Name: synthesis and catalytic performance of gold intercalated in the walls of mesoporous silica
Uploaded: 2015-07-09T14:00:00
Description: Watch this Scientific Journal Video about Synthesis and Catalytic Performance of Gold Intercalated in the Walls of Mesoporous Silica at JoVE.com

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) i...

<ol>
	<li>Liguras, D. K., Kondarides, D. I., Verykios, X. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Production+of+hydrogen+for+fuel+cells+by+steam+reforming+of+ethanol+over+supported+noble+metal+catalysts.">Production of hydrogen for fuel cells by steam reforming of ethanol over supported noble metal catalysts.</a> Appl. Catal. B-Environ. 43 (4), 345-354 (2003).</li><li>Gelin, P., Primet, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Complete+oxidation+of+methane+at+low+temperature+over+noble+metal+based+catalysts:+a+review.">Complete oxidation of methane at low temperature over noble metal based catalysts: a review.</a> Appl. Catal. B-Environ. 39 (1), 1-37 (2002).</li><li>Lu, S. F., Pan, J., Huang, A. B., Zhuang, L., Lu, J. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alkaline+polymer+electrolyte+fuel+cells+completely+free+from+noble+metal+catalysts.">Alkaline polymer electrolyte fuel cells completely free from noble metal catalysts.</a> Proc. Natl. Acad. Sci. U. S. A. 105 (52), 20611-20614 (2008).</li><li>Ma, C. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Catalytic+oxidation+of+benzyl+alcohol+on+Au+or+Au&#8211;Pd+nanoparticles+confined+in+mesoporous+silica.">Catalytic oxidation of benzyl alcohol on Au or Au&#8211;Pd nanoparticles confined in mesoporous silica.</a> Applied Catalysis B: Environmental. 92 (1-2), 202-208 (2009).</li><li>Bamwenda, G. R., Tsubota, S., Nakamura, T., Haruta, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+influence+of+the+preparation+methods+on+the+catalytic+activity+of+platinum+and+gold+supported+on+TiO2+for+CO+oxidation.">The influence of the preparation methods on the catalytic activity of platinum and gold supported on TiO2 for CO oxidation.</a> Catalysis Letters. 44 (1-2), 83-87 (1997).</li><li>Brown, K. R., Walter, D. G., Natan, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Seeding+of+colloidal+Au+nanoparticle+solutions.+2.">Seeding of colloidal Au nanoparticle solutions. 2.</a> Improved control of particle size. 12 (2), 306-313 (2000).</li><li>Niesz, K., Grass, M., Somorjai, G. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Precise+control+of+the+Pt+nanoparticle+size+by+seeded+growth+using+EO13PO30EO13+triblock+copolymers+as+protective+agents.">Precise control of the Pt nanoparticle size by seeded growth using EO13PO30EO13 triblock copolymers as protective agents.</a> Nano Lett. 5 (11), 2238-2240 (2005).</li><li>Yuranov, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pd/SiO2+catalysts:+synthesis+of+Pd+nanoparticles+with+the+controlled+size+in+mesoporous+silicas.">Pd/SiO2 catalysts: synthesis of Pd nanoparticles with the controlled size in mesoporous silicas.</a> J. Mol. Catal. A-Chem. 192, 1-2 (2003).</li><li>Brinas, R. P., Hu, M. H., Qian, L. P., Lymar, E. S., Hainfeld, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gold+nanoparticle+size+controlled+by+polymeric+Au(I)+thiolate+precursor+size.">Gold nanoparticle size controlled by polymeric Au(I) thiolate precursor size.</a> J. Am. Chem. Soc. 130 (3), 975-982 (2008).</li><li>Zhu, H. G., Liang, C. D., Yan, W. F., Overbury, S. H., Dai, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+highly+active+silica-supported+Au+catalysts+for+CO+oxidation+by+a+solution-based+technique.">Preparation of highly active silica-supported Au catalysts for CO oxidation by a solution-based technique.</a> J. Phys. Chem. B. 110 (22), 10842-10848 (2006).</li><li>Gabaldon, J. P., Bore, M., Datye, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mesoporous+silica+supports+for+improved+thermal+stability+in+supported+Au+catalysts.">Mesoporous silica supports for improved thermal stability in supported Au catalysts.</a> Top. Catal. 