Gold nanoparticles core-shell structure

Mizukoshi Y, Fujimoto T, Nagata Y, Oshima R, Maeda Y (2000) Characterization and catalytic activity of core-shell structured gold/palladium bimetallic nanoparticles synthesized by the sonochemical method. J Phys Chem B 104 6028-6032... 

M. M. Maye, J. Luo, L. Han, N. Kariuki, and C. J. Zhong, Synthesis, processing, assembly and activation of core-shell structured gold nanoparticle catalysts. Gold Bull. 36, 75-82 (2003). 

Successive Reduction of Metal Ions. Successive reduction of two metal salts can be considered as one of the most suitable methods to prepare core/shell structured bimetallic particles (Fig. 9.1.3). In 1970, Turkevich and Kim tried to grow gold on Pd nanoparticles to obtain gold-layered Pd nanoparticles (39). The deposition of one... 

Figure 21.4 Influence of nanoparticle size on silica-type mesostructuie. (a, b) TEM micrographs showing mesostructuies with a nanoparticle volume fraction

In Fig. 6, we illustrate some different ways that the core-shell topology could be varied for silica and gold. So far we have considered the two normal core-shell structures. We now focus on the third example the assembly of Au Si02 nanoparticles onto spherical polystyrene latex colloids. The resulting spheres are also essentially different to continuous metal shells grown on colloid templates, which have been reported by Halas and colleagues [17] and by van Blaaderen and coworkers [18]. Such continuous shells display optical properties associated with resonances of the whole shell, and are therefore extremely sensitive to both core size and shell thickness, while in the system presented here... 

Xing, S., Tan, L.H., Yang, M., Pan, M., Lv, Y, Tang, Q., Yang, Y, Chen, H., 2009. Highly controlled core/shell structures tunable conductive polymer shells on gold nanoparticles and nanochains. J. Mater. Chem. 19,3286-3291. 

Some work has also been recently carried out on the solution synthesis of bimetallic nanorods, employing gold nanorods as preformed cores. Jang and co-workers synthesized Au Ag core-shell nanorods using the electrochemical method to obtain the gold nanorods and the seed-mediated mechanism to get the desired core-shell structure. The combination of the different optical resonances from the core and the shell metals leads to a quite spectacular optical spectrum from these composite, anisotropic nanoparticles. 

Competitive reduction of Au(III) and Ag(I) ions occurs simultaneously in solution during exposure to neem leaf extract leads to the preparation of bimetallic Au-core/Ag-shell nanoparticles in solution. TEM revealed that the silver nanoparticles are adsorbed onto the gold nanoparticles, forming a core/sheU structure. Panigrahi et al. [121] reported that sugar-assisted stable Au-core/Ag-shell nanoparticles with particles size of ca. 10 nm were prepared by a wet chemical method. Fructose was found to be the best suited sugar for the preparation of smallest particles. 

We have extended the seed-mediated technique for the synthesis of bimetallic nanoparticles, having core-shell type structure appending photoreduction of metal ions. It has been proved that the deposition of a less noble metal (M) as shell on a preformed nobler nanoparticle core (M ) seems to be very effective by UV activation. Using this seed-mediated method we were able to synthesize Aucore Agsheii particles. First for the preparation of gold seeds (S), TX-lOO (10 M) and HAuC (5.0 x 10 %) were taken in a quartz cuvette so that the final concentration of Au(III) ion remained 5.0 x 10 M. Then the... 

Osterloh, F. Hiramatsu, H. Porter, R. Guo, T., Alkanethiol induced structural rearrange ments in silica gold core shell type nanoparticle clusters An opportunity for chemical sensor engineering, Langmuir. 2004, 20, 5553 5558... 

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