Decoration of Carbon Nanotubes with CoO and Co Nanoparticles

M Belesi,D Niarchos,G Papavassiliou,S Pal,V Tzitzios,I Panagiotopoulos,D Tsitrouli,S Hariharan,N Boukos,M Fardis

doi:10.1155/2011/320516

Abstract

Multiwall carbon nanotubes (MWNTs) decorated with CoO nanocrystals were synthesized by in-situ thermal decomposition of Co(acac)2 in oleyl amine under reflux conditions open in the air. The CoO/MWNTs composite material can be easily converted to metallic Co/MWNTs through annealing under reducing atmosphere (4% H2) at 500°C without any significant sintering effect. The composite materials characterized by X-ray diffraction, transmission electron microscopy, and Nuclear Magnetic Resonance (NMR) spectroscopy. The structural and morphological characterization shows that the CoO has cubic face (fcc) and the particles deposited uniformly on the external surface of the carbon nanotubes. In the annealed materials, the NMR shows that the fcc and hcp metallic Co phases coexist with a significant percentage of stacking faults. The magnetic measurements indicated that the CoO/MWNTs composite is largely composed of CoO nanoparticles with uncompensated surface spins. The fluctuations of spins persist in partially reduced CoO grains as shown by nuclear spin-lattice relaxation measurements.

Highlights

In the past several years, there has been a growing interest in synthesizing carbon nanotube- (CNT-) inorganic nanocrystals composites including magnetic, semiconducting, and optic materials [1]
The magnetic measurements indicated that the CoO/Multiwall carbon nanotubes (MWNTs) composite is largely composed of CoO nanoparticles with uncompensated surface spins
Nanocomposite CoO or Co/carbon nanotubes materials were synthesized by one pot chemical route

Summary

Introduction

In the past several years, there has been a growing interest in synthesizing carbon nanotube- (CNT-) inorganic nanocrystals composites including magnetic, semiconducting, and optic materials [1]. Due to their high specific surface area, electrical conductivity, and chemical stability, carbon nanotube nanohybrids are assumed ideal materials for catalytic applications, from fuel cells to heterogeneous catalysis, for hydrogen storage and for chemical and biochemical sensing applications. The method is facile, based on environmental friendly raw materials, inexpensive, and reproducible for the large-scale synthesis of analogous composite nanomaterials These hybrid structures may combine the applications of the bare nanotubes structures and potentially enhance their properties giving considerable impact on the potential applications of nanotubes. The NMR measurements demonstrate the allotropic phase transformation of nanometric Co particles in the annealed samples and provide evidence for slow fluctuations of uncompensated spins in CoO nanoparticles which are still present in the sample annealed at 500◦C

Experimental Section

Results and Discussion

Conclusions