Micro-structural, electron-spectroscopic and field-emission studies of carbon nitride nanotubes grown from cage-like and linear carbon sources

Using conventional chemical vapor deposition at 800 degrees C at atmospheric pressure, N-doped carbon nanotubes (CNTs) were grown from two precursors: (i) from a cage-like carbon source: camphor, using dimethylformamide (DMF) as a nitrogen source; and (ii) from a linear-chain aminohydrocarbon: octadecylamine, as a dual source of carbon and nitrogen. The study suggests that the molecular structure of the precursor plays an important role in governing the structural proper-ties of the resulting nanotubes. Although the nanotubes have bamboo-like structure in either case, electron-microscopy reveals remarkable differences in their microstructure. While camphor-DMF-grown carbon nanotubes (CD-CNTs) have corrugated outer walls and rounded tips, the octadecylamine-grown ones (OD-CNTs) are straight and have tapered tips. Quantitative as well as qualitative determination of nitrogen level is done based on XPS and EELS analyses, assigning different nitrogen moieties (pyridinic, pyrrolinic and graphitic-substitute) in the CNT-body and tip regions. Relative to CD-CNTs, the OD-CNTs have higher crystallinity, higher thermal stability and higher specific surface area, as determined by micro-Raman, TGA and BET analyses, respectively The field emission properties of CD-CNTs are typically good, while those of OD-CNTs are better. These behavioral differences are explained in terms of the growth chemistry as well as the role of different nitrogen moieties in the CNT matrix. (C) 2009 Elsevier Ltd. All rights reserved.