Graphene nanoflakes (GNFs) with average diameters of ∼30 nm have been prepared by a single-step oxidation procedure using single-wall carbon nanotube arc-discharge material and nitric acid. The GNFs are predominately single sheets containing a small number of internal defects. The edges are decorated with primarily carboxylic acid groups which allow facile chemical functionalisation and cross-linking of the fragments using multivalent cations.

A polymeric dispersing agent for single-wall carbon nanotubes (SWCNTs) in water was synthesized by 4-(pyren-1-yl)butanoylation of the amine groups of poly-L-lysine. The pyrene content of 4-(pyren-1-yl)butanoylated polylysine (PBPL) was optimized so that a maximal dispersion effect of the SWCNTs was obtained. High molecular weight PBPL (>300000 g mol−1) exceeds the widely used surfactant sodium dodecylsulfate (SDS) as a dispersing agent yielding a 27% higher SWCNT concentration in dispersion. The high stability of the PBPL/SWCNT conjugates is demonstrated by removing the conjugates from dispersion through filtration, washing, and redispersion in only water. The resulting redispersions do not contain free PBPL and the importance of having SWCNT dispersions in the absence of free dispersing agent is discussed. For SDS dispersions, poor redispersion properties have been observed. The binding of PBPL onto the SWCNTs was studied by atomic force microscopy, optical absorbance spectroscopy, and fluorescence spectroscopy.

Doped ice V samples made from solutions containing 0.01 M HCl (DCl), HF (DF), or KOH (KOD) in H2O (D2O) were slow-cooled from 250 to 77 K at 0.5 GPa. The effect of the dopant on the hydrogen disorder → order transition and formation of hydrogen ordered ice XIII was studied by differential scanning calorimetry (DSC) with samples recovered at 77 K. DSC scans of acid-doped samples are consistent with a reversible ice XIII ↔ ice V phase transition at ambient pressure, showing an endothermic peak on heating due to the hydrogen ordered ice XIII → disordered ice V phase transition, and an exothermic peak on subsequent cooling due to the ice V → ice XIII phase transition. The equilibrium temperature (To) for the ice V ↔ ice XIII phase transition is 112 K for both HCl doped H2O and DCl doped D2O. From the maximal enthalpy change of 250 J mol−1 on the ice XIII → ice V phase transition and To of 112 K, the change in configurational entropy for the ice XIII → ice V transition is calculated as 2.23 J mol−1K−1 which is 66% of the Pauling entropy. For HCl, the most effective dopant, the influence of HCl concentration on the formation of ice XIII was determined: on decreasing the concentration of HCl from 0.01 to 0.001 M, its effectiveness is only slightly lowered. However, further HCl decrease to 0.0001 M drastically lowered its effectiveness. HF (DF) doping is less effective in inducing formation of ice XIII than HCl (DCl) doping. On heating at a rate of 5 K min−1, kinetic unfreezing starts in pure ice V at ∼132 K, whereas in acid doped ice XIII it starts at about 105 K due to acceleration of reorientation of water molecules. KOH doping does not lead to formation of hydrogen ordered ice XIII, a result which is consistent with our powder neutron diffraction study (C. G. Salzmann, P. G. Radaelli, A. Hallbrucker, E. Mayer, J. L. Finney, Science, 2006, 311, 1758). We further conjecture whether or not ice XIII has a stable region in the water/ice phase diagram, and on a metastable triple point where ice XIII, ice V and ice II are in equilibrium.

Raman spectra of recovered ordered H2O (D2O) ice XIII doped with 0.01 M HCl (DCl) recorded in vacuo at 80 K are reported in the range 3600–200 cm−1. The bands are assigned to the various types of modes on the basis of isotope ratios. On thermal cycling between 80 and 120 K, the reversible phase transition to disordered ice V is observed. The remarkable effect of HCl (DCl) on orientational ordering in ice V and its phase transition to ordered ice XIII, first reported in a powder neutron diffraction study of DCl doped D2O ice V (C. G. Salzmann, P. G. Radaelli, A. Hallbrucker, E. Mayer, J. L. Finney, Science, 2006, 311, 1758), is demonstrated by Raman spectroscopy and discussed. The dopants KOH and HF have only a minor effect on hydrogen ordering in ice V, as shown by the Raman spectra.

