Multi-color Reversible Photochromisms via Tunable Light-Dependent Responses

Summary Reversible multi-color chromic systems are critical for the development of advanced sensors, encryption devices, and rewritable media. While many systems show chromic responses to applied stimuli, few show distinct multi-colored states within the same system and exhibit limited flexibility in manipulation of the stimuli source. Light-responsive materials have shown promise because of high precision and controllable parameters of the incident light but suffer from slow kinetics limiting the versatility of the photochromic systems. Here, we report a highly active oxygen vacant titanium oxide/reduced graphene oxide photocatalyst that significantly accelerates the color switching of commercial redox dyes. With the improved catalyst, four photochromic devices are realized: (1) multi-wavelength photochromism, (2) intensity-dependent photochromism, (3) time-dependent photochromism, and (4) dual-response hydro-/photochromism. These devices are based on manipulating the interactions between the light and semiconductor and exhibit a broad range of photochromic behaviors with multi-color states and high reversibility.