SERS studies of self-assembled DNA monolayer – characterization of adsorption orientation of oligonucleotide probes and their hybridized helices on gold substrate

The electrochemical ex situ SERS spectra indicate that under atmosphere, the conformation of most of helices on gold substrate is B-form, but A-form conformation also exists. The band intensities of the in situ SERS spectra of oligonucleotide probes and their hybridized helices decrease substantially when the potentials are made more positive, especially for two ring vibration modes of the out-of-plane contribution of adenine, which indicates that conversion of the vertical adsorption orientation to flattened adsorption orientation occurs when the potential is changed from negative to more positive potentials according to SERS `surface selection rulesʹ.