Probing the charging mechanisms of carbon nanomaterial polyelectrolytes

Chemical charging of single-walled carbon nanotubes (SWCNTs) and graphenes to generate soluble salts shows great promise as a processing route for electronic applications, but raises fundamental questions. The reduction potentials of highly-charged nanocarbon polyelectrolyte ions were investigated by considering their chemical reactivity towards metal salts/complexes in forming metal nanoparticles. The redox activity, degree of functionalisation and charge utilisation were quantified via the relative metal nanoparticle content, established using thermogravimetric analysis (TGA), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and X-ray photoelectron spectroscopy (XPS). The fundamental relationship between the intrinsic nanocarbon electronic density of states and Coulombic effects during charging is highlighted as an important area for future research

Carbon nanotube anions for the preparation of gold nanoparticle–nanocarbon hybrids

Gold nanoparticles (AuNPs) can be evenly deposited on single-walled carbon nanotubes (SWCNTs) via the reduction of the highly stable complex, chloro(triphenylphosphine) gold(I), with SWCNT anions (‘nanotubides’). This methodology highlights the unusual chemistry of nanotubides and provides a blueprint for the generation of many other hybrid nanomaterials

Induced migration of fines during waterflooding in communicating layer-cake reservoirs

The effects of fines migration induced by injection of water with a different salinity than the reservoir brine are incorporated into the upscaling model for waterflooding in a layer cake reservoir with good communication between the layers. Mobilization and re-capturing of the reservoir fines may give rise to reduction of the permeability in water swept zones, which subsequently leads to the diversion of water flow from the initially more permeable layers to the less permeable ones. As a result, the displacement is more even, the water cut at the producer is decreased, and the oil recovery is increased. On the other hand, more energy for the pressure drop is required to maintain a constant flow rate. These effects are studied within a new upscaling model developed previously (Zhang et al., 2011). In a communicating layer cake reservoir, higher end-point mobility ratio (water to oil) leads to more crossflow between layers and lowers the water sweep efficiency. However, this ratio facilitates the fluid diversion caused by the fines migration, leading to a more efficient enhanced oil recovery. The positive contribution from the mobility ratio to the increased oil recovery due to fines migration seems to be limited

A systematic method for parametrising periodic minimal surfaces : the F-RD surface

An algorithm for the exact construction of triply periodic minimal surfaces recently developed by the author is illustrated simply with the first parametrisation of the F-RD surface discovered by Alan Schoen. An exact expression for the F-RD Weierstrass function is derived, from which all quantitative features of this surface may be readily established

WEIERSTRASS REPRESENTATION OF PERIODIC MINIMAL SURFACES

A general algorithm for the construction of infinite periodic minimal surfaces (IPMS) via their Weierstrass function is outlined, enabling parameterisation of known examples, and forming the bases of a systematic search for all such surfaces. For the 'regular' class of IPMS (including the low genus surfaces) the Weierstrass function has a simple form, permitting a complete listing of all possibilities. The method is then readily extended to parametrisation of the 'irregular' class of IPMS, and its generally illustrated with several previously unsolved examples

Continuous Transformation of Cubic Minimal Surfaces

Although the primitive (P), diamond (D) and gyroid (G) minimal surfaces form the structural basis for a multitude of self-assembling phases, such as the bicontinuous cubics, relatively little is known regarding their geometrical transformations, beyond the existence of the Bonnet isometry. Here their highest symmetry deformation modes, the rhombohedral and tetragonal distortions, are fully elucidated to provide a unified description of these simplest minimal surface families, with all quantities expressed in terms of complete elliptic integrals. The rhombohedral distortions of the gyroid are found to merge continuously with those which bridge the P and D surfaces, furnishing direct transformations between all three cubics, preserving both topology and zero mean curvature throughout. The tetragonal distortions behave analogously, offering an alternative route from the gyroid to the D surface. The cell axis ratios, surface areas and Gaussian curvature moments of all families are given, supplying the necessary geometrical input to a curvature energy description of cubic and intermediate phase stability

Electrostatics of Curved Fluid Membranes: The Interplay of Direct Interactions and Fluctuations in Charged Lamellar Phase

Our understanding of the Poisson-Boltzmann electrostatics of curved fluid monolayers and bilayers of ionic amphiphiles, and its status within the Helfrich bending-energy formulation, is reviewed and subsequently extended. The two limiting scenarios, namely excess salt (non-overlapping interfaces) and zero salt (counterions only) are briefly discussed to couch their generalization to intermediate screening. This general situation of arbitrary composition is treated first within the cylindrical and spherical cell models, to harmonic order in their curvatures, leading on to the geometry of undulating planar confinement, now harmonic in amplitude but covering the entire spectrum of wavelengths. The latter derivation extends previous results, and moreover, provides analytic expressions for the electrostatic free energy using theta function developments. This in turn supplies the Hamiltonian for the generalized harmonic theory of fluctuating lamellar phases with added salt. Finally, the statistical mechanical predictions for the area increase, and relative amplitudes, of bilayer thermal undulations are compared to existing light-scattering data from dilute lamellar phases doped with anionic surfactant