Name: a salt-templated synthesis method for porous platinum-based macrobeams and macrotubes
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Description: Watch this Scientific Journal Video about A Salt-Templated Synthesis Method for Porous Platinum-based Macrobeams and Macrotubes at JoVE.com

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. Mag...

<ol>
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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(NH3)4SO4&#159;&#8226;H2O</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>K2PtCl4</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>Na2PdCl4</td>
			<td>Sigma-Aldrich</td>
			<td>13820-40-1</td>
			<td></td>
		</tr>
		<tr>
			<td>NaBH4</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(NH3)4Cl2&#159;&#8226;H2O</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&#8482; 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...

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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 ...

This protocol offers a simple, relatively fast method for synthesizing high surface area, high aspect ratio platinum in platinum alloys macrobeams and macrotubes with a square cross-section. The salts and plating method allows control of the template metal ion ratio and resulting mass composition, and of the macrobeam and macrotube nano structures. Macrobeam and macrotube pressed films may address the need for integral three-dimensional electrodes for catalysis and sensing applications.The ability of Magna salt derivatives to be chemically reduced to form macrobeams and macrotubes, suggest that the salt templating synthesis method may be applied to a wider range of metal salts. To prepare Magnus salts with a one to zero to one platinum two positive to platinum two negative ratio, add 0.5 milliliters of 100 millimolar potassium tetrachloroplatinate into a microfuge tube, and forcefully pipette 0.5 milliliters of 100 millimolar tetraammineplatinum(II)chloride hydrate in water into the tube. The resulting one milliliter volume salt needle template solutions will exhibit an opaque like green color.To prepare a one to one to zero platinum-palladium salt needle template, add 0.5 milliliters of tetraammineplatinum(II)chloride hydrate in water to a microcentrifuge tube and forcefully pipette 0.5 milliliters of 100 millimolar sodium tetrachloropalladate to the tube. To prepare a two to one to one platinum-palladium salt needle template, add 0.25 milliliters of 100 millimolar sodium tetrachloropalladate and 0.25 milliliters of 100 millimolar potassium tetrachloroplatinate to a microfuge tube. Vortex the tube for three to five seconds, before forcefully pipetting 0.5 milliliters of 100 millimolar tetraamminePlatinum(II)chloride hydrated water to the tube.To prepare a three to one to two platinum-palladium salt needle template, pipette 0.167 milliliters of 100 millimolar sodium tetrachloropalladate and 0.333 milliliters of 100 millimolar potassium tetrachloroplatinate to a microfuge tube. After vortexing, forcefully pipette 0.5 milliliters of 100 millimolar tetraamminePlatinum(II)chloride hydrated water to the tube. Salt-templates with a higher platinum ratio should yield a greener color, while templates with increasing palladium contents result in more orange, pink, and brown colors within the solution.To prepare a one to zero to one salt ratio copper-platinum salt needle template, add 0.5 milliliters of 100 millimolar potassium tetrachloroplatinate to a microfuge tube and forcefully add 0.5 milliliters of 100 millimolar tetraammineCopper(II)sulfate in water to the microfuge tube. To prepare a three to one-to-two salt ratio copper-platinum salt needle template, add 0.167 milliliters of 100 millimolar tetraamminePlatinum(II)chloride hydrated water and 0.333 milliliters of 100 millimolar tetraammineCopper(II)sulfate in water to the tube. After vortexing, forcefully add 0.5 milliliters of 100 millimolar potassium tetrachloroplatinate to the tube.To prepare the two to one-to-one salt ratio copper-platinum salt needle template, add 0.25 milliliters of 100 millimolar tetraamminePlatinum(II)chloride hydrated water and 0.25 milliliters of 100 millimolar tetraammineCopper(II)sulfate in water to a microfuge tube, and vortex the microfuge tube for three to five seconds. Then, forcefully pipette 0.5 milliliters of 100 millimolar potassium tetrachloroplatinate to the tube. To prepare the one to one to zero salt ratio copper-platinum salt needle template, pipette 0.5 milliliters of 100 millimolar tetraamminePlatinum(II)chloride hydrated water to a microfuge tube, and forcefully pipette 0.5 milliliters of 100 millimolar potassium tetrachloroplatinate into the tube, to obtain a one milliliter salt needle template solution.The combination of copper and platinum ions will result in the formation of a purple cloudy solution that is not as opaque as the platinum and palladium solutions. To perform a chemical reduction of the platinum-palladium salt-templates, add 50 milliliters of 0.1 molar sodium borohydride solution into each of four 50 milliliter conical