherwise. All of the resulting structures have been thoroughly characterized by gel electrophoresis and cryogenic electron microscopy. This strategy greatly expands the scope of accessible DNA nanostructures and would facilitate technological applications such as nanoguest encapsulation, drug delivery, and nanoparticle organization. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    Science.gov (United States)

    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.

  14. Self-Assembly in Biosilicification and Biotemplated Silica Materials

    Directory of Open Access Journals (Sweden)

    Francisco M. Fernandes

    2014-09-01

    Full Text Available 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. Self-Assembly in Biosilicification and Biotemplated Silica Materials.

    Science.gov (United States)

    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.

  16. Bioprinting synthetic self-assembling peptide hydrogels for biomedical applications

    International Nuclear Information System (INIS)

    Loo, Yihua; Hauser, Charlotte A E

    2016-01-01

    Three-dimensional (3D) bioprinting is a disruptive technology for creating organotypic constructs for high-throughput screening and regenerative medicine. One major challenge is the lack of suitable bioinks. Short synthetic self-assembling peptides are ideal candidates. Several classes of peptides self-assemble into nanofibrous hydrogels resembling the native extracellular matrix. This is a conducive microenvironment for maintaining cell survival and physiological function. Many peptides also demonstrate stimuli-responsive gelation and tuneable mechanical properties, which facilitates extrusion before dispensing and maintains the shape fidelity of the printed construct in aqueous media. The inherent biocompatibility and biodegradability bodes well for in vivo applications as implantable tissues and drug delivery matrices, while their short length and ease of functionalization facilitates synthesis and customization. By applying self-assembling peptide inks to bioprinting, the dynamic complexity of biological tissue can be recreated, thereby advancing current biomedical applications of peptide hydrogel scaffolds. (paper)

  17. Hydrodynamic Self-Assembly of Topographical Patterns on Soft Materials

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Satish [Univ. of Minnesota, Minneapolis, MN (United States)

    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.

  18. A combined experimental and theoretical study of the supramolecular self-assembly of the natural benzopyran 2,2-dimethyl-3-hydroxy-6-acetyl-chromane and its isomeric benzofuran 10,11-dihydro-10-hydroxytremetone

    Science.gov (United States)

    Gil, Diego M.; Lizarraga, E.; Echeverría, G. A.; Piro, O. E.; Catalán, C. A. N.; Ben Altabef, A.

    2017-10-01

    Epoxidation of 4HMBA, the main metabolite of the medicinal plant Sencecionutans, produces an unstable epoxide eventually giving rise to a mixture of four derivatives, three of them previously reported as natural products. The epoxide product easily undergoes an intra-molecular attack of the phenolic hydroxyl against the epoxide group carbons to produce either a benzofuran or a chromane derivative. When dissolved in methanol-water mixture at room temperature the epoxide is completely solvolyzed to give the corresponding diol (hydrolysis) or vicinal hydroxyl-methoxy (methanolysis) derivative. All the compounds involved in the above reactions were characterized by IR, Raman, H NMR and UV-vis spectroscopies, and by mass spectrometry. Density functional theory (DFT) computations were used to optimize the structure conformations. The optimized structures were further subjected to a Natural Bond Orbital (NBO) and electrostatic potentials analysis. The crystal structures of the title compounds (for short, 3 and 4 respectively) were determined by X-ray diffraction methods. Compound 3 crystallizes in the triclinic P-1 space group with a = 6.4289 (6) Å, b = 8.7120 (6) Å, c = 10.952 (1) Å, α = 92.280 (7)°, β = 95.738 (7)°, γ = 103.973 (7)°, and Z = 2 molecules per unit cell and 4 in the monoclinic P21/c space group with a = 11.2891 (6) Å, b = 9.1902 (4) Å, c = 12.4272 (7) Å. Β = 113.689 (7)°, and Z = 4. In 3 neighboring molecules are linked to each other by OH⋯O (keto) bonds giving rise to a polymeric structure. In 4 the OH group is a bifurcate H-bond donor. It forms a weak intra-molecular OH⋯O (furan) bond and also a much stronger inter-molecular Osbnd H⋯O (keto) bond giving rise to a zig-zag polymeric structure. A detailed analysis of the solid state molecular interactions of compounds 3 and 4 has been performed using Hirshfeld surface analysis and their associated 2D fingerprint plots.

