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

1. Preparazione di GMS <ol><li> Utilizzare tutte le sostanze chimiche nel processo seguente come ricevuto. </li><li> Preparare 75 ml di 2 M di soluzione di acido cloridrico (HCl). Pesare 2,0 g di poli (glicole etilenico) -block-poli (glicole propilenico) -block-poli (glicole etilenico) (P123, MW = 5.800) e trasferire nel preparato 75 ml di soluzione 2 M HCl. A RT, applicare agitazione magnetica alla soluzione ad una velocità di 350 giri / min fino P123 è completamente sciolto. La soluzione sarà limpida. </li><li> Pesare 4 g di tetraetossisilano (TEOS, PM = 208,33) in una piccola fiala e trasferire 180 ml di bis [3- (trietossisilil) propil] -tetrasulfide (TESPTS, PM = 538,94) nel flaconcino. Agitare lentamente il flacone per miscelare le due sostanze chimiche. In un altro flacone, pesare 38 mg di acido cloroaurico (HAuCl4, 99,90%) e si dissolvono in 1 ml di acqua deionizzata. </li><li> Aumentare la temperatura della soluzione P123 a 35 ° C in un bagno d&#39;olio con temperatura controllata da termocoppia. </li><li> Aggiungere tutta la miscela di TEOS eTESPTS preparata al punto 1.3 alla soluzione P123, e mantenere la soluzione a vigorosa agitazione magnetica di 700 giri / min. Mantenere la soluzione mescolando per 2 minuti, quindi aggiungere tutti HAuCl4 soluzione preparata al punto 1.3, goccia a goccia in 30 secondi. </li><li> Mantenere la soluzione sotto agitazione a 700 giri / min per 24 ore a 35 ° C. </li><li> Dopo 24 ore, trasferire la soluzione in una bottiglia sigillata e conservare in forno a 100 ° C per 72 ore. Questo è chiamato trattamento idrotermale. </li><li> Dopo il trattamento idrotermico, filtrare la soluzione con una carta # 1 filtrazione e pressione negativa in un imbuto, poi lavare con acqua due volte e etanolo tre volte per rimuovere residuo HCl. Nel corso di ogni processo di lavaggio, aggiungere acqua o etanolo 1 cm sopra solida e attendere che il materiale si asciughi. </li><li> Trasferire precipitazione da filtrazione crogiolo ceramico e calcinato a 550 ° C per 4 ore. Impostare il programma rampa come segue: 25 ° C a 550 ° C per 2 ore, mantenere a 550 ° C per 4hr, quindi permettere al campione di rimanere nel forno con la porta chiusa fino a quando la temperatura scende al di sotto di 40 ° C. </li><li> Dopo calcinazione, trasferire il prodotto ad una fiala di vetro con una spatola di plastica. Il materiale sintetizzato ha un colore rosso. </li></ol> 2. Reazione catalitica, ossidazione di alcool benzilico <ol><li> Poiché l&#39;ossidazione di alcool benzilico è una reazione in fase liquida senza solventi separata, misura 5 ml di alcool benzilico (99,8%) e trasferirlo in un pallone da 25 ml a tre colli, si pesa 10 mg di GMS catalizzatore e aggiungere al benzile alcol. </li><li> Impostare un bagno d&#39;olio a temperatura controllata con agitazione magnetica per assicurare il controllo preciso e uniforme della temperatura di reazione. </li><li> Mettere il pallone con alcool benzilico e il catalizzatore nel bagno d&#39;olio, quindi impostare la temperatura a 100 ° C e agitare a 150 giri / min. </li><li> Flusso di gas di ossigeno con il 99,9% di purezza nel pallone a 2 ml / min controllati da un controllore di flusso di massa. </li><li> Quando iltemperatura del bagno ad olio raggiunge 100 ° C e si stabilizza, introdurre gas ossigeno nel pallone a tre colli. </li><li> Mantenere costante la portata di ossigeno e la temperatura, e lasciare che la reazione proceda per 6 ore. </li><li> Dopo la reazione, filtrata del prodotto con una carta # 1 filtrazione. Raccogliere la fase liquida e trasferire una parte in una gascromatografia (GC) flaconcino. Nella fiala GC, mescolare acido acetico quattro parti HPLC grado per ogni campione da una parte (ad esempio, utilizzare 36 ml del campione e 144 ml di acido acetico.) Posizionare il flaconcino su una auto campionatore gascromatografo per l&#39;analisi. Lavare il precipitato solido sulla carta da filtro con acqua deionizzata ed etanolo poi lasciare asciugare all&#39;aria. Raccogliere il solido essiccato con una spatola come catalizzatore riciclato. </li><li> Ripetere la stessa procedura esperimento dal punto 2.3 a 2.7 con catalizzatore riciclato tre volte. In ogni ripetizione, regolare la quantità di alcool benzilico per abbinare il rapporto descritto al punto 2.2. </li></ol> 3. Thermal Trattamento di GMS per il test di stabilità termica <ol><li> Pesare tre distinte porzioni 300 mg di GMS sintetizzati, e conservarli in fiale di vetro. Questi sono contrassegnati come lotto 1, lotto 2 e lotto 3. Tenere lotto 1 come gruppo di controllo, e mettere dei lotti 2 e lotto 3 in una fornace per trattamento termico. </li><li> Programma del forno come segue per la lavorazione a 400 ° C: rampa da 25 ° C a 400 ° C in 0,5 ore, mantenere a 400 ° C per 4 ore, consentire il campione di rimanere nel forno con la porta chiusa fino cascate temperatura sotto i 40 ° C. Mettere lotto 2 in un crogiolo e avviare il programma. </li><li> Programma del forno come segue per la lavorazione a 650 ° C: rampa da 25 ° C a 650 ° C in 0,75 ore, mantenere a 650 ° C per 4 ore, consentire il campione di rimanere in forno con la porta chiusa fino a quando la temperatura scende sotto 40 ° C. Mettere lotto 3 in un crogiolo e avviare il programma. </li></ol> 4. Caratterizzazionedei materiali GMS 21,22 <ol><li> Sullo strumento fisisorbimento, degassare GMS materiali con il seguente programma: 90 ° C per 60 minuti e poi a 350 ° C per 480 min. Eseguire un&#39;analisi completa-isoterma sui materiali degassificata per ottenere i dati fisisorbimento. </li><li> Disperse campione GMS su una griglia TEM carbonio 200 mesh holey e osservare il campione al microscopio elettronico a trasmissione. Limitare ingrandimenti in 44,000X per proteggere il materiale. </li><li> XRD Corri con radiazione Cu Kα (λ = 1,5418 Å). Set tensione del tubo di 45 kV, e la corrente del tubo di 40 mA. Raccogliere intensità nell&#39;intervallo 2θ tra 10 ° e 90 ° con un passo di 0,008 ° e un tempo di misura di 5 sec ad ogni passo. </li></ol>

