Voltage-controlled spectral tuning of photoelectric signals in a conducting polymer-bacteriorhodopsin device

Abstract

Bacteriorhodopsin (bR), a protein existing in the halobacterial purple membrane serves as a light-driven pump which sets up an electrochemical gradient and transports protons across the cell membrane. In this report, we explore the synergetic processes at a conducting polymer/bR interface due to photoexcitation in presence of a voltage bias. The possibility of changing the oxidation state of the polymer electrochemically is coupled to the optically activated proton gradient in the bR side. This approach of controlling the nature of the conducting polymer-bR interface demonstrates a facile route to stabilize the deprotonated, long-lived intermediate state present in the bR photocycle. These processes result in interesting solid- state device properties such as incident-wavelength-controlled rectification of the photoinduced current and voltage-controlled spectral responses.