جستجوی مقالات مرتبط با کلیدواژه « مایکروویو » در نشریات گروه « شیمی »

Carbon nanotube/polystyrene nanocomposites were synthesized via microwave-assisted in-situ polymerization. Since carbon nanotubes can absorb microwave irradiation, they can form hot spots in the mixture, and the auto thermal polymerization of styrene monomers can be initiated from their surface without using any chemical initiator. In order to investigate the effectiveness of the microwave irradiation on the polymerization process, carbon nanotube/polystyrene nanocomposites were synthesized via heating. Samples were characterized by TEM, FESEM, FT-IR, TGA and Raman spectra, and the electrical conductivity of samples were also measured. The results showed that using microwave irradiation can result in forming a polymeric layer on carbon nanotubes, and the resultant nanocomposite had a few agglomerations. In addition, by increasing the power of microwave irradiation, the thickness of the polymeric layer increased and electrical conductivity decreased.

In this paper, to develop green chemistry, a catalyst based on layered double hydroxides (LDHs) attached by hexamethylene-1,6-diisocyanate (HMDI) and citric acid (LDH-g-HMDI-citric acid) were prepared and characterized by FT-IR, XRD, EDX, SEM, TGA, and DTG analytical methods. The catalytic activity of this recyclable heterogeneous catalyst was evaluated for the synthesis of new imidodicarbonate diamide derivatives (biuret) under microwave conditions. The use of the microwave method led to the use of organic solvents in small amounts, reduced reaction times, and increased yields of products, which was achieved for the development of green chemistry and environmental protection. These biurets were evaluated for inhibitory activity on human immunodeficiency virus type 1 (HIV-1) by HIV-1 p24 antigen ELISA kit and three of them (5b, 5c, and 5f) had moderate activity on HIV -1 virus with IC50 values in the range of 55.1 to 100 μM compared to azidothymidine as the reference drug (IC50 = 0.11 μM). Finally, to investigate the mechanism of the effect of biuret compounds on the virus protease enzyme, docking analysis studies were performed and the results of in vitro test and docking study were in good correlation.

Today, biodiesel is being produced and consumed around the world as one of the main sources for replacing fossil fuels. In current research, cobalt doped zinc oxide was used as nanocatalyst to produce biodiesel from soybean oil by transesterification reaction. The nanocatalysts used were first prepared by microwave method and identified by X-ray diffraction (XRD), scanning electron microscopy (SEM) and x-ray energy dispersive spectroscopy (EDS). In the next step, the prepared catalysts were used in the reaction of biodiesel production from soybean oil. The produced biodiesel was characterized using nuclear magnetic resonance spectroscopy (NMR) and gas chromatography-mass spectroscopy (GC-MS). Optimal reaction conditions of biodiesel production with cobalt doped zinc oxide nanocatalyst obtained, at 3 h, temperature 60 ˚C, catalyst concentration 3% by weight, and molar ratio of oil to methanol 1 to 41 resulted in 98% efficiency. In another part of this research, microwave radiation with a power of 250 W was used as a source of energy in the biodiesel production reaction which in the presence of 4% by weight of catalyst and molar ratio of oil to methanol 1 to 20 resulted in 91% efficiency in 180 s.

2-Amino-4H-chromene compounds are belonged to an important heterocyclic groups that have extensive important in organic chemistry and medicine. The compounds have anti-cancer, anti-bacterial, anti-coagulation and anti-tumor properties and have applications to produce dye, make up and hygienic materials. Until know, several methods have been reported for the synthesis of the compounds. Most of them, suffers defects such as poisoning and volatile solvents, low yield, high length reaction time, and no reusability of used catalyst. In the present work, Sr2As2O7 pyrochlore material was used as a catalyst for the synthesis of 2-amino-4H-cromens derivatives using a three component one-pot synthesis method under microwave irradiation. The raw materials were aromatic aldehydes, malononitrile and beta-naphtol. Sr2As2O7 was synthesized by an ultrasonic assisted solvothermal method using H2O and C2H5OH solvents mixtures at the 1:1 volumetric ratio. The materials were characterized by PXRD, FESEM and FTIR techniques. Then, the catalytic performance of the synthesized nanomaterial was used for the synthesis of 2-amino-4H-chromene derivatives. To do the process, the reaction parameters such as reaction time, solvent type and catalyst amount were optimized and the reactions were performed under the conditions. It was found that the optimum conditions were 15 mg catalyst, H2O as solvent and 6-9 min reaction time.

In this study, iron-doped tin oxide semiconductor nanoparticles with an iron to tin mole ratio of 0, 1, 2 and 3% synthesized by microwave method. The crystal structure, surface morphology, chemical bonds, and optical properties of the samples were studied by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), infrared fourier transform spectroscopy (FTIR), and UV–Vis spectroscopy. Elements analysis was performed by EDAX. The X-ray diffraction results showed that the samples were polycrystalline, and have the preferred peaks of plates (110), (101), (200), (211), (220), (002), (310), (112), and (301) SnO2 phase with rutile rectangular structure. Increasing the iron impurity density from zero to three percent causes the reducing average size of nanocrystals from 23.53 to 11.03 nm, reducing grain size from 37 to 28 nm, and increasing unit cell volume from 70.61 to 71.40  and the optical band gap from 3.3 to 4.2 eV. The results of FTIR analysis confirm the SnO2 bond in the samples. Investigation of the sensing properties of ethanol gas by the samples showed that the response time of the sensors is in the range of 15.75 to 38.85 s. The sensor made with nanoparticles with a concentration of 1% iron exhibited optimum sensing conditions.

Photocatalytic wastewater treatment as an important member of advanced oxidation processes with a high energy efficiency plays important role in wastewater treatment. This method is known as an energy efficient method because of solar light utilization availability. In this work, TiO2 nanophotocatalyst has been synthesized using titanium (IV) butoxide as a Ti precursor. Then, the nitrogen doping was considered to activate the photocatalytic ability in the visible part of the light spectrum. N-TiO2 nanophotocatalysts were synthesized using a hybrid method of hydrothermalmicrowave. The analyses of XRD, FESEM, BET, EDX and UV-vis spectroscopy were carried out to evaluate the physicochemical and optical properties of the catalysts. The XRD analysis has confirmed the successful synthesis of the TiO2 with anatase crystalline phase. FESEM images have confirmed the nano-sized structure of the catalysts. The BET surface area coincided the FESEM results by representation of surface area enhancement after doping with nitrogen. EDX has verified the presence of nitrogen in the sample and demonstrated uniform dispersion and no agglomeration of Nitrogen presented on the catalyst surface. The photocatalytic degradation of dye from the synthetic wastewater was carried out resulting the highest photocatalytic activity for N-TiO2 in comparison to undoped samples. The experiment resulted 90 percent of degradation after 140 min while undoped TiO2 represented just 52 percent of degradation. Also, to have a better comparison, the industrial photocatalyst P25 was used in the same experiment time and operational conditions. The results depicted higher photocatalytic activity for hydrothermal-microwave synthesis of TiO2 compared to industrial TiO2 with 15 percent higher degradation.