Enhancement of ablation rate and production of colloidal nanoparticles by irradiation of metals with nanosecond pulsed laser in presence of external electric field

This paper presents the results of experimental study on the effect of electric field on the ablation rate during the nanosecond pulsed laser ablation of aluminum and copper in deionized water. The effect of electric field strength on the material removal rate and its mechanisms were investigated both in the electric field parallel and perpendicular to the laser beam path schemes. The ablation rate was estimated by measuring the dimensions of craters on the target induced by laser. The crater dimensions and optical properties of the produced colloidal nanoparticles were characterized by means of optical microscopy and UV–Vis absorption spectroscopy, respectively. The results indicate that pulsed laser ablation in the presence of an electric field significantly leads to higher material removal rate. The experimental results also confirm that the crater geometry extremely depends on the direction of the electric field with respect to the laser beam direction. The UV–Vis spectra show that the nanoparticles production efficiency increases with increasing the electric field strength.     

Optical transmission and reflection of aluminum film irradiated by nanosecond laser beam and experimental studying of phase-explosion

In this paper we present evidence for a phase explosion during the laser-induced ablation process by studying the optical reflectivity of the ablated plume. The ablation was produced by irradiating thin film aluminum coated on a quartz substrate with a single pulse laser beam in ambient air. The laser pulse was provided by the second harmonic of a Q-switched Nd:YAG laser with ∼10 ns pulse duration. The transmission of a low power He–Ne laser beam through the hot ablated material plume and its reflection (from the front surface, and rear surface of aluminum film) were also monitored during the duration of the ablation event. The results show that the front surface reflectivity is enhanced at an early time of ablation which is described as strong evidence for the creation of a phase explosion in this process.     

Three-component reactions of isocyanides, dialkyl acetylenedicarboxylates, and trans-cinnamoyl chlorides for the synthesis of highly functionalized 2-vinyl furans

Abstract  

In this study, we present a convenient and efficient method for the synthesis of novel, highly substituted 2-vinyl furans using a three-component reaction. The zwitterions generated from the reaction of isocyanides and dialkyl acetylenedicarboxylates are reacted with trans-cinnamoyl chlorides to produce the desired products in good yields.     

Microwave-assisted degradation of guaifenesin (GGE) to produce novel compounds in the presence of imidazolium-based ionic liquids

Journal of Thermal Analysis and Calorimetry - Nanocomposites based on poly(3-hydroxybutyrate) (P3HB) and Cloisite®30B were prepared by direct mixing in a co-rotating twin-screw micro-extruder....     

A Thermodynamic and Kinetic Insight into the Pathways Leading to a Highly Functionalized Ketenimine: A Computational Study

All steps of two mechanistic pathways for the synthesized ketenimine through a multicomponent reaction between cyclohexyl isocyanide 1 and acetylen ester 2 in the presence of CH‐acid 3 have been thermodynamically and kinetically evaluated. Intrinsic reaction coordinate calculations were performed for the optimized structures to verify the connectivity of all transition states with reactants and products. The kinetic data showed that the step 1 of the two proposed mechanisms was a rate‐determining step. Also, activation (ΔG^?, ΔH^?, ΔS^?) and thermodynamic (ΔG°, ΔH°, ΔS°) parameters confirmed that the second mechanism for generation product 4b was favored energetically. In addition, the single‐point ¹H and ¹³C NMR (GIAO) chemical shift calculations showed that the product obtained from the approval pathway was according to the experimental data.     

Steric and electronic substitution effects on the thermal oxidation of 5-carboethoxy-2-oxo-1,2,3,4-tetrahydropyridines

Various 4-aryl substituted 5-carboethoxy-2-oxo-1,2,3,4-tetrahydropyridines were oxidized to their corresponding 4-aryl-5-carboethoxy-2-oxo-1,2-dihydropyridines by potassium peroxydisulfate in aqueous acetonitrile under thermal conditions. The products were obtained in good to excellent yields. Based on the proposed mechanism, the removal of the hydrogen from the C₄-atom of the heterocyclic ring by the hydroxyl radical formed in situ is occurred in the rate determining step, which is influenced by the steric and electronic effects of the substituted aryl group attached to this atom and also the stability of the radical intermediate involved in the oxidation reaction. The experimental results were supported by the computational studies.     

One-Pot and Solvent-Free Synthesis of 1,4-Dihydropyridines and 3,4-Dihydropyrimidine-2-ones Using New Synthetic Recyclable Catalyst via Biginelli and Hantzsch Reactions

Pyridine dicarboxylic acid guanidine–cobalt complex (PDAG-Co) (3) catalyzes one-pot, three-component coupling of aldehydes, β-dicarbonyl compounds, and ammonium acetate to afford the corresponding 1,4-dihydropyridines (1,4-DHPs) via Hantzsch reaction. 3,4-Dihydropyrimidine-2-ones (3,4-DHPMs) and their sulfur analogs are also synthesized under the same conditions via Biginelli condensation protocol. The catalyst is reusable at least five times, highly efficient, easily prepared, and used under mild reaction conditions.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view free supplemental file.     

Amperometric determination of L-tyrosine by an enzymeless sensor based on a carbon ceramic electrode modified with copper oxide nanoparticles

We report on the electrochemical formation of copper oxide nanoparticles (CuO-NPs) at a carbon ceramic electrode (CCE) as a highly-porous substrate. A copper film was deposited on the surface of the CCE and derivatized in situ to give CuO-NPs by potential cycling between ?0.8 and 0.35?V in strongly alkaline solution. The electrode was characterized by scanning electron microscopy and cyclic voltammetry. The CuO-NPs exhibited excellent electrocatalytic activity toward the oxidation of L-tyrosine (L-Tyr) in responding linearly in the 2 to 1,350???M concentration range, an associated detection limit (S/N?=?3) of 160?nM, and a sensitivity of 0.61?A?M^?1?cm^?2.

Efficient Organic Transformations Mediated by ZrOCl2·8H2O in Water

Abstract

Operationally simple and environmentally benign methods for some organic transformations comprising reductive coupling of sulfonyl chlorides, chemoselective deoxygenation of sulfoxides, and halogenation of alcohols mediated by ZrOCl₂·8H₂O/MX in water have been developed.

GRAPHICAL ABSTRACT     

A fuzzy goal programming and meta heuristic algorithms for solving integrated production: distribution planning problem

Integrated production–distribution planning is one of the most important issues in supply chain management (SCM). We consider a supply chain (SC) network to consist of a manufacturer, with multiple plants, products, distribution centers (DCs), retailers and customers. A multi-objective linear programming problem for integrating production–distribution, which considers various simultaneously conflicting objectives, is developed. The decision maker’s imprecise aspiration levels of goals are incorporated into the model using a fuzzy goal programming approach. Due to complexity of the considered problem we propose three meta-heuristics to tackle the problem. A simple genetic algorithm and a particle swarm optimization (PSO) algorithm with a new fitness function, and an improved hybrid genetic algorithm are developed. In order to show the efficiency of the proposed methods, two classes of problems are considered and their instances are solved using all methods. The obtained results show that the improved hybrid genetic algorithm gives us the best solutions in a reasonable computational time.