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Sample records for microwave assisted derivatization

  1. 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

  2. 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

  3. Determination of herbicides and its metabolite in soil and water samples by capillary electrophoresis-laser induced fluorescence detection using microwave-assisted derivatization.

    PubMed

    Cao, Liwei; Deng, Tao; Liang, Siliu; Tan, Xiaofang; Meng, Jianxin

    2014-01-01

    Methods were developed to determine glufosinate (GLUF), glyphosate (GLYP) and its metabolite, aminomethylphosphonic acid (AMPA) by capillary electrophoresis-laser induced fluorescence detection using 5-(4,6-dichlorotriazinylamino) fluorescein (DTAF) and fluorescein isothiocyanate (FITC) as the derivatizing reagents. To accelerate the labeling speed, a microwave-assisted derivatization method was adopted. The derivatizing reaction time was reduced to 180 and 150 s for DTAF and FITC, whose reaction time for conventional labeling was 50 min and 5 h, respectively. The optimum separation conditions for derivatives were as follows: a back ground electrolyte (BGE) of 30 mmol L(-1) sodium tetraborate containing 15 mmol L(-1) brij-35, hydrodynamic injection 15 s and a 10 kV separation voltage. Under these conditions, the LODs (S/N = 3) for DTAF derivatives were 0.32, 0.19 and 0.15 nmol L(-1) for GLUF, GLYP, and AMPA, respectively. The LODs (S/N = 3) for FITC derivatives were 2.60, 3.88 and 2.42 nmol L(-1) for GLUF, GLYP, and AMPA, respectively. The applicability of the developed method was demonstrated by the detection of the above herbicides and metabolite in water and soil samples. PMID:25007936

  4. Microwave-assisted on-line derivatization for sensitive flow injection fluorometric determination of formaldehyde in some foods.

    PubMed

    Zhao, Xiao-Qing; Zhang, Zhi-Qi

    2009-11-15

    A rapid and sensitive flow injection fluorometry has been developed for the determination of formaldehyde based on the microwave on-line accelerating its Hantzsch reaction with cyclohexane-1,3-dione. Under the optimized conditions, the fluorescent intensity is proportional to formaldehyde content in the range from 0.05 ng/mL to 2.000 microg/mL. The detection limit (S/N=3) is 0.02 ng/mL and the analytical frequency is 28 injections per hour. The relative standard deviations are 2.2% and 3.1% for eleven injections of 0.100 and 0.001 microg/mL of formaldehyde, respectively. With the assistance of microwave irradiation, a best sensitive fluorometry was established for the determination of formaldehyde at a high analytical frequency. This method was successfully applied to food analysis without requiring any sample pretreatment, and the determination results were correlated well with those obtained by the standard method with a sample pretreatment of steam distillation. PMID:19782221

  5. 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

  6. Dual ultrasonic-assisted dispersive liquid-liquid microextraction coupled with microwave-assisted derivatization for simultaneous determination of 20(S)-protopanaxadiol and 20(S)-protopanaxatriol by ultra high performance liquid chromatography-tandem mass spectrometry.

    PubMed

    Zhao, Xian-En; Lv, Tao; Zhu, Shuyun; Qu, Fei; Chen, Guang; He, Yongrui; Wei, Na; Li, Guoliang; Xia, Lian; Sun, Zhiwei; Zhang, Shijuan; You, Jinmao; Liu, Shu; Liu, Zhiqiang; Sun, Jing; Liu, Shuying

    2016-03-11

    This paper, for the first time, reported a speedy hyphenated technique of low toxic dual ultrasonic-assisted dispersive liquid-liquid microextraction (dual-UADLLME) coupled with microwave-assisted derivatization (MAD) for the simultaneous determination of 20(S)-protopanaxadiol (PPD) and 20(S)-protopanaxatriol (PPT). The developed method was based on ultra high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) detection using multiple-reaction monitoring (MRM) mode. A mass spectrometry sensitizing reagent, 4'-carboxy-substituted rosamine (CSR) with high reaction activity and ionization efficiency was synthesized and firstly used as derivatization reagent. Parameters of dual-UADLLME, MAD and UHPLC-MS/MS conditions were all optimized in detail. Low toxic brominated solvents were used as extractant instead of traditional chlorinated solvents. Satisfactory linearity, recovery, repeatability, accuracy and precision, absence of matrix effect and extremely low limits of detection (LODs, 0.010 and 0.015ng/mL for PPD and PPT, respectively) were achieved. The main advantages were rapid, sensitive and environmentally friendly, and exhibited high selectivity, accuracy and good matrix effect results. The proposed method was successfully applied to pharmacokinetics of PPD and PPT in rat plasma. PMID:26877173

  7. Development of C18-functionalized magnetic silica nanoparticles as sample preparation technique for the determination of ergosterol in cigarettes by microwave-assisted derivatization and gas chromatography/mass spectrometry.

    PubMed

    Sha, Yunfei; Deng, Chunhui; Liu, Baizhan

    2008-07-11

    Ergosterol is one of the important precursors of tumorigenic polynuclear aromatic hydrocarbons. A large amount of ergosterol is present in mildewy cigarettes, which derives from fungal contaminations. In this paper, a novel approach based on C(18)-functionalized magnetic silica nanoparticles (C(18)-f-MS NPs) coupled with microwave-assisted derivatization and gas chromatography/mass spectrometry (GC/MS) was developed for the rapid enrichment and determination of ergosterol in cigarettes. Due to that, microwave-assisted derivatization requires very short time (several minutes), and the extraction and concentration of ergosterol become the key step in the sample preparation process. In this study, the prepared C(18)-f-MS NPs with its unique properties (high surface area and strong magnetism) provided an efficient way for extraction and concentration of ergosterol in the samples. Additionally, the analyte of ergosterol adsorbed with C(18)-f-MS NPs in cigarettes can be simply and rapidly isolated (only about 2s) through placing a strong magnet on the bottom of container. In this work, different parameters such as added amounts of C(18)-f-MS NPs, extraction temperature, and extraction time were optimized to enhance the extraction efficiency. Method validations (linear range, detection limit, precision, and recovery) were also studied. The results obtained by the optimal conditions showed that the proposed method based on C(18)-f-MS NPs was a simple, high efficient, and had a rapid approach for the enrichment of ergosterol in cigarettes and was successfully applied to the analysis of ergosterol in normal and mildewy cigarettes followed by microwave-assisted derivatization and GC/MS. PMID:18533171

  8. Microwave-accelerated derivatization prior to GC-MS determination of sex hormones.

    PubMed

    Xu, Xu; Zhao, Xin; Zhang, Yupu; Li, Dan; Su, Rui; Yang, Qiuling; Li, Xueyuan; Zhang, Huihui; Zhang, Hanqi; Wang, Ziming

    2011-06-01

    A new microwave-accelerated derivatization method was developed for rapid determination of 13 natural sex hormones in feeds. Sex hormones were isolated from the sample matrix by ultrasonic extraction, followed by solid-phase extraction, derivatized under microwave irradiation, and then analyzed directly by gas chromatography-mass spectrometry (GC-MS) in selective ion monitoring (SIM) mode. The key parameters affecting derivatization efficiency, including microwave irradiation time, microwave power, and reaction solvent were studied. Under microwave power of 360 W and microwave irradiation for 3 min, 13 natural sex hormones were simultaneously derivatized using heptafluorobutyric acid anhydride (HFBA) as derivatization reagent. This method was applied to the determination of 13 natural sex hormones in different feed samples, and the obtained results were compared with those obtained by the traditional thermal derivatization. The recoveries from 58.1 to 111% were obtained at sex hormone concentrations of 10-300 μg/kg with RSDs ≤12.0%. The results showed that the proposed method was fast, simple, efficient and can be applied to the determination of 13 natural sex hormones in different feed samples. PMID:21567948

  9. 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...

  10. Ultrasound-assisted extraction and in situ derivatization.

    PubMed

    Delgado-Povedano, M M; Luque de Castro, M D

    2013-06-28

    Ultrasound (US) is a type of energy of growing interest for analytical chemists. The favorable effect of US on mass transfer between two phases in the same or different state has been widely demonstrated as did the number of chemical reactions accelerated/improved under ultrasonic influence. The action of US on both mass transfer and chemical reaction developed in a simultaneous manner results in a synergistic effect as a consequence of the "removal" of the target extracted species by conversion into a product. Both US-assisted solid-liquid extraction and liquid-liquid extraction have been developed with in situ derivatization at the meso- and microscale and the advantages involved in their implementation are discussed in this article. PMID:23639123

  11. Multiwalled carbon nanotubes as a solid-phase extraction adsorbent for the determination of three barbiturates in pork by ion trap gas chromatography-tandem mass spectrometry (GC/MS/MS) following microwave assisted derivatization.

    PubMed

    Zhao, Haixiang; Wang, Liping; Qiu, Yueming; Zhou, Zhiqiang; Zhong, Weike; Li, Xiang

    2007-03-14

    A new method was developed for the rapid screening and confirmation analysis of barbital, amobarbital and phenobarbital residues in pork by gas chromatography-tandem mass spectrometry (GC/MS/MS) with ion trap MSD. The residual barbiturates in pork were extracted by ultrasonic extraction, cleaned up on a multiwalled carbon nanotubes (MWCNTs) packed solid phase extraction (SPE) cartridge and applied acetone-ethyl acetate (3:7, v/v) mixture as eluting solvent and derivatized with CH3I under microwave irradiation. The methylated barbiturates were separated on a TR-5MS capillary column and detected with an ion trap mass detector. Electron impact ion source (EI) operating MS/MS mode was adopted for identification and external standard method was employed for quantification. One precursor ion m/z 169 was selected for analysis of barbital and amobarbital and m/z 232 was selected for phenobarbital. The product ions were obtained under 1.0 V excitation voltage. Good linearities (linear coefficient R > 0.99) were obtained at the range of 0.5-50 microg kg(-1). Limit of detection (LOD) of barbital was 0.2 microg kg(-1) and that of amobarbital and phenobarbital were both 0.1 microg kg(-1) (S/N > or = 3). Limit of quantification (LOQ) was 0.5 microg kg(-1) for three barbiturates (S/N > or = 10). Satisfying recoveries ranging from 75% to 96% of the three barbiturates spiked in pork were obtained, with relative standard deviations (R.S.D.) in the range of 2.1-7.8%. PMID:17386740

  12. Gas chromatography-mass spectrometry determination of pharmacologically active substances in urine and blood samples by use of a continuous solid-phase extraction system and microwave-assisted derivatization.

    PubMed

    Azzouz, Abdelmonaim; Ballesteros, Evaristo

    2012-04-01

    A sensitive method based on gas chromatography-mass spectrometry was used to determine 22 pharmacologically active substances (frequently used in the treatment of human and animal's diseases) including analgesics, antibacterials, anti-epileptics, antiseptics, β-blockers, hormones, lipid regulators and non-steroidal anti-inflammatories in blood and urine samples. Samples were subjected to continuous solid-phase extraction in a sorbent column (Oasis HLB), and then the target analytes were eluted with ethyl acetate and derivatized in a household microwave oven at 350 W for 3 min. Finally, these products were determined in a gas chromatograph-mass spectrometer equipped with a DB-5 fused silica capillary column. The analyte detection limits thus obtained ranged from 0.2 to 1.3 ng L⁻¹ for urine samples and 0.8-5.6 ng L⁻¹ for blood samples. Recoveries from both blood and urine ranged from 85 to 102%, and within-day and between-day relative standard deviations were all less than 7.5%. The proposed method offers advantages in reduction of the exposure danger to toxic solvents used in conventional sample pretreatment, simplicity of the extraction processes, rapidity, and sensitivity enhancement. The method was successfully used to quantify pharmacologically active substances in human and animal (lamb, veal and pig) blood and urine. The hormones estrone and 17β-estradiol were detected in virtually all samples, and so were other analytes such as acetylsalicylic acid, ibuprofen, ketoprofen and triclosan in human samples, and florfenicol, pyrimethamine and phenylbutazone in animal samples. PMID:22391330

  13. Microwave-assisted synthesis and reversed-phase high-performance liquid chromatographic separation of diastereomers of (R,S)-baclofen using ten chiral derivatizing reagents designed from trichloro-s-triazine.

    PubMed

    Bhushan, Ravi; Dixit, Shuchi

    2010-10-01

    Four dichloro-s-triazine (DCT) and five monochloro-s-triazine (MCT) chiral derivatizing reagents (CDRs) were synthesized by incorporating amino acid amide moieties as chiral auxiliaries in trichloro-s-triazine and its 6-methoxy derivative, respectively. Another MCT reagent was synthesized by substitution of two chlorine atoms with two different amino acid amides in trichloro-s-triazine. These reagents were used for synthesis of diastereomers of (R,S)-baclofen under microwave irradiation (i.e. 60 s at 85% power using DCT reagents and 90 s at 85% power using MCT reagents). The diastereomers were separated on a reversed-phase C18 column using mixtures of methanol with aqueous trifluoroacetic acid (TFA) with UV detection at 230 nm. The separation behavior in terms of retention times and resolutions obtained for the two sets of diastereomers prepared with DCT and MCT reagents were compared among themselves and among the two groups. Longer retention times and better resolutions were observed with DCT reagents as compared to MCT reagents. The calibration curves were linear for both (R)- and (S)-baclofen in the concentration range 50-500 μg/ml. The average regression was 0.999 for both (R)- and (S)-baclofen. The RSD for (R)-baclofen was 0.40-0.86% for intra-day precision and 0.60-1.40% for inter-day precision and these values for (S)-baclofen were 0.52-0.75% and 0.64-1.32%, respectively. The recovery was 97.2-98.9% for (R)- and 97.0-98.9% for (S)-baclofen. The limit of detection was 1.63 ng/ml and 1.52 ng/ml for (R)- and (S)-baclofen, respectively. PMID:20817188

  14. Plasma-assisted microwave processing of materials

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin (Inventor); Ylin, Tzu-yuan (Inventor); Jackson, Henry (Inventor)

    1998-01-01

    A microwave plasma assisted method and system for heating and joining materials. The invention uses a microwave induced plasma to controllably preheat workpiece materials that are poorly microwave absorbing. The plasma preheats the workpiece to a temperature that improves the materials' ability to absorb microwave energy. The plasma is extinguished and microwave energy is able to volumetrically heat the workpiece. Localized heating of good microwave absorbing materials is done by shielding certain parts of the workpiece and igniting the plasma in the areas not shielded. Microwave induced plasma is also used to induce self-propagating high temperature synthesis (SHS) process for the joining of materials. Preferably, a microwave induced plasma preheats the material and then microwave energy ignites the center of the material, thereby causing a high temperature spherical wave front from the center outward.

  15. 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.

  16. 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.

  17. Ion-beam and microwave-stimulated functionalization and derivatization of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Makala, Raghuveer S.

    Derivatizing carbon nanotubes (CNTs) with other low-dimensional nanostructures is of widespread interest for creating CNT-based nanocomposites and devices. Conventional routes based on wet-chemical oxidation or hydrophobic adsorption do not allow premeditated control over the location or spatial extent of functionalization. Moreover, aggressive oxidative treatments and agitation in corrosive environments lead to CNT shortening, damage, and incorporation of excess impurity concentrations. Thus, it is imperative to explore and develop alternative functionalization methods to overcome these shortcomings. The work presented in this thesis outlines two such methodologies: one based on focused ion irradiation for siteselective functionalization and the other that employs microwave-stimulation for mild, yet rapid and homogenous CNT functionalization. The utility of 10 and 30 kcV Ga+ focused ion beams (FIB) to thin, slice, weld, and alter the structure and composition at precise locations along the CNT axis is presented. This strategy of harnessing ion-beam-induced defect generation and doping is attractive for modulating chemical and electrical properties along the CNT length, and fabricate CNT-based heterostructures and networks. A novel approach that utilizes focused ion irradiation to site-selectively derivatize preselected segments of CNTs with controlled micro-/nano-scale lateral spatial resolution is demonstrated. Irradiation followed by air-exposure results in functionalized CNT segments ranging from the nanoscopic to the macroscopic scale. The functional moieties are utilized to site-selectively anchor Au nanoparticles, fluorescent nanospheres, an amino acid---lysine, a charge-transfer metalloprotein---azurin, and a photoactive protein---bacteriorhodopsin by means of electrostatic or covalent interactions. This approach is versatile and can be extended to obtaining other molecular moieties and derivatives opening up possibilities for building new types of nano

  18. 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...

  19. Microwave-assisted cobinamide synthesis.

    PubMed

    O Proinsias, Keith; Karczewski, Maksymilian; Zieleniewska, Anna; Gryko, Dorota

    2014-08-15

    We present a new method for the preparation of cobinamide (CN)2Cbi, a vitamin B12 precursor, that should allow its broader utility. Treatment of vitamin B12 with only NaCN and heating in a microwave reactor affords (CN)2Cbi as the sole product. The purification procedure was greatly simplified, allowing for easy isolation of the product in 94% yield. The use of microwave heating proved beneficial also for (CN)2Cbi(c-lactone) synthesis. Treatment of (CN)2Cbi with triethanolamine led to (CN)2Cbi(c-lactam). PMID:25058239

  20. Microwave assisted hard rock cutting

    DOEpatents

    Lindroth, David P.; Morrell, Roger J.; Blair, James R.

    1991-01-01

    An apparatus for the sequential fracturing and cutting of subsurface volume of hard rock (102) in the strata (101) of a mining environment (100) by subjecting the volume of rock to a beam (25) of microwave energy to fracture the subsurface volume of rock by differential expansion; and , then bringing the cutting edge (52) of a piece of conventional mining machinery (50) into contact with the fractured rock (102).

  1. 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...

  2. 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.

  3. Microwave assisted chemical vapor infiltration

    SciTech Connect

    Devlin, D.J.

    1993-12-31

    The purpose of this program is to develop a new process for the fabrication of ceramic matrix composites by chemical vapor infiltration. This period has been devoted in part to the exploration of material systems suitable for MACVI processing. A number of potential processing schemes are possible using combinations of absorbing and transparent material as composite components. This includes the use of an absorbing preform (nicalon fiber) combined with a transparent matrix (silicon nitride). Composites 5 cm in diameter by 1 cm. thick have been fabricated to densities of 65% theoretical. Processing times for these materials are under 20 hours. Higher densities will require additional microwave power now possible with the new reactor. The most effective MACVI scheme will involve the use of a transparent fiber with an absorbing matrix. The hot spot will be initiated by appropriate treatment of the central region of the preform. To this end alumna fibers with pretreatments to control thermal gradients has been explored. Nextel 610 fibers have been effectively pretreated carbon coating resulting in preferential heating in the interior of the preform. Possible matrix materials include siliconized silicon carbide, doped silicon carbide, alumna and zirconia. A patent for MACVI has been issued 10/19/93.

  4. 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.

  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. Phase Transformation of VO2 Nanoparticles Assisted by Microwave Heating

    PubMed Central

    Sikong, Lek.

    2014-01-01

    The microwave assisted synthesis nowadays attracts a great deal of attention. Monoclinic phase VO2 (M) was prepared from NH4VO3 and H2C2O4 · 2H2O by a rapid microwave assisted technique. The synthesis parameters, microwave irradiation time, microwave power, and calcinations temperature were systematically varied and their influences on the structure and morphology were evaluated. The microwave power level has been carried out in range 180–600 W. TEM analysis demonstrated nanosized samples. The structural and morphological properties were measured using XRD, TEM, and thermal analyses. The variations of vanadium phase led to thermochromic properties. PMID:24688438

  7. [Applications of multi-micro-volume pressure-assisted derivatization reaction device for analysis of polar heterocyclic aromatic amines by gas chromatography-mass spectrometry].

    PubMed

    Wang, Yiru; Chen, Fangxiang; Shi, Yamei; Tan, Connieal; Chen, Xi

    2013-01-01

    A multi-micro-volume pressure-assisted derivatization reaction device has been designed and made for the silylation derivatization of polar heterocyclic aromatic amines by N-(tert-butyldimethylsilyl )-N-methyl-trifluoroacetamide (MTBSTFA) with 1% catalyst tert-butyldimethylchlorosilane (TBDMCS) at a high temperature. The tert-butyldimethylsilyl derivatives then could be automatically analyzed by gas chromatography-mass spectrometry. Using the pressure-assisted device, the silylation reaction may occur at a temperature higher than the boiling points of the reagents, and several micro-volume samples can be simultaneously pretreated in the same device to shorten the sample-preparation time and to improve the repeatability. The derivatization conditions including the headspace volume of the vial, the evaporative surface area of the reagent, derivatization temperature and time have been discussed for the use of the pressure-assisted device. The experimental results proved that the device is an effective way for the simultaneous derivatization of several micro-volume samples at a high temperature. Compared with a common device, the derivative amounts were obviously increased when using the pressure-assisted device at 90 degrees C. Quantitative derivatization can be achieved even at 150 degrees C while there was no common device could be applied at such a high temperature due to the heavy losses of reagents by evaporation. However, no obviously higher reaction speed has been observed in such a circumstance with a higher temperature and a higher pressure using the pressure-assisted device. PMID:23667982

  8. 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

  9. Microwave assisted centrifuge and related methods

    DOEpatents

    Meikrantz, David H [Idaho Falls, ID

    2010-08-17

    Centrifuge samples may be exposed to microwave energy to heat the samples during centrifugation and to promote separation of the different components or constituents of the samples using a centrifuge device configured for generating microwave energy and directing the microwave energy at a sample located in the centrifuge.

  10. 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

  11. Atmospheric pressure microwave assisted heterogeneous catalytic reactions.

    PubMed

    Chemat-Djenni, Zoubida; Hamada, Boudjema; Chemat, Farid

    2007-01-01

    The purpose of the study was to investigate microwave selective heating phenomena and their impact on heterogeneous chemical reactions. We also present a tool which will help microwave chemists to answer to such questions as "My reaction yields 90% after 7 days at reflux; is it possible to obtain the same yield after a few minutes under microwaves?" and to have an approximation of their reactions when conducted under microwaves with different heterogeneous procedures. This model predicting reaction kinetics and yields under microwave heating is based on the Arrhenius equation, in agreement with experimental data and procedures. PMID:17909495

  12. 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…

  13. Microwave-assisted 'greener' synthesis of organics and nanomaterials

    EPA Science Inventory

    Microwave selective heating techniques in conjunction with 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 ...

  14. 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.

  15. 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

  16. [Rapid determination of fatty acids in Ranunculus ternatus Thunb by microwave-ultrasonic synergistic one-step extraction-derivatization and gas chromatography-mass spectrometry].

    PubMed

    Zhan, Hanying; Liu, Ruilin; Wang, Dejin; Yuan, Jing; Xu, Shengjie; Zhang, Zhiqi

    2013-03-01

    A rapid and simple microwave-ultrasonic synergistic one-step extraction-derivatization (MUED) method and gas chromatography-mass spectrometry was established for the determination of low content fatty acids (FAs) profile in Ranunculus ternatus Thunb. The critical experimental parameters for MUED method were optimized with response surface methodology by taking the chromatographic peak areas of total FAs as a major response index. The best technological parameters were determined as 5.0 g of Ranunculus ternatus Thunb. powder, 50.0 mL of n-hexane, 500 W of microwave power, 50 degree C of reaction temperature, 0.30 g of catalyst (KOH), 4.0 mL of derivatization reagent (methanol) and the time of extraction-derivatization of 8 min. The contents of individual FAs were quantified by internal standard method. The results showed that the chromatographic peak areas of the total FAs and the total unsaturated FAs contents obtained with MUED were (3.327 +/- 0.023) x 10(7) (n = 3) and (13.59 +/- 0.30) mg/g (n = 3) respectively. They were markedly higher than those obtained by the conventional method which were (2.410 +/- 0.036) x 10(7) (n = 3) and (12.05 +/- 0.34) mg/g (n = 3) respectively. The MUED method simplified the complicated sample handling steps, shortened the sample preparation time, reduced the cost of analysis, and improved the extraction and derivatization efficiency of the lipids, especially weakened the oxidization and decomposition of the unsaturated FAs. The simplicity, speed and practicability suggest the proposed method has significant potential for the determination of lowcontent FAs in herbal medicines. PMID:23785996

  17. Simultaneous in situ derivatization and ultrasound-assisted dispersive magnetic solid phase extraction for thiamine determination by spectrofluorimetry.

