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Self assembly

Xingjuan Zhao, Xiaoli Yu, Yong-Ill Lee, Hong-Guo Liu
Composite thin films with well-defined and parallel nanowires were fabricated from the binary blends of a diblock copolymer polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) and several homo-polystyrenes (h-PSs) at the air/liquid interface through a facile technique, which involves solution self-assembly, interface adsorption, and further self-organization processes. It was confirmed that the nanowires that appeared at the air/water interface came from the cylindrical micelles formed in solution. Interestingly, the diameters of the nanowires are uniform and can be tuned precisely from 45 to 247 nm by incorporating the h-PS molecules into the micellar core...
October 26, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Feng Zhou, Ke-Hua Gu, Zhen-Yu Zhang, Meng-Yao Zhang, Sheng Zhou, Zhihao Shen, Xing-He Fan
By making use of the host-guest interactions between the host molecule tris-o-phenylenedioxycyclotriphosphazene (TPP) and the rod-coil block copolymer (BCP) poly(ethylene oxide)-block-poly(octyl 4'-octyloxy-2-vinylbiphenyl-4-carboxylate) (PEO-b-PVBP), the supramolecular rod-rod block copolymer P(EO@TPP)-b-PVBP was constructed. It consists of a crystalline segment P(EO@TPP) with a hexagonal crystalline structure and a columnar nematic liquid-crystalline segment (PVBP). As the PVBP segments arrange themselves as columnar nematic phases, the crystalline structure of the inclusion complex P(EO@TPP), which has a smaller diameter, is destroyed...
October 26, 2016: Angewandte Chemie
Ingo Hoffmann, Miriam Simon, Bela Farago, Ralf Schweins, Peter Falus, Olaf Holderer, Michael Gradzielski
Oppositely charged polyelectrolyte (PE) surfactant mixtures can self-assemble into a large variety of mesoscopic structures, so-called polyelectrolyte surfactant complexes (PESCs). These structures directly affect the macroscopic behavior of such solutions. In this study, we investigated mixtures of the cationically charged PE JR 400 and the anionic surfactant SDS with the help of different neutron scattering and fluorescence methods. While an excess of PE charges in semi-dilute solutions causes an increase of viscosity, it has been observed that an excess of surfactant charges reduces the viscosity while precipitation is observed at charge equilibrium...
September 28, 2016: Journal of Chemical Physics
Bin Huang, Xiaomeng Wang, Chengwei Li, Jiajing Yi, Rongsheng Lu, Jiayue Tao
This paper describes the design, working principle, as well as calibration of an air-floating six-axis force measurement platform, where the floating plate and nozzles were connected without contact, preventing inter-dimensional coupling and increasing precision significantly. The measurement repeatability error of the force size in the platform is less than 0.2% full scale (FS), which is significantly better than the precision of 1% FS in the six-axis force sensors on the current market. We overcame the difficulties of weight loading device in high-precision calibration by proposing a self-calibration method based on the floating plate gravity and met the calibration precision requirement of 0...
September 2016: Review of Scientific Instruments
Marco A Blanco, Vincent K Shen
A generic but simple model is presented to evaluate the effect of the heterogeneous surface charge distribution of proteins and zwitterionic nanoparticles on their thermodynamic phase behavior. By considering surface charges as continuous "patches," the rich set of surface patterns that is embedded in proteins and charged patchy particles can readily be described. This model is used to study the fluid phase separation of charged particles where the screening length is of the same order of magnitude as the particle size...
October 21, 2016: Journal of Chemical Physics
Christian Urban, Roberto Otero, David Écija, Marta Trelka, Nazario Martín, José M Gallego, Rodolfo Miranda
We have measured STM movies to study the diffusion of individual vacancies in a self-assembled layer of a tetrathiafulvalene derivative (exTTF) on Au(111) at room temperature. The diffusion is anisotropic, being faster along the compact direction of the molecular lattice. A detailed analysis of the anisotropic displacement distribution of the single vacancies shows that the relative abundance of double jumps (that is, the collective motion of molecular dimers) with respect to single jumps is rather large, the number of double jumps being more than 20% of the diffusion events...
October 21, 2016: Journal of Chemical Physics
Kirill Bobrov, Nataliya Kalashnyk, Laurent Guillemot
We present a room temperature STM study of perylene adsorption on Ag(110) at the monolayer coverage regime. We found that structure and symmetry of the perylene monolayer are settled by thermodynamic balance of the three factors: (i) the ability of perylene molecules to recognize specific adsorption sites on the (110) lattice, (ii) the intermolecular interaction, and (iii) the accommodation of thermal motion of the molecules. The moderate strength of the site recognition and the intermolecular interaction, of the same order of magnitude as kT ∼ 25 meV, represents a key feature of the thermodynamic balance...
