Enhancement of infrared absorption (SEIRA) of adsorbed biological molecules by a nanostructured metal surface is one of the main routes to increasing the sensitivity of modern optical biosensors. The FTIR absorption spectra of thin films of the RNA base uracil deposited on low-temperature substrate (T = 6 K) with nanoscale silver structures were investigated in the spectral range 2700-600 cm-1. It was shown that the intensity of the absorption bands corresponding to νCO stretching vibrations (range 1800-1600 cm-1) of uracil (Ur) thin films increases 3-4 fold. For multilayer films, the influence of the nanostructures on the vibrational spectra weakens, and for the film layers more than 15 nm away from the surface, the enhancement is essentially absent. The energies and the vibrational spectra of the complexes of uracil monomers and dimers with 20-atom tetrahedral silver nanoclusters were calculated by the quantum-mechanical method DFT/B3LYP. The most stable complexes have the coordination bond between the top of the silver tetrahedron and the oxygen of the carbonyl group C4O. It was found that the formation of such complexes significantly (3-5 fold) enhances the intensity of the νC4O stretching vibration of uracil, while the intensities of the βNH, βCH and ring bending vibrations do not increase significantly.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)