This work was funded by a United States Military Academy Faculty Development Research Fund grant. The authors are grateful for the assistance of Dr. Christopher Haines at the U.S Army Combat Capabilities Development Command. The authors would also like to thank Dr. Joshua Maurer for the use of the FIB-SEM at the U.S. Army CCDC-Armaments Center at Watervliet, New York.

CAUTION: Consult all relevant chemical 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 during electrochemical reduction 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. Conduct all electrochemical reductions in a fume hood.
1. Magnus&#8217; salt derivatives template preparation
NOTE: All salt templates should be chemically reduced within a few hours after preparation as prolonged storage results in a degradation of salt structure. This method describes each platinum-based macrotube and macrobeam product. To obtain additional specific product yield, conduct the method with replicate sets of salt template and reducing agent solutions.
<ol>
	<li>Prepare metal salt solutions.
	<ol>
		<li>Add 0.4151 g of K2PtCl4 to 10 mL of deionized water to prepare a 0.1 M (100 mM) solution of &#8220;Pt2-&#8221;.</li>
		<li>Add 0.3521 g of Pt(NH3)4Cl2&#8729;H2O to 10 mL of deionized water to prepare a 0.1 M (100 mM) solution of &#8220;Pt2+&#8221;.</li>
		<li>Add 0.2942 g of Na2PdCl4 to 10 mL of deionized water to prepare a 0.1 M (100 mM) solution of &#8220;Pd2-&#8221;.</li>
		<li>Add 0.2458 g of Cu(NH3)4SO4&#8729;H2O to 10 mL of deionized water to prepare a 0.1 M (100 mM) solution of &#8220;Cu2+&#8221;.</li>
		<li>Vigorously shake and vortex platinum and copper salt solutions to aid in the dissolution of the salts until they are fully dissolved.</li>
	</ol>
	</li>
	<li>Prepare platinum salt needle templates.
	<ol>
		<li>To prepare Magnus&#8217; salts with a 1:1 Pt2+:Pt2- ratio, pipette 0.5 mL of 100 mM K2PtCl4 into a microfuge tube. Forcefully pipette 0.5 mL of 100 mM Pt(NH3)4Cl2&#8729;H2O into the microfuge tube for a total of 1 mL of salt needle template solution. 
		NOTE: The solution will present an opaque light green color. The use of 50 mM K2PtCl4 and Pt(NH3)4Cl2&#8729;H2O will result in longer and wider salt needles for larger platinum macrotubes after chemical reduction29. Forceful pipetting is dispensing the full reagent volume within 1 s to ensure rapid mixing of chemicals within microfuge tubes.</li>
	</ol>
	</li>
	<li>Prepare platinum-palladium salt needle templates. 
	NOTE: Salt template platinum-palladium ion ratios are designated as Pt2+:Pd2-:Pt2-. The platinum-only salts prepared in Step 1.2.1. equate to a 1:0:1 ratio.
	<ol>
		<li>To prepare the salt ratio 1:1:0, pipette 0.5 mL of 100 mM Pt(NH3)4Cl2&#8729;H2O into a microfuge tube. Forcefully pipette 0.5 mL of 100 mM Na2PdCl4 into the microfuge tube for a total of 1 mL of salt needle template solution.</li>
		<li>To prepare the salt ratio 2:1:1, pipette 0.25 mL of 100 mM Na2PdCl4 and 0.25 mL of 100 mM of K2PtCl4 in a microfuge tube. Vortex the microfuge tube for 3-5 s. Then forcefully pipette 0.5 mL of 100 mM Pt(NH3)4Cl2&#8729;H2O into the microfuge tube for a total of 1 mL of salt needle template solution.</li>
		<li>To prepare a 3:1:2 salt template solution, pipette 0.167 mL of 100 mM Na2PdCl4 and 0.333 mL of 100 mM of K2PtCl4 into a microfuge tube. Vortex the microfuge tube for 3-5 s. Then forcefully pipette 0.5 mL of 100 mM Pt(NH3)4Cl2&#8729;H2O into the microfuge tube for a total of 1 mL salt needle template solution. 
		NOTE: The higher ratio of platinum in the salt templates should yield a greener color, while increasing palladium content results in more orange, pink, and brown color in the solution. Solutions will be opaque in appearance.</li>
	</ol>
	</li>
	<li>Prepare copper-platinum salt needle templates. 
	NOTE: Salt template copper-platinum ion ratios are designated as Pt2-:Pt2+:Cu2+. The 1:1:0 ratio equates to the platinum-only salts prepared in Step 1.2.1.
	<ol>
		<li>To prepare the salt ratio 1:0:1, pipette 0.5 mL of 100 mM K2PtCl4 into a microfuge tube. Forcefully pipette 0.5 mL of 100 mM Cu(NH3)4SO4&#8729;H2O into the microfuge tube for a total of 1 mL of salt needle template solution.</li>
		<li>To prepare the salt ratio 3:1:2, pipette 0.167 mL of 100 mM Pt(NH3)4Cl2&#8729;H2O and 0.333 mL of 100 mM of Cu(NH3)4SO4&#183;H2O into a microfuge tube. Vortex the microfuge tube for 3-5 s. Then forcefully pipette 0.5 mL of 100 mM K2PtCl4 into the microfuge tube for a total of 1 mL of salt needle template solution.</li>
		<li>To prepare the salt ratio 2:1:1, pipette 0.25 mL of 100 mM Pt(NH3)4Cl2&#8729;H2O and 0.25 mL of 100 mM of Cu(NH3)4SO4&#183;H2O into a microfuge tube. Vortex the microfuge tube for 3-5 s. Then forcefully pipette 0.5 mL of 100 mM K2PtCl4 into the microfuge tube for a total of 1 mL salt needle template solution.</li>
		<li>To prepare the salt ratio 1:1:0, pipette 0.5 mL of 100 mM Pt(NH3)4Cl2&#8729;H2O into a microfuge tube. Forcefully pipette 0.5 mL of 100 mM K2PtCl4 into the microfuge tube for a total of 1 mL salt needle template solution. 
		NOTE: The combination of copper and platinum ions forms a purple, cloudy solution that is not as opaque as the solutions of steps 1.2 and 1.3. Leaving solutions of Magnus&#8217; salts for 24 hours or longer will cause the templates to degrade and change to a purple-grey or black color.</li>
	</ol>
	</li>
	<li>Polarized optical microscope (POM) imaging of salt needle templates
	<ol>
		<li>Pipette 0.05 mL of salt template solutions prepared in Steps 1.2 &#8211; 1.4 onto a glass slide and mount on the stage of a polarized optical microscope. Adjust the focus onto salt needles and rotate cross polarizers until the background is black. 
		NOTE: If salt solutions do not present needle-like structures with POM imaging, verify the water quality used for salt solution preparation. Salt needle formation is sensitive to both high and low pH.</li>
	</ol>
	</li>
</ol>
2. Salt-template chemical reduction
NOTE: DMAB is toxic. Avoid breathing dust and skin contact by wearing PPE and conduct all associated tasks in a fume hood.
<ol>
	<li>Prepare reducing agent solutions
	<ol>
		<li>Add 0.7568 g of sodium borohydride (NaBH4) to 200 mL of deionized water in a 500 mL beaker to prepare a 0.1 M (100 mM) NaBH4 solution. Stir solution with a spatula until the NaBH4 is fully dissolved.</li>
		<li>Pour 50 mL of 0.1 M NaBH4 solution into a 50 mL conical tube. Repeat 3x.</li>
		<li>Add 1.1768 g of dimethylamine borane (DMAB) to 200 mL of deionized water in a 500 mL beaker to prepare a 0.1 M (100 mM) DMAB solution.</li>