44 (1-2), 253-262 (2007).</li><li>Li, F. B., Li, X. Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+enhancement+of+photodegradation+efficiency+using+Pt-TiO2+catalyst.">The enhancement of photodegradation efficiency using Pt-TiO2 catalyst.</a> Chemosphere. 48 (10), 1103-1111 (2002).</li><li>Sakthivel, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhancement+of+photocatalytic+activity+by+metal+deposition:+characterisation+and+photonic+efficiency+of+Pt,+Au+and+Pd+deposited+on+TiO2+catalyst.">Enhancement of photocatalytic activity by metal deposition: characterisation and photonic efficiency of Pt, Au and Pd deposited on TiO2 catalyst.</a> Water Res. 38 (13), 3001-3008 (2004).</li><li>Jia, C. G., Wang, Y. P., Feng, H. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+and+Catalytic+Properties+Of+Polymer-Supported+Fe-Co-Cu+And+Fe-Co-Au+Pentametallic+Clusters.">Preparation and Catalytic Properties Of Polymer-Supported Fe-Co-Cu And Fe-Co-Au Pentametallic Clusters.</a> React. Polym. 18 (3), 203-211 (1992).</li><li>Yu, X. Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reduced+graphene+oxide+supported+Au+nanoparticles+as+an+efficient+catalyst+for+aerobic+oxidation+of+benzyl+alcohol.">Reduced graphene oxide supported Au nanoparticles as an efficient catalyst for aerobic oxidation of benzyl alcohol.</a> Appl. Surf. Sci. 280, 450-455 (2013).</li><li>Xu, Y. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Au@Pt+core-shell+nanoparticles+supported+on+multiwalled+carbon+nanotubes+for+methanol+oxidation.">Au@Pt core-shell nanoparticles supported on multiwalled carbon nanotubes for methanol oxidation.</a> Catal. Commun. 13 (1), 54-58 (2011).</li><li>Baker, C. O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Size+Control+of+Gold+Nanoparticles+Grown+on+Polyaniline+Nanofibers+for+Bistable+Memory+Devices.">Size Control of Gold Nanoparticles Grown on Polyaniline Nanofibers for Bistable Memory Devices.</a> ACS Nano. 5 (5), 3469-3474 (2011).</li><li>Wei, G. -. T., Yang, Z., Lee, C. Y., Yang, H. Y., Wang, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aqueous&#8722;Organic+Phase+Transfer+of+Gold+Nanoparticles+and+Gold+Nanorods+Using+an+Ionic+Liquid.">Aqueous&#8722;Organic Phase Transfer of Gold Nanoparticles and Gold Nanorods Using an Ionic Liquid.</a> J. Am. Chem. Soc. 126 (16), 5036-5037 (2004).</li><li>Gadenne, B., Hesemann, P., Moreau, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Supported+ionic+liquids:+ordered+mesoporous+silicas+containing+covalently+linked+ionic+species.">Supported ionic liquids: ordered mesoporous silicas containing covalently linked ionic species.</a> Chemical Communications. 15, 1768-1769 (2004).</li><li>Yang, J. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Understanding+preparation+variables+in+the+synthesis+of+Au/Al2O3+using+EXAFS+and+electron+microscopy.">Understanding preparation variables in the synthesis of Au/Al2O3 using EXAFS and electron microscopy.</a> Applied Catalysis A: General. 291 (1-2), 73-84 (2005).</li><li>Chen, L. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intercalation+of+aggregation-free+and+well-dispersed+gold+nanoparticles+into+the+walls+of+mesoporous+silica+as+a+robust+&#8216;green&#8217;+catalyst+for+n-alkane+oxidation.">Intercalation of aggregation-free and well-dispersed gold nanoparticles into the walls of mesoporous silica as a robust &#8216;green&#8217; catalyst for n-alkane oxidation.</a> Journal of the American Chemical Society. 131, 914-915 (2009).</li><li>Wang, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanoscale+gold+intercalated+into+mesoporous+silica+as+a+highly+active+and+robust+catalyst.">Nanoscale gold intercalated into mesoporous silica as a highly active and robust catalyst.</a> Nanotechnology. 23, 294010-294018 (2012).</li><li>Chen, L. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlled+synthesis+of+nanoscale+icosahedral+gold+particles+at+room+temperature.">Controlled synthesis of nanoscale icosahedral gold particles at room temperature.</a> Chemcatchem. 4, 1662-1667 (2012).</li></ol>

