Web Release Date: February 5,
Adsorption of L-Phenylalanine on Single-Walled Carbon Nanotubes
and
National Center for Nanoscience and Technology, Beijing 100080, People's Republic of China, and Department of Catalysis Science and Technology, School of Chemical Engineering, Tianjin University, Tianjin 300072, People's Republic of China
Received: September 2, 2007
In Final Form: November 20, 2007
Abstract:
Single-walled carbon nanotubes (SWNTs) became soluble in water and formed a stable solution when
L-phenylalanine (Phe) was adsorbed. The adsorption selectivity of Phe zwitterions for larger diameter SWNTs
was confirmed by analysis of Fourier transform infrared spectra and by differential thermogravimetric analysis.
Enhanced adsorption of Phe on the oxidized single-walled carbon nanotubes (OSWNT) was observed in
comparison with that of the purified single-walled carbon nanotubes (PSWNT). The Phe zwitterions are thought
to adsorb on the surface of OSWNT by joint interaction of the 
- stacking, hydrogen bond, and part of the
covalent bond. The - stacking is the dominant interaction in the sidewall of OSWNT without defects.
The hydrogen bond and covalent bond formed with oxygen-containing groups becomes dominant on the end
of OSWNT. For the PSWNT system, - stacking is an important factor to realize the adsorption of Phe
zwitterions on the sidewall of PSWNT. The intermolecular hydrogen bond between Phe zwitterions is also
formed when Phe zwitterions are adsorbed on the PSWNT.
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