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Carbon nanotubes are extremely thin hollow cylinders made of carbon atoms.
Their diameter can be as small as a few nanometers, while their length can be up
to several millimeters. Nanotubes, depending on their structure, can be metals
or semiconductors. They are also extremely strong materials and have good
thermal conductivity. The above characteristics have generated interest in their
possible use in nano-electronic and nano-mechanical devices. Other applications
include optics, materials science, and architecture.
In this applications paper, we examine a sample of carbon nanotubes deposited
on a circular glass cover slip. In particular, microspectral analysis in
absorbance and reflectance, as well as micro imaging analysis at ultraviolet
wavelengths are studied.
For microspectral analysis in absorbance and reflectance, 50 scans were
averaged with each measurement, the sampling area was 14 by 14 microns, and the
spectral range was 300 to 800 nm. In absorbance, the reference was acquired
through an open area on the circular glass slide. For reflectance, an aluminum
mirror was used as the reference. Measurements were made at several locations
across the sample.
Imaging was also performed in both transmitted and reflected light. Since
glass blocks ultraviolet light below ~320 nm in wavelength, the presence of the
glass cover slip limited the choice of imaging wavelengths to above that cutoff.
The imaging wavelengths were thus chosen as 320 nm and 365 nm. Imaging was
performed with a 100X ultraviolet capable objective.
The following two figures display absorbance
and reflectance microspectra of the carbon nanotube sample, as well as
image captures. The black square in the center of each image is the sampling
area (14 x 14 microns) and the field of view of each image is 480 x 430 microns.
The first two images below are shown in transmitted light at imaging
wavelengths of 365 and 320 nm respectively. For reference, the field of view for
these images is 84 x 64 microns.
Reflectance images at wavelengths of 365 nm and 320 nm are shown in the
remaining two images below.
microspectra from the carbon nanotubes show a decrease in absorbance as
the wavelength increases. This is indicative of the brown color of the sample
in transmitted light. In reflected light, there is a gradual increase in reflectance
with wavelength, as well as some variable peaks and valleys in wavelength below
450 nm that depend on the sample measurement location.
Ultraviolet imaging of the carbon nanotube sample reveals several distinct
characteristics at the micro scale. If the sample had been mounted on a more
ultraviolet transmitting material, such as quartz instead of glass, this would
have allowed imaging at shorter wavelengths, and thus the opportunity to resolve
Primary author: Dr. Jim Thorne
Source: Carbon NAnotube Sample Analysis by CRAIC
For more information on this source please visit CRAIC