Water Encapsulation
Control in Individual Single-Walled
Carbon Nanotubes by Laser Irradiation
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Abstract
Owing
to one-dimensionality, nanoscale curvature, and high chemical
stability, single-walled carbon nanotubes (SWNTs) have unique surfaces
for gas molecules: outer surface as adsorption (exohedral) site and
inner surface that provides encapsulation (endohedral) space. Because
as-grown SWNTs have different structure (chirality and diameter) and
they are normally bundled, it is extremely difficult to investigate
the intrinsic properties of SWNTs as adsorbent. Here we demonstrate
controlling adsorption and encapsulation states of water in individual
suspended SWNTs using laser irradiation with monitoring of their behavior
by photoluminescence measurement and perform molecular dynamics simulation.
The laser heating and the pressure control make water molecules encapsulated
or ejected for SWNTs, which are individually oxidized and opened with
laser heating. The precise control of oxidization makes it possible
to observe the cluster formation of water molecules during the encapsulation
process and to confine water molecules inside SWNTs even in vacuum