Journal of the American Chemical Society, Vol.130, No.43, 14040-14040, 2008
Correlation of Molecular Orientation and Packing Density in a dsDNA Self-Assembled Monolayer Observable with Surface-Enhanced-Raman Spectroscopy
Observations of two spectrally distinct ring breathing modes of guanine and adenine in the surface-enhanced Raman spectrum (SERS) of a dsDNA self-assembled monolayer on an Au nanoshell SERS substrate provide information concerning the orientation of its Constituent molecules. The two modes vary with DNA concentration in a highly systematic manner, consistent with studies suggesting DNA molecules tend toward a more horizontal orientation at low-surface concentrations and a more vertical conformation at high concentrations. The introduction of small molecular spacers coadsorbed onto the Au nanoshell surface to "raise" the DNA molecules yields a SERS spectrum consistent with a more upright molecular orientation.