Nanoparticle synthesis homogeneous nucleation

A microemulsion is a thermodynamically stable, optically clear dispersion of two immiscible liquids such as water and oil, stabilized by the presence of a surfactant and, in some cases, a co-surfac-tant.i i7i,265-267 synthesis of nanoparticles by microemulsions has two main advantages. On the one hand, particle size can be controlled by adjusting the size of the micelle containing the metal precursors. Therefore, thermal treatments for particle size control can be avoided. On the other hand, since the micelles have the same composition, i.e. metal precursors are distributed homogeneously the nucleation of metallic particles renders particles of the same composition. This latter feature is very important for the synthesis of bimetallic (or ternary) catalysts. The main drawback of the microemulsion, or any other approach using surfactants, is surfactant removal. Severe thermal treatments are required in order to achieve complete removal of the surfactant which may result in particle aggregation and/or surface enrichment, or complete phase segregation of the components of the bimetallic samples. ... 

In the experiments, a modified upward thermal diffusion cloud chamber is used for the synthesis of the nanoscale particles (10,31,32), A sketch of the chamber with the relevant components necessary for the synthesis of nanoparticles is shown in Figure 2. This chamber has been commonly used for the production of steady state supersaturated vapors for the measurements of homogeneous and photo-induced nucleation rates of a variety of substances (33). Detailed description of the chamber and its major components can be found in several references (33,34), Here we only offer a very brief description of the modifications relevant to the synthesis of the... 

Many researchers have identified the difference in the presence of hot spots (which locally enhance or promote some selected reactions or transformations). The narrow temperature distribution obtained by simulation can justify the formation of nanoparticles (having a narrower particle size distribution) with respect to conventionally heated synthetic routes in case of nucleation and growth of nanoparticles (microwave hydrothermal synthesis). The large-scale production of nanoparticles requires the development of microwave reactors, which can reflect the laboratory temperature profile homogeneity. It will provide a new dedicated eontinuous-flow reactor, made of two twin prismatic applicators for a microwave-assisted process in aqueous solution. The reactor can produce upto 1000 L/day of nanoparticles eolloi-dal suspension at ambient pressirre and relatively low temperature and henee, it ean be considered a green chemistry approach. 

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