Abstract
This review focuses on the recent advances in the lesser-studied microemulsion synthesis methodologies of the following noble metal colloid systems (i.e., Os, Re, Ir, and Rh) using either a normal or reverse micelle templating system. The aim is to demonstrate the utility and potential of using this microemulsion-based approach to synthesize these noble metal nanoparticle systems. Firstly, some fundamentals and important factors of the microemulsion synthesis methodology are introduced. Afterward, a review of the investigations on the microemulsion syntheses of Os, Re, Ir, and Rh nanoparticle (NP) systems (in all forms, viz., metallic, oxide, mixed-metal, and discrete molecular complexes) is presented for work published in the last ten years. The chosen noble metals are traditionally very reactive in nanosized dimensions and have a strong tendency to aggregate when prepared via other methods. Also, the particle size and particle size distribution of these colloids can have a significant impact on their catalytic performance. It is shown that the microemulsion approach has the capability to better stabilize these metal colloids and can control the size of the synthesized NPs. This generally leads to smaller particles and higher catalytic activity when they are tested in applications.
Highlights
Nanotechnology can be defined as the synthesis and development of materials of nano-sized dimensions (1 to 100 nm)
We review recent developments in the synthesis of some noble metal NPs (Re, Ir, Rh, and Os) via microemulsion-based methodologies as these media have the capability to stabilize, allow control of particle sizes, and in some cases, alter the morphology of the prepared NPs
It has been shown that both the water in oil (W/O) and oil in water (O/W) microemulsion-based preparation methodologies can be successfully applied for synthesizing a number of metal nanostructures, for those NP
Summary
Nanotechnology can be defined as the synthesis and development of materials of nano-sized dimensions (1 to 100 nm). In nanoparticle science, NPs can be classified based on their overall shape, ranging from zero-dimensional (0D) to three-dimensional (3D) This classification measures the dimensions of nano structural materials (NSMs) which are not measured in nanoscales. As a bottom-up subclass synthesis method, is a classical and established NP preparation method which is applied in the preparation of a variety of metal and metal oxide NPs, e.g., silver, gold, copper, Re2 O7 , and Cu2 O [9,10,11,12,13,14] In this method, metal salts and other compositions are reduced chemically by a reducing agent to achieve NPs. Controlling the reaction to reach a desired size and shape, usually by adjustment to the reaction conditions and constituents, is an available strategy in this bottom up synthesis method [15]
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