(Color online) Microfabrication scheme for TLC plates. Surfaces are photolithographically patterned. Al2O3 and Fe are deposited sequentially. The devices then undergo lift-off of the photoresist, leaving a pattern of Fe on Al2O3, which is followed by CNT growth, infiltration of Si by LPCVD of SiH4, and oxidation to remove the CNT framework and convert Si to SiO2.
Representative SEM micrographs of annealed Fe surfaces with initial Fe thicknesses of (a) 4 nm, (b) 6 nm, (c) 8 nm, (d) 10 nm, (e) 12 nm, (f) 14 nm, (g) 16 nm, and (h) 18 nm.
Diameter, Dp, of iron nanoparticles as a function of initial Fe film thickness, tFe. Data points (averages) and error bars (standard deviations) were obtained from three different surfaces annealed under the same conditions—examples of the data used are in Fig. 2 . The fits are Dp = 6.06 tFe (solid line, R2 = 0.95) and Dp = 7.00 tFe − 12.15 (dashed line, R2 = 0.97).
(Color online) AFM images of annealed Fe surfaces that had initial Fe film thicknesses of (a) 4 nm, (b) 8 nm, (c) 12 nm, and (d) 16 nm.
Average diameters of CNTs, DCNT, as measured by SEM, as a function of the initial Fe layer thickness, tFe. Twenty measurements were taken from each of three different images from two different samples. Data points are the averages and error bars are the standard deviations of the data. Fits to lines are (from left to right on the plot): DCNT = 1.25 tFe + 6.59, R2 = 0.98, and DCNT = 9.51 tFe − 110.52, R2 = 0.99.
SEM micrographs showing side (left), top (middle), and side (right, at higher magnification) views of CNTs grown from initial Fe catalyst thickness of (a) 6 nm, (b) 8 nm, (c) 10 nm, (d) 12 nm, (e) 14 nm, (f) 16 nm, and (g) 18 nm.
TEM images of the tops of CNT forests grown with 6 nm of annealed Fe. Catalyst nanoparticles are not seen – they are not embedded or inside the tips of the nanotubes, which suggests “base growth” of CNTs at this tFe.
(Color online) Separation of a CAMAG test dye mixture, with toluene as the mobile phase, on TLC plates made with Fe thicknesses of (a) 4 nm, (b) 6 nm, (c) 8 nm, and (d) 10 nm.
(Color online) Separation of three analgesics (from left to right: caffeine, phenacetine, and propyphenazone) using 4:1 toluene:acetonitrile (v/v) with 0.1% TEA with sample volume of (a) 1.8 μl and (b) 3.6 μl. The run time was 3:05 min for both plates. The vertical lines on the left and right correspond to the positions of spotting and the solvent front, respectively, where the difference between these points was 3.5 cm on the plates.
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