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

Abstract

Direct fabrication of uniform patterns of Fe 2 O 3 ‚xH 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 ‚xH 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 ‚xH 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.

Wafer scale synthesis of dense aligned arrays of single-walled carbon nanotubes

“…F i r s t , o r d e r e d c a t a l y s t s t ru c t u re s w e re e a s i l y a n d reproducibly patterned on quartz wafers by photolithography and PDMS stamp μCP techniques. Otherwise, FeCl 3 as the catalytic precursor is hard to uniformly pattern on the surface of wafers, especially for high concentrations of FeCl 3 [28]. Other catalysts such as ferritin [29,30], FeMo clusters [31], and Fe/Mo [32] nanoparticles also cannot be directly patterned on a wafer surface.…”

How Catalysts Affect the Growth of Single‐Walled Carbon Nanotubes on Substrates

“…We found that PDMS stamps without ozone oxidization are very suitable to host both the formation and transfer of iron oxide nanoparticles of proper sizes onto substrates for CVD growth of SWNTs (Scheme 2). [18] An ethanol solution of FeCl 3 Á H 2 O can wet the as-prepared PDMS stamp very well. With the evaporation of ethanol, Fe 2 O 3 Á nH 2 O nanoparticles are formed from hydrolysis.…”

“…Figure 1B shows the tapping-mode atomic force microscopy (AFM) image of the obtained Fe 2 O 3 Á nH 2 O nanoparticles on a SiO x /Si substrate. [18] Polystyrene (53 800)-block-poly(2-vinyl-pyridine) (8800) can form micelles with monodispersed size of $13.3 nm in toluene solution. Therefore, a fixed amount of FeCl 3 , which can be altered by using FeCl 3 aqueous solution of different concentration, can be loaded in the nanometer-sized water pools of the micelles.…”

“…It is generally considered that the proper size of nanoparticles for initiating the growth of SWNTs is around 1 nm [18] though the size of the catalyst precursors might be much larger. It is also widely accepted that the diameters of the produced SWNTs are determined by the size of the catalyst nanoparticles.…”

Aligned silane-treated MWCNT/liquid crystal polymer films

“…• C) rules out many substrates, not least flexible polymeric ones [4][5][6] which would allow subsequent ease of device production; in addition, the lateral size on which it is possible to grow such 'forests' of nanotubes by CVD is quite limited. Attempts at aligning nanotubes in composite systems using polymeric matrices have also often proven unsatisfactory.…”