Small Au Nanoparticles Supported on MCM-41 Containing a Surfactant

Gold nanoparticles (AuNPs) have been incorporated into undoped Si-MCM-41 by direct one-pot and post-synthesis approaches. Through a "modified deposition-precipitation'' (mDP) method, whereby ethylenediamine served as both a base and complexing agent for the Au(III) species, Au nanoparticles have been prepared exclusively inside the pore channels of Si-MCM-41 materials. The method exploits Coulombic interactions between the occluded cationic surfactant template and the anionic [AuCl4](-) to yield a controlled distribution and in-pore generation of AuNPs, i.e., DP of the Au precursor was aided by electrostatics. This method is simple and yields well-dispersed gold nanoparticles (AuNPs). The nanoparticles inside the matrix were seen to aggregate and migrate to the surface upon calcination at 500 degrees C, but showed a narrow Au particle size distribution. The nanocomposite materials synthesized in this study exhibited catalytic activity for the CO oxidation reaction, with CO conversion of <100% even at temperatures as high as 500 degrees C.