Comparison of silver nanoparticles confined in nanoporous silica prepared by chemical synthesis and by ultra-short pulsed laser ablation in liquid

Abstract

Hexagonally ordered mesoporous silica materials MCM-41 and SBA-15 have been synthesized and loaded with Ag nanoparticles, utilizing both chemical synthesis and ultrashort pulsed laser ablation in liquid.In laser ablation, a silver target, immersed in aqueous suspension of ordered mesoporous silica SBA-15, was irradiated by ultra-short laser pulses to generate silver nanoparticles. For comparison samples of similar silver contents were prepared either by incorporating silver into the SBA-15 during a hydrothermal synthesis or by introducing silver in MCM-41 by template ion-exchange. Samples were characterized by XRD, N 2 physisorption, TEM and UV-vis spectroscopy. All preparations contained significant amount of 5-50 nm size silver 2 agglomerates on the outer surface of the silica particles. The laser ablation process did not cause significant destruction of the SBA-15 structure and metallic silver (Ag 0 ) nanoparticles were mainly generated. It is demonstrated that by laser ablation in aqueous silica suspension smaller and more uniform metallic silver particles can be produced and loaded on the surface of the silica support than by synthesis procedures. Catalytic properties of the samples have been tested in the total oxidation of toluene. Because of its favorable Ag dispersity the Ag/SBA-15 catalyst, generated by the laser ablation method, had better catalytic stability and, relative to its Ag load, higher activity than the conventional Ag/SBA-15 preparations.

Pulsed Laser in Liquids Made Nanomaterials for Catalysis

“…308 Laser-synthesized silver nanoparticles confined in a chemically prepared mesoporous silica support (SBA-15) were reported by Santagata and co-workers for toluene oxidation to CO 2 . 78 The composite was produced by 800 nm, 100 fs pulsed laser ablation of an Ag target in aqueous SBA-15 suspension. Duration of the laser treatment was 10 or 20 min and led to Ag loadings of 5 or 8 wt %, respectively.…”

“…The laser-made Ag− SBA-15 catalysts showed higher activity than a hydrothermally prepared control material that consisted of silver nanoparticles on an MCM-41 mesoporous silica support, presumably due to smaller and more homogeneously dispersed silver nanoparticles in the laser-made material. 78 Small gold nanoparticles were obtained by Luo et al for two glycerol oxidation reactions by 532 nm pulsed laser ablation of a gold targets in water. 361,362 Catalytic cycles were elucidated by density functional theory calculations and modeling.…”

“…Catalysis of total oxidation of toluene was studied using a fixed-bed flow-through reactor setup at temperatures of 250–450 °C. The laser-made Ag–SBA-15 catalysts showed higher activity than a hydrothermally prepared control material that consisted of silver nanoparticles on an MCM-41 mesoporous silica support, presumably due to smaller and more homogeneously dispersed silver nanoparticles in the laser-made material …”

“…Uniform small (ca. 1–20 nm) nanoparticles have been obtained from laser ablation by chemical control. − …”

The Pros and Cons of the Use of Laser Ablation Synthesis for the Production of Silver Nano-Antimicrobials

“…In particular, the possibility of fragmenting a metal target without making use of capping and reducing agents intrinsically lowers the risk of contamination of the resulting colloid from unknown chemical agents and provides NPs with unique surface characteristics [ 90 ]. In the field of nano-antimicrobials, LASiS-generated NPs are expected to exhibit higher reactivity and antimicrobial effects in comparison to their chemically synthesized homologous NPs, due to the absence of ligands and/or stabilizers on the NP surface [ 91 , 92 ].…”