Abstract: A detailed study is conducted for the electrochemical ex situ and in situ surface enhanced Raman scattering(SERS) studies of oligonucleotide probe self-assembled monolayer on gold substrate before and after hybridization. Ex situ SERS results indicate that dsDNA molecules on gold substrate are not only in B-form but also in A-form helices and that the DNA molecules have the adsorption orientation change after the hybridization. According to the in situ SERS results, the intensities of most of the SERS bands of ssDNA and dsDNA decrease substantially toward more positive potentials, especially for two out-of-plane vibration modes of adenine. By utilizing SERS "surface selection rules", it can be concluded that as the potential is progressively changed from negative to more positive potentials, the adsorption orientation of ssDNA and dsDNA changes from standing straight up to lying flat down on the gold substrate.

Key words: Oligonucleotide probe, Hybridization, Surface Enhanced Raman Scattering(SERS), Adsorptive orientation