    PubMed

    Tarigh, Ghazale Daneshvar; Shemirani, Farzaneh

    2014-06-01

    A simple and rapid method for the simultaneous in situ derivatizaion, preconcentration and extraction of thiamine (vitamin B1) as a model analyte was developed by a novel quantitative method, namely ultrasound-assisted dispersive magnetic solid phase extraction spectrofluorimetry (USA-DMSPE-FL) from different real samples. This method consists of sample preparation, in situ derivatization, exhaustive extraction and clean up by a single process. High extraction efficiency and in situ derivatization in a short period of time is the main advantages of this procedure. For this purpose, the reusable magnetic multi-wall carbon nanotube (MMWCNT) nanocomposite was used as an adsorbent for preconcentration and determination of thiamine. Thiamine was, simultaneously, in situ derivatized as thiochrome by potassium hexacyanoferrate (III) and adsorbed on MMWCNT in an ultrasonic water bath. The MMWCNTs were then collected using an external magnetic field. Subsequently, the extracted thiochrome was washed from the surface of the adsorbent and determined by spectrofluorimetry. The developed method, which has been analytically characterized under its optimal operating conditions, allows the detection of the analyte in the samples with method detection limits of 0.37 µg L(-1). The repeatability of the method, expressed as the relative standard deviation (RSD, n=6), varies between 2.0% and 4.8% in different real samples, while the enhancement factor is 197. The proposed procedure has been applied for the determination of thiamine in biological (serum and urine), pharmaceutical (multivitamin tablet and B complex syrup) and foodstuff samples (cereal, wheat flour, banana and honey) with the good recoveries in the range from 90% to 105%. PMID:24725866

  18. Microwave-assisted FLP-catalyzed hydrogenations.

    PubMed

    Tussing, S; Paradies, J

    2016-03-30

    FLP-catalyzed hydrogenations of 15 substrates were compared using microwave irradiation and conventional heating. The direct comparison revealed that a rate acceleration of up to 2.5 was achieved in the presence of microwaves. This heating method is particularly promising for the hydrogenation of nitrogen-containing heterocycles. Acridine, quinines and especially 1-methyl indole were reduced very efficiently under mild conditions and only 4 bar hydrogen pressure in high yields. PMID:26580129

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. Determination of "new psychoactive substances" in postmortem matrices using microwave derivatization and gas chromatography-mass spectrometry.

    PubMed

    Margalho, Cláudia; Castanheira, Alice; Real, Francisco Corte; Gallardo, Eugenia; López-Rivadulla, Manuel

    2016-05-01

    Despite worldwide efforts aiming to ban the marketing and subsequent abuse of psychoactive substances such as synthetic cathinones and phenethylamines, there has been an alarming growth of both in recent years. Different compounds similar to those already existing are continuously appearing in the market in order to circumvent the legislation. An analytical methodology has been validated for qualitative and quantitative determinations of D-cathine (D-norpseudoehedrine), ephedrine, methcathinone, 1-(4-methoxyphenyl)-propan-2-amine (PMA), mephedrone, methedrone, 2,5-dimethoxy-4-methylamphetamine (DOM), 4-bromo-2,5-dimethoxyamphetamine (DOB), 2,5-dimethoxyphenethylamine (2C-H), 4-bromo-2,5-dimethoxyphenethylamine (2C-B), 4-iodo-2,5-dimethoxyphenethylamine (2C-I), 2-[2,5-dimethoxy-4-(ethylthio)phenyl]ethanamine (2C-T-2), 2,5-dimethoxy-4-isopropylthiophenethylamine (2C-T-4) and 2-[2,5-dimethoxy-4-(propylthio)phenyl]ethanamine (2C-T-7), in low volumes of vitreous humor (100 μL), pericardial fluid (250 μL) and whole blood (250 μL), using deutered amphetamine, ephedrine and mephedrone as internal standards. The validation parameters included selectivity, linearity and limits of detection and quantification, intra- and interday precision and trueness, recovery and stability. The method included mixed-mode solid phase extraction, followed by microwave fast derivatization and analysis by gas chromatography-mass spectrometry operated in selected ion monitoring mode. The procedure was linear between 5 and 600 ng/mL, with determination coefficients higher than 0.99 for all analytes. Intra- and interday precision ranged from 0.1 to 13.6%, while accuracy variability was within 80-120% interval from the nominal concentration at all studied levels. The extraction efficiencies ranged from 76.6 to 112.8%. Stability was considered acceptable for all compounds in the studied matrices. The developed assay was applied to authentic samples of the Laboratory of Chemistry and Forensic

  4. Microwave Assisted Wolff-Kishner Reduction Reaction

    NASA Astrophysics Data System (ADS)

    Parquet, Eric; Lin, Qun

    1997-10-01

    A Wolff-Kishner reduction of a carbonyl group was carried out in a household microwave oven. Isatin was first converted to the hydrazone with 55% hydrazine and ethylene glycol by irradiation in the microwave oven at medium power for 30 seconds. Then, isatin 3-hydrazone was mixed with ethylene glycol and potassium hydroxide and irradiated in the microwave oven for only 10 seconds. After simple work-up and recrystallization, oxindole was obtained in a yield of 32.4%. The two step syntheses described here offer several advantages: (1) very short reaction time with no need for special microscale glassware, (2) mild experimental conditions (hot oil baths and heating mantles are not required), (3) the reagents are easy to handle (students do not need to prepare sodium ethoxide from sodium metal and absolute ethanol).

  5. Microwave-assisted regeneration of activated carbon.

    PubMed

    Foo, K Y; Hameed, B H

    2012-09-01

    Microwave heating was used in the regeneration of methylene blue-loaded activated carbons produced from fibers (PFAC), empty fruit bunches (EFBAC) and shell (PSAC) of oil palm. The dye-loaded carbons were treated in a modified conventional microwave oven operated at 2450 MHz and irradiation time of 2, 3 and 5 min. The virgin properties of the origin and regenerated activated carbons were characterized by pore structural analysis and nitrogen adsorption isotherm. The surface chemistry was examined by zeta potential measurement and determination of surface acidity/basicity, while the adsorptive property was quantified using methylene blue (MB). Microwave irradiation preserved the pore structure, original active sites and adsorption capacity of the regenerated activated carbons. The carbon yield and the monolayer adsorption capacities for MB were maintained at 68.35-82.84% and 154.65-195.22 mg/g, even after five adsorption-regeneration cycles. The findings revealed the potential of microwave heating for regeneration of spent activated carbons. PMID:22728787

  6. 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.

  7. 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...

  8. Microwave-Assisted Green Synthesis of Silver Nanostructures

    EPA Science Inventory

    This account summarizes a microwave (MW)-assisted synthetic approach for producing silver nanostructures. The rapid and in-core MW heating has received considerable attention as a promising new method for the one-pot synthesis of metallic nanostructures in solutions. Conceptually...

  9. Microwave-Assisted Synthesis – Catalytic Applications in Aqueous Media

    EPA Science Inventory

    The development of sustainable methods directed towards the synthesis of molecules is due to the heightened awareness and recognition of alternative eco-friendly and economical protocols that have minimum impact on environment. Among others, microwave (MW)-assisted methodology ha...

  10. Microwave-assisted synthesis using ionic liquids.

    PubMed

    Martínez-Palou, Rafael

    2010-02-01

    The research and application of green chemistry principles have led to the development of cleaner processes. In this sense, during the present century an ever-growing number of studies have been published describing the use of ionic liquids (ILs) as solvents, catalysts, or templates to develop more environmentally friendly and efficient chemical transformations for their use in both academia and industry. The conjugation of ILs and microwave irradiation as a non-conventional heating source has shown evident advantages when compared to conventional synthetic procedures for the generation of fast, efficient, and environmental friendly synthetic methodologies. This review focuses on the advances in the use of ILs in organic, polymers and materials syntheses under MW irradiation conditions. PMID:19507045

  11. 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

  12. 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

  13. On-Tissue Derivatization via Electrospray Deposition for Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging of Endogenous Fatty Acids in Rat Brain Tissues.

    PubMed

    Wu, Qian; Comi, Troy J; Li, Bin; Rubakhin, Stanislav S; Sweedler, Jonathan V

    2016-06-01

    Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) is used for the multiplex detection and characterization of diverse analytes over a wide mass range directly from tissues. However, analyte coverage with MALDI MSI is typically limited to the more abundant compounds, which have m/z values that are distinct from MALDI matrix-related ions. On-tissue analyte derivatization addresses these issues by selectively tagging functional groups specific to a class of analytes, while simultaneously changing their molecular masses and improving their desorption and ionization efficiency. We evaluated electrospray deposition of liquid-phase derivatization agents as a means of on-tissue analyte derivatization using 2-picolylamine; we were able to detect a range of endogenous fatty acids with MALDI MSI. When compared with airbrush application, electrospray led to a 3-fold improvement in detection limits and decreased analyte delocalization. Six fatty acids were detected and visualized from rat cerebrum tissue using a MALDI MSI instrument operating in positive mode. MALDI MSI of the hippocampal area allowed targeted fatty acid analysis of the dentate gyrus granule cell layer and the CA1 pyramidal layer with a 20-μm pixel width, without degrading the localization of other lipids during liquid-phase analyte derivatization. PMID:27181709

  14. Constant pressure-assisted head-column field-amplified sample injection in combination with in-capillary derivatization for enhancing the sensitivity of capillary electrophoresis.

    PubMed

    Yan, Na; Zhou, Lei; Zhu, Zaifang; Zhang, Huige; Zhou, Ximin; Chen, Xingguo

    2009-05-15

    In this work, a novel method combining constant pressure-assisted head-column field-amplified sample injection (PA-HC-FASI) with in-capillary derivatization was developed for enhancing the sensitivity of capillary electrophoresis. PA-HC-FASI uses an appropriate positive pressure to counterbalance the electroosmotic flow in the capillary column during electrokinetic injection, while taking advantage of the field amplification in the sample matrix and the water of the "head column". Accordingly, the analytes were stacked at the stationary boundary between water and background electrolyte. After 600s PA-HC-FASI, 4-fluoro-7-nitro-2,1,3-benzoxadiazole as derivatization reagent was injected, followed by an electrokinetic step (5kV, 45s) to enhance the mixing efficiency of analytes and reagent plugs. Standing a specified time of 10min for derivatization reaction under 35 degrees C, then the capillary temperature was cooled to 25 degrees C and the derivatives were immediately separated and determined under 25 degrees C. By investigating the variables of the presented approach in detail, on-line preconcentration, derivatization and separation could be automatically operated in one run and required no modification of current CE commercial instrument. Moreover, the sensitivity enhancement factor of 520 and 800 together with the detection limits of 16.32 and 6.34pg/mL was achieved for model compounds: glufosinate and aminomethylphosphonic acid, demonstrating the high detection sensitivity of the presented method. PMID:19342058

  15. On-Tissue Derivatization via Electrospray Deposition for Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging of Endogenous Fatty Acids in Rat Brain Tissues

    PubMed Central

    2016-01-01

    Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) is used for the multiplex detection and characterization of diverse analytes over a wide mass range directly from tissues. However, analyte coverage with MALDI MSI is typically limited to the more abundant compounds, which have m/z values that are distinct from MALDI matrix-related ions. On-tissue analyte derivatization addresses these issues by selectively tagging functional groups specific to a class of analytes, while simultaneously changing their molecular masses and improving their desorption and ionization efficiency. We evaluated electrospray deposition of liquid-phase derivatization agents as a means of on-tissue analyte derivatization using 2-picolylamine; we were able to detect a range of endogenous fatty acids with MALDI MSI. When compared with airbrush application, electrospray led to a 3-fold improvement in detection limits and decreased analyte delocalization. Six fatty acids were detected and visualized from rat cerebrum tissue using a MALDI MSI instrument operating in positive mode. MALDI MSI of the hippocampal area allowed targeted fatty acid analysis of the dentate gyrus granule cell layer and the CA1 pyramidal layer with a 20-μm pixel width, without degrading the localization of other lipids during liquid-phase analyte derivatization. PMID:27181709

  16. Microwave Assisted 2D Materials Exfoliation

    NASA Astrophysics Data System (ADS)

    Wang, Yanbin

    Two-dimensional materials have emerged as extremely important materials with applications ranging from energy and environmental science to electronics and biology. Here we report our discovery of a universal, ultrafast, green, solvo-thermal technology for producing excellent-quality, few-layered nanosheets in liquid phase from well-known 2D materials such as such hexagonal boron nitride (h-BN), graphite, and MoS2. We start by mixing the uniform bulk-layered material with a common organic solvent that matches its surface energy to reduce the van der Waals attractive interactions between the layers; next, the solutions are heated in a commercial microwave oven to overcome the energy barrier between bulk and few-layers states. We discovered the minutes-long rapid exfoliation process is highly temperature dependent, which requires precise thermal management to obtain high-quality inks. We hypothesize a possible mechanism of this proposed solvo-thermal process; our theory confirms the basis of this novel technique for exfoliation of high-quality, layered 2D materials by using an as yet unknown role of the solvent.

  17. 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

  18. Microwave heating for the rapid generation of glycosylhydrazides.

    PubMed

    Mallevre, F; Roget, A; Minon, T; Kervella, Y; Ropartz, D; Ralet, M C; Canut, H; Livache, T

    2013-07-17

    Conditions for simple derivatization of reducing carbohydrates via adipic acid dihydrazide microwave-assisted condensation are described. We demonstrate with a diverse set of oligo- and polysaccharides how to improve a restrictive and labor intensive conventional conjugation protocol by using microwave-assisted chemistry. We show that 5 min of microwave heating in basic or acidic conditions are adequate to generate, in increased yields, intact and functional glycosylhydrazides, whereas hours to days and acidic conditions are generally required under conventional methods. PMID:23731134

  19. 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

  20. 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.

  1. 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

  2. Determination of alternative preservatives in cosmetic products by chromophoric derivatization followed by vortex-assisted liquid-liquid semimicroextraction and liquid chromatography.

    PubMed

    Miralles, Pablo; Vrouvaki, Ilianna; Chisvert, Alberto; Salvador, Amparo

    2016-07-01

    An analytical method for the simultaneous determination of phenethyl alcohol, methylpropanediol, phenylpropanol, caprylyl glycol, and ethylhexylglycerin, which are used as alternative preservatives in cosmetic products, has been developed. The method is based on liquid chromatography with UV spectrophotometric detection after chromophoric derivatization with benzoyl chloride and vortex-assisted liquid-liquid semimicroextraction. Different chromatographic parameters, derivatization conditions, and sample preparation variables were studied. Under optimized conditions, the limits of detection values for the analytes ranged from 0.02 to 0.06µgmL(-1). The method was validated with good recovery values (84-118%) and precision values (3.9-9.5%). It was successfully applied to 10 commercially available cosmetic samples. The good analytical features of the proposed method besides of its environmentally-friendly characteristics, make it useful to carry out the quality control of cosmetic products containing the target compounds as preservative agents. PMID:27154641

  3. 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

  4. 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

  5. Dynamic ultrasound-assisted extraction coupled on-line with solid support derivatization and high-performance liquid chromatography for the determination of formaldehyde in textiles.

    PubMed

    Chen, Ligang; Jin, Haiyan; Wang, Liguang; Sun, Lei; Xu, Haoyan; Ding, Lan; Yu, Aimin; Zhang, Hanqi

    2008-05-23

    An on-line method was developed for the extraction, derivatization and determination of formaldehyde in textile samples. Formaldehyde was first extracted with water by ultrasound assisted, and directly introduced into a derivatization column which was packed with a moderately sulfonated cation-exchange resin. The resin used as solid support for the derivatization was charged with 2,4-dinitrophenylhydrazine (DNPH) previously. The formaldehyde DNPH derivative was eluted with the chromatographic mobile phase into an analytical column for the separation, and then monitored by UV detector. The maximum extraction yield was achieved when the extraction vessel was located at 10mm from the ultrasonic source and 10mg textile sample was extracted with 5mL pure water at a flow rate of 1.0mLmin(-1) at 50 degrees C. The detection limit of the proposed method was 0.06mgkg(-1). This method was applied to the determination of formaldehyde in different textile samples, and compared with the state standard method (off-line spectrophotometry) used in China. The similar contents of formaldehyde were obtained for most samples by the two methods, but little higher for some samples obtained by the proposed method. The average relative standard deviation (RSD) obtained by the on-line method was 3.2% which is lower than 29.5% obtained by the standard method. PMID:18378258

  6. Determination of three antidepressants in urine using simultaneous derivatization and temperature-assisted dispersive liquid-liquid microextraction followed by gas chromatography-flame ionization detection.

    PubMed

    Nabil, Ali Akbar Alizadeh; Nouri, Nina; Farajzadeh, Mir Ali

    2015-07-01

    This paper presents a fast and simple method for the extraction, preconcentration and determination of fluvoxamine, nortriptyline and maprotiline in urine using simultaneous derivatization and temperature-assisted dispersive liquid-liquid microextraction (TA-DLLME) followed by gas chromatography-flame ionization detection (GC-FID). An appropriate mixture of dimethylformamide (disperser solvent), 1,1,2,2-tetrachloroethane (extraction solvent) and acetic anhydride (derivatization agent) was rapidly injected into the heated sample. Then the solution was cooled to room temperature and cloudy solution formed was centrifuged. Finally a portion of the sedimented phase was injected into the GC-FID. The effect of several factors affecting the performance of the method, including the selection of suitable extraction and disperser solvents and their volumes, volume of derivatization agent, temperature, salt addition, pH and centrifugation time and speed were investigated and optimized. Figures of merit of the proposed method, such as linearity (r(2)  > 0.993), enrichment factors (820-1070), limits of detection (2-4 ng mL(-1)) and quantification (8-12 ng mL(-1)), and relative standard deviations (3-6%) for both intraday and interday precisions (concentration = 50 ng mL(-1)) were satisfactory for determination of the selected antidepressants. Finally the method was successfully applied to determine the target pharmaceuticals in urine. PMID:25516238

  7. Sensitivity enhancement in the fluorometric determination of aliphatic amines using naphthalene-2,3-dicarboxaldehyde derivatization followed by vortex-assisted liquid-liquid microextraction.

    PubMed

    Wang, Chin-Yi; Tung, Shu-Yin; Lo, Yu-Shiu; Huang, Hsien-Lu; Ko, Chun-Han; Wu, Chien-Hou

    2016-05-15

    A highly sensitive liquid chromatographic method was developed for the fluorometric determination of trace amounts of linear aliphatic primary amines. Prior to extraction, amines were derivatized with naphthalene-2,3-dicarboxaldehyde (NDA) in the presence of cyanide ion (CN) and extracted by vortex-assisted liquid-liquid microextraction (VALLME). The optimum conditions were as follows: derivatization reaction time for 5min in 2.0mL aqueous donor samples with 50μM NDA/CN, and 10mM borate buffer at pH 9; vortex extraction time for 20s in the VALLME step with 50μL of isooctane as the extractant phase; centrifugation for 1min at 6000rpm. Under the optimum conditions, the limits of detection (LOD) were between 0.01 and 0.04nmolL(-1). The calibration curves showed good linearity in the range of 0.1-20nmolL(-1). In comparison with previous work using o-phthalaldehyde/2-mercaptoethanol derivatization, the method has much more stable fluorescent derivatives, higher fluorescence intensities, and greater extraction efficiencies. The sensitivity enhancement factors (SEF) were between 2 and 70, which is in good agreement with the theoretical values calculated from partition coefficients in VALLME system. PMID:26992544

  8. 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

  9. 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}.

  10. 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

  11. 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.

  12. 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

  13. 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

  14. 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…

  15. 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...

  16. Microwave-assisted green synthesis of silver nanostructures.

    PubMed

    Nadagouda, Mallikarjuna N; Speth, Thomas F; Varma, Rajender S

    2011-07-19

    Over the past 25 years, microwave (MW) chemistry has moved from a laboratory curiosity to a well-established synthetic technique used in many academic and industrial laboratories around the world. Although the overwhelming number of MW-assisted applications today are still performed on a laboratory (mL) scale, we expect that this enabling technology may be used on a larger, perhaps even production, scale in conjunction with radio frequency or conventional heating. Microwave chemistry is based on two main principles, the dipolar mechanism and the electrical conductor mechanism. The dipolar mechanism occurs when, under a very high frequency electric field, a polar molecule attempts to follow the field in the same alignment. When this happens, the molecules release enough heat to drive the reaction forward. In the second mechanism, the irradiated sample is an electrical conductor and the charge carriers, ions and electrons, move through the material under the influence of the electric field and lead to polarization within the sample. These induced currents and any electrical resistance will heat the sample. This Account summarizes a microwave (MW)-assisted synthetic approach for producing silver nanostructures. MW heating has received considerable attention as a promising new method for the one-pot synthesis of metallic nanostructures in solutions. Researchers have successfully demonstrated the application of this method in the preparation of silver (Ag), gold (Au), platinum (Pt), and gold-palladium (Au-Pd) nanostructures. MW heating conditions allow not only for the preparation of spherical nanoparticles within a few minutes but also for the formation of single crystalline polygonal plates, sheets, rods, wires, tubes, and dendrites. The morphologies and sizes of the nanostructures can be controlled by changing various experimental parameters, such as the concentration of metallic salt precursors, the surfactant polymers, the chain length of the surfactant polymers

  17. 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

  18. 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

  19. 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.

  20. 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

  1. 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

  2. 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.

  3. 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.

  4. Ultra sound assisted one step rapid derivatization and dispersive liquid-liquid microextraction followed by gas chromatography-mass spectrometric determination of amino acids in complex matrices.

    PubMed

    Mudiam, Mohana Krishna Reddy; Ratnasekhar, Ch

    2013-05-24

    A rapid and economical method for the simultaneous determination of 20 amino acids in complex biological and food matrices (hair, urine and soybean seed samples) has been developed using ultrasound assisted dispersive liquid-liquid micro extraction (UA-DLLME). The method involves simultaneous derivatization and extraction followed by gas chromatography-mass spectrometric (GC-MS) analysis of amino acids. The parameters of UA-DLLME were optimized with the aid of design of experiments approach. The procedure involves the rapid injection of mixture of acetonitrile (disperser solvent), trichloroethylene (TCE) (extraction solvent) and ethylchloroformate (derivatization reagent) into the aqueous phase of sample extract containing pyridine. The Plackett-Burman design has indicated that, the factors such as volume of disperser and extraction solvents and pH were found to be significantly affects the extraction efficiency of the method. The optimum conditions of these factors based on central composite design were found to be 250μL of acetonitrile, 80μL of TCE and pH of 10. The limit of detection and limit of quantification were found to be in the range of 0.36-3.68μgL(-1) and 1.26-12.01μgL(-1) respectively. This is the first application of DLLME for the analysis of amino acids in any matrices. The advantages like (i) in situ derivatization and extraction of amino acids without any prior lyophilization and cleanup of sample, (ii) low consumption of extraction solvent, (iii) fast and simple, (iv) cost-effective and (iv) good repeatability make the method amenable for the routine analysis of amino acids in clinical, toxicological, nutritional and quality control laboratories. PMID:23602642

  5. Simultaneous derivatization and ultrasound-assisted dispersive liquid-liquid microextraction of chloropropanols in soy milk and other aqueous matrices combined with gas-chromatography-mass spectrometry.

    PubMed

    Carro, A M; González, P; Lorenzo, R A

    2013-12-01

    A novel approach involving ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) and derivatization combined with gas chromatography-mass spectrometry was developed for the determination of chloropropanols in water and beverages. UA-DLLME was optimized as less solvent-consuming and cost-effective extraction method for water, fruit juice, milk and soy milk samples. The effect of parameters such as the type and volume of extraction solvent, the type and volume of dispersive solvent, amount of derivatization agent, temperature, pH of sample and ionic strength was investigated and optimized for each specimen, using experimental designs. By adding acetonitrile as dispersive solvent, N-heptafluorobutyrylimizadole (HFBI) as derivatization agent and chloroform as extraction solvent, the extraction-derivatization and preconcentration were simultaneously performed. The analytical concentration range was investigated in detail for each analyte in the different samples, obtaining linearity with R(2) ranging between 0.9990 and 0.9999. The method detection limits were in the range of 0.2-1.8μgL(-1) (water), 0.5-15μgL(-1) (fruit juices) and 0.9-3.6μgkg(-1) (milk) and 0.1-1.0μgkg(-1) (soy milk). The method was applied to the analysis of a variety of specimens, with recoveries of 98-101% from water, 97-102% from juices, 99-103% from milk and 97-105% from soy beverage. The relative standard deviation (precision, n=6) varied between 1.3 and 4.9%RSD in water, 2.3 and 5.8%RSD in juices, 1.0 and 5.7%RSD in milk and 3.9 and 9.3%RSD in soy milk. The proposed method was applied to analysis of twenty-eight samples. 1,3-Dichloro-2-propanol was found in an influent water sample from urban wastewater treatment plant (WWTP) (2.1±0.04mgL(-1)) but no chloropropanols were found in the corresponding effluent water sample. This result suggests that the purification system used in the WWTP has been effective for this compound. Moreover, the results revealed the presence of 3

  6. 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

  7. 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.

