Wall-to-wall stress induced in (6,5) semiconducting nanotubes by encapsulation in metallic outer tubes of different diameters: A resonance Raman study of individual C(60)-derived double-wall carbon nanotubes

We measure resonant Raman scattering from 11 individual C(60)-derived double-wall carbon nanotubes all having inner semiconducting (6,5) tubes and various outer metallic tubes. The Raman spectra show the radial breathing modes (RBM) of the inner and the outer tubes to be simultaneously in resonance with the same laser energy. We observe that an increase in the RBM frequency of the inner tubes is related to an increase in the RBM frequency of the outer tubes. The Raman spectra also contain a sharp G(-) feature that increases in frequency as the nominal diameter of the outer metallic tubes decreases. Finally, the one-phonon second-order D-band mode shows a two-way frequency splitting that decreases with decreasing nominal wall-to-wall distance. We suggest that the stress which increases with decreasing nominal wall-to-wall distance is responsible for the hardening that is observed in the frequencies of the RBM, D and G(-) modes of the inner (6,5) semiconducting tubes.ArticleNANOSCALE. 2(3):406-411 (2010)journal articl

A Single-Walled Carbon Nanotube Network Gas Sensing Device

The goal of this research was to develop a chemical gas sensing device based on single-walled carbon nanotube (SWCNT) networks. The SWCNT networks are synthesized on Al2O3-deposted SiO2/Si substrates with 10 nm-thick Fe as the catalyst precursor layer using microwave plasma chemical vapor deposition (MPCVD). The development of interconnected SWCNT networks can be exploited to recognize the identities of different chemical gases by the strength of their particular surface adsorptive and desorptive responses to various types of chemical vapors. The physical responses on the surface of the SWCNT networks cause superficial changes in the electric charge that can be converted into electronic signals for identification. In this study, we tested NO2 and NH3 vapors at ppm levels at room temperature with our self-made gas sensing device, which was able to obtain responses to sensitivity changes with a concentration of 10 ppm for NO2 and 24 ppm for NH3