Assistance Of Microwave Irradiation Research Articles

NiAl-layered Double Hydroxide/Reduced Graphene Oxide Composite: Microwave-assisted Synthesis and Supercapacitive Properties

Pure NiAl-layered double hydroxides (LDHs) and graphene oxide (GO)/NiAl-LDHs composites are both fabricated by refluxing solution with the assistance of microwave irradiation within 2hours. The structural characterization and morphological observation of the composites suggest that small NiAl-LDHs crystals are in situ grown on the surface of GO nanosheets, preventing the compact stacking of GO as an intercalated spacer. The electrochemical performances of pure LDHs and GO/NiAl-LDHs composites with different content of GO are investigated and compared. The GO/NiAl-LDHs composite containing 23 wt% GO exhibits a higher specific capacitance of 1630 F g−1 at 1 A g−1 in 6M KOH solution and more stable rate capability than others. When GO is substituted by microwave reduced graphene oxide (rGO) or the GO in the GO/NiAl-LDHs composite is thermally reduced at a rational temperature, rGO/NiAl-LDHs composites are obtained with enhanced electrochemical behavior in rate capability and cycle life. Critical comparisons indicate that rGO/NiAl-LDHs composite prepared by thermal reducing GO/NiAl-LDHs has better cycling performance and rate capability than the counterpart directly prepared with rGO.

ChemInform Abstract: Convenient and Reliable Routes Towards 2‐Aminothiazoles: Palladium‐Catalyzed versus Copper‐Catalyzed Aminations of Halothiazoles.

Two efficient methods for the amination of 2-halothiazoles are presented here. A first protocol requires a Pd/L system. Several 2-aminothiazoles were synthesized under optimized conditions and isolated in good yields. The first palladium-catalyzed CN coupling reactions between 2-halothiazoles and primary alkylamines are presented. In a second part, ligand-free copper-catalyzed aminations of 2-halothiazoles by alkylamines and aniline in a green solvent have been developed. The protocol is very effective for primary and secondary amines and perfectly tolerates the presence of another halide moiety on the 2-halothiazole. The reaction occurs under the assistance of microwave irradiation, which drastically decreases the reaction time. The reaction leads to the formation of 2-aminothiazoles, key molecules in pharmaceutical research.

Original access to 5-aryluracils from 5-iodo-2′-deoxyuridine via a microwave assisted Suzuki-Miyaura cross-coupling/deglycosylation sequence in pure water

A facile and efficient methodology to obtain various 5-aryluracil derivatives was developed through a two steps sequence: a ligand-free Suzuki-Miyaura cross-coupling reaction starting from totally deprotected 5-iodo-(2′-deoxy)uridine followed by a very simple deglycosylation procedure in pure water with assistance of microwave irradiation.

Microwave synthesis of high rate nanostructured LiMnBO3 with excellent cyclic behavior for lithium ion batteries

LiMnBO3 nanobeads (LMB-NB) prepared using a urea assisted microwave irradiation method delivered 67 mA h g−1 capacity at 0.6 C rate between 1.25 and 4.8 V, showing 88% cyclability after 100 cycles.

Convenient and Reliable Routes Towards 2‐Aminothiazoles: Palladium‐Catalyzed versus Copper‐Catalyzed Aminations of Halothiazoles

AbstractTwo efficient methods for the amination of 2‐halothiazoles are presented here. A first protocol requires a Pd/L system. Several 2‐aminothiazoles were synthesized under optimized conditions and isolated in good yields. The first palladium‐catalyzed CN coupling reactions between 2‐halothiazoles and primary alkylamines are presented. In a second part, ligand‐free copper‐catalyzed aminations of 2‐halothiazoles by alkylamines and aniline in a green solvent have been developed. The protocol is very effective for primary and secondary amines and perfectly tolerates the presence of another halide moiety on the 2‐halothiazole. The reaction occurs under the assistance of microwave irradiation, which drastically decreases the reaction time. The reaction leads to the formation of 2‐aminothiazoles, key molecules in pharmaceutical research.magnified image

ChemInform Abstract: Improved Microwave‐Assisted Ligand‐Free Suzuki—Miyaura Cross‐Coupling of 5‐Iodo‐2′‐deoxyuridine in Pure Water.

