The authors acknowledge National Science Foundation grant CHE- 1214068 for supporting this research project.

1. Preparación de GMS <ol><li> Utilice todos los productos químicos en el siguiente proceso en que se recibieron. </li><li> Preparar 75 ml de 2 M de ácido clorhídrico solución (HCl). Pesar 2,0 g de poli (etilenglicol) -bloque-poli (propilenglicol) -bloque-poli (etilenglicol) (P123, MW = 5800) y transferir en el preparado 75 ml de solución de HCl 2 M. A RT, aplicar agitación magnética a la solución a una velocidad de 350 r / min hasta que P123 se disuelva completamente. La solución será clara. </li><li> Pesar 4 g de tetraetoxisilano (TEOS, MW = 208,33) en un pequeño vial y la transferencia de 180 l de bis [3- (trietoxisilil) propil] tetrasulfuro (TESPTS, MW = 538,94) en el vial. Lentamente agitar el frasco para mezclar los dos productos químicos. En otro vial, pesan 38 mg de ácido cloroáurico (HAuCl4, 99,90%) y se disuelven en 1 ml de agua DI. </li><li> Aumentar la temperatura de la solución P123 a 35 ° C en un baño de aceite con la temperatura controlada por termopar. </li><li> Añadir toda la mezcla de TEOS yTESPTS preparados en el paso 1.3 de la solución P123, y mantener la solución en agitación magnética vigorosa de 700 r / min. Mantener la solución de agitar durante 2 min, a continuación, añadir todo de HAuCl4 solución preparada en el paso 1.3 gota a gota dentro de 30 seg. </li><li> Mantener la solución se agitaba a 700 r / min durante 24 horas a 35 ° C. </li><li> Después de 24 horas, transferir la solución en una botella sellada y guárdelos en un horno a 100 ° C durante 72 horas. Esto se llama procesamiento hidrotérmico. </li><li> Después del procesamiento hidrotérmico, filtrar la solución con un papel # 1 filtración y presión negativa en virtud de un embudo, luego lavar con agua dos veces y etanol tres veces para eliminar el HCl restante. Durante cada proceso de lavado, agregue agua o etanol 1 cm por encima de sólidos y esperar a que el material se seque. </li><li> Transferencia de precipitación a partir de la filtración a un crisol de cerámica y calcinado a 550 ° C durante 4 h. Establecer el programa de rampa de la siguiente manera: 25 ° C a 550 ° C durante 2 horas, mantener a 550 ° C durante 4h, y luego permitir que la muestra permanezca en el horno con la puerta cerrada hasta que la temperatura cae por debajo de 40 ° C. </li><li> Después de la calcinación, transferir el producto a un vial de vidrio con una espátula de plástico. El material sintetizado tiene un color rojo. </li></ol> 2. La reacción catalítica, oxidación del alcohol bencílico <ol><li> Dado que la oxidación de alcohol bencílico es una reacción en fase líquida sin un disolvente separado, medida 5 ml de alcohol bencílico (99,8%) y la transfiere en un matraz de tres bocas ml 25, a continuación, pesar 10 mg de catalizador de GMS y añadir a bencílico alcohol. </li><li> Establecer un baño de aceite a temperatura controlada con agitación magnética para asegurar un control preciso y uniforme de la temperatura de reacción. </li><li> Ponga el frasco con alcohol de bencilo y catalizador en el