Micelles with embedded nanoparticles

An example of a consecutive use of block copolymer micelles as endo- and exo-templates is the preparation of mesoporous silica with embedded Pd-nanoparticles [113]. As a first step Pd-nanoparticles are prepared in the micellar core (see Sect. 4.1). In a lyotropic phase of these micelles they are further employed as exotemplates for the preparation of mesoporous silica (see Sect. 5). After removal of the block copolymer by calcination, nanoparticles within the open mesopore structure are obtained (Fig. 20). This represents a promising way to incorporate catalytically active nanoparticles into mesoporous oxides as stable catalyst supports. 

A major obstacle in making precise structures with metal colloids has been the control of aggregation and particle size distribution. The use of micelles has allotted some success in this regard with the formation of different metal colloid geometries [30]. It is known that the nanoparticles must be stabilized by organic molecules attached to their surface [31] and in general must be embedded in a solid matrix [32], This is done to prevent agglomeration and precipitation as... 

Toshiba and Takahashi [214] prepared nanoparticles of colloidal Pt embedded in a micelle (Fig. 18.22). With such a system the initial rate of hydrogenation of 2-undecenoic acid is almost 6 times lower than the initial rate of hydrogenation of 10-undecenoic acid. The explanation is based on the polar effect of the amphiphilic ligand whose polar head stays outside the particle. The polar head fadhtates the coordination of the double bond by preventing the carboxyUc function from approaching the surface of Pt but considering such a micellar system, one can see easily their fragility. 

---