Name: a rapid synthesis method for au, pd, and pt aerogels via direct solution-based reduction
Uploaded: 2018-06-18T15:00:00
Description: Watch this Scientific Journal Video about A Rapid Synthesis Method for Au, Pd, and Pt Aerogels Via Direct Solution-Based Reduction at JoVE.com

The authors are grateful to Stephen Steiner at Aerogel Technologies for his inspiration and technical insights, and to Dr. Deryn Chu at the Army Research Laboratory-Sensors and Electron Devices Directorate, Dr. Christopher Haines at the Armament Research, Development and Engineering Center, U.S. Army RDECOM-ARDEC, and Dr. Stephen Bartolucci at the U.S. Army Benet Laboratories for their assistance. This work was supported by a Faculty Development Research Fund grant from the United States Military Academy, West Point.

CAUTION: Consult all relevant safety data sheets (SDS) before use. Use appropriate safety practices when performing chemical reactions, to include the use of a fume hood and personal protective equipment. Rapid hydrogen gas evolution can cause high pressure in reaction tubes causing caps to pop and solutions to spray out. Ensure that reaction tube caps remain open as specified in the protocol.
1. Metal Gel Preparation
<ol>
	<li>Preparation of metal ion solutions. 
	<ol>
		<l...

<ol>
	<li>Rolison, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Catalytic+Nanoarchitectures-the+Importance+of+Nothing+and+the+Unimportance+of+Periodicity.">Catalytic Nanoarchitectures-the Importance of Nothing and the Unimportance of Periodicity.</a> Science. 299, 1698-1701 (2003).</li><li>Wei, T., Chen, C., Chang, K., Lu, S., Hu, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cobalt+Oxide+Aerogels+of+Ideal+Supercapacitive+Properties+Prepared+with+an+Epoxide+Synthetic+Route.">Cobalt Oxide Aerogels of Ideal Supercapacitive Properties Prepared with an Epoxide Synthetic Route.</a> Chemistry of Materials. 21, 3228-3233 (2009).</li><li>Anderson, M., Morris, C., Stroud, R., Merzbacher, C., Rolison, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Colloidal+Gold+Aerogels:+Preparation,+Properties,+and+Characterization.">Colloidal Gold Aerogels: Preparation, Properties, and Characterization.</a> Langmuir. 15, 674-681 (1999).</li><li>Gaponik, N., Herrmann, A., Eychmuller, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Colloidal+Nanocrystal-Based+Gels+and+Aerogels:+Material+Aspects+and+Application+Perspectives.">Colloidal Nanocrystal-Based Gels and Aerogels: Material Aspects and Application Perspectives.</a> Journal of Physical Chemistry Letters. 3, 8-17 (2012).</li><li>Olsson, R., 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=Making+flexible+magnetic+aerogels+and+stiff+magnetic+nanopaper+using+cellulose+nanofibrils+as+templates.">Making flexible magnetic aerogels and stiff magnetic nanopaper using cellulose nanofibrils as templates.</a> Nature Nanotechnology. 5, 584-588 (2010).</li><li>Anderson, M., Morris, C., Stroud, R., Merzbacher, C., Rolison, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Colloidal+Gold+Aerogels:+Preparation,+Properties,+and+Characterization.">Colloidal Gold Aerogels: Preparation, Properties, and Characterization.</a> Langmuir. 15, 674-681 (1999).</li><li>Gaponik, N., Herrmann, A., Eychmuller, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Colloidal+Nanocrystal-Based+Gels+and+Aerogels:+Material+Aspects+and+Application+Perspectives.">Colloidal Nanocrystal-Based Gels and Aerogels: Material Aspects and Application Perspectives.</a> Journal of Physical Chemistry Letters. 3, 8-17 (2012).</li><li>Hodge, A., Hayes, J., Cao, J., Biener, J., Hamza, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+and+Mechanical+Behavior+of+Nanoporous+Gold.">Characterization and Mechanical Behavior of Nanoporous Gold.</a> Advanced Engineering Materials. 8, 853-857 (2006).</li><li>Hodge, A., 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=Scaling+equation+for+yield+strength+of+nanoporous+open-cell+foams.">Scaling equation for yield strength of nanoporous open-cell foams.</a> Acta Materialia. 55, 1343-1349 (2007).