tubes, and add the entire one milliliter volume of one platinum-palladium salt-template solution to each tube. To perform a chemical reduction of the copper-platinum salt-templates, add 50 milliliters of 0.1 molar DMAB solution into each of four 50 milliliter conical tubes, and add the entire one milliliter volume of one copper-platinum salt-template solution to each tube under a fume hood.After 24 hours, slowly decaf the supernatant from each reduced solution into a waste container, taking care, not to pour out the samples and transfer the precipitates into new 50 milliliter tubes. Fill each tube with 50 milliliters of deionized water and incubate the tightly capped tubes for 24 hours with gentle rocking. The next day, place the tubes upright in a tube rack for 15 minutes to allow the samples to sediment before slowly pouring off the supernatant.Refill each tube with 50 milliliters of the ionized water, and rock the samples for an additional 24 hours. At the end of the incubation, place the tubes in a rack for 15 minutes before decanting as much of the clear or gray supernatants as possible. To prepare macrotube and macrobeam films, use a pipette or a spatula to gently transfer the precipitant material from each to tube onto individual glass slides, and consolidate the samples into uniform piles, approximately 0.5 millimeters.Then place the slides in a location that will not be disturbed by air currents for 24 hours. When the samples have dried, place a second glass slide onto each dried reduced sample, and manually apply approximately 200 kilopascals of force to the top slide to create a thin film of macrotubes, or macrobeams on the bottom slide. For scanning electron microscopy of the samples, use carbon tape to fix the thin film to a scanning electron microscopy sample stub, and set the initial accelerating voltage to 15 kilovolts, and the beam current to 2.7 to 5.4 picoamps.Then zoom out to a large sample area, and collect an energy dispersive X-Ray spectrum to quantify the elemental composition of the sample. For X-Ray diffract-dimetric analysis, place the thin film sample slide onto the scanning stage and perform X-Ray diffractometry scans for diffraction angles to theta, from five to 90 degrees at 45 kilovolts and 40 milliamps with Copper K-alpha radiation, a two theta step size of 0.0130 degrees and 20 seconds per step. To normalize the electrochemical measurements by milligrams of active materials, transfer the samples into individual electrochemical vials, and gently add 0.5 molar sulfuric acid to each sample for a 24 hour incubation at room temperature.The next day place the lacquer coated wire with a one millimeter exposed tip from individual three electrode cells in contact with the top surface of the film at the bottom of each electrochemical vial. And perform electrochemical impedance spectroscopy from one megahertz to one millihertz with a 10 millivolt sine wave at zero volts. Then perform cyclic voltammetry using a voltage range of negative 0.2 to 1.2 volts, with scan rates of 10, 25, 50, 75 and 100 millivolts per second.The addition of oppositely charged square planar noble metal ions results in near instantaneous formation of high aspect ratio salt crystals. The chemical reduction of Magnus salts formed with a one-to-one ratio of platinum positive to platinum negative ions, and reduced sodium borohydride results with macrotubes with generally a hollow inner cavity and porous sidewalls. The macrotubes generally conform to the geometry of the salt needle templates, with flat sidewalls and a square cross-section, DMAB reduced copper-platinum macrotubes present the most distinct and largest square cross-sections, with approximately three micrometers sides.The DMAB be reduced copper-platinum macrotube sidewalls also demonstrate a highly textured surface without a significant porosity. Platinum and platinum-palladium macrotube and macrobeam chemical composition can be initially characterized with X-Ray diffraction. X-Ray diffraction analysis of DMAB reduced macrotubes reveal super-imposed peaks that shift towards either platinum or copper, depending on the relative salt-template stoichiometry, suggesting an alloy composition.Sodium borohydride reduced copper-platinum macrobeams, exhibit distinct copper and platinum X-Ray diffraction peaks suggesting a bimetallic composition. X-Ray photo electron spectra for Platinum macrotubes indicate little evidence of an oxide species, suggesting a catalytically active surface. X-Ray photo electron spectra for platinum-palladium macrobeams also present no indication of metal oxide content.Well, the pressed films can be manipulated with tweezers. Care must be taken when transferring the films into the electrochemical vials to prevent fracturing. Given the ability to press macrobeams and macrotubes into integral films, mechanical characterization to determine elastic and flexible modular can also be performed.Salt-templates, for the synthesis of pores, high surface area materials should enable researchers to explore a wider range of metal salts and resulting metal, alloy and multi metallic materials.

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Chemistry

Seeded Synthesis of CdSe/CdS Rod and Tetrapod Nanocrystals

We demonstrate a method for the synthesis of multicomponent nanostructures consisting of CdS and CdSe with rod and tetrapod morphologies. A seeded synthesis strategy is used in which spherical seeds of CdSe are prepared first using a hot-injection technique. By controlling the crystal structure of the seed to be either wurtzite or zinc-blende, the subsequent hot-injection growth of CdS off of the seed results in either a rod-shaped or tetrapod-shaped nanocrystal, respectively. The phase and morphology of the synthesized nanocrystals are confirmed using X-ray diffraction and transmission electron microscopy, demonstrating that the nanocrystals are phase-pure and have a consistent morphology. The extinction coefficient and quantum yield of the synthesized nanocrystals are calculated using UV-Vis absorption spectroscopy and photoluminescence spectroscopy. The rods and tetrapods exhibit extinction coefficients and quantum yields that are higher than that of the bare seeds. This synthesis demonstrates the precise arrangement of materials that can be achieved at the nanoscale by using a seeded synthetic approach.

A protocol for the seeded synthesis of rod-shaped and tetrapod-shaped multicomponent nanostructures consisting of CdS and CdSe is presented.

We demonstrate a method for the synthesis of multicomponent nanostructures consisting of CdS and CdSe with rod and tetrapod morphologies. A seeded ...

Synthesis and Purification of Iodoaziridines Involving Quantitative Selection of the Optimal Stationary Phase for Chromatography

The highly diastereoselective preparation of cis-N-Ts-iodoaziridines through reaction of diiodomethyllithium with N-Ts aldimines is described. Diiodomethyllithium is prepared by the deprotonation of diiodomethane with LiHMDS, in a THF/diethyl ether mixture, at -78 &#176;C in the dark. These conditions are essential for the stability of the LiCHI2 reagent generated. The subsequent dropwise addition of N-Ts aldimines to the preformed diiodomethyllithium solution affords an amino-diiodide intermediate, which is not isolated. Rapid warming of the reaction mixture to 0 &#176;C promotes cyclization to afford iodoaziridines with exclusive cis-diastereoselectivity. The addition and cyclization stages of the reaction are mediated in one reaction flask by careful temperature control.
Due to the sensitivity of the iodoaziridines to purification, assessment of suitable methods of purification is required. A protocol to assess the stability of sensitive compounds to stationary phases for column chromatography is described. This method is suitable to apply to new iodoaziridines, or other potentially sensitive novel compounds. Consequently this method may find application in range of synthetic projects. The procedure involves firstly the assessment of the reaction yield, prior to purification, by 1H NMR spectroscopy with comparison to an internal standard. Portions of impure product mixture are then exposed to slurries of various stationary phases appropriate for chromatography, in a solvent system suitable as the eluent in flash chromatography. After stirring for 30 min to mimic chromatography, followed by filtering, the samples are analyzed by 1H NMR spectroscopy. Calculated yields for each stationary phase are then compared to that initially obtained from the crude reaction mixture. The results obtained provide a quantitative assessment of the stability of the compound to the different stationary phases; hence the optimal can be selected. The choice of basic alumina, modified to activity IV, as a suitable stationary phase has allowed isolation of certain iodoaziridines in excellent yield and purity.

