Dielectric properties of water inside single-walled carbon nanotubes.

In this paper, we report novel ferroelectric properties of a new form of ice inside single-walled carbon nanotubes (SWCNTs). These are called "ice nanotubes" (ice NTs) and they consist of polygonal water rings stacked one-dimensionally along the SWCNT axis. We performed molecular dynamics (MD) calculations for the ice NTs under an external electric field and in a temperature range between 100 and 350 K. It is revealed that ice NTs show stepwise polarization with a significant hysteresis loop as a function of the external field strength. In particular, pentagonal and heptagonal ice NTs are found to be the world's smallest ferroelectrics with spontaneous polarization of around 1 microC/cm(2). The n-gonal ice NT, where n = 5, 6, or 7, has (n + 1)-polarized structures with different polarizations. These findings suggest potential applications of SWCNTs encapsulating dielectric materials for the fabrication of the smallest ferroelectric devices. Experimental evidence for the presence of ice NTs inside SWCNTs is also discussed in great detail.

[1]  Hiromichi Kataura,et al.  Water-filled single-wall carbon nanotubes as molecular nanovalves. , 2007, Nature materials.

[2]  H. Kataura,et al.  Water dynamics inside single-wall carbon nanotubes: NMR observations , 2006 .

[3]  Jun Wang,et al.  Multiwalled ice helixes and ice nanotubes , 2006, Proceedings of the National Academy of Sciences.

[4]  Wei Fa,et al.  Ferroelectric ordering in ice nanotubes confined in carbon nanotubes. , 2008, Nano letters.

[5]  G. Hummer,et al.  Water conduction through the hydrophobic channel of a carbon nanotube , 2001, Nature.

[6]  Alberto Striolo,et al.  Simulated water adsorption in chemically heterogeneous carbon nanotubes. , 2006, The Journal of chemical physics.

[7]  M. S. de Vries,et al.  Cobalt-catalysed growth of carbon nanotubes with single-atomic-layer walls , 1993, Nature.

[8]  H. Kataura,et al.  Anomaly of X-ray Diffraction Profile in Single-Walled Carbon Nanotubes , 1999 .

[9]  Kenichiro Koga,et al.  Phase diagram of water in carbon nanotubes , 2008, Proceedings of the National Academy of Sciences.

[10]  W. S. Veeman,et al.  High resolution NMR of water absorbed in single-wall carbon nanotubes , 2006 .

[11]  Kenichiro Koga,et al.  Ab initio studies of quasi-one-dimensional pentagon and hexagon ice nanotubes , 2003 .

[12]  H. Kataura,et al.  Highly rotationalC60dynamics inside single-walled carbon nanotubes: NMR observations , 2008 .

[13]  H. Kataura,et al.  How confinement affects the dynamics of c60 in carbon nanopeapods. , 2008, Physical review letters.

[14]  A. Pathak,et al.  Ab initio study of ice nanotubes in isolation or inside single-walled carbon nanotubes , 2007 .

[15]  Yang Wang,et al.  Unusual hydrogen bonding in water-filled carbon nanotubes. , 2006, Journal of the American Chemical Society.

[16]  M. Karplus,et al.  Simulation of activation free energies in molecular systems , 1996 .

[17]  T. Ichihashi,et al.  Single-shell carbon nanotubes of 1-nm diameter , 1993, Nature.

[18]  Chun-Keung Loong,et al.  Anomalously soft dynamics of water in a nanotube: a revelation of nanoscale confinement. , 2004, Physical review letters.

[19]  K. Gubbins,et al.  Water in carbon nanotubes: adsorption isotherms and thermodynamic properties from molecular simulation. , 2005, The Journal of chemical physics.

[20]  Kenichiro Koga,et al.  Formation of ordered ice nanotubes inside carbon nanotubes , 2001, Nature.

[21]  W. Vogel,et al.  Structural sensitivity of the standard platinum/silica catalyst EuroPt-1 to hydrogen and oxygen exposure by in situ x-ray diffraction , 1990 .

[22]  J. Shiomi,et al.  Molecular Dynamics of Ice-Nanotube Formation Inside Carbon Nanotubes , 2007, cond-mat/0702541.

[23]  Hiromichi Kataura,et al.  Phase Transition in Confined Water Inside Carbon Nanotubes , 2002 .

[24]  Susumu Okada,et al.  Energetics of ice nanotubes and their encapsulation in carbon nanotubes from density-functional theory , 2007 .

[25]  W. L. Jorgensen,et al.  Comparison of simple potential functions for simulating liquid water , 1983 .

[26]  A. Nakatani,et al.  Hydrogen bond dynamics and microscopic structure of confined water inside carbon nanotubes. , 2006, The Journal of chemical physics.

[27]  Yue Wu,et al.  Temperature-Induced Hydrophobic-Hydrophilic Transition Observed by Water Adsorption , 2008, Science.

[28]  Yutaka Okabe,et al.  Ordered water inside carbon nanotubes: formation of pentagonal to octagonal ice-nanotubes , 2005 .

[29]  Jordi Martí,et al.  Structure and dynamics of liquid water adsorbed on the external walls of carbon nanotubes , 2003 .