The Raman spectra of recovered hydrogen ordered H2O and D2O ice XIV were recorded and compared with the spectra of the corresponding hydrogen disordered phase (ice XII). On heating ice XIV, the transition to ice XII is observed. Subsequent cooling leads to the weak reappearance of ice XIV lattice vibrational peaks which demonstrates the reversibility of the hydrogen order ↔ disorder phase transition. However, cooling at ambient pressure produces a less ordered ice XIV than cooling under pressure which implies that pressure favours hydrogen ordering of ice XII.We present the Raman spectra of recovered H2O and D2O ice XIV and discuss the effects of hydrogen order by comparing with the spectra of hydrogen disordered ice XII. Upon heating ice XIV, the transition to ice XII is observed. Slow cooling shows the reversibility of the phase transition. However, hydrogen ordering seems to be more difficult at ambient pressure than at high pressure.

A polymeric dispersing agent for single-wall carbon nanotubes (SWCNTs) in water was synthesized by 4-(pyren-1-yl)butanoylation of the amine groups of poly-L-lysine. The pyrene content of 4-(pyren-1-yl)butanoylated polylysine (PBPL) was optimized so that a maximal dispersion effect of the SWCNTs was obtained. High molecular weight PBPL (>300000 g mol−1) exceeds the widely used surfactant sodium dodecylsulfate (SDS) as a dispersing agent yielding a 27% higher SWCNT concentration in dispersion. The high stability of the PBPL/SWCNT conjugates is demonstrated by removing the conjugates from dispersion through filtration, washing, and redispersion in only water. The resulting redispersions do not contain free PBPL and the importance of having SWCNT dispersions in the absence of free dispersing agent is discussed. For SDS dispersions, poor redispersion properties have been observed. The binding of PBPL onto the SWCNTs was studied by atomic force microscopy, optical absorbance spectroscopy, and fluorescence spectroscopy.

Graphene nanoflakes (GNFs) with average diameters of ∼30 nm have been prepared by a single-step oxidation procedure using single-wall carbon nanotube arc-discharge material and nitric acid. The GNFs are predominately single sheets containing a small number of internal defects. The edges are decorated with primarily carboxylic acid groups which allow facile chemical functionalisation and cross-linking of the fragments using multivalent cations.

Doped ice V samples made from solutions containing 0.01 M HCl (DCl), HF (DF), or KOH (KOD) in H2O (D2O) were slow-cooled from 250 to 77 K at 0.5 GPa. The effect of the dopant on the hydrogen disorder → order transition and formation of hydrogen ordered ice XIII was studied by differential scanning calorimetry (DSC) with samples recovered at 77 K. DSC scans of acid-doped samples are consistent with a reversible ice XIII ↔ ice V phase transition at ambient pressure, showing an endothermic peak on heating due to the hydrogen ordered ice XIII → disordered ice V phase transition, and an exothermic peak on subsequent cooling due to the ice V → ice XIII phase transition. The equilibrium temperature (To) for the ice V ↔ ice XIII phase transition is 112 K for both HCl doped H2O and DCl doped D2O. From the maximal enthalpy change of 250 J mol−1 on the ice XIII → ice V phase transition and To of 112 K, the change in configurational entropy for the ice XIII → ice V transition is calculated as 2.23 J mol−1K−1 which is 66% of the Pauling entropy. For HCl, the most effective dopant, the influence of HCl concentration on the formation of ice XIII was determined: on decreasing the concentration of HCl from 0.01 to 0.001 M, its effectiveness is only slightly lowered. However, further HCl decrease to 0.0001 M drastically lowered its effectiveness. HF (DF) doping is less effective in inducing formation of ice XIII than HCl (DCl) doping. On heating at a rate of 5 K min−1, kinetic unfreezing starts in pure ice V at ∼132 K, whereas in acid doped ice XIII it starts at about 105 K due to acceleration of reorientation of water molecules. KOH doping does not lead to formation of hydrogen ordered ice XIII, a result which is consistent with our powder neutron diffraction study (C. G. Salzmann, P. G. Radaelli, A. Hallbrucker, E. Mayer, J. L. Finney, Science, 2006, 311, 1758). We further conjecture whether or not ice XIII has a stable region in the water/ice phase diagram, and on a metastable triple point where ice XIII, ice V and ice II are in equilibrium.