Simultaneous detection of Raman scattering and near-infrared photoluminescence in one imaging microscope

Chirality Pure Carbon Nanotubes: Growth, Sorting, and Characterization

Single-walled carbon nanotubes (SWCNTs) have been attracting tremendous attention owing to their structure (chirality) dependent outstanding properties, which endow them with great potential in a wide range of applications. The preparation of chirality-pure SWCNTs is not only a great scientific challenge but also a crucial requirement for many high-end applications. As such, research activities in this area over the last two decades have been very extensive. In this review, we summarize recent achievements and accumulated knowledge thus far and discuss future developments and remaining challenges from three aspects: controlled growth, postsynthesis sorting, and characterization techniques. In the growth part, we focus on the mechanism of chirality-controlled growth and catalyst design. In the sorting part, we organize and analyze existing literature based on sorting targets rather than methods. Since chirality assignment and quantification is essential in the study of selective preparation, we also include in the last part a comprehensive description and discussion of characterization techniques for SWCNTs. It is our view that even though progress made in this area is impressive, more efforts are still needed to develop both methodologies for preparing ultrapure (e.g., >99.99%) SWCNTs in large quantity and nondestructive fast characterization techniques with high spatial resolution for various nanotube samples.

Characterizing the chiral index of a single-walled carbon nanotube

The properties of single-walled carbon nanotubes (SWCNTs) mainly depend on their geometry. However, there are still formidable difficulties to determine the chirality of SWCNTs accurately. In this review, some efficient methods to characterize the chiral indices of SWCNTs are illuminated. These methods are divided into imaging techniques and spectroscopy techniques. With these methods, diameter, helix angle, and energy states can be measured. Generally speaking, imaging techniques have a higher accuracy and universality, but are time-consuming with regard to the sample preparation and characterization. The spectroscopy techniques are very simple and fast in operation, but these techniques can be applied only to the particular structure of the sample. Here, the principles and operations of each method are introduced, and a comprehensive understanding of each technique, including their advantages and disadvantages, is given. Advanced applications of some methods are also discussed. The aim of this review is to help readers to choose methods with the appropriate accuracy and time complexity and, furthermore, to put forward an idea to find new methods for chirality characterization.

Spectroscopic characterization of the chiral structure of individual single-walled carbon nanotubes and the edge structure of isolated graphene nanoribbons

The chiral structure of single-walled carbon nanotubes (SWNTs) and the edge structure of graphene nanoribbons (GNRs) play an important role in determining their electronic and phonon structures. Spectroscopic methods, which require simple sample preparation and cause minimal sample damage, are the most commonly utilized techniques for determining the structures of SWNTs and graphene. In this review the current status of various spectroscopic methods are presented in detail, including resonance Raman, photoluminescence (PL), and Rayleigh scattering spectroscopies, for determination of the chiral structure of individual SWNTs and the edge structure of isolated graphene, especially of graphene nanoribbons. The different photophysical processes involved in each spectroscopic method are reviewed to achieve a comprehensive understanding of the electronic and phonon properties of SWNTs and graphene. The advantages and limitations of each spectroscopic method as well as the challenges in this area are discussed.