ABSTRACT
Methylviologen dications (MV2+) were immobilized between layers of manganese oxide during their electrochemical assembly by an anodic route in a homogeneous aqueous Mn2+ solution. This approach yielded a well-ordered multilayer film on a platinum substrate as a result of dense packing of planar MV2+ molecules to stabilize the layered framework. A grazing angle in-plane X-ray diffraction study revealed that the manganese oxide sheets and the molecular planes of inserted MV2+ ions are oriented parallel to the electrode surface. Cyclic voltammetry of the product film indicated an electron transfer from the underlying Pt substrate to inserted methylviologen ions through the manganese oxide sheets.
Subject(s)
Chemistry, Physical/methods , Electrochemistry/methods , Manganese Compounds/chemistry , Oxides/chemistry , Paraquat/chemistry , Adsorption , Electrodes , Electrons , Ions , Kinetics , Manganese/chemistry , Microscopy, Electron, Transmission , Oxidation-Reduction , Platinum/chemistry , X-Ray DiffractionABSTRACT
Crystallographic structures and elemental distributions of grain boundaries in cobalt (Co)-based hard disk drive (HDD) media of CoCrTa and CoPtCrB were analysed by analytical transmission electron microscopy (TEM). CoCrTa medium had crystalline grain boundaries with extremely distorted (0002) planes of hexagonal close-packed structure. The width of grain boundaries of 1.5 nm obtained by high-resolution TEM (HRTEM) imaging agreed with that of 1.5 nm obtained by energy-dispersive spectroscopy (EDS) mapping. The EDS analysis revealed that Cr was segregated to grain boundaries while Ta was not segregated to either grain boundaries or grains. Cobalt was retained within grains. CoPtCrB medium had amorphous grain boundaries and spots in grains. The EDS and electron energyloss spectroscopy analyses revealed that both Cr and B were segregated to grain boundaries and spots. Both Co and Pt were retained within grains. The width of the boundaries of 0.4 nm obtained by HRTEM differed from that of 1.5 nm obtained by high-angle angular dark-field scanning TEM; the former indicates the crystallographic boundary and the later corresponds to the magnetic boundary, which is significantly correlated to the magnetic properties of HDD media.
