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Sample records for microwave-assisted mcmurry polymerization

  1. Microwave-assisted atmospheric pressure plasma polymerization of hexamethyldisiloxane

    NASA Astrophysics Data System (ADS)

    Matsubayashi, Toshiki; Hidaka, Hiroki; Muguruma, Hitoshi

    2016-07-01

    Microwave-assisted atmospheric pressure plasma polymerization is presented. A system with a re-entrant microwave cavity realizes simple matching, stable plasma, and free space under the orifice of plasma steam. Hexamethyldisiloxane is employed as a monomer, while argon is used as a carrier gas. The effective area of the hydrophobic coating film used corresponds to a circle of 20 mm diameter and the deposition rate considered is 5 nm/min. Matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy shows that the coating film has a large molecular weight (>200 kDa), suggesting that a high-crosslinking and three-dimensional polymer matrix is formed and microwave-assisted atmospheric pressure plasma polymerization is fulfilled.

  2. Fabrication of Vertical Array CNTs/Polyaniline Composite Membranes by Microwave-Assisted In Situ Polymerization

    NASA Astrophysics Data System (ADS)

    Ding, Jie; Li, Xiaoyan; Wang, Xia; Zhang, Jinrui; Yu, Dengguang; Qiu, Biwei

    2015-12-01

    A vertical array carbon nanotubes (VACNTs)/polyaniline (PANi) composite membrane was prepared by microwave-assisted in situ polymerization. With microwave assistance, the morphology of PANi revealed a smaller diameter and denser connection. Meanwhile, thermogravimetric analysis showed improved thermal stability of microwave-assisted PANi for higher molecular weight. Focused ion beam thinning method was used to cut the VACNTs/PANi membrane into dozen-nanometer thin strips along the cross-sectional direction, and transmission electron microscopy observation showed seamless deposition of PANi between VACNT gaps, without damaging the vertical status of CNTs. Meanwhile, stronger conjugate interaction between the quinoid ring of PANi and VACNTs of the composite membrane were prompted by microwave-assisted in situ polymerization. By using nanoindentation technology, the VACNTs/PANi composite membrane showed exponential increasing of modulus and hardness. Meanwhile, the elasticity was also improved, which was proved by the calculated plastic index. The results can provide helpful guidance for seamlessly infiltrating matrix into CNT array and also demonstrate the importance of structural hierarchy for getting proper behavior of nanostructures.

  3. Polymerization of tellurophene derivatives via microwave-assisted palladium-catalyzed ipso-arylative polymerization**

    PubMed Central

    Park, Young S.; Wu, Qin; Nam, Chang-Yong; Grubbs, Robert B.

    2014-01-01

    We report the synthesis of a tellurophene-containing low bandgap polymer, PDPPTe2T, via microwave-assisted palladium-catalyzed ipso-arylative polymerization of 2,5-bis[(α-hydroxy-α,α-diphenyl)methyl]tellurophene with a diketopyrrolopyrrole (DPP) monomer. Compared with the corresponding thiophene analog, PDPPTe2T absorbs light of longer wavelengths and has a smaller bandgap. Bulk heterojunction solar cells prepared from PDPPTe2T and PC71BM show PCE values of up to 4.4%. External quantum efficiency measurements show that PDPPTe2T produces photocurrent at wavelengths up to 1 μm. DFT calculations suggest that the atomic substitution from sulfur to tellurium increases electronic coupling to decrease the length of the carbon-carbon bonds between the tellurophene and thiophene rings, which results in the red-shift in absorption upon substitution of tellurium for sulfur. PMID:25145499

  4. Rapid synthesis of polymer brush surfaces via microwave-assisted surface-initiated radical polymerization.

    PubMed

    Guo, Wei; Hensarling, Ryan M; LeBlanc, Arthur L; Hoff, Emily A; Baranek, Austin D; Patton, Derek L

    2012-05-14

    Microwave-assisted surface-initiated radical polymerization (μW-SIP) is demonstrated for the rapid synthesis of polymer brush surfaces on two-dimensional substrates. μW-SIP is carried out at constant temperature and microwave power allowing comparison with conventional SIP carried out in an oil bath at the same effective solution temperature. We show μW-SIP enables significant enhancements (up to 39-fold increase) in brush thickness at reduced reaction times for a range of monomer types (i.e. acrylamides, acrylates, methacrylates, and styrene). The effects of reaction time, monomer concentration, and microwave power on film thickness are explored. PMID:22514123

  5. Chemosynthesis of poly(ε-lysine)-analogous polymers by microwave-assisted click polymerization.

    PubMed

    Guo, Jinshan; Wei, Ying; Zhou, Dongfang; Cai, Pingqiang; Jing, Xiabin; Chen, Xue-Si; Huang, Yubin

    2011-03-14

    Poly(ε-lysine) (ε-PL)-analogous click polypeptides with not only similar α-amino side groups but also similar main chain to ε-PL were chemically synthesized for the first time through click polymerization from aspartic (or glutamic)-acid-based dialkyne and diazide monomers. With microwave-assisting, the reaction time of click polymerization was compressed into 30 min. The polymers were fully characterized by NMR, ATR-FTIR, and SEC-MALLS analysis. The deprotected click polypeptides had similar pK(a) value (7.5) and relatively low cytotoxicity as ε-PL and could be used as substitutes of ε-PL in biomedical applications, especially in endotoxin selective removal. Poly(ethylene glycol) (PEG)-containing alternating copolymers with α-amino groups were also synthesized and characterized. After deprotection, the polymers could be used as functional gene vector with PEG shadowing system and NCA initiator to get amphiphilic graft polymers. PMID:21302898

  6. Microwave assisted synthesis of polyacrylamide grafted dextrin (Dxt-g-PAM): Development and application of a novel polymeric flocculant.

    PubMed

    Pal, Sagar; Nasim, T; Patra, A; Ghosh, S; Panda, A B

    2010-12-01

    An efficient polymeric flocculant was synthesized by microwave assisted grafting of polyacrylamide to dextrin. By varying the reaction conditions, various grades of graft copolymers were synthesized to obtain the optimized one. Viscometry, elemental analysis, FTIR spectroscopy, (13)C NMR spectroscopy, determination of molecular weight and radius of gyration using SLS analysis, thermal analysis and SEM analysis were employed to confirm that polyacrylamide has been grafted onto the dextrin backbone. The flocculation efficiency of the grafted products in kaolin suspension was dependent on the molecular weight, radius of gyration and length of the grafted polyacrylamide chains. The flocculant obtained by microwave assisted grafting method was superior to dextrin and polyacrylamide-based commercial flocculant (Rishfloc 226 LV) in flocculation tests. PMID:20728467

  7. Microwave-assisted synthesis of titania coating onto polymeric separators for improved lithium-ion battery performance

    NASA Astrophysics Data System (ADS)

    Juang, Ruey-Shin; Hsieh, Chien-Te; Chen, Po-An; Chen, Yu-Fu

    2015-07-01

    This study adopts an efficient microwave-assisted method to deposit TiO2 into tri-layered polymeric membranes, forming composite separators for Li-ion batteries (LIBs) consisted of Li4Ti5O12 (LTO) anode/Li cathode. The microwave deposition is capable of growing TiO2 crystals into the porous membranes at 40 °C in a short period of ∼8 min. Both improved thermal and dimensional stability are achieved by the deposition of TiO2 in the separators. The improvement can be attributed to the formation of robust skeleton to stabilize the separators, imparting a superior insulation and mass transport barrier against volatile compounds formed during the thermal decomposition process. After depositing an appropriate amount of TiO2, the TiO2-coated separator still features well-developed porous structure, allowing favorable liquid wettability and high mass uptake of electrolyte. The amount of TiO2 deposits plays as a crucial role in facilitating the cell performance, including high ionic conductivity, low inner resistance, high operation temperature, high energy density, and excellent cycleability. Accordingly, this low-temperature deposition method of modifying polymeric separators is attractive for application in high-performance LIBs.

  8. Evaluation of microwave assisted grafted sago starch as controlled release polymeric carrier.

    PubMed

    Singh, Akhilesh Vikram; Nath, Lila Kanta

    2013-09-01

    In the present investigation an attempt has been made to develop a new co-polymeric material for controlled release tablet formulations. The acrylamide grafting was successfully performed on the backbone of sago starch. The modified starch was tested for acute toxicity and drug-excipient compatibility study. The grafted material was used in making of controlled release tablets of lamivudine. The formulations were evaluated for physical characteristics such as hardness, friability, %drug content and weight variations. The in vitro release study showed that the optimized formulation exhibited highest correlation (R) value in case of Higuchi model and the release mechanism of the optimized formulation predominantly exhibited combination of diffusion and erosion process. There was a significant difference in the pharmacokinetic parameters (T(max), C(max), AUC, V(d), T(1/2) and MDT) of the optimized formulation as compared to the marketed conventional tablet Lamivir(®) was observed. The pharmacokinetics parameters were showed controlled pattern and better bioavailability. The optimized formulation exhibited good stability and release profile at the accelerated stability conditions. PMID:23707750

  9. Microwave-assisted chemical-vapor-induced in situ polymerization of polyaniline nanofibers on graphite electrode for high-performance supercapacitor.

    PubMed

    Li, Xiaoqin; Yang, Li; Lei, Ying; Gu, Li; Xiao, Dan

    2014-11-26

    Polyaniline (PANI) nanofibers-coated graphite electrode is fabricated by microwave-assisted chemical vapor induced in situ polymerization in the presence of ammonium persulfate. The microstructure and electrochemical performance of the as-prepared nanofibers are investigated in detail. The obtained PANI nanofibers at the optimum volume ratio of 4% aniline, with some protuberances on the surface and the diameter from 50 to 100 nm, are coated onto the surface of graphite electrode. The PANI-coated graphite electrodes display the best electrochemical performance in 6 M H2SO4 electrolyte, including a large reversible capacity of 2136 F g(-1) at the current density of 1 A g(-1) and excellent rate capability. In particular, The PANI-coated graphite electrode exhibits a long cycle life by retaining 91% of the initial specific capacitance after 1000 cycles. More importantly, a symmetric supercapacitor was fabricated using PANI-coated graphite electrode, showing maximum energy density and power density of 24 Wh kg(-1) and 6000 W kg(-1), respectively. PMID:25361469

  10. Rapid preparation of molecularly imprinted polymers by microwave-assisted emulsion polymerization for the extraction of florfenicol in milk.

    PubMed

    Chen, Haiyan; Son, Sunil; Zhang, Fengshuang; Yan, Jin; Li, Yi; Ding, Hong; Ding, Lan

    2015-03-01

    In this study, we proposed a rapid and simple method for the preparation of molecularly imprinted polymers (MIPs) by emulsion polymerization. The polymerization process was accelerated by microwave heating, and the reaction time was greatly shortened. The obtained MIPs were spherical in shape and exhibited a uniform morphology. The MIPs with selectivity and high affinity to florfenicol were successfully applied as solid-phase extraction materials to extract and clean up the florfenicol in milk, followed by liquid chromatography-tandem mass spectrometry (LC-MS) analysis. The parameters affecting the performance of extraction and LC-MS analysis were evaluated. The detection limit of the method was 4.1ngmL(-1). The relative standard deviations of intra- and inter-day were in the range of 3.5-4.7% and 3.9-7.5%, respectively. PMID:25614968

  11. Microwave-assisted click polymerization for the synthesis of Abeta(16-22) cyclic oligomers and their self-assembly into polymorphous aggregates.

    PubMed

    Elgersma, Ronald C; van Dijk, Maarten; Dechesne, Annemarie C; van Nostrum, Cornelus F; Hennink, Wim E; Rijkers, Dirk T S; Liskamp, Rob M J

    2009-11-01

    We report on the design, synthesis, and structural analysis of cyclic oligomers with an amyloidogenic peptide sequence as the repeating unit to obtain novel self-assembling bionanomaterials. The peptide was derived from the Alzheimer Abeta(16-22) sequence since its strong tendency to form antiparallel beta-sheets ensured the formation of intermolecular hydrogen bridges on which the supramolecular assembly of the individual cyclic oligomers was based. The synthesis of the cyclic oligomers was performed via a microwave-assisted Cu(I)-catalyzed 1,3-dipolar cycloaddition reaction of azido-Lys-Leu-Val-Phe-Phe-Ala-Glu-propargyl amide as the monomer. The formation of cyclic oligomers, up to pentamers (35 amino acid residues), was verified by MALDI-TOF analysis and the individual cyclic monomer and dimer could be isolated by HPLC. Gelation behavior and the self-assembly of the linear monomer and the cyclic monomer and dimer were studied by TEM, FTIR and CD. Significant differences were observed in the morphology of the supramolecular aggregates of these three peptides that could be explained by alterations of the hydrogen bond network. PMID:19830304

  12. Microwave-assisted Functionalization of Poly(ethylene glycol) and On-resin Peptides for Use in Chain Polymerizations and Hydrogel Formation

    PubMed Central

    Van Hove, Amy H.; Wilson, Brandon D.; Benoit, Danielle S. W.

    2013-01-01

    One of the main benefits to using poly(ethylene glycol) (PEG) macromers in hydrogel formation is synthetic versatility. The ability to draw from a large variety of PEG molecular weights and configurations (arm number, arm length, and branching pattern) affords researchers tight control over resulting hydrogel structures and properties, including Young’s modulus and mesh size. This video will illustrate a rapid, efficient, solvent-free, microwave-assisted method to methacrylate PEG precursors into poly(ethylene glycol) dimethacrylate (PEGDM). This synthetic method provides much-needed starting materials for applications in drug delivery and regenerative medicine. The demonstrated method is superior to traditional methacrylation methods as it is significantly faster and simpler, as well as more economical and environmentally friendly, using smaller amounts of reagents and solvents. We will also demonstrate an adaptation of this technique for on-resin methacrylamide functionalization of peptides. This on-resin method allows the N-terminus of peptides to be functionalized with methacrylamide groups prior to deprotection and cleavage from resin. This allows for selective addition of methacrylamide groups to the N-termini of the peptides while amino acids with reactive side groups (e.g. primary amine of lysine, primary alcohol of serine, secondary alcohols of threonine, and phenol of tyrosine) remain protected, preventing functionalization at multiple sites. This article will detail common analytical methods (proton Nuclear Magnetic Resonance spectroscopy (;H-NMR) and Matrix Assisted Laser Desorption Ionization Time of Flight mass spectrometry (MALDI-ToF)) to assess the efficiency of the functionalizations. Common pitfalls and suggested troubleshooting methods will be addressed, as will modifications of the technique which can be used to further tune macromer functionality and resulting hydrogel physical and chemical properties. Use of synthesized products for the

  13. Microwave-assisted Chemical Transformations

    EPA Science Inventory

    In recent years, there has been a considerable interest in developing sustainable chemistries utilizing green chemistry principles. Since the first published report in 1986 by Gedye and Giguere on microwave assisted synthesis in household microwave ovens, the use of microwaves as...

  14. MICROWAVE-ASSISTED SYNTHESIS OF NOBLE NANOSTRUCTURES

    EPA Science Inventory

    Microwave-assisted (MW) spontaneous reduction of noble metal salts, silver (Ag), gold (Au), platinum (Pt) and palladium (Pd) is reported using sugar solutions such as -D glucose, sucrose and maltose, etc. to generate nanomaterials. These MW-assisted reactions, conducted in aqueo...

  15. Microwave-assisted synthesis of cyclodextrin polyurethanes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cyclodextrin (CD) has often been incorporated into polyurethanes in order to facilitate its use in encapsulation or removal of organic species for various applications. In this work a microwave-assisted method has been developed to produce polyurethanes consisting of alpha-, ß-, and gamma-CD and thr...

  16. Ultrafast microwave-assisted in-tip digestion of proteins.

    PubMed

    Hahn, Hans W; Rainer, Matthias; Ringer, Thomas; Huck, Christian W; Bonn, Günther K

    2009-09-01

    Trypsin was immobilized on glycidylmethacrylate-co-divinylbenzene (GMA/DVB) polymerized in pipet tips for online enzymatic digestion of proteins. The major advantages of in-tip digestion are easy handling and small sample amount required for analysis. Microwave-assisted digestion was applied for highly efficient and time saving proteolysis. Adaption to an automated robotic system allowed fast and reproducible sample treatment. Investigations with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) and liquid chromatography coupled with electrospray-ionization mass spectrometry (LC-ESI/MS) attested high sequence coverages (SCs) for the three standard proteins, myoglobin (Myo, 89%), bovine serum albumin (BSA, 78%) and alpha-casein (alpha-Cas, 83%). Compared to commercially available trypsin tips, clear predominance concerning the digestion performance was achieved. Storageability was tested over a period of several weeks and results showed only little decrease (<5%) of protein sequence coverages. The application of microwave-assisted in-tip digestion (2 min) with full automation by a robotic system allows high-throughput analysis (96 samples within 80 min) and highly effective proteolysis. PMID:19639939

  17. Ceramic matrix composites by microwave assisted CVI

    SciTech Connect

    Currier, R.P.; Devlin, D.J.

    1993-05-01

    Chemical vapor infiltration (CVI) processes for producing continuously reinforced ceramic composites are reviewed. The potential advantages of microwave assisted CVI are noted. Recent numerical studies of microwave assisted CVI are then reviewed. These studies predict inverted thermal gradients in fibrous ceramic preforms subjected to microwave radiation and suggest processing strategies for achieving uniformly dense composites. Comparisons are made to experimental results obtained using silicon based composite systems. The importance of microwave-material interactions is stressed. In particular, emphasis is placed on the role played by the relative ability of fiber and matrix to dissipate microwave energy. Results suggest that microwave induced inverted gradients can in fact be exploited using the CVI technique to promote inside-out densification.

  18. Ceramic matrix composites by microwave assisted CVI

    SciTech Connect

    Currier, R.P.; Devlin, D.J.

    1993-01-01

    Chemical vapor infiltration (CVI) processes for producing continuously reinforced ceramic composites are reviewed. The potential advantages of microwave assisted CVI are noted. Recent numerical studies of microwave assisted CVI are then reviewed. These studies predict inverted thermal gradients in fibrous ceramic preforms subjected to microwave radiation and suggest processing strategies for achieving uniformly dense composites. Comparisons are made to experimental results obtained using silicon based composite systems. The importance of microwave-material interactions is stressed. In particular, emphasis is placed on the role played by the relative ability of fiber and matrix to dissipate microwave energy. Results suggest that microwave induced inverted gradients can in fact be exploited using the CVI technique to promote inside-out densification.

  19. Extended Maxwell Garnett formalism for composite adhesives for microwave-assisted adhesion of polymer surfaces

    SciTech Connect

    Shanker, B.; Lakhtakia, A. )

    1993-01-01

    Adhesives with dielectric loss are needed for microwave-assisted joining of polymeric substances. The dielectric loss in an otherwise suitable adhesive may be enhanced by doping it with fine metallic particles. Here we use a recently extended Maxwell Garnett formalism to estimate the complex dielectric constant of a metal-doped composite adhesive, with specific focus on the imaginary part of the dielectric constant of the composite adhesive. 14 refs.

  20. Crossed McMurry Coupling Reactions for Porphycenic Macrocycles: Non-Statistical Selectivity and Rationalisation

    PubMed Central

    Cowie, Thomas Y; Kennedy, Lorna; Żurek, Justyna M; Paterson, Martin J; Bebbington, Magnus W P

    2015-01-01

    Crossed McMurry reactions of bifuran- or bithiophenedicarbaldehydes with bipyrroledicarbaldehydes have been studied for the first time. Only those porphycenic macrocycles derived from homocoupled McMurry products were formed. The results are explained by using both density functional theory and electron propagator computations to model the electron affinity of the dialdehyde starting materials. It was predicted that bifuran\\bithiophene cross-coupling would indeed occur, and this was demonstrated by the first synthesis of a novel dioxa,dithio hetero-porphycenoid annulene. This approach will allow the prior identification of viable substrates for related crossed McMurry reactions. PMID:26213484

  1. Flocculation properties of polyacrylamide grafted carboxymethyl guar gum (CMG-g-PAM) synthesised by conventional and microwave assisted method.

    PubMed

    Pal, Sagar; Ghorai, S; Dash, M K; Ghosh, S; Udayabhanu, G

    2011-09-15

    A novel polymeric flocculant based on polyacrylamide grafted carboxymethyl guar gum (CMG-g-PAM) has been synthesised by grafting polyacrylamide chains onto CMG backbone using conventional redox grafting and microwave assisted grafting methods. Under optimum grafting conditions, 82% and 96% grafting efficiencies have been observed in case of conventional and microwave assisted methods respectively. The optimum sample has been characterized using viscometry, spectroscopic analysis, elemental analysis, molecular weight and radius of gyration determination. The flocculation characteristics of grafted and ungrafted polysaccharides have been evaluated in kaolin suspension, municipal sewage wastewater and decolourization efficiency of a dye solution (methylene blue). It is evident from results that CMG-g-PAM synthesised by microwave assisted grafting method is showing best flocculation characteristics. PMID:21802849

  2. Synthesis of 4-vinylpyridine-divinylbenzene copolymer adsorbents for microwave-assisted desorption of benzene.

    PubMed

    Meng, Qing Bo; Yang, Go-Su; Lee, Youn-Sik

    2012-02-29

    Reports on the development of polymer adsorbents for microwave-assisted desorption of nonpolar volatile organic compounds (VOCs) are rare. In this study, we synthesized macroporous polymeric adsorbents with hydrophilic methyl pyridinium units for microwave-assisted desorption of nonpolar VOCs. The benzene adsorption and desorption properties of the adsorbents were investigated under both dry and humid conditions. Under humid conditions, as the content of the hydrophilic methyl pyridinium units in the adsorbents increased from 0 to 20%, the adsorption capacity of benzene decreased from about 21 to 7 mg/g, while the desorption efficiency of benzene increased significantly from 48 to 87%. The maximum concentration of desorbate also increased significantly as the content of the hydrophilic units was increased under humid conditions. We attributed the enhanced desorption efficiency mainly to more adsorbed moisture, which indirectly allowed heating of the polymer adsorbents to higher temperatures upon irradiation with 600 W microwaves. PMID:22236950

  3. Microwave assisted pultrusion of an epoxy composite

    SciTech Connect

    Methven, J.M.; Abidin, A.Z.

    1995-12-01

    A 6mm diameter cylindrical profile based on E-glass fibers and a BF{sub 3}-triamine-epoxy resin system has been manufactured by Microwave Assisted Pultrusion (MAP) using a single mode resonant microwave cavity operating in a TM{sub 010} mode at 2450 MHz. Power transfer is at least 70% and pulling speeds of more than 2m/minute have been achieved for a power input of about 800W. The results are consistent with earlier MAP studies using unsaturated polyesters, epoxies urethane acrylates and vinyl esters. The results provide a sound basis for proposing the use of this type of epoxy system as a material that is suitable for a high speed gel-cure pultrusion process that uses both a microwave heating cavity and a conventional pultrusion die.

  4. Microwave-assisted synthesis of cyclodextrin polyurethanes.

    PubMed

    Biswas, Atanu; Appell, Michael; Liu, Zengshe; Cheng, H N

    2015-11-20

    Cyclodextrin (CD) has often been incorporated into polyurethanes in order to facilitate its use in encapsulation or removal of organic species for various applications. In this work a microwave-assisted method has been developed to produce polyurethanes consisting of α-, β-, and γ-CD and three common diisocyanates. As compared to conventional heating, this new synthetic method saves energy, significantly reduces reaction time, and gets similar or improved yield. The reaction products have been fully characterized with (13)C, (1)H, and two-dimensional NMR spectroscopy. With suitable stoichiometry of starting CD and diisocyanate, the resulting CD polyurethane is organic-soluble and water-insoluble and is shown to remove Nile red dye and phenol from water. Possible applications include the removal of undesirable materials from process streams, toxic compounds from the environment, and encapsulation of color or fragrance molecules. PMID:26344257

  5. Microwave-assisted synthesis of organics and nanomaterials

    EPA Science Inventory

    Microwave-assisted chemistry techniques and greener reaction media are dramatically reducing chemical waste and reaction times in several organic transformations and material synthesis. This presentation summarizes author’s own experience in developing MW-assisted chemical proces...

  6. Physical principles of microwave assisted magnetic recording

    SciTech Connect

    Rivkin, Kirill; Benakli, Mourad; Yin, Huaqing; Tabat, Ned

    2014-06-07

    While the basic physics of Microwave Assisted Magnetization Reversal (MAMR) phenomenon is well established both theoretically and experimentally, its application in a practical magnetic recording environment was so far studied primarily with the help of micromagnetic recording models. In this work, we instead attempt to use analytical formulation and simple numerical models to understand the main challenges as well as benefits that are associated with such a system. It appears that the main difference between the previously introduced theory [G. Bertotti et al., Phys. Rev. Lett. 86, 724 (2001); K. Rivkin et al., Appl. Phys. Lett. 92, 153104 (2008); S. Okamoto et al., J. Appl. Phys. 107, 123914 (2010).] and recording environment is that both the RF and DC magnetic fields are applied at a substantial angle to the anisotropy axis. While the associated symmetry breaking prevents one from describing the reversal process explicitly, it is possible to approximate the solutions well enough to satisfactorily match numerical models both in the case of wire and Spin Torque Oscillator generated RF fields. This approach allows for physical explanation of various effects associated with MAMR such as high gradient of writeable anisotropy and reduction of track width, and offers a clear guidance regarding future optimization of MAMR recording.

  7. Microwave assisted formation of magnetic carbon nanostructures

    NASA Astrophysics Data System (ADS)

    Yerra, Narendranath

    Magnetic epoxy carbon nanostructures from microwave energy assisted- and conventional-pyrolysis processes are compared. Unlike graphitized carbon shell in the conventional heating, different carbon shell morphologies including carbon nanotubes, carbon nanoflakes and amorphous carbon were observed. Crystalline metallic iron and cementite were observed in the magnetic core, different from a single cementite produced in the conventional process. Carbon coated magnetic nanostructures as well as dielectric semiconductors can be produced using this process. Microwave assisted pyrolysis process is also used to form the magnetic core-shell carbon nanostructure from polyaniline (PANI)-magnetite (Fe 3O4) nanocomposites. The amorphous combined with graphitized carbon shell is observed by the transmission electron microscopy (TEM). The crystalline metallic iron, cementite, Fe3O4 and iron oxide (Fe2O 3) are observed in the magnetic core in the Mossbauer spectra measurements. The increased magnetic properties are observed in the formed core-shell carbon nanostructure after microwave annealing compared with PANI-Fe3O 4 nanocomposites. The formed solid carbon nanostructure can protect the material from the acid dissolution and magnetic core favors the recycling of material. This magnetic carbon nanostructure has the potential application in the removal of heavy metals from waste water.

  8. System to continuously produce carbon fiber via microwave assisted plasma processing

    DOEpatents

    White, Terry L [Knoxville, TN; Paulauskas, Felix L [Knoxville, TN; Bigelow, Timothy S [Knoxville, TN

    2010-11-02

    A system to continuously produce fully carbonized or graphitized carbon fibers using microwave-assisted plasma (MAP) processing comprises an elongated chamber in which a microwave plasma is excited in a selected gas atmosphere. Fiber is drawn continuously through the chamber, entering and exiting through openings designed to minimize in-leakage of air. There is a gradient of microwave power within the chamber with generally higher power near where the fiber exits and lower power near where the fiber enters. Polyacrylonitrile (PAN), pitch, or any other suitable organic/polymeric precursor fibers can be used as a feedstock for the inventive system. Oxidized or partially oxidized PAN or pitch or other polymeric fiber precursors are run continuously through a MAP reactor in an inert, non-oxidizing atmosphere to heat the fibers, drive off the unwanted elements such as oxygen, nitrogen, and hydrogen, and produce carbon or graphite fibers faster than conventionally produced carbon fibers.

  9. Adding value to ethanol production byproducts through microwave assisted pyrolysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The aim of this project is to increase the value of distillers grain by utilizing it as a feedstock for microwave assisted pyrolysis (MAP). Pyrolysis is the chemical/thermal conversion of biomass without the presence of oxygen into newly formed products: gases, liquids and solids. This conversion pr...

  10. Microwave-Assisted Synthesis of "N"-Phenylsuccinimide

    ERIC Educational Resources Information Center

    Shell, Thomas A.; Shell, Jennifer R.; Poole, Kathleen A.; Guetzloff, Thomas F.

    2011-01-01

    A microwave-assisted synthesis of "N"-phenylsuccinimide has been developed for the second-semester organic teaching laboratory. Utilizing this procedure, "N"-phenylsuccinimide can be synthesized in moderate yields (40-60%) by heating a mixture of aniline and succinic anhydride in a domestic microwave oven for four minutes. This technique reduces…

  11. Determination of fructooligosaccharides in burdock using HPLC and microwave-assisted extraction.

    PubMed

    Li, Jing; Liu, Xiaomei; Zhou, Bin; Zhao, Jing; Li, Shaoping

    2013-06-19

    The root of burdock ( Arctium lappa L.) is a commonly used vegetable in Asia. Fructooligosaccharides (FOS) are usually considered as its main bioactive components. Thus, quantitative analysis of these components is very important for the quality control of burdock. In this study, an HPLC-ELSD and microwave-assisted extraction method was developed for the simultaneous determination of seven FOS with degrees of polymerization (DP) between 3 and 9, as well as fructose, glucose, and sucrose in burdock from different regions. The separation was performed on a Waters XBridge Amide column (4.6 × 250 mm i.d., 3.5 μm) with gradient elution. All calibration curves for investigated analytes showed good linear regression (r > 0.9990). Their LODs and LOQs were lower than 3.63 and 24.82 μg/mL, respectively. The recoveries ranged from 99.2 to 102.6%. The developed method was successfully applied to determination of ten sugars in burdock from different locations of Asia. The results showed that the contents of FOS in different samples of burdock collected at appropriate times were similar, and the developed HPLC-ELSD with microwave-assisted extraction method is helpful to control the quality of burdock. PMID:23745967

  12. Preparation of κ-carra-oligosaccharides with microwave assisted acid hydrolysis method

    NASA Astrophysics Data System (ADS)

    Li, Guangsheng; Zhao, Xia; Lv, Youjing; Li, Miaomiao; Yu, Guangli

    2015-04-01

    A rapid method of microwave assisted acid hydrolysis was established to prepare κ-carra-oligosaccharides. The optimal hydrolysis condition was determined by an orthogonal test. The degree of polymerization (DP) of oligosaccharides was detected by high performance thin layer chromatography (HPTLC) and polyacrylamide gel electrophoresis (PAGE). Considering the results of HPTLC and PAGE, the optimum condition of microwave assisted acid hydrolysis was determined. The concentration of κ-carrageenan was 5 mg mL-1; the reaction solution was adjusted to pH 3 with diluted hydrochloric acid; the solution was hydrolyzed under microwave irradiation at 100 for 15 °C min. Oligosaccharides were separated by a Superdex 30 column (2.6 cm × 90 cm) using AKTA Purifier UPC100 and detected with an online refractive index detector. Each fraction was characterized by electrospray ionization mass spectrometry (ESI-MS). The data showed that odd-numbered κ-carra-oligosaccharides with DP ranging from 3 to 21 could be obtained with this method, and the structures of the oligosaccharides were consistent with those obtained by traditional mild acid hydrolysis. The new method was more convenient, efficient and environment-friendly than traditional mild acid hydrolysis. Our results provided a useful reference for the preparation of oligosaccharides from other polysaccharides.

  13. Microwave-assisted stripping of oil contaminated drill cuttings.

    PubMed

    Robinson, J P; Kingman, S W; Onobrakpeya, O

    2008-07-01

    The application of microwave heating technology to conventional gas stripping processes has been investigated in the remediation of contaminated drill cuttings. The technical feasibility and limitations of nitrogen and steam stripping processes are demonstrated, and it is shown that the combination of microwave heating with the stripping process offers a step change in performance. Order of magnitude improvements in processing time are shown for the microwave-assisted processes, as well as greatly improved levels of remediation. The mechanisms of contaminant removal are discussed, along with the phenomena which occur with microwave heating processes. The energy requirements of each of pure gas and microwave-assisted processes are also discussed, and the potential applications of each technology are highlighted relative to the overall remediation requirements. PMID:17433529

  14. Microwave-assisted methanolysis of green coffee oil.

    PubMed

    Oigman, S S; de Souza, R O M A; Dos Santos Júnior, H M; Hovell, A M C; Hamerski, L; Rezende, C M

    2012-09-15

    Optimisation of a microwave-assisted methanolysis was performed to obtain cafestol and kahweol directly from green coffee oil (Coffea arabica). A two-factor (the methanolysis period and temperature), three-level, factorial experimental design (3(2)) was adopted. The methanolysis procedure was performed under microwave irradiation, using closed vessel and accurate fast responding internal fibre-optic temperature probe. The effects on the responses were measured by HPLC. After 3 min of microwave irradiation (hold time) at 100°C, with 500 mg of green coffee oil, a yield higher than 99% was obtained. The yield of this reaction is 26% after 2h when working under conventional heating. The methods described in the literature lead to long reaction times, poor yields and formation of side products. The microwave-assisted technique proved to be faster, avoided undesired side products and gave better conversion, when compared to conventional heating process. PMID:23107719

  15. Microwave assisted synthesis of a mono organoimido functionalized Anderson polyoxometalate.

    PubMed

    Ritchie, C; Bryant, G

    2015-12-28

    The synthesis of an aliphatic organoimido functionalized polyoxometalate has been achieved through a microwave assisted reaction protocol in the absence of any activating reagents. Characterization of the pendant amine containing polyanion [Mo6O18NC(OCH2)3MnMo6O18(OCH2)3CNH2](5-) (1) includes single crystal XRD, NMR, ESI-MS, IR and SAXS. PMID:26583488

  16. Development of A Microwave Assisted Particulate Filter Regeneration System

    SciTech Connect

    Popuri, Sriram

    2001-08-05

    The need for active regeneration of diesel particulate filters and the advantages of microwave assisted regeneration are discussed. The current study has multiple objectives, which include developing a microwave assisted particulate filter regeneration system for future generation light-duty diesel applications, including PNGV type applications. A variable power 2.0 kW microwave system and a tuned waveguide were employed. Cavity geometry is being optimized with the aid of computational modeling and temperature measurements during microwave heating. A wall-flow ceramic-fiber filter with superior thermal shock resistance, high filtration efficiency, and high soot capacity was used. The microwave assisted particulate filter regeneration system has operated for more than 100 hours in an engine test-cell with a 5.9-liter diesel engine with automated split exhaust flow and by-pass flow capabilities. Filter regeneration was demonstrated using soot loads up to 10 g/liter and engine exhaust at idling flow rates as the oxygen source. A parametric study to determine the optimal combination of soot loading, oxidant flow rate, microwave power and heating time is underway. Preliminary experimental results are reported.

  17. Microwave-Assisted Extraction of Fucoidan from Marine Algae.

    PubMed

    Mussatto, Solange I

    2015-01-01

    Microwave-assisted extraction (MAE) is a technique that can be applied to extract compounds from different natural resources. In this chapter, the use of this technique to extract fucoidan from marine algae is described. The method involves a closed MAE system, ultrapure water as extraction solvent, and suitable conditions of time, pressure, and algal biomass/water ratio. By using this procedure under the specified conditions, the penetration of the electromagnetic waves into the material structure occurs in an efficient manner, generating a distributed heat source that promotes the fucoidan extraction from the algal biomass. PMID:26108504

  18. Analytical expression for critical frequency of microwave assisted magnetization switching

    NASA Astrophysics Data System (ADS)

    Arai, Hiroko; Imamura, Hiroshi

    2016-02-01

    The microwave-assisted switching (MAS) of magnetization in a perpendicularly magnetized circular disk is studied based on the macrospin model in a rotating frame. The analytical expression for the critical frequency of MAS is derived by analyzing the presence of a quasiperiodic mode. The critical frequency is expressed as a function of the radio frequency (rf) field Hrf and the effective anisotropy field H\\text{k}\\text{eff}. For a small rf field such that H\\text{rf} \\ll H\\text{k}\\text{eff}, the critical frequency is approximately equal to (γ /π )\\root 3 \\of{\\smash{H\\text{k}\\text{eff}H\\text{rf}2}\\mathstrut}.

  19. Microwave-assisted extraction of phycobiliproteins from Porphyridium purpureum.

    PubMed

    Juin, Camille; Chérouvrier, Jean-René; Thiéry, Valérie; Gagez, Anne-Laure; Bérard, Jean-Baptiste; Joguet, Nicolas; Kaas, Raymond; Cadoret, Jean-Paul; Picot, Laurent

    2015-01-01

    In the present study, microwave-assisted extraction was first employed to extract the phycobiliproteins of Porphyridium purpureum (Pp). Freeze-dried Pp cells were subjected to microwave-assisted extraction (MAE) to extract phycoerythin (PE), phycocyanin (PC), and allophycocyanin (APC). MAE combined reproducibility and high extraction yields and allowed a 180- to 1,080-fold reduction of the extraction time compared to a conventional soaking process. The maximal PE extraction yield was obtained after 10-s MAE at 40 °C, and PE was thermally damaged at temperatures higher than 40 °C. In contrast, a flash irradiation for 10 s at 100 °C was the best process to efficiently extract PC and APC, as it combined a high temperature necessary to extract them from the thylakoid membrane to a short exposure to thermal denaturation. The extraction order of the three phycobiliproteins was coherent with the structure of Pp phycobilisomes. Moreover, the absorption and fluorescence properties of MAE extracted phycobiliproteins were stable for several months after the microwave treatment. Scanning electron microscopy indicated that MAE at 100 °C induced major changes in the Pp cell morphology, including fusion of the exopolysaccharidic cell walls and cytoplasmic membranes of adjacent cells. As a conclusion, MAE is a fast and high yield process efficient to extract and pre-purify phycobiliproteins, even from microalgae containing a thick exopolysaccharidic cell wall. PMID:25231233

  20. Magnetic gold nanotriangles by microwave-assisted polyol synthesis

    NASA Astrophysics Data System (ADS)

    Yu, Siming; Hachtel, Jordan A.; Chisholm, Matthew F.; Pantelides, Sokrates T.; Laromaine, Anna; Roig, Anna

    2015-08-01

    Simple approaches to synthesize hybrid nanoparticles with magnetic and plasmonic functionalities, with high control of their shape and avoiding cytotoxic reactants, to target biomedical applications remain a huge challenge. Here, we report a facile, fast and bio-friendly microwave-assisted polyol route for the synthesis of a complex multi-material consisting of monodisperse gold nanotriangles around 280 nm in size uniformly decorated by superparamagnetic iron oxide nanoparticles of 5 nm. These nanotriangles are readily dispersible in water, display a strong magnetic response (10 wt% magnetic fraction) and exhibit a localized surface plasmon resonance band in the NIR region (800 nm). Moreover, these hybrid particles can be easily self-assembled at the liquid-air interfaces.Simple approaches to synthesize hybrid nanoparticles with magnetic and plasmonic functionalities, with high control of their shape and avoiding cytotoxic reactants, to target biomedical applications remain a huge challenge. Here, we report a facile, fast and bio-friendly microwave-assisted polyol route for the synthesis of a complex multi-material consisting of monodisperse gold nanotriangles around 280 nm in size uniformly decorated by superparamagnetic iron oxide nanoparticles of 5 nm. These nanotriangles are readily dispersible in water, display a strong magnetic response (10 wt% magnetic fraction) and exhibit a localized surface plasmon resonance band in the NIR region (800 nm). Moreover, these hybrid particles can be easily self-assembled at the liquid-air interfaces. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03113c

  1. Microwave-assisted synthesis of highly fluorescent nanoparticles of a melamine-based porous covalent organic framework for trace-level detection of nitroaromatic explosives.

    PubMed

    Zhang, Wang; Qiu, Ling-Guang; Yuan, Yu-Peng; Xie, An-Jian; Shen, Yu-Hua; Zhu, Jun-Fa

    2012-06-30

    Covalent organic frameworks (COFs) are a new generation of porous materials constructed from light elements linked by strong covalent bonds. Herein we present rapid preparation of highly fluorescent nanoparticles of a new type of COF, i.e. melamine-based porous polymeric network SNW-1, by a microwave-assisted synthesis route. Although the synthesis of SNW-1 has to be carried out at 180°C for 3d under conventional reflux conditions, SNW-1 nanoparticles could be obtained in 6h by using such a microwave-assisted method. The results obtained have clearly demonstrated that microwave-assisted synthesis is a simple yet highly efficient approach to nanoscale COFs or other porous polymeric materials. Remarkably, the as-synthesized SNW-1 nanoparticles exhibit extremely high sensitivity and selectivity, as well as fast response to nitroaromatic explosives such as 2,4,6-trinitrotoluene (TNT), 2,4,6-trinitrophenylmethylnitramine (Tetryl) and picric acid (PA) without interference by common organic solvents, which is due to the nanoscaled size and unique hierarchical porosity of such fluorescence-based sensing material. PMID:22560174

  2. Microwave-assisted sample preparation of coal and coal fly ash for subsequent metal determination

    SciTech Connect

    Srogi, K.

    2007-01-15

    The aim of this paper is to review microwave-assisted digestion of coal and coal fly ash. A brief description of microwave heating principles is presented. Microwave-assisted digestion appears currently to be the most popular preparation technique, possibly due to the comparatively rapid sample preparation and the reduction of contamination, compared to the conventional hot-plate digestion methods.

  3. A Microwave-Assisted Reduction of Cyclohexanone Using Solid-State-Supported Sodium Borohydride

    ERIC Educational Resources Information Center

    White, Lori L.; Kittredge, Kevin W.

    2005-01-01

    The reduction of carbonyl groups by sodium borohydride though is a well-known reaction in most organic lab texts, a difficulty for an instructor adopting this reaction in a student lab is that it is too long. Using a microwave assisted organic synthesis solves this difficulty and one such reaction, which is the microwave-assisted reduction of…

  4. Bio-based products via microwave-assisted maleation of tung oil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A simple “green” and convenient chemical modification of tung oil for maleinized tung oil (TOMA) was developed via microwave-assisted one-step maleation. The mechanism of this microwave-assisted maleation was investigated by nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). T...

  5. Microwave-assisted synthesis of bioactive quinazolines and quinazolinones.

    PubMed

    Besson, Thierry; Chosson, Elizabeth

    2007-12-01

    This paper aims to review recent developments in the synthesis of quinazolines and quinazolinone derivatives under conditions that include the application of microwave heating in the ring forming step. Recently, two reviews on the synthesis and chemistry of natural and synthetic quinazolines and quinazolinones have been published. This review highlights significant examples where microwave heating has been either synthetically enabling or has provided a key advantage over conventional thermal methods. Wherever possible, this review will focus on chemistry carried out using monomode systems and well-designed type of instrumentation. The review is grouped according to the main heterocycle types in order of increasing complexity; commencing with quinazolines and their derivatives. The microwave-assisted synthesis of quinazolines and quinazolinones will be classified and based on the substitution patterns of the ring system. Syntheses of heterocyclic systems of particular biological or commercial interest are emphasized. PMID:18288950

  6. Microwave assisted combustion synthesis of non-equilibrium intermetallic compounds.

    PubMed

    Veronesi, Paolo; Rosa, Roberto; Colombini, Elena; Leonelli, Cristina; Poli, Giorgio; Casagrande, Angelo

    2010-01-01

    A simplified model of the microwave-assisted combustion synthesis of Ni and Al metal powders to form the NiAl intermetallic on titanium and steel substrates is presented. The simulation couples an electro-thermal model with a chemical model, accounting for local heat generation due to the highly exothermic nature of the reactions between the powders. Numerical results, validated by experimental values, show that the capability of microwaves to convey energy, and not heat, can be used to alter the temperature profiles during and after the combustion synthesis, leading to unique intermetallic microstructures. This phenomenon is ascribed to the extended existence of high temperature liquid intermetallic phases, which react with the metallic substrates at the interface. Moreover, microwave heating selectivity allows to maintain the bulk of the substrate metallic materials to a much lower temperature, compared to combustion synthesis in conventionally heated furnaces, thus reducing possible unwanted transformations like phase change or oxidation. PMID:21721328

  7. Microwave-Assisted Rapid Enzymatic Synthesis of Nucleic Acids.

    PubMed

    Hari Das, Rakha; Ahirwar, Rajesh; Kumar, Saroj; Nahar, Pradip

    2016-07-01

    Herein we report microwave-induced enhancement of the reactions catalyzed by Escherichia coli DNA polymerase I and avian myeloblastosis virus-reverse transcriptase. The reactions induced by microwaves result in a highly selective synthesis of nucleic acids in 10-50 seconds. In contrast, same reactions failed to give desired reaction products when carried out in the same time periods, but without microwave irradiation. Each of the reactions was carried out for different duration of microwave exposure time to find the optimum reaction time. The products produced by the respective enzyme upon microwave irradiation of the reaction mixtures were identical to that produced by the conventional procedures. As the microwave-assisted reactions are rapid, microwave could be a useful alternative to the conventional and time consuming procedures of enzymatic synthesis of nucleic acids. PMID:27159147

  8. Formation of nanostructured fluorapatite via microwave assisted solution combustion synthesis.

    PubMed

    Nabiyouni, Maryam; Zhou, Huan; Luchini, Timothy J F; Bhaduri, Sarit B

    2014-04-01

    Fluorapatite (FA) has potential applications in dentistry and orthopedics, but its synthesis procedures are time consuming. The goal of the present study is to develop a quick microwave assisted solution combustion synthesis method (MASCS) for the production of FA particles. With this new processing, FA particles were successfully synthesized in minutes. Additionally, unique structures including nanotubes, hexagonal crystals, nanowhiskers, and plate agglomerates were prepared by controlling the solution composition and reaction time. In particular, the as-synthesized FA nanotubes presented a "Y" shape inner channel along the crystal axis. It is supposed that the channel formation is caused by the crystal growth and removal of water soluble salts during processing. The as-synthesized FA nanotubes showed good cytocompatibility, the cells cultured with a higher FA concentration demonstrated greater growth rate. With this new and easily applied MASCS processing application, FA nanoparticles have increased potential in dental and orthopedic applications. PMID:24582261

  9. Microwave assisted synthesis of amorphous magnesium phosphate nanospheres.

    PubMed

    Zhou, Huan; Luchini, Timothy J F; Bhaduri, Sarit B

    2012-12-01

    Magnesium phosphate (MgP) materials have been investigated in recent years for tissue engineering applications, attributed to their biocompatibility and biodegradability. This paper describes a novel microwave assisted approach to produce amorphous magnesium phosphate (AMP) in a nanospherical form from an aqueous solution containing Mg(2+) and HPO(4) (2-)/PO(4) (3-). Some synthesis parameters such as pH, Mg/P ratio, solution composition were studied and the mechanism of AMP precursors was also demonstrated. The as-produced AMP nanospheres were characterized and tested in vitro. The results proved these AMP nanospheres can self-assemble into mature MgP materials and support cell proliferation. It is expected such AMP has potential in biomedical applications. PMID:22890518

  10. Microwave-assisted synthesis and characterization of nickel ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Carpenter, Gopal; Sen, Ravindra; Malviya, Nitin; Gupta, Nitish

    2015-08-01

    Nickel ferrite nanoparticles (NiFe2O4) were successfully prepared by microwave-assisted combustion method (MWAC) using citric Electron acid as a chelating agent. NiFe2O4 nanoparticles were characterized by X-ray diffraction (XRD) pattern, Scanning Microscopy (SEM), Fourier transform infrared (FTIR) and UV-Visible techniques. XRD analysis revealed that NiFe2O4 nanoparticles have spinel cubic structure with the average crystalline size of 26.38 nm. SEM analysis revealed random and porous structural morphology of particles and FTIR showed absorption bands related to octahedral and tetrahedral sites, in the range 400-600cm-1 which strongly favor the formation of NiFe2O4 nanoparticles. The optical band gap is determined by UV Visible method and found to be 5.4 eV.

  11. Microwave-assisted synthesis and characterization of nickel ferrite nanoparticles

    SciTech Connect

    Carpenter, Gopal; Sen, Ravindra; Gupta, Nitish; Malviya, Nitin

    2015-08-28

    Nickel ferrite nanoparticles (NiFe{sub 2}O{sub 4}) were successfully prepared by microwave-assisted combustion method (MWAC) using citric Electron acid as a chelating agent. NiFe{sub 2}O{sub 4} nanoparticles were characterized by X-ray diffraction (XRD) pattern, Scanning Microscopy (SEM), Fourier transform infrared (FTIR) and UV-Visible techniques. XRD analysis revealed that NiFe{sub 2}O{sub 4} nanoparticles have spinel cubic structure with the average crystalline size of 26.38 nm. SEM analysis revealed random and porous structural morphology of particles and FTIR showed absorption bands related to octahedral and tetrahedral sites, in the range 400–600cm{sup −1} which strongly favor the formation of NiFe{sub 2}O{sub 4} nanoparticles. The optical band gap is determined by UV Visible method and found to be 5.4 eV.

  12. Microwave assisted magnetization switching in Co/Pt multilayer

    SciTech Connect

    Okamoto, S.; Kikuchi, N.; Kitakami, O.; Shimatsu, T.; Aoi, H.

    2011-04-01

    In this study, we have experimentally investigated the microwave assisted magnetization by switching (MAS) on the microstructured Co/Pt multilayer. The sample exhibits the typical magnetization curve peculiar to perpendicular anisotropy films, that is, a steep reversal initiated by nucleation of a reversed domain followed by its subsequent gradual expansion by the domain wall displacement. By applying microwaves with the frequency of GHz order, the nucleation field H{sub n} is significantly reduced at three frequencies. Taking into account the effective anisotropy field of our sample, the first dip of H{sub n} at the lowest frequency probably corresponds to the Kittel mode excitation, and the other two dips at higher frequencies correspond to unidentified excitation modes other than the Kittel mode. Among them, the last dip of H{sub n} at the highest frequency reaches about 1/3 of that without microwave application. These results suggest the existence of more effective excitation modes for MAS than the Kittel mode.

  13. Microwave-assisted extraction of cyclotides from Viola ignobilis.

    PubMed

    Farhadpour, Mohsen; Hashempour, Hossein; Talebpour, Zahra; A-Bagheri, Nazanin; Shushtarian, Mozhgan Sadat; Gruber, Christian W; Ghassempour, Alireza

    2016-03-15

    Cyclotides are an interesting family of circular plant peptides. Their unique three-dimensional structure, comprising a head-to-tail circular backbone chain and three disulfide bonds, confers them stability against thermal, chemical, and enzymatic degradation. Their unique stability under extreme conditions creates an idea about the possibility of using harsh extraction methods such as microwave-assisted extraction (MAE) without affecting their structures. MAE has been introduced as a potent extraction method for extraction of natural compounds, but it is seldom used for peptide and protein extraction. In this work, microwave irradiation was applied to the extraction of cyclotides. The procedure was performed in various steps using a microwave instrument under different conditions. High-performance liquid chromatography (HPLC) and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) results show stability of cyclotide structures on microwave radiation. The influential parameters, including time, temperature, and the ratio of solvents that are affecting the MAE potency, were optimized. Optimal conditions were obtained at 20 min of irradiation time, 1200 W of system power in 60 °C, and methanol/water at the ratio of 90:10 (v/v) as solvent. The comparison of MAE results with maceration extraction shows that there are similarities between cyclotide sequences and extraction yields. PMID:26706804

  14. Microwave assisted laser-induced breakdown spectroscopy at ambient conditions

    NASA Astrophysics Data System (ADS)

    Viljanen, Jan; Sun, Zhiwei; Alwahabi, Zeyad T.

    2016-04-01

    Signal enhancements in laser-induced breakdown spectroscopy (LIBS) using external microwave power are demonstrated in ambient air. Pulsed microwave at 2.45 GHz and of 1 millisecond duration was delivered via a simple near field applicator (NFA), with which an external electric field is generated and coupled into laser induced plasma. The external microwave power can significantly increase the signal lifetime from a few microseconds to hundreds of microseconds, resulting in a great enhancement on LIBS signals with the use of a long integration time. The dependence of signal enhancement on laser energy and microwave power is experimentally assessed. With the assistance of microwave source, a significant enhancement of ~ 100 was achieved at relatively low laser energy that is only slightly above the ablation threshold. A limit of detection (LOD) of 8.1 ppm was estimated for copper detection in Cu/Al2O3 solid samples. This LOD corresponds to a 93-fold improvement compared with conventional single-pulse LIBS. Additionally, in the microwave assisted LIBS, the self-reversal effect was greatly reduced, which is beneficial in measuring elements of high concentration. Temporal measurements have been performed and the results revealed the evolution of the emission process in microwave-enhanced LIBS. The optimal position of the NFA related to the ablation point has also been investigated.

  15. Microwave-assisted extraction of phenolic antioxidants from potato peels.

    PubMed

    Singh, Ashutosh; Sabally, Kebba; Kubow, Stan; Donnelly, Danielle J; Gariepy, Yvan; Orsat, Valérie; Raghavan, G S V

    2011-01-01

    A response surface method was used to optimize the microwave-assisted extraction parameters such as extraction time (t) (min), solvent (methanol) concentration (S) (v/v) and microwave power level (MP) for extraction of antioxidants from potato peels. Max. total phenolics content of 3.94 mg g⁻¹ dry weight (dw) was obtained at S of 67.33%, t of 15 min and a MP of 14.67%. For ascorbic acid (1.44 mg g⁻¹ dw), caffeic acid (1.33 mg g⁻¹ dw), ferulic acid (0.50 mg g⁻¹ dw) max contents were obtained at S of 100%, t of 15 min, and MP of 10%, while the max chlorogenic acid content (1.35 mg g⁻¹ dw) was obtained at S of 100%, t of 5 min, and MP of 10%. The radical scavenging activity of the extract was evaluated by using the DPPH assay and optimum antioxidant activity was obtained at S of 100%, t of 5 min, and MP of 10%. PMID:21383659

  16. Spectrophotometric determination of paracetamol with microwave assisted alkaline hydrolysis

    NASA Astrophysics Data System (ADS)

    Xu, Chunli; Li, Baoxin

    2004-07-01

    A novel and rapid spectrophotometric method for the determination of paracetamol is proposed in this paper. The proposed method is based on the microwave assisted alkaline hydrolysis of paracetamol to p-aminophenol that reacts with S 2- in the presence of Fe 3+ as oxidant to produce a methylene blue-like dye having an absorptivity maximum at 540 nm. The experiment showed that paracetamol could be hydrolysed quantitatively to p-aminophenol in only 1.5 min under radiation power 640 W using a microwave in NaOH medium. The system obeys Beer's law in the range of 0-3.0×10 -4 mol l -1 paracetamol. The molar absorptivity and Sandell's sensitivity were found to be 3.2×10 3 l mol -1 cm -1 and 0.047 μg cm -2, respectively. The relative standard deviation ( n=11) was 1.7% for 8.0×10 -5 mol l -1 paracetamol. The method has been applied successfully to analysis of paracetamol in pharmaceutical preparation.

  17. Saponins: a renewable and biodegradable surfactant from its microwave-assisted extraction to the synthesis of monodisperse lattices.

    PubMed

    Schmitt, C; Grassl, B; Lespes, G; Desbrières, J; Pellerin, V; Reynaud, S; Gigault, J; Hackley, V A

    2014-03-10

    Synthetic surfactants are widely used in emulsion polymerization, but it is increasingly desirable to replace them with naturally derived molecules with a reduced environmental burden. This study demonstrates the use of saponins as biodegradable and renewable surfactants for emulsion polymerization. This chemical has been extracted from soapnuts by microwave assisted extraction and characterized in terms of surfactant properties prior to emulsion polymerization. The results in terms of particle size distribution and morphology control have been compared to those obtained with classical nonionic (NP40) or anionic (SDS) industrial surfactants. Microwave-extracted saponins were able to lead to latexes as stable as standard PS latex, as shown by the CMC and CCC measurements. The saponin-stabilized PS particles have been characterized in terms of particle size and distribution by Dynamic Light Scattering and Asymmetrical Flow Field Flow Fractionation. Monomodal and monodispersed particles ranging from 250 to 480 nm in terms of diameter with a particle size distribution below 1.03 have been synthesized. PMID:24443771

  18. Central composite rotatable design for investigation of microwave-assisted extraction of ginger (Zingiber officinale)

    NASA Astrophysics Data System (ADS)

    Fadzilah, R. Hanum; Sobhana, B. Arianto; Mahfud, M.

    2015-12-01

    Microwave-assisted extraction technique was employed to extract essential oil from ginger. The optimal condition for microwave assisted extraction of ginger were determined by resposnse surface methodology. A central composite rotatable design was applied to evaluate the effects of three independent variables. The variables is were microwave power 400 - 800W as X1, feed solvent ratio of 0.33 -0.467 as X2 and feed size 1 cm, 0.25 cm and less than 0.2 cm as X3. The correlation analysis of mathematical modelling indicated that quadratic polynomial could be employed to optimize microwave assisted extraction of ginger. The optimal conditions to obtain highest yield of essential oil were : microwave power 597,163 W : feed solvent ratio and size of feed less than 0.2 cm.

  19. Extraction of Vanadium from Stone Coal by Microwave Assisted Sulfation Roasting

    NASA Astrophysics Data System (ADS)

    Wang, Mingyu; Xian, Pengfei; Wang, Xuewen; Li, Bowen

    2015-02-01

    The extraction of vanadium from stone coal was investigated by microwave-assisted sulfation roasting followed by water leaching. The results showed that this process is an effective method for the extraction of vanadium from stone coal. Microwave-assisted sulfation roasting promotes the reaction of sulfuric acid with vanadium oxides and decreases roasting time. Under optimized conditions (roasting temperature 200°C, heating rate of 10°C/min, 25% sulfuric acid addition, water leaching at 75°C for 1 h, and liquid/solid ratio of 1.5 ml/g), the leaching rate of vanadium reached 92.6%.

  20. Phase dependence of microwave-assisted switching of a single magnetic nanoparticle.

    PubMed

    Piquerel, R; Gaier, O; Bonet, E; Thirion, C; Wernsdorfer, W

    2014-03-21

    Microwave-assisted switching of the magnetization is an efficient way to reduce the magnetic field required to reverse the magnetization of nanostructures. Here, the phase sensitivity of microwave-assisted switching of an individual cobalt nanoparticle is studied using a pump-probe technique. The pump microwave pulse prepares an initial state of the magnetization, and the probe pulse tests its stability against switching. Precession states are established, which are stable against switching. Their basin of attraction is measured and is in qualitative agreement with numerical macrospin calculations. The damping parameter is evaluated using the variable delay pump-probe technique. PMID:24702409

  1. Phase Dependence of Microwave-Assisted Switching of a Single Magnetic Nanoparticle

    NASA Astrophysics Data System (ADS)

    Piquerel, R.; Gaier, O.; Bonet, E.; Thirion, C.; Wernsdorfer, W.

    2014-03-01

    Microwave-assisted switching of the magnetization is an efficient way to reduce the magnetic field required to reverse the magnetization of nanostructures. Here, the phase sensitivity of microwave-assisted switching of an individual cobalt nanoparticle is studied using a pump-probe technique. The pump microwave pulse prepares an initial state of the magnetization, and the probe pulse tests its stability against switching. Precession states are established, which are stable against switching. Their basin of attraction is measured and is in qualitative agreement with numerical macrospin calculations. The damping parameter is evaluated using the variable delay pump-probe technique.

  2. MICROWAVE-ASSISTED SHAPE-CONTROLLED BULK SYNTHESIS OF NOBLE NANOCRYSTALS AND THEIR CATALYTIC PROPERTIES

    EPA Science Inventory

    Bulk and shape-controlled synthesis of gold (Au) nanostructures with various shapes such as prisms, cubes and hexagons is described that occurs via microwave-assisted spontaneous reduction of noble metal salts using an aqueous solution of α-D-glucose, sucrose and maltose. The exp...

  3. Global structure of microwave-assisted flash extracted sugar beet pectin

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We have studied the global structure of microwave assisted, flash extracted pectins isolated from fresh sugar beet pulp. The objective was to minimize the disassembly and possibly the degradation of pectin molecules during extraction. We have characterized these pectins by HPSEC with light scatter...

  4. Microwave-Assisted Copper-Catalyzed Oxidative Cyclization of Acrylamides with Non-Activated Ketones.

    PubMed

    Zhao, Yaping; Sharma, Nandini; Sharma, Upendra K; Li, Zhenghua; Song, Gonghua; Van der Eycken, Erik V

    2016-04-18

    An operationally simple and efficient microwave-assisted protocol for the oxidative cyclization of acrylamide derivatives with non-activated ketones to generate 3,3-disubstituted oxindoles is described. The reaction proceeds by a copper-catalyzed tandem radical addition/cyclization strategy and tolerates a series of functional groups with moderate to excellent yields. PMID:26868308

  5. Metal-Free Microwave-Assisted Decarboxylative Elimination for the Synthesis of Olefins.

    PubMed

    Wu, Shu-Wei; Liu, Jia-Li; Liu, Feng

    2016-01-01

    A metal-free efficient synthesis of olefins via microwave-assisted direct decarboxylative elimination of arylacetic acids is described. This reaction, using commercially available reagent PIFA as oxidant, readily provides a variety of desired products in moderate to good yields. PMID:26652663

  6. MICROWAVE-ASSISTED SYNTHESIS OF NOBLE NANOSTRUCTURES USING BIODEGRADABLE POLYMER CARBOXYMETHYL CELLULOSE

    EPA Science Inventory

    Microwave-assisted (MW) synthesis of noble metals such as Au, Pt and Pd is reported using biodegradable polymer carboxymethyl cellulose (CMC) at 100°C within few seconds. The possible reduction entails the coupling of polar hydroxyl units in beta-glucopyranose units with micr...

  7. Microwave-assisted maleation of tung oil for bio-based products with versatile applications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this work, a simple, “green” and convenient chemical modification of tung oil for maleinized tung oil (TOMA) was developed via microwave-assisted one-step maleation. This modifying process did not involve any solvent, catalyst, or initiator, but demonstrated the most efficiency of functionalizing...

  8. MICROWAVE ASSISTED PREPARATION OF CYCLIC UREAS FROM DIAMINES IN THE PRESENCE OF ZNO

    EPA Science Inventory

    A microwave-assisted facile method for the preparation of various ureas, cyclic ureas, and urethanes has been developed that affords nearly quantitative yield of products at 120 degrees C (150 W), 71 kPa within 10 min using ZnO as a catalyst. The enhanced selectivity in this rea...

  9. Microwave-assisted fabrication of porous hematite photoanodes for efficient solar water splitting.

    PubMed

    Hou, Yidong; Zheng, Chong; Zhu, Zezhou; Wang, Xinchen

    2016-05-25

    Porous hematite photoanodes with wormlike networks were prepared by microwave-assisted rapid annealing of β-FeOOH grown directly on a FTO glass. The enhanced electrochemical characteristics such as large surface area and good permeation of an electrolyte lead to the excellent photoelectrochemical performance toward the solar-driven water splitting for hydrogen production. PMID:27140504

  10. Microwave assisted apatite coating deposition on Ti6Al4V implants.

    PubMed

    Zhou, Huan; Nabiyouni, Maryam; Bhaduri, Sarit B

    2013-10-01

    In this work we report a novel microwave assisted technology to deposit a uniform, ultra-thin apatite coating without any cracks on titanium implants in minutes. This method comprises of conventional biomimetic coating in synergism with microwave irradiation to result in alkaline earth phosphate nucleation. The microwave assisted coating process mainly follows the initial stages of biomimetic coating until the step of the Ca-P nuclei formation. After that, due to microwave irradiation more Ca-P nuclei are formed to cover the whole surface of the implant instead of the growth of deposited Ca-P nuclei to Ca-P globules and coatings. It is interesting to note the doping of Mg(2+) to Ca-P apatite coating can significantly change the properties and performances of as-deposited coatings. The hydrophilicity, physical properties, bioactivity, cell adhesion, and growth capability of as-deposited microwave assisted coatings were investigated. The study shows that this coating technology has great potential in biomedical applications. Additionally, since biomimetic coating can be applied to series of implant materials such as polymer, metals and glass, it is expected this microwave assisted coating technology can also be applied to these materials if they can remains stable at 100 °C, the boiling point of water. PMID:23910363

  11. MICROWAVE-ASSISTED EXTRACTION OF ORGANIC COMPOUNDS FROM STANDARD REFERENCE SOILS AND SEDIMENTS

    EPA Science Inventory

    As part of an ongoing evaluation of new sample preparation techniques by the U.S. Environmental Protection Agency (EPA), especially those that minimize waste solvents, microwave-assisted extraction (MAE) of organic compounds from solid materials (or "matrices") was evaluated. Six...

  12. Microwave-Assisted Organic Synthesis in the Organic Teaching Lab: A Simple, Greener Wittig Reaction

    ERIC Educational Resources Information Center

    Martin, Eric; Kellen-Yuen, Cynthia

    2007-01-01

    A greener, microwave-assisted Wittig reaction has been developed for the second-semester organic teaching laboratory. Utilizing this microwave technique, a variety of styrene derivatives have been successfully synthesized from aromatic aldehydes in good yields (41-68%). The reaction not only occurs under neat reaction conditions, but also employs…

  13. Microwave-Assisted Solvent Extraction and Analysis of Shikimic Acid from Plant Tissues

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A simple method using microwave-assisted extraction (MWAE) using water as the extraction solvent was developed for the determination of shikimic acid in plant tissue of Brachiaria decumbens Stapf, an important Poaceae forage and weed species widely spread in agricultural and non-agricultural areas t...

  14. MICROWAVE-ASSISTED SYNTHESIS OF NOBLE NANOSTRUCTURES USING BIODEGRADABLE POLYMER CARBOXYMETHYL CELLULOSE

    EPA Science Inventory

    Microwave-assisted synthesis of noble nanostructures (Au, Pt, and Pd) using biodegradable polymer carboxymethyl cellulose (CMC) under microwave irradiation (MW) at 100 0C is reported. The reaction occurs within a few minutes, whereas at room temperature the reaction does not pro...

  15. DEXTROSE-TEMPLATED MICROWAVE-ASSISTED COMBUSTION SYNTHESIS OF SPONGY METAL OXIDES

    EPA Science Inventory

    Microwave-assisted combustion synthesis of porous nanocrystalline titania and carbon coated titania is reported using dextrose as template and the product was compared with the one obtained using conventional heating furnace. Out of three compositions viz., 1:1, 1:3, and 1:5 (met...

  16. Microwave assisted total synthesis of a benzothiophene-based new chemical entity (NCE)

    EPA Science Inventory

    Pharmaceutical scientists are required to generate diverse arrays of complex targets in short span of time, which can now be achieved by microwave-assisted organic synthesis. New chemical entities (NCE) can be built in a fraction of the time using this technique. However, there a...

  17. Microwave-Assisted Synthesis of Mesoporous Nano-Hydroxyapatite Using Surfactant Templates

    EPA Science Inventory

    Mesoporous nano-hydroxyapatite (n-HAP) was expeditiously synthesized using the pseudo sol-gel microwave-assisted protocol (30 min) in the presence of two novel templates, namely sodium lauryl ether sulfate (SLES) and linear alkylbenzenesulfonate (LABS). The cooperative self-assem...

  18. Cd–cysteine precursor nanowire templated microwave-assisted transformation route to CdS nanotubes

    SciTech Connect

    Liu, Xiao-Lin; Zhu, Ying-Jie; Zhang, Qian; Li, Zhi-Feng; Yang, Bin

    2012-12-15

    Graphical abstract: Cadmium sulfide polycrystalline nanotubes have been successfully synthesized by microwave-assisted transformation method using Cd–cysteine precursor nanowires as the source material and template in ethylene glycol at 160 °C or ethanol at 60 °C. Display Omitted Highlights: ► Cd–cysteine precursor nanowires were successfully synthesized in alkaline solution. ► CdS nanotubes were prepared by templated microwave-assisted transformation method. ► CdS nanotubes can well duplicate the size and morphology of precursor nanowires. ► This method has the advantages of the simplicity and low cost. -- Abstract: We report the Cd–cysteine precursor nanowire templated microwave-assisted transformation route to CdS nanotubes. In this method, the Cd–cysteine precursor nanowires are synthesized using CdCl{sub 2}·2.5H{sub 2}O, L-cysteine and ethanolamine in water at room temperature. The Cd–cysteine precursor nanowires are used as the source material and template for the subsequent preparation of CdS nanotubes by a microwave-assisted transformation method using ethylene glycol or ethanol as the solvent. This method has the advantages of the simplicity and low cost, and may be extended to the synthesis of nanotubes of other compounds. The products are characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

  19. Microwave-Assisted Extraction Followed by Solid-Phase Extraction for the Chromatographic Analysis of Alkaloids in Stephania cepharantha.

    PubMed

    Liu, Ying; Xie, Daotao; Kang, Yun; Wang, Yaqin; Yang, Ping; Guo, Jixian; Huang, Jianming

    2016-04-01

    A procedure involving microwave-assisted extraction (MAE) followed by solid-phase extraction (SPE) was established for the extraction and purification of three bisbenzylisoquinoline alkaloids from Stephania cepharantha, and a reversed-phase high-performance liquid chromatography (HPLC) method was developed for the quantification of the target alkaloids. Chromatographic separation was achieved on a Phenomenex Luna Phenyl-Hexyl column. Prior to the HPLC analysis, the alkaloids were rapidly extracted by an optimized MAE process using 0.01 mol/L hydrochloric acid as the solvent. The MAE extract was subsequently purified by SPE using a cation-exchange polymeric cartridge. The MAE-SPE procedure extracted the three alkaloids with satisfactory recoveries ranging from 100.44 to 102.12%. In comparison with the MAE, Soxhlet and ultrasonic-assisted extractions, the proposed MAE-SPE method showed satisfactory cleanup efficiency. Thus, the validated MAE-SPE-HPLC method is specific, accurate and applicable to the determination of alkaloids in S. cepharantha. PMID:26759486

  20. Rapid microwave-assisted synthesis of molecularly imprinted polymers on carbon quantum dots for fluorescent sensing of tetracycline in milk.

    PubMed

    Hou, Juan; Li, Huiyu; Wang, Long; Zhang, Ping; Zhou, Tianyu; Ding, Hong; Ding, Lan

    2016-01-01

    In this paper, a novel, selective and eco-friendly sensor for the detection of tetracycline was developed by grafting imprinted polymers onto the surface of carbon quantum dots. A simple microwave-assisted approach was utilized to fabricate the fluorescent imprinted composites rapidly for the first time, which could shorten the polymerization time and simplify the experimental procedure dramatically. The novel composites not only demonstrated excellent fluorescence stability and special binding sites, but also could selectively accumulate target analytes. Under optimal conditions, the relative fluorescence intensity of the composites decreased linearly with increasing the concentration of tetracycline from 20 nM to 14 µM. The detection limit of tetracycline was 5.48 nM. The precision and reproducibility of the proposed sensor were also acceptable. Significantly, the practicality of this ultrasensitive sensor for tetracycline detection in milk was further validated, revealing the advantages of simplicity, sensitivity, selectivity and low cost. This approach combines the high selective adsorption property of molecular imprinted polymers and the sensitivity of fluorescence detection. It is envisioned that the development of fluorescent molecularly imprinted composites will offer a new way of thinking for rapid analysis in complex samples. PMID:26695231

  1. A microwave-assisted sol-gel Pechini method for the synthesis of BaCe{sub 0.65}Zr{sub 0.20}Y{sub 0.15}O{sub 3-{delta}} powders

    SciTech Connect

    Barison, S.; Fabrizio, M.; Fasolin, S.; Montagner, F.; Mortalo, C.

    2010-09-15

    In this work, BaCe{sub 0.65}Zr{sub 0.20}Y{sub 0.15}O{sub 3-{delta}} powders with a perovskite-type structure were successfully synthesized by a microwave-assisted sol-gel Pechini method (SGP). By comparison, powders having the same nominal stoichiometry were also prepared without the microwave assistance. For the syntheses, nitrates were used as metal precursors, and ethylenediaminetetraacetic acid and ethylene glycol were used as complexing and polymerizing agents, respectively. An extensive structural and morphological investigation by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) has been performed. Moreover, in order to check the phase transitions, simultaneous thermogravimetric and differential thermal analyses were (TG-DTA) performed on gels. With respect to the conventional Pechini method, the microwave-assisted process guaranteed a faster, energy-saving procedure for obtaining single-phase nanopowders of high purity. Moreover, a significant increase in pellet densities was achieved owing to a higher grain coalescence.

  2. Microwave-assisted Facile and Ultrafast Growth of ZnO Nanostructures and Proposition of Alternative Microwave-assisted Methods to Address Growth Stoppage

    PubMed Central

    Rana, Abu ul Hassan Sarwar; Kang, Mingi; Kim, Hyun-Seok

    2016-01-01

    The time constraint in the growth of ZnO nanostructures when using a hydrothermal method is of paramount importance in contemporary research, where a long fabrication time rots the very essence of the research on ZnO nanostructures. In this study, we present the facile and ultrafast growth of ZnO nanostructures in a domestic microwave oven within a pressurized environment in just a few minutes. This method is preferred for the conventional solution-based method because of the ultrafast supersaturation of zinc salts and the fabrication of high-quality nanostructures. The study of the effect of seed layer density, growth time, and the solution’s molar concentration on the morphology, alignment, density, and aspect ratio of ZnO nanorods (ZNRs) is explored. It is found in a microwave-assisted direct growth method that ~5 mins is the optimum time beyond which homogeneous nucleation supersedes heterogeneous nucleation, which results in the growth stoppage of ZNRs. To deal with this issue, we propound different methods such as microwave-assisted solution-replacement, preheating, and PEI-based growth methods, where growth stoppage is addressed and ZNRs with a high aspect ratio can be grown. Furthermore, high-quality ZnO nanoflowers and ZnO nanowalls are fabricated via ammonium hydroxide treatment in a very short time. PMID:27103612

  3. Microwave-assisted Facile and Ultrafast Growth of ZnO Nanostructures and Proposition of Alternative Microwave-assisted Methods to Address Growth Stoppage.