ChemInformVolume 44, Issue 48 Natural Products ChemInform Abstract: Improved Microwave-Assisted Ligand-Free Suzuki—Miyaura Cross-Coupling of 5-Iodo-2′-deoxyuridine in Pure Water. Shawn Gallagher-Duval, Shawn Gallagher-Duval Cent. Rech. Royallieu, ESCOM-UTC, Univ. Technol. Compiegne, F-60200 Compiegne, Fr.Search for more papers by this authorGwenaelle Herve, Gwenaelle Herve Cent. Rech. Royallieu, ESCOM-UTC, Univ. Technol. Compiegne, F-60200 Compiegne, Fr.Search for more papers by this authorGuillaume Sartori, Guillaume Sartori Cent. Rech. Royallieu, ESCOM-UTC, Univ. Technol. Compiegne, F-60200 Compiegne, Fr.Search for more papers by this authorGerald Enderlin, Gerald Enderlin Cent. Rech. Royallieu, ESCOM-UTC, Univ. Technol. Compiegne, F-60200 Compiegne, Fr.Search for more papers by this authorChristophe Len, Christophe Len Cent. Rech. Royallieu, ESCOM-UTC, Univ. Technol. Compiegne, F-60200 Compiegne, Fr.Search for more papers by this author Shawn Gallagher-Duval, Shawn Gallagher-Duval Cent. Rech. Royallieu, ESCOM-UTC, Univ. Technol. Compiegne, F-60200 Compiegne, Fr.Search for more papers by this authorGwenaelle Herve, Gwenaelle Herve Cent. Rech. Royallieu, ESCOM-UTC, Univ. Technol. Compiegne, F-60200 Compiegne, Fr.Search for more papers by this authorGuillaume Sartori, Guillaume Sartori Cent. Rech. Royallieu, ESCOM-UTC, Univ. Technol. Compiegne, F-60200 Compiegne, Fr.Search for more papers by this authorGerald Enderlin, Gerald Enderlin Cent. Rech. Royallieu, ESCOM-UTC, Univ. Technol. Compiegne, F-60200 Compiegne, Fr.Search for more papers by this authorChristophe Len, Christophe Len Cent. Rech. Royallieu, ESCOM-UTC, Univ. Technol. Compiegne, F-60200 Compiegne, Fr.Search for more papers by this author First published: 08 November 2013 https://doi.org/10.1002/chin.201348202Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume44, Issue48November 26, 2013 RelatedInformation

Microwave-Enhanced Fenton-Like System, Fe<sub>3</sub>O<sub>4</sub>/H<sub>2</sub>O<sub>2</sub> for Rhodamine B Wastewater Degradation

Fenton reactions have been increasingly applied to emergent pollutants degradation. Although homogeneous reaction by classical Fenton enables organic wastewater degradation, long treatment time and high iron catalyst concentrations are needed, raising environmental concerns. This paper proposed an innovative and cheap solution to degrade Rhodamine B (RmB) by combining magnetic nanomaterials of Fe3O4as the catalyst with microwave-enhanced fenton-like system. The main operational parameters were optimized systematically (hydrogen peroxide concentration; Fe3O4dosage; catalyst cycles; reaction time and reaction temperature). The degradation rate of Rhodamine B was increased and accelerated due to the assistance of microwave irradiation, with value of 99% after heated for only 5 min, even higher than that of treated by traditional Fenton process for 20 min. Moreover, six cyclic tests for Rhodamine B degradation showed that the magnetic catalyst was very stable, recoverable, highly active, and easy to separate using an external magnet. Hence, microwave-enhanced Fenton-like system with magnetic nanomaterials of Fe3O4as the catalyst has potential use in organic pollutant removal.