  8. Identification of oxidized methionine residues in peptides containing two methionine residues by derivatization and matrix-assisted laser desorption/ionization mass spectrometry.

    PubMed

    Hollemeyer, Klaus; Heinzle, Elmar; Tholey, Andreas

    2002-11-01

    Oxidation of methionine residues in peptides and proteins occurs in vivo or may be an artifact resulting from purification steps. We present a three step method for the localization of methionine sulfoxides in peptides with two methionine residues. In the first step, the N-terminus as well as other reactive side chain functions are blocked by acetylation. The resulting protected peptides are cleaved by cyanogen bromide. The cleavage does not occur at methionine sulfoxide but only at reduced methionine residues forming new amino termini. The newly formed amino group is then derivatized with a bromine containing compound in the last step of the procedure. The resulting peptide can easily be identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry using both the characteristic isotope pattern of the halogen and the metastable loss of methanesulfenic acid from oxidized residues. This procedure allows the unequivocal localization of oxidized methionines even in complex peptide mixtures. PMID:12442252

  9. Ultrasound-assisted emulsification microextraction with simultaneous derivatization coupled to fibre optics-based cuvetteless UV-vis micro-spectrophotometry for formaldehyde determination in cosmetic samples.

    PubMed

    Lavilla, Isela; Cabaleiro, Noelia; Pena, Francisco; de la Calle, Inmaculada; Bendicho, Carlos

    2010-07-26

    In this work, ultrasound-assisted emulsification microextraction in combination with fibre optics-based cuvetteless UV-vis micro-spectrophotometry has been proposed as a novel method for the determination of formaldehyde in water-based cosmetics such as shampoo, conditioner and shower gel. The use of a powerful cup-horn sonoreactor allows simultaneous extraction and derivatization of the samples without any pre-treatment. The type and volume of organic extractant solvent, need for a disperser solvent, sonication conditions (sonication time and amplitude), ionic strength and centrifuging time have been carefully studied. Matrix effects were also evaluated. The European official method for quantification of formaldehyde in cosmetic products was used for comparison purposes. An important improvement in sensitivity and sample throughput as well as miniaturization was achieved. A limit of detection of 0.02 microg g(-1) of formaldehyde and a repeatability expressed as relative standard deviation of 5.9% were obtained. PMID:20638500

  10. 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.

  11. Microwave-Assisted Organic Synthesis and Transformations using Benign Reaction Media

    EPA Science Inventory

    The nonclassical heating technique using microwaves, termed as 'Bunsen burner of the 21st century, is rapidly becoming popular and is dramatically reducing the reaction times. The significant outcomes of microwave (MW)-assisted green chemistry endeavors are summarized that have r...

  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 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...

  14. Development of ultrasonic-assisted closed in-syringe extraction and derivatization for the determination of labile abietic acid and dehydroabietic acid in cosmetics.

    PubMed

    Liu, Jianjun; Liu, Mengge; Li, Xiu; Lu, Xiaomin; Chen, Guang; Sun, Zhiwei; Li, Guoliang; Zhao, Xianen; Zhang, Shijuan; Song, Cuihua; Wang, Hua; Suo, Yourui; You, Jinmao

    2014-12-01

    Two resin acids, abietic acid (AA) and dehydroabietic acid (DHAA), in cosmetics may cause allergy or toxicoderma, but remain inaccurately investigated due to their lability. In this work, an accurate, sensitive, efficient and convenient method, utilizing the ultrasonic-assisted closed in-syringe extraction and derivatization (UCSED) prior to high performance liquid chromatography (HPLC) coupled with fluorescence detection (FLD) and on-line tandem mass spectra (MS/MS), has been developed. Analytes are extracted by acetonitrile (10/1, v/m) in a sealed syringe under safe condition (60°C; 15 min; nitrogen atmosphere) and then in-syringe derivatized by 2-(2-(anthracen-10-yl)-1H-naphtho[2,3-d]imidazol-1-yl) ethyl-p-toluenesulfonate (ANITS) (8-fold, 93°C, 30 min, DMF as co-solvent, K2CO3 as catalyst). In UCSED, derivatization contributes to increase both analytical sensitivity and stability of analytes. Excellent linearity (r2≥0.9991) is achieved in wide range (75-3000 ng/mL (AA); 150-4500 ng/mL (DHAA)). Quite low detection limits (AA: 8.2-10.8 ng/mL; DHAA: 19.4-24.3 ng/mL) and limits of analyte concentration (LOAC) (AA: 30.0-44.5 ng/mL; DHAA: 70.9-86.7 ng/mL) ensure the trace analysis. This method is applied to the analysis of cosmetic samples, including depilatory wax strip, liquid foundation, mascara, eyeliner, eyebrow pencil and lip balm. No additional purification is required and no matrix effect is observed, demonstrating obvious advantages over conventional pretreatment such as solid phase extraction (SPE). Accuracy (RE: -3.2% to 2.51%), precision (RSD: 1.29-2.84%), recovery (95.20-103.63%; 95.51-104.22%) and repeatability (<0.23%; <2.87%) are significantly improved. Furthermore, this work plays a guiding role in developing a reasonable method for labile analytes. PMID:25456583

  15. 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

  16. 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.

  17. 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

  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. Preliminary evaluation of a microwave-assisted metal-labeling strategy for quantification of peptides via RPLC-ICP-MS and the method of standard additions.

    PubMed

    Christopher, Steven J; Kilpatrick, Eric L; Yu, Lee L; Davis, W Clay; Adair, Blakely M

    2012-01-15

    NIST has performed preliminary research on applying a calibration methodology based on the method of standard additions to the quantification of peptides via reverse-phase liquid chromatography coupled to inductively coupled plasma mass spectrometry (RPLC-ICP-MS). A microwave-assisted lanthanide labeling procedure was developed and applied to derivatize peptides using the macrocyclic bifunctional chemical chelator DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid), which significantly improved the lanthanide labeling yield and reduced reaction times compared to benchtop labeling procedures. Biomolecular MS technologies of matrix-assisted laser desorption ionization (MALDI)-MS and electrospray ionization (ESI)-MS/MS were used in concert with ICP-MS to confirm the results of microwave labeling, sample cleanup and standard additions experiments for several test peptides. The calibration scheme is outlined in detail and contextualized against complementary high accuracy calibration strategies currently employed for ICP-MS detection of biomolecules. Standard additions experiments using native, non-isotopic peptide calibrants confirm the simplicity of the scheme and the potential of applying a blending (recombined sample and spike) procedure, facilitating calibration via co-elution of lanthanide labeled peptides. Ways to improve and fully leverage the analytical methodology are highlighted. PMID:22265570

  20. Microwave assisted synthesis and characterization of graphene nanoplatelets

    NASA Astrophysics Data System (ADS)

    Kumar, Dinesh; Singh, Karamjit; Verma, Veena; Bhatti, H. S.

    2016-01-01

    Graphene Nanoplatelets were fabricated from expandable graphite by rapid microwave exfoliation. Expandable graphite was irradiated in microwave in full power for 3 min, then was soaked in mixed nitric acid and sulphuric acid at volume ratio of 1:1 for 24 h and re-irradiated, thus graphene nanoplatelets (GNPs) were obtained. Extensive characterization techniques showed that GNPs synthesized using this technique are highly pure with traces of oxide groups and without serious unrecoverable oxidation damage. GNPs synthesized by microwave technique have high crystallinity, with variable size and little layer thickness.

  1. Simultaneous derivatization and extraction of chlorophenols in water samples with up-and-down shaker-assisted dispersive liquid-liquid microextraction coupled with gas chromatography/mass spectrometric detection.

    PubMed

    Wang, Ke-Deng; Chen, Pai-Shan; Huang, Shang-Da

    2014-03-01

    A new up-and-down shaker-assisted dispersive liquid-liquid microextraction (UDSA-DLLME) for extraction and derivatization of five chlorophenols (4-chlorophenol, 4-chloro-2-methylphenol, 2,4-dichlorophenol, 2,4,6-trichloro-phenol, and pentachlorophenol) has been developed. The method requires minimal solvent usage. The relatively polar, water-soluble, and low-toxicity solvent 1-heptanol (12 μL) was selected as the extraction solvent and acetic anhydride (50 μL) as the derivatization reagent. With the use of an up-and-down shaker, the emulsification of aqueous samples was formed homogeneously and quickly. The derivatization and extraction of chlorophenols were completed simultaneously in 1 min. The common requirement of disperser solvent in DLLME could be avoided. After optimization, the linear range covered over two orders of magnitude, and the coefficient of determination (r (2)) was greater than 0.9981. The detection limit was from 0.05 to 0.2 μg L(-1), and the relative standard deviation was from 4.6 to 10.8 %. Real samples of river water and lake water had relative recoveries from 90.3 to 117.3 %. Other emulsification methods such as vortex-assisted, ultrasound-assisted, and manual shaking-enhanced ultrasound-assisted methods were also compared with the proposed UDSA-DLLME. The results revealed that UDSA-DLLME performed with higher extraction efficiency and precision compared with the other methods. PMID:23727731

  2. 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

  3. 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

  4. 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

  5. Microwave-assisted Low-temperature Growth of Thin Films in Solution

    PubMed Central

    Reeja-Jayan, B.; Harrison, Katharine L.; Yang, K.; Wang, Chih-Liang; Yilmaz, A. E.; Manthiram, Arumugam

    2012-01-01

    Thin films find a variety of technological applications. Assembling thin films from atoms in the liquid phase is intrinsically a non-equilibrium phenomenon, controlled by the competition between thermodynamics and kinetics. We demonstrate here that microwave energy can assist in assembling atoms into thin films directly on a substrate at significantly lower temperatures than conventional processes, potentially enabling plastic-based electronics. Both experimental and electromagnetic simulation results show microwave fields can selectively interact with a conducting layer on the substrate despite the discrepancy between the substrate size and the microwave wavelength. The microwave interaction leads to localized energy absorption, heating, and subsequent nucleation and growth of the desired films. Electromagnetic simulations show remarkable agreement with experiments and are employed to understand the physics of the microwave interaction and identify conditions to improve uniformity of the films. The films can be patterned and grown on various substrates, enabling their use in widespread applications. PMID:23256037

  6. Low-temperature-compatible tunneling-current-assisted scanning microwave microscope utilizing a rigid coaxial resonator

    NASA Astrophysics Data System (ADS)

    Takahashi, Hideyuki; Imai, Yoshinori; Maeda, Atsutaka

    2016-06-01

    We present a design for a tunneling-current-assisted scanning near-field microwave microscope. For stable operation at cryogenic temperatures, making a small and rigid microwave probe is important. Our coaxial resonator probe has a length of approximately 30 mm and can fit inside the 2-in. bore of a superconducting magnet. The probe design includes an insulating joint, which separates DC and microwave signals without degrading the quality factor. By applying the SMM to the imaging of an electrically inhomogeneous superconductor, we obtain the spatial distribution of the microwave response with a spatial resolution of approximately 200 nm. Furthermore, we present an analysis of our SMM probe based on a simple lumped-element circuit model along with the near-field microwave measurements of silicon wafers having different conductivities.

  7. Low-temperature-compatible tunneling-current-assisted scanning microwave microscope utilizing a rigid coaxial resonator.

    PubMed

    Takahashi, Hideyuki; Imai, Yoshinori; Maeda, Atsutaka

    2016-06-01

    We present a design for a tunneling-current-assisted scanning near-field microwave microscope. For stable operation at cryogenic temperatures, making a small and rigid microwave probe is important. Our coaxial resonator probe has a length of approximately 30 mm and can fit inside the 2-in. bore of a superconducting magnet. The probe design includes an insulating joint, which separates DC and microwave signals without degrading the quality factor. By applying the SMM to the imaging of an electrically inhomogeneous superconductor, we obtain the spatial distribution of the microwave response with a spatial resolution of approximately 200 nm. Furthermore, we present an analysis of our SMM probe based on a simple lumped-element circuit model along with the near-field microwave measurements of silicon wafers having different conductivities. PMID:27370458

  8. 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.

  9. 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

  10. 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%.

  11. Organo- and nano-catalyst in greener reaction medium: Microwave-assisted expedient synthesis of fine chemicals

    EPA Science Inventory

    The use of emerging microwave (MW) -assisted chemistry techniques is dramatically reducing chemical waste and reaction times in several organic syntheses and chemical transformations. A brief account of our experiences in developing MW-assisted organic transformations, which invo...

  12. Microwave-assisted synthesis of chromenes: biological and chemical importance.

    PubMed

    Patil, Shivaputra A; Patil, Siddappa A; Patil, Renukadevi

    2015-01-01

    Chromenes constitute chemically important class of heterocyclic compounds having diverse biological and chemical importance. Development of environmentally benign, efficient and economical methods for the synthesis of chromenes remains a significant challenge in synthetic chemistry. The synthesis of chromenes, therefore, has attracted enormous attention from medicinal and organic chemists. Researchers have embraced the concepts of microwave (high speed) synthesis to produce biologically and chemically important chromenes in a time sensitive manner. This review will summarize the recent biological applications such as anticancer, antimicrobial, neurodegenerative and insecticidal activity of new chromenes prepared via microwave irradiation. The development of new methodologies for the synthesis of chromenes including green chemistry processes has also been discussed. PMID:26061107

  13. Theory of microwave-assisted supercurrent in quantum point contacts.

    PubMed

    Bergeret, F S; Virtanen, P; Heikkilä, T T; Cuevas, J C

    2010-09-10

    We present a microscopic theory of the effect of a microwave field on the supercurrent through a quantum point contact of arbitrary transmission. Our theory predicts that (i) for low temperatures and weak fields, the supercurrent is suppressed at certain values of the superconducting phase, (ii) at strong fields, the current-phase relation is strongly modified and the current can even reverse its sign, and (iii) at finite temperatures, the microwave field can enhance the critical current of the junction. Apart from their fundamental interest, our findings are also important for the description of experiments that aim at the manipulation of the quantum state of atomic point contacts. PMID:20867598

  14. 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

  15. 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.

  16. 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.

  17. 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%.

  18. Microwave-Assisted Synthesis of Nanomaterials and Nanocomposites

    EPA Science Inventory

    The aqueous preparation of nanoparticles using vitamins B1 and B2, and vitamin C which can function both as reducing and capping agents prompted us accomplished the bulk syntheses of Ag and Fe nanorods using polyethylene glycol (PEG) under microwave (MW) irradiation conditions; t...

  19. Microwave-assisted synthesis of transition metal phosphide

    SciTech Connect

    Viswanathan, Tito

    2014-12-30

    A method of synthesizing transition metal phosphide. In one embodiment, the method has the steps of preparing a transition metal lignosulfonate, mixing the transition metal lignosulfonate with phosphoric acid to form a mixture, and subjecting the mixture to a microwave radiation for a duration of time effective to obtain a transition metal phosphide.

  20. Microwave-Assisted Hydantoins Synthesis on Solid Support

    ERIC Educational Resources Information Center

    Coursindel, Thibault; Martinez, Jean; Parrot, Isabelle

    2010-01-01

    In this laboratory activity, students are introduced to a three-step synthesis of hydantoin (imidazolidine-2,4-dione), a moiety that is found in many biologically active compounds. Using a microwave oven and solid-support technology, this synthetic experiment is designed for masters-degree candidates working in organic chemistry or upper-level…

  1. DEXTRON TEMPLATED MICROWAVE-ASSISTED SYNTHESIS OF POROUS TITANIUM DIOXIDE

    EPA Science Inventory

    An alternative route to the preparation and formation of porous titania powders and carbon coated titania using microwave radiation is described. Inexpensive dextrose was chosen as capping agent or template in view of its high water solubility when compared to other sugar templat...

  2. Microwave-assisted synthesis of alkyl cellulose in aqueous medium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Alkyl celluloses are commercial products that are made typically in an alcohol medium over the course of several hours. In this work an alternative, simplified synthesis of alkyl cellulose is reported, using microwave irradiation and aqueous alkaline medium. No alcohol is needed during the reaction....

  3. 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

  4. 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.

  5. Rapid determination of alkylphenols in aqueous samples by in situ acetylation and microwave-assisted headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry.

    PubMed

    Wu, Yu-Pei; Wang, Yu-Chen; Ding, Wang-Hsien

    2012-08-01

    A rapid and solvent-free procedure for the determination of 4-tert-octylphenol and 4-nonylphenol isomers in aqueous samples is described. The method involves in-situ acetylation and microwave-assisted headspace solid-phase microextraction prior to their determination using gas chromatography-ion trap mass spectrometry operated in the selected ion storage mode. The dual experimental protocols to evaluate the effects of various derivatization and extraction parameters were investigated and the conditions optimized. Under optimized conditions, 300 μL of acetic anhydride mixed with 1 g of potassium hydrogencarbonate and 2 g of sodium chloride in a 20 mL aqueous sample were efficiently extracted by a 65 μm polydimethylsiloxane-divinylbenzene fiber that was located in the headspace when the system was microwave irradiated at 80 W for 5 min. The limits of quantitation were 5 and 50 ng/L for 4-tert-octylphenol and 4-nonylphenol isomers, respectively. The precision for these analytes, as indicated by relative standard deviations, were less than 8% for both intra- and inter-day analysis. Accuracy, expressed as the mean extraction recovery, was between 74 to 88%. A standard addition method was used to quantitate 4-tert-octylphenol and 4-nonylphenol isomers, and the concentrations ranged from 120 to 930 ng/L in various environmental water samples. PMID:22899640

  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. A sensitive and efficient method for trace analysis of some phenolic compounds using simultaneous derivatization and air-assisted liquid-liquid microextraction from human urine and plasma samples followed by gas chromatography-nitrogen phosphorous detection.

    PubMed

    Farajzadeh, Mir Ali; Afshar Mogaddam, Mohammad Reza; Alizadeh Nabil, Ali Akbar

    2015-12-01

    In present study, a simultaneous derivatization and air-assisted liquid-liquid microextraction method combined with gas chromatography-nitrogen phosphorous detection has been developed for the determination of some phenolic compounds in biological samples. The analytes are derivatized and extracted simultaneously by a fast reaction with 1-flouro-2,4-dinitrobenzene under mild conditions. Under optimal conditions low limits of detection in the range of 0.05-0.34 ng mL(-1) are achievable. The obtained extraction recoveries are between 84 and 97% and the relative standard deviations are less than 7.2% for intraday (n = 6) and interday (n = 4) precisions. The proposed method was demonstrated to be a simple and efficient method for the analysis of phenols in biological samples. PMID:26014445

  8. 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

  9. 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.

  10. 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

  11. Photonic-assisted microwave phase shifter using a DMZM and an optical bandpass filter.

    PubMed

    Li, Wei; Sun, Wen Hui; Wang, Wen Ting; Wang, Li Xian; Liu, Jian Guo; Zhu, Ning Hua

    2014-03-10

    We propose and demonstrate a photonic-assisted wideband 360° microwave phase shifter based on a conventional dual-drive Mach-Zehnder modulator (DMZM) and an optical bandpass filter (OBPF). The two arms of the DMZM are driven by the fundamental microwave signal to be phase shifted and its frequency doubled component, respectively. The OBPF followed after the DMZM is used to remove the optical carrier and the sidebands at either side of the optical carrier. As a result, only two sidebands corresponding to the fundamental microwave signal and its frequency doubled component, respectively, are left. Moreover, the phase shift between the two sidebands can be continuously tunable by adjusting the bias voltage of the DMZM. This phase shift is mapped to the fundamental microwave signal which is recovered by beating the two sidebands in a photodetector (PD). The proposed approach is theoretically analyzed and experimentally verified. PMID:24663892

  12. 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

  13. 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.

  14. Photonic-assisted microwave frequency multiplication with a tunable multiplication factor.

    PubMed

    Gao, Liang; Liu, Weilin; Chen, Xiangfei; Yao, Jianping

    2013-11-01

    Photonic-assisted microwave frequency multiplication with a tunable multiplication factor (MF) based on an optical comb generator and an embedded single-passband microwave photonic filter (MPF) is proposed and demonstrated. The optical comb is generated using two cascaded modulators which are driven by a microwave reference signal. By applying the optical comb to a photodetector, a fundamental frequency corresponding to the comb spacing and its harmonics is generated. Thanks to the embedded single-passband MPF, only one harmonic is selected by the single-passband MPF. Thus, a single-frequency frequency-multiplied microwave signal is generated. In the proposed system, the embedded single-passband MPF is formed by using a sliced broadband optical source and a section of dispersion-compensating fiber (DCF). By tuning the central frequency of the passband at a frequency corresponding to that of a specific harmonic, a microwave signal at that specific frequency is generated. The proposed system is experimentally demonstrated. A frequency-multiplied microwave signal with an MF from 1 to 5 is generated. The phase noise and frequency tunability of the generated microwave signal are also investigated. PMID:24177126

  15. 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

  16. 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

  17. 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.

  18. 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

  19. 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.

  20. 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...

  1. 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...

  2. 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

  3. 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

  4. 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...

  5. 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...

  6. 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...

  7. 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

  8. 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...

  9. Magnetic carbon nanostructures: microwave energy-assisted pyrolysis vs. conventional pyrolysis.

    PubMed

    Zhu, Jiahua; Pallavkar, Sameer; Chen, Minjiao; Yerra, Narendranath; Luo, Zhiping; Colorado, Henry A; Lin, Hongfei; Haldolaarachchige, Neel; Khasanov, Airat; Ho, Thomas C; Young, David P; Wei, Suying; Guo, Zhanhu

    2013-01-11

    Magnetic carbon nanostructures from microwave assisted- and conventional-pyrolysis processes are compared. Unlike graphitized carbon shells from conventional heating, different carbon shell morphologies including nanotubes, nanoflakes and amorphous carbon were observed. Crystalline iron and cementite were observed in the magnetic core, different from a single cementite phase from the conventional process. PMID:23172110

  10. 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.

  11. 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...

  12. 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...

  13. Microwave-Assisted Chemistry: Synthetic Applications for Rapid Assembly of Nanomaterials and Organics

    EPA Science Inventory

    The magic of microwave (MW) heating technique, termed as the Bunsen burner of the 21th Century, has emerged as valuable alternative in synthesis of organics, polymers, inorganics, and nanomaterials. Important innovations in MW-assisted chemistry now enable chemists to prepare cat...

  14. 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...

  15. 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...

  16. 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).

  17. 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

  18. 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

  19. 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

  20. 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

  1. 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

  2. Non-incineration microwave assisted sterilization of medical waste.

    PubMed

    Veronesi, Paolo; Leonelli, Cristina; Moscato, Umberto; Cappi, Angelo; Figurelli, Ornella

    2007-01-01

    A non-incineration method for sterilizing hospital infectious wastes has been studied and realized. A small apparatus operating at 2.45 GHz and at a power of 3 kW was designed to optimize power transfer from the electromagnetic field to the infectious materials, which have been previously shredded and moisture-corrected. The high pressure reached in the reactor, 7 atm, was enough to ensure complete sterilization in just a few minutes for a batch of several hundred grams of waste. Sterilization efficacy during microwave irradiation was also optimized with a new procedure using thermal, microbiological and water vapour sensors in a single test. PMID:17847675

  3. 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.