		<li>Pour 50 mL of 0.1 M DMAB solution into into a 50 mL conical tube. Repeat 3x.</li>
	</ol>
	</li>
	<li>Adding salts to reducing agent solutions
	<ol>
		<li>In a fume hood, pipette the entire 1 mL volume of each of the salt template solutions from Steps 1.2 and 1.3 into each of 4 x 50 mL conical tubes of 0.1 M NaBH4 reducing agent. Allow the chemical reduction to continue for 24 h with the cap off the tube.</li>
		<li>In a fume hood, pipette the entire 1 mL volume of each of the salt template solutions from Step 1.4 into each of 4 x 50 mL conical tubes of 0.1 M DMAB reducing agent. Allow the electrochemical reduction to continue for 24 h with the cap off the tube. 
		NOTE: Upon the addition of the 1 mL of Magnus&#8217; salts, the reducing agent will turn a cloudy-black color and begin to vigorously form hydrogen gas. Leaving the conical tube caps off prevents the buildup of hydrogen gas pressure and potential explosion and spraying of the solutions. Loose parafilm or foil may be placed over the tubes if dust contamination is a concern.</li>
	</ol>
	</li>
	<li>Rinsing reduced macrotubes and macrobeams
	<ol>
		<li>After 24 hours of reduction, slowly decant the supernatant of each of the reduced 50 mL chemical reducing solutions into a waste container and ensure not to pour the samples out of the tubes.</li>
		<li>Pour each of the precipitates into new 50 mL conical tubes. The use of a spatula may be required to dislodge sample adhering to the tube sidewalls. Fill each of the new tubes with 50 mL of deionized water and place on a rocker with tube caps secured at a low setting for 24 h.</li>
		<li>Remove the tubes from the rocker and place upright in a test tube rack for 15 min to allow the samples to sediment. Slowly pour the supernatant off the top of the tube sample into a waste container. Refill tube with 50 mL of deionized water and place on a rocker with tube caps secured for an additional 24 h.</li>
		<li>Remove tubes from the rocker and place upright in a test tube rack for 15 min. Pour the supernatant off the top of the tube into a waste container. 
		NOTE: The supernatant will be a clear or grey color and the precipitate will be a black and generally sediment to the bottom of the conical tubes. If pouring the supernatant agitates and resuspends the reduced product, place the tube upright in a rack and wait approximately 15 minutes before pouring again. A small volume of water will remain mixed with the product.</li>
	</ol>
	</li>
</ol>
3. Prepare macrotube and macrobeam films
<ol>
	<li>Drying of the samples on glass slides
	<ol>
		<li>Pipette as much supernatant as possible out of the 50 mL tubes without removing the reduction product.</li>
		<li>Using a spatula, gently transfer the precipitate material to a glass slide. Using a spatula, consolidate the sample into a pile with uniform height of approximately 0.5 mm. 
		NOTE: The more water that is removed from the 50 mL tube sample prior to transferring the reduced material to the glass slide, the easier the transfer is. This makes the material behave more like a paste. Sample consolidation and uniform height aids in pressing films after drying.</li>
		<li>Place glass slides with the reduced samples in a location that will not be disturbed by air currents. Dry samples for 24 h at ambient temperature. 
		NOTE: If more sample is needed for x-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), or other testing, multiple reduced samples from the same salt ratio may be consolidated on the same glass slide for drying.</li>
	</ol>
	</li>
	<li>Pressing of samples and massing the materials
	<ol>
		<li>Place a second glass slide on top of a slide with dried mass of reduced samples. With fingers, press down on the glass slide above the material with ample force (approximately 200 kPa) to form a thin film of macrotubes or macrobeams. 
		NOTE: Pressing the reduced material between glass slides should result in a free-standing film. Occasionally pressing the dried mass of macrotubes or macrobeams results in multiple film fragments. Films can be trimmed by pressing down with a razor blade.</li>
	</ol>
	</li>
</ol>
4. Material and electrochemical characterization
<ol>
	<li>Scanning electron microscopy (SEM): Affix a thin film or lose powder sample with carbon tape on a SEM sample stub. Initially use an accelerating voltage of 15 kV and beam current of 2.7 - 5.4 pA to perform imaging. Zoom out to a large sample area and collect an energy dispersive x-ray (EDS) spectra to quantify elemental composition.</li>
	<li>X-ray diffractometry (XRD): Place the macrotube or macrobeam dried sample in a sample holder. Alternatively, place a thin film sample section, as in Step 4.1, on a glass slide. Perform XRD scans for diffraction angles 2&#920; from 5&#176; to 90&#176; at 45 kV and 40 mA with Cu K&#945; radiation (1.54060 &#197;), a 2&#920; step size of 0.0130 &#176;, and 20 s per step. 
	NOTE: XRD can be done for either the pressed or un-pressed samples. Powder sample holders typically require a significant volume of materials and the use of pressed thin films is recommended.</li>
	<li>X-ray photoelectron microscopy (XPS): Use a monochromated Al K&#945; source with a 100 &#956;m spot size, 25 W x-ray beam and 45&#176; take-off angle, an operating pressure &#60; 6 x 10-6 Pa. Neutralize surface charging with a low-voltage Ar-ion beam and a barium oxide electron neutralizer. Set analyzer pass energy to 55 eV for high-resolution scans.</li>
	<li>Electrochemical characterization
	<ol>
		<li>Measure the mass of pressed film samples to normalize electrochemical measurements by milligrams of active materials.</li>
		<li>Transfer film samples into an electrochemical vial using either flat tweezers or by gently sliding the film from a glass slide onto the inner sidewall of the vial. Gently pipette 0.5 M H2SO4 or 0.5 M KCl electrolyte over the film&#160;samples and let sit for 24 hours.</li>
		<li>Use a 3-electrode cell with a Ag/AgCl (3 M NaCl) reference electrode, a 0.5 mm diameter Pt wire auxiliary/counter electrode, and a lacquer coated 0.5 mm diameter platinum working electrode. Place the lacquer coated wire with a 1 mm exposed tip in contact with the top surface of the aerogel at the bottom of the electrochemical vial22.</li>
		<li>Perform electrochemical impedance spectroscopy (EIS) from 1 MHz to 1 mHz with a 10 mV sine wave at 0 V (vs. Ag/AgCl).</li>
		<li>Perform cyclic voltammetry (CV) using a voltage range of &#8722;0.2 to 1.2 V (vs. Ag/AgCl) with scan rates of 0.5, 1, 5, 10, 25, 50, 75, and 100 mVs-1.</li>
	</ol>
	</li>
</ol>

