Stable dispersions of both as-produced (raw soot) and purified laser-generated single-wall carbon nanotubes (SWNTs) have been demonstrated with several alkyl amide solvents. Optical absorption analysis over a range of concentrations has been utilized to estimate the dispersion limits for as-produced SWNTs in N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), N,N-diethylacetamide (DEA), and N,N-dimethylpropanamide (DMP). In addition, extinction coefficients have been calculated using Beer's law for each solvent at energies of 1.27 and 1.77 eV, corresponding to the electronic transitions of semiconducting and metallic SWNTs, respectively. The results imply that high polarizability and optimal geometries (appropriate bond lengths and bond angles) may account for the favorable interaction between SWNTs and the alkyl amide solvents. The successful dispersion of purified SWNTs in DMA has enabled extinction coefficients of 43.4 and 39.0 mL·mg-1·cm-1 to be calculated at the selected energies, respectively. The magnitude of the dispersion limit and extinction coefficient values has been shown to be strongly dependent on the SWNT sample purity. These findings offer the potential for solution-phase analysis of SWNTs directed at purity assessment and electrophoretic separations in a simple organic solvent.

A demand currently exists for a method of assessing the purity of single-wall carbon nanotubes (SWNTs), which will allow for meaningful material comparisons. An established metric and protocol will enable accurate and reproducible purity claims to be substantiated. In the present work, the ability to accurately quantify the mass fraction of SWNTs in the carbonaceous portion of a given sample is demonstrated, using optical absorption spectroscopy on both laser and arc discharge-generated SWNT-N,N-dimethylacetamide (DMA) dispersions. Verification of purity assessment protocols is based upon constructed sample sets comprising designed mass fractions of purified SWNTs and representative carbonaceous synthesis byproducts. Application of a previously reported method based on a ratio of the areal absorbance from linear subtractions of the second interband electronic transitions of semiconducting SWNTs ((S)E(22)) has shown a severe overestimation of SWNT purity (average error >24%). Instead, the development of a nonlinear pi-plasmon model, which considers overlap of electronic transitions and peak broadening, has dramatically improved the purity assessment accuracy (average error <7%), derived from a strong correlation to the constructed sample sets. This approach has enabled corroboration of rapid assessment procedures, such as absorbance peak maxima ratio and Beer's law analysis, directed at purification monitoring and synthesis sample screening. Specifically, a simple protocol for purity assessment of laser and arc-discharge SWNTs has been established that can be extended to other synthetic types (i.e. CVD, HiPco, etc.) and diameter distributions.

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Focused sound field measurements typically involve needle- or membrane-type transducers stepped across the sound field. This process produces an apparent image of the sound field limited by probe linearity, effective aperture size, and experimental alignment. Historically, acousto-optic schlieren imaging has provided an effective, qualitative technique for examining a sound-pressure field. In this paper the schlieren technique is extended to provide quantitative measurements of the peak focused sound-pressure field without in situ disruptions. A numerical solution of the Khokhlov–Zabolotskaya–Kuznetsov parabolic equation is used to predict the sound-pressure field for a line focused transducer. Enhancements in the standard numerical solution include a floating boundary condition and an adaptive technique for adjusting the computation effectiveness consistent with nonlinearity induced harmonic growth. Key features of the experimental setup are outlined and theoretical predictions compared with experimental measurements made with the extended schlieren technique.

The ability to dissociate the photo-generated excitons and transport the resulting charge carriers are the major impediments in improving the efficiency of polymeric solar cells. In order to simultaneously address both of these issues, we have investigated the use of quantum dotsingle wall carbon nanotube (QD-SWNT) complexes as a suitable nanomaterial dopant in these devices. The formation of CdSe-SWNT complexes occurred through covalent attachment of carboxylic acid-functionalized SWNTs with CdSe-aminoethanethiol (AET) quantum dots. An additional synthetic approach was evaluated using both electrostatic and covalent attachment schemes for CuInS 2 -mercaptoacetic acid (MA) quantum dots and amine terminated SWNTs. The efficacy of each approach is discussed, including the necessary transmission electron microscopy (TEM) and optical absorption spectroscopy data to probe the interactions between nanomaterials. The potential effects of charge transfer between components may have important implications in the efficiency of these materials for polymeric photovoltaic devices.

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The potential of the extremely high energy densities that may be possible with a hydrogenic fuel cell makes it an attractive alternative as a future microsystem power source. Additionally, the potential for integration of such devices could be enhanced if they were manufactured in a manner that is compatible with standard microelectronic and MEMS applications. A combination of silicon micromaching and direct writing was used to produce a microelectronic PEM fuel cell. The fuel cell was fabricated on a silicon wafer containing inter-digitated microchannels which were synthesized using an STS Systems Inc. deep reactive ion etcher. The anode and cathode composite materials were deposited using the MicroPen™. The MicroPen™ system is a fluid dispensing system that is capable of “writing” lines of materials with virtually any viscosity onto a wide range of potential substrates. Final assembly was accomplished by the application of a Nafion™ cover plate. These techniques were successfully employed to produce a working microelectronic fuel cell in silicon. The electrical characterization of the device demonstrated an open circuit voltage of 250 mV with a short circuit of 10 μA measured at room temperature when the cell was provided with hydrogen and oxygen at 1 ATM.