One-pot three-component synthesis of α-amino nitriles catalyzed by nano powder TiO_2 P 25

A simple and efficient method has been developed for the synthesis ofα-amino nitriles from aldehydes,amines and trimethylsilyl cyanide（Me₃SiCN） in the presence of a catalytic amount of cyanuric acid at room temperature.     

Design,two-directional synthesis,DFT study of new pyrimido[5,4-d]pyrimidine-2,8-dione derivatives

A facile two-directional synthesis of new pyrimido[5,4-d]pyrimidine-2,8-dione was reported via an efficient reaction of premade bis-aldehydes and 1-(2-amino-1,2-dicyanovinyl)-3-phenylurea in the presence of triethylamine as the base and Cu (II) as catalyst. As there is controversy about the formation of two types of products, that is, purine or pyrimidine ring containing compounds in the reaction of diaminomaleonitrile with isocyanates and aldehydes, the computational model chemistry has been employed to obtain new insight about this reaction and determining the dominant pathway of the process. Using DFT model, two alternative pathways have been explored and geometrical isomerization of central double bond has been considered. Accordingly, the evaluated energy barriers affirm the formation of six-membered pyrimidine ring as the major product in the presence of CuCl₂ as the catalyst and MeOH as solvent.     

Synthesis of new TCH/Ni‐based nanocomposite supported on SBA‐15 and its catalytic application for preparation of benzimidazole and perimidine derivatives

A stable nickel‐decorated SBA‐15 nanocomposite (Ni/TCH@SBA‐15) was synthesized through surface modification of silica nanoparticles with 3‐chloropropyltriethoxysilane (CPTES) and thiocarbohydrazide (TCH) followed by metal–ligand coordination with Ni (II). The structure of this organometallic nanocomposite was characterized by Fourier transform‐infrared, field emission‐scanning electron microscopy, EDAX, transmission electron microscopy, atomic absorption spectroscopy and N₂ adsorption–desorption (Brunauer–Emmett–Teller) techniques. The catalytic performance of Ni/TCH@SBA‐15 (NNTS‐15) was determined for the synthesis of 2‐aryl‐substituted benzimidazoles and 2,3‐dihydroperimidines. The excellent yields within shorter reaction times, simplicity of catalytic methods, non‐toxicity and clean reactions, mild reaction conditions and easy work‐up procedure are the important merits of these synthetic protocols. Moreover, the Ni (II) bonded to the SBA‐15 surface was stable under the catalytic reaction conditions resulting in its efficient recycling and reuse.     

Nanocrystalline TiO_2 as an efficient and reusable catalyst for the chemoselective trimethylsilylation of primary and secondary alcohols and phenols

Nanocrystalline TiO₂ was used as an efficient and recyclable catalyst for the chemoselective trimethylsilylation of primary and less hindered secondary alcohols and phenols with hexamethyldisilazane（HMDS）.All reactions were performed under mild and completely heterogeneous conditions in good to excellent yields.     

Homogeneous Liquid–Liquid Microextraction Via Flotation Assistance (HLLME-FA) Method for the Pretreatment of Organochlorine Pesticides in Aqueous Samples and Determination by GC–MS

This work proposes a new, rapid and simple homogeneous liquid–liquid microextraction via flotation assistance technique for the analysis of six organochlorine pesticides in water samples. A special extraction cell was used to facilitate collection of the low-density solvent extract. No centrifugation was required in this procedure. Determination was carried using gas chromatography–mass spectrometry. The water sample solution was then added into the extraction cell containing appropriate mixture of extract and homogeneous solvents. In the first step, a homogeneous solution and then with the continuation of water sample injection, a cloudy solution was formed. Using air flotation, the organic solution was collected at the conical part of the designed cell. The optimized levels of effective parameters were found based on response surface methodology approach. Applying the optimized conditions to the system understudy, the limits of detection of all target analytes were obtained in the range of 1.4–7 ng mL⁻¹, while the precisions were found to be in the range of 11.08–14.87 (RSD, n = 3). The linearity of the method lay in the range of 10–150 ng mL⁻¹ with the coefficients of correlation (r ²) ranging from 0.998 to 0.999.

     

Vesicular release dynamics are altered by the interaction between the chemical cargo and vesicle membrane lipids

The release of the cargo from soft vesicles, an essential process for chemical delivery, is mediated by multiple factors. Among them, the regulation by the interaction between the chemical cargo species and the vesicular membrane, widely existing in all vesicles, has not been investigated to date. Yet, these interactions hold the potential to complicate the release process. We used liposomes loaded with different monoamines, dopamine (DA) and serotonin (5-HT), to simulate vesicular release and to monitor the dynamics of chemical release from isolated vesicles during vesicle impact electrochemical cytometry (VIEC). The release of DA from liposomes presents a longer release time compared to 5-HT. Modelling the release time showed that DA filled vesicles had a higher percentage of events where the time for the peak fall was better fit to a double exponential (DblExp) decay function, suggesting multiple kinetic steps in the release. By fitting to a desorption–release model, where the transmitters adsorbed to the vesicle membrane, the dissociation rates of DA and 5-HT from the liposome membrane were estimated. DA has a lower desorption rate constant, which leads to slower DA release than that observed for 5-HT, whereas there is little difference in pore size. The alteration of vesicular release dynamics due to the interaction between the chemical cargo and vesicle membrane lipids provides an important mechanism to regulate vesicular release in chemical and physiological processes. It is highly possible that this introduces a fundamental chemical regulation difference between transmitters during exocytosis.