<ol><li>Chen, A., Holt-Hindle, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Platinum-Based+Nanostructured+Materials%3A+Synthesis%2C+Properties%2C+and+Applications%5BTitle%5D)+AND+%22Chemical+Reviews%22%5BJournal%5D)">Platinum-Based Nanostructured Materials: Synthesis, Properties, and Applications.</a> Chemical Reviews. 110 (6), 3767-3804 (2010).</li>
<li>Narayanan, R., El-Sayed, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Shape-Dependent+Catalytic+Activity+of+Platinum+Nanoparticles+in+Colloidal+Solution%5BTitle%5D)+AND+%22Nano+Letters%22%5BJournal%5D)">Shape-Dependent Catalytic Activity of Platinum Nanoparticles in Colloidal Solution.</a> Nano Letters. 4 (7), 1343-1348 (2004).</li>
<li>Wang, C., Daimon, H., Onodera, T., Koda, T., Sun, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+General+Approach+to+the+Size+and+Shape-Controlled+Synthesis+of+Platinum+Nanoparticles+and+Their+Catalytic+Reduction+of+Oxygen%5BTitle%5D)+AND+%22Angewandte+Chemie+International+Edition%22%5BJournal%5D)">A General Approach to the Size and Shape-Controlled Synthesis of Platinum Nanoparticles and Their Catalytic Reduction of Oxygen.</a> Angewandte Chemie International Edition. 47 (19), 3588-3591 (2008).</li>
<li>Song, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Synthesis+of+Platinum+Nanowire+Networks+Using+a+Soft+Template%5BTitle%5D)+AND+%22Nano+Letters%22%5BJournal%5D)">Synthesis of Platinum Nanowire Networks Using a Soft Template.</a> Nano Letters. 7 (12), 3650-3655 (2007).</li>
<li>Liu, L., Yoo, S. H., Park, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Synthesis+of+Vertically+Aligned+Hollow+Platinum+Nanotubes+with+Single+Crystalline+Nanoflakes%5BTitle%5D)+AND+%22Chemistry+of+Materials%22%5BJournal%5D)">Synthesis of Vertically Aligned Hollow Platinum Nanotubes with Single Crystalline Nanoflakes.</a> Chemistry of Materials. 22 (8), 2681-2684 (2010).</li>
<li>Ehrburger, P., Mahajan, O. P., Walker, P. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Carbon+as+a+support+for+catalysts%3A+I.+Effect+of+surface+heterogeneity+of+carbon+on+dispersion+of+platinum%5BTitle%5D)+AND+%22Journal+of+Catalysis%22%5BJournal%5D)">Carbon as a support for catalysts: I. Effect of surface heterogeneity of carbon on dispersion of platinum.</a> Journal of Catalysis. 43 (1), 61-67 (1976).</li>
<li>Liu, H. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+review+of+anode+catalysis+in+the+direct+methanol+fuel+cell%5BTitle%5D)+AND+%22Journal+of+Power+Sources%22%5BJournal%5D)">A review of anode catalysis in the direct methanol fuel cell.</a> Journal of Power Sources. 155 (2), 95-110 (2006).</li>
<li>Zhang, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+review+of+platinum-based+catalyst+layer+degradation+in+proton+exchange+membrane+fuel+cells%5BTitle%5D)+AND+%22Journal+of+Power+Sources%22%5BJournal%5D)">A review of platinum-based catalyst layer degradation in proton exchange membrane fuel cells.</a> Journal of Power Sources. 194 (2), 588-600 (2009).</li>
<li>Wei, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Bimetallic+Aerogels%3A+High-Performance+Electrocatalysts+for+the+Oxygen+Reduction+Reaction%5BTitle%5D)+AND+%22Angewandte+Chemie+International+Edition%22%5BJournal%5D)">Bimetallic Aerogels: High-Performance Electrocatalysts for the Oxygen Reduction Reaction.</a> Angewandte Chemie International Edition. 52 (37), 9849-9852 (2013).</li>
<li>Liu, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Noble+Metal+Aerogels-Synthesis%2C+Characterization%2C+and+Application+as+Electrocatalysts%5BTitle%5D)+AND+%22Accounts+of+Chemical+Research%22%5BJournal%5D)">Noble Metal Aerogels-Synthesis, Characterization, and Application as Electrocatalysts.</a> Accounts of Chemical Research. 48 (2), 154-162 (2015).</li>
<li>Naskar, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Porous+Aerogels+from+Shape-Controlled+Metal+Nanoparticles+Directly+from+Nonpolar+Colloidal+Solution%5BTitle%5D)+AND+%22Chemistry+of+Materials%22%5BJournal%5D)">Porous Aerogels from Shape-Controlled Metal Nanoparticles Directly from Nonpolar Colloidal Solution.</a> Chemistry of Materials. 29 (21), 9208-9217 (2017).</li>
<li>Du, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Emerging+Noble+Metal+Aerogels%3A+State+of+the+Art+and+a+Look+Forward%5BTitle%5D)+AND+%22Matter%22%5BJournal%5D)">Emerging Noble Metal Aerogels: State of the Art and a Look Forward.</a> Matter. 1 (1), 39-56 (2019).</li>
<li>Qiu, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Template-engaged+synthesis+of+hollow+porous+platinum%E2%80%93palladium+alloy+nanospheres+for+efficient+methanol+electro-oxidation%5BTitle%5D)+AND+%22Journal+of+Power+Sources%22%5BJournal%5D)">Template-engaged synthesis of hollow porous platinum–palladium alloy nanospheres for efficient methanol electro-oxidation.</a> Journal of Power Sources. 302, 195-201 (2016).</li>
<li>Yamauchi, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Electrochemical+Synthesis+of+Mesoporous+Pt%E2%80%93Au+Binary+Alloys+with+Tunable+Compositions+for+Enhancement+of+Electrochemical+Performance%5BTitle%5D)+AND+%22Journal+of+the+American+Chemical+Society%22%5BJournal%5D)">Electrochemical Synthesis of Mesoporous Pt–Au Binary Alloys with Tunable Compositions for Enhancement of Electrochemical Performance.</a> Journal of the American Chemical Society. 134 (11), 5100-5109 (2012).</li>
<li>Lim, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Twin-Induced+Growth+of+Palladium%E2%80%93Platinum+Alloy+Nanocrystals%5BTitle%5D)+AND+%22Angewandte+Chemie+International+Edition%22%5BJournal%5D)">Twin-Induced Growth of Palladium–Platinum Alloy Nanocrystals.</a> Angewandte Chemie International Edition. 48 (34), 6304-6308 (2009).</li>
<li>Lim, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Pd-Pt+Bimetallic+Nanodendrites+with+High+Activity+for+Oxygen+Reduction%5BTitle%5D)+AND+%22Science%22%5BJournal%5D)">Pd-Pt Bimetallic Nanodendrites with High Activity for Oxygen Reduction.</a> Science. 324 (5932), 1302-1305 (2009).</li>
<li>Han, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+seed-mediated+approach+to+the+morphology-controlled+synthesis+of+bimetallic+copper-platinum+alloy+nanoparticles+with+enhanced+electrocatalytic+performance+for+the+methanol+oxidation+reaction%5BTitle%5D)+AND+%22Journal+of+Power+Sources%22%5BJournal%5D)">A seed-mediated approach to the morphology-controlled synthesis of bimetallic copper-platinum alloy nanoparticles with enhanced electrocatalytic performance for the methanol oxidation reaction.</a> Journal of Power Sources. 286, 488-494 (2015).</li>
