02369nas a2200205   4500008004100000245015500041210006900196260000800265300001400273490000800287520159000295100001901885700002001904700002101924700002401945700002001969700001801989700002402007856013202031       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  uhttps://library.ncl.res.in/content/effective-noncovalent-functionalization-polyethylene-glycol-reduced-graphene-oxidenanosheets