Vertically aligned multi-walled carbon nanotubes (MWCNTs) synthesized by the alcohol catalytic CVD (ACCVD) technique are dispersed in water with the aid of water-dispersible conjugated polymer nanoparticles (CPNs). The interactions between CPNs and CNTs are studied with spectroscopy (UV-Vis, fluorescence and Raman) and electron microscopy techniques are used to confirm attachment of CPNs to the CNT sidewalls.

Cataloged from PDF version of article.Multi-walled carbon nanotubes (MWCNTs) were synthesized through pyrolysis of the sulfuric acid-carbonized byproduct of sucrose. While the presence of sulfur in the reaction media has a key role in the formation and population density of MWCNTs, we have not observed the formation of Y-junctions or encountered other novel carbon nanotube formations. Results indicate the presence of sulfur in catalyst particles trapped inside nanotubes, but failed to find sulfur in the side-walls of the CNTs. In order to verify and explain these findings, we analyzed the behavior of sulfur and its possible effects on the side-wall structure of CNTs by using density functional theory-based calculations on various atomic models depicting sulfur inclusion in the side-walls. The results of the computational study were in line with the experimental results and also provided a new perspective by suggesting that the defects such as pentagons may act as nucleation sites for the Y-branches. The results indicated that sulfur prefers to adsorb on these defective regions, but it is not responsible for the formation of these structures or defects. (C) 2010 Elsevier Ltd. All rights reserved

In this study, we report on a unique, one-step fabrication technique enabling the simultaneous synthesis of vertically aligned multi-walled carbon nanotubes (VA-MWCNTs) with dual height scales through alcohol catalyzed chemical vapor deposition (ACCVD). Regions of VA-MWCNTs with different heights were well separated from each other leading to a self-patterning on the surface. We devised a unique layer-by-layer process for application of catalyst and inhibitor precursors on oxidized Si (100) surfaces before the ACCVD step to achieve a hierarchical arrangement. Patterning could be controlled by adjusting the molarity and application sequence of precursors. Contact angle measurements on these self-patterned surfaces indicated that manipulation of these hierarchical arrays resulted in a wide range of hydrophobic behavior changing from that of a sticky rose petal to a lotus leaf.Inspired by the self-cleaning effect of lotus leaves, researchers have paid increasing attention to the generation of superhydrophobic surfaces having hierarchical structures with features ranging from micro-to nanoscale. The lotus leaf has a highly textured surface with protruding nubs (20-40 mm) which are further covered with nanometre sized wax crystals.1 Lotus leaf-like surfaces can be created either by covering a rough surface with a low surface energy material or by roughening/ etching/patterning the surface of a hydrophobic material. 10,11Functionalized vertically aligned multi-walled carbon nanotube (VA-MWCNT) arrays synthesized by CVD have also demonstrated superhydrophobic properties. 9,12Moreover, combining the CVD technique with photolithography for generating patterned carbon nanotube (CNT) arrays on surfaces has also been shown to improve and tailor superhydrophobicity of these surfaces.13 However, additional steps such as patterning with lithography for creating complex structures to improve hydrophobic behavior or imparting self-cleaning properties are not often cost efficient. Therefore, a simple, one-step production technique is required for the generation of artificial lotus leaf-like surfaces.Hence, the aim of this study is to imitate lotus leaf structures by creating dual-scale micro/nanostructures of aligned and patterned CNTs during the growth. For this purpose, we developed a unique technique based on the layer-by-layer application of catalyst and inhibitor precursors which is normally used to grow VA-MWCNTs by our group.14 By tuning the molarity, types, sequence and number of precursor and catalyst layers, we were able to not only generate hierarchical and patterned superhydrophobic VA-MWCNT arrays but also tailor the wettability properties. The resultant hierarchical structures were fully characterized (contact angle, surface topography, physical properties, and geometry) in order to identify the contribution of micro-and nano-structured aspects on water repellency. These hierarchical CNT arrays with micro-and nanoscales can be further developed to potentially find applications as self-cleaning dry-adhesives (gecko ...

Saccharides, ranging from simple table sugar (sucrose) to lactulose were successfully used as solid-state precursors for the synthesis of multi-walled carbon nanotubes (MWCNT). Dehydrated saccharide residues mixed with catalyst powders were subjected to pyrolysis at high temperatures (up to 1300°C) under flowing Argon atmosphere. Pyrolysis products were investigated using TEM, SEM, Raman spectroscopy and EDS. Images taken using the S/TEM and bright field mode of TEM showed the presence of helical multi-walled carbon nanotube (H-MWCNT) and regular MWCNT formation. More than two or three catalyst particles were observed to be present inside the hollow core of some of the nanotubes synthesized, suggesting a high level of capillary activity inside the tubes during synthesis.