<li>Xu, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Nanotubular+Mesoporous+PdCu+Bimetallic+Electrocatalysts+toward+Oxygen+Reduction+Reaction%5BTitle%5D)+AND+%22Chemistry+of+Materials%22%5BJournal%5D)">Nanotubular Mesoporous PdCu Bimetallic Electrocatalysts toward Oxygen Reduction Reaction.</a> Chemistry of Materials. 21 (14), 3110-3116 (2009).</li>
<li>Xu, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Solution-Based+Evolution+and+Enhanced+Methanol+Oxidation+Activity+of+Monodisperse+Platinum-Copper+Nanocubes%5BTitle%5D)+AND+%22Angewandte+Chemie+International+Edition%22%5BJournal%5D)">Solution-Based Evolution and Enhanced Methanol Oxidation Activity of Monodisperse Platinum-Copper Nanocubes.</a> Angewandte Chemie International Edition. 48 (23), 4217-4221 (2009).</li>
<li>Stamenkovic, V. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Improved+Oxygen+Reduction+Activity+on+Pt3Ni%28111%29+via+Increased+Surface+Site+Availability%5BTitle%5D)+AND+%22Science%22%5BJournal%5D)">Improved Oxygen Reduction Activity on Pt3Ni(111) via Increased Surface Site Availability.</a> Science. 315 (5811), 493-497 (2007).</li>
<li>Burpo, F. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Direct+solution-based+reduction+synthesis+of+Au%2C+Pd%2C+and+Pt+aerogels%5BTitle%5D)+AND+%22Journal+of+Materials+Research%22%5BJournal%5D)">Direct solution-based reduction synthesis of Au, Pd, and Pt aerogels.</a> Journal of Materials Research. 32 (22), 4153-4165 (2017).</li>
<li>Burpo, F. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+Rapid+Synthesis+Method+for+Au%2C+Pd%2C+and+Pt+Aerogels+Via+Direct+Solution-Based+Reduction%5BTitle%5D)+AND+%22Journal+of+Visualized+Experiments%22%5BJournal%5D)">A Rapid Synthesis Method for Au, Pd, and Pt Aerogels Via Direct Solution-Based Reduction.</a> Journal of Visualized Experiments. (136), e57875(2018).</li>
<li>Burpo, F. J., Mitropoulos, A. N., Nagelli, E. A., Ryu, M. Y., Palmer, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Gelatin+biotemplated+platinum+aerogels%5BTitle%5D)+AND+%22MRS+Advances%22%5BJournal%5D)">Gelatin biotemplated platinum aerogels.</a> MRS Advances. , 1-6 (2018).</li>
<li>Burpo, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Cellulose+Nanofiber+Biotemplated+Palladium+Composite+Aerogels%5BTitle%5D)+AND+%22Molecules%22%5BJournal%5D)">Cellulose Nanofiber Biotemplated Palladium Composite Aerogels.</a> Molecules. 23 (6), 1405(2018).</li>
<li>Burpo, F. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Synthesis+Method+for+Cellulose+Nanofiber+Biotemplated+Palladium+Composite+Aerogels%5BTitle%5D)+AND+%22Journal+of+Visualized+Experiments%22%5BJournal%5D)">Synthesis Method for Cellulose Nanofiber Biotemplated Palladium Composite Aerogels.</a> Journal of Visualized Experiments. (147), e59176(2019).</li>
<li>Mitropoulos, A. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Metal+Composite+Porous+Silk+Fibroin+Aerogel+Fibers%5BTitle%5D)+AND+%22Materials%22%5BJournal%5D)">Metal Composite Porous Silk Fibroin Aerogel Fibers.</a> Materials. 12 (6), 894(2019).</li>
<li>Xiao, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Salt-Templated+Synthesis+of+2D+Metallic+MoN+and+Other+Nitrides%5BTitle%5D)+AND+%22ACS+Nano%22%5BJournal%5D)">Salt-Templated Synthesis of 2D Metallic MoN and Other Nitrides.</a> ACS Nano. 11 (2), 2180-2186 (2017).</li>
<li>Xiao, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Scalable+salt-templated+synthesis+of+two-dimensional+transition+metal+oxides%5BTitle%5D)+AND+%22Nature+Communications%22%5BJournal%5D)">Scalable salt-templated synthesis of two-dimensional transition metal oxides.</a> Nature Communications. 7, 11296(2016).</li>
<li>Burpo, F. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Salt-Templated+Hierarchically+Porous+Platinum+Macrotube+Synthesis%5BTitle%5D)+AND+%22Chemistry+Select%22%5BJournal%5D)">Salt-Templated Hierarchically Porous Platinum Macrotube Synthesis.</a> Chemistry Select. 3 (16), 4542-4546 (2018).</li>
<li>Burpo, F., Nagelli, E., Morris, L., Woronowicz, K., Mitropoulos, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Salt-Mediated+Au-Cu+Nanofoam+and+Au-Cu-Pd+Porous+Macrobeam+Synthesis%5BTitle%5D)+AND+%22Molecules%22%5BJournal%5D)">Salt-Mediated Au-Cu Nanofoam and Au-Cu-Pd Porous Macrobeam Synthesis.</a> Molecules. 23 (7), 1701(2018).</li>
<li>Burpo, F. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Salt-templated+platinum-palladium+porous+macrobeam+synthesis%5BTitle%5D)+AND+%22MRS+Communications%22%5BJournal%5D)">Salt-templated platinum-palladium porous macrobeam synthesis.</a> MRS Communications. 9 (1), 280-287 (2019).</li>
<li>Burpo, F. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Salt-Templated+Platinum-Copper+Porous+Macrobeams+for+Ethanol+Oxidation%5BTitle%5D)+AND+%22Catalysts%22%5BJournal%5D)">Salt-Templated Platinum-Copper Porous Macrobeams for Ethanol Oxidation.</a> Catalysts. 9 (8), 662(2019).</li>
<li>Magnus, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Ueber+einige+Verbindungen+des+Platinchlor%C3%BCrs%5BTitle%5D)+AND+%22Annalen+der+Physik%22%5BJournal%5D)">Ueber einige Verbindungen des Platinchlorürs.</a> Annalen der Physik. 90 (10), 239-242 (1828).</li>
<li>Vauquelin, N. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Memoire+sur+le+Palladium+et+le+Rhodium%5BTitle%5D)+AND+%22Annales+de+Chimie%22%5BJournal%5D)">Memoire sur le Palladium et le Rhodium.</a> Annales de Chimie. 88, 167-198 (1813).</li>
<li>Bremi, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((From+Vauquelin%27s+and+Magnus%27+Salts+to+Gels%2C+Uniaxially+Oriented+Films%2C+and+Fibers%3A+Synthesis%2C+Characterization%2C+and+Properties+of+Tetrakis%281-aminoalkane%29metal%28II%29+Tetrachlorometalates%28II%29%5BTitle%5D)+AND+%22Chemistry+of+Materials%22%5BJournal%5D)">From Vauquelin's and Magnus' Salts to Gels, Uniaxially Oriented Films, and Fibers: Synthesis, Characterization, and Properties of Tetrakis(1-aminoalkane)metal(II) Tetrachlorometalates(II).</a> Chemistry of Materials. 11 (4), 977-994 (1999).</li>
<li>Bremi, J., Caseri, W., Smith, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+new+compound+derived+from+Magnus%27+green+salt%3A+solid+state+structure+and+evidence+for+platinum+chains+in+solution%5BTitle%5D)+AND+%22Journal+of+Materials+Chemistry%22%5BJournal%5D)">A new compound derived from Magnus' green salt: solid state structure and evidence for platinum chains in solution.</a> Journal of Materials Chemistry. 11 (10), 2593-2596 (2001).</li>
<li>Caseri, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Derivatives+of+Magnus%27+Green+Salt%5BTitle%5D)+AND+%22Platinum+Metals+Review%22%5BJournal%5D)">Derivatives of Magnus' Green Salt.</a> Platinum Metals Review. 48 (3), 91(2004).</li>
</ol>