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 border="0" cellpadding="0" cellspacing="0">
	<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&#39;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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Research

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Chemistry

Isolation and Preparation of Bacterial Cell Walls for Compositional Analysis by Ultra Performance Liquid Chromatography

The bacterial cell wall is critical for the determination of cell shape during growth and division, and maintains the mechanical integrity of cells in the face of turgor pressures several atmospheres in magnitude. Across the diverse shapes and sizes of the bacterial kingdom, the cell wall is composed of peptidoglycan, a macromolecular network of sugar strands crosslinked by short peptides. Peptidoglycan&#8217;s central importance to bacterial physiology underlies its use as an antibiotic target and has motivated genetic, structural, and cell biological studies of how it is robustly assembled during growth and division. Nonetheless, extensive investigations are still required to fully characterize the key enzymatic activities in peptidoglycan synthesis and the chemical composition of bacterial cell walls. High Performance Liquid Chromatography (HPLC) is a powerful analytical method for quantifying differences in the chemical composition of the walls of bacteria grown under a variety of environmental and genetic conditions, but its throughput is often limited. Here, we present a straightforward procedure for the isolation and preparation of bacterial cell walls for biological analyses of peptidoglycan via HPLC and Ultra Performance Liquid Chromatography (UPLC), an extension of HPLC that utilizes pumps to deliver ultra-high pressures of up to 15,000 psi, compared with 6,000 psi for HPLC. In combination with the preparation of bacterial cell walls presented here, the low-volume sample injectors, detectors with high sampling rates, smaller sample volumes, and shorter run times of UPLC will enable high resolution and throughput for novel discoveries of peptidoglycan composition and fundamental bacterial cell biology in most biological laboratories with access to an ultracentrifuge and UPLC.

The bacterial cell wall is composed of peptidoglycan, a macromolecular network of sugar strands crosslinked by peptides. Ultra Performance Liquid Chromatography provides high resolution and throughput for novel discoveries of peptidoglycan composition. We present a procedure for the isolation of cell walls (sacculi) and their subsequent preparation for analysis via UPLC.

The bacterial cell wall is critical for the determination of cell shape during growth and division, and maintains the mechanical integrity of cells in the ...

A Simple Method for the Size Controlled Synthesis of Stable Oligomeric Clusters of Gold Nanoparticles under Ambient Conditions

Reducing dilute aqueous HAuCl4 with sodium thiocyanate (NaSCN) under alkaline conditions produces 2 to 3 nm diameter nanoparticles. Stable grape-like oligomeric clusters of these yellow nanoparticles of narrow size distribution are synthesized under ambient conditions via two methods. The delay-time method controls the number of subunits in the oligoclusters by varying the time between the addition of HAuCl4 to alkaline solution and the subsequent addition of reducing agent, NaSCN. The yellow oligoclusters produced range in size from ~3 to ~25 nm. This size range can be further extended by an add-on method utilizing hydroxylated gold chloride (Na+[Au(OH4-x)Clx]-) to auto-catalytically increase the number of subunits in the as-synthesized oligocluster nanoparticles, providing a total range of 3 nm to 70 nm. The crude oligocluster preparations display narrow size distributions and do not require further fractionation for most purposes. The oligoclusters formed can be concentrated &#62;300 fold without aggregation and the crude reaction mixtures remain stable for weeks without further processing. Because these oligomeric clusters can be concentrated before derivatization they allow expensive derivatizing agents to be used economically. In addition, we present two models by which predictions of particle size can be made with great accuracy.

