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

1. Preparation of GMS
<ol>
	<li>Use all chemicals in the following process as received.</li>
	<li>Prepare 75 ml of 2 M of hydrochloric acid (HCl) solution. Weigh 2.0 g of poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P123, MW = 5,800) and transfer into the prepared 75 ml of 2 M HCl solution. At RT, apply magnetic stirring to the solution at a speed of 350 r/min until P123 is completely dissolved. The solution will be clear.</li>
	<li>Weigh 4 g of tetraethoxysilane (TEOS, MW = 208.33) in a small vial and transfer 180 &#181;l of Bis[3-(triethoxysilyl)propyl]-tetrasulfide (TESPTS, MW = 538.94) into the vial. Slowly shake the vial to mix the two chemicals. In another vial, weigh 38 mg of chloroauric acid (HAuCl4, 99.90%) and dissolve in 1 ml of DI water.</li>
	<li>Increase the P123 solution temperature to 35 &#176;C in an oil bath with temperature controlled by thermocouple.</li>
	<li>Add all of the mixture of TEOS and TESPTS prepared in step 1.3 to the P123 solution, and keep the solution at vigorous magnetic stirring of 700 r/min. Keep the solution stirring for 2 min, then add all of HAuCl4 solution prepared in step 1.3 dropwise within 30 sec.</li>
	<li>Keep the solution stirring at 700 r/min for 24 hr at 35 &#176;C.</li>
	<li>After 24 hr, transfer the solution into a sealed bottle and store in an oven set at 100 &#176;C for 72 hr. This is called hydrothermal processing.</li>
	<li>After the hydrothermal processing, filter the solution with a #1 filtration paper and negative pressure under a funnel, then wash with water two times and ethanol three times to remove remaining HCl. During each wash process, add water or ethanol 1 cm above solid and wait for the material to dry.</li>
	<li>Transfer precipitation from filtration to a ceramic crucible and calcine at 550 &#176;C for 4 hr. Set the ramp program as follows: 25&#160;&#176;C to 550&#160;&#176;C for 2 hr, keep at 550&#160;&#176;C for 4 hr, then allow the sample to remain in furnace with the door closed until the temperature falls below 40 &#176;C.</li>
	<li>After calcination, transfer the product to a glass vial with a plastic spatula. The synthesized material has a red color.</li>
</ol>
2. Catalytic Reaction, Oxidation of Benzyl Alcohol
<ol>
	<li>Since the oxidation of benzyl alcohol is a liquid phase reaction without a separate solvent, measure 5 ml of benzyl alcohol (99.8%) and transfer it into a 25 ml three-neck flask, then weigh 10 mg of GMS catalyst and it add to benzyl alcohol.</li>
	<li>Set up a temperature-controlled oil bath with magnetic stirring to ensure accurate and uniform control of the reaction temperature.</li>
	<li>Put the flask with benzyl alcohol and catalyst into the oil bath, then set the temperature to 100&#160;&#176;C and stir at 150 r/min.</li>
	<li>Flow oxygen gas with 99.9% purity into the flask at 2 ml/min controlled by a mass flow controller.</li>
	<li>When the temperature of the oil bath reaches 100&#160;&#176;C and stabilizes, introduce oxygen gas into the three neck flask.</li>
	<li>Keep the oxygen flow rate and temperature constant, and allow the reaction to proceed for 6 hr.</li>
	<li>After the reaction, filter the product with a #1 filtration paper. Collect the liquid phase and transfer an aliquot to a gas chromatography (GC) vial. In the GC vial, mix four parts HPLC grade acetic acid for every one part sample (For example, use 36 &#181;l sample and 144 &#181;l acetic acid.) Put the vial on a gas chromatograph auto sampler for analysis. Wash off the solid precipitate on the filter paper with DI water and ethanol then allow to dry in air. Collect the dried solid with a spatula as recycled catalyst.</li>
	<li>Repeat the same experiment procedure from step 2.3 through 2.7 with recycled catalyst three times. In each repeat, adjust the amount of benzyl alcohol to match the ratio described in step 2.2.</li>
</ol>
3. Thermal Treatment of GMS for Testing of Thermal Stability
<ol>
	<li>Weigh three separate 300 mg portions of synthesized GMS, and store them in glass vials. These are marked as batch 1, batch 2 and batch 3. Keep batch 1 as control group, and put batch 2 and batch 3 into a furnace for thermal processing.</li>
	<li>Program the furnace as follows for processing at 400 &#176;C: ramp from 25&#160;&#176;C to 400&#160;&#176;C in 0.5 hr, maintain at 400&#160;&#176;C for 4 hr, allow the sample to remain in the furnace with the door closed until the temperature falls below 40 &#176;C. Put batch 2 in a crucible and start the program.</li>
	<li>Program the furnace as follows for processing at 650 &#176;C: ramp from 25 &#176;C to 650&#160;&#176;C in 0.75 hr, maintain at 650&#160;&#176;C for 4 hr, allow the sample to remain in furnace with the door closed until the temperature falls below 40 &#176;C. Put batch 3 in a crucible and start the program.</li>
</ol>
4. Characterization of GMS Materials21,22
<ol>
	<li>On the physisorption instrument, degas GMS materials with the following program: 90 &#176;C for 60 min and then 350 &#176;C for 480 min. Run full-isotherm analysis on the degased materials to obtain physisorption data.</li>
	<li>Disperse GMS sample on a 200-mesh holey carbon TEM grid and observe the sample under a transmission electron microscope. Restrict magnification under 44,000X to protect the material.</li>
	<li>Run XRD with Cu K&#945; radiation (&#955; = 1.5418 &#197;). Set tube voltage of 45 kV, and tube current of 40 mA. Collect intensity in the 2&#952; range between 10&#176; and 90&#176; with a step size of 0.008&#176; and a measuring time of 5 sec at each step.</li>
</ol>

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The authors have nothing to disclose.

