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Keywords = intermicellar exchange rate

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17 pages, 3386 KB  
Article
The Interplay between Nucleation and the Rates of Chemical Reduction in the Synthesis of Bimetallic Nanoparticles in Microemulsions: A Computer Study
by Concha Tojo
Metals 2024, 14(9), 987; https://doi.org/10.3390/met14090987 - 29 Aug 2024
Cited by 2 | Viewed by 1209
Abstract
Monte Carlo simulations were conducted to investigate the interaction between nucleation and the rates of chemical reduction in Au/Ag, Au/Pt and Au/Pd nanoparticles prepared in microemulsions using a one-pot method. The impact of nucleation on final nanostructure depends on the critical nucleus size [...] Read more.
Monte Carlo simulations were conducted to investigate the interaction between nucleation and the rates of chemical reduction in Au/Ag, Au/Pt and Au/Pd nanoparticles prepared in microemulsions using a one-pot method. The impact of nucleation on final nanostructure depends on the critical nucleus size value: at a high critical nucleus size, nucleation becomes the main factor in determining the final nanostructure, even with a very large difference in reduction rates, as seen in the Au/Pd pair. However, when the critical nucleus size is small, the difference in reduction rates of the two metals becomes the key parameter determining the final nanostructure. Furthermore, the relevance of heteroatomic nucleation on the mechanism of nanoparticle formation depends on the difference between the reduction rates of the two metals. Smaller differences, such as in the Au/Ag or Au/Pt pairs, result in a greater impact of heteroatomic nucleation on the final nanostructure. In contrast, in the Au/Pd pair, heteroatomic nucleation becomes less important due to the low availability of Pd until late stages of synthesis. This study provides deeper insight into the complex mechanisms that govern reactions in microemulsions. Full article
(This article belongs to the Section Computation and Simulation on Metals)
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17 pages, 1917 KB  
Review
On Metal Segregation of Bimetallic Nanocatalysts Prepared by a One-Pot Method in Microemulsions
by Concha Tojo, David Buceta and Manuel Arturo López-Quintela
Catalysts 2017, 7(2), 68; https://doi.org/10.3390/catal7020068 - 17 Feb 2017
Cited by 17 | Viewed by 6291
Abstract
A comparative study on different bimetallic nanocatalysts prepared from microemulsions using a one-pot method has been carried out. The analysis of experimental observations, complemented by simulation studies, provides detailed insight into the factors affecting nanoparticle architecture: (1) The metal segregation in a bimetallic [...] Read more.
A comparative study on different bimetallic nanocatalysts prepared from microemulsions using a one-pot method has been carried out. The analysis of experimental observations, complemented by simulation studies, provides detailed insight into the factors affecting nanoparticle architecture: (1) The metal segregation in a bimetallic nanocatalysts is the result of the combination of three main kinetic parameters: the reduction rate of metal precursors (related to reduction standard potentials), the material intermicellar exchange rate (determined by microemulsion composition), and the metal precursors concentration; (2) A minimum difference between the reduction standard potentials of the two metals of 0.20 V is needed to obtain a core-shell structure. For values ∆ε0 smaller than 0.20 V the obtaining of alloys cannot be avoided, neither by changing the microemulsion nor by increasing metal concentration; (3) As a rule, the higher the film flexibility around the micelles, the higher the degree of mixture in the nanocatalyst; (4) A minimum concentration of metal precursors is required to get a core-shell structure. This minimum concentration depends on the microemulsion flexibility and on the difference in reduction rates. Full article
(This article belongs to the Special Issue Soluble Nanoparticles in Catalytic Applications)
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20 pages, 854 KB  
Article
Kinetic Study on the Formation of Bimetallic Core-Shell Nanoparticles via Microemulsions
by Concha Tojo and Nuria Vila-Romeu
Materials 2014, 7(11), 7513-7532; https://doi.org/10.3390/ma7117513 - 21 Nov 2014
Cited by 9 | Viewed by 6265
Abstract
Computer calculations were carried out to determine the reaction rates and the mean structure of bimetallic nanoparticles prepared via a microemulsion route. The rates of reaction of each metal were calculated for a particular microemulsion composition (fixed intermicellar exchange rate) and varying reduction [...] Read more.
Computer calculations were carried out to determine the reaction rates and the mean structure of bimetallic nanoparticles prepared via a microemulsion route. The rates of reaction of each metal were calculated for a particular microemulsion composition (fixed intermicellar exchange rate) and varying reduction rate ratios between both metal and metal salt concentration inside the micelles. Model predictions show that, even in the case of a very small difference in reduction potential of both metals, the formation of an external shell in a bimetallic nanoparticle is possible if a large reactant concentration is used. The modification of metal arrangement with concentration was analyzed from a mechanistic point of view, and proved to be due to the different impact of confinement on each metal: the reaction rate of the faster metal is only controlled by the intermicellar exchange rate but the slower metal is also affected by a cage-like effect. Full article
(This article belongs to the Special Issue Inorganic Core-Shell Structures)
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