October 21, 2016: Journal of Chemical Physics
Mario Einax, Tobias Richter, Markus Nimmrich, Philipp Rahe, Irena G Stará, Ivo Starý, Angelika Kühnle, Philipp Maass
Molecular self-assembly of racemic heptahelicene-2-carboxylic acid on a dielectric substrate at room temperature can be used to generate wire-like organic nanostructures consisting of single and double molecular rows. By means of non-contact atomic force microscopy, we investigate the growth of the wire-like pattern after deposition by experimental and theoretical means. From analyzing the time dependence of the mean row length, two distinct regimes were found. At the early post-deposition stage, the mean length grows in time...
October 7, 2016: Journal of Chemical Physics
Chandrashekhar V Kulkarni, Anan Yaghmur, Miloš Steinhart, Manfred Kriechbaum, Michael Rappolt
We present the first report on the effect of hydrostatic pressure on colloidally stabilized lipid nanoparticles enveloping inverse non-lamellar self-assemblies in their interiors. These internal self-assemblies were systematically tuned into bicontinuous cubic (Pn3m and Im3m), micellar cubic (Fd3m), hexagonal (H2), and inverse micellar (L2) phases by regulating the lipid-oil ratio while the hydrostatic pressure was varied from atmospheric pressure to 1200 bar, and back to the atmospheric pressure. The pressure effect on these lipid nanoparticles was compared with their equilibrium bulk, non-dispersed counterparts, i...
October 26, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Zhendong Fu, Yinguo Xiao, Artem Feoktystov, Vitaliy Pipich, Marie-Sousai Appavou, Yixi Su, Erxi Feng, Wentao Jin, Thomas Brückel
The magnetic-field-induced assembly of magnetic nanoparticles (NPs) provides a unique and flexible strategy in the design and fabrication of functional nanostructures and devices. We have investigated the field-induced self-assembly of core-shell iron oxide NPs dispersed in toluene by means of small-angle neutron scattering (SANS). The form factor of the core-shell NPs was characterized and analyzed using SANS with polarized neutrons. Large-scale aggregates of iron oxide NPs formed above 0.02 T as indicated by very-small-angle neutron scattering measurements...
October 26, 2016: Nanoscale
Iam Choon Khoo, Chun-Wei Chen, Tsung-Jui Ho
In this paper, we show that photosensitive azo-dye doped Blue-phase liquid crystals (BPLC) formed by natural molecular self-assembly are capable of high diffraction efficiency holographic recording with memory that can be prolonged from few seconds to several minutes by uniform illumination with the reference beam. Operating in the Bragg regime, we have observed 50 times improvement in the grating diffraction efficiency and shorter recording time compared to previous investigations. The enabling mechanism is BPLC's lattice distortion and index modulation caused by the action of light on the azo-dopant; upon photo-excitation, the azo-molecules undergo transformation from the oblong-shaped Trans-state to the bent-shaped Cis-state, imparting disorder and also cause the surrounding BPLC molecules to undergo coupled flow &reorientation leading to lattice distortion and index modulation...
October 26, 2016: Scientific Reports
Farooq Khurum Shehzad, Ningning Qu, Yunshan Zhou, Lijuan Zhang, Huanyao Ji, Zonghai Shi, Jiaqi Li, Sadaf Ul Hassan
Composite films with the general formula (POM/CuTAPc)n derived from water-soluble Keggin-type polyoxometalates (POMs = H5PMo10V2O40, H4SiW12O40, H3PMo12O40 and H3PW12O40) and water-insoluble 4,9,16,23-copper tetraaminophthalocyanine (denoted CuTAPc) are successfully fabricated by a layer-by-layer self-assembly technique and systematically characterized. The structure of the polyoxometalate anions in the multilayers is kept intact; the deposition amounts of POM and CuTAPc remain constant in every adsorption cycle of the composite film assembly process...
October 26, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Wendao You, Liang Xu, Xing Zhang, Huan Zou, Dongtao Shi, Hanshuo Zhang, Juan Li, Weichang Chen, Rui Li
MicroRNAs (miRNAs) are globally dysregulated in human carcinomas. However, the specific miRNAs that mediate gastric cancer metastasis have not been identified. We identified 100 miRNAs that are dysregulated in gastric cancer and used a self-assembled cell microarray method to systematically evaluate their capacity to regulate cell migration. MiR-451, which is down-regulated in human gastric cancer samples, potently modulated multiple metastatic phenotypes including cell migration, invasion, proliferation, and epithelial-mesenchymal transition...
October 25, 2016: Journal of Laboratory Automation
Romana Baltic, Marina Pivetta, Fabio Donati, Christian Wäckerlin, Aparajita Singha, Jan Dreiser, Stefano Rusponi, Harald Brune
Regular arrays of single atoms with stable magnetization represent the ultimate limit of ultra-high density storage media. Here we report a self-assembled superlattice of individual and non-interacting Dy atoms on graphene grown on Ir(111), with magnetic hysteresis up to 5.6 T and spin lifetime of 1000 s at 2.5 K. The observed magnetic stability is a consequence of the intrinsic low electron and phonon densities of graphene and the six-fold symmetry of the adsorption site. Our single atom magnet array has a density of 115 Tbit/inch(2)...
