Sonochemical preparation, nanoparticles bimetallic

Mizukoshi Y, Okitsu K, Yamamoto T, Oshima J, Nagata Y, Maeda Y (1997) Sonochemical preparation of bimetallic nanoparticles of gold/palladium in aqueous solution. J Phys Chem B 101 7033-7037... 

Other one-pot preparations of bimetallic nanoparticles include NOct4(BHEt3) reduction of platinum and ruthenium chlorides to provide Pto.sRuo.s nanoparticles by Bonnemann et al. [65-67] sonochemical reduction of gold and palladium ions to provide AuPd nanoparticles by Mizukoshi et al. [68,69] and NaBH4 reduction of dend-rimer—PtCl4 and -PtCl " complexes to provide dend-rimer-stabilized PdPt nanoparticles by Crooks et al. [70]. 

Vinodgopal K, He Y, Ashokkumar M, Grieser F (2006) Sonochemically prepared platinum-ruthenium bimetallic nanoparticles. J Phys Chem B 110 3849-3852... 

Sonochemical Preparation of Monometallic, Bimetallic and Metal-Loaded Semiconductor Nanoparticles... 

Abstract A convenient method to synthesize metal nanoparticles with unique properties is highly desirable for many applications. The sonochemical reduction of metal ions has been found to be useful for synthesizing nanoparticles of desired size range. In addition, bimetallic alloys or particles with core-shell morphology can also be synthesized depending upon the experimental conditions used during the sonochemical preparation process. The photocatalytic efficiency of semiconductor particles can be improved by simultaneous reduction and loading of metal nanoparticles on the surface of semiconductor particles. The current review focuses on the recent developments in the sonochemical synthesis of monometallic and bimetallic metal nanoparticles and metal-loaded semiconductor nanoparticles. 

Vinodgopal et al. prepared Pt/Ru bimetallic nanoparticles by sonochemical reduction of Pt(II) and Ru(III) in aqueous solutions. TEM images indicated that sequential reduction of the Pt(II) followed by the Ru(III) produced Pt-core/Ru-shell bimetallic nanoparticles. In the presence of sodium dodecyl sulfate (SDS), as a stabilizer, the nanoparticles had diameters between 5 and 10 nm. When PVP was used as the stabilizer, the rate of reduction is much faster, giving ultrasmall bimetallic nanoparticles of ca. 5nm diameter [141]. 

Kan et al. reported preparation of Au-core/Pd-shell bimetallic nanoparticles by successive or simultaneous sonochemical irradiation of their metal precursors in ethylene glycol, respectively. In the successive method, Pd clusters or nanoparticles are first formed by reduction of Pd(N03)2, followed by adding HAUCI4 solution. As a result, Au-core/Pd-shell structured particles are formed, although Pd-core/Au-shell had been expected. In their investigations, the successive method was more effective than the simultaneous one in terms of the formation of the Au-core/Pd-shell nanoparticles [143]. 

It has been reported that bimetallic nanoparticles with core/shell structure can be prepared by ultrasonic irradiation. Mizukoshi et al. reported the formation of bimetallic nanoparticles of Au core/Pd shell structure [42,43] from the sonochemical reduction of Au(III) and Pd(II), where the stepwise reduction of metal ions was observed to proceed during ultrasonic irradiation. That is, the reduction of Pd(II) started after the reduction of Au(III) finished. Vinodgopal et al. reported... 

Catalytic activities of Au core/Pd shell bimetallic nanoparticles have also been investigated [43,44], Okitsu et al. reported that catalytic activities are closely related to the nanostructure of bimetallic nanoparticles [44], where Au core/Pd shell bimetallic nanoparticles on and inside Si02 are prepared by consecutive sonochemical and sol-gel processes. 

Fig. 6.10 UV-vis absorption spectra of gold - ruthenium bimetallic nanoparticles prepared by the sonochemical co-reduction method using (a) 1 1 and (b) 1 5 gold - ruthenium compositions, respectively [45]...

In this review, the potential uses of sonochemistry for the preparation of monometallic and bimetallic metal nanoparticles and metal-loaded semiconductor nanoparticles have been highlighted. While specific examples available in the literature were discussed, the sonochemical technique seems to offer a platform technique that could be used for synthesizing a variety of functional materials. Most of the studies to date deal with laboratory scale exploration , it would be ideal if the concepts are tested under large scale experimental conditions involving specific applications. The authors sincerely hope that the information provided in this review would prompt such experimental investigation in a new dimension. 

Recently it was proposed that PEMLC electrocatalysts may also be prepared by water-in-oil microemulsions. These are optically transparent, isotropic, and thermodynamically stable dispersions of two nonmiscible liquids. The method of particle preparation consists of mixing two microemulsions carrying appropriate reactants (metal salt + reducing agent), to obtain the desired particles. The reaction takes place during the collision of water droplets, and the size of the particles is controlled by the size of the droplets. Readers are referred to the early work of Boutonnet et al. [149], the review paper of Capek [150] and refs. [128,151], and 152 for fuel cell apphcations. The carbonyl route has the ability to control the stoichiometry between bimetallic nanoparticles, but also the particle size. The reader is referred to review papers for more details [106,107]. Other methods, including sonochemical and radiation-chemical, have been used successfully for the preparation of fuel cell catalysts (see, e.g., review articles 100 and 153). 

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