    PubMed

    Rana, Abu Ul Hassan Sarwar; Kang, Mingi; Kim, Hyun-Seok

    2016-01-01

    The time constraint in the growth of ZnO nanostructures when using a hydrothermal method is of paramount importance in contemporary research, where a long fabrication time rots the very essence of the research on ZnO nanostructures. In this study, we present the facile and ultrafast growth of ZnO nanostructures in a domestic microwave oven within a pressurized environment in just a few minutes. This method is preferred for the conventional solution-based method because of the ultrafast supersaturation of zinc salts and the fabrication of high-quality nanostructures. The study of the effect of seed layer density, growth time, and the solution's molar concentration on the morphology, alignment, density, and aspect ratio of ZnO nanorods (ZNRs) is explored. It is found in a microwave-assisted direct growth method that ~5 mins is the optimum time beyond which homogeneous nucleation supersedes heterogeneous nucleation, which results in the growth stoppage of ZNRs. To deal with this issue, we propound different methods such as microwave-assisted solution-replacement, preheating, and PEI-based growth methods, where growth stoppage is addressed and ZNRs with a high aspect ratio can be grown. Furthermore, high-quality ZnO nanoflowers and ZnO nanowalls are fabricated via ammonium hydroxide treatment in a very short time. PMID:27103612

  4. An evaluation of microwave-assisted fusion and microwave-assisted acid digestion methods for determining elemental impurities in carbon nanostructures using inductively coupled plasma optical emission spectrometry.

    PubMed

    Patole, Shashikant P; Simões, Filipa; Yapici, Tahir F; Warsama, Bashir H; Anjum, Dalaver H; Costa, Pedro M F J

    2016-02-01

    It is common for as-prepared carbon nanotube (CNT) and graphene samples to contain remnants of the transition metals used to catalyze their growth; contamination may also leave other trace elemental impurities in the samples. Although a full quantification of impurities in as-prepared samples of carbon nanostructures is difficult, particularly when trace elements are intercalated or encapsulated within a protective layer of graphitic carbon, reliable information is essential for reasons such as quantifying the adulteration of physico-chemical properties of the materials and for evaluating environmental issues. Here, we introduce a microwave-based fusion method to degrade single- and double-walled CNTs and graphene nanoplatelets into a fusion flux thereby thoroughly leaching all metallic impurities. Subsequent dissolution of the fusion product in diluted hydrochloric and nitric acid allowed us to identify their trace elemental impurities using inductively coupled plasma optical emission spectrometry. Comparisons of the results from the proposed microwave-assisted fusion method against those of a more classical microwave-assisted acid digestion approach suggest complementarity between the two that ultimately could lead to a more reliable and less costly determination of trace elemental impurities in carbon nanostructured materials. PMID:26653428

  5. Stable microwave-assisted magnetization switching for nanoscale exchange-coupled composite grain

    PubMed Central

    2013-01-01

    Magnetization mechanisms of nanoscale magnetic grains greatly differ from well-known magnetization mechanisms of micrometer- or millimeter-sized magnetic grains or particles. Magnetization switching mechanisms of nanoscale exchange-coupled composite (ECC) grain in a microwave field was studied using micromagnetic simulation. Magnetization switching involving a strongly damped or precessional oscillation was studied using various strengths of external direct current and microwave fields. These studies imply that the switching behavior of microwave-assisted magnetization switching of the ECC grain can be divided into two groups: stable and unstable regions, similar to the case of the Stoner-Wahlfarth grain. A significant reduction in the switching field was observed in the ECC grain when the magnetization switching involved precessional oscillations similar to the case of the Stoner-Wohlfarth grain. This switching behavior is preferred for the practical applications of microwave-assisted magnetization switching. PMID:24191895

  6. Microwave-assisted fast vapor-phase transport synthesis of MnAPO-5 molecular sieves

    SciTech Connect

    Shao Hui; Yao Jianfeng; Ke Xuebin; Zhang Lixiong Xu Nanping

    2009-04-02

    MnAPO-5 was prepared by a microwave-assisted vapor-phase transport method at 180 deg. C in short times. The products were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectra, UV-vis spectroscopic measurement, NH{sub 3}-temperature-programmed desorption and esterification reaction. It was found that dry gels prepared with aluminum isopropoxide, phosphoric acid and manganese acetate could be transferred to MnAPO-5 in the vapors of triethylamine and water by the microwave-assisted vapor-phase transport method at 180 deg. C for less than 30 min. The crystallization time was greatly reduced by the microwave heating compared with the conventional heating. The resulting MnAPO-5 exhibited much smaller particle sizes, higher surface areas and slightly higher catalytic activity in the esterification of acetic acid and butyl alcohol than those prepared by the conventional vapor-phase transport method and hydrothermal synthesis.

  7. Microwave-assisted fabrication of strontium doped apatite coating on Ti6Al4V.

    PubMed

    Zhou, Huan; Kong, Shiqin; Pan, Yan; Zhang, Zhiguo; Deng, Linhong

    2015-11-01

    Strontium has been shown to be a beneficial dopant to calcium phosphates when incorporated at nontoxic level. In the present work we studied the possibility of solution derived doping strontium into calcium phosphate coatings on titanium alloy Ti6Al4V based implants by a recently reported microwave-assisted method. By using this method strontium doped calcium phosphate nuclei were deposited to pretreated titanium alloy surface dot by dot to compose a crack-free coating layer. The presence of strontium in solution led to reduced roughness of the coating and finer nucleus size formed. In vitro study found that proliferation and differentiation of osteoblast cells seeded on the coating were influenced by strontium content in coatings, showing an increasing followed by a decreasing behavior with increasing substitution of calcium by strontium. It is suggested that this new microwave-assisted strontium doped calcium phosphate coatings may have great potential in implant modification. PMID:26249578

  8. Optimization of microwave-assisted extraction of polysaccharide from Psidium guajava L. fruits.

    PubMed

    Amutha Gnana Arasi, Michael Antony Samy; Gopal Rao, Manchineela; Bagyalakshmi, Janardanan

    2016-10-01

    This study deals with the optimization of microwave assisted extraction of polysaccharide from Psidium guajava L. fruit using Response surface methodology. To evaluate the effect of three independent variables, Water to plant material ratio, microwave power used for extraction and Irradiation time, central composite design has been employed. The yield is considered as dependent variable. The design model estimated the optimum yield of 6.81677% at 200W microwave power level, 3:1 water to plant material ratio and 20min of irradiation time. Three factors three levels Central composite design coupled with RSM was used to model the extraction process. ANOVA was performed to find the significance of the model. The polysaccharide extracted using microwave assisted extraction process was analyzed using FTIR Spectroscopy. PMID:27180292

  9. Building Conjugated Organic Structures on Si(111) Surfaces via Microwave-Assisted Sonogashira Coupling

    SciTech Connect

    Lin, Jui-Ching; Kim, Jun-Hyun; Kellar, Joshua A.; Hersam, Mark C.; Nguyen, SonBinh T.; Bedzyk, Michael J.

    2010-08-27

    A novel step-by-step method employing microwave-assisted Sonogashira coupling is developed to grow fully conjugated organosilicon structures. As the first case study, p-(4-bromophenyl)acetylene is covalently conjugated to a p-(4-iodophenyl)acetylene-derived monolayer on a Si(111) surface. By bridging the two aromatic rings with C {triple_bond} C, the pregrown monolayer is structurally extended outward from the Si surface, forming a fully conjugated (p-(4-bromophenylethynyl)phenyl)vinylene film. The film growth process, which reaches 90% yield after 2 h, is characterized thoroughly at each step by using X-ray reflectivity (XRR), X-ray standing waves (XSW), and X-ray fluorescence (XRF). The high yield and short reaction time offered by microwave-assisted surface Sonogashira coupling chemistry make it a promising strategy for functionalizing Si surfaces.

  10. Efficient rapid microwave-assisted route to synthesize InP micrometer hollow spheres

    SciTech Connect

    Zheng Xiuwen Hu Qitu; Sun Chuansheng

    2009-01-08

    The efficiencies of two methods of synthesizing InP micro-scale hollow spheres are compared via the analogous solution-liquid-solid (ASLS) growth mechanism, either through a traditional solvothermal procedure, or via a microwave-assisted method. Scanning electronic microscopy (SEM) images show that most of the as-grown samples are micrometer hollow spheres, which indicates the efficiency of both methods. For traditional solvothermal route, long time (10 h) is necessary to obtain the desired samples, however, for the microwave-assisted route, 30 min is enough for hollow spherical products. An optimal choice of microwave irradiating time allows reducing the reaction time from hours to minutes. The proposed ASLS growth mechanism has also been discussed in detail.

  11. Synthesis of potassium niobates by the microwave-assisted solvothermal method

    NASA Astrophysics Data System (ADS)

    Duarte, T. M.; Honorio, L. M. C.; Brito, A. S.; Souza, J. K. D.; Longo, E.; Tranquilin, R. L.; Souza, A. G.; Santos, I. M. G.; Maia, A. S.

    2015-11-01

    Potassium niobates have been synthesized by different methods, but few papers use the microwave-assisted solvothermal method, with possibility of a deeper evaluation in this area. In this work, the synthesis of KNbO3, KNb3O8 and K4Nb6O17 was performed by calcinations of precursors obtained by the microwave-assisted solvothermal method. This study evaluates the influence of various synthesis parameters such as reaction time, pH of the reaction medium, K+ concentration in the precursor solution. The results show the formation of different niobates, KNbO3, KNb3O8, K4Nb6O17, depending on the short and long-range order of the precursor used in the post annealing process.

  12. Application of Ionic Liquids in the Microwave-Assisted Extraction of Proanthocyanidins from Larix gmelini Bark

    PubMed Central

    Yang, Lei; Sun, Xiaowei; Yang, Fengjian; Zhao, Chunjian; Zhang, Lin; Zu, Yuangang

    2012-01-01

    Ionic liquid based, microwave-assisted extraction (ILMAE) was successfully applied to the extraction of proanthocyanidins from Larix gmelini bark. In this work, in order to evaluate the performance of ionic liquids in the microwave-assisted extraction process, a series of 1-alkyl-3-methylimidazolium ionic liquids with different cations and anions were evaluated for extraction yield, and 1-butyl-3-methylimidazolium bromide was selected as the optimal solvent. In addition, the ILMAE procedure for the proanthocyanidins was optimized and compared with other conventional extraction techniques. Under the optimized conditions, satisfactory extraction yield of the proanthocyanidins was obtained. Relative to other methods, the proposed approach provided higher extraction yield and lower energy consumption. The Larix gmelini bark samples before and after extraction were analyzed by Thermal gravimetric analysis, Fourier-transform infrared spectroscopy and characterized by scanning electron microscopy. The results showed that the ILMAE method is a simple and efficient technique for sample preparation. PMID:22606036

  13. Microwave-Assisted Azidation Reaction for Rapid Synthesis of Poly(3,3ʹ-Bisazidomethyl Oxetane)

    NASA Astrophysics Data System (ADS)

    Zhang, Chi; Li, Jie; Luo, Yun-Jun; Zhai, Bin

    2016-04-01

    We successfully designed and developed a new strategy for synthesizing an energetic material, poly(3,3ʹ-bisazidomethyl oxetane) (PBAMO), by microwave assistance, which dramatically shortened the reaction time and improved the safety of the synthetic process.

  14. MICROWAVE-ASSISTED PREPARATION OF 1-BUTYL-3-METHYLIMIDAZOLIUM TETRACHLOROGALLATE AND ITS CATALYTIC USE IN ACETAL FORMATION UNDER MILD CONDITIONS

    EPA Science Inventory

    1-Butyl-3-methylimidazolium tetrachlorogallate, [bmim][GaCl4], prepared via microwave-assisted protocol, is found to be an active catalyst for the efficient acetalization of aldehydes under mild conditions.

  15. MCRs reshaped into a switchable microwave-assisted protocol toward 5-aminoimidazoles and dihydrotriazines

    PubMed Central

    Bell, Christan E.; Shaw, Arthur Y.; De Moliner, Fabio; Hulme, Christopher

    2014-01-01

    A tunable microwave-assisted protocol for the synthesis of two biologically relevant families of heterocycles has been designed. Via a simple switch of reaction conditions, the same starting materials can be engaged in either an improved synthesis of the dihydrotriazine scaffold or a novel, first-in-class MCR to render the challenging 5-aminoimidazole nucleus in a single step. An additional first in class MCR is also reported utilizing guanidines to afford 2,5-aminoimidazoles. PMID:24535889

  16. Preliminary study: kinetics of oil extraction from sandalwood by microwave-assisted hydrodistillation

    NASA Astrophysics Data System (ADS)

    Kusuma, H. S.; Mahfud, M.

    2016-04-01

    Sandalwood and its oil, is one of the oldest known perfume materials and has a long history (more than 4000 years) of use as mentioned in Sanskrit manuscripts. Sandalwood oil plays an important role as an export commodity in many countries and its widely used in the food, perfumery and pharmaceuticals industries. The aim of this study is to know and verify the kinetics and mechanism of microwave-assisted hydrodistillation of sandalwood based on a second-order model. In this study, microwave-assisted hydrodistillation is used to extract essential oils from sandalwood. The extraction was carried out in ten extraction cycles of 15 min to 2.5 hours. The initial extraction rate, the extraction capacity and the second-order extraction rate constant were calculated using the model. Kinetics of oil extraction from sandalwood by microwave-assisted hydrodistillation proved that the extraction process was based on the second-order extraction model as the experimentally done in three different steps. The initial extraction rate, h, was 0.0232 g L-1 min-1, the extraction capacity, C S, was 0.6015 g L-1, the second-order extraction rate constant, k, was 0.0642 L g-1 min-1 and coefficient of determination, R 2, was 0.9597.

  17. A study of thermal properties of sodium titanate nanotubes synthesized by microwave-assisted hydrothermal method

    SciTech Connect

    Preda, Silviu; Rutar, Melita; Umek, Polona; Zaharescu, Maria

    2015-11-15

    Highlights: • The microwave-assisted hydrothermal route was used for titanate nanotubes synthesis. • Conversion to single-phase nanotube morphology completes after 8 h reaction time. • The nanotube morphology is stable up to 600 °C, as determined by in-situ XRD and SEM. • Sodium ions migrate to the surface due to thermal motion and structure condensation. - Abstract: Sodium titanate nanotubes (NaTiNTs) were synthesized by microwave-assisted hydrothermal treatment of commercial TiO{sub 2}, at constant temperature (135 °C) and different irradiation times (15 min, 1, 4, 8 and 16 h). The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, differential scanning calorimetry and specific surface area measurements. The irradiation time turned out to be the key parameter for morphological control of the material. Nanotubes were observed already after 15 min of microwave irradiation. The analyses of the products irradiated for 8 and 16 h confirm the complete transformation of the starting TiO{sub 2} powder to NaTiNTs. The nanotubes are open ended with multi-wall structures, with the average outer diameter of 8 nm and specific surface area up to 210 m{sup 2}/g. The morphology, surface area and crystal structure of the sodium titanate nanotubes synthesized by microwave-assisted hydrothermal method were similar to those obtained by conventional hydrothermal method.

  18. Preparation of Silica Nanoparticles Through Microwave-assisted Acid-catalysis

    PubMed Central

    Lovingood, Derek D.; Owens, Jeffrey R.; Seeber, Michael; Kornev, Konstantin G.; Luzinov, Igor

    2013-01-01

    Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle diameters ranging from 30-250 nm by varying the reaction conditions. Through the selection of a microwave compatible solvent, silicic acid precursor, catalyst, and microwave irradiation time, these microwave-assisted methods were capable of overcoming the previously reported shortcomings associated with synthesis of silica nanoparticles using microwave reactors. The siloxane precursor was hydrolyzed using the acid catalyst, HCl. Acetone, a low-tan δ solvent, mediates the condensation reactions and has minimal interaction with the electromagnetic field. Condensation reactions begin when the silicic acid precursor couples with the microwave radiation, leading to silica nanoparticle sol formation. The silica nanoparticles were characterized by dynamic light scattering data and scanning electron microscopy, which show the materials' morphology and size to be dependent on the reaction conditions. Microwave-assisted reactions produce silica nanoparticles with roughened textured surfaces that are atypical for silica sols produced by Stöber's methods, which have smooth surfaces. PMID:24379052

  19. Carbohydrate Conjugation through Microwave-Assisted Functionalization of Single-Walled Carbon Nanotubes Using Perfluorophenyl Azides

    PubMed Central

    Kong, Na; Shimpi, Manishkumar R.; Park, Jae Hyeung

    2015-01-01

    Carbohydrate-functionalized single-walled carbon nanotubes (SWNTs) were synthesized using microwave-assisted reaction of perfluorophenyl azide with the nanotubes. The results showed that microwave radiation provides a rapid and effective means to covalently attach carbohydrates to SWNTs, producing carbohydrate-SWNT conjugates for biorecognition. The carbohydrate-functionalized SWNTs were furthermore shown to interact specifically with cognate carbohydrate-specific proteins (lectins), resulting in predicted recognition patterns. The carbohydrate-presenting SWNTs constitute a new platform for sensitive protein- or cell recognition, which pave the way for glycoconjugated carbon nanomaterials in biorecognition applications. PMID:25746392

  20. Theoretical study of thermally activated magnetization switching under microwave assistance: Switching paths and barrier height

    NASA Astrophysics Data System (ADS)

    Suto, H.; Kudo, K.; Nagasawa, T.; Kanao, T.; Mizushima, K.; Sato, R.; Okamoto, S.; Kikuchi, N.; Kitakami, O.

    2015-03-01

    Energy barrier height for magnetization switching is theoretically studied for a system with uniaxial anisotropy in a circularly polarized microwave magnetic field. A formulation of the Landau-Lifshitz-Gilbert equation in a rotating frame introduces an effective energy that includes the effects of both the microwave field and static field. This allows the effective-energy profiles to rigorously describe the switching paths and corresponding barrier height, which govern thermally activated magnetization switching under microwave assistance. We show that fixed points and limit cycles in the rotating frame lead to various switching paths and that under certain conditions, switching becomes a two-step process with an intermediate state.

  1. Microwave-assisted synthesis and electrochemical evaluation of VO2 (B) nanostructures.

    PubMed

    Ashton, Thomas E; Hevia Borrás, David; Iadecola, Antonella; Wiaderek, Kamila M; Chupas, Peter J; Chapman, Karena W; Corr, Serena A

    2015-12-01

    Understanding how intercalation materials change during electrochemical operation is paramount to optimizing their behaviour and function and in situ characterization methods allow us to observe these changes without sample destruction. Here we first report the improved intercalation properties of bronze phase vanadium dioxide VO2 (B) prepared by a microwave-assisted route which exhibits a larger electrochemical capacity (232 mAh g(-1)) compared with VO2 (B) prepared by a solvothermal route (197 mAh g(-1)). These electrochemical differences have also been followed using in situ X-ray absorption spectroscopy allowing us to follow oxidation state changes as they occur during battery operation. PMID:26634729

  2. Microwave-assisted synthesis of II-VI semiconductor micro-and nanoparticles towards sensor applications

    NASA Astrophysics Data System (ADS)

    Majithia, Ravish Yogesh

    Engineering particles at the nanoscale demands a high degree of control over process parameters during synthesis. For nanocrystal synthesis, solution-based techniques typically include application of external convective heat. This process often leads to slow heating and allows decomposition of reagents or products over time. Microwave-assisted heating provides faster, localized heating at the molecular level with near instantaneous control over reaction parameters. In this work, microwave-assisted heating has been applied for the synthesis of II-VI semiconductor nanocrystals namely, ZnO nanopods and CdX (X = Se, Te) quantum dots (QDs). Based on factors such as size, surface functionality and charge, optical properties of such nanomaterials can be tuned for application as sensors. ZnO is a direct bandgap semiconductor (3.37 eV) with a large exciton binding energy (60 meV) leading to photoluminescence (PL) at room temperature. A microwave-assisted hydrothermal approach allows the use of sub-5 nm ZnO zero-dimensional nanoparticles as seeds for generation of multi-legged quasi one-dimensional nanopods via heterogeneous nucleation. ZnO nanopods, having individual leg diameters of 13-15 nm and growing along the [0001] direction, can be synthesized in as little as 20 minutes. ZnO nanopods exhibit a broad defect-related PL spanning the visible range with a peak at ~615 nm. Optical sensing based on changes in intensity of the defect PL in response to external environment (e.g., humidity) is demonstrated in this work. Microwave-assisted synthesis was also used for organometallic synthesis of CdX(ZnS) (X = Se, Te) core(shell) QDs. Optical emission of these QDs can be altered based on their size and can be tailored to specific wavelengths. Further, QDs were incorporated in Enhanced Green-Fluorescent Protein -- Ultrabithorax (EGFP-Ubx) fusion protein for the generation of macroscale composite protein fibers via hierarchal self-assembly. Variations in EGFP- Ubx˙QD composite

  3. Portable microwave assisted extraction: An original concept for green analytical chemistry.

    PubMed

    Perino, Sandrine; Petitcolas, Emmanuel; de la Guardia, Miguel; Chemat, Farid

    2013-11-01

    This paper describes a portable microwave assisted extraction apparatus (PMAE) for extraction of bioactive compounds especially essential oils and aromas directly in a crop or in a forest. The developed procedure, based on the concept of green analytical chemistry, is appropriate to obtain direct in-field information about the level of essential oils in natural samples and to illustrate green chemical lesson and research. The efficiency of this experiment was validated for the extraction of essential oil of rosemary directly in a crop and allows obtaining a quantitative information on the content of essential oil, which was similar to that obtained by conventional methods in the laboratory. PMID:24079550

  4. Microwave assistance effect on magnetization switching in Co-Cr-Pt granular film

    NASA Astrophysics Data System (ADS)

    Okamoto, Satoshi; Kikuchi, Nobuaki; Hotta, Akira; Furuta, Masaki; Kitakami, Osamu; Shimatsu, Takehito

    2013-11-01

    Experimental verification of microwave assistance effect on a perpendicular magnetic CoCrPt based granular film is demonstrated. Significant reduction of coercivity under the assistance of a radio frequency (rf) field is clearly observed. But the coercivity strongly depends on the duration of rf field, indicating that the magnetic moments of constituent grains are severely perturbed by thermal agitation. Analysis based on the Néel-Arrhenius law has revealed that the dynamic coercivity in nanosecond region can be reduced by 50% only by applying a small rf field with the amplitude less than 2% of the anisotropy field.

  5. Fast and safe microwave-assisted glass channel-shaped microstructure fabrication.

    PubMed

    Zacheo, A; Zizzari, A; Perrone, E; Carbone, L; Giancane, G; Valli, L; Rinaldi, R; Arima, V

    2015-06-01

    Glass micromachining is a basic technology to achieve microfluidic networks for lab-on-a-chip applications. Among several methods to microstructure glass, the simplest and most widely applied is wet chemical etching (WE). However, accurate control of the reaction conditions to perform reproducible, fast and safe glass etching is not straightforward. Herein, microwave-assisted WE is demonstrated to intensify the glass etching action under safe working and finely monitored operative conditions and to produce smooth deep channels in short processing times with reduced underetching effects. PMID:25920905

  6. Application of Response Surface Methodology to Optimize Microwave-assisted Extraction of Polysaccharide from Tremella

    NASA Astrophysics Data System (ADS)

    Chen, Yuzhen; Zhao, Lei; Liu, Benguo; Zuo, Sasa

    Tremella is an excellent source of polysaccharides. In this study, microwave-assisted extraction was employed to extract polysaccharides from Tremella with water. By using response surface methodology, the effects of microwave output power, extraction time, and solid-liquid ratio on polysaccharide yield were investigated and the optimal conditions were determined as follows: extraction time 60 s, microwave output power 750 w, liquid-solid ratio 20. The average experimental polysaccharide yield under the optimum conditions was found to be 65.07±0.99%, which agreed with the predicted value of 69.07%.

  7. Microwave-Assisted Switching of Microscopic Rings: Correlation Between Nonlinear Spin Dynamics and Critical Microwave Fields

    NASA Astrophysics Data System (ADS)

    Podbielski, Jan; Heitmann, Detlef; Grundler, Dirk

    2007-11-01

    We have studied the spin dynamics of microscopic permalloy rings at GHz frequencies. Increasing the irradiation power, we observe first nonlinear spin dynamics and second microwave-assisted switching (MAS). We explore the MAS phase diagram as a function of microwave power and frequency f and, in particular, extract the critical microwave field hc(f). Its frequency dependence reflects characteristic eigenfrequencies from both the linear and nonlinear spin-wave spectrum. By comparing hc(f) with the different susceptibilities, we gain insight into the microscopic processes which might be the basis of a predictive theory of MAS.

  8. Microwave-assisted polyol synthesis of carbon nitride dots from folic acid for cell imaging

    PubMed Central

    Guan, Weiwei; Gu, Wei; Ye, Ling; Guo, Chenyang; Su, Su; Xu, Pinxiang; Xue, Ming

    2014-01-01

    A green, one-step microwave-assisted polyol synthesis was employed to prepare blue luminescent carbon nitride dots (CNDs) using folic acid molecules as both carbon and nitrogen sources. The as-prepared CNDs had an average size of around 4.51 nm and could be well dispersed in water. Under excitation at 360 nm, the CNDs exhibited a strong blue luminescence and the quantum yield was estimated to be 18.9%, which is greater than that of other reported CNDs. Moreover, the CNDs showed low cytotoxicity and could efficiently label C6 glioma cells, demonstrating their potential in cell imaging. PMID:25382977

  9. Biodiesel Production from Chlorella protothecoides Oil by Microwave-Assisted Transesterification

    PubMed Central

    Gülyurt, Mustafa Ömer; Özçimen, Didem; İnan, Benan

    2016-01-01

    In this study, biodiesel production from microalgal oil by microwave-assisted transesterification was carried out to investigate its efficiency. Transesterification reactions were performed by using Chlorella protothecoides oil as feedstock, methanol, and potassium hydroxide as the catalyst. Methanol:oil ratio, reaction time and catalyst:oil ratio were investigated as process parameters affected methyl ester yield. 9:1 methanol/oil molar ratio, 1.5% KOH catalyst/oil ratio and 10 min were optimum values for the highest fatty acid methyl ester yield. PMID:27110772

  10. Microwave-assisted polyol synthesis of carbon nitride dots from folic acid for cell imaging.

    PubMed

    Guan, Weiwei; Gu, Wei; Ye, Ling; Guo, Chenyang; Su, Su; Xu, Pinxiang; Xue, Ming

    2014-01-01

    A green, one-step microwave-assisted polyol synthesis was employed to prepare blue luminescent carbon nitride dots (CNDs) using folic acid molecules as both carbon and nitrogen sources. The as-prepared CNDs had an average size of around 4.51 nm and could be well dispersed in water. Under excitation at 360 nm, the CNDs exhibited a strong blue luminescence and the quantum yield was estimated to be 18.9%, which is greater than that of other reported CNDs. Moreover, the CNDs showed low cytotoxicity and could efficiently label C6 glioma cells, demonstrating their potential in cell imaging. PMID:25382977

  11. Microwave-assisted synthesis and electrochemical evaluation of VO2 (B) nanostructures

    SciTech Connect

    Ashton, Thomas E.; Borras, David Hevia; Iadecola, Antonella; Wiaderek, Kamila Magdalena; Chapman, Karena W.; Corr, Serena A.

    2015-12-01

    Abstract Understanding how intercalation materials change during electrochemical operation is paramount to optimising their behaviour and function and in situ characterisation methods allow us to observe these changes without sample destruction. Here, we first report the improved intercalation properties of bronze phase vanadium dioxide VO2 (B) prepared by a microwave assisted route which exhibits a larger electrochemical capacity (232 mAh g-1) compared to VO2 (B) prepared by a solvothermal route (197 mAh g-1). These electrochemical differences have also been followed using in situ X-ray absorption spectroscopy allowing us to follow oxidation state changes as they occur during battery operation.

  12. Biodiesel Production from Chlorella protothecoides Oil by Microwave-Assisted Transesterification.

    PubMed

    Gülyurt, Mustafa Ömer; Özçimen, Didem; İnan, Benan

    2016-01-01

    In this study, biodiesel production from microalgal oil by microwave-assisted transesterification was carried out to investigate its efficiency. Transesterification reactions were performed by using Chlorella protothecoides oil as feedstock, methanol, and potassium hydroxide as the catalyst. Methanol:oil ratio, reaction time and catalyst:oil ratio were investigated as process parameters affected methyl ester yield. 9:1 methanol/oil molar ratio, 1.5% KOH catalyst/oil ratio and 10 min were optimum values for the highest fatty acid methyl ester yield. PMID:27110772

  13. Microwave-assisted Organic Synthesis of a High-affinity Pyrazolo-pyrimidinyl TSPO Ligand

    PubMed Central

    Tang, Dewei; Buck, Jason R.; Hight, Matthew R.; Manning, H. Charles

    2010-01-01

    We herein report a dramatically improved total synthesis of the high-affinity translocator protein (TSPO) ligand DPA-714, featuring microwave-assisted organic synthesis (MAOS). Compared with previously described approaches, our novel MAOS method dramatically reduces overall reaction time without adversely effecting reaction yields. We envision that the described MAOS protocol may be suitably applied to high-throughput, diversity-oriented synthesis of novel compounds based on the pyrazolo-pyrimidinyl scaffold. Such an approach could accelerate the development of focused libraries of novel TSPO ligands with potential for future development as molecular imaging and therapeutic agents. PMID:20689673

  14. Investigation of microwave assisted drying of samples and evaporation of aqueous solutions in trace element analysis.

    PubMed

    Maichin, B; Kettisch, P; Knapp, G

    2000-01-01

    Investigations of microwave assisted drying of sample materials and microwave assisted evaporation of aqueous sample solutions and acidic digestion residues were accomplished by means of special rotors for the microwave digestion system MULTIWAVE. To check the results obtained by microwave assisted drying, the samples were also conventionally dried at 105 degrees C in an oven. The following samples have been dried: 10 g each of meat, fish, apple, cucumber, potato, mustard, yogurt, clay and marl; 1 g each of certified reference material TORT 2 (lobster hepatopancreas), BCR 278 (mussel tissue) and BCR 422 (cod muscle); 500 g garden mould. Microwave assisted drying takes 40 min for organic samples and 30 min for inorganic material. Important is a slow increase of microwave power during the first 20 min. The results agree well with conventional drying at 105 degrees C. Losses of As, Se and Hg have been investigated for 3 CRMs. Only Se shows losses in the range of 20%. Losses of As, Be, Cd, Co, Cr, Cu, Fe, Hg, Li, Mg, Mn, Mo, Ni, Pb, Sb, Se, Sr, Ti, Tl, V and Zn after evaporation of aqueous samples and acidic solutions after wet digestion, respectively, have been investigated. 50 mL aqueous solution was evaporated almost to dryness within 25 min. The recovery of Hg is 40-50%, of Se 90-95% and of the other elements 97-102%. 0.2 g each of TORT 2, BCR 278 and BCR 422 have been digested with 4 mL nitric acid and 1 mL hydrochloric acid by means of the microwave digestion system MULTIWAVE. The digestion residue was evaporated almost to dryness and dissolved again in 10 mL diluted nitric acid. In this case no element losses have been observed. The measured concentration of As, Cd, Cu, Fe, Mn, Hg, Pb, Mo, Ni, Se, Sr, V and Zn agree very well with the certified values. An important prerequisite for good recoveries is not to evaporate the solutions to complete dryness. PMID:11225810

  15. Indium triflate catalyzed microwave-assisted alkenylation of methoxyphenols: synthesis of indenes and chromenes.

    PubMed

    Rao, V Kameswara; Kaswan, Pinku; Parang, Keykavous; Kumar, Anil

    2015-12-01

    In(OTf)3 catalyzed microwave-assisted alkenylation of methoxyphenols was investigated. Exclusive formation of either indenes or chromenes was observed depending on the position of the methoxy group on phenol. The structures of 1H-inden-4-ol derivatives (4a-e) and 4H-chromene derivatives (5a-j) were established by NMR ((1)H & (13)C) and high-resolution mass spectra, which were further supported by single crystal X-ray analysis of 4c and 5a. PMID:26395017

  16. Microwave assisted combustion synthesis of nanocrystalline CoFe2O4 for LPG sensing

    NASA Astrophysics Data System (ADS)

    Chaudhari, Prashant; Acharya, S. A.; Darunkar, S. S.; Gaikwad, V. M.

    2015-08-01

    A microwave-assisted citrate precursor method has been utilized for synthesis of nanocrystalline powders of CoFe2O4. The process takes only a few minutes to obtain as-synthesized CoFe2O4. Structural properties of the synthesized material were investigated by X-ray diffraction; scanning electron microscopy, Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy. The gas sensing properties of thick film of CoFe2O4 prepared by screen printing towards Liquid Petroleum Gas (LPG) revealed that CoFe2O4 thick films are sensitive and shows maximum sensitivity at 350°C for 2500 ppm of LPG.

  17. Use of microwave-assisted evaporation for the complete recovery of volatile species of inorganic trace analytes

    PubMed

    Link; Kingston

    2000-07-01

    Solutions must often be evaporated prior to analysis either to preconcentrate the analyte or to eliminate an incompatible matrix component. Elimination of the halogen-based acids HCI and HF using traditional evaporation methods poses recovery problems because of volatilization of the target analyte as the chloride or fluoride species. A new sample preparation chemistry for trace analysis, where losses of analyte due to volatilization during the evaporation process are minimized, is explored using the unique heating mechanisms of the microwave-assisted evaporation process. The heating mechanisms of hot plate evaporation and microwave-assisted evaporation are compared, and temperatures throughout the evaporation process using each method are predicted and experimentally verified. Because the solution actually cools during microwave-assisted evaporation, volatilization due to overheating at dryness is minimized. Elemental standard solutions and SRM soil and tissue digestates were evaporated using a hot plate method and a newly developed reduced-pressure microwave-assisted evaporation apparatus. Redissolution and analysis of the residue by ICPMS showed that complete recovery was achieved using microwave-assisted evaporation while losses of several classically volatile analytes occurred using hot plate evaporation. PMID:10905326

  18. Synthesis of PbMoO4 nanoparticles by microwave-assisted hydrothermal process and their photocatalytic activity.

    PubMed

    Song, Young In; Lim, Kwon Taek; Lee, Gun Dae; Lee, Man Sig; Hong, Seong-Soo

    2014-11-01

    Lead molybdate (PbMoO4) was successfully synthesized using a microwave-assisted method and characterized by XRD, Raman spectroscopy, SEM, PL and DRS. We also investigated the photocatalytic activity of these materials for the decomposition of Rhodamin B under UV-light irradiation. The XRD and Raman results revealed the successful synthesis of 42-52 nm, well-crystallized PbMoO4 crystals with the microwave-assisted hydrothermal method. The PbMoO4 catalysts prepared using the microwave-assisted process enhanced the photocatalytic activity compared to that prepared by hydrothermal method and the catalysts prepared at a solution pH = 11 and temperature of 105 degrees C showed the highest photocatalytic activity. The PL peaks appeared at about 540 nm for all catalysts and the excitonic PL signal was proportional to the photocatalytic activity for the decomposition of Rhodamin B. PMID:25958553

  19. Microwave-assisted extraction of polysaccharides from Yupingfeng powder and their antioxidant activity

    PubMed Central

    Wang, Dan; Zhang, Bi-Bo; Qu, Xiao-Xia; Gao, Feng; Yuan, Min-Yong

    2015-01-01

    Background: Microwave-assisted reflux extraction of polysaccharides YPF-P from the famous Chinese traditional drug, Yupingfeng powder, optimization of extracting conditions and evaluation of their antioxidant activity were conducted in this study. Results: Single factor effect trends were achieved through yields and contends of YPF-P obtained from different extracting conditions. Then through a three-level, four-variable Box-Behnken design of response surface methodology adopting yield as response, the optimal conditions were determined as follows: Material/solvent ratio 1:23.37, microwave power 560 W, Extraction temperature 64°C, and extraction time 9.62 min. Under the optimal conditions, the YPF-P extraction yield was 3.23%, and its content was detected as 38.52%. In antioxidant assays, the YPF-P was tested to possess 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities with an IC50 value of 0.262 mg/ml. In addition, YPF-P was also proved to have relatively low ferric reducing antioxidant power (FRAP), compared to Vc, through FRAP assay. Conclusion: In the microwave assisted reflux extraction research, good YPF-P yield was achieved from materials with relatively low YPF-P content. And for the first time, both DPPH and FRAP assays were conducted on YPF-P, which proved that the antioxidant activity of YPF-P contributed to the functions of this medicine. PMID:26246730

  20. Microwave-assisted synthesis of carbon nanodots through an eggshell membrane and their fluorescent application.

    PubMed

    Wang, Qi; Liu, Xing; Zhang, Lichun; Lv, Yi

    2012-11-21

    Carbon nanodots (C-Dots) as a new form of carbonaceous nanomaterials have aroused much interest and intensive research due to their inspiring properties. Compared to traditional semiconductor quantum dots, these newly emergent nanodots possess a number of advantageous characteristics, among which low-toxicity is particularly fascinating. More and more research into C-Dots have focused on synthesis methods and biology-related applications. Microwave-assisted approaches have attracted attention because microwave treatment can provide intensive and efficient energy, and as a consequence shorten the reaction time. In this article, we designed a "green", rapid, eco-friendly and waste-reused approach to synthesize fluorescent and water-soluble C-Dots from eggshell membrane (ESM) ashes according to a microwave-assisted process. ESM selected as the carbon source was a common protein-rich waste in daily life and can be obtained easily and cheaply. The C-Dots from our method showed the maximal fluorescence emission peak at 450 nm and the fluorescence quantum yield was about 14%. We further designed a sensitive probe for glutathione based on the fluorescence turn off and on of the C-Dots-Cu(2+) system, which showed a linear range of 0.5-80 μmol L(-1) and detection limit of 0.48 μmol L(-1). In general, the C-Dots prepared briefly and inexpensively from ESM revealed excellent fluorescent property with promising potential for applications such as sample detection and biotechnology. PMID:23037913

  1. Fast microwave-assisted catalytic gasification of biomass for syngas production and tar removal.

    PubMed

    Xie, Qinglong; Borges, Fernanda Cabral; Cheng, Yanling; Wan, Yiqin; Li, Yun; Lin, Xiangyang; Liu, Yuhuan; Hussain, Fida; Chen, Paul; Ruan, Roger

    2014-03-01

    In the present study, a microwave-assisted biomass gasification system was developed for syngas production. Three catalysts including Fe, Co and Ni with Al2O3 support were examined and compared for their effects on syngas production and tar removal. Experimental results showed that microwave is an effective heating method for biomass gasification. Ni/Al2O3 was found to be the most effective catalyst for syngas production and tar removal. The gas yield reached above 80% and the composition of tar was the simplest when Ni/Al2O3 catalyst was used. The optimal ratio of catalyst to biomass was determined to be 1:5-1:3. The addition of steam was found to be able to improve the gas production and syngas quality. Results of XRD analyses demonstrated that Ni/Al2O3 catalyst has good stability during gasification process. Finally, a new concept of microwave-assisted dual fluidized bed gasifier was put forward for the first time in this study. PMID:24508907

  2. Microwave-assisted steam distillation for the determination of organochlorine pesticides and pyrethroids in Chinese teas.

    PubMed

    Ji, Jie; Deng, Chunhui; Zhang, Huiqin; Wu, Yunyun; Zhang, Xiangmin

    2007-02-28

    In this work, microwave-assisted steam distillation (MASD) extraction method followed by gas chromatography/electron capture detection (GC/ECD) was developed for the determination of organochlorine pesticides (OCPs) and pyrethroids in the Chinese teas. MASD is a combination of microwave-assisted extraction (MAE) and steam distillation techniques. Water vapor generated by microwave irradiation is used to accelerate desorption of the analytes from the sample, and the nonpolar organic solvent used for trapping the analytes is kept from direct contact with the sample by the water. Therefore, relatively clean extracts were obtained compared to the method directly using organic solvent as extraction solvent, such as ultrasonic extraction (USE). Microwave power of 200W and irradiation time of 2min was found to be the optimum conditions for the MASD process, and n-heptane was chosen as the analyte-trapping solvent in the study. Five OCPs (alpha-HCH, gamma-HCH, dicofol, p,p'-DDE, p,p'-DDT) and two pyrethroids (bifenthrin, fenvalate) were determined using this extraction method in the tea samples. The relative standard deviation (R.S.D.) of the analytes varied from 2.2 to 8.4%, and the method detection limits (MDLs) found were lower than 0.23mug/kg. The recoveries of the seven compounds in the Jasmine tea sample were between 84.04 and 110.1%. Comparative results obtained by MASD and USE were also discussed in the study. PMID:19071414

  3. Microwave-assisted Bi2Se3 nanoparticles using various organic solvents

    NASA Astrophysics Data System (ADS)

    Vijila, J. Joy Jeba; Mohanraj, K.; Henry, J.; Sivakumar, G.

    2016-01-01

    Microwave assisted Bi2Se3 nanoparticles were synthesized from five different solvents DMF, EG, EG + H2O, EDA + dil.HNO3 and N2H4 + H2O + Ethanol. The influence of solvents on purity of the compound was analysed by using X-ray diffraction patterns. The result indicates pure rhombohedral Bi2Se3 nanoparticles formed for N2H4 + H2O + Ethanol. The presence of vibrational bands in the range of 400-800 cm- 1 is confirmed the formation of Bi2Se3. The maximum optical absorption observed around 450 nm and the band gap values are found in the range of 1.5 eV-2.17 eV for all the solvents. The nanostructure of the Bi2Se3 particles change with solvents. From the experimental results, the solvent N2H4 + H2O + Ethanol produces pure nanosize Bi2Se3 particles under the microwave assisted method.

  4. Solvent effects on focused microwave assisted extraction of polyphenolic acids from Eucommia ulmodies.

    PubMed

    Li, Hui; Chen, Bo; Nie, Lihua; Yao, Shouzhuo

    2004-01-01

    An open microwave-assisted extraction system was used to extract gallic acid, protocatechuic acid, chlorogenic acid and caffeic acid from Eucommia ulmodies. The effect of extraction variables, especially solvent, on the recoveries of these polyphenolic compounds was investigated using factorial design. As extracting solvent for these compounds, methanol produced a higher recovery than pure water. For straight chain alcohol solvents, the lower the carbon number, the higher the recoveries of the polyphenolic acids. The optimal ratio of methanol:water:glacial acetic acid in the solvent mixture used in microwave-assisted extraction was 2:8:0.3 (v/v) and this solvent could be directly used as the mobile phase in HPLC separation without additional intermittent treatment as reported in literature. The extraction under the condition of 50% microwave power and 30 s irradiation at a solvent:sample ratio of 10 (mL/g) was found to be the most advantageous. The repeatability test of extraction and chromatographic analysis was satisfactory for the analysis of these polyphenolic compounds. PMID:15508835

  5. Microwave-assisted chemical oxidation of biological waste sludge: simultaneous micropollutant degradation and sludge solubilization.

    PubMed

    Bilgin Oncu, Nalan; Akmehmet Balcioglu, Isil

    2013-10-01

    Microwave-assisted hydrogen peroxide (MW/H2O2) treatment and microwave-assisted persulfate (MW/S2O8(2-)) treatment of biological waste sludge were compared in terms of simultaneous antibiotic degradation and sludge solubilization. A 2(3) full factorial design was utilized to evaluate the influences of temperature, oxidant dose, and holding time on the efficiency of these processes. Although both MW/H2O2 and MW/S2O8(2-) yielded ≥97% antibiotic degradation with 1.2g H2O2 and 0.87 g S2O8(2-) per gram total solids, respectively, at 160 °C in 15 min, MW/S2O8(2-) was found to be more promising for efficient sludge treatment at a lower temperature and a lower oxidant dosage, as it allows more effective activation of persulfate to produce the SO4(-) radical. Relative to MW/H2O2, MW/S2O8(2-) gives 48% more overall metal solubilization, twofold higher improvement in dewaterability, and the oxidation of solubilized ammonia to nitrate in a shorter treatment period. PMID:23928124

  6. Microwave-assisted low temperature synthesis of wurtzite ZnS quantum dots

    SciTech Connect

    Shahid, Robina; Toprak, Muhammet S.; Muhammed, Mamoun

    2012-03-15

    In this work we report, for the first time, on microwave assisted synthesis of wurtzite ZnS quantum dots (QDs) in controlled reaction at temperature as low as 150 Degree-Sign C. The synthesis can be done in different microwave absorbing solvents with multisource or single source precursors. The QDs are less than 3 nm in size as characterized by transmission electron microscopy (TEM) using selected area electron diffraction (SAED) patterns to confirm the wurtzite phase of ZnS QDs. The optical properties were investigated by UV-Vis absorption which shows blue shift in absorption compared to bulk wurtzite ZnS due to quantum confinement effects. The photoluminescence (PL) spectra of QDs reveal point defects related emission of ZnS QDs. - Graphical abstract: Microwave assisted synthesis of wurtzite ZnS quantum dots (QDs) have been achieved in controlled reaction at temperature as low as 150 Degree-Sign C. The synthesis was performed in different microwave absorbing solvents with multisource or single source precursors for very short reaction periods due to effective heating with microwaves. Highlights: Black-Right-Pointing-Pointer Wurtzite a high temperature phase of ZnS was synthesized at low temperature. Black-Right-Pointing-Pointer Low temperature synthesis was possible because of the use of microwave absorbing solvents. Black-Right-Pointing-Pointer Capping agent was used to control the size of Quantum Dots. Black-Right-Pointing-Pointer Two different systems were developed using single molecular precursor and multisource precursors.

  7. Fast microwave-assisted catalytic pyrolysis of sewage sludge for bio-oil production.

    PubMed

    Xie, Qinglong; Peng, Peng; Liu, Shiyu; Min, Min; Cheng, Yanling; Wan, Yiqin; Li, Yun; Lin, Xiangyang; Liu, Yuhuan; Chen, Paul; Ruan, Roger

    2014-11-01

    In this study, fast microwave-assisted catalytic pyrolysis of sewage sludge was investigated for bio-oil production, with HZSM-5 as the catalyst. Pyrolysis temperature and catalyst to feed ratio were examined for their effects on bio-oil yield and composition. Experimental results showed that microwave is an effective heating method for sewage sludge pyrolysis. Temperature has great influence on the pyrolysis process. The maximum bio-oil yield and the lowest proportions of oxygen- and nitrogen-containing compounds in the bio-oil were obtained at 550°C. The oil yield decreased when catalyst was used, but the proportions of oxygen- and nitrogen-containing compounds were significantly reduced when the catalyst to feed ratio increased from 1:1 to 2:1. Essential mineral elements were concentrated in the bio-char after pyrolysis, which could be used as a soil amendment in place of fertilizer. Results of XRD analyses demonstrated that HZSM-5 catalyst exhibited good stability during the microwave-assisted pyrolysis of sewage sludge. PMID:25260179

  8. MALDI MS analysis of oligonucleotides: desalting by functional magnetite beads using microwave-assisted extraction.

    PubMed

    Chen, Wei-Yu; Chen, Yu-Chie

    2007-11-01

    The presence of alkali cation adductions of oligonucleotides commonly deteriorates matrix-assisted laser desorption/ionization (MALDI) mass spectra. Thus, desalting is required for oligonucleotide samples prior to MALDI MS analysis in order to prevent the mass spectra from developing poor quality. In this paper, we demonstrate a new approach to extract traces of oligonucleotides from aqueous solutions containing high concentrations of salts using microwave-assisted extraction. The C18-presenting magnetite beads, capable of absorbing microwave irradiation, are used as affinity probes for oligonucleotides with the addition of triethylammonium acetate as the counterions. This new microwave-assisted extraction approach using magnetite beads as the trapping agents and as microwave-absorbers has been demonstrated to be very effective in the selective binding of oligonucleotides from aqueous solutions. The extraction of oligonucleotides from solutions onto the C18-presenting magnetite beads takes only 30 s to enrich oligonucleotides in sufficient quantities for MALDI MS analysis. After using this desalting approach, alkali cation adductions of oligonucleotides are dramatically reduced in the MALDI mass spectra. The presence of saturated NaCl (approximately 6 M) in the oligonucleotide sample is tolerated without degrading the mass spectra. The detection limit for d(A)6 is approximately 2.8 fmol. PMID:17902633

  9. Acid-catalyzed conversion of xylose, xylan and straw into furfural by microwave-assisted reaction.

    PubMed

    Yemiş, Oktay; Mazza, Giuseppe

    2011-08-01

    Furfural is a biomass derived-chemical that can be used to replace petrochemicals. In this study, the acid-catalyzed conversion of xylose and xylan to furfural by microwave-assisted reaction was investigated at selected ranges of temperature (140-190°C), time (1-30 min), substrate concentration (1:5-1:200 solid:liquid ratio), and pH (2-0.13). We found that a temperature of 180°C, a solid:liquid ratio of 1:200, a residence time of 20 min, and a pH of 1.12 gave the best furfural yields. The effect of different Brønsted acids on the conversion efficiency of xylose and xylan was also evaluated, with hydrochloric acid being found to be the most effective catalyst. The microwave-assisted process provides highly efficient conversion: furfural yields obtained from wheat straw, triticale straw, and flax shives were 48.4%, 45.7%, and 72.1%, respectively. PMID:21620690

  10. Box-Behnken design for investigation of microwave-assisted extraction of patchouli oil

    NASA Astrophysics Data System (ADS)

    Kusuma, Heri Septya; Mahfud, Mahfud

    2015-12-01

    Microwave-assisted extraction (MAE) technique was employed to extract the essential oil from patchouli (Pogostemon cablin). The optimal conditions for microwave-assisted extraction of patchouli oil were determined by response surface methodology. A Box-Behnken design (BBD) was applied to evaluate the effects of three independent variables (microwave power (A: 400-800 W), plant material to solvent ratio (B: 0.10-0.20 g mL-1) and extraction time (C: 20-60 min)) on the extraction yield of patchouli oil. The correlation analysis of the mathematical-regression model indicated that quadratic polynomial model could be employed to optimize the microwave extraction of patchouli oil. The optimal extraction conditions of patchouli oil was microwave power 634.024 W, plant material to solvent ratio 0.147648 g ml-1 and extraction time 51.6174 min. The maximum patchouli oil yield was 2.80516% under these optimal conditions. Under the extraction condition, the experimental values agreed with the predicted results by analysis of variance. It indicated high fitness of the model used and the success of response surface methodology for optimizing and reflect the expected extraction condition.

  11. TiO{sub 2} synthesized by microwave assisted solvothermal method: Experimental and theoretical evaluation

    SciTech Connect

    Moura, K.F.; Maul, J.; Albuquerque, A.R.; Casali, G.P.

    2014-02-15

    In this study, a microwave assisted solvothermal method was used to synthesize TiO{sub 2} with anatase structure. The synthesis was done using Ti (IV) isopropoxide and ethanol without templates or alkalinizing agents. Changes in structural features were observed with increasing time of synthesis and evaluated using periodic quantum chemical calculations. The anatase phase was obtained after only 1 min of reaction besides a small amount of brookite phase. Experimental Raman spectra are in accordance with the theoretical one. Micrometric spheres constituted by nanometric particles were obtained for synthesis from 1 to 30 min, while spheres and sticks were observed after 60 min. - Graphical abstract: FE-SEM images of anatase obtained with different periods of synthesis associated with the order–disorder degree. Display Omitted - Highlights: • Anatase microspheres were obtained by the microwave assisted hydrothermal method. • Only ethanol and titanium isopropoxide were used as precursors during the synthesis. • Raman spectra and XRD patterns were compared with quantum chemical calculations. • Time of synthesis increased the short-range disorder in one direction and decreased in another.

  12. Central composite rotatable design for investigation of microwave-assisted extraction of okra pod hydrocolloid.

    PubMed

    Samavati, Vahid

    2013-10-01

    Microwave-assisted extraction (MAE) technique was employed to extract the hydrocolloid from okra pods (OPH). The optimal conditions for microwave-assisted extraction of OPH were determined by response surface methodology. A central composite rotatable design (CCRD) was applied to evaluate the effects of three independent variables (microwave power (X1: 100-500 W), extraction time (X2: 30-90 min), and extraction temperature (X3: 40-90 °C)) on the extraction yield of OPH. The correlation analysis of the mathematical-regression model indicated that quadratic polynomial model could be employed to optimize the microwave extraction of OPH. The optimal conditions to obtain the highest recovery of OPH (14.911±0.27%) were as follows: microwave power, 395.56 W; extraction time, 67.11 min and extraction temperature, 73.33 °C. Under these optimal conditions, the experimental values agreed with the predicted ones by analysis of variance. It indicated high fitness of the model used and the success of response surface methodology for optimizing OPH extraction. After method development, the DPPH radical scavenging activity of the OPH was evaluated. MAE showed obvious advantages in terms of high extraction efficiency and radical scavenging activity of extract within the shorter extraction time. PMID:23817104

  13. Microwave-assisted rapid synthesis, characterization and application of poly (D,L-lactide)-graft-pullulan.

    PubMed

    Tang, Xiao-Jiao; Huang, Jun; Xu, Liang-Yu; Li, Yang; Song, Juan; Ma, Yue; Yang, Li; Yuan, Dan; Wu, Hai-Yang

    2014-07-17

    A novel microwave-assisted method was developed to synthetize amphiphilic copolymer poly (d,l-lactide)-graft-pullulan (PL) in a monomode microwave reactor. The effects of microwave power, ratio of catalyst/lactide, ratio of lactide/hydroxyl group of pullulan (lactide/OH-P) and solvent on the synthesis were further investigated. Three samples (designated as PL 8, 9, and 6), characterized by FT-IR and NMR, were applied to form nanoparticles and microparticles investigated by dynamic light scattering, fluorescence spectroscopy and transmission electron microscopy. PL9 and PL6 were used for loading model drug curcumin. The results indicated that microwave-assisted synthesis shortened the copolymerization of PL, with higher yield and lactide conversion, from 24h to 5 min and showed some specific microwave effects compared with conventional oil heating. PL with a relative higher substitution degree gave nanoparticles with smaller sizes and critical aggregation concentrations. The solubility of curcumin was increased to 1.97 mg mL(-1) as the forms of nanoparticles. PMID:24702912

  14. Microwave-Assisted Extraction of Oleanolic Acid and Ursolic Acid from Ligustrum lucidum Ait

    PubMed Central

    Xia, En-Qin; Wang, Bo-Wei; Xu, Xiang-Rong; Zhu, Li; Song, Yang; Li, Hua-Bin

    2011-01-01

    Oleanolic acid and ursolic acid are the main active components in fruit of Ligustrum lucidum Ait, and possess anticancer, antimutagenic, anti-inflammatory, antioxidative and antiprotozoal activities. In this study, microwave-assisted extraction of oleanolic acid and ursolic acid from Ligustrum lucidum was investigated with HPLC-photodiode array detection. Effects of several experimental parameters, such as type and concentration of extraction solvent, ratio of liquid to material, microwave power, extraction temperature and microwave time, on the extraction efficiencies of oleanolic acid and ursolic acid from Ligustrum lucidum were evaluated. The influence of experimental parameters on the extraction efficiency of ursolic acid was more significant than that of oleanolic acid (p < 0.05). The optimal extraction conditions were 80% ethanol aqueous solution, the ratio of material to liquid was 1:15, and extraction for 30 min at 70 °C under microwave irradiation of 500 W. Under optimal conditions, the yields of oleanolic acid and ursolic acid were 4.4 ± 0.20 mg/g and 5.8 ± 0.15 mg/g, respectively. The results obtained are helpful for the full utilization of Ligustrum lucidum, which also indicated that microwave-assisted extraction is a very useful method for extraction of oleanolic acid and ursolic acid from plant materials. PMID:21954361

  15. Microwave-assisted Bi₂Se₃ nanoparticles using various organic solvents.

    PubMed

    Vijila, J Joy Jeba; Mohanraj, K; Henry, J; Sivakumar, G

    2016-01-15

    Microwave assisted Bi2Se3 nanoparticles were synthesized from five different solvents DMF, EG, EG+H2O, EDA+dil.HNO3 and N2H4+H2O+Ethanol. The influence of solvents on purity of the compound was analysed by using X-ray diffraction patterns. The result indicates pure rhombohedral Bi2Se3 nanoparticles formed for N2H4+H2O+Ethanol. The presence of vibrational bands in the range of 400-800 cm(-1) is confirmed the formation of Bi2Se3. The maximum optical absorption observed around 450 nm and the band gap values are found in the range of 1.5 eV-2.17 eV for all the solvents. The nanostructure of the Bi2Se3 particles change with solvents. From the experimental results, the solvent N2H4+H2O+Ethanol produces pure nanosize Bi2Se3 particles under the microwave assisted method. PMID:26363730

  16. Microwave-assisted synthesis of porous carbon-titania and highly crystalline titania nanostructures.

    PubMed

    Parker, Alison; Marszewski, Michal; Jaroniec, Mietek

    2013-03-01

    Porous carbon-titania and highly crystalline titania nanostructured materials were obtained through a microwave-assisted one-pot synthesis. Resorcinol and formaldehyde were used as carbon precursors, triblock copolymer Pluronic F127 as a stabilizing agent, and titanium isopropoxide as a titania precursor. This microwave-assisted one-pot synthesis involved formation of carbon spheres according to the recently modified Stöber method followed by hydrolysis and condensation of titania precursor. This method afforded carbon-titania composite materials containing anatase phase with specific surface areas as high as 390 m(2) g(-1). The pure nanostructured titania, obtained after removal of carbon through calcination of the composite material in air, was shown to be the anatase phase with considerably higher degree of crystallinity and the specific surface area as high as 130 m(2) g(-1). The resulting titania, because of its high surface area, well-developed porosity, and high crystallinity, is of great interest for catalysis, water treatment, lithium batteries, and other energy-related applications. PMID:23432344

  17. Mechanism on microwave-assisted acidic solvolysis of black-liquor lignin.

    PubMed

    Dong, Chengjian; Feng, Chunguang; Liu, Qian; Shen, Dekui; Xiao, Rui

    2014-06-01

    Microwave-assisted degradation of black-liquor lignin with formic acid was studied, concerning the product yield and distribution of phenolic compounds against reaction temperature (110-180°C) and reaction time (5-90 min). The liquid product consisting of bio-oil 1 and bio-oil 2, achieved the maxima yield of 64.08% at 160°C and 30 min (bio-oil 1: 9.69% and bio-oil 2: 54.39%). The chemical information of bio-oil 1 and bio-oil 2 were respectively identified by means of Gas Chromatography-Mass Spectrometer (GC-MS) and Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), while the solid residue was analyzed by Gel Permeation Chromatography (GPC) and Fourier Transform Infrared Spectroscopy (FTIR). A possible mechanism was proposed for the microwave-assisted acidic solvolysis of lignin, specifying the kinetic relationship among the primary cracking of lignin, repolymerization of the oligomers and formation of solid residue. PMID:24747392

  18. Extraction of Dihydroquercetin from Larix gmelinii with Ultrasound-Assisted and Microwave-Assisted Alternant Digestion

    PubMed Central

    Ma, Chunhui; Yang, Lei; Wang, Wenjie; Yang, Fengjian; Zhao, Chunjian; Zu, Yuangang

    2012-01-01

    An ultrasound and microwave assisted alternant extraction method (UMAE) was applied for extracting dihydroquercetin (DHQ) from Larix gmelinii wood. This investigation was conducted using 60% ethanol as solvent, 1:12 solid to liquid ratio, and 3 h soaking time. The optimum treatment time was ultrasound 40 min, microwave 20 min, respectively, and the extraction was performed once. Under the optimized conditions, satisfactory extraction yield of the target analyte was obtained. Relative to ultrasound-assisted or microwave-assisted method, the proposed approach provides higher extraction yield. The effect of DHQ of different concentrations and synthetic antioxidants on oxidative stability in soy bean oil stored for 20 days at different temperatures (25 °C and 60 °C) was compared. DHQ was more effective in restraining soy bean oil oxidation, and a dose-response relationship was observed. The antioxidant activity of DHQ was a little stronger than that of BHA and BHT. Soy bean oil supplemented with 0.08 mg/g DHQ exhibited favorable antioxidant effects and is preferable for effectively avoiding oxidation. The L. gmelinii wood samples before and after extraction were characterized by scanning electron microscopy. The results showed that the UMAE method is a simple and efficient technique for sample preparation. PMID:22942735

  19. Efficient microwave assisted synthesis of metal-organic framework UiO-66: optimization and scale up.

    PubMed

    Taddei, Marco; Dau, Phuong V; Cohen, Seth M; Ranocchiari, Marco; van Bokhoven, Jeroen A; Costantino, Ferdinando; Sabatini, Stefano; Vivani, Riccardo

    2015-08-21

    A highly efficient and scalable microwave assisted synthesis of zirconium-based metal-organic framework UiO-66 was developed. In order to identify the best conditions for optimizing the process, a wide range of parameters was investigated. The efficiency of the process was evaluated with the aid of four quantitative indicators. The properties of the materials prepared by microwave irradiation were compared with those synthesized by conventional heating, and no significant effects on morphology, crystal size, or defects were found from the use of microwave assisted heating. Scale up was performed maintaining the high efficiency of the process. PMID:26165508

  20. Microwave-assisted synthesis and characterization of hierarchically structured calcium fluoride

    SciTech Connect

    Yang, Zhenxing; Wang, Guangjian; Guo, Yajie; Kang, Fangfang; Huang, Yanhong; Bo, Dongsheng

    2012-12-15

    Graphical abstract: CaF{sub 2} with different morphologies and hierarchical structure such as dendrites, spherical and cube was prepared under microwave-assisted condition by a simple solvothermal synthesis route using CaCl{sub 2} and [BMIM]BF{sub 4} as initial reagents, respectively. It was found that the species of precursor was of vital importance for the formation of CaF{sub 2} crystals. That is, precursors itself also acted as structure directing agent. The outstanding features of the approach to obtain hierarchical structure CaF{sub 2} were its simplicity, effectiveness and ease of assembly. On the basis of the experimental results, a possible growth mechanism of the CaF{sub 2} crystals was proposed. Display Omitted Highlights: ► CaF{sub 2} with hierarchical structure was synthesized under microwave-assisted conditions. ► Characteristic morphologies with cube, dendrite, hierarchical sphere, etc. were observed. ► Thin cubes assembled into a spherical structure. ► Ionic liquid of [BMIM]BF{sub 4} was fluorine source. ► Possible growth mechanisms of CaF{sub 2} crystals were discussed. -- Abstract: CaF{sub 2} with different morphologies and hierarchical structures was prepared under microwave-assisted condition by a simple hydrothermal route using CaCl{sub 2} and ionic liquid [BMIM]BF{sub 4} as initial reagents, respectively. It was found that both the precursor and pH values played an important role in the formation of CaF{sub 2} crystals with different morphologies. The results suggested that the CaF{sub 2} with cube and spherical structures was obtained at different pH values (4, 8, 11), while the CaF{sub 2} with dendrite shape was formed through an oriented self-assembly growth using (NH{sub 4}){sub 2}HPO{sub 4} as a structure directing agent. Scanning electron microscope observation showed that the as-prepared CaF{sub 2} was of three-dimensional eight-horn-shaped dendritic structure. The influence of the pH values for the reaction solution and

  1. DETERMINATION OF PCBS IN SOILS/SEDIMENTS BY MICROWAVE-ASSISTED EXTRACTION AND GC/ECD OR ELISA

    EPA Science Inventory

    This article describes the application of microwave-assisted extraction (MAE) combined either with gas chromatography and electron capture detection (GC/ECD) or with enzyme-linked immunosorbent assay (ELISA) to the determination of PCBs in soil and sediment samples. CBs were extr...

  2. A Student-Centered First-Semester Introductory Organic Laboratory Curriculum Facilitated by Microwave-Assisted Synthesis (MAOS)

    ERIC Educational Resources Information Center

    Russell, Cianán B.; Mason, Jeremy D.; Bean, Theodore G.; Murphree, S. Shaun

    2014-01-01

    An instructional laboratory curriculum for a first-semester introductory organic chemistry course has been developed using microwave-assisted organic synthesis (MAOS). Taking advantage of short reaction times, materials were developed to facilitate collaborative experimental design, analysis, and debriefing of results during the normal laboratory…

  3. Microwave-Assisted Copper-Catalyzed Four-Component Tandem Synthesis of 3-N-Sulfonylamidine Coumarins.

    PubMed

    Murugavel, Govindarasu; Punniyamurthy, Tharmalingam

    2015-06-19

    Microwave-assisted copper-catalyzed four-component tandem synthesis of 3-N-sulfonylamidine coumarins has been accomplished by the coupling of salicylaldehydes, propiolates, sulfonyl azides, and secondary amines. This one-pot protocol affords an effective route for the construction of functionalized coumarin structural frameworks in a single operation with moderate to high yields. PMID:26024048

  4. Microwave-assisted decarboxylative three-component coupling of a 2-oxoacetic acid, an amine, and an alkyne.

    PubMed

    Feng, Huangdi; Ermolat'ev, Denis S; Song, Gonghua; Van der Eycken, Erik V

    2011-09-16

    A novel and efficient microwave-assisted decarboxylative three-component coupling of a 2-oxoacetic acid, an amine, and an alkyne (OA(2)-coulpling) has been developed. This new multicomponent coupling constitutes an efficient approach for the synthesis of polysubstituted propargylamines in the presence of a catalytic amount of copper(I) catalyst. PMID:21823621

  5. Application of response surface methodology to optimize microwave-assisted extraction of silymarin from milk thistle seeds

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Several parameters of Microwave-assisted extraction (MAE) including extraction time, extraction temperature, ethanol concentration and solid-liquid ratio were selected to describe the MAE processing. The silybin content, measured by an UV-Vis spectrophotometry, was considered as the silymarin yield....

  6. Water based microwave assisted extraction of thiamethoxam residues from vegetables and soil for determination by HPLC.

    PubMed

    Karmakar, Rajib; Singh, Shashi Bala; Kulshrestha, Gita

    2012-02-01

    A microwave assisted extraction (MAE) method for determination of thiamethoxam residues in vegetable and soil samples was standardized. Insecticide spiked vegetable and soil samples were extracted by MAE using water as an extraction solvent, cleaned up by solid phase extraction and analysed by high performance liquid chromatography on photodiode array detector. The recoveries of the insecticide from various vegetable (tomato, radish, brinjal, okra, French been, sugarbeet) and soil (sandy loam, silty clay loam, sandy clay loam, loamy sand) samples at 0.1 and 0.5 μg g(-1) spiking levels ranged from 79.8% to 86.2% and from 82.1% to 87.0%, respectively. The recoveries by MAE were comparable to those obtained by the conventional blender and shake-flask extraction techniques. The precision of the MAE method was demonstrated by relative standard deviations of <3% for the insecticide. PMID:22065124

  7. Development of microwave assisted spectrophotometric method for the determination of glucose

    NASA Astrophysics Data System (ADS)

    Ali, Asif; Hussain, Zahid; Arain, Muhammad Balal; Shah, Nasrullah; Khan, Khalid Mohammad; Gulab, Hussain; Zada, Amir

    2016-01-01

    A spectrophotometric method was developed based on the microwave assisted synthesis of Maillard product. Various conditions of the reaction were optimized by varying the relative concentration of the reagents, operating temperature and volume of solutions used in the reaction in the microwave synthesizer. The absorbance of the microwave synthesized Maillard product was measured in the range of 360-740 nm using UV-Visible spectrophotometer. Based on the maximum absorbance, 370 nm was selected as the optimum wave length for further studies. The LOD and LOQ of glucose was found 3.08 μg mL- 1 and 9.33 μg mL- 1 with standard deviation of ± 0.05. The developed method was also applicable to urine sample.

  8. Microwave-assisted synthesis of Pt/CNT nanocomposite electrocatalysts for PEM fuel cells.

    PubMed

    Zhang, Weimin; Chen, Jun; Swiegers, Gerhard F; Ma, Zi-Feng; Wallace, Gordon G

    2010-02-01

    Microwave-assisted heating of functionalized, single-wall carbon nanotubes (FCNTs) in ethylene glycol solution containing H(2)PtCl(6), led to the reductive deposition of Pt nanoparticles (2.5-4 nm) over the FCNTs, yielding an active catalyst for proton-exchange membrane fuel cells (PEMFCs). In single-cell testing, the Pt/FCNT composites displayed a catalytic performance that was superior to Pt nanoparticles supported by raw (unfunctionalized) CNTs (RCNTs) or by carbon black (C), prepared under identical conditions. The supporting single-wall carbon nanotubes (SWNTs), functionalized with carboxyl groups, were studied by thermogravimetric analysis (TGA), cyclic voltammetry (CV), and Raman spectroscopy. The loading level, morphology, and crystallinity of the Pt/SWNT catalysts were determined using TGA, SEM, and XRD. The electrochemically active catalytic surface area of the Pt/FCNT catalysts was 72.9 m(2)/g-Pt. PMID:20644806

  9. Microwave assisted reconstruction of optical interferograms for distributed fiber optic sensing.

    PubMed

    Huang, Jie; Hua, Lei; Lan, Xinwei; Wei, Tao; Xiao, Hai

    2013-07-29

    This paper reports a distributed fiber optic sensing technique through microwave assisted separation and reconstruction of optical interferograms in spectrum domain. The approach involves sending a microwave-modulated optical signal through cascaded fiber optic interferometers. The microwave signal was used to resolve the position and reflectivity of each sensor along the optical fiber. By sweeping the optical wavelength and detecting the modulation signal, the optical spectrum of each sensor can be reconstructed. Three cascaded fiber optic extrinsic Fabry-Perot interferometric sensors were used to prove the concept. Their microwave-reconstructed interferogram matched well with those recorded individually using an optical spectrum analyzer. The application in distributed strain measurement has also been demonstrated. PMID:23938685

  10. Fabrication of silica nanostructures with a microwave assisted direct patterning process

    NASA Astrophysics Data System (ADS)

    Shin, Ju-Hyeon; Go, Bit-Na; Choi, Je-Hong; Kim, Jin-Seoung; Jung, Gun-Young; Kim, Heetae; Lee, Heon

    2014-06-01

    Silica nanostructures were fabricated on glass substrate using a microwave assisted direct patterning (MADP) process, which is a variety of soft lithography. During the MADP process using polydimethylsiloxane (PDMS), mold and microwave heating are performed simultaneously. Blanket thin film and micro- to nano-sized structures, including moth-eye patterns of SiO2, which consisted of coalesced silica nanoparticles, were formed on glass substrates from SiO2 nano-particle dispersed solutions with varied microwave heating time. Optical properties and surface morphologies of micro-sized hemisphere, nano-sized pillar, moth-eye and 50 nm sized line/space silica patterns were measured using UV-vis and a scanning electron microscope. X-ray diffraction analysis of SiO2 thin films with and without microwave heating was also carried out.

  11. Microwave assisted alkali-catalyzed transesterification of Pongamia pinnata seed oil for biodiesel production.

    PubMed

    Kumar, Ritesh; Kumar, G Ravi; Chandrashekar, N

    2011-06-01

    In this study, microwave assisted transesterification of Pongamia pinnata seed oil was carried out for the production of biodiesel. The experiments were carried out using methanol and two alkali catalysts i.e., sodium hydroxide (NaOH) and potassium hydroxide (KOH). The experiments were carried out at 6:1 alcohol/oil molar ratio and 60°C reaction temperature. The effect of catalyst concentration and reaction time on the yield and quality of biodiesel was studied. The result of the study suggested that 0.5% sodium hydroxide and 1.0% potassium hydroxide catalyst concentration were optimum for biodiesel production from P. pinnata oil under microwave heating. There was a significant reduction in reaction time for microwave induced transesterification as compared to conventional heating. PMID:21482464

  12. Influence of polarity on the scalability and reproducibility of solvent-free microwave-assisted reactions.

    PubMed

    Díaz-Ortiz, Angel; de la Hoz, Antonio; Alcázar, Jesús; Carrillo, José R; Herrero, María A; Fontana, Alberto; Muñoz, Juan de M; Prieto, Pilar; de Cózar, Abel

    2011-02-01

    Organic reactions performed in the absence of solvent in domestic ovens without appropriate temperature control are generally considered as not reproducible, particularly when different instruments are used. For this reason, reproducibility has historically been one of the major issues associated with Microwave-Assisted Organic Synthesis (MAOS) especially when domestic ovens are involved. The lack of reproducibility limits the general applicability and the scale up of these reactions. In this work several solvent-free reactions previously carried out in domestic ovens have been translated into a single-mode microwave reactor and then scaled up in a multimode oven. The results show that most of these reactions, although not considered as reproducible, can be easily updated and applied in microwave reactors using temperature-controlled conditions. Furthermore, computational calculations can assist to explain and/or predict whether a reaction will be reproducible or not. PMID:21143180

  13. Microwave-assisted hydrothermal extraction of sulfated polysaccharides from Ulva spp. and Monostroma latissimum.

    PubMed

    Tsubaki, Shuntaro; Oono, Kiriyo; Hiraoka, Masanori; Onda, Ayumu; Mitani, Tomohiko

    2016-11-01

    Microwave-assisted hydrothermal extraction was applied for production of sulfated polysaccharides from Ulva spp. and Monostroma latissimum. The maximum ulvan yields attained 40.4±3.2% (Ulva meridionalis) and 36.5±3.1% (Ulva ohnoi) within 4min of come-up time and 10min of extraction time at 160°C, respectively. The rhamnan sulfate yield from M. latissimum further attained 53.1±7.2% at 140°C. The sulfated polysaccharides were easily recovered from the extract by simple ethanol precipitation. In addition, molecular weights and viscosity of the extracted polysaccharides could be controlled by varying the extraction temperature. Dielectric measurement revealed that ionic conduction was the important parameter that affect the microwave susceptibility of algae-water mixture. The sulfated polysaccharides extracts are expected as potential feedstock for medical and food applications. PMID:27211652

  14. Self-assembled zinc oxide nanostructures via a rapid microwave-assisted route

    NASA Astrophysics Data System (ADS)

    Mohajerani, Matin Sadat; Mazloumi, Mahyar; Lak, Aidin; Kajbafvala, Amir; Zanganeh, Saeid; Sadrnezhaad, S. K.

