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Journal ArticleDOI

Polyoxometalate based soft chemical route for preparation of Pt nanorods and self-assemblies

TL;DR: In this paper, a soft chemical route is described for the preparation of platinum nanorods and self-assemblies over photochemically reduced polyoxometalate (silicotungstate) containing composite films.
Abstract: A soft chemical route is described for the preparation of platinum nanorods and self-assemblies over photochemically reduced polyoxometalate (silicotungstate) containing composite films. Transmission electron microscopy shows that the diameters of the platinum nanorods are around 55–60 nm. The formation of platinum nanorods on solid-liquid interface reactions was explained on the basis of single site growth mechanism and diffusion limitation aggregation process.

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TL;DR: In this paper, zinc oxide nanoparticles were prepared by a wet chemical method using zinc nitrate and sodium hydroxide as precursors and soluble starch as stabilizing agent.
Abstract: Nanotechnology, according to the National Nanotechnology Initiative (NNI), is defined as utilization of structure with at least one dimension of nanometer size for the construction of materials, devices or systems with novel or significantly improved properties due to their nano-size. The nanostructures are capable of enhancing the physical properties of conventional textiles, in areas such as anti-microbial properties, water repellence, soil-resistance, anti-static, anti-infrared and flame-retardant properties, dyeability, colour fastness and strength of textile materials. In the present work, zinc oxide nanoparticles were prepared by wet chemical method using zinc nitrate and sodium hydroxide as precursors and soluble starch as stabilizing agent. These nanoparticles, which have an average size of 40 nm, were coated on the bleached cotton fabrics (plain weave, 30 s count) using acrylic binder and functional properties of coated fabrics were studied. On an average of 75%, UV blocking was recorded for the cotton fabrics treated with 2% ZnO nanoparticles. Air permeability of the nano-ZnO coated fabrics was significantly higher than the control, hence the increased breathability. In case of nano-ZnO coated fabric, due to its nano-size and uniform distribution, friction was significantly lower than the bulk-ZnO coated fabric as studied by Instron® Automated Materials Testing System. Further studies are under way to evaluate wash fastness, antimicrobial properties, abrasion properties and fabric handle properties.

423 citations


Cites methods from "Polyoxometalate based soft chemical..."

  • ...A method for the preparation of platinum nanorods and self-assemblies of nanorods using reduced silicotungstate-based composite at room temperature is demonstrated (Shanmugam et al 2005)....