Formation of vaterite regulated by silk sericin and its transformation towards hydroxyapatite microsphere

The influence of soluble silk sericin (SS) protein on the formation of CaCO3 particles was investigated and the CaCO3 particles were then used as a template to synthesize the hydroxyapatite microspheres. The SS showed a strong preference to the mineralization of vaterite and the fine controls over the shape, size and uniformity of vaterite were carried out by the variation of pH value and reaction time in the presence of SS. Using the vaterites as a template, the homogeneous and monodispersed hydroxyapatite microspheres, copying faithfully the shape and size of original vaterites, were fabricated under the assistance of microwave irradiation. The research may provide a feasible method for the fabrication of hydroxyapatite-based biomaterials with controllable configuration.

Facile synthesis of bimetallic Cu–Ag nanoparticles under microwave irradiation and their oxidation resistance

Air-stable bimetallic Cu–Ag nanoparticles in the range of 12–30 nm have been synthesized at gram scale by a facile alcohol reduction in the absence of surfactants with the assistance of microwave irradiation. The synthesized nanoparticles were analyzed by x-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning TEM, ultraviolet–visible spectroscopy, x-ray photoelectron spectroscopy and thermogravimetry (TG). The stability of the bimetallic nanoparticles against oxidation was examined by TG and in situ temperature-programmed XRD analyses in the atmosphere. No oxidation of copper was confirmed by XRD after storing for longer than 6 months in the atmosphere at room temperature. No oxidation took place below 118 ° C and the Cu(200) diffraction peak decreased by only 7% after heating at 100 ° C for 30 min. The oxidation resistance has been ascribed to a Cu core–Ag shell structure, probably owing to the suppressive effect of Ag on the surface through the electronic interaction with Cu and a physical barrier of oxygen.

An analytical ultracentrifugation based study on the conformation of lambda carrageenan in aqueous solution

The conformation and heterogeneity of lambda-carrageenan, a sulphonated galactan from red seaweed, solubilised in aqueous solvent with the assistance of microwave irradiation, has been assessed by a combination of analytical ultracentrifugation, size-exclusion chromatography, light scattering and capillary viscometry. Preparations appeared generally unimodal on the basis of sedimentation coefficient distributions from sedimentation velocity although at the highest concentrations a shoulder appears with a sedimentation coefficient approximately 1.1 times greater than that of the main component. Even under conditions commensurate with charge suppression simple linear regression was insufficient to represent non-ideal concentration dependence and the extraction of the Grálen concentration dependence parameter ks. A more general fitting algorithm was therefore employed. Mark-Houwink-Kuhn-Sakurada analysis of the change in intrinsic viscosity [η] with molecular weight, together with the Wales-van Holde ratio (combination of ks with [η]) point to an extended flexible conformation for lambda-carrageenan in the (weight average) molecular weight range Mw=340,000-870,000g/mol. The origin of the larger sedimentation coefficient component appearing at the higher concentrations is considered.

A new approach to sample preparation for the determination of trace metals in petroleum source rocks

The dissolution and extraction of petroleum source rocks using a nonionic surfactant to determine their trace metal (V, Ni, Co, Mn, and Mo) content with the assistance of microwave irradiation were investigated and the conditions for obtaining the optimum yield were determined. A complementary microwave-assisted acid dissolution method was also optimized. The results showed that the temperature and time have significant effects on yields of the trace metals. Factors such as surfactant concentration and sample/solvent ratio had little influence on the digestion and extraction efficiencies for these metals. The optimum temperature for microwave-assisted nonionic surfactant dissolution of petroleum source rocks for trace metal determination was 200 °C and the best yields of the metals were obtained in 40 min. The optimum temperature and time for nonionic surfactant extraction of trace metals from petroleum source rocks were 90 °C and 45 min, respectively. The microwave-assisted acid digestion gave optimum yields of the trace metals in 70 min. The new nonionic surfactant digestion and extraction methods showed efficiencies comparable to those afforded by using the acid digestion method for three out of five elements determined in this study, although the recoveries of vanadium and manganese were relatively low, but the reduction of the digestion/extraction time and environmentally friendliness of the new nonionic surfactant based methods are clear advantages. The new method showed a very good reproducibility. The results of this study also show that the microwave-assisted nonionic surfactant digestion method is a good, efficient and better alternative green analytical preparatory technique for the determination of some trace metals in petroleum source rocks.

