Qingze Jiao

Vapor diffusion synthesis of CoFe2O4 hollow sphere/graphene composites as absorbing materials

Novel CoFe2O4 hollow sphere/graphene composites were synthesized by a facile vapor diffusion method in combination with calcination at 550 °C. The structure and morphology of as-prepared hybrid materials were characterized by electron microscopy, X-ray diffractometry, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. Uniform CoFe2O4 hollow spheres with a diameter of about 500 nm and a shell thickness of approximately 50 nm were homogeneously distributed on graphene sheets. The electromagnetic parameters were measured using a vector network analyzer. A minimum reflection loss of −18.5 dB was observed at 12.9 GHz for the CoFe2O4 hollow sphere/graphene composites with a thickness of 2 mm, and the effective absorption frequency ranged from 11.3 to 15.0 GHz. The CoFe2O4 hollow sphere/graphene composites exhibited better microwave absorbing performance than the CoFe2O4 hollow spheres. A possible formation mechanism for CoFe2O4 hollow sphere/graphene composites was proposed.

Preparation of hollow Co3O4 microspheres and their ethanol sensing properties.

The hollow Co(3)O(4) microspheres were prepared by a gas-liquid diffusion reaction in the presence of ionic liquid [Bmim][BF(4)] in combination with calcination at 300 °C. Their structures and morphologies were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectrometry, and X-ray photoelectron spectroscopy. The growth mechanism of hollow Co(3)O(4) microspheres was proposed. The ethanol sensing properties were measured using a WS-30A gas sensor measurement system. The influence of working temperatures, ethanol concentrations, and specific surface areas of Co(3)O(4) microspheres on the ethanol sensing properties was investigated. The hollow Co(3)O(4) microspheres showed excellent sensitivity to ethanol vapor at a lower operating temperature.

Preparation of rugby-shaped CoFe2O4 particles and their microwave absorbing properties

Porous rugby-shaped CoFe2O4 particles were synthesized using a vapor diffusion method in combination with calcination. The morphologies and structures of the as-prepared CoFe2O4 particles were characterized by field emission scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, energy-dispersive spectroscopy, and N2 adsorption–desorption measurement. Results showed that uniform CoFe2O4 rugbies were about 1.1 μm in length and 500 nm in width at the widest point. Rugby-shaped CoFe2O4 nanoparticles were assembled by the layers of nanoparticles and exhibit porous structures. The magnetic and electromagnetic parameters were measured using a vibrating sample magnetometer and a vector network analyzer, respectively. The obtained rugby-shaped products exhibited a saturation magnetization of 73.4 emu g−1 and a coercivity of 2218.7 Oe at room temperature. A minimum reflection loss of −34.1 dB was observed at 13.4 GHz for the sample with a thickness of 2.5 mm, and the effective absorption frequency (RL < −10 dB) ranged from 12.3 to 14.9 GHz, indicating the excellent microwave absorption performance of the novel products. The absorbing performance of the CoFe2O4 rugbies was better than that of the CoFe2O4 nanoparticles.

One-step vapor diffusion synthesis of uniform CdS quantum dots/reduced graphene oxide composites as efficient visible-light photocatalysts

CdS quantum dots (QDs)/reduced graphene oxide (RGO) composites were synthesized through a one-step vapor diffusion process in the presence of ethylene glycol. The in situ growth of CdS QDs and the reduction of graphene oxide (GO) were completed simultaneously. Fourier transform infrared spectra, X-ray diffraction patterns, X-ray photoelectron spectroscopy and Raman spectroscopy confirmed the reduction of GO. Electron microscopy indicated uniform CdS QDs with size around 4–7 nm were well distributed on the RGO sheets. The transient photocurrent response, electrochemical impedance spectroscopy and diffuse reflectance UV-visible spectra of CdS QDs/RGO composites and CdS were tested to explain the role of RGO for the photocatalytic reaction. As-obtained composites exhibited better photocatalytic properties than pure CdS under visible light irradiation. The influence of different contents of GO on photocatalytic performance was also investigated. A possible photocatalytic mechanism of CdS QDs/RGO composites was proposed.

