ABSTRACT
A macroscopic system of single-walled carbon nanotubes (SWNTs) created by a novel DNA/protein complex-assisted assembly is investigated. Due to a point-like nature of connectors, the resulting SWNT aerogel represents a network of self-suspended nanotubes with a record-low density of less than 0.75 mg cm(-3). The assembly method and low density enable a direct comparison of optical properties of nanotubes in solvent and air to surfactant solubilized nanotubes. Optical properties of SWNT gels are investigated using optical absorption, photoluminescence, and Raman spectroscopy. Gelled nanotubes in water and in the low-energy regime behave similar to solubilized nanotubes. In contrast, the photoluminescence of SWNT aerogels exhibits a previously unobserved peak at 1.3 eV that corresponds to a phonon-assisted recombination of photoexcited charges. This new emission pathway is the result of the unique nature of self-suspended nanotubes in aerogel and a reduced phonon decay.
ABSTRACT
A single-walled carbon nanotube self-suspended network of exceptionally low density is formed by DNA-streptavidin-assisted assembly where the DNA complex serves as a cross-shaped point connector. The macroscopic nanotube aerogel is conductive and luminescent and presents an excellent scaffold for subsequent functionalization. For example, platinum and titanium dioxide coating of the nanotube network is demonstrated.
Subject(s)
DNA/chemistry , Nanotechnology/methods , Nanotubes, Carbon/chemistry , Nanotubes/chemistry , Electric Conductivity , Electronics , Luminescence , Microscopy, Electron, Scanning/methods , Nanostructures , Optics and Photonics , Polymers/chemistry , Porosity , Scattering, Radiation , Spectrum Analysis, Raman/methods , Streptavidin/chemistry , Surface Properties , Surface-Active AgentsABSTRACT
A method for noncovalent functionalization of DNA-wrapped single-walled carbon nanotubes (SWNTs) using platinum-based DNA cross-linkers is investigated. In particular, cisplatin and potassium tetrachloroplatinate are shown to bind to DNA that encapsulates SWNTs in aqueous solution. The bound platinum salt can then be reduced to decorate the DNA-encapsulated SWNTs with platinum nanoparticles. The resulting SWNT/DNA/Pt hybrids are investigated by optical absorption spectroscopy, circular dichroism spectroscopy, Raman spectroscopy, X-ray diffraction, transmission electron microscopy, and atomic force microscopy. The unique combination of catalytic activity of nanoscale platinum, biological functionality of DNA, and optoelectronic properties of SWNTs suggests a myriad of applications including fuel cells, catalysts, biosensors, and electrochemical devices.
Subject(s)
DNA/chemistry , Metal Nanoparticles/chemistry , Nanotechnology/methods , Nanotubes, Carbon/chemistry , Platinum/chemistry , Catalysis , Chlorides/pharmacology , Circular Dichroism , Cisplatin/pharmacology , Cross-Linking Reagents/chemistry , Electrochemistry , Microscopy, Atomic Force , Microscopy, Electron, Transmission , Platinum Compounds/pharmacology , Spectrum Analysis, Raman , X-Ray DiffractionABSTRACT
We report interband magneto-optical spectra for single-walled carbon nanotubes in high magnetic fields up to 45 tesla, confirming theoretical predictions that the band structure of a single-walled carbon nanotube is dependent on the magnetic flux phi threading the tube. We have observed field-induced optical anisotropy as well as red shifts and splittings of absorption and photoluminescence peaks. The amounts of shifts and splittings depend on the value of phi/phi(0) and are quantitatively consistent with theories based on the Aharonov-Bohm effect. These results represent evidence of the influence of the Aharonov-Bohm phase on the band gap of a solid.