    2008-07-01

    Self-assembled ZnO nanostructures with various morphologies were prepared via a rapid and simple microwave-assisted technique. The spherical, raspberry-like and hollow spherical nanostructures were synthesized in the presence of triethanolamine (TEA) as a capping agent and in different adjusted pHs. The volumetric amount of TEA has affected the particle size and crystallite size of the obtained nanostructures significantly. The ZnO nanostructures were obtained due to self-assembly of Zn 2+ ionic complexes, and the internal voids of the hollow spheres were formed by the Ostwald ripening mechanism. The obtained nanostructures were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. The optical properties of the synthesized materials were investigated by Raman spectroscopy.

  15. Microwave-assisted synthesis of nanocrystalline TiO2 for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Kuo, Ta-Chuan; Guo, Tzung-Fang; Chen, Peter

    2012-09-01

    The main purposes of this study are replacing conventional hydro-thermal method by microwave heating using water as reaction medium to rapidly synthesize TiO2.Titanium tetraisopropoxide (TTIP) was hydrolyzed in water. The solution is subsequently processed with microwave heating for crystal growth. The reaction time could be shortened into few minutes. Then we chose different acids as dispersion agents to prepare TiO2 paste for investigating the effects of dispersion on the power conversion efficiency of dye-sensitized solar cells (DSCs). The photovoltaic performance of the microwave-assisted synthesized TiO2 achieved power conversion efficiency of 6.31% under AM 1.5 G condition (100 mW/cm2). This PCE value is compatible with that of the devices made from commercial TiO2.

  16. Microwave assisted synthesis and characterization of barium titanate nanoparticles for multi layered ceramic capacitor applications.

    PubMed

    Thirumalai, Sundararajan; Shanmugavel, Balasivanandha Prabu

    2011-01-01

    Barium titanate is a common ferroelectric electro-ceramic material having high dielectric constant, with photorefractive effect and piezoelectric properties. In this research work, nano-scale barium titanate powders were synthesized by microwave assisted mechano-chemical route. Suitable precursors were ball milled for 20 hours. TGA studies were performed to study the thermal stability of the powders. The powders were characterized by XRD, SEM and EDX Analysis. Microwave and Conventional heating were performed at 1000 degrees C. The overall heating schedule was reduced by 8 hours in microwave heating thereby reducing the energy and time requirement. The nano-scale, impurity-free and defect-free microstructure was clearly evident from the SEM micrograph and EDX patterns. LCR meter was used to measure the dielectric constant and dielectric loss values at various frequencies. Microwave heated powders showed superior dielectric constant value with low dielectric loss which is highly essential for the fabrication of Multi Layered Ceramic Capacitors. PMID:24427875

  17. Pb(core)/ZnO(shell) nanowires obtained by microwave-assisted method

    PubMed Central

    2011-01-01

    In this study, Pb-filled ZnO nanowires [Pb(core)/ZnO(shell)] were synthesized by a simple and novel one-step vapor transport and condensation method by microwave-assisted decomposition of zinc ferrite. The synthesis was performed using a conventional oven at 1000 W and 5 min of treatment. After synthesis, a spongy white cotton-like material was obtained in the condensation zone of the reaction system. HRTEM analysis revealed that product consists of a Pb-(core) with (fcc) cubic structure that preferentially grows in the [111] direction and a hexagonal wurtzite ZnO-(Shell) that grows in the [001] direction. Nanowire length was more than 5 μm and a statistical analysis determined that the shell and core diameters were 21.00 ± 3.00 and 4.00 ± 1.00 nm, respectively. Experimental, structural details, and synthesis mechanism are discussed in this study. PMID:21985637

  18. Fabrication of silica nanostructures with a microwave assisted direct patterning process.

    PubMed

    Shin, Ju-Hyeon; Go, Bit-Na; Choi, Je-Hong; Kim, Jin-Seoung; Jung, Gun-Young; Kim, Heetae; Lee, Heon

    2014-06-01

    Silica nanostructures were fabricated on glass substrate using a microwave assisted direct patterning (MADP) process, which is a variety of soft lithography. During the MADP process using polydimethylsiloxane (PDMS), mold and microwave heating are performed simultaneously. Blanket thin film and micro- to nano-sized structures, including moth-eye patterns of SiO2, which consisted of coalesced silica nanoparticles, were formed on glass substrates from SiO2 nano-particle dispersed solutions with varied microwave heating time. Optical properties and surface morphologies of micro-sized hemisphere, nano-sized pillar, moth-eye and 50 nm sized line/space silica patterns were measured using UV-vis and a scanning electron microscope. X-ray diffraction analysis of SiO2 thin films with and without microwave heating was also carried out. PMID:24833169

  19. Rapid and Facile Microwave-Assisted Surface Chemistry for Functionalized Microarray Slides.

    PubMed

    Lee, Jeong Heon; Hyun, Hoon; Cross, Conor J; Henary, Maged; Nasr, Khaled A; Oketokoun, Rafiou; Choi, Hak Soo; Frangioni, John V

    2012-02-22

    We describe a rapid and facile method for surface functionalization and ligand patterning of glass slides based on microwave-assisted synthesis and a microarraying robot. Our optimized reaction enables surface modification 42-times faster than conventional techniques and includes a carboxylated self-assembled monolayer, polyethylene glycol linkers of varying length, and stable amide bonds to small molecule, peptide, or protein ligands to be screened for binding to living cells. We also describe customized slide racks that permit functionalization of 100 slides at a time to produce a cost-efficient, highly reproducible batch process. Ligand spots can be positioned on the glass slides precisely using a microarraying robot, and spot size adjusted for any desired application. Using this system, we demonstrate live cell binding to a variety of ligands and optimize PEG linker length. Taken together, the technology we describe should enable high-throughput screening of disease-specific ligands that bind to living cells. PMID:23467787

  20. Microwave-Assisted γ-Valerolactone Production for Biomass Lignin Extraction: A Cascade Protocol.

    PubMed

    Tabasso, Silvia; Grillo, Giorgio; Carnaroglio, Diego; Calcio Gaudino, Emanuela; Cravotto, Giancarlo

    2016-01-01

    The general need to slow the depletion of fossil resources and reduce carbon footprints has led to tremendous effort being invested in creating "greener" industrial processes and developing alternative means to produce fuels and synthesize platform chemicals. This work aims to design a microwave-assisted cascade process for a full biomass valorisation cycle. GVL (γ-valerolactone), a renewable green solvent, has been used in aqueous acidic solution to achieve complete biomass lignin extraction. After lignin precipitation, the levulinic acid (LA)-rich organic fraction was hydrogenated, which regenerated the starting solvent for further biomass delignification. This process does not requires a purification step because GVL plays the dual role of solvent and product, while the reagent (LA) is a product of biomass delignification. In summary, this bio-refinery approach to lignin extraction is a cascade protocol in which the solvent loss is integrated into the conversion cycle, leading to simplified methods for biomass valorisation. PMID:27023511

  1. Microwave-assisted synthesis of SrFe 12O 19 hexaferrites

    NASA Astrophysics Data System (ADS)

    Zhanyong, Wang; Liuming, Zhong; Jieli, Lv; Huichun, Qian; Yuli, Zheng; Yongzheng, Fang; Minglin, Jin; Jiayue, Xu

    2010-09-01

    Ultra-fine and homogeneous SrFe 12O 19 hexaferrites were synthesized by a microwave-assisted calcination route. The calcined precursors were prepared by a sol-gel auto-combustion method using Fe(NO 3) 3·9H 2O, Sr(NO 3) 2 and citric acid as starting materials. The structures, powder morphology and magnetic properties of the products were characterized by X-ray diffraction, scanning electron microscope and vibrating sample magnetometer. The results showed that microwaves are helpful to reduce the calcination temperature and shorten the calcination time. The ferrites with saturation magnetization, remanence and intrinsic coercivity of 54.80 emu/g, 29.52 emu/g and 5261 Oe, respectively, were obtained in samples calcined at 800 °C for 80 min.

  2. Rapid microwave-assisted synthesis and electrochemical characterization of gold/carbon nanotube composites

    NASA Astrophysics Data System (ADS)

    Hu, Qitu; Gan, Zibao; Zheng, Xiuwen; Lin, Qingfu; Xu, Baofeng; Zhao, Aihua; Zhang, Xu

    2011-05-01

    Hybrid nanostructures composed of gold nanoparticles (NPs) and carbon nanotubes (CNTs) have been prepared by a microwave-assisted method in the mixed solvents of oleylamine and oleic. The morphology, structure and composition of as-obtained Au/CNT composites are characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD). The composites show characteristic plasmon absorption of Au NPs in the Ultraviolet-visual spectrum. Fourier transform infrared spectrum shows the successful introduction of functional groups on the surface of CNTs, which are crucial factors to assist the nucleation in situ of Au NPs on the surface of CNTs. Electrochemical measurements show the enhancement electrochemical response for the gold electrode modified with Au/CNT composites.

  3. Determination of thiophanate methyl and carbendazim residues in vegetable samples using microwave-assisted extraction.

    PubMed

    Singh, Shashi B; Foster, Gregory D; Khan, Shahamat U

    2007-05-01

    Microwave-assisted extraction (MAE) was carried out for the determination of the fungicides thiophanate methyl [1.2-alpha-(3-methoxycarbonyl-2-thioureido)benzene] and carbendazim (methyl benzimidazol-2-ylcarbamate) in vegetable samples. Two vegetable samples, cabbage and tomatoes, were fortified with the two pesticides and subjected to MAE followed by cleanup to remove co-extractives prior to analysis by high-performance liquid chromatography (HPLC). Using the selected microwave exposure time and power setting, the recoveries of carbendazim ranged from 69 to 75%. But thiophanate methyl could not be recovered as the parent compound. It was converted and recovered as carbendazim. The conversion was quantitative as confirmed by high-performance liquid chromatography-mass spectrometry (HPLC-MS). PMID:17382951

  4. Microwave-assisted synthesis of carbon-supported carbides catalysts for hydrous hydrazine decomposition

    NASA Astrophysics Data System (ADS)

    Mnatsakanyan, Raman; Zhurnachyan, Alina R.; Matyshak, Valery A.; Manukyan, Khachatur V.; Mukasyan, Alexander S.

    2016-09-01

    Microwave-assisted synthesis of carbon-supported Mo2C and WC nanomaterials was studied. Two different routes were utilized to prepare MoO3 (WO3) - C precursors that were then subjected to microwave irradiation in an inert atmosphere. The effect of synthesis conditions, such as irradiation time and gas environment, was investigated. The structure and formation mechanism of the carbide phases were explored. As-synthesized nanomaterials exhibited catalytic activity for hydrous hydrazine (N2H4·H2O) decomposition at 30-70 °C. It was shown that the catalyst activity significantly increases if microwave irradiation is applied during the decomposition process. Such conditions permit complete conversion of hydrazine to ammonia and nitrogen within minutes. This effect can be attributed to the unique nanostructure of the catalysts that includes microwave absorbing carbon and active carbide constituents.

  5. Microwave-assisted activation for electroless nickel plating on PMMA microspheres

    NASA Astrophysics Data System (ADS)

    Chen, Yen-Chung; Liu, Robert Lian-Huey; Chen, Xin-Liang; Shu, Hsiou-Jeng; Ger, Ming-Der

    2011-05-01

    A novel microwave-assisted activation method for electroless plating on PMMA microspheres is presented in this study. When the microwave irradiation was applied during the activation step, the amount of the Pd species adsorbed on PMMA surfaces was much higher than that of sample pretreated with a conventional activation process without microwave irradiation. With this activation method, it was also shown that the adsorbed Pd species with a size of 4-6 nm were uniformly distributed on the surfaces of the PMMA microspheres, thus a smooth and uniform nickel-phosphorus coating on the PMMA microspheres was obtained by subsequent electroless plating. The samples after each step were characterized by XPS, TEM, ICP and SEM.

  6. Microwave-assisted synthesis of gold nanoparticles self-assembled into self-supported superstructures

    PubMed Central

    Esparza, R.; Vargas-Hernández, C.; Fernández García, M. E.; José-Yacamán, M.

    2014-01-01

    Passivated gold nanoparticles were synthesized through a microwave-assisted process in a two-phase system, in the presence of 1-dodecanethiol. An average particle size of 1.8 nm of the gold nanoparticles obtained and 0.35 S.D. was determined through HRTEM and STEM analysis. It was observed that these nanoparticles spontaneously self-assemble into self-supported superstructures of 1 μm in diameter avg and 400 nm thickness, yielding an off-white powder which can be handled as a simple powder. XRD analysis indicates that n-alkanethiol molecules used as a passivating compound, besides protecting against crystal growth, interact to form cubic ordered arrays between the nanoparticles. This interaction leads to the superstructure formation, with an average distance between nanoparticles in the array, of 3.56 nm. Theoretical calculations and molecular dynamics simulations were performed to analyze the resulting structure. PMID:22398420

  7. Microwave-assisted, one-pot syntheses and fungicidal activity of polyfluorinated 2-benzylthiobenzothiazoles.

    PubMed

    Huang, Wei; Yang, Guang-Fu

    2006-12-15

    Polyfluorinated 2-benzylthiobenzothiazoles 3a-l are prepared via a microwave-assisted, one-pot procedure. The advantages, such as good to excellent yields, shorter reaction time (14-21min), readily available starting material, and simple purification procedure, distinguish the present protocol from other existing methods used for the synthesis of 2-benzylthiobenzothiazoles. Bioassay indicated that most of the compounds showed significant fungicidal activity against Rhizoctonia solani, Botrytis cinereapers, and Dothiorella gregaria at a dosage of 50microg/mL. Interestingly, compared to the control of commercial fungicide, triadimefon, compound 3c exhibited much higher activities against R. solani, B. cinereapers, and D. gregaria, which showed that the polyfluorinated 2-benzylthiobenzothiazoles can be used as lead compound for developing novel fungicides. PMID:17008103

  8. Rapid and Facile Microwave-Assisted Surface Chemistry for Functionalized Microarray Slides

    PubMed Central

    Lee, Jeong Heon; Hyun, Hoon; Cross, Conor J.; Henary, Maged; Nasr, Khaled A.; Oketokoun, Rafiou; Choi, Hak Soo; Frangioni, John V.

    2011-01-01

    We describe a rapid and facile method for surface functionalization and ligand patterning of glass slides based on microwave-assisted synthesis and a microarraying robot. Our optimized reaction enables surface modification 42-times faster than conventional techniques and includes a carboxylated self-assembled monolayer, polyethylene glycol linkers of varying length, and stable amide bonds to small molecule, peptide, or protein ligands to be screened for binding to living cells. We also describe customized slide racks that permit functionalization of 100 slides at a time to produce a cost-efficient, highly reproducible batch process. Ligand spots can be positioned on the glass slides precisely using a microarraying robot, and spot size adjusted for any desired application. Using this system, we demonstrate live cell binding to a variety of ligands and optimize PEG linker length. Taken together, the technology we describe should enable high-throughput screening of disease-specific ligands that bind to living cells. PMID:23467787

  9. Development of microwave assisted spectrophotometric method for the determination of glucose.

    PubMed

    Ali, Asif; Hussain, Zahid; Arain, Muhammad Balal; Shah, Nasrullah; Khan, Khalid Mohammad; Gulab, Hussain; Zada, Amir

    2016-01-15

    A spectrophotometric method was developed based on the microwave assisted synthesis of Maillard product. Various conditions of the reaction were optimized by varying the relative concentration of the reagents, operating temperature and volume of solutions used in the reaction in the microwave synthesizer. The absorbance of the microwave synthesized Maillard product was measured in the range of 360-740 nm using UV-Visible spectrophotometer. Based on the maximum absorbance, 370 nm was selected as the optimum wave length for further studies. The LOD and LOQ of glucose was found 3.08 μg mL(-1) and 9.33 μg mL(-1) with standard deviation of ±0.05. The developed method was also applicable to urine sample. PMID:26342822

  10. One step microwaved-assisted hydrothermal synthesis of nitrogen doped graphene for high performance of supercapacitor

    NASA Astrophysics Data System (ADS)

    Sari, Fitri Nur Indah; Ting, Jyh-Ming

    2015-11-01

    Nitrogen doped graphene (NDG) has been synthesized using a microwave-assisted hydrothermal (MHT) method within only several minute. In the method, homemade graphene oxide was reduced using ethylene glycol (EG) to obtain the graphene while ammonia liquid was used as the nitrogen source. However, it was found that the reduction and doping simultaneously occurred and the addition of ammonia further enhanced the reduction. The reduction and doping were examined through various analysis and the mechanisms were proposed. The effects of the hydrothermal temperature and time on the reduction and doping were discussed. It was also shown that the doping leads to enhanced specific capacitance by as much as 54%, a high specific energy density of 42.8 W h kg-1 at a power density of 4330 W kg-1, and excellent long term stability up to 98% retention after 1000 cycles at wide working voltage of 1.6 V in 2 M H2SO4.

  11. Fast synthesis and morphology control of lead tungstate microcrystals via a microwave-assisted method

    SciTech Connect

    Wang Guizhen; Hao Chuncheng

    2009-02-04

    Lead tungstate (PbWO{sub 4}) microcrystals with different morphologies, such as tetragonal flowerlike, amygdaloidal, and multiple-lamellar, have been successfully synthesized via a simple microwave-assisted method. Various factors, such as the pH value and the concentration of the cetyltrimethylammonium bromide (CTAB), play an important role in the morphological control of PbWO{sub 4} microcrystals. The products were characterized by the techniques of powder X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The possible formation mechanisms of PbWO{sub 4} samples of various morphologies were discussed. The luminescence properties of the final products were investigated and the as-prepared PbWO{sub 4} microcrystals showed special room-temperature photoluminescence intensity compared to the solid structures.

  12. Total fractionation of green tea residue by microwave-assisted alkaline pretreatment and enzymatic hydrolysis.

    PubMed

    Tsubaki, Shuntaro; Azuma, Jun-ichi

    2013-03-01

    Total refinery of constituents of green tea residue was achieved by combination of microwave-assisted alkaline pretreatment and enzymatic hydrolysis. Alkaline pretreatment was effective at separating pectic polysaccharides, protein, phenolic compounds and aliphatic compounds (probably originating from cuticular components), and the solubilization rate was attained 64–74% by heating at 120–200 °C. The higher heating value (HHV) of alkali-soluble fraction attained 20.1 MJ/kg, indicating its usability as black-liquor-like biofuel. Successive cellulolytic enzymatic hydrolysis mainly converted cellulose into glucose and attained the maximum solubilization rate of 89%. Final residue was predominantly composed of aliphatic cuticular components with high proportion in 9,10,18-trihydroxyoctadecanoic acid (30.1–48.6%). These cuticular components are potential alternative feedstock for aliphatic compounds commonly found in oil plants. PMID:23384782

  13. Microwave-assisted carboxymethylation of cellulose extracted from brewer's spent grain.

    PubMed

    dos Santos, Danilo Martins; Bukzem, Andrea de Lacerda; Ascheri, Diego Palmiro Ramirez; Signini, Roberta; de Aquino, Gilberto Lucio Benedito

    2015-10-20

    Cellulose was extracted from brewer's spent grain (BSG) by alkaline and bleaching treatments. The extracted cellulose was used in the preparation of carboxymethyl cellulose (CMC) by reaction with monochloroacetic acid in alkaline medium with the use of a microwave reactor. A full-factorial 2(3) central composite design was applied in order to evaluate how parameters of carboxymethylation process such as reaction time, amount of monochloroacetic acid and reaction temperature affect the average degree of substitution (DS) of the cellulose derivative. An optimization strategy based on response surface methodology has been used for this process. The optimized conditions to yield CMC with the highest DS of 1.46 follow: 5g of monochloroacetic acid per gram of cellulose, reaction time of 7.5min and temperature of 70°C. This work demonstrated the feasibility of a fast and efficient microwave-assisted method to synthesize carboxymethyl cellulose from cellulose isolated of brewer's spent grain. PMID:26256168

  14. Microwave-assisted reconstruction of Ni,Al hydrotalcite-like compounds

    SciTech Connect

    Benito, P.; Guinea, I.; Labajos, F.M.; Rives, V.

    2008-05-15

    The microwave-assisted reconstruction of Ni,Al hydrotalcite-like compounds (HTlcs) with Ni/Al molar ratios 2/1 and 3/1 has been studied. Mixed oxides obtained after calcination of the HTlcs are immersed in three different solutions containing carbonate, distilled water and an aqueous NH{sub 3} solution, and then heated at different temperatures for increasing periods of time under microwave radiation. The evolution of the structure during the treatment is followed by powder X-ray diffraction, FT-IR and vis-UV spectroscopies and SEM and TEM microscopies. Full recovery of the original layered structure is achieved in short periods of time for the 2/1 samples when the calcined HTlcs are rehydrated in the Na{sub 2}CO{sub 3} solution, but more drastic conditions are necessary for the 3/1 samples and the reconstruction seems not to be complete. Finally, only a partial reconstruction is observed in distilled water or NH{sub 3} aqueous solution. - Graphical abstract: The microwave-assisted reconstruction of Ni,Al HTlcs with Ni/Al molar ratios 2/1 and 3/1 has been studied. Full recovering of the original layered structure is achieved in short periods of time for the 2/1 in the Na{sub 2}CO{sub 3} solution, but more drastic conditions are necessary for the 3/1 samples and the reconstruction seems not to be completed. Only a partial reconstruction is observed in distilled water or NH{sub 3} aqueous solution.

  15. Microwave-assisted hydrothermal synthesis of zinc oxide particles starting from chloride precursor

    SciTech Connect

    Tseng, Chun-Chieh; Chou, Yu-Hsien; Liu, Chung-Ming; Liu, Yih-Ming; Ger, Ming-Der; Shu, Youn-Yuen

    2012-01-15

    Graphical abstract: Schematic of the mechanism for ZnO nanoparticles obtained by the calcination. Highlights: Black-Right-Pointing-Pointer Nanocrystalline ZnO particles were successfully prepared by a microwave-assisted method. Black-Right-Pointing-Pointer Sponge-like morphology of ZnO change to a net-like structure after thermal treatment. Black-Right-Pointing-Pointer The PL spectra exhibited a nearband-edge emission at 393 nm. -- Abstract: Zinc oxide (ZnO) was synthesized using a microwave assisted hydrothermal (MAH) process based on chloride/urea/water solution and under 800 W irradiation for 5 min. In the bath, Zn{sup 2+} ions reacted with the complex carbonate and hydroxide ions to form zinc carbonate hydroxide hydrate (Zn{sub 4}CO{sub 3}(OH){sub 6}{center_dot}H{sub 2}O), and the conversion from Zn{sub 4}CO{sub 3}(OH){sub 6}{center_dot}H{sub 2}O to ZnO was synchronously achieved by a MAH process. The as-prepared ZnO has a sponge-like morphology. However, the initial sponge-like morphology of ZnO could change to a net-like structure after thermal treatment, and compact nano-scale ZnO particles were finally obtained when the period of thermal treatment increased to 30 min. Pure ZnO nanoparticles was obtained from calcination of loose sponge-like ZnO particles at 500 Degree-Sign C. The analysis of optical properties of these ZnO nanoparticles showed that the intensity of 393 nm emission increased with the calcination temperature because the defects were reduced and the crystallinity was improved.

  16. Microwave-assisted synthesis and optical properties of cuprous oxide micro/nanocrystals

    SciTech Connect

    Sun, Dandan; Du, Yi; Tian, Xiuying; Li, Zhongfu; Chen, Zhongtao; Zhu, Chaofeng

    2014-12-15

    Graphical abstract: Cuprous oxide micro/nanocrystals were fabricated by a facile and green microwave-assisted method using soluble starch as reductant and dispersant. Spheres with the diameter of about 100 and 600 nm, octahedron and truncated octahedron with the edge length of about 0.8–3 μm cuprous oxide micro/nanocrystals were successfully obtained. Microwave heating was proved to be a efficient method and was advantageous to the homogeneous nucleation. Growth mechanism of the prepared Cu{sub 2}O microcrystals were investigated carefully. Furthermore, the optical properties of the prepared cuprous oxide microcrystals were investigated by UV–vis diffuse reflectance spectroscopy, demonstrating that their band gaps of obtained samples were 1.96–2.07 eV, assigned to their different sizes and morphologies. - Abstract: Cuprous oxide micro/nanocrystals were fabricated by a facile and green microwave-assisted method using soluble starch as reductant and dispersant. It was observed that the addition amounts of NaOH had a prominent effect on the morphologies and size of cuprous oxide products, and microwave heating was proved to be a efficient method and was advantageous to the homogeneous nucleation. The as-obtained samples were characterized by X-ray diffraction (XRD), and field-emission scanning electron microscopy (FESEM). The results indicated that the samples were pure cuprous oxide. Spheres with the diameter of about 100 and 600 nm, octahedron and truncated octahedron with the edge length of about 0.8–3 μm cuprous oxide micro/nanocrystals were successfully obtained. Furthermore, the UV–vis diffuse reflectance spectroscopy was used to investigate the optical properties of the prepared cuprous oxide microcrystals, demonstrating that their band gaps of obtained samples were 1.96–2.07 eV, assigned to their different sizes and morphologies.

  17. Microwave assisted synthesis and biomedical potency of salicyloyloxy and 2-methoxybenzoyloxy androstane and stigmastane derivatives.

    PubMed

    Penov Gaši, Katarina M; Djurendić, Evgenija A; Szécsi, Mihály; Gardi, János; Csanádi, János J; Klisurić, Olivera R; Dojčinović-Vujašković, Sanja V; Nikolić, Andrea R; Savić, Marina P; Ajduković, Jovana J; Oklješa, Aleksandar M; Kojić, Vesna V; Sakač, Marija N; Jovanović-Šanta, Suzana S

    2015-02-01

    A convenient microwave assisted solvent free synthesis as well as conventional synthesis of salicyloyloxy and 2-methoxybenzoyloxy androstane and stigmastane derivatives 7-19 from appropriate steroidal precursors 1-6 and methyl salicylate is reported. The microwave assisted synthesis in most cases was more successful regarding reaction time and product yields. It was more environmentally friendly too, compared to the conventional method. The antioxidant activity and cytotoxicity of the synthesized derivatives were evaluated in a series of in vitro tests, as well as their inhibition potency exerted on hydroxysteroid dehydrogenase enzymes (Δ(5)-3βHSD, 17βHSD2 and 17βHSD3). All of the tested compounds were effective in OH radical neutralization, particularly compounds 9, 11 and 14, which exhibited about 100-fold stronger activity than commercial antioxidants BHT and BHA. In DPPH radical scavenging new compounds were effective, but less than reference compounds. 2-Methoxybenzoyl ester 10 exhibited strong cytotoxicity against MDA-MB-231 cells. Most compounds inhibited growth of PC-3 cells, where salicyloyloxy stigmastane derivative 15 showed the best inhibition potency. Compounds 9, 10 and 11 were the best inhibitors of 17βHSD2 enzyme. X-ray structure analysis and molecular mechanics calculations (MMC) were performed for the best cytotoxic agents, compounds 10 and 15. A comparison of crystal and MMC structures of compounds 10 and 15 revealed that their molecules conformations are stable even after releasing of the influence of crystalline field and that the influence of crystal packing on molecular conformation is not predominant. PMID:25541058

  18. Kinetics and Quality of Microwave-Assisted Drying of Mango (Mangifera indica).

    PubMed

    Abano, Ernest Ekow

    2016-01-01

    The effect of microwave-assisted convective air-drying on the drying kinetics and quality of mango was evaluated. Both microwave power and pretreatment time were significant factors but the effect of power was more profound. Increase in microwave power and pretreatment time had a positive effect on drying time. The nonenzymatic browning index of the fresh samples increased from 0.29 to 0.60 while the ascorbic acid content decreased with increase in microwave power and time from 3.84 mg/100g to 1.67 mg/100g. The effective moisture diffusivity varied from 1.45 × 10(-9) to 2.13 × 10(-9) m(2)/s for microwave power range of 300-600 W for 2 to 4 minutes of pretreatment. The Arrhenius type power-dependent activation energy was found to be in the range of 8.58-17.48 W/mm. The fitting of commonly used drying models to the drying data showed the Midilli et al. model as the best. Microwave power of 300 W and pretreatment time of 4 minutes emerged as the optimum conditions prior to air-drying at 7°C. At this ideal condition, the energy savings as a result of microwave application was approximately 30%. Therefore, microwave-assisted drying should be considered for improved heat and mass transfer processes during drying to produce dried mangoes with better quality. PMID:26904667

  19. Kinetics and Quality of Microwave-Assisted Drying of Mango (Mangifera indica)

    PubMed Central

    Abano, Ernest Ekow

    2016-01-01

    The effect of microwave-assisted convective air-drying on the drying kinetics and quality of mango was evaluated. Both microwave power and pretreatment time were significant factors but the effect of power was more profound. Increase in microwave power and pretreatment time had a positive effect on drying time. The nonenzymatic browning index of the fresh samples increased from 0.29 to 0.60 while the ascorbic acid content decreased with increase in microwave power and time from 3.84 mg/100g to 1.67 mg/100g. The effective moisture diffusivity varied from 1.45 × 10−9 to 2.13 × 10−9 m2/s for microwave power range of 300-600 W for 2 to 4 minutes of pretreatment. The Arrhenius type power-dependent activation energy was found to be in the range of 8.58–17.48 W/mm. The fitting of commonly used drying models to the drying data showed the Midilli et al. model as the best. Microwave power of 300 W and pretreatment time of 4 minutes emerged as the optimum conditions prior to air-drying at 7°C. At this ideal condition, the energy savings as a result of microwave application was approximately 30%. Therefore, microwave-assisted drying should be considered for improved heat and mass transfer processes during drying to produce dried mangoes with better quality. PMID:26904667

  20. Room temperature ferromagnetism in undoped and Fe doped ZnO nanorods: Microwave-assisted synthesis

    SciTech Connect

    Limaye, Mukta V.; Singh, Shashi B.; Das, Raja; Poddar, Pankaj; Kulkarni, Sulabha K.

    2011-02-15

    One-dimensional (1D) undoped and Fe doped ZnO nanorods of average length {approx}1 {mu}m and diameter {approx}50 nm have been obtained using a microwave-assisted synthesis. The magnetization (M) and coercivity (H{sub c}) value obtained for undoped ZnO nanorods at room temperature is {approx}5x10{sup -3} emu/g and {approx}150 Oe, respectively. The Fe doped ZnO samples show significant changes in M -H loop with increasing doping concentration. Both undoped and Fe doped ZnO nanorods exhibit a Curie transition temperature (T{sub c}) above 390 K. Electron spin resonance and Moessbauer spectra indicate the presence of ferric ions. The origin of ferromagnetism in undoped ZnO nanorods is attributed to localized electron spin moments resulting from surface defects/vacancies, where as in Fe doped samples is explained by F center exchange mechanism. -- Graphical abstract: Room temperature ferromagnetism has been reported in undoped and Fe doped ZnO nanorods of average length {approx}1 {mu}m and diameter {approx}50 nm. Display Omitted Research Highlights: {yields} Microwave-assisted synthesis of undoped and Fe doped ZnO nanorods. {yields} Observation of room temperature ferromagnetism in undoped and Fe doped ZnO nanorods. {yields} Transition temperature (T{sub c}) obtained in undoped and doped samples is above 390 K. {yields} In undoped ZnO origin of ferromagnetism is explained in terms of defects/vacancies. {yields} Ferromagnetism in Fe doped ZnO is explained by F-center exchange mechanism.

  1. Defect chemistry of phospho-olivine nanoparticles synthesized by a microwave-assisted solvothermal process

    SciTech Connect

    Bridges, Craig A.; Harrison, Katharine L.; Unocic, Raymond R.; Idrobo, Juan-Carlos; Parans Paranthaman, M.; Manthiram, Arumugam

    2013-09-15

    Nanocrystalline LiFePO{sub 4} powders synthesized by a microwave-assisted solvothermal (MW-ST) process have been structurally characterized with a combination of high resolution powder neutron diffraction, synchrotron X-ray diffraction, and aberration-corrected HAADF STEM imaging. A significant level of defects has been found in the samples prepared at 255 and 275 °C. These temperatures are significantly higher than what has previously been suggested to be the maximum temperature for defect formation in LiFePO{sub 4}, so the presence of defects is likely related to the rapid MW-ST synthesis involving a short reaction time (∼5 min). A defect model has been tentatively proposed, though it has been shown that powder diffraction data alone cannot conclusively determine the precise defect distribution in LiFePO{sub 4} samples. The model is consistent with other literature reports on nanopowders synthesized at low temperatures, in which the unit cell volume is significantly reduced relative to defect-free, micron-sized LiFePO{sub 4} powders. - Graphical abstract: Temperature-dependent antisite defect formation has been observed in nanocrystalline LiFePO{sub 4} powders synthesized by a microwave solvothermal process, using high resolution diffraction and STEM imaging. Display Omitted - Highlights: • LiFePO{sub 4} nanopowders synthesized by a microwave-assisted solvothermal process. • Defects directly observed by aberration-corrected HAADF STEM imaging. • Antisite defects present from synthesis at 255 and 275 °C. • Defects present from higher temperature synthesis than previously reported. • Powder diffraction data have been analyzed in detail for various defect models.

  2. Final Technical Report Microwave Assisted Electrolyte Cell for Primary Aluminum Production

    SciTech Connect

    Xiaodi Huang; J.Y. Hwang

    2007-04-18

    This research addresses the high priority research need for developing inert anode and wetted cathode technology, as defined in the Aluminum Industry Technology Roadmap and Inert Anode Roadmap, with the performance targets: a) significantly reducing the energy intensity of aluminum production, b) ultimately eliminating anode-related CO2 emissions, and c) reducing aluminum production costs. This research intended to develop a new electrometallurgical extraction technology by introducing microwave irradiation into the current electrolytic cells for primary aluminum production. This technology aimed at accelerating the alumina electrolysis reduction rate and lowering the aluminum production temperature, coupled with the uses of nickel based superalloy inert anode, nickel based superalloy wetted cathode, and modified salt electrolyte. Michigan Technological University, collaborating with Cober Electronic and Century Aluminum, conducted bench-scale research for evaluation of this technology. This research included three sub-topics: a) fluoride microwave absorption; b) microwave assisted electrolytic cell design and fabrication; and c) aluminum electrowinning tests using the microwave assisted electrolytic cell. This research concludes that the typically used fluoride compound for aluminum electrowinning is not a good microwave absorbing material at room temperature. However, it becomes an excellent microwave absorbing material above 550°C. The electrowinning tests did not show benefit to introduce microwave irradiation into the electrolytic cell. The experiments revealed that the nickel-based superalloy is not suitable for use as a cathode material; although it wets with molten aluminum, it causes severe reaction with molten aluminum. In the anode experiments, the chosen superalloy did not meet corrosion resistance requirements. A nicked based alloy without iron content could be further investigated.

  3. Novel biodegradable polymeric flocculant based on polyacrylamide-grafted tamarind kernel polysaccharide.

    PubMed

    Ghosh, Sandipta; Sen, Gautam; Jha, U; Pal, Sagar

    2010-12-01

    Novel biodegradable polymeric flocculants were produced by conventional redox grafting, microwave-initiated and microwave-assisted grafting of acrylamide to tamarind kernel polysaccharide (TKP). The graft copolymers were characterized by viscometry, elemental analysis, molecular weight determination using SLS analysis, and NMR spectroscopy. The flocculation efficiency of the grafting products in kaolin suspension, municipal sewage wastewater and textile industry wastewater was primarily dependent on the length of the grafted polyacrylamide chain. The flocculant obtained by microwave-assisted grafting method was superior to TKP and polyacrylamide-based commercial flocculant (Rishfloc 226 LV) in flocculation tests. PMID:20702087

  4. Closed vessel miniaturized microwave assisted chelating extraction for determination of trace metals in plant materials

    NASA Astrophysics Data System (ADS)

    Czarnecki, Sezin; Duering, Rolf-Alexander

    2013-04-01

    In recent years, the use of closed vessel microwave assisted extraction (MAE) for plant samples has shown increasing research interest which will probably substitute conventional procedures in the future due to their general disadvantages including consumption of time and solvents. The objective of this study was to demonstrate an innovative miniaturized closed vessel microwave assisted extraction (µMAE) method under the use of EDTA (µMAE-EDTA) to determine metal contents (Cd, Co, Cu, Mn, Ni, Pb, Zn) in plant samples (Lolio-Cynosuretum) by inductively coupled plasma-optical emission spectrometry (ICP-OES). Validation of the method was done by comparison of the results with another miniaturized closed vessel microwave HNO3 method (µMAE-H) and with two other macro scale MAE procedures (MAE-H and MAE-EDTA) which were applied by using a mixture of nitric acid (HNO3) and hydrogen peroxide (H2O2) (MAE-H) and EDTA (MAE-EDTA), respectively. The already established MAE-H method is taken into consideration as a reference validation MAE method for plant material. A conventional plant extraction (CE) method, based on dry ashing and dissolving of the plant material in HNO3, was used as a confidence comparative method. Certified plant reference materials (CRMs) were used for comparison of recovery rates from different extraction protocols. This allowed the validation of the applicability of the µMAE-EDTA procedure. For 36 real plant samples with triplicates each, µMAE-EDTA showed the same extraction yields as the MAE-H in the determination of Cd, Co, Cu, Mn, Ni, Pb, and Zn contents in plant samples. Analytical parameters in µMAE-EDTA should be further investigated and adapted for other metals of interest. By the reduction and elimination of the use of hazardous chemicals in environmental analysis and thus allowing a better understanding of metal distribution and accumulation process in plants and also the metal transfer from soil to plants and into the food chain, µ

  5. Microwave-Assisted Synthesis of a MK2 Inhibitor by Suzuki-Miyaura Coupling for Study in Werner Syndrome Cells

    PubMed Central

    Bagley, Mark C.; Baashen, Mohammed; Chuckowree, Irina; Dwyer, Jessica E.; Kipling, David; Davis, Terence

    2015-01-01

    Microwave-assisted Suzuki-Miyaura cross-coupling reactions have been employed towards the synthesis of three different MAPKAPK2 (MK2) inhibitors to study accelerated aging in Werner syndrome (WS) cells, including the cross-coupling of a 2-chloroquinoline with a 3-pyridinylboronic acid, the coupling of an aryl bromide with an indolylboronic acid and the reaction of a 3-amino-4-bromopyrazole with 4-carbamoylphenylboronic acid. In all of these processes, the Suzuki-Miyaura reaction was fast and relatively efficient using a palladium catalyst under microwave irradiation. The process was incorporated into a rapid 3-step microwave-assisted method for the synthesis of a MK2 inhibitor involving 3-aminopyrazole formation, pyrazole C-4 bromination using N-bromosuccinimide (NBS), and Suzuki-Miyaura cross-coupling of the pyrazolyl bromide with 4-carbamoylphenylboronic acid to give the target 4-arylpyrazole in 35% overall yield, suitable for study in WS cells. PMID:26046488

  6. Microwave-assisted digestion using nitric acid for heavy metals and sulfated ash testing in active pharmaceutical ingredients.

    PubMed

    Pluhácek, T; Hanzal, J; Hendrych, J; Milde, D

    2016-04-01

    The monitoring of inorganic impurities in active pharmaceutical ingredients plays a crucial role in the quality control of the pharmaceutical production. The heavy metals and residue on ignition/sulfated ash methods employing microwave-assisted digestion with concentrated nitric acid have been demonstrated as alternatives to inappropriate compendial methods recommended in United States Pharmacopoeia (USP) and European Pharmacopoeia (Ph. Eur.). The recoveries using the heavy metals method ranged between 89% and 122% for nearly all USP and Ph. Eur. restricted elements as well as the recoveries of sodium sulfate spikes were around 100% in all tested matrices. The proposed microwave-assisted digestion method allowed simultaneous decomposition of 15 different active pharmaceutical ingredients with sample weigh up to 1 g. The heavy metals and sulfated ash procedures were successfully applied to the determination of heavy metals and residue on ignition/sulfated ash content in mycophenolate mofetil, nicergoline and silymarin. PMID:27209695

  7. Crystal quality and optical property of MnWO4 nanoparticles synthesized by microwave-assisted method

    NASA Astrophysics Data System (ADS)

    Van Hanh, Pham; Huy Hoang, Luc; Van Hai, Pham; Van Minh, Nguyen; Chen, Xiang-Bai; Yang, In-Sang

    2013-03-01

    MnWO4 nanoparticles were prepared using a microwave-assisted method followed by low-temperature treatment. The crystal quality and optical property of the MnWO4 nanoparticles were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and ultraviolet-visible (UV-vis) absorption spectroscopy. Our results show that good crystal quality MnWO4 nanoparticles can be prepared by the microwave-assisted method, and best crystal quality nanoparticles can be obtained with synthesizing pH value of 7. Furthermore, by calcination treatments, crystal quality can be further improved with less defect states and the particle size increases when the calcining temperature increases from 150 to 600 °C. In addition, our study shows that the MnWO4 nanoparticles have strong absorption in the visible light region, suggesting that these nanoparticles are promising for photocatalytic applications.

  8. Kinetic study on microwave-assisted esterification of free fatty acids derived from Ceiba pentandra Seed Oil.

    PubMed

    Lieu, Thanh; Yusup, Suzana; Moniruzzaman, Muhammad

    2016-07-01

    Recently, a great attention has been paid to advanced microwave technology that can be used to markedly enhance the biodiesel production process. Ceiba pentandra Seed Oil containing high free fatty acids (FFA) was utilized as a non-edible feedstock for biodiesel production. Microwave-assisted esterification pretreatment was conducted to reduce the FFA content for promoting a high-quality product in the next step. At optimum condition, the conversion was achieved 94.43% using 2wt% of sulfuric acid as catalyst where as 20.83% conversion was attained without catalyst. The kinetics of this esterification reaction was also studied to determine the influence of factors on the rate of reaction and reaction mechanisms. The results indicated that microwave-assisted esterification was of endothermic second-order reaction with the activation energy of 53.717kJ/mol. PMID:27019128

  9. Photocatalytic Decomposition of Methylene Blue Over MIL-53(Fe) Prepared Using Microwave-Assisted Process Under Visible Light Irradiation.

    PubMed

    Trinh, Nguyen Duy; Hong, Seong-Soo

    2015-07-01

    Iron-based MIL-53 crystals with uniform size were successfully synthesized using a microwave-assisted solvothermal method and characterized by XRD, FE-SEM and DRS. We also investigated the photocatalytic activity of MIL-53(Fe) for the decomposition of methylene blue using H2O2 as an electron acceptor. From XRD and SEM results, the fully crystallized MIL-53(Fe) materials were obtained regardless of preparation method. From DRS results, MIL-53(Fe) samples prepared using microwave-assisted process displayed the absorption spectrum up to the visible region and then they showed the high photocatalytic activity under visible light irradiation. The MIL-53(Fe) catalyst prepared by two times microwave irradiation showed the highest activity. PMID:26373158

  10. Microwave assisted esterification of acidified oil from waste cooking oil by CERP/PES catalytic membrane for biodiesel production.

    PubMed

    Zhang, Honglei; Ding, Jincheng; Zhao, Zengdian

    2012-11-01

    The traditional heating and microwave assisted method for biodiesel production using cation ion-exchange resin particles (CERP)/PES catalytic membrane were comparatively studied to achieve economic and effective method for utilization of free fatty acids (FFAs) from waste cooking oil (WCO). The optimal esterification conditions of the two methods were investigated and the experimental results showed that microwave irradiation exhibited a remarkable enhanced effect for esterification compared with that of traditional heating method. The FFAs conversion of microwave assisted esterification reached 97.4% under the optimal conditions of reaction temperature 60°C, methanol/acidified oil mass ratio 2.0:1, catalytic membrane (annealed at 120°C) loading 3g, microwave power 360W and reaction time 90min. The study results showed that it is a fast, easy and green way to produce biodiesel applying microwave irradiation. PMID:22940301

  11. Ultra fast microwave-assisted leaching for the recovery of copper and tellurium from copper anode slime

    NASA Astrophysics Data System (ADS)

    Ma, Zhi-yuan; Yang, Hong-ying; Huang, Song-tao; Lü, Yang; Xiong, Liu

    2015-06-01

    The decomposition of copper anode slime heated by microwave energy in a sulfuric acid medium was investigated. Leaching experiments were carried out in a multi-mode cavity with microwave assistance. The leaching process parameters were optimized using response surface methodology (RSM). Under the optimized conditions, the leaching efficiencies of copper and tellurium were 99.56% ± 0.16% and 98.68% ± 0.12%, respectively. Meanwhile, a conventional leaching experiment was performed in order to evaluate the influence of microwave radiation. The mechanism of microwave-assisted leaching of copper anode slime was also investigated. In the results, the microwave technology is demonstrated to have a great potential to improve the leaching efficiency and reduce the leaching time. The enhanced recoveries of copper and tellurium are believed to result from the presence of a temperature gradient due to the shallow microwave penetration depth and the superheating at the solid-liquid interface.

  12. One-pot microwave-assisted protocol for the synthesis of substituted 2-amino-1H-imidazoles.

    PubMed

    Ermolat'ev, D S; Savaliya, B; Shah, A; Van der Eycken, E

    2011-05-01

    An efficient microwave-assisted one-pot two-step protocol was developed for the construction of disubstituted 2-amino-1H-imidazoles. This process involves the sequential formation of 2,3-dihydro-2-hydroxyimidazo[1,2-a]pyrimidinium salts from readily available 2-aminopyrimidines and α-bromoketones, followed by cleavage of the pyrimidine ring with hydrazine. PMID:20740313

  13. The microwave adsorption behavior and microwave-assisted heteroatoms doping of graphene-based nano-carbon materials

    PubMed Central

    Tang, Pei; Hu, Gang; Gao, Yongjun; Li, Wenjing; Yao, Siyu; Liu, Zongyuan; Ma, Ding

    2014-01-01

    Microwave-assisted heating method is used to treat graphite oxide (GO), pyrolytic graphene oxide (PGO) and hydrogen-reduced pyrolytic graphene oxide (HPGO). Pure or doped graphene are prepared in the time of minutes and a thermal deoxygenization reduction mechanism is proposed to understand their microwave adsorption behaviors. These carbon materials are excellent catalysts in the reduction of nitrobenzene. The defects are believed to play an important role in the catalytic performance. PMID:25109492

  14. The microwave adsorption behavior and microwave-assisted heteroatoms doping of graphene-based nano-carbon materials

    NASA Astrophysics Data System (ADS)

    Tang, Pei; Hu, Gang; Gao, Yongjun; Li, Wenjing; Yao, Siyu; Liu, Zongyuan; Ma, Ding

    2014-08-01

    Microwave-assisted heating method is used to treat graphite oxide (GO), pyrolytic graphene oxide (PGO) and hydrogen-reduced pyrolytic graphene oxide (HPGO). Pure or doped graphene are prepared in the time of minutes and a thermal deoxygenization reduction mechanism is proposed to understand their microwave adsorption behaviors. These carbon materials are excellent catalysts in the reduction of nitrobenzene. The defects are believed to play an important role in the catalytic performance.

  15. Efficient microwave-assisted one-pot preparation of angular 2,2-dimethyl-2H-chromone containing compounds

    PubMed Central

    Zhou, Ting; Shi, Qian; Lee, Kuo Hsing

    2010-01-01

    A novel and efficient microwave-assisted one-pot reaction was developed to synthesize angular 2,2-dimethyl-2H-chromone containing compounds, which is the first and key step in the synthesis of potent DCK and DCP anti-HIV agents. The newly developed microwave synthesis conditions dramatically shortened the reaction time from 2 days to 4 hours with improved yields. PMID:20936082

  16. Microwave-assisted total digestion of sulphide ores for multi-element analysis.

    PubMed

    Al-Harahsheh, M; Kingman, S; Somerfield, C; Ababneh, F

    2009-04-01

    A new two-stage microwave-assisted digestion procedure using concentrated HNO(3), HCl, HF and H(3)BO(3) has been developed for the chemical analysis of major and trace elements in sulphide ore samples prior to inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis. In the first stage 0.2 g of the certified reference material (CRM) sample was digested with a combination of acids (HNO(3), HCl, and HF) in a closed Teflon vessel and heated in the microwave to 200 degrees C for 30 min. After cooling, H(3)BO(3) was added and the vessel was reheated to 170 degrees C for 15 min. The precision of the method was checked by comparing the results against six certified reference materials. The analytical results obtained were in good agreement with the certified values, in most cases the recoveries were in the range 95-105%. Based on at least 17 replicates of sample preparation and analysis, the precision of the method was found to be < or = 5%. PMID:19298886

  17. A First Microwave-Assisted Synthesis of a New Class of Purine and Guanine Thioglycoside Analogs.

    PubMed

    Elgemeie, Galal; Abu-Zaied, Mamdouh; Hebishy, Ali; Abbas, Nermen; Hamed, Mai

    2016-09-01

    A first microwave-assisted synthesis of a new class of novel purine thioglycoside analogs from readily available starting materials has been described. The key step of this protocol is the formation of sodium pyrazolo[1,5-a]pyrimidine-7-thiolate and 7-mercaptopyrazolo[1,5-a]pyrimidine derivatives via condensation of 5-amino-1H-pyrazoles with sodium 2,2-dicyanoethene-1,1-bis(thiolate) salts or 2-(dimercaptomethylene)malononitrile, respectively, under microwave irradiation, followed by coupling with halo sugars to give the corresponding purine thioglycoside analogs. The obtained purines and purines thioglycosides derivatives were evaluated in vitro against lung (A549), colon (HCT116), liver (HEPG2), and prostate (PC3) cancer cell lines. Some of these compounds (5b, 5d, 5f, and 9a-d) exhibited little potency toward the four cell lines. On the other hand, compound 5a elicited higher cytotoxicity on both prostate (PC3) and colon (HCT116), respectively, while it was found moderate on lung (A549), and inactive on liver (HEPG2). Moreover, compound 5c was found moderate with LC50 values 52.0-88.9 μM for almost all the cell lines. PMID:27556784

  18. Development of continuous microwave-assisted protein digestion with immobilized enzyme.

    PubMed

    Chen, Zhengyi; Li, Yongle; Lin, Shuhai; Wei, Meiping; Du, Fuyou; Ruan, Guihua

    2014-03-01

    In this study, an easy and efficiency protein digestion method called continuous microwave-assisted protein digestion (cMAED) with immobilized enzyme was developed and applied for proteome analysis by LC-MS(n). Continuous microwave power outputting was specially designed and applied. Trypsin and bromelain were immobilized onto magnetic micropheres. To evaluate the method of cMAED, bovine serum albumin (BSA) and protein extracted from ginkgo nuts were used as model and real protein sample to verify the digestion efficiency of cMAED. Several conditions including continuous microwave power, the ratio of immobilized trypsin/BSA were optimized according to the analysis of peptide fragments by Tricine SDS-PAGE and LC-MS(n). Subsequently, the ginkgo protein was digested with the protocols of cMAED, MAED and conventional heating enzymatic digestion (HED) respectively and the LC-MS(n) profiles of the hydrolysate was compared. Results showed that cMAED combined with immobilized enzyme was a fast and efficient digestion method for protein digestion and microwave power tentatively affected the peptide producing. The cMAED method will be expanded for large-scale preparation of bioactive peptides and peptide analysis in biological and clinical research. PMID:24530398

  19. Numerical simulation of an industrial microwave assisted filter dryer: criticality assessment and optimization.

    PubMed

    Leonelli, Cristina; Veronesi, Paolo; Grisoni, Fabio

    2007-01-01

    Industrial-scale filter dryers, equipped with one or more microwave input ports, have been modelled with the aim of detecting existing criticalities, proposing possible solutions and optimizing the overall system efficiency and treatment homogeneity. Three different loading conditions have been simulated, namely the empty applicator, the applicator partially loaded by both a high-loss and low loss load whose dielectric properties correspond to the one measured on real products. Modeling results allowed for the implementation of improvements to the original design such as the insertion of a wave guide transition and a properly designed pressure window, modification of the microwave inlet's position and orientation, alteration of the nozzles' geometry and distribution, and changing of the cleaning metallic torus dimensions and position. Experimental testing on representative loads, as well as in production sites, allowed for the confirmation of the validity of the implemented improvements, thus showing how numerical simulation can assist the designer in removing critical features and improving equipment performances when moving from conventional heating to hybrid microwave-assisted processing. PMID:18350999

  20. Rapid preparation of functional polysaccharides from Pyropia yezoensis by microwave-assistant rapid enzyme digest system.

    PubMed

    Lee, Ji-Hyeok; Kim, Hyung-Ho; Ko, Ju-Young; Jang, Jun-Ho; Kim, Gwang-Hoon; Lee, Jung-Suck; Nah, Jae-Woon; Jeon, You-Jin

    2016-11-20

    This study describes a simple preparation of functional polysaccharides from Pyropia yezoensis using a microwave-assistant rapid enzyme digest system (MAREDS) with various carbohydrases, and evaluates their antioxidative effects. Polysaccharide hydrolysates were prepared using MAREDS under different hydrolytic conditions of the carbohydrases and microwave powers. Polysaccharides less than 10kDa (Low molecular weight polysaccharides, LMWP, ≤10kDa) were efficiently obtained using an ultrafiltration (molecular weight cut-off of 10kDa). MAREDS increases AMG activation via an increased degree of hydrolysis; the best AMG hydrolysate was prepared using a 10:1 ratio of substrate to enzyme for 2h in MAREDS with 400W. LMWP consisted of galactose (27.3%), glucose (64.5%), and mannose (8.3%) from the AMG hydrolysate had stronger antioxidant effects than the high molecular weight polysaccharides (>10kDa). We rapidly prepared functional LMWPs by using MAREDS with carbohydrases, and suggest that LMWP might be potentially a valuable algal polysaccharide antioxidant. PMID:27561523

  1. Microwave-assisted synthesis of 4'-azaflavones and their N-alkyl derivatives with biological activities.

    PubMed

    Yaşar, Ahmet; Akpinar, Kurtuluş; Burnaz, Nesibe Arslan; Küçük, Murat; Karaoğlu, Sengül Alpay; Doğan, Neşe; Yayli, Nurettin

    2008-05-01

    4'-Azaflavone (=2-(pyridin-4-yl)-4H-1-benzopyran-4-one; 4) and 3-[(pyridin-4-yl)methyl]-4'-azaflavone (5) were synthesized by a simple environmentally friendly microwave-assisted one-pot method through the cyclization of 3-hydroxy-1-(2-hydroxyphenyl)-3-(pyridin-4-yl)propan-1-one (1), (E)-2'-hydroxy-4-azachalcone (2; chalcone=1,3-diphenylprop-2-en-1-one), and 2'-hydroxy-2-[(hydroxy)(pyridin-4-yl)methyl]-4''-azachalcone (3) under solventless conditions using silica-supported NaHSO(4), followed by treatment with base. In addition, N-alkyl-substituted 4'-azaflavonium bromides 6 and 7 were prepared from compounds 4 and 5, respectively. The antimicrobial and antioxidant activities of compounds 1-7 were tested. The N-alkyl-substituted 4'-azaflavonium bromides 6 and 7 showed high antimicrobial activity against the Gram-positive bacteria and the fungus tested, with MIC values close to those of reference antimicrobials ampicilline and fluconazole. The alkylated compounds 6 and 7 also showed a good antioxidant character in the two antioxidant methods, DPPH (=1,1-diphenyl-2-picrylhydrazyl) radical-scavenging and ferric reducing/antioxidant power (FRAP) tests. PMID:18493968

  2. Microwave-assisted ultrafast synthesis of silver nanoparticles for detection of Hg2 +

    NASA Astrophysics Data System (ADS)

    Ma, Yun; Pang, Yuehong; Liu, Fei; Xu, Hanqi; Shen, Xiaofang

    2016-01-01

    Silver nanoparticles (AgNPs) were successfully prepared in aqueous solution by a one-pot procedure based on a rapid microwave-assisted green approach. L-Cysteine acted as a capping agent in the process of AgNP formation. The structural and morphological characteristics of the L-cysteine-capped AgNPs were investigated by the UV-vis, CD, FL, FTIR, XRD, TEM and EDX analysis. It was found that the well-dispersed crystalline AgNPs were formed after irradiation for 90 s and had sphere-like morphology. Such strategy may facilitate new ways to the synthesis of other metal nanoparticles, such as Au, Pt and Pd. In addition, the synthesized AgNPs were developed as a platform for the detection of Hg2 + and showed a high sensitivity on the order of 1 × 10- 8 M. This sensing system could discriminate Hg2 + from a wide range of cations (Ca2 +, Ba2 +, Mn2 +, etc.). The selectivity and sensitivity of AgNPs indicated its potential use as a sensor for Hg2 + detection in the ecosystems.

  3. Enhancement of biomass conversion in catalytic fast pyrolysis by microwave-assisted formic acid pretreatment.

    PubMed

    Feng, Yu; Li, Guangyu; Li, Xiangyu; Zhu, Ning; Xiao, Bo; Li, Jian; Wang, Yujue

    2016-08-01

    This study investigated microwave-assisted formic acid (MW-FA) pretreatment as a possible way to improve aromatic production from catalytic fast pyrolysis (CFP) of lignocellulosic biomass. Results showed that short duration of MW-FA pretreatment (5-10min) could effectively disrupt the recalcitrant structure of beech wood and selectively remove its hemicellulose and lignin components. This increased the accessibility of cellulose component of biomass to subsequent thermal conversion in CFP. Consequently, the MW-FA pretreated beech wood produced 14.0-28.3% higher yields (26.4-29.8C%) for valuable aromatic products in CFP than the untreated control (23.2C%). In addition, the yields of undesired solid residue (char/coke) decreased from 33.1C% for the untreated control to 28.6-29.8C% for the MW-FA pretreated samples. These results demonstrate that MW-FA pretreatment can provide an effective way to improve the product distribution from CFP of lignocellulose. PMID:27176672

  4. Efficient Catalytic Activity BiFeO3 Nanoparticles Prepared by Novel Microwave-Assisted Synthesis.

    PubMed

    Zou, Jing; Gong, Wanyun; Ma, Jinai; Li, Lu; Jiang, Jizhou

    2015-02-01

    A novel microwave-assisted sol-gel method was applied to the synthesis of the single-phase perovskite bismuth ferrite nanoparticles (BFO NPs) with the mean diameter ca. 73.7 nm. The morphology was characterized by scanning electron microscope (SEM). The X-ray diffraction (XRD) revealed the rhombohedral phase with R3c space group. The weak ferromagnetic behavior at room temperature was affirmed by the vibrating sample magnetometer (VSM). According to the UV-vis diffuse reflectance spectrum (UV-DSR), the band gap energy of BFO NPs was determined to be 2.18 eV. The electrochemical activity was evaluated by BFO NPs-chitosan-glassy carbon electrode (BFO-CS-GCE) sensor for detection of p-nitrophenol contaminants. The material showed an efficient oxidation catalytic activity by degrading methylene blue (MB). It was found that the degradation efficiency of 10 mg L-1 MB at pH 6.0 was above 90.9% after ultrasound- and microwave-combined-assisted (US-MW) irradiation for 15 min with BFO NPs as catalyst and H202 as oxidant. A possible reaction mechanism of degradation of MB was also proposed. PMID:26353647

  5. Microwave-assisted synthesis of sensitive silver substrate for surface-enhanced Raman scattering spectroscopy.

    PubMed

    Xia, Lixin; Wang, Haibo; Wang, Jian; Gong, Ke; Jia, Yi; Zhang, Huili; Sun, Mengtao

    2008-10-01

    A sensitive silver substrate for surface-enhanced Raman scattering (SERS) spectroscopy is synthesized under multimode microwave irradiation. The microwave-assisted synthesis of the SERS-active substrate was carried out in a modified domestic microwave oven of 2450 MHz, and the reductive reaction was conducted in a polypropylene container under microwave irradiation with a power of 100 W for 5 min. Formaldehyde was employed as both the reductant and microwave absorber in the reductive process. The effects of different heating methods (microwave dielectric and conventional) on the properties of the SERS-active substrates were investigated. Samples obtained with 5 min of microwave irradiation at a power of 100 W have more well-defined edges, corners, and sharper surface features, while the samples synthesized with 1 h of conventional heating at 40 degrees C consist primarily of spheroidal nanoparticles. The SERS peak intensity of the approximately 1593 cm(-1) band of 4-mercaptobenzoic acid adsorbed on silver nanoparticles synthesized with 5 min of microwave irradiation at a power of 100 W is about 30 times greater than when it is adsorbed on samples synthesized with 1 h of conventional heating at 40 degrees C. The results of quantum chemical calculations are in good agreement with our experimental data. This method is expected to be utilized for the synthesis of other metal nanostructural materials. PMID:19045112

  6. Microwave-assisted synthesis of sensitive silver substrate for surface-enhanced Raman scattering spectroscopy

    NASA Astrophysics Data System (ADS)

    Xia, Lixin; Wang, Haibo; Wang, Jian; Gong, Ke; Jia, Yi; Zhang, Huili; Sun, Mengtao

    2008-10-01

    A sensitive silver substrate for surface-enhanced Raman scattering (SERS) spectroscopy is synthesized under multimode microwave irradiation. The microwave-assisted synthesis of the SERS-active substrate was carried out in a modified domestic microwave oven of 2450MHz, and the reductive reaction was conducted in a polypropylene container under microwave irradiation with a power of 100W for 5min. Formaldehyde was employed as both the reductant and microwave absorber in the reductive process. The effects of different heating methods (microwave dielectric and conventional) on the properties of the SERS-active substrates were investigated. Samples obtained with 5min of microwave irradiation at a power of 100W have more well-defined edges, corners, and sharper surface features, while the samples synthesized with 1h of conventional heating at 40°C consist primarily of spheroidal nanoparticles. The SERS peak intensity of the ˜1593cm-1 band of 4-mercaptobenzoic acid adsorbed on silver nanoparticles synthesized with 5min of microwave irradiation at a power of 100W is about 30 times greater than when it is adsorbed on samples synthesized with 1h of conventional heating at 40°C. The results of quantum chemical calculations are in good agreement with our experimental data. This method is expected to be utilized for the synthesis of other metal nanostructural materials.

  7. Facile Microwave-Assisted Synthesis of Klockmannite CuSe Nanosheets and Their Exceptional Electrical Properties

    PubMed Central

    Liu, Yong-Qiang; Wang, Feng-Xia; Xiao, Yan; Peng, Hong-Dan; Zhong, Hai-Jian; Liu, Zheng-Hui; Pan, Ge-Bo

    2014-01-01

    Klockmannite copper selenide nanosheets (CuSe NSs) are synthesized by a facile microwave-assisted method and fully characterized. The nanosheets have smooth surface and hexagonal shape. The lateral size is 200–500 nm × 400–800 nm and the thickness is 55 ± 20 nm. The current-voltage characteristics of CuSe NS films show unique Ohmic and high-conducting behaviors, comparable to the thermally-deposited gold electrode. The high electrical conductivity of CuSe NSs implies their promising applications in printed electronics and nanodevices. Moreover, the local electrical variation is observed, for the first time, within an individual CuSe NS at low bias voltages (0.1 ~ 3 V) by conductive atomic force microscopy (C-AFM). This is ascribed to the quantum size effect of NS and the presence of Schottky barrier. In addition, the influence of the molar ratio of Cu2+/SeO2, reaction temperature, and reaction time on the growth of CuSe NSs is explored. The template effect of oleylamine and the intrinsic crystal nature of CuSe NS are proposed to account for the growth of hexagonal CuSe NSs. PMID:25104467

  8. Parameters affecting microwave-assisted extraction of organophosphorus pesticides from agricultural soil.

    PubMed

    Fuentes, Edwar; Báez, María E; Labra, Ronnie

    2007-10-26

    This work describes an optimised method for the determination of six representative organophosphorus pesticides (OPPs) (diazinon, parathion, methyl pirimiphos, methyl parathion, ethoprophos, and fenitrothion) in agricultural soils. The method is based on microwave-assisted extraction using a water-methanol modified mixture for desorption and simultaneous partitioning on n-hexane (MAEP), together with gas chromatography-flame photometric detection (GC-FPD). To improve GC-FPD signals (peak intensity and shape) olive oil was used effectively as a "matrix mimic". The optimisation of the extraction method was achieved in two steps: an initial approach through experimental design and principal component analysis where recovery of compounds using a water-methanol mixture ranged from 54 to 77%, and the second one by studying the addition of KH2PO4 to the extracting solution where recoveries were significantly increased, molecular replacing of OPPs from adsorption sites by phosphate being the probable extraction mechanism. Under optimised conditions, recoveries of pesticides from different soils were higher than 73%, except for methyl parathion in some soils, with SD equal or lower than 11% and detection limits ranging from 0.004 to 0.012 microg g(-1). The proposed method was used to determine OPPs in soil samples from different agricultural zones of Chile. PMID:17870081

  9. Microwave-assisted synthesis of sensitive silver substrate for surface-enhanced Raman scattering spectroscopy

    SciTech Connect

    Xia Lixin; Wang Haibo; Wang Jian; Gong Ke; Jia Yi; Zhang Huili; Sun Mengtao

    2008-10-07

    A sensitive silver substrate for surface-enhanced Raman scattering (SERS) spectroscopy is synthesized under multimode microwave irradiation. The microwave-assisted synthesis of the SERS-active substrate was carried out in a modified domestic microwave oven of 2450 MHz, and the reductive reaction was conducted in a polypropylene container under microwave irradiation with a power of 100 W for 5 min. Formaldehyde was employed as both the reductant and microwave absorber in the reductive process. The effects of different heating methods (microwave dielectric and conventional) on the properties of the SERS-active substrates were investigated. Samples obtained with 5 min of microwave irradiation at a power of 100 W have more well-defined edges, corners, and sharper surface features, while the samples synthesized with 1 h of conventional heating at 40 deg. C consist primarily of spheroidal nanoparticles. The SERS peak intensity of the {approx}1593 cm{sup -1} band of 4-mercaptobenzoic acid adsorbed on silver nanoparticles synthesized with 5 min of microwave irradiation at a power of 100 W is about 30 times greater than when it is adsorbed on samples synthesized with 1 h of conventional heating at 40 deg. C. The results of quantum chemical calculations are in good agreement with our experimental data. This method is expected to be utilized for the synthesis of other metal nanostructural materials.

  10. Histology-directed microwave assisted enzymatic protein digestion for MALDI MS analysis of mammalian tissue.

    PubMed

    Taverna, Domenico; Norris, Jeremy L; Caprioli, Richard M

    2015-01-01

    This study presents on-tissue proteolytic digestion using a microwave irradiation and peptide extraction method for in situ analysis of proteins from spatially defined regions of a tissue section. The methodology utilizes hydrogel discs (1 mm diameter) embedded with trypsin solution. The enzyme-laced hydrogel discs are applied to a tissue section, directing enzymatic digestion to a spatially confined area of the tissue. By applying microwave radiation, protein digestion is performed in 2 min on-tissue, and the extracted peptides are then analyzed by matrix assisted laser desorption/ionization mass spectrometry (MALDI MS) and liquid chromatography tandem mass spectrometry (LC-MS/MS). The reliability and reproducibility of the microwave assisted hydrogel mediated on-tissue digestion is demonstrated by the comparison with other on-tissue digestion strategies, including comparisons with conventional heating and in-solution digestion. LC-MS/MS data were evaluated considering the number of identified proteins as well as the number of protein groups and distinct peptides. The results of this study demonstrate that rapid and reliable protein digestion can be performed on a single thin tissue section while preserving the relationship between the molecular information obtained and the tissue architecture, and the resulting peptides can be extracted in sufficient abundance to permit analysis using LC-MS/MS. This approach will be most useful for samples that have limited availability but are needed for multiple analyses, especially for the correlation of proteomics data with histology and immunohistochemistry. PMID:25427280

  11. ZnS nanosheets: Egg albumin and microwave-assisted synthesis and optical properties

    NASA Astrophysics Data System (ADS)

    Tian, Xiuying; Wen, Jin; Hu, Jilin; Chen, Zhanjun; Wang, Shumei; Peng, Hongxia; Li, Jing

    2016-09-01

    ZnS nanosheets were prepared via egg albumin and microwave-assisted method. The phases, crystalline lattice structures, morphologies, chemical and optical properties were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), field-emission scanning electron microscope(FE-SEM), selected area electron diffraction (SAED), Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy and fluorescence(FL) spectrometer and growth mechanism of ZnS nanosheets was investigated. The results showed that all samples were pure cubic zinc blende with polycrystalline structure. The width of ZnS nanosheets with a rectangular nanostructure was in the range of 450-750 nm. The chemical interaction existed between egg albumin molecules and ZnS nanoparticles via the amide/carboxylate group. The band gap value calculated was 3.72 eV. The band at around 440 nm was attributed to the sulfur vacancies of the ZnS nanosheets. With increasing volumes of egg albumin, the photoluminescence (PL) intensity of ZnS samples firstly increased and then decreased, attributed to concentration quenching.

  12. The Formation of Nanocrystalline Diamond Coating on WC Deposited by Microwave Assisted Plasma CVD

    NASA Astrophysics Data System (ADS)

    Toff, M. R. M.; Hamzah, E.; Purniawan, A.

    2010-03-01

    Diamond is one form of carbon structure. The extreme hardness and high chemical resistant of diamond coatings determined that many works on this area relate to coated materials for tribological applications in biomedicine, as mechanical seals or cutting tools for hard machining operations. In the work, nanocrystalline diamond (NCD) coated tungsten carbide (WC) have been deposited by microwave assisted plasma chemical vapor deposition (MAPCVD) from CH4/H2 mixtures. Morphology of NCD was investigated by using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The quality of NCD is defined as ratio between diamond and non diamond and also full width at half maximum (FWHM) was determined using Raman spectra. The result found that the NCD structure can be deposited on WC surface using CH4/H2 gas mixture with grain size ˜20 nm to 100 nm. Increase %CH4 concentration due to increase the nucleation of NCD whereas decrease the quality of diamond. Based on Raman spectra, the quality of NCD is in the range ˜98.82-99.01% and 99.56-99.75% for NCD and microcrystalline (MCD), respectively. In addition, FWHM of NCD is high than MCD in the range of 8.664-62.24 cm-1 and 4.24-5.05 cm-1 for NCD and MCD respectively that indicate the crystallineity of NCD is smaller than MCD.

  13. Microwave-assisted extraction and mild saponification for determination of organochlorine pesticides in oyster samples.

    PubMed

    Carro, N; García, I; Ignacio, M-C; Llompart, M; Yebra, M-C; Mouteira, A

    2002-10-01

    A sample-preparation procedure (extraction and saponification) using microwave energy is proposed for determination of organochlorine pesticides in oyster samples. A Plackett-Burman factorial design has been used to optimize the microwave-assisted extraction and mild saponification on a freeze dried sample spiked with a mixture of aldrin, endrin, dieldrin, heptachlor, heptachorepoxide, isodrin, transnonachlor, p, p'-DDE, and p, p'-DDD. Six variables: solvent volume, extraction time, extraction temperature, amount of acetone (%) in the extractant solvent, amount of sample, and volume of NaOH solution were considered in the optimization process. The results show that the amount of sample is statistically significant for dieldrin, aldrin, p, p'-DDE, heptachlor, and transnonachlor and solvent volume for dieldrin, aldrin, and p, p'-DDE. The volume of NaOH solution is statistically significant for aldrin and p, p'-DDE only. Extraction temperature and extraction time seem to be the main factors determining the efficiency of extraction process for isodrin and p, p'-DDE, respectively. The optimized procedure was compared with conventional Soxhlet extraction. PMID:12373408

  14. Microwave-assisted polyol synthesis of PtCu/carbon nanotube catalysts for electrocatalytic oxygen reduction

    NASA Astrophysics Data System (ADS)

    El-Deeb, Heba; Bron, Michael

    2015-02-01

    PtCu/CNT alloy electrocatalysts were prepared by microwave assisted polyol synthesis. The influence of preparation pH and the presence of polyvinylpyrrolidone (PVP) as stabilizer on catalysts nanostructure and activity towards electrocatalytic oxygen reduction was evaluated. The catalysts were alloyed at 400-600 °C for 6 h in reductive atmosphere, and characterized by TEM and XRD. The XRD patterns display a positive shift in 2θ of the Pt 111 peak, which is a good evidence for Pt-Cu alloy formation. Alloy nanoparticles already form at temperatures as low as 400 °C. Highly agglomerated PtCu nanoparticles were obtained in the absence of PVP while PVP addition resulted in dispersed and uniform nanoparticles with a mean particle size of 3.7 nm. Such small particles are a result of the considerably low temperature used during the heat treatment/alloying step. However, while Pt is nearly completely deposited on the CNTs, only smaller fractions of Cu are found in the final catalyst. A high extent of agglomeration was also noticed when the pH during polyol synthesis was increased, which is attributed to Cu-hydroxides precipitation. Pt-Cu core shell catalysts were obtained after voltammetric dealloying. Catalyst prepared at higher pH in the presence of PVP display the highest electrocatalytic activity.

