Electron spin resonance investigation of ultra-small double walled carbon nanotubes embedded in zeolite nanochannels

• Published in: Journal of physics. Condensed matter 2011-11, Vol.23 (45), p.455801-6
• Main Authors: Rao, S S, Stesmans, A, Noyen, J V, Jacobs, P, Sels, B
• Format: Article
• Language: English
• Subjects: Carbon; Carbon nanotubes; Condensed matter; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Density; Electron paramagnetic resonance; Electron paramagnetic resonance and relaxation; Electron spin resonance; Exact sciences and technology; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Nanostructure; Physics; Zeolites
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/23/45/455801

We report on the low temperature electron spin resonance (ESR) properties of ultra-small (0.45 nm) double walled carbon nanotubes (DWCNTs) embedded in zeolite nanochannels. An isotropic ESR signal is observed at g(c) = 2.002 77 with the spin density (S = 1/2) ∼ 10(19) g(-1), which is suggested to originate from the carbon related point defects in the DWCNTs. Measurements of the ESR line width and signal intensity as a function of temperature indicate that the spins are of a localized nature as opposed to the conduction type electrons observed in large diameter CNTs. The results are consistent with the suggestion that electrons are trapped at interstitial defects. The observed linear frequency dependence of the ESR line width of embedded DWCNTs points to 'strain' as the prime source of broadening. By contrast, the study of free standing DWCNTs shows the presence of a distinctly superlinear frequency dependence of the signal width at low temperatures. The possible origin of the frequency dependence is discussed.