Gelation of a Highly Fluorescent Urea‐Containing Triarylmelamine Derivative: 2,4,6‐Tris(p‐N′‐Octadecylureido‐Anilino)Triazine in Organic Solvents

A new gelator of urea‐containing triazine derivatives was synthesized and tested in order to explore the gelation potential in different organic solvents. This compound has been found to form organogels with a variety of organic solvents such as decalin and other solvents. The resulting thermo‐reversible gel was characterized by using the dropping ball method and a number of other instruments. The melting temperature of the gel increased with the gel concentration. The intermolecular hydrogen bonding of gelation was demonstrated through an FT‐IR spectrometer. UV‐Vis and fluorescence analysis showed that the gel displayed various optical effects in different organic solvents. The blue fluorescence of the gel in decalin and the quenched effect of gel in CHCl³ were displayed, respectively. Morphological features in decalin and CHCl₃ were studied by applying atomic force microscopy (AFM), and the morphological features demonstrated that there were different aggregations in different solvents. In conductivity electrolyte experiments, the organogel electrolytes indicated high conductivity (σ) comparable to the corresponding NaClO₄/THF solution. The conductivity of gel electrolytes was increased with electrolyte salt.     

Thionicotinamide SAM on Gold: Adsorption Studies and Electroactivity

STM and impedance results of the self‐assembled monolayer (SAM) formed with thionicotinamide (TNA) on gold indicate the presence of defects that increase with the immersion time of the electrode in the TNA solution affecting the SAM electroactivity toward the electron transfer reaction of the cytochrome c metalloprotein and [Fe(CN)₆]^4? and [Ru(NH₃)₆]³⁺ complexes. It was observed that this electroactivity was also affected by the pH of the electrolyte solution. SERS and STM data indicate sulfur coordination to the surface with contribution of the NH₂ group. From the dependence of the TNA surface coverage on the temperature and concentration in solution, thermodynamic parameters of adsorption were determined.     

Photostabilizing of bisphenol A polycarbonate by using UV-absorbers and self protective block copolymers based on resorcinol polyarylate blocks

Bisphenol A polycarbonate degrades due to sunlight, humidity and oxygen. In this study two possible techniques to stabilize the polymer were compared, i.e. blending of UV-absorbers (UVAs) into the polymer or using block copolymers based on resorcinol polyarylates. Combination of different analysis techniques shows that the protection by UVAs is not as good as by the resorcinol polyarylate block copolymers. The block copolymer rearranges itself through a photo-Fries rearrangement within hours into a UV-absorbing top layer. Two different block compositions were studied, and the copolymer with the highest concentration of resorcinol polyarylate groups shows the best protection.     

Assembly of a Novel Dumbbell‐type Dinuclear Copper(II) Complex: Synthesis,Structure and Properties

A new dumbbell‐type 4,4′‐bipy‐bridged dinuclear copper(II) complex, [Cu₂(4,4′‐bipy)L₂(H₂O)₂](ClO₄)₄ · 8CH₃OH · 10H₂O, where L = 1‐[bis(3‐aminopropyl)amino]‐2‐ propanol and bipy = bipyridine, has been synthesized and characterized, X‐ray crystallographic analysis shows that the [Cu₂(4,4′‐bipy)L₂(H₂O)₂]⁴⁺ cations and water molecules generate layer structures extending parallel to bc planes through hydrogen bonding interactions of O–H ··· O and C–H ··· O. The layers are also connected by hydrogen bonding interactions involving methanol, water, and perchlorate anions. These interactions lead to the formation of rectangular channels of 12.3 Å × 6.0 Å along the crystallographic c axis. Perchlorate anions fill in each channel in a sandwich‐like packing mode, they are joined with the adjacent layers by water heptamers. Magnetic susceptibility measurements show that the magnetic exchange interaction is weak although it has a regular π‐type electron transfer pathway. Furthermore, the electrochemical and thermogravimetric properties of the complex were also investigated.     

Comparison of Two Theories for the Relativistic Self Focusing of Laser Beams in Plasma

In the present paper, self‐focusing of laser beams in relativistic plasmas is studied by the moment theory approach. The equilibrium beam radius of the self‐trapped laser beams is also derived. Results are compared with the paraxial ray theory. It is observed from the analysis that at higher intensities, the equilibrium beam radius increases in case of the paraxial ray theory, whereas it becomes independent of the beam intensity in case of the moment theory. Analysis also confirms the role of relativistic electrons travelling with the light pulse in (3D PIC) simulation studies (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Homotopy, Δ-equivalence and concordance for knots in the complement of a trivial link

Link-homotopy and self Δ-equivalence are equivalence relations on links. It was shown by J. Milnor (resp. the last author) that Milnor invariants determine whether or not a link is link-homotopic (resp. self Δ-equivalent) to a trivial link. We study link-homotopy and self Δ-equivalence on a certain component of a link with fixing the other components, in other words, homotopy and Δ-equivalence of knots in the complement of a certain link. We show that Milnor invariants determine whether a knot in the complement of a trivial link is null-homotopic, and give a sufficient condition for such a knot to be Δ-equivalent to the trivial knot. We also give a sufficient condition for knots in the complements of the trivial knot to be equivalent up to Δ-equivalence and concordance.     

