02599nas a2200205   4500008004100000022001400041245012300055210006900178260011000247300001600357490000600373520176200379100001902141700002102160700002002181700002402201700001802225700002402243856012602267       2015                        eng d  a2046-206900aChemically grafted graphite nanosheets dispersed in poly(ethylene-glycol) by gamma-radiolysis for enhanced lubrication0 aChemically grafted graphite nanosheets dispersed in polyethylene  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcJUN  a53766-537750 v53 a<p>Graphite nanosheets (Gr-NS) dispersed in poly(ethylene-glycol) (PEG200) medium were subjected to various doses of gamma-irradiation. Hydroxyl functional groups present in PEG are chemically grafted through hydrogen bonding with hydroxyl, carbonyl and carboxylic groups of Gr-NS. The grafting process is driven by the generation of active radicals from solvent radiolysis. Chemical grafting was investigated using X-ray photoelectron spectroscopy (XPS) and Fourier transform infra-red (FTIR) spectroscopy. The results of spectroscopic studies revealed reduction in oxygen functionality of PEG-Gr-NS at higher doses of gamma-irradiation. The gamma-irradiation not only bridges the functionalities between PEG and PEG-Gr-NS but edge and basal plane defects in Gr-NS are further reduced as is evident from Raman analysis. The inter-planar sheet distance in Gr-NS is increased due to intercalated chemical grafting with PEG molecules. The chemical grafting between PEG and Gr-NS and reduction in defects enhance the tribological properties with a decrease of 26% and 32% for the friction coefficient and wear, respectively as compared to PEG alone. The lubrication mechanism is mediated through inter-planar weak forces when PEG is chemically grafted with Gr-NS. The electrostatic interaction of PEG with Gr-NS acts as a molecular bridge thus enhancing the sustainability of tribo-stress. Additionally, in the presence of functionalized PEG-Gr-NS tribo-contact conditions, evidence of deposited graphitic tribo-film was observed from micro-Raman spectroscopy inside the steel wear track. This film further enhanced lubrication mediated through low shear strength interlayer graphite sheets and therefore, antiwear properties were synergistically improved.</p>1 aGupta, Bhavana1 aPanda, Kalpataru1 aKumar, Niranjan1 aMelvin, Ambrose, A.1 aDash, Sitaram1 aTyagi, Ashok, Kumar  uhttp://library.ncl.res.in/content/chemically-grafted-graphite-nanosheets-dispersed-polyethylene-glycol-gamma-radiolysis-002368nas a2200205   4500008004100000245015500041210006900196260000800265300001400273490000800287520159000295100001901885700002001904700002101924700002401945700002001969700001801989700002402007856013102031       2016                        eng d00aEffective noncovalent functionalization of poly(ethylene glycol) to reduced graphene oxidenanosheets through gamma-radiolysis for enhanced lubrication0 aEffective noncovalent functionalization of polyethylene glycol t  cFEB  a2139-21480 v1203 aHigh-quality reduced graphene oxide (rGO) nanosheets (NSs) were synthesized by the oxidation of graphite followed by hydrazine treatment for the reduction of the oxygen functionalities. gamma-Radiolysis was then used for the functionalization of the rGO-NSs with poly(ethylene glycol) 200 (PEG200). The functionalization resulted in the intercalation of PEG200 molecules in rGO through hydrogen bonding between the hydroxyl groups of rGO and the oxygen atoms of PEG200 molecules. This resulted in an increase in the d spacing of the graphene sheets and a decrease in the defect density of the carbon network in the rGO. The friction coefficient and wear of sliding steel surfaces were reduced by 38% and 55%, respectively, when 0.03 mg mL(-1) PEG200-functionalized rGO dispersed in PEG200 was used. The lubrication properties can be described by bipolar interactions between PEG200 and rGO, leading to effective dispersion. Chemical analysis of wear particles showed decomposition of rGO into nanosized graphite domains, as exhibited by mechanical energy produced in tribo-contact. Moreover, these domains formed effective and stable tribofilms on the steel wear tracks that easily sheared under the action of contact stress. This significantly enhanced the antifriction and antiwear properties, resulting in improved oxidation resistance of PEG200 under the tribo-contact. It was found that, at high rGO concentrations, the lubrication efficiency decreased as a result of graphene-graphene intersheet collisions, producing mechanical energy and chemical defects at contact interfaces.1 aGupta, Bhavana1 aKumar, Niranjan1 aPanda, Kalpataru1 aMelvin, Ambrose, A.1 aJoshi, Shailesh1 aDash, Sitaram1 aTyagi, Ashok, Kumar  uhttp://library.ncl.res.in/content/effective-noncovalent-functionalization-polyethylene-glycol-reduced-graphene-oxidenanosheets02169nas a2200205   4500008004100000022001400041245010200055210006900157260006700226300001200293490000600305520141000311100001901721700002001740700002101760700002401781700002001805700001801825856012001843       2016                        eng d  a2196-735000aMolecular-Pillar-supported functionalized reduced graphene-oxide for energy efficient lubrication0 aMolecularPillarsupported functionalized reduced grapheneoxide fo  a111 RIVER ST, HOBOKEN 07030-5774, NJ USAbWILEY-BLACKWELLcJUL  a16001610 v33 a<p>Molecular-pillar-supported basal plane of reduced graphene oxide (rGO) is fabricated by polymerizing polyaniline (PANI). In the presence of poly(ethylene glycol) (PEG200), the gamma-radiolysis is used for modifying the functionalization and improving the structural symmetry of PANI and PEG grafted rGO (PANI-PEG-g-rGO). The PANI is covalently and noncovalently grafted onto the surface of the graphene sheets. Carboxyl groups of rGO are linked to the nitrogen atoms in the PANI backbone and an accompanying noncovalent interaction between alkyl chains of grafted PANI and hydrooxylated rGO is formed. Raman and Fourier transform infra-red results confirm existence of stretching vibrations of benzenoid and quinonoid rings in PANI-PEG-g-rGO-functionalized composite, indicating grafting between PANI and rGO through pi-pi interaction. Furthermore, PEG-functionalization through hydrogen bonding with rGO is confirmed when hydroxyl group from the rGO combines with oxygen of PEG. X-ray photoelectron spectroscopy reveals significant increase in carbon, while loading PANI network with rGO followed by gamma-irradiation. Antifriction and antiwear properties of graphene nanocomposite are considerably enhanced to 68.4% and 48%, respectively, as compared to pristine PEG. The unique lubrication properties are explained by PEG functionalized molecular PANI-pillar structure across basal plane of rGO.</p>1 aGupta, Bhavana1 aKumar, Niranjan1 aPanda, Kalpataru1 aMelvin, Ambrose, A.1 aJoshi, Shailesh1 aDash, Sitaram  uhttp://library.ncl.res.in/content/molecular-pillar-supported-functionalized-reduced-graphene-oxide-energy-efficient