  19. Self-assembly patterning of organic molecules on a surface

    Energy Technology Data Exchange (ETDEWEB)

    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. Self-assembled three-dimensional chiral colloidal architecture

    Science.gov (United States)

    Ben Zion, Matan Yah; He, Xiaojin; Maass, Corinna C.; Sha, Ruojie; Seeman, Nadrian C.; Chaikin, Paul M.

    2017-11-01

    Although stereochemistry has been a central focus of the molecular sciences since Pasteur, its province has previously been restricted to the nanometric scale. We have programmed the self-assembly of micron-sized colloidal clusters with structural information stemming from a nanometric arrangement. This was done by combining DNA nanotechnology with colloidal science. Using the functional flexibility of DNA origami in conjunction with the structural rigidity of colloidal particles, we demonstrate the parallel self-assembly of three-dimensional microconstructs, evincing highly specific geometry that includes control over position, dihedral angles, and cluster chirality.

  1. Sambot II: A self-assembly modular swarm robot

    Science.gov (United States)

    Zhang, Yuchao; Wei, Hongxing; Yang, Bo; Jiang, Cancan

    2018-04-01

    The new generation of self-assembly modular swarm robot Sambot II, based on the original generation of self-assembly modular swarm robot Sambot, adopting laser and camera module for information collecting, is introduced in this manuscript. The visual control algorithm of Sambot II is detailed and feasibility of the algorithm is verified by the laser and camera experiments. At the end of this manuscript, autonomous docking experiments of two Sambot II robots are presented. The results of experiments are showed and analyzed to verify the feasibility of whole scheme of Sambot II.

  2. Self-Assembly of "Chalcone" Type Push-Pull Dye Molecules into Organic Single Crystalline Microribbons and Rigid Microrods for Vis/NIR Range Photonic Cavity Applications.

    Science.gov (United States)

    Vattikunta, Radhika; Venkatakrishnarao, Dasari; Mohiddon, Mahamad Ahamad; Chandrasekar, Rajadurai

    2016-11-04

    A novel supramolecular fluorescent donor-acceptor type dye molecule, (2E,4E)-1-(2-hydroxyphenyl)-5-(pyren-1-yl)penta-2,4-dien-1-one (HPPD) self-assembles in a mixture of ethanol/chloroform through intermolecular π-π stacking (distance ca. 3.384 Å) to form J-aggregated single-crystalline microribbons displaying Fabry-Pèrot (F-P) type visible-range optical resonance. The corresponding borondifluoride dye (HPPD-BF), with a reduced HOMO-LUMO gap, self-assembles into crystalline microrods acting as an F-P type resonator in the near-infrared (NIR) range. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. White-Emissive Self-Assembled Organic Microcrystals.

    Science.gov (United States)

    Li, Zhi Zhou; Liang, Feng; Zhuo, Ming Peng; Shi, Ying Li; Wang, Xue Dong; Liao, Liang Sheng

    2017-05-01

    Organic semiconductor micro-/nanocrystals with regular shapes have been demonstrated for many applications, such as organic field-effect transistors, organic waveguide devices, organic solid-state lasers, and therefore are inherently ideal building blocks for the key circuits in the next generation of miniaturized optoelectronics. In the study, blue-emissive organic molecules of 1,4-bis(2-methylstyryl)benzene (o-MSB) can assemble into rectangular microcrystals at a large scale via the room-temperature solution-exchange method. Because of the Förster resonance energy transfer, the energy of the absorbed photons by the host matrix organic molecules of o-MSB can directly transfer to the dopant organic molecules of tetracene or 1,2:8,9-dibenzopentacene (DBP), which then emit visible photons in different colors from blue to green, and to yellow. More impressively, by modulating the doping molar ratios of DBP to o-MSB, bright white-emissive organic microcrystals with well-preserved rectangular morphology can be successfully achieved with a low doping ratio of 1.5%. These self-assembled organic semiconductor microcrystals with multicolor emissions can be the white-light sources for the integrated optical circuits at micro-/nanoscale. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Fatigue crack propagation in self-assembling nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Klingler, Andreas; Wetzel, Bernd [Institute for Composite Materials (IVW GmbH) Technical University of Kaiserslautern, 67633 Kaiserslautern (Germany)

    2016-05-18

    Self-assembling block-copolymers allow the easy manufacturing of nanocomposites due to the thermodynamically driven in situ formation of nanosized phases in thermosetting resins during the curing process. Complex mechanical dispersion processes can be avoided. The current study investigates the effect of a block-copolymer on the fatigue crack propagation resistance of a cycloaliphatic amine cured epoxy resin. It was found that a small amount of MAM triblock-copolymer significantly increases the resistance to fatigue crack propagation of epoxy. Crack growth rate and the Paris law exponent for fatigue-crack growth were considerably reduced from m=15.5 of the neat epoxy to m=8.1 of the nanocomposite. To identify the related reinforcing and fracture mechanisms structural analyses of the fractured surfaces were performed by scanning electron microscope. Characteristic features were identified to be deformation, debonding and fracture of the nano-phases as well as crack pinning. However, the highest resistance against fatigue crack propagation was achieved in a bi-continuous microstructure that consisted of an epoxy-rich phase with embedded submicron sized MAM inclusions, and which was surrounded by a block-copolymer-rich phase that showed rupture and plastic deformation.

  5. Self-assembled patterns from evaporating layered fluids

    International Nuclear Information System (INIS)

    Govor, L V; Parisi, J; Bauer, G H; Reiter, G

    2009-01-01

    We studied the formation of tree-like patterns of polymer aggregates and rings of nanoparticles during evaporation from a fluid film. We utilize phase separation between two immiscible fluids to generate a double-layer film which dries up in a sequential manner. Both fluid layers may contain a solute, polymer aggregates or nanoparticles. During evaporation of the top layer, instabilities may occur and direct a self-assembly process of the solute which may be further affected by an instability of the bottom layer at a later stage. We present two cases where, after evaporation of the top fluid layer, the solute was adsorbed on the surface of the bottom fluid layer. In comparison to dewetting of a single fluid layer on a solid substrate, the advantage of our double-layer approach lies in the deposition of the solute on the surface of the bottom fluid layer. The relatively high mobility of the solute on such a fluid surface favors the formation of ordered patterns, driven by an instability of the bottom layer.

  6. Graphene controlled H- and J-stacking of perylene dyes into highly stable supramolecular nanostructures for enhanced photocurrent generation

    Science.gov (United States)

    Gan, Shiyu; Zhong, Lijie; Engelbrekt, Christian; Zhang, Jingdong; Han, Dongxue; Ulstrup, Jens; Chi, Qijin; Niu, Li

    2014-08-01

    We report a new method for controlling H- and J-stacking in supramolecular self-assembly. Graphene nanosheets act as structure inducers to direct the self-assembly of a versatile organic dye, perylene into two distinct types of functional nanostructures, i.e. one-dimensional nanotubes via J-stacking and two-dimensional branched nanobuds through H-stacking. Graphene integrated supramolecular nanocomposites are highly stable and show significant enhancement of photocurrent generation in these two configurations of photosensing devices, i.e. solid-state optoelectronic constructs and liquid-junction solar cells.We report a new method for controlling H- and J-stacking in supramolecular self-assembly. Graphene nanosheets act as structure inducers to direct the self-assembly of a versatile organic dye, perylene into two distinct types of functional nanostructures, i.e. one-dimensional nanotubes via J-stacking and two-dimensional branched nanobuds through H-stacking. Graphene integrated supramolecular nanocomposites are highly stable and show significant enhancement of photocurrent generation in these two configurations of photosensing devices, i.e. solid-state optoelectronic constructs and liquid-junction solar cells. Electronic supplementary information (ESI) available: Material and methods, spectroscopic data, AFM and TEM images, materials functional tests and supplementary discussions. See DOI: 10.1039/c4nr02308k

