Adsorption and Catalytic Activity of Gold Nanoparticles in Mesoporous Silica: Effect of Pore Size and Dispersion Salinity

Abstract

The assembled state of nanoparticles (NPs) within porous matrices plays a governing role in directing their biological, electronic, and catalytic properties. However, the effects of the spatial confinement and environmental factors, such as salinity, on the NP assemblies within the pores are poorly understood. In this study, we use adsorption isotherms, spectrophotometry, and small-angle neutron scattering to develop a better understanding of the effect of spatial confinement on the assembled state and catalytic performance of gold (Au) NPs in propylamine-functionalized SBA-15 and MCM-41 mesoporous silica materials ( m SiO 2 ). We carry out a detailed investigation of the effect of pore diameter and ionic strength on the packing and spatial distribution of AuNPs within m SiO 2 to get a comprehensive insight into the structure, functioning, and activity of these NPs. We demonstrate the ability of the adsorbed AuNPs to withstand aggregation under high salinity conditions. We attribute the observed preservation of the adsorbed state of AuNPs to the strong electrostatic attraction between oppositely charged pore walls and AuNPs. The preservation of the structure allows the AuNPs to retain their catalytic activity for a model reaction in high salinity aqueous solution, here, the reduction of p -nitrophenol to p -aminophenol, which otherwise is significantly diminished due to bulk aggregation of the AuNPs. This fundamental study demonstrates the critical role of confinement and dispersion salinity on the adsorption and catalytic performance of NPs.

Controlling the Physical Properties of Fe3O4-Immobilized Palladium Complexes towards Reusable Catalysts in the Methoxycarbonylation of 1-Hexene

“…A more detailed analysis of the data shows that catalyst Pd4 (calcined at 200 • C) had the lowest total pore volume and specific surface area of 0.1748 cm 3 /g and 41 m 2 /g, respectively (Table 3, entry 3). These have the overall effects of minimizing substrate/catalyst interactions, consistent with the lower catalytic activities observed for Pd4 [48].…”

Synthesis of Mesoporous Silica Using the Sol–Gel Approach: Adjusting Architecture and Composition for Novel Applications

“…Subsequently, noble metals [ 43 ], strong acid [ 44 ], or other compounds can be loaded into the mesoporous walls, playing a role as heterogeneous catalysts [ 45 , 46 ]. These supported mesoporous catalysts not only improve the dispersion, stability, and catalytic activity in complex reactions, but also serve as channels for the adsorption/desorption of free guest molecules [ 47 ].…”

Computational Reverse-Engineering Analysis for Scattering Experiments for Form Factor and Structure Factor Determination (“P(q) and S(q) CREASE”)

“…The SANS experiments were performed at Oak Ridge National Laboratory (ORNL) SNS facility using the EQ-SANS instrument with pinhole collimation at a neutron wavelength of 6 Å. Further details about the SANS experiments can be found in previous publications. − …”