Optoelectronic Signatures of DNA-Based Hybrid Nanostructures

This paper presents a characterization of the vibrational modes of nanostructure–DNA complexes immobilized on substrates, such as silver-coated microspheres and silver nanostructure array DNA strands end terminated with titanium dioxide (
${\rm TiO}_{2}$
) nanoparticles are used to study UV-induced cleaving of DNA molecules functionalized with indirect-bandgap semiconductors. In addition, conventional DNA-based molecular beacons were designed and applied in the detection of DNA of selected organisms. Micro-Raman (μRaman) measurements of DNA in water have proven to be a major challenge because of: 1) weak DNA signatures in solution; 2) changes in structural conformations of the DNA; and 3) environmental effects, such as temperature and pH of the solution in which DNA is suspended. We have studied optoelectronic properties of nanostructure–DNA complexes immobilized on silver nanosphere substrates as well as on Ag-coated micro- and nanostructures. In this research, self-assembled monolayers of DNA formed on these substrates were studied using μRaman techniques. These Raman spectra were used to identify prominent vibrational modes of DNA, and to characterize DNA Raman spectra for both B-DNA with a right-handed double helix, and Z-DNA with a left-handed double helix (S. C. Ha, K. Lowenhaupt, A. Rich, Y. Kim, and K. Kim, “Crystal structure of a junction between B-DNA and Z-DNA reveals two extruded bases,” Nature, Vol. 437, pp. 1183–1186, 2005). These Raman-based studies of the conformational states of DNA employ pH-changing trivalent salts, methylation of cytosine bases, and alternating GC bases. Moreover, DNA strands terminated with titanium dioxide (
${\rm TiO}_{2}$
) nanoparticles were observed to undergo cleaving upon UV illumination.