The authors have nothing to disclose.

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. The use of Magnus&#8217; salt derivatives as high aspect ratio needle shaped templates provides the means to control resulting metal composition through salt-template stoichiometry, and when combined with choice of reducing agent, control over the nano...

Numerous synthesis methods have been developed to obtain high surface area, porous platinum-based materials primarily for catalysis applications including fuel cells1. One strategy to achieve such materials is to synthesize monodisperse nanoparticles in the form of spheres, cubes, wires, and tubes2,3,4,5. To integrate the discrete nanoparticles into a porous structure for a functional device, polymeric binders and carbon additives are often required6,7. This strategy requires extra processing steps, time, and can lead to a decrease in mass specific performance, as well as agglomeration of nanoparticles during extended device use8. Another strategy is to drive the coalescence of synthesized nanoparticles into a metal gel with subsequent supercritical drying9,10,11. While advancements in the sol-gel synthesis approach for noble metals has reduced gelation time from weeks to as fast as hours or minutes, the resulting monoliths tend to be mechanically fragile impeding their practical use in devices12.
Platinum-alloy and multi-metallic 3-dimensional porous nanostructures offer tunability for catalytic specificity, as well as address the high cost and relative scarcity of platinum13,14. While there have been numerous reports of platinum-palladium15,16 and platinum-copper17,18,19 discrete nanostructures, as well as other alloy combinations20, there have been few synthesis strategies to achieve a solution-based technique for 3-dimensional platinum alloy and multi-metallic structures.
Recently we demonstrated the use of high concentration salt solutions and reducing agents to rapidly yield gold, palladium, and platinum metal gels21,22. The high concentration salt solutions and reducing agents were also used in synthesizing biopolymer noble metal composites using gelatin, cellulose, and silk23,24,25,26. Insoluble salts represent the highest concentrations of ions available to be reduced and were used by Xiao and colleagues to demonstrate the synthesis of 2-dimensional metal oxides27,28. Extending on the demonstration of porous noble metal aerogels and composites from high concentration salt solutions, and leveraging the high density of available ions of insoluble salts, we used Magnus&#8217; salts and derivatives as shape templates to synthesize porous noble metal macrotubes and macrobeams29,30,31,32.
Magnus&#8217; salts assemble from the addition of oppositely charged square planar platinum ions [PtCl4]2- and [Pt(NH3)4]2+&#160;33. In a similar manner, Vauquelin&#8217;s salts form from the combination of oppositely charged palladium ions, [PdCl4]2- and [Pd(NH3)4]2+&#160;34. With precursor salt concentrations of 100 mM, the resulting salt crystals form needles 10s to 100s of micrometers long, with square widths approximately 100 nm to 3 &#956;m. While the salt-templates are charge neutral, varying the Magnus&#8217; salt derivatives stoichiometry between ion species, to include [Cu(NH3)4]2+, allows control over the resulting reduced metal ratios. The combination of ions, and the choice of chemical reducing agent, result in either macrotubes or macrobeams with a square cross section and a porous nanostructure comprised of either fused nanoparticles or nanofibrils. Macrotubes and macrobeams were also pressed into free standing films, and electrochemically active surface area was determined with electrochemical impedance spectroscopy and cyclic voltammetry. The salt-template approach was used to synthesize platinum macrotubes29, platinum-palladium macrobeams31, and in an effort to lower material costs and tune catalytic activity by incorporating copper, copper-platinum macrotubes32. The salt-templating method was also demonstrated for Au-Pd and Au-Pd-Cu binary and ternary metal macrotubes and nanofoams30.
Here, we present a method to synthesize platinum, platinum-palladium, and copper-platinum bi-metallic porous macrotubes and macrobeams from insoluble Magnus&#8217; salt needle templates29,31,32. Control of the ion stoichiometry in the salt needle templates provides control over resulting metal ratios after chemical reduction and can be verified with x-ray diffractometry and x-ray photoelectron spectroscopy. The resulting macrotubes and macrobeams may be assembled and formed into a free-standing film with hand pressure. The resulting films exhibit high electrochemically active surface areas (ECSA) determined by electrochemical impedance spectroscopy and cyclic voltammetry in H2SO4 and KCl electrolyte. This method provides a synthesis route to control platinum-based metal composition, porosity, and nanostructure in a rapid and scalable manner that may be generalizable to a wider range of salt-templates.