  4. 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

  5. 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

  6. Using X-Ray Mammograms to Assist in Microwave Breast Image Interpretation

    PubMed Central

    Curtis, Charlotte; Frayne, Richard; Fear, Elise

    2012-01-01

    Current clinical breast imaging modalities include ultrasound, magnetic resonance (MR) imaging, and the ubiquitous X-ray mammography. Microwave imaging, which takes advantage of differing electromagnetic properties to obtain image contrast, shows potential as a complementary imaging technique. As an emerging modality, interpretation of 3D microwave images poses a significant challenge. MR images are often used to assist in this task, and X-ray mammograms are readily available. However, X-ray mammograms provide 2D images of a breast under compression, resulting in significant geometric distortion. This paper presents a method to estimate the 3D shape of the breast and locations of regions of interest from standard clinical mammograms. The technique was developed using MR images as the reference 3D shape with the future intention of using microwave images. Twelve breast shapes were estimated and compared to ground truth MR images, resulting in a skin surface estimation accurate to within an average Euclidean distance of 10 mm. The 3D locations of regions of interest were estimated to be within the same clinical area of the breast as corresponding regions seen on MR imaging. These results encourage investigation into the use of mammography as a source of information to assist with microwave image interpretation as well as validation of microwave imaging techniques. PMID:22536208

  7. 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

  8. Microwave assisted antibacterial chitosan-silver nanocomposite films.

    PubMed

    Raghavendra, Gownolla Malegowd; Jung, Jeyoung; Kim, Dowan; Seo, Jongchul

    2016-03-01

    In the current approach, antibacterial chitosan-silver nanocomposite films were fabricated through microwave irradiation. During the process, by utilizing chitosan as reducing agent, silver nanoparticles were synthesized within 11 min by microwave irradiation. Further, films were fabricated within 90 min. It involved an energy consumption of just 0.146 kWh to synthesize silver nanoparticles. This is many times less than the energy consumed during conventional methods. The silver nanoparticles were examined through UV-vis spectrum and transmission electron microscopy (TEM). The fabricated films were characterized by using scanning electron microscopy coupled with an energy dispersive spectrometer (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and contact angle (CA) measurements. The films exhibited antibacterial properties against both Gram-negative micro-organisms (Escherichia coli; E. coli) and Gram-positive micro-organisms (Staphylococcus aureus; S. aureus). In overall, the procedure adopted for fabricating these antibacterial films is environmental friendly, time-saving and energy-saving. PMID:26706842

  9. Microwave-assisted synthesis of palladium nanocubes and nanobars

    SciTech Connect

    Yu, Yanchun; Zhao, Yanxi; Huang, Tao; Liu, Hanfan

    2010-02-15

    Microwave was employed in the shape-controlled synthesis of palladium nanoparticles. Palladium nanocubes and nanobars with a mean size of about 23.8 nm were readily synthesized with H{sub 2}PdCl{sub 4} as a precursor, tetraethylene glycol (TEG) as both a solvent and a reducing agent in the presence of PVP and CTAB in 80 s under microwave irradiation. The structures of the as-prepared palladium nanoparticles were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and ultraviolet-visible (UV-vis) absorption spectroscopy. The formation of PdBr{sub 4}{sup 2-}due to the coordination replacement of the ligand Cl{sup -} ions in PdCl{sub 4}{sup 2-} ions by Br{sup -} ions in the presence of bromide was responsible for the synthesis of Pd nanocubes and nanobars. In addition, a milder reducing power, a higher viscosity and a stronger affinity of TEG were beneficial to the larger sizes of Pd nanocubes and nanobars.

  10. 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

  11. Microwave and blanch-assisted drying of white yam (Dioscorea rotundata).

    PubMed

    Abano, Ernest Ekow; Amoah, Robert Sarpong

    2015-11-01

    The effect of microwave and blanch pretreatments on the drying kinetics and quality of white yam (Dioscorea rotundata) was investigated. Yam cubes destined for hot air drying at temperatures 70-90°C were predried in a domestic microwave or blanched in hot water for 1-5 min. Microwave pretreatment time had a positive significant effect on drying rate but both pretreatments had a negative influence on the ascorbic acid content and the nonenzymatic browning. The optimum drying conditions were a microwave pretreatment time of 5 min and a temperature of 70°C and a blanching time of 1 min at a temperature of 80°C. Among the models fitted, the Midilli et al. and the Page models gave the best fits for yam cubes predried with microwave and blanch, respectively. The effective moisture diffusivity for microwave-assisted drying increased from 1.05 × 10(-8 )m(2 )s(-1) to 2.00 × 10(-8) m(2 )s(-1) while the hot water blanched samples decreased from 1.53 × 10(-8) to 8.81 × 10(-9 )m(2 )s(-1) with time. The study demonstrates that microwave-assisted drying could be used to enhance heat and mass transfer processes to produce better quality dried yam products. PMID:26788300

  12. 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.

  13. 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.

  14. 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

  15. Characterization of low-molecular weight iodine-terminated polyethylenes by gas chromatography/mass spectrometry and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with the use of derivatization.

    PubMed

    Zaikin, Vladimir G; Borisov, Roman S; Polovkov, Nikolai Yu; Zhilyaev, Dmitry I; Vinogradov, Aleksei A; Ivanyuk, Aleksei V

    2013-01-01

    Gas chromatography/mass spectrometry (GC/MS) and matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectrometry, in conjunction with various derivatization approaches, have been applied to structure determination of individual oligomers and molecular-mass distributions (MMD) in low-molecular mass polyethylene having an iodine terminus. Direct GC/MS analysis has shown that the samples under investigation composed of polyethyelene-iodides (major components) and n-alkanes. Exchange reaction with methanol in the presence of NaOH gave rise to methoxy-derivatives and n-alkenes. Electron ionization mass spectra have shown that the former contained terminal methoxy groups indicating the terminal position of the iodine atom in the initial oligomers. MMD parameters have been determined with the aid of MALDI mass spectrometry followed by preliminary derivatization-formation of covalently bonded charge through the reaction of iodides with triphenylphosphine, trialkylamines, pyridine or quinoline. The mass spectra revealed well-resolved peaks for cationic parts of derivatized oligomers allowing the determination of MMD. The latter values have been compared with those calculated from GC/MS data. PMID:24308197

  16. 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

  17. Rapid and Selective Crystallization of Acetaminophen using Metal-Assisted and Microwave-Accelerated Evaporative Crystallization

    PubMed Central

    Mohammed, Muzaffer; Syed, Maleeha F; Bhatt, Mona J; Hoffman, Eugene J; Aslan, Kadir

    2012-01-01

    In this paper, we demonstrate the application of Metal-Assisted and Microwave-Accelerated Evaporative Crystallization (MA-MAEC) technique to rapid and selective crystallization of a small drug compound. i.e. acetaminophen. Subsequent characterization of the crystals by optical microscopy, powder X-ray diffraction (PXRD) and Raman spectroscopy showed quantitatively selective growth of different crystal forms at various experimental conditions. Acetaminophen crystals were grown predominantly as Form I (99%) on blank glass slides at room temperature. Form II crystals with 39% purity grown on SIFs using microwave energy. PMID:22485195

  18. OH(A,X) radicals in microwave plasma-assisted combustion of methane/air

    NASA Astrophysics Data System (ADS)

    Wu, Wei; Fuh, Che; Wang, Chuji; Laser Spectroscopy and Plasma Team

    2014-10-01

    A novel microwave plasma-assisted combustion (PAC) system, which consists of a microwave plasma-assisted combustor, a gas flow control manifold, and a set of optical diagnostic systems, was developed as a new test platform to study plasma enhancement of combustion. Using this system, we studied the state-resolved OH(A,X) radicals in the plasma-assisted combustion and ignition of a methane/air mixture. Experimental results identified three reaction zones in the plasma-assisted combustor: the plasma zone, the hybrid plasma-flame zone, and the flame zone. The OH(A) radicals in the three distinct zones were characterized using optical emission spectroscopy (OES). Results showed a surge of OH(A) radicals in the hybrid zone compared to the plasma zone and the flame zone. The OH(X) radicals in the flame zone were measured using cavity ringdown spectroscopy (CRDS), and the absolute number density distribution of OH(X) was quantified in two-dimension. The effect of microwave argon plasma on combustion was studied with two different fuel/oxidizer injection patterns, namely the premixed methane/air injection and the nonpremixed (separate) methane/air injection. Parameters investigated included the flame geometry, the lean flammability limit, the emission spectra, and rotational temperature. State-resolved OH(A,X) radicals in the PAC of both injection patterns were also compared. This work is supported by the National Science Foundation through the Grant No. CBET-1066486.

  19. 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.

  20. Extraction and characterization of polysaccharides from Semen Cassiae by microwave-assisted aqueous two-phase extraction coupled with spectroscopy and HPLC.

    PubMed

    Chen, Zhi; Zhang, Wei; Tang, Xunyou; Fan, Huajun; Xie, Xiujuan; Wan, Qiang; Wu, Xuehao; Tang, James Z

    2016-06-25

    A novel and rapid method for simultaneous extraction and separation of the different polysaccharides from Semen Cassiae (SC) was developed by microwave-assisted aqueous two-phase extraction (MAATPE) in a one-step procedure. Using ethanol/ammonium sulfate system as a multiphase solvent, the effects of MAATPE on the extraction of polysaccharides from SC such as the composition of the ATPS, extraction time, temperature and solvent-to-material ratio were investigated by UV-vis analysis. Under the optimum conditions, the yields of polysaccharides were 4.49% for the top phase, 8.80% for the bottom phase and 13.29% for total polysaccharides, respectively. Compared with heating solvent extraction and ultrasonic assisted extraction, MAATPE exhibited the higher extraction yields in shorter time. Fourier-transform infrared spectra showed that two polysaccharides extracted from SC to the top and bottom phases by MAATPE were different from each other in their chemical structures. Through acid hydrolysis and PMP derivatization prior to HPLC, analytical results by indicated that a polysaccharide of the top phases was a relatively homogeneous homepolysaccharide composed of dominant gucose glucose while that of the bottom phase was a water-soluble heteropolysaccharide with multiple components of glucose, xylose, arabinose, galactose, mannose and glucuronic acid. Molar ratios of monosaccharides were 95.13:4.27:0.60 of glucose: arabinose: galactose for the polysaccharide from the top phase and 62.96:14.07:6.67: 6.67:5.19:4.44 of glucose: xylose: arabinose: galactose: mannose: glucuronic acid for that from the bottom phase, respectively. The mechanism for MAATPE process was also discussed in detail. MAATPE with the aid of microwave and the selectivity of the ATPS not only improved yields of the extraction, but also obtained a variety of polysaccharides. Hence, it was proved as a green, efficient and promising alternative to simultaneous extraction of polysaccharides from SC. PMID

  1. 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.

  2. 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.

  3. 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

  4. 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.

  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. 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

  7. 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

  8. Microwave plasma assisted pyrolysis of refuse derived fuels

    NASA Astrophysics Data System (ADS)

    Khongkrapan, Parin; Thanompongchart, Patipat; Tippayawong, Nakorn; Kiatsiriroat, Tanongkiat

    2014-03-01

    This work combined plasma reactivity and pyrolysis for conversion of solid wastes. Decomposition of refuse derived fuel (RDF) and its combustible components (paper, biomass, and plastic) in an 800 W microwave plasma reactor was investigated at varying argon flow rates of 0.50 to 1.25 lpm for 3 minutes. The characteristic bright light emission of plasma was observed with calculated maximum power density of about 35 W/cm3. The RDF and its components were successfully converted into char and combustible gas. The average char yield was found to be 12-21% of the original mass, with a gross calorific value of around 39 MJ/kg. The yield of the product gas was in the range 1.0-1.7 m3/kg. The combustible gas generated from the pyrolysis of the RDF contained about 14% H2, 66% CO, and 4% CH4 of the detected gas mass, with a heating value of 11 MJ/m3. These products are potentially marketable forms of clean energy.

  9. Investigations on oxyhalide glasses synthesized by microwave assisted process

    NASA Astrophysics Data System (ADS)

    Vijayatha, D.; Viswanatha, R.; Somashekaraiah, C. S.; Reddy, C. Narayana

    2016-05-01

    Glass formation and properties in the system xPbCl2-15PbO-(85-x) PbBr2 (where 0 ≤ x ≤ 25) has been prepared by microwave method. The glass forming tendency of the admixtures was also been studied by determining the Hurby's factor (HR). HR values of the investigated glasses lie in a short range of 0.14 to 0.24; hence preparation of these glasses is very difficult and requires suitable experimental conditions. Lead bromide and lead chloride are inter-substituted by keeping the concentration of PbO at 15 mol%. Properties like glass transition temperature (Tg), jump in heat capacity (ΔCp) at Tg, width of glass transition (ΔT), show a composition dependent trend. The stability indices such as H' and S have also been calculated. These values reveal that PbCl2 rich glasses are less stable while PbBr2 rich glasses are stable, which is well supported by chemical durability studies. The calculated values of glass formation indices fall in right range (G≥20 for glass formers, for conditional glass formers 10≤G≤20 and G<10 for glass modifiers) for compositions studied in the present work.

  10. 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

  11. Microwave Photon-Assisted Incoherent Cooper-Pair Tunneling in a Josephson STM

    NASA Astrophysics Data System (ADS)

    Roychowdhury, A.; Dreyer, M.; Anderson, J. R.; Lobb, C. J.; Wellstood, F. C.

    2015-09-01

    We observe photon-assisted Cooper-pair tunneling in an atomic-scale Josephson junction formed between a superconducting Nb tip and a superconducting Nb sample in a scanning tunneling microscope (STM) at 30 mK. High-resolution tunneling spectroscopy data show a zero-bias conduction peak and other sharp subgap peaks from coupling of the STM junction to resonances in the electromagnetic environment. The subgap peaks respond to incident microwave radiation by splitting into multiple peaks with the position and height depending on the frequency and amplitude of the microwaves. The interpeak spacing shows that the charge carriers are Cooper pairs rather than quasiparticles, and the power dependence reveals that the current originates from photon-assisted phase-incoherent tunneling of pairs rather than the more conventional phase-coherent tunneling of pairs that yields Shapiro steps.

  12. 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

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. A facile microwave-assisted protocol for rapid synthesis of N-acetylneuraminic acid congeners

    PubMed Central

    Saludes, Jonel P.; Sahoo, Dhananjaya; Monreal, I. Abrrey

    2014-01-01

    We developed a simple, rapid and efficient microwave irradiation-assisted protocol that is 1- to 2-orders of magnitude faster than conventional techniques, providing an expedient access to the sialic acid congeners Neu5Ac1Me (1), Neu5Acβ1,2Me2 (2), Neu5Ac1Me O-peracetate (3) and 4,5-oxazoline of Neu5Ac2en1Me O-peracetate (4). PMID:24678239

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. Microwave-irradiation-assisted hybrid chemical approach for titanium dioxide nanoparticle synthesis: microbial and cytotoxicological evaluation.

    PubMed

    Ranjan, Shivendu; Dasgupta, Nandita; Rajendran, Bhavapriya; Avadhani, Ganesh S; Ramalingam, Chidambaram; Kumar, Ashutosh

    2016-06-01

    Titanium dioxide nanoparticles (TNPs) are widely used in the pharmaceutical and cosmetics industries. It is used for protection against UV exposure due to its light-scattering properties and high refractive index. Though TNPs are increasingly used, the synthesis of TNPs is tedious and time consuming; therefore, in the present study, microwave-assisted hybrid chemical approach was used for TNP synthesis. In the present study, we demonstrated that TNPs can be synthesized only in 2.5 h; however, the commonly used chemical approach using muffle furnace takes 5 h. The activity of TNP depends on the synthetic protocol; therefore, the present study also determined the effect of microwave-assisted hybrid chemical approach synthetic protocol on microbial and cytotoxicity. The results showed that TNP has the best antibacterial activity in decreasing order from Escherichia coli, Bacillus subtilis, and Staphylococcus aureus. The IC50 values of TNP for HCT116 and A549 were found to be 6.43 and 6.04 ppm, respectively. Cell death was also confirmed from trypan blue exclusion assay and membrane integrity loss was observed. Therefore, the study determines that the microwave-assisted hybrid chemical approach is time-saving; hence, this technique can be upgraded from lab scale to industrial scale via pilot plant scale. Moreover, it is necessary to find the mechanism of action at the molecular level to establish the reason for greater bacterial and cytotoxicological toxicity. Graphical abstract A graphical representation of TNP synthesis. PMID:26976013

  5. Dispersive liquid-liquid microextraction followed by microwave-assisted silylation and gas chromatography-mass spectrometry analysis for simultaneous trace quantification of bisphenol A and 13 ultraviolet filters in wastewaters.

    PubMed

    Cunha, S C; Pena, A; Fernandes, J O

    2015-10-01

    A novel multi-residue gas chromatography-mass spectrometry (GC-MS) method was validated for the simultaneous determination of trace levels (ng/L) of 13 UV-filters and bisphenol A (BPA) in wastewater samples. It was based on dispersive liquid-liquid microextraction (DLMME) followed by rapid microwave-assisted silylation of the analytes. Several parameters of both extraction and derivatization steps such as type of extractive and dispersive solvents, solvent volumes, pH, salt addition, time and power of microwave were evaluated to achieve the highest yield and to attain the lowest detection limits. Optimized DLLME consisted in the formation of a cloudy solution promoted by the fast addition to the sample (10mL) of a mixture of tetrachloroethylene (50μL, extraction solvent) in acetone (1mL, dispersive solvent). The sedimented phase obtained was evaporated and further silylated under the irradiation of 600W microwave for 5min, being the derivatization yields similar to those obtained after a conventional heating process for 30min at 75°C. Limits of detection and quantification of the method using real samples were 2ng/L and 10ng/L, respectively. Mean extraction efficiency of 82% for three concentrations were achieved, supporting the accuracy of the method. Intra-day and inter-day repeatability of measurements (expressed as relative standard deviation) were lower than 22%. The method was successfully applied to the determination of UV-filters and BPA in samples collected from 15 wastewater treatment plants (WWTPs) in Portugal. Eight analytes were detected, among which 2-hydroxy-4-methoxybenzophenone, 2-ethylhexyl-4-(dimethylamino)benzoate, octocrylene, and BPA were consistently found in the three seasons of collection. PMID:26341596

  6. 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

  7. 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

  8. Microwave frequency effects on dielectric properties of some common solvents and on microwave-assisted syntheses: 2-Allylphenol and the C12-C2-C12 Gemini surfactant

    NASA Astrophysics Data System (ADS)

    Horikoshi, Satoshi; Matsuzaki, Shohei; Mitani, Tomohiko; Serpone, Nick

    2012-12-01

    Microwave radiation emitted at a frequency of 915 MHz and 5.8 GHz from a newly fabricated single-mode resonance microwave apparatus is herein proposed for use in microwave-assisted organic syntheses. The usefulness of 5.8-GHz microwaves is demonstrated by the solvent-free synthesis of 2-allylphenol through a Claisen rearrangement process, and by the synthesis of the C12-C2-C12 Gemini surfactant in ethanol solvent undertaken to verify the usefulness of the 915-MHz frequency. These two model reactions have shown the advantage of these two microwave frequencies in that the observed efficiencies were greater than when employing the more commonly used 2.45-GHz microwaves. Dielectric parameters (dissipation factor: tan δ, dielectric constant: ɛ', and dielectric loss: ɛ'') have also been assessed for water and 22 common organic solvents typically used in organic syntheses, together with the temperature dependence of the dielectric parameters. Temperature-time profiles have been determined and rates of increase of temperature computed. The 5.8-GHz microwaves were effective in heating non-polar solvents, while the 915-MHz microwave frequency was most suitable for heating the alcohols.

  9. Microscopic imaging mass spectrometry assisted by on-tissue chemical derivatization for visualizing multiple amino acids in human colon cancer xenografts.

    PubMed

    Toue, Sakino; Sugiura, Yuki; Kubo, Akiko; Ohmura, Mitsuyo; Karakawa, Sachise; Mizukoshi, Toshimi; Yoneda, Junya; Miyano, Hiroshi; Noguchi, Yasushi; Kobayashi, Tsuyoshi; Kabe, Yasuaki; Suematsu, Makoto

    2014-04-01

    Imaging MS combined with CE/MS serves as a method to provide semi-quantitative and spatial information of small molecular metabolites in tissue slices. However, not all metabolites including amino acids have fully been visualized, because of low-ionization efficiency in MALDI MS. This study aimed to acquire semi-quantitative spatial information for multiple amino acids in frozen tissue slices. As a derivatization reagent, p-N,N,N-trimethylammonioanilyl N'-hydroxysuccinimidyl carbamate iodide (TAHS) was applied to increase their ionization efficiency and detection sensitivity. Semi-quantitative MALDI-imaging MS allowed us to visualize and quantify free amino acid pools in human colon cancer xenografts using a model of liver metastases in super-immunodeficient NOD/scid/γ(null) mice (NOG mice). Because the m/z values of several TAHS-derivatized amino acids overlap with those of the 2,5-dihydroxybenzoic acid background and other endogenous compounds, we imaged them with tandem MS. The results indicated that regional contents of glutamate, glutamine, glycine, leucine/isoleucine/hydroxyproline, phenylalanine, and alanine were significantly elevated in metastatic tumors versus parenchyma of tumor-bearing livers. On-tissue TAHS derivatization thus serves as a useful method to detect alterations in many amino acid levels in vivo, thereby enabling understanding of the spatial alterations of these metabolites under varied disease conditions including cancer. PMID:23818158

  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. 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

  12. The Production of Biodiesel and Bio-kerosene from Coconut Oil Using Microwave Assisted Reaction

    NASA Astrophysics Data System (ADS)

    SAIFUDDIN, N.; SITI FAZLILI, A.; KUMARAN, P.; PEI-JUA, N.; PRIATHASHINI, P.

    2016-03-01

    Biofuels including biodiesel, an alternative fuel, is renewable, environmentally friendly, non-toxic and low emissions. The raw material used in this work was coconut oil, which contained saturated fatty acids about 90% with high percentage of medium chain (C8-C12), especially lauric acid and myristic acid. The purpose of this research was to study the effect of power and NaOH catalyst in transesterification assisted by microwave for production of biofuels (biodiesel and bio-kerosene) derived from coconut oil. The reaction was performed with oil and methanol using mole ratio of 1:6, catalyst concentration of 0.6% with microwave power at 100W, 180W, 300W, 450W, 600W, and 850W. The reaction time was set at of 3, 5, 7, 10 and 15 min. The results showed that microwave could accelerate the transesterification process to produce biodiesel and bio-kerosene using NaOH catalyst. The highest yield of biodiesel was 97.17 %, or 99.05 % conversion at 5 min and 100W microwave power. Meanwhile, the bio-kerosene obtained was 65% after distillation.

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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

  1. 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.

  2. 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

  3. 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.

  4. 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

  5. Multiple substrate microwave plasma-assisted chemical vapor deposition single crystal diamond synthesis

    SciTech Connect

    Asmussen, J.; Grotjohn, T. A.; Reinhard, D. K.; Schuelke, T.; Becker, M. F.; Yaran, M. K.; King, D. J.; Wicklein, S.

    2008-07-21

    A multiple substrate, microwave plasma-assisted chemical vapor deposition synthesis process for single crystal diamond (SCD) is demonstrated using a 915 MHz reactor. Diamond synthesis was performed using input chemistries of 6-8% of CH{sub 4}/H{sub 2}, microwave input powers of 10-11.5 kW, substrate temperatures of 1100-1200 deg. C, and pressures of 110-135 Torr. The simultaneous synthesis of SCD over 70 diamond seeds yielded good quality SCD with deposition rates of 14-21 {mu}m/h. Multiple deposition runs totaling 145 h of deposition time added 1.8-2.5 mm of diamond material to each of the 70 seed crystals.

  6. 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

  7. 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.

  8. In situ derivatization-ultrasound-assisted dispersive liquid-liquid microextraction for the determination of neurotransmitters in Parkinson's rat brain microdialysates by ultra high performance liquid chromatography-tandem mass spectrometry.

    PubMed

    He, Yongrui; Zhao, Xian-En; Zhu, Shuyun; Wei, Na; Sun, Jing; Zhou, Yubi; Liu, Shu; Liu, Zhiqiang; Chen, Guang; Suo, Yourui; You, Jinmao

    2016-08-01

    Simultaneous monitoring of several neurotransmitters (NTs) linked to Parkinson's disease (PD) has important scientific significance for PD related pathology, pharmacology and drug screening. A new simple, fast and sensitive analytical method, based on in situ derivatization-ultrasound-assisted dispersive liquid-liquid microextraction (in situ DUADLLME) in a single step, has been proposed for the quantitative determination of catecholamines and their biosynthesis precursors and metabolites in rat brain microdialysates. The method involved the rapid injection of the mixture of low toxic bromobenzene (extractant) and acetonitrile (dispersant), which containing commercial Lissamine rhodamine B sulfonyl chloride (LRSC) as derivatization reagent, into the aqueous phase of sample and buffer, and the following in situ DUADLLME procedure. After centrifugation, 50μL of the sedimented phase (bromobenzene) was directly injected for ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) detection in multiple reaction monitoring (MRM) mode. This interesting combination brought the advantages of speediness, simpleness, low matrix effects and high sensitivity in an effective way. Parameters of in situ DUADLLME and UHPLC-MS/MS conditions were all optimized in detail. The optimum conditions of in situ DUADLLME were found to be 30μL of microdialysates, 150μL of acetonitrile containing LRSC, 50μL of bromobenzene and 800μL of NaHCO3-Na2CO3 buffer (pH 10.5) for 3.0min at 37°C. Under the optimized conditions, good linearity was observed with LODs (S/N>3) and LOQs (S/N>10) of LRSC derivatized-NTs in the range of 0.002-0.004 and 0.007-0.015 nmol/L, respectively. It also brought good precision (3.2-12.8%, peak area CVs%), accuracy (94.2-108.6%), recovery (94.5-105.5%) and stability (3.8-8.1%, peak area CVs%) results. Moreover, LRSC derivatization significantly improved chromatographic resolution and MS detection sensitivity of NTs when compared with the

  9. 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

  10. Heterogeneous Phase Microwave-Assisted Reactions under CO₂ or CO Pressure.

    PubMed

    Calcio Gaudino, Emanuela; Rinaldi, Laura; Rotolo, Laura; Carnaroglio, Diego; Pirola, Camillo; Cravotto, Giancarlo

    2016-01-01

    The present review deals with the recent achievements and impressive potential applications of microwave (MW) heating to promote heterogeneous reactions under gas pressure. The high versatility of the latest generation of professional reactors combines extreme reaction conditions with safer and more efficient protocols. The double aims of this survey are to provide a panoramic snapshot of MW-assisted organic reactions with gaseous reagents, in particular CO and CO₂, and outline future applications. Stubborn and time-consuming carbonylation-like heterogeneous reactions, which have not yet been studied under dielectric heating, may well find an outstanding ally in the present protocol. PMID:26927033

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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.

