Stine Nalum Naess

Carbon nanocones: wall structure and morphology

Abstract Large-scale production of conical carbon nanostructures is possible through pyrolysis of hydrocarbons in a plasma torch process. The resulting carbon cones occur in five distinctly different forms, and disc-shaped particles are produced as well. The structure and properties of these carbon cones and discs have been relatively little explored until now. Here we characterize the structure of these particles using transmission electron microscopy, synchrotron x-ray and electron diffraction. The carbon nanocones are found to exhibit several interesting structural features; instead of having a uniform cross-section, the walls consist of a relatively thin inner graphite-like layer with a non-crystalline envelope, where the amount of the latter can be modified significantly by annealing. The cones appear with a well-defined faceting along the cone edge, demonstrating strict long-range atomic ordering; they also present occasional examples of symmetry breaking, such as two apexes appearing in the same carbon nanocone.

Brownian dynamics simulation of rigid bodies and segmented polymer chains. Use of Cartesian rotation vectors as the generalized coordinates describing angular orientations

The three Eulerian angles constitute the classical choice of generalized coordinates used to describe the three degrees of rotational freedom of a rigid body, but it has long been known that this choice yields singular equations of motion. The latter is also true when Eulerian angles are used in Brownian dynamics analyses of the angular orientation of single rigid bodies and segmented polymer chains. Starting from kinetic theory we here show that by instead employing the three components of Cartesian rotation vectors as the generalized coordinates describing angular orientation, no singularity appears in the configuration space diffusion equation and the associated Brownian dynamics algorithm. The suitability of Cartesian rotation vectors in Brownian dynamics simulations of segmented polymer chains with spring-like or ball-socket joints is discussed.

Brownian Dynamics of Segmented Biopolymers: A Formal Theory and Numerical Simulations

The motivation and basic concepts of Brownian dynamics of segmented biopolymers using spatial coordinates rather than the standard bead-rod-spring polymer model are well accounted for the literature. Here we report on recent advances in the theoretical description of polymer chains consisting of rigid subunits with arbitrary shape. The new results include a more generalized analysis of the metric force and the differences between biopolymers linked by springs or holonomic constraints, respectively. We also discuss numerical algorithms at different levels of coordinate contraction. Finally, in order to test the validity of the formal theory and numerical algorithms a detailed example is presented. For two-needle chains with holonomic constraint and in thermodynamic equilibrium we find perfect agreement between theory and results from the numerical simulations.

Hydrophilic carotenoids: facile syntheses of carotenoid oxime hydrochlorides as long-chain, highly unsaturated cationic (bola)amphiphiles

Stable cationic carotenoid aggregates - predominantly of the J-type - develop when the hydrochlorides of carotenoid aldoximes and ketoximes are exposed to water. The oxime hydrochlorides are obtained by simple syntheses from commercially available food color carotenoids. Bluish-purple, unstable transient compounds were observed during hydrochlorination performed at liquid nitrogen temperature.

Studies on the mechanism of the Carr–Price blue colour reaction

The reaction of retinoids (retinol, retinyl acetate and anhydroretinol) with Brønsted acids was studied as a model system for the Carr-Price reaction. The anhydroretinylic cation was characterised by VIS and 2D NMR spectroscopy, including an estimate of the charge distribution and region of bond inversion, observed in a mixture of identified E/Z isomers. Products obtained by quenching with NaOMe-MeOH were identified by HPLC and MS. The classical Carr-Price reaction between retinol (vitamin A) and the Lewis acid SbCl(3) in saturated chloroform solution was reinvestigated by VIS, NMR, EPR, dynamic light scattering and chemical quenching. Whereas product instability and failure to provide informative NMR spectra indicated a radical cation, EPR results excluded free-radical species. Dynamic light scattering experiments, in comparison with model systems, revealed strong aggregation for the Carr-Price complex, rationalizing the low stability, NMR problems and dimerisation observed by chemical quenching. The VIS data support structural similarity of the blue Carr-Price product with the delocalized anhydroretinylic cation, and a detailed structure of the antimony complex is evaluated.

Carbon Cones - a Structure with Unique Properties

Large-scale production of perfect conical carbon nanostructures that are fundamentally different from the other nanocarbon materials, such as buckyballs and nanotubes, can be made using the so-called Kvaerner Carbon Black & Hydrogen Process. This involves pyrolysis of hydrocarbons using a torch plasma process. The carbon cones that occur appear in five distinctly different forms. In addition, disk-shaped particles may be produced. Here we report about the current status for the experimental research and theoretical modeling of these particles, which have properties different from the other known forms of carbon.