We describe a simple method for producing highly stable oligomeric clusters of gold nanoparticles via the reduction of chloroauric acid (HAuCl4) with sodium thiocyanate (NaSCN). The oligoclusters have a narrow size distribution and can be produced with a wide range of sizes and surface coats.

Reducing dilute aqueous HAuCl4 with sodium thiocyanate (NaSCN) under alkaline conditions produces 2 to 3 nm diameter nanoparticles. Stable grape-like ...

Sequencing of Plant Wall Heteroxylans Using Enzymic, Chemical (Methylation) and Physical (Mass Spectrometry, Nuclear Magnetic Resonance) Techniques

This protocol describes the specific techniques used for the characterization of reducing end (RE) and internal region glycosyl sequence(s) of heteroxylans. De-starched wheat endosperm cell walls were isolated as an alcohol-insoluble residue (AIR)1 and sequentially extracted with water (W-sol Fr) and 1 M KOH containing 1% NaBH4 (KOH-sol Fr) as described by Ratnayake et al. (2014)2. Two different approaches (see summary in Figure 1) are adopted. In the first, intact W-sol AXs are treated with 2AB to tag the original RE backbone chain sugar residue and then treated with an endoxylanase to generate a mixture of 2AB-labelled RE and internal region reducing oligosaccharides, respectively. In a second approach, the KOH-sol Fr is hydrolyzed with endoxylanase to first generate a mixture of oligosaccharides which are subsequently labelled with 2AB. The enzymically released ((un)tagged) oligosaccharides from both W- and KOH-sol Frs are then methylated and the detailed structural analysis of both the native and methylated oligosaccharides is performed using a combination of MALDI-TOF-MS, RP-HPLC-ESI-QTOF-MS and ESI-MSn. Endoxylanase digested KOH-sol AXs are also characterized by nuclear magnetic resonance (NMR) that also provides information on the anomeric configuration. These techniques can be applied to other classes of polysaccharides using the appropriate endo-hydrolases.

Sequencing of Plant Wall Heteroxylans Using Enzymic, Chemical Methylation and Physical Mass Spectrometry, Nuclear Magnetic Resonance Techniques

This protocol describes the specific techniques used for the structural characterization of reducing end (RE) and internal region glycosyl sequence(s) of heteroxylans by tagging the RE with 2 aminobenzamide prior to enzymatic (endoxylanase) hydrolysis and then analysis of the resultant oligosaccharides using mass spectrometry (MS) and nuclear magnetic resonance (NMR).

This protocol describes the specific techniques used for the characterization of reducing end (RE) and internal region glycosyl sequence(s) of ...

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the development of antibody drug conjugates (ADCs) and nanomedicine, fluorescent microscopy and systems chemistry. For many of these applications, specificity of the bioconjugation method used is of prime concern. The Michael addition of maleimides with cysteine(s) on the target proteins is highly selective and proceeds rapidly under mild conditions, making it one of the most popular methods for protein bioconjugation.
We demonstrate here the modification of the only surface-accessible cysteine residue on yeast cytochrome c with a ruthenium(II) bisterpyridine maleimide. The protein bioconjugation is verified by gel electrophoresis and purified by aqueous-based fast protein liquid chromatography in 27% yield of isolated protein material. Structural characterization with MALDI-TOF MS and UV-Vis is then used to verify that the bioconjugation is successful. The protocol shown here is easily applicable to other cysteine - maleimide coupling of proteins to other proteins, dyes, drugs or polymers.