</li><li>Ambrosi, A., Chua, C., Bonanni, A., Pumera, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrochemistry+of+Graphene+and+Related+Materials.">Electrochemistry of Graphene and Related Materials.</a> Chemical Reviews. 114, 7150-7188 (2014).</li><li>Maillard, 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=Influence+of+particle+agglomeration+on+the+catalytic+activity+of+carbon-supported+Pt+nanoparticles+in+CO+monolayer+oxidation.">Influence of particle agglomeration on the catalytic activity of carbon-supported Pt nanoparticles in CO monolayer oxidation.</a> Physical Chemistry Chemical Physics. 7, 385-393 (2005).</li><li>Zhao, P., Li, N., Astruc, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=State+of+the+art+in+gold+nanoparticle+synthesis.">State of the art in gold nanoparticle synthesis.</a> Coordination Chemistry Reviews. 257, 638-665 (2013).</li><li>Wen, D., 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=Controlling+the+Growth+of+Palladium+Aerogels+with+High-Performance+toward+Bioelectrocatalytic+Oxidation+of+Glucose.">Controlling the Growth of Palladium Aerogels with High-Performance toward Bioelectrocatalytic Oxidation of Glucose.</a> Journal of American Chemical Society. 136, 2727-2730 (2014).</li><li>Jana, N., Gearheart, L., Murphy, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Seed-Mediated+Growth+Approach+for+Shape-Controlled+Synthesis+of+Spheroidal+and+Rod-like+Gold+Nanoparticles+Using+a+Surfactant+Template.">Seed-Mediated Growth Approach for Shape-Controlled Synthesis of Spheroidal and Rod-like Gold Nanoparticles Using a Surfactant Template.</a> Advanced Materials. 13, 1389-1392 (2001).</li><li>Ding, Y., Chen, M., Erlebacher, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metallic+Mesoporous+Nanocomposites+for+Electrocatalysis.">Metallic Mesoporous Nanocomposites for Electrocatalysis.</a> Journal of American Chemical Society. 126, 6876-6877 (2004).</li><li>Liu, W., 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=High-Performance+Electrocatalysis+on+Palladium+Aerogels.">High-Performance Electrocatalysis on Palladium Aerogels.</a> Angewandte Chemie. International Edition. 51, 5743-5747 (2012).</li><li>Herrmann, A., 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=Multimetallic+Aerogels+by+Template-Free+Self-Assembly+of+Au,+Ag,+Pt,+and+Pd+Nanoparticles.">Multimetallic Aerogels by Template-Free Self-Assembly of Au, Ag, Pt, and Pd Nanoparticles.</a> Chemistry of Materials. 26, 1074-1083 (2014).</li><li>Ameen, K., Rajasekharan, T., Rajasekharan, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Grain+size+dependence+of+physico-optical+properties+of+nanometallic+silver+in+silica+aerogel+matrix.">Grain size dependence of physico-optical properties of nanometallic silver in silica aerogel matrix.</a> Journal of Non-Crystalline Solids. 352, 737-746 (2006).</li><li>Qin, G., 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=A+Facile+and+Template-Free+Method+to+Prepare+Mesoporous+Gold+Sponge+and+Its+Pore+Size+Control.">A Facile and Template-Free Method to Prepare Mesoporous Gold Sponge and Its Pore Size Control.</a> Journal of Physical Chemistry C. 112, 10352-10358 (2008).</li><li>Krishna, K., Sandeep, C., Philip, R., Eswaramoorthy, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mixing+Does+the+Magic:+A+Rapid+Synthesis+of+High+Surface+Area+Noble+Metal+Nanosponges+Showing+Broadband+Nonlinear+Optical+Response.">Mixing Does the Magic: A Rapid Synthesis of High Surface Area Noble Metal Nanosponges Showing Broadband Nonlinear Optical Response.</a> ACS Nanotechnology. 5, 2681-2688 (2010).</li><li>Kistler, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coherent+Expanded+Aerogels+and+Jellies.">Coherent Expanded Aerogels and Jellies.</a> Nature. 127, 741-741 (1931).</li><li>Du, A., Zhou, B., Zhang, Z., Shen, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Special+Material+or+a+New+State+of+Matter:+A+Review+and+Reconsideration+of+the+Aerogel.">A Special Material or a New State of Matter: A Review and Reconsideration of the Aerogel.</a> Materials. 6, 941-968 (2013).