“Naked” Magnetically Recyclable Mesoporous Au–γ‐Fe₂O₃ Nanocrystal Clusters: A Highly Integrated Catalyst System

Abstract

Naked magnetically recyclable mesoporous Au–γ‐Fe2O3 clusters, combining the inherent magnetic properties of γ‐Fe2O3 and the high catalytic activity of Au nanoparticles (NPs), are successfully synthesized. Hydrophobic Au–Fe3O4 dimers are first self‐assembled to form sub‐micrometer‐sized Au–Fe3O4 clusters. The Au–Fe3O4 clusters are then coated with silica, calcined at 550 °C, and finally alkali treated to dissolve the silica shell, yielding naked‐Au–γ‐Fe2O3 clusters containing Au NPs of size 5–8 nm. The silica protection strategy serves to preserve the mesoporous structure of the clusters, inhibit the phase transformation from γ‐Fe2O3 to α‐Fe2O3, and prevent cluster aggregation during the synthesis. For the reduction of p‐nitrophenol by NaBH4, the activity of the naked‐Au–γ‐Fe2O3 clusters is ≈22 times higher than that of self‐assembled Au–Fe3O4 clusters. Moreover, the naked‐Au–γ‐Fe2O3 clusters display vastly superior activity for CO oxidation compared with carbon‐supported Au–γ‐Fe2O3 dimers, due to the intimate interfacial contact between Au and γ‐Fe2O3 in the clusters. Following reaction, the naked‐Au–γ‐Fe2O3 clusters can easily be recovered magnetically and reused in different applications, adding to their versatility. Results suggest that naked‐Au–γ‐Fe2O3 clusters are a very promising catalytic platform affording high activity. The strategy developed here can easily be adapted to other metal NP–iron oxide systems.

Surfactant‐directed Pd‐nanoparticle assemblies as efficient nanoreactors for water remediation

“…On these grounds, the making of tailor-made PdNPs assemblies can be successfully achieved. Overall, the surfactant plays a critical role in forming the wellordered PdNPs-decorated assemblies, as it can effectively prevent aggregation of the PdNPs, and thereby, ensure good NPs dispersibility in the assemblies [55][56][57] ; importantly, it also directs the formation of specific structures. We now focus on the physiochemical property of the PdNPs assemblies and their environment implications as nanoreactors for effective water remediation.…”

3D Porous Carbon Framework Stabilized Ultra‐Uniform Nano γ‐Fe2O3: A Useful Catalyst System

“…[23] However,i n this work, the size of iron oxide NPs was kept below the critical size (25 nm) needed for a-Fe 2 O 3 formation. [24] Figure 1(c) confirms that the iron oxide crystal grains on the 3DPCF are about 20 nm, that is, smaller than 25 nm. Furthermore, Philip et al demonstrated that NaOH in the sample can increaset he Fe 2 O 3 phase transition temperature.…”

Preparation of magnetic Fe3O4/P (GMA‐DVB)‐PEI/Pd highly efficient catalyst with core‐shell structure

“…To visualize the performance of the catalyst directly, the data in Figure 7 (a) are processed. Since the concentration of NaBH 4 in the reaction system far exceeds that of 4-NP, the rate A t A 0 ¼ −kt: [40,41] Where A t and A 0 are 4-NP absorbance at reaction time t and initial time 0, respectively. k is the rate constant.…”