The release of the cargo from soft vesicles, an essential process for chemical delivery, is mediated by multiple factors.     

Dispersive liquid–liquid microextraction based on the solidification of floating organic drop followed by inductively coupled plasma-optical emission spectrometry as a fast technique for the simultaneous determination of heavy metals

A simple, rapid and efficient dispersive liquid–liquid microextraction based on the solidification of floating organic drop (DLLME–SFO) method, followed by inductively coupled plasma-optical emission spectrometry (ICP-OES) was developed for the simultaneous preconcentration and determination of heavy metals in water samples. One variable at a time method was applied to select the type of extraction and disperser solvents. Then, an orthogonal array design (OAD) with OA₁₆ (4⁵) matrix was employed to study the effects of different parameters on the extraction efficiency. Under the best experimental conditions (extraction solvent: 140 μL of 1-undecanol; disperser solvent: 2.0 mL of acetone; ligand to metal mole ratio: 20; pH: 6 and without salt addition), the enhancement factor ranged from 57 to 96. The calibration graphs were linear in the range of 0.5–250 μg L⁻¹ for Mn, 1.25–250 μg L⁻¹ for Cr, Co and Cu with correlation coefficient (r) better than 0.990. The detection limits were between 0.1 and 0.3 μg L⁻¹. Finally, the developed method was successfully applied to extraction and determination of the mentioned metal ions in the tap, sea and mineral water samples and satisfactory results were obtained.     

Extraction of trace amounts of mercury with sodium dodecyle sulphate-coated magnetite nanoparticles and its determination by flow injection inductively coupled plasma-optical emission spectrometry

A new method for solid-phase extraction and preconcentration of trace amounts Hg(II) from environmental samples was developed by using sodium dodecyle sulphate-coated magnetite nanoparticles (SDS-coated Fe₃O₄ NPs) as a new extractant. The procedure is based on the adsorption of the analyte, as mercury-Michler's thioketone [Hg₂(TMK)₄]²⁺ complex on the negatively charged surface of the SDS-coated Fe₃O₄ NPs and then elution of the preconcentrated mercury from the surface of the SDS-coated Fe₃O₄ NPs prior to its determination by flow injection inductively coupled plasma-optical emission spectrometry. The effects of pH, TMK concentration, SDS and Fe₃O₄ NPs amounts, eluent type, sample volume and interfering ions on the recovery of the analyte were investigated. Under optimized conditions, the calibration curve was linear in the range of 0.2-100 ng mL⁻¹ with r² = 0.9994 (n = 8). The limit of detection for Hg(II) determination was 0.04 ng mL⁻¹. Also, relative standard deviation (R.S.D.) for the determination of 2 and 50 ng mL⁻¹ of Hg(II) was 5.2 and 4.7% (n = 6), respectively. Due to the quantitative extraction of Hg(II) from 1000 mL of the sample solution an enhancement factor as large as 1230-fold can be obtained. The proposed method has been validated using a certified reference materials, and also the method has been applied successfully for the determination of Hg(II) in aqueous samples.     

Magnetic nanoparticles: Synthesis, stabilization, functionalization, characterization, and applications

This review focuses on the synthesis, protection, functionalization, characterization and with some applications of magnetic nanoparticles (MNPs). The review begins with an overview on magnetic property and single domain particles. The synthetic strategies developed for the generation of MNPs, with a focus on particle formation mechanism and recent modifications made on the synthesis of monodisperse samples of relatively large quantities are also discussed. Then, different methodologies for the protection and functionalization of the synthesized MNPs, together with the characterization techniques are explained. Finally, some of the recent industrial, biological, environmental and analyticals application of MNPs are briefly reviewed, and some future trends and perspectives in these research areas will be outlined.     

Microwave-assisted extraction combined with dispersive liquid-liquid microextraction as a new approach to determination of chlorophenols in soil and sediments

A new method was applied for extraction of five chlorophenols from soil and marine sediment samples. Microwave-assisted extraction coupled with dispersive liquid-liquid microextraction followed by semi-automated in-syringe back-extraction technique was used as an extraction technique. Microwave-assisted extraction was performed by using 2.0 mL of alkaline water at pH 10.0. After extraction, the pH of extraction solution was adjusted at 6.0 and dispersive liquid-liquid microextraction procedure was done using 1.0 mL of acetone as a disperser solvent and 37.0 μL of chlorobenzene as extraction solvent. About 20.0 ± 0.5 μL sedimented phase was collected after centrifugation step. Then, chlorophenols were back extracted into 20 μL of alkaline water at pH 12.0 within the microsyringe. Finally, 20.0 μL of aqueous solution was injected into high performance liquid chromatography with ultra violet detection for analysis. The obtained recovery and preconcentration factors for the analytes were in the range of 68.0-82.0% and 25-30, respectively, with relative standard deviations ≤7.6%. The limits of the detection were found in the range of 0.0005-0.002 mg/kg. The method provides a simple and fast procedure for the extraction and determination of chlorophenols in soil and marine sediment samples.