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Noble Metals (noble + metal)
Terms modified by Noble Metals Selected AbstractsNoble metal-based catalysts for total oxidation of chlorinated hydrocarbonsENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2001José M. Toledo Catalytic total oxidation of selected chlorinated hydrocarbons utilizing several noble metal (Pt, Pd, Ru)-based catalysts was studied. Chlorinated hydrocarbons used were trichloroethylene, dichloromethane, and chlorobenzene, alone or mixed with other hydrocarbons, such as toluene. Catalysts tested were both commercially available, manufactured by Degussa AG, Süd-Chemie AG, Kataleuna GmbH, Chimet, Johnson Matthey, Prototech Co., etc., and new ones developed by Universities of Leiden in The Netherlands, Budapest in Hungary, and Wroclaw in Poland. Both forms of catalyst, sphere (particulate) and monolith, were used. Selection of the best catalyst(s) was made based on its activity, selectivity, and life. Apparent energies of activation for the reactions on these catalysts, using an empirical firstorder reaction rate, are also given. [source] A New Method of Carbon-Nanotube Patterning Using Reduction PotentialsADVANCED MATERIALS, Issue 12 2009Jong Hak Lee Noble metals promote the oxidation of carbon nanotubes (CNTs) at the relatively low temperature of 350,°C. The reduction potential of multiwalled CNTs is located between those of W and Ni, while that of single-walled CNTs is between those of Ni and In. Nanometer-sized patterns on CNT films were successfully fabricated using differences in reduction potential between the CNTs and noble metals. [source] Noble metal-based catalysts for total oxidation of chlorinated hydrocarbonsENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2001José M. Toledo Catalytic total oxidation of selected chlorinated hydrocarbons utilizing several noble metal (Pt, Pd, Ru)-based catalysts was studied. Chlorinated hydrocarbons used were trichloroethylene, dichloromethane, and chlorobenzene, alone or mixed with other hydrocarbons, such as toluene. Catalysts tested were both commercially available, manufactured by Degussa AG, Süd-Chemie AG, Kataleuna GmbH, Chimet, Johnson Matthey, Prototech Co., etc., and new ones developed by Universities of Leiden in The Netherlands, Budapest in Hungary, and Wroclaw in Poland. Both forms of catalyst, sphere (particulate) and monolith, were used. Selection of the best catalyst(s) was made based on its activity, selectivity, and life. Apparent energies of activation for the reactions on these catalysts, using an empirical firstorder reaction rate, are also given. [source] Recent Progress in Syntheses and Applications of Dumbbell-like NanoparticlesADVANCED MATERIALS, Issue 30 2009Chao Wang Abstract This paper reviews the recent research progress in the syntheses and applications of dumbbell-like nanoparticles (NPs). It first describes the general synthesis of dumbbell-like NPs that contain noble metal and magnetic NPs/or quantum dots. It then outlines the interesting optical and magnetic properties found in these dumbbell NPs. The review further highlights several exciting application potentials of these NPs in catalysis and biomedicine. [source] Support-dependent activity of noble metal substituted oxide catalysts for the water gas shift reactionAICHE JOURNAL, Issue 10 2010Parag A. Deshpande Abstract The water gas shift reaction was carried out over noble metal ion substituted nanocrystalline oxide catalysts with different supports. Spectroscopic studies of the catalysts before and after the reaction showed different surface phenomena occurring over the catalysts. Reaction mechanisms were proposed based upon the surface processes and intermediates formed. The dual site mechanism utilizing the oxide ion vacancies for water dissociation and metal ions for CO adsorption was proposed to describe the kinetics of the reaction over the reducible oxides like CeO2. A mechanism based on the interaction of adsorbed CO and the hydroxyl group was proposed for the reaction over ZrO2. A hybrid mechanism based on oxide ion vacancies and surface hydroxyl groups was proposed for the reaction over TiO2. The deactivation of the catalysts was also found to be support dependent. Kinetic models for both activation and deactivation were proposed. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] A mechanistic model for the water-gas shift reaction over noble metal substituted ceriaAICHE JOURNAL, Issue 5 2010Parag A. Deshpande Abstract The water-gas shift (WGS) reaction was carried out in the presence of Pd and Pt substituted nanocrystalline ceria catalysts synthesized by solution combustion technique. The catalysts were characterized by powder XRD and XPS. The noble metals were found to be present in ionic form substituted for the cerium atoms. The catalysts showed high activity for the WGS reaction with high conversions below 250°C. The products of reaction were only carbon dioxide and hydrogen, and no hydrocarbons were observed even in trace quantities. The reactions were carried out with different amounts of noble metal ion substitution and 2% Pt substituted ceria was found to be the best catalyst. The various possible mechanisms for the reaction were proposed and tested for their consistency with experimental data. The dual site mechanism best described the kinetics of the reaction and the corresponding rate parameters were obtained. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Millisecond catalytic reforming of monoaromatics over noble metalsAICHE JOURNAL, Issue 4 2010C. M. Balonek Abstract The millisecond autothermal reforming of benzene, toluene, ethylbenzene, cumene, and styrene were independently studied over five noble metal-based catalysts: Pt, Rh, Rh/,-Al2O3, Rh,Ce, and Rh,Ce/,-Al2O3, as a function of carbon-to-oxygen feed ratio. The Rh,Ce/,-Al2O3 catalyst exhibited the highest feedstock conversion as well as selectivities to both synthesis gas and hydrocarbon products (lowest selectivities to H2O and CO2). Experimental results demonstrate a high stability of aromatic rings within the reactor system. Benzene and toluene seem to react primarily heterogeneously, producing only syngas and combustion products. Ethylbenzene and cumene behaved similarly, with higher conversions than benzene and toluene, and high product selectivity to styrene, likely due to homogeneous reactions involving their alkyl groups. Styrene exhibited low conversions over Rh,Ce/,-Al2O3, emphasizing the stability of styrene in the reactor system. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Effect of three adhesive primers for a noble metal on the shear bond strengths of three resin cementsJOURNAL OF ORAL REHABILITATION, Issue 1 2001K. Yoshida The purpose of this study was to evaluate the durability and shear bond strengths of the different combinations of three adhesive primers and three resin cements to a silver,palladium,copper,gold (Ag,Pd,Cu,Au) alloy. The adhesive primers Alloy Primer® (AP), Metal PrimerII® (MPII) and Metaltite® (MT), and the resin cements BistiteII® (BRII), Panavia Fluoro Cement® (PFC) and Super-Bond C&B® (SB) were used. Two sizes of casting alloy disks were either non-primed or primed and cemented with each of the three resin cements. The specimens were stored in a 37 °C water bath for 24 h and then immersed alternately in 4 and 60 °C water baths for 1 min each for up to 100 000 thermal cycles. Shear mode testing at a crosshead speed of 0·5 mm/min was then performed. The application of MPII or MT was effective for improving the shear bond strength between each of the three resin cements and the Ag,Pd,Cu,Au alloy compared with non-primed specimens. However, when primed with MPII or MT and cemented with SB, the bond strength at 100 000 thermal cycles was significantly lower than that at thermal cycle 0. When primed with AP, the specimens cemented with BRII or PFC showed lower bond strength than non-primed specimens and failed at the metal,resin cement interface at 100 000 thermal cycles. On the other hand, AP was effective in enhancing the shear bond strength of SB to the Ag,Pd,Cu,Au alloy. The five combined uses of an adhesive metal primer and resin cement (combinations of MPII or MT and BRII or PFC and AP and SB) are applicable to the cementation of prosthodontic restorations without complicated surface modification of the noble alloy. [source] Preparation of Core,Shell-Structured Nanoparticles (with a Noble-Metal or Metal Oxide Core and a Chromia Shell) and Their Application in Water Splitting by Means of Visible LightCHEMISTRY - A EUROPEAN JOURNAL, Issue 26 2010Kazuhiko Maeda Dr. Abstract Core,shell-structured nanoparticles, consisting of a noble metal or metal oxide core and a chromia (Cr2O3) shell, were studied as promoters for photocatalytic water splitting under visible light. Core nanoparticles were loaded by impregnation, adsorption or photodeposition onto a solid solution of gallium nitride and zinc oxide (abbreviated GaN:ZnO), which is a particulate semiconductor photocatalyst with a band gap of approximately 2.7,eV, and a Cr2O3 shell was formed by photodeposition using a K2CrO4 precursor. Photodeposition of Cr2O3 on GaN:ZnO modified with a noble metal (Rh, Pd and Pt) or metal oxide (NiOx, RuO2 and Rh2O3) co-catalyst resulted in enhanced photocatalytic activity for overall water splitting under visible light (,>400,nm). This enhancement in activity was primarily due to the suppression of undesirable reverse