Adsorption of amino acids by functionalized carbon nanotubes (CNTs) can affect the environmental and biological behaviors of CNTs. We investigated adsorption mechanisms of zwitterionic phenylalanine, tyrosine and glycine on carboxylated (CM), hydroxylated (HM) and graphitized (GM) CNTs at different pHs. All the adsorption isotherms were well fitted with Polani-Mane model and adsorption maxima followed: CM>HM>GM for all amino acids. For a given CNTs, both adsorption maxima and affinity followed: tyrosine>phenylalanine>glycine. Phenylalanine and tyrosine at neutral pH have higher adsorption than at acidic (pH=2) and alkaline (pH=12) solution. Our results indicate p-p  and hydrophobic interactions along with covalent bond could be important for tyrosine and phenylalanine adsorption at different pHs, relative to electrostatic interaction. In addtion, phenol structure of tyrosine enhanced the p-p interaction with the benzene rings on the surface of CNTs compared to phenylalanine. However, the covalent bond and electrostatic interaction may be responsible for glycine adsorption.

Adsorption of amino acids on functionalized carbon nanotubes

247th National Meeting (2014)

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