Controllable growth of single walled CNTs using nanotemplates from diblock copolymers
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Controllable growth of single walled CNTs using nanotemplates from diblock copolymers Jennifer Lu, Jia Bai, Nick Moll, Daniel Roitman, Dorothy Yang, Agilent Technologies Qiang Fu, Jie Liu, Duke University David Rider, Ian Manners, Mitch Winnik, University of Toronto Abstract We use diblock copolymers as nanotemplates to produce various catalyst nanoclusters or catalyst-containing inorganic nanostructures with controlled size and spacing for carbon nanotube growth. We are able to generate periodically ordered catalytic nanostructures by spin coating polymer-based catalyst systems. As a result, uniformly distributed, low defect density single walled nanotubes(CNTs) have been obtained. CNTs with diameters of 1nm or less have been produced from iron-containing inorganic nanostructures using conventional chemical vapor deposition. The superior film forming ability of polymer-based catalyst systems enables selective growth of carbon nanotubes on lithographically predefined catalyst islands over a large surface area. The ability to control the density and location of CNTs offers great potential for practical applications. The initial MALDI-MS (Matrix Assisted Laser Desorption Ionization-Mass Spectrometry) results indicate that we can positively identify bovine serum albumin (BSA) at 500 attomoles using CNT surfaces produced by this method. Introduction Carbon nanotubes have become the most studied novel building block in the field of nanotechnology due to their remarkable electrical, thermal, and mechanical properties. CNTs are being exploited as field-emitter tips in displays1, as transistors2, 3, as interconnect and memory elements in integrated circuits4, as scan tips for atomic force microscopy5, and as sensor elements for chemical and biological sensing6. The ability to control the size and location of CNTs is the key to many of these applications. Chemical vapor deposition has gained popularity for carbon nanotube growth in which carbon nanotubes are grown selectively on catalytic sites. It has become the standard technique to synthesize single-walled and multi-walled CNTs for substrate-based applications. Even though progress has been made toward developing methods for controlling the diameters of carbon nanotubes7, all available methods do not provide a means to control catalyst size, spacing and density, and arrangement simultaneously on the nano-, micro- and macro scales, especially when a catalyst support is used. In this work, various catalyst nanoclusters or catalytically active inorganic nanostructures with controlled size and periodicity have been produced by catalyst-containing diblock copolymers. Using this polymer approach, we have produced uniformly distributed CNTs having very low defect density. The CNTs grown from iron-containing inorganic nanostructures have diameters of 1nm or less. More significantly, we have demonstrated selective growth of carbon nanotubes at lithographically defined locations across large areas. The application of carbon nanotube-coated surfaces as a MALDI-MS target has
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