Self-assembly of supermicro- and meso-porous silica and silica/gold nanoparticles using double-chained surfactants

Porous silica nanosized particles were prepared using tetramethylorthosilicate and two double carbon chained templates, n-didecyldimethylammonium bromide and n-didodecyldimethylammonium bromide. Samples were prepared using a simple modification of the Stöber method for synthesis of colloidal silica for template to silica ratios of 0.2 and 0.1 under homogeneous cosolvent conditions. Silica/gold nanocomposites were prepared similarly except for the addition of a gold colloid suspension prior to self-assembly. All samples were analyzed using X-ray diffraction, transmission electron microscopy and liquid nitrogen adsorption. The diameters of the pores were measured using three methods: volumetric-XRD; Gurvitsch; and BJH. The diameters of the pores ranged from 1.9 to 2.5nm using the Volumetric-XRD method with pore wall diameters from 0.64 to 1.1nm. The presence of supermicro- and meso-pores were confirmed using comparison t-plots. Both the volumetric-XRD and Gurvitsch methods were consistent with the t-plot analysis, whereas the BJH method underestimated pore diameters significantly. Samples had pore volumes in excess of 0.37cmg−1 at STP and surface areas greater than 700m2g−1. The symmetry of the silica pore structure was found to vary depending on both the template to silica ratio and the addition of a gold tag. The diameter of nanoparticles ranged from 58 to 590nm and the position of the gold seed in each particle was consistent with a three-stage aggregative growth model.