Site‐Selective Functionalization of Carbon Nanotubes

Abstract

Carbon nanotubes (CNTs) are attractive nanodevice components due to their unique electronic structure, molecular dimensions, and shape.[1] The remarkable structural integrity of CNTs [2] and progress in techniques to assemble them into mesoarchitectures [3] make them attractive templates to assemble other low-dimensional structures (e.g., nanoparticles, biomolecules) to create hybrid nano-and mesostructures, composites, [4] and devices. Hybrid structures allow access to new electronic, electrical, and magnetic properties and provide additional degrees of freedom that enable the assembly and interconnection of nanostructures into architectures for nanodevice fabrication. For example, CNTs derivatized with Au [5] or Co [6] nanoparticles exhibit single-electron transport or enhanced spin polarization, respectively, which could be harnessed for nanoelectronics and spintronics. Molecular-recognition-based self-assembly of DNA-modified CNTs has also been demonstrated for fabricating test devices. [7,8] However, lack of control over the functionalization location in the CNTs remains a major challenge for realizing hybrid mesoarchitectures, e.g., with molecularly networked CNTs, or CNTs decorated with nanoparticles or biomolecules at preselected locations. Site-specific functionalization of CNTs will not only facilitate the assembly of nanoscale blocks, but will also allow addressing preselected segments of the CNTs using nanoparticles or biomolecules, thereby paving the way for new up-scalable device concepts. Creating CNT templates with specific chemically active locations is a crucial step towards achieving such possibilities.Several strategies have been devised to functionalize CNTs to harness them for applications such as CNT-filled composites, field emitters, sensors, and catalyst supports. Examples include acid-based wet-chemical oxidation, amidation, or esterification, diimide activation and solubilization of CNTs, or hydrophobic adsorption of aromatic derivatives.[9-13] These strategies typically rely on random defect creation or adsorption, and do not allow precise control over the functionalization location. For example, ultrasonication in oxidative environments generates dangling bonds at random spots on CNT sidewalls, and enables the formation of functional groups at these locations via decomposition of the reactive organic molecules used. [14] The type and location of defects, however, are difficult to control, rendering such methods unsuitable for applications where the electronic properties of CNT need to be preserved. Although hydrophobic derivatization [13] does not need defect creation, the lack of site selectivity limits its use for anchoring nanostructures to specific locations of CNTs for site-specific addressing or to utilize them as nodes for further organization and assembly.Here, we demonstrate a new approach using focused-ionbeam (FIB) irradiation and subsequent mild chemical treatments to functionalize multiwalled CNTs at preselected locations. This approach involves the use of kiloelectronvol...

Ion and electron irradiation-induced effects in nanostructured materials

“…One of most widely used techniques for defect identification in covalently bonded carbon, 24,[27][28][29]150,151 BN, 152 or Si ͑Refs. 65, 153, and 154͒ nanostructures is Raman scattering.…”

“…Experiments on electron 72 and ion 334 24. ͑Color online͒ Sequential TEM images of the interlayer defects which appear and disappear in DWNTs recorded at 573 K. In the ͓͑a͒-͑d͔͒ side wall, several bridges connecting two graphene layers frequently appear in dark contrast ͑marked by red arrows͒ and disappear just after the observation.…”

“…Spatially localized ion irradiation was also used for the fabrication of a single-electron inverter in MWNTs. 26 Because irradiation-induced defects normally increase the reactivity of nanotubes ͑e.g., due to dangling bonds at the surface defects͒, focused-ion-beam irradiation, followed by mild chemical treatment, was used to functionalize nanotubes at preselected locations, 24 Fig. 47.…”

“…[6][7][8][9][10][11][12][13][14][15][16] Besides, it was demonstrated that nanotubes can be interconnected or merged 9,12,17,18 and that irradiation can give rise to many interesting phenomena, such as extreme pressure inside nanotubes 19 or fullerenelike "onions," 6,20 so that these systems can be used as nanolaboratories for studying pressure-induced transformations at the nanoscale. Furthermore, recent experiments indicate that ion, [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] electron, 6,39-52 and high energy photon [53][54][55][56] irradiation can be used to tailor the mechanical, 8,10 electronic, 11,[21][22][23] and even magnetic …”

Imaging and Spectroscopy of Multiwalled Carbon Nanotubes during Oxidation: Defects and Oxygen Bonding

“…[11][12][13][14] Another important issue is the role of structural defects, which can act as active centers promoting the oxidation and/or favoring the formation of certain functional groups. In fact, even the highest quality CNTs contain various structural defects, [17] which can alter their electrical, [18] transport, [19] and chemical [20,21] properties. In a recent study, we showed that the C 1s core level spectrum is an excellent fingerprint for the structural quality of C-based materials.…”