baño de aceite, a continuación, establecer la temperatura a 100 ° C y se agita a 150 r / min. </li><li> Flujo de gas oxígeno con 99.9% de pureza en el matraz a 2 ml / min controlados por un controlador de flujo másico. </li><li> Cuando eltemperatura del baño de aceite alcanza 100 ° C y se estabiliza, introducir gas oxígeno en el matraz de tres bocas. </li><li> Mantenga el caudal de oxígeno y temperatura constante, y permitir que la reacción tenga lugar durante 6 horas. </li><li> Después de la reacción, se filtra el producto con un papel de filtración # 1. Recoger la fase líquida y la transferencia de una parte alícuota a una cromatografía de gases (GC) vial. En el vial de GC, mezclar ácido acético cuatro partes grado HPLC para cada una parte de muestra (por ejemplo, utilizar 36 l de muestra y 144 l de ácido acético.) Ponga el vial en un muestreador automático cromatógrafo de gases para su análisis. Lavar el precipitado sólido en el papel de filtro con agua DI y etanol luego dejar secar en el aire. Recoger el sólido se secó con una espátula como catalizador reciclado. </li><li> Repita el mismo procedimiento experimento de la etapa 2.3 a la 2.7 con el catalizador reciclado en tres ocasiones. En cada repetición, ajustar la cantidad de alcohol bencílico para que coincida con la relación descrita en el paso 2.2. </li></ol> 3. Thermal tratamiento de la GMS para Pruebas de Estabilidad térmica <ol><li> Pesar tres porciones separadas 300 mg de GMS sintetizados, y guardarlas en viales de vidrio. Estos están marcados como lote 1, lote 2 y lote 3. Mantenga lote 1 como grupo de control, y poner lote 2 y lote 3 en un horno para el procesamiento térmico. </li><li> Programa el horno de la siguiente manera para su procesamiento a 400 ° C: rampa de 25 ° C a 400 ° C en 0,5 horas, mantener a 400 ° C durante 4 horas, dejar que la muestra permanezca en el horno con la puerta cerrada hasta que las caídas de temperatura por debajo de 40 ° C. Ponga lote 2 en un crisol e iniciar el programa. </li><li> Programa el horno de la siguiente manera para su procesamiento a 650 ° C: rampa de 25 ° C a 650 ° C en 0,75 horas, mantener a 650 ° C durante 4 horas, dejar que la muestra permanezca en el horno con la puerta cerrada hasta que la temperatura cae por debajo 40 ° C. Ponga lote 3 en un crisol e iniciar el programa. </li></ol> 4. CaracterizaciónMateriales de GMS 21,22 <ol><li> En el instrumento fisisorción, desgasifique GMS materiales con el siguiente programa: 90 ° C durante 60 min y después 350 ° C durante 480 min. Ejecutar análisis isoterma completa de los materiales desgasificado para obtener datos de fisisorción. </li><li> Dispersar muestra de GMS en una rejilla de malla holey 200 TEM de carbono y observar la muestra bajo un microscopio electrónico de transmisión. Restringir aumentos con 44,000X para proteger el material. </li><li> DRX Ejecutar con radiación Cu Ka (λ = 1,5418 Å). Set tensión del tubo de 45 kV y corriente del tubo de 40 mA. Recoge la intensidad en el rango 2θ entre 10 ° y 90 ° con un tamaño de paso de 0,008 ° y un tiempo de medición de 5 segundos en cada paso. </li></ol>

