Charge Transport In Nanotubes Research Articles

Carrier Transport Engineering in Carbon Nanotubes by Chirality-Induced Spin Polarization.

Carbon nanotubes (CNTs), helically wrapped with single-stranded DNA, have recently emerged as a spin-filtering material. The inversion asymmetric helical potential of DNA creates a spin-filtering effect (commonly known as "chirality-induced spin selectivity" or CISS), which polarizes carrier spins in the nanotube. Thus, tuning of the DNA-CNT interaction is expected to affect carrier spins in nanotubes. The CISS effect induces spin polarization, which is coupled with the carrier's momentum direction, and therefore, in one-dimensional systems, such as nanotubes, momentum flip must be accompanied by a simultaneous spin flip. This spin momentum locking can have a profound impact on charge transport in nanotubes as backscattering due to phonons and disorder will be suppressed as these mechanisms are spin-independent. Here, we report DNA-CNT spin filters in which CNTs have been functionalized with two different classes of sequences, exhibiting different degrees of interaction with the CNT. They induce different degrees of spin polarization in the channel, with significant impact on temperature-dependent charge transport and interference phenomena arising from carrier backscattering. This work raises the intriguing possibility of engineering charge transport in nanotubes via CISS-induced spin polarization by tailor-made DNA sequences.

Dye-sensitized solar cells based on a nanoparticle/nanotube bilayer structure and their equivalent circuit analysis

Dye-sensitized solar cells (DSSCs) were prepared by capitalizing on a TiO(2) bilayer structure composed of P-25 nanoparticles and freestanding crystalline nanotube arrays as photoanodes. After being subjected to sequential TiCl(4) treatment and O(2) plasma exposure, the bilayer photoanode was sensitized with N719 dye. DSSCs based on a 20 μm TiO(2) nanoparticle film solely and a bilayer of 13 μm TiO(2) nanoparticles and 7 μm TiO(2) nanotubes exhibited the highest power conversion efficiency, PCE, of 8.02% and 7.00%, respectively, compared to the devices made of different TiO(2) thicknesses. On the basis of J-V parameter analysis acquired by equivalent circuit model simulation, in comparison to P-25 nanoparticles, charge transport in nanotubes was found to be facilitated due to the presence of advantageous nanotubular structures, while photocurrent was reduced owing to their small surface area, which in turn resulted in low dye loading, as well as the lack of cooperative effect of anatase and rutile phases.