Facile "needle-scratching" method for fast catalyst patterns used for large-scale growth of densely aligned single-walled carbon-nanotube arrays**

A simple, fast, machine-controlled and environmentally friendly, called the 'needle-scratching' method (NSM), for generating large-area catalyst patterns on Si/SiOx and single-crystal quartz substrates for the growth of densely aligned SWCNT arrays, was reported. A common syringe needle was used to randomly scratch lines on a Si/SiO₂ substrate. After ultrasonication in acetone for 10 min and rinsing with Milli-Q water, the single-crystal quartz substrates were immersed in piranha solution. NSM was used to generate catalyst stripes on the substrates after the cleaned substrates were rinsed with Milli-Q water and dried with a N₂ flow. The observations suggest that the high quality of the catalyst NPs generated by NSM could be the reason for the growth of high-density SWCNTs, which indicates that the syringe needle plays an important role in producing such high-quality catalyst NPs.