查看完整版本: Pt nanoparticles, nanowire and nanopores structures

[b][size=5]Polyol synthesis of platinum nanostructures: Control of morphology through the manipulation of reduction kinetics[/size][/b]
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G)[+V\a/cPG ANGEWANDTE CHEMIE-INTERNATIONAL EDITION[/i][/b] [b]44[/b] (17): 2589-2592 2005 d!Grg:iqg
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In summary, we have demonstrated that Pt nanostructures with four different morphologies could be synthesized by controlling the reduction kinetics of a polyol process. The presence of both iron species and oxygen (or air) was found to be critical to the control of the reduction kinetics and hence morphology. Depending on the way the FeII/FeIII redox pair and oxygen (from air) were supplied to the reaction system, Pt nanostructures in the form of spheres, star-shaped particles, branched multipods, and nanowires could be obtained as the major product for each run of synthesis. Although the strategy described here may resemble what has been widely explored in the general area of biomineralization,[17] the exact approaches are very different. In biomineralization, a biopolymer is used to mediate the diffusion rate of reactive species toward the surface of nuclei and thus to control the morphology. In the approach presented here, the growth of nuclei is retarded by blocking their surface with oxygen and/or by facilitating the dissolution of atoms from the nuclei. The net results of these two different approaches are the same: a reduction in supersaturation and the induction of morphologies that deviate from those favored thermodynamically.[18]"hIp1]-v^
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[i]Four different ways to control the kinetics of polyol reduction and the corresponding morphologies observed for the Pt nanostructures. As the same amount of PVP was present in all four illustrated syntheses, the striking difference in morphology was not caused by PVP concentration. We believe that the PVP molecules in these syntheses only function as a stabilizer to prevent the resultant nanoparticles from aggregating into larger structures.[/i]
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[i]TEM (A-D) and SEM (E, F) images of Pt nanostructures that have been obtained by controlling the reduction rate of a polyol process. The products correspond to the morphology labeled A to E in Figure 1. The inset of (D) shows a typical electron-diffraction pattern of the branched nanostructures; F) enlarged section of the SEM image shown in (E) of the nanowires grown at the surface layer.[/i]

[b][size=5]Single-crystal nanowires of platinum can be synthesized by controlling the reaction rate of a polyol process[/size][/b]3c-M$MuX"G&I

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J. Am. Chem. Soc.,[/i][/b] [b]126 [/b](35), 10854 -10855, 2004. 10.1021/ja0468224 S0002-7863(04)06822-2 3~XEH6S'H4W'~~x3^

R&Bv@5}-P| Platinum nanowires of ~100 nm in length and ~5 nm in diameter have been synthesized by reducing H2PtCl6 with ethylene glycol in the presence of poly(vinyl pyrrolidone) (PVP) and a trace amount of Fe3+ or Fe2+. The wires were generated at the final stage of the synthesis, which involved the formation of several intermediate species. The Fe3+ or Fe2+ ions had dual functions in the synthesis: they induced aggregation of Pt nanoparticles into larger structures that served as the nucleation sites, and they greatly reduced the reaction rate and supersaturation level to induce anisotropic growth. The reaction mechanism was studied by X-ray photoelectron spectroscopy (XPS) and UV-vis spectral analysis. The Pt nanowires could be readily separated from the surfaces of the agglomerates by sonication and obtained as pure samples by centrifugation.

[b][size=5]Shape-dependent catalytic activity of platinum nanoparticles in colloidal solution[/size][/b]
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GI#|.a*w;{%tz [b][i] NANO LETTERS[/i][/b] 4 (7): 1343-1348 JUL 2004

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Abstract: The activation energies and the average rate constants are determined in the 298 K-318 K temperature range for the early stages of the nanocatalytic reaction between hexacyanoferrate (111) and thiosulfate ions using 4.8 +/- 0.1 nm tetrahedral, 7.1 +/- 0.2 nm cubic, and 4.9 +/- 0.1 nm "near spherical" nanocrystals. These kinetic parameters are found to correlate with the calculated fraction of surface atoms located on the corners and edges in each size and shape.