</li><li>Tappan, B., Steiner, S., Luther, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanoporous+Metal+Foams.">Nanoporous Metal Foams.</a> Angewandte Chemie. International Edition. 49, 4544-4565 (2010).</li><li>Burpo, 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=Direct+solution-based+reduction+synthesis+of+Au,+Pd,+and+Pt+aerogels.">Direct solution-based reduction synthesis of Au, Pd, and Pt aerogels.</a> Journal of Materials Research. 32, 4153-4165 (2017).</li><li>Ostwald, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Blocking+of+Ostwald+ripening+allowing+long-term+stabilization.">Blocking of Ostwald ripening allowing long-term stabilization.</a> PhysicalChemistry. 37, 385 (1901).</li><li>Wang, S., Tseng, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aggregate+structure+and+crystallite+size+of+platinum+nanoparticles+synthesized+by+ethanol+reduction.">Aggregate structure and crystallite size of platinum nanoparticles synthesized by ethanol reduction.</a> Journal of Nanoparticle Research. 11, 947-953 (2009).</li><li>Schneider, C., Rasband, W., Eliceiri, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NIH+Image+to+ImageJ:+25+years+of+image+analysis.">NIH Image to ImageJ: 25 years of image analysis.</a> Nature Methods. 9, 671-675 (2012).</li><li>Thommes, M., 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=Physisorption+of+gases,+with+special+reference+to+the+evaluation+of+surface+area+and+pore+size+distribution+(IUPAC+Technical+Report).">Physisorption of gases, with special reference to the evaluation of surface area and pore size distribution (IUPAC Technical Report).</a> Pure and Applied Chemistry. 87, 1051-1069 (2015).</li><li>Barrett, E., Joyner, L., Halenda, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Determination+of+Pore+Volume+and+Area+Distributions+in+Porous+Substances.+I.+Computations+from+Nitrogen+Isotherms.">The Determination of Pore Volume and Area Distributions in Porous Substances. I. Computations from Nitrogen Isotherms.</a> Journal of the American Chemical Society. 73, 373-380 (1951).</li><li>Brunauer, B., Emmett, P., Teller, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adsorption+of+Gases+in+Multimolecular+Layers.">Adsorption of Gases in Multimolecular Layers.</a> Journal of the American Chemical Society. 60, 309-319 (1938).</li><li>Herrmann, A., 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=Multimetallic+Aerogels+by+Template-Free+Self-Assembly+of+Au,+Ag,+Pt,+and+Pd+Nanoparticles.">Multimetallic Aerogels by Template-Free Self-Assembly of Au, Ag, Pt, and Pd Nanoparticles.</a> Chemistry of Materials. 26, 1074-1083 (2014).</li><li>Kornyshev, A., Irbakh, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Double-layer+capacitance+on+a+rough+metal+surface.">Double-layer capacitance on a rough metal surface.</a> Physical Review E. 53, 6192-6199 (1996).</li><li>Bisquert, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+the+boundaries+in+the+impedance+of+porous+film+electrodes.">Influence of the boundaries in the impedance of porous film electrodes.</a> Physical Chemistry Chemical Physics. 2, 4185-4192 (2000).</li><li>Bisquert, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Theory+of+the+Impedance+of+Electron+Diffusion+and+Recombination+in+a+Thin+Layer.">Theory of the Impedance of Electron Diffusion and Recombination in a Thin Layer.</a> Journal of Physical Chemistry B. 106, 325-333 (2002).</li><li>Lu, K., Yuan, L., Xin, X., Xu, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hybridization+of+graphene+oxide+with+commercial+graphene+for+constructing+3D+metal-free+aerogel+with+enhanced+photocatalysis.">Hybridization of graphene oxide with commercial graphene for constructing 3D metal-free aerogel with enhanced photocatalysis.</a> Applied Catalysis B. 226, 16-22 (2018).</li><li>Nystron, G., Roder, L., Fernandez-Ronco, M., Mezzenga, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Amyloid+Templated+Organic+Inorganic+Hybrid+Aerogels.">Amyloid Templated Organic Inorganic Hybrid Aerogels.</a> Advanced Functional Materials. , 1703609-1703620 (2017).</li></ol>

