Electrochemical modification of boron-doped chemical vapor deposited diamond surfaces with covalently bonded monolayers

Electrochemical reduction of phenyl diazonium salts in acetonitrile at boro n-doped diamond electrodes yielded covalent bonding of aromatic groups to t he sp(3) carbon surface. Diamond surfaces modified with nitrophenyl, triflu oromethylphenyl, and nitroazobenzene showed strong X-ray photoelectron spec troscopy (XPS) signals for surface nitrogen or fluorine, which were stable to exposure to air or solvents. Raman spectra of chemisorbed nitroazobenzen e on boron-doped diamond were obtained, and were similar to those observed for derivatized glassy carbon. Estimated surface coverages of 50-70% of a c ompact monolayer were calculated from XPS spectra, indicating that the cove rage is too high to be attributed solely to modification of sp(2) carbon im purities or boron dopant. The high coverages of covalently bonded molecules on diamond achievable by diazonium reduction imply that a variety of surfa ce functionalities may be introduced on the normally unreactive diamond sur face. (C) 1999 The Electrochemical Society. S1099-0062(98)12-080-1. All rig hts reserved.