Diazonium ion chemistry has been used to electrochemically graft aminophenyl layers onto p-type silicon (100) substrates. A condensation reaction was used to immobilise single-walled carbon nanotubes with high carboxylic acid functionality directly to this layer. Electrochemical monitoring of the aminophenyl groups confirmed the formation of an amide linkage between the single-walled carbon nanotubes and the aminophenyl layer. The carbon nanotube electrode showed high stability and good electrochemical performance in aqueous solution. At moderate scan rates the Ru(NH3)(6)(+3/+2) couple exhibited quasi-reversible electron transfer kinetics with a standard heterogenous rate constant of 1.2 x 10(-3) cm s(-1) at the covalently-linked carbon nanotube surface. The electrode thus combines the advantages of a silicon substrate for easy integration into sophisticated electrical and electronic devices, carbon nanotubes for desirable electrochemical properties, and stability in aqueous medium for future applications in environmental sensing. (C) 2010 Elsevier Ltd. All rights reserved.