<table><tbody><tr><td>50 mL Conical Tubes</td><td>Corning Costar Corp.</td><td>430290</td><td></td></tr><tr><td>Ag/AgCl Reference Electrode</td><td>BASi</td><td>MF-2052</td><td></td></tr><tr><td>Cu(NH&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;4&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;&amp;Yuml;&amp;bull;H&lt;sub&gt;2&lt;/sub&gt;O</td><td>Sigma-Aldrich</td><td>10380-29-7</td><td></td></tr><tr><td>dimethylamine borane (DMAB)</td><td>Sigma-Aldrich</td><td>74-94-2</td><td></td></tr><tr><td>K&lt;sub&gt;2&lt;/sub&gt;PtCl&lt;sub&gt;4&lt;/sub&gt;</td><td>Sigma-Aldrich</td><td>10025-99-7</td><td></td></tr><tr><td>Miccrostop Lacquer</td><td>Tober Chemical Division</td><td>NA</td><td></td></tr><tr><td>Na&lt;sub&gt;2&lt;/sub&gt;PdCl&lt;sub&gt;4&lt;/sub&gt;</td><td>Sigma-Aldrich</td><td>13820-40-1</td><td></td></tr><tr><td>NaBH&lt;sub&gt;4&lt;/sub&gt;</td><td>Sigma-Aldrich</td><td>16940-66-2</td><td></td></tr><tr><td>Polarized Optical Microscope</td><td>AmScope</td><td>PZ300JC</td><td></td></tr><tr><td>Potentiostat</td><td>Biologic-USA</td><td>VMP-3</td><td>Electrochemical analysis-EIS, CV</td></tr><tr><td>Pt wire electrode</td><td>BASi</td><td>MF-4130</td><td></td></tr><tr><td>Pt(NH&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;4&lt;/sub&gt;Cl&lt;sub&gt;2&lt;/sub&gt;&amp;Yuml;&amp;bull;H&lt;sub&gt;2&lt;/sub&gt;O</td><td>Sigma-Aldrich</td><td>13933-31-8</td><td></td></tr><tr><td>Scanning Electron Microscope</td><td>FEI</td><td>Helios 600</td><td>EDS performed with this SEM</td></tr><tr><td>Shelf Rocker</td><td>Thermo Scientific</td><td>Vari-Mix&amp;trade; Platform Rocker</td><td></td></tr><tr><td>Snap Cap Microcentrifuge Tubes, 1.7 mL</td><td>Cole Parmer</td><td>UX-06333-60</td><td></td></tr><tr><td>X-ray diffractometer</td><td>PanAlytical</td><td>Empyrean</td><td>X-ray diffractometry</td></tr><tr><td>X-ray photoelectron spectrometer</td><td>ULVAC PHI - Physical Electronics</td><td>VersaProbe III</td><td></td></tr></tbody></table>

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.

The addition of oppositely charged square planar noble metal ions results in near instantaneous formation of high aspect ratio salt crystals. The linear stacking of square planar ions is shown schematically in Figure 1, with the polarized optical microscopy images revealing salt needles that are 10&#8217;s to 100&#8217;s of micrometers long. A concentration of 100 mM was used for all platinum, palladium, and copper salt solutions. While the salt needle templates are charge neutral in that th...

Watch this Scientific Journal Video about A Salt-Templated Synthesis Method for Porous Platinum-based Macrobeams and Macrotubes at JoVE.com

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

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 ...

a-salt-templated-synthesis-method-for-porous-platinum-based

Research

JoVE Journal

Chemistry

8.4K Views.  United States Military Academy. Dit protocol biedt een eenvoudige, relatief snelle methode voor het synthetiseren van een hoog oppervlak, hoge aspect ratio platina in platina legeringen macrobeams en macrobuisjes met een vierkante dwarsdoorsnede. De zout- en beplatingsmethode maakt de controle van de sjabloonmetaalionverhouding en de resulterende massasamenstelling en van de macrostraal- en macrobuisnanostructuren mogelijk. Macrobeam en macrotube geperste films kunnen in te gaan op de behoefte aan integrale driedimensionale...

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

Template Directed Synthesis of Plasmonic Gold Nanotubes with Tunable IR Absorbance

A nearly parallel array of pores can be produced by anodizing aluminum foils in acidic environments1, 2. Applications of anodic aluminum oxide (AAO) membranes have been under development since the 1990's and have become a common method to template the synthesis of high aspect ratio nanostructures, mostly by electrochemical growth or pore-wetting. Recently, these membranes have become commercially available in a wide range of pore sizes and densities, leading to an extensive library of functional nanostructures being synthesized from AAO membranes. These include composite nanorods, nanowires and nanotubes made of metals, inorganic materials or polymers 3-10. Nanoporous membranes have been used to synthesize nanoparticle and nanotube arrays that perform well as refractive index sensors, plasmonic biosensors, or surface enhanced Raman spectroscopy (SERS) substrates 11-16, as well as a wide range of other fields such as photo-thermal heating 17, permselective transport 18, 19, catalysis 20, microfluidics 21, and electrochemical sensing 22, 23. Here, we report a novel procedure to prepare gold nanotubes in AAO membranes. Hollow nanostructures have potential application in plasmonic and SERS sensing, and we anticipate these gold nanotubes will allow for high sensitivity and strong plasmon signals, arising from decreased material dampening 15.

Solution-suspendable gold nanotubes with controlled dimensions can be synthesized by electrochemical deposition in porous anodic aluminum oxide (AAO) membranes using a hydrophobic polymer core. Gold nanotubes and nanotube arrays hold promise for applications in plasmonic biosensing, surface-enhanced Raman spectroscopy, photo-thermal heating, ionic and molecular transport, microfluidics, catalysis and electrochemical sensing.

A nearly parallel array of pores can be produced by anodizing aluminum foils in acidic environments1, 2. Applications of anodic aluminum oxide (AAO) ...

