Dna Electronic Structure And Optical Properties

With the progress of nanotechnology, DNA have drawn the scientists extensive attention because of its woven, self-assembly, low maintenance and unique nature of biological. However, the basic physical property of DNA is still controversial, which will be the potential hinder to the development of the new materials and new device of DNA in the future. Many works have focused on investigating the electrical properties but few in the optical with the research of the basic physical properties of DNA. In the present paper, we mainly investigate the optical absoiption properties of poly(G)-poly(C) double-stranded DNA (dsDNA) and poly (A)-poly(T) dsDNA chains and the dangling backbone ladder DNA with the two different base components.Because of the complexity of DNA structure, we calculate the energy band structure and the optical transitions absoiption spectrum of poly(G)-poly(C) and poly (A)-poly(T) chains and the dangling backbone ladder DNA with the two different base components based on the tight-binding model. The results show that the electronic band structure of the poly (G)-poly(C) and poly(A)-poly(T) chains turn out the indirect band gap semiconducting electronic structure behavior. The band gap gradually disappears and the energy region broadens with the increasing of the magnitude of disorder. The parallel polarization absorption peak sites of the poly(G)-poly(C) DNA and poly(A)-poly(T) DNA are 1.87 eVand 0.76 eVrespectively, while the perpendicular polarization absorption edges of poly(G)-poly(C) DNA and poly(A)-poly(T) DNA are 1.84eV and 0.68eVrespectively. In both low-energy and high-energy range, there exist perpendicular polarization absorption peaks. And there exist competition effect between the perpendicular and parallel polarization. With increasing of the disorder, the parallel polarization absorption spectrum of both chains broadens. However, the phenomenon that the poly(A)-poly(T) DNA change more significantly than the poly(G)-poly(C) DNA in the low energy region is revealed. As for the perpendicular polarization absorption spectrum, the peak in high energy region disappears with the increasing of disorder while the one in low energy region exhibits more tendency towards to lower frequency for poly(G)-poly(C) DNA.With the backbone-induced effects, the energy band structure of the two base components of dangling backbone ladder DNA chains changes into four energy band. In the perpendicular polarization absorption spectrum, the numbers of absorption peaks of both G-C and A-T dangling backbone ladder DNA chains increase into four and the absoiption scope broadens, besides the position of the absoiption edge and the absorption range move to the high energy region. In the parallel polarization absorption spectrum, the symmetry broken, the absoiption peaks of both chains move to the high energy region while only with the A-T chain the number of the absorption peaks increase to two. With the effects of the backbone hopping integral disorder, In the perpendicular polarization absorption spectrum, the numbers of absorption peaks of both chains reduced by one and the peak gradually lower, meanwhile the absorption energy range gradually expanded with the increase of the disorder; In the parallel polarization absoiption spectrum, the height of absorption peaks gradually lower and the site of the peak move to the high energy region, meanwhile the absorption energy range gradually spreads, moreover the spectrum symmetry forms.