ABSTRACT
Two types of graphene nanoribbons: (a) potassium-split graphene nanoribbons (GNRs), and (b) oxidative unzipped and chemically converted graphene nanoribbons (CCGNRs) were investigated for their magnetic properties using the combination of static magnetization and electron spin resonance measurements. The two types of ribbons possess remarkably different magnetic properties. While a low-temperature ferromagnet-like feature is observed in both types of ribbons, such room-temperature feature persists only in potassium-split ribbons. The GNRs show negative exchange bias, but the CCGNRs exhibit a "positive exchange bias". Electron spin resonance measurements suggest that the carbon-related defects may be responsible for the observed magnetic behavior in both types of ribbons. Furthermore, information on the proton hyperfine coupling strength has been obtained from hyperfine sublevel correlation experiments performed on the GNRs. Electron spin resonance finds no evidence for the presence of potassium (cluster) related signals, pointing to the intrinsic magnetic nature of the ribbons. Our combined experimental results may indicate the coexistence of ferromagnetic clusters with antiferromagnetic regions leading to disordered magnetic phase. We discuss the possible origin of the observed contrast in the magnetic behaviors of the two types of ribbons studied.
Subject(s)
Crystallization/methods , Graphite/chemistry , Magnets , Nanostructures/chemistry , Nanostructures/ultrastructure , Electromagnetic Fields , Macromolecular Substances/chemistry , Materials Testing , Molecular Conformation , Oxidation-Reduction , Particle Size , Surface PropertiesABSTRACT
Small-diameter (ca. 0.7 nm) single-wall carbon nanotubes are predicted to display enhanced reactivity relative to larger-diameter nanotubes due to increased curvature strain. The derivatization of these small-diameter nanotubes via electrochemical reduction of a variety of aryl diazonium salts is described. The estimated degree of functionalization is as high as one out of every 20 carbons in the nanotubes bearing a functionalized moiety. The functionalizing moieties can be removed by heating in an argon atmosphere. Nanotubes derivatized with a 4-tert-butylbenzene moiety were found to possess significantly improved solubility in organic solvents. Functionalization of the nanotubes with a molecular system that has exhibited switching and memory behavior is shown. This represents the marriage of wire-like nanotubes with molecular electronic devices.
ABSTRACT
[reaction: see text]. Monoiodinated anilines were prepared in good to excellent yields by the action of benzyltriethylammonium dichloroiodate on anilines in the presence of sodium bicarbonate and methanol. The iodinating reagent was prepared in an environmentally friendly fashion without the use of organic solvents.
ABSTRACT
[reaction: see text]. Functionalized diazonium salts for molecular electronic devices are prepared by the reaction of the corresponding anilines with NOBF4 in sulfolane-acetonitrile solvent.
