Two–parameter scaled memoryless BFGS methods with a nonmonotone choice for the initial step length

Numerical Algorithms - A class of two–parameter scaled memoryless BFGS methods is developed for solving unconstrained optimization problems. Then, the scaling parameters are determined in a...     

Immobilized ionic liquid on superparamagnetic nanoparticles as an effective catalyst for the synthesis of tetrasubstituted imidazoles under solvent-free conditions and microwave irradiation

The ionic liquid 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium chloride was immobilized on superparamagnetic Fe₃O₄ nanoparticles (IL-MNPs) and used as an efficient heterogeneous catalyst for the one-pot synthesis of 1,2,4,5-tetrasubstituted imidazoles under solvent-free conditions using microwave irradiation. The reactions in conventional heating conditions were compared with the microwave-assisted reactions. The combined merits of microwave irradiation and immobilized ionic liquid on superparamagnetic nanoparticles make the four-component condensation with safe operation, low pollution, and rapid access to products and simple work-up.     

Modified-cold induced aggregation microextraction based on ionic liquid and fibre optic-linear array detection spectrophotometric determination of palladium in saline solutions

In this research, a novel microextraction technique based on ionic liquids (ILs) termed in modified-cold induced aggregation microextraction (M-CIAME) was used for determination of palladium in saline solution. 1-(2-pyridylazo)-2-naphtol (PAN) was chosen as the complexing agent. Analysis was carried out using fibre optic-linear array detection spectrophotometric method which is suitable for analyte determination after microextraction. M-CIAME is based on phase separation phenomenon of ionic liquids in aqueous solutions. This method is simple and rapid for extraction and preconcentration of metal ions from water samples. It can be applied for the sample solutions containing much higher concentrations of salt, in comparison with CIAME (cold induced aggregation microextraction). Furthermore, this technique is much safer in comparison with other microextraction techniques in which organic solvent is used as the extraction solvent. Some effective parameters on extraction and complex formation such as amount of IL, salt effect, pH, concentration of the chelating agent and the other parameters were optimised. Under the optimum conditions, the limit of detection (LOD) and repeatability, expressed as relative standard deviation (n?=?5) for 20?ng?mL^?1 of palladium were 0.4?ng?mL^?1 and 2.23%, respectively. The extraction percentage was 86%.     

Amphiphilic star copolymers containing cyclodextrin core and their application as nanocarrier

Amphiphilic copolymers containing β-cyclodextrin (β-CD) core were synthesized successfully. Synthesis was initiated from tosylated cyclodextrin ((Tosyl)₇-β-CD) which is containing two types of functional groups. Hydroxyl functional groups of (Tosyl)₇-β-CD were used as initiator for ring opening polymerization of lactide. This step led to star polymers containing tosylated cyclodextrin core and polylactide arms (PLA-(Tosyl)₇-β-CD). In the next step, tosyl groups of PLA-(Tosyl)₇-β-CD were used as initiator for ring opening polymerization of 2-ethyl-2-oxazoline and amphiphilic copolymers containing cyclodextrin core, PLA and poly(2-ethyl-2-oxazoline) arms (PLA-β-CD-POX) were obtained. Loading of Congo red as guest molecule by amphiphilic copolymers was investigated. The release of guest molecule from chloroform solution of copolymers to water phase was also investigated.     

Ni ion-containing immobilized ionic liquid on magnetic Fe3O4 nanoparticles: An effective catalyst for the Heck reaction

In this work, we synthesized Ni²⁺-containing 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium chloride ionic liquid on magnetic Fe₃O₄ nanoparticles. The catalytic activity of these novel nanocomposites was finally evaluated for the Heck reaction at 100 °C, and can be reused after washing without loss in activity. The immobilized ionic liquid catalysts proved to be effective and easily separated from the reaction media by applying an external magnetic field. This procedure has many obvious advantages compared to those reported in the previous literature, including avoidance of the use of the expensive Pd catalysts, mild reaction conditions, high yields, and simplicity of the methodology.     

