A combined analytical approach is proposed to investigate the spin-selectivity properties of DNA nanowires considering the spin degree of freedom in the extended Peyrard–Bishop–Holstein model. On the basis of a real chain of DNA sequence, no completely pure spin current through DNA is shown, instead, one of the spin currents is dominant over another and creates a spin filtering effect. In several parameter regions, the net charge current is low, and thus a nearly pure spin current could be reported. We examined the effects of external fields, temperature, and sequence variation on spin-dependent charge transfer in DNA. The results show peaks in the DNA spin polarization in some parameter values. A DNA coder can be created according to these polarization peaks. Transporting information by using the DNA spin polarization is interested in information theory. Meanwhile, other parameter values exist, where nearly pure spin currents appear. The appearance of these islands can be confirmed and predicted using the Rényi fractal dimension approach.

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An analytical approach is proposed for the investigation of the conductivity properties of DNA. The charge mobility of DNA is studied based on an extended Peyrard-Bishop-Holstein model when the charge carrier is also subjected to an external electrical field. We have obtained the values of some of the system parameters, such as the electron-lattice coupling constant, by using the mean Lyapunov exponent method. On the other hand, the electrical current operator is calculated directly from the lattice operators. Also, we have studied Landauer resistance behavior with respect to the external field, which could serve as the interface between chaos theory tools and electronic concepts. We have examined the effect of two types of electrical fields (dc and ac) and variation of the field frequency on the current flowing through DNA. A study of the current-voltage (I-V) characteristic diagram reveals regions with a (quasi-)Ohmic property and other regions with negative differential resistance (NDR). NDR is a phenomenon that has been observed experimentally in DNA at room temperature. We have tried to study the affected agents in charge transfer phenomena in DNA to better design nanostructures.

Designing a molecular switch with bistable on/off states is of particular interest in molecular electronics. Motivated by experimental studies of molecular conductors, interplays of photons and electrons and their effects on electrical properties are studied theoretically. We have tried to model a molecular optical switch based on DNA sequences of the hepatitis delta virus and Toxocara canis parasite. The electrical response of chains to the light irradiation was examined to optimize the function of an optical switch. The switch turns on when the amplitude of incident irradiation and its frequency approach to 0.3 at the unit of (ℏc)/(er 0) and 2 THz, respectively. We can modulate the switching of the system via the simultaneous variation of effective factors and obtain different islands in the parameter settings. The appearance of different islands in the parameter surface relates to the on/off states of electrical current, which can be verified and estimated through the multifractal analysis.

Molecule-based transistors have attracted much attention due to their exclusive properties. Creation of a molecular transistor as well as engineering its structure have become one of the greatest aims of scientists. We have focused on the environmental dependent behavior of a DNA-templated transistor. Using the statistical distribution of the energy levels, we were able to distinguish the delocalized states of charge carriers and the transition between the localized and delocalized behaviors. On the other hand, we can determine the stability conditions of our quantum dynamical system. The results are verified by the inverse participation ratio method. Therefore, the most appropriate parameters for designing the DNA transistor are chosen. The DNA sequence is an important factor for its transport properties, but the results have shown that in the presence of the bath, the bath parameters are important, too. As is shown, it is possible that via the adjustment of bath parameters, one can design a conductivity channel for all nucleotide contents. Thus, one can engineer a DNA based transistor simply through the setting of only one parameter.