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

This protocol details the important steps required for the bioconjugation of a cysteine containing protein to a maleimide, including reagent purification, reaction conditions, bioconjugate purification and bioconjugate characterization.

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the ...

Hydroquinone Based Synthesis of Gold Nanorods

Gold nanorods are an important kind of nanoparticles characterized by peculiar plasmonic properties. Despite their widespread use in nanotechnology, the synthetic methods for the preparation of gold nanorods are still not fully optimized. In this paper we describe a new, highly efficient, two-step protocol based on the use of hydroquinone as a mild reducing agent. Our approach allows the preparation of nanorods with a good control of size and aspect ratio (AR) simply by varying the amount of hexadecyl trimethylammonium bromide (CTAB) and silver ions (Ag+) present in the "growth solution". By using this method, it is possible to markedly reduce the amount of CTAB, an expensive and cytotoxic reagent, necessary to obtain the elongated shape. Gold nanorods with an aspect ratio of about 3 can be obtained in the presence of just 50 mM of CTAB (versus 100 mM used in the standard protocol based on the use of ascorbic acid), while shorter gold nanorods are obtained using a concentration as low as 10 mM.

This paper describes a protocol for the synthesis of gold nanorods, based on the use of hydroquinone as reducing agent, plus the different mechanisms for controlling their size and aspect ratio.

Gold nanorods are an important kind of nanoparticles characterized by peculiar plasmonic properties. Despite their widespread use in nanotechnology, the ...

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. Detailed and generalized protocols are also presented for testing the catalytic activity of such complexes in arylation and Suzuki-Miyaura cross-coupling reactions. Representative results are shown for the catalytic activity of the four complexes in arylation and Suzuki-Miyaura type reactions. For each of the reactions investigated, at least one of the four complexes successfully catalyzed the reaction, qualifying them as promising candidates for catalysis of many carbon-carbon bond-forming reactions. The protocols presented are general enough to be adapted for the synthesis, purification and catalytic activity testing of new palladium N-heterocyclic carbene complexes.

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. The complexes were tested for catalytic activity in arylation and Suzuki-Miyaura reactions. For each reaction investigated, at least one of the four complexes successfully catalyzed the reaction.

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from ...

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of NixNb1-xO nanoparticles with different atomic compositions (x = 0.03, 0.08, 0.15, and 0.20) have been prepared by chemical precipitation. These NixNb1-xO catalysts are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The study revealed the sponge-like and fold-like appearance of Ni0.97Nb0.03O and Ni0.92Nb0.08O on the NiO surface, and the larger surface area of these NixNb1-xO catalysts, compared with the bulk NiO. Maximum surface area of 173 m2/g can be obtained for Ni0.92Nb0.08O catalysts. In addition, the catalytic hydroconversion of lignin-derived compounds using the synthesized Ni0.92Nb0.08O catalysts have been investigated.

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

A protocol for the synthesis of sponge-like and fold-like Ni1-xNbxO nanoparticles by chemical precipitation is presented.

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of ...

Rapid Nanoprobe Signal Enhancement by In Situ Gold Nanoparticle Synthesis

The use of nanoprobes such as gold, silver, silica or iron-oxide nanoparticles as detection reagents in bioanalytical assays can enable high sensitivity and convenient colorimetric readout. However, high densities of nanoparticles are typically needed for detection. The available synthesis-based enhancement protocols are either limited to gold and silver nanoparticles or rely on precise enzymatic control and optimization. Here, we present a protocol to enhance the colorimetric readout of gold, silver, silica, and iron oxide nanoprobes. It was observed that the colorimetric signal can be improved by up to a 10000-fold factor. The basis for such signal enhancement strategies is the chemical reduction of Au3+ to Au0. There are several chemical reactions that enable the reduction of Au3+ to Au0. In the protocol, Good&#39;s buffers and H2O2 are used and it is possible to favor the deposition of Au0 onto the surface of existing nanoprobes, in detriment of the formation of new gold nanoparticles. The protocol consists of the incubation of the microarray with a solution consisting of chloroauric acid and H2O2 in 2-(N-morpholino)ethanesulfonic acid pH 6 buffer following the nanoprobe-based detection assay. The enhancement solution can be applied to paper and glass-based sensors. Moreover, it can be used in commercially available immunoassays as demonstrated by the application of the method to a commercial allergen microarray. The signal development requires less than 5 min of incubation with the enhancement solution and the readout can be assessed by naked eye or low-end image acquisition devices such as a table-top scanner or a digital camera.

