ABSTRACT
Solubilization of single-walled carbon nanotubes in aqueous solution by surface functionalization is of great interest for biosensor applications and separation of individual nanotubes. Here we have observed that HiPco nanotubes can be stably dispersed into double-stranded DNA aqueous solutions. Interestingly, the first optical interband transitions of the DNA wrapped semiconducting HiPco nanotubes possess a unique pH dependence, a phenomenon observed in SDS-encased and carboxylic group functionalized single-walled carbon nanotubes. The unique optical pH dependence of surface modified semiconducting nanotubes may have promising applications in optical biosensors.
Subject(s)
Carbon Monoxide/chemistry , DNA/chemistry , Nanotubes, Carbon/analysis , Animals , Biosensing Techniques , Hydrogen-Ion Concentration , Male , Nanotubes, Carbon/chemistry , Nucleic Acid Conformation , Pressure , Salmon , Sodium Dodecyl Sulfate/chemistry , Spectrophotometry , Spectrum Analysis, Raman , Testis/metabolism , WaterABSTRACT
We demonstrate the continued growth of single-walled carbon nanotubes (SWNTs) from ordered arrays of open-ended SWNTs in a way analogous to epitaxy. Nanometer-sized metal catalysts were docked to the SWNT open ends and subsequently activated to restart growth. SWNTs thus grown inherit the diameters and chirality from the seeded SWNTs, as indicated by the closely matched frequencies of Raman radial breathing modes before and after the growth.
Subject(s)
Nanotechnology/methods , Nanotubes, Carbon , Catalysis , Ethanol/chemistry , Materials Testing , Microscopy, Electron, Scanning , Microscopy, Electron, Transmission , Spectrum Analysis, Raman , Surface Properties , TemperatureABSTRACT
The effect of aggregation on surfactant-suspended individual single-walled carbon nanotube (SWNT) Raman spectroscopy has been explored in the context of dielectrophoretic separation. The Raman spectra of individual surfactant-suspended HiPco SWNTs deposited on a substrate and the same suspension deposited via dielectrophoresis were compared as a function of iterative aggregation states. The evolution of the samples' radial breathing modes and tangential modes at multiple excitation wavelengths (514, 633, and 785 nm) illustrates a direct correlation between changes in the Raman spectra and a broadening and downshifting of resonance transition energies. Dielectrophoresis samples exhibited Raman changes similar to control samples, indicating characterization of electronic separation is compromised by aggregation effects.
ABSTRACT
Well-aligned macroscopic fibers composed solely of single-walled carbon nanotubes (SWNTs) were produced by conventional spinning. Fuming sulfuric acid charges SWNTs and promotes their ordering into an aligned phase of individual mobile SWNTs surrounded by acid anions. This ordered dispersion was extruded via solution spinning into continuous lengths of macroscopic neat SWNT fibers. Such fibers possess interesting structural composition and physical properties.