The noble metal aerogel synthesis method presented here results in the rapid formation of porous, high surface area monoliths that are comparable to slower synthesis techniques. The 1:1 (v/v) metal ion solution to reducing agent solution ratio is critical in facilitating the proposed gel formation model. The rapid hydrogen gas evolution as a by-product of the electrochemical reduction of metal ions serves as a secondary reducing agent and facilitates the densification, and fusion of growing nanoparticles during gel forma...

A wide range of energy storage and conversion, catalysis, and sensor applications benefit from three-dimensional metallic nanostructures which provide control over chemical reactivity, and mass transport properties1,2,3,4,5. Such 3-dimensional metallic nanostructures further enhance conductivity, ductility, malleability, and strength8,9. Integration into devices necessitates that materials be free-standing or combined with support materials. Incorporation of nanomaterials onto support structures provides a means of minimizing active material, but may suffer from weak adsorption and eventual agglomeration during device operation10,11.
While there are a variety of synthesis methods to control individual nanoparticle size and shape, few approaches enable control over contiguous 3-dimensional nanomaterials12,13,14. Noble metal 3-dimensional nanostructures have been formed through dithiol linkage of monodisperse nanoparticles, sol-gel formation, nanoparticle coalescence, composite materials, nanosphere chains, and biotemplating15,16,17,18. Many of these approaches require synthesis times on the order of days to weeks to yield desired materials. Noble metal nanofoams synthesized from the direct reduction of precursor salt solutions have been prepared with a faster synthesis timescale and with short-range order of hundreds of micrometers in length, but require mechanical pressing for device integration19,20.
First reported by Kistler, aerogels provide a synthesis route to achieve porous structures with high specific surface areas that are orders of magnitude less dense than their bulk material counterparts21,22,23. Extending 3-dimensional structures to the macroscopic length scale of bulk materials offers an advantage over nanoparticle aggregates or nanofoams that require support materials or mechanical processing. While aerogels provide a synthesis route to control porosity and particle feature size, however, extended synthesis times, and in some cases the use of capping agents or linker molecules, increases overall processing steps and time.
Here a method to synthesize gold, palladium, and platinum aerogels via a rapid, direct solution-based reduction is presented24. Combining 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. The use of a microcentrifuge tube or small volume conical tube takes advantage of the vigorous hydrogen gas evolution as a by-product of the reduction step facilitating a proposed nucleation, growth, densification, fusion, equilibration model for gel formation. A close correlation in aerogel nanostructure feature sizes is determined with scanning electron microscopy image analysis, X-ray diffractometry, nitrogen gas adsorption, electrochemical impedance spectroscopy, and cyclic voltammetry. The solvent accessible specific surface area is determined with both electrochemical impedance spectroscopy and cyclic voltammetry. This synthesis method for noble metal aerogels demonstrates that high specific surface area monoliths may be achieved with a rapid and direct reduction approach.

<table border="0" cellpadding="0" cellspacing="0" width="691">
	<tbody>
		<tr height="25">
			<td height="25" style="height:25px;width:215px;">HAuCl4&#376;&#8226;3H2O&#160;</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:119px;">16961-25-4</td>
			<td style="width:229px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:215px;">Na2PdCl4</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:119px;">13820-40-1</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:215px;">K2PtCl6</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:119px;">16921-30-5</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Pd(NH3)4Cl2</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:119px;">13933-31-8</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">K2PtCl4</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:119px;">10025-99-7</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Pt(NH3)4Cl2&#376;&#8226;H2O</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:119px;">13933-31-8</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">dimethylamine borane (DMAB)</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:119px;">74-94-2</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:215px;">NaBH4</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:119px;">16940-66-2</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:215px;">NaH2PO2&#376;&#8226;H2O</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td style="width:119px;">10039-56-2</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Ethanol</td>
			<td style="width:128px;">Sigma-Aldrich</td>
			<td>792780</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">Snap Cap Microcentrifuge Tubes, 2.0 mL</td>
			<td style="width:128px;">Cole Parmer</td>
			<td>UX-06333-70</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">Snap Cap Microcentrifuge Tubes, 1.7 mL</td>
			<td style="width:128px;">Cole Parmer</td>
			<td>UX-06333-60</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Conical Centrifuge Tubes 15mL</td>
			<td style="width:128px;">Stellar Scientific</td>
			<td>T15-101&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Ag/AgCl Reference Electrode</td>
			<td style="width:128px;">BASi</td>
			<td style="width:119px;">MF-2052</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Pt wire electrode</td>
			<td style="width:128px;">BASi</td>
			<td style="width:119px;">MF-4130</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">Miccrostop Lacquer</td>
			<td style="width:128px;">Tober Chemical Division</td>
			<td style="width:119px;">NA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Potentiostat</td>
			<td style="width:128px;">Biologic-USA</td>
			<td style="width:119px;">VMP-3</td>
			<td>Electrochemical analysis-EIS, CV</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">Freeze Dryer</td>
			<td style="width:128px;">Labconco</td>
			<td style="width:119px;">Freezone 2.5 Liter</td>
			<td>Aerogel freeze drying</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">XRD</td>
			<td style="width:128px;">PanAlytical</td>
			<td style="width:119px;">Empyrean</td>
			<td>X-ray diffractometry</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:215px;">Surface and Pore Analyzer</td>
			<td style="width:128px;">Quantachrome</td>
			<td style="width:119px;">NOVA 4000e</td>
			<td>Nitrogen gas adsorption</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:215px;">ImageJ, Image analysis software</td>
			<td style="width:128px;">National Institute of Health</td>
			<td style="width:119px;">NA</td>
			<td>SEM image analysis</td>
		</tr>
	</tbody>
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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.

The addition of metal ion and reducing agent solutions together results in solutions immediately turning a dark black color with vigorous gas evolution. Observation of the reaction progress suggests the proposed gel formation mechanism shown in Figure 1. Gel formation proceeds through five steps of 1) nanoparticle nucleation, 2) growth, 3) densification, 4) fusion, and 5) equilibration. The first four steps are observed to occur during the first few minutes o...

