Promoting Effect of Ball Milling on the Functionalization and Catalytic Performance of Carbon Nanotubes in Glycerol Etherification.

A facile and eco-friendly approach using in situ-generated 4-benzenediazonium sulfonate (BDS) was applied to prepare highly functionalized carbon nanotubes (CNTs). The effectiveness of this functionalization was additionally enhanced by a green and short-time ball milling process applied beforehand. The obtained BDS-modified CNTs presented significant activity in glycerol etherification, producing tert-butyl glycerol ethers, which are considered promising fuel additives. Excellent results of ~56% glycerol conversion and ~10% yield of higher-substituted tert-butyl glycerol ethers were obtained within just 1 h of reaction at 120 °C using a low catalyst loading of only 2.5 wt.%. Furthermore, the sulfonated CNTs were reusable over several reaction cycles, with only a minor decrease in activity. Additionally, the sample activity could be restored by a simple regeneration approach. Finally, a clear correlation was found between the content of -SO3H groups on the surface of CNTs and the catalytic performances of these materials in glycerol etherification. Improved interaction between functionalized ball-milled CNTs and the reactants was also suggested to positively affect the activity of these catalysts in the tested process.

Gold Nanoparticles Deposited on Surface Modified Carbon Xerogels as Reusable Catalysts for Cyclohexane C-H Activation in the Presence of CO and Water.

The use of gold as a promotor of alkane hydrocarboxylation is reported for the first time. Cyclohexane hydrocarboxylation to cyclohexanecarboxylic acid (up to 55% yield) with CO, water, and peroxodisulfate in a water/acetonitrile medium at circa 50 °C has been achieved in the presence of gold nanoparticles deposited by a colloidal method on a carbon xerogel in its original form (CX), after oxidation with HNO3 (-ox), or after oxidation with HNO3 and subsequent treatment with NaOH (-ox-Na). Au/CX-ox-Na behaves as re-usable catalyst maintaining its initial activity and selectivity for at least seven consecutive cycles. Green metric values of atom economy or carbon efficiency also attest to the improvement brought by this novel catalytic system to the hydrocarboxylation of cyclohexane.

Ethyl Acetate Abatement on Copper Catalysts Supported on Ceria Doped with Rare Earth Oxides.

Different lanthanide (Ln)-doped cerium oxides (Ce0.5Ln0.5O1.75, where Ln: Gd, La, Pr, Nd, Sm) were loaded with Cu (20 wt. %) and used as catalysts for the oxidation of ethyl acetate (EtOAc), a common volatile organic compound (VOC). For comparison, both Cu-free (Ce-Ln) and supported Cu (Cu/Ce-Ln) samples were characterized by N2 adsorption at -196 °C, scanning/transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and temperature programmed reduction in H2. The following activity sequence, in terms of EtOAc conversion, was found for bare supports: CeO2 ≈ Ce0.5Pr0.5O1.75 > Ce0.5Sm0.5O1.75 > Ce0.5Gd0.5O1.75 > Ce0.5Nd0.5O1.75 > Ce0.5La0.5O1.75. Cu addition improved the catalytic performance, without affecting the activity order. The best catalytic performance was obtained for Cu/CeO2 and Cu/Ce0.5Pr0.5O1.75 samples, both achieving complete EtOAc conversion below ca. 290 °C. A strong correlation was revealed between the catalytic performance and the redox properties of the samples, in terms of reducibility and lattice oxygen availability. Νo particular correlation between the VOC oxidation performance and textural characteristics was found. The obtained results can be explained in terms of a Mars-van Krevelen type redox mechanism involving the participation of weakly bound (easily reduced) lattice oxygen and its consequent replenishment by gas phase oxygen.

Impact of Thermal Treatment of Nb2O5 on Its Performance in Glucose Dehydration to 5-Hydroxymethylfurfural in Water.

