Impedance modulation of polymer nanosheet capacitor by light stimuli

We report the modulation of dielectric properties of photoactive ultrathin polymer film capacitor (polymer nanosheet capacitor) constructed from polymer nanosheet assemblies. The capacitor was fabricated from multi-heterodeposition of passive polymer nanosheet, poly(N-dodecylacrylamide) (p(DDA)) and two photoactive nanosheets, which contain ruthenium and ferrocene, respectively. The impedance spectroscopy measurement indicates that the photoactive capacitor acts as an ideal capacitor in a dark condition. To modulate dielectric properties of the photoactive capacitor, the capacitor was irradiated with a visible light to excite the ruthenium complex. After 5 min irradiation, the impedance spectrum of the photoactive capacitor shows deviation from an ideal capacitor behavior. The deviation was derived from a vectorial photoinduced electron transfer between ruthenium and ferrocene. An equivalent-circuit for the irradiated nano-capacitor was proposed and the capacitance derived from the photoinduced electron transfer was determined to 8.6 nF/cm2.