Novel flower-like Sn–Cu and cactus-like Sn–Ag nanocatalysts for photo catalytically removal of toxic pollutant

In this study, dendrite-like Sn nanocomposites were achieved by engineering the synthesis parameters. The dendritic Sn nanostructures show higher photocatalytic activity compared to nanoplate Sn and hierarchical Sn nanostructures. Flower-like Sn–Cu and cactus-like Sn–Ag nanostructures were prepared to improve the photocatalytic activity of Sn nanostructures. Adding Cu and Ag improved the photocatalytic activity of Sn by 24% and 46%, respectively. The photodegradation results revealed that the cactus-like Sn–Ag has a high degradation rate (5.3 × 10⁻⁴ mmol L⁻¹ min⁻¹) compared to the Sn nanostructures (2.9 × 10⁻⁴ mmol L⁻¹ min⁻¹). This work provides new insight into the design of highly efficient photocatalysts by engineering the morphology.     

Excellent photocatalytic reduction of nitroarenes to aminoarenes by BiVO4 nanoparticles grafted on reduced graphene oxide (rGO/BiVO4)

A novel heterogeneous composite material based on reduced graphene oxide (rGO) and bismuth vanadate (BiVO₄) was prepared and characterized by various techniques such as powder XRD, HRTEM, EADX, UV–Vis‐DRS, FT‐IR, Raman, BET and XPS analyses. The characterization results reveal that the rGO well decorated by BiVO₄. The electrochemical impedance spectroscopy (EIS) shows the increasing of charge transfer of rGO/BiVO₄ in presence of light irradiation. In this research, the pure BiVO₄ and rGO/BiVO₄ composite have been explored for photocatalytic reduction of nitroarenes. Among the prepared nanocomposites, rGO loaded with 10% BiVO₄ catalyst (noted as rGO/BiVO₄–10%) shows the best performance for the photo‐reduction of various nitroaromatic molecules to their corresponding amine compounds under visible‐light irradiation at room temperature. The catalyst exhibited in particular excellent photocatalytic activity for the conversion of 1,4‐dinitrobenzene to 4‐nitroanilline (100% conversion) in 20 min, 4‐chloronitrobenzene to 4‐chloroaniline and 2‐nitrophenol to 2‐aminophenol (100% conversion) in only 30 min. In addition, the conversion of 4‐bromonitrobenzene, 4‐iodonitrobenzene to their corresponding amine compounds (100% conversion) was achieved in 60 min. The catalyst was recovered for several times and reused without decreasing of its efficiency.     

Development and molecular recognition of Calixcrownchip as an electrochemical ALT immunosensor

The developments of immunosensors with a variety of formats are increasingly finding applications in clinical diagnostics and biological researches. A strategy for the immunoassay and preparation of Calixcrownchips is proposed. This strategy is based on the immobilization of antigens or antibodies on the surface of Calixcrown and the direct electrochemistry of horseradish peroxidase (HRP) that was labeled to an antibody or antigen, with its activity determined by using tetramethylbenzidine (TMB) as an electrochemical substrate. The present study includes general considerations of the competitive immunoreaction protocols. Alanine aminotransferase (ALT) monoclonal antibody (anti-ALT-mAb) was successfully immobilized on thiol derivative of Calixcrown fixed to a gold surface. ALT antigen was detected by competitive immunoreactions based on microarrays of anti-ALT-mAb or antigen immobilized on the surface of the Calixcrownchip. For the anti-ALT-mAb immobilized microarray the dynamic range is 0.05 ng/mL–10 μg/mL, the detection limit is 0.05 ng/mL and the sensitivity is 10 nA/(ng/mL) respectively. The Calixcrownchip immunosensor microarray provided much better technical performance than a comparable enzyme sensor with immobilized-anti-ALT-mAb. To investigate the complexation site, the structures of the complexes formed between the crown-5-ether moiety of Calix[4]arene and protonated Arginine and Lysine were determined by minimizing the complex formation energies. The complex stability depends on the number of amine groups in the alkyl chain of the amino acid and also the number of methylene groups between the amine groups of the amino acid.     

Supported palladium oxide nanoparticles in Al-SBA-15 as an efficient and reusable catalyst for the synthesis of pyranopyrazole and benzylpyrazolyl coumarin derivatives via multicomponent reactions

An eco-friendly method for diversity-oriented synthesis of substituted dihydropyrano[2,3-c]pyrazole and benzylpyrazolyl coumarin derivatives has been achieved via one-pot and multicomponent reaction in the presence of PdO/Al-SBA-15 as an efficient and recyclable catalyst in H₂O/EtOH under reflux conditions. The significant merits of this method are wide scope, high yields of the desired products, short reaction times and simple workup procedure. In addition, this nanocatalyst was simply recovered and reused five times without significant loss in catalytic activity and also performance.

Graphical abstract

     

Determination of citric acid in fermentation media by pyrolysis mass spectrometry

Rapid and sensitive determination of citric acid in fermentation media by pyrolysis mass spectrometry (Py–MS) is proposed. Owing to high specificity of this method, distinguishing the citric acid from the matrix and by-products formed in the Krebs cycle is possible. Selected ion monitoring (SIM) mode is used for quantitative measurements, in which mass to charge (m/z) values of 175 of citric acid and 138 of 3-nitroaniline as internal standard are chosen. Limit of detection (LOD) for this method has been found to be 1 ng ml⁻¹ and the linear working range was 10 ng ml⁻¹–100 mg ml⁻¹. Relative standard deviation (R.S.D.) of the method for five replicates was 0.84%. Results of Py–MS are compared with those obtained by UV–vis spectrophotometric method. Also, factor analysis is used for evaluating the influence of pH, molasses concentration, time and shaker intensity on the production of citric acid by Aspergillus niger.     

Solid-phase extraction, separation, and visible spectrophotometric determination of trace amounts of iron in water samples.

A simple and reliable method is presented for the rapid extraction, separation, preconcentration, and determination of iron as its bathophenanthroline complex by the use of octadecylsilica membrane disks and spectrophotometry. We evaluted extraction efficiency, the influence of sample matrix, type and optimum amount of extractant, flow rates of sample solution and eluent, pH, amounts of bathophenanthroline and hydroxylamine hydrochloride, breakthrough volume, and limit of detection. We also studied the effects of various cationic interferences on percent recovery of iron. Complete elution of the complex from disks was obtained with a minimal amount of solvent. The limit of detection of the proposed method is 0.080 ppb. The method was applied to the recovery and determination of iron in natural waters.