reactions (H2,O2 recombination and/or O2 photoreduction) and/or protection of the core component from chemical corrosion, depending on the core type. Among the core materials examined, Rh species exhibited relatively high performance for this application. The activity for visible-light water splitting on GaN:ZnO modified with an Rh/Cr2O3 core,shell configuration was dependent on both the dispersion of Rh nanoparticles and the valence state. In addition, the morphology of the Cr2O3 photodeposits was significantly affected by the valence state of Rh and the pH at which the photoreduction of K2CrO4 was conducted. When a sufficient amount of K2CrO4 was used as the precursor and the solution pH ranged from 3 to 7.5, Cr2O3 was successfully formed with a constant shell thickness (,2,nm) on metallic Rh nanoparticles, which resulted in an effective promoter for overall water splitting. [source] Embedded Phases: A Way to Active and Stable CatalystsCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 1 2010Loredana De, Rogatis Dr. Abstract Industrial catalysts are typically made of nanosized metal particles, carried by a solid support. The extremely small size of the particles maximizes the surface area exposed to the reactant, leading to higher reactivity. Moreover, the higher the number of metal atoms in contact with the support, the better the catalyst performance. In addition, peculiar properties have been observed for some metal/metal oxide particles of critical sizes. However, thermal stability of these nanostructures is limited by their size; smaller the particle size, the lower the thermal stability. The ability to fabricate and control the structure of nanoparticles allows to influence the resulting properties and, ultimately, to design stable catalysts with the desired characteristics. Tuning particle sizes provides the possibility to modulate the catalytic activity. Unique and unexpected properties have been observed by confining/embedding metal nanoparticles in inorganic channels or cavities, which indeed offers new opportunities for the design of advanced catalytic sytems. Innovation in catalyst design is a powerful tool in realizing the goals of more green, efficient and sustainable industrial processes. The present Review focuses on the catalytic performance of noble metal- and non precious metal-based embedded catalysts with respect to traditional impregnated systems. Emphasis is dedicated to the improved thermal stability of these nanostructures compared to conventional systems. [source] Surface-Protected Etching of Mesoporous Oxide Shells for the Stabilization of Metal NanocatalystsADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Qiao Zhang Abstract Nanoparticles of transition metals, particularly noble metals, are widely used in catalysis. However, enhancing their stability during catalytic reactions has been a challenge that has limited the full use of the benefits associated with their small size. In this Feature Article, a general "encapsulation and etching" strategy for the fabrication of nanocatalyst systems is introduced in which catalyst nanoparticles are protected within porous shells. The novelty of this approach lies in the use of chemical etching to assist the creation of mesopores in a protective oxide shell to promote efficient mass transfer to encapsulated metal nanoparticles. The etching process allows for the direct transformation of dense silica coatings into porous shells so that chemical species can reach the catalyst surface to participate in reactions while the shells act as physical barriers against aggregation of the catalyst particles. By using the surface-protected etching process, both yolk,shell and core,satellite type nanoreactors are synthesized and their utilization in liquid- and gas-phase catalysis is demonstrated. The thermal and chemical stability of the metallic cores during catalytic reactions is also investigated, and further work is carried out to enhance recyclability via the introduction of superparamagnetic components into the nanoreactor framework. [source] Mussel-Inspired Polydopamine Coating as a Universal Route to Hydroxyapatite CrystallizationADVANCED FUNCTIONAL MATERIALS, Issue 13 2010Jungki Ryu Abstract Bone tissue is a complex biocomposite material with a variety of organic (e.g., proteins, cells) and inorganic (e.g., hydroxyapatite crystals) components hierarchically organized with nano/microscale precision. Based on the understanding of such hierarchical organization of bone tissue and its unique mechanical properties, efforts are being made to mimic these organic,inorganic hybrid biocomposites. A key factor for the successful designing of complex, hybrid biomaterials is the facilitation and control of adhesion