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Cyrene, a green bioderived solvent from waste cellulose, was applied to the synthesis of novel α-acyloxyamide derivatives through a Passerini-3CR with carboxylic acids and isocyanides with good yields and diastereoselectivities under mild conditions. Cyrene showed exceptionally high reactivity and the degree of diastereoselection was dependent mostly on the isocyanide. DFT calculations as well as the experimental findings indicated that both kinetic and thermodynamic effects might explain the results.

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In this work, unsupported Pd aerogel catalysts were synthesized for the very first time by using microwaves as a heating source followed by a lyophilization drying process and used towards formic acid electro-oxidation in a microfluidic fuel cell. Aerogels were also made by heating in a conventional oven to evaluate the microwave effect during the synthesis process of the unsupported Pd aerogels. The performance of the catalysts obtained by means of microwave heating favored the formic acid electro-oxidation with H2SO4 as the electrolyte. The aerogels' performance as anodic catalysts was carried out in a microfluidic fuel cell, giving power densities of up to 14 mW cm-2 when using mass loads of only 0.1 mg on a 0.019 cm2 electrode surface. The power densities of the aerogels obtained by microwave heating gave a performance superior to the resultant aerogel prepared using conventional heating and even better than a commercial Pd/C catalyst.

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Microwave heating of asphalt pavement is a promising technique to reduce the maintenance and increase the service life of materials through self-healing of cracks. Previous studies have shown that microwave heating technology at high temperatures could damage the bitumen of asphalt mixture, which is an unwanted effect of the crack-healing technique. In this study, the effects of microwave heating and long-term aging on the rheological and chemical properties of recovered bitumen were quantified using a frequency sweep test and Fourier Transform Infrared Spectrometry analysis, respectively. The main results indicate that microwave heating has no significant effect on the aging performance of G* and δ for aged asphalt mixtures. However, for newer bitumens, the rheological properties G* and δ show minor changes after microwave heating was applied. Overall, this study confirms that microwave heating is a potential alternative for maintenance of asphalt pavements, without severely affecting the rheological and chemical properties of bitumen.

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The effect of microwave radiation on the hydrothermal synthesis of the double perovskite Sr2FeMoO6 has been studied based on a comparison of the particle size and structural characteristics of products from both methods. A temperature, pressure, and pH condition screening was performed, and the most representative results of these are herein presented and discussed. Radiation of microwaves in the hydrothermal synthesis method led to a decrease in crystallite size, which is an effect from the reaction temperature. The particle size ranged from 378 to 318 nm when pH was 4.5 and pressure was kept under 40 bars. According to X-ray diffraction (XRD) results coupled with the size-strain plot method, the product obtained by both synthesis methods (with and without microwave radiation) have similar crystal purity. The Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) techniques showed that the morphology and the distribution of metal ions are uniform. The Curie temperature obtained by thermogravimetric analysis indicates that, in the presence of microwaves, the value was higher with respect to traditional synthesis from 335 K to 342.5 K. Consequently, microwave radiation enhances the diffusion and nucleation process of ionic precursors during the synthesis, which promotes a uniform heating in the reaction mixture leading to a reduction in the particle size, but keeping good crystallinity of the double perovskite. Precursor phases and the final purity of the Sr2FeMoO6 powder can be controlled via hydrothermal microwave heating on the first stages of the Sol-Gel method.

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The present study was aimed to develop nitrogen-doped nanostructured ZnO thin films. These films were produced in a sequential procedure involving the atomic layer deposition technique, and a hydrothermal process supported by microwave heating. Employing the atomic layer deposition technique, through self-limited reactions of diethylzinc (DEZn) and H2O, carried out at 3.29 × 10-4atm and 190 °C, a high-quality ZnO seed was grown on a Si (100) substrate, producing a textured film. In a second stage, columnar ZnO nanostructures were grown perpendicularly oriented to the silicon substrate on those films, using a solvothermal process in a microwave heating facility, employing Zn(NO3)2as zinc precursor, while hexamethylenetetramine (HMTA) was used to produce the bridging of Zn2+ions. The consequence of N-doping concentration on the physicochemical properties of ZnO thin films was studied. The manufactured films were structurally analyzed by scanning electron microscopy and x-ray diffraction. Also, x-ray photoelectron spectroscopy, Raman, and UV-vis spectroscopies were used to provide further insight on the effect of nitrogen doping. The N-doped films displayed textured wurtzite-like structures that changes their preferential growth from the (002) to the (100) crystallographic plane, apparently promoted by the increase of nitrogen precursor. It is also shown that nitrogen-doped films undergo a reduction in their bandgap, compared to ZnO. The methodology presented here provides a viable way to perform high-quality N-ZnO nanostructured thin films.

