Hui-Ling Ma

Functionalization and reduction of graphene oxide with p-phenylene diamine for electrically conductive and thermally stable polystyrene composites

A facile and efficient approach was developed to simultaneously functionalize and reduce graphene oxide (GO) with p-phenylene diamine (PPD) by simple refluxing. This was possible by the nucleophilic substitution reaction of epoxide groups of GO with amine groups of PPD aided by NH(3) solution. As a consequence, electrical conductivity of GO-PPD increased to 2.1 × 10(2) S/m, which was nearly 9 orders of magnitude higher than that of GO. Additionally, after the incorporation of GO-PPD in polystyrene (PS), the composites exhibited a sharp transition from electrically insulating to conducting behavior with a low percolation threshold of ~0.34 vol %, which was attributed to the improved dispersion and the reduction of GO-PPD. Thermal stability of the PS/GO-PPD composite was also ~8 °C higher than that of PS.

Facile synthesis of well-dispersed graphene by γ-ray induced reduction of graphene oxide

We demonstrate a facile and environmentally friendly approach to prepare well-dispersed graphene sheets by γ-ray induced reduction of a graphene oxide (GO) suspension in N,N-dimethyl formamide (DMF) at room temperature. GO is reduced by the electrons generated from the radiolysis of DMF under γ-ray irradiation. The reduced GO by γ-ray irradiation (G-RGO) can be re-dispersed in many organic solvents, and the resulting suspensions are stable for two weeks due to the stabilization of N(CH3)2+ groups on G-RGO. Additionally, G-RGO is efficient in improving the conductivity of polystyrene (PS). Its PS nanocomposites exhibit a sharp transition from electrically insulating to conducting with a low percolation threshold of 0.24 vol% and a high electrical conductivity of 45 S m−1 is obtained with only 2.3 vol% of G-RGO. The superior electrical conductivity is attributed to the uniform dispersion of the G-RGO sheets in the PS matrix.

A facile synthesis of platinum nanoparticle decorated graphene by one-step γ-ray induced reduction for high rate supercapacitors

A facile method has been developed to synthesize a high-quality platinum nanoparticle (PtNP) decorated graphene via one-step γ-ray induced reduction of graphite oxide (GO) and chloroplatinic acid at room temperature. GO and Pt(IV) precursor salt could be co-reduced by the electrons generated from the radiolysis of ethylene glycol under γ-ray irradiation. The synchronous reduction of the metal precursor and regulation of pH greatly increased the ratio of C/O in the reduced GO (RGO). PtNPs with an average diameter of 1.8 nm were uniformly dispersed on the surface of RGO sheets. The as-prepared PtNP–RGO composites as supercapacitor electrodes displayed a specific capacitance of 154 F g−1 at a current density of 0.1 A g−1 and the value retained as high as 72.3% at 20 A g−1 which was significantly enhanced compared to 16.2% capacity retention of RGO prepared by the same method. The investigation of electrochemical performances suggests that PtNPs play an important role in enhancing supercapacitor performance with high rate capability by accelerating the electron transfer and increasing the electrochemical active surface area of RGO.