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The authors have nothing to disclose.

Dentro del protocolo de síntesis, la atención a la concentración de tensioactivo, el pH de la solución de reacción y la temperatura es crítica para la formación exitosa de GMS. Los pasos críticos son 1.2, 1.3, 1.4 y 1.6. Los parámetros mencionados anteriormente controlar el parámetro crítico de embalaje y la fase de micelas formadas a partir de tensioactivo. La fase y la morfología de la micela determina el estado final de la matriz de sílice, que sirve como marco para GMS. También es importante en el proc...

Como una tecnología emergente que tiene un gran potencial en aplicaciones de catálisis, materiales a nanoescala han recibido interés de investigación intensiva en las últimas décadas. Entre los catalizadores nanoescala reportados, catalizadores de metales nobles como Au, Ag, Pd y Pt han atraído la atención mundial 1.3. Seleccione reacciones catalíticas incluyen la oxidación de los investigadores de monóxido de carbono en Au, reacción de Heck en catalizadores de Pd, y la división de agua con Pt. A pesar de la potencial catalítico prometedor, oro nanoescala está limitada en su aplicabilidad debido a la desactivación de la intoxicación, coquización, la degradación térmica, y la sinterización. Se ha informado de que el oro, como representante de los metales nobles, tiene una alta selectividad y es menos propenso a la lixiviación del metal, la sobre-oxidación, y la auto-envenenamiento 4. Sin embargo, el rendimiento catalítico de oro depende en gran medida el tamaño de partícula. Haruta et al. Ha informado de la relación entre el rendimiento catalítico e irdiámetro clúster ld, lo que demuestra la mayor actividad de los catalizadores de oro con el tamaño de partícula ~ 2.7 nm 5. El tamaño de partícula de los metales nobles puede ser controlado por el método de preparación 6-9; Sin embargo, el mayor obstáculo hacia la amplia aplicación sigue siendo la agregación y la pérdida de actividad. Para resolver el problema de la sinterización, un método común es inmovilizar partículas a nanoescala en un material de soporte. Diversos materiales de apoyo se han aplicado incluyendo sílice porosa 10-11, óxidos metálicos semiconductores 12-13, polímeros 14, el grafeno y los nanotubos de carbono 15 16. Entre los materiales utilizados, sílice poroso es un material atractivo como un soporte, ya que es sólo ligeramente ácido, relativamente inerte, térmicamente y químicamente estables, y se puede preparar con meso / micro-porosidad muy bien definido. La estructura porosa proporciona un buen apoyo para las partículas de metal, sino también imparte Acceso tamaño del sustrato selectivolos catalizadores de metal. Esta selectividad es particularmente prometedor debido a la capacidad de ajuste asociado con estos materiales porosos. A menudo, las partículas de oro se encuentran para ser extremadamente móvil sobre superficies de sílice 17-18 y fácilmente formar muy grandes (50+ nm) partículas no reactivos cuando se expone a altas temperaturas, por lo que es difícil preparar nanopartículas de oro sobre sílice 19. Mukherjee et al. Inmovilización informado de nanopartículas de oro monodispersados ​​en mesoporoso MCM-41 de sílice en un 3-aminopropil-trimetoxisilano y 3-mercaptopropil-trietoxisilano, y las nanopartículas de oro soportadas resultaron ser altamente activo para reacciones de hidrogenación y se constató la existencia de lixiviación de oro en la reacción 20. Tras el informe de la modificación de la superficie de la sílice mesoporosa, reportamos un método para preparar el oro intercaladas en la pared de la sílice mesoporosa (GMS). Además, el enfoque apoyado sílice mesoporosa ofrece una ap escalableabordaje potencialmente altera de forma independiente el catalizador y el medio ambiente poroso. Dado que los procesos catalíticos son de vital importancia económica, los beneficios podrían ser de largo alcance. La capacidad de desarrollar catalizadores &quot;verdes&quot; tendría un profundo impacto positivo en el medio ambiente y mejorar la viabilidad y eficiencia de los recursos económicos de los procesos industriales importantes.

<table><tbody><tr><td>poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol)</td><td>Aldrich</td><td>435465-250ML</td><td></td></tr><tr><td>tetraethoxysilane</td><td>TCI</td><td>201-083-8</td><td></td></tr><tr><td>bis[3-(triethoxysilyl)propyl]-tetrasulfide</td><td>GELEST</td><td>SIB1825.0-100GM</td><td></td></tr><tr><td>chloroauric acid</td><td>Aldrich</td><td>520918-1G</td><td></td></tr><tr><td>benzyl alcohol</td><td>Sigma-Aldrich</td><td>305197-1L</td><td></td></tr><tr><td>nitrogen physisorption</td><td>Micromeritics</td><td>Tristar II</td><td></td></tr><tr><td>X-ray diffraction</td><td>Philips</td><td>X&#039;Pert Pro</td><td></td></tr><tr><td>transmission electron microscopy</td><td>Philips</td><td>CM200</td><td></td></tr><tr><td>gas chromatography</td><td>Shimadzu</td><td>GC-2010</td><td></td></tr></tbody></table>

synthesis and catalytic performance of gold intercalated in the walls of mesoporous silica