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Luminescent inorganic materials are used in several technological applications such as light-emitting displays, white LEDs for illumination, bioimaging, and photodynamic therapy. Usually, inorganic phosphors (e.g., complex oxides, silicates) need high temperatures and, in some cases, specific atmospheres to be formed or to obtain a homogeneous composition. Low ionic diffusion and high melting points of the precursors lead to long processing times in these solid-state syntheses with a cost in energy consumption when conventional heating methods are applied. Microwave-assisted synthesis relies on selective, volumetric heating attributed to the electromagnetic radiation interaction with the matter. The microwave heating allows for rapid heating rates and small temperature gradients yielding homogeneous, well-formed materials swiftly. Luminescent inorganic materials can benefit significantly from the microwave-assisted synthesis for high homogeneity, diverse morphology, and rapid screening of different compositions. The rapid screening allows for fast material investigation, whereas the benefits of enhanced homogeneity include improvement in the optical properties such as quantum yields and storage capacity.

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BACKGROUND: Bacaba (Oenocarpus bacaba Mart.) has a high yield of oil, with the potential to produce biologically active natural products and can be considered a new "superfruit" with high value added. METHODS: Acid value, peroxide value, refractive index, saponification value, p-anisidine value, relative density, iodine value, total oxidation value, specific extinction coefficients at 232 and 270 nm (K232 and K270), ΔK, and color were determined. RESULTS: The most significant changes in the quality values, such as peroxide (26.25 mEq·kg-1), p-anisidine (11.41), acidity (14.66 mg KOH·g-1 oil), and total oxidation (63.92) were determined for 15 min of microwave heating. CONCLUSIONS: The microwave heating promoted the acceleration of oxidative processes showing that, overall, much care should be taken when heating the bacaba oil by microwave to avoid oil degradation.

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A simple and rapid synthesis of a CoFeRu-based electrocatalyst by a microwave-assisted method (using water as the microwave absorbing solvent) is reported in this work. Agglomerates with different sizes and shapes are observed by scanning electron microscopy technique. The energy dispersive X-ray spectroscopy shows a low atomic percentage of Co and similar atomic percentage of Fe and Ru. However, the X-ray diffraction exhibits only the presence of metallic Ru and Fe2O3 (hematite) phases. The oxygen reduction without and with 2 mol L-1 methanol is studied using the rotating disk electrode technique. The electrochemical kinetic parameters obtained are compared to a similar electrocatalyst reported in the literature, which was synthesized using a mixture of an organic solvent with DI water as the microwave absorbing solvent. An improvement on the activity of the electrocatalyst synthesized is observed, where high Tafel slopes are not observed. The electrocatalyst also showed tolerance to the presence of methanol during the oxygen reduction reaction.

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The effect of microwave heating (MH, 65 and 75 °C for 15, 30, and 60 s) on the bioactive compounds, fatty acid profile, and volatile compounds of orange juice-milk beverage (OJMB) was evaluated during 28 days of refrigerated (4 °C) storage. Conventionally pasteurized (75 °C/15 s) and untreated beverages were used as controls. MH-OJMB presented a lower browning index and higher levels of ascorbic acid, total phenolics, and carotenoids, higher antioxidant activity, and greater α-amylase, α-glucosidase, and ACE inhibitory activity than the pasteurized product, similar to the untreated beverage. No significant differences were observed in the volatile organic compounds and fatty acids levels. Lower temperatures (65 °C) and longer process times (60 s) resulted in higher retention of bioactive compounds. MH can be an alternative to conventional pasteurization for OJMB processing.

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Organoclays have been applied as efficient adsorbents for pharmaceutical pollutants from aqueous solution. In this work, dodecylpyridinium chloride (C12pyCl) and hexadecylpyridinium chloride (C16pyCl) cationic surfactants were used for the preparation of organobentonites destined for diclofenac sodium (DFNa) adsorption, an anionic drug widely detected in wastewater. The organofunctionalization of the clay samples was performed under microwave irradiation at 50 °C for 5 min with surfactant amounts of 100% and 200% in relation to the cation exchange capacity (CEC) of the pristine bentonite. The amount of incorporated ammonium salts based on CHN elemental analysis was higher for all samples prepared with 200% of the CEC. The basal spacings of the organoclays ranged from 1.54 to 2.13 nm, indicating the entrance of organic cations into the interlayer spacing of the clay samples, and the spacing depended on the size of the alkyl organic chain. The hydrophobic character of the organobentonites was verified by thermogravimetry and infrared spectroscopy (FTIR). The adsorption isotherms showed that the drug capacity adsorption was influenced by the amount of surfactant incorporated into the bentonite, the packing density and the arrangement of the surfactants in the interlayer spacing. Zeta potential measurements of the organobentonites and FTIR analysis after drug adsorption suggested that electrostatic and nonelectrostatic interactions contributed to the mechanism of adsorption.

