Laser-flash photolysis study of dithiobis (tetrazole); reactivities of tetrazole-thio radical

The photo-cleavage of S S bond of 5,5′-dithiobis (1-phenyl-1H-tetrazole) has been studied by the nanosecond-laser flash photolysis method. The transient absorption band at ca. 430 nm was attributed to 1-phenyl-1H-tetrazole-5-thio radical forming by the S S bond fission. For the reaction with conjugated dienes, an addition reaction takes place forming the S C bond, suggesting that unpaired electron of the radical localizes mainly on the S-atom. From the decay rates of the radical, the addition reaction rate constant for 2-methyl-1,3-butadiene is evaluated to be 5.5 × 10⁹ M⁻¹ s⁻¹ in THF at 23°C, which is as fast as diffusion controlled limit. The reactivity of the radical is ca. 100 times higher than that of the PhS˙. The reactivity of the thio radical to O₂ was too low to evaluate, which is one of the characteristics of a S-centered radical. The rate constant for 1,4-cyclohexadienene (1.4 × 10⁸ M⁻¹ s⁻¹) is larger than that of cyclohexene (2.8 × 10⁷ M⁻¹ s⁻¹) suggesting the hydrogen abstraction is a main reaction. The MO calculations have been performed for these radicals to reveal the reason of the high reactivity of the radical. © 1996 John Wiley & Sons, Inc.     

Micronization of Iron Oxide Particles Using Gas Antisolvent Process

Iron oxide particles were micronized by supercritical carbon dioxide (CO₂) as an antisolvent in a batch gas antisolvent (GAS) process. In the present study, the feasibility of GAS process to micronize the iron oxide particles using dimethyl sulfoxide (DMSO) as a solvent was investigated. In this direction, particle size and morphology changes were investigated with changing solution pressure (80–150 bar), temperature (308.15–328.15 K), and concentration (1.5–6 g/l). Based on the different experimental conditions, the particle size of the original iron oxide was decreased in the range of 17.25 to 4.23 µm, which shows a the success of the GAS process to reduce the particle size of the intact iron oxide particles. Simultaneously, morphology changes were observed starting from the irregular morphology for synthesized particles to more regular shapes that included fused and spherical-fused particles.     

An experimental investigation of polyacrylamide and sulfonated polyacrylamides based gels crosslinked with cr(III)-acetate for water shutoff in fractured oil reservoirs

Abstract

Water injection as one of the most efficient and worldwide extensively employed approach in homogenous oil reservoirs suffers from early water breakthrough time as well as low oil sweep efficiency values in fractured oil reservoirs. This study investigates the potential application of Cr(III)-acetate based gel polymer system in a typical water injection process using one fractured micromodel. For this purpose, three sulfonated polyacrylamides, different in solfunation degree, and one hydrolyzed polyacrylamide were studied regarding gelation time, gel strength and stability to find the optimized conditions in terms of polymer type and concentration, and polymer/Cr(III)-acetate ratio, which were subsequently used for one dynamic test. Results illustrated the optimized conditions as AN 105 polymer with concentration of 5000?ppm and polymer/Cr(III) ratio of 5. Moreover, results showed that implementing such gel system yields an increased oil recovery value of 24.46% OOIP at 1.55 PV and delays the breakthrough time from 0.47 PV to 0.51 PV.     

Increased dwell time and occurrence of dsDNA translocation events through solid state nanopores by LiCl concentration gradients

Solid‐state nanopore based biosensors are cost effective, high‐throughput engines for single molecule detection of biomolecules with the added benefit of size modification. Progress in the translation of the science into a viable diagnostic tool is impeded by inadequate sensitivity of data acquisition systems in detection of fast DNA translocations through the pore. To combat this, slowing the transport of DNA through the nanopore by use of various media or by altering experimental parameters is common. Applying a concentration gradient of KCl in the experimental ionic solution has been shown to effectively prolong dwell times as well as increase the capture rate of DNA by the nanopore. Our previous work has corroborated the ability of LiCl ionic solution to slow down the transport of dsDNA through the nanopore by up to 10‐fold through cation‐DNA interactions. However, this drastically reduced the event occurrence frequency, thus hindering the efficacy of this system as a reliable biosensor downstream. Here, we present the use of a concentration gradient of lithium chloride ionic solution to increase the event frequency of single molecule dsDNA translocation through a solid state nanopore. By using 0.5 M/3 M LiCl on the cis/trans chambers respectively, average dwell times experienced up to a 3‐fold increase when compared to experiments run in symmetric 1 M LiCl. Additionally, experiments using the 0.5 M/3 M displayed a greater than 10‐fold increase in event frequency, confirming the capture propensity of the asymmetric conditions.     