A protocol for the diastereoselective one-pot preparation of cis-N-Ts-iodoaziridines is described. The generation of diiodomethyllithium, addition to N-Ts aldimines and cyclization of the amino gem-diiodide intermediate to iodoaziridines is demonstrated. Also included is a protocol to rapidly and quantitatively assess the most appropriate stationary phase for purification by chromatography.

The highly diastereoselective preparation of cis-N-Ts-iodoaziridines through reaction of diiodomethyllithium with N-Ts aldimines is described. ...

Supercritical Nitrogen Processing for the Purification of Reactive Porous Materials

Supercritical fluid extraction and drying methods are well established in numerous applications for the synthesis and processing of porous materials. Herein, nitrogen is presented as a novel supercritical drying fluid for specialized applications such as in the processing of reactive porous materials, where carbon dioxide and other fluids are not appropriate due to their higher chemical reactivity. Nitrogen exhibits similar physical properties in the near-critical region of its phase diagram as compared to carbon dioxide: a widely tunable density up to ~1 g ml-1, modest critical pressure (3.4 MPa), and small molecular diameter of ~3.6 &#197;. The key to achieving a high solvation power of nitrogen is to apply a processing temperature in the range of 80-150 K, where the density of nitrogen is an order of magnitude higher than at similar pressures near ambient temperature. The detailed solvation properties of nitrogen, and especially its selectivity, across a wide range of common target species of extraction still require further investigation. Herein we describe a protocol for the supercritical nitrogen processing of porous magnesium borohydride.

Nitrogen is an effective supercritical fluid for extraction or drying processes due to its small molecular size, high density in the near-liquid supercritical regime, and chemical inertness. We present a supercritical nitrogen drying protocol for the purification treatment of reactive, porous materials.

Supercritical fluid extraction and drying methods are well established in numerous applications for the synthesis and processing of porous materials. ...

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

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

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

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

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

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

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

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

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

Deposition of Porous Sorbents on Fabric Supports

A microwave deposition technique for silanes, previously described for production of oleophobic fabrics, is adapted to provide a fabric support material that can be subsequently treated by dip coating. Dip coating with a sol preparation provides a supported porous layer on the fabric. In this case, the porous layer is a porphyrin functionalized sorbent system based on a powdered material that has been demonstrated previously for the capture and conversion of phosgene. A representative coating is applied to cotton fabric at a loading level of 10 mg/g. This coating has minimal impact on water vapor transport through the fabric (93% of the support fabric rate) while significantly reducing transport of 2-chloroethyl ethyl sulfide (CEES) through the material (7% of support fabric rate). The described approaches are suitable for use with other fabrics providing amine and hydroxyl groups for modification and can be used in combination with other sol preparations to produce varying functionality.

This report details a microwave-initiated approach for deposition of porphyrin functionalized porous organosilicate sorbents on a cotton fabric and demonstrates reduction in 2-chloroethyl ethyl sulfide (CEES) transport through the fabric resulting from this treatment.

A microwave deposition technique for silanes, previously described for production of oleophobic fabrics, is adapted to provide a fabric support material ...