  19. 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

  20. 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

  1. 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

  2. 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.

  3. Field emission from carbon nanotubes produced using microwave plasma assisted CVD

    SciTech Connect

    Zhang, Q.; Yoon, S.F.; Ahn, J.; Gan, B.; Rusli; Yu, M.B.; Cheah, L.K.; Shi, X.

    2000-01-30

    Electron field emission from carbon nanotubes prepared using microwave plasma assisted CVD has been investigated. The nanotubes, ranging from 50 to 120 nm in diameter and a few tens of microns in length, were formed under methane and hydrogen plasma at 720 C with the aid of iron-oxide particles. The morphology and growth direction of the nanotubes are found to be strongly influenced by the flow ratio of methane to hydrogen. However, the electron field emission from these massive nanotubes show similar characteristics, i.e., high emission current at low electric fields.

  4. 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

  5. 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

  6. Oil extraction from sheanut (Vitellaria paradoxa Gaertn C.F.) kernels assisted by microwaves.

    PubMed

    Nde, Divine B; Boldor, Dorin; Astete, Carlos; Muley, Pranjali; Xu, Zhimin

    2016-03-01

    Shea butter, is highly solicited in cosmetics, pharmaceuticals, chocolates and biodiesel formulations. Microwave assisted extraction (MAE) of butter from sheanut kernels was carried using the Doehlert's experimental design. Factors studied were microwave heating time, temperature and solvent/solute ratio while the responses were the quantity of oil extracted and the acid number. Second order models were established to describe the influence of experimental parameters on the responses studied. Under optimum MAE conditions of heating time 23 min, temperature 75 °C and solvent/solute ratio 4:1 more than 88 % of the oil with a free fatty acid (FFA) value less than 2, was extracted compared to the 10 h and solvent/solute ratio of 10:1 required for soxhlet extraction. Scanning electron microscopy was used to elucidate the effect of microwave heating on the kernels' microstructure. Substantial reduction in extraction time and volumes of solvent used and oil of suitable quality are the main benefits derived from the MAE process. PMID:27570267

  7. 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

  8. 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

  9. 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

  10. 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.

  11. 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

  12. 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

  13. 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.

  14. 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

  15. 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

  16. 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

  17. 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.

  18. 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

  19. 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

  20. 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

  1. 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.

  2. 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

  3. 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

  4. 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

  5. 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.

  6. 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.

  7. 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

  8. Determination of parabens and endocrine-disrupting alkylphenols in soil by gas chromatography-mass spectrometry following matrix solid-phase dispersion or in-column microwave-assisted extraction: a comparative study.

    PubMed

    Pérez, R A; Albero, B; Miguel, E; Sánchez-Brunete, C

    2012-03-01

    Two rapid methods were evaluated for the simultaneous extraction of seven parabens and two alkylphenols from soil based on matrix solid-phase dispersion (MSPD) and microwave-assisted extraction (MAE). Soil extracts were derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide and analyzed by gas chromatography with mass spectrometry. Extraction and clean-up of samples were carried out by both methods in a single step. A glass sample holder, inside the microwave cell, was used in MAE to allow the simultaneous extraction and clean-up of samples and shorten the MAE procedure. The detection limits achieved by MSPD were lower than those obtained by MAE because the presence of matrix interferences increased with this extraction method. The extraction yields obtained by MSPD and MAE for three different types of soils were compared. Both procedures showed good recoveries and sensitivity for the determination of parabens and alkylphenols in two of the soils assayed, however, only MSPD yielded good recoveries with the other soil. Finally, MSPD was applied to the analysis of soils collected in different sites of Spain. In most of the samples analyzed, methylparaben and butylparaben were detected at levels ranging from 1.21 to 8.04 ng g(-1) dry weight and 0.48 to 1.02 ng g(-1) dry weight, respectively. PMID:21792551

  9. 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

  10. Determination of bisphenol A, 4-octylphenol, and 4-nonylphenol in soft drinks and dairy products by ultrasound-assisted dispersive liquid-liquid microextraction combined with derivatization and high-performance liquid chromatography with fluorescence detection.

    PubMed

    Lv, Tao; Zhao, Xian-En; Zhu, Shuyun; Qu, Fei; Song, Cuihua; You, Jinmao; Suo, Yourui

    2014-10-01

    A novel hyphenated method based on ultrasound-assisted dispersive liquid-liquid microextraction coupled to precolumn derivatization has been established for the simultaneous determination of bisphenol A, 4-octylphenol, and 4-nonylphenol by high-performance liquid chromatography with fluorescence detection. Different parameters that influence microextraction and derivatization have been optimized. The quantitative linear range of analytes is 5.0-400.0 ng/L, and the correlation coefficients are more than 0.9998. Limits of detection for soft drinks and dairy products have been obtained in the range of 0.5-1.2 ng/kg and 0.01-0.04 μg/kg, respectively. Relative standard deviations of intra- and inter-day precision for retention time and peak area are in the range of 0.47-2.31 and 2.76-8.79%, respectively. Accuracy is satisfactory in the range of 81.5-118.7%. Relative standard deviations of repeatability are in the range of 0.35-1.43 and 2.36-4.75% for retention time and peak area, respectively. Enrichment factors for bisphenol A, 4-octylphenol, and 4-nonylphenol are 170.5, 240.3, and 283.2, respectively. The results of recovery and matrix effect are in the range of 82.7-114.9 and 92.0-109.0%, respectively. The proposed method has been applied to the determination of bisphenol A, 4-octylphenol, and 4-nonylphenol in soft drinks and dairy products with much higher sensitivity than many other methods. PMID:25045130

  11. 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

  12. Determining the microwave coupling and operational efficiencies of a microwave plasma assisted chemical vapor deposition reactor under high pressure diamond synthesis operating conditions

    SciTech Connect

    Nad, Shreya; Gu, Yajun; Asmussen, Jes

    2015-07-15

    The microwave coupling efficiency of the 2.45 GHz, microwave plasma assisted diamond synthesis process is investigated by experimentally measuring the performance of a specific single mode excited, internally tuned microwave plasma reactor. Plasma reactor coupling efficiencies (η) > 90% are achieved over the entire 100–260 Torr pressure range and 1.5–2.4 kW input power diamond synthesis regime. When operating at a specific experimental operating condition, small additional internal tuning adjustments can be made to achieve η > 98%. When the plasma reactor has low empty cavity losses, i.e., the empty cavity quality factor is >1500, then overall microwave discharge coupling efficiencies (η{sub coup}) of >94% can be achieved. A large, safe, and efficient experimental operating regime is identified. Both substrate hot spots and the formation of microwave plasmoids are eliminated when operating within this regime. This investigation suggests that both the reactor design and the reactor process operation must be considered when attempting to lower diamond synthesis electrical energy costs while still enabling a very versatile and flexible operation performance.

  13. Determining the microwave coupling and operational efficiencies of a microwave plasma assisted chemical vapor deposition reactor under high pressure diamond synthesis operating conditions.

    PubMed

    Nad, Shreya; Gu, Yajun; Asmussen, Jes

    2015-07-01

    The microwave coupling efficiency of the 2.45 GHz, microwave plasma assisted diamond synthesis process is investigated by experimentally measuring the performance of a specific single mode excited, internally tuned microwave plasma reactor. Plasma reactor coupling efficiencies (η) > 90% are achieved over the entire 100-260 Torr pressure range and 1.5-2.4 kW input power diamond synthesis regime. When operating at a specific experimental operating condition, small additional internal tuning adjustments can be made to achieve η > 98%. When the plasma reactor has low empty cavity losses, i.e., the empty cavity quality factor is >1500, then overall microwave discharge coupling efficiencies (η(coup)) of >94% can be achieved. A large, safe, and efficient experimental operating regime is identified. Both substrate hot spots and the formation of microwave plasmoids are eliminated when operating within this regime. This investigation suggests that both the reactor design and the reactor process operation must be considered when attempting to lower diamond synthesis electrical energy costs while still enabling a very versatile and flexible operation performance. PMID:26233399

  14. Determining the microwave coupling and operational efficiencies of a microwave plasma assisted chemical vapor deposition reactor under high pressure diamond synthesis operating conditions

    NASA Astrophysics Data System (ADS)

    Nad, Shreya; Gu, Yajun; Asmussen, Jes

    2015-07-01

    The microwave coupling efficiency of the 2.45 GHz, microwave plasma assisted diamond synthesis process is investigated by experimentally measuring the performance of a specific single mode excited, internally tuned microwave plasma reactor. Plasma reactor coupling efficiencies (η) > 90% are achieved over the entire 100-260 Torr pressure range and 1.5-2.4 kW input power diamond synthesis regime. When operating at a specific experimental operating condition, small additional internal tuning adjustments can be made to achieve η > 98%. When the plasma reactor has low empty cavity losses, i.e., the empty cavity quality factor is >1500, then overall microwave discharge coupling efficiencies (ηcoup) of >94% can be achieved. A large, safe, and efficient experimental operating regime is identified. Both substrate hot spots and the formation of microwave plasmoids are eliminated when operating within this regime. This investigation suggests that both the reactor design and the reactor process operation must be considered when attempting to lower diamond synthesis electrical energy costs while still enabling a very versatile and flexible operation performance.

  15. 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

  16. 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

  17. 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.

  18. Microwave-assisted solvent extraction of solid matrices and subsequent detection of pharmaceuticals and personal care products (PPCPs) using gas chromatography-mass spectrometry.

    PubMed

    Rice, Stacie L; Mitra, Siddhartha

    2007-04-18

    Concentrations of pharmaceuticals and personal care products (PPCPs) in natural solids remain largely unknown. Contributing to this, is a lack of methods permitting the simultaneous detection of the diverse, low-level contaminants present in these complex matrices. We have developed a microwave-assisted solvent extraction (MASE)-based method targeting seven diverse PPCPs (caffeine, 17beta-estradiol, ibuprofen, ketoprofen, musk ketone, naproxen, and triclosan) and a molecular marker for fecal waste (epicoprostanol). The method consisted of optimizing the following variables: derivatization of the polar target analytes, silica gel open column clean-up, and gas chromatographic-mass spectrometric (GC-MS) analysis of sample extracts for analysis and detection of the compounds noted above. Testing of the method on spiked soil allowed for 89.6+/-2.89% recovery of three target compounds and 25.0+/-1.93% recovery of five of the compounds. Although the latter recoveries were low, the precision across all recoveries was high, suggesting good reproducibility in application of the method. Furthermore, we suspect that matrix effects are likely responsible for the lower recoveries. Techniques with the exclusive incorporation of organic solvents were found inapplicable in the study of a pharmaceutical salt, diphenhydramine HCl. Application of the developed method to sediment collected directly downstream of the effluent pipe of a wastewater treatment plant allowed detection of ibuprofen, naproxen, ketoprofen, and epicoprostanol at ng-mug per gram dry weight concentrations. The observation of acidic pharmaceuticals, previously believed to exhibit insignificant sorption to solid matrices, in the tested sediment samples, coupled with application of biosolids for agricultural purposes, demonstrates the need for expanded investigation of PPCP contamination of natural solid matrices. PMID:17397662

  19. 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

  20. 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.

  1. 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

  2. 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

  3. 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

  4. 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...

  5. 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…

  6. 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

  7. 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

  8. 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....

  9. 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

  10. 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

  11. 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

  12. Rapid Covalent Modification of Silicon Oxide Surfaces through Microwave-Assisted Reactions with Alcohols.

    PubMed

    Lee, Austin W H; Gates, Byron D

    2016-07-26

    We demonstrate the method of a rapid covalent modification of silicon oxide surfaces with alcohol-containing compounds with assistance by microwave reactions. Alcohol-containing compounds are prevalent reagents in the laboratory, which are also relatively easy to handle because of their stability against exposure to atmospheric moisture. The condensation of these alcohols with the surfaces of silicon oxides is often hindered by slow reaction kinetics. Microwave radiation effectively accelerates this condensation reaction by heating the substrates and/or solvents. A variety of substrates were modified in this demonstration, such as silicon oxide films of various thicknesses, glass substrates such as microscope slides (soda lime), and quartz. The monolayers prepared through this strategy demonstrated the successful formation of covalent surface modifications of silicon oxides with water contact angles of up to 110° and typical hysteresis values of 2° or less. An evaluation of the hydrolytic stability of these monolayers demonstrated their excellent stability under acidic conditions. The techniques introduced in this article were successfully applied to tune the surface chemistry of silicon oxides to achieve hydrophobic, oleophobic, and/or charged surfaces. PMID:27396288

  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 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.

  15. Microbead-assisted high resolution microwave planar ring resonator for organic-vapor sensing

    NASA Astrophysics Data System (ADS)

    Zarifi, Mohammad H.; Fayaz, Mohammadreza; Goldthorp, Jordan; Abdolrazzaghi, Mohammad; Hashisho, Zaher; Daneshmand, Mojgan

    2015-02-01

    A microbead-assisted planar microwave resonator for organic vapor sensing applications is presented. The core of this sensor is a planar microstrip split-ring resonator, integrated with an active feedback loop to enhance the initial quality factor from 200 to ˜1 M at an operational resonance frequency of 1.42 GHz. Two different types of microbeads, beaded activated carbon (BAC) and polymer based (V503) beads, are investigated in non-contact mode for use as gas adsorbents in the gas sensing device. 2-Butoxyethanol (BE) is used in various concentrations as the target gas, and the transmitted power (S21) of the two port resonator is measured. The two main microwave parameters of resonance frequency and quality factor are extracted from S21 since these parameters are less susceptible to environmental and instrumental noise than the amplitude. Measured results demonstrate a minimum resonance frequency shift of 10 kHz for a 35 ppm concentration of BE exposure to carbon beads and 160 kHz for the polymer based adsorbent at the same concentration. The quality factor of the resonator also changed for different concentrations, but a distinguishable variation is observed for the BAC adsorbents. The high quality factor of the sensor provides the opportunity of real time monitoring of the adsorbent behaviors in remote sensing mode with very high resolution.

  16. 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

  17. 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

  18. Metal-assisted and microwave accelerated-evaporative crystallization: Application to lysozyme protein

    NASA Astrophysics Data System (ADS)

    Mauge-Lewis, Kevin

    In response to the growing need for new crystallization techniques that afford for rapid processing times along with control over crystal size and distribution, the Aslan Research Group has recently demonstrated the use of Metal-Assisted and Microwave-Accelerated Evaporative Crystallization MA-MAEC technique in conjunction with metal nanoparticles and nanostructures for the crystallization of amino acids and organic small molecules. In this study, we have employed the newly developed MA-MAEC technique to the accelerated crystallization of chicken egg-white lysozyme on circular crystallization platforms in order to demonstrate the proof-of-principle application of the method for protein crystallization. The circular crystallization platforms are constructed in-house from poly (methyl methacrylate) (PMMA) and silver nanoparticle films (SNFs), indium tin oxide (ITO) and iron nano-columns. In this study, we prove the MA-MAEC method to be a more effective technique in the rapid crystallization of macromolecules in comparison to other conventional methods. Furthermore, we demonstrate the use of the novel iCrystal system, which incorporates the use of continuous, low wattage heating to facilitate the rapid crystallization of the lysozyme while still retaining excellent crystal quality. With the incorporation of the iCrystal system, we observe crystallization times that are even shorter than those produced by the MA-MAEC technique using a conventional microwave oven in addition to significantly improved crystal quality.

  19. 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

  20. 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

  1. 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

  2. Synthesis and characterization of Eu-doped hydroxyapatite through a microwave assisted microemulsion process

    NASA Astrophysics Data System (ADS)

    Yang, Chun; Yang, Piaoping; Wang, Wenxin; Gai, Shili; Wang, Jun; Zhang, Milin; Lin, Jun

    2009-11-01

    Europium doped hydroxyapatite (Eu:HAp) nanosized particles with multiform morphologies have been successfully prepared via a simple microemulsion-mediated process assisted with microwave heating. The physicochemical properties of the samples were well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) spectra, and the kinetic decays, respectively. The results reveal that the obtained Eu:HAp particles are well assigned to the hexagonal lattice structure of the hydroxyapatite phase. Additionally, it is found that samples exhibit uniform morphologies which can be controlled by altering the pH values. Furthermore, the samples show the characteristic 5D 0- 7F 1-4 emission lines of Eu 3+ excited by UV radiation.

  3. 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

  4. 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.

  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. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. Rapid and solvent-saving liquefaction of woody biomass using microwave-ultrasonic assisted technology.

    PubMed

    Lu, Zexiang; Wu, Zhengguo; Fan, Liwei; Zhang, Hui; Liao, Yiqiang; Zheng, Deyong; Wang, Siqun

    2016-01-01

    A novel process to rapidly liquefy sawdust using reduced quantities of solvent, was successfully carried out via microwave-ultrasonic assisted technology (MUAT) in a sulphuric acid/polyethylene glycol 400-glycerol catalytic system. The influences of some key parameters on the liquefaction yield were investigated. The results showed that compared with traditional liquefaction, the introduction of MUAT allowed the solvent dosage to be halved and shortened the liquefaction time from 60 to 20 min. The liquefaction yield reached 91% under the optimal conditions. However, the influence on the yield of some parameters such as catalyst concentration, was similar to that of traditional liquefaction, indicating that the application of MUAT possibly only intensified heat and mass transfer rather than altering either the degradation mechanism or pathway. The introduction of MUAT as a process intensification technology has good industrial application potential for woody biomass liquefaction. PMID:26419964

  13. 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

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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

  19. 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.

  20. 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

  1. 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.

  2. 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

  3. Microwave plasma-assisted ignition and flameholding in premixed ethylene/air mixtures

    NASA Astrophysics Data System (ADS)

    Fuh, Che A.; Wu, Wei; Wang, Chuji

    2016-07-01

    In this study, a 2.45 GHz microwave source and a surfatron were used, coupled with a T-shaped quartz combustor, to investigate the role of a nonthermal microwave argon plasma jet on the plasma-assisted ignition and flameholding of a premixed ethylene/air mixture. A modified U-shaped plot of the minimum plasma power required for ignition versus fuel equivalence ratio was obtained, whereby the plasma power required for plasma-assisted ignition decreased with increase in fuel equivalence ratios in the range 0.2–0.6, but for fuel equivalence ratios of 0.7 and above, the plasma power required for ignition remained fairly constant throughout. It was observed that leaner fuel/air mixtures were more sensitive to heat losses to the surrounding and this sensitivity decreased with increase in the fuel equivalence ratio. Comparison with results obtained from previous studies suggested that the mixing scheme between the plasma and the premixed fuel/air mixture and the energy density of the fuel used played an important role in influencing the minimum plasma power required for ignition with the effect being more pronounced for near stoichiometric to rich fuel equivalence ratios (0.7–1.4). Flame images obtained showed a dual layered flame with an inner white core and a bluish outer layer. The images also showed an increased degree of flameholding (tethering of the flame to the combustor orifice) with increase in plasma power. The concurrency of the dual peaks in the emission intensity profiles for OH(A), CH(A), C2(d), and the rotational temperature profiles obtained via optical emission spectroscopy along with the ground state OH(X) number density profiles in the flame using cavity ringdown spectroscopy led to the proposal that the mechanism of plasma-assisted flameholding in ethylene/air flames is predominantly radical dependent with the formation of an inner radical rich flame core which enhances the ignition and stabilization of the surrounding coflow.

  4. 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

  5. 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.

  6. Effect of far-infrared radiation assisted microwave-vacuum drying on drying characteristics and quality of red chilli.

    PubMed

    Saengrayap, Rattapon; Tansakul, Ampawan; Mittal, Gauri S

    2015-05-01

    Fresh red chilli (Capsicum frutescens L.) was dried using microwave-vacuum drying (MVD) and the far-infrared radiation assisted microwave-vacuum drying (FIR-MVD) method. The MVD was operated using the microwave power of 100, 200 and 300 W under absolute pressure of 21.33, 28.00 and 34.66 kPa. In terms of FIR-MVD, far-infrared power was applied at 100, 200 and 300 W. The effect of drying conditions, i.e., microwave power, absolute pressure and FIR power, on drying characteristics and qualities of dried product were investigated. It was observed that an increase in microwave power and FIR power with a decrease in absolute pressure could accelerate the drying rate. It was also found that FIR-MVD method required shorter drying time than MVD. Moreover, qualities, i.e., color changes, texture, rehydration ability and shrinkage, of FIR-MVD chilli were found to be better than those of MVD. Consequently, the optimum drying condition of FIR-MVD within this study was microwave power of 300 W under absolute pressure of 21.33 kPa with FIR power of 300 W. PMID:25892759

  7. Synthesis of hexagonal wurtzite Cu2ZnSnS4 prisms by an ultrasound-assisted microwave solvothermal method

    NASA Astrophysics Data System (ADS)

    Long, Fei; Chi, Shangsen; He, Jinyun; Wang, Jilin; Wu, Xiaoli; Mo, Shuyi; Zou, Zhengguang

    2015-09-01

    Wurtzite Cu2ZnSnS4 (CZTS) hexagonal prisms were synthesized by a simple ultrasound-microwave solvothermal method. The product was characterized by XRD, FESEM, EDS, TEM, Raman and UV-vis spectrometer. The hexagonal prisms were 0.5-2 μm wide and 5-12 μm long. The PVP played an important role in the formation of the CZTS hexagonal prisms. In addition, the ultrasound-assisted microwave process was helpful for synthesis of wurtzite rather than kesterite phase CZTS. A nucleation-dissolution-recrystallization mechanism was also proposed to explain the growth of the CZTS hexagonal prisms.

  8. 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

  9. 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

  10. 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.

  11. Characterization and antibacterial properties of stable silver substituted hydroxyapatite nanoparticles synthesized through surfactant assisted microwave process

    SciTech Connect

    Iqbal, Nida; Abdul Kadir, Mohammed Rafiq; Nik Malek, Nik Ahmad Nazim; Mahmood, Nasrul Humaimi Bin; Murali, Malliga Raman; Kamarul, T.

    2013-09-01

    Highlights: • Stable nano sized silver substitute hydroxyapatite is prepared under surfactant assisted microwave process at 600 W power for 7 min. • The nanoparticles are in the size range of 58–72 nm and exert uniform elongated spheroid morphology. • Increase in silver concentration resulted in better dielectric properties. • Good antibacterial activity and silver release. - Abstract: The present study reports a relatively simple method for the synthesis of stable silver substituted hydroxyapatite nanoparticles with controlled morphology and particle size. In order to achieve this, CTAB is included as a surfactant in the microwave refluxing process (600 W for 7 min). The nanoparticles produced with different silver ion concentrations (0.05, 0.1 and 0.2 wt%) were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscope (FESEM), energy dispersive X-ray (EDX) and Brunauer–Emmett–Teller (BET) analysis. XRD and FTIR analyses reveal that the Ag-HA nanoparticles were phase pure at 1000 °C. FESEM images showed that the produced nanoparticles are in the size range of 58–72 nm and exert uniform elongated spheroid morphology. The dielectric properties suggest that the increase in dielectric constant (ε′) and dissipation factor (D) values with increasing Ag concentrations. Antibacterial performance of the Ag-HA samples elucidated using disk diffusion technique (DDT) and minimum inhibitory concentration (MIC) demonstrates anti-bacterial activity against Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa and Escherichia coli. This effect was dose dependent and was more pronounced against Gram-negative bacteria than Gram-positive organisms.