Equisetum arvense As an abundant source of silica nanoparticles. SiO2/H3PW12O40 nanohybrid material as an efficient and environmental benign catalyst in the synthesis of 2‐amino‐4H‐chromenes under solvent‐free conditions

Uniform SiO₂ nanoparticles were successfully prepared from Equisetum arvense obtained from the north‐east of Iran. Then, surface modification of the extracted nanoparticles was performed with a methanol solution of H₃PW₁₂O₄₀ via wet impregnation method. The prepared nanocatalyst was characterized by XRD, FESEM, ICP, UV–Vis, and FT‐IR spectroscopy. The supported heterogeneous nanocatalyst was successfully applied as a Lewis/Bronsted acid catalyst in the synthesis of a series of substituted 4H–chromenes via condensation of aromatic aldehydes, malononitrile, and 4‐hydroxycoumarin under solventless conditions with fine yields in appropriately short times.     

Carbon nanotube reinforced hollow fiber solid/liquid phase microextraction: A novel extraction technique for the measurement of caffeic acid in Echinacea purpurea herbal extracts combined with high-performance liquid chromatography

A new design of hollow fiber solid–liquid phase microextraction (HF-SLPME) was developed for the determination of caffeic acid in medicinal plants samples as Echinacea purpure. The membrane extraction with sorbent interface used in this research is a three-phase supported liquid membrane consisting of an aqueous (donor phase), organic solvent/nano sorbent (membrane) and aqueous (acceptor phase) system operated in direct immersion sampling mode. The multi-walled carbon nanotube dispersed in the organic solvent is held in the pores of a porous membrane supported by capillary forces and sonification. It is in contact with two aqueous phases: the donor phase, which is the aqueous sample, and the acceptor phase, usually an aqueous buffer. All microextraction experiments were supported using an Accurel Q3/2 polypropylene hollow fiber membrane (600 μm I.D., 200 μm wall thicknesses, and 0.2 μm pore size). The experimental setup is very simple and highly affordable. The hollow fiber is disposable, so single use of the fiber reduces the risk of cross-contamination and carry-over problems. The proposed method allows the very effective and enriched recuperation of an acidic analyte into one single extract. In order to obtain high enrichment and extraction efficiency of the analyte using this novel technique, the main parameters were optimized. Under the optimized extraction conditions, the method showed good linearity (0.0001–50 μg/L), repeatability, low limits of detection (0.00005 μg/L) and excellent enrichment (EF = 2108).     

Catalytic performance in 4-nitrophenol reduction by Ag nanoparticles stabilized on biodegradable amphiphilic copolymers

Biodegradable copolymers have received much more attention in the last decades due their potential applications in the fields related to environmental protection, medicine, agriculture, and the chemical processes. Silver nanoparticles (Ag NPs) were prepared via reduction of silver nitrate (AgNO₃) using biodegradable amphiphilic copolymers in aqueous solution. The micelles were constructed from the amphiphilic copolymer composed of poly(2-ethyl-2-oxazoline) and poly(ε-caprolactone). The Ag NPs with a diameter of 10–15?nm were found to show a comparable high catalytic activity toward the reduction of 4-nitrophenol (4-NP) in the presence of an excess amount of NaBH₄. The synthesized Ag NPs-loaded copolymer exhibits high catalytic activity for the reduction of 4-NP to 4-aminophenol.     

Sonochemical synthesis of methyl-4-(hetero)arylmethylene isoxazole-5(4H)-ones using SnII-montmorillonite

Tin exchanged montmorillonite K10 (Sn^II-Mont K10) was prepared by ion exchange between SnCl₂ and montmorillonite K10. The Sn^II-Mont K10 was characterized by X-ray diffraction, scanning electron microscope and energy-dispersive X-ray spectroscopy. The synthesized Sn^II-Mont K10 was used as a recoverable solid catalyst for synthesis of 3-methyl-4-arylmethylene isoxazole-5(4H)-ones via one-pot multicomponent cyclocondensation of hydroxylamine hydrochloride, ethyl acetoacetate and benzaldehyde derivatives in water under ultrasound irradiations. The yields of products were obtained 87–96%. The remarkable advantages of this method are a low-cost and eco-friendliness catalyst, rapid completion of the reactions, and avoidance of using organic solvents, excellent yield and mild conditions.     

Fe3O4@zeolite-SO3H as a magnetically bifunctional and retrievable nanocatalyst for green synthesis of perimidines

Research on Chemical Intermediates - In the current study, a new catalytic system based on Fe3O4 nanoparticles immobilized on zeolite-SO3H (Fe3O4@zeolite-SO3H) is introduced. In the first stage,...