Impedimetric Sensing of DNA with Silicon NanowirernTransistors as Alternative Transducer Principle

摘要

Silicon nanowires (SiNW) are highly sensitive to biomolecules. In somernpublications, changes of SiNW conductance in relation to their concentrationrnlevels are displayed. Upon binding, biomolecule charges change the surfacernpotential and, thereby, the SiNW conductance. We discussed earlier thatrnSiNWs can be regarded as long-channel, ion-sensitive field-effect transistorsrn(ISFETs). The choice of a stable working point is important and defines thernSiNW conductance. The common detection principle is based on the shift inrnthreshold voltage. Regardless of conductance change or threshold voltagernshift, relative values are related to biomolecule concentrations. However,rnpotentiometric detection suffers from Debye screening of biomoleculerncharges by counter ions of the test solution. This makes biosensing inrnphysiological buffer solutions difficult if not impossible. In this report, arnmethod for impedance sensing with SiNWs, which was earlier used for ISFETrndevices is introduced. This method gains comparable results to potentiometricrnsensing. The change of interface impedance is indirectly linked with thernbiomolecule charges. In addition, the dielectric property of the interface layerrnplays an important role. At elevated frequencies, our method can be regardedrnas an alternative mechanism similar to dielectric spectroscopy at lowrnfrequencies. Thereby, Debye screening does no longer dominate thernrecordings.