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

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 ...

This method can help answer key questions in the aerogel field about the possibility of directly synthesizing metal aerogels from aqueous solutions rather than from preformed nanoparticles. Other methods, such as sol gels, require much longer times for nanoparticle coalescence. The implications of this technique extend toward catalysis and sensing applications due to the high surface area of the noble metal aerogels and the lack of support materials.Though this method can provide insight into direct aerogel synthesis, it can also be applied to other synthesis techniques, such as biotemplating, to achieve better shape control over aerogel monoliths. To begin the procedure, prepare two milliliters each of 0.1 molar solutions of gold(III)chloride trihydrate and sodium tetrachloropalladate in deionized water. Vigorously shake and vortex the solutions to dissolve the salts.Let the palladium solution sit for a few hours to ensure complete dissolution. Prepare two milliliters of 0.1 molar potassium hexachloroplatinate in a one to one by volume mixture of deionized water and ethanol. Vigorously shake and vortex the mixture until the salts have dissolved.Prepare 10 milliliters each of 0.1 molar solutions of dimethylamine borane and sodium borohydride in deionized water. Vortex the solutions for one to two minutes to ensure complete dissolution. Then, transfer 0.5 milliliters of the gold solution to a 1.7-milliliter or two-milliliter microcentrifuge tube.Forcefully pipette 0.5 milliliters of DMAB into the tube to rapidly mix the salt and reducing agent. Place the microcentrifuge tube in a rack, leaving the cap open to allow hydrogen gas to escape. In the same way, combine 0.5 milliliters of the platinum solution with 0.5 milliliters of DMAB and 0.5 milliliters of the palladium solution with 0.5 milliliters of sodium borohydride.Approximately five minutes after starting the reaction, cap the microcentrifuge tubes, and gently invert them three to five times to aid coalescence of metal particles not part of the metal gel. Immediately uncap the tubes, and return them to the rack after inversion. Leave the nascent metal gels in the reducing agent solutions for three to six hours to allow complete reduction of metal ions and surface free energy minimization to occur.Then, carefully remove excess reducing agent from each tube, ensuring that enough solution remains so that the meniscus does not contact the gel. Slowly pipette deionized water into the microcentrifuge tubes until they are filled completely. Then, fill three 50-milliliter conical tubes with deionized water.Submerge each microcentrifuge tube in a tube of deionized water, and allow each gel to slide from its microcentrifuge tube into the larger tube. Gently move the gel with a spatula if needed. Cap the tubes, and leave the gels in deionized water for 24 hours.Replace the water after 12 hours by solvent exchange. Do not allow the meniscus to contact the gels while replacing the water. To begin the EIS procedure for wet metal gels, remove as much water as possible without the meniscus contacting the rinsed gels.Add 50 milliliters of 0.5 molar potassium chloride to each tube, and allow the gels to soak for 24 hours. Then, use a fine bristle brush to coat a one-millimeter potassium wire electrode with non-reactive lacquer, leaving four to five millimeters exposed at the tip. Allow the lacquer to dry for 20 minutes.Apply at least one more coat of lacquer in the same way. Next, cut a 50-milliliter conical tube in half to serve as the electrochemical vial. Insert a saturated silver-silver chloride reference electrode and a 0.5-millimeter potassium wire counter electrode through a perforated cap or gasket for the modified tube.Connect the three electrodes to a potentiostat. Transfer one of the gels and its electrolyte to the modified tube by gently pouring the electrolyte and equilibrated gel into the tube without letting the gel contact the liquid-air interface. Ensure that the gel is settled at the bottom of the tube, and add electrolyte if necessary.Then, place the cap on the tube, and adjust the reference and counter electrodes as needed. For the gold gel, gently insert the bare tip of the lacquer-coated working electrode into the gel. For the palladium and platinum gels, place the lacquer-coated working electrode in the conical vial along the inner surface, and rest the metal gel on top of the bare platinum wire tip.Perform potentiostatic EIS scans with frequencies between 100 megahertz and one millihertz using a 10 millivolt amplitude sine wave. In the event of current overflow, use a galvanostatic EIS with the same frequency range and a 100 to 200 milliamp sine wave amplitude. Following electrochemical characterization, rinse the gels with deionized water for 24 hours as described at the end of the gel synthesis.Then, remove as much of the rinse as possible without letting the meniscus contact the gels. Freeze the gels at negative 80 degrees Celsius for 30 minutes. Lastly, freeze dry the gels in a freeze dryer with a pressure set point of four pascals or lower to obtain the metal aerogels.The gold, palladium, and platinum aerogels all showed characteristic hydrophobicity and had properties comparable to gels formed by slower synthesis techniques. Scanning electron microscopy showed that gold aerogels had large nanopores and smooth ligaments. Palladium and platinum aerogels had a beads-on-a-string structure with fused nanoparticles and narrower ligaments.The platinum aerogel had a greater range of macropore structure diameters than the palladium aerogel, which was attributed to platinum nanoparticle stability requiring the use of ethanol to drive coalescence and the consequent ease of large hydrogen gas bubble evolution during gel formation. X-ray diffraction showed characteristic peaks for the respective metals with no detectable oxides. Nitrogen gas physisorption isotherms were Type IV, which is characteristic of mesoporous materials.The pore size distribution and cumulative pore volume modeled from the isotherms showed pore sizes predominantly in the two to 50 nanometer range, confirming that the aerogels were mesoporous. The electrochemical impedance spectra were fit with a transmission line model based on a modified Randle's equivalent circuit model. The specific capacitances and specific surface areas were calculated from the EIS data.These values were consistent with the specific capacitances and surface areas determined from cyclic voltammetry experiments. We first developed the idea for this method based on combining 100 millimolar noble metal solutions and reducing agents for other projects prior to discarding them and observing the rapid formation of metal gels. Once mastered, this technique can result in noble metal gels within minutes prior to rinsing and drying steps.While attempting this procedure, remember to avoid contact of the metal gels with the liquid-air interface in order to prevent gel compaction. Following this procedure, other methods like biotemplating may be performed to address the challenges of aerogel shape control.

