The effect of liquid environment on size and aggregation of gold nanoparticles prepared by pulsed laser ablation

The effects of liquid environment on nucleation, growth and aggregation of gold nanoparticles were studied. Gold nanoparticles were prepared by pulsed laser ablation in deionised water with various concentrations of ethanol and also in pure ethanol. UV/visible extinction and TEM observations were employed for characterization of optical properties and particle sizes respectively. Preparation in water results in smaller size, shorter wavelength of maximum extinction and stable solution with an average size of 6 nm. Nanoparticles in solution with low concentration ethanol up to 20 vol% are very similar to those prepared in water. In the mixture of deionised water and 40 up to 80 vol% ethanol, wavelength of maximum extinction shows a red shift and mean size of nanoparticles was increased to 8.2 nm. Meanwhile, in this case, nanoparticles cross-linked each other and formed string type structures. In ethanol, TEM experiments show a mean size of 18 nm and strong aggregation of nanoparticles. The data were discussed qualitatively by considering effects of polarity of surrounding molecules on growth mechanism and aggregation. This study provided a technique to control size, cross-linking and aggregation of gold nanoparticles via changing the nature of liquid carrier medium.     

An efficient four-component reaction for the synthesis of chromeno[4,3-<Emphasis Type="Italic">b</Emphasis>]quinolone derivatives

Chromenoquinolines have been prepared via an efficient one-pot, multi-component reaction of 4-hydroxy coumarin, aqueous ammonia, dimedone and different aldehydes.     

Synthesis and Cytotoxic Activity of Some Novel Dihyrobenzo[h]pyrano[3,2‐c]chromene Derivatives

Three‐component reaction of 4‐hydroxy‐2H‐benzo[h]chromen‐2‐one, aromatic aldehydes, and malononitrile in the presence of 1,4‐diazabicyclo[2.2.2]octane (DABCO) in ethanol at room temperature affords good yields of novel dihyrobenzo[h]pyrano[3,2‐c]chromene derivatives. The synthesized compounds examined by MTT assays for cytotoxic activity in two human cancer cell lines (MOLT‐4, HL‐60). Most of the evaluated compounds showed low inhibitory activity against tumor cell line at micromolar concentrations.     

Cu(II)-β-cyclodextrin-catalyzed synthesis of spiro[indoline-3,4′-pyrano[3,2-c]chromene]-3′-carbonitrile derivatives

Cu(II)-β-cyclodextrin-catalyzed synthesis of spiro[indoline-3,4′-pyrano[3,2-c]chromene]-3′-carbonitriles through the reaction of isatin derivatives, 4-hydroxycoumarin, and malononitrile in ethanol at room temperature.     

Evaluation of poly ε-caprolactone electrospun nanofibers loaded with Hypericum perforatum extract as a wound dressing

Research on Chemical Intermediates - In this study, for the first time, a biocompatible and non-toxic herbal wound dressing was made by encapsulation of Hypericum perforatum alcoholic extract at...     

HKUST-1 metal-organic framework for dispersive solid phase extraction of 2-methyl-4-chlorophenoxyacetic acid (MCPA) prior to its determination by ion mobility spectrometry

The authors describe a method for the extraction of the herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA) from agricultural products. The metal organic framework (MOF) HKUST-1 (a copper(II) benzene-1,3,5-tricarboxylate) was used as a sorbent for efficient clean-up and preconcentration of MCPA. The effects of pH value, stirring time, amount of sorbent on extraction were optimized by central composite design. Ultrasonic waves were used for desorption procedure and its advantage was demonstrated for an increase in extraction recovery. Corona discharge ion mobility spectrometry (IMS) was then applied for fast and sensitive determination of MCPA. The method was validated in terms of sensitivity, recovery and reproducibility. Under the optimum conditions the calibration plot is linear between 0.035–0.200 μg. L^?1. The detection limit is 10 ng L^?1, with relative standard deviations of <5%. Real samples (water, soil and agricultural product) were spiked and then analyzed by this method, and the results revealed efficient solid phase extraction and recovery.

Open image in new window

Graphical abstract Schematic presentation of a procedure for extraction of an organochlorine pesticide (2-methyl-4-chlorophenoxyacetic acid) from agriculture products using the HKUST-1 metal-organic framework prior to determination by ion mobility spectrometry based on its ionization in drift cell.

     

CuBr/Et3N‐Promoted Reactions of 2‐Aminobenzamides and Isothiocyanates: Efficient Synthesis of Novel Quinazolin‐4(3H)‐ones

A series of novel quinazolin‐4(3H)‐one derivatives were efficiently synthesized starting from isatoic anhydride. First, reaction of isatoic anhydride and amines in H₂O at room temperature afforded 2‐aminobenzamides. Then, CuBr/Et₃N promoted reaction of 2‐aminobenzamides and different aryl isothiocyanates in DMF at 80° afforded the title compounds in good yield.     

Dynamic simulation of a heat recovery steam generator dedicated to a brine concentration plant

Journal of Thermal Analysis and Calorimetry - Considering water level and pressure variation in drum of a&nbsp;natural circulation heat recovery steam generator (HRSG) is very crucial to...     

Novel (thio)barbituric-phenoxy-N-phenylacetamide derivatives as potent urease inhibitors: synthesis,in vitro urease inhibition,and in silico evaluations

Structural Chemistry - A novel series of (thio)barbituric-phenoxy-N-phenylacetamide derivatives 7a-l was synthesized and evaluated against Helicobacter pylori urease. The latter assay revealed that...     

Thermal–hydraulic efficiency management of spiral heat exchanger filled with Cu–ZnO/water hybrid nanofluid

Journal of Thermal Analysis and Calorimetry - In this paper, the effect of different channel spacing in spiral heat exchanger filled with Cu–ZnO–water hybrid nanofluid was investigated...