Vimlesh Chandra

Functionalization of graphene: covalent and non-covalent approaches, derivatives and applications.

Approaches, Derivatives and Applications Vasilios Georgakilas,† Michal Otyepka,‡ Athanasios B. Bourlinos,‡ Vimlesh Chandra, Namdong Kim, K. Christian Kemp, Pavel Hobza,‡,§,⊥ Radek Zboril,*,‡ and Kwang S. Kim* †Institute of Materials Science, NCSR “Demokritos”, Ag. Paraskevi Attikis, 15310 Athens, Greece ‡Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University Olomouc, 17. listopadu 12, 771 46 Olomouc, Czech Republic Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Namgu, Pohang 790-784, Korea Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo naḿ. 2, 166 10 Prague 6, Czech Republic

Water-Dispersible Magnetite-Reduced Graphene Oxide Composites for Arsenic Removal

Magnetite-graphene hybrids have been synthesized via a chemical reaction with a magnetite particle size of approximately 10 nm. The composites are superparamagnetic at room temperature and can be separated by an external magnetic field. As compared to bare magnetite particles, the hybrids show a high binding capacity for As(III) and As(V), whose presence in the drinking water in wide areas of South Asia has been a huge problem. Their high binding capacity is due to the increased adsorption sites in the M-RGO composite which occurs by reducing the aggregation of bare magnetite. Since the composites show near complete (over 99.9%) arsenic removal within 1 ppb, they are practically usable for arsenic separation from water.

Enhanced Cr(vi) removal using iron nanoparticle decorated graphene.

Nanoscale iron particles decorated graphene sheets synthesized via sodium borohydride reduction of graphene oxide, showed enhanced magnetic property, surface area and Cr(vi) adsorption capacity compared to bare iron nanoparticles.

Graphene?SnO2 composites for highly efficient photocatalytic degradation of methylene blue under sunlight

Graphene sheets decorated with SnO(2) nanoparticles (RGO-SnO(2)) were prepared via a redox reaction between graphene oxide (GO) and SnCl(2). Graphene oxide (GO) was reduced to graphene (RGO) and Sn(2+) was oxidized to SnO(2) during the redox reaction, leading to a homogeneous distribution of SnO(2) nanoparticles on RGO sheets. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show uniform distribution of the nanoparticles on the RGO surface and high-resolution transmission electron microscopy (HRTEM) shows an average particle size of 3-5 nm. The RGO-SnO(2) composite showed an enhanced photocatalytic degradation activity for the organic dye methylene blue under sunlight compared to bare SnO(2) nanoparticles. This result leads us to believe that the RGO-SnO(2) composite could be used in catalytic photodegradation of other organic dyes.

Synthesis of nano zerovalent iron nanoparticles – Graphene composite for the treatment of lead contaminated water

A Nano zerovalent iron nanoparticles graphene composite (G-nZVI) was prepared via a sodium borohydride reduction of graphene oxide and iron chloride under an argon atmosphere. Powder X-ray diffraction patterns showed the formation of the magnetic graphene/nanoscale-zerovalent-iron (G-nZVI) composites and bare nanoscale-zerovalent-iron (nZVI) particles. TEM analysis shows the formation of ~10 nm particles. Adsorption experiments show a maximum Pb(II) adsorption capacity for the G-nZVI composite with 6 wt% graphene oxide loading. Additionally the effects of pH, temperature, contact time, ionic strength and initial metal ion concentration on Pb(II) ion removal were studied. X-ray photoelectron spectroscopy analysis after adsorption results confirmed the composites ability to adsorb and immobilize lead more efficiently in its zerovalent and bivalent forms, as compared to bare iron nanoparticles. The adsorption of Pb(II) ions fit a pseudo-second-order kinetic model, and adsorption isotherms can be described using the Freundlich equations. G-nZVI shows great potential as an efficient adsorbent for lead immobilization from water, as it exhibits stability, reducing power, a large surface area, and magnetic separation.

Synthesis of N-doped microporous carbon via chemical activation of polyindole-modified graphene oxide sheets for selective carbon dioxide adsorption.

A polyindole-reduced graphene oxide (PIG) hybrid was synthesized by reducing graphene oxide sheets in the presence of polyindole. We have shown PIG as a material for capturing carbon dioxide (CO2). The PIG hybrid was chemically activated at temperatures of 400-800 °C, which resulted in nitrogen (N)-doped graphene sheets. The N-doped graphene sheets are microporous with an adsorption pore size of 0.6 nm for CO2 and show a maximum (Brunauer, Emmet and Teller) surface area of 936 m(2) g(-1). The hybrid activated at 600 °C (PIG6) possesses a surface area of 534 m(2) g(-1) and a micropore volume of 0.29 cm(3) g(-1). PIG6 shows a maximum CO2 adsorption capacity of 3.0 mmol g(-1) at 25 °C and 1 atm. This high CO2 uptake is due to the highly microporous character of the material and its N content. The material retains its original adsorption capacity on recycling even after 10 cycles (within experimental error). PIG6 also shows high adsorption selectivity ratios for CO2 over N2, CH4 and H2 of 23, 4 and 85 at 25 °C, respectively.

Radioactive iodine capture and storage from water using magnetite nanoparticles encapsulated in polypyrrole

The effective capture and storage of radioactive iodine is of importance for nuclear waste storage during nuclear power station accidents. Here we report Fe3O4@PPy powder containing ∼12nm magnetite (Fe3O4) nanoparticles encapsulated in the polypyrrole (PPy) matrix. It shows 1627mg/g uptake of iodine dissolved in water, within 2h at room temperature. Fe3O4@PPy is ferromagnetic in nature and can be separated from water using external magnetic field. The nitrogen gas sweeping test at 30°C shows release of 2% iodine from iodine adsorbed Fe3O4@PPy, revealing stable storage of iodine for a moderate period. The iodine-adsorbed magnetic powder can be regenerated by washing with ethanol. The XPS spectrum of iodine adsorbed Fe3O4@PPy confirmed the presence of polyiodides (I3- and I5-) bound to the PPy surface. This excellent iodine capture and storage from iodine contaminated water is an environment friendly, inexpensive and large scale method.