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Research

JoVE Journal

Chemistry

Preparing Silica Aerogel Monoliths via a Rapid Supercritical Extraction Method

A procedure for the fabrication of monolithic silica aerogels in eight hours or less via a rapid supercritical extraction process is described. The procedure requires 15-20 min of preparation time, during which a liquid precursor mixture is prepared and poured into wells of a metal mold that is placed between the platens of a hydraulic hot press, followed by several hours of processing within the hot press. The precursor solution consists of a 1.0:12.0:3.6:3.5 x 10-3 molar ratio of tetramethylorthosilicate (TMOS):methanol:water:ammonia. In each well of the mold, a porous silica sol-gel matrix forms. As the temperature of the mold and its contents is increased, the pressure within the mold rises. After the temperature/pressure conditions surpass the supercritical point for the solvent within the pores of the matrix (in this case, a methanol/water mixture), the supercritical fluid is released, and monolithic aerogel remains within the wells of the mold. With the mold used in this procedure, cylindrical monoliths of 2.2 cm diameter and 1.9 cm height are produced. Aerogels formed by this rapid method have comparable properties (low bulk and skeletal density, high surface area, mesoporous morphology) to those prepared by other methods that involve either additional reaction steps or solvent extractions (lengthier processes that generate more chemical waste).The rapid supercritical extraction method can also be applied to the fabrication of aerogels based on other precursor recipes.

This article describes a rapid supercritical extraction method for fabricating silica aerogels. By utilizing a confined mold and hydraulic hot press, monolithic aerogels can be made in eight hours or less.

A procedure for the fabrication of monolithic silica aerogels in eight hours or less via a rapid supercritical extraction process is described. The ...

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 ...

A Method to Manipulate Surface Tension of a Liquid Metal via Surface Oxidation and Reduction

Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales, where interfacial tension is a dominant force. A variety of methods exist for controlling the interfacial tension of aqueous and organic liquids on this scale; however, these techniques have limited utility for liquid metals due to their large interfacial tension.
Liquid metals can form soft, stretchable, and shape-reconfigurable components in electronic and electromagnetic devices. Although it is possible to manipulate these fluids via mechanical methods (e.g., pumping), electrical methods are easier to miniaturize, control, and implement. However, most electrical techniques have their own constraints: electrowetting-on-dielectric requires large (kV) potentials for modest actuation, electrocapillarity can affect relatively small changes in the interfacial tension, and continuous electrowetting is limited to plugs of the liquid metal in capillaries.
Here, we present a method for actuating gallium and gallium-based liquid metal alloys via an electrochemical surface reaction. Controlling the electrochemical potential on the surface of the liquid metal in electrolyte rapidly and reversibly changes the interfacial tension by over two orders of magnitude ( &#820;500 mN/m to near zero). Furthermore, this method requires only a very modest potential (&#60; 1 V) applied relative to a counter electrode. The resulting change in tension is due primarily to the electrochemical deposition of a surface oxide layer, which acts as a surfactant; removal of the oxide increases the interfacial tension, and vice versa. This technique can be applied in a wide variety of electrolytes and is independent of the substrate on which it rests.

We present a method to control the interfacial energy of a liquid metal in an electrolyte via electrochemical deposition (or removal) of a surface oxide layer. This simple method can control the capillary behavior of gallium-based liquid metals by tuning the interfacial energy rapidly, significantly, and reversibly using modest voltages.

Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales, where ...

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 ...

Combining Solid-state and Solution-based Techniques: Synthesis and Reactivity of Chalcogenidoplumbates(II or IV)

The phases of &#34;PbCh2&#34; (Ch = Se, Te) are obtained from solid-state syntheses (i.e., by the fusion of the elements under inert conditions in silica glass ampules). Reduction of such phases by elemental alkaline metals in amines affords crystalline chalcogenidoplumbate(II) salts comprised of [PbTe3]2- or [Pb2Ch3]2- anions, depending upon which sequestering agent for the cations is present: crown ethers, like 18-crown-6, or cryptands, like [2.2.2]crypt. Reactions of solutions of such anions with transition-metal compounds yield (poly-)chalcogenide anions or transition-metal chalcogenide clusters, including one with a &#181;-PbSe ligand (i.e., the heaviest-known CO homolog).
In contrast, the solid-state synthesis of a phase of the nominal composition &#34;K2PbSe2&#34; by successive reactions of the elements and by the subsequent solvothermal treatment in amines yields the first non-oxide/halide inorganic lead(IV) compound: a salt of the ortho-selenidoplumbate(IV) anion [PbSe4]4-. This was unexpected due to the redox potentials of Pb(IV) and Se(-II). Such methods can further be applied to other elemental combinations, leading to the formation of solutions with binary [HgTe2]2- or [BiSe3]3- anions, or to large-scale syntheses of K2Hg2Se3 or K3BiSe3 via the solid-state route.
All compounds are characterized by single-crystal X-ray diffraction and elemental analysis; solutions of plumbate salts can be investigated by 205Pb and 77Se or 127Te NMR techniques. Quantum chemical calculations using density functional theory methods enable energy comparisons. They further allow for insights into the electronic configuration and thus, the bonding situation. Molecular Rh-containing Chevrel-type compounds were found to exhibit delocalized mixed valence, whereas similar telluridopalladate anions are electron-precise; the cluster with the &#181;-PbSe ligand is energetically favored over a hypothetical CO analog, in line with the unsuccessful attempt at its synthesis. The stability of formal Pb(IV) within the [PbSe4]4- anion is mainly due to a suitable stabilization within the crystal lattice.

Combining Solid-state and Solution-based Techniques: Synthesis and Reactivity of ChalcogenidoplumbatesII or IV

The synthesis of chalcogenidoplumbates(II,IV) via the in situ reduction of nominal "PbCh2" (Ch = Chalcogen) and via a solid-state reaction and subsequent solvothermal reactions is presented. Additionally, reactivities of plumbate(II) solutions are portrayed, which yield the heaviest-known CO homolog known to date: the &#181;-PbSe ligand.

The phases of &#34;PbCh2&#34; (Ch = Se, Te) are obtained from solid-state syntheses (i.e., by the fusion of the elements under inert conditions in silica ...

Synthesis and Testing of Supported Pt-Cu Solid Solution Nanoparticle Catalysts for Propane Dehydrogenation

A convenient method for the synthesis of bimetallic Pt-Cu catalysts and performance tests for propane dehydrogenation and characterization are demonstrated here. The catalyst forms a substitutional solid solution structure, with a small and uniform particle size around 2 nm. This is realized by careful control over the impregnation, calcination, and reduction steps during catalyst preparation and is identified by advanced in situ synchrotron techniques. The catalyst propane dehydrogenation performance continuously improves with increasing Cu:Pt atomic ratio.

A convenient method for the synthesis of 2 nm supported bimetallic nanoparticle Pt-Cu catalysts for propane dehydrogenation is reported here. In situ synchrotron X-ray techniques allow for the determination of the catalyst structure, which is typically unobtainable using laboratory instruments.

A convenient method for the synthesis of bimetallic Pt-Cu catalysts and performance tests for propane dehydrogenation and characterization are ...

Synthesis of Platinum-nickel Nanowires and Optimization for Oxygen Reduction Performance

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen reduction reaction. Spontaneous galvanic displacement was used to deposit Pt layers onto Ni nanowire substrates. The synthesis approach produced catalysts with high specific activities and high Pt surface areas. Hydrogen annealing improved Pt and Ni mixing and specific activity. Acid leaching was used to preferentially remove Ni near the nanowire surface, and oxygen annealing was used to stabilize near-surface Ni, improving durability and minimizing Ni dissolution. These protocols detail the optimization of each post-synthesis processing step, including hydrogen annealing to 250 &#176;C, exposure to 0.1 M nitric acid, and oxygen annealing to 175 &#176;C. Through these steps, Pt-Ni nanowires produced increased activities more than an order of magnitude than Pt nanoparticles, while offering significant durability improvements. The presented protocols are based on Pt-Ni systems in the development of fuel cell catalysts. These techniques have also been used for a variety of metal combinations, and can be applied to develop catalysts for a number of electrochemical processes.