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References
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Journal ArticleDOI
TL;DR: In this article, the authors demonstrate the first successful fabrication of crystalline silver nanowire arrays with a high aspect ratio by electrodeposition from a reverse hexagonal liquid-crystalline phase containing one-dimensional aqueous channels.
Abstract: One-dimensional (1D) nanowires and nanowire arrays of metal, semiconductor, and conductive polymers have attracted much attention because of their unique electrical, magnetic, optical, and mechanical properties, and their potential application in nanodevices. Although other successful approaches such as vapor±solid and liquid±solid phase methods exist for silicon and other semiconductor nanowires, the most widely used method for fabrication of nanowires and nanowire arrays is still chemical or electrochemical deposition guided by an appropriate porous ahardo template such as anodized alumina, track-etched polycarbonate and mica, carbon nanotubes, zeolite/mesoporous silica, and diblock copolymers. Step edges of freshly cleaved graphite and a conducting quantum well in a semiconductor multilayer prepared by molecular beam epitaxy also have been used as nanowire growth guides. The hard template approach is an effective route to metal, semiconductor, and polymer nanowires; however, most of the templates are tedious to fabricate and dissolution of the template in corrosive media is required to retrieve the nanowires if separate single wires are desired. Surfactant mesophases have proved to be a useful and versatile asofto template for the synthesis of nanostructured materials. For example, syntheses of porous zeolite-type materials using normal (oil in water) surfactant mesophases as a template are well established. Reverse (water in oil) micelles and microemulsions with spherical aqueous microdomains have been used for nanoparticle and sometimes nanowire synthesis (mainly compounds such as BaSO4 and BaCrO4). [21±24] All of the aforementioned syntheses use low surfactant concentrations where liquid-crystalline phases are not present. In contrast, at high surfactant concentrations, homogeneous normal or reverse hexagonal liquid-crystalline phases can be obtained. Attard et al. and others have demonstrated that normal hexagonal liquid crystals can template the synthesis of bulk porous materials and porous metal films by electrodeposition. Very recently, a reverse hexagonal liquid crystal was used as a template to synthesize ZnS nanowires by gamma ray irradiation. The ZnS nanowires so obtained are fairly short (<2 lm) probably due to the random orientation of the reverse hexagonal liquid crystal. In this communication, we demonstrate for the first time fabrication of crystalline silver nanowire arrays with a high aspect ratio by electrodeposition from a reverse hexagonal liquid-crystalline phase containing one-dimensional aqueous channels. We provide evidence that a high electric field during electrodeposition helps align the reverse hexagonal liquidcrystalline phase, which is believed to be essential for production of high aspect ratio crystalline metal nanowires. For growth of silver nanowires, a reverse hexagonal liquidcrystalline phase was first prepared according to the wellknown ternary phase diagram consisting of the anionic surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT), an oil phase of p-xylene, and water. For our synthesis the water phase was substituted by an aqueous 0.1 M AgNO3 solution. The resulting mixture has the characteristic birefringence of a hexagonal liquid crystal when viewed under a polarized light microscope. The electrodeposition was conducted by using a potentiostat in a two-electrode configuration with the two electrodes narrowly spaced (0.5±1.0 mm) and the aforementioned reverse liquid-crystalline phase as electrolyte. The nanowire product deposited on the cathode substrate (polished stainless steel) was thoroughly washed with ethanol. High-density nanowire arrays were obtained over a short deposition time of 15 min with the nanowires roughly perpendicular to the cathode surface (Fig. 1A). The slight disorder in the nanowire array may arise from the washing process after deposition. After a deposition time of 2 h, nanowires tens of micrometers long were obtained (Fig. 1B). The nanowires were almost parallel (no longer perpendicular) to the electrode surface, most probably due to the washing process after deposition. The high-density nanowire array can be separated into single wires after ultrasonic dispersion in ethanol (Fig. 1C), indicating that the nanowires can be used in a bundle form or as single wires for nanodevices. Figure 2 shows the X-ray diffraction (XRD) pattern of the silver nanowire arrays deposited on a stainless steel substrate. It shows the diffraction peaks with d-spacings of 2.36 Š, 2.04 Š, 1.44 Š, 1.23 Š, and 1.18 Š, which are consistent with that of face centered cubic (fcc) Ag metal phase. Energy dispersive X-ray (EDX) analysis shows that the wires are made of pure silver, suggesting that surfactant molecules can be totally removed from the nanowire arrays by a simple washing process. Transmission electron microscopy (TEM) images and electron diffraction of nanowires are shown in Figure 3. Figures 3A and 3B show a bright field (BF) and dark field (DF) image, respectively, of a fragment of a single silver nanowire. The entire crystal is bright in DF mode with operating reflection (11Å1), confirming the single crystal nature of the nanowire. The individual wire is either a single crystal or consists of symmetrically oriented domains that are twinned on {111} planes. The twinned nanowire crystals are made of multiple

129 citations


"Polyoxometalate based soft chemical..." refers methods in this paper

  • ...…and their arrays, the widely used method is still chemical or electrochemical deposition directed by an appropriate porous “hard” template such as alumina membranes, diblock copolymers, carbon nanotubes and zeolite/mesoporous silica (Sloan et al 1999; Zhang et al 1999; Huang et al 2000, 2002)....

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Journal ArticleDOI
TL;DR: In this paper, the photo-reduction method was used for the catalysts for the hydrogenation of hexachloroplatinic acid in an aqueous solution, and the results showed that the colloidal clusters prepared by the photo reduction method showed higher activity than those prepared by other methods.
Abstract: Colloidal dispersions of platinum and palladium clusters were prepared by the reduction of the corresponding metal salts in the presence of various surfactants. Hydrogen- and photo-reduction methods were examined for the micellar solution of hexachloroplatinic acid. The photo-reduction was proved to be more suitable than the hydrogen-reduction from the viewpoint of small size and good dispersion in the colloidal clusters. The higher surfactant concentration than the critical micelle concentration (cmc) is favorable for the production of the homogeneous colloidal dispersions. The photo-reduction method is also available for the case of palladium. The colloidal platinum and palladium clusters, thus obtained, act as highly active catalysts for the hydrogenation of olefin in an aqueous solution. The colloidal clusters prepared by the photo-reduction method showed higher activity than those prepared by other methods. The roles of the surfactant micelle for the hydrogenation are not only protecting hydrophobic ...

