Recovery and reuse of expensive catalysts after catalytic reactions are important factors for sustainable process management. The aim of this Review is to highlight the progress in the formation and catalytic applications of magnetic nanoparticles and magnetic nanocomposites. Directed functionalization of the surfaces of nanosized magnetic materials is an elegant way to bridge the gap between heterogeneous and homogeneous catalysis. The introduction of magnetic nanoparticles in a variety of solid matrices allows the combination of well-known procedures for catalyst heterogenization with techniques for magnetic separation.

Magnetically Separable Nanocatalysts: Bridges between Homogeneous and Heterogeneous Catalysis

Synthesis, properties, and applications of magnetic iron oxide nanoparticles

https://iopscience.iop.org/article/10.1088/1468-6996/16/2/023501/pdf

Recent progress on magnetic iron oxide nanoparticles: synthesis, surface functional strategies and biomedical applications.

Surface functionalization of nano-magnetic nanoparticles is a well-designed way to bridge the gap between heterogeneous and homogeneous catalysis. The introduction of magnetic nanoparticles (MNPs) in a variety of solid matrices allows the combination of well-known procedures for catalyst heterogenization with techniques for magnetic separation. Magnetite is a well-known material, also known as ferrite (Fe3O4), and can be used as a versatile support for functionalization of metals, organocatalysts, N-heterocyclic carbenes, and chiral catalysts. It is used as a support for important homogeneous catalytically active metals such as Pd, Pt, Cu, Ni, Co, Ir, etc. to obtain stable and magnetically recyclable heterogeneous catalysts. Homogeneous organocatalysts can be successfully decorated with linkers/ligands on the surface of magnetite or alternatively the organocatalysts can be directly immobilized on the surface of magnetite. The functionalized magnetically retrievable catalysts or nanocatalysts that are increasingly being used in catalysis, green chemistry and pharmaceutically significant reactions are summarized in this review.

Nano-magnetite (Fe3O4) as a support for recyclable catalysts in the development of sustainable methodologies

Control of spontaneously emitted light lies at the heart of quantum optics. It is essential for diverse applications ranging from miniature lasers and light-emitting diodes, to single-photon sources for quantum information, and to solar energy harvesting. To explore such new quantum optics applications, a suitably tailored dielectric environment is required in which the vacuum fluctuations that control spontaneous emission can be manipulated. Photonic crystals provide such an environment: they strongly modify the vacuum fluctuations, causing the decay of emitted light to be accelerated or slowed down, to reveal unusual statistics, or to be completely inhibited in the ideal case of a photonic bandgap. Here we study spontaneous emission from semiconductor quantum dots embedded in inverse opal photonic crystals. We show that the spectral distribution and time-dependent decay of light emitted from excitons confined in the quantum dots are controlled by the host photonic crystal. Modified emission is observed over large frequency bandwidths of 10%, orders of magnitude larger than reported for resonant optical microcavities. Both inhibited and enhanced decay rates are observed depending on the optical emission frequency, and they are controlled by the crystals’ lattice parameter. Our experimental results provide a basis for all-solid-state dynamic control
of optical quantum systems.

Controlling the dynamics of spontaneous emission from quantum dots by photonic crystals

1 before use (a) and afterreuse five times (b).[*]Dr. F. Shi, Dr. M. K. Tse, Prof. Dr. M. BellerLeibniz-Institut fr Katalyse e.V. an der Universitt RostockAlbert-Einstein-Strasse 29a, 18059 Rostock (Germany)andCenter for Life Science Automation (CELISCA)University of RostockFriedrich-Barnewitz-Strasse 818119 Rostock-Warnemnde (Germany)Fax: ( +49)381-1281-5000E-mail: matthias.beller@catalysis.deDr. M.-M. Pohl, Dr. A. BrcknerLeibniz-Institut fr Katalyse e.V.Universitt Rostock, Ausenstelle BerlinRichard-Willsttter-Strasse 3, 12489 Berlin (Germany)Dr. S. ZhangSpecial Functional Material Laboratory, Henan University475001, Kaifeng (China)[**]This work was supported by the State of Mecklenburg-WesternPommerania, the Deutsche Forschungsgemeinschaft (SPP 1118and Leibniz prize), and the Deutsche FMER (BMBF). F.S. thanks theAlexander-von-Humboldt-Stiftung for an AvH Fellowship.Supporting information for this article is available on the WWWunder http://www.angewandte.org or from the author.