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The authors have nothing to disclose.

Nel protocollo di sintesi, l&#39;attenzione alla concentrazione di tensioattivo, pH della soluzione di reazione e la temperatura è fondamentale per la formazione di successo di GMS. I passaggi critici sono 1.2, 1.3, 1.4 e 1.6. I suddetti parametri controllano il parametro imballaggio critica e la fase di micelle formate da tensioattivo. La fase e la morfologia del micelle determina lo stato finale della matrice di silice, che funge da quadro per GMS. Altrettanto importante nel processo di formazione è la sequenza e il...

Come una tecnologia emergente che ha un grande potenziale nelle applicazioni di catalisi, materiali su scala nanometrica hanno ricevuto l&#39;interesse intensa attività di ricerca negli ultimi decenni. Tra i catalizzatori nanoscala segnalati, catalizzatori di metalli nobili, come Au, Ag, Pd e Pt hanno attirato l&#39;attenzione in tutto il mondo 1-3. Seleziona reazioni catalitiche includono l&#39;ossidazione dei ricercatori di monossido di carbonio su Au, Heck reazione catalizzatori Pd, e la scissione dell&#39;acqua con Pt. Nonostante il potenziale catalitico promettente, oro nanoscala è limitata nella sua applicazione a causa della disattivazione di avvelenamento, coking, degradazione termica, e sinterizzazione. E &#39;stato riportato che l&#39;oro, come rappresentante per metalli nobili, ha l&#39;alta selettività ed è meno soggetto a lisciviazione metallo, over-ossidazione, e di auto-avvelenamento 4. Tuttavia, la prestazione catalitica di oro dipende fortemente dalla granulometria. Haruta et al. Ha riportato il rapporto tra prestazioni catalitiche e andarediametro grappolo ld, dimostrando la più alta attività di catalizzatori oro con granulometria ~ 2.7 nm 5. La dimensione delle particelle di metalli nobili può essere controllato dal metodo di preparazione 6-9; Tuttavia, il principale ostacolo verso un&#39;ampia applicazione rimane aggregazione e perdita di attività. Per risolvere il problema di sinterizzazione, un metodo comune è quella di immobilizzare nanoparticelle su un materiale di supporto. Vari materiali di supporto sono state applicate compresa la silice porosa 10-11, ossidi metallici semiconduttori 12-13, polimeri 14, grafene 15 e nanotubi di carbonio 16. Tra i materiali impiegati, silice porosa è un materiale attraente come un supporto perché è solo leggermente acido, relativamente inerte, termicamente e chimicamente stabile, e può essere preparata con molto ben definito meso / microporosità. La struttura porosa fornisce un buon supporto per particelle di metallo, ma conferisce anche accesso dimensione substrato selettivoi catalizzatori metallici. Questa selettività è particolarmente promettente per la tunability associato con questi materiali porosi. Spesso, particelle d&#39;oro si trovano ad essere estremamente mobile su superfici silice 17-18 e facilmente formare molto grandi (50+ nm) particelle reattivi quando esposto a temperature elevate, rendendo così difficile preparare nanoparticelle di oro su silice 19. Mukherjee et al. Segnalato l&#39;immobilizzazione di nanoparticelle d&#39;oro monodisperse su mesoporosi silice MCM-41 da 3 amminopropil-trimetossisilano e 3-mercaptopropil-trietossisilano, e le nanoparticelle d&#39;oro supportati sono risultati essere molto attivo per reazioni di idrogenazione e stata trovata nessuna lisciviazione dell&#39;oro nella reazione 20. A seguito della relazione di modifica della superficie della silice mesoporosa, abbiamo riportato un metodo per preparare oro intercalati nella parete della silice mesoporosa (GMS). Inoltre, l&#39;approccio di silice mesoporosa supportato offre un ap scalabileproccio potenzialmente modificare autonomamente il catalizzatore e l&#39;ambiente poroso. Dal momento che i processi catalitici sono di vitale importanza economica, i benefici potrebbero essere di vasta portata. La capacità di sviluppare catalizzatori &quot;verdi&quot; avrebbe un profondo impatto positivo sull&#39;ambiente e migliorare la fattibilità e l&#39;efficienza delle risorse economiche di importanti processi industriali.

