Patterning of Three-dimensional Carbon Nanotube Architectures by a Composition Transfer Approach

Introduction Creating three-dimensional patterned nanoarchitectures on the surface of a substrate is an essential step towards the investigations on their novel properties and the developments of nanomaterials and nanodevices at different length scales. Patterned nano-architectures composed of one-dimensional (1D) nanowires/nanotubes on two-dimensional substrates always exhibit tailored mechanical, thermal, catalytic or optical properties. Among various 1D nanomaterials, carbon nanotube (CNT) is one of most attractive building blocks because of their unique properties originating from the small size, cylindrical structure, and high aspect ratio. If CNTs can be controllably patterned into 3D nanoarchitectures, they will hold promise for a variety of applications in intelligent nanocomposites with hydrophobic surfaces, field emission display, energy conversion and storage, sensor, and catalysis. The construction of patterned CNT architectures generally relies on the fabrication of patterned catalyst layers or substrates through complicated procedures. Shadow mask, block copolymer micellar films, soft-lithography, and photolithography, were used to pattern iron catalysts for the self oriented growth of CNT architectures [1]. Recently, numerous works on CNT growth with multi-composition catalysts were reported [2], and it was noticed that the growth of CNTs were sensitive to the catalyst composition. Herein, we proposed the gas-phase transfer process of a second phase metallic composition to modulate the activities and controllably construct the CNT architectures. The appearance of small amount additives may great change the activities of catalyst for CNT growth by over an order of magnitude. As shown in Fig.1. During the annealing process, the compositions on the covering mask were sublimated onto the Fe catalyst layer, which tuned the catalytic activities for