  15. Defect chemistry of phospho-olivine nanoparticles synthesized by a microwave-assisted solvothermal process

    NASA Astrophysics Data System (ADS)

    Bridges, Craig A.; Harrison, Katharine L.; Unocic, Raymond R.; Idrobo, Juan-Carlos; Parans Paranthaman, M.; Manthiram, Arumugam

    2013-09-01

    Nanocrystalline LiFePO4 powders synthesized by a microwave-assisted solvothermal (MW-ST) process have been structurally characterized with a combination of high resolution powder neutron diffraction, synchrotron X-ray diffraction, and aberration-corrected HAADF STEM imaging. A significant level of defects has been found in the samples prepared at 255 and 275 °C. These temperatures are significantly higher than what has previously been suggested to be the maximum temperature for defect formation in LiFePO4, so the presence of defects is likely related to the rapid MW-ST synthesis involving a short reaction time (˜5 min). A defect model has been tentatively proposed, though it has been shown that powder diffraction data alone cannot conclusively determine the precise defect distribution in LiFePO4 samples. The model is consistent with other literature reports on nanopowders synthesized at low temperatures, in which the unit cell volume is significantly reduced relative to defect-free, micron-sized LiFePO4 powders.

  16. Microwave-assisted direct liquefaction of Ulva prolifera for bio-oil production by acid catalysis.

    PubMed

    Zhuang, Yingbin; Guo, Jingxue; Chen, Limei; Li, Demao; Liu, Junhai; Ye, Naihao

    2012-07-01

    Production of bio-oil by microwave-assisted direct liquefaction (MADL) of Ulva prolifera was investigated, and the bio-oil was analyzed by elementary analysis, Fourier transform infrared spectroscopic analysis (FT-IR), and gas chromatography-mass spectrometry (GC-MS). The results indicate that the liquefaction yield is influenced by the microwave power, liquefaction temperature, liquefaction time, catalyst content, solvent-to-feedstock ratio and moisture content. The maximum liquefaction yield of U. prolifera (moisture content of 8%) was 84.81%, which was obtained under microwave power of 600 W for 30 min at 180 °C with solvent-to-feedstock ratio of 16:1 and 6% H(2)SO(4). The bio-oil was composed of benzenecarboxylic acid, diethyl phthalate, long-chain fatty acids (C(13) to C(18)), fatty acid methyl esters and water. The results suggest that U. prolifera is a viable eco-friendly, green feedstock substitute for biofuels and chemicals production. PMID:22609667

  17. Microwave-assisted extraction: Application to the determination of emerging pollutants in solid samples.

    PubMed

    Sanchez-Prado, Lucia; Garcia-Jares, Carmen; Llompart, Maria

    2010-04-16

    Flame retardants, surfactants, pharmaceutical and personal care products, among other compounds, have been the object of numerous environmental studies. In this chapter, the application of microwave-assisted extraction (MAE) in the development of analytical methods for several groups of organic compounds with growing concern as emerging pollutants has been considered. Compared to other extraction techniques, optimization of MAE experimental conditions is rather easy owing to the low number of influential parameters (i.e. matrix moisture, nature of the solvent, time, power, and temperature in closed vessels). The great reduction in the extraction time and solvent consumption, as well as the possibility of performing multiple extractions, increasing the sample throughput, can also be highlighted among MAE advantages. In summary, the study of several applications of MAE to environmental problems demonstrates that this technique constitutes a good alternative for the determination of organic compounds in environmental samples. It can be used as a rapid screening tool, and also to obtain detailed information on the sources, behaviour and fate of emerging pollutants in environmental matrices. PMID:20038465

  18. Wastewater standards and extraction chemistry in validation of microwave-assisted EPA method 3015A

    SciTech Connect

    Link, D.D.; Walter, P.J.; Kingston, H.M. . Dept. of Chemistry and Biochemistry)

    1999-07-15

    The difficulties associated with the control and transfer of environmental leach methods are discussed. Optimized EPA Method 3015A, a microwave-assisted leach of wastewater and drinking water matrices and aqueous extracts, is evaluated. The option to add HCl in addition to HNO[sub 3] provides better complexation and recovery of certain metals that are regulated by the Resource Conservation and Recovery Act (RCRA) than the original HNO[sub 3]-only Method 3015. Also discussed is the preparation and appropriate use of simulated wastewater standards. Standard reference materials for a wastewater matrix are unavailable, and this novel approach provides NIST-traceability of results for the first time on this matrix type. Leach concentrations from these simulated standards were determined using both the 5 mL HNO[sub 3] and the 4 mL HNO[sub 3] and 1 mL HCl leach options of new Method 3015A. Validation of the new mixed-acid option of Method 3015A has been provided by evaluating its performance on the 23 elements for which original Method 3015 was validated. In addition, validation is provided for boron, mercury, and strontium, elements that were not validated in original Method 3015. Method 3015A has been developed into a method capable of evaluating 26 elements in a single, efficient, 20-min procedure.

  19. Microwave assisted leaching and electrochemical recovery of copper from printed circuit boards of computer waste

    NASA Astrophysics Data System (ADS)

    Ivǎnuş, R. C.; ǎnuş, D., IV; Cǎlmuc, F.

    2010-06-01

    Due to the rapid technological progress, the replacement of electronic equipment is very often necessary, leading to huge amounts that end up as waste. In addition, waste electrical and electronic equipment (WEEE) contains metals of high commercial value and others that are supposed to be hazardous for the environment. Consequently, WEEE could be considered as a significant source for recovery of nonferrous metals. Among these wastes, computers appear to be distinctive, as far as further exploitation is concerned. The most ″useful″ parts of the computers are the printed circuit boards that contain many metals of interest. A study on microwave assisted electronic scrap (printed circuit boards of computer waste - PCBs) leaching was carried out with a microwave hydrothermal reactor. The leaching was conducted with thick slurries (50-100 g/L). The leaching media is a mixed solution of CuCl2 and NaCl. Preliminary electrolysis from leaching solution has investigated the feasibility of electrodeposition of copper. The results were discussed and compared with the conventional leaching method and demonstrated the potential for selective extraction of copper from PCBs.

  20. Optimization of microwave assisted extraction of pectin from sour orange peel and its physicochemical properties.

    PubMed

    Hosseini, Seyed Saeid; Khodaiyan, Faramarz; Yarmand, Mohammad Saeid

    2016-04-20

    Microwave assisted extraction technique was used to extract pectin from sour orange peel. Box-Behnken design was used to study the effect of irradiation time, microwave power and pH on the yield and degree of esterification (DE) of pectin. The results showed that the optimum conditions for the highest yield of pectin (29.1%) were obtained at pH of 1.50, microwave power of 700W, and irradiation time of 3min. DE values of pectin ranged from 1.7% to 37.5%, indicating that the obtained pectin was low in methoxyl. Under optimal conditions, the galacturonic acid content and emulsifying activity were 71.0±0.8% and 40.7%, respectively. In addition, the emulsion stability value ranged from 72.1% to 83.4%. Viscosity measurement revealed that the solutions of pectin at low concentrations showed nearly Newtonian flow behavior, and as the concentration increased, pseudoplastic flow became dominant. PMID:26876828

  1. Optimization of microwave-assisted hot air drying conditions of okra using response surface methodology.

    PubMed

    Kumar, Deepak; Prasad, Suresh; Murthy, Ganti S

    2014-02-01

    Okra (Abelmoschus esculentus) was dried to a moisture level of 0.1 g water/g dry matter using a microwave-assisted hot air dryer. Response surface methodology was used to optimize the drying conditions based on specific energy consumption and quality of dried okra. The drying experiments were performed using a central composite rotatable design for three variables: air temperature (40-70 °C), air velocity (1-2 m/s) and microwave power level (0.5-2.5 W/g). The quality of dried okra was determined in terms of color change, rehydration ratio and hardness of texture. A second-order polynomial model was well fitted to all responses and high R(2) values (>0.8) were observed in all cases. The color change of dried okra was found higher at high microwave power and air temperatures. Rehydration properties were better for okra samples dried at higher microwave power levels. Specific energy consumption decreased with increase in microwave power due to decrease in drying time. The drying conditions of 1.51 m/s air velocity, 52.09 °C air temperature and 2.41 W/g microwave power were found optimum for product quality and minimum energy consumption for microwave-convective drying of okra. PMID:24493879

  2. Dynamic microwave assisted extraction coupled with dispersive micro-solid-phase extraction of herbicides in soybeans.

    PubMed

    Li, Na; Wu, Lijie; Nian, Li; Song, Ying; Lei, Lei; Yang, Xiao; Wang, Kun; Wang, Zhibing; Zhang, Liyuan; Zhang, Hanqi; Yu, Aimin; Zhang, Ziwei

    2015-09-01

    Non-polar solvent dynamic microwave assisted extraction was firstly applied to the treatment of high-fat soybean samples. In the dispersive micro-solid-phase extraction (D-µ-SPE), the herbicides in the high-fat extract were directly adsorbed on metal-organic frameworks MIL-101(Cr). The effects of several experimental parameters, including extraction solvent, microwave absorption medium, microwave power, volume and flow rate of extraction solvent, amount of MIL-101(Cr), and D-µ-SPE time, were investigated. At the optimal conditions, the limits of detection for the herbicides ranged from 1.56 to 2.00 μg kg(-1). The relative recoveries of the herbicides were in the range of 91.1-106.7%, and relative standard deviations were equal to or lower than 6.7%. The present method was simple, rapid and effective. A large amount of fat was also removed. This method was demonstrated to be suitable for treatment of high-fat samples. PMID:26003690

  3. Copper Granule-Catalyzed Microwave-Assisted Click Synthesis of Polyphenol Dendrimers

    PubMed Central

    Lee, Choon Young; Held, Rich; Sharma, Ajit; Baral, Rom; Nanah, Cyprien; Dumas, Dan; Jenkins, Shannon; Upadhaya, Samik; Du, Wenjun

    2013-01-01

    Syringaldehyde and vanillin-based antioxidant dendrimers were synthesized via microwave-assisted alkyne-azide 1,3-dipolar cycloaddition using copper granules as a catalyst. The use of Cu(I) as a catalyst resulted in copper contaminated dendrimers. In order to produce copper-free antioxidant dendrimers for biological applications, Cu(I) was substituted with copper granules. Copper granules were ineffective at both room temperature and under reflux conditions (< 5% yield). However, it was an excellent catalyst when dendrimer synthesis was performed under microwave irradiation, giving yields up to 94% within 8 h. ICP-mass analysis of the antioxidant dendrimers obtained with this method showed virtually no copper contamination (9 ppm), which was the same as background level. The synthesized antioxidants, free from copper contamination, demonstrated potent radical scavenging with IC50 values of less than 3 µM in the DPPH assay. In comparison, dendrimers synthesized from Cu(I)-catalyzed Click chemistry showed a high level of copper contamination (4800 ppm) and no detectable antioxidant activity. PMID:24127771

  4. Ultrafast Preparation of Monodisperse Fe3 O4 Nanoparticles by Microwave-Assisted Thermal Decomposition.

    PubMed

    Liang, Yi-Jun; Zhang, Yu; Guo, Zhirui; Xie, Jun; Bai, Tingting; Zou, Jiemeng; Gu, Ning

    2016-08-01

    Thermal decomposition, as the main synthetic procedure for the synthesis of magnetic nanoparticles (NPs), is facing several problems, such as high reaction temperatures and time consumption. An improved a microwave-assisted thermal decomposition procedure has been developed by which monodisperse Fe3 O4 NPs could be rapidly produced at a low aging temperature with high yield (90.1 %). The as-synthesized NPs show excellent inductive heating and MRI properties in vitro. In contrast, Fe3 O4 NPs synthesized by classical thermal decomposition were obtained in very low yield (20.3 %) with an overall poor quality. It was found for the first time that, besides precursors and solvents, magnetic NPs themselves could be heated by microwave irradiation during the synthetic process. These findings were demonstrated by a series of microwave-heating experiments, Raman spectroscopy and vector-network analysis, indicating that the initially formed magnetic Fe3 O4 particles were able to transform microwave energy into heat directly and, thus, contribute to the nanoparticle growth. PMID:27381301

  5. Direct formation of LiFePO4/graphene composite via microwave-assisted polyol process

    NASA Astrophysics Data System (ADS)

    Lim, Jinsub; Gim, Jihyeon; Song, Jinju; Nguyen, Dang Thanh; Kim, Sungjin; Jo, Jeonggeun; Mathew, Vinod; Kim, Jaekook

    2016-02-01

    The present study reports on the direct synthesis of LiFePO4 nanoparticles and graphene nanosheets to form a composite cathode (LFP/GNs) in a one-step microwave-assisted polyol reaction. The polyol reaction induced by microwave irradiation for a few minutes produces nanocrystalline LFP and graphene nanosheets simultaneously from lithium, iron and phosphorus and carbon (5 wt% of graphite oxide) sources, respectively, used as starting precursors. Powder X-ray diffraction (XRD), electron microscopy, and atomic force microscopy (AFM) studies on microwave-reacted sample obtained using just graphite oxide confirms the formation of graphene nanosheets separately. Whereas, electron microscopy studies on the LFP/GNs composite reveals that olivine nanoparticles of average sizes ranging between 5 and 20 nm are well-dispersed on the graphene nanosheets. Electrochemical measurements reveal that the LiFePO4/GNs nanocomposite cathodes registered enhanced discharge capacities (79 and 108 mAh g-1 for the as-prepared and annealed composite cathodes, respectively) at 32 C rates with good capacity retention capabilities. The AC impedance measurements confirm that the enhanced cathode properties of the LFP/GNs nanocomposite are ascribed to the improved electronic conductivity of the graphene nanosheets and the nano-sized particles. The slightly better electrochemical properties of the annealed LFP/GNs are attributed to its higher crystallinity.

  6. Investigation of analyte losses using microwave-assisted sample digestion and closed vessels with venting.

    PubMed

    Amaral, Clarice D B; Fialho, Lucimar L; Camargo, Felipe P R; Pirola, Camillo; Nóbrega, Joaquim A

    2016-11-01

    Microwave-assisted sample digestion using closed vessels is becoming the standard for trace analysis because contamination and losses can be better controlled. Gases are generated during digestion and there is an increment of the internal vessel pressure. Consequently, vessels venting may occur depending on the design of the vessel and the maximum pressure it can stand for. In the present work it was observed that it is possible to allow venting during the digestion without losing volatile analytes, such as As, when properly controlling heating and chemical conditions. Recoveries for As in certified reference materials of animal tissues ranged from 94 to 112% despite mass losses as high as 62%mm(-1) observed in the digests. However, for Hg(II) in medium containing chlorides recoveries were poor. The efficiency of digestion was measured by determination of organic carbon contents in digests and they ranged from 0.10 to 0.19% for plant and animal tissues. The temperature gradient along the vessel height is important for avoiding losses of volatile elements. PMID:27591624

  7. Copper-granule-catalyzed microwave-assisted click synthesis of polyphenol dendrimers.

    PubMed

    Lee, Choon Young; Held, Rich; Sharma, Ajit; Baral, Rom; Nanah, Cyprien; Dumas, Dan; Jenkins, Shannon; Upadhaya, Samik; Du, Wenjun

    2013-11-15

    Syringaldehyde- and vanillin-based antioxidant dendrimers were synthesized via microwave-assisted alkyne-azide 1,3-dipolar cycloaddition using copper granules as a catalyst. The use of Cu(I) as a catalyst resulted in copper contaminated dendrimers. To produce copper-free antioxidant dendrimers for biological applications, Cu(I) was substituted with copper granules. Copper granules were ineffective at both room temperature and under reflux conditions (<5% yield). However, they were an excellent catalyst when dendrimer synthesis was performed under microwave irradiation, giving yields up to 94% within 8 h. ICP-mass analysis of the antioxidant dendrimers obtained with this method showed virtually no copper contamination (9 ppm), which was the same as the background level. The synthesized antioxidants, free from copper contamination, demonstrated potent radical scavenging with IC50 values of less than 3 μM in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. In comparison, dendrimers synthesized from Cu(I)-catalyzed click chemistry showed a high level of copper contamination (4800 ppm) and no detectable antioxidant activity. PMID:24127771

  8. Microwave-assisted chemical process for treatment of hazardous waste: Annual report

    SciTech Connect

    Varma, R.; Nandi, S.P.; Cleaveland, D.C.

    1987-10-01

    Microwave energy provides rapid in situ uniform heating and can be used to initiate chemical processes at moderate temperatures. We investigate the technical feasibility of microwave-assisted chemical processes for detoxification of liquid hazardous waste. Trichloroethylene, a major constituent of waste streams, was selected for this detoxification study. Experiments were performed to investigate the oxidative degradation of trichloroethylene over active carbons (with and without catalysts) in air streams with microwave in situ heating, and to examine the feasibility of regenerating the used carbons. This study established that trichloroethylene in a vapor stream can be adsorbed at room temperature on active carbon beds that are loaded with Cu and Cr catalysts. When the bed is heated by a microwave radiation to moderate temperatures (<400/sup 0/C) while a moist air stream is passed through it, the trichloroethylene is readily converted into less-noxious products such as HCl, CO, CO/sub 2/ and C/sub 2/H/sub 2/Cl/sub 2/. Conversion higher than 80% was observed. Furthermore, the used carbon bed can be conveniently regenerated by microwave heating while a moist-N/sub 2/ or moist-air stream is passed through the bed. 4 refs., 5 figs., 10 tabs.

  9. Microwave-assisted hydrothermal synthesis and characterization of ZnO nanorods.

    PubMed

    Ocakoglu, K; Mansour, Sh A; Yildirimcan, S; Al-Ghamdi, Ahmed A; El-Tantawy, F; Yakuphanoglu, F

    2015-09-01

    For the purpose of this study, the nanorods of zinc oxide were synthesized by rapid microwave-assisted hydrothermal route. The microstructure and surface morphology of the sensitized nanorods were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). XRD results indicate that synthesized ZnO nanorods have wurtzite phase. The calculated value of the particle size using Debye Scherrer formula and Williamson Hall plot was found to be 20-28 nm and 35.3 nm, respectively. Low uniformity distribution of rod-like morphology (60-80 nm in diameter and average length about 250 nm) are seen in TEM micrographs. The optical parameters of the prepared ZnO nanorods have been calculated using Kubeleka-Munk approach for the UV-vis diffuse reflectance spectrum. It is found that the direct transition optical band gap of the studied sample is 3.17 eV. The direct current electrical conductivity (σ) was increased from 6.7×10(-8) to 3×10(-7) Ω(-1) cm(-1) with increasing the temperature (T) in the range (300-425 K). The obtained variation of σ with T refers that the conductivity mechanism is controlled by thermally activated process. PMID:25913135

  10. Microwave Assisted Synthesis of Ferrite Nanoparticles: Effect of Reaction Temperature on Particle Size and Magnetic Properties.

    PubMed

    Kalyani, S; Sangeetha, J; Philip, John

    2015-08-01

    The preparation of ferrite magnetic nanoparticles of different particle sizes by controlling the reaction temperature using microwave assisted synthesis is reported. The iron oxide nanoparticles synthesized at two different temperatures viz., 45 and 85 °C were characterized using techniques such as X-ray diffraction (XRD), small angle X-ray scattering (SAXS), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The average size of iron oxide nanoparticles synthesized at 45 and 85 °C is found to be 10 and 13.8 nm, respectively, and the nanoparticles exhibited superparamagantic behavior at room temperature. The saturation magnetization values of nanoparticles synthesized at 45 and 85 °C were found to be 67 and 72 emu/g, respectively. The increase in particle size and saturation magnetization values with increase in incubation temperature is attributed to a decrease in supersaturation at elevated temperature. The Curie temperature was found to be 561 and 566 0C for the iron oxide nanoparticles synthesized at 45 and 85 °C, respectively. The FTIR spectrum of the iron oxide nanoparticles synthesized at different temperatures exhibited the characteristic peaks that corresponded to the stretching of bonds between octahedral and tetrahedral metal ions to oxide ions. Our results showed that the ferrite nanoparticle size can be varied by controlling the reaction temperature inside a microwave reactor. PMID:26369150

  11. Microwave-assisted extraction of jujube polysaccharide: Optimization, purification and functional characterization.

    PubMed

    Rostami, Hosein; Gharibzahedi, Seyed Mohammad Taghi

    2016-06-01

    The operational parameters involved in microwave-assisted extraction (MAE) of jujube polysaccharide including microwave power, water to raw material ratio and extraction temperature and time were optimized by RSM. MAE at 400W, 75°C, 60min, using 30g water/g powdered jujube was the best condition for maximum yield (9.02%) of polysaccharide. Two novel water-soluble polysaccharides (JCP-1 and JCP-2) with average molecular weights of 9.1×10(4)-1.5×10(5)Da in term of the symmetrical narrow peaks were identified using the analytical purification procedures. The JCP-1 and JCP-2 mainly composed of glucose, arabinose, galactose and rhamnose in molar ratios of 1.4:2.1:4.2:0.9 and 1.2:1.8:4.1:1.1, respectively. The use of 1.5% JCP-1 led to a high emulsifying stability (95.5%) in a model oil-in-water type emulsion with a reduced surface tension (44.1mN/m) and droplet size (1.32μm), and an increased apparent viscosity (0.13Pas) during 21-day cold storage. The antioxidant activities were increased in dose-dependent manners (25-200μg/mL). PMID:27083348

  12. Application of ionic liquids in the microwave-assisted extraction of polyphenolic compounds from medicinal plants.

    PubMed

    Du, Fu-You; Xiao, Xiao-Hua; Luo, Xue-Jun; Li, Gong-Ke

    2009-05-15

    Ionic liquids (ILs) solutions as solvents were successfully applied in the microwave-assisted extraction (MAE) of polyphenolic compounds from medicinal plants. ILs, its concentration and MAE conditions were investigated in order to extract polyphenolic compounds effectively from Psidium guajava Linn. (P. guajava) leaves and Smilax china (S. china) tubers. The results obtained indicated that the anions and cations of ILs had influences on the extraction of polyphenolic compounds as well as the ILs with electron-rich aromatic pi-system enhanced extraction ability. Under the optimized conditions, the extraction yields of the polyphenolic compounds were in the range of 79.5-93.8% with one-step extraction, and meanwhile the recoveries were in the range of 85.2-103% with relative standard deviations (R.S.D.s) lower than 5.6%. Compared to conventional extraction procedures, the results suggested that the proposed method was effective and alternative for the extraction of polyphenolic compounds from medicinal plants. In addition, the extraction mechanisms and the structures of samples before and after extraction were also investigated. ILs solutions as green solvents in the MAE of polyphenolic compounds from medicinal plant samples showed a great promising prospect. PMID:19269490

  13. Microwave assisted synthesis of ZnO nanoparticles for lighting and dye removal application

    NASA Astrophysics Data System (ADS)

    Kumar, Vijay; Gohain, M.; Som, S.; Kumar, Vinod; Bezuindenhoudt, B. C. B.; Swart, Hendrik C.

    2016-01-01

    In this study, we report on the synthesis of ZnO nanoparticles (NPs) via the microwave-assisted technique. The as-synthesized ZnO nanoparticles were annealed at 500 °C for three hours. The ZnO NPs were characterized by X-ray diffraction (XRD) and scanning electron microscopic techniques. XRD results confirmed the formation of as-synthesized ZnO powder oriented along the (101) direction. The Kubelka-Munk function has been employed to determine the band gap of the ZnO powder. ZnO powder has been studied by photoluminescence (PL) before and after annealing to identify the emission of defects in the visible range. The intensity of the PL emission has decreased after annealing. The synthesized ZnO samples were also studied for methyl orange dye removal from waste water. It has been found that the as-synthesized ZnO shows better adsorption behaviour as compared to the annealed sample.

  14. Quality and high yield synthesis of Ag nanowires by microwave-assisted hydrothermal method

    NASA Astrophysics Data System (ADS)

    Meléndrez, Manuel F.; Medina, Carlos; Solis-Pomar, Francisco; Flores, Paulo; Paulraj, Mani; Pérez-Tijerina, Eduardo

    2015-02-01

    Silver nanowires (Ag-NWs) were obtained using microwave-assisted hydrothermal method (MAH). The main advantage of the method is its high NWs production which is greater than 90%. It is also easy, fast, and highly reproducible process. One of the drawbacks presented so far in the synthesis of nanostructures by polyol path is the high temperature used in the process, which is superior than the boiling point of solvent (ethylene glycol), and also its excessive reaction time. Here, Ag-NWs with diameters of 70 to 110 nm were synthesized in 5 min in large quantities. Results showed that dimensions and shape of nanowires were very susceptible to changes with reaction parameters. The reactor power and reactor fill capacity were important for the synthesis. It was found that the reaction time needs to be decreased because of the NWs which start to deform and break up due to significant increase in the pressure's system. Energy-dispersive X-ray spectroscopy and electron diffraction analysis (SAED) did not show corresponding phases of AgO. Some aspects about synthesis parameters which are related to the percent yield and size of nanowires are also discussed.

  15. Comparative study on conventional, ultrasonication and microwave assisted extraction of γ-oryzanol from rice bran.

    PubMed

    Kumar, Pramod; Yadav, Devbrat; Kumar, Pradyuman; Panesar, Paramjeet Singh; Bunkar, Durga Shankar; Mishra, Diwaker; Chopra, H K

    2016-04-01

    In present study, conventional, ultrasonic and microwave assisted extraction methods were compared with the aim of optimizing best fitting solvent and method, solvent concentration and digestion time for high yield of γ-oryzanol from rice bran. Petroleum ether, hexane and methanol were used to prepare extracts. Extraction yield were evaluated for giving high crude oil yield, total phenolic content (TPC) and γ-oryzanol content. Gas chromatography-mass spectrophotometry was used for the determination of γ-oryzanol concentration. The highest concentration of γ-oryzanol was detected in methanolic extracts of microwave treatment (85.0 ppm) followed by ultrasonication (82.0 ppm) and conventional extraction method (73.5 ppm). Concentration of γ-oryzanol present in the extracts was found to be directly proportional to the total phenolic content. A combination of 80 % methanolic concentration and 55 minutes digestion time of microwave treatment yielded the best extraction method for TPC and thus γ-oryzanol (105 ppm). PMID:27413233

  16. Response surface methodology applied to the study of the microwave-assisted synthesis of quaternized chitosan.

    PubMed

    dos Santos, Danilo Martins; Bukzem, Andrea de Lacerda; Campana-Filho, Sérgio Paulo

    2016-03-15

    A quaternized derivative of chitosan, namely N-(2-hydroxy)-propyl-3-trimethylammonium chitosan chloride (QCh), was synthesized by reacting glycidyltrimethylammonium chloride (GTMAC) and chitosan (Ch) in acid medium under microwave irradiation. Full-factorial 2(3) central composite design and response surface methodology (RSM) were applied to evaluate the effects of molar ratio GTMAC/Ch, reaction time and temperature on the reaction yield, average degree of quaternization (DQ) and intrinsic viscosity ([η]) of QCh. The molar ratio GTMAC/Ch was the most important factor affecting the response variables and RSM results showed that highly substituted QCh (DQ = 71.1%) was produced at high yield (164%) when the reaction was carried out for 30min. at 85°C by using molar ratio GTMAC/Ch 6/1. Results showed that microwave-assisted synthesis is much faster (≤30min.) as compared to conventional reaction procedures (>4h) carried out in similar conditions except for the use of microwave irradiation. PMID:26794768

  17. Microwave-assisted hydrothermal synthesis and characterization of ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Ocakoglu, K.; Mansour, Sh. A.; Yildirimcan, S.; Al-Ghamdi, Ahmed A.; El-Tantawy, F.; Yakuphanoglu, F.

    2015-09-01

    For the purpose of this study, the nanorods of zinc oxide were synthesized by rapid microwave-assisted hydrothermal route. The microstructure and surface morphology of the sensitized nanorods were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). XRD results indicate that synthesized ZnO nanorods have wurtzite phase. The calculated value of the particle size using Debye Scherrer formula and Williamson Hall plot was found to be 20-28 nm and 35.3 nm, respectively. Low uniformity distribution of rod-like morphology (60-80 nm in diameter and average length about 250 nm) are seen in TEM micrographs. The optical parameters of the prepared ZnO nanorods have been calculated using Kubeleka-Munk approach for the UV-vis diffuse reflectance spectrum. It is found that the direct transition optical band gap of the studied sample is 3.17 eV. The direct current electrical conductivity (σ) was increased from 6.7 ×10-8 to 3 ×10-7Ω-1cm-1 with increasing the temperature (T) in the range (300-425 K). The obtained variation of σ with T refers that the conductivity mechanism is controlled by thermally activated process.

  18. Microwave-assisted ultrafast synthesis of silver nanoparticles for detection of Hg²⁺.

    PubMed

    Ma, Yun; Pang, Yuehong; Liu, Fei; Xu, Hanqi; Shen, Xiaofang

    2016-01-15

    Silver nanoparticles (AgNPs) were successfully prepared in aqueous solution by a one-pot procedure based on a rapid microwave-assisted green approach. L-Cysteine acted as a capping agent in the process of AgNP formation. The structural and morphological characteristics of the L-cysteine-capped AgNPs were investigated by the UV-vis, CD, FL, FTIR, XRD, TEM and EDX analysis. It was found that the well-dispersed crystalline AgNPs were formed after irradiation for 90 s and had sphere-like morphology. Such strategy may facilitate new ways to the synthesis of other metal nanoparticles, such as Au, Pt and Pd. In addition, the synthesized AgNPs were developed as a platform for the detection of Hg(2+) and showed a high sensitivity on the order of 1×10(-8) M. This sensing system could discriminate Hg(2+) from a wide range of cations (Ca(2+), Ba(2+), Mn(2+), etc.). The selectivity and sensitivity of AgNPs indicated its potential use as a sensor for Hg(2+) detection in the ecosystems. PMID:26312737

  19. Microwave-assisted synthesis of bismuth oxybromochloride nanoflakes for visible light photodegradation of pollutants

    NASA Astrophysics Data System (ADS)

    Bijanzad, Keyvan; Tadjarodi, Azadeh; Moghaddasi Khiavi, Mohammad; Akhavan, Omid

    2015-10-01

    BiOBrxCl1-x (0microwave-assisted synthesis method. The X-ray diffraction (XRD) studies confirmed the formation of pure crystalline phase of BiOBrxCl1-x. The UV-visible diffuse reflectance and photoluminescence (PL) spectroscopies revealed the indirect band gap of ~2.82 eV for the bismuth oxybromochloride nanoflakes. Visible light-assisted photocatalytic studies showed that the degradation efficiency of the as-prepared BiOBrxCl1-x for (100 mL of 10 mg L-1) Rhodamine B (RhB), Natural Red 4 (N-Red) dye solutions was 98.14% and for the colorless organic pentachlorophenol (PCP) solution was 91.09% over 150 min. The possible mechanisms involved in the visible light photodegradation of the pollutants by BiOBrxCl1-x photocatalyst were also discussed.

  20. Analysis of parameter and interaction between parameter of the microwave assisted transesterification process of coconut oil using response surface methodology

    NASA Astrophysics Data System (ADS)

    Hidayanti, Nur; Suryanto, A.; Qadariyah, L.; Prihatini, P.; Mahfud, Mahfud

    2015-12-01

    A simple batch process was designed for the transesterification of coconut oil to alkyl esters using microwave assisted method. The product with yield above 93.225% of alkyl ester is called the biodiesel fuel. Response surface methodology was used to design the experiment and obtain the maximum possible yield of biodiesel in the microwave-assisted reaction from coconut oil with KOH as the catalyst. The results showed that the time reaction and concentration of KOH catalyst have significant effects on yield of alkyl ester. Based on the response surface methodology using the selected operating conditions, the time of reaction and concentration of KOH catalyst in transesterification process were 150 second and 0.25%w/w, respectively. The largest predicted and experimental yield of alkyl esters (biodiesel) under the optimal conditions are 101.385% and 93.225%, respectively. Our findings confirmed the successful development of process for the transesterification reaction of coconut oil by microwave-assisted heating, which is effective and time-saving for alkyl ester production.

  1. Antioxidative Peptides Derived from Enzyme Hydrolysis of Bone Collagen after Microwave Assisted Acid Pre-Treatment and Nitrogen Protection

    PubMed Central

    Lin, Yun-Jian; Le, Guo-Wei; Wang, Jie-Yun; Li, Ya-Xin; Shi, Yong-Hui; Sun, Jin

    2010-01-01

    This study focused on the preparation method of antioxidant peptides by enzymatic hydrolysis of bone collagen after microwave assisted acid pre-treatment and nitrogen protection. Phosphoric acid showed the highest ability of hydrolysis among the four other acids tested (hydrochloric acid, sulfuric acid and/or citric acid). The highest degree of hydrolysis (DH) was 9.5% using 4 mol/L phosphoric acid with a ratio of 1:6 under a microwave intensity of 510 W for 240 s. Neutral proteinase gave higher DH among the four protease tested (Acid protease, neutral protease, Alcalase and papain), with an optimum condition of: (1) ratio of enzyme and substrate, 4760 U/g; (2) concentration of substrate, 4%; (3) reaction temperature, 55 °C and (4) pH 7.0. At 4 h, DH increased significantly (P < 0.01) under nitrogen protection compared with normal microwave assisted acid pre-treatment hydrolysis conditions. The antioxidant ability of the hydrolysate increased and reached its maximum value at 3 h; however DH decreased dramatically after 3 h. Microwave assisted acid pre-treatment and nitrogen protection could be a quick preparatory method for hydrolyzing bone collagen. PMID:21151439

  2. Standardization of process parameters for microwave assisted convective dehydration of ginger.

    PubMed

    Mohanta, B; Dash, S K; Panda, M K; Sahoo, G R

    2014-04-01

    Ginger (Zingiber Officinale, Cv. Suprava) slices (4 mm thick) were dehydrated at 25°, 40°, 50° and 60 °C with three different microwave power levels, viz. 120, 240, and 360 W in microwave assisted convective dryer up to 0.07 g moisture/g dry solid to observe the feasibility of microwave assisted convective drying for ginger. The samples were also dried without application of microwaves (0 W) at the above air temperatures. The final product quality was compared in terms of rehydration characteristics, oleoresin and volatile oil contents, hardness, color and organoleptic quality. The maximum rehydration ratio of 3.86 ± 0.06 was obtained at 50 °C without application of microwaves and was followed by 120 W-40 °C combination treatment (3.64 ± 0.15). The minimum rehydration ratio was 2.34 ± 0.20 for 360 W with 60 °C. The yield of oleoresin content was higher for 120 W as compared to other power levels, which ranged between 5.12 ± 0.85% and 6.34 ± 0.89%. The maximum retention of oleoresin was observed in case of 120 W-40 °C. The samples dried with microwave power level of 120 W also gave better yields of volatile oil as compared to other power levels. The best color was observed at 120 W-50 °C and 120 W-60 °C conditions with Hunter 'a' (redness) values at 0.50 ± 0.03 and 0.35 ± 0.03, respectively. The sensory analysis also indicated that drying at 120 W-50 °C and 240 W-50 °C combinations gave the most acceptable quality product. Drying ginger with 120 W-50 °C combination helped in a saving of 53% and 44% in drying time as compared to hot air drying at 50° and 60 °C, respectively. Drying at 240 W-50 °C also gave a reasonably acceptable quality product with a net saving of 91% and 89% in drying time as compared to hot air drying at 50° and 60 °C, respectively. However, on the basis of rehydration characteristics, the acceptable process conditions were hot air drying at 50° or 60 °C, or with

  3. Microwave-assisted double insert vapour-phase digestion of organic samples.

    PubMed

    Eilola, Keijo; Perämäki, Paavo

    2009-02-23

    A microwave-assisted double insert multimode vapour-phase digestion method was developed for the digestion of organic samples. The experimental set-up was based on a third generation-type teflon microwave vessel, equipped with an automatic pressure regulating type vessel cover. A borosilicate glass holder insert, containing a smaller quartz sample insert, was fitted inside the vessel. Sulphuric acid was added to the holder insert as a microwave absorbing and temperature transferring liquid, which transferred heat to the sample insert (into which the sample was weighed) and charred the sample material. Oxidation of the sample material was carried out simultaneously with charring using nitric acid vapour, which was generated by the 1:1 (v/v) sulphuric acid-nitric acid mixture located in the bottom of the microwave vessel. This set-up generated high digestion efficiency, without any of the interferences normally associated with direct sulphuric acid usage. The method was used for determining the concentrations of Cd, Cr, Cu, Mn, Mo, Zn and Fe in certified organic reference materials using ICP-OES instrumentation. The certified organic reference materials were NRCC DOLT-2 dogfish liver, NIST-SRM 1577b bovine liver and IRMM VDA cadmium in polyethylene No. 001 and No. 004. The results were in good agreement with the certified values, forepart from Cd. For Cd the results were lower than the certified values due to volatilization losses. Sample materials that could not be digested by an earlier procedure were completely digested during a single-step, 30 min digestion. The tested sample materials included certified reference materials, 3-nitrobenzoic acid (3-NBA) and pike (Esox lucius) muscle. The residual carbon concentrations in the digestion solutions were below the detection limit of the TOC instrument. This type of digestion method is described here for the first time in the literature. PMID:19185121

  4. Shape effect on the antibacterial activity of silver nanoparticles synthesized via a microwave-assisted method.

    PubMed

    Hong, Xuesen; Wen, Junjie; Xiong, Xuhua; Hu, Yongyou

    2016-03-01

    Silver nanoparticles (AgNPs) are used as sustained-release bactericidal agents for water treatment. Among the physicochemical characteristics of AgNPs, shape is an important parameter relevant to the antibacterial activity. Three typically shaped AgNPs, nanocubes, nanospheres, and nanowires, were prepared via a microwave-assisted method and characterized by TEM, UV-vis, and XRD. The antibacterial activity of AgNPs was determined by OD growth curves tests, MIC tests, and cell viability assay against Escherichia coli. The interaction between AgNPs and bacterial cells was observed by TEM. The results showed that the three differently shaped AgNPs were nanoscale, 55 ± 10 nm in edge length for nanocubes, 60 ± 15 nm in diameter for nanospheres, 60 ± 10 nm in diameter and 2-4 μm in length for nanowires. At the bacterial concentration of 10(4) CFU/mL, the MIC of nanocubes, nanospheres, and nanowires were 37.5, 75, and 100 μg/mL, respectively. Due to the worst contact with bacteria, silver nanowires exhibited the weakest antibacterial activity compared with silver nanocubes and silver nanospheres. Besides, silver nanocubes mainly covered by {100} facets showed stronger antibacterial activity than silver nanospheres covered by {111} facets. It suggests that the shape effect on the antibacterial activity of AgNPs is attributed to the specific surface areas and facets reactivity; AgNPs with larger effective contact areas and higher reactive facets exhibit stronger antibacterial activity. PMID:26511259

  5. Bit patterned media with composite structure for microwave assisted magnetic recording

    NASA Astrophysics Data System (ADS)

    Eibagi, Nasim

    Patterned magnetic nano-structures are under extensive research due to their interesting emergent physics and promising applications in high-density magnetic data storage, through magnetic logic to bio-magnetic functionality. Bit-patterned media is an example of such structures which is a leading candidate to reach magnetic densities which cannot be achieved by conventional magnetic media. Patterned arrays of complex heterostructures such as exchange-coupled composites are studied in this thesis as a potential for next generation of magnetic recording media. Exchange-coupled composites have shown new functionality and performance advantages in magnetic recording and bit patterned media provide unique capability to implement such architectures. Due to unique resonant properties of such structures, their possible application in spin transfer torque memory and microwave assisted switching is also studied. This dissertation is divided into seven chapters. The first chapter covers the history of magnetic recording, the need to increase magnetic storage density, and the challenges in the field. The second chapter introduces basic concepts of magnetism. The third chapter explains the fabrication methods for thin films and various lithographic techniques that were used to pattern the devices under study for this thesis. The fourth chapter introduces the exchanged coupled system with the structure of [Co/Pd] / Fe / [Co/Pd], where the thickness of Fe is varied, and presents the magnetic properties of such structures using conventional magnetometers. The fifth chapter goes beyond what is learned in the fourth chapter and utilizes polarized neutron reflectometry to study the vertical exchange coupling and reversal mechanism in patterned structures with such structure. The sixth chapter explores the dynamic properties of the patterned samples, and their reversal mechanism under microwave field. The final chapter summarizes the results and describes the prospects for future

  6. Microwave assisted transformation of N,N-diphenylamine as precursors of organic light emitting diodes (OLED)

    SciTech Connect

    Jefri,; Wahyuningrum, Deana

    2015-09-30

    In this research, study on the transformation of N,N-diphenylamine (DPA) using iodine (I2) utilizing solid state Microwave Assisted Organic Synthesis (MAOS) method has been carried out. The reaction was performed by variations of three parameters namely the mole of reagents, the amount and type of solid support (alumina/Al2O3), and the reaction conditions. Experimental results showed that neutral-alumina was a better solid support than basic-alumina. The optimum temperature for the reaction was approximately at 125-133 °C with reaction time of 15 minutes and microwave reactor power at 500-600 W. The separation of the yellowish green product solution with preparative Thin Layer Chromatography (TLC) method using n-hexane:ethyl acetate = 4:1 (v/v) as eluent yielded two fractions (I and II) and both fractions can undergo fluorescence under 365 nm UV light. Based on the LC chromatogram with methanol:water = 95:5 (v/v) as eluent and its corresponding mass spectra (ESI+), fraction I contained three compounds, which were tetracarbazole A, triphenylamine, and impurities in the form of plasticizer such as bis(2-ethylhexyl) phthalate. Fraction II also contained three compounds, which were tetracarbazole C, tetraphenylhydrazine, and plasticizer such as bis(2-ethylhexyl) phthalate. Both FT-IR (KBr disks) and NMR (500 MHz, CDCl{sub 3}) spectra of fraction I and II confirmed the aromatic amine groups in those compounds. The observed fluorescence colors of fraction I and II were violet and violet-blue, respectively. Based on their structures and fluorescence characters, the compounds in fraction I and II have the potential to be used as Organic Light Emitting Diode (OLED) compound precursors.

  7. Supercritical Carbon Dioxide and Microwave-Assisted Extraction of Functional Lipophilic Compounds from Arthrospira platensis

    PubMed Central

    Esquivel-Hernández, Diego A.; López, Víctor H.; Rodríguez-Rodríguez, José; Alemán-Nava, Gibrán S.; Cuéllar-Bermúdez, Sara P.; Rostro-Alanis, Magdalena; Parra-Saldívar, Roberto

    2016-01-01

    Arthrospira platensis biomass was used in order to obtain functional lipophilic compounds through green extraction technologies such as supercritical carbon dioxide fluid extraction (SFE) and microwave-assisted extraction (MAE). The temperature (T) factor was evaluated for MAE, while for SFE, pressure (P), temperature (T), and co-solvent (ethanol) (CS) were evaluated. The maximum extraction yield of the obtained oleoresin was (4.07% ± 0.14%) and (4.27% ± 0.10%) for SFE and MAE, respectively. Extracts were characterized by gas chromatography mass spectrometry (GC-MS) and gas chromatography flame ionization detector (GC-FID). The maximum contents of functional lipophilic compounds in the SFE and MAE extracts were: for carotenoids 283 ± 0.10 μg/g and 629 ± 0.13 μg/g, respectively; for tocopherols 5.01 ± 0.05 μg/g and 2.46 ± 0.09 μg/g, respectively; and for fatty acids 34.76 ± 0.08 mg/g and 15.88 ± 0.06 mg/g, respectively. In conclusion, the SFE process at P 450 bar, T 60 °C and CS 53.33% of CO2 produced the highest yield of tocopherols, carotenoids and fatty acids. The MAE process at 400 W and 50 °C gives the best extracts in terms of tocopherols and carotenoids. For yield and fatty acids, the MAE process at 400 W and 70 °C produced the highest values. Both SFE and MAE showed to be suitable green extraction technologies for obtaining functional lipophilic compounds from Arthrospira platensis. PMID:27164081

  8. Microwave assisted transformation of N,N-diphenylamine as precursors of organic light emitting diodes (OLED)

    NASA Astrophysics Data System (ADS)

    Jefri, Wahyuningrum, Deana

    2015-09-01

    In this research, study on the transformation of N,N-diphenylamine (DPA) using iodine (I2) utilizing solid state Microwave Assisted Organic Synthesis (MAOS) method has been carried out. The reaction was performed by variations of three parameters namely the mole of reagents, the amount and type of solid support (alumina/Al2O3), and the reaction conditions. Experimental results showed that neutral-alumina was a better solid support than basic-alumina. The optimum temperature for the reaction was approximately at 125-133 °C with reaction time of 15 minutes and microwave reactor power at 500-600 W. The separation of the yellowish green product solution with preparative Thin Layer Chromatography (TLC) method using n-hexane:ethyl acetate = 4:1 (v/v) as eluent yielded two fractions (I and II) and both fractions can undergo fluorescence under 365 nm UV light. Based on the LC chromatogram with methanol:water = 95:5 (v/v) as eluent and its corresponding mass spectra (ESI+), fraction I contained three compounds, which were tetracarbazole A, triphenylamine, and impurities in the form of plasticizer such as bis(2-ethylhexyl) phthalate. Fraction II also contained three compounds, which were tetracarbazole C, tetraphenylhydrazine, and plasticizer such as bis(2-ethylhexyl) phthalate. Both FT-IR (KBr disks) and NMR (500 MHz, CDCl3) spectra of fraction I and II confirmed the aromatic amine groups in those compounds. The observed fluorescence colors of fraction I and II were violet and violet-blue, respectively. Based on their structures and fluorescence characters, the compounds in fraction I and II have the potential to be used as Organic Light Emitting Diode (OLED) compound precursors.

  9. Thrust Stand Measurements of the Microwave Assisted Discharge Inductive Plasma Accelerator

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley K.; Polzin, Kurt A.; Emsellem, Gregory D.

    2011-01-01

    Pulsed inductive plasma thrusters [1-3] are spacecraft propulsion devices in which electrical energy is capacitively stored and then discharged through an inductive coil. This type of pulsed thruster is electrodeless, with a time-varying current in the coil interacting with a plasma covering the face of the coil to induce a plasma current. Propellant is accelerated and expelled at a high exhaust velocity (O(10-100 km/s)) by the Lorentz body force arising from the interaction of the magnetic field and the induced plasma current. While this class of thruster mitigates the life-limiting issues associated with electrode erosion, pulsed inductive plasma thrusters require high pulse energies to inductively ionize propellant. The Microwave Assisted Dis- charge Inductive Plasma Accelerator (MAD-IPA), shown in Fig. 1, is a pulsed inductive plasma thruster that addressees this issue by partially ionizing propellant inside a conical inductive coil before the main current pulse via an electron cyclotron resonance (ECR) discharge. The ECR plasma is produced using microwaves and a static magnetic field from a set of permanent magnets arranged to create a thin resonance region along the inner surface of the coil, restricting plasma formation, and in turn current sheet formation, to a region where the magnetic coupling between the plasma and the theta-pinch coil is high. The use of a conical theta-pinch coil also serves to provide neutral propellant containment and plasma plume focusing that is improved relative to the more common planar geometry of the Pulsed Inductive Thruster (PIT) [1, 2]. In this paper, we describe thrust stand measurements performed to characterize the performance (specific impulse, thrust efficiency) of the MAD-IPA thruster. Impulse data are obtained at various pulse energies, mass flow rates and inductive coil geometries. Dependencies on these experimental parameters are discussed in the context of the current sheet formation and electromagnetic plasma

  10. Cadmium and lead in grey wolf liver samples: optimisation of a microwave-assisted digestion method.

    PubMed

    Vihnanek Lazarus, Maja; Sekovanić, Ankica; Kljaković-Gašpić, Zorana; Orct, Tatjana; Jurasović, Jasna; Kusak, Josip; Reljić, Slaven; Huber, Duro

    2013-09-01

    A microwave-assisted digestion method for the determination of cadmium (Cd) and lead (Pb) by inductively coupled plasma mass spectrometry (ICP-MS) was optimised on certified reference material (CRM) (bovine liver, BCR-185R) and wolf liver samples. Different factors influencing digestion efficiency (temperature, time, composition of the digestion mixture, sample mass) were tested. Validation included linearity (up to 200 μg L(-1) for Cd and Pb), detection (0.003 μg L(-1) for Cd and 0.035 μg L(-1) for Pb), and quantification (0.008 μg L(-1) for Cd and 0.081 μg L(-1) for Pb) limits. Good agreement between measured and certified values was achieved in all conditions, with recoveries ranging from 94 % to 111 % for Cd and from 95 % to 105 % for Pb. The precision of the method, expressed as relative standard deviation, was up to 3 % for Cd and 8 % for Pb. The best digestion parameters (260 °C, 30 min, 1 mL HNO3+4 mL H2O, 0.1 g of CRM) based on accuracy and precision were applied on two wolf liver samples to evaluate the need for the predigestion step (freeze-drying) and appropriate mass of the sample. Freeze-drying improved precision and minimising the tissue mass to 0.1 g reduced the matrix effect. Using these optimised digestion conditions, we determined Cd and Pb in 40 wolf livers collected in Croatia, and their medians (0.055 μg g(-1) and 0.107 μg g(-1), respectively) were in the range of previously reported data for the grey wolf. PMID:24084348

  11. Evaluation of oxygen pressurized microwave-assisted digestion of botanical materials using diluted nitric acid.

    PubMed

    Bizzi, Cezar Augusto; Barin, Juliano Smanioto; Müller, Edson Irineu; Schmidt, Lucas; Nóbrega, Joaquim A; Flores, Erico Marlon Moraes

    2011-02-15

    The feasibility of diluted nitric acid solutions for microwave-assisted decomposition of botanical samples in closed vessels was evaluated. Oxygen pressurized atmosphere was used to improve the digestion efficiency and Al, Ca, K, Fe, Mg and Na were determined in digests by inductively coupled plasma optical emission spectrometry (ICP OES). Efficiency of digestion was evaluated taking into account the residual carbon content (RCC) and residual acidity in digests. Samples were digested using nitric acid solutions (2, 3, 7, and 14 mol L(-1) HNO(3)) and the effect of gas phase composition inside the reaction vessels by purging the vessel with Ar (inert atmosphere, 1 bar), air (20% of oxygen, 1 bar) and pure O(2) (100% of oxygen, 1 bar) was evaluated. The influence of oxygen pressure was studied using pressures of 5, 10, 15 and 20 bar. It was demonstrated that a diluted nitric acid solution as low as 3 mol L(-1) was suitable for an efficient digestion of sample masses up to 500 mg of botanical samples using 5 bar of oxygen pressure. The residual acidities in final digests were lower than 45% in relation to the initial amount of acid used for digestion (equivalent to 1.3 mol L(-1) HNO(3)). The accuracy of the proposed procedure was evaluated using certified reference materials of olive leaves, apple leaves, peach leaves and pine needles. Using the optimized conditions for sample digestion, the results obtained were in agreement with certified values. The limit of quantification was improved up to a factor of 14.5 times for the analytes evaluated. In addition, the proposed procedure was in agreement with the recommendations of the green chemistry once it was possible to obtain relatively high digestion efficiency (RCC<5%) using only diluted HNO(3), which is important to minimize the generation of laboratory residues. PMID:21238716

  12. Supercritical Carbon Dioxide and Microwave-Assisted Extraction of Functional Lipophilic Compounds from Arthrospira platensis.

    PubMed

    Esquivel-Hernández, Diego A; López, Víctor H; Rodríguez-Rodríguez, José; Alemán-Nava, Gibrán S; Cuéllar-Bermúdez, Sara P; Rostro-Alanis, Magdalena; Parra-Saldívar, Roberto

    2016-01-01

    Arthrospira platensis biomass was used in order to obtain functional lipophilic compounds through green extraction technologies such as supercritical carbon dioxide fluid extraction (SFE) and microwave-assisted extraction (MAE). The temperature (T) factor was evaluated for MAE, while for SFE, pressure (P), temperature (T), and co-solvent (ethanol) (CS) were evaluated. The maximum extraction yield of the obtained oleoresin was (4.07% ± 0.14%) and (4.27% ± 0.10%) for SFE and MAE, respectively. Extracts were characterized by gas chromatography mass spectrometry (GC-MS) and gas chromatography flame ionization detector (GC-FID). The maximum contents of functional lipophilic compounds in the SFE and MAE extracts were: for carotenoids 283 ± 0.10 μg/g and 629 ± 0.13 μg/g, respectively; for tocopherols 5.01 ± 0.05 μg/g and 2.46 ± 0.09 μg/g, respectively; and for fatty acids 34.76 ± 0.08 mg/g and 15.88 ± 0.06 mg/g, respectively. In conclusion, the SFE process at P 450 bar, T 60 °C and CS 53.33% of CO₂ produced the highest yield of tocopherols, carotenoids and fatty acids. The MAE process at 400 W and 50 °C gives the best extracts in terms of tocopherols and carotenoids. For yield and fatty acids, the MAE process at 400 W and 70 °C produced the highest values. Both SFE and MAE showed to be suitable green extraction technologies for obtaining functional lipophilic compounds from Arthrospira platensis. PMID:27164081

  13. Synthesis and characterization of nano ZnO rods via microwave assisted chemical precipitation method

    SciTech Connect

    Uma Sangari, N.; Chitra Devi, S.

    2013-01-15

    A microwave assisted chemical precipitation method has been employed for the synthesis of nano zinc oxide rods by reacting zinc nitrate and potassium hydroxide. The amount of potassium hydroxide was adjusted for three different pHs to achieve ZnO nano rods with varying aspect ratio. The mechanism of growth of nano rods is explained briefly. The average crystallite size of the as synthesized samples was analyzed by means of powder XRD pattern and estimated to vary from 25.6 nm to 43.1 nm. The existence of rods was confirmed using scanning electron microscopy (SEM). The samples were also analyzed using FT-IR. The optical properties of the samples were also studied by means of UV-visible spectra and Room Temperature Photo Luminescence studies. The band gap of the samples was determined from the DRS spectrum. A strong near band emission peaks due to surface defects are observed in the PL spectrum. - Graphical abstract: At the solution pH of 11 and 9, tetrapod-like and flower-like ZnO nano rods were formed along with separated rods respectively due to the formation of activated nuclei of different sizes. Highlights: Black-Right-Pointing-Pointer Increase in alkalinity of the precursor solution results in longer rods. Black-Right-Pointing-Pointer Beyond a saturation limit, the excess of added OH{sup -} ions inhibited the growth of rods. Black-Right-Pointing-Pointer Keeping all parameters the same, the alkalinity can only modify the aspect ratio of the rods and not their morphology.

  14. Optimization of microwave-assisted extraction for six inorganic and organic arsenic species in chicken tissues using response surface methodology.

    PubMed

    Zhang, Wenfeng; Hu, Yuanan; Cheng, Hefa

    2015-09-01

    Response surface methodology was applied to optimize the parameters for microwave-assisted extraction of six major inorganic and organic arsenic species (As(III), As(V), dimethyl arsenic acid, monomethyl arsenic acid, p-arsanilic acid, and roxarsone) from chicken tissues, followed by detection using a high-performance liquid chromatography with inductively coupled mass spectrometry detection method, which allows the simultaneous analysis of both inorganic and organic arsenic species in the extract in a single run. Effects of extraction medium, solution pH, liquid-to-solid ratio, and the temperature and time of microwave-assisted extraction on the extraction of the targeted arsenic species were studied. The optimum microwave-assisted extraction conditions were: 100 mg of chicken tissue, extracted by 5 mL of 22% v/v methanol, 90 mmol/L (NH4 )2 HPO4 , and 0.07% v/v trifluoroacetic acid (with pH adjusted to 10.0 by ammonium hydroxide solution), ramping for 10 min to 71°C, and holding for 11 min. The method has good extraction performance for total arsenic in the spiked and nonspiked chicken tissues (104.0 ± 13.8% and 91.6 ± 7.8%, respectively), except for the ones with arsenic contents close to the quantitation limits. Limits of quantitation (S/N = 10) for As(III), As(V), dimethyl arsenic acid, monomethyl arsenic acid, p-arsanilic acid, and roxarsone in chicken tissues using this method were 0.012, 0.058, 0.039, 0.061, 0.102, and 0.240 mg/kg (dry weight), respectively. PMID:26106064

  15. Microwave-assisted hydrothermal synthesis of porous SnO{sub 2} nanotubes and their lithium ion storage properties

    SciTech Connect

    Wang, H.E.; Xi, L.J.; Ma, R.G.; Lu, Z.G.; Chung, C.Y.; Bello, I.; Zapien, J.A.

    2012-06-15

    Porous SnO{sub 2} nanotubes have been synthesized by a rapid microwave-assisted hydrothermal process followed by annealing in air. The detailed morphological and structural studies indicate that the SnO{sub 2} tubes typically have diameters from 200 to 400 nm, lengths from 0.5 to 1.5 {mu}m and wall thicknesses from 50 to 100 nm. The SnO{sub 2} nanotubes are self-assembled by interconnected nanocrystals with sizes {approx}8 nm resulting in a specific surface area of {approx}54 m{sup 2} g{sup -1}. The pristine SnO{sub 2} nanotubes are used to fabricate lithium half cells to evaluate their lithium ion storage properties. The porous SnO{sub 2} nanotubes are characteristic with high lithium ion storage capacity, that is found to be 1258, 951, 757, 603, 458, and 288 mAh g{sup -1}, at 0.1, 0.2, 0.5, 1, 2, and 4C, respectively. The enhanced electrochemical properties of the SnO{sub 2} nanotubes can be ascribed to their unique geometry and porous structures. - Graphical abstract: Porous SnO{sub 2} nanotubes are synthesized by a fast microwave-assisted hydrothermal process and exhibit high lithium ion storage properties due to their unique geometry and porous characteristics. Highlights: Black-Right-Pointing-Pointer A microwave-assisted hydrothermal method was used to prepare porous SnO{sub 2} nanotubes. Black-Right-Pointing-Pointer The porous SnO{sub 2} nanotubes have abundant mesopores on their tube walls. Black-Right-Pointing-Pointer The porous SnO{sub 2} nanotubes possess high lithium ion storage properties. Black-Right-Pointing-Pointer Our results may promote the development of high-performance anode materials.

  16. Microwave-assisted synthesis of (aminomethylene)bisphosphine oxides and (aminomethylene)bisphosphonates by a three-component condensation.

    PubMed

    Bálint, Erika; Tajti, Ádám; Dzielak, Anna; Hägele, Gerhard; Keglevich, György

    2016-01-01

    A practical method was elaborated for the synthesis of (aminomethylene)bisphosphine oxides comprising the catalyst- and solvent-free microwave-assisted three-component condensation of primary amines, triethyl orthoformate and two equivalents of diphenylphosphine oxide. The method is also suitable for the preparation of (aminomethylene)bisphosphonates using (MeO)2P(O)H/(MeO)3CH or (EtO)2P(O)H/(EtO)3CH reactant pairs and even secondary amines. Several intermediates referring to the reaction mechanism together with a few by-products could also be identified. PMID:27559402

  17. Microwave-assisted Synthesis and antifungal activity of coumarin[8,7-e][1,3]oxazine derivatives.

    PubMed

    Zhang, Ming-Zhi; Zhang, Rong-Rong; Yin, Wen-Zheng; Yu, Xiang; Zhang, Ya-Ling; Liu, Pin; Gu, Yu-Cheng; Zhang, Wei-Hua

    2016-08-01

    The synthesis of novel coumarin[8,7-e][1,3]oxazine derivatives through a microwave-assisted three-component one-pot Mannich reaction is described in this study. All the target compounds were evaluated in vitro for their antifungal activity against Botrytis cinerea, Colletotrichum capsici, Alternaria solani, Gibberella zeae, Rhizoctonia solani, and Alternaria mali. The preliminary bioassays showed that 5e, 5m, and 5s exhibited good antifungal activity and the most active compound was 5m with an [Formula: see text] value as low as 2.1 nM against Botrytis cinerea. PMID:26880591

  18. Microwave-assisted isolation of essential oils from Nepeta crispa and N. racemosa and comparisons with the conventional method.

    PubMed

    Daryasari, Ameneh Porgham; Soleimani, Mojtaba; Ghorbani, Azam; Kheiri, Homayon; Daryasarie, Mohammad Porgham

    2012-11-01

    In this study microwave-assisted hydrodistillation (MAHD) has been compared with the conventional method of hydrodistillation for the extraction of the essential oils from two Iranian Lamiaceae species: Nepeta crispa Willd and N. racemosa Lam. The essential oils extracted by MAHD for 40 min were quantitatively and qualitatively (aromatic profile) similar to those obtained by conventional hydrodistillation for 3.5 h. The MAHD method yields an essential oil with higher amounts of more valuable oxygenated compounds, and allows substantial savings of costs in terms of time, energy and plant material. PMID:23285819

  19. Microwave-assisted synthesis of (aminomethylene)bisphosphine oxides and (aminomethylene)bisphosphonates by a three-component condensation

    PubMed Central

    Tajti, Ádám; Dzielak, Anna; Hägele, Gerhard

    2016-01-01

    Summary A practical method was elaborated for the synthesis of (aminomethylene)bisphosphine oxides comprising the catalyst- and solvent-free microwave-assisted three-component condensation of primary amines, triethyl orthoformate and two equivalents of diphenylphosphine oxide. The method is also suitable for the preparation of (aminomethylene)bisphosphonates using (MeO)2P(O)H/(MeO)3CH or (EtO)2P(O)H/(EtO)3CH reactant pairs and even secondary amines. Several intermediates referring to the reaction mechanism together with a few by-products could also be identified. PMID:27559402

  20. Microwave-assisted multicomponent reaction in water leading to highly regioselective formation of benzo[f]azulen-1-ones

    PubMed Central

    Wang, Shu-Liang; Cheng, Chuang; Wu, Fei-Yue; Jiang, Bo; Shi, Feng; Tu, Shu-Jiang; Rajale, Trideep; Li, Guigen

    2011-01-01

    Microwave-assisted three-component reaction has been established for the regioselective synthesis of benzo[f]azulen-1-ones. The reaction was performed in aqueous media under microwave irradiation by using readily available and inexpensive starting materials. A total of 38 examples were examined to show a broad substrate scope and good overall yields (70–89%). The present new synthesis shows attractive green chemistry characteristics, such as the use of water as reaction media, concise one-pot conditions, short reaction periods (7–24 min), easy work-up/purification and reduced waste production without the use of any strong acids or metal promoters. PMID:21731115

  1. Microwave discharge electrodeless lamps (MDEL). V. Microwave-assisted photolytic disinfection of Bacillus subtilis in simulated electroplating wash wastewaters.

    PubMed

    Horikoshi, Satoshi; Tsuchida, Akihiro; Abe, Masahiko; Ohba, Naoki; Uchida, Masayoshi; Serpone, Nick

    2010-01-01

    This short article examines the microwave-assisted photolytic disinfection of aqueous solutions contaminated by Bacillus subtilis microorganisms using UV and vacuum-UV radiation emitted from a microwave discharge electrodeless lamp (MDEL), a device containing a Hg/Ar gas-fill that was proposed recently for use in Advanced Oxidation Processes (AOPs). Results of the disinfection are compared with those obtained from UV radiation emitted by a low-pressure electrode Hg lamp and by an excimer lamp. Also examined is the disinfection of B. subtilis aqueous media that contained Au3+ or Ni2+ ions, species often found in the treatment of electroplating wash wastewaters. PMID:21721320

  2. Microwave-assisted hydrothermal synthesis of coralloid nanostructured nickel hydroxide hydrate and thermal conversion to nickel oxide

    SciTech Connect

    Lai, Teh-Long; Lai, Yuan-Lung; Yu, Jen-Wei; Shu, Youn-Yuen; Wang, Chen-Bin

    2009-10-15

    Coralloid nanostructured nickel hydroxide hydrate has been successfully synthesized by a simple microwave-assisted hydrothermal process using nickel sulfate hexahydrate as precursor and urea as hydrolysis-controlling agent. A pure coralloid nanostructured nickel oxide can be obtained from the nickel hydroxide hydrate after calcination at 400 deg. C. The thermal property, structure and morphology of samples were characterized by thermogravimetry (TG), temperature-programmed reduction (TPR), X-ray (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

  3. Closed vessel microwave assisted extraction - An innovative method for determination of trace metals in plant materials

    NASA Astrophysics Data System (ADS)

    Oeztan, S.; Duering, R.-A.

    2012-04-01

    Determination of metal concentrations in plant samples is important for better understanding of effects of toxic metals that are biologically magnified through the food chain and compose a great danger to all living beings. In recent years the use of microwave assisted extraction for plant samples has shown tremendous research interest which will probably substitute conventional procedures in the future. Generally conventional procedures have disadvantages including consuming of time and solvents. The objective of this study is to investigate and compare a new closed vessel microwave extraction (MAE) method with the combination of EDTA (MAE-EDTA) for the determination of metal contents (Cd, Mn, Pb, Zn) in plant samples (Lolio-Cynosuretum) by ICP-OES. Validation of the method was done by comparison of the results with another MAE procedure (MAE-H) which is applied with the mixture of 69% nitric acid (HNO3) and 30% hydrogen peroxide (H2O2). Moreover, conventional plant extraction (CE) method, for which the dissolution of plant samples were handled in HNO3 after dry ashing at 420° C, was used as a reference method. Approximately 0.5 g of sample was digested in 5 ml HNO3, 3 ml H2O2, and 5 ml deionized H2O for MAE-H and in 8 ml EDTA solution for MAE-EDTA. Certified plant reference materials (CRMs) were used for comparison of recovery rates from different extraction protocols. Thereby, the applicability of both MAE-H and MAE-EDTA procedures could be demonstrated. For 58 plant samples MAE-H showed the same extraction yields as CE in the determination of trace metal contents of the investigated elements in plant samples. MAE-EDTA gave similar values when compared to MAE-H and highly linear relationships were found for determination of Cd, Mn, Pb and Zn amounts. The recoveries for the CRMs were within the range 89.6-115%. Finally, strategic characteristics of MAE-EDTA for determination metal contents (Cd, Mn, Pb, Zn) in plant samples are: (i) applicability to a large set

  4. Thrust Stand Measurements Using Alternative Propellants in the Microwave Assisted Discharge Inductive Plasma Accelerator

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley K.; Polzin, Kurt A.

    2011-01-01

    Storable propellants (for example water, ammonia, and hydrazine) are attractive for deep space propulsion due to their naturally high density at ambient interplanetary conditions, which obviates the need for a cryogenic/venting system. Water in particular is attractive due to its ease of handling and availability both terrestrially and extra-terrestrially. While many storable propellants are reactive and corrosive, a propulsion scheme where the propellant is insulated from vulnerable (e.g. metallic) sections of the assembly would be well-suited to process these otherwise incompatible propellants. Pulsed inductive plasma thrusters meet this criterion because they can be operated without direct propellant-electrode interaction. During operation of these devices, electrical energy is capacitively stored and then discharged through an inductive coil creating a time-varying current in the coil that interacts with a plasma covering the face of the coil to induce a plasma current. Propellant is accelerated and expelled at a high exhaust velocity (O(10-100 km/s)) by the Lorentz body force arising from the interaction of the magnetic field and the induced plasma current. While this class of thruster mitigates the life-limiting issues associated with electrode erosion, many pulsed inductive plasma thrusters require high pulse energies to inductively ionize propellant. The Microwave Assisted Discharge Inductive Plasma Accelerator (MAD-IPA) is a pulsed inductive plasma thruster that addressees this issue by partially ionizing propellant inside a conical inductive coil before the main current pulse via an electron cyclotron resonance (ECR) discharge. The ECR plasma is produced using microwaves and a static magnetic field from a set of permanent magnets arranged to create a thin resonance region along the inner surface of the coil, restricting plasma formation, and in turn current sheet formation, to a region where the magnetic coupling between the plasma and the theta

  5. Resilience of Oocyte Germinal Vesicles to Microwave-Assisted Drying in the Domestic Cat Model

    PubMed Central

    Lee, Pei-Chih; Paramore, Elisha; Van Vorst, Matthew; Comizzoli, Pierre

    2015-01-01

    The ability to compact and inject the cat germinal vesicle (GV) into a recipient cytoplast allows exploration of a new fertility preservation strategy that avoids whole oocyte freezing. The objective of the present study was to understand the impact of water loss and storage time on GV DNA integrity. Immature cat oocytes were exposed to 1.5 M trehalose for 10 min before microwave-assisted dehydration for 0, 5, 10, 15, 20, 25, 30, or 40 min. Oocytes then were rehydrated to assess chromatin configuration and the incidence of DNA fragmentation (TUNEL assay). The moisture content progressively decreased (p<0.05) from 1.7 to 0.1 gH2O/gDW over the first 30 min, but did not decrease further (p>0.05) after 40 min. Chromatin configuration was unaffected (p>0.05) over time. The percentage of GVs with DNA fragmentation was unaltered (p>0.05) from 0 to 30 min of treatment (range, 6.1%–12%), but increased (p<0.05) to 32.5% after 40 min. Next, the influence of storage at two different supra-zero temperatures after 30 min of drying was investigated. Oocyte-loaded, microwave-treated filters were individually sealed in Dri-Shield moisture barrier bags and stored at 4°C or ambient temperature for 0 to 8 weeks. Moisture contents gradually decreased (p<0.05) from 0.12 to 0.10 gH2O/gDW after 8 weeks of storage at 4°C or ambient temperature. The percentage of GVs with DNA fragmentation more than doubled (p<0.05) from 0 (14.3%) to 2 days (30.0%–33.0%), but remained stable (p>0.05) thereafter (1 through 4 weeks, 25.0%–35.0%). Collective results demonstrate the feasibility of using microwave processing to dehydrate the mammalian GV to a moisture content that is nonlethal and enables nonfrozen storage, an alternative approach for preserving the maternal genome at cool or ambient temperature. PMID:26035005

  6. Resilience of oocyte germinal vesicles to microwave-assisted drying in the domestic cat model.

    PubMed

    Elliott, Gloria D; Lee, Pei-Chih; Paramore, Elisha; Van Vorst, Matthew; Comizzoli, Pierre

    2015-06-01

    The ability to compact and inject the cat germinal vesicle (GV) into a recipient cytoplast allows exploration of a new fertility preservation strategy that avoids whole oocyte freezing. The objective of the present study was to understand the impact of water loss and storage time on GV DNA integrity. Immature cat oocytes were exposed to 1.5 M trehalose for 10 min before microwave-assisted dehydration for 0, 5, 10, 15, 20, 25, 30, or 40 min. Oocytes then were rehydrated to assess chromatin configuration and the incidence of DNA fragmentation (TUNEL assay). The moisture content progressively decreased (p<0.05) from 1.7 to 0.1 gH2O/gDW over the first 30 min, but did not decrease further (p>0.05) after 40 min. Chromatin configuration was unaffected (p>0.05) over time. The percentage of GVs with DNA fragmentation was unaltered (p>0.05) from 0 to 30 min of treatment (range, 6.1%-12%), but increased (p<0.05) to 32.5% after 40 min. Next, the influence of storage at two different supra-zero temperatures after 30 min of drying was investigated. Oocyte-loaded, microwave-treated filters were individually sealed in Dri-Shield moisture barrier bags and stored at 4°C or ambient temperature for 0 to 8 weeks. Moisture contents gradually decreased (p<0.05) from 0.12 to 0.10 gH2O/gDW after 8 weeks of storage at 4°C or ambient temperature. The percentage of GVs with DNA fragmentation more than doubled (p<0.05) from 0 (14.3%) to 2 days (30.0%-33.0%), but remained stable (p>0.05) thereafter (1 through 4 weeks, 25.0%-35.0%). Collective results demonstrate the feasibility of using microwave processing to dehydrate the mammalian GV to a moisture content that is nonlethal and enables nonfrozen storage, an alternative approach for preserving the maternal genome at cool or ambient temperature. PMID:26035005

  7. Synthesis of nanostructured and microstructured ZnO and Zn(OH)2 on activated carbon cloth by hydrothermal and microwave-assisted chemical bath deposition methods

    NASA Astrophysics Data System (ADS)

    Mosayebi, Elham; Azizian, Saeid; Hajian, Ali

    2015-05-01

    Nanostructured and microstructured ZnO and Zn(OH)2 loaded on activated carbon cloth were synthesized by microwave-assisted chemical bath deposition and hydrothermal methods. By hydrothermal method the deposited sample on carbon fiber is pure ZnO with dandelion-like nanostructures. By microwave-assisted chemical bath method the structure and composition of deposited sample depends on solution pH. At pH = 9.8 the deposited sample on carbon fiber is pure ZnO with flower-like microstructure; but at pH = 10.8 the sample is a mixture of ZnO and Zn(OH)2 with flower-like and rhombic microstructures, respectively. The mechanism of crystal grow by microwave-assisted chemical bath method was investigated by SEM method at both pH.

  8. The physicochemical properties of microwave-assisted encapsulated anthocyanins from Ipomoea batatas as affected by different wall materials

    PubMed Central

    Mohd Nawi, Norazlina; Muhamad, Ida Idayu; Mohd Marsin, Aishah

    2015-01-01

    This study focuses on the impact of different wall materials on the physicochemical properties of microwave-assisted encapsulated anthocyanins from Ipomoea batatas. Using the powder characterization technique, purple sweet potato anthocyanin (PSPAs) powders were analysed for moisture content, water activity, dissolution time, hygroscopicity, color and morphology. PSPAs were produced using different wall materials: maltodextrin (MD), gum arabic (GA) and a combination of gum arabic and maltodextrin (GA + MD) at a 1:1 ratio. Each of the wall materials was homogenized to the core material at a core/wall material ratio of 5 and were microencapsulated by microwave-assisted drying at 1100 W. Results indicated that encapsulated powder with the GA and MD combination presented better quality of powder with the lowest value of moisture content and water activity. With respect to morphology, the microcapsule encapsulated with GA + MD showed several dents in coating surrounding its core material, whereas other encapsulated powders showed small or slight dents entrapped onto the bioactive compound. Colorimetric analysis showed changes in values of L, a*, b*, hue and chroma in the reconstituted powder compared to the initial powder. PMID:25838887

  9. Microwave-assisted synthesis of reduced graphene oxide/titania nanocomposites as an adsorbent for methylene blue adsorption

    NASA Astrophysics Data System (ADS)

    Wang, Huan; Gao, Haihuan; Chen, Mingxi; Xu, Xiaoyang; Wang, Xuefang; Pan, Cheng; Gao, Jianping

    2016-01-01

    In this study microwave-assisted reduction (MrGO) and direct reduction of graphene oxide (rGO) by Ti powders were established, and the effect of the reaction conditions on the reduction were discussed. The results showed that GO can be effectively reduced by both methods, however, microwave assistance can greatly shorten the reduction time. The produced Ti ions from the reaction of Ti powder with GO were transferred to TiO2 by hydrolysis and formed MrGO/TiO2 and rGO/TiO2. They were used as adsorbents for the removal of methylene blue (MB). MrGO/TiO2 showed a higher adsorption capacity (qmax, 845.6 mg/g) than rGO/TiO2 (qmax, 467.6 mg/g). Investigation on the adsorption MB onto MrGO/TiO2 was conducted and demonstrated that adsorption kinetics followed the pseudo second-order kinetics model and the adsorption isotherm was well described by the Langmuir isotherm model. The recycling of MrGO/TiO2 was achieved by photocatalytic degradation of MB catalyzed by MrGO/TiO2 itself.