at the interfaces, as many current synthetic biomaterials are inert, lacking interfacial bioactivity. In this regard, researchers have focused on controlling the interface by surface modifications, but the development of a simple, unified way to biofunctionalize diverse organic and inorganic materials remains a critical challenge. Here, a universal biomineralization route, called polydopamine-assisted hydroxyapatite formation (pHAF), that can be applied to virtually any type and morphology of scaffold materials is demonstrated. Inspired by the adhesion mechanism of mussels, the pHAF method can readily integrate hydroxyapatites on ceramics, noble metals, semiconductors, and synthetic polymers, irrespective of their size and morphology (e.g., porosity and shape). Surface-anchored catecholamine moieties in polydopamine enriches the interface with calcium ions, facilitating the formation of hydroxyapatite crystals that are aligned to the c -axes, parallel to the polydopamine layer as observed in natural hydroxyapatites in mineralized tissues. This universal surface biomineralization can be an innovative foundation for future tissue engineering. [source] Nonspherical Noble Metal Nanoparticles: Colloid-Chemical Synthesis and Morphology ControlADVANCED MATERIALS, Issue 16 2010Tapan K. Sau Abstract Metal nanoparticles have been the subject of widespread research over the past two decades. In recent years, noble metals have been the focus of numerous studies involving synthesis, characterization, and applications. Synthesis of an impressive range of noble metal nanoparticles with varied morphologies has been reported. Researchers have made a great progress in learning how to engineer materials on a nanometer length scale that has led to the understanding of the fundamental size- and shape-dependent properties of matter and to devising of new applications. In this article, we review the recent progress in the colloid-chemical synthesis of nonspherical nanoparticles of a few important noble metals (mainly Ag, Au, Pd, and Pt), highlighting the factors that influence the particle morphology and discussing the mechanisms behind the nonspherical shape evolution. The article attempts to present a thorough discussion of the basic principles as well as state-of-the-art morphology control in noble metal nanoparticles. [source] A New Method of Carbon-Nanotube Patterning Using Reduction PotentialsADVANCED MATERIALS, Issue 12 2009Jong Hak Lee Noble metals promote the oxidation of carbon nanotubes (CNTs) at the relatively low temperature of 350,°C. The reduction potential of multiwalled CNTs is located between those of W and Ni, while that of single-walled CNTs is between those of Ni and In. Nanometer-sized patterns on CNT films were successfully fabricated using differences in reduction potential between the CNTs and noble metals. [source] Trace Water-Promoted Oxidation of Benzylic Alcohols with Molecular Oxygen Catalyzed by Vanadyl Sulfate and Sodium Nitrite under Mild ConditionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2009Zhongtian Du Abstract An inexpensive catalytic system consisting of vanadyl sulfate and sodium nitrite was developed for the oxidation of benzylic alcohols with molecular oxygen under mild conditions. Benzyl alcohols with various substitutions were efficiently converted to their corresponding aldehydes with high conversion and selectivity under 80,°C (e.g., 4-nitrobenzyl alcohol was smoothly oxidized to 4-nitrobenzyl aldehyde with 94% yield under 0.5,MPa of molecular oxygen). Halogen, noble metals, extra base or complicated ligands were avoided. Addition of a trace of water to this system before the reaction was crucial for the high efficiency. [source] Millisecond catalytic reforming of monoaromatics over noble metalsAICHE JOURNAL, Issue 4 2010C. M. Balonek Abstract The millisecond autothermal reforming of benzene, toluene, ethylbenzene, cumene, and styrene were independently studied over five noble metal-based catalysts: Pt, Rh, Rh/,-Al2O3, Rh,Ce, and Rh,Ce/,-Al2O3, as a function of carbon-to-oxygen feed ratio. The Rh,Ce/,-Al2O3 catalyst exhibited the highest feedstock conversion as well as selectivities to both synthesis gas and hydrocarbon products (lowest selectivities to H2O and CO2). Experimental results demonstrate a high stability of aromatic rings within the reactor system. Benzene and toluene seem to react primarily heterogeneously, producing only syngas and combustion products. Ethylbenzene and cumene behaved similarly, with higher conversions than benzene and toluene, and high product selectivity to styrene, likely due to homogeneous reactions involving their alkyl groups. Styrene exhibited low conversions over Rh,Ce/,-Al2O3, emphasizing the stability of styrene in the reactor system. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] The effect of pH on the corrosion of dental metal alloysJOURNAL OF ORAL REHABILITATION, Issue 7 2000G. Bayramo The aim of this study was to determine the effects of the oral environment's pH on the corrosion of dental metals and alloys that have different compositions, using electrochemical methods. The corrosion rates and the cathodic Tafel slopes were obtained from the current,potential curves. The effect of pH on the corrosion of dental metals and alloys was dependent on their composition. Dissolution of the ions occurred in all of the tested pH states. The dissolution was moderately low for samples containing titanium because its surface was covered with a protective layer, whereas the dissolution was maximal for the samples containing tin and copper. Addition of cobalt and molybdenum to the alloys improved their corrosion resistance; these cobalt and molybdenum alloys were not effected by changes in the pH. Dissolution of the precious metal alloys increased as the percentage of noble metals increased. The corrosion characteristics of dental metals and alloys are important because the corrosion tendencies of dental alloys in the mouth may cause health hazards, weakening and the aesthetic loss of dental restorations. [source] Surface-enhanced Raman scattering from gold-coated germanium oxide nanowiresJOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2008Muhammad A. Khan Abstract We utilized bulk-synthesized nanowires (NWs) of germanium dioxide as nanoscale structures that can be coated with noble metals to allow the excitation of surface plasmons over a broad frequency range. The NWs were synthesized on substrates of silicon using gold-catalyst-assisted vapor,liquid,solid (VLS) growth mechanism in a simple quartz tube furnace setup. The resulting NWs have diameters of ,100,200 nm, with lengths averaging ,10,40 µm and randomly distributed on the substrate. The NWs are subsequently coated with thin films of gold, which provide a surface-plasmon-active surface. Surface-enhanced Raman scattering (SERS) studies with near-infrared (NIR) excitation at 785 nm show significant enhancement (average enhancement > 106) with good uniformity to detect submonolayer concentrations of 4-methylbenzenethiol (4-MBT), trans -1,2-bis(4-pyridyl)ethylene (BPE), and 1,2-benzendithiol (1,2-BDT) probe molecules. We also observed an intense, broad continuum in the Raman spectrum of NWs after metal coating, which tended to diminish with the analyte monolayer formation. Copyright © 2008 John Wiley & Sons, Ltd. [source] Noble Metal Decoration and Alignment of Carbon Nanotubes in Carboxymethyl CelluloseMACROMOLECULAR RAPID COMMUNICATIONS, Issue 2 2008Mallikarjuna N. Nadagouda Abstract A facile microwave method (MW) is described that accomplishes alignment and decoration of noble metals on carbon nanotubes (CNT) wrapped with carboxymethyl cellulose (CMC). Carbon nanotubes such as single- and multi-walled, and Buckminsterfullerene (C-60) are well dispersed using the sodium salt of CMC under sonication. Addition of respective noble metal salts then generates noble metal-decorated CNT composites at room temperature. However, aligned nanocomposites of CNTs could only be generated by exposing the above nanocomposites to MW irradiation. The CNT composites are characterized using scanning electron microscopy, energy dispersive X-ray analysis, X-ray mapping, transmission electron microscopy, and UV-visible spectroscopy. The general preparative procedure is versatile and provides a simple route to manufacturing useful metal-coated CNT nanocomposites. [source] Silver nanocluster containing diamond like carbonPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2008F. Schwarz Abstract Applying Diamond Like Carbon (DLC) as medical coating has become well established since large scale plasma processes like Plasma Immersion Ion Implantation and Deposition (PIII&D) are available. Now the focus of research lies on systematic modification of certain biological relevant properties and the most recent field of interest turned to generating antimicrobial behaviour. This is desirable for medical tools as well as for different types of medical implants. Since silver and copper are known to provide a bactericidal effect, one tries to introduce clusters of these noble metals into the carbon matrix. The basic principle of the method presented is to convert a metal containing polymer film into DLC by ion bombardment. In this paper the hydrogenated DLC matrix is characterized and the evolution of the metal particles is studied. By means of film composition (RBS/ERD), bonding structure (Raman spectroscopy) and hardness (nanoindentation), the dependency of these material properties on ion species, energy and fluence is investigated. TEM imaging is used to visualize the film structure. Upon ion irradiation of the polymer films, increased density and considerable loss of hydrogen can be observed, which both are controlled by ion fluence and mass. The crosslinking of the carbon network, caused by hydrogen drive out as well as atomic displacements in collision cascades, results in the formation of a-C:H. The silver particles in the film some ion induced growth, but still remain as nanoclusters in the a-C:H matrix. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Cretaceous Volcanic Events in Southeastern Jilin Province, China: Evidence from Single Zircon U-Pb AgesACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 6 2008CHEN Yuejun Abstract: Mesozoic volcanic rocks in southeastern Jilin Province are an important component of the huge Mesozoic volcanic belt in the northeastern area. Study of the age of their formation is of great significance to recognize Mesozoic volcanic rule in northeastern China. Along with the research of rare Mesozoic biota and extensive Mesozoic mineralization in western Liaoning, a number of researchers have focused on Mesozoic volcanic events. The authors studied the ages of the Cretaceous volcanic rocks in southeastern Jilin Province using single Zircon U-Pb. The result shows that the Sankeyushu Formation volcanic rocks in the Tonghua area are 119.2 Ma in age, the Yingcheng Formation in the Jiutai area 113.4±3.1 Ma, the Jinjiatun Formation in Pinggang Town of Liaoyuan City and the Wufeng volcanic rocks in the Yanji area 103.2±4.7 Ma and 103.6±1 Ma, respectively. Combined with the data of recent publication on volcanic rocks ages; the Cretaceous volcanic events in southeastern Jilin Province can be tentatively subdivided into three eruption periods: 119 Ma, 113 Ma and 103 Ma. The result not only provides important chronology data for subdividing Mesozoic strata in southeastern Jilin Province, establishing Mesozoic volcanic event sequence, discussing geological tectonic background, and surveying the relation between noble metals to the Cretaceous volcanic rocks, but also offers important information of Mesozoic volcanism in northeastern China. [source] A General Approach to Fabricate Diverse Noble-Metal (Au, Pt, Ag, Pt/Au)/Fe2O3 Hybrid NanomaterialsCHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2010Jun Zhang Dr. Abstract A novel, facile, and general one-pot strategy is explored for the synthesis of diverse noble-metal (Au, Pt, Ag, or Pt/Au)/Fe2O3 hybrid nanoparticles with the assistance of lysine (which is a nontoxic, user friendly amino acid that is compatible with organisms) and without using any other functionalization reagents. Control experiments show that lysine, which contains both amino and carboxylic groups, plays dual and crucial roles as both linker and capping agents in attaching noble metals with a small size and uniform distribution onto an Fe2O3 support. Considering the perfect compatibility of lysine with organism, this approach may find potentials in biochemistry and biological applications. Furthermore, this novel route is also an attractive alternative and supplement to the current methods using a silane coupling agent or polyelectrolyte for preparing hybrid nanomaterials. To demonstrate the usage of such hybrid nanomaterials, a chemical gas sensor has been fabricated from the as-synthesized Au/Fe2O3 nanoparticles and investigated for ethanol detection. Results show that the hybrid sensor exhibits significantly improved sensor performances in terms of high sensitivity, low detection limit, better selectivity, and good reproducibility in comparison with pristine Fe2O3. Most importantly, this general approach can be further employed to fabricate other hybrid nanomaterials based on different support materials. [source] Facile Synthesis of Gold Octahedra by Direct Reduction of HAuCl4 in an Aqueous SolutionCHEMISTRY - AN ASIAN JOURNAL, Issue 6 2010Weiyang Li Abstract This paper describes a water-based protocol that provides a simple, convenient, and environmentally benign route to the synthesis of Au octahedra. Specifically, we obtained single-crystal Au octahedra (ca.,85,% of the product) with an edge length of 32.4±2.3,nm and singly twinned, truncated bipyramids (ca.,15,%) by reducing HAuCl4 with N -vinyl pyrrolidone in an aqueous solution in the presence of a proper amount of cetyltrimethylammonium chloride (CTAC). Our mechanistic study indicates that the formation of Au octahedra could be explained by oxidative etching, a pathway that has already been validated for the synthesis of nanocrystals for a number of different noble metals. [source] | |||||||||||||