  12. 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.

  13. Microwave engineering of plasma-assisted CVD reactors for diamond deposition

    NASA Astrophysics Data System (ADS)

    Silva, F.; Hassouni, K.; Bonnin, X.; Gicquel, A.

    2009-09-01

    The unique properties of CVD diamond make it a compelling choice for high power electronics. In order to achieve industrial use of CVD diamond, one must simultaneously obtain an excellent control of the film purity, very low defect content and a sufficiently rapid growth rate. Currently, only microwave plasma-assisted chemical vapour deposition (MPACVD) processes making use of resonant cavity systems provide enough atomic hydrogen to satisfy these requirements. We show in this paper that the use of high microwave power density (MWPD) plasmas is necessary to promote atomic hydrogen concentrations that are high enough to ensure the deposition of high purity diamond films at large growth rates. Moreover, the deposition of homogeneous films on large surfaces calls for the production of plasma with appropriate shapes and large volumes. The production of such plasmas needs generating a fairly high electric field over extended regions and requires a careful design of the MW coupling system, especially the cavity. As far as MW coupling efficiency is concerned, the presence of a plasma load represents a mismatching perturbation to the cavity. This perturbation is especially important at high MWPD where the reflected fraction of the input power may be quite high. This mismatch can lead to a pronounced heating of the reactor walls. It must therefore be taken into account from the very beginning of the reactor design. This requires the implementation of plasma modelling tools coupled to detailed electromagnetic simulations. This is discussed in section 3. We also briefly discuss the operating principles of the main commercial plasma reactors before introducing the reactor design methodology we have developed. Modelling results for a new generation of reactors developed at LIMHP, working at very high power density, will be presented. Lastly, we show that scaling up this type of reactor to lower frequencies (915 MHz) can result in high density plasmas allowing for fast and

  14. Microwave engineering of plasma-assisted CVD reactors for diamond deposition.

    PubMed

    Silva, F; Hassouni, K; Bonnin, X; Gicquel, A

    2009-09-01

    The unique properties of CVD diamond make it a compelling choice for high power electronics. In order to achieve industrial use of CVD diamond, one must simultaneously obtain an excellent control of the film purity, very low defect content and a sufficiently rapid growth rate. Currently, only microwave plasma-assisted chemical vapour deposition (MPACVD) processes making use of resonant cavity systems provide enough atomic hydrogen to satisfy these requirements. We show in this paper that the use of high microwave power density (MWPD) plasmas is necessary to promote atomic hydrogen concentrations that are high enough to ensure the deposition of high purity diamond films at large growth rates. Moreover, the deposition of homogeneous films on large surfaces calls for the production of plasma with appropriate shapes and large volumes. The production of such plasmas needs generating a fairly high electric field over extended regions and requires a careful design of the MW coupling system, especially the cavity. As far as MW coupling efficiency is concerned, the presence of a plasma load represents a mismatching perturbation to the cavity. This perturbation is especially important at high MWPD where the reflected fraction of the input power may be quite high. This mismatch can lead to a pronounced heating of the reactor walls. It must therefore be taken into account from the very beginning of the reactor design. This requires the implementation of plasma modelling tools coupled to detailed electromagnetic simulations. This is discussed in section 3. We also briefly discuss the operating principles of the main commercial plasma reactors before introducing the reactor design methodology we have developed. Modelling results for a new generation of reactors developed at LIMHP, working at very high power density, will be presented. Lastly, we show that scaling up this type of reactor to lower frequencies (915 MHz) can result in high density plasmas allowing for fast and

  15. 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

  16. 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

  17. 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

  18. 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.

  19. Steady-state domain wall motion driven by adiabatic spin-transfer torque with assistance of microwave field

    SciTech Connect

    Wang, Xi-guang; Guo, Guang-hua Nie, Yao-zhuang; Xia, Qing-lin; Tang, Wei; Wang, D.; Zeng, Zhong-ming

    2013-12-23

    We have studied the current-induced displacement of a 180° Bloch wall by means of micromagnetic simulation and analytical approach. It is found that the adiabatic spin-transfer torque can sustain a steady-state domain wall (DW) motion in the direction opposite to that of the electron flow without Walker Breakdown when a transverse microwave field is applied. This kind of motion is very sensitive to the microwave frequency and can be resonantly enhanced by exciting the domain wall thickness oscillation mode. A one-dimensional analytical model was established to account for the microwave-assisted wall motion. These findings may be helpful for reducing the critical spin-polarized current density and designing DW-based spintronic devices.

  20. Microwave blanching and drying characteristics of Centella asiatica (L.) urban leaves using tray and heat pump-assisted dehumidified drying.

    PubMed

    Trirattanapikul, W; Phoungchandang, S

    2014-12-01

    The appropriate stage of maturity of Centella asiatica (L.) Urban leaves was investigated. Mature leaves with large diameter contained high total phenolics and % inhibition. Microwave blanching for 30 s retained the highest total phenolics and the microwave blanching for 30 s and 45 s retained the highest % inhibition. Modified Henderson and Modified Chung-Pfost models showed the best fit to both fresh and blanched leaves for equilibrium moisture content, Xe = f(RHe, T) and equilibrium relative humidity, RHe = f(Xe, T), respectively. The Modified Page model was the most effective model in describing the leaf drying. All drying was in the falling rate period. The drying constant was related to drying air temperature using the Arrhenius model. Effective moisture diffusivities increased with increasing temperature and blanching treatments as well as dehumidification by heat pump-assisted dehumidified dryer. The heat pump-assited dehumidified drying incorporated by the microwave blanching could reduce the drying time at 40 °C by 31.2 % and increase % inhibition by 6.1 %. Quality evaluation by total phenolics, % inhibition and rehydration ratio showed the best quality for C. asiatica leaves pretreated by microwave blanching and dried at 40 °C in heat pump-assisted dehumidified dryer. PMID:25477629

  1. 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

  2. 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

  3. 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.

  4. 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

  5. The microwave-assisted photo-catalytic degradation of organic dyes.

    PubMed

    Jung, S C

    2011-01-01

    In this study, TiO(2) photo-catalyst balls produced by the chemical vapour deposition method were used for degradation of organic dyes in which simultaneous irradiation of microwave and UV was evaluated. An electrodeless UV lamp that emits UV upon the irradiation of microwave was developed to irradiate microwave and UV simultaneously. The degradation reaction rate was shown to be higher with higher microwave intensity, under stronger acidic or basic conditions, and with a larger amount of O(2) gas or H(2)O(2) addition. The effect of addition of H(2)O(2) was not significant when photo-catalysis was used without additional microwave irradiation or when microwave was irradiated without the use of photo-catalysts. When H(2)O(2) was added under simultaneous use of photo-catalysis and microwave irradiation, however, considerably higher degradation reaction rates were observed. PMID:21508555

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

    SciTech Connect

    White, Terry L; Paulauskas, Felix L; Bigelow, Timothy S

    2014-03-25

    A method for continuously processing carbon fiber including establishing a microwave plasma in a selected atmosphere contained in an elongated chamber having a microwave power gradient along its length defined by a lower microwave power at one end and a higher microwave power at the opposite end of the elongated chamber. The elongated chamber having an opening in each of the ends of the chamber that are adapted to allow the passage of the fiber tow while limiting incidental gas flow into or out of said chamber. A continuous fiber tow is introduced into the end of the chamber having the lower microwave power. The fiber tow is withdrawn from the opposite end of the chamber having the higher microwave power. The fiber to is subjected to progressively higher microwave energy as the fiber is being traversed through the elongated chamber.

  7. 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

  8. 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

  9. 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.

  10. 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

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  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. 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

  20. 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

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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

  8. Photonic-assisted microwave signal multiplication and modulation using a silicon Mach-Zehnder modulator.

    PubMed

    Long, Yun; Zhou, Linjie; Wang, Jian

    2016-01-01

    Photonic generation of microwave signal is obviously attractive for many prominent advantages, such as large bandwidth, low loss, and immunity to electromagnetic interference. Based on a single integrated silicon Mach-Zehnder modulator (MZM), we propose and experimentally demonstrate a simple and compact photonic scheme to enable frequency-multiplicated microwave signal. Using the fabricated integrated MZM, we also demonstrate the feasibility of microwave amplitude-shift keying (ASK) modulation based on integrated photonic approach. In proof-of-concept experiments, 2-GHz frequency-doubled microwave signal is generated using a 1-GHz driving signal. 750-MHz/1-GHz frequency-tripled/quadrupled microwave signals are obtained with a driving signal of 250 MHz. In addition, a 50-Mb/s binary amplitude coded 1-GHz microwave signal is also successfully generated. PMID:26832305

  9. Photonic-assisted microwave signal multiplication and modulation using a silicon Mach-Zehnder modulator

    NASA Astrophysics Data System (ADS)

    Long, Yun; Zhou, Linjie; Wang, Jian

    2016-02-01

    Photonic generation of microwave signal is obviously attractive for many prominent advantages, such as large bandwidth, low loss, and immunity to electromagnetic interference. Based on a single integrated silicon Mach-Zehnder modulator (MZM), we propose and experimentally demonstrate a simple and compact photonic scheme to enable frequency-multiplicated microwave signal. Using the fabricated integrated MZM, we also demonstrate the feasibility of microwave amplitude-shift keying (ASK) modulation based on integrated photonic approach. In proof-of-concept experiments, 2-GHz frequency-doubled microwave signal is generated using a 1-GHz driving signal. 750-MHz/1-GHz frequency-tripled/quadrupled microwave signals are obtained with a driving signal of 250 MHz. In addition, a 50-Mb/s binary amplitude coded 1-GHz microwave signal is also successfully generated.

  10. Photonic-assisted microwave signal multiplication and modulation using a silicon Mach–Zehnder modulator

    PubMed Central

    Long, Yun; Zhou, Linjie; Wang, Jian

    2016-01-01

    Photonic generation of microwave signal is obviously attractive for many prominent advantages, such as large bandwidth, low loss, and immunity to electromagnetic interference. Based on a single integrated silicon Mach–Zehnder modulator (MZM), we propose and experimentally demonstrate a simple and compact photonic scheme to enable frequency-multiplicated microwave signal. Using the fabricated integrated MZM, we also demonstrate the feasibility of microwave amplitude-shift keying (ASK) modulation based on integrated photonic approach. In proof-of-concept experiments, 2-GHz frequency-doubled microwave signal is generated using a 1-GHz driving signal. 750-MHz/1-GHz frequency-tripled/quadrupled microwave signals are obtained with a driving signal of 250 MHz. In addition, a 50-Mb/s binary amplitude coded 1-GHz microwave signal is also successfully generated. PMID:26832305

  11. 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

  12. 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

  13. 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

  14. Salting-out assisted liquid-liquid extraction for the determination of biogenic amines in fruit juices and alcoholic beverages after derivatization with 1-naphthylisothiocyanate and high performance liquid chromatography.

    PubMed

    Jain, Archana; Gupta, Manju; Verma, Krishna K

    2015-11-27

    A new method for determining biogenic amines in fruit juices and alcoholic beverages is described involving reaction of biogenic amines with 1-naphthylisothiocyanate followed by extraction of 1-naphthylthiourea derivatives with water-miscible organic solvent acetonitrile when solvents phase separation occurred using ammonium sulphate, a process called salting-out assisted liquid-liquid extraction. The extract was analyzed by high-performance liquid chromatography with UV detection at 254nm. The new reagent avoided many of the inconveniences as observed with existing derivatizing agents, such as dansyl chloride and benzoyl chloride, in regard to their inselectivity, instability, adverse effect of excess reagent, and necessity to remove excess reagent. The procedure has been optimized with respect to reaction time and temperature, water-miscible extraction solvent, and salt for solvents phase separation. Use of reagent as dispersed phase in aqueous medium produced derivatives in high yield. A linear calibration was obtained between the amount of biogenic amines in range 1-1000μgL(-1) and peak areas of corresponding thioureas formed; the correlation coefficient was 0.9965, and the limit of detection and limit of quantification found were 1.1μgL(-1) and 3.2μgL(-1), respectively. The pre-concentration method gave an average enrichment factor of 94. The application of the method has been demonstrated in the determination of biogenic amines in commercial samples of fruit juices and alcoholic beverages. In spiking experiments to real samples, the average recovery found by the present method was 94.5% that agreed well with 95.8% obtained by established comparison methods. PMID:26518497

  15. A new strategy to determine the protein mutation site using matrix-assisted laser desorption ionization in-source decay: derivatization by ionic liquid.

    PubMed

    Guo, Mengzhe; Zhai, Yixing; Guo, Cheng; Liu, Yaqin; Tang, Daoquan; Pan, Yuanjiang

    2015-03-20

    Matrix-assisted laser desorption ionization (MALDI) time-of-flight mass spectrometry (TOF-MS) can be considered as state of the art in the field of proteins and peptides analysis. In this work, we have designed an ionic liquid derivative strategy to obtain abundant fragment ions in MALDI in-source decay (ISD) and used the analysis of angiogenin with mutation in the fortieth (K40I) as an instance. Firstly, we have synthesized two types of ionic liquids, 3-allyl-4-methyl-1H-imidazol-3-ium and 4-methyl-3-(pent-4-yn-1-yl)-1H-imidazol-3-ium. Then in the light-catalyzed reaction, the alkenyl ionic liquid can open the disulfide bond of K40I protein and add to the thiol. And the derived protein can process in-source decay under the effect of ionic liquid group to produce c-z type ions. Additionally this fragmentation is potentiated to support widely range of fragment ions which can cover the location of mutation. Our results have supplied a new top-down method about how to analyze the mutation or even post-translational modification of proteins in MALDI mass spectrometry. PMID:25732582

  16. 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

  17. Widely tunable single bandpass microwave photonic filter based on Brillouin-assisted optical carrier recovery.

    PubMed

    Wang, Wen Ting; Liu, Jian Guo; Sun, Wen Hui; Wang, Wei Yu; Wang, Sun Long; Zhu, Ning Hua

    2014-12-01

    A widely tunable single bandpass microwave photonic filter (MPF) based on Brillouin-assisted optical carrier recovery in a highly nonlinear fiber (HNLF) with only one optical filter is proposed and experimentally demonstrated. The fundamental principle lies in the fact that the suppressed optical carrier of the phase modulated optical signal could be recovered by the stimulated Brillouin scattering (SBS) amplification effect. When phase modulated optical signals go through an optical filter with a bandpass response, the optical carrier and the upper sidebands suffer from the suppression of the optical filter because they fall in the stopband of that. In our system, the optical carrier could be recovered by the SBS operation around 38 dB. The MPF is achieved by one-to-one mapping from the optical domain to the electrical domain only when one of phase modulated sidebands lies in the bandpass of the optical filter. It shows an excellent selectivity with a 3-dB bandwidth of 170 MHz over a tuning frequency range of 9.5-32.5 GHz. The out-of-band suppression of the MPF is more than 20 dB. Moreover, the MPF shows an excellent shape factor with 10-dB bandwidth of only 520 MHz. The frequency response of the MPF could be widely tuned by changing the frequency difference between the frequency of the optical carrier and the center frequency of the bandpass of the optical filter. A proof-of-concept experiment is carried out to verify the proposed approach. PMID:25606864

  18. 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

  19. 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

  20. 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

  1. 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

  2. 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.

  3. 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

  4. Continuous flow microwave-assisted processing and aseptic packaging of purple-fleshed sweetpotato purees

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pumpable purees from purple-flesh sweetpotatoes (PFSP) were subjected to microwave heating using a 915 MHz continuous flow system, followed by aseptic packaging in flexible containers to obtain a shelf-stable product. Initial test runs were conducted using a 5 kW microwave unit to measure dielectr...

  5. Comparison of microwave, ultrasound and accelerated-assisted solvent extraction for recovery of polyphenols from Citrus sinensis peels.

    PubMed

    Nayak, Balunkeswar; Dahmoune, Farid; Moussi, Kamal; Remini, Hocine; Dairi, Sofiane; Aoun, Omar; Khodir, Madani

    2015-11-15

    Peel of Citrus sinensis contains significant amounts of bioactive polyphenols that could be used as ingredients for a number of value-added products with health benefits. Extraction of polyphenols from the peels was performed using a microwave-assisted extraction (MAE) technique. The effects of aqueous acetone concentration, microwave power, extraction time and solvent-to-solid ratio on the total phenolic content (TPC), total antioxidant activity (TAA) (using DPPH and ORAC-values) and individual phenolic acids (IPA) were investigated using a response surface method. The TPC, TAA and IPA of peel extracts using MAE was compared with conventional, ultrasound-assisted and accelerated solvent extraction. The maximum predicted TPC under the optimal MAE conditions (51% acetone concentration in water (v/v), 500 W microwave power, 122 s extraction time and 25 mL g(-1) solvent to solid ratio), was 12.20 mg GAE g(-1) DW. The TPC and TAA in MAE extracts were higher than the other three extracts. PMID:25977057

  6. 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.

  7. 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.

  8. 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

  9. 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

  10. Ligand-free Pd-catalyzed and copper-assisted C-H arylation of quinazolin-4-ones with aryl iodides under microwave heating.

    PubMed

    Laclef, Sylvain; Harari, Marine; Godeau, Julien; Schmitz-Afonso, Isabelle; Bischoff, Laurent; Hoarau, Christophe; Levacher, Vincent; Fruit, Corinne; Besson, Thierry

    2015-04-01

    A microwave-assisted method for the palladium-catalyzed direct arylation of quinazolin-4-one has been developed under copper-assistance. This method is applicable to a wide range of aryl iodides and substituted (2H)-quinazolin-4-ones. This protocol provides a simple and efficient way to synthesize biologically relevant 2-arylquinazolin-4-one backbones. PMID:25781369

  11. 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.

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. Microwave-assisted catalytic pyrolysis of switchgrass for improving bio-oil and biochar properties.

    PubMed

    Mohamed, Badr A; Kim, Chang Soo; Ellis, Naoko; Bi, Xiaotao

    2016-02-01

    Solid additives were used as a microwave absorber to improve the low microwave absorption rate of switchgrass going through pyrolysis, and as a catalyst to improve the bio-oil and biochar characteristics. The synergistic effects were manifested in the presence of a mixture of K3PO4 and clinoptilolite or bentonite compared with single catalyst, resulting in increased microwave absorption rate, and improved bio-oil and biochar quality. The sample of microwave heating switchgrass with 10wt.% K3PO4+10wt.% bentonite reached 400°C after 2.8min, compared with 28.8min through conventional heating, producing biochar with increase in BET surface area from 0.33m(2)/g to 76.3m(2)/g compared with conventional heating. Furthermore, water content of the bio-oil reduced from 22.7 to 15.0wt.% compared with biomass mixed with 20wt.% SiC, a chemically-inert microwave absorbing material used to increase microwave heating. Introducing catalysts showed a great potential for accelerating microwave heating and improving bio-oil and biochar qualities. PMID:26642217

  18. Microwave plasma jet assisted combustion of premixed methane-air: Roles of OH(A) and OH(X) radicals

    NASA Astrophysics Data System (ADS)

    Wang, Chuji; Wu, Wei

    2013-09-01

    Plasma assisted combustion (PAC) technology can enhance combustion performance by pre-heating combustion fuels, shortening ignition delay time, enhancing flame holding, or increasing flame volume and flame speed. PAC can also increase fuel efficiency by extending fuel lean flammability limit (LFL) and help reduce combustion pollutant emissions. Experiment results have shown that microwave plasma could modify flame structure, increase flame volume, flame speed, flame temperature, and flame stability, and could also extend the fuel lean flammability limit. We report on a novel microwave PAC system that allows us to study PAC using complicated yet well-controlled combinations of operating parameters, such as fuel equivalence ratio (φ) , fuel mixture flow rate, plasma gas flow rate, plasma gases, plasma jet configurations, symmetric or asymmetric fuel-oxidant injection patterns, etc. We have investigated the roles of the stated-resolved OH(A, X) radicals in plasma assisted ignition and combustion of premixed methane-air fuel mixtures. Results suggest that that both the electronically excited state OH(A) and the electronic ground state OH(X) enhance the methane-air ignition process, i.e. extending the fuel LFL, but the flame stabilization and flame holding is primarily determined by the electronic ground state OH(X) as compared to the role of the OH(A). E-mail: cw175@msstate.edu. Supported by National Science Foundation through the grant of ``A quantitative survey of combustion intermediates toward understanding of plasma-assisted combustion mechanism'' (CBET-1066486).

  19. 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

  20. 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.

  1. REVISITING NUCLEOPHILIC SUBSTITUTION REACTIONS: MICROWAVE-ASSISTED SYNTHESIS OF AZIDES, THIOCYANATES AND SULFONES IN AQUEOUS MEDIUM

    EPA Science Inventory

    A practical, rapid and efficient microwave (MW) promoted synthesis of various azides, thiocyanates and sulfones, is described in aqueous medium. This general and expeditious MW-enhanced nucleophilic substitution approach uses easily accessible starting materials such as halides o...

  2. Microwave assisted growth of copper germanide thin films at very low temperatures

    SciTech Connect

    Das, Sayantan; Alford, T. L.

    2013-08-26

    Herein the synthesis of Cu{sub 3}Ge films by exposing Cu-Ge alloy films to microwave radiation is reported. It is shown that microwave radiation led to the formation of copper germanide at temperatures ca. 80 °C. The electrical properties of the Cu{sub 3}Ge films are presented and compared for various annealing times. X-ray diffraction shows that the Cu{sub 3}Ge films formed after microwave annealing is crystalline in the orthorhombic phase. Rutherford backscattering and X-ray photoelectron spectroscopy confirms the formation of copper oxide encapsulation layer. Despite the slight oxidation of Cu during the microwave anneal the lowest resistivity of Cu{sub 3}Ge films obtained is 14 μΩ-cm.

  3. Alternative energy input: Mechanochemical, microwave and ultrasound-assisted organic synthesis

    EPA Science Inventory

    Microwave, ultrasound, sunlight and mechanochemical mixing can be used to augment conventional laboratory techniques. By applying these alternative means of activation, a number of chemical transformations have been achieved thereby improving many existing protocols with superi...

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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).

  9. Simultaneous multi-mycotoxin determination in nutmeg by ultrasound-assisted solid-liquid extraction and immunoaffinity column clean-up coupled with liquid chromatography and on-line post-column photochemical derivatization-fluorescence detection.

    PubMed

    Kong, Wei-Jun; Liu, Shu-Yu; Qiu, Feng; Xiao, Xiao-He; Yang, Mei-Hua

    2013-05-01

    A simple and sensitive analytical method based on ultrasound-assisted solid-liquid extraction and immunoaffinity column clean-up coupled with high performance liquid chromatography and on-line post-column photochemical derivatization-fluorescence detection (USLE-IAC-HPLC-PCD-FLD) has been developed for simultaneous multi-mycotoxin determination of aflatoxins B1, B2, G1, G2 (AFB1, AFB2, AFG1, AFG2) and ochratoxin A (OTA) in 13 edible and medicinal nutmeg samples marketed in China. AFs and OTA were extracted from nutmeg samples by ultrasonication using a methanol : water (80 : 20, v/v) solution, followed by an IAC clean-up step. Different USL extraction conditions, pre-processing ways for nutmeg sample and clean-up columns for mycotoxins, as well as HPLC-PCD-FLD parameters (mobile phase, column temperature, elution procedure, excitation and emission wavelengths) were optimized. This method, which was appraised for analyzing nutmeg samples, showed satisfactory results with reference to limits of detection (LODs) (from 0.02 to 0.25 μg kg(-1)), limits of quantification (LOQs) (from 0.06 to 0.8 μg kg(-1)), linear ranges (up to 30 ng mL(-1) for AFB1, AFG1 and OTA and 9 ng mL(-1) for AFB2 and AFG2), intra- and inter-day variability (all <2%) and average recoveries (from 79.6 to 90.8% for AFs and from 93.6 to 97.3% for OTA, respectively). The results of the application of developed method in nutmeg samples have elucidated that four samples were detected with contamination of AFs and one with OTA. AFB1 was the most frequently found mycotoxin in 30.8% of nutmeg samples at contamination levels of 0.73-16.31 μg kg(-1). At least two different mycotoxins were co-occurred in three samples, and three AFs were simultaneously detected in one sample. PMID:23486692

  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. 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

  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 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

  14. Development of new UV-vis spectroscopic microwave-assisted method for determination of glucose in pharmaceutical samples.

