SAM-modified microdisc electrode arrays (MDEAs) with functionalized carbon nanotubes

The construction of a novel voltammetric transducer employing mixed acid-chopped, oxidatively modified, single-walled carbon nanotubes (HOOC-SWNT-COOH) covalently coupled to alkane thiol self-assembled monolayers (SAMs) that were deposited onto gold microdisc electrode arrays (MDEA-Au) (1296 microdiscs, 100 μm diameter each) has been demonstrated. The chemisorption of cysteamine (CA) and 11-amino-1-undecanethiol (11-AUT) SAMs onto the MDEAs resulted in MDEA-Au|CA and MDEA-Au|11-AUT, which when conjugated with the HOOC-SWNT-COOH produced MDEA-Au|CA|SWNT and MDEA-Au|11-AUT|SWNT electrodes. Electrodes were characterized by multiple scan rate cyclic voltammetry in the presence of ferrocene monocarboxylic acid and by AFM and compared. As expected, CA modification of MDEA-Au produced a disordered film that did not alter the effective surface area of the MDEA while 11-AUT modification resulted in passivation and a 50% reduction in effective surface area. The conjugation of the SWNT to the CA-modified and the 11-AUT-modified MDEA-Au surface returned well-resolved voltammograms with highest peak currents (I_pa = 5.54 × 10^-4 A, I_pc = 2.34 × 10^-4 A at 100 mV/s). The effective area of MDEA-Au|CA|SWNT was increased by 200% while that of MDEA-Au|11-AUT|SWNT was increased by 100%. AFM showed SWNTs to be vertically oriented on the CA-modified surface but to be horizontally arranged and bundled on the 11-AUT surface.