Polymer multilayer film formation studied by in situ ellipsometry and electrochemistry

Polyelectrolyte multilayer films adsorbed on gold surfaces were studied by combined ellipsometric and electrochemical methods. Multilayers were composed of “synthetic” (poly(4-styrenesulfonic acid) ammonium salt (PSS) and poly(allylamine hydrochloride) (PAH) (PSS/PAH)) and “semi-natural” (carboxymethyl cellulose (CMC) and chitosan (CHI) (CMC/CHI)) polyelectrolytes. It was found that only PSS/PAH Layer-by-Layer (LbL) assembled structures result in dense surface confined films that limit permeability of small molecules, such as ferri-/ferrocyanide. The PSS/PAH assemblies can be envisaged as films with pinholes, through which small molecules diffuse. During the LbL deposition process of these films a number of pinholes quickly decay. A representative pinhole diameter was found to be approximately 20 μm, which determines the diffusion of small molecules through LbL films, and yet remains constant when the film consists of a few LbL assembled polyelectrolyte bilayers. CMC/CHI LbL assemblies at gold electrode surfaces give very low density films, which do not limit the diffusion of ferri-/ferrocyanide between the surface of the electrode and the solution.     

Electroanalysis of Norepinephrine at Bare Gold Electrode Pure and Modified with Gold Nanoparticles and S‐Functionalized Self‐Assembled Layers in Aqueous Solution

Gold nanoparticles (Au‐NPs), cystamine (CA) and 3,3′‐dithiodipropionic acid (DTDPA) modified gold bare electrodes were applied in voltammetric sensors for simultaneous detection of norepinephrine (NEP), ascorbic (AA) and uric (UA) acids. A linear relationship between norepinephrine concentration and current response was obtained in the range of 0.1 μM to 600 μM M with the detection limit ≤0.091 μM for the electrodes modified at 2D template and in the range of 0.1 μM to 700 μM M with the detection limit ≤0.087 μM for the electrodes modified at 3D template The results have shown that using modified electrodes it is possible to perform electrochemical analysis of norepinephrine without interference of ascorbic and uric acids, whose presence is the major limitation in norepinephrine determination at a bare gold electrode. The modified SAMs electrodes show good selectivity, sensitivity, reproducibility and high stability.     

Stepwise and Self‐Assembly Synthesis of Tetranuclear Iron–Thiolate–Diisocyanide Metallocyclophane Complexes

Treatment of known complex [Cp₂Fe₂ (μ‐SEt )₂(CH₃CN )₂](BF₄ )₂ ( 1 (BF₄ )₂) with 2 equiv of 1,4‐bis(isocyanomethyl)benzene (1,4‐CNCH₂C₆H₄CH₂NC ; L1 ) or 4,4′‐diisocyanophenyl ether (4,4′‐CNC₆H₄OC₆H₄NC ; L2 ) result in the formation of two new‐type diisocyanide complexes [Cp₂Fe₂ (μ‐SEt )₂(1,4‐CNCH₂C₆H₄CH₂NC )₂](BF₄ )₂ ( 2a (BF₄ )₂) or [Cp₂Fe₂ (μ‐SEt )₂(4,4′‐CNC₆H₄OC₆H₄NC )₂](BF₄ )₂ ( 2b (BF₄ )₂), respectively. The new‐type 24‐membered ring tetranuclear iron–thiolate–aryldiisocyanide metallocyclophane complex [Cp₄Fe₄ (μ‐SEt )₄(μ‐1,4‐CNCH₂C₆H₄CH₂NC )₂](BF₄ )₄ ( 3a (BF₄ )₄) has been synthesized by using a self‐assembly reaction between equimolar amounts of 1 (BF₄ )₂ and 1,4‐bis(isocyanomethyl)benzene or by a stepwise route involving mixing a 1:1 molar ratio of complexes 1 (BF₄ )₂ and 2a (BF₄ )₂. A similar approach was used through the application of equal molar ratio of complexes 1 (BF₄ )₂ and 2b (BF₄ )₂ to give a 30‐membered ring tetranuclear iron–thiolate–aryldiisocyanide metallocyclophane complex [Cp₄Fe₄ (μ‐SEt )₄(4,4′‐CNC₆H₄OC₆H₄NC )₂][BF₄ ]₄ ( 3b (BF₄ )₄). The spectroscopic and electrochemical properties of four iron–sulfur core complexes were determined.