Photocurrent Response of Photoreceptive Devices Using a Retinoid Immobilized in a Chitosan Gel Film

Abstract

In order to realize a biophotonic device with biomimetic functions, we focus on the retinal in human eyes. A photoreceptive device was prepared using all-trans retinal immobilized in a gel film chitosan. This device was prepared with either indium tin oxide (ITO)-coated glass and gold-coated glass electrodes (ITO–Au), or using ITO electrodes for both ends (ITO–ITO). Each device was irradiated with 365 nm ultraviolet light for 20 s intervals at an applied voltage of 4 V. The photocurrent response was synchronized to the ON–OFF states of the ultraviolet light and was about 16 times higher for an ITO–ITO device than for an ITO–Au device. We searched for the optimum applied voltage because the ITO–ITO devices deteriorated on the second day at 4 V and found that 3 V produced a photocurrent response in both pre- and post-regenerated devices. Further ITO–ITO devices using three kinds of retinoids (all-trans retinal, all-trans retinoic acid, and all-trans retinol) were prepared. Photocurrent responses measured by a similar method persisted for 331 days using retinal, 313 days using retinoic acid, and 59 days using retinol. Furthermore, the photocurrent response was also observed in post-regenerated gel films of these ITO–ITO devices. These photoreceptive devices could be applied to bio-functional optical sensing or to future visual information processing devices.