Synthesis of polyoxymethylene dimethyl ethers from methylal and trioxane catalyzed by Brønsted acid ionic liquids with different alkyl groups

Bronsted acid ionic liquids with different alkyl group carbon chain lengths and an alkane sulfonic acid group were synthesized through bromoalkane, imidazole and 1,4-butane sultone as raw materials. The structures and properties of the ionic liquids were experimentally characterized. Catalytic reaction of methylal (DMM) with trioxane (TOX) for preparation of polyoxymethylene dimethyl ethers (PODMEn, CH3O(CH2O)nCH3, where n > 1) was investigated in various Bronsted acid ionic liquids with different carbon chain length of alkyl groups. The carbon chain length of alkyl groups and activity correlation for the ionic liquids was studied. It was found that the structures of ionic liquids were consistent with the designed structure and their purities were high. They possessed high thermal stability and wide liquid range. The hydrophobicity of ionic liquids became stronger with the increase of carbon chain length. With increasing the carbon chain length of ionic liquids, the selectivity of PODME3–8 is increased at first and then decreased. Among all the ionic liquids, [C6ImBS][HSO4] shows the best catalytic performance and the selectivity of PODME3–8 is 57.85%.

Synthesis of zinc–nickel ferrite nanorods and their magnetic properties

Zinc–nickel (Zn–Ni) ferrite nanorods were synthesized by a microemulsion-based method in combination with calcination at different temperatures. The morphologies and structures of Zn–Ni ferrite nanorods and their precursors of Zn–Ni–Fe composite oxalate nanorods were characterized using field emission scanning electron microscopy and X-ray diffraction. Magnetization measurements were carried out using a vibrating sample magnetometer at room temperature. It was shown that the Zn–Ni ferrite nanorods were around 50–200 nm in diameter and several micrometers in length. Their saturation magnetization increased with increasing calcination temperature from 350 to 900 °C. In addition, the magnetic properties of the Zn–Ni ferrite nanorods were also affected by their composition.

Hydrogenation of Multi-walled Carbon Nanotubes in Ethylenediamine

Multi‐walled carbon nanotubes (MWNTs) were hydrogenated by using lithium in ethylenediamine under Benkesers conditions, which is convenient due to the avoidance of liquid ammonia used in the classical Birch reaction. The hydrogenated MWNTs were characterized by Raman, infrared spectroscopy, transmission electron microscopy and thermogravimetric analysis. The hydrogenation degree was also studied.

Basic polymerized imidazolide-based ionic liquid: an efficient catalyst for aqueous Knoevenagel condensation

A novel basic polymerized ionic liquid (BPIL): polymeric 1-[(4-ethenylphenyl)methyl]-3-propylimidazolium imidazolide was synthesized and characterized by Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR) and electron spray ionization mass spectrometry (ESI-MS). The BPIL was used as an efficient catalyst for aqueous Knoevenagel condensations with extended substrates. In comparison with common base catalysts, the BPIL showed high catalytic activity, which was ascribed to the cooperation between the strong basicity and the high surface activity. Moreover, the BPIL with high molecular weight has high surface activity and low catalytic activity. In addition, the BPIL was easily recovered and maintained high catalytic activity after five cycles of use in the system using benzaldehyde and malononitrile as substrates.

Graphitic carbon nitride quantum dot decorated three-dimensional graphene as an efficient metal-free electrocatalyst for triiodide reduction

We demonstrate a new strategy for the development of graphitic carbon nitride quantum dots decorated on three-dimensional graphene as an efficient electrocatalyst for triiodide reduction. The special architecture of these hybrids endows them with an abundance of exposed sites and multiple pathways of charge and mass transport, resulting in synergistically enhanced electrochemical performance.

Synthesis of methylal from methanol and formaldehyde catalyzed by Brønsted acid ionic liquids with different alkyl groups

The catalytic reaction of methanol with formaldehyde for the preparation of methylal was investigated in various Bronsted acid ionic liquids with different carbon chain length of alkyl groups. The structures, acidities, and properties of ionic liquids were experimentally characterized and theoretically analyzed. The Bronsted acidity–viscosity–activity correlation for the ionic liquids was studied. Among all these ionic liquids, [C6ImBS][HSO4] exhibited the best catalytic performance, which was ascribed to its strong Bronsted acidity and low viscosity. The catalytic activity of the ionic liquid was near that of concentrated sulfuric acid. The influences of ionic liquid dosage, reaction temperature and molar ratio of methanol to formaldehyde were explored using [C6ImBS]HSO4 as the catalyst. Under the optimal conditions of n(methanol) : n(formaldehyde) : n(ILs) = 2.5 : 1 : 0.0258, 60 °C, and 4 h, the conversion of formaldehyde can reach 63.37%. The ionic liquid [C6ImBS]HSO4 could be reused.