Como un reactor nano catalíticamente activo prometedor, nanopartículas de oro intercaladas en sílice mesoporosos (GMS) se sintetizaron con éxito y propiedades de los materiales fueron investigados. Se utilizó un enfoque de sol-gel de una olla para intercalar las nanopartículas de oro en las paredes de sílice mesoporosa. Para comenzar con la síntesis, P123 se utilizó como molde para formar micelas. Entonces TESPTS fue utilizado como un agente de modificación de la superficie para intercalar nano partículas de oro. Después de este proceso, se añadió en TEOS como una fuente de sílice que se sometió a un proceso de polimerización en medio ácido. Después del procesamiento hidrotérmico y de calcinación, el producto final fue adquirida. Se utilizaron varias técnicas para caracterizar la porosidad, la morfología y la estructura del oro intercalado de sílice mesoporosa. Los resultados mostraron una estructura estable de sílice mesoporosa después de la intercalación de oro. A través de la oxidación del alcohol bencílico como una reacción de referencia, los materiales GMS mostraron alta selectividad y reciclabilidad.

Este método se utilizó para comparar los niveles de síntesis de hemo en normal (HBEC30KT) vs. cáncer (HCC4017 células pulmonares). La Figura 2 muestra un nivel más alto de la síntesis de hemo en células de cáncer (HCC4017) que las células pulmonares normales (HBEC30KT). El nivel de la síntesis de hemo también se midió en células normales y cancerosas en la presencia de cianuro de carbonilo desacoplador mitocondrial 3-clorofenilhidrazona (CCCP). Las células fueron tratadas con CCCP 10 mM d...

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Synthesis and Catalytic Performance of Gold Intercalated in the Walls of Mesoporous Silica

Here, we present a protocol with a sol-gel process to synthesize gold intercalated in the walls of mesoporous materials (GMS), which is confirmed to possess a mesoporous matrix with gold intercalated in the walls imparting great stability and recyclability.

Síntesis y rendimiento catalítico de Oro intercalados en las Murallas de sílice mesoporoso

As a promising catalytically active nano reactor, gold nanoparticles intercalated in mesoporous silica (GMS) were successfully synthesized and properties ...

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10.0K vistas.  Colorado School of Mines. Here, we present a protocol with a sol-gel process to synthesize gold intercalated in the walls of mesoporous materials (GMS), which is confirmed to possess a mesoporous matrix with gold intercalated in the walls imparting great stability and recyclability.

Video: Synthesis and Catalytic Performance of Gold Intercalated in the Walls of Mesoporous Silica

Preparation of Silica Nanoparticles Through Microwave-assisted Acid-catalysis

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 &#948; 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&#39; 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 St&#246;ber&#39;s methods, which have smooth surfaces.

Silica nanoparticles were prepared using acid-catalysis of a siloxane precursor and microwave-assisted synthetic techniques resulting in the controlled growth of nanomaterials ranging from 30-250 nm in diameter. The growth dynamics can be controlled by varying the initial silicic acid concentration, time of the reaction, and temperature of reaction.

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle ...

