Carbon nanotube research is going on at a number of UBC departments including Electrical and Computer Engineering, Chemistry, and Physics and Astronomy.
Electrical and Computer Engineering
Mirfakhrai, Tissaphern; Kozlov, Mikhail; Fang, Shaoli; Zhang, Mei; Baughman, Ray H.; Madden, John D. Carbon nanotube yarns: sensors, actuators, and current carriers. Proceedings of SPIE (2008), 6927.
Carbon nanotubes (CNTs) have attracted extensive attention in the past few years because of their appealing mechanical and electronic properties. Yarns made through spinning multi-walled carbon nanotubes (MWNTs) have been reported. Here we report the application of these yarns as electrochemical actuators, force sensors and microwires. When extra charge is stored in the yarns, change in length. This actuation is thought to be because of electrostatic as well as quantum chemical effects in the nanotube backbones. We report strains up to 0.7 %. At the same time, the charged yarns can respond to a change in the applied tension by generating a current or a potential difference that is related to the applied tension force. As current carriers, the yarns offer a conductivity of [similar to] 300 S/cm, which increases linearly with temperature. We report a current capacity of more than 108 A/m2, which is comparable to those of macroscopic metal wires. However, these nanotube yarns have a density (0.8 g/cm3) that is an order of magnitude lower than metallic wires. The MWNT yarns are mechanically strong with tensile strengths reaching 700 MPa. These properties together make them a candidate material for use in many applications including sensors, actuators and light-weight current carriers.
Chemistry
Adsorption of small gas molecules onto Pt-doped single-walled carbon nanotubes
Author(s): Yeung CS (Yeung, Charles See), Liu LV (Liu, Lei Vincent), Wang YA (Wang, Yan Alexander)
Source: JOURNAL OF PHYSICAL CHEMISTRY C Volume: 112 Issue: 19 Pages: 7401-7411 Published: MAY 15 2008
Abstract: The adsorption of small gaseous molecules to the metal center in Pt-doped (5,5) single-walled carbon nanotubes has been explored within density functional theory. A model system consisting of a single Pt atom residing in the middle of a carbon nanotube with capping H atoms is used for our investigation. For all gases studied, the overall process of adsorption was found to be exothermic, where the affinity strongly depended on the orientation of the molecule. By examining the density of states and molecular orbitals of these nanotube-adsorbate complexes in comparison to the bare Pt-doped nanotube, we show that the electronic structure of these materials is strongly influenced by the presence of gases. Hence, we propose an application of Pt-doped single-walled carbon nanotubes as gas sensors and hope to motivate experimental work in this field.
Physics
Pereira RG , Laflorencie N, Affleck I, Halperin BI. PHYSICAL REVIEW B 77 12 125327 2008
Abstract: We propose that the finite size of the Kondo screening cloud, xi(K), can be probed by measuring the charge quantization in a one-dimensional system coupled to a small quantum dot. When the chemical potential mu in the system is varied at zero temperature, one should observe charge steps whose locations are at values of mu that are controlled by the Kondo effect when the system size L is comparable to xi(K). We show that, if the standard Kondo model is used, the ratio between the widths of the Coulomb blockade valleys with odd or even number of electrons is a universal scaling function of xi(K)/L. If we take into account electron-electron interactions in a single-channel wire, this ratio also depends on the parameters of the effective Luttinger model; in addition, the scaling is weakly violated by a marginal bulk interaction. For the geometry of a quantum dot embedded in a ring, we show that the dependence of the charge steps on a magnetic flux through the ring is controlled by the size of the Kondo screening cloud.
Submitted by kevin.lindstrom Liaison Librarian for the Departments of Electrical and Computer Engineering, Chemistry, and Physics.