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 hRF values of 76 and 88, respectively. Run times on these new plates were much faster than on conventional TLC plates.
A.P. Boichenko, Open Surf. Sci. J. 1 (2009) 40–45.