Ag nanowire

Linic and co-workers provided two additional examples of modifying selectivity for the ethylene epoxidation reaction. They demonstrated the promotional effect of Cs on EO formation using DFT calculations Cs atoms increase AEa by up to 0.2 eV vs. Ag only, via an induced electric field that interacts with the different dipoles of the two TS s." More recently Christopher et al. synthesized and tested (100) facet-dominated Ag nanowire catalysts, based on the DFT results that AEa is ca. 0.1 eV larger on Ag(lOO) than on Ag(lll), because of the extra elongation of the Ag-adsorbate bonds required to form the TS to AC on Ag(lOO). The Ag nanowire catalysts were indeed more selective than conventional Ag catalysts, in which Ag particles mainly exposes the (111) facet." Incidentally,... 

The synthesis of conductive metallic nanowires that bridged two microelectrodes separated by a gap of 12-16 im was demonstrated by the growth of a silver nanowire on a DNA template that bridged the gap (Fig. 12.26).92 Short thiolated nucleic acids (12 bases long) were attached to the microelectrodes, and these acted as sticky ends for the hybridization of /.-DNA that bridged the gap. The association of Ag+ to the phosphate groups of the template, followed by their reduction with hydroquinone under basic conditions, resulted in the formation of Ag° nanoclusters on the DNA template. The subsequent enlargement of the Ag° seeds by the catalytic reduction of Ag+ by hydroquinone, under acidic conditions, yielded continuous Ag nanowires with a width of ca. lOOnm. The nanowires revealed nonlinear I—V... 

A popular method for the synthesis of metal nanowires is the use of the polyol process,lal wherein the metal salt Is reduced in the presence of PVP to yield nanowires of the desired metal. For example, Ag nanowires have been rapidly synthesized using a microwave-assisted polyol method.161 CoNi nanowires are obtained by heterogeneous nucleation in liquid polyol.162 While Bi nanowires have been prepared employing NaBiO, as the bismuth source.161 Pd nanobars are synthesized by varying the type and concentration of reducing agent as well as reaction temperature.1 ... 

One family of new materials with potential use in metal catalysis is that of metal nanostructures such as metal nanoparticles (see Metal Nanoparticles, Synthesis of and Metal Nanoparticles, Organization Applications of), nanoshells, nanowires, nanorods, nanotubes, nanobelts, and nanoplates. " For instance, it has been recently shown that Ag nanowires and nanoparticles can be produced by... 

Figure 9 Examples of novel materials with potential catalytic applications. From left to right and top to bottom, these pictures represent (a) Ag nanowires. (Reprinted with permission from Ref 63. 2002 American Chemical Society) (h)Ag nanoparticles. (Reprinted with permission from Y. Sim and Y. Xia, Science, 2002, 298, 2176. 2002 AAAS (www.sciencemag.org)) (c) zeolite monolith. (Ref. 67. Reproduced hy permission of Kluwer Academic/Plenum Publishers) (d) zeolite coatings on stainless steel grids. (Ref 68. Reproducedby permission of Wiley-VCH) (e) arrays of Pt nano lithography-made particles on Si02. (Ref. 70. Reproduced by permission of Kluwer Academic/Plenum Publishers) and (f) Ag nanoparticles vapor deposited on an AI2O3 thin film ...

Stoermer, R. L. and Keating, C. D. (2006). Distance-dependent emission from dye-labeled oligonucleotides on striped Au/Ag nanowires Effect of secondary structure and hybridization efficiency. J. Am. Chem. Soc. 128 13243-13254. 

Recently, Sun et al. [60] proposed to fabricate Ag nanostructures by electrochemical deposition of Ag in anodic aluminum oxide templates with each pore diameter of 100 nm. The morphology of Ag substrates was characterized by EESEM. The length of the Ag nanowires is estimated to be about 2 pm from the EESEM images. In addition, the SERS enhancement factor calculated for Ag nano wires SERS substrates is approximately 10 in magnitude. The Ag nano wire arrays are expected to have important applications in the development of high sensitivity SERS-based substrates. 

Fig. 10.15 (a) OWL methodology, (b, c) SEM images of multi-segment metallic Au-Ag nanowires with gaps of 25, 50, and 100 nm. (d, e) SEM and Raman microscopy of smooth and rough gapped rods produced by OWL (Figure reproduced from Refs. [67] and [178])... 

Fig. 9 TEM image of Ag nanowires electrodeposited from the Hn mesophase of AOT. Reproduced with permission from [50]. 2002 by Wiley-VCH...

Composites with one-dimensional structure can also be fabricated by template-free method. They are formed via an in situ synthetic process. For instance, Ag/PPy nanocables have been prepared through the redox reaction between pyrrole and silver nitrite in aqueous solution in the presence of polyvinylpyrrolidone. During the reaction process, the formation of Ag nanowires and the polymerization of a pyrrole sheath were proceeded simultaneously. The as-synthesized Ag/PPy nanocables displayed a coaxial nanostructure with a dark core and a lighter sheath (Fig. 4.3I-J) (Chen et al., 2005). The diameter of the Ag nanowire core was about 20 nm, while the outer diameter of PPy sheath reached about 50 nm. 

Kang MG, Xu T, Park HJ, Luo X, Guo LJ (2010) Effi-citaicy enhancement of organic solar cells using transparent plasmonic Ag nanowire electrodes. Adv Mater 22 4378... 

Fig. 11.8 Magic numbers for Ag nanowires for the thinning process (changes in cross section) and the fractional quantum conductance (Reproduced from Ref. [27] with kind permission of The American Physical Society)...

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