TY  - JOUR
AU  - Bellissent-Funel, Marie-Claire
AU  - Kaneko, Katsumi
AU  - Ohba, Tomonori
AU  - Appavou, Marie-Sousai
AU  - Soininen, Antti
AU  - Wuttke, Joachim
TI  - Crossover from localized to diffusive water dynamics in carbon nanohorns: A comprehensive quasielastic neutron-scattering analysis
JO  - Physical review / E
VL  - 93
IS  - 2
SN  - 2470-0045
CY  - College Park, Md.
PB  - APS
M1  - FZJ-2016-01521
SP  - 022104
PY  - 2016
AB  - 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.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000369437700004
DO  - DOI:10.1103/PhysRevE.93.022104
UR  - https://juser.fz-juelich.de/record/281859
ER  -