Encapsulation of Metal (Au, Ag, Pt) Nanoparticles into the Mesoporous SBA-15 Structure

Abstract

Mesoporous silica was synthesized in the presence of metal (Au, Pt, and Ag) nanoparticles in the 2-20 nm range. Sample characterization was performed by X-ray diffraction and electron microscopy. The metal nanoparticles in the 2-10 nm range were successfully incorporated into the ordered mesoporous SBA-15 structures; 20 nm particles, whose diameter is larger than the SBA-15 pore size, could not be inserted. In the case of 5 and 10 nm diameter nanoparticles, regardless of which metal, the mesopore channels expanded in order to accommodate the metal particles. By using mixtures of metal nanoparticles of two different sizes, it was found that the inclusion and the resultant pore size were controlled by the larger size metal particles.

Synthesis of Gold Catalysts Supported on Mesoporous Silica Materials: Recent Developments

“…The second strategy to prepare Au/MSM using gold colloids or presynthesized AuNPs involves mainly two steps: the synthesis of AuNPs in the presence of a block copolymer, and the synthesis of the MSM using the gold-nanoparticle copolymer unit as template [46]. Notwithstanding the catalytic activity was not evaluated, from the interesting works of the Somorjai group [46,47,164], who have used this approach to encapsulate AuNPs of different sizes (2, 5, 10 and 20 nm) into the channels of SBA-15, MCM-41 and MCM 48 using P123, hexadecylamine and cetylbenzyldimethylammonium chloride as templates, respectively, it can be highlighted that: (i) the presence of small Au nanocrystals (2-10 nm) influences only slightly the well-ordered structure but changes the lattice spacing of the MSM; (ii) although the mesopore channels of the MSM expand when small AuNPs are included, the narrow pore size distribution is preserved; (iii) when high amounts of AuNPs or large AuNPs (20 nm) are used, the structure of the materials remains porous, but their crystallinity decreases and a worm like structure appears, instead the hexagonal arrangement; (iv) after calcination, the small AuNPs are incorporated within the channels of the mesoporous host matrixes, but nanoparticles whose diameter is larger than the MSM pore size (20 nm fro SBA-15 and 10 nm for MCM-41 and MCM-48), cannot be inserted and they remains exclusively outside of the channels; (v) when using bimodal AuNPs (2 and 5 nm, or 2 and 10 nm), the resultant pore size of the SBA-15 material is controlled by the larger size of nanoparticles; (vi) the AuNPs incorporated inside the pores are accessible to reactant molecules, as confirmed by XANES used in combination with the adsorption of thiols.…”

“…The most used methods for preparing Au/MSM catalysts include the modification of the MSM support with organic functional groups by post-grafting or co-condensation before gold loading [41,42], one-pot synthesis by the incorporation of both gold and the coupling agent containing functional groups into the MSM synthesis [43], the use of cationic gold complexes such as [Au(en) 2 ]Cl 3 (en = ethylenediamine) [44], chemical vapor deposition using expensive organometallic gold precursors [45], synthesis of the MSM in the presence of gold colloids [46,47], dispersion of gold colloids protected by ligands or polymers onto SiO 2 [46,47], and modification of the mesoporous SiO 2 supports with other metal oxides, such as TiO 2 , Al 2 O 3 and CeO 2 to prepare SiO 2 -based gold catalysts [48,49].…”

Clusters, surfaces, and catalysis

“…These particles can readily be used for catalysis and monitored by the characterization techniques used in surface science such as Auger electron spectroscopy, x-ray photoelectron spectroscopy, and atomic force microscopy (47,50).…”

Bimetallic Nanocatalysts in Mesoporous Silica for Hydrogen Production from Coal-Derived Fuels

“…A brief description of each synthesis procedure is included in this section. Impregnation: The incipient wetness impregnation is generally used for the preparation of supported metal catalysts [27,28]. In this method, the solution of metal precursor is added to the template-free mesoporous material to embed or impregnate metal ions or complex into the mesochannels.…”

“…A two-step co-synthesis of metal (Au, Ag, or Pt) -containing SBA-15 mesoporous silica was initiated and developed by Somorjai and co-workers [27,28,33]. Their method is based on growing the surfactant-silica composites around the preformed metal nanoparticles, which have been capped and stabilized by tri-block copolymer.…”