127 citations


"Polyoxometalate based soft chemical..." refers methods in this paper

  • ...Soft chemical methods have been employed for the synthesis of noble metal sols (Toshima and Takahashi 1992; Duff et al 1995; Attard et al 1997; Thurn-Albrecht et al 2000; Chen and Kimura 2001; Pol et al 2003) which in- volve the reduction of relevant metal salt in the presence of a suitable…...

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Journal ArticleDOI
TL;DR: In this paper, water-dispersible, isolable thiolate-stabilized platinum nanoparticles are synthesized by two one-phase methods: one is conducted in water; another mainly in methanol, through the reduction of chloroplatinic acid with sodium borohydride, using mercaptosuccinic acid (MSA) as the stabilizer.
Abstract: Water-dispersible, isolable thiolate-stabilized platinum nanoparticles are synthesized by two one-phase methods: one is conducted in water; another mainly in methanol, through the reduction of chloroplatinic acid with sodium borohydride, using mercaptosuccinic acid (MSA) as the stabilizer. The well-separated particles with mean diameter of 2.5 nm are obtained in water when the initial molar ratio of MSA to chloroplatinic acid (S/Pt) is 0.7. High-resolution transmission electron microscopy reveals that most particles are fcc single crystals of cuboctahedral or truncated octahedral morphology with cell parameter similar to that of bulk Pt. The average particle diameter increases from 2.5 nm to around 4.7 nm upon decreasing the S/Pt ratio from 0.7 to 0.1; at the same time, particle aggregation occurs due to the incomplete coverage of thiolate molecules on the particle surface. The particles with mean diameter of 2.3 nm are also obtained while using methanol as the solvent at an initial S/Pt ratio of 0.5. Ex...

123 citations

Journal ArticleDOI
TL;DR: In this paper, the coagulation of Au nanoparticles dispersed in organic liquids was dramatically accelerated under the illumination of light and was clarified through the wavelength dependence of the irradiation that particles coagulated with visible light and coalesced upon irradiation of UV light.
Abstract: The coagulation of Au nanoparticles dispersed in organic liquids was dramatically accelerated under the illumination of light It was clarified through the wavelength dependence of the irradiation that particles coagulated with the illumination of visible light and coalesced upon irradiation of UV light The coagulation process was characteristic of the surface plasmon oscillation of small metallic particles but not of the interband transition The enhanced van der Waals attraction force or the photoinduced deionization of particles is suggested to be a cause of this finding Particle clustering proceeded 1-dimensionally at the early stage and 17-dimensionally in the fractal dimension at the later stage of the coagulation

120 citations


"Polyoxometalate based soft chemical..." refers background in this paper

  • ...For silver and gold nanoparticles, the red shift of surface plasmon band have been observed as the particles grow (Satoh et al 1994), but for the platinum nanoparticles (Weaver et al 1981), the surface plasmon band is weak and blue shifted....

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Journal ArticleDOI
TL;DR: Controlled colloidal synthesis (CCS) was developed to prepare monodisperse palladium particles in the nano-scale range on suspended SiO2 particles in an ethanol-toluene mixture as mentioned in this paper.
Abstract: Controlled colloidal synthesis (CCS) was developed to prepare monodisperse palladium particles in the nano-scale range on suspended SiO2 particles in an ethanol–toluene mixture. On colloidal SiO2 an about 1 nm thick ethanol-rich adsorption layer was produced in adsorption equilibrium with the liquid mixture. Ethanol served as a reducing agent for the Pd(II) ions diffusing from a toluene-rich liquid solution into the interfacial layer. The low reduction rate ensures the dominancy of particle growth over the nucleation of palladium during the reduction process after the initial nucleation. The relation between the reduction time and the particle size produced was studied. XRF, XPS, TEM, CO chemisorption, and benzene hydrogenation as catalytic test were employed to characterize the samples prepared using different reduction time.

57 citations


"Polyoxometalate based soft chemical..." refers background in this paper

  • ...Beck et al (2000) reported a controlled growth of palladium particles at the solid/liquid interface on silica....

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