Molecular electronic device based on pH indicator by ab initio and non-equilibrium Green function methodology

In the present work we simulate the transport properties and absorption spectra of the organic compound ethyl red. This is the first theoretical study of a specific pH indicator utilized as nano-device, based on first principle quantum mechanics calculations and a non-diffusive transport model. The charge distribution along the molecule is calculated via ab initio technique as a function of an external electric field. Based on a resonant multilevel model we also calculate the current against bias voltage. Both the charge accumulation and the current present similar behavior, like resonant type conduction and asymmetric charge–voltage and current–voltage curves. We also find an agreement between the theoretical absorption spectrum and experimental results for the zero-bias regime. Results for absorption spectra in several regimes under forward and reverse bias are analyzed. Our main results suggest that the present system could operate as a bi-directional molecular transistor.