BYU Physics and Astronomy

We describe the direct, conformal, atomic layer deposition (ALD) of silica onto carbon nanotubes (CNTs) in the microfabrication of thinlayer chromatography (TLC) plates. As before, these plates were prepared with zig-zag hedge and channel microstructures, with high aspect ratio, porous hedges. After ALD, scanning electron microscopy (SEM) showed an increase in the radius of the CNTs of 8–40 nm. X-ray photoelectron spectroscopy (XPS) showed that the plates were composed almost entirely of silicon and oxygen, without contamination of metals or other elements that might compromise chromatographic performance, e.g., aluminum. Time-of-flight secondary ion mass spectrometry confirmed the extremely low level of aluminum in the plates. The final TLC layer thickness was ca. 50 μm. Separations of a test mixture of dyes from CAMAG (Muttenz, Switzerland) on an uncoated silica plate under traditional, normal phase conditions gave efficiencies of 40,000–140,000 plates m⁻¹ with migration distances ranging from 2 to 36 mm. A separation of two fluorescent dyes, eosin Y disodium salt and sulforhodamine B, on an amino silane-coated plate gave efficiencies of ca. 170,000 and 200,000 plates m⁻¹, with hR_F values of 76 and 88, respectively. Run times on these new plates were much faster than on conventional TLC plates.

An important aspect of the robustness of an electronic device is its ability to resist water, fingerprints, dirt, and smudges that may compromise its ability to function and/or the information within it. Here, we report a chemical analysis by ToF-SIMS, wetting, and XPS of the surfaces in a commercially available Apple iPod nano (8GB, MC525LL/A), which showed good resistance to its environment. This analysis reveals that the front panel (touchscreen) of the device is coated with a low free energy fluorinated polymer that may consist of short segments of a fluorinated hydrocarbon connected through ether linkages. No other part of the device appears to have this hydrophobic coating. A plasma treatment of the device leads to a deterioration of its performance. This work demonstrates how different analytical techniques can complement each other and contribute to a better understanding of a surface or a material.

Described is a method for ultrasonically spraying thin films of carbon nanotubes that have been suspended in organic solvents. Nanotubes were sonicated in N -methyl-2-pyrrolidone or N -cyclohexyl-2-pyrrolidone (CHP) and then sprayed onto a heated substrate using an ultrasonic spray nozzle. The solvent was quickly evaporated, leaving a thin film of randomly oriented nanotubes. Unlike other methods of spraying nanotube films, this does not require removal of surfactant after spraying and is compatible with creating films of functionalized nanotubes. Film thickness was controlled by the spray time and films were sprayed with thicknesses between 10 and 500 nm. Single-walled, multiwalled, and functionalized multiwalled nanotubes were sprayed. Transparent conducting thin films prepared by spraying single-walled carbon nanotubes dispersed in CHP demonstrated similar sheet resistance (for a given optical transmittance) as those prepared by spraying aqueous polymer-based dispersions that required postdeposition polymer removal.

Here, we report efficiencies up to 112000 plates per meter (a reduced plate height, h, of 2.22) for RP, carbon/nanodiamond/aminopolymer particles using conventional injection conditions in HPLC. This efficiency greatly exceeds our best previously reported value of 71000 N/m (h = 3.52). The carbon cores used in this study were derived from carbonized poly(divinylbenzene) spheres that were either made in-house by a two-step polymerization procedure or obtained commercially. The resulting particles showed good uniformity and were oxidized in nitric acid to increase their dispersability. X-ray photoelectron spectroscopy confirms particle oxidation and subsequent aminopolymer deposition. Layer-by-layer (LbL) growth of poly(allyamine) and nanodiamond was demonstrated to produce core-shell particles. After LbL growth, the particles were functionalized, sieved, and packed into columns. The column functionalization and packing were reproducible. Van Deemter curves indicated that the commercially obtained poly(divinylbenzene) spheres outperformed those synthesized in our laboratory. The columns appear to be stable at 120 degrees C in a pH 11.3 mobile phase. Longer columns (2.1 x 50 mm) than previously reported were packed. Four essential oils were separated by gradient elution.