    PubMed

    Mabood, Fazal; Hussain, Z; Haq, H; Arian, M B; Boqué, R; Khan, K M; Hussain, K; Jabeen, F; Hussain, J; Ahmed, M; Alharasi, A; Naureen, Z; Hussain, H; Khan, A; Perveen, S

    2016-01-15

    A new UV-Visible spectroscopic method assisted with microwave for the determination of glucose in pharmaceutical formulations was developed. In this study glucose solutions were oxidized by ammonium molybdate in the presence of microwave energy and reacted with aniline to produce a colored solution. Optimum conditions of the reaction including wavelength, temperature, and pH of the medium and relative concentration ratio of the reactants were investigated. It was found that the optimal wavelength for the reaction is 610 nm, the optimal reaction time is 80s, the optimal reaction temperature is 160°C, the optimal reaction pH is 4, and the optimal concentration ratio aniline/ammonium molybdate solution was found to be 1:1. The limits of detection and quantification of the method are 0.82 and 2.75 ppm for glucose solution, respectively. The use of microwaves improved the speed of the method while the use of aniline improved the sensitivity of the method by shifting the wavelength. PMID:26312738

  15. Rapid Crystallization of L-Alanine on Engineered Surfaces using Metal-Assisted and Microwave-Accelerated Evaporative Crystallization.

    PubMed

    Alabanza, Anginelle M; Pozharski, Edwin; Aslan, Kadir

    2012-01-01

    This study demonstrates the application of metal-assisted and microwave-accelerated evaporative crystallization (MA-MAEC) technique to rapid crystallization of L-alanine on surface engineered silver nanostructures. In this regard, silver island films (SIFs) were modified with hexamethylenediamine (HMA), 1-undecanethiol (UDET), and 11-mercaptoundecanoic acid (MUDA), which introduced -NH(2), -CH(3) and -COOH functional groups to SIFs, respectively. L-Alanine was crystallized on these engineered surfaces and blank SIFs at room temperature and using MA-MAEC technique. Significant improvements in crystal size, shape, and quality were observed on HMA-, MUDA- and UDET-modified SIFs at room temperature (crystallization time = 144, 40 and 147 min, respectively) as compared to those crystals grown on blank SIFs. Using the MA-MAEC technique, the crystallization time of L-alanine on engineered surfaces were reduced to 17 sec for microwave power level 10 (i.e., duty cycle 100%) and 7 min for microwave power level 1 (duty cycle 10%). Raman spectroscopy and powder x-ray diffraction (XRD) measurements showed that L-Alanine crystals grown on engineered surfaces using MA-MAEC technique had identical characteristic peaks of L-alanine crystals grown using traditional evaporative crystallization. PMID:22267957

  16. Development of new UV-vis spectroscopic microwave-assisted method for determination of glucose in pharmaceutical samples

    NASA Astrophysics Data System (ADS)

    Mabood, Fazal; Hussain, Z.; Haq, H.; Arian, M. B.; Boqué, R.; Khan, K. M.; Hussain, K.; Jabeen, F.; Hussain, J.; Ahmed, M.; Alharasi, A.; Naureen, Z.; Hussain, H.; Khan, A.; Perveen, S.

    2016-01-01

    A new UV-Visible spectroscopic method assisted with microwave for the determination of glucose in pharmaceutical formulations was developed. In this study glucose solutions were oxidized by ammonium molybdate in the presence of microwave energy and reacted with aniline to produce a colored solution. Optimum conditions of the reaction including wavelength, temperature, and pH of the medium and relative concentration ratio of the reactants were investigated. It was found that the optimal wavelength for the reaction is 610 nm, the optimal reaction time is 80 s, the optimal reaction temperature is 160 °C, the optimal reaction pH is 4, and the optimal concentration ratio aniline/ammonium molybdate solution was found to be 1:1. The limits of detection and quantification of the method are 0.82 and 2.75 ppm for glucose solution, respectively. The use of microwaves improved the speed of the method while the use of aniline improved the sensitivity of the method by shifting the wavelength.

  17. 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

  18. Synthesis of hexagonal wurtzite Cu{sub 2}ZnSnS{sub 4} prisms by an ultrasound-assisted microwave solvothermal method

    SciTech Connect

    Long, Fei; Chi, Shangsen; He, Jinyun; Wang, Jilin; Wu, Xiaoli; Mo, Shuyi; Zou, Zhengguang

    2015-09-15

    Wurtzite Cu{sub 2}ZnSnS{sub 4} (CZTS) hexagonal prisms were synthesized by a simple ultrasound-microwave solvothermal method. The product was characterized by XRD, FESEM, EDS, TEM, Raman and UV–vis spectrometer. The hexagonal prisms were 0.5–2 μm wide and 5–12 μm long. The PVP played an important role in the formation of the CZTS hexagonal prisms. In addition, the ultrasound-assisted microwave process was helpful for synthesis of wurtzite rather than kesterite phase CZTS. A nucleation–dissolution–recrystallization mechanism was also proposed to explain the growth of the CZTS hexagonal prisms. - Graphical abstract: Wurtzite Cu{sub 2}ZnSnS{sub 4} hexagonal prisms were synthesized by ultrasound-microwave solvothermal method. The ultrasound-assisted microwave process and PVP were useful to the growth of CZTS. A nucleation–dissolution–recrystallization growth mechanism was also proposed. - Highlights: • Wurtzite Cu{sub 2}ZnSnS{sub 4} was prepared by ultrasound-assisted microwave solvothermal method. • The wurtzite CZTS hexagonal prisms are demonstrated a band gap of 1.49 eV. • Synergistic effect of ultrasound and microwave is helpful to prepare Wurtzite CZTS. • PVP plays an important role in the formation of the CZTS hexagonal prisms. • Nucleation–dissolution–recrystallization growth mechanism of the CZTS was proposed.

  19. Microwaved assisted fast synthesis of n and p-doped Mg{sub 2}Si

    SciTech Connect

    Berthebaud, David Gascoin, Franck

    2013-06-15

    Magnesium silicide based alloys fast syntheses have been carried out using microwave heating. Precursors were first ball milled powders together under inert gas. Resulting powders were then placed into a glassy carbon crucible before being heated by microwave irradiation. Sintering of the powder was performed by spark plasma method. XRD and SEM/EDS were used to investigate composition, structure and morphology. Thermoelectric performances of the samples were measured in the temperature range of 320–775 K. The doping effect of several elements such as silver, tin, antimony, cobalt and bismuth has been studied. n-Type and p-type Mg{sub 2}Si based materials have been successfully synthesized, with maximum ZT value up to 0.7 and 0.35 at 770 K for a n-type and a p-type sample, respectively. We demonstrate here that the use of microwave irradiation to prepare doped Mg{sub 2}Si is possible, and we discuss here the thermoelectric properties of such samples. - Schematic representation of microwave hybrid heating. - Highlights: • A promising method for fast production of Mg{sub 2}Si in the frame of heat harvesting applications is presented. • A novel technological approaches towards nanostructured materials is proposed. • Thermoelectric properties of Mg{sub 2}Si doped materials prepared under microwave irradiation are discussed.

  20. 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

  1. Microwave-assisted solvent extraction of polynuclear aromatic hydrocarbons from soils -- report of an interlaboratory study

    SciTech Connect

    Jassie, L.B.; Kierstead, T.; Hays, M.J.; Wise, S.A.

    1995-12-31

    Solvent extractions are among the oldest and most widely practiced sample preparation techniques for chemical analysis. Solvents are selected to dissolve target analytes based on the affinity between solvent and solute and range from highly polar molecules like water to lipophilic hydrocarbons, depending on the target analyte. Although traditional liquid/solid extraction methods are labor intensive and often time consuming, newer extraction techniques using microwave heating more efficiently leach additives from plastics, natural products from botanicals, and pesticides and PAHs from sediment. Certain solvent molecules heat well in microwave fields because the electromagnetic radiation couples with the polar species and energy is transferred to the solution through dipole rotation. We`ll show why some solvents are more logical choices for matching microwave heating technology with an extraction application. Results will be presented of a study extracting PAHs from materials of environmental interest along with the results of a round robin we conducted comparing the recovery efficiency of microwave extractions with conventional extractions. We have also been evaluating solvents with good dielectric properties which may lead to more efficient and environmentally friendly extraction systems. Closed vessel microwave extraction dramatically reduces the solvent volumes needed and the length of the extraction step. With automated cleanup, improved sample throughput is possible.

  2. 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.

  3. Microwave-Assisted Chemistry: A Rapid and Sustainable Route to Synthesis of Organics and Nanomaterials

    EPA Science Inventory

    The use of emerging MW-assisted chemistry techniques in conjunction with benign reaction media is dramatically reducing chemical waste and reaction times in several organic syntheses and chemical transformations. This review summarizes recent developments in MW-assisted synthesis...

  4. 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

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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

  10. 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

  11. 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

  12. 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.

  13. 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

  14. Microwave-assisted regeneration of synthetic zeolite used in tritium removal systems

    SciTech Connect

    Tanaka, M.; Takayama, S.; Sano, S.

    2015-03-15

    The regeneration process using synthetic honeycomb type 5A zeolite under microwave irradiation was experimentally investigated using a single-mode cavity at 2.46 GHz. In order to investigate the effect of electromagnetic fields, inductive heating by a magnetic field was applied to synthetic zeolite containing water. Because the microwave energy absorbed in the sample was less than 15 W, the zeolite sample was only heated to a temperature of 71 C. degrees. Water desorption was observed based on the increased temperature of the zeolite sample and the thermogravimetric curve that indicated a single step phenomenon. As a result, the regeneration process of zeolite was not complete over a period of 6000 s. A comparison of dielectric heating by an electric field with inductive heating by a magnetic field showed that the regeneration process by microwave irradiation was particularly beneficial in dielectric heating. (authors)

  15. Preparation of bitumen and kerogen through microwave assisted extraction and digestion

    SciTech Connect

    Dickneider, T.A.; Martin, S.

    1996-12-31

    Microwave procedures are replacing Soxhlet and ultrasonic extractions in many applications and are also finding widespread use in acid digestion procedures. In microwave extractions solvent choice is not dictated by boiling point considerations, so the choice of solvent(s) can be made based on polarity. It is possible to operate at temperatures above the solvent boiling point and at increased pressures. As a result these extractions are characterized by high solvent efficiency, small sample size, low solvent volumes, and short extraction times. These characteristics are ideal for bitumen extractions. Similarly, in digestion procedures, a high recovery yield is obtained in a minimum time using smaller volumes of acids. We report a convenient procedure for preparation of both bitumen and kerogen from shale samples based on a study of the efficiency of a series of solvents of varying polarity for bitumen recovery and testing of acid composition and volumes at different microwave powers and digestion times.

  16. Microwave-Assisted Synthesis of Bioactive Six-Membered Heterocycles and Their Fused Analogues.

    PubMed

    Driowya, Mohsine; Saber, Aziza; Marzag, Hamid; Demange, Luc; Benhida, Rachid; Bougrin, Khalid

    2016-01-01

    This review describes the formation of six-membered heterocyclic compounds and their fused analogues under microwave activation using modern organic transformations including cyclocondensation, cycloaddition, multicomponents and other modular reactions. The review is divided according to the main heterocycle types in order of increasing complexity, starting with heterocyclic systems containing one, two and three heteroatoms and their fused analogues. Recent microwave applications are reviewed, with special focus on the chemistry of bioactive compounds. Selected examples from the 2006 to 2015 literature are discussed. PMID:27089315

  17. REVISITING CLASSICAL NUCLEOPHILIC SUBSTITUTIONS IN AQUEOUS MEDIUM: MICROWAVE-ASSISTED SYNTHESIS OF ALKYL AZIDES

    EPA Science Inventory

    An efficient and clean synthesis of alkyl azides using microwave (MW) radiation is described in aqueous medium by reacting alkyl halides or tosylates with alkali azides. This general and expeditious MW-enhanced approach to nucleophilic substitution reactions is applicable to the ...

  18. Microwave plasma assisted supersonic gas jet deposition of thin film materials

    DOEpatents

    Schmitt, III, Jerome J.; Halpern, Bret L.

    1993-01-01

    An apparatus for fabricating thin film materials utilizing high speed gas dynamics relies on supersonic free jets of carrier gas to transport depositing vapor species generated in a microwave discharge to the surface of a prepared substrate where the vapor deposits to form a thin film. The present invention generates high rates of deposition and thin films of unforeseen high quality at low temperatures.

  19. Microwave-assisted Extraction of Phenolics from Bean (Phaseolus vulgaris L.)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The phenolic phytochemicals are associated with many health benefits, and it is useful to develop improved methods for its extraction from beans. In this work, we showed that extraction with microwave irradiation is an effective method for the determination of extractable phenolic content in beans....

  20. Production of Feruloyated Arabinoxylo-oligosaccharides from Maize (Zea mays) Bran by Microwave-Assisted Autohydrolysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Maize bran was treated with microwave irradiation (160 – 200 °C for 2 – 20 min) to release feruolyated arabinoxylo-oligosaccharides (AXOS). Lower temperatures and shorter treatment times were consistent with low AXOS yields, while higher temperatures and longer reaction times also resulted in low y...

  1. Student-Driven Design of Peptide Mimetics: Microwave-Assisted Synthesis of Peptoid Oligomers

    ERIC Educational Resources Information Center

    Pohl, Nicola L. B.; Kirshenbaum, Kent; Yoo, Barney; Schulz, Nathan; Zea, Corbin J.; Streff, Jennifer M.; Schwarz, Kimberly L.

    2011-01-01

    An experiment for the undergraduate organic laboratory is described in which peptide mimetic oligomers called "peptoids" are built stepwise on a solid-phase resin. Students employ two modern strategies to facilitate rapid multistep syntheses: solid-phase techniques to obviate the need for intermediate purifications and microwave irradiation to…

  2. Microwave-Assisted Esterification: A Discovery-Based Microscale Laboratory Experiment

    ERIC Educational Resources Information Center

    Reilly, Maureen K.; King, Ryan P.; Wagner, Alexander J.; King, Susan M.

    2014-01-01

    An undergraduate organic chemistry laboratory experiment has been developed that features a discovery-based microscale Fischer esterification utilizing a microwave reactor. Students individually synthesize a unique ester from known sets of alcohols and carboxylic acids. Each student identifies the best reaction conditions given their particular…

  3. Microwave and plasma-assisted modification of composite fiber surface topography

    DOEpatents

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

    2003-02-04

    The present invention introduces a novel method for producing an undulated surface on composite fibers using plasma technology and microwave radiation. The undulated surface improves the mechanical interlocking of the fibers to composite resins and enhances the mechanical strength and interfacial sheer strength of the composites in which they are introduced.

  4. Microwave-Assisted Organic Synthesis Using Benign Reaction Medium and Reagents

    EPA Science Inventory

    Account of chemical reactions expedited by microwave (MW) exposure of neat reactants for the rapid one-pot assembly of heterocyclic compounds from in situ generated reactive intermediates via enamines or using hypervalent iodine reagents will be described that can be adapted for ...

  5. Photonic-assisted chirped microwave pulses generation with a flexible and fine parameter manipulation.

    PubMed

    Liu, Xinkai; Pan, Wei; Zou, Xihua; Yan, Lianshan; Luo, Bin; Zheng, Di; Ye, Jia; Lu, Bing

    2016-08-22

    A photonic approach for generating chirped microwave pulses with a flexible and fine parameter manipulation is proposed and experimentally demonstrated. In the proposed system, an intensity modulator (IM) biased at the minimum transmission point is used to generate two ± 1st-order optical sidebands which are then sent to a phase modulator (PM) for implementing large-signal phase modulations. A de-interleaver combined with an optical variable delay line (OVDL) is utilized to introduce a time delay between two phase-modulated optical signals. A second IM that acts as a time domain intensity switch (TDIS) is used to select different phase modulation ranges of the two phase-modulated optical signals. After the optical-electrical conversion in a photodetector (PD), chirped microwave pulses are generated. The key feature of this approach is that the parameters of the generated chirped microwave pulses including central frequency, pulse repetition frequency, and chirp rate can be flexibly and precisely manipulated by the radio frequency (RF) signals applied to modulators. A proof-of-principle experiment is carried out to verify the proposed approach. Consequently, positive or negative chirped microwave pulses with different central frequencies at 20, 22, 24 or 26 GHz and different pulse repetition frequencies at 1.5 or 2 GHz are generated, respectively. PMID:27557237

  6. Design and Microwave Assisted Synthesis of Coumarin Derivatives as PDE Inhibitors.

    PubMed

    Kumbar, Mahadev N; Kamble, Ravindra R; Kamble, Atulkumar A; Salian, Sujith Raj; Kumari, Sandhya; Nair, Ramya; Kalthur, Guruprasad; Adiga, Satish Kumar; Prasad, D Jagadeesh

    2016-01-01

    Coumarins appended to benzimidazole through pyrazole are designed and synthesized using microwave irradiation. These compounds were analyzed for phosphodiesterase (PDE) inhibition indirectly by motility pattern in human spermatozoa. Some of the synthesized compounds, namely, 5d, 5e, 5f, 5g, 5h, and 5k, have exhibited potent inhibitory activity on PDE. PMID:26998358

  7. Design and Microwave Assisted Synthesis of Coumarin Derivatives as PDE Inhibitors

    PubMed Central

    Kumbar, Mahadev N.; Kamble, Ravindra R.; Kamble, Atulkumar A.; Salian, Sujith Raj; Kumari, Sandhya; Nair, Ramya; Kalthur, Guruprasad; Adiga, Satish Kumar; Prasad, D. Jagadeesh

    2016-01-01

    Coumarins appended to benzimidazole through pyrazole are designed and synthesized using microwave irradiation. These compounds were analyzed for phosphodiesterase (PDE) inhibition indirectly by motility pattern in human spermatozoa. Some of the synthesized compounds, namely, 5d, 5e, 5f, 5g, 5h, and 5k, have exhibited potent inhibitory activity on PDE. PMID:26998358

  8. 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

  9. 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.

  10. 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.

  11. Microwave-assisted transformations and synthesis of polymer nanocomposites and nanomaterials

    EPA Science Inventory

    The use of emerging MW-assisted chemistry techniques in conjunction with greener reaction media is dramatically reducing chemical waste and reaction times in several organic transformations and material synthesis. This account summarizes our own experience in developing MW-assist...

  12. Selenium Derivatization of Nucleic Acids for Crystallography

    SciTech Connect

    Jiang,J.; Sheng, J.; Carrasco, N.; Huang, Z.

    2007-01-01

    The high-resolution structure of the DNA (5'-GTGTACA-C-3') with the selenium derivatization at the 2'-position of T2 was determined via MAD and SAD phasing. The selenium-derivatized structure (1.28 {angstrom} resolution) with the 2'-Se modification in the minor groove is isomorphorous to the native structure (2.0 {angstrom}). To directly compare with the conventional bromine derivatization, we incorporated bromine into the 5-postion of T4, determined the bromine-derivatized DNA structure at 1.5 {angstrom} resolution, and found that the local backbone torsion angles and solvent hydration patterns were altered in the structure with the Br incorporation in the major groove. Furthermore, while the native and Br-derivatized DNAs needed over a week to form reasonable-size crystals, we observed that the Se-derivatized DNAs grew crystals overnight with high-diffraction quality, suggesting that the Se derivatization facilitated the crystal formation. In addition, the Se-derivatized DNA sequences crystallized under a broader range of buffer conditions, and generally had a faster crystal growth rate. Our experimental results indicate that the selenium derivatization of DNAs may facilitate the determination of nucleic acid X-ray crystal structures in phasing and high-quality crystal growth. In addition, our results suggest that the Se derivatization can be an alternative to the conventional Br derivatization.

  13. Microwave-Assisted Synthesis and Characterization of CaS Nanoparticles

    NASA Astrophysics Data System (ADS)

    Roy, Arup; Bhattacharya, Jayanta

    2012-10-01

    CaS nanoparticles have been synthesized by microwave irradiation, using Ca(Ac)2 as Ca-precursor, and thioacetamide as S-source. The as-prepared sample has a uniform morphology and high purity. After heat treatment similar results were observed. Synthesized nanoparticles were characterized by X-ray powder analysis (XRD), field emission scanning microscopy (FESEM), high resolution transmission electron microscopy (TEM), and UV-Vis absorption spectroscopy. X-ray diffraction patterns suggest the formation of single cubical face of CaS having average particle size of 22 nm. HRTEM micrographs reveal well dispersed cubical morphology with a size distribution of 18-30 nm. Ultraviolet-visible (UV-Vis) spectroscopy shows absorption at 268 nm. In nutshell, microwave irradiation is proved to be a convenient, efficient and environmental-friendly one-step route to synthesize nanoparticles.

  14. Microwave-assisted rapid synthesis of anisotropic Ag nanoparticles by solid state transformation

    NASA Astrophysics Data System (ADS)

    Navaladian, S.; Viswanathan, B.; Varadarajan, T. K.; Viswanath, R. P.

    2008-01-01

    Anisotropic silver nanoparticles (NPs) have been synthesized rapidly using microwave irradiation by the decomposition of silver oxalate in a glycol medium using polyvinyl pyrolidone (PVP) as the capping agent. The obtained Ag nanoparticles have been characterized by UV-visible spectroscopy, powder x-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) studies. Anisotropic Ag nanoparticles of average size around 30 nm have been observed in the case of microwave irradiation for 75 s whereas spherical particles of a size around 5-6 nm are formed for 60 s of irradiation. The texture coefficient and particle size calculated from XRD patterns of anisotropic nanoparticles reveal the preferential orientation of (111) facets in the Ag sample. Ethylene glycol is found to be a more suitable medium than diethylene glycol. A plausible mechanism has been proposed for the formation of anisotropic Ag nanoparticles from silver oxalate.

  15. Photon-assisted tunnelling with nonclassical microwaves in hybrid circuit QED systems

    NASA Astrophysics Data System (ADS)

    Souquet, Jean-René; Woolley, Matthew; Gabelli, Julien; Simon, Pascal; Clerk, Aashish

    2015-03-01

    Motivated by recent experiments where superconducting microwave circuits have been coupled to electrons in semiconductor nanostructures, we study theoretically the interplay of non-classical light produced in a cavity with electron transport through a tunnel junction. We demonstrate that this basic light-matter interaction is naturally characterized by non-positive definite quasi-probability distributions which are intimately connected to the Glauber-Sudarshan P-function. We further demonstrate that this negative quasiprobability has unequivocal signatures on the differential conductance that should be easily detectable in state of art experiments. This thus turns the tunnel junction into a non-trivial probe of the microwave state. We also discuss the non-trivial backaction of the junction current on the cavity.

  16. Stabilization of Co{sup 2+} in layered double hydroxides (LDHs) by microwave-assisted ageing

    SciTech Connect

    Herrero, M.; Benito, P.; Labajos, F.M.; Rives, V.

    2007-03-15

    Co-containing layered double hydroxides at different pH have been prepared, and aged following different routes. The solids prepared have been characterized by element chemical analysis, powder X-ray diffraction, thermogravimetric and differential thermal analyses (both in nitrogen and in oxygen), FT-IR and Vis-UV spectroscopies, temperature-programmed reduction and surface area assessment by nitrogen adsorption at -196 deg. C. The best conditions found to preserve the cobalt species in the divalent oxidation state are preparing the samples at controlled pH, and then submit them to ageing under microwave irradiation. - Graphical abstract: The use of microwave-hydrothermal treatment, controlling both temperature and ageing time, permits to synthesize well-crystallized nanomaterials with controlled surface properties. An enhancement in the crystallinity degree and an increase in the particle size are observed when the irradiation time is prolonged.

  17. Microwave-assisted incorporation of silver nanoparticles in paper for point-of-use water purification

    PubMed Central

    Dankovich, Theresa A.

