Guowang Diao

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.

Fabrication of Core–Shell α-Fe2O3@ Li4Ti5O12 Composite and Its Application in the Lithium Ion Batteries

In this work, a novel carbon-free core-shell α-iron oxide (α-Fe2O3)@ spinel lithium titanate (Li4Ti5O12, LTO) composite has been synthesized via a facile hydrothermal process. Element mapping confirmed the core-shell structure of α-Fe2O3@LTO. The effects of various experimental parameters, including thickness of TiO2 coating, reaction temperature, and time on the morphologies of the resulted products, were systematically investigated. The electrochemical measurements demonstrate that uniform α-Fe2O3 ellipsoids are coated with LTO to avoid forming a solid electrolyte interface (SEI) layer, to reduce initial capacity loss, and to improve the reversibility of α-Fe2O3 for Li ion storage. Compared with naked α-Fe2O3 ellipsoids, the α-Fe2O3@LTO composites exhibit lower initial capacity loss, higher reversible capacity, and better cycling performance for lithium storage. The electrochemical performance of α-Fe2O3@LTO composite heavily depends on the thickness and density of LTO coating shells. The carbon-free coating of LTO is highly effective in improving the electrochemical performance of α-Fe2O3, promising advanced batteries with high surface stability and excellent security.

One-Step Facile Solvothermal Synthesis of Copper Ferrite–Graphene Composite as a High-Performance Supercapacitor Material

In this work, we reported a facile approach to prepare a uniform copper ferrite nanoparticle-attached graphene nanosheet (CuFe2O4-GN). A one-step solvothermal method featuring the reduction of graphene oxide and formation of CuFe2O4 nanoparticles was efficient, scalable, green, and controllable. The composite nanosheet was fully characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), which demonstrated that CuFe2O4 nanoparticles with a diameter of approximately 100 nm were densely and compactly deposited on GN. To investigate the formation mechanism of CuFe2O4-GN, we discussed in detail the effects of a series of experimental parameters, including the concentrations of the precursor, precipitation agent, stabilizer agent, and graphene oxide on the size and morphology of the resulting products. Furthermore, the electrochemical properties of the CuFe2O4-GN composite were studied by cyclic voltammetry and galvanostatic charge-discharge measurements. The composite showed high electrochemical capacitance (576.6 F·g(-1) at 1 A·g(-1)), good rate performance, and cycling stability. These results demonstrated that the composite, as a kind of electrode materials, had a high specific capacitance and good retention. The versatile CuFe2O4-GN holds great promise for application in a wide range of electrochemical fields because of the remarkable synergistic effects between CuFe2O4 nanoparticles and graphene.

Synergistically enhanced electrochemical response of host-guest recognition based on ternary nanocomposites: reduced graphene oxide-amphiphilic pillar[5]arene-gold nanoparticles.

An amphiphilic pillar[5]arene (AP5) was modified onto the surface of reduced graphene oxide (RGO) to form the water-dispersive RGO-AP5 nanocomposite. And then, as-prepared gold nanoparticles (AuNPs) self-assembled onto the surface of RGO-AP5 through amido groups of AP5 to achieve RGO-AP5-AuNPs nanocomposites. It was verified that a large amount of AP5 molecules had been effectively loaded onto the surface of RGO and lots of AuNPs could be uniformly dispersed on RGO-AP5. Electrochemical results showed that the RGO-AP5 could exhibit selective supramolecular recognition and enrichment capability toward guest molecules. More significantly, in electrochemical sensing the guest molecules, ternary nanocomposites RGO-AP5-AuNPs performed the synergetic action of multifunctional properties, which were excellent performances of RGO, selective supramolecular recognition, and enrichment capability of AP5 and catalytic property of AuNPs for guest molecules. Therefore, RGO-AP5-AuNPs showed an outstanding analyzing performance for DA with broad linear range (1.5 × 10(-8) to 1.9×10(-5) M) and low detection limit (1.2 × 10(-8) M) at a signal-to-noise ratio of 3.

Calix[4,6,8]arenesulfonates functionalized reduced graphene oxide with high supramolecular recognition capability: fabrication and application for enhanced host-guest electrochemical recognition.

Reduced graphene oxide (rGO) modified with three kinds of water-soluble p-sulfonated calix[4,6,8]arene sodium (SCn: SC4, SC6, SC8) were successfully prepared by using a simple wet chemical strategy. Three obtained SCn-rGO nanocomposites were characterized by Fourier transform infrared spectroscopy, Ultraviolet-visible spectroscopy, static contact angle measurement, thermogravimetric analysis, scanning electron microscope and electrochemical impedance spectroscopy, which confirmed that different amount of SCn molecules had been effectively loaded onto the surface of rGO, and the water-dispersity and stability of SCn-rGO increased with the increase of the value of n in SCn (n = 4, 6, 8). More significantly, cyclic voltammetry measurement showed that the SCn-rGO could exhibit high supramolecular recognition and enrichment capability and consequently displayed excellent electrochemical response toward four probe molecules (biological and organic dye molecules). Especially, SC8-rGO exhibited an excellent electrochemical performance for dopamine with high current densities of 73.04 mA mM(-1) L cm(-2), broad linear range (1 × 10(-8) to 2.1 × 10(-5) M) and very low detection limit (8 × 10(-9) M) at a signal-to-noise ratio of 3.

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.

Magnetic-responsive supramolecular vesicles from self-organization of amphiphilic pillar[5]arene and application in controlled release.

A new amphiphilic pillar[5]arene (AP5-glycol) with five oligomeric glycol groups and five alkyl chains was prepared. AP5-glycol spontaneously formed bilayer vesicles in water, and these vesicles were still stable after several weeks. Additionally, when they were exposed to external physical stimuli, these vesicles also showed reversible thermal and dynamic properties. Interestingly, oleic-acid-stabilized magnetic iron oxide nanoparticles could be incorporated into the bilayer of the AP5-glycol vesicles to form hybrid magnetic-responsive supramolecular vesicles.

Stimulus-responsive light-harvesting complexes based on the pillararene-induced co-assembly of β-carotene and chlorophyll

The locations and arrangements of carotenoids at the subcellular level are responsible for their designated functions, which reinforces the necessity of developing methods for constructing carotenoid-based suprastructures beyond the molecular level. Because carotenoids lack the binding sites necessary for controlled interactions, functional structures based on carotenoids are not easily obtained. Here, we show that carotene-based suprastructures were formed via the induction of pillararene through a phase-transfer-mediated host–guest interaction. More importantly, similar to the main component in natural photosynthesis, complexes could be synthesized after chlorophyll was introduced into the carotene-based suprastructure assembly process. Remarkably, compared with molecular carotene or chlorophyll, this synthesized suprastructure exhibits some photocatalytic activity when exposed to light, which can be exploited for photocatalytic reaction studies of energy capture and solar conversion in living organisms.

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.