Sutinder Behal

The reactivity of MoS2 single crystal edge planes

The reactivity of the edge planes of MoS2 have been studied on single crystals. MoS2 edge planes have been shown to be reactive toward oxygen by both optical and scanning Auger studies. In addition it has been shown that Co incorporated at low levels into single crystals tends to surface segregate at MoS2 edge planes.

Surface chemistry on transition metal colloids—an infrared and NMR study of carbon monoxide adsorption on colloidal platinum

Highly dispersed (<10{angstrom}) platinum has been prepared in colloidal solution by condensing platinum vapor into a solution of triisobutylaluminoxane in methylcyclohexane. Carbon monoxide, adsorbed in a linear mode on the surface of the colloidal metal, has been characterized by infrared spectroscopy and {sup 13}C NMR. The chemical shift of the adsorbed CO is 192 ppm, and the absence of a Knight shift is interpreted in terms of a pseudomolecular description of the highly dispersed platinum particles, which are not large enough to exhibit metallic properties. The CO covered colloid is converted by hydrolysis into the molecular platinum carbonyl anion clusters (Pt{sub 3}(CO){sub 6}){sub n}{sup 2 {minus}}, n = 3, 4.

Edge plane segregation in cobalt-doped MoS2 crystals

Abstract Single crystals of cobalt-doped MoS 2 have been examined by Auger spectroscopy. Segregation of cobalt to growth steps (edge planes) of the faceted crystals has been detected. Edge planes are preferred sites for oxygen adsorption. Some evidence has been obtained that oxygen adsorption enhances cobalt segregation. These findings are consistent with the pseudo-intercalation model of segregation in MoS 2 crystals.

Self-organization of graft copolymers at surfaces, interfaces and in bulk

The morphology in bulk and thin film of high-integrity graft copolymers has been investigated by small-angle neutron and light scattering, neutron reflectity and transmission electron microscopy. The model graft copolymers are based on two chemically incompatible blocks composed of an elastomeric poly(ethyl acrylate)(PEA) backbone onto which pendant monodisperse thermoplastic polystyrene (PS) are statistically placed. Two different levels of graft corresponding to an average of one and three per chain were investigated. In the bulk phase, the low graft-level shows irregular fractal-like structures while the high graft-level exhibits lamellar microdomains. In thin film, ordered structures were observed also in both compositions. The interphase adhesion between the PS and the PEA microdomain was investigated by elongating the copolymer films uniaxially. The low graft-level material exhibits normal behaviour characteristic of filler-reinforced rubber: the isotropic scattering pattern deforms in an anisotropic manner, i.e. ellipsoid-shaped with the long axis perpendicular to the stretching direction. An ‘abnormal butterfly’ pattern was observed with the high graft-level. The butterfly pattern is attributed to the deformation of the lamellar morphology of the copolymer.