Chemical Synthesis of Porous Barium Titanate Thin Film and Thermal Stabilization of Ferroelectric Phase by Porosity-Induced Strain

Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its well-balanced ferroelectricity, piezoelectricity, and dielectric constant. In addition, BT does not contain any toxic elements. Therefore, it is considered to be an eco-friendly material, which has attracted considerable interest as a replacement for lead zirconate titanate (PZT). However, bulk BT loses its ferroelectricity at approximately 130 &#176;C, thus, it cannot be used at high temperatures. Because of the growing demand for high-temperature ferroelectric materials, it is important to enhance the thermal stability of ferroelectricity in BT. In previous studies, strain originating from the lattice mismatch at hetero-interfaces has been used. However, the sample preparation in this approach requires complicated and expensive physical processes, which are undesirable for practical applications.
In this study, we propose a chemical synthesis of a porous material as an alternative means of introducing strain. We synthesized a porous BT thin film using a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles were used as an organic template. Through a series of studies, we clarified that the introduction of pores had a similar effect on distorting the BT crystal lattice, to that of a hetero-interface, leading to the enhancement and stabilization of ferroelectricity. Owing to its simplicity and cost effectiveness, this fabrication process has considerable advantages over conventional methods.

Here, we present a protocol for the synthesis of porous barium titanate (BaTiO3) thin film by a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles are used as an organic template.

Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its ...

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 ...

Synthesis Method for Cellulose Nanofiber Biotemplated Palladium Composite Aerogels

Here, a method to synthesize cellulose nanofiber biotemplated palladium composite aerogels is presented. Noble metal aerogel synthesis methods often result in fragile aerogels with poor shape control. The use of carboxymethylated cellulose nanofibers (CNFs) to form a covalently bonded hydrogel allows for the reduction of metal ions such as palladium on the CNFs with control over both nanostructure and macroscopic aerogel monolith shape after supercritical drying. Crosslinking the carboxymethylated cellulose nanofibers is achieved using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) in the presence of ethylenediamine. The CNF hydrogels maintain their shape throughout synthesis steps including covalent crosslinking, equilibration with precursor ions, metal reduction with high concentration reducing agent, rinsing in water, ethanol solvent exchange, and CO2 supercritical drying. Varying the precursor palladium ion concentration allows for control over the metal content in the final aerogel composite through a direct ion chemical reduction rather than relying on the relatively slow coalescence of pre-formed nanoparticles used in other sol-gel techniques. With diffusion as the basis to introduce and remove chemical species into and out of the hydrogel, this method is suitable for smaller bulk geometries and thin films. Characterization of the cellulose nanofiber-palladium composite aerogels with scanning electron microscopy, X-ray diffractometry, thermal gravimetric analysis, nitrogen gas adsorption, electrochemical impedance spectroscopy, and cyclic voltammetry indicates a high surface area, metallized palladium porous structure.

A synthesis method for cellulose nanofiber biotemplated palladium composite aerogels is presented.The resulting composite aerogel materials offer potential for catalysis, sensing, and hydrogen gas storage applications.

Here, a method to synthesize cellulose nanofiber biotemplated palladium composite aerogels is presented. Noble metal aerogel synthesis methods often ...

Iron Nanowire Fabrication by Nano-Porous Anodized Aluminum and its Characterization

Magnetic nanowires possess unique properties that have attracted the interest of different fields of research, including basic physics, biomedicine, and data storage. We demonstrate a fabrication method for iron (Fe) nanowires&#160;via electrochemical deposition into anodic&#160;alumina oxide (AAO) templates. The templates are fabricated by anodization of aluminum (Al) discs, and the pore length and diameter are controlled by changing the anodizing conditions. Pores with an average diameter of around 120 nm are created using oxalic acid as the electrolyte. Using this method, cylindrical nanowires are synthesized, which are released by dissolving the alumina using a selective chemical etchant.

In this work, we describe a&#160;protocol to fabricate iron nanowires, including the formation of the porous alumina membrane that is used as the template, electrodeposition into templates using electrolyte solution, and the release of the nanowires into the solution.

Magnetic nanowires possess unique properties that have attracted the interest of different fields of research, including basic physics, biomedicine, and ...