The cascade dehydration of glucose to 5-hydroxymethylfurfural (HMF) was carried out in water over a series of Nb2O5 catalysts, which were derived from the thermal treatment of niobic acid at 300 and 550 °C, under air or inert atmosphere. Amorphous niobic acid showed high surface area (366 m2/g) and large acidity (2.35 mmol/g). With increasing the temperature of the thermal treatment up to 550 °C, the amorphous Nb2O5 was gradually transformed into a pseudohexagonal phase, resulting in a decrease in surface area (27-39 m2/g) and total acidity (0.05-0.19 mmol/g). The catalysts' performance in cascade dehydration of glucose realized in pure water was strongly influenced by the total acidity of these materials. A remarkable yield of 37% HMF in one-pot reaction in water was achieved using mesoporous amorphous niobium oxide prepared by thermal treatment of niobic acid at 300 °C in air. The best-performing catalyst displayed a total acidity lower than niobic acid (1.69 mmol/g) which afforded a correct balance between a high glucose conversion and limited further conversion of the target product to numerous polymers and humins. On the other hand, the treatment of niobic acid at 550 °C, independently of the atmosphere used during the sample preparation (i.e., air or N2), resulted in Nb2O5 catalysts with a high ratio of Lewis to Brønsted acid sites and poor total acidity. These materials excelled at catalyzing the isomerization step in the tandem process.

Carbon-Supported Mo2C for Oxygen Reduction Reaction Electrocatalysis.

Molybdenum carbide (Mo2C)-based electrocatalysts were prepared using two different carbon supports, commercial carbon nanotubes (CNTs) and synthesised carbon xerogel (CXG), to be studied from the point of view of both capacitive and electrocatalytic properties. Cation type (K+ or Na+) in the alkaline electrolyte solution did not affect the rate of formation of the electrical double layer at a low scan rate of 10 mV s-1. Conversely, the different mobility of these cations through the electrolyte was found to be crucial for the rate of double-layer formation at higher scan rates. Molybdenum carbide supported on carbon xerogel (Mo2C/CXG) showed ca. 3 times higher double-layer capacity amounting to 75 mF cm-2 compared to molybdenum carbide supported on carbon nanotubes (Mo2C/CNT) with a value of 23 mF cm-2 due to having more than double the surface area size. The electrocatalytic properties of carbon-supported molybdenum carbides for the oxygen reduction reaction in alkaline media were evaluated using linear scan voltammetry with a rotating disk electrode. The studied materials demonstrated good electrocatalytic performance with Mo2C/CXG delivering higher current densities at more positive onset and half-wave potential. The number of electrons exchanged during oxygen reduction reaction (ORR) was calculated to be 3, suggesting a combination of four- and two-electron mechanism.

Glucose-derived carbon materials with tailored properties as electrocatalysts for the oxygen reduction reaction.

Nitrogen-doped biomass-derived carbon materials were prepared by hydrothermal carbonization of glucose, and their textural and chemical properties were subsequently tailored to achieve materials with enhanced electrochemical performance towards the oxygen reduction reaction. Carbonization and physical activation were applied to modify the textural properties, while nitrogen functionalities were incorporated via different N-doping methodologies (ball milling and conventional methods) using melamine. A direct relationship between the microporosity of the activated carbons and the limiting current density was found, with the increase of microporosity leading to interesting improvements of the limiting current density. Regardless of the doping method used, similar amounts of nitrogen were incorporated into the carbon structures. However, significant differences were observed in the nitrogen functionalities according to the doping method applied: ball milling appeared to originate preferentially quaternary and oxidized nitrogen groups, while the formation of pyridinic and pyrrolic groups was favoured by conventional doping. The onset potential was improved and the two-electron mechanism of the original activated sample was shifted closer to a four-electron pathway due to the presence of nitrogen. Interestingly, the high pyridinic content related to a high ratio of pyridinic/quaternary nitrogen results in an increase of the onset potential, while a decrease in the quaternary/pyrrolic nitrogen ratio favors an increase in the number of electrons. Accordingly, the electrocatalyst with the highest performance was obtained from the activated sample doped with nitrogen by the conventional method, which combined the most appropriate textural and chemical properties: high microporosity and adequate proportion of the nitrogen functionalities.

Influence of Multiwalled Carbon Nanotubes as Additives in Biomass-Derived Carbons for Supercapacitor Applications.

