A computational analysis of interaction between inorganic semiconductor nanowire and molecular partial charge for DNA sensor application
Abstract
This research aimed to investigate the effects of partial charge due to DNA hybridization on the conductance of the silicon nanowire through finite element calculations. A biosensor was designed with the silicon nanowire of 15 nm radius at the
core and surrounded by a silicon dioxide (2 SiO) layer of 2 nm thickness. The oxide layer was surrounded by a 5 nm thick functional bio-interface layer incorporating probe ssDNA and this whole system was immersed in an electrolyte of 80 nm radius. For the purpose of modeling and simulation, each of this layers was treated as a continuum medium characterized by the corresponding dielectric constant. In order to determine the effects of hybridization on nanowire conductance, the distribution of the electrostatic potential in the nanowire and other layers were first computed using Poisson equation with Boltzmann statistics without adding target DNA in the electrolyte layer. The conductance of the nanowire in this condition was computed by integrating
the effect of the potential charge carriers within the nanowire and partial charge due to probe ssDNA. Then, the potential distribution was again calculated with the target DNA in the electrolyte and the conductance of the nanowire was re-calculated. Partial charge due to hybridization between probe and target DNAs was first computed using molecular dynamics simulation and integrated into the finite element calculation. The Finite element calculations showed that the nanowire conductance depended nonlinearly on the external charge (partial charge) of the bio-interface due to the hybridization of the target DNA with probe DNA in the functional layer.