Ultrahigh Density Array of Vertically Aligned Small-molecular Organic Nanowires on Arbitrary Substrates

In recent years &pi;-conjugated organic semiconductors have emerged as the active material in a number of diverse applications including large-area, low-cost displays, photovoltaics, printable and flexible electronics and organic spin valves. Organics allow (a) low-cost, low-temperature processing and (b) molecular-level design of electronic, optical and spin transport characteristics. Such features are not readily available for mainstream inorganic semiconductors, which have enabled organics to carve a niche in the silicon-dominated electronics market. The first generation of organic-based devices has focused on thin film geometries, grown by physical vapor deposition or solution processing. However, it has been realized that organic nanostructures can be used to enhance performance of above-mentioned applications and significant effort has been invested in exploring methods for organic nanostructure fabrication.	
A particularly interesting class of organic nanostructures is the one in which vertically oriented organic nanowires, nanorods or nanotubes are organized in a well-regimented, high-density array. Such structures are highly versatile and are ideal morphological architectures for various applications such as chemical sensors, split-dipole nanoantennas, photovoltaic devices with radially heterostructured "core-shell" nanowires, and memory devices with a cross-point geometry. Such architecture is generally realized by a template-directed approach. In the past this method has been used to grow metal and inorganic semiconductor nanowire arrays. More recently &pi;-conjugated polymer nanowires have been grown within nanoporous templates. However, these approaches have had limited success in growing nanowires of technologically important &pi;-conjugated small molecular weight organics, such as tris-8-hydroxyquinoline aluminum (Alq3), rubrene and methanofullerenes, which are commonly used in diverse areas including organic displays, photovoltaics, thin film transistors and spintronics.	
Recently we have been able to address the above-mentioned issue by employing a novel "centrifugation-assisted" approach. This method therefore broadens the spectrum of organic materials that can be patterned in a vertically ordered nanowire array. Due to the technological importance of Alq3, rubrene and methanofullerenes, our method can be used to explore how the nanostructuring of these materials affects the performance of aforementioned organic devices. The purpose of this article is to describe the technical details of the above-mentioned protocol, demonstrate how this process can be extended to grow small-molecular organic nanowires on arbitrary substrates and finally, to discuss the critical steps, limitations, possible modifications, trouble-shooting and future applications.

We report a simple method for fabricating an ultrahigh density array of vertically ordered small-molecular organic nanowires. This method allows for synthesis of complex heterostructured hybrid nanowire geometries, which can be inexpensively grown on arbitrary substrates. These structures have potential applications in organic electronics, optoelectronics, chemical sensing, photovoltaics and spintronics.

In  recent years &pi;-conjugated  organic semiconductors have emerged as the active material in a number of  diverse applications including large-area, ...

Engineering

Preparation of Highly Porous Coordination Polymer Coatings on Macroporous Polymer Monoliths for Enhanced Enrichment of Phosphopeptides

We describe a protocol for the preparation of hybrid materials based on highly porous coordination polymer coatings on the internal surface of macroporous polymer monoliths. The developed approach is based on the preparation of a macroporous polymer containing carboxylic acid functional groups and the subsequent step-by-step solution-based controlled growth of a layer of a porous coordination polymer on the surface of the pores of the polymer monolith. The prepared metal-organic polymer hybrid has a high specific micropore surface area. The amount of iron(III) sites is enhanced through metal-organic coordination on the surface of the pores of the functional polymer support. The increase of metal sites is related to the number of iterations of the coating process.
The developed preparation scheme is easily adapted to a capillary column format. The functional porous polymer is prepared as a self-contained single-block porous monolith within the capillary, yielding a flow-through separation device with excellent flow permeability and modest back-pressure. The metal-organic polymer hybrid column showed excellent performance for the enrichment of phosphopeptides from digested proteins and their subsequent detection using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The presented experimental protocol is highly versatile, and can be easily implemented to different organic polymer supports and coatings with a plethora of porous coordination polymers and metal-organic frameworks for multiple purification and/or separation applications.

A procedure for the preparation of porous hybrid separation media composed of a macroporous polymer monolith internally coated by a high surface area microporous coordination polymer is presented.

We describe a protocol for the preparation of hybrid materials based on highly porous coordination polymer coatings on the internal surface of macroporous ...

Microbubble Fabrication of Concave-porosity PDMS Beads

Microbubble fabrication (by use of a fine emulsion) provides a means of increasing the surface-area-to-volume (SAV) ratio of polymer materials, which is particularly useful for separations applications. Porous polydimethylsiloxane (PDMS) beads can be produced by heat-curing such an emulsion, allowing the interface between the aqueous and aliphatic phases to mold the morphology of the polymer. In the procedures described here, both polymer and crosslinker (triethoxysilane) are sonicated together in a cold-bath sonicator. Following a period of cross-linking, emulsions are added dropwise to a hot surfactant solution, allowing the aqueous phase of the emulsion to separate, and forming porous polymer beads. We demonstrate that this method can be tuned, and the SAV ratio optimized, by adjusting the electrolyte content of the aqueous phase in the emulsion. Beads produced in this way are imaged with scanning electron microscopy, and representative SAV ratios are determined using Brunauer&#8211;Emmett&#8211;Teller (BET) analysis. Considerable variability with the electrolyte identity is observed, but the general trend is consistent: there is a maximum in SAV obtained at a specific concentration, after which porosity decreases markedly.

Procedures used to generate microstructured concave-porosity polydimethylsiloxane beads are presented. Effects of electrolyte concentration and identity within the aqueous phase are particularly emphasized.

Microbubble fabrication (by use of a fine emulsion) provides a means of increasing the surface-area-to-volume (SAV) ratio of polymer materials, which is ...

Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in industrialized countries. Here, the development of optical mesosensors/adsorbents (MSAs) for efficient recognition and selective recovery of Pd(II), Au(III), and Co(II) from urban mine was achieved. A simple, general method for preparing MSAs based on using high-order mesoporous monolithic scaffolds was described. Hierarchical cubic Ia3d wagon-wheel-shaped MSAs were fabricated by anchoring chelating agents (colorants) into three-dimensional pores and micrometric particle surfaces of the mesoporous monolithic scaffolds. Findings show, for the first time, evidence of controlled optical recognition of Pd(II), Au(III), and Co(II) ions and a highly selective system for recovery of Pd(II) ions (up to ~95%) in ores and industrial wastes. Furthermore, the controlled assessment processes described herein involve evaluation of intrinsic properties (e.g., visual signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability); thus, expensive, sophisticated instruments are not required. Results show evidence that MSAs will attract worldwide attention as a promising technological means of recovering and recycling palladium, gold and cobalt metals.

