Tuning DNA electrical conductivity by silver photo-doping

Photodoping of silver into bulk DNA is studied by measuring its ambient electrical conductivity. Mechanically pressed pellets of pure DNA and chemically modified Ag-DNA were prepared and were further coated with silver paste on either side of pellets to monitor the photodoping process. The electrical conductivity of these pellets was continuously measured under white light irradiation. The initial electrical conductivity of these pellets was smaller, that progressively increased with increase in number of current-voltage scan cycles under constant illumination of visible light. The change in electrical conductivity by photodoping is more in a pure DNA as compared to that of chemically modified Ag-DNA. The temperature dependent electrical conductivity exhibits the Arrhenius behavior. A detailed elemental depth profile was studied by core level x-ray photo-electron spectroscopy (XPS). The results clearly suggest that photodoping of silver can alter the DNA's starting electrical conductivity.