  10. Microwave-assisted rapid synthesis of birnessite-type MnO{sub 2} nanoparticles for high performance supercapacitor applications

    SciTech Connect

    Zhang, Xiong; Miao, Wang; Li, Chen; Sun, Xianzhong; Wang, Kai; Ma, Yanwei

    2015-11-15

    Highlights: • Birnessite-type MnO{sub 2} nanoparticles were prepared by the microwave-assisted reflux. • The microwave reaction duration was only 5 min. • A specific capacitance of 329 F g{sup −1} was obtained for birnessite-type MnO{sub 2}. - Abstract: Birnessite-type MnO{sub 2} nanoparticles have been successfully synthesized by the microwave-assisted reflux as short as 5 min. The microstructure and morphology of the products were characterized by X-ray diffraction, N{sub 2} adsorption–desorption isotherms, scanning electron microscopy, transmission electron microscopy. The electrochemical properties of the as-prepared MnO{sub 2} as an electrode material for supercapacitor were investigated by cyclic voltammetry and galvanostatic charge-discharge measurements in 1 M Na{sub 2}SO{sub 4} electrolyte, and a high specific capacitance of 329 F g{sup −1} was achieved at a current density of 0.2 A g{sup −1}. The specific capacitance retention was 92% after 1000 cycles at 2 A g{sup −1}, suggesting that it is a promising electrode material for supercapacitors.

  11. Fast and accurate preparation fatty acid methyl esters by microwave-assisted derivatization in the yeast Saccharomyces cerevisiae.

    PubMed

    Khoomrung, Sakda; Chumnanpuen, Pramote; Jansa-ard, Suwanee; Nookaew, Intawat; Nielsen, Jens

    2012-06-01

    We present a fast and accurate method for preparation of fatty acid methyl esters (FAMEs) using microwave-assisted derivatization of fatty acids present in yeast samples. The esterification of free/bound fatty acids to FAMEs was completed within 5 min, which is 24 times faster than with conventional heating methods. The developed method was validated in two ways: (1) through comparison with a conventional method (hot plate) and (2) through validation with the standard reference material (SRM) 3275-2 omega-3 and omega-6 fatty acids in fish oil (from the Nation Institute of Standards and Technology, USA). There were no significant differences (P>0.05) in yields of FAMEs with both validations. By performing a simple modification of closed-vessel microwave heating, it was possible to carry out the esterification in Pyrex glass tubes kept inside the closed vessel. Hereby, we are able to increase the number of sample preparations to several hundred samples per day as the time for preparation of reused vessels was eliminated. Pretreated cell disruption steps are not required, since the direct FAME preparation provides equally quantitative results. The new microwave-assisted derivatization method facilitates the preparation of FAMEs directly from yeast cells, but the method is likely to also be applicable for other biological samples. PMID:22569641

  12. Fabrication and morphology control of BaWO{sub 4} thin films by microwave assisted chemical bath deposition

    SciTech Connect

    Wang Rui; Liu Chen; Zeng Jia; Li KunWei; Wang Hao

    2009-04-15

    Highly crystallized barium tungstate (BaWO{sub 4}) thin films with dumbbell-like, kernel-like, bowknot-like and cauliflower-like microstructure were synthesized from an aqueous solution containing barium nitrate, ethylenediamine tetraacetate acid disodium and sodium tungstate, via mild microwave assisted chemical bath deposition process. The resulting BaWO{sub 4} films with different morphologies were characterized by X-ray diffraction spectrum, scanning electron microscope, Raman and photoluminescence spectra. The results indicate that the morphologies of final products significantly depend on the reaction conditions including the reaction time, the initial concentration of precursor reagent and the physicochemical characteristics of the substrates. Furthermore, the oriented aggregation mechanism is proposed as a possible formation mechanism of the films with specific morphologies. - Graphical abstract: Highly crystallized BaWO{sub 4} thin films with controllable morphologies have been synthesized via mild microwave assisted chemical bath deposition. The oriented aggregation mechanism has been proposed as the possible formation mechanism of specific films.

  13. The microwave-assisted ionic liquid nanocomposite synthesis: platinum nanoparticles on graphene and the application on hydrogenation of styrene

    NASA Astrophysics Data System (ADS)

    Lee, Jer-Yeu; Yung, Tung-Yuan; Liu, Ling-Kang

    2013-10-01

    The microwave-assisted nanocomposite synthesis of metal nanoparticles on graphene or graphite oxide was introduced in this research. With microwave assistance, the Pt nanoparticles on graphene/graphite oxide were successfully produced in the ionic liquid of 2-hydroxyethanaminium formate [HOCH2CH2NH3][HCO2]. On graphene/graphite oxide, the sizes of Pt nanoparticles were about 5 to 30 nm from transmitted electron microscopy (TEM) results. The crystalline Pt structures were examined by X-ray diffraction (XRD). Since hydrogenation of styrene is one of the important well-known chemical reactions, herein, we demonstrated then the catalytic hydrogenation capability of the Pt nanoparticles on graphene/graphite oxide for the nanocomposite to compare with that of the commercial catalysts (Pt/C and Pd/C, 10 wt.% metal catalysts on activated carbon from Strem chemicals, Inc.). The conversions with the Pt nanoparticles on graphene are >99% from styrene to ethyl benzene at 100°C and under 140 psi H2 atmosphere. However, ethyl cyclohexane could be found as a side product at 100°C and under 1,520 psi H2 atmosphere utilizing the same nanocomposite catalyst.

  14. The microwave-assisted ionic liquid nanocomposite synthesis: platinum nanoparticles on graphene and the application on hydrogenation of styrene.

    PubMed

    Lee, Jer-Yeu; Yung, Tung-Yuan; Liu, Ling-Kang

    2013-01-01

    The microwave-assisted nanocomposite synthesis of metal nanoparticles on graphene or graphite oxide was introduced in this research. With microwave assistance, the Pt nanoparticles on graphene/graphite oxide were successfully produced in the ionic liquid of 2-hydroxyethanaminium formate [HOCH2CH2NH3][HCO2]. On graphene/graphite oxide, the sizes of Pt nanoparticles were about 5 to 30 nm from transmitted electron microscopy (TEM) results. The crystalline Pt structures were examined by X-ray diffraction (XRD). Since hydrogenation of styrene is one of the important well-known chemical reactions, herein, we demonstrated then the catalytic hydrogenation capability of the Pt nanoparticles on graphene/graphite oxide for the nanocomposite to compare with that of the commercial catalysts (Pt/C and Pd/C, 10 wt.% metal catalysts on activated carbon from Strem chemicals, Inc.). The conversions with the Pt nanoparticles on graphene are >99% from styrene to ethyl benzene at 100°C and under 140 psi H2 atmosphere. However, ethyl cyclohexane could be found as a side product at 100°C and under 1,520 psi H2 atmosphere utilizing the same nanocomposite catalyst. PMID:24103100

  15. The microwave-assisted ionic liquid nanocomposite synthesis: platinum nanoparticles on graphene and the application on hydrogenation of styrene

    PubMed Central

    2013-01-01

    The microwave-assisted nanocomposite synthesis of metal nanoparticles on graphene or graphite oxide was introduced in this research. With microwave assistance, the Pt nanoparticles on graphene/graphite oxide were successfully produced in the ionic liquid of 2-hydroxyethanaminium formate [HOCH2CH2NH3][HCO2]. On graphene/graphite oxide, the sizes of Pt nanoparticles were about 5 to 30 nm from transmitted electron microscopy (TEM) results. The crystalline Pt structures were examined by X-ray diffraction (XRD). Since hydrogenation of styrene is one of the important well-known chemical reactions, herein, we demonstrated then the catalytic hydrogenation capability of the Pt nanoparticles on graphene/graphite oxide for the nanocomposite to compare with that of the commercial catalysts (Pt/C and Pd/C, 10 wt.% metal catalysts on activated carbon from Strem chemicals, Inc.). The conversions with the Pt nanoparticles on graphene are >99% from styrene to ethyl benzene at 100°C and under 140 psi H2 atmosphere. However, ethyl cyclohexane could be found as a side product at 100°C and under 1,520 psi H2 atmosphere utilizing the same nanocomposite catalyst. PMID:24103100

  16. Microwave-assisted derivatisation and LC-MS/MS determination of nitrofuran metabolites in farm-raised prawns (Penaeus monodon).

    PubMed

    Palaniyappan, Venkatesh; Nagalingam, Arun Kumar; Ranganathan, Hari Prasad; Kandhikuppam, Krishnamoorthy Bharathi; Kothandam, Hari Prasath; Vasu, Soumya

    2013-01-01

    A new microwave-assisted derivatisation and LC-MS/MS method has been developed for the analysis of nitrofuran metabolites - 3-amino-5-morpholino-methyl-1,3-oxa-zolidinone (AMOZ), 3-amino-2-oxazolidinone (AOZ), 1-aminohydantoin (AHD) and semicarbazide (SEM) - in farm-raised prawns (Penaeus monodon) from the coastal regions of South India. Analysis was carried out by reverse-phase column (Phenomenex Luna C18) with gradient elution using mobile phase A (0.02% acetic acid in water) and mobile phase B (0.02% acetic acid in acetonitrile), at a flow rate of 200 μl min(-1) and an injection volume of 20 μl. Microwave-assisted derivatisation was achieved in 6 min with good recovery. The results showed that the samples collected from Andhra Pradesh and Karnataka contained residues of nitrofuran metabolites in the range from 5.0 to 40 ng g(-1). This work emphasises the importance of ensuring the safety of seafood and that a new method of derivatisation is applicable for the analysis of nitrofuran metabolites in seafood. PMID:23883190

  17. Extending lean operating limit and reducing emissions of methane spark-ignited engines using a microwave-assisted spark plug

    DOE PAGESBeta

    Rapp, Vi H.; DeFilippo, Anthony; Saxena, Samveg; Chen, Jyh-Yuan; Dibble, Robert W.; Nishiyama, Atsushi; Moon, Ahsa; Ikeda, Yuji

    2012-01-01

    Amore » microwave-assisted spark plug was used to extend the lean operating limit (lean limit) and reduce emissions of an engine burning methane-air. In-cylinder pressure data were collected at normalized air-fuel ratios of λ = 1.46, λ = 1.51, λ = 1.57, λ = 1.68, and λ = 1.75. For each λ, microwave energy (power supplied to the magnetron per engine cycle) was varied from 0 mJ (spark discharge alone) to 1600 mJ. At lean conditions, the results showed adding microwave energy to a standard spark plug discharge increased the number of complete combustion cycles, improving engine stability as compared to spark-only operation. Addition of microwave energy also increased the indicated thermal efficiency by 4% at λ = 1.68. At λ = 1.75, the spark discharge alone was unable to consistently ignite the air-fuel mixture, resulting in frequent misfires. Although microwave energy produced more consistent ignition than spark discharge alone at λ = 1.75, 59% of the cycles only partially burned. Overall, the microwave-assisted spark plug increased engine performance under lean operating conditions (λ = 1.68) but did not affect operation at conditions closer to stoichiometric.« less

  18. Microwave-assisted Intramolecular Dehydrogenative Diels-Alder Reactions for the Synthesis of Functionalized Naphthalenes/Solvatochromic Dyes

    PubMed Central

    Kocsis, Laura S.; Benedetti, Erica; Brummond, Kay M.

    2013-01-01

    Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to the preparation of new organic dyes. Although numerous strategies have been reported to access naphthalene scaffolds, many procedures still present limitations in terms of incorporating functionality, which in turn narrows the range of available substrates. The development of versatile methods for direct access to substituted naphthalenes is therefore highly desirable. The Diels-Alder (DA) cycloaddition reaction is a powerful and attractive method for the formation of saturated and unsaturated ring systems from readily available starting materials. A new microwave-assisted intramolecular dehydrogenative DA reaction of styrenyl derivatives described herein generates a variety of functionalized cyclopenta[b]naphthalenes that could not be prepared using existing synthetic methods. When compared to conventional heating, microwave irradiation accelerates reaction rates, enhances yields, and limits the formation of undesired byproducts. The utility of this protocol is further demonstrated by the conversion of a DA cycloadduct into a novel solvatochromic fluorescent dye via a Buchwald-Hartwig palladium-catalyzed cross-coupling reaction. Fluorescence spectroscopy, as an informative and sensitive analytical technique, plays a key role in research fields including environmental science, medicine, pharmacology, and cellular biology. Access to a variety of new organic fluorophores provided by the microwave-assisted dehydrogenative DA reaction allows for further advancement in these fields. PMID:23609566

  19. Co3O4-reduced graphene oxide nanocomposite synthesized by microwave-assisted hydrothermal process for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Park, Sang-Hoon; Kim, Hyun-Kyung; Roh, Kwang Chul; Kim, Kwang-Bum

    2015-03-01

    A nanocomposite of Co3O4 and reduced graphene oxide (Co3O4-rGO) was successfully synthesized as an anode material for lithium-ion batteries by a one-pot microwave-assisted hydrothermal process. In the nanocomposite, Co3O4 nanoparticles with narrow size distribution in the range of 10-30 nm uniformly decorated the surface of rGO, indicating that rGO could act as a two-dimensional template for the heterogeneous precipitation of Co3O4 nanoparticles. To investigate the effect of mass ratios of Co3O4 and rGO on the electrochemical properties, the Co3O4 loading in the nanocomposite was controlled during the microwave-assisted hydrothermal synthesis. The resulting nanocomposite electrode exhibited high electrochemical performance in terms of specific capacity and cyclability, indicating that rGO served as an efficient template material to provide a highly conducting and buffering network for Co3O4 nanoparticles. [Figure not available: see fulltext.

  20. Microwave-assisted chemistry: synthetic applications for rapid assembly of nanomaterials and organics.

    PubMed

    Gawande, Manoj B; Shelke, Sharad N; Zboril, Radek; Varma, Rajender S

    2014-04-15

    The magic of microwave (MW) heating technique, termed the Bunsen burner of the 21st century, has emerged as a valuable alternative in the synthesis of organic compounds, polymers, inorganic materials, and nanomaterials. Important innovations in MW-assisted chemistry now enable chemists to prepare catalytic materials or nanomaterials and desired organic molecules, selectively, in almost quantitative yields and with greater precision than using conventional heating. By controlling the specific MW parameters (temperature, pressure, and ramping of temperature) and choice of solvents, researchers can now move into the next generation of advanced nanomaterial design and development. Microwave-assisted chemical reactions are now well-established practices in the laboratory setting although some controversy lingers as to how MW irradiation is able to enhance or influence the outcome of chemical reactions. Much of the discussion has focused on whether the observed effects can, in all instances, be rationalized by purely thermal Arrhenius-based phenomena (thermal microwave effects), that is, the importance of the rapid heating and high bulk reaction temperatures that are achievable using MW dielectric heating in sealed reaction vessels, or whether these observations can be explained by so-called "nonthermal" or "specific microwave" effects. In recent years, innovative and significant advances have occurred in MW hardware development to help delineate MW effects, especially the use of silicon carbide (SiC) reaction vessels and the accurate measurement of temperature using fiber optic (FO) temperature probes. SiC reactors appear to be good alternatives to MW transparent borosilicate glass, because of their high microwave absorptivity, and as such they serve as valuable tools to demystify the claimed magical MW effects. This enables one to evaluate the influence of the electromagnetic field on the specific chemical reactions, under truly identical conventional heating

  1. Microwave assisted synthesis of sheet-like Cu/BiVO{sub 4} and its activities of various photocatalytic conditions

    SciTech Connect

    Chen, Xi; Li, Li; Yi, Tingting; Zhang, WenZhi; Zhang, Xiuli; Wang, Lili

    2015-09-15

    The Cu/BiVO{sub 4} photocatalyst with visible-light responsivity was prepared by the microwave-assisted hydrothermal method. The phase structures, chemical composition and surface physicochemical properties were well-characterized via X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance absorption (UV–vis/DRS), scanning electron microscopy (SEM), and N{sub 2} adsorption–desorption tests. Results indicate that the crystal structure of synthetic composite materials is mainly monoclinic scheelite BiVO{sub 4}, which is not changed with the increasing doping amount of Cu. In addition, the presence of Cu not only enlarges the range of the composite materials under the visible-light response, but also increases the BET value significantly. Compared to pure BiVO{sub 4}, 1% Cu/BiVO{sub 4}-160 performs the highest photocatalytic activity to degrade methylene blue under the irradiation of ultraviolet, visible and simulated sunlight. In addition, the capture experiments prove that the main active species was superoxide radicals during photocatalytic reaction. Moreover, the 1% Cu/BiVO{sub 4}-160 composite shows good photocatalytic stability after three times of recycling. - Graphical abstract: A series of BiVO{sub 4} with different amounts of Cu doping were prepared by the microwave-assisted method, moreover, which performed the high photocatalytic activities to degrade methylene blue under multi-mode. - Highlights: • A series of Cu/BiVO{sub 4} with different amounts of Cu doping were prepared by microwave-assisted synthesis. • The morphologies of as-samples were different with the amount of Cu doping increased. • Compared with pure BiVO{sub 4}, as-Cu/BiVO{sub 4} showed stronger absorption in the visible light region obviously. • 1% Cu/BiVO{sub 4}-160 performed the high photocatalytic activities to degrade methylene blue under multi-mode. • OH{sup •} and h{sup +} both play important roles in the photocatalytic reaction.

  2. Extraction of Maltol from Fraser Fir: A Comparison of Microwave-Assisted Extraction and Conventional Heating Protocols for the Organic Chemistry Laboratory

    ERIC Educational Resources Information Center

    Koch, Andrew S.; Chimento, Clio A.; Berg, Allison N.; Mughal, Farah D.; Spencer, Jean-Paul; Hovland, Douglas E.; Mbadugha, Bessie; Hovland, Allan K.; Eller, Leah R.

    2015-01-01

    Two methods for the extraction of maltol from Fraser fir needles are performed and compared in this two-week experiment. A traditional benchtop extraction using dichloromethane is compared to a microwave-assisted extraction using aqueous ethanol. Students perform both procedures and weigh the merits of each technique. In doing so, students see a…

  3. CATALYST-FREE REACTIONS UNDER SOLVENT-FEE CONDITIONS: MICROWAVE-ASSISTED SYNTHESIS OF HETEROCYCLIC HYDRAZONES BELOW THE MELTING POINT OF NEAT REACTANTS: JOURNAL ARTICLE

    EPA Science Inventory

    NRMRL-CIN-1437 Jeselnik, M., Varma*, R.S., Polanc, S., and Kocevar, M. Catalyst-free Reactions under Solvent-fee Conditions: Microwave-assisted Synthesis of Heterocyclic Hydrazones below the Melting Point of Neat Reactants. Published in: Chemical Communications 18:1716-1717 (200...

  4. Mathematical modeling and Monte Carlo simulation of thermal inactivation of non-proteolytic Clostridium botulinum spores during continuous microwave-assisted pasteurization

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study is to develop a mathematical method to simulate the internal temperature history of products processed in a prototype microwave-assisted pasteurization system (MAPS) developed by Washington State University. Two products (10 oz. beef meatball trays and 16 oz. salmon fill...

  5. A NOVEL HIGH-SPEED METHOD FOR THE GENERATION OF 4-ARYLDIHYDROPYRIMIDINE COMPOUND LIBRARIES USING A MICROWAVE-ASSISTED BIGINELLI CONDENSATION PROTOCOL -

    EPA Science Inventory

    In this presentation we report the application of microwave assisted chemistry to the parallel synthesis of 4-aryl-3,4-dihydropyrimidin-2(1H)-ones employing a solventless Biginelli multicomponent condensation protocol. The novel method employs neat mixtures of B-ketoesters, aryl ...

  6. Microwave-Assisted Synthesis of a Natural Insecticide on Basic Montmorillonite K10 Clay. Green Chemistry in the Undergraduate Organic Laboratory

    ERIC Educational Resources Information Center

    Dintzner, Matthew R.; Wucka, Paul R.; Lyons, Thomas W.

    2006-01-01

    A detailed investigation of the clay-catalyzed condensation of sesamol and other phenols with 3-methyl-2-butenal to give methylenedioxyprecocene (MDP) and other chromenes is presented. The clay-catalyzed microwave-assisted condensation of sesamol with 3-methyl-2-butenal is appropriate for incorporation into undergraduate organic laboratory…

  7. Morphology-controlled synthesis of nanostructured zinc hydroxide fluoride via a microwave-assisted ionic liquid route

    NASA Astrophysics Data System (ADS)

    Zhang, Songtao; Zheng, Mingbo; Song, Jiakui; Li, Nianwu; Lu, Hongling; Cao, Jieming

    2014-12-01

    Zinc hydroxide fluoride (Zn(OH)F) with multiform morphologies such as flower-like particles, pumpkin-like aggregates, and hollow orange-like aggregates are prepared by a microwave-assisted ionic liquid method. During synthesis, microwave irradiation accelerates the reaction rate and shortens the reaction time. 1-Butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) or 1-2-hydroxylethyl-3-methylimidazolium tetrafluoroborate ([C2OHmim][BF4]) is used as both reactant and template. Experimental results indicate that the morphology evolution of Zn(OH)F is mainly controlled by the concentration of zinc acetate solution. A possible mechanism underlying the formation of nanostructured Zn(OH)F with diverse morphologies is proposed. Furthermore, nanoporous ZnO is obtained by the thermal decomposition of as-prepared Zn(OH)F in air, and the morphology is well retained.

  8. The advantage of temperature feedbackcontrolled microwave assisted leaching under atmospheric pressure in comparison with conventional methods for environmental applications

    SciTech Connect

    Lorentzen, E.M.L.; Kingston, H.M.

    1995-12-31

    Temperature is an important key parameter for reactions, digestions and extractions. Therefore the control of temperature is the critical variable in environmental leach testing. Currently, many leach methods are accomplished on hot plates in beakers or flasks. These methods are very traditional, inefficient and imprecise. An advantage may be obtained by substituting microwave dissolution, improving efficiency, accuracy and precision through direct microwave energy coupling. Microwave assisted modified 3050 leaching of key elements (Chromium, Copper, Nickel, Lead, and Zinc) of environmental importance using temperature feedback control has been tested and compared to conventional EPA Method 3050. Different temperature feedback control procedures, regulating the temperature from inside and outside the sample flask, are evaluated. The temperature inside the flask is acquired by a glass bulb thermometer based on gas law principles. An IR-Sensor is used for temperature acquiring for non invasive vessel control. A comparison of advantages and drawbacks of power controlled, temperature controlled, and conventional digestions will be discussed.

  9. Microwave-assisted solid-phase synthesis of side-chain to side-chain lactam-bridge cyclic peptides.

    PubMed

    Tala, Srinivasa R; Schnell, Sathya M; Haskell-Luevano, Carrie

    2015-12-15

    Side-chain to side-chain lactam-bridged cyclic peptides have been utilized as therapeutic agents and biochemical tools. Previous synthetic methods of these peptides need special reaction conditions, form side products and take longer reaction times. Herein, an efficient microwave-assisted synthesis of side-chain to side-chain lactam-bridge cyclic peptides SHU9119 and MTII is reported. The synthesis time and efforts are significantly reduced in the present method, without side product formation. The analytical and pharmacological data of the synthesized cyclic peptides are in accordance with the commercially obtained compounds. This new method could be used to synthesize other side-chain to side-chain lactam-bridge peptides and amenable to automation and extensive SAR compound derivatization. PMID:26555357

  10. Microwave assisted preparation of n-butylacrylate grafted chitosan and its application for Cr(VI) adsorption.

    PubMed

    Santhana Krishna Kumar, A; Uday Kumar, Chinta; Rajesh, Vidya; Rajesh, N

    2014-05-01

    Biopolymers such as chitosan possess excellent properties suited for varied applications. In this work, we describe a novel microwave assisted method for the preparation of n-butylacrylate grafted chitosan adsorbent and its utility for the adsorption of chromium(VI). A 3 min irradiation time was enough to prepare the adsorbent, and techniques such as FT-IR, powder XRD, SEM and EDS were used for comprehensive characterization. The adsorption was effective at pH 3.5 with 25 mL of 20 ppm Cr(VI) solution. Langmuir, Freundlich, Dubinin-Radushkevich, Temkin, Elovich and Redlich isotherms were studied in detail. The ΔG, ΔH and ΔS parameters were evaluated to understand the adsorption thermodynamics. The adsorption involves the interaction of Cr(VI) with the hydroxyl and amino groups in chitosan. PMID:24530325

  11. Polyphenolic contents and antioxidant activities of Lawsonia inermis leaf extracts obtained by microwave-assisted hydrothermal method.

    PubMed

    Zohourian, Tayyebeh Haleh; Quitain, Armando T; Sasaki, Mitsuru; Goto, Motonobu

    2011-01-01

    Extracts obtained by microwave-assisted hydrothermal extraction of Lawsonia inermis leaves were evaluated for the presence of polyphenolic compounds and antioxidant activities. Extraction experiments were performed in temperature-controlled mode at a range of 100 to 200 degrees C, and extraction time of 5 to 30 min, and microwave-controlled mode at a power from 300-700 W, in irradiation time of 30 to 120 s. Polyphenolic contents were measured using Folin-Ciocalteau method, while antioxidant properties were analyzed using DPPH radical scavenging activities (RSA) expressed in BHA equivalents. Results showed that best values of RSA were obtained at mild temperature range of 100-120 degrees C. Controlling microwave power at short irradiation time gave better results than temperature-controlled treatment as well. Furthermore, comparison with the result obtained at room temperature confirmed that the use of microwave was more effective for extracting polar components that normally possess higher antioxidant activities. PMID:24428109

  12. Microwave assisted synthesis of porous ZnO/SnS heterojunction and its application in visible light degradation of ciprofloxacin

    NASA Astrophysics Data System (ADS)

    Makama, A. B.; Salmiaton, A.; Saion, E. B.; Choong, T. S. Y.; Abdullah, N.

    2016-07-01

    Porous ZnO/SnS heterojunctions were successfully synthesized via microwave-assisted heating of aqueous solutions containing different amounts of SnS precursors (SnCl2 and Na2S) in the presence of fixed amount of ZnCO3 nanoparticles. The experimental results revealed that the heterojunctions exhibited much higher visible light-driven photocatalytic activity for the degradation of the ciprofloxacin than pure SnS nanocrystals. The photocatalytic degradation efficiency (1-Ct/C0) of the pollutant for the most active heterogeneous nanostructure is about four times more efficient than pure SnS. The enhanced photocatalytic efficiency is ascribed to the synergic effect of high photon absorption and reduction in the recombination of electrons and holes because of efficient separation and electron transfer from the SnS to ZnO nanoparticles.

  13. Microwave-assisted rapid synthesis of luminescent gold nanoclusters for sensing Hg2+ in living cells using fluorescence imaging.

    PubMed

    Shang, Li; Yang, Linxiao; Stockmar, Florian; Popescu, Radian; Trouillet, Vanessa; Bruns, Michael; Gerthsen, Dagmar; Nienhaus, G Ulrich

    2012-07-21

    A microwave-assisted strategy for synthesizing dihydrolipoic acid (DHLA) capped fluorescent gold nanoclusters (AuNCs) has been developed. Irradiation with microwaves during synthesis enhanced the fluorescence quantum yield (QY) of AuNCs by about five-fold and shortened the reaction time from hours to several minutes. The as-synthesized DHLA-AuNCs possessed bright near-infrared fluorescence (QY: 2.9%), ultrasmall hydrodynamic diameter (3.3 nm), good colloidal stability over the physiologically relevant pH range of 5-10 as well as low cytotoxicity toward HeLa cells. Moreover, these DHLA-AuNCs were capable of sensing Hg(2+) through the specific interaction between Hg(2+) and Au(+) on the surface of AuNCs; the limit of detection (LOD) was 0.5 nM. A potential application in imaging intracellular Hg(2+) in HeLa cells was demonstrated by using spinning disc confocal microscopy. PMID:22460520

  14. Using Microwave-Assisted Powder Metallurgy Route and Nano-size Reinforcements to Develop High-Strength Solder Composites

    NASA Astrophysics Data System (ADS)

    Nai, S. M. L.; Kuma, J. V. M.; Alam, M. E.; Zhong, X. L.; Babaghorbani, P.; Gupta, M.

    2010-04-01

    In the present study, Sn-0.7Cu and Sn-3.5Ag lead-free solders used in the electronics packaging industry were reinforced with different volume percentages of nano-size alumina and tin oxide particulates, respectively, to synthesize two new sets of nanocomposites. These composites were developed using microwave-assisted powder metallurgy route followed by extrusion. The effects of addition of particulates on the physical, microstructural, and mechanical properties of the nanocomposites were investigated. Mechanical properties (microhardness, 0.2% YS, and UTS) for both composite systems increase with the presence of particulates. The best tensile strength was realized for composite solders reinforced with 1.5 vol.% alumina and 0.7 vol.% tin oxide particulates, which far exceeds the strength of eutectic Sn-Pb solder. The morphology of pores was observed to be one of the most dominating factors affecting the strength of materials.

  15. Microwave-assisted solvothermal synthesis of spinel AV2O4 (M = Mg, Mn, Fe, and Co).

    PubMed

    Gutierrez, Arturo; Manthiram, Arumugam

    2014-08-18

    Lower-valent vanadium oxide spinels AV2O4 (A = Mg, Mn, Fe, and Co) consisting of A(2+) and V(3+) ions have been synthesized by a low-temperature microwave-assisted solvothermal (MW-ST) synthesis process in a tetraethylene glycol (TEG) medium. The oxides are formed within a short reaction time of 30 min at 300 °C. Subsequent postheat treatment of the oxides at elevated temperatures in inert or reducing atmospheres results in an instability of the spinel phase, especially CoV2O4 due to the ease of formation of metallic Co, demonstrating the advantage of the low-temperature MW-ST process in accessing these oxides. This MW-ST synthesis approach is attractive for synthesizing other lower-valent transition-metal oxides that are otherwise difficult to obtain by conventional synthesis methods and for subsequent study of their unique physical and chemical properties. PMID:25100260

  16. Microwave-assisted extraction and a new determination method for total steroid saponins from Dioscorea zingiberensis C.H. Wright.

    PubMed

    Ren, Yao; Chen, Yu; Hu, Bohan; Wu, Hui; Lai, Furao; Li, Xiaofeng

    2015-12-01

    An efficient microwave-assisted extraction (MAE) technique was applied to isolate total steroid saponins from Dioscorea zingiberensis C.H. Wright (DZW). The optimal extracting conditions were established as 75% ethanol as solvent, ratio of solid/liquid 1:20 (g/ml), temperature 75 °C, irradiation power 600 W and three extraction cycles of 6 min each. Scanning electron microscopy (SEM) images of DZW processed by four different extractions provided visual evidence of the disruption effect on DZW. Diosgenin was quantified by HPLC and examined further by LC-ESI/MS after acid hydrolysis. Total steroid saponins were calculated using diosgenin from total steroid saponins. The MAE procedure was optimized, validated and compared with other conventional extraction processes. This report provides a convenient technology for the extraction and quantification of total saponins of DZW combining MAE with HPLC and LC-ESI/MS for the first time. PMID:26432686

  17. Innovative biofilm inhibition and anti-microbial behavior of molybdenum sulfide nanostructures generated by microwave-assisted solvothermal route

    NASA Astrophysics Data System (ADS)

    Qureshi, Nilam; Patil, Rajendra; Shinde, Manish; Umarji, Govind; Causin, Valerio; Gade, Wasudev; Mulik, Uttam; Bhalerao, Anand; Amalnerkar, Dinesh P.

    2015-03-01

    The incessant use of antibiotics against infectious diseases has translated into a vicious circle of developing new antibiotic drug and its resistant strains in short period of time due to inherent nature of micro-organisms to alter their genes. Many researchers have been trying to formulate inorganic nanoparticles-based antiseptics that may be linked to broad-spectrum activity and far lower propensity to induce microbial resistance than antibiotics. The way-out approaches in this direction are nanomaterials based (1) bactericidal and (2) bacteriostatic activities. We, herein, present hitherto unreported observations on microbial abatement using non-cytotoxic molybdenum disulfide nanostructures (MSNs) which are synthesized using microwave assisted solvothermal route. Inhibition of biofilm formation using MSNs is a unique feature of our study. Furthermore, this study evinces antimicrobial mechanism of MSNs by reactive oxygen species (ROS) dependent generation of superoxide anion radical via disruption of cellular functions.

  18. Microwave-assisted synthesis, characterization and spectral properties of non-peripherally tetra-substituted phthalocyanines containing eugenol moieties

    NASA Astrophysics Data System (ADS)

    Kantar, Cihan; Şahin, Zarife Sibel; Büyükgüngör, Orhan; Şaşmaz, Selami

    2015-06-01

    The microwave-assisted synthesis and characterization of novel non-peripherally eugenol substituted metallophthalocyanines (M: Co(II), Ni(II), Cu(II), Zn(II)) have been reported for the first time in this study. All the new compounds were characterized by a combination of FT-IR, 1H NMR, 13C NMR, and UV/vis spectroscopy techniques. The crystal structure of compound (1) was also determined by the single crystal diffraction technique. Newly synthesized eugenol substituted phthalocyanines have more redshift Q bands (about 17-18 nm) than previously reported eugenol substituted phthalocyanines. Zinc(II)phthalocyanine (1d) has an extra absorption band at 746 nm that calling "X band" at UV/vis spectrum.

  19. Microwave-assisted polyol synthesis of gadolinium-doped green luminescent carbon dots as a bimodal nanoprobe.

    PubMed

    Gong, Ningqiang; Wang, Hao; Li, Shuai; Deng, Yunlong; Chen, Xiao'ai; Ye, Ling; Gu, Wei

    2014-09-16

    The development of multimodal nanoprobes is highly desired in medical imaging because it integrates the advantages of multiple imaging modes. In this study, the gadolinium-doped green luminescent carbon dots (Gd-CDs) were prepared by the simple one-step microwave-assisted polyol method. The obtained Gd-CDs emitted a unique green photoluminescence with a quantum yield of 5.4%. The Gd-CDs exhibited a low cytotoxicity and could optically label the C6 glioma cells. Meanwhile, the r1 relaxivity of Gd-CDs was measured to be 11.356 mM(-1) s(-1). This high r1 value together with the r2/r1 ratio close to 1 nominates Gd-CDs as an excellent T1 contrast agent for magnetic resonance imaging. These Gd-CDs combining two complementary imaging modalities are therefore a promising bimodal nanoprobe in medical imaging for a better diagnosis. PMID:25157595

  20. Microwave-assisted synthesis of hydrophilic BaYF5:Tb/Ce,Tb green fluorescent colloid nanocrystals.

    PubMed

    Lei, Yongqian; Pang, Min; Fan, Weiqiang; Feng, Jing; Song, Shuyan; Dang, Song; Zhang, Hongjie

    2011-01-01

    Hydrophilic Ce, Tb doped BaYF(5) nanocrystals with uniform size were synthesized by a microwave-assisted route. The synthesized nanocrystals can be well dispersed in hydrophilic solutions (DMSO, DMF, EG, H(2)O). This synthesis procedure represents a less time consuming method, with high product yield and without using any assistant or/and template reagents, which may be expected to be a general method for rapid synthesis of other hydrophilic RE doped fluoride fluorescent nanocrystals. The Ce(3+), Tb(3+) codoped BaYF(5) nanocrystals show bright green fluorescence emission. The Ce(3+) acts as an effective energy transfer medium and the emission at the high (5)D(3) energy level of Tb is enhanced in this host material. PMID:21076744

  1. Morphological evolution of Cu2O based on a solvent effect in a microwave-assisted system

    NASA Astrophysics Data System (ADS)

    Luo, Xiao-Lin; Wang, Min-Juan; Chen, Yashao

    2015-12-01

    Evolution of Cu2O morphology, from a cubic aggregate to a mono-dispersed cube, then to a {100} planes etched cube, with respect to solvent composition is presented in the microwave-assisted system. The solvent composition has a great impact on crystallization kinetics and oxidation etching. A series of contrast experiments were designed to reveal the critical parameters in the etching process according to the oxidation reaction equation of Cu2O. {100} planes etched Cu2O cubes exhibit preferable absorbability on methyl orange in the dark, whereas Cu2O polycrystals show better photo-catalytic activity because of the highly active apexes and edges exposed on the surface.

  2. Efficient Microwave-Assisted Functionalization of the Aurivillius-Phase Bi2SrTa2O9.

    PubMed

    Wang, Yanhui; Delahaye, Emilie; Leuvrey, Cédric; Leroux, Fabrice; Rabu, Pierre; Rogez, Guillaume

    2016-04-18

    A new method of acidification and subsequent functionalization of the Aurivillius-phase Bi2SrTa2O9 (BST), using microwave irradiation, was developed. This method enables to obtain hybridized phases from layered BST. Functionalization of BST by various kinds of amines and diamines can be achieved in a few hours only, compared to much longer time (over a week) using conventional heating. Good crystallinity of the compounds is kept. In addition, a microwave-assisted preintercalation strategy was developed, allowing inserting new amines (bearing cyclic or aromatic groups) between the oxide layers previously unseen in this type of compound. This work opens new perspectives for the fast and easy functionalization of layered oxides with more elaborated molecules. PMID:27042754

  3. Fabrication and morphology control of BaWO 4 thin films by microwave assisted chemical bath deposition

    NASA Astrophysics Data System (ADS)

    Wang, Rui; Liu, Chen; Zeng, Jia; Li, KunWei; Wang, Hao

    2009-04-01

    Highly crystallized barium tungstate (BaWO 4) thin films with dumbbell-like, kernel-like, bowknot-like and cauliflower-like microstructure were synthesized from an aqueous solution containing barium nitrate, ethylenediamine tetraacetate acid disodium and sodium tungstate, via mild microwave assisted chemical bath deposition process. The resulting BaWO 4 films with different morphologies were characterized by X-ray diffraction spectrum, scanning electron microscope, Raman and photoluminescence spectra. The results indicate that the morphologies of final products significantly depend on the reaction conditions including the reaction time, the initial concentration of precursor reagent and the physicochemical characteristics of the substrates. Furthermore, the oriented aggregation mechanism is proposed as a possible formation mechanism of the films with specific morphologies.

  4. A microwave-assisted and heteropolyacids-catalysed cyclocondensation reaction for the synthesis of 4(3H)-quinazolinones.

    PubMed

    Ighilahriz, Karima; Boutemeur, Baya; Chami, Fariza; Rabia, Cherifa; Hamdi, Maâmar; Hamdi, Safouane M

    2008-01-01

    We have investigated a microwave-assisted synthesis of 4(3H)-quinazolinones by condensation of anthranilic acid, orthoesters (or formic acid) and substituted anilines,using Keggin-type heteropolyacids (H(3)PW(12)O(40).13H(2)O, H(4)SiW(12)O(40).13H(2)O,H(4)SiMo(12)O(40).13H(2)O or H(3)PMo(12)O(40).13H(2)O) as catalysts. We found that the the use of H(3)PW(12)O(40).13H(2)O acid coupled to microwave irradiation allows a solvent-free, rapid (approximately 13min) and high-yielding reaction. PMID:18463579

  5. Conventional and microwave assisted synthesis of pyrazolone Mannich bases possessing anti-inflammatory, analgesic, ulcerogenic effect and antimicrobial properties.

    PubMed

    Sivakumar, Kullampalayam Krishnasamy; Rajasekaran, Aiyalu; Senthilkumar, Palaniappan; Wattamwar, Prasad P

    2014-07-01

    In the present study, an efficient synthesis of some Mannich base of 5-methyl-2-[(2-oxo-2H-chromen-3-yl)carbonyl]-2,4-dihydro-3H-pyrazol-3-one (4a-j) have been described by using conventional and non-conventional (microwave) techniques. Microwave assisted reactions showed that require shorter reaction time and good yield. The newly synthesized compounds were screened for their anti-inflammatory, analgesic activity, antioxidant, and antibacterial effects were compared with standard drug. Among the compounds studied, compound (4f) showing nearly equipotent anti-inflammatory and analgesic activity than the standard drug (indomethacin), along with minimum ulcerogenic index. Compounds (4b and 4i) showing 1.06 times more active than ciprofloxacin against tested Gram-negative bacteria. PMID:24835630

  6. Reduced leakage current and improved ferroelectricity in magneto-electric composite ceramics prepared with microwave assisted radiant hybrid sintering

    SciTech Connect

    Upadhyay, Sanjay Kumar; Reddy, V. Raghavendra E-mail: vrreddy.ugcdaecsr@nic.in; Gupta, S. M.; Chauhan, N.; Gupta, Ajay

    2015-04-15

    Structural, electrical and magnetic properties of magneto-electric composite ceramics viz., 0.9 BaTi{sub 0.95}Sn{sub 0.05}O{sub 3} (BTSO)- 0.1 Ni{sub 0.8}Zn{sub 0.2}Fe{sub 2}O{sub 4} (NZFO) prepared with microwave assisted radiant hybrid sintering (MARH) are reported. Phase purity and isovalent substitution of Ti{sup 4+} by Sn{sup 4+} of the samples is confirmed from x-ray diffraction and {sup 119}Sn Mossbauer measurements respectively. Significant suppression of leakage current and improvement of ferroelectricity is observed for the composites prepared with MARH. The observed results are explained in terms of uniform dispersion of ferrite (NZFO) phase in the ferroelectric (BTSO) matrix as evidenced from back-scattered scanning electron micrographs.

  7. Microwave-assisted synthesis of CdO-ZnO nanocomposite and its antibacterial activity against human pathogens.

    PubMed

    Karthik, K; Dhanuskodi, S; Gobinath, C; Sivaramakrishnan, S

    2015-03-15

    CdO-ZnO nanocomposite was prepared by microwave-assisted method and characterized by X-ray crystallography (XRD), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FT-IR). It exhibits hexagonal cubic structure with an average crystallite size of 27 nm. From the UV-Vis spectra, the bandgap is estimated as 2.92 eV. The fluorescence spectrum shows a near band edge emission at 422 nm. In addition the antibacterial activity of CdO-ZnO nanocomposite was carried out in-vitro against two kinds of bacteria: gram negative bacteria (G -ve) i.e. Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and gram positive bacteria (G +ve): Staphylococcus aureus, Proteus vulgaris and Bacillus spp. This study indicates the zone of inhibition of 40 mm has high antibacterial activity towards the gram positive bacterium S. aureus. PMID:25546491

  8. Microwave-Assisted Organocatalyzed Rearrangement of Propargyl Vinyl Ethers to Salicylaldehyde Derivatives: An Experimental and Theoretical Study.

    PubMed

    Tejedor, David; Cotos, Leandro; Márquez-Arce, Daniel; Odriozola-Gimeno, Mikel; Torrent-Sucarrat, Miquel; Cossío, Fernando P; García-Tellado, Fernando

    2015-12-01

    The microwave-assisted imidazole-catalyzed transformation of propargyl vinyl ethers (PVEs) into multisubstituted salicylaldehydes is described. The reaction is instrumentally simple, scalable, and tolerates a diverse degree of substitution at the propargylic position of the starting PVE. The generated salicylaldehyde motifs incorporate a broad range of topologies, spanning from simple aromatic monocycles to complex fused polycyclic systems. The reaction is highly regioselective and takes place under symmetry-breaking conditions. The preparative power of this reaction was demonstrated in the first total synthesis of morintrifolin B, a benzophenone metabolite isolated from the small tree Morinda citrifolia L. A DFT study of the reaction was performed with full agreement between calculated values and experimental results. The theoretically calculated values support a domino mechanism comprising a propargyl Claisen rearrangement, a [1,3]-H shift, a [1,7]-H shift (enolization), a 6π electrocyclization, and an aromatization reaction. PMID:26515241

  9. Microwave-assisted green synthesis of silver nanoparticles from Fraxinus excelsior leaf extract and its antioxidant assay

    NASA Astrophysics Data System (ADS)

    Parveen, Mehtab; Ahmad, Faheem; Malla, Ali Mohammed; Azaz, Shaista

    2016-02-01

    The biosynthesis of nanoparticles has been proposed as a cost effective and environmentally benevolent alternative to chemical and physical methods. In the present study, microwave assisted synthesis of silver nanoparticles (AgNPs) has been demonstrated using leaf extract of Fraxinus excelsior reducing aqueous AgNO3 solution. The synthesized nanoparticles have been characterized on the basis of fourier transform infrared spectroscopy (FT-IR), UV-Vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analysis. The presence of a characteristic surface plasmon resonance (SPR) absorption band at 425 nm in UV-Vis reveals the reduction of silver metal ions into silver nanoparticles. FT-IR analysis was carried out to probe the possible functional group involved in the synthesis of AgNPs. Further leaf extracts and AgNPs were evaluated for antiradical scavenging activity by 1,1-diphenyl-2-picryl-hydrazyl (DPPH) assay.

  10. Effect of deposition parameters on the structural properties of ZnO nanopowders prepared by microwave-assisted hydrothermal synthesis

    NASA Astrophysics Data System (ADS)

    Caglar, Yasemin; Gorgun, Kamuran; Aksoy, Seval

    2015-03-01

    ZnO nanopowders were synthesized via microwave-assisted hydrothermal method at different deposition (microwave irradiation) times and pH values. The effects of pH and deposition (microwave irradiation) time on the crystalline structure and orientation of the ZnO nanopowders have been investigated by X-ray diffraction (XRD) study. XRD observations showed that the crystalline quality of ZnO nanopowders increased with increasing pH value. The crystallite size and texture coefficient values of ZnO nanopowders were calculated. The structural quality of ZnO nanopowder was improved by deposition parameters. Field emission scanning electron microscope (FESEM) was used to analyze the surface morphology of the ZnO nanopowders. Microwave irradiation time and pH value showed a significant effect on the surface morphology.

  11. Rapid microwave-assisted synthesis of PVP-coated ultrasmall gadolinium oxide nanoparticles for magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Vahdatkhah, Parisa; Madaah Hosseini, Hamid Reza; Khodaei, Azin; Montazerabadi, Ali Reza; Irajirad, Rasoul; Oghabian, Mohamad Ali; Delavari H., Hamid

    2015-05-01

    Synthesis of polyvinyl pyrrolidone (PVP) coated ultrasmall Gd2O3 nanoparticles (NPs) with enhanced T1-weighted signal intensity and r2/r1 ratio close to unity is performed by a microwave-assisted polyol process. PVP coated Gd2O3NPs with spherical shape and uniform size of 2.5 ± 0.5 nm have been synthesized below 5 min and structure and morphology confirmed by HRTEM, XRD and FTIR. The longitudinal (r1) and transversal relaxation (r2) of Gd2O3NPs is measured by a 3 T MRI scanner. The results showed considerable increasing of relaxivity for Gd2O3NPs in comparison to gadolinium chelates which are commonly used for clinical magnetic resonance imaging. In addition, a mechanism for Gd2O3NPs formation and in situ surface modification of PVP-grafted Gd2O3NPs is proposed.

  12. Microwave assisted combustion synthesis of nanocrystalline CoFe{sub 2}O{sub 4} for LPG sensing

    SciTech Connect

    Chaudhari, Prashant; Acharya, S. A. Darunkar, S. S.; Gaikwad, V. M.

    2015-08-28

    A microwave-assisted citrate precursor method has been utilized for synthesis of nanocrystalline powders of CoFe{sub 2}O{sub 4}. The process takes only a few minutes to obtain as-synthesized CoFe{sub 2}O{sub 4}. Structural properties of the synthesized material were investigated by X-ray diffraction; scanning electron microscopy, Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy. The gas sensing properties of thick film of CoFe{sub 2}O{sub 4} prepared by screen printing towards Liquid Petroleum Gas (LPG) revealed that CoFe{sub 2}O{sub 4} thick films are sensitive and shows maximum sensitivity at 350°C for 2500 ppm of LPG.

  13. Microwave-assisted synthesis of CdO-ZnO nanocomposite and its antibacterial activity against human pathogens

    NASA Astrophysics Data System (ADS)

    Karthik, K.; Dhanuskodi, S.; Gobinath, C.; Sivaramakrishnan, S.

    2015-03-01

    CdO-ZnO nanocomposite was prepared by microwave-assisted method and characterized by X-ray crystallography (XRD), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FT-IR). It exhibits hexagonal cubic structure with an average crystallite size of 27 nm. From the UV-Vis spectra, the bandgap is estimated as 2.92 eV. The fluorescence spectrum shows a near band edge emission at 422 nm. In addition the antibacterial activity of CdO-ZnO nanocomposite was carried out in-vitro against two kinds of bacteria: gram negative bacteria (G -ve) i.e. Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and gram positive bacteria (G +ve): Staphylococcus aureus, Proteus vulgaris and Bacillus spp. This study indicates the zone of inhibition of 40 mm has high antibacterial activity towards the gram positive bacterium S. aureus.

  14. Microwave-Assisted Syntheses of Bioactive Seven-Membered, Macro-Sized Heterocycles and Their Fused Derivatives.

    PubMed

    Driowya, Mohsine; Saber, Aziza; Marzag, Hamid; Demange, Luc; Bougrin, Khalid; Benhida, Rachid

    2016-01-01

    This review describes the recent advances in the microwave-assisted synthesis of 7-membered and larger heterocyclic compounds. Several types of reaction for the cyclization step are discussed: Ring Closing Metathesis (RCM), Heck and Sonogashira reactions, Suzuki-Miyaura cross-coupling, dipolar cycloadditions, multi-component reactions (Ugi, Passerini), etc. Green syntheses and solvent-free procedures have been introduced whenever possible. The syntheses discussed herein have been selected to illustrate the huge potential of microwave in the synthesis of highly functionalized molecules with potential therapeutic applications, in high yields, enhanced reaction rates and increased chemoselectivity, compared to conventional methods. More than 100 references from the recent literature are listed in this review. PMID:27517892

  15. Microwave-assisted hydrolysis of Zymomonas mobilis levan envisaging oligofructan production.

    PubMed

    de Paula, Valdemir Cordeiro; Pinheiro, Irapuan Oliveira; Lopes, Carlos Edison; Calazans, Gli Cia Maria Torres

    2008-05-01

    Levan, a polysaccharide from Zymomonas mobilis, was hydrolyzed to obtain oligofructans or fructooligosaccharides with a degree of polymerization varying from 4 to 14. Fructooligosaccharides (FOS) are short chain fructans that beneficially affects the host by selective stimulation of growth and activity of one or a number of bacteria including probiotic bacteria in the colon. The hydrolysis was performed in a microwave oven to shorten the reaction time. The experiments showed that it is possible to maximize selected oligomers by interrupting the hydrolysis at the due time. The results allow one to infer that the procedure may also be useful for production of oligomers from other polysaccharides. PMID:17604160

  16. Tamoxifen derivatives for delivery of the antitumoral (DACH)Pt group: selective synthesis by McMurry coupling, and biochemical behaviour.

    PubMed

    Top, Siden; Kaloun, El Bachir; Vessières, Anne; Leclercq, Guy; Laïos, Ioanna; Ourevitch, Michèle; Deuschel, Christine; McGlinchey, Michael J; Jaouen, Gérard

    2003-08-01

    The goal of our study was to potentiate the effects of the ((R,R)-trans-1,2-diaminocyclohexane)-platinum(II) fragment [(DACH)Pt], known for its cytotoxic properties, either with tamoxifen (Tam), the most widely used antiestrogen in the treatment of hormone-dependent breast cancers, or with its active metabolite hydroxytamoxifen (hydroxy-Tam). We coupled Tam or hydroxy-Tam derivatives bearing a malonato group at the para position of the beta aromatic ring with the (DACH)Pt fragment. The malonato-Tam and malonato-hydroxy-Tam compounds were prepared through McMurry coupling of the appropriate ketones. The presence of the malonate group resulted in a pronounced stereospecificity in the reaction, since malonato-Tam was obtained only as the Z isomer, while malonato-hydroxy-Tam was obtained as an 80/20 E/Z mixture. Attribution of the isomeric structures was achieved by 2D NMR spectroscopy. The platinum complexes (DACH)Pt-malonato-Tam and (DACH)Pt-malonato-hydroxy-Tam were then prepared by coupling the barium salts derived from the malonato-Tam and malonato-hydroxy-Tam with the nitrate derived from (DACH)PtCl(2). Study of the biochemical properties of these two platinum complexes showed that, while the hydroxy-Tam complex is satisfactorily recognized by the estrogen receptor (relative binding affinity, RBA=6.4 %), the Tam complex is less well recognized (RBA=0.5 %). The effects of these complexes on two hormone-dependent breast cancer cell lines (MCF7 and MVLN) were studied in vitro. Both complexes showed an antiproliferative effect on MCF7 cells, and an antiestrogenic effect on MVLN cells. The observed effects appear to be essentially antihormonal, since incorporation of the (DACH)Pt fragment into the tamoxifen skeleton did not cause an increase in the cytotoxicity of the complexes. PMID:12898627

  17. Rapid, facile microwave-assisted synthesis of xanthan gum grafted polyaniline for chemical sensor.

    PubMed

    Pandey, Sadanand; Ramontja, James

    2016-08-01

    Grafting method, through microwave radiation procedure is extremely productive in terms of time consumption, cost effectiveness and environmental friendliness. In this study, conductive and thermally stable composite (mwXG-g-PANi) was synthesized by grafting of aniline (ANi) on to xanthan gum (XG) using catalytic weight of initiator, ammonium peroxydisulfate in the process of microwave irradiation in an aqueous medium. The synthesis of mwXG-g-PANi were confirm by FTIR, XRD, TGA, and SEM. The influence of altering the microwave power, exposure time of microwave, concentration of monomer and the amount of initiator of graft polymerization were studied over the grafting parameters, for example, grafting percentage (%G) and grafting efficiency (%E). The maximum %G and %E achieved was 172 and 74.13 respectively. The outcome demonstrates that the microwave irradiation strategy can increase the reaction rate by 72 times over the conventional method. Electrical conductivity of XG and mwXG-g-PANi composite film was performed. The fabricated grafted sample film were then examined for the chemical sensor. The mwXG-g-PANi, effectively integrated and handled, are NH3 sensitive and exhibit a rapid sensing in presence of NH3 vapor. Chemiresistive NH3 sensors with superior room temperature sensing performance were produced with sensor response of 905 at 1ppb and 90% recovery within few second. PMID:27118045

  18. Microwave assisted EDTA extraction-determination of pseudo total contents of distinct trace elements in solid environmental matrices.

    PubMed

    Öztan, Sezin; Düring, Rolf-Alexander

    2012-09-15

    Quantitative determination of metals in environmental matrices became important in the past few decades because of increasing pollutant concentrations in aquatic and terrestrial ecosystems. The extraction phase in the process of determining metals is crucial but very time-consuming. Consequently, new extraction techniques for extractable metals have been developed which probably will substitute conventional procedures in the future. The aim of this study was to improve a closed vessel microwave assisted extraction (MAE) by using EDTA as an exclusive extraction agent (MAE-EDTA) for the determination of pseudo total metal contents in solid environmental samples. For this purpose, a large set of soil and compost samples were analyzed. MAE-EDTA was compared with both closed vessel microwave assisted aqua regia extraction (MAE-AR) and a conventional aqua regia extraction (AR) method for the determination of pseudo total Cd, Cu, Mn, and Pb contents of soil and compost samples. Certified reference materials were used for comparison of recovery rates from different extraction protocols. Metal concentrations in soil and compost extracts were determined by ICP-OES. MAE-AR which was considered as a reference MAE method for further steps of the study, showed the same extraction yields in the determination of pseudo total metal contents of the investigated elements (As, Ba, Be, Cd, Co, Cr, Cu, Mn, Ni, Pb, V, Zn) in soil and compost samples as the conventional AR. MAE-EDTA gave similar values as the reference methods in the determination of Cd, Cu, and Pb amounts in soil samples and Cd, Mn, and Pb amounts in compost samples. The recovery rates ranged between 89.0-117.1% for soil samples and 93.5-104.0% for compost samples. MAE-EDTA provides fast processing of the samples that is less than one hour, including time for cooling of the samples. Apart from significantly less processing time, minimal consumption of sample and reagent chemicals is a strategic characteristic of MAE

  19. Microwave-assisted synthesis of BSA-protected small gold nanoclusters and their fluorescence-enhanced sensing of silver(i) ions

    NASA Astrophysics Data System (ADS)

    Yue, Yuan; Liu, Tian-Ying; Li, Hong-Wei; Liu, Zhongying; Wu, Yuqing

    2012-03-01

    A one-step microwave-assisted method is used for the synthesis of small gold nanoclusters, Au16NCs@BSA, which are used as a fluorescence enhanced sensor for detection of silver(i) ions with high selectivity and sensitivity.A one-step microwave-assisted method is used for the synthesis of small gold nanoclusters, Au16NCs@BSA, which are used as a fluorescence enhanced sensor for detection of silver(i) ions with high selectivity and sensitivity. Electronic supplementary information (ESI) available: Experimental details of the synthesis of AuNCs@BSA and fluorescent detection, and Fig. S1-S10. See DOI: 10.1039/c2nr12056a

  20. Micro-PIXE and micro-RBS characterization of micropores in porous silicon prepared using microwave-assisted hydrofluoric acid etching.

    PubMed

    Ahmad, Muthanna; Grime, Geoffrey W

    2013-04-01

    Porous silicon (PS) has been prepared using a microwave-assisted hydrofluoric acid (HF) etching method from a silicon wafer pre-implanted with 5 MeV Cu ions. The use of microbeam proton-induced X-ray emission (micro-PIXE) and microbeam Rutherford backscattering techniques reveals for the first time the capability of these techniques for studying the formation of micropores. The porous structures observed from micro-PIXE imaging results are compared to scanning electron microscope images. It was observed that the implanted copper accumulates in the same location as the pores and that at high implanted dose the pores form large-scale patterns of lines and concentric circles. This is the first work demonstrating the use of microwave-assisted HF etching in the formation of PS. PMID:23388452

  1. Synthesis and photoluminescence properties of LaPO4:Ce3+, Tb3+ nanophosphors by microwave-assisted co-precipitation method at low temperature

    NASA Astrophysics Data System (ADS)

    Dong, Wei-Li; Zhang, Xi-Yan; Shi, Hui; Mi, Xiao-Yun; Wang, Neng-Li; Han, Ke-Xuan

    2015-08-01

    Nanosized green phosphor LaPO4:Ce3+, Tb3+ has been synthesized by microwave-assisted co-precipitation method. The morphology, crystal structure and photoluminescence properties have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectrophotometer. The lanthanum phosphate phosphors with monoclinic crystal structure and fine crystallinity and dispersibility were synthesized at 900°C for 1 h and the particle size of the phosphors is ˜ 100 nm. The strongest photoluminescence emission peak is located at 543 nm due to the (5D4→7F5) transition of Tb3+ ion. The experimental results indicate that nanosized green phosphor 40% Ce3+ and 20% Tb3+ doped LaPO4 synthesized by microwave-assisted co-precipitation method is a beneficial phosphor for high resolution display devices.

  2. Superelectrophilic Activation of Crotonic/Methacrylic Acids: Direct Access to Thiochroman-4-ones from Benzenethiols by Microwave-Assisted One-Pot Alkylation/Cyclic Acylation.

    PubMed

    Vaghoo, Habiba; Prakash, G K Surya; Narayanan, Arjun; Choudhary, Rohit; Paknia, Farzaneh; Mathew, Thomas; Olah, George A

    2015-12-18

    An efficient microwave-assisted protocol for the synthesis of 2-/3-methylthiochroman-4-ones by superacid-catalyzed alkylation followed by cyclic acylation (cyclization via intramolecular acylation) is described. Using easily accessible benzenethiols and crotonic acid/methacrylic acid with triflic acid (as catalyst of choice for needed optimal acidity), the reaction was tuned toward the formation of the cyclized products in good selectivity and yield. A mechanism involving the formation of carbenium-carboxonium superelectrophilic species is suggested. PMID:26636718

  3. Microwave-Assisted Syntheses of Amino Acid Ester Substituted Benzoic Acid Amides: Potential Inhibitors of Human CD81-Receptor HCV-E2 Interaction.

    PubMed

    Holzer, Marcel; Ziegler, Sigrid; Kronenberger, Bernd; Klein, Christian D; Hartmann, Rolf W

    2008-01-01

    Results from our group showed benzyl salicylate to be a moderate inhibitor of the CD81-LEL-HCV-E2 interaction. To increase the biological activity, heterocyclic substituted benzoic acids were coupled to amino acid esters via microwave assisted DCC-reaction. The prepared compounds were tested for their inhibitory potency by means of a fluorescence labeled antibody assay system using HUH7.5 cells. PMID:19662141

  4. A one-step microwave-assisted synthetic method for an O/S-chemoselective route to derivatives of the first adenosine A3 PET radiotracer.

    PubMed

    Shanab, Karem; Neudorfer, Catharina; Holzer, Wolfgang; Mitterhauser, Markus; Wadsak, Wolfgang; Spreitzer, Helmut

    2014-01-01

    The synthesis of reference standards and expected in vivo metabolites of the first adenosine A3 PET radiotracer [18F]FE@SUPPY ([18F]fluoroethyl 4,6-diethyl-5-[(ethyl-sulfanyl)carbonyl]-2-phenylpyridine-3-carboxylate) was achieved by using a straightforward microwave assisted alkylation method, which allowed O/S-chemoselective alkylation of the starting material 1 to give each target compound 2-8 in a single step. PMID:24699149

  5. Synthesis and biological activity of novel 5'-arylamino-nucleosides by microwave-assisted one-pot tandem Staudinger/aza-Wittig/reduction.

    PubMed

    Chen, Hua; Zhao, Jianpeng; Li, Yanan; Shen, Fengjuan; Li, Xiaoliu; Yin, Qingmei; Qin, Zhanbin; Yan, Xinhao; Wang, Yanfei; Zhang, Pingzhu; Zhang, Jinchao

    2011-01-01

    Novel pseudonucleosides with benzylamino group on 5'-position (4) were synthesized by using the microwave-assisted one-pot tandem Staudinger/aza-Wittig/reduction reaction in good yields of 55.2-71.7%. The deacetylation of 4 afforded compounds 5. HIV-1 reverse transcriptase (RT) inhibitory and antitumor activities were preliminarily evaluated with 5. The results showed that the new pseudonucleosides (5) could effectively inhibit HIV-1 RT activity, but no antitumor activity. PMID:21095125

  6. Can electromagnetic fields influence the structure and enzymatic digest of proteins? A critical evaluation of microwave-assisted proteomics protocols

    PubMed Central

    Damm, Markus; Nusshold, Christoph; Cantillo, David; Rechberger, Gerald N.; Gruber, Karl; Sattler, Wolfgang; Kappe, C. Oliver

    2012-01-01

    This study reevaluates the putative advantages of microwave-assisted tryptic digests compared to conventionally heated protocols performed at the same temperature. An initial investigation of enzyme stability in a temperature range of 37–80 °C demonstrated that trypsin activity declines sharply at temperatures above 60 °C, regardless if microwave dielectric heating or conventional heating is employed. Tryptic digests of three proteins of different size (bovine serum albumin, cytochrome c and β-casein) were thus performed at 37 °C and 50 °C using both microwave and conventional heating applying accurate internal fiber-optic probe reaction temperature measurements. The impact of the heating method on protein degradation and peptide fragment generation was analyzed by SDS-PAGE and MALDI-TOF-MS. Time-dependent tryptic digestion of the three proteins and subsequent analysis of the corresponding cleavage products by MALDI-TOF provided virtually identical results for both microwave and conventional heating. In addition, the impact of electromagnetic field strength on the tertiary structure of trypsin and BSA was evaluated by molecular mechanics calculations. These simulations revealed that the applied field in a typical laboratory microwave reactor is 3–4 orders of magnitude too low to induce conformational changes in proteins or enzymes. PMID:22889711

  7. Microwave assisted SPPS of amylin and its toxicity of the pure product to RIN-5F cells.

    PubMed

    Muthusamy, Karen; Albericio, Fernando; Arvidsson, Per I; Govender, Patrick; Kruger, Hendrik G; Maguire, Glenn E M; Govender, Thavendran

    2010-01-01

    The 37-amino acid polypeptide islet amyloid polypeptide (IAPP), or amylin, is found as amyloid aggregates in the islets of Langerhans in patients with type II diabetes. Herein, we report an efficient microwave assisted solid phase peptide synthesis of amylin (IAPP). The most efficient synthesis used double and triple couplings and 10 equiv. of amino acids. Double couplings were used for most amino acids, whereas triple couplings were utilized for amino acids in selected regions. The most effective method for formation of the disulfide bond in amylin was found to be iodine oxidation. The highest purity amylin was obtained when the crude peptide was purified with HPLC before formation of the disulfide bond. The cytotoxicity of the synthesized amylin product to RIN-5F cells was determined. The synthesized amylin exhibits an exponential increase of cytotoxicity at concentrations >35 microM. Transmission electron microscope studies of a sample of amylin shows that insoluble amyloid fibrils spontaneously formed when 45 microM solution of synthesized amylin was incubated in a suitable buffer for 6 h. PMID:20069542

  8. Extraction and separation of nickel and cobalt from saprolite laterite ore by microwave-assisted hydrothermal leaching and chemical deposition

    NASA Astrophysics Data System (ADS)

    Zhao, Yan; Gao, Jian-ming; Yue, Yi; Peng, Ben; Que, Zai-qing; Guo, Min; Zhang, Mei

    2013-07-01

    Extraction and separation of nickel and cobalt from saprolite laterite ore were studied by using a method of microwave-assisted hydrothermal leaching and chemical deposition. The effects of leaching temperature and time on the extraction efficiencies of Ni2+ and Co2+ were investigated in detail under microwave conditions. It is shown that the extraction efficiencies of Ni2+ and Co2+ from the ore pre-roasted at 300°C for 5 h were 89.19% and 61.89% when the leaching temperature and time were about 70°C and 60 min, respectively. For the separation process of Ni and Co, the separation of main chemical components was performed by adjusting the pH values of sulfuric leaching solutions using a NaOH solution based on the different pH values of precipitation for metal hydroxides. The final separation efficiencies of Ni and Co were 77.29% and 65.87%, respectively. Furthermore, the separation efficiencies of Fe of 95.36% and Mg of 92.2% were also achieved at the same time.

  9. Dynamic microwave-assisted extraction combined with continuous-flow microextraction for determination of pesticides in vegetables.

    PubMed

    Wu, Lijie; Hu, Mingzhu; Li, Zhanchao; Song, Ying; Yu, Cui; Zhang, Hanqi; Yu, Aimin; Ma, Qiang; Wang, Ziming

    2016-02-01

    A simple, rapid, solventless and cost-effective dynamic microwave-assisted extraction (DMAE) combined with continuous-flow microextraction (CFME) system was firstly assembled and validated for extraction of eight organophosphorus pesticides in vegetables. The method combines the advantages of DMAE and CFME, and extends the application of the single drop microextraction to complex solid samples. The extraction, separation, and enrichment were performed in a single step, which could greatly simplify the operation and reduce the whole pretreatment time. In the developed method, analytes were first extracted from the vegetables using 3% NaCl solution as extraction solvent, then concentrated into microextraction solvent. After extraction, the microextraction solvent containing the enriched analyte was directly analyzed by GC-MS without any filtration or clean-up process. Several parameters affecting the extraction efficiency were investigated and optimized. Real vegetable samples were analyzed, satisfactory recoveries were obtained in the range of 80.7-106.7%, and relative standard deviations were lower than 8.7%. PMID:26304388

  10. Microwave-assisted alkaline extraction of galactan-rich rhamnogalacturonan I from potato cell wall by-product.

    PubMed

    Khodaei, Nastaran; Karboune, Salwa; Orsat, Valérie

    2016-01-01

    Galactan-rich rhamnogalacturonan I (RG I), exhibiting promising health benefits, is the most abundant polysaccharide in potato pulp by-product. In the present study, the microwave-assisted alkaline extraction of galactan-rich RG I was investigated. Solid/liquid ratio was identified as the most significant parameter affecting linearly yield and galactose/rhamnose contents. Microwave power and solid/liquid ratio exhibited a significant adverse interactive effect on the yield. Galactose content of extracted polysaccharides can be modulated by compromising between KOH concentration and extraction time, which exhibited adverse interaction. Optimum conditions were identified using the established predicted models and consisted of treatment of potato cell wall at solid/liquid ratio of 2.9% (w/v) with 1.5M KOH under microwave power of 36.0 W for 2.0 min. Yield of intact galactan-rich RG I of 21.6% and productivity of 192.0 g/Lh were achieved. The functional properties of RG I-rich polysaccharides were comparable or superior to potato galactan and oranges homogalacturonan. PMID:26213002

  11. Single-step microwave assisted headspace liquid-phase microextraction of trihalomethanes and haloketones in biological samples.

    PubMed

    Alsharaa, Abdulnaser; Basheer, Chanbasha; Sajid, Muhammad

    2015-12-15

    A single-step microwave assisted headspace liquid-phase microextraction (MA-HS-LPME) method was developed for determination of trihalomethanes (THMs) and haloketones (HKs) in biological samples. In this method, a porous membrane envelope was filled with few microliters of extraction solvent and then placed inside the microwave extraction vial. A PTFE ring was designed to support the membrane envelope over a certain height inside the vial. An optimum amount of biological sample was placed in the vial equipped with magnetic stirrer. After that nitric acid was added to the vial for digestion of biological sample. The sample was digested and the volatile THMs and HKs were extracted at headspace in the solvent containing porous membrane. After simultaneous digestion and extraction, the extract was injected to gas chromatography/mass spectrometry for analysis. Factors affecting the extraction efficiency were optimized to achieve higher extraction performance. Quantification was carried out over a concentration range of 0.3-100ngg(-1) for brominated compounds while for the chlorinated ones linear range was between 0.5-100ngg(-1). Limit of detections (LODs) were ranged from 0.051 to 0.110ngg(-1) while limit of quantification (LOQ) were in the range of 0.175-0.351ngg(-1). The relative standard deviations (RSDs) of the calibrations were ranged between 1.1 and 6.8%. The MA-HS-LPME was applied for the determination of trace level THMs and HKs in fish tissue and green alga samples. PMID:26571453

  12. Rapid tea catechins and caffeine determination by HPLC using microwave-assisted extraction and silica monolithic column.

    PubMed

    Rahim, A A; Nofrizal, S; Saad, Bahruddin

    2014-03-15

    A rapid reversed-phase high performance liquid chromatographic method using a monolithic column for the determination of eight catechin monomers and caffeine was developed. Using a mobile phase of water:acetonitrile:methanol (83:6:11) at a flow rate of 1.4 mL min(-1), the catechins and caffeine were isocratically separated in about 7 min. The limits of detection and quantification were in the range of 0.11-0.29 and 0.33-0.87 mg L(-1), respectively. Satisfactory recoveries were obtained (94.2-105.2 ± 1.8%) for all samples when spiked at three concentrations (5, 40 and 70 mg L(-1)). In combination with microwave-assisted extraction (MAE), the method was applied to the determination of the catechins and caffeine in eleven tea samples (6 green, 3 black and 2 oolong teas). Relatively high levels of caffeine were found in black tea, but higher levels of the catechins, especially epigallocatechin gallate (EGCG) were found in green teas. PMID:24206716

  13. Optimization of a microwave-assisted extraction of secondary metabolites from crustose lichens with quantitative spectrophotodensitometry analysis.

    PubMed

    Bonny, Sarah; Hitti, Eric; Boustie, Joël; Bernard, Aurélie; Tomasi, Sophie

    2009-11-01

    A focused and rapid microwave-assisted extraction (MAE) process was carried out and optimized for secondary metabolites from crustose lichens using Taguchi experimental design and quantitative analysis on TLC by a Camag((R)) spectrophotodensitometer. The procedure was improved by quantitative determination of norstictic acid (NA), a common depsidone isolated from Pertusaria pseudocorallina (Sw.) Arn. Various experimental parameters that can potentially affect the NA extraction yields including extraction time, irradiation power, volume and the percentage of tetrahydrofuran (THF) were optimized. Results suggest that THF percentage and solvent volume were statistically the most significant factors. The optimal conditions were determined as follows: THF level of 100%, solvent volume of 15mL, microwave power of 100W and extraction time of 7min. Compared to the reflux method, MAE showed a drastic reduction of extraction time (7min vs. 3h) and solvent consumption (15mL vs. 30mL). The NA in total yield was 90% using the two methods. The optimal conditions were applied to other crustose lichens, Aspicilia radiosa, Diploicia canescens and Ochrolechia parella for the extraction of NA, diploicine (DP) and variolaric acid (VA), with 83%, 90% and 95% of recovery, respectively. PMID:19796768

  14. The influence of microwave-assisted drying techniques on the rehydration behavior of blueberries (Vaccinium corymbosum L.).

