Direct Preparation and Patterning of Iron Oxide Nanoparticles via Microcontact Printing on Silicon Wafers for the Growth of Single-Walled Carbon Nanotubes

Direct fabrication of uniform patterns of Fe 2 O 3 · x H 2 O nanoparticles on the SiO x /Si surface was achieved by microcontact printing (μCP). The as-prepared poly(dimethylsiloxane) (PDMS) stamps with a hydrophobic surface were used. The “ink” was an FeCl 3 ·6H 2 O ethanol solution. Fe 2 O 3 · x H 2 O nanoparticles were formed on the stamps from the hydrolysis of FeCl 3 during the ink drying process and were then directly deposited onto the SiO x /Si surface with μCP. The nanoparticles were transferred to the areas beneath the “raised” portions of the stamp at low ink concentration but populated at the areas beneath the “recessed” portions of the stamp at high ink concentration. The hydrophobic property of the stamp surface cooperated with the gravity of the particles in bringing on such an exchange of recession and repousse. The density and size of the formed nanoparticles could be tuned by varying the ink concentration. The patterned Fe 2 O 3 · x H 2 O nanoparticles were used as the catalysts for the growth of single-walled carbon nanotubes (SWCNTs) by CVD. By skillfully patterning the inks of different concentrations on the same SiO x /Si wafer, we studied the effect of the ink concentration on the growth of SWCNTs. It is also shown that this simple method could be extended to the fabrication of other metal-containing nanoparticles.