Indexed on: 02 Mar '17Published on: 02 Mar '17Published in: Nanotechnology
We report on a technique that can extend the use of nanowire sensors to the detection of interactions involving nonpolar and neutral molecules in ionic solution environment. This technique makes use of the fact that molecular interactions result in a change in the permittivity of the involving molecules. For the interactions taking place at the surface of nanowires, this permittivity change can be determined from the analysis of the measured nanowire complex impedance. To demonstrate this technique, histidine with different charge polarities controlled by the solutions pH value was detected, including the detection of electrically neutral histidine at a sensitivity of 1 pM. Furthermore, it is shown that nonpolar molecules, such as hexane, can also be detected. The technique is applicable to the use of nanowires with and without surface insulating oxide. We show that the information about the changes in the amplitude and phase of the complex impedance reveals the fundamental characteristics of the molecular interactions, including the molecular field and the permittivity.