Because of the importance and extensive use of palladium, gold and cobalt metals in high-technology equipment, their recovery and recycling constitute an important industrial challenge. The metal recovery system described herein is a simple, low-cost means for the effective detection, removal, and recovery of these metals from the urban mine.

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in ...

Liquid-cell Transmission Electron Microscopy for Tracking Self-assembly of Nanoparticles

Drying a nanoparticle dispersion is a versatile way to create self-assembled structures of nanoparticles, but the mechanism of this process is not fully understood. We have traced the trajectories of individual nanoparticles using liquid-cell transmission electron microscopy (TEM) to investigate the mechanism of the assembly process. Herein, we present the protocols used for liquid-cell TEM studies of the self-assembly mechanism. First, we introduce the detailed synthetic protocols used to produce uniformly sized platinum and lead selenide nanoparticles. Next, we present the microfabrication processes used to produce liquid cells with silicon nitride or silicon windows and then describe the loading and imaging procedures of the liquid-cell TEM technique. Several notes are included to provide helpful tips for the entire process, including how to manage the fragile cell windows. The individual motions of nanoparticles tracked by liquid-cell TEM revealed that changes in the solvent boundaries caused by evaporation affected the self-assembly process of nanoparticles. The solvent boundaries drove nanoparticles to primarily form amorphous aggregates, followed by flattening of the aggregates to produce a 2-dimensional (2D) self-assembled structure. These behaviors are also observed for different nanoparticle types and different liquid-cell compositions.

Here we introduce experimental protocols for the real-time observation of a self-assembly process using liquid-cell transmission electron microscopy.

Drying a nanoparticle dispersion is a versatile way to create self-assembled structures of nanoparticles, but the mechanism of this process is not fully ...

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 ...

Fabrication of Mechanically Tunable and Bioactive Metal Scaffolds for Biomedical Applications

Biometal systems have been widely used for biomedical applications, in particular, as load-bearing materials. However, major challenges are high stiffness and low bioactivity of metals. In this study, we have developed a new method towards fabricating a new type of bioactive and mechanically reliable porous metal scaffolds-densified porous Ti scaffolds. The method consists of two fabrication processes, 1) the fabrication of porous Ti scaffolds by dynamic freeze casting, and 2) coating and densification of the porous scaffolds. The dynamic freeze casting method to fabricate porous Ti scaffolds allowed the densification of porous scaffolds by minimizing the chemical contamination and structural defects. The densification process is distinctive for three reasons. First, the densification process is simple, because it requires a control of only one parameter (degree of densification). Second, it is effective, as it achieves mechanical enhancement and sustainable release of biomolecules from porous scaffolds. Third, it has broad applications, as it is also applicable to the fabrication of functionally graded porous scaffolds by spatially varied strain during densification.

Bioactive and mechanically reliable metal scaffolds have been fabricated through a method which consists of two processes, dynamic freeze casting for the fabrication of porous Ti, and coating and densification of the Ti scaffolds. The densification process is simple, effective and applicable to the fabrication of functionally graded scaffolds.

Biometal systems have been widely used for biomedical applications, in particular, as load-bearing materials. However, major challenges are high stiffness ...

Bioengineering

Microscopic Visualization of Porous Nanographenes Synthesized through a Combination of Solution and On-Surface Chemistry

On-surface synthesis has recently been regarded as a promising approach for the generation of new molecular structures. It has been particularly successful in the synthesis of graphene nanoribbons, nanographenes and intrinsically reactive and instable, yet attractive species. It is based on the combination of solution chemistry aimed at preparation of appropriate molecular precursors for further ultra-high vacuum surface assisted transformations. This approach also owes its success to an incredible development of characterization techniques, such as scanning tunneling/atomic force microscopy and related methods, which allow detailed, local characterization at atomic scale. While the surface-assisted synthesis can provide molecular nanostructures with outstanding precision, down to single atoms, it suffers from basing on metallic surfaces and often limited yield. Therefore, the extension of the approach away from metals and the struggle to increase productivity seem to be significant challenges toward wider applications. Herein, we demonstrate the on-surface synthesis approach for generation of non-planar nanographenes, which are synthesized through a combination of solution chemistry and sequential surface-assisted processes, together with the detailed characterization by scanning probe microscopy methods.

A combination of solution and surface assisted synthesis opens new directions in the atomically precise synthesis of nanostructures. Scanning tunneling microscopy (STM) supplemented by non-contact atomic force microscopy (nc-AFM) enables detailed characterization of newly designed and generated carbon-based nano-objects.

On-surface synthesis has recently been regarded as a promising approach for the generation of new molecular structures. It has been particularly ...

Catalytic Reactions at Amine-Stabilized and Ligand-Free Platinum Nanoparticles Supported on Titania During Hydrogenation of Alkenes and Aldehydes

Ligands like amines are used in the colloidal synthesis approach to protect platinum nanoparticles (Pt NP&#39;s) from agglomeration. Normally, ligands like amines are removed by diverse pre-treatment procedures before use in heterogeneous catalysis as amines are considered as a catalyst poison. However, a possible beneficial influence of these surface modifiers on hydrogenation reactions, which is known from spectator species on metal surfaces, is often neglected.
Therefore, amine-stabilized Pt nanoparticles supported by titania (P25) were used without any pre-treatment in order to elucidate a possible influence of the ligand in liquid phase hydrogenation reactions. The catalytic activity of amine-stabilized Pt nanoparticles of two different sizes was investigated in a double-walled stirring tank reactor at 69 &#176;C to 130 &#176;C and 1 atm hydrogen pressure. The conversion of cyclohexene to cyclohexane was determined by gas chromatography (GC) and was compared to ligand-free Pt particles. All catalysts were checked before and after reaction by transmission electron spectroscopy (TEM) and X-ray photoelectron spectroscopy (XPS) for possible changes in size, shape, and ligand shell. The hydrogenation of cyclohexene in liquid phase revealed a higher conversion for amine-stabilized Pt nanoparticles on titania than the ligand-free particles. The hydrogenation of 5-methylfurfural (5-MF) was chosen for a further test reaction, since the hydrogenation of &#945;, &#946;-unsaturated aldehydes is more complex and exhibits various reaction paths. However, XPS and infrared spectroscopy (IR) proved that 5-MF acts as catalyst poison at the given reaction conditions.

This protocol shows a convenient method for comparing the catalytic properties of supported platinum catalysts, synthesized by deposition of nanosized colloids or by impregnation. The hydrogenation of cyclohexene serves as a model reaction to determine the catalytic activity of the catalysts.

Ligands like amines are used in the colloidal synthesis approach to protect platinum nanoparticles (Pt NP&#39;s) from agglomeration. Normally, ligands ...

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

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