ABSTRACT
Wrapping of carbon nanotubes (CNTs) by single-stranded DNA (ssDNA) was found to be sequence-dependent. A systematic search of the ssDNA library selected a sequence d(GT)n, n = 10 to 45 that self-assembles into a helical structure around individual nanotubes in such a way that the electrostatics of the DNA-CNT hybrid depends on tube diameter and electronic properties, enabling nanotube separation by anion exchange chromatography. Optical absorption and Raman spectroscopy show that early fractions are enriched in the smaller diameter and metallic tubes, whereas late fractions are enriched in the larger diameter and semiconducting tubes.
Subject(s)
DNA, Single-Stranded/chemistry , Nanotechnology , Nanotubes, Carbon , Anions , Base Sequence , Chromatography, Ion Exchange , Deoxyribonucleotides/chemistry , Gene Library , Hydrogen Bonding , Microscopy, Atomic Force , Nucleic Acid Conformation , Repetitive Sequences, Nucleic Acid , Semiconductors , Spectrum Analysis , Spectrum Analysis, Raman , Static ElectricityABSTRACT
Carbon nanotubes yield to mechanical force by a primary dislocation dipole whose formation energy describes the thermodynamic stability of the tubule. However, the real-time strength is determined by the rate of defect formation, defined in turn by the activation barrier for the bond flip. First extensive computations of the kinetic barriers for a variety of strain-lattice orientations lead to predictions of the yield strength. Its value depends on nanotube chiral symmetry, in a way very different from the thermodynamic assessment.