Investigación

Química

In Situ SIMS and IR Spectroscopy of Well-defined Surfaces Prepared by Soft Landing of Mass-selected Ions

Soft landing of mass-selected ions onto surfaces is a powerful approach for the highly-controlled preparation of materials that are inaccessible using conventional synthesis techniques. Coupling soft landing with in situ characterization using secondary ion mass spectrometry (SIMS) and infrared reflection absorption spectroscopy (IRRAS) enables analysis of well-defined surfaces under clean vacuum conditions. The capabilities of three soft-landing instruments constructed in our laboratory are illustrated for the representative system of surface-bound organometallics prepared by soft landing of mass-selected ruthenium tris(bipyridine) dications, [Ru(bpy)3]2+ (bpy = bipyridine), onto carboxylic acid terminated self-assembled monolayer surfaces on gold (COOH-SAMs). In situ time-of-flight (TOF)-SIMS provides insight into the reactivity of the soft-landed ions. In addition, the kinetics of charge reduction, neutralization and desorption occurring on the COOH-SAM both during and after ion soft landing are studied using in situ Fourier transform ion cyclotron resonance (FT-ICR)-SIMS measurements. In situ IRRAS experiments provide insight into how the structure of organic ligands surrounding metal centers is perturbed through immobilization of organometallic ions on COOH-SAM surfaces by soft landing. Collectively, the three instruments provide complementary information about the chemical composition, reactivity and structure of well-defined species supported on surfaces.

In Situ SIMS and IR Spectroscopy of Well-defined Surfaces Prepared by Soft Landing of Mass-selected Ions

Soft landing of mass-selected ions onto surfaces is a powerful approach for the highly-controlled preparation of novel materials. Coupled with analysis by in situ secondary ion mass spectrometry (SIMS) and infrared reflection absorption spectroscopy (IRRAS), soft landing provides unprecedented insights into the interactions of well-defined species with surfaces.

In Situ SIMS y espectroscopia IR de superficies bien definidas Preparado por Soft Landing de iones seleccionados-Mass

Soft landing of mass-selected ions onto surfaces is a powerful approach for the highly-controlled preparation of materials that are inaccessible using ...

Synthesis, Characterization, and Functionalization of Hybrid Au/CdS and Au/ZnS Core/Shell Nanoparticles

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large extinction coefficients which can be tuned across the visible spectrum. Research into the plasmonic enhancement of optical transitions has become popular, due to the possibility of altering and in some cases improving photo-absorption or emission properties of nearby chromophores such as molecular dyes or quantum dots. The electric field of the plasmon can couple with the excitation dipole of a chromophore, perturbing the electronic states involved in the transition and leading to increased absorption and emission rates. These enhancements can also be negated at close distances by energy transfer mechanism, making the spatial arrangement of the two species critical. Ultimately, enhancement of light harvesting efficiency in plasmonic solar cells could lead to thinner and, therefore, lower cost devices. The development of hybrid core/shell particles could offer a solution to this issue. The addition of a dielectric spacer between a gold nanoparticles and a chromophore is the proposed method to control the exciton plasmon coupling strength and thereby balance losses with the plasmonic gains. A detailed procedure for the coating of gold nanoparticles with CdS and ZnS semiconductor shells is presented. The nanoparticles show high uniformity with size control in both the core gold particles and shell species allowing for a more accurate investigation into the plasmonic enhancement of external chromophores.

The synthesis of uniform gold nanoparticles coated with semiconductor shells of CdS or ZnS is performed. The semiconductor coating is conducted by first depositing a silver sulfide shell and exchanging the silver cations for zinc or cadmium cations.

Síntesis, caracterización y funcionalización de híbridos Au / CdS y Au / ZnS Core / Shell nanopartículas

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large ...

Millifluidics for Chemical Synthesis and Time-resolved Mechanistic Studies

Procedures utilizing millifluidic devices for chemical synthesis and time-resolved mechanistic studies are described by taking three examples. In the first, synthesis of ultra-small copper nanoclusters is described. The second example provides their utility for investigating time resolved kinetics of chemical reactions by analyzing gold nanoparticle formation using in situ X-ray absorption spectroscopy. The final example demonstrates continuous flow catalysis of reactions inside millifluidic channel coated with nanostructured catalyst.

Millifluidic devices are utilized for controlled synthesis of nanomaterials, time-resolved analysis of reaction mechanisms and continuous flow catalysis.

