4 research outputs found
Separation of Single-Walled Carbon Nanotubes with a Gel Permeation Chromatography System
A gel permeation chromatography system is used to separate aqueous sodium dodecyl sulfate suspensions of single-walled carbon nanotubes (SWCNTs). This automated procedure requires no precentrifugation, is scalable, and is found to yield monochiral SWCNT fractions of semiconducting SWCNTs with a purity of 61–95%. Unsorted and resulting monochiral fractions are characterized using optical absorption and photoluminescence spectroscopy
Fitting Single-Walled Carbon Nanotube Optical Spectra
In
this work, a comprehensive methodology for the fitting of single-walled
carbon nanotube absorption spectra is presented. Different approaches
to background subtraction, choice of line profile, and calculation
of full width at half-maximum are discussed both in the context of
previous literature and the contemporary understanding of carbon nanotube
photophysics. The fitting is improved by the inclusion of exciton–phonon
sidebands, and new techniques to improve the individualization of
overlapped nanotube spectra by exploiting correlations between the
first- and second-order optical transitions and the exciton–phonon
sidebands are presented. Consideration of metallic nanotubes allows
an analysis of the metallic/semiconducting content, and a process
of constraining the fit of highly congested spectra of carbon nanotube
solid films according to the spectral weights of each (<i>n</i>, <i>m</i>) species in solution is also presented, allowing
for more reliable resolution of overlapping peaks into single (<i>n</i>, <i>m</i>) species contributions
Sorting of Double-Walled Carbon Nanotubes According to Their Outer Wall Electronic Type <i>via</i> a Gel Permeation Method
In this work, we demonstrate the application of the gel permeation technique to the sorting of double-walled carbon nanotubes (DWCNTs) according to their outer wall electronic type. Our method uses Sephacryl S-200 gel and yields sorted fractions of DWCNTs with impurities removed and highly enriched in nanotubes with either metallic (M) or semiconducting (S) outer walls. The prepared fractions are fully characterized using optical absorption spectroscopy, transmission electron microscopy, and atomic force microscopy, and the entire procedure is monitored in real time using process Raman analysis. The sorted DWCNTs are then integrated into single nanotube field effect transistors, allowing detailed electronic measurement of the transconductance properties of the four unique inner@outer wall combinations of S@S, S@M, M@S, and M@M
Separation of Double-Walled Carbon Nanotubes by Size Exclusion Column Chromatography
In this report we demonstrate the separation of raw carbon nanotube material into fractions of double-walled (DWCNTs) and single-walled carbon nanotubes (SWCNTs). Our method utilizes size exclusion chromatography with Sephacryl gel S-200 and yielded two distinct fractions of single- and double-walled nanotubes with average diameters of 0.93 ± 0.03 and 1.64 ± 0.15 nm, respectively. The presented technique is easily scalable and offers an alternative to traditional density gradient ultracentrifugation methods. CNT fractions were characterized by atomic force microscopy and Raman and absorption spectroscopy as well as transmission electron microscopy