Interação entre DNA e nanoaglomerados de Au e Ag: propriedades ópticas por meio da DFT

Abstract

In this work, the study of optical properties due to the interaction between DNA and nanoclusters of Ag, Au, and Ag-Au mixed is performed by the Density Functional Theory (DFT). The formation of these complexes and photoluminescence measurements are reported in previous experimental studies. First, the study of the structure and energetic stability of the nanoclusters is presented, followed by a discussion of the study of the DNA:nanoclusters absorption spectra. Regarding structural features, the calculations performed provide results from interactions at the molecular level and show that the favorable geometry for the cluster Au3 is dierent from Ag3 and Ag-Au mixed clusters; the nanoclusters are strongly bound to the guanine-cytosine base-pairs; and the Au-rich nanoclusters are located on top the cytosine. Regarding optical properties the calculations performed provide semi-qualitative results. It was observed that the Ag3 nanocluster presents no absorption in the infrared range, however when in a complex with DNA, the complex absorbs in the infrared frequencies. Finally, calculations show that dierencies between the absorption spectra of DNA with mixed nanoclusters may be used to determine the stoichiometry of these structures.