Distinctive Potential Behavior at the Oxidized Surface of a Semiconductor Device in a Concentrated Aqueous Salt Solution

Conventional electric double layer (EDL) models do not necessarily apply to concentrated solutions such as those found in physiological environments. In this study, we investigated the effect of changing the concentration of a concentrated NaCl solution on the EDL structure formed at the SiO2 surface of a semiconductor-based ion sensor and backed up the study by using a classical molecular dynamics (MD) simulation. The interfacial potential in the concentrated NaCl solution measured by using the ion sensor showed behavior that differed from that in the dilute solution, which was supported by the calculated potential profile based on the MD simulation. The simulated potential behavior at the SiO2/NaCl solution interface depended strongly on the electrical charge distribution caused by the dipole structure of water molecules and the spatial separation of hydrated ions against the surface charge, unlike that in the bulk solution. Characterization of the solid/liquid interface in concentrated solutions is expected to aid the detection of biomolecular recognition events under biological conditions.