Glucose-derived carbon/carbon nanotube (CNT) hybrid materials were prepared by hydrothermal carbonization of glucose in the presence of CNTs and subsequent carbonization, physical activation, or chemical activation. The proportion of CNTs added during the hydrothermal polymerization of glucose was varied to ascertain the optimum dose to maximize the performance of the carbon hybrids in supercapacitor applications. Both the thermal treatment applied and the addition of CNTs lead to changes in the textural and chemical properties of the activated carbons. It was observed that samples bearing CNTs exhibit higher number of nucleation centers for glucose oligomers to polymerize, and consequently, the behavior of the hydrothermal carbon toward activation differs according to the activating agent employed. Moreover, the initial chemical speciation dominated by acidic groups shifts to more basic functionalities (quinones and carbonyl groups) with the addition of CNTs. The effect of the different physicochemical properties of the prepared carbons on their electrochemical behavior was evaluated. The addition of 2 wt % of CNTs and subsequent chemical activation leads to electrode materials yielding 206 F g-1 and 78% of capacitance retention up to 0.8 V and 20 A g-1 and high rate cyclability (97% after 5000 cycles). The outstanding performance is ascribed to the high surface area, narrow mesopores, and phenol/carbonyl surface functionalities, which enhance molecular diffusion, the amount of stored energy, and electronic transportation, respectively.

Reabilitação bucal através da odontologia conservadora moderna: relato de caso / Oral rehabilitation through the modern conservative dentistry: case report

A crescente busca de pacientes por restaurações estéticas para transformar sorrisos levou o mercado a uma incansável busca por materiais que atendam as necessidades. As lentes de contato são um tratamento conservador e o avanço contínuo das cerâmicas nos permite aliar restaurações com excelente estética e funcionalidade mecânica elevada. As facetas tornaram-se um tratamento altamente conservador graças a alta confiabilidade dos sistemas adesivos. Já as próteses metal-free apresentam uma elevada estética natural conservando também a estética vermelha das gengivas. Nosso objetivo foi apresentar um reabilitação bucal dos dentes anteriores superiores de forma conservadora respeitando particularidades de cada elemento. A paciente procurou uma clínica odontológica insatisfeita com a estética anterior do seu sorriso, ao iniciar o tratamento, a paciente tinha o elemento 13 íntegro, 12 com restauração extensa, 11 com coroa metalo cerâmica, elemento 21 com restauração extensa, 22 com uma coroa metalo cerâmica e elemento 23 íntegro. Após a realização do mock-up direto com resina composta, realizou-se a moldagem para o enceramento diagnóstico. O mock-up indireto, obteve a aprovação após algumas pequena correções, seguindo os protocolos necessários foram feitas as moldagens e a prova e cimentação do trabalho realizado com as corretas indicações de cimento para cada material utilizado. A satisfação procedeu com o caso concluído satisfazendo sua necessidades funcionais e estéticas onde o elemento 13 e 23 receberam lentes de contato, os elementos 11 e 22 coroas metal free e os elementos 12 e 21 facetas, respeitando suas indicações

The increasing search for patients restorations to transform smiles led the market to a relentless search for materials that meet the needs. Contact lenses are a conservative treatment and the continuous advancement of the ceramic allows us to combine restorations with excellent aesthetics and high mechanical functionality. The facets have become a highly conservative treatment thanks to high reliability of adhesive systems. As for the metal-free prostheses have a high natural aesthetics also preserving the aesthetics of red gums. The objective was to present an oral rehabilitation of the upper front teeth conservatively respecting the particularities of each element. The patient went to a dental clinic unsatisfied with the previous aesthetics of your smile, to start treatment, the patient had the element integrate 13, 12 with extensive restoration, with 11 metal ceramic crown, element 21 with extensive restoration, with a 22 ceramic crown metal element 23 and healthy. After the completion of the direct mock-up with composite resin, there was molding for diagnostic waxing. The indirect mock-up, was approved after some small fixes, following the necessary protocols were made moldings and evidence and cementing of the work done with the correct concrete indications for each material used. The satisfaction proceeded with the case concluded satisfying their functional and aesthetic needs where the element 13:23 received contact lenses, the elements 11:22 crowns metal free and elements 0:21 facets, respecting its indications

