Zhang and co-workers developed a rational approach to growing a new family of semiconducting SWNTs: (n, n À 1) carbon nanotubes. Combined with catalyst design, both large-diameter (>2 nm) (n, n À 1) SWNTs and single-chirality (10, 9) SWNTs with abundances of 88% and >80%, respectively, were successfully realized. This strategy opens up a new route for the growth of SWNT families beyond catalyst design.

The accurate characterization of the chiral indices (n,m) of carbon nanotubes has greatly facilitated fundamental investigations and practical applications ranging from electronic circuits and quantum emission to biological detection 1-4 . To meet the growing miniaturizationdriven demand, handedness, the key structural quantity associated with mirror symmetry breaking, needs to be identified both accurately and efficiently 5-7 . To date, optical spectroscopic techniques with unprecedented high-throughput and noninvasive characteristics have achieved great success in identifying chiral indices even at the single-tube level 8-13 . However, none of these optical methods are capable of handedness characterization for single nanotubes due to their extremely weak chiroptical signals (~10 -7 ) compared to the excitation light 14,15 . Here, we demonstrate the complete structure identification of single nanotubes in terms of both chiral indices and handedness by Rayleigh scattering circular dichroism. The success originates from the background-free feature of Rayleigh scattering collected at an oblique angle, which enhances the chiroptical signal from nanotubes by three to four orders of magnitude compared to that using conventional absorption circular dichroism. We measured a total of 30 single-walled carbon nanotubes (including both semiconducting and metallic nanotubes) and found that their absolute chiroptical signals show an obvious structure dependence, which can be qualitatively understood through tightbinding calculations. Our strategy not only opens up exciting opportunities for unlocking the sophisticated functionality of nanotubes but also provides a new platform for chiral discrimination and chiral device exploration at the level of individual nanomaterials.

High-quality large 1T phase of TiX 2 (X = Te, Se, and S) single crystals have been grown by chemical vapor transport using iodine as a transport agent. The samples are characterized by compositional and structural analyses, and their properties are investigated by Raman spectroscopy. Several phonon modes have been observed, including the widely reported A 1g and Eg modes, the rarely reported Eu mode (∼183 cm−1 for TiTe2, and ∼185 cm−1 for TiS2), and even the unexpected K mode (∼85 cm−1) of TiTe2. Most phonons harden with the decrease of temperature, except that the K mode of TiTe2 and the Eu and “A 2u /Sh” modes of TiS2 soften with the decrease of temperature. In addition, we also found phonon changes in TiSe2 that may be related to charge density wave phase transition. Our results on TiX 2 phonons will help to understand their charge density wave and superconductivity.

Rate constants and the product branching ratio for hydrogen abstraction from CHOH by O(P) were computed with multistructural variational transition-state theory including microcanonically optimized multidimensional tunneling. Benchmark calculations of the forward and reverse classical barrier heights and the reaction energetics have been carried out by using coupled cluster theory and multireference calculations to select the most reliable density functional method for direct dynamics computations of the rate constants. The dynamics calculations included the anharmonicity of the zero-point energies and partition functions, with specific-reaction-parameter scaling factors for reactants and transition states, and multistructural torsional anharmonicity was included for the torsion around the C-O bond in methanol and in the transition states. The resulting rate constants are presented over a wider range than they are available from experiment, but in the temperature range where experiments are available, they agree well with experimental values, which is encouraging for their reliability over the wider temperature range and for future computations of oxygen atom reaction rates. In contrast to a previous computational prediction, the branching ratio predicted by the present work shows that the formation of CHOH + OH is the dominant channel over the whole range of temperature from 250 to 2000 K.