    PubMed

    Zielinska, Magdalena; Markowski, Marek

    2016-04-01

    The aim of this study was to determine the effect of: (a) different drying methods, (b) hot air temperature in a convection oven, and (c) the moisture content of fruits dehydrated by multi-stage drying which involves a transition between different stages of drying, on the rehydration kinetics of dry blueberries. Models describing rehydration kinetics were also studied. Blueberries dehydrated by multi-stage microwave-assisted drying, which involved a hot air pre-drying step at 80 °C until the achievement of a moisture content of 1.95 kg H2O kg(-1)DM, were characterized by significantly higher rates of initial and successive rehydration as well as smaller initial loss of soluble solids in comparison with the samples dried by other methods. The highest initial rehydration rate and the smallest loss of soluble solids after 30 min of soaking were determined at 0.46 min(-1) and 0.29 kg DM kg(-1)DM, respectively. The Peleg model and the first-order-kinetic model fit the experimental data well. PMID:26593606

  15. Microwave-Assisted Extraction and Purification of Arctiin and Arctigenin from Fructus Arctii by High-Speed Countercurrent Chromatography.

    PubMed

    Lü, Haitao; Sun, Zhaoyun; Shan, Hu; Song, Jiying

    2016-03-01

    An efficient method for the rapid extraction, separation and purification of bioactive lignans, arctiin and arctigenin, from Fructus arctii by microwave-assisted extraction coupled with high-speed countercurrent chromatography was developed. The optimal extraction conditions of arctiin and arctigenin were evaluated by orthogonal array. Arctigenin could be converted from arctiin by hydrochloric acid hydrolysis. The separations were performed at a preparative scale with two-phase solvents composed of ethyl acetate-ethanol-water (5 : 1 : 5, v/v/v) for arctiin, and n-hexane-ethyl acetate-ethanol-water (4 : 4 : 3 : 4, v/v/v/v) for arctigenin. From 500 mg of crude extract sample, 122.3 mg of arctiin and 45.7 mg of arctigenin were obtained with the purity of 98.46 and 96.57%, and the recovery of 94.3 and 81.6%, respectively. Their structures were determined by comparison with the high-performance liquid chromatography retention time of standard substance as well as UV, FT-IR, electrospray ion source (ESI)-MS, (1)H-NMR and (13)C-NMR spectrum. According to the antioxidant activity assay, arctigenin had stronger 1,1-diphenyl-2-picrylhydrazyl free radicals scavenging activity. PMID:26590235

  16. Physical and electrochemical characterizations of microwave-assisted polyol preparation of carbon-supported PtRu nanoparticles.

    PubMed

    Liu, Zhaolin; Lee, Jim Yang; Chen, Weixiang; Han, Ming; Gan, Leong Ming

    2004-01-01

    PtRu nanoparticles supported on Vulcan XC-72 carbon and carbon nanotubes were prepared by a microwave-assisted polyol process. The catalysts were characterized by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy (XPS). The PtRu nanoparticles, which were uniformly dispersed on carbon, were 2-6 nm in diameter. All PtRu/C catalysts prepared as such displayed the characteristic diffraction peaks of a Pt face-centered cubic structure, excepting that the 2theta values were shifted to slightly higher values. XPS analysis revealed that the catalysts contained mostly Pt(0) and Ru(0), with traces of Pt(II), Pt(IV), and Ru(IV). The electro-oxidation of methanol was studied by cyclic voltammetry, linear sweep voltammetry, and chronoamperometry. It was found that both PtRu/C catalysts had high and more durable electrocatalytic activities for methanol oxidation than a comparative Pt/C catalyst. Preliminary data from a direct methanol fuel cell single stack test cell using the Vulcan-carbon-supported PtRu alloy as the anode catalyst showed high power density. PMID:15745018

  17. Microwave-assisted headspace solid-phase microextraction for the analysis of bioemissions from Eucalyptus citriodora leaves.

    PubMed

    Xiong, Guohua; Goodridge, Carolyn; Wang, Limei; Chen, Yong; Pawliszyn, Janusz

    2003-12-31

    Microwave-assisted headspace solid-phase microextraction (MA-HS-SPME) was developed as a simple and effective method for fast sampling of volatile organic compounds (VOCs) from Eucalyptus citriodora Hook (E. citriodora) leaves. During microwave heating, a simple shielding device made of aluminum foil was used to protect the SPME fiber from microwave irradiation while allowing the sample to be heated. A room temperature water bath was also used to allow microwave heating to be conducted in a more controlled manner. The inner heating caused by microwave irradiation dramatically accelerated the emission of VOCs from the sample, but no marked change in headspace temperature in the sample vial was found. Under optimum conditions, the extraction efficiencies obtained with microwave heating were much higher than those obtained without microwave heating for all fibers used, namely, 7-microm polydimethylsiloxane (PDMS), 100-microm polydimethylsiloxane (PDMS), 65-microm polydimethylsiloxane/divinylbenzene (PDMS/DVB), and 75-microm carboxen/polydimethylsiloxane (CAR/PDMS). The improvement of extraction efficiency using MA-HS-SPME allowed more VOC events to be detected, with more balanced extraction of VOCs of lower and higher molecular masses. Moreover, a good linear relationship was found between sample size and GC-FID response (total peak area of VOCs), indicating the usefulness of MA-HS-SPME for quantitative analysis of individual volatile compounds in E. citriodora leaves. PMID:14690362

  18. Simultaneous recovery of organic and inorganic content of paper deinking residue through low-temperature microwave-assisted pyrolysis.

    PubMed

    Zhang, Zhanrong; Macquarrie, Duncan J; Aguiar, Pedro M; Clark, James H; Matharu, Avtar S

    2015-02-17

    Significant amounts of paper deinking residue (DIR) has been and is still being generated from paper deinking processes, representing both an economic and environmental burden for recycled paper mills. Our research on low-temperature (<200 °C) microwave-assisted (MW-assisted) pyrolysis of DIR allows for simultaneously efficient fast separation and recovery of the organic and inorganic content of DIR at relatively low temperature and within 15 min. Our study is the first highly detailed account of the use low-temperature MW-assisted pyrolysis to effect this change. The obtained liquid and solid products were characterized by a variety of analytical techniques (e.g., attenuated total reflection infrared, gas chromatography-mass spectrometry, liquid-state nuclear magnetic resonance (NMR), X-ray diffraction, solid-state cross-polarization/magic-angle spinning (13)C NMR, and Bloch-decay (13)C NMR). The results reveal that the process efficiently separates the inorganic minerals as microwave residue (mainly calcite and kaolinite) from organic matter, and hence the microwave residue could be reused to produce new paper/cardboard products. The organic fraction bio-oil generated is energy-densified and rich in carbohydrates and is a potential source for valuable aromatic compounds. PMID:25590264

  19. Microwave assisted facile green synthesis of silver and gold nanocatalysts using the leaf extract of Aerva lanata

    NASA Astrophysics Data System (ADS)

    Joseph, Siby; Mathew, Beena

    2015-02-01

    Herein, we report a simple microwave assisted method for the green synthesis of silver and gold nanoparticles by the reduction of aqueous metal salt solutions using leaf extract of the medicinal plant Aerva lanata. UV-vis., FTIR, XRD, and HR-TEM studies were conducted to assure the formation of nanoparticles. XRD studies clearly confirmed the crystalline nature of the synthesized nanoparticles. From the HR-TEM images, the silver nanoparticles (AgNPs) were found to be more or less spherical and gold nanoparticles (AuNPs) were observed to be of different morphology with an average diameter of 18.62 nm for silver and 17.97 nm for gold nanoparticles. In order to evaluate the effect of microwave heating upon rate of formation, the synthesis was also conducted under ambient condition without the assistance of microwave radiation and the former method was found to be much faster than the later. The synthesized nanoparticles were used as nanocatalysts in the reduction of 4-nitrophenol to 4-aminophenol by NaBH4.

  20. Application of microwave-assisted micro-solid-phase extraction for determination of parabens in human ovarian cancer tissues.

    PubMed

    Sajid, Muhammad; Basheer, Chanbasha; Narasimhan, Kothandaraman; Choolani, Mahesh; Lee, Hian Kee

    2015-09-01

    Parabens (alkyl esters of p-hydroxybenzoic acid) are widely used as preservatives in food, cosmetics and pharmaceutical products. However, weak estrogenicity of some parabens has been reported in several studies, which provided the impetus for this work. Here, a simple and efficient analytical method for quantifying parabens in cancer tissues has been developed. This technique involves the simultaneous use of microwave-assisted solvent extraction (MASE) and micro-solid phase extraction (μ-SPE), in tandem with high performance liquid chromatography (HPLC/UV) analysis for the determination of parabens. The pollutants studied included four parabens (methyl, ethyl, propyl and butyl parabens). Optimization of the experimental parameters for MASE and μ-SPE was performed. Good relative standard deviation (%RSD) ranged from 0.09 to 2.81% and high enrichment factors (27-314) were obtained. Coefficients of determination (r(2)) up to 0.9962 were obtained across a concentration range of 5.0-200ngg(-1). The method detection limits for parabens ranged from 0.005 to 0.0244ngg(-1). The procedure was initially tested on prawn samples to demonstrate its feasibility on a complex biological matrix. Preliminary studies on human ovarian cancer (OC) tissues showed presence of parabens. Higher levels of parabens were detected in malignant ovarian tumor tissues compared to benign tumor tissue samples. PMID:26245364

  1. Microwave-assisted synthesis, characterization and antibacterial activity of Ag/ZnO nanoparticles supported bentonite clay.

    PubMed

    Motshekga, Sarah C; Ray, Suprakas S; Onyango, Maurice S; Momba, Maggie N B

    2013-11-15

    Composites of silver-zinc oxide nanoparticles supported on bentonite clay were synthesized by the microwave-assisted synthesis method for use as an antibacterial material. Silver nitrate was used as the precursor of silver nanoparticles while zinc oxide nanoparticles were commercially sourced. The composites were characterized by powder X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared (FTIR) and BET surface area measurements. XRD spectra showed peaks of silver confirming the formation of the silver and not of the silver nitrate or any other impurity of the metal. Meanwhile TEM confirmed the formation of silver and zinc oxide nanoparticles on the clay layers, with particle sizes ranging from 9-30 nm and 15-70 nm, respectively. The antibacterial activities of the composites were evaluated against Gram negative Escherichia coli bacteria and Gram positive Enterococcus faecalis bacteria by the disc diffusion method. Whereas both composites of Ag-clay and ZnO-clay showed good antibacterial activity against bacteria, a better antibacterial activity was observed with Ag/ZnO-clay composite. The results therefore reveal that Ag/ZnO-clay composite is a promising bactericide that can be used for deactivating microbes in water. PMID:24076479

  2. Determination of trace nickel in hydrogenated cottonseed oil by electrothermal atomic absorption spectrometry after microwave-assisted digestion.

    PubMed

    Zhang, Gai

    2012-01-01

    Microwave digestion of hydrogenated cottonseed oil prior to trace nickel determination by electrothermal atomic absorption spectrometry (ETAAS) is proposed here for the first time. Currently, the methods outlined in U.S. Pharmacopeia 28 (USP28) or British Pharmacopeia (BP2003) are recommended as the official methods for analyzing nickel in hydrogenated cottonseed oil. With these methods the samples may be pre-treated by a silica or a platinum crucible. However, the samples were easily tarnished during sample pretreatment when using a silica crucible. In contrast, when using a platinum crucible, hydrogenated cottonseed oil acting as a reducing material may react with the platinum and destroy the crucible. The proposed microwave-assisted digestion avoided tarnishing of sample in the process of sample pretreatment and also reduced the cycle of analysis. The programs of microwave digestion and the parameters of ETAAS were optimized. The accuracy of the proposed method was investigated by analyzing real samples. The results were compared with the ones by pressurized-PTFE-bomb acid digestion and ones obtained by the U.S. Pharmacopeia 28 (USP28) method. The new method involves a relatively rapid matrix destruction technique compared with other present methods for the quantification of metals in oil. PMID:22133102

  3. Highly selective NH3 gas sensor based on Au loaded ZnO nanostructures prepared using microwave-assisted method.

    PubMed

    Shingange, K; Tshabalala, Z P; Ntwaeaborwa, O M; Motaung, D E; Mhlongo, G H

    2016-10-01

    ZnO nanorods synthesized using microwave-assisted approach were functionalized with gold (Au) nanoparticles. The Au coverage on the surface of the functionalized ZnO was controlled by adjusting the concentration of the Au precursor. According to X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) results, it was confirmed that Au form nanoparticles loaded on the surface of ZnO. The small Au loading level of 0.5wt% showed the highest response of 1600-100ppm of NH3 gas at room temperature (RT) whereas further increase of Au loading level resulted in poor detection of NH3. All Au loaded ZnO (Au/ZnO) based sensors exhibited very short recovery and response times compared to unloaded ZnO sensing materials. The responses of ZnO and Au/ZnO based sensors (0.5-2.5wt%) to other flammable gases, including H2, CO and CH4, were considerably less, demonstrating that Au/ZnO based sensors were highly selective to NH3 gas at room temperature. Spill over mechanism which is the main reason for the observed enhanced NH3 response with 0.5 Au loading level is explained in detail. PMID:27388126

  4. Ionic liquid-based microwave-assisted extraction of essential oil and biphenyl cyclooctene lignans from Schisandra chinensis Baill fruits.

    PubMed

    Ma, Chun-hui; Liu, Ting-ting; Yang, Lei; Zu, Yuan-gang; Chen, Xiaoqiang; Zhang, Lin; Zhang, Ying; Zhao, Chunjian

    2011-12-01

    Ionic liquid-based microwave-assisted extraction (ILMAE) has been successfully applied in extracting essential oil and four kinds of biphenyl cyclooctene lignans from Schisandra chinensis Baill. 0.25 M 1-lauryl-3-methylimidazolium bromide ionic liquid is selected as solvent. The optimum parameters of dealing with 25.0 g sample are 385 W irradiation power, 40 min microwave extraction time and 1:12 solid-liquid ratio. The yields of essential oil and lignans are 12.12±0.37 ml/kg and 250.2±38.2 mg/kg under the optimum conditions. The composition of the essential oil extracted by hydro-distillation, steam-distillation and ILMAE is analyzed by GC-MS. With ILMAE method, the energy consumption time has not only been shortened to 40 min (hydro-distillation 3.0 h for extracting essential oil and reflux extraction 4.0 h for extracting lignans, respectively), but also the extraction efficiency has been improved (extraction of lignans and distillation of essential oil at the same time) and reduces the environmental pollution. S. chinensis materials treated by different methods are observed by scanning electronic microscopy. Micrographs provide more evidence to prove that ILMAE is a better and faster method. The experimental results also indicate that ILMAE is a simple and efficient technique for sample preparation. PMID:22018714

  5. Focused microwave assistance for extracting some pesticide residues from strawberries into water before their determination by SPME/HPLC/DAD.

    PubMed

    Falqui-Cao, C; Wang, Z; Urruty, L; Pommier, J J; Montury, M

    2001-11-01

    A novel and simple method for the determination of some pesticide residues in strawberries using both focused microwave-assisted extraction (FMAE) and solid-phase micro extraction (SPME), coupled with high-performance liquid chromatography (HPLC), has been developed. The pesticides were first extracted from strawberries with water and the assistance of focused microwaves at 30 W for 7 min. Then, an aliquot of the resulting aqueous extract was subjected to SPME with a 60-microm thick poly(dimethylsiloxane)/divinylbenzene (PDMS/DVB) fiber for 45 min at room temperature, with the solution being stirred at 1000 rpm. The extracted pesticides on the SPME fiber were desorbed into the SPME/HPLC interface for quantitative analysis with a diode array detector (DAD). The whole sample pretreatment procedure before chromatographic analysis did not use any organic solvents or involve any blending or centrifugation steps. The five compounds (carbendazim, diethofencarb, azoxystrobine, napropamide, and bupirimate) were chosen because they cannot be analyzed easily by GC. The efficiency of this relatively fast procedure was comparable to that of previously reported methods, with detection limits at low microg/kg levels and linear responses in the range from 0.05 to 1 mg/kg of pesticide in strawberries, with RSDs between 3 and 7.3%, depending on the analyte. In all but one case results obtained by this method for field-incurred samples were comparable to those obtained with traditional methods. PMID:11714287

  6. Excellent microwave-absorbing properties of elliptical Fe₃O₄ nanorings made by a rapid microwave-assisted hydrothermal approach.

    PubMed

    Liu, Yun; Cui, Tingting; Wu, Tong; Li, Yana; Tong, Guoxiu

    2016-04-22

    High-quality elliptical polycrystalline Fe3O4 nanorings (NRs) with continuously tunable size have been synthesized in large amounts via a rapid microwave-assisted hydrothermal approach. The surface-protected glucose reducing/etching/Ostwald ripening mechanism is responsible for the formation of NRs. Ring size can be modulated by selecting iron glycolate nanosheets with various sizes as precursors. The size-dependent magnetic behavior of the NRs was observed. Our research gives insights into the understanding of the microwave absorption mechanism of elliptical Fe3O4 NRs. Owing to their large specific surface area, shape anisotropy, and closed ring-like configuration, elliptical polycrystalline Fe3O4 NRs exhibited significantly enhanced microwave absorption performance compared with Fe3O4 circular NRs, nanosheets, microspheres, nanospindles, and nanotubes. An optimal reflection loss value of -41.59 dB is achieved at 5.84 GHz and R(L) values (≤-20 dB) are observed at 3.2-10.4 GHz. Some new mechanisms including multiple scattering, oscillation resonance absorption, microantenna radiation, and interference are also crucial to the enhanced absorption properties of NRs. These findings indicate that ring-like nanostructures are a promising structure for devising new and effective microwave absorbers. PMID:26962718

  7. Extraction of bioactive carbohydrates from artichoke (Cynara scolymus L.) external bracts using microwave assisted extraction and pressurized liquid extraction.

    PubMed

    Ruiz-Aceituno, Laura; García-Sarrió, M Jesús; Alonso-Rodriguez, Belén; Ramos, Lourdes; Sanz, M Luz

    2016-04-01

    Microwave assisted extraction (MAE) and pressurized liquid extraction (PLE) methods using water as solvent have been optimized by means of a Box-Behnken and 3(2) composite experimental designs, respectively, for the effective extraction of bioactive carbohydrates (inositols and inulin) from artichoke (Cynara scolymus L.) external bracts. MAE at 60 °C for 3 min of 0.3 g of sample allowed the extraction of slightly higher concentrations of inositol than PLE at 75 °C for 26.7 min (11.6 mg/g dry sample vs. 7.6 mg/g dry sample). On the contrary, under these conditions, higher concentrations of inulin were extracted with the latter technique (185.4 mg/g vs. 96.4 mg/g dry sample), considering two successive extraction cycles for both techniques. Both methodologies can be considered appropriate for the simultaneous extraction of these bioactive carbohydrates from this particular industrial by-product. To the best of our knowledge this is the first time that these techniques are applied for this purpose. PMID:26593602

  8. Microwave-assisted synthesis of SnO2 nanorods for oxygen gas sensing at room temperature

    PubMed Central

    Azam, Ameer; Habib, Sami S; Salah, Numan A; Ahmed, Faheem

    2013-01-01

    High-quality single-crystalline SnO2 nanorods were synthesized using a microwave-assisted solution method. The nanorods were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), ultraviolet-visible and Raman spectroscopy, Brunauer–Emmett–Teller (BET), and electrical resistance measurements. The XRD pattern indicated the formation of single-phase SnO2 nanorods with rutile structure. FE-SEM and TEM images revealed tetragonal nanorods of about 450–500 nm in length and 60–80 nm in diameter. The nanorods showed a higher BET surface area of 288 m2/g, much higher than that of previously reported work. The Raman scattering spectra indicated a typical rutile phase of the SnO2. The absorption spectrum showed an absorption peak centered at 340 nm, and the band-gap value was found to be 3.64 eV. The gas-sensing properties of the SnO2 nanorods for oxygen gas with different concentrations were measured at room temperature. It was found that the value of resistance increased with the increase in oxygen gas concentration in the test chamber. The SnO2 nanorods exhibited high sensitivity and rapid response-recovery characteristics to oxygen gas, and could detect oxygen concentration as low as 1, 3, 5, and 10 ppm. PMID:24143091

  9. Microwave-assisted and gram-scale synthesis of ultrathin SnO2 nanosheets with enhanced lithium storage properties.

    PubMed

    Zhu, Youqi; Guo, Huizi; Zhai, Huazhang; Cao, Chuanbao

    2015-02-01

    The rational design and fabrication of SnO2-based anode materials could offer a powerful way of effectively alleviating their large volume variation and guaranteeing excellent reaction kinetics for electrochemical lithium storage. Herein, we present an ultrarapid, low-cost, and simple microwave-assisted synthesis of ultrathin SnO2 nanosheets at the gram-scale. The two-dimensional (2D) anisotropic growth depends on microwave dielectric irradiation coupled with surfactant structural direction, and is conducted under low-temperature atmospheric conditions. The ultrathin 2D nanostructure holds a great surface tin atom percentage with high activity, where the electrochemical reaction processes could be facilitated that highly dependent on the surface. Compared with 1D SnO2 nanorods, the ultrathin SnO2 nanosheets exhibit remarkably improved electrochemical lithium storage properties with a high reversible capacity of 757.6 mAh g(-1) at a current density of 200 mA g(-1) up to 40 cycles as well as excellent rate capability and cycling stability. Specifically, the ultrathin 2D nanosheet could significantly reduce ion diffusion paths, thus allowing faster phase transitions, while the sufficient external surface interspace and interior porous configuration could successfully accommodate the huge volume changes. Even more importantly, we develop a promising strategy to produce ultrathin SnO2 nanosheets to tackle their intrinsic problems for commercial applications. PMID:25594865

  10. Microwave-assisted synthesis of NiS2 nanostructures for supercapacitors and cocatalytic enhancing photocatalytic H2 production

    PubMed Central

    Pang, Huan; Wei, Chengzhen; Li, Xuexue; Li, Guochang; Ma, Yahui; Li, Sujuan; Chen, Jing; Zhang, Jiangshan

    2014-01-01

    Uniform NiS2 nanocubes are successfully synthesized with a microwave-assisted method. Interestingly, NiS2 nanocubes, nanospheres and nanoparticles are obtained by controlling microwave reaction time. NiS2 nanomaterials are primarily applied to supercapacitors and cocatalytic enhancing photocatalytic H2 production. Different morphologies of NiS2 nanostructures show different electrochemical and cocatalytic enhancing H2 production activities. Benefited novel nanostructures, NiS2 nanocube electrodes show a large specific capacitance (695 F g−1 at 1.25 A g−1) and excellent cycling performance (the retention 93.4% of initial specific capacitance after 3000 cycles). More importantly, NiS2 nanospheres show highly cocatalytic enhancing photocatalytic for H2 evolution, in which the photocatalytic H2 production is up to 3400 μmol during 12 hours under irradiation of visible light (λ>420 nm) with an average H2 production rate of 283 μmol h−1. PMID:24389929

  11. A study of the mechanism of microwave-assisted ball milling preparing ZnFe2O4

    NASA Astrophysics Data System (ADS)

    Zhang, Yingzhe; Wu, Yujiao; Qin, Qingdong; Wang, Fuchun; Chen, Ding

    2016-07-01

    In this paper, well dispersed ZnFe2O4 nano-particles with high magnetization saturation of 82.23 emu/g were first synthesized by microwave assisted ball milling and then the influences of pre-treatments and microwave powers to the progress were studied. It was found that under the both function of crack effect induced by ball milling and rotary motion induced by microwave the synthesized ferrtie nano-particles were well dispersed that is much different from the powders synthesized by normal high energy ball milling. The pre-treatment of ball milling can only enhance the reaction rate in the first several hours but the pre-irradiation of microwave can enhance the hole reaction rate. Further more, it was also been found that with increasing the microwave power, the more raw materials will converted into zinc ferrite in the first 5 h. 5 h latter the microwave power of 720 W is high enough for the coupling effect of microwave and ball milling with stirrer rotation speed of 256 rpm.

  12. Microwave-Assisted Simultaneous Extraction of Luteolin and Apigenin from Tree Peony Pod and Evaluation of Its Antioxidant Activity

    PubMed Central

    Wang, Hongzheng; Yang, Lei; Zu, Yuangang; Zhao, Xiuhua

    2014-01-01

    An efficient microwave-assisted extraction (MAE) technique was employed in simultaneous extraction of luteolin and apigenin from tree peony pod. The MAE procedure was optimized using response surface methodology (RSM) and compared with other conventional extraction techniques of macerate extraction (ME) and heat reflux extraction (HRE). The optimal conditions of MAE were as follows: employing 70% ethanol volume fraction as solvent, soaking time of 4 h, liquid-solid ratio of 10 (mL/g), microwave irradiation power of 265 W, microwave irradiation time of 9.6 min, and 3 extraction cycles. Under the optimal conditions, 151 μg/g luteolin and 104 μg/g apigenin were extracted from the tree peony pod. Compared with ME and HRE, MAE gave the highest extraction efficiency. The antioxidant activities of the extracts obtained by MAE, ME, and HRE were evaluated using a 2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl (DPPH) free radical-scavenging assay, a ferric reducing antioxidant power assay (FRAP), and a reducing power assay. Meanwhile, the structural changes of the unprocessed and processed tree peony pod samples were analyzed by scanning electron microscopy. PMID:25405227

  13. Microwave-assisted phase-transfer catalysis for the rapid one-pot methylation and gas chromatographic determination of phenolics.

    PubMed

    Fiamegos, Yiannis C; Karatapanis, Andreas; Stalikas, Constantine D

    2010-01-29

    Microwave-assisted phase-transfer catalysis (PTC) is reported for the first time, for the one-step extraction-derivatization-preconcentration and gas chromatographic determination of twenty phenols and ten phenolic acids. The well established phase-transfer catalytic methylation is largely accelerated when heating is replaced with the "greener" microwave irradiation. The overall procedure was thoroughly optimized and the analytes were determined by GC/MS. The method presented adequate analytical characteristics being more sensitive in analyzing phenols than phenolic acids. The limits of detection without any additional preconcentration steps (e.g. solvent evaporation) were adequate and ranged from 0.4 to 15.8ng/mL while limits of quantitation were between 1.2 and 33.3ng/mL. The method was applied to the determination of phenols, in spiked environmental samples and phenolic acids in aqueous infusions of commercially available pharmaceutical dry plants. The recoveries of fortified composite lake water samples and Mentha spicata aqueous infusions ranged from 89.3% to 117.3% for phenols and 93.3% to 115.2% for phenolic acids. PMID:20022019

  14. Highly Luminescent Carbon Dots Synthesized by Microwave-Assisted Pyrolysis and Evaluation of Their Toxicity to Physa acuta.

    PubMed

    Sun, Xiaobo; Jin, Xiaozhe; Pan, Wei; Guo, Enmian; Liu, Weijian; Li, Denghui; Lu, Kunchao; Si, Shuxin; Zhang, Nianxing; Jia, Zhenzhen; Shi, Yanping; Li, Qianqian; Wang, Jinping

    2016-01-01

    As a newly emerging class of nanomaterials, carbon dots have increasingly attracted researchers' attention. However, their potentially adverse environmental effects are yet largely unknown. In this work, the highly luminescent carbon dots were synthesized by microwave-assisted pyrolysis of tris(hydroxymethyl)aminomethane (Tris) and citric acid. Then acute and chronic toxicities of carbon dots to Physa acuta (P. acuta), as well as their effect on reproduction, were evaluated using the as-synthesized dots as an example. The quantum yield of the as-synthesized carbon dots was up to 53.5% excited at 360 nm with the most fluorescent fraction of 82.6% after simple purification by gel column. The results showed that no acute but chronic toxicities to P. acuta exposed to different treatment concentrations of the as-synthesized carbon dots were observed with dose- dependence. In addition, the fecundity of P. acuta was promoted significantly by the carbon dots at the concentrations of 0.5 and 1.0 mg/mL, yet inhibited at the concentration of 3.0 mg/mL after 12-day exposure. Mainly distributing in the visceral mass might be responsible for the effects of the carbon dots on the survival and fecundity of P. acuta. And there was no further evidence to confirm that the carbon dots can cause malformation in developing embryos. PMID:27398502

  15. Microwave-assisted extraction for the simultaneous determination of thiamethoxam, imidacloprid, and carbendazim residues in fresh and cooked vegetable samples.

    PubMed

    Singh, Shashi B; Foster, Gregory D; Khan, Shahamat U

    2004-01-14

    Microwave-assisted extraction (MAE) was carried out for the simultaneous determination of the insecticides thiamethoxam [(EZ)-3-(2-chloro-1,3-thiazol-5-ylmethyl)-5-methyl-1,3,5-oxadiazinan-4-ylidene(nitro)amine], imidacloprid [1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine], and the fungicide carbendazim (methyl benzimidazol-2-ylcarbamate) in vegetable samples. Five crop samples consisting of cabbage, tomatoes, chilies, potatoes, and peppers were fortified with the three pesticides and subjected to MAE followed by cleanup to remove coextractives prior to analysis by high-performance liquid chromatography. Using the selected microwave exposure time and power setting, the recoveries of the three pesticides from the fortified vegetable samples ranged from 68.1 to 106%. The corresponding recoveries for samples processed simultaneously but without microwave exposure ranged from 37.2 to 61.4%. The recoveries by MAE were comparable to those obtained by the conventional blender extraction technique. The precision of the MAE method was demonstrated by relative standard deviations of <7% for the three pesticides. The cooked cabbage and tomato samples showed no breakdown of the parent compounds, and the recoveries of three pesticides were comparable to those obtained with the uncooked samples. PMID:14709021

  16. Microwave-assisted synthesis of gold, silver, platinum and palladium nanostructures and their use in electrocatalytic applications.

    PubMed

    Safavi, Afsaneh; Tohidi, Maryam

    2014-09-01

    Microwave-assisted ionic liquid method was used for synthesis of various noble metals, such as gold, silver, platinum and palladium nanomaterials. This route does not employ any template agent, surface capping agents or reducing agents. The process is fast, simple and of high yield. Different metal precursors in various ionic liquids media (1-butyl-3-methylimidazolium tetrafluoroborate, octyl pyridinium hexaflurophosphate and 1-octyl-3-methylimidazolium hexaflurophosphate) were applied to produce metal nanomaterials. Silver, platinium and palladium nanoparticles exhibit spherical morphology while nanosheets with high aspect ratio were obtained for gold. These metal nanostructures were incorporated into a carbon ionic liquid electrode to investigate their electrocatalytic properties. It was found that synthesis in different ionic liquids result in different activity. Excellent electrocatalytic effects toward adenine, hydrazine, formaldehyde and ethanol were observed for the modified electrodes with different nanoparticles synthesized in 1-butyl-3-methylimidazolium tetrafluoroborate. The high conductivity, large surface-to-volume ratio and active sites of nanosized metal particles are responsible for their electrocatalytic activity. In contrast, the carbon ionic liquid electrode modified with synthesized metal nanoparticles in octyl pyridinium hexaflurophosphate and 1-octyl-3-methylimidazolium hexaflurophosphate showed negligible activity for detection of these probes. PMID:25924389

  17. The effects of fuel type in synthesis of NiFe2O4 nanoparticles by microwave assisted combustion method

    NASA Astrophysics Data System (ADS)

    Karcıoğlu Karakaş, Zeynep; Boncukçuoğlu, Recep; Karakaş, İbrahim H.

    2016-04-01

    In this study, it was investigated the effects of the used fuels on structural, morphological and magnetic properties of nanoparticles in nanoparticle synthesis with microwave assisted combustion method with an important method in quick, simple and low cost at synthesis of the nanoparticles. In this aim, glycine, urea and citric acid were used as fuel, respectively. The synthesised nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmet-Teller surface area (BET), and vibrating sample magnetometry (VSM) techniques. We observed that fuel type is quite effective on magnetic properties and surface properties of the nanoparticles. X-ray difractograms of the obtained nanoparticles were compared with standard powder diffraction cards of NiFe2O4 (JCPDS Card Number 54-0964). The results demonstrated that difractograms are fully compatible with standard reflection peaks. According to the results of the XRD analysis, the highest crystallinity was observed at nanoparticles synthesized with glycine. The results demonstrated that the nanoparticles prepared with urea has the highest surface area. The micrographs of SEM showed that all of the nanoparticles have nano-crystalline behaviour and particles indication cubic shape. VSM analysis demonstrated that the type of fuel used for synthesis is highly effective a parameter on magnetic properties of nanoparticles.

  18. ZnO/TiO2 nanocomposite rods synthesized by microwave-assisted method for humidity sensor application

    NASA Astrophysics Data System (ADS)

    Ashok, CH.; Venkateswara Rao, K.

    2014-12-01

    The nanocomposite rods shows well known properties compared with nano structured materials for various applications like light-emitting diodes, electron field emitters, solar cells, optoelectronics, sensors, transparent conductors and fabrication of nano devices. Present paper investigates the properties of ZnO/TiO2 nanocomposite rods. The bi component of ZnO/TiO2 nanocomposite rods was synthesized by microwave-assisted method which is very simple, rapid and uniform in heating. The frequency of microwaves 2.45 GHz was used and temperature maintained 180 °C. Zinc acetate and titanium isopropoxide precursors were used in the preparation. The obtained ZnO/TiO2 nanocomposite rods were annealed at 500 °C and 600 °C. ZnO/TiO2 nanocomposite rods have been characterized by X-ray Diffraction (XRD) for average crystallite size and phase of the composite material, Particle Size Analyser (PSA) for average particle size, Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) for morphology study, Energy Dispersive X-ray Spectrometry (EDX) for elemental analysis, and Thermal Gravimetric and Differential Thermal Analysis (TG-DTA) for thermal property.

  19. Microwave-assisted synthesis and antimicrobial evaluation of novel spiroisoquinoline and spiropyrido[4,3-d]pyrimidine derivatives.

    PubMed

    Faty, Rasha M; Rashed, Mohamed S; Youssef, Mohamed M

    2015-01-01

    Bromination of N-substituted homophthalimides and tetrahydropyrido[4,3-d]- pyrimidine-5,7-diones produces 4,4-dibromohomophthalimide and 8,8-dibromo-tetrahydropyrido[4,3-d]pyrimidine-5,7-dione derivatives, respectively, that can be used as precursors for spiro derivatives. The dibromo derivatives react with different binucleophilic reagents to produce several spiroisoquinoline and spirotetrahydropyrido[4,3-d]- pyrimidine-5,7-dione derivatives, respectively. Reaction of the dibromo derivatives with malononitrile produces dicyanomethylene derivatives which react with different binucleophiles to produce new spiro derivatives. All new compounds are prepared by using the usual chemical conditions and microwave assisted conditions. The latter conditions improved the reaction yields, reduced reaction times and ameliorated the effects on the surrounding environment as the reactions are carried out in closed systems. Structures of the newly synthesized compounds are proved using spectroscopic methods such as IR, MS, 1H-NMR and 13C-NMR and elemental analyses. Some of the newly synthesized compounds were tested for their antimicrobial activities, whereby four of them showed moderate activities and the rest showed low or no activities towards the investigated species. PMID:25625680

  20. Microwave-assisted rapid photocatalytic degradation of malachite green in TiO2 suspensions: mechanism and pathways.

    PubMed

    Ju, Yongming; Yang, Shaogui; Ding, Youchao; Sun, Cheng; Zhang, Aiqian; Wang, Lianhong

    2008-11-01

    Microwave-assisted photocatalytic (MPC) degradation of malachite green (MG) in aqueous TiO2 suspensions was investigated. A 20 mg/L sample of MG was rapidly and completely decomposed in 3 min with the corresponding TOC removal efficiency of about 85%. To gain insight into the degradation mechanism, both GC-MS and LC-ESI-MS/MS techniques were employed to identify the major intermediates of MG degradation, including N-demethylation intermediates [(p-dimethylaminophenyl)(p-methylaminophenyl)phenylmethylium (DM-PM), (p-methylaminophenyl)(p-methylaminophenyl)phenylmethylium (MM-PM), (p-methylaminophenyl)(p-aminophenyl)phenylmethylium (M-PM)]; a decomposition compound of the conjugated structure (4-dimethylaminobenzophenone (DLBP)); products resulting from the adduct reaction of hydroxyl radical; products of benzene removal; and other open-ring intermediates such as phenol, terephthalic acid, adipic acid, benzoic acid, etc. The possible degradation mechanism of MG included five processes: the N-demethylation process, adduct products of the hydroxyl radical, the breakdown of chromophores such as destruction of the conjugated structure intermediate, removal of benzene, and an open-ring reaction. To the best of our knowledge, it is the first time the whole MG photodegradation processes have been reported. PMID:18841945

  1. Microwave assisted facile green synthesis of silver and gold nanocatalysts using the leaf extract of Aerva lanata.

    PubMed

    Joseph, Siby; Mathew, Beena

    2014-10-18

    Herein, we report a simple microwave assisted method for the green synthesis of silver and gold nanoparticles by the reduction of aqueous metal salt solutions using leaf extract of the medicinal plant Aerva lanata. UV-vis., FTIR, XRD, and HR-TEM studies were conducted to assure the formation of nanoparticles. XRD studies clearly confirmed the crystalline nature of the synthesized nanoparticles. From the HR-TEM images, the silver nanoparticles (AgNPs) were found to be more or less spherical and gold nanoparticles (AuNPs) were observed to be of different morphology with an average diameter of 18.62nm for silver and 17.97nm for gold nanoparticles. In order to evaluate the effect of microwave heating upon rate of formation, the synthesis was also conducted under ambient condition without the assistance of microwave radiation and the former method was found to be much faster than the later. The synthesized nanoparticles were used as nanocatalysts in the reduction of 4-nitrophenol to 4-aminophenol by NaBH4. PMID:25459695

  2. Open focused microwave-assisted sample preparation for rapid total and mercury species determination in environmental solid samples.

    PubMed

    Tseng, C M; Garraud, H; Amouroux, D; Donard, O F; de Diego, A

    1998-01-01

    This paper describes rapid, simple microwave-assisted leaching/ digestion procedures for total and mercury species determination in sediment samples and biomaterials. An open focused microwave system allowed the sample preparation time to be dramatically reduced to only 24 min when a power of 40-80 W was applied. Quantitative leaching of methylmercury from sediments by HNO(3) solution and complete dissolution of biomaterials by an alkaline solution, such as 25% TMAH solution, were obtained. Methylmercury compounds were kept intact without decomposition or losses by evaporation. Quantitative recoveries of total mercury were achieved with a two-step microwave attack using a combination of HNO(3) and H(2)0(2) solutions as extractant. The whole pretreatment procedure only takes 15 min, which can be further shortened by an automated robust operation with an open focused system. These analytical procedures were validated by the analysis of environmental certified reference materials. The results confirm that the open focused microwave technique is a promising tool for solid sample preparation in analytical and environmental chemistry. PMID:18924826

  3. Quantification of triazine herbicides in soil by microwave-assisted extraction and high-performance liquid chromatography.

    PubMed

    Shah, Jasmin; Rasul Jan, M; Ara, Behisht; Shehzad, Farhat-Un-Nisa

    2011-07-01

    A method for the determination of herbicides residues, triazine (atrazine, metribuzin, ametryn, and terbutryn), in soil samples with high-performance liquid chromatography (HPLC)-UV detection is described. The proposed method is based on microwave-assisted extraction (MAE) of soil samples for 4 min at 80% of 850-W magnetron outputs in the presence of mixture of solvents (methanol/acetonitrile/ethylacetate). Related important factors influencing the MAE efficiency, such as the solvent type and volume, irradiation energy, and time, were optimized in detail. Calibration curve ranges established using HPLC for metribuzin, atrazine, ametryn, and terbutryn are 1.0-19.0, 0.9-18.0, 0.6-11.0, and 0.7-11.0 µg mL( -1), respectively. The limits of detection of metribuzin, atrazine, ametryn, and terbutryn are 0.30, 0.24, 0.16, and 0.20 µg mL( -1) while limits of quantification are 1.0, 0.80, 0.50, and 0.60 µg mL( -1), respectively. A Plackett-Burman factorial design was used as a screening method in order to select the variables that influence MAE extraction. The recoveries of the method at three different spiked levels were assessed by analyzing real soil samples and were found to be in the range of 83.33 ± 0.12-96.33 ± 0.23 with good precision (<8%). PMID:20824333

  4. A facile synthesis of ZnWO{sub 4} nanoparticles by microwave assisted technique and its application in photocatalysis

    SciTech Connect

    Garadkar, K.M.; Ghule, L.A.; Sapnar, K.B.; Dhole, S.D.

    2013-03-15

    Highlights: ► Nanocrystalline ZnWO{sub 4} particles were successfully prepared by a microwave method. ► Spherical morphology with a 10 nm size. ► The band is 3.4 eV. ► The photodegradation of RhB was 95% within 25 min. - Abstract: A simple microwave assisted technique has been successfully developed to synthesize ZnWO{sub 4} nanoparticles. The X-ray diffraction results indicated that the synthesized nanoparticles exhibited only wolframite structure. Structural, morphological and optical properties of ZnWO{sub 4} nanoparticles have been analyzed by XRD, SEM, TEM EDAX, UV–vis and FT-IR spectral measurements. The transmission electron microscopy (TEM) image revealed that particle size of ZnWO{sub 4} nanoparticles was found to be 10 nm, the band-gap of ZnWO{sub 4} nanoparticles was found to be 3.4 eV. The photocatalytic activities for aqueous Rhodamine B and Methylene Blue samples were investigated and observed that ZnWO{sub 4} nanoparticles exhibited highly enhanced photocatalytic activity towards RhB than MB.

  5. Microwave-assisted synthesis of graphene-Ni composites with enhanced microwave absorption properties in Ku-band

    NASA Astrophysics Data System (ADS)

    Zhu, Zetao; Sun, Xin; Li, Guoxian; Xue, Hairong; Guo, Hu; Fan, Xiaoli; Pan, Xuchen; He, Jianping

    2015-03-01

    Recently, graphene has been applied as a new microwave absorber because of its high dielectric loss and low density. Nevertheless, the high dielectric constant of pristine graphene has caused unbalanced electromagnetic parameters and results in a bad impedance matching characteristic. In this study, we report a facile microwave-assisted heating approach to produce reduced graphene oxide-nickel (RGO-Ni) composites. The phase and morphology of as-synthesized RGO-Ni composites are characterized by XRD, Raman, FESEM and TEM. The results show that Ni nanoparticles with a diameter around 20 nm are grown densely and uniformly on the RGO sheets. In addition, enhanced microwave absorption properties in Ku-band of RGO-Ni composites is mainly due to the synergistic effect of dielectric loss and magnetic loss and the dramatically electron polarizations caused by the formation of large conductive network. The minimum reflection loss of RGO-Ni-2 composite with the thickness of 2 mm can reaches -42 dB at 17.6 GHz. The RGO-Ni composite is an attractive candidate for the new type of high performance microwave absorbing material.

  6. Microwave-assisted synthesis and photocatalytic properties of sulphur and platinum modified TiO2 nanofibers

    NASA Astrophysics Data System (ADS)

    Drunka, R.; Grabis, J.; Jankovica, Dz; Krumina, A.; Rasmane, Dz

    2015-03-01

    In the present work formation of active TiO2 nanofibers in microwave synthesis and their modification with platinum were studied. Mixture of anatase and rutile nanopowder and 10M KOH solution were used as raw materials. Microwave assisted synthesis method permitted to obtain TiO2 nanofibres with a diameter of 10nm and a specific surface area up to 40.2 m2/g. In order to modify TiO2 nanofibers with platinum it was stirred in H2PtCl6 solution and illuminated with UV irradiation or reduced with sodium boronhydride. To modify titania with sulphur and prepare co-doped nanofibers platinum doped samples were extra treated in hydrogen sulphide atmosphere. Photocatalytic activity was determined by degradation of the methylene blue (MB) solution under UV and visible light irradiation. The obtained samples showed higher photocatalytic activity with respect to pure TiO2 nanofibers. The doped TiO2 nanofibers were appropriate for degradation of harmful organic compounds.

  7. Synthesis via a Microwave-Assisted Wet Chemical Method and Characterization of Bi2Te3 with Various Morphologies

    NASA Astrophysics Data System (ADS)

    Chen, Song; Cai, Kefeng; Shen, Shirley

    2016-03-01

    Bi2Te3 with various morphologies, such as microrods, nanoplates, and nanoflowers, has been successfully fabricated by a microwave-assisted method in ethylene glycol solution without any surfactant. The structures and morphologies of the obtained products have been characterized by powder x-ray diffraction and field-emission scanning electron microscopy. Based on time-dependent experiments, a possible formation mechanism of the Bi2Te3 has been proposed. The concentration of KOH in the solution controls the rate of the disproportionation reaction of Te and plays an important role in the formation of the various morphologies of Bi2Te3. The electrical properties of bulk Bi2Te3 materials obtained by cold pressing and then vacuum heat treatment of the Bi2Te3 nanostructures with various morphologies have also been investigated. The highest power factor among the studied samples, ˜17.3 μW cm-1 K-2, was achieved using Bi2Te3 nanoflowers.

  8. Microwave assisted synthesis of sheet-like Cu/BiVO4 and its activities of various photocatalytic conditions

    NASA Astrophysics Data System (ADS)

    Chen, Xi; Li, Li; Yi, Tingting; Zhang, WenZhi; Zhang, Xiuli; Wang, Lili

    2015-09-01

    The Cu/BiVO4 photocatalyst with visible-light responsivity was prepared by the microwave-assisted hydrothermal method. The phase structures, chemical composition and surface physicochemical properties were well-characterized via X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance absorption (UV-vis/DRS), scanning electron microscopy (SEM), and N2 adsorption-desorption tests. Results indicate that the crystal structure of synthetic composite materials is mainly monoclinic scheelite BiVO4, which is not changed with the increasing doping amount of Cu. In addition, the presence of Cu not only enlarges the range of the composite materials under the visible-light response, but also increases the BET value significantly. Compared to pure BiVO4, 1% Cu/BiVO4-160 performs the highest photocatalytic activity to degrade methylene blue under the irradiation of ultraviolet, visible and simulated sunlight. In addition, the capture experiments prove that the main active species was superoxide radicals during photocatalytic reaction. Moreover, the 1% Cu/BiVO4-160 composite shows good photocatalytic stability after three times of recycling.

  9. Effects of different precursors on size and optical properties of ceria nanoparticles prepared by microwave-assisted method

    SciTech Connect

    Samiee, Sara; Goharshadi, Elaheh K.

    2012-04-15

    Highlights: Black-Right-Pointing-Pointer A rapid and efficient microwave method was applied for synthesis of nano ceria. Black-Right-Pointing-Pointer Changing precursor has great effects on optical properties and size of nano ceria. Black-Right-Pointing-Pointer Fabrication of ceria nanoparticles using Ce{sup 4+} salts leads to better results. Black-Right-Pointing-Pointer Band gap energies of ceria nanoparticles were evaluated by UV-vis spectroscopy. -- Abstract: Cerium oxide, ceria (CeO{sub 2}), is one of the favourable nanoparticles (NPs) that possesses many remarkable properties so that it can be used in medicine, chemistry, environment, energy, information, industry, and so on. In this study, the crystalline ceria NPs were successfully prepared by an efficient microwave-assisted heating technique from an aqueous solution using different cerium salts (Ce(IV) and Ce(III) salts). The products were characterized by X-ray powder diffraction (XRD), transmission electron microscope (TEM), FTIR spectroscopy, Raman spectroscopy, and UV-vis absorption spectroscopy. The results revealed that changing the precursor led to great effects on size, band gap energy, and the reaction time of preparing the ceria NPs. The significant feature of this manuscript is that the effects of different precursors on the structural and optical properties of ceria NPs were investigated for the first time. The average particle size of different samples was below 8 nm.

  10. Analysis of nonylphenol and nonylphenol ethoxylates in sewage sludge by high performance liquid chromatography following microwave-assisted extraction.

    PubMed

    Fountoulakis, Michalis; Drillia, Panagiota; Pakou, Constantina; Kampioti, Adamantia; Stamatelatou, Katerina; Lyberatos, Gerasimos

    2005-09-30

    Nonylphenol polyethoxylates (NPnEOs) constitute a significant portion of the non-ionic surfactant market. The presence of nonylphenol (NP) in the aquatic environment is often a product of the microbial breakdown of NPEOs through discharge of industrial effluents and sewage treatment plants. The aim of this work is to develop the microwave-assisted extraction for the determination of the NP and NPEO in sewage sludge and compare this method with more traditional methods such as Soxhlet extraction and sonication. The method efficiency was evaluated as to the linearity, repeatability, accuracy, and sensitivity. Recoveries were 61.4% for NPEO and 91.4% for NP with repeatability less than 5%. The detection limit was 1.82 microg/g for NPEO and 2.86 microg/g for NP. The developed method was applied on sewage sludge samples from the sewage treatment plants of three Greek cities: Athens, Patras and Heraklion and were ranged 12.8-233.5 mg/kg for NPEO and 3.6-93 mg/kg for NP. PMID:16130770

  11. Optimization of microwave-assisted extraction of cottonseed oil and evaluation of its oxidative stability and physicochemical properties.

    PubMed

    Taghvaei, Mostafa; Jafari, Seid Mahdi; Assadpoor, Elham; Nowrouzieh, Shahram; Alishah, Omran

    2014-10-01

    Microwave assisted extraction (MAE) is a novel method, which can reduce the extraction time and solvent consumption. This study aimed to evaluate the influence of MAE on oxidative stability and physicochemical properties of cottonseed oil. We found that the optimum extraction conditions were: irradiation time 3.57 min; cottonseed moisture content 14% and cottonseed to solvent ratio 1:4, which resulted in an extraction efficiency of 32.6%, 46 ppm total phenolic content, 0.7% free fatty acids, peroxide value of 0.2 and 11.5 h of Rancimat oxidative stability at 110 °C. GC analysis for MAE cottonseed oil determined palmitic acid (23.6%), stearic acid (2.3%), oleic acid (15.6%) and linoleic acid (55.1%), which were not significant different (P>0.05) than conventionally-extracted (control) cottonseed oil. MAE oil samples from whole cottonseed (without dehulling) had the greatest long-term stability, more than oil samples containing BHT. PMID:24799213

  12. Aqueous microwave-assisted solid-phase peptide synthesis using Fmoc strategy. III: racemization studies and water-based synthesis of histidine-containing peptides.

    PubMed

    Hojo, Keiko; Shinozaki, Natsuki; Hidaka, Koushi; Tsuda, Yuko; Fukumori, Yoshinobu; Ichikawa, Hideki; Wade, John D

    2014-10-01

    In this study, we describe the first aqueous microwave-assisted synthesis of histidine-containing peptides in high purity and with low racemization. We have previously shown the effectiveness of our synthesis methodology for peptides including difficult sequences using water-dispersible 9-fluorenylmethoxycarbonyl-amino acid nanoparticles. It is an organic solvent-free, environmentally friendly method for chemical peptide synthesis. Here, we studied the racemization of histidine during an aqueous-based coupling reaction with microwave irradiation. Under our microwave-assisted protocol using 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride, the coupling reaction can be efficiently performed with low levels of racemization of histidine. Application of this water-based microwave-assisted protocol with water-dispersible 9-fluorenylmethoxycarbonyl-amino acid nanoparticles led to the successful synthesis of the histidine-containing hexapeptide neuropeptide W-30 (10-15), Tyr-His-Thr-Val-Gly-Arg-NH₂, in high yield and with greatly reduced histidine racemization. PMID:24965528

  13. Microwave-assisted hydrothermal synthesis of marigold-like ZnIn{sub 2}S{sub 4} microspheres and their visible light photocatalytic activity

    SciTech Connect

    Chen Zhixin; Li Danzhen; Xiao Guangcan; He Yunhui; Xu Yijun

    2012-02-15

    Marigold-like ZnIn{sub 2}S{sub 4} microspheres were synthesized by a microwave-assisted hydrothermal method with the temperature ranging from 80 to 195 Degree-Sign C. X-ray diffraction, X-ray photoelectron spectroscopy, nitrogen sorption analysis, UV-visible spectroscopy, scanning electron microscopy and transmission electron microscopy were used to characterize the products. It was found that the crystallographic structure and optical property of the products synthesized at different temperatures were almost the same. The degradation of methyl orange (MO) under the visible light irradiation has been used as a probe reaction to investigate the photocatalytic activity of as-prepared ZnIn{sub 2}S{sub 4}, which shows that the ZnIn{sub 2}S{sub 4} sample synthesized at 195 Degree-Sign C shows the best photocatalytic activity for MO degradation. In addition, the photocatalytic activities of all the samples prepared by the microwave-assisted hydrothermal method are better than those prepared by a normal hydrothermal method, which could be attributed to the formation of more defect sites during the microwave-assisted hydrothermal treatment. - Graphical abstract: Marigold-like ZnIn{sub 2}S{sub 4} microspheres were synthesized by a fast microwave-assisted hydrothermal method at 80-195 Degree-Sign C with a very short reaction time of 10 min. The as-prepared ZnIn{sub 2}S{sub 4} sample can be used as visible light photocatalyst for degradation of organic dyes. Highlights: Black-Right-Pointing-Pointer ZnIn{sub 2}S{sub 4} microspheres were synthesized by microwave-assisted hydrothermal method. Black-Right-Pointing-Pointer The crystal structure and optical property of the products were almost the same. Black-Right-Pointing-Pointer Increment of the temperature renders high surface area due to the bubbling effect. Black-Right-Pointing-Pointer The ZnIn{sub 2}S{sub 4} synthesized at 195 Degree-Sign C shows the best visible catalytic activity for MO.

  14. Fast low-pressurized microwave-assisted extraction of benzotriazole, benzothiazole and benezenesulfonamide compounds from soil samples.

    PubMed

    Speltini, Andrea; Sturini, Michela; Maraschi, Federica; Porta, Alessio; Profumo, Antonella

    2016-01-15

    Benzotriazoles (BTRs), benzothiazoles (BTs) and benzenesulfonamides (BSAs), compounds largely used in industrial and household applications, are ubiquitous emerging contaminants. In this work a novel, straightforward procedure for the simultaneous determination of two BTRs (1H-benzotriazole, 5-methyl-1H-benzotriazole), three BTs (benzothiazole, 2-hydroxybenzothiazole, 2-methylthiobenzothiazole) and two BSAs (benzenesulfonamide, toluenesulfonamide) in soil has been developed. The target analytes were extracted from soil by a single low-pressurized microwave-assisted extraction (MAE) cycle (120°C, 10min) and quantified by high-performance liquid chromatography with UV detection. For all the seven analytes, quantitative extraction yields (72-119%, n=4) were observed from recovery tests on soil samples (1g) spiked with 5, 10 and 50mg kg(-1), using 4mL water-methanol (85:15) as extracting solution. For the lower concentrations levels (100, 250 and 500μg kg(-1)), the analytes were extracted from soil samples (2-3g) using 6mL methanol, and the extract was pre-concentrated by evaporation before analysis; recoveries in the range 70-117% were obtained (n=4). Suitable intra-day and inter-day precision were observed, with values of relative standard deviation generally below 6% and 11% (n=4), respectively. Linearity was evaluated in the concentration range 0.5-10mg L(-1) by matrix-matched standards, obtaining r(2)>0.9996. The experimental method quantification limit (MQL) was 100μg kg(-1). The entire procedure has been successfully applied to the analysis of real impacted soil samples. PMID:26592614

  15. Comparison of essential oil composition and antimicrobial activity of Coriandrum sativum L. extracted by hydrodistillation and microwave-assisted hydrodistillation.

    PubMed

    Sourmaghi, Mohammad Hossein Salehi; Kiaee, Gita; Golfakhrabadi, Fereshteh; Jamalifar, Hossein; Khanavi, Mahnaz

    2015-04-01

    Coriander (Coriandrum sativum L.), is an annual herb in the Apiaceae family which disperses in Mediterranean and Middle Eastern regions. The Coriander essential oil has been used in food products, perfumes, cosmetics and pharmaceutical industries for its flavor and odor. In Iran, fruits of Coriander used in pickle, curry powders, sausages, cakes, pastries, biscuits and buns. The aim of this study was to investigate microwave radiation effects on quality, quantity and antimicrobial activity of essential oil of Coriander fruits. The essential oils were obtained from the Coriander fruits by hydrodistillation (HD) and Microwave-assisted hydrodistillation (MAHD) then, the oils were analyzed by GC and GC-MS. Antimicrobial activities of essential oils were evaluated against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans by microdilution method. The results indicated that the HD and MAHD essential oils (EO) were dominated by monoterpenoids such as linalool, geranyl acetate and γ-terpinene. The major compound in both EO was linalool which its amount in HD and MAHD was 63 % and 66 %, respectively. The total amount of monoterpenes hydrocarbons in HD EO differ significantly with the amount in MAHD EO (12.56 % compare to 1.82 %). HD EO showed greater activity against Staphylococcus aureus and Candida albicans than MAHD EO. Moreover, their activities against Ecoli and P. aeruginosa were the same with Minimum Inhibitory Concentration (MIC) 0.781 and 6.25 μL mL(-1), respectively. By using MAHD method, it was superior in terms of saving energy and extraction time, although the oil yield and total composition decrease by using this method. PMID:25829632

  16. Fast low-pressure microwave assisted extraction and gas chromatographic determination of polychlorinated biphenyls in soil samples.

    PubMed

    Bruzzoniti, M C; Maina, R; Tumiatti, V; Sarzanini, C; Rivoira, L; De Carlo, R M

    2012-11-23

    A new technology equipment for low-pressure microwave assisted extraction (usually employed for organic chemistry reactions), recently launched in the market, is used for the first time in environmental analysis for the extraction of commercial technical Aroclor mixtures from soil. Certified reference materials of Aroclor 1260, Aroclor 1254 and Aroclor 1242 in transformer oils were used to contaminate the soil samples and to optimize the extraction method as well as the subsequent gas chromatographic electron capture detection (GC-ECD) analytical method. The study was performed optimizing the extraction, the purification and the gas chromatographic separation conditions to enhance the resolution of difficult pairs of congeners (C28/31 and C141/179). After optimization, the recovery yields were included within the range 79-84%. The detection limits, evaluated for two different commercial polychlorinated biphenyl (PCB) mixtures (Aroclor 1260 and Aroclor 1242) were 0.056 ± 0.001 mg/kg and 0.290 ± 0.006 mg/kg, respectively. The method, validated with certified soil samples, was used to analyze a soil sample after an event of failure of a pole-mounted transformer which caused the dumping of PCB contaminated oil in soil. Moreover, the method provides simple sample handling, fast extraction with reduced amount of sample and solvents than usually required, and simple purification step involving the use of solvent (cyclohexane) volumes as low as 5 mL. Reliability and reproducibility of extraction conditions are ensured by direct and continuous monitoring of temperature and pressure conditions. PMID:23084486

  17. Fluoroquinolone residues in compost by green enhanced microwave-assisted extraction followed by ultra performance liquid chromatography tandem mass spectrometry.

    PubMed

    Speltini, Andrea; Sturini, Michela; Maraschi, Federica; Viti, Simona; Sbarbada, Davide; Profumo, Antonella

    2015-09-01

    A novel, simple and straightforward method for determination of fluoroquinolones (FQs) in compost has been developed. The procedure entails a low-pressurized microwave-assisted extraction (MAE) carried out by a high performance instrument, in alkaline aqueous solution containing magnesium ions as FQs complexing agent, followed by ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS). Ciprofloxacin (CIP), Enrofloxacin (ENR), Levofloxacin (LEV) and Norfloxacin (NOR), four widely used FQ antibiotics, were simultaneously extracted from compost by a single MAE cycle (20min, 135°C). The method was validated in terms of linearity, selectivity, sensitivity and accuracy. Quantitative absolute recovery (70-112%, n=3) and suitable precision (RSD<15%, n=3) were observed, at concentration levels ranging from 25 ng g(-1) to 2500 ng g(-1). Analytes were separated in a 10min chromatographic run and quantified/confirmed in single reaction monitoring (SRM) mode. UPLC coupled to SRM-MS detection allowed to achieve improved sensitivity, and selective detection. Method detection and quantification limits, MDLs and MQLs, were in the range 2.2-3.0 ng g(-1) and 6.6-9.0 ng g(-1), respectively. The high-performance microwave system here used strongly improved the extraction efficiency with respect to a conventional apparatus. The procedure proved to be simpler, less expensive, faster, and more green with respect to the few methods currently described in literature, providing at the same time suitable recovery and reproducibility. The analytical method has been applied to the analysis of actual compost samples, wherein FQs have been quantified at concentrations up to 88 ng g(-1). PMID:26250963

  18. Quantitative phase analysis and microstructure characterization of magnetite nanocrystals obtained by microwave assisted non-hydrolytic sol–gel synthesis

    SciTech Connect

    Sciancalepore, Corrado; Bondioli, Federica; Manfredini, Tiziano; Gualtieri, Alessandro

    2015-02-15

    An innovative preparation procedure, based on microwave assisted non-hydrolytic sol–gel synthesis, to obtain spherical magnetite nanoparticles was reported together with a detailed quantitative phase analysis and microstructure characterization of the synthetic products. The nanoparticle growth was analyzed as a function of the synthesis time and was described in terms of crystallization degree employing the Rietveld method on the magnetic nanostructured system for the determination of the amorphous content using hematite as internal standard. Product crystallinity increases as the microwave thermal treatment is increased and reaches very high percentages for synthesis times longer than 1 h. Microstructural evolution of nanocrystals was followed by the integral breadth methods to obtain information on the crystallite size-strain distribution. The results of diffraction line profile analysis were compared with nanoparticle grain distribution estimated by dimensional analysis of the transmission electron microscopy (TEM) images. A variation both in the average grain size and in the distribution of the coherently diffraction domains is evidenced, allowing to suppose a relationship between the two quantities. The traditional integral breadth methods have proven to be valid for a rapid assessment of the diffraction line broadening effects in the above-mentioned nanostructured systems and the basic assumption for the correct use of these methods are discussed as well. - Highlights: • Fe{sub 3}O{sub 4} nanocrystals were obtained by MW-assisted non-hydrolytic sol–gel synthesis. • Quantitative phase analysis revealed that crystallinity up to 95% was reached. • The strategy of Rietveld refinements was discussed in details. • Dimensional analysis showed nanoparticles ranging from 4 to 8 nm. • Results of integral breadth methods were compared with microscopic analysis.

  19. Accurate quantification of tio2 nanoparticles collected on air filters using a microwave-assisted acid digestion method.

    PubMed

    Mudunkotuwa, Imali A; Anthony, T Renée; Grassian, Vicki H; Peters, Thomas M

    2016-01-01

    Titanium dioxide (TiO(2)) particles, including nanoparticles with diameters smaller than 100 nm, are used extensively in consumer products. In a 2011 current intelligence bulletin, the National Institute of Occupational Safety and Health (NIOSH) recommended methods to assess worker exposures to fine and ultrafine TiO(2) particles and associated occupational exposure limits for these particles. However, there are several challenges and problems encountered with these recommended exposure assessment methods involving the accurate quantitation of titanium dioxide collected on air filters using acid digestion followed by inductively coupled plasma optical emission spectroscopy (ICP-OES). Specifically, recommended digestion methods include the use of chemicals, such as perchloric acid, which are typically unavailable in most accredited industrial hygiene laboratories due to highly corrosive and oxidizing properties. Other alternative methods that are used typically involve the use of nitric acid or combination of nitric acid and sulfuric acid, which yield very poor recoveries for titanium dioxide. Therefore, given the current state of the science, it is clear that a new method is needed for exposure assessment. In this current study, a microwave-assisted acid digestion method has been specifically designed to improve the recovery of titanium in TiO(2) nanoparticles for quantitative analysis using ICP-OES. The optimum digestion conditions were determined by changing several variables including the acids used, digestion time, and temperature. Consequently, the optimized digestion temperature of 210°C with concentrated sulfuric and nitric acid (2:1 v/v) resulted in a recovery of >90% for TiO(2). The method is expected to provide for a more accurate quantification of airborne TiO(2) particles in the workplace environment. PMID:26181824

  20. Microwave-Assisted Extraction, Chemical Structures, and Chain Conformation of Polysaccharides from a Novel Cordyceps Sinensis Fungus UM01.

    PubMed

    Cheong, Kit-Leong; Wang, Lan-Ying; Wu, Ding-Tao; Hu, De-Jun; Zhao, Jing; Li, Shao-Ping

    2016-09-01

    Cordyceps sinensis is a well-known tonic food with broad medicinal properties. The aim of the present study was to investigate the optimization of microwave-assisted extraction (MAE) and characterize chemical structures and chain conformation of polysaccharides from a novel C. sinensis fungus UM01. Ion-exchange and gel filtration chromatography were used to purify the polysaccharides. The chemical structure of purified polysaccharide was determined through gas chromatography-mass spectrometry. Moreover, high performance size exclusion chromatography combined with refractive index detector and multiangle laser light scattering were conducted to analyze the molecular weight (Mw ) and chain conformation of purified polysaccharide. Based on the orthogonal design L9 , optimal MAE conditions could be obtained through 1300 W of microwave power, with a 5-min irradiation time at a solid to water ratio of 1:60, generating the highest extraction yield of 6.20%. Subsequently, the polysaccharide UM01-S1 was purified. The UM01-S1 is a glucan-type polysaccharide with a (1→4)-β-d-glucosyl backbone and branching points located at O-3 of Glcp with a terminal-d-Glcp. The Mw , radius of gyration (Rg ) and hydrodynamic radius (Rh ) of UM01-S1 were determined as 5.442 × 10(6)  Da, 21.8 and 20.2 nm, respectively. Using the polymer solution theory, the exponent (ν) value of the power law function was calculated as 0.38, and the shape factor (ρ = Rg /Rh ) was 1.079, indicating that UM01-S1 has a sphere-like conformation with a branched structure in an aqueous solution. These results provide fundamental information for the future application of polysaccharides from cultured C. sinensis in health and functional food area. PMID:27514485

  1. Microwave assisted extraction of iodine and bromine from edible seaweed for inductively coupled plasma-mass spectrometry determination.

    PubMed

    Romarís-Hortas, Vanessa; Moreda-Piñeiro, Antonio; Bermejo-Barrera, Pilar

    2009-08-15

    The feasibility of microwave energy to assist the solubilisation of edible seaweed samples by tetramethylammonium hydroxide (TMAH) has been investigated to extract iodine and bromine. Inductively coupled plasma-mass spectrometry (ICP-MS) has been used as a multi-element detector. Variables affecting the microwave assisted extraction/solubilisation (temperature, TMAH volume, ramp time and hold time) were firstly screened by applying a fractional factorial design (2(5-1)+2), resolution V and 2 centre points. When extracting both halogens, results showed statistical significance (confidence interval of 95%) for TMAH volume and temperature, and also for the two order interaction between both variables. Therefore, these two variables were finally optimized by a 2(2)+star orthogonal central composite design with 5 centre points and 2 replicates, and optimum values of 200 degrees C and 10 mL for temperature and TMAH volume, respectively, were found. The extraction time (ramp and hold times) was found statistically non-significant, and values of 10 and 5 min were chosen for the ramp time and the hold time, respectively. This means a fast microwave heating cycle. Repeatability of the over-all procedure has been found to be 6% for both elements, while iodine and bromine concentrations of 24.6 and 19.9 ng g(-1), respectively, were established for the limit of detection. Accuracy of the method was assessed by analyzing the NIES-09 (Sargasso, Sargassum fulvellum) certified reference material (CRM) and the iodine and bromine concentrations found have been in good agreement with the indicative values for this CRM. Finally, the method was applied to several edible dried and canned seaweed samples. PMID:19576469

  2. Microwave assisted preparation of magnesium phosphate cement (MPC) for orthopedic applications: a novel solution to the exothermicity problem.

    PubMed

    Zhou, Huan; Agarwal, Anand K; Goel, Vijay K; Bhaduri, Sarit B

    2013-10-01

    There are two interesting features of this paper. First, we report herein a novel microwave assisted technique to prepare phosphate based orthopedic cements, which do not generate any exothermicity during setting. The exothermic reactions during the setting of phosphate cements can cause tissue damage during the administration of injectable compositions and hence a solution to the problem is sought via microwave processing. This solution through microwave exposure is based on a phenomenon that microwave irradiation can remove all water molecules from the alkaline earth phosphate cement paste to temporarily stop the setting reaction while preserving the active precursor phase in the formulation. The setting reaction can be initiated a second time by adding aqueous medium, but without any exothermicity. Second, a special emphasis is placed on using this technique to synthesize magnesium phosphate cements for orthopedic applications with their enhanced mechanical properties and possible uses as drug and protein delivery vehicles. The as-synthesized cements were evaluated for the occurrences of exothermic reactions, setting times, presence of Mg-phosphate phases, compressive strength levels, microstructural features before and after soaking in (simulated body fluid) SBF, and in vitro cytocompatibility responses. The major results show that exposure to microwaves solves the exothermicity problem, while simultaneously improving the mechanical performance of hardened cements and reducing the setting times. As expected, the cements are also found to be cytocompatible. Finally, it is observed that this process can be applied to calcium phosphate cements system (CPCs) as well. Based on the results, this microwave exposure provides a novel technique for the processing of injectable phosphate bone cement compositions. PMID:23910345

  3. Adsorption of Cu2+ ions using chitosan-modified magnetic Mn ferrite nanoparticles synthesized by microwave-assisted hydrothermal method

    NASA Astrophysics Data System (ADS)

    Meng, Yuying; Chen, Deyang; Sun, Yitao; Jiao, Dongling; Zeng, Dechang; Liu, Zhongwu

    2015-01-01

    Chitosan-modified Mn ferrite nanoparticles were synthesized by a one-step microwave-assisted hydrothermal method. These Mn ferrite magnetic composite nanoparticles were employed to absorb Cu2+ ions in water. XRD verified the spinel structure of the MnFe2O4 nanoparticles. Chitosan modification does not result in any phase change of MnFe2O4. FTIR and zeta potentials curves for all samples suggest that chitosan can be successfully coated on the Mn ferrites. TEM characterization showed that the modified MnFe2O4 nanoparticles have a cubic shape with a mean diameter of ∼100 nm. For adsorption behavior, the effects of experiment parameters such as solution pH value, contact time and initial Cu2+ ions concentration on the adsorption efficiency were systematically investigated. The results showed that increasing solution pH value and extending contact time are favorable for improving adsorption efficiency. Especially, adsorption efficiency can reach up to 100% and 96.7% after 500 min adsorption at pH 6.5 for the solutions with initial Cu2+ ions concentration of 50 mg/L and 100 mg/L. Adsorption data fits well with the Langmuir isotherm models with a maximum adsorption capacity (qm) and a Langmuir adsorption equilibrium constant (K) of 65.1 mg/g and 0.090 L/mg, respectively. The adsorption kinetic agrees well with pseudo second order model with the pseudo second rate constants (K2) of 0.0468 and 0.00189 g/mg/min for solutions with initial Cu2+ ions of 50 and 100 mg/L, respectively.

  4. Rapid synthesis of Ti-MCM-41 by microwave-assisted hydrothermal method towards photocatalytic degradation of oxytetracycline.

    PubMed

    Chen, Hanlin; Peng, Yen-Ping; Chen, Ku-Fan; Lai, Chia-Hsiang; Lin, Yung-Chang

    2016-06-01

    This study employed microwave-assisted hydrothermal method to synthesize Ti-MCM-41, which are mesoporous materials with a high surface area and excellent photocatalytic ability. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and ultraviolet-visible spectroscopy (UV-Vis) were employed. The XRD findings showed that Ti-MCM-41 exhibited a peak at 2θ of 2.2°, which was attributed to the hexagonal MCM-41 structure. The BET (Brunauer-Emmett-Teller) results agreed with the TEM findings that Ti-MCM-41 has a pore size of about 3-5nm and a high surface area of 883m(2)/g. FTIR results illustrated the existence of Si-O-Si and Si-O-Ti bonds in Ti-MCM-41. The appearance of Ti 2p peaks in the XPS results confirmed the FTIR findings that the Ti was successfully doped into the MCM-41 structure. Zeta (ζ)-potential results indicated that the iso-electric point (IEP) of Ti-MCM-41 was at about pH3.02. In this study, the photocatalytic degradation of oxytetracycline (OTC) at different pH was investigated under Hg lamp irradiation (wavelength 365nm). The rate constant (K'obs) for OTC degradation was 0.012min(-1) at pH3. Furthermore, TOC (total organic carbon) and high resolution LC-MS (liquid chromatography-mass spectrometry) analyses were conducted to elucidate the possible intermediate products and degradation pathway for OTC. The TOC removal efficiency of OTC degradation was 87.0%, 74.4% and 50.9% at pH3, 7 and 10, respectively. LC-MS analysis results showed that the degradation products from OTC resulted from the removal of functional groups from the OTC ring. PMID:27266304

  5. Experimental data in support of continuous microwave effect on emulsion polymerization of styrene.

    PubMed

    Ergan, Başak Temur; Bayramoğlu, Mahmut; Özcan, Seval

    2015-09-01

    This article contains original experimental data, figures and methods to the study of Microwave-assisted emulsion polymerization of styrene under the frame of "Enhanced Microwave Synthesis" (EMS), has been examined to investigate the advantages of Microwave (MW) power use in emulsion polymerization (Ergan et al., Eur. Polym. J. 69, 2015, 374-384). For comparative purpose, MW and conventional heating (CH) method experiments were conducted under similar conditions. By externally cooling the reaction vessel with 1,4-dioxane, constant and continuous MW power was successfully applied at isothermal condition during the polymerization. Here we give the MW power calibration data of MW-experimental system, the complete set of the experimental polymerization data and the analysis data obtained from different polymer characterization test devices (GPC, DSC and Viscometer). PMID:26306319

  6. Microwave-assisted synthesis of Mn{sub 3}O{sub 4} nanoparticles@reduced graphene oxide nanocomposites for high performance supercapacitors

    SciTech Connect

    She, Xiao; Zhang, Xinmin; Liu, Jingya; Li, Liang; Yu, Xianghua; Huang, Zhiliang; Shang, Songmin

    2015-10-15

    Highlights: • Mn{sub 3}O{sub 4}@rGO nanocomposites were prepared by one-step microwave-assisted method. • The growth of Mn{sub 3}O{sub 4} and the reduction of graphene oxide occurred simultaneously. • Specific capacitance of the nanocomposite is higher than those of rGO and Mn{sub 3}O{sub 4}. • The nanocomposites have good rate capability and cycling stability. - ABSTRACT: One-step microwave-assisted synthetic route for the fabrication of Mn{sub 3}O{sub 4} nanoparticles@reduced graphene oxide (Mn{sub 3}O{sub 4}@rGO) nanocomposites has been demonstrated. The morphological structures of the nanocomposites are characterized by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), thermogravimetric analyses (TGA), and scanning electron microscopy (SEM), respectively. All of the results indicate that the microwave-assisted synthesis results in the growth of Mn{sub 3}O{sub 4} and the reduction of graphene oxide simultaneously in ethylene glycol-water system. The specific capacitance of the as-prepared Mn{sub 3}O{sub 4}@rGO nanocomposite is higher than those of rGO and pure Mn{sub 3}O{sub 4}, which indicates the synergetic interaction between rGO and Mn{sub 3}O{sub 4}. The nanocomposites also have good rate capability and cycling stability in electrochemical experiments. This facile technique may be extended to the large scale and cost effective production of other composites based on graphene and metal oxide for many applications.