Microwave-assisted simultaneous reduction and titanate treatment of graphene oxide

Simultaneous reduction and functionalization of graphene oxide was conducted with the assistance of microwave irradiation. A titanate coupling agent was utilized for the functionalization of graphene. TEM, XPS and FTIR were employed to characterize the changes in graphene morphology and chemistry. The results suggested that the titanate coupling agent was bonded covalently on the graphene surfaces. The surface of graphene remained hydrophilic after the reduction of graphene oxide, while the electrical conductivity of graphene was partially restored. Titanate functionalized graphene was mixed with the waterborne polyurethane (PU) to prepare nanocomposites. The graphene/PU nanocomposites exhibited a conductive percolation threshold of 0.1 wt%.

Improved microwave-assisted ligand-free Suzuki–Miyaura cross-coupling of 5-iodo-2′-deoxyuridine in pure water

A facile and efficient methodology for direct synthesis of 5-aryl-2′-deoxyuridines was developed through ligand-free Suzuki–Miyaura cross-coupling reactions starting from totally deprotected 5-iodo-2′-deoxyuridine and various boronic acids. Reactions were performed, in pure water, in the presence of very low loading of palladium either by classical thermal heating or with the assistance of microwave irradiation yielding 5-arylated uridine derivatives in moderate to good yields within short reaction times.

Application of Zn2SnO4 photocatalyst prepared by microwave-assisted hydrothermal route in the degradation of organic pollutant under sunlight

Abstract Zn 2 SnO 4 crystals were successfully synthesized under microwave-assisted irradiation. The structural properties of the powders were investigated by X-ray diffraction (XRD) and N 2 adsorption/desorption isotherms (BET). Through a microwave-assisted hydrothermal route, porous Zn 2 SnO 4 particles with a high specific surface area were obtained in a short synthesis time. In addition, Zn 2 SnO 4 particles were tested as a photocatalyst for the degradation of textile dye under sunlight. The results showed that the maximum photocatalytic activity of Zn 2 SnO 4 particles was about 50% degradation of the Reactive Red 141 dye in 270 min under sunlight irradiation, and that photocatalytic process followed zero-order kinetics. After sunlight exposure, 37% of total organic carbon (TOC) was removed. The photocatalytic results indicated that the Zn 2 SnO 4 particles can be promising in the degradation of dye from aqueous solution under sunlight.

An Efficient and Environmentally Friendly Procedure for Synthesis of Quinazolinone Derivatives by Use of a Biginelli-Type Reaction

A Biginelli one-pot three-component reaction involving cyclohexanone, aromatic/or heterocyclic aldehyde, and urea thiourea or guanidine HCl was applied in this work to prepare quinazolin-2(1H)one derivatives under solvent free and microwave irradiation assistance as well as conventional method. The major advantages of this protocol are high yields, operational simplicity, short reaction time and environment friendly. The purity of the synthesized compounds was characterized by means of IR, 1 H NMR, 13 C NMR, mass spectral and elemental analysis.

Microwave enhanced Fenton process for the removal of methylene blue from aqueous solution

Fenton process is an effective treatment for organic wastewater. In this study, we introduced a microwave enhanced Fenton process to remove dye from aqueous solution. The conversion rate of methylene blue (MB) was increased and accelerated due to the assistance of microwave irradiation, with value of 93.0% after heated for only 1min, even higher than that of treated by traditional Fenton process for 65min. The MB conversion increases with initial concentrations of H2O2 and Fe2+ because of the increased generation of hydroxyl radicals. The MB conversion changes slightly with pH at values of below 7 and declines dramatically when the pH is higher than 8, with optimum pH value of about 3. During the microwave treatment, the maximum UV–Vis absorption peak decreased much quicker than that of other two peaks, and blue shifted from wavelength of 664–629nm, indicating the decomposition of dimethylamino and methyl groups in MB molecules. The microwave enhanced Fenton process is a promising treatment for organic contaminants due to advantages of fast and effective processing.