  7. Solvent-dependent self-assembly and ordering in slow-drying semi-crystalline conjugated polymer solutions

    KAUST Repository

    Zhao, Kui

    2015-09-07

    The mechanistic understanding of the intrinsic molecular self-assembly of conjugated polymers is of immense importance to controlling the microstructure development in organic semiconducting thin films, with meaningful impact on charge transport and optoelectronic properties. Yet, to date the vast majority of studies have focused on the fast solution process itself, with studies of slower intrinsic molecular self-assembly in formulations lagging behind. Here we have investigated molecular self-assembly during spontaneous organization and uncovered how changes in formulation influence the microstructure, morphology and transport properties of conjugated polymer thin films. Our results suggest that the polymer-solvent interaction is the key factor for the molecular self-assembly and changes in macroscopic charge transport, which is in contrast with most solution processes, such as spin-coating and blade coating, where solvent drying kinetics dominates the aggregation and crystallization processes. Energetically favourable interactions between the polymer and its solvent are shown to cause chain expansion, resulting in a large hydrodynamic volume and few chain entanglements in solution. This provides molecular freedom for self-assembly and is shown to greatly enhance the local and long range order of the polymer, intra-chain backbone planarity and crystallite size. These improvements, in turn, are shown to endow the conjugated polymer with high carrier transport, as demonstrated by organic thin film transistors.

  8. Fluid-Mediated Stochastic Self-Assembly at Centimetric and Sub-Millimetric Scales: Design, Modeling, and Control

    Directory of Open Access Journals (Sweden)

    Bahar Haghighat

    2016-08-01

    Full Text Available Stochastic self-assembly provides promising means for building micro-/nano-structures with a variety of properties and functionalities. Numerous studies have been conducted on the control and modeling of the process in engineered self-assembling systems constituted of modules with varied capabilities ranging from completely reactive nano-/micro-particles to intelligent miniaturized robots. Depending on the capabilities of the constituting modules, different approaches have been utilized for controlling and modeling these systems. In the quest of a unifying control and modeling framework and within the broader perspective of investigating how stochastic control strategies can be adapted from the centimeter-scale down to the (sub-millimeter-scale, as well as from mechatronic to MEMS-based technology, this work presents the outcomes of our research on self-assembly during the past few years. As the first step, we leverage an experimental platform to study self-assembly of water-floating passive modules at the centimeter scale. A dedicated computational framework is developed for real-time tracking, modeling and control of the formation of specific structures. Using a similar approach, we then demonstrate controlled self-assembly of microparticles into clusters of a preset dimension in a microfluidic chamber, where the control loop is closed again through real-time tracking customized for a much faster system dynamics. Finally, with the aim of distributing the intelligence and realizing programmable self-assembly, we present a novel experimental system for fluid-mediated programmable stochastic self-assembly of active modules at the centimeter scale. The system is built around the water-floating 3-cm-sized Lily robots specifically designed to be operative in large swarms and allows for exploring the whole range of fully-centralized to fully-distributed control strategies. The outcomes of our research efforts extend the state-of-the-art methodologies

  9. Self-assembled monolayers of metallosalophenes on gold

    NARCIS (Netherlands)

    Beulen, M.W.J.; van Veggel, F.C.J.M.; Reinhoudt, David

    2000-01-01

    Salophene complexes of transition metals exhibit a reversible electro- chemistry. We have synthesized salophene complexes with sulfur-containing substituents aimed at the formation of self-assembled monolayers on a gold surface. Such monolayers have interesting cation complexating properties. The

  10. Self-assembly of hydrofluorinated Janus graphene monolayer

    DEFF Research Database (Denmark)

    Jin, Yakang; Xue, Qingzhong; Zhu, Lei

    2016-01-01

    With remarkably interesting surface activities, two-dimensional Janus materials arouse intensive interests recently in many fields. We demonstrate by molecular dynamic simulations that hydrofluorinated Janus graphene (J-GN) can self-assemble into Janus nanoscroll (J-NS) at room temperature. The van...

  11. Self-Assembly on Gold and Graphene for Molecular Electronics

    DEFF Research Database (Denmark)

    Reeler, Nini Elisabeth Abildgaard

    to take place before full coverage of the AuNPs. After full coverage the negatively charged dithiocarbamate end groups tended to repel each other leading to a stabilization of the AuNPs and clusters in the solution. An additional project concerned the fabrication of various self-assembled monolayers (SAMs...

  12. Encapsulation of gold nanoparticles into self-assembling protein nanoparticles

    OpenAIRE

    Yang Yongkun; Burkhard Peter

    2012-01-01

    Abstract Background Gold nanoparticles are useful tools for biological applications due to their attractive physical and chemical properties. Their applications can be further expanded when they are functionalized with biological molecules. The biological molecules not only provide the interfaces for interactions between nanoparticles and biological environment, but also contribute their biological functions to the nanoparticles. Therefore, we used self-assembling protein nanoparticles (SAPNs...

