Printing gel-like catalysts for the directed growth of multiwall carbon nanotubes

Microcontact printing is used to transfer an Fe(III)-containing gel-like ca talyst precursor from a hydrophilized elastomeric stamp to a substrate. The catalytic pattern activates the growth of multiwall carbon nanotubes using chemical vapor deposition of acetylene. Our results show that the choice o f the catalyst is of extreme importance. Most of the aqueous and ethanolic Fe(III) inks used give rise to drying effects on the stamp surface, which l ead to the formation of islands of the catalyst within the pattern. To avoi d these shortcomings, we developed a catalyst precursor, which has better p erformance on the stamp and as a catalyst on the substrate. Simple aging of the ethanolic Fe(III) ink results in a polymerized gel-like catalyst, whic h can be printed homogeneously on the substrate with excellent contrast. Ch anging the concentration of the catalyst in the ink allows the density of t he carbon nanotubes in the film to be tuned. A scanning anode field emissio n microscope was used to investigate the microscopic field emission propert ies of the samples. The emission images reproduce the topographical contras t nicely and prove the high quality of the patterning process.