Conventional and microwave-assisted solvent-free synthesis of fused [1,2,5]thiadiazolo[3,4-b]quinoxaline-2,2-dioxide derivatives

A simple, highly efficient and environmentally friendly procedure for the condensation of $o$-phenylenediamine with 2,5-dialkyl-1,2,5-thiadiazolidine-3,4-dione-1,1-dioxides via two microwave-assisted reactions is described. These compounds were also prepared via a conventional heating method to provide a comparison with the microwave-assisted irradiation reaction protocol. The structures of the synthesized compounds were confirmed using infrared, 1H NMR and mass spectral analysis.

A Facile Microwave Avenue to Electrochemiluminescent Two‐Color Graphene Quantum Dots

AbstractWith the assistance of microwave irradiation, greenish‐yellow luminescent graphene quantum dots (gGQDs) with a quantum yield (QY) up to 11.7% are successfully prepared via cleaving graphene oxide (GO) under acid conditions. The cleaving and reduction processes are accomplished simultaneously using microwave treatment without additional reducing agent. When the gGQDs are further reduced with NaBH4, bright blue luminescent graphene quantum dots (bGQDs) are obtained with a QY as high as 22.9%. Both GQDs show well‐known excitation‐dependent PL behavior, which could be ascribed to the transition from the lowest unoccupied molecular orbital (LUMO) to the highest occupied molecular orbital (HOMO) with a carbene‐like triplet ground state. Electrochemiluminescence (ECL) is observed from the graphene quantum dots for the first time, suggesting promising applications in ECL biosensing and imaging. The ECL mechanism is investigated in detail. Furthermore, a novel sensor for Cd2+ is proposed based on Cd2+ induced ECL quenching with cysteine (Cys) as the masking agent.

Factors Controlling Leaching of Polycyclic Aromatic Hydrocarbons from Petroleum Source Rock Using Nonionic Surfactant

The extraction of polycyclic aromatic hydrocarbons (PAHs) from petroleum source rock by nonionic surfactants with the assistance of microwave irradiation was investigated and the conditions for maximum yield were determined. The results showed that the extraction temperatures and type of surfactant have significant effects on extraction yields of PAHs. Factors such as surfactant concentration, irradiation power, sample/solvent ratio and mixing surfactants (i.e., mixture of surfactant at specific ratio) also influence the extraction efficiencies for these compounds. The optimum temperature for microwave-assisted nonionic surfactant extraction of PAHs from petroleum source rock was 120 °C and the best suited surfactant was Brij 35. The new method showed extraction efficiencies comparable to those afforded by the Soxhlet extraction method, but a reduction of the extraction times and environmentally friendliness of the new nonionic surfactant extraction system are clear advantages. The results also show that microwave-assisted nonionic surfactant extraction is a good and efficient green analytical preparatory technique for geochemical evaluation of petroleum source rock.

Synthesis and Characterization of CeO2-SiO2Nanoparticles by Microwave-Assisted Irradiation Method for Photocatalytic Oxidation of Methylene Blue Dye

CeO2-SiO2nanoparticles were synthesized for the first time by a facile microwave-assisted irradiation process. The effect of irradiation time of microwave was studied. The materials were characterized by N2adsorption, XRD, UV-vis/DR, and TEM. All solids showed mesoporous textures with high surface areas, relatively small pore size diameters, and large pore volume. The X-ray diffraction results indicated that the as-synthesized nanoparticles exhibited cubic CeO2without impurities and amorphous silica. The transmission electron microscopy (TEM) images revealed that the particle size of CeO2-SiO2nanoparticles, which were prepared by microwave method for 30 min irradiation times, was around 8 nm. The photocatalytic activities were evaluated by the decomposition of methylene blue dye under UV light irradiations. The results showed that the irradiation under the microwave produced CeO2-SiO2nanoparticles, which have the best crystallinity under a shorter irradiation time. This indicates that the introduction of the microwave really can save energy and time with faster kinetics of crystallization. The sample prepared by 30 min microwave irradiation time exhibited the highest photocatalytic activity. The photocatalytic activity of CeO2-SiO2nanoparticles, which were prepared by 30 min irradiation times was found to have better performance than commercial reference P25.