[b][size=5]In situ surface enhanced Raman spectroscopy on electrodes with platinum and palladium nanoparticle ensembles[/size][/b]
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Gomez R, Perez JM, Solla-Gullon J, Montiel V, Aldaz A}L@1CI7x7lN
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[b][i]JOURNAL OF PHYSICAL CHEMISTRY B[/i][/b] [b]108[/b] (28): 9943-9949 JUL 15 2004Ws+Do!N3]
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Abstract: In situ Raman spectra have been obtained for different species (CN-, CO, H) adsorbed on nanostructured electrodes prepared by deposition of pure Pt and Pd nanoparticles (around 4 nm in size) on either gold or platinum electrodes in acidic solutions. The surface enhancement factor has been estimated on the basis of cyanide spectra obtained both at the surface and in solution. It attains a value as high as 550, around 3-4 times higher than that reported for roughened Pt electrodes for the same adsorbate. In the case of CO, typical bands for the stretching of the Pt/Pd-C and C-O bonds have been observed for low acquisition times (ca. 1 s), evidencing that pure Pt and Pd nanoparticles sustain significant surface enhancement effects. The spectra show mainly atop CO coordination for Pt nanoparticles whereas both linear and bridge CO are detected for Pd nanoparticles. The potential advantages of the nanoparticle-on-electrode approach in Raman spectroelectrochemical studies are highlighted.

[b][size=5]Effect of nanocatalysis in colloidal solution on the tetrahedral and cubic nanoparticle SHAPE: Electron-transfer reaction catalyzed by platinum nanoparticles[/size][/b]h|f6I2V4ow d
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[b][i]JOURNAL OF PHYSICAL CHEMISTRY B[/i][/b] [b]108[/b] (18): 5726-5733 MAY 6 2004
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Abstract: The stability of tetrahedral and cubic platinum nanoparticles during the catalysis of the electron-transfer reaction between hexacyanoferrate (III) and thiosulfate ions in colloidal solution at room temperature was studied by using TEM and HRTEM. Before the reaction, the dominantly tetrahedral nanoparticles have a shape distribution of 55 +/- 4% regular tetrahedral, 22 +/- 2% distorted tetrahedral, and 23 +/- 2% spherical nanoparticles, and the dominantly cubic nanoparticles have an initial shape distribution of 56 4% regular cubes, 13 +/- 1% distorted cubes, and 31 +/- 3% truncated octahedral nanoparticles. The amount of tetrahedral nanoparticles decreases by 60 +/- 5% after the first cycle and by 62 +/- 4% after the second cycle of the reaction. In the case of cubic nanoparticles, the amount of cubic nanoparticles decreases by 39 +/- 5% after the first cycle and by 66 +/- 5% after the second cycle compared to before the reaction. After the first and second cycles of the reaction, there are a greater percentage of distorted tetrahedral and distorted cubic nanoparticles present. The rate of the dissolution of the surface Pt atoms is faster for the tetrahedral nanoparticles than for the cubic nanoparticles. This suggests that tetrahedral nanoparticles, with their sharp corners and edges, are more sensitive and more liable to shape changes during nanocatalysis. The presence of just hexacyanoferrate ions in the solution with the nanoparticles is found to increase the amount of distorted tetrahedral and distorted cubes present much more than during the reaction. The presence of only the thiosulfate ions does not seem to affect the size or shape distribution which might result from the capping ability of this anion and thus protects the nanoparticles.

[i][i][b][size=5] Pt hollow nanospheres: Facile synthesis and enhanced electrocatalysts[/size][/b][/i][/i]
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C9{(Jz? Liang HP, Zhang HM, Hu JS, Guo YG, Wan LJ, Bai CL
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`S%t"pIx}3\ [b][i]ANGEWANDTE CHEMIE-INTERNATIONAL EDITION[/i][/b] [b]43[/b] (12): 1540-1543 2004 0h!`VgONs-@(O7m5v
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In summary, a facile procedure for the large-scale synthesis of Pt hollow nanosphere catalysts was developed. The catalysts can be simply prepared at room temperature in a homogeneous solution with Co nanoparticles as sacrificial templates. The method presented herein is more cost-effective than previous methods. The incomplete and porous shells of the Pt hollow nanospheres have a higher surface area and therefore exhibit enhanced electrocatalytic performance. This approach was successfully extended to the fabrication of Au, Pd, and their bimetallic hollow nanospheres. These metallic hollow nanospheres could be useful in industrial applications including catalytic nanoreactors, plasmonic devices, and near-infrared absorbers.u-WCItn%W

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[size=5][b] Pt nanoshell tubes by template wetting[/b][/size]
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Luo Y, Lee SK, Hofmeister H, Steinhart M, Gosele U
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+f NeVs#|0qaM [b][i] NANO LETTERS [/i][/b][b]4[/b] (1): 143-147 JAN 2004D8CJlPYU`

