Optoelectronic Signatures of Biomolecules Including Hybrid Nanostructure-DNA Ensembles

Biological macromolecules such as DNA, proteins, and polysaccharides often display unique absorptive signatures in the THz region, useful in their identification and imaging through Raman and Fourier transform transmission spectroscopy. The optoelectronic properties of nanostructure-DNA complexes immobilized on transparent, semi-rigid substrates such as polymethyl methacrylate (PMMA) have been studied. By chemically modifying the PMMA substrates with amine terminal groups and using suitable linking agents, amine terminated DNA can be localized on these substrates. THz Fourier transform transmission spectroscopy was used to detect low-frequency vibrational modes (10-25 cm^-1) within single- and double-stranded DNA molecules immobilized on PMMA attached to TiO₂ nanoparticles. Additionally, DNA strands end terminated with TiO₂ nanoparticles are used in this study to cleave the DNA at guanine (G) rich sites due to trapping of photo-induced charge carriers from the TiO₂ at these sites. Theoretical modeling of charge transport through DNA via polaron transport is discussed in detail. By examining the vibrational modes of DNA, as well as the transport of charge in DNA this study underlies potential applications involving DNA micro-arrays, DNA-based sensors, and DNA-based THz devices.