Au nanoparticles embedded within mesoporous aluminosilicate particles have been prepared and used as catalyst for CO oxidation. In the presence of C(16)TMAB, a stable aqueous solution of An nanoparticles-surfactant without apparent aggregations was obtained by chemical reduction. After combining with aluminosilicates in an alkaline solution, the Au nanoparticles were mostly embedded within the mesoporous aluminosilicate particles, and the maximum loading of Au nanoparticle can reach around 36 wt.%. The diameter of An nanoparticles in mesoporous aluminosilicates are < 10 nm after calcination at 560 degreesC under air. In this research, the quaternary ammonium surfactants serve as dual function agents, protecting agent for Au nanoparticle and templates for mesoporous silica. When the mesoporous aluminosilicate supports are in micron-size, the highest CO conversion is only about 16% over the catalyst with gold loading, Au/SiO2 = 8%. The conversion decreases to nearly zero at higher gold loadings due to extensive pore blocking. Reducing the dimension of mesoporous aluminosilicates to tens of nanometers makes the An nanoparticles more accessible for CO oxidation, and the highest CO conversion reaches 70% over the catalyst with gold loading, Au/SiO2 = 24 wt.%. (C) 2004 Elsevier B.V. All rights reserved.