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Abstract: Large-scale fabrication of platinum (Pt) nanoshell tubes has been accomplished via a simple and convenient method: porous templates are wetted at ambient conditions with a polymer/Pt precursor solution. Annealing yields functionalized membranes having Pt-coated pore walls. Unsupported Pt nanoshell tubes are accessible by selectively removing the template. We have also synthesized composite tubes having an outer Pt shell and an inner polymer core by performing consecutive wetting steps. The tube diameter is adjustable by using templates with respective pore diameters. We demonstrate that "giant" nanoshell tubes with a diameter of 1 mum can be fabricated. They exhibit nanostructured walls consisting of sintered crystallites extending approximately 10 nm and can thus be considered as a hierarchical system combining nano-and microscale features.

[b][size=5]Size-controlled synthesis and catalytic performance of Pt nanoparticles in micro- and mesoporous silica prepared using supercritical solvents[/size][/b]
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UL6GG$C\T6F [b][i]ADVANCED MATERIALS[/i][/b] [b]15[/b] (9): 742-745 MAY 2 2003
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[url=http://www3.interscience.wiley.com/cgi-bin/abstract/104528444/ABSTRACT]
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Morphological Control of Catalytically Active Platinum Nanocrystals

[size=5]Morphological Control of Catalytically Active Platinum Nanocrystals[/size]
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J0t-Q?A+F [b][i]Angewandte Chemie International Edition[/i][/b] Volume [b]45[/b], Issue 46, Pages 7824-7828, 2006?-aZ)iSH
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Hyunjoo Lee, Susan E. Habas, Sasha Kweskin, Derek Butcher, Gabor A. Somorjai, Prof., Peidong Yang, Prof. *
hy4x.] J5q Department of Chemistry, University of California, Berkeley, Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA, Fax: (+1) 510-642-7301
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email: Peidong Yang ([email]p_yang@uclink.berkeley.edu[/email]) *@ y]1GcGYb+r
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*Correspondence to Peidong Yang, Department of Chemistry, University of California, Berkeley, Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA, Fax: (+1) 510-642-7301
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Cubic, cuboctahedral, and porous Pt nanoparticles have been prepared using tetradecyltrimethylammonium bromide as a surface-stabilizing reagent. The morphology was controlled by adjusting the reduction method. H2 production in situ from NaBH4 has enabled the synthesis of uniform nanoparticles. By changing the pH value, which contributes to controlling the reduction rate, shape evolution from cuboctahedra to cubes was observed. These nanoparticles, which are electrostatically capped with alkylammonium ions and shape-controlled without the aid of foreign metal ions, show superior catalytic activity to nanoparticles prepared with a polymeric stabilizing reagent and silver.
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[url]http://www.nanost.net/bbs/thread-19067-1-1.html[/url]
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The many faces of Pt nanoparticlesnext term Nanotechnology
P.A2c+a9dK*dEU An unusual form of Pt nanocrystals with 24 high-index facets has been prepared by a team of researchers from Georgia Institute of Technology and Xiamen University, China [Tian et al., Science (2007) 316, 732]. The tetrahexahedral (THH)-shaped crystals were prepared by electrochemical treatment of Pt nanospheres supported on glassy carbon (GC) using a square-wave potential. They show higher catalytic activity per surface area compared with other forms of Pt.(qWwEI*Uz R
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Pt is an important catalyst and is used in a range applications from industrial chemical processing to catalytic converters in vehicles. Fundamental studies of single-crystal surfaces of bulk Pt have shown previously that high-index planes generally exhibit much higher catalytic activity than that of the most common stable planes, such as {111} and {100}. This is because the high-index planes have a high density of atomic steps, ledges, and kinks, which usually serve as active sites for breaking chemical bonds. So the shape-controlled synthesis of metal nanocrystals bounded by high-index facets is a potential route for enhancing their catalytic activity. This is not a trivial challenge since high-index planes are rapidly eliminated during particle formation because the crystal growth rates in the direction perpendicular to a high-index plane are usually much faster than those along the normal direction of a low-index plane.
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The synthesis of THH Pt nanocrystals of high purity was achieved using an electrochemical method, where polycrystalline Pt nanospheres were electrodeposited on a GC electrode in a standard three-electrode cell at room temperature. The Pt nanospheres were then subjected to a square-wave treatment, with an upper potential of 1.20 V and a lower potential of between −0.10 V and −0.20 V. THH Pt nanocrystals were grown exclusively on the GC surface at the expense of the Pt nanospheres.
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The THH nanocrystals have a high density of atomic steps and dangling bonds, and show enhanced catalytic performance of up to 400% per unit surface area higher than that of Pt nanospheres or a commercial catalyst. However, because of the size of the crystals, they are currently less efficient in terms of relative mass.$Sq!l4x[V,j
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The next step is to improve the synthesis technique so that smaller THH nanocrystals are made in high yield. “If we can make it small enough, it may have much enhanced catalytic performance per unit mass for fuel cell and other catalytic applications,” says Wang of Georgia Tech. “This will need a detailed and in depth study on the experimental conditions and structure analysis.”
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It is hoped that THH shape nanocrystals can be made for other metals such as Pd and that these nanocrystals could have very different catalytic behavior from the conventional low-energy facet bounded Pd nanocrystals. Using this technique, it may be possible to find an alternative metal catalyst that may replace Pt for fuel cells.[From Material news]

