Single walled carbon nanotubes 1 were used
throughout this work. Twenty milligrams of the
nanotubes were dispersed in 20 ml of isopropyl
alcohol using a magnetic stirrer bar for 2 h. The
solution was then filtered through a 1 lm PTFE
membrane under vacuum. The membranes were
then left to dry, resulting in the adhesion of a
bucky paper to the top of the membrane.
The bucky papers were then exposed to a
plasma environment within the Vacutech RIE
system using either SF6 at 20 sscm flow rate or CF4
at 40 sccm flow rate as the plasma gas. The samples
were exposed to the plasma for 1 min at different
bias voltages to determine the effect of bias
on the subsequent bonding of fluorine to the
SWNTs. The chemical attachments were investigated
by X-ray Photoelectron spectroscopy 2
(XPS) using a monochromatic Al(Ka)¼1486.6 eV
source. The F1s peaks have also been studied with
emphasis on the binding energy, using XPS Peak
software whereby subtraction of a linear background
is performed and Gaussian curves are fitted
to the measured data. Attention has been paid
to the relative concentrations of fluorine to carbon
and oxygen to carbon and after subtraction of a
linear background and with use of AlWagner coefficients
in the Avantage data system, both 2 days
after the initial functionalisation and also after 4
weeks. The AlWagner coefficients are used to limit
any possible atomic percentage errors which may
occur due to the sample preparation and positioning
in the XPS equipment.
The reactor conditions are characterised with
use of optical emission spectroscopy (OES) and
Langmuir probe measurements. The OES data
confirms the relative concentrations of radical
fluorine within the plasma, whilst the Langmuir
probe is used to determine the ion current density,
hence relating to the ion bombardment factors
taking place on the bucky paper surface.
Transmission electron microscope (TEM) images
of the SWNTs are also taken to test the
structural integrity of the SWNTs after plasma
exposure. For the TEM images, 2 mg of SWNT
bucky paper were suspended in 2 ml of IPA and a
drop of the solution was then suspended onto 300
lm carbon grids.