Millifluidics para la síntesis química y Estudios mecanicistas Tiempo de resolver

Procedures utilizing millifluidic devices for chemical synthesis and time-resolved mechanistic studies are described by taking three examples. In the ...

Bioingeniería

In Situ Synthesis of Gold Nanoparticles without Aggregation in the Interlayer Space of Layered Titanate Transparent Films

Combinations of metal oxide semiconductors and gold nanoparticles (AuNPs) have been investigated as new types of materials. The in situ synthesis of AuNPs within the interlayer space of semiconducting layered titania nanosheet (TNS) films was investigated here. Two types of intermediate films (i.e., TNS films containing methyl viologen (TNS/MV2+) and 2-ammoniumethanethiol (TNS/2-AET+)) were prepared. The two intermediate films were soaked in an aqueous tetrachloroauric(III) acid (HAuCl4) solution, whereby considerable amounts of Au(III) species were accommodated within the interlayer spaces of the TNS films. The two types of obtained films were then soaked in an aqueous sodium tetrahydroborate (NaBH4) solution, whereupon the color of the films immediately changed from colorless to purple, suggesting the formation of AuNPs within the TNS interlayer. When only TNS/MV2+ was used as the intermediate film, the color of the film gradually changed from metallic purple to dusty purple within 30 min, suggesting that aggregation of AuNPs had occurred. In contrast, this color change was suppressed by using the TNS/2-AET+ intermediate film, and the AuNPs were stabilized for over 4 months, as evidenced by the characteristic extinction (absorption and scattering) band from the AuNPs.

In Situ Synthesis of Gold Nanoparticles without Aggregation in the Interlayer Space of Layered Titanate Transparent Films

Here, we present a protocol for the in situ synthesis of gold nanoparticles (AuNPs) within the interlayer space of layered titanate films without the aggregation of AuNPs. No spectral change was observed even after 4 months. The synthesized material has expected applications in catalysis, photo-catalysis, and the development of cost-effective plasmonic devices.

In Situ Síntesis de nanopartículas de oro sin agregación en el espacio entre capas de Capas de titanato películas transparentes

Combinations of metal oxide semiconductors and gold nanoparticles (AuNPs) have been investigated as new types of materials. The in situ synthesis of AuNPs ...

Ingeniería

Preparation of Functional Silica Using a Bioinspired Method

The goal of the protocols described herein is to synthesize bioinspired silica materials, perform enzyme encapsulation therein, and partially or totally purify the same by acid elution. By combining sodium silicate with a polyfunctional bioinspired additive, silica is rapidly formed at ambient conditions upon neutralization. 
The effect of neutralization rate and biomolecule addition point on silica yield are investigated, and biomolecule immobilization efficiency is reported for varying addition point. In contrast to other porous silica synthesis methods, it is shown that the mild conditions required for bioinspired silica synthesis are fully compatible with the encapsulation of delicate biomolecules. Additionally, mild conditions are used across all synthesis and modification steps, making bioinspired silica a promising target for the scale-up and commercialization as both a bare material and active support medium.
The synthesis is shown to be highly sensitive to conditions, i.e., the neutralization rate and final synthesis pH, however tight control over these parameters is demonstrated through the use of auto titration methods, leading to high reproducibility in reaction progression pathway and yield. 
Therefore, bioinspired silica is an excellent active material support choice, showing versatility towards many current applications, not limited to those demonstrated here, and potency in future applications.

Here, we present a protocol to synthesize bioinspired silica materials and immobilize enzymes therein. Silica is synthesized by combining sodium silicate and an amine &#39;additive&#39;, which neutralize at a controlled rate. Material properties and function can be altered either by in situ enzyme immobilization or post-synthetic acid elution of encapsulated additives.

Preparación de sílice funcional utilizando un método Bioinspirados

The goal of the protocols described herein is to synthesize bioinspired silica materials, perform enzyme encapsulation therein, and partially or totally ...