  7. Pd/C-catalyzed aerobic oxidative esterification of alcohols and aldehydes: a highly efficient microwave-assisted green protocol.

    PubMed

    Caporaso, Marina; Cravotto, Giancarlo; Georgakopoulos, Spyros; Heropoulos, George; Martina, Katia; Tagliapietra, Silvia

    2014-01-01

    We herein describe an environmentally friendly microwave-assisted oxidative esterification of alcohols and aldehydes in the presence of molecular oxygen and a heterogeneous catalysis (Pd/C, 5 mol %). This efficient and ligandless conversion procedure does not require the addition of an organic hydrogen acceptor. The reaction rate is strongly enhanced by mild dielectric heating. Furthermore, it is a versatile green procedure which generally enables the isolation of esters to be carried out by simple filtration in almost quantitative yields. PMID:24991300

  8. Pd/C-catalyzed aerobic oxidative esterification of alcohols and aldehydes: a highly efficient microwave-assisted green protocol

    PubMed Central

    Caporaso, Marina; Georgakopoulos, Spyros; Heropoulos, George; Martina, Katia; Tagliapietra, Silvia

    2014-01-01

    Summary We herein describe an environmentally friendly microwave-assisted oxidative esterification of alcohols and aldehydes in the presence of molecular oxygen and a heterogeneous catalysis (Pd/C, 5 mol %). This efficient and ligandless conversion procedure does not require the addition of an organic hydrogen acceptor. The reaction rate is strongly enhanced by mild dielectric heating. Furthermore, it is a versatile green procedure which generally enables the isolation of esters to be carried out by simple filtration in almost quantitative yields. PMID:24991300

  9. Comparative study of carbon dioxide sensing by Sn-doped TiO2 nanoparticles synthesized by microwave-assisted and solid-state diffusion route

    NASA Astrophysics Data System (ADS)

    Nemade, K. R.; Waghuley, S. A.

    2015-04-01

    Gas sensor based on Sn-doped titanium dioxide (TiO2) nanoparticles has been fabricated and evaluated for carbon dioxide (CO2) sensing. The Sn-doped TiO2 nanoparticles were synthesized by microwave-assisted and solid-state diffusion route. The structure and morphology of resulting samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Ultraviolet-visible (UV-VIS) spectroscopy was employed to study the optical properties. The weight loss of samples was analyzed through thermo gravimetric analysis (TGA). The Sn-doped TiO2 nanoparticles synthesized through microwave route exhibited good sensing characteristics.

  10. Micromagnetic model analysis of integrated single-pole-type head with tilted spin-torque oscillator for high-frequency microwave-assisted magnetic recording

    SciTech Connect

    Katayama, Takuto; Kanai, Yasushi; Yoshida, Kazuetsu; Greaves, Simon; Muraoka, Hiroaki

    2015-05-07

    The spin-torque oscillator (STO) is the most important component in microwave-assisted magnetic recording. Some requirements for the STO are: large amplitude and stable oscillation, small injected current, and oscillation at a frequency that excites resonance in a recording medium. It is also necessary for the STO oscillation to closely follow the head coil current. In this paper, STOs were integrated into write heads and micromagnetic analyses carried out to obtain a write head structure with stable STO oscillation that could follow a high-frequency head coil current.

  11. New IKK inhibitors: Synthesis of new imidazo[1,2-a]quinoxaline derivatives using microwave assistance and biological evaluation as IKK inhibitors.

    PubMed

    Moarbess, Georges; Guichou, Jean-François; Paniagua-Gayraud, Stéphanie; Chouchou, Adrien; Marcadet, Olivier; Leroy, Fiona; Ruédas, Rémi; Cuq, Pierre; Deleuze-Masquéfa, Carine; Bonnet, Pierre-Antoine

    2016-06-10

    The inhibition of the NF-κB-dependent pathways by IKK inhibitors plays an important role in immunity, inflammation, and cancer. New imidazoquinoxalines tricyclic derivatives are prepared using microwave assistance and their biological activities as IKK inhibitors are described. Compounds 6a present a potent inhibition activity and selectivity for IKK2. Docking studies in the IKK2 binding site allowed identification of residues most likely to interact with theses inhibitors and explain their potent IKK2 inhibition activity and selectivity. PMID:27017554

  12. Effect of Inductive Coil Geometry on the Thrust Efficiency of a Microwave Assisted Discharge Inductive Plasma Accelerator

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley; Polzin, Kurt; Emsellem, Gregory

    2012-01-01

    Pulsed inductive plasma thrusters [1-3] are spacecraft propulsion devices in which electrical energy is capacitively stored and then discharged through an inductive coil. The thruster is electrodeless, with a time-varying current in the coil interacting with a plasma covering the face of the coil to induce a plasma current. Propellant is accelerated and expelled at a high exhaust velocity (O(10-100 km/s)) by the Lorentz body force arising from the interaction of the magnetic field and the induced plasma current. While this class of thruster mitigates the life-limiting issues associated with electrode erosion, pulsed inductive plasma thrusters require high pulse energies to inductively ionize propellant. The Microwave Assisted Discharge Inductive Plasma Accelerator (MAD-IPA) [4, 5] is a pulsed inductive plasma thruster that addressees this issue by partially ionizing propellant inside a conical inductive coil via an electron cyclotron resonance (ECR) discharge. The ECR plasma is produced using microwaves and permanent magnets that are arranged to create a thin resonance region along the inner surface of the coil, restricting plasma formation, and in turn current sheet formation, to a region where the magnetic coupling between the plasma and the inductive coil is high. The use of a conical theta-pinch coil is under investigation. The conical geometry serves to provide neutral propellant containment and plasma plume focusing that is improved relative to the more common planar geometry of the Pulsed Inductive Thruster (PIT) [2, 3], however a conical coil imparts a direct radial acceleration of the current sheet that serves to rapidly decouple the propellant from the coil, limiting the direct axial electromagnetic acceleration in favor of an indirect acceleration mechanism that requires significant heating of the propellant within the volume bounded by the current sheet. In this paper, we describe thrust stand measurements performed to characterize the performance

  13. Facile microwave-assisted aqueous synthesis of CdS nanocrystals with their photocatalytic activities under visible lighting

    SciTech Connect

    Deng, Chonghai; Tian, Xiaobo

    2013-10-15

    Graphical abstract: - Highlights: • Three kinds of CdS nanostructures have been controllably synthesized. • Ethanediamine acts as a phase and morphology controlling reagent. • Three CdS nanostructures display high visible light photocatalytic activities. • Cubic CdS-3 shows superior photocatalytic activity to the other hexagonal CdS. • The growth processes for fabrication of CdS nanocrystals are also discussed. - Abstract: Three kinds of CdS nanostructures, that is, hexagonal nanospheres (CdS-1), hierarchical caterpillar-fungus-like hexagonal nanorods (CdS-2) and hierarchical cubic microspheres (CdS-3), were controllably synthesized by a facile and one-pot microwave-assisted aqueous chemical method using ethanediamine as a phase and morphology controlling reagent. The as-prepared products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectra (DRS) and photoluminescence (PL) spectra. The results show that CdS-1 is mainly composed of monodispersed hexagonal nanospheres with average diameters of about 100 nm; hexagonal CdS-2 has lengths in the range of 600–800 nm and diameters of 40–60 nm, assembled by nanoparticles about 20 nm in diameter; and CdS-3 is pure cubic microspheres with diameters in the range of 0.8–1.3 μm, aggregated by tiny nanograins with size of 5.8 nm. The band gap energies of CdS products were calculated to be 2.30, 2.31 and 2.24 eV observed from UV–vis DRS for CdS-1, CdS-2 and CdS-3, respectively. PL spectra of CdS samples showed that sphalerite CdS-3 possesses a very weak fluorescence, while wurtzite CdS-2 has a strongest green near-band edge emission (NBE) at 550 nm. The visible light photodegradation of methylene blue and rhodamine B in the presence of CdS photocatalysts illustrates that all of them display high photocatalytic activities. Significantly, the cubic CdS-3 exhibits more excellent photocatalytic

  14. Polymeric microspheres

    DOEpatents

    Walt, David R.; Mandal, Tarun K.; Fleming, Michael S.

    2004-04-13

    The invention features core-shell microsphere compositions, hollow polymeric microspheres, and methods for making the microspheres. The microspheres are characterized as having a polymeric shell with consistent shell thickness.

  15. Optimization of ultrasonic/microwave assisted extraction (UMAE) of polysaccharides from Inonotus obliquus and evaluation of its anti-tumor activities.

    PubMed

    Chen, Yiyong; Gu, Xiaohong; Huang, Sheng-quan; Li, Jinwei; Wang, Xin; Tang, Jian

    2010-05-01

    Recently, the use of ultrasonic and microwave has attracted considerable interest as an alternative approach to the traditional extraction methods. In this paper, in order to maximize the yield and purity of polysaccharides from Inonotus obliquus, response surface methodology (RSM) was employed to optimize the ultrasonic/microwave assisted extraction (UMAE) conditions. The results indicated that the optimal conditions for UMAE were 90W microwave power, 50W ultrasonic power together with 40kHz ultrasonic frequency, solid/water ratio was 1:20 (W/V) and the extracting time was 19min, respectively. Under the optimal conditions, the yield and purity of polysaccharides were 3.25% and 73.16%, respectively, which are above that of traditional hot water extraction and close to the predicted value (3.07% and 72.54%, respectively). These results confirmed that ultrasonic/microwave assisted extraction (UMAE) of polysaccharides had great potential and efficiency compared with traditional hot water extraction. At the same time, the anti-tumor activities of the polysaccharides from I. obliquus with UMAE were evaluated. The results suggested that polysaccharides from I. obliquus exhibited obvious anti-tumor activities. PMID:20149817

  16. High-throughput dynamic microwave-assisted extraction on-line coupled with solid-phase extraction for analysis of nicotine in mushroom.

    PubMed

    Wang, Hui; Zhao, Qi; Song, Weitao; Xu, Yang; Zhang, Xiaopan; Zeng, Qinglei; Chen, Haiyan; Ding, Lan; Ren, Nanqi

    2011-07-15

    A simple and low-cost high-throughput dynamic microwave-assisted extraction (HTDMAE) device was firstly assembled and validated by the extraction of nicotine in mushroom samples. In this device, a household microwave oven was applied to provide the microwave energy; a vacuum pump was used to deliver the solvent. Compared with traditional dynamic microwave-assisted extraction method, the sample throughput and microwave energy utilization were improved by the HTDMAE, up to 20 samples could be treated simultaneously in 9 min. Taking extraction of nicotine in mushroom sample as an example, a method was established with extraction, separation and enrichment of nicotine in a single step by the device on-line coupled with solid-phase extraction (SPE). Nicotine was first extracted from the mushroom samples with water under the action of microwave energy, and then directly introduced into the SPE column which was packed with cation-exchange resins. Subsequently, the nicotine trapped on the resins was eluted with methanol-ammonia (95:5, v/v) and determined by high-performance liquid chromatography. The limit of detection of nicotine obtained is 5.6 μg kg(-1) in fresh mushroom sample. The recovery of nicotine in mushroom samples is in the range of 87.4-104.0%. The proposed method which significantly reduced the overall analysis time and increased sample throughput should be favored for routine analyse of complex solid sample. PMID:21645768

  17. Fast and selective determination of triterpenic compounds in olive leaves by liquid chromatography-tandem mass spectrometry with multiple reaction monitoring after microwave-assisted extraction.

    PubMed

    Sánchez-Avila, N; Priego-Capote, F; Ruiz-Jiménez, J; de Castro, M D Luque

    2009-04-15

    A method for fast and selective determination of the main triterpenic compounds present in olive leaves - oleanolic, ursolic and maslinic acids as triterpenic acids and, uvaol and erythrodiol as triterpenic dialcohols - is reported here. Quantitative isolation of the analytes has been accomplished in 5min by microwave assistance using ethanol as extractant. Due to the medium polarity of triterpenic acids and dialcohols, different ethanol-water ratios were tested in order to select the optimum extractant composition for their solubilisation. Microwave assistance provided a significant shortening of the leaching time as compared to conventional procedures by maceration, which usually requires at least 5h. After extraction, determination was carried out by liquid chromatography-tandem mass spectrometry (LC-MS-MS) with a triple quadrupole (qQq) mass detector without any clean-up step prior to chromatographic analysis. Highly selective identification of triterpenes was confirmed by multiple reaction monitoring (MRM) using the most representative transitions from the precursor ion to the different product ions, while the most sensitive transitions were used for MS-MS quantitation. Total analysis performed in 25 min enables the characterization of a fraction with particular interest in the pharmacological area. PMID:19174200

  18. Microwave-assisted synthesis: A fast and efficient route to produce LaMO{sub 3} (M = Al, Cr, Mn, Fe, Co) perovskite materials

    SciTech Connect

    Prado-Gonjal, J.; Arevalo-Lopez, A.M.; Moran, E.

    2011-02-15

    Research highlights: {yields} Lanthanum perovskites can be prepared by microwave irradiation in a domestic set-up. {yields} Microwave-assisted synthesis yields well crystallized and pure materials, sometimes nanosized. {yields} Rietveld analysis has been performed to refine the structures. {yields} Magnetic and electric measurements are similar to those previously reported. {yields} Microwave-assisted synthesis is a fast and efficient method for the synthesis of lanthanum perovskites. -- Abstract: A series of lanthanum perovskites, LaMO{sub 3} (M = Al, Cr, Mn, Fe, Co), having important technological applications, have been successfully prepared by a very fast, inexpensive, reproducible, environment-friendly method: the microwave irradiation of the corresponding mixtures of nitrates. Worth to note, the microwave source is a domestic microwave oven. In some cases the reaction takes place in a single step, while sometimes further annealings are necessary. For doped materials the method has to be combined with others such as sol-gel. Usually, nanopowders are produced which yield high density pellets after sintering. Rietveld analysis, oxygen stoichiometry, microstructure and magnetic measurements are presented.

  19. Microwave-assisted one-step extraction-derivatization for rapid analysis of fatty acids profile in herbal medicine by gas chromatography-mass spectrometry.

    PubMed

    Liu, Rui-Lin; Zhang, Jing; Mou, Zhao-Li; Hao, Shuang-Li; Zhang, Zhi-Qi

    2012-11-01

    A rapid and practical microwave-assisted one-step extraction-derivatization (MAED) method was developed for gas chromatography-mass spectrometry analysis of fatty acids profile in herbal medicine. Several critical experimental parameters for MAED, including reaction temperature, microwave power and the amount of derivatization reagent (methanol), were optimized with response surface methodology. The results showed that the chromatographic peak areas of total fatty acids and total unsaturated fatty acids content obtained with MAED were markedly higher than those obtained by the conventional Soxhlet or microwave extraction and then derivatization method. The investigation of kinetics and thermodynamics of the derivatization reaction revealed that microwave assistance could reduce activation energy and increase the Arrhenius pre-exponential factor. The MAED method simplified the sample preparation procedure, shortened the reaction time, but improved the extraction and derivatization efficiency of lipids and reduced ingredient losses, especially for the oxidization and isomerization of unsaturated fatty acids. The simplicity, speed and practicality of this method indicates great potential for high throughput analysis of fatty acids in natural medicinal samples. PMID:22968083

  20. Analysis of volatile oil composition of Citrus aurantium L. by microwave-assisted extraction coupled to headspace solid-phase microextraction with nanoporous based fibers.

    PubMed

    Gholivand, Mohammad Bagher; Piryaei, Marzieh; Abolghasemi, Mir Mahdi

    2013-03-01

    Nanoporous silica was prepared and functionalized with amino propyl-triethoxysilane to be used as a highly porous fiber-coating material for solid-phase microextraction (SPME). The prepared nanomaterials were immobilized onto a stainless steel wire for fabrication of the SPME fiber. The proposed fiber was evaluated for the extraction of volatile component of Citrus aurantium L. leaves. A homemade microwave-assisted extraction followed by headspace (HS) solid-phase apparatus was used for the extraction of volatile components. For optimization of factors affecting the extraction efficiency of the volatile compounds, a simplex optimization method was used. The repeatability for one fiber (n = 4), expressed as RSD, was between 3.1 and 8.6% and the reproducibility for five prepared fibers was between 10.1 and 14.9% for the test compounds. Using microwave-assisted distillation HS-SPME followed by GC-MS, 53 compounds were separated and identified in C. aurantium L., which mainly included limonene (62.0%), linalool (7.47%), trans-β-Ocimene (3.47%), and caryophyllene (2.05%). In comparison to a hydrodistillation method, the proposed technique could equally monitor almost all the components of the sample, in an easier way, which was rapid and required a much lower amount of sample. PMID:23483734

  1. imFASP: An integrated approach combining in-situ filter-aided sample pretreatment with microwave-assisted protein digestion for fast and efficient proteome sample preparation.

    PubMed

    Zhao, Qun; Fang, Fei; Wu, Ci; Wu, Qi; Liang, Yu; Liang, Zhen; Zhang, Lihua; Zhang, Yukui

    2016-03-17

    An integrated sample preparation method, termed "imFASP", which combined in-situ filter-aided sample pretreatment and microwave-assisted trypsin digestion, was developed for preparation of microgram and even nanogram amounts of complex protein samples with high efficiency in 1 h. For imFASP method, proteins dissolved in 8 M urea were loaded onto a filter device with molecular weight cut off (MWCO) as 10 kDa, followed by in-situ protein preconcentration, denaturation, reduction, alkylation, and microwave-assisted tryptic digestion. Compared with traditional in-solution sample preparation method, imFASP method generated more protein and peptide identifications (IDs) from preparation of 45 μg Escherichia coli protein sample due to the higher efficiency, and the sample preparation throughput was significantly improved by 14 times (1 h vs. 15 h). More importantly, when the starting amounts of E. coli cell lysate decreased to nanogram level (50-500 ng), the protein and peptide identified by imFASP method were improved at least 30% and 44%, compared with traditional in-solution preparation method, suggesting dramatically higher peptide recovery of imFASP method for trace amounts of complex proteome samples. All these results demonstrate that the imFASP method developed here is of high potential for high efficient and high throughput preparation of trace amounts of complex proteome samples. PMID:26920773

  2. Synthesis and electrochemical properties of LiAl 0.1Mn 1.9O 4 by microwave-assisted sol-gel method

    NASA Astrophysics Data System (ADS)

    Bao, Shu-Juan; Liang, Yan-Yu; Zhou, Wen-Jia; He, Ben-Lin; Li, Hu-Lin

    Aluminum-doped spinel-type LiMn 2O 4 cathode active materials have been synthesized by a microwave-assisted sol-gel method. The influence of synthesis conditions on the structural and electrochemical properties of LiAl 0.1Mn 1.9O 4 was investigated by thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and charge/discharge experiments. The powders resulting from the microwave-assisted sol-gel method with good crystallinity and cubic spinel shapes deliver an initial discharge capacity of 120 mAh g -1, present excellent rate capability, and the Coulombic efficiency of it almost approaches 99% after 30 cycles. These advantages make it attractive particularly for a practical application. In addition, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to characterize the reactions of Li ion insertion into and extraction from LiAl 0.1Mn 1.9O 4 electrodes.

  3. Sample preparation of sewage sludge and soil samples for the determination of polycyclic aromatic hydrocarbons based on one-pot microwave-assisted saponification and extraction.

    PubMed

    Pena, M Teresa; Pensado, Luis; Casais, M Carmen; Mejuto, M Carmen; Cela, Rafael

    2007-04-01

    A microwave-assisted sample preparation (MASP) procedure was developed for the analysis of polycyclic aromatic hydrocarbons (PAHs) in sewage sludge and soil samples. The procedure involved the simultaneous microwave-assisted extraction of PAHs with n-hexane and the hydrolysis of samples with methanolic potassium hydroxide. Because of the complex nature of the samples, the extracts were submitted to further cleaning with silica and Florisil solid-phase extraction cartridges connected in series. Naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[e]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[a,h]anthracene, benzo[g,h,i]perylene, and indeno[1,2,3-cd]pyrene, were considered in the study. Quantification limits obtained for all of these compounds (between 0.4 and 14.8 microg kg(-1) dry mass) were well below of the limits recommended in the USA and EU. Overall recovery values ranged from 60 to 100%, with most losses being due to evaporation in the solvent exchange stages of the procedure, although excellent extraction recoveries were obtained. Validation of the accuracy was carried out with BCR-088 (sewage sludge) and BCR-524 (contaminated industrial soil) reference materials. PMID:17268774

  4. Synthesis of BiFeO3 thin films on single-terminated Nb : SrTiO3 (111) substrates by intermittent microwave assisted hydrothermal method

    NASA Astrophysics Data System (ADS)

    Velasco-Davalos, Ivan; Ambriz-Vargas, Fabian; Kolhatkar, Gitanjali; Thomas, Reji; Ruediger, Andreas

    2016-06-01

    We report on a simple and fast procedure to create arrays of atomically flat terraces on single crystal SrTiO3 (111) substrates and the deposition of ferroelectric BiFeO3 thin films on such single-terminated surfaces. A microwave-assisted hydrothermal method in deionized water and ammonia solution selectively removes either (SrO3)4- or Ti4+ layers to ensure the same chemical termination on all terraces. Measured step heights of 0.225 nm (d111) and uniform contrast in the phase image of the terraces confirm the single termination in pure and Nb doped SrTiO3 single crystal substrates. Multiferroic BiFeO3 thin films were then deposited by the same microwave assisted hydrothermal process on Nb : SrTiO3 (111) substrates. Bi(NO3)3 and Fe(NO3)3 along with KOH served as the precursors solution. Ferroelectric behavior of the BiFeO3 films on Nb : SrTiO3 (100) substrates was verified by piezoresponse force microscopy.

  5. Effects of moisture content in cigar tobacco on nicotine extraction. Similarity between soxhlet and focused open-vessel microwave-assisted techniques.

    PubMed

    Ng, Lay-Keow; Hupé, Michel

    2003-09-01

    The effects of tobacco moisture on nicotine yield were investigated in this study. Soxhlet and microwave-assisted techniques were used to extract nicotine from cigar fillers of varying moisture contents (5-20%), using a polar (methanol) and a non-polar (isooctane) solvent. The extracts were analyzed by a gas chromatograph equipped with a flame-ionization detector. For both extraction techniques, higher nicotine yields were consistently obtained with methanol than with isooctane from the same samples. Solubility of nicotine salts in methanol but not in isooctane is the major cause of this observation. Moreover, pronounced effects of the tobacco moisture content on extraction efficiency were observed with isooctane but not with methanol. For microwave assisted extraction (MAE) with isooctane, nicotine yield increased from 3 to 70% as the moisture level in tobacco was raised from 3 to 13%, and leveled off thereafter. Similar observations were made with Soxhlet extraction. While MAE results were rationalized by the known cell-rupture process, a mechanism based on the interaction between the solvents and the structural components of the plant cells has been proposed to account for the observations made with Soxhlet extraction. PMID:14518778

  6. Microwave-assisted extraction and high-throughput monolithic-polymer-based micro-solid-phase extraction of organophosphorus, triazole, and organochlorine residues in apple.

    PubMed

    Bagheri, Habib; Es'haghi, Ali; Es-Haghi, Ali; Basiripour, Fatemeh

    2016-02-01

    A high-throughput micro-solid-phase extraction device based on a 96-well plate was constructed and applied to the determination of pesticide residues in various apple samples. Butyl methacrylate and ethylene glycol dimethacrylate were copolymerized as a monolithic polymer and placed in the cylindrically shaped stainless-steel meshes of 96-micro-solid-phase extraction device and used as an extracting unit. Before the micro-solid-phase extraction, microwave-assisted extraction was employed to facilitate the transfer of the pesticide residues from the apple matrix to liquid media. Then, 1 mL of the aquatic samples was transferred into the 96-well plate and the 96-micro-solid-phase extraction device was applied for the extraction of the selected pesticides. Influential parameters, such as sorbent-to-sorbent reproducibility, microwave-assisted extraction time, ionic strength and micro-solid-phase extraction time, were optimized. The limits of quantitation were below 120 μg/kg, which are lower than the maximum residue limits. The developed method was successfully implemented for the extraction and determination of the selected pesticides from 20 different apple samples gathered from local markets. Phosalone was identified and quantified at the concentration level of 147 (±16.4) μg/kg in one of the samples. PMID:26614571

  7. Preparation of highly photocatalytic active CdS/TiO2 nanocomposites by combining chemical bath deposition and microwave-assisted hydrothermal synthesis

    NASA Astrophysics Data System (ADS)

    Li, Li; Wang, Lili; Hu, Tianyu; Zhang, Wenzhi; Zhang, Xiuli; Chen, Xi

    2014-10-01

    CdS/TiO2 nanocomposites were prepared from Cd and Ti (1:1 M ratio) using cetyltrimethylammonium bromide by a two-step chemical bath deposition (CBD) and microwave-assisted hydrothermal synthesis (MAHS) method. A series of nanocomposites with different morphologies and activities were prepared by varying the reaction time in the MAHS (2, 4, and 6 h). The crystal structure, morphology, and surface physicochemical properties of the nanocomposites were characterized by X-ray diffraction, UV-visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and N2 adsorption-desorption measurements. The results show that the CdS/TiO2 nanocomposites were composed of anatase TiO2 and hexagonal CdS phases with strong absorption in the visible region. The surface morphologies changed slightly with increasing microwave irradiation time, while the Brunauer-Emmett-Teller surface area increased remarkably. The photocatalytic degradation of methyl orange (MO) was investigated under UV light and simulated sunlight irradiation. The photocatalytic activity of the CdS/TiO2 (6 h) composites prepared by the MAHS method was higher than those of CdS, P25, and other CdS/TiO2 nanocomposites. The CdS/TiO2 (6 h) nanocomposites significantly affected the UV and microwave-assisted photocatalytic degradation of different dyes. To elucidate the photocatalytic reaction mechanism for the CdS/TiO2 nanocomposites, controlled experiments were performed by adding different radical scavengers.

  8. Microwave-assisted extraction: a simpler and faster method for the determination of ethyl glucuronide in hair by gas chromatography-mass spectrometry.

    PubMed

    Alvarez, Iván; Bermejo, Ana María; Tabernero, María Jesús; Fernández, Purificación; Cabarcos, Pamela; López, Patricia

    2009-02-01

    Alcohol is the most frequently abused "addictive substance" that causes serious social problems throughout the world; thus, alcoholism is of particular interest in clinical and forensic medicine. Alcohol biomarkers are physiological indicators of alcohol exposure or ingestion and may reflect the presence of an alcohol use disorder. The glucuronide conjugation is a minor pathway of ethanol metabolism. Ethyl glucuronide (EtG) is a marker of recent alcohol consumption that detects alcohol use reliably over a definite time period. The present paper describes a new method for the determination of EtG in hair. It is based both in the microwave-assisted extraction (MAE), to extract the analyte from hair samples, and gas chromatography-mass spectrometry (GC-MS), to identify and quantify the EtG in selected ion monitoring (SIM) mode. The method was applied to 15 hair samples from occasional alcohol users, obtaining positive results in all cases. It was fully validated, including a linear range (0.3-10 ng/mg) and the main precision parameters. In summary, the use of microwave-assisted extraction turned out to be a substantially simpler, faster, and a more sensitive procedure than any other conventional sample preparations. PMID:19082582

  9. Microwave-assisted combustion synthesis of Ag/ZnO nanocomposites and their photocatalytic activities under ultraviolet and visible-light irradiation

    SciTech Connect

    Zhang, Dafeng; Pu, Xipeng; Li, Huaiyong; Yu, Young Moon; Shim, Jae Jeong; Cai, Peiqing; Kim, Sun Il; Seo, Hyo Jin

    2015-01-15

    Highlights: • Ag/ZnO nanocomposites were synthesized by a microwave-assisted combustion method. • Ag/ZnO nanocomposites exhibited improved photocatalytic activities under UV irradiation. • Poorer photocatalytic performances were obtained under visible-light irradiation. - Abstract: Ag/ZnO nanocomposites were synthesized by a rapid one-step microwave-assisted combustion method. The as-synthesized samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence and ultraviolet–visible spectrophotometry. XRD results showed that hexagonal ZnO and cubic Ag were obtained. Ag nanoparticles were chemically attached on the surface of ZnO. The decrease in the energy band gap of Ag/ZnO nanocomposites and the photoluminescence quenching were observed while the Ag content was increased. Furthermore, the introduction of Ag nanoparticles leads to significantly improved photocatalytic activities in the case of ultraviolet irradiation, but in the case of visible-light irradiation opposite results were obtained. The corresponding mechanism was discussed in detail.

  10. Clean and time-effective synthesis of anatase TiO2 nanocrystalline by microwave-assisted solvothermal method for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Shen, Po-Shen; Tai, Yu-Chuen; Chen, Peter; Wu, Yu-Chun

    2014-02-01

    In this article, we report a clean and time-effective solvothermal synthesis route using microwave-assisted heating method to prepare nanocrystalline anatase TiO2 with its application for dye-sensitized solar cells. With this proposed method, pure anatase TiO2 nanoparticles with size about 20 nm are successfully obtained at 220 °C for 30 min. Our method of microwave-assisted organic solvothermal route significantly reduces the elaborating process of washing and solvent exchange for the subsequent paste formation. The as-synthesized TiO2 colloidal solution is ready for particle dispersion that markedly simplified the preparation procedures. Material characterizations of the anatase TiO2 nanoparticles are performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), respectively. The photovoltaic performances of the dye-sensitized solar cells assembled with the as-synthesized TiO2 nanocrystallines as photoanodes in various film thicknesses are examined. An excellent energy conversion efficiency of 7.8% is achieved which is comparable to the previously reported dye-sensitized solar cells made of hydrothermal microwave-synthesized TiO2.

  11. Application of ionic liquids in vacuum microwave-assisted extraction followed by macroporous resin isolation of three flavonoids rutin, hyperoside and hesperidin from Sorbus tianschanica leaves.

    PubMed

    Gu, Huiyan; Chen, Fengli; Zhang, Qiang; Zang, Jing

    2016-03-01

    Rutin, hyperoside and hesperidin were effectively extracted from Sorbus tianschanica leaves by an ionic liquid vacuum microwave-assisted method. A series of ionic liquids with various anions and alkyl chain length of the cations were studied and the extraction was performed in [C6mim][BF4] aqueous solution. After optimization by a factorial design and response surface methodology, total extraction yield of 2.37mg/g with an error of 0.12mg/g (0.71±0.04mg/g, 1.18±0.06mg/g and 0.48±0.02 for rutin, hyperoside and hesperidin, respectively) was achieved under -0.08MPa for vacuum, 19min and 420W for microwave irradiation time and power, and 15mL/g for liquid-solid ratio. The proposed method here is more efficient and needs a shorter extraction time for rutin, hyperoside and hesperidin from S. tianschanica leaves than reference extraction techniques. In stability studies performed with standard rutin, hyperoside and hesperidin, the target analytes were stable under the optimum conditions. The proposed method had a high reproducibility and precision. In addition, separation of rutin, hyperoside and hesperidin from [C6mim][BF4] extraction solution was completed effectively by AB-8 macroporous resin adsorption and desorption process. Ionic liquid vacuum microwave-assisted extraction is a simple, rapid and efficient sample extraction technique. PMID:26874229

  12. Fast preparation of flower-like Bi{sub 4}Ge{sub 3}O{sub 12} microstructures via a microwave-assisted hydrothermal process

    SciTech Connect

    Li, Zhao-Qian; Zhang, Lei; Chen, Xue-Tai

    2012-09-15

    In the present paper, we report a facile and fast microwave-assisted solution-phase approach for the preparation of flower-like bismuth germanate (Bi{sub 4}Ge{sub 3}O{sub 12}) microstructures, employing bismuth nitrate pentahydrate (Bi(NO{sub 3}){sub 3}{center_dot}5H{sub 2}O) and germanium dioxide (GeO{sub 2}) as starting materials. The phase and morphology of the products were characterized by powder X-ray diffraction, X-ray photoelectron spectrum, energy dispersive spectrometry, and scanning electron microscopy. Some control experiments have been carried out to reveal the influencing factors involved in the formation, which suggested that reaction time, reaction temperature, the volume of ammonia and glycerol play crucial roles in the formation of the flower-like Bi{sub 4}Ge{sub 3}O{sub 12}. The optical absorption property of the product has been investigated. - Highlights: Black-Right-Pointing-Pointer Flower-like Bi4Ge3O12 was synthesized via a microwave-assisted solution route. Black-Right-Pointing-Pointer The phases and morphologies of the product have been characterized. Black-Right-Pointing-Pointer The optical property of the product has been studied.

  13. A fast and accurate microwave-assisted digestion method for arsenic determination in complex mining residues by flame atomic absorption spectrometry.

    PubMed

    Pantuzzo, Fernando L; Silva, Julio César J; Ciminelli, Virginia S T

    2009-09-15

    A fast and accurate microwave-assisted digestion method for arsenic determination by flame atomic absorption spectrometry (FAAS) in typical, complex residues from gold mining is presented. Three digestion methods were evaluated: an open vessel digestion using a mixture of HCl:HNO(3):HF acids (Method A) and two microwave digestion methods using a mixture of HCl:H(2)O(2):HNO(3) in high (Method B) and medium-pressure (Method C) vessels. The matrix effect was also investigated. Arsenic concentration from external and standard addition calibration curves (at a 95% confidence level) were statistically equal (p-value=0.122) using microwave digestion in high-pressure vessel. The results from the open vessel digestion were statistically different (p-value=0.007) whereas in the microwave digestion in medium-pressure vessel (Method C) the dissolution of the samples was incomplete. PMID:19345010

  14. A novel one-pot and one-step microwave-assisted cyclization-methylation reaction of amino alcohols and acetylated derivatives with dimethyl carbonate and TBAC.

    PubMed

    Ochoa-Terán, Adrián; Guerrero, Leticia; Rivero, Ignacio A

    2014-01-01

    A simple and efficient microwave-assisted methodology for the synthesis of 4-substituted-3-methyl-1,3-oxazolidin-2-ones from amino alcohols catalyzed by a ionic liquid was developed. This novel one-pot and one-step cyclization-methylation reaction represents an easier and faster method than any other reported protocols that can be used to obtain the desired products in good yields and high purity. Applying microwave irradiation at 130°C in the presence of TBAC, dimethyl carbonate acts simultaneously as carbonylating and methylating agent and surprisingly promotes an in situ basic trans esterification when a N-acetylated amino alcohol is used as starting material. Furthermore, dimethyl carbonate worked better than diethyl carbonate in performing this reaction. PMID:25692177

  15. Simultaneous determination of seven bioactive components in Guizhi Fuling capsule by microwave-assisted extraction combined with ultra performance liquid chromatography tandem mass spectrometry.

    PubMed

    Sui, Yang; Zhao, Long-Shan; Wang, Zhen-Zhong; Zhao, Yu-Tong; Xiao, Wei; Xiong, Zhi-Li

    2016-01-01

    A simple, rapid and reliable microwave-assisted extraction (MAE) combined with ultra performance liquid chromatography tandem mass spectrometry method was developed for simultaneous determination of the seven bioactive constituents in Guizhi Fuling capsule (GFC), namely gallic acid, amygdalin, albiflorin, paeoniflorin, paeonol, cinnamic acid and pachymic acid, respectively. The operation of MAE optimised through orthogonal array design experiment was performed at 80°C for 10 min with methanol-water (70:30, v/v) as the extracting solvent. The method was validated including intra- and inter-day precision, repeatability and stability, with relative standard deviation less than 3.9%, 3.3%, 4.4% and 3.1%, respectively. All analytes showed the good linearity (r >0.999), and their average recoveries varied between 98.2% and 101.2%. The results indicated that this method was simple, effective and suitable for the quality control of GFC. PMID:26189716

  16. Microwave-assisted one-pot synthesis of water-soluble rare-earth doped fluoride luminescent nanoparticles with tunable colors

    PubMed Central

    Mi, Cong-Cong; Tian, Zhen-huang; Han, Bao-fu; Mao, Chuan-bin; Xu, Shu-kun

    2012-01-01

    Polyethyleneimine (PEI) functionalized multicolor luminescent LaF3 nanoparticles were synthesized via a novel microwave-assisted method, which can achieve fast and uniform heating under eco-friendly and energy efficient conditions. The as-prepared nanoparticles possess a pure hexagonal structure with an average size of about 12 nm. When doped with different ions (Tb3+ and Eu3+), the morphology and structure of the nanoparticles were not changed, whereas the optical properties varied with doped ions and their molar ratio, and as a result emission of four different colors (green, yellow, orange and red) were achieved by simply switching the types of doping ions (Eu3+ versus Tb3 +) and the molar ratio of the two doping ions. PMID:22879690

  17. Green Upconversion Emissions in Er³⁺/Yb³⁺ Co-Doped CaMoO₄Prepared by Microwave-Assisted Metathetic Method.

    PubMed

    Liu, Jing; Liu, Yunzhao; Li, Changlin; Wang, Xinze; Gao, Hongjian; Liu, Zhongxin; Chen, Wei

    2016-01-01

    In this study Er³⁺ doped CaMoO₄ (CaMoO₄:Er³⁺), and Er³⁺/Yb³⁺-co-doped CaMoO₄ (CaMoO₄:Er³⁺Yb³⁺) nanoparticles have been synthesized by the microwave-assisted metathetic method. Er³⁺/Yb³⁺ co-doped CaMoO₄ nanoparticles sintered at 600 °C showed the strongest photoluminescence intensity, and crystallized well. At the excitation of 980 nm, the CaMoO₄ nanoparticles show the strongest green emission at the 520 nm and 550 nm emission bands. Moreover, the green light produced has a better color purity. PMID:27398526

  18. A Novel One-Pot and One-Step Microwave-Assisted Cyclization-Methylation Reaction of Amino Alcohols and Acetylated Derivatives with Dimethyl Carbonate and TBAC

    PubMed Central

    Ochoa-Terán, Adrián; Guerrero, Leticia; Rivero, Ignacio A.

    2014-01-01

    A simple and efficient microwave-assisted methodology for the synthesis of 4-substituted-3-methyl-1,3-oxazolidin-2-ones from amino alcohols catalyzed by a ionic liquid was developed. This novel one-pot and one-step cyclization-methylation reaction represents an easier and faster method than any other reported protocols that can be used to obtain the desired products in good yields and high purity. Applying microwave irradiation at 130°C in the presence of TBAC, dimethyl carbonate acts simultaneously as carbonylating and methylating agent and surprisingly promotes an in situ basic trans esterification when a N-acetylated amino alcohol is used as starting material. Furthermore, dimethyl carbonate worked better than diethyl carbonate in performing this reaction. PMID:25692177

  19. Microwave-assisted synthesis and antifungal activity of novel coumarin derivatives: Pyrano[3,2-c]chromene-2,5-diones.

    PubMed

    Zhang, Rong-Rong; Liu, Jia; Zhang, Yu; Hou, Meng-Qing; Zhang, Ming-Zhi; Zhou, Fenger; Zhang, Wei-Hua

    2016-06-30

    A series of novel fused coumarin analogues pyrano[3,2-c]chromene-2,5-diones have been synthesized through an optimized microwave-assisted protocol. All target compounds were tested and evaluated for their antifungal activity against Botrytis cinerea, Colletotrichum copsica, Alternaria solani, Gibberella zeae and Rhizoctorzia solani. The bioassay results indicated that some of the compounds exhibited potent antifungal activities at concentration less than 50 ppm. For the compounds 5d, 6c and 7b, EC50 values against B. cinerea were as low as 0.141, 0.082 and 0.091 μM, respectively, which represents better antifungal activity than that of the commonly used fungicide Azoxystrobin. Compounds 5d (57%) and 6c (55%) also exhibited more effective control than Azoxystrobin (44%) against Colletotrichum capsica. PMID:27060759

  20. α-Fe2O3 nanosheet-assembled hierarchical hollow mesoporous microspheres: Microwave-assisted solvothermal synthesis and application in photocatalysis.

    PubMed

    Sun, Tuan-Wei; Zhu, Ying-Jie; Qi, Chao; Ding, Guan-Jun; Chen, Feng; Wu, Jin

    2016-02-01

    α-Fe2O3 nanosheet-assembled hierarchical hollow mesoporous microspheres (HHMSs) were prepared by thermal transformation of nanosheet-assembled hierarchical hollow mesoporous microspheres of a precursor. The precursor was rapidly synthesized using FeCl3·6H2O as the iron source, ethanolamine (EA) as the alkali source, and ethylene glycol (EG) as the solvent by the microwave-assisted solvothermal method. The samples were characterized by X-ray powder diffraction (XRD), thermogravimetric (TG) analysis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption-desorption isotherm. The effects of the microwave solvothermal temperature and EA amount on the morphology of the precursor were investigated. The as-prepared α-Fe2O3 HHMSs exhibit a good photocatalytic activity for the degradation of salicylic acid, and are promising for the application in wastewater treatment. PMID:26520817

  1. Microwave Assistant Synthesis, Antifungal Activity and DFT Theoretical Study of Some Novel 1,2,4-Triazole Derivatives Containing Pyridine Moiety

    PubMed Central

    Sun, Guo-Xiang; Yang, Ming-Yan; Shi, Yan-Xia; Sun, Zhao-Hui; Liu, Xing-Hai; Wu, Hong-Ke; Li, Bao-Ju; Zhang, Yong-Gang

    2014-01-01

    In order to investigate the biological activity of novel 1,2,4-triazole compounds, seventeen novel 1,2,4-triazole derivatives containing pyridine moiety were synthesized under microwave assistant condition by multi-step reactions. The structures were characterized by 1H NMR, MS and elemental analyses. The target compounds were evaluated for their fungicidal activities against Stemphylium lycopersici (Enjoji) Yamamoto, Fusarium oxysporum. sp. cucumebrium, and Botrytis cinerea in vivo, and the results indicated that some of the title compounds displayed excellent fungicidal activities. Theoretical calculation of the title compound was carried out with B3LYP/6-31G (d,p). The full geometry optimization was carried out using 6-31G (d,p) basis set, and the frontier orbital energy, atomic net charges were discussed, and the structure-activity relationship was also studied. PMID:24815069

  2. Use of cyclohexylisocyanide and methyl 2-isocyanoacetate as convertible isocyanides for microwave-assisted fluorous synthesis of 1,4-benzodiazepine-2,5-dione library.

    PubMed

    Zhou, Hongyu; Zhang, Wei; Yan, Bing

    2010-01-01

    A new protocol in which cyclohexylisocyanide and methyl 2-isocyanoacetate are used as convertible isocyanides for Ugi/de-Boc/cyclization/Suzuki synthesis of biaryl-substituted 1,4-benzodiazepine-2,5-diones has been developed. Ugi reactions of Boc-protected anthranilic acids, fluorous benzaldehydes, amines, and cyclohexylisocyanide or methyl 2-isocyanoacetate were carried out at room temperature. Microwave-promoted de-Boc/cyclization reactions afforded 1,4-benzodiazepine-2,5-diones (BZDs). Suzuki coupling reactions further derivatized the BZD ring by removing the fluorous tag and introducing the biaryl group. A thirty three-member biaryl-substituted BZD library containing four points of diversity was prepared by microwave-assisted solution-phase fluorous parallel synthesis. PMID:19947585

  3. Microwave assisted preparation of Eu[superscript 2+]-doped Åkermanite Ca[subscript 2]MgSi[subscript 2]O[subscript 7

    SciTech Connect

    Birkel, Alexander; Darago, Lucy E.; Morrison, Alasdair; Lory, Laurianne; George, Nathan C.; Mikhailovsky, Alexander A.; Birkel, Christina S.; Seshadri, Ram

    2012-12-10

    A rapid and energy efficient microwave assisted solid state preparative route for europium-doped Akermanite (Ca{sub 2}MgSi{sub 2}O{sub 7}) has been developed. This method reduces the reaction time and energy needed by more than 90%, compared to the preparation carried out in a conventional furnace. The obtained samples are phase pure as has been determined using synchrotron X-ray powder diffraction data and Rietveld analyses. Scanning electron microscopy was employed to investigate the morphology of the microwave prepared compounds whilst energy dispersive X-ray spectroscopy (EDX) was used to verify the elemental composition of the specimens. A systematic investigation of the influence of the utilized microwave setup is presented. Finally, the microwave prepared materials were subject to temperature dependent photoluminescence measurements in order to investigate the thermal quenching of the luminescence.

  4. An application of new microwave absorption tube in non-polar solvent microwave-assisted extraction of organophosphorus pesticides from fresh vegetable samples.

    PubMed

    Zhao, Xin; Xu, Xu; Su, Rui; Zhang, Hanqi; Wang, Ziming

    2012-03-16

    A new self-designed microwave absorption tube was used in microwave-assisted extraction of seven organophosphorus pesticides from four kinds of vegetable samples. The non-polar solvent was used as extraction solvent, and a new portable microwave extraction apparatus was used. By sealing graphite powder in glass tube, microwave absorption tube was made and used to heat samples directly. The extracts were directly analyzed by GC-MS without any clean-up process. The effects of some experimental parameters on extraction efficiency were investigated and optimized. 3.0 g of sample, 25 mL of hexane and three microwave absorption tubes were added in the microwave extraction vessel, the extraction was carried out under 425 W irradiation power at 70 °C for 8 min. The recoveries were in the range of 76.5-109.4% and the relative standard deviations were lower than 13.1%. PMID:22321952

  5. Microwave-assisted solvent extraction and gas chromatography ion trap mass spectrometry procedure for the determination of persistent organochlorine pesticides (POPs) in marine sediment.

    PubMed

    Carro, Nieves; García, Isabel; Ignacio, María; Mouteira, Ana

    2006-07-01

    Microwave-assisted solvent extraction of persistent organochlorine pesticides (POPs) in marine sediment was developed and optimized by means of two-level factorial designs. Six variables (microwave power, extraction time and temperature, amount of sample, solvent volume, and sample moisture) were considered as factors in the optimization process. The results show that the amount of sample to be extracted and solvent volume are statistically significant for the overall recovery of the studied pesticides, although compromise conditions have to be established with the object of avoiding overpressure in closed vessels. After extraction, a clean up step including the use of a silica cartridge was performed prior to chromatographic determination in order to remove interferences. The optimized procedure was compared to conventional Soxhlet extraction. The MS-MS ion preparation mode was applied to improve the sensitivity and selectivity of the chromatographic technique. PMID:16791571

  6. Microwave-Assisted Synthesis of Glutathione-Capped CdTe/CdSe Near-Infrared Quantum Dots for Cell Imaging

    PubMed Central

    Chen, Xiaogang; Li, Liang; Lai, Yongxian; Yan, Jianna; Tang, Yichen; Wang, Xiuli

    2015-01-01

    These glutathione (GSH)-conjugated CdTe/CdSe core/shell quantum dot (QD) nanoparticles in aqueous solution were synthesized using a microwave-assisted approach. The prepared type II core/shell QD nanoparticles were characterized by UV–Vis absorption, photoluminescence (PL) spectroscopy, X-ray powder diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM). Results revealed that the QD nanoparticles exhibited good dispersity, a uniform size distribution and tunable fluorescence emission in the near-infrared (NIR) region. In addition, these nanoparticles exhibited good biocompatibility and photoluminescence in cell imaging. In particular, this type of core/shell NIR QDs may have potential applications in molecular imaging. PMID:25997004

  7. One-pot microwave assisted approach for synthesis of CdSe/CdS core-shell quantum dots (QDs) and investigating optical properties

    NASA Astrophysics Data System (ADS)

    Molaei, M.; Bardsiri, F. Salari; Bahador, A. R.; Karimipour, M.

    2016-02-01

    In this work, CdSe QDs were synthesized using a microwave assisted method and chemical reaction between NaHSe, CdSO4 at the presence of TGA as capping molecule. Thereafter without CdSe extraction, CdS shell was grown subsequently around CdSe cores by a reaction based on the heat sensitivity of Na2S2O3 dissociation. Synthesized QDs were characterized by means of X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), UV-Vis and photoluminescence (PL) spectroscopy. All of these analyzes confirmed formation of CdSe QDs and successfully growth of CdS shell on surface of CdSe to forming CdSe/CdS core-shell structure.

  8. Synthesis of original spherical α-Ni(OH) 2 architectures by microwave-assisted hydrothermal method and their in situ thermal convention to NiO

    NASA Astrophysics Data System (ADS)

    Zhu, Zhenfeng; Zhang, Yanli; Liu, Hui; Wei, Na

    2012-02-01

    The original spherical α-Ni(OH) 2 architectures with many cubic particles growing from the surface were successfully synthesized by a microwave-assisted hydrothermal method using urea as hydrolysis-controlling agent and polyethylene glycol (PEG) as surfactant. The NiO architectures with similar morphology were obtained by simple thermal decomposition of the precursor α-Ni(OH) 2. The as-obtained products were well characterized by XRD, FTIR, TGA, SEM, TEM, UV-Vis and CVs. The experimental results showed that the diameter of spherical α-Ni(OH) 2 architectures was in the range of 2-4 μm. The side length of the cubic particles was uniform about 200 nm. The cyclic voltammetric results showed that the reversible behavior of NiO electrode change better with the increasing of the cycle index. The original NiO we have prepared are expected to have good electrochemical behavior.

  9. Direct Synthesis of Fe-Pt Nanoparticles in Ordered Face Centered (fct)LI{sub o} Phase by Microwave Assisted Route

    SciTech Connect

    Acharya, S. A.; Bhoga, S. S.; Khule, S. M.; Singh, K.

    2011-07-15

    In the present work, microwave-assisted chemical reduction route has been explored for the direct synthesis of fct LIo-phase of Fe-Pt nanoparticles. Effects of microwave power and irradiation time on the growth process were investigated. Using this facile and high yield technique we could tune particle size from 7 to 17 nm. The as-prepared FePt were found to be sensitive to the microwave irradiation power, while influence of exposure time was insignificant. The hysteresis measurements were performed at room temperature (300 K) to study magnetic properties of as-synthesized Fe-Pt as a function of crystallize size. The coercivity and saturation magnetization was observed to be decrease with diminishing for direct synthesis of metal alloys.

  10. Development of microwave assisted extraction for the simultaneous determination of isoflavonoids and saponins in radix astragali by high performance liquid chromatography.

    PubMed

    Song, Jing-Zheng; Mo, Shi-Fu; Yip, Yue-Keung; Qiao, Chun-Feng; Han, Quan-Bin; Xu, Hong-Xi

    2007-04-01

    A microwave assisted extraction (MAE) procedure was first developed for the simultaneous determination of isoflavonoids and astragalosides in Radix Astragali (RA). MAE showed the highest extraction efficiency when compared to Soxhlet, reflux, and ultrasonic extraction. It was found that flavonoid glycoside malonates were converted into their related glycosides during the prolonged conventional extraction, thus affecting the reproducibility. However, the conversion was inhibited when using MAE. After being optimized in terms of solvents, microwave power, and irradiation time, MAE was used for the simultaneous determination of isoflavonoids and astragalosides in RA with HPLC-UV-evaporative light scattering detection (ELSD). Our results indicated that extraction by MAE was more effective than by other conventional techniques. Moreover, the MAE method followed by HPLC-UV-ELSD determination was a simple, rapid, and reliable method for the quality assessment of RA. PMID:17536726

  11. Applicability of microwave-assisted extraction combined with LC-MS/MS in the evaluation of booster biocide levels in harbour sediments.

    PubMed

    Sánchez-Rodríguez, Alvaro; Sosa-Ferrera, Zoraida; Santana-Rodríguez, José Juan

    2011-01-01

    A new sample treatment method for the determination of four common booster biocides (Diuron, TCMTB, Irgarol 1051 and Dichlofluanid) in harbour sediment samples has been developed that uses liquid chromatography-tandem mass spectrometry (LC-MS/MS) after microwave-assisted extraction, followed by clean-up and a solid phase extraction preconcentration step (MAE-SPE). The effects of different variables on MAE-SPE were studied. The recoveries obtained were greater than 75%, and the relative standard deviation was less than 7%. The detection limits ranged between 0.1 and 0.3 ng g⁻¹. The developed methodology was successfully applied to the evaluation of the presence of booster biocides in sediment samples from different harbours and marinas of Gran Canaria Island (Canary Islands, Spain). PMID:20947123

  12. Synthesis of CdS/CdSe core/shell ultra small nanostructures using new microwave assisted ultrasonic sol gel route

    SciTech Connect

    Goswami, Y. C. Kumar, Vijay; Sharma, Ranjana; Singh, Rajeev

    2014-04-24

    Core-shell CdS/CdSe nanostructures have been synthesized by new microwave assisted ultrasonic sol gel route. The solution was obtained by dissolving cadmium acetate and Thiourea in the molar ratio 1:1 in Triethlioamine. The solution was Ultrasonically irradiated by Ultrasonic crystal at 40 Hz for 3 hours at 70°C. The sol was kept for another 24 hours for gel formation. Selenium dioxide was used as a selenium source and added separately. The gel was spin coated on Quartz and Glass slides followed by microwave heat treatment. The samples were characterized by structural morphological and optical characterization. XRD studies confirm the zinc blende phase of the CdS nanoparticles. The mean nanocrystal sizes calculated using Scherrer equation is ∼1.2nm. Optical studies show the strong blue shift in the spectra due to very small size of the nanocrystals. TEM and HRTEM confirm the formation of core shell structures.

  13. A rapid microwave-assisted synthesis of a sodium-cadmium metal-organic framework having improved performance as a CO2 adsorbent for CCS.

    PubMed

    Palomino Cabello, Carlos; Arean, Carlos Otero; Parra, José B; Ania, Conchi O; Rumori, P; Turnes Palomino, G

    2015-06-01

    We report on a facile and rapid microwave-assisted method for preparing a sodium-cadmium metal-organic framework (having coordinatively unsaturated sodium ions) that considerably shortens the conventional synthesis time from 5 days to 1 hour. The obtained (Na,Cd)-MOF showed an excellent volumetric CO2 adsorption capacity (5.2 mmol cm(-3) at 298 K and 1 bar) and better CO2 adsorption properties than those shown by the same metal-organic framework when synthesized following a more conventional procedure. Moreover, the newly prepared material was found to display high selectivity for adsorption of carbon dioxide over nitrogen, and good regenerability and stability during repeated CO2 adsorption-desorption cycles, which are the required properties for any adsorbent intended for carbon dioxide capture and sequestration (CSS) from the post-combustion flue gas of fossil fuelled power stations. PMID:25939594

  14. The Use of Microwave-Assisted Solid-Phase Peptide Synthesis and Click Chemistry for the Synthesis of Vaccine Candidates Against Hookworm Infection.

    PubMed

    Fuaad, Abdullah A H Ahmad; Skwarczynski, Mariusz; Toth, Istvan

    2016-01-01

    A protein-based vaccine approach against hookworm infection has failed to deliver the expected outcome, due to a problem with an allergic response in the patient or difficulties in the proteins' production. This implication could be overcome by using a chemically synthesized peptide-based vaccine approach. This approach utilizes minimal pathogenic components that are necessary for the stimulation of the immune response without triggering adverse side effects. To boost the peptide's immunogenicity, a lipid core peptide (LCP) system can be utilized as a carrier molecule/immunostimulant. This chapter describes in detail the synthesizing of protected lipoamino acid, the self-adjuvanting moiety (LCP core), the peptide epitope, and the final vaccine candidate. The subunit peptide and the LCP core were synthesized using microwave-assisted solid-phase peptide synthesis (SPPS). Then the final hookworm vaccine construct was assembled using the copper-catalyzed azide-alkyne cycloaddition, or "click," reaction. PMID:27076158

  15. Complexation-flocculation combined with microwave-assisted headspace solid-phase microextraction in determining the binding constants of hydrophobic organic pollutants to dissolved humic substances.

    PubMed

    Hsieh, Ping-Chieh; Lee, Chon-Lin; Jen, Jen-Fon; Chang, Kuei-Chen

    2015-02-21

    The binding constants, KDOC, of selected polycyclic aromatic hydrocarbons (PAHs)-phenanthrene, anthracene, fluoranthene, and pyrene-to dissolved humic substances (DHS) were determined by complexation-flocculation combined with microwave-assisted headspace solid-phase microextraction (CF-MA-HS-SPME). The results obtained are comparable with KDOC data reported in the literature. No disruption of the PAH to DHS binding equilibrium was observed during the complexation-flocculation process. The present study, which is the first to determine KDOC by CF-MA-HS-SPME, provides an alternative approach to determine the KDOC of PAHs. CF-MA-HS-SPME provides some advantages over other methods, such as no limitation of fluorescent compounds, greater determination speed, and the capability of measuring various compounds simultaneously. PMID:25568896

  16. Use of zirconium oxychloride to neutralize HF in the microwave-assisted acid dissolution of ceramic glazes for their chemical analysis by ICP-OES.

    PubMed

    Dondi, M; Fabbri, B; Mingazzini, C

    1998-04-01

    The use of a zirconium compound (ZrOCl(2)) to neutralize HF in the microwave-assisted acid dissolution of ceramic glazes for their chemical analysis was tested. Zr is a strong complexing agent for the fluorine ion and permits the determination of those elements which would form insoluble fluorides. The use of Zr implies strong spectral interferences and a high salt content; however, we found that at least 27 elements can be measured with low detection limits, and satisfactory precision and accuracy. In addition, the use of ZrOCl(2) would permit the complete analysis of a ceramic glaze with a single attack when acid-resistant mineral phases are not present. For potassium determinations in acid matrix, the addition of an ionization buffer was studied in order to increase sensitivity, avoiding ionization interferences and non-linear calibration curves. PMID:18967112

  17. Microwave-Assisted Synthesis of Glutathione-Capped CdTe/CdSe Near-Infrared Quantum Dots for Cell Imaging.

    PubMed

    Chen, Xiaogang; Li, Liang; Lai, Yongxian; Yan, Jianna; Tang, Yichen; Wang, Xiuli

    2015-01-01

    These glutathione (GSH)-conjugated CdTe/CdSe core/shell quantum dot (QD) nanoparticles in aqueous solution were synthesized using a microwave-assisted approach. The prepared type II core/shell QD nanoparticles were characterized by UV-Vis absorption, photoluminescence (PL) spectroscopy, X-ray powder diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM). Results revealed that the QD nanoparticles exhibited good dispersity, a uniform size distribution and tunable fluorescence emission in the near-infrared (NIR) region. In addition, these nanoparticles exhibited good biocompatibility and photoluminescence in cell imaging. In particular, this type of core/shell NIR QDs may have potential applications in molecular imaging. PMID:25997004

  18. Comparison of heat and mass transfer of different microwave-assisted extraction methods of essential oil from Citrus limon (Lisbon variety) peel.

    PubMed

    Golmakani, Mohammad-Taghi; Moayyedi, Mahsa

    2015-11-01

    Dried and fresh peels of Citrus limon were subjected to microwave-assisted hydrodistillation (MAHD) and solvent-free microwave extraction (SFME), respectively. A comparison was made between MAHD and SFME with the conventional hydrodistillation (HD) method in terms of extraction kinetic, chemical composition, and antioxidant activity. Higher yield results from higher extraction rates by microwaves and could be due to a synergy of two transfer phenomena: mass and heat acting in the same way. Gas chromatography/mass spectrometry (GC/MS) analysis did not indicate any noticeable differences between the constituents of essential oils obtained by MAHD and SFME, in comparison with HD. Antioxidant analysis of the extracted essential oils indicated that microwave irradiation did not have adverse effects on the radical scavenging activity of the extracted essential oils. The results of this study suggest that MAHD and SFME can be termed as green technologies because of their less energy requirements per ml of essential oil extraction. PMID:26788292

  19. Synthesis and characterization of MnWO4 nanoparticles encapsulated in mesoporous silica SBA-15 by fast microwave-assisted method

    NASA Astrophysics Data System (ADS)

    Hoang, Luc Huy; Hanh, Pham Van; Phu, Nguyen Dang; Chen, Xiang-Bai; Chou, Wu Ching

    2015-02-01

    The MnWO4 nanoparticles encapsulated in mesoporous silica (MnWO4/SBA-15) was successfully synthesized by a fast microwave-assisted method. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen absorption-desorption isotherm, and Fourier transform infrared spectroscopy (FTIR). Our results showed that the MnWO4/SBA-15 nanocomposites have the ordered hexagonal meso-structure of SBA-15, indicating MnWO4 nanoparticles were successfully distributed into the channels of SBA-15. The size of MnWO4 nanoparticles in SBA-15 is significantly smaller than the size of MnWO4 nanoparticles prepared without SBA-15, indicating that the MnWO4/SBA15 nanocomposites would be very promising for improving photocatalytic activity of MnWO4 nanoparticles.

  20. Silicon oxide-on-graphite planar composite synthesized using a microwave-assisted coating method for use as a fast-charging lithium-ion battery anode

    NASA Astrophysics Data System (ADS)

    Yang, Nai-Hsuan; Wu, Yu-Shiang; Chou, Jackey; Wu, Hung-Chun; Wu, Nae-Lih

    2015-11-01

    A high-performance Si oxide-coated graphite flake (SGF) composite anode for Li-ion batteries (LIBs) is synthesized using a microwave-assisted coating method. In this synthesis, a solution comprising liquid polysiloxanes is used as the Si-containing precursor. Heating the graphite flakes (GFs) with microwave induces the deposition of a Si-containing conformal layer on the GF surfaces, which is subsequently calcined to produce SGFs. When tested as a LIB anode, the resulting SGF exhibits a reversible specific capacity of nearly 480 mAh g-1, 97% capacity retention at a current density of 2.5 A g-1 (approximately 5 C-rate), and 94% capacity retention after 500 cycles with an average Coulombic efficiency > 99.9%. The results suggest new strategies for both designing and synthesizing high-performance anode materials for LIB applications.

  1. Layered nickel sulfide-reduced graphene oxide composites synthesized via microwave-assisted method as high performance anode materials of sodium-ion batteries

    NASA Astrophysics Data System (ADS)

    Qin, Wei; Chen, Taiqiang; Lu, Ting; Chua, Daniel H. C.; Pan, Likun

    2016-01-01

    Layered nickel sulfide (NS)-reduced graphene oxide (RGO) composites are prepared via a simple microwave-assisted method and subsequent annealing in N2/H2 atmosphere. A detailed array of characterization tools are used to study their morphology, structure and electrochemical performance. It was found that these composites exhibit significantly improved sodium-ion storage ability as compared with pure NS under galvanostatic cycling at a specific current of 100 mA g-1 in a potential limitation of 0.005-3.0 V. Furthermore, the composite with the RGO content of 35 wt.% achieves a high maximum reversible specific capacity of about 391.6 mAh g-1 at a specific current of 100 mA g-1 after 50 cycles. These results prove that NS-RGO composites are highly promising when applied directly as anode materials in sodium-ion batteries.

  2. Evaluation of microwave-assisted enzymatic digestion and tandem mass spectrometry for the identification of protein residues from an inorganic solid matrix: implications in archaeological research.

    PubMed

    Stevens, Stanley M; Wolverton, Steve; Venables, Barney; Barker, Andrew; Seeley, Kent W; Adhikari, Prem

    2010-02-01

    A method based on microwave-assisted enzymatic digestion and liquid chromatography-tandem mass spectrometry analysis is presented for the identification of proteins incorporated within solid matrices using protein standards bound to experimental cooking pottery as a validation model. The implementation of microwave irradiation allowed for a significant decrease in overall analysis time in addition to select enhancement of peptide recovery as determined by label-free relative quantitation. We envision that the reported methodology will provide new avenues for scientific discovery in areas such as archaeology and forensics. Results of this series of experiments are part of an ongoing project directed at developing a comprehensive methodology for extracting proteinaceous residues from archaeological pottery. PMID:20052580

  3. Structural and magnetic studies of tin doped α-Fe2O3 (α-SnxFe2-xO3) nanoparticles prepared by microwave assisted synthesis

    NASA Astrophysics Data System (ADS)

    K., Bindu; Chowdhury, P.; Ajith K., M.; Nagaraja, H. S.

    2016-05-01

    Hematite (α-Fe2O3) doped with tetravalent ions have potential applications in various fields such as gas sensors, memories, energy storage devices because of their electrical and magnetic properties. Microwave assisted synthesis was used to prepare Tin doped α-Fe2O3 [α-SnxFe2-xO3]. The structural and morphological studies were investigated using X-ray diffraction (XRD) and Scanning electron microscopy (SEM). XRD patterns revealed that α-Fe2O3 and α-SnxFe2-xO3 were having rhombohedral structure. The compositional study was done by Energy dispersive X-ray Spectroscopy (EDS). The magnetic properties were studied by Vibrating Sample Magnetometry (VSM). Results shows that the prepared samples were found to be antiferromagnetic in nature and the results are discussed in detail.

  4. Microwave assisted facile hydrothermal synthesis and characterization of zinc oxide flower grown on graphene oxide sheets for enhanced photodegradation of dyes

    NASA Astrophysics Data System (ADS)

    Kashinath, L.; Namratha, K.; Byrappa, K.

    2015-12-01

    Microwave assisted hydrothermal process of synthesis of ZnO-GO nanocomposite by using ZnCl2 and NaOH as precursors is being reported first time. In this investigation, a novel route to study on synthesis, interaction, kinetics and mechanism of hybrid zinc oxide-graphene oxide (ZnO-GO) nanocomposite using microwave assisted facile hydrothermal method has been reported. The results shows that the ZnO-GO nanocomposite exhibits an enhancement and acts as stable photo-response degradation performance of Brilliant Yellow under the UV light radiation better than pure GO and ZnO nanoparticles. The microwave exposure played a vital role in the synthesis process, it facilitates with well define crystalline structure, porosity and fine morphology of ZnO/GO nanocomposite. Different molar concentrations of ZnO precursors doped to GO sheets were been synthesized, characterized and their photodegradation performances were investigated. The optical studies by UV-vis and Photo Luminescence shows an increase in band gap of nanocomposite, which added an advantage in photodegradation performance. The in situ flower like ZnO nano particles are were densely decorated and anchored on the surfaces of graphene oxide sheets which aids in the enhancement of the surface area, adsorption, mass transfer of dyes and evolution of oxygen species. The nanocomposite having high surface area and micro/mesoporous in nature. This structure and morphology supports significantly in increasing photo catalytic performance legitimate to the efficient photosensitized electron injection and repressed electron recombination due to electron transfer process with GO as electron collector and transporter dependent on the proportion of GO in ZnO/GO composite.

  5. 1,2,3-Triazole-Functionalized Polysulfone Synthesis through Microwave-Assisted Copper-Catalyzed Click Chemistry: A Highly Proton Conducting High Temperature Membrane.

    PubMed

    Sood, Rakhi; Donnadio, Anna; Giancola, Stefano; Kreisz, Aurélien; Jones, Deborah J; Cavaliere, Sara

    2016-07-01

    Microwave heating holds all the aces regarding development of effective and environmentally friendly methods to perform chemical transformations. Coupling the benefits of microwave-enhanced chemistry with highly reliable copper-catalyzed azide-alkyne cycloaddition (CuAAC) click chemistry paves the way for a rapid and efficient synthesis procedure to afford high performance thermoplastic materials. We describe herein fast and high yielding synthesis of 1,2,3-triazole-functionalized polysulfone through microwave-assisted CuAAC as well as explore their potential as phosphoric acid doped polymer electrolyte membranes (PEM) for high temperature PEM fuel cells. Polymers with various degrees of substitution of the side-chain functionality of 1,4-substituted 1,2,3-triazole with alkyl and aryl pendant structures are prepared by sequential chloromethylation, azidation, and microwave-assisted CuAAC using a range of alkynes (1-pentyne, 1-nonyne, and phenylacetylene). The completeness of reaction at each step and the purity of the clicked polymers were confirmed by (1)H-(13)C NMR, DOSY-NMR and FTIR-ATR spectroscopies. The thermal and thermochemical properties of the modified polymers were characterized by differential scanning calorimetry and thermogravimetric analysis coupled with mass spectroscopy (TG-MS), respectively. TG-MS analysis demonstrated that the commencement of the thermal degradation takes place with the decomposition of the triazole ring while its substituents have critical influence on the initiation temperature. Polysulfone functionalized with 4-phenyl-1,2,3-triazole demonstrates significantly higher Tg, Td, and elastic modulus than the ones bearing 4-propyl-1,2,3-triazole and 4-heptyl-1,2,3-triazole groups. After doping with phosphoric acid, the functionalized polymers with acid doping level of 5 show promising performance with high proton conductivity in anhydrous conditions (in the range of 27-35 mS/cm) and satisfactorily high elastic modulus (in the range

  6. Engineered biochar from microwave-assisted catalytic pyrolysis of switchgrass for increasing water-holding capacity and fertility of sandy soil.

    PubMed

    Mohamed, Badr A; Ellis, Naoko; Kim, Chang Soo; Bi, Xiaotao; Emam, Ahmed El-Raie

    2016-10-01

    Engineered biochars produced from microwave-assisted catalytic pyrolysis of switchgrass have been evaluated in terms of their ability on improving water holding capacity (WHC), cation exchange capacity (CEC) and fertility of loamy sand soil. The addition of K3PO4, clinoptilolite and/or bentonite as catalysts during the pyrolysis process increased biochar surface area and plant nutrient contents. Adding biochar produced with 10wt.% K3PO4+10 wt.% clinoptilolite as catalysts to the soil at 2wt% load increased soil WHC by 98% and 57% compared to the treatments without biochar (control) and with 10wt.% clinoptilolite, respectively. Synergistic effects on increased soil WHC were manifested for biochars produced from combinations of two additives compared to single additive, which may be the result of increased biochar microporosity due to increased microwave heating rate. Biochar produced from microwave catalytic pyrolysis was more efficient in increasing the soil WHC due to its high porosity in comparison with the biochar produced from conventional pyrolysis at the same conditions. The increases in soil CEC varied widely compared to the control soil, ranging from 17 to 220% for the treatments with biochars produced with 10wt% clinoptilolite at 400°C, and 30wt% K3PO4 at 300°C, respectively. Strong positive correlations also exist among soil WHC with CEC and biochar micropore area. Biochar from microwave-assisted catalytic pyrolysis appears to be a novel approach for producing biochar with high sorption affinity and high CEC. These catalysts remaining in the biochar product would provide essential nutrients for the growth of bioenergy and food crops. PMID:27232966

  7. Microwave-assisted enzymatic hydrolysis followed by extraction with restricted access nanocomposites for rapid analysis of glucocorticoids residues in liver tissue.

    PubMed

    Feng, Jianan; Liu, Xiaodan; Li, Yan; Duan, Gengli

    2016-10-01

    We developed a novel, simple and fast method for the determination of glucocorticoids residues in liver tissue by combining microwave-assisted enzymatic hydrolysis and restricted access matrix dispersive solid phase extraction (RAM-dSPE) followed with liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Firstly, microwave-assisted enzymatic hydrolysis was introduced in order to obtain a maximum amount of unconjugated parent drug in a short time (8s), while the traditional method commonly needs 4-12h. Secondly, further cleanup was carried out by RAM-dSPE based on the graphene@mSiO2-C8 nanomaterials which were synthesized by coating mesoporous silica onto hydrophilic graphene nano-sheets through a surfactant-mediated co-condensation sol-gel process. The enzymatic hydrolysis influencing factors (pH of the buffer, microwave radiation power, incubation time) and the experimental conditions of RAM-dSPE (sorbents amount, type and volume of the elution solvent, adsorption and desorption time) were optimized. Three glucocorticoids (prednisolone (PREL), betamethasone (BE) and dexamethasone (DE)) were selected as models to evaluate the feasibility of the method. According to the results, the developed method provided low detection limit (S/N=3) of 0.01-0.05μgkg(-1) and good linearity range of 0.25-800μgkg(-1) (R(2)>0.996) for glucocorticoids. The limit of quantification (S/N=10) range from 0.03 to 0.19μgkg(-1). Compared with other traditional methods, the developed method could provide similar or even better results in a greatly reduced analysis time. PMID:27474293

  8. Polymerization catalyst

    SciTech Connect

    Graves, V.

    1987-05-12

    A process is described for polymerizing at least one alpha olefin under conditions characteristic of Ziegler polymerization wherein the polymerization is conducted in the presence of a catalyst system which comprises: a supported catalyst prepared under anhydrous conditions by the sequential steps of: preparing a slurry of inert particulate support material; adding to the slurry a solution of an organomagnesium compound; adding to the slurry and reacting a solution of a zirconium halide compound, hafnium compound or mixtures thereof; adding to the slurry and reacting a halogenator; adding to the slurry and reacting a tetravalent titanium halide compound; and recovering solid catalyst.

