TY - JOUR A1 - Lamiel, C. A1 - Nguyen, V. H. A1 - Tuma, Dirk A1 - Shim, J.-J. T1 - Non-aqueous synthesis of ultrasmall NiO nanoparticle-intercalated graphene composite as active electrode material for supercapacitors N2 - With the vast exploration of the applications of graphene, researchers are assessing different methods for fabricating graphene-based electrode material with high capacitance but low material and energy costs. In this study, reduced graphene oxide/nickel oxide (RGO/NiO) nanocomposites were prepared using a non-aqueous solvent-based method followed by calcination. Nickel acetate tetrahydrate and tert-butanol were used as the precursor and solvent, respectively. Ultrasmall nickel oxide nanoparticles, ca. 8.0 nm in size, were deposited on the surface of the graphene sheets simultaneously with the partial reduction of graphene oxide. The resulting RGO/NiO electrode exhibited a high capacitance of 689 F g⁻1 at a current density of 0.8 A g⁻1. After 1500 cycles, the specific retention and the coulombic efficiency yielded to 86.34% and 96.39%, respectively, which supports the viability of this composite as an alternative activated material with high electrochemical performance. KW - Nanocomposite KW - Graphene KW - Supercapacitor PY - 2016 DO - https://doi.org/10.1016/j.materresbull.2016.06.005 SN - 0025-5408 SN - 1873-4227 VL - 83 SP - 275 EP - 283 PB - Elsevier Ltd. CY - London AN - OPUS4-36812 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tuma, Dirk A1 - Kharismadevi, D. A1 - Haldorai, Y. A1 - Nguyen, V. H. A1 - Shim, J.-J. T1 - Synthesis of graphene oxide-poly(2-hydroxyethylmethacrylate) composite by dispersion polymerization in supercritical CO2: adsorption behavior for the removal of organic dye N2 - The use of a biocompatible and thermoresponsive polymer, poly (2-hydroxyethyl methacrylate) (PHEMA) grafted onto the surface of graphene oxide (GO) as an adsorbent for the removal of a cationic dye (methylene blue [MB]) from an aqueous solution is examined in this work. GO–PHEMA forms a hydrogel in water thus overcoming the problem faced by carbon-based adsorbent materials during post-treatment (i.e., separation of adsorbent from the aqueous phase). The GO–PHEMA composite was synthesized using a green approach through dispersion polymerization in supercritical CO2. The successful preparation of this composite was confirmed by a series of characterization techniques. The adsorption behavior of the composite toward MB, such as the effect of the adsorbent dosage, pH, contact time, dye concentration, and recyclability was observed. In addition, the adsorption isotherm, kinetics and thermodynamics were investigated. According to the experimental data, the adsorption parameters were found to fit well into the Freundlich adsorption isotherm with a correlation coefficient of 0.975 and a maximum predicted adsorption capacity of 39.41 mg g−1 at 25 °C. The adsorption kinetics studies showed that the adsorption behavior followed a pseudo-second-order reaction. On the other hand, the thermodynamics studies showed that the adsorption of MB on GO–PHEMA composite followed spontaneous and endothermic adsorption process with an efficient adsorption temperature at 45 °C. The experimental results also showed that the GO–PHEMA composite could remove 99.8 % of the dye in 45 min. Therefore, GO–PHEMA composite is a favorable green adsorbent for environmental applications. KW - graphene oxide KW - poly (2-hydroxyethyl methacrylate) (PHEMA) KW - adsorption KW - composite materials PY - 2016 DO - https://doi.org/10.1080/09276440.2016.1169707 SN - 0927-6440 SN - 1568-5543 VL - 23 IS - 7 SP - 719 EP - 739 PB - Taylor & Francis CY - London, UK AN - OPUS4-36293 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tran, V. C. A1 - Nguyen, V. H. A1 - Tuma, Dirk A1 - Shim, J.-J. T1 - Ionic liquid mediated synthesis of poly(2-hydroxyethyl methacrylate-block-methyl methacrylate)/Fe3O4 core–shell structured nanocomposite by ATRP method N2 - A hybrid nanocomposite of magnetic nanoparticles (Fe3O4) and poly(2-hydroxyethyl methacrylate)-blockpoly(methyl methacrylate) (PHEMA-b-PMMA) was synthesized successfully by the atom transfer radical polymerization (ATRP) in an ionic liquid (IL), 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF6). Fe3O4 nanoparticles were first surface-modified with the initiator, 2-bromoisobutyryl bromide (BiBBr), in dimethylformamide (DMF) solvent, which produced the macro-initiator, Fe3O4-BiB, to initiate the polymerization reactions for the synthesis of the block polymer, PHEMA-b-PMMA. After immobilizing the Initiator on the surface of Fe3O4, the block polymer chains were grafted successfully onto the Fe3O4 surface, causing the Formation of a core-shell nanostructure. The incorporation of Fe3O4 in the nanocomposite was confirmed by attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. The thermal stability and magnetic properties increased with increasing amount of Fe3O4 in the nanocomposite. KW - Nanocomposite KW - Block copolymer KW - Fe3O4 nanoparticles KW - Ionic liquid KW - Atom transfer radical polymerization PY - 2016 DO - https://doi.org/10.1007/s00396-016-3835-5 SN - 1435-1536 SN - 0303-402X VL - 294 IS - 4 SP - 777 EP - 785 PB - Springer International Publishing AG CY - Berlin AN - OPUS4-35893 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -