Maiyong Zhu

In situ synthesis of silver nanostructures on magnetic Fe3O4@C core–shell nanocomposites and their application in catalytic reduction reactions

In this article, a study was presented on the catalytic activity of silver nanoparticles immobilized on magnetic Fe3O4@C (MFC) core–shell nanocomposites (Ag/MFC) that were used as carriers. MFC composites consist of a magnetic core of an Fe3O4 microsphere onto which a thin layer of carbon was coated by in situ carbonization of glucose under hydrothermal conditions. The catalytic activity of the as-prepared Ag/MFC is investigated by photometrically monitoring the reduction of 4-nitrophenol and methylene blue by an excess of NaBH4. The kinetic data of both reduction reactions could be explained by the assumption of a pseudo-first-order reaction with regard to 4-nitrophenol or methylene blue. Significantly, the Ag/MFC catalysts can be easily separated from the reaction media by applying an external magnet, and can be reused for several cycles.

Facile Fabrication of Hierarchically Porous CuFe2O4 Nanospheres with Enhanced Capacitance Property

In this work, CuFe2O4 nanospheres with hierarchically porous structure have been synthesized via a facile solvothermal procedure. The superstructures consist of the textured aggregations of nanocrystals with high specific surface area, pore volume, and uniform pore size distribution.To figure out the formation mechanism, we discussed in detail the effects of a series of experimental parameters, including the concentrations of the precipitation agent, stabilizer agent, and reaction temperature and time on the size and morphology of the resulting products. Furthermore, the electrochemical properties of CuFe2O4 nanospheres were evaluated by cyclic voltammetry and galvanostatic charge-dischrge studies. The results demonstrate that the as-prepared CuFe2O4 nanospheres are excellent electrode material in supercapacitor with high specific capacitance and good retention. The hierarchically CuFe2O4 nanospheres show the highest capacitance of 334F/g, and 88% of which can still be maintained after 600 charge-discharge cycles.

High catalytic activity of CuO nanorods for oxidation of cyclohexene to 2-cyclohexene-1-one

Copper oxide (CuO) nanorods were synthesized via a facile hydrothermal process, which exhibit excellent catalytic oxidation of cyclohexene to 2-cyclohexene-1-one by tert-butyl hydrogen peroxide (TBHP) in acetonitrile. This would provide a novel method for directly synthesizing α,β-unsaturated ketones from olefins.

Facile solvothermal synthesis of porous ZnFe2O4 microspheres for capacitive pseudocapacitors

A facile and cost-effective solvothermal approach to the fabrication of ZnFe2O4 microspheres composed of nanocrystals has been developed. The morphology and structure of the products were characterized by X-ray powder diffraction, transmission electron microscopy, and field-emission scanning electronic microscopy, and N2-adsorption–desorption. Meanwhile, the magnetic properties of the product were investigated via vibrating sample magnetism. Finally, the electrochemical performance of the obtained ZnFe2O4 microspheres was measured by cyclic voltammetry and galvanostatic charge–discharge techniques. The results show that such structured ZnFe2O4 has a specific capacitance of 131 F g−1 and stable cycling performance with 92% capacitance retention after 1000 cycles, which make it have a potential application as a supercapacitor electrode material.

Hematite nanoparticle-templated hollow carbon nanonets supported palladium nanoparticles: preparation and application as efficient recyclable catalysts

Hollow carbon nanonets (HCN), which are attractive materials for catalyst support, were fabricated using the pre-synthesized hematite nanoparticles as the hard template. And then the HCN supported Pd nanoparticles (Pd/HCN) were prepared by precipitation-reduction method. The catalytic performance of Pd/HCN was investigated using Suzuki and Heck coupling reactions as model reactions. The results demonstrated that the as-prepared Pd/HCN nanocomposites exhibit high catalytic activity for the two types of coupling reactions under ligand free conditions. Especially, the Suzuki reactions between various aryl halides and phenylboronic acid gave excellent yields in water. Moreover, the as-prepared Pd/HCN catalysts can be easily recovered from the reaction medium by centrifugation for recycling, and the catalytic efficiency shows no obvious loss even after 6 repeated cycles.

