Direct current and impedance spectroscopic studies on MoO3 modified ZnPc/ITO Schottky diodes

We use experimental results of direct current and low signal impedance spectroscopy to investigate the conduction mechanism in organic semiconductor ZnPc. The experimental results demonstrate an increase in current and holes mobility by the introduction of a thin MoO₃ film at the ITO/ZnPc interface. This significantly improves the device performance. The improvement is explained in terms of the reduction in the effective barrier for charge transfer from ZnPc to ITO.     

The weak McShane integral

We present a weaker version of the Fremlin generalized McShane integral (1995) for functions defined on a σ-finite outer regular quasi Radon measure space (S,Σ, T, µ) into a Banach space X and study its relation with the Pettis integral. In accordance with this new method of integration, the resulting integral can be expressed as a limit of McShane sums with respect to the weak topology. It is shown that a function f from S into X is weakly McShane integrable on each measurable subset of S if and only if it is Pettis and weakly McShane integrable on S. On the other hand, we prove that if an X-valued function is weakly McShane integrable on S, then it is Pettis integrable on each member of an increasing sequence (S _l ) _l?1 of measurable sets of finite measure with union S. For weakly sequentially complete spaces or for spaces that do not contain a copy of c ₀, a weakly McShane integrable function on S is always Pettis integrable. A class of functions that are weakly McShane integrable on S but not Pettis integrable is included.     

A Synthetic Route to Chiral Dihydrobenzothiazines through Ring Opening of Activated Aziridines with 2‐Halothiophenols/Copper‐Powder‐Mediated C−N Cyclization

A simple protocol for the synthesis of dihydrobenzothiazines through regio‐ and stereoselective S_N2‐type ring opening of N‐tosylaziridines with sulfur nucleophiles followed by copper‐powder‐mediated intramolecular C?N cyclization in excellent yields (up to 95 %) with high diastereo‐ and enantioselectivity (up to >99 %) is reported.     

Multicomponent reaction of amine,carbon disulfide,and fluoronitrobenzene via nucleophilic attack on the fluorinated carbon for the synthesis of nitrophenyl methylcarbamodithioates

In this paper, multicomponent reaction of amine, carbon disulfide and fluoronitrobenzene is reported for the synthesis of nitrophenyl methylcarbamodithioate derivatives. The method is based on the nucleophilic attack of the activated methylcarbamodithioate salt to fluoronitrobenzene. Several starting materials are tested and successfully produced the corresponding nitrophenyl methylcarbamodithioate. A possible mechanism for the reaction is suggested.     

Amphiphilicity-driven organization of nanoparticles into discrete assemblies

We present a method for organizing metallic nanoparticles in solution that is based on the hydrophobic effect and does not require either hydrogen bonding or molecular recognition. When amphiphilic V-shaped molecules are attached to a gold cluster, an aggregation process ensues in aqueous solution and leads to the formation of well-defined cylindrical and vesicular nanoarrays of particles. The metallic clusters densely pack at the boundary separating the hydrophobic core from the hydrophilic corona of the hybrid micelle-like aggregates. This design allows one to assemble and disassemble the nanoparticles in a reversible manner and control the size and the morphology of the arrays by changing the conditions of the solution preparation. The versatility of this method is demonstrated by its applicability to different metals with covalently attached amphiphilic arms with various chemical compositions (PS-PEO and PB-PEO) and molecular weights.     

Investigating wettability alteration due to asphaltene precipitation: Imprints in surface multifractal characteristics

In the present study, multifractality and its formalism were employed to investigate the surface characteristics of an asphaltene deposited heterogeneous solid surface. Wettability alteration of the solid surface was found to affect the multifractal characteristics of an asphaltene deposited heterogeneous surface. Multifractal spectra f(α) show that the more oil wet the surface, the wider the spectrum, and the higher the f_max. The notable distinction between the multifractal spectra associated with different surface wettabilities can be used as a new aspect of wettability alteration.     

