Topics Covered
Background
Recording the Fluorescence Spectra
from Single Wall Carbon Nanotubes (SWNTs) - Description of the Experimental
Process
The Results that Emerged from this
Experiment
Conclusions
Background
Single-wall carbon nanotubes (SWNTs), consisting of rolled-up
single sheets of carbon atoms, have received much attention recently. SWNTs are
known to emit in the IR region, and their emission can be used to characterize
their diameter and other structural properties. The NanoLog™
(see figure 1), the modular spectrofluorometer from HORIBA
Scientific, is designed with near-IR detectors and a TRIAX spectrometer for
efficient spectral analysis of SWNT emission. Near-IR detectors available
include both liquid-N2-cooled Symphony
series of InGaAs arrays (see figure 2), which can take a full spectrum
rapidly, as well as economical single-element InGaAs detectors. These detectors
are sensitive to photons from 800–1700 nm, with optional detection to longer
wavelengths. In addition, for extra sensitivity and time-resolved measurements,
a near-IR-sensitive photomultiplier-tube may be used as the detector.
Figure 1. NanoLog™ spectrofluorometer
from HORIBA Scientific.
Figure 2. Symphony InGaAs array, the
standard detector on the NanoLog™.
Recording the Fluorescence Spectra
from Single Wall Carbon Nanotubes (SWNTs) - Description of the Experimental
Process
Fluorescence spectra from high-pressure-CO SWNTs (in aqueous
1% sodium dodecyl sulfate) were recorded using a NanoLog™,
incorporating a double-grating excitation monochromator (600 grooves/mm, blazed
at 1000 nm) and TRIAX emission spectrograph (150 grooves/mm, blazed at 1200 nm)
for emission. To detect the nanotubes’ fluorescence, a Symphony-series near-IR
InGaAs CCD-array (512 pixels × 1” [2.54 cm], liquid-N2 cooled) was
used, with 2 s integration time per emission scan. The slit-width was 4 mm on
both excitation and emission. The step size was 2 nm between points for each
scan. Excitation was scanned from 620–815 nm; emission was scanned from
1080–1356 nm. Photoluminescence intensity was measured as (signal - dark
counts)/reference. The total acquisition time for the data was about 10 min.
The Results that Emerged from this
Experiment
A 3-D excitation-emission matrix scan (see figure 3) of the
entire near-IR spectral region of interest shows an overview of the fluorescence
characteristics of the SWNT mixture. The chirality of each species is given
by its (n,m) coordinates.
The simulation and assignment of spectral peaks provided by HORIBA Scientific’s NanosizerTM
software package is presented in figures 3 and 4 (see below). In figure 3, the
upper flat plot includes white contour lines from a simulated spectrum. Assignment
of the peaks is shown in figure 4; the diameter and chiral angle of rolling-up
of the nanotubes is related to the wavelength of the emission peaks.
Figure 3. Emission-excitation matrix scan
of a mixture of SWNTs recorded with the NanoLog™. Chirality of each species is
presented as (n,m). The white lines on the upper
surface of the “cube” are from a simulation of the same matrix performed by the
Nanosizer™ software.
Figure 4. Analysis, in chiral-map format,
by the Nanosizer™ of a mixture of SWNTs recorded with the NanoLog™ in figure 3.
Chirality of each species is presented as (n,m). The
diameters and colors of the circles are related to their peak intensities in
figure 3.
Conclusions
Near-IR spectra - including matrix scans - from single-wall
carbon nanotubes are easily recorded and analyzed using the NanoLog™
spectrofluorometer with the NanosizerTM software, respectively. The
NanoLog™
is useful in a wide array of research related to nanostructures, quantum dots,
and materials science for the future.
Note: A complete set of references can be found by
referring to the original document.
Source: Horiba Scientific.
For more information on this source please visit Horiba
Scientific.