    2014-01-01

    This work reports an environmentally benign method for the in situ preparation of silver nanoparticles (AgNPs) in paper using microwave irradiation. Through thermal evaporation, microwave heating with an excess of glucose relative to the silver ion precursor yields nanoparticles on the surface of cellulose fibers within three minutes. Paper sheets were characterized by electron microscopy, UV-Visible reflectance spectroscopy, and atomic absorption spectroscopy. Antibacterial activity and silver release from the AgNP sheets were assessed for model Escherichia coli and Enterococci faecalis bacteria in deionized water and in suspensions that also contained with various influent solution chemistries, i.e. with natural organic matter, salts, and proteins. The paper sheets containing silver nanoparticles were effective in inactivating the test bacteria as they passed through the paper. PMID:25400935

  18. Microwave assisted thermal treatment of defective coffee beans press cake for the production of adsorbents.

    PubMed

    Franca, Adriana S; Oliveira, Leandro S; Nunes, Anne A; Alves, Cibele C O

    2010-02-01

    Defective coffee press cake, a residue from coffee oil biodiesel production, was evaluated as an adsorbent for removal of basic dyes (methylene blue--MB) from aqueous solutions. The adsorbent was prepared by microwave treatment, providing a significant reduction in processing time coupled to an increase in adsorption capacity in comparison to conventional carbonization in a muffle furnace. Batch adsorption tests were performed at 25 degrees C and the effects of particle size, contact time, adsorbent dosage and initial solution pH were investigated. Adsorption kinetics was better described by a second-order model. The experimental adsorption equilibrium data were fitted to Langmuir, Freundlich and Tempkin adsorption models, with Langmuir providing the best fit. The results presented in this study show that microwave activation presents great potential as an alternative method in the production of adsorbents. PMID:19767204

  19. Effective dopant activation by susceptor-assisted microwave annealing of low energy boron implanted and phosphorus implanted silicon

    SciTech Connect

    Zhao, Zhao; Vemuri, Rajitha N. P.; Alford, T. L.; David Theodore, N.; Lu, Wei; Lau, S. S.; Lanz, A.

    2013-12-28

    Rapid processing and reduced end-of-range diffusion result from susceptor-assisted microwave (MW) annealing, making this technique an efficient processing alternative for electrically activating dopants within ion-implanted semiconductors. Sheet resistance and Hall measurements provide evidence of electrical activation. Susceptor-assisted MW annealing, of ion-implanted Si, enables more effective dopant activation and at lower temperatures than required for rapid thermal annealing (RTA). Raman spectroscopy and ion channeling analyses are used to monitor the extent of ion implantation damage and recrystallization. The presence and behavior of extended defects are monitored by cross-section transmission electron microscopy. Phosphorus implanted Si samples experience effective electrical activation upon MW annealing. On the other hand, when boron implanted Si is MW annealed, the growth of extended defects results in reduced crystalline quality that hinders the electrical activation process. Further comparison of dopant diffusion resulting from MW annealing and rapid thermal annealing is performed using secondary ion mass spectroscopy. MW annealed ion implanted samples show less end-of-range diffusion when compared to RTA samples. In particular, MW annealed P{sup +} implanted samples achieve no visible diffusion and equivalent electrical activation at a lower temperature and with a shorter time-duration of annealing compared to RTA. In this study, the peak temperature attained during annealing does not depend on the dopant species or dose, for susceptor-assisted MW annealing of ion-implanted Si.

  20. Quantitative O-Glycomics by Microwave-Assisted β-Elimination in the Presence of Pyrazolone Analogues.

    PubMed

    Furukawa, Jun-ichi; Piao, Jinhua; Yoshida, Yasunobu; Okada, Kazue; Yokota, Ikuko; Higashino, Kenichi; Sakairi, Nobuo; Shinohara, Yasuro

    2015-08-01

    O-Linked glycosylation of serine/threonine residues is a posttranslational modification of proteins and is essential for protein recognition and lipid functions on cell surfaces and within cells. The characterization of differently structured O-linked glycans (O-glycans) is particularly challenging because there is no known endoglycosidase for such groups. Therefore, chemical digestion approaches have been widely used; however, it is sometimes difficult to suppress unwanted side reactions. Recently, we reported a novel O-glycomics procedure using β-elimination in the presence of pyrazolone analogues (BEP). In the present study, we describe a microwave (MW)-assisted BEP procedure for rapid and quantitative O-glycomic analysis. Following optimization of the reaction conditions, the MW-assisted BEP reaction substantially improved the recovery of total O-glycans from model glycoproteins (PSM) and the reaction time was reduced from 16 to 2 h. Combined with sequential solid-phase extractions, this MW-assisted BEP procedure enabled O-glycomic analyses of various biological samples. PMID:26132640

  1. An examination of pentafluorobenzoyl derivatization strategies for the analysis of fatty alcohols using gas chromatography/electron capture negative ion chemical ionization-mass spectrometry.

    PubMed

    Bowden, John A; Ford, David A

    2011-05-15

    Gas chromatography/electron capture negative ion chemical ionization-mass spectrometry (GC/ECNICI-MS) combined with pentafluorobenzoyl derivatization (PFBoyl) is frequently used for the sensitive detection of fatty alcohols (FOH). However, this derivatization technique suffers from a lack of established reaction protocols, time-consuming reactions, and the presence of reagent artifacts or unwanted derivatization by-products which can hinder analyte detection. Here, strategies are presented to reduce the problems associated with PFBoyl-derivatization, including (1) the optimization of reaction conditions (derivatization time and temperature) for a variety of PFBoyl-derivatized FOH, (2) an investigation of microwave-accelerated derivatization (MAD) as a rapid alternative heating mechanism for the PFBoyl-derivatization of FOH, and (3) an analysis of an alternative strategy employing a solvent extraction procedure post-derivatization to reduce the detrimental effects commonly associated with PFBoyl derivatization reagents. The optimal reaction conditions for the PFBoyl-derivatization of FOH were determined to be 60°C for 45 min. The investigation in MAD demonstrated the potential of obtaining comparable PFBoyl-derivatizations to those obtained using traditional heating methods, albeit in a reaction time of 3 min. An examination of several solvents for post-derivatization extraction revealed improved relative response factors in comparison to those obtained without solvent extraction. The best solvents for the PFBoyl-FOH extraction, dichloromethane and tert-butyl methyl ether, were also compared to the no solvent extraction samples with standard response curves and PFBoyl-derivatized FOH in Bligh-Dyer extracted rat plasma. PMID:21094100

  2. Microwave plasma assisted supersonic gas jet deposition of thin film materials

    DOEpatents

    Schmitt, J.J. III; Halpern, B.L.

    1993-10-26

    An apparatus for fabricating thin film materials utilizing high speed gas dynamics relies on supersonic free jets of carrier gas to transport depositing vapor species generated in a microwave discharge to the surface of a prepared substrate where the vapor deposits to form a thin film. The present invention generates high rates of deposition and thin films of unforeseen high quality at low temperatures. 5 figures.

  3. Microwave-assisted pyrolysis of SiC and its application to joining

    SciTech Connect

    Ahmad, I.; Silberglitt, R.; Shan, T.A.

    1995-07-01

    Microwave energy has been used to pyrolyze silicon carbide from commercially available polycarbosilane precursor. The pyrolysis was performed on SiC surfaces having various surface treatments, to identify conditions which improve the wetting and adherence. Grinding and etching of the surfaces in hydrofluoric (HF) acid promotes the bonding of precursor derived ceramic to the SiC ceramic. Finally, the polycarbosilane precursor mixed with fine silicon carbide powder was used as the interlayer material to join silicon carbide specimens.

  4. Highly efficient and reusable CNT supported iron(ii) catalyst for microwave assisted alcohol oxidation.

    PubMed

    Martins, L M D R S; Ribeiro, A P C; Carabineiro, S A C; Figueiredo, J L; Pombeiro, A J L

    2016-04-19

    The highly efficient eco-friendly synthesis of ketones (yields over 99%) from secondary alcohols is achieved by combination of [FeCl2{η(3)-HC(pz)3}] (pz = pyrazol-1-yl) supported on functionalized multi-walled carbon nanotubes and microwave irradiation, in a solvent-free medium. The carbon homoscorpionate iron(ii) complex is the first one of this class to be used as catalyst for the oxidation of alcohols. PMID:27007743

  5. Aqueous microwaves assisted cross-coupling reactions applied to unprotected nucleosides.

    NASA Astrophysics Data System (ADS)

    Len, Christophe; Hervé, Gwénaelle

    2015-02-01

    Nucleoside analogues have attracted much attention due to their potential biological activities. Amongst all synthetic nucleosides, C5-modified pyrimidines and C7- or C8-modified purines have mostly been prepared using palladium cross-coupling reactions and then studied as antitumoral and antiviral agents. Our objective is to focus this review on the Suzuki-Miyaura and on the Heck cross-couplings of nucleosides using microwave irradiations which are an alternative technology compatible with green chemistry and sustainable development.

  6. 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

  7. 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.

  8. 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

  9. Peroxide-assisted microwave activation of pyrolysis char for adsorption of dyes from wastewater.

    PubMed

    Nair, Vaishakh; Vinu, R

    2016-09-01

    In this study, mesoporous activated biochar with high surface area and controlled pore size was prepared from char obtained as a by-product of pyrolysis of Prosopis juliflora biomass. The activation was carried out by a simple process that involved H2O2 treatment followed by microwave pyrolysis. H2O2 impregnation time and microwave power were optimized to obtain biochar with high specific surface area and high adsorption capacity for commercial dyes such as Remazol Brilliant Blue and Methylene Blue. Adsorption parameters such as initial pH of the dye solution and adsorbent dosage were also optimized. Pore size distribution, surface morphology and elemental composition of activated biochar were thoroughly characterized. H2O2 impregnation time of 24h and microwave power of 600W produced nanostructured biochar with narrow and deep pores of 357m(2)g(-1) specific surface area. Langmuir and Langmuir-Freundlich isotherms described the adsorption equilibrium, while pseudo second order model described the kinetics of adsorption. PMID:27268436

  10. Microwave-assisted autohydrolysis of Prunus mume stone for extraction of polysaccharides and phenolic compounds.

    PubMed

    Tsubaki, S; Ozaki, Y; Azuma, J

    2010-03-01

    Stone of Prunus mume (P. mume) is a by-product of pickled P. mume industry. Stones of native and pickled P. mume, mainly composed of holocellulose (83.8 +/- 1.8% and 65.1 +/- 0.3%, respectively) and acid-insoluble lignin (25.3 +/- 2.2% and 30.6 +/- 0.9%, respectively), were autohydrolyzed by microwave heating to extract polysaccharides and phenolic compounds. By heating at 200 to 230 degrees C, 48.0% to 60.8% of polysaccharide and 84.1% to 97.9% of phenolic compound were extracted in water along with partial degradation of hemicelluloses and lignin. The extracted liquors showed antioxidant activity against hydroxyl radical and DPPH radical originated from phenolic compounds. The pickled P. mume stone showed higher autohydrolyzability and microwave absorption capacity than the native stone due to absorbed salts and acids during pickling in fruit juice of P. mume with external addition of sodium chloride. Pickling process in salty and weak acidic juice seemed to be a kind of pretreatment for softening the stones prior to autohydrolysis induced by microwave heating. PMID:20492219

  11. Multiphysics numerical modeling of the continuous flow microwave-assisted transesterification process.

    PubMed

    Muley, Pranjali D; Boldor, Dorin

    2012-01-01

    Use of advanced microwave technology for biodiesel production from vegetable oil is a relatively new technology. Microwave dielectric heating increases the process efficiency and reduces reaction time. Microwave heating depends on various factors such as material properties (dielectric and thermo-physical), frequency of operation and system design. Although lab scale results are promising, it is important to study these parameters and optimize the process before scaling up. Numerical modeling approach can be applied for predicting heating and temperature profiles including at larger scale. The process can be studied for optimization without actually performing the experiments, reducing the amount of experimental work required. A basic numerical model of continuous electromagnetic heating of biodiesel precursors was developed. A finite element model was built using COMSOL Multiphysics 4.2 software by coupling the electromagnetic problem with the fluid flow and heat transfer problem. Chemical reaction was not taken into account. Material dielectric properties were obtained experimentally, while the thermal properties were obtained from the literature (all the properties were temperature dependent). The model was tested for the two different power levels 4000 W and 4700 W at a constant flow rate of 840ml/min. The electric field, electromagnetic power density flow and temperature profiles were studied. Resulting temperature profiles were validated by comparing to the temperatures obtained at specific locations from the experiment. The results obtained were in good agreement with the experimental data. PMID:24432470

  12. Rapid synthesis of white-light emissive ZnO nanorods using microwave assisted method

    NASA Astrophysics Data System (ADS)

    Karimipour, M.; Mohammad-Sadeghipour, A.; Molaei, M.; Khanzadeh, M.

    2015-12-01

    In this paper, firstly we have synthesized ZnO nanowires using zinc acetate, ethanol and ammonium hydroxide by a thermo-chemical method and then ZnO nanorods (NRs) have been prepared by microwave irradiation (MI) of an initial solution containing ZnO nanowires. X-ray diffraction (XRD) analysis showed the rare zinc-blende phase which grows on the surface of NRs and its crystallite size increases with the increase of microwave power. The average length and width of rods were observed several hundreds of nanometer and 80nm, respectively, from scanning electron microscope (SEM) analysis. Ultraviolet-visible (UV-vis) absorption spectroscopy indicates that a band tail forms due to MI, which has roughly 2eV energy gap. Photoluminescence (PL) spectroscopy indicated a blue emission and a white emission for ZnO nanowires and NRs, respectively. MI quenches the UV emission from ZnO NRs and enhances the surface defects’ emission. The resultant visible PL of the samples increases with the increase of microwave power that shows the growth of zinc-blende phase which has crucial effect on the defect density of NRs.

  13. Apparatus and method for investigation of energy consumption of microwave assisted drying systems.

    PubMed

    Göllei, Attila; Vass, András; Magyar, Attila; Pallai, Elisabeth

    2009-10-01

    Convective, hot air drying by itself is relatively efficient for removing water from the surface environment of agricultural seed products. However, moving internal moisture to the surface needs rather a long time, as a rule. The major research aim of the authors was to decrease the processing time and processing costs, to improve the quality of the dried product, and to increase drying efficiency. For this reason their research activities focused on the development of a special drying apparatus and a method suitable for measuring of energy conditions in a hybrid (microwave and convective) dryer. Experimental investigations were made with moistened wheat as model material. Experiments were carried out in microwave, convective and hybrid drying systems. The microwave drying alone was more efficient than the convective method. The lowest energy consumption and shortest drying time were obtained by the use of a hybrid method in which the waste energy of magnetron was utilized and the temperature was controlled. In this way, it was possible to keep the temperature of the dried product at a constant and safe value and to considerably decrease the energy consumption. PMID:19895084

  14. Microwave assisted enzymatic kinetic resolution of (±)-1-phenyl-2-propyn-1-ol in nonaqueous media.

    PubMed

    Devendran, Saravanan; Yadav, Ganapati D

    2014-01-01

    Kinetic resolution of 1-phenyl-2-propyn-1-ol, an important chiral synthon, was studied through trans-esterification with acyl acetate to investigate synergism between microwave irradiation and enzyme catalysis. Lipases from different microbial origins were employed for the kinetic resolution of (R/S)-1-phenyl-2-propyn-1-ol, among which Candida antarctica lipase B, immobilized on acrylic resin (Novozym 435), was found to be the best catalyst in n-hexane as solvent. Vinyl acetate was the most effective among different acyl esters studied. The effect of various parameters was studied in a systematic manner. Definite synergism between microwave and enzyme was observed. The initial rate was improved around 1.28 times under microwave irradiation than conventional heating. Under optimum conditions, maximum conversion (48.78%) and high enantiomeric excess (93.25%) were obtained in 2 h. From modeling studies, it is concluded that the reaction follows the Ping-Pong bi-bi mechanism with dead end alcohol inhibition. Kinetic parameters were obtained by using nonlinear regression. This process is green, clean, and easily scalable as compared to the chemical process. PMID:24707487

  15. All-optical tuning of a nonlinear silicon microring assisted microwave photonic filter: theory and experiment.

    PubMed

    Long, Yun; Wang, Jian

    2015-07-13

    We propose and demonstrate an all-optical tuning mechanism to tune the response of a microwave photonic filter (MPF) based on a nonlinear silicon microring resonator (MRR). The tuning mechanism relies on the optical nonlinearities induced resonant wavelength shift in the silicon MRR, leading to the change of frequency difference between the optical carrier frequency and resonant frequency of the silicon MRR. A detailed theoretical model is established to describe the operation of the proposed all-optical tunable MPF. Two cases are studied in the experiment, i.e. the optical carrier frequency is located at the left or right side of the MRR resonant frequency. Both forward and backward pumping configurations in each case are demonstrated. Using the fabricated silicon MRR and exploiting light to control light, the central frequency of the notch MPF can be flexibly tuned by adjusting the pump light power. Moreover, the presented all-optical tuning mechanism might also facilitate interesting applications such as microwave switching and microwave modulation. PMID:26191838

  16. Microwave Assisted Enzymatic Kinetic Resolution of (±)-1-Phenyl-2-propyn-1-ol in Nonaqueous Media

    PubMed Central

    Devendran, Saravanan; Yadav, Ganapati D.

    2014-01-01

    Kinetic resolution of 1-phenyl-2-propyn-1-ol, an important chiral synthon, was studied through trans-esterification with acyl acetate to investigate synergism between microwave irradiation and enzyme catalysis. Lipases from different microbial origins were employed for the kinetic resolution of (R/S)-1-phenyl-2-propyn-1-ol, among which Candida antarctica lipase B, immobilized on acrylic resin (Novozym 435), was found to be the best catalyst in n-hexane as solvent. Vinyl acetate was the most effective among different acyl esters studied. The effect of various parameters was studied in a systematic manner. Definite synergism between microwave and enzyme was observed. The initial rate was improved around 1.28 times under microwave irradiation than conventional heating. Under optimum conditions, maximum conversion (48.78%) and high enantiomeric excess (93.25%) were obtained in 2 h. From modeling studies, it is concluded that the reaction follows the Ping-Pong bi-bi mechanism with dead end alcohol inhibition. Kinetic parameters were obtained by using nonlinear regression. This process is green, clean, and easily scalable as compared to the chemical process. PMID:24707487

  17. An Automated Microwave-Assisted Synthesis Purification System for Rapid Generation of Compound Libraries.

    PubMed

    Tu, Noah P; Searle, Philip A; Sarris, Kathy

    2016-06-01

    A novel methodology for the synthesis and purification of drug-like compound libraries has been developed through the use of a microwave reactor with an integrated high-performance liquid chromatography-mass spectrometry (HPLC-MS) system. The strategy uses a fully automated synthesizer with a microwave as energy source and robotic components for weighing and dispensing of solid reagents, handling liquid reagents, capper/crimper of microwave reaction tube assemblies, and transportation. Crude reaction products were filtered through solid-phase extraction cartridges and injected directly onto a reverse-phase chromatography column via an injection valve. For multistep synthesis, crude products were passed through scavenger resins and reintroduced for subsequent reactions. All synthetic and purification steps were conducted under full automation with no handling or isolation of intermediates, to afford the desired purified products. This approach opens the way to highly efficient generation of drug-like compounds as part of a lead discovery strategy or within a lead optimization program. PMID:26085482

  18. Apparatus and method for investigation of energy consumption of microwave assisted drying systems

    NASA Astrophysics Data System (ADS)

    Göllei, Attila; Vass, András; Magyar, Attila; Pallai, Elisabeth

    2009-10-01

    Convective, hot air drying by itself is relatively efficient for removing water from the surface environment of agricultural seed products. However, moving internal moisture to the surface needs rather a long time, as a rule. The major research aim of the authors was to decrease the processing time and processing costs, to improve the quality of the dried product, and to increase drying efficiency. For this reason their research activities focused on the development of a special drying apparatus and a method suitable for measuring of energy conditions in a hybrid (microwave and convective) dryer. Experimental investigations were made with moistened wheat as model material. Experiments were carried out in microwave, convective and hybrid drying systems. The microwave drying alone was more efficient than the convective method. The lowest energy consumption and shortest drying time were obtained by the use of a hybrid method in which the waste energy of magnetron was utilized and the temperature was controlled. In this way, it was possible to keep the temperature of the dried product at a constant and safe value and to considerably decrease the energy consumption.

  19. Surfactant-assisted solvothermal synthesis of pure nickel submicron spheres with microwave-absorbing properties.

    PubMed

    Guo, Heng; Pu, Bingxue; Chen, Haiyuan; Yang, Jin; Zhou, Yajun; Yang, Jian; Bismark, Boateng; Li, Handong; Niu, Xiaobin

    2016-12-01

    Pure metallic nickel submicron spheres (Ni-SSs), flower-like nickel nanoflakes, and hollow micrometer-sized nickel spheres/tubes were controllably synthesized by a facile and efficient one-step solvothermal method with no reducing agent. The characteristics of these nickel nanostructures include morphology, structure, and purification. Possible synthesis mechanisms were discussed in detail. The resultant Ni-SSs had a wide diameter distribution of 200~800 nm through the aggregation of small nickel nanocrystals. The ferromagnetic behaviors of Ni-SSs investigated at room temperature showed high coercivity values. Furthermore, the microwave absorption properties of magnetic Ni-SSs were studied in the frequency range of 0.5-18.0 GHz. The minimum reflection loss reached -17.9 dB at 17.8 GHz with a thin absorption thickness of 1.2 mm, suggesting that the submicron spherical structures could exhibit excellent microwave absorption properties. More importantly, this one-pot synthesize route provides a universal and convenient way for preparation of larger scale pure Ni-SSs, showing excellent microwave absorption properties. PMID:27473115

  20. Surfactant-assisted solvothermal synthesis of pure nickel submicron spheres with microwave-absorbing properties

    NASA Astrophysics Data System (ADS)

    Guo, Heng; Pu, Bingxue; Chen, Haiyuan; Yang, Jin; Zhou, Yajun; Yang, Jian; Bismark, Boateng; Li, Handong; Niu, Xiaobin

    2016-07-01

    Pure metallic nickel submicron spheres (Ni-SSs), flower-like nickel nanoflakes, and hollow micrometer-sized nickel spheres/tubes were controllably synthesized by a facile and efficient one-step solvothermal method with no reducing agent. The characteristics of these nickel nanostructures include morphology, structure, and purification. Possible synthesis mechanisms were discussed in detail. The resultant Ni-SSs had a wide diameter distribution of 200~800 nm through the aggregation of small nickel nanocrystals. The ferromagnetic behaviors of Ni-SSs investigated at room temperature showed high coercivity values. Furthermore, the microwave absorption properties of magnetic Ni-SSs were studied in the frequency range of 0.5-18.0 GHz. The minimum reflection loss reached -17.9 dB at 17.8 GHz with a thin absorption thickness of 1.2 mm, suggesting that the submicron spherical structures could exhibit excellent microwave absorption properties. More importantly, this one-pot synthesize route provides a universal and convenient way for preparation of larger scale pure Ni-SSs, showing excellent microwave absorption properties.

  1. Microwave assisted synthesis and characterization of sodium alginate-graft-poly(N,N'-dimethylacrylamide).

    PubMed

    Akın, Alper; Işıklan, Nuran

    2016-01-01

    Modification of sodium alginate (NaAlg) was carried out using N,N'-dimethylacrylamide (DMAAm) as a monomer and azobisizobutyronitrile (AIBN) as an initiator under microwave irradiation. The effect of reaction conditions such as concentrations of DMAAm, AIBN, NaAlg as well as microwave power and temperature on grafting and grafting efficiency has been explored. Maximum grafting and grafting efficiency has been observed at 1h of grafting time, 0.291 M of DMAAm concentration, 500 W microwave irradiation power, 0.134 M of AIBN concentration, 75°C of reaction temperature and 0.5 g/dL of NaAlg concentration. The grafted copolymer has been characterized by FTIR, DSC, TGA, (13)C NMR, XRD, SEM, and GPC analysis. Cytotoxicity as standard MTT assay, apoptotic and necrotic effects of graft copolymer were investigated on L929 fibroblast cell. It has been found that the grafted copolymer is biocompatible and thermally more stable than the ungrafted alginate. PMID:26549441

  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. 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.

  8. 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

  9. 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

  10. Effect of microwave-assisted sintering on dielectric properties of CaCu3Ti4O12 ceramic

    NASA Astrophysics Data System (ADS)

    Rani, Suman; Ahlawat, Neetu; Punia, R.; Kundu, R. S.; Ahlawat, N.

    2016-05-01

    In this present work, CaCu3Ti4O12 (CCTO) was synthesized by conventional solid-state reaction technique. The synthesis process was carried out in two phases; by conventional process (calcination and sintering at 1080°C for 10 hours) and phase II involves the micro assisted pre sintering of conventionally calcined CCTO for very short soaking time of 30 min at 1080°C in a microwave furnace followed by sintering at 1080°C for 10 hours in conventional furnace. X-ray diffraction (XRD) patterns confirmed the formation of single phase ceramic. Dielectric properties were studied over the frequency range from 50Hz -5MHz at temperatures (273K-343K). It was observed that pre- microwave sintering enhance the dielectric constant values from 10900 to 11893 and respectively reduces the dielectric loss values from 0.49 to 0.34 at room temperature(1 KHz). CCTO ceramics which are found desirable for many technological applications. The effect is more pronounced at low frequencies of applied electric field.

  11. 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

  12. 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

  13. 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

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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