From small building blocks to complex molecular architecture

[reaction: see text] We describe a synthesis of a dendrimer-like amphiphile containing a flat rigid core and 12 hydrophobic and hydrophilic arms. We employ a modular approach based on stepwise protection chemistry starting from simple building blocks. The key feature of this approach is the absence of a polymerization step, which makes it applicable for linear monofunctionalized precursors of any kind. This strategy also allows for precise control of the number of arms and ensures their alternating arrangement.     

Investigating the effect of different asphaltene structures on surface topography and wettability alteration

This paper aims at investigation of the effect of asphaltene structure on wettability and topography alteration of a glass surface as a result of asphaltene precipitation. In order to provide a better insight into the topography alteration, a bi-fractal approach was employed. Such an approach is capable of discriminating topography alteration in two different surface types, namely, macro-asperities and micro-asperities. The observed variation of the fractal dimension in the two surface types could be considered as the consequence of different asphaltene sources. Therefore, the structure of different asphaltene sources was carefully examined. The effect of asphaltene structure is more pronounced for asphaltene precipitation at higher pressure. It was revealed that asphaltene particles of high complexity and with larger poly-aromatic rings tend to be detached easier at higher pressure than those with smaller poly-aromatic rings. Another evidence to emphasize the significance of asphaltene structure was given through wettability alteration. It was found that asphaltene particles with larger poly-aromatic rings turn the surface less oil wet at higher pressure. It seems that the difference in wetting condition and surface topography alteration of different asphaltene sources roots in their different structures.     

Amphiphilic gold nanoparticles with V-shaped arms

Here we describe a very efficient method to produce well-defined amphiphilic gold nanoparticles (Au NPs) with an equal number of hydrophobic and hydrophilic arms which are distributed along the surface of a 2-nm gold core in an alternating fashion. The strategy involves direct coupling of V-shaped block copolymer amphiphile 2 with a carboxylic group at its junction point to mercaptophenol-terminated Au NPs. The reaction proceeds under mild esterification conditions and yields the product with a molecular weight of 40 kDa, high grafting density (2.9 chains/nm2), and extremely low polydispersity (1.07). The big advantage of this approach is the opportunity to avoid the use of expensive and often inaccessible polymeric thiols. The method described here is applicable to any carboxyl-terminated molecules and can be used for the preparation of complex, yet well-defined, macromolecular hybrid structures such as 1 (Au(PB-PEG)n). The new product, which was characterized by a combination of SEC, NMR, UV-vis, DLS, and TEM, represents a unique example of gold nanoparticles soluble in any conventional solvent.     

Fabrication and characterization of ZnTPP:PCBM bulk heterojunction (BHJ) solar cells

Bulk heterojunction (BHJ) solar cells were fabricated based on blended films of a porphyrin derivative 5,10,15,20-Tetraphenyl-21H,23H-porphine zinc (ZnTPP) and a fullerene derivative [6,6]-phenyl-C₆₁ butyric acid methyl ester (PCBM) as the active layer. The ZnTTP:PCBM BHJ solar cells were fabricated by spin-casting of the blended layer. The weight ratios of ZnTPP and PCBM were varied from 1:1 to 0:10. The electronic and optical properties of each cell were investigated. Optical density (OD) of the blended film for each cell was extracted from its reflection and transmission curves. OD and average absorption coefficients of the active materials were used to determine film thicknesses. Absorption spectra of each component material were compared with the spectra of the blended films. Current density–Voltage (J–V) characteristics were recorded under dark as well as under the illumination of AM 1.5G (1 sun) solar spectrum. The BHJ solar cell with ZnTPP:PCBM ratio of 1:9 showed the best performance . The values of RR, V_OC , J_SC , FF and η for these ratios were 106.3, 0.4 V, 1.316 mA/cm², 0.4 and 0.21%, respectively. The cross-section of this device using SEM was also examined.