Teslaphoresis of Carbon Nanotubes.

This paper introduces Teslaphoresis, the directed motion and self-assembly of matter by a Tesla coil, and studies this electrokinetic phenomenon using single-walled carbon nanotubes (CNTs). Conventional directed self-assembly of matter using electric fields has been restricted to small scale structures, but with Teslaphoresis, we exceed this limitation by using the Tesla coil's antenna to create a gradient high-voltage force field that projects into free space. CNTs placed within the Teslaphoretic (TEP) field polarize and self-assemble into wires that span from the nanoscale to the macroscale, the longest thus far being 15 cm. We show that the TEP field not only directs the self-assembly of long nanotube wires at remote distances (>30 cm) but can also wirelessly power nanotube-based LED circuits. Furthermore, individualized CNTs self-organize to form long parallel arrays with high fidelity alignment to the TEP field. Thus, Teslaphoresis is effective for directed self-assembly from the bottom-up to the macroscale.

Length- and defect-dependent fluorescence efficiencies of individual single-walled carbon nanotubes.

Using near-infrared fluorescence videomicroscopy with spectrally selective excitation and imaging, more than 400 individual (10,2) single-walled carbon nanotubes (SWCNTs) have been studied in unsorted liquid dispersions. For each nanotube, the spatially integrated emission intensity was measured under controlled excitation conditions while its length was found either from direct imaging or from the diffusion coefficient computed by analyzing its Brownian motion trajectory. The studied nanotubes ranged in length from 170 to 5300 nm. For any length, a wide variation in emission intensities was observed. These variations are attributed to differing densities of nanotube imperfections that cause fluorescence quenching. The brightest nanotubes at each length (presumed near-pristine) show total emission nearly proportional to length. This implies a nearly constant fluorescence quantum yield and a constant absorption cross section per carbon atom, validating conventional Beer-Lambert analysis for finding concentrations of SWCNT species. Ensemble-averaged emission is also proportional to length, but at only ca. 40% of the near-pristine values. Further research is needed to investigate the extrinsic effects causing wide variation in quantum yields and assess their implications for SWCNT fluorimetry.