Angw 上刚出的一篇

A General Approach to the Size- and Shape-Controlled Synthesis of Platinum Nanoparticles and Their Catalytic Reduction of Oxygen*SqY8J+r*Zd
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Chao Wang , Hideo Daimon , Taigo Onodera , Tetsunori Koda , Shouheng Sun, Prof. {'i0S'L T7iA
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Abstract: Monodisperse Pt nanoparticles with controlled sizes (3-7 nm) and shapes (polyhedron, truncated cube or cube) are prepared. The cubic nanoparticles show (100) texture in the self-assembled array and are much more active cathode catalyst for oxygen reduction reaction (ORR). Among the nanoparticles tested in H2SO4, the current density for ORR from 7 nm Pt nanocubes is 4 folds of that from other shaped Pt nanoparticles, indicating great potential of cubic Pt for fuel cell applications.  r#d4~|
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[url]http://www3.interscience.wiley.c[/url] ... ETRY=1&SRETRY=0
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本文转自 [url]http://chem8.org/bbs/viewthread.php?tid=13811#zoom[/url]
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Making a Platinum Nanocube
l_$[9h5mr4_ Transmission electron microscopy, far left, shows 7-nm. platinum nanocubes used for oxygen reduction reaction. In the upper right corner is a high-resolution picture of a single nanocube. The illustration depicts oxygen reduction on the surface of a nanocubeuH"g8vAK)J

&|9Lz~.R2|3a [[i] 本帖最后由 happyboy2008 于 2008-04-12 12:28 编辑 [/i]]

08--先进材料--合成Pt纳米花

Template- and Surfactant-free Room Temperature Synthesis of Self-Assembled 3D Pt Nanoflowers from Single-Crystal Nanowires (p 571-574)
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Y8c"O S. H. Sun, D. Q. Yang, D. Villers, G. X. Zhang, E. Sacher, J. P. Dodelet8P [ \1T1w'A{YyO
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Adv. Mater. 2008, 20, 571–574
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3D Pt nanoflowers, which are composed of numerous single-crystal nanowires, are successfully synthesized by a facile chemical procedure, at room temperature, without surfactant or template. The Pt nanoflowers adhere to carbon paper, exhibiting an enlarged electroactive surface area comparable to that of a commercial Pt/C electrode. k cv7pd q5h.\!d
全文连接
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[url]http://www3.interscience.wiley.com/cgi-bin/abstract/117887218/ABSTRACT[/url]

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Angw 上又出的一篇

title:Mesoporous Platinum with Giant Mesocages Templated from Lyotropic Liquid Crystals Consisting of Diblock Copolymers'ZEOS/{5p R8V*X
Author:Yusuke Yamauchi, Atsushi Sugiyama, Ryoichi Morimoto, Azusa Takai, Kazuyuki Kuroda
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2HPApC[D] Giant metal cages: Mesoporous Pt particles, with mesocages connected closely in three dimensions (see picture), are prepared by an electrodeposition process through soft templating from lyotropic liquid crystals of diblock copolymers. The size of the mesocages is the largest (about 15 nm) reported in mesoporous metals. The method can be extended to other metals and mesostructures, and the mesopores can be controlled over a range of pore sizesabktT^^2[Lc
Full paper online:
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HT6a3jDG [url=http://www3.interscience.wiley.com/journal/119818564/abstract]http://www3.interscience.wiley.com/journal/119818564/abstract[/url]
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(CB9s&I0~8E0^ [[i] 本帖最后由 happyboy2008 于 2008-06-13 18:37 编辑 [/i]]

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