Rapid Nanoprobe Signal Enhancement by In Situ Gold Nanoparticle Synthesis

In this work, a protocol for signal enhancement of nanoprobe-based biosensing is presented. The protocol is based on the reduction of chloroauric acid onto the surface of existing nanoprobes that consist of gold, silver, silica or iron-oxide nanoparticles.

The use of nanoprobes such as gold, silver, silica or iron-oxide nanoparticles as detection reagents in bioanalytical assays can enable high sensitivity ...

Synthesis and Characterization of Amphiphilic Gold Nanoparticles

Gold nanoparticles covered with a mixture of 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS) have been extensively studied because of their interactions with cell membranes, lipid bilayers, and viruses. The hydrophilic ligands make these particles colloidally stable in aqueous solutions and the combination with hydrophobic ligands creates an amphiphilic particle that can be loaded with hydrophobic drugs, fuse with the lipid membranes, and resist nonspecific protein adsorption. Many of these properties depend on nanoparticle size and the composition of the ligand shell. It is, therefore, crucial to have a reproducible synthetic method and reliable characterization techniques that allow the determination of nanoparticle properties and the ligand shell composition. Here, a one-phase chemical reduction, followed by a thorough purification to synthesize these nanoparticles with diameters below 5 nm, is presented. The ratio between the two ligands on the surface of the nanoparticle can be tuned through their stoichiometric ratio used during synthesis. We demonstrate how various routine techniques, such as transmission electron microscopy (TEM), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), and ultraviolet-visible (UV-Vis) spectrometry, are combined to comprehensively characterize the physicochemical parameters of the nanoparticles.

Amphiphilic gold nanoparticles can be used in many biological applications. A protocol to synthesize gold nanoparticles coated by a binary mixture of ligands and a detailed characterization of these particles is presented.

Gold nanoparticles covered with a mixture of 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS) have been extensively studied because of ...

Gold Nanoparticle Synthesis

Gold nanoparticles (Au nanoparticles) that are ~12 nm in diameter were synthesized by rapidly injecting a solution of 150 mg (0.15 mmol) of tetrachloroauric acid in 3.0 g (3.7 mmol, 3.6 mL) of oleylamine (technical grade) and 3.0 mL of toluene into a boiling solution of 5.1 g (6.4 mmol, 8.7 mL) of oleylamine in 147 mL of toluene. While boiling and mixing the reaction solution for 2 hours, the color of the reaction mixture changed from clear, to light yellow, to light pink, and then slowly to dark red. The heat was then turned off, and the solution was allowed to gradually cool down to room temperature for 1 hour. The gold nanoparticles were then collected and separated from the solution using a centrifuge and washed three times; by vortexing and dispersing the gold nanoparticles in 10 mL portions of toluene, and then precipitating the gold nanoparticles by adding 40 mL portions of methanol and spinning them in a centrifuge. The solution was then decanted to remove any remaining byproducts and unreacted starting materials. Drying the gold nanoparticles in a vacuum environment produced a solid black pellet; which could be stored for long periods of time (up to one year) for later use, and then redissolved in organic solvents such as toluene.

A protocol for synthesizing ~12 nm diameter gold nanoparticles (Au nanoparticles) in an organic solvent is presented. The gold nanoparticles are capped with oleylamine ligands to prevent agglomeration. The gold nanoparticles are soluble in organic solvents such as toluene.