Alloys nanoparticle formation

Scheme 3. Reaction mechanism of Au-Ag alloy nanoparticle formation.

Oezaslan M, Hasche F, Strasser P (2011) In situ observation of bimetallic alloy nanoparticle formation and growth using high-temperature XRD. Chem Mater 23(8) 2159-2165... 

Bimetallic nanoparticles, either as alloys or as core-shell structures, exhibit unique electronic, optical and catalytic properties compared to pure metallic nanopartides [24]. Cu-Ag alloy nanoparticles were obtained through the simultaneous reduction of copper and silver ions again in aqueous starch matrix. The optical properties of these alloy nanopartides vary with their composition, which is seen from the digital photographs in Fig. 8. The formation of alloy was confirmed by single SP maxima which varied depending on the composition of the alloy. 

Ag-core/Au-shell bimetallic nanoparticles were prepared by NaBH4 reduction method [124]. UV-Vis spectra were recorded and compared with various ratios of AuAg alloy nanoparticles. The UV-Vis spectra of bimetallic nanoparticles suggested the formation of core/shell structure. Furthermore, the high-resolution transmission electron microscopy (HRTEM) image of the nanoparticles confirmed the core/shell type configuration directly. 

By XPS spectra, Endo et al. [96] confirmed that formation of binary structure prevented Pd atoms from oxidation in the AuPd and PtPd bimetallic nanoparticles which exhibited higher catal5hic activity than monometallic ones. Wang et al. [112]. characterized PtCu bimetallic alloy nanoparticles Ijy XPS. XPS revealed that both elements in the nanoparticles are in zero-valence and possess the characteristic metallic binding energy. 

Chen YH, Yeh CS (2001) A new approach for the formation of alloy nanoparticles laser synthesis of gold-silver alloy from gold-silver colloidal mixtures. Chem Commun 371-372... 

The phase behavior of alloy nanoparticles may differ from that in the bulk due to the increased significance of surface effects. Ge and coworkers examined the heats of formation of Pt-Au nanoparticles up to 13 atoms and compared them to bulk heats of formation.For bulk systems they found the heats of formation of Pt-Au alloys were all small and positive indicating a tendency to phase separate at low temperatures. In contrast, the heats of formation of some of the alloy atom clusters were significantly negative indicating that alloy nanoparticles may readily form. The adsorption of CO on the Pt-Au nanoparticles was larger than that on the bulk surfaces, and CO preferentially adsorbs on Pt sites that are adjacent to Au atoms. 

Gold I Silver Alloy Formation A simple and usually not quite justified approach to predicting the position of the SPR maximum of an (Au/Ag)-alloy nanoparticle would be to calculate a linear combination of the dielectric functions of gold and silver nanoparticles [g(a) = (1 )sau + Unfortunately, this approach... 

Figure 16.4 Effect of gold-silver alloy formation on the surface plasmon absorption. Part (a) shows the UV/Vis absorption spectra of spherical gold-silver alloy nanoparticles of varying composition. The gold mole fraction Xau varies between 1.0 and 0.27. The dependence of the maximum of the plasmon absorption as a function of the nanoparticle composition and the particle diameter are given in (b) and (c), respectively. (Reproduced with permission from S. Link and M. El-Sayed, 1999 J. Phys. Chem. B 103 8410-8426. Copyright 1999 American Chemical Society.)...

Fig. 5.36 Schematic view of the mechanisms occurring at the surface of the silicon nanoparticles. Formation of the SEI at the beginning of discheirge. Formation of the Li-Si alloy upon further discharge, together with Li20 and LLSiOy interfacied phases (reproduced with permission by the American Chemical Society from [102])...

An attempt to produce PtBi alloy nanoparticles on carbon produced highly active catalysts for formic acid oxidation, although XRD showed no evidence of alloy formation [27]. Highest performances were obtained with a Bi Pt mole ratio of just 0.07. 

Corrias A, Navarra G, Casula MF, Marras S, Mountjoy, G (2005) An X-ray absorption spectroscopy investigation of the formation of FeCo alloy nanoparticles in AI2O3 xerogel and aerogel matrixes. J Phys Chem B 109 13964-13970... 

A continuous tuning of the positions of the plasmon absorption peak by alloy formation has been demonstrated. The dependence of the absorption spectra of Au—Ag alloy nanoparticles on the composition is reproduced in Fig. 5.3-16 [3.74]. 

Fig. 5.3-16 Effect of formation of a gold-silver alloy on the surface plasmon absorption measured UV-VIS absorption spectra of spherical Au—Ag alloy nanoparticles of various compositions. The gold mole fraction xau varies between 1 and 0.27. The plasmon absorption maximum is blueshifted with decreasing Xau- (After [3.74])...

Figure IS Schematic representation of the formation of a Pt-enriched core-shell alloy nanoparticle by voltammet-ric dealloying of a Cu-rich alloy precursor (Pt, gray Cu. red Co, blue). Reproduced with permission from [25] copyright Wiley-VCH Verlag GmbH, Co. KGaA.

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