Aerogels Containing Metal and Alloy Nanoparticles

The preparation of nanocomposite aerogels made out of zero-valent metal or alloy nanoparticles in an insulating aerogel matrix has attracted a great deal of effort in view of the preparation of materials for catalysis, biomedicine, optoelectronics, and sensors. As it is the case for aU sol-gel nanocomposites, silica is by far the most investigated matrix for supporting metal/alloy nanoparticles, although alumina, titania, chromia, and polymer supports have also been proposed. 

On the other hand, a variety of metal nanoparticles have been considered either on the basis of the ease of reducibility, with the aim of developing optimized synthetic protocols, or in order to provide the desired functionality to the nanocomposite. Noble metal nanoparticles are the most investigated as they meet both requisites they can be easily obtained and stored in the zero-valent state they are catalytically active toward a wide range of 

Transition metals and their alloys have also attracted much attention due to their magnetic properties and due to their potential in catalysis thanks to the occurrence of different oxidation states. 

In the following, we will summarize how the issue of the control over the nanocomposite formation has been recently addressed. 

A more general procedure for the preparation of metal-siUca aerogel nanocomposites is based on the supercritical drying of a silica alcogel previously soaked in a metal solution. 

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