Pumping Metallic Nanoparticles with Spatial Precision within Magnetic Mesoporous Platforms: 3D Characterization and Catalytic Application

Abstract

┴ Araid Foundation. KEYWORDSRecyclable, magnetically recoverable self-assembled structures, mesoporous silica, waterdispersible nanoparticles, magnetic properties, peptide-like bonding and hydrogenation. ABSTRACTThe present work shows an efficient strategy to assemble two types of functional nanoparticles onto mesoporous MCM-41 silica nanospheres with high degree of spatial precision. In a first stage, magnetite nanoparticles are synthesized with a size larger than the support pores and grafted covalently through a peptide-like bonding onto its external surface. This endowed the silica nanoparticles with a strong superparamagnetic response, while preserving the highly ordered interior space for the encapsulation of other functional guest species. Secondly, we report the finely controlled pumping of preformed Pt nanoparticles (1.5 nm) within the channels of the magnetic MCM-41 nanospheres to confer an additional catalytic functionality to the multi-assembled nanoplatform. The penetration depth of the metallic nanoparticles can be explained as a result of the interplay between particle-wall electrostatic attraction and the repulsive forces between neighbouring Pt nanoparticles. A detailed transmission electron microscopy (TEM) and 3-D HighResolution HAADF electron Tomography study was carried out to characterize the material and to explain the assembly mechanism. Finally, the performance of these multifunctional nanohybrids as magnetically recoverable catalysts has been evaluated in the selective hydrogenation of pnitrophenol, a well-known pollutant and intermediate in multiple industrial processes.3

Triangular and Prism‐Shaped Gold‐Zinc Oxide Plasmonic Nanostructures: In situ Reduction, Assembly, and Full‐Range Photocatalytic Performance

“…The LED‐assisted hydrogenation of 4‐NP into 4‐AP in the presence of sodium borohydride (NaBH 4 ) (Figure c) was monitored by UV/Vis spectroscopy through the evolution of its absorption band at 400 nm (in the form of the p‐nitrophenolate ion), that is progressively reduced to p‐aminophenol with the concomitant formation of a new band at 300 nm if the reaction is successful (see Figure d) , , . The reaction was assumed to follow a pseudo‐first kinetic order due to the excess of both catalyst and NaBH 4 , and an apparent kinetic constant could be estimated , …”

“…The comparative photocatalytic performance of the ZnO and Au/ZnO nanohybrids under selected LED irradiation wavelengths has been displayed in Figure and summarized in Table for all the explored conditions including control experiments. The photo‐induced conversion profile of the catalysts was calculated as the number of mols of 4‐NP hydrogenated at a time t per mols of 4‐NP when t = 0 min (see Figure a‐ Figure c and Table ). Likewise, since the concentration of NaBH 4 was in great excess and considered as approximately constant throughout the reaction, the hydrogenation rate was approximated by a pseudo‐first kinetic order regarding the 4‐NP concentration.…”

Functionalized Ordered Mesoporous Silicas (MCM-41): Synthesis and Applications in Catalysis

“…A strategy to assemble superparamagnetic iron oxide and platinum nanoparticles onto mesoporous MCM-41 silica host with a high degree of spatial precision has been reported by Santamaria and Martinez et al [171]. The system was prepared by a size-exclusion strategy that allows a highly precise segregation of iron nanoparticles outside the MCM-41 and platinum inside the pores.…”

“…Pt nanoparticles pumped within the channels of the magnetic MCM-41 nanospheres. Reproduced with permission from[171]. Copyright 2017 American Chemical Society.…”

Gold-Based Nanoparticles on Amino-Functionalized Mesoporous Silica Supports as Nanozymes for Glucose Oxidation

“…For instance, supports with high density of -OH groups on their surface promote the anchoring of Au NPs [27,57]. Likewise, -NH 2 surface functional groups can endorse stronger affinity with AuNPs by electrostatic attraction thereby resulting in a more efficient immobilization of both the active metallic nanoparticles and the glucose sustrate [58][59][60].…”