  13. Self-assembled three-dimensional non-volatile memories

    NARCIS (Netherlands)

    Abelmann, Leon; Tas, Niels Roelof; Berenschot, Johan W.; Elwenspoek, Michael Curt

    2010-01-01

    The continuous increase in capacity of non-volatile data storage systems will lead to bit densities of one bit per atom in 2020. Beyond this point, capacity can be increased by moving into the third dimension. We propose to use self-assembly of nanosized elements, either as a loosely organised

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

    Science.gov (United States)

    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.

  15. Multiphonon capture processes in self-assembled quantum dots

    DEFF Research Database (Denmark)

    Magnúsdóttir, Ingibjörg; Uskov, A.; Bischoff, Svend

    2001-01-01

    We investigate capture of carriers from states in the continuous part of the energy spectrum into the discrete states of self-assembled InAs/GaAs QDs via emission of one or two phonons. We are not aware of any other investigations of two-phonon mediated capture processes in QDs, but we show that ...

  16. Synthesis, characterization and self-assembly of Co 3 complexes ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 126; Issue 5. Synthesis, characterization and self-assembly of Co3+ complexes appended with phenol and catechol groups. Afsar Ali Deepak Bansal Rajeev Gupt. Special issue on Chemical Crystallography Volume 126 Issue 5 September 2014 pp 1535-1546 ...

  17. Self-Assembled Microwires of Terephthalic Acid and Melamine

    Directory of Open Access Journals (Sweden)

    Hong Wang

    2017-07-01

    Full Text Available Self-assembled microwires of terephthalic acid (TPA and melamine are prepared through the evaporation of water in a solution mixture of TPA and melamine. The microwires were characterized by using scanning electron microscope (SEM, attenuated total reflection infrared (ATR-IR spectra, and cross-polarized optical microscopy (CPOM. The TPA•M microwires showed semi-conductive properties.

  18. Dynamics of self-assembled cytosine nucleobases on graphene

    Science.gov (United States)

    Saikia, Nabanita; Johnson, Floyd; Waters, Kevin; Pandey, Ravindra

    2018-05-01

    Molecular self-assembly of cytosine (C n ) bases on graphene was investigated using molecular dynamics methods. For free-standing C n bases, simulation conditions (gas versus aqueous) determine the nature of self-assembly; the bases prefer to aggregate in the gas phase and are stabilized by intermolecular H-bonds, while in the aqueous phase, the water molecules disrupt base-base interactions, which facilitate the formation of π-stacked domains. The substrate-induced effects, on the other hand, find the polarity and donor-acceptor sites of the bases to govern the assembly process. For example, in the gas phase, the assembly of C n bases on graphene displays short-range ordered linear arrays stabilized by the intermolecular H-bonds. In the aqueous phase, however, there are two distinct configurations for the C n bases assembly on graphene. For the first case corresponding to low surface coverage, the bases are dispersed on graphene and are isolated. The second configuration archetype is disordered linear arrays assembled with medium and high surface coverage. The simulation results establish the role of H-bonding, vdW π-stacking, and the influence of graphene surface towards the self-assembly. The ability to regulate the assembly into well-defined patterns can aid in the design of self-assembled nanostructures for the next-generation DNA based biosensors and nanoelectronic devices.

  19. Self-assembled monolayers on metal oxides : applications in nanotechnology

    NARCIS (Netherlands)

    Yildirim, O.

    2010-01-01

    The thesis describes the use of phosph(on)ate-based self-assembled monolayers (SAMs) to modify and pattern metal oxides. Metal oxides have interesting electronic and magnetic properties such as insulating, semiconducting, metallic, ferromagnetic etc. and SAMs can tailor the surface properties. FePt

  20. Photophysical characterization of layer-by-layer self-assembled ...

    Indian Academy of Sciences (India)

    D DEY, M N ISLAM∗, S A HUSSAIN and D BHATTACHARJEE. Department of Physics, Tripura University, Suryamaninagar 799 130, India. *Corresponding author. E-mail: md nurulislam@rediffmail.com. Abstract. This communication reports the photophysical characterization of self- assembled layer-by-layer (LbL) films of ...