Negative Differential Resistance in Hydrated DNA Thin Film

The electrical properties of DNA and charge transport mechanisms have been extensively investigated during past decade. However, the outcome is a wide discrepancy due to different types of DNA used, the electrode configuration, different range of variables, and different environmental condition, it is extremely hard to bring out the common denominator from them to explain the unified conduction mechanism of DNA. In this book, DNA thin films were systematically studied to reveal DNA conduction in macro-scale. dc I-V characteristics of DNA films under variable relative humidity (RH) were obtained showing an exponential increase in current with increasing RH from 20% to 85%. Protonic conduction was signified in details by the presence of a negative differential resistance (NDR) in highly hydrated films. NDR was seen when RH was over 70% at which the full coordination of DNA backbone with water molecules was expected. It is concluded that the protonic conduction is originated from water redox reactions and the NDR is the result of the limited diffusion of water on the surface of DNA molecules.