Clay mineral-supported gold nanoparticles

Supported gold nanoparticles were prepared on clay minerals from the smectite and sepiolite–palygorskite groups (particularly montmorillonite and sepiolite) by cation adsorption from the cationic gold precursor Au(en)2Cl3 (en = ethylenediamine). Thermal gravimetric analysis, X-ray diffraction, transmission electron microscopy (TEM), high resolution TEM (HRTEM) and energy dispersive X-ray spectroscopy (EDS) were used to characterize these potential gold catalysts. The results show that the mean diameters of gold particles supported both on sepiolite and on montmorillonite are below 5 nm after calcination at 350–450 °C when the gold loading is lower than 2 wt.%. An increase of the amount of the gold precursor results in agglomeration of gold nanoparticles. An organosilane functionalized sepiolite was also used as support to obtain highly dispersed gold nanoparticles on the modified mineral surfaces, with narrow size distribution and an average size of 2.7 nm.