Mechanical property evaluation of glass–jute fiber reinforced polymer composites

The natural fibers such as jute, coir, hemp, sisal etc. are randomly used as reinforcements for composite materials because of its various advantages such as low cost, low densities, low energy consumption over conventional fibers. In addition, they are renewable as well as biodegradable, and indeed wide varieties of fibers are locally available. In this study, glass–jute fiber reinforced polymer composite is fabricated, and the mechanical properties such as tensile, flexural and impact behavior are investigated. The materials selected for the studies were jute fiber and glass fiber as the reinforcement and epoxy resin as the matrix. The hand lay‐out technique was used to fabricate these composites. Fractured surface were comprehensively examined in scanning electron microscope (SEM) to determine the microscopic fracture mode. A numerical procedure based on the finite element method was then applied to evaluate the overall behavior of this composite using the experimentally applied load. Results showed that by incorporating the optimum amount of jute fibers, the overall strength of glass fiber reinforced composite can be increased and cost saving of more than 30% can be achieved. It can thus be inferred that jute fiber can be a very potential candidate in making of composites, especially for partial replacement of high‐cost glass fibers for low load bearing applications. Copyright © 2016 John Wiley & Sons, Ltd.     

New n-type organic semiconductors: synthesis, single crystal structures, cyclic voltammetry, photophysics, electron transport, and electroluminescence of a series of diphenylanthrazolines

The synthesis, properties, and electroluminescent device applications of a series of five new diphenylanthrazoline molecules 1a-1e are reported. Compounds 1b, 1c, and 1d crystallized in the monoclinic system with the space groups P2(1)/c, C2/c, and P2(1)/c, respectively, revealing highly planar molecules. Diphenylanthrazolines 1a-1e have a formal reduction potential in the range -1.39 to -1.58 V (versus SCE) and estimated electron affinities (LUMO levels) of 2.90-3.10 eV. Compounds 1a-1e emit blue light with fluorescence quantum yields of 58-76% in dilute solution, whereas they emit yellow-green light as thin films. The diphenylanthrazoline molecules as the emissive layers in light-emitting diodes gave yellow light with a maximum brightness of 133 cd/m(2) and an external quantum efficiency of up to 0.07% in ambient air. Bilayer light-emitting diodes using compounds 1a-1e as the electron-transport layer and poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene) as the emissive layer had a maximum external efficiency of 3.1% and 2.0 lm/W and a brightness of up to 965 cd/m(2) in ambient air. These results represent enhancements of up to 50 times in external quantum efficiency and 17 times in brightness when using 1a-1e as the electron-transport materials in polymer light-emitting diodes. These results demonstrate that the new diphenylanthrazolines are promising n-type semiconductors for organic electronics.     

Binary Blends of Polymer Semiconductors: Nanocrystalline Morphology Retards Energy Transfer and Facilitates Efficient White Electroluminescence

Summary: Blends of poly(9,9‐dioctylfluorene) (PFO) and poly(2‐methoxy‐5(2′‐ethyl‐hexyloxy)‐1,4‐phenylenevinylene) (MEH‐PPV) were found to phase separate into 40–50 nm crystalline PFO domains and to exhibit efficient white electroluminescence when the composition is below 30 wt.‐% MEH‐PPV. The 5 wt.‐% nanocrystalline blends had a luminance of 4 000 cd · m⁻², an external quantum efficiency of 3.1%, and a current efficiency of 3.7 cd · A⁻¹. Transmission electron microscopy, electron diffraction, and atomic force microscopy of blends with higher MEH‐PPV content and the two homopolymers showed them to be amorphous. Only orange‐red electroluminescence, characteristic of MEH‐PPV, was observed from the amorphous blends due to efficient energy transfer from PFO. These results demonstrate that energy transfer processes in binary PFO:MEH‐PPV blends and light‐emitting devices based on them can be controlled through the morphology and composition.

TEM image of a PFO:MEH‐PPV blend.     

Theoretical and experimental investigation of desalting and dehydration of crude oil by assistance of ultrasonic irradiation

In this paper desalting/dehydration process of crude oil by ultrasonic irradiation in a novel batch standing-wave resonator reactor is studied both theoretically and experimentally. The effect of main parameters including ultrasonic irradiation parameters, namely irradiation input power and irradiation time, and also operating parameters, such as temperature and injected water, on the removal efficiencies of salt and water is examined. The obtained results demonstrate that finding the optimum values of the above mentioned parameters is important to prevent a significant decrease in the removal efficiencies of water and especially salt. Thus, crude oil was subjected to optimal ultrasonic irradiation with an input power of 57.7 W, and irradiation time of 6.2 min at temperature of 100 °C. The injected water to dissolve the salt of crude oil was 7 vol.%. Also, the applied settling time and dosage of chemical demulsifier were 60 min and 2 ppm, respectively. Under these optimum conditions the removal efficiencies of the desalting/dehydration process were 84% and 99.8%, respectively, which are suitable for refineries.Also, based on the optimal experimental data, two inferential estimators are developed to obtain the relationships between the salt and water removal efficiencies, and input energy density. These empirical relationships can offer a proper estimation for the salt and water removal efficiencies with irradiation input energy.