Produção de seis gramíneas manejadas por corte sob efeito de diferentes lâminas de irrigação e estações anuais / Yield of six grasses cultivated under cut management and effect of different irrigation depths and annual seasons

Objetivou-se avaliar a produtividade e o teor de matéria seca de gramíneas manejadas por corte sob efeito de diferentes lâminas de irrigação e estações do ano. O experimento foi conduzido em esquema de parcelas sub-subdivididas, tendo nas parcelas seis gramíneas (Xaraés, Mombaça, Tanzânia, Pioneiro, Marandu e Estrela), nas subparcelas seis lâminas de irrigação (0, 18, 45, 77, 100 e 120 por cento da referência) e nas sub-subparcelas as estações (outono/inverno e primavera/verão) no delineamento inteiramente casualizado, com duas repetições. Para diferenciar a aplicação das lâminas de irrigação, utilizou-se o sistema por aspersão em linha. A produtividade e o teor de matéria seca foram obtidos por meio do material seco em estufa ventilada a 60ºC, por 72 h. Observou-se efeito das gramíneas, estações anuais e lâminas de irrigação nas duas características avaliadas. Na estação outono/inverno as gramíneas não diferiram e na primavera/verão a gramínea Pioneiro apresentou maior produtividade de matéria seca. Independente da estação, essa mesma gramínea apresentou o menor teor de matéria seca. A estação primavera/verão proporcionou maior produtividade e não afetou o teor de matéria seca. As lâminas de irrigação aumentaram a produtividade das gramíneas na estação outono/inverno e não afetaram ou diminuíram na estação primavera/verão. Esse mesmo fator reduziu o teor de matéria seca.

This study was aimed at evaluating the yield and dry matter content of grasses cultivated under cut management and different annual seasons and irrigation depths. The experiment was carried out in a completely randomized arrangement, with two replications, in a split-split plot design. Six grasses (Xaraes, Mombaça, Tanzania, Pioneiro, Marandu, and Estrela) constituted the plots, six irrigation depths (0 percent, 18 percent, 45 percent, 77 percent, 100 percent, and 120 percent of the control) constituted the split-plots and two seasons (autumn/winter and spring/summer) the split-split-plots. To differentiate the application of irrigation depths the line source sprinkler system was used. The yield and dry matter content were obtained by drying the material in ventilated stoves at 60ºC, for 72 h. The effect of the grasses, annual seasons and irrigation depths were observed for the two characteristics studied. In the autumn/winter season the grasses did not differ and in the spring/summer the Pioneiro presented larger yield. Independently of the season, this same grass presented the smallest dry matter content. The spring/summer season provided larger yield and it did not affect the dry matter content. The irrigation depths increased the yield of the grasses in the autumn/winter season and they did not affect or they decreased the yield in the spring/summer. This same factor reduced the dry matter content of the grasses.

Restauração estética pós-tratamento ortodôntico lingual: relato de caso / Esthetic restoration after lingual orthodontic treatment: case repor

A Ortodontia Lingual já alcançou um lugar de destaque entre as técnicas utilizadas atualmente. São muitos os pacientes que têm optado por uma opção de tratamento mais estético. Como na Ortodontia convencional, alguns problemas são muito similares aos encontra dos quando se opta pelo tratamento com a Ortodontia Invisível. Deve-se sempre estar atento aos problemas de origem periodontal e de discrepâncias de tamanho dentário. O caso apresentado mostra um tratamento ortodôntico lingual, onde após a correção da Classe II, foi necessário uma reanatomização dos dentes anteriores para alcançar uma estética maior para o sorriso da paciente.

Lingual Orthodontics has reached a place of prominence among the techniques currently used. There are many patients who have opted for a more aesthetic treatment. As in conventional Orthodontics, some problems are very similar to those found when opting for Invisible Orthodontics treatment. One should always be mindful of periodontal problems and tooth size discrepancies. This case shows a lingual orthodontic treatment, in which after correction of Class II, a reanatomization of anterior teeth was needed in order to achieve better aesthetic for the patients’ smile.