Au@Pt core-shell

Au/Pt Core/shell - Au(III), Pt(IV) Trisodiimi citrate Tannic acid UV-Vis, TEM, EXAFS [123]... 

It is worthwhile to point out that during the last decade, carbon-supported Au Pt core—shell nanostructured catalysts were explored and synthesized to improve the ORR performance of the electrocatalyst. ° The results showed that the limiting... 

Guo S, Fang Y, Dong S, Wang E (2007) High-efficiency and low-cost hybrid nanomaterial as enhancing electrocatalyst spongelike Au/Pt core/shell nanomaterial with hollow cavity. JPhys Chem C 111(45) 17104-17109... 

Au-Pt core-shell water/AOT/isooctane N2H5OH, AuCU, PtClg " rigid 111]... 

Duan, M.Y, Liang, R., Tian, N. Li, Y.X Self-assembly of Au-Pt core-shell nanoparticles for effective enhancement of methanol electrooxidation. Electrochim. Acta 87 (2013), pp. 432-437. 

Zhai J, Huang M, Dong S (2007) Electrochemical designing of Au/Pt core shell nanoparticles as nanostructured cateilyst with tunable activity for oxygen reduction. Electroantilysis 19 506... 

In a similar vein of using nanomaterials, graphene has also been used as a support material in the form of a flexible graphene paper loaded with Au Pt core-shell nanoparticles the fabrication approach is shown in Fig. 16.11 where the hybrid electrode was fabricated through a modular approach in which the nanoparticle assembly was transferred onto graphene paper through dip-coating. ... 

Alayoglu S, Nilekar AU, Mavrikakis M et al (2008) Ru-Pt core-shell nanoparticles for preferential oxidation of carbon monoxide in hydrogen. Nat Mater 7 333-338... 

Harpeness et al. reported the synthesis of roughly spherical Au-Pd core-shell NCs by the MW-polyol-assisted simultaneous reduction of gold and palladium salts. In this case the largely different Au + or Au+ and PdJ redox potentials firstly ensured gold reduction and the formation of metal seeds which in turn promoted heterogeneous nucleation of Pd [255] (Fig. 10.11a). In a similar fashion Pd-Pt core-shell NCs consisting of cubic Pd NC evenly decorated by Pt pellets was very recently described [256] (Fig. 10.11b). 

The XRD and TEM showed that the bimetallic nanoparticles with Ag-core/Rh-shell structure spontaneously form by the physical mixture of Ag and Rh nanoparticles. Luo et al. [168] carried out structure characterization of carbon-supported Au/Pt catalysts with different bimetallic compositions by XRD and direct current plasma-atomic emission spectroscopy. The bimetallic nanoparticles were alloy. Au-core/Pd-shell structure of bimetallic nanoparticles, prepared by co-reduction of Au(III) and Pd(II) precursors in toluene, were well supported by XRD data [119]. Pt/Cu bimetallic nanoparticles can be prepared by the co-reduction of H2PtClg and CuCl2 with hydrazine in w/o microemulsions of water/CTAB/ isooctane/n-butanol [112]. XRD results showed that there is only one peak in the pattern of bimetallic nanoparticles, corresponding to the (111) plane of the PtCu3 bulk alloy. 

Recently characterization of bimetallic nanoparticles by EXAFS were extensively reported [122-124,176], Structural transformation of bimetallic Pd/Pt nanoparticles, which were prepared by a sequential loading of H2PtClg onto the Pd loaded catalyst, was investigated with EXAFS at high temperatures [176], The results of EXAFS at Pd K and Pt L-III edges showed that Pt was surface-enriched or anchored on the Pd metal core with an increase of the Pt content. The structure of the obtained bimetallic Pd/Pt nanoparticles seemed to be retained upon heating up to 1273 K under ambient condition [176], Pt/ Au bimetallic nanoparticles can be prepared by polyol method and stabilized by PVP [122], XANES and EXAFS studies were also performed on the samples and their results supported the idea of a Pt-core/Au-shell structure with the elements segregated from each other [122],... 

Chen et al. [123] examined the amount-dependent change in morphology for a series of Au/Pt bimetallic nanoparticles. The EXAFS results confirmed the formation of a core/shell structure and inter-diffusion between Au and Pt atoms. The composition of the shell layer was found to be Pt-enriched AuPt alloy. They also characterized bimetallic Ag-core/Au-shell nanoparticles by the EXAFS [124]. 

In Figure 12a (Pd Pt = 1 2) and 12b (Pd Pt = 1 1), only the spectral feature of CO adsorbed on the Pt atoms, i.e., a strong band at 2068 cm and a very weak broad band at around 1880 cm was observed, while that derived from CO adsorbed on Pd atoms at 1941 cm is completely absent, which proved that the Pd-core has been completely covered by a Pt-shell. Recently we also characterized Au-core/Pd-shell bimetallic nanoparticles by the CO-IR [144]. Reduction of two different precious metal ions by refluxing in ethanol/ water in the presence of poly(A-vinyl-2-pyrrolidone) (PVP) gave a colloidal dispersion of core/shell structured bimetallic nanoparticles. In the case of Pd and Au ions, the bimetallic nanoparticles with a Au-core/Pd-shell structure are usually produced. In contrast, it is difficult to prepare bimetallic nanoparticles with the inverted core/shell, i.e., Pd-core/Au-shell structure. A sacrificial hydrogen strategy is useful to construct the inverted core/shell structure, where the colloidal dispersions of Pd cores are treated with hydrogen and then the solution of the second element, Au ions, is slowly... 

Recently five monometallic (Au, Pd, Pt, Ru, Rh) nanoparticles were investigated as electron mediators together with four core/shell bimetallic (Au/Pd, Au/Pt, Au/Rh, Pt/ Ru) nanoparticles [53,194-196]. The linear relationship was observed between the electron transfer rate coefficients and the hydrogen generation rate coefficient as shown in Figure 15. 

Maye et al. studied gold nanoparticles supported on carbon black for ORR in both acidic and alkaline media.210 The gold nanoparticles were of a core-shell type where the particle consisted of a gold nanocrystal core of 1-6 nm in diameter that was surrounded by an organic monolayer shell.214 While the Au/C catalyst was found to be active for ORR, its activity was much lower than that of Pt/C, PtRu/C and AuPt/C. The electron transfer in 0.5 M H2S04 was reported as 2.9 0.2, indicating a mixed reduction pathway.210... 

Figure 5 shows two typical core-shell structures (a) contains a metal core and a dye doped silica shell [30, 32, 33, 78-85] and (b) has a dye doped silica core and a metal shell [31, 34]. There is a spacer between the core and the shell to maintain the distance between the fluorophores and the metal to avoid fluorescence quenching [30, 32, 33, 78-80, 83]. Usually, the spacer is a silica layer in this type of nanostructures. Various Ag and Au nanomaterials in different shapes have been used for fluorescence enhancement. Occasionally, Pt and Au-Ag alloys are selected as the metal. A few fluorophores have been studied in these two core-shell structures including Cy3 [30], cascade yellow [78], carboxyfluorescein [78], Ru(bpy)32+ [31, 34], R6G [34], fluorescein isothiocyanate [79], Rhodamine 800 [32, 33], Alexa Fluor 647 [32], NIR 797 [82], dansylamide [84], oxazin 725 [85], and Eu3+ complexes [33, 83]. 

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