A Rapid Synthesis Method for Au, Pd, and Pt Aerogels Via Direct Solution-Based Reduction

Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various precursor noble metal ions with reducing agents in a 1:1 (v/v) ratio results in the formation of metal gels within seconds to minutes compared to much longer synthesis times for other techniques such as sol-gel. Conducting the reduction step in a microcentrifuge tube or small volume conical tube facilitates a proposed nucleation, growth, densification, fusion, equilibration model for gel formation, with final gel geometry smaller than the initial reaction volume. This method takes advantage of the vigorous hydrogen gas evolution as a by-product of the reduction step, and as a consequence of reagent concentrations. The solvent accessible specific surface area is determined with both electrochemical impedance spectroscopy and cyclic voltammetry. After rinsing and freeze drying, the resulting aerogel structure is examined with scanning electron microscopy, X-ray diffractometry, and nitrogen gas adsorption. The synthesis method and characterization techniques result in a close correspondence of aerogel ligament sizes. This synthesis method for noble metal aerogels demonstrates that high specific surface area monoliths may be achieved with a rapid and direct reduction approach.

A rapid, direct solution-based reduction synthesis method to obtain Au, Pd, and Pt aerogels is presented.

Un método de síntesis rápida de Au, Pd y Pt Aerogels vía reducción directa basada en la solución

Here, a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented. The combination of various ...

Surface Properties of Synthesized Nanoporous Carbon and Silica Matrices

In this work, we report the synthesis and characterization of ordered nanoporous carbon material (also called ordered mesoporous carbon material [OMC]) with a 4.6 nm pore size, and ordered silica porous matrix, SBA-15, with a 5.3 nm pore size. This work describes the surface properties of nanoporous molecular sieves, their wettability, and the melting behavior of D2O confined in the differently ordered porous materials with similar pore sizes. For this purpose, OMC and SBA-15 with highly ordered nanoporous structures are synthesized via impregnation of the silica matrix by applying a carbon precursor and by the sol-gel method, respectively. The porous structure of investigated systems is characterized by an N2 adsorption-desorption analysis at 77 K. To determine the electrochemical character of the surface of synthesized materials, potentiometric titration measurements are conducted; the obtained results for OMC shows a significant pHpzc shift toward the higher values of pH, relative to SBA-15. This suggests that investigated OMC has surface properties related to oxygen-based functional groups. To describe the surface properties of the materials, the contact angles of liquids penetrating the studied porous beds are also determined. The capillary rise method has confirmed the increased wettability of the silica walls relative to the carbon walls and an influence of the pore roughness on the fluid/wall interactions, which is much more pronounced for silica than for carbon mesopores. We have also studied the melting behavior of D2O confined in OMC and SBA-15 by applying the dielectric method. The results show that the depression of the melting temperature of D2O in the pores of OMC is about 15 K higher relative to the depression of the melting temperature in SBA-15 pores with a comparable 5 nm size. This is caused by the influence of adsorbate/adsorbent interactions of the studied matrices.

Here we report the synthesis and characterization of ordered nanoporous carbon (with a 4.6 nm pore size) and SBA-15 (with a 5.3 nm pore size). The work describes the surface and textural properties of nanoporous molecular sieves, their wettability, and the melting behavior of D2O confined in the materials.

Propiedades de superficie de carbono nanoporosos sintetizada y Matrices de sílice

In this work, we report the synthesis and characterization of ordered nanoporous carbon material (also called ordered mesoporous carbon material [OMC]) ...

Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry

With this protocol, a well-defined singlesite silica-supported heterogeneous catalyst [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] is designed and prepared according to the methodology developed by surface organometallic chemistry (SOMC). In this framework, catalytic cycles can be determined by isolating crucial intermediates. All air-sensitive materials are handled under inert atmosphere (using gloveboxes or a Schlenk line) or high vacuum lines (HVLs, &#60;10-5 mbar). The preparation of SiO2-700 (silica dehydroxylated at 700 &#176;C) and subsequent applications (the grafting of complexes and catalytic runs) requires the use of HVLs and double-Schlenk techniques. Several well-known characterization methods are used, such as Fourier-transform infrared spectroscopy (FTIR), elemental microanalysis, solid-state nuclear magnetic resonance spectroscopy (SSNMR), and state-of-the-art dynamic nuclear polarization surface enhanced NMR spectroscopy (DNP-SENS). FTIR and elemental microanalysis permit scientists to establish the grafting and its stoichiometry. 1H and 13C SSNMR allows the structural determination of the hydrocarbon ligands coordination sphere. DNP SENS is an emerging powerful technique in solid characterization for the detection of poorly sensitive nuclei (15N, in our case). SiO2-700 is treated with about one equivalent of the metal precursor compared to the amount of surface silanol (0.30 mmol&#183;g-1) in pentane at room temperature. Then, volatiles are removed, and the powder samples are dried under dynamic high vacuum to afford the desired materials [(&#8801;Si-O-)Hf(&#951;2&#960;-MeNCH2)(&#951;1-NMe2)(&#951;1-HNMe2)]. After a thermal treatment under high vacuum, the grafted complex is converted into metal imido silica complex [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)]. [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] effectively promotes the metathesis of imines, using the combination of two imine substrates, N-(4-phenylbenzylidene)benzylamine, or N-(4-fluorobenzylidene)-4-fluoroaniline, with N-benzylidenetert-butylamine as substrates. A significantly lower conversion is observed with the blank runs; thus, the presence of the imido group in [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] is correlated to the catalytic performance.

A new group IV metal catalyst for imine metathesis is prepared by grafting amine metal complex onto dehydroxylated silica. Surface metal fragments are characterized using FT-IR, elemental microanalysis, and solid-state NMR spectroscopy. Further dynamic nuclear polarization surface enhanced NMR spectroscopy experiments complement the determination of the coordination sphere.

Imine Metathesis de Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry

With this protocol, a well-defined singlesite silica-supported heterogeneous catalyst [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] is designed and prepared ...

A Salt-Templated Synthesis Method for Porous Platinum-based Macrobeams and Macrotubes

The synthesis of high surface area porous noble metal nanomaterials generally relies on time consuming coalescence of pre-formed nanoparticles, followed by rinsing and supercritical drying steps, often resulting in mechanically fragile materials. Here, a method to synthesize nanostructured porous platinum-based macrotubes and macrobeams with a square cross section from insoluble salt needle templates is presented. The combination of oppositely charged platinum, palladium, and copper square planar ions results in the rapid formation of insoluble salt needles. Depending on the stoichiometric ratio of metal ions present in the salt-template and the choice of chemical reducing agent, either macrotubes or macrobeams form with a porous nanostructure comprised of either fused nanoparticles or nanofibrils. Elemental composition of the macrotubes and macrobeams, determined with x-ray diffractometry and x-ray photoelectron spectroscopy, is controlled by the stoichiometric ratio of metal ions present in the salt-template. Macrotubes and macrobeams may be pressed into free standing films, and the electrochemically active surface area is determined with electrochemical impedance spectroscopy and cyclic voltammetry. This synthesis method demonstrates a simple, relatively fast approach to achieve high-surface area platinum-based macrotubes and macrobeams with tunable nanostructure and elemental composition that may be pressed into free-standing films with no required binding materials.

A synthesis method to obtain porous platinum-based macrotubes and macrobeams with a square cross section through chemical reduction of insoluble salt-needle templates is presented.

Un método de síntesis con plantillas de sal para macrobeames y macrotubos basados en platino poroso

The synthesis of high surface area porous noble metal nanomaterials generally relies on time consuming coalescence of pre-formed nanoparticles, followed ...