  9. Polymerization catalyst

    SciTech Connect

    Graves, V.

    1986-10-21

    A process is described for polymerizing at least one alpha-olefin under conditions characteristic of Ziegler polymerization wherein the polymerization is conducted in the presence of a catalyst comprising: a supported catalyst prepared under anhydrous conditions by the steps of: (1) sequentially; (a) preparing a slurry of inert particulate support material; (b) adding to the slurry a solution of an organomagnesium compound; (c) adding to the slurry and reacting a solution of zirconium compound; and (2) thereafter; (d) adding to the slurry and reacting a halogenator; (e) adding to the slurry and reacting a tetravalent titanium compound; (f) recovering solid catalyst; and an organoaluminum compound.

  10. Preparation of highly photocatalytic active CdS/TiO{sub 2} nanocomposites by combining chemical bath deposition and microwave-assisted hydrothermal synthesis

    SciTech Connect

    Li, Li; Wang, Lili; Hu, Tianyu; Zhang, Wenzhi; Zhang, Xiuli; Chen, Xi

    2014-10-15

    CdS/TiO{sub 2} nanocomposites were prepared from Cd and Ti (1:1 M ratio) using cetyltrimethylammonium bromide by a two-step chemical bath deposition (CBD) and microwave-assisted hydrothermal synthesis (MAHS) method. A series of nanocomposites with different morphologies and activities were prepared by varying the reaction time in the MAHS (2, 4, and 6 h). The crystal structure, morphology, and surface physicochemical properties of the nanocomposites were characterized by X-ray diffraction, UV–visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and N{sub 2} adsorption–desorption measurements. The results show that the CdS/TiO{sub 2} nanocomposites were composed of anatase TiO{sub 2} and hexagonal CdS phases with strong absorption in the visible region. The surface morphologies changed slightly with increasing microwave irradiation time, while the Brunauer–Emmett–Teller surface area increased remarkably. The photocatalytic degradation of methyl orange (MO) was investigated under UV light and simulated sunlight irradiation. The photocatalytic activity of the CdS/TiO{sub 2} (6 h) composites prepared by the MAHS method was higher than those of CdS, P25, and other CdS/TiO{sub 2} nanocomposites. The CdS/TiO{sub 2} (6 h) nanocomposites significantly affected the UV and microwave-assisted photocatalytic degradation of different dyes. To elucidate the photocatalytic reaction mechanism for the CdS/TiO{sub 2} nanocomposites, controlled experiments were performed by adding different radical scavengers. - Graphical abstract: CdS/TiO{sub 2} nanocomposites were prepared using CTAB by CBD combined with MAHS method. In addition, with increasing microwave irradiation time, the morphology of CdS/TiO{sub 2} changed from popcorn-like to wedge-like structure. - Highlights: • The CdS/TiO{sub 2} was prepared by CBD combined with MAHS two-step method under CTAB. • The morphologies of as-samples were different with the time of

  11. Rapid microwave-assisted sol-gel preparation of Pd-substituted LnFeO3 (Ln = Y, La): phase formation and catalytic activity

    SciTech Connect

    Misch, Lauren M.; Birkel, Alexander; Figg, C. Adrian; Fors, Brett P.; Hawker, Craig J.; Stucky, Galen D.; Seshadri, Ram

    2014-02-13

    We present a rapid microwave-assisted sol–gel approach to Pd-substituted LnFeO3 (Ln = Y, La) for applications in C–C coupling reactions. These materials could be prepared in household microwave ovens in less than 15 minutes of reaction time with the final materials displaying well-defined structure and morphology. Phase evolution was studied using time-dependent microwave heatings and then compared with the results obtained from thermogravimetric analyses. Materials were confirmed to be phase pure by laboratory and synchrotron X-ray diffraction. Substituted Pd is ionic as shown by the binding energy shift from X-ray photoelectron spectroscopy. The short heating periods required for phase purity allow these materials less time for sintering as compared to conventional solid state preparation methods, making relatively high surface areas achievable. These materials have been successfully used as catalyst precursor materials for C–C coupling reactions in which the active species is Pd0. Pd-substituted LnFeO3 (Ln = Y, La) provides Pd0 in solution which can be complexed by the ligand SPhos, allowing for aryl chloride coupling.

  12. Downscaling Effect on the Superconductivity of Pd3Bi2X2 (X = S or Se) Nanoparticles Prepared by Microwave-Assisted Polyol Synthesis.

    PubMed

    Roslova, Maria; Opherden, Lars; Veremchuk, Igor; Spillecke, Lena; Kirmse, Holm; Herrmannsdörfer, Thomas; Wosnitza, Joachim; Doert, Thomas; Ruck, Michael

    2016-09-01

    Pd3Bi2S2 and Pd3Bi2Se2 have been successfully prepared in the form of nanoparticles with diameters of ∼50 nm by microwave-assisted modified polyol synthesis at low temperatures. The composition and morphology of the samples have been studied by means of powder X-ray diffraction as well as electron microscopy methods, including X-ray intensity mapping on the nanoscale. Superconducting properties of the as-prepared samples have been characterized by electrical resistivity measurements down to low temperatures (∼0.2 K). Deviations from the bulk metallic behavior originating from the submicrometer nature of the samples were registered for both phases. A significant critical-field enhancement up to 1.4 T, i.e., 4 times higher than the value of the bulk material, has been revealed for Pd3Bi2Se2. At the same time, the critical temperature is suppressed to 0.7 K from the bulk value of ∼1 K. A superconducting transition at 0.4 K has been observed in nanocrystalline Pd3Bi2S2. Here, a zero-temperature upper critical field of ∼0.5 T has been estimated. Further, spark plasma-sintered Pd3Bi2S2 and Pd3Bi2Se2 samples have been investigated. Their superconducting properties are found to lie between those of the bulk and nanosized samples. PMID:27518909

  13. Development of a microwave-assisted-extraction-based method for the determination of aflatoxins B1, G1, B2, and G2 in grains and grain products.

    PubMed

    Chen, Si; Zhang, Hong

    2013-02-01

    This article describes the use of microwave-assisted extraction (MAE) as a pretreatment technique for the determination of aflatoxins B(1), G(1), B(2), and G(2) in grains and grain products. The optimal operation parameters, including extraction solvent, temperature, and time, were identified to be acetonitrile as the extraction solvent at 80 °C with 15 min of MAE. The extracts were cleaned up using solid-phase extraction followed by derivatization with trifluoroacetic acid and were determined by liquid chromatography-fluorescence detection. A Sep-Pak cartridge was chosen over Oasis HLB and Bond Elut cartridges. By the use of aflatoxin M(1) as an internal standard, relative recoveries of the aflatoxins ranged from 90.7 to 105.7 % for corn and from 88.1 to 103.4 % for wheat, with relative standard deviations between 2.5 and 8.7 %. A total of 36 samples from local markets were analyzed, and aflatoxin B(1) was found to be the predominant toxin, with concentrations ranging from 0.42 to 3.41 μg/kg. PMID:23314480

  14. Microwave-assisted synthesis of nanosphere-like NiCo2O4 consisting of porous nanosheets and its application in electro-catalytic oxidation of methanol

    NASA Astrophysics Data System (ADS)

    Gu, Li; Qian, Lei; Lei, Ying; Wang, Yanyan; Li, Jing; Yuan, Hongyan; Xiao, Dan

    2014-09-01

    A fast microwave-assisted synthesis method followed by a post-calcining process is used to prepare three-dimensional (3D) nanosphere-like NiCo2O4 nanostructure. The 3D NiCo2O4 nanospheres are constructed by intertwined two-dimensional (2D) ultrathin mesoporous nanosheets. The nanosphere-like NiCo2O4 has a large specific surface area (SSA, 146.5 m2 g-1) and is successfully applied to electro-catalytic oxidation of methanol. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and chronoamperometry (CA) measurements are used to investigate electro-catalytic performance of the as-prepared NiCo2O4. The current density of NiCo2O4/Ni foam (NiCo2O4/NF) electrode in 1 M KOH with 0.5 M methanol is up to 40.9 A g-1. And the current density can be returned to 97% of the original value by replacing new 1 M KOH electrolyte with 0.5 M methanol after a long-term CV cycle (500 cycles). These results show that our prepared NiCo2O4 possesses high electro-catalytic activity and good long-term stability for methanol oxidation. This may be benefit from the unique porous nanosphere-like structure and large SSA.

  15. Determination of volatile nitrosamines in meat products by microwave-assisted extraction and dispersive liquid-liquid microextraction coupled to gas chromatography-mass spectrometry.

    PubMed

    Campillo, Natalia; Viñas, Pilar; Martínez-Castillo, Nelson; Hernández-Córdoba, Manuel

    2011-04-01

    Microwave-assisted extraction (MAE) and dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry (GC-MS) were evaluated for use in the extraction and preconcentration of volatile nitrosamines in meat products. Parameters affecting MAE, such as the extraction solvent used, and DLLME, including the nature and volume of the extracting and disperser solvents, extraction time, salt addition and centrifugation time, were optimized. In the MAE method, 0.25g of sample mass was extracted in 10mL NaOH (0.05M) in a closed-vessel system. For DLLME, 1.5mL of methanol (disperser solvent) containing 20μL of carbon tetrachloride (extraction solvent) was rapidly injected by syringe into 5mL of the sample extract solution (previously adjusted to pH 6), thereby forming a cloudy solution. Phase separation was performed by centrifugation, and a volume of 3μL of the sedimented phase was analyzed by GC-MS. The enrichment factors provided by DLLME varied from 220 to 342 for N-nitrosodiethylamine and N-nitrosopiperidine, respectively. The matrix effect was evaluated for different samples, and it was concluded that sample quantification can be carried out by aqueous calibration. Under the optimized conditions, detection limits ranged from 0.003 to 0.014ngmL(-1) for NPIP and NMEA, respectively (0.12-0.56ngg(-1) in the meat products). PMID:21376329

  16. Analysis of dextromethorphan and dextrorphan in decomposed skeletal tissues by microwave assisted extraction, microplate solid-phase extraction and gas chromatography- mass spectrometry (MAE-MPSPE-GCMS).

    PubMed

    Fraser, Candice D; Cornthwaite, Heather M; Watterson, James H

    2015-08-01

    Analysis of decomposed skeletal tissues for dextromethorphan (DXM) and dextrorphan (DXT) using microwave assisted extraction (MAE), microplate solid-phase extraction (MPSPE) and gas chromatography-mass spectrometry (GC-MS) is described. Rats (n = 3) received 100 mg/kg DXM (i.p.) and were euthanized by CO2 asphyxiation roughly 20 min post-dose. Remains decomposed to skeleton outdoors and vertebral bones were recovered, cleaned, and pulverized. Pulverized bone underwent MAE using methanol as an extraction solvent in a closed microwave system, followed by MPSPE and GC-MS. Analyte stability under MAE conditions was assessed and found to be stable for at least 60 min irradiation time. The majority (>90%) of each analyte was recovered after 15 min. The MPSPE-GCMS method was fit to a quadratic response (R(2)  > 0.99), over the concentration range 10-10 000 ng⋅mL(-1) , with coefficients of variation <20% in triplicate analysis. The MPSPE-GCMS method displayed a limit of detection of 10 ng⋅mL(-1) for both analytes. Following MAE for 60 min (80 °C, 1200 W), MPSPE-GCMS analysis of vertebral bone of DXM-exposed rats detected both analytes in all samples (DXM: 0.9-1.5 µg⋅g(-1) ; DXT: 0.5-1.8 µg⋅g(-1) ). PMID:25487525

  17. Microwave assisted hydrothermal synthesis of Ag/AgCl/WO{sub 3} photocatalyst and its photocatalytic activity under simulated solar light

    SciTech Connect

    Adhikari, Rajesh; Gyawali, Gobinda; Sekino, Tohru; Wohn Lee, Soo

    2013-01-15

    Simulated solar light responsive Ag/AgCl/WO{sub 3} composite photocatalyst was synthesized by microwave assisted hydrothermal process. The synthesized powders were characterized by X-Ray Diffraction (XRD) spectroscopy, X-Ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy (TEM), Diffuse Reflectance Spectroscopy (UV-Vis DRS), and BET surface area analyzer to investigate the crystal structure, morphology, chemical composition, optical properties and surface area of the composite photocatalyst. This photocatalyst exhibited higher photocatalytic activity for the degradation of rhodamine B under simulated solar light irradiation. Dye degradation efficiency of composite photocatalyst was found to be increased significantly as compared to that of the commercial WO{sub 3} nanopowder. Increase in photocatalytic activity of the photocatalyst was explained on the basis of surface plasmon resonance (SPR) effect caused by the silver nanoparticles present in the composite photocatalyst. Highlights: Black-Right-Pointing-Pointer Successful synthesis of Ag/AgCl/WO{sub 3} nanocomposite. Black-Right-Pointing-Pointer Photocatalytic experiment was performed under simulated solar light. Black-Right-Pointing-Pointer Nanocomposite photocatalyst was very active as compared to WO{sub 3} commercial powder. Black-Right-Pointing-Pointer SPR effect due to Ag nanoparticles enhanced the photocatalytic activity.

  18. Microwave-assisted hydrothermal synthesis of Ag2(W1 -xMox)O4 heterostructures: Nucleation of Ag, morphology, and photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Silva, M. D. P.; Gonçalves, R. F.; Nogueira, I. C.; Longo, V. M.; Mondoni, L.; Moron, M. G.; Santana, Y. V.; Longo, E.

    2016-01-01

    Ag2W1 -xMoxO4 (x = 0.0 and 0.50) powders were synthesized by the co-precipitation (drop-by-drop) method and processed using a microwave-assisted hydrothermal method. We report the real-time in situ formation and growth of Ag filaments on the Ag2W1 -xMoxO4 crystals using an accelerated electron beam under high vacuum. Various techniques were used to evaluate the influence of the network-former substitution on the structural and optical properties, including photoluminescence (PL) emission, of these materials. X-ray diffraction results confirmed the phases obtained by the synthesis methods. Raman spectroscopy revealed significant changes in local order-disorder as a function of the network-former substitution. Field-emission scanning electron microscopy was used to determine the shape as well as dimensions of the Ag2W1 -xMoxO4 heterostructures. The PL spectra showed that the PL-emission intensities of Ag2W1 -xMoxO4 were greater than those of pure Ag2WO4, probably because of the increase of intermediary energy levels within the band gap of the Ag2W1 -xMoxO4 heterostructures, as evidenced by the decrease in the band-gap values measured by ultraviolet-visible spectroscopy.

  19. Fabrication and characterization of ZnO nanorods/p-6H-SiC heterojunction LED by microwave-assisted chemical bath deposition

    NASA Astrophysics Data System (ADS)

    Hassan, J. J.; Mahdi, M. A.; Ramizy, Asmiet; Abu Hassan, H.; Hassan, Z.

    2013-01-01

    High-quality vertically aligned zinc oxide nanorods were successfully grown on p-type 6H-SiC substrate by microwave-assisted chemical bath deposition. The novel seed material poly(vinyl alcohol)-Zn(OH)2 nanocomposites was used to seed the 6H-SiC substrate. X-ray diffraction analysis and field emission scanning electron microscopy showed that the synthesized ZnO nanorods were vertically well aligned in the direction of the (0 0 2) plane of the hexagonal structure. The optical properties were examined by photoluminescence spectroscopy, which showed a high-intensity UV peak compared with visible defect peaks. The current-voltage property proved the good rectifier characteristic of the n-type ZnO nanorod/p-type SiC diode heterojunction. The electroluminescence emission of the heterojunction LED was sufficiently high to be seen with the naked eye, with a broad peak centered at the green part of the visible spectrum.

  20. ILs-based microwave-assisted extraction coupled with aqueous two-phase for the extraction of useful compounds from Chinese medicine.

    PubMed

    Lin, Xiao; Wang, Yuzhi; Liu, Xiaojie; Huang, Songyun; Zeng, Qun

    2012-09-01

    Ionic liquids-based microwave-assisted extraction (ILs-MAE) of medicinal or useful compounds from plants was investigated as an alternative to conventional organic solvent extractions. The extraction and the preconcentration of aqueous two-phase (ATP) systems have been integrated. Various operating parameters were systematically considered by single-factor and L(9) (3(4)) orthogonal array experiments. 1-Butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF(4)]) has been selected to extract Apocynum venetum. The extract was then converted to the top phase by [bmim][BF(4)]/NaH(2)PO(4) system which was suitable for the preconcentration. Reversed phase high performance liquid chromatography (RP-HPLC) with ultraviolet detection was employed for the analysis of hyperin and isoquercitrin in Apocynum venetum. The optimal experiment approach could provide higher detection limit of hyperin and isoquercitrin which were 3.82 μg L(-1) and 3.00 μg L(-1) in Apocynum venetum. The recoveries of hyperin and isoquercitrin were 97.29% (RSD = 1.02%) and 99.40% (RSD = 1.13%), respectively, from aqueous samples of Apocynum venetum by the proposed method. Moreover, the extraction mechanism of ILs-MAE and the microstructures and chemical structures of the herb before and after extraction were also investigated. The method exhibited potential applicability with other complicated samples. PMID:22785248

  1. Simultaneous extraction, identification and quantification of phenolic compounds in Eclipta prostrata using microwave-assisted extraction combined with HPLC-DAD-ESI-MS/MS.

    PubMed

    Fang, Xinsheng; Wang, Jianhua; Hao, Jifu; Li, Xueke; Guo, Ning

    2015-12-01

    A simple and rapid method was developed using microwave-assisted extraction (MAE) combined with HPLC-DAD-ESI-MS/MS for the simultaneous extraction, identification, and quantification of phenolic compounds in Eclipta prostrata, a common herb and vegetable in China. The optimized parameters of MAE were: employing 50% ethanol as solvent, microwave power 400 W, temperature 70 °C, ratio of liquid/solid 30 mL/g and extraction time 2 min. Compared to conventional extraction methods, the optimized MAE can avoid the degradation of the phenolic compounds and simultaneously obtained the highest yields of all components faster with less consumption of solvent and energy. Six phenolic acids, six flavonoid glycosides and one coumarin were firstly identified. The phenolic compounds were quantified by HPLC-DAD with good linearity, precision, and accuracy. The extract obtained by MAE showed significant antioxidant activity. The proposed method provides a valuable and green analytical methodology for the investigation of phenolic components in natural plants. PMID:26041227

  2. Microwave-Assisted Hydrothermal Rapid Synthesis of Amorphous Calcium Phosphate Mesoporous Microspheres Using Adenosine 5'-Diphosphate and Application in pH-Responsive Drug Delivery.

    PubMed

    Qi, Chao; Zhu, Ying-Jie; Sun, Tuan-Wei; Wu, Jin; Chen, Feng

    2015-11-01

    Herein we report a rapid and green strategy for the preparation of amorphous calcium phosphate mesoporous microspheres (ACP-MSs) using adenosine 5'-diphosphate disodium salt (ADP) as an organic phosphorus source by a microwave-assisted hydrothermal method. The effects of the pH value, the reaction time, and temperature on the crystal phase and morphology of the product are investigated. The ADP biomolecules used in this strategy play an important role in the formation of ACP-MSs. The as-prepared ACP-MSs are efficient for anticancer drug delivery by using doxorubicin (Dox) as a model drug, and the Dox-loaded ACP-MSs show a high ability to damage cancer cells. Moreover, the ACP-MSs drug delivery system exhibits a pH-responsive drug-release behavior due to the degradation of ACP-MSs at a low pH value, thus, it is promising for applications in pH-responsive drug delivery. PMID:26248600

  3. Microwave-assisted extraction in combination with HPLC-UV for quantitative analysis of six bioactive oxoisoaporphine alkaloids in Menispermum dauricum DC.

    PubMed

    Wei, Jinxia; Chen, Jing; Liang, Xinlei; Guo, Xingjie

    2016-02-01

    A novel and reliable method based on microwave-assisted extraction (MAE) followed by HPLC-UV was developed and validated for the simultaneous quantification of six pharmacologically important oxoisoaporphine alkaloids in the total plants of Menispermum dauricum DC. The optimal MAE extraction condition was performed at 60°C for 11 min with ethanol-water (70:30, v/v) as the extracting solvent, and the solvent to solid ratio was 20:1. Chromatographic separation was achieved on a reversed-phase YMC C18 column (250 × 4.6 mm, i.d., 5 µm) with a gradient mobile phase consisting of A (1% aqueous formic acid) and B (acetonitrile containing 1% formic acid) at a flow rate of 1.5 mL/min. The detection wavelength was set at 422 nm. Excellent linearity over the investigated concentration ranges was observed with values of r >0.999 for all analytes. The method developed was validated with acceptable sensitivity, intra- and inter-day precision and extraction recoveries. It was successfully applied to the determination of six alkaloids in Menispermum dauricum DC from different sources and different parts of Menispermum dauricum DC. The results obtained indicated that the method is suitable for the quality control of Menispermum dauricum DC. PMID:26094998

  4. Continuous syntheses of Pd@Pt and Cu@Ag core-shell nanoparticles using microwave-assisted core particle formation coupled with galvanic metal displacement.

    PubMed

    Miyakawa, Masato; Hiyoshi, Norihito; Nishioka, Masateru; Koda, Hidekazu; Sato, Koichi; Miyazawa, Akira; Suzuki, Toshishige M

    2014-08-01

    Continuous synthesis of Pd@Pt and Cu@Ag core-shell nanoparticles was performed using flow processes including microwave-assisted Pd (or Cu) core-nanoparticle formation followed by galvanic displacement with a Pt (or Ag) shell. The core-shell structure and the nanoparticle size were confirmed using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) observation and EDS elemental mapping. The Pd@Pt nanoparticles with a particle size of 6.5 ± 0.6 nm and a Pt shell thickness of ca. 0.25 nm were synthesized with appreciably high Pd concentration (Pd 100 mM). This shell thickness corresponds to one atomic layer thickness of Pt encapsulating the Pd core metal. The particle size of core Pd was controlled by tuning the initial concentrations of Na2[PdCl4] and PVP. Core-shell Cu@Ag nanoparticles with a particle size of 90 ± 35 nm and an Ag shell thickness of ca. 3.5 nm were obtained using similar sequential reactions. Oxidation of the Cu core was suppressed by the coating of Cu nanoparticles with the Ag shell. PMID:24948122

  5. Chemical characteristics of different parts of Coreopsis tinctoria in China using microwave-assisted extraction and high-performance liquid chromatography followed by chemometric analysis.

    PubMed

    Lam, Shing-Chung; Liu, Xin; Chen, Xian-Qiang; Hu, De-Jun; Zhao, Jing; Long, Ze-Rong; Fan, Bing; Li, Shao-Ping

    2016-08-01

    Coreopsis tinctoria, also called "snow chrysanthemum" in China, is a flower tea material that has been reported to possess excellent pharmacological properties such as antioxidant and antidiabetic activities. The chemical characteristics of different parts (flowers, buds, seeds, stems, and leaves) of C. tinctoria were investigated based on microwave-assisted extraction and the simultaneous determination of 13 major active compounds by high-performance liquid chromatography, including taxifolin-7-O-glucoside, chlorogenic acid, (R/S)-flavanomarein, isocoreopsin, quercetagetin-7-O-glucoside, isookanin, 5,7,3',5'-tetrahydroxyflavanone-7-O-glucoside, marein, 3,5-dicaffeoylquinic acid, coreopsin, okanin, 5,7,3',5'-tetrahydroxyflavanone, and N(1) ,N(5) ,N(10) ,N(14) -tetra-p-coumaroylspermine. Chemometric analysis based on the contents of investigated compounds from 13 samples showed that C. tinctoria and the related flower tea materials, Chrysanthemum morifolium cv "Hangju" and "Gongju," were in different clusters, and different parts (flowers, buds, seeds, stems, and leaves) of C. tinctoria were obviously different. This study is helpful for the quality control and pharmacological evaluation of different parts from C. tinctoria and its related products. PMID:27291468

  6. Microwave-Assisted Synthesis of Highly-Crumpled, Few-Layered Graphene and Nitrogen-Doped Graphene for Use as High-Performance Electrodes in Capacitive Deionization.

    PubMed

    Amiri, Ahmad; Ahmadi, Goodarz; Shanbedi, Mehdi; Savari, Maryam; Kazi, S N; Chew, B T

    2015-01-01

    Capacitive deionization (CDI) is a promising procedure for removing various charged ionic species from brackish water. The performance of graphene-based material in capacitive deionization is lower than the expectation of the industry, so highly-crumpled, few-layered graphene (HCG) and highly-crumpled nitrogen-doped graphene (HCNDG) with high surface area have been introduced as promising candidates for CDI electrodes. Thus, HCG and HCNDG were prepared by exfoliation of graphite in the presence of liquid-phase, microwave-assisted methods. An industrially-scalable, cost-effective, and simple approach was employed to synthesize HCG and HCNDG, resulting in few-layered graphene and nitrogen-doped graphene with large specific surface area. Then, HCG and HCNDG were utilized for manufacturing a new class of carbon nanostructure-based electrodes for use in large-scale CDI equipment. The electrosorption results indicated that both the HCG and HCNDG have fairly large specific surface areas, indicating their huge potential for capacitive deionization applications. PMID:26643279

  7. Effects of activated carbon characteristics on the electrosorption capacity of titanium dioxide/activated carbon composite electrode materials prepared by a microwave-assisted ionothermal synthesis method.

    PubMed

    Liu, Po-I; Chung, Li-Ching; Ho, Chia-Hua; Shao, Hsin; Liang, Teh-Ming; Horng, Ren-Yang; Chang, Min-Chao; Ma, Chen-Chi M

    2015-05-15

    Titanium dioxide (TiO2)/ activated carbon (AC) composite materials, as capacitive deionization electrodes, were prepared by a two-step microwave-assisted ionothermal synthesis method. The electrosorption capacity of the composite electrodes was studied and the effects of AC characteristics were explored. These effects were investigated by multiple analytical techniques, including X-ray photoelectron spectroscopy, thermogravimetry analysis and electrochemical impedance spectroscopy, etc. The experimental results indicated that the electrosorption capacity of the TiO2/AC composite electrode is dependent on the characteristics of AC including the pore structure and the surface property. An enhancement in electrosorption capacity was observed for the TiO2/AC composite electrode prepared from the AC with higher mesopore content and less hydrophilic surface. This enhancement is due to the deposition of anatase TiO2 with suitable amount of Ti-OH. On the other hand, a decline in electrosorption capacity was observed for the TiO2/AC composite electrode prepared from the AC with higher micropore content and highly hydrophilic surface. High content of hydrogen bond complex formed between the functional group on hydrophilic surface with H2O, which will slow down the TiO2 precursor-H2O reaction. In such situation, the effect of TiO2 becomes unfavorable as the loading amount of TiO2 is less and the micropore can also be blocked. PMID:25576198

  8. Anomalous Temperature-Dependent Upconversion Luminescence of α-NaYF₄:Yb³⁺/Er³⁺ Nanocrystals Synthesized by a Microwave-Assisted Hydrothermal Method.

    PubMed

    Tong, Lili; Li, Xiangping; Hua, Ruinian; Tianxiang Peng; Wang, Yizhuo; Zhang, Xizhen; Chen, Baojiu

    2016-01-01

    Yb³⁺/Er³⁺co-doped cubic-(α-) phase NaYF₄ nanocrystals were prepared through a microwave- assisted hydrothermal method. Temperature-dependent upconversion luminescence (UCL) and sensing properties were systematically studied. It is interesting that anomalous temperature- dependent UCL behavior is observed. With increasing temperature (303-573 K), the UCL intensity of Er³⁺ does not quench monotonously but reaches a minimum around 483 K and then increases. However, it was found that the UCL spectra change in a different way with decreasing temperature (573-303 K) from the one measured with increasing temperature. The fluorescence intensity ratio of ²H₁₁/₂ --> ⁴I₁₅/₂ to ⁴S₃/₂ --> ⁴I₁₅/₂ at any measured temperature point remains almost constant in all measurement processes, indicating the consistency of temperature in each spectrum measurement at all temperature points regardless of the heating or the cooling process in our experiments. The results demonstrate that NaYF₄:Yb³⁺/Er³⁺ UC nanocrystal has good sensing stability and may have potential application in the nanoscale thermal sensor. PMID:27398529

  9. Microwave-assisted extraction of rare earth elements from petroleum refining catalysts and ambient fine aerosols prior to inductively coupled plasma-mass spectrometry.

    PubMed

    Kulkarni, Pranav; Chellam, Shankararaman; Mittlefehldt, David W

    2007-01-01

    A robust microwave-assisted acid digestion procedure followed by inductively coupled plasma-mass spectrometry (ICP-MS) was developed to quantify rare earth elements (REEs) in fluidized-bed catalytic cracking (FCC) catalysts and atmospheric fine particulate matter (PM(2.5)). High temperature (200 degrees C), high pressure (200 psig), acid digestion (HNO(3), HF and H(3)BO(3)) with 20 min dwell time effectively solubilized REEs from six fresh catalysts, a spent catalyst and PM(2.5). This method was also employed to measure 27 non-REEs including Na, Mg, Al, Si, K, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Zr, Mo, Cd, Cs, Ba, Pb and U. Complete extraction of several REEs (Y, La, Ce, Pr, Nd, Tb, Dy and Er) required HF indicating that they were closely associated with the aluminosilicate structure of the zeolite FCC catalysts. Internal standardization using (115)In quantitatively corrected non-spectral interferences in the catalyst digestate matrix. Inter-laboratory comparison using ICP-optical emission spectroscopy (ICP-OES) and instrumental neutron activation analysis (INAA) demonstrated the applicability of the newly developed analytical method for accurate analysis of REEs in FCC catalysts. The method developed for FCC catalysts was also successfully implemented to measure trace to ultra-trace concentrations of La, Ce, Pr, Nd, Sm, Gd, Eu and Dy in ambient PM(2.5) in an industrial area of Houston, TX. PMID:17386451

  10. The microwave assisted synthesis of 1-alkyl-3-methylimidazolium bromide as potential corrosion inhibitor toward carbon steel in 1 M HCl solution saturated with carbon dioxide

    NASA Astrophysics Data System (ADS)

    Pasasa, Norman Vincent A.; Bundjali, Bunbun; Wahyuningrum, Deana

    2015-09-01

    Injection of corrosion inhibitor into the fluid current of oil and gas pipelines is an effective way to mitigate corrosion rate on the inner-surface parts of pipelines, especially carbon steel pipelines. In this research, two alkylimidazolium ionic liquids, 1-decyl-3-methylimidazolium bromide (IL1) and 1-dodecyl-3-methylimidazolium bromide (IL2) have been synthesized and studied as a potential corrosion inhibitor towards carbon steel in 1 M HCl solution saturated with carbon dioxide. IL1 and IL2 were synthesized using microwave assisted organic synthesis (MAOS) method. Mass Spectrometry analysis of IL1 and IL2 showed molecular mass [M-H+] peak at 223.2166 and 251.2484, respectively. The FTIR,1H-NMR and 13C-NMR spectra confirmed that IL1 and IL2 were successfully synthesized. Corrosion inhibition activity of IL1 and IL2 were determined using weight loss method. The results showed that IL1 and IL2 have the potential as good corrosion inhibitors with corrosion inhibition efficiency of IL1 and IL2 are 96.00% at 100 ppm (343 K) and 95.60% at 50 ppm (343 K), respectively. The increase in the concentration of IL1 and IL2 tends to improve their corrosion inhibition activities. Analysis of the data obtained from the weight loss method shows that the adsorption of IL1 and IL2 on carbon steel is classified into chemisorption which obeys Langmuir's adsorption isotherm.

  11. PCDDs, PCDFs and PCNs in products of microwave-assisted pyrolysis of woody biomass--Distribution among solid, liquid and gaseous phases and effects of material composition.

    PubMed

    Gao, Qiuju; Budarin, Vitaliy L; Cieplik, Mariusz; Gronnow, Mark; Jansson, Stina

    2016-02-01

    Microwave-assisted pyrolysis (MAP) of lignocellulosic biomass is a technique that could potentially be used to produce and upgrade renewable energy carriers. However, there is no available information about the formation of dioxins and other organic pollutants in MAP treatment of woody biomass. In this study, MAP experiments were conducted in lab-scale using virgin softwood, bark, and impregnated wood as feedstocks. The non-condensable gas, liquid (fractionated into aqueous and oil phases), and char fractions generated during pyrolysis were collected and analysed for polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and naphthalenes (PCNs). The concentrations of PCDDs, PCDFs and PCNs in the pyrolysis products ranged from 0.52 to 43.7 ng kg(-1). All investigated compound groups were most abundant in the oil fraction, accounting for up to 68% (w/w) of the total concentrations. The highest PCDD, PCDF and PCN concentrations were found from the pyrolysis of bark, which has relatively high contents of chlorine and mineral matter, followed by impregnated wood, which contains organic and metal-based preservatives. The homologue profiles of all three compound groups were dominated by the less chlorinated homologues. The homologue abundance decreased as the degree of chlorination increased. This trend was observed for all three feedstocks. PMID:26688256

  12. Accurate Analysis and Evaluation of Acidic Plant Growth Regulators in Transgenic and Nontransgenic Edible Oils with Facile Microwave-Assisted Extraction-Derivatization.

    PubMed

    Liu, Mengge; Chen, Guang; Guo, Hailong; Fan, Baolei; Liu, Jianjun; Fu, Qiang; Li, Xiu; Lu, Xiaomin; Zhao, Xianen; Li, Guoliang; Sun, Zhiwei; Xia, Lian; Zhu, Shuyun; Yang, Daoshan; Cao, Ziping; Wang, Hua; Suo, Yourui; You, Jinmao

    2015-09-16

    Determination of plant growth regulators (PGRs) in a signal transduction system (STS) is significant for transgenic food safety, but may be challenged by poor accuracy and analyte instability. In this work, a microwave-assisted extraction-derivatization (MAED) method is developed for six acidic PGRs in oil samples, allowing an efficient (<1.5 h) and facile (one step) pretreatment. Accuracies are greatly improved, particularly for gibberellin A3 (-2.72 to -0.65%) as compared with those reported (-22 to -2%). Excellent selectivity and quite low detection limits (0.37-1.36 ng mL(-1)) are enabled by fluorescence detection-mass spectrum monitoring. Results show the significant differences in acidic PGRs between transgenic and nontransgenic oils, particularly 1-naphthaleneacetic acid (1-NAA), implying the PGRs induced variations of components and genes. This study provides, for the first time, an accurate and efficient determination for labile PGRs involved in STS and a promising concept for objectively evaluating the safety of transgenic foods. PMID:26309068

  13. Microwave-assisted Extraction of Rare Earth Elements from Petroleum Refining Catalysts and Ambient Fine Aerosols Prior to Inductively Coupled Plasma - Mass Spectrometry

    NASA Technical Reports Server (NTRS)

    Mittlefehldt, David W.; Kulkarni, Pranav; Chellam, Shankar

    2006-01-01

    In the absence of a certified reference material, a robust microwave-assisted acid digestion procedure followed by inductively coupled plasma - mass spectrometry (ICP-MS) was developed to quantify rare earth elements (REEs) in fluidized-bed catalytic cracking (FCC) catalysts and atmospheric fine particulate matter (PM2.5). High temperature (200 C), high pressure (200 psig), acid digestion (HNO3, HF, and H3BO3) with 20 minute dwell time effectively solubilized REEs from six fresh catalysts, a spent catalyst, and PM2.5. This method was also employed to measure 27 non-REEs including Na, Mg, Al, Si, K, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Zr, Mo, Cd, Cs, Ba, Pb, and U. Complete extraction of several REEs (Y, La, Ce, Pr, Nd, Tb, Dy, and Er) required HF indicating that they were closely associated with the aluminosilicate structure of the zeolite FCC catalysts. Internal standardization using 115In quantitatively corrected non-spectral interferences in the catalyst digestate matrix. Inter-laboratory comparison using ICP-optical emission spectroscopy (ICP-OES) and instrumental neutron activation analysis (INAA) demonstrated the applicability of the newly developed analytical method for accurate analysis of REEs in FCC catalysts. The method developed for FCC catalysts was also successfully implemented to measure trace to ultra-trace concentrations of La, Ce, Pr, Nd, Sm, Gd, Eu, and Dy in ambient PM2.5 in an industrial area of Houston, TX.

  14. The Successful Diagnosis and Typing of Systemic Amyloidosis Using A Microwave-Assisted Filter-Aided Fast Sample Preparation Method and LC/MS/MS Analysis.

    PubMed

    Sun, Weiyi; Sun, Jian; Zou, Lili; Shen, Kaini; Zhong, Dingrong; Zhou, Daobin; Sun, Wei; Li, Jian

    2015-01-01

    Laser microdissection followed by mass spectrometry has been successfully used for amyloid typing. However, sample contamination can interfere with proteomic analysis, and overnight digestion limits the analytical throughput. Moreover, current quantitative analysis methods are based on the spectrum count, which ignores differences in protein length and may lead to misdiagnoses. Here, we developed a microwave-assisted filter-aided sample preparation (maFASP) method that can efficiently remove contaminants with a 10-kDa cutoff ultrafiltration unit and can accelerate the digestion process with the assistance of a microwave. Additionally, two parameters (P- and D-scores) based on the exponentially modified protein abundance index were developed to define the existence of amyloid deposits and those causative proteins with the greatest abundance. Using our protocol, twenty cases of systemic amyloidosis that were well-typed according to clinical diagnostic standards (training group) and another twenty-four cases without subtype diagnoses (validation group) were analyzed. Using this approach, sample preparation could be completed within four hours. We successfully subtyped 100% of the cases in the training group, and the diagnostic success rate in the validation group was 91.7%. This maFASP-aided proteomic protocol represents an efficient approach for amyloid diagnosis and subtyping, particularly for serum-contaminated samples. PMID:25984759

  15. Microwave-Assisted Synthesis of Highly-Crumpled, Few-Layered Graphene and Nitrogen-Doped Graphene for Use as High-Performance Electrodes in Capacitive Deionization

    PubMed Central

    Amiri, Ahmad; Ahmadi, Goodarz; Shanbedi, Mehdi; Savari, Maryam; Kazi, S. N.; Chew, B. T.

    2015-01-01

    Capacitive deionization (CDI) is a promising procedure for removing various charged ionic species from brackish water. The performance of graphene-based material in capacitive deionization is lower than the expectation of the industry, so highly-crumpled, few-layered graphene (HCG) and highly-crumpled nitrogen-doped graphene (HCNDG) with high surface area have been introduced as promising candidates for CDI electrodes. Thus, HCG and HCNDG were prepared by exfoliation of graphite in the presence of liquid-phase, microwave-assisted methods. An industrially-scalable, cost-effective, and simple approach was employed to synthesize HCG and HCNDG, resulting in few-layered graphene and nitrogen-doped graphene with large specific surface area. Then, HCG and HCNDG were utilized for manufacturing a new class of carbon nanostructure-based electrodes for use in large-scale CDI equipment. The electrosorption results indicated that both the HCG and HCNDG have fairly large specific surface areas, indicating their huge potential for capacitive deionization applications. PMID:26643279

  16. Automated radioanalytical system incorporating microwave-assisted sample preparation, chemical separation, and online radiometric detection for the monitoring of total 99Tc in nuclear waste processing streams.

    PubMed

    Egorov, Oleg B; O'Hara, Matthew J; Grate, Jay W

    2012-04-01

    An automated fluidic instrument is described that rapidly determines the total (99)Tc content of aged nuclear waste samples, where the matrix is chemically and radiologically complex and the existing speciation of the (99)Tc is variable. The monitor links microwave-assisted sample preparation with an automated anion exchange column separation and detection using a flow-through solid scintillator detector. The sample preparation steps acidify the sample, decompose organics, and convert all Tc species to the pertechnetate anion. The column-based anion exchange procedure separates the pertechnetate from the complex sample matrix, so that radiometric detection can provide accurate measurement of (99)Tc. We developed a preprogrammed spike addition procedure to automatically determine matrix-matched calibration. The overall measurement efficiency that is determined simultaneously provides a self-diagnostic parameter for the radiochemical separation and overall instrument function. Continuous, automated operation was demonstrated over the course of 54 h, which resulted in the analysis of 215 samples plus 54 hly spike-addition samples, with consistent overall measurement efficiency for the operation of the monitor. A sample can be processed and measured automatically in just 12.5 min with a detection limit of 23.5 Bq/mL of (99)Tc in low activity waste (0.495 mL sample volume), with better than 10% RSD precision at concentrations above the quantification limit. This rapid automated analysis method was developed to support nuclear waste processing operations planned for the Hanford nuclear site. PMID:22440010

  17. Preparation of N doped TiO2 via microwave-assisted method and its photocatalytic activity for degradation of Malathion.

    PubMed

    Kadam, A N; Dhabbe, R S; Kokate, M R; Gaikwad, Y B; Garadkar, K M

    2014-12-10

    We report herein, nitrogen doped TiO2 nanostructure synthesized by simple microwave assisted method, where ammonia was used as hydrolyzing agent. The synthesized nanomaterials were characterized by means of X-ray diffraction (XRD) which demonstrated that N-doped TiO2 is in anatase phase with average crystallite size of 10nm. Doping of N into the lattice of TiO2 was supported by X-ray photoelectron spectroscopy (XPS), Fourier transform-infrared spectroscopy (FT-IR), CHNS analysis, energy dispersive spectroscopy (EDS). The diffuse reflectance spectroscopy (DRS) showed shifting of absorption edge toward the visible region. Thermogravimetric-differential thermal analysis (TGA-DTA) points out N-doped TiO2 nanoparticles are thermally stable. In order to achieve maximum degradation efficiency, the effect of catalyst loading, pH and light sources (UV and sunlight) were studied. A maximum 97% degradation efficiency was achieved under optimized conditions. A 80% reduction in the chemical oxygen demand (COD) was observed after 150min that indicated mineralization of Malathion. The cytotoxicological studies indicate that photocatalytically degraded products were less toxic as compared to Malathion. PMID:24996208

  18. Microwave-assisted synthesis of biocompatible europium-doped calcium hydroxyapatite and fluoroapatite luminescent nanospindles functionalized with poly(acrylic acid).

    PubMed

    Escudero, Alberto; Calvo, Mauricio E; Rivera-Fernández, Sara; de la Fuente, Jesús M; Ocaña, Manuel

    2013-02-12

    Europium-doped calcium hydroxyapatite and fluoroapatite nanophosphors functionalized with poly(acrylic acid) (PAA) have been synthesized through a one-pot microwave-assisted hydrothermal method from aqueous basic solutions containing calcium nitrate, sodium phosphate monobasic, and PAA, as well as sodium fluoride in the case of the fluoroapatite particles. In both cases a spindlelike morphology was obtained, resulting from an aggregation process of smaller subunits which also gave rise to high specific surface area. The size of the nanospindles was 191 (32) × 40 (5) nm for calcium hydroxyapatite and 152 (24) × 38 (6) nm for calcium fluoroapatite. The luminescent nanoparticles showed the typical red luminescence of Eu(3+), which was more efficient for the fluoroapatite particles than for the hydroxyapatite. This is attributed to the presence of OH(-) quenchers in the latter. The nanophosphors showed negligible toxicity for Vero cells. Both PAA-functionalized nanophosphors showed a very high (up to at least 1 week) colloidal stability in 2-(N-morpholino)ethanesulfonic acid (MES) at pH 6.5, which is a commonly used buffer for physiological pH. All these features make both kinds of apatite-based nanoparticles promising tools for biomedical applications, such as luminescent biolabels and tracking devices in drug delivery systems. PMID:23317411

  19. Solution-phase microwave assisted parallel synthesis, biological evaluation and in silico docking studies of N,N'-disubstituted thioureas derived from 3-chlorobenzoic acid.

    PubMed

    Rauf, Muhammad Khawar; Zaib, Sumera; Talib, Ammara; Ebihara, Masahiro; Badshah, Amin; Bolte, Michael; Iqbal, Jamshed

    2016-09-15

    A facile and robust microwave-assisted solution phase parallel synthesis protocol was exercised for the development of a 38-member library of N,N'-disubstituted thiourea analogues (1-38) by using an identical set of conditions. The reaction time for synthesis of N,N'-disubstituted thiourea analogues was drastically reduced from a reported duration of 8-12h for conventional methods to only 1.5-2.0min. All the derivatives (1-38) were characterized by physico-analytical techniques such as elemental analysis in combination with FT-IR, (1)H, (13)C NMR and by single crystal XRD analysis have also been performed. These compounds were screened for their in vitro urease inhibition activities. Majority of compounds exhibited potent urease inhibition activities, however, the most significant activity was found for 16, with an IC50 value of 1.23±0.1μM. Furthermore, the synthesized compounds were screened for their cytotoxic potential against lungs cancer cell lines. Cell culture studies demonstrated significant toxicity of the compounds on the cell lines, and the levels of toxicity were altered in the presence of various side groups. The molecular docking studies of the most potent inhibitors were performed to identify the probable binding modes in the active site of the urease enzymes. These compounds have a great potential and significance for further investigations. PMID:27480030

  20. Arsenic speciation in edible alga samples by microwave-assisted extraction and high performance liquid chromatography coupled to atomic fluorescence spectrometry.

    PubMed

    García-Salgado, S; Quijano, M A; Bonilla, M M

    2012-02-10

    Twelve commercially available edible marine algae from France, Japan and Spain and the certified reference material (CRM) NIES No. 9 Sargassum fulvellum were analyzed for total arsenic and arsenic species. Total arsenic concentrations were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) after microwave digestion and ranged from 23 to 126 μg g(-1). Arsenic species in alga samples were extracted with deionized water by microwave-assisted extraction and showed extraction efficiencies from 49 to 98%, in terms of total arsenic. The presence of eleven arsenic species was studied by high performance liquid chromatography-ultraviolet photo-oxidation-hydride generation atomic-fluorescence spectrometry (HPLC-(UV)-HG-AFS) developed methods, using both anion and cation exchange chromatography. Glycerol and phosphate sugars were found in all alga samples analyzed, at concentrations between 0.11 and 22 μg g(-1), whereas sulfonate and sulfate sugars were only detected in three of them (0.6-7.2 μg g(-1)). Regarding arsenic toxic species, low concentration levels of dimethylarsinic acid (DMA) (<0.9 μg g(-1)) and generally high arsenate (As(V)) concentrations (up to 77 μg g(-1)) were found in most of the algae studied. The results obtained are of interest to highlight the need to perform speciation analysis and to introduce appropriate legislation to limit toxic arsenic species content in these food products. PMID:22244135

  1. Fast microwave-assisted catalytic co-pyrolysis of corn stover and scum for bio-oil production with CaO and HZSM-5 as the catalyst.

    PubMed

    Liu, Shiyu; Xie, Qinglong; Zhang, Bo; Cheng, Yanling; Liu, Yuhuan; Chen, Paul; Ruan, Roger

    2016-03-01

    This study investigated fast microwave-assisted catalytic co-pyrolysis of corn stover and scum for bio-oil production with CaO and HZSM-5 as the catalyst. Effects of reaction temperature, CaO/HZSM-5 ratio, and corn stover/scum ratio on co-pyrolysis product fractional yields and selectivity were investigated. Results showed that co-pyrolysis temperature was selected as 550°C, which provides the maximum bio-oil and aromatic yields. Mixed CaO and HZSM-5 catalyst with the weight ratio of 1:4 increased the aromatic yield to 35.77 wt.% of feedstock, which was 17% higher than that with HZSM-5 alone. Scum as the hydrogen donor, had a significant synergistic effect with corn stover to promote the production of bio-oil and aromatic hydrocarbons when the H/C(eff) value exceeded 1. The maximum yield of aromatic hydrocarbons (29.3 wt.%) were obtained when the optimal corn stover to scum ratio was 1:2. PMID:26773959

  2. Microwave-assisted catalytic fast pyrolysis of biomass for bio-oil production using chemical vapor deposition modified HZSM-5 catalyst.

    PubMed

    Zhang, Bo; Zhong, Zhaoping; Chen, Paul; Ruan, Roger

    2015-12-01

    Chemical vapor deposition with tetra-ethyl-orthosilicate as the modifier was applied to deposit the external acid sites of HZSM-5, and the modified HZSM-5 samples were used for the microwave-assisted catalytic fast pyrolysis (MACFP) of biomass for bio-oil production. The experimental results showed that the external acid sites of HZSM-5 decreased significantly when SiO2 deposited amount increased from 0% to 5.9%. For product distribution, the coke yield decreased, the oil fraction yield decreased at first and then increased, and the yields of water and gas first increased and then decreased over the range of SiO2 deposited amount studied. For chemical compositions in oil fraction, the relative contents of aliphatic hydrocarbons, aromatic hydrocarbons and oxygen-containing aromatic compounds first increased to maximum values and then decreased, while the relative content of oxygen-containing aliphatic compounds first decreased and then increased with increasing SiO2 deposited amount. PMID:26318925

  3. Deposition of photocatalytically active TiO2 films by inkjet printing of TiO2 nanoparticle suspensions obtained from microwave-assisted hydrothermal synthesis.

    PubMed

    Arin, Melis; Lommens, Petra; Hopkins, Simon C; Pollefeyt, Glenn; Van der Eycken, Johan; Ricart, Susagna; Granados, Xavier; Glowacki, Bartek A; Van Driessche, Isabel

    2012-04-27

    In this paper, we present an inkjet printing approach suited for the deposition of photocatalytically active, transparent titanium oxide coatings from an aqueous, colloidal suspension. We used a bottom-up approach in which a microwave-assisted hydrothermal treatment of titanium propoxide aqueous solutions in the presence of ethylenediaminetetraacetic acid and triethanolamine was used to create suspensions containing titania nanoparticles. Different inkjet printing set-ups, electromagnetic and piezoelectric driven, were tested to deposit the inks on glass substrates. The presence of preformed titania nanoparticles was expected to make it possible to reduce the heating temperature necessary to obtain the functionality of photocatalysis which can widen the application range of the approach to heat-sensitive substrates. We investigated the crystallinity and size of the obtained nanoparticles by electron microscopy and dynamic light scattering. The rheological properties of the suspensions were evaluated against the relevant criteria for inkjet printing and the jettability was analyzed. The photocatalytic activity of the obtained layers was analyzed by following the decomposition of a methylene blue solution under UV illumination. The influence of the heat treatment temperature on the film roughness, thickness and photocatalytic activity was studied. Good photocatalytic performance was achieved for heat treatments at temperatures as low as 150 °C, introducing the possibility of using this approach for heat-sensitive substrates. PMID:22460736

  4. Microwave-assisted aqueous enzymatic extraction of oil from pumpkin seeds and evaluation of its physicochemical properties, fatty acid compositions and antioxidant activities.

    PubMed

    Jiao, Jiao; Li, Zhu-Gang; Gai, Qing-Yan; Li, Xiao-Juan; Wei, Fu-Yao; Fu, Yu-Jie; Ma, Wei

    2014-03-15

    Microwave-assisted aqueous enzymatic extraction (MAAEE) of pumpkin seed oil was performed in this study. An enzyme cocktail comprised of cellulase, pectinase and proteinase (w/w/w) was found to be the most effective in releasing oils. The highest oil recovery of 64.17% was achieved under optimal conditions of enzyme concentration (1.4%, w/w), temperature (44°C), time (66 min) and irradiation power (419W). Moreover, there were no significant variations in physicochemical properties of MAAEE-extracted oil (MAAEEO) and Soxhlet-extracted oil (SEO), but MAAEEO exhibited better oxidation stability. Additionally, MAAEEO had a higher content of linoleic acid (57.33%) than SEO (53.72%), and it showed stronger antioxidant activities with the IC50 values 123.93 and 152.84, mg/mL, according to DPPH radical scavenging assay and β-carotene/linoleic acid bleaching test. SEM results illustrated the destruction of cell walls and membranes by MAAEE. MAAEE is, therefore, a promising and environmental-friendly technique for oil extraction in the food industry. PMID:24206680

  5. Synthesis and characterization of [BMIM]bromide using microwave-assisted organic synthesis method and its application for dissolution of palm empty fruit bunch

    NASA Astrophysics Data System (ADS)

    Arianie, Lucy; Wahyuningrum, Deana; Nurrachman, Zeily; Natalia, Dessy

    2014-03-01

    The decrease of cellulose crystallinity index of palm empty fruit bunch is crucial for the next application of cellulose as raw material for various biofuel and its derivatives. The aim of this research is to decrease the cellulose crystallinity index of palm empty fruit bunch using 1-butyl-3-methylimidazoliumbromide or [BMIM] bromide which has been synthesized using Microwave-Assisted Organic Synthesis (MAOS) method. Conventional reaction method has also been carried out to synthesize [BMIM]bromide for comparison as well. The characterization of synthesized product using FTIR, 1H-NMR, 13C-NMR and LC-MS showed that these reactions have been carried out successfully. The results showed that MAOS method is up to 90% faster in producing [BMIM]bromide compare to the conventional method. The application of [BMIM]bromide for dissolution of palm empty fruit bunch showed that cellulose and lignin could be extracted using stirring process for 20 hours. The decrease of cellulose crystallinity index and its morphology changes were identified using FTIR and Scanning Electron Microscope.

  6. Microwave-assisted ionic liquid homogeneous liquid-liquid microextraction coupled with high performance liquid chromatography for the determination of anthraquinones in Rheum palmatum L.

    PubMed

    Wang, Zhibing; Hu, Jianxue; Du, Hongxia; He, Shuang; Li, Qing; Zhang, Hanqi

    2016-06-01

    The microwave-assisted ionic liquid homogeneous liquid-liquid microextraction (MA-IL-HLLME) coupled with high performance liquid chromatography with diode array detection (HPLC-DAD) was developed for the determination of anthraquinones, including aloe-emodin, emodin, chrysophanol and physcion in root of Rheum palmatum L. Several experimental parameters influencing the extraction efficiency, including amount of sample, type and volume of ionic liquid, volume and pH value of extraction medium, microwave power and extraction time, concentration of NH4PF6 as well as centrifugal condition were optimized. When 140μL of ionic liquid ([C8MIM][BF4]) was used as an extraction solvent, target analytes can be extracted from sample matrix in one minute with the help of microwave irradiation. The MA-IL-HLLME is simple and quick. The calibration curves exhibited good linear relationship (r>0.9984). The limits of detection and quantification were in the range of 0.015-0.026 and 0.051-0.088μgmL(-1), respectively. The spiked recovery for each analyte was in the range of 81.13-93.07% with relative standard deviations lower than 6.89%. The present method is free of volatile organic solvents, and represents lower expenditures of sample, extraction time and solvent, compared with ultrasonic and heat reflux extraction. The results indicated that the present method can be successfully applied to the determination of anthraquinones in medicinal plant. PMID:27023130

  7. The Successful Diagnosis and Typing of Systemic Amyloidosis Using A Microwave-Assisted Filter-Aided Fast Sample Preparation Method and LC/MS/MS Analysis

    PubMed Central

    Zou, Lili; Shen, Kaini; Zhong, Dingrong; Zhou, Daobin; Sun, Wei; Li, Jian

    2015-01-01

    Laser microdissection followed by mass spectrometry has been successfully used for amyloid typing. However, sample contamination can interfere with proteomic analysis, and overnight digestion limits the analytical throughput. Moreover, current quantitative analysis methods are based on the spectrum count, which ignores differences in protein length and may lead to misdiagnoses. Here, we developed a microwave-assisted filter-aided sample preparation (maFASP) method that can efficiently remove contaminants with a 10-kDa cutoff ultrafiltration unit and can accelerate the digestion process with the assistance of a microwave. Additionally, two parameters (P- and D-scores) based on the exponentially modified protein abundance index were developed to define the existence of amyloid deposits and those causative proteins with the greatest abundance. Using our protocol, twenty cases of systemic amyloidosis that were well-typed according to clinical diagnostic standards (training group) and another twenty-four cases without subtype diagnoses (validation group) were analyzed. Using this approach, sample preparation could be completed within four hours. We successfully subtyped 100% of the cases in the training group, and the diagnostic success rate in the validation group was 91.7%. This maFASP-aided proteomic protocol represents an efficient approach for amyloid diagnosis and subtyping, particularly for serum-contaminated samples. PMID:25984759

  8. Two-step fast microwave-assisted pyrolysis of biomass for bio-oil production using microwave absorbent and HZSM-5 catalyst.

    PubMed

    Zhang, Bo; Zhong, Zhaoping; Xie, Qinglong; Liu, Shiyu; Ruan, Roger

    2016-07-01

    A novel technology of two-step fast microwave-assisted pyrolysis (fMAP) of corn stover for bio-oil production was investigated in the presence of microwave absorbent (SiC) and HZSM-5 catalyst. Effects of fMAP temperature and catalyst-to-biomass ratio on bio-oil yield and chemical components were examined. The results showed that this technology, employing microwave, microwave absorbent and HZSM-5 catalyst, was effective and promising for biomass fast pyrolysis. The fMAP temperature of 500°C was considered the optimum condition for maximum yield and best quality of bio-oil. Besides, the bio-oil yield decreased linearly and the chemical components in bio-oil were improved sequentially with the increase of catalyst-to-biomass ratio from 1:100 to 1:20. The elemental compositions of bio-char were also determined. Additionally, compared to one-step fMAP process, two-step fMAP could promote the bio-oil quality with a smaller catalyst-to-biomass ratio. PMID:27372139

  9. Free MoS2 Nanoflowers Grown on Graphene by Microwave-Assisted Synthesis as Highly Efficient Non-Noble-Metal Electrocatalysts for the Hydrogen Evolution Reaction.

    PubMed

    Cao, Jiamu; Zhang, Xuelin; Zhang, Yufeng; Zhou, Jing; Chen, Yinuo; Liu, Xiaowei

    2016-01-01

    Advanced approaches to preparing non-noble-metal electrocatalysts for the hydrogen evolution reaction (HER) are considered to be a significant breakthrough in promoting the exploration of renewable resources. In this work, a hybrid material of MoS2 nanoflowers (NFs) on reduced graphene oxide (rGO) was synthesized as a HER catalyst via an environmentally friendly, efficient approach that is also suitable for mass production. Small-sized MoS2 NFs with a diameter of ca. 190 nm and an abundance of exposed edges were prepared by a hydrothermal method and were subsequently supported on rGO by microwave-assisted synthesis. The results show that MoS2 NFs were distributed uniformly on the remarkably reduced GO and preserved the outstanding original structural features perfectly. Electrochemical tests show that the as-prepared hybrid material exhibited excellent HER activity, with a small Tafel slope of 80 mV/decade and a low overpotential of 170 mV. PMID:27556402

  10. Excellent microwave-absorbing properties of elliptical Fe3O4 nanorings made by a rapid microwave-assisted hydrothermal approach

    NASA Astrophysics Data System (ADS)

    Liu, Yun; Cui, Tingting; Wu, Tong; Li, Yana; Tong, Guoxiu

    2016-04-01

    High-quality elliptical polycrystalline Fe3O4 nanorings (NRs) with continuously tunable size have been synthesized in large amounts via a rapid microwave-assisted hydrothermal approach. The surface-protected glucose reducing/etching/Ostwald ripening mechanism is responsible for the formation of NRs. Ring size can be modulated by selecting iron glycolate nanosheets with various sizes as precursors. The size-dependent magnetic behavior of the NRs was observed. Our research gives insights into the understanding of the microwave absorption mechanism of elliptical Fe3O4 NRs. Owing to their large specific surface area, shape anisotropy, and closed ring-like configuration, elliptical polycrystalline Fe3O4 NRs exhibited significantly enhanced microwave absorption performance compared with Fe3O4 circular NRs, nanosheets, microspheres, nanospindles, and nanotubes. An optimal reflection loss value of -41.59 dB is achieved at 5.84 GHz and R L values (≤-20 dB) are observed at 3.2-10.4 GHz. Some new mechanisms including multiple scattering, oscillation resonance absorption, microantenna radiation, and interference are also crucial to the enhanced absorption properties of NRs. These findings indicate that ring-like nanostructures are a promising structure for devising new and effective microwave absorbers.

  11. Microwave-assisted hydrothermal synthesis of Cu/Cu2O hollow spheres with enhanced photocatalytic and gas sensing activities at room temperature.

    PubMed

    Zou, Xinwei; Fan, Huiqing; Tian, Yuming; Zhang, Mingang; Yan, Xiaoyan

    2015-05-01

    Cu/Cu2O nano-heterostructure hollow spheres with a submicron diameter (200-500 nm) were prepared by a microwave-assisted hydrothermal method using Cu(OAc)2·H2O, PVP and ascorbic acid solution as the precursors. The morphology of the products could evolve with the hydrothermal time from solid spheres to thick-shell hollow spheres, then to thin-shell hollow spheres, and finally to nanoparticles. Moreover, the content of Cu in the products could be controlled by adjusting the hydrothermal time. The spontaneous forming of the hollow structure spheres was found to result from the Ostwald ripening effect during the low temperature (100 °C) hydrothermal reaction process. The photocatalytic degradation activities on MO under visible-light irradiation and the gas sensing activities toward the oxidizing NO2 gas of different Cu/Cu2O nano-heterostructure hollow spheres were investigated. As a result, the Cu/Cu2O nano-heterostructure hollow spheres obtained at the hydrothermal time of 30 min, with a rough/porous thin-shell structure and a Cu content of about 10.5 wt%, exhibited the best photocatalytic and gas sensing performances compared with others. PMID:25820327

  12. Microwave-assisted extraction of herbacetin diglucoside from flax (Linum usitatissimum L.) seed cakes and its quantification using an RP-HPLC-UV system.

    PubMed

    Fliniaux, Ophélie; Corbin, Cyrielle; Ramsay, Aina; Renouard, Sullivan; Beejmohun, Vickram; Doussot, Joël; Falguières, Annie; Ferroud, Clotilde; Lamblin, Frédéric; Lainé, Eric; Roscher, Albrecht; Grand, Eric; Mesnard, François; Hano, Christophe

    2014-01-01

    Flax (Linum usitatissimum L.) seeds are widely used for oil extraction and the cold-pressed flaxseed (or linseed) cakes obtained during this process constitute a valuable by-product. The flavonol herbacetin diglucoside (HDG) has been previously reported as a constituent of the flaxseed lignan macromolecule linked through ester bonds to the linker molecule hydroxymethylglutaric acid. In this context, the development and validation of a new approach using microwave-assisted extraction (MAE) of HDG from flaxseed cakes followed by quantification with a reverse-phase HPLC system with UV detection was purposed. The experimental parameters affecting the HDG extraction yield, such as microwave power, extraction time and sodium hydroxide concentration, from the lignan macromolecule were optimized. A maximum HDG concentration of 5.76 mg/g DW in flaxseed cakes was measured following an irradiation time of 6 min, for a microwave power of 150 W using a direct extraction in 0.1 M NaOH in 70% (v/v) aqueous methanol. The optimized method was proven to be rapid and reliable in terms of precision, repeatability, stability and accuracy for the extraction of HDG. Comparison with a conventional extraction method demonstrated that MAE is more effective and less time-consuming. PMID:24619301

  13. Development and application of microwave assisted extraction (MAE) for the extraction of five polycyclic aromatic hydrocarbons in sediment samples in Johannesburg area, South Africa.

    PubMed

    Sibiya, Precious; Chimuka, Luke; Cukrowska, Ewa; Tutu, Hlanganani

    2013-07-01

    A microwave-assisted extraction (MAE) method was verified and applied for the extraction of polycyclic aromatic hydrocarbons (PAHs) in sediment samples. Soxhlet extraction was used as the reference method. The optimum MAE was carried out with 20 mL of hexane/acetone (1:1, v/v) mixture in a 1-g sample at 250 W for 20 min. Soxhlet extraction was carried out with 250 mL of dichloromethane:hexane (1:1, v/v) mixture in a 15-g sample for 24 h in a water bath maintained at 60 °C. The collected extracts were both cleaned up, reduced to 1 mL under nitrogen and then injected into an HPLC fluorescence. To increase the sample throughput, simultaneous MAE was performed. The obtained percentage recoveries ranged from 61 to 93 and 88-98 for MAE and SE, respectively. The optimised MAE method was validated using certified reference material. It was then applied to real sediment samples from in and around the greater Johannesburg area. The sediments from Jukskei River were found to be the most polluted while Hartbeespoort Dam sediments were found to be least polluted. The overall order of concentrations for the studied PAHs per site was as follows: Jukskei River > Kempton Park > Centurion Dams > Natalspruit River (PIT) > Hartbeespoort Dam. PMID:23108712

  14. Free MoS2 Nanoflowers Grown on Graphene by Microwave-Assisted Synthesis as Highly Efficient Non-Noble-Metal Electrocatalysts for the Hydrogen Evolution Reaction

    PubMed Central

    Cao, Jiamu; Zhang, Xuelin; Zhang, Yufeng; Zhou, Jing; Chen, Yinuo; Liu, Xiaowei

    2016-01-01

    Advanced approaches to preparing non-noble-metal electrocatalysts for the hydrogen evolution reaction (HER) are considered to be a significant breakthrough in promoting the exploration of renewable resources. In this work, a hybrid material of MoS2 nanoflowers (NFs) on reduced graphene oxide (rGO) was synthesized as a HER catalyst via an environmentally friendly, efficient approach that is also suitable for mass production. Small-sized MoS2 NFs with a diameter of ca. 190 nm and an abundance of exposed edges were prepared by a hydrothermal method and were subsequently supported on rGO by microwave-assisted synthesis. The results show that MoS2 NFs were distributed uniformly on the remarkably reduced GO and preserved the outstanding original structural features perfectly. Electrochemical tests show that the as-prepared hybrid material exhibited excellent HER activity, with a small Tafel slope of 80 mV/decade and a low overpotential of 170 mV. PMID:27556402

  15. TiO2-reduced graphene oxide nanocomposites by microwave-assisted forced hydrolysis as excellent insertion anode for Li-ion battery and capacitor

    NASA Astrophysics Data System (ADS)

    Kim, Hyun-Kyung; Mhamane, Dattakumar; Kim, Myeong-Seong; Roh, Ha-Kyung; Aravindan, Vanchiappan; Madhavi, Srinivasan; Roh, Kwang Chul; Kim, Kwang-Bum

    2016-09-01

    TiO2-reduced graphene oxide (rGO) nanocomposite (TiO2-rGO) is fabricated by microwave-assisted forced hydrolysis and examined as prospective electrode for energy storage applications, especially in Li-ion battery (LIB) and Li-ion capacitor (LIC). First, the uniformly distributed nanoscopic TiO2 particulates (∼3 nm) over rGO nanosheets is evaluated as anode in half-cell assembly to ascertain the Li-insertion behavior and found that ∼0.68 mol Li (∼227 mAh g-1) is reversible. Then, "rocking-chair" type LIB is fabricated with spinel LiMn2O4 cathode, and the LiMn2O4/TiO2-rGO assembly exhibits high capacity (∼120 mAh g-1 at 0.1 C rate), good rate capability (∼53 mAh g-1 at 1 C rate), and excellent cycleability (∼90% initial reversible capacity after 1000 cycle) as well. Similarly, the LIC is also constructed with activated carbon cathode, and such configuration delivered a maximum energy density of ∼50 Wh kg-1 with ∼82% retention after 4000 cycles. The synergistic effect of both rGO and anatase nanoparticles provides excellent energy efficiency and battery performance in different kind of Li-ion based energy storage devices.

  16. Multilayer CuO@NiO Hollow Spheres: Microwave-Assisted Metal-Organic-Framework Derivation and Highly Reversible Structure-Matched Stepwise Lithium Storage.

    PubMed

    Guo, Wenxiang; Sun, Weiwei; Wang, Yong

    2015-11-24

    A unique CuO@NiO microsphere with three-layer ball-in-ball hollow morphology is successfully synthesized by Cu-Ni bimetallic organic frameworks. The beforehand facile microwave-assisted production of the Ni organic framework sphere is used as the template to induce the morphology control of bimetallic oxides. Designed by the controlled surface cationic exchange reactions between Cu and Ni ions, there is an elemental gradient (decreased amount of CuO but increased amount of NiO) from the shell to the core of the microsphere product. This ternary metal oxide hollow structure is found to be very suitable for solving the critical volume expansion problem, which is critical for all high-capacity metal oxide electrodes for lithium ion batteries. A reversible larger-than-theoretical capacity of 1061 mAh·g(-1) can be retained after a repetitive 200 cycles without capacity fading compared to the initial cycle. These excellent electrochemical properties are ascribed to the step-by-step lithium insertion reactions induced by the matched CuO@NiO composition from the shell to the core and facilitated lithium/electron diffusion and accommodated volume change in the porous bimetallic oxides microsphere with a multiple-layer yolk-shell nanostructure. PMID:26442790

  17. Microwave assisted aqua regia extraction of thallium from sediment and coal fly ash samples and interference free determination by continuum source ETAAS after cloud point extraction.

    PubMed

    Meeravali, Noorbasha N; Madhavi, K; Kumar, Sunil Jai

    2013-01-30

    A simple cloud point extraction method is described for the separation and pre-concentration of thallium from the microwave assisted aqua regia extracts of sediment and coal fly ash samples. The method is based on the formation of extractable species of thallium and its interaction with hydrophobic solubilizing sites of Triton X-114 micelles in the presence of aqua regia and electrolyte NaCl. These interactions of micelles are used for extraction of thallium from a bulk aqueous phase into a small micelles-rich phase. The potential chloride interferences are eliminated effectively, which enabled interference free determination of thallium from aqua regia extracts using continuum source ETAAS. The parameters affecting the extraction process are optimized. Under the optimized conditions, pre-concentration factor and limit of detection are 40 and 0.2 ng g(-1), respectively. The recoveries are in the range of 95-102%. A characteristic mass, 13 pg was obtained. The accuracy of the method is verified by analyzing certified reference materials such as NIST 1633b coal fly ash, NIST 1944 marine sediment and GBW 07312 stream sediments. The results obtained are in good agreement with the certified values and method is also applied to real samples. PMID:23597907

  18. Microwave-assisted synthesis of simonkolleite nanoplatelets on nickel foam-graphene with enhanced surface area for high-performance supercapacitors.

    PubMed

    Khamlich, S; Mokrani, T; Dhlamini, M S; Mothudi, B M; Maaza, M

    2016-01-01

    Simonkolleite (Zn5(OH)8Cl2·H2O) nanoplatelets has been deposited on nickel foam-supported graphene by using an efficient microwave-assisted hydrothermal method. The three-dimensional (3D) porous microstructure of the as-fabricated nickel foam-graphene/simonkolleite (NiF-G/SimonK) composite is beneficial to electrolyte penetration and ions exchange, whereas graphene provide improved electronic conductivity. Structural and morphological characterizations confirmed the presence of highly crystalline hexagonal-shaped nanoplatelets of simonkolleite. Field emission scanning electron microscope (FE-SEM) of the NiF-G/SimonK composite revealed that the SimonK nanoplatelets were evenly distributed on the surface of NiF-G and interlaced with each other, resulting in a higher specific surface area of 35.69 m(2) g(-1) compared to SimonK deposited directly on NiF 17.2 m(2) g(-1). Electrochemical measurements demonstrated that the NiF-G/SimonK composite exhibit a high specific capacitance of 836 F g(-1) at a current density of 1 A g(-1), and excellent rate capability and cycling stability with capacitance retention of 92% after 5000 charge/discharge cycles. PMID:26397922

  19. Microwave-Assisted Synthesis of Highly-Crumpled, Few-Layered Graphene and Nitrogen-Doped Graphene for Use as High-Performance Electrodes in Capacitive Deionization

    NASA Astrophysics Data System (ADS)

    Amiri, Ahmad; Ahmadi, Goodarz; Shanbedi, Mehdi; Savari, Maryam; Kazi, S. N.; Chew, B. T.

    2015-12-01

    Capacitive deionization (CDI) is a promising procedure for removing various charged ionic species from brackish water. The performance of graphene-based material in capacitive deionization is lower than the expectation of the industry, so highly-crumpled, few-layered graphene (HCG) and highly-crumpled nitrogen-doped graphene (HCNDG) with high surface area have been introduced as promising candidates for CDI electrodes. Thus, HCG and HCNDG were prepared by exfoliation of graphite in the presence of liquid-phase, microwave-assisted methods. An industrially-scalable, cost-effective, and simple approach was employed to synthesize HCG and HCNDG, resulting in few-layered graphene and nitrogen-doped graphene with large specific surface area. Then, HCG and HCNDG were utilized for manufacturing a new class of carbon nanostructure-based electrodes for use in large-scale CDI equipment. The electrosorption results indicated that both the HCG and HCNDG have fairly large specific surface areas, indicating their huge potential for capacitive deionization applications.

  20. Determination of polycyclic aromatic hydrocarbons in coastal sediments from the Porto region (Portugal) by microwave-assisted extraction, followed by SPME and GC-MS.

    PubMed

    Rocha, Maria João; Rocha, Eduardo; Cruzeiro, Catarina; Ferreira, Paula C; Reis, Pedro A

    2011-10-01

    A simple low-cost, analytical method based on microwave-assisted extraction of sediments, followed by solid phase micro-extraction and gas chromatography mass spectrometry, was developed and validated for the quantification of sixteen polycyclic aromatic hydrocarbons (PAHs) in marine and estuarine sediment samples. The PAHs were those included in the United States Environmental Protection Agency (US EPA) priority list. Method detection limits were between 0.07 and 0.76 µg/kg dry weight (dw), which makes the current method suitable for environmental analysis. Sediments screened for PAHs from the Douro River estuary and the Porto seacoast exhibit total concentrations that ranged from 58.98 to 156.45 µg/kg dw, and from 51.98 to 54.79 µg/kg dw, respectively. The presence of almost all human carcinogenic PAHs in the analyzed areas indicate that these sediments can be considered polluted, suggesting that future monitoring programs together with an effective coastal management program must be implemented to guarantee the safe usage of the current areas for fishing and bathing. PMID:22586246