Self-switchable catalysis by a nature-inspired polymer nanoreactor containing Pt nanoparticles

A nature-inspired polymer nanoreactor with self-switchable catalytic ability is reported. This nanoreactor was made of platinum nanoparticles and a unique polymer composite of poly(1-vinylimidazole) (PVI) and poly(2-(trifluoromethyl)acrylic acid) (PTFMA) that exhibited “self-healing” properties. This nanoreactor revealed weak reactivity at relatively low temperatures due to the complementary interaction between PVI and PTFMA, which inhibited access to the catalytic sites of platinum. In contrast, the nanoreactor demonstrated significant reactivity at relatively high temperatures, resulting from the dissociation of the interpolymer interaction. Unlike reported nanoreactors which usually involve the thermal phase transition of PNIPAm, this novel nanoreactor has adopted the “self-healing” properties of supramolecular building blocks. The proposed design suggests new opportunities for developing smart nanoreactors capable of self-switchable catalysis.

A Cascade‐Reaction Nanoreactor Composed of a Bifunctional Molecularly Imprinted Polymer that Contains Pt Nanoparticles

This study was aimed at addressing the present challenge of cascade reactions, namely, how to furnish the catalysts with desired and hierarchical catalytic ability. This issue was addressed by constructing a cascade-reaction nanoreactor made of a bifunctional molecularly imprinted polymer containing acidic catalytic sites and Pt nanoparticles. The acidic catalytic sites within the imprinted polymer allowed one specified reaction, whereas the encapsulated Pt nanoparticles were responsible for another coupled reaction. To that end, the unique imprinted polymer was fabricated by using two well-coupled templates, that is, 4-nitrophenyl acetate and 4-nitrophenol. The catalytic hydrolysis of the former compound at the acidic catalytic sites led to the formation of the latter compound, which was further reduced by the encapsulated Pt nanoparticles to 4-aminophenol. Therefore, this nanoreactor demonstrated a catalytic-cascade ability. This protocol opens up the opportunity to develop functional catalysts for complicated chemical processes.

“Key-vs.-Lock”-Like Polymer Reactor Made of Molecularly Imprinted Polymer Containing Metal Nanoparticles

This study aimed at the present dilemma in selective catalysis, about how to furnish metal-nanoparticle catalysts with predictable selectivity. This issue was addressed by developing a “key-vs.-lock”-like polymer reactor made of an elaborate molecularly imprinted polymer containing metal nanoparticles, which was capable of predictably and selectively catalyzing its specified substrate. Unlike reported polymer reactors and enzyme-like imprinted polymer catalysts, which lack either predictable selectivity or reactive metal nanoparticles, this polymer reactor has incorporated both of the molecular recognition ability of the polymer carrier and the catalytic sites of metal nanoparticles into one entire entity and thereby dictated selective catalysis. This study highlighted how this polymer reactor works in a selective way in contrast to reported catalytic polymers or polymer reactors, which thus opens opportunities of tailoring selective catalysts for controlled chemical processes.

An “active” and self-switchable nanoreactor

An “active” and self-switchable nanoreactor is reported. This nanoreactor was made of nickel nanoparticles and a unique polymer composite of poly(1-vinylimidazole) (PVIm) and poly(acrylic acid) (PAAc) that exhibited “self-healing” properties. This nanoreactor revealed a weak reactivity at relatively low temperatures due to the complementary interaction between the PVIm and PAAc, which inhibited access to the catalytic sites of the nickel. In contrast, the nanoreactor demonstrated significant reactivity at relatively high temperatures, resulting from the dissociation of the interpolymer interaction. Unlike conventional nanoreactors, which usually involve the thermal phase transition of PNIPAm, this novel nanoreactor has employed the “self-healing” properties of supramolecular building blocks. The proposed incorporation of “active” supports to metal nanoparticles creates a new protocol for developing catalytic nanoreactors.

One-Step Fabrication of Magnetic Carbon Nanocomposite as Adsorbent for Removal of Methylene Blue

Magnetic Fe3O4@C nanocomposites with well-defined core@shell structure were synthesized via a facile one-step solvothermal process using ferrocene as both iron and carbon resource in the presence of hydrogen peroxide (H2O2). The as-prepared Fe3O4@C nanocomposites were employed as adsorbent materials for removal of methylene blue (MB) from aqueous solution. Several experimental parameters, including contact time, acidity of the solution, and initial MB concentration were investigated. The result showed that the equilibrium uptake of MB was related to the MB initial concentration as well as acidity of the solution. The adsorption kinetics of MB was dominated by the pseudo-second order reaction model. Significantly, the synthesized Fe3O4@C nanocomposites could be easily isolated from the adsorption system after adsorbing MB and showed prominent reusability. All results indicated that the prepared Fe3O4@C composites had the potential to be used as adsorbents for the removal of dye pollutant from wastewater.