A fundamental boron cluster, [closo-BH], mainly known as an inert agent for boron neutron capture therapy, can also serve as a bi-functional reductant and a capping agent for the formation of monodispersed size-controlled gold nanoparticles (AuNPs) under mild reaction conditions. The obtained AuNPs remained thermo-dynamically stable over 3 months, and exhibited high performance in phase transfer and sensing of heavy metal ions.
A new class of core–shell magnetic gold nanocomposites is prepared in a raspberry‐like fashion by the controlled supramolecular host–guest assembly of γ‐cyclodextrins (γ‐CDs) and boron clusters. In this work, Cs2[closo‐B12H12], a fundamental boron cluster, can play a dual role in the preparation of highly monodispersed Au nanoparticles and in the immobilization of Au nanoparticles on the γ‐CDs@Fe3O4 surface as an effective anchor. This facile and spontaneous supramolecular strategy allows for the control of the size and composition of the highly stable gold composites. Furthermore, the obtained AuNPs@Fe3O4 composites exhibit an excellent catalytic activity and recyclability for the selective reduction of nitroaromatics to their corresponding aniline compounds, and the fastest reaction can be achieved within 20 s with a high conversion and selectivity at room temperature, which is better than that obtained previously in studies on metal nanoparticle composites as catalysts.
Self-assembled
nanotechnology has been used widely in various well-defined
microstructures fabrication. Herein, this synthetic protocol was successfully
utilized to in situ or hierarchically prepare magnetic Pt nanocomposites
Fe3O4@Pt via a distinguishing two-step process.
The distinction of these two pathways is due to the different synthetic
processes. In the case of in situ preparation (Path I), it involves
a supramolecular self-assembly of boron clusters with γ-CD on
Fe3O4 substrate and then followed by in situ
formation of Pt nanoparticles (NPs). But in the case of hierarchical
preparation (Path II), the first step is preparing Pt NPs colloids
reduced by boron clusters Cs2[closo-B12H12], and subsequent step is immobilizing the
as-prepared [closo-B12H12]2–-capped Pt NPs on the Fe3O4@γ-CD.
The success of these two fabrication strategies lies in the use of
trifunctional boron clusters (reductant, stabilizer, and superchaotropic
anchor). Both of the as-prepared Fe3O4@Pt nanocomposites
showed good catalytic performance in the selective nitro-group reduction
of nitroaromatics. A control test further indicated that the in situ
prepared Fe3O4@Pt nanocomposites, with smaller
size and higher loading of Pt NPs, exhibited a better catalytic performance
and recyclability.
Supramolecular chaotropic effect is a new topic in the field of nanocomposites (NCs) fabrication. Herein, this strategy was applied to prepare magnetic Fe3O4@γ‐CD‐boron cluster (SSAs)@Pd NCs in situ via a facile two‐step process, involving a supramolecular assembly process on Fe3O4 NPs and in situ formation of Pd nanoparticles. Boron clusters ([closo‐B12H12]2−) played a dual role in this synthetic process, and were used as a superchaotropic anion to interact with γ‐CD to form supramolecular self‐assemblies (SSAs), as well as efficient reductant to in situ reduce Pd(II) to Pd(0). Ascribed to the electrostatic attraction of boron clusters and capping effect of γ‐CD, ultrafine Pd nanoparticles were successfully coated on the Fe3O4@SSAs composites to fabricate Fe3O4@SSAs@Pd NCs. A combination of UV spectra, Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, transmission electron microscopy, X‐ray diffraction, and energy dispersive X‐ray spectroscopy was used to verify the formation of these magnetic Pd NCs. The ultrafine metallic Pd NPs imparted the magnetic composites with great potential in catalysis, especially for Suzuki coupling reactions. Remarkably, the obtained Fe3O4@SSAs@Pd NCs showed good catalytic performance, high stability and easy recycling via an external magnet.
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