&#160; The protocol describes the synthesis and electrochemical testing of platinum-nickel nanowires. Nanowires were synthesized by the galvanic displacement of a nickel nanowire template. Post-synthesis processing, including hydrogen annealing, acid leaching, and oxygen annealing were used to optimize nanowire performance and durability in the oxygen reduction reaction.

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen ...

Fabrication and Testing of Catalytic Aerogels Prepared Via Rapid Supercritical Extraction

Protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms are presented. Three preparation methods are described: (a) the incorporation of metal salts into silica or alumina wet gels using an impregnation method; (b) the incorporation of metal salts into alumina wet gels using a co-precursor method; and (c) the addition of metal nanoparticles directly into a silica aerogel precursor mixture. The methods utilize a hydraulic hot press, which allows for rapid (&#60;6 h) supercritical extraction and results in aerogels of low density (0.10 g/mL) and high surface area (200-800 m2/g). While the work presented here focuses on the use of copper salts and copper nanoparticles, the approach can be implemented using other metal salts and nanoparticles. A protocol for testing the three-way catalytic ability of these aerogels for automotive pollution mitigation is also presented. This technique uses custom-built equipment, the Union Catalytic Testbed (UCAT), in which a simulated exhaust mixture is passed over an aerogel sample at a controlled temperature and flow rate. The system is capable of measuring the ability of the catalytic aerogels, under both oxidizing and reducing conditions, to convert CO, NO and unburned hydrocarbons (HCs) to less harmful species (CO2, H2O and N2). Example catalytic results are presented for the aerogels described.

Here we present protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms. Methods for preparing materials using copper salts and copper-containing nanoparticles are featured. Catalytic testing protocols demonstrate the effectiveness of these aerogels for three-way catalysis applications.

Protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms are presented. Three ...

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

This protocol presents both the synthesis method of the Ni single atom catalyst, and the electrochemical testing of its catalytic activity and selectivity in aqueous CO2 reduction. Different from traditional metal nanocrystals, the synthesis of metal single atoms involves a matrix material that can confine those single atoms and prevent them from aggregation. We report an electrospinning and thermal annealing method to prepare Ni single atoms dispersed and coordinated in a graphene shell, as active centers for CO2 reduction to CO. During the synthesis, N dopants play a critical role in generating graphene vacancies to trap Ni atoms. Aberration-corrected scanning transmission electron microscopy and three-dimensional atom probe tomography were employed to identify the single Ni atomic sites in graphene vacancies. Detailed setup of electrochemical CO2 reduction apparatus coupled with an on-line gas chromatography is also demonstrated. Compared to metallic Ni, Ni single atom catalyst exhibit dramatically improved CO2 reduction and suppressed H2 evolution side reaction.

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

Here, we present a protocol for the synthesis and electrochemical testing of transition metal single atoms coordinated in graphene vacancies as active centers for selective carbon dioxide reduction to carbon monoxide in aqueous solutions.

This protocol presents both the synthesis method of the Ni single atom catalyst, and the electrochemical testing of its catalytic activity and selectivity ...

Synthesis of Substrate-Bound Au Nanowires Via an Active Surface Growth Mechanism

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a challenge, as it requires asymmetric growth of symmetric crystals. Here, we report a distinctive synthesis of substrate-bound Au nanowires. This template-free synthesis employs thiolated ligands and substrate adsorption to achieve the continuous asymmetric deposition of Au in solution at ambient conditions. The thiolated ligand prevented the Au deposition on the exposed surface of the seeds, so the Au deposition only occurs at the interface between the Au seeds and the substrate. The side of the newly deposited Au nanowires is immediately covered with the thiolated ligand, while the bottom facing the substrate remains ligand-free and active for the next round of Au deposition. We further demonstrate that this Au nanowire growth can be induced on various substrates, and different thiolated ligands can be used to regulate the surface chemistry of the nanowires. The diameter of the nanowires can also be controlled with mixed ligands, in which another &#34;bad&#34; ligand could turn on the lateral growth. With the understanding of the mechanism, Au nanowire-based nanostructures can be designed and synthesized.

We report a solution-based method to synthesize substrate-bound Au nanowires. By tuning the molecular ligands used during the synthesis, the Au nanowires can be grown from various substrates with different surface properties. Au nanowire-based nanostructures can also be synthesized by adjusting the reaction parameters.