October 25, 2016: Nano Letters
Mattia Riccardo Monaco, Daniele Fazzi, Nobuya Tsuji, Markus Leutzsch, Saihu Liao, Walter Thiel, Benjamin List
The heterodimerizing self-assembly between a phosphoric acid catalyst and a carboxylic acid has recently been established as a new activation mode in Brønsted acid catalysis. In this article, we present a comprehensive mechanistic investigation on this activation principle, which eventually led to its elucidation. Detailed studies are reported, including computational investigations on the supramolecular heterodimer, kinetic studies on the catalytic cycle, and a thorough analysis of transition states by DFT calculations for the rationalization of the catalyst structure-selectivity relationship...
October 25, 2016: Journal of the American Chemical Society
Saminathan Ramakrishnan, Sivaraman Subramaniam, Adrian Francis Stewart, Guido Grundmeier, Adrian Keller
DNA origami has become a widely used method for synthesizing well-defined nanostructures with promising applications in various areas of nanotechnology, biophysics, and medicine. Recently, the possibility to transfer the shape of single DNA origami nanostructures into different materials via molecular lithography approaches has received growing interest due to the great structural control provided by the DNA origami technique. Here, we use ordered monolayers of DNA origami nanostructures with internal cavities on mica surfaces as molecular lithography masks for the fabrication of regular protein patterns over large surface areas...
October 25, 2016: ACS Applied Materials & Interfaces
Zohar A Arnon, Andreas Vitalis, Aviad Levin, Thomas C T Michaels, Amedeo Caflisch, Tuomas P J Knowles, Lihi Adler-Abramovich, Ehud Gazit
The dynamic nature of supramolecular polymers has a key role in their organization. Yet, the manipulation of their dimensions and polarity remains a challenge. Here, the minimalistic diphenylalanine building block was applied to demonstrate control of nano-assemblies growth and shrinkage using microfluidics. To fine-tune differential local environments, peptide nanotubes were confined by micron-scale pillars and subjected to monomer flows of various saturation levels to control assembly and disassembly. The small-volume device allows the rapid adjustment of conditions within the system...
October 25, 2016: Nature Communications
Kai Ma, Ruirui Xing, Ti-Feng Jiao, Guizhi Shen, Chengjun Chen, Junbai Li, Xuehai Yan
Self-assembling peptide-based materials are playing an important role in fabricating drug delivery carriers, however, they are often limited by several challenges, such as precise structure modulation, desirable nanoscale size and sufficient circulation lifetime in the body. To address this issue, herein one type of injectable dipeptide-based nanocarriers with well-modulated size and structure has been developed by adjusting glutaraldehyde (GA) assisted cationic dipeptide (CDP) assembly. After loading a model photosensitive drug (Ce6) and further decorating CDP nanoparticles (NPs) with heparin polymers (Hep), the desired dipeptide-based NPs are achieved with average diameter of 100 nm and surface charge of -25 mV, which are favorable for the enhanced permeability and retention effects...
October 25, 2016: ACS Applied Materials & Interfaces
Jianbo Tan, Xuechao Zhang, Dongdong Liu, Yuhao Bai, Chundong Huang, Xueliang Li, Li Zhang
Carbon dioxide (CO2 )-responsive polymer nano-objects are prepared by photoinitiated reversible addition-fragmentation chain transfer dispersion polymerization of 2-hydroxypropyl methacrylate and 2-(dimethylamino)ethyl methacrylate (DMAEMA) in water at room temperature using a poly(poly(ethylene glycol) methyl ether methacrylate) macromolecular chain transfer agent. Kinetic studies confirm that full monomer conversions are achieved in all cases within 10 min of visible-light irradiation (405 nm, 0.5 mW cm(-2) )...
October 25, 2016: Macromolecular Rapid Communications
Guoliang Liu, Matthias Zeller, Kongzhao Su, Jiandong Pang, Zhanfeng Ju, Daqiang Yuan, Maochun Hong
Multiple orthogonal coordinative interactions were utilized to construct heterometal-decorated tetrahedral cages from in situ formed trinuclear Zr(IV) clusters through the combination with other metal ions such as Cu(II) or Pd(II) . Through effective use of the hard/soft acid/base principle, the orthogonal self-assembly process of Zr-bpydc-CuCl2 (H2 bpydc=2,2-bipyridine-5,5-dicarboxylic acid) can be finely controlled using three strategies: post-synthetic metallization, a stepwise metalloligand approach, or a one-pot reaction...
October 25, 2016: Chemistry: a European Journal
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