Qun Chen

Cobalt ferrite–polyaniline heteroarchitecture: a magnetically recyclable photocatalyst with highly enhanced performances

A cobalt ferrite–polyaniline photocatalyst is successfully prepared by in situ oxidative polymerization. The excellent magnetic properties of CoFe2O4 are maintained in the composite to some extent, and therefore the photocatalyst can be separated easily by an external magnetic field. A significant adsorption can be observed in the case of the anionic dyes and neutral dyes because the negatively charged groups or the electron-rich groups of these dyes undergo chemical interactions with the positively charged backbone of polyaniline (PANI). Such an adsorption helps in promoting the photodegradation of the dyes. It is interesting that although CoFe2O4 alone is an inactive visible-light-driven photocatalyst, the combination of CoFe2O4 nanoparticles with PANI leads to high photocatalytic activity for the degradation of the dyes under visible light irradiation. The dramatic enhancement in photoactivity can be attributed to the excited state electrons in PANI which can migrate to the conduction band (CB) of CoFe2O4, and the photogenerated holes in the valence band (VB) of CoFe2O4 which can directly transfer to the HOMO of PANI, effectively preventing a direct recombination of electrons and holes. Due to electrostatic repulsion, the cationic dyes containing positively charged groups cannot easily gain access to the positively charged backbone of PANI, giving very low photodegradation rates.

Solvent-thermal preparation of a CuCo2O4/RGO heterocomposite: an efficient catalyst for the reduction of p-nitrophenol

The reduction of a nitro group on the benzene ring is a process of great significance in chemical engineering, as the reduction of p-nitrophenol to p-aminophenol presents a classic example. In this study, a low-cost CuCo2O4/RGO (RGO: reduced graphene oxide) heterocomposite was prepared via the solvent-thermal method to facilitate catalytic reduction of p-nitrophenol, and its properties were investigated by means of XRD, FTIR, TEM and N2 adsorption–desorption measurements. Also, the catalytic activity of the as-synthesized CuCo2O4/RGO composite was investigated in the reduction of p-nitrophenol to p-aminophenol by NaBH4, which achieved complete conversion within 6 min. The CuCo2O4/RGO composite is superior to the current catalysts including some noble metals, in terms of the catalytic activity, recycling stability and cost, which indicated the possibility of realizing the industrial production of p-aminophenol in the future.

A facile novel preparation of three-dimensional Ni@graphene by catalyzed glucose blowing for high-performance supercapacitor electrodes

Three-dimensional Ni@graphene (NG) was prepared for the first time at a low temperature by a one-step facile calcination method. The obtained NG showed a high specific capacitance of 765 F g−1 at a current density of 1 A g−1 and only 5% loss of the initial specific capacitance after 3000 charge–discharge cycles.

A facile synthesis of Ag@graphene-nanosheet composite with enhanced antibacterial activity and acceptable environmental safety

In this work, Ag@graphene-nanosheet (Ag@GNS) composite was prepared by ball milling using AgNO3 as a precursor. XRD results showed silver nanoparticles were formed in the presence of graphene without the addition of a chemical reducing agent. TEM tests showed silver nanoparticles were uniformly anchored on the surface of a graphene nanosheet and were mostly in the size of 1–5xa0nm. ICP-AES revealed that silver makes up 9.42xa0% of the composite by weight. The antibacterial activities of the composite against gram-negative bacteria E. coli and gram-positive bacteria S. aureus were investigated. It was found that the Ag@GNS composite has enhanced antibacterial activity and outstanding stability, which makes it a potential antibacterial agent. Moreover, the cytotoxicity to the environment was assessed using L-929 mouse fibroblast cells using an MTT assay, which proved the composite has acceptable environmental safety for non-medical use.Graphical Abstract