%0 Journal Article
%A Bellissent-Funel, Marie-Claire
%A Kaneko, Katsumi
%A Ohba, Tomonori
%A Appavou, Marie-Sousai
%A Soininen, Antti
%A Wuttke, Joachim
%T Crossover from localized to diffusive water dynamics in carbon nanohorns: A comprehensive quasielastic neutron-scattering analysis
%J Physical review / E
%V 93
%N 2
%@ 2470-0045
%C College Park, Md.
%I APS
%M FZJ-2016-01521
%P 022104
%D 2016
%X Incoherent neutron scattering by water confined in carbon nanohorns was measured with the backscattering spectrometer SPHERES and analyzed in exemplary breadth and depth. Quasielastic spectra admit δ-plus-Kohlrausch fits over a wide q and T range. From the q and T dependence of fitted amplitudes and relaxation times, however, it becomes clear that the fits do not represent a uniform physical process, but that there is a crossover from localized motion at low T to diffusive α relaxation at high T. The crossover temperature of about 210 to 230 K increases with decreasing wave number, which is incompatible with a thermodynamic strong-fragile transition. Extrapolated diffusion coefficients D(T) indicate that water motion is at room temperature about 2.5 times slower than in the bulk; in the supercooled state this factor becomes smaller. At even higher temperatures, where the α spectrum is essentially flat, a few percentages of the total scattering go into a Lorentzian with a width of about 1.6μeV, probably due to functional groups on the surface of the nanohorns.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000369437700004
%R 10.1103/PhysRevE.93.022104
%U https://juser.fz-juelich.de/record/281859