Spectral and cyclic voltammetric characterization of self-assembled monolayers on gold of pyrene end-labeled oligonucleotide duplexes

Self-assembled monolayers of sulfur-terminated oligonucleotide duplexes wer e formed on flat gold surfaces, either by exposure of a self-assembled mono layer bearing one oligonucleotide strand to the complementary strand or by preformation of a oligonucleotide duplex that was then deposited on a fresh gold surface. Virtually identical spectral behavior was observed whether t he duplex was produced before deposition or by in situ complementary associ ation. With a duplex bearing an appropriate pyrene end-label, the resulting thin film was photoresponsive. Surface emission measurements show no evide nce for pyrene aggregation on the modified surfaces. The polarity of the ph otocurrent, reflecting photoinduced electron transfer initiated by photoexc itation of pyrene, is opposite that expected from the oligonucleotide-media ted reduction of the appended pyrene excited state.