<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

Come promettendo reattore nano cataliticamente attivo, nanoparticelle d&#39;oro intercalate in silice mesoporosa (GMS) sono stati sintetizzati con successo e le proprietà dei materiali sono stati studiati. Abbiamo utilizzato un approccio sol-gel una pentola a intercalare nano particelle d&#39;oro nelle pareti di silice mesoporosa. Per iniziare con la sintesi, P123 è stato utilizzato come modello per formare micelle. Poi TESPTS è stato usato come agente modifica superficiale intercalare nano particelle d&#39;oro. A seguito di questo processo, TEOS stato aggiunto come una fonte di silice che ha subito un processo di polimerizzazione in ambiente acido. Dopo trattamento idrotermale e calcinazione, il prodotto finale è stato acquisito. Diverse tecniche sono stati utilizzati per caratterizzare la porosità, la morfologia e la struttura del oro intercalato silice mesoporosa. I risultati hanno mostrato una struttura stabile della silice mesoporosa dopo l&#39;oro intercalazione. Attraverso l&#39;ossidazione di alcool benzilico come reazione di riferimento, i materiali GMS mostrato alta Selectività e la riciclabilità.

Questo metodo è stato utilizzato per confrontare i livelli di sintesi dell&#39;eme nel normale (HBEC30KT) vs. cancro (HCC4017) cellule polmonari. La Figura 2 mostra un più alto livello di sintesi dell&#39;eme nelle cellule tumorali (HCC4017) rispetto alle cellule polmonari normali (HBEC30KT). Il livello di sintesi dell&#39;eme stata anche misurata in cellule normali e tumorali in presenza di cianuro di carbonile mitocondriale disaccoppiatore 3-chlorophenylhydrazone (CCCP). Le cellule sono state tratta...

Watch this Scientific Journal Video about Synthesis and Catalytic Performance of Gold Intercalated in the Walls of Mesoporous Silica at JoVE.com

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.

Sintesi e prestazioni catalitica dell&#39;oro intercalata nelle Mura di mesoporosi silice

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 Views.  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 ...

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Chimica

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 e IR Spettroscopia di superfici ben definite Preparato da atterraggio morbido di ioni Mass-selezionati

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.

Sintesi, Caratterizzazione, e funzionalizzazione di ibrida UA / CdS e Au / ZnS core / shell nanoparticelle

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 per sintesi chimica e risolte nel tempo meccanicistici Studies

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

Bioingegneria

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 Sintesi di oro nanoparticelle senza aggregazione nel Interfalda spazio di Layered titanato pellicole trasparenti

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

Ingegneria

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.

Preparazione di silice funzionale utilizzando un metodo bioinalati

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 metodo di sintesi rapida per Au, Pd e Pt Aerogels tramite riduzione diretta basata su soluzione

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.

Proprietà della superficie di sintetizzato nanoporosi carbonio e matrici di silice

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.

Metatesi imine da silice-supported Catalysts Utilizzando la metodologia della chimica dell'organimetallico di superficie

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 metodo di sintesi basato sul sale per macrobeam e macrotubi porosi a base di platino

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

Sintesi e prestazioni catalitica dell'oro intercalata nelle Mura di mesoporosi silice

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