Tuning catalytic activity between homogeneous and heterogeneous catalysis: improved activity and selectivity of free nano-Fe2O3 in selective oxidations.

This paper describes a novel solution-based chemical process to architect hollow spheres of β-Ni(OH)2 with controllable sizes in submicrometer and micrometer regimes. In the synthesis, starting nickel salt (nitrate) is first converted to 6-coordinated nickel ion complex [Ni(EDA)3]2+ (bidentate ligand EDA = C2H4(NH2)2) to avoid rapid solid formation. Hollow and core−shell β-Ni(OH)2 spheres can be obtained with this template-free approach under one-pot conditions. The β-Ni(OH)2 spheres are constructed from petal-like nanobuilding units which in turn are formed from even smaller nanocrystallites. The obtained porous β-Ni(OH)2 spheres have a large specific surface area and show a unimodal pore-size distribution. Several preparative parameters have been examined and optimized. In particular, the concentration of divalent nickel in the starting solutions plays an important role in controlling thickness of the petal-like β-Ni(OH)2 flakes and diameter of spheres. The β-Ni(OH)2 flakes self-assemble into final sphe...

Self-Assembled Hollow Spheres of β-Ni(OH)2 and Their Derived Nanomaterials

Unsupported “free” nano-γ-Fe 2 O 3 is an active, stable, and reusable catalyst for selective oxidations of alcohols and olefins applying hydrogen peroxide as terminal oxidant. Catalyst activity and selectivity are controlled by tuning the particle size. The formation of a thin carbon-layer on the surface of the nano-iron oxide during the reaction permits for high catalyst stability. All catalysts were characterized by TEM, X-ray photoelectron spectroscopy (XPS), XRD, and EPR.

Nano-iron oxide-catalyzed selective oxidations of alcohols and olefins with hydrogen peroxide

Preparation and tribological properties of surface modified Cu nanoparticles

Cu nanoparticle surface-capped by methoxylpolyethyleneglycol xanthate was synthesized using in situ surface-modification technique. The size, morphology and phase structure of as-prepared Cu nanoparticle were analyzed by means of X-ray diffraction and transmission electron microscopy. The tribological properties of as-synthesized Cu nanoparticle as an additive in distilled water were investigated with a four-ball machine, and the morphology and elemental composition of worn steel surfaces were examined using X-ray photoelectron spectroscopy and scanning electron microscope equipped with an energy-dispersive spectrometer attachment. Results show that as-synthesized Cu nanoparticle as a water-based lubricant additive is able to significantly improve the tribological properties and load-carrying capacity of distilled water, which is ascribed to the deposition of Cu nanoparticles on steel sliding surfaces giving rise to a protective and lubricious Cu layer thereon. In the meantime, they may also tribochemically react with rubbing steel surfaces to generate a boundary lubricating film consisting of Cu, FeS and FeSO4 on the rubbed steel surface, which helps to result in greatly improved tribological properties of distilled water, thereby reducing friction and wear of the steel–steel pair.

Shengmao Zhang

Papers

Tuning catalytic activity between homogeneous and heterogeneous catalysis: improved activity and selectivity of free nano-Fe2O3 in selective oxidations.

Self-Assembled Hollow Spheres of β-Ni(OH)2 and Their Derived Nanomaterials

Nano-iron oxide-catalyzed selective oxidations of alcohols and olefins with hydrogen peroxide

Preparation and tribological properties of surface modified Cu nanoparticles

Preparation and Tribological Properties of Surface-Capped Copper Nanoparticle as a Water-Based Lubricant Additive