Within the synthesis protocol, attention to surfactant concentration, pH of solution and reaction temperature is critical to the successful formation of GMS. The critical steps are 1.2, 1.3, 1.4 and 1.6. The above mentioned parameters control the critical packing parameter and phase of micelles formed from surfactant. The phase and morphology of micelle determines the final state of silica matrix, which serves as the framework for GMS. Also important in the formation process is the sequence and time to add the HAuCl solu...

As an emerging technology that has great potential in catalysis applications, nanoscale materials have received intensive research interest in the past decades. Amongst the nanoscale catalysts reported, noble metal catalysts such as Au, Ag, Pd and Pt have attracted world-wide attention 1-3. Select&#160;catalytic reactions include the oxidation of carbon monoxide researchers on Au, Heck reaction on Pd catalysts, and water splitting with Pt. In spite of the promising catalytic potential, nanoscale gold is limited in its applicability due to deactivation from poisoning, coking, thermal degradation, and sintering. It has been reported that gold, as a representative for noble metals, has high selectivity and is less prone to metal leaching, over-oxidation, and self-poisoning4. However, the catalytic performance of gold strongly depends on the particle size. Haruta et al. has reported the relationship between catalytic performance and gold cluster diameter, demonstrating the highest activity of gold catalysts with particle size ~ 2.7 nm5.
The particle size of noble metals can be controlled by the preparation method6-9; however, the major hindrance towards broad application remains aggregation and loss of activity. To solve the problem of sintering, a common method is to immobilize nanoscale particles on a support material. Various support materials have been applied including porous silica10-11, semiconducting metal oxides12-13, polymers14, graphene15 and carbon nanotubes16. Amongst the materials used, porous silica is an attractive material as a support because it is only mildly acidic, relatively inert, thermally and chemically stable, and can be prepared with very well defined meso-/micro-porosity. The porous structure provides good support for metal particles but also imparts size selective substrate access to the metal catalysts. This selectivity is particularly promising because of the tunability associated with these porous materials. Often, gold particles are found to be extremely mobile on silica surfaces17-18 and readily form very large (50+ nm) unreactive particles when exposed to high temperatures, thus making it difficult to prepare gold nanoparticles on silica19. Mukherjee et al. reported immobilization of monodispersed gold nanoparticles on mesoporous silica MCM-41 by 3-aminopropyl-trimethoxysilane and 3-mercaptopropyl-triethoxysilane, and the supported gold nanoparticles were found to be highly active for hydrogenation reactions and no leaching of gold was found in the reaction20.
Following the report of surface modification of mesoporous silica, we reported a method to prepare gold intercalated into the wall of mesoporous silica (GMS). Additionally, the mesoporous silica supported approach offers a scalable approach to potentially independently alter the catalyst and porous environment. Since catalytic processes are of vital economic importance, the benefits could be far reaching. The ability to develop &#8220;green&#8221; catalysts would have a profound positive impact on the environment and improve the economic feasibility and resource efficiency of important industrial processes.

<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

As a promising catalytically active nano reactor, gold nanoparticles intercalated in mesoporous silica (GMS) were successfully synthesized and properties of the materials were investigated. We used a one pot sol-gel approach to intercalate gold nano particles in the walls of mesoporous silica. To start with the synthesis, P123 was used as template to form micelles. Then TESPTS was used as a surface modification agent to intercalate gold nano particles. Following this process, TEOS was added in as a silica source which underwent a polymerization process in acid environment. After hydrothermal processing and calcination, the final product was acquired. Several techniques were utilized to characterize the porosity, morphology and structure of the gold intercalated mesoporous silica. The results showed a stable structure of mesoporous silica after gold intercalation. Through the oxidation of benzyl alcohol as a benchmark reaction, the GMS materials showed high selectivity and recyclability.

This method was used to compare the levels of heme synthesis in normal (HBEC30KT) vs. cancer (HCC4017) lung cells. Figure 2 shows a higher level of heme synthesis in cancer cells (HCC4017) than normal lung cells (HBEC30KT). The level of heme synthesis was also measured in normal and cancer cells in the presence of mitochondrial uncoupler carbonyl cyanide 3-chlorophenylhydrazone (CCCP). Cells were treated with 10 &#956;M CCCP for 24 hr before the measurement of heme synthesis levels. As expected, the leve...

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.

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 ...

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.

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.

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.

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

Bioengineering

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.

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

Engineering

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.

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.

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.

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.

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.

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

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

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Chapters in this video

Preparation of Silica Nanoparticles Through Microwave-assisted Acid-catalysis

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

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

Millifluidics for Chemical Synthesis and Time-resolved Mechanistic Studies

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

Preparation of Functional Silica Using a Bioinspired Method

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

Surface Properties of Synthesized Nanoporous Carbon and Silica Matrices

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

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