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A series of nickel-decorated covalent organic frameworks, NiCl@RIO-12, were prepared using the post-synthetic modification strategy, that is, by reacting NiCl2 with pristine RIO-12 under alkaline conditions. Interestingly, they retained their crystallinity and the amount of nickel incorporated could be tuned from 3.6 to 25 wt % according to the reaction conditions. The incorporation of a higher amount of nickel in NiCl@RIO-12 consistently led to a lower Brunauer-Emmett-Teller surface area. Additionally, no agglomeration of nickel particles was found and a relatively homogeneous dispersion of nickel could be ascertained by SEM and TEM-EDS. The paramagnetic material exhibited promising catalytic activity in Suzuki-Miyaura cross-coupling under microwave heating. Thus, NiCl@RIO-12 notably demonstrated good thermal stability and its recyclability showed no substantial loss of activity after 3 cycles.

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There are two principal types of nickel (Ni) deposits: sulfide and laterite ores. Interest in low-grade Ni-laterite ores has increased in recent years as high-grade Ni-sulfide deposits are being quickly depleted. However, processing of Ni laterites has proven technically difficult and costly, and the development of alternative low-cost biotechnologies for Ni solubilization has been encouraged. In this context, by the first time, a sample of Brazilian Ni-laterite ore was analyzed mineralogically and subjected to bioleaching tests using a heterotrophic Bacillus subtilis strain. SEM-analysis indicated that the primary Ni carrier mineral is goethite. Chemical analysis of different grain size fractions indicated a homogeneous distribution of Ni. XRF-analysis showed that the ore consists mainly in lizardite (32.6% MgO) and contains1.0% NiO (0.85% Ni). Bioleaching batch experiments demonstrated that about 8.1% Ni (0.7 mg Ni/g ore) were solubilized by the B. subtilis after 7 days. Application of microwave heating as a Ni-laterite pretreatment was also tested. This pretreatment increased the bioextraction of Ni from 8% to 26% (2.3 mg Ni g-1 ore).

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In this study, microwave heating was employed for controlling Oryzaephilus surinamensis adult beetles infesting stored Iranian dried figs. The dried fig samples were artificially infested with O. surinamensis and then heated in a microwave oven (2,450 MHz) at power outputs of 450, 720, and 900 W for 20, 30, 40, and 50 s. Changes in the color of the samples after these microwave applications were evaluated for lightness (ΔL*), redness (Δa*), and yellowness (Δb*) using an image processing technique. Both parameters of microwave power and exposure time had significant effects on beetle mortality ( P < 0.01). A direct positive relationship was found between the mortality rate and microwave power. Complete mortality was achieved at 900 W and for 50 s. The color parameters of the dried fig samples did not change significantly. These results indicate that microwave irradiation can be introduced as an appropriate alternative to chemical fumigants without affecting product quality.

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A simple and efficient method to synthesize the immunogenic glycolipid BbGL1 is introduced. Two simple steps were required to obtain the desired product in good yield. First, a highly efficient glycosylation of cholesterol using galactosyl trichloroacetimidate as a donor was performed to produce cholesteryl-ß-d-galactoside. Finally, an efficient palmitoylation on the C6-OH of the galactose of the synthesized saponin using sym-collidine and acyl chloride under microwave heating that produced BbGL1 in good yield. The procedure is a convenient and cheaper alternative to the reported procedures allowing a rapid preparation of multiple analogs and conjugates.

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Solid-phase synthetic strategies toward the generation of libraries of biologically relevant molecules were developed using olefin cross-metathesis as a key step. It is remarkably the formal alkane metathesis based on a one-pot, microwave-assisted, ruthenium-catalyzed cross-metathesis and reduction to obtain Csp3-Csp3 linkages.

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Whole, ground and abrasively dehulled grains from both normal (H-34 and H-34) and quality protein (QPM and QPMa) maize were mixed with water contents of 70, 95 and 100 g kg-1 and calcium hydroxide concentrations of 0.0, 0.3, 0.5 and 2.0 g kg-1 and heated (operating frequency 2.450 MHz, high-power setting) for 10, 15 and 20 min in a commercial microwave oven. The cooked grain was then oven dried and milled to obtain nixtamalised maize flour (NMF). The protein contents and test weights of QPM were higher than for the normal hybrids. The highest yields of masa and tortillas were found for the normal hybrids, and these samples did not show significant differences, as compared with the commercial nixtamalised flour (CNMF) used as control, with respect to masa firmness and adhesiveness and tortilla tensile strength. The cutting force of tortillas from hybrid H-30 and QPM did not show significant differences from the control. The highest values of tortilla rollability were found for the control followed by hybrid H-34. The values of residual cooking liquor for microwave-heated samples were lower than for the control. Ground or dehulled maize grain gave sticky masa and poor mechinical characteristics. Tortillas from whole grain showed good characteristics of texture and consistency of masa, and the tortillas were subjectively similar in colour, flavour and rollability to the tortillas prepared with CNMF. These results indicate a potential use of microwave energy to produce NMF for tortillas and derivatives. © 2000 Society of Chemical Industry.